The Need for US Indoor Air Quality Guidelines
Advancing Policy for Healthy Buildings at the Federal and State Level
Executive Summary
Indoor Air Quality Guidelines Inform Climate and Health Solutions
Climate change and human health are both tightly linked to fossil fuel use in energy systems, including those within residential and commercial buildings. Greenhouse gas emissions will increase the frequency and severity of extreme climate events over the next century, while exacerbating current health problems and introducing new ones. In the near-term, indoor and outdoor air pollution from combustion contributes to poor health outcomes, including respiratory and cardiovascular disease.
However, the importance of indoor air quality is often overlooked. Decarbonizing the buildings in which we live, work, and play is a key solution to both limit climate impacts and promote human health and safety by reducing combustion pollution exposure. Adopting indoor air quality guidelines in the US would improve our understanding of indoor environments and inform health-protective strategies in the building sector, including electrification and beyond.
Understanding and Protecting Indoor Air
Poor indoor air quality is one of the top five major public health risks, yet “healthy” indoor air quality is not well defined, and indoor air is largely unregulated by federal and most state governments.
Setting indoor air quality (IAQ) guidelines provides a foundation for understanding and addressing indoor health risks. Guidelines can inform standards, regulations, and policies to ensure that indoor environments are safe and healthy. IAQ guidelines are not new or novel. More than 50 organizations — including the World Health Organization (WHO) — across 38 countries have established IAQ guidelines. In the United States, the Environmental Protection Agency (EPA) has already set an indoor guideline for radon, and states including California, Illinois, and Texas have established some form of IAQ guidelines.
Federal and state agencies can and should act to protect families from unhealthy indoor air by setting new IAQ guidelines, using existing IAQ guidelines as models, and increasing research to inform and update guidelines. In this report, RMI provides a comprehensive, novel review of IAQ guidelines, summarizes their real-world applications, and provides recommended actions for policymakers.
Introduction
The Evidence Is Clear: Indoor Air Has an Impact on Health
Exposure to indoor air pollutants poses a serious health threat. We spend almost 90% of our time indoors, where pollutant concentrations may be two to five times higher than outdoors. Behavioral shifts since the COVID-19 pandemic have further increased time spent indoors, and many of those behavioral changes have been sustained. Changes to outdoor environmental conditions due to climate change are projected to cause additional adverse effects to indoor air quality that will harm human health, including increased indoor heat stress, mold, ozone exposure, and wildfire smoke exposure.
Exhibit 1: Key Indoor Air Pollutants
Pollutants were selected based on their inclusion in published guidelines, established scientific evidence of human health effects from exposure, and their known presence in indoor environments. This list of pollutants and descriptions are non-exhaustive.
A growing body of research links poor IAQ with adverse health outcomes. Exposure to indoor air pollution can contribute to respiratory issues, hospital visits, absences from school and work, and serious conditions such as heart disease, stroke, and cancer.
Risks may be more severe for vulnerable populations including children, the elderly, and people with existing respiratory issues, who are likely to spend more time indoors. Low-socioeconomic households experience a disproportionately high risk of pollutant exposure indoors, where housing conditions may be smaller, more crowded, older, and closer to outdoor pollutant sources. Health risks may also be higher for homes that use gas stoves, where nitrogen dioxide (NO2) levels can be around 50 to 400 times higher than in homes with electric stoves. More guidance about healthy IAQ is needed to better inform building occupants about IAQ risks, especially for vulnerable groups who already face increased risk of health impacts from climate change.
Indoor Air and Outdoor Air: Similar but Different
The Clean Air Act (CAA), EPA’s ambient air regulation, has sometimes been used to assess IAQ. Ambient air is defined in the CAA as outdoor air: “air external to buildings.” Although ambient pollutants do travel indoors, the indoor environment is distinct, and it is therefore not precise to apply ambient air guidance.
Indoor air contains disparate and often higher concentrations of pollutants than ambient air. Some indoor air pollutant concentrations can also be greatly influenced by seasonal variability, and as previously noted, people spend most of their time indoors.
Because of these factors, indoor environments have the largest influence on personal pollutant exposure, and ambient measurements of pollutants may underestimate long-term health risks associated with exposure. Indoor-specific guidelines for key pollutants (see Exhibit 1) are necessary to accurately understand health risks.
Although not applicable indoors, the CAA’s regulatory framework shows the potential of US policy to protect air quality and human health. Under CAA enforcement, collective emissions of the six most common ambient air pollutants decreased 78% from 1970 to 2020. This drastic reduction drives lower mortality rates as well as fewer respiratory illness cases, emergency visits, and absences from school and work.
Benefits of CAA pollutant control are estimated to exceed costs by more than 30-to-1, resulting in over $2 trillion in estimated avoided health costs in 2020. Parallel protections for indoor air could result in additional reductions in illnesses, deaths, hospital admissions, and absences.
By setting IAQ guidelines, federal and state agencies can help reduce harmful pollutants indoors and associated health risks and costs.
What Are Indoor Air Quality Guidelines?
Generally, and as defined in this report, IAQ guidelines are science-based, voluntary limits on indoor air pollutant concentrations. As opposed to standards, guidelines are not mandatory or enforced. Rather, guidelines give health- or risk-based benchmarks on safe pollutant thresholds. Guidelines may be developed using various methods:
- Some guidelines set health-based pollutant concentration limits that eliminate all health risks or minimize risks as much as possible.
- WHO 2010 guidelines identify a pollutant exposure threshold (“reference concentration”) at which health risks are eliminated or minimized. WHO 2021 guidelines similarly identify the lowest level of exposure for which there is evidence of adverse health effects.
- Other guidelines set feasibility-based pollutant concentration limits that minimize major health risks and set achievable exposure limits.
- Health Canada’s guidelines, such as the 2021 guideline for carbon dioxide (CO2), identify a reference concentration below which serious health problems are unlikely to occur. A feasibility analysis is then conducted to ensure that the reference concentration can be achieved through controlling indoor pollutant sources and other mitigations. If pollutant levels cannot be lowered to the reference concentration value, the reference concentration may be set at a higher, more achievable value.
Report Methods
The report findings are primarily derived from a review of existing guidelines, studies, and interviews with US-based subject matter experts. The scope of this report is limited to indoor air pollutants commonly included in existing IAQ guidelines and does not include biological contaminants related to infectious disease transmission.
The cited literature is not exhaustive but synthesizes our current understanding of how IAQ guidelines are established and their potential to inform health considerations. Based on this understanding, recommendations focus on how policymakers can advance IAQ guidelines.
How IAQ Guidelines Are Developed
International
More than 50 organizations across at least 38 countries have established IAQ guidelines in occupational, commercial, or residential settings (see Exhibit 2). Guidelines cover pollutants and other risks such as mold, moisture, and temperature. Although general pollutant information and source control measures are important, guidelines that include health-based numerical pollutant exposure limits are the most informative for assessing IAQ.
World Health Organization
As the health agency of the United Nations, WHO influences health-protective policies globally. Current WHO publications of IAQ guidelines have varying levels of tailored assessment and relevance to the indoor environment. WHO guidelines are not legally binding. They are intended to inform health professionals, specialists, and policymakers and to provide a scientific basis for legally enforceable IAQ standards. Most recently in 2021, WHO published global air quality guidelines applicable indoors and outdoors. WHO commissioned six systematic literature reviews to determine the 2021 guidelines. Five reviews omitted studies that evaluated indoor-specific pollutant exposures exclusively, and the sixth review did not reference indoor air pollution
To ensure that future guidelines accurately apply indoors, additional review of indoor-specific studies is warranted. In 2010, WHO published IAQ guidelines for common indoor pollutants. While indoor guidelines for mold and dampness were published in 2009, the 2010 guidelines are the first WHO guidelines with a methodology specific to indoor air pollutants. Although no additional review of the literature was included, WHO also published guidelines for household fuel combustion in 2014, influenced by WHO guidelines from 2010 and 2006.
Health Canada
Health Canada, the health department of the Canadian government, first released residential IAQ guidelines for pollutants in 1987. Guidelines have been revised to reflect updated scientific understanding, most recently for xylenes and acrolein in 2021, and spanning as far back as formaldehyde in 2006. Guideline updates incorporate new scientific findings of health effects, sources, and exposure levels for each pollutant, including assessments conducted by external agencies such as WHO and EPA.
For fine particulate matter (PM2.5), Health Canada rescinded its initial guideline after determining that there is no apparent safe level of this pollutant indoors. Sources of PM2.5 are virtually impossible to eliminate because they are essential, for instance, for such everyday life activities as cooking and cleaning. Considering the inability to eliminate indoor PM2.5, Health Canada has provided action-based guidance to reduce concentrations, including eliminating smoking indoors and using a range hood when cooking.
United States
Federal
Although there are no comprehensive US IAQ guidelines, federal agencies are involved in IAQ-relevant initiatives, including the Federal Interagency Committee on Indoor Air Quality (CIAQ), the 1986 Superfund Amendments and Reauthorization Act (SARA), radon abatement, pollutant risk assessments, and occupational exposure limits.
Broadly, the EPA is responsible for IAQ issues at the federal level and leads the CIAQ, created in 1983 and tasked with coordinating and communicating federal IAQ research to the public. Other federal agencies involved in the CIAQ include the Consumer Product Safety Commission (CPSC), Department of Energy (DOE), National Institute for Occupational Safety and Health (NIOSH), Department of Health and Human Services (HHS), Occupational Safety and Health Administration (OSHA), and Department of Labor (DOL).
EPA Authority under SARA
Publishing voluntary IAQ guidelines is consistent with EPA’s authority under Title IV, Section 403 of SARA, which authorizes actions related to IAQ and air pollutants in the indoor environment.
Federal IAQ Actions Required Under the Superfund Amendments and Reauthorization Act
Title IV, Sec. 403 of SARA, Radon Gas and Indoor Air Quality Research Program, requires EPA to take actions to address IAQ, including to:
- Gather information on all aspects of IAQ to contribute to the understanding of health problems (42 USC 7403(a)(1))
- Coordinate federal, state, local, and private research relating to the improvement of IAQ (42 USC 7403(a)(2))
- Assess appropriate federal government actions to mitigate environmental and health risks (42 USC 7403(a)(3))
EPA is also required to establish a research program that must include:
- Research and development on the identification, characterization, and monitoring of sources and levels of indoor air pollution, including the measurement of pollutant concentrations (42 USC 7403(b)(1))
- Research relating to the effects of indoor air pollution and radon on human health (42 USC 7403(b)(2))
- Demonstration of methods for reducing or eliminating indoor air pollution and radon (42 USC 7403(b)(4))
- Dissemination of information to assure public availability of findings under the activity of this section (42 USC 7403(b)(6))
Per SARA requirements, EPA released a report to Congress on IAQ in 1989 summarizing the assessment and control of IAQ and IAQ-relevant federal authorities. Although SARA does not grant EPA authority to regulate indoor air pollutants, Title IV of SARA “provides EPA the authority to conduct research, coordinate activities in the public and private sectors, and disseminate information on indoor air,” according to the 1989 report.
Furthermore, the CIAQ website states that the committee supports EPA’s IAQ research program requirements under Title IV of SARA. Based on this authority and available supporting information from CIAQ, EPA could publish a report that reflects current scientific understanding of IAQ and health risks, including IAQ guidelines.
EPA’s Model for IAQ Guidance: Radon
The EPA has published indoor pollutant concentration limits before. The agency set an indoor exposure limit for radon, a radioactive and carcinogenic gas, at 4 picocuries per liter (pCi/L). The radon indoor exposure limit was created as a voluntary consensus standard through the Indoor Radon Abatement Act (1988). This act set a goal for indoor air to be as free of radon as outdoor air and authorized funding for EPA-developed construction standards and public guidance, state radon abatement programs, technical assistance to states, research on radon in schools, proficiency programs for radon testing firms, and regional radon training centers.
EPA’s indoor exposure limit for radon has informed radon testing protocols and standards to reduce risks to health and safety, such as Federal Housing Finance Agency abatement requirements in some multifamily properties. This radon limit can be used as a model for additional federal IAQ guidelines. Related authorizations and funding under the Indoor Radon Abatement Act may also influence similar IAQ-protective policy measures.
Pollutant Risk Assessment Methodology
EPA has conducted risk assessments on many air pollutants under other federal programs, including the 1976 Toxic Substances Control Act (TSCA) and Integrated Risk Information System (IRIS) program. These are relevant to IAQ guidelines because they are examples of ways the federal government already has assessed health risks of indoor air pollutants.
The TSCA provides EPA with authority to require reporting, testing, and restrictions on toxic chemicals. EPA’s 1989 Report to Congress on IAQ clarified that the TSCA gives EPA the ability to restrict manufacturing, distribution, and use of toxic chemicals, “including any that may be significant indoor pollutants.” This act has influenced EPA’s approach to its risk assessments for ambient air pollutants and could inform a similar approach to assessing indoor air pollutants.
EPA has published health-based lifetime and daily chemical exposure limits through IRIS; however, these assessments are missing for some key pollutants and are slow to publish. IRIS assessments inform federal and state risk assessments to address public health hazards such as PFAS chemicals, lead, and mercury. Experts have criticized IRIS methods for the lack of assessments for key health-harming indoor pollutants, like CO2 and NO2, lack of transparency in scientific methods, and the lengthy publication process. Some scientific experts are concerned that a lack of IRIS assessments for some pollutants will be misinterpreted as a lack of risk.
State and Local
Although federal support of IAQ guideline development is important, it is not a prerequisite for states to set their own guidelines. Whereas some states operate a central air quality program, others may house state initiatives to protect IAQ in other programs related to air and health. Referencing existing guidelines can support IAQ guideline development by state agencies. Examples of state IAQ guidelines are outlined below:
- In California, the state Air Resources Board (CARB) published recommended pollutant exposure limits in its 2005 Indoor Air Quality Report. Many of these guidelines have not been updated and are based on California’s ambient air quality standards. As of 2021, CARB is actively developing updated IAQ guidelines for NO2 to reflect scientific advances and hosted the first public workshop for this update in May 2023.
- In Illinois, the state Department of Public Health (IDPH) created voluntary guidelines for acceptable IAQ under Illinois’ Indoor Air Quality Act of 1994 for homes and workplaces, although they are not protective of sensitive groups and are outdated. IDPH has indicated it is in the process of reviewing and updating its guidelines.
Certain states have established IAQ guidelines for specific building types — schools and state agency buildings are common examples.
- In Texas, the state Department of Health, under the state Health and Safety Code, established voluntary guidelines for IAQ in government buildings and public schools in 2002. These guidelines outline “minimum risk levels” for common indoor air pollutants.
- In Pennsylvania, the state Department of Health’s Indoor Air Quality Guidelines for Pennsylvania Schools refers to EPA, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), and NIOSH thresholds for indoor pollutants. Pennsylvania’s IAQ guidelines for schools have not been updated; however, a copy from 2011 is labeled “under review.”
- In Indiana and Ohio, as well as other states, health departments have established a maximum exposure limit only for CO2 in schools and state agencies.
Some states and local jurisdictions have established IAQ protections that do not specify health-based thresholds for indoor pollutant concentrations.
- In Delaware, the Division of Public Health requires IAQ monitoring in schools related to temperature and humidity.
- In New York, the state Clean Indoor Air Act has reduced smoking and vaping activity, and New York City’s Indoor Allergen Hazards law requires building owners to mitigate mold and pests.
- In Washington, D.C., the Healthy Public Buildings Assessment Act requires indoor environmental quality assessments at federal properties and public guidance for maintaining acceptable IAQ, without defining threshold levels for indoor pollutant concentrations.
Exhibit 2: Existing IAQ Guidelines
Although not exhaustive, Exhibit 2 represents a first-of-its-kind consolidation of key guidelines across the United States in one table. Pollutants were selected based on their inclusion in published guidelines, established scientific evidence of human health effects from exposure, and their known presence in indoor environments.
Note: Some pollutant exposure limit units were converted for consistency across guidelines; original unit values are available in the endnote sources or upon request.
How IAQ Guidelines Can Be Applied
While IAQ guidelines are often voluntary, they have several important uses. Application of IAQ guidelines will require action from policymakers, public health professionals, building industry members, researchers, and the public.
Product Safety
Controlling pollutant sources indoors can reduce exposure to multiple pollutants at once. IAQ guidelines may help inform safe benchmarks for emissions from products, appliances, and building materials. For example, CARB set ozone emissions limits for air cleaners (often called air purifiers). Canada’s IAQ guidelines informed standards for air cleaners, carbon monoxide alarms, and composite wood products.
Product safety agencies like the CPSC can use IAQ guidelines in creating product assessments, standards, and related efforts, including stakeholder group meetings and safety guides to address IAQ concerns. Additionally, the CPSC can set federal voluntary or mandatory product performance standards to limit pollution indoors and are not required to rely on voluntary processes if they would unreasonably delay the development of standards that align with existing IAQ guidelines.
Building Upgrades
Building owners, operators, and design and construction teams can perform building upgrades to comply with IAQ guidelines. Upgrades to improve IAQ may be desirable for residential buildings, commercial office space, academic or medical campuses, military housing, or other building types because of evidence-based benefits to indoor air, occupant well-being and productivity, and energy savings potential, among other outcomes.
For instance, Health Canada has provided guidance for office buildings to improve IAQ that suggests reducing or eliminating indoor contaminants, with direct reference to Canada’s IAQ guidelines. Existing federal programs to promote IAQ-related building upgrades, such as the US Clean Air in Buildings Challenge, can set requirements for program participants to comply with IAQ guidelines.
Building Codes, Voluntary Standards, and Certifications
Codes
Agencies responsible for building codes, such as state energy offices, can use IAQ guidelines in assessment protocols for modeling new building standards, energy codes, and requirements for efficiency, performance, and ventilation. For instance, the California Energy Commission requires that new building efficiency standard assessments include “the impact that those standards would have on indoor air pollution problems.” Additionally, California requires IAQ improvement considerations in the state Energy Code and IAQ-related operation measures such as mechanical ventilation and kitchen exhaust requirements that take into account kitchen range fuel type.
Voluntary Standards
Voluntary standard organizations, including the American National Standards Institute, American Society for Testing and Materials (ASTM), ASHRAE, and others, can incorporate IAQ guidelines into the review process for new and existing standards. Standards in adherence with IAQ guidelines should ensure that consumer products, building operations, and other materials will not contribute to harmful levels of pollutant concentrations indoors.
Building Certification Programs
Voluntary labeling and certificate programs such as WELL, LEED, and Enterprise Green Communities have accreditations for IAQ and health, but many pollutant exposure limits currently refer to ambient air quality standards from WHO or EPA. Indoor airPLUS, EPA’s voluntary partnership program to protect IAQ in homes, does not require adherence with IAQ guidelines and does not provide suggested limits on indoor air pollutants aside from radon. Such programs could refer to existing health-based, indoor-specific guidelines as the basis of accreditations relevant to indoor air, appliance and fuel use, and healthy indoor spaces.
Building Inspections
Traditionally, code enforcement programs or inspections have been driven by complaints. However, proactive home inspections are becoming more common. Benchmarking against IAQ guidelines can better inform building inspections and pollutant abatement actions. For example, radon inspections are typically conducted before the sale or rental of a property.
Exact protocols vary by state (e.g., Florida requires adherence to existing EPA guidelines for radon, whereas Illinois requires that sellers inform buyers of radon risk with educational material on radon testing guidelines). There are several other examples of inspection programs that can improve health outcomes, including lead poisoning inspection requirements in Massachusetts, the US Department of Housing and Urban Development’s (HUD) smoke-free housing lease policy, and state policies allowing health professionals to refer asthma patients for in-home inspections.
Following inspection, further abatement actions can be taken to address health risks. Such actions can reduce costs for individuals and the government by avoiding hospitalizations and other health costs.
Informational Resource
Established IAQ guidelines can serve as an informational resource to improve health considerations for states seeking to set IAQ guidelines, researchers or officials prioritizing health risks for vulnerable populations, or members of the public wanting to improve IAQ in their home or community.
Policymakers
States seeking to develop IAQ guidelines and related policy measures, such as standards, may adopt or reference existing guidelines from other agencies. For example, Health Canada’s residential IAQ guidelines referenced WHO IAQ guidelines, and CARB has referenced Health Canada’s IAQ guidelines.
Risk Management
Guidelines can influence pollutant risk management strategies and identify areas or communities experiencing high IAQ risks. For healthcare professionals, IAQ guidelines can inform patient evaluation questions related to indoor pollutant sources, similar to secondhand smoke exposure evaluation resources for pediatric patients. Air monitors may be able to help determine pollutant levels, associated health risks, and diagnoses, similarly to how radon monitors have been recommended to test and identify major health risks.
Consumer Awareness
People living in the United States are concerned about IAQ. In fact, since the COVID-19 pandemic, over 53% of US consumers say that IAQ is a greater concern than it was pre-pandemic, and over 90% believe IAQ is important in preventing the spread of infectious disease. This awareness likely drives behavior and consumer choices.
One example is the increased sales of low-cost pollutant monitors. There are now more options than ever to test indoor air, but often consumers are left without clear guidance on how to interpret measurement levels.
To address concerns about reentering buildings post-pandemic, 76% of US consumers stated interest in a “rating system” for IAQ to better inform them about indoor air risks. Guidance on pollutant levels in public spaces could inform building operation system triggers, such as increasing ventilation. In fact, post-COVID-19, 77% of consumers say that seeing a hotel’s IAQ rating advertised would have an impact on their choice of where to stay.
Frequently Asked Questions
What about Occupational Pollutant Exposure Limits?
Federal agencies have set IAQ guidelines for occupational settings, but these guidelines only apply to work settings for adults during an 8- to 10-hour workday. Occupational pollutant exposure limits for toxic chemicals such as asbestos, lead, and carbon monoxide have been established by OSHA and NIOSH.
However, OSHA states that many of its enforceable pollutant exposure limits are outdated and do not adequately protect worker health. Because they are outdated, OSHA recommends the use of occupational exposure limits from California’s division of OSHA, NIOSH, and the American Conference of Governmental Industrial Hygienists (ACGIH). In 1994, OSHA proposed a rulemaking to adopt IAQ standards in indoor work environments, but it was withdrawn in 2001. Further protections for worker’s health indoors could be established through a similar proposed rulemaking and could be informed by IAQ guidelines.
What About ASHRAE Standards for Indoor Air Quality?
ASHRAE is a professional US organization that has developed standards for ventilation system design, maintenance, and operation to achieve acceptable IAQ and minimize adverse health effects, including ASHRAE Standards 62.1 and 62.2 for commercial and residential properties, respectively. In previous guidance for achieving better IAQ, ASHRAE has stated that it does not propose any contaminant concentration standard or guideline values, and instead uses values developed by leading authorities such as EPA and WHO.
For example, ASHRAE Standard 62.1 references EPA’s ambient air quality standards to determine if pollutant concentration limits (“design limits”) in the standard cause certain health effects. Similarly, ASHRAE could reference IAQ guidelines from leading authorities to help develop design limits in future indoor-relevant ASHRAE standard updates.
Recommendations
Improving IAQ will require collaborative action by federal and state policymakers.
Conclusion — Now Is the Time for IAQ Guidelines
We’ve witnessed the impact of poor indoor air quality on our lives, from the spread of infectious disease to building and vehicle greenhouse gas emissions to wildfire smoke. These risks will not disappear — asthma rates continue to rise in the United States, and climate change caused primarily by burning fossil fuels such as oil and gas continues to amplify ground-level ozone and other IAQ impacts.
While these risks will continue, our collective response can improve to ensure healthier buildings and neighborhoods. Americans deserve to be well-prepared and well-educated about the safety of indoor air. Federal agencies have created best practices to fight infectious disease, but by continuing to overlook indoor air pollutants in homes and buildings, the United States risks leaving a major health threat unaddressed.
Setting IAQ guidelines is a necessary tool to begin protecting indoor air and can inform subsequent protective policy measures. All avenues should be pursued to protect IAQ; in addition to IAQ guidelines, state and local jurisdictions should adopt the most health-protective policy measures under their authority, such as codes, standards, and regulations.
Mirroring the existing CAA, some scientific experts have called on policymakers to create an IAQ task force and enact an “Indoor Air Quality Act,” whereas others have published model IAQ legislation. IAQ guidelines also support existing US initiatives to limit disease transmission, improve building performance and electrification, and advance equity.
If US ambient air policy is any indication, protecting the air we breathe indoors has the potential to save lives and strengthen the economy.
Citations for Exhibit 1
- Hazard Summary: Acetaldehyde, EPA, 2000, https://www.epa.gov/sites/default/files/2016-09/documents/acetaldehyde.pdf; “Medical Management Guidelines for Acrolein,” US Agency for Toxic Substances and Disease Registry, accessed August 2023, https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=552&toxid=102#.
- “BTEX,” Science Direct, accessed August 2023, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/btex; “Carbon Dioxide in Your Home,” Health Canada, accessed August 2023, https://www.canada.ca/en/health-canada/services/publications/healthy-living/carbon-dioxide-home.html.
- Seals, Health Effects from Gas Stove Pollution, 2020; WHO Guidelines for Indoor Air Quality: Selected Pollutants, WHO, 2010, https://www.who.int/publications/i/item/9789289002134.
- “Nitrogen Dioxide,” American Lung Association, accessed August 2023, https://www.lung.org/clean-air/outdoors/what-makes-air-unhealthy/nitrogen-dioxide.
- “Ozone & Health,” State of California Air Resources Board, accessed August 2023, https://ww2.arb.ca.gov/resources/ozone-and-health; and “Radon,” EPA, accessed August 2023, https://www.epa.gov/radon.
Citations for Exhibit 2
- WHO Global Air Quality Guidelines: Particulate Matter, WHO, 2021; WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010.
- “Residential Indoor Air Quality Guideline: Acetaldehyde,” Health Canada, 2017, https://publications.gc.ca/site/eng/9.835076/publication.html.
- “Residential Indoor Air Quality Guideline: Acrolein,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-acrolein.html.
- “Guidance for Benzene in Residential Indoor Air,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidance-benzene-residential-indoor-air.html.
- “Residential Indoor Air Quality Guideline for Xylenes,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-xylenes.html.
- “Residential Indoor Air Quality Guideline: Carbon Monoxide,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-carbon-monoxide.html.
- “Residential Indoor Air Quality Guideline: Carbon Dioxide,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-carbon-dioxide.html.
- “Residential Indoor Air Quality Guideline: Formaldehyde,” Health Canada, 2006, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-formaldehyde.html.
- “Residential Indoor Air Quality Guideline: Naphthalene,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-naphthalene.html.
- “Residential Indoor Air Quality Guideline: Nitrogen Dioxide,” Health Canada, 2015, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-nitrogen-dioxide.html.
- “Residential Indoor Air Quality Guideline: Ozone,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-ozone.html.
- “Radon Guideline,” Health Canada, 2009, https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon/government-canada-radon-guideline.html.
- A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon, EPA, 2016, https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf.
- “IDPH Guidelines for Indoor Air Quality,” Illinois Department of Public Health, accessed August 2023, https://dph.illinois.gov/topics-services/environmental-health-protection/toxicology/indoor-air-quality-healthy-homes/idph-guidelines-indoor-air-quality.html,
- Comprehensive Indoor Air Quality Report, California Air Resources Board, 2005, https://ww2.arb.ca.gov/resources/documents/comprehensive-indoor-air-quality-report-2005.
- “Texas Voluntary Indoor Air Quality Guidelines for Government Buildings,” Texas Department of Health, 2002, https://gato-docs.its.txst.edu/jcr:afe38366-c8fe-4e39-8e6f-9eab96d729ba/Gov_Bld_Gd.pdf.
CONTACTS
Nina Prescott, nina.prescott@rmi.org
Mike Henchen, mhenchen@rmi.org
COPYRIGHTS AND CITATION
Nina Prescott, The Need for US Indoor Air Quality Guidelines: Advancing Policy for Healthy Buildings at the Federal and State Level, RMI, 2023.
RMI values collaboration and aims to accelerate the energy transition through sharing knowledge and insights. We therefore allow interested parties to reference, share, and cite our work through the Creative Commons CC BY-SA 4.0 license. https://creativecommons.org/licenses/by-sa/4.0/.
All images used are from iStock.com unless otherwise noted.
ACKNOWLEDGMENTS
Thank you to subject matter experts who offered their valuable comments and suggestions, which helped to inform this report, including:
Carbon-Free Buildings Program team, RMI
Noah Cordoba, Lawrence Garber, and Amy Rider, Building Decarbonization Coalition (BDC)
Iain Walker, Lawrence Berkeley National Lab
David Jacobs and Jonathan Wilson, National Center for Healthy Housing (NCHH)
Matt Casale (in his former capacity) and Abe Scarr, Public Interest Research Group (PIRG)
Annika Larson, environmental justice policy expert
Aaron Martin, Illinois Department of Public Health
Ruth Ann Norton, Green & Healthy Homes Initiative
Indoor Air Quality Guidelines Inform Climate and Health Solutions
Climate change and human health are both tightly linked to fossil fuel use in energy systems, including those within residential and commercial buildings. Greenhouse gas emissions will increase the frequency and severity of extreme climate events over the next century, while exacerbating current health problems and introducing new ones. In the near-term, indoor and outdoor air pollution from combustion contributes to poor health outcomes, including respiratory and cardiovascular disease.
However, the importance of indoor air quality is often overlooked. Decarbonizing the buildings in which we live, work, and play is a key solution to both limit climate impacts and promote human health and safety by reducing combustion pollution exposure. Adopting indoor air quality guidelines in the US would improve our understanding of indoor environments and inform health-protective strategies in the building sector, including electrification and beyond.
Understanding and Protecting Indoor Air
Poor indoor air quality is one of the top five major public health risks, yet “healthy” indoor air quality is not well defined, and indoor air is largely unregulated by federal and most state governments.
Setting indoor air quality (IAQ) guidelines provides a foundation for understanding and addressing indoor health risks. Guidelines can inform standards, regulations, and policies to ensure that indoor environments are safe and healthy. IAQ guidelines are not new or novel. More than 50 organizations — including the World Health Organization (WHO) — across 38 countries have established IAQ guidelines. In the United States, the Environmental Protection Agency (EPA) has already set an indoor guideline for radon, and states including California, Illinois, and Texas have established some form of IAQ guidelines.
Federal and state agencies can and should act to protect families from unhealthy indoor air by setting new IAQ guidelines, using existing IAQ guidelines as models, and increasing research to inform and update guidelines. In this report, RMI provides a comprehensive, novel review of IAQ guidelines, summarizes their real-world applications, and provides recommended actions for policymakers.
The Evidence Is Clear: Indoor Air Has an Impact on Health
Exposure to indoor air pollutants poses a serious health threat. We spend almost 90% of our time indoors, where pollutant concentrations may be two to five times higher than outdoors. Behavioral shifts since the COVID-19 pandemic have further increased time spent indoors, and many of those behavioral changes have been sustained. Changes to outdoor environmental conditions due to climate change are projected to cause additional adverse effects to indoor air quality that will harm human health, including increased indoor heat stress, mold, ozone exposure, and wildfire smoke exposure.
Exhibit 1: Key Indoor Air Pollutants
Pollutants were selected based on their inclusion in published guidelines, established scientific evidence of human health effects from exposure, and their known presence in indoor environments. This list of pollutants and descriptions are non-exhaustive.
A growing body of research links poor IAQ with adverse health outcomes. Exposure to indoor air pollution can contribute to respiratory issues, hospital visits, absences from school and work, and serious conditions such as heart disease, stroke, and cancer.
Risks may be more severe for vulnerable populations including children, the elderly, and people with existing respiratory issues, who are likely to spend more time indoors. Low-socioeconomic households experience a disproportionately high risk of pollutant exposure indoors, where housing conditions may be smaller, more crowded, older, and closer to outdoor pollutant sources. Health risks may also be higher for homes that use gas stoves, where nitrogen dioxide (NO2) levels can be around 50 to 400 times higher than in homes with electric stoves. More guidance about healthy IAQ is needed to better inform building occupants about IAQ risks, especially for vulnerable groups who already face increased risk of health impacts from climate change.
Indoor Air and Outdoor Air: Similar but Different
The Clean Air Act (CAA), EPA’s ambient air regulation, has sometimes been used to assess IAQ. Ambient air is defined in the CAA as outdoor air: “air external to buildings.” Although ambient pollutants do travel indoors, the indoor environment is distinct, and it is therefore not precise to apply ambient air guidance.
Indoor air contains disparate and often higher concentrations of pollutants than ambient air. Some indoor air pollutant concentrations can also be greatly influenced by seasonal variability, and as previously noted, people spend most of their time indoors.
Because of these factors, indoor environments have the largest influence on personal pollutant exposure, and ambient measurements of pollutants may underestimate long-term health risks associated with exposure. Indoor-specific guidelines for key pollutants (see Exhibit 1) are necessary to accurately understand health risks.
Although not applicable indoors, the CAA’s regulatory framework shows the potential of US policy to protect air quality and human health. Under CAA enforcement, collective emissions of the six most common ambient air pollutants decreased 78% from 1970 to 2020. This drastic reduction drives lower mortality rates as well as fewer respiratory illness cases, emergency visits, and absences from school and work.
Benefits of CAA pollutant control are estimated to exceed costs by more than 30-to-1, resulting in over $2 trillion in estimated avoided health costs in 2020. Parallel protections for indoor air could result in additional reductions in illnesses, deaths, hospital admissions, and absences.
By setting IAQ guidelines, federal and state agencies can help reduce harmful pollutants indoors and associated health risks and costs.
What Are Indoor Air Quality Guidelines?
Generally, and as defined in this report, IAQ guidelines are science-based, voluntary limits on indoor air pollutant concentrations. As opposed to standards, guidelines are not mandatory or enforced. Rather, guidelines give health- or risk-based benchmarks on safe pollutant thresholds. Guidelines may be developed using various methods:
- Some guidelines set health-based pollutant concentration limits that eliminate all health risks or minimize risks as much as possible.
- WHO 2010 guidelines identify a pollutant exposure threshold (“reference concentration”) at which health risks are eliminated or minimized. WHO 2021 guidelines similarly identify the lowest level of exposure for which there is evidence of adverse health effects.
- Other guidelines set feasibility-based pollutant concentration limits that minimize major health risks and set achievable exposure limits.
- Health Canada’s guidelines, such as the 2021 guideline for carbon dioxide (CO2), identify a reference concentration below which serious health problems are unlikely to occur. A feasibility analysis is then conducted to ensure that the reference concentration can be achieved through controlling indoor pollutant sources and other mitigations. If pollutant levels cannot be lowered to the reference concentration value, the reference concentration may be set at a higher, more achievable value.
Report Methods
The report findings are primarily derived from a review of existing guidelines, studies, and interviews with US-based subject matter experts. The scope of this report is limited to indoor air pollutants commonly included in existing IAQ guidelines and does not include biological contaminants related to infectious disease transmission.
The cited literature is not exhaustive but synthesizes our current understanding of how IAQ guidelines are established and their potential to inform health considerations. Based on this understanding, recommendations focus on how policymakers can advance IAQ guidelines.
How IAQ Guidelines Are Developed
International
More than 50 organizations across at least 38 countries have established IAQ guidelines in occupational, commercial, or residential settings (see Exhibit 2). Guidelines cover pollutants and other risks such as mold, moisture, and temperature. Although general pollutant information and source control measures are important, guidelines that include health-based numerical pollutant exposure limits are the most informative for assessing IAQ.
World Health Organization
As the health agency of the United Nations, WHO influences health-protective policies globally. Current WHO publications of IAQ guidelines have varying levels of tailored assessment and relevance to the indoor environment. WHO guidelines are not legally binding. They are intended to inform health professionals, specialists, and policymakers and to provide a scientific basis for legally enforceable IAQ standards. Most recently in 2021, WHO published global air quality guidelines applicable indoors and outdoors. WHO commissioned six systematic literature reviews to determine the 2021 guidelines. Five reviews omitted studies that evaluated indoor-specific pollutant exposures exclusively, and the sixth review did not reference indoor air pollution
To ensure that future guidelines accurately apply indoors, additional review of indoor-specific studies is warranted. In 2010, WHO published IAQ guidelines for common indoor pollutants. While indoor guidelines for mold and dampness were published in 2009, the 2010 guidelines are the first WHO guidelines with a methodology specific to indoor air pollutants. Although no additional review of the literature was included, WHO also published guidelines for household fuel combustion in 2014, influenced by WHO guidelines from 2010 and 2006.
Health Canada
Health Canada, the health department of the Canadian government, first released residential IAQ guidelines for pollutants in 1987. Guidelines have been revised to reflect updated scientific understanding, most recently for xylenes and acrolein in 2021, and spanning as far back as formaldehyde in 2006. Guideline updates incorporate new scientific findings of health effects, sources, and exposure levels for each pollutant, including assessments conducted by external agencies such as WHO and EPA.
For fine particulate matter (PM2.5), Health Canada rescinded its initial guideline after determining that there is no apparent safe level of this pollutant indoors. Sources of PM2.5 are virtually impossible to eliminate because they are essential, for instance, for such everyday life activities as cooking and cleaning. Considering the inability to eliminate indoor PM2.5, Health Canada has provided action-based guidance to reduce concentrations, including eliminating smoking indoors and using a range hood when cooking.
United States
Federal
Although there are no comprehensive US IAQ guidelines, federal agencies are involved in IAQ-relevant initiatives, including the Federal Interagency Committee on Indoor Air Quality (CIAQ), the 1986 Superfund Amendments and Reauthorization Act (SARA), radon abatement, pollutant risk assessments, and occupational exposure limits.
Broadly, the EPA is responsible for IAQ issues at the federal level and leads the CIAQ, created in 1983 and tasked with coordinating and communicating federal IAQ research to the public. Other federal agencies involved in the CIAQ include the Consumer Product Safety Commission (CPSC), Department of Energy (DOE), National Institute for Occupational Safety and Health (NIOSH), Department of Health and Human Services (HHS), Occupational Safety and Health Administration (OSHA), and Department of Labor (DOL).
EPA Authority under SARA
Publishing voluntary IAQ guidelines is consistent with EPA’s authority under Title IV, Section 403 of SARA, which authorizes actions related to IAQ and air pollutants in the indoor environment.
Federal IAQ Actions Required Under the Superfund Amendments and Reauthorization Act
Title IV, Sec. 403 of SARA, Radon Gas and Indoor Air Quality Research Program, requires EPA to take actions to address IAQ, including to:
- Gather information on all aspects of IAQ to contribute to the understanding of health problems (42 USC 7403(a)(1))
- Coordinate federal, state, local, and private research relating to the improvement of IAQ (42 USC 7403(a)(2))
- Assess appropriate federal government actions to mitigate environmental and health risks (42 USC 7403(a)(3))
EPA is also required to establish a research program that must include:
- Research and development on the identification, characterization, and monitoring of sources and levels of indoor air pollution, including the measurement of pollutant concentrations (42 USC 7403(b)(1))
- Research relating to the effects of indoor air pollution and radon on human health (42 USC 7403(b)(2))
- Demonstration of methods for reducing or eliminating indoor air pollution and radon (42 USC 7403(b)(4))
- Dissemination of information to assure public availability of findings under the activity of this section (42 USC 7403(b)(6))
Per SARA requirements, EPA released a report to Congress on IAQ in 1989 summarizing the assessment and control of IAQ and IAQ-relevant federal authorities. Although SARA does not grant EPA authority to regulate indoor air pollutants, Title IV of SARA “provides EPA the authority to conduct research, coordinate activities in the public and private sectors, and disseminate information on indoor air,” according to the 1989 report.
Furthermore, the CIAQ website states that the committee supports EPA’s IAQ research program requirements under Title IV of SARA. Based on this authority and available supporting information from CIAQ, EPA could publish a report that reflects current scientific understanding of IAQ and health risks, including IAQ guidelines.
EPA’s Model for IAQ Guidance: Radon
The EPA has published indoor pollutant concentration limits before. The agency set an indoor exposure limit for radon, a radioactive and carcinogenic gas, at 4 picocuries per liter (pCi/L). The radon indoor exposure limit was created as a voluntary consensus standard through the Indoor Radon Abatement Act (1988). This act set a goal for indoor air to be as free of radon as outdoor air and authorized funding for EPA-developed construction standards and public guidance, state radon abatement programs, technical assistance to states, research on radon in schools, proficiency programs for radon testing firms, and regional radon training centers.
EPA’s indoor exposure limit for radon has informed radon testing protocols and standards to reduce risks to health and safety, such as Federal Housing Finance Agency abatement requirements in some multifamily properties. This radon limit can be used as a model for additional federal IAQ guidelines. Related authorizations and funding under the Indoor Radon Abatement Act may also influence similar IAQ-protective policy measures.
Pollutant Risk Assessment Methodology
EPA has conducted risk assessments on many air pollutants under other federal programs, including the 1976 Toxic Substances Control Act (TSCA) and Integrated Risk Information System (IRIS) program. These are relevant to IAQ guidelines because they are examples of ways the federal government already has assessed health risks of indoor air pollutants.
The TSCA provides EPA with authority to require reporting, testing, and restrictions on toxic chemicals. EPA’s 1989 Report to Congress on IAQ clarified that the TSCA gives EPA the ability to restrict manufacturing, distribution, and use of toxic chemicals, “including any that may be significant indoor pollutants.” This act has influenced EPA’s approach to its risk assessments for ambient air pollutants and could inform a similar approach to assessing indoor air pollutants.
EPA has published health-based lifetime and daily chemical exposure limits through IRIS; however, these assessments are missing for some key pollutants and are slow to publish. IRIS assessments inform federal and state risk assessments to address public health hazards such as PFAS chemicals, lead, and mercury. Experts have criticized IRIS methods for the lack of assessments for key health-harming indoor pollutants, like CO2 and NO2, lack of transparency in scientific methods, and the lengthy publication process. Some scientific experts are concerned that a lack of IRIS assessments for some pollutants will be misinterpreted as a lack of risk.
State and Local
Although federal support of IAQ guideline development is important, it is not a prerequisite for states to set their own guidelines. Whereas some states operate a central air quality program, others may house state initiatives to protect IAQ in other programs related to air and health. Referencing existing guidelines can support IAQ guideline development by state agencies. Examples of state IAQ guidelines are outlined below:
- In California, the state Air Resources Board (CARB) published recommended pollutant exposure limits in its 2005 Indoor Air Quality Report. Many of these guidelines have not been updated and are based on California’s ambient air quality standards. As of 2021, CARB is actively developing updated IAQ guidelines for NO2 to reflect scientific advances and hosted the first public workshop for this update in May 2023.
- In Illinois, the state Department of Public Health (IDPH) created voluntary guidelines for acceptable IAQ under Illinois’ Indoor Air Quality Act of 1994 for homes and workplaces, although they are not protective of sensitive groups and are outdated. IDPH has indicated it is in the process of reviewing and updating its guidelines.
Certain states have established IAQ guidelines for specific building types — schools and state agency buildings are common examples.
- In Texas, the state Department of Health, under the state Health and Safety Code, established voluntary guidelines for IAQ in government buildings and public schools in 2002. These guidelines outline “minimum risk levels” for common indoor air pollutants.
- In Pennsylvania, the state Department of Health’s Indoor Air Quality Guidelines for Pennsylvania Schools refers to EPA, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), and NIOSH thresholds for indoor pollutants. Pennsylvania’s IAQ guidelines for schools have not been updated; however, a copy from 2011 is labeled “under review.”
- In Indiana and Ohio, as well as other states, health departments have established a maximum exposure limit only for CO2 in schools and state agencies.
Some states and local jurisdictions have established IAQ protections that do not specify health-based thresholds for indoor pollutant concentrations.
- In Delaware, the Division of Public Health requires IAQ monitoring in schools related to temperature and humidity.
- In New York, the state Clean Indoor Air Act has reduced smoking and vaping activity, and New York City’s Indoor Allergen Hazards law requires building owners to mitigate mold and pests.
- In Washington, D.C., the Healthy Public Buildings Assessment Act requires indoor environmental quality assessments at federal properties and public guidance for maintaining acceptable IAQ, without defining threshold levels for indoor pollutant concentrations.
Exhibit 2: Existing IAQ Guidelines
Although not exhaustive, Exhibit 2 represents a first-of-its-kind consolidation of key guidelines across the United States in one table. Pollutants were selected based on their inclusion in published guidelines, established scientific evidence of human health effects from exposure, and their known presence in indoor environments.
Note: Some pollutant exposure limit units were converted for consistency across guidelines; original unit values are available in the endnote sources or upon request.
How IAQ Guidelines Can Be Applied
While IAQ guidelines are often voluntary, they have several important uses. Application of IAQ guidelines will require action from policymakers, public health professionals, building industry members, researchers, and the public.
Product Safety
Controlling pollutant sources indoors can reduce exposure to multiple pollutants at once. IAQ guidelines may help inform safe benchmarks for emissions from products, appliances, and building materials. For example, CARB set ozone emissions limits for air cleaners (often called air purifiers). Canada’s IAQ guidelines informed standards for air cleaners, carbon monoxide alarms, and composite wood products.
Product safety agencies like the CPSC can use IAQ guidelines in creating product assessments, standards, and related efforts, including stakeholder group meetings and safety guides to address IAQ concerns. Additionally, the CPSC can set federal voluntary or mandatory product performance standards to limit pollution indoors and are not required to rely on voluntary processes if they would unreasonably delay the development of standards that align with existing IAQ guidelines.
Building Upgrades
Building owners, operators, and design and construction teams can perform building upgrades to comply with IAQ guidelines. Upgrades to improve IAQ may be desirable for residential buildings, commercial office space, academic or medical campuses, military housing, or other building types because of evidence-based benefits to indoor air, occupant well-being and productivity, and energy savings potential, among other outcomes.
For instance, Health Canada has provided guidance for office buildings to improve IAQ that suggests reducing or eliminating indoor contaminants, with direct reference to Canada’s IAQ guidelines. Existing federal programs to promote IAQ-related building upgrades, such as the US Clean Air in Buildings Challenge, can set requirements for program participants to comply with IAQ guidelines.
Building Codes, Voluntary Standards, and Certifications
Codes
Agencies responsible for building codes, such as state energy offices, can use IAQ guidelines in assessment protocols for modeling new building standards, energy codes, and requirements for efficiency, performance, and ventilation. For instance, the California Energy Commission requires that new building efficiency standard assessments include “the impact that those standards would have on indoor air pollution problems.” Additionally, California requires IAQ improvement considerations in the state Energy Code and IAQ-related operation measures such as mechanical ventilation and kitchen exhaust requirements that take into account kitchen range fuel type.
Voluntary Standards
Voluntary standard organizations, including the American National Standards Institute, American Society for Testing and Materials (ASTM), ASHRAE, and others, can incorporate IAQ guidelines into the review process for new and existing standards. Standards in adherence with IAQ guidelines should ensure that consumer products, building operations, and other materials will not contribute to harmful levels of pollutant concentrations indoors.
Building Certification Programs
Voluntary labeling and certificate programs such as WELL, LEED, and Enterprise Green Communities have accreditations for IAQ and health, but many pollutant exposure limits currently refer to ambient air quality standards from WHO or EPA. Indoor airPLUS, EPA’s voluntary partnership program to protect IAQ in homes, does not require adherence with IAQ guidelines and does not provide suggested limits on indoor air pollutants aside from radon. Such programs could refer to existing health-based, indoor-specific guidelines as the basis of accreditations relevant to indoor air, appliance and fuel use, and healthy indoor spaces.
Building Inspections
Traditionally, code enforcement programs or inspections have been driven by complaints. However, proactive home inspections are becoming more common. Benchmarking against IAQ guidelines can better inform building inspections and pollutant abatement actions. For example, radon inspections are typically conducted before the sale or rental of a property.
Exact protocols vary by state (e.g., Florida requires adherence to existing EPA guidelines for radon, whereas Illinois requires that sellers inform buyers of radon risk with educational material on radon testing guidelines). There are several other examples of inspection programs that can improve health outcomes, including lead poisoning inspection requirements in Massachusetts, the US Department of Housing and Urban Development’s (HUD) smoke-free housing lease policy, and state policies allowing health professionals to refer asthma patients for in-home inspections.
Following inspection, further abatement actions can be taken to address health risks. Such actions can reduce costs for individuals and the government by avoiding hospitalizations and other health costs.
Informational Resource
Established IAQ guidelines can serve as an informational resource to improve health considerations for states seeking to set IAQ guidelines, researchers or officials prioritizing health risks for vulnerable populations, or members of the public wanting to improve IAQ in their home or community.
Policymakers
States seeking to develop IAQ guidelines and related policy measures, such as standards, may adopt or reference existing guidelines from other agencies. For example, Health Canada’s residential IAQ guidelines referenced WHO IAQ guidelines, and CARB has referenced Health Canada’s IAQ guidelines.
Risk Management
Guidelines can influence pollutant risk management strategies and identify areas or communities experiencing high IAQ risks. For healthcare professionals, IAQ guidelines can inform patient evaluation questions related to indoor pollutant sources, similar to secondhand smoke exposure evaluation resources for pediatric patients. Air monitors may be able to help determine pollutant levels, associated health risks, and diagnoses, similarly to how radon monitors have been recommended to test and identify major health risks.
Consumer Awareness
People living in the United States are concerned about IAQ. In fact, since the COVID-19 pandemic, over 53% of US consumers say that IAQ is a greater concern than it was pre-pandemic, and over 90% believe IAQ is important in preventing the spread of infectious disease. This awareness likely drives behavior and consumer choices.
One example is the increased sales of low-cost pollutant monitors. There are now more options than ever to test indoor air, but often consumers are left without clear guidance on how to interpret measurement levels.
To address concerns about reentering buildings post-pandemic, 76% of US consumers stated interest in a “rating system” for IAQ to better inform them about indoor air risks. Guidance on pollutant levels in public spaces could inform building operation system triggers, such as increasing ventilation. In fact, post-COVID-19, 77% of consumers say that seeing a hotel’s IAQ rating advertised would have an impact on their choice of where to stay.
Frequently Asked Questions
What about Occupational Pollutant Exposure Limits?
Federal agencies have set IAQ guidelines for occupational settings, but these guidelines only apply to work settings for adults during an 8- to 10-hour workday. Occupational pollutant exposure limits for toxic chemicals such as asbestos, lead, and carbon monoxide have been established by OSHA and NIOSH.
However, OSHA states that many of its enforceable pollutant exposure limits are outdated and do not adequately protect worker health. Because they are outdated, OSHA recommends the use of occupational exposure limits from California’s division of OSHA, NIOSH, and the American Conference of Governmental Industrial Hygienists (ACGIH). In 1994, OSHA proposed a rulemaking to adopt IAQ standards in indoor work environments, but it was withdrawn in 2001. Further protections for worker’s health indoors could be established through a similar proposed rulemaking and could be informed by IAQ guidelines.
What About ASHRAE Standards for Indoor Air Quality?
ASHRAE is a professional US organization that has developed standards for ventilation system design, maintenance, and operation to achieve acceptable IAQ and minimize adverse health effects, including ASHRAE Standards 62.1 and 62.2 for commercial and residential properties, respectively. In previous guidance for achieving better IAQ, ASHRAE has stated that it does not propose any contaminant concentration standard or guideline values, and instead uses values developed by leading authorities such as EPA and WHO.
For example, ASHRAE Standard 62.1 references EPA’s ambient air quality standards to determine if pollutant concentration limits (“design limits”) in the standard cause certain health effects. Similarly, ASHRAE could reference IAQ guidelines from leading authorities to help develop design limits in future indoor-relevant ASHRAE standard updates.
Recommendations
Improving IAQ will require collaborative action by federal and state policymakers.
Conclusion — Now Is the Time for IAQ Guidelines
We’ve witnessed the impact of poor indoor air quality on our lives, from the spread of infectious disease to building and vehicle greenhouse gas emissions to wildfire smoke. These risks will not disappear — asthma rates continue to rise in the United States, and climate change caused primarily by burning fossil fuels such as oil and gas continues to amplify ground-level ozone and other IAQ impacts.
While these risks will continue, our collective response can improve to ensure healthier buildings and neighborhoods. Americans deserve to be well-prepared and well-educated about the safety of indoor air. Federal agencies have created best practices to fight infectious disease, but by continuing to overlook indoor air pollutants in homes and buildings, the United States risks leaving a major health threat unaddressed.
Setting IAQ guidelines is a necessary tool to begin protecting indoor air and can inform subsequent protective policy measures. All avenues should be pursued to protect IAQ; in addition to IAQ guidelines, state and local jurisdictions should adopt the most health-protective policy measures under their authority, such as codes, standards, and regulations.
Mirroring the existing CAA, some scientific experts have called on policymakers to create an IAQ task force and enact an “Indoor Air Quality Act,” whereas others have published model IAQ legislation. IAQ guidelines also support existing US initiatives to limit disease transmission, improve building performance and electrification, and advance equity.
If US ambient air policy is any indication, protecting the air we breathe indoors has the potential to save lives and strengthen the economy.
Citations for Exhibit 1
- Hazard Summary: Acetaldehyde, EPA, 2000, https://www.epa.gov/sites/default/files/2016-09/documents/acetaldehyde.pdf; “Medical Management Guidelines for Acrolein,” US Agency for Toxic Substances and Disease Registry, accessed August 2023, https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=552&toxid=102#.
- “BTEX,” Science Direct, accessed August 2023, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/btex; “Carbon Dioxide in Your Home,” Health Canada, accessed August 2023, https://www.canada.ca/en/health-canada/services/publications/healthy-living/carbon-dioxide-home.html.
- Seals, Health Effects from Gas Stove Pollution, 2020; WHO Guidelines for Indoor Air Quality: Selected Pollutants, WHO, 2010, https://www.who.int/publications/i/item/9789289002134.
- “Nitrogen Dioxide,” American Lung Association, accessed August 2023, https://www.lung.org/clean-air/outdoors/what-makes-air-unhealthy/nitrogen-dioxide.
- “Ozone & Health,” State of California Air Resources Board, accessed August 2023, https://ww2.arb.ca.gov/resources/ozone-and-health; and “Radon,” EPA, accessed August 2023, https://www.epa.gov/radon.
Citations for Exhibit 2
- WHO Global Air Quality Guidelines: Particulate Matter, WHO, 2021; WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010.
- “Residential Indoor Air Quality Guideline: Acetaldehyde,” Health Canada, 2017, https://publications.gc.ca/site/eng/9.835076/publication.html.
- “Residential Indoor Air Quality Guideline: Acrolein,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-acrolein.html.
- “Guidance for Benzene in Residential Indoor Air,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidance-benzene-residential-indoor-air.html.
- “Residential Indoor Air Quality Guideline for Xylenes,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-xylenes.html.
- “Residential Indoor Air Quality Guideline: Carbon Monoxide,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-carbon-monoxide.html.
- “Residential Indoor Air Quality Guideline: Carbon Dioxide,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-carbon-dioxide.html.
- “Residential Indoor Air Quality Guideline: Formaldehyde,” Health Canada, 2006, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-formaldehyde.html.
- “Residential Indoor Air Quality Guideline: Naphthalene,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-naphthalene.html.
- “Residential Indoor Air Quality Guideline: Nitrogen Dioxide,” Health Canada, 2015, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-nitrogen-dioxide.html.
- “Residential Indoor Air Quality Guideline: Ozone,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-ozone.html.
- “Radon Guideline,” Health Canada, 2009, https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon/government-canada-radon-guideline.html.
- A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon, EPA, 2016, https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf.
- “IDPH Guidelines for Indoor Air Quality,” Illinois Department of Public Health, accessed August 2023, https://dph.illinois.gov/topics-services/environmental-health-protection/toxicology/indoor-air-quality-healthy-homes/idph-guidelines-indoor-air-quality.html,
- Comprehensive Indoor Air Quality Report, California Air Resources Board, 2005, https://ww2.arb.ca.gov/resources/documents/comprehensive-indoor-air-quality-report-2005.
- “Texas Voluntary Indoor Air Quality Guidelines for Government Buildings,” Texas Department of Health, 2002, https://gato-docs.its.txst.edu/jcr:afe38366-c8fe-4e39-8e6f-9eab96d729ba/Gov_Bld_Gd.pdf.
CONTACTS
Nina Prescott, nina.prescott@rmi.org
Mike Henchen, mhenchen@rmi.org
COPYRIGHTS AND CITATION
Nina Prescott, The Need for US Indoor Air Quality Guidelines: Advancing Policy for Healthy Buildings at the Federal and State Level, RMI, 2023.
RMI values collaboration and aims to accelerate the energy transition through sharing knowledge and insights. We therefore allow interested parties to reference, share, and cite our work through the Creative Commons CC BY-SA 4.0 license. https://creativecommons.org/licenses/by-sa/4.0/.
All images used are from iStock.com unless otherwise noted.
ACKNOWLEDGMENTS
Thank you to subject matter experts who offered their valuable comments and suggestions, which helped to inform this report, including:
Carbon-Free Buildings Program team, RMI
Noah Cordoba, Lawrence Garber, and Amy Rider, Building Decarbonization Coalition (BDC)
Iain Walker, Lawrence Berkeley National Lab
David Jacobs and Jonathan Wilson, National Center for Healthy Housing (NCHH)
Matt Casale (in his former capacity) and Abe Scarr, Public Interest Research Group (PIRG)
Annika Larson, environmental justice policy expert
Aaron Martin, Illinois Department of Public Health
Ruth Ann Norton, Green & Healthy Homes Initiative
The Clean Air Act (CAA), EPA’s ambient air regulation, has sometimes been used to assess IAQ. Ambient air is defined in the CAA as outdoor air: “air external to buildings.” Although ambient pollutants do travel indoors, the indoor environment is distinct, and it is therefore not precise to apply ambient air guidance.
Indoor air contains disparate and often higher concentrations of pollutants than ambient air. Some indoor air pollutant concentrations can also be greatly influenced by seasonal variability, and as previously noted, people spend most of their time indoors.
Because of these factors, indoor environments have the largest influence on personal pollutant exposure, and ambient measurements of pollutants may underestimate long-term health risks associated with exposure. Indoor-specific guidelines for key pollutants (see Exhibit 1) are necessary to accurately understand health risks.
Although not applicable indoors, the CAA’s regulatory framework shows the potential of US policy to protect air quality and human health. Under CAA enforcement, collective emissions of the six most common ambient air pollutants decreased 78% from 1970 to 2020. This drastic reduction drives lower mortality rates as well as fewer respiratory illness cases, emergency visits, and absences from school and work.
Benefits of CAA pollutant control are estimated to exceed costs by more than 30-to-1, resulting in over $2 trillion in estimated avoided health costs in 2020. Parallel protections for indoor air could result in additional reductions in illnesses, deaths, hospital admissions, and absences.
By setting IAQ guidelines, federal and state agencies can help reduce harmful pollutants indoors and associated health risks and costs.
What Are Indoor Air Quality Guidelines?
Generally, and as defined in this report, IAQ guidelines are science-based, voluntary limits on indoor air pollutant concentrations. As opposed to standards, guidelines are not mandatory or enforced. Rather, guidelines give health- or risk-based benchmarks on safe pollutant thresholds. Guidelines may be developed using various methods:
- Some guidelines set health-based pollutant concentration limits that eliminate all health risks or minimize risks as much as possible.
- WHO 2010 guidelines identify a pollutant exposure threshold (“reference concentration”) at which health risks are eliminated or minimized. WHO 2021 guidelines similarly identify the lowest level of exposure for which there is evidence of adverse health effects.
- Other guidelines set feasibility-based pollutant concentration limits that minimize major health risks and set achievable exposure limits.
- Health Canada’s guidelines, such as the 2021 guideline for carbon dioxide (CO2), identify a reference concentration below which serious health problems are unlikely to occur. A feasibility analysis is then conducted to ensure that the reference concentration can be achieved through controlling indoor pollutant sources and other mitigations. If pollutant levels cannot be lowered to the reference concentration value, the reference concentration may be set at a higher, more achievable value.
Report Methods
The report findings are primarily derived from a review of existing guidelines, studies, and interviews with US-based subject matter experts. The scope of this report is limited to indoor air pollutants commonly included in existing IAQ guidelines and does not include biological contaminants related to infectious disease transmission.
The cited literature is not exhaustive but synthesizes our current understanding of how IAQ guidelines are established and their potential to inform health considerations. Based on this understanding, recommendations focus on how policymakers can advance IAQ guidelines.
International
More than 50 organizations across at least 38 countries have established IAQ guidelines in occupational, commercial, or residential settings (see Exhibit 2). Guidelines cover pollutants and other risks such as mold, moisture, and temperature. Although general pollutant information and source control measures are important, guidelines that include health-based numerical pollutant exposure limits are the most informative for assessing IAQ.
World Health Organization
As the health agency of the United Nations, WHO influences health-protective policies globally. Current WHO publications of IAQ guidelines have varying levels of tailored assessment and relevance to the indoor environment. WHO guidelines are not legally binding. They are intended to inform health professionals, specialists, and policymakers and to provide a scientific basis for legally enforceable IAQ standards. Most recently in 2021, WHO published global air quality guidelines applicable indoors and outdoors. WHO commissioned six systematic literature reviews to determine the 2021 guidelines. Five reviews omitted studies that evaluated indoor-specific pollutant exposures exclusively, and the sixth review did not reference indoor air pollution
To ensure that future guidelines accurately apply indoors, additional review of indoor-specific studies is warranted. In 2010, WHO published IAQ guidelines for common indoor pollutants. While indoor guidelines for mold and dampness were published in 2009, the 2010 guidelines are the first WHO guidelines with a methodology specific to indoor air pollutants. Although no additional review of the literature was included, WHO also published guidelines for household fuel combustion in 2014, influenced by WHO guidelines from 2010 and 2006.
Health Canada
Health Canada, the health department of the Canadian government, first released residential IAQ guidelines for pollutants in 1987. Guidelines have been revised to reflect updated scientific understanding, most recently for xylenes and acrolein in 2021, and spanning as far back as formaldehyde in 2006. Guideline updates incorporate new scientific findings of health effects, sources, and exposure levels for each pollutant, including assessments conducted by external agencies such as WHO and EPA.
For fine particulate matter (PM2.5), Health Canada rescinded its initial guideline after determining that there is no apparent safe level of this pollutant indoors. Sources of PM2.5 are virtually impossible to eliminate because they are essential, for instance, for such everyday life activities as cooking and cleaning. Considering the inability to eliminate indoor PM2.5, Health Canada has provided action-based guidance to reduce concentrations, including eliminating smoking indoors and using a range hood when cooking.
United States
Federal
Although there are no comprehensive US IAQ guidelines, federal agencies are involved in IAQ-relevant initiatives, including the Federal Interagency Committee on Indoor Air Quality (CIAQ), the 1986 Superfund Amendments and Reauthorization Act (SARA), radon abatement, pollutant risk assessments, and occupational exposure limits.
Broadly, the EPA is responsible for IAQ issues at the federal level and leads the CIAQ, created in 1983 and tasked with coordinating and communicating federal IAQ research to the public. Other federal agencies involved in the CIAQ include the Consumer Product Safety Commission (CPSC), Department of Energy (DOE), National Institute for Occupational Safety and Health (NIOSH), Department of Health and Human Services (HHS), Occupational Safety and Health Administration (OSHA), and Department of Labor (DOL).
EPA Authority under SARA
Publishing voluntary IAQ guidelines is consistent with EPA’s authority under Title IV, Section 403 of SARA, which authorizes actions related to IAQ and air pollutants in the indoor environment.
Federal IAQ Actions Required Under the Superfund Amendments and Reauthorization Act
Title IV, Sec. 403 of SARA, Radon Gas and Indoor Air Quality Research Program, requires EPA to take actions to address IAQ, including to:
- Gather information on all aspects of IAQ to contribute to the understanding of health problems (42 USC 7403(a)(1))
- Coordinate federal, state, local, and private research relating to the improvement of IAQ (42 USC 7403(a)(2))
- Assess appropriate federal government actions to mitigate environmental and health risks (42 USC 7403(a)(3))
EPA is also required to establish a research program that must include:
- Research and development on the identification, characterization, and monitoring of sources and levels of indoor air pollution, including the measurement of pollutant concentrations (42 USC 7403(b)(1))
- Research relating to the effects of indoor air pollution and radon on human health (42 USC 7403(b)(2))
- Demonstration of methods for reducing or eliminating indoor air pollution and radon (42 USC 7403(b)(4))
- Dissemination of information to assure public availability of findings under the activity of this section (42 USC 7403(b)(6))
Per SARA requirements, EPA released a report to Congress on IAQ in 1989 summarizing the assessment and control of IAQ and IAQ-relevant federal authorities. Although SARA does not grant EPA authority to regulate indoor air pollutants, Title IV of SARA “provides EPA the authority to conduct research, coordinate activities in the public and private sectors, and disseminate information on indoor air,” according to the 1989 report.
Furthermore, the CIAQ website states that the committee supports EPA’s IAQ research program requirements under Title IV of SARA. Based on this authority and available supporting information from CIAQ, EPA could publish a report that reflects current scientific understanding of IAQ and health risks, including IAQ guidelines.
EPA’s Model for IAQ Guidance: Radon
The EPA has published indoor pollutant concentration limits before. The agency set an indoor exposure limit for radon, a radioactive and carcinogenic gas, at 4 picocuries per liter (pCi/L). The radon indoor exposure limit was created as a voluntary consensus standard through the Indoor Radon Abatement Act (1988). This act set a goal for indoor air to be as free of radon as outdoor air and authorized funding for EPA-developed construction standards and public guidance, state radon abatement programs, technical assistance to states, research on radon in schools, proficiency programs for radon testing firms, and regional radon training centers.
EPA’s indoor exposure limit for radon has informed radon testing protocols and standards to reduce risks to health and safety, such as Federal Housing Finance Agency abatement requirements in some multifamily properties. This radon limit can be used as a model for additional federal IAQ guidelines. Related authorizations and funding under the Indoor Radon Abatement Act may also influence similar IAQ-protective policy measures.
Pollutant Risk Assessment Methodology
EPA has conducted risk assessments on many air pollutants under other federal programs, including the 1976 Toxic Substances Control Act (TSCA) and Integrated Risk Information System (IRIS) program. These are relevant to IAQ guidelines because they are examples of ways the federal government already has assessed health risks of indoor air pollutants.
The TSCA provides EPA with authority to require reporting, testing, and restrictions on toxic chemicals. EPA’s 1989 Report to Congress on IAQ clarified that the TSCA gives EPA the ability to restrict manufacturing, distribution, and use of toxic chemicals, “including any that may be significant indoor pollutants.” This act has influenced EPA’s approach to its risk assessments for ambient air pollutants and could inform a similar approach to assessing indoor air pollutants.
EPA has published health-based lifetime and daily chemical exposure limits through IRIS; however, these assessments are missing for some key pollutants and are slow to publish. IRIS assessments inform federal and state risk assessments to address public health hazards such as PFAS chemicals, lead, and mercury. Experts have criticized IRIS methods for the lack of assessments for key health-harming indoor pollutants, like CO2 and NO2, lack of transparency in scientific methods, and the lengthy publication process. Some scientific experts are concerned that a lack of IRIS assessments for some pollutants will be misinterpreted as a lack of risk.
State and Local
Although federal support of IAQ guideline development is important, it is not a prerequisite for states to set their own guidelines. Whereas some states operate a central air quality program, others may house state initiatives to protect IAQ in other programs related to air and health. Referencing existing guidelines can support IAQ guideline development by state agencies. Examples of state IAQ guidelines are outlined below:
- In California, the state Air Resources Board (CARB) published recommended pollutant exposure limits in its 2005 Indoor Air Quality Report. Many of these guidelines have not been updated and are based on California’s ambient air quality standards. As of 2021, CARB is actively developing updated IAQ guidelines for NO2 to reflect scientific advances and hosted the first public workshop for this update in May 2023.
- In Illinois, the state Department of Public Health (IDPH) created voluntary guidelines for acceptable IAQ under Illinois’ Indoor Air Quality Act of 1994 for homes and workplaces, although they are not protective of sensitive groups and are outdated. IDPH has indicated it is in the process of reviewing and updating its guidelines.
Certain states have established IAQ guidelines for specific building types — schools and state agency buildings are common examples.
- In Texas, the state Department of Health, under the state Health and Safety Code, established voluntary guidelines for IAQ in government buildings and public schools in 2002. These guidelines outline “minimum risk levels” for common indoor air pollutants.
- In Pennsylvania, the state Department of Health’s Indoor Air Quality Guidelines for Pennsylvania Schools refers to EPA, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), and NIOSH thresholds for indoor pollutants. Pennsylvania’s IAQ guidelines for schools have not been updated; however, a copy from 2011 is labeled “under review.”
- In Indiana and Ohio, as well as other states, health departments have established a maximum exposure limit only for CO2 in schools and state agencies.
Some states and local jurisdictions have established IAQ protections that do not specify health-based thresholds for indoor pollutant concentrations.
- In Delaware, the Division of Public Health requires IAQ monitoring in schools related to temperature and humidity.
- In New York, the state Clean Indoor Air Act has reduced smoking and vaping activity, and New York City’s Indoor Allergen Hazards law requires building owners to mitigate mold and pests.
- In Washington, D.C., the Healthy Public Buildings Assessment Act requires indoor environmental quality assessments at federal properties and public guidance for maintaining acceptable IAQ, without defining threshold levels for indoor pollutant concentrations.
Exhibit 2: Existing IAQ Guidelines
Although not exhaustive, Exhibit 2 represents a first-of-its-kind consolidation of key guidelines across the United States in one table. Pollutants were selected based on their inclusion in published guidelines, established scientific evidence of human health effects from exposure, and their known presence in indoor environments.
Note: Some pollutant exposure limit units were converted for consistency across guidelines; original unit values are available in the endnote sources or upon request.
How IAQ Guidelines Can Be Applied
While IAQ guidelines are often voluntary, they have several important uses. Application of IAQ guidelines will require action from policymakers, public health professionals, building industry members, researchers, and the public.
Product Safety
Controlling pollutant sources indoors can reduce exposure to multiple pollutants at once. IAQ guidelines may help inform safe benchmarks for emissions from products, appliances, and building materials. For example, CARB set ozone emissions limits for air cleaners (often called air purifiers). Canada’s IAQ guidelines informed standards for air cleaners, carbon monoxide alarms, and composite wood products.
Product safety agencies like the CPSC can use IAQ guidelines in creating product assessments, standards, and related efforts, including stakeholder group meetings and safety guides to address IAQ concerns. Additionally, the CPSC can set federal voluntary or mandatory product performance standards to limit pollution indoors and are not required to rely on voluntary processes if they would unreasonably delay the development of standards that align with existing IAQ guidelines.
Building Upgrades
Building owners, operators, and design and construction teams can perform building upgrades to comply with IAQ guidelines. Upgrades to improve IAQ may be desirable for residential buildings, commercial office space, academic or medical campuses, military housing, or other building types because of evidence-based benefits to indoor air, occupant well-being and productivity, and energy savings potential, among other outcomes.
For instance, Health Canada has provided guidance for office buildings to improve IAQ that suggests reducing or eliminating indoor contaminants, with direct reference to Canada’s IAQ guidelines. Existing federal programs to promote IAQ-related building upgrades, such as the US Clean Air in Buildings Challenge, can set requirements for program participants to comply with IAQ guidelines.
Building Codes, Voluntary Standards, and Certifications
Codes
Agencies responsible for building codes, such as state energy offices, can use IAQ guidelines in assessment protocols for modeling new building standards, energy codes, and requirements for efficiency, performance, and ventilation. For instance, the California Energy Commission requires that new building efficiency standard assessments include “the impact that those standards would have on indoor air pollution problems.” Additionally, California requires IAQ improvement considerations in the state Energy Code and IAQ-related operation measures such as mechanical ventilation and kitchen exhaust requirements that take into account kitchen range fuel type.
Voluntary Standards
Voluntary standard organizations, including the American National Standards Institute, American Society for Testing and Materials (ASTM), ASHRAE, and others, can incorporate IAQ guidelines into the review process for new and existing standards. Standards in adherence with IAQ guidelines should ensure that consumer products, building operations, and other materials will not contribute to harmful levels of pollutant concentrations indoors.
Building Certification Programs
Voluntary labeling and certificate programs such as WELL, LEED, and Enterprise Green Communities have accreditations for IAQ and health, but many pollutant exposure limits currently refer to ambient air quality standards from WHO or EPA. Indoor airPLUS, EPA’s voluntary partnership program to protect IAQ in homes, does not require adherence with IAQ guidelines and does not provide suggested limits on indoor air pollutants aside from radon. Such programs could refer to existing health-based, indoor-specific guidelines as the basis of accreditations relevant to indoor air, appliance and fuel use, and healthy indoor spaces.
Building Inspections
Traditionally, code enforcement programs or inspections have been driven by complaints. However, proactive home inspections are becoming more common. Benchmarking against IAQ guidelines can better inform building inspections and pollutant abatement actions. For example, radon inspections are typically conducted before the sale or rental of a property.
Exact protocols vary by state (e.g., Florida requires adherence to existing EPA guidelines for radon, whereas Illinois requires that sellers inform buyers of radon risk with educational material on radon testing guidelines). There are several other examples of inspection programs that can improve health outcomes, including lead poisoning inspection requirements in Massachusetts, the US Department of Housing and Urban Development’s (HUD) smoke-free housing lease policy, and state policies allowing health professionals to refer asthma patients for in-home inspections.
Following inspection, further abatement actions can be taken to address health risks. Such actions can reduce costs for individuals and the government by avoiding hospitalizations and other health costs.
Informational Resource
Established IAQ guidelines can serve as an informational resource to improve health considerations for states seeking to set IAQ guidelines, researchers or officials prioritizing health risks for vulnerable populations, or members of the public wanting to improve IAQ in their home or community.
Policymakers
States seeking to develop IAQ guidelines and related policy measures, such as standards, may adopt or reference existing guidelines from other agencies. For example, Health Canada’s residential IAQ guidelines referenced WHO IAQ guidelines, and CARB has referenced Health Canada’s IAQ guidelines.
Risk Management
Guidelines can influence pollutant risk management strategies and identify areas or communities experiencing high IAQ risks. For healthcare professionals, IAQ guidelines can inform patient evaluation questions related to indoor pollutant sources, similar to secondhand smoke exposure evaluation resources for pediatric patients. Air monitors may be able to help determine pollutant levels, associated health risks, and diagnoses, similarly to how radon monitors have been recommended to test and identify major health risks.
Consumer Awareness
People living in the United States are concerned about IAQ. In fact, since the COVID-19 pandemic, over 53% of US consumers say that IAQ is a greater concern than it was pre-pandemic, and over 90% believe IAQ is important in preventing the spread of infectious disease. This awareness likely drives behavior and consumer choices.
One example is the increased sales of low-cost pollutant monitors. There are now more options than ever to test indoor air, but often consumers are left without clear guidance on how to interpret measurement levels.
To address concerns about reentering buildings post-pandemic, 76% of US consumers stated interest in a “rating system” for IAQ to better inform them about indoor air risks. Guidance on pollutant levels in public spaces could inform building operation system triggers, such as increasing ventilation. In fact, post-COVID-19, 77% of consumers say that seeing a hotel’s IAQ rating advertised would have an impact on their choice of where to stay.
Frequently Asked Questions
What about Occupational Pollutant Exposure Limits?
Federal agencies have set IAQ guidelines for occupational settings, but these guidelines only apply to work settings for adults during an 8- to 10-hour workday. Occupational pollutant exposure limits for toxic chemicals such as asbestos, lead, and carbon monoxide have been established by OSHA and NIOSH.
However, OSHA states that many of its enforceable pollutant exposure limits are outdated and do not adequately protect worker health. Because they are outdated, OSHA recommends the use of occupational exposure limits from California’s division of OSHA, NIOSH, and the American Conference of Governmental Industrial Hygienists (ACGIH). In 1994, OSHA proposed a rulemaking to adopt IAQ standards in indoor work environments, but it was withdrawn in 2001. Further protections for worker’s health indoors could be established through a similar proposed rulemaking and could be informed by IAQ guidelines.
What About ASHRAE Standards for Indoor Air Quality?
ASHRAE is a professional US organization that has developed standards for ventilation system design, maintenance, and operation to achieve acceptable IAQ and minimize adverse health effects, including ASHRAE Standards 62.1 and 62.2 for commercial and residential properties, respectively. In previous guidance for achieving better IAQ, ASHRAE has stated that it does not propose any contaminant concentration standard or guideline values, and instead uses values developed by leading authorities such as EPA and WHO.
For example, ASHRAE Standard 62.1 references EPA’s ambient air quality standards to determine if pollutant concentration limits (“design limits”) in the standard cause certain health effects. Similarly, ASHRAE could reference IAQ guidelines from leading authorities to help develop design limits in future indoor-relevant ASHRAE standard updates.
Recommendations
Improving IAQ will require collaborative action by federal and state policymakers.
Conclusion — Now Is the Time for IAQ Guidelines
We’ve witnessed the impact of poor indoor air quality on our lives, from the spread of infectious disease to building and vehicle greenhouse gas emissions to wildfire smoke. These risks will not disappear — asthma rates continue to rise in the United States, and climate change caused primarily by burning fossil fuels such as oil and gas continues to amplify ground-level ozone and other IAQ impacts.
While these risks will continue, our collective response can improve to ensure healthier buildings and neighborhoods. Americans deserve to be well-prepared and well-educated about the safety of indoor air. Federal agencies have created best practices to fight infectious disease, but by continuing to overlook indoor air pollutants in homes and buildings, the United States risks leaving a major health threat unaddressed.
Setting IAQ guidelines is a necessary tool to begin protecting indoor air and can inform subsequent protective policy measures. All avenues should be pursued to protect IAQ; in addition to IAQ guidelines, state and local jurisdictions should adopt the most health-protective policy measures under their authority, such as codes, standards, and regulations.
Mirroring the existing CAA, some scientific experts have called on policymakers to create an IAQ task force and enact an “Indoor Air Quality Act,” whereas others have published model IAQ legislation. IAQ guidelines also support existing US initiatives to limit disease transmission, improve building performance and electrification, and advance equity.
If US ambient air policy is any indication, protecting the air we breathe indoors has the potential to save lives and strengthen the economy.
Citations for Exhibit 1
- Hazard Summary: Acetaldehyde, EPA, 2000, https://www.epa.gov/sites/default/files/2016-09/documents/acetaldehyde.pdf; “Medical Management Guidelines for Acrolein,” US Agency for Toxic Substances and Disease Registry, accessed August 2023, https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=552&toxid=102#.
- “BTEX,” Science Direct, accessed August 2023, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/btex; “Carbon Dioxide in Your Home,” Health Canada, accessed August 2023, https://www.canada.ca/en/health-canada/services/publications/healthy-living/carbon-dioxide-home.html.
- Seals, Health Effects from Gas Stove Pollution, 2020; WHO Guidelines for Indoor Air Quality: Selected Pollutants, WHO, 2010, https://www.who.int/publications/i/item/9789289002134.
- “Nitrogen Dioxide,” American Lung Association, accessed August 2023, https://www.lung.org/clean-air/outdoors/what-makes-air-unhealthy/nitrogen-dioxide.
- “Ozone & Health,” State of California Air Resources Board, accessed August 2023, https://ww2.arb.ca.gov/resources/ozone-and-health; and “Radon,” EPA, accessed August 2023, https://www.epa.gov/radon.
Citations for Exhibit 2
- WHO Global Air Quality Guidelines: Particulate Matter, WHO, 2021; WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010.
- “Residential Indoor Air Quality Guideline: Acetaldehyde,” Health Canada, 2017, https://publications.gc.ca/site/eng/9.835076/publication.html.
- “Residential Indoor Air Quality Guideline: Acrolein,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-acrolein.html.
- “Guidance for Benzene in Residential Indoor Air,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidance-benzene-residential-indoor-air.html.
- “Residential Indoor Air Quality Guideline for Xylenes,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-xylenes.html.
- “Residential Indoor Air Quality Guideline: Carbon Monoxide,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-carbon-monoxide.html.
- “Residential Indoor Air Quality Guideline: Carbon Dioxide,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-carbon-dioxide.html.
- “Residential Indoor Air Quality Guideline: Formaldehyde,” Health Canada, 2006, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-formaldehyde.html.
- “Residential Indoor Air Quality Guideline: Naphthalene,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-naphthalene.html.
- “Residential Indoor Air Quality Guideline: Nitrogen Dioxide,” Health Canada, 2015, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-nitrogen-dioxide.html.
- “Residential Indoor Air Quality Guideline: Ozone,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-ozone.html.
- “Radon Guideline,” Health Canada, 2009, https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon/government-canada-radon-guideline.html.
- A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon, EPA, 2016, https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf.
- “IDPH Guidelines for Indoor Air Quality,” Illinois Department of Public Health, accessed August 2023, https://dph.illinois.gov/topics-services/environmental-health-protection/toxicology/indoor-air-quality-healthy-homes/idph-guidelines-indoor-air-quality.html,
- Comprehensive Indoor Air Quality Report, California Air Resources Board, 2005, https://ww2.arb.ca.gov/resources/documents/comprehensive-indoor-air-quality-report-2005.
- “Texas Voluntary Indoor Air Quality Guidelines for Government Buildings,” Texas Department of Health, 2002, https://gato-docs.its.txst.edu/jcr:afe38366-c8fe-4e39-8e6f-9eab96d729ba/Gov_Bld_Gd.pdf.
CONTACTS
Nina Prescott, nina.prescott@rmi.org
Mike Henchen, mhenchen@rmi.org
COPYRIGHTS AND CITATION
Nina Prescott, The Need for US Indoor Air Quality Guidelines: Advancing Policy for Healthy Buildings at the Federal and State Level, RMI, 2023.
RMI values collaboration and aims to accelerate the energy transition through sharing knowledge and insights. We therefore allow interested parties to reference, share, and cite our work through the Creative Commons CC BY-SA 4.0 license. https://creativecommons.org/licenses/by-sa/4.0/.
All images used are from iStock.com unless otherwise noted.
ACKNOWLEDGMENTS
Thank you to subject matter experts who offered their valuable comments and suggestions, which helped to inform this report, including:
Carbon-Free Buildings Program team, RMI
Noah Cordoba, Lawrence Garber, and Amy Rider, Building Decarbonization Coalition (BDC)
Iain Walker, Lawrence Berkeley National Lab
David Jacobs and Jonathan Wilson, National Center for Healthy Housing (NCHH)
Matt Casale (in his former capacity) and Abe Scarr, Public Interest Research Group (PIRG)
Annika Larson, environmental justice policy expert
Aaron Martin, Illinois Department of Public Health
Ruth Ann Norton, Green & Healthy Homes Initiative
While IAQ guidelines are often voluntary, they have several important uses. Application of IAQ guidelines will require action from policymakers, public health professionals, building industry members, researchers, and the public.
Product Safety
Controlling pollutant sources indoors can reduce exposure to multiple pollutants at once. IAQ guidelines may help inform safe benchmarks for emissions from products, appliances, and building materials. For example, CARB set ozone emissions limits for air cleaners (often called air purifiers). Canada’s IAQ guidelines informed standards for air cleaners, carbon monoxide alarms, and composite wood products.
Product safety agencies like the CPSC can use IAQ guidelines in creating product assessments, standards, and related efforts, including stakeholder group meetings and safety guides to address IAQ concerns. Additionally, the CPSC can set federal voluntary or mandatory product performance standards to limit pollution indoors and are not required to rely on voluntary processes if they would unreasonably delay the development of standards that align with existing IAQ guidelines.
Building Upgrades
Building owners, operators, and design and construction teams can perform building upgrades to comply with IAQ guidelines. Upgrades to improve IAQ may be desirable for residential buildings, commercial office space, academic or medical campuses, military housing, or other building types because of evidence-based benefits to indoor air, occupant well-being and productivity, and energy savings potential, among other outcomes.
For instance, Health Canada has provided guidance for office buildings to improve IAQ that suggests reducing or eliminating indoor contaminants, with direct reference to Canada’s IAQ guidelines. Existing federal programs to promote IAQ-related building upgrades, such as the US Clean Air in Buildings Challenge, can set requirements for program participants to comply with IAQ guidelines.
Building Codes, Voluntary Standards, and Certifications
Codes
Agencies responsible for building codes, such as state energy offices, can use IAQ guidelines in assessment protocols for modeling new building standards, energy codes, and requirements for efficiency, performance, and ventilation. For instance, the California Energy Commission requires that new building efficiency standard assessments include “the impact that those standards would have on indoor air pollution problems.” Additionally, California requires IAQ improvement considerations in the state Energy Code and IAQ-related operation measures such as mechanical ventilation and kitchen exhaust requirements that take into account kitchen range fuel type.
Voluntary Standards
Voluntary standard organizations, including the American National Standards Institute, American Society for Testing and Materials (ASTM), ASHRAE, and others, can incorporate IAQ guidelines into the review process for new and existing standards. Standards in adherence with IAQ guidelines should ensure that consumer products, building operations, and other materials will not contribute to harmful levels of pollutant concentrations indoors.
Building Certification Programs
Voluntary labeling and certificate programs such as WELL, LEED, and Enterprise Green Communities have accreditations for IAQ and health, but many pollutant exposure limits currently refer to ambient air quality standards from WHO or EPA. Indoor airPLUS, EPA’s voluntary partnership program to protect IAQ in homes, does not require adherence with IAQ guidelines and does not provide suggested limits on indoor air pollutants aside from radon. Such programs could refer to existing health-based, indoor-specific guidelines as the basis of accreditations relevant to indoor air, appliance and fuel use, and healthy indoor spaces.
Building Inspections
Traditionally, code enforcement programs or inspections have been driven by complaints. However, proactive home inspections are becoming more common. Benchmarking against IAQ guidelines can better inform building inspections and pollutant abatement actions. For example, radon inspections are typically conducted before the sale or rental of a property.
Exact protocols vary by state (e.g., Florida requires adherence to existing EPA guidelines for radon, whereas Illinois requires that sellers inform buyers of radon risk with educational material on radon testing guidelines). There are several other examples of inspection programs that can improve health outcomes, including lead poisoning inspection requirements in Massachusetts, the US Department of Housing and Urban Development’s (HUD) smoke-free housing lease policy, and state policies allowing health professionals to refer asthma patients for in-home inspections.
Following inspection, further abatement actions can be taken to address health risks. Such actions can reduce costs for individuals and the government by avoiding hospitalizations and other health costs.
Informational Resource
Established IAQ guidelines can serve as an informational resource to improve health considerations for states seeking to set IAQ guidelines, researchers or officials prioritizing health risks for vulnerable populations, or members of the public wanting to improve IAQ in their home or community.
Policymakers
States seeking to develop IAQ guidelines and related policy measures, such as standards, may adopt or reference existing guidelines from other agencies. For example, Health Canada’s residential IAQ guidelines referenced WHO IAQ guidelines, and CARB has referenced Health Canada’s IAQ guidelines.
Risk Management
Guidelines can influence pollutant risk management strategies and identify areas or communities experiencing high IAQ risks. For healthcare professionals, IAQ guidelines can inform patient evaluation questions related to indoor pollutant sources, similar to secondhand smoke exposure evaluation resources for pediatric patients. Air monitors may be able to help determine pollutant levels, associated health risks, and diagnoses, similarly to how radon monitors have been recommended to test and identify major health risks.
Consumer Awareness
People living in the United States are concerned about IAQ. In fact, since the COVID-19 pandemic, over 53% of US consumers say that IAQ is a greater concern than it was pre-pandemic, and over 90% believe IAQ is important in preventing the spread of infectious disease. This awareness likely drives behavior and consumer choices.
One example is the increased sales of low-cost pollutant monitors. There are now more options than ever to test indoor air, but often consumers are left without clear guidance on how to interpret measurement levels.
To address concerns about reentering buildings post-pandemic, 76% of US consumers stated interest in a “rating system” for IAQ to better inform them about indoor air risks. Guidance on pollutant levels in public spaces could inform building operation system triggers, such as increasing ventilation. In fact, post-COVID-19, 77% of consumers say that seeing a hotel’s IAQ rating advertised would have an impact on their choice of where to stay.
What about Occupational Pollutant Exposure Limits?
Federal agencies have set IAQ guidelines for occupational settings, but these guidelines only apply to work settings for adults during an 8- to 10-hour workday. Occupational pollutant exposure limits for toxic chemicals such as asbestos, lead, and carbon monoxide have been established by OSHA and NIOSH.
However, OSHA states that many of its enforceable pollutant exposure limits are outdated and do not adequately protect worker health. Because they are outdated, OSHA recommends the use of occupational exposure limits from California’s division of OSHA, NIOSH, and the American Conference of Governmental Industrial Hygienists (ACGIH). In 1994, OSHA proposed a rulemaking to adopt IAQ standards in indoor work environments, but it was withdrawn in 2001. Further protections for worker’s health indoors could be established through a similar proposed rulemaking and could be informed by IAQ guidelines.
What About ASHRAE Standards for Indoor Air Quality?
ASHRAE is a professional US organization that has developed standards for ventilation system design, maintenance, and operation to achieve acceptable IAQ and minimize adverse health effects, including ASHRAE Standards 62.1 and 62.2 for commercial and residential properties, respectively. In previous guidance for achieving better IAQ, ASHRAE has stated that it does not propose any contaminant concentration standard or guideline values, and instead uses values developed by leading authorities such as EPA and WHO.
For example, ASHRAE Standard 62.1 references EPA’s ambient air quality standards to determine if pollutant concentration limits (“design limits”) in the standard cause certain health effects. Similarly, ASHRAE could reference IAQ guidelines from leading authorities to help develop design limits in future indoor-relevant ASHRAE standard updates.
Recommendations
Improving IAQ will require collaborative action by federal and state policymakers.
Conclusion — Now Is the Time for IAQ Guidelines
We’ve witnessed the impact of poor indoor air quality on our lives, from the spread of infectious disease to building and vehicle greenhouse gas emissions to wildfire smoke. These risks will not disappear — asthma rates continue to rise in the United States, and climate change caused primarily by burning fossil fuels such as oil and gas continues to amplify ground-level ozone and other IAQ impacts.
While these risks will continue, our collective response can improve to ensure healthier buildings and neighborhoods. Americans deserve to be well-prepared and well-educated about the safety of indoor air. Federal agencies have created best practices to fight infectious disease, but by continuing to overlook indoor air pollutants in homes and buildings, the United States risks leaving a major health threat unaddressed.
Setting IAQ guidelines is a necessary tool to begin protecting indoor air and can inform subsequent protective policy measures. All avenues should be pursued to protect IAQ; in addition to IAQ guidelines, state and local jurisdictions should adopt the most health-protective policy measures under their authority, such as codes, standards, and regulations.
Mirroring the existing CAA, some scientific experts have called on policymakers to create an IAQ task force and enact an “Indoor Air Quality Act,” whereas others have published model IAQ legislation. IAQ guidelines also support existing US initiatives to limit disease transmission, improve building performance and electrification, and advance equity.
If US ambient air policy is any indication, protecting the air we breathe indoors has the potential to save lives and strengthen the economy.
Citations for Exhibit 1
- Hazard Summary: Acetaldehyde, EPA, 2000, https://www.epa.gov/sites/default/files/2016-09/documents/acetaldehyde.pdf; “Medical Management Guidelines for Acrolein,” US Agency for Toxic Substances and Disease Registry, accessed August 2023, https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=552&toxid=102#.
- “BTEX,” Science Direct, accessed August 2023, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/btex; “Carbon Dioxide in Your Home,” Health Canada, accessed August 2023, https://www.canada.ca/en/health-canada/services/publications/healthy-living/carbon-dioxide-home.html.
- Seals, Health Effects from Gas Stove Pollution, 2020; WHO Guidelines for Indoor Air Quality: Selected Pollutants, WHO, 2010, https://www.who.int/publications/i/item/9789289002134.
- “Nitrogen Dioxide,” American Lung Association, accessed August 2023, https://www.lung.org/clean-air/outdoors/what-makes-air-unhealthy/nitrogen-dioxide.
- “Ozone & Health,” State of California Air Resources Board, accessed August 2023, https://ww2.arb.ca.gov/resources/ozone-and-health; and “Radon,” EPA, accessed August 2023, https://www.epa.gov/radon.
Citations for Exhibit 2
- WHO Global Air Quality Guidelines: Particulate Matter, WHO, 2021; WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010.
- “Residential Indoor Air Quality Guideline: Acetaldehyde,” Health Canada, 2017, https://publications.gc.ca/site/eng/9.835076/publication.html.
- “Residential Indoor Air Quality Guideline: Acrolein,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-acrolein.html.
- “Guidance for Benzene in Residential Indoor Air,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidance-benzene-residential-indoor-air.html.
- “Residential Indoor Air Quality Guideline for Xylenes,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-xylenes.html.
- “Residential Indoor Air Quality Guideline: Carbon Monoxide,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-carbon-monoxide.html.
- “Residential Indoor Air Quality Guideline: Carbon Dioxide,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-carbon-dioxide.html.
- “Residential Indoor Air Quality Guideline: Formaldehyde,” Health Canada, 2006, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-formaldehyde.html.
- “Residential Indoor Air Quality Guideline: Naphthalene,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-naphthalene.html.
- “Residential Indoor Air Quality Guideline: Nitrogen Dioxide,” Health Canada, 2015, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-nitrogen-dioxide.html.
- “Residential Indoor Air Quality Guideline: Ozone,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-ozone.html.
- “Radon Guideline,” Health Canada, 2009, https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon/government-canada-radon-guideline.html.
- A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon, EPA, 2016, https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf.
- “IDPH Guidelines for Indoor Air Quality,” Illinois Department of Public Health, accessed August 2023, https://dph.illinois.gov/topics-services/environmental-health-protection/toxicology/indoor-air-quality-healthy-homes/idph-guidelines-indoor-air-quality.html,
- Comprehensive Indoor Air Quality Report, California Air Resources Board, 2005, https://ww2.arb.ca.gov/resources/documents/comprehensive-indoor-air-quality-report-2005.
- “Texas Voluntary Indoor Air Quality Guidelines for Government Buildings,” Texas Department of Health, 2002, https://gato-docs.its.txst.edu/jcr:afe38366-c8fe-4e39-8e6f-9eab96d729ba/Gov_Bld_Gd.pdf.
CONTACTS
Nina Prescott, nina.prescott@rmi.org
Mike Henchen, mhenchen@rmi.org
COPYRIGHTS AND CITATION
Nina Prescott, The Need for US Indoor Air Quality Guidelines: Advancing Policy for Healthy Buildings at the Federal and State Level, RMI, 2023.
RMI values collaboration and aims to accelerate the energy transition through sharing knowledge and insights. We therefore allow interested parties to reference, share, and cite our work through the Creative Commons CC BY-SA 4.0 license. https://creativecommons.org/licenses/by-sa/4.0/.
All images used are from iStock.com unless otherwise noted.
ACKNOWLEDGMENTS
Thank you to subject matter experts who offered their valuable comments and suggestions, which helped to inform this report, including:
Carbon-Free Buildings Program team, RMI
Noah Cordoba, Lawrence Garber, and Amy Rider, Building Decarbonization Coalition (BDC)
Iain Walker, Lawrence Berkeley National Lab
David Jacobs and Jonathan Wilson, National Center for Healthy Housing (NCHH)
Matt Casale (in his former capacity) and Abe Scarr, Public Interest Research Group (PIRG)
Annika Larson, environmental justice policy expert
Aaron Martin, Illinois Department of Public Health
Ruth Ann Norton, Green & Healthy Homes Initiative
Improving IAQ will require collaborative action by federal and state policymakers.
We’ve witnessed the impact of poor indoor air quality on our lives, from the spread of infectious disease to building and vehicle greenhouse gas emissions to wildfire smoke. These risks will not disappear — asthma rates continue to rise in the United States, and climate change caused primarily by burning fossil fuels such as oil and gas continues to amplify ground-level ozone and other IAQ impacts.
While these risks will continue, our collective response can improve to ensure healthier buildings and neighborhoods. Americans deserve to be well-prepared and well-educated about the safety of indoor air. Federal agencies have created best practices to fight infectious disease, but by continuing to overlook indoor air pollutants in homes and buildings, the United States risks leaving a major health threat unaddressed.
Setting IAQ guidelines is a necessary tool to begin protecting indoor air and can inform subsequent protective policy measures. All avenues should be pursued to protect IAQ; in addition to IAQ guidelines, state and local jurisdictions should adopt the most health-protective policy measures under their authority, such as codes, standards, and regulations.
Mirroring the existing CAA, some scientific experts have called on policymakers to create an IAQ task force and enact an “Indoor Air Quality Act,” whereas others have published model IAQ legislation. IAQ guidelines also support existing US initiatives to limit disease transmission, improve building performance and electrification, and advance equity.
If US ambient air policy is any indication, protecting the air we breathe indoors has the potential to save lives and strengthen the economy.
Citations for Exhibit 1
- Hazard Summary: Acetaldehyde, EPA, 2000, https://www.epa.gov/sites/default/files/2016-09/documents/acetaldehyde.pdf; “Medical Management Guidelines for Acrolein,” US Agency for Toxic Substances and Disease Registry, accessed August 2023, https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=552&toxid=102#.
- “BTEX,” Science Direct, accessed August 2023, https://www.sciencedirect.com/topics/earth-and-planetary-sciences/btex; “Carbon Dioxide in Your Home,” Health Canada, accessed August 2023, https://www.canada.ca/en/health-canada/services/publications/healthy-living/carbon-dioxide-home.html.
- Seals, Health Effects from Gas Stove Pollution, 2020; WHO Guidelines for Indoor Air Quality: Selected Pollutants, WHO, 2010, https://www.who.int/publications/i/item/9789289002134.
- “Nitrogen Dioxide,” American Lung Association, accessed August 2023, https://www.lung.org/clean-air/outdoors/what-makes-air-unhealthy/nitrogen-dioxide.
- “Ozone & Health,” State of California Air Resources Board, accessed August 2023, https://ww2.arb.ca.gov/resources/ozone-and-health; and “Radon,” EPA, accessed August 2023, https://www.epa.gov/radon.
Citations for Exhibit 2
- WHO Global Air Quality Guidelines: Particulate Matter, WHO, 2021; WHO Guidelines for Indoor Air Quality: Selected Pollutants, 2010.
- “Residential Indoor Air Quality Guideline: Acetaldehyde,” Health Canada, 2017, https://publications.gc.ca/site/eng/9.835076/publication.html.
- “Residential Indoor Air Quality Guideline: Acrolein,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-acrolein.html.
- “Guidance for Benzene in Residential Indoor Air,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidance-benzene-residential-indoor-air.html.
- “Residential Indoor Air Quality Guideline for Xylenes,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-xylenes.html.
- “Residential Indoor Air Quality Guideline: Carbon Monoxide,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-carbon-monoxide.html.
- “Residential Indoor Air Quality Guideline: Carbon Dioxide,” Health Canada, 2021, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guidelines-carbon-dioxide.html.
- “Residential Indoor Air Quality Guideline: Formaldehyde,” Health Canada, 2006, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-formaldehyde.html.
- “Residential Indoor Air Quality Guideline: Naphthalene,” Health Canada, 2013, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-naphthalene.html.
- “Residential Indoor Air Quality Guideline: Nitrogen Dioxide,” Health Canada, 2015, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-nitrogen-dioxide.html.
- “Residential Indoor Air Quality Guideline: Ozone,” Health Canada, 2010, https://www.canada.ca/en/health-canada/services/publications/healthy-living/residential-indoor-air-quality-guideline-ozone.html.
- “Radon Guideline,” Health Canada, 2009, https://www.canada.ca/en/health-canada/services/environmental-workplace-health/radiation/radon/government-canada-radon-guideline.html.
- A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Your Family from Radon, EPA, 2016, https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf.
- “IDPH Guidelines for Indoor Air Quality,” Illinois Department of Public Health, accessed August 2023, https://dph.illinois.gov/topics-services/environmental-health-protection/toxicology/indoor-air-quality-healthy-homes/idph-guidelines-indoor-air-quality.html,
- Comprehensive Indoor Air Quality Report, California Air Resources Board, 2005, https://ww2.arb.ca.gov/resources/documents/comprehensive-indoor-air-quality-report-2005.
- “Texas Voluntary Indoor Air Quality Guidelines for Government Buildings,” Texas Department of Health, 2002, https://gato-docs.its.txst.edu/jcr:afe38366-c8fe-4e39-8e6f-9eab96d729ba/Gov_Bld_Gd.pdf.
CONTACTS
Nina Prescott, nina.prescott@rmi.org
Mike Henchen, mhenchen@rmi.org
COPYRIGHTS AND CITATION
Nina Prescott, The Need for US Indoor Air Quality Guidelines: Advancing Policy for Healthy Buildings at the Federal and State Level, RMI, 2023.
RMI values collaboration and aims to accelerate the energy transition through sharing knowledge and insights. We therefore allow interested parties to reference, share, and cite our work through the Creative Commons CC BY-SA 4.0 license. https://creativecommons.org/licenses/by-sa/4.0/.
All images used are from iStock.com unless otherwise noted.
ACKNOWLEDGMENTS
Thank you to subject matter experts who offered their valuable comments and suggestions, which helped to inform this report, including:
Carbon-Free Buildings Program team, RMI
Noah Cordoba, Lawrence Garber, and Amy Rider, Building Decarbonization Coalition (BDC)
Iain Walker, Lawrence Berkeley National Lab
David Jacobs and Jonathan Wilson, National Center for Healthy Housing (NCHH)
Matt Casale (in his former capacity) and Abe Scarr, Public Interest Research Group (PIRG)
Annika Larson, environmental justice policy expert
Aaron Martin, Illinois Department of Public Health
Ruth Ann Norton, Green & Healthy Homes Initiative