A Health Professional's Guide
Intended for health professionals, advocates, and anyone interested in the climate-health nexus.
Learn more about the health impacts of fossil fuel combustion in buildings and the benefits of electrifying buildings.
Carbon-free buildings not only combat climate change but are critical in protecting our health. RMI promotes electrification as a triple-win strategy benefiting climate, health, and air quality. Done right, building electrification should also be cost-effective and promote environmental and climate justice. As trusted messengers treating the health concerns of their communities, health professionals can also play a vital role in advocating for building electrification. This guide provides science-based information on how fossil fuels in buildings contribute to air pollution and health problems and explores beneficial solutions.
Fact Sheets about Building Electrification and Health
A Health Professional's Guide to Clean Cooking
Discusses how to minimize the health risks of gas stoves or switch to induction stoves for better health.
All-Electric Buildings Are Healthy Buildings
Defines building electrification and overviews the health benefits.
Gas Appliance Pollution Inequitably Impacts Health
Explains why gas appliance pollution inequitably impacts health and who would gain the most from electrification.
Health Professionals Can Play a Role in Electrification
Encourages health professionals to engage in electrification efforts through education and advocacy.
Commonly Asked Questions about Building Pollutants
Carbon Monoxide (CO) FAQ
CO is an invisible pollutant that is released when fuels are burned. Because indoor CO is chemically identical to the CO that appears outdoors, it can cause the same health effects at the same exposure levels and duration.
Nitrogen Dioxide (NO2) FAQ
NO2 is a toxic gas commonly associated with fossil fueled appliances and traffic pollution. The EPA found that short-term exposure to NO2 can cause asthma attacks.
Particulate Matter (PM2.5) FAQ
PM2.5 is made up of small particles and liquid droplets that are released when fuels are burned. It can also be formed by other pollutants in the atmosphere. Due to the tiny size, these particles can penetrate deep into the lungs and bloodstream, making PM2.5 a leading predictor of mortality from cardiovascular, respiratory, and other types of disease.
Carbon monoxide (CO) is an odorless, invisible gas that can cause illness and death.
Burning fuels in buildings produces trace amounts of pollutants like CO. Unvented gas-burning household appliances like gas stoves are a significant source of CO indoors. When vented properly, other gas appliances, like water heaters, furnaces, fireplaces, and clothing dryers, should contribute more minimally to indoor air pollution.
Indoor concentrations of carbon monoxide vary with factors like the age of a gas appliance and whether it is properly vented to the outdoors. The highest levels of CO are found indoors when gas appliances are incorrectly installed or poorly ventilated, or when maintenance is ignored. And current safety standards are insufficient to prevent CO poisoning.
It is critical that healthcare professionals can explain how fossil fuel combustion in buildings contributes to CO exposure indoors, make safety recommendations to prevent exposure, and recognize symptoms of CO poisoning in their patients.
If people can’t see or smell carbon monoxide, how can they tell if it's making them sick?
Anyone can breathe in air laced with CO, including children, adults, and even pets. Higher concentrations are deadly because CO displaces oxygen in the bloodstream, denying oxygen to the heart, brain, and other parts of the body.
Mild to moderate cases of CO poisoning can cause an upset stomach, dizziness, headache, vomiting, chest pain, weakness, and/or confusion. Sometimes symptoms look very similar to the flu, although the flu is more likely to also cause a fever.
Each year more than 100 people in the United States die from indoor CO poisoning, and thousands more land in the emergency room.
Are there health impacts from exposure to low levels of carbon monoxide?
Researchers have noted in some instances that long-term exposure to low-level CO can lead to lasting, mild neurological effects. Although more research is needed, studies do show cause for concern. Studies published in 1990 and 1998 noted neuropsychological symptoms connected to low levels of CO exposure including changes in memory, sleep, vison, sense of smell and sense of direction, anxiety, balance problems, and psychomotor dysfunction.
A 2002 report points to several tools available to health professionals to measure carbon monoxide levels in patients, including blood tests that measure carboxyhemoglobin (COHB) concentration.
How much carbon monoxide is dangerous indoors?
The EPA does not currently set standards for indoor air quality. Because indoor CO is chemically identical to the CO that appears outdoors, it can cause the same health effects at the same exposure levels and duration. The National Ambient Air Quality Standards (NAAQS) for outdoor CO are 35 parts per million (ppm) for one hour and 9 ppm for eight hours. This means the EPA has determined that exposure above those levels is not safe.
There are currently no national requirements for household carbon monoxide detectors, but three-quarters of US states require homes to have CO detectors in at least some cases. Most detectors are only capable of detecting higher concentrations, where the health impacts can be acute. The nonprofit organization Underwriters Laboratories worked with the Consumer Product Safety Commission to set the UL 2034 safety standards for alarms (see table below).
It’s important to note that standard detectors will not sound at very low levels of CO that could cause chronic exposures and impact sensitive populations. Individuals with underlying conditions like cardiovascular issues may want to consider purchasing a low-level CO detector.
Do gas stoves produce carbon monoxide?
Yes. CO is produced through the incomplete combustion of gas. Homes with properly installed and maintained gas stoves see CO levels between 5 ppm and 15 ppm—higher than average CO levels in homes without gas stoves, which average between 0.5 ppm and 5 ppm, according to the EPA. Poorly installed and maintained stoves can result in CO levels that are 30 ppm or higher. A 2015 study found that gas stoves can substantially increase the risk of elevated CO in the home. Out of the 316 homes studied, about 5 percent had short-term levels that went above California’s ambient air quality standard of 20 ppm over a one-hour period or 9 ppm over an eight-hour period.
Ventilation of gas stoves is important, but it does not eliminate indoor exposures to pollutants. Since the transition to electric stoves will greatly reduce exposure to CO, some US cities are beginning to limit the use of gas stoves in homes.
Do the pilot lights on gas appliances release carbon monoxide?
If a pilot light on a gas stove is continuously burning, make sure that the flame is blue. A blue flame is an indication of complete combustion with no CO produced. If the flame is orange or yellow, the pilot light could be emitting CO. It’s important to get a stove serviced if the burner flames are not blue, if the burners or pilot light produce soot, or if the burners do not light properly.
Do indoor propane heaters produce carbon monoxide?
Yes. Propane heaters produce CO, so avoid their use to eliminate this exposure. At a minimum, reduce CO exposure by following all safety instructions and ensuring that the heater is a contemporary model that is safe for indoor use, equipped with an oxygen depletion sensor that will automatically shut off the unit when CO levels are too high.
How can people protect themselves against carbon monoxide poisoning indoors?
If the home has CO detectors, it’s important to test them to make sure they’re working properly. If the home does not have CO detectors, consider installing one outside each sleeping area. The EPA recommends placing one detector on each floor of the home, about five feet above the floor or on the ceiling. For rentals without a CO detector, there's a chance that the property owner may be required to purchase one, so check the law in your state.
To greatly reduce exposure to CO from gas appliances, households and communities can transition to all-electric appliances, including stoves, water heaters, furnaces, fireplaces, and clothing dryers.
Nitrogen dioxide (NO2) is a gas that can cause numerous health impacts.
Burning fuels in buildings produces NO2 and other pollutants. Out of all gas-burning household appliances, gas stoves are the most significant source of indoor NO2, especially when unvented. When vented properly to the outdoors, other gas appliances like water heaters, furnaces, fireplaces, and clothing dryers contribute far more to outdoor air pollution than indoor air pollution.
It is critical that healthcare professionals can explain how fossil fuel combustion in buildings contributes to NO2 exposure both indoors and outdoors, leading to health impacts, so that patients can identify sources and limit their exposure to this pollutant.
Why is nitrogen dioxide harmful to human health?
Breathing elevated levels of NO2 inflames the lining of the lungs and can cause respiratory problems such as wheezing, coughing, chest tightness, and chronic obstructive pulmonary disease.
The Environmental Protection Agency (EPA) recently found a causal relationship between short-term exposure to NO2 and respiratory effects. It found that long-term exposure to NO2 is likely linked to asthma development.
Diseases like diabetes and cancer, as well as reproductive and developmental effects, are also linked to elevated levels of NO2.
Who can experience health impacts from nitrogen dioxide? Who is most at risk?
Anyone can breathe in air containing high concentrations of NO2.
Children are particularly at risk. Even small increases in short-term exposure to indoor NO2 can increase their asthma risks. Asthma has numerous triggers and widely varying impacts. Children living in a home with a gas stove have a 42 percent higher risk of experiencing asthma symptoms than those in homes without gas stoves, and a 24 percent higher risk of being diagnosed with asthma by a doctor.
Lower-income households may also be at a higher risk of exposure to gas stove pollution. Many factors contribute to higher levels of NO2 in lower-income households, including smaller unit size, more residents per home, and inadequate ventilation. These factors—compounded by a disproportionate asthma burden—put lower-income households at risk of negative health outcomes related to elevated indoor NO2.
How much nitrogen dioxide is dangerous?
The EPA regulates NO2 outdoors. The outdoor federal standard for NO2, created in 1971, is 53 parts per billion (ppb) over the course of a year. In 2010, the EPA created a one-hour NO2 exposure standard for outdoor air of 100 ppb. This means the EPA has determined that exposure above those levels is not safe.
However, the EPA does not regulate NO2 indoors, even though concentrations of indoor NO2 regularly reach levels that would be illegal outdoors (under state or federal standards).
There is also a growing body of research (summarized in this analysis) that suggests that indoor NO2 levels much lower than the federal outdoor standards can still lead to negative health outcomes. For example, a 2013 study of asthmatic children found that exposure to NO2 at levels as low as 11 ppb worsened children’s asthma symptoms and increased the need for medication. In September 2021, the World Health Organization (WHO) decreased the safe threshold of recommended NO2 exposure by a factor of 4. The new guideline is for annual exposure of 10 μg/m3 (about 5 parts per billion, or ppb) and 24-hour exposure of 25 μg/m3 (about 13 ppb).
Do gas stoves produce nitrogen dioxide?
Gas stoves are one of the primary sources of NO2 in homes. The EPA states that homes with gas stoves can have concentrations of NO2 that are 50 to 400 percent greater than homes with electric stoves. While cooking on a gas stove, NO2 pollution peaks and often reaches levels so high indoors that it would violate EPA outdoor air quality standards. Studies have shown that using a gas stove or oven can cause indoor spikes of NO2 as high as 230 ppb while baking a cake or 184 ppb while boiling water.
Ventilation of gas stoves is important, but it does not eliminate indoor exposure to pollutants. Since the transition to electric stoves will greatly reduce exposure to NO2, some US cities are beginning to limit the use of gas stoves in homes.
How can people limit their exposure to nitrogen dioxide while cooking with gas stoves?
If a stove is equipped with an exhaust hood, be sure to use it throughout the cooking process. Check to make sure that it is vented to the outdoors, because some exhaust hoods simply recirculate air back into the room. Using the back burner of your stove for cooking, which is typically closer to the exhaust hood, will also limit your exposure to NO2. If a stove does not have a hood, open the windows for ventilation whenever possible.
Is ventilation alone enough to limit exposure to nitrogen dioxide?
No. Although it’s important to always ventilate, not all exhaust hoods can reduce pollution to safe levels. Many are recirculating, meaning they move emissions around the kitchen and home without venting it outdoors. California’s latest 2023 building code update will have differentiated requirements for gas and electric stoves. These requirements aim to maintain acceptable levels of NO2, which is emitted by gas stoves but not electric stoves. This is the first time a state has instituted ventilation requirements specific to gas stoves.
Research from Lawrence Berkeley National Laboratory, which helped inform the new California building code for ventilation, showed that exhaust hoods over gas stoves would need to meet more stringent requirements to protect health, as compared with hoods over electric stoves. This is particularly true in the smallest of units.
Lastly, surveys show that people generally do not use their exhaust hoods—either because they don’t believe the hoods are needed, they don’t believe the hoods are efficient, or the hoods are too noisy.
Fundamentally, replacing a gas stove with an electric stove may dramatically reduce indoor NO2 levels in the kitchen and improve air quality throughout the rest of the home.
Do fireplaces produce nitrogen dioxide?
There are two types of natural gas fireplaces: vented and unvented. Unvented gas fireplaces carry the largest health risk because they have the potential for incomplete combustion of natural gas. When that occurs, carbon monoxide and NO2 can be released into the home. Odorless carbon monoxide gas has been linked to health issues and, in extreme cases, death.
Studies in 2010 and 2011 found elevated levels of the pollutants with unvented gas fireplaces. This suggests that unvented fireplaces should be used sparingly. When doing so, make sure there is proper ventilation, and buy a carbon monoxide sensor for the room with the fireplace. There are two types of sensors: standard and low-level detectors.
What impact does nitrogen dioxide pollution have when it is vented outside the home from appliances like furnaces and water heaters?
Even gas appliances that properly vent outdoors represent a significant and overlooked portion of nitrogen oxide emissions (NOx), which include NO2. According to EPA emissions data, gas appliances contribute twice as much NOx as gas power plants in the United States. In California, burning fuels in buildings releases nearly as much NOx as light-duty passenger vehicles and nearly six times more than power plants.
NO2 represents a triple threat. Not only is direct exposure to NO2 harmful to human health, but the gas is also a main ingredient in the formation of two of the most health-damaging pollutants: secondary particulate matter (soot) and ground-level ozone (smog). Many counties in the United States have high outdoor concentrations of ozone and particulate matter that do not meet EPA standards.
Switching to all-electric appliances will greatly reduce people’s indoor and outdoor exposure to NO2, while simultaneously reducing ozone and particulate matter pollution outdoors.
Particulate matter (PM2.5) refers to fine inhalable particles and liquid droplets 2.5 microns in diameter or smaller. Research on indoor and outdoor air pollution has clearly shown that particulate matter can penetrate deep into the lungs and cause numerous health impacts and premature death. In fact, PM2.5 is a leading predictor of mortality from cardiovascular, respiratory, and other types of disease.
Burning fuels in buildings produces pollutants including PM2.5. Gas-burning household appliances like water heaters, furnaces, fireplaces, and clothing dryers are vented outdoors and therefore contribute heavily to outdoor air pollution. Another household appliance, the gas stove, is one of the most significant sources of PM2.5 generated by fossil fuels indoors, especially when unvented. Other indoor sources of PM2.5 include mold, dust, pet dander, and cleaning products.
There are scientifically robust bodies of research on both indoor and outdoor air pollution, and how exposure impacts human health. Health professionals and policymakers are now beginning to understand how indoor and outdoor air quality relate.
It is critical that healthcare professionals are able to explain how fossil fuel combustion in buildings contributes to PM2.5 exposure so they can help patients identify sources and limit their indoor and outdoor exposure to this pollutant.
How is PM2.5 harmful to human health?
When PM2.5 lands on the lung’s surface, it can cause tissue damage, lung inflammation, and can even enter the blood stream. Numerous studies have shown that PM2.5 can also cause asthma and respiratory inflammation, resulting in respiratory symptoms like coughing, phlegm, chest pain, or wheezing. Prolonged exposure can even result in premature death.
A 2021 study estimated that PM2.5 emissions from burning fossil fuels and wood/biomass in commercial and residential buildings are responsible for approximately 18,300 early deaths and $205 billion in health impacts in the United States.
Who can experience health impacts from PM2.5? Who is most at risk?
Anyone can breathe in air containing high concentrations of PM2.5, both indoors and outdoors. The groups most likely to experience adverse health impacts from PM2.5 include older adults with chronic heart or lung disease, children, and asthmatics.
Recent research has shown that communities of color and low-income communities bear a disproportionate brunt of health impacts from PM2.5 in the United States. A 2016 study found that individuals with long-term PM2.5 exposure living in locations with lower socioeconomic status experienced increased mortality compared to individuals living in higher socioeconomic status locations. Historical residential redlining has also been linked to higher PM2.5 pollution and higher rates of emergency department visits.
Children and infants are also at higher risk of PM2.5-related health outcomes. Because of their small lungs, they can breathe in more air per pound of body weight compared to adults. Children also breathe faster. A study initiated by the California Air Resources Board found that kids living in communities with high levels of PM2.5 had slower lung growth and smaller lungs at age 18 compared to a similar age group that grew up in a community with lower PM2.5 levels. This means that high concentrations of PM2.5 have the potential to harm children’s lungs for the rest of their lives.
How much PM2.5 is dangerous?
Outdoor exposure to more than 12 micrograms per cubic meter (µg/m3) of PM2.5 annually, or 35 µg/m3 in a 24-hour period, is considered harmful to health based on standards set by the Environmental Protection Agency (EPA).
In 2020, EPA scientists sought to strengthen the annual standard to further reduce health harms. Although those recommendations were rejected by the Trump administration, they are now being revisited under the Biden administration.
While the EPA does not currently have an indoor standard for PM2.5, scientific research shows that high concentrations of PM2.5 can be problematic indoors as well—especially for children. One 2009 study found high concentrations of particulates indoors correlated to respiratory symptoms and increased rescue medication use.
Internationally, the World Health Organization (WHO) recommends lower thresholds. In 2021, the WHO roughly halved the safe threshold for PM2.5 exposure. The WHO recommends outdoor exposure to no more than 5 μg/m3 of PM2.5 annually and 15 μg/m3 for a 24-hour period. These apply to both indoor and outdoor environments. According to the WHO there is no difference in the hazardous nature of PM2.5 indoors compared to outdoors. Additionally, the health effects resulting from fossil fuel and biomass combustion of PM2.5 emissions are broadly the same.
Do gas stoves produce PM2.5?
Gas flames (even in the absence of cooking emissions) are a crucial source of PM2.5. Emissions from gas stoves are higher than from electric stoves. A 2021 study that evaluated cooking in 132 Canadian homes found that gas stoves emit twice as much PM2.5 compared to electric stoves. Although cooking activities like deep frying on electric stoves do emit particulates, studies note that that the same cooking activities on gas stoves can result in more PM2.5 emitted.
Ventilation of gas stoves is important, but it does not eliminate indoor exposures to pollutants. Since the transition to electric stoves will greatly reduce exposure to PM2.5, some US cities are beginning to limit the use of gas stoves in homes.
How can people limit their exposure to PM2.5 while cooking with gas stoves?
There are many ways to reduce the amount of PM2.5 entering the home from cooking. If the stove is equipped with an exhaust hood, be sure to use it throughout the cooking process. Check to make sure that it is vented to the outdoors because some exhaust hoods simply recirculate air back into the room. Using the back burner of your stove for cooking, which is typically closer to the exhaust hood, will also limit exposure. If the stove does not have a hood, open the windows for ventilation whenever possible. Air purifiers can also remove particulates if proper ventilation is not available.
Is ventilation alone enough to limit exposure to PM2.5?
Research has shown that when properly ventilated to the outdoors, many exhaust hoods can be effective at removing PM2.5 from gas stoves indoors. If there are questions about a specific hood’s ability to remove particulates, there are resources that can help determine the unit’s capabilities.
It's important to note that while some people are likely to be prompted by PM2.5 to turn on their exhaust hoods, many still do not use them. This may be because they don’t believe they are needed, they are too noisy, or they don’t believe they are efficient. In one California utility district, the annual public health burden of not using a range hood while cooking has been estimated to be nearly $1 million per 100,000 people.
Fundamentally, replacing a gas stove with an electric stove may dramatically reduce indoor PM2.5 levels in the kitchen and improve air quality throughout the rest of the home.
Gas-powered appliances like furnaces and water heaters vent outdoors. What kind of impact does PM2.5 pollution have outside the home?
Gas-powered water heaters, furnaces, fireplaces, and clothing dryers produce PM2.5 that is vented outdoors and contributes to ambient air pollution, which is regulated by the EPA. Gas appliances not only produce primary PM2.5 (which is released directly when burned), but they also release other gases and pollutants (like nitrogen dioxide), which react in the atmosphere to form secondary PM2.5.
PM2.5 pollution from household gas appliances vented outdoors compounds with that of other combustion sources, including wood, biomass, coal, gasoline, and diesel. A 2021 study found that the sum of PM2.5 emissions from gas, biomass, and wood burned in industrial boilers and buildings surpassed the emissions from coal-fired power plants. A 2020 MIT study published in Nature showed that residential and commercial buildings are now the leading source of early deaths from PM2.5 and ozone pollution generated from all sectors (including transportation).
These emissions disproportionately impact people of color. A 2021 study found that PM2.5 pollution formed from gas combustion in residential buildings and commercial cooking were among the largest sources of pollution disparities for Black, Hispanic, and Asian Americans.