This report by Amory Lovins and Walter Patterson is a response to the controversy of the toxicity of plutonium. The Medical Research Council’s 1975 report, The Toxicity of Plutonium concludes that “there is no evidence that irradiation by ‘hot particles’ in the Img is markedly more hazardous than the same activity uniformly distributed or that the currently recommended standards for inhalation of plutonium are seriously in error.” Report R29 (1974) of the National Radiological Protection Board states that “there is no biological evidence available at present which suggests that ‘hot spots’ carry a higher risk of cancer induction.” But Dr A. R. Tampfin warns: “The plutonium exposure standards . . . must and will eventually be made more restrictive by a factor approaching 1,000.” Behind this disagreement is a major controversy over the risk of lung cancer from inhaled insoluble particles of intensely radioactive alpha emitters such as plutonium. In that controversy—unresolved by any direct data—lies a source of uncertainty about the future of nuclear power.”