LAUSR

The United States Environmental Protection Agency (EPA) was founded in 1970 with bipartisan support and under a Republican president, Richard Nixon. The central laws authorizing it to protect the health of US residents from pollution (the Clean Air Act, the Safe Drinking Water Act, etc.) similarly enjoyed bipartisan support. Beginning in the 1980s this began to change, with increased ideological opposition to regulation. In the 1980s that opposition focused on arguments that the costs of pollution controls were not justified by the modest health impacts produced. This opposition was generally accompanied by the argument that more science is needed. However, by the late 1990s, these arguments became untenable, because the science had been done, and the impacts were not modest. First PM 2.5 and more recently ozone have been shown to be associated with substantial health risks; these include early deaths and myocardial infarctions; and hospital admissions for pneumonia, heart attacks, and stroke show similar associations. The estimated attributable health impact is large. Using dose–response curves vetted by EPA’s Science Advisory Board, Fann et al. estimated that PM 2.5 was associated with 130,000 early deaths in 2005, 180,000 nonfatal myocardial infarctions, and 2.5 million asthma exacerbations. The associations in the epidemiology studies used have been replicated in dozens of cohort studies and hundreds of time-series studies across the world. The World Health Organization has used them in the Global Burden of Disease estimates, reporting over 5 million of early deaths per year due to these pollutants. The Royal College of Physicians similarly estimated 40,000 deaths per year in the United Kingdom due to air pollution. A large number of toxicology and controlled human exposure studies showing associations of these pollutants with changes in intermediary outcomes (blood pressure, inflammation, autonomic function, endothelial function, thrombosis, oxygen uptake, etc.) provide support to those findings. Similar results have been reported in panel studies of humans. A doubleblinded study using true versus sham particle filters in residences demonstrated that lowering particle levels decreased inflammatory markers and increased methylation of proinflammatory genes. More recently, causal modeling methods have added to the evidence. This body of evidence is too large to be reviewed here, but it has been reviewed by expert scientific committees convened by multinational (e.g., the World Health Organization, the UN Environment Program, the European Union), as well as national governments, such as the United Kingdom, and EPA’s own external Clean Air Scientific Advisory Board. All these review groups, as well as major medical organizations such as the American Heart Association, the American College of