EPA Air Pollution Decision Threatens Public Health

Science disregarded, misrepresented on particulate matter standard

NOTE: The following is one of a series of case studies produced by the Union of Concerned Scientists' Scientific Integrity Program between 2004 and 2010 to document the abuses highlighted in our 2004 report, Scientific Integrity in Policy Making.

Disregarding and misrepresenting recommendations from its staff scientists, the Environmental Protection Agency (EPA) proposed air pollution standards that fail to sufficiently protect public health. The new rules apply to fine particulate matter pollution, sources of which include agricultural activity, vehicle exhaust, and emissions from coal-fired power plants. Over 2,000 recent studies have linked particulate matter exposure to heart disease, respiratory ailments, and premature death.

Particulate Matter & Public Health

Fine particulate matter (known as PM 2.5) consists of particles less than 2.5 micrometers in diameter, or about one third the diameter of a human hair. Sources of PM 2.5 pollution include agricultural activity, vehicle exhaust, and emissions from coal-fired power plants.

PM 2.5 has a profound effect on public health. It can easily become trapped in the human body and can have negative consequences for a person’s health. Over 2,000 peer-reviewed studies published since the current PM 2.5 standards went into effect in 1997 link fine particle pollution to strokes, heart disease, respiratory ailments, and premature death.

For example, one study showed that for each decrease of one microgram of soot per cubic meter of air, death rates from respiratory and cardiovascular diseases decrease by three percent (1). The EPA estimates that PM 2.5 kills 20,000 people and hospitalizes many more each year. It is important that fine particulate matter standards are low enough to prevent these severe negative health effects.

In 2005, the EPA’s Clean Air Scientific Advisory Committee (CASAC) recommended fine particulate standards with a maximum daily limit between 30 and 35 micrograms per cubic meter, and an average annual limit between 13 and 14 micrograms. While the EPA’s final proposed standards lowered the maximum daily limit from 65 to 35 micrograms, they left the average annual limit at 15 micrograms. According to the CASAC scientists, such a high average annual limit would have a significant, negative effect on public health.

A study funded by the EPA and the National Institutes of Health published in the Journal of the American Medical Association in March 2006 concluded that even an exposure level of 13.4 micrograms of PM 2.5 would put 11.5 million elderly Americans at increased risk of cardiovascular and respiratory disease. The study's findings "provide compelling evidence that fine particle concentrations well below the national standard are harmful to the cardiovascular and respiratory health of our elderly citizens," said National Institute of Environmental Health Sciences Director David A. Schwartz.(2)

The EPA's proposed standards do little to reduce the burden of death and disease from fine particle pollution. The number of people protected by the proposed standards increase by a mere 15 percent (from 56 million to 65 million). Meanwhile, more than 165 million people live in areas with PM 2.5 levels above that which research shows can adversely affect health.

Prior to the EPA's final ruling on the new standards, the scientists on CASAC wrote a letter to EPA Administrator Stephen Johnson to re-explain the science behind their recommendations and to urge him to reconsider the proposed standards, a move that was unprecedented. A second scientific advisory committee, the Children’s Health Protection Advisory Committee, also wrote a letter to the EPA administrator claiming that the proposed standards did not adequately protect public health.

CASAC members alleged that the EPA had twisted or misrepresented the panel’s recommendations on a number of issues related to the proposed standards. According to the Los Angeles Times, Bart Ostro, an epidemiologist for the California Environmental Protection Agency, charged that the EPA had incorporated "last-minute opinions and edits" by the White House Office of Management and Budget that "circumvented the entire peer review process." The LA Times also quoted Ostro as saying that the White House changes were "very close to some of the letters written by some of the trade associations" (3).

The Philadelphia Inquirer also weighed in on this issue, saying that "reports have surfaced showing that the White House worked to cast doubt on the scientific need for tougher standards, making dozens of changes to the EPA's draft standards before the policy was made public. For instance, the White House removed a sentence from the policy stating that the air-quality standards 'may have a substantial impact on the life expectancy of the U.S. population'" (4).

In September 2006, EPA Administrator Johnson issued a final ruling that failed to lower the proposed levels of PM 2.5 as the scientists had advised, but left them unchanged at the higher levels considered by CASAC members to be unsafe.  No other EPA administrator has disregarded CASAC’s advice in its almost 30 year history. 

To justify his decision to ignore the committee’s recommendations, Johnson stated that there had been disagreement within CASAC and that their endorsement of the stronger standards had not been unanimous.  However, 20 out of 22 members of CASAC's Particulate Matter Review Panel and 7 out of 7 standing members of the committee had voted in favor of the original recommendations. 

Within a few days of when the rule was finalized, CASAC members again voiced their objections in a letter to Johnson, emphasizing that “there is clear and convincing scientific evidence that significant adverse human-health effects occur” with the new PM 2.5 standard, and that it “does not provide an ‘adequate margin of safety … requisite to protect the public health’ (as required by the Clean Air Act).” 

The letter also noted that CASAC’s recommendations “were consistent with the mainstream scientific advice that EPA received from virtually every major medical association and public health organization that provided their input to the Agency, including the American Medical Association, the American Thoracic Society, the American Lung Association, the American Academy of Pediatrics, the American College of Cardiology, the American Heart Association, the American Cancer Society, the American Public Health Association, and the National Association of Local Boards of Health.”

The Clean Air Act requires the EPA to create National Ambient Air Quality Standards (NAAQS) for PM 2.5 and several other pollutants that protect human health based on the best available science, particularly the health of "vulnerable groups" including children and the elderly. When considering safe levels of pollution in the air that we breathe, the EPA is only allowed to consider health effects. Nothing else can be considered, including economic, or even environmental, effects. According to its own scientific advisors, the EPA did not use the best available public health science in issuing the new standards, but may instead have emphasized the costs to industry of limiting fine particulate emissions. 

An EPA analysis recently made public shows that an annual limit of 14 micrograms per cubic meter would result in high costs to industry. According to a recent Harvard study, tightening the annual PM 2.5 pollution standard would save an estimated 10,000 to 12,000 lives per year (5). 

Dr. Phillip Hopke and Dr. Bernard Goldstein, both members of CASAC, have warned that the EPA’s standards open up the agency to lawsuits by not setting the standard based on the best available science.

A larger air pollutant—coarse particulate matter--is also regulated by the EPA. But standards for coarse particulate matter only apply in urban centers. This effectively exempts smaller towns and rural areas with populations under 100,000 from monitoring requirements. Under its new rule, the EPA won’t monitor coarse particulate matter levels in non-urban areas. In their letter to Stephen Johnson, CASAC had also urged the EPA to keep monitoring particulate matter pollution in both rural and urban areas to help inform critical future research in this area.

The coarse particulate matter standards will not apply to mining and agricultural operations—major beneficiaries of a relaxed rule.

Perhaps most troubling of all, the EPA has proposed changes to the NAAQS that would challenge the Clean Air Act’s requirement of basing air pollution standards on the best available science. An EPA working group has recommended that the Staff Paper, a document which identifies the most policy-relevant science and presents results from quantitative risk assessments, be replaced by a "narrowly focused policy assessment document" that should "reflect the agency's views."(6) If these changes are adopted, future rulemakings on many types of air pollution would be subject to a lesser scientific standard. Click here for more information on this proposal.  

Update: On February 24, 2009, the U.S. Court of Appeals for the D.C. Circuit held that scientific evidence did not support the EPA’s particulate matter standards, which violated the Clean Air Act “in several respects.”(7) The EPA failed to provide proper reasoning for its rejections of the Clean Air Scientific Advisory Committee's recommendations. Even though the court did not annul the current standards, the EPA must now reconsider them and explain how the standard is adequate to protect public health.(8) The EPA will likely combine its response to this court’s decision with its ongoing review of air quality standards.(9) Additionally, on May 21, 2009, EPA Administrator Lisa Jackson overturned a Bush-era process and reinstated the role of EPA staff scientists and CASAC advisors in developing science-based air quality standards.(10)


(1) Laden, F., et al. “Reduction in Fine Particulate Air Pollution and Mortality: Extended Follow-up of the Harvard Six Cities Study.” American Journal of Respiratory and Critical Care Medicine. 173 (2006): 667-672.

(2) NIEHS press release, Accessed 10/23/2006 at http://www.niehs.nih.gov/oc/news/particle.htm

(3) Wilson, Janet. “EPA Panel Advises Agency Chief to Think Again.” Los Angeles Times. February 4, 2006.

(4) “Time to Speak Up for Clean Air.” Editorial. Philadelphia Inquirer. March 8, 2006.

(5) Nesmith, Jeff. “EPA Advisors Unhappy over Air Particulates Decision.” Cox News Service. January 14, 2006.   

(6) CASAC comments on the NAAQS proposal, accessed 10/23/2006 at http://www.epa.gov/sab/pdf/casac_initial_comments_epa_naaqs_proc_rev_2006_final_ltr.pdf

(7) Am. Farm Bureau Fedn v. EPA, 559 F.3d 512, 521 (D.C. Cir. 2009). Online at


(8) Robin Bravender, Air Pollution: Appeals court strikes down Bush EPA's soot rule, Greenwire (2009).

(9) EPA May Fold Fine PM Remand Response Into Ongoing NAAQS Review, Risk Policy Report (2009). 

(10) EPA Administrator Lisa P. Jackson Brings Science, Transparency Back to Air Quality Standards Decisions, EPA News Release (2009). Online at http://yosemite.epa.gov/opa/admpress.nsf/0/20A6491703E9172E852575BD00585B81.

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