While there is a need for revised emissions standards, those currently proposed should give us pause

Under court order, Stephen Johnson, administrator of the Environmental Protection Agency (EPA), has proposed revised standards for fine (for PM2.5, particles less than 2.5 µm in aerodynamic diameter) and coarse particle (PM10-2.5) emissions under the Clean Air Act.¹ While the proposal released by Johnson is complex, the respiratory community should be concerned about three main points that are quite clear in the proposal. First, Johnson is more concerned about protecting Americans from daily exposures to fine particles than he is in annual exposures to PM2.5 air pollution. Second, exposure to coarse particles in rural America is not expressed as a health concern at any level. Third, Johnson is so confident that rural PM10-2.5 is not a health issue that he is proposing to cease monitoring coarse particles in rural communities. In reaching these three conclusions, Johnson is ignoring scientific evidence, the advice of the experts, and, ultimately, the law.

The Proposed Rule
For PM2.5, the EPA is proposing to maintain the existing average annual standard of 15 µg/m3 and is proposing tightening the 24-hour exposure standard to 35 µg/m3 (from the current standard of 65 µg/m3).

For PM10-2.5, the EPA is proposing a standard of 70 µg/m3 24-hour exposure for urban areas only. Rural areas and emissions from agriculture and mining activities would be exempted from both the PM10-2.5 standard and further monitoring.

Ignoring the Data
In announcing his decision, Johnson said he based his recommendation on all scientific literature published before June 2003. This cutoff date excludes several important studies published since then that show adverse health effects, including mortality and hospitalizations, at lower levels of particulate pollution.^2-8 Since 2003, studies have also been published that provide a mechanistic explanation of these effects, including systemic inflammation, autonomic effects, and accelerated atherosclerosis.^9,10 Time-series studies show a linear relationship between PM concentration and risk at concentrations measured at or below 15 µg/m3.11 By not including these studies in setting the standard, the EPA is effectively ignoring the available data.

Ignoring the Scientists
To assist in analyzing and interpreting the scientific data, the EPA has convened a panel of experts called the Clean Air Scientific Advisory Committee (CASAC). The panel is composed of recognized experts from the field of health toxicology and also includes experts with industry backgrounds. Prior to the EPA releasing its proposal, CASAC analyzed the available data and provided the EPA with a range of where it should set a new standard, and recommends an PM2.5 average annual standard between 13 and 14 µg/m3.12 The EPA career staff also recommended a standard stricter than that proposed by Johnson.¹³ By choosing an average annual standard above what the CASAC recommended, Johnson is ignoring the advice of the experts.

Ignoring Rural America
In proposing a standard for PM10-2.5 that applies only to urban areas, Johnson is ignoring the health of rural Americans. There is a significant body of literature documenting the adverse health effects of PM10-2.5 from urban composition coarse particles (diesel engines, power plants, etc). While the research on PM10-2.5 from rural sources (farming, mining, etc) is less robust, there is no literature to suggest rural coarse particles are safe.¹⁴ Johnson further compounds the problem by proposing that rural PM10-2.5 not even be measured.

Ignoring the Law
The Clean Air Act states that the EPA must set a standard for emissions that protects the American public, including vulnerable populations like the elderly and children, with an adequate margin of safety. There is a growing body of research and peer-reviewed published science that demonstrates adverse health effects for PM2.5 at levels equal to or below 15 µg/m3 average annual exposure.^15,16 If the science documents adverse health effects at 15 µg/m3, then, by law, the EPA must set the standard lower to ensure an adequate margin of safety. By retaining the current average annual standard of 15 µg/m3, Johnson is not providing an adequate margin of safety required by the Clean Air Act. In effect, he is ignoring the law.

Where to Set the Standard
It is clear that the standard proposed by Johnson is not supported by available science, experts, or law. The American Thoracic Society (ATS) strongly recommends that the EPA issue a final rule that significantly tightens both the average annual exposures and the 24-hour exposure. We further see no justification for excluding rural areas from the coarse particle monitoring. The ATS, joined by five other national medical professional organizations, supports the following aggressive standard for PM2.5:

12 µg/m3 average annual standard

25 µg/m3 24-hour standard

While it is unlikely that EPA administrator Johnson will adopt the strict standard supported by the ATS, science, expert opinion, public health, and, ultimately, the law, require a more stringent standard than that initially proposed.

Peter D. Wagner, MD, is president of the American Thoracic Society, an international medical association of more than 13,000 clinicians and scientists who specialize in pulmonary, critical care, and sleep medicine.

References
1. Environmental Protection Agency: National ambient air quality standards for particulate matter; proposed rule. Federal Register: 2006;71(10):2619-2708.

2. Ito K. Associations of particulate matter components with daily mortality and morbidity in Detroit, Michigan. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2003:143-56.

3. Klemm RJ, Mason R. Replication of reanalysis of Harvard Six-City mortality study. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2003:165-172.

4. Mar TF, Norris GA, Larson TV, Wilson WE, Koenig JQ. Air pollution and cardiovascular mortality in Phoenix, 1995-1997. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2003:177-82.

5. Gauderman WJ, Gilliland GF, Vora H, et al. Association between air pollution and lung function growth in southern California children: results from a second cohort. Am J Respir Crit Care Med. 2002;166(1):76-84.

6. Moolgavkar SH. Air pollution and daily deaths and hospital admissions in Los Angeles and Cook counties. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2002:183-98.

7. Schwartz J, Zanobetti A, Bateson T. Morbidity and mortality among elderly residents of cities with daily PM measurements. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2003:25-58.

8. Sheppard L. Ambient air pollution and nonelderly asthma hospital admissions in Seattle, Washington, 1987-1994. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2003:227-230.

9. Brook RD, Franklin B, Cascio W, et al. Air pollution and cardiovascular disease: a statement for healthcare professionals from the Expert Panel on Population and Prevention Science of the American Heart Association. Circulation. 2004;109(21):2655-71.

10. van Eeden SF, Yeung A, Quinlam K, Hogg JC. Systemic response to ambient particulate matter: relevance to chronic obstructive pulmonary disease. Proc Am Thorac Soc. 2005;21(1):61-7.

11. Bell ML, Samet JM, Dominici F. Time-series studies of particulate matter. Annu Rev Public Health. 2004;25:247-80.

12. Clean Air Scientific Advisory Committee letter to Environmental Protection Agency administrator (June 6, 2005) regarding particulate matter (PM) review panel’s peer review of the agency’s review of the National Ambient Air Quality Standards for Particulate Matter: Policy assessment of scientific and technical information (second draft PM staff paper, January 2005); and Particulate matter health risk assessment for selected urban areas: second draft report (second draft PM risk assessment, January 2005).

13. Environmental Protection Agency: Review of the national ambient air quality standards for particulate matter: policy assessment of scientific and technical information. OAQPS staff paper—second draft (5-74).

14. Ostro BD, Broadwin R, Lipsett MJ. Coarse particles and daily mortality in Coachella Valley, California. In: Revised Analyses of Time-Series Studies of Air Pollution and Health. Special Report. Boston: Health Effects Institute; 2003:199-204.

15. US Environmental Protection Agency (EPA) and Clean Air Scientific Advisory Committee (CASAC). Review of the national ambient air quality standards for particulate matter: policy assessment of scientific and technical information. OAQPS staff paper. Research Triangle Park, NC: USEPA; 2005.

16. Pope CA 3rd, Burnett RT, Thun MJ, et al. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA. 2002;287(9):1132-41.