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Contact Amy Schulz (ajschulz@umich.edu) for additional information. Produced by the Detroit Reproductive 

Environmental Advocacy Matters Working Group: Donele Wilkins, Amy Schulz, Natalie Sampson, Kelly 

Ferguson, Chris Coombe, and Trish Koman. April 5, 2015.

ACCOUNTING FOR VULNERABILITY IN THE NAAQS REVIEW PROCESS

RECOMMENDATION: EPA should expand its efforts to quantify the combined risks to health for 

populations exposed to multiple chemical and social exposures (due to, for example, residence in 

lower income neighborhoods), using clear and consistent population level criteria for risk.[1]

BACKGROUND

Populations or groups that experience multiple social, physical and chemical environmental stressors 

are at increased risk of disease. Residents of low to moderate income urban communities, who are 

disproportionately Non-Hispanic Black (NHB) and Latino, are more likely to be exposed to multiple air 

pollutants.[2] Such communities also experience heightened vulnerability to adverse health effects of 

air pollutants due to higher rates of chronic conditions such as asthma, obesity, diabetes, and 

cardiovascular disease.[3-5] These vulnerabilities coincide with social stressors, including poverty, poor 

housing, psychosocial stress, and reduced access to nutritious foods and health care, further 

exacerbating adverse effects.[6]

The combined effects of these multiple social, physical and chemical exposures, along with reduced 

access to resources necessary to maintain health (e.g., healthy foods, health care) have important 

implications for population health. Pregnant women, infants and children through puberty may be 

particularly susceptible to the adverse effects of these multiple exposures, due to differential dose as

well as the disproportionate impacts of exposures during critical developmental windows.[7]

Several reports have highlighted the importance of understanding the aggregation of risks from multiple 

environmental stressors. These include the National Research Council's (NRC) 1994 report Science and 

Judgment in Risk Assessment,[8] the 1997 report by the Presidential/ Congressional Commission on Risk 

Assessment and Risk Management,[9] and the NRC’s 2009 report on Science and Decisions.[10]

Despite these recommendations, the EPA has not applied consistent criteria to assess the joint effects of 

multiple exposures in recent NAAQS review processes. The absence of a clear and consistent process for 

identifying the combined effects of multiple exposures and vulnerabilities contributes to inadequate 

efforts to capture these joint effects. New, more encompassing processes for assessing vulnerability that 

account for the combined effects of multiple exposures and vulnerabilities are needed.[2]

ACCOUNTING FOR VULNERABILITY IN POPULATIONS WITH MULTIPLE RISK FACTORS 

The EPA should set clear and consistent criteria to account for the combined health effects of 

exposures to multiple social, physical and chemical stressors, such as those in low income communities 

and communities of color, in the Integrated Science Assessment (ISA). Evidence using these criteria for

assessing cumulative risks should be explicitly taken into account when setting the NAAQS standards. 

Different criteria for identifying vulnerable populations were used in the two most recent NAAQS review 

processes. Specifically, the Ozone HREA (2014) did not account for more adverse effects due to already 

compromised health, a criterion laid out in the PM2.5 decision (2012). Previously, EPA has defined four 

ways to establish vulnerable populations: 1) Higher levels of exposure; 2) Higher dose at a given level of 

ambient exposure; 3) More adverse effects at a given level of ambient exposure; and 4) More adverse 

effects due to already compromised health. The most recent NAAQS review process for PM2.5 applied all 
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Contact Amy Schulz (ajschulz@umich.edu) for additional information. Produced by the Detroit Reproductive 

Environmental Advocacy Matters Working Group: Donele Wilkins, Amy Schulz, Natalie Sampson, Kelly 

Ferguson, Chris Coombe, and Trish Koman. April 5, 2015.

four of these ways to establish a margin of safety for at-risk populations.[11, 12] However, the EPA only 

included criteria 1-3 above for the development of the revised Ozone standard. Although contained in 

the American Thoracic Society statement [13], EPAs Ensuring Risk Reduction in Communities with 

Multiple Stressors: Environmental Justice and Cumulative Risks/Impact [1] and applied in previous 

NAAQS reviews, the fourth criteria was omitted from correspondence with Administrator Jackson in the 

February 2013 memo to CASAC.[14] The rationale for eliminating the fourth criteria of population 

consequence is not discussed.

The EPA should apply a clear and consistent methodology to account for the population effects due to 

already compromised health from multiple social and chemical exposures. There is scientific 

consensus that the effects of exposures to environmental contaminants differ based on vulnerabilities 

such as underlying health status and the presence of co-pollutants.[10] Furthermore, there is increasing 

recognition that social conditions can amplify the adverse effects of environmental agents on health,[10, 

15] contributing to excess risk and racial, ethnic and socioeconomic disparities in health. Failure to 

include criteria that specifically assess the population effects of exposures, particularly in populations 

which experience already-compromised health due to multiple exposures, underestimates these effects, 

and is inconsistent with recent scientific guidance. The EPA has developed such population risk criteria, 

but has not applied them consistently in its review processes. Failure to establish and apply consistent 

methodologies for cumulative risk assessment contributes to an underestimate of the margin of 

safety, is a departure from previous considerations, and is inconsistent with scientific guidance.

Specifically, guidance from ATS states that “Exposure to air pollution that increases the risk of an 

adverse effect to the entire population is adverse, even though it may not increase the risk of any 

individual to an unacceptable level. For example, a population of asthmatics could have a distribution of 

lung function such that no individual has a level associated with clinically important impairment. 

Exposure to air pollution could shift the distribution to levels that still do not bring any individuals to a 

level that is associated with clinically relevant effects. However this would be considered to be adverse 

because individuals within the population would have diminished reserve function, and therefore would 

be at increased risk for further environmental insult” (Part II, Section B, Part 3).[11, 16]

For example, a recent multicity time series study cited in the Federal Register followed four cohorts of 

Medicare enrollees with chronic conditions that might predispose them to ozone related effects from 

1985-2006.[17] This study reported an association between long term (warm season) exposure to ozone 

and elevated risk of mortality in the cohort that had previously experienced an emergency hospital 

admission due to chronic obstructive pulmonary disease. Given socioeconomic, racial and ethnic 

disparities in risk factors for COPD, these findings suggest that failure to apply consistent population risk 

criteria for vulnerability may underestimate adverse health effects in communities where residents 

experiences the combined effects of multiple exposures and vulnerabilities.[18-24]

The purpose of selecting primary standards that provide an adequate margin of safety is to both prevent 

pollution levels that have been demonstrated as harmful, and to prevent lower pollution levels that may 

pose an unacceptable risk of harm, even if the risk is not precisely identified. The EPA’s current methods 

for identifying populations at risk are inconsistent between the PM and Ozone NAAQS. They do not 

adequately account for multiple amplifying risk factors, including physical, social, and chemical 

exposures, and their combined impact on health. Consequently, the standards set with these methods 

are inadequate to protect health in communities with multiple risk factors. 
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Contact Amy Schulz (ajschulz@umich.edu) for additional information. Produced by the Detroit Reproductive 

Environmental Advocacy Matters Working Group: Donele Wilkins, Amy Schulz, Natalie Sampson, Kelly 

Ferguson, Chris Coombe, and Trish Koman. April 5, 2015.

CONCLUSIONS

The failure to set clear and consistent criteria to account for the combined health effects of exposures

to multiple social, physical and chemical stressors, such as those in low income communities and 

communities of color, can lead to an underestimate of risks, and makes the review process

inconsistent and not transparent. This failure may contribute to underestimates in the adverse health 

effects of criteria pollutants, particularly for populations with multiple exposures and vulnerabilities. 

Under the Clean Air Act, EPA has a duty to protect at-risk populations with an adequate margin of 

safety. To do so, EPA must fully assess the risk to populations experiencing the cumulative effects of 

multiple social and chemical exposures, and, particularly, pregnant women, infants and children within 

those populations. Future ISAs and HREAs should more adequately account for the vulnerabilities of 

pregnant women and populations exposed to multiple social, physical and chemical stressors, using 

for example, the population level criteria for risk described above.

1. Group, N.E.J.A.C.C.R.I.W. Ensuring Risk Reduction in Communities with Multiple Stressors: Environmental Justice and 

Cumulative Risks/Impact 2004; Available from: 

http://www.epa.gov/compliance/ej/resources/publications/nejac/nejac-cum-risk-rpt-122104.pdf.

2. Morello-Frosch, R., et al., Understanding the cumulative impacts of inequalities in environmental health: implications 

for policy. Health Aff (Millwood), 2011. 30(5): p. 879-87.

3. Wasilevich, E., et al., Detroit - The epicenter of asthma burden, in Epidemiology of Asthma in Michigan, M.D.o.C. 

Health, Editor. 2008: Lansing, MI.

4. (MDCH), M.D.o.C.H. Heart Disease Deaths and Death Rates Three Year Moving Average 2005-2007. 2007 [cited 2012 

05/21/2012]; Available from: http://www.mdch.state.mi.us/pha/osr/CHI/CRI/frame.asp.

5. Kannan, S., et al., Exposure to fine particulate matter and acute effects on blood pressure: effect modification by 

measures of obesity and location. J Epidemiol Community Health, 2010. 64(1): p. 68-74.

6. Zenk, S., et al., Neighborhood racial composition, neighborhood poverty, and supermarket accessibility in metropolitan 

Detroit. American Journal of Public Health, 2005. 95(4): p. 660-667.

7. Exposure to toxic environmental agents. Fertil Steril, 2013. 100(4): p. 931-4.

8. Committee on Improving Risk Assessment of Hazardous Air Pollutants, C.o.L.S., National Research Council, Science 

and Judgement in Risk Assessment. 1994, The National Academies Press.

9. Omenn, G. Framework for Environmental Health Risk Management: Final Report by the Presidential/Congressional 

Commission on Risk Assessment and Risk Management. . 1997.

10. Committee on Improving Risk Analysis Approaches Used by the US EPA, N.R.C., Science and Decisions: Advancing Risk 

Assessment 2009, The National Academies Press.

11. Agency, E.P. Federal Register. National Ambient Air Quality Standards for Ozone; Proposed Rule. 2014.

12. Koman, P. Public Comment on Ozone Risk and Exposure Assessment and Policy Assessment. Comment on the Federal 

Register, 2014.

13. American Thoracic Society, What constitutes an adverse health effect of air pollution? Official statement of the 

American Thoracic Society. Am J Respir Crit Care Med, 2000. 161: p. 665-73.

14. Jackson, L. Response to Ozone Integrated Science Assessment (Third External Review Draft) for National Ambient Air 

Quality Standards Review. 2013.

15. Payne-Sturgis, D. and L. Martin, The Cumulative Risk Assessment Webinar Series: What We Learned, 

N.C.f.E.R.a.O.o.t.S.A. Office of Research and Development, Risk Assessment Forum Cumulative Risk Technical Panel, 

Environmental Protection Agency., Editor. 2014.

16. Mannino, D.M., What constitutes an adverse health effect of air pollution? American journal of respiratory and critical 

care medicine, 2000. 161(2 pt 1): p. 665-673.

17. Zanobetti, A. and J. Schwartz, Ozone and survival in four cohorts with potentially predisposing diseases. American 

journal of respiratory and critical care medicine, 2011. 184(7): p. 836-841.

18. Brulle, R.J. and D.N. Pellow, Environmental justice: human health and environmental inequalities. Annu Rev Public 

Health, 2006. 27: p. 103-24.

19. EPA, U. Regulatory Impact Analysis of the Proposed Revisions to the National Ambient Air Quality Standards for 

Ground-Level Ozone. 2014.
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Contact Amy Schulz (ajschulz@umich.edu) for additional information. Produced by the Detroit Reproductive 

Environmental Advocacy Matters Working Group: Donele Wilkins, Amy Schulz, Natalie Sampson, Kelly 

Ferguson, Chris Coombe, and Trish Koman. April 5, 2015.

20. Evans, G.W. and E. Kantrowitz, Socioeconomic status and health: the potential role of environmental risk exposure.

Annu Rev Public Health, 2002. 23: p. 303-31.

21. Farley, T.A., et al., The relationship between the neighbourhood environment and adverse birth outcomes. Paediatric 

and perinatal epidemiology, 2006. 20(3): p. 188-200.

22. O'Neill, M.S., et al., Air pollution, inflammation and preterm birth in Mexico City: study design and methods. Sci Total 

Environ, 2013. 448: p. 79-83.

23. Ritz, B. and M. Wilhelm, Ambient air pollution and adverse birth outcomes: methodologic issues in an emerging field.

Basic Clin Pharmacol Toxicol, 2008. 102(2): p. 182-90.

24. Woodruff, T.J., et al., Disparities in exposure to air pollution during pregnancy. Environ Health Perspect, 2003. 111(7): 

p. 942-6.