Questions & Answers – Responses from Beth Hassett-Sipple, Nov. 2, 2011

Health Effects of PM Exposure

  1. How does socio-economic status effect risk levels?

Response: Stronger evidence is available in the current PM NAAQS review indicating that people from lower socioeconomic strata are a susceptible population relative to PM exposures (US EPA, 2009, section 8.1.7). Persons with lower socioeconomic status (SES)[1] have been generally found to have a higher prevalence of pre?existing diseases; limited access to medical treatment; and increased nutritional deficiencies, which can increase this population’s risk to PM-related effects. Evidence available in the last PM NAAQS review from the American Cancer Society (ACS) and Harvard Six Cities cohort studies indicated increased mortality risk with long-term exposure to PM2.5 in the cohort subgroups with lower education levels (US EPA 2004, section In this review, additional support is available to identify persons with lower SES as a susceptible population. For example, Krewski et al. (2009) found moderate evidence for increased lung cancer mortality in individuals with a high school education or less in response to long-term exposure to PM2.5. However, ischemic heart disease (IHD)-related mortality associated with long-term PM2.5 exposures was most strongly associated with individuals with higher education levels (US EPA, 2009, p. 8-15). Source – US EPA, 2011, p. 2-30.


  1. Have studies been conducted to determine which component of PM2.5 is most likely responsible for the adverse health effects of fine particle pollution?

Response: In considering the currently available evidence for health effects associated with specific PM2.5 components or groups of components associated with any source categories of fine particles, EPA’s Integrated Science Assessment (ISA) concludes that additional information available in the current PM NAAQS review continues to provide evidence that many different constituents of the fine particle mixture as well as groups of components associated with specific source categories of fine particles are linked to adverse health effects. However, as noted in the ISA, while “[t]here is some evidence for trends and patterns that link particular ambient PM constituents or sources with specific health outcomes…there is insufficient evidence to determine whether these patterns are consistent or robust” (US EPA, 2009, p. 6-210). Furthermore, the ISA concludes that “the evidence is not yet sufficient to allow differentiation of those constituents or sources that are more closely related to specific health outcomes” (US EPA, 2009, pp. 2-26 and 6-212). For more information see US EPA 2011, pp. 2-52 to 2-56.

[1] SES is a composite measure that usually consists of economic status, measured by income; social status measured by education; and work status measured by occupation (US EPA, 2009, p. 8-14).



Krewski D, Jerrett M, Burnett RT, Ma R, Hughes E, Shi Y, Turner MC, Pope AC III, Thurston G, Calle EE,
       Thun MJ (2009). Extended Follow-Up and Spatial Analysis of the American Cancer Society Study Linking
       Particulate Air Pollution and Mortality. HEI Research Report 140, Health Effects Institute, Boston, MA.

US EPA (2004). Air Quality Criteria for Particulate Matter. National Center for Environmental Assessment,
       Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park,
       NC 27711, report no. EPA/600/P-99/002aF and EPA/600/P-99/002bF. October 2004.

US EPA (2009). Integrated Science Assessment for Particulate Matter (Final Report). U.S. Environmental
      Protection Agency, Washington, DC, EPA/600/R-08/139F, December 2009.

US EPA (2011). Policy Assessment for the Review of the Particulate Matter National Ambient Air Quality
      Standards. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency,
      Research Triangle Park, NC. EPA 452/R-11-003. April 2011.