Spatial and Temporal Variation in PM2.5 Chemical Composition in the United States for Health Effects Studies

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Abstract

Background

Although numerous studies have demonstrated links between particulate matter (PM) and adverse health effects, the chemical components of the PM mixture that cause injury are unknown.

Objectives

This work characterizes spatial and temporal variability of PM _2.5 (PM with aerodynamic diameter < 2.5 μm) components in the United States; our objective is to identify components for assessment in epidemiologic studies.

Methods

We constructed a database of 52 PM _2.5 component concentrations for 187 U.S. counties for 2000–2005. First, we describe the challenges inherent to analysis of a national PM _2.5 chemical composition database. Second, we identify components that contribute substantially to and/or co-vary with PM _2.5 total mass. Third, we characterize the seasonal and regional variability of targeted components.

Results

Strong seasonal and geographic variations in PM _2.5 chemical composition are identified. Only seven of the 52 components contributed ≥ 1% to total mass for yearly or seasonal averages [ammonium (NH ₄ ⁺), elemental carbon (EC), organic carbon matter (OCM), nitrate (NO ₃ ⁻), silicon, sodium (Na ⁺), and sulfate (SO ₄ ²⁻)]. Strongest correlations with PM _2.5 total mass were with NH ₄ ⁺ (yearly), OCM (especially winter), NO ₃ ⁻ (winter), and SO ₄ ²⁻ (yearly, spring, autumn, and summer), with particularly strong correlations for NH ₄ ⁺ and SO ₄ ²⁻ in summer. Components that co-varied with PM _2.5 total mass, based on daily detrended data, were NH ₄ ⁺, SO ₄ ²⁻ _, OCM, NO ₃ ²⁻, bromine, and EC.

Conclusions

The subset of identified PM _2.5 components should be investigated further to determine whether their daily variation is associated with daily variation of health indicators, and whether their seasonal and regional patterns can explain the seasonal and regional heterogeneity in PM ₁₀ (PM with aerodynamic diameter < 10 μm) and PM _2.5 health risks.

Related collections

Most cited references 25

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Association of fine particulate matter from different sources with daily mortality in six U.S. cities.

F Laden, L Neas, D W Dockery … (2000)

Previously we reported that fine particle mass (particulate matter [less than and equal to] 2.5 microm; PM(2.5)), which is primarily from combustion sources, but not coarse particle mass, which is primarily from crustal sources, was associated with daily mortality in six eastern U.S. cities (1). In this study, we used the elemental composition of size-fractionated particles to identify several distinct source-related fractions of fine particles and examined the association of these fractions with daily mortality in each of the six cities. Using specific rotation factor analysis for each city, we identified a silicon factor classified as soil and crustal material, a lead factor classified as motor vehicle exhaust, a selenium factor representing coal combustion, and up to two additional factors. We extracted daily counts of deaths from National Center for Health Statistics records and estimated city-specific associations of mortality with each source factor by Poisson regression, adjusting for time trends, weather, and the other source factors. Combined effect estimates were calculated as the inverse variance weighted mean of the city-specific estimates. In the combined analysis, a 10 microg/m(3) increase in PM(2.5) from mobile sources accounted for a 3.4% increase in daily mortality [95% confidence interval (CI), 1.7-5.2%], and the equivalent increase in fine particles from coal combustion sources accounted for a 1.1% increase [CI, 0.3-2.0%). PM(2.5) crustal particles were not associated with daily mortality. These results indicate that combustion particles in the fine fraction from mobile and coal combustion sources, but not fine crustal particles, are associated with increased mortality.

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Health effects of fine particulate air pollution: lines that connect.

D W Dockery, C Pope (2006)

Efforts to understand and mitigate thehealth effects of particulate matter (PM) air pollutionhave a rich and interesting history. This review focuseson six substantial lines of research that have been pursued since 1997 that have helped elucidate our understanding about the effects of PM on human health. There hasbeen substantial progress in the evaluation of PM health effects at different time-scales of exposure and in the exploration of the shape of the concentration-response function. There has also been emerging evidence of PM-related cardiovascular health effects and growing knowledge regarding interconnected general pathophysiological pathways that link PM exposure with cardiopulmonary morbidiity and mortality. Despite important gaps in scientific knowledge and continued reasons for some skepticism, a comprehensive evaluation of the research findings provides persuasive evidence that exposure to fine particulate air pollution has adverse effects on cardiopulmonaryhealth. Although much of this research has been motivated by environmental public health policy, these results have important scientific, medical, and public health implications that are broader than debates over legally mandated air quality standards.

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Association between PM2.5 and all-cause and specific-cause mortality in 27 US communities.

Joel Schwartz, Meredith Franklin, Ariana Zeka (2007)

While fine mode particulate matter (PM(2.5)) forms the basis for regulating particles in the US and other countries, there is a serious paucity of large population-based studies of its acute effect on mortality. To address this issue, we examined the association between PM(2.5) and both all-cause and specific-cause mortality using over 1.3 million deaths in 27 US communities between 1997 and 2002. A two-stage approach was used. First, the association between PM(2.5) and mortality in each community was quantified using a case-crossover design. Second, meta-analysis was used to estimate a summary effect over all 27 communities. Effect modification of age and gender was examined using interaction terms in the case-crossover model, while effect modification of community-specific characteristics including geographic location, annual PM(2.5) concentration above 15 microg/m(3) and central air conditioning prevalence was examined using meta-regression. We observed a 1.21% (95% CI 0.29, 2.14%) increase in all-cause mortality, a 1.78% (95% CI 0.20, 3.36%) increase in respiratory related mortality and a 1.03% (95% CI 0.02, 2.04%) increase in stroke related mortality with a 10 microg/m(3) increase in previous day's PM(2.5). The magnitude of these associations is more than triple that recently reported for PM(10), suggesting that combustion and traffic related particles are more toxic than larger sized particles. Effect modification occurred in all-cause and specific-cause deaths with greater effects in subjects >or=75 years of age. There was suggestive evidence that women may be more susceptible to PM(2.5) effects than men, and that effects were larger in the East than in the West. Increased prevalence of central air conditioning was associated with a decreased effect of PM(2.5). Our findings describe the magnitude of the effect on all-cause and specific-cause mortality, the modifiers of this association, and suggest that PM(2.5) may pose a public health risk even at or below current ambient levels.

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Author and article information

Journal

Journal ID (nlm-ta): Environ Health Perspect

Title: Environmental Health Perspectives

Publisher: National Institute of Environmental Health Sciences

ISSN (Print): 0091-6765

Publication date (Print): July 2007

Publication date (Electronic): 20 April 2007

Volume: 115

Issue: 7

Pages: 989-995

Affiliations

[1 ] School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut, USA

[2 ] Department of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

[3 ] School of Public Health, Yale University, New Haven, Connecticut, USA

[4 ] Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

Author notes

Address correspondence to M.L. Bell, Yale University, School of Forestry and Environmental Studies, 205 Prospect St., New Haven, Connecticut, USA. Telephone: (203) 432-9869. Fax: (203) 432-3817. E-mail: michelle.bell@ 123456yale.edu

The authors declare they have no competing financial interests.

Article

Publisher ID: ehp0115-000989

DOI: 10.1289/ehp.9621

PMC ID: 1913582

PubMed ID: 17637911

SO-VID: edc92b6e-d57b-4b7a-8cfc-5fe5226469c5

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