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. 2015 Jun;123(6):549-56.
doi: 10.1289/ehp.1408565. Epub 2015 Jan 23.

Associations of mortality with long-term exposures to fine and ultrafine particles, species and sources: results from the California Teachers Study Cohort

Bart Ostro  1 , Jianlin Hu, Debbie Goldberg, Peggy Reynolds, Andrew Hertz, Leslie Bernstein, Michael J Kleeman
Affiliations

Associations of mortality with long-term exposures to fine and ultrafine particles, species and sources: results from the California Teachers Study Cohort

Bart Ostro et al. Environ Health Perspect. 2015 Jun.

Abstract

Background: Although several cohort studies report associations between chronic exposure to fine particles (PM2.5) and mortality, few have studied the effects of chronic exposure to ultrafine (UF) particles. In addition, few studies have estimated the effects of the constituents of either PM2.5 or UF particles.

Methods: We used a statewide cohort of > 100,000 women from the California Teachers Study who were followed from 2001 through 2007. Exposure data at the residential level were provided by a chemical transport model that computed pollutant concentrations from > 900 sources in California. Besides particle mass, monthly concentrations of 11 species and 8 sources or primary particles were generated at 4-km grids. We used a Cox proportional hazards model to estimate the association between the pollutants and all-cause, cardiovascular, ischemic heart disease (IHD), and respiratory mortality.

Results: We observed statistically significant (p < 0.05) associations of IHD with PM2.5 mass, nitrate, elemental carbon (EC), copper (Cu), and secondary organics and the sources gas- and diesel-fueled vehicles, meat cooking, and high-sulfur fuel combustion. The hazard ratio estimate of 1.19 (95% CI: 1.08, 1.31) for IHD in association with a 10-μg/m3 increase in PM2.5 is consistent with findings from the American Cancer Society cohort. We also observed significant positive associations between IHD and several UF components including EC, Cu, metals, and mobile sources.

Conclusions: Using an emissions-based model with a 4-km spatial scale, we observed significant positive associations between IHD mortality and both fine and ultrafine particle species and sources. Our results suggest that the exposure model effectively measured local exposures and facilitated the examination of the relative toxicity of particle species.

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Conflict of interest statement

Although the research described in the article has been partially funded by the U.S. EPA, it has not been subject to the agency’s required peer and policy review and therefore does not necessarily reflect the views of the agency and no official endorsement should be inferred. All PM2.5 and ultrafine PM exposure data used in the present study is available free of charge at http://faculty.engineering.ucdavis.edu/kleeman/.

The authors declare they have no actual or potential competing financial interests.

Figures

Figure 1
Figure 1
Modeled concentrations (μg/m3) of PM2.5 nitrate (A), ultrafine anthropogenic secondary organic aerosols (B), and population in the Los Angeles Basin (C) using 4‑km grids (the star in the figures indicates the site of the U.S. EPA monitor).
Figure 2
Figure 2
Association of PM2.5 constituents and sources with IHD mortality (HRs and 95% CIs using interquartile range. Abbreviations: comb, combustion; comps, components.
See this image and copyright information in PMC

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