Background: Population-based studies have estimated health risks of short-term exposure to fine
particles using mass of PM2.5 (particulate matter ≤ 2.5 μm in aerodynamic diameter) as the indicator. Evidence
regarding the toxicity of the chemical components of the PM2.5 mixture is limited.
Objective: In this study we investigated the association between hospital admission for cardiovascular
disease (CVD) and respiratory disease and the chemical components of PM2.5 in the United States.
Methods: We used a national database comprising daily data for 2000–2006 on emergency hospital
admissions for cardiovascular and respiratory outcomes, ambient levels of major PM2.5 chemical components [sulfate, nitrate, silicon, elemental carbon (EC), organic carbon
matter (OCM), and sodium and ammonium ions], and weather. Using Bayesian hierarchical
statistical models, we estimated the associations between daily levels of PM2.5 components and risk of hospital admissions in 119 U.S. urban communities for 12 million
Medicare enrollees (≥ 65 years of age).
Results: In multiple-pollutant models that adjust for the levels of other pollutants, an interquartile
range (IQR) increase in EC was associated with a 0.80% [95% posterior interval (PI),
0.34–1.27%] increase in risk of same-day cardiovascular admissions, and an IQR increase
in OCM was associated with a 1.01% (95% PI, 0.04–1.98%) increase in risk of respiratory
admissions on the same day. Other components were not associated with cardiovascular
or respiratory hospital admissions in multiple-pollutant models.
Conclusions: Ambient levels of EC and OCM, which are generated primarily from vehicle emissions,
diesel, and wood burning, were associated with the largest risks of emergency hospitalization
across the major chemical constituents of PM2.5.
Background: Recent toxicological and epidemiological studies have shown associations between particulate
matter (PM) and adverse health effects, but which PM components are most influential
is less well known.
Objectives: In this study, we used time-series analyses to determine the associations between
daily fine PM [PM ≤ 2.5 μm in aerodynamic diameter (PM2.5)] concentrations and daily mortality in two U.S. cities—Seattle, Washington, and
Methods: We obtained daily PM2.5 filters for the years of 2002–2004 and analyzed trace elements using X-ray fluorescence
and black carbon using light reflectance as a surrogate measure of elemental carbon.
We used Poisson regression and distributed lag models to estimate excess deaths for
all causes and for cardiovascular and respiratory diseases adjusting for time-varying
covariates. We computed the excess risks for interquartile range increases of each
pollutant at lags of 0 through 3 days for both warm and cold seasons.
Results: The cardiovascular and respiratory mortality series exhibited different source and
seasonal patterns in each city. The PM2.5 components and gaseous pollutants associated with mortality in Detroit were most
associated with warm season secondary aerosols and traffic markers. In Seattle, the
component species most closely associated with mortality included those for cold season
traffic and other combustion sources, such as residual oil and wood burning.
Conclusions: The effects of PM2.5 on daily mortality vary with source, season, and locale, consistent with the hypothesis
that PM composition has an appreciable influence on the health effects attributable
Background: Growing evidence indicates that toxicity of fine particulate matter ≤
2.5 μm in diameter (PM2.5) differs by chemical component. Exposure to components may differ by population.
Objectives: We investigated whether exposures to PM2.5 components differ by race/ethnicity, age, and socioeconomic status (SES).
Methods: Long-term exposures (2000 through 2006) were estimated for 215 U.S. census
tracts for PM2.5 and for 14 PM2.5 components. Population-weighted exposures were combined to generate overall estimated
exposures by race/ethnicity, education, poverty status, employment, age, and earnings.
We compared population characteristics for tracts with and without PM2.5 component monitors.
Results: Larger disparities in estimated exposures were observed for components than
for PM2.5 total mass. For race/ethnicity, whites generally had the lowest exposures. Non-Hispanic
blacks had higher exposures than did whites for 13 of the 14 components. Hispanics
generally had the highest exposures (e.g., 152% higher than whites for chlorine, 94%
higher for aluminum). Young persons (0–19 years of age) had levels as high as or higher
than other ages for all exposures except sulfate. Persons with lower SES had higher
estimated exposures, with some exceptions. For example, a 10% increase in the proportion
unemployed was associated with a 20.0% increase in vanadium and an 18.3% increase
in elemental carbon. Census tracts with monitors had more non-Hispanic blacks, lower
education and earnings, and higher unemployment and poverty than did tracts without
Conclusions: Exposures to PM2.5 components differed by race/ethnicity, age, and SES. If some components are more
toxic than others, certain populations are likely to suffer higher health burdens.
Demographics differed between populations covered and not covered by monitors.