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Environ Health Perspect. 2012 Jul;120(7):965-70. doi: 10.1289/ehp.1104660. Epub 2012 Mar 28.

Chronic exposure to fine particles and mortality: an extended follow-up of the Harvard Six Cities study from 1974 to 2009.

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  • 1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02215, USA. jlepeule@hsph.harvard.edu

Abstract

BACKGROUND:

Epidemiologic studies have reported associations between fine particles (aerodynamic diameter ≤ 2.5 µm; PM2.5) and mortality. However, concerns have been raised regarding the sensitivity of the results to model specifications, lower exposures, and averaging time.

OBJECTIVE:

We addressed these issues using 11 additional years of follow-up of the Harvard Six Cities study, incorporating recent lower exposures.

METHODS:

We replicated the previously applied Cox regression, and examined different time lags, the shape of the concentration-response relationship using penalized splines, and changes in the slope of the relation over time. We then conducted Poisson survival analysis with time-varying effects for smoking, sex, and education.

RESULTS:

Since 2001, average PM2.5 levels, for all six cities, were < 18 µg/m3. Each increase in PM2.5 (10 µg/m3) was associated with an adjusted increased risk of all-cause mortality (PM2.5 average on previous year) of 14% [95% confidence interval (CI): 7, 22], and with 26% (95% CI: 14, 40) and 37% (95% CI: 7, 75) increases in cardiovascular and lung-cancer mortality (PM2.5 average of three previous years), respectively. The concentration-response relationship was linear down to PM2.5 concentrations of 8 µg/m3. Mortality rate ratios for PM2.5 fluctuated over time, but without clear trends despite a substantial drop in the sulfate fraction. Poisson models produced similar results.

CONCLUSIONS:

These results suggest that further public policy efforts that reduce fine particulate matter air pollution are likely to have continuing public health benefits.

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PMID:
22456598
[PubMed - indexed for MEDLINE]
PMCID:
PMC3404667
Free PMC Article
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