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The concentration-response relation between PM(2.5) and daily deaths
Joel Schwartz1, Francine Laden, Antonella Zanobetti
1Environmental Epidemiology Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts 02115, USA. jschwrtz@hsph.harvard.edu
Environmental Health Perspectives
|October 4, 2002
Summary
Exposure to fine particulate matter (PM2.5) air pollution is linked to daily deaths, even at low concentrations. This study found a linear relationship with no safe threshold, suggesting significant public health benefits from reducing PM2.5.
Area of Science:
- Environmental Health
- Epidemiology
- Toxicology
Background:
- Particulate air pollution, particularly fine particulate matter (PM2.5), is a known contributor to daily mortality.
- Previous studies on PM10 suggested a linear association with mortality without a threshold, but PM2.5 has not been as extensively studied at low doses.
Purpose of the Study:
- To investigate the concentration-response relationship between fine particulate matter (PM2.5) and daily mortality in a multi-city analysis.
- To determine if a threshold exists for the association between PM2.5 exposure and daily deaths.
Main Methods:
- A hierarchical modeling approach was used across six U.S. cities.
- Log-linear models with smooth functions of PM2.5 were fitted in each city, controlling for seasonality, weather, and day of the week.
- Estimated city-specific curves were combined to allow for heterogeneity and robust estimation.
Main Results:
- An essentially linear association between PM2.5 and daily deaths was observed down to concentrations of 2 microg/m(3).
- No evidence of a threshold was found for the association between PM2.5 and daily mortality.
- Similar findings were observed for traffic particles, even after controlling for other particle sources.
Conclusions:
- The relationship between fine particulate matter (PM2.5) and daily mortality is linear and extends to low concentrations, indicating no safe threshold.
- Reducing fine particle air pollution could prevent thousands of premature deaths annually.
- These findings underscore the public health importance of stringent air quality standards for PM2.5.