The Phase I.A Report of the Particle Epidemiology Evaluation Project.
The Health Effects Institute began the Particle Epidemiology Evaluation Project in 1994 to evaluate the emerging epidemiologic evidence of a relation between particulate air pollution and daily mortality. A growing number of studies reported that daily mortality rates rose in association with levels of particulate air pollution below the current National Ambient Air Quality Standard (NAAQS) for particulate matter. Some investigators interpreted their findings as indicating that particulate air pollution has a causal effect on increases in daily mortality. Critics disputed this interpretation, and questioned whether other scientists could replicate the results. Some critics asserted that the reported associations might be artifacts of the particular statistical methods used, or might be due to incomplete statistical adjustment for the effects of weather factors or other air pollutants.
In Phase I.A, Drs. Jonathan M. Samet and Scott L. Zeger and their colleagues at the Johns Hopkins University School of Hygiene and Public Health (1) reconstructed from original sources the data set for Philadelphia used in earlier studies and confirmed previous numerical results from analyzing these data; (2) developed an analytic approach (including new statistical methods) based on the Philadelphia data set; and (3) applied this approach to data sets for six locations: Philadelphia; Utah Valley; St. Louis, MO; Eastern Tennessee; Birmingham, AL; and Santa Clara County, CA.