The Sixteenth Conference of the International Society for Environmental Epidemiology (ISEE): Abstracts
Studies using the American Cancer Society (ACS) cohort to assess the relation between air pollution and mortality have been criticized for modeling effects over metropolitan areas that fail to capture gradients in exposure and confounders at the correct scale of influence. We have addressed this criticism by modeling the association between air pollution and mortality at the intra-urban scale in Los Angeles, California.
We extracted 22,905 subjects from the ACS Cancer Prevention II survey for the Los Angeles Metropolitan area (5891 deaths). Pollution exposures were interpolated from 23 PM2.5 monitoring locations and 42 O3 fixed-site monitors. Associations were tested in both standard and multilevel Cox regression models.
We observed much larger PM2.5 effects than in previous ACS studies. Based on a 10 mg/m3 contrast, all cause morality had a relative risk (RR) of 1.17 (95% CI: 1.05-1.30) with control for 44 individual variables, and a RR of 1.11 (0.99-1.25) with maximal control for individual and ecologic confounders. The RR for ischemic heart disease deaths were significantly elevated and in the range of 1.24-1.46.
Our results suggest the chronic health effects of exposure to PM2.5 are probably larger than previously reported. Using the direct comparison to earlier ACS studies, we see effects nearly three times larger than in models relying on between-community exposure contrasts. We also found convincing evidence of specificity in our health effects, with a stronger association between ischemic heart disease and air pollution than between the more general measures of cardio-pulmonary deaths or all-cause mortality.