Association among socioeconomic factors, acute PM 2.5 exposure and cause-specific mortality

Background: Our aim was to evaluate the acute effect of fine particulate matter (PM 2.5) on cause-specific mortality with special focus on high and low socioeconomic status (SES) regions in the Sacramento Valley Air Basin, California from 1999-2002.

Methods: Mortality data were obtained from the California Department of Health Services and categorized by ICD-10 code into daily counts of cardiovascular, respiratory, central nervous system, and diabetic deaths. Air pollution and meteorological data were obtained from the Air Resources Board. Factor analysis was performed on 16 socio-economic indicators, drawn from U.S. Census 2000. The resulting distribution of SES index was dichotomized above and below the median. Generalized estimating equations were performed to investigate the association between acute effect of PM 2.5 and daily mortality.

Results: The effects were more pronounced among regions with lower SES index. The estimated increase in the crude relative rates for cardiovascular, respiratory, central nervous, and diabetes related mortalities were 13%, 19%, 27% and 19% respectively among regions with lower SES and 6%, 8%, 13% and 1% respectively among regions with higher SES per 10 µg/m3 increment of 3 days lag PM 2.5. There were no significant differences detected in other non-injury deaths and PM 2.5 exposures.

Conclusions: Our results provide evidence of a mortality effect of PM 2.5 and suggest a stronger effect of PM 2.5 in regions with low SES. This may indicate that one potential mechanism by which SES affects health is by increasing susceptibility to air pollution impacts.