Air pollution and mortality: A case study of ozone and respiratory disease mortality in the United States

Background: Exposure to air pollution is associated with numerous effects on human health, including pulmonary, cardiac, vascular, and neurological impairments. Epidemiological studies typically have shown a link between respiratory disease mortality and exposure to ambient ozone, although most have been limited to certain geographic areas. This nationwide case study examines the ecological association between ozone exposure and chronic lower respiratory disease (CLRD) mortality at the county level, where prevention strategies could be initiated or enhanced. Material and Method: Median daily ozone levels during 2001-2006 were derived from EPA modeled data, deaths from CLRD (ICD10: J40-J47) during 2002-2007 from the NCHS, poverty from U.S. Census Bureau SAIPE, smoking and obesity form CDC BRFSS, and urbanization data from NCHS urban-rural classification. We developed a multilevel Poisson Bayesian hierarchical model to estimate the association between county-level ozone exposure and CLRD mortality, adjusted for poverty, smoking, obesity, and urbanization, with random effects at county and state levels. We restricted our analysis to non-Hispanic white, aged 65 years and older, accounting for 78% of all CLRD deaths (592,822 out of 756,601). Results: Annual county-level median ozone exposure ranged from 27ppb to 52ppb (median 39ppb) during 2001-2006. The estimated relative risk of death from respiratory causes associated with 10 ppb increment in median ozone exposure was 1.020 (95% CI, 1.019 to 1.021). Conclusions: We found ozone exposure and CLRD mortality were positively associated at the county level. Thus, prevention strategies in reducing ambient ozone and precursor concentrations should be considered in order to reduce deaths from respiratory causes. The study highlights where the prevention should be initiated or enhanced.