Spatial analysis of air pollution and mortality in California

Rationale: Although substantial scientific evidence suggests that chronic exposure to ambient air pollution contributes to premature mortality, uncertainties exist in the size and consistency of this association. Uncertaintymayarise from inaccurate exposure assessment. Objectives: To assess the associations of three types of air pollutants (fine particulate matter, ozone [O₃], and nitrogen dioxide [NO₂]) with the risk of mortality in a large cohort of California adults using individualized exposure assessments. Methods: For fine particulate matter and NO₂, we used land use regression models to derive predicted individualized exposure at the home address. For O₃, we estimated exposure with an inverse distance weighting interpolation. Standard and multilevel Cox survival models were used to assess the association between air pollution and mortality. Measurements and Main Results: Data for 73,711 subjects who resided in California were abstracted from the American Cancer Society Cancer Prevention II Study cohort, with baseline ascertainment of individual characteristics in 1982 and follow-up of vital status through to 2000. Exposure data were derived from government monitors. Exposure to fine particulate matter, O₃, and NO₂ was positively associated with ischemic heart disease mortality. NO₂ (a marker for traffic pollution) and fine particulate matter were also associated with mortality from all causes combined. Only NO₂ had significant positive association with lung cancer mortality. Conclusions: Using the first individualized exposure assignments in this important cohort, we found positive associations of fine particulate matter,O₃,andNO ₂ with mortality.Thepositive associations of NO₂ suggest that traffic pollution relates to premature death.