Is there a causal association between excess mortality and exposure to PM-10 air pollution? additional analyses by location, year, season, and cause of death

We examined the association between exposure to PM-10 air pollution and daily mortality in Utah County, Utah, for 1985-1992. We confirmed the previous finding that exposure to fine particulate air pollution (particulate diameter of <10 μm) in amounts of 50+ μg/m³ increased daily mortality by 4% The potential importance of this observation led us to test the association more rigorously by assessing rate ratios (RR) of PM-10 for year, season, and location at time of death. For individual years there was no statistically significant association between increased mortality and exposure to PM-10 air pollution. The strongest mortality effect was seen in the spring, not the winter. The largest numeric contribution to excess mortality was from individuals age 75 + yr dying in a hospital, and the largest RR was for individuals ages 15-59 yr dying at home, primarily of cancer. These findings do not support a causal association between exposure to PM-10 air pollution and daily mortality.