Abstract
BackgroundMost health effects studies of ozone and temperature have been performed in urban areas, due to the available monitoring data. We used observed and interpolated data to examine temperature, ozone, and mortality in 91 urban and non-urban counties.MethodsOzone measurements were extracted from the Environmental Protection Agency’s Air Quality System. Meteorological data were supplied by the National Center for Atmospheric Research. Observed data were spatially interpolated to county centroids. Daily internal-cause mortality counts were obtained from the National Center for Health Statistics (1988–1999). A two-stage Bayesian hierarchical model was used to estimate each county’s increase in mortality risk from temperature and ozone. We examined county-level associations according to population density and compared urban (≥1,000 persons/mile2) to non-urban (<1,000 persons/mile2) counties. Finally, we examined county-level characteristics that could explain variation in associations by county.ResultsA 10 ppb increase in ozone was associated with a 0.45% increase in mortality (95% PI: 0.08, 0.83) in urban counties, while this same increase in ozone was associated with a 0.73% increase (95% PI: 0.19, 1.26) in non-urban counties. An increase in temperature from 70°F to 90°F (21.2°C 32.2°C) was associated with a 8.88% increase in mortality (95% PI: 7.38, 10.41) in urban counties and a 8.08% increase (95% PI: 6.16, 10.05) in non-urban counties. County characteristics, such as population density, percentage of families living in poverty, and percentage of elderly residents, partially explained the variation in county-level associations.ConclusionsWhile most prior studies of ozone and temperature have been performed in urban areas, the impacts in non-urban areas are significant, and, for ozone, potentially greater. The health risks of increasing temperature and air pollution brought on by climate change are not limited to urban areas.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-069X-14-3) contains supplementary material, which is available to authorized users.
Highlights
Ground level ozone and temperature are current environmental health stressors that are expected to worsen with climate change
Observed data analysis In the analysis of 12 counties with observed data, we found that an increase in exposure to ozone was associated with an increase in risk of mortality in the majority of counties (Figure 1a)
When we generated an overall effect across counties by combining county-specific effect estimates, we found that a 10 ppb increase in daily 8-hour maximum ozone was associated with a 0.80% increase in mortality [95% Posterior Interval (PI): 0.31, 1.30], after adjusting for temperature
Summary
Ground level ozone and temperature are current environmental health stressors that are expected to worsen with climate change. Most health effects studies of ozone and temperature have been performed in urban areas [1,9,10,11] and very limited work has been done in suburban and rural areas [12,13,14] with conflicting results as to whether the magnitude of risk is the same in urban and non-urban areas. If non-urban areas are at risk, local public health departments may be ill equipped to deal with the health impacts of a changing climate, or even to develop efficient policies to mitigate the current risks. Most health effects studies of ozone and temperature have been performed in urban areas, due to the available monitoring data. We used observed and interpolated data to examine temperature, ozone, and mortality in 91 urban and non-urban counties
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