Daily mortality is typically higher on hot days in urban areas, and certain population groups experience disproportionate risk. Air conditioning (AC) has been recommended to mitigate heat-related illness and death. We examined whether AC prevalence explained differing heat-related mortality effects by race. Poisson regression was used to model daily mortality in Chicago, Detroit, Minneapolis, and Pittsburgh. Predictors included natural splines of time (to control seasonal patterns); mean daily apparent temperature on the day of death, and averaged over lags 1–3; barometric pressure; day of week; and a linear term for airborne particles. Separate, city-specific models were fit to death counts stratified by race (Black or White) to derive the percent change in mortality at 29°C, relative to 15°C (lag 0). Next, city-specific effects were regressed on city-and race-specific AC prevalence. Combined effect estimates across all cities were calculated using inverse variance-weighted averages. Prevalence of central AC among Black households was less than half that among White households in all four cities, and deaths among Blacks were more strongly associated with hot temperatures. Central AC prevalence explained some of the differences in heat effects by race, but room-unit AC did not. Efforts to reduce disparities in heat-related mortality should consider access to AC.

Background— Epidemiological studies suggest that people with diabetes are vulnerable to cardiovascular health effects associated with exposure to particle air pollution. Endothelial and vascular function is impaired in diabetes and may be related to increased cardiovascular risk. We examined whether endothelium-dependent and -independent vascular reactivity was associated with particle exposure in individuals with and without diabetes. Methods and Results— Study subjects were 270 greater-Boston residents. We measured 24-hour average ambient levels of air pollution (fine particles [PM _2.5 ], particle number, black carbon, and sulfates [SO ₄ ²⁻ ]) ≈500 m from the patient examination site. Pollutant concentrations were evaluated for associations with vascular reactivity. Linear regressions were fit to the percent change in brachial artery diameter (flow mediated and nitroglycerin mediated), with the particulate pollutant index, apparent temperature, season, age, race, sex, smoking history, and body mass index as predictors. Models were fit to all subjects and then stratified by diagnosed diabetes versus at risk for diabetes. Six-day moving averages of all 4 particle metrics were associated with decreased vascular reactivity among patients with diabetes but not those at risk. Interquartile range increases in SO ₄ ²⁻ were associated with decreased flow-mediated (−10.7%; 95% CI, −17.3 to −3.5) and nitroglycerin-mediated (−5.4%; 95% CI, −10.5 to −0.1) vascular reactivity among those with diabetes. Black carbon increases were associated with decreased flow-mediated vascular reactivity (−12.6%; 95% CI, −21.7 to −2.4), and PM _2.5 was associated with nitroglycerin-mediated reactivity (−7.6%; 95% CI, −12.8 to −2.1). Effects were stronger in type II than type I diabetes. Conclusions— Diabetes confers vulnerability to particles associated with coal-burning power plants and traffic.

We evaluated temperature-related morbidity and mortality for the 2007 U.S. national assessment on impacts of climate change and variability on human health. We assessed literature published since the 2000 national assessment, evaluating epidemiologic studies, surveys, and studies projecting future impacts. Under current climate change projections, heat waves and hot weather are likely to increase in frequency, with the overall temperature distribution shifting away from the colder extremes. Vulnerable subgroups include communities in the northeastern and Midwestern U.S.; urban populations, the poor, the elderly, children, and those with impaired health or limited mobility. Temperature extremes and variability will remain important determinants of health in the United States under climate change. Research needs include estimating exposure to temperature extremes; studying nonfatal temperature-related illness; uniform criteria for reporting heat-related health outcomes; and improving effectiveness of urban heat island reduction and extreme weather response plans.