FINE PARTICULATE AIR POLLUTION AND MORTALITY IN 20 U.S. CITIES, 1987â 1994

BACKGROUND: Air pollution in cities has been linked to increased rates of mortality and morbidity in developed and developing countries. Although these findings have helped lead to a tightening of air-quality standards, their validity with respect to public health has been questioned. METHODS: We assessed the effects of five major outdoor-air pollutants on daily mortality rates in 20 of the largest cities and metropolitan areas in the United States from 1987 to 1994. The pollutants were particulate matter that is less than 10 microm in aerodynamic diameter (PM10), ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. We used a two-stage analytic approach that pooled data from multiple locations. RESULTS: After taking into account potential confounding by other pollutants, we found consistent evidence that the level of PM10 is associated with the rate of death from all causes and from cardiovascular and respiratory illnesses. The estimated increase in the relative rate of death from all causes was 0.51 percent (95 percent posterior interval, 0.07 to 0.93 percent) for each increase in the PM10 level of 10 microg per cubic meter. The estimated increase in the relative rate of death from cardiovascular and respiratory causes was 0.68 percent (95 percent posterior interval, 0.20 to 1.16 percent) for each increase in the PM10 level of 10 microg per cubic meter. There was weaker evidence that increases in ozone levels increased the relative rates of death during the summer, when ozone levels are highest, but not during the winter. Levels of the other pollutants were not significantly related to the mortality rate. CONCLUSIONS: There is consistent evidence that the levels of fine particulate matter in the air are associated with the risk of death from all causes and from cardiovascular and respiratory illnesses. These findings strengthen the rationale for controlling the levels of respirable particles in outdoor air

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Abstract Background: Time-series analyses have linked contemporary levels of air pollution, particularly particles, to daily mortality counts. These findings have contributed to the rationale for tightening air quality standards, but the validity of these findings has been questioned. We have developed analytic methods to address limitations of prior single-city time-series analyses by combining evidence across multiple locations. Methods: Using a two-stage analytic approach that pools evidence from multiple locations, we have assessed the effects of five major outdoor air pollutants, particulate matter less than 10 µm in aerodynamic diameter (PM 10 ), ozone (O 3 ), carbon monoxide (CO), sulfur dioxide (SO 2 ), and nitrogen dioxide (NO 2 ), on daily mortality in 20 of the largest cities in the United States, from 1987-1994. Results: We found consistent evidence that PM 10 is associated with total and cardiorespiratory mortality after taking into account potential confounding by other pollutants. For total mortality, the estimated relative rate was approximately a 0.5% increase in mortality per 10 µg/m 3 increase in PM 10 and the effect was not likely to be due to chance. There was weaker evidence that ozone increased mortality during the summer but not the winter months. Other pollutants did not have effects on mortality. Conclusions: The analyses provide evidence that air pollution with particles is still adversely affecting the public's health and strengthen the rationale for limiting concentrations of respirable particles in outdoor air. Air Pollution and Mortality in 20 U.S. Cities