Fine particulate air pollution and mortality in 20 US Cities, 1987-1994.

Background: Air pollution in cities has been linked to increased rates of m ortality and morbidity in developed and developing countries. Although thes e 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 da ily mortality rates in 20 of the largest cities and metropolitan areas in t he United States from 1987 to 1994. The pollutants were particulate matter that is less than 10 mum in aerodynamic diameter (PM10), ozone, carbon mono xide, sulfur dioxide, and nitrogen dioxide. We used a two-stage analytic ap proach that pooled data from multiple locations. Results: After taking into account potential confounding by other pollutant s, we found consistent evidence that the level of PM(sub 10) is associated with the rate of death from all causes and from cardiovascular and respirat ory illnesses. The estimated increase in the relative rate of death from al l causes was 0.51 percent (95 percent posterior interval, 0.07 to 0.93 perc ent) for each increase in the PM10 level of 10 mug per cubic meter. The est imated increase in the relative rate of death from cardiovascular and respi ratory causes was 0.68 percent (95 percent posterior interval, 0.20 to 1.16 percent) for each increase in the PM10 level of 10 mug per cubic meter. Th ere was weaker evidence that increases in ozone levels increased the relati ve rates of death during the summer, when ozone levels are highest, but not during the winter. Levels of the other pollutants were not significantly r elated to the mortality rate. Conclusions: There is consistent evidence that the levels of fine particula te matter in the air are associated with the risk of death from all causes and from cardiovascular and respiratory illnesses. These findings strengthe n the rationale for controlling the levels of respirable particles in outdo or air. (N Engl J Med 2000;343:1742-9.) (C) 2000, Massachusetts Medical Soc iety.