Mortality and air pollution : Is there a meaningM connection ? “ We grow weary of speculations about the Air ” -

764 Envimn. Sci. Technol.. MI. 19. No. 9. Is& control, and the specter of people dying in the streets during severe pollution episodes still remains. The worst episodes in terms of percentages of people affected, the Meuse (1) and Donora (2), were recognized as unfortunate incidents, but it was not until the effects of air pollution on major cities were identified, in London (3) and New York (9, that control efforts were taken seriously. It is the nahlre of the problem that even in a serious episode the dimension of the problem-the number of “excess” deaths-is not apparent until much later, when detailed statistid analysis has been done. The recent tragedy in Bhopal, India, involving methylisocyanate, a highly toxic gas, is one notable exception. Determining the chronic effects of air pollution on health and mortality presents an extremely subtle challenge to physicians and statisticians alike. Direct experiments involving long-term