Air pollution and health - good news and bad.

Early concerns regarding the health-related effects of air pollution originated from severe episodes in Meuse Valley, Belgium, in 1930; Donora, Pennsylvania, in 1948; and London, in 1952. Although the overall effects of these episodes continue to be debated, well-documented, episode-related increases in morbidity and mortality from cardiopulmonary causes provided dramatic evidence that extremely high concentrations of air pollution can have serious adverse effects on health. Early public-policy efforts to improve air quality in the United States, Britain, and elsewhere were largely attempts to avert such “killer” episodes of air pollution. In the United States, a series of national legislative and regulatory efforts to control air pollution were initiated (Fig. 1); National Ambient Air Quality Standards were mandated and established; and dramatic, extremely severe episodes of air pollution were essentially eliminated. From the 1960s through the 1980s, a few scattered studies continued to suggest that air pollution had adverse effects on health. 1,2 Then, during the relatively short period of 1989 through 1995, several loosely connected epidemiologic studies reported adverse effects of unexpectedly low levels of particulate-matter air pollution. 3-6 Although highly controversial, 7 these results prompted serious reconsideration of the particulate-matter standards and health guidelines (Fig. 1). They also prompted extensive efforts to reanalyze key studies 8 (which were largely confirmatory) and motivated rapid growth in epidemiologic, toxicologic, and other studies of fine particulate matter and other combustion-related air pollutants. Research has continued to suggest that a level of air pollution that is common in many urban and industrial environments is an important risk factor for various adverse health effects in humans. Although many such studies have focused on respiratory disease, substantial and growing evidence indicates that fine particulate air pollution is also a risk factor for cardiovascular disease. 9,10 Short-term exposure exacerbates existing pulmonary and cardiovascular disease and increases the risk of symptoms, the need for medical attention, and death. 1