PARTICULATE AIR-POLLUTION AND DAILY MORTALITY - WHO IS AT RISK

Major episodes of air pollution, such as the London fog incident in 19 52, have shown conclusively that relatively high levels of particulate air pollution can Lead to serious adverse health effects, including d eath. Recent data suggest that exposure to respirable particulates [wi th an aerodynamic diameter less than or equal to 10 mu m (PM(10))] und er the current American standard (150 mu g/m(3) for 24 h) is associate d with increased daily mortality. These results have sparked an intens e debate regarding the veracity of the reported associations and wheth er they should be interpreted causally. Most investigators have relied on a time-series approach to investigate the short-term effects of ai r pollution on daily mortality. Concerns have been expressed that the results may vary with the type of statistical methods used and the pot ential for uncontrolled and residual confounding effects, Of perhaps g reater importance is that cause-specific mortality, temporal aspects o f the exposure-disease relationship, and subgroups of the population h ave not been studied adequately, Under the hypothesis that only person s with impaired physiologic systems should be at risk, the identificat ion of susceptible subgroups is of great importance in discerning caus al mechanisms and in setting public health policies. In this paper, th e main methodologic issues are discussed and a novel design to identif y at-risk subgroups is presented.