Air Pollution and Daily Mortality in Three U.S. Counties
Moolgavkar, Suresh H., Environmental Health Perspectives
I used generalized additive models to analyze the time-series of daily total nonaccidental and cause-specific (cardiovascular, cerebrovascular, and chronic obstructive pulmonary disease) deaths over the period 1987-1995 in three major U.S. metropolitan areas: Cook County, Los Angeles County, and Maricopa County. In all three counties I had monitoring information on particulate matter [is less than or equal to] 10 [micro]m ([PM.sub.10]), carbon monoxide, sulfur dioxide, nitrogen dioxide, and ozone. In Los Angeles, monitoring information on particulate matter [is less than or equal to] 2.5 [micro]m ([PM.sub.2.5]) was available as well. I present the results of both single and multi-pollutant analyses. Air pollution was associated with each of the mortality end points. With respect to the individual components of the pollution mix, the results indicate considerable heterogeneity of air pollution effects in the different geographic locations. In general, the gases, particularly CO, but not ozone, were much more strongly associated with mortality than was particulate matter. This association was particularly striking in Los Angeles County. Key words: carbon monoxide, cardiovascular disease, cerebrovascular disease, chronic obstructive pulmonary disease, nitrogen dioxide, ozone, particulate matter, sulfur dioxide. Environ Health Perspect 108:777-784 (2000). [Online 12 July 2000] http.//ehpnet1.niehs.nih.gov/docs/2000/108p777-784moolgavkar/abstract.html
A substantial body of epidemiologic literature indicates that air pollution, even at the generally low concentrations found in contemporary U.S., Canadian, and western European cities, is associated with adverse effects on human health. Reported effects of air pollution include decreased lung function (1,2), increased emergency room visits for asthma (3), increased hospital admissions (4,5) and, most importantly, increased mortality (6-16). Although human populations are exposed to a complex mixture of air pollutants that vary in composition with geography and climatic conditions, much of the recent work on air pollution epidemiology has focused on individual components of air pollution, rather than sources of pollution or the entire pollution mix. Because the estimated risks of adverse health effects from exposure are small, it is difficult to investigate the effect of individual components on human health. Therefore, consistency of results from different geographic areas with different climatic conditions and pollution mixes is an important consideration in drawing conclusions regarding the health effects of individual components of air pollution.
In this paper I analyzed the association between air pollution and the time-series of daily deaths in three large U.S. metropolitan areas, Cook County, Illinois, Los Angeles County, California, and Maricopa County, Arizona, with different pollution mixes and climatic conditions. Specifically, I investigated the association between monitored components of air pollution and daily nonaccidental deaths in these three areas over the 9-year period 1987-1995. In addition to total nonaccidental deaths, I also analyzed deaths from cardiovascular disease (CVD), cerebrovascular disease (CrD), and chronic obstructive lung disease and allied conditions (COPD). I undertook the analyses described in this paper to determine whether, when identical methods of analyses over the same period of time are used in different geographic locations, the results for individual components of pollution are consistent. My analyses indicated that, although air pollution was associated with daily mortality in all three metropolitan areas, there was considerable heterogeneity from one location to another. I conclude that, while a direct effect of individual components of air pollution on mortality cannot be ruled out, individual monitored components of air pollution are best thought of as indices of the air pollution mix associated with mortality and that the best index varies from one location to another. …