Academic journal article Environmental Health Perspectives

Air Pollution and Daily Hospital Admissions in Metropolitan Los Angeles

Academic journal article Environmental Health Perspectives

Air Pollution and Daily Hospital Admissions in Metropolitan Los Angeles

Article excerpt

We used daily time-series analysis to evaluate associations between ambient carbon monoxide, nitrogen dioxide, particulate matter [is greater than or equal to] 10 [micro]m in aerodynamic diameter ([PM.sub.10]), or ozone concentrations, and hospital admissions for cardiopulmonary illnesses in metropolitan Los Angeles during 1992-1995. We performed Poisson regressions for the entire patient population and for subgroups defined by season, region, or personal characteristics, allowing for effects of temporal variation, weather, and autocorrelation. CO showed the most consistently significant (p [is less than] 0.05) relationships to cardiovascular admissions. A wintertime 25th-75th percentile increase in CO (1.1-2.2 ppm) predicted an increase of 4% in cardiovascular admissions. [NO.sub.2], and, to a lesser extent, [PM.sub.10] tracked CO and showed similar associations with cardiovascular disease, but [O.sub.3] was negatively or nonsignificantly associated. No significant demographic differences were found, although increased cardiovascular effects were suggested in diabetics, in whites and blacks (relative to Hispanics and Asians), and in persons older than 65 years of age. Pulmonary disease admissions associated more with [NO.sub.2] and [PM.sub.10] than with CO. Pulmonary effects were generally smaller than cardiovascular effects and were more sensitive to the choice of model. We conclude that in Los Angeles, atmospheric stagnation with high primary (CO/[NO.sub.2]/[PM.sub.10]) pollution, most common in autumn/winter, increases the risk of hospitalization for cardiopulmonary illness. Summer photochemical pollution (high [O.sub.3]) apparently presents less risk. Key words: air pollutants, carbon monoxide, epidemiology, Los Angeles, morbidity, nitrogen dioxide, ozone, particulate matter. Environ Health Perspect 108:427-434 (2000). [Online 27 March 2000] http://ehpnet1.niehs.nih.gov/docs/2000/108p427-434linn/abstract.html

Time-series analyses of daily mortality or morbidity have shown statistical associations with air pollution in cities throughout the world. Physiologic/toxicologic mechanisms of these phenomena remain unknown, and time-series analyses have not clearly linked specific pollutants with specific health outcomes (1-3); thus, their application to pollution-control policy decisions remains controversial (4). Combustion-related particulate matter, the only pollutant common to virtually all locations of time-series studies, has been the focus of scientific and regulatory attention (1,2,4-6). However, recent studies in a number of North American cities also associate cardiovascular and/or pulmonary disease incidence with pollutant gases such as carbon monoxide, nitrogen dioxide, and/or ozone (7-12). Where they are not highly correlated, gas and particulate pollutants appear to have separate statistically and medically significant influences on cardiopulmonary morbidity (9,11,12).

The Los Angeles metropolitan area has been studied relatively little by time-series analysis, but is a good candidate for study because of its large diverse population ([approximately equals] 14 million); detailed monitoring of air quality and hospital admissions; mild climate, which should limit confounding of pollution effects by weather stresses; and severe but widely variable air pollution (with maximum levels of primary pollutant gases, secondary photochemical oxidant gases, and particulate pollution occurring at somewhat different times and places). Powerful tests of pollution effects should be possible in the entire metropolitan population and in subpopulations defined geographically, demographically, or clinically. We hypothesized that regional and/or seasonal differences in time-series analysis results in the general population and/or in particular subgroups, would allow us to distinguish effects associated with primary pollutants (CO or [NO.sub.2]), photochemical oxidants ([O.sub.3]), or particulate matter more clearly than has been possible elsewhere. …

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