A CRITICAL-REVIEW OF STUDIES OF THE ASSOCIATION BETWEEN DEMANDS FOR HOSPITAL SERVICES AND AIR-POLLUTION

Studies of the associations between air pollution and hospital admissi ons and emergency room use are reviewed, including studies of air poll ution episodes, time-series analyses, and cross-sectional analyses. Th ese studies encompass a variety of,methods of analysis and levels of a ir quality. Findings from all three types of studies were generally co nsistent in that almost all of the studies reviewed found statisticall y significant associations between hospital use and air pollution; thi s unanimity may have resulted in part from publication bias. These ass ociations were characterized by elasticities of the order of 0.20; i.e , a 100% change in air pollution was associated with a change in hospi tal use of about 20%, for specific diagnoses. Respiratory diagnoses we re emphasized by most studies; cardiac diagnoses were included in five of them. The air pollutants most often associated with changes in hos pital use were particulate matter, sulfur oxides, and oxidants. Apart from the major air pollution episodes, there was no obvious link betwe en air pollution level and the significance or magnitudes of the assoc iations. Long-term indicators of hospitalization appeared to also be i nfluenced by medical care supply factors, including the numbers of bed s and physicians per capita. These nonpathological causal factors coul d also have influenced the findings of the time-series studies by intr oducing extraneous factors in the patterns of admissions. Although con sistent associations have been shown between hospital use and air poll ution, further research is required to distinguish among potentially r esponsible pollutants and to deduce specific dose-response relationshi ps of general utility.