Effects of air pollution on daily clinic visits for lower respiratory tract illness.

The authors used data obtained from clinic records and environmental monitoring stations in Taiwan during 1998 to estimate the association between air pollution and daily numbers of clinic visits for lower respiratory tract illness. A small-area design and hierarchical modeling were used for the analysis. Rates of daily clinic visits were associated with current-day concentrations of nitrogen dioxide, carbon monoxide, sulfur dioxide, and particulate matter less than or equal to 10 microm in aerometric diameter. People over age 65 years were the most susceptible, and estimated pollution effects decreased as the exposure time lag increased. The analysis also suggested that several community-specific variables, such as a community's population density and yearly air pollution levels, modified the effects of air pollution. In this paper, the authors demonstrate the use of a small-area design to assess acute health effects of air pollution.