Particulate air pollution and hospitalization for asthma

Age-specific quarterly asthmatic hospital discharge rates in Hong Kong during 1983 to 1989 were examined in relation to mean levels of six pollutants: sulfur dioxide (SO2), ozone (O3), total suspended particles (TSP), respiratory suspended particles (RSP), nitrogen dioxide (NO2), and nitrogen oxides (NOX). Discharges from the hospital of children under 14 years of age represented 56% of 33,952 discharges recorded in all age groups. Trends of adult hospitalization rates over time remained stable during the study period. In children, however, there was an increase in these rates, particularly marked in the age group of 1 to 4 years. Univariate analysis revealed a strong correlation between quarterly mean TSP and hospital discharge rate for the 1 to 4-year-old children (r = .62, P less than .001). In the 5 to 14-year-old age group, there was an inverse relationship between hospital discharge rate and sulfur dioxide level (r = -.38, P less than .05). Stepwise multiple regression analysis, controlling for confounding variables (seasonal and annual trends of asthma hospitalizations) confirmed these relationships. A highly significant linear regression equation was derived between hospitalization rate for ages 1 to 4 years and total suspended particles (P less than .001). The highly significant correlation between pollution and asthmatic hospitalization rate for the 1 to 4-year-old group suggests that young children are vulnerable to the adverse environmental effects of pollution. Auditing these relationships offers a logical basis for approaching control.