Respiratory health effects of air pollution gases: modification by education and income.

The authors' purpose was to determine whether community income and education modify the effect of gaseous air pollution on respiratory hospitalizations. The authors used daily time-series analyses to test the association between daily respiratory hospitalizations and daily concentrations of ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide in 10 large Canadian cities. They calculated the percentage increase in hospitalizations for an increase in each air pollutant that was equivalent in magnitude to its mean value. The effect of nitrogen dioxide was stronger with decreasing levels of household income (p = .023). For the combined pollutant effect, percentage increases in hospitalizations ranged from 7.0% (95% confidence interval = 2.5-11.5) to -0.7% (95% confidence interval = -4.7-3.3) from lowest to highest quartile of education (trend test p = .001). Living in communities in which the individuals have lower household education and income levels may increase the individuals' vulnerability to air pollution.