II. Incidence of Acute Respiratory Illness

A study of acute respiratory illness was conducted from November 1968 through April 1969 among families residing in an area of relatively high nitrogen dioxide exposure, in an area of elevated suspended particulate exposure, and in two control areas of Greater Chattanooga. Respiratory illness rates were consistently higher in all family segments in the high-nitrogen dioxide exposure area when rates were averaged for the entire 24 weeks of study, the A2/Hong-Kong epidemic period, or post-epidemic interval. A relative excess in respiratory illness of 18.8 percent was found among families exposed to elevated NO2 concentrations and an excess of 10.4 percent was found among families in the elevated-suspended particulate exposure area.