PERSONAL EXPOSURE TO NITROGEN-DIOXIDE IN THE LOS-ANGELES BASIN

A large scale study of human exposure to nitrogen dioxide (NO2) was co nducted in the Los Angeles Basin, the only metropolitan area in the Un ited States that exceeds the NO2 NAAQS. Data are available for a popul ation representative sample of 482 households and 682 individuals. Per sonal exposures, as well as indoor and outdoor home levels, were monit ored using passive time-integ rating filter badges. Monitoring extende d over a one-year period (May 1987 to May 1988), with each individual providing two consecutive days of data. Information was also collected on activity patterns, household and personal characteristics, and spa tial and temporal variables. This paper describes the study design, su mmarizes the sample characteristics and representativeness, and presen ts the distribution of personal, indoor, and outdoor NO2 concentration s recorded by the monitors. Over the entire sample, median personal an d outdoor levels were 35 ppb; median indoor levels were 24 ppb. Person al exposures for those in homes with gas ranges with pilot lights aver age 10 ppb greater than those with electric ranges, and 4 ppb greater than those with gas ranges without pilot lights. Forty percent of the variation in indoor concentrations is explained by outdoor levels; 59 percent of the variation in personal exposures is explained by indoor levels; and 48 percent of the variation in personal exposures is expla ined by outdoor levels.