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A large scale study of human exposure to nitrogen dioxide (NO2) was conducted in the Los Angeles Basin, the only metropolitan area in the United States that exceeds the NO2 NAAQS. Data are available for a population representative sample of 482 households and 682 individuals. Personal exposures, as well as indoor and outdoor home levels, were monitored using passive time-integrating filter badges. Monitoring extended 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 spatial and temporal variables. This paper describes the study design, summarizes the sample characteristics and representativeness, and presents the distribution of personal, indoor, and outdoor NO2 concentrations recorded by the monitors. Over the entire sample, median personal and outdoor levels were 35 ppb; median indoor levels were 24 ppb. Personal exposures for those in homes with gas ranges with pilot lights average 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 explained by outdoor levels.

Needleman, H. L.; Gunnoe, C.; Leviton, A.; Reed, R.; Peresie, H.; Maher, C.; Barrett, P. N. Engl. Continuous analyzers for NO, NO2, and HONO were used to study the production and decay of these gases in two indoor air quality research houses, using unvented gas space heaters and ranges as combustion sources. In agreement with previous studies, indoor HONO concentrations were elevated during unvented combustion. Peak (15-min) levels up to 100 ppb HONO and 24-h averages as high as 40 ppb were measured. The observed kinetics suggest the secondary formation of HONO, possibly as a result of heterogeneous reactions involving NOz, in addition to primary production of HONO during combustion.

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Measurement of nitrogen dioxide (N0 2 ) and other oxidized nitrogen compounds in indoor environments can present some measurement difficulties not normally encountered in sampling outdoor air. This paper examines three methods that are in current use for monitoring indoor nitrogen dioxide. The methods include ozone-based and luminol-based chemiluminescence, and an electrochemical technique. We have examined these methods for accuracy, linear dynamic range, and interferences. Each of the methods was subject to interference. For indoor measurements, nitrous acid probably represents the most significant interference for the ozone-based chemiluminescence and electrochemical monitors.