Abstract
Nitrogen dioxide is one of the most important indoor air pollutants which can be generated from sources inside the private home and is one of the criteria pollutants for which ambient air quality standards have been promulgated. Investigation of the relationship between indoor and outdoor levels of these pollutants is important for epidemiological studies on the adverse health effects of air pollutants.
Simultaneous measurements were made of the concentrations of nitrogen dioxide (NO2) and nitrogen monoxide (NO) for a year at a home in Tokyo. It was seen that indoor NO levels roughly corresponded to those of outdoors over the long-term. In regard to diurnal variations, two peaks were observed, i. e., in the mornings and in the evenings, for indoor and outdoor levels of NO. The long-term and the diurnal variations of indoor NO2 levels were different from those of outdoor NO2 levels. It was shown that the relationships between indoor and outdoor NO2 concentrations varied seasonally. There was not a close correlation between the daily average of indoor NO2 concentrations and the daily maximum of hourly indoor NO2 concentrations. Thus it appears to be difficult to estimate the peak levels of indoor NO2 from daily average concentrations.
