Environmental NO2 concentration and exposure in daily life along main roads in Tokyo

Environmental suspended particulate matter and NO2 are possible factors causing chronic obstructive pulmonary diseases. These and other pollutants are monitored at the National Ambient Air Pollution Monitoring Stations and local monitoring stations. Environmental NO2 concentrations in large cities exceed the Japanese Environmental Quality Standards (JEQS); in particular, more than 30% of the Roadside Air Pollution Monitoring Stations (RAMS) do not achieve JEQS. To evaluate the exposure levels to environmental NO2 and its health effects, the data from the monitoring stations are useful. However, there are few reports on the relationships between these data and the exposure level in daily life. In this study, environmental NO2 concentrations in homes and its exposure levels were investigated by using passive samplers. Two areas along main roads in the south and north of metropolitan Tokyo were selected and about 150 junior high school students and their family members took part in the study. The investigation was conducted five times seasonally, 3 days each, from February 1998 to January 1999. The residence of each subject was plotted on a map, and the distance from the main road was entered on the same map. Environmental NO2 was measured outside of the house and indoors, that is, living room, kitchen, bedroom, and student's room. The average NO2 concentration of outdoors was within JEQS, and the highest value was 52.9 ppb. There was a tendency for outdoor NO2 concentrations to decrease with distance from the roadside, but the NO2 concentration differences between the roadside and the site far from the roadside were less than 10 ppb. The average outdoor NO2 concentrations and the value obtained at RAMS are slightly correlated, but not significant. The stations' data showed about 10 ppb higher values than the average outdoor concentrations obtained at each house. NO2 concentrations in living rooms based on the distance from the main road and NO2 exposure levels in daily life of students and family members were also investigated. This study clearly showed that in wintertime we are highly exposed to NO2 emitted from many types of heaters such as kerosene heater, and the family members' study suggested that the indoor NO2 levels were similar to the personal exposure levels in all seasons.