Indoor Nitrogen Dioxide Pollution Associated with Gas Stoves and Unvented Heaters in Japan

Abstract

We have conducted a study of nitrogen dioxide (NO2) concentrations in nearly 200 houses, including newly built homes supplied by electricity in Tokyo. NO2 levels were measured in the kitchen and living room of each house for 1 week simultaneously using a Yanagisawa badge and some houses were measured outside in the winter and fall. In both of the kitchen and living room, NO2 concentrations for homes supplied by gas were higher during both the fall and winter than those supplied by electricity. The mean NO2 concentrations in the kitchen and the living room for homes with electricity was 6 ppb in the winter. Unvented heaters were used in the approximately 20 % of gas homes. Average NO2 concentration in the living room for homes with gas with vented and unvented heaters was 22 ppb and 72 ppb, respectively. In the fall, the mean NO2 concentrations in the living room for homes supplied by electricity and gas was 9 ppb and 14 ppb, respectively. The mean levels of NO2 measured outside homes were 29 ppb in the winter and 20 ppb in the fall, respectively. Mean indoor NO2 concentrations in homes supplied by gas with unvented heaters were two times higher than those outdoors in the winter. The health consequences of the differences among the three types of households should be investigated. NO2 levels in this study are likely to be different from those of a lot of studies in Europe and North America. It might depend on the characteristics of houses, e.g., house structure, ventilation, type of cooking facility, and type of heater, in Japan.