A comparison of indoor air pollutants in Japan and Sweden: formaldehyde, nitrogen dioxide, and chlorinated volatile organic compounds.

Indoor and outdoor concentrations of formaldehyde (HCHO), nitrogen dioxide (NO2), and selected chlorinated volatile organic compounds (chlorinated VOC) were measured in 37 urban dwellings in Nagoya, Japan, and 27 urban dwellings in Uppsala, Sweden, using the same sampling procedures and analytical methods. Indoor as well as outdoor air concentrations of HCHO, NO2, and chlorinated VOC were significantly higher in Nagoya than in Uppsala (P<0.01), with the exception of tetrachlorocarbon in outdoor air. In Nagoya, HCHO and NO2 concentrations were significantly higher in modern concrete houses than in wooden houses and higher in newer (less than 10 years) than in older dwellings (P<0.01), possibly due to less natural ventilation and more emission sources in modern buildings. Dwellings heated with unvented combustion sources had significantly higher indoor concentrations of NO2 than those with clean heating (P<0.05). Moreover, dwellings with moth repellents containing p-dichlorobenzene had significantly higher indoor concentrations of p-dichlorobenzene (P<0.01). In conclusion, there appear to be differences between Nagoya and Uppsala with respect to both indoor and outdoor pollution levels of the measured pollutants. More indoor pollution sources could be identified in Nagoya than in Uppsala, including construction and interior materials emitting VOC, use of unvented combustion space heaters, and moth repellents containing p-dichlorobenzene.