What interaction does indoor nitrogen dioxide have on the effect of the automobile exhaust.

An attempt was made to investigate the effects of automobile exhaust to the people living alongside major traffic arterial in Tokyo. Several hundreds of housewives aged from 40 to 59 who lived more than 3 years were sampled both from the area A; within 20 m from road side, and from the area B which extended from 20 m to 150 m along the road next to the area A. ATS-DLD questionnaire was used to check the prevalence of respiratory symptom, its results was analysed with a deliberate consideration on smoking habits and using status of unvented kerosene space heater. Among each symptom prevalence, difference between the area A and the B was observed significantly in symptom rate related persistent cough and phlegm. These differences became much distinguished in non-smoking group and people not using unvented heater. For about one tenth of sample subject, joined the study of measurement of personal exposure to NO2 for 24 hr using NO2 filter badge. The average concentration of exposure depends largely on heater using status but does not on the study area, even though the atmospheric concentration of NO2 in the area A was higher than that of the area B. The difference of symptom prevalence between the study area becomes not significant compared with the group of using unvented heater. This means that, we suppose, the substantial higher symptom prevalence which observed in the area along the roadside is masked by repeated exposure to elevated indoor concentration of NO2 resulted from using kerosene space heater.