Abstract
The change in yearly mean of nitrogen dioxide (NO2) concentrations in 100 larger cities of Japan from 1985 to 1990 was investigated by means of time series analysis. During these 6 years, NO2concentrations had been increased in 91 cities. The increase was the greatest in Keihin, Tokai and Hanshin districts. On the basis of this investigation, it was anticipated that the environmental quality standard for NO2would not be achieved in 1995 in 20 cities, most of which are situated in Tokyo and Osaka areas.
