Yealy means of suspended particulate matter concentration in 137 cities of Japan from 1985 to 1990 were statistically compared by using t-test.
The results obtained were as follows:
(1) SPM concentrations increased in many cities during 6 years.
(2) In the cities whose population is more than 500, 000 SPM concentrations increased appreciably. In addition, SPM-pollution extended to the cities whose population is less than 500, 000.
(3) SPM concentrations increased in particular in Tokyo and Osaka areas.
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