Changes in ratio of aged population 65 and over to adults aged 15-64 -hereafter reffered to as “index”- in Japan were followed-up from 1920 to 1970. In the process of rapid population change, differences among prefectures in this index became clear in such a fact that Hokkaido and Tohoku districts have relatively lower value than Sanin and a part of Shikoku districts. This fact has continued up to present . It is natural that the change of this index is mainly affected by the interpref ectural migration of working ages, but we can also see the relation between this index and death rates of old age untill 1955. This relation may suggest that large differences in death rates of old age among prefectures were found till that time . Then, we will have to obtain detailed data about the population composition in pre-census days, say Meiji and Edo era, in order to understand the causes or factors of regional differences shown by this index.
Conditions and factors on the emergence of air pollution caused by photochemical reaction and its effects on plants have been intensively studied at the Air Pollution Division of The Tokyo Metropolitan Research Institute for Environmental Protection. As a result so far, Report 1 (July, 1971), Report 2 (March, 1972) and Report 3 (March, 1974) of ?gSurveys and Research on Photochemical Smog in Tokyo" have been made pablic. These reports were written by fellow researchers and compiled by the author, the Director of Air Pollution Division. In this paper, the author summarizes the three reports, which consist of total 1671 pages, and adds some of his interpretations and implications to them, categorizing the content as follows1) Facts about photochemical smog found out in Tokyo and in U.S.A. in the past.2) Comparisons of primary and secondary pollutants concentration between in Tokyo and in Los Angeles.3) Announcements of warning made in emergencies of photochemical smog in Japan.4) Announcements of warning made in emergencies of photochemical smog in Tokyo.5) Human injury suspected to have been caused by photochemical smog.6) Relations between weather conditions and oxidants concentration in Tokyo Metropolitan Area.7) Behavior of atmospheric lower layer and pollutants concentration in Tokyo Metropolitan Area.8) Secondary pollutants and their causing substances.9) Plant damage due to photochemical smog in Tokyo.