抄録
Correlation between natural background radiation exposure rates and cancer mortality rates in 46 Japanese prefectures was statistically studied over the period of 1950-1978. With regard to the correlation between natural background radiation exposure rates and crude (non-age-adjusted) cancer mortality rates, statistically significant positive correlation coefficients were observed in most cases of cancers with only a few exceptions. But the significance of correlation mostly disappeared through age-adjustment with only three exceptions of female stomach and uterine cancers in 1968-1978 and uterine cancer in 1958-1978. Both crude and age-adjusted male esophagus cancer mortality rates in 1968-1978 showed significant negative correlation. Female lung and breast cancers in 1958-1967, female esophagus and pancreas cancers in 1968-1978, and female breast cancer in 1958-1978 came to be negatively correlated with exposure rate through age-adjustment. It was suggested that natural radiation levels are positively correlated with prefectural population component ratios for those older than 40, 50 and 65 yrs, which was considered to be one of the causes of apparent correlation between exposure rates and crude cancer mortality rates.
