A possible population monitoring system on environmental mutagens: statistical studies on retinoblastoma in Japan

Because an increasing number of environmental mutagens have been detected by laboratory screening, the need to monitor human populations directly for mutational risk has been emphasized by many geneticists. They have proposed various monitoring systems but none of them has been practically applied because a large number of samples would need to be studied systematically in such systems. Recent studies by KNUDSON on some malignant tumors give hope that these diseases might be used to assess somatic mutation rates, as suggested by SUTTON (1972). According to KNUDSON, the age of first diagnosis of the diseases may be related to the annual somatic mutation rate. The ages of first diagnosis of unilateral and bilateral retinoblastomas have been compared among four university hospitals in Japan for cases since 1965. Three different types of analysis have been tried: (1) normal distribution; (2) KNUDSON's method; and (3) a modification of VERSCHUER's method for calculating penetration. The age at diagnosis of unilateral cases has fallen in the past ten years. A significant difference in the age of first diagnosis in bilateral retinoblastoma has been found in a hospital in Japan. The changes observed may result from the increased rate of somatic mutations induced by some environmental mutagens.