[Estimations of organ dose and health risk of the mass chest X-ray examinations in children].

: In Japan, mass chest X-ray examinations are mandated by law for schoolchildren and students. Recently, questions of the justification of such X-ray examination have arisen. In this study the absorbed doses of each organ, and the health detriments from the mass chest X-ray examinations to schoolchildren and students were estimated. The doses of organs were measured by the TLDs (Mg2SiO4), slab phantom, and anthropomorphic phantom. The probability of fatal cancer, and the resultant reduction in life expectancy induced by mass chest X-ray examinations were calculated by the multiplicative risk projection model of the ICRP-1990. The absorbed doses of lung, thyroid glands, esophagus, stomach, breast, and red bone marrow in first-year elementary schoolchildren were 90, 30, 90, 60, 90, and 30 muGy, respectively, and the doses in ovaries and testes were almost nil. Each organ dose of first-year students of junior high school was about 1.5 times that for elementary schoolchildren. The total radiation-induced lifetime cancer risk of schoolchildren and students was from 0.3 x 10(-5) to 0.9 x 10(-5) per person by the multiplicative risk projection model of the ICRP-1990 and a factor of 2 for the DDREF (dose and dose rate effectiveness factor). The reduction in life expectancy by radiation induced fatal cancer was from 15 x 10(-5) years to 50 x 10(-5) years per person. The results of this study suggest that subjects of mass chest X-ray examinations should be carefully selected from the viewpoint of radiation protection.