Risk analysis of multiple environmental factors: radiation, zinc, cadmium, and calcium

Simultaneous effects of four risk factors, i.e., radiation exposure at a sublethal dose and excessive administration of zinc or cadmium and calcium deprivation, were examined by animal experiments. Deaths among 360 mice within 30 days after the whole body irradiation of 524-617 rad gamma rays were observed under 36 experimental conditions set by all possible combinations of varied levels of the four risk factors. A similar experiment was conducted a month later to check the reproducibility by using another 360 mice. The reproducibility of the experiment was confirmed and therefore the data from the two experiments were pooled. The analysis of data based on a multiple logistic model suggested that administration of zinc acts protectively against radiation.