Role of animal toxicity studies in the evaluation of human health risks from internally deposited transuranics

The extrapolation of animal data to man has always been a problem for those concerned with human biology. Especially if one is interested in the effects of toxicants, opportunities for direct observation in man are usually limited, and approval of planned experiments employing human subjects is difficult to obtain. In no case are these limitations more restrictive than for transuranic elements, for which no life-threatening effects have yet been demonstrated in man. This lack of human experience is coupled with a massive public concern over possible future effects of transuranics, which contrasts sharply with the general public apathy toward a multitude of present environmental pollutants of clearly established toxicity. This concern for the transuranics, especially 239Pu, and for other radionuclides has prompted the expenditure of many millions of dollars (and francs and marks and pounds and roubles) on studies to investigate their toxicity in animals. Results of these studies are extensive, and still accumulating, but in many quarters there is now a reluctance to accept these results as relevant to the prediction of human effects