Mesotheliomas in Man and Experimental Animals

Abstract

In considering the use of experimental animals in the assessment of risk to man, it is paramount that the interest remains with the possible effects on man and that precise interpretation of the fate of the animal must be considered in this light. Therefore it is essential to use the epidemiological evidence that has been obtained from human exposure in known situations to calibrate the results obtained experimentally. When human evidence is lacking we are fortunate in having an end-point against which other fibers can be assessed. This material is a form of zeolite known as erionite. Where this material occurs in the form of fine fibers, that is, less than 0.25 microns in diameter and greater than 5.0 microns in length, it causes an extremely high rate of mesotheliomas in man, as reported by Baris et al., (1978) and by Simonato and his colleagues (1989). In experimental studies with this fiber in rats and mice exposure intrapleurally results in 100% mesotheliomas (Wagner et al., 1985; Maltoni et al., 1982) and 100% by inhalation (Wagner et al., 1985). When these results with erionite in man and experimental animals are compared with the other mineral fibers, the effects of the latter are far less severe.