1-3 Butadiene, an important industrial chemical and a common environmental air pollutant, has been shown to be a weak carcinogen in the rat, but a potent carcinogen in the B6C3F1 mouse. This species difference makes risk extrapolation to humans difficult, and the underlying mechanism must be clarified before meaningful risk extrapolation to humans can be made.
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From a comparison of the results of the present study with those of other studies, one can draw the following conclusions: compounds that cause hepatomas (liver cancers) in mice, may not always be carcinogenic in rats, or if carcinogenic in both species, the compounds may have different primary target sites. The extrapolation of such results to define any risk to humans remains a troublesome problem.'-
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…one of the great fallacies in this calculation is that they are assuming that the mouse or rat or the hamster predicts for man, and we have no basis for this prediction…So it’s again a half-baked guess… Does the animal model have any relevance to human disease? If not we’re wasting a lot of time, a lot of money, a lot of good scientists, and a lot of good space at NIH… I completely agree with Dr. Clayton that extrapolation is unscientific… the chief objective here is to keep us all employed and to make sure we do interesting experiments so we can keep coming back to nice places like this.
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Unfortunately, extrapolations from animal results to man remains largely problematic and no amount of mathematical sophistication can render such extrapolation more certain. .
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