Do long-term scientific animal experiments provide objective and testable evidence of human risk?

Regulatory Forum Opinion Piece: Long-term animal bioassays: Is the end near?

From Toxicologic Pathology

This piece argues that the scientific testing of rats and mice – the officially prescribed animals – are not relevant to humans and cannot reliably forecast risks to humans, especially cancer risks. It outlines how official regulations based on irrelevant information are unethical, contrary to the law, and contrary to the expectations of free citizens in free societies. Ethical regulatory alternatives exist, either grounded on science or on transparent precautionary decisions when scientific evidence may not be available. This is the first in the scientific literature to document the technical and ethical fallacies on which regulators in the US and worldwide have presumed to assess long term human cancer risks from tests in rats and mice. The article is timely within the current scenario of financial restrictions, as it highlights alternatives that would save millions of animals and hundreds of $ millions in the US alone, while being compatible with transparent scientific or precautionary evidence.


Long term bioassays in animals cannot reliably forecast unknown potential but distant human risks, and especially cancer risks. The genetic, anatomic, physiologic, behavioral and environmental adaptations of rats and mice – the officially prescribed animals – are not relevant to humans. Even bioassay results for the two prescribed species are not mutually predictive. The dearth of human relevance is augmented by arbitrary and incongruous default assumptions, also officially prescribed for the conduct and interpretation of bioassays in rats and mice. Moreover, and contrary to publicized perceptions, bioassay results are freely evaded in the markup of regulations, with the imposition of arbitrary safety factors and the guided opinions of ad hoc appointed advisory committees. Regardless of bioassay results, actual regulations of unknowable distant risks end up allowing those minimum exposures that are still compatible with uses deemed necessary or useful for the common welfare. Thus it would seem sensible to do away with very costly long-term bioassays irrelevant to humans and whose results are anyway bypassed, and to focus regulations on short-term effects relevant to humans, and on transparent cost and benefit considerations toward minimizing useful exposures.

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Article details
Gori, G. (2012). Regulatory Forum Opinion Piece: Long-term Animal Bioassays: Is the End Near? Toxicologic Pathology DOI: 10.1177/0192623312467524

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