“Even if a chemical is found to be nontoxic in animal studies, the safety of the chemical cannot be assured.”
– Dr. Barbara Shane, U.S. National Toxicology Program 
“Currently available animal models, used for evaluating potential therapies prior to human clinical trials, have limited predictive value in many disease states.”
– U.S. Food & Drug Administration 
“The problem is, we don’t know what the findings [from animal testing] really mean.”
– Dr. Robert Maronpot, U.S. National Institute of Environmental Health Sciences 
“[E]ven if the LD50 could be measured exactly and reproducibly, the knowledge of its precise numerical value would barely be of practical importance, because an extrapolation from experimental animals to humans is hardly possible.”
– Dr. D. Lorke, Bayer AG, Germany 
“[R]egulators have chosen animal tests to forecast human cancer risks. To this end, animal data are filtered through a series of preconceived assumptions that are presumed to overcome a host of human/animal differences in biology, exposure and statistics—differences that in reality are insurmountable.”
– Dr. Gio Batta Gori 
“In the present state of the art, making quantitative assessments of human risk from animal experiments has little scientific merit.”
– Statisticians Drs. David Freedman and Hans Zeisel 
“Animal studies of lead, mercury, and PCB’s each underestimated the levels of exposures that cause effects in human by 100 to 100,000-fold. Regulatory decisions that rely largely on toxicity testing in genetically similar animals under controlled laboratory conditions will continue to fail to reflect threats to the capacities and complexity of the human brain as well as important gene-environment interactions.”
– Physicians for Social Responsibility 
“The one or two or three hundred millions of dollars a year that we’re now spending on routine animal tests are almost all worthless from the point of view of standard setting…. [I]t is simply not possible with all the animals in the world to go through new chemicals in the blind way that we have at the present time, and reach credible conclusions about the hazards to human health. We are at an impasse. It is one that has deep scientific roots, and we had better do something about it.”
– Nobel Laureate Dr. Joshua Lederberg 
1 Shane BS. Human reproductive hazards. Environmental Science and Technology 30, 1193 (1989).
2 FDA [Food & Drug Administration]. Challenge and Opportunity on the Critical Path to New Medical Products. Bethesda, MD: FDA (2004).
3 Maronpot R, cited in Brinkley J. Many say lab-animal tests fail to measure human risk. The New York Times, A-1 (23 May 1993).
4 Lorke D. A new approach to practical acute toxicity testing. Archives of Toxicology 54, 275-87 (1983).
5 Gori GB. The costly illusion of regulating unknowable risks. Regulatory Toxicology and Pharmacology 34, 205-12 (2001).
6 Freedman DA & Zeisel H. From mouse-to-man: the quantitative assessment of cancer risks. Statistical Science 3, 3-56 (1988).
7 Physicians for Social Responsibility. In Harms Way: Toxic Threats to Child Development. Boston: PSR (2000).
8 Lederberg J. A challenge for toxicologists. Chemical Engineering News 1, 5 (1981).