Our risk models are based on at least 50 assumptions, none of which has been scientifically demonstrated. For example, we assume that there is no difference between continuous (as in animal tests) or intermittent (as in human experience) dosages. But that ignores our growing knowledge of the way in which DNA repairs the human system . . .We feed rodents `all-you-can-eat' buffets every day, yet we know that caloric intake is the single greatest contributing cause of cancer [in rodents]. In fact, we found you can modify the cancer causing impact of one of the most potent carcinogens from 90% down to less than 3%, just by cutting caloric intake 20%.
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... numerous chemicals have been found to have potential toxicity/carcinogenicity in rat or mouse, which, we are reasonably certain, have little or no potential hazard in man. The reason for this is again species differences, for the biological defence mechanism which protects against toxic chemicals is most highly evolved in man, who therefore generally has a higher resistance to chemical toxicity and carcinogenicity than have rodents and other species.
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'Bats. They do not 'multiply like rabbits', most bear only a single young each year. They do not chew through wiring/ insulation/ other. They aren't blind, they don't get into women's hair, and they aren't rodents. In fact, bats are more closely related to humans.'
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It has been conventional practice to test potential carcinogens using highly inbred strains of rodents. The rationale was the supposed superior reproducibility of results compared with those obtained from wild-type animals. However, that assumption can be questioned. At least three examples of genetic drift of inbred strains can be cited... Lifetime expectation [in an inbred strain of mice] of developing one or another form of neoplasm ['spontaneous tumour'] had risen from 10 to 80 percent.
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A book is a fragile creature, it suffers the wear of time, it fears rodents, the elements and clumsy hands. so the librarian protects the books not only against mankind but also against nature and devotes his life to this war with the forces of oblivion.
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The principal method of determining potential carcinogenicity of substances is based on studies of daily administration of huge doses of chemicals to inbred rodents for a lifetime. Then by questionable models, which include large safety factors, the results are extrapolated to effects of minuscule doses in humans... The rodent MTD test that labels plant chemicals as cancer-causing in humans is misleading. The test is likewise of limited value for synthetic chemicals. The standard carcinogen tests that use rodents are an obsolescent relic of the ignorance of past decades.
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Sandy Carl I want you to kill all the gophers on the golf course Carl Spackler Correct me if I'm wrong Sandy, but if I kill all the golfers they'll lock me up and throw away the key. Sandy Not golfers, you great fool. Gophers. THE LITTLE BROWN, FURRY RODENTS. Carl Spackler We can do that. We don't even need a reason.
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Results of the animal studies raise questions about the validity of federal regulations that are based on ad lib-fed inbred strains of rodents. Are humans to be regarded as behaving biochemically like huge, obese, inbred cancer-prone rodents?
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[Regarding tamoxifen, an anti-cancer drug] 'Experimentally, tamoxifen has carcinogenic potential. In some strains of rat, but not mouse or hamster, tamoxifen can cause liver cancers at doses as low as 5mg/kg per day... However, there are doubts about the correlation of [the results] with the risk of malignant disease even in rats, let alone in other rodents, mammals, or human beings. There are many uncertainties in extrapolating these experimental data from rats to women. The effect depends on bioavailability, hepatic [liver] blood flow, and hepatic [liver] metabolism to active genotoxic carcinogens, all of which differ enormously between rat and man.
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Let us look at some animal carcinogens – gold, DDT, clofibrate and bromocriptine. There is no doubt that all of these can rightly be regarded as carcinogenic for rodents, and yet there is really quite good evidence that they are not carcinogenic to man.
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