Cancer In animals

Other Sweeteners. Two other sweeteners, sucralose and cyclamates, are approved for use outside of the United States. Sucralose, a chlorinated derivative of sucrose which is 500—600 times as sweet as sugar, has received limited approval in Canada, and petitions for its approval are pending in the United States and Europe (71). Cyclamate sweeteners, once available in the United States, but now baimed because they caused bladder cancer in animals, are stiU available in Canada and Europe. Table 7 gives several examples of nonnutritive sweeteners that have been developed. 

A toxic component of braken fern, perhaps either quercetin (105) or ptaquiloside, a glucoside (106), has a mixed history of carcinogenicity. It is sometimes impHcated in an increased incidence of bladder cancer in animals and esophageal cancer in humans. Multiple other dietary components seem to either promote or interfere with its action, and the significance of braken fern in human carcinogenesis remains unproven. 

Carcinogen Any substance that has been shown to cause cancer in animals or humans. 

No studies were located regarding cancer in animals after inhalation exposure to endosulfan. 

Many vimses, both DNA and RNA containing, will cause cancer in animals. This so-called oncogenic achvity of a vims can be demonstrated by the observahon of tumour formahon in inoculated experimental animals and by the ability of the vims to transform normal tissue culture cells into cells with malignant characteristics. These transformed cells are easily recognizable as they exhibit such properties as rapid growth and frequent mitosis, or loss of normal cell contact inhibition, so that they pile up on top of each other instead of remaining in a well-organized layer. 

Based on the above data and on other available experimental work showing that nitroso compounds can induce gastric cancer in animals (O and that nitrosation reactions leading to synthesis of carcinogens can take place in the gastric cavity environment (27, 28, 29), we have formulated an etiologic hypothesis for gastric cancer (S) ... 

Hydrogen sulfide has not been shown to cause cancer in humans, and its possible ability to cause cancer in animals has not been studied thoroughly. Hydrogen sulfide has not been classified for its ability to cause or not cause cancer. There is some evidence that exposure to hydrogen sulfide may lead to an increase in spontaneous abortions in humans. However, the studies where this effect was reported are complicated by exposures to other chemicals and a lack of information on the amount of exposure to hydrogen sulfide. 

Certain RNA viruses, particularly retroviruses, have also proven capable of inducing cancer. Retroviruses known to induce cancer in animals include Rous sarcoma virus, Kirsten murine... 

Latent period for cancer in animals receiving 4-8 Gy ranged from 13 months to 20 years... 

There is no evidence that exposure to //-hexane increases the risk of cancer in people. No reliable information is available on whether //-hexane causes cancer in animals. In an animal experiment with commercial hexane (which contains //-hexane), an increase in liver cancer was found in female mice after exposure for 2 years. No increase was found in male mice or in rats of either sex. Commercial hexane is a mixture, and we do not know what parts of the mixture caused the cancer in the female mice. //-Hexane has not been characterized for carcinogenicity by the Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), or the Environmental Protection Agency (EPA). 

These few examples reveal the practical applications of some of the emerging scientific views regarding the actions of chemicals that induce cancers in animals. The development of information to test the LNT hypothesis (the standard default) is an important area of research that can not only improve the basis for risk assessment, but can also more generally advance knowledge of carcinogenic processes. 

MAb-based constructs represent, as described, a heterogeneous class of anti-tumour agents with remarkable efficacy in the treatment of experimental cancers in animals. Several MAb and immunoconjugates have been evaluated further in cancer patients, and the results have indicated that some have activity at safe doses. 

Results of studies in animals show that effects of 1,3-DNB and 1,3,5-TNB on the blood are similar to the effects seen in people. Results from animal studies also show some other effects of 1,3-DNB exposure, such as behavioral changes, damaged sperm production, and male reproductive damage. We do not know if these other effects could occur in people. Animal studies also show that, in certain cases, a large enough single oral dose of 1,3-DNB can cause death. Neither 1,3-DNB or 1,3,5-TNB have been tested to see whether or not they cause cancer in animals. 

In 1958, in response to the increased awareness that chemicals can cause cancer, the US Congress passed the Delaney clause, which prohibited the addition to the food supply of any substance known to cause cancer in animals or humans. Compared with today s standards, the analytical methods to detect a potentially harmful substance were very poor. As the analytical methods improved, it became apparent that the food supply had low levels of substances that were known to cause cancer in either animals or humans. The obvious question was Is a small amount of a substance safe to consume. This question in turn raised many others about how to interpret data or extrapolate data to very low doses. The 1970s saw a flourishing of activity to develop and refine risk assessment methodologies. 

Elemental Be and its compounds are very poisonous by inhalation or intravenous route. Chronic inhalation of beryUium dusts or fumes can cause a serious lung disease, beryUiosis, after a latent period ranging from several months to many years. Inhalation of airborne dusts can also cause an acute disease manifested as dyspnea, pneumonitis and tracheobronchitis with a short latency period of a few days. Skin contact with soluble salts of the metal can cause dermatitis. Beryllium also is a carcinogen. There is sufficient evidence of its inducing cancer in animals and humans. 

Because these are based on upper-bound estimates, the true risk could be lower. These values, along with doses of carbon tetrachloride that have been observed to cause cancer in animals, are presented in Figure 2-2. 

Certain RNA viruses, particularly retroviruses, have also proven capable of inducing cancer. Retroviruses known to induce cancer in animals include Rous sarcoma virus, Kirsten murine sarcoma virus, avian myelocytomatosis virus, as well as various murine leukaemia viruses. Thus far, the only well-characterized human RNA transforming virus is that of human T cell lymphocytotropic virus-1 (HTLV-1), which can induce adult T cell leukaemia/lymphoma (ATL). Identification of antigens uniquely associated with various tumour types, and identification of additional cancer-causing viruses, remain areas of very active research. 

Cropper et al. (1992) examined the effects of costs and benefits on EPA decisions, between 1975 and 1989, to suspend the use of pesficides fhaf have been shown to cause cancer in animals. They conclude that the agency does indeed weigh benefits against costs (suspending use only if risks are high and benefits are low) and estimate the cost per cancer case avoided by these pesticide regulations is 35 million, a sum that seems well above the implicit value of approximately 5 million to 6 million that workers place on known death risks (Viscusi 1989a, 81). 

If one believes that the large rate at which substances induce cancer in animals (ie., 50 percent) is an artifact of the dosages used, then one cannot use the findings of such experiments to make claims about the relative cancer risks created by exposure to natural and synthetic chemicals. Ames uses the results of experiments with natural products to demonstrate the absurdity of the current testing regime. 

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