Cancer-causing chemicals

It is not known if phenol causes cancer in humans. However, cancer has been shown to occur in mice when phenol was applied to the skin several times each week during the whole lifetime of the animal. When it is applied in combination with certain cancer-causing chemicals, a higher rate of cancer occurs than when the carcinogens are applied alone. Phenol did not cause cancer in mice or rats when they drank water containing phenol for 2 years. The International Agency for Research on Cancer (IARC) considers phenol not classifiable as to its carcinogenicity in humans. 

The FDA s decision was based on the conclusion that no completely safe level of human intake could be established for a cancer-causing chemical. This position led, in turn, to the position that if analytical chemists could be sure aflatoxins were present in a food, then the food could not be consumed without threatening human health. The question then was what is the smallest amount of aflatoxin that... 

But we are moving too quickly. Before we can begin to contemplate the contribution of all these environmental carcinogens to the total cancer problem we need to acquire a better understanding of what is meant by the terms carcinogen or cancer-causing chemical and of how certain substances get to carry these labels. 

The acceptance of the Substitution Principle as a workable legal act was demonstrated in a European Court of Justice (ECJ) court case in 2000. Trichloroethylene (TRI), a cancer-causing chemical, was banned in Sweden and companies had to find alternatives. Exemptions were only given when a suitable alternative was not available, when use did not lead to unacceptable exposure and on the condition that the company continued to seek alternatives. Forthe majority of exemptions, the firms had managed to substitute TRI in most of their production, but had not found a suitable alternative for a specific use in the production process. One firm appealed against the ban, but the European Court of Justice ruled against them. The ECJ ruling demonstrates acceptance of the Substitution Principle in EU courts. 

McCann, J., In Vitro Testing for Cancer-Causing Chemicals, Hosp. Prac., 73-85, September (1983). 

In California, five of the top nine pesticides used on cotton are cancer-causing chemicals (cyanazine, dicofol, naled, propargite, and trifluralin). 

The oxidation state (oxidation number) of an element in a compound may have a strong influence on the hazards and toxicities posed by the compound. For example, chromium from which each atom has lost three electrons to form a chemical compound, designated as chromium(III) or Cr(III), is not toxic, whereas chromium in the +6 oxidation state (Cr(VI), chromate) is regarded as a cancer-causing chemical when inhaled. 

However, the public is being inundated with stories about cancer-causing chemicals. 

Cancer-Causing Chemical Substances and Occupation Affected... 

For possible cancer-causing chemicals (EPA Class C—some evidence exists that they may cause cancer, but it is not very convincing), a value equivalent to the MCLG is calculated as if they were not carcinogens. This value is then divided by a factor of ten to give the final MCL. Division by ten provides a margin of safety in case the chemical is later determined to be a carcinogen. 

Just before Thanksgiving in 1959 the federal government issued a public warning, urging people not to eat cranberries, which had been found to be contaminated with amitrole, an herbicide thought to cause cancer in laboratory animals. This created widespread fear and awareness of cancer-causing chemicals in the nation s food. 

In assembling his scientific information, McKee followed the innocent until proven guilty approach that Robert Kehoe had introduced in his studies of tetraethyl lead and that industry-friendly scientists had subsequently applied to synthetic pesticides. Only those studies that determined limiting or threshold concentrations were included in the compilation. When no minimum concentration was known below which a substance did not cause harm—as in the case of cancer-causing chemicals—McKee often omitted... 

To McKee a pollution control expense occasioned by unneeded safety factors would not be fair. No such unfairness arose when the public was denied knowledge that cancer-causing chemicals were in the water they drank. In placing the financial interests of waste dischargers ahead of the health of those exposed to the wastes, Water Quality Criteria encapsulates the spirit of the Dickey Act. 

For more on chemical carcinogens there are two notable references CRC Handbook of Identified Carcinogens and Noncarcinogens, and Irving Sax s Cancer Causing Chemicals, both published in the early 1980s. The EPA, of course, is the main governmental source. 

Sax, N.I. 1981. Cancer Causing Chemicals. New York Van Nostrand Reinhold. 

A chemical agent may alter the absorption of a cancer causing chemical at the point of entry or at the level of cellular uptake, can alter carcinogenicity. An example of altered absorption may be found in the latency period in the development of subcutaneous neoplasm by the same dose of benzo(rst) pentaphene applied in different vehicles. The latency period was 16 weeks in peanut oil, 37 weeks in lipoprotein, and 62 weeks in Ringer s solution (16). Likewise,... 

Altered absorption of cancer-causing chemical, example, 123-124 Amitrole, carcinogenicity, 219 Animal-to-human oarapolation of immune system data, 102—103 Apigenin, inhibition of tumor promotion, 117r... 

Figure 21.28 Benzopyrene is a cancer-causing chemical that is found in soot, cigarette smoke, and car exhaust. 

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