Carcinogenicity results, comparison

The risk characterization is carried out by quantitatively comparing the outcome of the hazard (effects assessment) to the outcome of the exposure assessment, i.e., a comparison of the NOAEL, or LOAEL, and the exposure estimate. The ratio resulting from this comparison is called the Margin of Safety (MOS) (MOS = N(L)OAEL/Exposure). This is done separately for each potentially exposed population, i.e., workers, consumers, and man exposed via the environment, and for each toxicological endpoint, i.e., acute toxicity, irritation and corrosion, sensitization, repeated dose toxicity, mutagenicity, carcinogenicity, and toxicity to reproduction. 

Reifferscheid, G. and Heil, J. (1996) Validation of the SOS/umu test using test results of 486 chemicals and comparison with the Ames test and carcinogenicity data. Mutation Research, 369, 129-145. 

Other, more sensitive, tests have been suggested for the evaluation of potential carcinogenic risk of exposure to chemicals. These include the bacterial mutagenesis test devised by Dr. Bruce Ames ( ). This test has been applied to many of the amines listed in Table 1, both alone and after reaction with nitrite in weakly acid solution, followed by neutralization and application to the bacteria. In Table 3 are given the results of a number of such tests, together with comparison of the results of chronic... 

Table IV lists the results of risk calculations provided in the preliminary proposal for the substances that were proposed as potential carcinogens in the regulatory context at that time (44). 1,1-Dichloroethylene was later converted to a listing of equivocal evidence of carcinogenicity. The table includes calculations made by the USEPA CAG and the NAS Safe Drinking Water Committee. These calculations attempt to project concentrations of each chemical in drinking water that, if consumed for a lifetime (70 years) at the rate of 2 L of water per day would contribute an excess lifetime cancer risk of up to 1 in 100,000 and up to 1 in 1,000,000. The quality of evidence of carcinogenicity ranging from sufficient in humans to limited in animals is also included for each chemical. Provisional ADI values calculated from chronic toxicity data only are included for the sake of comparison.

Benigni R, Pellizzone G, Giuliani A. Comparison of different computerized classification methods for predicting carcinogenicity from short-term test results. J Toxicol Environ Health 1989 28 427 14. 

An oral 90-120-day study in rats of a commercial hexane containing 40% //-hexane, 24% each of 3-methylpentane and dimethylbutane, 9% cyclopentane, 2.5% cyclohexane, and 12% 2-methylpentane was conducted in comparison with //-hexane. This mixture includes compounds in both the EC5-EC6 and EC>6-EC8 range. Peripheral neuropathy was not seen when commercial hexane was tested at the same dose as was effective for pure //-hexane (ATSDR 1999b), but the dose of //-hexane resulting from this dose of commercial mixture was only 40% the effective dose of the pure //-hexane. Some evidence of carcinogenic potential has been reported in chronic inhalation studies in mice, as discussed in the previous section. 

Pentachlorophenol is an effective broad-spectrum biocide widely used as a wood preservative. Two-year carcinogenicity studies had been conducted in B6C3F1 mice and similar studies were planned in Fischer 344 rats. To aid in future comparison of the results of the toxicology studies in both species and to provide information for dose-response relationships, toxicokinetic evaluations were conducted. In singlc-and multiple-exposure studies the toxicokinetics of... 

Combustion particles are of complex chemistry, carrying most of the trace elements, toxins or carcinogens generated from the combustion process. Combustion of different types of fuels results in emissions of various trace elements which are present in the fuel material. In most cases there is not just one specific element that is related to the combustion of a particular fuel, but a source profile of elements [2]. For example, motor vehicle emissions contain Br, Ba, Zn, Fe and Pb (in countries where leaded petrol is used) and coal combustion results in the emission of Se, As, Cr, Co, Cu and Al. For comparison, the crustal elements include Mg, Ca, Al, K, Sc, Fe and Mn. Since most of the trace elements are nonvolatile, associated with ultrafine particles and less prone to chemical transformations, they often remain in the air for prolonged periods of time in the form in which they were emitted. 

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