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3.2 Chemicals

Forensic Identification Services Chemical Carcinogenicity Evaluation

A tabular summary of the classification of each of the chemicals and exposure limits, where available, for chemicals considered to be "Not reported to have carcinogenic potential, but may have theoretical risk" is presented in Table 3. Since there are no reports of associations between cancers in humans or in animals due to exposure to these chemicals, potential target organs, if any, cannot be identified.

Table 3 - Summary of Chemicals Classified as "Not Reported to Have Carcinogenic Potential, but May Have Theoretical Risk"
Chemical CAS# Use Level Exposure Limit
Amido Black 1064-48-8 Seldom Not established
Basic/Brilliant yellow 29556-33-0 Often Not established
Oil Red O 1320-06-5 Being tested Not established
Sodium perborate 7632-04-4 Seldom Not established
trans-Dichloroethylene 156-60-5 Very often Not established
1,8-diazafluoren-9-one 54078-29-4 In use Not established

A brief assessment of each of the chemicals follows. These reviews are not intended to be comprehensive, but to show the key data involved in regulatory classifications and the underpinning of the category ascribed by Cantox.

3.2.1 Dyes/Pigments (Amido Black, Oil Red O, and Basic Yellow)

Two chemicals (Amido black and Oil Red O) fall into the category of ‘AZO’ dyes, and though information pertaining to the carcinogenic potential of these chemicals was not identified, it has been concluded that though the toxicity of the parent compounds - the azo colorants - is low, some of the metabolic cleavage products or impurities (aromatic amines) are potentially carcinogenic (Danish EPA, 1998). Specifically, azo dyes based on benzidine, 3,3' dimethoxybenzidine and 3,3'-dimethylbenzidine have been classified in the EU as carcinogens of category 2 as "substances which should be regarded as if they are carcinogenic to man". Though the carcinogenic risk is considered small, there is still a possibility that a hazard exists. The carcinogenic hazard of the azo dyes is directly related to their water solubility, ease of metabolism to carcinogenic amines, or to the presence of carcinogenic impurities resulting from the dyes manufacture.

Amido black has reportedly shown activity tested in an Ames assay (test for mutagenic potential in bacteria) (Kaur et al., 1993). It also contains a structural alert for carcinogenicity/genotoxicity (Benigni and Bossa, 2008).

No information was available regarding Oil Red O, but, like amido black contains the aromatic azo structural alert (Benigni and Bossa, 2008) and, to be conservative, Oil Red O was considered to have theoretic risk for carcinogenic activity.

Basic Yellow has not been shown to be carcinogenic or genotoxic in any system and it is not an azo-dye. However, this chemical does contain the aromatic mono- and dialkylamine structural alert for carcinogenicity/genotoxicity (Benigni and Bossa, 2008) and, therefore, has been conservatively categorized as "Not reported to have carcinogenic potential, but may have theoretical risk".

3.2.2 trans-1,2-Dichloroethylene

trans-1,2-Dichloroethylene is used as a solvent for waxes and resins and in the extraction of rubber, as a refrigerant, in the manufacture of pharmaceuticals and in the extraction of oils and fats from fish and meat (HSDB, 2001). No epidemiological or animal carcinogenicity studies were available for this compound. EPA has placed cis-1,2-dichloro-ethene in weight-of-evidence group D, not classifiable as to human carcinogenicity, based on the lack of or negative human or animal cancer data.

Cis- and trans-1,2-dichloroethylene were tested for mutagenic effects in a diploid strain (D7) of the yeast Saccharomyces cerevisiae in suspension tests with and without a mammalian microsomal activation system. In addition, both of the cis- and trans-isomers of 1,2 dichloroethylene were evaluated in an in vivo intrasanguineous host-mediated assay conducted in mice (Bronzetti et al., 1984). Both isomers exhibited dose-dependent toxicity in yeast, and survival was lower with metabolic activation than without. In the host-mediated assay in mice, only the cis-isomer showed evidence of mutagenic activity. Such mutagenic activity was found after both acute and chronic doses and in liver, kidney, and lung tissue. The trans-isomer was not mutagenic in the host mediated assay. trans-1,2-Dichloroethylene does not contain structural alerts for carcinogenicity as it is a dihalokene, and it is the monohaloalkenes that are of the greatest concern (Benigni and Bossa, 2008).

While the data profile for trans-1,2-dichloroethylene may warrant its placement in the "Not reported to have carcinogenic potential and without theoretical risk " category, it has been included in the "Not reported to have carcinogenic potential, but may have theoretical risk" category largely due to the lack of data available and given the finding of carcinogenic effects of 1,2 dichloroethane (not dichloroethylene) in both rats and mice. 1,2-Dichloroethane is reasonably anticipated to be a human carcinogen according to NTP Report on Carcinogens (NTP, 2005b) based on sufficient evidence of carcinogenicity in experimental animals (NCI, 1978; IARC, 1979, 1987b, 1999b).

3.2.3 1,8-Diazafluoren-9-one (DFO)

No information was identified on 1,8 diazafluoren-9-one (DFO), however, there were some structural alerts based on the chemical structure. Of particular concern are the aza moieties. Given this alert, this chemical was classified as "Not reported to have carcinogenic potential, but may have theoretical risk".

3.2.4 Sodium Perborate

Sodium perborate is a chemical used in teeth bleaching agents. There were no epidemiological or animal carcinogenicity studies available for review. Sodium perborate was reported to be positive in an Ames assay (without S9 only), caused chromosome aberrations in Chinese hamster ovary cells, and was positive in a DNA damage assay (Seiler, 1989). However, the author of this study concluded that the positive results would be minimized by the activity of mammalian defensive systems and are thus not of significant concern to humans. As a conservative measure, sodium perborate was classified as "Not reported to have carcinogenic potential, but may have theoretical risk" on the basis of the limited genetic toxicity data reported for this chemical.