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4.0 Discussion and Conclusion

Forensic Identification Services Chemical Carcinogenicity Evaluation

Following a review of the public literature, including government and occupational health and safety databases, the list of 66 chemicals provided by the RCMP were evaluated for potential carcinogenicity. In instances where no data was identified, chemical structures were evaluated in order to identify possible structural alerts that could indicate reactivity and consequently mutagenicity and/or carcinogenicity. Though not 100% precise, structure alerts provide at least a certain amount of information as to potential hazard where additional information is lacking.

Out of the 66 chemicals evaluated, 10 chemicals were conservatively classified as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive" based on information in the literature or classifications outlined by regulatory agencies (see Table 5).

Table 5 - Summary of Chemicals Classified as "Reported to Produce Tumours in Experimental Animals, but for Which Human Evidence is Either lacking or Inconclusive"
Chemical CAS# Use level Exposure Limit Target Organ (Animal Species)
Chloroform 67-66-3 Seldom

20 μg/day (oral)
40 μg/day (inhalation) (CalEPA, 2009)

Kidney, liver
(rats and mice)
Methanol 67-56-1 Often 500 μg/kg bw/day
(US EPA, 2009a)
testes, head/neck
(rats)
Phenol 108-95-2 Rare 300 μg/kg bw/day
(US EPA, 2009b)
adrenal gland, blood
(rats)
Coomassie brilliant blue 6104-59-2 In use 30 µg/day (CalEPA, 2009) (based on Coomassie violet) mammary gland, skin
(rats)
Petroleum ether 8032-32-4 Until 2000, rare 300 ppm in air TWA* (ACGIH, 2009) skin
(mice)
Hydrogen peroxide 7722-84-1 Not stated 1 ppm in air (ACGIH, 2009) intestine
(mice)
Trichloroacetic acid 76-03-9 Rare 1 ppm in air TWA* (ACGIH, 2009) liver
(mice)
Crystal/Gentian violet 548-62-9 In use Not established liver, blood
(rats and mice)
Rhodamine 6G 989-38-8 Seldom Not established adrenal gland, integument
(rats)
Leucomalachite Green 129-73-7 Seldom Not established thyroid, testes, liver
(rats)

*TWA - time-weighted average

Only 3 of the chemicals, chloroform, crystal/Gentian violet, and, indirectly, Coomassie brilliant blue (based on the NSRL for Coomassie violet) of the listed chemicals have been specifically evaluated for carcinogenic potency. Other chemicals listed in Table 5 have exposure limits based on effects noted in the workplace. These generally relate to irritation, or, occasionally to organ toxicity. These exposure limits are not intended to be protective of carcinogenic effects. Exposure limits based on carcinogenicity and those based on other endpoints cannot be compared to other chemicals directly, as they have been derived based on different methodologies or testing protocols. Furthermore, most of the chemicals considered as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive" are primarily based on animal data, and as such only indicate that a hazard could exist to humans exposed to them.

Only 3 of the chemicals, chloroform, crystal/Gentian violet, and, indirectly, Coomassie brilliant blue (based on the NSRL for Coomassie violet) of the listed chemicals have been specifically evaluated for carcinogenic potency. Other chemicals listed in Table 5 have exposure limits based on effects noted in the workplace. These generally relate to irritation, or, occasionally to organ toxicity. These exposure limits are not intended to be protective of carcinogenic effects. Exposure limits based on carcinogenicity and those based on other endpoints cannot be compared to other chemicals directly, as they have been derived based on different methodologies or testing protocols. Furthermore, most of the chemicals considered as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive" are primarily based on animal data, and as such only indicate that a hazard could exist to humans exposed to them.

Whether actual carcinogenic effects would be observed in humans is unknown for each of the 10 chemicals classified as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive" is unknown as no human based data are available. In any case assessment of potential risk, a function of both hazard (i.e., inherent potential to cause cancer, in this case for the 10 chemicals classified as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive") and exposure. The nature of the exposure would determine the potential risk associated with each of the chemicals. In other words, the potential risk will depend on how the chemicals are used in the laboratory, what safety precautions (i.e., personal protective equipment, fume hoods, etc.) are in place to protect workers, the purity/composition of the chemical and the actual duration of exposure.

Based on the data shown in Table 5, of the 10 chemicals considered as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive" exposures to Coomassie brilliant blue, Crystal/Gentian violet, and methanol appear to be the most prevalent or of the longest duration. This assessment is based only on the preliminary data provided by FIS. A future phase of the evaluation could focus more on the actual exposures of FIS personnel to the chemicals of greatest concern. From a toxicological standpoint, of the 3 chemicals classified as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive" and which are listed as in use, often used, or very often used, those of highest concern could include: Coomassie brilliant blue and crystal/Gentian violet since they have shown carcinogenic activity in experimental animals, show structural alerts for genotoxicity/ carcinogenicity, and, in the case of Coomassie brilliant blue, are closely related to chemicals that have shown carcinogenic activity in animals.

In addition to the chemicals classified as "Reported to produce tumours in experimental animals, but for which human evidence is either lacking or inconclusive", basic/brilliant yellow, trans-dichloroethylene, and 1,8-diazafluoren-9-one were classified as "Not reported to have carcinogenic potential, but may have theoretical risk" and noted to be in use often or very often. Given the results of genetic toxicity testing and/or presence of structural alerts for genotoxic/carcinogenic activity, each of these 3 chemicals were also considered of potential concern.

Overall, it is important to note that none of Coomassie brilliant blue, Crystal/Gentian violet, basic/brilliant yellow, trans-dichloroethylene, and 1,8-diazafluoren-9-one are clearly carcinogenic to humans (none are classified as "Known to be human carcinogens"). In all probability, given reasonable exposure scenarios, these chemicals are unlikely to increase carcinogenic risk significantly above background.