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Environmental and Workplace Health

Hazard-Specific Issues - Substances Assessed For Carcinogenicity

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Information contained in this section is of a general nature only and is not intended to constitute advice for any specific fact situation.

Carcinogenesis - Overview:

Cancer is one of the leading causes of death in industrialized countries. In Canada, the cancer rate has risen from 1 in 10 in 1930 to 1 in 3 today. The International Agency for Research on Cancer (IARC) identified a number of substances, other than tobacco, that cause lung cancer through studies of workers who died as a result of exposure to carcinogens in the workplace. The debate on how many cancers are occupationally related continues and estimates range widely. Scientists have estimated that as may as 33% of all cancers are related to workplace exposures to carcinogens, (ref.: U. S. Civil Service Employees Association, 1998).

Although a number of factors have been related to the incidence of cancer, "It is not possible to predict with complete certainty from animal studies alone which agents, substances, mixtures, or exposure circumstances will be carcinogenic in humans. However, all known human carcinogens that have been tested adequately also produce cancers in laboratory animals. In many cases, an agent was found to cause cancer in animals and only subsequently confirmed to cause cancer in humans. Experimental carcinogenesis research is based on the scientific assumption that chemicals causing cancer in animals will have similar effects in humans. Laboratory animals' adverse responses to chemicals (of which cancer is only one) do not always strictly correspond to human responses; however, laboratory animals remain the best tool for detecting potential human health hazards of all kinds, including cancer." (Ref.: U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program, 9th Report on Carcinogens Revised January 2001).

WHMIS Classification And Hazard Communication:

Section 54 of the [WHMIS] Controlled Products Regulations (CPR) refers to specific "groupings" in the TLV booklet published by ACGIH, and the IARC list of carcinogens. The substances included in these groupings are considered to be carcinogens under the CPR.

In 1987, the ACGIH modified Appendix A of their referenced publication to eliminate the designations A1a and A1b and replace them by the designation A1. This modification also removed listings of carcinogens from Appendix A to the table of chemical substances with adopted TLVs. The applicable portion of the ACGIH publication was modified again breaking what had been four groupings into five.

The multi-stakeholder WHMIS committee through which policies employed in the administration of the program have been developed agreed that paragraph 54(a) of the CPR be revised to include categories A1, A2 and A3. However, as the proposed revision to paragraph 54(a) has not been published in the Canada Gazette Part II, if a controlled product does not otherwise fall within any other Class D criteria specified in the CPR, a supplier would not be legally obliged to depict the symbol corresponding to Division 2 of Class D (i.e., the stylized "T") on the sole basis that it is included in ACGIH A3; (i.e., inclusion in A3 would not constitute the sole criterion for classification as a controlled product in the absence of a regulatory amendment).

Note: Although the classification criteria specified in sections 34 to 66 of the CPR may provide a useful guideline for certain MSDS information, subject to certain exemptions, it is section 12 and Schedule I to the CPR which set out what information must be disclosed on a MSDS; paragraph 13(a) of the HPA sets out what ingredients are subject to disclosure on the MSDS; section 4 of the CPR specifies the concentration above which those ingredients must be disclosed; and section 19 which sets out the information to be disclosed on the label of a WHMIS controlled product.

In general, if an IARC monograph does not specifically address a chemical or group of chemicals, the results of the assessment described in the monograph may not apply. The chemical or group of chemicals would not necessarily, as a consequence of the chemical or group of chemicals sharing a common element or functional group with a substance that has been assessed, fall within the criteria specified in paragraph 54(b) of the CPR.

Similarly if a chemical or a group of chemicals is not specifically encompassed under ACGIH A1, A2 nor A3, the chemical or group of chemicals would not, as a consequence of the chemical or group of chemicals sharing a common element or functional group with a substance that has been assessed, necessarily fall within the criteria specified in paragraph 54(a) of the CPR. However, consistent with section 33 of the CPR, the fact that a product or a group of products was not specifically addressed in the IARC monograph nor classified under group A1, A2, or A3 by the ACGIH does not relieve the supplier or importer of his / her obligation to consider other evidence that carcinogenic (or other health) effects may result from exposure to the substance(s) and communicate those hazards on the product label and MSDS.

The list of substances assessed for carcinogenicity posted on this page of the Health Canada website may provide assistance in determining the appropriate health and safety information to be disclosed on the label and MSDS.

Designations - Explanatory Notes:

American Conference of Governmental Industrial Hygienists
A1 A2 A3 A4 A5
Confirmed human carcinogen Suspected human carcinogen Animal carcinogen. The agent is not likely to cause cancer in humans except under uncommon or unlikely routes or levels of exposure. Not classifiable as a human carcinogen Not suspected as a human carcinogen

California Environmental Protection Agency

Yes - substances "Known to the State to cause cancer" included on list of carcinogens (Proposition 65 list)

European Union
Category 1 Category 2 Category 3
Substances known to be carcinogenic to man Substances which should be regarded as if they
are carcinogenic to man
Substances which cause concern for man owing to possible carcinogenic effects but in respect of which the available information is not adequate for making a satisfactory assessment
International Agency for Research on Cancer
Group 1 Group 2A Group 2B Group 3 Group 4
The agent is carcinogenic to humans The agent is probably carcinogenic to humans The agent is possibly carcinogenic to humans The agent is unclassifiable as to carcinogenicity in humans The agent is probably not carcinogenic to humans
National Toxicology Program
Group 1 Group 2

"Known Carcinogen"
(Sufficient information from human studies to indicate causal relationship)

"Reasonably Anticipated"
(Limited evidence of carcinogenicity in humans; or sufficient evidence of carcinogenicity
in experimental animals)

Substances Assessed For Carcinogenicity (pdf files):

This list, (current to April 2002), consists of substances assessed for carcinogenicity by the American Conference of Governmental Industrial Hygienists (ACGIH), the California Environmental Protection Agency (Cal-EPA), the International Agency of Research on Cancer (IARC), the European Union (E.U.), and the National Toxicology Program (NTP).

A to M (PDF Version - 760K)
N to Z (PDF Version - 510K)

References / Related Sites:



International Agency for Research on Cancer

United States