Substance-Specific Issues

Cobalt, organometallic complexes, carcinogenicity of,

Substances:

organometallic compounds of cobalt

Issue:

As both the IARC and ACGIH have classified cobalt, inorganic cobalt compounds and other specific cobalt compounds as possible carcinogens, questions have arisen as to whether organometallic compounds of cobalt, in general, would also fall within the CPR criteria for carcinogenicity.

Background:

As opposed to referencing tests, the criteria for carcinogenicity specified in section 54 of the CPR for pure substances and tested mixtures refer to classifications established by ACGIH and IARC. The criteria for untested mixtures in section 58 of the CPR cross-reference section 54.

The Threshold Limit Values and Biological Exposure Indices, 2001 edition, published by the ACGIH, includes cobalt and inorganic cobalt compounds in A3 "Confirmed animal carcinogen with unknown relevance to humans".

As reflected in their monograph (vol. 52, 1991) (last updated, November, 1997), IARC have also concluded that a number of inorganic and carbonyl cobalt compounds are "possibly carcinogenic to humans (Group 2B)."

Cobalt compounds have been used as pigments in glass ceramics for thousands of years. In the twentieth century, cobalt has been used for the production of metal alloys, high-strength steels, and hard-metal cemented carbides. In the last twenty years, cobalt compounds have been used as catalysts. Occupational exposure to cobalt is primarily through inhalation of dusts, fumes, mists containing cobalt in hard-metal production and the production and painting of porcelain products.

The question of whether organometallic compounds of cobalt are considered carcinogenic had been asked to the U.S. OSHA which provided the following response:

"Your question has been addressed in OSHA's compliance directive, Inspection Procedures for the Hazard Communication Standard (CPL 2-2.38C). This directive states the following: 'For purposes of compliance with the MSDS and labeling requirements, the IARC monograph's summary evaluation for the chemical can generally be relied upon but it may be necessary to review the actual evaluations. In some cases, a group of compounds may be listed in the summary as carcinogenic but closer examination of the appropriate monograph will reveal that IARC had data to support the carcinogenicity of only certain compounds. Those compounds are the only ones covered by the HCS.'

Under the Hazard Communication Standard chemical manufacturers have the responsibility to "identify and consider"all available scientific evidence for the chemicals they produce or import to determine if they are hazardous. In general, if an IARC monograph does not address a specific chemical or group of chemicals, the results of the monograph would not apply. However, it is your duty as the chemical manufacturer to evaluate all other scientific evidence and available studies to determine if any other evidence exists that may indicate a carcinogenic health hazard is associated with exposure to the cobalt phthalocyanine sulfonate compounds. The fact that your product was not addressed in the IARC monograph does not relieve you of the mandate to look elsewhere for other statistically significant evidence that carcinogenic or other health effects may result from employee exposure to cobalt phthalocyanine sulfonate compounds."

Considerations:

In relation to the carcinogenicity criteria specified in section 54 of the CPR, the following guidelines on the use of professional judgement were developed by a tripartite technical subcommittee and endorsed by the WHMIS Current Issues Committee, a committee comprised of representatives of suppliers, employers, organized labour and federal, provincial and territorial governments:

"There is no opportunity to use professional judgement in the classification of carcinogens when the substance or tested mixture is included in the referenced lists.... Where a substance or tested mixture does not appear on the referenced lists and the supplier has information to show that the product may be a carcinogen, the supplier should use professional judgement to decide if the product should be classified as carcinogenic."

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

Conclusions:

Organometallic compounds of cobalt have not been assessed by either ACGIH or IARC. The assessments made in relation to inorganic and other specific cobalt compounds can not be extrapolated to draw definitive conclusions in relation to organometallic compounds of cobalt in general.

Organometallic compounds of cobalt are not encompassed by the classifications established by ACGIH nor IARC and thus not considered to fall within the criteria for "a pure substance or tested mixture" specified in section 54 of the CPR.

Note: 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 organometallic compounds of cobalt.

References:

ACGIH, 2001. Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs). 192 p.

Government of Canada, Health Canada; "Use of Professional Judgement in Classification"; http://www.hc-sc.gc.ca/ehp/ehd/psb/whmis/classification.htm

IARC monograph, Cobalt and Cobalt Compounds (Group 2B). Vol. 52 (1997) (p. 363).

U.S. Dept. of Labor, OSHA; "OSHA Standard Interpretation and Compliance Letters"; letter of February 2, 1994 to Angela M. Mack, Product Safety Information Coordinator, UOP; http://www.osha-slc.gov/OshDoc/ Interp_data/I19940202B.html

U.S. Dept. of Labor, OSHA; CPL 2-2.38C, October 22, 1990, [superseded by CPL 2-2.38D, March 20, 1998], "Inspection Procedures for the Hazard Communication Standard", 29 CFR 1910.1200, 1915.99, 1917.28, 1918.90, 1926.59, 1928.21.