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CPL 02-02-079, Appendix C

Evaluation of Carcinogenicity

A carcinogen is a substance or mixture of substances which induce cancer or increase its incidence.

  1. A chemical must be classified as a carcinogen if the chemical is regulated as a carcinogen by 29 CFR part 1910, Subpart Z, Toxic and Hazardous Substances.

  2. When classifying carcinogens, chemical manufacturers and importers must do one of the following:

    1. Conduct their own weight-of-evidence hazard evaluation, or

    2. Use the International Agency for Research on Cancer (IARC) or the National Toxicology Program (NTP) as sources to establish whether a chemical is a carcinogen.

Weight-of-evidence evaluation

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Chemical manufacturers and importers are to conduct a hazard classification of the chemicals they produce or import. This includes classifying carcinogens based on the strength and weight of evidence in accordance with 29 CFR 1910.1200(d) and Appendix A, chapter A.6. After determining the classification of the chemical, the appropriate hazard communication elements must be provided on the label and SDS.

Hazard categories for carcinogenicity include:

  1. Category 1: Known or presumed human carcinogens.

    1. Category 1A: Known to have carcinogenic potential for humans.

    2. Category 1B: Presumed to have carcinogenic potential for humans.

  2. Category 2: Suspected human carcinogens.

Use of IARC or NTP

The standard provides chemical manufacturers and importers the option of relying on the evaluations of the IARC "Monographs on the Evaluation of Carcinogenic Risks to Humans" (latest edition) or the NTP "Report on Carcinogens (RoC)" (latest edition) or when classifying carcinogens rather than conducting their own hazard classification. To help with converting IARC and NTP classifications to HCS 2012 classifications for carcinogenicity, Table C.1 relates the HCS 2012 hazard categories for carcinogenicity to the classifications provided by IARC and NTP.

Table C.1 - Approximate Equivalents Among Carcinogen Classification Schemes (Adapted from Appendix F to 1910.1200)

Category 1A - Known to have carcinogenic potential for humans Group 1 - Carcinogenic to humans Known to be human carcinogen
Category 1B - Presumed to have carcinogenic potential for humans Group 2A - Probably carcinogenic to humans Reasonably anticipated to be a human carcinogen (see Note 1 below)
Category 2 - Suspected human carcinogens Group 2B - Possibly carcinogenic to humans*

* A classifier not relying on Table C.1 when performing their hazard classification may find that some IARC 2B agents, based on sufficient evidence of carcinogenicity in experimental animals but inadequate evidence in humans, essentially correspond to HCS 1B.

Note 2 (includes all the points outlined below):

NTPs Reasonably Anticipated to be Human Carcinogens aligns with both HCS Category 1B and Category 2, and IARC Group 2A and Group 2B. To help determine where these classifications correspond, the following guidance is provided.

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  1. If there is limited evidence of carcinogenicity from studies in humans, an NTP Reasonably Anticipated to be a Human Carcinogen would correspond to IARC 2A/HCS 1B.
  2. If there is sufficient evidence of carcinogenicity from studies in experimental animals, an NTP Reasonably Anticipated to be a Human Carcinogen would correspond to IARC 2A/ HCS 1B.
  3. In cases where there is less than sufficient evidence of carcinogenicity in humans or laboratory animals, follow the guidance outlined below:

    1. If the agent, substance, or mixture belongs to a well-defined, structurally-related class of substances whose members are listed in a previous RoC as either "Known" "Reasonably Anticipated" to be a human carcinogen, it would align at minimum with HCS Category 2, or

    2. If there is convincing relevant information that the agent acts through mechanisms indicating it would likely cause cancer in humans, it would align at minimum with HCS Category 2.

Other requirements for classification of carcinogens

  1. One Positive Study

    If the weight of evidence for the carcinogenicity of a substance does not meet the criteria in Appendix A, chapter A.6 of the standard, any positive study conducted in accordance with established scientific principles that reports statistically significant findings regarding the carcinogenic potential of the substance must be noted on the safety data sheet.

  2. Category 2 Carcinogens

    If a Category 2 carcinogen ingredient is present in a mixture at a concentration between 0.1% and 1%, that information is required on the SDS. If a Category 2 carcinogen ingredient is present in a mixture at a concentration of ≥ 1%, the information must be included on both the SDS and the label.

  3. IARC and NTP Evaluations

    Whether the chemical manufacturer or importer chooses to use IARC or NTP for classification of carcinogens or conduct their own evaluation, the classification results of IARC and NTP must be listed on the SDS in Section 11.


Those chemicals identified as being "known to be a human carcinogen" and those substances that may "reasonably anticipated to be a human carcinogen" by NTP must have that carcinogen determination information listed on the SDS. Appearing in NTP's biannual Report on Carcinogens constitutes a positive finding of being a known or reasonably anticipated carcinogen.


IARC evaluates chemicals , manufacturing processes, and occupational exposures as to their carcinogenic potential. The IARC criteria for judging the adequacy of available data and for evaluating carcinogenic risk to humans were established in 1971 (Volumes 1-16) and revised in 2006 (Volumes 17 and following).

IARC Monographs contain evaluations on specific chemicals or processes. At the conclusion of each evaluation, IARC provides a summary evaluation. Periodically, IARC publishes supplements in which chemicals that have already been evaluated in previous monographs are reevaluated. In cases where a chemical has been reevaluated, the most recent IARC evaluation shall be relied upon.

IARC provides a summary in Supplement 7 of the chemicals which have been evaluated in Volumes 1-42. Table I of Supplement 7 provides a summary evaluation of all chemicals for which human and animal data were considered and a summary classification of a chemical's carcinogenic risk:

Group 1 - The agent is carcinogenic to humans.
Group 2A - The agent is probably carcinogenic to humans.
Group 2B - The agent is possibly carcinogenic to humans.
Group 3 - The agent is not classifiable as to its carcinogenicity to humans.
Group 4 - The agent is probably not carcinogenic to humans.

All IARC listed chemicals in Groups 1, 2A, and 2B must be noted on the SDS.

Individual monographs have been published subsequent to Supplement 7. For purposes of compliance with the SDS requirements, the IARC monograph's summary evaluation for the chemical can generally be relied upon. However, in some cases it may be necessary to review the evaluations as a group of compounds may be listed in the summary as carcinogenic. Upon closer examination of the appropriate monograph it may be revealed that IARC had data to support the carcinogenicity of only certain compounds. The compounds where IARC has the data are the only ones covered by the HCS.

IARC also evaluates specific industrial processes or occupations for evidence of increased carcinogenicity. Findings that an occupation is at increased risk of carcinogenicity, without identification of specific causative agents, do not affect SDS requirements.

What CSHOs should look for when evaluating the SDS

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When performing an inspection, the CSHO [Compliance Safety and Health Officer] must determine the type of company they are evaluating (downstream user, manufacturer, distributor or importer). If the company is a downstream user or distributor and the CSHO finds an inadequate SDS, the CSHO will initiate the referral procedures in Appendix G of this Instruction. If the company is the manufacturer or importer, the CSHO shall follow the instructions detailed below.

  1. When a chemical has been determined to be a carcinogen by NTP or IARC:

  2. If the designation of a carcinogen by NTP or IARC appears on the SDS but the chemical is not classified as a carcinogen by the manufacturer or importer:

    If the neither the label nor Section 2 of the SDS indicate the chemical is a carcinogen, but Section 11 of the SDS notes positive findings of carcinogenicity by NTP or IARC, it indicates the hazard evaluation performed by the manufacturer or importer conflicts with the evaluation of NTP and/or IARC.

    In these cases, the CSHO [Compliance Safety and Health Officer] should request that manufacturer or importer provide any data and justification it has for the classification.

    The Area Director (AD) shall refer the this information to the Regional Hazard Communication Coordinator who shall refer it to OSHA's Directorate of Technical Support and Emergency Management (DTSEM), Health Response Team (HRT). HRT scientists will conduct a review of the carcinogen evaluation for conformance with 29 CFR 1910.1200(d) and Appendix A, chapter A.6. A bulk sample of the chemical may be needed by the SLTC (HRT) to assist in their review.

    If HRT scientists find that the manufacturer has followed appropriate classification procedures as discussed in Appendix B of this Instruction, then no further action will be taken. If there are deficiencies in the classification procedures (e.g., relevant data not adequately addressed, weight of evidence not performed in accordance with Appendix A.0 and A.6 of the HCS standard, criteria not applied appropriately), a citation may be issued. Table C-2 provides a general guide regarding the labeling and SDS requirements under the HCS.

Table C-2: Guidance for Label and SDS Notations for Carcinogens

Source Label SDS
Regulated by OSHA as a carcinogen X X
If a manufacturer has NOT performed its own weight-of-evidence evaluation
Classification of carcinogen based on positive evaluations from IARC/NTP X X
If a manufacturer has performed an appropriate weight-of-evidence evaluation
Weight of evidence for carcinogenicity meets the criteria listed in A.6 X X
If manufacturer finds weight of evidence does not meet Appendix A.6 of the HCS standard  
Listed on NTP Report on Carcinogens (see Note) Not required X
Listed in IARC Monographs
 IARC - Group 1 (see Note)
 IARC - Group 2A (see Note)
 IARC - Group 2B (see Note)
 IARC - Group 3
 IARC - Group 4
Not required
Not required
Not required
Not required
Not required
Not required
Not required
Other Considerations
One positive study
(see Note)
Not required X
Category 2 Carcinogen ingredients ≥ 1% in a mixture X X
Category 2 Carcinogen ingredients ≥ 0.1% and < 1% in a mixture Optional X

Note: If the weight of evidence supports non-classification.

IARC information can be found at http://www.iarc.fr.

NTP information can be found at http://ntp.niehs.nih.gov/pubhealth/roc/roc13/index.html, or most recent report.

Carcinogen of lubricating oils

On December 20, 1985, OSHA published an interpretive notice in the Federal Register regarding the carcinogenicity of lubricating oils (Vol. 50 FR 51852). The notice was published in response to a number of inquiries which were received regarding the applicability of the HCS requirements to naphthenic lubricating oils which are refined using a hydrotreatment process. These types of oils may be found in a number of industrial operations, including ink manufacture and the production of synthetic rubber.

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Positive findings of carcinogenicity by the International Agency for Research on Cancer (IARC) must be reported under the HCS. The IARC Monograph 33 concludes that there is sufficient evidence to indicate that mildly hydrotreated and mildly solvent refined oils are carcinogenic. Therefore, under the requirements of the HCS, producers of such materials must report such findings on the MSDS for the substance and include appropriate hazard warnings on labels.

IARC also stated that there is inadequate evidence to conclude that severely hydrotreated oils are carcinogenic, and that there is no evidence to indicate that severely solvent-refined oils are carcinogenic. In the absence of any valid, positive evidence from sources other than IARC regarding the carcinogenicity of severely hydrotreated or severely solvent-refined oils, no reference to carcinogenicity need be included on the MSDS and label for such materials. IARC has also concluded that when an oil is refined using sequential processing of mild hydrotreatment and mild solvent refining, there is no evidence of carcinogenicity.

The questions posed to OSHA concerned the process parameters used for mild hydrotreatment. OSHA examined the studies upon which IARC based its positive findings and concluded that any oil will be considered to be mildly hydrotreated if the hydrotreatment process was conducted using pressure of 800 pounds per square inch or less, and temperatures of 800 degrees Fahrenheit or less, independent of other process parameters. If the oil is produced within these parameters, it must be considered to be potentially carcinogenic under the requirements of the HCS.

1 Chemical manufacturers and importers have three months to update the SDS after becoming newly aware of information on a hazard. If a chemical has been listed by IARC or NTP within the past three months, then a citation is not appropriate.

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