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OSHA Hazard Communication Letters of Interpretation
Hazard evaluation of mixtures containing established mutagens.
- Issued
- Record type
- Interpretation
- Historical standard
- 1910.1200, 1987 expanded rule (PDF)
- Current standard
- HCS 2024, as amended
ILPI assessment: Old mutagenicity and mixture shortcuts are superseded
This letter addresses the obsolete 1987 version of the Hazard Communication Standard (HCS). Its statement that HazCom does not require new testing remains consistent, but the old dismissal of in-vitro evidence and universal mixture thresholds must not be used as current classification or SDS guidance.
Under the current HCS, apply all relevant evidence, germ-cell mutagenicity criteria, mixture criteria and ingredient disclosure. In-vitro results must be considered in the weight of evidence; they are not automatically irrelevant merely because no animal/human study accompanies them. The criteria distinguish categories and mixture cutoffs. No new test is required, but the available evidence must be evaluated. Mutagen, in vitro (outside a living organism) and sensitizer explain the concepts. OSHA marks its matching source corrected December 6, 2024.
Last reviewed: .
About this ILPI assessment
This comparison with current requirements is not a finding that OSHA has formally withdrawn this letter. This assessment reflects editorial judgment informed by human review and AI assistance. It is an opinion, may contain errors or omissions, and is not an official OSHA determination. For guidance on how OSHA requirements apply to your circumstances, contact your local OSHA office.
OSHA's notice about interpretation letters
The following notice is published on OSHA's interpretation pages; it is general guidance, not a letter-specific withdrawal notice.
OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.
Source: OSHA's original letter page.
November 4, 1993
Mrs. J. L. Bunyan
Deputy Registration Manager
SafePharm Laboratories Ltd.
Post Office Box No. 45
Derby DEI 2BT
England
Dear Mrs. Bunyan:
This is a response to your letter of April 21, concerning the requirements under the Occupational Safety and Health Administration's (OSHA) Hazard Communication Standard (HCS), 29 CFR 1910.1200 [ILPI: Original HCS 1987 context (PDF) · Current HCS], for hazard evaluation of mixtures containing established mutagens. We will respond to your questions as they were presented in your correspondence.
- If a mixture contains a known quantity of one or more mutagenic ingredients, is the mixture deemed to be mutagenic, or is further testing required to prove mutagenic potential?
- Is there a minimum level of a mutagenic ingredient contained in a mixture above which the mixture does not need testing, but can be assumed to be mutagenic?
OSHA's Hazard Communication Standard (HCS) (29 CFR 1910.1200 [ILPI: Original HCS 1987 context (PDF) · Current HCS]) does not specifically address mutagenicity in either the text of the standards final rule (Federal Register, August 24, 1987) or the preamble discussions. It is the agency's position that in vitro [ILPI note: "outside a living organism, such as in cultured cells"] tests, independent of other data, do not establish a health hazard as specified under the hazard determination provisions of the standard. Under the HCS the manufacturer does have the responsibility to review all available scientific data when performing a hazard determination for the chemicals they produce. If an in vitro study is the only data available linking a mutagenic response to a chemical exposure, then these studies do not have to be reported on the product's MSDS. Also in terms of testing for mutagenic potential, the HCS [ILPI: Original HCS 1987 context (PDF) · Current HCS] does not require testing of chemicals to determine their hazards.
[ILPI note: At issuance: 1910.1200, 1987 expanded rule (PDF). The modern germ-cell mutagenicity criteria expressly consider in-vitro evidence in classification. Do not discard it categorically. Current mixture criteria and SDS ingredient disclosure replace the old universal-percentage shorthand.]
Please refer to the answer above, the standard does not require testing. For mixtures of hazardous chemicals the HCS requires the following:
If a hazardous chemical is present in the mixture in quantities (i.e., 0.1% for carcinogens, and 1% for other health hazards), it must be reported unless the mixture has been tested as a whole or unless the material is bound in such a way that employees cannot be exposed. If there really is no exposure (and the standard defines exposure as including potential as well as measurable exposure by any route of entry), either under normal conditions of use or in a foreseeable emergency, then the chemical is not covered by the standard, (See Paragraph (b)(2) of 29 CFR 1910.1200 [ILPI: Original HCS 1987 context (PDF) · Current HCS]). Further, information must also be included on a MSDS for ingredients of a mixture present in concentrations of less than 1% (or 0.1% for carcinogens) when the hazardous substance may be released in a concentration which exceeds an OSHA Permissible Exposure Limit or an American Conference of Governmental Industrial Hygienist's Threshold Limit Value or may present a health risk to exposed employees. An example of the latter may be TDI [ILPI note: "Toluene-2,4-diisocyanate"] because it is a sensitizer in very small concentrations, thereby presenting a health risk that must be noted on the MSDS.
We hope this information is helpful. If you have any further questions please contact the Office of Health Compliance Assistance at (202) 219-8036.
Sincerely,
Roger A. Clark, Director
Directorate of Compliance Programs
The original official public domain version of this document is available from OSHA at https://www.osha.gov/laws-regs/standardinterpretations/1993-11-04.