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OSHA Hazard Communication Letters of Interpretation
Clarification of the terms "appropriate hazard warning" and "mandatory".
- Issued
- Record type
- Interpretation
- Historical standard
- 1910.1200, original 1983 rule (PDF)
- Current standard
- HCS 2024, as amended
ILPI assessment: Current classification and label criteria replace historical wording discretion
This letter addresses the original 1983 Hazard Communication Standard (HCS), which is now obsolete. Its requirement to examine relevant evidence remains useful, but current hazard classification and prescribed shipped-label elements replace the old freely chosen warning approach. Apply paragraph (d), acute-toxicity criteria, single-exposure/repeated-exposure target-organ criteria, and shipped-container label requirements and Appendix C.
The oral-dose example below prints “LC(50)” with mg/kg. That wording also appears on OSHA's matching page and is preserved here. In current Appendix A.1, oral-dose criteria use LD50 in mg/kg; inhalation LC50 uses concentration units. Do not carry this historical notation or example warning into a modern classification without applying the actual route-specific criteria.
The original Appendix B required hazard determination, not classification; today's Appendix B addresses physical hazards, while health criteria are in Appendix A. These are not interchangeable appendices. The historical CPL 2-2.38A also differs from the later 1998 directive; its exact historical text has not been independently verified here. Current enforcement counterpart: current HCS inspection procedures.
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This comparison with current requirements is not a finding that OSHA has formally withdrawn this letter.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.
January 20, 1987
Mr. D. S. Richardson
2655 Harland Drive
Hudson, Ohio 44236
Dear Mr. Richardson:
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This is in response to your letter of December 13, 1986, requesting clarification of the terms "appropriate hazard warning" and "mandatory" as used in the Occupational Safety and Health Administration's (OSHA) (OSHA) Hazard Communication Standard .
[ILPI note: At issuance: original 1983 rule, including its health-hazard Appendix A and hazard-determination Appendix B (PDF). Current counterparts: evidence evaluation, health-hazard criteria in Appendix A, and shipped labels with Appendix C. Today's Appendix B concerns physical hazards. The historical CPL text has not independently been verified; current enforcement counterpart: HCS inspection procedures.]
Concerning "appropriate hazard warning," OSHA's guidelines to its compliance staff on the Hazard Communication Standard OSHA Instruction CPL 2-2.38A Change 1, page A-11, enclosed states that the specific hazards indicated in the standards definition for "physical" and "health" hazards must be used in evaluating the appropriateness of specific warnings. In the example you presented, if the only scientific information available is the LC(50) of 5 milligrams per kilogram administered orally to rats, "highly toxic if ingested" may be the appropriate warning . If the chemical causes specific target organ effects when ingested, then the specific target organ effects would be appropriate.
[ILPI note: The source prints LC(50) for this oral mg/kg example. Current oral acute-toxicity criteria use LD50 in mg/kg, while inhalation LC50 uses concentration units. The historical warning example is not a current classification instruction.]
As stated in Appendix B of the Hazard Communication Standard , the hazard determination is performance-oriented and relies heavily on the professional judgment of the evaluator. Nevertheless, the hazard determination must examine all relevant data and produce a scientifically defensible evaluation. The results of any studies which are designed and conducted according to established scientific principles must be reported if statistically significant health effects are found. If these statistically significant health effects are known to the target organ level, then these health effects would be "appropriate."
If only general health effects are known, then it would be "appropriate" to list these on the label.
The Hazard Communication Standard at 29 CFR 1910.1200(d)(2)
states, Appendix A shall be consulted for the scope of health hazards covered.
The term "mandatory" refers to the requirement to consult Appendix A for the scope of health hazards.
Please feel free to contact us, if further assistance is needed.
Sincerely,
John A. Pendergrass
Assistant Secretary
The original official public domain version of this document is available from OSHA at https://www.osha.gov/laws-regs/standardinterpretations/1987-01-20.