Target-organ toxicity classification for mixtures

March 4, 2014

Erik C. Baptist

Counsel

American Petroleum Institute

[Recipient address omitted]

Re: Request for Interpretation of OSHA's Amended Hazard Communication Standard (HCS 2012) about classification criteria for Single Target Organ Toxicity

Dear Mr. Baptist:

This letter is being issued to API to provide additional guidance on how to apply the classification criteria for Single Target Organ Toxicity (STOT) to mixtures under the March 26, 2012, revisions to OSHA's Hazard Communication Standard (HCS 2012).

In particular, for mixtures containing from 1% to less than 10% of a Category 1 STOT (single exposure (SE) or repeat exposure (RE)), you asked whether there were any circumstances in which OSHA might accept a classification of the mixture as a Category 2 STOT. OSHA agrees that under the following limited circumstances, such a classification would be acceptable.

Mixtures containing from 1% to less than 10% of Category 1 STOT-SE ingredients may be classified as Category 2 STOT-SE under the limited following circumstances. A.8.3.1 allows for the classification of mixtures under the criteria as used for substances. Where the classification of the ingredients is based on animal data only (see A.8.2.1.6), the use of the guidance values in Table A.8.1 is appropriate as a part of the total weight of evidence approach. It may be appropriate, in light of the guidance values, to classify a mixture containing from 1% to less than 10% of Category 1 STOT-SE substances as a Category 2 STOT-SE hazard, where warranted by the weight of evidence. Such a classification must be consistent with all of the criteria in A.8.2.1 ("Substances of Category 1 and Category 2"), including consideration of the severity of the effect observed. However, OSHA would not accept a determination not to classify a mixture based on this approach.

Mixtures containing from 1% to less than 10% of Category 1 STOT-RE ingredients may be classified as Category 2 STOT-RE under the limited following circumstances. A.9.3.1 allows for the classification of mixtures under the criteria as used for substances. Where the classification of the ingredients is based on animal data only (see A.9.2.6) the use of the guidance values in Tables A.9.1 and A.9.2 is appropriate as a part of the total weight of evidence approach. It may be appropriate, in light of the guidance values, to classify a mixture containing from 1% to less than 10% of Category 1 STOT-RE substances as a Category 2 STOT-RE hazard, where warranted by the weight of evidence. Such a classification must be consistent with all of the criteria in A.9.2 ("Classification Criteria for Substances"), including consideration of the severity of the effect observed. However, OSHA would not accept a determination not to classify a mixture based on this approach.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. 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.

Sincerely,

David Michaels, Ph.D, MPH

cc: Lawrence P. Halprin, Esq.

Keller and Heckman LLP

Attorney for API