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.

November 7, 1996




SUBJECT:          29 CFR 1910.120(a)(3): Definition of a
                 Hazardous Substance

Thank you for your inquiry concerning OSHA's Hazardous Waste Operations and Emergency Response (HAZWOPER) standard, 29 CFR 1910.120. You requested clarification on the meaning of the definition of "hazardous substance" under paragraph (a)(3) of the standard, where it states under subparagraph (B) of the definition, "any biological agent or other disease-causing agent..." You inquired whether the term "other disease-causing agent" would include any chemical which presents a health hazard, and if so, whether health effects such as irritation or heat stress would be included in the definition of "hazardous substance."

In HAZWOPER, OSHA defined the term "hazardous substance" in such a way as to encompass those substances defined as hazardous by the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Transportation (DOT). This was necessary to ensure consistency and compatibility between the OSHA standard and the rules and regulations of the other agencies.

In the original final rule for HAZWOPER, the language in question was incorporated by reference to section 101(33) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980. To improve clarity, the pertinent language was incorporated directly into the HAZWOPER standard on April 13, 1990, under subparagraph (B) of the definition for "hazardous substance," which reads:


Any biological agent and other disease-causing agent which after release into the environment and upon exposure, ingestion, inhalation, or assimilation into any person...will or may reasonably be anticipated to cause death, disease, behavioral abnormalities, cancer, genetic mutation, physiological malfunctions...or physiological deformations in such persons or their offspring.

As implied by the plain language of this definition, the phrase "other disease-causing agents" refers to any substance not otherwise covered under subparagraphs (A)-(D) of the definition, which causes death, disease, behavioral abnormalities, etc. Correspondingly, crystalline silica, which as you mentioned, causes silicosis and is not otherwise covered under the definition for "hazardous substance," would be considered a hazardous substance under the criteria established in subparagraph (B). Conversely, heat would not be covered under this definition, since heat is not a substance but rather a form of potential energy.

In considering the applicability of the HAZWOPER standard, however, this definition is not the sole determining factor. As stated in paragraph (a)(1) of the standard, HAZWOPER does not apply to operations that do not involve employee exposure or the reasonable possibility of employee exposure to safety or health hazards. In determining whether employees are exposed to safety or health hazards, an employer must not only consider the presence of a hazardous substance but must also evaluate the potential for, as well as the level and duration of, exposure to the hazardous substance.

For example, for operations involving crystalline silica, which after prolonged and extensive exposure can cause silicosis, an employer would evaluate the potential level and duration of exposure to silica dust and would determine whether this exposure scenario presented a potential health hazard. In spill response scenarios, an employer would likely consider the very short duration of exposure and determine that potential health hazards do not exist and thus HAZWOPER would not apply. For a long term cleanup project involving crystalline silica, however, the employer may determine that HAZWOPER does apply based on the potential for prolonged exposure to silica dust and the related silicosis hazard that such exposure would present to workplace employees.

In regards to your question of whether irritation would be considered a disease under subparagraph (B) of the definition for hazardous substance, it would depend on the type of irritation you refer to. For instance, dermatitis is a disease; thus, chemical substances that cause dermatitis would fall under the definition of a hazardous substance. Physical abrasion of the skin (another form of irritation), however, would not be considered a disease; therefore, substances that present only a physical skin abrasion hazard would not fall under the definition of a hazardous substance. As discussed above, determination of the applicability of the HAZWOPER standard to operations that involve hazardous substances (including "other disease-causing agents") must be made on a case-by-case basis depending on the potential for exposure to safety and health hazards.

We hope this information is helpful. If you have any further concerns, please call this office at (202) 219-8036.