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.

May 21, 1976

Donald L. Morgan, Esquire
Cleary, Gottlieb, Steen & Hamilton
1250 Connecticut Avenue, N.W.
Washington, D.C. 20036

Dear Mr. Morgan:

This is in response to your November 5, 1975 and March 3, 1976 letters requesting an interpretation of the scope of the carcinogens standard, 29 CFR 1910.1003 - 1910.1016. Specifically, you inquired as to whether liquid particles and gases or vapors which are emitted from solid or liquid mixtures which are exempt from the standard because they contain less than 1.0 or 0.1 percent of a specified carcinogen, are themselves exempt from the standard. You pointed out that by letter dated July 22, 1975 we advised you that dusts emitted from such substances were exempt.

Each section of [T]he carcinogens standard provides that solid or liquid mixtures containing less than 1.0 (or 0.1) percent by weight or volume of a specified carcinogen are exempt from the standard. For instance, 29 CFR [1910.1003(a)(2)] provides: "This section shall not apply to solid or liquid mixtures containing less than 0.1 percent by weight or volume of beta-Naphthylamine."

(Correction 06/27/00)

Solid or liquid mixtures containing less than 0.1 percent by weight or volume of 4-Nitrobiphenyl; methyl chloromethyl ether; bis-chloromethyl ether; beta-Naphthylamine; benzidine or 4-Aminodiphenyl; and

Solid or liquid mixtures containing less than 1.0 percent by weight or volume of alpha-Naphthylamine; 3,3'-Dichlorobenzidine (and its salts); Ethyleneimine; beta-Propiolactone; 2-Acetylaminofluorene; 4-Dimethylaminoazobenzene, or N-Nitrosodimethylamine.]

The purpose of the exemptions, as stated in the preamble to the standard, is to allow the use of mixtures containing minute amounts of known or suspected carcinogenic substances because insufficient evidence exists that these mixtures present a risk to employee health and that they are ingredients essential to the production of necessary materials used by large segments of industry, 39 Fed. Reg. 3758-3759.

The exemption, read narrowly, applies only to solid or liquid mixtures containing less than 0.1 or 1.0 percent by weight or volume of a specified carcinogen. However, it is our understanding that many of these mixtures cannot be used without the emission of liquid particles, vapors or dust and therefore, we believe that the exemption must be read in light of its purpose to include minute unavoidable emissions in order to avoid substantial obstruction of many processes essential to American industry. Thus, unavoidable emissions from exempt mixtures, in the form of dust, vapors and liquid particles would be exempt so long as there is insufficient evidence available to conclude that such emissions present a carcinogenic hazard to employees and so long as use of exempt mixtures resulting in such emissions must continue to prevent closing down large segments of industry.

You inquired specifically about the emission of beta-Naphthylamine (BNA) as dust and vapor from exempt mixtures in the production of tobias acid by your client, American Cyanamid. We believe such emissions to be exempt from the standard because there is no available evidence that they will present a carcinogenic hazard to employees (even though BNA is a known carcinogen), because tobias acid is essential to the production of printing ink, and because tobias acid cannot be produced without such emissions. However, if evidence does become available in the future suggesting a link between cancer and such small quantities of BNA, or changes in technology render employee exposure to emissions containing BNA unnecessary, we would have to reconsider our position. Reconsideration would be necessary because the exemption is extrapolated to allow employee exposure to liquid particles, dusts and vapors emitted from exempt mixtures is not meant to allow such exposure if evidence becomes available that BNA in these emissions exposes employees to the risk of developing cancer. Also, it is not intended to allow employee exposure to BNA in the emissions if such exposure could be avoided without obstruction of an essential industrial process.

Finally, you should be aware of the fact that we are considering proposing amendments to the carcinogen standards to set specific exposure or contamination limits for each carcinogenic substance. These amended standards would possibly not contain any exemptions such as presently stated and would most likely require monitoring of employee exposure, medical surveillance and other provisions which characterize other health standards, such as the one regulating vinyl chloride exposure.


Morton Corn
Assistant Secretary of Labor