May 19, 2009 Gerald S. Zavorsky, Ph.D. Department of Obstetrics, Gynecology and Women's Health School of Medicine/Saint Louis University 6420 Clayton Road, Suite 290 St. Louis, MO 63117 Dear Dr. Zavorsky: Thank you for your February 19, 2009, letter, to the Occupational Health and Safety Administration (OSHA). Your letter has been referred to the Directorate of Enforcement Programs for an answer to your question regarding the permissible exposure limit (PEL) for nitric oxide (NO). This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any question not detailed within your original correspondence.

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Question: Does the OSHA PEL for nitric oxide, which is 25 parts per million (ppm) as an 8-hour time-weighted average (TWA), apply to pregnant women? If not, what is the OSHA PEL for pregnant women exposed to nitric oxide?

Reply: OSHA's Air Contaminants standard (29 CFR 1910.1000) provides limits for employee exposures. In Table Z-1 of 1910.1000, limits for air contaminants are provided for many substances, including nitric oxide. OSHA's permissible exposure limit of 25 ppm for occupational exposure to nitric oxide measured as an 8-hour TWA is applicable to all employee exposures to nitric oxide, including employees who may be pregnant. Please be mindful that, in addition to the requirement to limit occupational exposures to a level below the OSHA PEL, employers may have other responsibilities for ensuring employee protection. As an example, employers having employees exposed to hazardous chemicals must comply with OSHA's Hazard Communication Standard (29 CFR 1910.1200) . This standard requires employers to provide information to their employees about the hazardous chemicals to which they are exposed. In accordance with this standard, employers must establish a hazard communication program [29 CFR 1910.1200(e)] and must make labeling and material safety data sheets available to employees [29 CFR 1910.1200(f) and (g), respectively] and provide for employee training [29 CFR 1910.1200(h)]. Pregnant employees and their employers should consult the MSDSs for the chemicals they use to determine whether those chemicals present reproductive or pregnancy-related hazards.

Sincerely,

Richard E. Fairfax, Director
Directorate of Enforcement Programs