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Standard Interpretations - Table of Contents
• Standard Number: 1910.1000; 1910.1200; 1910.1200(e); 1910.1200(f); 1910.1200(g); 1910.1200(h)

This letter constitutes OSHA's interpretation only of the requirements discussed and may not be applicable to any situation not delineated within the original correspondence.

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 Safety and Health 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.

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.

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 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 If you have any further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.


Richard E. Fairfax, Director
Directorate of Enforcement Programs

Standard Interpretations - Table of Contents

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