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.

August 4, 1999

Charles H. Rose (MA,MSPH,D(ABSNM))
Executive Director
American Association for Nuclear Cardiology, Inc.
5660 Airport Boulevard
Suite 101
Boulder Colorado 80301

Dear Mr. Rose:

This is in response to your January 19, 1999 letter regarding the measurement of employee exposures to ionizing radiation. We apologize for the delay in our reply.

You report that some organizations have proposed and implemented a new method of monitoring the occupational radiation exposure of individuals who wear a protective apron. You state that these individuals may be monitored, for example, as follows:

One monitoring device is worn under the protective apron and a second one is worn outside the protective apron at the neck. An effective dose equivalent for external radiation is determined by multiplying the reading of the device located at the waist under the protective apron by 1.5 and adding this value to 0.04 of the reading of the device located at the neck.

You state that, "The American Association for Nuclear Cardiology (AANC) strongly opposes this "new" method of calculating occupational exposure." The AANC requests that the Occupational Safety and Health Administration (OSHA) state its position on this issue.

The "new" method of determining occupational exposure to external radiation does not conform with OSHA's standard for ionizing radiation, 29 CFR 1910.1096. As indicated by Table G-18 within 29 CFR 1910.1096(b)(1), OSHA considers the components of the whole body to be the head and trunk, the active blood-forming organs, the lenses of the eyes, and the gonads. The head and trunk includes the neck, thus the neck is part of the whole body. According to 29 CFR 1910.1096(a)(5), a dose to the whole body is the quantity of ionizing radiation absorbed, per unit mass, by any portion of the whole body. Therefore, the actual reading of the monitoring device that is positioned at the individual's neck indicates the whole body dose received by the individual. In point of fact, the whole body dose must be reported as the highest dose received by any region of the whole body.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. Please be aware that OSHA's enforcement guidance is subject to periodic review and clarification, amplification, or correction. Subsequent rulemaking could also affect such guidance. In the future, should you wish to verify that the guidance provided herein remains current, you may consult OSHA's website at http://www.osha.gov. If you have any further questions, please feel free to contact OSHA's Office of Health Compliance Assistance at (202) 693-2190.


Richard E. Fairfax, Director
Directorate of Compliance Programs