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 16, 1989



MEMORANDUM FOR: Harvey E. Harris, Director
Office of Training and Education
THROUGH: Bruce Hillenbrand, Director
Directorate of Federal-State Operations
FROM: Patricia K. Clark, Acting Director
Directorate of Compliance Programs
SUBJECT: The Ionizing Radiation Standard, 29 CFR 1910.1096


This is in response to your memorandum of October 20, 1988, requesting some interpretations and policy determinations for the standard for ionizing radiation, 29 CFR 1910.1096.

Neither 29 CFR 1910.1096 nor the original standard on which it is based, 10 CFR 20, define restricted areas for ionizing radiation or airborne radioactive materials in terms of the potential level of exposure. "Unrestricted area" is defined at 10 CFR 20.105(b)(1) and (2) and at 10 CFR 20.106(a), however. It follows, therefore, that areas that cannot qualify as "unrestricted areas" are "restricted areas."

"Unrestricted areas" for ionizing radiation are areas where even if an employee were continuously present in the area (1) the dose received in any one hour could not exceed two millirems, or (2) the dose received in any seven consecutive days could not exceed 100 millirems. "Unrestricted areas" for airborne radioactive materials are areas where concentrations do not exceed the limits specified in Table 2 of Appendix B to 10 CFR 20. The concentrations may be averaged over a period not greater than one year.

Standard 29 CFR 1910.1096 defines three types of restricted areas that must be identified and have their boundaries demarcated with special warning signs. They are "radiation area," "high radiation area," and "airborne radioactive area."

An employer possesses radioactive material and comes under the scope of 29 CFR 1910.1096 if there are artificially enhanced concentrations of environmental radon-222 in the workplace. If environmental radon-222 concentrations have not been artificially enhanced, they are very much lower than the permissible exposure limit (PEL) Accordingly, only artificially enhanced concentrations of environmental radon-222 would be sufficiently high that provisions of 29 CFR 1910.1096 would go into effect. The most common places for significant artificial enhancement of radon-222 concentrations to occur are the inside of buildings or other types of enclosures constructed on or in the ground.

As you noted, footnote 3 to Table 1 of Appendix B to 10 CFR 20 states that "the limit on [exposure to] radon-222 concentrations in restricted areas may be based on an annual average." OSHA must permit employers to follow this option.

[This document was edited on 06/24/2003 to strike information that no longer reflects current OSHA policy. See the 12/23/2002 Letter to
Ms. Connie DeWitte Letter for the current policy.]

OSHA obviously cannot spare enough resources to measure the annual average concentration of airborne radon-222 exposure received by an employee. It is not necessary for OSHA to do this measurement in order to determine and enforce compliance with the exposure limit, however. Rather, OSHA can reach these objectives by enforcing compliance with the survey requirement described at 29 CFR 1910.1096(d) and assuring that employers take appropriate corrective action when their measurements show any employees overexposed to radon-222.

A survey is defined as "... an evaluation of the radiation hazards incident to the production, use, release, disposal, or presence of radioactive materials or other sources of radiation under a specific set of conditions. When appropriate such evaluation includes measurements of concentrations of radioactive material present." An employer's evaluation of a radon-222 hazard will frequently have to be done in two stages. The first stage would consist of several short duration samples intended to find any areas where radon-222 concentrations may be excessive. The second stage would involve long duration sampling to accurately determine the long-term, time-weighted average radon-222 concentrations in the areas where short duration samples indicated that the concentrations might be excessive.

Before citing an employer for not doing a survey to evaluate the radiation hazard incident to the presence of radon-222 gas, OSHA will have to obtain information supporting the need for the survey. Usually OSHA will have to produce this information through its own exploratory measurements of radon-222 concentration levels.

Decisions on when to sample for radon-222 may be done in the area offices at the level of the supervisory industrial hygienist. You will note that the exposure limits for airborne radioactive materials listed in Appendix B to 10 CFR 20 are expressed as concentrations above natural background radioactivity. However, true background radioactivity is so small relative to the limit for radon-222 in Table I, that it may be disregarded. We have referred your inquiry about sampling instruments and procedures to the [Directorate Science,Technology, and Medicine(DSTM)].

Twenty-nine states have entered into agreements with the Nuclear Regulatory Commission (NRC). All twenty-nine states operate regulatory programs covering all ionizing radiation hazards, but their agreements with NRC pertain only to specific materials called "agreement materials." Agreement materials are (1) source material, special nuclear material, and byproduct material, as these terms are defined in 10 CFR Part 20, and (2) uranium and thorium tailings resulting from recovery operations. A circular issued by NRC in June, 1987, entitled, "Summary Of the Nuclear Regulatory Commission's Agreement State Program," (copy enclosed) identifies the current NRC agreement States.

NRC periodically reviews agreement State programs for adequacy and compatibility. NRC's authority over agreement States pertain only to agreement materials, however. Thus NRC considers only activities involving agreement materials when determining the acceptability of an agreement State's regulatory program. Consequently, an agreement State that maintains a satisfactory regulatory program for agreement materials will retain the regulatory authority granted by NRC even if it operates a poor program for regulating nonagreement sources and materials, such as x-ray machines. Accordingly, OSHA Instruction STD 1-4.1 and OSHA Instruction STP 2.8 with its attached memorandum from NRC contain correct information and the policy and guidelines contained in them must still be observed.

Some individuals, perhaps even some State officials, may construe 29 CFR 1910.1096(p)(3)(ii) to transfer OSHA's authority for regulating ionizing radiation to NRC agreement States, provided their program for controlling nonagreement materials is compatible with 29 standard CFR 1910.1096. This is a misinterpretation of 29 CFR 1910.1096(p)(3)(ii), however. It does not transfer authority, but describes the conditions when compliance with State requirements will also comply with Federal OSHA requirements.

No NRC agreement State that is not an OSHA State Plan State has had a recent formal determination by the Assistant Secretary of Labor as to whether the State's program for controlling nonagreement materials is compatible with 29 CFR 1910.1096. The lack of a recent determination has no practical effect on OSHA enforcement responsibility, however. That is, OSHA will issue citations to employers not in compliance with 29 CFR 1910.1096 regardless of whether the State's regulatory program is compatible with 29 CFR 1910.1096.

OSHA does not have jurisdiction over Department of Defense ionizing radiation sources that are part of uniquely military equipment, systems, or operations. The use of an ionizing radiation source for medical purposes is not a uniquely military operation so OSHA has jurisdiction over those sources that are not licensed by NRC. In the case where radioactive isotopes are used as a radiation source for medical purposes, any isotopes not produced by nuclear reactors come under the jurisdiction of OSHA as they are not licensed by NRC.

Attachment (Copy of 7-1-89 edition of 29 CFR 1910.5, 1910.6, 1910.7 and 1910.1096)