What are the Standards and Regulations for Environmental Radon Levels?

Learning Objectives

Upon completion of this section, you will be able to

  • Identify the U.S. Environmental Protection Agency’s (EPA) recommended maximum indoor residential radon level.

Currently, no federal regulations govern acceptable radon levels for indoor residential and school environments. But guidelines are available. EPA based its guidelines not only on risk considerations, but also on technical feasibility.

Regulators periodically review radon standards and guidelines, and changes may occur over time. Consult EPA or state health departments for the most up-to-date standards.

Some estimates are that if homes with radon concentrations exceeding the EPA action level were to reduce concentrations below that level, approximately one-third of radon-induced lung cancer could be avoided. Eliminating all radon exposure is, however, not possible (ACS 2006).

EPA Maximum Recommended Level Guidelines

EPA has set guidelines for maximum environmental radon levels based on limiting the risk of developing lung cancer from radon exposure. EPA has also developed methods for remediating sites to reduce radon levels effectively.

The EPA environmental radon level recommends remediation at a maximum of 4 picocuries/liter (pCi/L) of radon in air, with the caveat that radon concentrations below this level still carry a risk and in many cases are reducible (EPA 2009c).

For example, an area of a house has concentrations of radon between 2-4 pCi/L and this area is inhabited or heavily used—especially by children. To minimize potential health risks, consider remediating and lowering the environmental radon level.

The Indoor Radon Abatement Act of 1988

In October 1988, Congress enacted the Indoor Radon Abatement Act (EPA 1988), which established a long-term goal of indoor air as radon-free as the ambient, outside air. The law authorized funding for radon-related activities at the state and federal levels to

  • Establish state programs and providing technical assistance,
  • Conduct radon surveys of schools and federal buildings,
  • Establish training centers and a proficiency program for firms offering radon services,
  • Develop a citizen’s guide to radon, and
  • Develop model construction standards.
Table 1. Standards and regulations for radon in air
Source* Focus Level Comments
Indoor Radon Abatement Act Indoor air (residential) Indoor = outdoor (~0.4 pCi/L National goal
National Council on Radiation Protection and Measurements (NCRP) Indoor air (residential) 2 WLM
= 8-10 pCi/L if the equilibrium ratio is 40-50%
NCRP 1993 Guideline
(EPA) Indoor air (residential)

4 pCi/L

4 pCi/L

Current action level

Guideline for action

NIOSH Occupational (mining) 1 WLM/year and ALARA§ Advisory; exposure limit
OSHA Occupational

4 WLM/year

100 pCi/L averaged over a 40-hour work week



MSHA Mining

4 WLM/year

1 WL in active, working mines

NRC Occupational

7000 pCi/L

9 pCi/L

4000 pCi/L

30 pCi/L

220Rn w/o daughters

220Rn w/daughters

222Rn w/o daughters

222Rn w/daughters

USNRC Annual average effluent air concentration

20 pCi/L

0.03 pCi/L

10 pCi/L

0.1 pCi/L

220Rn w/o daughters

220Rn w/daughters

222Rn w/o daughters

222Rn w/daughters

WHO (2009) Residential

2.7 pCi/L (preferred)

8.1 pCi/L (if the lower level is unreachable due to prevailing country-specific conditions).

Proposed national reference level

* NCRP = National Council for Radon Protection; EPA = U.S. Environmental Protection Agency; NIOSH = National Institute for Occupational Safety and Health; OSHA = Occupational Safety and Health Administration; MSHA = Mine Safety and Health Administration; USNRC = U.S. Nuclear Regulatory Commission; WHO = World Health Organization

EPA recommends action below 4 pCi/L in schools on a case-by-case basis

WLM = working level month; a unit of measure commonly used in occupational environments (since WLM bears a complex relationship to pCi/L, physicians with responsibility for mine workers are urged to contact NIOSH or EPA for further information)

§ ALARA = As low as reasonably achievable

Key Points
  • Currently, no federal, enforceable regulations control indoor radon levels—only guidelines with recommendations and a national goal.
  • EPA recommends abatement or remediation when indoor radon air concentrations equal or exceed 4 pCi/L.