Radon gas is released naturally by radioactive decay within rock formations, from where it can percolate to the surface and infiltrate basement and trenching, and then produce hazardous concentrations if trapped or spread throughout the structure by the ventilation system. Because of its radioactive origin, radon can pose health risks – it’s the leading cause of lung cancer in non-smokers. The US Environmental Protection Agency (EPA) administers extensive information programs, which encourage in-building testing (especially in housing), and provides guidance for hazard reduction. EPA’s authority derives primarily from the Indoor Radon Abatement Act of 1988 (codified as Title III of the Toxic Substances Control Act (TSCA)). In addition, the Occupational Safety and Health Administration (OSHA) considers radon a type of ionizing radiation subject to worker protection requirements. The remainder of this note provides background to radon hazards and their management, referencing information from EPA, OSHA and other agencies and professional organizations.
How do radon hazards arise?
As uranium naturally decays, its radioactive “decay chain” produces a series of decay products that themselves decay further, including radon. Most uranium exists in subsurface rocks, where radon gas is generated. Some of that gas percolates to the surface, where it can release directly into the atmosphere or can infiltrate basements, lower levels of buildings, and utility and other trenching. Once inside, it may be trapped and/or can be circulated through the building by ventilation systems.
When someone breathes air containing radon, they are exposed to the radioactivity from the radon and its decay products (including longer exposures if particles are trapped in lung tissue). These radioactive exposures can lead to lung cancer. EPA cites statistics identifying radon as the second leading cause of lung cancer, responsible for about 21,000 lung cancer deaths annually (2,900 among people who have never smoked).
How can building-related radon hazards be managed and reduced?
Methods for managing radon hazards in buildings can be incorporated into construction practices, and some can be readily applied to retrofit existing buildings.
New construction
Buildings can be constructed in ways that reduce hazards of radon infiltration and concentration, at relatively low cost. Guidance from EPA and others focuses on residential construction, but many of the same approaches apply to commercial and other building types as well. EPA identifies the following techniques for radon exclusion and management:
- Gravel - below the foundation/slab, to allow soil gases, including radon in the soil to move freely underneath the house.
- Plastic Sheeting or Vapor Retarder - heavy duty plastic sheeting or a vapor retarder on top of the gravel to prevent soil gases from entering the house.
- A Vent Pipe – 3 or 4 inch pipe, run vertically from the gravel layer through the conditioned space and roof to safely vent radon and other soil gases outside above the house.
- Sealing and Caulking - all openings, cracks, and crevices in the foundation floor and basement walls to exclude radon and other soil gases.
- Junction Box - install an electrical junction box in the attic, in case testing shows a need for a vent fan.
EPA also references technical codes from the International Code Council (ICC), National Fire Protection Association (NFPA), and American National Standards Institute (ANSI) and Indoor Environments Association (AARST).
Radon mitigation in existing construction
Some of the new-construction techniques may not be realistic in mitigation activities (particularly activities under an existing foundation), but mitigation measures are available and beneficial:
- Sealing basement and other underground areas, including around pipe/conduit entries
- Venting basement and other underground areas – standpipe through the structure to roof, or ventilation pipe directly to outside (with suction and any appropriate safeguards)
What testing and monitoring does EPA recommend?
EPA recommends that homes (and other buildings) be tested to identify possible radon contamination. Testing kits are available for purchase, including from the National Radon Program Services at Kansas State University. EPA recommends homes be fixed if the radon level is 4 picocuries per liter (pCi/L) or more. Because there is no known safe level of exposure to radon, EPA also recommends that homeowners consider mitigation if radon levels exceed 2 pCi/L (EPA identifies a national study that found average indoor radon concentration in homes of about 1.3 pCi/L).
What worker protections does OSHA require?
OSHA considers radon to be a Naturally Occurring Radioactive Material (NORM), subject to evaluation and possible controls under OSHA’s Ionizing Radiation Standard (29 CFR 1910.1096) (I wrote about it HERE). OSHA notes situations where workers can be exposed to radon include:
- in a structure controlled by an employer
- when working in trenches or excavations
- during radon remediation work or other work in areas with elevated radon levels.
OSHA’s Ionizing Radiation Standard requires employers to conduct surveys as necessary to comply with its protective provisions. OSHA notes that sealing to minimize infiltration may successfully mitigate the hazard. OSHA provides a Permissible Exposure Limit (PEL) Time Weighted Average (TWA) of 100 pCi/L for adult workers during 40 hours in a consecutive 7-day period (note this level is much higher than EPA’s, which covers residents including children, elderly, and health-impaired individuals).
What happens now?
Radon-related activities by EPA, OSHA and others have not changed recently, However, organizations have ongoing responsibilities to mitigate radon hazards, and those hazards are not self-minimizing, so organizations should review their locations to evaluate and respond to such hazards.
Self-evaluation checklist
Does the organization conduct any activities in areas subject to radon infiltration (e.g., buildings or trenches)?
If so, has the organization tested the potentially affected areas for radon levels?
- Once or periodically
- On an ongoing basis
Has the organization taken steps to mitigate radon intrusion/concentration in affected areas?
Where can I go for more information?
- EPA –
- Indoor Air Quality web portal
- OSHA
- Ionizing Radiation web portal
- National Radon Program Services (Kansas State University)
- Centers for Disease Control and Prevention (CDC) Radon web portal
About the Author
Jon Elliott is President of Touchstone Environmental and has been a major contributor to STP’s product range for over 30 years.
Mr. Elliott has a diverse educational background. In addition to his Juris Doctor (University of California, Boalt Hall School of Law, 1981), he holds a Master of Public Policy (Goldman School of Public Policy [GSPP], UC Berkeley, 1980), and a Bachelor of Science in Mechanical Engineering (Princeton University, 1977).
Mr. Elliott is active in professional and community organizations. In addition, he is a past chairman of the Board of Directors of the GSPP Alumni Association, and past member of the Executive Committee of the State Bar of California's Environmental Law Section (including past chair of its Legislative Committee).
You may contact Mr. Elliott directly at: tei@ix.netcom.com