Radon Testing Requirements in Uranium Mines, Non-Uranium Mines, and Underground Caverns

The link between lung cancer and radon exposure in uranium mine workers was discovered long before radon was noted as a health risk in homes, schools, and other workplaces. Underground miners, surface miners, and supporting personnel are all susceptible to radon exposure risk.

The “dose” a person receives from the presence of radon gas is derived from the energy emitted from its radioactive decay products. To determine the amount of radon exposure people are exposed to in workplaces, a dose calculation is used to describe the hazard associated with radon. Regulatory requirements for radon testing in mines vary depending on the type of facility and jurisdiction, but the goal is the same: to protect workers from long-term exposure that can lead to lung cancer.

Radon in Uranium Mines

Uranium mines are tightly regulated when it comes to radon testing because of the likelihood of radon gas being released from the uranium-bearing rock.

Regulations:

• In the United States, the Mine Safety and Health Administration (MSHA) and Occupational Safety and Health Administration (OSHA) have established exposure limits for radon decay products to be kept below 4 WLM (Working Level Months) per year (WLM).

• The U.S. Nuclear Regulatory Commission (NRC), formerly the Atomic Energy Commission (AEC), also plays a role for licensed uranium recovery operations.

• The Canadian Nuclear Safety Commission (CNSC) regulates radon and radon progeny exposure in Canadian uranium mines, having set the annual worker exposure limit at 50 mSv (millisieverts) in one year and 100 mSv in five consecutive years.

• Routine monitoring and exposure data must be recorded and reported.

• Engineering controls (like ventilation) and administrative controls (like limiting time in high-radon areas) must be used to keep exposures as low as reasonably achievable (ALARA).

Testing Requirements:

• Continuous and periodic sampling using specialized radon detectors.
• Personal dosimeters for workers to track individual radon exposure.
• Outdoor detectors can establish baseline radon levels for ventilation system design and comparison.

Internationally, assessing occupational/workplace radon exposure has evolved. A radon detector can measure the radon in the workplace air, but a separate calculation is needed to measure the individual radon risk that a person is exposed to in a mine or workplace. Since the 1970s there have been ongoing conversations focusing on a standard to evaluate individual radon exposure in a way that can be adopted across countries to help protect the public.

Radon in Non-Uranium Mines

Non-uranium mines, such as copper, coal, manganese, metal ore, granite and phosphate can also harbor significant radon levels due to the uranium in the surrounding rock.

Regulations:

• MSHA requires radon progeny exposure to be kept below 4 WLM per year, regardless of the mine type. NIOSH suggests the recommended exposure limit (REL) be kept below 1 WLM per year.

• Non-uranium mines in Canada require a radon level of 200 Bq/m³ or less and each worker should not be exposed to more than 1 WLM per year.

• Specific state regulations (United States) and provincial and territory recommendations (Canada) may apply based on the mine characteristics.

Testing Recommendations:

• Initial site assessments to establish baseline levels.
• Ongoing monitoring in work areas, particularly in poorly ventilated zones.
• Deployment of passive radon detectors or continuous radon monitors.

Radon in Underground Caverns

Underground spaces used for research and tourism (like show caves) can accumulate radon to dangerous levels due to poor ventilation and natural rock emissions.

Regulations:

• OSHA sets limits for indoor workplaces but does not have radon-specific regulations for underground caverns.

• Many facilities voluntarily monitor radon to protect workers and visitors.

• For tourist-accessible caverns, liability and public health standards encourage radon assessments.

• The OSHA General Duty Clause or Canada’s duty of care obligation can apply if radon is a recognized hazard.

Recommended Testing Practices:

• Seasonal long-term radon testing with passive detector.
• Passive radon detectors in buildings near the caverns such as tourist visitor centers or administrative offices.
• Radon detector placement in areas with low airflow or high rock exposure.
• Evaluation of ventilation systems and potential mitigation measures.

This CDC report called “Evaluation of Exposure to Radon and Radon Progeny in an Underground Tourist Cavern and Its Connected Buildings” provides a list of what cavern employers can do when concerned about radon and radon decay products.

The Role of Outdoor Radon Detectors Near Mines

While most focus is placed on indoor or underground radon levels, outdoor radon testing is essential for accurate interpretation of radon data and exposure risk.

Why Use Outdoor Detectors?

• Outdoor detectors help distinguish between naturally high ambient radon and elevated levels caused by site-specific conditions.

• Outdoor levels provide context for determining whether ventilation systems are drawing radon in from outside or effectively diluting indoor air.

• Byproducts or waste from uranium mining, called tailings, can release radon gas and other radioactive materials in surrounding environment, affecting nearby communities.

Placement and Timing:

• Detectors should be placed upwind and downwind of facilities to capture variations.
• Long-term outdoor measurements are recommended to average out daily and seasonal fluctuations.

Radon testing is critical in uranium mines and also a safety imperative in non-uranium mines, underground caverns, and outdoor environments near such areas. Mine operators and radiation safety officers can meet their regulatory obligations using Radonova’s indoor and outdoor radon detection products especially for mines and caverns. Not only is this needed for compliance, but it’s a vital component of protecting workers and nearby communities.

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