What are the common sources of radon (Rn) gas exposure?

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Last updated: May 20, 2025View editorial policy

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From the Guidelines

Radon gas exposure primarily occurs in homes, buildings, and underground spaces where the gas can seep in from the surrounding soil and accumulate, with the most common exposure happening in basements, crawl spaces, and lower levels of buildings. The gas enters these areas through cracks in foundations, floor drains, sump pumps, and construction joints 1. Workplaces such as mines, underground tunnels, and water treatment facilities can also have elevated radon levels. This colorless, odorless radioactive gas forms naturally when uranium in soil and rock breaks down, and it can reach dangerous concentrations when trapped indoors. Some key factors that influence radon exposure include:

  • Local geology, with some regions having naturally higher uranium deposits 1
  • The presence of cracks in foundations and other entry points for the gas 1
  • The use of well-water or building materials containing certain bedrock, which can also be a source of radon 1 The risk of radon exposure varies geographically, and testing your home is essential since radon is the second leading cause of lung cancer after smoking, and exposure has no immediate symptoms 1. Simple test kits can determine if mitigation systems are needed to reduce indoor radon concentrations to safe levels. According to the WHO, a maximum value of 100 Bq/m3 should be used as a national regulation limit value in homes to minimize health hazards 1.

From the Research

Sources of Radon Gas Exposure

  • Radon gas can penetrate homes from many sources and in various fashions 2
  • The upper Midwest is especially prevalent in radon gas 3
  • Radon gas exposure can occur in residential homes, rental properties, and schools 3, 4

Locations with High Radon Levels

  • Rural Appalachia has been identified as an area with high radon levels 4
  • Wisconsin has been found to have high radon levels, with approximately 30% of homeowners testing their properties for radon 3
  • High radon areas can have average levels higher than 4-8 pCi/liter, with the NCRP recommended level being 8 pCi/liter and the EPA recommended level being 4 pCi/liter 2

Factors Influencing Radon Gas Exposure

  • Age can be a significant factor associated with completion of radon testing, with older individuals being more likely to test their home for radon 4
  • Socioeconomic factors, such as economic barriers, can result in delaying behaviors and increased exposure to radon gas 5
  • Psychological factors, such as risk perception and attitudes towards radon testing, can also influence radon gas exposure 6, 5

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Survey of Radon Testing and Mitigation by Wisconsin Residents, Landlords, and School Districts.

WMJ : official publication of the State Medical Society of Wisconsin, 2019

Research

Home Radon Testing in Rural Appalachia.

The Journal of rural health : official journal of the American Rural Health Association and the National Rural Health Care Association, 2022

Research

Experimental evidence for stages of health behavior change: the precaution adoption process model applied to home radon testing.

Health psychology : official journal of the Division of Health Psychology, American Psychological Association, 1998

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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