Radon-222 Gas (College Board AP® Environmental Science): Study Guide

Radon-222 gas

What is radon-222?

• Radon-222 is a radioactive gas that is colorless, odorless, and tasteless

• It is produced by the natural decay of uranium found in certain rocks, soils, and groundwater

• As a noble gas, radon can easily move through the ground and enter buildings

• It is a leading cause of lung cancer among non-smokers and the second leading cause of lung cancer overall, according to the EPA

Where is radon found?

• Radon is commonly found in areas with high uranium content in the soil and rock formations

• It is most prevalent in granite, shale, phosphate rock, and certain volcanic soils

• Some areas of the United States have higher radon levels than others due to their geological composition

• Water from underground sources can also contain radon, releasing it into the air when water is abstracted

Radon gas in homes

• Radon can enter a building through:

• Soil gas infiltration:

  • The most common way radon enters homes is through the soil beneath the foundations

  • Since buildings create slight negative pressure relative to the soil, radon gas gets drawn inside

• Cracks and gaps:

  • Radon enters through cracks in floors and walls, gaps around pipes, and construction joints

• Basements and crawl spaces:

  • Homes with basements or crawl spaces are particularly vulnerable because these areas are in direct contact with the soil

• Well water:

  • Radon can dissolve into groundwater and be released when water is used indoors

Impacts of radon gas on people

• Lung cancer:

  • Radon-222 emits alpha radiation, which damages lung tissue when inhaled

  • Prolonged exposure significantly increases the risk of lung cancer, especially for smokers

• No immediate symptoms:

  • Unlike carbon monoxide poisoning, radon exposure does not cause immediate symptoms like headaches or dizziness

  • Its effects develop over time, making early detection through testing crucial

Reducing and managing indoor radon levels

• Radon testing:

  • Radon levels should be tested using radon detection kits or professional testing services

  • The EPA recommends action if indoor radon levels exceed 4.0 pCi/L (picocuries per liter)

• Improve ventilation:

  • Increasing ventilation in basements and crawl spaces can help disperse radon gas

• Seal cracks and openings:

  • Use caulk and sealants to close gaps in floors, walls, and foundations to reduce radon entry

• Radon mitigation systems:

  • Sub-slab depressurization systems (radon mitigation systems) use a vent pipe and fan to remove radon gas from beneath a home and release it outside

• Water treatment:

  • If radon is present in well water, aeration systems or activated carbon filters can help remove it

• New construction prevention:

  • In high-risk areas, builders can install radon-resistant materials and venting systems during construction to minimize radon infiltration