Sources: Earth, uranium and rock beneath home; well water.

Health Effects: No immediate symptoms. Estimated to cause about 10% of lung cancer deaths. Smokers are at higher risk of developing radon-induced lung cancer.

Steps to Reduce Exposure:

• Test your home for radon. Easy-to-administer home test kits, that include lab analysis, are sold at most hardware stores and often can be obtained through local departments of health.
• Get professional advice before planning and carrying out radon reduction measures.
• Seal cracks and other openings in basement floor.
• Ventilate crawl space.
• Install active sub-slab depressurization system. A heat recovery ventilator (air-to-air heat exchanger) can also help.
• Treat radon-contaminated well water by aerating or filtering through granulate-activated charcoal.