What is radon?

Radon is a colorless, oderless, tasteless radioactive gas released from the decay of rock and soil. It seeps through the ground and diffuses into the air. In areas without adequate ventilation, such as basements, radon can accumulate and increase the risk of lung cancer. Basement and first floors typically have the highest radon levels because of their contact with the soil.

Radon is often the single largest contributor to an individual’s background radiation dose and the second leading cause of lung cancer in the United States, with an estimated 15,000 – 22,000 lung cancer deaths in the United States each year associated with radon.

For both adults and children, most exposure to radon comes from being indoors in homes, offices, schools, and other buildings. The levels of radon in homes and other buildings depend on the characteristics of the rock and soil in the area. As a result, radon levels vary greatly in different parts of the United States, sometimes even within neighborhoods. Elevated radon levels have been found in every state.

Small amounts of radon can also be released from the water supply into the air. As the radon moves from the water to air, it can be inhaled. Water that comes from deep, underground wells in rock may have higher levels of radon, whereas surface water (from lakes or rivers) usually has very low radon levels. For the most part, water does not contribute much to overall exposure to radon.

According to the EPA, the average indoor radon level is about 1.3 picocuries per liter (pCi/L). People should take action to lower radon levels in the home if the level is 4.0 pCi/L or higher. The EPA estimates that nearly 1 out of every 15 homes in the United States has elevated radon levels.