Key points
- Radon is an odorless and invisible radioactive gas that can lead to lung cancer.
- Radon can enter your home through construction joints, cavities and cracks inside walls, and sump pumps.
- High radon levels in the water supply are more likely when its source is groundwater.
![Side profile view of a person's chest and hands scrolling on a tablet device. Title reads "Radon" and get the facts about radon. Lower left is the CDC logo and lower right is cdc.gov/radon](/radon/images/RadonAwareness_TextOnly_CDC.jpg)
Overview
![A house with rooms sectioned out showing radon entering the house through the soil, bedrock, and ground water](/radon/images/radonHouse-1165px.png)
Radon is the 2nd leading cause of lung cancer in the United States. It is found in bedrock, soil and groundwater. Radon can seep into the home through
- Construction joints
- Cavities and cracks inside walls
- The sump hole or opening
- Cracks in floors
- Gaps around service pipes
- Gaps in suspended floors
- Private wells and groundwater supplies*
*High radon levels in the water supply are more likely when its source is ground water, e.g. a private well or a public water supply system that uses ground water. Most public water supplies are sourced from surface water (lakes, rivers, and reservoirs).
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