Los Angeles, California – A dangerous gas could already be building inside homes along the West Coast as cool spring nights and shifting coastal temperatures keep windows closed, allowing radon—known as the “invisible killer”—to accumulate indoors within hours. The risk can increase quickly overnight as marine air and temperature swings limit ventilation.
According to the U.S. Environmental Protection Agency, radon is a radioactive gas that forms naturally in soil and can enter homes through foundation cracks, crawl spaces, and slab floors. The West Coast—including California, Oregon, and Washington—is generally considered a low to moderate radon-risk region, but elevated levels have been detected in inland valleys, foothills, and select metro areas.
Across cities like Los Angeles, San Francisco, Portland, and Seattle, homes with crawl spaces and basements are especially vulnerable during seasonal transitions. Coastal moisture and cooler overnight air often lead residents to seal homes, trapping radon indoors and allowing concentrations to build without detection.
Health officials warn radon is the second leading cause of lung cancer in the United States, linked to about 21,000 deaths annually. The gas produces no smell or immediate symptoms, making testing the only reliable way to detect it.
Residents along the West Coast are urged to test homes now as conditions through April continue to support indoor buildup. Free and low-cost test kits are widely available, and mitigation systems can significantly reduce indoor levels before risks increase into early summer.
