The U.S. Surgeon General has called indoor radon the second leading cause of lung cancer nationwide, after smoking, with the Environmental Protection Agency estimating the gas contributes to approximately 21,000 lung cancer deaths nationally each year.
The city’s Public Health Department department has received 50 free radon test kits from the California Department of Public Health and is offering them to Pasadena residents on a first-come, first-served basis. The kits are available for pickup at the Environmental Health Services Division, 1845 N. Fair Oaks Avenue, Suite 1200, during business hours. Residents must show proof of residency, such as a valid ID or utility bill. For availability and pickup times, call (626) 744-6004.
Pasadena’s 2022 Mortality Report explicitly identifies radon exposure as a risk factor for lung cancer and recommends that residents “test your home for environmental radon in the soil.”
Manuel Carmona, Pasadena’s Director of Public Health, said in a statement announcing the program that breathing air containing radon increases the risk of lung cancer, “especially for people who do not smoke.” According to federal health data, radon-related lung cancer kills more Americans annually than drunk driving, home fires, or drowning.
Pasadena is classified by the EPA as a Zone 2 area, indicating “moderate potential” for indoor radon levels to exceed the federal action threshold of 4 picocuries per liter. That designation, based on a California Geological Survey assessment of the region’s geology and soil conditions, does not mean every home has dangerous levels — but it does mean some will, and testing is the only way to know.
The problem is that almost no one tests. Statewide data shows that fewer than one in 1,000 of California’s more than 14 million housing units have been tested for radon. No systematic survey of residential radon levels has ever been conducted specifically in Pasadena, and no comprehensive data exists for the city’s six ZIP codes. The California Department of Public Health maintains radon testing records, but Pasadena-specific results remain sparse.
Radon forms naturally when uranium in soil and rock breaks down. The gas rises through the ground and can enter buildings through cracks in foundations, construction joints, gaps around pipes, and other openings. Because it cannot be seen, smelled, or tasted, it can accumulate indoors without any indication to occupants.
The EPA estimates that roughly one in 15 American homes has elevated radon levels.
Health officials emphasize that radon risk should be understood in context. Los Angeles County’s average indoor radon level, based on available testing data, is estimated at 1.2 to 1.9 picocuries per liter — below the EPA’s action level of 4.0. The California Department of Public Health recommends considering home modifications if levels exceed 2 picocuries per liter, a stricter threshold than the federal standard.
But averages can obscure individual risk. “Homes with elevated radon levels have been found in all three zones — high, moderate, and low — within Los Angeles County,” according to EPA guidance accompanying the radon zone maps. “Radon levels can be different from house to house, even on the same street.”
The combination of radon exposure and smoking is particularly dangerous. Federal estimates suggest that among 1,000 people who smoke and are exposed to 4 picocuries per liter over a lifetime, about 62 could develop lung cancer — approximately nine times the risk for nonsmokers at the same exposure level. The synergistic effect means that smokers living in homes with elevated radon face compounded risk.
In Pasadena, lung cancer has claimed an average of 42.9 lives per year over the past 13 years, according to city mortality records. The 2022 report documented significant racial disparities: Black residents died from lung cancer at a rate of 55.5 per 100,000, more than four times the rate among Hispanic residents. While smoking remains the primary cause of lung cancer, health officials note that radon contributes to a meaningful share of cases, particularly among people who have never smoked.
The free test kits being offered by the Pasadena Public Health Department are short-term charcoal samplers designed to measure radon levels over two to three days. The department advises residents to place the kit on the lowest regularly occupied level of the home, in a frequently used room such as a living room or bedroom, but not in a kitchen or bathroom. Windows and exterior doors should remain closed as much as possible during testing, and the test should not be conducted during severe storms or unusually high winds.
Winter is considered an optimal time for testing because closed-house conditions and pressure differentials between indoor and outdoor air can cause radon levels to rise. After the testing period, residents reseal the kit and mail it to a designated laboratory; results typically arrive within a few weeks.
If elevated levels are found, solutions exist. According to the EPA, radon reduction systems can lower indoor concentrations by up to 99 percent. The most common approach uses a vent pipe and fan to pull radon from beneath the home and exhaust it outside. The cost of installation is generally comparable to other common home repairs, and the EPA recommends retesting every two years to ensure levels remain low.
The 50 test kits represent a limited supply. Residents interested in testing can visit the Pasadena Public Health Department’s Environmental Health Services Division at 1845 N. Fair Oaks Avenue, Suite 1200, or call (626) 744-6004 for current availability. Additional information about radon testing and health effects is available from the EPA at epa.gov/radon.
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