California Stoves Are Leaking Cancerous Gases, Study Finds

Gas stoves in California homes are leaking cancer-causing benzene, researchers found in a new study published Thursday, though they say more research is needed to understand how many homes have leaks.

In the study, published in Environmental Science and Technology, researchers also estimated that over 4 tons of benzene per year are being leaked into the atmosphere from outdoor pipes that deliver the gas to buildings around California. And those emissions are unaccounted for by the state.

Eric Lebel is a co-author of the study and a senior scientist at PSE Healthy Energy, the nonprofit energy research and policy institute that conducted the research. He says that even low-level gas leaks can generate concentrations of benzene seven times California's recommended exposure limits, and that these leaks can also affect outdoor air quality.

"We estimate that leaks from gas appliances and the pipes that feed them in cities can emit the same amount of benzene each year in the state of California as 60,000 passenger cars," said Lebel.

The researchers collected samples of gas from 159 homes in different regions of California and measured to see which types of gases were being emitted into homes when stoves were off. They found at least 12 hazardous air pollutants in all the samples they tested, including benzene, toluene, ethylbenzene and xylene (together known as BTEX), all of which can have adverse health effects in humans with chronic exposure or acute exposure in larger amounts.

Of most concern to the researchers was benzene, a known carcinogen that can lead to leukemia and other cancers and blood disorders, according to the National Cancer Institute.

The finding could have major implications for indoor and outdoor air quality in California, which has the second highest level of residential natural gas use in the United States.

“What our science shows is that people in California are exposed to potentially hazardous levels of benzene from the gas that is piped into their homes,” said Drew Michanowicz, study co-author and senior scientist at PSE Healthy Energy. “We hope that policymakers will consider this data when they are making policy to ensure current and future policies are health-protective in light of this new research."

Homes in the greater Los Angeles, North San Fernando Valley and Santa Clarita Valley areas had the highest benzene in gas levels. Leaks from stoves in these regions could emit enough benzene to significantly exceed the limit determined to be safe by the California Office of Environmental Health Hazards Assessment.

This finding in particular didn't surprise residents and health care workers in the region who spoke to The Associated Press about the study. That's because many of them experienced the largest-known natural gas leak in the nation in Aliso Canyon in 2015.

Back then, 100,000 tons of methane and other gases, including benzene, leaked from a failed well operated by Southern California Gas Co. It took nearly four months to get the leak under control and resulted in headaches, nausea and nosebleeds.

Dr. Jeffrey Nordella was a physician at an urgent care in the region during this time and remembers being puzzled by the variety of symptoms patients were experiencing. “I didn't have much to offer them,” except to help them try to detox from the exposures, he said.

That was an acute exposure of a large amount of benzene, which is different from chronic exposure to smaller amounts, but “remember what the World Health Organization said: There's no safe level of benzene,” he said.

Kyoko Hibino was one of the residents exposed to toxic air pollution as a result of the Aliso Canyon gas leak. After the leak, she started having a persistent cough and nosebleeds and eventually was diagnosed with breast cancer, which also has been linked to benzene exposure. Her cats also started having nosebleeds and one recently passed away from leukemia.

“I'd say let's take this study really seriously and understand how bad (benzene exposure) is,” she said.

State regulators have committed to phasing out the sale of gas furnaces and water heaters by 2030.

KQED's Keith Mizuguchi contributed to this story.