Gas stoves can leak cancer-causing chemical, even when turned off, study shows

Gas stoves in California homes are leaking cancer-causing benzene, researchers found in a new study. Their findings add to a growing body of research that indicate that gas stoves may be hazardous for people’s health as well as the environment — and it’s not just affecting people in California.

In the study, published in Environmental Science and Technology on Thursday, researchers collected samples of gas from 159 homes in different regions of California and measured what types of gases were being emitted into homes when stoves were off. They found that all of the samples they tested had hazardous air pollutants, like benzene, toluene, ethylbenzene and xylene, all of which can have adverse health effects in humans.

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. Benzene was also the culprit behind a mass recall of dry shampoo products after Health Canada found “potentially elevated levels” of the chemical in some products.

According to the World Health Organization, there is no safe level of benzene exposure and Health Canada recommends that Canadians reduce their exposure to it as much as possible.

“Just having a gas stove in your kitchen can create benzene concentrations comparable to the benzene found from secondhand smoke,” said Eric Lebel, the study’s lead author, in a press briefing. Lebel noted that benzene was detected in households regardless of what gas provider or brand of appliance they were using.

“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, a study co-author and senior scientist at PSE Healthy Energy, an energy research and policy institute. “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.”

Michanowicz was also involved in a similar study investigating air pollutants from gas stoves in Boston homes and found similar results, except California had much higher concentrations of pollutants.

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“We think it has something to do with where the gas is being sourced from,” said Lebel, though researchers are unsure why the concentrations are so varied between locations. “California has two major pipelines where it imports gas from: one coming from the Rockies and then one coming in from the north from Canada.”

Benzene was found in households at an average concentration ranging between 0.7-12 parts per million (ppm), with the highest detected concentration being 66 ppm.

The California Office of Environmental Health Hazard Assessment’s reference exposure level for benzene, where no adverse health outcomes are expected, is just 0.94 ppm.

“We found that the leakiest stoves coupled with the highest benzene concentrations can exceed this level in California by up to seven times in indoor air just from benzene from gas stoves leaking while they’re off,” Lebel said.

Authors of the study also noted that since the study measured leaks when stoves were turned off, their estimates might not reflect the real extent of pollution occurring. Most of the leaks they observed were so low that people wouldn’t be able to smell the gas.

In Health Canada’s guidelines regarding benzene exposure, the agency points to attached garages as being the major indoor source of benzene in homes because of vehicle exhaust. Homes with attached garages saw three times higher benzene levels indoors than homes without a garage, the agency notes.

Smoking also significantly contributes to indoor benzene levels, the agency writes. Health Canada does not identify gas stoves as a major contributor to benzene pollution but did say that more research is needed in this area.

Despite warning of the risks of benzene exposure, Health Canada has no numerical guideline on recommended exposure levels.

Benzene may not be the only harmful chemical leaking from gas stoves that people need to worry about, however. A Canadian study from 2018 found that high levels of nitrogen oxides exist in homes after cooking with gas stoves.

The researchers found that the levels of nitrogen oxide, which is linked to asthma and decreased lung function especially in children, exceeded Health Canada’s guidelines for a one-hour exposure, though the pollutants often lingered for multiple hours.

Earlier this year, California researchers found that gas stoves also leak methane, even while they’re off, which can be detrimental for the environment.

The study found that U.S. gas stoves were contributing 2.4 million tonnes of carbon dioxide to the atmosphere each year. The amount of greenhouse gases being produced was equivalent to around 500,000 cars.

— with files from the Associated Press