Natural gas stoves and ovens can leak harmful chemicals inside homes even when not in use.
About 47 million American homes use such devices, according to the federal Energy Information Administration.
A study published Thursday in the journal Environmental Science and Technology found at least 12 dangerous air pollutants emitted from gas stoves in California, including benzene – a chemical known to cause cancer in some people exposed long-term.
The researchers behind the study — a group from the nonprofit PSE Healthy Energy Energy Research Institute — took gas samples from 159 residential stoves in 16 California counties. They found benzene in 99% of the samples.
They also calculated a household’s benzene exposure based on the size of the kitchen, the level of ventilation in the room, the amount of chemical present and whether stoves leaked when turned off. The results showed that the most leaky stoves exposed people to indoor concentrations of benzene up to seven times the safe exposure level set by the California Environmental Protection Agency.
Over time, such exposure could increase the risk of blood disorders or reproductive problems, although scientists are still learning how benzene affects health.
The chemical has been more conclusively linked to leukemia, multiple myeloma, and non-Hodgkin’s lymphoma. The World Health Organization has said there is no safe level of exposure to benzene when it comes to cancer risk.
But benzene isn’t the only chemical of concern from stoves, and emissions aren’t limited to California. Decades of research have suggested that gas stoves are a source of indoor air pollution.
“Wherever natural gas leaks, hazardous air pollutants are also likely to be released,” co-author of the new study, Kelsey Bilsback, senior scientist at PSE Healthy Energy, said on a media call.
Previous research has shown that gas stoves in California homes emit nitrogen oxideswhich can irritate the eyes, nose, throat or lungs and cause some people to feel tired, dizzy or short of breath.
Another study co-author, Drew Michanowicz, previously identified 21 hazardous air pollutants from gas stoves and outdoor gas lines in Boston homes. Several of the pollutants were volatile organic compounds: a large group of chemicals, including benzene, which may increase the risk of certain cancers, birth defects or cognitive impairment in people exposed long-term.
But Michanowicz said some of the lowest pollutant concentrations in California were still about 10 times higher than the averages in his Boston study. Researchers don’t know why concentrations vary from place to place.
“We think it has something to do with where the gas is coming from,” said Eric Lebel, another study co-author. “California has two main pipelines from which it imports gas: one from the Rocky Mountains and then one from northern Canada.”
Bilsback said benzene can enter a gas supply at different points in the system due to how it is stored or transported. From there, it could be pushed back into the kitchen by a leaky stove.
The presence of benzene in California homes was constant, regardless of their gas suppliers or appliance brands, Lebel said. But stoves in the northern San Fernando and Santa Clarita valleys had the highest levels, followed by those in greater Los Angeles.
“Benzene emissions from a gas stove, even when turned off, can in some cases produce concentrations of benzene in your home that are equivalent to living with a smoker,” Lebel said.
The American Gas Association, however, said in a statement that the new study was based on questionable airflow assumptions that were inconsistent with typical American homes.
“It is difficult to draw conclusions from measurements of 159 homes in one state when there are more than 77 million residential, commercial and industrial natural gas customers in all fifty states,” the association said.
Andrea De Vizcaya Ruiz, associate professor of environmental and occupational health at the University of California, Irvine, who was not involved in the study, said people can be exposed to small amounts of benzene when filling the gas tanks of their cars. or sitting near a fireplace, but exposure to high amounts over long periods of time is concerning.
“It’s one of the most direct cancer-causing chemicals because it transforms bone marrow cells,” she said.
Pregnant women, infants and young children may be particularly susceptible to adverse health effects from long-term exposure to benzene, De Vizcaya Ruiz said.
But Lebel said it can be hard to tell if your home has a leak. Gas companies add compounds to the gas that give off a rotten egg smell so major leaks don’t go unnoticed, but the smell is usually not noticeable unless the gas is leaking in high concentrations. When this happens, De Vizcaya Ruiz said, people may also start vomiting, feel sleepy or confused, or develop headaches.
“If you ever smell gas, you should immediately leave your house, call the gas company,” Lebel said.
De Vizcaya Ruiz said opening windows can better ventilate rooms in the short term, which helps mitigate potential exposure, but it won’t eliminate the risk or the root cause. People in California might consider calling their gas companies as a precaution to make sure there are no leaks, she added.
One of the easiest solutions, Lebel said, is to replace a gas stove with an electric stove.
“Just having a gas appliance in your home can be a potential health risk,” he said. “Total gas elimination is the only sure way to completely eliminate this risk.”