Cooking with a gas stove in your kitchen can emit as much benzene into a home as second-hand tobacco smoke, depending on ventilation and the size of the house, according to new research from Stanford University conducted in part in metro Denver.
The findings showed the benzene produced when a gas stove is ignited migrated through homes — including into bedrooms that were the furthest from the kitchen — and reached levels above acceptable health benchmarks, said Yannai Kashtan, the lead researcher and a Ph.D. candidate at Stanford’s Earth Systems Science Department.
“I’m surprised, not so much that we found benzene, but just how much we found,” Kashtan said.
Researchers studied 87 homes in California and Colorado to determine how much benzene a gas stove released when in use and to look at how it spread throughout a house. They chose to study homes in the Denver area because of its proximity to a sizable oil and gas industry and because it was within driving distance of California, making it easier to transport heavy scientific instruments, Kashtan said.
“Our findings suggest that the concentrations of benzene produced by combustion from gas stoves and ovens indoors may increase health risks under some conditions,” the Stanford report said. “Further research is needed to assess actual exposures and the full health impacts of benzene emitted indoors from combustion by gas stoves. We also showed that using a gas burner or oven may increase kitchen and bedroom benzene concentrations above chronic exposure guidelines, depending on ventilation conditions and home size.”
The research is the latest to target the health and environmental impacts of cooking with gas and propane.
A February report by Colorado-based RMI, which studies energy use and its environmental impact, connected gas stoves to childhood asthma. That report received criticism for its research methods and led oil and gas industry leaders, including some in Colorado, to say that regulating appliances will hurt their business.
Research into the health and environmental impacts of gas-fueled appliances is not new, but this year’s criticism of gas stoves launched another front in the culture wars, which intensified after a commissioner with the U.S. Consumer Product Safety Commission indicated that a ban on gas appliances was needed.
Most of the research has centered on the health impacts of cooking with gas and whether toxic compounds found in natural gas have adverse health impacts on people. Those same harmful compounds that can cause human health problems, though, also contribute to air pollution, which quickens the pace of global climate change.
Conservative politicians and climate-change deniers fired back. Republicans in the U.S. House of Representatives filed two bills aimed at preventing any bans on the stoves.
In Denver, the city is phasing out natural gas appliances in large commercial buildings but City Councilman Jolon Clark has pushed his colleagues to consider a total ban on gas-fired appliances as climate change and the city’s air quality worsen.
Some cooks insist gas stoves are better than their electric counterparts for preparing food. The U.S. Energy Information Administration estimates that 4% of the country’s natural gas consumption is used for in-home cooking.
The controversy over gas stoves is not lost on Kashtan, who told The Denver Post when discussing the research, “As you know it’s gotten all politicized and I want to be very precise about my language.”
The Stanford study, which was published in June in the Environmental and Science Technology journal, found benzene levels exceeded health benchmarks in one-third of the 87 homes studied. When measuring benzene in bedrooms that were in opposite ends of the home, high levels sometimes were found hours after a stove was turned off, the study found.
Other studies have found that gas stoves release nitrogen dioxide, carbon dioxide and methane into the air, but no one previously looked at benzene emissions, Kashtan said.
Benzene is a chemical found in crude oil, gasoline and cigarette smoke that can cause lymphoma, leukemia, breathing problems and irregular menstrual cycles after long-term exposure, according to the Centers for Disease Control and Prevention.
The team is not advising people to get rid of their gas stoves, understanding that home appliances are expensive. But researchers suggest using a hood above gas ranges or opening windows and doors to ventilate the house when a gas stove is in use, Kashtan said.
“Gas stoves emit benzene. It’s a potent carcinogen,” he said. “The danger from this is cumulative, so you don’t need to freak out and throw your stove away tonight. But the risk is there over time.”
The Colorado Public Interest Research Group, which advocates for a healthier and safer environment, has been critical of gas stoves for years. This new research only strengthens the group’s argument that consumers should shift away from gas appliances, said Danny Katz, CoPIRG’s executive director.
“There’s evidence to suggest that gas stoves are a contributor to climate change,” Katz said. “But the primary reason to be concerned about cooking with gas is the indoor air pollution that comes with it.”
Dan Haley, president of the Colorado Oil and Gas Association, criticized the Stanford study, pointing out that it was funded by a “ban gas stoves campaign.”
The Stanford report acknowledges financial support from the High Tide Foundation, which focuses on methane reduction and promotes carbon credits in the private sector. High Tide’s founders also direct a foundation that installs fuel-efficient, clean-cook stoves in Latin America.
Haley declined an interview with The Post. He sent an emailed statement that criticized the study but did not specifically deny that gas stoves can release pollutants into a home.
He accused the researchers of flawed methodology and “using scare tactics and attention-grabbing headlines to disseminate misinformation.”
“Gas stoves have been a staple in American homes for over 100 years, and we believe consumers should be able to make choices that best suit their families and their needs,” Haley wrote. “Reports like this aim to influence consumer choice with misinformation and are unnecessarily scaring American consumers.”
Haley criticized the research methods, including using plastic tarps to seal off kitchens for testing because that does not replicate realistic cooking conditions.
But Kashtan said the teams sealed off kitchens in one phase of testing so they could accurately measure volumes and emissions rates from the stoves. The plastic seals were removed when the teams measured concentration levels throughout the homes, he said.
The research was peer-reviewed, meaning scientists who are unknown to the Stanford team reviewed their work and it is open for others to try to replicate.
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