The United States’ never-ending culture wars have moved to the kitchen, as Republicans turn up the heat on nascent efforts to shift Americans away from gas stoves.
The latest skirmish started after Richard Trumka Jr., a member of the U.S. Consumer Product Safety Commission, told Bloomberg News that his agency was considering a ban on gas stoves, given research showing they pose a serious threat to public health. That sparked outraged tweets from Republican lawmakers, despite White House denials a ban was on the table, and the introduction of two separate House bills (the Gas Act and the Stove Act) aimed at blocking any ban.
One could be forgiven for thinking that this surge in attention stems from groundbreaking new research that shocked scientists and policymakers. But the truth is that air quality scientists have been documenting the dangers of gas stoves since the 1970s.
“It’s a pretty long-standing literature spanning at least 40 or 50 years,” said Jon Levy, an environmental health researcher at Boston University. “I think it starts from the intuitive sense that if you’re burning a fossil fuel inside your home, it can cause air pollution.”
Scientists have followed that intuitive sense along two major lines of research: measuring the concentrations of pollutants produced by burning methane gas indoors and tracking the health consequences of living with a stove. They’ve discovered gas stoves emit a variety of pollutants that can harm health in myriad ways, from causing asthma to raising the risk of diabetes or cancer. Just this month, a study concluded that roughly 12 percent of all childhood asthma cases may be attributable to gas stoves, suggesting this latest focus of the culture war may be as big a risk factor for asthma as living among smokers.
This isn’t the first time regulators have weighed new rules for gas stoves, either. In 1985, the CPSC raised concerns to the Environmental Protection Agency, citing studies that found unvented gas cooking can cause nitrogen dioxide levels to exceed outdoor standards. More recently, dozens of U.S. cities — starting with Berkeley, California, in 2019 — have banned gas stoves in new construction. Much of the regulatory action has been in California, where 70 percent of households have a gas stove, compared with 38 percent nationwide.
“This was already being actively looked at based on the literature to date under the Reagan administration,” said Levy. “What’s been coming up recently, it’s new, but it’s also extremely old.”
Decades of research
Gas stoves work by combustion, igniting natural gas to produce heat. But a blue flame isn’t the only product of that chemical reaction; burning gas also produces pollutants you can’t see or smell. Particles of varying sizes — most notably PM2.5, particles whose diameter is one-thirtieth that of a human hair — get spewed out during combustion, along with carbon monoxide (CO), nitrogen oxide (NO) and nitrogen dioxide (NO2).
Scientists have loads of data on the health impacts of these pollutants, especially NO2, though many of these studies focused on air outdoors, since regulators have historically been more interested in pollution from industrial factories or cars. Research into indoor air quality is a relatively newer field, “but there’s no real reason to think that nitrogen dioxide you breathe outdoors affects your body any differently than breathing it indoors,” said Josiah Kephart, an environmental epidemiologist at Drexel University. “It’s the same molecules in the same bodies.”
NO2 acts as a respiratory irritant, aggravating the lining of airways. Short-term exposure can exacerbate conditions like asthma, leading to coughing and wheezing. Over the long term, breathing in elevated levels of NO2 can actually cause asthma, especially in children. There’s so much evidence of this that the EPA determined “there is likely to be a causal relationship between long-term NO2 exposure and respiratory effects based on the evidence for the development of asthma” in a 2016 report.
Recognizing these dangers, the EPA has set outdoor standards for NO2 since the 1970s, with a one-hour exposure limit of 100 parts per billion. There are no indoor standards, but evidence suggests homes with gas stoves often have NO2 levels that would be illegal outdoors. “There have been publications for decades showing that homes that use gas stoves can have substantially elevated levels of nitrogen dioxide relative to homes that do not” — anywhere from 50 to 400 percent higher, according to a 2020 report from the Rocky Mountain Institute, a sustainability think tank.
Just how much NO2 builds up from gas stove use depends on how much gas is emitted and how quickly the air can be cleared. “NO2 levels are proportional to how much gas a stove burns,” said Eric Lebel, a senior scientist at P.S.E. Healthy Energy, a nonprofit science and policy research institute. “And the concentrations of NO2 that build up in a kitchen depend on how big your kitchen is and ventilation levels,” he said.
In small kitchens with poor ventilation, Lebel and his colleagues recently found that just a few minutes of gas stove use can send NO2 levels well beyond outdoor EPA limits. For other pollutants, Lebel has found that the gas stove doesn’t even need to be on to be a problem. Benzene — recognized as a carcinogen by the EPA — leaks from gas stoves that aren’t in use, according to two recent studies.
“We found that in the most extreme circumstances, concentrations of benzene could build up inside a kitchen comparable to what you’d expect if you were living with a smoker,” said Lebel. Benzene exposure can increase risk of blood disorders, including leukemia, and may also be a reproductive toxin. According to the World Health Organization, there’s no safe level of benzene exposure.
Getting a handle on precisely how harmful gas stoves are to children and adults is inherently more challenging than just measuring the concentrations of gases in homes, but a worrying picture is emerging from observational studies. The clearest threat is asthma.
While gas stoves have been associated with asthma flare-ups in adults, kids are at highest risk. In 2013, researchers analyzed more than 40 studies to conclude that children living in households with gas stoves were 42 percent more likely to experience asthma symptoms and 24 percent more likely to ever get diagnosed. Other work suggests the degree of exposure matters too; every 5 ppb increase above a 6 ppb baseline (itself well below the EPA’s outdoor NO2 limit of 100) was associated with a significant uptick in asthma severity, wheezing and medication use.
“The data are pretty robust,” said Stephanie Holm, a pediatric environmental medicine specialist at the University of California San Francisco. Children’s smaller, still developing lungs are especially susceptible to this kind of pollution, Holm said, and the level of exposure really matters. “There’re data showing that in families that use ventilation, kids are less likely to have asthma than families who are not venting.”
Asthma is a profoundly unequal disease with stark socio-economic disparities — about 7 percent of white children have asthma, compared with about 15 percent of Black children — and gas stoves could play a role in shaping these differences. Households with lower incomes tend to be smaller and have less adequate stovetop ventilation, which could increase NO2 concentrations in disadvantaged areas. “We’re still trying to understand how gas stoves contribute, but they’re probably one of many environmental factors that are contributing to racial and socio-economic disparities in asthma,” said Kephart.
Air pollution can be toxic to a developing brain, and there are numerous epidemiological studies associating air pollution with neurodevelopmental disorders. Studies of gas stoves in particular are sparse, but one found that kids who experienced higher NO2 levels from gas stoves as newborns scored slightly worse on cognitive tasks as toddlers and were at a slightly higher risk of developing ADHD. The overall effect was small — a percentage point or two — but seemed to be dependent on NO2 levels, suggesting NO2 played a causal role.
There are other health concerns, too, though the weight of evidence varies. Cardiovascular issues, diabetes, cancer and reproductive problems have all been linked to NO2 and gas stoves. In general, the evidence is less robust for non-respiratory illnesses, said Holm. “But I think the evidence base is strong enough to support stronger regulations around gas stoves,” she said.
“Is there more that we can learn? Absolutely. But we know enough to know that they’re harmful,” said Holm. “Why would I wait to find out exactly how harmful? Why would I put myself and my kid at that kind of risk?”
Thanks to Brett Zach for copy editing this article.