If you live in one of the 40 million American households with a gas stove, it could be leaking even when it’s turned off.
According to a new study from Stanford scientists, many stoves are constantly emitting gasses that can warm the planet and pose serious health risks when inhaled. The research, which appeared in the journal Environmental Science & Technology, found methane emissions from gas stoves across the United States are roughly equivalent to the carbon dioxide released by half a million gas-powered cars in a year.
“The mere existence of the stoves is really what’s driving those methane emissions,” says study author Eric Lebel, a research scientist with PSE Healthy Energy, to Danielle Renwick for Nexus Media News. “We found that over three-quarters of the methane emissions from stoves are emitted while the stove is off. So these little tiny leaks from the stoves, they really do add up.”
While leaky natural gas pipelines have been studied extensively, scientists know less about the climate and health impacts of gas-burning stoves. More than a third of Americans cook with gas, and some get additional exposure from space and water heaters. All of these natural gas-burning appliances can emit gasses that can trigger asthma, coughing, and potentially increase susceptibility to respiratory infections.
To guage the impact of these emissions, researchers measured three key gasses from stoves in 53 homes across seven California counties. The team chose two gasses—methane and carbon dioxide—because of their contribution to climate change, and selected nitrogen oxides because of their known risk to human health. The scientists set up plastic partitions between the kitchens and other rooms and used instruments that measure wavelengths of light to determine the concentration of certain gases.
To their surprise, they found that more than three-quarters of the methane emissions happened when both old and new gas stoves were turned off.
The most significant health risks happen when the stove is lit, the authors note, because the process creates nitrogen dioxide as a byproduct. Increasing airflow by using a range hood can help reduce the personal health risk of natural gas-burning appliances, but most individuals report rarely using their ventilation system.
In a small kitchen, it only took a few minutes of unventilated stove use to generate emissions levels above national health standards. According to a meta-analysis from 2013, children living in homes with gas stoves were 42 percent more likely to experience symptoms associated with asthma, and 24 percent more likely to be diagnosed with lifetime asthma.
In addition to health risks, natural gas burning stoves also imperil the planet by releasing methane. While carbon dioxide gets the most attention in conversations about climate change, methane is a huge contributor to planetary warming. Following carbon dioxide, methane is the second most abundant greenhouse gas that humans have pumped into the atmosphere, accounting for about 20 percent of global emissions. Although methane dissipates more quickly than carbon dioxide, it is especially concerning because of its heat-trapping power, which is more than 25 times as potent as carbon dioxide. The team estimated that stoves emit between 0.8 and 1.3 percent of the natural gas they consume as unburned methane.
“This is a really important study,” says Maryann Sargent, an environmental scientist at Harvard University who was not involved with the study, to Vox’s Rebecca Leber. “[It] is one piece that says these stoves are actually a pretty significant emitter. It’s filling in this gap of unknown emissions.”
The results of the study have reignited efforts by scientists and activists to encourage Americans to switch to all-electric stoves and appliances. Last month, New York City joined San Francisco and Seattle in curtailing the use of natural gas in new buildings to protect the health of their climate and residents. But pushback from the natural gas industry has caused other states like Florida, Pennsylvania, and Texas to preemptively pass laws to stop cities from banning gas in new appliances.
“If you have the financial ability to swap out a gas stovetop for an electric induction cooktop, I do think it’s a good idea,” says Rob Jackson, a Stanford earth science professor and co-author of the study, to Maxine Joselow for the Washington Post. “It’s a good idea for the planet and for air quality.”