Residents of households with gas or propane stoves are regularly inhaling pollutants that are both exacerbating childhood asthma rates and causing early death, a coast-to-coast study of U.S. homes found.
A mix of pollutants, with nitrogen dioxide (NO2) chief among them, may be responsible for as many as 200,000 current such asthma cases, according to the study, published Friday in Science Advances.
Long-term exposure to NO2 from gas stoves also may be causing as many as 19,000 adult deaths each year — equivalent to 40 percent of the annual fatalities linked to secondhand smoke, the researchers determined.
“I didn’t expect to see pollutant concentrations breach health benchmarks in bedrooms within an hour of gas stove use, and stay there for hours after the stove is turned off,” senior author Rob Jackson, a professor at Stanford University’s Doerr School of Sustainability, said in a statement.
Although most NO2 exposure in the country comes from vehicles burning fossil fuels, gas stoves are making no small contribution, the scientists found.
A quarter of the 200,000 current childhood asthma cases that they attributed to gas stoves are likely linked to NO2 alone, the authors noted. The 200,000-case total, the researchers noted, represents about a $1 billion annual health cost to the country in general.
To draw their conclusions, the researchers used sensors to measure concentrations of NO2 in more than 100 homes of various sizes, layouts and ventilation methods — before, during and after stove use — in California, Texas, Colorado, New York and Washington, D.C.
They then incorporated their data into a model created by National Institute of Standards and Technology scientists to simulate airflow and room-by-room occupant exposure.
Their results demonstrated that typical American use of a gas or propane stove heightens annual exposure to NO2 by about 4 parts per billion — or 75 percent of the way to the World Health Organization’s cap for safe outdoor air exposure.
Considering, however, that the study didn’t include outdoor sources, such a surge from indoor contaminants “makes it much more likely you’re going to exceed the limit,” according to lead author Yannai Kashtan, a Ph.D. student at Stanford.
The biggest factor in both long- and short-term stove-attributable NO2 exposure was the duration and intensity of burner use, the study confirmed.
Households that fell in the 95th percentile of such use were exposed to three times more than the average residence, according to the study. The authors defined this category as those who used two burners on medium for 30 minutes daily in the morning and four on medium for that time length in the evening, as well as lighting the oven for about 2.25 hours at 350 degrees Fahrenheit.
“We found that just how much gas you burn in your stove is by far the biggest factor affecting how much you’re exposed,” Kashtan said. “And then, after that, do you have an effective range hood — and do you use it?”
While earlier studies have demonstrated the rate at which gas stoves release a variety of pollutants, including methane and benzene as well, the authors wanted to determine how much the contaminants spread through a home.
“We’re moving from measuring how much pollution comes from stoves to how much pollution people actually breathe,” Jackson said.
The scientists found that even in larger homes, concentrations of NO2 spiked to unhealthy levels during and after cooking — including when the range hood was operating and windows were open.
However, families that live in homes smaller than 800 square feet — about the size of a two-bedroom apartment — were exposed to twice as much NO2 in a year in comparison to the average, according to the study. Their exposure was four times the levels incurred by residents of homes larger than 3,000 square feet, per the research.
Due to these discrepancies relative to home size, the authors also identified differences in NO2 exposure regarding racial, ethnic and income groups.
The researchers observed that in comparison to the national average, long-term NO2 exposure was 60 percent higher among American Indian and Alaska Native households and 20 percent higher among Black and Hispanic or Latino households.
Such disproportionate levels of indoor air pollution exposure add to the already heightened contact with outdoor contamination sources — such as vehicle exhaust — that tends to have an outsized impact on lower-income and minority populations.
“People in poorer communities can’t always afford to change their appliances, or perhaps they rent and can’t replace appliances because they don’t own them,” Jackson said. “People in smaller homes are also breathing more pollution for the same stove use.”