People with gas and propane heaters breathe in more unhealthy nitrogen dioxide, research shows

A study of air pollution in American homes found that households with gas or propane heaters regularly inhale unhealthy levels of nitrogen dioxide.

“I did not expect that pollutant concentrations would exceed health standards in bedrooms within an hour of using the gas heater, and would remain there for hours after the heater is turned off,” said Rob Jackson, professor at the Stanford Doerr School of Sustainability , senior author of the book. paper appear in Scientific progress.

Pollution from gas and propane stoves isn’t just a problem for cooks or people in the kitchen, he said. “It’s the whole family’s problem.”

Among other negative health consequences is breathing high levels of nitrogen dioxide, or NO₂can intensify asthma attacks over time and has been linked to impaired lung development in children and early deaths.

Although most exposure to NO₂ is caused by cars and trucks that burn fossil fuels, researchers estimate that the mix of pollutants from gas and propane stoves overall may be responsible for as many as 200,000 current cases of asthma in children. A quarter of this can be attributed to nitrogen dioxide alone, according to the paper’s authors, who include scientists from Central California Asthma Collaborative, PSE Healthy Energy and the Harvard TH Chan School of Public Health.

“We found that the amount of gas you burn in your stove is by far the biggest factor affecting how much exposure you get. And then do you have an effective extractor hood, and do you use it?” said lead study author Yannai Kashtan, a Ph.D. student of earth system science.

Little room for extra exposure

In addition to cases of asthma, there is also long-term exposure to NO₂ in American households with gas stoves is high enough to cause thousands of deaths annually – possibly as many as 19,000 or 40% of the annual deaths attributable to passive smoking. This estimate is based on the researchers’ new measurements and calculations of how much nitrogen dioxide people breathe in at home due to gas stoves and the best available data on deaths from long-term exposure to NO in the open air.₂which is regulated by the US Environmental Protection Agency.

The death toll estimate is partly approximate because it does not take into account the harmful effects of repeated exposure to extremely high levels of nitrogen dioxide over short periods of time, as happens in homes with gas heaters. It is also based on previous studies on the health effects of nitrogen dioxide found outdoors, where additional pollutants from vehicles and power plants are present.

The researchers used sensors to measure concentrations of NO₂ in more than 100 homes of different sizes, layouts and ventilation methods, before, during and after using the stove.

They incorporated these measurements and other data into a model powered by National Institutes for Standards and Technology (NIST) software known as CONTAM to simulate airflow, pollutant transport, and occupant exposure on a room-by-room basis. in buildings.

This allowed them to estimate national averages and short-term exposures under a range of realistic conditions and behaviors, and compare the model results with their home measurements.

The results show that nationwide, typical use of a gas or propane stove increases nitrogen dioxide exposure by an estimated 4 parts per billion, averaged over a year. That’s three-quarters of the way to the nitrogen dioxide exposure level that the World Health Organization considers unsafe in outdoor air. “That excludes all outdoor sources combined, so it makes it much more likely that you’re going to exceed the limit,” Kashtan says.

Understanding how gas heaters affect health

The study is the latest in a series from Jackson’s group at Stanford looking at indoor air pollution from gas stoves. Previous studies documented the rate at which gas stoves emit other pollutants, including the greenhouse gas methane and the carcinogen benzene.

But to understand the implications of stove emissions for human health, the researchers needed to figure out how many pollutants spread through a home, build up and eventually dissipate. “We’re going from measuring how much pollution comes from heaters to how much pollution people are actually breathing,” says Jackson, the Michelle and Kevin Douglas Provostial Professor in Earth System Science.

With any fuel source, particulate pollution can be created by cooking food in a hot pan. However, the new research confirms that food emits little or no nitrogen dioxide during cooking, and that electric hobs do not produce NO.₂. “It’s about the fuel, not the food,” Jackson said. “Electric heaters do not emit nitrogen dioxide or benzene. If you own a gas or propane heater, you should reduce exposure to pollutants through ventilation.”

The size of the house is important

Even in larger homes, nitrogen dioxide levels routinely rose to unhealthy levels during and after cooking, even when a range hood was on and air was being vented outside. But people living in homes smaller than 800 square feet (about the size of a small two-bedroom apartment) are exposed to twice as much nitrogen dioxide over the course of a year compared to the national average, and four times as much compared to who live in the largest houses, more than 3,000 square meters.

Because home size makes such a big difference, there are also differences in exposure across racial, ethnic, and income groups. Compared to the national average, the researchers found NO in the long term₂ Exposure is 60% higher among American Indian and Alaska Native households, and 20% higher among Black, Hispanic, or Latino households.

This exposure to indoor air pollution from gas stoves reinforces the fact that exposure to outdoor sources of nitrogen dioxide pollution, such as vehicle exhaust, also tends to be higher among people in poorer communities, often minorities.

“People in poorer communities can’t always afford to replace their appliances, or maybe they rent appliances and can’t replace them because they don’t own them,” Jackson said. “People in smaller homes also breathe in more pollution for the same amount of stove use.”