Gas stoves degrade indoor air quality

Gas stoves degrade indoor air quality

Using a gas stove degrades indoor air quality and very often exceeds Canada’s nitrogen dioxide recommendations. This “insidious” pollution harms the health of occupants, starting with children, for whom it increases the risk of developing asthmatic symptoms.

Emmanuelle Viau “loves” her gas stove. However, she never thought that this device could contribute to her three-year-old son’s asthma attacks. “No specialist has mentioned this to me. They ask if we have a cat, a dog, but no gas stove,” she says.

Last summer, Ms Viau agreed to let Le Devoir install a device to measure the air quality in her home. After several months of sampling, the results illustrate, in full agreement with the scientific literature, that it is difficult to maintain a healthy level of nitrogen dioxide (NO2) in a home equipped with a gas stove.

In November and December, the average NO2 concentration in Ms Viau’s large apartment was 95 µg/m3, almost five times the Canadian guideline for long-term exposure to this pollutant, which is set at 20 µg/m3. “I took the plunge when I saw the results,” confirms this Montreal resident.

According to the World Health Organization (WHO), gas stoves are the main source of indoor nitrogen dioxide. The agency estimates that in homes with gas stoves, the average NO2 concentration is 43 µg/m3, compared to just 15 µg/m3 in homes with electric stoves.

“Right” in the house

The experiment carried out by Le Devoir in Mrs Viau’s house does not certify that her gas stove is the sole cause of the high NO2 concentration in her house. However, the data regularly shows a sudden spike in nitrogen dioxide around lunchtime or dinnertime when the family is cooking. (To see the detailed results, click here.)

Any form of combustion produces nitrogen dioxide. It is the flames that produce this pollutant by reacting with the air. Stoves, heaters, and cigarettes are other indoor sources. Infiltration from the outside air, where car traffic is the main source of NO2, must also be considered.

“Stoves are different from other household appliances,” says Eric Lebel, an American scientist who published an article last year on the pollution caused by gas stoves. “They emit gases directly into your home, unlike, say, stoves that are plugged into a drain,” he explains.

According to Mr. Lebel’s study, using a gas stove without a hood can temporarily increase the NO2 concentration to over 190 µg/m, especially in small kitchens. The pollutant then quickly mixes with the air throughout the home. If the windows are closed, it can accumulate in the apartment.

Pollution from gas stoves has made headlines in recent weeks. In December, a study announced that the symptoms of 13% of asthmatic children in the United States could be linked to these household appliances. A US agency responsible for safety standards then brought up the idea of ​​banning gas stoves, which caused an outcry.

In response to that uproar, Quebec environmental groups and a medical association called on the government of François Legault to ban the connection of gas appliances in new homes and urged the province’s gas distributors to shed light on risks associated with gas cooking.

asthma in children

The health effects of NO2 have been known for decades. According to Health Canada, intense exposure, even short-lived, can make breathing difficult and cause inflammation. Moderate exposure, however sustained over several months, is associated with an increase in respiratory symptoms, particularly in asthmatic children.

A meta-analysis published in 2013 listing the results of about forty studies on the subject estimated that children who lived in a home with a gas stove had a 42% greater risk of developing asthma symptoms. For every 28 μg/m3 increase in the NO2 concentration in the air in their house, the exposed children were also 15% more likely to wheeze.

In 2015, the Canadian government revised its indoor nitrogen dioxide guidelines. For short-term exposure (hourly mean) the limit is 170 µg/m3. For long-term exposure spanning several months, the limit is 20 µg/m3. These guidelines are among the strictest in the world, but Canadian health is not fully guaranteed.

“It’s practically impossible to meet these guidelines when using a gas stove,” says Dr. Melissa Lem, President of the Canadian Association of Physicians for the Environment. “Burning fossil fuels and inhaling the smoke is not good for anyone,” she adds. Gas stoves also emit particulate matter, carbon monoxide, nitrous oxide, formaldehyde and benzene.

In 2021, the WHO revised its own guidelines based on the latest scientific evidence. The limit for long-term exposure to nitrogen dioxide has been lowered to 10 µg/m3 – twice as stringent as the Canadian guideline. To arrive at this threshold, the UN agency looked at the risks posed by this pollutant to mortality in general.

Maximize ventilation

According to Health Canada, homes with a gas stove can meet NO2 guidelines if they take precautions. “It is possible to stay below 20 μg/m3 [la ligne directrice pour l’exposition de longue durée] by using a suitable extractor hood,” says Marie-Eve Héroux, Acting Head of Air Quality and Risk Assessment in this department.

As for short-term exposure, “most households can meet that ceiling there. [de 170 µg/m3] says Mrs. Héroux. “However, yes, it is possible that some households that have a gas stove will briefly exceed the limit after cooking. Again, maximizing ventilation helps reduce exposure.

As such, Health Canada recommends that gas range users invariably turn on their range hoods every time they cook. This extractor hood must direct the air outside and not just filter it. You should also give priority to using the rear burners as they inhale the exhaust gases less directly. And if possible, they should open the windows.

Emmanuelle Viau already applied most of these precautions. “I’m exiting the hood religiously,” she said. And yet, in her opinion, the results achieved at home are “surprising and disturbing”. “Now I ask myself the question: should I change my stove? She says. After seeing the results, she bought two portable electric torches to reduce her reliance on gas.

She doesn’t rule out any way to reduce this “insidious” pollution and improve her son’s respiratory health. He has had two asthma attacks in recent months, including one at home. “His asthma is better controlled at the moment, but he still has too many attacks compared to the drug cocktail he’s using,” notes Ms. Viau.

It is estimated that 350,000 children and adolescents in Quebec suffer from asthma. Thousands of them live in a house equipped with a gas stove. There are 100,000 gas stoves in Quebec cottages, or 3% of all stoves.

The pollution caused by gas stoves is often in the blind spot of doctors. “Right from the start, this isn’t something that we regularly discuss with our patients,” admits Dr. Antoine Delage, President of the Association des pneumologues du Quebec. However, he points out that gas stoves are usually part of the questionnaire used in pediatric asthma in children.

“Health professionals are not always very good at assessing environmental risks,” admits Dr. Lem in. We know the classic risks such as diet, exercise and sleep, but we don’t always think about the family environment. »

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