Using a gas stove degrades indoor air quality, very often beyond the recommendations in effect in Canada for nitrogen dioxide. This “insidious” pollution damages the health of the occupants, starting with that of the children, in whom it increases the risk of asthmatic symptoms.
Emmanuelle Viau “loves” her gas stove. However, she never imagined that this appliance could contribute to her three-year-old son’s asthma attacks. “No medical specialist has mentioned this to me. They ask if we have a cat, a dog, but not a gas cooker,” she says.
Last summer, M.me Via a accept that The duty installs a device to measure the air quality in his home. After several months of sampling, the results illustrate, in full coherence with the scientific literature, that it is difficult to maintain a healthy concentration of nitrogen dioxide (NO2) in a home with a gas stove.
In November and December, the average concentration of NO2 in M’s big apartmentme Viau amounted to 95 µg/m3almost five times the Canadian guideline for long-term exposure to this pollutant, which is set at 20 µg/m3. “I took the leap when I saw the results,” confirms this Montreal resident.
According to the World Health Organization (WHO), gas stoves are the main source of nitrogen dioxide indoors. The agency considers that in homes equipped with a gas stove, the average concentration of NO2 amounts to 43 µg/m3against only 15 µg/m3 in homes with an electric stove.
“Directly” in the house
The experience carried out by The duty at M’sme Viau cannot certify that its gas stove is the sole cause of the high concentration of NO2 At her place. However, the data regularly show sudden increases in nitrogen dioxide around lunchtime or suppertime, when the family is cooking.
Any form of combustion generates nitrogen dioxide. It is the flames which, by reacting with the air, produce this pollutant. Stoves, heating systems and cigarettes are other sources in indoor environments. Outdoor air infiltration, where automobile traffic is the main source of NO2should also be taken into account.
“Stoves are different from other household appliances,” says Eric Lebel, an American scientist who last year published an article on the pollution generated by gas stoves. “They emit gases directly into your home, unlike furnaces, for example, which are hooked up to a drain,” he explains.
According to Mr. Lebel’s studyusing a gas cooker without a hood can temporarily increase the NO concentration2 above 190µμg/m, particularly in small kitchens. The pollutant then quickly mixes with the air throughout the home. If the windows are closed, it can accumulate in the residence.
Pollution caused by 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 related to these household appliances. A US agency responsible for safety standards then raised the idea of banning gas stoves, which sparked an outcry.
In response to this tumult, in Quebec, environmental organizations and a medical association asked the government of François Legault prohibit the connection of gas appliances in new buildings, and to summon the gas distributors of the province to shed light on their knowledge of the risks associated with cooking with gas.
asthma in children
The effects of NO2 on health are known for decades. According to Health Canada, intense exposure, even of short duration, can make breathing more difficult and cause inflammation. Moderate exposure, but maintained for several months, is associated with an increase in respiratory symptoms, especially in asthmatic children.
A meta-analysis published in 2013, which identified the results of forty studies on the subject, estimated that children living in a house with a gas stove had a 42% higher risk of having asthma symptoms. For each 28 μg/m increment3 in NO concentration2 the air in their home, exposed children were also 15% more likely to have wheezing.
In 2015, the Government of Canada revised its guidelines on indoor nitrogen dioxide. For short-term exposure (hourly average), the limit is set at 170µμg/m3. For long-term exposures, which extend over several months, the limit is set at 20µμg/m3. These guidelines are among the strictest in the world, but the health of Canadians is not fully guaranteed.
“It’s essentially impossible to meet these guidelines when using a gas stove,” says Dr.re 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 fine particles, carbon monoxide, nitrogen monoxide, formaldehyde and benzene.
In 2021, the WHO revised its own guidelines according to the latest advances in science. That for long-term exposure to nitrogen dioxide has been lowered to 10µμg/m3 — it is therefore twice as strict as the Canadian guideline. To arrive at this threshold, the UN agency considered the risks posed by this pollutant for mortality in general.
Maximize Ventilation
Households with gas stoves can meet NO guidelines, according to Health Canada.2 if they take precautions. “It is possible to stay below 20 μg/m3 [la ligne directrice pour l’exposition de longue durée] by using an adequate ventilation hood,” says Marie-Eve Héroux, acting manager of the Air Quality and Risk Assessment Division in this department.
As for short-term exposure, “most homes are able to meet that maximum limit there. [de 170µμg/m3] “says M.me Heroux. “However, yes, it is possible for some homes that have a gas stove to exceed the maximum limit for a brief period after cooking. Again, maximizing ventilation helps reduce exposure.
Thus, Health Canada recommends that gas stove users activate their range hood each time they cook, without exception. This hood must expel the air to the outside of the house, not just filter it. They should also use the rear burners as a priority, since they breathe in the fumes less directly. And, when possible, they should open the windows.
Emmanuelle Viau was already applying most of these precautionary measures. “I religiously leave the hood,” she said. And yet, the results obtained at home are “surprising and disturbing”, in her opinion. “Now I ask myself the question: should I change my stove? she says. After seeing the results, she bought two portable electric burners to reduce her reliance on gas.
She is not ruling out any option to reduce this “insidious” pollution and improve her son’s respiratory health. He has had two asthma attacks in the last few months, including one at home. “His asthma is better controlled at the moment, but he is still having too many attacks compared to the cocktail of drugs he is using,” notes Ms.me Viau.
It is estimated that 350,000 children and adolescents suffer from asthma in Quebec. Thousands of them live in a house equipped with a gas stove. We count 100,000 gas stoves in Quebec cottages, i.e. 3% of all cooks.
The pollution caused by gas stoves is often in doctors’ blind spot. “From the outset, it’s not something we regularly discuss with our patients,” admits Dr.r Antoine Delage, President of the Association of Pneumologists of Quebec. However, he indicates that gas stoves are normally part of the questionnaire used in pediatrics in cases of asthma in children.
“Health professionals are not always very good at assessing environmental risks, admits the Dre Lem. We know the classic risks, like diet, exercise, and sleep, but we don’t always think about what’s in the family environment. »