Even in the comfort of our homes, the air we breathe is often polluted. One of the typical pollutants, nitrogen dioxide (NO2), is generated by any form of combustion. In homes with a gas stove, this appliance is the main source of NO2.
For decades, scientific evidence of the harms of NO2 for health accumulate. Primarily, it is asthma symptoms in children that get worse.
To illustrate this phenomenon concretely, The duty measured the air quality in the home of a family equipped with a gas cooker for several months. This family — that of Emmanuelle Viau, whose three-year-old son has asthma — lives in Montreal, in the Rosemont–La Petite-Patrie district.
The device we chose, a uHoo brand detector, continuously measures nine variables related to indoor air quality, including NO2. Used in hospitals in several countries around the world, this device is efficient enough for our needs. Its margin of uncertainty is less than 5%.
We installed this detector on the kitchen counter. The concentrations there are representative of those breathed in by the people in that room. First, here are the average daily concentrations measured from September to December (1).
The first observation is that the values measured greatly exceed the recommendations. In Canada, the guideline for long-term exposure to NO2 is fixed at 20µμg/m3. The average concentration measured in Mme Viau in November and December (95µμg/m3) is almost five times greater than this.
There is also significant variability from day to day. In addition, the concentrations increase over the months, from September to December. It is quite possible that, since the family closes its windows with the onset of cold weather, the fumes from the gas stove accumulate more in the house.
Outside air matters too
Another phenomenon must be taken into account: outdoor air pollution. Outside, it is cars that mainly generate NO2. The concentration of this pollutant is higher near road arteries. Necessarily, this gas infiltrates inside the houses.
However, outdoor air pollution varies with the seasons. In winter, the average concentration of NO2 measured in Montreal is approximately 20µμg/m3. The days when it climbs to 40µμg/m3 are not uncommon, especially in the most polluted neighborhoods (2).
Three days to see more clearly
To better discern the effect of the gas stove, let’s take a closer look at the data. Here are three days where his influence is particularly evident.
On Friday, September 16, we see that the curve rises suddenly around supper time. This most likely corresponds to a time when the family was using their gas cooker (3).
On Saturday, December 10, we observe a sharp peak in the morning. “I think we had a good lunch; we were about to watch a soccer world cup match,” recalls Mme Viau (4).
And on Monday, December 19 — “a typical day of teleworking” — we see a peak in NO2 around supper time, but also in the afternoon. “I’m a big tea drinker, that’s probably when I boiled water on the stove,” says Ms.me Viau (5).
“You can clearly see that there is a repeated pattern with dinnertime,” says Patrick Hayes, a chemistry professor at the University of Montreal and an air pollution specialist, to whom The duty presented the data. “It seems important compared to the basic exposure in a city like Montreal. »
Note that these peaks occur even if Mme Viau and his family always use the hood when they cook. The slower and more gradual variations seen on the graphs are probably due to outside air infiltration.
Short term exposure
High concentrations of NO2, even if they don’t last long, can make it harder to breathe and cause inflammation. The Canadian guideline for short-term exposure is set at 170µμg/m3. This concentration should never be exceeded on an hourly basis.
From September to December, such a concentration was measured at least nine times in Mme Viau (including December 10 and 19). However, the associated peaks never lasted more than a few minutes. Thus, the guideline was not violated on an hourly basis.
And elsewhere in the house?
In general, the concentration of NO2 depends on the sources involved, but also on the size of the residence. A large house further dilutes the pollutant, and therefore reduces the exposure of the occupants. Mme Viau and his family live in a large apartment, located on the upper floor of a duplex.
What is the concentration outside the kitchen? For a week in January, we moved the detector to Mrs. son’s bedroom.me Viau.
The average concentration there is very similar to that measured in the kitchen. However, the concentration peaks associated with the use of the oven seem less pronounced. Here are the measurements for January 14, for example (6).
In short, the son of Mr.me Viau is exposed to a considerable concentration of NO2and the gas stove has something to do with it.
The duty presented the data to Alberto Baldelli, a postdoctoral researcher at the University of British Columbia. Around 2019, he conducted a battery of tests to assess the reliability of the uHoo detector. Mr. Baldelli is sorry that the concentrations measured in Mr.me Viau are also high, but is not surprised. “People don’t know it, but we breathe a lot of crap,” he says bluntly.
With Catherine Bombardier