Recently we wrote about researchers abandoning their gas stoves after measuring the high levels of dangerous indoor air pollution they produce.
Some scientists and chefs, concerned about the health and environmental impacts of gas stoves, switch to electromagnetic induction cookers or even portable induction burners boasting a few extra benefits.
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These stories prompted questions from readers. What about gas fireplaces or furnaces? Or propane stoves? Are new gas stoves less polluting? Are induction cookers safe for people with pacemakers?
Here are the answers to some of these questions.
Where do pollutants come from when cooking with gas?
Dave Rose of Innisfil, Ontario asked if nitrogen oxides – contaminants linked to negative health effects such as asthma – occur naturally in small amounts in gas or come from its combustion.
The answer is that they are produced during combustion, when nitrogen and oxygen in the air react with each other when heated hot gas.
During this time, carbon monoxide is produced by incomplete combustion of the gas.
Eric Lebel, researcher at PSE Healthy Energy in California and lead author of a recent study on pollution from gas stovessaid his team is starting to look at the composition of natural gas in different cities, including Toronto and Vancouver.
Although it’s mostly methane, he said, “there could also be other pollutants in the gas.” These could include volatile organic compounds and sulfur compounds used to make natural gas – which is normally odorless – smelly and therefore detectable in the event of a leak.
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Of course, some pollutants are generated by heating cooking ingredients such as oil and grease (and any food you burn) no matter what type of pan you’re using, so turning on the hood fan is a good idea.
Do propane cooktops have the same problems as natural gas cooktops?
While our stories dealt with natural gas stoves, Peter Gosse of St. John’s, NL has another type of gas stove and wrote in to ask how it compares.
Tara Kahan, a University of Saskatchewan professor who has studied stove pollution, said high levels of nitrogen oxides are also emitted when cooking with propane stoves. health effects should be similar: “From an air quality perspective, this is not an obvious improvement over methane.”
Lebel said pollution from cooking with propane is something his team is “actively investigating.”
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He acknowledged that the climate impacts should be lower with propane. Indeed, natural gas is composed of methane, itself a much more potent greenhouse gas than carbon dioxide. Lebel’s research has shown leaks into the atmosphere even when the stove is not in use.
“We’re not as concerned about propane leaks because it’s not as potent a greenhouse gas as methane,” Lebel said. “However, CO2 is still produced when it is burned, similar to how it is produced from methane.”
Do newer, more expensive and better maintained gas stoves leak less and generate fewer pollutants?
As part of Lebel’s study, the researchers looked at stoves that were between three and 30 years old.
The study found no relationship between stove age or purchase price with respect to methane or nitrogen oxide emissionsonce energy production (which affects emissions) is taken into account.
Rob Jackson, a Stanford University professor and co-author of the study, said there are many connectors between the stove and the natural gas lines, all of which leak a little. “Often, even when installed correctly, there is no way to properly seal the system.”
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Maintenance can reduce CO emissions to some extent. In the United States, since 1926, stoves have been allowed to emit up to 800 ppm of CO (far more than the Environmental Protection Agency’s nine ppm exposure standard), according to an article by TH Greiner, engineer at Iowa State University: “A new range can emit as much as the old one.” However, the article states that field technicians report that most cookers can be set to produce less than 50ppm.
What about pollution from gas fireplaces and furnaces?
Lorraine Mccannell asked, “Any research done on gas fireplaces and furnaces having the same effect as stoves?”
While gas fireplaces, furnaces and water heaters all burn and leak methane, and are therefore a concern from a climate perspective, Lebel and Jackson say there is less concern than with cookers. to gas from a health point of view.
This is because, unlike stoves, they generally must have a vent (or chimney) to the outside.
Jackson said, “I don’t really expect gas fireplaces to be such a big source of indoor air pollution.” But he added that his team was starting to measure them to find out for sure.
Furnaces and water heaters also tend to be in places like basements, where people spend less time than in kitchens.
That said, Michael Thomas, founder of Carbon Switch, blogged about his experience measuring nitrogen oxides in his home earlier this year, and found they peaked in the early morning when the furnace was on, suggesting pollutants were leaking from the furnace.
If I have gas appliances in my house, is there a way to test for pollutants in the air?
Thomas tested his air with an air quality monitor he purchased online. He said those that measure nitrogen oxides are unfortunately expensive (around US$300; a Canadian retailer sells Thomas’s model for over C$450) and hard to find.
If you are interested in other types of pollutants and live in Toronto or Vancouver, you can volunteer to follow-up to Lebel’s studywhich takes place in May.
This part of the study will not test for pollutants from burning gas, such as oxides of nitrogen, but pollutants in the unburned gas from your stove.
Is it true that people with pacemakers can’t use induction cookers?
It is true that the magnetic fields generated by induction cookers can interfere with devices such as pacemakers and insulin pumps.
Organizations such as the British Heart Foundation and manufacturers of induction cookers say that people with such devices should keep them 60 centimeters from an induction cooktop when it is on.
Do you have questions about this story? We answer as much as possible in the comments.