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On Gas Stoves and Asthma, a Surprising Finding

June 19/2023

By Heidi Singer

DLSPH researchers have found a strong correlation between gas stove emissions and childhood asthma in Canadian cities – particularly in Toronto.

Profs. Jeff Brook, Padmaja Subbarao, Dr. Marc-Antoine Bedard, and PhD student Myrtha E. Reyna, working with colleagues across Canada, analysed asthma rates among children in major Canadian cities, and found almost double the asthma risk in 5-year old children living in Toronto homes with gas stoves versus electric ones.

They published their results in a letter to the Canadian Journal of Public Health.

“I was surprised by the results,” says Reyna. “I think I was a bit skeptical going into the analysis. When we talk about environmental exposures, it’s never straightforward. It’s always different exposures working together to increase or decrease risk. We don’t often get such a clear signal from isolated exposures.”

The researchers were also surprised to find that geography mattered far more than the presence of mitigating factors like hood fans.

The correlation in Vancouver was significantly less than Toronto, with a relative risk of 0.75 versus 1.95 – suggesting that milder weather (and therefore the ability to open windows more often) plays a role in mitigating gas buildup. But, cautions Reyna, there could be other factors at play that warrant further examination, such as a different types of gas used in the two cities, baseline levels of pollution, and the age of the housing.

The researchers also found that the existence or use of an exhaust fan didn’t seem to help – but there too, it wasn’t clear why. It may be that not all fans are built equally. Some push the air outside, while others merely circulate it indoors.

The researchers drew their data from the CHILD Study – almost 3,500 children born between 2008 and 2012 from the general population, who have been followed since they were in the womb. For this study, Bedard and team studied data from parents of mostly middle to high income in four major Canadian cities. However, only Toronto and Vancouver had enough participants with gas stoves to make city-specific analysis (n=442).

The authors have called for a closer look into the reasons behind the strong correlation they uncovered. But Reyna is hoping enough is already known about the climate effects of natural gas to change building practices. “About 20 per cent of households used gas for cooking, so we are talking about a high prevalence of exposure in Canadian homes.”

Replacing existing gas stoves is expensive, “but I think it’s more about what we’re doing moving forward when we build new housing,” she says. “We could simply move away from gas in general and toward electric.”