Cooking with gas: How bad for your health is it, really?

In November last year an international study co-authored by researchers at UNSW Sydney published the startling results that around 12.7% of current childhood asthma in the US is attributable to the use of a gas stove in the house.

In fact, those results came four years after a 2018 Australian study identified gas stoves as responsible for 12.3% of childhood asthma in the country.

This groundswell of concern peaked at the beginning of this year when the US Consumer Product Safety Commission announced it was considering tightening restrictions on the use and sale of gas stoves across the country.

The American Gas Association (AGA), a gas industry peak body in the US, published a statement accusing the study of being unsubstantiated because it did not rely on measurements of real-life appliance use – notwithstanding the obvious ethical barriers to deliberately exposing children to an environmental hazard – and citing a 2013 study that found no apparent link between NO2 and childhood asthma globally.

But experts at UNSW maintain that cooking with gas is a net negative for health. So what about gas stoves is so risky for human health?

Burning the methane in natural gas produces a not insubstantial load of toxic compounds, explains Associate Professor Donna Green, Chief Investigator of the Digital Grid Futures Institute at UNSW Sydney.

Those compounds include nitrogen dioxide (NO2).

“NO2 is a problem because it can cause a range of very serious health problems, including asthma,” explains Green.

For some people, small amounts of these toxic pollutants will be nothing more than in irritant (though there’s limited evidence about the long-term impact on human health). But exposure to NO2 in particular can increase the likelihood of children developing a respiratory illness by about 20%.

Other studies have pointed to other potential adverse health effects, including an Iranian study that linked NO2 and chronic obstructive pulmonary disease, while another global study found a link between traffic-sourced NO2 and all-cause mortality.

And NO2 isn’t the only toxic culprit. Burning natural gas can also produce carbon monoxide, nitrous oxides and formaldehyde, explains Dr Christine Cowie, an environmental epidemiologist at UNSW Medicine & Health.

“Carbon monoxide is emitted when gas is burnt and will deplete the oxygen in the air, and deplete oxygen in the blood too,” she explains.

Poisoning from elevated levels of carbon monoxide can cause headaches and dizziness.

“But people can also become unconscious from carbon monoxide poisoning, and in extreme cases it can lead to death,” says Cowie. “Such cases have been linked to the use of faulty or inadequately vented gas heaters, more so than gas stoves, although anywhere where that gas is used in an enclosed space can lead to elevated carbon monoxide levels in air.”

Other studies suggest gas stoves can release other harmful compounds, like benzene, a known carcinogen.

But it’s the asthma association that’s most powerfully supported by current research.

“We have known there is an association between NO2 and asthma in that it can exacerbate symptoms in people with respiratory disease such as asthma and chronic obstructive pulmonary disease (COPD),” says Cowie, one of the authors on the 2019 Australian asthma study.

“In particular, exposure to nitrogen dioxide in ambient air has been linked to an increased risk of asthma and other respiratory symptoms, but more recently there is increasing evidence to suggest that NO2 is likely to be a direct cause of asthma in children,” she says.

Making the change

If gas stoves are both bad for health and the planet, there are ways to make the change. The main alternative to gas cooking is electrical stoves, including induction cooktops – the most energy efficient method.

But, switching from gas can involve rewiring the whole stove, which can be costly. So what do experts say you can do in the meantime?

“To reduce the impact on your health from cooking with gas, you want to get as much ventilation as possible, so open windows and doors – cross-ventilation is the best because it just clears the air out,” says Green.

Turning on the extractor fan can also dramatically reduce the impact of gas pollution. Cowie and he research team’s work found that the burden of asthma associated with gas stoves could be reduced from 12.3% to 3.4% if all homes with gas stoves used high efficiency range hoods that vented emissions outdoors.

“We try and look at solutions and alternatives to the status quo because policies often move very slowly,” says Cowie.

“As well as raising awareness with consumers, I think the big industries, such as the gas industry, but also the building and appliance industries, have an important part to play. For instance, the building industry can move away from the use of gas in new home-builds and lead by example.”