New York: Cooking with gas stoves can raise indoor levels of a chemical linked to a higher risk of leukaemia and other blood cell cancers, finds an alarming study.

The study, published in the journal Environmental Science & Technology, showed that a single gas cooktop burner on high or a gas oven set to 350 degrees Fahrenheit can raise indoor levels of the carcinogen benzene above those found in second-hand tobacco smoke.

Benzene also drifts throughout a home and lingers for hours in home air, said researchers.

"Benzene forms in flames and other high-temperature environments, such as the flares found in oil fields and refineries. We now know that benzene also forms in the flames of gas stoves in our homes," said Rob Jackson, Professor of Earth system science at the Stanford Doerr School of Sustainability.

"Good ventilation helps reduce pollutant concentrations, but we found that exhaust fans were often ineffective at eliminating benzene exposure," he added.

The researchers found gas and propane burners and ovens emitted 10 to 50 times more benzene than electric stoves. Induction cooktops emitted no detectable benzene whatsoever.

The rates of benzene emitted during combustion were hundreds of times higher than benzene emission rates identified in other recent studies from unburned gas leaking into homes.

They also found residential range hoods are not always effective at reducing concentrations of benzene and other pollutants, even when the hoods vent outdoors.

Importantly, the researchers also tested whether foods being cooked emit benzene and found zero benzene emissions from pan-frying salmon or bacon. All benzene emissions the investigators measured came from the fuel used rather than any food cooked.

The new study is the first to analyse benzene emissions when a stove or oven is in use. Previous studies focused on leaks from stoves when they are off, and did not directly measure resulting benzene concentrations.

A previous Stanford-led study showed that gas-burning stoves inside US homes leak methane with a climate impact comparable to the carbon dioxide emissions from about 500,000 gasoline-powered cars. They also expose users to pollutants, such as nitrogen dioxide, which can trigger respiratory diseases.

A 2013 meta-analysis concluded that children who live in homes with gas stoves had a 42 per cent greater risk of asthma than children living in homes without gas stoves, and a 2022 analysis calculated that 12.7 per cent of childhood asthma in the US is attributable to gas stoves.

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