Gas stoves leak a cancer-causing chemical

Many people in Europe may be exposed to dangerous chemicals as a result of slow leaks from gas stoves or ovens. Almost 10 percent of homes tested in the UK, the Netherlands and Italy had leaks large enough to exceed exposure limits for the cancer-causing chemical benzene.

“It’s like living with a smoker,” he says Drew Michanowicz in a research institute PSE Healthy energy in Oakland, California. “Secondhand smoke creates a similar level of benzene in the interior.”

In addition to methane, natural gas can contain many volatile organic compounds (VOCs). Some are known to be harmful, including benzene, toluene, ethylbenzene, xylene, and hexane. Benzene is a major concern because it can cause cancer, especially leukemia, suppress the immune system, and cause anemia and excessive bleeding.

Previous studies have found high levels of benzene in natural gas from the North Sea and the Netherlands, but it was unclear what levels people were exposed to. So Michanowicz’s team first collected gas samples from stoves in 72 homes in the UK, the Netherlands and Italy.

Compared to US levels, benzene concentrations were 9 times higher in Italy, 37 times higher in the UK and 66 times higher in the Netherlands.

In 35 houses, the team sealed off kitchens to check for gas leaks. They then estimated the levels of benzene in these homes based on the leakage rate and found that 9 per cent would exceed safety limits for the UK and the European Union – although there may be no safe level of benzene.

“That’s just benzene from leaks,” says Michanowicz. “We know there are other sources of benzene, so the actual benzene levels may be even higher.”

“Depending on the balance between these different sources and the amount of ventilation, natural gas leakage from stoves can be a potentially important source of benzene,” he says Nicola Carslaw at the University of York in the United Kingdom, who was not involved in the study. “But so much depends on the specific behavior within the individual home.”

Michanowicz thinks the 35 houses they studied are “within the range of being representative of the larger population.”

Stove leak rates in Europe were, on average, lower than those the team had previously measured in the US, he says. So it could be that gas leakage is actually lower in Europe, or that if more homes were tested, the average leakage rate in Europe would turn out to be higher.

For Paul Monks at the University of Leicester in Great Britain, the solution is obvious. “There is increasing evidence of indoor air pollution and gas stoves,” says Monks. “Given the dual benefit of reducing potential health risk and decarbonising, it’s worth leaving.”

Induction hobs are more energy efficient and safer in several ways – no pollution, less risk of fire and zero chance of blowing up entire buildings. But some people love to cook with gas, says Michanowicz.

Cooking with gas can also produce pollutants, including benzene and nitrogen oxides. But people typically cook for short periods of time and often with the hood on, Michanowicz says, so spills can be more of a risk.

Most leaks were below levels theoretically detectable by smell. Increasing the level of odorants in the gas would allow more of these slow leaks to be detected, but not all, Michanowicz says. “Our noses are extremely imperfect. They vary a thousand times from person to person.”

Good ventilation will improve indoor air quality if the outdoor air is clean, Michanowicz says, but measures to improve energy efficiency often reduce ventilation rates.

“I think we still have a long way to go in terms of building codes that are not just about energy efficiency, but also ventilation and indoor sources of pollution,” he says. For example, installing heat recovery ventilation systems, also known as heat exchangers, can improve ventilation while minimizing energy losses.

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