Cancer-causing chemical found to be leaking from gas cookers

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

“It’s like living with a smoker,” says Drew Michanowicz of the PSE Healthy Energy Research Institute in Oakland, California. “Second-hand smoke creates a similar level of benzene indoors.”

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 the main concern because it can trigger cancers, especially leukemia, weaken 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 the levels people are exposed to are unclear. So Michanowicz’s team first collected gas samples from stoves in 72 homes in the United Kingdom, the Netherlands and Italy.

Compared to U.S. levels, benzene concentrations were 9 times higher in Italy, 37 times higher in the United Kingdom, and 66 times higher in the Netherlands.

In 35 of the homes, the team sealed the kitchens to check for gas leaks. They then estimated the benzene levels in these homes based on the leak rate, finding that 9% would exceed UK and EU safety limits – although there may not be a safe level of benzene.

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

“Depending on the balance between these different sources and ventilation rates, natural gas leaks from cookers could be a potentially important source of benzene,” says Nicola Carslaw of the University of York in the United Kingdom, who was not involved in the study. “But a lot depends on specific behavior within an individual household.”

Michanowicz believes the 35 households studied are “roughly representative of the population as a whole.”

Stove leak rates in Europe were on average lower than those the team had previously measured in the United States, he said. So it could be that gas leaks are actually lower in Europe, or that if more houses were tested the average leak rate in Europe would turn out to be higher.

For Paul Monks of the University of Leicester in the United Kingdom, the solution is obvious. “There is growing evidence about indoor air pollution and gas stoves,” Monks says. “Given the dual benefits of reducing a potential health risk and decarbonizing, it’s worth going.”

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

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

Most leaks were below the level theoretically detectable by smell. Increasing the level of odorants in the gas would detect more of these slow leaks, but not all, Michanowicz says. “Our nose is extremely imperfect. It varies a thousand times from one person to another.”

Good ventilation will improve indoor air quality provided 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 not only address energy efficiency, but also include ventilation and indoor pollution sources,” he says. For example, installing heat recovery ventilation systems, also called heat exchangers, can improve ventilation while minimizing energy loss.