Gas stoves kill 40,000 Europeans every year by pumping pollutants into their lungs, a report has found, a death toll twice that of car crashes.

The stoves emit harmful gases linked to heart and lung disease, but experts warn there is little public awareness of their dangers. According to a survey of households in the EU and Great Britain, using a gas stove saves an average of almost two years off a person’s life.

“The scale of the problem is much worse than we thought,” said lead author Juana María Delgado-Saborit, who heads the Environmental Health Research Laboratory at Jaume I University in Spain.

The researchers attributed 36,031 premature deaths to gas stoves each year in the EU, and a further 3,928 in the UK. They say their estimates are conservative because they only took into account the health effects of nitrogen dioxide (NO₂), and not other gases such as carbon monoxide and benzene.

“In 1978 we first learned that NO₂ Pollution is many times greater in gas kitchens than in electric stoves,” Delgado-Saborit said. “But only now can we put a figure on the number of lives that are being cut short.”

One in three households in the EU cooks on gas, rising to 54% of households in Great Britain and over 60% in Italy, the Netherlands, Romania and Hungary. The stoves burn fossil gas and emit harmful substances that set the respiratory tract on fire.

The report, which was supported by the European Climate Foundation, builds on last year’s research that measured air quality in homes to find out how much gas cooking caused indoor air pollution. This allowed scientists from Jaume I University and the University of Valencia to calculate the ratios between indoor and outdoor air pollution when cooking with gas, and to map indoor exposure to NO.₂.

They then applied disease risk percentages from studies of outdoor NO₂ pollution, to calculate the number of lives lost.

“The most important uncertainty is whether the mortality risk found with NO outdoors₂ of mainly traffic can be applied to NO indoors₂ by cooking on gas,” says Steffen Loft, an air pollution expert at the University of Copenhagen, who was not involved in the study. “But it is a reasonable assumption and required for the assessment.”

The results are consistent with a May study in the U.S. that found gas and propane heaters contribute to 19,000 adult deaths each year.

The EU tightened its rules on outdoor air quality this month, but has not set standards for indoor air quality. The European Public Health Alliance (EPHA) has urged policymakers to phase out gas stoves by setting limits on emissions, offering money to help switch to cleaner stoves and forcing manufacturers to label stoves with their pollution risks .

“For too long it has been easy to ignore the dangers of gas stoves,” says EPHA’s Sara Bertucci. “Like cigarettes, people didn’t think much about the health consequences – and like cigarettes, gas stoves are a small fire that fills our homes with pollution.”

People can partially protect themselves from fumes while cooking by opening windows and turning on exhaust fans while cooking.

Delgado-Saborit said she and her husband grew up in homes that cooked on electric stoves, which are “cleaner, safer and healthier,” but later moved to a home with a gas stove in the kitchen.

“We are now in the middle of some home improvements and I am counting down the days until I have a new electric hob installed in my kitchen.”