diesel exhaust causes cancer, the World Health Organisation has said, in a ruling that makes the fumes as important a threat as second-hand smoke.
The WHO’s International Agency for Research on Cancer said yesterday that because so many people breathe in the fumes, it has raised the status of diesel exhaust from “probable carcinogen” to “carcinogen”.
Kurt Straif, director of the IARC, which evaluates risks of the disease, said: “It’s on the same order of magnitude as passive smoking.”
Particles in the exhaust can cause inflammation in the lungs which over time can lead to the disease. Mr Straif said there could be numerous cases of lung cancer connected to the contaminant, with affected groups including pedestrians, ship passengers and crew, railway workers, lorry drivers, mechanics, miners and people operating heavy machinery.
He urged countries around the world to “clean up exhaust from diesel engines”.
The new classification followed a week-long discussion in Lyon, France, by an expert panel organised by the IARC.
Ken Donaldson, a professor of respiratory toxicology at the University of Edinburgh, said: “It’s pretty well known that if you get enough exposure to diesel, it’s a carcinogen.”
However Prof Donaldson added that lung cancer was caused by multiple factors and he believes that other things such smoking are still far more deadly.
“For the man on the street, nothing has changed,” he said.
“It’s a known risk but a low one for the average person, so people should go about their business as normal ... you could wear a mask if you want to, but who wants to walk around all the time with a mask on?”
The last time the agency considered the status of diesel exhaust was in 1989, when it was classed a “probable” carcinogen.
Reclassifying diesel exhaust as carcinogenic puts it into the same category as other known hazards such as asbestos, alcohol and ultraviolet radiation. Experts in Lyon had analysed published studies, evidence from animals and limited research in humans.
One of the biggest studies was published in March by the American National Cancer Institute. That paper analysed 12,300 miners for several decades starting in 1947. Researchers found miners heavily exposed to diesel exhaust had a higher risk of dying from lung cancer.
Lobbyists for the diesel industry have argued the study was not credible because researchers did not have exact data on how much exposure miners got in the early years of the study.
Further restrictions on diesel could force the industry to spend more on developing expensive new technology. Diesel engine makers and car companies were quick to point out emissions from lorries and buses have been slashed by more than 95 per cent in terms of nitrogen oxides, particulate and sulphur emissions.
“Diesel exhaust is only a very small contributor to air pollution,” said a statement from the Diesel Technology Forum, a group representing firms including Mercedes, Ford and Chrysler.