Diesel exhaust causes cancer, the World Health Organization's cancer agency has declared, a ruling it says could make exhaust as important a public health threat as second-hand smoke.
The risk of getting cancer from diesel fumes is small, but since so many people breathe in the fumes in some way, the science panel says raising the status of diesel exhaust to carcinogen from 'probable carcinogen' is an important shift.
'It's on the same order of magnitude as passive smoking,' said Kurt Straif, director of the IARC department that evaluates cancer risks.
'This could be another big push for countries to clean up exhaust from diesel engines.'
Since so many people are exposed to exhaust, Straif said there could be many cases of lung cancer connected to the contaminant. He said the fumes affected groups including pedestrians on the street, ship passengers and crew, railroad workers, truck drivers, mechanics, miners and people operating heavy machinery.
The new classification followed a weeklong discussion in Lyon, France by an expert panel organised by the International Agency for Research on Cancer. The panel's decision stands as the ruling for the IARC, the cancer arm of the World Health Organization.
The last time the agency considered the status of diesel exhaust was in 1989, when it was labelled 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 said new diesel engines spew out fewer fumes but further studies are needed to assess any potential dangers.
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 US National Cancer Institute.
That paper analysed 12,300 miners for several decades starting in 1947. Researchers found that miners heavily exposed to diesel exhaust had a higher risk of dying from lung cancer.
Lobbyists for the diesel industry argued the study wasn't credible because researchers didn't have exact data on how much exposure miners got in the early years of the study; they simply asked them to remember what their exposure was like.
A person's risk for cancer depends on many variables, from genetic makeup to the amount and length of time of exposure to dangerous substances.
