Diesel fumes cause cancer, the World Health
Organization's cancer agency declared Tuesday, a ruling it said 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 said raising
the status of diesel exhaust to carcinogen from "probable carcinogen"
was an important shift.
"It's on the same order of magnitude as passive smoking," said Kurt
Straif, director of the department that evaluates cancer risks. "This
could be another big push for countries to clean up exhaust from diesel
engines."
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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, railway workers, truck drivers, mechanics, miners
and people operating heavy machinery.
The new classification followed a weeklong discussion in Lyon, France,
by an expert panel organized by the International Agency for Research on
Cancer (IARC). The panel's decision stands as the ruling for the agency,
which is the cancer arm of WHO.
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.
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The U.S. government, however, still classifies diesel exhaust as a
likely carcinogen. Experts said new diesel engines spew out fewer fumes,
but further studies are needed to assess any potential dangers.
"We don't have enough evidence to say these new engines are zero risk,
but they are certainly lower risk than before," said Vincent Cogliano of
the U.S. Environmental Protection Agency. He added the agency had not
received any requests to re-evaluate whether diesel definitely causes
cancer but said its assessments tend to be in line with those made by
the UN agency.
Experts in Lyon had analyzed published studies, evidence from animals
and limited research in humans. One of the biggest studies was published
in March by the U.S. National Cancer Institute. That paper analyzed
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.
Further restrictions on diesel fumes 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 trucks and buses
have been slashed by more than 95 per cent for nitrogen oxides,
particulate and sulphur emissions.
"Diesel exhaust is only a very small contributor to air pollution," the
Diesel Technology Forum, a group representing companies, including
Mercedes, Ford and Chrysler, said in a statement. "In Southern
California, more fine particles come from brake and tire wear than from
diesel engines."
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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.
Some experts said the new cancer classification wasn't surprising.
"It's pretty well known that if you get enough exposure to diesel, it's
a carcinogen," said Ken Donaldson, a professor of respiratory toxicology
at the University of Edinburgh who was not part of the IARC panel. He
said the thousands of particles, including some harmful chemicals, in
the exhaust could cause inflammation in the lungs and that could lead to
cancer.
But Donaldson said lung cancer was caused by multiple factors and that
other things like smoking were far more deadly. He said the people most
at risk were those whose jobs exposed them to high levels of diesel
exhaust, like truck drivers, mechanics and miners.
"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?" |