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 secondhand
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 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 organized 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 labeled 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.
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 that the agency had not received any
requests to reevaluate whether diesel definitely causes
cancer but said their assessments tend to be in line with
those made by IARC.
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 percent for nitrogen oxides,
particulate and sulfur 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.”
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 over
time, 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 or 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?”