The International Agency for Research on
Cancer declared late last week that air pollution is a carcinogen,
alongside known dangers such as asbestos, tobacco and ultraviolet
radiation.
The decision came after a consultation by an expert panel
organized by IARC, the cancer agency of the World Health Organization,
which is based in Lyon, France.
"We consider this to be the most important
environmental carcinogen, more so than passive smoking," said Kurt
Straif, head of the IARC department that evaluates cancer-causing
substances.
IARC had previously deemed some of the
components in air pollution such as diesel fumes to be carcinogens, but
this is the first time it has classified air pollution in its entirety
as cancer causing.
The risk to the individual is low, but
Straif said the main sources of pollution are widespread, including
transportation, power plants, and industrial and agricultural emissions.
Air pollution is a complex mixture that
includes gases and particulate matter, and IARC said one of its primary
risks is the fine particles that can be deposited deep in the lungs.
"These are difficult things for the
individual to avoid," he said, observing the worrying dark clouds from
nearby factories that he could see from his office window in Lyon.
"When
I walk on a street where there's heavy pollution from diesel exhaust, I
try to go a bit further away," he said. "So that's something you can
do."
The fact that nearly everyone on the planet
is exposed to outdoor pollution could prompt governments and other
agencies to adopt stricter controls on spewing fumes.
Straif noted that
WHO and the European Commission are reviewing their recommended limits
on air pollution.
Previously, pollution had been found to boost the chances of heart and respiratory diseases.
The expert panel's classification was made
after scientists analyzed more than 1,000 studies worldwide and
concluded there was enough evidence that exposure to outdoor air
pollution causes lung cancer.
In 2010, IARC said there were more than
220,000 lung cancer deaths worldwide connected to air pollution. The
agency also noted a link with a slightly higher risk of bladder cancer.
Straif said there were dramatic differences
in air quality between cities around the world and that the most
polluted metropolises were in China and India, where people frequently
don masks on streets to protect themselves.
"This is something governments and
environmental agencies need to take care of," Straif said. "People can
certainly contribute by doing things like not driving a big diesel car,
but this needs much wider policies by national and international
authorities."
Other experts emphasized the cancer risk
from pollution for the average person was very low — but virtually
unavoidable.
"You can choose not to drink or not to
smoke, but you can't control whether or not you're exposed to air
pollution," said Francesca Dominici, a professor of biostatistics at
Harvard University's School of Public Health. "You can't just decide not
to breathe," she said. Dominici was not connected to the IARC expert
panel.
A person's risk for cancer depends on
numerous variables, including genetics, exposure to dangerous substances
and lifestyle choices regarding issues such as drinking alcohol,
smoking and exercising.
Dominici said scientists are still trying to
figure out which bits of pollution are the most lethal and called for a
more targeted approach.
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