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June 21, 2002
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Smoking Goes From Bad to Worse,
New Research Finds
It’s a deadlier
carcinogen and causes more types of the disease
than
scientists believed .
By Thomas H. Maugh II, Los
Angeles Times Staff
Writer
Tobacco smoke is a much deadlier
carcinogen and triggers a broader variety of cancers than researchers
had
previously believed, according to the most comprehensive study of
smoking ever
undertaken.
The new study also provides the
first definitive evidence that secondhand smoke causes lung cancer,
increasing the
risk to those people exposed by about 20%. The new study firmly links
smoking
to stomach, liver, cervical and kidney cancer, as well as to myeloid
leukemia.
Such links were suspected, but not proved. “We are still learning just
how
damaging cigarette smoking is,” Dr. Jonathan Samet of the Johns Hopkins
School
of Public Health told a London news conference Wednesday. “Only now are
we
beginning to see the full picture of what happens when a generation
begins to
smoke at an early age ... the full picture is more disturbing than what
we saw
when we only had the smaller pieces.”
Samet chaired an international
panel of 29 experts convened by the United Nations’ International
Agency for
Research on Cancer to conduct the first comprehensive evaluation of
smoking
research since 1986. The team examined more than 3,000 studies
involving
millions of smokers. Their report will be published later this year,
but parts
of it are scheduled to be posted on the agency’s Web
site--www.iarc.fr--today.
“When we put all that
information
together, the picture becomes much clearer,” said Dr. Patricia A.
Buffler of UC
Berkeley, a member of the research group. “This confirms many things
that
people were concerned about.”
An estimated 1.2 billion people
worldwide smoke, and their prognosis is grim, according to the study.
At least
half of them will be killed prematurely by smoking-related diseases,
including
cancer, heart disease and emphysema. Half of those deaths will occur in
middle
age, with an average loss of 20 to 25 years of life expectancy.
In addition to finding new
links,
researchers concluded that the risks for some tumors previously linked
to
smoking was higher than suspected.
For tumors of the bladder and
kidney, for example, researchers had previously thought smokers had
three to
four times the normal risk. The new data indicate the actual risk is
five to
six times normal, IARC director Dr. Paul Kleihuis said.
Some of the cancers are
associated
with other factors as well. Cervical cancer is associated with the
human
papilloma virus, stomach cancer with the bacterium Helicobacter pylori,
and
liver cancer with hepatitis viruses. But in each of those cases,
Buffler said,
smoking doubles the risk.
The study, which Buffler said
was
the most comprehensive ever undertaken, found no evidence, however,
that
smoking increases the risk of prostate, breast or endometrial cancers.
That is
probably because these tumors are triggered primarily by hormones
rather than
by exposure to chemicals in the environment, said Sir Richard Doll of
Oxford
University, a member of the panel.
The team also looked at more
than
50 studies focused on exposure to secondhand smoke and concluded that
such
exposure is linked to lung cancer, but no others. “It is a very strong
association,” Buffler said. There are more than 4,000 chemicals in
cigarette
smoke and new studies have shown that they can be measured in the body
fluids
and urine of nonsmokers.
“It is now well established
that
they are being breathed in by nonsmokers, absorbed, and are having an
impact on
genetic material,” Buffler said.
Some national agencies,
including
the U.S. Environmental Protection Agency and the National Cancer
Institute, had
concluded that secondhand smoke causes cancer, but this is the first
time an
international group like the U.N. has reached the same conclusion.
The study also pointed to some disturbing trends, such as
the marked increase in the number of women smoking and the growing
incidence of
smoking in developing countries. |
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