Change in cigarettes more dangerous to lungs?
WASHINGTON - It may be
riskier on the lungs to smoke cigarettes today than it was a few
decades ago — at least in the U.S., says new research that blames
changes in cigarette design for fueling a certain type of lung
cancer.
Up to half of the
nation's lung cancer cases may be due to those changes, Dr. David
Burns of the University of California, San Diego, told a recent
meeting of tobacco researchers.
It's not the first time
that scientists have concluded the 1960s movement for lower-tar
cigarettes brought some unexpected consequences. But this study,
while preliminary, is among the most in-depth looks. And
intriguingly it found the increase in a kind of lung tumor called
adenocarcinoma was higher in the U.S. than in Australia even though
both countries switched to so-called milder cigarettes at the same
time.
That's circumstantial
evidence that requires more research, he acknowledged.
But anti-smoking
advocates are citing the study as Congress considers whether the
Food and Drug Administration should regulate tobacco, legislation
that would give the agency power to decide such things as whether
to set caps on certain chemicals in tobacco smoke.
Smokers once tended to
get lung cancer in larger air tubes, particularly a type named
"squamous cell carcinoma." Then doctors noticed a jump in
adenocarcinoma, which grows in small air sacs far deeper in the
lung. Initial studies blamed introduction of filtered, lower-tar
cigarettes. When smokers switched, they began inhaling more deeply
to get their nicotine jolt, pushing cancer-causing smoke deeper
than before.
Burns' study, presented
at a meeting of the Society for Research on Nicotine and Tobacco,
took a closer look. He compared smoking behaviors of different age
groups over four decades — how much they smoked, when they started,
when they quit — and how cancer-risk changed.
The risk of squamous cell
carcinoma stayed about the same over those years, Burns found. But
adenocarcinoma rose. It makes up 65 percent to 70 percent of newly
occurring U.S. lung cancer cases, but no more than 40 percent of
Australia's lung cancer, he said.
While the nation's total
lung cancer cases have inched down as the number of smokers has
dropped in recent years, the study suggests an individual smoker's
risk of getting cancer is higher.
It's well known that
cigarettes differ from country to country, because of different
tobacco crops grown locally and smokers' varying tastes.
Nitrosamines are a byproduct of tobacco processing and levels vary
for several reasons, including differences in curing
practices.
Australian cigarettes
contain about 20 percent of the nitrosamine content of U.S.
cigarettes, making the chemical a prime suspect, concluded Burns,
who has been scientific editor of several surgeon general reports
on tobacco.
That doesn't rule out a
role for deeper inhaling, cautioned Dr. Michael Thun of the
American Cancer Society: "There's several strong suspects in the
lineup. They may have acted in combination."
Philip Morris USA
spokesman David Sutton called the study speculative and hard to
evaluate until it's published in a medical journal, something Burns
plans to do.
Still, Philip Morris,
which supports FDA tobacco regulation, began taking steps with its
growers in 2000 that have yielded "significantly lower" nitrosamine
levels in recent years' supplies, Sutton said.
Be careful in assuming
lower-nitrosamine cigarettes are less lethal, said Dr. Neal
Benowitz of the University of California, San Francisco, a
well-known tobacco expert. Lung cancer is only one of tobacco's
many risks — it causes heart disease and other killer diseases,
too.
"If you reduce someone's
(lung cancer) risk by 10 percent, that's not really meaningful for
an individual," he said. "The goal still is to get them to
stop."