marc
Holofractale de l'hypervérité
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- 5/12/03
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From Scientific American magazine:
"The smoke from burning marijuana leaves contains several known
carcinogens and the tar it creates contains 50 percent more of some of
the chemicals linked to lung cancer than tobacco smoke. A marijuana
cigarette also deposits four times as much of that tar as an equivalent
tobacco one. Scientists were therefore surprised to learn that a study
of more than 2,000 people found no increase in the risk of developing
lung cancer for marijuana smokers.
"We expected that we would find that a history of heavy marijuana
use--more than 500 to 1,000 uses--would increase the risk of cancer from
several years to decades after exposure to marijuana," explains
physician Donald Tashkin of the Uinversity of California, Los Angeles
and lead researcher on the project. But looking at residents of Los
Angeles County, the scientists found that even those who smoked more
than 20,000 joints in their life did not have an increased risk of lung
cancer.
The researchers interviewed 611 lung cancer patients and 1,040 healthy
controls as well as 601 patients with cancer in the head or neck region
under the age of 60 to create the statistical analysis. They found that
80 percent of those with lung cancer and 70 percent of those with other
cancers had smoked tobacco while only roughly half of both groups had
smoked marijuana. The more tobacco a person smoked, the greater the risk
of developing cancer, as other studies have shown.
But after controlling for tobacco, alcohol and other drug use as well as
matching patients and controls by age, gender and neighborhood,
marijuana did not seem to have an effect, despite its unhealthy aspects.
"Marijuana is packed more loosely than tobacco, so there's less
filtration through the rod of the cigarette, so more particles will be
inhaled," Tashkin says. "And marijuana smokers typically smoke
differently than tobacco smokers; they hold their breath about four
times longer allowing more time for extra fine particles to deposit in
the lungs."
The study does not reveal how marijuana avoids causing cancer. Tashkin
speculates that perhaps the THC chemical in marijuana smoke prompts
aging cells to die before becoming cancerous. Tashkin and his colleagues
presented the findings yesterday at a meeting of the American Thoracic
Society in San Diego."
"The smoke from burning marijuana leaves contains several known
carcinogens and the tar it creates contains 50 percent more of some of
the chemicals linked to lung cancer than tobacco smoke. A marijuana
cigarette also deposits four times as much of that tar as an equivalent
tobacco one. Scientists were therefore surprised to learn that a study
of more than 2,000 people found no increase in the risk of developing
lung cancer for marijuana smokers.
"We expected that we would find that a history of heavy marijuana
use--more than 500 to 1,000 uses--would increase the risk of cancer from
several years to decades after exposure to marijuana," explains
physician Donald Tashkin of the Uinversity of California, Los Angeles
and lead researcher on the project. But looking at residents of Los
Angeles County, the scientists found that even those who smoked more
than 20,000 joints in their life did not have an increased risk of lung
cancer.
The researchers interviewed 611 lung cancer patients and 1,040 healthy
controls as well as 601 patients with cancer in the head or neck region
under the age of 60 to create the statistical analysis. They found that
80 percent of those with lung cancer and 70 percent of those with other
cancers had smoked tobacco while only roughly half of both groups had
smoked marijuana. The more tobacco a person smoked, the greater the risk
of developing cancer, as other studies have shown.
But after controlling for tobacco, alcohol and other drug use as well as
matching patients and controls by age, gender and neighborhood,
marijuana did not seem to have an effect, despite its unhealthy aspects.
"Marijuana is packed more loosely than tobacco, so there's less
filtration through the rod of the cigarette, so more particles will be
inhaled," Tashkin says. "And marijuana smokers typically smoke
differently than tobacco smokers; they hold their breath about four
times longer allowing more time for extra fine particles to deposit in
the lungs."
The study does not reveal how marijuana avoids causing cancer. Tashkin
speculates that perhaps the THC chemical in marijuana smoke prompts
aging cells to die before becoming cancerous. Tashkin and his colleagues
presented the findings yesterday at a meeting of the American Thoracic
Society in San Diego."
