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Lung Disease & Respiratory Health Center

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Pot as Tough on Lungs as Tobacco

Today's Cannabis Stronger, With More Carcinogens, Than in the 1960s
WebMD Health News


Nov. 12, 2002 -- Strong words of warning for those who smoke pot: British researchers have found that smoking pure cannabis harms your lungs as much as tobacco does.

Smoking three cannabis joints a day causes the same damage to the lining of the airways as 20 cigarettes. In fact, the tar from a joint contains 50% more cancer-causing substances than tobacco, says the report, published by the British Lung Foundation.

"These statistics will come as a surprise to many people, especially those who choose to smoke cannabis rather than tobacco in the belief that it is 'safer' for them," says Mark Britton, MD, chairman of the British Lung Foundation.

The report surveys all current medical and scientific research into the direct effects of smoking marijuana -- both alone and with tobacco -- on the smoker's respiratory health.

Among the findings:

  • The cannabis smoked today is much more potent than that smoked in the 1960s -- more than 15 times as potent.
  • People who smoke cannabis have significantly more respiratory symptoms such as chronic cough and mucus production, wheezing, and acute bronchitis.
  • Smoking three or four cannabis cigarettes a day causes the same degree of damage to the lining of the airways as 20 or more tobacco cigarettes a day.
  • Cannabis tends to be smoked in a way that increases the puff volume by two-thirds and the depth of inhalation by one-third. There is an average fourfold longer breath-holding time with cannabis than with tobacco. This means that there is a greater respiratory burden of carbon monoxide and smoke particulates such as tar than when smoking a similar quantity of tobacco.
  • As with tobacco smoking, the research also shows a possible link between cannabis smoking and emphysema.

A survey earlier this year showed that 79% of children believe that cannabis was 'safe,' according to the British Lung Foundation's news release. Only 2% understood correctly that there are health risks associated with smoking pot.

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