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Smoking a joint is equivalent to 20 cigarettes in terms of lung cancer risk, New Zealand scientists have found. They warned of an "epidemic" of lung cancers linked to cannabis.
Other studies show that cannabis can cause cancer, but few established a strong link between cannabis use and the incidence of lung cancer.
In an article published in the European Respiratory Journal, the scientists said cannabis could be expected to harm the airways more than tobacco as its smoke contained twice the level of carcinogens, such as polyaromatic hydrocarbons, compared with tobacco cigarettes.
The method of smoking also increases the risk. Joints are typically smoked without a proper filter and almost to the very tip, which increases the smoke inhaled.
The cannabis smoker inhales more deeply and for longer, facilitating the deposition of carcinogens in the airways. The researchers interviewed 79 lung cancer patients to identify the main risk factors for the disease, such as smoking, family history and occupation.
In this high-exposure group, lung cancer risk rose by 5.7 times for patients who smoked more than a joint a day for 10 years, or two joints a day for five years.
"Cannabis use could already be responsible for one-in-20 lung cancers diagnosed in New Zealand. In the near future we may see an 'epidemic' of lung cancers connected with this new carcinogen," wrote team leader Richard Beasley, of the Medical Research Institute of New Zealand
"And the future risk probably applies to many other countries, where increasing use of cannabis among young adults and adolescents is becoming a major public health problem."
- REUTERS
