I made no such claim.
Cannabis smoke has up to twice the concentration of
cancer-causing polyaromatic hydrocarbons as tobacco
smoke. In addition, people tend to inhale higher
concentrations of cancer-causing components when
smoking cannabis because they tend to smoke the
cigarettes without filters and to a smaller butt size than
tobacco cigarettes
Cannabis smokers also inhale more
deeply and hold their breath for longer, so carcinogenic
products deposit in the lower respiratory tract. Taken
together, this evidence forms a legitimate rationale that
smoking cannabis may have greater potential to cause
lung cancer than smoking tobacco.
A rigorous case-control study by Aldington and
colleagues in 2008 made significant progress in
showing that the link exists. The authors analysed the
smoking habits of people diagnosed with lung cancer
and a control group without lung cancer. Their major
finding was that smoking cannabis increases the risk of
developing lung cancer in young adults. The study also
suggests that smoking one cannabis cigarette a day for
one year increases the risk of lung cancer by 8 per cent.
Importantly, researchers took variables including tobacco
smoking into account when calculating this figure.
By way of comparison, the same study suggests that
smoking one pack of tobacco cigarettes (20 cigarettes)
a day for one year increased the risk of lung cancer by 7
per cent. This suggests that smoking just one cannabis
cigarette increases the risk of developing lung cancer
by a similar amount as smoking 20 tobacco cigarettes.
The study also concluded that 5 per cent of lung cancers
in those aged 55 or under may be caused by smoking
cannabis.
A study by Berthiller and colleagues looking at cannabis
smoking in North African men showed a 2.4-fold increase
in the risk of lung cancer among men who had smoked
cannabis compared with those who had never smoked
it. This was after adjustment for age, tobacco smoking,
occupational exposures and country.
I dont want to get into a debate here but that report was critiqued by medical experts due to several methodological flaws.
The report displays its partisan nature when it says Aldington made
"significant progress in showing that the link exists".
A critique of Aldington's report in the European Respiratory Journal
from several eminent doctors said:
We read with interest the article by ALDINGTON et al. [1] entitled
‘‘Cannabis use and risk of lung cancer: a case–control study’’.
However, we are concerned that the conclusion stating that
‘‘long-term cannabis use increases the risk of lung cancer in
young adults’’ is inadequately supported by the data, given the
study’s several methodological flaws..... Finally, an observational
study such as ALDINGTON et al. cannot establish causality, only
correlation. Even presupposing that the study was methodologically
impeccable, the strongest conclusion that could be drawn would be that
‘‘long-term cannabis use is associated with an increased risk of lung
cancer’’, not that cannabis use causes lung cancer.
Given the acrimonious debate over the role of cannabis in
society, and the substantial chance that this paper will
contribute to public policy decisions, we feel it is important
to keep conclusions that are stated in abstracts and papers as
close to the actual scientific findings as possible.