I will address one of the claims made by the previous author. He claims that..
"This fallacious conclusion is derived from a study by Dr. Donald Tashkin in which the UCLA researcher examined airflow resistance in the lungs of tobacco smokers compared to that in the lungs of marijuana smokers. Dr. Tashkin did find that daily pot smokers experience a “mild but significant” increase in airflow resistance in the large airways, greater than that seen in persons smoking 16 cigarettes per day."
This is not true. There have been many studies that arive at the same conclusion . Here is the latest one that i am aware of.
ScienceDaily (June 15, 2009) — Using a highly sensitive new test, scientists in Europe are reporting "convincing evidence" that marijuana smoke damages the genetic material DNA in ways that could increase the risk of cancer.
The researchers add that the ability of cannabis smoke to damage DNA has significant human health implications especially as users tend to inhale more deeply than cigarette smokers, which increases respiratory burden. "The smoking of 3-4 cannabis cigarettes a day is associated with the same degree of damage to bronchial mucus membranes as 20 or more tobacco cigarettes a day," the team adds.
"In conclusion, these results provide evidence for the DNA damaging potential of cannabis [marijuana] smoke, implying that the consumption of cannabis cigarettes may be detrimental to human health with the possibility to initiate cancer development," the article states. "The data obtained from this study suggesting the DNA damaging potential of cannabis smoke highlight the need for stringent regulation of the consumption of cannabis cigarettes, thus limiting the development of adverse health effects such as cancer."
Singh et al. Evaluation of the DNA Damaging Potential of Cannabis Cigarette Smoke by the Determination of Acetaldehyde Derived N 2 -Ethyl-2′-deoxyguanosine Adducts. Chemical Research in Toxicology, 2009; 22 (6): 1181 DOI: 10.1021/tx900106y