Researchers in the UK have found evidence that smoking cannabis can damage human DNA in ways that could potentially increase the risk of developing cancer. The findings, published in the journal Chemical Research in Toxicology, are an outcome of the ECNIS ('Environmental cancer risk, nutrition and individual susceptibility') Network of Excellence, which was funded with EUR 11 million under the 'Food Quality and Safety' Thematic area of the Sixth Framework Programme (FP6) to study how diet and hereditary factors can influence environmental cancer risk. The study used a new technique of highly sensitive liquid chromatography-tandem mass spectrometry to look at the formation of a cancer-causing compound in calf thymus DNA that had been exposed to cannabis cigarette smoke in vitro. Their findings indicated that cannabis does damage DNA under laboratory conditions. The positive and negative effects of using cannabis have been hotly debated for decades. Smoked for relaxation by people all over the world and used in both Chinese and Indian traditional medicine, the use of cannabis dates back centuries and is has been a part of many ancient cultures. 'Parts of the plant Cannabis sativa, also known as marijuana, ganja, and by various street names, are commonly smoked as a recreational drug, although its use for such purposes is illegal in many countries,' explained Dr Rajinder Singh of the University of Leicester, who led the study. 'There have been many studies on the toxicity of tobacco smoke,' he added. 'It is known that tobacco smoke contains 4,000 chemicals of which 60 are classed as carcinogens. Cannabis, in contrast, has not been so well studied. It is less combustible than tobacco and is often mixed with tobacco in use. Cannabis smoke contains 400 compounds, including 60 cannabinoids. However, because of its lower combustibility it contains 50% more carcinogenic polycyclic aromatic hydrocarbons including naphthalene, benzanthracene, and benzopyrene, than tobacco smoke.' It is known that toxic substances in tobacco can lead to lung and other cancers and damage DNA, but the link with cannabis smoking was not clarified. The study focused on the toxic substance acetaldehyde, which is found in both tobacco and cannabis. The ability of cannabis smoke to damage DNA has serious implications for human health. Another concern is that cannabis smokers tend to inhale the smoke more deeply than tobacco smokers, which increases toxic overload in the respiratory system. 'The smoking of three to four 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 researchers said. 'These results provide evidence for the DNA damaging potential of cannabis smoke, implying that the consumption of cannabis cigarettes may be detrimental to human health with the possibility to initiate cancer development,' the study reads. 'The data obtained from this study suggesting the DNA damaging potential of cannabis smoke highlight the need for the stringent regulation of the consumption of cannabis cigarettes, thus limiting the development of adverse health consequences such as cancer,' the authors conclude. The study was also an outcome of the NewGeneris ('Development and application of biomarkers of dietary exposure to genotoxic and immunotoxic chemicals and of biomarkers of early effects, using mother-child birth cohorts and biobanks') project, funded with EUR 13.6 million under FP6 to study the effects of maternal exposure to dietary compounds with carcinogenic and immunotoxic properties during pregnancy on cancer and other disease risks in the child.