"SAN FRANCISCO -- It might take Californians a puff or two to get their heads around an apparent contradiction recently enshrined in state law. The same marijuana smoke that doctors can recommend to ease cancer patients' suffering must soon come with a warning saying it causes the disease.
Medical marijuana advocates sought to downplay the significance of the state's decision, arguing researchers have long known that the smoke contains cancer-causing compounds.
"This does not mean in any way that those carcinogens that appear in smoked marijuana, smoked cannabis, have any kind of causal relationship to cancer," said Kris Hermes, spokesperson for Americans for Safe Access, a pro-medical marijuana group.
Regulators disagree. Scientists with the state's Office of Environmental Health Hazard Assessment reviewed 27 studies of the links between marijuana and cancer in humans. Though not all the studies showed a link, regulators found that "marijuana smoke was clearly shown, through scientifically valid testing according to generally accepted principles, to cause cancer," according to an agency statement."