While secondhand exposure to cigarette smoking is linked with numerous health maladies, cannabis smoke is currently under a halo of no harm. Yet second-hand marijuana can cause an effect that cigarettes cannot - problems with memory and coordination, and in some cases testing positive for the drug in a urinalysis. At least in a very small study.
Cannabis is the most widely used illicit drug in the world. The authors say the new research is the most comprehensive study of secondhand cannabis smoke and its effects since the 1980s, when researchers found the drug's active ingredient, tetrahydrocannabinol, or THC, and other cannabis byproducts could turn up in nonsmokers' bodies after an hour or more spent in extreme conditions with heavy smokers in an enclosed space.