Second hand marijuana smoke can affect non-smokers, study says

Girl Smoking

MARYLAND, United States, Friday May 22, 2015 – One of the many marijuana-related issues that has sparked hot debate is the question of “contact highs” — or how smoky an area has to be before non-smokers get high simply from being there — and whether this can lead to false-positive drug tests.

In pursuit of an answer with genuine scientific weight behind it, a team led by Dr Evan S Herrmann of the Johns Hopkins University School of Medicine ran what they say is “the first study . . . to examine the influence of room ventilation on second-hand exposure to cannabis smoke, and the first study to examine the effects of second-hand cannabis smoke exposure on behavioural/cognitive performance”.

The experiment tested secondhand exposure under “extreme conditions” in an unventilated room filled with marijuana smoke.

After spending an hour in such conditions, nonsmokers showed “positive drug effects in the first few hours, a mild sense of intoxication, and mild impairment on measures of cognitive performance,” said study author Ryan Vandrev, associate professor of psychiatry and behavioral science at John Hopkins.

For the experiment, full details of which were published in The Journal of Drug and Alcohol Dependence, the scientists recruited six regular marijuana smokers and six non-smokers and constructed a special Plexiglas compartment designed to be about the size of a small room.

The key part of the experiment began after blood tests were administered both to confirm that the non-smokers hadn’t smoked recently and the marijuana smokers had remained abstinent overnight.

The smokers and non-smokers then entered the Plexiglas “room” and sat around a table in alternating seats. All wore protective clothing during the exposure session and were provided with swimming goggles to prevent eye irritation from accumulated smoke.

The six smokers were each provided with 10 spliffs, obtained from the National Institute on Drug Abuse (NIDA) Drug Supply Program, and a CReSS Pocket smoking topography device. Each spliff contained approximately 1 gram of high potency (11.3 percent THC) cannabis.

The door to the chamber was sealed at the start of the 60-minute exposure session, and active smokers were instructed to smoke through the CReSS device, which measured the number of puffs taken, puff volume, and other parameters of smoking behaviour.

Participants were asked to remain seated, but were allowed to engage in such leisure activities as talking, reading, using personal electronic devices, and the like.

Researchers monitored the exposure session from outside the chamber to ensure non-smokers did not actively inhale from the marijuana cigarettes and that smokers only consumed cigarettes from their own supply.

To determine how ventilation affected the non-smokers, the scientists ran sessions with vents open and closed.

After an hour in the room, participants had their physiological readings taken, were given tests designed to determine how the marijuana affected their ability to complete certain tasks, and were asked how they were feeling.

The findings revealed that exposure to second-hand cannabis smoke in an unventilated chamber the size of a small room produced minor increases in heart rate, mild to moderate subjective drug effects, and minor, but detectable, levels of performance impairment on some behavioural/cognitive assessments.

The [THC] concentration in one specimen was sufficient to trigger a positive urine drug screen at a cut-off of >50 [nanograms per millilitre], the cut-off recommended for use by the mandatory guidelines for federal workplace drug testing programmes.

Multiple positive urine results were observed for four participants using a more stringent cut-off of >20 ng/ml, which is used by some commercial/private workplace drug testing programs, within a day of exposure.

The scientists nevertheless found that ventilating the chamber “reduced levels of exposure among non-smokers, evidenced by much lower (in some cases undetectable) levels of cannabinoids in blood and urine and the absence of subjective and behavioural/cognitive effects”.

Herrmann, noted that testing conditions constituted “a worst-case scenario”.

Those conditions, replicated in “the real world . . . couldn’t happen to someone without him or her being aware of it,” said the postdoctoral fellow in psychiatry and behavioral sciences at John Hopkins.

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