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Study Debunks “Zero Tolerance” of THC

Since the first announcement that marijuana was going to be legalized across the country, everybody has been weighing in on what role a THC limit should play in criminal courts or workplace safety requirements.


Many workplace safety requirements have a zero tolerance for TCH, citing a need to ensure people are not impaired at the work place. Further, many Provinces have imposed regulations that allow for zero tolerance of THC while operating a motor vehicle. Despite this, under the Criminal Code and its regulations, the prescribed maximum THC concentration allowed for operating a motor vehicle is 5 ng/mL of blood (see other allowable blood alcohol concentrations here).


However, a newly published study shows little to no connection between THC levels and on-going signs of impairment. Briefly, the study conducted by Toronto’s Center for Addiction and Mental Health had people smoke cannabis to a level of their choosing in a ten-minute period.


Shortly after, the people were put into a driving simulator, on a nine-kilometer track with a speed limit of 80 km/h. Immediately after consuming the cannabis, the results were as expected: subjects drove at a slower than necessary pace and had a difficult time maintaining their lane in the simulator.


However, 24 hours and 48 hours later (when the TCH was still detectable in their bodies), the subjects showed little to no signs of impairment associated with the THC.


This study could call into the question the arbitrary assignment of blood THC levels and force the powers that be to substantiate their claim that zero tolerance (or 5 ng/mL of blood tolerance), is based on any scientific date – and if not, if the rules are reasonable.


To read more news coverage on this study, click here.

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