Per se laws criminalize blood content rather than impaired driving. This is systemic chemical bigotry and these laws are ineffective at detecting or deterring impairment.
A new study examines the plasma and blood levels of both occasional and frequent cannabis users, before and after smoking cannabis: “Frequent and occasional smokers resided on a closed research unit and smoked one 6.8% THC cannabis cigarette ad libitum. Blood and plasma cannabinoids were quantified on admission (approximately 19 h before), 1 h before, and up to 15 times (0.5–30 h) after smoking.”
“Cannabinoid blood and plasma concentrations were significantly higher in frequent smokers compared with occasional smokers at most time points for THC and 11-OH-THC and at all time points for THCCOOH and THCCOO-glucuronide.” Both the participants’ baseline concentration levels & how much THC was in their blood when the study began did not change the outcome. The study found that the median time blood THC levels over 5 ng/ml were detectable was 3.5 hours in frequent smokers (ranging from 1.1 – 30 hours), and 1 hour in most occasional smokers (ranging from 0 – 2.1 hours). Particularly interesting is that 2 occasional smokers did not test over 5 ng/ml at all.
These results highlight how occasional cannabis users could pass a blood test even if impaired while a frequent cannabis user would fail even when not impaired at all. There is a dramatic difference in the amount of time THC remains in the blood of users that is not based on the amount of cannabis consumed, but rather on the frequency of cannabis use. Because THC remains in frequent users blood much longer than in those who consume cannabis occasionally, frequent cannabis users are significantly more likely to be charged with impaired driving despite their lower chance of impairment due to higher tolerance and experience. A first time user with no experience or tolerance would very likely pass a roadside blood test while being the most likely users to feel impaired.
The study concludes; “Cannabis smoking history plays a major role in cannabinoid detection. These differences may impact clinical and impaired driving drug detection.”
Testing drivers blood for ng/ml of THC is stupid policy which does not determine if a driver is impaired. On top of the policy being ineffective at determining impairment, decades of studies show that cannabis does not typically impair driving to begin with.
Cannabis users are safe drivers
In 1983 a study by the US National Highway Transportation Safety Administration (NHTSA) tested drivers on simulators, and concluded that the only statistically significant effect associated with marijuana use was slower driving. A NHTSA study in 1992 found that marijuana is rarely involved in driving accidents, except when combined with alcohol, concluding, “the THC-only drivers had an [accident] responsibility rate below that of the drug free drivers. While the difference was not statistically significant, there was no indication that cannabis by itself was a cause of fatal crashes.” A separate NHTSA study from1993 tested Dutch drivers high on THC on real Dutch roads, concluding, “THC’s adverse effects on driving performance appear relatively small.” In 1998 a study by the University of Adelaide and Transport South Australia analyzed blood samples from 2,500 accidents, and found that drivers with cannabis in their system were less likely to cause accidents than those without. A University of Toronto study from 1999 found that cannabis users typically refrained from passing cars and drove at a more consistent speed than sober drivers.
More recently, studies have found that fatal car accidents are reduced by 9% when medicinal marijuana is legalized. The rate of fatal crashes where a driver has consumed alcohol drops by 12% and crashes involving high levels of alcohol fall by 14%.
Sources for this article:
1. Phase I and II Cannabinoid Disposition in Blood and Plasma of Occasional and Frequent Smokers Following Controlled Smoked Cannabis. http://www.ncbi.nlm.nih.gov/pubmed/24563491?report=abstract
2. Stoned Drivers Are Safe Drivers http://www.cannabisculture.com/articles/1775.html
3. Why Medical Marijuana Laws Reduce Traffic Deaths http://healthland.time.com/2011/12/02/why-medical-marijuana-laws-reduce-traffic-deaths/
Written by Alternative Free Press
Study shows THC blood tests can’t test impairment by AlternativeFreePress.com is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.