Detection and reliability of cannabis-related driving tests are challenged by science
Attempts to detect and track down people driving under the influence of illicit drugs began in the 1980s in the United States. The European Union took an interest in this issue in the 90s. The main obstacle facing governments is twofold. On the one hand is the lack of reliable methods to detect and measure the presence of drugs in the body. On the other hand, the lack of conclusive scientific information on how cannabis affects driving. In addition, Quebec promises zero tolerance. But the experts warn that it would be simply impossible ... And whether it is a saliva test, a urine test and blood ...
Zero tolerance questioned
according to THE DUTY, zero tolerance for cannabis while driving will not be possible in Canada and Quebec. From a scientific point of view cannabis and THC remains particularly long in the blood and the body, and without remaining active ... Once legalized, cannabis will be present in all consumers and patients ... whether they are intoxicated or not ... Indeed, scientifically, detection tests by saliva do not are unreliable ...
"Saliva is not a good indicator," says Ryan Vandrey of Johns Hopkins University School of Medicine. "At present, there is no biological marker that can accurately predict the level of intoxication at the roadside"
On the other hand there is a lack of scientific information findings on how cannabis affects driving. A complete ban on driving after cannabis use is unrealistic. Additionally, Ottawa has yet to announce which screening devices will be recommended to police across the country. As for occasional users, they will also be difficult to catch ...
"You could have someone who smokes every night at his house before going to bed, and the next day he will be positive for a test all day long. Even though he did not smoke, says Ryan Vandrey at Le Devoir. He will no longer be intoxicated, but he will have a cannabinoid level higher than zero. "
On the other hand, an occasional consumer who had just eaten a cannabis brownie would have a lower THC level than a regular fasting consumer, even if he is very intoxicated, Vandrey said in his research. .
"Distinguishing a new use from a residual use is incredibly difficult, regardless of the verification method," notes the expert.
Zero tolerance for cannabis and driving, in Quebec and Ontario
Quebec is not alone in wanting to impose a zero tolerance. Ontario and New Brunswick have plans to do the same, but only for drivers under the age of 21 and those with novice driver licenses. The Ontario government also wants to impose zero tolerance on commercial drivers.
Could a government set a maximum legal THC level that would be considered zero to account for frequent smokers? No, Ryan Vandrey slice. Because science does not allow anyway to determine the level of cannabis intoxication by simply analyzing the saliva, blood or urine of an individual ...
Science is lacking
The observation: THC is detectable in saliva for a shorter time than is felt by psychotropic effectswhether the drug is smoked or consumed in an edible manner. The gap is greater when the cannabis is swallowed. THC is detectable in saliva on average two hours after consumption. But already, at the second hour, the rates fall quickly.
However, the effects can last from four to five hours when smoked, and up to six to eight hours when consumed in edible form… Edible cannabis reaches its peak effect approximately three hours after consumption, ie after the period of detection of THC in saliva.
"This does not correspond to the level of intoxication," argues Ryan Vandrey, who was invited to testify before the parliamentary committee that studied the bill on the legalization of marijuana in Ottawa. "Unless you stop people right after they have eaten, you will still be able to detect it and they may still be addicted," he warns.
"It's good to watch saliva. It's convenient, it's easy. The problem is that it is not reliable, "observes Pierre Beaulieu, professor of pharmacology at the University of Montreal and anesthesiologist at the CHUM.
Cannabis driving, a challenge for police
THC appears longer in the blood: three to four hours when cannabis is smoked, six to eight hours in edible form. But the delays for this further test are important: the time a police officer intercepts a driver, makes him undergo a first coordination test, he analyzes the saliva of the driver and then goes to the police station to take a blood test and analyze it in turn.
The Sûreté du Québec explains, and it is the same thing with the Service de police de la Ville de Montréal, that it checks urine more often than blood, which is more complicated to collect ... But the THC and the active ingredients cannabis remains there for several days or even up to two weeks. Again, the THC level of a frequent user would be a problem ...
The federal draft law on impaired driving sets 5 nanograms per milliliter of blood (ng / ml) the amount of THC a driver can have in their body to get behind the wheel. A frequent user will have, without having consumed for 24 hours, 5 ng / ml in the blood ...
There have also been a few cases of second-hand smoke causing THC levels in saliva. They are not, however, conclusive, agrees Ryan Vandrey. Because half of the subjects exposed to second-hand smoke for an hour in a room without ventilation had a positive THC result afterwards… In short, science shows that controlling cannabis on the road will be “complex and uncertain”.
"It is not tomorrow that the police will be ready to do this screening. Or he will be questionable and very questionable. "
Unreliable driving tests in Europe and Spain
Over the past twenty years, the European Union has carried out various studies to determine whether the methods available to detect drugs are reliable or not. The first was the ROSITA project. An inconclusive study that took place in the late 1990s and early 2000s… This study was followed by the ROSITA II project, carried out between 2005 and 2006. The two studies, coordinated by the Spanish professor Manuel López- Revadulla, revealed that the methods available at that time were not sufficiently reliable. Despite this, they began to be used in some parts of Spain.
The third European study was DRUID, which started in 2006 and ended in 2010. Spanish institutions say this report “recognizes the reliability of early detection devices”. However, as reported 2015 when cannabis associations appeared before the drug commission of the Spanish parliament, the conclusions of DRUID specify that:
“None of the tests achieved the required levels of efficiency in sensitivity, specificity and precision for all. separate tests included. “
Conflict of interest
The person in charge of the evaluation of the tests, Manuel López-Rivadulla, says that “a positive result means that the person consumed between three and nine hours before testing the sample, which is very generous”. But there are regular cannabis users for whom, instead of “nine hours, it can take up to twelve hours.” That is four times as long as the effect persists… Looking at the estimates of manufacturer, it turns out that the detection period would be between a few minutes and 24 hours. However, that doesn't seem to be true at all… Because when the Energy Control association - one of the leading harm reduction organizations in Spain - wrote to Dräger asking how long it took to go without cannabis to be negative , they replied that they did not know...
This interest in minimizing the imprecision of Drugtest 5000 is perfectly understandable from the point of view of the manufacturer; at the end of the day, they want to sell the product. But what is the point of so-called independent evaluators? Probably economical… Since the Department of Forensic Toxicology of the University of Santiago, headed by López-Rivadulla, was awarded the contract - by almost 1,5 million euros per year. And this to carry out additional blood laboratory tests. Of course, if they had told the European Union that the test was not precise enough, they would have found themselves without a contract… This obvious conflict of interest should make us doubt the objectivity of their demands. And for us France, the same music; the new generation salivary test seems formidable in efficiency, while they are scientifically imprecise and therefore obsolete ...