Cannabis tests Although cannabis legislation is being liberalised around the world, many countries do not have evidence-based THC limits for drivers. This means that there are many different national provisions in place that sanction driving in public with THC or its metabolites in the blood. Here, we explore different approaches to THC limits and THC tests for drivers.
The amount of THC that has to be in your blood before you are defined as being under the influence of a drug is interpreted very differently, depending on what country you are in. In the US, many federal states that have legalised cannabis as a medicine or for recreational use have defined a threshold of five nanograms of active THC in the blood. In Canada, it is likely that a precise THC limit will be defined once the country legalises it, and the relevant plans are ready and waiting.
Some THC tests include THC-COOH, which is not psychoactive
But in Europe, the legislation is still full of discrepancies. While in most European states only active THC is measured, in some EU countries the non-psychoactive metabolite THC-COOH is also included when testing whether someone is fit to drive or not. In some countries, a saliva or urine test is obligatory before the blood test. In others, it is voluntary. In a third variant, many countries make do without the preliminary test and rely on the experienced eye of a police officer to decide when to ask for a blood test. In doing so, they are opening the door to stereotypical prejudices against cannabis users. In all countries it is, however, only the blood values that can be used in court. The penalties range from fines to driving bans, which are frequently handed down for many years or even for life.
The difference between THC limits in blood and blood serum is very important
In Germany, the number of cannabis users who have had their fitness to drive reviewed has been rising steadily since the mid-1990s. Anyone who has more than 1 nanogram (ng) of the active substance tetrahydrocannabinol, or THC, in their blood serum, is given a three-month suspension of their driving licence by the driving license authority.
The German THC limit is the most stringent in the world, compared to other countries that have a fixed value, and therefore a fixed upper limit for THC. Other countries such as Luxembourg or Belgium have defined the same upper limit, but in these countries the result is determined relative to the blood in its entirety. In Germany, the THC volume is calculated based on the blood serum, which therefore leads to a reading that is more than twice as high.
Germany has different penalties for drivers on cannabis and drivers on alcohol
As a result, the German licensing authorities consider the ability to drive to be impaired even when the already low threshold for the blood sample under internationally applicable standards is met, and the requirement for sobriety is met. The punishment for driving under the influence of either cannabis or alcohol, at €800 and one month’s suspension, is the same for first-time offenders. However, for the cannabis users, this is usually followed by another letter, months after the punishment, that uses an administrative legal rule to ask for their driving licence to be surrendered until they have proven that they are not addicted to cannabis. Objections are useless, and in any case only possible after handing over this valuable document.
THC limit for drivers much higher in Switzerland
Switzerland has also defined driving under the influence of cannabis very precisely, and sanctions it just as strictly as Germany. But at 3 ng in total blood, it applies a much higher THC limit . The Swiss threshold, which is comparable to the 0.0 level for taxi drivers, is 1.5 ng/ml THC in total blood. At first sight, the German THC limit of 1 ng/ml does not appear to be much lower. But if you take into account that the Swiss THC limit for drivers is measured in the total blood and not, as in Germany, in the blood serum, then this equates to a threshold of 3 ng/ml of serum. Therefore, the threshold value for professional drivers in Switzerland is at least 3 ng/ml measured German style against the serum.
Norway has a surprisingly clear set of rules on cannabis and driving
Although far from being a leader in terms of decriminalisation, Norway has a surprisingly evidence-based approach. As is planned in Canada, here there is already a three-tier system in place. More than 1.3 ng is treated like 0.2 permille blood alcohol levels. More than 3 ng is treated like 0.5 permille, and anything over 9 ng attracts the same drastic penalties as for drunk driving with over 1.2 permille.
The determination of the THC-COOH value, from which the level of consumption and therefore the frequency of consumption can supposedly be calculated, is equally disputed. “So far it has been assumed that demonstrating the presence of specific decomposition products from the active cannabis ingredient THC in the hair was certain proof of consumption. Researchers at the Institute of Legal Medicine at Freiburg University Hospital, led by toxicologist Prof. Volker Auwärter, have shown in experimental studies that this conclusion can lead to false conclusions,” says the journal Nature in its “Scientific Reports” October 2015. Only the active THC value is relevant for the question of driving under the influence.
The ‘Clear Head. Clear Rules’ cannabis and driving campaign
In order to change the system in the long-term, at least in Germany, the German Hemp Association (DHV) launched the “Clear Head. Clear Rules” campaign in June 2017. In Germany, the often long-term loss of their driving licence due to cannabis use is destroying people’s lives. The unequal treatment of drivers on cannabis and drivers on alcohol leads to severe consequences for cannabis users and for society. Taxpayers, without putting traffic at risk or even causing an accident, are turned into benefit recipients, because without their driving licence they lose their job or even their own company. This is not punishing any real threat to road safety, but the use of cannabis itself. Experts call this an ersatz criminal law, because these excessive measures came into being almost simultaneously with the decriminalisation of the possession of small amounts of cannabis for personal consumption, in the 1990s.
Prof. Volker Auwärter is a toxicologist from Freiburg who advises the German Federal government as a member of the Expert Committee on narcotics, including in relation to traffic legislation. Auwärter criticises the lack of any scientific basis for the current legislation. There is a threat of having a licence withdrawn for quantities that have virtually no effect. The risk of an accident at the legal limit for alcohol of 0.5 permille is twice as high as at 0.0 permille. At the current THC limit of 1 ng /ml of blood serum, the narcotic effect has long since dissipated.
Drivers on cannabis cause fewer accidents than drivers on alcohol
In addition, people driving under the influence of cannabis cause fewer accidents than those who have consumed alcohol. Unlike alcohol, cannabis does not remove inhibitions, meaning that the ability to make decisions remains in place. In 2014 Auwärter stated, at an expert conference in the city of Frankfurt on the topic of cannabis pilot projects, that people who have consumed cannabis tend not to drive afterwards. And if they do drive, then a driver under the influence of cannabis tends to drive much more defensively then someone who is drunk. Auwärter believes the current THC limit is too low, and told the “Süddeutsche Zeitung” newspaper that he was in favour of changing it to “2-5” ng.
A guide to THC limits for drivers in different countries:
Belgium: 1 ng
Denmark 1 ng
Germany: 1 ng in the blood serum, equivalent to 0.5 ng in total blood. THC-COOH value.
UK 2 ng
Estonia No specific threshold, any “negative effect”, blood test on suspicion
Finland: No specific threshold, any “negative effect”, blood test on suspicion
France: No specific threshold, any “negative effect”, blood test on suspicion
Ireland: 1 ng
Italy: No specific threshold, any “negative effect”, blood test on suspicion
Croatia: No specific threshold, any “negative effect”, blood test on suspicion
Latvia: No specific threshold, any “negative effect”, blood test on suspicion
Lithuania: No specific threshold, any “negative effect”, blood test on suspicion
Luxembourg: 1 ng
Malta: No specific threshold, any “negative effect”, blood test on suspicion
The Netherlands: 3 ng, if consumed together with other drugs or alcohol then 1 ng. Since 2017, there have been regular checks as part of a zero-tolerance policy for drugs and alcohol on the roads. Previously, testing was only on specific suspicion of illegal substances.
Norway: More than 1.3 ng is treated like 0.2 permille blood alcohol levels,more than 3 ng like 0.5 permille,
more than 9 ng is treated as a criminal offence, like 1.2 permille blood alcohol
Austria: No specific threshold, any “negative effect”, blood test on suspicion
Poland: No specific threshold, any “negative effect”, blood test on suspicion
Portugal: No specific threshold, any “negative effect”, blood test on suspicion
Romania: No specific threshold, any “negative effect”, blood test on suspicion
Sweden No specific threshold, any “negative effect”, blood test on suspicion
Slovenia: No specific threshold, any “negative effect”, blood test on suspicion
Slovakia: No specific threshold, any “negative effect”, blood test on suspicion
Czech Republic: 2 ng
Hungary: No specific threshold, any “negative effect”, blood test on suspicion
Cyprus: No specific threshold, any “negative effect”, blood test on suspicion
Canada is planning to introduce a three-tier system.
Less than 2 ng THC per millilitre (ml) of blood is not punished.
From 2 to 5 ng THC per millilitre (ml) of blood is treated as a minor offence, punishable by a fine of up to 1,000 Canadian dollars.
5 ng or more THC per ml in blood is treated as a criminal offence. It will be decided in individual cases whether a case is pursued or a fine is applied.
Combining THC and alcohol: More than 0.5 permille blood alcohol and more than 2.5 ng are defined as criminal and treated the same as driving with over 5 ng.
All blood levels must be measured within 2 hours of a driver being stopped.
In the US, driving under the influence is basically regarded as a criminal act. Here too, it is decided in individual cases whether a case is pursued or a fine is applied.
Montana 5 ng
Ohio 2 ng
Pennsylvania 1 ng
Washington State: 5 ng. Drivers with less than 5 ng can still be charged with driving “under the influence of cannabis” if the police can prove that the driver is impaired.
Colorado: 5 g
Nevada: 2 ng
Alaska: No specific threshold, any “negative effect”, blood test on suspicion
California: In California you are deemed to be under the influence if the police can prove through tests that:
– the person gives the impression of being intoxicated by cannabis
– there is an obvious impairment of physical and mental capacities due to consumption
– a person is unable under the circumstances to drive as carefully as someone who is sober
Oregon: The state prosecutor must prove that the driver is visibly or detectably impaired.
Massachusetts: No specific threshold, any “negative effect”, blood test on suspicion. You are deemed to be under the influence if cannabis affects your ability to drive a car safely.
Maine: 5.0 ng
Washington/District of Columbia: The state prosecutor must prove that the driver is visibly or detectably impaired.
In the following states, even the tiniest traces of THC in your blood is enough to represent a criminal act: