Re: The failed war on weed
posted at 6/19/2013 10:47 AM EDT
In response to GreginMeffa's comment:
In response to WhatDoYouWantNow's comment:
In response to GreginMeffa's comment:
What is the legal Blood THC Content (BTC) to drive?
Really? How do they test? What does that equal in doobers?
I believe CO is considering 5 nanograms.
Well right now I think - think - that the only way they can test is to first say you failed an ordinary roadside sobriety test and then get a warrant for a blood draw at a hospital.
I know that companies have been working on developing breathalyzers for drugs, including pot, but I don't know whether they have actually entered production or how accurate they would be.
I don't know how much 5 nanograms/ml is, but it sounds like if someone is a regular user, they might be nabbed even if entirely sober.
They have to aim for an amount that would be high enough that they aren't netting people who regularly smoke and therefore have a detectable amount in their blood (for up to months after they stop).
I poked around a bit. No idea on the veracity of these sources, but....
The most meaningful recent study measuring driver "culpability" (i.e., who is at fault) in 3,400 crashes over a 10-year period indicated that drivers with THC concentrations of less than five ng/mL in their blood have a crash risk no higher than that of drug-free users.2 The crash risk begins to rise above the risk for sober drivers when a marijuana user's THC concentrations in whole blood3 reach five to 10 ng/mL.
How long does it take for the psychoactive effects of marijuana to wear off?
Because smoked THC is rapidly transferred into the blood stream, THC levels in the blood rise quickly immediately after inhalation. Depending on the dose, THC typically reaches peak concentrations of more than 100 ng/mL five to 10 minutes after inhalation and then rapidly decreases to between one and four ng/mL within three to four hours.
However, heavy marijuana users’ blood can contain detectable amounts of THC even after periods of abstention. In one controlled study, six of 25 participants tested positive for active levels of THC after a full seven days of abstention, with the highest concentration detected being three ng/ml of whole blood.4 In addition, the blood serum of heavy to moderate users may contain more than two ng/mL of THC at 24 or even 48 hours after smoking a single joint, a level that studies have shown does not produce impairment.5
This is a particular concern for medical marijuana patients who are using marijuana in compliance with state laws and their doctors' advice, but who would likely test positive for marijuana while sober. While the Colorado Legislature debated a per se THC limit of five ng/ml, Denver News’ medical marijuana reviewer (and medical marijuana patient), William Breathes, subjected himself to blood draws to test his THC levels. After a 15-hour period of abstinence, Mr. Breathes’ THC levels were still 13.5 ng/ml. According to his physician, Mr. Breathes was in “no way incapacitated” at the time.6 This first-person account demonstrates the very real possibility that medical marijuana patients and other heavy marijuana users could face criminal charges under a per se system even if they are not actually impaired.
The graphic below shows the mean plasma levels of THC and its metabolites (11-OH-THC and THCCOOH) for six subjects smoking a marijuana cigarette containing 34 mg of THC, following several days of abstinence (which would reflect an occasional user's pattern of usage).7
Additionally, several studies show that exposure to secondhand marijuana smoke (which could result from being in the same room with a person who is using marijuana) may cause a non-user to show THC concentrations in blood serum of several nanograms per milliliter.8
This blog contests the notion that sober drivers would be nabbed:
And an article:
The real problem is that there is significantly less variation in metabolization of alcohol between people, which we're used to testing for, than pot.
Of course, there is a whole different issue which should affect this debate (but probably won't): Recently a large study was done.
Inexperienced users of pot showed marked impairment in tests that measured people's reactions to discrete portions of the driving experience, and showed marked impairment in a driving simulator.
Experienced users of pot showed some but less marked impairment in tests that measured people's reactions to discrete portions of the driving experience, and showed virtually no impariment in a driving simulator.
Alcohol users across the board showed impairment in both, and marked aggressiveness in driving.
So, on the one hand, a low cutoff might be likely to nab regular smokers who didn't actually smoke for several hours before driving; but on the other, they will be less likely to be pulled over because they probably aren't going to be impaired even if they did smoke before driving.