LETTERS TO THE EDITOR
To the Editor:
We believe that our article clearly asserts that best practice does not allow safety-sensitive employees to be under the influence of marijuana on the job; this could also be applied to all workers regardless of the safety sensitivity of their jobs as an employer's overarching policy. The Task Force was concerned that there are likely a number of people in the workplace who are impaired from prescribed substances and other causes who are currently not being identified. Thus, the article emphasizes the identification of impairment and the need for medical evaluation of such workers.
There are some data suggesting a small subset of chronic marijuana users may have less impairment than naive users at the same THC serum levels, due to tolerance. Previously published predictive models for estimating time since last use of marijuana (for estimating time of expected impairment after smoking), which were developed on testing of non-chronic users, are less accurate in daily cannabis users.1 It has been suggested that some of these individuals may not constitute a hazard for non–safety-sensitive work, and therefore individual evaluation for signs of impairment along with serum testing may be necessary.2 Naturally, employers involved in federal work or those who are legally allowed to forbid all marijuana use by their employees would not need to consider individual evaluation.
1. Karschner EL, Schwope DM, Schwilke EW, et al. Predictive model accuracy in estimating last Δ9-tetrahydrocannabinol (THC) intake from plasma and whole blood cannabinoid concentrations in chronic, daily cannabis smokers administered subchronic oral THC. Drug Alcohol Depend
2. Huestis MA. Cannabis-impaired driving: a public health and safety concern. Clin Chem
. 2015. pii: clinchem.2015.245001. [Epub ahead of print].