Can a donor test positive through passive inhalation because he was in the same room with someone smoking marijuana?
This is a question that has had a long history. It has been shown that it is possible to have minute detectable levels of THC from passive inhalation, although with the standard DOT/SAMHSA screening cutoff (50 ng/ml) this is not possible. The controversy came from studies that showed that it is possible to produce a positive urine test when an initial cutoff of 20 ng/ml is used. There are numerous scientific articles that validate this point; however, exposure conditions were so unrealistic that they were characterized as nearly intolerable certainly not passive but active participation. Since all certified labs must use the 50 ng/ml for federally covered workers, a positive due to second hand smoke is not possible.
