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Your Good Health: Second-hand pot smoke likely no problem

Tests can reveal detectable levels, but well below amounts that would determine actual use
Dr. Keith Roach writes a medical question-and-answer column weekdays.

Dear Dr. Roach: My son is studying aviation maintenance, and the instructors tell the students to expect random urine tests for drugs when they are employed. Drinking alcohol is fine, but using marijuana and other drugs are cause for losing your licence and thus your career. Recently we were walking around Boston for a day and we smelled pot frequently. Recreational and medical marijuana are legal in Massachusetts. He asked if one could fail a urine test by inhaling secondhand pot smoke. I doubt you could just by walking through a park, but what about attending a party or sitting in a car with someone who is smoking?


Several studies have shown that a person sitting in a car or a closed room where cannabis is being smoked can result in low, but detectable, levels in a person’s urine, even if they were not using the cannabis themselves.

However, most laboratories choose a threshold for calling a sample positive that is higher than was shown to be possible in the passive smoke experiments.

On the other hand, the concentration of THC in cannabis is much higher now than it was in those experiments, done mostly in the 1980s.

In a 2010 study from the Netherlands (looking at a real-life coffee shop), urine levels in nonusers (between 5 and 8 ng/mL) still were well below the thresholds used to detect cannabis use that I found in the published literature (25 to 50).

I think it is unlikely that secondhand cannabis smoke will turn a urine test positive.

Dear Dr. Roach: I have tongue-tie. My dentist recently mentioned it after several years with her and suggested that she use a laser to eliminate the issue. I am 63. Do you think that this would be useful or helpful to me at my age? My tongue-tie is not severe, probably considered pretty mild. If I stick my tongue out of my mouth, I can touch the outside of my lips. The dentist, on the other hand, can almost touch her chin with her tongue.


Ankyloglossia is a condition where the tongue is tied to the floor of the mouth by an unusually long or thick band of connective tissue, called the lingual frenulum. In infants and children, surgery is considered when there are problems with feeding or speech that have not gotten better with time.

I have never had an adult patient ask me about having a procedure to eliminate the issue, but it is a fairly easy procedure for an expert to perform.

However, if you aren’t having any problems, I don’t think I would recommend it being done. I have heard of professional wind instrument players undergoing the procedure to improve their playing, or people who speak publicly who develop tongue pain getting the procedure to reduce symptoms.

There has been some controversy about whether ankyloglossia is related to obstructive sleep apnea in adults and whether treatment, such as the laser procedure you mentioned, would be effective at relieving the sleep apnea. There is not enough evidence for me to recommend surgical treatment for ankyloglossia for obstructive sleep apnea at this time.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to