Blood and Urinary nicotine in non-smokers.

Of 39 urban non-smokers about half had measurable quantities of nicotine in their plasma (range 0 to 5times5 ng. per ml.) and almost all had nicotine in their urine during the early afternoon. The average concentration of urinary nicotine in non-smokers under natural conditions was 10times7 ng. per ml., but after deliberate exposure to tobacco smoke (mean duration seventy-eight minutes) in an unventilated room (38 p.p.m. of carbon monoxide) the average urinary nicotine level (80 ng. per ml.) was significantly higher than in non-smokers who had not been deliberately exposed to smoke (P less than 0times 001). Under natural conditions there was no overlap between the urine levels of non-smokers and the far higher levels of 18 smokers (mean 1236 ng. per ml.), suggesting that urinary nicotine may provide a more accurate assessment of an individual's smoking-status than blood-carboxyhaemoglobin. It is concluded that, as a result of passive smoking, most urban non-smokers have measurable amounts of nicotine in their bodyfluids for most of their lives.