The health and psychological consequences of cannabis use - chapter 4

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4. Cannabis the drug

4.10 Passive inhalation

In the United States, urine testing for drug traces and metabolites is increasingly used to identify illicit drug users in the workplace (Hayden, 1991). A technical concern raised by the opponents of this practice has been the possibility of a person having a urine positive for cannabinoids as the result of the passive inhalation of marijuana smoke at a social event immediately prior to the provision of the urine sample. A number of research studies have attempted to determine the relationship between passive inhalation of marijuana smoke and consequent production of urinary cannabinoids (Hayden, 1991).
In one of the first studies on passive inhalation, Perez-Reyes and colleagues (1983) found that non-smokers who had been confined for over an hour in a very small unventilated space containing the smoke of at least eight cannabis cigarettes over three consecutive days had insignificant amounts of urinary cannabinoids. Law and colleagues (1984) and Mule et al (1988) also showed that passive inhalation produced urinary cannabinoid concentrations well below the detection limit of 20ng/ml 9-carboxy-THC used in workplace drug screens.

Morland et al (1985) produced urinary cannabinoid levels above 20ng/ml in non-smokers but the conditions were extreme, namely, confinement in a space the size of a packing box with exposure to the smoke of six cannabis cigarettes. The studies of Cone and colleagues (1986; 1987a, 1987b) confirmed the necessity to apply extreme experimental conditions, which they claimed non-smokers were unlikely to submit themselves to for the long periods of time required to produce urinary metabolites above 20ng/ml. They also showed that non-smokers with significant amounts of cannabinoids in their urine experienced the subjective effects of intoxication.