Urinalysis passive exposure

The most frequently cited low probability event, that became apparent as a defense argument for urinalysis, was passive exposure to marijuana smoke. An explanation for a marijuana positive urinalysis was that the service member was exposed to significant quantities of marijuana sidestream smoke in close proximity to the service member. Because this defense may have had validity, the Navy commissioned subsequent scientific studies to resolve this issue. These studies showed conclusively that environmental exposure would result in a marijuana positive, providing the exposure was severe enough. However, in the experiment the exposure needed to be repeated for many hours and at a level such that the subjects needed to wear eye goggles to protect themselves from the marijuana smoke. Exposures at these levels could hardly be considered to be inadvertent or unwilling. As a result of these studies, cutoff levels could be defended and the credibUity of the passive exposure defense was diminished. 

These considerations show clearly that endogenous interpretive false positives are the main problem confronting urinalysis. It is, however, a problem with which hair analysis can provide considerable assistance, since passive exposure as a cause for a positive urinalysis result can be excluded by a positive hair analysis result. As indicated previously, this support is particularly critical in the case of opiates, where considerations of public safety demand that the numerous overturned urinalysis results be further investigated. 

Particularly troublesome to urinalysis are challenges that a positive result was caused by subversive actions (e.g., spiked food or drink), by passive drug exposure (e.g., poppy seed ingestion), or by sample contamination. We will show in the present paper that hair analysis, by being able to detect such interpretive false positives, is in a much stronger probative position than urinalysis and that this advantage can... 

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