In April 2004, when the Substance Abuse and Mental Health Services Administration (SAMSHA) suggested new regulations and procedures for drug testing, it requested that saliva testing be added to the repertoire. Even as the request was made, SAMHSA admitted, "Less is known about the pharmacokinetics and disposition of drugs into oral fluid as compared to urine." Meanwhile, government science showed that almost all other drugs enter oral fluid through diffusion from the bloodstream into saliva, but THC does not. Not at all.

Saliva tests that detect marijuana in the mouth therefore cannot differentiate between use ("I smoked a joint") and environmental contamination ("I was in the room when you smoked the joint"). The Department of Health and Human Services suggested a procedural make-good to compensate for the medium's inherent limitations: "In order to protect federal workers from incorrect test results for marijuana, the Department proposes that a second biological specimen, a urine specimen, will need to be collected."

Since the saliva-test window is only good for spotting the most recent use (two to three days), after that time has passed your spit will be as clean as a nonuser. Nevertheless, the saliva test is increasingly popular with the drug warriors since it's considered less invasive than the urine test and hence provides them with a bit of political cover. As with the urine test, they plan to fix its flaws as they go along. So even though SAMHSA's request to formalize saliva has not yet gone through, workers in the private sector may be asked to open wide and give up a gob. If you find yourself among them, you need to get one of the effervescent tablet products that negate a saliva sample for at least two hours.