Many drug testing aids are advertised with money-back guarantees if you test positive. BEWARE: guarantees do not assure good test results! Vendors often exaggerate product reliability and ignore customer complaints.
Accuracy: No test is infallible. Surveys of drug testing labs have found remarkably high error rates from poor quality control. While good labs have added safeguards to minimize the risk of “false positives,” even if error rates are only one in 10,000, the extension of drug testing to tens of millions of workers as proposed by the government means that many workers will be falsely accused of drug abuse.
It has been suggested that the ingestion of certain substances might alter body chemistry so as to disguise drug use. Although many products are currently being marketed as drug screens in head shops, High Times ads, etc., few have any solid scientific basis. Activated charcoal, a common detoxifier, might help lower metabolite levels a bit in long-term users if taken over the course of some days or weeks. It has been suggested on theoretical grounds that lecithin, a food emulsifier, might also be useful if taken over extended periods, but this hasn’t been proven. A number of high-priced herbal teas and powders are promoted as urine cleansers, with no good medical rationale. While some users have reported remarkable success with them, many others have not. Independent experiments suggest that it may be water dilution, not the screen itself, that accounts for success.
Efficacy: Urine testing has never been scientifically shown to be safe or effective at improving workplace safety or productivity, and studies indicate that the great majority of drug-positive workers are just as reliable as others (John Horgan, “Test Negative,” Scientific American, March 1990; Dr. John Morgan, “Impaired Statistics and the Unimpaired Worker,” The Drug Policy Letter, May/June 1989). Medically, the consensus of expert opinion is that drug tests are an inherently unreliable indicator of drug impairment (Consensus Report, National Institute on Drug Abuse, Journal of the American Medical Association, Nov. 8, 1985). Dr. George Lundberg of the American Medical Association has called them “Chemical McCarthyism” (editorial, Journal of the American Medical Association, Dec. 5 1986).
In some situations, including accidents and roadside sobriety checks, blood tests may be used. Blood tests detect the actual presence of THC in the system; however, they can be sensitive to other metabolites as well. Blood tests generally register positive for just a few hours after smoking, though heavy chronic smokers may be positive for up to seven days. Less sensitive are saliva/oral fluid tests, which register positive for about 2-4 hours after smoking.
Prospective employees have no legal right to challenge pre-employment drug screens. However, workers who are already employed may be able to challenge their employers’ drug testing plans in certain situations depending on labor law and local regulations. Avoid signing anything that gives your boss the right to arbitrarily test you; by stating your objections, you will strengthen your right to refuse a test. If you think you are being unjustly tested, you may have cause for legal action. San Francisco, Berkeley and some other jurisdictions forbid on-the-job drug testing except in safety-sensitive positions.