Evaluating Interference of THC in Hemp Food Products With Employee Drug Testing

The study will be presented in detail by Mr Gero Leson at the BIORESOURCE HEMP® 2000 in Wolfsburg, 16 September 2000
Diese Studie wird von Gero Leson auf der BIOROHSTOFF HANF® 2000 in Wolfsburg am 16. September ausführlich vorgestellt.

Persons who frequently consume food items containing hemp seeds and oil are very unlikely to fail a workplace urine test for marijuana. This is the main finding of a recent toxicological study commissioned by the Agricultural Research and Development Initiative (ARDI), a program funded by the Canadian federal and the Manitoba provincial governments; the North American Industrial Hemp Council (NAIHC), and several manufacturers of hemp foods.

The study was motivated by past reports of positive drug tests caused by hemp oil and snacks from seeds with relatively high levels of Delta-9-tetrahydrocannabinol (THC). Traces of this main psychoactive ingredient of marijuana are present in industrial hemp plants, grown for fiber and seeds. Regulations in Canada, the main supplier of hemp seeds to the U.S., limit THC levels in hemp seed products to 10 parts per million (ppm). While there is currently no standard in the U.S., the federal Drug Enforcement Agency (DEA) cites potential interference with drug testing as their main objection to the importation and sale of hemp foods.

The study monitored concentrations of THC metabolites in the urine of 15 volunteers who ate, over four consecutive ten-day-periods, one tablespoon per day of a hemp/canola oil blend. Corresponding THC doses increased stepwise from 0.09 to 0.45 milligrams (mg) per day, much below the 10 mg threshold for psychoactivity. Daily intake of 0.45 mg of THC translates into eating daily 6 tablespoons of hemp oil or a half a pound of hulled hemp seeds of commercial quality. Even hemp food connoisseurs rarely consume such quantities.

At this dose, no volunteer exceeded, during the initial urine screening test, the 50 parts per billion (ppb) cutoff applied by federal and most private employers to detect marijuana use. THC doses as low as 0.2 mg/day caused several exceedances of the lower, more stringent 20 ppb cutoff used by few employers and law enforcement agencies. Yet, “confirmation testing” of these samples by the more specific GC/MS (gas-chromatography / mass spectrometry) method always found THC metabolite levels much below the 10 ppb cutoff (for GC/MS). Above this cutoff, some drug testing programs consider a sample “confirmed positive” for marijuana. One of three volunteers consuming up to 0.6 mg/day of THC screened positive at the 50 ppb level but was not confirmed positive by GC/MS.

The study was coordinated by Leson Environmental Consulting, Berkeley, CA. A scientific advisory board of internationally acknowledged experts in pharmacology and toxicology reviewed study design and results. Says Gero Leson, the study’s principal investigator: “Our results demonstrate that even people who frequently consume hemp foods of the quality now found in stores will not fail urine tests for marijuana – as long as:

  • Hemp seed processors continue to adhere to thorough seed cleaning methods. These now generally keep THC levels in hemp oil and hulled seeds below 5 and 2 ppm, respectively; and
  • Employers and administrators of drug testing programs follow established federal guidelines for urine testing, requiring that urine samples, which fail the screening test, must be confirmed by GC/MS.

The study results are being submitted for publication in a peer-reviewed journal. For a summary, visit www.naihc.org/hemp_information/content/THC_emp_drug_testing.html.

About NAIHC: The North American Industrial Hemp Council is a 501 (c)(3) organization comprised of industrial, agricultural, governmental and environmental interests who seek the recommercialization of industrial hemp. Contact the NAIHC at: +1-608-224-5135.

For more information contact John W. Roulac: +1-707-823-2800, Extension 201


Renewable Carbon News – Daily Newsletter

Subscribe to our daily email newsletter – the world's leading newsletter on renewable materials and chemicals