How we tested for pesticides

photo illustration of cannabis in a pair of tweezers over a parabolic graph of test results
(Photo illustration by Jim Cooke / Los Angeles Times; Photos via SC Labs, Getty Images)

California currently performs no independent checks on pesticide levels in cannabis sold to consumers or the accuracy of private pesticide tests certifying cannabis for sale.

To see where that leaves consumers, The Times and WeedWeek undertook their own tests. Reporters bought products from licensed dispensaries across the state. Two licensed cannabis testing labs — Anresco Laboratories in San Francisco and SC Labs in Santa Cruz — agreed to screen the samples for an expanded list of pesticides.

Samples were selected for a variety of reasons: sales promotions, unusually high potency levels, or they were named in complaints to regulators. Testing also focused on vapes, which because of their concentrated oils can pose a greater health threat to consumers.

Reporters removed packaging and obscured labels so labs did not know the products being tested. In many cases, both labs tested the same product, and other products were retested.

In total, 66 tests were run to check for more than 100 pesticides, well beyond California’s required screening of 66 chemicals. It is possible that other pesticides are present. Results from a state agriculture lab conducting tests for regulators showed 16 additional pesticides that Anresco and SC Labs were not set up to measure.

Additional test results were provided to The Times by Anresco and a third lab, Infinite Chemical Analysis Labs in San Diego, which had sent those results to state regulators. In these cases, the labs selected which products to test.

Alex Halperin is editor of the industry newsletter WeedWeek.

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This story originally appeared in Los Angeles Times.