Why cannabis that failed Illinois’ state-mandated testing flunked

State data shows that 3,072 samples of cannabis failed at least one state-required test from 2019 through last June.

Most of those failed samples were cannabis flower — the dried plant material that’s smoked. It usually flunked for having too much mold or yeast. About 90% of the flower samples that failed at least one microbiological test were flagged for excessive mold or yeast.

Nearly 13% of cannabis flower tested — 330 samples — failed two or more microbiological tests.

Rarely do flower samples flunk for the presence of E. coli or salmonella: only three in a year and a half.

The Illinois Department of Agriculture would not provide any data on testing for mycotoxins, which are produced by certain types of mold, despite repeated requests for that information over a span of months.

Nor would state officials release any data on any failures involving the heavy metals lead, inorganic arsenic, mercury, cadmium and chromium.

State officials provided documentation of 17 samples that failed for having pesticide residue above acceptable limits: 16 in 2016, one in 2018. But they won’t say whether that means no samples failed pesticide testing in 2019, 2020 or 2021.

Illinois uses the U.S. Environmental Protection Agency’s “pesticide action” limits and requires cannabis flower to meet the strictest EPA standard for each type of pesticide. EPA limits for individual pesticides vary according to the product tested, with different limits for, say, berries or grains or meat.

Failures of processed hydrocarbon wax — used to make vape products — were due to higher-than-allowed concentrations of solvents. Those commonly used in wax processing include butane and propane. Five wax samples also flunked for E. coli or salmonella.

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Anthony Vazquez / Sun-Times file

There were only a 40 failures for potency, the vast majority for edibles. Under Illinois’ rules, potency can vary by 15% — higher or lower — from the labeled potency.

The Illinois weed failure data doesn’t show which cultivators have the highest failure rates. Some larger weed producers could have a lot of failures in the data but still have an overall cleaner crop than a very small grower with fewer failed tests.

Contributing: Jesse Howe, Andy Boyle