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Cannabis Crops Grown in Washington County May Be Contaminated With Banned Pesticide, Regulator Warns

By Leo Bear-McGuinness

Published: Apr 11, 2023   
Cannabis crops in a field near a hill.

Image credit: iStock

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Many cannabis products grown in the Okanogan County area of Washington may be contaminated with a banned pesticide, according to the state regulator.

In a memo to state licensees sent on April 6, the Washington State Liquor and Cannabis Board (LCB) announced that its staff had identified “a pattern of pesticide testing failures” among cannabis cultivators in the Okanogan region.

According to the LCB, cannabis products grown from this area were found to contain significant levels of dichlorodiphenyldichloroethylene (DDE) following random testing. DDE is a by-product of the pesticide DDT, which was banned in the US in 1972 due to the threat it posed to wildlife.

The mystery of the banned pesticide

In response to the findings, the LCB has placed “administrative holds” on all cannabis businesses in the Okanogan area associated with high DDE levels.

The Washington regulator has also requested that all licensees in the geographic area with DDE test results above actionable limits conduct a recall on all their products.

To prevent any further DDE contamination, the LCB plans to roll out new rules that require a result of 50% of the actionable level of DDE for any plants grown in Okanogan. Cannabis testing labs in Washington are not currently required to test for DDE.

While the LCB doesn’t suggest how so many cannabis products in Washington became contaminated with DDE, it says it plans to reduce further contamination incidents, in part, by testing the state’s soil; it plans to work with “appropriate state agencies” to conduct soil and water testing in the Okanogan region.

So, given the cannabis crop’s affinity for bio-accumulating chemicals from the soil it’s grown in, the DDE may have been in the Okanogan soil all along, at residual levels, and not newly sprayed on the cannabis crops. Further research by the LCB will be needed to confirm this presumption.


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