Cannabis plants are hyperaccumulators. They can efficiently absorb long-lasting toxins from the soil into their leaves– positive news for cleaning up contaminated soil, but the plants become toxic after accumulating substances like DDE. Hyperaccumulation becomes an issue when growing plants for consumption in contaminated soil.
The Washington Liquor Control Board (LCB) put administrative holds on products from five cannabis cultivation licenses along the Okanogan River due to soil contamination, according to an April 6 memo from the agency. Random testing showed that the land, formerly fruit orchards, contained “detectable levels” of DDE. The contaminated land is north of Brewster, west of the Okanogan River.
What is DDE, and where does it come from?
DDE is a breakdown product of DDT, an insecticide previously common in American agriculture before a 1972 ban. Human exposure occurs most often through food. However, since banning DDT, the concentration of DDE found in human fat, blood, urine, semen, and breast milk continues to shrink, according to the Environmental Protection Agency.
Research shows that ingesting DDT and DDE can adversely affect the liver, immune system, and CNS. Oral exposure can also cause reproductive issues, including miscarriage and an increased cancer risk. Limited data is available on the consequences of burning and inhaling the insecticide.
Next steps for affected farms
The LCB didn’t require Washington cannabis brands to test for pesticides until April 2022, but DDE is not on the list. If farms choose to test for the insecticide, cannabis testing labs in the state don’t currently offer DDE testing.
The agency is investigating contamination in the surrounding area now, and 13 other cultivation sites could be affected. Just days from planting season, affected licensees await a meeting with LCB agents that promises guidance. In the meantime, the farm schedule is on hold.
According to the memo, the LCB plan includes immediately putting administrative holds on licensees with positive DDE soil tests. If the soil tests are positive for DDE, all cannabis farms in the region will experience an administrative hold. Agents will gather a list of all products from the region since August 2022, secure and test all listed products, and request licensee-initiated recall on all products produced in this geographic area.
Soon the agency will initiate the process of new rules regarding actionable levels of DDE in soil and DDE/DDT testing. In addition, the LCB will engage relevant state agencies to conduct adequate soil and water testing while continuing to monitor and research the affected geographical area.
As Washington farms grapple with shutting down during planting season and the LCB assesses testing protocols– cannabis and hemp farmers may consider testing their soil.