Due to marijuana’s illegal status under federal law, states have written their own rules about pesticides in cannabis. There is wide variety about which are regulated and how much of a trace can remain in products. It's unclear how many states require cannabis to be tested for legacy pesticides such as DDT.
There were 108 samples tested from the companies and 59 came back with unapproved levels of DDE, the board said. Christopher Simpson, deputy director of the Pacific Northwest Agricultural Safety and Health Center at the University of Washington, said the risk from DDE in cannabis is probably low, though possibly more of a concern for anyone using the marijuana medicinally, since they already may have health issues.
Given a lack of scientific evidence about what constitutes a dangerous level of DDE in cannabis, Taylor and other affected growers argued that regulators had overreacted by having them halt operations, rather than just issue recalls. It isn't clear how the DDE wound up in the products. Cannabis is known for its ability to remove contaminants from soil and has been studied for use in environmental cleanup. Taylor said he believed the contamination most likely came from dust settling on the plants as he and others drove or walked on the farm, or even from DDT present in wildfire smoke in the region.