The Environmental Protection Agency (EPA) released a statement in which it refused to regulate pesticides used on cannabis crops because of its federally illegal status.

With 29 states allowing medical or social cannabis use, many states are beginning to check for pesticides, while some have no testing program at all. Cannabis regulation was referenced as a state issue, which prevented the EPA from evaluating safe pesticides as it does for other crops. 

Colorado last year found 49 percent of cannabis samples tested in response to complaints had residue of unapproved pesticides, according to state Department of Agriculture data. The failure rate so far this year is 13 percent, showing how testing improves the safety of cannabis.

Julianne Nassif, director of environmental health at the Association of Public Health Laboratories, said many states struggle with implementing cannabis-testing programs.

“Lacking federal guidance, they must develop regulations, license private labs if they aren’t going to test samples in state facilities and determine what types of pesticides, pathogens, fungal toxins and heavy metals to monitor,” she said. “And funding is always an issue.”

Cannabis regulation is further complicated by the number of ways the plant can be consumed in social use markets. John Scott, pesticide section chief for the Colorado Department of Agriculture said “smokable extracts not only concentrate marijuana’s active ingredients, but also any pesticide residue.”

State agencies are beginning to raise their testing standards as states like California plan on enacting regulations by January of 2018.