Many Gray Areas So Far With A New Pot Grow Concern: Pesticides

DENVER (CBS4) - Tens of thousands of marijuana plants have been put on hold from curation or destroyed all together at 11 different legal pot grow operations in the city of Denver after certain pesticides were discovered being used in grow processes.

"It came to the attention of the city that there were some pesticides being found during the course of routine fire department investigations and inspections," said Danica Lee, environmental public health program manager with the Denver Department of Environmental Health.

"Unapproved pesticides may have been applied on plants and may pose a contamination issue with those plants," Lee said.

Lee's department has been working with the state's Department of Agriculture Pesticide section to find out what is and is not okay for growers to use.

"But the vast majority of products have very tight label language. It's very specific. And so the vast majority of products on the market would not allow use of those products on marijuana," said John Scott, Pesticide section chief.

The state was asked to come up with a list of products not approved, but there were so many to list they instead came up with a list of products that can be used. They admit more work needs to be done.

"No risk assessments have been conducted for pesticide use on marijuana, so no one knows whether these products can be safely used on marijuana or not," Scott said.

The approved pesticides have low toxicity.

The city's health department admits their oversight is relatively new and unapproved pesticides could have been used for years on medical marijuana.

"I know it's been a challenge for everybody to keep up with the inspections," Lee said. "It's definitely a possible that these pesticides have been used longer."

"Ultimately until those risk assessments can occur no one can make those determinations on whether a product can be applied safely or not."

The Environmental Protection Agency at the federal level oversees all pesticide products. The state says they've worked with the EPA but at this point wish they could have more guidance.

Some state legislators are trying to add $300,000 to the Department of Agriculture's efforts to monitor pesticide usage in the industry.