Chemists from the University of Iowa and the U.S. Food and Drug Administration have found that Iowa honey contains a key herbicide ingredient suspected of causing cancer, Iowa Environmental Focus reported.

UI’s John Vargo and Narong Chamkasem of the FDA started testing for glyphosate, a key ingredient in Roundup, after some studies found it is a probable carcinogen. Their research found levels in honey as high as 653 parts per billion, more than 10 times the limit of 50 ppb set by the European Union for residue in honey. Most samples showed 23 ppb and 123 ppb of residue.

Previous tests found a maximum of 107 ppb.

Glyphosate is the most widely used weedkiller in the world. Bees pick it up when they collect pollen.

“According to recent reports, there has been a dramatic increase in the usage of these herbicides, which are of risk to both human health and the environment.,” the scientists wrote.

The U.S. Environmental Protection Agency hasn’t set a limit, and contends the levels found in honey “do not raise a concern for consumers.” The EPA reportedly has considered setting a residue limit of 100 ppb for glyphosate in honey.

The Organic Consumers Association and Beyond Pesticides sued an Iowa business, the Sioux Honey Association Cooperative, over contamination of honey supplies. The honey, called Sue Bee Honey, is labeled as “pure.” Prosecutors contend that such language is false advertising given the amount of pesticide residue found in Sue Bee Honey during the FDA’s study, Environmental Focus reported.

Darren Cox, president of the American Honey Association, said, “It’s a chemical intrusion, a chemical trespass into our product.” He added: “We have really no way of controlling it. I don’t see an area for us to put our bees. We can’t put them in the middle of the desert. They need to be able to forage in ag areas. There are no ag areas free of this product.”