A weedkiller so common in global agriculture that it turns up in rainwater and animal tissue is giving some CBD producers a strategy to stand out in a crowded market – by advertising their CBD doesn’t contain it.

Several CBD producers, including RE Botanicals and Bluebird Botanicals, are rolling out product labels promoting the absence of glyphosate, a weedkiller commonly known by its original brand name, Roundup.

Glyphosate is legal in the U.S., though an agency of the World Health Organization concluded in 2015 that glyphosate probably causes cancer. In response, some nations have banned it, most recently Germany.

Glyphosate kills cannabis, so growers of hemp and marijuana wouldn’t intentionally use it. But the weedkiller can show up in cannabis plants exposed to it through soil or wind.

“Hemp has a serious issue with pesticide residues, and not just glyphosate, because of the structure of the plants,” said Henry Rowlands, director of The Detox Project, a European advocacy group that issues glyphosate-free certification for thousands of products.

Hemp and marijuana plants are bioaccumulators, meaning that they absorb contaminants in the soil faster than they excrete them.

“Literally the plants suck out the pesticides into the structure of the plant because of the way the hemp is formed,” Rowlands told Hemp Industry Daily.