The federal Environmental Protection Agency on Monday said glyphosate, the primary ingredient in the weed killer Roundup and one of the most widely used herbicides in agriculture, likely does not cause cancer.
The assessment contradicts the conclusion of a European scientific panel as well as California regulators, who have included the chemical on the Proposition 65 list of probable carcinogens.
Environmentalists worldwide have fought to encourage governments to ban or strictly limit use of the pesticide.
The European Union in November voted to extend the license of the chemical for five years. EPA will be considering a similar extension of the product's registration for use in 2019, and Monday's draft assessment is a foundational document in that process.
The controversy over the chemical is tied to opposition to genetically modified crops — Monsanto (which is merging with agrochemical giant Bayer) has patented versions of several major commodity crops that have been altered to resist its patented Roundup weed killer.
The Center for Biological Diversity, one of the groups fighting to limit use of glyphosate, said the EPA had been unduly swayed by the chemical's manufacturer.
"The only way the EPA could conclude that glyphosate poses no significant risks to human health was to only analyze industry studies and ignore its own guidelines when estimating cancer risk," said Nathan Donley, a senior scientist for the group.
The National Assn. of Wheat Growers, one of several groups suing California over its Proposition 65 decision, said the EPA's conclusion further isolates the state, which relied on "unscientific findings" from the World Health Organization's cancer review panel.
Glyphosate is sprayed on more than 200 crops across 4 million acres in California, including 1.5 million acres of almonds, making it the most widely used herbicide, according to the state Department of Pesticide Regulation, a branch of the state EPA.