Originally published in California Today.

It’s sprayed on home gardens, Little League Baseball fields and, most heavily, the corn, soybean and other crops of the Central Valley.

More than 10 million pounds of glyphosate, the active ingredient in the weedkiller Roundup, are applied in California each year, according to government figures.

Now, after a yearlong legal battle, California’s environmental health agency has announced that it will list it as a known carcinogen.

The move would make the agency the first American regulatory body to do so. Yet the science is not settled, researchers say.

Two years ago, the cancer research arm of the World Health Organization deemed glyphosate a probable carcinogen. But other regulators have played down concerns of a cancer risk, including the U.S. Environmental Protection Agency which has said glyphosate poses “low toxicity for humans.”

The mixed science can be attributed in part to the way studies have been designed, said Nathan Donley, a senior scientist at the Center for Biological Diversity. “There’s a lot of controversy around it,” he said.

In court, the manufacturer of Roundup, Monsanto, argued that California had no basis to make the cancer designation and said it would hurt the company financially.

In January, a judge rejected the lawsuit. Monsanto, based in Missouri, has appealed.

Read the full story here.