For Immediate Release

Organization Profile: 

Dr. Nathan Donley, (971) 717-6406,

California to List World's Most Commonly Used Herbicide as Carcinogen

SACRAMENTO, Calif. - California’s Environmental Protection Agency has announced that it will list glyphosate — a widely used herbicide dangerous to people and linked to the dramatic decline of monarch butterflies — as a chemical known to cause cancer. Earlier this year the World Health Organization found that glyphosate, commonly known as Roundup, was a probable human carcinogen based on extensive research.

“California’s taking an important step toward protecting people and wildlife from this toxic pesticide,” said Dr. Nathan Donley, a staff scientist with the Center for Biological Diversity. “More than 250 million pounds of glyphosate are used each year in the United States, and the science is clear that it’s a threat to public health and countless wildlife species. It’s long past time to start reining in the out-of-control use of glyphosate in the United States.”

World usage of glyphosate is at an all-time high. Its use increased more than 20-fold, from 10 million pounds in 1990, largely due to the widespread adoption of crops, particularly corn and soy, that are genetically engineered to withstand what would otherwise be fatal doses of glyphosate. Accordingly, glyphosate residues are now found on 90 percent of soybean crops. In addition to being carcinogenic, recent research indicates, chronic, low-dose exposure to glyphosate can lead to liver and kidney damage.

“The spike in usage of glyphosate is really concerning because more use equals more exposure,” said Donley. “It’s nearly impossible for people to limit exposure to this toxin because it is just so widespread. That’s why we need much tighter controls on its use.”

Recent studies have pointed to glyphosate as one of the leading causes of the decline in monarch butterflies because it destroys milkweed, the monarch caterpillar’s sole food source. The ever-increasing use of Roundup on genetically engineered crops has nearly eliminated milkweed from midwestern agricultural fields, with devastating consequences for monarchs. Monarch butterflies have declined by more than 80 percent in the past 20 years — the same period of time during which glyphosate use has grown exponentially.

Last year the Center filed a petition to protect monarch butterflies under the Endangered Species Act because of the population declines associated with glyphosate. In June the U.S. Environmental Protection Agency agreed to analyze the effects of glyphosate on 1,500 endangered species in a historic settlement agreement with the Center.

This proposed listing from California under Proposition 65 will also include tetrachlorvinphos, parathion and malathion, three other pesticides with demonstrated carcinogenic potential.


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At the Center for Biological Diversity, we believe that the welfare of human beings is deeply linked to nature - to the existence in our world of a vast diversity of wild animals and plants. Because diversity has intrinsic value, and because its loss impoverishes society, we work to secure a future for all species, great and small, hovering on the brink of extinction. We do so through science, law, and creative media, with a focus on protecting the lands, waters, and climate that species need to survive.

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