Center for Biological Diversity

For Immediate Release, March 23, 2015

Contact: Jonathan Evans, (415) 436-9682 x 318,

New Report Links World's Most Commonly Used Herbicide to Cancer

SAN FRANCISCO— A new report by the World Health Organization has linked the world’s most commonly used herbicides to cancer. Glyphosate — widely known as Roundup and marketed by Monsanto — has also been linked to the decline of many wildlife species, including the monarch butterfly. The WHO determined that glyphosate and two other insecticides, malathion and diazinon, are “probably carcinogenic to humans.”

“For too long the pesticide industry has taken the approach of ‘spray first and ask questions later’ and meanwhile these products are posing grave risks to people and wildlife across the globe,” said Jonathan Evans, legal director of the Center for Biological Diversity’s Environmental Health program. “These dangerous and far too common pesticides are having cascading effects on our health and environment, and it’s high time we took the worst of the worst chemical cocktails off the market.”

The use of glyphosate has increased sharply to more than 250 million pounds per year in the U.S. with the widespread adoption of genetically engineered crops such as corn and soy. Glyphosate residues are found on 90 percent of soybean crops. Approximately 1 million to 2 million pounds of malathion are used annually, most commonly in mosquito and fruit fly control programs. The Environmental Protection Agency has determined that the use of malathion is likely to harm endangered birds, mammals, fish and insects. Diazinon is commonly used in U.S. agriculture, with the highest use on almonds and stone fruits. EPA found that diazinon is “very highly toxic to freshwater fish and invertebrates” and is also likely to harm endangered birds and mammals. Manufacturers of diazinon at have opposed limits on pesticide use to protect endangered species.

“The science is clear that these dangerous pesticides are a threat to public health and wildlife,” said Evans. “It’s time for our government to put public welfare before profits and pull these products from the shelves.”

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 has nearly eliminated milkweed from Midwestern agricultural fields, with devastating consequences for monarchs. Monarch butterflies have declined by more than 90 percent in less than 20 years — the period of time during which glyphosate use has grown exponentially.

The Center for Biological Diversity recently filed a petition to protect monarch butterflies under the Endangered Species Act because of the population declines associated with glyphosate. It also challenged a recent EPA approval of the increased use of glyphosate that inadequately addressed the impacts to endangered wildlife. 

Today’s report was produced by the International Agency for Research on Cancer, a WHO branch that convened experts from 11 countries to assess the cancer risk of five commonly used organophosphate pesticides. In addition to increasing cancer risk, the report found there was increased risk of DNA and chromosomal damage from all three pesticides. The Center recently reached a settlement requiring the EPA to analyze the impacts of malathion and diazinon on endangered species.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 825,000 members and online activists dedicated to the protection of endangered species and wild places.

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