Crops specialist: Glyphosate risk is in ignoring science

Glyphosate LD50 chart.jpg

WORTHINGTON — “Roundup and Cancer” ads are becoming ubiquitous in television, radio and print advertising, leading some to question the veracity of claims that use of the pesticide Roundup is linked to cancer diagnosis.

Liz Stahl, University of Minnesota Extension crops educator, argues that “there’s no less toxic product on the market.”

Any use of pesticide comes with some amount of risk, Stahl said, but lawsuits that seek compensation for cancer after use of glyphosate — the active ingredient in Roundup — are not rooted in science.

“I challenge anyone to find a pesticide that is less risky to use than glyphosate,” she said.

Stahl, who has an academic background in weed ecology, cited the National Agriculture Health Study — what she calls “a gold standard study when looking at the long-term effects of using pesticides” — which found no connection between glyphosate and cancer.


She pointed out that personal protective equipment for pesticide use does its job effectively, so glyphosate users should read the manual and follow instructions.

As a comparison, Stahl noted the relative acute toxicity of glyphosate with other common substances. Acute toxicity is measured by the LD50, the amount of a given substance required to kill 50% of the population, expressed in milligrams per kilogram of body weight. A lower LD50 means a substance is more toxic.

The LD50 of glyphosate is 4,900, making it less acutely toxic than table salt, acetaminophen, paraquat (another pesticide) and nicotine.

Although the concern around glyphosate centers on chronic, rather than acute, exposure, Stahl maintains that the relative risk is fairly low.

In almost all of the studies done on glyphosate, researchers have reported 95% confidence that long-term glyphosate exposure has “no effect,” Stahl said.

“There’s a real risk when we ignore the science,” she said. If these lawsuits prevail, glyphosate could be removed from the market, eliminating a “key product” for crop farmers.

Glyphosate is so effective for cover crops because it’s tightly bound to the soil — it doesn’t travel with the plants when they are harvested, Stahl noted.

According to the Environmental Protection Agency, the U.S. uses 280 million pounds of glyphosate on 298 million acres each year. Of that, 84% of U.S. glyphosate usage is on corn, soybeans and cotton.


The U.S. Geological Survey reports that in Minnesota, glyphosate accounts for 67.98% of total pesticide use.

Given its widespread use and effectiveness, glyphosate needs to remain available for farmers, Stahl said. She referred to an August statement issued by the Weed Science Society of America.

“In 2015, glyphosate was classified as a ‘probable carcinogen’ by the International Agency for Research on Cancer (IARC),” the statement reads, in part. “IARC has applied the same classification to red meat, hot beverages and emissions from high-temperature frying, as well as to more than 70 other chemicals.”

WSSA’s statement points out that international regulatory bodies, as well as private research agencies, “have consistently concluded that glyphosate-based herbicides are not likely to be carcinogenic.”

Stahl said one reason the lawsuits continue is because many people are removed from farming and do not understand how decisions about pesticide use are made.

“It’s unfamiliar with a lot of people being removed from agriculture,” Stahl said. “I encourage people to take the time and make sure it’s a reputable source of information.”

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