© 2023 WYPR
WYPR 88.1 FM Baltimore WYPF 88.1 FM Frederick WYPO 106.9 FM Ocean City
Play Live Radio
Next Up:
0:00 0:00
Available On Air Stations

Weed Killer Implicated in Monarch Die-Off Now Hit by Cancer Lawsuits

Over the last decade, an increasing amount of scientific evidence has linked the world’s most popular weed killer – RoundUp – to the disappearance of more than 90 percent of the Monarch butterflies in the U.S.

Concerns about RoundUp increased in March, when the World Health Organization concluded that the herbicide’s active ingredient – glyphosate, which is sprayed on many farms, lawns, and gardens – is a probable human carcinogen.

Since then, a growing number of attorneys have been filing lawsuits against RoundUp’s manufacturer, Monsanto, claiming that farmers and homeowners are suffering from cancer that was caused by the weed killer.

For example, Colorado attorney Michael McDivitt last month filed a lawsuit against Monsanto, claiming that his client, Emanuel Giglio, developed non-Hodjkins lymphoma after being exposed to RoundUp.  This is one of dozens of similar cases being filed across the U.S.

“Monsanto, which produces the herbicide glyphosate, has known about its cancer causing propensity for many, many years, and they have failed to do anything to inform the public about it,” McDivitt said.  “In fact, they’ve gone the opposite direction and have gone out of their way to create an aura of disinformation.  So the public has not been adequately informed about what the dangers of (glyphosate) are.”

Monsanto said that claims that the company has been hiding or manipulating information about the herbicide are baseless.

In a written statement, the company said:  “While sympathetic to individuals experiencing health problems, including those alleged by the plaintiff in this case, we believe that glyphosate is safe for human health when used as labeled and that this suit is without merit.”

So who is right?  The issue is a major one, because the use of RoundUp has increased dramatically over the last decade as Monsanto has genetically engineered crops that can tolerate the weed-killer.  Every year, about 250 million pounds of glyphosate are sprayed on corn and soybean fields, as well as on suburban lawns, commercial nurseries,  parks, and golf courses.

As Round Up has become more common, one of the weeds that it kills – milkweed – has nearly disappeared from much of the American landscape, depriving monarch butterfly caterpillars of their only source of food.

Doug Gurian-Sherman is senior scientist at the Center for Food Safety.  He said the World Health Organization did not specify at what dose glyphosate probably causes cancer. But he said that scientific studies in Iowa have suggested a link between higher rates of lymphoma and real-world exposure to the weed killer.

 “At the actual levels that farmers and farm workers are exposed to, there is an increased incidence of cancer of non-hodjkins lymphoma,” Gurian Sherman said. “And also troubling is that studies in Iowa have shown that non farm workers have levels of glyphosate in their urine to people who do work on farms.  It is troubling.”

Dr. Lynn Goldman, dean of the George Washington University School of Public Health, said a prudent step for consumers would be to avoid using not only RoundUp on their yards, but all weed killers.

“Without a compelling need to have an herbicide – a weed killer – on your lawn, my advice would be to not use them,” Goldman said.  “Or if you do use them, use them in a way so that there are several days would pass between the time that you use them and when you would have your children playing in the grass, your pets playing in the grass.”

Over the next few months, the U.S. Environmental Protection Agency will be considering the World Health Organization conclusions about the cancer risks of RoundUp and its environmental impact and will decide whether to re-approve its use on farms and gardens across the U.S.


Tom Pelton, a national award-winning environmental journalist, has hosted "The Environment in Focus" since 2007. He also works as director of communications for the Environmental Integrity Project, a non-profit organization dedicated to holding polluters and governments accountable to protect public health. From 1997 until 2008, he was a journalist for The Baltimore Sun, where he was twice named one of the best environmental reporters in America by the Society of Environmental Journalists.