Of all the pesticides out there, few have sparked more controversy than glyphosate. The most commonly used herbicide in the world, glyphosate is probably better known by the brand name Roundup. It works by killing weeds and other unwanted vegetation in the way of agricultural crops, many of which have been genetically engineered to be immune to the lethal effects of glyphosate.
The use of chemical herbicides such as glyphosate has long been discredited by environmental groups and health advocates, including supporters of U.S. Health and Human Services Secretary Robert F. Kennedy, Jr., who in the past argued That glyphosate causes cancer.
Then, on Monday, President Donald Trump issued an executive order Increase Glyphosate production – Many within the “Make America Healthy Again” (MAHA) movement reacted immediately.
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Kennedy supported the President’s order, surprising his followers. But other MHA leaders aren’t so convinced: Casey Means, a wellness influencer and Trump’s choice for the next surgeon general, Said She was concerned about the use of “toxic” chemicals to grow food crops during a Senate hearing on Wednesday. He said, “As a country we must avoid using toxic inputs in our food supply and we must study these chemicals more to understand their effects.”
We spoke to two experts to understand what the research shows on the health effects of glyphosate and what we know about how it enters the environment and our bodies.
What is glyphosate?
Glyphosate is a “amino acid blockerWhich means it stops weeds from growing by blocking their ability to produce amino acids, which are the building blocks of proteins. is herbicide generally applicable Crops such as corn and soybeans have been genetically modified to withstand its effects.
But glyphosate can definitely enter our bodies through our food – grains and legumes are among the crops most likely to be contaminated with herbicides or through contact with surfaces. People can even smell it.
Glyphosate was originally manufactured and sold by Monsanto as Roundup, which was acquired by German pharmaceutical giant Bayer in 2018. Bayer says it faces about 200,000 claims over alleged harm from glyphosate exposure, including a high-profile case that the U.S. Supreme Court is scheduled to review this year. And earlier this month Bayer agreed to pay $7.25 billion To settle a class-action lawsuit that alleged glyphosate exposure played a role in causing non-Hodgkin lymphoma, a form of cancer that attacks the lymph nodes.
A Monsanto spokesperson said scientific American That the agreement did not involve an admission of liability or wrongdoing.
“Leading regulators around the world, including the U.S. (Environmental Protection Agency) and (European Union) regulatory bodies, are concluding, based on an extensive body of science, that glyphosate-based herbicides—crucial tools that farmers rely on to produce affordable food and feed the world—can be used safely and are not carcinogens,” the spokesperson said.
What is the research on the health effects of glyphosate?
Most research has focused on glyphosate, exploring its links to cancer. In 2015 the World Health Organization’s International Agency for Research on Cancer (IARC) classified the herbicide as “probably carcinogenic to humans”. This means that there is some evidence that glyphosate causes cancer risk.
Other public health bodies disagree with this assessment. in 2016 Food and Agriculture Organization of the United Nations and this US EPA The prescribed glyphosate was probably not carcinogenic.
The research is more nuanced. In 2018, researchers at the National Cancer Institute found “no consistency“Between glyphosate exposure and non-Hodgkin lymphoma in farmworkers. But a year later, in 2019, a meta-analysis found”compelling link“Between Glyphosate Exposure and Cancer. This meta-analysis “was unique because it focused on the most exposed groups,” says Lianne Shepard, senior author of that paper and a University of Washington professor who studies the health effects of chemical exposure.
The effects of glyphosate on other animals are also under research investigation. Studies show that glyphosate may have risks harass honey beesharming their ability to find food, and herbicides can have harmful effects on plants, birds and mammals, according to EPA.
One reason for the apparent contradictions between IARC, EPA and other bodies is that different experts may weigh the merits of certain studies differently, leading to quite different conclusions, says Professor Brenda Eskenazi, professor emeritus of public health at the University of California, Berkeley.
Potential conflicts of interest may also impact studies: last year, citing “ethical concerns“Academic Journal Regulatory Toxicology and Pharmacology turned away An influential 2000 study supported by Monsanto concluded that glyphosate was not carcinogenic.
Shepard, who served on an EPA panel that reviewed glyphosate’s cancer-causing potential in 2016, says that since then the scientific evidence for the herbicide’s potential impact on human health “has grown stronger for cancer and other endpoints.”
Why don’t we know more about what glyphosate does?
Glyphosate is difficult to study: while animal and human cell studies have shown an association between exposure to the herbicide and health effects such as cancer, endocrine disruptor, oxidative stressAnd what’s more, human studies are very difficult to do.
Glyphosate has a short half-life in the body—by a guessAt least 5.5 to 10 hours — so trying to predict the effects of glyphosate by looking at the levels in someone’s urine, for example, provides only a snapshot of that moment in time and doesn’t tell much about their long-term exposure, Eskenazi says. Long-term studies, which may involve collecting and analyzing urine samples taken from participants over a period of time, are logistically difficult and expensive. Scientists may instead be able to look at geographic data to estimate long-term glyphosate exposure, but this is still an imprecise measure.
More research may be on the way. Eskenazi says studies that examine groups, such as pregnant women and fetuses, who may be most sensitive to exposure to glyphosate and research into whether glyphosate could affect human fertility and reproduction would be particularly useful.
“We are just at the beginning of studying glyphosate, but we should definitely be studying it, because it is the most commonly used herbicide in the world,” she says. “Even a small effect, if it’s real, could have a big impact on public health because so many people will be exposed.”
