Brazil Prosecutors Sue to Ban Weed Killer Glyphosate
Brazilian prosecutors are suing health agency Anvisa and the federal government to ban the use of top-selling weed killer glyphosate, dealing a potential blow to chemical companies in Latin America’s largest economy.
A special division of the prosecutor’s office tasked with protecting workers’ rights filed a lawsuit Friday seeking to ban the registration of products containing glyphosate and its derivatives. The suit also seeks to prohibit authorization for the production, export, import, sale and use of the active ingredient and its compounds, citing risks to human life, occupational health and the workplace environment.
An effective cancellation of glyphosate’s registration in Brazil would hit companies such as Germany’s Bayer AG and others that have used the active ingredient in some formulations since its patent expired 2000.
Read more: Supreme Court Split Over Bayer’s Fight Against Roundup Lawsuits
Bayer said in a written statement that scientists from regulatory authorities worldwide have repeatedly concluded that glyphosate can be used safely and is not carcinogenic, adding that it is confident that “the scientific facts will prevail during the proceedings.”
Anvisa reevaluated potential risks associated with glyphosate and in 2020 maintained registration of the active ingredient in Brazil, with restrictions on its use, the regulator said Monday in an emailed statement.
The Brazilian Attorney General’s Office, which represents the federal government in courts, didn’t reply to a request for comment.
The Brazilian lawsuit comes months after the Regulatory Toxicology and Pharmacology journal retracted a decades-old paper that said the use of glyphosate didn’t pose health risks after “potential conflicts of interest of the authors” became clear. The report specifically referenced Bayer’s Roundup, which is typically used in large-scale agriculture and until recently in lawn and gardening products in the US.
The Brazilian prosecutors said the now-retracted study was used by regulatory agencies worldwide as a reference to allow registration and sale of glyphosate. The lawsuit also cites studies showing residues of the substance in drinking water as posing a threat to human health.
Anvisa said in its statement that the now-withdrawn article “did not play a central role in the reevaluation of glyphosate.”
Bayer said that the paper in question is “a review article of properly conducted studies” with no original data. It added that the European Union didn’t consider it in its most recent approval process while US and Canadian authorities have stated that the retraction has no impact on their assessment.
In March 2015, the International Agency for Research on Cancer classified glyphosate as “probably carcinogenic to humans.”
“It is a matter of public health,” Brazilian prosecutor Leomar Daroncho said in a statement. “The competent authority must take steps to reassess the risks when there is an alert or warning against the use of pesticides from international organizations responsible for health.”
MAHA Backlash
The widely used weed killer has also emerged as a flash point in US politics, riling supporters of Robert F. Kennedy Jr.’s “Make America Healthy Again” movement who are frustrated that Trump administration lawyers are asking the Supreme Court to shield Bayer from liability for a “failure to warn” about glyphosate’s harmful effects.
A large number of lawsuits have been filed in the US alleging that the use of glyphosate, including in Roundup-branded herbicide products manufactured by Bayer, can cause non-Hodgkin lymphoma cancer and multiple myeloma.
The German company is counting on the Supreme Court to pare down those lawsuits and help corral the decade-long litigation that has cost the company more than $10 billion. As of end-2025, Bayer’s provision and liabilities for glyphosate litigation totaled $11.3 billion.
In public disclosures, Bayer says there is no reason for safety concerns in connection with glyphosate products.
In 2016, Bayer agreed to acquire US-based Monsanto, the company that popularized the use of glyphosate in the 1970s. Eventually, the active ingredient became the world’s most widely used substance for weed control. In 1996, Monsanto launched a genetically modified soy designed to thrive even when sprayed with the herbicide. Subsequently corn, cotton and canola seeds were engineered with the technology.
In 2023, Brazilian labor prosecutors requested a court order to ban the use of pesticide ingredient atrazine, but no final decision was made.
Photograph: Herbicide is sprayed on a soybean field in the Cerrado plains near Campo Verde, Mato Grosso state, Brazil; photo credit: AFP/Getty Images