What is Roundup?
Roundup is a widely-used herbicide manufactured by Monsanto (now owned by Bayer AG) since the 1970s. The active ingredient in Roundup is glyphosate, which is designed to kill weeds by inhibiting a specific enzyme essential for plant growth.
While Bayer has been phasing out the use of glyphosate in Roundup products, it was used for decades and Roundup became the world’s most popular herbicide, used by farmers, landscapers, and homeowners globally.
Current Case Status
By some estimates, over 65,000 claims remain pending against Monsanto, alleging that Roundup causes cancer. Those cases continue to proceed to trial in various state courts, including several scheduled for trial in 2025.
Monsanto has also asked the Supreme Court to decide whether the federal law regulating pesticide registration “preempts” state laws related to pesticide labels. That decision could significantly impact the types of claims individuals may bring related to Roundup. The Supreme Court is still considering whether to take the case.
The Legal Theory
Roundup lawsuits are primarily based on product liability, design defect, and failure-to-warn claims. Plaintiffs typically allege:
- Failure to Warn: Monsanto failed to adequately warn users about the cancer risks associated with exposure to Roundup.
- Defective Design: Roundup was unreasonably dangerous when used as intended.
- Negligence: Monsanto failed to conduct adequate safety testing or ignored evidence of cancer risks.
The Scientific Debate
The litigation centers on whether glyphosate causes non-Hodgkin’s lymphoma and other cancers. In 2015, the International Agency for Research on Cancer (IARC) classified glyphosate as a “probable human carcinogen.” However, regulatory agencies including the EPA maintain that glyphosate is unlikely to cause cancer in humans. This scientific disagreement forms the core of the legal disputes, with each side presenting conflicting expert testimony and studies.
Key Legal Issues
- Federal Preemption: Whether federal pesticide regulation “preempts” state labeling requirements, potentially limiting certain claims related to Roundup’s label.
- Causation: Whether plaintiffs can establish that Roundup exposure specifically caused their cancer diagnoses.
- Product Design: Whether Monsanto should reasonably have known of the risks of Roundup, and designed a safer product.
- Warning Adequacy: Whether Roundup’s label provided sufficient cancer risk warnings to users.
- Damages: Calculation of compensatory damages for medical costs, pain and suffering, and, in some courts, punitive damages.
Roundup Timeline
March 2015 – IARC Classification
International Agency for Research on Cancer (WHO) classifies glyphosate as “probably carcinogenic to humans” (Group 2A), triggering the initial wave of lawsuits against Monsanto.
Fall 2015 – First Roundup Lawsuits Filed
Plaintiffs begin filing cancer lawsuits against Monsanto following IARC classification, establishing litigation foundation for thousands of subsequent claims.
October 2016 – MDL Formation
U.S. Judicial Panel creates MDL No. 2741 “In re: Roundup Products Liability Litigation” in Northern District of California under Judge Vince Chhabria.
June 2018 – Bayer Acquisition
Bayer completes $63 billion acquisition of Monsanto, inheriting the entire Roundup litigation portfolio.
August 10, 2018 – Johnson v. Monsanto Verdict
San Francisco jury awards $289.25 million to groundskeeper Dewayne Johnson. First major trial victory establishing precedent that Roundup causes cancer.
March 19, 2019 – Federal Jury Decides Roundup Causes Cancer
Federal jury unanimously finds Roundup was substantial factor in causing Edwin Hardeman’s non-Hodgkin lymphoma, representing first federal MDL causation victory.
January 30, 2020 – EPA Interim Registration Decision (Major Milestone)
The EPA concludes glyphosate poses no human health risks and is “not likely to be carcinogenic,” directly contradicting IARC findings.
May 14, 2021 – Ninth Circuit Affirms Early Roundup Decision
The Ninth Circuit, a federal appeals court, upholds Hardeman verdict, rejecting federal preemption arguments and establishing federal circuit precedent.
June 17, 2022 – Ninth Circuit Vacates EPA Interim Registration
The court vacated the EPA’s human health assessment, finding the agency “did not adequately consider whether glyphosate causes cancer.”
June 21, 2022 – Supreme Court Denies Review of Early Roundup Decision
U.S. Supreme Court declines to review an early decision favorable to plaintiffs, leaving Ninth Circuit decision in place.
April 4, 2025 – Durnell Supreme Court Petition
Bayer files petition for certiorari in Durnell v. Monsanto case, representing latest attempt to secure federal preemption ruling.
June 30, 2025 – Supreme Court Requests Solicitor General Views
Court asks DOJ for input on Bayer’s preemption arguments, signaling potential Supreme Court interest in reviewing the case.