Does Roundup Cause Cancer? What Environmental Health Experts Know So Far

Contemporary food production relies on herbicides to safeguard crops against aggressive weeds. These herbicides can dramatically improve production, leading to impressive yields that support our global food system. Unfortunately, the very herbicides that promise agricultural abundance can pose huge threats to our environment and even to human health.

The ultimate example? Roundup. Once regarded as the pinnacle of weed control, Roundup has sparked major concerns among environmental health experts, with some research suggesting that this particular herbicide could increase the risk of certain types of cancer or even act as an endocrine disruptor.

On a global scale, many agencies have responded to this research by placing major restrictions on the use of glyphosate. Others, however, are slow to act, in part because the research surrounding glyphosate has prompted conflicting interpretations. This has sparked a fierce debate that revolves around one central question: is Roundup safe?

Due to the complexity of the issue, there is no simple answer. That being said, this question can be explored in detail while pursuing an online MPH in Environmental Health from Texas A&M. Keep reading for an overview of the glyphosate debate and to discover how an MPH can help you make sense of ethics, regulatory oversight, and public health.

What Is Roundup (and What’s in It)?

Before we can answer the question of “Is Roundup safe?”, it’s important to understand what it is. Roundup is a brand-name herbicide product that contains a broad-spectrum, chemical herbicide known as glyphosate, which is made up of phosphonomethyl and glycine components. While Monsanto received the original patent, glyphosate-based herbicides are now produced by many other companies.

Glyphosate inhibits the plant enzyme 5-enolpyruvylshikimate 3-phosphate (EPSPS). This enzyme is crucial to the shikimate pathway by which plants create amino acids. As the building blocks that form protein, these amino acids support everything from the cell structure to the metabolism of plants. In blocking this enzyme, glyphosate stunts the growth of targeted plants. This was not initially believed to pose risks to animals, which lack the shikimate pathway present in plant life.

Epidemiological Evidence: What Studies Show (and Don’t)

Controversy surrounding the use of glyphosate largely stems from the lack of consensus in available research. At the surface level, studies seem to indicate some potential danger. As skeptics point out, however, these studies may be limited in scope or contradicted by research that lacks any indication of glyphosate-related health risks.

Key Cohort and Case-Control Studies

In the last decade, several noteworthy studies have shed light on the potential impact of glyphosate. These include a variety of cohort and case control studies, with some arguing that the study designs themselves may have contributed to differing conclusions.

Remember: cohort studies follow individuals who do not initially have the central outcome (in this case, cancer). Case-control studies, meanwhile, compare those with the outcome to those who lack it, looking back in time to reveal who may have been exposed.

Agricultural Health Study (AHS). As one of the most influential studies surrounding the use of pesticides and herbicides, the AHS was launched in 1993 in hopes of answering pressing questions surrounding the health of farming populations. Results from this prospective study ultimately concluded that "no association was apparent between glyphosate and any solid tumors or lymphoid malignancies overall."
Italian multicenter case-control study. A noteworthy study published in the journal Environmental Health explored ties between occupational glyphosate exposure and lymphoma, with findings suggesting limited support for the prior classification of the herbicide as a "probable human carcinogen."
Meta-analysis exploring link to non-Hodgkin lymphoma. Drawing on insights from the previously discussed AHS cohort — along with several case-control studies — a meta-analysis published in Reviews in Mutation Research concluded that there was a "compelling link between exposures to GBHs [glyphosate-based herbicides] and increased risk for NH [non-Hodgkin lymphoma]."

Limitations and Uncertainties

Even well-designed studies can lead to seemingly contradictory outcomes, simply because so many factors are difficult to control. Limitations worth considering when examining glyphosate research include:

Exposure assessment. Many glyphosate studies rely on self-reporting to determine the extent to which individuals were exposed to the herbicide. This can introduce concerns surrounding accuracy, especially as exposure can vary based on application method or even according to the use of personal protective equipment.
Confounding. Glyphosate is just one of many potentially harmful products that farmers have relied on to control weeds. Other chemicals could "confound" study results, suggesting that glyphosate may not be the primary cause of problematic health outcomes.
Heterogeneity in formulations. Glyphosate is often used in formulations that may include other potentially toxic chemicals. This issue is similar to confounding, but with a stronger emphasis on the various additives found in herbicide products.
Selection bias. Participants involved in glyphosate studies may not truly represent farming populations. Individuals who are uniquely proactive about their personal health are more likely to enroll in studies, which means said studies may underestimate the actual impact of glyphosate within broader populations.
Latency and dose–response. Health issues potentially associated with glyphosate could take years to develop, which means short-term studies may fail to capture the long-term effects of exposure. The dose–response relationship aims to determine how the level of exposure relates to the severity of potential health outcomes. Unfortunately, this relationship can be affected by many different factors, including exposure methods or pre-existing conditions.
Publication bias & small-study effects. Publication bias describes the tendency for studies involving major (and positive) findings to be published more frequently than those with muted results. Simply put, these studies may attract more attention because they are more interesting.

Mechanistic and Animal Evidence: How Could Glyphosate Cause Cancer?

Some research highlights concerns surrounding long-term exposure to glyphosate-based herbicides, even when used at doses deemed 'safe' by the European Union. These relate not only to the risk of cancer but also to endocrine disruption. While human studies offer a wealth of insight, additional perspectives can be gained by examining animal studies, along with mechanistic evidence regarding glyphosate's potential interference with biological systems.

Animal Studies and Bioassays

Animal studies can help overcome some of the deficits of human-centered cohort and case-control studies, in which lifestyle and other factors can be difficult to control. A comprehensive analysis of animal carcinogenicity studies, for example, linked glyphosate exposure with numerous health issues, including kidney tumors and malignant lymphomas. However, according to a report published in the journal Carcinogenesis, it remains "unclear whether observed differences can be relied upon as predictive for human health risks."

Tests known as bioassays can also be insightful, revealing cumulative toxicity based on measurements of biological activity. These tests demonstrate how glyphosate behaves at the cellular level, pinpointing seemingly subtle changes that can have a profound impact on biological systems. That being said, a notable analysis of multiple bioassays lacked "strong evidence that glyphosate is an animal carcinogen," highlighting discrepancies between different studies.

Regulatory Assessments and Consensus: The Official Position

Guided by the previously mentioned studies — along with the recommendations of industry experts — federal and global regulators have established various rules and guidelines that reflect different perceptions of risk.

IARC (International Agency for Research on Cancer)

The IARC takes a strong stance on glyphosate, having classified it as "probably carcinogenic to humans" in 2015. These findings were widely criticized, with the IARC accused of cherry-picking research and "edit[ing] parts of the glyphosate monograph to achieve a particular outcome."

The agency has since referred to critiques of this stance as "coordinated efforts to undermine the evaluation, the program, and the organization," insisting that its evaluations have proven transparent and that there are no conflicts of interest.

U.S. EPA and Other National Regulators

Much of the current confusion surrounding the risks of glyphosate stems from differences in classifications between the IARC and the U.S. Environmental Protection Agency (EPA).

The EPA has made it abundantly clear that it does not agree with the IARC's findings. After reviewing glyphosate's uses and overall safety, the EPA has concluded that there are "no risks of concern to human health when glyphosate is used in accordance with its current label." EPA guidance adds that "glyphosate is unlikely to be a human carcinogen."

EPA Deputy Assistant Administrator Nancy Beck has expressed a commitment to maintaining the agency's previous stance on glyphosate, explaining, "The science is still telling us that glyphosate is safe."

Regulatory “Safe Use” Caveats

Even when the use of glyphosate is permitted, caveats may be imposed, serving as a middle ground between the IARC's precautionary approach and the risk-based assessments carried out by various regulatory agencies. This suggests that glyphosate is only safe when strict conditions are followed.

Concepts such as the acceptable daily intake (ADI), for example, offer insight into the maximum amount that individuals can be exposed to without experiencing significant health risks over time. Furthermore, agencies such as Health Canada draw attention to skin irritation, respiratory concerns, and other effects linked to over-exposure — especially if "label directions are not followed."

Reconciling the Differences: Why Experts Disagree

Disagreements surrounding glyphosate are often a matter of hazard versus risk assessment. When focusing on hazards (or whether glyphosate "can" cause cancer), classifications are more likely to highlight potential dangers. If, however, the focus is on "how likely" glyphosate is to cause harm at typical levels of exposure, conclusions may suggest that it is actually safe.

These core differences can be exacerbated by differing data sources, including the potential use of industry studies and variations in study design. For instance, human and animal studies may prompt different takeaways, as do studies involving different methodologies and exposure periods. Critics worry that industry lobbying has influenced decisions surrounding glyphosate, although regulatory agencies are quick to frame their review processes as transparent and strictly science-based.

What the Legal Cases Reveal (But Don’t Prove)

High-profile lawsuits offer additional insight into the potential risks associated with glyphosate, as well as the public's evolving perception of this herbicide. Jury verdicts could potentially be impacted by deeply emotional narratives while also shining a light on the complexity of the ongoing Roundup debate.

When examining these cases, it's important to remain mindful of the considerable differences between legal and scientific evidence. Legal standards tend to prioritize probability over certainty and focus on the concerns of the individual — such as whether a specific person is likely to have been harmed. Scientific research maintains stricter standards, moving beyond correlation to determine whether larger controlled studies reference clear causal links between glyphosate and concerning health outcomes.

Ongoing appeals and other cases may cast doubt on the future legal status of glyphosate. For example, the Missouri Supreme Court is unwilling to take up Bayer's appeal of a major verdict, in which $611 million was awarded to individuals who believed that their cancer was caused by Roundup.

Has Roundup Been Banned or Restricted in Any Countries Because of Cancer Risks?

While some countries have sought to ban Roundup, it still remains approved for use in much of the world. However, restrictions increasingly determine when or how this herbicide can be used.

Despite implementing dramatically different policies, governments share a similar goal of supporting a productive global food system without placing human health at risk. Ultimately, how they accomplish this depends on interpretations of glyphosate-centered research, which, as we've already revealed, can differ dramatically.

To shed light on the sheer range of responses to the glyphosate debate, we've highlighted bans, restrictions, and other actions taken on a global scale. Keep in mind that these varying stances and actions do not necessarily indicate proof of harm.

Vietnam. Glyphosate has been banned in Vietnam for several years, with cited reasons including "low biological effectiveness" and harm to human health. This decision prompted significant criticism in 2019, with then U.S. Secretary of Agriculture Sonny Perdue suggesting that "Vietnam’s farmers will turn to unregulated, illegal chemical products in place of glyphosate.”
Thailand. At one point expected to ban glyphosate, Thailand reversed course, possibly (according to documents reviewed by Reuters) in response to pressure from the U.S. government. Spokeswoman Ratchada Dhanadirek referenced the lack of a viable alternative as playing into the ban's reversal.
Sri Lanka. Although Sri Lanka was the first country to fully ban glyphosate, this effort was short-lived; the ban was partially reversed in 2018 and then revoked in its entirety in 2022. Critics believe that lobbying and political concerns influenced this reversal, but there were also reports of smuggled glyphosate at the time.
Mexico. Although Mexico once decreed a phaseout of glyphosate (along with genetically modified corn), this plan was later revised. A report from Mexico's National Council of Humanities, Sciences, and Technologies (CONAHCYT), however, casts doubt on the use of this herbicide, claiming that it prompts "carcinogenic effects through different routes, acting as an endocrine disruptor, altering reproductive systems, and causing various metabolic diseases and affectations in different organs and systems."
Argentina. While Argentina is one of the world's largest users of products such as glyphosate, the herbicide is already banned in several Argentinian towns. Meanwhile, the province of Misiones has sparked considerable controversy by stating the intention to ban glyphosate and "promote products of biological origin."
Germany. Offering yet another example of delayed phase-out plans, Germany has yet to fully commit to ending the herbicide. However, the country has heavily restricted its use. The agricultural ministry tells Reuters that the use of glyphosate is generally prohibited in "protected water areas, domestic gardens, and allotments."
Canada. In a 2017 review of the use of glyphosate, Health Canada concluded that, if "used properly according to product label instructions," glyphosate-containing products were not likely to cause harmful effects. In Quebec, however, glyphosate has been banned in Crown land forests since 2001.

So, Does Roundup Cause Cancer — and Is Roundup Safe?

Question	Summary of Evidence
Does Roundup cause cancer?	IARC deems Roundup/glyphosate “probably carcinogenic” (Group 2A) based on limited human, sufficient animal, and mechanistic evidence. However, many regulatory bodies remain unconvinced or classify the hazard as low.
Is Roundup safe under realistic exposure?	Regulatory assessments (e.g., EPA) generally conclude that glyphosate is unlikely to be carcinogenic at real-world doses—assuming correct product use.
Where is the evidence strongest?	The strongest (though still modest) associations are between glyphosate exposure and non-Hodgkin lymphoma in high-exposure groups (e.g., some agricultural workers).
What are major uncertainties?	Exposure misclassification, confounding, co-formulant effects, unstudied populations (infants, long-latency), and evolving mechanistic data.
What should public health practice emphasize?	Apply the precautionary principle: minimize unnecessary exposure, promote safer alternatives, and continue rigorous monitoring and research.

Explore Complex Health Issues With TAMU's MPH Program

Glyphosate exposure represents just one of many complex concerns within the field of environmental health. Explore these issues from new perspectives as you pursue your Master of Public Health. Through advanced, research-focused coursework, you will learn to examine studies with a critical eye.

The online MPH in Environmental Health from Texas A&M covers complex global health concerns, including the influence of glyphosate and other agricultural products. Learn more about TAMU's online MPH and discover your role in safeguarding the public.