Glyphosate in Breast Milk? What the Research Found, How the EPA Reviews Pesticides, and How the Public Can Weigh In

In 2014, a group of mothers met with officials at the U.S. Environmental Protection Agency to demand answers about glyphosate, the active ingredient in Roundup. The group had commissioned tests of a small number of breast milk samples and reported detecting the herbicide. The meeting and the test results spread quickly online, with headlines warning that a weed killer was showing up in mothers’ milk.

The episode raised two questions that still matter. First, does glyphosate actually get into breast milk? Second, how does the EPA decide whether a pesticide is safe, and how can members of the public influence those decisions? This article answers both, drawing on peer-reviewed research and on EPA’s own descriptions of its process.

What the 2014 Tests Found, and Why They Were Questioned

The advocacy group reported that some of the breast milk samples it had tested contained glyphosate at levels it described as far above what would be expected. The findings were widely shared but were never published in a peer-reviewed journal. Scientists raised several concerns about the testing. The method used was an immunoassay test kit designed for measuring glyphosate in water, not in a complex fluid like breast milk, which contains fats, proteins, and sugars that can interfere with such tests and produce false positives. The number of samples was small, and the results were not independently replicated.

None of this means the mothers’ concerns were unreasonable. Glyphosate is the most widely used herbicide in the world, and questions about where it ends up in the body are legitimate. But answering those questions requires validated methods and transparent data.

What Peer-Reviewed Research Found

In 2016, researchers at Washington State University and the University of Idaho published a study in the American Journal of Clinical Nutrition designed to answer the question directly. Michelle McGuire and colleagues collected 41 breast milk samples and 40 urine samples from healthy lactating women living in or near the Pullman, Washington, and Moscow, Idaho, area. They analyzed the samples for glyphosate and its main breakdown product, AMPA, using highly sensitive and specific methods validated for milk.

Glyphosate and AMPA were not detectable in any of the milk samples. Low levels were detected in some urine samples. The authors concluded that their data provided evidence that glyphosate and AMPA are not bioaccumulating in breast milk at detectable levels and that typical exposure to glyphosate from food and the environment is low. The milk assay could detect concentrations down to 1 microgram per liter, and mean urinary glyphosate levels were about 0.28 micrograms per liter. The study was registered in advance at ClinicalTrials.gov, and the authors disclosed their funding sources.

The finding is consistent with glyphosate’s chemistry. Glyphosate dissolves readily in water, does not accumulate in fat, and is excreted from the body mainly through urine within days. That is why national biomonitoring finds it commonly in urine: a CDC-led analysis of 2013–2014 national survey data detected glyphosate in the urine of about 81 percent of Americans aged six and older, generally at low concentrations. Chemicals that do build up in breast milk, such as some older pesticides like DDT, PCBs, and certain PFAS compounds, tend to be persistent, fat-soluble, or both.

For breastfeeding parents, the practical message is reassuring. Major health organizations continue to recommend breastfeeding, noting that its benefits for infants and mothers far outweigh known risks from environmental contaminants. People who want to reduce their own glyphosate exposure can do so through diet, for example by choosing organic versions of foods most likely to carry residues.

How the EPA Approves a Pesticide

Pesticides in the United States are regulated mainly under two laws. The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) requires that pesticides be registered by the EPA before they can be sold or distributed. The Federal Food, Drug, and Cosmetic Act gives the EPA authority to set tolerances, the maximum legal residue levels allowed on food.

According to the EPA, before a pesticide can be registered, the manufacturer must submit data showing that, when used according to label directions, it will not cause unreasonable adverse effects on people or the environment. Applicants typically submit a large package of studies on toxicity, environmental fate, effects on wildlife, and residues on crops. EPA scientists evaluate these studies, conduct human health and ecological risk assessments, and decide whether to register the product, what uses to allow, and what label restrictions, protective equipment, and application rules to require.

Protecting children: the Food Quality Protection Act

The Food Quality Protection Act of 1996 changed how the EPA sets food tolerances. It requires the agency to ensure a reasonable certainty of no harm from aggregate exposure to a pesticide, considering residues in food, drinking water, and residential uses together. It also requires the EPA to consider the special susceptibility of infants and children and to apply an additional tenfold safety factor to protect them unless reliable data show a different factor is safe. And it requires consideration of cumulative effects from pesticides that share a common mechanism of toxicity.

Re-evaluation over time

Registration is not permanent. Under its registration review program, the EPA must re-evaluate each registered pesticide at least every 15 years to determine whether it still meets the legal standard in light of new science, changes in use, and updated risk assessment methods. Registration review can lead to new restrictions, label changes, cancellation of some uses, or, in some cases, cancellation of the product.

A Short History of U.S. Pesticide Regulation

Federal pesticide law began in 1947 with the original Federal Insecticide, Fungicide, and Rodenticide Act, which focused mainly on labeling and product effectiveness. Public concern grew in the 1960s, especially after the publication of Rachel Carson’s Silent Spring in 1962 drew attention to the effects of DDT and other pesticides on wildlife. The Environmental Protection Agency was created in 1970 and took over pesticide regulation. Amendments to FIFRA in 1972 shifted the law toward protecting health and the environment, and the same year the EPA canceled most uses of DDT.

The next major change came with the Food Quality Protection Act of 1996, passed unanimously by Congress, which tightened standards for pesticide residues in food, added special protections for infants and children, and required the EPA to reassess existing tolerances. The registration review program, requiring periodic re-evaluation of every registered pesticide, followed in later amendments. Each reform responded to new science and public pressure, a pattern that continues today.

How Food Residue Limits Are Set

Setting a tolerance involves several steps. EPA scientists first identify the lowest dose at which a pesticide causes adverse effects in animal studies, or the highest dose at which no adverse effects are observed. They then divide that dose by uncertainty factors to derive a reference dose considered safe for daily exposure over a lifetime. Typically, a factor of 10 accounts for differences between animals and humans, and another factor of 10 accounts for variation among people. Under the Food Quality Protection Act, an additional factor, by default 10, is applied to protect infants and children unless reliable data show a smaller factor is adequate.

The agency then estimates how much of the pesticide people are likely to consume from all foods and drinking water, together with residential exposure, using data on food consumption and residue levels. Tolerances are set so that estimated aggregate exposure stays below the reference dose for all population groups, including young children, who eat more food relative to their body weight. Critics argue that the process relies too heavily on industry-generated studies and may not fully capture effects of mixtures or low-dose endocrine effects; supporters point to the large built-in safety margins.

What Biomonitoring Can and Cannot Tell Us

Measuring chemicals in urine, blood, or breast milk shows whether people have been exposed and roughly how much. It is a powerful tool for tracking exposure over time and comparing groups, such as farmworkers and the general public. But detecting a chemical is not the same as showing harm. Modern analytical methods can detect extremely small amounts, and the health significance of a measured level depends on comparing it with levels associated with effects in toxicology and epidemiological studies.

For glyphosate, national biomonitoring shows widespread low-level exposure, mostly from diet, at concentrations well below those associated with effects in toxicology studies. Whether chronic low-level exposure has subtle long-term effects remains an active research question. For persistent chemicals that accumulate in the body, biomonitoring has been especially valuable in showing that bans and restrictions reduce exposure over time.

Where Glyphosate Stands at the EPA

Glyphosate is currently in registration review. The EPA has repeatedly concluded that glyphosate is not likely to be carcinogenic to humans at expected exposures, a conclusion that differs from the 2015 classification by the World Health Organization’s cancer research agency of glyphosate as probably carcinogenic. In 2022, a federal appeals court found that the EPA had not adequately supported parts of its human health analysis, and the agency withdrew its interim decision while it continues the review. The EPA’s glyphosate page tracks the status of the review.

In June 2026, the U.S. Supreme Court ruled in Monsanto Co. v. Durnell that federal pesticide law preempts state-law failure-to-warn claims seeking cancer warnings beyond those EPA has approved. The ruling makes the EPA’s labeling decisions even more consequential and increases the importance of public participation in the agency’s review.

How Other Regulators Approach Pesticides

The European Union approves pesticide active substances at the EU level and authorizes products at the national level. Its system includes hazard-based cut-off criteria: substances classified as certain categories of carcinogens, mutagens, reproductive toxicants, or endocrine disruptors can generally not be approved, regardless of exposure levels, with limited exceptions. Approvals are time-limited and must be renewed. Glyphosate’s approval was renewed in 2023 for ten years after European agencies concluded it did not meet the criteria for classification as a carcinogen, though the renewal included conditions and was politically contentious.

The U.S. system relies more on risk assessment, weighing hazard against expected exposure. Each approach has supporters and critics: hazard-based systems are seen as more precautionary, while risk-based systems are seen as more tailored to real-world exposure.

How Residues in Food Are Monitored

The USDA’s Pesticide Data Program tests thousands of food samples each year, focusing on foods commonly eaten by children, and publishes annual summaries. The FDA tests domestic and imported foods for compliance with EPA tolerances. These programs have generally found that most samples have residues below tolerances or no detectable residues, with a small percentage of violations, more often in imported foods. Glyphosate has been included in monitoring less consistently than many pesticides because it requires specialized testing methods, a gap that advocacy groups and some researchers have highlighted.

How the Public Can Weigh In

Many people assume regulatory decisions happen behind closed doors. In practice, the EPA’s pesticide program publishes many of its key documents and invites public comment at several stages.

Find the docket. Each registration review and many new registration decisions have a public docket on regulations.gov, the federal government’s online portal for rulemaking. Searching for a pesticide’s name and “registration review” usually finds it. Dockets contain risk assessments, proposed decisions, supporting studies summaries, and comments submitted by others.

Watch for comment periods. The EPA announces comment periods in the Federal Register and on its website. Typical periods last 30 to 60 days and may be extended on request.

Write an effective comment. Comments carry the most weight when they are specific. Identify the document and section you are responding to, explain your concern clearly, provide evidence such as peer-reviewed studies or data, and suggest concrete changes, such as additional label restrictions or monitoring. Personal experience, such as how a pesticide is used in your community, can be valuable when it adds information the agency may lack. Large numbers of identical form letters are counted but generally carry less weight than substantive, evidence-based comments.

Know what comments can and cannot do. The EPA must consider substantive comments and respond to significant issues raised, but decisions are based on the legal standard and the scientific record, not on the number of comments for or against.

Use other channels. Citizens and organizations can petition the EPA to take specific actions, such as revoking tolerances. Agencies also hold stakeholder meetings, and members of the public can contact their congressional representatives about pesticide policy.

State-Level Actions

States also regulate pesticide use, sometimes more strictly than federal rules, for example by restricting certain pesticides near schools or limiting cosmetic lawn use. California listed glyphosate under Proposition 65 in 2017 as a chemical known to the state to cause cancer, based on the IARC classification. Litigation followed over whether companies could be required to place cancer warnings on glyphosate products, and a federal appeals court ruled in 2023 that requiring the warning would violate the First Amendment because the warning was not purely factual and uncontroversial given the scientific disagreement. State and local restrictions on glyphosate use in parks and public spaces exist in many places.

Why Testing Methods Matter

The contrast between the 2014 advocacy tests and the 2016 peer-reviewed study comes down largely to methods. Measuring trace chemicals in biological fluids is technically demanding.

Immunoassays, such as ELISA test kits, use antibodies that bind to a target chemical. They are fast and inexpensive and work well for the samples they were designed and validated for, such as drinking water. In complex fluids like milk, fats, proteins, and other compounds can interfere with the antibody reaction and produce false positive or inaccurate results unless the method has been specifically validated for that matrix.

Liquid or gas chromatography with tandem mass spectrometry separates the components of a sample and identifies chemicals by their exact molecular mass and fragmentation pattern. These methods are more specific and, when validated, can measure very low concentrations reliably. They are the standard for regulatory and research measurements of pesticide residues.

Validation and quality control mean demonstrating that a method can accurately detect and measure a chemical in a specific type of sample, using spiked samples with known amounts, blanks, and replicate measurements. Results from unvalidated methods should be treated as preliminary at best.

These technical points are not a reason to dismiss citizen science. Community testing can raise important questions and prompt rigorous follow-up research, as happened in this case. But conclusions about health risks need to rest on validated measurements.

What Breast Milk Monitoring Has Shown Over Time

Breast milk has been used for decades to monitor human exposure to persistent chemicals, because many of them accumulate in body fat and are released into milk. Monitoring programs in several countries documented high levels of the pesticide DDT and industrial PCBs in breast milk in the mid-20th century. After those chemicals were banned or restricted in the 1970s, levels in breast milk declined substantially, one of the clearest demonstrations that regulation can reduce human exposure.

More recent monitoring has focused on newer persistent chemicals, such as certain flame retardants and PFAS compounds, some of which have also declined after being phased out. Glyphosate, being water-soluble and rapidly excreted, behaves differently from these chemicals, which is consistent with the 2016 finding that it was not detectable in milk.

Who Regulates What

Agency	Role in pesticide oversight
U.S. EPA	Registers pesticides, sets label requirements and food residue tolerances, conducts registration review
U.S. FDA	Enforces tolerances for most foods by testing domestic and imported products for residues
USDA	Enforces residue limits in meat, poultry, and eggs; runs the Pesticide Data Program measuring residues in foods
CDC	Measures chemical exposures in the U.S. population through national biomonitoring
State agencies	License applicators, enforce use rules, may impose stricter local restrictions and warning requirements

Reducing Exposure During Pregnancy and Breastfeeding

For parents who want to minimize pesticide exposure while pregnant or breastfeeding, several practical steps help without giving up the benefits of a varied diet.

Keep eating plenty of fruits and vegetables. Their nutritional benefits are well established. If budget allows, choose organic versions of produce that tends to carry more residues, such as berries, leafy greens, and apples.

Wash produce under running water. This removes some surface residues along with dirt and microbes.

Limit home pesticide use. Use non-chemical methods for weeds and pests where possible, and if pesticides are necessary, have someone else apply them, follow label directions, and stay away until sprays have dried.

Take care near agricultural spraying. If you live near fields that are sprayed, keep windows closed during applications and ask about local notification programs.

Continue breastfeeding. Health authorities recommend breastfeeding because its benefits for infants and mothers outweigh known risks from environmental contaminants.

Advocacy and Science Working Together

The glyphosate breast milk episode illustrates how public concern and scientific research can interact productively. An advocacy group raised a question that mattered to many parents. Its testing was not rigorous enough to answer that question, but it prompted researchers to conduct a careful study, which provided a clearer answer. Along the way, the EPA heard directly from concerned mothers.

The lesson for both sides is that concerns deserve to be taken seriously and investigated, and that investigations need methods capable of producing reliable answers. Public participation in regulatory review works best when it combines lived experience with evidence.

Farmworkers and Rural Communities

While dietary exposure to glyphosate is generally low, people who mix and apply it, and families living near treated fields, can have higher exposure. A 2024 biomonitoring study of farmers and non-farmers in the Agricultural Health Study found that farmers who had recently applied glyphosate had higher urinary concentrations than non-farmers. Protective equipment, careful mixing and loading, maintained equipment, and washing after use all reduce exposure. For families near treated fields, keeping windows closed during spraying, removing shoes at the door, and washing work clothes separately help limit take-home exposure.

Concerns raised by mothers in 2014 were about everyday dietary exposure. The evidence suggests the populations that most need attention are those with occupational and residential proximity to heavy use, which is where research and protection efforts are most valuable.

“Detected” Does Not Mean “Dangerous”

Modern laboratory methods can measure chemicals at parts per billion or even parts per trillion. Reports that a chemical was “detected” in food, water, or body fluids often sound alarming, but the important questions are how much was found and how that compares with levels associated with harm. A detection near the limit of a sensitive method may represent an exposure thousands of times lower than levels shown to cause effects. At the same time, the absence of established harm at low levels is not proof that no effect exists, especially for chemicals with incomplete research on long-term or developmental effects. Good reporting provides both the measured level and a meaningful comparison.

Resources for Concerned Parents

Parents who want to follow pesticide decisions can find official risk assessments and proposed decisions in EPA dockets on regulations.gov, and summaries on the EPA’s pesticide pages. National biomonitoring reports from the CDC describe exposure levels in the U.S. population. Pediatricians and lactation consultants can help families weigh specific concerns about diet and breastfeeding. Local cooperative extension offices offer guidance on reducing pesticide use at home and in gardens.

Key Terms

Registration: EPA approval allowing a pesticide product to be sold and used in the United States under specific label conditions.

Tolerance: The maximum amount of a pesticide residue legally allowed in or on a food.

Reference dose: An estimate of daily exposure to a substance that is likely to be without appreciable risk over a lifetime.

Registration review: The EPA’s periodic re-evaluation of each registered pesticide, at least every 15 years.

Docket: The public online file of documents and comments for a regulatory action, found on regulations.gov.

Biomonitoring: Measuring chemicals or their breakdown products in human samples such as urine, blood, or breast milk.

AMPA: Aminomethylphosphonic acid, the main breakdown product of glyphosate.

Immunoassay: A test using antibodies to detect a chemical; fast but requires validation for each sample type.

Frequently Asked Questions

Is glyphosate in breast milk?

A 2016 peer-reviewed study using validated methods found no detectable glyphosate or its main breakdown product in any of 41 breast milk samples. Earlier advocacy testing that reported detections used methods not validated for milk.

Why is glyphosate found in urine but not breast milk?

Glyphosate is water-soluble, does not accumulate in fat, and is excreted mainly in urine within days. Chemicals that build up in breast milk tend to be persistent and fat-soluble.

Should I stop breastfeeding because of pesticides?

No. Health authorities continue to recommend breastfeeding; its benefits far outweigh known risks from environmental chemicals. Reducing your own exposure through diet and limiting home pesticide use are reasonable steps.

How often does the EPA review pesticides?

Each registered pesticide must be re-evaluated at least every 15 years through the registration review program.

Can I comment on EPA pesticide decisions?

Yes. Proposed decisions are posted in public dockets on regulations.gov with comment periods, typically 30 to 60 days. Specific, evidence-based comments are most influential.

What extra protections exist for children?

The Food Quality Protection Act requires the EPA to consider children’s special susceptibility and apply an extra tenfold safety factor unless reliable data support a different margin.

References

1. McGuire MK, McGuire MA, Price WJ, et al. Glyphosate and aminomethylphosphonic acid are not detectable in human milk. American Journal of Clinical Nutrition. 2016;103(5):1285–1290. PMID 27030536
2. Ospina M, Schütze A, Morales-Agudelo P, et al. Exposure to glyphosate in the United States: Data from the 2013–2014 National Health and Nutrition Examination Survey. Environment International. 2022;170:107620. PMID 36368224
3. U.S. Environmental Protection Agency. About Pesticide Registration. epa.gov
4. U.S. Environmental Protection Agency. Registration Review Process. epa.gov
5. U.S. Environmental Protection Agency. Summary of the Food Quality Protection Act. epa.gov
6. U.S. Environmental Protection Agency. Glyphosate. epa.gov
7. Regulations.gov. Federal rulemaking dockets. regulations.gov

Last updated: October 1, 2026