Children, Dogs and the Chemically Treated Lawn

The Cancer Risk Underfoot

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American families have spent decades applying herbicides and pesticides to American lawns. Dogs walk through them barefoot. Children crawl and play on them. The remarkable thing is how little serious research has been done to determine the extent of the biological injury and long-term health effects associated with these exposures.

Every spring, lawn-care trucks begin making their rounds through American neighborhoods. Herbicides kill the broadleaf weeds. Insecticides kill the grubs and other insects. Fungicides may be added where needed. On some occasions, a small sign is planted in the yard advising people and pets to remain off the grass for a period of time. Then the sign disappears, the children and dogs go back outside, and everyone assumes the problem has disappeared with it. Or, more likely, no signage is ever posted, and no one questions whether that lawn has a toxic film lingering on its blades of grass.

There is an important distinction that is easily overlooked in studies of residential pesticide exposure: adults, children, and dogs do not use a lawn in the same way. An adult generally walks across grass wearing shoes, remains upright, and has little direct contact with the ground. A dog walks across it on bare paws, lies in it, rolls in it, carries residues on its feet and coat into the house, and then licks its paws and grooms its body. A young child sits and plays on the grass, repeatedly touches the ground, puts hands and objects into the mouth, and then spends considerable time playing on the floors of the same house.

Those are fundamentally different routes of exposure. And the limited research that has actually measured what happens after a lawn is treated suggests that distinction matters.

There is also the matter of residue. Sunlight breaks down some chemicals more readily than others. Rain may wash residues from treated surfaces, while dew can dilute or redistribute them. How long these chemicals remain on grass, soil, and other surfaces varies considerably depending on the chemical, weather conditions, and how and where it was applied.

The rules governing treated lawns are a patchwork of federal and state law. At the federal level, EPA-approved pesticide labels are legally enforceable under FIFRA, and many lawn products instruct applicators to keep people and pets off treated turf until the spray has dried, or until a granular product has been watered in and the surface is dry. States can impose additional notification requirements, and these vary considerably.

New York, for example, requires commercial lawn applicators to post markers and instructs that they remain for at least 24 hours, while New Jersey requires signs for commercial turf applications that may be removed after 72 hours. Virginia is much less restrictive: its pesticide law does not generally require commercial applicators to notify or post residential lawns unless the pesticide label itself requires it, although HOAs must post conspicuous notice in common areas at least 48 hours before an application.

A national review published in 2000 found that roughly 30 states had no statewide requirement for posting treated lawns. More than two decades later, there appears to be no comprehensive, publicly available 50-state review documenting how those laws have changed, leaving even the current extent of pesticide-notification requirements surprisingly difficult to determine.

Most importantly, “dry” does not mean “gone.” It means that the liquid carrier has dried sufficiently to satisfy the product's reentry instruction. The pesticide and its residues may remain on grass, soil, leaves, shoes, paws and other surfaces well after the lawn is dry.

There is no federal requirement that pesticide-treated public parks be routinely posted for the public, and state requirements vary widely. That means a baby crawling on exposed grass is more likely than not to come into contact with herbicides and pesticides soon after application.

Federal law also does not require warning signs after pesticides are applied in public parks, on school grounds, or at playgrounds.

Lawn Chemicals, Dogs and Cancer

In 2004, researchers studied Scottish Terriers, a breed with an unusually high susceptibility to transitional cell carcinoma of the bladder. Eighty-three dogs with bladder cancer were compared with 83 controls. Dogs exposed to lawns or gardens treated with herbicides had 3.6 times the odds of developing bladder cancer compared with dogs exposed to untreated lawns. Exposure to both herbicides and insecticides was associated with 7.2 times the odds, while exposure specifically to phenoxy herbicides, the family that includes 2,4-D, was associated with approximately 4.4 times the odds.

This was an observational study and cannot establish with 100% certainty that the chemicals caused the cancers; the genetic susceptibility of Scottish Terriers makes them an unusual study population. Nevertheless, the magnitude of the associations raised an obvious additional question: were dogs living around treated lawns actually absorbing these chemicals?

An earlier study had measured the common lawn herbicide 2,4-D in canine urine. Among 44 dogs potentially exposed to 2,4-D-treated lawns, 75 percent had urinary concentrations of at least 10 μg/L. Dogs with access to lawns treated within the preceding seven days had the highest urinary concentrations.

In 2013, Purdue researchers examined this question more directly by measuring common herbicides on residential lawns and in the urine of dogs living at those homes. Herbicides were detected in the animals, including in some dogs whose owners reported that their own lawns had not been treated. The authors raised the possibility that these dogs were being exposed through neighboring properties, walks, or other environmental sources.

There is also evidence involving canine lymphoma. A 1991 case-control study reported an association between owners’ use of 2,4-D herbicides and malignant lymphoma in their dogs, although the finding subsequently became controversial and an industry-funded reanalysis challenged the strength of the association. A larger 2012 study involving more than 700 dogs found that professionally applied lawn pesticides were associated with approximately 70 percent higher odds of canine malignant lymphoma.

Given the widespread use of these products, the findings warranted a much larger and more systematic research effort. That research effort largely failed to materialize.

A Brief History of 2,4-D

2,4-D (2,4-dichlorophenoxyacetic acid) emerged from wartime research in the early 1940s and became one of the first widely used selective herbicides, killing broadleaf weeds while leaving most grasses relatively unharmed. It rapidly became a mainstay of agriculture and later of residential lawn care.

During the Vietnam War, 2,4-D was one of the two principal chemicals combined to make Agent Orange.

Despite more than 80 years of widespread use, scientific research on the chronic health effects of 2,4-D remains limited. Cancer has received the most attention, particularly non-Hodgkin lymphoma.

The human cancer literature is concerning. An early National Cancer Institute study found increasing odds of non-Hodgkin lymphoma with increasing frequency of 2,4-D exposure, with approximately threefold higher odds among farmers who mixed or applied it more than 20 days per year after adjustment for certain other pesticide exposures. Other studies did not find an association with non-Hodgkin lymphoma. But a later meta-analysis of 12 observational studies found that nine reported elevated risk estimates and calculated a 38 percent higher risk of non-Hodgkin lymphoma overall and a 73 percent higher risk among the more highly exposed groups.

Other potential chronic effects, including neurological, reproductive, endocrine, thyroid, and immune effects, have been studied much less extensively. Much of the available human research involves farmers and pesticide applicators, frequently relies on estimated rather than measured exposure, and must contend with exposure to multiple agricultural chemicals.

What is particularly lacking is long-term, independent research using measured exposure to determine the effects of repeated low-level residential exposure among children, adults, and other people who routinely use treated lawns and public spaces.

In 2015, the World Health Organization’s International Agency for Research on Cancer classified 2,4-D as “possibly carcinogenic to humans” (Group 2B). IARC found inadequate evidence of carcinogenicity in humans, limited evidence in experimental animals, strong evidence that 2,4-D induces oxidative stress, and moderate evidence that it causes immunosuppression. Importantly, “inadequate evidence” does not mean that studies demonstrated no cancer risk. It means that there have not been enough human studies to establish whether 2,4-D causes cancer in humans.

EPA, by contrast, continues to permit 2,4-D and states that registered products can be used safely when label directions are followed.

Residential Transport of 2,4-D Indoors

One of the most informative studies was not a cancer study at all. Researchers applied 2,4-D to residential lawns and then sampled the interiors of the homes before and after application. They tested indoor air, floors, tables, windowsills and household dust.

After the lawn was treated, 2,4-D was detected in indoor air and on surfaces throughout the homes. The investigators identified the homeowner who applied the chemical and an active family dog as the two most important mechanisms carrying 2,4-D indoors. Once inside, contaminated floor dust was resuspended into the air and redistributed onto tables and other surfaces.

This is where the canine and childhood questions converge. The dog is not merely exposed to the treated lawn. It can become a vehicle carrying residues from the lawn into the environment where a child spends much of the day.

The investigators estimated that nondietary 2,4-D exposure for young children after lawn treatment could be approximately ten times higher than before application. Their estimated exposures from contact with floors alone were 1–10 μg per day, with additional exposure estimated from contact with tabletops.

That finding also challenges the comforting assumption that the principal exposure ends once the spray has dried. The lawn is only the beginning of the pathway. Material can move from grass to shoes and paws, from shoes and paws to floors, from floors into dust and air, and ultimately from hands to mouths.

The Childhood Cancer Studies

A systematic review and meta-analysis of 15 studies found that residential herbicide exposure during pregnancy was associated with 61 percent higher odds of childhood leukemia. Residential insecticide exposure during pregnancy showed an even larger association, approximately doubling the odds. Childhood exposure to residential insecticides was also associated with increased leukemia risk, although childhood herbicide exposure itself was not statistically significant in that particular analysis.

A separate meta-analysis published in Pediatrics in 2015 examined 16 studies involving approximately 7,400 childhood cancer cases and 9,400 controls. Childhood exposure to residential herbicides was associated with 26 percent higher odds of leukemia. Indoor residential insecticide exposure was associated with 47 percent higher odds of leukemia and 43 percent higher odds of lymphoma. The authors emphasized that the relatively small number of available studies remained an important limitation.

What these studies generally do not tell us is what happens decades later. We have remarkably little prospective research following children with documented pesticide or herbicide exposure into their thirties, forties, and beyond to determine whether early-life exposure alters their subsequent cancer risk.

That question has become more important as the incidence of several cancers in younger adults has increased. A major review in Nature Reviews Clinical Oncology concluded that early-onset cancers, generally defined as cancers diagnosed before age 50, have been increasing in multiple countries since the 1990s. The increases involve cancers of the breast, colorectum, endometrium, kidney, pancreas, stomach, thyroid and several other organs. The authors specifically identified changes in the early-life exposome, including environmental exposures, as one area requiring much more investigation and called for prospective studies capable of linking childhood exposures with cancers occurring decades later.

The trend is also apparent in U.S. cancer-registry data. An analysis of more than 562,000 Americans diagnosed with cancer before age 50 found that overall early-onset cancer incidence increased between 2010 and 2019, while cancer incidence among people 50 and older declined. The increase was particularly apparent among adults aged 30 to 39, and gastrointestinal cancers showed the fastest increase as a group. Globally, an analysis of the Global Burden of Disease database reported a 79 percent increase in the number of early-onset cancer cases between 1990 and 2019, although population growth and demographic changes account for part of that increase.

We have evidence that children are exposed, epidemiological evidence associating residential pesticide exposure with childhood cancers, and a documented rise in several cancers among younger adults. What is largely missing are the long-term studies needed to determine whether those observations are connected.

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What Is MAHA-GOV Doing?

The MAHA initiative has begun to address some of these larger questions. In 2026, the Administration directed HHS, USDA, and EPA to develop a research framework for cumulative chemical exposures and directed HHS to establish an NIH challenge to improve the measurement and evaluation of those exposures. NIH and NIEHS have also begun encouraging new research that combines environmental monitoring, biomonitoring, and biomedical research to understand how environmental chemicals, including pesticides, affect health over a lifetime. EPA, meanwhile, is currently conducting its registration review of 2,4-D, with an interim regulatory decision scheduled for 2026.

These are important developments. But I can find no new federal research program specifically following children and companion animals living in homes where lawns are chemically treated, despite decades of evidence showing that lawn chemicals enter homes, are absorbed by exposed animals, and are associated in epidemiological studies with serious health outcomes.

Studies have reported associations between lawn herbicide and pesticide exposure and bladder cancer and lymphoma in dogs, while human studies and meta-analyses have associated residential pesticide exposure during pregnancy and childhood with increased risks of childhood leukemia and lymphoma.

Nor do I find a new MAHA-era federal requirement for warning signs following pesticide applications to residential lawns, parks or school grounds. EPA’s current public guidance on 2,4-D continues to state that registered products can be used safely when label directions are followed.

MAHA has therefore identified the larger problem of environmental and cumulative chemical exposure, but the residential lawn remains an important gap. A prospective study measuring lawn residues, household contamination, and biological exposure in children, adults, and dogs would align closely with MAHA’s stated commitment to studying environmental contributors to chronic disease. After more than thirty years of preliminary evidence, this would seem an appropriate time to conduct it.

MAHA-Gov has apparently decided that independent “truth-tellers” like me are no longer welcome to communicate directly with government officials. So I am asking readers to do it instead.

Please contact your members of Congress, the EPA and NIH and ask them to support independent, prospective research into the long-term health effects of residential herbicide and pesticide exposure, particularly in children and companion animals.

Ask EPA to reconsider whether current notification, signage and reentry requirements adequately protect children and pets on lawns, school grounds and public parks. Feel free to reference or send them this article.

Contact your government:

Congress: Find and contact your U.S. Representative
All elected officials: USAGov directory of federal, state and local officials
EPA Office of Pesticide Programs: Contact EPA about pesticides
EPA pesticide regulation and registration review: EPA pesticide regulatory contacts
NIH: Contact the National Institutes of Health

Thirty Years of Evidence, but No Prospective Answer

This is ultimately what I find most troubling about the literature. The first study reporting an association between lawn use of 2,4-D and canine lymphoma appeared in 1991. Researchers measured 2,4-D in the urine of dogs exposed to treated lawns in 1994. By 2001, researchers had demonstrated that lawn-applied 2,4-D could be transported into homes and estimated that nondietary exposure among young children increased substantially following application. In 2004, the Scottish Terrier study reported strong associations between exposure to treated lawns and bladder cancer.

The federal government participated in some of this research. EPA supported work examining the movement of lawn-applied 2,4-D into homes and children’s potential exposure. NIH, NCI and EPA supported important research examining residential pesticide exposure and childhood leukemia, and National Cancer Institute investigators participated in the original canine lymphoma study. These were not obscure observations occurring entirely outside the federal research establishment.

This early work done decades ago, was followed by… crickets.

What did not follow was a large, prospective research program designed to determine what these exposures mean over time. Much of the subsequent canine research depended instead upon universities, breed organizations, the American Kennel Club Canine Health Foundation, and private funding. Despite decades of concern about environmental exposures and cancer, including the Cancer Moonshot’s emphasis on cancer prevention, I can find no major federal program that followed children and dogs living in households with chemically treated lawns while directly measuring their exposures and subsequent health outcomes.

Such research is entirely feasible. Households could be enrolled before the lawn-treatment season, including families that use professional lawn services and those that do not chemically treat their lawns. Every product and concentration applied could be documented. Grass, soil and household dust could be sampled before and after treatment, while urine or other biological samples could be collected repeatedly from adults, children and dogs living in the same homes. Rather than attempting to reconstruct exposure years later from questionnaires, investigators could measure what actually enters the body, how long residues remain in the home, and how repeated applications affect exposure over an entire season. Long-term follow-up could then begin to address the much more important question of whether these measured exposures are associated with chronic disease. This could have all been done by now, including adult follow-up of pregnancy and childhood exposures.

But after more than thirty years of findings involving measurable canine exposure, transport of lawn chemicals into homes, associations with cancers in dogs, and epidemiological associations between residential pesticide exposure and childhood cancers, the absence of definitive evidence of harm cannot reasonably be treated as evidence of safety.

These are also largely avoidable exposures. We are not discussing a drug needed to treat disease or an unavoidable environmental contaminant. Residential herbicides and insecticides are commonly applied because homeowners want lawns without weeds or insects, to public parks and school grounds. Children and dogs, meanwhile, have substantially more direct contact with grass, soil and household floors than most adults and have behaviors that can increase ingestion of residues.

More than thirty years after the first of these findings, we are still applying these chemicals to lawns, parks, and other places where children and animals play without adequately answering the long-term health question.

A green, weed-free lawn is a trivial benefit against which to accept an avoidable and still poorly characterized exposure. Until we know considerably more, I see little justification for routinely applying these chemicals where children and animals live and play.

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References

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10. International Agency for Research on Cancer. 2,4-Dichlorophenoxyacetic acid. In: DDT, Lindane, and 2,4-D. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 113. Lyon, France: International Agency for Research on Cancer; 2018.

11. Ugai T, Sasamoto N, Lee HY, et al. Is early-onset cancer an emerging global epidemic? Current evidence and future implications. Nat Rev Clin Oncol. 2022;19(10):656–673. doi:10.1038/s41571-022-00672-8.

12. Koh B, Tan DJH, Ng CH, et al. Patterns in cancer incidence among people younger than 50 years in the US, 2010 to 2019. JAMA Netw Open. 2023;6(8). doi:10.1001/jamanetworkopen.2023.28171.

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14. U.S. Environmental Protection Agency. 2,4-D. Ingredients Used in Pesticide Products. Updated January 23, 2026. EPA notes that 2,4-D has been used since the 1940s, is used on turf and residential lawns, remains under registration review, and states that registered products can be safely used when label directions are followed.

15. U.S. Environmental Protection Agency. Introduction to Pesticide Labels. EPA. 2026. Describes pesticide labeling requirements under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and explains that pesticide labels are legally enforceable.

16. New York Environmental Conservation Law § 33-1003. Visual Notification. Requires commercial lawn applicators to place visible markers on treated property and instructs that the markers not be removed for at least 24 hours.

17. New Jersey Administrative Code § 7:30-9.13. Notification: Turf or Ornamental Applications. Requires posting following commercial turf pesticide applications, including applications at residences, schools, institutions and parks; signs may be removed after 72 hours.

18. Code of Virginia § 55.1-1818. Common Areas; Notice of Pesticide Application. Requires property owners’ associations to post conspicuous notice in common areas at least 48 hours before pesticide application.

19. U.S. Environmental Protection Agency. Pest Control in the School Environment: Implementing Integrated Pest Management (IPM). EPA 735-F-17-004. Washington, DC: EPA; 2017. Discusses pesticide notification and posting at schools and notes that requirements vary by state and locality.

20. The White House. Executive Order 14414: Advancing Regenerative Agriculture and Strengthening American Farm Resilience. June 25, 2026. Directs USDA, HHS and EPA to develop a research and evaluation framework for cumulative chemical exposure and directs HHS, in consultation with USDA and EPA, to establish an NIH challenge addressing cumulative chemical exposures.

21. U.S. Department of Health and Human Services. President Trump Signs Executive Order Advancing Regenerative Agriculture as Part of Make America Healthy Again Agenda. June 25, 2026. Announces an NIH Grand Prize Challenge addressing cumulative chemical exposures and ARPA-H research intended to reduce reliance on conventional chemical crop-protection tools.

22. National Institutes of Health. Integrating Environmental Science and Engineering with Biomedical Research for Effective Exposure Prevention and Disease Intervention. NIH Highlighted Topics. Posted June 18, 2026. Encourages research combining environmental monitoring, personal exposure monitoring, biomonitoring and biomedical research involving environmental chemicals, including pesticides.

23. National Institutes of Health. Characterizing Indoor Exposures to Advance Exposome Research. NIH Highlighted Topics. Posted July 9, 2026. Calls for research identifying sources of indoor environmental exposure, quantifying exposure, and evaluating contributions to health burden.

24. National Institutes of Health. Detecting and Evaluating Contaminants of Emerging Concern: Optimizing Data-driven Exposure Characterization. NIH Highlighted Topics. Posted July 31, 2026. Identifies major gaps in understanding environmental exposure pathways, biological uptake and chronic outcomes including endocrine disruption, neurotoxicity, immune dysfunction, reproductive toxicity and cancer.