2,4-D and Enlist Crops: What Dr. Oz Warned About, What Happened Next, and What Research Shows

What are Enlist crops, and is 2,4-D safe? Enlist corn, soybeans, and cotton are genetically engineered to tolerate 2,4-D, a herbicide in use since the 1940s, so farmers can spray it to kill weeds that glyphosate no longer controls. The World Health Organization’s cancer agency rates 2,4-D as possibly carcinogenic, and a meta-analysis linked heavy exposure to non-Hodgkin lymphoma, though evidence is mixed. U.S. regulators have approved its use with drift and runoff restrictions.

In 2014, as federal agencies prepared to approve a new generation of genetically engineered crops resistant to 2,4-D, television host Mehmet Oz urged viewers to speak out, warning that the change could greatly increase use of an old and controversial herbicide. Environmental groups and some farm groups raised similar concerns about drift damage to neighboring crops and about weeds evolving resistance yet again. The crops and the herbicide were approved, and 2,4-D-tolerant soybeans are now widely planted. This article explains what 2,4-D is, why Enlist crops were developed, what research shows about health risks and human exposure, and what the shift means for farmers, neighbors, and consumers.

What Is 2,4-D?

2,4-Dichlorophenoxyacetic acid, or 2,4-D, is one of the oldest synthetic herbicides, introduced in the 1940s. It mimics a plant growth hormone called auxin and causes broadleaf weeds to grow uncontrollably and die, while grasses such as corn and wheat are naturally less affected. It is used on farms, pastures, lawns, golf courses, and roadsides, and it appears in many home lawn weed killers. 2,4-D is often associated with Agent Orange, the defoliant used in the Vietnam War, which was a mix of 2,4-D and another herbicide, 2,4,5-T. The dioxin contamination responsible for Agent Orange’s worst health effects came from the manufacture of 2,4,5-T, which was later banned in the United States; 2,4-D itself remained on the market, as covered in our article on Monsanto’s chemical legacy and Agent Orange.

Why Were 2,4-D-Tolerant Crops Developed?

Because glyphosate stopped working on key weeds. After Roundup Ready crops spread in the late 1990s and 2000s, farmers relied heavily on glyphosate, and weeds adapted. A 2019 review in Plants by Vijay Nandula described how overreliance on herbicide-only weed control hastened the evolution of herbicide-resistant weeds, led by glyphosate-resistant Palmer amaranth, which severely reduced farm returns. Crops tolerant to auxin herbicides such as 2,4-D and dicamba were developed as a short-term answer. A 2016 analysis in Environmental Sciences Europe by Charles Benbrook documented the steep rise in glyphosate use driven by herbicide-tolerant crops, the pattern critics feared would repeat with 2,4-D.

How Were Enlist Crops and Herbicides Approved?

Through separate reviews by the USDA, which decides whether a genetically engineered plant can be grown commercially, and the EPA, which regulates the herbicide sprayed on it. The USDA cleared 2,4-D-tolerant corn and soybeans in 2014. According to the EPA, Enlist Duo, which combines 2,4-D choline salt with glyphosate, was first registered in 2014, and Enlist One, which contains only 2,4-D choline, was first registered in 2017. In January 2022, the EPA renewed time-limited registrations for both products in 34 states, with required measures to limit runoff and spray drift and with use prohibited in counties where the agency identified risks to endangered species. The legal history was rocky: environmental groups challenged the approvals in court, and the EPA briefly moved to withdraw the original registration in 2015 to review new information before reissuing it.

Does 2,4-D Cause Cancer?

The evidence is mixed and debated. In 2015, the International Agency for Research on Cancer classified 2,4-D as “possibly carcinogenic to humans” (Group 2B), as summarized in The Lancet Oncology by Dana Loomis and colleagues, citing strong evidence that 2,4-D causes oxidative stress and moderate evidence of immune suppression, with inadequate evidence in humans and limited evidence in experimental animals. A 2017 meta-analysis in Annals of Epidemiology by Smith and colleagues combined 12 observational studies and found a 38 percent higher risk of non-Hodgkin lymphoma among people ever exposed to 2,4-D, rising to 73 percent among the most highly exposed groups, mostly farmers and herbicide applicators. An analysis published in the same journal by Julie Goodman and colleagues, drawing on the large U.S. Agricultural Health Study, reached a more skeptical view of the association. Regulators in the United States, Canada, and Europe have concluded that 2,4-D used according to label directions does not pose unacceptable cancer risks, while acknowledging the need to limit exposure for workers who mix and spray it.

Are Americans Being Exposed to More 2,4-D?

National biomonitoring suggests so. A 2022 study in Environmental Health by Freisthler and colleagues analyzed urine samples from 14,395 participants in the National Health and Nutrition Examination Survey from 2001 to 2014. The share with 2,4-D above a set threshold rose from 17.1 percent in 2001–02 to 39.6 percent in 2011–12, and higher agricultural use of 2,4-D was associated with higher odds of elevated levels. Children aged 6 to 11 had about twice the odds of higher levels as adults aged 20 to 59, and women of childbearing age had higher odds than men of the same age. These data predate the widest adoption of Enlist crops. A 2012 review in Critical Reviews in Toxicology by Carol Burns and Gerard Swaen found that general-population urinary levels were at or near detection limits, with much higher exposures among people who mix and apply the herbicide.

What About Drift Damage to Neighboring Crops?

Drift was one of the biggest concerns raised in 2014. 2,4-D can harm sensitive crops such as grapes, tomatoes, cotton, and many vegetables and trees if spray droplets or vapor move off target. Older 2,4-D ester formulations were especially prone to evaporating and drifting. Enlist products use a choline salt form of 2,4-D designed to be less volatile, and EPA labels require measures such as nozzle types, wind speed limits, buffer zones, and restrictions near sensitive areas. Drift complaints have been more prominent with dicamba, another auxin herbicide used on tolerant soybeans, which caused widespread crop damage and court rulings against its registrations. Farmers growing crops that are not 2,4-D-tolerant, including organic farmers, still worry about drift from neighboring fields.

Will Weeds Become Resistant to 2,4-D Too?

Some already have. Weed scientists have documented several weed species resistant to 2,4-D and other auxin herbicides, though resistance has spread more slowly than it did with glyphosate. Experts warn that relying on any single herbicide, or a pair of them, repeats the pattern that created glyphosate-resistant weeds. Integrated weed management, which combines crop rotation, cover crops, varied herbicide modes of action, tillage where appropriate, and harvest weed seed control, is widely recommended to slow resistance. Enlist crops are often stacked with tolerance to glyphosate and glufosinate to give farmers more options, but the long-term outcome depends on how they are used.

Does 2,4-D End Up in Food?

Residues can occur, generally at low levels. The EPA sets legal residue limits, called tolerances, for 2,4-D on crops, and federal testing programs periodically measure residues in foods. Because 2,4-D is applied to tolerant crops during the growing season, residues may appear in grains and soybeans, which mostly go to animal feed, oil, and processed ingredients. The rise in urinary 2,4-D in national surveys suggests people are exposed through diet, drift, and lawn use, though levels in the general population remain far lower than among applicators. Shoppers who want to minimize exposure can choose USDA Organic products, which prohibit synthetic herbicides like 2,4-D, as explained in our guide to organic versus conventional food.

Is 2,4-D Used on Lawns?

Yes, widely. 2,4-D is a common ingredient in lawn weed killers and “weed and feed” products sold to homeowners, often combined with other herbicides such as mecoprop and dicamba. Lawn use may be a more direct exposure source for many families than food. Research has detected 2,4-D tracked indoors on shoes and pets after lawn applications. Reducing exposure at home is straightforward: follow label directions, keep children and pets off treated lawns until the product has dried or as the label instructs, remove shoes at the door, and consider spot-treating weeds or hand-pulling instead of broadcasting herbicide over the whole lawn.

What Did Supporters and Critics Argue in 2014?

Supporters, including many farm groups and the developer, argued that farmers urgently needed new tools against glyphosate-resistant weeds, that 2,4-D had decades of use and regulatory review behind it, and that the new choline formulation reduced drift. Without new options, they said, farmers would return to more tillage, which increases soil erosion, or to older, harsher herbicides. Critics, including environmental groups, some vegetable and fruit growers, and public figures such as Dr. Oz, argued that the crops would drive a large increase in 2,4-D spraying, that drift would damage neighboring farms, that weeds would evolve resistance again, and that health risks, particularly for rural communities, had not been adequately studied. Both sides made points that later events partly confirmed.

Why Did the EPA Revisit Its Approval in 2015?

About a year after first registering Enlist Duo, the EPA asked a federal court to let it withdraw the registration so it could review new information. The issue arose from the manufacturer’s patent filings, which described the combination of 2,4-D and glyphosate as having synergistic effects on plants, meaning the mixture might be more potent than expected from its parts. The EPA had not evaluated that possibility for non-target plants, including endangered species. After further review, the agency kept the product on the market and later issued new registrations with added protections. The episode showed how information outside the formal review process can prompt regulators to reconsider, and it fueled critics’ arguments that combination products deserved closer scrutiny.

Is 2,4-D Banned Anywhere?

2,4-D remains approved for agricultural use in the United States, Canada, the European Union, and many other countries. Some jurisdictions restrict nonessential uses. Ontario and several other Canadian provinces and municipalities banned many lawn and garden pesticides, including 2,4-D, for cosmetic purposes in the late 2000s, while allowing agricultural use. Some U.S. cities and school districts limit herbicide use on public parks and playgrounds. These local policies reflect precaution about unnecessary exposure, especially for children, rather than formal findings that 2,4-D is unsafe at all levels.

How Widely Are Enlist Crops Grown Today?

Enlist soybeans spread quickly after full commercial launch, becoming one of the most widely planted soybean trait packages in the United States within a few years, and Enlist corn and cotton are also grown. Their popularity reflects farmers’ need for weed control options, the flexibility of stacked tolerance to three herbicides, and the drift problems that made some farmers wary of dicamba-tolerant systems. The scale of adoption means 2,4-D use on row crops has grown, which is why biomonitoring and drift monitoring remain important.

What Can Organic and Specialty Growers Do About Drift?

Growers of sensitive crops, such as vineyards, orchards, vegetable farms, and organic operations, can register their fields on voluntary mapping services such as FieldWatch, which alert nearby applicators to sensitive sites. Talking with neighboring farmers before the season, planting buffer strips or windbreaks, and documenting any suspected drift injury quickly with photos and samples help protect their crops and support complaints to state pesticide regulators. Organic certification is not lost because of accidental drift, but contaminated crops may not be sold as organic if residues exceed set thresholds.

Does 2,4-D Affect Wildlife and Water?

It can, depending on formulation and use. Some ester forms of 2,4-D are more toxic to fish and aquatic life than the salt forms used in Enlist products. Runoff from treated fields can carry herbicides into streams, and drift can harm non-target plants that wildlife depend on, including milkweed and other wildflowers used by pollinators. These concerns led the EPA to require runoff and drift controls on Enlist labels and to prohibit use in some counties where endangered species could be harmed. 2,4-D breaks down in soil and water within days to weeks under most conditions, which limits long-term buildup but not short-term exposure after application.

Who Faces the Highest Exposure?

Farmers, herbicide applicators, and farmworkers who mix, load, or spray 2,4-D have by far the highest exposures, and the studies linking 2,4-D to non-Hodgkin lymphoma focus on these groups. Protective equipment such as chemical-resistant gloves, long sleeves, and eye protection, along with careful mixing practices and washing after use, substantially lowers exposure. Rural families living next to sprayed fields may also be exposed through drift. Because the strongest risk signals appear at high exposures, worker protection is where regulation and practice matter most.

How Do the Main Herbicides Used With Tolerant Crops Compare?

How Should Viewers Judge TV Health Warnings?

Television health segments can raise legitimate issues, as Dr. Oz’s 2014 warning did about increased herbicide use, but they often compress complex evidence into dramatic messages. Useful questions include: Does the warning cite specific studies, and are they about the same exposure people actually face? Does it distinguish between farmworkers who spray chemicals and consumers who eat trace residues? Does it acknowledge evidence on both sides? In the case of 2,4-D, concerns about more herbicide use and drift were reasonable, and later data showed rising exposure, while the cancer evidence remains genuinely uncertain rather than settled in either direction. Our article on glyphosate and human health shows how similar debates played out with another herbicide.

Common Myths

“2,4-D is Agent Orange.” Agent Orange combined 2,4-D with 2,4,5-T, whose dioxin contamination caused its worst harms.

“2,4-D is a proven carcinogen.” It is rated possibly carcinogenic; evidence in people is mixed.

“2,4-D is completely harmless.” Studies of highly exposed workers suggest a possible lymphoma link, and drift can damage crops.

“Tolerant crops eliminate herbicide resistance problems.” Weeds have already evolved resistance to 2,4-D in some places.

“Only farm communities are exposed.” Lawn products are a common household source.

Key Terms

2,4-D: A synthetic auxin herbicide that kills broadleaf weeds.

Enlist: A system of crops engineered to tolerate 2,4-D, often stacked with glyphosate and glufosinate tolerance.

Herbicide-tolerant crop: A crop engineered or bred to survive a specific herbicide.

Drift: Movement of pesticide spray or vapor away from the target area.

Biomonitoring: Measuring chemicals or their breakdown products in human samples such as urine.

The Bottom Line

Enlist crops were engineered to tolerate 2,4-D because weeds evolved resistance to glyphosate, and despite warnings in 2014, including from Dr. Oz, the crops and herbicides were approved and later renewed with drift and endangered species restrictions. The World Health Organization’s cancer agency rates 2,4-D as possibly carcinogenic, and a meta-analysis linked high exposure to non-Hodgkin lymphoma, though other analyses disagree. National data show rising 2,4-D levels in Americans, especially children. Protecting workers, preventing drift, and using integrated weed management matter most, and consumers can reduce exposure through lawn practices and organic food choices.

Frequently Asked Questions

What are Enlist crops?

Enlist crops are corn, soybeans, and cotton genetically engineered to tolerate the herbicide 2,4-D, usually along with glyphosate and glufosinate. They let farmers spray 2,4-D over growing crops to control weeds that have become resistant to glyphosate. The USDA cleared Enlist corn and soybeans in 2014, and Enlist soybeans have since become widely planted.

Is 2,4-D linked to cancer?

The World Health Organization’s cancer agency classified 2,4-D as possibly carcinogenic to humans in 2015. A 2017 meta-analysis found 38 percent higher non-Hodgkin lymphoma risk with any exposure and 73 percent higher risk among the most highly exposed, mainly farmers and applicators. Other analyses found weaker evidence, and regulators consider label-directed use acceptable.

Is 2,4-D the same as Agent Orange?

No. Agent Orange was a mixture of 2,4-D and another herbicide, 2,4,5-T. Its most serious health effects are attributed to dioxin contamination produced during the manufacture of 2,4,5-T, which was banned in the United States. 2,4-D remains in use, though it has its own health and environmental concerns.

How can I reduce my exposure to 2,4-D?

Avoid broadcast lawn weed killers containing 2,4-D or spot-treat instead, keep children and pets off treated lawns as labels direct, and remove shoes at the door. Choosing USDA Organic foods avoids synthetic herbicides. People who apply 2,4-D should wear gloves, long sleeves, and eye protection and wash after use.

Why did the EPA approve Enlist Duo?

The EPA concluded that Enlist Duo, which combines 2,4-D choline salt and glyphosate, does not pose unreasonable risks when used according to its label. It first registered the product in 2014 and renewed it in 2022 in 34 states with required drift and runoff measures and prohibitions in counties where endangered species could be harmed.

References

1. Loomis D, Guyton K, Grosse Y, et al. Carcinogenicity of lindane, DDT, and 2,4-dichlorophenoxyacetic acid. Lancet Oncology. 2015;16(8):891–892. PMID 26111929
2. Smith AM, Smith MT, La Merrill MA, et al. 2,4-dichlorophenoxyacetic acid (2,4-D) and risk of non-Hodgkin lymphoma: a meta-analysis accounting for exposure levels. Annals of Epidemiology. 2017;27(4):281–289.e4. PMID 28476329
3. Goodman JE, Loftus CT, Zu K. 2,4-Dichlorophenoxyacetic acid and non-Hodgkin’s lymphoma: results from the Agricultural Health Study and an updated meta-analysis. Annals of Epidemiology. 2017;27(4):290–292.e5. PMID 28292638
4. Freisthler MS, Robbins CR, Benbrook CM, et al. Association between increasing agricultural use of 2,4-D and population biomarkers of exposure: findings from the National Health and Nutrition Examination Survey, 2001–2014. Environmental Health. 2022;21(1):23. PMID 35139875
5. Burns CJ, Swaen GM. Review of 2,4-dichlorophenoxyacetic acid (2,4-D) biomonitoring and epidemiology. Critical Reviews in Toxicology. 2012;42(9):768–786. PMID 22876750
6. Nandula VK. Herbicide resistance traits in maize and soybean: current status and future outlook. Plants. 2019;8(9):337. PMID 31505748
7. Benbrook CM. Trends in glyphosate herbicide use in the United States and globally. Environmental Sciences Europe. 2016;28(1):3. PMID 27752438
8. U.S. Environmental Protection Agency. Registration of Enlist One and Enlist Duo. epa.gov

Last updated: October 10, 2026