5 Things to Know About 2,4-D, the “Possibly” Cancer-Causing Herbicide | Civil Eats

5 Things to Know About 2,4-D, the “Possibly” Cancer-Causing Herbicide

Use of the third most popular pesticide in the U.S. is predicted to grow dramatically in the next few years.

The majority of America’s farms rely heavily on herbicides—lots of them. So when the World Health Organization (WHO) classified the United States’ most widely used weed-killer, glyphosate, as “probably” carcinogenic to humans three months ago, it was big news.

Now, the same group–the WHO’s International Agency for Research on Cancer (IARC) has concluded that 2,4-D, another commonly used weed killer, is “possibly” carcinogenic to humans. Here’s what you need to know about the decision and the chemical, which is the third most-widely used herbicide in the U.S.

1. Use of 2,4-D is About to Skyrocket

2,4-D was introduced nearly 70 years ago and is used to control weeds in agriculture, landscaping, and forestry. It is also in many products sold for home use. 2,4-D is approved by the U.S. Environmental Protection Agency (EPA) for use on many fruits and vegetables, as well as on corn and soy. According to the Industry Task Force on 2,4-D Research, it is used in over 90 countries. 2,4-D was also an ingredient in Agent Orange, the highly toxic defoliant used by the U.S. during the war in Vietnam.

While 2,4-D use has remained fairly steady over the past 20 years, it’s expected to increase dramatically in the next five years, thanks to the EPA’s recent approval of a new pesticide called Enlist Duo. Manufactured by Dow AgroSciences, Enlist Duo combines a form of 2,4-D and glyphosate and has been approved for use in 15 states on corn and soy genetically engineered to tolerate the herbicide. The U.S. Department of Agriculture (USDA) predicts Enlist Duo could cause an enormous jump in use. The agency estimates that use could grow between 300 and 700 percent by 2020.

EPA says Enlist Duo is safe for use as directed, but a number of farm and environmental groups—including the Center for Food Safety, Earthjustice, Environmental Working Group (EWG), Natural Resources Defense Council, Pesticide Action Network North America, and the National Farm Family Coalition—have filed suit against the agency for its approval of the herbicide. They contend that the EPA did not adequately consider adverse impacts to the environment and human health, especially considering the expected increase in use.

2. 2,4-D is a Potential Endocrine Disruptor Increasingly Found in Ground and Surface Water

The National Pesticide Information Center says that while some forms of 2,4-D can be very toxic to fish and other forms of aquatic life, particularly in warmer water temperatures, 2,4-D is not toxic to honey bees or other beneficial insects. Some studies, however, suggest that 2,4-D is a potential endocrine disruptor and may interfere with thyroid hormones. A recent study also suggests that 2,4-D exposure may promote antibiotic resistance. Yet other studies have linked 2,4-D exposure to immune and neurological system problems, including Parkinson’s disease.

2,4-D breaks down fairly quickly in soil and water, but due to its widespread use, particularly, in the Midwestern U.S., it has been detected in surface and groundwater. 2,4-D is also being found in urban streams, especially after rainstorms. Weeds resistant to 2,4-D have also been found in the Midwest.

3. WHO Gives 2,4-D a 3 out of 5

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According to IARC, people can be exposed to 2,4-D while it’s being applied or where the chemical and herbicide products are manufactured. People may also be exposed through food, water, dust or when 2,4-D is being sprayed on crops and drifts through the air. 2,4-D is known to drift both in liquid and vapor form. This drift can destroy more than weeds, as Midwestern vegetable farmers have discovered when herbicide sprayed on nearby farms damaged their crops. Responding to these concerns, the 2,4-D formulation in Enlist Duo was designed to be less prone to drift. And as always, when it comes to pesticide exposure, those most directly affected are farmworkers and those who live near where these chemicals are sprayed. In this case, people who use it on their lawns might also be affected.

The IARC assessment, conducted by 26 experts from 13 countries, considered evidence from studies that looked at exposure to the chemical in animals and people. They found “limited evidence” linking 2,4-D exposure to cancer in experimental animals and what they call “inadequate evidence” in people. Some studies found an increased risk of leukemia and lymphoma in people exposed to high levels of 2,4-D, but questions about direct cause and effect remain in part because those people were also often exposed to multiple pesticides at once.

However, IARC says “there is strong evidence that 2,4-D induces oxidative stress, a mechanism that can operate in humans, and moderate evidence that 2,4-D causes immunosuppression.” Weighing this combined evidence, IARC classified 2,4-D as “possibly” carcinogenic to humans—or the equivalent of a three on its 1-5 scale.

4. Advocates Say Ranking Might Not Reflect Danger

The IARC conclusion means that, as a chemical, 2,4-D might possibly cause cancer in people. But because IARC does not make regulatory decisions about pesticides—in the U.S., that’s the EPA’s job—its classifications do not dictate how a chemical should or should not be used.

The EPA says its most recent review of the science found that 2,4-D exposure does not cause non-Hodgkin’s lymphoma. However, the agency is now conducting a new review that will include this new assessment. Based on these findings, the “EPA will determine whether any risk mitigation is needed to address unreasonable risks to humans,” the agency said in a statement. EPA expects to release a draft of this new human health risk assessment next March.

Industry response has been blunter. In a statement posted to its website, Dow AgroSciences called the IARC classification “inconsistent with government findings in nearly 100 countries.” The findings, said Dow AgroSciences, “should not be mischaracterized in ways that are misleading and harmful to farmers and consumers.”

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“I don’t think it’s going to impact how it’s used,” said Julie Goodman, toxicologist and consultant to the Industry Task Force on 2,4-D, in an interview with Civil Eats. 2,4-D manufacturers say the herbicide is safe to use as directed and that the IARC classification is not a cause for concern.

But environmental advocacy groups say there is additional evidence linking 2,4-D exposure to non-Hodgkin’s lymphoma and that use of Enlist Duo will mean far wider potential 2,4-D exposure. “Now that farmers are planting 2,4-D-tolerant GMO crops, this herbicide is slated to explode in use much the way glyphosate did with the first generation of GMO crops,” said EWG senior policy analyst Mary Ellen Kustin in a statement.

5. There’s Only One Way for Consumers to Avoid 2,4-D

The U.S. Food and Drug Administration (FDA) does not currently monitor 2,4-D residue on crops, so only limited information is available about its presence in the food supply. (FDA doesn’t monitor for glyphosate residue either.) And when it comes to health impacts of 2,4-D combined with glyphosate or any other pesticides, very little if any research has been done. As with most synthetic pesticides, the only way to avoid 2,4-D for sure is by buying food that is certified organic.

Elizabeth Grossman was a senior reporter for Civil Eats from 2014 to 2017, where she focused on environmental and science issues. She is the author of Chasing Molecules, High Tech Trash, Watershed and other books. Her work appeared in a variety of publications, including National Geographic News, The Guardian, The Intercept, Scientific American, Environmental Health Perspectives, Yale e360, Ensia, High Country News, The Washington Post, Salon, The Nation, and Mother Jones. She passed away in July 2017, leaving behind a legacy of dedication to her mission of journalism that supports and protects people and the planet. Read more >

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  1. David A. Carlson
    You make no mention of the known carcinogenic impurities in the original millions of pounds of 2,4-D as used as Agent Orange in VietNam. Any facts about whether or not these nasty impurities are present in modern 2,4-D is NOT mentioned. Until it is, I cannot take your warning as valid.
  2. Don Huber
    It is not only from indirect exposure (drift, water), but with Enlist Duo, it is applied directly to our food. With the anticipated 200-700 % increased use from being applied to genetically engineered food and feed crops, both glyphosate and 2,4-D are systemic and accumulate in the food/feed components we consume. The most serious form of exposure is unavoidable! Both chemicals are endocrine hormone disrupters with multiple other health consequences when consumed! With the recently reported apparent scientific fraud in industry safety studies who knows the full danger?
  3. Chuck Schmitt
    The article does not address why the use of 2,4-D will skyrocket in the near future??

    Also, I believe Agent Orange is 2,4,5-T....not 2,4-D

    This product has been on the market for 70 years and it is just now being considered a "possible carcinogen"...seems odd?
  4. potato farmer
    Agent orange was contaminated with dioxin. The chemical 2,4-D or 2,4-T was not the cause of people getting sick.
  5. J. Carter
    It's fascinating how "science" is used to deem highly toxic chemicals being sprayed on our food, but dismissed when applied to global warming.
  6. Wil
    My wife and I do as much certified organic shopping as we can and we try to buy as much locally grown as we can. What bothers us is the fact that organic farming has no control over "chemical drift". Not only the drift in the air but also drift through the soil. Living in a bubble isn't practical. But demanding that government agencies do their job to best protect us (that's the reason they were created in the first place) isn't asking too much, is it? Like the FDA not currently monitoring 2,4-D residue on crops, just to name one. We truly need them to get back to the basic reason they were created. To protect the people, not the chemical companies! Certified organic. Right now you can't beat it.
  7. Russel Deroche Jr
    Testing one chemical at a time to find a connection to health problems is a farce. We have so many chemicals in our food and water that it is nearly impossible to test how they will interact with each other in the body. All we do is find bad ones after a problem is discovered and move on to adding another one to the environment. We are destroying ourselves and the environment with chemicals. We never know the truth until it is too late.
  8. ted redalen
    the obvious question is: what is the likelihood of prompting the FDA to initiate testing for glyphosate & 2,4-D in the food supply, and test the effects of those residues in the lab?
  9. Teri
    My dog has lymphoma and I have seen many articles mentioning 24-D as a potential cause. I'm not clear where the evidence is about this...but it seems to me no one is paying attention to, nor collecting information about our pets that may be dying as a result of exposure to weed killers. I live where there is an HOA and they spray weed killers/spread fertilizers all the time and no one knows how toxic they are to our animals. One woman told me every time the spread something her dog becomes ill.

    Is there anyone doing research on this?
  10. Hello,
    A local, politically based corporation is planning to spray 2,4-D, in the form of DMA 4 IVM (Dow AgroSciences), onto our local lake in order to control milfoil. They are spraying it directly on and near docks, beaches and boats, where people are swimming and ingesting this water. These are homes along the lake, so animals are drinking from water that was poisoned 20' from the shore. Do I need to worry?
    John Ely
    Coeur D'Alene Idaho
  11. ann
    my life became an earthly hell after Hi-Dep 2,4-D drift contaminated my yard, laundry, garden and standing water. My son had temporary symptoms and I developed both short term and long term problems. I'm still using oxygen and have to stay away from stores and land that has been sprayed. For more info write me @ P.O. Box 1124, Polson, MT I just have a few questions to ask those who think poisons are safe. " Is it ever completely safe to play russion roulette? Is it ever ok to harm even one person? "
  12. greg weeda
    i just want to kill the different weeds in my lawn something good, now you say this stuff is bad.
  13. Ryan Ellis
    What does the chemical breakdown into And what's it's Half life?
  14. Mernie Jacobsen
    Why do you call it a pesticide. Isn't it a herbicide?
  15. Richard Civera
    can 24 -d cause stomach cancer in dogs
  16. Roderick Blake
    was involved with aerial spraying 24D in mid north of South Australia. This in aereas of Burra, My.Bryan and Hallet. I spent quite same time being a "marker" for plane, which meant I would get spray over myself. I did this work in late 60's early 70's. I have bladder cancer since 2005. Would this be a possibility of using this herbicide
  17. Gordon Friess
    I have lost two brothers to the cancers listed as possibly linked to 24d both farmers with excessive exposure to this chemical !!! All of our university research is profit driven not health ! University of Kansas done studies many years ago on this which never became public knowledge !!!!
  18. Jerry Beverage
    I put 2-4-D on my fence rows. Spilt some on my fingers, washed it off within 5 min of being exposed. Should I use gloves when I use 2-4-D?
  19. arthur
    how are GMOs the cause of this? I'm trying write a paper on the pro's and con's of this for a college course but I'm finding it really hard to find any negative sources on it. If some could send me some links it would be appreciated.
  20. David Mack
    Any one who doesn't believe that this info and the regulatory issues behind its use is totally controlled by Big Corporate America must be living on a different planet. The FDA and EPA should be monitoring the levels of these products in our food and water. Soils on large corporate farms is totally sterile. Biodiversity is destroyed. Many of our insects depend on "weeds" to survive. Our insect diversity, population numbers are in catastrophic decline. We are in trouble. How does corporate America respond, by introducing a combined product, the toxic effects of which are completely unknown and quite possibly enhanced.
  21. Sandra Volkmann
    I have serious concerns with any use of 2,4-D. My property and I have been exposed to 2,4-D drift. My trees in my yard are dyeing and I am concerned about my lungs and wondering why I get headaches when I am in the sun too long. I was raising non-chemical and non-GMO produce on my property. Atleast 2 times across the road 2,4-D was sprayed heavily and I smelled the chemical smell as I was sitting in the hammock while resting after cutting the grass. I look the direction the wind was from and saw the water system running on the ball field. It came from there. So I went into the house and shut the windows and turned on the air purifier, both times.
    Now I cough often and get head aches when I am in the sun. My sinus is very sensitive to any chemical or manure smell.
    I am considering going into the clinic to get tested for 2,4-D toxicity.

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