Frequently Asked Questions

What is 2,4-D?

2,4-D, one of the most popular, trusted, successful and heavily researched selective herbicides in North America, is applied by agricultural producers to protect crops such as wheat, corn, rice, soybeans, potatoes, asparagus, pome fruits, stone fruits and nuts from harmful weeds.

It is the most widely used herbicide in the world and is also applied to control weeds in turf grass and invasive species in aquatic ecosystems and environmentally sensitive areas.

The original patent on 2,4-D was issued in 1945 to Dr. Franklin D. Jones, a plant physiologist. Dr. Jones was working with the naturally occurring plant auxin, indole acetic acid (IAA). IAA is present in all plant matter and humans ingest it daily whenever fruit, vegetables and cereals are consumed. In an effort to work with a more chemically stable, auxin-like compound, Dr. Jones included 2,4-D, an analog of IAA, in his experiments.

2,4-D has been used to protect turf grass and crops for over 65 years. The July 1945 edition of “Timely Turf Topics” published by the United States Golf Association was dedicated to explaining the use and benefits of 2,4-D for golf courses and turf grass. In 2004, The Henry Ford organization in Dearborn, Michigan identified 2,4-D as one of the 75 most important innovations in the previous 75 years.

Few scientific innovations have done as much to increase food production throughout the world as 2,4-D..

Are pesticides like 2,4-D adequately researched?

In addition to being the most widely used agricultural herbicide worldwide, 2,4-D was the first selective herbicide developed (a selective herbicide controls weeds in agricultural production without harming the crop), something that stimulated an enormous amount of research on 2,4-D across the globe.

Because of this fact, more is known about 2,4-D and how it works than almost any other chemical tool. The toxicology database alone exceeds 4,000 peer-reviewed, published studies, plus hundreds of unpublished studies that manufacturers of 2,4-D must provide to various regulatory agencies throughout the world so registrations of products containing 2,4-D are kept constant and up to date.

Additionally, there are now more than 160 peer-reviewed, published epidemiologic (human) studies pertinent to 2,4-D.

2,4-D is banned in some countries like Sweden and Denmark, why?

It is true that 2,4-D is no longer registered for use in Sweden or Norway, and its use is restricted in Denmark.

However, in repsonse to these independent regulatory actions in 1989, the European Commission, conducted a major re-evaluation of 2,4-D which was completed in October 2001, concluding that 2,4-D was acceptable for continued registration in all European member countries.

2,4-D was an active ingredient in Agent Orange. Even though Agent Orange has been banned for years, 2,4-D is still on the market today.

2,4-D and Agent Orange are two very different substances.

2,4-D was a component of Agent Orange, along with another phenoxy, 2,4,5-T.

Researchers have found that it was 2,4,5-T that was the compound of concern in Agent Orange for dioxin contamination. As a result, 2,4,5-T was discontinued from use in Canada and other countries around the world more than 25 years ago (production and registration) while 2,4-D continues to be the one of the most trusted and widely used herbicides in the world.

Is 2,4-D contaminated with dioxin?

All 2,4-D Task Force members’ production standards for products containing 2,4-D meet the guidelines established by the Canadian PMRA and the U.S. EPA, developed over many decades of testing.

The overwhelming conclusion of the analysis of dioxin data with respect to 2,4-D is that the current regulations and production limits provide margins of safety that fully and responsibly protect the public and the environment.

Some reports claim children are more susceptible to pesticides due to their behavior and unique physiological characteristics, is this true?

Specific risk assessments for children, taking into consideration their unique physiology, diets, behaviors and play-habits (including their body weight and hand-to-mouth contact while playing on treated grass), are undertaken before a pesticide is granted a registration in both the United States and Canada.

To quote from the Canadian government's response to the House of Commons Standing Committee on Environment and Sustainable Development 3:

“The hazard, exposure and risk assessments specifically include consideration of the potential effects of a pesticide on fetuses, infants, children, pregnant women, seniors, applicators or agricultural workers.

The toxicology studies are conducted to assess potential effects during preconception, through the reproductive and developmental life cycle, the post-natal period, weaning and through to adulthood.

Assessment of children’s potential exposure includes direct and indirect skin contact with surfaces treated with pesticides, ingestion through the transfer of residues from the hands to the mouth, soil ingestion and inhalation.

Children’s unique play and activity patterns, including higher contact with surfaces and increased teething and mouthing activity, and children’s unique physiology, are factored into these exposure estimates.

The unique food consumption patterns of infants and children are considered, including their consumption of maternal milk, packaged milk and fruit juice.”

Does 2,4-D cause cancer (Canine Malignant Lymphoma ‘CML’) in dogs?

No, it does not.

All agencies that have examined the available scientific data on the subject have reached the same conclusion: 2,4-D does not cause cancer in animals.

A 1991 article by a former researcher at the National Cancer Institute (NCI) suggested a link between dogs with CML and dog-owners that applied 2,4-D to their lawn.

An independent panel concluded in 1992 that the study design was severely flawed and, in fact, did not show an association between CML and 2,4-D use. In 1999, scientists at the School of Veterinary Medicine at Michigan State University re-examined the NCI data and also concluded that there was no relationship between 2,4-D use and CML:

“The weight of this evidence, combined with the lack of any indicators for lymphoma in short- and long-term dietary studies in dogs, indicates that the original report of an association between homeowner use of 2,4-D and CML cannot be substantiated or supported.” 

Pesticides are often found in the blood and urine of children, what does this mean?

It is normal to find trace amounts of many chemicals in tissues or fluids when an individual has been exposed to them. However, exposure does not mean there will be any associated negative health effects, particularly if the levels are very small as they most often are. With the advancement of technology, these measurements are commonly assessed in the parts per trillion.

To put this into context:

one part per trillion is the equivalent of 1 second in the span of 32,000 years.

The presence of a trace amount of any chemical or compound, whether it is from cosmetics, tap water, soaps and shampoos or herbicides like 2,4-D, is very common and does not necessarily equate to any potential health consequenses.

Most studies of 2,4-D use rats to test for toxicity. It has been suggested that rats have detoxification genes missing in humans, therefore, studies based on rat experiments are no longer viable for human risk assessment. Is this true?

Rats are only one species used in the toxicology studies. It is true that they differ physiologically from humans, but decades of research with rats, mice and rabbits has proven that these laboratory animals are the best to represent the human toxicological responses.

Additionally, animals used in laboratory studies are bred from very specific pedigreed lines to maintain a consistent, controlled animal source for testing purposes. The 2,4-D molecule is readily cleared by the kidney in mammals, including humans, unchanged.

Since 2,4-D is not metabolized in either animals or humans, the metabolic pathways for detoxification are not of concern. By required regulatory testing of pesticides, there is sufficient opportunity to reveal potential impacts on inter-species genetic differences on toxicology expression.

More importantly however, regulatory decisions are not based on toxicology alone. Human epidemiological studies in conjunction with toxicology studies provide researchers and regulators with a more complete picture of health risks and effects.

Should I be concerned about exposure to 2,4-D from track-in residues into my home?

No. A risk assessment conducted for adults and children exposed to 2,4-D as a result of playing on recently treated turf considered the combined oral and dermal exposure and indicated no unacceptable risks.

Since the levels of 2,4-D that have been measured in house dust are much lower than the concentrations on soil and turf, for which no concern was identified, the potential exposure from 2,4-D residues inside the home is not a cause for concern.

Also, 2,4-D is not considered to be persistent on turf. Independent studies over the past 50 years demonstrate that 2,4-D residues on turf decline rapidly after application.

Are bystanders to turf applications exposed to 2,4-D?

Several researchers at the University of Guelph, in Canada, have completed studies on human exposure to applications of 2,4-D for the Ontario Ministry of the Environment. These studies show the highest observed exposures for homeowners and commercial applicators were well below the lifetime ADI (acceptable daily intake) as established by the World Health Organization.

The most recent research demonstrates that there were no detectable exposures for the bystanders who reside in homes of homeowner or commercially treated lawns or for barefoot, barelegged bystanders who actively walked or sat on turf grass for one hour on the day of spraying.

Does 2,4-D persist in the soil?

Soil dissipation of 2,4-D is well understood. The recent data from 30 soil dissipation studies on various soil types around North America illustrate a median 2,4-D half-life of 5.6 days.

2,4-D is classified as non-persistent to slightly persistent in soil and natural water because of aerobic microbial biotransformation.

Should 2,4-D be a concern for groundwater contamination?

No. The rapid breakdown of 2,4-D minimizes the potential for movement in soil, and greater than 90 – 95 percent dissipates in the top six inches of soil.

Eventually 2,4-D breaks down to CO2 and is integrated into other carbon compounds in the soil. Any findings of 2,4-D in ground water have been extremely rare. These have been attributed to spot contamination or spills near water wells or unique soil conditions with high rainfall or irrigation shortly following application.

Is exposure to the odor of 2,4-D hazardous?

Pure 2,4-D is odorless. Odor associated with the application of 2,4-D comes from a small amount of the primary breakdown product, 2,4-dichlorophenol (DCP).

Another odor may come from a small amount of dimethylamine, a neutralizing agent of the 2,4-D formulation. Both of these compounds are considered to possess extremely low toxicity as a vapor, though low levels are can be quite odorous. Government agencies have indicated low toxicological concern for inhalation of 2,4-D.

Odor exposure of 2,4-D is not of toxicological concern.

What did Health Canada decide about 2,4-D with its most recent announcement?

After years of analyzing all the pertinent science and considering the public’s input in 2005 and again in 2007, Health Canada has determined that 2,4-D may be used safely according to label directions.

With specific regard to use on lawns, the PMRA stated:

“Risks to homeowners and their children from contact with treated lawns and turf are not of concern.”

In 2008 the PMRA released its Re-evaluation Decision on 2,4-D.  In its decision Health Canada concluded that:

"Products containing 2,4-D do not pose unacceptable risks to human health or the environment."

They also have value for lawn and turf, agriculture, forestry and industrial uses when used according to the label directions proposed in previous consultation documents .”

What is the PMRA’s position on 2,4-D and cancer?

Not one pesticide regulatory agency in the world classifies 2,4-D as a human or animal carcinogen.

In issuing the final re-evaluation decision, the PMRA stated in its Information Note,

“Health Canada also consulted an independent Science Advisory Panel comprised of government and university experts/researchers in toxicology, epidemiology and biology. The Panel agreed with Health Canada’s assessment that 2,4-D can be used safely when used according to label directions, with some uses requiring additional protective measures .”

In 2005 the United States Environmental Protection Agency released its final decision on the registration of 2,4-D. What are some of the key EPA findings concerning 2,4-D reregistration?

After examining the combined risk from exposure through food, drinking water and residential uses, using all the required safety factors, the EPA concluded that 2,4-D would “not exceed” the Agency’s level of concern. Additionally, the EPA concluded that short-term margins of exposure for homeowner applications to lawns were “not of concern.”

For additional information, see the EPA’s fact sheet on the 2,4-D Reregistration Decision:
http://www.epa.gov/oppsrrd1/REDs/factsheets/24d_fs.htm

Why has IARC classified 2,4-D as a ‘possible’ carcinogen?

IARC (the International Agency for Research on Cancer) has not classified 2,4-D as a ‘possible’ carcinogen, this is a common misconception.

Understanding the basis and context of IARC’s classification is critical to the full understanding of this important topic. The IARC review of the chlorophenoxy herbicides (which includes 2,4-D) was first conducted in 1977 and is based on data collected in the late 1960s and early 1970s.

It is important to note that the human carcinogenicity potential of 2,4-D was not and never has been fully evaluated by IARC. The updated Monograph published in 1987 concluded that chlorophenoxy herbicides as a group were classified as Group 2B or “possible” carcinogens for increased occupational cancer risk in pesticide applicators (e.g. lawn care applicators and farmers).

Because 2,4-D belongs to this chlorophenoxy group of substances, the compound was given the same classification, in the absence of data that would make a full evaluation of the individual substance possible.

A limitation that is recognized in the footnotes of the Monograph, which state:

“This evaluation applies to the group of chemicals as a whole and not necessarily to all individual chemicals within the group”.

In 1996 IARC's parent organization, the World Health Organization, completed a comprehensive review of 2,4-D and concluded

“There was no evidence of carcinogenicity” in all 2,4-D animal feeding studies.

I have heard that regulatory agencies base their decisions on “secret studies” paid for by the pesticide industry, is this true?

The Task Force did not conduct a single research study of the more than 300 Good Laboratory Practices (GLP) studies required by the EPA and the PMRA for the reregistration/re-evaluation of the herbicide 2,4-D.

Regulatory decisions regarding 2,4-D are based on an enormous body of research that has been conducted by some 30 EPA GLP accredited laboratories in concert with studies and reports published in scientific journals, as well as other foreign nations’ and international organizations’ reviews.

Regulators carefully review all studies for GLP compliance and any intentional GLP violation (such as false or misleading information about the health or environmental risks) is a violation of federal law. These laws are enforced, so both the company responsible and the laboratory doing the work take GLP guidelines very seriously.

In sum, no, regulators do not base any registration decisions on secret studies.

What is a Research Task Force?

The Industry Task Force II on 2,4-D Research Data was organized to provide funding for some 300 Good Laboratory Practice (GLP) research studies required to respond to the EPA reregistration and PMRA pesticide re-evaluation programs.

The 2,4-D Task Force is comprised of those companies owning the technical registrations on the active ingredient in 2,4-D herbicides. They are Dow AgroSciences (U.S.), Nufarm, Ltd. (Australia) and Agro-Gor Corp., a U.S. corporation jointly owned by Atanor, S.A. (Argentina) and PBI Gordon Corp. (U.S.).

It is important to note that the Task Force does not conduct the studies submitted for review by EPA and PMRA, it simply funds the process.