Dacthal Birth Defect Risks Lead EPA To Finalize Ban on Use, Sale or Distribution of Weedkiller

The pesticide Dacthal has officially been removed from the market in the United States, after federal regulators determined that it poses too great of a risk to unborn children, who may be left with severe birth defects.

Dacthal is the brand name of Dimethyl Tetrachloroterephthalate (DCPA), which is a weedkiller made by AMVAC Chemical that has been widely used on vegetables like broccoli and onions. It is also often used on turfs, such as golf courses and athletic fields.

However, after years of looking at data and scientific studies, the U.S. Environmental Protection Agency (EPA) determined earlier this year that pregnant women exposed to high levels of Dacthal face an unreasonably high risk of fetal thyroid hormone disruption. This can result in their child experiencing impaired brain development, impaired motor skills and low birth weight, among other Dacthal birth defect risks.

Although the European Union banned the use of Dacthal in 2009, it has remained on the market in the United States.

In August 2024, the EPA finally issued an emergency Dacthal recall order, suspending all DCPA use permits. It was the first time the EPA had taken such an extreme act to remove a pesticide from the market in nearly 40 years, and the agency finalized the ban this week, canceling use permits for all products containing Dacthal.

In an October 22 press release announcing the final Dacthal (DCPA) cancellation, the EPA indicates that the decision came from an analysis of the best available science, including “robust” studies showing the fetal thyroid hormonal effects and unjustifiable risk of birth defects for unborn children.

“With the final cancellation of DCPA, we’re taking a definitive step to protect pregnant women and their unborn babies,” Michal Freedhoff, assistant administrator of the EPA Office of Chemical Safety and Pollution Prevention, said in the press release. “The science showing the potential for irreversible harm to unborn babies’ developing brains, in addition to other lifelong consequences from exposure, demands decisive action to remove this dangerous chemical from the marketplace.”

Years of Dacthal Birth Defect Concerns

EPA scientists began expressing concern about the safety of the weedkiller as early as 1999, when studies on rats revealed Dacthal’s effects on thyroid function. The agency then requested the manufacturer, AMVAC, submit additional data on the potential Dacthal birth defect risks.

AMVAC submitted some of the data in May 2021, but EPA officials said the report did not satisfy the agency’s data requirements. The agency issued a Notice of Intent to suspend Dacthal approval in April 2022, and the company finally submitted the data EPA requested that August.

After assessments earlier this year by the EPA, AMVAC and the agency discussed how to limit exposure to the chemical, with the manufacturer submitting proposals in April and May. However, even agreements to limit exposure in residential use were not enough to alleviate the risk of birth defects from Dacthal, the EPA determined.

Following the EPA’s emergency order, AMVAC sent the agency a letter indicating its plans to voluntarily cancel the remaining Dacthal products on the market in the U.S. and around the world, according to the agency.  However, while cooperating, American Vanguard officials expressed doubts about Dacthal health risks, which the company claimed were based off “one rat study.”

“While the Company continues to question EPA’s conclusions in support of the suspension, we believe that the best course of action is to voluntarily cancel registrations of this product,” AMVAC officials stated in an August 21 press release.” We are working apace with both state and federal authorities to effect product return and to remove Dacthal from channels of distribution. It is the Company’s position that product stewardship be international in scope; thus, we will now proceed to voluntarily cancel all international registrations as well.”

The EPA published a Federal Register notice on August 29, announcing AMVAC’s voluntary cancellation and requesting public comments. The period for accepting public comments ended, resulting in Tuesday’s announcement.

Permanent Dacthal Ban Effective Immediately

According to the EPA, Dacthal’s final cancellation “prohibits anyone from distributing, selling or carrying out other similar activities for the remaining pesticide products containing DCPA.” No one is allowed to continue using existing stocks of the herbicide either.

AMVAC has a voluntary return program in place for Dacthal products still on the market, in inventories, or being used by customers, according to the agency.

The EPA says the company also has a plan to identify those individuals or companies with existing stocks and has coordinated a collection process.

The agency indicates it will continue to monitor the return process to ensure that the weedkiller is collected and disposed of properly.

The final cancellation of the weedkiller comes as the manufacturer already faces a number of potential Dacthal birth defect lawsuits being investigated by families of children left with brain development or motor development problems after mothers were exposed to the chemical during pregnancy.