US EPA finalizes cancellation of the pesticide dacthal

On Oct. 22, the U.S. Environmental Protection Agency is announcing the cancellation of all products containing the pesticide dimethyl tetrachloroterephthalate (DCPA or Dacthal) under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).

In making this decision, EPA relied on the best available science, which included robust studies demonstrating thyroid toxicity. Unborn babies whose pregnant mothers are exposed to DCPA from handling, entering or working in areas where DCPA has already been applied, could experience changes to fetal thyroid hormone levels. These changes are generally linked to low birth weight, impaired brain development, decreased IQ, and impaired motor skills later in life, some of which may be irreversible.

″With the final cancellation of DCPA, we’re taking a definitive step to protect pregnant women and their unborn babies,″ said Assistant Administrator for the Office of Chemical Safety and Pollution Prevention Michal Freedhoff. ″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.″

Background on DCPA and Biden-Harris Administration Efforts to Assess and Address Risks

DCPA is a pesticide that was registered to control weeds in both agricultural and non-agricultural settings, but was primarily used on crops such as broccoli, brussels sprouts, cabbage and onions.

In 2013, the agency issued a Data Call-In (DCI) to AMVAC Chemical Corporation (AMVAC), the sole manufacturer of DCPA, requiring it to submit more than 20 studies to support the then-existing registrations of DCPA. The required data, due in January 2016, included a comprehensive study of the effects of DCPA on thyroid development and function in adults and in developing young before and after birth. Several of the studies that AMVAC submitted from 2013-2021 were considered insufficient to address the DCI, while the thyroid study and other studies were not submitted at all.

In April 2022, EPA issued a very rarely used Notice of Intent to Suspend the DCPA technical-grade product (used to manufacture end-use products) based on AMVAC’s failure to submit the complete set of required data for almost 10 years, including the thyroid study. Although AMVAC submitted the required thyroid study in August 2022, EPA suspended the registration based solely on AMVAC’s continued failure to submit other outstanding data following an administrative hearing. In November 2023, EPA lifted the data submission suspension after AMVAC submitted sufficient data. Most DCPA use on turf was voluntarily canceled by AMVAC in December 2023, but unacceptable risks from other uses remained.

In May 2023, EPA released its assessment on the risks of occupational and residential exposure to products containing DCPA, following its analysis of the thyroid study submitted by AMVAC. The assessment found health risks associated with DCPA use and application, even when personal protective equipment and engineering controls are used. The most serious risks were to the unborn babies. EPA estimated that some pregnant mothers handling DCPA products could be subjected to exposures four to 20 times greater than what EPA had estimated is safe for unborn babies. Also of concern were risks to unborn babies of pregnant mothers entering or working in areas where DCPA had been applied or living near areas where DCPA was used. Levels of DCPA in a treated field could remain at unsafe levels for 25 days or more.  In April 2024, EPA issued a public warning regarding the significant health risks to unborn babies of pregnant mothers exposed to DCPA and its intent to pursue action to address the health risks associated with the pesticide as quickly as possible.

The August 2024 emergency suspension issued by EPA was the first time in almost 40 years EPA has taken this type of emergency action. Following EPA’s emergency suspension EPA received a letter from AMVAC stating its intent to voluntarily cancel the remaining pesticide products containing DCPA in the U.S. AMVAC subsequently announced that it intends to cancel all international registrations as well. On Aug. 29, 2024, EPA published a notice in the Federal Register requesting public comments on the voluntary cancellation. The comment period has concluded, and EPA is publishing the final cancellation order.

The final cancellation prohibits anyone from distributing, selling or carrying out other similar activities for the remaining pesticide products containing DCPA. It also means that no person can continue using existing stocks of those products. AMVAC has developed a voluntary return program for existing DCPA products. In advance of the cancellation order, AMVAC implemented a plan to identify existing stocks and coordinated a collection process. When the return program concludes in the fall of 2024, EPA will continue monitoring this process to ensure that the collected DCPA products are disposed in a manner in accordance with applicable laws. EPA plans to release additional information about any remaining stocks in the coming months.

Read the public inspection version of the Federal Register notice on the DCPA Final Cancellation Order for Pesticide Registrations. Upon publication of the Federal Register notice, the final order will be is available at docket EPA-HQ-OPP-2011-0374 at the Regulations.gov page.  

For answers to frequently asked questions about DCPA, please see the DCPA Questions and Answers webpage. For additional background on the DCPA and EPA’s efforts to assess and address risks, see the Aug. 6, 2024, or Aug. 28, 2024, press releases.