On Oct. 22, the U.S. Environmental Protection Agency announced 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, the EPA relied on studies demonstrating thyroid toxicity to unborn babies whose mothers were exposed to DCPA. According to the EPA, such exposure could lead to low birth weight, impaired brain development, decreased IQ and impaired motor skills later in life, some of which may be irreversible.
DCPA is a pesticide used to control weeds in both agricultural and non-agricultural settings. It’s primarily used on crops such as broccoli, Brussels sprouts, cabbage and onions.
Final Notice
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 Chemical Corporation (AMVAC), the sole manufacturer of DCPA, 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, the EPA will continue monitoring this process to ensure collected DCPA products are disposed of in a manner in accordance with applicable laws. The EPA said in a press statement, it plans to release additional information about any remaining stocks in the coming months.
More Background on Ban
In 2013, the EPA issued a Data Call-In (DCI) to AMVAC requiring it to submit more than 20 studies to support the chemical's then-existing registrations. The required data included a comprehensive study of the effects of DCPA on thyroid development and function in adults and in developing young before and after birth. According to the EPA, several of the studies AMVAC submitted from 2013 to 2021 were considered insufficient, while the thyroid study and other studies were not submitted at all.
In April 2022, the 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, the EPA suspended the registration based solely on AMVAC’s continued failure to submit other outstanding data following an administrative hearing. In November 2023, the EPA lifted the data submission suspension after AMVAC submitted sufficient data. In December 2023, AMVAC voluntarily canceled most DCPA use on turf, but unacceptable risks from other uses remained.
In May 2023, the 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. According to the EPA, some pregnant mothers handling DCPA products could be subjected to exposures four to 20 times greater than what the 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, the 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 EPA’s August 2024 emergency suspension was the first time in almost 40 years the agency declared this type of emergency action. Following the suspension, the agency received a letter from AMVAC stating its intent to voluntarily cancel the remaining pesticide products containing DCPA in the United States.
AMVAC subsequently announced it would cancel all international registrations as well. On Aug. 29, 2024, the EPA published a notice in the Federal Register requesting public comments on the voluntary cancellation. The comment period has concluded, leading to the EPA’s publication of the final cancellation order.
