In an unprecedented move, the Environmental Protection Agency (EPA), in consultation with the U.S. Department of Agriculture (USDA), issued an emergency order to suspend all dimethyl tetrachloroterephthalate (DCPA), commonly known as Dacthal, products due to serious health risks. DCPA is a pesticide registered to control weeds in both agricultural and non-agricultural settings but is primarily used on crops such as broccoli, brussels sprouts, cabbage, and onions.
AMVAC Chemical Corporation is the sole manufacturer of DCPA. Despite a Data Call-In (DCI) issued in 2013 requiring extensive studies, including on thyroid effects, AMVAC failed to provide complete data until November 2023.
"DCPA is so dangerous that it needs to be removed from the market immediately,” said Assistant Administrator for the Office of Chemical Safety and Pollution Prevention Michal Freedhoff. “It’s EPA’s job to protect people from exposure to dangerous chemicals. In this case, pregnant women who may never even know they were exposed could give birth to babies that experience irreversible lifelong health problems. That’s why for the first time in almost 40 years, EPA is using its emergency suspension authority to stop the use of a pesticide.”
In May 2023, the EPA's risk assessment identified significant health risks from DCPA, particularly for pregnant individuals and their unborn babies. Exposure levels were found to be four to 20 times higher than safe limits, even with protective measures. Additionally, unsafe levels of DCPA could persist in treated fields for over 25 days, and spray drift posed risks to nearby residents.
The order, issued under the authority of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), mandates the immediate cessation of the sale, distribution, and use of all DCPA products. This includes popular formulations such as Dacthal Flowable Herbicide, Dacthal W-75 Herbicide, and Technical Chlorthal Dimethyl. The agency determined that allowing these products to remain on the market would have unreasonable adverse effects on human health and the environment.
Central to the EPA's decision are the significant health risks associated with DCPA exposure, particularly for pregnant women and their unborn children. A comparative thyroid assay (CTA) study revealed that even extremely low levels of DCPA exposure can disrupt thyroid hormone levels in fetal rats. These disruptions are critical because thyroid hormones are essential in fetal brain development. Disruptions in these hormones can lead to a range of developmental issues:
Occupational handlers, including farmers and agricultural workers, are at the highest risk due to direct contact with DCPA. However, the risk extends to bystanders and residents near treated fields, who may be exposed through drift and residue. The EPA’s comprehensive exposure assessment highlighted that the risk remains unacceptably high even with maximum personal protective equipment (PPE) and engineering controls.
The persistence of DCPA residues on treated foliage means that even individuals who do not directly handle the pesticide can be exposed to environmental contamination. This widespread potential for exposure underscores the urgent need for the suspension.
While DCPA is valued for its effectiveness in controlling weeds in high-value crops such as specialty Brassica and Allium varieties, the EPA’s analysis indicates that the overall economic impact of the suspension will be minimal. Alternative herbicides are available for most uses, and the global market for these crops is resilient enough to absorb the changes. The benefits of safeguarding public health far outweigh the limited economic disruptions.
AMVAC proposed some changes, including canceling DCPA use on turf, which reduced recreational exposure. However, agricultural uses remained a concern. In April 2024, the EPA warned of significant health risks and indicated regulatory actions, including possible cancellation or emergency suspension of DCPA.
Due to the severe and imminent harm posed by DCPA, EPA Administrator Regan determined that an emergency suspension was necessary. The EPA plans to issue a notice of intent to cancel DCPA products within 90 days.
