In an unprecedented move, the Environmental Protection Agency (EPA), in consultation with the U.S. Department of Agriculture (USDA), has issued an emergency order suspending all dimethyltetrachloroterephthalate (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 thyroid effects, AMVAC failed to provide complete data until November 2023.

“DCPA is so dangerous that it must be removed from the market immediately,” said Michal Freedhoff, assistant administrator of the Office of Chemical Safety and Pollution Prevention. “EPA’s job is to protect people from exposure to dangerous chemicals. In this case, pregnant women who may not even know they’ve been exposed could be giving birth to babies who will have irreversible lifelong health problems. That’s why, for the first time in nearly 40 years, EPA is using its emergency suspension authority to stop the use of a pesticide.”

Imminent danger and regulatory measures

In May 2023, the EPA’s risk assessment identified significant health risks from DCPA, particularly to pregnant individuals and their unborn babies. Exposure levels were found to be four to 20 times higher than safe limits, even with protective measures in place. Additionally, unsafe levels of DCPA in treated fields could persist for more than 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), requires an immediate halt to 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 on the market would cause unreasonable adverse effects on human health and the environment.

Health risks and scientific evidence

Central to the EPA’s decision is 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 for fetal brain development. Disruptions in these hormones can lead to a range of developmental problems:

• Reduced IQChildren exposed to DCPA in the womb may experience decreased intellectual abilities.
• Reduced motor skills:Exposure may lead to delays in motor skill development, affecting coordination and physical abilities.
• Reduced bone depositionAnother important effect is a decrease in bone density and strength, which can have long-term consequences for physical health.

Exposure pathways and risks

Professionals, including farmers and farm workers, are at greatest risk from direct contact with DCPA. However, the risk extends to bystanders and residents near treated fields, who may be exposed via drift and residue. The EPA’s comprehensive exposure assessment emphasized that the risk remains unacceptably high, even with maximum personal protective equipment (PPE) and engineering controls.

The persistence of DCPA residues on treated leaves means that even people who do not directly handle the pesticide could be exposed to environmental contamination. This widespread potential for exposure underscores the urgent need for the suspension.

Economic considerations and impact

While DCPA is valued for its effectiveness in controlling weeds in high-value crops such as specialty Brassica and Allium varieties, EPA analysis indicates that the overall economic impact of the suspension will be minimal. Alternative herbicides are available for most applications, and the global market for these crops is resilient enough to absorb the changes. The benefits of protecting public health far outweigh the limited economic disruption.

AMVAC proposed some changes, including canceling DCPA use on turf, which would reduce recreational exposure. However, agricultural use remained a concern. In April 2024, the EPA warned of significant health risks and indicated that regulatory action would be needed, including possible cancellation or emergency phaseout of DCPA.

Because of the serious and imminent harm caused by DCPA, EPA Administrator Regan determined that an emergency shutdown was necessary. The EPA plans to issue a notice of intent to cancel DCPA products within 90 days.