EPA bans long-used herbicide to safeguard vulnerable populations

On Aug. 6, the Environmental Protection Agency (EPA) announced an emergency ban of the pesticide dimethyl tetrachloroterephthalate (DCPA or Dacthal). This is the first time in nearly 40 years the agency has issued an order to stop use of a pesticide, citing health risks to children born to pregnant women who are exposed to DCPA. EPA has long been aware of the chemical’s risks, so the immediacy of the agency’s action is surprising.

In the Federal Register announcement, EPA called the use of DCPA an imminent hazard. “An emergency exists that does not permit EPA to hold a hearing before suspending such products,” the notice said. “Effective immediately, no person in any state may distribute, sell, offer for sale, hold for sale, ship, deliver for shipment, or receive and (having so received) deliver or offer to deliver to any person any pesticide product containing DCPA.”

While the chemical is used in non-agricultural settings such as sod and nursery ornamental production, it is widely used as an herbicide to control weeds on crops like broccoli, brussels sprouts, cabbage and onions. Other previously registered uses include cucurbits (cucumbers, squash, watermelons and melons), root vegetables and fruiting vegetables. Farmworkers face the greatest risk, though people living near fields where DCPA is used may be exposed to spray drift. A press release by EPA cautions, “Current product labels specify that entry into treated fields must be restricted for 12 hours after application. However, the evidence indicates that for many crops and tasks, levels of DCPA in a treated field remain at unsafe levels for 25 days or more.”

Trevor Craig, corporate senior technical director of engagement and consulting at Microbac, said, “The EPA bans things all the time, but this is one of the few times where they have come in very quickly and said that the use has to be stopped immediately.” Craig added that EPA estimates field workers may have been exposed at up to 20 times the safe exposure level. He questions why it took so long to act on information that DCPA is potentially dangerous.

DCPA was approved in 1958. EPA undertakes registration reviews every 15 years. EPA’s press release sheds light on the agency’s responses to growing evidence. In 2013, the agency required DCPA’s manufacturer, AMVAC Chemical Corporation, to submit more than 20 studies to support the existing registration of the pesticide. In April 2022, EPA issued a Notice of Intent to Suspend based on AMVAC’s failure, for almost 10 years, to submit the complete set of data. In May 2023, EPA’s assessment of a thyroid study submitted by AMVAC found health risks associated with the chemical. Suspension was announced on Sept. 1, 2023, and on April 1, 2024, EPA issued a public warning to farmworkers. Yet, another four months passed before prohibition of the product.

It's unlikely that consumers have suffered adverse effects from the chemical’s use. FDA’s pesticide residue monitoring program tests food samples for various pesticides. DCPA residue was found in as few as 0.51% (2021) and as high as 6.2% (2017) of samples tested during the most recent available years (2017-2021). The reports indicated that no foods contained violative pesticide levels.

“If you're very concerned about it as a consumer, I would recommend washing your vegetables that are most at risk, broccoli, onions, brussels sprouts, some leafy greens, to help remove any of that additional residue if it does exist,” Craig said. He suggests using warm water and dismisses the need for special chemicals or soaps.