EPA bans use of Dacthal, a common weed killer used on crops

Federal regulators issued a rare emergency order Tuesday to stop the use of a popular weed killer that they say causes significant risk to farmworkers and fetuses.

The product, dimethyl tetrachloroterephthalate, better known as DCPA or Dacthal, “is so dangerous that it needs to be removed from the market immediately,” said Michael Freedhoff, assistant administrator for the Environmental Protection Agency’s Office of Chemical Safety and Pollution Prevention.

The chemical is commonly used for weed control with crops such as broccoli, Brussels sprouts, cabbage and onions. The EPA has warned of the chemical’s health risks in the past, but this is the first time in nearly 40 years it has issued an emergency order to suspend its use and comes after more than a decade of studying its risks and effects.

“It’s EPA’s job to protect people from exposure to dangerous chemicals,” Freedhoff said in the statement. “In this case, pregnant women who may never even know they were exposed could give birth to babies that experience irreversible lifelong health problems.”

Pregnant women exposed to Dacthal, often unknowingly, could experience changes in fetal thyroid hormone levels, which could result in low birth weight, impaired brain development, lower IQ and impaired motor skills later in life, the EPA warned.

Pregnant women handling Dacthal could be exposing their unborn children to dangerous chemicals at levels 4 to 20 times greater than is deemed safe, according to agency estimates. Health risks persisted even when personal protective equipment was being used, the agency found.

For example, package labels recommend restricting access to herbicide-treated fields for only 12 hours after use, but the EPA alleges levels of Dacthal in treated fields were still unsafe 25 days after it was applied. The movement of the weed killer through the air to areas near treated fields could also put unborn babies and pregnant women at risk, the EPA said.

The EPA’s decision was applauded by groups advocating for farmworker safety.

“This emergency decision is a great first step that we hope will be in a series of others that are based on listening to farmworkers, protecting our reproductive health, and safeguarding our families,” said Mily Treviño, executive director of Alianza Nacional de Campesinas. “Alianza is pleased to see the EPA make this historic decision.”

According to the EPA, in 2013 the agency asked AMVAC Chemical Corp., the manufacturer of Dacthal, to submit paperwork, including more than 20 studies on the chemical, to the agency to review the herbicide’s registration.

The EPA considered much of the data submitted by the company between 2013 and 2021 to be insufficient, and found that a required study looking into the weed killer’s effects on thyroid development due in 2016 was never submitted.

The thyroid study was ultimately submitted in August 2022, but the EPA had already issued a notice of intent to suspend the technical-grade production of Dacthal.

Since then, AMVAC has voluntarily suspended the use of the weed killer on turf, but the EPA alleges that any continued use of the herbicide presents unacceptable risks.

In a brief email, AMVAC did not address the EPA’s concerns or whether it would challenge the order.

“AMVAC is working in good faith with both the EPA and our customers to ensure full compliance,” said Anthony Young, director of investor relations at the company.

Despite the emergency order, the EPA said it could still take months before the product is pulled off shelves because of procedural requirements. If the order is contested, it could take several years.