EPA emergency order immediately suspends all uses of highly toxic weedkiller DCPA, sold under brand name Dacthal

Today the Environmental Protection Agency announced an emergency order immediately suspending all uses of the highly toxic weedkiller sold under the brand name Dacthal due to its significant health risks – particularly for farmworkers and pregnant people.

Also known as DCPA, dimethyl tetrachloroterephthalate and chlorthal-dimethyl, the herbicide was banned in the European Union in 2009, and the EPA has long known of its potential harm to people.

“The EPA’s decision to finally suspend DCPA is welcome news, but it’s long overdue,” said Environmental Working Group Senior Toxicologist Alexis Temkin, Ph.D. “For years, EWG and other public health advocates have warned about the serious risks the weedkiller poses to farmworkers, pregnant people and other vulnerable populations.”

In 1995

– nearly 30 years ago – the agency classified DCPA as a “possible carcinogen.”. That decision was based on a study conducted by Dacthal’s manufacturer in 1993, which showed it caused thyroid tumors in animals, suggesting similar potential threats to people.

In 2013, the EPA required AMVAC, the sole DCPA manufacturer in the U.S., to submit an additional study showing the chemical’s effects on the fetal thyroid among other information.

AMVAC’s research, finally submitted to the EPA in 2022, showed even low doses of DCPA exposure can harm the developing fetus.

During the nearly 10 years before it finally complied with the EPA’s requirement, the company continued producing and selling Dacthal.

And AMVAC didn’t submit other data requested. So in August 2023, the agency suspended use of the pesticide, a de facto temporary ban.

Yet three months later the EPA lifted that suspension

, once again allowing Dachtal’s use – until today.

The EPA’s emergency order immediately halts all uses of the herbicide.

Permanently banning DCPA

The new suspension means DCPA is banned even while the EPA begins the cancellation process for the pesticide, which will lead to a permanent ban of DCPA.

It is the first time in nearly 40 years the EPA has exercised its emergency authority to suspend the use of a pesticide to “prevent imminent hazard.”

This means the EPA believes continued use of the pesticide while the lengthy cancellation process plays out would cause harm to people, and that no mitigation measures would be adequate to protect people.

DCPA has been in use in this country since the late 1950s. These days, it can be found on vegetables like cilantro, kale, mustard greens, broccoli and green onions. That’s because, after it’s used to kill weeds, the chemical can linger in the soil for long periods of time, contaminating crops later grown in those fields.

EWG research published in 2019 identified DCPA on nearly 60 percent of kale samples tested by the Department of Agriculture. The USDA also found the pesticide on many collard and mustard green samples.

DCPA’s toxic effects on people

The EPA identified DCPA’s ability to harm the thyroid in the 1990s,

based on studies submitted by the pesticide manufacturer. According to a 2011 agency document

, a 2004 human health risk assessment identified the need to understand how DCPA harms the thyroid in the developing fetus.

A 2022 peer-reviewed study

by EWG scientists identified DCPA as a pesticide of concern, due to its toxicity and capacity to harm the thyroid and its classification as a possible cause of cancer.

Other EWG research found that, even though the EPA had evidence of DCPA’s health risks, up to 200,000 pounds of the chemical were sprayed during some years in California – even as the agency delayed action.

A 2019 study

led by scientists at the University of California at Berkeley School of Public Health found that more than half of adolescent girls from farmworker communities in the Salinas Valley had been exposed to DCPA.

Since 2019, EWG has warned about DCPA's risks to human health, calling on the EPA to ban it in 2021 public comments and again in official comments to the agency in July 2023.

“Countless people have been exposed to DCPA while the EPA abdicated its responsibility,” said Temkin. “The agency should have taken action decades ago, when it first identified the human health risks posed by this toxic crop chemical.”