For the first time in 40 years, the Environmental Protection Agency has taken emergency action to stop the use of a pesticide linked to serious health risks for unborn babies.

Tuesday’s emergency order applies to dimethyl tetrachloroterephthalate, also known as DCPA, a weedkiller used on crops such as broccoli, Brussels sprouts, cabbage and onions. When pregnant farmworkers and others are exposed to the pesticide, their babies can experience changes to fetal thyroid hormone levels, which are linked to low birth weight, impaired brain development, decreased IQ and impaired motor skills later in life.

“DCPA is so dangerous that it needs to be removed from the market immediately,” Michal Freedhoff, assistant administrator for the EPA’s Office of Chemical Safety and Pollution Prevention, said in a statement. “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.”

The European Union banned DCPA in 2009. But the EPA has been slower to act, frustrating some environmental and public health advocates.

In an interview, Freedhoff said that EPA scientists have tried for years to get more information on health risks from the sole manufacturer of the pesticide, AMVAC Chemical. But she said the company refused to turn over the data, including a study on the effects of DCPA on thyroid development and function, until November 2023.

“We did make some good-faith efforts to work with the company,” Freedhoff said. “But in the end, we didn’t think any of the measures proposed by the company would be implementable, enforceable or effective.”

AMVAC, which sells the pesticide under the brand name Dacthal, did not immediately respond to a request for comment.

The company had sought to avoid the emergency action. In December, AMVAC voluntarily pulled all Dacthal used on turf, reducing the risks to golfers, other athletes and workers who maintain turf fields.

But in a March letter to AMVAC, EPA officials wrote that this voluntary step was not sufficient to protect farmworkers and others exposed to the herbicide. The officials wrote that changes to thyroid hormone levels in the fetuses of pregnant rats exposed to DCPA suggested “serious risks of concern in humans.”

DCPA has been used in the United States since the late 1950s. After the pesticide is applied, it can linger in the soil, contaminating crops later grown in those fields, including broccoli, cilantro, green onions, kale and mustard greens.

In 2017, the Agriculture Department identified DCPA residue on nearly 6 in 10 kale samples it tested. The agency also found the pesticide on many collard green and mustard green samples.

In April, the EPA warned farmworkers about the risks of DCPA, saying it planned to take emergency action “as quickly as possible.” The emergency order Tuesday temporarily suspends all registrations of the pesticide under the Federal Insecticide, Fungicide and Rodenticide Act. The agency plans to permanently suspend these registrations within the next 90 days.

Mily Treviño Sauceda, executive director of Alianza Nacional de Campesinas, also known as the National Farmworkers Women’s Alliance, praised the agency’s action Tuesday, calling it “a great first step” to protect the reproductive health of farmworkers.

But Jeannie Economos, coordinator of the pesticide safety and environmental health program at the Farmworker Association of Florida, said the emergency order came too late for workers who have been exposed to DCPA for decades.

“It shouldn’t have taken this long, but we are glad that they did it finally,” she said. “How many people got sick in the meantime? How many babies were born with low birth weight? We don’t know.”

Economos said she hopes the EPA will ban more widely used, harmful pesticides and that the industry will move away from toxic agrochemicals.

“We cannot keep going this way because we’re hurting farmworkers, wildlife, the planet and ourselves,” she said.