EPA yanks pesticide Dacthal from US market

The US Environmental Protection Agency is taking an unusual step to immediately halt all sales and uses of the herbicide dimethyl tetrachloroterephthalate (DCPA), sold under the trade name Dacthal. The move comes 11 years after the agency first ordered Amvac Chemical, the sole manufacturer of the product in the US, to hand over toxicity data, including effects on fetal thyroid hormones.

The EPA gave the company a deadline of 2016. In April 2022, the agency still had not received the data, so it warned Amvac that it was planning to cancel the DCPA registration. A few months later, Amvac provided the EPA with results from a thyroid study in pregnant rats. The study showed that DCPA’s effects on fetal thyroid hormones are unique in that they occur at low levels that don’t cause adverse effects in maternal rats.

The EPA used Amvac’s study to assess the human health risks of exposure to DCPA. In a May 2023 assessment, the agency found serious risks to unborn babies of pregnant people exposed to the chemical, including workers who transplant, weed, and harvest crops that it is sprayed on.

Current labels allow workers to enter treated fields 12 h after DCPA is applied. But the herbicide can remain in treated fields at unsafe levels for 25 days or more, the EPA says in a press release.

Pregnant farmworkers handling DCPA and crops that it is sprayed on such as broccoli, cabbage, and onions could be exposed to levels 4–20 times as high as those the EPA estimates are safe for unborn babies, the agency says. Such exposure can lead to fetal thyroid hormone changes that are associated with low birth weight, altered brain development, and impaired motor skills.

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

In the past year, Amvac has proposed several changes to reduce the risks of DCPA, including canceling products used on turf. Those changes eliminate risks from recreational activities, such as golf, but do not adequately address agricultural risks, the EPA says.

Groups representing agricultural workers applauded the EPA’s decision. “Farmworkers should not have to put their children at risk by doing the work needed to grow our food,” Teresa Romero, president of United Farm Workers, says in a statement. “EPA is taking the right step in immediately stopping use of this pesticide.”