By: Taylor Hill

One year after approving a powerful and highly toxic weed killer, the U.S. Environmental Protection Agency has reversed course, announcing on Wednesday it will revoke its approval of the product called Enlist Duo.

Enlist Duo’s chemical combination of glyphosate and 2,4-D—intended for use as a weed killer on genetically modified corn and soybean crops—is probably more toxic to other plants than the agency thought when it approved the substance in October 2014.

Dow AgroSciences created the herbicide cocktail. It is similar to Monsanto’s Roundup, one of the most widely used herbicides on genetically modified seeds, but designed to kill weeds that have developed a resistance to it.

Despite Enlist Duo’s potential for further decimating milkweed—the only plant that the world’s declining population of monarch butterflies lay eggs on—the EPA gave Dow AgroSciences the green light.

Environmental groups immediately petitioned for a reversal. The National Resources Defense Council, the Center for Biological Diversity, the Center for Food Safety, and other groups filed a lawsuit against the EPA, arguing that the agency had failed to show the impact the new herbicide would have on plants and animals surrounding crops.

The EPA’s reversal on Enlist Duo comes a few months after the International Agency for Research on Cancer, an arm of the World Health Organization, released findings showing that 2,4-D was “possibly carcinogenic to humans” and demonstrating “strong evidence that 2,4-D induces oxidative stress, a mechanism that can operate in humans, and moderate evidence that 2,4-D causes immunosuppression, based on in vivo and in vitro studies.”

The EPA’s decision to “withdraw the illegally approved Enlist Duo crops is a huge victory for the environment and the future of our food," George Kimbrell, the Center for Food Safety's senior attorney, said in a statement. “We will remain vigilant to ensure industry does not pressure the agency into making the same mistake in the future."

Following the announcement, shares of Dow Chemical—Dow AgroSciences’ parent company—went down 2.7 percent in midday trading. The company said in a statement that it is working with the EPA to provide further assurances that Enlist Duo meets environmental safety requirements.

“Dow AgroSciences is confident in the extensive data supporting Enlist Duo herbicide,” the company statement read.  “We are working with the EPA to quickly provide further assurances that our product’s conditions of registered use will continue to protect the environment, including threatened and endangered species.”

According to Pesticide Action Network Director Judy Hatcher, the product never should not have been given the go-ahead.

“EPA is taking a step in the right direction, but Enlist Duo shouldn’t have been given the green light in the first place,” Hatcher said. “Too often, [genetically engineered] seeds and the herbicides designed to accompany them are rushed to market without thorough evaluation of their real-world impacts on community health and farmer livelihoods.”

Originally Published: TakePart