Green groups on Wednesday sued the Environmental Protection Agency over its recent approval of Dow AgroSciences' herbicide Enlist Duo, which farmers and scientists warn threatens human and environmental health.

"The toxic treadmill has to stop," said Jay Feldman, executive director of Beyond Pesticides. "EPA and USDA cannot continue to ignore the history, science, and public opinion surrounding these dangerous chemicals so that a failed and unnecessary system of chemically-dependent agriculture can continue to destroy our health and environment."

The EPA last week approved Enlist Duo for use on corn and soybean crops that are genetically engineered to survive exposure to the herbicide. Wednesday's suit charges the approval was unlawful because the agency failed to adequately consider the human impacts and did not consult with the Fish and Wildlife Service.

Enlist Duo's key ingredient, known as 2,4-D, was also used in Agent Orange, the toxic defoliant used as a weapon by the U.S. military during the Vietnam War. Studies find 2,4-D interferes with hormonal and reproductive function and is linked to cancer, liver disease, Parkinson's disease, and other health problems. Scientists warn that 2,4-D builds up in the environment and spreads from one field to another, posing a risk to animals as well as people.

"EPA’s unfortunate decision to approve Enlist Duo for use on genetically engineered crops will more than triple the amount of 2,4-D sprayed in the U.S. by the end of this decade," said Environmental Working Group’s senior policy analyst Mary Ellen Kustin. "Such an increase of a known toxic defoliant linked to Parkinson’s disease, non-Hodgkin’s lymphoma and reproductive problems is unconscionable."

While the EPA moved to limit Enlist Duo to six Midwestern states, it is expected that the approval will spread to other states. "This case will determine to a large extent the direction of U.S. agriculture in the coming years," said Andrew Kimbrell, Executive Director of Center for Food Safety.

"Rural communities rely on EPA to take its job seriously—to fully consider potential health impacts before introducing new products or allowing a dramatic increase in use of a hazardous and volatile chemical like 2,4-D," said Pesticide Action Network North America’s senior scientist Marcia Ishii-Eiteman, PhD.

The lawsuit was levied by Center for Food Safety and Earthjustice in the Ninth Circuit Court of Appeals on behalf of Beyond Pesticides, Center for Biological Diversity, Center for Food Safety, Environmental Working Group, the National Family Farm Coalition, and Pesticide Action Network North America.