American agriculture is in a losing battle with a villain of its own design: chemical-resistant superweeds. The newly evolved weeds are popping up in millions of acres of fields sprayed with Glyphosate or 2,4-D, two of the most widely used herbicides on the market. Dow Chemical thinks it has the solution: it wants to combine the two chemicals into a new super-chemical called Enlist Duo. The EPA’s comment period on Enlist Duo has just ended, and they are on track to approve Dow’s new combination for market. But environmentalists and doctors are calling foul.
“[Dow Chemical] is right in the short term, but they’re super, super wrong in the long term,” Mary Ellen Custin, a senior policy analyst at the nonprofit research organization Environmental Working Group (EWG) tells Newsweek. After a while, weeds will develop resistance to Enlist Duo as well, she says, and by then, farmers will have added huge sums of the chemicals to the environment. The USDA is in the process of vetting the corresponding GMO seed for Enlist Duo, and per the agency’s analysis, the new spray would lead to a two- to six-fold increase in 2,4-D use in the U.S. by 2020.
“[I]ncreased 2,4-D application is likely to accelerate and exacerbate the evolution of yet more 2,4-D-resistant weeds,” reads a letter from 35 physicians and experts to EPA Administrator Gina McCarthy urging the EPA not to approve Enlist Duo. They refer to the cycle of using ever-more and different chemicals to combat weed resistance as the “pesticide treadmill.”
The new herbicide comes in the form of a choline salt, instead of a liquid spray, which would limit its ability to drift during application, according to Dow. Using Dow’s assessment, which indicated a drift radius of 200 feet, according to EWG, the EPA called for a 200-foot buffer zone to protect non-target plants from exposure. The EPA has conducted its own risk assessment, and has determined that Enlist Duo, if used as directed, poses “no risks of concern” to human health [PDF]. But in a new report out Wednesday, EWG has determined that 5,609 schools are within 200 feet of fields that could be sprayed with Enlist Duo, if it is approved.
"When it comes to dousing crops with noxious chemicals, EPA focused on buffer zones for plants, not people," reads a statement announcing the report. "In its assessment, the EPA called for a 200-foot buffer zone to protect non-weed plants from the product but glosses over the health risks to children."
Exposure to 2,4-D has been linked to thyroid conditions, non-Hodgkin’s lymphoma, suppressed immune function, and other adverse health effects. According to the letter from the 35 doctors, Dow “did not conduct any toxicity tests for simultaneous exposure to the combination of 2,4-D and glyphosate, which could pose a much higher human and environmental toxicity risk than either herbicide alone.”
In an email response to Newsweek, the EPA wrote that “there would be no reason for concern regarding risks to humans and children resulting from drift, based on the properties and the proposed label directions.”