Updated with comments from Syngenta.

EPA released the draft ecological risk assessments for atrazine, propazine and simazine, which evaluate risks to animals and plants including amphibians, birds, mammals, fish, reptiles, aquatic invertebrates, aquatic plant communities and terrestrial plants on June 2. All three pesticides are in the triazine class of pesticides.

Related: Purdue study raises questions about atrazine

EPA released the draft ecological risk assessments for atrazine, propazine and simazine. Atrazine, first approved in 1958, is one of the most widely used agricultural pesticides in the United States. (Photo: fotokostic/Thinkstock)

EPA invites stakeholders to comment on the draft ecological risk assessments when the Federal Register notice publishes and the public comment period opens within a week. The draft assessments are available on the agency's website.  EPA will be accepting public comments for 60 days after the Federal Register publishes. It was published in the Federal Register on June 6. After receiving and reviewing public comments, the agency will amend the assessments, as appropriate.  EPA will have atrazine's assessment peer reviewed by the Scientific Advisory Panel in 2017.

With regard to atrazine, the herbicide is one of the most widely used agricultural pesticides in the United States. It is used primarily on corn and sorghum in the Midwest and sugarcane in the South Central and Southeastern United States to control broadleaf and grassy weeds.

Points from the Refined Ecological Risk Assessment for Atrazine:

-Atrazine is slightly toxic to birds and mammals and is practically non-toxic to terrestrial invertebrates on an acute exposure basis. Risk to birds and mammals is primarily through chronic exposure. Levels of concern for terrestrial plants are exceeded following spray drift or runoff after applications of rates as low as .25 pounds per acre.

-Based on a tier 1 terrestrial spray drift analysis, chronic risk levels of concern for mammals are exceeded at distances of 25 to 250 feet off the field following ground spray application. The distance for risk to birds is less.

-Atrazine is practically non-toxic to honey bees based on acute contact toxicity.

-Atrazine and atrazine formulations are highly toxic to both monocot and dicot terrestrial plants.

-Chronic exposure to atrazine for freshwater fish, aquatic phase amphibians and aquatic invertebrates resulted in significant effects on survival, growth or reproduction.

-Rainbow trout is the most sensitive freshwater fish in the acute study.

EPA's human health assessment for the three triazines is currently under review, and is expected to be released later in 2016.

Once the Federal Register notice publishes on the three triazines, the assessments and all related materials will be available on and comments can be submitted at www.regulations.gov in dockets EPA-HQ-OPP-2013-0266 (atrazine); EPA-HQ-OPP-2013-0250 (propazine); and EPA-HQ-OPP-2013-0251 (simazine).

NCGA, Syngenta respond. -- >>>

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Response

In a statement following the releases of the draft ecological risk assessment, the National Corn Growers Association defended the judicious use of atrazine.

“Atrazine is a safe and effective crop management tool for farmers,” said NCGA president Chip Bowling, a Maryland farmer. “It is widely used because it is among the most reliable herbicides available, and it plays a critical role in combating the spread of resistant weeds. It reduces soil erosion, increases crop yields, and improves wildlife habits. Over the last 50 years, atrazine has passed some of the most rigorous safety testing in the world. More than 7,000 scientific studies have found atrazine to be safe.”

Bowling cited a 2012 University of Chicago study that found removing atrazine from farmer’s herbicide toolbox would cost farmers as much as $59 per acre.

He said NCGA will encourage farmers to comment on the proposal and urge the EPA to base their decision on the use of atrazine on sound science.

“We’re troubled the draft assessment discounted several rigorous, high-quality scientific studies and didn’t adhere to EPA’s own high standards,” said Marian Stypa, Ph.D., head, product development for Syngenta in North America. “The draft report erroneously and improperly estimated atrazine’s levels of concern for birds, fish, mammals and aquatic communities that are not supported by science.”

The Triazine Network, a national coalition of farm organizations representing more than 30 agricultural crops in more than 40 states, insists if EPA continues to use the same false logic or endpoints as noted in the preliminary risk assessment, it could lead to a de facto ban on atrazine.

“EPA’s flawed atrazine report is stomping science into the dirt and setting farmers up for significant economic hardship. We challenge this latest proposal and insist EPA abide by federal law that requires the agency to make determinations based on credible scientific evidence,” said Triazine Network Chairman Gary Marshall. Marshall is executive director of the Missouri Corn Growers Association. “Again and again, we must ask EPA to follow the law. A regulatory agency should not need to be reminded of that detail.”

The Triazine Network asserts the federal agency discounted several high-quality studies and instead used studies EPA‘s own 2012 Scientific Advisory Panel (SAP) deemed flawed. According to the latest report, EPA is recommending aquatic life level of concern (LOC) be set at 3.4 parts per billion (ppb) on a 60-day average. The EPA’s current LOC for atrazine is 10 ppb, however a diverse universe of scientific evidence points to a safe aquatic life LOC at 25 ppb or greater. The proposed level cuts average field application rates down to 8 ounces (one cup) per acre. An acre is the size of a football field.

“At the proposed level, atrazine would be rendered useless in controlling weeds in a large portion of the Corn Belt, effectively eliminating the product,” notes Marshall. “It sets a dangerous precedent when it comes to approving crop protection tools, puts farmers at a great economic disadvantage and would drastically set back conservation efforts. If EPA abandons the recommendations of their own Science Advisory Panels and more than 7,000 science-based studies in favor of activist agenda’s and politics; they will have lost all credibility”

EPA reregistered atrazine in 2006 and began its regularly scheduled registration re-review June 2013.

Source: EPA, NCGA, Missouri Corn Growers Association, Syngenta