The U.S. EPA is now clearly on record as confirming that atrazine is not likely to cause cancer or any other disease when used according to the label directions, the Iowa Farm Bureau said in a November 21 letter to the federal agency regarding its recent draft human health risk assessment. The agency has also confirmed its safety for farmers using atrazine with typical, agronomically recommended application methods. In addition, it has correctly reduced the uncertainty and safety factors used in previous risk assessments. It is also good to see that the agency has affirmed the mode of action and selection of new toxicological endpoints in this human health risk assessment, the IFBF said.
Farm Bureau supports the continued safe use of atrazine and other triazines. Atrazine is the most widely used herbicide on corn, applied on at least 58 percent of Iowa corn acres in 2017 to control broadleaf weeds because it works, it's cost-effective, and it's safe for farmers and the environment, the largest general farm organization told the EPA. It is also a key tool in Iowa’s Nutrient Reduction Strategy developed to reduce phosphorus and nitrogen loss and improve surface water quality, and also in our pest resistance management program.
However, given that the agency appears to have considered every available study and publication in this human health risk assessment, it is concerning that it is still greatly overstating the potential concentrations in drinking water. EPA should look at all the studies again and the most extensive monitoring data available for any crop protection compound and correct these values to be more representative of real-world experiences, the IFBF said.
In addition, the agency has not yet responded to the IFBF's draft ecological risk assessment comments in 2016 where the farm organization said it is critical for EPA to incorporate the best available science to correct errors in the Level of Concern (LOC) for fish, frogs and birds. The greatest policy concern is that if the EPA continues to use the same faulty science relied on in that older preliminary risk assessment, it could effectively eliminate use of the herbicide on Iowa corn acres, thus jeopardizing state efforts to control soil erosion and phosphorus loss to surface water. Atrazine is especially effective in today’s high-residue fields, virtually eliminating the need for in-season weed-control tillage and enabling wider adoption of no-till and reduced-till production systems.
The IFBF said in 2016 and continues to assert today that the agency discounted several high-quality studies and instead used studies that the EPA's own 2012 Scientific Advisory Panel deemed flawed. That draft report erroneously and improperly estimated atrazine’s LOC for fish, frogs and birds and aquatic communities in ways not supported by science, resulting in an aquatic life LOC of 3.4 parts per billion (ppb) on a 60-day average. However, a diverse universe of scientific evidence – in particular, a January 2016 Baylor University published study - Effects of Pulsed Atrazine Exposures on Autotrophic Community Structure, Biomass, And Production in Field-Based Stream Mesocosms - continues to support a safe aquatic life LOC at 25 ppb. In the study, the authors found that the high levels of primary production and accumulation of algal biomass in all streams likely do not represent ecologically significant adverse outcomes to periphyton, phytoplankton and aquatic macrophytes, particularly in agricultural streams subjected to high nutrient loads.
Although this more recent human health risk assessment is more accurate and science-based, the agency must also correct its previous mistakes, the IFBF said. EPA must correct the previous ecological risk assessment record to demonstrate it understands how important it is to rely on sound, accurate, peer reviewed science in the regulation of all crop protection compounds. The agency must avoid a dangerous precedent of abandoning the recommendations of its own SAPs and the more than 7,000 science-based studies already submitted during some 24 years of ongoing atrazine review. Not following a robust, science-based regulatory process in every risk assessment severely damages EPA's credibility with Iowa farmers and the public and violates and expands the agency’s authority beyond Congressional intent, the IFBF said.