Regulatory Timeline

U.S. regulators approve atrazine.

Atrazine classified as “possible human carcinogen” after research on one species of rat.

Atrazine in the environment drops significantly after stewardship programs introduced.

EPA initiates the Special Review of the Triazine Herbicides, leading to an EPA Special Advisory Panel to review safety of triazine products, reviewing hundreds of studies and more than 80,000 public comments.

Triazine Network is formed, providing growers a seat at the table in regulatory issues surrounding atrazine and other triazine herbicides.

World Health Organization’s International Agency for Research on Cancer (IARC) re-catergorizes atrazine as “not classifiable as to carcinogenicity in humans.”

An EPA Special Advisory Panel, then the full EPA, say atrazine is not likely to cause cancer, after finding the 1980s research used was not relevant to humans.

EPA’s Interim Re-registration Eligibility Decision reconfirms the safety of atrazine, after public forums, tens of thousands of public comments, and input from environmentalists, manufacturers and consumers.

2 Scientific Advisory Panel: Potential Developmental Effects of Atrazine on Amphibians and Epidemiology Data Related to Prostate Cancer and Exposure to Atrazine– After reviewing dozens of studies, including four by Prof. Tyrone Hayes, EPA Science Advisory Panel rules evidence inconclusive on whether atrazine exposure affects amphibian life.

Shortly after EPA’s 2003 Interim Re-registration Eligibility Decision reconfirming the safety of atrazine, the trial attorney firm of Korein Tillery files the Holiday Shores class action lawsuits in Madison County Illinois seeking damages against the makers of atrazine.

EPA releases Triazine Cumulative Risk Assessment, finding triazine herbicides (one of which is atrazine) pose “no harm that would result to the general U.S. population, infants, children, or other consumers.”

EPA issues atrazine re-registration decision saying “levels of atrazine that Americans are exposed to in their food and drinking water are below the level that would potentially cause health effects.”

EPA concludes atrazine does not affect amphibian development; says “no additional testing is warranted…”

EPA issues White Paper on recent amphibian research, saying there is “no compelling reason to pursue more testing” on the question of the effect of atrazine on amphibian life.

Independent Science Advisory Panel meets to review and comment on the ecological monitoring program for atrazine.

A joint meeting of the Food and Agricultural Organization and the World Health Organization on pesticide residues concludes that atrazine is not likely to pose a risk of cancer to humans.

Activist Researcher Tyrone Hayes submits “Atrazine induces complete feminization and chemical castration in male African clawed frogs” to the Proceedings of the National Academy of Sciences (PNAS) for publication

New York Times article “Debating how much weedkiller is safe in your water glass” is published. Also, the Peoria Journal Star (Ill.) publishes “Lawsuit questions safety of herbicide”

Huffington Post Investigative Fund website publishes “EPA Fails to Inform Public About Atrazine”  with an accompanying video

Holiday Shores Sanitary District adds additional plaintiffs to Madison County, Illinois, lawsuit

EPA holds meeting to “present SAP its plan for the new atrazine evaluation”

EPA announces a new re-evaluation of atrazine with six Scientific Advisory Panels.

Pesticide Action Network (PANNA) and Land Stewardship Project (of Minn.) release “The Syngenta Corporation and Atrazine: The Cost to the Land, People and Democracy”; groups submit letter from organic farmers to EPA

State of Minnesota announces “atrazine regulations protect human health and the environment.”

More than 50 agricultural groups send letter to EPA Administrator Lisa Jackson in support of atrazine

EPA convenes Scientific Advisory Panel (SAP) on reviewing epidemiology in regulatory risk assessments

Huffington Post Investigative Fund publishes “Cities Sue Manufacturer of Weed-Killer Found in Tap Water”

Federal class action lawsuit filed in Southern District of Illinois

33 members of Congress sign and submit letter to EPA Administrator Lisa Jackson in support of atrazine

Rep. Ellison (D-MN) introduces federal bill to ban atrazine

EPA announces new SAP on possible cancer effects of atrazine

EPA convenes SAP on animal studies and water monitoring

“Save the Frogs Day” introduces petition to ban atrazine; threatens “International Day of Pesticide Action” and march on Washington this year on October 24

NRDC releases “Still Poisoning the Well”

University of Illinois releases study saying “without alternatives, atrazine elimination would severely compromise sweet corn production”

Report from Agricultural Health Study says “no correlation between atrazine and cancer”

President’s Cancer Panel releases report including section on atrazine, including quotes from Hayes

EPA initiates routine Registration Review of atrazine which is supposed to occur every 15 years.

Papoulias Medaka Study – Conducted in 2004 but not published until 2014, this questionable study indicates detrimental impact of atrazine to medaka fish, which has not been found in other studies. Study was not submitted during several recent EPA Science Advisory Panels. Read more

Sadinski, Hayes Amphibian Study – Dr. Tyrone Hayes coauthors a study that shows frogs in the Midwest where atrazine is used are actually thriving, disproving his theory that atrazine is detrimental to frogs.
Read more

EPA posts a signed Refined Ecological Risk Assessment for Atrazine report dated 4-12-16, on the EPA website recommending an aquatic life “Level of Concern” (LOC) of 3.4 parts per billion, dramatically lower than the 10 ppb LOC currently being used by EPA.

EPA removes the 1,100-page Refined Ecological Risk Assessment for Atrazine report dated 4-12-16, on the EPA website recommending an aquatic life “Level of Concern” (LOC) of 3.4 parts per billion, dramatically lower than the already low 10 ppb LOC currently being used by EPA. EPA officials said the report was posted accidentally and said it would be released in a few months.

EPA released its Ecological Risk Assessment for atrazine. In its recommendations, EPA ignored several high-quality studies and instead used studies the agency’s own 2012 Scientific Advisory Panel (SAP) found to be flawed. Using the flawed research, EPA recommended the aquatic life level of concern (LOC) be set at 3.4 parts per billion (ppb) on a 60-day average. EPA’s current LOC for atrazine is 10 ppb, however all credible scientific evidence points to a safe aquatic life LOC at 25 ppb or greater.

Comment period ends for the Ecological Risk Assessment for atrazine. Over 77,000 comments were received by EPA.

EPA releases the Cumulative Human Health Risk Assessment for atrazine as part of the registration review process.

EPA Grants Triazine Network request to extend the Human Health Risk Assessment comment period to Nov. 23, 2018. Growers and farm organizations submit comments to EPA.

Growers and the Triazine Network hold several meetings with EPA to help the agency understand the importance of atrazine to farming and conservation practices, as well as the need to “get the science right” in the atrazine registration review. See actions here

EPA publishes the Preliminary Interim Decision for the atrazine registration review in the Federal Register. The registration review began in 2013. The PID corrects a recommendation made in the 2016 Ecological Risk Assessment to set the LOC at 3.4 parts per billion, an ultra-low level that would have banned the use of atrazine in much of farm country. The lower LOC was based on questionable research, including studies that had been turned down by EPA’s 2012 Science Advisory Panel (SAP). Relying on several points of information, including EPA’s SAP recommendations, the agency modified the LOC to 15 parts per billion over a 60-day average.  Read more here.

NGO’s file lawsuit against EPA  alleging that the agency violated its duties under FIFRA by issuing the atrazine ID without substantial evidence supporting the decision.

In an unprecedented move, EPA requests from the court considering the lawsuit against EPA’s atrazine interim decision,  a voluntary partial remand allowing EPA to reevaluate its own 2020 registration review decision to use 15 ppb as the level of concern  (CELOC) for aquatic plant communities.

EPA releases a revision to the Atrazine Registration Review Decision (IRED), changing the Atrazine CELOC to from 15 ppb to 3.4 ppb, and uses a flawed modeling system that would severely impact atrazine use for 72 percent of corn acres.

More than 16,000 farmers and agricultural organizations representing corn, citrus, grain sorghum, sugar cane, and other crops submitted comments opposing EPA’s revisions to the 2020 Atrazine IRED for the registration review.

The Triazine Network requests a Scientific Advisory Panel to consider low quality studies used in EPA’s proposed revisions to the IRED. EPA agrees to convene an SAP

EPA releases a white paper for use by the upcoming Scientific Advisory Panel, recommending exclusion or rescoring of the low quality studies.

The SAP holds a virtual 3-day hearing. Several growers and agriculture groups with the Triazine Network provide testimony. Triazine Network’s request to include two additional low-quality studies  for review by the SAP is denied.

EPA agreed with the recommendations of the atrazine Scientific Advisory Panel (SAP), removing several poor-quality studies that played a role in the agency’s recommendation for an ultra-low aquatic level of concern (CELOC) for atrazine.

EPA announced an update to the level at which atrazine is expected to adversely affect aquatic plants. The new revised atrazine concentration of 9.7 parts per billion, which was derived following an August 2023 Scientific Advisory Panel, will be used to develop a revised regulatory decision

EPA’s updated atrazine proposal contained positive changes for growers, solidifying the 9.7 ppb level of concern and improving the mitigation practices, but concerns remain with poor quality studies remaining, and use of a deeply flawed model and mapping system to predict atrazine runoff. Comment period received two extensions to April 4, 2025.