Atrazine - Background and Updates

Atrazine is a widely used herbicide that can be applied before and after planting to control broadleaf and grassy weeds. Atrazine is part of the triazine chemical class, which includes simazine and propazine due to their common mechanism of toxicity. It is primarily used in agriculture (with the greatest use on corn, sorghum, and sugarcane). To a lesser extent, it is used on residential lawns and golf courses, particularly in Florida and the Southeast. 

The Agency's oversight of atrazine is dynamic and includes periodic pesticide re-evaluation and intensive monitoring programs. Over the years, the Agency has consulted with the FIFRA Scientific Advisory Panel (SAP) on a variety of atrazine topics.

On this page:

Registration Review of Atrazine

Atrazine is undergoing registration review, our periodic re-evaluation program for existing pesticides. All documents related to the registration review of atrazine can be found in the registration review docket: EPA-HQ-OPP-2013-0266. In particular:

If at any time EPA determines there are urgent human or environmental risks from atrazine exposure that require prompt attention, we will take appropriate regulatory action, regardless of the status of the registration review process.

Additional Information

Additional information on atrazine’s registration review, reregistration, and food tolerance reassessment is available in the atrazine dockets:

Docket # at regulations.gov Docket Title and/or SAP Title
EPA-HQ-OPP-2003-0367 Atrazine Interim Reregistration Eligibility Decision (IRED)
EPA-HQ-OPP-2005-0481 Triazine Cumulative Risk Assessment
EPA-HQ-OPP-2009-0759 Presentation of the Atrazine Reevaluation Plan
EPA-HQ-OPP-2009-0851" Draft Framework and Case Studies on Atrazine, Human Incidents, and the Agricultural Health Study: Incorporation of Epidemiology and Human Incident Data into Human Health Risk Assessment
EPA-HQ-OPP-2010-0125 Re-Evaluation of Human Health Effects of Atrazine: Review of Experimental Animal and In Vitro Studies and Drinking Water Monitoring Frequency
EPA-HQ-OPP-2010-0481 Re-Evaluation of Human Health Effects of Atrazine: Review of Non-Cancer Effects and Drinking Water Monitoring Frequency
EPA-HQ-OPP-2011-0399 Re-Evaluation of Human Health Effects of Atrazine: Review of Non-Cancer Effects, Drinking Water Monitoring Frequency, and Cancer Epidemiology
EPA-HQ-OPP-2012-0230 Problem Formulation for Reassessment of Ecological Risks from Use of Atrazine
EPA-HQ-OPP-2013-0266 Atrazine Registration Review

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Atrazine Monitoring Program - Drinking Water

The Atrazine Monitoring Program (AMP) monitors approximately 150 community drinking water systems (CWS), primarily in the Midwest, to determine whether concentrations of atrazine and its chemical degradates pose a risk to public health. This monitoring program is required as a result of the 2003 Atrazine Interim Reregistration Eligibility Decision (IRED) and the Memorandum of Agreement (2004). 

Community water systems, which are a subset of public water systems (PWS), are selected for intensive monitoring based on a history of atrazine use and a screen of EPA's Office of Water monitoring data. CWSs included in the AMP are monitored on a weekly basis during peak atrazine use season and biweekly during the rest of the year. All other CWSs are monitored on a 90-day basis as part of the Office of Water’s routine monitoring under the Safe Drinking Water Act (SDWA).

  • Any CWS with a total combined triazine (TCT) concentration exceeding the trigger values of 2.6 ppb for finished water or 12.5 ppb for raw water over a 90-day rolling average will be inducted into the AMP intensive water monitoring program for 5 years. Pesticide registrants implement the AMP.
  • If any CWS in the AMP meets or exceeds the trigger value for one year, registrants must submit a mitigation plan and begin implementation within 90 days of the exceedance.
  • If any CWS in the AMP meets or exceeds the trigger value for 2 out of 5 consecutive years, atrazine use is banned in the water system’s watershed.
  • If any CWS in the AMP does not exceed a TCT concentration of 37.5 ppb for five consecutive years, intensive monitoring can be terminated.

To date, EPA has determined that more than 100 systems no longer require monitoring under the program, and no system has exceeded the maximum allowable concentration more than once. More than 30 CWSs have been added to the program.

View Atrazine Monitoring Program Data and Results

Atrazine Ecological Exposure Monitoring Program

The Atrazine Ecological Exposure Monitoring Program assesses atrazine levels in streams in watersheds that are exposed to atrazine runoff from corn and sorghum production (small streams, high atrazine use areas, and vulnerable soils). This monitoring program is required as a result of the 2003 Atrazine Interim Reregistration Eligibility Decision and the Memorandum of Agreement (2004). 

EPA currently regulates on an aquatic plant Concentration Equivalent Level of Concern (CE-LOC) of 10 ppb as a 60-day average concentration, which ensures that atrazine levels will not cause significant changes in aquatic plant community structure, function and productivity. 

If a watershed shows atrazine concentrations above this level of concern in any two years of monitoring, atrazine registrants must initiate watershed-based mitigation activities in concert with state or local watershed programs to reduce atrazine exposure. These mitigation activities can include, for example, label education, stewardship and outreach programs for growers and distributors. A watershed can be decommissioned from the monitoring program if the 60-day running average falls below the CE-LOC for two consecutive years.

  • Since the program's inception, up to 33 watersheds have been monitored for atrazine in corn-, sorghum- and sugarcane-producing areas.
  • As of 2015, nine watersheds in five states (Iowa, Texas, Missouri, Louisiana and Nebraska) are in the monitoring program.
  • As of 2013, all sugarcane sites were decommissioned from the monitoring program.
  • The registrant has addressed exceedances by implementing label education, stewardship, and outreach programs in these watersheds, and is attempting to quantify the impact and effectiveness of the mitigation activities through a grower survey.

View Atrazine Ecological Exposure Monitoring Program Data and Results

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Triazine Cumulative Risk Assessment

Atrazine is chemically related to two other herbicides, simazine and propazine, which together are called "triazines." The triazines have a common mechanism of toxicity, and are often evaluated together in cumulative risk assessments. As part of EPA’s registration review process, the Agency is currently conducting an updated cumulative human health risk assessment for the triazines. EPA expects to issue this risk assessment in 2016. 

The Agency conducted a triazine cumulative human health risk assessment in 2006, which concluded:

  • Cumulative exposures to atrazine and simazine through food and drinking water are safe and meet the rigorous human health standards set forth in the Food Quality Protection Act.
  • Levels of atrazine and simazine that Americans are exposed to in their food and drinking water, combined, are below the level that would potentially cause health effects.

View the 2006 Triazine Cumulative Risk Assessment (Docket ID: EPA-HQ-OPP-2005-0481-0003 at www.regulations.gov)

Triazine Ecological Risk Assessments

EPA released the draft ecological risk assessments for atrazine, simazine and propazine, which evaluate risks to animals and plants including, amphibians, birds, mammals, fish, reptiles, aquatic invertebrates, aquatic plant communities, and terrestrial plants. For ecological risks, each of the triazines (atrazine, propazine, and simazine) was assessed separately.

FIFRA Scientific Advisory Panel Meetings on Atrazine

The Agency has consulted with the FIFRA Scientific Advisory Panel on 12 occasions on various topics regarding the evaluation of atrazine data and key aspects of its risk assessments since 2000, all of which are listed in the table below. The SAP is composed of independent scientists who advise on technically challenging scientific assessment issues.

Meeting materials and summaries are available on the FIFRA Scientific Advisory Panel website or in www.regulations.gov (search by the Docket number).

EPA’s FIFRA Scientific Advisory Panel Meetings on Atrazine
Meeting Title Docket Number Date
Problem Formulation for Reassessment of Ecological Risks from Use of Atrazine EPA-HQ-OPP-2012-0230 6/12-15/12
Re-Evaluation of Human Health Effects of Atrazine:  Review of Non-Cancer Effects, Drinking Water Monitoring Frequency, and Cancer Epidemiology EPA-HQ-OPP-2011-0399 7/26-29/11
Re-Evaluation of Human Health Effects of Atrazine:  Review of Non-Cancer Effects and Drinking Water Monitoring Frequency EPA-HQ-OPP-2010-0481 9/14-17/10
Re-Evaluation of Human Health Effects of Atrazine:  Review of Experimental Animal and In Vitro Studies and Drinking Water Monitoring Frequency EPA-HQ-OPP-2010-0125 4/26-29/10
Draft Framework and Case Studies on Atrazine, Human Incidents, and the Agricultural Health Study:  Incorporation of Epidemiology and Human Incident Data into Human Health Risk Assessment EPA-HQ-OPP-2009-0851 2/2-5/10
Presentation of the Atrazine Reevaluation Plan EPA-HQ-OPP-2009-0759 11/3/09
Ecological Significance of Atrazine Effects on Primary Producers in Surface Water Streams in the Corn and Sorghum Growing Region of the United States EPA-HQ-OPP-2009-0104 5/12-15/09
Interpretation of the Ecological Significance of Atrazine Stream-Water Concentrations Using a Statistically-Designed Monitoring Program EPA-HQ-OPP-2007-0934 12/4-7/07
Potential for Atrazine to Affect Amphibian Gonadal Development EPA-HQ-OPP-2007-0498 10/9-12/07
Characterization of Epidemiology Data Related to Prostate Cancer and Exposure to Atrazine EPA-HQ-OPP-2003-0186 7/17-18/03
Potential Developmental Effects of Atrazine on Amphibians EPA-HQ-OPP-2003-0024 6/17-20/03
Issues Pertaining to Atrazine Cancer Risk Assessment Search EPA Archive Not available 6/27-29/00

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