Atrazine
Atrazine is a chlorinated triazine systemic herbicide that is used to selectively control annual grasses and broadleaf weeds before they emerge. Pesticide products containing atrazine are registered for use on several agricultural crops, with the highest use on field corn, sweet corn, sorghum, and sugarcane. Additionally, atrazine products are registered for use on wheat, macadamia nuts, and guava, as well as non-agricultural uses such as nursery/ornamental and turf.
EPA's oversight of atrazine is dynamic and includes periodic re-evaluation through the registration review process. Over the years, EPA has consulted with the FIFRA Scientific Advisory Panel (SAP) on a variety of atrazine topics.
- Registration review of atrazine
- Monitoring atrazine in drinking water
- Atrazine ecological exposure monitoring program
- Triazine registration review
- Triazine cumulative human health risk assessment
- Triazine ecological risk assessments
- FIFRA Scientific Advisory Panel Meetings on Atrazine
Registration Review of Atrazine
The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requires EPA to periodically re-evaluate pesticides through registration review to ensure that risk assessments and pesticide decisions reflect the best available science. All documents related to the registration review for atrazine can be found in the atrazine registration review docket EPA-HQ-OPP-2013-0266 at www.regulations.gov.
In September 2020, EPA released the Interim Registration Review Decision for atrazine, finalizing mitigation measures to protect human health and mitigate potential ecological risks. EPA completes interim registration review decisions to impose interim risk mitigation measures necessary to protect human health and the environment, while the Agency conducts other longer-term assessments, such as the endangered species assessment. Labels implementing the mitigation required by the September 2020 interim decision (ID) were stamped and approved in November 2021.
In November 2021, EPA released the final Biological Evaluation (BE) assessing risks to listed species from labeled uses of atrazine. The final BE was conducted according to the Revised Method for National Level Listed Species Biological Evaluations of Conventional Pesticides. EPA solicited public comments on the draft BE for atrazine, which was released in November 2020, and prepared a response to comments document.
June 2022 Updates
In October 2020, EPA received a petition alleging that the agency violated its duties under FIFRA by issuing the atrazine ID without substantial evidence supporting the decision. In August 2021, EPA sought a voluntary partial remand in light of President Biden’s executive order on protecting public health and the environment and restoring a commitment to science and scientific integrity. On December 14, 2021, the Ninth Circuit Court of Appeals granted EPA a voluntary partial remand, which provided the agency the opportunity to reevaluate the policy decision to use 15 μg/L as the level of regulation for aquatic plant communities.
Based on its review of the substantial evidence associated with the atrazine ecological risk assessment and a consideration of growers’ need for flexible and manageable mitigation measures, EPA is now proposing, for public comment, additional mitigation to protect aquatic plant communities. EPA is proposing the following measures for all atrazine labels in order to decrease atrazine runoff from treated fields:
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Prohibit application when soils are saturated or above field capacity (i.e., the soil’s ability to retain water);
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Prohibit application during rain or when a storm event, likely to produce runoff from the treated area, is forecasted to occur within 48 hours following application;
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Prohibit aerial applications of all formulations; and
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Restrict annual application rates to 2 pounds of active ingredient or less per acre per year or less for applications to sorghum, field corn, and sweet corn.
In addition to the measures listed above, EPA is proposing to add a “picklist” to labels that would require growers to select a combination of application rate reductions and/or runoff control measures to further mitigate potential risks to aquatic plant communities. The number of runoff control practices from the picklist that a grower would be required to implement depends on the estimated atrazine concentration in the watershed where the field is located and that watershed’s vulnerability to atrazine runoff, as well as the grower’s selected application rate. The higher the application rate and the higher the estimated atrazine concentration in the watershed, the greater the number of mitigation practices that may be necessary.
The picklist approach provides growers with the flexibility to select the runoff control practices that would be least burdensome to adopt. The practices a grower selects may depend on a variety of factors including crop, geographic region, and field topography. The picklist mitigation requirements are tailored geographically, down to the watershed level, in order to focus the mitigation on the areas with the greatest risk and vulnerability.
The public comment period is now open for the Proposed Revisions to the Atrazine Interim Registration Review Decision in the atrazine registration review docket ID number EPA-HQ-OPP-2013-0266 at www.regulations.gov. Public comments will be accepted for 60 days upon publication of the Federal Register notice.
After considering comments on the proposed revisions to the atrazine ID, EPA will determine if any changes are warranted to the proposed revisions and then release its decision on this re-evaluation. The Agency also intends to seek external peer review of the risks to the aquatic plant community that underlies this proposed risk management strategy. This is in line with the Agency’s commitment to science and scientific integrity, and will incorporate the feedback it receives into its final revisions to the ID.
More information on the registration review process is available here.
Additional information on atrazine’s registration review and reregistration is available in the atrazine dockets at www.regulations.gov:
Docket ID | Docket Title |
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EPA-HQ-OPP-2003-0367 | Atrazine Interim Reregistration Eligibility Decision |
EPA-HQ-OPP-2013-0266 | Atrazine Registration Review |
EPA-HQ-OPP-2013-0266-0008 | Preliminary Work Plan |
EPA-HQ-OPP-2013-0266-0308 | Final Work Plan |
EPA-HQ-OPP-2013-0266-0315 | Refined Ecological Risk Assessment for Atrazine |
EPA-HQ-OPP-2013-0266-1159 | Atrazine Draft Human Health Risk Assessment for Registration Review |
EPA-HQ-OPP-2013-0266-1274 | Atrazine Proposed Interim Decision |
EPA-HQ-OPP-2013-0266-1605 | Atrazine Interim Decision |
EPA-HQ-OPP-2013-0266-1625 | Proposed Revisions to the Atrazine Interim Registration Review Decision |
EPA-HQ-OPP-2013-0266-1623 |
EFED Support Documentation for the Proposed Revisions to the Atrazine Interim Registration Review Decision Regarding Risks to Aquatic Plant Communities |
EPA-HQ-OPP-2013-0266-1624 | Assessment of the Benefits of Atrazine and the Impacts of Potential Mitigation for Field Corn, Sweet Corn, Sorghum, and Sugarcane |
Monitoring Atrazine in Drinking Water
Community water systems (CWS) are required, under the Safe Drinking Water Act, to monitor for atrazine.
In addition, for more than 15 years, the atrazine technical registrants were required to monitor for atrazine in surface drinking water per the 2003 Atrazine Interim Reregistration Eligibility Decision (IRED) and the 2004 Memorandum of Agreement (MOA) between EPA and the atrazine technical registrants.
- 2006 Atrazine Interim Reregistration Eligibility Decision (RED) (PDF) (323 pp, 1.9 MB, About PDF) This document contains the January 2003 IRED and October 2003 revised IRED.
- Memorandum of Agreement with registrants (2004) (PDF) (36 pp, 132 K, About PDF)
The monitoring program conducted by the atrazine technical registrants, called the Atrazine Monitoring Program (AMP), monitored approximately 150 surface water CWS, primarily in the Midwest, to determine whether concentrations of atrazine and its chemical degradates were present at a level that could potentially pose a risk to public health. Under the AMP, CWSs were selected for intensive monitoring based on a history of atrazine use and a screen of EPA's data collected under the Safe Drinking Water Act. CWSs included in the AMP were monitored on a weekly basis during peak atrazine use season and biweekly during the rest of the year.
While having monitoring data specific to community water systems is useful, given the conclusions of the 2018 draft triazine human health risk assessments, EPA discontinued the requirement for atrazine drinking water monitoring (the AMP). Model-estimated atrazine concentrations, as well as measured concentrations for community water systems are well below the drinking water level of concern (DWLOC). The vast majority of atrazine samples from the AMP showed concentrations below 1 ppb, while the highest atrazine concentration ever measured was 227 ppb, which is well below the triazine DWLOC of 580 ppb. Therefore, the Agency did not see value in continuation of the AMP. For these reasons, EPA suspended the requirements for the AMP for calendar year 2020 during which time the Agency solicited comments (during the 60-day comment period for the PID) about the proposal to end the requirement for the AMP. The Agency did not receive significant comments that illustrated a continued need for monitoring through this program and therefore the Agency ended the requirement for the AMP. EPA will continue to require monitoring for atrazine under the Safe Drinking Water Act.
View Atrazine Monitoring Program Data and Results.
View Atrazine Data Collected under the Safe Drinking Water Act.
Atrazine Ecological Exposure Monitoring Program
The Atrazine Ecological Exposure Monitoring Program (AEEMP) 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 by the 2003 Atrazine Interim Reregistration Eligibility Decision and the 2004 Atrazine Memorandum of Agreement.
- 2006 Atrazine Interim Reregistration Eligibility Decision (PDF) (323 pp, 1.9 MB, About PDF) This document contains the January 2003 IRED and October 2003 revised IRED.
- Memorandum of Agreement with registrants (2004) (PDF) (36 pp, 132 K, About PDF)
On June 30, 2022, EPA released proposed revisions to the September 2020 atrazine interim decision for public comment. Based on a reevaluation of the atrazine concentration level that triggers required monitoring and/or mitigation to protect aquatic plant communities, EPA determined that the scientifically derived concentration equivalent level of concern (CE-LOC) of 3.4 µg/L as a 60-day average, presented in the 2016 atrazine ecological risk assessment, continued to be supported by the best available science and is proposing, for public comment, additional mitigation to protect aquatic plant communities where the concentration of atrazine in a watershed is expected to exceed the CE-LOC.
Continued water monitoring in streams and watersheds (the AEEMP) is needed to determine when and where additional stewardship and/or runoff mitigation is necessary to protect aquatic plant communities from potential affects, as well as to monitor the success of the proposed mitigation described above.
EPA believes there is the potential to sample less frequently and still have a robust data set for use in future ecological risk assessment and risk management of atrazine. EPA held a FIFRA Scientific Advisory Panel (SAP) in November 2019 to obtain feedback about tools and approaches to interpret pesticide monitoring data collected at less frequent sampling intervals. EPA is considering ways to update the current AEEMP that could lessen the burden associated with the current monitoring program while still providing valuable data for use in ecological risk assessment and management of atrazine.
View Atrazine Ecological Exposure Monitoring Program Data and Results
View Atrazine Data Collected under the Safe Drinking Water Act
Triazine Registration Review
Atrazine is chemically related to two other herbicides, simazine and propazine, which together are called "triazines." The chemical class, triazines, recently underwent registration review, our periodic re-evaluation program for existing pesticides.
The triazines have a common mechanism of toxicity, and therefore EPA has conducted both individual chemical and cumulative human health risk assessments.
Interim Registration Review Decision
In September 2020, EPA released the triazine (atrazine, propazine and simazine) interim decisions. In June 2022, EPA released for public comment the proposed revisions to the atrazine interim decision. In June 2022, EPA released for public comment the Proposed Revisions to the Atrazine Interim Registration Review Decision. After considering comments on the proposed revisions, EPA will proceed with a revised interim decision for atrazine.
- Read the atrazine interim decision.
- Read the propazine interim decision.
- Read the simazine interim decision.
Triazine Cumulative Human Health Risk Assessment
In July 2018 as part of EPA’s registration review process, the Agency released the cumulative human health risk assessment for the triazines. In addition to the cumulative human health risk assessment, the Agency also released atrazine, simazine and propazine human health risk assessments.
- Read the cumulative human health risk assessment.
- Note: the cumulative assessment can be found in all triazine dockets
- Read the atrazine human health risk assessment.
- Read the simazine human health risk assessment.
- Read the propazine human health risk assessment.
In the cumulative assessment, EPA reviewed all available scientific data, including published toxicity and epidemiology literature. EPA’s assessment found no risks of concern when evaluating all dietary exposure sources including drinking water.
The assessment identifies potential risks to:
- children who crawl and play on lawns treated with atrazine or simazine and
- workers who mix, load, and apply atrazine
In the December 2019 proposed interim registration review decisions, EPA is proposing mitigation that would address these risks of concern.
Triazine Ecological Risk Assessments
In 2016, 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.
- View the Federal Register Notice.
- Find the triazine ecological risk assessments.
- View the Atrazine Regulatory Update Memo (October 2019), regarding the Community Effects Level of Concern (CE-LOC) for regulating aquatic plants.
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 FIFRA 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).
Meeting Title | Docket Number | Date |
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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 |