Atrazine

Atrazine is a widely used herbicide that can be applied before and after planting to control broadleaf and grassy weeds. Atrazine is a member of the triazine chemical class, which includes simazine and propazine. It is used in primarily 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 the Southeast United States. 

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

In September 2020, EPA released the Interim Registration Review Decisions for atrazine, propazine, and simazine, 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.

• 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

Atrazine completed its first round of registration review in 2020, which is the Agency’s periodic re-evaluation program for existing, registered pesticides. Each registered pesticide must be re-reviewed every 15 years, so EPA will complete the next round of registration review for atrazine by 2035. All documents related to this round of registration review for atrazine can be found in the registration review docket: EPA-HQ-OPP-2013-0266. In particular:

• The Preliminary Work Plan (June 2013) described our process for reevaluating atrazine, recent actions, planned human health and ecological risk assessments, and the expected review timeline. 
• The Final Work Plan (December 2013) addressed public comments received on the Preliminary Work Plan and finalized our anticipated schedule for registration review.
• Atrazine Ecological Risk Assessment (June 2016) evaluated potential risks to animals and plants.
• Triazine (atrazine, simazine and propazine) Human Health Risk Assessment (July 2018).
• Letter to National Corn Growers Association on registration review of atrazine (August 2019).
• Atrazine Regulatory Update (October 2019)
• Atrazine Proposed Interim Registration Decision (December 2019)
• Atrazine Interim Registration Decision (September 2020)

Upon publication of the Federal Register notice, the atrazine Interim Registration Decision will be available in docket # EPA-HQ-OPP-2013-0266. In this document EPA is finalizing the following new, stronger protections to reduce exposure to atrazine.

• Rate reduction for residential turf applications
  • Reduce application rate for granular atrazine products applied to residential turf from 2.2 pounds active ingredient per acre (lb ai/A) to 2.0 lb ai/A
  • Reduce application rate for atrazine spray applications to residential turf from 2.0 lb ai/A to 1.0 lb ai/A
• Additional personal protective equipment (PPE)
  • Combination of single- and double-layer clothing with gloves, PF10 respirators, and engineering controls

• Add mandatory spray drift reduction language
• Add herbicide resistance management language

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:

Monitoring Atrazine in Drinking Water

Community water systems (CWS) are required, under the Safe Drinking Water Act, to monitor for atrazine.

In addition, for the past 15 years, the atrazine technical registrants have been 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), monitors approximately 150 surface water CWS, primarily in the Midwest, to determine whether concentrations of atrazine and its chemical degradates are present at a level that could potentially pose a risk to public health. Under the AMP, CWSs are 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 are monitored on a weekly basis during peak atrazine use season and biweekly during the rest of the year.

As part of registration review and decades of study, EPA is considering amendments to the 2004 Memorandum of Agreement that would end the requirement for continued drinking water monitoring under the AMP. The totality of available atrazine monitoring data collected through the AMP is robust and comprehensive, which enabled the EPA to refine and characterize its most recent (2018) human health risk assessment. Estimates in the 2018 draft human health risk, as well as measured concentrations for community water systems, are well below the drinking water level of comparison (DWLOC) of 580 parts per billion. EPA accepted comments on the proposal to discontinue the AMP during the comment period on the Proposed Interim Decision on Atrazine. The Agency did not receive significant comments illustrating the continued need for monitoring through this program, and therefore intends to proceed with discontinuing this requirement. 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 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 (IRED) and the 2004 Atrazine Memorandum of Agreement (MOA).

• 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)

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, 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

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.

• 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 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).