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INTRODUCTION

This is the Environmental Protection Agency’s (EPA or the Agency) Final Work Plan (FWP) for 

the registration review of simazine. This work plan addresses public comments received 

concerning the Preliminary Work Plan (PWP), which was posted in the simazine registration 

review docket (EPA-HQ-OPP-2013-0251). Simazine is a non-selective systemic triazine 

herbicide registered for use for pre- and post-emergent applications to control annual and 

perennial grasses and broadleaf weeds on a variety of crops, such as oranges and corn; and nonagricultural use sites, such as residential turf. For human health risk assessment, simazine is part 

of the triazine common mechanism group based on a common toxicity end-point and known 

mechanism of toxicity. The triazine common mechanism group consists of the pesticide active 

ingredients atrazine, simazine, propazine, and the metabolites desethyl-s-atrazine (DEA), 

desisopropyl-s-atrazine (DIA), and diaminochlorotriazine (DACT).1 

The Agency is implementing the registration review program pursuant to Section 3(g) of the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and will review each registered 

pesticide every 15 years to determine whether it continues to meet the FIFRA standard for 

registration. Changes in science, public policy, and pesticide use practices occur over time. The 

registration review program is intended to make sure that, as the ability to assess risk evolves and 

as policies and practices change, all registered pesticides continue to meet the statutory standard. 

The public phase of registration review begins when the initial docket is opened for each case. 

Information on this program is provided on the Agency’s website.2

The FWP begins with any updates since the PWP was issued. Next is a summary of a comment, 

which is not addressed in a separate respone to comments document or elsewhere in this 

document, and the Agency’s response. This section is followed by registration review planned 

data needs, risk assessments expected to be conducted, and the projected registration review 

timeline for simazine. Lastly, there is a discussion of next steps. 

UPDATES SINCE THE PWP WAS ISSUED

The case number for simazine was erroneously listed as # 7280 in the PWP. The FWP reflects 

the accurate case number for simazine, which is # 70. 

The table of data requirements has been modified to clarify that environmental chemistry 

methods (ECM) and associated independent laboratory validations (ILVs) for soil are required 

for parent simazine as well as the degradates hydroxysimazine, DIA, and DACT. 

SUMMARY OF COMMENTS AND AGENCY RESPONSES

During the 60-day public comment period on the Simazine Preliminary Work Plan, which 

opened on June 26, 2013 and closed on August 26, 2013, the Agency received 14 sets of public 

comments. The comments were submitted by a citizen, individual growers, registrants 

 

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 There are other triazine pesticides, such as ametryn, prometryn, and prometon, but they are excluded from the 

triazine common mechanism group because they do not share the same toxicity profile. (Triazine Cumulative 

Risk Assessment. J. Morales. March 28, 2006.) 2

 http://www.epa.gov/oppsrrd1/registration_review/ 
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[Syngenta Crop Protection, LLC (Syngenta) and Reg West Company, LLC], the FIFRA 

Endangered Species Task Force (FESTF), and trade associations (grower and industry groups). 

The comments received do not address the timeline or data requirement described in the PWP, 

but do address the planned ecological risk assessment. In the PWP, EPA also solicited 

comments on the specific topics of environmental justice, water quality concerns, and trade 

irritants, but no comments or information were received on those issues. 

Two commenters, an individual grower and a citizen, submitted comments indicating that 

simazine use should be discontinued because there are safer alternatives. Other individual 

growers and the following grower groups, trade associations, and industry groups commented on 

the importance of simazine to growers, describing, among other things, its importance as a tool 

in weed management and weed resistance, and stewardship efforts used to limit potential nontarget exposures (South Dakota Corn Growers Association; Maryland Grain Growers 

Association; Illinois Farm Bureau; Ohio Corn and Wheat Growers Association; Illinois Soybean 

Association; Triazine Network; and Chemical Industry Council of Illinois). 

Syngenta submitted technical comments on the Problem Formulation and Scoping Document; 

recommended corrections to the use and usage information described in the PWP and BEAD 

Chemical Profile (BCP); and submitted a detailed crop matrix describing the use parameters of 

simazine (e.g., application rate, timing, etc.). FESTF commented that Syngenta is a member of 

FESTF and is entitled to rely on FESTF data to help address species proximity to simazine use 

sites for the planned endangered species assessment. EPA will consider these comments during 

registration review. 

Public comments and EPA responses in their entirety are located in the docket, EPA-HQ-OPP2013-0251. Summarized public comments and Agency responses related to the anticipated 

ecological risk assessment are in the EFED Response to Comments Submitted by Syngenta Crop 

Protection, LLC. Concerning the Registration Review of Simazine, while those relevant to the 

anticpated human health risk assessment are in the Simazine: Responses to Comments on Human 

Health Assessment Scoping Document in Support of Registration Review. Summarized public

comments and responses on simazine use and usage unformation described in the PWP and 

BEAD Chemical Profile (BCP) are in the BEAD Responses to the Comments on the Simazine 

BEAD Chemical Profile and Preliminary Work Plan. 

This section does not capture every comment made about the PWP nor all of the Agency’s 

responses. Summarized below is a public comment not addressed in the Agency’s response to 

comments documents or elsewhere in this document. 

Comment submitted by Reg West, LLC in EPA-HQ-OPP-2013-0251-0013. 

Comment: There is a registered use pattern of simazine, as an algicide in aquariums and 

containerized ornamental fish ponds and fountains of 1000 gallons or less, not mentioned in 

either the “Human Health Risk Scoping Document in Support of Registration Review” or the 

“Simazine Preliminary Work Plan.” In addition, the “Simazine Preliminary Work Plan” states 

there are 22 Section 3 registration, and there are 23 Section 3 registrations. 

Response: EPA is aware that there is an aquarium/ornamental pond use of simazine, and this use 
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is listed on page 6 of the PWP. There are currently 24 Section 3 registrations for simazine. At 

the time of PWP completion, there were 22 Section 3 registrations. All of the active registrations 

will be considered in the registration review preliminary risk assessments (PRAs). 

PLANNED DATA NEEDS

Table 1 below summarizes planned data needs for simazine. For additional discussion of the 

data needs, see the Registration Review – Preliminary Problem Formulation for the Ecological 

Risk Assessment for Simazine and Atrazine, Propazine and Simazine. Human Health Risk 

Scoping Document in Support of Registration Review. The planned data needs have not changed 

from what was included in the PWP, but the test substances have been clarified. 

Table 1: Planned Data Needs for the Simazine Registration Review 

Guideline 

Number1 Study Title1

Test Material 

Estimated 

Timeframe 

(Months from 

receipt of DCI) 

850.6100 

Environmental chemistry methods (ECM) and 

associated independent laboratory validation (ILV) 

for soil2 

TGAI and 

Degradates3 12 

TGAI = technical grade active ingredient 

1

 On June 27, 2012, EPA announced certain revisions in harmonized guideline series 850 – Ecological Effects Tests 

– including renumbering and other designations or changes for some guideline studies. See “Final Test 

Guidelines; OCSPP 850 Series; Notice of Availability” 77 FR 38282, June 27, 2012. 

http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0154-0028 2

ECM and ILVs are used in the testing and identification of chemicals. 3

ECM and ILVs for soil are required for parent simazine and degradates hydroxysimazine, DIA, and DACT. 

RISK ASSESSMENTS FOR REGISTRATION REVIEW

During registration review, the Agency will conduct a comprehensive ecological risk assessment, 

including an endangered species assessment, for all uses of simazine. For human health, EPA 

will conduct revised dietary, residential, occupational, and cumulative risk assessments during 

registration review. If toxicological endpoints or points of departure are revised, they will be 

considered in the new assessments, as well as any changes to the standard operating procedures 

or default exposure assumptions. 

Table 2 below summarizes the planned registration review risk assessments based on the EFED 

Problem Formulation and HED Scoping Document and the planned assessments have not 

changed from what was included in the PWP. 
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Table 2: Planned Risk Assessments for the Simazine Registration Review 

Type of Risk Assessment Conduct? Notes 

Ecological and Environmental Fate 

Comprehensive ecological 

(species to be assessed 

include terrestrial and aquatic 

organisms), including 

endangered species 

Y The stressors of concern for terrestrial organisms are 

parent simazine and the degradate DIA. The stressor 

of concern for aquatic organisms is parent simazine 

alone. For additional information, see page 23 of the 

Problem Formulation. 

Incidents Will check for 

updates 

For a discussion of reported ecological incidents for 

simazine, see page 21 of the Problem Formulation. 

Human Health 

Dietary 

Food Y During registration review, an updated dietary 

assessment will be conducted to include any updates 

to toxicological endpoints, dietary exposure estimates, 

and changes to assessment SOPs. 

Drinking water Y EPA plans to use the data collected in the SMP in its 

drinking water assessment for simazine during 

registration review. EPA also plans to use data 

collected in the Atrazine Monitoring Program (AMP) 

in the drinking water assessment for simazine, as 

simazine is also detected in water samples analyzed 

for the AMP. 

Occupational 

Handlers (mixers, loaders, 

applicators) 

Y Since the most recent occupational risk assessment 

for simazine was conducted, EPA finalized new 

occupational risk assessment standard operating 

procedures (SOPs), including new potential exposure 

scenarios applicable to simazine that were not 

previously assessed (e.g. handheld equipment for turf 

and ornamentals). During registration review, EPA 

plans to update all relevant occupational exposure 

scenarios, along with any changes to toxicity 

endpoints and/or safety factors. 

Post-application Y 

Residential 

Handlers Y Since the most recent residential assessment for 

simazine was conducted, new residential risk 

assessment procedures containing additional turf 

scenarios have been finalized. During registration 

review, EPA plans to update all relevant residential 

handler and post-application assessments, along with 

any changes to toxicity endpoints and/or safety 

factors. 

Post-application Y 
Docket Number EPA-HQ-OPP-2013-0251 

www.regulations.gov 

Table 2: Planned Risk Assessments for the Simazine Registration Review

Type of Risk Assessment Conduct? Notes 

Human Health

Other 

Aggregate Y Evaluates the combined risk from dietary and 

residential exposures. 

Cumulative Y An assessment of the triazine cumulative group is 

planned as part of registration review. 

Tolerances Y Tolerances are established under 40 CFR §180.213 

for the combined residues of simazine and its two 

chlorinated metabolites in/on a variety of crops and 

livestock commodities. EPA plans to update the 

residue definition for the tolerance expression for 

simazine in accordance with current policy on 

tolerance definitions. 

Incidents Will check for 

updates 

For a discussion of reported human incidents for 

simazine, see page 12 of the Scoping Document and 

the Atrazine, Propazine, and Simazine: Review of 

Human Incident Reports. 

TIMELINE

EPA has created the following estimated timeline for the completion of the simazine registration 

review in Table 3 below. The projected timeline has not changed since the PWP 

Registration Review for Simazine – Projected Registration Review Timeline

Activities Estimated Date

Opening the Docket 

Open Docket and 60-day Public Comment Period 2013 – June 

Close Public Comment 2013 – August 

Case Development 

Final Work Plan 2013 – Decmeber 

Issue DCI 2014 – July - September 

60-day Public Comment Period for Draft Risk Assessments1,2 2015 – April - June 

Data Submission 2016 – July - September 

Registration Review Decision 

60-day Public Comment Period for Proposed Registration Review 

Decision 

2015 – Oct. - Dec. 

Registration Review Decision and Begin Post-Decision Follow-up 2016 

Total (years) 3 1

 The registration review schedule for most conventional pesticides includes a 6 month period after the Final Work 

Plan to issue a data call-in and then an appropriate time period for the required data to be submitted to EPA. 

However, because the one data requirement for simazine, Guideline 850.6100 (environmental chemistry methods 

and associated independent laboratory validation for soil), will not affect the preliminary risk assessments for 

simazine registration review, the schedule has been modified as appropriate. 
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 The regulations governing Registration Review generally require the Agency to provide a public comment period 

of at least 30 calendar days for draft risk assessments; see 40 CFR Part 155.53(c). For conventional pesticides, the 

Agency plans to provide a 60 calendar day public comment period for draft risk assessments. 

NEXT STEPS

As noted previously, the Agency plans to require one study for simazine through a Data Call-In 

Notice, expected to be issued by September 2014.