2

 Table of Contents 

Contents

I. INTRODUCTION .................................................................................................................. 3

A. Summary of Sulfentrazone Registration Review ..............................................................4

B. Public Comments ..............................................................................................................5

II. USE AND USAGE .............................................................................................................. 9

III. SCIENTIFIC ASSESSMENTS ......................................................................................... 10

A. Human Health Risk Assessment ...........................................................................................10

1. Risk Conclusions ........................................................................................................ 10

2. Human Incidents ......................................................................................................... 10

3. Tolerances ................................................................................................................... 11

B. Ecological Risk Assessment ................................................................................................11

1. Risk Conclusions ........................................................................................................ 12

2. Ecological Incidents ................................................................................................... 14

3. Characterization of Ecological Risk ........................................................................... 14

C. Benefits Assessment .............................................................................................................15

D. Endangered Species Assessment ..........................................................................................17

E. Endocrine Disruptor Screening Program ...............................................................................18

IV. INTERIM REGISTRATION REVIEW DECISION......................................................... 19

A. Risk Mitigation and Regulatory Rationale ......................................................................19

B. Tolerance Amendments ...................................................................................................20

C. Endangered Species .........................................................................................................21

D. Interim Registration Review Decision ............................................................................21

E. Data Requirements ..........................................................................................................21

V. NEXT STEPS AND TIMELINE .......................................................................................... 22

A. Interim Registration Review Decision ............................................................................22

B. Implementation of Mitigation Measures .........................................................................22

Appendix A: SULFENTRAZONE Label Table .......................................................................... 23
3

I. INTRODUCTION 

This document is the Environmental Protection Agency’s (EPA or the Agency) Interim 

Registration Review Decision for Sulfentrazone (case 7231, PC code 129801) and is being issued 

pursuant to 40 CFR sections 155.56 and 155.58. A registration review decision is the Agency's 

determination whether a pesticide meets, or does not meet, the standard for registration in the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The Agency may issue, when it 

determines it to be appropriate, an Interim Registration Review Decision before completing a 

registration review. Among other things, the Interim Registration Review Decision may: 1) 

require new risk mitigation measures; 2) impose interim risk mitigation measures; 3) identify 

additional data or other information required to complete the review; and 

4) include schedules for submitting the required data, conducting the new risk assessment, and 

completing the registration review. For further information on sulfentrazone, additional 

documents can be found in EPA’s public docket (EPA-HQ-OPP-2009-0624) at 

www.regulations.gov. 

 FIFRA, as amended by the Food Quality Protection Act (FQPA) of 1996, mandated the 

continuous review of existing pesticides. All pesticides distributed or sold in the United States 

generally must be registered by the EPA based on scientific data showing that they will not cause 

unreasonable risks to human health or to the environment when used as directed on product 

labeling. The registration review program is intended to make sure that, as the ability to assess 

and reduce risk evolves and as policies and practices change, all registered pesticides continue to 

meet the statutory standard of no unreasonable adverse effects. Changes in science, public 

policy, and pesticide use practices will occur over time. Through the registration review 

program, the Agency periodically re-evaluates pesticides to make sure that as these changes 

occur, products in the marketplace can continue to be used safely. Information on this program is 

provided at www.epa.gov/oppsrrd1/registration_review/. In 2006, the Agency implemented the 

registration review program pursuant to FIFRA section 3(g) and will review each registered 

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

registration. 

EPA is issuing an interim registration review decision for sulfentrazone so that it can (1) 

move forward with aspects of the registration review that are complete and (2) implement 

interim risk mitigation. The Agency is currently working with the U.S. Fish and Wildlife 

Service and the National Marine Fisheries Service to develop methodologies for conducting 

national endangered species assessments for pesticides. Therefore, although EPA has not yet 

fully evaluated risks to threatened and endangered species, the Agency will complete its 

endangered species assessment and any necessary consultation with the Services for 

sulfentrazone prior to completing the sulfentrazone registration review. Likewise, the Agency 

will complete endocrine screening for sulfentrazone, pursuant to the Federal Food, Drug, and 

Cosmetic Act (FFDCA) section 408(p), before completing this registration review. Last, EPA 

will determine whether additional pollinator exposure and effects data are necessary to make a 

final registration review decision for sulfentrazone and issue a data call-in (DCI) to obtain any 

such data prior to completing the sulfentrazone registration review. 

 

Sulfentrazone is a broad-spectrum herbicide registered to control broadleaf weeds on a 

variety of field crops, fruits, vegetables, ornamentals and turf. It is primarily applied as a pre-
4

emergent herbicide. Because sulfentrazone was first registered in 1997, it was not subject to 

reregistration. 

This document is organized in five sections: the Introduction, which includes this 

summary and a summary of public comments and EPA’s response; Use and Usage, which 

describes how and why sulfentrazone is used and summarizes data on its use; Scientific 

Assessments, which summarizes EPA’s risk assessment, any revisions, and risk conclusions; 

Interim Registration Review Decision, which describes the mitigation measures necessary to 

address risks of concern and the regulatory rationale for EPA’s registration review decision; and, 

last, the Next Steps and Timeline for completion of this registration review. 

A. Summary of Sulfentrazone Registration Review 

Pursuant to 40 CFR section 155.50, EPA formally initiated registration review for 

sulfentrazone (case 7231) in 2009. The following list highlights significant events that have 

occurred during the registration review of sulfentrazone. Documentation of these events for 

sulfentrazone can be found in EPA’s public docket, EPA-HQ-OPP-2009-0624, accessed at 

www.regulations.gov: 

 September 23, 2009 – Publication of Sulfentrazone Preliminary Work Plan (PWP) for a 

60-day public comment period. The Preliminary Work Plan (PWP) was accompanied by 

the scoping document and problem formulation. 

 April 5, 2010 – Final Work Plan (FWP) for Sulfentrazone was issued. Three public 

comments were received during the 60-day comment period for the sulfentrazone PWP; 

however, these comments did not change the risk assessment or data needs identified in 

the PWP. Therefore, the FWP did not modify the PWP. 

 September 28, 2010 – Generic Data Call-In (GDCI) Notice for sulfentrazone was issued. 

 July 3, 2014 – EPA published the preliminary risk assessments for sulfentrazone for a 60-

day public comment period: Preliminary Ecological Risk Assessment for the 

Registration Review of Sulfentrazone and Proposed New Uses on Apples and 

Sulfentrazone – Preliminary Human Health Risk Assessment for Registration Review and 

the Risk Assessment for the Section 3 Registration Request for a New Use on Apples. 

EPA received comments from the Center for Biological Diversity (CBD) and FMC 

Corporation (FMC), the sulfentrazone technical registrant. 

 August 2015 – The Agency published the Sulfentrazone Proposed Interim Registration 

Review Decision, dated June 17, 2015, for a 60-day public comment period. In addition 

to that document, the Agency also published the following supporting documents: 

o Response to Comments on the Preliminary Ecological Risk Assessment for the 

Registration Review of Sulfentrazone;

o Response to Comments on the Preliminary Human Health Risk Assessment for the 

Registration Review of Sulfentrazone;
5

o Addendum to the Environmental Fate and Ecological Risk Assessment for 

Sulfentrazone Registration Review; 

o Sulfentrazone Usage Information; and 

o Sulfentrazone Qualitative Benefits Assessment. 

 December 2015 – The Agency is now publishing the Sulfentrazone Interim Registration 

Review Decision in the registration review docket (EPA-HQ-OPP-2009-0624). 

 

B. Public Comments 

During the 60-day public comment period on the Sulfentrazone Proposed Interim 

Registration Review Decision, which opened on August 8, 2015 and closed on October 9, 2015, 

the Agency received two comments, from the sulfentrazone technical registrant, FMC 

Corporation, and from the Center for Biological Diversity (CBD), an environmental and public 

interest group. FMC’s comments focused on the risk mitigation for sulfentrazone and the timing 

of label amendments. CBD’s comments focused on EPA’s obligations under Section 7 of the 

Endangered Species Act (ESA) to complete a national endangered species assessment and to 

initiate consultation with the U.S. Fish and Wildlife Service and the National Marine Fisheries 

Service (the Services) prior to completion of the sulfentrazone registration review. The public 

comments, and EPA’s response, are summarized below. Public comments in their entirety are 

located in the docket, EPA-HQ-OPP-2009-0624. 

COMMENTS SUBMITTED BY FMC IN EPA-HQ-OPP-2009-0624-0040

 

Comment: FMC requests that the time frame to submit amended labels, which implement the 

label changes summarized in Appendix A of the Proposed Interim Decision Document, be 

extended to 90 days (rather than the original 60 days) due to the numerous complexities of the 

labels and the large number of actively registered sulfentrazone products. 

Response: EPA will allow 90 days for submission of amended labels. FMC has over 60 FIFRA 

Section 3 products registered for sulfentrazone and approximately 50 FIFRA Section 24(c) 

special local need products. Given the large number of sulfentrazone product labels, EPA 

considers this to be a reasonable request. 

Comment: FMC emphasizes that there are other registrants with active sulfentrazone technical 

registrations as well as end-use product registrations containing sulfentrazone. The proposed 

label mitigation should apply to all sulfentrazone technical and agricultural end-use products. 

FMC requests that the Agency notify all registrants of the required mitigation and that each 

registrant be required to adhere to the same label mitigations at the same time. 

Response: The sulfentrazone label mitigation applies to all sulfentrazone technical products and 

all agricultural end-use products. Through this document and the associated Notice of 

Availability, EPA is notifying all affected registrants of (1) their obligation to implement the 

mitigation and (2) the timeframe for submission of amended labels implementing the mitigation. 
6

Comment: The summary of labeling changes for sulfentrazone on page 20 of the proposed 

interim decision, includes a the following statement: “Select coarse to very coarse droplet size 

when sulfentrazone is used alone and a medium to coarse droplet size when sulfentrazone is tank 

mixed with a contact burndown herbicide.” FMC’s June 24, 2015 commitment letter1, submitted 

after discussions with the Agency on risk mitigation, stated that coarse to very coarse droplet 

sizes should be used when sulfentrazone is applied as a preemergent/preplant application. There 

are certain applications where medium to coarse droplet size is required for adequate product 

performance. Therefore, coarse to very coarse droplet size restrictions should be limited to 

preemergent/preplant applications. 

Response: The Agency has amended the Summary of Labeling Changes for Sulfentrazone to 

clarify the droplet size to be used during preemergent/preplant applications to more accurately 

reflect the mitigation negotiated with FMC. In addition, the Agency is requiring registrants to 

amend product labels to specify application situations where a medium to coarse droplet size is 

required for reasons of product performance. 

Comment: The summary of labeling changes for sulfentrazone section, on page 21 of the 

proposed interim decision, includes the following statement: “Ground applicators must use a 

finished spray volume of 15 gallons per acre.” FMC’s commitment letter, following discussions 

with the Agency on mitigation measures, stated that “A minimum spray volume of 10 gallons per 

acre is required when applying with ground application equipment.” Only when tank mixing 

with a contact burndown herbicide should 15 gallons per acre be required. Further detail is 

provided in the FMC commitment letter as point #5. 

Response: The Agency has amended the Summary of Labeling Changes for Sulfentrazone to 

clarify the minimum spray volume to be used to more accurately reflect the mitigation negotiated 

with FMC, as specified in Section IVA2 of this document. In addition, EPA has amended the 

summary of labeling changes to specify “When sulfentrazone is tank mixed with a contact 

burndown herbicide, ground applicators must use a minimum spray volume of 15 gallons per 

acre.” 

Comment: Amended anaerobic soil and aerobic aquatic metabolism reports (MRIDs 49501101 

and 49501102, respectively) were submitted to the Agency to fully satisfy the data requirement 

and reclassify their status from supplemental to full. FMC requests that these studies be 

reviewed, and if EPA finds these data useful, that the Agency use the data in future risk 

assessments for sulfentrazone. FMC also requests data evaluation records (DERs) for these 

reports be provided once they become available. 

Response: EPA has received and is reviewing these amended study reports. The anaerobic soil 

and aerobic aquatic metabolism data will be used in future risk assessments for sulfentrazone, 

including the endangered species assessment, as appropriate. The study DERs will be sent to 

FMC upon completion of the data reviews and added to the public docket. 

 

1

 This letter is in the public docket, under EPA-HQ-OPP-2009-0624-0038. 
7

Comment: As a condition of sulfentrazone registration, the Agency required FMC conduct three 

prospective groundwater monitoring studies on soils highly vulnerable to leaching of 

sulfentrazone to groundwater. FMC committed to satisfying the conditional registration and 

submitted numerous progress reports and a final report for each (MRIDs 47453602, 47453601, 

and 46816001, respectively). FMC believes the condition of registration has been fulfilled and 

requests that the condition of registration be removed and its status indicated as full. FMC also 

requests DERs for these reports are provided once they become available. 

Response: EPA has received and reviewed the prospective groundwater studies for 

sulfentrazone. The Agency will send the completed DERs for these studies and inform FMC 

whether the submitted data fulfill the condition of registration. However, the decision on the 

conditional registration is separate from the registration review. 

 

COMMENTS SUBMITTED BY CBD IN EPA-HQ-2009-0624-0041

Comment: CBD opposes the proposed reregistration of sulfentrazone at this time as premature 

because they assert that the Agency has determined that sulfentrazone has the potential to cause 

adverse effects to species. In CBD’s comments on the Proposed Interim Registration Review 

Decision for Sulfentrazone, they focus on EPA’s duty to initiate consultation with the U.S. Fish 

and Wildlife Service and the National Marine Fisheries Service (the Services) prior to 

completion of the registration review process for sulfentrazone. CBD states that the reregistration 

of sulfentrazone cannot be completed in compliance with EPA’s obligations under both FIFRA 

and the ESA until the EPA concludes that the continued use of sulfentrazone will have “no 

effect” on listed species or critical habitat or completes consultation. CBD contends that there 

are readily available data and information sources that would allow EPA to complete Step 1 of 

the Interim Approaches for National Level Endangered Species Assessments Based on the 

Recommendations of the National Academy of Science. CBD refers to their previous comments2

on EPA’s draft ecological risk assessment, which provided specific label language to implement 

the Bulletins Live! System, stating that this label language would enable EPA to comply with 

current and continuing ESA duties. (CBD incorporated these and all other previous comments on 

the draft ecological risk assessment by reference.) Last, they state that EPA must take a 

precautionary approach and enter into consultations with the Services on sulfentrazone as 

outlined in the Interim Approaches document. 

Response: As an initial matter, CBD’s comments suggest that it may not fully appreciate the 

distinction between EPA’s interim and final registration review decision. Additionally, CBD 

seems to use “reregistration” interchangeably with “registration review.” Both are separate 

programs mandated by FIFRA; sulfentrazone is currently undergoing Registration Review. As 

provided in EPA’s registration review regulations at 40 CFR section 155.56, EPA may, in its 

discretion, issue an interim decision before the completion of registration review when, among 

other things, it determines that it cannot complete registration review because additional 

information is necessary to complete the Agency’s assessment. In addition, section 155.56 also 

provides that EPA may require risk mitigation measures in an interim decision. Consistent with 

 

2

 Docket number EPA-HQ-OPP-2009-0624-0018. 
8

this provision, EPA is issuing this interim registration review decision for sulfentrazone in part 

so that it can move forward with aspects of the registration review decision that are complete 

while EPA continues to work with the Services on developing the interim approaches that will be 

used to complete its registration review endangered species assessment for sulfentrazone. Under 

section 3(g) of FIFRA, EPA must complete the registration review of sulfentrazone by October 

1, 2022. While EPA could, therefore, choose not to complete any aspect of the sulfentrazone 

registration review for several more years until it completes its endangered species assessment 

and any necessary consultation, EPA believes the public and the environment benefit from 

EPA’s early action on the matters covered by this interim decision -- including risk mitigation, 

such as use of spray nozzles limiting sulfentrazone droplet size, a spray minimum release height, 

limitation on aerial application, and other drift reduction measures -- as described in Section IV 

of this document. EPA does not believe the Endangered Species Act compels a contrary result. 

Taking early action to address some risks now serves to benefit the environment and does not 

preclude EPA from taking any additional necessary actions to address effects to listed species 

that EPA concludes are necessary as it works to complete registration review. 

Accordingly, EPA’s previous response to CBD’s comments on the draft ecological risk 

assessment (in the Proposed Interim Decision) stated that EPA plans to address CBD’s concerns 

with the development of its Final Registration Review Decision. This is still EPA’s plan. EPA 

anticipates initiating consultation with the Services after issuing the Interim Registration Review 

Decision, but prior to issuing the Final Registration Review Decision. This Interim Registration 

Review Decision, like the Proposed Interim Decision, states that EPA is not making a complete 

endangered species finding, and that the Agency’s Final Registration Review Decision for 

sulfentrazone will depend upon the results of an ESA Section 7 consultation with the Services, 

an assessment of nontarget exposure to bees, as well as the results of a FFDCA Section 408(P) 

endocrine screening. 

EPA is still in the process of developing the interim approaches based on the 2013 NAS Report 

recommendations, including Steps 1 and 2 of the Biological Evaluation for listed species. 

CBD’s previous comments provide reference to the available critical habitat; however, as CBD 

noted, not all species have critical habitat. Furthermore, critical habitat is just one piece of the 

species’ range. EPA is working with the Services to obtain the best available species range 

information for all listed species. We are also working together to determine the appropriate 

pesticide use footprint. EPA will be taking public comment on our interim approaches as 

developed and implemented for the three pilot chemicals: chlorpyrifos, diazinon and malathion. 

As a result, EPA may develop a revised approach for Steps 1 and 2 through work on the three 

pilot chemicals before completing Step 1 for sulfentrazone. 

CBD’s previous comments also provided label language referring pesticide applicators to EPA’s 

Bulletins Live! System, and a statement that all product labels for sulfentrazone must contain this 

language. However, since there are no Bulletins for sulfentrazone in Bulletins Live! Two, it is 

unnecessary, at this point in time, to include this language on the label for sulfentrazone. 

Inclusion of a reference to Bulletins on the product label when no Bulletins exist is likely to 

result in confusion for pesticide applicators and growers. However, EPA is in agreement with 

CBD that Bulletins are the appropriate mechanism to implement any necessary geographicallyspecific pesticide use limitations intended to protect listed species. EPA plans to use Bulletins 
9

Live! Two to implement any Bulletins that would be generated as we complete the evaluation of 

potential risks of sulfentrazone to listed species and designated critical habitat. 

II. USE AND USAGE 

Sulfentrazone is a soil-applied, pre-emergent herbicide which can be applied either 

preplant incorporated or preemergence to the weeds. Sulfentrazone is a protoporphyrinogen 

Oxidase (PPO) Inhibitor, classified by the Weed Science Society of America (WSSA) as a 

Group 14 herbicide. WSSA Group 14 herbicides inhibit the protoporphyrinogen oxidase enzyme 

(important in the production of chlorophyll), causing a peroxidation of lipids in the cell 

membrane leading to cell leakage. Therefore, first symptoms are water-soaked lesions followed 

by necrosis of these lesions. Sulfentrazone is absorbed primarily by the roots and leads to rapid 

foliar desiccation (WSSA, 2014)3. Because sulfentrazone inhibits seed and propagule 

germination, it needs to be applied as close to the soil surface as possible with the lowest 

possible amount of pesticide remaining on any leaf surfaces and the minimum amount of 

exposure to evaporation or the wind. 

Sulfentrazone is registered for use to control a broad spectrum of broadleaf, grass, and 

sedge weed species on a wide variety of field crops, fruits, ornamentals, turfgrass, and vegetable 

crops. The greatest use of sulfentrazone between 2004 and 2013, in terms of pounds applied, 

was on soybeans and sunflowers, followed by dry beans and peas and tobacco. In terms of 

percent crop treated, the greatest use was on tobacco (45-65 percent crop treated), followed by 

asparagus (15-30%) and dry beans and peas (15-25%). 

To supplement the summary information provided above, EPA reviewed national usage 

data for sulfentrazone for individual crops to provide information for potential refinements to the 

preliminary risk assessment. EPA compiled summary data on average annual acres grown for 

major agricultural crops treated with sulfentrazone; average annual acres treated with 

sulfentrazone; the maximum single application rate (from product labels), average application 

rate, and the high-end application rate (between the 80th and 100th percentile). The Agency also 

reviewed data on application timing. 

In general, the Agency found that sulfentrazone is usually applied at rates below the 

maximum registered application rate, primarily by ground application in either the early spring 

(before planting) or late fall (after harvest). Proprietary usage data show that aerial application 

of sulfentrazone is limited to a few crops: soybeans in four states, sugarcane in two states, and 

sunflowers in three states. In addition, EPA found that sulfentrazone is often used to control 

weeds that have become resistant to other herbicides. Please see the April 6, 2015 memo, 

Sulfentrazone Usage Information, and the June 4, 2015 memo, Sulfentrazone Qualitative 

Benefits Assessment, for details. 

 

 

3

 Weed Science Society of America. 2014. Herbicide Handbook, 10th Edition. Dale L. Shaner Ed. Herbicide 

Handbook Committee. 
10

III. SCIENTIFIC ASSESSMENTS 

 A. Human Health Risk Assessment 

A summary of the Agency’s human health risk assessment is presented below. The 

Agency used the most updated Agency science policies and risk assessment methodologies to 

prepare a quantitative risk assessment in support of the sulfentrazone registration review. For a 

detailed discussion of the human health assessment for sulfentrazone, see Sulfentrazone – 

Preliminary Human Health Risk Assessment for Registration Review and the Risk Assessment for 

the Section 3 Registration Request for a New Use on Apples dated June 5, 2014, available in the 

public docket EPA-HQ-OPP-2009-0624, at http://www.regulations.gov/. 

1. Risk Conclusions 

EPA has no dietary risks of concern for sulfentrazone from exposure to residues in 

either food or drinking water. The Agency has no risk concerns for residential use of 

sulfentrazone on residential turf or golf courses or for use on ornamentals. Furthermore, EPA 

has no risk concern from aggregate exposure to sulfentrazone from food, drinking water, and 

residential/bystander exposure. 

Sulfentrazone does not appear to share a common mechanism of toxicity with other 

substances. In addition, sulfentrazone does not appear to produce any toxic metabolite or 

degradate also produced by other substances. Therefore, EPA has not made a common 

mechanism of toxicity finding for sulfentrazone and any other substance. For more information 

on EPA’s efforts to determine which pesticides share a common mechanism of toxicity and to 

evaluate cumulative effects, see EPA’s website, http://www2.epa.gov/pesticide-science-andassessing-pesticide-risks/cumulative-assessment-risk-pesticides. 

For pesticide handlers receiving occupational exposure to sulfentrazone, EPA has no risk 

concerns associated with inhalation exposure. However, handlers who are mixing and loading 

liquid and dry flowable formulations of sulfentrazone have dermal exposures and risks of 

concern (for high acreage crops) unless chemical-resistant gloves are worn. Most sulfentrazone 

labels require chemical-resistant gloves, and EPA is requiring that the remaining labels be 

amended to require chemical-resistant gloves. (See Section IVA1 of this document). 

The Agency also evaluated exposure and risk to agricultural workers who enter areas 

treated with sulfentrazone after application. EPA determined that postapplication exposures and 

risks were not of concern on the day of application. Therefore, the sulfentrazone re-entry interval 

is based on its acute toxicity, Category III and the restricted entry interval (REI) is 12 hours in 

accordance with 40 CFR 156.208c(2)(iii). 

2. Human Incidents 

EPA consulted the Office of Pesticide Programs Incident Data System (IDS) for potential 

human poisonings related to sulfentrazone. Between 2002 and 2009, four incidents were found, 

with generic symptoms not confirmed to be related to sulfentrazone exposure. In addition, there 
11

was no clear evidence of a trend or exposure pattern. At this time, there is no evidence 

suggesting a plausible association between exposure to sulfentrazone and a moderate or severe 

health outcome. Therefore, the Agency believes that no further investigation of human incidents 

is warranted. 

3. Tolerances 

EPA has determined that there are no adverse human health effects from use of 

sulfentrazone. The Agency will pursue changes to the tolerances for sulfentrazone to correct the 

commodity definition for flax, update crop tolerances for tree nuts, and correct the tolerance 

values for indirect or inadvertent residues. Specific changes are described in the June 5, 2014 

document, Preliminary Human Health Risk Assessment for Registration Review and the Risk 

Assessment for the Section 3 Registration Request for a New Use on Apples, and in Section IVB 

of this document. 

B. Ecological Risk Assessment 

A summary of the Agency’s ecological risk assessment is presented below. EPA used 

the most up-to-date Agency science policies and risk assessment methodologies to prepare a 

quantitative ecological risk assessment in support of the registration review of sulfentrazone. 

When EPA published the preliminary ecological risk assessment for sulfentrazone in July 2014, 

the Agency received extensive comments from FMC on the assessment. These comments 

prompted revisions to the preliminary ecological risk assessment for sulfentrazone. For a 

detailed discussion of the ecological assessment for sulfentrazone, see the following documents, 

all available in the public docket EPA-HQ-OPP-2009-0624, which can be accessed at 

http://www.regulations.gov/: 

 Preliminary Ecological Risk Assessment for the Registration Review of Sulfentrazone and 

Proposed New Uses on Apples, dated June 11, 2014, 

 Addendum to the Environmental Fate and Ecological Risk Assessment for Sulfentrazone 

Registration Review, dated June 9, 2015, and 

 Response to Comments on the Preliminary Ecological Risk Assessment for the 

Registration Review of Sulfentrazone, dated June 9, 2015. 

EPA is currently working with the Services and other stakeholders to implement an 

interim approach for assessing potential risk to listed species and their designated critical 

habitats. Once the scientific methods necessary to complete risk assessments for listed species 

and their designated critical habitats are finalized, the Agency will complete its endangered 

species assessment for sulfentrazone. As such, potential risks to listed species will not be 

described further in this document. The risk concerns for nonlisted species only are described 

herein. The Agency will complete its endangered species assessment for sulfentrazone, and any 

necessary consultation with the Services, before completing the sulfentrazone registration 

review. 
12

1. Risk Conclusions 

In 2014, the Agency conducted a preliminary ecological risk assessment for 

sulfentrazone. This conservative assessment showed that both acute and chronic risk estimates 

for mammals, freshwater and estuarine/marine fish, and freshwater invertebrates were below 

EPA’s level of concern.4

 This assessment also showed that acute risk estimates for birds, reptiles, 

amphibians, and estuarine/marine invertebrates were below the level of concern. Therefore, 

EPA does not have risk concerns for nonlisted species in these taxa for these exposure durations. 

When initially scoping the registration review for sulfentrazone, EPA did not identify the 

need for any additional studies to evaluate potential effects on pollinators. However, since the 

issuance of the June 2014 Guidance for Assessing Pesticide Risks to Bees,5 EPA has begun to 

require these data where applicable. EPA is currently determining whether additional 

pollinator data are needed for active ingredients in registration review whose dockets opened 

prior to June 2014. For those active ingredients where EPA determines that additional pollinator 

exposure and effects data are necessary to help make a final registration review decision, EPA 

intends to issue a DCI to obtain these data. In the near future, EPA will provide further 

information and guidance on this effort. The pollinator studies that could be required for 

sulfentrazone are included in Table 1 below; the table does not list studies previously submitted 

to EPA and found to be acceptable. The Agency will require data it believes are needed to help 

inform the pollinator risk assessment. 

Table 1. Potential Pollinator Data Requirements for Sulfentrazone 

Guideline # Study

850.3020* Acute Contact Toxicity with Adult Honey Bees 

850.3030*† Honey bee toxicity of residues on foliage

850.3040‡ Full-Field testing for pollinators

Non-Guideline (OECD 237)* Honey bee larvae acute oral toxicity 

Non-Guideline* Honey bee adult chronic oral toxicity 

Non-Guideline* Honey bee larvae chronic oral toxicity 

Non-Guideline‡ Field trial of residues in pollen and nectar

Non-Guideline (OECD 75)‡ Semi-field testing for pollinators *

Tier 1, laboratory studies. † 

‡

Tier 2 and 3 Semi-field and full-field colony level studies. The need for a higher tier test for pollinators will be 

determined based upon lower tiered tests and/or other lines of data and the need for a refined pollinator risk 

assessment. 

The preliminary ecological risk assessment showed potential chronic risks of concern to 

birds and to estuarine/marine invertebrates. In addition, the assessment showed risks of concern 

for terrestrial and semi-aquatic nontarget plants. In these instances, EPA refined the preliminary 

risk assessment by reviewing additional plant toxicity data; incorporating a new plant endpoint, 

and considering additional usage data for sulfentrazone. In addition, information on typical 

 

4

 For nonlisted species, the Level of Concern (LOC) is 1; RQs > 1 exceed the LOC. For listed species, the LOC is 

0.1; RQs > 0.1 exceed the LOC. 

5 http://www2.epa.gov/sites/production/files/2014-

06/documents/pollinator_risk_assessment_guidance_06_19_14.pdf
13

agricultural practices was considered in order to provide additional context and perspective for 

these risk concerns. 

 

Birds. In the preliminary risk assessment for sulfentrazone, the Agency estimated acute 

and chronic risks to birds, expressed as risk quotients (RQs), using a No Adverse Effects 

Concentration (NOAEC) from an avian reproductive toxicity study and environmental effects 

concentrations (EECs) of sulfentrazone on various avian food items, grouped together into five 

generic diets. These EECs were derived from the Kenaga Nomogram. The resulting acute RQs 

ranged from 0 to 0.02, and were below the Agency’s level of concern for all generic avian diets. 

However, chronic RQs ranged from 1.18 to 9, for all avian diets except for one 

(fruits/pods/seeds), and exceeded the Agency’s level of concern (1.0). 

EPA revised the avian RQs using average application rates representative of actual 

sulfentrazone use.6

 These application rates varied from 0.05 to 0.3 lb a.i./A. The resulting RQs 

ranged from 0.2 to 7.2 with all application rates exceeding the LOC for at least one dietary item. 

RQs derived from mean Kenaga values ranged from <0.1 to 2.6 with RQs exceeding the LOC for 

at least one dietary item for all application rates with the exception of the lowest application rate 

modeled (0.05 lb a.i./A.) 

Aquatic Invertebrates. In the preliminary risk assessment, EPA estimated acute and 

chronic RQs for freshwater and estuarine/marine aquatic invertebrates. EPA provided bounding 

estimates of exposure and risk to invertebrates in both clear and turbid waters because photolysis 

contributes to the degradation of sulfentrazone in aquatic environments.7

 Although the 

preliminary risk assessment indicated that the chronic RQs for estuarine/marine invertebrates 

exceeded the level of concern, the RQs are based on both the worst-case exposure scenario and a 

chronic NOAEC of 0.003 mg a.i./L based on an acute-to-chronic ratio. EPA has no chronic 

toxicity data for the mysid shrimp. There is inherent uncertainty in the use of an acute-tochronic ratio because it represents an unbounded measure of risk. Therefore, the Agency has 

low confidence in the chronic risk estimates for mysid. 

Terrestrial and Semi-aquatic Plants. Initial Findings. In the preliminary risk assessment 

for sulfentrazone, the Agency used the TerrPlant model to calculate RQs for nontarget terrestrial 

and semiaquatic plants exposed to sulfentrazone from spray drift alone and for spray drift and 

runoff combined, in both dry upland and semi-aquatic wetland habitats. In addition, EPA 

examined the effect of spray drift to nontarget plants using the AgDrift model. The preliminary 

risk assessment showed risk concerns for nontarget plants from use of sulfentrazone. When 

sulfentrazone is applied by ground, nontarget plant RQs ranged from 0.17 to 10 for monocots 

and from 1.1 to 31.9 for dicots. For aerial applications, RQs ranged from 1.6 to 11 for monocots 

and from 3.4 to 43 for dicots. Initial spray drift effects distances ranged from 56 to > 1000 feet 

from the edge of treated fields. 

 

Revised Risk Estimates. In response to public comments submitted by FMC, EPA 

revisited the Tier II Vegetative Vigor data for cucumber8, reviewed all of the raw data, and 

 

6

 The application rates were taken from proprietary agricultural survey data. 

7

 EPA adjusted EECs for clear water and turbid water by using different rates of photolysis. 

8

 The cucumber is the most sensitive species in the vegetative vigor study for sulfentrazone. 
14

recalculated the 25% Inhibition Concentration (IC25) value using current statistical models. The 

new cucumber IC25 value is 0.0016 lbs a.i./A. Previously, EPA used an IC25 of 0.00052 lbs a.i./A 

from the cucumber study to calculate terrestrial plant RQs and buffer distances for dicots. EPA 

recalculated risk quotients (RQs) for dicots using the cucumber endpoint to determine the 

reasonable worst case risk to non-target broadleaf plants. Revised RQs for a range of application 

rates, bracketing both labeled rates and use rates from agricultural survey data, range from 0.19 

to 17.39 for both ground and aerial application of sulfentrazone. Please see the June 9, 2015 

memo, Addendum to the Environmental Fate and Ecological Risk Assessment for Sulfentrazone 

Registration Review, for additional details. 

Revised Spray Drift Analysis. EPA ran the Ag-Drift model using the new cucumber 

endpoint to calculate effects distances for sulfentrazone. The effects distance is the off-field area 

of potential adverse effects to non-target plants. Beyond this distances, there would be low 

potential to adversely affect non-target plants. The revised Ag-Drift runs provide the effects 

distances at a range of application rates, for both ground and aerial application, for different 

boom heights and droplet sizes. For ground application of sulfentrazone, low boom, and fine to 

medium coarse droplets, the effects distance ranged from 40 to 105 feet for agricultural crops. 

For aerial application, using an application height 10 feet above the crop canopy, the effects 

distance ranged from 220 to 640 feet for coarse to very coarse droplets and 335 to >1000 feet for 

medium to coarse droplets. 

2. Ecological Incidents 

Between 2002 and 2005, EPA received reports of 19 incidents involving injury to nontarget plants associated with herbicide products containing sulfentrazone. Most of these 

incidents were the result of legal registered use of herbicides containing sulfentrazone, although 

some of the products contained more than one herbicide active ingredient. A total of 7,707 acres 

were affected. According to the last search of EPA’s environmental incident database performed 

on June 1, 2015, no incidents have been reported since 2005. However, a lack of reports does 

not necessarily mean that there were no incidents. 

3. Characterization of Ecological Risk 

The preliminary risk assessment and risk assessment addendum for sulfentrazone 

identified some RQs that exceeded EPA’s level of concern (LOC) for nonlisted species. The 

Agency uses the LOC as an indicator of potential adverse effects to nontarget organisms. LOC 

exceedances are only one line of evidence used by EPA to describe the risks posed by a pesticide 

to nontarget organisms. This risk characterization section describes other lines of evidence for 

sulfentrazone, and puts the LOC exceedances into a broader context. 

Birds. For sulfentrazone, although the chronic RQs for birds exceed the LOC, EPA does 

not expect risk to birds for the following reasons. RQ exceedances were seen for birds eating a 

diet of arthropods or short grass, exposed to sulfentrazone at a rate of 0.3 lb a.i./A, with RQs of 

2.8 and 7.2, respectively. In addition, the avian RQs are based on a NOAEC from an avian 

reproductive toxicity study in the bobwhite quail, which showed an 8% reduction in body weight 

of 14 day old hatchlings at the NOAEC, relative to the control group. No adverse effects were 

seen in an avian reproductive study in the mallard duck. In addition, sulfentrazone was 
15

practically nontoxic in acute oral and subacute dietary toxicity studies in birds. Thus, EPA has a 

low level of concern and does not expect sulfentrazone to pose chronic risks to birds. 

Aquatic Invertebrates. Although the preliminary risk assessment for sulfentrazone 

indicated chronic RQs of concern for estuarine/marine invertebrates, the Agency has low 

confidence in these RQ values. These RQs are based on both the worst-case exposure scenario 

and a chronic NOAEC with high uncertainty. The mysid NOAEC of 0.003 mg a.i./L is based on 

an acute-to-chronic ratio because EPA has no chronic toxicity data for the mysid shrimp. There 

is inherent uncertainty in the use of an acute-to-chronic ratio because it represents an unbounded 

measure of risk. Therefore, EPA does not expect risks to estuarine/marine invertebrates 

associated with use of sulfentrazone. 

Terrestrial Plants. The RQs for nontarget terrestrial plants range from 0.19 to 17.9 

following exposure to sulfentrazone at both labeled rates and actual use rates. These RQs are 

based on the vegetative vigor endpoint for cucumber (the most sensitive species), which is within 

the same order of magnitude of the IC25 for soybean. These data indicate that sulfentrazone can 

harm nontarget plants exposed during the vegetative growth phase. However, the timing of 

sulfentrazone application may partially mitigate adverse effects to nontarget plants. 

Sulfentrazone is most typically applied in early spring or late fall. In addition, available usage 

data show that sulfentrazone is typically applied at rates below the maximum labelled application 

rate, resulting in lower exposure and risk than indicated by the RQs. 

Although the modeled spray drift effects distances for sulfentrazone are as high as 105 

feet from edge of field for ground application and >1000 feet for aerial application at the 

maximum labeled application rate, these calculated effects distances are proportional to 

application rate. Sulfentrazone is seldom applied at the maximum label rate. Effects distances 

do not consider many of the drift reduction measures on current sulfentrazone product labels due 

to model limitations. Furthermore, aerial application of sulfentrazone is limited to three crops; of 

these, sulfentrazone is aerially applied to 2% of all soybeans and 5% of all sunflowers grown in 

the US. Application to sugarcane is limited to two states in accordance with FIFRA 24(c) 

special local need registrations. To address concerns for off-target spray drift, especially from 

aerial application, EPA is requiring various mitigation measures to reduce drift. FMC, the lead 

technical registrant for sulfentrazone, has agreed to these drift reduction measures. 

See the April 4, 2015 memo, Sulfentrazone Usage Information, and the June 9, 2015 

memo, Addendum to the Environmental Fate and Ecological Risk Assessment for Sulfentrazone 

Registration Review, for details. 

C. Benefits Assessment 

Sulfentrazone has been shown to provide cost-effective weed control in several field and 

row crops including corn, dry beans and peas, soybeans, sunflowers, and tobacco. It is used in 

certain crops to control weeds that are resistant to glyphosate or sulfonylurea herbicides, such as 

Palmer amaranth and kochia. The major benefits of sulfentrazone are summarized below; 

additional details may be found in the June 4, 2015 memo, Sulfentrazone Qualitative Benefits 

Assessment. 
16

Corn. Sulfentrazone is applied to corn at an average application rate of 0.06 lb/A to 

approximately 28,700 total acres annually, or less than one percent of the corn crop. Although 

sulfentrazone is only applied to a limited number of acres, EPA considered this crop in the 

qualitative benefits analysis because of the overall importance of this crop in U.S. agriculture. 

Sulfentrazone is recommended for the control of a number of difficult to control weeds such as 

common waterhemp, giant ragweed, and marestail. Overall, sulfentrazone controls several 

difficult to control weeds and is slightly less expensive than several of the competing herbicides. 

Dry beans/peas. Sulfentrazone is applied at an average application rate of 0.09 lb/A to 

approximately 415,000 total acres annually, or 15% of the total crop of dry beans and peas 

grown in the US. Sulfentrazone is used in North and South Dakota for the control of acetolactate 

synthase (ALS)9

 herbicide-resistant kochia, an emerging problem weed, where it provides 6 to 8 

weeks of residual control. According to EPA Proprietary Data (2009-2013), sulfentrazone is the 

second most used herbicide for the control of kochia and other resistant weeds. In dry 

beans/peas, sulfentrazone effectively controls ALS-resistant kochia and is comparable in price to 

available herbicides. 

Soybeans. Sulfentrazone is applied at an average application rate of 0.15 lb/A to over 3 

million acres of soybeans annually, or 5% of the soybean crop. In soybeans, sulfentrazone is 

recommended as part of a resistance management program for control of glyphosate-resistant 

Palmer amaranth, which can cause extensive crop loss. Of the herbicides used to control Palmer 

amaranth on soybeans, on average, sulfentrazone was the sixth most used active ingredient and 

accounted for 9% of total acre applications. Sulfentrazone is applied aerially to 2% of total 

soybean acres nationally. In soybeans, sulfentrazone effectively controls glyphosate-resistant 

Palmer amaranth and is comparable in price to other available herbicides. 

Sunflower. Sulfentrazone is applied at an average application rate of 0.11 lb/A to over 

1.2 million acres annually, or 50% of the sunflower crop. In terms of percent crop treated, 

sulfentrazone appears to be an important chemical control in sunflower production. In 

sunflowers, sulfentrazone is recommended in Montana for control of ALS-resistant kochia, a 

difficult to control weed. Across the United States, sulfentrazone is the most used active 

ingredient for controlling kochia on sunflowers. Sulfentrazone is applied aerially to 5% of 

sunflower fields, effectively controls ALS-resistant kochia on sunflowers, and is comparable in 

price to other available herbicides. 

Tobacco. Sulfentrazone is applied at an average application rate of 0.18 lb/A to 174,000 

acres annually, or 45% of the tobacco crop, and appears to be an important chemical control for 

tobacco production. For tobacco grown in North Carolina sulfentrazone is one of the few 

herbicides recommended for control of yellow nutsedge, an aggressive and difficult to control 

perennial weed. According to proprietary data, sulfentrazone is primarily used against morning 

glory, redroot pigweed, and nutsedge species. In tobacco, sulfentrazone effectively controls 

yellow nutsedge and is comparable in price to available herbicides. 

Please see the April 6, 2015 memo, Sulfentrazone Usage Information, and the June 4, 

2015 memo, Sulfentrazone Qualitative Benefits Assessment, for details. 

 

9

 Herbicide group number 2, sulfonylureas. 
17

D. Endangered Species Assessment 

In November 2013, the EPA, along with the Services and the USDA, released a summary 

of their joint Interim Approaches for assessing risks to endangered and threatened (listed) species 

from pesticides. The Interim Approaches10 were developed jointly by the agencies in response to 

the National Academy of Sciences’ (NAS) recommendations and reflect a common approach to 

risk assessment shared by the agencies as a way of addressing scientific differences between the 

EPA and the Services. The NAS report11 outlines recommendations on specific scientific and 

technical issues related to the development of pesticide risk assessments that EPA and the 

Services must conduct in connection with their obligations under the ESA and FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on 

November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the 

December 2013 Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues 

Research and Evaluation Group (SFIREG) meetings. The agencies also held stakeholder 

workshops - in April and October 2014, and in April 2015 - allowing additional opportunities for 

stakeholders to comment on the Interim Approaches. Additional workshops are planned to 

enhance stakeholder involvement. As part of a phased, iterative process for developing the 

Interim Approaches, the agencies will also consider public comments on the Interim Approaches 

in connection with the development of upcoming Registration Review decisions. The details of 

the joint Interim Approaches are contained in the white paper Interim Approaches for NationalLevel Pesticide Endangered Species Act (ESA) Assessments Based on the Recommendations of 

the National Academy of Sciences April 2013 Report12, dated November 1, 2013. 

Given that the agencies are continuing to develop and work toward implementation of the 

Interim Approaches to assess the potential risks of pesticides to listed species and their 

designated critical habitat, the ecological risk assessment supporting this Interim Decision for 

Sulfentrazone does not contain a complete ESA analysis that includes effects determinations for 

specific listed species or designated critical habitat. Although EPA has not yet completed effects 

determinations for specific species or habitats, for this interim decision, EPA’s evaluation 

assumed, for all taxa of non-target wildlife and plants, that listed species and designated critical 

habitats may be present in the vicinity of the application of sulfentrazone. This assessment 

allows EPA to focus its future evaluations on the types of species where the potential for effects 

exists once the scientific methods being developed by the agencies have been fully vetted. 

When the Agencies have fully developed and implemented the scientific methodology for 

evaluating risks for listed species and their designated critical habitats, these methods will be 

applied to subsequent analyses for sulfentrazone as part of completing the final registration 

review decision. 

 

10 Interim Approaches for National-Level Pesticide Endangered Species Act (ESA) Assessments Based on the 

Recommendations of the National Academy of Sciences April 2013 Report. Available at 

http://www2.epa.gov/endangered-species/interim-approaches-pesticide-endangered-species-act-assessments-basednas-report

11 Assessing Risks to Endangered and Threatened Species from Pesticides. National Academy of Sciences. 1983. 

Available from http://www.nap.edu/catalog.php?record_id=18344 12 Available at http://www.epa.gov/espp/2013/nas.html
18

E. Endocrine Disruptor Screening Program 

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential 

adverse outcomes from exposure to chemicals. Collectively, these studies include acute, 

subchronic and chronic toxicity, including assessments of carcinogenicity, neurotoxicity, 

developmental, reproductive, and general or systemic toxicity. These studies include endpoints 

which may be susceptible to endocrine influence, including effects on endocrine target organ 

histopathology, organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, 

reproductive loss, and sex ratios in offspring. For ecological hazard assessments, EPA evaluates 

acute tests and chronic studies that assess growth, developmental and reproductive effects in 

different taxonomic groups. As part of its most recent registration decision for sulfentrazone, 

EPA reviewed these data and selected the most sensitive endpoints for relevant risk assessment 

scenarios from the existing hazard database. However, as required by FFDCA section 408(p), 

sulfentrazone is subject to the endocrine screening part of the Endocrine Disruptor Screening 

Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including 

pesticide active and other ingredients) may have an effect in humans or wildlife similar to an 

effect produced by a “naturally occurring estrogen, or other such endocrine effects as the 

Administrator may designate.” The EDSP employs a two-tiered approach to making the 

statutorily required determinations. Tier 1 consists of a battery of 11 screening assays to identify 

the potential of a chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or 

T) hormonal systems. Chemicals that go through Tier 1 screening and are found to have the 

potential to interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP 

where EPA will determine which, if any, of the Tier 2 tests are necessary based on the available 

data. Tier 2 testing is designed to identify any adverse endocrine-related effects caused by the 

substance, and establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of 

chemicals identified for EDSP screening was published on June 14, 201313 and includes some 

pesticides scheduled for Registration Review and chemicals found in water. Neither of these 

lists should be construed as a list of known or likely endocrine disruptors. For further 

information on the status of the EDSP, the policies and procedures, the lists of chemicals, future 

lists, the test guidelines and the Tier 1 screening battery, please visit EPA’s EDSP website.14 

In this interim decision, EPA is making no human health or environmental safety findings 

associated with the EDSP screening of sulfentrazone. Before completing this Registration 

Review, the Agency will make an EDSP FFDCA section 408(p) determination. 

 

13 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 

14 http://www.epa.gov/endo/
19

IV. INTERIM REGISTRATION REVIEW DECISION 

A. Risk Mitigation and Regulatory Rationale 

1. Occupational Exposure 

To address risk concerns associated with occupational exposure, pesticide handlers who 

are mixing and loading dry flowable and liquid formulations of sulfentrazone must wear 

chemical-resistant gloves. Most, but not all, sulfentrazone dry flowable and liquid product labels 

currently require either waterproof or chemical-resistant gloves. Therefore, certain product 

registrations need to be amended to require use of chemical-resistant gloves. FMC, the lead 

sulfentrazone registrant, has agreed to this label amendment. 

The re-entry interval (REI) for sulfentrazone is 12 hours, based on the acute toxicity of 

this herbicide (Category III). This re-entry interval is established in accordance with 40 CFR § 

156.208c(2)(iii). This REI applies to all pesticide products containing sulfentrazone that do not 

also contain another pesticide active ingredient with a more restrictive (longer) REI. Therefore, 

certain product registrations need to be amended to require a 12 hour REI. 

2. Environmental Effects 

 

As discussed in the Ecological Risk Assessment section of this document, sulfentrazone 

has been determined to pose a potential risk concern for nontarget terrestrial plants, especially 

dicot species. In addition, there is a lack of consistency among sulfentrazone product labels 

regarding mitigation measures to minimize nontarget effects from spray drift. To address these 

concerns, the Agency is requiring label changes for sulfentrazone technical and agricultural enduse products to reduce off-target spray drift. EPA’s intention is to establish a baseline level of 

protection against spray drift that is consistent across all sulfentrazone products registered for use 

in agricultural, wide area, or rights-of-way settings. The following label restrictions are required 

for all sulfentrazone technical grade products and all agricultural end-use products: 

 Use of spray nozzles limiting product droplet size during applications to medium or coarse in 

accordance with the American Society of Agricultural and Biological Engineering (ASABE) 

standard S-572; 

 For boom spraying, the minimum release height must be 30 inches from the soil for ground 

applications and 10 feet from the top of the crop canopy for aerial applications (unless a 

greater application height is required for pilot safety); 

 Applicators may spray only when wind speed is between 3 and 10 mph; 

 Aerial application is allowed only when local environmental conditions15 prohibit ground 

application; 

 

15 Aerial application will be allowed when the field is too wet to safely apply pesticides using ground equipment. 
20

 When aerial application is allowed, the minimum finished spray volume is 5 gallons per acre; 

and 

 For ground application, the minimum finished spray volume is 10 gallons per acre for preemergence use and 15 gallons per acre for use in a tank mix with one or more contact, burndown herbicides. 

All registrants who have sulfentrazone technical grade or agricultural end-use products are 

subject to these requirements and must amend their labels accordingly. 

3. Herbicide Resistance 

To prevent the development of resistance to sulfentrazone among common weeds, the 

Agency is requiring that all herbicide products containing sulfentrazone (except for those 

registered solely for homeowner use) contain resistance-management labeling. These 

specifications follow the recommendations of the Weed Science Society of America publication, 

Reducing the Risks of Herbicide Resistance, Best Management Practices and 

Recommendations16. The Agency first provided guidance on resistance management labeling in 

Pesticide Registration (PR) Notice 2001-5, Guidance for Pesticide Registrants on Resistance 

Management Labeling. EPA is requiring the following herbicide-resistance labeling for 

sulfentrazone: 

 Mandatory listing of herbicide mechanism of action, and the Weed Science Society of 

America herbicide group number, at the top of the first page of each product label; 

 Instructions to alternate use of products containing sulfentrazone with other herbicides 

with different mechanisms of action; 

 Recommendations to scout for weeds before and after sulfentrazone application, to 

ensure proper identification of weeds and growth stage and to confirm product 

performance; and 

 Instructions to report herbicide failure to local extensions specialists, certified crop 

advisors, and/or sulfentrazone registrants. 

EPA believes that the inclusion of herbicide-resistance management language on 

sulfentrazone labels is important to slowing the development of resistance to this herbicide while 

maintaining flexibility for growers. Weed resistance is a complex issue and registrants play an 

important role in ensuring effective resistance management. Educating all stakeholders about 

managing herbicide-resistance is important, and the product label is a critical part of this effort. 

B. Tolerance Amendments 

The Agency has determined that there are no adverse human health effects from use of 

sulfentrazone, and that the sulfentrazone tolerances established in 40 CFR § 180.498 continue to 

meet the safety standard of FFDCA. However, some changes to the sulfentrazone tolerances are 

necessary to correct commodity definitions, update crop group tolerances, and correct tolerance 

 

16 Norsworthy et al. 2012. Weed Science 2012. Special Issue: 31-62. 
21

values for indirect or inadvertent residues. Therefore, EPA is pursuing the following changes to 

the sulfentrazone tolerances listed in 40 CFR § 180.498: 

 The tolerance for “Flax” (at 0.15 ppm) will be changed to “Flax, seed” to correct the 

commodity definition. The tolerance level remains unchanged at 0.15 ppm. 

 The tolerance for “Nut, tree, group 14” will be updated to “Nut, tree, group 14-12.” The 

tolerance level remains unchanged at 0.15 ppm. 

 The tolerance for “Pistachio” will be revoked concomitant with the revision of the tolerance 

for tree nuts to include pistachio. 

 The tolerances for indirect or inadvertent residues of sulfentrazone established in 40 CFR § 

180.498(d) will be corrected to three significant figures, in accordance with current policy. 

EPA will conduct rulemaking to implement these tolerance changes, in accordance with FFDCA. 

C. Endangered Species 

As previously mentioned, EPA is currently working with the Services and other 

stakeholders to implement an interim approach for assessing potential risk to listed species and 

their designated critical habitats in accordance with the ESA. When the Agencies have fully 

developed and implemented the scientific methodology for evaluating risks for listed species and 

their designated critical habitats, these methods will be applied to subsequent analyses for 

sulfentrazone as part of completing the final registration review decision. 

D. Interim Registration Review Decision 

In accordance with 40 CFR Sections 155.56 and 155.58, the Agency is issuing this 

Interim Registration Review Decision. Except for the EDSP, pollinator, and ESA components of 

this case, the Agency has made the following Interim Registration Review Decision: (1) with the 

possible exception of pollinator studies listed in Section IIIB of this document, no additional data 

are required at this time; and (2) changes to the affected registrations and their labeling are 

necessary at this time. 

 

In this Interim Registration Review Decision, EPA is making no human health or 

environmental safety findings associated with the EDSP screening of sulfentrazone, nor is it 

making a complete endangered species finding or a complete assessment for effects to 

pollinators. The Agency’s final registration review decision for sulfentrazone will depend upon 

the result of an ESA Section 7 consultation with the Services, an EDSP FFDCA section 408(p) 

determination, and an assessment of non-target exposure to pollinators. 

E. Data Requirements 

At this time, with the possible exception of pollinator studies listed in Section IIIB of this 

document, no additional data are required as part of this Interim Registration Review Decision. 

Although the Proposed Interim Decision mentioned the need for additional analytical reference 

standards to replenish supplies, these were subsequently submitted to the EPA analytical 

chemistry lab in Fort Meade, MD, and are no longer needed. 
22

V. NEXT STEPS AND TIMELINE 

A. Interim Registration Review Decision 

In accordance with 40 CFR Sections 155.56 and 155.58, the Agency is issuing this 

Interim Registration Review Decision document for sulfentrazone. Except for the EDSP, 

pollinator, and ESA components of this registration review case, EPA has made the following 

Interim Registration Review Decision for sulfentrazone: (1) with the possible exception of 

pollinator studies listed in Section IIIB of this document, no additional data are needed at this 

time, and (2) changes to affected sulfentrazone product registrations and product labeling are 

necessary at this time. These changes will incorporate the mitigation measures described in this 

document into the terms and conditions of registration and be implemented through amendment 

of the affected labels. 

In this Interim Registration Review Decision, the Agency is making no human health or 

environmental safety findings associated with the EDSP screening of sulfentrazone, nor is it 

making a complete endangered species finding or a complete assessment for effects to 

pollinators. EPA’s final registration review decision for sulfentrazone will depend upon the 

results of an ESA Section 7 Consultation with the Services, an EDSP FFDCA Section 408(p) 

determination, and an assessment of non-target exposure to pollinators. 

B. Implementation of Mitigation Measures 

All sulfentrazone technical registrants and all end-use registrants of agricultural products 

containing sulfentrazone must submit amended labels, which implement the label changes 

summarized in Appendix A, to EPA within 90 days of issuance of this Interim Registration 

Review Decision for sulfentrazone. 

 
23

Appendix A: SULFENTRAZONE Label Table 

Summary of Labeling Changes for Sulfentrazone 

Description Amended Labeling Language for Sulfentrazone Products Placement on Label 

Technical and Manufacturing Use Products 

Use Limitations “Only for formulation into a/n [insert pesticide class] for the 

following use(s) [list only those uses and application 

methods that are being supported by technical and MP 

registrant].” 

Directions for Use 

Products Labeled for Agricultural Use 

HERBICIDE RESISTANCE MANAGEMENT 

Herbicide Mode of 

Action 

“Group 14 HERBICIDE” Front Panel, upper right 

quadrant, surrounded by a 

black (or suitable color) 

rectangle 

Weed Resistance 

Management 

 Instructions to alternate use of products containing 

sulfentrazone with other herbicides with different 

mechanisms of action; 

 Recommendations to scout for weeds before 

sulfentrazone application for identification and 

growth stage and after sulfentrazone application to 

look for poor performance or likely resistance; 

 Instructions to report herbicide failure to local 

extension specialists, certified crop advisors, and/or 

sulfentrazone registrants. 

Directions for Use, prior to 

directions for specific crops 

under the heading” 

WEED RESISTANCE 

MANAGEMENT” 

PERSONAL PROTECTIVE EQUIPMENT AND RE-ENTRY INTERVAL 

PPE Labeling 

Requirements for all 

agricultural end-use 

products containing 

sulfentrazone 

“PERSONAL PROTECTIVE EQUIPMENT (PPE) 

Applicators, mixers, loaders, and other pesticide handlers 

must wear: 

 Chemical-resistant gloves”

Precautionary Statements 

section, under the heading 

Hazards to Humans and 

Domestic Animals “Personal 

Protective Equipment (PPE)” 

REI Requirement  The REI for sulfentrazone products is 12 hours, 

unless the acute toxicity of the product indicates the 

need for a longer REI. 

Precautionary Statements 

section, under the heading “Reentry Interval” 

ENVIRONMENTAL HAZARDS 

Environmental Hazard  Warning that drift and runoff of sulfentrazone 

products may be hazardous to plants in adjacent 

areas. 

Environmental Hazards 

SPRAY DRIFT 

Spray Drift Language 

SprayNozzles & 

Droplet Size 

 Select nozzles and application pressure that deliver 

medium to coarse or larger spray droplets as 

indicated in the nozzle manufacturer’s 

recommendations and in accordance with ASABE* 

Standard S-572. 

 Select coarse to very coarse droplet size when 

sulfentrazone is used as a preemergent/preplant 

application. 

Directions for Use, prior to 

directions for specific crops 

under the heading “SPRAY 

DRIFT” 
24

Summary of Labeling Changes for Sulfentrazone 

Description Amended Labeling Language for Sulfentrazone Products Placement on Label 

 Select medium to very coarse droplet size when 

sulfentrazone is used postemergence with a contact 

burndown herbicide. 

 Applicators may spray only when wind speed is 

between 3 and 10 mph. 

 Do not apply as spray droplets smaller than medium 

to coarse (defined by the ASABE* standard). 

Spray Drift Language 

Spray Volume 

 Ground applicators must use a minimum finished 

spray volume of 10 gallons per acre. 

 When sulfentrazone is tank mixed with a contact 

burndown herbicide, ground applicators must use a 

minimum spray volume of 15 gallons per acre. 

Directions for Use, prior to 

directions for specific crops 

under the heading “SPRAY 

DRIFT” 

Spray Drift Language 

Aerial Application 

 Aerial application is allowed only when 

environmental conditions prohibit ground 

application. 

 For aerial applications, the maximum release height 

must be 10 feet from the top of the crop canopy, 

unless a greater application height is required for 

pilot safety. 

 “When this product is allowed to be applied by air, 

applicator must use a minimum finished spray 

volume of 5 gallons per acre.” 

Directions for Use, prior to 

directions for specific crops 

under the heading “SPRAY 

DRIFT” “Aerial Application” 

DIRECTIONS FOR USE 

Language to restrict use 

to target species only 

“This product may only be used to control [insert pests and 

sites]...” 

Directions for Use 

Under “Use Restrictions” 

Maximum single and 

annual application rates 

“The maximum single application rate for [insert product 

name] is [insert amount of product equivalent to the 

maximum application rate for each crop or crop group,] the 

equivalent of [insert maximum application rate in units of lb 

a.i./A].” 

“The maximum annual application rate for [insert product 

name] is [insert amount of product equivalent to the 

maximum annual application rate for each crop or crop 

group,] the equivalent of [insert maximum application rate in 

units of lb a.i./A].” 

Directions for Use for Specific 

Crops 

Aerial Application “Aerial application is allowed only when environmental 

conditions prohibit ground application.” 

Directions for Use 

Under “Use Restrictions” 

“Aerial Application” 

Aerial Application “When this product is allowed to be applied by air, applicator 

must use a minimum finished spray volume of 5 gallons per 

acre.” 

Directions for Use 

Under “Use Restrictions” 

“Aerial Application” 

Aerial Application  The maximum release height must be 10 feet from 

the top of the crop canopy, unless a greater 

application height is required for pilot safety. 

*ASABE – American Society for Agricultural and Biological Engineers.