Docket Number EPA-HQ-OPP-2010-0815

www.regulations.gov

Carfentrazone-ethyl

Summary Document

Registration Review: Initial Docket

March 2011

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TABLE OF CONTENTS

 

I. Preliminary Work Plan (PWP) 4

II. Fact Sheet 12

This Preliminary Work Plan and Fact Sheet summarize the Environmental Protection Agency’s 

current position based on the following documents:

1. Registration Review: Preliminary Problem Formulation for Environmental Fate, 

Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for 

Carfentrazone-ethyl, March 8, 2011.

2. Carfentrazone-ethyl. Human Health Assessment Scoping Document in Support of 

Registration Review, February 9, 2011.

3. Carfentrazone-ethyl: Review of Human Incidents, November 30, 2010.

4. Carfentrazone-ethyl Screening Level Usage Analysis (SLUA), July 21, 2010.

5. Carfentrazone-ethyl California Department of Pesticide Regulation Usage Data, May 26, 

2010

6. Appendix A: Uses of Carfentrazone-ethyl Considered in Registration Review Work 

Planning, August 17, 2010.

7. BEAD Chemical Profile for Registration Review: Carfentrazone-ethyl, February 23, 

2011.

All supporting documents for the registration review of carfentrazone-ethyl are located in docket 

EPA-HQ-OPP-2010-0815 at www.regulations.gov. 
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I. PRELIMINARY WORK PLAN

Introduction

The Food Quality Protection Act (FQPA) of 1996 mandated a registration review program. All 

pesticides distributed or sold in the United States (U.S.) generally must be registered by the 

Environmental Protection Agency (EPA or the Agency), based on scientific data showing that 

they will not cause unreasonable risks to human health or the environment when used as directed 

on product labeling. 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 of no unreasonable adverse effects to human health or the 

environment. Changes in science, public policy, and pesticide use practices will occur over time. 

Through the registration review program, the Agency periodically reevaluates pesticides to make 

sure that as change occurs, products in the marketplace can be used safely. Information on this 

program is provided at: http://www.epa.gov/oppsrrd1/registration_review/ . 

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. The Agency will consider benefits information and data as required by FIFRA. The 

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

docket is the Agency’s opportunity to state what it knows about the pesticide and what additional 

risk analyses and data or information it believes are needed to make a registration review 

decision. After reviewing and responding to comments and data received in the docket during 

this initial comment period, the Agency will develop and commit to a final work plan and 

schedule for the registration review of carfentrazone-ethyl.

Carfentrazone-ethyl is a post-emergent herbicide registered for use to control broadleaf weeds. It 

is registered for use on a variety of agricultural crops, turf (including golf courses and residential 

lawns), aquatic areas (including water bodies and wetlands), and industrial and utility sites. 

Carfentrazone-ethyl is part of the class of herbicides referred to as Light Dependent Peroxidizing 

Herbicides (LDPH), which have enhanced toxicity in the presence of solar ultraviolet light. 

Carfentrazone-ethyl was first registered in the United States in 1998, and therefore it was not 

subject to the FIFRA reregistration program.

Anticipated Risk Assessment and Data Needs

The Agency anticipates requiring data considered necessary to conduct a comprehensive 

ecological risk assessment, including an endangered species risk assessment, and to update the 

human health risk assessment for all uses of carfentrazone-ethyl. Below is a summary of the 

issues relevant to the registration review of carfentrazone-ethyl and the data the Agency 

anticipates requiring. 
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Ecological Risk:

The most recent ecological risk assessment for carfentrazone-ethyl was conducted in

2004 in support of new uses on grapes, tobacco, citrus, pome and stone fruits, and tree 

nuts.

Since carfentrazone-ethyl products are registered for direct applications to water, the 

Agency anticipates requiring additional data to assess potential risk to aquatic organisms. 

The Agency anticipates requiring data on the degradate carfentrazone acid, which is 

expected to be dominant in water after application of carfentrazone-ethyl.

Given that carfentrazone-ethyl is an herbicide, and incident reports confirm adverse 

effects to non-target plants, the Agency anticipates requiring additional data to assess 

potential risk to terrestrial plants. Toxicity data using a typical end-use product is 

anticipated to be required to evaluate risk to plants.

Toxicity data are not available for passerine bird species that may, in some cases, be 

more sensitive than the waterfowl and upland game birds that were tested in previous 

carfentrazone-ethyl studies. The Agency anticipates requiring passerine data.

LDPH registrants are in the process of conducting a modified freshwater fish early life 

stage study to quantitatively determine the increase in toxicity of this class of herbicides 

in the presence of direct sunlight. The Agency expects to receive these data in the 

summer of 2011 in response to the Data Call-in (DCI) for this study. These data will be 

used in the registration review ecological risk assessment for carfentrazone-ethyl.

The Agency has not conducted an ecological risk assessment that supports a complete 

endangered species determination for carfentrazone-ethyl. The ecological risk 

assessment planned during registration review will allow the Agency to determine

whether carfentrazone-ethyl’s use has “no effect” or “may affect” federally listed 

threatened or endangered species (listed species) or their designated critical habitats. 

When an assessment concludes that a pesticide’s use “may affect” a listed species or its 

designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife 

Service (FWS) and/or National Marine Fisheries Service (NMFS) (the Services), as 

appropriate.

The Agency anticipates requiring the following data in order to conduct a complete 

ecological risk assessment, including an endangered species assessment, for 

carfentrazone-ethyl:

Environmental fate

o Guideline No. 835.2240 – Photodegradation in water (carfentrazone acid)

o Guideline No. 835.4400 – Anaerobic aquatic metabolism
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o Guideline No. 835.6100 – Terrestrial field dissipation (only an independent 

laboratory validation (ILV) of the submitted analytical method would likely be 

required to satisfy this guideline)

o Guideline No. 835.6200 – Aquatic) field dissipation (only frozen storage stability 

data would likely be required to satisfy this guideline)

Ecological toxicity

o Guideline No. 850.1025 – Invertebrates acute toxicity – mollusk (saltwater) 

(carfentrazone acid)

o Guideline No. 850.1075 – Fish acute toxicity (saltwater) (carfentrazone acid)

o Guideline No. 850.1300 – Aquatic invertebrate life-cycle (freshwater) (carfentrazone 

acid)

o Guideline No. 850.1350 – Aquatic invertebrate life-cycle (saltwater) (carfentrazone 

acid)

o Guideline No. 850.1400 – Fish early life stage (saltwater) (carfentrazone acid)

o Guideline No. 850.1500 – Fish life-cycle (freshwater) (carfentrazone acid)

o Guideline No. 850.1735 – Whole sediment: acute freshwater invertebrates

o Guideline No. 850.1740 – Whole sediment: acute marine invertebrates

o Guideline No. 850.2100 – Avian acute oral toxicity (passerine species) 

o Guideline No. 850.4100 - Seeding Emergence (Tier II)

o Guideline No. 850.4150 - Vegetative Vigor (Tier II)

Please refer to the March 8, 2011 “Registration Review: Preliminary Problem 

Formulation for Environmental Fate, Ecological Risk, Endangered Species, and 

Drinking Water Exposure Assessments for Carfentrazone-ethyl,” for a more detailed 

discussion of the anticipated ecological risk assessment and data needs.

Human Health Risk:

The most recent human health risk assessment was conducted in 2006 in support of use 

on cereal grain, peanut, soybean, and sugarcane as a harvest-aid.

The Agency anticipates conducting a drinking water assessment in registration review. 

Results of the updated drinking water assessment may necessitate a revised dietary 

exposure assessment.

The Agency anticipates conducting new occupational exposure assessments in 

registration review. Several occupational handler scenarios need to be assessed, which 

have not been assessed previously, or need to be reassessed based on higher application 

rates or area treated.

A revised residential exposure assessment may need to be performed to include 

residential handler scenarios and updated residential post-application scenarios (higher 
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turf/home lawn application rate). This may necessitate a new aggregate exposure 

assessment.

If new policies or procedures are put into place, the Agency may revisit the need for a 

quantitative post-application inhalation exposure assessment for carfentrazone-ethyl.

The analytical tolerance enforcement method for livestock, fish, and shellfish was 

considered acceptable pending validation from EPA’s Analytical Chemistry Laboratory. 

However, the validation procedure has changed, and now laboratory validation is not 

required. As part of registration review, the Agency may evaluate the suitability of the 

existing analytical tolerance enforcement method for livestock, fish, and shellfish

according to new procedures. If the method is found to be unsuitable for tolerance 

enforcement, then the technical registrant would need to propose and validate a new 

method.

As part of registration review, the Agency anticipates making the following tolerance 

changes:

o The banana tolerance may be lowered to 0.10 ppm.

o The following currently-established tolerances may be deleted: cotton hulls, cotton 

meal, cotton oil, barley flour, barley bran, millet flour, oat flour, rye flour, rye bran, 

wheat bran, wheat flour, wheat middlings, wheat shorts, wheat germ, and caneberry 

subgroup 13A. 

o The cereal grain forage, hay, stover, and straw tolerances may be altered as there are 

conflicting commodity definitions and/or tolerance levels. 

o The tolerance expression may be updated as follows to conform to current standards: 

Tolerances are established for residues of carfentrazone-ethyl, including its 

metabolites and degradates, in or on the commodities listed below. Compliance with 

the following tolerance levels is to be determined by measuring carfentrazone-ethyl 

(ethyl alpha-2-dichloro-5-[4-(difluoromethyl)-4,5-dihydro-3-methyl-5-oxo-1H-1,2,4-

triazol-1-yl]-4-fluorobenzenepropanoate) and its metabolite carfentrazonechloropropionic acid (alpha, 2-dichloro-5-[4-difluoromethyl)-4,5-dihydro-3-methyl5-oxo-1H-1,2,4-triazol-1-yl]-4-fluorobenzenepropanoic acid). 

The Agency anticipates requiring the following data in order to conduct a complete 

human health risk assessment for carfentrazone-ethyl:

A 28-day inhalation toxicity study was previously waived for carfentrazone-ethyl. 

However, the Agency is re-evaluating its inhalation waiver criteria, so this study may be 

required for registration review.
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o Guideline No. 870.3465 – 901-day inhalation - rat

o Guideline No. 870.7800 – Immunotoxicity

In addition, the Agency anticipates requiring the following residue chemistry data to 

complete the residue chemistry database for carfentrazone-ethyl.

o Guideline No. 860.1500 Crop Field Trials – soybeans

In lieu of conducting this study the registrant may revise label language to include a 

restriction prohibiting the feeding of soybean forage and hay to livestock.

o Guideline No. 860.1500 Crop Field Trials - cranberry

In lieu of conducting this study the registrant may remove instructions for application to 

cranberry from all labels. 

o Guideline No. 860.1500 Crop Field Trials – dry peas, vegetable legume (Group 6), 

and vegetable foliage of legume (group 7)

In lieu of conducting these studies the registrant may revise label language to restrict 

harvest-aid application to only the following crops: cereal grains, soybean, cotton, 

peanut, sugarcane, and potato.

o Guideline No. 860.1900 Field Rotational Crops

In lieu of conducting this study the registrant may revise label language that indicate the 

following rotational crop restrictions: seasonal application rate of <0.031 lb ai/acre -

rotate to a registered crop at anytime and to all other crops 12 months after application; 

seasonal application rate of >0.031 lb ai/acre - rotate to only a registered crop.

Provided these changes are made, the residue chemistry database will be adequate to 

support carfentrazone-ethyl registrations.

Please refer to the January 19, 2011 “Carfentrazone-ethyl. Human Health Assessment 

Scoping Document in Support of Registration Review,” available in the docket, for a 

detailed discussion of the anticipated human health risk assessment and data needs.

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 

 

1 A 28-day study may be sufficient to satisfy guideline requirement.
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chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. As part of its most recent registration decision, 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), carfentrazone-ethyl 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. Carfentrazoneethyl is not among the group of 58 pesticide active ingredients on the initial list to be screened 

under the EDSP. Accordingly, as part of registration review, EPA will issue future EDSP 

orders/data call-ins, requiring the submission of EDSP screening assays for carfentrazone-ethyl. 

For further information on the status of the EDSP, the policies and procedures, the list of 67 

chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website: http://www.epa.gov/endo/.

Timeline

 

The Agency has created the following estimated timeline for the completion of the registration 

review for carfentrazone-ethyl.

Registration Review for Carfentrazone-ethyl – Projected Registration Review Timeline

Activities Estimated Date

Opening the docket

Open Docket and Public Comment Period 2011 – March

Close Public Comment 2011 – May

Case Development

Final Work Plan 2011 – August

Issue DCI 2012 – Apr. - June

Data Submission 2014 – Apr. - June

Open Public Comment Period for Preliminary Risk Assessments 2015 – Oct. - Dec.
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Close Public Comment Period 2016 – Jan. - March

Registration Review Decision

Open Public Comment Period for Proposed Registration Review 

Decision 

2016 – Apr. - June

Close Public Comment Period 2016 – July – Sept.

Registration Review Decision and Begin Post-Decision Follow-up 2017

Total (years) 6

Guidance for Commenters

The public is invited to comment on EPA’s preliminary work plan and rationales. The Agency 

will carefully consider all comments, as well as any additional information or data provided in a 

timely manner, prior to issuing a final work plan for the carfentrazone-ethyl case.

Trade Irritants

Through the registration review process, the Agency intends to solicit information on trade 

irritants and, to the extent feasible, take steps toward facilitating irritant resolution. Growers and 

other stakeholders are asked to comment on any trade irritant issues resulting from lack of 

Maximum Residue Limits (MRLs) or disparities between U.S. tolerances and MRLs in key 

export markets, providing as much specificity as possible regarding the nature of the concern.

Environmental Justice

EPA seeks to achieve environmental justice, the fair treatment and meaningful involvement of all 

people, regardless of race, color, national origin, or income, in the development, implementation, 

and enforcement of environmental laws, regulations, and policies. To help address potential 

environmental justice issues, the Agency seeks information on any groups or segments of the 

population who, as a result of their location, cultural practices, or other factors, may have 

atypical, unusually high exposure to carfentrazone-ethyl compared to the general population. 

Please comment if you are aware of any sub-populations that may have atypical, unusually high 

exposure, compared to the general population.

Water Quality

Carfentrazone-ethyl is not identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act2. In addition, no Total Maximum Daily 

Loads (TMDL) have been developed for carfentrazone-ethyl3. More information on impaired 

water bodies and TMDLs can be found at the Agency’s website4. The Agency invites submission 

of water quality data for this pesticide. To the extent possible, data should conform to the quality 

 

2

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

3

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_group_name=PESTICIDES

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http://www.epa.gov/owow/tmdl/
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standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired 

Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and 

Management Process5in order to ensure they can be used quantitatively or qualitatively in 

pesticide risk assessments.

Other Information

Stakeholders are also specifically asked to provide information and data that will assist the 

Agency in refining risk assessments, including any species-specific ecological effects 

determinations for carfentrazone-ethyl. The Agency is interested in receiving the following 

information:

1. Confirmation on the following label information.

a. sites of application

b. formulations

c. application methods and equipment

d. maximum application rates

e. frequency of application, application intervals, and maximum number of 

applications per season and per year

f. geographic limitations on use

2. Use or potential use distribution (e.g. geographical distribution of relevant uses).

3. Use history.

4. Median and 90th percentile reported use rates (lb/A, lb 1K sq.ft) from usage data –

national, state and county.

5. Application timing (date of first application and application intervals) by use – national, 

state, and county.

6. Usage/use information for non-agricultural uses. 

7. Directly acquired county-level usage data (not derived from state level data).

a. maximum reported use rate (lb/cc) from usage data – county

b. median and 90th percentile number of applications – county

c. total pounds per year – county

d. the year the pesticide was last used in the county/sub-county area

e. the years in which the pesticide was applied in the county/sub-county area

8. Typical application interval (days).

9. State or local use restrictions.

10. Ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian, 

mammalian mortalities, and bee or beneficial insect mortalities) not already reported to 

the Agency.

11. Information on decline in usage, such as on cotton and rice.

 

5

http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm
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Next Steps

After the 60-day comment period closes, the Agency will consider and respond to any comments 

received in a timely manner. The Agency expects to issue a Final Work Plan in August of 2011

for carfentrazone-ethyl.

II. FACT SHEET

Background Information

Carfentrazone-ethyl case number: 7422

Carfentrazone-ethyl PC Code: 128712; CAS # 128639-02-1

Carfentrazone-ethyl was first registered in 1998 and therefore it was not subject to the 

FIFRA reregistration program.

Technical registrant: FMC Corp. Agricultural Products Group 

Active registrations as of January 2011:

o 46 Section 3 registrations

o 10 Section 24(c) registrations (Special Local Need)

Pesticide Re-evaluation Division Contact: Jose Gayoso (gayoso.jose@epa.gov)

Registration Division Contact: Kathryn Montague (montague.kathryn@epa.gov)

Use and Usage Information

For additional details, please refer to “Carfentrazone-ethyl Screening Level Usage Analysis 

(SLUA), “ July 21, 2010, “Appendix A: Uses of Carfentrazone-ethyl Considered in Registration 

Review Work Planning,” August 17, 2010, “Carfentrazone-ethyl California Department of 

Pesticide Regulation Usage Data,” May 26, 2010, and “BEAD Chemical Profile for Registration 

Review: Carfentrazone-ethyl,” February 23, 2011,” which are available in the carfentrazoneethyl docket.

In agriculture, carfentrazone-ethyl is an herbicide used mainly in cotton as a harvest 

aid/defoliant and as an at-planting or pre-plant burndown to control many broadleaf 

weeds in corn, soybean, rice, and small grain crops.

The primary use of carfentrazone-ethyl is in commercial turf grass maintenance and 

production. 

Carfentrazone-ethyl is also registered for use in aquatic and non-agricultural/industrial 

sites. 

Weeds controlled by carfentrazone-ethyl include many species and biotypes that are 

resistant to several classes of herbicides.

Carfentrazone-ethyl is formulated as water dispersible granules, emulsifiable concentrate, 

and soluble concentrate, ready-to-use solution and also as water-soluble packaging.

Types of application include broadcast, spot treatment, water treatment (surface), water 

treatment (subsurface), and directed spray. Equipment used includes various types of 

sprayers (backpack, boom, compression, tank-type etc.), aircrafts, and boats. 
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According to the Agency’s Screening Level Usage Analysis (SLUA), based on data from 

2001-2008, carfentrazone-ethyl agricultural usage is highest on cotton and rice, with

annual averages of 20,000 lbs and 10,000 lbs of active ingredient (lbs a.i.) applied, 

respectively. The crop with the highest max percent crop treated with carfentrazoneethyl is caneberries (65%), followed by hops (60%).

Based on private market pesticide usage data from 1998-2008, the annual total 

agricultural usage averaged approximately 32,000 lbs a.i. for almost 2 million acres. The

largest markets in terms of total pounds of active ingredient applied are cotton (36%), 

rice (24%), and corn (13%). The highest acreage crops treated are cotton (37%), corn 

(24%), and rice (10%). The states with the most agricultural usage in terms of pounds 

carfentrazone-ethyl applied are California (20%), Arkansas (13%), and Texas (11%).

Non-agricultural usage data are limited. Based on private market pesticide usage data

from 2002-2006, golf course and lawn care usage has increased.

Recent and Pending Actions

There are no recent or pending actions for carfentrazone-ethyl.

Ecological Risk Assessment Status

The following are key findings from the most recent ecological risk assessments regarding the 

environmental fate, ecological effects and risks of carfentrazone-ethyl. For a detailed discussion,

please refer to the March 8, 2011 “Registration Review: Preliminary Problem Formulation for 

Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure 

Assessments for Carfentrazone-ethyl,” located in the docket.

Previous ecological risk assessments identified risks of concern for aquatic and terrestrial 

plants from many uses, especially aerial application to corn and sorghum and use in rice 

paddies; acute and chronic risks to fish, aquatic plants and shoreline terrestrial plants 

from use as an aquatic herbicide; and chronic risk to fish from use on caneberries.

Available carfentrazone-ethyl degradate toxicity data suggest that degradates are less 

toxic to aquatic organisms than the parent.

Human Health Risk Assessment Status

The following are key findings from the human health risk assessments conducted for

carfentrazone-ethyl registered uses. Please refer to the February 9, 2011 “Carfentrazone-ethyl. 

Human Health Assessment Scoping Document in Support of Registration Review,” located in the 

docket, for a detailed discussion of the human health risk assessment status.

Human Studies:

Past carfentrazone-ethyl risk assessments rely in part on data from studies in which adult 

human subjects were intentionally exposed to a pesticide to determine their dermal and 

inhalation exposure. Many such studies, involving exposure to many different pesticides, 

comprise generic pesticide exposure databases such as the Outdoor Residential Exposure 
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Task Force (ORETF) Database. EPA has reviewed all the studies supporting these multipesticide generic exposure databases, and has found no clear and convincing evidence 

that the conduct of any of them was either fundamentally unethical or significantly 

deficient relative to the ethical standards prevailing at the time the research was 

conducted. All applicable requirements of EPA’s Rule for the Protection of Human 

Subjects of Research (40 CFR Part 26) have been satisfied, and there is no regulatory 

barrier to continued reliance on these studies.

Hazard Characterization:

Carfentrazone-ethyl acts as an inhibitor of protoporphyrinogen oxidase, which in 

mammals interferes with the heme biosynthetic pathway and results in increased 

porphyrin levels.

Carfentrazone-ethyl has low acute oral, dermal, and inhalation toxicity (Toxicity 

Categories III and IV). It is minimally irritating to the eyes, non-irritating to the skin, and 

is not a skin sensitizer.

The mutagenic test battery demonstrated that carfentrazone-ethyl is not mutagenic. In 

carcinogenicity studies in mice and rats, there was no indication of increased incidence of 

neoplasms and spontaneous tumor formation at the doses tested.

Dietary Risk:

In the most recent dietary risk assessment for carfentrazone-ethyl, children 1-2 years old 

were identified as the most highly exposed subgroup with an aPAD of ≤1%;) and a 

cPAD of 89%. Therefore, acute and chronic exposure estimates did not exceed the 

Agency’s level of concern. 

Residential Risk:

In the most recent carfentrazone-ethyl human health risk assessment, the product label 

used for review only allowed for application by professional lawn care operators to 

residential lawns and to golf courses; therefore, exposure to homeowners was not 

expected. 

In the most recent carfentrazone-ethyl human health risk assessment, a residential postapplication exposure assessment was conducted that assessed incidental oral exposure to 

children from the home lawn use, as well as inhalation and ingestion exposure to adult 

and child swimmers from the aquatic use. All residential incidental oral exposure and 

risk estimates for the home lawn use were below the Agency’s level of concern at an 

application rate of 0.031 lb ai/A. All incidental oral and inhalation exposure and risk 

estimates for the aquatic uses were below the Agency’s level of concern at an application 

rate of 0.2 lb ai/A.
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Aggregate Risk:

In the most recent carfentrazone-ethyl human health risk assessment, acute and chronic 

aggregate risks are made up only of dietary sources; therefore, the exposure estimates 

provided in the dietary exposure analysis represent acute and chronic aggregate 

exposures, respectively, and are not of concern to the Agency. Short-term aggregate 

exposures to carfentrazone-ethyl were not of concern to Agency.

Occupational Risk:

In the most recent occupational handler exposure assessment, the Agency concluded that, 

provided commercial pesticide handlers used label-prescribed personal protective 

equipment (i.e., long pants, long-sleeved shirt, shoes + socks and protective gloves), 

exposures to carfentrazone-ethyl were not of concern to Agency

An appropriate endpoint attributable to exposure through the dermal route for 

carfentrazone-ethyl was not identified. Therefore, dermal post-application exposure 

assessments have not been performed for carfentrazone-ethyl. 

Incidents

Ecological:

An incident review was made on October 27, 2010 by querying the Ecological Incident 

Information System (EIIS, version 2.1) and the Avian Monitoring Information System 

(AIMS). Ten incidents involving carfentrazone-ethyl have been reported. All reported 

incidents involved plant damage; no animal incidents have been reported. The two 

incidents (I014796-001 and I014796-002) from registered use of carfentrazone-ethyl 

were both from use on sweet corn in 2003, and involved extensive damage (145 and 515 

acres, respectively); however, both were determined “not likely” to have been caused by 

carfentrazone- ethyl. Two incidents classified as “highly probable” for attribution to 

carfentrazone-ethyl were both due to misuses, one intentional. Of the two incidents 

classified “probable,” one was deemed accidental (I020725-055), but one was 

undetermined (I019519-043), and therefore, may have been due to a registered use. Of 

the three incidents classified as “possible,” two were determined to be from misuse (one 

accidental) of carfentrazone-ethyl, while the legality of use for the other was 

undetermined, and therefore, may have been due to a registered use. 

Human Health:

The OPP Incident Data System (IDS) was utilized for poisoning incident data on the 

active ingredient carfentrazone-ethyl. IDS records incidents of generally high severity in 

more detail, in software called the main IDS. This system stores incident data for death, 

major and moderate incidents, and it includes more details about the location, date and 

nature of the incident. The less-severe human incidents are reported by registrants as 

counts, which are called aggregate summaries and are recorded in separate software. For 

IDS aggregate summaries, from January 1, 2002 to May 27, 2010, there are 37 cases
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reported for carfentrazone-ethyl. Because it falls within the categories reported as counts

(which includes minor, unknown, or no effects), there is no unique report that provides 

details about the incident, and single-chemical incidents are not distinguished from 

multiple-chemical incidents. For the main IDS, from January 1, 2002 to October 7, 2010,

there is one case reported for single-chemical carfentrazone-ethyl only in the database. 

For this incident, the symptoms were unknown or not specified.

Based on the low frequency and severity of incident cases, there does not appear to be a 

concern at this time that would warrant further investigation. The Agency will continue 

to monitor the incident information and if a concern is triggered, additional analysis will 

be included in the risk assessment.

Tolerances and International Harmonization

U.S. permanent tolerances and Canadian, Mexican, and Codex maximum residue limits (MRLs) 

are summarized in the February 9, 2011 “Carfentrazone-ethyl. Human Health Assessment 

Scoping Document in Support of Registration Review.” The U.S. and Canadian carfentrazoneethyl residue definitions are harmonized and the numerical values are also harmonized for milk 

(0.05 ppm) and sorghum grain (0.25 ppm). For the remaining commodities for which both the 

U.S. and Canada have tolerances/ MRLs, the U.S. tolerance is expressed with two significant 

figures (0.10 ppm or 0.80 ppm), while the Canadian MRL is expressed with one significant 

figure (0.1 or 0.8 ppm). It is noted that Mexico adopts U.S. tolerances and/or Codex MRLs for 

its export purposes. Since there are no carfentrazone-ethyl Codex MRLs, EPA is working to 

harmonize the U.S. tolerances and Mexican MRLs.

Data Call-Ins

In response to DCIs issued to them, LDPH technical registrants are in the process of conducting 

a modified freshwater fish early life stage study to quantitatively determine the increase in 

toxicity of this class of herbicides in the presence of direct sunlight. While carfentrazone-ethyl is 

not one of the test substances in the study, the Agency has agreed that three LDPHs selected for 

the study may serve as surrogates for the remaining currently registered LDPHs, including 

carfentrazone-ethyl. The Agency expects to receive these data in the summer of 2011. These 

data will be used in the registration review ecological risk assessment for carfentrazone-ethyl.

Labels

Active Section 3 labels for carfentrazone-ethyl can be obtained from the Pesticide Product Label 

System (PPLS) website: http://oaspub.epa.gov/pestlabl/ppls.home.