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## Executive Summary

Clomazone is a broad spectrum flowable (emuls ifiable concentrate, wettable powder, or micro-encapsulated) herbicide used to control annual grasses and broadleaf weeds in a wide variety of crops and locations. Clomazone, as an emulsifiable concentrate, was first registered for use in 1986; the micro-encapsulate d formulation was first registered for use in
1995. Clomazone is an isoxazolidinone herb icide and there are no other registered compounds currently in this class. Clomaz one is absorbed by the roots and shoots and translocated upwards in the xylem throughout the plant. It inhibits carotenoid biosynthesis; the specific target enzyme is not known. Clomazone toxicity is believed to be in part caused by a plant metabolite, 5-ketoclomazone, and is de pendent upon a plant’s ability to oxidize the parent compound to this active metabolite. Case s have been identified where this is not the sole mechanism of toxicity, not all mechanis ms are known. With foliar contact clomazone is not translocated throughout the plant and effect s are more localized at the point of contact. Clomazone is registered for use on several cr ops, including soybeans, cotton, sweet potato, sugarcane, peppers (bell, hot, pimento, a nd sweet), pumpkin, tobacco, winter and summer squash, cabbage, mint, peas (succulent), bean s (succulent), melons, watermelons, rice, and the root crops arracacia, cassava, yam, and yautia. It is genera lly applied as a pre-plant, preemergent, although there are a few uses where it is applied as a post-pl ant, pre-emergent or early emergence (1- to 2 leaf stage).

Environmental Fate

Clomazone is a semi-volatile compound of low to high persistence in various environmental compartments, and of moderate mobility in soil (see Chapter 2for details). The major exposure route of concern is displacement of sorbed clomazone from soil by water vapor after rain or during episodes of high humidity, volatilizati on from the soil, and downwind transport of clomazone vapors. Once displaced from soil clomazone is not expected to be persistent in air for more than a couple of days.

Risks to Nonlisted Species from Uses Other Than Rice

Considering all lines of evidence risks to nonl isted mammals, birds, reptiles, amphibians, beneficial insects, freshwater and estuarine-ma rine fish and invertebrates were concluded to be within acceptable acute and chronic levels for all clomazone uses with the exception of
wet seeded rice. Direct effect s on non-target vegetation off the fi eld are expected for all uses. Incident and field data were used along with existing spray drift e xposure models to help
define to what extent clomazone is expected to move off-site , and when it does move off-site to provide some insight on the t ypes and severity of effects to exposed nontarget plants. ThisExecutive Summary

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### approach was taken due to the lack of a vi able air dispersion mode l, and relationships quantifying environmental and/or application fa ctors that control clomazone displacement from the soil, especially in re gards to differences between th e EC, WP and ME formulations.

Effects to off-site diverse plant communities with emergent vegetation are expected to be reduction of growth and whitened foliage, with mortality potentially amongst highly sensitive species based on laboratory results . Growth effects, when seve re enough, have the potential to cause population dynamic changes in wh ich competition among plant communities can change. Effects to nontarget plants are expected to be restricted to relatively localized areas from a treated site, with the greatest o ccurrence likely being associated with areas immediately adjacent to the field margin out about 1,500 feet due to transport of clomazone in runoff, spray drift and/or vapor. Effect s on non-target plants from use of clomazone, associated with displacement from the soil have been observed out a couple of miles from a use site. Most of these events occurred when clomazone was first registered for use on soybeans with the EC formulation before spray drift and soil displacement reduction measures were incorporated on the label, esp ecially for areas with temperature and weather
conditions vulnerable to soil di splacement. The furthest di stance non-target plant effects
have been observed for the lower volatiliza tion prone ME formulation is about a mile. Events outside 1,500 feet for the EC, WP, and ME formulations are expected to be infrequent as indicated by the incident information.

There is buffer language on current Section 3 labels which either explicitly prohibits application to non-field areas in cluding fence rows, waterways, ditches, and road sites or implicitly prohibits application to non-fiel d areas by limiting application to only those surfaces that will be soil incorpor ated. Section 3 labels for EC and WP registrations prohibit preemergent soil incorporated applications within 1,000 ft of towns and subdivisions, commercial vegetable production 1 

### , commercial fruit production, commercial nurseries, and commercial greenhouses and 100 ft of desirable plants 2 

### whereas soil unincorporated applications are prohibited within 1,500 ft of towns and subdivisions, commercial vegetable production, commercial fruit production, commercial nurseries, commercial greenhouses and desirable plants. Section 3 labels for ME regi strations prohibit applica tions within1,200 ft of towns and subdivisions, commercial vege table production, commercial fruit production,

1 Most labels have at least an exception for sweet corn so me labels also include exceptions which include one or more of the following: peppers, pumpkins, succulent peas, sweet potato, and winter squash. 2 Spruce trees and deciduous trees (apple (fruit and ornamental), ash (green, white, mountain), basswood, boxelder, catalpa, cherry (fruit and ornamental), cottonwood, elm, ginkgo, hackberry, mulberry, peach, pear (fruit and ornamental), pecan, poplar, Russian olive, tr ee of heaven, tulip tree, walnut trees, willow species); shrubs and vines (azalea, burn ingbush, grape, honeysuckle, roses, yew); agronomic crops (alfalfa, oats); ferns; herbs; strawberry; raspberry; and blackberryExecutive Summary

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### commercial nurseries, commercial greenhouses and so me labels have 200 ft and others 300 ft of desirable plants. Effects to off-site dive rse plant communities with emergent vegetation are expected to be reduction of growth and whitening of folia ge, with mortality potentially amongst highly sensitive species. Growth effect s, when severe enough, have the potential to cause population dynamic changes in whic h competition among plant communities can change.

Risks to Nonlisted Species from Use on Rice

Dry Seeded Rice . Based on measured field residue leve ls in flood water, effects to aquatic plants, freshwater fish, amphibians, and i nvertebrates and marine-estuarine fish and
invertebrates are considered w ithin acceptable risk levels for the dry seeded rice use. Residue levels on dietary items from spray drif t are also within acceptable risk levels for birds, reptiles, amphibians (land phase), and mamm als. There are direct effects expected to non-target vegetation off the field. At the rice use label rate of 0.6 lbs ai/A direct effects above the level of concern (LOC) potentially exist for dicots and nonflowering plants ( e.g ., lichens, ferns and allies), but monocot exposure le vels are below the LOC. For those labels which do not state use of a coarse droplet size, es pecially for aerial applications to rice this effect may potentially reach seve ral thousand feet. For other labe ls with such restrictions in place, this effect is expected to be restricted to relatively localized areas off a treated site, the highest occurrence and likelihood being adjacent to the site from spray drift and/or vapor drift. Effects to off-site diverse plant comm unities with emergent vegetation are expected to be reduction of growth and whitened foliage, with mortality potentially amongst highly sensitive species. Growth effects, whensevere enough, have the potential to cause population dynamic changes in which competition among plant communities can change.

Wet Seeded Rice . Effects to nonlisted vascular a quatic plants, and freshwater fish, amphibians, and invertebrates and estuarine-mari ne fish are within ac ceptable risk levels. Acute RQ values for freshwater fish and amphi bians, and invertebrates exceeded endangered species LOC values but the individual risk of mortality based on mean slope responses are 1 in 89 for fish and amphibians and <1 in 10 11 

### for invertebrates on the day of application which
reduces to 1 in 586 for fish and amphibians and 1 in <1 in 10 27 

### for invertebrates 14 days postapplication, the holding time required on one Secti on 3 label. Acute risks to estuarine-marine
invertebrates exceed acute LOC for unto 97 da ys post-application, however, the odds of mortality reduce to <1 in 6,000 by 28 days post- application. Nonvascular plant RQ values exceed the nonlisted species LOC at up to 42 days post-application. However, an evaluation of the range of nonvascular plants likely to be affected indica ted only one of the four test species, a freshwater diatom, exceeded the nonlisted species LOC. The other threeExecutive Summary

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### nonvascular plants (a cyanobact erium, a green alga, and a sa ltwater diatom) would not. Therefore risks to the nonvascular, algal bioma ss and primary productivity are likely within acceptable levels but the diversity of species is likely affected. Residue levels on dietary items from spray drift are also within acceptabl e risk levels for birds, reptiles, amphibians (land phase), and mammals. There are direct effects to non-target vegetation off the field.
For those labels which do not state use of a coarse droplet size, especially for aerial applications to rice this effect may potentiall y reach several thousand fe et. For other labels with such restrictions in place, this effect is expected to be restricted to relatively localized areas off a treated site, the hi ghest occurrence and lik elihood being adjacent to the site from spray drift and/or vapor drift. Effects to off-site diverse plant communities with emergent vegetation are expected to be mainly reduc tion of growth and whitened foliage, with mortality potentially amongst highly sensitive species.

Effects Determination for Listed Species by Formulation and Use

Clomazone was formulated as an ME to redu ce volatilization of clom azone from soil during events ( e.g ., rain, high humidity) that would otherwis e displace clomazone applied as the EC
or WP. These formulation differences have re sulted in notable differe nces observed in at
least the off-field distal extent of clomazone effects reported in incident reports. Because the action area for the endangered species effects de termination is based on the furthest distal extent for any effect, the difference in distal extent between these formulations result in
different conclusions about the size of the affected area. Be cause formulation type in the case of clomazone plays a role in the size of the area affected, and may play a role for consideration for potential options for mitigation, if any are needed, a separate analysis for
the extent of effects for the ME from EC a nd WP formulations was performed. Additionally because in the case of clomazone, rice versus no nrice uses have a significant impact on the downstream distal extent of aquatic animal and plant effects, a separate analysis was performed for the downstream extent of e ffects for rice versus nonrice uses.

The furthest distal extent for expected direct or indirect e ffects to terrestrial plants and animals from spray drift and volatilization was determined based on an assessment of reported distances from treated fields in the inci dent report data base. The furthest distance for which effects to plants have been observe d is 2 miles for the EC formulation (the WP formulation is assumed to have the same potentia l), and 1 mile for the ME formulation. Rice uses are only registered with the ME formula tion. For nonrice uses and dry seeded rice use aquatic organisms are not affect ed or effects do not extend beyond the field or edge-of-field.
For wet seeded rice the extent of downstream effe cts is assumed to extend to the ocean. This extent is highly conservative given that for wet seeded rice the estimated concentration willExecutive Summary

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### only occur on the day of release but the tools to evaluate downstream dilution from releases off an agricultural field has not been devel oped for the contiguous United States, Hawaii, Alaska, or its te rritories.

For convenience these areas of effect are referred to as action areas with in the assessment but it is recognized that for the ove rall review the action area is the furthest extent considering all uses simultaneously. Specifically the effect ar eas evaluated for the co-occurrence analysis included (1) for EC and WP formulation nonrice uses, a 2 mile radius out from clomazone use sites; (2) for ME formulati on nonrice uses and dry seeded rice use, a 1 mile radius out from clomazone use sites; and (3) for ME formul ation wet seeded rice uses, a 1 mile radius
out from use sites for effects to the terre strial environment and all downstream miles extending from rice sites to the ocean. The actio n area for the clomazone registration review
action consists of a 2 mile radius out from a ny clomazone use site which then further extends for adjacent flowing waters downstream to the o cean for rice uses. Operationally locations
where clomazone is used are defined as all cult ivated land that has had one or more of the crops for which clomazone is registered cultivated on it, except California where the only registered clomazone use is wet seeded rice.

The geographical extent of a 2 mile radius out from a use s ite is based on the farthest physical extent direct or indirect effects from exposure to clomazone are predicted to occur
based on best available information. This action area should not be misconstrued as automatically meaning that unreasonable adve rse effects to nonlisted species or the environment is occurring. The extent of the action area is based on any effect adverse or not, the effect may be to a single individual, and ma y not result in decrease d survival, growth, or reproduction. The effects determination consid ers all available lines of evidence including estimates of risk, probability of mortality, type , degree, and magnitude of indirect and direct effects to listed and nonlisted sp ecies within the acti on area to make an effects determination for a specific listed species and potential for habitat modification to critical habitat.

Effects Determination Associated with All Uses Except Rice

The effect areas evaluated for the co-occurren ce analysis included (1) for the EC and WP
formulations a 2 mile radius out from clomazone use sites; and (2) for the ME formulations a
1 mile radius out from clomazone use sites. The effects determination summarized here for all uses except rice is based on the action area of a 2 mile radius out from clomazone use
sites.

May affect but NLAA determinations were made for listed vascular aqua tic plants (there are no nonvascular listed species), freshwater and mari ne listed fish and invertebrates, aquaticExecutive Summary

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### amphibians, and marine mammals. May affect but NLAA determinations were made for listed large land birds, mammals and reptiles not known to be reliant on one or a limited
number of nonlisted or listed terrestrial or semi-aquatic plant species. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included estimates of ris k, odds of mortality, timi ng of application, and refinement of exposure levels where appropriate . Additionally, some species were identified as being outside the action ar ea of clomazone, and a no effect determination was made for these. Species designated as NE or May aff ect but NLAA, are listed in Appendix I of this
document.

May affect and LAA determinations were made for 8 amphibians, 1 freshwater crustacean, 1 arachnid, 1 conifer, 26 ferns and allies, 2 lich ens, 2 aquatic plants, 507 flowering plants, 51 birds, 23 terrestrial insects, 20 mammals, 47 land and arboreal snails, and 8 land reptiles. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to cr itical habitat, and in cluded estimates of risk, odds of mortality, and refinement of exposure levels where appropr iate. This list likely includes species that upon further refinement fall outside the acti on area. For locations where there was no National Land Cover Data for cultivated land ( e.g. , U.S. territories and Hawaii) in the version of the IMS system used for the cooccurrence an alysis, it was assumed that any listed species at these locations would overlap with the cl omazone action area except those listed species known to occur only on islands that do not suppor t agribusiness and/or the whole island is a
nature reserve such as Nihoa Island in the No rthwestern Hawaiian Islands, Mona and Monito Island of Puerto Rico, the Calif ornia Channel Islands. Species designated as May affect and LAA, are listed in Appendix I of this document.

Effects Determination for Listed Species Associated with Wet Seeded Rice

The action area for reregistration of clomazone us e on wet seeded rice consists of a 1 mile
radius out from rice use sites a nd all flowing waters downstream of rice fields. Operationally
rice field sites are defined as all cultivated land that has had rice cultivated on it. No direct effect to listed vascular aquati c plants, estuarine and marine fish, marine mammals and birds are expected. Direct effects to freshwater invertebrates are considered discountable as the
risk of individual mortal ity is less than 1 in 10 11 

### . No direct effects to land mammals, birds, reptiles, or amphibians are expect ed. Direct effects to freshw ater fish and amphibians, and
estuarine and marine invertebra tes are expected. There are direct effects to non-target vegetation off the field. For those labels whic h do not state use of a coarse droplet size, especially for aerial applications to rice this effect may potentially reach several thousand feet. For other labels with such restrictions in pl ace, this effect is expected to be restricted toExecutive Summary

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### relatively localized areas off a treated site, the highest occurrence and likelihood being adjacent to the site from spray drift and/or va por drift. Effects to off-site diverse plant communities with emergent vegetation are expect ed to be mainly reduction of growth, with mortality potentially amongst hi ghly sensitive species. Ther efore, for large mammalian and avian listed species not reliant on a listed plan t species or not reliant on one or a limited number of nonlisted plant species either as prey or habitat indirect eff ects are expected to be insignificant.

May affect but NLAA determinations were made for listed vascular aqua tic plants (there are no nonvascular listed species), freshwater and mari ne listed fish and invertebrates, aquatic amphibians, and marine mammals. May affect but NLAA determinations were made for listed large land birds, mammals and reptiles not known to be reliant on one or a limited
number of nonlisted or listed terrestrial or semi-aquatic plant species. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included, estimates of ris k, odds of mortality, and refinement of exposure levels where appropriate. Additionally, some species were identified as being outside the action area of clomazone, and a no effect dete rmination was made for these. Species designated as no effect and may affect but NLAA, are listed in Appendix K of this document.

May affect and LAA determinations were made for flowering and nonflowering plants because of exceedance of endangered species LOC. May affect and LAA determinations were made for listed freshwater fish and amphibi ans, and estuarine and marine invertebrates. May affect and LAA determinations were made for listed freshwater invertebrates that are obligate on a specific freshwater fish species an d for estuarine and marine fish that are obligate on a specific estuarine-marine inverteb rate. May affect and LAA determinations were made for small mammals, reptiles, and amphi bians that because of their size and home range may rely on a limited number of plant spec ies for their food resource or habitat.

May affect and LAA determinations were ma de for 10 amphibians, 14 birds, 1 fern and allies, 2 lichen, 2 conifers and cycad, 185 flower ing plants, 16 land mammals, 9 land reptiles, 34 fish, 6 freshwater insects, 2 marine invert ebrates, and 22 terrestrial insects.. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and in cluded estimates of risk, odds of mortality, and refinement of exposure levels where appropriate. Based on th e co-occurrence analysis there are some locations for these species which fall ou tside the action area. Species designated as May affect and LAA, are listed in Appendix K of this document.Executive Summary

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### Effects Determination for Listed Species Associated with Dry Seeded Rice

The action area for use on dry seeded rice consis ts of a 1 mile radius out from rice fields, except California where its use is prohibited by the label. Operationally rice field sites are
defined as all cultivated land that has had ri ce cultivated on it. Ba sed on measured field residue levels in flood water, di rect effects to freshwater fis h, amphibians, and invertebrates
and marine-estuarine fish and invertebrates ar e below the acute endangered species LOC, and effects to aquatic plants are below the listed species LOC. No direct effects to birds, reptiles, amphibians (land phase), and mammals are expect ed. There are direct effects to non-target vegetation off the field. For those labels whic h do not state use of a coarse droplet size, especially for aerial applications to rice this effect may potentially reach several thousand feet. For other labels with such restrictions in pl ace, this effect is expected to be restricted to relatively localized areas off a treated site, the highest occurrence and likelihood being adjacent to the site from spray drift and/or vapor drift.

May affect but NLAA determinations were made for listed vascular aqua tic plants (there are no nonvascular listed species), freshwater and mari ne listed fish and invertebrates, aquatic amphibians, and marine mammals. May affect but NLAA determinations were made for listed large land birds, mammals and reptiles not known to be reliant on one or a limited
number of nonlisted or listed terrestrial or semi-aquatic plant species. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included, estimates of ris k, odds of mortality, and refinement of exposure levels where appropriate. Additionally, some species were identified as being outside the action area of clomazone, and a no effect dete rmination was made for these. Species designated as no effect and may affect but NLAA, are listed in Appendix J of this document.

May affect and LAA determinations were made for flowering and nonflowering plants because of exceedance of endangered species LOC. May affect and LAA determinations were made for small mammals, reptiles, and amphi bians that because of their size and home range may rely on a limited number of plant species for a food resource or habitat.

May affect and LAA determinations were made for x amphibians, 3 amphibians, 11 birds, 1 fern and allies, 1 lichen, 45 flowering plants , and 7 land mammals. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included estimates of ris k, odds of mortality, and refinement of exposure levels where appropriate. Based on the co-occu rrence analysis there are locations for some of these species which fall outside the action area. Species designate d as May affect and LAA, are listed in Appendix K of this document.Table of Contents

Registration Review Ecological Risk Assessment Clomazone xi 

## Table of Contents

Chapter 1 Introducti on....................................................................................... 1
1.1 Purpose of Assessment .......................................................................................................1 1.2 Clomazone Use.................................................................................................................. .2 1.2.1 Existing Registered Uses................................................................................................2 1.3 Problem Formulation..........................................................................................................8 1.3.1 Application Rates ...........................................................................................................8 1.3.2 Analysis Plan.................................................................................................................. 8 1.3.2.1 Exposure Assessment .................................................................................................8 1.3.2.2 Degradates ................................................................................................................10 1.3.2.3 Effects Assessment...................................................................................................11 1.3.2.4 Risk Characterization ...............................................................................................11 

### Chapter 2 Exposure Asses sment ................................................................... 13
2.1 Aquatic Exposure Assessment .........................................................................................13 2.1.1 Nonrice Uses--Modeled................................................................................................13 2.1.2 Screening Analysis – Rice Uses ...................................................................................17 2.1.2.1 Wet Seeded Rice.......................................................................................................17 2.1.2.2 Dry Seeded Rice .......................................................................................................17 2.1.3 Aquatic Rice Field Studies ...........................................................................................19 2.1.4 Volatilization: Trans port and Exposure........................................................................22 2.2 Terrestrial Exposure .........................................................................................................24 2.2.1 Dietary-Based and Dose-Based Clomazone Residue Levels .......................................24 2.2.1.1 On-Field....................................................................................................................24 2.2.1.2 Spray-Drift................................................................................................................27 2.2.1.3 Volatilization ............................................................................................................28 2.2.2 Off-Field Terrestrial and Wetland/Ripari an Plant Clomazone Exposure Levels .........29 2.2.2.1 Runoff and Spray Drift Loading...............................................................................29 2.2.2.2 Volatilization Loading..............................................................................................30 

### Chapter 3 Effects Charact erization................................................................. 32
3.1 Terrestrial Vertebrate Toxicology ....................................................................................32 3.1.1 Effects on Birds ............................................................................................................34 3.1.2 Effects on Mammals.....................................................................................................35 3.2 Terrestrial Inverteb rate Toxicology..................................................................................36 3.3 Fish Toxicology................................................................................................................ 37 3.3.1 Effects to Freshwater Fish ............................................................................................38 3.3.2 Effects to Estuarine-Marine Fish..................................................................................39 3.4 Aquatic Invertebrate Toxicology......................................................................................40 3.4.1 Effects to Freshwater Invertebrates ..............................................................................41 3.4.2 Effects to Estuarine-Marine Invertebrates....................................................................41 3.5 Plant Toxicology ..............................................................................................................4 2 3.5.1 Effects to Terrestrial Plants ..........................................................................................43 3.5.2 Effects to Aquatic Plants ..............................................................................................48 

### Chapter 4 Results: Risk Char acteriza tion ...................................................... 49
4.1 Risk Estimation ................................................................................................................ 49 4.1.1 Direct Effects to Non-Target Terrestrial Vertebrates ...................................................49 4.1.1.1 Direct Effects to Birds, Reptiles, and (Land-Phase) Amphibians ............................49Table of Contents

Registration Review Ecological Risk Assessment Clomazone xii 4.1.1.2 Direct Effects to Mammals.......................................................................................49 4.1.2 Direct Effects to Non-Target Terrestrial Invertebrates.................................................53 4.1.3 Direct Effects to Terrestrial and Wetland/Riparian Plants ...........................................53 4.1.3.1 Runoff And Spray drift Loading ..............................................................................53 4.1.3.2 Volatilization Loading..............................................................................................54 4.1.4 Direct Effects to Freshwater Fish (Amphibians) and Plants ........................................55 4.1.4.1 Label Uses Other Than Rice.....................................................................................55 4.1.4.2 Rice Use....................................................................................................................58 4.1.5 Probit Slope Response Analysis of LOC Values and Acute RQ Values......................60 4.2 Risk Description ............................................................................................................... 62 4.2.1 Non-Listed Species.......................................................................................................63 4.2.1.1 Direct Effects to Terrestrial Plants and Animals ......................................................63 4.2.1.2 Direct Effects to Aquatic Plants and Animals ..........................................................81 4.2.2 Listed Species Effects Analysis....................................................................................86 4.2.2.1 Action Area ..............................................................................................................86 4.2.2.2 Direct Effects To Listed Species For Uses Other Than Rice .................................103 4.2.2.3 Direct Effects to Listed Species For Use on Wet Seeded Rice ..............................109 4.2.2.4 Direct Effects to Listed Species For Use on Dry Seeded Rice...............................114 4.2.2.5 Indirect Effects to Listed Species For Uses Other Than On Rice ..........................116 4.2.2.6 Indirect Effects to Listed Species For Rice Uses....................................................117 4.2.2.7 Effects to Critical Habitat.......................................................................................119 4.2.2.8 Co-Occurrence Analysis.........................................................................................120 4.2.2.9 Effects Determination.............................................................................................122 

### Chapter 5 Uncertainti es ................................................................................. 125
5.1 Exposure Assessment Uncertainties...............................................................................125 5.1.1 Volatilized Clomazone ...............................................................................................125 5.1.1.1 Maximum Exposure analysis: Edge-of-field PRZM Analysis ...............................126 5.1.1.2 Maximum Exposure Analysis: Agriculture............................................................127 5.2 Effects and Risk Assessment Uncertainties....................................................................128 5.2.1 Lack of definitive avian acute oral and subacute dietary clomazone test results .......128 5.2.2 Lack of ELS or life cycle test results for the most acutely sensitive freshwater fish species 129 5.2.3 Lack of ELS test results for the most acutely sensitive estuarine/marine fish ...........130 5.2.4 Lack of life cycle test results for th e most acutely sensitive estuarine/marine invertebrate................................................................................................................... ..............130 5.2.5 Use of most sensitive species toxicity endpoint .........................................................131 5.2.6 Single and multiple active ingredient form ulations relative to TGAI effects.............131 5.2.7 Lack of NLCD 82 (cultivated land) data for U.S. Territories, Hawaii, and Alaska ...132 

### Chapter 6 Bibliography.................................................................................. 133 Appendix A Clomazone Regi strations .......................................................... 135 Appendix B Clomazone Toxic ity Data .......................................................... 137 Appendix C Back Calculation of Acute LD 50 

### and LC 50 

### Values for No Mortality Test Results.......................................................................................... 156 Appendix D Formulation Effects Evaluation – Single Active and Multiple Active Ingred ients................................................................................................ 159 Appendix E ECOTOX Open Literature Whic h Passed Initial Screens ....... 165 Appendix F Bibliography of ECOTOX Open Literature Excluded From The Effects Assessm ent............................................................................................. 172Table of Contents

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### Appendix G Non-Target Plant Incident s ....................................................... 245 Appendix H Field Studies – Plan t Effects..................................................... 304 Appendix I Effect Determinations and Habitat Modification Determinations for Nonrice Uses .................................................................................................. 310 Appendix J Effect Determinations and Cr itical Habitat Modification Determinations for Dry Seeded Rice Uses ........................................................ 399 Appendix K Effects Determinations and Critical Habitat Determinations for Wet Seeded Ri ce Uses ........................................................................................ 430List of Figures

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## List of Figures

Figure 1 Clomazone Concentration (ppb) at Three Sites on Cache River Arkansas, 2005.20 Figure 2 Clomazone Concentration (ppb) at Four Sites on L’Anguille River, Arkansas, 2005

............................................................................................................................... ........21 Figure 3 Seedling Emergence IC 25 Species Sensitivity Distribution for Clomazone ............45 Figure 4 Seedling Emergence IC 50 Species Sensitivity Distribution for Clomazone ............46 Figure 5 Distribution of Distances from a Treated Field to Clomazone Effects....................66 Figure 6 Reported Number of Non-Target Plant Incidents Associated with Clomazone Formulations and Key Regulatory Decisions.................................................................67 Figure 7 Terrestrial Plant EEC Values Compared to Seedling Emergence IC 25 Species Sensitivity Distribution for Clomazone ...........................................................................69 Figure 8 Wetland or Semi-Aquatic Plant EEC Values Compared to Seedling Emergence IC 25 Species Sensitivity Distribution for Clomazone ......................................................71 Figure 9 Terrestrial, Wetland, and Semi-Aquatic Plant EEC Values Due to Volatilization Compared to Seedling Emergence IC 25 Species Sensitivity Distribution.......................73List of Tables

Registration Review Ecological Risk Assessment Clomazone xv 

## List of Tables

Table 1 Summary of Current Clomazone Labeled Uses........................................................6 Table 2 PRZM Scenarios, Application Date s, and Application Rates Used to Model Clomazone EECs...........................................................................................................13 Table 3 Physical-Chemical Properties of Clomazone..........................................................14 Table 4 Environmental Fate Properties of Clomazone ........................................................14 Table 5 PRZM/EXAMS Modeling Input Parameters ............................................................15 Table 6 Screening Exposure Analysis: PRZM/EXAMS Standing Water Body.....................16 Table 7 Summary of Marchesan et al. (2007) Clomazone Monitoring Results in Brazil......22 Table 8 Dietary-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, and for Both a Broadcast and a Banded Treatment ...........................25 Table 9 Avian Dose-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, as a Banded Application Treatment....................................................25 Table 10 Mammalian Dose-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, as a Banded Application Treatment..........................................25 Table 11 Mammalian Dose-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, as a Broadcast Treatment.........................................................26 Table 12 Mammalian Dose-Based Commence EC Formulation EEC Values for Cotton and Soybeans t Potatoes, as a Banded Treatment ..............................................................27 Table 13 Dietary-Based Clomazone EEC Values Due to Volatilization for the Highest Application Rate Crop, Sweet Potato at 1.5 lbs ai/A......................................................28 Table 14 Avian Dose-Based Clomazone EEC Values Due to Volatilization for the Highest Application Rate Crop, Sweet Potatoes at 1.5 lbs ai/A..................................................28 Table 15 Mammalian Dose-Based Clomazone EEC Values Due to Volatilization for the Highest Application Rate Crop, Sweet Potatoes at 1.5 lbs ai/A.....................................29 Table 16 Estimated Clomazone Loading to Off-Site Terrestrial and Semi-Aquatic Areas Adjacent to a Treated Field for Ground Spray Applications at the Upper and Lower Maximum Application Rate Range.................................................................................30 Table 17 Input Parameters for TerrPlant v1.2.2 Used for Modeling Runoff and Spray Drift Loading to Off-Field Terrestrial And Semi-Aquatic Areas Adjacent to a Treated Field..30 Table 18 Off-Site Loading Due to Volatilization Based on Relative Humidity ......................31 Table 19 Off-Site Loading Due to Volatilization Assuming 50% of Rate Based on Relative Humidity....................................................................................................................... ..31 Table 20 Summary of Specific Measurement Endpoint Values Selected to Calculate RQ Values to Evaluate Risk for Birds and Mammal Assessment Endpoints .......................33 Table 21 Body Weight Adjusted Acute Oral LD 50 Values Based on Extrapolated Mallard Duck LD 50 Values from Limit Test Results .....................................................................35 Table 22 Summary of Specific Measurement Endpoint Values Selected To Calculate RQ Values to Evaluate Risk for Terrestrial Invertebrate Assessment Endpoints.................37 Table 23 Summary of Specific Measurement Endpoint Values Selected To Calculate RQ Values to Evaluate Risk for Fish and Amphibian Assessment Endpoints .....................38 Table 24 Summary of Specific Measurement Endpoint Values Selected to Calculate RQ Values to Evaluate Risk for Aquatic Invertebrate Assessment Endpoints .....................40 Table 25 Summary of Specific Measurement Endpoint Values Selected to Calculate RQ Values to Evaluate Risk for Terrestrial and Aquatic Plant Assessment Endpoints........42 Table 26 Vegetative Vigor Study Morphological Observation Results – Clomazone Dose at Which Discoloration and Mortalities were First Observed .............................................47 Table 27 Avian chronic dietary-based RQ values for a banded application on sweet potatoes ....................................................................................................................... ..49List of Tables

Registration Review Ecological Risk Assessment Clomazone xvi Table 28 Upper bound acute and chronic clomazone dose-based RQ values for mammals for a banded application on sweet potatoes ..................................................................51 Table 29 Upper bound acute and chronic clomazone dose-based RQ values for mammals for a broadcast application on sweet potatoes...............................................................51 Table 30 Upper bound acute and chronic clomazone dose-based RQ values for mammals ingesting short grass at application rates from 0.75 lbs ai/A to 2.5 lbs ai/A...................52 Table 31 Mammalian chronic dietary-based clomazone RQ values for a banded application on sweet potatoes..........................................................................................................52 Table 32 Upper bound and average acute Commence EC dose-based RQ values for mammals for a banded application on cotton or soybeans............................................52 Table 33 RQ values for plants in dry and semi-aquatic areas exposed to clomazone through runoff and/or spray drift..................................................................................................53 Table 34 RQ values for near field plants ex posed to clomazone from volatilization............54 Table 35 RQ values for near field plants ex posed to clomazone from volatilization............55 Table 36 RQ values for freshwater fish, invertebrates, and plants based on 1-in-10 year acute and chronic exposure concentrations in a vulnerable receiving water.................55 Table 37 RQ values for estuarine-marine fish, invertebrates, and aquatic plants based on 1- in-10 year acute and chronic exposure concentrations in a vulnerable receiving water, With and Without PRZM Volatilization ...........................................................................56 Table 38 Wet Seeded Rice Non-Listed and Listed Aquatic Plant RQs and Acute Fish and Aquatic Invertebrate RQ Values for Clomazone Residues in Rice Paddy Water at Various Holding Times...................................................................................................58 Table 39 Dry Seeded Non-Listed and Listed Aquatic Plant RQs and Acute Fish and Aquatic Invertebrate RQ Values for Clomazone Residues in Rice Paddy Water at Permanent Flood.......................................................................................................................... ....60 Table 40 Probit Slope and Odds of Mortality for an Individual at the LOC...........................61 Table 41 Odds of Mortality for an Individual Bird or Mammal at a Given Acute RQ Value for the TGAI and Commence EC ........................................................................................61 Table 42 Odds of Mortality for an Individual Fish or Aquatic Invertebrate at a Given Acute RQ Value ....................................................................................................................... 62 Table 43 Distance from Treated Field Spray Drift Loading Exceeds LOC...........................64 Table 44 Upper bound avian dietary levels for a banded application on sweet potatoes compared to extrapolated dietary acute toxicity values .................................................76 Table 45 Upper bound mammalian dietary levels for a banded application on sweet potatoes compared to extrapolated dietary acute toxicity values ..................................78 Table 46 Mean acute and chronic dose-based RQ values for mammals for a banded application on sweet potatoes........................................................................................80 Table 47 Summary of Indirect and Direct Effects to Listed Species and Preliminary Effects Determination for Clomazone Uses Other Than Rice....................................................90 Table 48 Summary of Indirect and Direct Effects to Listed Species and Preliminary Effects Determination for Clomazone Uses On Wet Seeded Rice ............................................95 Table 49 Summary of Indirect and Direct Effects to Listed Species and Preliminary Effects Determination for Clomazone Uses On Dry Seeded Rice...........................................100 Table 50 Clomazone uses designated in problem formulation and corresponding IMS sites

............................................................................................................................... ......121 Table 51 PRZM Edge-of-Field Exposure ...........................................................................127 Table 52 Maximum Surface Water EEC Values from PRZM/EXAMS Model .....................128List of Abbreviated Terms

Registration Review Ecological Risk Assessment Clomazone xvii 

## List of Abbreviated Terms and Symbols

@ symbol for “at” # symbol for “number” % symbol for “percent” > symbol for “greater than”

> symbol for “greater than or equal to” < symbol for “less than”

< symbol for “less than or equal to” μg/kg symbol for “micrograms per kilogram” μg/L symbol for “micrograms per liter” oC symbol for “degrees Celsius”
2-CBA 2-chlorobenzoic acid Ai active ingredient
AAPCO Association of American Pesticide Control Officials
Acc# accession number
amu atomic mass unit Apr April Aug August bw body weight
CA California
CARB California Air Resources Board CDPR California Department of Pesticide Regulation
CI confidence interval
CL confidence limit
CT Connecticut
DE Delaware
DP#
EC emulsifiable concentrate
EC 05 

### 5% effect concentration
EC 25 

### 25% effect concentration
EC 50 

### 50% (or median) effect concentration ECOTOX EPA managed database
EEC estimated environmental concentration
EFED Environmental Fa te and Effects Division

e.g . Latin exempli gratia (“for example”)List of Abbreviated Terms

Registration Review Ecological Risk Assessment Clomazone xviii 

### E EIM Environmental Information Management System EPI Estimation Programs Interface ESU Evolutionarily significant unit
et al. Latin et alii (“and others”)

etc. Latin et cetera (“and the rest” or “and so forth”)
EXAMS FESTF FIFRA Endangered Species Task Force FIFRA Federal Insecticide Fungicide and Rodenticide Act FMC65317 N-[(2-chlorophenyl ) methyl]-3-hydroxy-2,2- dimenthylpropanamide FQPA Food Quality Protection Act
ft Feet
GENEEC Generic Estimated E xposure Concentration model
HMONC habitat modification of no concern HMOPC habitat modification of potential concern HPLC high pressure liquid chromatography
IA Iowa
IC 05 

### 5% inhibition concentration
IC 50 

### 50% (or median) inhibition concentration

i.e . Latin for id est (“that is”)
IL Illinois IMS Information Management System
IN Indiana Jan January
Jun June kg Kilogram(s) kJ/mole kilojoules per mole km kilometer(s)

K oc 

### symbol for the organic ca rbon partitioning coefficient KY Kentucky LAA likely to adversely affect lb ai/acre pound(s) of activ e ingredient per acre
LC 50 

### 50% (or median) lethal concentration

LD 50 

### 50% (or median) lethal dose lg largeList of Abbreviated Terms

Registration Review Ecological Risk Assessment Clomazone xix 

### LOAEC lowest observable a dverse effect concentration
LOAEL lowest observabl e adverse effect level
LOC level of concern
LOD level of detection
LOEC lowest observabl e effect concentration LOQ level of quantitation m meter(s) MA may affect MATC maximum acceptable toxicant concentration MD Maryland

m 2 

### /day square meters per days ME Microencapsulated mg milligram(s) mg/kg milligrams per kilogram (equivalent to ppm) mg/L milligrams per liter (equivalent to ppm) mi mile(s) MI Michigan
MJD Multi-Jurisdictional Database MLRA major land resource area mmHg millimeter of mercury
MN Minnesota
MRID master record identification number MW molecular weight NASS National Agricultural Statistics Service NAWQA National Water Quality Assessment
NCOD National Contaminant Occurrence Database
NE no effect NLAA not likely to adversely affect
NLCD National Land Cover Dataset NH New Hampshire NJ New Jersey
NM New Mexico NMC N-methyl carbamates
NMFS National Marine Fisheries Service
NOAA National Oceanic and Atmospheric Administration
NOAEC no observable adverse effect concentrationList of Abbreviated Terms

Registration Review Ecological Risk Assessment Clomazone xx 

### NOAEL no observable adverse effect level
NOEC no observable effect concentration
NRCS Natural Resources Conservation Service NTU nephelometric turbidity unit
NY New York
Oct October
OH Ohio OPP Office of Pesticide Programs OPPTS Office of Prevention, Pes ticides and Toxic Substances PA Pennsylvania pH symbol for the negative logarithm of the hydrogen ion activity in an aqueous solution, dimensionless pKa symbol for the negative loga rithm of the acid dissociation constant, dimensionless ppb parts per billion (equival ent to μg/L or μg/kg) ppm parts per million (equivalent to mg/L or mg/kg)

PRZM
RI Rhode Island SLN Special Local Need
sm small UCL upper confidence limit USDA United States Department of Agriculture USEPA United States Environmental Protection Agency
USFWS United States Fish and Wildlife Service VA Virginia
VT Vermont
WI Wisconsin WP wettable powder wt weight WV West VirginiaChapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 1 

# Chapter 1 Introduction

1.1 Purpose of Assessment

The purpose of this assessment is to evaluate the potential risk to populations of non-listed ( i.e ., not federally endangered or threatened) spec ies and the potential risk to endangered and threatened (listed) species from exposure to cl omazone from its registered uses. This risk assessment incorporates the latest effects da ta, modeling, and risk methodologies that may
not have been available at the time clomazone registration actions occurred. Risks from
direct and indirect effects are derived and ev aluated in accordance with the risk assessment methodology described in the Agency’s Overvi ew Document (USEPA, 2004). These risk findings are then used as part of an “effects determination” for listed species. The Agency will reach one of the following three conclusions regarding the potential for each registered clomazone use to affect federally listed species:

• “No effect”;

• “May affect, but not likely to adversely affect”; or

• “May affect, and likely to adversely affect”.

If the results of the risk asse ssment show no indirect effects a nd the levels of concern (LOC)
are not exceeded for direct effects for a given listed species taxonomic grouping ( e.g ., freshwater fish, small herbivorous mammal), a “no effect” (NE) determination is made,
based on use of clomazone within the action ar ea for a “species” with the given taxonomic group. If, however, there is a potential for indi rect effects and/or exposure exceeds the listed species LOC values for direct effects for a given group, the Agency concludes a preliminary “may affect” (MA) “species” within the taxonomic group. The Agency then considers additional lines of evidence such as the geographi cal nature of the exposure, as well as more in-depth evaluations of the t oxicological and ecological require ments to determine a rationale for a “not likely to adversely affect” (NL AA) or “likely to adversely affect” (LAA)
determination.

Similarly the Agency will reach one of the fo llowing conclusions regarding the potential for
clomazone uses to result in destruction or adverse modificatio n of critical habitat:

• “No effect”;Chapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 2 

### • “Habitat modification(s) of no concern”;

• “Habitat modification(s) of potential concern”.

The Agency uses the risk assessment analysis fo r direct effects to cate gories of biological resource requirements to draw conclusions about effects to principle c onstituent elements of critical habitat. The Agency is limited in a practical sense, to those principle constituent elements of critical habitat that are of a biologi cal nature. If the results of the risk assessment show that no LOC is exceeded for all taxonomic groups a “no effect” (NE) determination for
habitat modification is made. If a LOC is exceeded for one or more taxonomic groupings the Agency then considers additional lines of evidence such as the type and degree of effect on the taxonomic groupings, expected resultant e ffects on biologically mediated environmental processes ( e.g ., increased sedimentation from loss of vegetation) as compared to baseline environmental conditions, cooccurrence of the acti on area with critical habitat, the type of principle constituent elements associated with critical habitat for listed species in a taxonomic grouping to determine a rationale fo r a “habitat modification of no concern” (HMONC) or “habitat modification of potential concern” (HMOPC).



## 1.2 Clomazone Use

Clomazone is a broad spectrum herbicide used to control annual grasses and broadleaf
weeds. It is an isoxazolidinone herbicid e and there are no other registered compounds currently in this class. Exis ting registered uses are descri bed in Section 1.2.1. Clomazone end-use products may be applied alone mixed wi th water or also with liquid fertilizer. Emulsifiable concentrate formulations may be a pplied with dry fertilizer. Clomazone may be tank mixed with other crop registered herbicides 3 

### , insecticides, fungicides and/or
nematicides.

1.2.1 Existing Registered Uses
The existing FIFRA Section 3 and 24c register ed label uses of clomazone (trade names Command, Commence, CERANO, Strategy, and RiceMax) cons titute the action under review (Appendix A). The following provi des information on these registered uses.

3 Canopy®, Dual®, Lasso®, Lasso Micro-Tech®, Lexone®, Lorox Plus®, Prowl®, Pursuit®, Scepter®, Sencor®, Sonalan®, Squadron®Chapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 3 

### Summary of Uses :

Food : Existing registered food crop uses include arracacia (Peruvian carrot), succulent beans (lima, snap), cabbage, cucumber, manioc (cassava), melons, musk melons, watermelons, mint, succulent peas, peppers, pimento, pumpkin, rice, soybeans, summer squash, winter squash, sugarcane (newly planted or ratoon ), sweet potato, yam, yautia, and agricultural fallow land (to be plan ted for winter wheat). Tanier, cassava, yams, and arracacia are members of Crop Subgroup 1-D (Tuberous and corm vegetables), for which sweet potato is the representative commodity.

Non-Food : Existing registered non-food crop us es of clomazone include cotton and tobacco, except not for use on tobacco seedling beds.

Residential : There are no existing resi dential uses of clomazone.

Target Pests : Used to control annual grass weeds in dry-seeded ri ce and partial to full control of annual grasses 4 

### and broadleaf weeds 5 

### for the other agricultural crops. At lower rates of around 0.5 lbs ai/A the label indicates that clomazone only s uppresses some annual grasses and controls velvetleaf and spurred anoda. Rates of 1.0 lb ai/acre or higher
are recommended to control weeds in fi elds that have previously been in conservation programs, or wh ere heavy weed pressure is anticipated.

Formulation Types : Three formulations of clomazone are addressed in this document: wettable powder (WP), emulsifiab le concentrate (EC), and microencapsulated (ME). There are eleven FIFRA Section 3 registered endproducts, three emulsifiable concen trate end-products, one wettable powder, and seven micro-encapsulated (ME) end-products. Additionally, there are several FIFRA Special Local Need (SLN) Section 24(c) registrations (Appe ndix A). Comma nd 4EC, Command

4 Barbarnyardgrass; broadleaf signalgrass; large and smooth crabgrass; giant, green, purple, robust and yellow foxtail; goosegrass; common, fall and Texas panicum; s eedling Johnsongrass; field sa ndbur; South-western and wooly cupgrass; Bermudagrass; red rice; itchgrass; junglerice; shattercane; and wild proso millet 5 Velvetleaf; spurred anoda; black seeded plantain; balloonvine; carpet weed; cocklebur; common ragweed; curly dock; dayflower; Jimsonweed; lambsquarter; Penn sylvania smartweed; pricly sida; purslane; redweed; Venice mallow; Florida beggarweed; Florida pusley; kochia; redvine; tropic croton; wild poinsettia; black nighshade; joint vetch; pitted morningglory; and prostrate, redroot, smooth and spiny pigweedChapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 4 

### 4E, Command 3ME, Command 2ME, Cerano 5 MEG, and Command 50 WP are single active ingredient formulations of clomazone. Strategy is a mixture of clomazone and ethalfluralin 6 

### . RiceMax is a mixture of clomazone and propanil 7 

### . Commence EC is a mixture of
trifluralin 8 

### and clomazone.

Methods and Rates of Application :

Equipment : There are FIFRA Section 24(c) labels that allow an ME formulation to be applied to rice using aerial equipm ent. Otherwise all other labels do not allow clomazone to be applied either by air or in any type of irrigation system. Clomazone is app lied as a broadcast treatment or a band treatment using ground equipment, and is restricted to application at wind speeds at or below 10 miles per hour. Some labels specifically state to use equipment that produc es a large drop let size of 450 microns or larger, while other labels just indicate to use a large or coarse droplet size. Applications of the WP and EC formulations are required to be soil incorporated at 1 to 3 inches, depending on the crop, in given geographic locations (see Table 1) to reduce off-site
movement of clomazone.

The RiceMax label indicates that rice fields to which the product is applied should have a levee system that can hold a 3-6 inch flood.

Buffer Restrictions : There is language on current Section 3 labels which either explicitly prohibits application to non-fiel d areas including fence rows, waterways, ditches, and road sites or implicitly prohibits application to non-field areas by limiting applicati on to only those surfaces that will be soil incorporated. Section 3 la bels for EC and WP registrations prohibit preemergent soil incorporated applications within 1,000 ft of towns and subdivisions, co mmercial vegetable production 9



### , commercial fruit production, commerci al nurseries, and commercial greenhouses and 100 ft of desirable plants 10 

### whereas soil

6 N-ethyl-N-(2-methyl-2-propenyl)-2,6-dinitro-4-(trifluoromethyl)benzenamine 7 3’,4’-dichloropropionanilde) 8 α , α , α -trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine 9 Most labels have at least an exception for sweet corn so me labels also include exceptions which include one or more of the following: peppers, pumpkins, succulent peas, sweet potato, and winter squash. 10 Spruce trees and deciduous trees (apple (fruit and ornamental), ash (green, white, mountain), basswood, boxelder, catalpa, cherry (fruit and ornamental), cottonwood, elm, ginkgo, hackberry, mulberry, peach, pearChapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 5 

### unincorporated applications are pr ohibited within 1,500 ft of towns and subdivisions, commercial vege table production, commercial fruit production, commercial nurseries , commercial greenhouses and desirable plants. Section 3 labe ls for ME registrations prohibit applications within 1,200 ft of towns and subdivisions, commercial vegetable production, commercial fruit production, commercial nurseries, commercial greenhouses and some labels have 200 ft and others 300 ft of desirable plants. These buffer restrictions were not added to address a specific endangered species concern.

Application Rates : Clomazone is limited to one appl ication per year. Maximum label application rates for uses are contained in Table 1.

Timing : For essentially all crops, clomazone may be applied as a pre-emergent soil treatment prior to seeding, plan ting, or transplanting. For crops such as dry-seeded rice, tobacco, and vegetables, it may alternatively be applied as a pre-emergent or early pre-emergence post-planting or post-transplanting but prior to crop em ergence. For dry-seeded rice it also may be applied as an early post-emergent. For vegetables it is
recommended that the seed bed be free of crop and weed residue and clod free whereas cotton applications may be made under conventional tillage or conservation tillage syst ems. Application to soybeans may also be made under minimum-tillage or no-tillage systems.

Use Classification : General use.

(fruit and ornamental), pecan, poplar, Russian olive, tr ee of heaven, tulip tree, walnut trees, willow species); shrubs and vines (azalea, burn ingbush, grape, honeysuckle, roses, yew); agronomic crops (alfalfa, oats); ferns; herbs; strawberry; raspberry; and blackberry.Chapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 6 Table 1 Summary of Current Clomazone Labeled Uses

Crop Formulation Maximum lb ai/acre Application method* Geographic Restrictions

sweet potato ME 1.5 broadcast or band (no soil incorporation) Disallowed in CA

cotton, soybeans ME, EC 1.25 EC : broadcast or band (must be soil incorporated in some states)

ME : broadcast or band (no soil incorporation) Disallowed in CA EC : one EC label requires soil incorporation, one EC label requires soil incorporation in CT, DE, IL, IN, IA, Maine, MD, Massachusetts, MI, MN, NH, NJ, NY, OH, PA, RI, VT, VA, WV, WI, another EC label requires soil incorporation in these same states plus KY arracacia (Peruvian carrot), cassava (manioc), yam, yautia, sugarcane ME 1.24 broadcast or band (no soil incorporation) Disallowed in CA

Agricultural fallow land EC 1 broadcast (no soil incorporation) Disallowed in CA

peppers (bell, hot, pimento and sweet) ME, EC 1 ME : broadcast or band (no soil incorporation)

EC : broadcast or band (must be soil incorporated in some states) Disallowed in CA EC : requires soil incorporate in CT, DE, IL, IN, IA, Maine, MD, Massachusetts, MI, MN, NH, NJ, NY, OH, PA, RI, VT, VA, WV, WI, another EC label requires soil incorporation in these same states plus KY pumpkin EC, WP 1 broadcast or band (must be soil incorporated in some states) Disallowed in CA EC : one EC label has no soil incorporation requirement; one EC label requires soil incorporation in CT, DE, IL, IN, IA, Maine, MD, Massachusetts, MI, MN, NH, NJ, NY, OH, PA, RI, VT, VA, WV, WI; and two other EC labels require soil incorporation in these same states plus KY tobacco ME, EC 1 ME : broadcast or band (no soil incorporation)

EC : broadcast or band (must be soil incorporated in some states) Disallowed in CA EC : must be soil incorporated in CT, DE, IL, IN, IA, Maine, MD, Massachusetts, MI, MN, NH, NJ, NY, OH, PA, RI, VT, VA, WV, WI

p umpkin and squash (winter) ME 0.75 broadcast or band (no soil incorporation) Disallowed in CAChapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 7

Crop Formulation Maximum lb ai/acre Application method* Geographic Restrictions

rice ME 0.6 dry-seeded : broadcast by ground equipment (no soil incorporation)

water-seeded, flooded : broadcast by aircraft or ground equipment (one Section 3 label requires no release of rice paddy water for a minimum of 14 days post-application unless there is water treatment) dry-seeded : Disallowed in CA

cabbage, mint, peas (succulent), squash (summer) ME 0.5 broadcast or band (no soil incorporation) Disallowed in CA

Peas (succulent) EC,WP 0.5 br oadcast or band (must be soil incorporated in some states) Disallowed in CA EC : one EC label requires soil incorporation in CT, DE, IL, IN, IA, ME, MD, Massachusetts, MI, MN, NH, NJ, NY, OH, PA, RI, VT, VA, WV, WI, another EC label requires soil incorporation in these same states plus KY cucumber, melons, squash (summer), squash (winter), watermelons ME 0.375 broadcast or band (no soil incorporation) --

cucumber ME 0.375 broadcast or band (no soil incorporation) Disallowed in CA

beans (succulent), melons (musk), and watermelons ME 0.251 broadcast or band (no soil incorporation) Disallowed in CA

*Applied using ground equipment except where noted. All labels state that the product may not be applied through any type of irrigation system.



### For ME formulations where soil incorporati on is not recommended on the label, the tank mix instructions limit other pesticides in the tank mix to those that do not require soil incorporation. Use of a surf actant is recommended. For cotton, diuron is not recommended at planting when clomazone is used as plant injury may resu lt and either a disulfoton or phorate organophosphate insecticid e must be applied in-furro w with the cotton seed at planting time at a rate of 0.75 lb ai/acre othe rwise crop phytotoxicity an d/or stand reduction can occur. In addition, labels for use on rice warn to not tank mix or apply carbamate or organophosphate insecticides within 14 days of us e of clomazone or to apply to fields with rice treated with bird repe llents containing methiocarb.Chapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 8 

## 1.3 Problem Formulation

The problem formulation for this assessment a nd effects determination was provided in the USEPA (2007a) Clomazone Summary Document Registration Review : Initial Docket January 2007 11 

### and USEPA (2007b) Revised Clomazone Final Work Plan Registration Review July 2007 12 

### documents. Additional modifications to the problem formulation are
discussed in this section.

1.3.1 Application Rates
Maximum application rates were modified for a couple of uses, such as cotton, due to either
label modifications which were made about th e time of the problem formulation, and were
therefore not reflected in the problem formulation or typographi cal errors. Application rates in Table 1 reflect the maximum applicati on rates considered in this assessment.

1.3.2 Analysis Plan

1.3.2.1 E XPOSURE A SSESSMENT 

### As indicated in the problem formulation one of th e major routes of fate and transport off-site is volatilization. (Appendix G documents the well-demonstrated volatilization and downwind transport of clomazone). Clomaz one is a semi-volatile compound, but its vaporization is promoted by sorption of water to soil. Many incidents of bleaching in nontarget plants have been reported near clomazone use sites, especially af ter rain or during high humidity. Incidents have occurred repeatedly days after clomazone use, and so are not attributable to spray drift at the time of application. The severity of non-target plant bleaching, which led in some cases to plant deat h, and recorded distances of one mile and more, indicates that a substant ial portion of the applied clom azone may be volatilized and transported away from the use site.

The association of non-target plant bleaching incidents with rain and high humidity is consistent with the mechanism of displacement of clomazone from its soil sorption sites by water vapor. The desorbed clom azone partitions to the gas ph ase and is then free to be transported by the wind.

As proposed in the problem formulation, the California Air Resources Board (CARB) Air model, CALPUFF, was evaluated for use in estimating volatilization exposures for

11 http://www.regulations.gov/fdmspub lic/component/main?main =DocumentDetail&d=EPA-HQ-OPP-2006-0113-0017
12 http://www.regulations.gov/fdmspub lic/component/main?main =DocumentDetail&d=EPA-HQ-OPP-2006-0113-0022Chapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 9 

### clomazone. Scenario development and para meterization of CALPUFF for use in OPP exposure assessments was not sufficiently adva nced for it to be used in the clomazone

assessment.

A recent paper by Yang and Holmén (in press) m easured the effect of surfactant content, Henry’s Law constant, and rela tive humidity on the volatiliz ation of seven herbicides (alachlor, butachlor, metolachlor, propachlor, pendimethalin, prodiamine, and trifluralin) applied as emulsifiable concen trates from two soils (a CT sandy clay loam with 1.68% organic carbon, and a NM clay loam with 0.73% organic carbon). The authors developed an empirical model for volatilization based on th ese parameters. The amount of clomazone volatilized from agricultural fields and avai lable for deposition off-site under different relative humidity is estimated by this method of Yang and Holmén (in press). This is a provisional method for use in this assessment, and has not been vetted for use by the appropriate EFED technical team.

To account for the effect of volatilization on runoff load, aquatic exposure estimates were done in two ways. First, with the PRZM volat ilization routine turned off, and second with
the volatilization routine turn ed on. The volatilization routin e is invoked by entering values for the diffusion coefficient in air (estimated to be 3,802 m 2 

### /day, Table 5) and the enthalpy of vaporization (the PRZM default value of 20 kJ/mole was used).

Maximum exposures from PRZM-EXAMS (as opposed to 1-in-10 year peak daily exposures), and “edge-of-field” runoff water exposures from PRZM are given to assist in the
demarcation of the “action area” for the listed species effects determination. All of these
estimates are done both with and wi thout volatilization considered.

The Tier 1 Rice model is used for wet-seeded rice use, and is modified by considering the decay rate observed in an aquatic field diss ipation study done in a California rice paddy. The modification to include a decay rate from fiel d studies is a provisional modification of the Tier 1 Rice model. Ambient water exposures from rice uses, taken from the scientific literature, are also given.

If effects data indicate that a formulated product, whether a single or multiple active ingredient one, is more toxic than the active ingredient alone, the fo rmulation effects data may be used qualitatively or quantitatively in accordance with the Agency’s Overview
Document and the Services’ Evaluati on Memorandum (EPA 2004; USFWS/NMFS 2004). Except for mammals and freshwater fish no formul ation testing was available. The results of an analysis of formulation effects on acute or al toxicity to mammals as compared to the
TGAI show that an assessment based on the acute oral toxicity of the TGAI appearsChapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 10 

### appropriate, except potentially for Commence EC. The Commence EC formulation based on mammalian effects data was found to potentially be more toxic to terr estrial wildlife than indicated by active ingredient e ffects testing. In this case a qu antitative assessment of risk from exposure to this formulation was consider ed for mammals in addition to the analysis performed on the active ingred ient. Exposure modeling in this instance was limited to dietary exposure to residues for a time period immediately following pesticide product application based on the expectation that th e varying physical-chemi cal properties of the individual components of a form ulation will result in progressi vely different formulation. Commence EC is registered for only two uses , cotton and soybean. Because there are no formulation effects testing with other terrestrial species ( e.g ., birds) so no quantitative exposure analysis for this formulation was performed for other terrestrial taxa.

1.3.2.2 D EGRADATES 

### A major degradate in the anaerobic aquatic metabolism study (MRID 44348403) was FMC65317 (N-[(2-chlorophenyl)methyl]-3-hydro xy-2,2-dimenthylpropanamide), a ringopening product. It reached 49- 55% of parent at 120 to 365 days of the study. In the aerobic aquatic study (MRID 44348404), it reached only 11% of parent at one sampling interval. Thus, it would not be expected to form to the same degree under aerobic conditions, and would be expected to degrade once exposed to oxygen. Therefore, FMC65317 was not included in the exposure assessment for water.

Estimation Programs Interface (EPI) Suite v3.12, a Windows ® 

### -based suite of physical/chemical property and environmental fate estimation programs, was used to compare the estimated physical properties of FMC65317 to parent clomazone. The degradate was predicted to have a lower log K ow 

### (1.55 versus 2.55 measured for parent), a higher boiling point (403oC versus 275oC for pa rent), a higher water solubility (1,239 to 20,100 mg/L versus 1,100 for parent), and a lo wer vapor pressure (6.8E-09 mmHg versus 1.44E-04 mmHg for parent) than the parent. Al l of these properties indicate a greater propensity to remain in water or soil than parent clomazone. Thus, FMC65317 is much less likely to cause exposure via the volatilization route.

Another major degradate in the anaerobic a quatic metabolism study was 2-chlorobenzoic acid (2-CBA). This compound reached a maximum of 14% of parent at 189 days, and is an expected product of degradation of FMC65317. Because 2-CBA has a measured pKa of 2.89, it is expected to be ionized at environmental pH, and ther efore to remain in the water column rather than volatilize. 2-CBA is exp ected to be readily biode gradable, and thus to contribute little to exposure.Chapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 11 

### The uncertainty in the water exposure assessment due to volatilization (5 0% or more at peak exposure) is expected to overwhelm the uncerta inty due to non-inclusion of degradates at later times. There is no major degradate resulting in terrestri al exposure concern.

1.3.2.3 E FFECTS A SSESSMENT 

### Modifications to the toxicity data presented in the problem formula tion included correction
from test material to an activ e ingredient basis for several endpoints, inclusion of public
literature results which lowered acute and chroni c toxicity endpoint valu es for the freshwater fish, corrections and updates in the statistical analysis approa ch for plant toxicity data ( e.g ., a continuous response model was used for point estima tes, if all plants died in a replicate, a missing value rather than a zero value was used in height and weight analyses, where a
NOAEC could not be determined an IC 05 

### was calculated). All of these modifications resulted in lower toxicity endpoi nt values than used in previous assessments. Additionally,
an evaluation of available formulation eff ects data indicated that the Commence EC formulation may be more toxic to mammalian wildlife than that that indicated by active ingredient effects testing. In this case exposure to the form ulation was also evaluated for
mammals. The clomazone effects data and the va lues used in the risk assessment and effects determination are summarized in Chapter 3.

1.3.2.4 R ISK C HARACTERIZATION 

### Because exposure models and/or effects data differ from previous risk assessments performed for registration of these uses, risk estimates based on maximum exposure levels to
aid in the demarcation of the action area for list ed species, and screening level risk estimates for these clomazone registered uses were performed. As indicated in the problem
formulation more refined risk ch aracterizations were also perfor med as needed to support the effects determination for listed species.

The Information Management System (IMS), a work product of the industry-based FIFRA Endangered Species Task Force (FESTF) was used as a pilot to evaluate the co-occurrence of listed species and critical habitat within the clomazone action area. FESTF was formed to fulfill data requirements relative to species/pesticide use proximity. The registrant of clomazone, FMC Corporation, is a full member of FESTF.

Species Location Data. The species location data in the IMS were provided by EFED in June, 2003. In order to provide the most cu rrent information, location data from the
NatureServe Multi-Jurisdictional Database (MJD) licensed by FESTF (the FESTF MJD; McGaughey et al . 2007) was added to the IMS. In th e biological data for each Element Occurrence, representing an individual record of species presence in a defined area, theChapter 1 Introduction

Registration Review Ecological Risk Assessment Clomazone 12 

### FESTF MJD lists the counties in which that Elem ent Occurrence occurs. To ensure that all counties were included, the accompanying spatia l data (shape file) in the FESTF MJD was overlaid with county boundaries and all countie s that overlap with each shape file were determined. The lists derived from the biologic al data and spatial data were combined and incorporated into the IMS. Because some taxonomic and geographic gaps exist in the FESTF MJD dataset, the MJD-based informa tion was supplemented using county occurrence data lists issued by the USFWS for each state 13 

### or by contacting the responsible USFWS regional office. The source of each species location ( i.e ., the FESTF MJD and/or a USFWS county list) was indicated in the IMS.

In the investigation of indivi dual co-occurrences, the spatial data in the FESTF MJD were used to determine the proximity of Element O ccurrences to potential clomazone use sites. Species located within one or two miles of pot ential use sites were prioritized for further analysis; those outside two miles were cons idered to be not exposed to clomazone.

Critical Habitat Location Data. Spatial data from the USFWS Critical Habitat Portal 14 

### was overlaid on county boundaries to ge nerate a list of counties cont aining critical habitat. For species that are not included in the Critical Habitat Portal, attempts were made to obtain critical habitat spatial data by contacting the le ad USFWS region for that species. The list of counties containing critical habitat for each specie s was incorporated into the IMS, separate from the list of counties containing species locations.

In the investigation of indivi dual critical habitat co-occurren ces, subcounty critical habitat spatial data from the USFWS Critical Habitat Po rtal may be used to determine the proximity of critical habitat to poten tial clomazone use sites.

Crop Use Location Data. Counties containing specific crop us e sites were determined from the 2002 Census of Agriculture (USDA 2002). Th e Census of Agriculture is described by the USDA as “the only source of uniform, comp rehensive agricultural data for every state and county or county equivalent in the United States.” The Ce nsus is conducted every five years, and the 2002 Census is the most recent.

13 For example, http://www.fws.gov/mountain-p rairie/endspp/CountyLists/Colorado.pdf 14 http://criticalhabitat.fws.govChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 13 

# Chapter 2 Exposure Assessment

2.1 Aquatic Exposure Assessment

2.1.1 Nonrice Uses--Modeled
Exposure of aquatic organisms is calculated as detailed in the Overview Document (USEPA, 2004). Briefly, the PRZM model (10-hectare fi eld) with appropriate crop scenarios (or surrogates), soil type and meteorol ogical data is run for a 30-year simulation in a 1-hectare, 2-meter deep static pond in the EXAMS model, and the highest exposure expected once in ten years is reported. The 1-in-10-year peak daily, and 21-day and 60-day averages are used
for acute and chronic invertebra te and fish estimated environmental concentrations (EEC), respectively.

The following PRZM scenarios were chosen to represent registered clomazone uses. Application dates were set to 2 weeks before the emergence date in the PRZM scenario except for sugarcane and Florida potato, wher e clomazone is used as a pre-plant, preemergence treatment. An application date of January 15 was used for sugarcane and Florida potato. The Florida potato scenario was used as a surrogate for tropical tuber crops such as yautia, tanier, cassava, and arracacia.

Table 2 PRZM Scenarios, Application Dates, and Application Rates Used to Model Clomazone EECs

PRZM Use Scenario (standard unless noted) Clomazone Labeled Use represented Application Date Maximum Application rate, lb ai/acre Florida sugarcane Sugarcane Jan 15 1.25 Louisiana sugarcane Sugarcane Jan 15 1.25 Mississippi cotton Cotton Apr 15 1.25 North Carolina cotton Cotton May 15 1.25 Florida peppers Peppers Aug 15 1 Mississippi soybeans Soybeans Apr 1 1.25 North Carolina sweet potato Sweet potatoes May 1 1.5 North Carolina tobacco Tobacco Apr 1 1 Florida potato (NMC) 1 Tanier, cassava, arraca cia, yautia Jan 15 1.275 Michigan bean Dry peas/beans, green peas, green beans May 15 0.4875

Oregon snap beans Dry peas/beans, green peas, green beans Jun 1 0.4875

Florida cabbage Cabbage Oct 1 0.49Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 14 PRZM Use Scenario (standard unless noted) Clomazone Labeled Use represented Application Date Maximum Application rate, lb ai/acre Florida cucumber Cantaloupe, cucumbers, pumpkins, squash, watermelons Oct 1 1.0 (pumpkin)—WP 0.75 (pumpkin, winter squash) 0.5 (summer squash) 0.25 (pumpkin, melons, watermelons) Oregon mint mint Apr 1 0.5 (1) NMC: scenario developed for N-me thyl carbamate cumulative assessment. This Florida potato scenario was used as a surrogate for tropical tuber crops su ch as yautia, tanier, cassava, and arracacia.



### The following tables summarize the physical-chemi cal and environmental fate properties of
clomazone.

Table 3 Physical-Chemical Properties of Clomazone

Property Value Reference Chemical Name (IUPAC) 2-(2-chlorobenzyl)-4 ,4-dimethylisooxazolidin-3-one Ahrens, 1994 CAS Registry Number 81777-89-1 Ahrens, 1994
Molecular Formula C 12 H 14 ClNO 2 Ahrens, 1994 Molecular Weight 239.70 amu Ahrens, 1994 Physical State Colorless to pale yellow, viscous liquid at room temperature; white, crystalline solid below melting point Ahrens, 1994

Melting Point, o C 25 Ahrens, 1994
Boiling Point, o C 275.4 @ 760 mmHg Ahrens, 1994 Vapor Pressure, mmHg 0.000144 @ 25 oC Ahrens, 1994 Aqueous Solubility, mg/L 1100 @ 25 oC Ahrens, 1994

Octanol-Water Partition Coefficient (K ow ) 350 (Log K OW = 2.54) Ahrens, 1994

Henry’s Law constant 4.13 E-5 atm-m 3 /mol Calculated from vapor pressure and solubility

Table 4 Environmental Fate Properties of Clomazone

Input Parameter Value Source/comment Molecular weight 239.70 Vapor pressure 1.44E-4 mm Hg Ahrens, 1994 (Herbicide Handbook, WSSA, 7th ed.) Solubility in water 1100 mg/L Ahrens, 1994 Hydrolysis half-life St able at pH 5, 7, 9 Acc. No. 248476, ref. 29 Aqueous Photolysis half-l ife 87 days Acc. No. 073672
Aerobic Soil metabolism half-life 80 days (90% UCL on mean of 35, 65, 74 days) Acc. No. 248476, ref. 30

Anaerobic aquatic metabolism halflife 44 days for total system MRID 44348403Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 15 Input Parameter Value Source/comment Aerobic Aquatic metabolism half-life 79 days (90% UCL on mean of 75, 64, 40.3 days) MRID 44348404, 44348405

Organic carbon normalized soil partition coefficient K oc 300 Ahrens, 1994

Henry’s Law Constant 4.13E-5 atm-m3/mol Calculated from vapor pressure and solubility
Air Diffusion Coefficient 3802 cm 2 /day Calculated from molecular weight, Da = 1.55/((MW) 0.65 ) (Schwarzenbach, Gs chwend, Imboden, 1993, page 195) Enthalpy of Vaporization 20 kJ/mol PRZM default value



### Clomazone is a semi-volatile compound of low to high persistence (half-lives 13 to 173 days in various compartments) and moderate mobility in soil (FAO Koc range 100 to 1000). Reported incidents of vol atilization from soil and vapor-phase transport to off-site receptors
indicate that this rout e is the primary exposur e route of concern. An estimated atmospheric half-life of 0.487 days (EPISuite, AOP v1.91) indicat es that long-range (g lobal) transport is
not of concern. Volatilization from water is of less concern than from soil, as indicated by the Henry’s law constant.

Based on laboratory data submitted to EPA by th e registrant, the following input parameters
for the linked PRZM and EXAMS models were chosen in accordance with the February 2002 Input Parameter Guidance 15



### .

Table 5 PRZM/EXAMS Modeling Input Parameters

Input Parameter Value Source/comment Molecular weight 239.70 Vapor pressure 1.44E-4 mm Hg Ahrens, 1994 (Herbicide Handbook, WSSA, 7th ed.) Solubility in water 1100 mg/L Ahrens, 1994 Hydrolysis half-life St able at pH 5, 7, 9 Acc. No. 248476, ref. 29 Aqueous Photolysis half-l ife 87 days Acc. No. 073672
Aerobic Soil metabolism half-life 80 days (90% UCL on mean of 35, 65, 74 days) Acc. No. 248476, ref. 30

Anaerobic aquatic metabolism halflife 44 days for total system MRID 44348403

Aerobic Aquatic metabolism half-life 79 days (90% UCL on mean of 75, 64, 40.3 days) MRID 44348404, 44348405

Organic carbon normalized soil partition coefficient Koc 300 Ahrens, 1994

Henry’s Law Constant 4.13E-5 atm-m 3 /mol Calculated from vapor pressure and solubility

15 Available for download at http://www.epa.gov /oppefed1/models/water /input_guidance2_28_02.htmChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 16 Input Parameter Value Source/comment
Air Diffusion Coefficient 3802 cm 2 /day Calculated from molecular weight, Da = 1.55/((MW) 0.65 ) (Schwarzenbach, Gschwend, Imboden, 1993, p. 195) Enthalpy of Vaporization 20 kJ/mol PRZM default value Chemical Application Method 1 (so il applied, default incorporation depth 4 cm) Spray Drift 1% for ground applicati on Guidance for ground applications Application Efficiency 99% Guidance for soil applications without incorporation



### The following exposures were returned by PR ZM-EXAMS. These are 1-in-10 year peak exposures, and are given both with the PRZM vol atilization routine “o n” and “off.” This routine has not yet been subjec ted to full quality assurance, however both figures are given for characterization purposes, to account fo r the known volatility of clomazone. The
volatilization routine in PRZM is invoked by entering values for the diffusion coefficient in air and the enthalpy of vaporization. These pa rameters describe the ability of the vaporphase molecule to diffuse in air, and the amount of energy required to transfer the molecule from the liquid to the gas phase . Volatilization in EXAMS is invoked by entering a value for the Henry’s Law constant.

Table 6 Screening Exposure Analysis: PRZM/EXAMS Standing Water Body

1-in-10 year peak daily, ppb Without/With Volatilization 1-in-10 year, peak 21-day average, ppb Without/With Volatilization 1-in-10 year, peak 60- day average, ppb

Without/With Volatilization PRZM Scenario (standard unless noted)

Without With Without With Without With Florida sugarcane 36.4 23.2 18.8 13.5 9.1 6.4 Louisiana sugarcane 25.0 23.2 16.3 14.9 8.6 7.4 Mississippi cotton 29.3 16.0 17.9 8.9 8.9 5.2 North Carolina cotton 17.1 11.3 11.2 7.1 6.0 3.7 Florida peppers 29.0 12.8 14.5 7.1 7.4 3.2 Mississippi soybeans 19.4 12.3 12.3 8.3 6.0 4.4 North Carolina sweet potato 13.2 8.2 8.2 4.5 4.1 2.2 North Carolina tobacco 6.5 2.7 3.3 1.5 1.5 0.74 Florida potato (NMC) 1 28.3 12.4 14.3 6.9 6.6 3.1 Michigan bean 5.5 2.9 3.4 1.6 1.7 0.88 Oregon snap beans 3.2 2.1 1.8 1.4 0.98 0.66 Florida cabbage 6.8 3.7 3.2 1.7 1.8 0.73 Florida cucumber, 1.0 lb/A 41.1 20.2 18.9 8.8 8.1 4.0 Florida cucumber, 0.75 lb/A 31.6 15.1 14.6 6.6 6.3 3.0 Florida cucumber, 0.5 lb/A 20.5 10.1 9.5 4.4 4.1 2.0 Florida cucumber, 0.25 lb/A 10.3 5.0 4.7 2.2 2.0 1.0 Oregon mint 1.6 0.82 0.96 0.51 0.51 0.29 (1) NMC: scenario developed for N-methyl carbamate cumulative assessment. This Florida potato scenario was used as a surrogate for tropical tuber crop s such as yautia, tanier, cassava, and arracacia.Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 17 

### 2.1.2 Screening Anal ysis – Rice Uses

2.1.2.1 W ET S EEDED R ICE 

### The Tier 1 Rice model (EPA, May, 2007) 16 

### calculates the water-column exposure expected on the day of application to a flooded rice pa ddy, accounting only for sorption to sediment as a dissipation process. No other degradation processes, such as hydr olysis, photolysis, or metabolism, or dissipation process such as vol atilization, are consider ed. The resulting EECs are therefore expected to be conservative. Using inputs of Koc = 139 ml/g, and an application rate of 0.6 lb/acre (0.672 kg/hectare), the Tier 1 Ri ce model predicts an exposure
of 546 μ g/L (ppb), if paddy water were to be rele ased on the day of application. However, the wet seeded rice label (USEPA 279-3269) ha s a requirement to hold and not release water from the rice field for a minimum of 14 days, unless the water is contained in a tailwater recovery system or other system appropriate for preventing discharge from the rice fields.
An estimate of the clomazone concentration at 14 days post-applic ation is obtained by decaying the day of application concentra tion at a half-life of 23.7 days (MRID 45720601,
California wet-seeded rice fiel d dissipation study). An Austra lian study had a half-life of 7 days, which is a faster dissipation rate. The re levant fate studies (a erobic aquatic 79 days, anaerobic aquatic 44 days, and aqueous photolysis 87 days) combine to give a half-life of 21 days, which support the use of a longer half-life of 23.7 as a reasonable dissipation rate to use. The Australian study pot entially reflects different e nvironmental conditions. The exposure concentration predicted is 352 ppb on day 15 post-application using a 23.7 day
half-life. 17

2.1.2.2 D RY S EEDED R ICE 

### Clomazone used in dry-seeded rice culture is subject to dissipation by terrestrial processes (volatilization and aer obic metabolism) before flooding, so paddy water concentrations are expected to be lower than for wet-seeded rice ( i.e ., clomazone applied directly to water). For dry seeded rice, clomazone is applied around 14 days before rice is planted, and the earliest that permanent flood would occur is 2 week s (21 days) after planting (Sunil Ratnayke, Biological Analysis Branch, 11/06/2008 Use of Clomazone in Rice Production (DP# 336342). If we assume that only soil metabolis m is happening, the half-life of clomazone will be 80 days (this is the upper 90th percen tile of three values). Aerobic aquatic
metabolism has a similar half-life value of 79 days, and photolysis 87 days. The anaerobic aquatic half-life is 44 days. So, conservati vely assuming that volat ilization does not happen,

16 http://www.epa.gov/oppefed1/models/water/index.htm#rice
17 ppb 352 ) 15 ( * ) 0292

. 0 ( ppb 546 ln ln ln 0 = − = − = days kt C C t where C 0 is the initial concentration, 0.0292 is
the first-order rate constant, and C t is the concentration on day tChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 18 

### and the only process is aerobic soil (or aquatic) metabolism, the decay rate is ln(2)/80 = 0.0087/day for clomazone applied to the rice field. After 35 days, C = (0.6 lb ai/acre) x

e (0.0087 x 35) 

### = 0.44 lbs ai/acre. Feeding this remaining load into the Tier 1 Rice Model, a result about 4/6 (or 2/3) as large as what is estimated for the initia l concentration for wet-seeded rice is estimated, 364 ppb. Addition of other pr ocesses (photolysis, volatilization, etc) would all make the result smaller. A rigorous trea tment of this exposure route would in all likelihood give us a result somewhere in the range of results for the rice field studies discussed in the following paragraphs.

An aquatic field dissipation study (MRID 44348406) was conducted in rice fields in Arkansas and Texas at an application rate of 0.6 lb ai per acre. This corresponds to an expected concentration of 1,015 μ g/kg in the top 2 inches of soil or 338 μ g/kg in the top 6
inches 18



### .
In the Arkansas field study the initial concentration in the top 6 inches was 292 μ g/kg, or 86.4% of expected. This fell to 21 μ g/kg, or 7% of the initial by day 29. On day 30 (day of flooding), the concentration in the top 2 inches was 166 μ g/kg, or 16.4% of the expected 1,105 μ g/kg from day 1. Thus, there appeared to be more desorption of clomazone from the wet soil (day 30) than from the dry soil (day 29). By days 180-269, the soil concentration
was 12 to 17.6 μ g/kg. Parent clomazone was not dete cted in the floodwater above 5 ppb.

A similar pattern was seen in the Texas study. On day 0, the 6-inch soil concentration was
203 μ g/kg, or 60% of expected (338 μ g/kg). By day 29, this had fallen to 73 μ g/kg, or 21.6% of the expected initial concen tration. Upon flooding (day 30), the 2-inch soil concentration
was 140 μ g/kg, or 13.8% of the ex pected initial (1,015 μ g/kg). The soil concentration fell to
11 to 16 μ g/kg at 128 to 369 days post-treatment. Pa rent clomazone was not detected in the floodwater above 7 ppb.

Overall, it appears that aquatic exposure from paddy water releas ed from dry-seeded rice will be substantially lower than from wet-seeded rice.

18

column soil the of inches upper the in ion concentrat the is C and depth, soil the is D rate, n applicatio the is AR where mg/kg 015

. 1 inches 2 1
1300

1

m 102.79 inch

- acre 1
lb 1 mg 592
, 453 ai/acre lb 6

. 0 inches 1
1300

1

m 102.79 inch

- acre 1
lb 1 mg 592
, 453 ai/acre lb
, mg/kg
,

D 3

3 3

3

D kg m D kg m AR C D

= × × × × = × × × × =Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 19 

### 2.1.3 Aquatic Rice Field Studies

Based on the information discussed below, the Ti er 1 Rice model for wet seeded rice on day of application (Section 2.1.2) represents a highest expected exposure from labeled use.

Aquatic Field Dissipation Studies
A supplemental study (MRID 45720601) conducted in California on wet-seeded rice at the maximum label rate (0.6 lb ai/acre) yielde d a maximum water concentration of 237 ppb parent. The residues declined with a half-life of 23.7 days in the total sediment-water system. This study was used in the provision al modification of the Tier 1 rice model.

An acceptable study (MRID 44348406) conducted in Ar kansas and Texas on dry-seeded rice focused mainly on soil dissipation. Concentrat ions in water (5-7 ppb) were low because terrestrial dissipation processes (metabolism and volatilization) were active for 29 days before flooding.

Literature Studies: Rice Agriculture
There are also published studies that measured concentrations in both rice paddies and in receiving waters. These studies are from Arkansas (Mattice et al ., 2005), Australia (Quayle, 2005), and Brazil (Zanella, et al ., 2002; Marchesan et al ., 2007). These studies demonstrate that the Tier 1 Rice model result (546 ppb) gi ves a reasonable exposure estimate, compared to measured values, and that exposures in rece iving waters (up to 30 ppb) are lower than in rice fields, but persist over a period of weeks.

Mattice et al . (2005) measured rice pesticides (C lomazone, Imazethapyr, Molinate, Quinclorac, and Triclopyr) in Arkansas, at f our sites each on the L’Anguille and St. Francis
rivers from near Jonesboro in the north to Ma rianna in the south, ove r a period of six years (2000-2005). In 2002, four sites on Lagrue Bay ou from just below Peckerwood Lake north of Stuttgart to near the bayou’s mouth south east of DeWitt were added. In 2003, four sites
on the Cache River from near Jone sboro in the north to just be low Interstate 40 in the south
were added.

The authors presented all detections from th e 2005 sampling campaign, from April 27 to July 5. Clomazone and Quinclorac were the most commonly detected rice pesticide. Clomazone was detected in the Cache River on five samp ling dates from April 27 to June 21, with a maximum concentration of 28 ppb. It was al so detected on four sampling dates on the L’Anguille River, with a maximum concentrat ion of 25 ppb. Figure 1 and Figure 2 illustrate the data for these two rivers, respectively. Th e application rates that led to these exposures are unknown, but are not expected to have exceeded label rates.Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 20 Figure 1 Clomazone Concentration (ppb) at Three Sites on Cache River Arkansas, 2005

0 5 10 15 20 25 30

22-Apr 2-May 12-May 22-May 1-Jun 11-Jun 21-Jun 1-Jul

dateppb clomazoneChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 21 Figure 2 Clomazone Concentration (ppb) at Four Sites on L’Anguille River, Arkansas, 2005

0 5 10 15 20 25

7-May 12-May 17-May 22-May 27-May 1-Jun 6-Jun 11-Jun 16-Jun 21-Jun 26-Jun

dateppb clomazone



### In an Australian study of rice pesticides in New South Wales (Quayle, 2005), the fate of
clomazone in flooded rice fields was determ ined. In 2002, clomazone (MagisterTM, 450 g ai/liter) was applied at 0.5 lit er/hectare (225 g/hectare) and th e concentration in water was followed for 60 days. The peak concentration in water was 202 ppb, and it declined to less than 1 ppb over the 60 days. The exposure pr edicted by the Tier 1 Rice model for this application rate is 183 ppb. The difference is sm all, and indicates that the Tier 1 Rice model is accurate for clomazone day-1 exposure. The reported half-life in water was 7.2 days (95% confidence interval 5.8 to 9.7 days). The tim e required for clomazone to decline to a “nominal level” of 3 ppb was calculated as 14 days.

Two studies from Brazil (Zanella, et al ., 2002; Marchesan et al ., 2007) examined clomazone residues in rice paddies and su rrounding watersheds. Zanella et al . (2002) measured
clomazone concentrations in four Brazilian rive rs, and in two experimental rice paddies. The rice paddy experiments were conducted in Dece mber, 1999, and December, 2000, at a rate of 0.50 kg/hectare “formulated material.” The rate in kg active ingredient per hectare was not stated, thus a Tier 1 Rice model calculation is not possible. The maximum concentrationsChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 22 

### observed were 505 ppb and 377 ppb in 1999 and 2000, re spectively. These results are in the same order as the Tier 1 Rice model result ( 546 ppb), indicating the su itability of the model for use in estimating clomazone exposures Concentrations in river water were as high as 1.72 ppb in the Ibicuí River.

Marchesan (2007) studied the concentrations of three rice herbicides (c lomazone, quinclorac, and propanil) in the Vacacaí and Vacacaí-Mir im river basins from 2000 to 2003. The two basins have a total drainage area of 11,136 square kilometers, and 85,000 hectares is used to cultivate irrigated rice. During the study, 50 to 60% of the rice acres were treated with a tank mix of clomazone and propanil in post emergence, at rates of 350 and 1800 g/hectare, respectively. In the Vacacaí River, clomazone was detected at up to 8.85 ppb. Detection rates for clomazone were high (11 – 30% of samples), again indicating its persistence in receiving waters.

Table 7 Summary of Marchesan et al. (2007) Clomazone Monitoring Results in Brazil

Years Total No. Samples % Positive Minimum ppb Average ppb Maximum ppb

Vacacaí River
2001-2 36 30 1.32 4.09 7.72
2002-3 30 20 1.50 4.97 8.85
Vacacaí-Mirim River
2000-1 104 27 0.41 1.34 5.62
2001-2 45 11 1.24 2.38 4.82
2002-3 45 20 0.62 2.17 5.10



### 2.1.4 Volatilization: Transport and Exposure
A recent paper by Yang and Holmén (in press) m easured the effect of surfactant content, Henry’s Law constant, and rela tive humidity on the volatiliz ation of seven herbicides (alachlor, butachlor, metolachlor, propachlor, pendimethalin, prodiamine, and trifluralin) from two soils (a CT sandy clay loam with 1.68% organic carbon, and a NM clay loam with 0.73% o.c.). The authors conclude d that relative humidity ha d the greatest influence on volatilization (50% of varian ce), followed by Henry’s Law constant (8.4 to 28.5% of variance), and then surfactant content (1.4%). The equation describing the behavior of all
seven chemicals on both soils is:

4 3 2 1 48 

### log b K b RH b S b F H 

### + + + =

where F 48 

### is the fractional amount volat ilized in the first 48 hours, S is the fractional surfactant amount in the formulation, RH is the fractional relative humidity, KH is theChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 23 

### Henry’s Law constant (Pa•m 3 

### /mol), and the coefficients are b 1 

### = 0.42, b 2 

### = 0.78, b 3 

### = 0.07,
and b 4 

### = 0.04.

Provisional application of th is equation to clomazone ( KH = 0.0042 Pa•m 3 

### /mol, log KH = - 2.38) with the surfactant content S set to 0.0 for the microencapsulated formulation, indicates
that at 100% RH , 65% of the applied amount would volatil ize in the first 48 hours. At 50%
RH , 26% volatilization is predicted, and at 25% RH , 6.9% volatilization is predicted.

While the quantitative application of the Yang and Holmén equation to clomazone is uncertain and applied provisionally in this assessment, the physical mechanism is appropriate, and its vapor pressu re falls in the same range as the studied herbicides (log KH

= -3.07 to +1.02). The predicted amount of cl omazone volatilized (65% at 100% relative humidity) is consistent with the observed seve rity and distance of reported incidents, and
their association with ra infall or high humidity.

The mechanism of exposure described by this process is (1) displacement of clomazone sorbed to soil by the action of water vapor; (2) diffusion of vapor-phase clomazone to the soil surface; (3) transport of clomazone vapors to o ff-target sites by wind, and (4) redeposition of clomazone vapors to water or terrestrial surfaces.

Wetland Exposure Due to Volatilization Alone
The exposure of aquatic organisms in wetlands n ear use areas, due to volatilization alone, was estimated. This is a provi sional calculation for use with clomazone, and has not been evaluated by the appropriate EFED tech team fo r routine use in OPP risk assessments. As a screening estimate of exposure levels, 65% of the applied amount was assumed to volatilize, and subsequently be deposited in the AgDrift defined wetland 19 

### . It is not likely that the full amount volatilized would be transported to a wetl and of this size; the ca lculation is done only as a screening exercise. For purposes of this calculation, the Tier 1 AgDrift model was used to deliver 65% of the maximum application rate (1.5 lb/A) to the wetl and; the spray drift features of the model were not used. (In th e Aquatic Assessment window, a value for the application rate and a value for the Initial Av erage Deposition (Fracti on of Applied =0.65) were entered to simulate deposition of the fu ll 65% volatilized clomaz one to the wetland).
The result of this model run was an initial average concentration of 728 ppb.

19 208.7 feet wide and about 6 inches deepChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 24 

## 2.2 Terrestrial Exposure

2.2.1 Dietary-Based and Dose-B ased Clomazone Residue Levels

2.2.1.1 O N -F IELD



### Results of the TREX v3.1 mode ling of clomazone residue leve ls on those dietary food items which potentially occur on some treated fields, for mammals and birds 20 

### are provided in Table 8 through Table 10. Results in clude both dietary-based values ( i.e ., milligrams of clomazone per kilogram of diet (m g/kg-diet)) and dose-based values ( i.e ., milligrams of clomazone per kilogram of body weight of th e exposed animal (mg/kg-bw)), and both an upper-bound and mean estimate of these expos ure levels. The upper-bound values are derived using the upper-bound Kenaga nomogram which used the highest of the highest
normalized residue values from a number of studi es, as a tolerance limit approach. The mean Kenaga value is based on the average of th e highest normalized residue values from a number of studies, as modified by Fletcher et al . 1994.

Only residues predicted from the clomazone use with the highest application rate, sweet potatoes, were modeled both as a broadcast application (1.5 lbs a i/A), and as a banded application (equivalent rate of 3.0 lbs ai/A in band) 21 

### as a screening assessment. Additional modeling of residue levels on dietary items conducted as a refinement are presented and
discussed in the Risk Char acterization Section 4.2.1.1. Fo r sweet potatoes a maximum distance between rows of 48 inches, which results in a minimum linear row area of 10,900 feet per acre, and the assumpti on that the size of the band was half of the row distance (24 inches or 2 feet) were used as conservative input s to translate the broadcast label rate in lbs ai/A to an equivalent lbs ai/A within the band 21 

### for exposure input into TREX v3.1. For the foliar half-life input, the defau lt value of 35 days was used because all registered clomazone uses are limited to a single appl ication in a given year resultin g in the highest residue levels occurring at time of applicati on, therefore foliar half-life is not considered in the EEC
estimate.

20 Birds are also used as a surrogate for reptiles and terrestrial-phase amphibians.

21 

### ( ) ( )( ) 

## ( )
( ) ( )( ) 

## ( ) ai/A lbs 0

. 3 /A ft 560
, 43 ft/A linear 10,900 ft 2 ai/A lbs 5

. 1 /A ft 560
, 43 ft/A linear ft width, row treated ai/A lb
, Rate n Applicatio Broadcast Label band on rate ai/A lb Equivalent

2 2

= = =Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 25 Table 8 Dietary-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, and for Both a Broadcast and a Banded Treatment

Dietary-based EECs (ppm)

Broadcast Banded Dietary Item
Upper Bound Mean Upper Bound Mean

Short Grass 360 128 720 255
Tall Grass 165 54.0 330 108 Broadleaf plants/sm Insects 202 67.5 405 135 Fruits/pods/seeds/lg insects 22.5 10.5 45 21

Table 9 Avian Dose-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, as a Banded Application Treatment

Dose-based EECs (mg/kg-bw) Upper-Bound Mean for Birds of Body Weight: for Birds of Body Weight: Dietary Items

20 g 100 g 1000 g 20 g 100 g 1000 g
Short Grass 820 468 209 291 166 74.0
Tall Grass 376 214 96.0 123 70.2 31.3 Broadleaf plants/sm Insects 461 263 118 154 87.8 39.2 Fruits/pods/seeds/lg insects 51 29.2 13.1 23.9 13.6 6.09

Table 10 Mammalian Dose-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, as a Banded Application Treatment

Dose-based EECs (mgt/kg-bw) Upper Bound Mean for Mammals of Body Weight: for Mammals of Body Weight: Functional Feeding Group Dietary Item
15 g 35 g 1000 g 15 g 35 g 1000 g
Herbivores/Insectivores Short Grass 686 474 110 242 168 38.3
Tall Grass 315 217 50.4 103 71.3 16.2 Broadleaf plants/sm Insects 386 267 61.9 128 89.1 20.3 Fruits/pods/seeds/lg inse cts 42.9 29.7 6.9 20.0 13.9 3.15

Granivores Seeds 9.53 6.59 1.53 4.41 3.15 0.63Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 26 Table 11 Mammalian Dose-Based Clomazone EEC Values for the Highest Application Rate Crop, Sweet Potatoes, as a Broadcast Treatment

Dose-based EECs (mg/kg-bw) Upper-Bound Mean for Mammals of Body Weight: for Mammals of Body Weight: Functional Feeding Group Dietary Items
15 g 35 g 1000 g 15 g 35 g 1000 g
Herbivores/Insectivores
Short Grass 343 237 55 121 84.2 19.1
Tall Grass 157 109 25.2 51.3 35.6 8.1 Broadleaf plants/sm Insects 193 133 30.9 64.1 44.6 10.1 Fruits/pods/seeds/lg inse cts 21.5 14.8 3.44 9.98 6.93 1.58
Granivores Seeds 4.77 3.29 0.764 2.20 1.56 0.315



### An analysis of the available formulation acute oral toxicity data compared to data for the target grade active ingredient (TGAI) indicate that the Commence EC formulation, a multiple active ingredient mixture (clomazone and trif luralin), may be more toxic to terrestrial wildlife than indicated by the TGAI (Appe ndix D). Under these circumstances, a quantitative evaluation of exposure to the Commence EC formulation for mammals was considered. Exposure modeling in this instan ce was limited to dietary exposure to residues for a time period immediately following pe sticide product application based on the expectation that the varying physical-chemical properties of the individual components of a formulation will result in progressively diffe rent formulation constituents in the exposure
media over time and was limited to mammals becau se there is no avian formulation toxicity data to quantitatively assess risk to avian wildlife. The use of TGAI results appears appropriate for other formulati ons. Commence EC is registered for only two uses, cotton and soybeans. Modeled acute dose-based upper-bo und and average EEC values for mammals for these crops under banded applic ation (6.33 lbs formulation/A 22 

### ) are provided in Table 12,
where it is assumed that the ba nded application rate is equiva lent to twice that of the
broadcast rate.

22 5

. 9
n formulatio lb 1 clomazone lbs 218

. 0 gal clomazone/ lbs 07

. 2 (lbs/gal) Weight n Formulatio = =


### ( ) 167

. 3 pts/gal 8 pts/acre /3 8 n/gal formulatio lbs 5

. 9 (lbs/acre) Rate n Applicatio Broadcast n Formulatio = ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

= ; equivalent

banded rate is 6.33 lbs formulation/acreChapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 27 Table 12 Mammalian Dose-Based Commence EC Formulation EEC Values for Cotton and Soybeans t Potatoes, as a Banded Treatment

Dose-based EECs (mg/kg-bw) Upper-Bound Mean for Mammals of Body Weight: for Mammals of Body Weight: Functional Feeding Group Dietary Items
15 g 35 g 1000 g 15 g 35 g 1000 g
Herbivores/Insectivores
Short Grass 1448 1001 232 511 355 80.7
Tall Grass 664 459 106 216 150 34.2 Broadleaf plants/sm insects 815 563 131 271 188 42.7 Fruits/pods/seeds/lg inse cts 90.5 62.6 14.5 42.1 29.2 6.65
Granivores Seeds 20.1 13.9 3.22 9.31 6.65 1.33



### As birds are also used as a su rrogate for reptiles and terrestr ial-phase amphibians within this assessment, it is assumed that dose-based exposur e levels for these animals are the same as birds ( i.e ., food ingestion rate per body weight for a bi rd is the same as for an amphibian and reptile). However, reptiles and amphibians have a lower ingestion rate for a given body weight than birds (USEPA 1993). Therefore, the dose-based EECs presented here represent an overestimate of exposure for reptil es and amphibians of a given body size.

2.2.1.2 S PRAY -D RIFT 

### Not all dietary items will necessarily be presen t on a field at the time of treatment, for example, some uses of clomazone are applied afte r the field has been tilled in preparation for planting which would mean that dietary items such as short grass, tall grass, broadleaf plants, fruits and pods would not be present on the fi eld. However, as clomazone is applied as a ground spray for all registered uses except rice, which also includes aerial applications, there is the potential for residues on dietary items to occur off the treated field due to spray-drift, and in this case, the potential exists for all thes e dietary items to be present. Therefore, the on-field estimates of exposure provided in Section 2.2.1.1 are also used to screen for residue levels that potentially pose a problem off a treated field due to spray drif t. It is recognized that these estimates are an overestimate of expos ure levels off the treated field. To address this concern, modeling of how fa r off a treated field residue le vels would exceed LOC values was conducted as part of the refinement of risk in the Risk Characte rization (Section 4.2.1.1). Where the presence/absence of a dietary item on the treatment site makes a difference in the conclusion about risk from clomazone, this is also discussed in the Risk Characterization.Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 28 2.2.1.3 V OLATILIZATION 

### Residues on dietary items in ar eas near a treated field due to volatilization alone were estimated for the highest application rate crop, sweet potatoes. As the total mass applied on a per acre basis is the same for broadcast a nd banded applications, onl y the 1.5 lbs ai/A was modeled. A screening estimate of this e xposure was obtained by a ssuming that 65% of applied clomazone per acre woul d volatilize under 100% humidity as discussed in Section 2.1.4 and be deposited on one acre off site. As previously noted, this is a provisional model approach that has not been fully evaluated for use routinely in OPP risk assessments. Results of the TREX v3.1 modeling of re sidue levels on dietary food items for mammals and birds due to volatilization are provide d in Table 13 through Table 15. Results include both dietarybased values ( i.e ., mg/kg-diet) and dose-based values ( i.e ., mg/kg-bw), and both an upperbound and mean estimate of these exposure levels.

Table 13 Dietary-Based Clomazone EEC Values Due to Volatilization for the Highest Application Rate Crop, Sweet Potato at 1.5 lbs ai/A

Dietary-based EECs (ppm) Dietary Item Upper Bound Mean
Short Grass 234 82.9
Tall Grass 107 35.1 Broadleaf plants/sm Insects 132 43.9 Fruits/pods/seeds/lg insects 14.6 6.83

Table 14 Avian Dose-Based Clomazone EEC Values Due to Volatilization for the Highest Application Rate Crop, Sweet Potatoes at 1.5 lbs ai/A

Dose-based EECs (mg/kg-bw) Upper-Bound Mean for Birds of Body Weight: for Birds of Body Weight: Dietary Items

20 g 100 g 1000 g 20 g 100 g 1000 g
Short Grass 267 152 68.0 94.5 53.9 24.0
Tall Grass 122 69.7 31.2 40.0 22.8 10.2 Broadleaf plants/sm Insect s 150 85.5 38.3 50.0 28.5 12.7 Fruits/pods/seeds/lg insect s 16.7 9.50 4.25 7.78 4.44 1.98Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 29 Table 15 Mammalian Dose-Based Clomazone EEC Values Due to Volatilization for the Highest Application Rate Crop, Sweet Potatoes at 1.5 lbs ai/A

Dose-based EECs (mg/kg-bw) Upper-Bound Mean for Mammals of Body Weight: for Mammals of Body Weight: Functional Feeding Group Dietary Items
15 g 35 g 1000 g 15 g 35 g 1000 g
Herbivores/Insectivores
Short Grass 223 154 35.8 78.7 54.7 12.4
Tall Grass 102 70.7 16.4 33.3 23.2 5.27 Broadleaf plants/sm Insects 125 86.7 20.1 41.7 29.0 6.58 Fruits/pods/seeds/lg inse cts 13.9 9.64 2.23 6.48 4.50 1.02
Granivores Seeds 3.10 2.14 0.497 1.43 1.02 0.205



### 2.2.2 Off-Field Terrestrial and Wetland/Riparian Plant Clomazone Exposure
Levels

2.2.2.1 R UNOFF AND S PRAY D RIFT L OADING 

### Estimated clomazone exposure levels for non-targ et plants in terres trial and semi-aquatic areas in areas adjacent to a treated field ar e provided in Table 16. Exposure levels were estimated by calculating clomazone soil loading on a lb ai/acre basis from runoff and spray drift and by calculating foliar resi dues on a lb ai/acre basis from spray drift using TerrPlant v1.2.2. Input values for TerrPlant v1.2.2 modeling are listed in Table 17. Registered uses modeled include use on sweet pot atoes at the maximum broadcas t application rate of 1.5 lbs
ai/A 23 

### and use on succulent beans at its maximum broadcast application rate of 0.251 lbs ai/A by ground spray. These uses represent the upper and lower application rate range for ME formulations. In addition, estimated exposure due to spray drift from aerial applications for rice, which is the only ME use registered for application by air, was modeled. Exposure and associated risk for the other register ed uses will fall between these EECs.

The equations used in TerrPlant v1.2.2 to m odel loading EECs to non-target plants in terrestrial and semi-aquatic areas are shown in Table 16. Runoff is assumed to move to a one acre parcel from one acre of treated area fo r the dry upland model and from 10 acres of treated area for the low-lying semi-aquatic model.

23 While the application rate within a band when band applied is higher than 1.5 lbs a.i./A, the total mass applied per acre is equivalent to the broadcast rate.Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 30 Table 16 Estimated Clomazone Loading to Off-Site Terrestrial and Semi-Aquatic Areas Adjacent to a Treated Field for Ground Spray Applications at the Upper and Lower Maximum Application Rate Range

EEC (lbs ai/A)
Ground Spray Aerial Spray Loading Equation Application Rate of 1.5 lbs ai/A Application Rate of 0.251 lbs ai/A Application Rate of 0.6 lbs ai/A to rice Runoff to dry areas ( A/I )* R 0.075 0.0126 N/A Runoff to semi-aquatic areas ( A/I )* R *10 0.750 0.126 N/A Spray drift A * D 0.015 0.0025 0.030 Total for dry areas (( A/I )* R )+( A * D ) 0.090 0.0151 N/A Total for semi-aquatic areas (( A/I )* R *10)+( A * D ) 0.765 0.128 N/A N/A = not applicable be cause rice fields are assumed to have berms around the field which typically prevents runoff.

Table 17 Input Parameters for TerrPlant v1.2.2 Used for Modeling Runoff and Spray Drift Loading to Off-Field Terrestrial And Semi-Aquatic Areas Adjacent to a Treated Field

Input Parameter Symbol Value Units Basis Application Rate A 1.5 for sweet potatoes 0.251 for succulent beans 0.6 for rice lbs ai/A Registered label maximum application
range

Incorporation depth I 1 inch Default value when there is not explicit incorporation on the label Runoff Fraction R 0.05 none Model guidance value when solubility of pesticide is >100 ppm (clomazone solubility is 1,100 ppm) Drift Fraction D 0.01 for ground spray 0.05 for aerial spray none Model guidance values for ground spray and aerial spray applications

2.2.2.2 V OLATILIZATION L OADING 

### An estimate of maximum exposure was obt ained by assuming that 65% of applied clomazone per acre would volat ilize under 100% humidity as di scussed in Section 2.1.4 and be deposited on one acre off site 24 

### . Estimated loading to non-targ et plants in terrestrial or semi-aquatic areas near use areas, due to loading from volatilization alone, is contained in Table 18 for use on sweet potatoes and for use on succulent beans. The sweet potato and succulent bean uses represent the upper and lo wer label application range, respectively, of clomazone. As the total mass applied on a per acre basis is the same for broadcast and banded applications, only the broadcast lbs ai/A were modeled for these uses.

24 Volatilization Loading, lb a.i./A = (Broadcast Loading, lb a.i./A)(0.65) = (1.5)(0. 65) = 0.975 lb a.i./A for sweet potato and (0.251)(0.65) = 0.163 lb a.i./A for succulent beans.Chapter 2 Exposure Assessment

Registration Review Ecological Risk Assessment Clomazone 31 Table 18 Off-Site Loading Due to Volatilization Based on Relative Humidity

Off-site lbs ai/A Due to Volatilization at Relative Humidity of:

100% 1 50% 2 25% 3
Sweet potato, 1.5 lbs ai/A 0.975 0.39 0.104 Succulent beans, 0.251 lbs ai/A 0.163 0.065 0.017 1 65% of applied volatilizes in the first 48 hours at 100% humidity from Section 2.1.4 2 26% of applied volatilizes in the first 48 hours at 50% humidity from Section 2.1.4 3 6.9% of applied volatilizes in the firs t 48 hours at 25% humidity from Section 2.1.4



### The preceding estimate approach does not cons ider the impact to volatilization due to formulation differences ( i.e ., EC and WP versus ME) or effect of soil incorporation. Limited information on the impact of formulation to th e rate of volatilization from soil has been submitted to the Agency, but it does not provi de a sound quantitative relationship which can
be used to model volatilization. The ME form is patented as reducing volatilization by 50% as compared to other formulations 25 

### . Assuming that the rate of volatilization discussed in Section 2.1.2 is reduced by 50% the loading due to volatilization for the ME formulation is provided in Table 18 for use on sweet potat oes and for use on succulent beans.

Table 19 Off-Site Loading Due to Volatilization Assuming 50% of Rate Based on Relative Humidity

Off-site lbs ai/A Due to Volatiliza tion at Relative Humidity of:
100% 1 50% 2 25% 3
Sweet potato, 1.5 lbs ai/A 0.488 0.195 0.052 Succulent beans, 0.251 lbs ai/A 0.082 0.033 0.009 1 32.5% of applied volatilizes in th e first 48 hours at 100% humidity (50% of 65% rate from Section 2.1.4). 2 13% of applied volatilizes in the first 48 hours at 50% humidity (50% of 26% from Section 2.1.4). 3 3.45% of applied volatilizes in th e first 48 hours at 25% humidity (50% of 6.9% from Section 2.1.4).

25 http://www.wipo.int/pctdb/en/wo.jsp?wo=2007101019&IA=US2007062456&DISPLAY=DESCChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 32 

# Chapter 3 Effects Characterization

A detailed summary of all available toxici ty data for clomazone, except mammalian data submitted to HED to support the human health risk assessment is provided in Appendix B and is based on registrant submitted data and on open literature study results for clomazone
that have been reviewed and found to be scien tifically sound. A comple te characterization of the mammalian toxicity data set is provided in Memo, Kidwell et al ., 2/13/01; D259635, and for clarity only a summary of the effects is pr ovided in Appendix B. No new toxicity data have been submitted by the registrant since the Clomazone Summary Document Registration Review: Initial Docket (EPA 2007). However, a dditional toxicity data incorporated from the public literature, changes in an alyses performed on seedling em ergence data, and corrections for percent active ingredient resulted in change s to some of the previously reported values. Clomazone results that were found in the open literature but which we re not used in the
assessment and the reasons for their exclusion are provided in Appendi x E. A summary of the clomazone toxicity data and the environmen tal levels at which effects are expected are described in this Chapter.



## 3.1 Terrestrial Vertebrate Toxicology

In mammals, the primary target organ for clomaz one in rat, mouse, and dog studies is the liver. It is not classified as a carcinogen or mutagen. Clomazone is rapidly absorbed from the digestive tract after oral administration a nd is then rapidly and extensively metabolized by the liver. It is excreted pr edominately in the urine with mo st being excreted within 24 to 48 hours post exposure, and almost 100% excreted by 7 days. Clomazone has a low potential for bioaccumulation as indicated by its high wa ter solubility, low octanol-water partitioning coefficient, and rapid metabolism.

Information is available on acute and chronic reproductive effects of clomazone in birds and
mammals. No information was available on e ffects of clomazone on reptiles or to the terrestrial-phase of amphibians. Effects and effect levels in bird s will be used as a surrogate for reptiles and the terrestrial-phase of am phibians in this assessment. Toxicological endpoints selected for terrestrial animal assessm ent endpoints are contained in Table 20. The dose-based mammalian reproduction value differs from that identified in the Clomazone Summary Document Registration Review: Initia l Docket (EPA 2007a); this difference is
discussed in detail in Section 3.1.2. An analysis of acute toxi city effects of the TGAI as compared to available formulation effect s data (Appendix D), found that except for
Commence EC use of the TGAI results to assess effects appear approp riate. Commence ECChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 33 

### appears to be more toxic to terrestrial wild life than indicated by active ingredient effects testing. A quantitative analysis of acute diet ary exposure to Commence EC was included in
the assessment and the Commen ce EC mammalian acute oral t oxicity value and body weight adjusted values are also included in Ta ble 20 along with the TGAI effects data.

Table 20 Summary of Specific Measurement Endpoint Values Selected to Calculate RQ Values to Evaluate Risk for Birds and Mammal Assessment Endpoints

Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint and Effect(s) Source / Study Classification

Survival and Reproduction of Birds, Reptiles and Amphibians Acute mortality: most sensitive avian acute oral toxicity, LD 50 (single-dose) Mallard duck ( Anas platyrhynchos ) LD 50 >2,230 mg ai/kg-bw (14-d post exposure observation)

No mortality or behavior effects occurred at highest dose tested Acc # 248475 Beavers et al.
, 1982 /

Acceptable Mortality: most sensitive subacute avian LC 50 Bobwhite quail ( Colinus virginianus ) and Mallard duck ( A. platyrhynchos ) 8-d LC 50 > 4,990 mg ai/kg-diet (ppm ai) (8-d = 5 day exposure plus 3 day post exposure)

No mortality, behavioral effects, or significant growth effects occurred at the highest dose tested

Extrapolated values* 8-d LC 50 = 9, 731 ppm ai if probit slope =4.5 8-d LC 50 = 22,940 ppm ai if probit slope =2 8-d LC 50 = 6,905 ppm ai if probit slope =9 Acc # 248475 Beavers et al
., 1982 /

Acceptable

Reproduction: most sensitive avian reproductive NOAEC Bobwhite quail ( C. virginianus ) 20 week Offspring and paternal NOAEC > 1,020 mg ai/kgdiet (or ppm ai)

No toxicant-induced decrease observed in reproduction as measured by number of eggs laid, egg thickness, number of cracked eggs, eggs set, embryo viability, numbe r hatched, number of 14- d old survivors, and hatchling and survivor weight MRID 45178101 Frey et al ., 1998/

Acceptable

Survival and Reproduction of Terrestrial Mammals Acute mortality: most sensitive acute oral toxicity, LD 50 (single-dose) Rat ( Rattus norvegicus ) LD 50 = 1,369 mg ai/kg-bw (female)

Allometric adjusted LD 50 values for mammals of body weight: 15 g: 3,009 mg ai/kg-bw 35 g: 2,434 mg ai/kg-bw 1000 g: 1,053 mg ai/kg-bw Acc # 00117121 Seaman et al

. 1982 /

Acceptable

Commence EC (Formulation) Value LD 50 = 3,936 mg/kg-bw (female)

Allometric adjusted LD 50 values for mammals of body weight: 15 g: 8,651 mg/kg-bw 35 g: 6,999 mg ai/kg-bw 1000 g: 3,027 mg ai/kg-bw MRID 43431302 (Unpublished) Freeman, 1992/ AcceptableChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 34 Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint and Effect(s) Source / Study Classification Reproduction: most sensitive reproductive NOAEL Rat, ( R. norvegicus ) 2-generation Offspring and Parental NOAEL = 1000 mg ai/kgdiet [84.4 mg ai/kg-bw]**

Offspring effects obs erved at LOAEL (2000 mg/kg-diet) were reduced body weight in F2a and F2b litters

Allometric adjusted NOAEL values for mammals of body weight: 15 g: 194 mg ai/kg-bw 35 g: 157 mg ai/kg-bw 1000 g: 68.0 mg ai/kg-bw Acc # 00151108 /

Acceptable

*Back-calculated using defa ult probit slope of 4.5, and lower and upper slopes of 2 and 9, number of test organisms, 95% upper bound on the estimate of the proporti on of mortality, (see Appendix C). **Although a NOAEL of 50 mg/kg-bw/day was reported in the 2-generation reproduction study, the HIARC selected a NOAEL of 84.4 mg/kg-bw/day from the 2-year chronic rat stud y, since the dietary level wa s the same in both studies ( i.e
., 1000 mg/kg-diet) but the 2-year chronic study measured actual in take rates instead of the sta ndard conversion factor which was used in the 2-generation rat study.


### Summary Document Registration Review: Initia l Docket (EPA 2007a); this difference is
discussed in detail in Section 3.1.2.

3.1.1 Effects on Birds
Clomazone is practically non-t oxic acutely to birds, as i ndicated by single oral dose LD 50 

### values of >2,230 mg ai/k g-bw and dietary 8-d 26 

### LC 50 

### values of >4,990 mg ai/kg-diet for both northern bobwhite quail and mallard duck (Accession Number (Acc #) 248475). No
mortalities were observed at this dose in any of the oral dose or dietary exposure studies. No effect on either growth or behavior (50 birds exposed) was detected in the northern bobwhite quail oral dose study or mallard duck oral dose or dietary exposure studies. There was a temporary reduction of food consumption obser ved on day 7 in the mallard duck oral dose study. While these studies do not di rectly provide a definitive LD 50 

### (or LC 50 

### ) an estimate of these values may be obtained using the Hill et al . (1975) dose-response model, for assumption of response slopes ranging from 2 to 9 ( i.e ., 2, 4.5, and 9 27 

### ), the number of organisms tested in the study at the exposur e dose (or concentrati on), and the 95% upper bound on the proportion of mortality for the study (see Appendix C). This is a provisional
method used in this assessment and will not be us ed to specifically calcu late acute RQ values but will be used for characterization purposes only. The resulting back-calculated LD 50 

### values range from 3,142 mg ai/kg-bw for a slope of 9 to 10,440 mg ai/kg-bw for a slope of 2

26 Study duration consists of 5 days exposure plus 3 days post-exposure.Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 35 

### for the mallard duck and bobwhite quail acute oral studies and the back-calculated 8-d LC 50 

### values range from 6,905 ppm ai for a slope of 9 to 22,940 ppm ai for a slope of 2 for the mallard duck and bobwhite quail subacute dietary studies. Values adjusted for body weights of 20, 100, and 1000 g, which are used in estima tion of exposure doses in Section 2.2.1 are provided in Table 21.

Table 21 Body Weight Adjusted Acute Oral LD 50 Values Based on Extrapolated Mallard Duck LD 50 Values from Limit Test Results

Body Weight Adjusted Acute Oral LD 50 (mg/kg-bw) Values Using Extrapolated Mallard Duck Assuming Probit Response Slopes of 2, 4.5, and 9 Body weight Slope 2 1 Slope 4.5 1 Slope 9 1

20 g 5,421 2,300 1,631 100 g 6,900 2,928 2,076 1000 g 9,747 4,136 2,933
1 Mallard duck extrapolated acute oral LD 50 assuming response slope of 2 is 10,440 mg/kg-bw, assuming a response slope of 4.5 is 4.430 mg/kg-bw, and assuming a response slope of 9 is 3,142 mg/kg-bw (Appendix C).



### There is one avian reproduction study using northern bobwhite quail exposed to technical grade clomazone in the diet. Chronic e xposure during maturation and reproduction in northern bobwhite quail to clomazone at 1,020 mg ai/kg-diet, th e highest dietary concentration tested, did not re sult in any detectable effect on survival, food consumption, growth, behavior, or repr oduction of adults and no detectable effect on survival or growth of chicks. Therefore, there is no defi nitive avian reproduction NOAEC value ( i.e ., bobwhite quail reproduction NOAEC > 1,020 mg ai/kg-diet) however this value can still be used to
estimate chronic LOC values.

3.1.2 Effects on Mammals
A complete characterization of the mammalia n toxicity data submitted to support the registration of clomazone is presented in a Section 3 risk assessment for the use of clomazone on sugarcane (Memo, Kidwell et al ., 2/13/01; D259635). Only a summation is provided herein. Clomazone is considered a lo w to moderate acute toxicant to mammals.
The lowest acute oral dose LD 50 

### is 1,369 mg ai/kg-bw for fema le rats and 2,077 mg ai/kg-bw for male rats in the same study (Acc # 00117121). Clomazone residues in the diet appear less toxic than that applied as a single bolus dose as the highest dietary concentration tested in a 90-d test, 8000 ppm (1,200 mg ai/kg-bw ), exhibited no mortality (Acc # 00132586). Clomazone has low acute toxicity via dermal (LD 50 

### >2000 mg ai/kg-bw in rabbits) and

27 Cross-section of pesticide response-slopes and typical slope (USEPA 1986, 2000)Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 36 

### inhalation (LC 50 

### = 4.23 mg ai/L-air) routes. It is non- irritating to the eyes and mildly irritating to the skin.

The NOAEL for a 2-generation rat reproduc tion study (Acc # 00151108) was 1000 mg ai/kgdiet. Offspring effects at the LOAEL (2000 mg ai/kg-diet) were decreased body weights in the F2a and F2b litters and for the parental LOAEL (2000 mg ai/kg-diet) effects included decreased body weight and body weight gain dur ing critical developmental times and kidney
effects in males. The conversion of this diet ary level to the body we ight basis of 50 mg/kgbw was based on use of standard food convers ion values to estimate consumption. The
HIARC selected the NOAEL of 84.4 mg/kg-bw from a 2-year toxicity/carcinogenicity rat study as a sounder dose-basis value for observed effects on growth as compared to levels affecting growth in the 2-generation rat study since the 2-year rat study used actual consumption data (measured weekly). Develo pmental and subchronic effects all occur at dietary concentrations or doses higher than th e 2-generation rat or 2-year rat study results.



## 3.2 Terrestrial Invertebrate Toxicology

Clomazone is practically non-toxic to honey bees , as indicated by an acute dermal contact
48-h LD 50 

### value of >100 μg ai/bee or >781 mg ai/kg-bee 28 

### (MRID 45178102). This acute
contact dose is converted to a residue level based upon an average fresh weight for a honey bee of 128 mg (Mayer and Johansen. 1990). Wh ile this study does not directly provide a
definitive LD 50 

### a conservative estimate of this va lue may be obtained using the Hill et al

. (1975) dose-response model, the default slope of 4.5 and the upper and lower slopes of 2 and 9, the number of organisms tested in the study at the exposure dose (or concentration), and the 95% upper bound on the proportion of mortality for the study (see Appendix C). This is a provisional approach used in this assessmen t and results are used for characterization purposes only. The resulting back -calculated dermal contact LD 50 

### values from 135 μg ai/bee at a slope of 9 to 387 μg ai/bee at a slope of 2 (or 1,054 mg ai/kg-bee to 3,022 mg ai/kg-bee, respectively). These back-calculated LD 50 

### values are not used to calculate acute RQ values but are used to evaluate the potential for risks to terrestrial invertebrates as prey items and
direct effects to listed insects.

28 Honey bee 48-h LC 50 , mg a.i./kg-bee = (48-h LC50, μg a.i. / bee) / (0.128 g / bee) = (100) / (0.128) = 781 μg a.i./g-insect = 781 ppmChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 37 Table 22 Summary of Specific Measurement Endpoint Values Selected To Calculate RQ Values to Evaluate Risk for Terrestrial Invertebrate Assessment Endpoints

Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint and Effect(s) Source / Study Classification
Survival of Terrestrial Invertebrates and beneficial insects Acute mortality: most sensitive acute contact 48-h LD 50 Honey bee ( Apis mellifera ) 48-hr LD 50 >100 μg ai/bee (or >781 mg ai/kginsect)]

No mortality or behavior al effects noted at the highest dose tested

Extrapolated values*: 48-hr LD 50 =182 μg ai/bee (or 1,421 mg ai/kginsect at slope = 4.5 48-hr LD 50 =387 μg ai/bee (or 3,022 mg ai/kginsect at slope = 2 48-hr LD 50 =135 μg ai/bee (or 1,054 mg ai/kginsect at slope = 9 MRID 45178102 Nengel, 1998 /

Acceptable

*Back-calculated using defa ult probit slope of 4.5 [and lower and upper bound sl opes of 2 and 9], number of test organisms, 95% upper bound on the estimate of the propor tion of mortality (see Appendix C).



### There is also a subchronic test with earthworms exposed to clomazone residues in soil. The
resultant 7-d and 14-d LC 50 

### values were 215 and 156 mg ai/kg-soil.



## 3.3 Fish Toxicology

Information is available on acute effects and chronic reproductive effects of clomazone in fish. Chronic toxicity data were not available for the most sensitive acute freshwater species or for estuarine-marine species so a modeling approach using acute-to- chronic ratios (ACRs)
was used to estimate the chronic NOAEC. No information was available on effects of clomazone on amphibians. Therefore, effects and effect levels in freshwater fish will be used as a surrogate for amphibians in this assessm ent. Toxicological endpoints selected for
freshwater fish and estuarine-marine assessm ent endpoints are contai ned in Table 23. The resulting values differ from values used in pr evious risk assessments of clomazone because of new data found in public literat ure which provided lower endpoints.

The target organ(s) and toxic mode-of-action of clomazone in fish is unknown. However, as with terrestrial vertebrates, based on bioconcentration st udies clomazone is rapidly metabolized with accumulated levels being depurated within 72 hour s post exposure, and almost 100% excreted by 14 days post-exposur e. Clomazone has a low potential for bioaccumulation in fish as indicated by bioc oncentration factors (BCFs) of 10, 75, and 40 for fillet, viscera, and whole fish, respectively.Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 38 Table 23 Summary of Specific Measurement Endpoint Values Selected To Calculate RQ Values to Evaluate Risk for Fish and Amphibian Assessment Endpoints

Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint 1 and Effect(s) Source / Study Classification

Survival and reproduction of freshwater vertebrates (fish, amphibians) Acute mortality: most sensitive acute freshwater fish 96-h LC 50 Silver catfish ( Rhandia quelen ) 96-hr LC 50 = 2,900 mg ai/L (or ppb ai)

Effects on acetylcholines terase levels were investigated but the reported results contained irreconcilable errors in the paper and are not appropriate for use. dos Santos Miron et al . 2004, 2005 /

Supplemental

Reproduction: most sensitive early life stage (ELS) NOAEL Modeled silver catfish value ELS NOAEL = 350 ppb ai See Section 3.3.1

Survival and reproduction of marine/ estuarine fish Acute mortality: most sensitive acute freshwater fish 96-h LC 50 Sheepshead minnow ( Cyprinodon variegatus ) 96-hr LC 50 = 40,600 ppb ai Acc # 073830 and 073671 Surprenant 1985 /

Supplemental Reproduction: most sensitive early life stage (ELS) NOAEL Estimated sheepshead minnow value ELS NOAEL = 4,890 ppb ai See Section 3.3.2

1 All concentrations provided are in the dissolved or soluble form



### .

3.3.1 Effects to Freshwater Fish
Clomazone acute toxicity ranges fr om slightly toxic to moderately toxic to freshwater fish.
The acute effects of clomazone have been st udied with three species of fish, two with technical grade clomazone submitted to suppor t registration (Acc # 248475), and one with a formulation, Gamit, from the pub lic literature (dos Santos Miron et al . 2004, 2005) but which is not a registered formulation in the U.S. Clomazone acute 96-h LC 50 

### values for freshwater fish with technical grade clomazone range from 19,000 ppb ai for the cold water rainbow trout ( Oncorhynchus mykiss ) to 34,000 ppb ai for the warm water bluegill sunfish ( Lepomis
macrochirus ) (Acc # 248475). The formulation test 96-h LC 50 

### of 2,900 ppb ai for silver catfish ( Rhandia quelen ) is the lowest 96-h acute value. Because there are no paired clomazone technical and Gamit formulation specie s tests, it is unknown if the formulation is more toxic to fish than the active ingredient alone. As this is the lowest 96-h LC 50 

### value and the effect of formulation is unknown, this value wa s selected as the more conservative of the
available data.

If the formulation is more toxic than the active ingredient alone, risks to freshwater fish may be overestimated. Also, there were a number of study conditions and other information notChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 39 

### reported in the silver catfish pa per that are likely to affect the study and potentially result in
the 96-h LC 50 

### value being higher than that expected for a fo rmulation under guideline
conditions. These factors includ e the reported feeding of the fi sh during the test, aeration of the test chambers without measuring ai, use of plastic exposure chambers, unknown dilution water source, and unknown levels of total or ganic carbon (TOC) and particulate matter
concentration in the dilution water.

There is one fish early life stage study us ing rainbow trout exposed to technical grade clomazone in water (Acc # 073830). Fish were exposed from the eyed embryo stage (18- days post-fertilization) through hatching. The NOAEC for this study was 2,290 ppb ai.
Effects at the LOAEC included decreased survival of young and reduced growth as determined by both length and weight. While no effect on embryo hatchability was observed at concentrations at and below 8,450 ppb ai, non e of the young survived to the end of the study at 8,450 ppb ai.

Because silver catfish were more acutely sens itive than either rainbow trout or bluegill sunfish, and the only freshwater fish ELS NOAEC for rainbow trout is above the concentration that results in over 50% mortality in silver catfish, th is rainbow trout NOAEC is not appropriate assess risks to the silver catf ish or similar sensitive fr eshwater fish species. The silver catfish early life st age NOAEC for clomazone of 350 ppb ai 29 

### was modeled by dividing the silver catfish 96-h LC 50 

### value by a fish ACR derived from the rainbow trout
results of 8.297 30



### .

Sublethal effects of clomazone on brain and muscle actylcholinesterase (AChE) were reported in the open literature (dos Santos et al . 2005) but a review of the paper identified
inconsistencies which could not be resolved. The results as reported in the paper were considered unreliable (Appendix E).

3.3.2 Effects to Estuarine-Marine Fish

Effect information on clomazone to estuarine- marine fish is limited to a single acute study with the sheepshead minnow ( Cyprinodon variegates ). Clomazone is slightly toxic acutely to sheepshead minnow, as indicated by the 96-h LC 50 

### value of 40,600 ppb ai (Accession Number (Acc # 263081). Sheepshead minnow are le ss sensitive than the freshwater fish
tested.

29 ai ppb ai ppb ACR LC h NOAEC ELS catfish Silver 350 297

. 8 900
, 2 96 50 = = − =

30 297

. 8 290
, 2 000
, 19 96 50 = = − = ppb ppb NOAEC ELS LC h ACR trout RainbowChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 40 

### No fish early life stage or life cycle data were found for estuarin e-marine fish. Therefore, the fish ACR of 8.297 derived using the rainbow trout acute and ch ronic data, as discussed in Section 3.3.1, was used to model an early life stage NOAEC for the sheepshead minnow ( C variegates ) of 4,890 ppb ai 31



### .



## 3.4 Aquatic Invertebrate Toxicology

Information is available on both acute effects and chronic reproductive effects of clomazone in aquatic invertebrates. Chronic toxicity data were not available for the most sensitive acute estuarine-marine species, the mysid shrimp ( Americamysis bahia ) so a modeling approach using a freshwater invertebrate ACR for clom azone was used to estimate the reproductive NOAEC for the mysid shrimp. Toxicological endpoints selected for freshwater and
estuarine-marine invertebrate assessme nt endpoints are contained in Table 24.

The target organ(s) and toxic mode-of-action of clomazone in invertebrates are unknown and
no bioconcentration or metabolism studies were found for aquatic invertebrates. Because of
clomazone’s K oc 

### and the low BCF observed in fish, the potential for bioconcentration in aquatic invertebrates is also considered to be low.

Table 24 Summary of Specific Measurement Endpoint Values Selected to Calculate RQ Values to Evaluate Risk for Aquatic Invertebrate Assessment Endpoints

Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint 1 and Effect(s) Source / Study Classification

Survival and reproduction of freshwater invertebrates Acute mortality: most sensitive acute freshwater invertebrate 48-h or 96-h EC 50 or LC 50 Water flea ( Daphnia magna ) 48-hr EC 50 = 5,400 ppb ai Acc # 248475 Graney, 1982 /

Acceptable

31 ai ppb ai ppb ACR LC h NOAEC ELS now Sheepshead 890
, 4 297

. 8 600
, 40 96 min 50 = = − =Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 41 Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint 1 and Effect(s) Source / Study Classification Reproduction: most sensitive reproductive NOAEL Water flea ( D.
magna ) 21-d NOAEC = 2,200 ppb ai

Fecundity was the most sensitive endpoint Acc # 073997, 073616 Spare and Graney, 1982

Acceptable
Survival and reproduction of marine/ estuarine invertebrates Acute mortality: most sensitive acute invertebrate 48-h or 96-h EC 50 or LC 50 Mysid shrimp ( Americamysis bahia formally Mysidopsis bahia ) 96-hr LC 50 = 566 ppb ai Acc # 263080 Williams, 1986 /

Acceptable

Reproduction: most sensitive early life stage (ELS) NOAEL Modeled mysid shrimp reproduction Reproduction NOAEL = 68 ppb ai See Section

1 All concentrations provided are in the dissolved or soluble form.



### 3.4.1 Effects to Fr eshwater Invertebrates
Scientifically sound acute and reproductive info rmation on clomazone toxicity to freshwater
invertebrates is limited to the waterflea Daphnia magna . Clomazone is considered moderately toxic acutely to D. magna , as indicated by the 48-h EC 50 

### value of 5,400 ppb ai (Acc # 248475). The reproductive NOAEC for D. magna is 2,200 ppb ai and the LOAEC is 4,380 ppb ai. Reproduction as measured by the number of young produced was the most sensitive measurement endpoint affected at the LOAEC, and was reduced by approximately
40% from the control at this concentration.

3.4.2 Effects to Estuarine-Marine Invertebrates

There is an acute test with t echnical grade clomazone for a shrimp species, the mysid shrimp
A. bahia , and a mollusk, the Eastern oyster Crassostrea virginica . The Eastern oyster study, examines the acute effects on shell depositi on during 96 hours of exposure. Clomazone is considered highly toxic to aquatic in vertebrates based on the acute 96-h LC 50 

### value of 566 ppb ai. Shell deposition in the Eastern oyster with a 96-h EC 50 

### of 5,300 ppb ai is not as sensitive as mortality in the mysid shrimp.

No reproductive effects data were found for estuarine-marine inve rtebrates. Therefore, the fish ACR of 8.297 was used to model a reproductive NOAEC for the mysid shrimp ( A.Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 42 

### bahia ) of 68 ppb ai 32 

### . The ACR for D. magna based on its acute and chronic data of 2.454 33



### , appears smaller than that of fish but is within 10 times that of the fish value. Because there are no additional data by which to evaluate if there is a taxonomic effect on ACR values, and the values are within 10 times of each other, no taxonomic effect is assumed and the more
conservative ACR of 8.297 was used to estima te the reproductive NOAEC for mysid shrimp. The general policy within EFED for pesticides is to use an ACR derived from the same taxon
because the mode of action of some pesticides may be taxon specific. However, because in this case there is no known taxa specific m ode-of-action between fish, aquatic insects, or other aquatic invertebrates and the differen ce in ACR values are within the standard acceptable range of variability for ACR values , the more sensitive of the two were used.



## 3.5 Plant Toxicology

Clomazone is an isoxazolidinone herbicide a nd there are no other re gistered compounds currently in this class. It inhibits carotenoi d biosynthesis; the specifi c target enzyme is not known. Clomazone is absorbed by the roots an d shoots and translocated upwards throughout the plant. Scientifically s ound toxicity information on seedling emergence is available for 10 crop species for both the technical grade activ e ingredient and a ME formulation. No scientifically sound vegetative vigor study is ava ilable. However, results from one vegetative study do provide insight on loading levels at which mortality and bleaching conservatively occurs. Aquatic plant toxicity data are availa ble for the technical grade active ingredient for six species of aquatic plants and formulat ion data are available for one species. Toxicological endpoints selected for terrestria l plant and aquatic plant assessment endpoints
are contained in Table 25.

Table 25 Summary of Specific Measurement Endpoint Values Selected to Calculate RQ Values to Evaluate Risk for Terrestrial and Aquatic Plant Assessment Endpoints

Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint and Effect(s) Source / Study Classification

Survival and biomass of aquatic vascular and non-vascular plants Non-vascular species: the most sensitive biomass IC 50 for non-listed and its associated NOAEC for listed species Freshwater diatom ( Navicula pelliculosa ) 5-d IC 50 = 167 ppb ai 5-d NOAEC = 23.6 ppb ai MIRD 44994801 Kranzfelder and Goble, 1999/

Acceptable

32 ai ppb ai ppb ACR LC h NOAEC ve reproducti shrimp Mysid 68 279

. 8 566 96 50 = = − =

33 454

. 2 200
, 2 400
, 5 48 50 = = − = ppb ppb NOAEC Chronic EC h ACR WaterfleaChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 43 Selected Measurement E ndpoint Value and Source Assessment Endpoint Measurement Endpoint Species Toxicological Endpoint and Effect(s) Source / Study Classification Vascular species: the most sensitive biomass IC 50 for non-listed and its associated NOAEC for listed species Duckweed ( Lemna paucicostata ) 7-d IC 50 = 30,200 ppb ai 7-d NOAEC = 7,300 ppb ai Michel et al ., 2004 (Published) /

Supplemental

Survival andbiomass of nontarget plants in terrestrial and semi-aquatic

areas Monocots: the most sensitive seedling emergence or vegetative vigor IC 25 for non-listed and its associated NOAEC for listed species Onion Seedling Emergence IC 25 = 0.031 lbs ai/A NOAEC = 0.0062 lbs ai/A

Most sensitive endpoint was height MRID 41557501 Chetrem, 1990 /

Acceptable

Dicots: the most sensitive seedling emergence or vegetative vigor IC 25 for non-listed and its associated NOAEC for listed species Lettuce Seedling Emergence IC 25 = 0.0037 lbs ai/A NOAEC = 0.0008 lbs ai/A

Most sensitive endpoint was dry weight MRID 42165705 Chetrem, 1991 /

Acceptable



### 3.5.1 Effects to Terrestrial Plants
Scientifically sound toxicity information on seedling emergence is available for 10 crop species (monocots: corn, onion, and ryegrass; dicots: cucumber. soybean, carrot, cabbage, tomato, and lettuce) for both technical grad e active ingredient (TGAI) clomazone (MRID 41557501 and 42167505) and the formulation Command ME (MRID 45397701). For technical grade clomazone, the most sensitive IC 25 

### value for test species ranges from >1.5 lbs ai/A for soybeans (emergence, survival, height, dry weight) to 0.0037 lbs a i/A for lettuce (dry weight). For Command 3M E, the most sensitive IC 25 

### value for test species ranges from >1.25 lbs ai/A for soybeans (emergence, survival , height, dry weight) to 0.037 lbs ai/A for lettuce (length). For one species (soybean), the IC 25 

### value for both TGAI and Command ME was greater than the exposure level tested, for five of the plant species the TGAI value is lower than the Command 3ME value, and for thr ee species the TGAI value is higher than the
Command 3ME value. In the cases where the Command 3ME IC 25 

### values were lower they
were on the same order and do not appear to indicate that this formulation is more toxic than the active ingredient alone. The comparison between active ingredient and formulation was
made with the IC 25 

### rather than the NOAEC (or IC 05 

### ) values because it is the more accurate and precise endpoint measure. The most sens itive monocot and dicot results were for the TGAI with onion and lettuce, respectively.

Seedling emergence IC 25 

### results and the associated NOAEC (or IC 05 

### ) values were used in the absence of vegetative vigor values for height an d weight in determining risks to plants fromChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 44 

### spray drift and volatilize d clomazone off-site loading. Typically, the IC 25 

### values from the vegetative vigor studies would be used to asse ss risk to non-target terrestrial plants from spray drift and volatilization sin ce vegetative vigor studies m easure the phytotoxic effect on plants via foliar contact or uptake of the to xicant. The seedling emergence studies are usually used to assess risk to non-target terrestri al plants from runoff of toxicant residues that would be taken up by the plant via roots or st ems. Since only supplemental information on mortality is available from ve getative vigor studies to use fo r assessing risk to non-target terrestrial plants from spray drift exposure, it was decided to use the results of the seedling emergence studies to provide some measure of non-target plant risk since loading of spray
drift and volatilized clomazone to soil can al so be taken up by the roots and stems of nontarget plants. The level that results in mortality appears to be less sensitive for vegetative vigor than seedling emergence.

As several plant species were tested a species sensitivity distribution of seedling emergence
IC 25 

### values for each measurement endpoint was determined using the median plotting position and these are displayed in Figure 3. The species sensitivity distribution will be used to evaluate the proportion of sp ecies that are above or below le vels of concern in the risk
characterization.

As the percent emergent IC 25 

### was greater than 1.5 lbs ai/A fo r all test species, this effect measure is not on the figure. For soybeans the IC 25 

### was greater than 1.5 lbs ai/A for dry weight, height, and survival but for determinatio n of the species sensi tivity distribution these values were assumed to be equal to 1.5 lbs ai /A. For tomato and lettuce where there were
two IC 25 

### values for each measure of effect (MRID 41557501, 42165705), the geometric
mean of these values were taken before calcul ating the median plotting position. Biomass of half of the species tested is reduced by 25% or more, as measured by height, at clomazone
loads between 0.006 lbs ai/A to 0.1 lb ai/acre. Similarly biomass of the half of the species tested is reduced by 25% or more, as measur ed by dry weight, at clomazone loads between
0.0037 lbs ai/A to 0.2 lbs ai/A.Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 45 Figure 3 Seedling Emergence IC 25 Species Sensitivity Distribution for Clomazone

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

cab = cabbage; car = carrot; crn = corn; cuc = cucumber; ltc = lettuce; oni = onion; rye = ryegrass; soy = soybean; tom =

tomato



### A species sensitivity distribution of seedling emergence IC 50 

### values for each measurement endpoint was determined using the median plot ting position and these are displayed in Figure 4. As the percent emergent IC 50 

### was greater than 1.5 lbs ai/A fo r all test species, this effect measure is not on the display. Standing biomass of half of the species tested is reduced by at
least 50% at clomazone loads betw een 0.013 lbs ai/A to 0.75 lbs ai/A.Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 46 Figure 4 Seedling Emergence IC 50 Species Sensitivity Distribution for Clomazone

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.010 0.100 1.000 10.000 Concentration (lb ai/A)Probability Dry Weight Height
Survival 

# IC 50 

# Sensitivity Distribution

ltc ltc tom cab

rye soy

car oat crn cuc

oni

oni tom rye car cab crn cuc

cab

ltc oni tom crn rye

cuc oat soy

car oat soy

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.010 0.100 1.000 10.000 Concentration (lb ai/A)Probability Dry Weight Height
Survival 

# IC 50 

# Sensitivity Distribution

ltc ltc tom cab

rye soy

car oat crn cuc

oni

oni tom rye car cab crn cuc

cab

ltc oni tom crn rye

cuc oat soy

car oat soy

cab = cabbage; car = carrot; crn = corn; cuc = cucumber; ltc = lettuce; oni = onion; rye = ryegrass; soy = soybean; tom =

tomato



### No scientifically sound vegetative vigor study is available. In ve getative vigor studies
conducted either clomazone volatilized and cr oss-contaminated other treatments including
the controls or environmental conditions were highly variable and differed between controls and treatments resulting in stunting and dryi ng out of plants, which was unassociated with
clomazone effects. Because there is no wa y of knowing the degree of affect on the magnitude and variability or spread in weight an d height of controls, a ny estimates of growth (length and weight) effects of clomazone on tr eatments may be either underestimated or overestimated. However, results from one study with cross-contamination do provide an estimate as to dose levels at which bleaching a nd plant mortalities may occur when applied toChapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 47 

### foliar vegetation. The clomazone dose levels at which discoloration we re first observed and
the level at which mortalities occurred are summa rized in Table 26 for each test species. As cross-contamination occurred, as demonstrat ed by discoloration (bleaching) on some controls, the dose levels in Table 26 for discol oration are potentially lower than what would
have been observed under no cross-contamination.

Table 26 Vegetative Vigor Study Morphological Observation Results – Clomazone Dose at Which Discoloration and Mortalities were First Observed

Discoloration First Observed Mortalities First Observed Plant Species lb ai/acre Comment Lb ai/acre Comment

Cabbage 0.0054 2/4 reps with slight discoloration or stunting 0.401 4/4 replicates had seve re injury (mortalities or near mortalities);

1.2 lbs ai/ A: 2/4 and 2/4 were observed to have sever injury and stand loss (>50% mortality), respectively Carrot 0.0164 3/4 reps sli ght discoloration or stunting 0.401 4/4 replicates had se vere injury (stand loss >50% mortality);

1.20 lb ai/acre: 4/4 rep licates were observed to have few plants remaining Corn 0.0054 1/4 reps sli ght discoloration or stunting 1.20 4/4 replicates had severe injury (mortalities or near mortalities) Cucumber 0.016 2/4 reps with slight discoloration or stunting >1.20 no mortalities

Lettuce 0.0019 3/4 reps sli ght discoloration or stunting 1.20 4/4 replicates had severe injury (mortalities or near mortalities) Oat 0.0054 4/4 reps with slight discoloration or stunting 0.414 4/4 replicates had se vere injury (stand loss >50% mortality)

1.20 lbs ai/A: 4/4 replic ates were observed to have few plants remaining
Onion (study 1) 0.0019 4/4 reps with slight discoloration or stunting 0.401 1/4 replicates had seve re injury (mortalities or near mortalities);

1.20 lbs ai/A: 3/4 and 1/4 reps had stand loss (>50% mortalities0 and fe w plants remaining, respectively
Onion (study 2) 0.046 2/4 reps with slight discoloration or stunting 0.414 2/4 replicates had seve re injury (mortalities or near mortalities);

1.23 lbs ai/A: 4/4 replicates had stand loss (>50% mortalities) Ryegrass 0.016 2/4 reps with slight discoloration or stunting 1.20 1/4 replicates had severe injury (mortalities or near mortalities) Soybean 1.20 2/4 reps with slight discoloration or stunting >1.23 no mortalities

Tomato 0.0019 2/4 reps with slight discoloration or stunting >1.20 no mortalities

The lowest test dose was 0.0019 lb ai/acre for lettuce, onion, and tomato and 0.0054 lb ai/acr e for the other test species.Chapter 3 Effects Characterization

Registration Review Ecological Risk Assessment Clomazone 48 

### 3.5.2 Effects to Aquatic Plants
Aquatic plant toxicity data is available for the technical grade or analytic grade active ingredient for seven species of a quatic plants. The growth 7-d IC 50 

### values for three duckweed species range from 30,200 to 48,800 ppb ai . Nonvascular plant growth was more sensitive to clomazone with growth 4-d IC 50 

### and 5-d IC 50 

### values ranging from 115 ppb ai to 11,100 ppb ai. For vascular plants, the lowest 7-d IC 50 

### value for L. paucicostata of 30,200 ppb ai was selected and for nonvasc ular plants the lowest 4-d IC 50 

### value of 115 ppb ai for the freshwater diatom, N. pelliculosa

.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 49 

# Chapter 4 Results: Risk Characterization

4.1 Risk Estimation

4.1.1 Direct Effects to Non-Ta rget Terrestrial Vertebrates

4.1.1.1 D IRECT E FFECTS TO B IRDS , R EPTILES , AND (L AND -P HASE ) A MPHIBIANS 

### No dietary- or dose-based acute RQ values co uld be calculated because no definitive acute
values were available. At th e highest dietary level tested (4,900 mg ai/kg-diet) and dose tested (2,230 mg ai/kg-bw) neither mallard duc k or bobwhite quail had mo rtality or sublethal effects (N = 50 birds per test). Chronic RQ values were calculated for upper bound dietarybased residue levels based on the highest cl omazone application rate, sweet potato banded
rate of 3.0 lb ai/acre (Table 27). These chronic RQ valu es were all below the chronic LOC (1.0). As these are the highest residue levels of any use, all other labeled uses also have dietary-based chronic RQ values below the chro nic LOC. Because residues from volatilized and redeposited clomazone are expected to be lower (Table 13) this pathway for any use will also result in chronic RQ valu es below the chronic LOC. For dietary-based results, as birds are used as a surrogate for rept iles and the terrestrial-phase of amphibians in this assessment no chronic LOC are expected to be exceeded for these groups either.

Table 27 Avian chronic dietary-based RQ values for a banded application on sweet potatoes

Dietary Item EEC (mg/kg-diet) 1 Chronic RQ 2

Short Grass 720 < 0.7
Tall Grass 330 < 0.3 Broadleaf plants/sm Insects 405 < 0.4 Fruits/pods/seeds/lg insects 45.0 < 0.1
1 Dietary-based residue levels for a banded application on sweet potatoes from Table 8. 2 Chronic RQ = (EEC, mg/kg-diet) / chronic NOAE C, mg/kg-diet; where the chronic NOAEC is > 1,020 mg/kg-diet for bobwhite quail from Table 20.

4.1.1.2 D IRECT E FFECTS TO M AMMALS 

### For banded application of clomazone on sweet pota toes which is the highest application rate, and assuming exposure occurs at upper bound residue estimates, dose-based acute and chronic RQ values do not exceed acute e ndangered LOC or chronic LOC for mammals ingesting seeds, fruits, pods, and/or large in sects. However, dose- based acute and chronic RQ values do exceed the acute endangered LOC and the chronic LOC, respectively, forChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 50 

### mammals ingesting short grass, tall grass, broadl eaf plants, or small insects (Table 28). For broadcast applications of clomazone to sweet potatoes where exposure to upper bound residue levels is assumed, the acute endangere d LOC and chronic LOC are exceeded only for residues on short grass for 15 g and 35 g mammals (Table 29). To determine at which application level the dose-base d RQ values drop below the endangered acute and chronic LOC, dose-based acute and chronic RQ values were calculated for application rates ranging from 0.75 lbs ai/A to 2.5 lbs ai/A for short gr ass, the dietary group with the highest residue level of the five evaluated (Table 30). Ther e are application rates be low 0.75 lbs ai/A, but at this application rate all acut e and chronic RQ values are below the endangered acute LOC and chronic LOC, respectively.

For the volatilization pathway, the highest dose-ba sed EEC values (Table 15) are lower than those in Table 11 for the highest pound per acre a pplication rate (1.5 lb ai/acre, broadcast or 3.0 lbs ai/A in bands). Therefore, in addition to those acute RQ values that are at or below the acute endangered species LO C for the upper bound broadcast RQ values (Table 29), all dose-based short grass acute RQ values are below the LOC (15 g, acute RQ = 0.07; short grass 35 g, acute RQ = 0.06) and except for th e 15 g mammal all chronic RQ values are below the chronic LOC (15 g, chronic RQ = 1.1; 35 g, chronic RQ = 0.98).

While some dose-based chronic RQ values excee ded the chronic LOC, dietary-based chronic RQ values for upper bound dietary EEC values fo r all dietary items at the highest banded application rate do not exceed the chronic LO C (Table 31). Because residue levels from redeposited clomazone at the highest applica tion rate (1.5 lbs ai/A broadcast which is equivalent to 3.0 lbs ai/A) are expected to be lower (Table 13) the dietary-based chronic RQ for this pathway will also not exceed the chronic LOC on a dietary-basis.

Acute dose-based RQ values based on uppe r bound and mean Commence EC formulation dietary residue levels for banded applicati on on cotton and soybean sites are provided in Table 32. All acute RQ values for dietary ite ms were below the acu te endangered species LOC (0.1) except for short grass at upper bound residue estimates.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 51 Table 28 Upper bound acute and chronic clomazone dose-based RQ values for mammals for a banded application on sweet potatoes

15 g mammal 35 g mammal 1000 g mammal Functional Feeding Group Dietary Item Acute 1 Chronic 2 Acute 1 Chronic 2 Acute 1 Chronic 2

Herbivores/Insectivores
Short Grass 0.23 3.5 0.19 3.0 0.10 1.6
Tall Grass 0.10 1.6 0.09 1.4 0.05 0.7 Broadleaf plants/sm insects 0.13 2.0 0.11 1.7 0.06 0.9 Fruits/pods/lg insect s 0.01 0.2 0.01 0.2 0.01 0.1
Granivore
Seeds <0.01 <0.1 <0.01 <0.1 <0.01 <0.1 Bolded acute RQ values exceed the endangered LOC of 0.1, bolded and italicized acute RQ values exceed the acute restricted use LOC of 0.2, and the bolded chr onic RQ values exceed the chronic LOC of 1. 1 Acute RQ = (dose-based upper bound EEC, mg/kg-bw) / (LD 50 ; mg/kg-bw). Upper bound dose-based EEC values for a given body weight are from Table 10 and LD 50 values adjusted for the given body weight are from Table 20. 2 Chronic RQ = (dose-based upper bound EEC, mg/kg-bw) / (c hronic NOAEC, mg/kg-bw). The upper bound dose-based EEC values for a given body weight and dietary item are from Table 11 and the NOAEC values adjusted for a given body weight are from Table 20.

Table 29 Upper bound acute and chronic clomazone dose-based RQ values for mammals for a broadcast application on sweet potatoes

15 g mammal 35 g mammal 1000 g mammal Functional Feeding Group Dietary Item Acute 1 Chronic 2 Acute 1 Chronic 2 Acute 1 Chronic 2

Herbivores/Insectivores
Short Grass 0.11 1.8 0.10 1.5 0.05 0.8
Tall Grass 0.05 0.8 0.04 0.7 0.02 0.4 Broadleaf plants/sm ins ects 0.06 1.0 0.05 0.8 0.03 0.5 Fruits/pods/lg insects 0.01 0.1 0.01 0.1 <0.01 0.1
Granivore
Seeds <0.01 <0.1 <0.01 <0.1 <0.01 <0.1 Bolded acute RQ values exceed the endangered LOC of 0.1 a nd the bolded chronic RQ values exceed the chronic LOC of 1. 1 Acute RQ = (upper bound dose-ba sed EEC, mg/kg-bw) / (LD 50 ; mg/kg-bw). The upper bound EECs for a given body weight are from Table 11 and LD 50 values adjusted for the given body weight are in Table 20 2 Chronic RQ = (upper bound dose-based EEC, mg/kg-bw) / (chronic NOAEC, mg/kg-bw). The upper bound dose-based EEC values for a given body weight and dietary item are from Table 11 and the NOAEC values adjusted for a given body weight are in Table 20.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 52 Table 30 Upper bound acute and chronic clomazone dose-based RQ values for mammals ingesting short grass at application rates from 0.75 lbs ai/A to 2.5 lbs ai/A

15 g mammal 35 g mammal 1000 g mammal 15-g 35-g 1000-g Acute Chronic Acute Chronic Acute Chronic
Short Grass 2.5 lb/A 572 395 92 0.19 2.9 0.16 2.5 0.09 1.3
Short Grass 1.5 lb/A 343 237 55.0 0.11 1.8 0.10 1.5 0.05 0.8
Short Grass 1.25 lb/A 286 198 45.8 0.10 1.5 0.08 1.3 0.04 0.7
Short Grass 1.0 lb/A 229 158 36.7 0.08 1.2 0.06 1.0 0.03 0.5
Short Grass 0.75 lb/A 171 119 27.5 0.06 0.9 0.05 0.8 0.03 0.4 Bolded acute RQ values exceed the endangered LOC of 0.1 a nd the bolded chronic RQ values exceed the chronic LOC of 1. 1 Acute RQ = (dose-based upper bound EEC, mg/kg-bw) / (LD 50 ; mg/kg-bw). The LD 50 values adjusted for the given body weight are from Table 20. 2 Chronic RQ = (dose-based upper bound EEC, mg/kg-bw) / (c hronic NOAEC, mg/kg-bw). The NOAEC values adjusted for a given body weight are from Table 20.

Table 31 Mammalian chronic dietary-based clomazone RQ values for a banded application on sweet potatoes

Dietary Item Dietary-based EEC (mg/kg-diet) Chronic RQ Short grass 720 0.7 Tall grass 330 0.3 Broadleaf plants/sm insects 405 0.4 Fruits/pods/lg insects 45 <0.1

1 Dietary-based residue levels for a banded application on sweet potatoes from Table 8. 2 Chronic RQ = (EEC, mg/kg-diet) / chr onic NOAEC, mg/kg-diet; the chronic NOAEC > 1,020 mg/kg-diet for bobwhite quail from Table 20.

Table 32 Upper bound and average acute Commence EC dose-based RQ values for mammals for a banded application on cotton or soybeans

Upper bound acute RQ values Average RQ values Functional Feeding Group Dietary Item 15-g 35-g 1000-g 15-g 35-g 1000-g

Herbivores/Insectivores
Short Grass 0.17 0.14 0.08 0.05 0.05 0.03
Tall Grass 0.08 0.06 0.04 0.02 0.02 0.01 Broadleaf plants/sm ins ects 0.09 0.08 0.04 0.03 0.03 0.01 Fruits/pods/lg insects 0.01 <0.01 <0.01 <0.01 <0.01 <0.01
Granivore
Seeds <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 Bolded acute RQ values exceed the endangered LOC of 0.1 1 Acute RQ = (dose-based EEC, mg/kg-bw) / (LD 50 ; mg/kg-bw). EEC values for a given body weight are from Table 12 and LD 50 values adjusted for the given body weight are from Table 20.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 53 

### 4.1.2 Direct Effects to Non-Ta rget Terrestrial Invertebrates
No RQ values were calculated for beneficial or listed insects because no definitive acute
contact LD 50 

### value was available.

4.1.3 Direct Effects to Terrestri al and Wetland/Riparian Plants

4.1.3.1 R UNOFF A ND S PRAY DRIFT L OADING 

### Table 33 contains the RQ values for listed and non-listed plants in dry and semi-aquatic areas adjacent to a treated field for the highest ap plication rate, sweet potato at 1.5 lbs ai/A (equivalent to 3.0 lbs ai/A applied in a band) ground applied and the lowest label rate of 0.251 lbs ai/A, ground applied, for use on beans (s ucculent), melons (musk), and watermelon crops. Except for wet seeded rice, which is re gistered for aerial appl ications, these values cover the expected RQ range for label rates of registered clomazone uses. Table 33 also contains the RQ values for aerial spray of cl omazone on rice. Because these rice fields will have berms to maintain flood waters, runoff to adjacent areas is not expected and the risks estimated are therefore appli cable to spray drift alone.

Table 33 RQ values for plants in dry and semi-aquatic areas exposed to clomazone through runoff and/or spray drift

Application Type, Rate Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Ground Spray, 1.5 lb ai/acre

Monocot non-listed 1 2.9 25 0.5
Monocot listed 2 15 123 2.4

Dicot non-listed 24 207 4.0
Dicot listed 47 403 7.9 Aerial Spray, Rice 0.6 lb ai/acre

Monocot non-listed -- -- 1.0

Monocot Listed -- -- 4.8

Dicot non-listed -- -- 8.1

Dicot listed -- -- 16 Ground Spray, Rice 0.6 lb ai/acre

Monocot non-listed -- -- 0.2

Monocot Listed -- -- 1.0

Dicot non-listed -- -- 1.6

Dicot Listed -- -- 3.2Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 54 Application Type, Rate Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Ground Spray, 0.251 lb ai/acre

Monocot non-listed 0.5 4.1 <0.1
Monocot Listed 2.4 21 0.4

Dicot non-listed 4.1 35 0.7

Dicot listed 7.9 67 1.3 Bolded listed RQ values exceed the endangered species LOC of 1, and bolded non-listed RQ values exceed the non-listed species LOC of 1. 1 Monocot (or dicot) non-listed RQ = (EEC, lb ai/acre) / (IC 25 , lb ai/acre), where the EEC for dry, semi-aquatic, or spray drift is from Table 16 and the monocot (or dicot) IC 25 value is from Table 25. 2 Monocot (or dicot) listed RQ = (EEC, lb ai/acre) / (NOAEC, lb ai/acre), where th e EEC for dry, semi-aquatic, or spray drift is from Table 16 and the monocot (or dicot) NOAEC value is from Table 25.

4.1.3.2 V OLATILIZATION L OADING 

### Table 34 contains RQ values for listed and non-listed plants exposed to clomazone that volatilizes off a treated field with subseque nt near-field redepos ition for the highest application rate crop, sweet potato, and the lowest maximum label rate, use on beans (succulent), melons (musk), and watermelon cr ops. Estimated near field loading due to
volatilization alone is 0.975 lbs ai/A for use on sweet potatoes and 0.163 lbs ai/A for use on succulent beans, assuming 65% volatilizati on at 100% humidity conditions on day of application (Section 2.2.2.2). Th ese RQ values would be app licable to terrestrial upland plants and wetland/riparian plants. The assu mption of 100% humidity in conjunction with the assumption that no dilution occurs over the travel distance provides an upper bound estimate which in reality is expected to be lo wer either due to the humidity level being lower and/or aerial dispersion occurr ing over the travel distance. RQ values associated with volatilization at lower humidity levels of 50% and 25% with assumed subsequent loading with no dispersion are provided in Table 34.

Table 34 RQ values for near field plants exposed to clomazone from volatilization

Sweet Potato Use Potential Off-Site

Loading from Volatilization at Humidity of: Succulent Beans Use Potential OffSite Loading from Volatilization at Humidity of: Plant Group

100% 50% 25% 100% 50% 25%
Monocot Non-listed 1 31 13 3.4 5.3 2.1 0.5 Monocot Listed 2 157 63 17 26 10 2.7 Dicot Non-listed 1 264 105 28 44 18 4.6 Dicot Listed 2 513 205 55 86 34 8.9 Bolded listed RQ values exceed the endangered species LOC of 1, and bolded non-listed RQ values exceed the non-listed species LOC of 1

. 1 Monocot (or dicot) non-listed RQ = (EEC, lb ai/acre) / (IC 25 , lb ai/acre), where the EEC is the volatilization loading and the monocot (or dicot) IC 25 value is from Table 25. 2 Monocot (or dicot) listed RQ = (EEC, lb ai/acre) / (NOAEC, lb ai/acre), where th e EEC is the volat ilization loading and the monocot (or dicot) NOAEC value is from Table 25.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 55 Table 35 RQ values for near field plants exposed to clomazone from volatilization

Sweet Potato Use Potential Off-Site

Loading from Volatilization at Humidity of: Succulent Beans Use Potential OffSite Loading from Volatilization at Humidity of: Plant Group

100% 50% 25% 100% 50% 25%
Monocot Non-listed 1 16 6 1.7 2.6 1.1 0.3 Monocot Listed 2 79 31 8.0 13 5.0 1.5 Dicot Non-listed 1 132 53 14 22 9.0 2.4 Dicot Listed 2 257 103 27 43 17 4.7 Bolded listed RQ values exceed the endangered species LOC of 1, and bolded non-listed RQ values exceed the non-listed species LOC of 1. 1 Monocot (or dicot) non-listed RQ = (EEC, lb ai/acre) / (IC 25 , lb ai/acre), where the EEC is the volatilization loading and the monocot (or dicot) IC 25 value is from Table 25. 2 Monocot (or dicot) listed RQ = (EEC, lb ai/acre) / (NOAEC, lb ai/acre), where th e EEC is the volat ilization loading and the monocot (or dicot) NOAEC value is from Table 25.



### 4.1.4 Direct Effects to Freshwater Fish (Amphibians) and Plants

4.1.4.1 L ABEL U SES O THER T HAN R ICE


### Table 36 contains the acute and chronic RQ values for freshwater fish (amphibians) 34



### , aquatic invertebrates and aquatic plants for uses representative of all clomazone uses and use
rates. The EEC values used to calculate th ese RQ values were based on the conservative assumption for clomazone load in runoff, that none of the clomazone volatilizes from the soil due to displacement by water vapor (i.e., “without” volatilization). None of the animal acute RQ values exceed the acute e ndangered species LOC of 0.05 and none of the chronic RQ
values exceed the chronic LOC of 1.0. The va scular non-listed and listed species and nonvascular non-listed RQ values do not exceed the non-listed or listed species plant LOC (1.0).

Table 36 RQ values for freshwater fish, invertebrates, and plants based on 1-in-10 year acute and chronic exposure concentrations in a vulnerable receiving water

Freshwater Fish Freshwater Invertebrates Vascular Plants Nonvascular
Acute 1 Chronic 2 Acute 1 Chronic 2 NonList 3 List 4 NonList 3 PRZM Scenario (standard unless noted)

Without Without Without Witho ut Without Without Without Florida sugarcane 0.01 <0.1 0.01 <0.1 <0.5 <0.5 <0.5 Louisiana sugarcane 0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Mississippi cotton, 1.25 lb/A 0.01 <0.1 0.01 <0.1 <0.5 <0.5 <0.5 North Carolina cotton, 1.25 lb/A 0. 01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Florida peppers 0.01 <0.1 0.01 <0.1 <0.5 <0.5 <0.5 Mississippi soybeans, 1.25 lb/A 0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 North Carolina sweet potato <0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 North Carolina tobacco <0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Florida potato (NMC)1 0.01 <0.1 0.01 <0.1 <0.5 <0.5 <0.5 Michigan bean <0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Oregon snap beans <0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5

34 Fish results are used as a surrogate for risks to aquatic-phase amphibians.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 56 Freshwater Fish Freshwater Invertebrates Vascular Plants Nonvascular
Acute 1 Chronic 2 Acute 1 Chronic 2 NonList 3 List 4 NonList 3 PRZM Scenario (standard unless noted)

Without Without Without Witho ut Without Without Without Florida cabbage <0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Florida cucumber, 1 lb ai/acre 0.01 <0.1 0.01 <0.1 <0.5 <0.5 <0.5 Florida cucumber, 0.75 lb ai/acre 0. 01 <0.1 0.01 <0.1 <0.5 <0.5 <0.5 Florida cucumber, 0.5 lb ai/acre 0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Florida cucumber, 0.25 lb ai/acre <0. 01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5 Oregon mint, 0.5 lb/A <0.01 <0.1 <0.01 <0.1 <0.5 <0.5 <0.5
1 Acute RQ = (acute EEC, ppb) / (acute LC 50 or EC 50 , ppb), where the EEC is the 24-h 1 in 10 year peak without volatilization (Table 52) and the fish 96-h LC 50 is 2,900 ppb for silver catfish (Tab le 23) and the invertebrate 48-h EC 50 is 5.400 ppb for D. magna (Table 24). 2 Chronic RQ = (chronic EEC, ppb) / (chronic NOAEC, ppb), wher e the EEC is the 60-d 1 in 10 year peak for fish and the 21-d 1-in-10 year peak for invertebrates without volatilizati on (Table 52) and the fish chronic NOAEC is 350 ppb and the invertebrate chronic NOAEC is 2,200 ppb (Table 23 and Table 24, respectively). 3 Non-listed Plant RQ = (EEC, ppb) / (IC 50 , ppb), where the EEC is the 24-h 1 in 10 year peak without volatilization (Table 52) and the IC 50 is 30,200 ppb for vascular plants and 167 ppb for non-vascular plants (Table 25). 4 Listed Plant RQ = (EEC, ppb) / (NOAEC, ppb), where the EEC is the 24-h 1 in 10 year peak without volatiliz ation (Table 52) and the NOAEC is 7, 300 ppb (Table 25).



### Table 37 contains the acute and chronic RQ values for estuarin e-marine fish, invertebrates and aquatic plants at 1-in-10 year acute and chronic EEC leve ls for all clomazone uses and use rates. Conservatively assuming no volat ilization occurs off the field (“without” volatilization), no chronic LOC for fish or inve rtebrates is exceeded for any use and except for invertebrate acute RQ values for Florida sugarcane and cucurbits (also representative of squash and melons) at 1.25 and 1 lbs ai/A, resp ectively, none of the othe r uses exceed acute endangered LOC for fish or invertebrates. No listed or non-listed LOC is exceeded for vascular plants, no non-listed LOC is exceeded for non-vascular plants and except for sugarcane, pepper, and cucurbit (also represen tative of squash and melon) uses at 0.75 to 1.275 lbs ai/A, none of the other uses exceed the listed LOC for listed non-vascular plants. Accounting for volatilization on the field (“with” volatilization) results in no exceedence of the acute listed species LOC or chronic LOC for estuarine fish and invertebrates, or exceedence of the listed aquatic plant LOC.

Table 37 RQ values for estuarine-marine fish, invertebrates, and aquatic plants based on 1-in-10 year acute and chronic exposure concentrations in a vulnerable receiving water, With and Without PRZM Volatilization

Estuarine Fish EstuarineInvertebrates Vascular Plants Non-Vascular Plants

Acute 1 Chronic 2 Acute 1 Acute 1 Chronic 2 NonList 3 Listed 4 NonList 3 Listed 4 PRZM Scenario (standard unless noted) Without Without Without With Without Without With out Without Without With
Florida sugarcane 1.25 lb ai/acre <0.01 <0.1 0.06 <0.01 <0.1 <0.5 <0.5 <0.5 1.5 1.0Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 57 Estuarine Fish EstuarineInvertebrates Vascular Plants Non-Vascular Plants

Acute 1 Chronic 2 Acute 1 Acute 1 Chronic 2 NonList 3 Listed 4 NonList 3 Listed 4 PRZM Scenario (standard unless noted) Without Without Without With Without Without With out Without Without With

Louisiana
sugarcane, 1.25 lb ai/acre <0.01 <0.1 0.04 <0.01 <0.1 <0.5 <0.5 <0.5 1.1 1.0

Mississippi cotton, 1.25 lb ai/acre <0.01 <0.1 0.05 <0.01 <0.1 <0.5 <0.5 <0.5 1.2 0.7

North Carolina cotton, 1.25 lb/A <0.01 <0.1 0.03 <0.01 <0.1 <0.5 <0.5 <0.5 0.7 0.5

Florida peppers 1.0 lb ai/acre <0.01 <0.1 0.05 <0.01 <0.1 <0.5 <0.5 <0.5 1.2 0.5
Mississippi soybeans, 1.25 lb ai/acre <0.01 <0.1 0.03 <0.01 <0.1 <0.5 <0.5 <0.5 0.8 0.5

North Carolina sweet potato <0.01 <0.1 0.02 <0.01 <0.1 <0.5 <0.5 <0.5 0.6 <0.5

North Carolina tobacco <0.01 <0.1 0.01 <0.01 <0.1 <0 .5 <0.5 <0.5 <0.5 <0.5

Florida potato (NMC), 1.275 lb ai/acre <0.01 <0.1 0.05 <0.01 <0.1 <0.5 <0.5 <0.5 1.2 0.5

Michigan bean <0.01 <0.1 0.01 <0.01 <0.1 <0.5 <0.5 <0.5 <0.5 <0.5 Oregon snap beans <0.01 <0.1 0.01 <0.01 <0.1 <0 .5 <0.5 <0.5 <0.5 <0.5

Florida cabbage <0.01 <0.1 0.01 <0.01 <0.1 <0.5 <0.5 <0.5 <0.5 <0.5
Florida cucumber, 1 lb ai/acre <0.01 <0.1 0.07 <0.01 <0.1 <0.5 <0.5 <0.5 1.7 0.9

Florida cucumber, 0.75 lb ai/acre <0.01 <0.1 0.06 <0.01 <0.1 <0.5 <0.5 <0.5 1.3 0.6

Florida cucumber, 0.5 lb ai/acre <0.01 <0.1 0.04 <0.01 <0.1 <0.5 <0.5 <0.5 0.9 <0.5

Florida cucumber, 0.25 lb ai/acre <0.01 <0.1 0.02 <0.01 <0.1 <0 .5 <0.5 <0.5 <0.5 <0.5Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 58 Estuarine Fish EstuarineInvertebrates Vascular Plants Non-Vascular Plants

Acute 1 Chronic 2 Acute 1 Acute 1 Chronic 2 NonList 3 Listed 4 NonList 3 Listed 4 PRZM Scenario (standard unless noted) Without Without Without With Without Without With out Without Without With Oregon mint, 0.5 lb/A <0.01 <0.1 <0.01 <0.01 <0.1 <0.5 <0.5 <0.5 <0.5 <0.5

1 Acute RQ = (acute EEC, ppb) / (acute LC 50 or EC 50 , ppb), where the EEC is the 1-in-10 year 24-h peak value without (Without) and with (With) volatilization (Table 52) and the fish 96-h LC 50 is 40,600 ppb ai for sheepshead minnow (Table 23) and the mysid shrimp 96-h LC 50 is 566 ppb (Table 24). A wi th volatilization an alysis was included only where at least one RQ value exceeded a LOC under the conservation assumption that there was no volatilization from the land. 2 Chronic RQ = (chronic EEC, ppb) / (chronic NOAEC, ppb), where the EEC is the 1-in-10 60-d peak for fish and the 1-in10 year 21-d peak for invertebrates wit hout volatilization (T able 52) and the fish chronic NOAEC is 4,850 ppb and the invertebrate chronic NOAEC is 68 ppb (Tab le 23 and Table 24, respectively). 3 Non-listed Plant RQ = (EEC, ppb) / (IC 50 , ppb), where the EEC is the 1-in-10 year 24-h peak without vol atilization (Table 52) and the IC 50 is 30,200 ppb for vascular plants and 167 ppb for non-vascular plants (Table 25). 4 Listed Plant RQ = (EEC, ppb) / (NOAEC, ppb), where the EEC is the 1-in-10 year 24-h peak without and with volatilization (Table 52) and the NOAEC is 7,300 ppb for vascular plants a nd 23.6 ppb for nonvascular (Table 25).

4.1.4.2 R ICE U SE



### Wet Seeded
Table 38 contains the acute RQ values for freshwater and estuarine-marine fish and invertebrates and aquatic plants for wet-seeded rice use with holding times spanning from the day of application to 32 days post-treatment. This analysis assumes that clomazone is applied directly to flood water or that the field is flooded imme diately after treatment. Two of the Section 3 labels require applications be on fields with levees and that the levees, and application timing in terms of a rain event be such that runoff does not occur. Additionally, the water-seeded label prohibits release of the water from the treated field for 14 days posttreatment, unless the water is contained within a tailwater recovery system, or other system appropriate for preventing discha rge from rice fields. The other Section 3 labels do not have these prohibitions.

Table 38 Wet Seeded Rice Non-Listed and Listed Aquatic Plant RQs and Acute Fish and Aquatic Invertebrate RQ Values for Clomazone Residues in Rice Paddy Water at Various Holding Times

Freshwater Estuarine Vascular Nonvascular

Fish Invertebrates Fish Invertebrates Days after treatment EEC Clomazone ppb Acute 1 Acute 1 Acute 1 Acute 1 Non-Listed and Listed Plants 2, 3 NonListed Plants 2 Listed Plants 3

0 546 0.19 0.10 0.01 0.96 0.1 3.3 23.1

15 352 0.12 0.07 <0.01 0.62 <0.1 2.1 14.9

20 304 0.10 0.06 <0.01 0.54 <0.1 1.8 12.9

24 271 0.09 0.05 <0.01 0.48 <0.1 1.6 11.5Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 59 Freshwater Estuarine Vascular Nonvascular

Fish Invertebrates Fish Invertebrates Days after treatment EEC Clomazone ppb Acute 1 Acute 1 Acute 1 Acute 1 Non-Listed and Listed Plants 2, 3 NonListed Plants 2 Listed Plants 3

25 263 0.09 0.05 <0.01 0.46 <0.1 1.6 11.1

28 241 0.08 0.04 <0.01 0.43 <0.1 1.4 10.2

30 227 0.08 0.04 <0.01 0.40 <0.1 1.4 9.6

32 214 0.07 0.04 <0.01 0.38 <0.1 1.3 9.1

1 Acute RQ = (EEC, ppb) / (acute LC 50 or EC 50 , ppb), where the EEC is the paddy water residue (Section 2.1.2.1) and the fish 96-h LC 50 is 2,900 ppb for silver catfish (Table 23), the freshwater invertebrate 48-h EC 50 is 5.400 ppb for D. magna (Table 24), the estuarine fish 96-h LC 50 is 40,600 ppb ai (Table 23), and the estuarine-marine invertebrate 2 Non-listed Plant RQ = (EEC, ppb) / (IC 50 , ppb), where the EEC is the paddy wate r residue (Section 2.1.2.1) and the IC 50 is 30,200 ppb for vascular plants and 167 ppb for non-vascular plants (Table 25). 3 Listed Plant RQ = (EEC, ppb) / (NOAEC, ppb), where the EEC is the paddy water residue (Section 2.1.2.1) and the NOAEC is 7,300 ppb (Table 25).



### Dry Seeded

Modeled estimates of clomazone in rice flood wa ter using a provisional modification of input to the Tier I Rice model (Section 2.1.2.2) to ac count for clomazone loss in soil from time of application till permanent flood results in a c onservative estimate in the floodwater of 364 ppb on the day of flood. However, as demonstr ated in aquatic fiel d dissipation studies performed in Texas and Arkansas the level appe ars to more realistically not exceed 5 to 7 ppb (see Section 2.1.2.2.). Additionally, assumi ng release of floodwater on the day of application is highly conservative given that rice cultural practic es should result in the water being retained at least for a few days without release to surface wa ters, unless a flood event
occurs. The use of modeled versus measured values to assess risk makes a significant
difference in the conclusion of risk. Measur ed levels in floodwater are below acute and
chronic LOC values for freshwater and marine and estuarine fish and invertebrates, and below listed and nonlisted plant LOC values (Table 39). Modeled results indicate potential
concern for acute risks to freshwater fish and invertebrates and for estuarine-marine
invertebrates and exceedance of listed and non-listed LOC values for nonvascular and vascular plants.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 60 Table 39 Dry Seeded Non-Listed and Listed Aquatic Plant RQs and Acute Fish and Aquatic Invertebrate RQ Values for Clomazone Residues in Rice Paddy Water at Permanent Flood

Freshwater Estuarine Vascular Nonvascular

Fish Invertebrates Fish Invertebrates EEC Clomazone ppb Acute 1 Acute 1 Acute 1 Acute 1 Non-Listed and Listed Plants 2, 3 NonListed Plants 2 Listed Plants 3

Modeled 364 0.13 0.07 0.01 0.64 <0.1 2.2 15.4

Measured 7 <0.01 <0.01 <0.01 <0.01 <0.1 <0.1 0.3

1 Acute RQ = (EEC, ppb) / (acute LC 50 or EC 50 , ppb), where the EEC is the paddy water residue (Section 2.1.2.2) and the fish 96-h LC 50 is 2,900 ppb for silver catfish (Table 23), the freshwater invertebrate 48-h EC 50 is 5.400 ppb for D. magna (Table 24), the estuarine fish 96-h LC 50 is 40,600 ppb ai (Table 23), and the estuarine-marine invertebrate 2 Non-listed Plant RQ = (EEC, ppb) / (IC 50 , ppb), where the EEC is the paddy wate r residue (Section 2.1.2.2), and the IC 50 is 30,200 ppb for vascular plants and 167 ppb for non-vascular plants (Table 25). 3 Listed Plant RQ = (EEC, ppb) / (NOAEC, ppb), where the EEC is the paddy water residu e (Section 2.1.2.2), and the NOAEC is 7,300 ppb (Table 25).



### 4.1.5 Probit Slope Response Analysis of LOC Values and Acute RQ Values
As part of the risk estimation, the probability of mortality associated with the endangered acute LOC values is estimated along with the probability of acute mortality occurring if exposure at the estimated environmental concentr ation actually occurs. The probability of mortality calculations are based on the pr obit slope dose response relationship. The probability of mortality for an exposed indivi dual are calculated using an Excel spreadsheet tool IECV1.1 (Individual Effect Chance Model Ve rsion 1.1) developed by EFED of the U.S. EPA, OPP, Environmental Fate a nd Effects Division (June 22, 2004).

There were two probit slopes from clomazone toxi city results. The acu te mysid results fit a probit dose-response model with a prob it slope of 6.7259 (95% CL 3.8914, 9.5605). The
silver catfish acute results we re not a good probit dose-response fit, but a slope estimated from the data is 3.1657 (95% CL -0.3946, 6.726). Because the lower 95% CL of the slope for the silver catfish is not a valid slope value, the default lower 95% CL of 2 is used for fish. The other acute toxicity results either consisted of limit dose type tests ( e.g ., avian acute dose and dietary results) which do not provide data which can be used to calculate a probit doseresponse slope, the data did not fit a probit model and no probit slope could be estimated from the data, or the results availa ble from a study were limited to the LD 50 

### . In these cases the default slope of 4.5 (95% CL 2.9, 9) was used.

The odds of mortality for an individual at the endangered species LOC for terrestrial and aquatic animals based on the slopes discussed in the previous paragr aph are provided in Table 40. The odds of mortality for an individu al at a range of acute RQ values between 0.05Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 61 

### and 0.4 are provided in Table 42, using the slopes for the taxono mic groups listed in Table
40.

Table 40 Probit Slope and Odds of Mortality for an Individual at the LOC

Aquatic Invertebrates (TGAI) Listed Species Birds and Mammals

(TGAI) Mammals (Commence EC) Fish (TGAI) Freshwater Estuarine/Marine

LOC 0.1 0.1 0.05 0.05 0.05 Slope 4.5* 12.679 3.1657 6.7259 9.7919 Slope 95% CL 2, 9* 2.121, 23.237 2**, 6.726 3.8914, 9.5605 5.1804, 13.7658

Odds of individual effect 1 in 294,000 <1 in 10 36 1 in 52,500 <1 in 10 17 <5 in 10 36

95% CL 1 in 44, <1 in 10 18 1 in 59, <1 in 10 119 1 in 22, <1 in 10 17 <1 in 10 6 , in 10 35 <1 in 10 11 , <1 in 10 71

*Default mean slope value (4.5) and 95% CL (2, 9) is us ed due to specific dose-respons e information for this group. **The probit model is a poor fit for the tested doses and res ponse, therefore the lower 95% CL for the data was not a valid slope and the default lower 95% CL of 2 was used.

Table 41 Odds of Mortality for an Individual Bird or Mammal at a Given Acute RQ Value for the TGAI and Commence EC

Birds and Mammals, TGAI (Slope =4.5) Birds and Mammals, Commence EC (Slope =12.679) RQ
Odds 95% CL Odds 95% CL

0.01 <1 in 10 18 1 in 31,600; <1 in 10 72 <1 in 10 141 1 in 20,300; <1 in 10 273

0.02 <1 in 10 13 1 in 2,950; <1 in 10 52 <1 in 10 102 1 in 6,370; <1 in 10 273

0.03 <1 in 10 11 1 in 862; <1 in 10 42 <1 in 10 82 1 in 1,620; <1 in 10 273

0.04 <1 in 10 9 1 in 386; <1 in 10 35 <1 in 10 69 1 in 661; <1 in 10 231

0.05 <1 in 10 8 1 in 216; <1 in 10 31 <1 in 10 60 1 in 345; <1 in 10 200

0.06 <1 in 10 7 1 in 138; <1 in 10 27 <1 in 10 53 1 in 209; <1 in 10 176

0.07 <1 in 10 6 1 in 96; <1 in 10 24 <1 in 10 48 1 in 140; <1 in 10 158

0.08 <1 in 10 6 1 in 70; <1 in 10 24 <1 in 10 43 1 in 100; <1 in 10 142

0.09 1 in 791,000 1 in 55; <1 in 10 20 <1 in 10 39 1 in 75; <1 in 10 130

0.10 1 in 294,000 1 in 44; <1 in 10 18 <1 in 10 36 1 in 59; <1 in 10 119

0.11 1 in 125,000 1 in 36; <1 in 10 17 <1 in 10 33 1 in 47; <1 in 10 109

0.12 1 in 58,500 1 in 30; <1 in 10 16 <1 in 10 31 1 in 39; <1 in 10 101

0.13 1 in 29,900 1 in 26; <1 in 10 15 <1 in 10 28 1 in 33; <1 in 10 93

0.15 1 in 9,563 1 in 20; <1 in 10 13 <1 in 10 25 1 in 24; <1 in 10 81

0.19 1 in 1,710 1 in 13; <1 in 10 10 <1 in 10 19 1 in 16; <1 in 10 62

0.20 1 in 1,210 1 in 12; <1 in 10 9 , <1 in 10 18 1 in 14; <1 in 10 58

, 0.23 1 in 491 1 in 9.9; <1 in 10 8 <1 in 10 15 1 in 11; <1 in 10 49Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 62 Table 42 Odds of Mortality for an Individual Fish or Aquatic Invertebrate at a Given Acute RQ Value

Fish (Slope =3.1657) Freshwater Aquatic Invertebrates (Slope = 6.7259) Marine (Mysid) Invertebrates (Slope = 9.7919) RQ
Odds 95% CL Odds 95% CL Odds 95% CL

0.01 <1 in 10 9 1 in 31,600; <1 in 10 40 <1 in 10 40 <1 in 10 14 ; <1 in 10 40 <1 in 10 84 <1 in 10 24 ; <1 in 10 166

0.05 1 in 52,500 1 in 216; <1 in 10 17 <1 in 10 17 <1 in 10 6 ; <1 in 10 35 <5 in 10 36 <1 in 10 11 ; <1 in 10 71

0.06 1 in 18,200 1 in 138; <1 in 10 15 <1 in 10 15 1 in 10 6 ; <1 in 10 31 <3 in 10 32 <1 in 10 9 ; <1 in 10 63

0.07 1 in 7,810 1 in 96; <1 in 10 14 <1 in 10 14 1 in 286,000; <1 in 10 27 <1 in 10 29 <1 in 10 8 ; <1 in 10 56

0.09 1 in 2,150 1 in 55; <1 in 10 11 <1 in 10 11 1 in 42,400; <1 in 10 23 <1 in 10 24 <1 in 10 7 ; <1 in 10 46

0.10 1 in 1,290 1 in 44; <1 in 10 11 <1 in 10 11 1 in 20,100; <1 in 10 21 <1 in 10 22 <1 in 10 6 ; <1 in 10 42

0.11 1 in 831 1 in 36; <1 in 10 10 <1 in 10 10 1 in 10,500; <1 in 10 19 <1 in 10 20 <1 in 10 6 ; <1 in 10 39

0.12 1 in 562 1 in 30; <1 in 10 9 <1 in 10 9 1 in 5,890; <1 in 10 18 <1 in 10 19 <1 in 10 6 ; <1 in 10 36

0.13 1 in 397 1 in 26; <1 in 10 8 <1 in 10 8 1 in 3,540; <1 in 10 16 <4 in 10 17 1 in 451,000; <1 in 10 33

0.15 1 in 220 1 in 20; <1 in 10 7 <1 in 10 7 1 in 1,490; <1 in 10 14 <2 in 10 15 1 in 101,000; <1 in 10 29

0.19 1 in 89 1 in 13; 1.6 in 10 6 1.6 in 10 6 1 in 400; 1.6 in 10 6 <1 in 10 12 1 in 10,700; <1 in 10 22

0.20 1 in 74 1 in 12; 1 in 774,000 1 in 773,000 1 in 306; <1 in 10 10 <1 in 10 11 1 in 6,810; <1 in 10 21

0.23 1 in 46 1 in 9.9; 1 in 113,000 1 in 113,000 1 in 154; <1 in 10 9 <1 in 10 9 1 in 2,120; <1 in 10 18

0.25 1 in 35 1 in 8.8; 1 in 39,000 1 in 38,900 1 in 105; <1 in 10 8 <5 in 10 8 1 in 1,100; <1 in 10 16

0.30 1 in 20 1 in 6.8; 1 in 4,580 1 in 4,580 1 in 48; <1 in 10 6 <1 in 10 6 1 in 296; <1 in 10 12

0.35 1 in 13 1 in 5.5; 1 in 924 1 in 924 1 in 26; 1 in 153,000 1 in 249,000 1 in 110; <1 in 10 9

0.40 1 in 9.6 1 in 4.7; 1 in 269 1 in 269 1 in 16; 1 in 14,100 1 in 20,500 1 in 50; <1 in 10 7

0.43 1 in 8.1 1 in 4.3; 1 in 14.6 1 in 146 1 in 13; 1 in 4,370 1 in 6,030 1 in 34.7; <1 in 10 6

0.47 1 in 6.7 1 in 3.9; 1 in 72.9 1 in 72.9 1 in 9.9; 1 in 1,160 1 in 1,510 1 in 22.4; 1 in 314,000

0.62 1 in 3.9 1 in 2.9; 1 in 12.3 1 in 12.3 1 in 4.8; 1 in 42 1 in 45 1 in 7.1; 1 in 469

0.64 1 in 3.7 1 in 2.9; 1 in 10.4 1 in 10.4 1 in 4.4; 1 in 24.7 1 in 34 1 in 6.3; 1 in 262

0.96 1 in 2.0 1 in 2.0; 1 in 2.2 1 in 2.2 1 in 2.1; 1 in 2.3 1 in 2.3 1 in 2.1; 1 in 2.5



## 4.2 Risk Description

The following risk description explains the overall conclusions regarding the potential ecological risk from the vari ous uses of clomazone. The risk conclusions take into consideration the risk estimates, includes RQ values and information on odds of acute mortality, in conjunction with other informati on such as monitoring data, field studies, and incident data that may provide additional insi ghts into the likelihood of exposure, and other factors that modify the likeli hood of exposure such as timing of application, overlap of area affected and the degree of effect with the presence/absence of taxa, species sensitivity distribution, and presence/a bsence of dietary items.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 63 

### 4.2.1 Non-Listed Species

4.2.1.1 D IRECT E FFECTS TO T ERRESTRIAL P LANTS AND A NIMALS 

### Primary Productivity and Habitat Integrity

Environmental baseline condi tions from putting the land in to crop production includes a temporary loss of primary production or existin g standing crop on the fi eld at the time of preparation of the seed or transp lant bed and loss of habitat that the previous year’s crop trash provided or loss of habitat or plant diversity that a fallow fi eld provided before being put back into production. Herbicides like clomazone provide a chemical alternative to physical methods in eliminating target undesirable plants from the field. Clomazone is applied as a preemergent with preparation of the field genera lly occurring when the plant growth curve is low ( e.g ., <5% production, or coming out of dormanc y). For soybean and cotton, clomazone is registered for use under conservation tillage, which refers to a number of strategies and techniques for establishing crops with minimal cultivation of the soil.

Runoff and Spray Drift

Plant RQ exceedences of non-listed and listed speci es LOC values (Table 33) indicate that loading of clomazone from combined runoff a nd spray drift to terrestrial and semi-aquatic areas adjacent to a treated field potentially poses unreasonable risks to o ff-field plants at all existing clomazone use rates (0.251 to 1.5 lbs ai/A ). Effects from spra y drift loading were
below the LOC for non-listed monocots at all application rates (0.251 to 1.5 lbs ai/A), for listed monocots at application rates at and below 0.6 lbs ai/A, and for non-listed dicots at and
below 0.375 lbs ai/A. Distances from the field th at were estimated to exceed non-listed and listed species LOC values due to loading from spray drift are listed in Table 43. Except for the Cerano 5 MEG label for aerial or ground appli cation to rice fields, labels specifically state to use spray drift conditions that meet a droplet size classification of coarse or greater or to use a drift reducing additive. The distan ces for ground spray were calculated using the largest droplet size available in the terrestrial Tier I model in AGDRIFT, which is ASAE fine to median-coarse (there is no Tier 2 ground spra y model). The coarser droplet size called for on all labels, except the Cerano 5 MEG, would resu lt in smaller distances than listed in the table. The Cerano 5 MEG label does not pr ovide guidance on droplet size for ground or aerial spray so distances in table for ground sp ray would not necessarily be overestimated. Aerial spray was modeled for two droplet size categories avai lable in the Tier I Aerial AGDRIFT model, ASAE coarse to very coarse and ASAE medium to coarse.

Based on modeling the distance extending from th e field where spray drift loading exceeds non-listed or listed species LOC extends out over 1,000 feet for aerial applications, forChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 64 

### droplet size ASAE medium to coarse; distances are lower for coarser droplet size. For 1.5 lbs ai/A, spray drift out to 470 feet exceeds the listed LOC for dicots and out to 215 feet for non-listed dicots; spray drift lo ading does not exceed the non- listed LOC for monocots. For 1.0 lb ai/acre, spray drift exceed ing the listed species LOC exte nds out to 300 ft for dicots.

Table 43 Distance from Treated Field Spray Drift Loading Exceeds LOC

Distance in feet (Acres) affected
Aerial Spray Application Rate Load below LOC lbs ai/A Ground Spray Fine to Medium Coarse Droplet Size Coarse to Very Coarse Medium to Coarse

Monocot Listed 0.0062 110 (0.52 A)* N/A N/A
Dicot Non-Listed 0.0037 215 (~1 A) N/A N/A 1.5 lbs ai/A

Dicot Listed 0.0019 470 (2.25 A) N/A N/A

1.0 lb ai/acre Monocot Listed 0.0062 63 (0.30 A) N/A N/A Dicot Non-Listed 0.0037 127 (0.61 A) N/A N/A Dicot Listed 0.0019 300 (1.4 A) N/A N/A

0.75 lbs ai/A Monocot Listed 0.0062 43 (0.21 A) N/A N/A Dicot Non-Listed 0.0037 88 (0.42 A) N/A N/A Dicot Listed 0.0019 209 (1.0 A) N/A N/A

Monocot Listed 0.0062 N/A 270 (1.3 A) 425 (2.0 A)
Dicot Non-Listed 0.0037 63 (0.30 A) 450 (2.2 A) 810 (3.9 A) 0.6 lbs ai/A

Dicot Listed 0.0019 155 (0.74 A) 900 (4.3 A) >1000 (>4.8) 0.251 lbs ai/A Dicot Listed 0.0019 49 (0.23 A) N/A N/A *The acreage affected is calcul ated using the distance off the edge-of-field a nd the length of the treated field (208.7 ft alon g a side for a square acre). N/A: Not applicable because aerial application is not registered for the use or because the EEC was below the LOC.



### Non-Target Plant Incidents

Clomazone incident data for non-target plant effects provide some records with reported
distance to affected site or the farthest di stance effects were obser ved (Appendix G). The incident data for clomazone does not include for a majority of records a definitive determination of the spec ific route of exposure ( i.e ., spray drift, volatilization, runoff or a combination). Most incidents reported as adjacent to treated sites are identified as attributable to spray drift. However, there ar e some records where volat ilization is a definite contributing factor even to adja cent properties rather than spray drift or in addition to spray drift. An analysis of the incident distance information for the ME formulations (N = 52)
indicates that 76.9% of incidents were w ithin 300 feet, 21.1% were between 300 and 1,500 feet, and one incident (1.9%) was one mile fr om the nearest treated field (Figure 5).Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 65 

### Distances reported as adjacent to treated field were categorized as within 300 feet for this analysis. For the EC formulations (N = 160) 84.4% of incidents were within 300 feet, 10.0% were between 300 and 1,500 feet, 5.1% we re between 1,500 and 4,500 feet, and two incidents (1.9%) were greater than or equal to one mile from the nearest treated field (Figure 5). Most incidents were reported in 1986, 1993, and 1997 (Figure 6). The 1986 incidents were associated with the use of the newly regi stered EC formulation on soybeans. Most of
the incidents associated with distances above 1,500 ft with the EC fo rmulation (8 of 12) occurred during this time. Within a few mont hs buffer zones, soil incorporation, and spray drift reducing label language ( e.g ., use of additive to reduce spray drift, use of low boom and coarse spray) were added to the label. Th ere are no incident reports between 1987 and 1991. Several minor uses such as pumpkins and peas (s ucculent) were added to the label during this time period; additionally clomaz one use on soybeans declined during this time period. In 1993, cotton use was added and there was a major resurgence in reported incidents. Cotton use did not require soil incorporation. Emerge ncy meetings were held to address non-target plant effects from registered use on cotton; the state of Tennessee put an emergency ban on use of clomazone through the summer of 1993. Except for an incident in 1994, the remaining incidents above 1,500 feet associated with the EC occur during this time. The ME formulation was registered for use in 1995, with no soil incorporation required. The following year, 1996, there were reported inci dents with the ME formulation. Another resurgence of incidents occurr ed in 1997 along with increased use that year. After 1997 a number of minor incidents were reported but not much information is provided. This is in part due to a change in 1997 of the FIFR A 6(a)(2) reporting requirements changing the definition for minor non-target plant incidents to being defined as thos e affecting <45% of the area treated. For example, if 100 acres ar e treated 45 acres off th e treated field would need to be affected before it is required to be reported as a major incident. Although use of clomazone on Figure 6 appears to reduce belo w 100,000 lbs annually in 2001, this in part is likely due to reduced monitoring by USDA-NAS S. Alternative sources for 2001 to 2007
indicate that combined cotton a nd soybean use is over 100,000 pounds (100 x 1,000 lbs) annually during this time. Use on rice, which was first registered for use with the ME formulation in 2000 has become the highest use of clomazone annually (approximately 600,000 lbs). Approximately 13.5 percent of cl omazone is used on soybeans and cotton annually (2001-2007).

Discounting the 1986 data when spray drift re duction language was not on labels, the incident information supports that most effects ar e within the expected sp ray drift effect area. Additionally, during the 1993 meetings about incidents that ye ar, it was identified that except for some cases in Tennessee, effects occurred well within the label buffer zones in place on the label. The degree of clomazone effects associated with various distances from a treatedChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 66 

### field, however, is not readily identifiable from th e incident data base. Effects span the whole spectrum from minor whitening with all plants surviving, to seve re effects with some plant mortality.

Figure 5 Distribution of Distances from a Treated Field to Clomazone Effects

0 10 20 30 40 50 60 70 80 90

< 300 301-500 501-1,000 1,001-1,500 1,501-2,500 2,501-3,500 3,501-4,500 > 5,280

Distance (feet)Percent of Incidents ME (N = 52) EC (N = 160) Unknow n (N = 128) Total (N = 340)

_ _ 0 10 20 30 40 50 60 70 80 90

< 300 301-500 501-1,000 1,001-1,500 1,501-2,500 2,501-3,500 3,501-4,500 > 5,280

Distance (feet)Percent of Incidents ME (N = 52) EC (N = 160) Unknow n (N = 128) Total (N = 340)

_ _

The > 5,280 feet group is comprised of two incidents, one incident occurre d for the ME out to 1 mile from the site of application and one incident occurred for the EC out to 2 miles.Chapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone67Figure 6 Reported Number of Non-Target Plant Incidents Associated with Clomazone Formulations and Key RegulatoryDecisions01020304050607080901001101201986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007Year

Number of Reported Incidents050010001500200025003000 Cotton and Soybean Clomazone Total Lbs x 1,00 0Unknow n (minor)Unknow nME (minor)MEEClbs ai x 1,000EC Soybean Use Registered Feb ‘86>88* G R s o y b e a n i n t r o d u c e d ‘ 9 6Must soil incorporate, andbuffer zones** added to label inNov ‘86*Official reported incidents, but white areas were reported as observed to be widespread througout the midwest** Do not apply within 100 ft of desirable plants and 1,000 ft from towns, greenhouses and nurseries, commercial vegetable, fruit, and nut production** Request for registrant to submit 1-800 clomazone hotline incidentsEC Pumpkin and Peas(Succulent) UsesRegistered ‘88>1,173***EC Cotton Use Registered ‘93EC Fallow Land UseRegistered ‘89WP Pumpkinand Pea UseRegistered ‘91ME Registered ’95for all EC Usesexcept Fallow LandME Dry-SeededRice UseRegistered ’0001020304050607080901001101201986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007Year

Number of Reported Incidents050010001500200025003000 Cotton and Soybean Clomazone Total Lbs x 1,00 0Unknow n (minor)Unknow nME (minor)MEEClbs ai x 1,000EC Soybean Use Registered Feb ‘86>88* G R s o y b e a n i n t r o d u c e d ‘ 9 6Must soil incorporate, andbuffer zones** added to label inNov ‘86*Official reported incidents, but white areas were reported as observed to be widespread througout the midwest** Do not apply within 100 ft of desirable plants and 1,000 ft from towns, greenhouses and nurseries, commercial vegetable, fruit, and nut production** Request for registrant to submit 1-800 clomazone hotline incidentsEC Pumpkin and Peas(Succulent) UsesRegistered ‘88>1,173***EC Cotton Use Registered ‘93EC Fallow Land UseRegistered ‘89WP Pumpkinand Pea UseRegistered ‘91ME Registered ’95for all EC Usesexcept Fallow LandME Dry-SeededRice UseRegistered ’00Although use of clomazone on Figure 6 appears to reduce below 100,000lbs annually in 2001, this in part is likely due to reduced monitoring by USDA-NASS.Alternative sources for2001 to 2007 indicate that combined cotton and soybean use is over 100,000 pounds (100x1,000 lbs) annually during this time.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 68 

### Currently all Section 3 labels either explicitly prohibit application to non-field areas including fence rows, waterways, ditches, and road sites or imp licitly by restricting application to only those surfaces that will be so il incorporated. Section 3 labels for EC and WP registrations prohibit preemer gent soil incorporated applica tions within 1,000 ft of towns and subdivisions, commercial vegetable production 35 

### , commercial fruit production, commercial nurseries, and commercial greenhouses and 100 ft of desirable plants whereas soil unincorporated applications are prohibited within 1,500 ft of towns and subdivisions, commercial vegetable production, commercial fruit production, commercial nurseries, commercial greenhouses and desirable plants. Se ction 3 labels for ME registrations prohibit applications with 1,200 ft of towns and s ubdivisions, commercial vegetable production, commercial fruit production, commercial nurserie s, commercial greenhouses and some labels have 200 ft and others 300 ft of desirable pl ants. These buffers are not based on protection for any specific endangered spec ies but were set to reduce eff ects to off-field plants from spray drift and redeposition of volatilized clomazone.

Non-target Terrestrial Plant Effects

A diagram of the species IC 25 

### sensitivity distribution for dry weight, plant height, and survival with lines referencing the combined sheet runoff and spray drift EEC values for selected applications ranging fr om the highest application rate (sweet potato), to the lowest label application rate (succu lent beans) are provided in Figure 7. Such a comparison provides insight as to the number of species likely to be affect ed, as represented by the test species, within the area adjacent to the treated si te. At application rates of 0.5 lbs ai/A and lower, RQ values for non-listed monocot populat ions are at or belo w the LOC, indicating effects are within acceptable levels. For dicot species at the lowest application rate the IC 25 

### for seedling survival was exceeded for only one te st species, lettuce. Considering all species together, the lowest application ra te indicates the potential for at least 25% inhibition in plant height for about 12% of speci es and at least 25% inhibition in dry weight biomass of surviving plants for about 20% of species. At ground spray applications of 0.375 to 0.6 lbs ai/A, the situation does not appear to differ muc h. Seedling survival is still only exceeded for one test species, the dicot lett uce, and the potential for at leas t 25% inhibition in plant height has increased to about 15% of species, and dr y weight to about 25% of species. At the highest application rate of 1.5 lbs ai/A by ground spray, survival is reduced by at least 25% in approximately 15% of tested species, with at least 25% inhi bition in height in about 45% of species and dry weight in about 35% of species.

35 Most labels have at least an exception for sweet corn some labels also include exceptions which include one or more of the following: peppers, pumpkins, succulent peas, sweet potato, and winter squash.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 69 Figure 7 Terrestrial Plant EEC Values Compared to Seedling Emergence IC 25 Species Sensitivity Distribution for Clomazone

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0.03 lbs ai/A: total load for adjacent dry land – CB, MT, P 0.015 lbs ai/A: total load for adjacent dry land -- SB

Concentration at or below the non-listed monocot LOC 0.09 lbs ai/A: total load for adjacent dry land – SP

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0.03 lbs ai/A: total load for adjacent dry land – CB, MT, P 0.015 lbs ai/A: total load for adjacent dry land -- SB

Concentration at or below the non-listed monocot LOC 0.09 lbs ai/A: total load for adjacent dry land – SP

cab = cabbage; car = carrot; crn = corn; cuc = cucumber; ltc = le ttuce; oni = onion; rye = ryegrass; soy = soybean; tom = tomat o CB: cabbage use; MT: mint use; P: succulent pea use; SB: succulent bean use; SP: sweet potato use



### These estimates of impact are based solely on seedling emergence data. Other lines of evidence indicate that there are mitigating factors that will reduce the overall impact to plant communities. Such factors include that clomazone applied to surface soil or incorporated in the upper 1-3 inches of soil does not readily le ach to lower soil depths. With a couple of exceptions, crops that are plante d on fields treated with clom azone are typically planted at depths below clomazone treatment. This al lows the crop to germinate and grow without exposure in the root zone at le vels that impact the crop. Warnings on labels for EC and WP formulated products for crops such as succulent peas, peppers, and pumpkins state that “seed or transplants should be planted below the herb icide barrier to minimize” bleaching. As such impacts are expected to be lower for plants that have already emer ged or those which are dormant with roots, or with corms or tubers below clomazone depositi on in areas adjacent toChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 70 

### the field. Additionally, emerged plants may not be as sensitive to clomazone as seedlings. While there is only supplemental information on mortality available from vegetative vigor studies as discussed in Section 3.5.1, levels wh ere mortality occurs, garnered from one such study, were higher than in seedling emergence tests. Mortality in vegetative studies were not
observed until concentrations exceeded 0.137 lb s ai/A, whereas in seedling emergence increased mortality was observed at concen trations exceeding 0.0052 lbs ai/A. Because mortality does not appear to occur in emerge d vegetation until after 0.137 lbs ai/A, while the loading from sheet runoff and spray drift may reduce the height and weight of a limited number of species and result in some bleaching, plant survival w ould be at acceptable levels.
At rates of around 0.5 lbs ai/A clomazone labe ls indicate that clomazone only suppresses some annual grasses but does cont rol velvetleaf and spurred anoda . Rates of 1.0 lb ai/acre or higher are recommended to control fields that have previously been in conservation programs, or where heavy weed pressure is anticipated. Therefore while some bleaching would be observed on terrestrial plants adjacen t to the field, loss of the terrestrial plant community and its structural integrity is not considered likely at ground spray application
rates at and below 0.6 lbs ai/A. This is based on considerat ion that combined runoff and spray drift loading to areas ad jacent to the field are below the LOC for non-listed monocots, only species as sensitive as le ttuce would have reduction in survival, most plants would be expected to survive, and of those limited sp ecies impacted the effect would be limited inhibition in growth.

Non-target Semi-Aquatic (Wetland/Riparian) Plants

A diagram of the species IC 25 

### sensitivity distribution for dry weight, plant height, and survival with lines referencing the combined channel runoff and spray drift EEC values for selected applications ranging fr om the highest application rate (sweet potato), to the lowest label application rate (succulent beans) are provided in Figure 8. As indicated at the lowest label application rate at least 50% of plants are expected to have decreased height of at least 25%, in addition to about 40% of them having reduced dry weight by at least 25%, and about 20% having at least 25% mortality.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 71 Figure 8 Wetland or Semi-Aquatic Plant EEC Values Compared to Seedling Emergence IC 25 Species Sensitivity Distribution for Clomazone

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0.13 lbs ai/A: total load for adjacent semi-aquatic area – SB

Concentration at or below the non-listed monocot LOC 0.765 lbs ai/A: totalload for adjacent semiaquatic area – SP

0.306 lbs ai/A: totalload for adjacent semiaquatic area – R 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0.13 lbs ai/A: total load for adjacent semi-aquatic area – SB

Concentration at or below the non-listed monocot LOC 0.765 lbs ai/A: totalload for adjacent semiaquatic area – SP

0.306 lbs ai/A: totalload for adjacent semiaquatic area – R

cab = cabbage; car = carrot; crn = corn; cuc = cucumber; ltc = le ttuce; oni = onion; rye = ryegrass; soy = soybean; tom = tomat o SB: succulent bean use; SP: sweet potato use



### Volatilization

Plant RQ exceedences of non-listed and listed species LOC values (Table 34and Table 35) indicate that loading due to redeposition of volatilized cl omazone to near-field areas potentially poses risks to off-field plants at all existing label clomazone use rates (0.251 to 1.5 lbs ai/A). The level of risk, however, is very uncertain due to a number of unknowns such as the relationship between environmenta l factors and volatility of clomazone, the impact the ME formulation has on volatili zation as compared to the EC and WP formulations, how much dispersal and degr adation occurs between volatilization and deposition, and the use of seedling emergence re sults to estimate vege tative vigor risks.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 72 

### Loading attributable to vo latilization under 100% humidity for two assumptions (1)
formulation has no effect theref ore 65% volatilizes and (2) 50% reduction in volatility due to ME formulation for sweet potato (SP) applications are provided as references lines in a graph of seedling emergence IC 25 

### sensitivity values (Figure 9). Atthe highest applic ation rate (use on sweet potato) and assuming that form ulation (ME vs EC) does not reduce the volatilization rate (EEC=0.975 lb s ai/A), biomass (dry weig ht and seedling height) and seedling survival are reduced by at least 25% for all tested species except soybean. Under the assumption that the ME formulation does re sult in a 50% reduction in the volatility rate (EEC=0.488 lbs ai/A) there is st ill 70% of plant species havi ng 25% or more reduction in height and weight of surviving plants, and about 65% of species having 25% or greater mortality.

Also provided as references in Figure 9 are lo ading attributable to volatilization off treated succulent bean fields under the same assumpti ons discussed above for sweet potatoes. Under the assumption that formulation does not reduc e the volatilization rate (EEC=0.082 lbs ai/A) biomass of surviving plants, as measured by pl ant height is reduced by at least 25% in over 50% of species, and dry weight is also reduced by at least 25% in over 40% of species. Seedling survival is reduced by at least 25% for about 25% of species. Assuming that the
ME formulation results in a 50% reduction in th e volatility rate (EEC = 0.163 lbs ai/A), still results in an estimated 45% of plant species ha ving 25% or more reduction in plant height and 35% of species having 25% or more reducti on in dry weight. However, survival is reduced by at least 25% in only about 15% of species.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 73 Figure 9 Terrestrial, Wetland, and Semi-Aquatic Plant EEC Values Due to Volatilization Compared to Seedling Emergence IC 25 Species Sensitivity Distribution

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0.975 lbs ai/A, 100% humidity -- SP 0.163 lbs ai/A, 100% humidity -- SB 0.488 lbs ai/A (ME), 100% humidity -- SP 0.082 lbs ai/A, 100% humidity -- SB

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

1

0.001 0.01 0.1 1 10 Concentration (lb ai/A)Probability Dry Weight Height
Survival

ltc ltc ltc tom oni oni oni tom

rye car tom crn cab cuc oat soy

rye car cab oat crn cuc

rye car oat cab crn cuc 

# IC 25 

# Sensitivity Distribution

0.975 lbs ai/A, 100% humidity -- SP 0.163 lbs ai/A, 100% humidity -- SB 0.488 lbs ai/A (ME), 100% humidity -- SP 0.082 lbs ai/A, 100% humidity -- SB

car: carrot; cab: cabbage; crn: corn; cuc: cu cumber; ltc: lettuce; oat: oats; oni: onion; rye: rye; soy: soybean; tom: tomato SB: succulent bean use; SP: sweet potato use



### For this assessment it was conservatively a ssumed that the portion of clomazone that volatilized did not degrade nor did the mass of volatilized clomazone dilute before being redeposited. No air model for prediction of mass loading and spatial redeposition was identified that could be applied using th e available information, for the degree of parameterization required for the models. Inci dent data (Appendix G), with reported distance to effects, were analyzed to provide the best available information regarding the degree of spatial displacement of volatilized clomazone. In the incident database the farthest distance
associated with the ME formulation is 1 m ile (I005879-009) and the fa rthest with the EC formulation is 2 miles (B000602-001). There was a report of 30 incidents (I009610-009) where it was claimed that soil particles off EC tr eated cotton fields traveled for several milesChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 74 

### across state lines, and redeposited at sufficient loading to result in clomazone damage. There is a great deal of uncertainty in this claim as there were no measurements made of soil levels of clomazone, or any other investigation to s upport that clomazone on soil particles was the transport mechanism. Therefore, these 30 inci dents were not included in the assessment of
distance from field for clomazone effects.

According to non-target plant incident data, most clomazone incidents occur within a 300 foot area from treated fields. Within this area sensitive plant species among plant communities may be adversely affected by re duced growth and biomass, mortality, or reduced reproduction. These sens itive species because of adve rse effects may be replaced due to competition with other plant species a nd thereby shifting the distribution of the plant species in the ecosystem. As plant species ar e replaced by other plant species, such as an invasive species which may have an advantag e due to a lost plant or reduced growth competition, there is potential for change in habi tat, degree of cover, or wildlife food items. Invasive plant species often come into plan t communities to fill a niche vacated by weaker plant species, thereby cont ributing to more serious ecological stresses.

Also, incident data indicate th at beyond 300 foot from edge of treated field, the numbers of incidents fall off and thereby, the adverse e ffect on plant communities may be less uniform among sensitive species. This may contribute to less disruption to plant communities as a whole, however there may continue to be some adverse effects to more sensitive species
further out from treated fields in a more random fashion.

Birds, Reptiles, and Amphibians

Based on several lines of evidence acute and ch ronic direct risks to nonlisted birds and the taxonomic groups for which they are surrogates (re ptiles and amphibians) are considered to be within acceptable levels ( i.e ., below levels of concern fo r unreasonable adverse effects) for all existing labeled clomazone uses. The lines of evidence include that predicted on-field upper bound dietary residue levels at the highe st application rate, banded application on sweet potatoes 36 

### (Table 27), did not exceed the chr onic LOC for any use, which means all
other use rates are also below the chronic LOC and therefore no measureable effect on survival and reproduction of individuals is pred icted from chronic exposure to clomazone at
label rates. The acute risks we re not evaluated using acute RQ values because of a lack of definitive acute study results ( i.e ., highest dietary level tested a nd highest oral dose tested did not result in mortality or sublethal effects). However, the su bacute dietary data still provides evidence that predicted acute dietary residue leve ls are within acceptable risk levels. The use

36 1.5 lbs a.i./A broadcast is equivalent to 3.0 lbs a.i./A banded for clomazone registered useChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 75 

### of subacute dietary limit test data to evaluate acute dietary risks is de scribed in detail in the following paragraph. Because clomazone is applie d as a preemergent soil treatment or early preemergent ( i.e ., applied at the one- or tw o-leaf stage of target plan ts) dietary items such as short grass, tall grass, small broadleaf plants, fruits and pods would be essentially minimal to
non-existent on conventional tilled fields resulting in reduced or nonexistent exposure to the predicted upper bound residue levels for these it ems. Clomazone can be applied as a soil
treatment under conservation-tilla ge systems (minimum-till or no till) for cotton and soybean. In these systems, there is some potential for these dietary items to be represented on-field.

The highest acute dose and dietary concentra tions tested with both mallard ducks and bobwhite quail did not result in any mortality or subl ethal effect in exposed birds (sample size = 50 in each test). A provisional me thod described in Appendix C was used to extrapolate subacute dietary LC 50 

### values for this data (Table 20). Because no concentrationresponse relationship data is avai lable from a limit toxicity study, LC 50 

### values were modeled for a minimum slope of 2, a maximum slope of 9, and typical slope of 4.5 observed for pesticides in general (EPA, 1986; EPA, 2004). Then EEC residue levels were compared to
one-tenth of each modeled LC 50 

### value (0.1 x LC 50 

### ), the factor applied as the effects threshold for the acute toxicity LOC for an endangere d avian species (EPA, 2004). Except for short grass residues under the assump tion that the concentration re sponse slope is 9, predicted onfield upper bound dietary residue levels are lower than one -tenth of extrapolated LC 50 

### values (Table 44) indicating that no direct acute e ffects are expected. Additionally although the short grass residue level exceeds one -tenth of the extrapolated LC 50 

### of 6,905 ppm ai, based on its probit slope respon se of 9 the residue level of 720 pp m ai would be equivalent to an
individual risk of mortal ity of less than 1 in 2 x 10 18 

### . Therefore measureable direct acute mortality is not expected at the highest application rate, wh ich means all other use rates would also not be expected to result in acute effects.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 76 Table 44 Upper bound avian dietary levels for a banded application on sweet potatoes compared to extrapolated dietary acute toxicity values

Comparison of EEC to One-Te nth of the Extrapolated LC 50 values 2 Dietary Item EEC (mg/kgdiet) 1 22,940 ppm ai @ slope 2 9,731 ppm ai @ slope 4.5 6,905 ppm ai @ slope 9

Short Grass 720 <2,294 ppm ai <973 ppm ai >690 ppm ai 3
Tall Grass 330 <2,294 ppm ai <973 ppm ai <690 ppm ai Broadleaf plants/sm Insects 405 <2, 294 ppm ai <973 ppm ai <690 ppm ai Fruits/pods/seeds/lg insects 45.0 <2, 294 ppm ai <973 ppm ai <690 ppm ai
Bolded values are above one-tenth of the LC 50 value. 1 Dietary-based residue levels for a banded application on sweet potatoes from Table 8. 2 Extrapolated bobwhite quail and mallard duck subacute dietary LC 50 values from Appendix C

. 3 Based on a LC 50 of 6,905 ppm with a probit slope response of 9 the residue level of 720 ppm ai would correspond to odds of mortality for an exposed individual of less than 1 in 2 x 10 18

.



### A comparison of modeled acute oral LD 50 

### values from the bobwhite quail study with predicted residue dose levels were not perfor med because the estimated dietary equivalent
level is less than half of that tested in the dietary administration test . The acute oral dose tested for the bobwhite quail of 2,23 0 mg ai/kg-bw is estimated to be equivalent to a dietary level of 4,221 mg ai/kg-diet 37 

### using Nagy’s generalized food inges tion rate. This test value is less than the highest level te sted in the bobwhite quail 8-da y subacute dietary study (9,731 mg ai/kg-diet). While compounds administered as an acute oral bolus (single, large dose) may potentially be more toxic than when administ ered in the diet, in this case as neither study produced mortality or subletha l effects at the highest treatme nt the use of the acute oral
limit test dose is indicated to overestimate ris k. Additionally, for pestic ides it has been noted
that the LC 50 

### value may be a better indicator of acute toxicity to birds than the LD 50 

### when the
LD 50 

### values are greater than 50 mg/kg-bw and the pesticide persists in the environment with a foliar half-life greater th an one-day (USEPA, 2000).

Dietary- and dose-based EEC values for the highe st application rate ( 1.5 lbs ai/A broadcast which is equivalent to 3.0 lbs ai/A in band) due to off-site movement and deposition of volatilized clomazone (Table 13 and Table 14, re spectively) are lower than on-field residues at the highest application rate. Because meas ureable direct acute or chronic risks are not expected at the highest applic ation rate from residue levels on field as discussed in the

37 

### ( ) ( ) 221
, 4 094

. 0 178

. 0 230
, 2 /
, , /

. . , /

. . , 50 50 = ×

=

− − ×

− = − day diet kg FIR bw kg BW bw kg i a mg LD diet kg i a mg LC ;
where the bobwhite quail body weight ( BW ) is 0.178 kg, and the food ingestion rate ( FIR ) is 0.094 kg-diet, ww/day = ((0.648)(BW, g) 0.65 ÷ 0.2) ÷ 1000 g/kg, where 0.2 converts the dry weight (dw) to wet weight (ww).Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 77 

### preceding paragraphs, residue levels due to vola tilization and redeposition would also not be expected to result in acute or chronic effects of concern.

Mammals

Based on an evaluation of all lines of evidence acute and ch ronic risks based on clomazone exposure were considered overall not to pose unreasonable adverse acute or chronic effects for nonlisted species. The lines of evidence incl ude that chronic dietary-based RQ values for predicted upper bound residue levels at the hi ghest application rate, banded application on sweet potatoes, were below the chronic LOC fo r all dietary items (Table 27). No acute dietary study was performed but there was a 90- d dietary study with rats. Because a 90-d
LC 50 

### value is very likely lower than a subacute 5-d dietary study value (or at most equal if an asymptotic response with time was reached at 5 days), the use of a 90-d value in place of a 5- d value to assess risk is expected to be cons ervative. In the 90-d dietary study there was no mortality observed at any test group, the highest dietary concen tration was 8,000 ppm (1,200 mg ai/kg-bw) and there were 240 test anim als/dose (120 males and 120 females) (Acc # 00132586, Appendix B). A provisional method de scribed in Appendix C was used to extrapolate a dietary 90-d LC 50 

### value for this data. Because no concentration-response relationship data is available from a limit study, LC 50 

### values were modeled for a minimum slope of 2, a maximum slope of 9, and typical sl ope of 4.5 observed for pesticides in general (USEPA, 1986; USEPA, 2004). Then EEC residu e levels were compared to one-tenth of
each modeled LC 50 

### value (0.1 x LC 50 

### ), the factor applied as the effects threshold for the acute toxicity LOC for an endangered avian species (USEPA, 2004). Pred icted on-field upper bound dietary residue levels are lower than one-tenth of extrapolated LC 50 

### values (Table 45) indicating that no direct acute e ffects are expected either on a di etary basis. This means all
other use rates are also below the acute enda ngered species and chr onic LOC and therefore
no measureable effect on surviv al and reproduction of individuals in these dietary groups is predicted from acute or chr onic dietary exposure to clomazone at label rates.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 78 Table 45 Upper bound mammalian dietary levels for a banded application on sweet potatoes compared to extrapolated dietary acute toxicity values

Comparison of EEC to One-Te nth of the Extrapolated LC 50 values 2 Dietary Item EEC (mg/kgdiet) 1 85,102 ppm ai @ slope 2 22,880 ppm ai @ slope 4.5 13,529 ppm ai @ slope 9

Short Grass 720 <8,510 ppm ai <2,288 ppm ai <1,353 ppm ai
Tall Grass 330 <8,510 ppm ai <2,288 ppm ai <1,353 ppm ai Broadleaf plants/sm Insects 405 <8,510 ppm ai <2,288 ppm ai <1,353ppm ai Fruits/pods/seeds/lg insects 45.0 <8, 510 ppm ai <2,288 ppm ai <1,353ppm ai
Bolded values are above one-tenth of the LC 50 value. 1 Dietary-based residue levels for a banded application on sweet potatoes from Table 8. 2 Extrapolated rat 90-d dietary LC 50 value from Appendix C

.



### The dose-based assessment resulted in agreemen t that acute and chronic effects to mammals at the highest label applicati on rate were not expected from residues on some dietary items, such as granivores eating primarily seeds, he rbivores feeding on fruits and pods, insectivores feeding primarily on small insects, and agreement that acute and chronic effects are not expected for large (1000 grams bw and great er) mammalian herbivores, insectivores, or granivores from on-field resi dues on their dietary items, exce pt for herbivores feeding on short grass (Table 28). However unlike the di etary-based assessment the acute and chronic dose-based RQ values for mammals below 1000 grams bw, exceeded the acute endangered species LOC and chronic LOC indicating a poten tial for residues on short grass, tall grass, broadleaf plants, and small insects to pose a dverse acute and chronic effects. Further evaluation of the individual risk of mortality for the acute exceedances and the type and degree of effects for chronic effects are interprete d in this case as not significant for nonlisted species, these refinements are disc ussed in the following paragraphs.

The individual risk of mortality based on th e typical dose response slope (4.5) is 1 in 29,900 (RQ=0.013; 15 gram bw) to <1 in 10 milli on (RQ=0.06; 1000 gram bw) for residues on broadleaf plants and small insects; 1 in 294,000 (RQ=0.10; 15 gram bw) to <1 in 100 million (RQ=0.05; 1000 g bw) for residues on tall grass; and 1 in 491 (RQ=0.23; 15 gram bw) to 1 in 294,000 (RQ=0.10; 1000 g bw) for residues on short grass (Table 28 and Table 41). Therefore, although the dose-ba sed acute RQ values exceeded for some mammals and dietary items indicating a potential for acute mortality effects of concern, an evaluation of the individual mortality risk indicate such risk s are unlikely to occur or be measureable for nonlisted species in this case. Another consideration is that acute dose-based values were calculated using results from an acute oral gavage study where clomazone was administered as a single, large oral dose, which may potentia lly be more toxic than when administered inChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 79 

### the diet. The dose-based approach assumes th at the uptake and absorption kinetics of a gavage toxicity study approximate the absorpti on associated with uptake from a dietary matrix. While no acute dietary study was perfor med the lack of mortality in a 90-d dietary study with rats at 8,000 ppm ai with a calcu lated dose level of 1,200 mg ai/kg-bw would appear to support that clomazone administered in a dietary matrix is less toxic than that administered by gavage as the LD 50 

### of 1,369 mg/kg-bw is compar able to 1,200 mg ai/kg-bw but one study has 50% mortality at the dose level, the other none.

Dietary items that have exceedances of the chr onic LOC for dose-based residue levels at the highest application rate include short grass, tall grass, broadl eaf plants, and small insects. The chronic RQ values that exceed the ch ronic LOC range from 1.4 to 3.5. A closer examination of the type and magnitude of e ffects associated at doses 1.4 to 3.5 times the NOAEC (NOAEL) in the 2-generation reproducti on study are a modest decrease in body weight of female rats during premating in F2 a and F2b generations and during lactation with no detectable effect to reproduction ( e.g ., fertility, number of young produced) or viability of young, and no consistent statistical ly significant impact or correl ation between test group and growth of pups. Although statistical significan ce and dose responses ar e not consistent and
there is no strict correlation between combined weights at day 4 and day 21 in the 2000 and 4000 ppm (2 and 4 times the NOAEC (NOAEL)) dose groups for pups it was assumed that growth was indicated to be impacted at these levels for pups since grow th effects on parental females were significant at these levels. The decrease in body weight in F2a and F2b premating females were 26% and 11%, resp ectively, at 2 times the NOAEC (NOAEL) and 26% and 13%, respectively, at 4 times th e NOAEC (NOAEL). No significant effects associated with clomazone exposure were detect ed at any of the test doses; the highest dose was 4 times the NOAEC (NOAEL) for effect on body weight of females. Therefore, although the dose-based chronic RQ values exceeded for some mammals indicating a potential for reproductive effects of concern fu rther evaluation of the type and degree of expected effects indicate that reproductive effects are not expect ed at these residue levels.

Another consideration is that the above ev aluation of risk poten tial was based on upper
bound residue levels. While there is some uncerta inty in how representative predicted mean
residue levels based on the Fletcher et al . (1994) modified Kenaga nomogram values are of actual mean residues, risks calcu lated using these mean residue values (Table 46) indicate no exceedance of the endangered species LOC (0.1) and exceedence of the chronic LOC only for small- to medium-sized mammals ingesting short grass. As discussed in the previous paragraph, such a degree of exceedance of the chr onic LOC in this case is not expected to result in effects to reproduction.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 80 Table 46 Mean acute and chronic dose-based RQ values for mammals for a banded application on sweet potatoes

15 g mammal 35 g mammal 1000 g mammal Functional Feeding Group Dietary Item Acute 1 Chronic Acute 1 Chronic Acute 1 Chronic

Herbivores/Insectivores
Short Grass 0.08 1.2 0.07 1.1 0.04 0.6
Tall Grass 0.03 0.5 0.03 0.5 0.02 0.2 Broadleaf plants/sm ins ects 0.04 0.7 0.04 0.6 0.02 0.3 Bolded chronic RQ values exceed the chronic LOC of 1. 1 Acute RQ = (dose-based mean EEC, mg/kg-bw) / (LD 50 ; mg/kg-bw). The mean EEC values for a given body weight are from Table 11 and LD 50 values adjusted for the given body weight are in Table 20. 2 Chronic RQ = (dose-based mean EEC, mg/kg-bw) / (chronic N OAEC, mg/kg-bw). The dose-based mean EEC values for a given body weight and di etary item are from Table 11 and the NOAEC values adjust ed for a given body weight are in Table 20.



### Commence EC, a multiple active in gredient formulation, is regi stered for use on cotton and soybean sites. This formulation was identif ied as potentially being more toxic than
consideration of the indivi dual active ingredient compone nts. For Commence EC an assessment of acute exposure based on the fo rmulation was conducted in addition to the
assessment conducted on the basis of the activ e ingredient discussed in the previous paragraphs. All dietary item dose-based levels for were below the acute endangered species LOC (0.1) except for mammals smaller than 1000 g ingesting short grass. Therefore except for short grass, no effect to lis ted species feeding primarily on tall grass, broadleaf plants, small or large insects, fruits, or pods are expect ed. In addition, while th e acute RQ values of 0.17 and 0.14 exceed the endangered species LOC for 15-g and 35-g mammals, respectively, the odds of mortality at these RQ levels for an individual are considered discountable (<1 in
10 22 

### at the study probit slope of 12.679).

Dietary- and dose-based EEC values for the highe st application rate ( 1.5 lbs ai/A broadcast which is equivalent to 3.0 lbs ai/A in band) due to off-site movement and deposition of volatilized clomazone (Table 13) are lower than on-field residues at the highest application
rate. Because measureable direct acute or ch ronic risks are not expected at the highest application rate from dietary re sidue levels on field as discussed in the preceding paragraphs,
residue levels due to volatiliza tion and redeposition would also not be expected to result in
acute or chronic effects of concern on a dietar y-basis. Conservative dose-based EEC values due to volatilization are also lower (T able 15) than those estimated for the

Beneficial Insects
In terms of the environmental baseline risk, ag ricultural fields are not in general managed to maintain terrestrial invertebrate populations to support populations of other animals.Chapter 4 Results: Risk Characterization

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### Agronomic practices, irrespective of pesticid es, affect the diversity and magnitude of
terrestrial invertebrates on a fiel d. As such, except for the potential for a listed species to be directly affected, the loss of populations of terrestrial inverteb rates on a treated field are not
considered here for indirect effects due to loss of a prey population for other species. Because on-field upper bound residue levels at the highest application rate, banded application on sweet potatoes, were below the LOC off-field residues for all uses due to spray drift or redeposition of volatilized clomazone will also be at acceptable risk levels for nonlisted species.

4.2.1.2 D IRECT E FFECTS TO A QUATIC P LANTS AND A NIMALS



### Label Uses Other Then Rice
Primary Productivity and Habitat Integrity

Risks to non-listed aquatic plants both vascular and nonvascular are considered to be within acceptable levels for all register ed clomazone uses. Therefore, no direct effects on primary productivity and habitat integrity in aquatic systems are expecte d. All vascular and nonvascular aquatic plant RQ values ba sed on exposures estimated assuming no
volatilization from soil occurs a nd 1-in-10 year peak concentra tions in surface water were below the nonlisted species LOC (Table 36). The EEC values used in this assessment are considered to be conservative as most expect ed exposures in surface waters will be below
this level as some volatilization is expected to occur from surface soil.

Freshwater Fish, Invertebrates, and Amphibians (Aquatic-Phase)

Direct effect risks to freshwat er fish, and the amphibians for which they are surrogates, and
freshwater invertebrates are considered to be within acceptable levels for all registered
clomazone uses. All acute and chronic freshwat er fish and invertebrate RQ values based on 1-in-10 year peak concentra tions in surface water, assumi ng no volatilization occurs from soil were below the acute endangered species LOC and chronic LOC, respectively (Table 36). The EEC values used in this assessment are considered to be conservative as most expected exposures in surface waters will be below this level as some volatilization is expected to occur from soil.

Estuarine-Marine Fish

Direct effect risks to estuarine- marine fish are considered to be within acceptable levels for all registered clomazone uses. All acute and ch ronic estuarine-marine fish acute and chronic RQ values based on 1-in-10 year peak concentr ations in surface water were below the acuteChapter 4 Results: Risk Characterization

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### endangered species LOC and chronic LOC, resp ectively (Table 37). Additionally, the EEC
values used in this assessment are considered to be conservative as most expected exposures
in surface waters will be below this level as some volatilization is expected to occur.

Estuarine-Marine Invertebrates

Based on an evaluation of all lines of evidence risks to non-listed estuarine-marine
invertebrates were considered to be within acceptable levels for all registered clomazone
uses. All chronic estuarine-marine invertebra te RQ values in surface water were below the chronic LOC (Table 37). While some uses in a given region of the U.S. had acute RQ values that exceeded the acute endangered species LOC, this was for exposure estimates based on conservatively assuming no volatilization of clom azone off the treated field. The odds of mortality if exposure occurred at th ese levels (acute RQ values < 0.07) is <1 in 10 29 

### under the estimated mean mysid clomazone response slope (Table 41), which is considered to be within acceptable risk levels for populations of marine invertebrates. Additionally, if
volatilization is consider ed, none of the acute RQ values ex ceed the acute endangered species LOC (0.05) (Table 37); the odds of mort ality for an individual are <1 in 10 36



### .

Rice Uses—Wet Seeded
Primary Productivity and Habitat Integrity

Water seeded labels range from requiring no hol ding time (Section 24(c) labels) to a holding time of 14 days (Section 3 label), before rel ease of rice flood waters. Risks to non-listed vascular aquatic plants are considered to be within acceptable levels for wet seeded rice applications since the vascular plant RQ va lues from day of application are below the endangered species LOC (Table 38). However, the nonvascular plant RQ values exceed the non-listed aquatic plant LOC from day of application to the 14 day post-application holding time indicating the potential to affect listed vasc ular aquatic plants. Additionally, there is a potential to reduce biomass levels of nonvasc ular plants if rice paddy flood waters are released into surface waters during this time. It was estimated that up to 42 days of hold time
is needed to reduce levels below the nonlisted species LOC. An evaluation of the range of nonvascular plants likely to be affected indicated only one of the four species (freshwater diatom, N. pelliculosa ) tested had a 4-d IC 50 

### value of above the nonlisted species LOC. The other three nonvascular test sp ecies (cyanobacteria, green algae, and a saltwater diatom) have
4-d IC 50 

### values of > 950 ppb which are below the nonlisted sp ecies LOC and for two of these
the concentration is lower than their NOAEC. Given 75% of th e tested nonvascular species are below LOC, overall nonvascular, algal bioma ss and therefore primary productivity is not likely to be unreasonably adversel y affected but the diversity of species has the potential toChapter 4 Results: Risk Characterization

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### be affected. Additionally, given that some form of fertilizer has likely been added to the rice field, and in some cases is added concurrent with clomazone, clomazone is not likely to reduce nonvascular plant biomass in waters r eceiving rice flood water as those nonvascular plants not impacted are expected to take advant age of the additional nutrient resources. The diversity of species may be impacted, but this wo uld also be expected to occur due to cultural practices in rice fields. Ther efore the clomazone effect on nonva scular plants in receiving waters is considered to likely be brief and transient, and be within the background level of effects to nonvascular biomass and diversity at tributable to such cultural practices. For example, the creation of standing or slow m oving, shallow waters of a rice field will favor production of certain species of nonvascular plants over those present in a deeper, faster moving aquatic system and the added nutrients will favor some species over others both within the rice field and in the receiving water.

Freshwater Fish and Amphibians (Aquatic-Phase)

Freshwater fish and the amphibians for which they are surrogates were indicated to be potentially at risk acutely from release of rice paddy flood water into surface waters. The acute endangered species LOC is exceeded in ri ce paddy water from the day of application to 14 days post-application indicati ng the potential for acute effect s if released into surface waters. It was estimated that up to 43 days of hold time is needed to reduce levels to the acute endangered species LOC exceedence criteria . The odds of mortality for an individual fish are 1 in 89 if rice paddy wa ter is released on the day of application (acute RQ = 0.19), by day 14 post-application the odds of mortality are 1 in 397 (acute RQ = 0.12) (Table 41), 19 days post-application the odds of mortality of individual declin e to <1,000 (acute RQ = 0.10).
Therefore individual listed fres hwater and amphibian species ma y be directly affected and these prey bases may be acutely impacted.

There is a high degree of uncertainty in this risk determination. The silver catfish acute value used for this assessment was from a study testi ng a clomazone formulation. Because there is no TGAI study with the silver catfish, and no fo rmulation testing with the freshwater fish species that were tested with the TGAI, it is no t possible to determine if the difference is due to a difference in sensitivity to clomazone, to the formulation, or both. If the rainbow trout value (19,000 ppb), which is the more sensitive freshwater species tested with the TGAI, is
used to assess risk rather th an the silver catfish, the acute RQ (0.03) would be below the listed species LOC on the day of application.Chapter 4 Results: Risk Characterization

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### Freshwater Invertebrates

Freshwater invertebrates were i ndicated to be potentially at ri sk acutely from release of rice paddy flood water into surface waters. The acute endangered species LOC is exceeded in rice paddy water from the day of applicati on to 14 days post-a pplication indicating potentially unacceptable mortality e ffects. It was estimated that up to 24 days of hold time is needed to reduce levels to the nonlisted speci es LOC exceedence criteria. However, the odds of mortality at the concentra tion in rice paddy water on the day of application is <1 in 10 11 

### (acute RQ = 0.10) (Table 41). Based on this information, risks to nonlisted freshwater invertebrates prey are considered to be within acceptable levels.

Estuarine-Marine Fish

Acute effects to estuarine-marine fish species we re considered to be within acceptable levels for release of rice paddy water as the acute RQ was below the acute endangered species LOC on the day of application. The odds of mo rtality of an individual are <1 in 10 9



### .

Estuarine-Marine Invertebrates

Estuarine-marine invertebrates were indicated to be potentially at risk acutely from release of rice paddy flood water into estuarine-marine su rface waters. The acute restricted LOC is exceeded in rice paddy water from the day of application to 14 days post-application indicating potentially unacceptable mo rtality effects if water is re leased during this time. It was estimated that up to 98 days of hold time is needed to reduce levels to the acute endangered species LOC. However, given that the mean concentration response slope for the mysid study is 9.7919, the individual odds of mo rtality are <1 in 1,000 at 28 days postapplication for an acute RQ of 0.48 (Table 42).

Concentrations as high as that in the rice pa ddy will be highly transitory in flowing water systems. These acute effects are expected to be relatively localized as a 50% dilution of rice paddy water, if released on the day of applicat ion or a 25% dilution if released 14 days postapplication reduces effects to these as a prey base to insignificant ( e.g ., odds of mortality <1 in 1,000).

Rice Uses—Dry Seeded
Primary Productivity and Habitat Integrity

Based on measured concentrations in flood wa ter from two field studies, no effect is expected to primary productivity in surface wate rs if flood waters are released. EstimatedChapter 4 Results: Risk Characterization

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### concentrations using a provisional model which is expected to result in conservative results
for flood water also do not exceed the vascular plant LOC for non-listed species (Table 39) but do exceed the nonlisted LOC for nonvascular pl ants indicating the pot ential for concern. An evaluation of the range of nonvascular plan ts likely to be affected at the modeled concentration of 364 ppb indicated only one of the four species (freshwater diatom, N. pelliculosa ) tested had a 4-d IC 50 

### value of <364 ppb. The other th ree nonvascular test species (cyanobacteria, green algae, and a saltwater diatom) have 4-d IC 50 

### values of > 950 ppb which are below the nonlisted species LOC and for two of these the concentration is lower than their NOAEC. Given 75% of the tested nonvascular species are below LOC, overall nonvascular, algal biomass and therefore prim ary productivity is not likely to be unreasonably adversely affected but the diversity of species has th e potential to be affected. Even without the presence of clomazone rice cultural practices are expected to modify the biomass and species diversity of nonvascular a quatic plants. For example, the creation of standing or slow moving, shallow water of a rice field will favor production of certain species of nonvascular plants over those pres ent in a deeper, faster moving aquatic system,
and fertilizer or nutrients added to a rice fi eld will favor some aquatic plant species over others within the rice field in addition to providing nutritional resources that may not be as available in the same quantity in the receiving water. Clomaz one effects to nonvascular plant biomass and diversity is expect ed to insignificant as compared to impacts on diversity and biomass from these cultural practices.

Additionally because of the number of uncer tainties and conservative accounting for dissipation in the provisional model, the field results are considered more environmentally representative of levels in flood water than the provisional model results. These field
concentrations are below listed LOC resulti ng in a conclusion of no unreasonable adverse effects to primary productivity and associated habitat it provides from clomazone use on dry
seeded rice.

Freshwater Fish, Amphibians (Aquatic-Phase), and Invertebrates

Based on measured concentrations in flood wa ter from two studies, no acute effect is expected to freshwater fish, the amphibians for which they are surrogate s or invertebrates in
surface waters if flood waters ar e released on the day of flood. Acute RQ values are below the endangered acute LOC (Table 39). Estimated concentrations usi ng a provisional model which is expected to result in conservative results for flood water do exceed the endangered acute species LOC and acute restricted LOC for fish, and the endangered species LOC for invertebrates indicating the poten tial for concern (Table 39). However, consideration of the individual risk of mortality fo r the fish acute RQ (0.13) is 1 in 397 at the mean concentration-Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 86 

### response slope estimate of 3.1657 (Table 41), and the individual risk of mortality for the invertebrate acute RQ (0.07) is <1 in 10 14 

### at the mean concentration-response slope estimate of 6.7259 (Table 43). These rate s would indicate that even at the conservative modeled levels acute effects appear not to result in unreasonable adverse effects. Because of the
number of uncertainties and conservative accoun ting for dissipation in the provisional model
the field results are considered more environmen tally representative of levels in flood water than the provisional model results resulti ng in a conclusion of no unreasonable adverse effects to primary productivity and associated habitat it provides from clomazone use on dry
seeded rice.

Estuarine-Marine Fish and Invertebrates

Based on measured concentrations in flood wa ter from two studies, no acute effect is expected to marine and estuarine fish or inve rtebrates in surface waters if flood waters are released on the day of flood. Additionally although conservative, provisional modeled results are also below the endangered acute LOC for fish (Table 39). However, the provisional model results do exceed the endangere d species acute LOC and the restricted use LOC for invertebrates indicating th e potential for concern (Table 39). The individual risk of mortality for the invertebrate acute RQ ( 0.64) is approximately 1 in 34 at the mean concentration-response slope estimate of 9.7919 (Table 43). While the modeled results
indicate a concern for invertebrates because of the number of uncertainties and conservative accounting for dissipation in th e provisional model the field results are considered more environmentally representative of levels in flood water than the provisional model results resulting in a conclusion of no unreasonable adverse effects to primary productivity and associated habitat it provides from clomazone use on dry seeded rice.

4.2.2 Listed Species Effects Analysis

The direct and indirect effects analysis for listed species is summarized in Table 47 for uses other than rice, and in Table 48 and Table 49 for wet seeded and dry seeded rice uses, respectively. The analysis is based on the di rect and indirect eff ects concluded from the analysis of risk estimates. A co-occu rrence analysis (Sectio n 4.2.2.8) is conducted to evaluate if species within groups preliminarily identified in Table 47 are within the Action Area (Section 4.2.2.1).

4.2.2.1 A CTION A REA



### Clomazone was formulated as an ME to redu ce volatilization of clom azone from soil during events ( e.g ., rain, high humidity) that would otherwis e displace clomazone applied as the ECChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 87 

### or WP. These formulation differences have re sulted in notable differe nces observed in at
least the off-field distal extent of clomazone effects reported in incident reports. Because the action area for the endangered species effects de termination is based on the furthest distal extent for any effect, the difference in distal extent between these formulations result in
different conclusions about the size of the affected area. Be cause formulation type in the case of clomazone plays a role in the size of the area affected, and may play a role for consideration for potential options for mitigation, if any are needed, a separate analysis for
the extent of effects for the ME from EC a nd WP formulations was performed. Additionally because in the case of clomazone, rice versus no nrice uses have a significant impact on the downstream distal extent of aquatic animal and plant effects, a separate analysis was performed for the downstream extent of e ffects for rice versus nonrice uses.

The furthest distal extent for expected direct or indirect e ffects to terrestrial plants and animals from spray drift and volatilization was determined based on an assessment of reported distances from treated fields in the inci dent report data base. The furthest distance for which effects to plants have been observe d is 2 miles for the EC formulation (the WP formulation is assumed to have the same potential), and 1 mile for the ME formulation. For nonrice uses and dry seeded rice use aquatic organisms are not affect ed or effects do not extend beyond the field or edge-of-field. Fo r wet seeded rice the extent of downstream
effects is assumed to extend to the ocean. This extent is highly conser vative given that for wet seeded rice the estimated concentration will only occur on the day of release but the tools
to evaluate downstream dilution from releas es off an agricultural field has not been developed for the contiguous United States, Hawaii, Alaska, or its territories.

For convenience these areas of effect are referred to as action areas with in the assessment but it is recognized that for the ove rall review the action area is the furthest extent considering all uses simultaneously. Specifically the effect ar eas evaluated for the co-occurrence analysis included (1) for EC and WP formulation nonrice uses, a 2 mile radius out from clomazone use sites; (2) for ME formulati on nonrice uses and dry seeded rice use, a 1 mile radius out from clomazone use sites; and (3) for ME formul ation wet seeded rice uses, a 1 mile radius
out from use sites for effects to the terre strial environment and all downstream miles extending from rice sites to the ocean. The actio n area for the clomazone registration review
action consists of a 2 mile radius out from a ny clomazone use site which then further extends for adjacent flowing waters downstream to the o cean for rice uses. Operationally locations
where clomazone is used are defined as all cult ivated land that has had one or more of the crops for which clomazone is registered cultivated on it, except California where the only registered clomazone use is wet seeded rice.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 88 

### The geographical extent of a 2 mile radius out from a use s ite is based on the farthest physical extent direct or indirect effects from exposure to clomazone are predicted to occur
based on best available information. This action area should not be misconstrued as automatically meaning that unreasonable adve rse effects to nonlisted species or the environment is occurring. The extent of the action area is based on any effect adverse or not, the effect may be to a single individual, and ma y not result in decrease d survival, growth, or reproduction. The effects determination consid ers all available lines of evidence including estimates of risk, probability of mortality, type , degree, and magnitude of indirect and direct effects to listed and nonlisted sp ecies within the acti on area to make an effects determination for a specific listed species and potential for habitat modification to critical habitat.

Crop use sites are determined from the “best available information” on locations where the crop is grown, the 1997 and 2002 Census of Ag riculture (USDA 2002). The geographical
extent of a 2 mile radius out from a use site is based on the farthest phys ical extent direct or indirect effects from exposure to clomazone are predicted to occur. Volatilization of clomazone results in the greates t spatial extent off a treated site that exposure potentially results in any effects. The spatial extent of volatilization effects was set based on an
evaluation of information available on distan ce from treated field effects on plants from clomazone were observed (see Volatilization di scussion under Section 4.2.1.1). Except for aerial spray applications, spray drift effects were determined to extend out less than 500 feet from a use site. Aerial spray applications exte nd out just over 1,000 feet. No direct effects to insects above baseline are expected on-site. Dire ct effects to birds, re ptiles, terrestrial-phase amphibians, and mammals would be restricted to on-site or at most ex tend a few feet off the field. Except for rice, potential direct effects to freshwater fish, invertebrates, and aquatic plants, and estuarine-marine fish and vascul ar plants are at th e edge of field.

The geographical extent of a 2 mile radius out from a use s ite is based on the farthest physical extent direct or indirect effects from exposure to clom azone are expected to occur.
In the case of clomazone this is identified as effects on non-target plan ts in terrestrial or semi-aquatic areas from potential off-site tran sport of clomazone due to volatilization. Volatilization of clomazone results in the grea test spatial extent off a treated site that exposure potentially results in any effects. The spatial extent of volatilization effects was set
based on an evaluation of information availabl e on distance from treated field effects on plants from clomazone were observed (see Vo latilization discussion under Section 4.2.1.1). Except for aerial spray applications, spray drif t effects were determined to extend out less than 500 feet from a use site. Aerial spray a pplications extend out ju st over 1,000 feet. No
direct effects to insects above ba seline are expected on-site. Dir ect effects to birds, reptiles, terrestrial-phase amphibians, and mammals would be restricted to on-site or at most extend aChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 89 

### few feet off the field. Except for wet seeded rice, potential direct effect s to freshwater fish, invertebrates, and aquatic plants, and estuarine- marine fish and vascul ar plants are at the edge of field. Operationally locations where cl omazone is used are defined as all cultivated land that has had one or more of the crops fo r which clomazone is registered (Table 1) cultivated on it, except California where the only registered clomazone use is wet seeded rice. Crop use sites are determined from the “best available information” on locations where the crop is grown, the 1997 and 2002 Ce nsus of Agriculture (USDA 2002Chapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone90Table 47 Summary of Indirect and Direct Effects to Listed Species and Preliminary Effects Determination for ClomazoneUses Other Than RiceClomazoneUseListed speciesgroup(1)Direct EffectAssessment EndpointsDirect Effects IndirectEffectsEffectsDeterminationAll uses NonvascularAquatic PlantSpeciesPrimary productivityassessed from effects onbiomass as measuredusing cell count(density), and dry weightN/A N/A No listed nonvascularlisted speciesAll uses VascularAquatic PlantSpeciesEffects on biomass asmeasured using frondcount, dry weight, andarea under the growthcurveNo Effect – ListedRQ values belowlisted LOCPlants in terrestrial and semi-aquatic areas – May affect because of potentialaffects to non-target plants in terrestrial and semi-aquatic areas andsubsequent secondary or indirect effects to aquatic systems. Because themain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth, erosion is not expected to be abovebaseline and canopy cover is not expected to be significantly reducedcompared to baseline therefore these are considered insignificant effects andNLAA listed aquatic vascular plants.Nonvascular (nonlisted) and vascular aquatic plants – No effect.May affect butNLAAAll uses FreshwaterFish andAmphibiansAcute mortality andreproductive effects(hatching success,growth, and survival)No Effect – acuteand chronic RQvalues below acuteendangered speciesLOC and chronicLOC, respectivelyPlants in terrestrial and semi-aquatic areas – Main effect on terrestrial andsemi-aquatic vegetation off-field is expected to be short-term inhibition ingrowth, therefore erosion is not expected to be above baseline and canopycover is not expected to be significantly reduced compared to baseline duringthe application timing of clomazone – insignificant effectsEffects on primary productivity, and fish, amphibianand invertebrate preypopulations are within acceptable levels – no effectMay affect butNLAAAll uses FreshwaterInvertebratesAcute mortality andreproductive effects(fecundity, growth,survival)No Effect – acuteand chronic RQvalues are belowacute endangeredspecies LOC andchronic LOC,respectivelyMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth, therefore erosion is not expected to beabove baseline and canopy cover is not expected to be significantly reducedcompared to baseline during the application timing of clomazone –insignificant effectsEffects on primary productivity, and fish, amphibian,and invertebrate preypopulations are within acceptable levels – no effectMay affect butNLAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone91ClomazoneUseListed speciesgroup(1)Direct EffectAssessment EndpointsDirect Effects IndirectEffectsEffectsDeterminationAll uses Estuarinemarine FishAcute mortality andreproductive effects(hatching success,growth, and survival)No Effect – acuteand chronic RQvalues are belowacute endangeredspecies LOC andchronic LOC,respectivelyMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth, effects are not on the order to affectestuarine or marine environments – insignificant effectsEffects on primary productivity, and fish and invertebrate prey populationsare within acceptable levels – no effectMay affect butNLAAAll uses MarineInvertebratesAcute mortality andreproductive effects(fecundity, growth,survival) andadditionally formollusks, shelldepositionNo Effect -- acuteand chronic RQvalues are belowacute endangeredspecies LOC andchronic LOC,respectivelyMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth atdistances not immediately adjacent tothe field, effects are not on the order to affect estuarine or marineenvironments – insignificant effectsEffects on primary productivity, fish and invertebrate populations are withinacceptable levels – no effectMay affect butNLAAAll uses MarineMammalsQualitative assessmentof acute mortality andreproductive effectsNo Effect –extrapolated from noacute or chroniceffects from dietaryresidues for largeland mammalsMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth atdistances not immediately adjacent tothe field, effects are not on the order to affect estuarine or marineenvironments – insignificant effectsEffects on primary productivity, fish and invertebrate populations are withinacceptable levels – no effectMay affect butNLAAAll uses FreshwaterMammalQualitative assessmentof acute mortality andreproductive effectsNo Effect –extrapolated from noacute or chroniceffects from dietaryresidues for largeland mammalsMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth atdistances not immediately adjacent tothe field, effects are not on the order to affect estuarine or marineenvironments – insignificant effectsEffects on primary productivity, fish and invertebrate populations are withinacceptable levels – no effectMay affect butNLAAAll uses Marine Birds Qualitative assessmentof acute mortality andreproductive effectsNo Effect --extrapolated from noacute or chroniceffects from dietaryresidues for landbirdsMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth atdistances not immediately adjacent tothe field, effects are not on the order to affect estuarine or marineenvironments – insignificant effectsEffects on primary productivity, fish and invertebrate populations are withinacceptable levels – no effectMay affect butNLAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone92ClomazoneUseListed speciesgroup(1)Direct EffectAssessment EndpointsDirect Effects IndirectEffectsEffectsDeterminationAll uses MarineReptilesQualitative assessmentof acute mortality andreproductive effectsNo Effect –extrapolated from noacute or chroniceffects from dietaryresidues for landbirdsMain effect on terrestrial and semi-aquatic vegetation off-field is expected tobe short-term inhibition in growth atdistances not immediately adjacent tothe field, effects are not on the order to affect estuarine or marineenvironments – insignificant effectsEffects on primary productivity, fish and invertebrate populations are withinacceptable levels – no effectMay affect butNLAAEC uses Nontargetplants interrestrial andsemi-aquaticareasPrimary productivityassessed from effects onbiomass as measuredusing survival, length,and dry weight.1,500 ft from site:May affect and LAA2 miles from site::May affect and LAAMain effect on terrestrial and semi-aquatic vegetation is expected to be shortterm inhibition in growth. Listed plant species, which are reliant or obligateon another plant species or in a habitat that is dominated by a few species(e.g., prairie grassland) are expected to be indirectly affected.Effects on primary productivity, mammals, birds, reptiles, and insects arewithin acceptable levels – no effectMay affect and LAAME uses Nontargetplants interrestrial andsemi-aquaticareasPrimary productivityassessed from effects onbiomass as measuredusing survival, length,and dry weight.1,500 ft from site:May affect and LAA1 mile from site:May affect and LAAMain effect on terrestrial and semi-aquatic vegetation is expected to be shortterm inhibition in growth. Listed plant species, which are reliant or obligateon another plant species or in a habitat that is dominated by a few species(e.g., prairie grassland) are expected to be indirectly affected.Effects on primary productivity, mammals, birds, reptiles, and insects arewithin acceptable levels – no effectMay affect and LAA1.5 lbs ai/Abroadcastapplied as abandedapplication(~3.0 lbsai/A inband)Birds,Reptiles, and(Land-Phase)AmphibiansAcute mortality andreproductive effectsMay affect butNLAA –Dietary chronic RQvalues did not exceedchronic LOC butpotentially there is anexceedance of acutedietary levels, butthis was considereddiscountable as theindividual risk ofmortality is <1 in 2 x1018Main effect on terrestrial and semi-aquatic vegetation is expected to be shortterm inhibition in growth. Effects tooff-site diverse plant communities withemergent vegetation areexpected to be mainly reduction of growth.Therefore, indirect effects to food resources or habitat requirements of smallto large carnivorous or omnivorous listedbirds, reptiles, and terrestrial-phaseamphibians and large herbivores withlarge home ranges are expected to beinsignificant.Species which are reliant or obligate on a limited number of plant species, ahabitat that is dominated by a few species (e.g., prairie grassland), have smalllocalized populations, or are highly reliant on camouflage during late Maythrough late July may potentially beindirectly affected from impacts tovegetation.Small to largecarnivores andomnivores and largeherbivores:May affect butNLAAAll other listedspecies May affectand LAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone93ClomazoneUseListed speciesgroup(1)Direct EffectAssessment EndpointsDirect Effects IndirectEffectsEffectsDeterminationApplicationRates <1.5lbs ai/Abroadcast(or appliedas a band)Birds,Reptiles, and(Land-Phase)AmphibiansAcute mortality andReproductive effectsNo Effect – Dietarychronic RQ valuesdo not exceed thechronic LOC andacute effects arebelow levels ofconcernMain effect on terrestrial and semi-aquatic vegetation is expected to be shortterm inhibition in growth. Effects tooff-site diverse plant communities withemergent vegetation areexpected to be mainly reduction of growth.Therefore, indirect effects to food resources or habitat requirements of smallto large carnivorous or omnivorous listedbirds, reptiles, and terrestrial-phaseamphibians and large herbivores withlarge home ranges are expected to beinsignificant.Species which are reliant or obligate on a limited number of plant species, ahabitat that is dominated by a few species (e.g., prairie grassland), have smalllocalized populations, or are highly reliant on camouflage during late Maythrough late July may potentially beindirectly affected from impacts tovegetationSmall to largecarnivores andomnivores and largeherbivores:May affect butNLAAAll other listedspecies May affectand LAAApplicationRates >0.75lbs ai/Abroadcast(or bandedequivalent)LandMammalsAcute mortality andreproductive effectsMammals that eatshort grass, tall grass,broadleaf plants, orsmall insectsMayaffect but NLAA –see Land mammaldiscussion in text(Section 4.2.1.1)Mammals that eatseeds, fruits, pods, orlarge insects: NoEffect -- dietary anddose-based acute andchronic RQ valuesbelow acute andchronic LOCMain effect on terrestrial and semi-aquatic vegetation is expected to be shortterm inhibition in growth. Effects tooff-site diverse plant communities withemergent vegetation areexpected to be mainly reduction of growth.Therefore, indirect effects to food resources or habitat requirements of smallto large carnivorous or omnivorous listed mammals and large herbivores withlarge home ranges are expected to be insignificant.Species which are reliant or obligate on a limited number of plant species, ahabitat that is dominated by a few species (e.g., prairie grassland), have smalllocalized populations, or are highly reliant on camouflage during late Maythrough late July may potentially beindirectly affected from impacts tovegetation.Small to largecarnivores andomnivores and largeherbivores:May affect butNLAAAll other listedspecies May affectand LAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone94ClomazoneUseListed speciesgroup(1)Direct EffectAssessment EndpointsDirect Effects IndirectEffectsEffectsDeterminationApplicationRates <0.75lbs ai/Abroadcast(or bandedequivalent)LandMammalsAcute mortality andReproductive effectsNo Effect – dietaryand dose-based acuteand chronic RQvalues below acuteand chronic LOCMain effect on terrestrial and semi-aquatic vegetation is expected to be shortterm inhibition in growth. Effects tooff-site diverse plant communities withemergent vegetation areexpected to be mainly reduction of growth.Therefore, indirect effects to food resources or habitat requirements of smallto large carnivorous or omnivorous listed mammals and large herbivores withlarge home ranges are expected to be insignificant.Species which are reliant or obligate on a limited number of plant species, ahabitat that is dominated by a few species (e.g., prairie grassland), have smalllocalized populations, or are highly reliant on camouflage during late Maythrough late July may potentially beindirectly affected from impacts tovegetation.Small to largecarnivores andomnivores and largeherbivores:May affect butNLAAAll other listedspecies May affectand LAAAll uses SubterraneanGround andMold InsectsandSubterraneanGroundArachnidsAcute mortality No Effect -- nodirect exposureNo indirect effects expected. The base of the food web for these cavedwellers (troglobites) is driven by nutrients in the form of leaf litter, organicdebris, plant roots, feces, eggs, or dead bodies of other cave dwellers orvisitors.No EffectAll uses Surface Insectsand ArachnidAcute mortality No Effect Listed insects and arachnids reliant on a limited number of plant species maybe indirectly affected from impacts to vegetationMay affect and LAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone95Table 48 Summary of Indirect and Direct Effects to Listed Species and Preliminary Effects Determination for ClomazoneUses On Wet Seeded RiceListed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationNonvascularAquatic PlantSpeciesPrimary productivityassessed from effectson biomass asmeasured using cellcount (or density), anddry weightN/A – no listednonvascularlisted speciesN/A – no listed nonvascular listed species. N/A – No listed aquaticnonvascular listed speciesVascularAquatic PlantSpeciesPrimary productivityassessed from effectson biomass asmeasured using frondcount, and dry weightNE – plant RQvalues are belowlisted LOC at 0.6lbs ai/ANontarget plants in terrestrial and semi-aquatic areas – Clomazone does not have thepotential to volatize from wateras it does from soil, exposureof off-site plants is fromspray drift. No effect tomonocot primary productivity or biomass isexpected as spraydrift exposure is estimated to be belowthe nonlisted species LOC for both ground andaerial spray applications usingcoarse droplet size. Indirect affects may occur because thelisted LOC is exceeded for dicots for ground spray applications and monocots and dicotsfor aerial spray applications. Because the main effect to non-target plants in terrestrial andsemi-aquatic areas is expected to be short-term inhibition in growth on limited species (i.e.,survival not affected in vegetation vigor study at estimated spray drift load for rice,survival and recovery of plantsis high in field studies, the IC25for growth effects is onlyexceeded for 1 out of the 10 plants testedfor ground spray applications and 2 out of 10species tested for aerial applications) with no effect toexposed monocot population,erosion is not expected to be above baseline and canopy cover is not expected to besignificantly reduced compared to baseline, therefore these are considered insignificanteffects and NLAA listed aquatic vascular plants.Nonvascular aquatic plants– May affect because RQ exceeds the nonlisted LOC.However, the effect would be short term and amajority of species tested (75%, 3 out of the4 studies) are below the LOC such that overall biomass is not likely to be affected, maineffect is likely to be species diversity but this would also be expected to occur due to theaddition of fertilizer and effects to water quality due to the creation of standing or slowmoving, shallow ponded areas which favor different species over others and thereforeindirect effects are considered insignificant and NLAA over baseline rice field releasewater impacts.May affect but NLAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone96Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationFreshwater FishandAmphibiansAcute mortality May affect andLAA– No hold to14-day postapplication holdtime:acute RQexceeds acuteLOC(Note:uncertainty aboutsilver catfishvalue affects riskconclusions)Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Freshwater aquatic invertebrates –Loss of thisprey base is considered insignificant as theindividual odds of mortality is <1 in 1011and therefore NLAA.Freshwater fish and amphibians – At release onday of application LAA fish prey base. At14-days post-application LAA for species obligate on another fish or amphibian asindividuals may be affected but NLAA for nonobligate species as loss of this prey base isconsidered insignificantMay affect and LAAFreshwaterInvertebratesAcute mortality May affect butNLAA – No holdto 14-day postapplication holdtime:acute RQexceeds acuteLOC but risk ofmortality of anindividual (<1 in1011) isconsidereddiscountableNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Freshwater aquatic invertebrates –Loss of this prey base is considered insignificant(individual odds of mortality <1 in 1011), NLAAFreshwater fish and amphibians – At release onday of application LAA fish prey base. At14-days post-application LAA for species obligate on another fish or amphibian asindividuals may be affected but NLAA for nonobligate species as loss of this prey base isconsidered insignificant.May affect but NLAA –species not obligate on afish, or amphibian speciesMay affect and LAA –species obligate on a fishor amphibian speciesEstuarinemarine FishAcute mortality No Effect – acuteRQ is belowlisted speciesacute LOCNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Marine and estuarine invertebrates – No hold to 14-day post-application hold time:Mayaffect and LAA because the acute RQ value exceeds the nonlisted acute LOC and effectlevel is considered potentiallysignificant to this prey base. These acute effects areexpected to be relatively localized as a 50% dilution of rice paddy water, if released on theday of application or a 25% dilution if released 14days post-applicationdrops these effectsto insignificant (e.g., odds of mortality <1 in 1,000).Estuarine and marine fish – No effectMay affect and LAA ifreleased toestuarine/marine systemChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone97Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationMarineInvertebratesAcute mortality andadditionally formollusks, shelldepositionMay affect andLAA– No hold to14-day postapplication holdtime:acute RQexceeds acutelisted speciesLOCNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Marine and estuarine invertebrates – No hold to 14-day post-application hold time:Mayaffect and LAA because effects are considered potentially significant to this prey base asnonlisted species acute LOC is exceeded.Estuarine and marine fish – No effectMay affect and LAAMarineMammalsQualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Marine and estuarine invertebrates – No hold to 14-day post-application hold time:Mayaffect and LAA because effects are considered potentially significant to this prey base asnonlisted species acute LOC is exceeded.Estuarine and marine fish – No effectMay affect and LAAFreshwaterMammalQualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Freshwater aquatic invertebrates – May affect but NLAA (see discussion for FreshwaterAquatic Species)Freshwater fish and amphibians – NLAA for nonobligate species as loss of this prey baseis considered insignificant (no freshwaterlisted mammal obligate on a fish or amphibianspecies)May affect but NLAA –species not obligate on afish or amphibian species(there are no listedfreshwater mammalsobligate on a fish oramphibian species)Chapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone98Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationMarine Birds Qualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Marine and estuarine invertebrates – No hold to 14-day post-application hold time:Mayaffect and LAA because effects are considered potentially significant to this prey base asnonlisted species acute LOC is exceeded.Estuarine and marine fish – No effectMay affect and LAAMarine Reptiles Qualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Nonvascular aquatic plants –May affect but NLAA (see discussion for vascular aquaticplant species)Marine and estuarine invertebrates – No hold to 14-day post-application hold time:Mayaffect and LAA because effects are considered potentially significant to this prey base asnonlisted species acute LOC is exceeded.Estuarine and marine fish – No effectMay affect and LAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone99Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationNontargetplants interrestrial andsemi-aquaticareasSurvival of individualsand effects on growth(length, and dryweight).Ground sprayapplicationsMA/LAA dicots(dicot plant RQexceeds listedspecies LOC)Aerial sprayapplications:MA/LAAmonocots anddicots (listedspecies LOC isexceeded formonocots anddicots)Nontarget plants in terrestrial and semi-aquatic areas – Clomazone does not have thepotential to volatilize from water as it does from soil, exposure of off-site plants will beprimarily due to spray drift and potentially some subsequent volatilization from these spraydrift impacted areas.Ground spray applications: May affect because of potential affects todicot plants (nonlisted species LOC is exceeded). However exposure levels are below thelisted species LOC for monocots,and the main effect on dicot plants off the field isexpected to be primarily short-term inhibition in growth for a limited number of species(estimated spray drift exposurelevels are below levels exhibiting mortality in a vegetativevigor study and the IC25for growth effects is only exceeded for 1 out of the 10 plantstested). For listed plant species dependent ona community of plants these levels of effectsare considered insignificant and therefore NLAA, but for listed plants obligate on a plant(dicot) species, LAA. For the coarse droplet size required by the label, direct spray drifteffects to the limited dicot species drop below the listed species LOC at 155 ft from thefield margin.Aerial spray applications: May affect because of potential affects to dicot plants (nonlistedspecies LOC is exceeded for dicots, listedspecies LOC is exceeded for monocots).However, the main effect on plants off the field is expected to be primarily short-terminhibition in growth for a limited number of species (estimated spray drift exposure levelsare below levels exhibiting mortalityin a vegetative vigor study and the IC25for growtheffects is only exceeded for 2 out of the 10 plants tested). For listed plant speciesdependent on a community of plants these levelsof effects are considered insignificant andtherefore NLAA, but for listed plants obligate on a plant species, LAA.Birds, reptiles, amphibians (land-phase), mammals and insects – No EffectMay affect and LAABirds, Reptiles,and (LandPhase)AmphibiansAcute mortality andreproductive effectsNo Effect – driftresidues belowLOCNontarget plants in terrestrial and semi-aquatic areas – May affect and NLAA, for listedspecies not obligate on a plant species but LAA for listed species obligate on a plantspecies (see discussion of Nontarget plants in terrestrial and semi-aquatic areas indirecteffects)Birds, reptiles, amphibians (land-phase), mammals and insects – No EffectMay affect but NLAA –species not obligate on aplant speciesMay affect and LAA –species obligate on a plantspeciesLand Mammals Acute mortality andReproductive effectsNo Effect – driftresidues belowLOCNontarget plants in terrestrial and semi-aquatic areas – May affect and NLAA, for listedspecies not obligate on a plant species but LAA for listed species obligate on a plantspecies (see discussion of Nontarget plants in terrestrial and semi-aquatic areas indirecteffects)Birds, reptiles, amphibians (land-phase), mammals and insects – No EffectMay affect but NLAA –species not obligate on aplant speciesMay affect and LAA –species obligate on a plantspeciesChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone100Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationInsects andarachnidsAcute mortality No Effect – driftresidues belowLOCNontarget plants in terrestrial and semi-aquatic areas – May affect and NLAA, for listedspecies not obligate on a plant species but LAA for listed species obligate on a plantspecies (see discussion of Nontarget plants in terrestrial and semi-aquatic areas indirecteffects)Birds, reptiles, amphibians (land-phase), mammals and insects – No EffectMay affect but NLAA –species not obligate on aplant speciesMay affect and LAA –species obligate on a plantspeciesTable 49 Summary of Indirect and Direct Effects to Listed Species and Preliminary Effects Determination for ClomazoneUses On Dry Seeded RiceListed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationNonvascularAquatic PlantSpeciesPrimary productivityassessed from effectson biomass asmeasured using cellcount (or density), anddry weightN/A – no listednonvascularlisted speciesN/A – no listed nonvascular listed species. N/A – No listed aquaticnonvascular listed speciesVascularAquatic PlantSpeciesPrimary productivityassessed from effectson biomass asmeasured using frondcount, and dry weightNone – ListedRQ values arebelow listed LOCfor fieldmeasuredresiduesNontarget plants in terrestrial and semi-aquatic areas – May affect because of potentialaffects to non-target plants in terrestrial and semi-aquatic areas andsubsequent secondaryor indirect effects to aquatic systems. Because the main effect on terrestrial and semiaquatic vegetation off-field is expected to beshort-term inhibition in growth, erosion is notexpected to be above baseline and canopy coveris not expected to be significantly reducedcompared to baseline therefore these are considered insignificant effects and NLAA listedaquatic vascular plants.Nonvascular aquatic plants – No effectMay affect but NLAAFreshwater FishandAmphibiansAcute mortality No Effect – acuteRQ values arebelow listed LOCfor fieldmeasuredresiduesNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectFreshwater aquatic fish, amphibian, and invertebrateprey base – No effectMay affect but NLAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone101Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationFreshwaterInvertebratesAcute mortality No Effect – acuteRQ values arebelow listed LOCfor fieldmeasuredresiduesNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectFreshwater aquatic fish, amphibian, and invertebrateprey base – No effectMay affect but NLAAEstuarinemarine FishAcute mortality No Effect – acuteRQ values arebelow listed LOCfor fieldmeasuredresiduesNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectMarine and estuarine fish and invertebrate prey base – No effectMay affect but NLAAMarineInvertebratesAcute mortality No Effect – acuteRQ values arebelow listed LOCfor fieldmeasuredresiduesNontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectMarine and estuarine fish and invertebrate prey base – No effectMay affect but NLAAMarineMammalsQualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectMarine and estuarine fish and invertebrate prey base – No effectMay affect but NLAAFreshwaterMammalQualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectFreshwater aquatic fish, amphibian, and invertebrateprey base – No effectMay affect but NLAAMarine Birds Qualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectMarine and estuarine fish and invertebrate prey base – No effectMay affect but NLAAChapter 4 Results: Risk CharacterizationRegistration Review Ecological Risk Assessment Clomazone102Listed speciesattributegroup(1)Direct EffectAssessmentEndpointsDirect Effects IndirectEffectsEffects DeterminationMarine Reptiles Qualitative assessmentof acute mortalityNo Effect Nontarget plants in terrestrial and semi-aquatic areas --May affect but NLAA (seediscussion for vascular aquatic plant species)Vascular and nonvascular aquatic plants – No effectMarine and estuarine fish and invertebrate prey base – No effectMay affect but NLAANontargetplants interrestrial andsemi-aquaticareasSurvival of individualsand effects on growth(length, and dryweight).1,500 ft fromsite:May Effect andLAA1 mile from site:May Effect andLAANontarget plants in terrestrial and semi-aquatic areas – May affect because of potentialaffects to non-target plants in terrestrial and semi-aquatic areas andsubsequent secondaryor indirect effects to terrestrial system. Because the main effect on terrestrial and semiaquatic vegetation off-field is expected to beshort-term inhibition in growth, erosion is notexpected to be above baseline and canopy coveris not expected to be significantly reducedcompared to baseline therefore these are considered insignificant effects, NLAA, for listedplants not obligate on another species butLAA for listed plants obligate on anotherspecies.Bird, reptile, amphibian (land-phase), mammal and insect prey base – No EffectMay affect and LAABirds, Reptiles,and (LandPhase)AmphibiansAcute mortality andReproductive effectsNo Effect – onfield and driftresidues belowLOCNontarget plants in terrestrial and semi-aquatic areas – May affect and NLAA, for listedspecies not obligate on a plant species but LAA for listed species obligate on a plantspecies (see discussion of Nontarget plants in terrestrial and semi-aquatic areas indirecteffects)Bird, reptile, amphibian (land-phase), mammal and insect prey base – No EffectMay affect but NLAA –species not obligate on aplant speciesMay affect and LAA –species obligate on a plantspeciesLand Mammals Acute mortality andReproductive effectsNo Effect – onfield and driftresidues belowLOCNontarget plants in terrestrial and semi-aquatic areas – May affect and NLAA, for listedspecies not obligate on a plant species but LAA for listed species obligate on a plantspecies (see discussion of Nontarget plants in terrestrial and semi-aquatic areas indirecteffects)Bird, reptile, amphibian (land-phase), mammal and insect prey base – No EffectMay affect but NLAA –species not obligate on aplant speciesMay affect and LAA –species obligate on a plantspeciesInsects andarachnidsAcute mortality No Effect – driftresidues belowLOCNontarget plants in terrestrial and semi-aquatic areas – May affect and NLAA, for listedspecies not obligate on a plant species but LAA for listed species obligate on a plantspecies (see discussion of Nontarget plants in terrestrial and semi-aquatic areas indirecteffects)Bird, reptile, amphibian (land-phase), mammal and insect prey base – No EffectMay affect but NLAA –species not obligate on aplant speciesMay affect and LAA –species obligate on a plantspeciesChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 103 4.2.2.2 D IRECT E FFECTS T O L ISTED S PECIES F OR U SES O THER T HAN R ICE 

### Aquatic Plants
There are no listed aquatic nonvasc ular plants so no further e ndangered species determination is performed on this taxonomic functional group. There are vascular freshwater and estuarine-marine listed species. Direct effects to listed aquatic vascular plants in receiving waters are considered to be within acceptable le vels for all uses. All vascular aquatic plant RQ values based on 1-in-10 year peak concentrations in surface water, were below the listed species LOC (Table 36 and Table 37). Theref ore, a no effect determination is made for
direct effects to listed vascular aquatic plants.

Freshwater Fish and Amphibians (Aquatic-Phase)

Direct effects to listed freshwater fish and am phibians (aquatic-phase) in receiving waters are considered to be within acceptable levels for a ll uses. All freshwater fish acute and chronic RQ values based on 1-in-10 year peak concentr ations in the modeled receiving water, were below the listed species acute LOC and the chronic LOC (Table 36). Therefore, a no effect
determination is made for direct effects to listed freshwater fish and amphibians.

Freshwater Invertebrates

Direct effects to listed freshwater invertebrate s in receiving waters are considered to be within acceptable levels for all uses. All fr eshwater invertebrate acute and chronic RQ values based on 1-in-10 year peak concentrations in the modeled receiving water, were below the endangered species acute LOC and the chroni c LOC (Table 36). Therefore, a no effect
determination is made for direct effects to listed freshwater fish and amphibians.

Estuarine-Marine Fish

Direct effects to listed estuarin e or marine species in receivin g waters are considered to be within acceptable levels for all uses. All estuarine/marine acut e and chronic RQ values based on 1-in-10 year peak concentrations in th e modeled receiving water, were below the endangered species acute LOC and the chronic LOC (Table 37). Therefore, a no effect
determination is made for direct effects to listed estuarine or marine fish species.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 104 

### Estuarine-Marine Invertebrates

Direct effects to listed estu arine/marine invertebrate species in receiving waters are considered to be within acceptabl e levels for all uses. All estu arine/marine invertebrate acute and chronic RQ values based on 1-in-10 year pe ak concentrations in the modeled receiving water, were below the endangered species acu te LOC and the chronic LOC (Table 37). Therefore, a no effect determination is made for direct effects to listed estuarine or marine invertebrate species.

Marine Mammals
No direct effects from any registered clomaz one use are expected to listed marine mammal species. This conclusion is based on an evaluation of several lines of evidence.

Exposure routes for contaminants in water are expected to be passive uptake from water across the dermis, oral exposure from residues in food items and inci dental ingestion of water. Unlike fish, marine mammals breathe air and do not have gi lls by which uptake of
clomazone from water would occur. Additionally ingest ion of sea water is expected to be incidental as marine mammals, except for the ma natee, meet their water needs from water in their food and from formation of water during meta bolic processes to maintain ionic control. The listed manatee is found in freshwater, brack ish, and marine environments and may ingest freshwater from runoff, seeps, springs, streams, and rivers. Therefore the toxicity values in water for fish and invertebrates based on exposur e to water alone with gills being the primary uptake route are not expected to be dire ctly applicable to marine mammals.

In terms of dietary exposure, the oral and diet ary acute toxicity of clomazone to mammals is considered practically nontoxic. Modeled maximum residues on- dietary items on the field at the highest use rate were below endangered species acute LOC and chronic LOC, for 1,000 gram mammals (Table 29). Clomazone residu e levels in aquatic di etary items would be expected to be lower due to a number of factors and even if th e dietary residue levels were the same, risks to mammals above 1000 g such as sea otters, sea-lions, and whales, would be expected to be lower than th at of a 1000 g mammal. Second ary residues in the aquatic food chain due to bioaccumulation are expected to be low to not detectable since clomazone rapidly metabolizes as observed in both labora tory mammals and fish and residues on aquatic plants would also be less. Th erefore, no effects are expected.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 105 

### Freshwater Mammal
No direct effects from any regi stered clomazone use are expected to the one listed freshwater mammal, the manatee, which also occurs in brackish, and marine wa ters (see section on marine mammals above). The manatee breathes air and does not have gills by which uptake
of clomazone from water would occur.

Exposure routes for contaminants in water are expected to be passive uptake from water across the dermis, oral exposure from residues in food items and ingestion of freshwater. Unlike fish, the manatee breathes air and does not have gills by which uptake of clomazone from water would occur. The manatee may inge st freshwater from runoff, seeps, springs, streams, and rivers. Therefore the toxicity valu es in water for fish and invertebrates based on exposure to water alone with gi lls being the primary uptake r oute are not expected to be directly applicable to the manatee.

In terms of dietary exposure, the oral and diet ary acute toxicity of clomazone to mammals is considered practically nontoxic. Modeled maximum residues on- dietary items on the field at the highest use rate were below endangered species acute LOC and chronic LOC, for 1,000 gram mammals (Table 29). Clomazone residu e levels in aquatic di etary items would be expected to be lower due to a number of factors and even if th e dietary residue levels were the same, risks to the manatee which is much larger than 1000 g, would be expected to be lower than that of a 1000 g mammal. Secondary residues in the aquatic food chain due to bioaccumulation are expected to be low to not detectable since clomazone rapidly
metabolizes as observed in both laboratory mammals and fish a nd residues on aquatic plants
would also be less. Addi tionally, the movement of a manatee during a day may be considerable, such that the assumption of 100% of the diet would be from an affected location is highly conservative. Th erefore, no effects are expected.

Marine Birds
No direct effects from any regist ered clomazone use are expected to listed marine birds. This
conclusion is based on an evaluation of several lines of evidence. The acute toxicity of clomazone to birds is considered practica lly nontoxic. Modeled maximum residues ondietary items on the field at the highest use ra te are below the chronic LOCs (Table 27) and
below levels of acute concern (see Section 4.2.1.1 and Table 44) . Secondary residues in the aquatic food chain due to bioaccumulation would be expected to be significantly below onfield residue levels since clom azone rapidly metabolizes as observed in both laboratory
mammals and fish.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 106 

### Marine Reptiles
No direct effects from register ed clomazone nonrice uses are exp ected to listed marine reptile species. This conclusion is based on an evalua tion of several lines of evidence. The acute toxicity of clomazone to birds, which are a su rrogate for reptiles, is considered practically
nontoxic. Modeled maximum resi dues on-dietary items on the fi eld at the highest use rate are below the chronic LOCs (Table 27) and be low levels of acute concern (see Section 4.2.1.1 and Table 44). Secondary residues in the aquatic food chain due to bioaccumulation would be expected to be signi ficantly below on-field residue levels since clomazone rapidly
metabolizes as observed in bot h laboratory mammals and fish. Residues on aquatic plants would be lower than on-field. Additionally, the movement of sea turtles during a day may be considerable, such that the assumption of 100% of the diet would be from an affected location is highly conservative further. Therefore, no effects are expected.

Nontarget plants in terrest rial and semi-aquatic areas
Direct effects to listed plants are expected o ff the treated field for a ll clomazone uses. Off field transport may occur from runoff, and drift from spray at time of a pplication and drift of vapors post-application. Plant RQ values fr om runoff and spray drift loading exceed the listed species LOC (Table 33) for terrestrial a nd semi-aquatic habitats adjacent to a treated
field. Distances from the field that were estimated to exceed the listed species LOC due to loading from spray drift are listed in Table 43. These distances are based on label language to use a low boom and coarse spray to appl y clomazone. Based on modeling, the distance extending from the field where spray drift lo ading exceeds the listed species LOC extends out from the edge-of-the treated field to a ma ximum of 470 feet for the highest application rate (1.5 lbs ai/A broadcast, 3.0 lbs ai/A in band application) . There is a high degree of uncertainty in the magnitude of clomazone that will volatilize and drift off field, and in the
distance that this volatilized clomazone will travel and be redeposited off field in concentrations that will affect plants. Risk estimates were made on the highly conservative assumption that of the estimated 65% that w ould volatilize off a fiel d, 100% of the air mass would retain its integrity ( i.e. , not mix and become diluted ver tically or laterally) before redepositing, which is recognized to be highl y unlikely. An evaluation of incident data indicated that the vast majority of incidents appear to occur within about 300 feet of the site, followed by between 300 and 1,500 feet. There are distances out to 2 miles associated with the use of the EC formulation, but these occurred prim arily in the first year clomazone was registered for use in 1986, and in 1993 with a pplication to cotton. A number of label changes for the EC formulation were immediately instit uted within a few mont hs of registration and included buffer zones, soil incorporation in areas vulnerable to c onditions leading to volatilization, and spra y drift reducing label language ( e.g ., use of additive to reduce sprayChapter 4 Results: Risk Characterization

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### drift, use of low boom and coarse spray). Fr om the incident data combined with insights provided by modeled spray drift effect distance s, there is high degree of confidence that effects out to 1,500 feet are not un common for either the EC or ME formulations. No off-site
incidents with the WP formulation have been re ported but the volatility of clomazone for this formulation would not be expected to differ grea tly from that of the EC. Even though most incidents that occurred out past 1,500 feet were associated with use in 1986, there are still incidents reported to occur out to 1 mile fo r the ME formulation and 2 miles for the EC.

Land Birds, Reptiles, and Amphibians

Based on an evaluation of all lin es of evidence risks to listed birds and the taxonomic groups for which they are surrogates (reptiles and amph ibians) were concluded to be no effect for application rates of less than 1.5 lbs ai/A applied in bands (~3. 0 lbs ai/A) and may affect but NLAA for the highest application rate of 1.5 lbs ai/A applied in bands (~3.0 lbs ai/A). This conclusion was reached because clomazone applie d at and above 1.5 lbs ai/A in a band (~3.0 lbs ai/A) although not exceeding the chronic LOC (Table 27) did have one acute estimate for residues on short grass above 1/10 th 

### an extrapolated acute LC 50 

### (Table 44). However, the individual risk of mortality is on the order of <1 in 10 18 

### which is considered discountable. All other applications would not exceed chronic LOC values a nd extrapolated estimates of
acute effects would also be below concern levels.

Land Mammals

Based on an evaluation of all lin es of evidence risks to mammals were concluded to be no effect for application rates of 0.75 lbs ai/A or less (as a band or broadcast) and may affect but NLAA for rates resulting in greater than 0.75 lbs ai/A as a broadcast or within a band. This conclusion was reached because on a dietary-basi s residue levels for all uses do not exceed
chronic LOC and an evaluation of subchronic 90 -d mortality results indicate acute effects
should also be below acute conc ern levels (see Section 4.2.1.1). For application rates of 0.75 lbs ai/A broadcast or banded applications which would be at this leve l within the band, dosebased acute and chronic RQ values are al so below acute and chronic LOC values, respectively (Table 31 and s ee Section 4.2.1.1), and therefore these rates and lower are
determined to have no direct effect on mammal s. At the 1.0 lb ai/acre broadcast or banded applications which would be at this level w ithin the band, one or more dose-based acute or chronic RQ values exceed either or both the acute endangered LOC or chronic LOC and therefore these uses are determined to may directly affect a listed mammal. At the highest application rate, dose-based acute and chronic RQ values for mammalian granivores eating primarily seeds, herbivores feeding on fruits and pods, insectivores feeding primarily on
small insects are below acute and chronic LO C values, respectively, so these types ofChapter 4 Results: Risk Characterization

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### mammals would also not be directly affected. Further evaluation of the individual risk of mortality for the acute exceedances and the type and degree of effects for chronic effects are interpreted in this case as not significan t for nonlisted species, these refinements are discussed in the following paragraphs.

At the highest application rate, the chronic RQ values that exceed the chronic LOC range
from 1.4 to 3.5. A closer examination of the t ype and magnitude of effects associated at doses 1.4 to 3.5 times the NOAEC (NOAEL) in the 2-generation reproduction study are a modest decrease in body weight of female rats during premating in F2a and F2b generations and during lactation with no dete ctable effect to reproduction ( e.g ., fertility, number of young produced) or viability of young, and no consis tent statistically significant impact or correlation between test group a nd growth of pups. Although statistical significance and dose responses are not consistent and there is no strict corre lation between combined weights at day 4 and day 21 in the 2000 and 4000 ppm (2 and 4 times the NOAEL) dose groups for pups it was assumed that growth was indicated to be impacted at these levels for pups since growth effects on parental females were signif icant at these levels. The decrease in body weight in F2a and F2b premating females were 26% and 11%, respectively, at 2 times the NOAEL and 26% and 13%, respectively, at 4 times the NOAEL. No significant reproductive effects associated with clomazone exposure were detected at any of the test doses; the highest dose was 4 times the NOAEL for effect on body weight of females. Therefore, although the dose-based chronic RQ values exceeded for some mammals indicating a potential for reproduc tive effects of concern furthe r evaluation of the type and degree of expected effects indicate that reproduc tive effects are not expected at these residue
levels.

The individual risk of mortality based on th e typical dose response slope (4.5) is 1 in 29,900 (RQ=0.013; 15 gram bw) to <1 in 10 milli on (RQ=0.06; 1000 gram bw) for residues on broadleaf plants and small insects; 1 in 294,000 (RQ=0.10; 15 gram bw) to <1 in 100 million (RQ=0.05; 1000 g bw) for residues on tall grass; and 1 in 491 (RQ=0.23; 15 gram bw) to 1 in 294,000 (RQ=0.10; 1000 g bw) for residues on short grass (Table 28 and Table 41). Therefore, although the dose-base d acute RQ values exceeded the acute endangered species
LOC for some mammals and dietar y items indicating a potential fo r acute mortality effects of concern, except potentially for small mammals i ngesting primarily short grass, an evaluation of the individual mortality risk indicate such risks are unlikely to occur or be measureable for nonlisted species in this case. Another consideration is that acute dose-based values were calculated using results from an acute oral gavage study where clomazone was administered as a single, large oral dose, which may potentia lly be more toxic than when administered in the diet. The dose-based approach assumes th at the uptake and absorption kinetics of aChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 109 

### gavage toxicity study approximate the absorpti on associated with uptake from a dietary matrix. While no acute dietary study was perfor med the lack of mortality in a 90-d dietary study with rats at 8,000 ppm ai with a calcu lated dose level of 1,200 mg ai/kg-bw would appear to support that clomazone administered in a dietary matrix is less toxic than that administered by gavage as the LD 50 

### of 1,369 mg/kg-bw is compar able to 1,200 mg ai/kg-bw but one study has 50% mortality at the dose level, the other none.

Taking into consideration that dietary-based acute and chronic LOC do not exceed even at the highest application rate, that dose-based chronic values while potentially resulting in a slight decline in weight will not affect the number of young produced or the viability of the young, and that dose-based acute risks of morta lity are discountable or more reasonably represented by conclusions from dietary-based resu lts as there is some indication that dietary administration is less toxic than a single, oral bolus in the case of clomazone, it was
concluded that effects are not significant or are discountable at application rates above 0.75
lbs ai/A broadcast or in a band.

Insects and Arachnids

No direct effects to listed in sects or arachnids are expected to occur for any registered use because on-field upper bound residue levels at the highest application rate, banded application on sweet potatoes, were below the LOC for small and large insects.

Clomazone use is determined to have no di rect effect on subterranean ground and mold
insects and subterranean arachni ds. These animals spend thei r entire lives underground in subterranean voids (caves, sinkhol es, fractures, interconnections, etc .) in areas with low air movement, and elevated relative humidity, and reduced temperature fluctuations. Therefore
these animals would not be dire ctly exposed to clomazone from spray drift, runoff, or redeposited volatilized clomazone.

4.2.2.3 D IRECT E FFECTS TO L ISTED S PECIES F OR U SE ON W ET S EEDED R ICE 

### Aquatic Plants
There are no listed aquatic nonvasc ular plants so no further e ndangered species determination is performed on this taxonomic functional group. There are vascular freshwater and estuarine-marine listed species. Direct effects to listed aquatic vascular plants in rice paddy water are below listed species LOC (Table 38). Therefore, a no effect determination is made
for direct effects to listed vascular aquatic plants.Chapter 4 Results: Risk Characterization

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### Freshwater Fish and Amphibians (Aquatic-Phase)
Flood water clomazone levels are expected to exceed the acute listed species LOC (0.05) for 42 days post-application at the 23.7 day half-l ife based on field studies (Table 38). The national Section 3 label for wet seeded rice (C errano 5 MEG) prohibits release of flood water for up to 14 days post-application. Section 24(c ) labels for applicati on of Command 3 ME to wet seeded rice in TX, MS, MO, LA, and AR do not provide any time restrictions on release of flood water after treatment. In either case, the odds of mortality at the acute RQ values on the day of application and 14-da ys post-application are 1 in 89 and 1 in 562, respectively. Therefore, listed species may be affected by us e of clomazone on wet seeded rice and use is LAA listed species.

There is a high degree of uncertainty in this risk determination. The silver catfish acute value used for this assessment was from a study testi ng a clomazone formulation. Because there is no TGAI study with the silver catfish, and no fo rmulation testing with the freshwater fish species that were tested with the TGAI, it is no t possible to determine if the difference is due to a difference in sensitivity to clomazone, to the formulation, or both. If the rainbow trout value (19,000 ppb), which is the more sensitiv e freshwater species tested with the TGAI alone, were used to assess risk rather than the silv er catfish the acute RQ (0.03) would be below the listed species LOC on the day of application.

Freshwater Invertebrates
Flood water clomazone levels are expected to exceed the acute listed species LOC for 20 days post-application (Table 38) at the 23.7 day half-life base d on field studies. Therefore wet seed rice use may directly affect listed fr eshwater invertebrates. However, while the acute RQ (0.10) (Table 41) exceeds the acute LOC on the day of application the odds of mortality are <1 in 10 11 

### . Based on this information, direct effects to freshwater invertebrates
are considered to be discountable an d therefore not NLAA listed species.

Estuarine-Marine Fish
Acute RQ values are below the acute endange red species LOC (Table 38). Therefore no direct effects to listed species fr om wet seeded rice use are expected.

Estuarine-Marine Invertebrates

Estuarine-marine invertebrates were indicated to be potentially at risk acutely from release of rice paddy flood water into estuarine-marine su rface waters. The acute restricted LOC is exceeded in rice paddy water from the day of application to 14 days post-application indicating potentially unacceptable mo rtality effects if water is re leased during this time. ItChapter 4 Results: Risk Characterization

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### was estimated that up to 98 days of hold time is needed to reduce levels to the acute endangered species LOC exceedence criteria. On e rice label prohibits release of flood water for up to 14 days post-application; the others do not provided any time restrictions on release of flood water after treatment. Therefore, dire ct effects may affect and are considered LAA listed species.

Marine Mammals
No direct effects from any registered clomaz one use are expected to listed marine mammal species. This conclusion is based on an evaluation of several lines of evidence.

Exposure routes for contaminants in water are expected to be passive uptake from water across the dermis, oral exposure from residues in food items and inci dental ingestion of water. Unlike fish, marine mammals breathe air and do not have gi lls by which uptake of
clomazone from water would occur. Additionally ingest ion of sea water is expected to be incidental as marine mammals, except for the ma natee, meet their water needs from water in their food and from formation of water during meta bolic processes to maintain ionic control. The listed manatee is found in freshwater, brack ish, and marine environments and may ingest freshwater from runoff, seeps, springs, streams, and rivers. Therefore the toxicity values in water for fish and invertebrates based on exposur e to water alone with gills being the primary uptake route are not expected to be dire ctly applicable to marine mammals.

In terms of dietary exposure, the oral and diet ary acute toxicity of clomazone to mammals is considered practically nontoxic. Modeled maximum residues on- dietary items on the field at the highest use rate were below endangered species acute LOC and chronic LOC, for 1,000 gram mammals (Table 29), clomazone residue levels in aquatic di etary items would be expected to be lower due to a number of factors and even if th e dietary residue levels were the same, risks to mammals above 1000 g such as sea otters, sea-lions, and whales, would be expected to be lower than th at of a 1000 g mammal. Clom azone rapidly metabolizes as observed in both laboratory mammals and fish. Therefore, no direct effects are expected.

Freshwater Mammal
No direct effects from any regi stered clomazone use are expected to the one listed freshwater mammal, the manatee, which also occurs in brackish, and marine wa ters (see section on marine mammals above). The manatee breathes air and does not have gills by which uptake
of clomazone from water would occur.

Exposure routes for contaminants in water are expected to be passive uptake from water across the dermis, oral exposure from residues in food items and ingestion of freshwater.Chapter 4 Results: Risk Characterization

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### Unlike fish, the manatee breathes air and does not have gills by which uptake of clomazone from water would occur. The manatee may inge st freshwater from runoff, seeps, springs, streams, and rivers. Therefore the toxicity valu es in water for fish and invertebrates based on exposure to water alone with gi lls being the primary uptake r oute are not expected to be directly applicable to the manatee.

In terms of dietary exposure, the oral and diet ary acute toxicity of clomazone to mammals is considered practically nontoxic. Modeled maximum residues on- dietary items on the field at the highest use rate were below endangered species acute LOC and chronic LOC, for 1,000 gram mammals (Table 29). Clomazone residu e levels in aquatic di etary items would be expected to be lower due to a number of factors and even if th e dietary residue levels were the same, risks to the manatee which is much larger than 1000 g, would be expected to be lower than that of a 1000 g mammal. Additiona lly, the movement of a manatee during a day may be considerable, such that the assumption of 100% of the diet would be from an affected location is highly conservative. Therefore, no effects are expected.

Marine Birds
No direct effects from any regist ered clomazone use are expected to listed marine birds. This
conclusion is based on an evaluation of several lines of evidence. The acute toxicity of clomazone to birds is considered practica lly nontoxic. Modeled maximum residues ondietary items on the field at the highest use ra te are below the chronic LOCs (Table 27) and
below levels of acute concern (see Section 4.2.1.1 and Table 44) , residues in the aquatic food chain due to bioaccumulation would be expected to be significantly below on-field residue levels since clomazone rapidly metabolizes as observed in both laboratory mammals and
fish.

Marine Reptiles
No direct effects from any registered clomaz one use are expected to listed marine reptile species. This conclusion is based on an evalua tion of several lines of evidence. The acute toxicity of clomazone to birds, which are a su rrogate for reptiles, is considered practically
nontoxic. Modeled maximum resi dues on-dietary items on the fi eld at the highest use rate are below the chronic LOCs (Table 27) and be low levels of acute concern (see Section 4.2.1.1 and Table 44). Residues in the aquatic f ood chain due to bioaccumulation would be expected to be significantly below on-field residue leve ls since clomazone rapidly
metabolizes as observed in bot h laboratory mammals and fish. Residues on aquatic plants would be lower than on-field. Additionally, the movement of sea turtles during a day may beChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 113 

### considerable, such that the assumption of 100% of the diet would be from an affected location is highly conservative further. Therefore, no effects are expected.

Nontarget plants in terrest rial and semi-aquatic areas
Clomazone applied to soil in a rice field and then immediately flooded or directly applied to a flooded field is not expected to have the same volatility is sue as that observed for the
nonrice uses and the rice fields per the labels should have berm s such that transport by runoff should not be a viable pathway. However, clom azone may be transported to off-field sites from spray drift from ground or aerial applic ations to rice fields (see Sections 4.1.3.1 and 4.2.1.1). Ground spray applications do not result in spray drift that exceeds the listed species
LOC for monocots but does result in exceedance of the listed LOC for dicots (Table 33). Therefore, clomazone use may directly affect lis ted dicot plant species and is LAA. Aerial applications result in estimated spray drift exposure that exceeds listed plant LOC for both
monocots and dicots. The furthe st extent off-field for ground sp ay effects is estimated as 155 feet and more than 1,000 feet for aerial applica tions as some labels do not restrict droplet size, the estimate for those that do are 900 feet (Table 43). Volatiliz ation from these areas impacted by spray drift is a possibility. Because only ME formulations ar e registered for rice use, the furthest extent of any effect is cons idered 1 mile based on an evaluation of incident
data.

Land Birds, Reptiles, and Amphibians
Residues due to spray drift will be lower than those estimated for the highest application rate on field. As on-field residue levels for the highe st application rate resulted in no effect to listed avians, use on rice will also not effect birds and their surrogates.

Land Mammals
Off-field dietary- a nd dose-based residues are below acute endangered species LOC and
chronic LOC at 0.6 lbs ai/A. Therefore clom azone use on rice is determined to have no
effect on listed land mammals.

Insects and Arachnids

No direct effects to listed in sects or arachnids are expected to occur for any registered use because on-field upper bound residue levels at the highest application rate, banded application on sweet potatoes, were below the LOC for small and large insects and therefore would be below off-field spray drift exposure.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 114 

### Clomazone use is determined to have no di rect effect on subterranean ground and mold
insects and subterranean arachni ds. These animals spend thei r entire lives underground in subterranean voids (caves, sinkhol es, fractures, interconnections, etc .) in areas with low air movement, and elevated relative humidity, and reduced temperature fluctuations. Therefore
these animals would not be dire ctly exposed to clomazone from spray drift, runoff, or redeposited volatilized clomazone.

4.2.2.4 D IRECT E FFECTS TO L ISTED S PECIES F OR U SE ON D RY S EEDED R ICE 

### Aquatic Plants, Fish, Amphibian s, and Aquatic Invertebrates

Measured concentrations in flood water from field studies were used to make risk
determinations as these results are considered more environmentally relevant. Aquatic plant RQ values were below listed LOC, and acute RQ values for freshwater fish (includes amphibians) and invertebrates, and marine-estuarine fish and invertebrates were below the acute endangered species LOC. Based on these results, clomazone use on dry seeded rice is
determined to have no direct effect on listed vascular plants, freshwater fish (including amphibians) and invertebrates, and estu arine-marine fish and invertebrates.

Marine Mammals and Freshwater Mammals

Same conclusions as for wet seeded rice, fo r discussion see the di scussions for marine
mammals and the freshwater mammal in Section 4.2.2.3.

Marine Birds
No direct effects from any regist ered clomazone use are expected to listed marine birds. This
conclusion is based on an evaluation of several lines of evidence. The acute toxicity of clomazone to birds is considered practica lly nontoxic. Modeled maximum residues ondietary items on the field at the highest use ra te are below the chronic LOCs (Table 27) and
below levels of acute concer n (see Section 4.2.1.1 and Table 44) , residues in the aquatic food chain due to bioaccumulation would be expected to be significantly below on-field residue levels since clomazone rapidly metabolizes as observed in both laboratory mammals and
fish.

Marine Reptiles
No direct effects from any registered clomaz one use are expected to listed marine reptile species. This conclusion is based on an evalua tion of several lines of evidence. The acute toxicity of clomazone to birds, which are a su rrogate for reptiles, is considered practically
nontoxic. Modeled maximum resi dues on-dietary items on the fi eld at the highest use rate are below the chronic LOCs (Table 27) and be low levels of acute concern (see SectionChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 115 

### 4.2.1.1 and Table 44). Residues in the aquatic f ood chain due to bioaccumulation would be expected to be significantly below on-field residue leve ls since clomazone rapidly
metabolizes as observed in bot h laboratory mammals and fish. Residues on aquatic plants would be lower than on-field. Additionally, the movement of sea turtles during a day may be considerable, such that the assumption of 100% of the diet would be from an affected location is highly conservative further. Therefore, no effects are expected.

Nontarget plants in terrest rial and semi-aquatic areas
Clomazone applied to soil in a rice field and then not perman ently flooded for several days potentially faces the same volat ility issues as that observed for nonrice uses. Clomazone may also be transported to off-field sites from spra y drift from ground or aerial applications (see Sections 4.1.3.1 and 4.2.1.1) but runoff should not be an issue as per the label rice fields
clomazone is used on should have berms. Gr ound spray applications do not result in spray drift that exceeds the listed species LOC for monocots but does result in exceedance of the listed LOC for dicots (Table 33). Aerial spray exceeds listed LOC for monocots and dicots. Therefore, clomazone use may directly affect listed plant species and is LAA listed species. The furthest extent off-field for ground spay e ffects is estimated as 155 feet and more than 1,000 feet for aerial applications as some labels do not restrict droplet size, the estimate for
those that do are 900 feet (Table 43).

Land Birds, Reptiles, and Amphibians
Residues due to spray drift will be lower than those estimated for the highest application rate on field. As on-field residue levels for the highe st application rate resulted in no effect to listed avians, use on rice will also not affect birds and their surrogates.

Land Mammals

At 0.6 lbs ai/A, on-field dietar y- and dose-based residues are below acute endangered species LOC and chronic LOC (Table 28 and Table 30) . Therefore clomazone use on rice is
determined to have no effect on listed land mammals.

Insects and Arachnids

No direct effects to listed in sects or arachnids are expected to occur for any registered use because on-field upper bound residue levels at the highest application rate, banded application on sweet potatoes, were below the LOC for small and large insects and therefore would be below off-field spray drift exposure.Chapter 4 Results: Risk Characterization

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### Clomazone use is determined to have no di rect effect on subterranean ground and mold
insects and subterranean arachni ds. These animals spend thei r entire lives underground in subterranean voids (caves, sinkhol es, fractures, interconnections, etc .) in areas with low air movement, and elevated relative humidity, and reduced temperature fluctuations. Therefore
these animals would not be dire ctly exposed to clomazone from spray drift, runoff, or redeposited volatilized clomazone.

4.2.2.5 I NDIRECT E FFECTS TO L ISTED S PECIES F OR U SES O THER T HAN O N R ICE 

### As discussed in Section 4.2.1, no unacceptable direct acute or chronic risks above levels of concern are expected for nonlisted birds, la nd mammals, beneficial or listed insects, freshwater or estuarine-marine animals or aq uatic plants from regi stered clomazone nonrice uses. Therefore, no indirect effects to listed species that depend on these groups for food or habitat are expected.

There are indirect effects expected to listed sp ecies that are obligate or depend on plants in terrestrial or semi-aquatic areas as a food resource or for habitat. However, this effect is expected to be restricted to relatively localized areas from a treated site, the highest occurrence and likelihood being w ithin 300 feet of the site from combined runoff, spray drift and redeposition of volatilized clomazone, follo wed out to 1,500 feet from spray drift and drift of clomazone vapor. Redeposition even ts outside 1,500 feet are expected to be infrequent as indicated by the incident inform ation, and be confined to relatively scattered
small tracts of land. As discussed in Sec tion 4.1.3, effects to o ff-site diverse plant communities with emergent vegetation are expected to be mainly reduction of growth rather than plant mortality. According to non-target plant incident data, most clomazone incidents
occur within a 300 foot area from treated fields.

Therefore, indirect effects to food resources or habitat requirements of large carnivorous or omnivorous land mammals and birds with large home ranges are expected to be insignificant. Similarly such degree of effects should be insi gnificant for species not dependent or having a low dependency on terrestrial ve getation or are not obligate or dependent on limited plant species based on species profiles or recovery plans such as the Shenandoah salamander ( Plethodon shenandoa ) which occurs in dry, rocky, talus slopes and feeds on soil invertebrates; the sand skink ( Neoseps reynoldsi ) which is adapted to an underground existence, occurs in sandy soils free of roots and feeds on soil invertebrates; the Houston toad ( Bufo houstonensis ) which uses rain pools, flooded fiel ds, and natural or manmade ponds for breeding and as adults are re liant upon the presence of sand substrate inhabiting areas under logs, in leaf litter, in burrows, beneath undercut banks and in the actual sand substrate. Other listed land mammals, birds, reptiles, and land-ph ase amphibians, which are reliant or obligateChapter 4 Results: Risk Characterization

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### on a limited number of plant species, a habi tat that is dominated by a few species ( e.g ., prairie grassland), have small localized popul ations dependent on vegetation, or are highly reliant on vegetative camouflage during late May through late July may potentially be indirectly affected from impacts to vegetation.

For listed marine mammals (including the mana tee which may occur in freshwater, brackish, and marine environments), birds and reptiles i ndirect effects due to loss of food resources either plants or animals (fish, invertebrates) is not expected in aquati c systems. Additionally, for aquatic systems increased turbidity or er osion over baselin e levels is not expected. Tillage of fields is expected to be the predom inant factor affecting erosion, which clomazone use will not impact over baseline. Conservati on tillage systems for cotton and soybeans will reduce erosion as compared to conventional tillage for these crops. But again the use of clomazone is not expected to impact the baselin e erosion rate. Off-fiel d decreased short-term growth in a diverse plant community is not expe cted to impact erosi on over baseline levels.

4.2.2.6 I NDIRECT E FFECTS TO L ISTED S PECIES F OR R ICE U SES



### Wet Seeded Rice
As discussed in Section 4.2.1, no unacceptable acute or chronic risks above levels of concern are expected for listed or nonlisted birds, land amphibians, reptiles, land mammals, and
beneficial or listed insects.

For freshwater systems, while e ffects to aquatic invertebrates and vascular aquatic plants do not exceed the nonlisted species LOC values, the nonlisted LOC is exceeded for nonvascular plants and freshwater fish on the day of a pplication and at 14 days post-application. However, concentrations on these days do not exceed the nonlisted LOC for the other three nonvascular plants tested. Given that some form of fertilizer has likely be en added to the rice field, and in some cases is added concurrent with clomazone, clomazone is not likely to reduce nonvascular plant biomass in waters r eceiving rice flood water as those nonvascular plants not impacted are expected to take advant age of the additional nutrient resources. The diversity of species may be impacted, but this wo uld also be expected to occur due to cultural practices in rice fields. Ther efore the clomazone effect on nonva scular plants in receiving waters is considered to likely be brief and transient, and be within the background level of effects to nonvascular biomass and diversity at tributable to such cultural practices. For example, the creation of standing or slow m oving, shallow waters of a rice field will favor production of certain species of nonvascular plants over those present in a deeper, faster moving aquatic system and the added nutrients will favor some species over others both within the rice field and in the receiving water.Chapter 4 Results: Risk Characterization

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### As discussed in Section 4.1.3, effects to off-s ite diverse plant communities with emergent vegetation are expected to be mainly reduction of growth. Therefore, in direct effects to food resources or habitat requirements of larg e carnivorous or omnivorous land mammals and birds with large home ranges are expected to be insignificant. Other listed land mammals, birds, reptiles, and land amphibians, which ar e obligate on a plant species, or depends on a habitat that is dominated by a few species ( e.g ., prairie grassland), have small localized populations, or are highly reliant on camou flage during May through late July may potentially be indirectly affect ed from impacts to vegetation. For ground spray applications the species impacted is further reduced to thos e listed species that are obligate on either a dicot or a non-flowering plant ( e.g ., fern and its allies, conifers or cycads, lichen) as a food resource or for habitat. Additionally, for aqua tic systems increased turbidity or erosion over baseline levels is not expected from this degree of effect. Tillage of fields is expected to be the predominant factor affecti ng erosion, which clomazone use is not expected to impact over baseline. Off-field decreased short-term growth in a diverse plant community is not expected to impact erosion over baseline levels.

For ground spray applications direct spray drif t effects to the limite d dicot species drop below the listed species LOC at 155 ft from th e field margin. For aerial applications, the spray drift impact is estimated to extend to 270 and 900 feet for monocots and dicots, respectively, when a coarse spray is used, a nd 425 and >1000 feet for monocots and dicots, respectively, when a median to coar se spray is used (Table 43).

Clomazone has the potential to volatilize off the rice field or areas impa cted by spray drift. For rice uses, the distance volatilization may impact plants is estimated to be 1 mile from the site of application based on all rice registra tions being ME formulations and the use of incident data for distance of impact from a field for ME formulations. Frequency of redeposition events outside the spray drift imp act area are expected to be infrequent as indicated by the incident information and be c onfined to relatively scattered small tracts of
land.

Dry Seeded Rice
As discussed in Section 4.2.1, no unacceptable acute or chronic risks above levels of concern are expected for listed or nonlisted birds, land amphibians, reptiles, land mammals, and
beneficial or listed insects. Based on clomazone concentrations measured in field studies, which are considered a more appropriate measur e of exposure than modeled values in this case, no effects are expected for listed or nonlis ted freshwater fish and aquatic invertebrates,
estuarine-marine fish and invert ebrates or to aquatic plants.Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 119 

### For indirect effects from impact s to non-target plants in terres trial and semi-aquatic areas see
the discussion under wet seeded rice. However for aquatic plants there is no exceedance of nonlisted LOC for vascular or nonvascular plants so no indirect effects to listed species are expected from impacts to aquatic plants.

4.2.2.7 E FFECTS TO C RITICAL H ABITAT 

### Uses Other Than Rice and Dry Seeded Rice
As discussed in Section 4.2.1, no unacceptable direct acute or chronic risks are expected to nonlisted mammals, birds, reptiles, amphibians (aqua tic- or terrestrial-phases), beneficial or listed insects, fish, aquatic i nvertebrates or aquatic plants. Therefore, where these broad groups are principle constituent elements of criti cal habitat then no effect to these principle constituents are expected. Where critical habi tat principle constituent elements consist of a listed plant species or is reliant or obligate on a limited number of nonlisted plant species, or is a habitat that is dominated by a few species ( e.g ., prairie grassland) then these principal constituent elements may potentially be affected.

Clomazone is not expected to affect the physical structure or existence of subterranean caves. The base of the food web is driven by nutrients in the form of leaf litter and organic debris which washes or falls into caves through small hol es and fissures, plant roots, feces, eggs or dead bodies of cave visitors ( e.g ., cave crickets, small mammals, and raccoons). The subterranean ground and mold insects and subt erranean arachnids would not be directly exposed to clomazone from spray drift, r unoff, or redeposited volatilized clomazone. Clomazone effects on surface plants is not expect ed to result in indir ect effects to nutrient input below baseline conditions, or result in re duction of roots in the subterranean caves. Land use and cultural practices on a crop field ( e.g ., tilling, fertilizing, an d crop type) should be the significant driver in terms of nutrient inputs and moisture to surface and subsurface drainage basins below and near the field.

Wet Seeded Rice Use
As discussed in Section 4.2.1, no unacceptable direct acute or chronic risks are expected to nonlisted mammals, birds, reptiles, amphibians (aqua tic- or terrestrial-phases), beneficial or listed insects, or aquatic plants. There are potential affects on the freshwater fish and estuarine invertebrate prey base. Therefore, where thes e broad groups are principle
constituent elements of critical habitat then no effect to these principle constituents are expected. Where critical habitat principle c onstituent elements consist of a listed plant species, a listed freshwater fish or amphibian species, or is reliant or obligate on a limitedChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 120 

### number of nonlisted plant species, or is a habitat that is dominated by a few species ( e.g ., prairie grassland) then these principal consti tuent elements may potentially be affected.

Clomazone is not expected to affect the physical structure or existence of subterranean caves. The base of the food web is driven by nutrients in the form of leaf litter and organic debris which washes or falls into caves through small hol es and fissures, plant roots, feces, eggs or dead bodies of cave visitors ( e.g ., cave crickets, small mammals, and raccoons). The subterranean ground and mold insects and subt erranean arachnids would not be directly exposed to clomazone from spray drift, r unoff, or redeposited volatilized clomazone. Clomazone effects on surface plants is not expect ed to result in indir ect effects to nutrient input below baseline conditions, or result in re duction of roots in the subterranean caves. Land use and cultural practices on a crop field ( e.g ., tilling, fertilizing, an d crop type) should be the significant driver in terms of nutrient inputs and moisture to surface and subsurface drainage basins below and near the field.

4.2.2.8 C O -O CCURRENCE A NALYSIS



### The FESTF IMS data base contains land use co ver information, and agriculture census data (USDA 2002 Census of Agriculture) and speci es occurrence and cri tical habitat location
information. This data base was used to iden tify counties with specific crop use and adjacent counties, and was used to perform an analysis of listed species that occur within 1 mile of use
sites for the ME formulation and that occur within 2 miles of th e use sites for the EC and WP formulations. Crop use is represented in th e IMS by one-or more designated crop uses as shown in Table 50, taken from the IMS protocol document. The species locations in IMS are from EFED (June, 2003) and from the Nature Serve Multi-Jurisdicti onal Database (MJD) licensed by FESTF (the FESTF MJD; McGaughey et al. 2007).

There were some locations where NLCD cultiv ated land information was not available for incorporation into the ve rsion of the IMS used for this analys is such as HI, Puerto Rico (PR), U.S. Virgin Islands (VI), Guam (GU), and the Mari ana Islands (MP). In th e light of this lack of knowledge, species and their cr itical habitat at these locatio ns were assumed to overlap with the clomazone action area with the following exceptions (1) if the location of the species was restricted to a small island whic h does not support an agribusiness, and/or the whole island is a nature reserve ( e.g ., Northwestern Hawaiian Is lands, Mona Island, Monito Island), and (2) rice uses , USDA agricultural census for HI and these U.S. territories do not report rice as planted in these locations. 38

38 American Somoa, www.nass.usda.gov/census/census97/amsomoa/intro.htm ; Guam, www.nass.usda.gov/census/census97/guam/guam.htm ; Puerto Rico,Chapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 121 Table 50 Clomazone uses designated in problem formulation and corresponding IMS sites
Crop IMS Site Agricultural Fallow/Idleland Assumed would be covered by use sites for specific crops that clomazone is registered as use of land for crops after application is limited to species tolerant of clomazone which consists of these
crops. Arracacia (Persian Carrot) Vegetables, other Beans – Succulent (Snap) Beans – Succulent (Lima) Beans – snap Green lima beans Cabbage Cabbage - head Cotton (unspecified) Cotton, all Cucumber Cucumbers and pickles Manioc (cassava) Cassava (PR) 1 Melons, musk Honeydew melons, cantaloupes Melons, water Watermelons Mint Mint for oil, all Peas, succulent Peas, green (excluding southern) Peas, green southern (cowpeas ) - blackeyed, cr owder, etc. Pepper Peppers, bell Peppers, chile (all peppers - excluding bell) Pimiento Pimientos Pumpkin Pumpkins Rice Rice Soybeans (unspecified ) Soybeans for beans Squash, summer Squash Squash, winter Squash Sugarcane Sugarcane for seed Sugarcane for sugar Sweet potato Sweet potatoes Tobacco Tobacco Yam Yams (PR) 1
Yautia Taro 2 1The designation of (PR) indi cates that the data are for Puerto Rico. The 2002 Agricultural Census contains no records for cassava or yams outside Puerto Rico. 2The crop Yautia is not specifically included as a crop in the 2002 Agricultural Census. The crop Taro will be used to represent this crop in the IMS.



### The co-occurrence results were further evaluated to remove species that were identified in Section 4.2.2.2 to 4.2.2.6 as having NE or May affect but NLAA, independent of cooccurrence, the effects determination for each listed species is provi ded in Appendix I for nonrice uses, Appendix K for wet seeded rice, and Appendix J for dry seeded rice. Figures in Appendix I show the counties with listed species for all uses except rice identified as LAA.

www.agcensus.usda.gov/Publications/2007/ Full_Report/Outlying_Areas/prv1.pdf ; Commonwealth of Northern Mariana Islands, www.nass.usda.gov/census/census97/cnmi/cnmi.htm ; U.S. Virgin Islands, www.nass.usda.gov/census/cesus92/outlying/vi-54.pdfChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 122 4.2.2.9 E FFECTS D ETERMINATION 

### Listed Species Associated with All Uses Except Rice
The action area for reregistration of clomazone consists of a 2 mile radius out from clomazone use sites. Operationally locations where clomazone is used are defined as all
cultivated land that has had one or more of the crops for which clomazone is registered cultivated on it, except California where the only registered clomazone use is rice. The geographical extent of a 2 mile radius out from a use site is based on the farthest physical extent direct or indirect effects from exposur e to clomazone are predicted to occur based on
best available information.

May affect but NLAA determinations were made for listed vascular aqua tic plants (there are no nonvascular listed species), freshwater and mari ne listed fish and invertebrates, aquatic amphibians, and marine mammals. May affect but NLAA determinations were made for listed large land birds, mammals and reptiles not known to be reliant on one or a limited
number of nonlisted or listed terrestrial or semi-aquatic plant species. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included, estimates of ri sk, odds of mortality, tim ing of application, and refinement of exposure levels where appropriate . Additionally, some species were identified as being outside the action ar ea of clomazone, and a no effect determination was made for these. Species designated as may affect but NLAA, are listed in Appendix I of this
document.

May affect and LAA determinations were ma de for 10 amphibians, 1 arachnid, 17 birds, 1 conifer, 174 dicots, 5 ferns and allies, 14 inse cts, 2 lichens, 14 mamm als, 7 land snails, 23 monocots, and 17 reptiles. This conclusion was based on a review of multiple lines of
evidence for both direct and indir ect effects, effects to critical habitat, and included, estimates of risk, odds of mortality, and refinement of ex posure levels where appropriate. Based on the co-occurrence analysis there are locations for some of these species which fall outside the action area. Species designated as may affect and LAA, are listed in Appendix I of this
document.

Listed Species Associated with Wet Seeded Rice
The action area for reregistration of clomazone us e on wet seeded rice consists of all streams and rivers downstream of rice fields. Oper ationally rice field sites are defined as all
cultivated land that has had rice cultivated on it . No direct effect to listed vascular aquatic plants, estuarine and marine fish, marine mammals and birds are expecte d. Direct effects to
freshwater invertebrates are considered discountabl e as the risk of individual mortality is lessChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 123 

### than 1 in 10 11 

### . No direct effects to land mammals, birds, reptiles, or amphibians are expected. Direct effects to freshwater fish and amphibian s, and estuarine and marine invertebrates are expected. There are direct e ffects to non-target vegetation off the field. For
those labels which do not state use of a coarse dr oplet size, especially for aerial applications to rice this effect may potentia lly reach several thousand feet. For other labels with such restrictions in place, this effect is expected to be restricted to relatively localized areas off a treated site, the highest occurrence and likelihood being adjacent to the site from spray drift and/or vapor drift. Effects to off-site diverse plant communities with emergent vegetation are expected to be mainly reduction of growt h, with mortality pote ntially amongst highly sensitive species. Therefore, for large ma mmalian and avian listed species not reliant on a listed plant species or not reliant on one or a limited number of nonlisted plant species either as prey or habitat indirect effects are expected to be insignificant.

May affect but NLAA determinations were made for listed vascular aqua tic plants (there are no nonvascular listed species), freshwater and mari ne listed fish and invertebrates, aquatic amphibians, and marine mammals. May affect but NLAA determinations were made for listed large land birds, mammals and reptiles not known to be reliant on one or a limited
number of nonlisted or listed terrestrial or semi-aquatic plant species. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included, estimates of ris k, odds of mortality, and refinement of exposure levels where appropriate. Additionally, some species were identified as being outside the action area of clomazone, and a no effect dete rmination was made for these. Species designated as no effect and may affect but NLAA, are listed in Appendix K of this document.

May affect and LAA determinations were made for flowering and nonflowering plants because of exceedance of endangered species LOC. May affect and LAA determinations were made for listed freshwater fish and amphibi ans, and estuarine and marine invertebrates. May affect and LAA determinations were made for listed freshwater invertebrates that are obligate on a specific freshwater fish species an d for estuarine and marine fish that are obligate on a specific estuarine-marine inverteb rate. May affect and LAA determinations were made for small mammals, reptiles, and amphi bians that because of their size and home range may rely on a limited number of plant species for a food resource or habitat.

Listed Species Associated with Dry Seeded Rice
The action area for reregistration of clomazone us e on rice consists of a 2 mile radius out from rice fields, except California where its use is prohibited by the label. Operationally rice
field sites are defined as all cultivated land that has had rice cultivated on it. Based on
measured field residue levels in flood water, direct effects to freshwater fish, amphibians, andChapter 4 Results: Risk Characterization

Registration Review Ecological Risk Assessment Clomazone 124 

### invertebrates and marine-estuarine fish and invertebrates are below the acute endangered species LOC, and effects to aquatic plants ar e below the listed species LOC. No direct effects to birds, reptiles, amphibians (land phase), and mammals are expected. There are direct effects to non-target vegetation off the fi eld. For those labels which do not state use of a coarse droplet size, especially for aerial app lications to rice this effect may potentially
reach several thousand feet. For other labels with such restrictions in place, this effect is expected to be restricted to re latively localized areas off a tr eated site, the highest occurrence and likelihood being adjacent to the site fr om spray drift and/or vapor drift.

May affect but NLAA determinations were made for listed vascular aqua tic plants (there are no nonvascular listed species), freshwater and mari ne listed fish and invertebrates, aquatic amphibians, and marine mammals. May affect but NLAA determinations were made for listed large land birds, mammals and reptiles not known to be reliant on one or a limited
number of nonlisted or listed terrestrial or semi-aquatic plant species. This conclusion was based on a review of multiple lines of evidence for both direct and indirect effects, effects to critical habitat, and included, estimates of ris k, odds of mortality, and refinement of exposure levels where appropriate. Additionally, some species were identified as being outside the action area of clomazone, and a no effect dete rmination was made for these. Species designated as no effect and may affect but NLAA, are listed in Appendix J of this document.

May affect and LAA determinations were made for flowering and nonflowering plants because of exceedance of endangered species LOC. May affect and LAA determinations were made for small mammals, reptiles, and amphi bians that because of their size and home range may rely on a limited number of plant species for a food resource or habitat.Chapter 5 Uncertainties

Registration Review Ecological Risk Assessment Clomazone 125 

# Chapter 5 Uncertainties

A description of assumptions, un certainties, strengths, and li mitations of the basic risk assessment performed is described in Chapter 6 of the Agency’s Overview Document (EPA, 2004) and include those related to exposure for al l taxa, those related to exposure for aquatic species, those related to expos ure for terrestrial animals, those related to the effects assessment, and those associated with the acute LOC values. This Chapter discusses
additional uncertainties associated with refi nements made to the basic risk assessment.



## 5.1 Exposure Assessment Uncertainties

5.1.1 Volatilized Clomazone
The major source of uncertain ty in the exposure assessment for clomazone is the quantification of movement due to volatilization. Aquatic exposure estimates from PRZMEXAMS are reduced by approximately a factor of 2 when volatiliza tion is included as a transport route. The magnitude of the loss to volatilization is supporte d by the formula given by Yang and Holmen ( ES&T , in press) which indicates that over 50% of the applied mass
could be lost to volatiliz ation in the first 48 hours.

There are considerable uncertainties, both pos itive and negative, in the estimates of volatilization mass loss. The Yang and Holmen formula was derived for only two soils and clomazone was not among the 7 tested chemic als, although its vapor pressure and Henry’s Law constant were within the tested range. Volatilization could be lower or higher using other soils with high er sorption capacity.

The PRZM routine for volatilization is not se nsitive to temperature, which should have
considerable influence on the amount of chemi cal volatilized. The am ount volatilized would increase with increasing temperat ure, and vice versa, as the m odel temperature deviates from nominal room temperature.

Quantitative estimates of downwind exposures to volatilized clomazone are not given in this assessment. Such estimates should be possibl e with the development of computer models such as Calpuff for the specific requirements of OPP. However, given the estimate that up to 65% of applied clomazone could volatilize at 100% relative humid ity, downwind movement is considered to be a major exposure route. The importance of volatil ization as an exposure route is demonstrated by the la rge number of plant bleaching in cidents, their severity (up to plant death), the fact that effect s were seen at distances up to 2 miles from application sites,Chapter 5 Uncertainties

Registration Review Ecological Risk Assessment Clomazone 126 

### and label statements that buffer zones of 1000 feet and greater are n eeded to protect nontarget plants.

Aquatic exposure assessments are also affect ed by the magnitude of volatilization loss. PRZM-EXAMS estimates are given both with and without volatiliza tion loss to give an estimate of the possible effect on aquatic exposur es. Exposures should be no more than those
calculated with the PRZM volatilization rou tine “off,” other factor s being equal. The exposures calculated with the PRZM routine “ on” give an estimate of the remaining aquatic exposure, although because the volatilization rout ine only operate at room temperature, the actual loss to air could be lesser or greater.

5.1.2 Alternative Aquatic Expos ure Estimates for Non-Rice Uses

For non-rice uses, EEC values for evaluating di rect effects to aquatic listed species and
indirect effects from affects to aquatic habitat and the aquatic prey base are performed using 1-in-10 year peak daily values, and 21-day and 60-day averages for acute and chronic invertebrate and vertebrates exposures, respec tively (Section 2.1.2). These provide one of numerous alternative expr essions of exposure that can be ge nerated using the model. The set of selected values are considered representa tive reasonable upper-end exposure estimates, but are not the maximum predicted concentration in water which is a value of interest to the Services. A hierarchy of maximum concentra tions estimated with the model includes:

• Edge-of-field runoff water exposures (maxim um and 1-in-10 year maximum values),
calculated from PRZM model “zts” time-seri es output files, specifically dissolved mass and runoff volume, using an Excel spreadsheet (M. Corbin, Feb. 2008). The spreadsheet calculates daily runoff water c oncentrations for each day of a 30-year simulation, by dividing the dissolved mass by the volume of runoff water. Model runs were made with (ON) and w ithout (OFF) volatili zation from soil.

• The maximum exposures from the PRZM-E XAMS static pond analysis. These exposures were taken from the standard pe 5 output tables. Model runs were made with (ON) and without (OFF) volatilization from soil.

5.1.1.1 M AXIMUM E XPOSURE ANALYSIS : E DGE - OF - FIELD PRZM A NALYSIS 

### Exposure of organisms to runoff water as it l eaves the field, and before it enters the EXAMS pond, is approximated by the edge-of-field exposure calculation. This analysis estimates the concentration in runoff water from parameters in the PRZM *.zts output file, by dividing the mass flux of chemical in runoff (RFLX) by th e volume of runoff water (RUNF), using an Excel spreadsheet. This EEC represents the short-term (one to several days) exposureChapter 5 Uncertainties

Registration Review Ecological Risk Assessment Clomazone 127 

### expected in areas where runoff water could coll ect just off the agricultural field. The *.zts files were the same as used in the 1-in-10 y ear exposure analysis (Table 6). The maximum and 1-in-10 year maximum concentration of cl omazone in runoff at the edge-of-field are listed in Table 51, with and without volatilizat ion from soil. The maximum edge-of-field
modeled concentrations with and without volatilization from the soil, range from 48 to 300 ppb and 63 to 360 ppb, respectively. The 1- in-10 year maximum edge-of-field concentrations range from 25 to 166 ppb with volatilization, and from 37 to 236 ppb without
volatilization.

Table 51 PRZM Edge-of-Field Exposure

Edge-of-Field Exposure, ppb ( Volatilization OFF ) Edge-of-Field Exposure, ppb ( Volatilization ON ) PRZM Scenario (standard unless noted) 1-in-10 years Maximum 1-in-10 years Maximum Florida sugarcane 190 249 166 237 Louisiana sugarcane 170 290 141 230 Mississippi cotton 172 210 127 150
North Carolina cotton 177 200 152 160 Florida peppers 180 210 121 166 Mississippi soybeans 162 200 137 172 North Carolina sweet potato 236 353 135 291
North Carolina tobacco 120 190 82 137 Florida potato (NMC) 1 183 360 63 300 Michigan bean 131 180 83 132 Oregon snap beans 79 90 55 88 Florida cabbage 81 124 53 92 Florida cucumber (1 lb/A) 147 250 101 190 Florida cucumber (0.75 lb/A) 110 188 76 143 Florida cucumber (0.5 lb/A) 74 125 51 95 Florida cucumber (0.25 lb/A) 37 63 25 48 Oregon mint 63 74 31 56 (1) NMC: scenario developed for N-methyl carbamate cumulative assessment. This Florida potato scenario was used as a surrogate for tropical tuber crop s such as yautia, tanier, cassava, and arracacia.

5.1.1.2 M AXIMUM E XPOSURE A NALYSIS : A GRICULTURE 

### In the screening exposure anal ysis conducted in accordance with the Overview document (USEEPA, 2004), the reported EECs represen t the maximum exposure expected in the EXAMS pond once every 10 years. Because th e PRZM-EXAMS models are usually run for a thirty-year simulation, the 1-in -10 year EECs are not the highest calculated exposures (they are approximately the third-highest). The table below shows the maximum EECs from theChapter 5 Uncertainties

Registration Review Ecological Risk Assessment Clomazone 128 

### PRZM-EXAMS runs given in Table 6. The ma ximum 24-h peak concen trations ranged from 1.9 to 45.6 ppb and 4.1 to 71 ppb, with and without volatilization from soil, respectively.

Table 52 Maximum Surface Water EEC Values from PRZM/EXAMS Model

Maximum 24-h Peak, ppb Without/With Volatilization Maximum 21-day Average, ppb Without/With Volatilization Maximum 60-day Average, ppb Without/With Volatilization PRZM Scenario (standard unless noted)

Without With Without With Without With Florida sugarcane 64.4 38.9 36.5 19.9 15.9 9.5 Louisiana sugarcane 35.3 33.2 25.1 23.7 13.3 11.9 Mississippi cotton 53.2 45.6 29.6 25.3 13.8 11.8
North Carolina cotton 25.1 13.2 13.2 8.6 6.4 4.4 Florida peppers 53.2 34.2 27.3 18.2 12.2 8.1 Mississippi soybeans 22.5 20.0 12.9 10.8 7.0 5.3 North Carolina sweet potato 18.0 13.8 11.1 8.6 5.4 4.1
North Carolina tobacco 6.7 3.4 3.7 2.1 1.7 1.1 Florida potato (NMC) 1 42.2 22.7 24.3 11.4 10.4 5.1 Michigan bean 14.5 11.9 7.4 6.0 3.2 2.6 Oregon snap beans 7.9 5.9 4.7 3.5 2.2 1.7 Florida cabbage 9.3 5.5 5.8 2.7 2.7 1.2 Florida cucumber, 1.0 lb ai/acre 71.0 53.1 37.0 25.4 16.4 10.5 Florida cucumber, 0.75 lb ai/acre 54.7 39.8 28.5 19.0 12.6 7.9 Florida cucumber, 0.5 lb ai/acre 35.5 26.5 18.5 12.7 8.2 5.3 Florida cucumber, 0.25 lb ai/acre 17.8 13.3 9.3 6.3 4.1 2.6 Oregon mint 4.1 1.9 2.4 1.1 1.2 0.56 (1) NMC: scenario developed for N-methyl carbamate cumulative assessment. This Florida potato scenario was used as a surrogate for tropical tuber crop s such as yautia, tanier, cassava, and arracacia.



## 5.2 Effects and Risk Assessment Uncertainties

5.2.1 Lack of definitive avian acute or al and subacute dietary clomazone
test results
No definitive avian acute oral or subacute dietary toxicity test results were available to
calculate acute risks for avian taxa. Availabl e data consisted of limit test results with no mortality at the highest dosage s tested. A provisional method using the number of animals tested, the Binomial Theorem, a rearrangement of the Hill et al . (1975) dose-response model, and a range of slopes from 2 to 9 were used to estimate a subacute dietary LC 50 

### (Appendix C). These results were used to characterize th e potential for acute effects from exposure to dietary residue levels. The estimate d proportion of mortality based on the 95 th 

### upper confidence limit represents a high-end estimate of mortality for the study, and because theChapter 5 Uncertainties

Registration Review Ecological Risk Assessment Clomazone 129 

### higher the mortality the lower the estimated LC 50 

### value for a given slope this results in a lowend or conservative estimated LC 50 

### value for a given slope. Th e probability that mortality is greater is highly unlikely. Because exposure le vels, except for short grass at the highest banded application rate and a slope response of 9, were below 1/10 th 

### of estimated LC 50 

### values a lower estimate of mortality for the current data, i.e ., a higher LC 50 

### , would not affect
the conclusions about acute risks to birds and the taxa for which they are surrogates. For short grass, EEC values were below 1/10 th 

### of estimated LC 50 

### values from slopes at and below
4.5 but were above 1/10 th 

### at the slope assumption of 9. At a slope of 9 the odds of mortality for an individual at the exposure level was considered discountable at 1 in 2 x 10 18 

### . A less
conservative LC 50 

### would further decrease th e odds of mortality whic h would not affect the
current risk conclusions.

5.2.2 Lack of ELS or life cycle test results for the most acutely sensitive freshwater fish species
No ELS or life cycle test result was availabl e for the most acutely sensitive freshwater species, the silver catfish. An ACR approach was used to extrapolate a re productive NOAEC for the silver catfish. For extrapolation of a NOAEC, the higher an ACR value is the lower the resulting extrapolated NOAEC value. The NOAEC for reproduction for the silver catfish, the most acutely sensitive freshwater species, was extrapolated using the highest aquatic animal ACR value calculated which was 8.297 for rainbow trout. One other aquatic animal ACR was available for clomazone, 2.454 for the freshwater invertebrate, Daphia

magna . Unless circumstances provide evidence to the contrary, the general policy within EFED for pesticides is to use an ACR derived from within the same taxa because the mode of action of some pesticides may be taxa spec ific, and may also be affected by differences between freshwater and saltwater species. In this case the highest ACR is for a freshwater
fish and is therefore consistent with this policy. However while the data is limited the relative agreement of the ACR values ( e.g . within a factor of 10), and toxicity information
that indicates that clomazone appears to be primarily a live r toxicant in animals provides
evidence that ACR values for freshwater fish and invertebrates are likely representative across freshwater aquatic taxa. Given the likely range of ACR values, within a factor of 10,
the resultant chronic NOAEC values would all be below chronic EEC values for all nonrice and dry seeded exposure scenarios for freshwat er fish and wet seeded would still exceed therefore the degree of uncertainty associated with this limitation does not affect risk
conclusions.Chapter 5 Uncertainties

Registration Review Ecological Risk Assessment Clomazone 130 

### 5.2.3 Lack of ELS test results for the most acutely sensitive estuarine/marine fish
No ELS or life cycle test result was available fo r an estuarine/marine species. There was an acute test with the sheepshead minnow and an ACR approach was used to estimate an ELS NOAEC for the sheepshead minnow. The NOAEC fo r sheepshead minnow, the most acutely sensitive freshwater species, was extrapolated using the highest aquatic animal ACR value
calculated which was 8.297 for rainbow trout. One other aquatic animal ACR was available for clomazone, 2.454 for the fr eshwater invertebrate, Daphia magna . Unless circumstances provide evidence to the contrary, the general policy within EFED for pesticides is to use an
ACR derived from within the same taxa because the mode of action of some pesticides may be taxa specific, and may also differ between fr eshwater and saltwater species. While there
was an ACR ratio for a freshwater fish and a freshwater invertebrate by which differences
between a fish and invertebrate could be eval uated, no ACR for at least a saltwater species
was available to evaluate if there are diffe rences between freshwater and saltwater ACR values. Therefore there is uncertainty in what , if any, effect salinity would have on the ACR
for clomazone.

5.2.4 Lack of life cycle test resu lts for the most acutely sensitive estuarine/marine invertebrate
The NOAEC for reproduction for the mysid shri mp was extrapolated using the highest aquatic animal ACR value calculated which was 8.297 for rainbow trout data. One other aquatic animal ACR was available for clom azone, 2.454 for the freshw ater invertebrate, Daphia magna . Unless circumstances provide eviden ce to the contrary, the general policy within EFED for pesticides is to use an ACR derived from within the same taxa because the mode of action of some pesticides may be taxa specific, and may also differ between freshwater and saltwater species. While the da ta is limited the relative agreement of the ACR values ( e.g . within a factor of 10), a nd toxicity information that indicates that clomazone appears to be primarily a liver toxicant in animals provides evidence that ACR values for
freshwater fish and invertebrate s are likely representative acro ss at least freshwater aquatic
taxa. While there was an ACR ratio for a fres hwater fish and a fres hwater invertebrate by
which differences between a fish and invertebra te could be evaluated, no ACR for at least a saltwater species was available to evaluate if there are differences between freshwater and
saltwater ACR values.Chapter 5 Uncertainties

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### 5.2.5 Use of most sensitive species toxicity endpoint
Although the assessment relies on a selected toxicity endpoin t from the most sensitive species tested, it does not necessarily mean th at the selected toxicity endpoints reflect sensitivity of the most sensitive species existing in a given environment. The relative position of the most sensitive species tested in the distribution of all possible species is a function of the overall variability among species to a particular chemical. In the case of listed species, there is uncertainty regarding th e relationship of the list ed species’ sensitivity and the most sensitive species tested, in some cases it may be less sensitive. For example, for clomazone the most sensitive endpoint for freshw ater fish was the Silver Catfish but the Rainbow Trout also know as Steelhead when it is the ocean going and returning (anadromous) form was much less sensitive. Therefore, the potential direct risks of concern identified for salmonids may be overestimat ed. For nonrice and dry land rice uses as exposure levels were below the acute endangere d and chronic LOC values risk conclusions are not impacted. For wet seeded rice, di rect effects to liste d salmonids may be
overestimated.

5.2.6 Single and multiple active ingredie nt formulations relative to TGAI effects
In addition to registered single active ingredient clomazone form ulations there are registered multiple active formulations of clomazone. An analysis of the available toxicity data for multiple active ingredient products and single act ive ingredient formulations relative to the technical grade active ingredient (TGAI) is prov ided in Appendix D. There was no available toxicity information on registered formulations for birds, aquatic animal s, aquatic plants, or terrestrial plants. The silver catfish data, wh ich is from a study with Gamit (single active ingredient formulation not registered in the US). There is no silver catfish study with TGAI,
therefore it is unknown if formul ation affected study results potentially resulting in an overestimation of risks to fish from runoff, or in wet seeded rice. Fish species tested with the TGAI did not have formulation testing whic h means can not look at a different aquatic organisms and get insight into formulation test ing was compared to the TGAI. If difference
between silver catfish and the bl uegill and rainbow trout results is attributable to formulation versus TGAI then ( i.e ., TGAI less toxic than formulation) do es not affect risk conclusions for nonrice and dry seeded rice because acute values are already below endangered species LOC, potential to affect risk conclusi ons for wet seeded rice. If T GAI, results more representative of range for blue gill and rainbow trout, after 14 days holding us ing rainbow trout LD50 would be below acute endangered species LOC. This uncertainty affects risk conclusions for
wet seeded rice.Chapter 5 Uncertainties

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### There was acute oral mammalian toxicity data for multiple active in gredient products, and single active ingredient formulati ons which is provided in Appendix B. An analysis of the relative toxicity of the formulations to the T GAI is provided in Appendix D. The results of this analysis show that except for the multiple active Commence EC formulation, an assessment based on the toxicity of the clomaz one TGAI is appropriate. However, dietary effects on at least an acute basis may be unde restimated for the Commence EC registered uses which include only cotton and soybeans.

5.2.7 Lack of NLCD 82 (cultivated land) da ta for U.S. Territories, Hawaii, and
Alaska
Except for small islands which would not suppor t an agribusiness and/or the island is a nature reserve (e.g., Northwestern Hawaiian Is lands, Mona Island, Monito Island), where there was no cultivated land data available ( e.g ., U.S. territories, Hawa ii), the action area was assumed to overlap with the listed species. This potentially results in more species identified
as LAA.Chapter 6 Bibliography

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# Chapter 6 Bibliography

Brown et al . 2001. Interval Estimation for a Binomi al Proportion. Statistical Science 16(2):101-133.

Aherns, W.H. (editor). 1994. Herbicide Ha ndbook, Weed Science Society of America, Seventh Edition, 1994. WSSA, Champaign, IL.

Conover, W. 1980. Practical Nonparametric Statistics, 2 nd 

### Edition. John Wiley & Sons, New York, NY. 493 pp.

dos Santos Miron, D., Da Silva, L. V. F., Golo mbieski, J. I., De Oliveira Machado, S. L., Marchezan, E., and Baldisserotto, B. (2004) . Lethal Concentration of Clomazone, Metsulfuron-Metil, and Quinclorac for Silver Catfish, Rhamdia quelen , Fingerlings. Ciencia Rural 34: 1465-1469. (ECOTOX E087942)

dos Santos Miron, D., Crestani , M., Rosa Shettinger, M., Maria Morsch, V., Baldisserotto, B., Angel Tierno, M., Moraes, G., and Vieira, V. L. P (2005). Effects of the Herbicides Clomazone, Quinclorac, and Metsulfuron Methyl on Acetylcholinesterase Activity in the Silver Catfish ( Rhamdia quelen ) (Heptapteridae). Ecotoxico l. Environ. Saf. 61: 398-403. (ECOTOX E080936)

Fletcher, J., J. Nellessen and T Pfleeger. 1994. Literature re view and evaluation of the EPA Food-Chain (Kenaga) Nomogram, an Instrument for Estimating Pesticide Residues on Plants. Environ. Tox. Chem. 13(9): 1383-1391.

Kramer, G. and J Kidwell. Memorandum 10/2/2002 Ad Hoc HED Metabolism Assessment Review Committee (MARC) Meeting of 9/12/ 00. Clomazone. Residues of Concern in Drinking Water. PP#s 8F4985, 9E06063, & 6F4738. Chemical No. 125401. Barcode
D268905. Case 289118. Submission S568659.

Mayer, D. & C. Johansen. 1990. Pollinato r Protection: A Bee & Pesticide Handbook. Wicwas Press. Cheshire, Conn. p. 161

United States Environmental Protection Agen cy (EPA). 1986. Hazard Evaluation Division Standard Evaluation Procedure, Ecological Risk Assessment. Office of Pesticide Programs, Washington, D.C. EPA-540/9-85-001.Chapter 6 Bibliography

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### United States Environmental Protection Agency (EPA). 1993. Wildlife Exposure Handbook, Volume I of II. Office of Resear ch and Development, Washington, DC.
EPA/600/R-93/187a.

United States Environmental Protection Ag ency (EPA). 2000. Guidance for Conducting Screening Level Avian Risk assessments fo r Spray Applications of Pesticides. Environmental Fate & Effects Division, Office of Pesticide Programs, Washington, D.C. July 7, 2000.

United States Environmental Protection Agency (EPA). 2004. Overview of the Ecological
Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency, Endangered and Threatened Species Effects Determination. Office of Prevention, Pesticides and Toxic Substances , Office of Pesticide Programs, Washington, D.C., January 23, 2004.

United States Environmental Protection Ag ency (EPA). 2007a. Clomazone Summary Document Registration Review : Initial Docket January 2007. Docket Number: EPA-HQOPP-2006-0113, www.regulations.gov

United States Environmental Protection Agen cy (EPA). 2007b. Revised Clomazone Final Work Plan Registration Review July 2007. Docket Number: EPA-HQ-OPP-2006-0113, www.regulations.gov