U.S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Ecological Risk Assessment 

for the Registration of Orthosulfamuron 

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Orthosulfamuron 

1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl)phenylsulfamoyl]urea 

CAS Registry Number 213464-77-8 

PC Code 108209 

Prepared by: 

Christopher Salice, Biologist 

Greg Orrick, Environmental Scientist 

U. S. Environmental Protection Agency 

Reviewed by: Office of Pesticide Programs 

Edward Fite, Senior Scientist Environmental Fate and Effects Division 

R. David Jones, Senior Agronomist Environmental Risk Branch IV 

Elizabeth Behl, Branch Chief 1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington DC 20460 
1 Executive Summary 

1.1 Nature of Chemical Stressor 

Isagro is seeking registration for the use of the new chemical herbicide orthosulfamuron 

(IR5878; 1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl)phenylsulfamoyl]urea) and 

its end-use products IR5878 50 WG® (51.5% a.i., water dispersible granule) and IR5878 0.5 

GR® (0.51% a.i. dry granule). This is a national registration request for control of a number of 

weed species associated with rice cultivation. Ground or aerial applications are proposed once 

per year with rates of 0.0550 lbs a.i./A to 0.0689 lbs a.i./A for the water dispersible granule 

formulation and 0.0663 lbs a.i./A for the dry granule formulation. 

1.2 Potential Risks to Non-target Organisms 

The results of this screening-level assessment indicate a potential for direct adverse acute effects 

to non-target non-vascular plants, freshwater vascular plants, and terrestrial and semi-aquatic 

plants (Table 1.1). Although this screening-level analysis indicates a limited potential for direct 

adverse effects to animal species associated with the use of orthosulfamuron on rice, indirect 

effects may result as a consequence of potential direct effects on plants. 

Table 1.1. Summary of Direct and Indirect Effects for Federally Listed Species. 

Listed Species Taxonomic 

Group of Concern 

Direct Effects RQ Indirect Effects 

Potential Associated Taxa1 

Aquatic vascular plants Acute: growth 148 No 

Non-vascular plants None 0.14 No 

Estuarine/marine nonvascular plants 

Acute: cell density 1.84 No 

Dicot terrestrial plants Acute: plant growth 2.45-128 No 

Monocot terrestrial plants Acute: plant growth 2.04-2.45 No 

Freshwater fish None Yes Aquatic & Terrestrial Plants 

Saltwater fish None Yes Aquatic Plants 

Freshwater invertebrates None Yes Aquatic & Terrestrial Plants 

Estuarine/Marine 

Invertebrates None Yes Aquatic Plants 

Mollusks None Yes Aquatic Plants 

Mammals None Yes Aquatic & Terrestrial Plants 

Birds None Yes Aquatic & Terrestrial Plants 

Terrestrial invertebrates None Yes Aquatic & Terrestrial Plants 1

Associated Taxa refers to those taxa for which there are direct effects that may indirectly affect a listed species 

taxa. 

Overall, potential risks appear to be greatest for aquatic vascular plant species and terrestrial and 

semi-aquatic dicotyledonous plants since these organisms appear to be very sensitive. 

Functionally, estimated risks may translate to reduced survival, reproduction, or growth in 

affected species with the potential for subsequent effects at higher levels of biological 

organization. Importantly, the toxicity data also indicate that there is a potential for adverse 

effects on rice crops associated with the use of orthosulfamuron. A Tier II Seedling Emergence 

test indicated that rice dry weight was reduced by almost 20% at exposures of 0.044 lbs a.i./A, 

which is lower than the proposed use rate of (up to) 0.0689 lbs a.i./A. 

2
For federally listed endangered or threatened (hereafter “listed”) species, acute risk levels of 

concern were exceeded for aquatic vascular plants, semi-aquatic monocot and dicot plants, and 

terrestrial monocot and dicot plants. No listed species acute or chronic LOCs were exceeded for 

any animal species evaluated in this assessment. Because aquatic plant risk quotients are above 

the non-endangered species level of concern, the Agency considers this to be indicative of a 

potential for adverse effects to those listed species that rely either on a specific plant species 

(plant species obligate) or multiple plant species (plant dependant) for some component of their 

life cycle. 

There is a potential to affect some listed plant species and the species which depend upon listed 

or non-listed plant species. Indirect effects in this case should be considered for both terrestrial 

and aquatic animal species. The extent to which the proposed uses of orthosulfamuron will 

directly effect plant species and indirectly effect animal species will require further assessment; 

specifically, clear delineation of action area, identification of listed species that co-occur in areas 

of orthosulfamuron use, species-specific life history information, and an evaluation of critical 

habit. 

1.3 Conclusions - Exposure Characterization 

Orthosulfamuron has low volatility and exhibits acid-base behavior, being increasingly soluble in 

water as pH increases. It readily hydrolyzes in hours to days at low pH (<7), but slowly 

hydrolyzes (half-life of months) at high pH (>7). Moderate biodegradation and slow photolysis 

(half-lives of months) also occur in aquatic environments. Orthosulfamuron is moderately 

mobile in soil and shows affinity to organic carbon. The compound presents a ground water 

concern in alkaline, sandy soils with a Freundlich soil-to-water partition coefficient (Kf) as low 

as 2.0 (1/n = 1.02). 

Orthosulfamuron’s major route of degradation in acidic to neutral rice paddy water is hydrolysis, 

with a half-life of hours to days. Aerobic biodegradation is the major route of degradation in 

alkaline rice paddy water, with a half-life of weeks to months. Both routes of degradation are 

expected at similar rates (i.e. half-lives of weeks) in paddy water of neutral pH. 

Major degradates include hydrolysis products N-(4,6-dimethoxypyrimidin-2-yl)urea (DOP urea; 

S12), 2-dimethylcarbamoylphenyl sulfamic acid (DBS acid; S1), and 2 amino-N,Ndimethylbenzamide (DB amine; S4) and demethylation product 1-(4-hydroxy-6­

methoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl)phenylsulfamoyl]urea (o-desmethyl 

orthosulfamuron; S9). Both orthosulfamuron and its o-desmethyl degradate hydrolyze to DBS 

acid, which, in turn, hydrolyses to DB amine. However, all four degradates are moderately 

persistent, as peak detections of these degradates occurred at up to 100-186 days after 

application. 

The toxicity of orthosulfamuron’s major degradates has not been determined. For this 

assessment, the o-desmethyl degradate, which is the only degradate that retains the parent 

compound’s sulfamoylurea structural group, is of risk concern and assumed to have equal 

toxicity as the parent. Aquatic exposure estimates are based on an assumption of no degradation 

3
and, therefore, may be used to represent exposure to the parent compound alone or the parent 

compound and any number of its degradates of potential concern, including its o-desmethyl 

degradate. No methodologies are used to assess terrestrial exposure to o-desmethyl 

orthosulfamuron, as its contribution to risk is not expected to alter terrestrial risk conclusions that 

are based on the fate, transport, and toxicity of the parent compound alone. 

The screening Interim Rice Model was used to assess high-end exposure in paddy water and 

released tail water from the proposed orthosulfamuron use. The Interim Rice Model does not 

account for degradation and assumes 100% application efficiency, which means that spray drift 

is not accounted for separately. The single aqueous exposure estimate produced with the Interim 

Rice Model was used to represent both acute and chronic exposure for aquatic organisms. 

1.4 Conclusions - Effects Characterization 

Orthosulfamuron is practically non-toxic to birds, mammals, and honeybees under acute 

exposure conditions and only slightly toxic to fish and freshwater aquatic invertebrates. 

Orthosulfamuron is highly toxic to aquatic vascular plants, non-vascular plants, and terrestrial 

plants following acute exposure. In terrestrial plants, dicotyledonous plants appear more 

sensitive to orthosulfamuron compared to monocotyledonous plants. 

1.5 Uncertainties and Data Gaps 

No data are available to assess the potential risks associated with the major degradates of 

orthosulfamuron, including the degradate of risk concern, o-desmethyl orthosulfamuron. While 

these data are not required, the potential toxicity of orthosulfamuron degradates is a source of 

uncertainty for this assessment. In addition, there is some uncertainty associated with the 

addition of an adjuvant to increase efficacy of orthosulfamuron and the potential effects of the 

adjuvant and the adjuvant/active mixture. Studies on non-vascular plants indicate that the 

addition of an adjuvant results in toxicity endpoints considerably lower than with the water 

dispersible granule formulation alone. This suggests that that addition of the adjuvant may 

increase the potential for adverse effects to plants associated with the use of orthosulfamuron on 

rice. However, overall risk conclusions would not be altered for this screening-level assessment. 

Exposure estimate uncertainty is related to the degree to which Interim Rice Model assumptions 

do not describe actual use sites of orthosulfamuron. 

4
Table of Contents 

1 Executive Summary............................................................................................2

1.1 Nature of Chemical Stressor.............................................................................................. 2

1.2 Potential Risks to Non-target Organisms ......................................................................... 2

1.3 Conclusions - Exposure Characterization ........................................................................ 3

1.4 Conclusions - Effects Characterization............................................................................. 4

1.5 Uncertainties and Data Gaps ............................................................................................. 4

2 Problem Formulation .........................................................................................7

2.1 Stressor Source and Distribution ...................................................................................... 7

2.1.1 Overview of Pesticide Usage ......................................................................................... 7

2.1.2 Toxicity Profile.............................................................................................................. 7

3 Analysis ..............................................................................................................11

3.1 Methods.............................................................................................................................. 11

3.2 Use Characterization ........................................................................................................ 14

3.3 Exposure Characterization .............................................................................................. 16

3.3.1 Environmental Fate and Transport Characterization............................................... 16

3.3.1.1 Transport and Mobility...................................................................................... 17 

3.3.1.2 Degradation ......................................................................................................... 18 

3.3.1.3 Field Studies ........................................................................................................ 19 

3.3.1.4 Bioconcentration ................................................................................................. 20 

3.3.2 Degradates................................................................................................................... 20

3.3.4 Measures of Aquatic Exposure................................................................................... 22

3.3.5 Measures of Terrestrial Exposure.............................................................................. 23

3.3.5.1 Terrestrial Animal Species................................................................................. 23 

3.3.5.1.1 Terrestrial Animal Exposure Modeling ....................................................... 24

3.3.5.2 Terrestrial Plant Species .................................................................................... 26 

3.3.5.2.1 Terrestrial and Semi-Aquatic Plant Exposure Modeling............................ 26

3.3.5.3 Residue Studies ................................................................................................... 27 

3.4. Ecological Effects Characterization ............................................................................... 27

3.4.1. Aquatic Effects Characterization .............................................................................. 28

3.4.1.1 Aquatic Animal Species...................................................................................... 30 

3.4.1.1.a. Aquatic Animals: Acute Effects .................................................................. 30

3.4.1.1.b. Aquatic Animals: Chronic Effects .............................................................. 31

3.4.1.1.c. Aquatic Animals: Sublethal Effects ............................................................ 32

3.4.1.1.d. Aquatic Animals: Field Studies................................................................... 33

3.4.1.1.e. Plants Inhabiting Aquatic Areas ................................................................. 33

3.4.2. Terrestrial Effects Characterization.......................................................................... 34

3.4.2.1. Terrestrial Animals............................................................................................ 36 

3.4.2.1.a. Terrestrial Animals: Acute Effects.............................................................. 36

3.4.2.1.b. Terrestrial Animals: Chronic Effects.......................................................... 37

3.4.2.1.d. Terrestrial Animals: Field Studies .............................................................. 37

3.4.2.2. Terrestrial Plants ............................................................................................... 37 

4 Risk Characterization.......................................................................................38

4.1 Risk Estimation – Integration of Exposure and Effects Data....................................... 38

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4.1.1 Non-target Aquatic Organisms................................................................................... 38

4.1.1.1 Freshwater Fish and Invertebrates ................................................................... 38 

4.1.1.2 Estuarine/Marine Fish and Invertebrates ........................................................ 39 

4.1.1.3 Aquatic Plants ..................................................................................................... 39 

4.1.2 Non-target Terrestrial Organisms.............................................................................. 40

4.1.2.1 Birds ..................................................................................................................... 40 

4.1.2.2 Mammals ............................................................................................................. 41 

4.1.2.3 Terrestrial Plants ................................................................................................ 42 

4.2 Risk Description................................................................................................................ 43

4.2.1 Risk to Aquatic Organisms ......................................................................................... 43

4.2.1.1 Freshwater Fish................................................................................................... 43 

4.2.1.2 Freshwater Invertebrates................................................................................... 43 

4.2.1.3 Saltwater Fish...................................................................................................... 44 

4.2.1.4 Saltwater Invertebrates...................................................................................... 44 

4.2.1.5 Aquatic Plants ..................................................................................................... 44 

4.2.2 Risks to Terrestrial Organisms................................................................................... 45

4.2.2.1 Birds ..................................................................................................................... 45 

4.2.2.2 Mammals ............................................................................................................. 45 

4.2.2.3 Potential Risk to Birds and Mammals: BCF Analysis ................................ 45 

4.2.2.4 Plants.................................................................................................................... 46 

4.2.2.5 Non-Target Terrestrial Invertebrates............................................................... 47 

4.2.3 Federally Threatened and Endangered (Listed) Species of Concern....................... 48

4.2.3.1 Action Area.......................................................................................................... 48 

4.2.3.2 Taxonomic Groups Potentially at Risk ............................................................. 49 

4.2.3.2.1 Listed Species Direct Effects......................................................................... 50

4.2.3.2.2 Probit Dose-Response Analysis .................................................................... 51

4.2.3.2.3 Indirect Effects.............................................................................................. 52

4.2.3.2.4 Listed Species Occurrence Associated with Orthosulfamuron Uses .......... 53

4.3 Description of Assumptions, Limitations, and Data Gaps ............................................ 54

4.3.1 Assumptions and Limitations Related to Exposure for All Taxa.............................. 54

4.3.2 Assumptions and Limitations of Aquatic Exposure Estimates ................................. 55

4.3.3 Assumptions and Limitations of Terrestrial Exposure Estimates............................. 55

4.3.3.1 Location of plant species .................................................................................... 55 

4.3.3.2 Routes of exposure .............................................................................................. 55 

4.3.3.3 Incidental Pesticide Releases Associated with Use........................................... 55 

4.3.4 Effects Assessment Assumptions and Limitation ...................................................... 56

4.3.4.1 Age Class and Sensitivity of Effects Thresholds .............................................. 56 

4.3.4.2 Lack of Effects Data for Amphibians and Reptiles ......................................... 57 

4.3.4.3 Use of the Most Sensitive Species Tested .......................................................... 57 

4.3.4.4 Data Gaps ............................................................................................................ 58 

5 Literature Cited ................................................................................................59

Submitted Studies ................................................................................................................... 60

6
2 Problem Formulation 

The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requires that registered 

pesticide uses do not pose unreasonable adverse effects to the environment, and the Endangered 

Species Act requires that regulatory actions should not adversely affect Federally listed species 

or their habitats. The purpose of this assessment is to provide insight into the potential effects to 

the environment associated with the use of the herbicide orthosulfamuron, as part of the 

supporting information to determine the eligibility of orthosulfamuron for registration. This 

screening-level assessment follows methods detailed in the Overview Document (USEPA, 

2004). Briefly, the method involves comparing estimates of exposure (measures of exposure) 

with laboratory-derived toxicity estimates (measures of effect). If measures of effect exceed 

specified levels of concern (LOCs) for a given measure of exposure, deleterious effects on nontarget organisms may potentially occur and a more refined assessment may be warranted to 

better define potential risks. Although screening-level methods are similar for all chemicals, the 

problem formulation section helps to focus attention on unique or important characteristics of a 

given chemical, thereby providing a sense of the potential environmental risks of that chemical. 

2.1 Stressor Source and Distribution 

2.1.1 Overview of Pesticide Usage 

Orthosulfamuron (1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl)phenylsulfamoyl]­

urea; CAS#: 213464-77-8; PC code: 108209) is a systemic post-emergence herbicide belonging 

to the sulfamoylurea class of herbicides. Sulfamoylurea herbicides act through inhibition of 

branch-chain amino acid biosynthesis in plants. Orthosulfamuron’s specific mode of action is 

through the inhibition of the plant enzyme, acetolactate synthase, also known as acetohydroxy 

acid synthase (ALS/AHAS). Inhibition of ALS/AHAS blocks the branched-chain amino acid 

biosynthesis of valine, leucine, and isoleucine, which are involved in the plant growth process. 

Orthosulfamuron is formulated as both a water dispersible granule (IR5878 50 WG) and a 

granule (IR5878 0.5 GR). The manufacturer recommends that for maximum effectiveness in 

protection against competitive weed species, formulations of orthosulfamuron be applied to 

young, emerging rice plants at the 1 to 2 leaf (IR5878 0.5 GR) or 2 to 4 leaf (IR5878 50 WG) 

growth stage. The dispersible granule formulation of orthosulfamuron should be applied via 

ground or aerial foliar spray treatment to a partially or fully drained rice paddy and the granular 

formulation should be applied via direct dry application by ground or air equipment to a 

permanently flooded rice paddy. Proposed labels for orthosulfamuron (EPA Reg. No.s pending) 

specify use on rice only, with application rates of 0.0663 lbs a.i./A for the granule and ranging 

from 0.0550 to 0.0689 lbs a.i./A for the water dispersible granule. 

2.1.2 Toxicity Profile 

In addition to the environmental fate characteristics of orthosulfamuron, the toxicity of the 

chemical plays an important role in evaluating potential environmental risks. A complete 

toxicity dataset was provided for the parent, orthosulfamuron. The suite of toxicity studies 

7
provides the measures of effect, which are toxicity endpoints. These are intended to provide 

insight into the potential effects on assessment endpoints, defined as “explicit expressions of the 

actual environmental value to be protected” (USEPA, 1998). For most pesticides, including 

orthosulfamuron, the assessment endpoints relate to the sustainability of populations or the 

maintenance of community structure for plants and animals. While assessing risks at the 

population and community level are endpoints useful for risk management, the lack of adequate 

data limits the ability to address these endpoints with meaningful scientific rigor (ECOFRAM, 

1999). 

The toxicological profile for orthosulfamuron indicates that for most tested animal species, 

orthosulfamuron is not highly toxic with designations ranging from practically non-toxic 

(mammalian and avian species) to moderately toxic (some aquatic species). Orthosulfamuron, 

however, is extremely toxic to terrestrial and aquatic plant species. The toxicity of 

orthosulfamuron’s major degradates, DBS acid (max. 62% of applied at 7 days), DB amine 

(max. 13% of applied at 176 days), DOP urea (max. 111% of applied at 7 days), and o-desmethyl 

orthosulfamuron (max. 19% of applied at 100 days) have not been determined. The o-desmethyl 

degradate is the only identified degradate that contains the sulfamoylurea structural group that 

the parent compound contains. Therefore, the o-desmethyl degradate is assumed to have equal 

toxicity as the parent compound and is of risk concern. 

Table 2.1 provides a list of the taxonomic groups, measures of effect and most sensitive test 

species evaluated for the toxicological effects of orthosulfamuron; these provide the 

toxicological basis for risk estimations and conclusions in this assessment. Given the sensitivity 

of plant and algae species, it is likely that the most deleterious effects of orthosulfamuron may 

relate to the survival, growth, and reproduction of plants and algae with potential indirect effects 

to animal species dependent on impacted plant species. 

Table 2.1. Taxonomic Groups and Most Sensitive Species Evaluated for Ecological Effects of 

Orthosulfamuron. 

Assessment Endpoint for Each 

Taxonomic Group 

Representative Test Species Measure of Effect Used in 

Assessment 

Individual survival, growth and 

reproduction of birdsa 

Bobwhite quail (Colinus virginianus) 

Mallard duck (Anas platyrhynchos) 

Acute LD50/LC50 

Chronic NOAEC 

Individual survival, growth and 

reproduction of mammals 

Norway rat (Rattus norvegicus) Acute LD50 

Chronic NOAEC/NOAEL 

Terrestrial Insect survival Honeybee (Apis mellifera) Acute Oral LD50 

Individual survival of freshwater fishb Rainbow trout (Onchorhynchus mykiss) 

Fathead minnow (Pimephales promelas) 

Acute LC50 

Chronic NOAEC 

Freshwater invertebrate survival, growth 

and reproduction 

Water flea (Daphnia magna) 

Crayfish (Procambrus clarkia) 

Acute LC50 

Chronic NOAEC 

Individual survivalof saltwater fishb Sheepshead minnow (Cyprinidon 

variegatus) 

Acute LC50 

Saltwater invertebrate survival, growth 

and reproduction 

Mysid shrimp (Americamysis bahia) 

Eastern oyster (Crassostrea virginica) 

Acute LC50/EC50 

Survival and growth of terrestrial plants Cucumber (Cucumus sativa) Acute EC50 

Survival and growth of aquatic plants 

and algae 

Algae (Scenedesmus subspicatus) 

Duckweed (Lemna gibba) 

Acute LC50 

a

Birds are used as surrogates for reptiles and terrestrial-phase amphibians (USEPA, 2004). 

8 
b

Freshwater fish are used as surrogates for aquatic-phase amphibians (USEPA, 2004). 

For pesticides in general, the ecosystems at greatest risk are those in close proximity to the 

proposed use areas. These would include agricultural fields (surrounding non-agricultural 

terrestrial habitats) and water bodies directly adjacent to treated fields that may receive chemical 

residues via drift, runoff, and/or ground water discharge. The proposed use of orthosulfamuron 

on rice, however, is limited to application to rice paddies, which undergo periodic flooding and 

draining. Hence, for orthosulfamuron, the predominant ecosystems at risk are likely to be those 

aquatic and terrestrial habitats in close proximity to rice cultivation areas that receive rice paddy 

water (called tail water), ground water discharge, or spray drift from applications. Within these 

water bodies, the water column, sediments, and pore water are all compartments of concern. 

Organisms of concern include birds, mammals, reptiles, fish, and terrestrial and aquatic 

invertebrates, plants, and amphibians. The assessment endpoints are focused on the survival, 

growth, and reproduction of these organisms, which are intended to relate to population 

sustainability and community structure within ecosystems and hence relate back to ecosystems at 

risk. If risks are expected for given species/taxa based on the screening-level assessment, then 

risks may translate to higher levels of biological organization, such as populations, communities, 

or ecosystems. The following risk hypothesis provides a sense of the focus and intent of this risk 

assessment. 

The risk hypothesis is that the use of orthosulfamuron in accordance with the label results in 

adverse effects on survival, growth and/or reproduction of non-target terrestrial and/or aquatic 

animals; and that the use of orthosulfamuron in accordance with the label results in adverse 

effects on survival and/or growth of terrestrial, semi-aquatic, and aquatic plants. 

This screening assessment is designed to test this hypothesis. Failure to dismiss the risk 

hypothesis may indicate that there are risks of concern, or may be the result of the conservative 

assumptions inherent in a screening level assessment. Further refined assessment would be 

necessary to confirm that risks are indeed present if the risk hypothesis is accepted. 

The conceptual model (Figure 2.1) depicts the potential pathways for ecological risk associated 

with the proposed use of orthosulfamuron on rice. This model is fairly generic and assumes that 

as an herbicide, orthosulfamuron can affect terrestrial and aquatic organisms if environmental 

concentrations are sufficiently elevated as a result of proposed label uses. However, the model 

differs from most conceptual models in that the application of pesticides to rice is unlike most 

other pesticide applications to agricultural fields. Rice cultivation relies on the use of paddies 

that undergo a series of flooding and releasing for optimal growth and yield. Given the 

cultivation practices associated with rice, pesticides are frequently applied directly to rice paddy 

water. The release of rice paddy tail water may be an important source of environmental 

exposures. 

9
Birds, Mammals, Terrestrial Wetland/ 

Receptors Reptiles, Terrestrial Upland Riparian Aquatic Aquatic 

Phase Amphibians Plants Plants Plants Invertebrates, 

Stressor Orthosulfamuron Applied as a Ground/Aerial Spray or Dry Granules to Rice Paddies 

Source/ 

Transport 

Pathways 

Direct Application 

to Paddy Water 

Leaching 

(Infiltration/ 

Percolation 

Source/ 

Exposure 

Media 

Terrestrial Food 

Items (foliage, 

fruit, insects, 

seeds) 

Upland 

Foliage/Soil 

Riparian/ 

Wetland 

Foliage/Soil 

Receiving 

Water Body/ 

Sediment 

Ground Water 

Exposure 

Route 

Ingestion 

Direct Contact/ 

Root Uptake 

Direct Contact/ 

Root Uptake Gill/ 

 Integument 

Uptake 

Terrestrial Vertebrates: 

Uptake/ 

Adsorption 

Spray 

Granules Drift

Attribute 

Changes 

Individual Animals 

Reduced survival or 

reproduction 

Vertebrates 

Individual Plants 

Reduced survival, 

growth, or reproduction 

Individual 

Vertebrates and 

Invertebrates 

Reduced survival 

or reproduction 

Plant Population 

Reduced 

population 

growth 

Figure 2.1. Conceptual model of the transport and effects of orthosulfamuron in the 

environment. *Dotted lines indicate that although this exposure route was considered, it was not thought to contribute significantly 

to the fate and transport of orthosulfamuron. 

Ground water concentrations estimated with the screening model SCI-GROW (EEC=0.6 ppb) 

are insignificant compared to surface water concentrations estimated with the screening Interim 

Rice Model (EEC=38.6 ppb). This means that orthosulfamuron residues in discharged ground 

water leachate are not expected to contribute significantly to surface water exposure. Therefore, 

the potential pathways of aquatic exposure considered in risk estimation for this risk assessment, 

as indicated in the conceptual model, include surface water runoff and spray drift and do not 

include ground water discharge. Note that the spray application of orthosulfamuron is 

represented in the conceptual model because it likely represents a broader spectrum of potential 

exposures compared to the dry granule application. 

The conceptual model provides an overview of the expected exposure routes for organisms in 

and around the orthosulfamuron use area. For terrestrial organisms, the major route of exposure 

considered is the dietary route; consumption of food items such as plant leaves or insects that 

have orthosulfamuron residues as a result of spraying or from direct consumption of granules. 

Specifically for orthosulfamuron, consumption of residues on food items may be limited to the 

10
3 

dispersible granule formulation and to areas outside the rice paddy. In addition, there is the 

potential for dietary exposure to terrestrial organisms via the consumption of contaminated 

aquatic species in which orthosulfamuron may have bioaccumulated. For aquatic animal species, 

the major routes of exposure are considered to be via the respiratory surface (gills) or the 

integument. Direct contact and/or root uptake is the major route of exposure for terrestrial and 

wetland (riparian) plants, while aquatic plants may be exposed via direct uptake and adsorption. 

Because orthosulfamuron has not been previously registered, no monitoring data are available. 

Estimated exposure concentrations for all organisms are obtained through the use of several 

Agency exposure models. Aquatic exposure estimates are based on an assumption of no 

degradation and, therefore, may be used to represent exposure to the parent compound alone or 

the parent compound and any number of its degradates, including its o-desmethyl degradate of 

risk concern. No methodologies are used to assess terrestrial exposure to o-desmethyl 

orthosulfamuron, as its contribution to risk is not expected to alter terrestrial risk conclusions that 

are based on the fate, transport, and toxicity of the parent compound alone. 

To generate screening-level estimates of risk, the measures of exposure, (derived from modeled 

laboratory fate data) are compared to the measures of effect (obtained from laboratory toxicity 

studies). Functionally, the comparison involves dividing the measures of exposure (EECs) by 

the measures of effect for a given taxa. The resulting unitless value is the risk quotient (RQ). 

The RQ is then compared to the Agency’s levels of concern (LOC) for direct effects. The LOCs 

are the policy tool for analyzing potential risk to non-target organisms; if the RQ exceeds the 

LOC for a given taxa and exposure duration, there is a potential for adverse effects to non-target 

organisms. A more detailed description of the methods used to assess risks is provided in the 

next section (Section 3; Analysis). 

All environmental fate and effects data required to be submitted to the Agency have been 

submitted and are adequate, with the exception of those regarding anaerobic aquatic metabolism. 

The submitted data indicate that orthosulfamuron is most toxic to aquatic plants, hydrolyzes 

quickly in acidic environments, is moderately persistent in alkaline environments, and is 

moderately to slightly mobile in soil. 

Analysis 

3.1 Methods 

The primary method used to assess risk in this screening-level assessment is the deterministic 

risk quotient method as outlined in the Overview of the Ecological Risk Assessment Process in 

the Office of Pesticide Programs (USEPA, 2004). The RQ is a unitless value that is the result of 

comparing, by division, measures of exposure to measures of effect. Commonly used measures 

of exposure are the estimated exposure concentrations (EECs) and commonly used measures of 

effect include toxicity values such as the LD50 or the NOAEC. The assessment endpoints and 

the corresponding measures of exposure and measures of effect used to address risks to the 

assessment endpoints are outlined in Table 3.1. 

11
Table 3.1. Assessment Endpoints. 

Assessment Endpoints Measures of Effect Measures of Exposure 

Terrestrial Assessment Endpoints 

Avian Survival Avian acute oral LD50, dietary LC50 Maximum, peak residue 

concentration of food items 

Avian reproduction and/or 

survival 

NOAEC from avian chronic 

reproduction study 

Maximum, peak residue 

concentration of food items 

Mammalian Survival Mammalian acute oral LD50 Maximum, peak residue 

concentration of food items 

Mammalian reproduction and/or 

survival 

NOAEC from 2-generation 

reproduction study 

Maximum, peak residue 

concentration of food items 

Beneficial Insect Survival Honeybee acute contact LD50 Maximum application rate 

Terrestrial plant survival and 

growth 

Tier II plant toxicity data; EC25, 

NOAEC/EC05 

Peak estimate from Interim 

Rice Model and spray drift 

estimates to non-target areas 

Aquatic Assessment Endpoints 

Freshwater fish survival Freshwater fish acute LD50 Peak estimate from rice model 

Freshwater fish reproduction 

and/or survival 

Chronic fish study NOAEC Peak estimate from rice model 

Freshwater invertebrate survival Freshwater invertebrate acute EC50 Peak estimate from rice model 

Freshwater invertebrate 

reproduction and/or survival 

Freshwater invertebrate life cycle 

NOAEC 

Peak estimate from rice model 

Estuarine/marine fish survival Freshwater fish acute LD50 Peak estimate from rice model 

Estuarine/marine fish 

reproduction and/or survival 

Chronic fish study NOAEC Peak estimate from rice model 

Estuarine/marine invertebrate 

survival 

Freshwater invertebrate acute EC50 Peak estimate from rice model 

Estuarine/marine invertebrate 

reproduction and/or survival 

Freshwater invertebrate life cycle 

NOAEC 

Peak estimate from rice model 

Aquatic vascular and nonvascular plant survival and 

growth 

Tier I, Tier II plant toxicity data; 

EC25, NOAEC/EC05 

Peak estimate from rice model 

The RQ that results from a given comparison of exposure and effect is compared to a specified 

level of concern; if the RQ exceeds the LOC, then adverse effects are considered possible and a 

more refined assessment may be warranted to better define potential risks. Although not a true 

estimate of risk since there is no estimated probability or magnitude of an adverse effect, in 

general, the higher the RQ, the more concern for the likelihood of adverse effects (Table 3.2). 

Levels of concern are the policy tool for interpreting RQs in the context of risks to receptors as a 

result of direct pesticide effects. The magnitude of the LOC is set by the risk presumption for 

each endpoint (Tables 3.3-3.5). Importantly, there are implicit components of the LOC, which 

12
include duration, frequency and spatial considerations. Duration is determined primarily by the 

assessment endpoint evaluated and falls typically within the context of acute (shorter) and 

chronic (longer) continuous exposures. The exact duration is taxa-specific and relates to the 

general characteristics of that taxa’s life history. For example, many freshwater invertebrates 

have a relatively short life-span; hence chronic exposure estimates would be shorter than longerlived organisms such as fish. The proposed use of orthosulfamuron specifies only one 

application for use on rice; both terrestrial and aquatic exposure estimates are based on peak 

values. The spatial extent of the screening-level assessment is defined by the use area, and the 

areas downstream and those areas potentially affected by spray drift. For aquatic assessments, 

exposure will vary with proximity to the treated areas. Because the proposed use of 

orthosulfamuron is for rice, higher exposures are expected for organisms near paddies where tail 

water release would contain the highest levels of orthosulfamuron. 

Table 3.2. Risk presumptions for terrestrial animals (birds and wild mammals). 

Risk Presumption RQ LOC 

Acute EEC*/LC50 or LD50/ft

2**

 or 

LD50/day*** 

0.5 

Acute Restricted Use EEC/LC50 or LD50/ft

2

 or LD50/day 

(or LD50 < 50mg/kg) 

0.2 

Acute Listed Species EEC/LC50 or LD50/ft

2

 or LD50/day 0.1 

Chronic EEC/NOAEC 1.0 

* Estimated Exposure Concentration (ppm) on avian/mammalian food items 

** mg/ft2 / LD50 (body-weight scaled) 

*** mg of toxicant consumed/day / LD50 (body-weight scaled) 

Table 3.3. Risk presumptions for aquatic animals. 

Risk Presumption RQ LOC 

Acute EEC*/LC50 or EC50 0.5 

Acute Restricted Use EEC*/LC50 or EC50 0.1 

Acute Listed Species EEC*/LC50 or EC50 0.05 

Chronic EEC/NOAEC 1.0 

* EEC = (ppm or ppb) in water 

Table 3.4. Risk presumptions for terrestrial and semi-aquatic plants. 

Risk Presumption RQ LOC 

Acute EEC*/LC50 or EC50 1.0 

Acute Listed Species EEC/EC05 or NOAEC 1.0 

* EEC = lbs a.i./A 

Table 3.5. Risk presumptions for aquatic plants. 

Risk Presumption RQ LOC 

Acute High Risk EEC*/LC50 or EC50 1.0 

Acute Listed Species EEC/EC05 or NOAEC 1.0 

* EEC = (ppm or ppb) in water 

13 
The exposure estimates in this screening-level assessment are derived using the maximum label 

rate. Measures of effects are based on the lowest available toxicity endpoint for a given taxa and 

exposure duration. 

3.2 Use Characterization 

Orthosulfamuron is proposed for use in rice paddies as post-emergent weed control and is 

formulated as a dry granule and as a water dispersible granule. The label for the water 

dispersible granule formulation (IR5878 50 WG; 51.5% a.i.) directs users to mix with water at 

the appropriate rates and apply as spray via ground or air equipment to fully or partially drained 

wet-seeded or dry-seeded rice. The label for the granular formulation (IR5878 0.5 GR; 0.51% 

a.i.) directs users to apply via direct dry application by ground or air equipment to permanently 

flooded rice. For both formulations of orthosulfamuron, the proposed label recommends 

application when weeds are young, emerging and actively growing. Maximum seasonal 

applications for the proposed use on rice are similar for both formulations at approximately 0.07 

lbs a.i./A and limited to 1 application per year. Use rates and management practices by crop 

according to proposed labels are presented in Table 3.6, based on the Petition for Tolerances 

submitted by Isagro S.p.A. (June 20, 2005). 

Table 3.6. Proposed Uses of Orthosulfamuron; Maximum Application Rates. 

Crop/Use Formulated Product 

Application Rate 

fl. oz./A 

Maximum 

Application Rate 

(lbs a.i./A) 

Maximum 

Number of 

Applications 

Maximum Yearly 

Application 

(lbs a.i./A) 

IR5878 50 WG (Dispersible Granule) 

Rice 2.14 0.069 1 0.069 

IR5878 0.5 GR (Granule) 

Rice N/A (dry granule 

formulation) 0.066 1 0.066 

For purposes of this screening-level assessment, estimates of risk are based on maximum 

proposed label rates for the water dispersible granule formulation (IR5878 50 WG) since it is 

slightly greater than the application rate for the dry granule (Table 3.6). 

In the United States, rice is grown primarily in two regions. The Southern region consists of the 

Gulf Coast of Texas and Southwest Louisiana and the Mississippi River Valley in parts of 

Louisiana, Mississippi, Arkansas, and Missouri. The remainder of domestic rice production is 

located in the Sacramento Valley and San Joaquin Valley of California. Other states known to 

potentially produce small quantities of rice include Illinois, Florida, Oklahoma, and Tennessee 

(National Agricultural Statistics Service, 2002). 

Successful rice cultivation relies on three general rice paddy irrigation practices in accordance 

with the life cycle of the crop, dry seeding, wet seeding, and water seeding. Dry seeding is the 

most common practice in the Southern region of the United States, wherein seeds are grown in 

14
dry beds several weeks before establishing a permanent flood in the paddy. Small amounts of 

water are used to assist seed germination, but the field is left dry until the rice has sprouted and 

begun to grow. Wet seeding also occurs in the Southern region of the United States through "pin 

point" flood culture, wherein pre-sprouted rice is aerially applied to flooded fields that are 

drained a few days later and flooded again several days later. In California, the majority of rice 

production is water seeded with a continuous flood, wherein a steady flow of aerobic water is 

maintained through the paddy. 

Although actual water depth within a paddy may be shallow (1-4 inches), given the size of 

individual paddies and the co-location of many paddies, rice cultivation may involve large 

quantities of water. Importantly, for areas that may be dominated by rice cultivation, the 

simultaneous release or drainage of paddy tail water could contribute significant quantities of 

water to nearby water bodies. 

15
Figure 3.1. Location of Rice Harvested in the United States in 2002 (USDA, 2006). 

3.3 Exposure Characterization 

3.3.1 Environmental Fate and Transport Characterization 

Orthosulfamuron exhibits acid-base behavior, as its water solubility and octanol-to-water 

partitioning depend on environmental pH. It is predicted to have five dissociation constants 

(pKa of -1.4, 0.7, 3.5, 9.6, and 11.5) and to be fully neutral at ca. pH 2 to 2.5. The compound’s 

persistence depends on environmental pH as well, as the compound readily undergoes acid 

catalyzed hydrolysis (half-life of hours to days). As alkaline conditions increase, the compound 

is increasingly hydrolytically stable in water (half-life of 7 months). 

Biodegradation in aerobic and anaerobic aquatic conditions occurs on a scale of months. Due to 

its low vapor pressure and high water solubility, volatilization from water and soil surfaces is not 

expected to be an important route of environmental dissipation. Orthosulfamuron is moderately 

to slightly mobile in soils, presenting a ground water concern in alkaline sandy soils with low 

organic carbon content. Leaching and aquatic field dissipation data indicate that some of the 

transformation products of the compound are more susceptible to leaching than the parent. 

16
Orthosulfamuron’s major route of degradation in acidic to neutral rice paddy water is hydrolysis, 

with a half-life of hours to days. Aerobic biodegradation is the major route of degradation in 

alkaline rice paddy water, with a half-life of weeks to months. Both routes of degradation are 

expected at similar rates (i.e. half-lives of weeks) in paddy water of neutral pH. The general 

physical/chemical properties of orthosulfamuron are summarized in Table 3.7. 

Table 3.7. General chemical properties and environmental fate parameters of orthosulfamuron. 

Chemical/Fate Parameter Value Source 

Molecular mass 424.44 MRID 46219074 

Vapor pressure (20°C) 8.4 x 10-7 torr MRID 46219010 

Water solubility (20°C) 26.2 mg/L (pH 4) 

 629 mg/L (pH 7) 

38,900 mg/L (pH 8.5) 

MRID 46219009 

Octanol-to-water partition coefficient 

(KOW) 

104 (pH 4)

 20.5 (pH 7)

 <2.0 (pH 10) 

MRID 46219012 

Freundlich soil-to-water partition 

coefficients (Kf) for adsorption (soil type) 

2.0 (1/n = 1.02) (silt loam) 

2.4 (1/n = 0.97) (sandy loam) 

3.6 (1/n = 1.15) (sand) 

3.8 (1/n = 0.75) (sandy loam) 

5.5 (1/n = 0.92) (silt loam) 

5.7 (1/n = 0.96) (clay loam) 

6.6 (1/n = 0.86) (silt loam) 

6.9 (1/n = 0.99) (loam) 

8.2 (1/n = 1.06) (sandy loam) 

20 (1/n = 0.98) (clay loam) 

MRID 46219074 

MRID 46578971 

Organic carbon normalized partition 

coefficients (KOC)

1 

217, 228, 249, 283, 326, 350, 381, 547, 

653, 2330 L/kgOC 

MRID 46219074 

MRID 46578971 

Hydrolysis half-life (25°C) 0.442 d (pH 5) 

 24.4 d (pH 7) 

228 d (pH 9) 

MRID 46219015 

MRID 46578970 

Aqueous photolysis half-life 180 d (laboratory value) MRID 46588509 

Aerobic aquatic metabolism half-lives 30.3, 59.2, 65.4, 70.5 d MRID 46219017 

Anaerobic aqueous metabolism half-lives 88, 142, 161, 217 d MRID 46578967 1

 KOC values were calculated based on Kf values for adsorption (e.g., KOC = Kf (adsorption) ÷ % organic carbon). 

The environmental fate and transport properties of orthosulfamuron are characterized below. 

Our understanding of these properties is limited by the data set available. Many chemical 

properties and environmental fate parameters of orthosulfamuron listed in Table 3.7 are based on 

single, supplemental studies, summaries of which are in Appendix B. 

3.3.1.1 Transport and Mobility 

Orthosulfamuron exhibits acid-base behavior, as indicated by its ranges of water solubility and 

octanol-to-water partitioning across environmental pH values. The compound is predicted to 

17
have five dissociation constants (pKa of -1.4, 0.7, 3.5, 9.6, and 11.5) and to be fully neutral at ca. 

pH 2 to 2.5 (MRID 46219011, 46219012). As pH increases, orthosulfamuron residues are 

expected to become increasingly ionized, which is evidenced by the compound’s increasing 

water solubility and decreasing partitioning to octanol at higher pH values. As orthosulfamuron 

ionizes, it is expected to have greater mobility in soil as well as greater solubility in water. 

The compound demonstrates moderate to slight mobility in soils based upon Kf values from ten 

soils ranging from 2.0 (1/n=1.02) to 20 (1/n=0.98) (MRID 46219074; 46578971). Lack of 

mobility is partially explained by affinity to organic matter, as the organic carbon content of soils 

correlates with Kf values (p<0.05). The coefficient of variation (CV) for KOC (115%) is larger 

than that for Kf (79%) across all ten soils studied due to one outlying high KOC value (2330 

L/kgOC) that is likely the result of experimental error. Upon omission of the outlying KOC value 

from the remaining nine KOC values (range of 217 – 653 L/kgOC), the CV for KOC (42%) is less 

than that for Kf (86%), which is expected when organic carbon content in soil correlates with Kf 

values. 

Lack of mobility of orthosulfamuron may also be partially explained by affinity to clay particles, 

as Kf values correlate with the clay content of soils (p<0.05), but not soil pH (p>0.05; pH range 

4.7 to 8.0). Affinity to clay may be due to ionized congeners of orthosulfamuron. The anionic 

nature of these congeners would give orthosulfamuron greater mobility than expected for the 

neutral compound alone in high-pH, low-clay soils. 

Compounds with Kf values less than five present a ground water concern. Therefore, 

orthosulfamuron presents a ground water concern in some soils, especially those that are 

alkaline, sandy, and of low organic carbon content. 

A column leaching study of aged orthosulfamuron indicated that some degradates (DBS acid, 

DBS amide, and o-desmethyl orthosulfamuron) are capable of greater mobility than the parent 

and are more likely to leach to ground water (MRID 46219018). Unaged orthosulfamuron 

ranged from not detected to 2.1% of the applied in five to six pore volumes of leachate from five 

columns (MRID 46578968). Aged orthosulfamuron was not detected in six pore volumes of 

leachate from four soil columns; however, pyrimidinyl-labeled degradates (mostly o-desmethyl 

orthosulfamuron) averaged 4.6% of the applied in leachate and phenyl-labeled degradates 

(mainly DBS acid) averaged 62.5% of the applied in leachate (MRID 46219018). 

Volatilization of orthosulfamuron from water and soil systems is not expected to be an important 

environmental fate process based on the compound’s water solubility range of 26 mg/L to 39,000 

mg/L and vapor pressure of 8.4x10-7 torr, both at 20°C (MRID 46219009; 46219010). 

3.3.1.2 Degradation 

Orthosulfamuron hydrolyzed with half-lives of 0.442, 24.4, and 228 days at 25°C in pH 5, pH 7, 

and pH 9 buffered solutions, respectively (MRID 46219015, 46578970). The half-life at pH 9 is 

more uncertain, as it exceeds the study duration of 176 days. Major identified hydrolysis 

degradates were DBS acid and DB amine, as shown in Table 3.8. 

18
Orthosulfamuron degraded with a calculated phototransformation half-life of approximately 180 

solar days when irradiated continuously under a filtered xenon lamp for 6.92 days at 25oC in a 

pH 9 buffered solution (MRID 46588509). This half-life value was extrapolated far beyond the 

study duration and is highly uncertain. The environmental phototransformation half-life of 

orthosulfamuron could not be determined because the intensity of the artificial light was not 

compared to natural sunlight. No major photodegradates were detected. 

An anaerobic aquatic metabolism study was conducted for orthosulfamuron using a pond waterloam sediment system from Arkansas for 180 days and a pond water-clay sediment system from 

California for 150 days (MRID 46578967). Half-lives were calculated by counting nonextracted residues as parent compound, since multiple solvent systems were not employed in 

extraction and non-extractable residues in sediment were measured at >10% of applied by day 

15. Half-lives in the microcosm from Arkansas were 217 and 142 days for pyrimidinyl- and 

phenyl-labeled orthosulfamuron, respectively. Dissipation occurred more rapidly in the 

microcosm from California; half-lives were 161 and 88 days for pyrimidinyl- and phenyl-labeled 

orthosulfamuron, respectively. Half-lives calculated with extracted parent compound alone were 

89 and 80 days for the pyrimidinyl and phenyl labels in Arkansas, respectively, and 41 days for 

both labels in California. The major identified degradates were DBS acid, o-desmethyl 

orthosulfamuron, and DOP urea, as displayed in Table 3.8. 

The aerobic aquatic metabolism of orthosulfamuron was also studied using the pond watersediment systems from Arkansas and California (MRID 46219017). Once again, half-lives were 

calculated by counting non-extracted residues as parent compound, since multiple solvent 

systems were not employed in extraction and non-extracted residues reached 11-33% of applied. 

Degradation appeared to occur more rapidly under aerobic conditions as compared to anoxic 

conditions. Half-lives in the microcosm from Arkansas were 70.5 and 59.2 days for pyrimidinyland phenyl-labeled orthosulfamuron, respectively. Similar to the anaerobic aquatic metabolism 

study, degradation appeared to occur more rapidly in the California pond-sediment system; halflives were 65.4 and 30.3 days for pyrimidinyl- and phenyl-labeled orthosulfamuron, respectively. 

It is possible that degradation occurred more rapidly in the California system since it was more 

acidic (pH = 6 in sediment) than the Arkansas system (pH = 6.9 in sediment), and hydrolysis of 

orthosulfamuron appears to be an acid catalyzed reaction. Half-lives calculated with extracted 

parent compound alone were 40.6 and 36.3 days for the pyrimidinyl and phenyl labels in 

Arkansas, respectively, and 24.1 and 21.3 days for the pyrimidinyl and phenyl labels in 

California, respectively. The major identified degradates were DBS acid and DOP urea, as 

shown in Table 3.8. 

3.3.1.3 Field Studies 

A single aquatic field dissipation study was conducted for orthosulfamuron using a bare ground 

plot of silt loam soil (pH 6.7) in Arkansas and a bare ground plot of silty clay loam soil (pH 7.7) 

in California (MRID 46578985). The plots were flooded with water 1–2 days following the 

application of orthosulfamuron to approximate the timing of herbicide application to rice. Soil 

samples (0-60 cm depth) were collected through 550-553 days post-treatment. Water and the 

underlying soil (“sediment”; 0-5 cm depth) samples were collected from 3 days to 2 months 

post-treatment. At the Arkansas test site, orthosulfamuron dissipated in the soil (0-15 cm depth), 

19
sediment (0-5 cm depth), and water with half-lives of 4.1 days, 6.2 days, and 6.4 days, 

respectively. At the California site, orthosulfamuron dissipated in the soil (0-15 cm depth) and 

sediment (0-5 cm depth) with half-lives of 2.3 days and 4.3 days, respectively. No half-life was 

calculated for the water phase because the chemical was not detected in the water. 

Both test sites were analyzed for DOP urea, DBS acid, and o-desmethyl orthosulfamuron. The 

latter was below detection limits in all samples from both sites. At the Arkansas site, DOP urea 

and DBS acid were major degradates in the soil and sediment; DBS acid was the major degradate 

in water. At the California site, DOP urea was the major degradate in soil and sediment; no 

major degradates were detected in water. 

3.3.1.4 Bioconcentration 

A flow-through bioconcentration study of bluegill sunfish (Lepomis macrochirus) exposed to 

orthosulfamuron in pH 7.5-8.0 water for 14 days indicates that the compound does not 

bioaccumulate. Bioconcentration factors (BCF) were 0.29, 0.34, and 0.32 for edible, non-edible, 

and whole fish tissues, respectively, in low-dose samples (142 μg/L) and 0.72, 1.14, and 0.97 for 

edible, non-edible, and whole fish tissues, respectively, in high-dose samples (1420 μg/L). BCF 

values less than 1000 do not trigger criteria for bioaccumulative compounds [64 Fed. Reg. 

60194-60204 (November 4, 1999)]. 

3.3.2 Degradates 

The transformation products resulting from the environmental degradation processes of 

orthosulfamuron are: 2-dimethylcarbamoylphenyl sulfamic acid (DBS acid; IR7863; S1); 2­

sulfamoylamino-N,N-dimethylbenzamide (DBS amide; S2); 2-amino-N,N-dimethylbenzamide 

(DB amine; S4); 1-(4-hydroxy-6-methoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl) 

phenylsulfamoyl]urea (o-desmethyl orthosulfamuron; IR8181; S9); N-(4,6-dimethoxypyrimidin2-yl)urea (DOP urea; IR7825; S12); 4,6-dimethoxypyrimidin-2-yl amine (DOP amine; S13); and 

N-(4-hydroxy-6-methoxypyrimidin-2-yl)urea (o-desmethyl DOP urea; S15). Two other 

degradation products S5 and S11 are composed of multiple unresolved compounds. 

DBS acid (S1), DB amine (S4), o-desmethyl orthosulfamuron (S9), and DOP urea (S12) were 

the major degradates identified at a maximum of 62%, 13%, 19%, and 111% of the applied, 

respectively, detected at 7, 176, 100, and 7 days after treatment, respectively. These degradates 

are moderately persistent, as peak detections of these degradates occurred at up to 100-186 days 

after application. None of these degradates are known to be toxic, however the o-desmethyl 

degradate is assumed to have equal toxicity as the parent compound because it retains the parent 

compound’s sulfamoylurea structural group. Chemical structures of these degradation products 

are shown in Table B of Appendix B. 

The main degradation pathway of orthosulfamuron appears to be the hydrolytic cleavage of the 

sulfamoylurea linkage to give DOP urea (S12) and DBS acid (S1). Another degradation 

pathway is the demethylation of orthosulfamuron to its o-desmethyl degradate (S9), which may 

also degrade to DBS acid. Orthosulfamuron and DBS acid may hydrolyze to form DB amine 

(S4). The maximum amounts of these degradation products observed in hydrolysis, aerobic 

20
aquatic metabolism, anaerobic aquatic metabolism, soil column leaching, and aquatic field 

dissipation studies are summarized in Table 3.8. No degradation products were detected in the 

photolysis study. Degradation products were not analyzed for in the hydrolysis study at pH 5. 

Table 3.8. Maximum Reported Amounts of Orthosulfamuron Degradation Products.1 

Degradate Maximum % of Applied Study Type MRID 

S1 (DBS acid) 58 (37 d, pH 7) 

39 (150 d) 

61 (61 d) 

25 (55 d); 51 (leachate) 

62 (% of initial, 7 d, soil); 

23 (% of initial, 7 d, sediment); 

34 (% of initial, 15 d, water) 

Hydrolysis 

Anaerobic aquatic metabolism 

Aerobic aquatic metabolism 

Soil column leaching 

Aquatic Field Dissipation 

MRID 46219015 

MRID 46578967 

MRID 46219017 

MRID 46219018 

MRID 46578985 

S2 (DBS amide) 8.7 (113 d, pH 9) 

4.2 (180 d) 

4.0 (61 d) 

7.2 (34 d); 8.0 (leachate) 

Hydrolysis 

Anaerobic aquatic metabolism 

Aerobic aquatic metabolism 

Soil column leaching 

MRID 46219015 

MRID 46578967 

MRID 46219017 

MRID 46219018 

S4 (DB amine) 13 (176 d, pH 9) 

6.4 (71 d) 

<3 (55 d), 3.7 (leachate) 

Hydrolysis 

Anaerobic aquatic metabolism 

Soil column leaching 

MRID 46219015 

MRID 46578967 

MRID 46219018 

S5 (multiple unresolved 

compounds) 

22 (180 d) 

2.5 (leachate) 

Anaerobic aquatic metabolism 

Soil column leaching 

MRID 46578967 

MRID 46219018 

S9 (o-desmethyl 

orthosulfamuron) 

19 (100 d) 

9.2 (90 d) 

5.2 (55 d), 4.6 (leachate) 

Anaerobic aquatic metabolism 

Aerobic aquatic metabolism 

Soil column leaching 

MRID 46578967 

MRID 46219017 

MRID 46219018 

S11 (multiple 

unresolved compounds) 

23 (180 d) 

0.26 (leachate) 

Anaerobic aquatic metabolism 

Soil column leaching 

MRID 46578967 

MRID 46219018 

S12 (DOP urea) 19 (59 d) 

47 (90 d) 

36 (55 d), 52 (soil column) 

38 (soil column) 

64 (% of initial, 186 d, soil); 

111 (% of initial, 7 d, sediment) 

Anaerobic aquatic metabolism 

Aerobic aquatic metabolism 

Soil column leaching 

Soil column leaching 

Aquatic Field Dissipation 

MRID 46578967 

MRID 46219017 

MRID 46219018 

MRID 46578968 

MRID 46578985 

S13 (DOP amine) 1.1 (71 d) 

<3 (leachate) 

1.4 (soil column) 

Anaerobic aquatic metabolism 

Soil column leaching 

Soil column leaching 

MRID 46578967 

MRID 46219018 

MRID 46578968 

S15 (o-desmethyl DOP 

urea) 

4.9 (150 d) 

<3 (leachate) 

Anaerobic aquatic metabolism 

Soil column leaching 

MRID 46578967 

MRID 46219018 

1

 Percentages greater than 10% are in bold. 

The toxicities of orthosulfamuron’s major degradates are not determined. The o-desmethyl 

degradate is the only degradate that retains the parent compound’s sulfamoylurea structural 

group. Therefore, o-desmethyl orthosulfamuron is assumed to have equal toxicity as the parent 

compound and is of risk concern. The toxicities of orthosulfamuron’s major degradates other 

than the o-desmethyl degradate are assumed to be significantly less than that of the parent 

21 
compound because the sulfamoylurea linkage is severed. Therefore, the compounds of risk 

concern for this risk assessment are orthosulfamuron parent and its o-desmethyl degradate. 

Aquatic exposure estimates are based on an assumption of no degradation and, therefore, may be 

used to represent exposure to the parent compound alone or the parent compound and any 

number of its degradates, including its o-desmethyl degradate of risk concern. No 

methodologies are used to assess terrestrial exposure to o-desmethyl orthosulfamuron, as its 

contribution to risk is not expected to alter terrestrial risk conclusions that are based on the fate, 

transport, and toxicity of the parent compound alone. 

3.3.4 Measures of Aquatic Exposure 

Rice is grown in paddies that are periodically flooded with several inches of water, an agronomic 

practice that most surface water models currently used for pesticide risk assessment are not 

designed to represent. The Environmental Fate and Effects Division developed the Interim Rice 

Model to estimate surface water exposure to orthosulfamuron from use on rice (USEPA, 2002). 

The model estimates exposure as a function of the amount of pesticide applied and the 

pesticide’s soil-to-water partition coefficient. Regardless of irrigation practice, applications are 

assumed to occur over a rice paddy flooded with 4 inches of water. Concentrations are assumed 

to immediately and evenly distribute throughout the rice paddy water following application. The 

application efficiency is assumed to be 100%; therefore, runoff concentrations do not require 

adjustment for the contribution of downstream spray drift residues. Dissipation processes, such 

as degradation, volatilization, and potential dilution with uncontaminated water outside the 

paddy are not accounted for by the model. The single estimated environmental concentration 

(EEC) produced with the Interim Rice Model is used as both an acute and a chronic screening 

exposure estimate that is expected to represent high-end exposure in rice paddy water and tail 

water discharge (see Attachment C for calculation). Table 3.9 reports the peak and chronic 

screening EECs used for aquatic risk estimation. 

Table 3.9. Surface water estimated exposure concentrations (EEC) of orthosulfamuron from use 

on rice. 

Source App. Rate (lbs ai/A) Peak & Chronic EEC (ppb) 

Paddy water/tail water 0.069 38.6 

In some soils, particularly in alkaline areas with porous soil of low organic carbon content, 

transport to ground water and subsequent discharge of ground water to surface water bodies may 

occur. However, expected ground water concentrations estimated with the screening model SCIGROW (EEC=0.6 ppb) are insignificant compared to expected surface water concentrations 

estimated with the screening Interim Rice Model (EEC=38.6 ppb). Therefore, ground water 

discharge exposure estimates are not reported for risk estimation. 

The model input parameters used to generate the EEC for paddy water and tail water listed above 

are presented in Table 3.10. 

22
Table 3.10. Interim Rice Model input parameters for orthosulfamuron. Source data are in Table 

3.7. 

Input Parameter Value Justification Source 

Application Rate 

(kg a.i./ha) 

0.0772 0.0689 lbs a.i./A x 1.121 kg·A/ha·lbs 

= 0.0772 kg a.i./ha 

Proposed label 

Soil-to-Water Partition 

Coefficient (Kd) (L/kg) 

7.19 Mean KOC (359 L/kgOC) x 2% organic 

carbon content = 7.19 L/kg 

MRID 46219074 

MRID 46578971 

Because one KOC value (2330 L/kgOC) from the submitted studies was an outlier and likely the 

result of experimental error, the mean of the nine remaining KOC values (359 L/kgOC) was used 

to model partitioning to rice paddy sediment. In accordance with EFED guidance, the mean KOC 

value was multiplied by 2% organic carbon content in order to generate the soil-to-water 

partition coefficient (Kd) model input (7.19 L/kg) (USEPA, 2002). 

3.3.5 Measures of Terrestrial Exposure 

Orthosulfamuron is proposed for use on rice and will be applied by ground or aerial spray 

(IR5878 50 WG) or direct dry application by ground or air (IR5878 0.5 GR). Measures of 

exposure for terrestrial organisms can be obtained from a variety of sources including monitoring 

data, field studies, GIS analysis, and exposure modeling. For this assessment, exposure 

modeling was used to generate EECs for both terrestrial animals and plants. 

The screening-level assessment focuses on dietary exposure for terrestrial birds, mammals, 

reptiles, and amphibians that may come in contact with orthosulfamuron use areas. Although 

other routes of exposure can be important, for the most part dietary routes of exposure are 

considered to contribute most to total exposure and hence are the focus here. Moreover, suitable 

data are frequently unavailable to adequately assess other exposure routs such as dermal, 

inhalation, or incidental soil ingestion. 

3.3.5.1 Terrestrial Animal Species 

Exposure of free-ranging terrestrial animals is a function of the timing and extent of pesticide 

application with respect to the location and behavior of those species. OPP’s terrestrial exposure 

model generates exposure estimates assuming that the animal is present on the use site at the 

time that pesticide levels are highest. The upper-bound pesticide residue concentration on food 

items is calculated from both initial applications and any additional applications, taking into 

account pesticide degradation between applications, however, for orthosulfamuron only one 

application is required for the proposed use. Although this approach is conservative, it is 

reasonable, particularly when considering acute risks. For acute risks, the assumption is that the 

duration of exposure is a single day and, again, occurs when residue levels are highest. In 

evaluating chronic risks, longer-term exposure estimates are also based on the assumption that 

the animal is present on the use site when residue levels are highest and furthermore that it 

repeatedly forages on the use site although the frequency and duration of foraging events on the 

use site are not explicitly considered or specified. 

23
The current screening-level approach does not directly relate timing of exposure to critical or 

sensitive population, community, or ecosystem processes. Given that the application timing and 

location is crop-dependent, it is difficult to address the temporal and spatial co-occurrence of 

orthosulfamuron use and sensitive ecological processes. However, pesticides are frequently used 

from spring through fall; rice cultivation frequently starts in the spring, hence uses of 

orthosulfamuron are likely to occur in spring and perhaps summer. Spring and early summer are 

typically seasons of active migrating, feeding, and reproduction for many wildlife species. The 

increased energy demands associated with these activities (as opposed to hibernation, for 

example) can increase the potential for exposure to pesticide-contaminated food items since 

agricultural areas can represent a concentrated source of relatively easily obtained, high-energy 

food items. In this assessment, the spatial extent of exposure for terrestrial animal species is 

limited to the use area only and the area immediately surrounding the use area. Since the 

majority of applied orthosulfamuron will likely fall within the rice paddy, direct exposures to 

terrestrial animal species will result either from spray drift or, in the case of granules, application 

to non-target areas. It is likely that for aerial application of granules, the boundary regions 

between paddies may receive applications of orthosulfamuron similar to what is being applied to 

the rice paddy. In addition, given that orthosulfamuron is applied directly to water, it is possible 

that terrestrial animals that consume fish and aquatic invertebrates may be exposed to 

orthosulfamuron that has bioaccumulated in these types of aquatic organisms. 

Currently, the Agency does not require toxicity studies on reptiles and amphibians in support of 

pesticide registrations. To accommodate this data gap, birds are used as surrogates for 

terrestrial-phase amphibians and reptiles. It is assumed that, given the usually lower metabolic 

demands of reptiles and amphibians compared to birds, exposure to birds would be greater due to 

higher relative food consumption. While this assumption is likely true, there are no supported 

relationships regarding the relative toxicity of a compound to birds and herpetofauna. The lack 

of toxicity data on reptiles and amphibians represents a source of uncertainty in this assessment. 

3.3.5.1.1 Terrestrial Animal Exposure Modeling 

The approach used to estimate exposure of terrestrial animals to orthosulfamuron was based on 

potential foliar applications of IR5878 50 WG and dry granule applications of IR5878 0.5 G to 

non-target areas. These non-target areas are the dry paddy embankments and divisions 

immediately adjacent to the treated paddy and characteristic of rice cultivation areas; this 

represents a reasonable upper-bound exposure a terrestrial species may likely receive from foliar 

applications of orthosulfamuron. These exposure estimates were determined using the standard 

screening-level exposure model, TREX (v1[1].2.3) (USEPA, 2004). Upper-bound exposure 

levels were calculated for spray and granular applications of orthosulfamuron using maximum 

proposed application rates for one application for the proposed use on rice (Table 3.11). The 

exposure estimates for the water dispersible granule formulation are based on a database of 

pesticide residues on wildlife food sources associated with specified application rates (Kenaga, 

1972; Fletcher et al., 1994). Essentially, for a single application, there is a linear relationship 

between the amount of pesticide applied and the amount of pesticide residue present on a given 

food item. For 1.0 lb a.i. of pesticide per acre, the upper-bound, food item concentration in mg 

a.i./kg of diet (parts per million [ppm]) is: 240 for short grass, 110 for tall grass, 135 for 

broadleaf plants and small insects, and 15 for fruits pods, and large insects. Food item residue 

24
levels are then linearly adjusted based on application rate. The upper-bound estimates are used 

to estimate risks since these values represent the high-end exposure that may be encountered for 

terrestrial species that consume food items that have received label-specified pesticide 

application. Although these represent higher-end estimates, they do not represent the highest 

possible exposure estimates. For the granular formulation, the LD50/ft

2

 was used. This method 

compares the average concentration in a square foot of the use area to the LD50 and is a rough 

estimate of exposure taking into account multiple exposure pathways. In addition, birds can 

consume granules directly, either as a result of incidental ingestion or purposefully in an effort to 

acquire grit to facilitate digestion. Quantifying the number of granules consumed in relation to 

the LD50 provides a sense of the potential effects associated with this route of exposure. 

TREX is a simulation model that, in addition to incorporating the relationship between 

application rate and food item residue concentrations, accounts for pesticide degradation in the 

estimation of EECs. TREX calculates pesticide residues on each type of food item on a daily 

interval for one year. A first-order decay function is used to calculate the residue concentration 

at each day based on the concentrations present from both initial and all subsequent applications, 

although for orthosulfamuron only one application is proposed. The decay rate is dependent on 

the foliar dissipation half-life. The food item concentration on any given day is the sum of all 

concentrations up to that day, taking into account the first-order degradation. The initial 

application occurs on day 0 (t=0) and the model runs for 365 days. Over the 365-day run, the 

highest residue concentration is the measure of exposure (EEC) used to calculate RQs. 

The foliar dissipation half-life can be important in estimating exposure because it essentially 

determines how long the pesticide remains on food items after application. In many cases, an 

empirically determined foliar dissipation half-life value is not available, in which case the default 

value of 35 days is used (Willis and McDowell, 1987). For orthosulfamuron, the default foliar 

dissipation half-life was used. 

Although the focus of exposure estimates for this assessment is the dietary route, other exposure 

routes including dermal and inhalation can be important contributors to overall exposure levels. 

For orthosulfamuron, dermal and inhalation exposure may only be expected for use of the water 

dispersible granule formulation since dry granules are too large to be inhaled and are unlikely to 

contribute to dermal exposures. These alternate routes of exposure, however, were not explicitly 

incorporated into estimates of exposure for the water dispersible granule formulation of 

orthosulfamuron; using only the dietary route to assess potential effects likely captures the 

potential for adverse effects. Moreover, since orthosulfamuron is an herbicide, it is probably not 

very toxic to terrestrial animal species and, in addition, droplet size is likely to be larger further 

reducing the potential for adverse effects associated with dermal or inhalation exposures. 

Table 3.11 lists EECs for birds, reptiles, terrestrial amphibians, and mammals obtained from 

TREX simulation for all proposed uses of orthosulfamuron at the maximum label rates. 

25
Table 3.11. Terrestrial Food-Item Residue Estimates for Orthosulfamuron 

Proposed Uses Assuming a Foliar Dissipation Half-life of 35 Days. 

Crop 

Single Application 

Rate 

lbs. a.i./A 

(1 application only) 

Food Item Maximum EEC 

(mg/kg)1 

IR5878 50 WG 

Rice 0.069 

Short grass 16.56 

Tall grass 7.59 

Broadleaf plants/ small insects 9.32 

Fruits, pods, seeds, lg. insects 1.04 

IR5878 0.5 G 

Rice 0.066 0.69 mg a.i./ft2 

. 

3.3.5.2 Terrestrial Plant Species 

Exposure of naturally-occurring terrestrial and semi-aquatic (wetland) plant species is typically 

estimated using OPP’s TerrPlant (v1.2.1) model and is assumed to encompass areas outside the 

immediate use site. For non-wetland areas, exposure calculations are based on the amount of 

pesticide present in soil as a function of drift. Loading via drift to dry, non-target, adjacent areas 

is assumed to occur from one acre of treatment to one acre of the non-target area. In wetland 

areas, pesticide loading occurs from tail water release of rice paddy water. This is a departure 

from what TerrPlant calculates but better represents the proposed use of orthosulfamuron. In this 

case, water from the tail water release is assumed to reach semi-aquatic areas and the exposure 

level is equivalent to the EEC calculated using the Interim Rice Model. Spray drift is also a 

source of pesticide loading to non-target areas. The default spray drift assumptions are 1% for 

ground applications and 5% for aerial, airblast, forced air, and chemigation applications. Drift is 

not considered for formulations of pesticides that are not spray-applied (e.g., granules). 

3.3.5.2.1 Terrestrial and Semi-Aquatic Plant Exposure Modeling 

Orthosulfamuron exposure to terrestrial and semi-aquatic plants was estimated using OPP’s 

TerrPlant (v1.2.1) model and the Interim Rice Model. TerrPlant generates EECs for plants 

residing near a use area that may be exposed via spray drift, as explained above. The EECs are 

generated from one application at the maximum rate for a particular use and compound-specific 

solubility information. Only a single application is considered because it is assumed that for 

plants, toxic effects are likely to manifest shortly after the initial exposure and that subsequent 

exposures do not contribute to the response. The label for the proposed use of orthosulfamuron 

on rice indicates that only one application per season is allowed. TerrPlant estimates EECs 

based on application rate, solubility factor and default assumptions of drift. The EECs for 

terrestrial and semi-aquatic plants for a single application of the water dispersible granule 

formulation of orthosulfamuron at the maximum label rate for proposed uses are presented in 

Table 3.12. The Interim Rice Model was used to estimate tail water loading to semi-aquatic 

areas (see inputs in Table 3.10 and calculation in Appendix C). Although the EECs in Table 

3.12 are specific to the water dispersible granule formulation, these EECs are similar to what 

would be estimated from TerrPlant for the dry granule formulation. Moreover, for dry granule 

application, the two exposure routes are from sheet and/or channelized runoff. Because of the 

26
proposed use on rice, the tail water release exposure estimate from the Interim Rice Model is 

likely the best representation for exposure associated with the dry granule use. 

Table 3.12. EECs for Terrestrial and Semi-Aquatic Plants Near Orthosulfamuron Use 

Areas. 

Crop 

Single 

Max. 

Application 

Rate 

(lbs a.i./A) 

EECs (lbs a.i./A) 

(Ground Spray, Aerial Spray) 

Total Loading to SemiAquatic Areas Drift EEC 

Tail water release Ground spray Aerial spray 

Rice 0.069 0.0367 0.0007 0.0035 

3.3.5.3 Residue Studies 

Environmental residue studies can also provide useful information regarding the potential 

exposure of terrestrial wildlife and plant species in and around use areas. These data can be used 

to corroborate modeling results or to provide additional insights into chemical fate with respect 

to exposure. For orthosulfamuron, no studies are available; all estimates of exposure are based 

on model outputs. 

3.4. Ecological Effects Characterization 

In screening-level ecological risk assessments, effects characterization describes the types of 

effects a pesticide can have on aquatic and terrestrial organisms. This characterization is based 

on registrant-submitted studies that describe information regarding acute and chronic toxicity 

effects for various aquatic and terrestrial animals and acute studies on aquatic and terrestrial 

plants. Appendix E summarizes the results of all registrant-submitted toxicity studies used to 

characterize effects for this risk assessment while only those toxicity endpoints used in risk 

estimation are presented here. Toxicity testing reported in this section does not represent all 

species of birds, mammals, or aquatic organisms. Only a few surrogate species for both 

freshwater fish and birds are used to represent all freshwater fish (2000+) and bird (680+) 

species in the United States. For mammals, acute studies are usually limited to the Norway rat or 

the house mouse. Estuarine/marine testing is usually limited to a crustacean, a mollusk, and a 

fish. Importantly, results from submitted toxicity studies are not likely to capture the toxicity of 

orthosulfamuron to all species of birds, mammals, plants, or aquatic animals. Furthermore, there 

are no currently required toxicity tests for amphibian or reptiles; birds are used as surrogates for 

reptiles and terrestrial-phase amphibians and freshwater fish are used as surrogates for aquaticphase amphibians. In general, the representation of numerous species by a few commonly used 

laboratory species, which are often chosen for their ability to thrive under laboratory conditions, 

is a source of uncertainty. 

Orthosulfamuron is, for the most part, practically non-toxic to slightly toxic to birds and 

honeybees under acute exposure conditions. In addition, there were no significant effects of 

orthosulfamuron on survival, growth, or reproduction in submitted avian reproduction studies. 

27
Similarly, for aquatic animal species (fish and invertebrates), orthosulfamuron is classified as 

practically non-toxic to slightly toxic under acute exposure conditions. The few chronic toxicity 

studies involving exposure to aquatic organisms also indicate that orthosulfamuron is not 

particularly toxic, although NOAECs were established in these studies. In contrast to the toxicity 

to animal species, orthosulfamuron is very highly toxic to aquatic plants and exhibits significant 

toxicity towards terrestrial plant species as well. Given the intended use of orthosulfamuron as 

an herbicide, these results are not unexpected. It seems likely that any potential environmental 

risks of orthosulfamuron could be focused on direct effects to plants and potential indirect effects 

on animal species dependent on plant species. 

In addition to the data submitted in support of registration, the ECOTOX (ECOTOXicity) 

database was used to identify additional toxicity data from the open literature. The ECOTOX 

database is a user-friendly, publicly-available, quality-assured, comprehensive tool for locating 

toxicity data from the open literature and is maintained by EPA Mid-Atlantic Ecology Division. 

More information on ECOTOX can be found at: http://www.epa.gov/ecotox. Research papers 

are thoroughly screened using standard procedures before being accepted into ECOTOX thereby 

ensuring consistent, high quality information. For orthosulfamuron, no studies were identified in 

ECOTOX. 

3.4.1. Aquatic Effects Characterization 

The most sensitive acute and chronic effects measurement endpoints associated with 

orthosulfamuron exposure to freshwater and estuarine/marine species are summarized in Table 

3.13. All effects measurement endpoints used to assess the potential risks of orthosulfamuron 

exposure are obtained from studies using technical grade orthosulfamuron or orthosulfamuron 

formulated product. No studies using orthosulfamuron degradates were submitted. Appendix E 

provides a more detailed summary of all aquatic toxicity studies available for estimating and 

characterizing potential risks associated with orthosulfamuron use on rice. 

Results of acute toxicity studies in freshwater fish, freshwater invertebrates, estuarine/marine 

fish, and estuarine/marine invertebrates (shrimp and crustaceans) indicate that orthosulfamuron 

is not more than slightly toxic on an acute basis. Acute toxicity values for freshwater and 

estuarine/marine species indicate that estuarine/marine fish are similarly sensitive to orthosulfamuron. For orthosulfamuron, no sublethal effects were observed in freshwater or 

marine/estuarine fish during acute exposures. No acute toxicity studies of orthosulfamuron 

formulations were available for freshwater fish or invertebrates or estuarine/marine fish or 

invertebrates. 

Chronic toxicity studies are available for freshwater fish and invertebrates and estuarine/marine 

invertebrates. There were some effects of orthosulfamuron on survival in the chronic toxicity 

studies although lowest effect levels were associated with decreased growth. In freshwater fish, 

the only chronic effect was a reduction in dry weight in fathead minnow observed during a 

33-day chronic toxicity study. In freshwater invertebrates, effects on growth and first-generation 

survival were observed in a 21-day life-cycle toxicity study with the water flea. 

28
Results of acute toxicity studies of orthosulfamuron formulations in freshwater and marine algae 

and aquatic macrophytes indicate that orthosulfamuron is highly toxic to very highly toxic to 

aquatic plants. 

Table 3.13. Orthosulfamuron Toxicity Measurement Endpoints for Aquatic Organisms. 

Exposure 

Scenario Species 

Exposure 

Duration Toxicity Reference Value 

Reference 

(Classification) 

Freshwater Fish 

Acute Rainbow trout 96 hours LC50 >122 mg a.i./L MRID 46219042 

(Acceptable) 

Chronic Fathead 

minnow 

33 days NOAEC (dry weight) = 6.1 mg a.i./L MRID 46578953 

(Acceptable) 

Freshwater Invertebrates 

Acute Water flea 48 hours EC50 >97.3 mg a.i./L 

(mortality/immobility) 

MRID 46219044 

(Acceptable) 

Chronic Water flea 21 days NOAEC (total length) = 6.5 mg a.i./L MRID 46578956 

(Acceptable) 

Estuarine/Marine Fish 

Acute Sheepshead 

minnow 

96 hours LC50 >123 mg a.i./L MRID 46578951 

(Acceptable) 

Chronic No studies were submitted 

Estuarine/Marine Invertebrates 

Acute Eastern oyster 96 hours EC50 >97 mg a.i./L MRID 46578957 

(Acceptable) 

Acute Mysid shrimp 96 hours LC50 >122 mg a.i./L MRID 46578952 

(Acceptable) 

Chronic Mysid shrimp 29 days NOAEC = 27 mg a.i./L MRID 46578954 

(Supplemental) 

Aquatic Plants 

Macrophytes Duckweed 7 days EC50 (frond number) = 0.0007 mg 

a.i./L 

NOAEC = 0.00026 mg a.i./L 

MRID 46578939 

(Acceptable) 

Freshwater 

Algaea 

Navicula 

pelliculosa 

96 hours EC50 (biomass) = 0.8 mg a.i./L 

NOAEC = 0.28 mg a.i./L 

MRID 46578935 

(Supplemental) 

Marine 

Algaea 

Skeletonema 

costatum 

96 hours EC50 (biomass) = 0.08 mg a.i./L 

NOAEC = 0.021 mg a.i./L 

MRID 46578936 

(Supplemental) 

29
3.4.1.1 Aquatic Animal Species 

3.4.1.1.a. Aquatic Animals: Acute Effects 

Freshwater Fish 

The acute toxicity of technical grade orthosulfamuron to freshwater fish was evaluated in two 

species, with 96-hour LC50 values of >122 mg a.i./L in rainbow trout (MRID 46219042) and 

>142 mg a.i./L in bluegill sunfish (MRID 46219043). No mortalities were observed in controls 

or treated groups for both studies. Based on these results, orthosulfamuron is categorized as 

practically nontoxic to freshwater fish on an acute exposure basis. Taking the most conservative 

approach, the lowest 96-hour LC50 of >122 mg a.i./L in rainbow trout is used to evaluate acute 

toxicity for freshwater vertebrates. 

No studies assessing the acute toxicity of orthosulfamuron formulations or degradates in 

freshwater fish were submitted. 

Freshwater Invertebrates 

An acute toxicity study of technical grade orthosulfamuron in the water flea (MRID 46219044) 

yielded 48-hour EC50 and NOAEC values (where immobility was interpreted as lethality) of 

>97.3 mg a.i./L and 47.0 mg a.i./L, respectively, indicating that orthosulfamuron is classified as 

slightly toxic to freshwater invertebrates on an acute exposure basis. The 48-hour mortality was 

20% in the 97.3 mg a.i./L group (highest concentration tested). The EC50 of >97.3 mg a.i./L for 

mortality and immobility in the water flea will be used to assess the acute risk to freshwater 

invertebrates. 

An acute toxicity study of technical grade orthosulfamuron in crayfish (MRID 46578955) 

yielded 96-hour LC50 and the NOAEC values (both for mortality and sublethal effects) of >129 

and 129 mg a.i./L, respectively, indicating that orthosulfamuron was practically nontoxic to the 

crayfish on an acute basis. Although the latter study was not conducted in a U.S. EPArecommended species for toxicity testing with freshwater invertebrates and guidelines do not 

exist for this species, the study is scientifically sound and it provides support for the toxicity 

category established in the study in the water flea (MRID 46219044). 

No acute toxicity studies of orthosulfamuron formulations or degradates in freshwater 

invertebrates were submitted. 

Estuarine/Marine Fish 

The acute toxicity of technical grade orthosulfamuron to estuarine/marine fish was evaluated in 

the sheepshead minnow (MRID 46578951). The study reported a 96-hour LC50 >123 mg a.i./L, 

indicating that orthosulfamuron was practically nontoxic to estuarine/marine fish on an acute 

exposure basis. No sublethal effects were observed in sheepshead minnow exposed up to 123 

mg a.i./L. The 96-hour LC50 of >123 mg a.i./L in sheepshead minnow will be used to evaluate 

the acute toxic exposure of estuarine/marine fish to orthosulfamuron. 

30
No acute toxicity studies of orthosulfamuron formulations or degradates in estuarine/marine fish 

were submitted. 

Estuarine/Marine Invertebrates 

Acute toxicity tests with estuarine/marine invertebrates exposed to technical grade orthosulfamuron were conducted in eastern oyster (MRID 46578957) and mysid shrimp (MRID 

46578952). No effect on shell deposition or increased mortality were observed in an acute 

toxicity (96-hour) test in the eastern oyster exposed to orthosulfamuron TGAI, yielding a 

96-hour EC50 >97 mg a.i./L. These results indicate that orthosulfamuron is characterized as 

slightly toxic to estuarine/marine mollusks. An acute toxicity study of orthosulfamuron in the 

mysid shrimp reported a 96-hour LC50 >122 mg a.i./L, indicating that orthosulfamuron is 

practically nontoxic to estuarine/marine invertebrates on an acute exposure basis; no sublethal 

effects were observed. EFED will use the EC50 value of >97 mg a.i./L to assess acute risk to 

estuarine/marine mollusks and the LC50 value of >122 mg a.i./L to assess acute risk to 

estuarine/marine shrimp. 

No acute toxicity studies of orthosulfamuron formulations or degradates in estuarine/marine 

invertebrates were submitted. 

3.4.1.1.b. Aquatic Animals: Chronic Effects 

Freshwater Fish 

A 33-day, early life-stage toxicity study of orthosulfamuron in fathead minnow was submitted by 

the registrant to establish the chronic toxicity of orthosulfamuron to freshwater fish (MRID 

46578953). Fish were monitored for embryo survival, larval survival, terminal length, dry 

weight, wet weight, and clinical signs of toxicity. The reported NOAEC and LOAEC values of 

6.1 and 13 mg a.i./L, respectively, were based on decreased dry weight measurements, the only 

endpoint affected. The 33-day NOAEC value of 6.1 mg a.i./L for sublethal effects on growth 

will be used to assess the risk of chronic exposure of freshwater fish to orthosulfamuron. 

No chronic toxicity studies of orthosulfamuron formulations or degradates in freshwater fish 

were submitted. 

Freshwater Invertebrates 

A 21-day life-cycle toxicity study with orthosulfamuron in the water flea was submitted by the 

registrant to establish the chronic toxicity of orthosulfamuron to freshwater invertebrates (MRID 

46578956). First-generation survival, reproduction, total length, dry weight, and sublethal signs 

of toxicity were assessed. NOAEC and LOAEC values of 6.5 and 14 mg a.i./L, respectively, 

were established based on reductions in mean total length. In addition, first-generation survival 

was reduced at the highest concentration tested (EC50 >105 mg a.i./L; LOAEC = 105 mg a.i./L; 

NOAEC = 52 mg a.i./L). Reproduction and dry weight were not affected at any concentration 

tested. The NOAEC of 6.5 mg a.i./L (effect on total length) will be used to assess chronic risk of 

exposure of aquatic invertebrates to orthosulfamuron. 

31
No chronic toxicity studies of orthosulfamuron formulations or degradates in freshwater aquatic 

invertebrates were submitted. 

Estuarine/Marine Fish 

No chronic toxicity tests in estuarine/marine fish with orthosulfamuron, formulations, or 

degradates were submitted. 

Estuarine/Marine Invertebrates 

One life-cycle (29-day) toxicity study in the mysid shrimp was submitted to establish the chronic 

toxicity of orthosulfamuron to estuarine/marine invertebrates (MRID 46578954). NOAEC and 

LOAEC values of 27 and >27 mg a.i./L, respectively, were established for orthosulfamuron 

TGAI based on the absence of effects on mortality, reproduction, or growth after 29 days. The 

NOAEC of 27 mg a.i./L will be used to characterize chronic risk to estuarine/marine 

invertebrates exposed to orthosulfamuron. 

No chronic toxicity studies of orthosulfamuron formulations or degradates in estuarine/marine 

invertebrates were submitted. 

Benthic Organisms 

No toxicity studies of orthosulfamuron TGAI, formulations, or degradates in benthic organisms 

were submitted. 

3.4.1.1.c. Aquatic Animals: Sublethal Effects 

Freshwater Fish 

In addition to lethality endpoints, sublethal effects of orthosulfamuron TGAI exposure were 

assessed in acute toxicity studies in rainbow trout (MRID 46219042) and bluegill sunfish (MRID 

46219043) and in a chronic toxicity study in fathead minnow (MRID 46578953). No signs of 

sublethal toxicity were observed in acute toxicity studies, with NOAEC values in rainbow trout 

and bluegill sunfish of 122 mg a.i./L and 142 mg a.i./L, respectively. The only sublethal effect 

observed in the chronic exposure study in fathead minnow was a reduction in dry weight 

(NOAEC = 6.1 mg a.i./L; LOAEC = 13 mg a.i./L) (MRID 46578953). No effects on embryo 

survival, larval survival, terminal length, wet weight, or clinical signs of toxicity were observed. 

Freshwater Invertebrates 

Sublethal effects of acute orthosulfamuron TGAI exposure were assessed in a study of the water 

flea (MRID 46219044) and crayfish (MRID 46578955). No sublethal effects were observed in 

either study, with NOAEC values for water flea and crayfish of >97.3 mg a.i./L and 129 mg 

a.i./L, respectively. 

Sublethal effects in the total length and dry weight were observed in a 21-day life-cycle toxicity 

study with water flea (MRID 46578956). NOAEC and LOAEC values of 6.5 and 14 mg a.i./L, 

respectively, were established based on reductions in mean total length (the most sensitive 

endpoint). Reproduction and dry weight were not affected at any of the doses tested. 

32
Estuarine/Marine Fish 

No acute sublethal effects were observed in sheepshead minnow exposed to orthosulfamuron 

TGAI at 123 mg a.i./L. Thus, a NOAEC = 123 mg a.i./L for acute sublethal effects was reported 

(MRID 46578951). 

No chronic toxicity studies in estuarine/marine fish with orthosulfamuron were submitted, thus, 

no information is available regarding the sublethal effects of chronic exposure of 

estuarine/marine fish to orthosulfamuron. 

Estuarine/Marine Invertebrates 

No sublethal effects were observed in acute toxicity studies of orthosulfamuron TGAI in the 

eastern oyster (MRID 46578957) or mysid shrimp (MRID 46578952), yielding 96-hour NOAEC 

values of 97 mg a.i./L and 122 mg a.i./L, respectively. No sublethal effects on survival, growth, 

reproduction, or clinical signs were reported in a life-cycle toxicity study of orthosulfamuron in 

the mysid shrimp (MRID 46578954), yielding NOAEC and LOAEC values of 27 and >27 mg 

a.i./L, respectively. 

Benthic Organisms 

No studies were submitted of orthosulfamuron TGAI, formulations, or degradate toxicity in 

benthic organisms. 

3.4.1.1.d. Aquatic Animals: Field Studies 

Submitted studies for orthosulfamuron did not include aquatic field studies. 

3.4.1.1.e. Plants Inhabiting Aquatic Areas 

Studies were submitted for a freshwater vascular plant (duckweed, Lemna gibba), blue-green 

algae (Anabaena flos-aquae), a freshwater diatom (Navicula pelliculosa), a green algae 

(Pseudokirchneriella subcapitata formerly known as Selenastrum capricornutum), and a marine 

alga (Skeletonema costatum) exposed to the formulated product, IR5878 50WG (water 

dispersible granule formulation) containing approximately 50% orthosulfamuron. 

Orthosulfamuron (TEP) was very highly toxic to duckweed as indicated by reductions in frond 

number observed in two Tier II, 7-day studies. EC50 values of 0.7 μg a.i./L (MRID 46578939) 

and 0.75 μg a.i./L (MRID 46578940) were reported; the associated NOAECs were 0.26 μg a.i./L 

and 0.22 μg a.i./L, respectively. The EC50 value of 0.7 μg a.i./L and the NOAEC of 0.22 is used 

to assess the risk of orthosulfamuron to aquatic macrophytes. 

Tier II acute (96-hour) toxicity tests in freshwater nonvascular plants (MRID 46578931; 465789­

34; 46578959; 46578937; 46578938; 46578932; 46578935) resulted in 96-hour EC50 values 

ranging from 0.8 mg a.i./L for reductions in biomass in Navicula pelliculosa (MRID 46578935) 

to >54 mg a.i./L for the absence of effects on cell density, growth rate, or biomass in Navicula 

pelliculosa (MRID 46578932). The lowest EC50 value of 0.8 mg a.i./L and the associated 

33
NOAEC of 0.28 mg a.i./L for reductions in biomass in Navicula pelliculosa are used to assess 

the risk of orthosulfamuron to freshwater algae. Importantly, this study incorporated an adjuvant 

into the treatments to simulate a possible tank mixture for orthosulfamuron. The adjuvant 

control for this study showed high inhibition indicating an effect due to the adjuvant alone. 

Because it is likely that an adjuvant would be used to improve the efficacy of orthosulfamuron, 

toxicity endpoints based on these studies were considered suitable for risk assessment purposes 

although some uncertainty exists concerning the relative toxicity of the adjuvant and the active 

ingredient. 

Tier II acute (96-hour) toxicity tests in the marine diatom (MRID 46578936; 46578933) resulted 

in EC50 values from 0.08 mg a.i./L for reductions in biomass in Skeletonema costatum (MRID 

465789-36) to 12 mg a.i./L for reductions in biomass in Skeletonema costatum (MRID 

46578933). The EC50 value of 0.08 mg a.i./L and the associated NOAEC of 0.021 mg a.i./L for 

reductions in biomass in Skeletonema costatum (MRID 46578936) will be used to assess the risk 

of orthosulfamuron to marine plants. Similar to the study on Navicula pelliculosa described in 

the previous paragraph, an adjuvant was also added for this study on Skeletonema costatum, 

likely simulating a tank mixture for orthosulfamuron. Again, since it is likely that an adjuvant 

would be used to improve the efficacy of orthosulfamuron, use of these toxicity endpoints is 

considered reasonable for this assessment. 

Based on the data, orthosulfamuron is classified as very highly toxic to aquatic plants on an acute 

exposure basis. 

3.4.2. Terrestrial Effects Characterization 

The most sensitive acute and chronic toxicity reference values associated with orthosulfamuron 

exposure to mammals, birds, and terrestrial plants are summarized in Table 3.14. 

An acute oral toxicity study in rats indicates that orthosulfamuron is practically non-toxic to rats 

on an acute oral exposure basis with an LD50 > 5000mg/kg (MRID 46219019). 

A chronic, two-generation reproductive study in rats showed that orthosulfamuron resulted in 

some toxicological effects. The most sensitive endpoints were increased incidence of kidney 

lesions in adult rats and decreased motor activity in F1 males; the NOAEC for both endpoints is 

88.6 mg/kg/day. 

Studies of acute oral (dose-based) toxicity in mallard duck and bobwhite quail indicate that 

orthosulfamuron is not more than slightly toxic to mallard duck or bobwhite quail when 

administered a single oral dose. A subacute dietary toxicity study showed that orthosulfamuron 

TGAI is not more than slightly toxic to mallard duck and bobwhite quail on a subacute dietary 

exposure basis. No acute oral or dietary toxicity studies of orthosulfamuron formulations or 

degradates in avian species were submitted. 

No treatment-related effects on adult bird mortality, food consumption, body weight, or 

reproductive parameters and no clinical signs or treatment-related effects in offspring survival or 

34
body weight were observed in chronic studies of reproductive toxicity of orthosulfamuron in 

mallard duck and bobwhite quail. No chronic toxicity studies of orthosulfamuron formulations 

or orthosulfamuron degradates in avian species were submitted. 

Results of available toxicity studies indicate that orthosulfamuron is practically nontoxic to 

honey bees on an acute contact basis. 

Tier II seedling emergence and vegetative vigor studies with orthosulfamuron formulations 

(49.96% a.i.) in terrestrial plants showed reductions in dry weight (EC25) in both monocots and 

dicots at application rates of 0.0048 lbs a.i./A and 0.00012 lbs a.i./A, respectively. 

Table 3.14. Orthosulfamuron Toxicity Measurement Endpoints for Terrestrial Organisms. 

Exposure 

Scenario 

Species Exposure 

Duration 

Toxicity Reference Value Reference 

(Classification) 

Mammals 

Acute 

(Dose-based) 

Laboratory rat Single oral dose LD50 > 5000 mg a.i./kg bw MRID 46219019 

Acceptable 

Chronic 

(Dietary-based) 

Laboratory rat Two-generation NOAEC = 88.6 mg/kg/day 

NOAEL = 1400 ppm 

MRID 46219033 

Acceptable 

Birds 

Acute 

(Dose-based) 

Bobwhite quail 

and mallard 

duck 

Single oral dose LD50 >1960 mg a.i./kg bw MRID 46260107 

(duck; Acceptable) 

MRID 46260108 

(quail; Acceptable) 

Acute 

(Dietary-based) 

Mallard duck 8-day dietary LC50 >4790 mg a.i/kg diet MRID 46219040 

(Acceptable) 

Chronic 

(Dietary-based) 

Bobwhite quail 

and mallard 

duck 

Avian 

reproduction 

study 

NOAEC = 1280 mg a.i./kg diet MRID 46578949 

(duck; Acceptable) 

MRID 46578950 

(quail; Acceptable) 

Terrestrial Invertebrates 

Acute 

(Contact) 

Honeybee 48-hour LD50 >100 μg a.i./bee MRID 46219046 

(Acceptable) 

Acute 

(Oral) 

Honeybee 48-hour LD50 >109.4 μg a.i./bee MRID 46219046 

(Acceptable) 

Plants – Seedling Emergence 

Monocot Rice Single 

application 

EC25 (dry weight) = 0.078 lbs 

a.i./A 

NOAEC = 0.015 lbs a.i./A 

MRID 46578941 

(Acceptable) 

Dicot Radish Single 

application 

EC25 (dry weight) = 0.040 lbs 

a.i./A 

NOAEC = 0.015 lbs a.i./A 

MRID 46578941 

(Acceptable) 

Plants – Vegetative Vigor 

Monocot Onion Single 

application 

EC25 (dry weight) = 0.0048 lbs 

a.i./A 

NOAEC = 0.00169 lbs a.i./A 

MRID 46578942 

(Supplemental) 

35
Table 3.14. Orthosulfamuron Toxicity Measurement Endpoints for Terrestrial Organisms. 

Exposure 

Scenario 

Species Exposure 

Duration 

Toxicity Reference Value Reference 

(Classification) 

Dicot Carrot Single 

application 

EC25 (dry weight) = 0.00012 lbs 

a.i./A 

NOAEC = <0.000064 lbs a.i./A 

EC05 = 0.000027 lbs a.i./A 

MRID 46578942 

(Supplemental) 

3.4.2.1. Terrestrial Animals 

3.4.2.1.a. Terrestrial Animals: Acute Effects 

Birds 

Acute oral (dose-based) toxicity studies of orthosulfamuron in mallard duck (MRID 46260107) 

and bobwhite quail (MRID 46260108) were submitted. Single oral doses as high as 1960 mg 

a.i./kg body weight did not elicit adverse effects in mallard duck or bobwhite quail, indicating 

that orthosulfamuron TGAI is slightly toxic to mallard duck or bobwhite quail on an acute oral 

basis. Subacute (8-day) dietary toxicity studies in bobwhite quail (MRID 46219041) and mallard 

duck (MRID 46219040) established LC50 values of >4980 mg a.i./kg diet and >4790 mg a.i/kg 

diet, respectively, indicating that orthosulfamuron TGAI is slightly toxic to birds on a subacute 

dietary basis. Study details and results are summarized in Appendix E, Table E-10. The acute 

oral LD50 of >1960 mg a.i./kg body weight in bobwhite quail and mallard duck is used to assess 

risks of acute oral exposure and the subacute dietary LC50 value of >4790 mg a.i/kg diet is used 

to assess risks of acute dietary exposure of birds to orthosulfamuron. 

No acute toxicity studies were submitted for birds exposed to orthosulfamuron formulations or 

degradates. 

Mammals 

An acute oral toxicity study of orthosulfamuron in laboratory rats (Rattus norvegicus) indicated 

that orthosulfamuron is practically non-toxic to rats (MRID 46219019). The estimated LD50 is 

greater than 5000 mg/kg and there were no clinical or sub-lethal signs of toxicity. There were no 

observed sublethal effects in the orthosulfamuron acute oral toxicity study on rats. 

Terrestrial Invertebrates 

An acute contact toxicity study in honey bees using orthosulfamuron yielded a 48-hour contact 

LD50 >100 μg a.i./bee (MRID 46219046), indicating that orthosulfamuron is practically nontoxic 

to honey bees on an acute contact exposure basis. An acute oral toxicity test of orthosulfamuron 

TGAI in honey bees established an acute oral LD50 >109.4 μg a.i./bee (MRID 46219046). Study 

details and results are summarized in Appendix E, Table E-12. 

No acute contact tests in honey bees or other terrestrial invertebrates were submitted for orthosulfamuron formulations or degradates. 

36
3.4.2.1.b. Terrestrial Animals: Chronic Effects 

Birds 

Chronic studies of the reproductive toxicity of orthosulfamuron in mallard duck (MRID 

46578949) and bobwhite quail (MRID 46578950) administered orthosulfamuron TGAI for 

approximately 21 weeks. Study details and results are summarized in Appendix E, Table E-11. 

Results of both studies showed no treatment-related effects on adult bird mortality, food 

consumption, body weight, clinical signs, or reproductive endpoints at the highest dietary 

concentration tested (NOAEC = 1280 mg a.i./kg diet). In addition, no clinical signs or 

treatment-related effects in offspring survival or body weight were observed at the highest 

dietary concentration tested in these studies (1280 mg a.i/kg diet). The NOAEC of 1280 mg 

a.i/kg diet is used to assess the chronic risk of orthosulfamuron in avian species. 

No chronic toxicity studies of orthosulfamuron formulations or degradates in avian species were 

submitted. 

Mammals 

A chronic, 2-generation toxicity study was conducted to evaluate the potential chronic and 

reproductive effects of orthosulfamuron on laboratory rats, Rattus norvegicus (MRID 46219033). 

The most sensitive endpoints are increased incidence of kidney lesions and decreased motor 

activity. For this screening-level ecological risk assessment, the endpoint related to decreased 

motor activity was used because it is likely protective for reproductive effects. Moreover, 

decreased motor activity for species in the wild could result in a decrease in ability to avoid 

predators, acquire food, or obtain territories or mates. Decreased motor activity was observed in 

F1 males and had an associated NOAEC of 88.6 mg/kg/day (NOAEL = 1400 ppm). 

Terrestrial Invertebrates 

No chronic toxicity studies were submitted for orthosulfamuron TGAI, formulations, or 

degradates in terrestrial invertebrates. 

3.4.2.1.d. Terrestrial Animals: Field Studies 

No field studies were submitted for chronic effects of orthosulfamuron on terrestrial organisms. 

3.4.2.2. Terrestrial Plants 

The effects of the orthosulfamuron formulation, IR5878 50WG (TEP; 49.96% a.i.) on monocots 

(corn, oat, onion, and rice) and dicots (carrot, mung bean, oilseed rape, pea, radish, and soybean) 

were tested in Tier II seedling emergence (MRID 46578941) and vegetative vigor (MRID 

465789-42) studies. 

Results of the Tier II seedling emergence study identify rice as the most sensitive monocot and 

radish as the most sensitive dicot, with decreased dry weight as the most sensitive endpoint 

affected. The NOAEC and EC25 values of 0.015 lbs a.i./A and 0.078 lbs a.i./A, respectively, for 

37
4 

rice, and 0.015 lbs a.i./A and 0.040 lbs a.i./A, respectively, for radish is used to assess the effects 

of exposure to orthosulfamuron on seedling emergence in non-listed and listed terrestrial plants. 

Results of the Tier II vegetative vigor studies identify onion as the most sensitive monocot and 

carrot as the most sensitive dicot, with decreased dry weight as the most sensitive endpoint 

affected. The NOAEC and EC25 values of 0.00169 lbs a.i./A and 0.0048 lbs a.i./A, respectively, 

for onion, and the EC05 and EC25 values 0.000027 lbs a.i./A and 0.00012 lbs a.i./A, respectively, 

for carrot are used to assess the effects of exposure to orthosulfamuron on vegetative vigor in 

non-listed and listed terrestrial plants. The NOAEC for carrot is below the lowest tested 

concentrations (<0.000066 lbs a.i./A), hence the EC05 is used to estimate risks to dicotyledonous 

plants. 

Risk Characterization 

Risk characterization is the integration of exposure and effects to estimate the potential 

ecological risk from the proposed use of orthosulfamuron on rice. The goal of risk 

characterization is to provide an estimate and description of potential adverse effects and to 

articulate risk assessment assumptions, limitations, and uncertainties in order to synthesize an 

overall risk conclusion. 

4.1 Risk Estimation – Integration of Exposure and Effects Data 

Toxicity data and exposure estimates are used to evaluate the potential for adverse ecological 

effects on non-target species. For this screening-level assessment of orthosulfamuron, the 

deterministic risk quotient method is used to provide a metric of potential risks. The RQ is a 

comparison of exposure estimates to toxicity endpoints; estimated exposure concentrations are 

divided by acute and chronic toxicity values. The resulting unitless RQs are compared to the 

Agency’s LOCs, which are the Agency’s interpretive policy such that when LOCs are exceeded, 

the need for regulatory action should be considered. These criteria are used to indicate when the 

use of a pesticide, as directed on the label, has the potential to cause adverse effects on nontarget organisms. 

4.1.1 Non-target Aquatic Organisms 

The surface water EEC (peak and chronic value) from the Interim Rice Model was compared to 

acute and chronic toxicity endpoints to derive acute and chronic RQs for non-target aquatic 

organisms. Acute and chronic RQs for fresh- and saltwater organisms are summarized in Tables 

4.1 and 4.2, respectively. 

For aquatic vascular and non-vascular plants, peak EECs are compared to acute EC50 values to 

derive acute non-listed species RQs. In addition, peak EECs are also compared to NOAEC or 

EC05 values for aquatic plants to derive listed species RQs. All RQs for aquatic plants are 

presented in Table 4.3. 

4.1.1.1 Freshwater Fish and Invertebrates 

38
The RQs did not exceed non-listed or listed species acute or chronic risk LOCs for freshwater 

fish, aquatic-phase amphibians, or freshwater invertebrates. Table 4.1 lists the RQs for 

freshwater fish, aquatic-phase amphibians, and freshwater invertebrates potentially exposed to 

orthosulfamuron associated with the proposed use on rice. 

Table 4.1. Risk Quotients for Freshwater Fish and Invertebrates Exposed to 

Orthosulfamuron for Use on Rice. 

Use 

Annual 

Application 

Rate 

EECs 

(ppb) 

Fish and Amphibian RQs 

LC50 = 122000 

NOAEC = 6100 

Invertebrate RQs 

LC50 = 97300 

NOAEC = 6500 

Peak Acute Chronic Acute Chronic 

Rice 0.069 lbs a.i./A 38.6 <0.01 <0.01 <0.01 <0.01 

4.1.1.2 Estuarine/Marine Fish and Invertebrates 

The RQs did not exceed non-listed or listed species acute or chronic risk LOCs for 

estuarine/marine fish or invertebrates. Table 4.2 lists the RQs for estuarine/marine fish and 

invertebrates potentially exposed to orthosulfamuron associated with the proposed use on rice. 

Table 4.2. Risk Quotients for Estuarine/Marine Fish and Invertebrates Exposed 

to Orthosulfamuron. 

Use 

Application 

Rate 

lbs ai/A 

(1 application) 

EECs 

(ppb) 

Fish RQs 

LC50 = 123000 ppb 

NOAEC = N/A 

Invertebrate RQs 

LC50 = 122000 ppb 

NOAEC = 27000 ppb 

Mollusk RQs 

EC50= 97000 

ppb 

Peak Acute Acute Chronic Acute 

Rice 0.069 38.6 <0.01 <0.01 <0.01 <0.01 

4.1.1.3 Aquatic Plants 

The non-listed species acute risk LOC is exceeded for aquatic vascular plants (RQ = 55). For 

listed species, the acute risk LOC of 1.0 is exceeded for aquatic vascular plants and saltwater 

non-vascular plants with RQs of 148 and 1.8, respectively. The risk profile for aquatic plants 

seems to be driven by the higher toxicity of orthosulfamuron to vascular plants. Table 4.3 lists 

the RQs for aquatic vascular and non-vascular plants potentially exposed to orthosulfamuron. 

Table 4.3. Risk Quotients for Fresh- and Saltwater Plants Exposed to 

Orthosulfamuron for Use on Rice. 

Use 

Total 

Seasonal 

Application 

Rate 

lbs ai/A 

EECs 

(ppb) 

Freshwater 

Vascular Plant 

RQs 

EC50 = 0.7 ppb 

NOAEC = 0.26 ppb 

Freshwater 

Non-Vascular 

Plant RQs 

EC50 = 800 ppb 

NOAEC = 280 ppb 

Saltwater 

Non-Vascular 

Plant RQs 

EC50 = 80 ppb 

NOAEC = 21 ppb 

39
Peak Acute Acute 

Listed 

Species 

Acute 

Acute 

Listed 

Species 

Acute 

Acute 

Listed 

Species 

Rice 0.069 38.6 55* 148* 0.05 0.14 0.48 1.84* 

*Exceeds aquatic plant acute risk LOC (RQ > 1.0); applies to non-listed and listed species 

4.1.2 Non-target Terrestrial Organisms 

The EEC values for estimated exposure to terrestrial animals for spray applications of 

orthosulfamuron were derived using the Kenaga nomogram, as modified by Fletcher (Fletcher et 

al., 1994). Exposure estimates were generated for the proposed label use of orthosulfamuron on 

rice with a single application of the water dispersible granule formulation of 0.069 lbs a.i./A. 

The application rate represents the maximum as specified by the proposed label. Risk quotients 

for the dry granule formulation of orthosulfamuron were estimated using the LD50/ft

2

 method 

with an application rate of 0.067 lbs a.i./A. The RQs are based on these maximum exposure 

estimates and the lowest available toxicity endpoints for a given taxa and exposure duration (e.g. 

acute avian). Specifically for this assessment, the lowest LD50 and NOAEC values were used for 

birds and mammals. Note again that data from avian toxicity studies were used to represent 

reptiles and terrestrial-phase amphibians. 

Acute and chronic RQs for birds, reptiles, and terrestrial-phase amphibians are presented in 

Tables 4.4 and 4.5, respectively, acute and chronic RQs for mammals are summarized in Tables 

4.6, 4.7, and 4.8, respectively. 

4.1.2.1 Birds 

No RQs exceed non-listed or listed species acute risk LOCs with RQs <0.01. Table 4.4 lists the 

avian dose-based acute RQs for proposed use of the dry granule and water dispersible granule 

formulation of orthosulfamuron on rice. For the dry granule formulation, since an LD50 was not 

generated, it is difficult to estimate the amount of granules that need to be consumed to elicit a 

toxicological response. However, assuming that effects occur at the highest tested concentration 

of 1960 mg/kg bw for the mallard duck, a 1.0 kg bird would have to consume about 0.007 lbs of 

orthosulfamuron, which is equivalent to about %10 of the number of granules applied on a given 

acre. Because it is likely that a 1.0 kg bird would have to consume significantly more than this 

due to low orthosulfamuron toxicity and that dry granule consumption would be restricted to 

embankments and paddy divisions, adverse effects to birds associated with consumption of 

granules is low. 

Table 4.4. Avian Dose-Based Acute RQ Values for Orthosulfamuron Use on Rice; Based on 

Bobwhite Quail LD50 >1960 mg/kg bw and Upper-Bound Kenaga Residues. 

Use 

Application 

Rate 

lbs ai/A 

Body 

Weight 

(g) 

RQs for 

Granular 

Avian Acute RQs for Specified Food Items 

Short Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

Fruits/Pods/ 

Seeds/ 

Large Insects 

Rice 0.069 20 <0.01 <0.01 <0.01 <0.01 <0.01 

100 <0.01 <0.01 <0.01 <0.01 <0.01 

40
1000 <0.01 <0.01 <0.01 <0.01 <0.01 

Acute Risk LOCs; non-listed species RQ>0.5 and listed species RQ>0.1 

No acute or chronic LOCs are exceeded. Acute and chronic dietary-based RQs are <0.01. Table 

4.5 lists the acute and chronic dietary-based avian RQs for proposed use of orthosulfamuron. 

Table 4.5. Acute and Chronic Dietary-Based RQ Values for Birds Exposed to 

Orthosulfamuron Based on Upper-Bound Kenaga Values. 

Use 

Application Rate 

lbs ai/A 

1 application 

Food Items 

EEC 

(mg/kg) 

Acute 

Dietary RQ 

Chronic 

Dietary RQ 

Rice 

0.069 

Short Grass 16.56 <0.01 0.01 

Tall Grass 7.59 <0.01 0.01 

Broadleaf plants / small insects 9.32 <0.01 0.01 

Fruits, pods, seeds, large insects 1.04 <0.01 <0.01 

Acute Risk LOCs; non-listed species RQ>0.5 and listed species RQ>0.1 

Chronic Risk LOC; RQ>1.0 for non-listed and listed species 

4.1.2.2 Mammals 

No acute risk LOCs are exceeded with RQs ranging from <0.01 to 0.01. Table 4.6 lists the 

dose-based acute mammalian RQs for proposes use of both the dry granule and water dispersible 

granule formulations of orthosulfamuron. 

Table 4.6. Mammalian Dose-Based Acute RQ Values for Uses of Orthosulfamuron; Based 

on Rat LD50 >5000mg/kg bw and Upper-Bound Kenaga Residues. 

Use 

Applicati 

on Rate 

lbs ai/A 

Body 

Weight 

(g) 

RQs for 

Granular 

Mammalian Acute RQs for Specified Food Items 

Short 

Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

Fruits/Pods/ 

Lg Insects Seeds 

Rice 

0.069 

15 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 

35 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 

1000 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 

Acute Risk LOCs; non-listed species RQ>0.5 and listed species RQ>0.1 

The non-listed and listed species chronic risk LOC (RQ>1.0) is not exceeded for the proposed 

use of orthosulfamuron on rice for mammals (RQs range from <0.01-0.08). Table 4.7 lists the 

dose-based chronic mammalian RQs for proposed uses of orthosulfamuron. 

Table 4.7. Mammalian Dose-Based Chronic RQ Values for Uses of Orthosulfamuron; 

Based on Rat NOAEL of 88.6 mg/kg bw and Upper-Bound Kenaga Residues. 

Use 

Application 

Rate 

lbs ai/A 

Body 

Weight 

(g) 

Mammalian Acute RQs for Specified Food Items 

Short Grass Tall Grass 

Broadleaf 

Plants/Small 

Insects 

Fruits/Pods/ 

Lg Insects Seeds 

Rice 0.069 15 0.08 0.04 0.05 0.01 <0.01 

35 0.07 0.03 0.04 <0.01 <0.01 

41
1000 0.04 0.02 0.02 <0.01 <0.01 

Bolded values exceed the chronic risk LOC (RQ>1.0) for non-listed and listed mammalian species 

The RQs do not exceed the chronic risk LOCs for any proposed uses of orthosulfamuron with 

RQs <0.01. Table 4.8 lists chronic dietary-based mammalian RQs for proposed uses of 

orthosulfamuron. These RQs are based on effects levels associated with chemical concentrations 

in feed. 

Table 4.8. Chronic Dietary-Based RQ Values for Mammals Exposed to 

Orthosulfamuron Based on Upper-Bound Kenaga Values. 

Use 

Application Rate 

lbs ai/A Food Items 

EEC 

(mg/kg) Chronic Dietary RQ 

Rice 

0.069 

Short Grass 16.56 0.01 

Tall Grass 7.59 <0.01 

Broadleaf plants / small insects 9.32 0.01 

Fruits, pods, seeds, large insects 1.04 <0.01 

The chronic risk LOC for non-listed and listed mammalian species is RQ>1.0 

4.1.2.3 Terrestrial Plants 

Table 4.9 lists the terrestrial and semi-aquatic plant RQs for proposed uses of orthosulfamuron 

based on results from TerrPlant v. 1.2.1 and the Interim Rice Model. The analysis indicates that 

for dicotyledonous plants adjacent to orthosulfamuron treated paddies, the RQ exceeds the acute 

risk LOC (RQ > 1.0) as a result of drift. Alternatively, RQs based on tail water release for semiaquatic plants did not exceed the non-listed species acute risk LOC for either monocotyledonous 

or dicotyledonous plants although the RQ for semi-aquatic dicots is very close to the LOC (RQ = 

0.92). The difference in risk estimates for the two scenarios is in part due to the fact that results 

from the vegetative vigor study are used for risk estimates associated with drift; the other 

scenario incorporates toxicity values from the seedling emergence tests. For listed species, RQs 

exceeded the listed species acute risk LOC for semi-aquatic monocots and dicots. In addition, 

RQs exceeded the listed species acute risk LOC associated with spray drift for both monocots 

(aerial applications only) and dicots (ground and aerial spray). Although EECs were based on 

the application rate for the water dispersible granule formulation, results for semi-aquatic plant 

species can be applied to the dry granule formulation of orthosulfamuron as well since 

application rates for the two formulations are very similar. 

Table 4.9. RQ Values for Terrestrial and Semi-Aquatic Plants Exposed to 

Orthosulfamuron Based on Proposed Use on Rice of 0.069 lbs a.i./A. 

Plant 

Toxicity Measurement 

Endpoint 

RQs Based on Tier II Seedling Emergence and 

Vegetative Vigor Studies 

Semi-Aquatic Drift 

Tail water release Ground 

spray 

Aerial 

spray 

Non-Listed Plant Species (Based on EC25) 

42
Monocot 0.078 lbs ai./A Seed Emerg 

 0.0048 lbs ai/A Veg Vig 0.47 0.14 0.72 

Dicot 0.04 lbs ai/A Seed Emerg 

0.00012 lbs ai/A Veg Vig 

0.92 5.75 28.8 

Listed Plant Species (Based on NOAEC or EC05) 

Monocot 0.015 lbs ai/A Seed Emerg 

0.00169 lbs ai/A Veg Vig 2.45 0.41 2.04 

Dicot 0.015 lbs ai/A Seed Emerg 

0.000027 lbs ai/A Veg Vig 2.45 25.56 127.78 

Bolded values exceed non-listed or listed plant acute risk LOC (RQ>1.0). 

4.2 Risk Description 

The available data on the fate and effects of orthosulfamuron are sufficient to address the risk 

hypothesis for all taxa, as specified in the Overview Document (USEPA, 2004). The results of 

this screening-level risk assessment indicate some components of the risk hypothesis are 

accepted; there is potential for direct adverse acute effects for freshwater non-vascular plants, 

estuarine/marine non-vascular plants, and terrestrial and semi-aquatic plants, particularly dicots. 

These results are based on modeled spray application rates of 0.069 lbs a.i./A per year, which 

represents the proposed use of orthosulfamuron applied at the maximum label rate and is likely 

similar to the slightly lower rate of 0.066 lbs a.i./A per year associated with the dry granule 

formulation. 

4.2.1 Risk to Aquatic Organisms 

Aquatic EECs were based on the Interim Rice Model and represent peak or chronic values of 

orthosulfamuron that may be present in rice paddy tail water. The results of the screening-level 

analysis indicate that the potential of orthosulfamuron to adversely affect aquatic animals is low. 

Risk quotients for fresh- and saltwater fish and invertebrates are all below 0.01; no acute or 

chronic risk LOCs are exceeded. However, orthosulfamuron has the potential to adversely affect 

aquatic vascular plant species since the RQ for non-listed vascular plants is 55. Alternatively, 

orthosulfamuron is less toxic to non-vascular plants; RQs for non-listed non-vascular plants 

ranged from 0.05 to 0.48 and as such are below the acute risk LOC. 

4.2.1.1 Freshwater Fish 

Acute and chronic RQs for freshwater fish are below acute and chronic risk LOCs, indicating 

that a potential for direct effects to freshwater fish is low for the use of orthosulfamuron on rice. 

The freshwater fish toxicity data indicate that orthosulfamuron and degradates are slightly to 

practically non-toxic to tested species, which partly explains why RQ values were below the 

LOCs. Extrapolation to other freshwater fish is uncertain. In all likelihood, more sensitive 

species exist but given the low potential for adverse effect to tested species, the potential for 

adverse effects on freshwater fish or aquatic-phase amphibians is believed to be low. 

4.2.1.2 Freshwater Invertebrates 

43
Acute and chronic RQs for freshwater invertebrates are below acute and chronic risk LOCs, 

indicating a low potential for direct adverse effects to freshwater invertebrates for the use of 

orthosulfamuron on rice. 

The freshwater invertebrates’ toxicity data indicate that orthosulfamuron is slightly to practically 

non-toxic to tested species, which partly explains why RQ values were below the LOCs. 

Extrapolation to other freshwater invertebrates is uncertain. In all likelihood, more sensitive 

species exist but given the low potential for adverse effects based on tested species, the potential 

for adverse effects on other freshwater invertebrates is expected to be low. 

4.2.1.3 Saltwater Fish 

The potential for adverse effects including acute mortality for estuarine/marine fish is low, based 

on the results of the screening assessment; acute RQs for rice are below the acute risk LOC. No 

chronic estuarine/marine fish toxicity data were submitted for orthosulfamuron, however, given 

the low potential for acute adverse effects and the low potential for chronic effects in freshwater 

fish species, the potential for chronic effects in saltwater fish species is presumed to be low. 

4.2.1.4 Saltwater Invertebrates 

Acute and chronic RQs for estuarine/marine invertebrates are below acute risk LOCs, indicating 

that a potential for direct adverse effects to saltwater invertebrates is low for the proposed use of 

orthosulfamuron on rice. 

The saltwater invertebrate toxicity data indicate that orthosulfamuron is slightly to practically 

non-toxic to tested species, which partly explains why RQ values were below the LOCs. 

Extrapolation to other saltwater invertebrates is uncertain. In all likelihood, more sensitive 

species exist but given the low potential for effects to tested species, the potential for adverse 

effects on saltwater invertebrates is expected to be low. 

4.2.1.5 Aquatic Plants 

Based on predicted EECs for the modeled orthosulfamuron use and available toxicity data, LOCs 

are exceeded for non-listed, vascular aquatic plants by a factor of 55X. The relatively high RQs 

for these species are largely due to the very high acute toxicity of orthosulfamuron to vascular 

plant species. In contrast, non-vascular plant acute risk LOCs are not exceeded for the use of 

orthosulfamuron on rice; RQs are 0.05-0.48. 

Aquatic plants are key components to all aquatic ecosystems and provide a multitude of 

ecological functions. They provide food and shelter for a wide variety of aquatic animal species 

and help maintain water quality through temperature modulation, filtration, and oxygen supply. 

Any effects on aquatic plants as a result of orthosulfamuron use could result in significant 

ecosystem-level effects. Most notably, there would likely be a near instant decrease in water 

quality associated with plant decay and depletion of oxygen. In turn, sedimentation would likely 

increase due to decay and a loss in filtering capacity. The depletion of oxygen and increased 

44
siltation could result in widespread fish and invertebrate mortality. The cascade of effects due to 

effects on aquatic plants would pose a risk to any aquatic species near the use area as well as 

terrestrial species that rely on aquatic organisms as food items such as piscivorous birds, 

mammals, or reptiles. 

4.2.2 Risks to Terrestrial Organisms 

4.2.2.1 Birds 

No avian acute or chronic risk LOCs are exceeded for any uses of orthosulfamuron indicating 

that the potential for adverse effects on birds is low. Toxicity studies on orthosulfamuron 

indicated technical grade orthosulfamuron is practically non-toxic to birds on an acute oral 

exposure basis. For the subacute dietary study, orthosulfamuron is classified as slightly toxic 

with an LC50 of 4790 mg/kg feed. Results from the chronic study yielded a NOAEC for 

bobwhite quail exposed to orthosulfamuron of 1280 mg/kg feed, which was the highest exposure 

level tested. Taken as a whole, the risk estimation results and the toxicity data indicate a low 

potential for direct adverse effects to avian species associated with the proposed use of 

orthosulfamuron. However, given the potential for effects on terrestrial and aquatic plant species 

associated with the use of orthosulfamuron, indirect effects on birds are possible. Since plants 

comprise vital components of all habitats and ecosystems, if alterations in the abundance of 

plants or in the composition of habitats (plant community) were to occur as a result of 

orthosulfamuron use, then it is likely that at least some bird species would be affected. Indirect 

effects could range from a decrease or change in forage base or on the availability of suitable 

nesting habitats. 

4.2.2.2 Mammals 

Acute risks to wild mammals were evaluated using a common laboratory rat LD50 values, which 

exceeds the highest tested concentration (>5000 mg/kg bw). Orthosulfamuron is practically nontoxic to mammals on an acute exposure basis. Calculated dose-based RQs for all proposed uses 

of orthosulfamuron on rice are below the acute risk LOC. The low apparent acute toxicity of 

orthosulfamuron and the calculated RQs indicate a low potential for direct adverse effects to 

mammals associated with the use of orthosulfamuron on rice. Similarly, an evaluation of chronic 

risks showed that the dose-based chronic risk LOCs are not exceeded for the proposed use of 

orthosulfamuron on rice. Taken as a whole, the toxicity data and the risk estimates indicate that 

the potential for adverse effects to mammals associated with the use of orthosulfamuron on rice 

is low. However, similar to the potential for indirect effects to birds, the use of orthosulfamuron 

could indirectly affect mammals by altering critical habitat components. An alteration in the 

abundance or composition of plant species in a given habitat could result in an inability to 

acquire necessary energy for survival or alter the use of the habitat in such a way as to disrupt 

normal behaviors (like mating). 

4.2.2.3 Potential Risk to Birds and Mammals: BCF Analysis 

45
A fish bioconcentration study was submitted for orthosulfamuron indicating that 

bioconcentration of orthosulfamuron is unlikely; the highest estimated BCF is 1.14. Risk 

quotients for birds were calculated by comparing estimated orthosulfamuron concentrations in 

fish to the dietary-based NOAEC. For mammals, RQs were calculated using estimates of food 

ingestion rate (USEPA, 1993; Appendix D) and comparing a daily dose to dose-based NOAEL. 

Orthosulfamuron in fish was assumed to be 1.14 times the highest aquatic EEC, which was 46.17 

ppb (0.046 ppm) representing a maximum EEC for rice. This exercise indicates that the 

potential adverse chronic effects to avian and mammalian piscivorous species, is limited since 

chronic RQs are <0.01 for both mammals and birds. Since the acute toxicity values were 

significantly higher than chronic endpoints, there is also a very limited potential for acute risks. 

Hence this analysis indicates that risks to piscivorous birds and mammals associated with the 

proposed use of orthosulfamuron on rice are unlikely. 

4.2.2.4 Plants 

Tier II plant studies demonstrate the potential for orthosulfamuron to affect terrestrial dicot and 

monocot plants. Exposure levels equivalent to a 25% effect level were 0.0048 lbs a.i./A for 

monocots and 0.000012 lbs a.i./A for dicots for the vegetative vigor study. Results from the 

seedling emergence test indicated that a 25% effect level was 0.015 lbs a.i./a for both monocots 

and dicots. Risk quotients for terrestrial plants ranged from 0.14 to 28.8 and for semi-aquatic 

plants RQs ranged from 0.47-0.92. Taken as a whole, the toxicity studies and the RQs indicate a 

potential for adverse effects to terrestrial dicots as a result of exposures to orthosulfamuron. Risk 

quotients for both monocots and dicots exceeded the listed species acute risk LOC for semiaquatic plants and for the drift scenario (RQs ranged from 2.5-128) except for ground spray to 

terrestrial monocots. 

As with any toxicity test, there are uncertainties regarding whether test species adequately 

represent the range of possible sensitivities in the wild. Plants tested are crop plants, typically 

subjected to hundreds of years of human selection. It is likely that some native species are more 

sensitive than commonly used agricultural test species given the tremendous variation and 

number of wild plant species. Tests using a broader range of species may help reduce this 

uncertainty, but a critical review paper McKelvey et al. (2002) suggests that, in general, crop 

testing may be sufficiently protective of most plants. Further supporting this contention is a 

review paper by Clark et al. (2004) which indicated that the current agricultural species used for 

testing are at least as sensitive as non-crop species in 95% of cases evaluated. Importantly, 

however, these authors also point out that there is no one species or endpoint that is consistently 

the most sensitive for all species and that numerous factors can confound comparison of test 

results. Moreover, neither study was a comprehensive review of the relative sensitivity of all (or 

even most) plants so considerable uncertainty still remains concerning the adequacy of test 

species in representing non-test species. In the submitted toxicity tests for orthosulfamuron, 10 

species (4 monocots, 6 dicots) are used to represent all plant species. For orthosulfamuron, the 

EC25 for 3 of the 6 dicot species was low enough that RQs based on these toxicity values exceed 

the acute risk LOC. 

46
There are several uncertainties regarding the use of TerrPlant to assess risk to plants. One is 

whether the default assumption of 5% spray drift (from aerial application) is sufficiently 

protective. Estimates made from actual drift assessments range to higher than 20% for fine 

sprays, which could indicate that risk to plants is underestimated. To gain a better understanding 

of the potential for spray drift to affect terrestrial plants, Tier I AgDRIFT® modeling (v. 2.01) 

was used to determine how far off-field orthosulfamuron levels would remain above the EC25 for 

vegetative vigor of dicotyledonous plants (0.00012 lbs a.i./A). AgDRIFT® utilizes empirical 

data to estimate off-site deposition of aerial and ground applied pesticides, and acts as a tool for 

evaluating the potential of buffer zones to protect sensitive habitats from undesired exposures. 

Assuming the maximum single application rate of 0.069 lbs a.i./A, fine to medium droplet 

size,10 mph winds, and 10 ft application height, plants 550 ft or closer to the treated use area 

may be exposed to levels of orthosulfamuron above the EC25. If droplet size is increased to 

medium-course, plants closer than 275 feet may be exposed to levels of orthosulfamuron above 

the EC25, while the use of course to very course droplet size would result in plants closer than 

180 feet potentially being exposed to orthosulfamuron at levels above the EC25. Alternatively, if 

droplet size were reduced to very fine to fine, the distance from the treated paddy where spray 

drift might exceed the EC25 extends beyond the range that AgDRIFT® calculates (>997 ft). 

Clearly, droplet size has a significant impact on the extent of spray drift. For listed plant species, 

all estimated distances would be even greater. A number of factors other than droplet size can 

significantly impact spray drift including wind speed, height above ground, nozzle size and 

angle, boom width, etc. AgDRIFT® allows for higher tier assessments although these were not 

conducted for orthosulfamuron. More details concerning the specifics and uncertainties of 

AgDRIFT® are available online at www.agdrift.com. 

Exposure to semi-aquatic plants is typically estimated using TerrPlant, which combines exposure 

due to runoff and drift. However, for this assessment, runoff does not apply since 

orthosulfamuron is applied directly to rice paddy water. Exposure estimates for semi-aquatic 

plants were estimated using the Interim Rice Model with no contribution from spray drift since it 

is unlikely that tail water release and spray drift as a result of pesticide application would occur 

at the same time. Uncertainties associated with the Interim Rice Model are discussed elsewhere 

in this chapter (Section 4.3.2.). 

Another uncertainty associated with estimating risks to plants is that current assessment methods 

account for only a single application of the chemical since it is assumed that effects to plants 

would likely manifest after a single application and that toxicological response is less dependent 

on subsequent exposures. It may be difficult to confidently apply this reasoning to all plants 

under all circumstances and hence remains a source of some uncertainty, in general. However, 

for the proposed use of orthosulfamuron, only one application is permitted; if any future 

proposed uses require multiple applications, this source of uncertainty could play an important 

role. 

4.2.2.5 Non-Target Terrestrial Invertebrates 

EFED currently does not estimate risk quotients for terrestrial non-target insects. However, a 

label statement is required to protect foraging honeybees when the LD50 is < 11 μg/bee. Based 

47
on the acute contact toxicity study to honeybees, the LD50 for orthosulfamuron is >200 μg/bee. 

This classifies orthosulfamuron as practically non-toxic to honeybees on an acute contact 

exposure basis. 

4.2.3 Federally Threatened and Endangered (Listed) Species of Concern 

Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2), requires all federal 

agencies to consult with the National Marine Fisheries Service (NMFS) for marine and 

anadromous listed species, or the United States Fish and Wildlife Services (FWS) for listed 

wildlife and freshwater organisms, if they are proposing an "action" that may affect listed species 

or their designated habitat. Each federal agency is required under the Act to insure that any 

action they authorize, fund, or carry out is not likely to jeopardize the continued existence of a 

listed species or result in the destruction or adverse modification of designated critical habitat. 

To jeopardize the continued existence of a listed species means "to engage in an action that 

reasonably would be expected, directly or indirectly, to reduce appreciably the likelihood of both 

the survival and recovery of a listed species in the wild by reducing the reproduction, numbers, 

or distribution of the species" (50 C.F.R. § 402.02). 

To facilitate compliance with the requirements of the Endangered Species Act (subsection 

(a)(2)), the Office of Pesticide Programs has established procedures to evaluate whether a 

proposed registration action may directly or indirectly reduce appreciably the likelihood of both 

the survival and recovery of a listed species in the wild by reducing the reproduction, numbers, 

or distribution of any listed species (USEPA, 2004). After the Agency’s screening level risk 

assessment is conducted, if any of the Agency’s listed species LOCs are exceeded for either 

direct or indirect effects, an analysis is conducted to determine if any listed or candidate species 

may co-occur in the area of the proposed pesticide use or areas downstream or downwind that 

could be contaminated from drift or runoff/erosion. If listed or candidate species may be present 

in the proposed action areas, further biological assessment is undertaken. The extent to which 

listed species may be at risk then determines the need for the development of a more 

comprehensive consultation package as required by the Endangered Species Act. 

The federal action addressed herein is the proposed registration of pesticide products that contain 

the active ingredient orthosulfamuron. Orthosulfamuron is proposed for use on rice. Rice 

production areas are predominantly found in the states of California, Mississippi, Arkansas, 

Louisiana, Texas, and Missouri. However, rice production has been documented in Illinois, 

Florida, Oklahoma and Tennessee although to a lesser degree (National Agricultural Statistical 

Service, 2002). 

4.2.3.1 Action Area 

For listed species assessment purposes, the action area is considered to be the area affected 

directly or indirectly by orthosulfamuron use and not merely the immediate area where 

orthosulfamuron is applied. At the initial screening-level, the risk assessment considers broadly 

described taxonomic groups and so conservatively assumes that listed species within those broad 

48
groups are co-located with the pesticide treatment area. This means that terrestrial plants and 

wildlife are assumed to be located on or adjacent to the treated site and aquatic organisms are 

assumed to be located in a surface water body adjacent to the treated site. The assessment also 

assumes that the listed species are located within an assumed area, which has the relatively 

highest potential exposure to the pesticide, and that exposures are likely to decrease with 

distance from the treatment area. Section 1.0 of this risk assessment presents the proposed 

pesticide use sites that are used to establish initial co-location of species with treatment areas. 

4.2.3.2 Taxonomic Groups Potentially at Risk 

If the assumptions associated with the screening-level action area result in RQs that are below 

the listed species LOCs, a "no effect" determination conclusion is made with respect to listed 

species in that taxa, and no further refinement of the action area is necessary. Furthermore, RQs 

below the listed species LOCs for a given taxonomic group indicate no concern for indirect 

effects on listed species that depend upon the taxonomic group for which the RQ was calculated. 

However, in situations where the screening assumptions lead to RQs in excess of the listed 

species LOCs for a given taxonomic group, a potential for a "may affect" conclusion exists and 

may be associated with direct effects on listed species belonging to that taxonomic group or may 

extend to indirect effects upon listed species that depend upon that taxonomic group as a 

resource. In such cases, additional information on the biology of listed species, the locations of 

these species, and the locations of use sites are considered to determine the extent to which 

screening assumptions regarding an action area apply to a particular listed organism. These 

subsequent refinement steps will consider how this information would impact the action area for 

a particular listed organism and potentially include areas of exposure that are downwind and 

downstream of the pesticide use site. 

Assessment endpoints, exposure pathways, and the conceptual model addressing proposed 

orthosulfamuron uses, and the associated exposure and effects analyses conducted for the 

orthosulfamuron screening-level risk assessment are in Sections 2 to 3. The assessment 

endpoints used in the screening-level risk assessment include those defined operationally as 

reduced survival and reproductive impairment for both aquatic and terrestrial animal species and 

survival, reproduction, and growth of aquatic and terrestrial plant species from both direct acute 

and chronic exposures. These assessment endpoints address the standard set forth in the 

Endangered Species Act requiring federal agencies to ensure that any action they authorize does 

not reduce appreciably the likelihood of both the survival and recovery of a listed species in the 

wild by reducing the reproduction, numbers, or distribution of the species. Risk estimates, RQs, 

integrating exposure and effects are calculated for broad based taxa groups for the screeninglevel risk assessment are presented in Section 4.1. 

Both acute endangered species and chronic risk LOCs are considered in the screening-level risk 

assessment to identify direct and indirect effects to taxa of listed species. This section identifies 

direct effect concerns, by taxa, triggered by exceeding endangered LOCs in the screening level 

risk assessment with an evaluation of the potential probability of individual effects for exposures 

that may occur at the established endangered species LOC. Data on exposure and effects 

collected under field conditions are evaluated to make determinations on the predictive utility of 

49
the direct effect screening assessment findings to listed species. Additionally, the results of a 

screen for indirect effects to listed species, using direct effect acute and chronic LOCs for each 

taxonomic group, is presented and evaluated. 

A description of the potential direct effects associated with exposure to orthosulfamuron for each 

of the taxonomic groups is provided below. Table 4.10 provides a summary of the potential 

direct and indirect effects for federally listed species, including the range of RQ values. 

Table 4.10. Summary of Direct and Indirect Effects for Federally Listed Species. 

Listed Species Taxonomic 

Group of Concern 

Direct Effects RQ Indirect Effects 

Potential Associated Taxa1 

Aquatic vascular plants Acute: growth 148 No 

Non-vascular plants None 0.14 No 

Estuarine/marine nonvascular plants 

Acute: cell density 1.84 No 

Dicot terrestrial plants Acute: plant growth 2.45-128 No 

Monocot terrestrial plants Acute: plant growth 2.04-2.45 No 

Freshwater fish None Yes Aquatic & Terrestrial Plants 

Saltwater fish None Yes Aquatic Plants 

Freshwater invertebrates None Yes Aquatic & Terrestrial Plants 

Estuarine/Marine 

Invertebrates None Yes Aquatic Plants 

Mollusks None Yes Aquatic Plants 

Mammals None Yes Aquatic & Terrestrial Plants 

Birds None Yes Aquatic & Terrestrial Plants 

Terrestrial invertebrates None Yes Aquatic & Terrestrial Plants 1

Associated Taxa refers to those taxa for which there are direct effects that may indirectly affect a listed species 

taxa. 

4.2.3.2.1 Listed Species Direct Effects 

Freshwater Fish and Amphibians 

For the proposed use of orthosulfamuron on rice, acute and chronic LOCs are not exceeded for 

freshwater fish and aquatic phase amphibians with all RQs <0.01. 

Freshwater Invertebrates 

For the proposed use of orthosulfamuron on rice, acute and chronic LOCs are not exceeded for 

freshwater invertebrates with all RQs <0.01. 

Estuarine/Marine Fish 

The listed species acute risk LOCs for estuarine/marine fish are not exceeded for any uses of 

orthosulfamuron when applied at the maximum label rates. Acute RQs for estuarine marine fish 

were all <0.01; chronic RQs were not generated since there was no life-cycle estuarine/marine 

fish toxicity test. 

50
Estuarine/Marine Invertebrates 

The listed species acute risk LOCs are not exceeded for molluskan and non-molluskan 

estuarine/marine invertebrates for the modeled use of orthosulfamuron on rice (RQ<0.01). 

Aquatic Plants 

The listed species acute risk LOCs are exceeded for vascular and saltwater non-vascular aquatic 

plants for the use of orthosulfamuron on rice (RQ = 1.84 and 148), calculated as NOAEC or 

EC05/EEC). Risk quotients are the highest for aquatic vascular plants primarily due to the greater 

sensitivity of vascular plants to orthosulfamuron; vascular plants were approximately 100 and 

1000 times more sensitive compared to salt- and freshwater non-vascular plants, respectively. 

Birds 

The listed species acute and chronic risk LOCs for birds, reptiles, and terrestrial-phase 

amphibians are not exceeded for the use of orthosulfamuron on rice applied at the maximum 

label rates. Both acute and chronic RQs are <0.01. 

Mammals 

Listed species acute risk LOCs (RQ > 0.1) for direct effects of orthosulfamuron on mammals are 

not exceeded for the proposed use of orthosulfamuron on rice; all acute RQs <0.01. Similarly, 

listed species chronic risk LOCs (RQ > 1.0) are not exceeded for the proposed use of 

orthosulfamuron on rice. 

Terrestrial Plants 

Listed species acute risk LOCs (RQ>1.0) for direct effects of orthosulfamuron on semi-aquatic 

plants are exceeded for a single application for the proposed use of orthosulfamuron with RQs = 

2.45 for both monocots and dicots. In addition, for terrestrial plants exposed to orthosulfamuron 

via spray drift, the listed species acute risk LOC is exceeded for dicots from both ground and 

aerial spray and for monocots from aerial spray only. Listed species acute risk LOCs are not 

exceeded for terrestrial plants adjacent to treated areas. 

4.2.3.2.2 Probit Dose-Response Analysis 

Listed Animal Species Probability of Effects on Individuals 

The probability of individual effects at the acute endangered species LOC (RQ = 0.05 which is 

equivalent to 1/20 of the LC50 or EC50) for each major listed species’ taxonomic group and the 

probability of individual effects at estimated acute RQs above the endangered species acute risk 

LOC is provided here. In addition, extrapolation of low probability events such as those 

occurring at the LOC, are associated with a high degree of uncertainty. Since an an LD50 or LC50 

51
could not be estimated for any aquatic or terrestrial animal species and since no estimatd RQs 

exceeded the LOCs, the probit dose-response analysis was not conducted. 

Listed Plant Species Probability of Effects on Individuals 

For plants, a probit dose-response analysis is not conducted since the Tier II plant tests do not 

evaluate mortality (LC50) and instead measures the inhibitory effects of a chemical; therefore it is 

difficult to estimate the probability that an individual will be affected. 

Uncertainties and Assumptions of the Probit Dose-Response Analysis 

Estimates of the probability of affecting individual organisms are based on extrapolation of very 

low probability events and are associated with considerable uncertainty in the resulting 

estimates. To provide a sense of possible probability values, the analysis is also conducted using 

the lower and upper 95% confidence limits of the probit dose-response slope, when available. In 

addition to noting the relatively large uncertainty bounds around the probabilities, care should be 

employed in interpreting these probabilities beyond their intended purpose as an indication of a 

margin of safety, or lack there of, for the endangered species risk estimates based on the 

deterministic risk quotient model. 

4.2.3.2.3 Indirect Effects 

Pesticides have the potential to cause indirect effects to endangered or threatened species by, for 

example, perturbing forage or prey availability, altering the extent of nesting habitat, etc. The 

potential for indirect effects is determined by comparing RQs to the listed and non-listed species 

LOCs. If the RQ exceeds the listed species LOC then there is the potential for indirect effects to 

listed species dependent on those species for which the RQ exceeded the listed species LOC. 

Similarly, if the RQ exceeds the non-listed species LOC there is the potential for indirect effects 

to listed species that are generally dependent on organisms from the taxa for which RQs exceed 

the LOC. 

For aquatic species potentially exposed to orthosulfamuron, RQs exceeded the listed species 

acute risk LOCs to varying degrees for aquatic vascular and non-vascular plants and terrestrial 

and semi-aquatic plants. Aquatic vascular plants had the highest RQs for all uses of 

orthosulfamuron, ranging from 55-148. 

Given the sensitivities of the aquatic plant taxa to orthosulfamuron, indirect effects to listed 

species would be expected most for species dependent on fresh- and saltwater vascular and nonvascular plants based on the results of the above analysis. Because aquatic plants are vitally 

important components of any aquatic ecosystem, indirect effects on a number of aquatic (and 

terrestrial) listed species is possible. The most obvious indirect effects would likely relate 

directly to reductions in food availability or habitat alterations associated with reduced aquatic 

plant and invertebrate biomass. Other, less obvious, indirect effects might include disruptions of 

listed species life cycles if certain life-cycle components are dependent on particular plant or 

invertebrate species. 

52
For terrestrial species, the screening-level analysis indicated that, for the proposed use on rice, 

orthosulfamuron has the potential to cause deleterious effects in exposed terrestrial and semiaquatic plant species (Section 4.1). This suggests potential concern for indirect effects on listed 

organisms dependant upon these plant species as food items or as important habitat components. 

A potential drop in plant biomass associated with orthosulfamuron use, for example, may 

significantly alter habitat suitability. While it is likely that plant communities can be repopulated 

by immigrants and living breeders after the use of pesticides, if the habitat is altered at a critical 

life-cycle juncture, over a large area or of if it is altered for long enough duration, some species 

may have difficulty surviving. Importantly, even if the plant biomass of a particular habitat is 

not significantly altered in the long-term, changes in plant community structure as a result of 

differential sensitivity to orthosulfamuron could result in significant ecological changes. The 

toxicity data for orthosulfamuron indicates that monocotyledonous plants are less sensitive than 

dicotyledonous plants and that there is variation in sensitivity within the tested dicots; this 

variability suggests that plant community structure could be significantly altered in habitats 

where orthosulfamuron is present. Even if changes in habitat were not permanent, if they were 

to occur during a sensitive part of the life cycle, such as reproduction or development, significant 

indirect effects might be expected. A starting point for evaluating the potential risk of such 

scenarios would be to first identify listed species likely to occur in the proposed orthosulfamuron 

use areas and their associated life histories and determine if use is likely to overlap with a 

sensitive life-cycle component. Overlap in this case, would consist of temporal and spatial cooccurrence of orthosulfamuron use and species. 

The information presented on indirect effects serves as a guide to establish the need for and 

extent of additional analyses that may be performed using Services-provided “species profiles” 

as well as evaluations of the geographical and temporal nature of the exposure to ascertain if a 

“not likely to adversely affect” determination can be made. The degree to which additional 

analyses are performed is commensurate with the predicted probability of adverse effects from 

the comparison of the dose-response information with the EECs. The greater the probability that 

exposures will produce effects on a taxa, the greater the concern for potential indirect effects for 

listed species dependant upon that taxa, and therefore, the more intensive the analysis on the 

potential listed species of concern, their locations relative to the use site, and information 

regarding the use scenario (e.g., timing, frequency, and geographical extent of pesticide 

application). 

4.2.3.2.4 Listed Species Occurrence Associated with Orthosulfamuron 

Uses 

A preliminary analysis of the co-occurrence of listed plant species and the proposed use of 

orthosulfamuron was conducted using OPP’s LOCATES database (Version 2.10). The objective 

is to provide insight into the potential for exposure of listed species and to identify those areas, 

crop uses, and listed species that warrant further attention. A tabulation of the number of unique 

listed plant species in each state associated with proposed uses of orthosulfamuron is provided in 

Table 4.11. 

53
By this tabulation there are possibly a total of 134 listed species from all taxa associated with 

counties where orthosulfamuron may potentially be used on rice. A total of 8 states have listed 

species associated with crops on which orthosulfamuron may be used. California has the highest 

number (72) of listed species that may co-occur with proposed orthosulfamuron use areas. The 

taxa that has the highest number of listed species is dicot plants with a total of 40 unique species 

for all states for which there is a record of rice cultivation. 

In general, for all proposed uses of orthosulfamuron there is at least one, and usually more, listed 

species that may potentially occur in or near a proposed use area. Appendix H lists the 

occurrence in each state of counties that have a listed species of specified taxa and the total list of 

endangered species that may co-occur with proposed uses of orthosulfamuron and a 

comprehensive list of species in counties where orthosulfamuron may be used. This preliminary 

analysis indicates that there is a potential for orthosulfamuron use to overlap with listed species 

and that a more refined assessment is warranted. The more refined assessment should involve 

clear delineation of the action area associated with proposed uses of orthosulfamuron and best 

available information on the temporal and spatial co-location of listed species with respect to the 

action area. This analysis has not been conducted for this assessment. 

Table 4.11. Tabulation by State and Taxonomic Group of Listed Species that Occur in 

Orthosulfamuron Use Areas for All Proposed Uses. 

State 

Amphibians Arachnid BirdsBivalveConifer/cycadsCrustaceanDicotFerns & alliesFishGastropod InsectLichenMam

mal 

Monocot ReptilesTotal 

Arkansas 3 5 3 1 1 13 

California 2 6 3 27 16 5 7 3 3 72 

Florida 1 8 1 4 1 1 2 1 5 24 

Illinois 2 2 1 1 2 9 

Louisiana 6 2 2 2 2 5 19 

Mississippi 1 5 2 1 2 2 6 19 

Missouri 2 3 3 3 2 2 15 

Oklahoma 4 2 1 1 2 10 

Tennessee 2 1 1 4 

Texas 1 8 2 1 1 5 18 

Total Unique 

Species 5 23 10 3 40 1 20 7 1 12 4 11 134 

4.3 Description of Assumptions, Limitations, and Data Gaps 

4.3.1 Assumptions and Limitations Related to Exposure for All Taxa 

This screening-level risk assessment relies on proposed labeled statements of the maximum rate 

of orthosulfamuron application for use on rice. The label specifies that orthosulfamuron is only 

to be applied once per year. The frequency at which actual uses approach these maxima is 

dependant on agricultural conditions (presence of weeds) and market forces. Moreover, 

conditions can change from year to year as weed resistance changes through time. It is important 

54
to realize that while a certain use pattern may prevail at present; these patterns can change as a 

result of changing conditions. 

4.3.2 Assumptions and Limitations of Aquatic Exposure Estimates 

The Interim Rice Model does not capture degradation processes. This assumption leads to 

uncertainty in the model’s exposure estimate correlating to the degree to which degradation 

operates. Factors that affect whether the assumption of no degradation represents actual use 

scenarios include the length of time after application that orthosulfamuron is held in rice paddy 

water before release and the environmental pH, as orthosulfamuron’s major route of degradation 

in acidic to neutral water is hydrolysis, with a half-life of hours to days, and in alkaline water is 

biodegradation, with a longer half-life of weeks to months. Chronic risk estimates may be more 

conservative than acute risk estimates in acidic to neutral environments as well, due to 

degradation across the longer exposure period. In summary, the Interim Rice Model calculates 

screening exposure estimates that are not expected to underestimate exposure as agronomic 

practices and environmental pH values vary by location. Interim Rice Model exposure estimate 

uncertainty correlates to the degree to which model assumptions do not describe actual use sites 

of orthosulfamuron. 

4.3.3 Assumptions and Limitations of Terrestrial Exposure Estimates 

4.3.3.1 Location of plant species 

For screening-level risk assessments for terrestrial plants, all estimated exposures are for plants 

that occur off the treated field. Exposure is therefore a function of the amount of pesticide that 

leaves the treated area and enters surrounding habitat via spray drift, release of paddy tail water, 

or both. However, for this use, it is unlikely that tail water release and runoff would occur at the 

same time. 

4.3.3.2 Routes of exposure 

Screening-level risk assessments for spray applications of pesticides consider exposure to plants 

to occur either through soil mediated pathways or through topical application but not both. This 

is primarily due to the fact that submitted toxicity studies do not evaluate combined exposures. 

Moreover, the only way this would likely occur in the field is if there were multiple applications 

and root uptake occurs from left over residues of the first application and topical exposure occurs 

as a result of subsequent applications. Current approaches to assessing risks to plants, however, 

do not take into account multiple applications and proposed uses for orthosulfamuron are limited 

to single applications per year as well. 

4.3.3.3 Incidental Pesticide Releases Associated with Use 

This risk assessment is based on the assumption that the entire treatment area is subject to 

orthosulfamuron application at the proposed application rates. In reality, there is the potential for 

uneven application of orthosulfamuron through such plausible incidents as changes in calibration 

55
of application equipment, spillage, and localized releases at specific areas of the treated field that 

are associated with specifics of the type of application equipment used (e.g., increased 

application at turnabouts when using older ground application equipment). 

For this assessment, the default foliar dissipation half-life of 35 days (Willis and McDowell, 

1987) was used to estimate decline in food-item residues as a function of time after application. 

Frequently, studies are available that allow an estimation of the foliar dissipation half-life for a 

given chemical. In this assessment, since no terrestrial animal RQs exceeded any LOCs, use of a 

foliar dissipation half-life specific to orthosulfamuron would not have altered risk conclusions 

and hence was not used. For other uses, however, an orthosulfamuron specific foliar dissipation 

half-life may be important in more accurately characterizing potential risks. 

4.3.4 Effects Assessment Assumptions and Limitation 

4.3.4.1 Effects of an Adjuvant on Toxicity of Orthosulfamuron to Plants 

The proposed label for the water dispersible granule formulation of orthosulfamuron (IR5878 50 

WG) states that the use of an adjuvant such as a nonionic or an organo siliconic surfactant is 

recommended. Several studies on the effects of orthosulfamuron on non-vascular plants 

included exposure to an adjuvant in addition to the water dispersible granule formulation of 

orthosulfamuron (MRIDs 46578934, -35, -36); this represents a tank mixture for this herbicide. 

Results from these studies indicated that the adjuvant alone was highly toxic to non-vascular 

plants. Although it could not be determined from the studies, it is likely that the adjuvant may 

also exacerbate the toxicity of orthosulfamuron. For example, for the freshwater diatom, 

Navicula pelliculosa, the EC50 was 0.8 mg a.i./L based on the study that included the adjuvant 

and was 54 mg a.i./L based on the study on the formulation alone. For this assessment, the 

studies that incorporated the adjuvant into the treatments were used for non-vascular plant 

toxicity endpoints since the addition of the adjuvant represents a likely mixture of 

orthosulfamuron that will be used for weed control. Although the adjuvant appears to contribute 

or exacerbate the toxicity of orthosulfamuron to non-vascular plants, there were no similar 

studies on aquatic vascular plants or terrestrial plants. Given the results observed with the nonvascular plant studies, it seems likely that the presence of an adjuvant may cause toxicity or 

enhance the toxicity of orthosulfamuron to vascular aquatic plants and/or terrestrial plants. 

Although there is some uncertainty associated with the use of the adjuvant and the potential 

effects on plants, risk conclusions for this assessment would not be altered but it is possible that 

potential effects associated with orthosulfamuron use could, in fact, be higher if an adjuvant is 

used. In addition, given the toxicity of the orthosulfamuron formulation (without adjuvant) to 

rice plants, the use of an adjuvant may result in adverse effects on rice crops. 

4.3.4.2 Age Class and Sensitivity of Effects Thresholds 

It is generally recognized that test organism age may have a significant impact on the observed 

sensitivity to a toxicant. Although this source of variability is perhaps most well documented in 

animal species, it may apply to plant species as well. However, toxicity studies are generally 

56
limited to young plants or seedlings limiting the ability to interpret the differential sensitivity of 

various stages. Further complicating this issue is that some plants have very complex life 

histories that have hardly been characterized from a toxicological perspective. 

4.3.4.3 Lack of Effects Data for Amphibians and Reptiles 

Currently, toxicity studies on amphibians and reptiles are not required for pesticide registration. 

Since these data are lacking, the Agency uses fish as surrogates for aquatic phase amphibians and 

birds as surrogates for terrestrial phase amphibians and reptiles. These surrogates are thought to 

be reflective of or protective (more sensitive) of herpetofauna. Amphibians are characterized by 

a permeable skin. The most important route of exposure for aquatic amphibians would likely be 

the dermal route. Using freshwater fish may be suitable surrogates since exposure would likely 

be surface area dependent and the gill surface of many fish is a fairly large surface area. Also, 

both fish and amphibians are ectothermic so metabolic rates and demands would likely be 

similar. For terrestrial species, however, the difference between amphibians and birds and 

reptiles and birds is quite large. Terrestrial amphibians and reptiles are both ectothermic while 

birds are endothermic; birds have a higher basal metabolic rate required to maintain constant 

body temperature. The higher metabolic demands of birds may predispose birds to higher 

relative exposures. However, this does not address any potential differences in toxicity. To date, 

there are few controlled studies on reptile species that could be used to compare to similar 

studies on birds. A priori, there is no strong reason suggesting that one taxon is more or less 

sensitive than another. Further research is required to determine whether reptiles and terrestrialphase amphibians are suitably represented by bird species in assessing risks. 

4.3.4.4 Use of the Most Sensitive Species Tested 

Although the screening risk assessment relies on a selected toxicity endpoint from the most 

sensitive species tested, it does not necessarily mean that 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. The relationship between the 

sensitivity of the most tested species versus wild species (including listed species) is unknown 

and a source of significant uncertainty. The use of laboratory species has historically been 

driven by availability and ease of maintenance. A widespread comparison of species is lacking, 

however, even variation within a species can be quite high. Clark et al. (2004) conducted a fairly 

extensive review of available toxicity data on non-agricultural plants. The aim was to compare 

these toxicity data to toxicity data from typically used test species which are crop species. 

Although the authors identified several sources of uncertainty and variability that can complicate 

interpretation of results, they concluded that plants typically used for toxicity testing are at least 

as sensitive as non-crop species in 95% of the cases they evaluated. It is important to consider, 

however, that the available dataset on non-crop species is smaller than for crop species. 

Moreover, as mentioned previously, the complex and varied life history of plants, in general, 

may preclude a solid understanding of the relative sensitivities of plants used for toxicity testing 

and plants occurring in the wild. 

57
4.3.4.5 Data Gaps 

Although not a data requirement, toxicity data on the major degradates of orthosulfamuron, 

including the degradate of risk concern o-desmethyl orthosulfamuron, would reduce some of the 

uncertainty in this assessment associated with residues of concern. 

58
5 Literature Cited 

Clark, J., Ortega, L.S., and Fairbrother, A. 2004. Sources of variability in plant toxicity testing. 

Chemosphere 57; pp. 1599-1612. 

Cohen, S.Z., Creeger, S.M., Carsel, R.F., Enfield, C.G. In “Treatment and Disposal of Pesticide 

Wastes;” Krueger, R.F., Seiber, J.N., Eds.; ACS Symposium Series No. 259, American 

Chemical Society: Washington, DC, 1984; pp. 297-325. 

Ecological Committee on FIFRA Risk Assessment Methods (ECOFRAM). 1999. ECOFRAM 

Terrestrial Draft Report. Online at: http://www.epa.gov/oppefed1/ecorisk/terrreport.pdf 

EFED. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides, Version II. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Environmental Fate and Effects Division, Washington, DC. Online 

at: http://www.epa.gov/oppefed1/models/water/index.htm. 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, and instrument for estimating pesticide residues on 

plants. Environmental Toxicology and Chemistry 13 (9):1383-1391. 

Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL 

SERIES 8. Assessing Soil Contamination: A Reference Manual. Appendix 2. 

Parameters of pesticides that influence processes in the soil. Editorial Group, FAO 

Information Division: Rome, 2000. Online at: 

http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm 

Goring, C.A.I., D.A. Laskowki, J.H. Hamaker, and R.W. Meikle. 1975. Principles of pesticide 

degradation in soil. Pages 135-172 in (R. Haque and V.H. Freed, eds.) Environmental 

Dynamics of Pesticides. Plenum Press, New York. 

Hoerger, F., and E.E. Kenaga. 1972. Pesticide residues on plants: Correlation of representative 

data as a basis for estimation of their magnitude in the environment. In F. Coulston and 

F. Korte, eds., Environmental Quality and Safety: Chemistry, Toxicology, and 

Technology, Georg Thieme Publ, Stuttgart, West Germany, pp. 9-28. 

Kirkwood, J.H. 1983. A limit to metabolizable energy intake in mammals and birds. Comp. 

Biochem. Physiol. 75A:1-3. 

Mckelvey, R.A., Wright, J.P., and Honegger, J.L. 2002. A comparison of crop and non-crop 

plants as sensitive indicator species for regulatory testing. Pest Management Science 58; 

pp. 1161-1174. 

59
National Agricultural Statistics Service 2002. Table 24. Grains, Corn, Sorghum, Wheat and 

Other Field Crops: 2002 and 1997. 

http://www.nass.usda.gov/census/census02/volume1/us/st99_2_024_024.pdf 

USDA. 2006. 2002 Census of Agriculture: Agricultural Atlas of the United States. U.S. 

Department of Agriculture, National Agricultural Statistics Service. Online at: 

http://www.nass.usda.gov/research/atlas02/. Accessed on October 20, 2006. 

USEPA. 1993. Wildlife Exposure Factors Handbook. EPA/600/R-13/187a, Office of Research 

and Development, Washington, D.C. 

USEPA 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. 

USEPA. 2002. Policy for Estimating Aqueous Concentrations from Pesticides Labeled for Use 

on Rice. EFED Policy Memorandum. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Washington, DC. October 29, 2002. 3 pp. 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs, U.S. Environmental Protection Agency. Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington, DC. January 23, 2004. 

USEPA. 2006a. Water Models. U.S. Environmental Protection Agency, Pesticides: Science 

and Policy. Last updated May 2, 2006. Online at: 

http://www.epa.gov/oppefed1/models/water/. 

Willis, G.H., and L.L. McDowell. 1987. Pesticide Persistence on Foliage in Reviews of 

Environmental Contamination and Toxicology. 100:23-73. 

Submitted Studies 

MRID 46219009. Woolley, S. and D. Mullee. 2002. IR 5878 (Pure): Determination of Water 

Solubility. Unpublished study performed by Safepharm Laboratories Limited, Derby, 

U.K.; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. SPL Project Number: 

1700/005. Experiment initiation July 29, 2002 and completion October 3, 2002. Final 

report issued November 12, 2002. 25 pp. 

MRID 46219010. Tremain, S. 2002. IR 5878 (Pure): Determination of Vapour Pressure. 

Unpublished study performed by Safepharm Laboratories Limited, Derbyshire, U.K.; 

sponsored and submitted by ISAGRO S.p.A., Milano, Italy. SPL Project Number: 

1700/007. Experiment initiation August 6, 2002 and completion October 24, 2002. Final 

report issued December 17, 2002. 19 pp. 

MRID 46219011. Woolley, S. and D. Mullee. 2002. IR 5878 (Pure): Determination of 

Dissociation Constant. Unpublished study performed by Safepharm Laboratories 

60
Limited, Derby, U.K.; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. SPL 

Project Number: 1700/006. November 12, 2002. 7 pp. 

MRID 46219012. Woolley, S. and D. Mullee. 2002. IR 5878 (Pure): Determination of Partition 

Coefficient. Unpublished study performed by Safepharm Laboratories Limited, Derby, 

U.K.; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. SPL Project Number: 

1700/023. Experiment initiation August 2, 2002 and completion August 16, 2002. Final 

report issued November 5, 2002. 25 pp. 

MRID 46219017. Scacchi, A. et al. 2003. Aerobic Aquatic Metabolism of 14C-IR5878 in Two 

American Soils. Unpublished study performed by ISAGRO RICERCA Srl, Novara, 

Italy; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. Study and Report No.: 

MEF.02.14. Experiment initiation May 29, 2002 and completion November 11, 2002. 

Final report issued February 21, 2003. 298 pp. 

MRID 46219018. Scacchi, A. and G. Pizzingrilli. 2003. Aged Residue Column Leaching of 

14C-IR5878 in an American Soil. Unpublished study performed by Isagro Ricerca Srl, 

Novara, Italy; sponsored and submitted by Isagro S.p.A., Milano, Italy. Study Number: 

MEF.02.17. Experiment initiation July 08, 2002 and completion November 04, 2002. 

Final report issued February 18, 2003. 194 pp. 

MRID 46219040. Dias, N.A. 2001. IR5878: Dietary Toxicity (LC50) to the Mallard Duck. 

Unpublished study performed by Huntingdon Life Sciences, Ltd., Huntingdon, 

Cambridgeshire, England. Study No. IGA 005/012373. Study sponsored by ISAGRO 

S.p.A., Milano, Italy. Study initiated February 2, 2001, completed May 16, 2001. 

MRID 46219041. Rodgers, M. H. and Dias, N.A. 2001. IR5878: Dietary Toxicity (LC50) to the 

Bobwhite Quail. Unpublished study performed by Huntingdon Life Sciences, Ltd., 

Huntingdon, Cambridgeshire, England. Study No. IGA 002/012368. Study sponsored by 

ISAGRO S.p.A., Milano, Italy. Study initiated November 6, 2000, completed May 17, 

2001. 

MRID 46219042. Palmer, S.J., M.A. Stence, T.Z. Kendall, and H.O. Krueger. 2002. IR5878: A 

96-Hour Static Acute Toxicity Test With The Rainbow Trout (Onchorynchus mykiss). 

Unpublished study performed by Wildlife International, Ltd., Easton, MD. Laboratory 

Project Identification No. 544A-107. Study submitted by ISAGRO S.p.A, Centro Uffici 

San Siro, I-20153 Milano Italy. Study initiated May 23, 2002 and completed August 19, 

2002. 

MRID 46219043. Palmer, S.J., T.Z. Kendall, and H.O. Krueger. 2002. IR5878: A 96-Hour 

Static Acute Toxicity Test With The Bluegill (Lepomis macrochirus). Unpublished study 

performed by Wildlife International, Ltd., Easton, MD. Laboratory Project Identification 

No. 544A-111. Study submitted by ISAGRO S.p.A, Centro Uffici San Siro, I-20153 

Milano Italy. Study initiated December 18, 2002 and completed February 5, 2003. 

61
MRID 46219044. Hertl, J. 2000. Final Report: Acute toxicity of IR2878 to Daphnia magna in a 

48-hour immobilization test. Unpublished study performed by Institut für Biologische 

Analytik und Consulting IBACON GmbH, Arheilger Weg, Rossdorf, Germany. 

Laboratory Project Identification No. 8222220. Study sponsored by ISAGRO S.p.A., 

20153 Centro Uffici San Siro - Fabbricato D, Milano, Italy. Study initiated May 10, 

2000 and completed June 27, 2000. 

MRID 46219046. Schmitzer, S. 2001. Laboratory Testing for Toxicity (Acute Contact and 

Oral LD50) of IR5878 on Honey Bees (Apis Mellifera L.) Institute for Biological Analysis 

and Consulting, IBACON GmbH, Rossdorf, Germany. ISAGRO S.p.A., Centro Uffici 

San Siro, Milano, Italy. Study Completion Date July 10, 2001 (Revised March 3, 2003). 

MRID 46219074. Scacchi, A. and G. Pizzingrilli. 2000. Adsorption-desorption of 14C-IR5878 

in Soil. Unpublished study performed by Isagro Ricerca Srl, Novara, Italy; sponsored 

and submitted by Isagro S.p.A., Milano, Italy. Study Number: ABT.00.04. Experiment 

initiation February 10, 2000 and completion March 14, 2000. Final report issued April 

10, 2000. 129 pp. 

MRID 46219015. Castoldi, F. and G. Pizzingrilli. 2000. Hydrolysis of [14C-U-phenyl] IR5878 

in Buffered Solutions at pH 4, 7 and 9. Unpublished study performed by ISAGRO 

RICERCA Srl, Novara, Italy; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. 

Study ID: ABT.99.13. Experimental phase (hydrolysis experiment) initiated November 

9, 1999 and completed on June 14, 2000. Final report issued July 3, 2000. 120 pp. 

MRID 46260107. Dias, N.A. 2001. IR5878: Acute oral toxicity (LD50) to the Mallard duck. 

Unpublished study performed by Huntingdon Life Sciences, Ltd., Huntingdon, 

Cambridgeshire, England. Study No. IGA 003/012865. Study sponsored by ISAGRO 

S.p.A., Centro Uffici San Siro - Fabbricato D, Milano, Italy. Study initiated March 14, 

2001, completed March 28, 2001. 

MRID 46260108. Dias, N.A. 2001. IR5878: Acute oral toxicity (LD50) to the Bobwhite quail. 

Unpublished study performed by Huntingdon Life Sciences, Ltd., Huntingdon, 

Cambridgeshire, England. Study No. IGA 004/012894. Study sponsored by ISAGRO 

S.p.A., Centro Uffici San Siro - Fabbricato D, Milano, Italy. Study initiated March 30, 

2001, completed April 13, 2001. 

MRID 46578931. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50 WG 

Alone: A 96 hour Toxicity Test with the Freshwater Alga Selenastrum capricornutum. 

Unpublished study performed by Wildlife International, Ltd, Easton, MD, Project No. 

544A-121 and submitted by ISAGRO S.p.A., Milano, Italy. Final report issued March 

25, 2003. 

MRID 46578932. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50 WG 

Alone: A 96 hour Toxicity Test with the Freshwater Diatom (Navicula pelliculosa). 

Unpublished study performed by Wildlife International, Ltd, Easton, MD, Project No. 

62
544A-119 and submitted by ISAGRO S.p.A., Milano, Italy. Final report issued March 

26, 2003. 

MRID 46578933. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50 WG 

Alone: A 96 hour Toxicity Test with the Marine Diatom (Skeletonema costatum). 

Unpublished study performed by Wildlife International, Ltd, Easton, MD, Project No. 

544A-122 and submitted by ISAGRO S.p.A., Milano, Italy. Final report issued April 21, 

2003. 

MRID 46578934. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50WG: A 96 

hour Toxicity Test with the Freshwater Alga Selenastrum capricornutum. Unpublished 

study performed by Wildlife International, Ltd, Easton, MD, Project No. 544A-116 and 

submitted by ISAGRO S.p.A., Milano, Italy. Final report issued April 21, 2003. 

MRID 46578935. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50WG: A 96 

hour Toxicity Test with the Freshwater Diatom (Navicula pelliculosa). Unpublished 

study performed by Wildlife International, Ltd, Easton, MD, Project No. 544A-115 and 

submitted by ISAGRO S.p.A., Milano, Italy. Final report issued April 11, 2003. 

MRID 46578936. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50 WG: A 96 

hour Toxicity Test with the Marine Diatom (Skeletonema costatum). Unpublished study 

performed by Wildlife International, Ltd, Easton, MD, Project No. 544A-117A and 

submitted by ISAGRO S.p.A., Milano, Italy. Final report issued May 15, 2003. 

MRID 46578937. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50WG: A 96 

hour Toxicity Test with the Freshwater Alga Anabaena flos-aquae. Unpublished study 

performed by Wildlife International, Ltd, Easton, MD, Project No. 544A-113 and 

submitted by ISAGRO S.p.A., Milano, Italy. Final report issued June 20, 2003. 

MRID 46578938. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50 WG 

ALONE: A 96 hour Toxicity Test with the Freshwater Alga Anabaena flos-aquae. 

Unpublished study performed by Wildlife International, Ltd, Easton, MD, Project No. 

544A-118 and submitted by ISAGRO S.p.A., Milano, Italy. Final report issued June 27, 

2003. 

MRID 46578939. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50WG 

ALONE: A 96 hour Toxicity Test with Duckweed (Lemna gibba). Unpublished study 

performed by Wildlife International, Ltd, Easton, MD, Project No. 544A-120 and 

submitted by ISAGRO S.p.A., Milano, Italy. Final report issued September 22, 2003. 

MRID 46578940. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50WG: A 96 

hour Toxicity Test with Duckweed (Lemna gibba). Unpublished study performed by 

Wildlife International, Ltd, Easton, MD, Project No. 544A-114 and submitted by 

ISAGRO S.p.A., Milano, Italy. Final report issued July 6, 2003. 

63
MRID 46578941. Porch, John R., K. H. Martin and H. O. Krueger. 2003. IR5878 50WG: A 

Toxicity Test to Determine the Effects on Seedling Emergence of Ten Species of Plants. 

Performed by Wildlife International, Ltd., Easton, MD. Laboratory study number 

544-110. Sponsored by ISAGRO S.p.A., Milano, Italy. Study completed on October 27, 

2003. 

MRID 46578942. Porch, John R. and H. O. Krueger. 2003. IR5878 50WG: A Toxicity Test to 

Determine the Effects on Vegetative Vigor of Ten Species of Plants. Performed by 

Wildlife International, Ltd., Easton, MD. Laboratory study number 544-111. Sponsored 

by ISAGRO S.p.A., Milano, Italy. Study completed on December 23, 2003. 

MRID 46578949. Frey, L.T., et al. 2003. IR5878: A Reproduction Study with the Mallard. 

Unpublished study performed by Wildlife International Ltd., Easton, MD. Laboratory 

Project No. 544-109. Study submitted by Isagro S.p.A., Milano, Italy. Study initiated 

July 24, 2002 and submitted May 29, 2003. 

MRID 46578950. Frey, L.T., et al. 2003. IR5878: A Reproduction Study with the Northern 

Bobwhite. Unpublished study performed by Wildlife International Ltd., Easton, MD. 

Laboratory Project No. 544-108. Study submitted by Isagro S.p.A., Milano, Italy. Study 

initiated July 24, 2002 and submitted May 29, 2003. 

MRID 46578951. Palmer, S., Kendall, T., and Krueger, H. 2002. IR5878: A96-Hour Static 

Acute Toxicity Test with the Sheepshead Minnow. Unpublished study performed by 

Wildlife International, Ltd., Easton Maryland. Laboratory Report Number: 544A-109. 

Study submitted by ISAGRO S.p.A., Milano, Italy. Experimental start date was June 24, 

2002 and experimental termination date was June 28, 2002. The final report was issued 

July 31, 2002. 

MRID 46578952. Palmer, S., Kendall, T., and Krueger, H. 2002. IR5878: A 96-Hour Static 

Acute Toxicity Test with the Saltwater Mysid (Americamysis bahia). Unpublished study 

performed by Wildlife International, Ltd, Easton, Maryland. Laboratory Report Number 

544A-108. Study submitted by ISAGRO S.p.A., Milano, Italy. Study Completion Date: 

August 12, 2002. 

MRID 46578953. Palmer, S.J., T.Z. Kendall, and H.O. Krueger. 2003. IR5878: An Early LifeStage Toxicity Test with the Fathead Minnow (Pimephales promelas). Unpublished 

study performed by Wildlife International., Ltd., Easton, MD. Laboratory Project No. 

544A-110. Study submitted by Isagro S.p.A., Milano, Italy. Study initiated May 23, 

2002 and submitted January 15, 2003. 

MRID 46578954. Blankinship, A.S., T.Z. Znedall, and H.O. Krueger. 2003. IR5878: A FlowThrough Life-Cycle Toxicity Test with the Saltwater Mysid (Mysidopsis bahia). 

Completed by Wildlife International, Ltd., Easton, MD. Submitted by ISAGRO S.p.A., 

Milano Italy. Report ID 544A-112. Study initiated on February 12, 2003 and completed 

July 3, 2003. 

64
MRID 46578955. Sutherland, C., Kendall, T., and Krueger, H. 2002. IR5878: A 96-Hour Static 

Acute Toxicity Test with the Crayfish (Procambarus clarkii). Unpublished study 

performed by Wildlife International, Ltd., Easton Maryland. Laboratory Report Number: 

544A-124. Study submitted by ISAGRO S.p.A., Milano, Italy. The final report was 

issued July 14, 2003. 

MRID 46578956. Palmer, S.J., Thomas, S.T., Kendall, T.Z., and H.O. Krueger. 2003. IR5878: 

A Semi-Static Life-Cycle Toxicity Test with the Cladoceran (Daphnia magna). 

Unpublished study performed by Wildlife International., Ltd., Easton, MD. Laboratory 

Project No. 544A-123. Study submitted by Isagro S.p.A., Milano, Italy. Study initiated 

March 31, 2003 and completed September 22, 2003. 

MRID 46578957. Palmer, S., Kendall, T., and Krueger, H. 2004. IR5878: A 96-Hour Shell 

Deposition Test with the Eastern Oyster (Crassotrea virginica). Unpublished study 

performed by Wildlife International, Ltd, Easton, Maryland. Laboratory Report ID: 

544A-106. Study submitted by ISAGRO S.p.A., Milano, Italy. Study initiated May 23, 

2002 and completed January 7, 2004. 

MRID 46578959. Desjardins, D., T.Z. Kendall and H.O. Krueger. 2003. IR5878 50WG + 

ADJ2506: A 72 hour Toxicity Test with the Freshwater Alga (Pseudokircheriella 

subcapitata). Unpublished study performed by Wildlife International, Ltd, Easton, MD, 

Project No. 544A-132 and submitted by ISAGRO S.p.A., Milano, Italy. Final report 

issued April 12, 2005. 

MRID 46578967. Scacchi, A., R. Soddu, and G. Pizzingrilli. 2003. Anaerobic Aquatic 

Metabolism of 14C-IR5878 in Two American Soils. Unpublished study performed by 

Isagro Ricerca Srl, Environmental Chemistry, Metabolism & Environmental Fate, 

Novara, Italy; and sponsored and submitted by Isagro S.p.A., Milano, Italy. Study No.: 

MEF.02.16. Experiment initiated on August 26, 2002 and completed on November 10, 

2003; final report issued on December 12, 2003. 280 pp. 

MRID 46578968. Scacchi, A., L. Vanini, and G. Pizzingrilli. 2004. Soil Column Leaching of 

14C-IR5878. Unpublished study performed by Isagro Ricerca Srl, Novara, Italy; 

sponsored and submitted by Isagro S.p.A., Milano, Italy. Study Number: MEF.03.17. 

Experiment initiation January 08, 2004 and completion April 02, 2004. Final report 

issued May 26, 2004. 162 pp. 

MRID 46578970. Faltynski, K.H. 2005. Determination of Aquatic Dissolution Rate of 

IR5878GR and pH 5 Hydrolysis Rate of IR5878 Standard. Unpublished study performed 

by EN-CAS Analytical Laboratories, Winston-Salem, NC; and sponsored and submitted 

by Isagro, USA, Morrisville, NC. EN-CAS Study ID #: 04-0041. Experimental phase 

(hydrolysis experiment) initiated and completed on January 12, 2005. Final report issued 

March 17, 2005. 67 pp. 

65
MRID 46578971. Scacchi, A. and M. Trucco. 2005. Adsorption-desorption of 14C-IR5878 in 

American Soils. Unpublished study performed by ISAGRO RICERCA S.r.l., Novara, 

Italy; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. Study Number 

MEF.04.02. Experiment start date March 9, 2004, and completion date June 28, 2004. 

Final report issued January 10, 2005. 210 pp. 

MRID 46578985. Cooley, T.A. 2005. IR5878 Field Dissipation Study in Bare Ground Rice 

Soil. Unpublished study performed by Excel Research Services, Inc., Fresno, CA and 

PTRL West, Inc., Hercules, CA; and sponsored and submitted by ISAGRO S.p.A., 

Milano, Italy. Study No.: ERS23044. PTRL West Project No.: 1204W. Experiment 

initiation July 15, 2003 and completion February 14, 2005. Final report issued May 19, 

2005. 1013 pp. 

MRID 46588507. van Dijk, A. 2004. Bioconcentration: Flow-through fish test with IR5878 in 

bluegill sunfish (Lepomis macrochirus). Unpublished study performed by RCC Ltd., 

Itingen, Switzerland; sponsored and submitted by ISAGRO S.p.A., Milano, Italy. RCC 

Study No. 849257. Experiment initiated July 28, 2003, and completed February 10, 

2004. Final report issued May 11, 2004. 68 pp. 

MRID 46588508. Scacchi, A., L. Vanini, and D. Oriolo. 2005. Aerobic Aquatic Degradation of 

14C-IR5878 in Paddy-field Soil under Sunlight. Unpublished study performed by Isagro 

Ricerca Srl, Environmental Chemistry, Metabolism & Environmental Fate, Novara, Italy; 

sponsored and submitted by Isagro S.p.A. Department, Milano, Italy. Study No.: 

MEF.04.13. Experiment initiated on July 9, 2004 and completed on October 8, 2004. 

Final report issued on January 27, 2005. 198 pp. 

MRID 46588509. Hennecke, D. 2002. Aquatic Photodegradation and Quantum Yield of 

IR5878. Unpublished study performed by Fraunhofer Institute for Molecular Biology 

and Applied Ecology, Schmallenberg, Germany; sponsored and submitted by ISAGRO 

S.p.A., Milan, Italy. GLP-Code: ISA-003/7-05. Experiment started July 26, 2002, and 

completed August 13, 2002. Final report issued November 8, 2002. 52 pp. 

66
APPENDIX A. Preliminary Data Screen. 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF 

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES

June 29, 2006 

PC Code: 108209 

DP Barcode: D330511 

MEMORANDUM 

SUBJECT: Environmental Fate and Effects New Chemical Screen for Orthosulfamuron 

(PC Code 108209): Environmental Fate and Ecological Effects Data 

Requirements. 

TO: James Tompkins, Risk Manager 

HB/RD (7505P) 

FROM: Greg Orrick, Environmental Scientist 

Christopher Salice, Biologist 

 ERB4/EFED (7507P) 

THROUGH: Elizabeth Behl, Chief 

 ERB4/EFED (7507P) 

The Environmental Fate and Effects Division (EFED) has reviewed environmental fate and 

ecological effects studies submitted by Isagro in support of new chemical registration for 

orthosulfamuron. This chemical is described as a nonselective herbicide, which is labeled for 

use on rice as a both a granular (IR5878 0.5 GR; 0.5% a.i.) and water dispersible granular 

(IR5878 50 WG; 50% a.i.) end-use product. 

This screen included: 

• a check of the submission to ensure that all studies triggered by the use pattern are 

included in the package; 

• an evaluation as to whether each study is reviewable, i.e., has no fatal flaws rendering the 

study scientifically invalid. 

67
Please note that this screen is not intended to be a comprehensive evaluation of the overall 

quality of specific studies, but an assurance that a reasonably complete package has been 

submitted. Also, studies that pass the screen are not automatically assured of acceptance in 

support of the respective data requirement. 

The following table provides a brief summary of the studies evaluated. 

68
Table 1. Chemical Screen for Ecological Effects Studies of Orthosulfamuron. 

Guideline Study Title MRID Issues Reviewable 

(Yes/No) 

71-1 

Avian acute oral 

(Northern bobwhite) 

462601-08 Yes 

Avian acute oral 

(Mallard duck) 

462601-07 Yes 

71-2 

Avian dietary 

(Northern bobwhite) 

462190-41 . Yes 

Avian dietary 

(Mallard duck) 

462190-40 Yes 

71-3 Wild Mammals Not required. 

71-4a 

1-Gen. reproduction 

(Northern bobwhite) 

465789-50 Yes 

71-4b 1-Gen. reproduction 

(Mallard duck) 

465789-49 Yes 

71-5 Field monitoring Not required. 

72-1 

Acute toxicity 

(Bluegill sunfish) 

462190-43 Yes 

Acute toxicity 

(Rainbow trout) 

462190-42 Yes 

72-2a 

Acute toxicity 

(Daphnia) 

462190-44 Yes 

72-3a 

Acute toxicity 

estuarine/marine fish 

(sheepshead) 

465789-51 Yes 

72-3b Oyster acute 

(shell deposition) 

465789-57 Yes 

72-3c 

Acute toxicity 

(Marine shrimp) 

465789-52 Yes 

72-4a 

Fish early life stage 

(Fathead minnow) 

465789-53 Yes 

72-4b Chronic toxicity 

(Daphnia) 

465789-56 Yes 

72-4c 

Chronic toxicity 

(Marine shrimp) 

465789-54 Apparent omission of some endpoints. Yes 

72-5 Fish Life cycle Not required. 

72-6 Oyster/fish BCF Not required. 

72-7 

Field test 

(Aquatic organisms) 

 Not required. 

122-1a Terrestrial Plant Not Required. 

69
Guideline Study Title MRID Issues Reviewable 

(Yes/No) 

Tier I Seedling 

emergence 

122-1b Terrestrial Plant 

Tier I Vegetative 

Vigor 

 Not Required. 

123-1 Terrestrial Plant 

Tier II 

Seedling emergence 

465789-41 Data appear reviewable. Yes 

123-1 Terrestrial Plant 

Tier II Vegetative 

Vigor 

465789-42 NOAEC or EC05 could not be determined for 

carrot. 

Yes 

465789-31 Yes 

465789-32 Three replicates used instead of recommended 

four. 

Yes 

465789-33 Yes 

465789-34 High inhibition of adjuvant control; impossible 

to discern effects of orthosulfamuron alone. 

No 

465789-35 Not all experimental conditions reported. Yes 

123-2 Acute toxicity algae 

465789-36 Yes 

465789-37 Yes 

465789-38 Yes 

465789-39 Not all test concentration verified, higher than 

recommended temperature. 

Yes 

465789-40 Not all test concentration verified, higher than 

recommended temperature. 

Yes 

465789-59 Higher than recommended light intensity and 

pH. 

Yes 

141-1 Honeybee acute 

contact 

462190-46 Yes 

141-2 Honeybee acute foliar 

exposure 

 Not required. 

Non-guid. Acute Crayfish 465789-55 Yes 

70
Table 2. Chemical Screen for Environmental Fate Studies of Orthosulfamuron. 

Guideline Study Title MRID Issues Reviewable? 

161-1 Hydrolysis 46578970 

46219015 

46219016 

Collectively, these data appear reviewable 

for the hydrolysis data requirement. 

Yes 

161-2 Aqueous photolysis 46588509 The data appear reviewable. Yes 

161-3 Soil photolysis No study Not required. N/A 

161-4 Air photolysis No study Not required. N/A 

162-1 Aerobic soil 

metabolism 

No study Not required. N/A 

162-2 Anaerobic soil 

metabolism 

No study Not required. N/A 

162-3 Anaerobic aquatic 

metabolism 

46578967 The data appear reviewable. Yes 

162-4 Aerobic aquatic 

metabolism 

46588508 

46219017 

The data appear reviewable. Yes 

163-1 Batch equilibrium/ 

aged leaching 

46578968 

46578971 

46219018 

46219074 

The data appear reviewable. Yes 

163-2 Lab volatility No study Not required. N/A 

164-1 Terrestrial field 

dissipation 

No study Not required. N/A 

164-2 Aquatic field 

dissipation 

46578985 The submitted study appears reviewable for 

the water dispersible granular formulation. 

The submission requirement for a study of 

the granular formulation has been waived 

(DP Barcode 320283), as the active 

ingredient in both formulations is expected 

to behave similarly in aquatic ecosystems 

within 24 hours of application. 

Yes 

165-4 Fish 

bioaccumulation 

46588507 The data appear reviewable. Yes 

71
APPENDIX B. Environmental Fate Data. 

Detailed information regarding the fate and transport of orthosulfamuron in the environment is 

provided in the study summaries below. 

161-1. Hydrolysis 

MRID 46219015 (Supplemental) 

The hydrolysis of [phenyl-U-14C]-labeled 1-(4,6-dimethoxypyrimidin-2-yl)-3-[2­

(dimethylcarbamoyl)phenylsulfamoyl]urea (orthosulfamuron, radiochemical purity >97%), at 1 

μg a.i./mL, was studied in sterile aqueous buffered pH 4 (0.01M acetate), pH 7 (0.01M citrate), 

or pH 9 (0.01M borate) solutions that were incubated in the dark in three experiments: A 

definitive experiment was conducted at 25°C with pH 7 or pH 9 solutions for up to 176 days. 

The other two experiments were conducted at 50°C. 

In the pH 7 buffer at 25°C, [14C]orthosulfamuron decreased from 96.99% of the applied at day 0 

to 76.14% at 8 days post-treatment and 32.91% at 37 days, dissipating with a half-life of 22.1 

days. In the pH 9 buffer at 25°C, [14C]orthosulfamuron decreased from 96.57% of the applied at 

day 0 to 56.19% at 176 days, dissipating with a half-life of 231 days. Table B-1 lists the 

reported half-life and transformation product data of this study and MRIDs 46219016 and 

46578970. This study was classified as supplemental since the sterility of the test solutions was 

not confirmed and only pH 7 and pH 9 buffers were studied at 25°C. 

Table B-1. Orthosulfamuron Hydrolysis Half-lives and Transformation Products. 

pH Temperature 

(°C) Half-life Transformation products 

Major Minor 

5 25 0.442 days Undetermined. Undetermined. 

7 25 24.4 days DBS acid (H1) DBS amine (H2), DB amine (H4) 

9 25 228 days H1, H4 H2 

4 50 0.02 days H1, H4, DOP 

urea (H5) H2, DOP amine (H6) 

7 50 1.2-1.5 days H1, H4, H5, H6 H2 

9 50 8.0-8.6 days H1, H2, H4, H5, 

H6 None. 

MRID 46219016 (Supplemental) 

The hydrolysis of [pyrimidinyl-5-14C]-labeled 1-(4,6-dimethoxypyrimidin-2-yl)-3-[2­

(dimethylcarbamoyl)phenylsulfamoyl]urea (orthosulfamuron, radiochemical purity >95%), at 

72 
1.25 μg a.i./mL, was studied in the dark at 50°C in sterile aqueous buffered pH 4 (0.01M 

acetate), pH 7 (0.01M citrate) and pH 9 (0.01M borate) solutions for 60 minutes, 52 hours and 13 

days, respectively. Orthosulfamuron dissipated with a first-order half-life of 0.015 days (21.6 

minutes) in the pH 4 buffer, 1.2 days in the pH 7 buffer, and 8.6 days in the pH 9 buffer. Two 

transformation products were identified: N-(4,6-dimethoxypyrimidin-2-yl)urea (DOP urea; H5), 

which was a major transformation product at all pHs, and 2-amino-4,6-dimethoxypyrimidine 

(DOP amine; H6), which was a minor transformation product at pH 4 and a major product at pH 

7 and 9. This study was classified as supplemental, as it was conducted only at 50°C and the 

sterility of the test solutions was not confirmed. 

MRID 46578970 (Supplemental) 

Unlabeled orthosulfamuron (IR5878; 1-(4,6-dimethoxypyrimidin-2-yl)-3- 

[2-(dimethylcarbamoyl)phenylsulfamoyl]-urea) at 20 mg a.i./L was studied in an aqueous pH 5 

(phthalate) buffered solution in the dark at 25°C for 24 hours. The level of orthosulfamuron 

decreased from 87% of the nominal concentration at the start of the experiment to 51% at 

8 hours post-treatment and 18% at 24 hours (study termination). The first-order half-life in the 

pH 5 buffer solution was 10.6 hours (0.442 days), as reported in Table B-1. No degradation 

products were analyzed and a hydrolytic transformation pathway was not proposed. The study 

was classified as supplemental since the material balance was incomplete and no experiments 

were conducted on technical grade material at pH 7 and pH 9. 

161-2. Aqueous Photolysis 

MRID 46588509 (Supplemental) 

The aqueous phototransformation of unlabeled orthosulfamuron, at 10, 20, and 30 mg a.i./L, was 

studied in a pH 9 buffer (borate, molarity not reported) solution that was irradiated continuously 

using a filtered xenon lamp for 166 hours at 25oC. The nominal intensity of the lamp was 

700 W/m

2

. Orthosulfamuron was relatively stable in the irradiated solutions, declining 4.9-5.6% 

of the applied amount during the irradiation period. Orthosulfamuron was stable in the dark 

controls. No transformation products were isolated from either the irradiated samples or dark 

controls. Volatiles were not collected. Orthosulfamuron dissipated with first-order half-lives of 

85, 87, and 98 days, applied at 10, 20, and 30 mg a.i./L, respectively, yielding a half-life 

(combined data) of 90 days based on the continuous irradiation used in the study. These halflives are of uncertain value since they were extrapolated well beyond the 6.9-day duration of the 

study. Based on a 12-hour light/12-hour dark cycle, the calculated phototransformation half-life 

of orthosulfamuron is 180 days. An environmental phototransformation half-life of 

orthosulfamuron could not be determined because the intensity of the artificial light was not 

compared to natural sunlight. This study was classified supplemental because >94% of the 

applied remained undegraded at study termination (ca. 7 days post-treatment); sterility was not 

confirmed; the intensity of the artificial light was not compared to natural sunlight; and raw 

sample concentration and temperature data were not reported. 

73
162-3. Anaerobic Aquatic Metabolism 

MRID 46578967 (Supplemental) 

The anaerobic biotransformation of [14C-5-pyrimidinyl]-labeled and [14C-U-phenyl]-labeled 

orthosulfamuron was studied in darkness at 20 ± 2°C in a pond water-loam sediment system 

(water pH 7.8, dissolved organic carbon not reported; sediment pH 6.9, organic carbon 0.87%) 

from Arkansas, for 180 days and in a pond water-clay sediment system (water pH 7.7, dissolved 

organic carbon not reported; sediment pH 6.0, organic carbon 1.8%) from California, for 150 

days. The water/sediment ratio used was 2.2:1 for the Arkansas water-loam sediment system and 

2.5:1 for the California water-clay sediment system. 

First-order half-lives were calculated by counting non-extracted residues as parent compound, 

since multiple solvent systems were not employed in a reasonable extraction attempt. The halflives for pyrimidinyl-5-[14C]-labeled orthosulfamuron in the water, sediment, and total (watersediment) system were 68, >365, and 217 days, respectively, in the microcosm from Arkansas. 

Respective half-lives for orthosulfamuron parent alone were 68, 124, and 89 days. Three major 

degradation products were observed: o-desmethyl IR5878 (S9), maximum of 12.63%, 7.28%, 

and 17.47% in the water, sediment, and total system, respectively; DOP urea (S12), maximum of 

2.31%, 11.39%, and 12.47% in the water, sediment, and total system, respectively; and S11 

(composed of 5 compounds), maximum of 14.59%, 8.59%, and 23.18% in the water, sediment, 

and total system, respectively. One minor transformation product was observed: DOP amine 

(S13), with maximums of 0.42%, 0.75%, and 1.14% in the water, sediment, and total system, 

respectively. 

The first-order half-lives counting non-extracted residues as parent compound for 

[

14C-U-phenyl]-labeled orthosulfamuron in water, sediment, and total (water-sediment) system 

were 63, >365, and 142 days, respectively, in the microcosm from Arkansas. Respective halflives for orthosulfamuron parent alone were 63, 117, and 80 days. Three major degradation 

products were observed: DBS acid (S1), maximum of 6.78%, 6.23%, and 12.01% of the applied 

amount in the water, sediment, and total system, respectively; S9, maximum of 11.70%, 7.94%, 

and 18.59% in the water, sediment, and total system, respectively; and S5 (composed of 8 

compounds), maximum of 15.10%, 6.77%, and 21.86% in the water, sediment, and total system, 

respectively. Minor transformation products were DBS amide (S2), with maximums of 3.02%, 

2.1%, and 4.23% in the water, sediment, and total system, respectively, and DB amine (S4), with 

maximums of 4.92%, 2.56%, and 6.41% in the water, sediment, and total system, respectively. 

Dissipation occurred more readily in the California system. The first-order half-lives counting 

non-extracted residues as parent compound for pyrimidinyl-5-[14C]-labeled orthosulfamuron in 

the water, sediment, and total (water-sediment) system were 25, >365, and 161 days, 

respectively, in the microcosm from California. Respective half-lives for orthosulfamuron 

parent alone were 25, 57, and 41 days. Three major transformation products were observed: S9 

at a maximum of 9.51%, 3.29%, and 12.21% in the water, sediment, and total system, 

respectively; S12, maximum of 1.27%, 18.27%, and 18.97% in the water, sediment, and total 

system, respectively; and S11, maximum of 13.21%, 7.73%, and 20.94% of the applied amount 

in the water, sediment, and total system, respectively. 

74
The first-order half-lives counting non-extracted residues as parent compound for [phenylU-14C]-labeled orthosulfamuron in the water, sediment, and total (water-sediment) system were 

23, >365, and 88 days, respectively. Respective half-lives for orthosulfamuron parent alone 

were 23, 39, and 41 days. Three major transformation products were observed: S1, maximum of 

21.59%, 17.06%, and 38.65% in the water, sediment, and total system, respectively; S9, 

maximum of 8.96%, 5.27%, and 13.11% in the water, sediment, and total system, respectively; 

and S5, maximum of 12.39%, 3.71%, and 16.10% in the water, sediment, and total system, 

respectively. 

The study was classified as supplemental because microbial biomass was not measured at any 

time in sediment or water and the unextractable fraction may not have been thoroughly extracted; 

non-extractable [14C]residues in sediment were measured at >10% by day 15. 

162-4. Aerobic Aquatic Metabolism 

MRID 46219017 (Supplemental) 

The biotransformation of [pyrimidinyl-5-14C]- and [phenyl-U-14C]-labeled orthosulfamuron was 

studied in water-loam sediment (water pH 7.8, organic carbon not reported; sediment pH 6.2– 

6.9, organic carbon 0.87%) systems from Arkansas for 90 days and in water-clay sediment 

(water pH 7.7, organic carbon not reported; sediment pH 5.6–6.0, organic carbon 1.8%) systems 

from California for 61 days under aerobic conditions in darkness at 20 ± 2oC. The 

sediment:water ratios used were approximately 1:2.2–2.5. Dissipation and transformation of 

[

14C] orthosulfamuron occurred moderately in both systems, but was more rapid in the waterclay systems compared to the water-loam systems. 

First-order half-lives were calculated by counting non-extracted residues as parent compound, 

since multiple solvent systems were not employed in a reasonable extraction attempt. The firstorder half-lives for pyrimidinyl-5-[14C]-labeled orthosulfamuron in the water, sediment, and total 

(water-sediment) system were 29.1, >365, and 70.5 days, respectively, in the microcosm from 

Arkansas. Respective half-lives for orthosulfamuron parent alone were 29.1, 39.6, and 40.6 

days. S12 was observed as a major transformation product occurring at maximums of 6.09%, 

42.50%, and 47.78% of the applied in water, sediment, and total system, respectively. S9 was 

observed as a minor degradate with maximums of 6.68%, 2.69%, and 9.37% in water, sediment, 

and total system, respectively. 

The first-order half-lives counting non-extracted residues as parent compound for [phenylU-14C]-labeled orthosulfamuron in the water, sediment, and total (water-sediment) system were 

27.6, >365, and 59.2 days, respectively. Respective half-lives for orthosulfamuron parent alone 

were 27.6, 41.5, and 36.3 days. S1 was observed as a major degradate with maximums of 

46.53%, 9.24%, and 55.77% in water, sediment, and total system, respectively. The minor 

degradates were: S9, with maximums of 5.97%, 2.06%, and 8.03% in water, sediment, and total 

system, respectively, and S2, with maximums of 3.25%, 0.87%, and 4.07% in water, sediment, 

and total system, respectively. 

75
In the microcosm from California, the first-order half-lives counting non-extracted residues as 

parent compound for pyrimidinyl-5-[14C]-labeled orthosulfamuron in the water, sediment, and 

total (water-sediment) system were 13.1, >365, and 65.4 days, respectively. Respective halflives for orthosulfamuron parent alone were 13.1, 38.4, and 24.1 days. S12 was observed as a 

major transformation product occurring at maximums of 6.66%, 37.70%, and 40.52% of the 

applied in water, sediment, and total system, respectively. S9 was observed as a minor degradate 

with maximums of 4.98%, 2.32%, and 7.30% in water, sediment, and total system, respectively. 

The first-order half-lives counting non-extracted residues as parent compound for phenylU-[14C]-labeled orthosulfamuron in the water, sediment, and total (water-sediment) system were 

12.1, 101.9, and 30.3 days, respectively. Respective half-lives for orthosulfamuron parent alone 

were 12.1, 35.4, and 21.3 days. S1 was observed as a major degradate with maximums of 

49.88%, 11.11%, and 60.86% in water, sediment, and total system, respectively. The minor 

degradates were S9, with maximums of 4.60%, 1.84%, and 6.13% in water, sediment, and total 

system, respectively, and S2, with maximums of 2.81%, 1.28%, and 4.09% in water, sediment, 

and total system, respectively. 

This study is classified as supplemental because multiple solvent systems were not employed in a 

reasonable extraction attempt, leaving 11–33% of the applied unextracted. 

MRID 46588508 (Unacceptable) 

The aerobic biotransformation of [14C-5-pyrimidinyl]-labeled and [14C-U-phenyl]-labeled 

orthosulfamuron, at 0.75 mg a.i./L (equivalent to 75 g a.i./ha), was studied outdoors for 62 days 

in a water/loamy sand sediment (water pH 7.79, organic carbon not reported; sediment pH 6.3, 

organic carbon 1.30%) from Italy. Accurate half-lives could not be determined because >50% of 

the applied orthosulfamuron dissipated between time 0 and the next sampling interval (1 day 

post-treatment). In the system treated with [14C-5-pyrimidinyl]orthosulfamuron, the only major 

transformation product was S12, at an average maximum of 56.95% of the applied at 5 days 

post-treatment (maximums 14.42% at 7 days in the water, 44.52% at 5 days in the sediment), 

decreasing to 32.78% (2.48% in water, 30.30% in sediment) at study termination. The three 

identified minor transformation products, S9, S13, and S15, each averaged a maximum of <3% 

of the applied in the total system. In the system treated with [14C-U-phenyl]orthosulfamuron, the 

only major transformation product was S1 at a maximum of 54.47% of the applied in the total 

system at 7 days post-treatment (maximums 36.63% at 7 days in water, 19.45% at 4 days in 

sediment), decreasing to 13.13% (6.99% in water, 6.14% in sediment) at study termination 

(62 days). The three identified minor transformation products were S2, S4, and S9; each 

averaged a maximum of <2% of the applied in the total system. 

The study is classified as unacceptable because the experiments were conducted outdoors, where 

samples were exposed to sunlight and fluctuating temperatures. Radioactivity was lost over 

time, as the samples were open to the environment and volatiles were not collected, resulting in 

poor material balance. 

163-1. Leaching-Adsorption/Desorption 

76
MRID 46219074 (Supplemental) 

The adsorption/desorption characteristics of [14C-U-phenyl]-labeled orthosulfamuron were 

studied in four Italian soils in a batch equilibrium experiment: a sandy loam soil (pH 6.29, 

organic carbon 1.33%); two silt loam soils (pH 5.71, organic carbon 2.03% and pH 6.78, organic 

carbon 1.00%); and a clay loam soil (pH 7.98, organic carbon 2.30%). The adsorption phase of 

the study was carried out by equilibrating air-dried soil with [14C]orthosulfamuron at nominal 

test concentrations of 0.28, 1.4, 7.0, and 35.0 mg a.i./kg soil for all test soils at 20 ± 2°C for 2 

hours; lighting conditions were not reported. The equilibrating solution used was 0.01M CaCl2 

with soil:solution ratios of 1:7 (w:v) for all test soils. The desorption phase of the study was 

carried out by replacing most of the adsorption solution with an equivalent volume of 0.01M 

CaCl2 solution and equilibrating for 2 hours at 20 ± 2°C; lighting conditions were not reported. 

Four desorption cycles were conducted for all test soils. Soil properties and 

adsorption/desorption data are summarized in Table B-2. 

Table B-2. Orthosulfamuron Adsorption/Desorption in Four Soils. 

Textural 

Classification 

B1 

Sandy Loam 

G2 

Silt Loam 

M2 

Silt Loam 

VM-1 

Clay Loam 

% sand 62.0 28.3 37.0 24.3 

% silt 32.3 54.4 54.3 46.7 

% clay 5.7 17.3 8.7 29.0 

% organic matter 2.29 3.49 1.72 3.96 

% organic carbon 1.33 2.03 1.00 2.30 

pH 6.29 5.71 6.78 7.98 

CEC mEq/100g 7.65 12.17 10.7 20.06 

Adsorption phase 

Kd 6.01 ± 3.20 8.62 ± 2.46 6.26 ± 1.45 6.11 ± 0.63 

Kf 3.76 6.62 5.47 5.72 

1/n 0.751 0.856 0.920 0.955 

Koc 283 326 547 249 

Desorption phase 

Kd 58.0 ± 17.6 42.8 ± 12.2 105 ± 35 18.1 ± 3.0 

Kf 35.8 32.0 141 20.3 

1/n 0.902 0.935 1.074 1.033 

Koc 2690 1580 14100 882 

CEC = Cation exchange capacity 

Koc = Kf x 100% ÷ (% organic carbon) 

The study is classified as supplemental because material balances were determined for the 

highest test concentrations for all test soils, rather than for all test concentrations; none of the test 

soils had an organic matter content of <1%; and adsorption phase supernatants were not 

adequately decanted and volumes were not reported. 

MRID 46578971 (Supplemental) 

The adsorption/desorption characteristics of [14C-5-pyrimidinyl]-labelled orthosulfamuron were 

studied in a batch equilibrium experiment in two sandy loam soils (pH 6.5, organic carbon 

1.04%; pH 5.7, organic carbon 0.35%) from Arkansas, a sand soil (pH 4.7, organic carbon 

1.03%) from Minnesota, a clay loam soil (pH 5.4, organic carbon 3.01%), a loam soil (pH 7.4, 

77
organic carbon 1.8%) from North Dakota, and a silt loam soil (pH 7.5, organic carbon 0.92%) 

from Italy. The adsorption phase of the study was carried out by equilibrating air-dried soil with 

[

14C-5-pyrimidinyl]orthosulfamuron at 0.25, 0.75, 2.5, 7.5, and 25.0 mg a.i./kg soil at 20 ± 2°C 

for 2 hours (lighting conditions were not reported). The equilibrating solution used was 0.01M 

CaCl2, with soil/solution ratios of 1:5 (w:v) for all test soils. The desorption phase of the study 

was carried out by replacing the adsorption solution with an equivalent volume of pesticide-free 

0.01M CaCl2 solution and equilibrating at 20 ± 2°C for 2 hours (lighting conditions were not 

reported). The desorption step was conducted twice for all test soils. Soil properties and the 

adsorption/desorption data are summarized in Table B-3. 

Table B-3. Orthosulfamuron Adsorption/Desorption in Six Various Soils. 

Property Ark-1 Ark-2 Benson M-CL PC-1 Pratt 

Soil texture Sandy loam Sandy loam Sand Clay loam Silt loam Loam 

%Sand 58.25 60.00 87.25 24.75 13.50 42.00 

%Silt 36.25 32.00 11.00 44.50 72.50 38.00 

%Clay 5.50 8.00 1.75 30.75 14.00 20.00 

pH (0.01 CaCl2) 6.50 5.66 4.70 5.37 7.50 7.40 

Organic carbon (%) 1.04 0.35 1.03 3.01 0.92 1.80 

Organic matter (%) 1.77 0.60 1.75 5.12 1.56 3.06 

CEC (meq/100g) 7.19 5.89 1.46 27.18 17.01 22.40 

Adsorption 

Kf 2.37 8.17 3.61 19.7 2.00 6.86 

1/n 0.974 1.062 1.152 0.980 1.019 0.990 

Koc 228 2330 350 653 217 381 

Desorption 

Kf 4.01 8.38 5.11 13.8 3.17 4.72 

1/n 1.048 1.019 0.935 0.958 1.023 0.991 

Koc 385 2390 496 460 345 262 

Ark-1: Arkansas sandy loam soil; Ark-2: Arkansas sandy loam soil; Benson: Minnesota sand soil; M-CL: clay 

loam soil from North Dakota; PC-1: silt loam soil from Italy; Pratt: loam soil from North Dakota 

CEC = Cation exchange capacity 

Koc = Kf x 100% ÷ (% organic carbon) 

The study is classified as supplemental because material balances were determined only for test 

soils treated at one test concentration, rather than for all test concentrations/test soil groups. 

MRID 46219018 (Acceptable) 

The column leaching of aged [14C-5-pyrimidinyl]-labelled orthosulfamuron and [14C-U-phenyl]­

labeled orthosulfamuron applied at a rate of approximately 75 g/ha in a soil:water system 

(Arkansas loam soil, 51% sand, 38% silt, 11% clay, pH 6.2, organic matter 1.5%; Arkansas well 

water, pH 7.8) was investigated. The columns were continuously leached under saturated 

conditions with 997 mL (equivalent to 508 mm of rainfall) of 0.01M CaCl2 solution in the dark 

for 9 days (temperature not reported), resulting in ca. 6 pore volumes of leachate. The elution 

78
flow rate was 4.6 mL/hour and the infiltration rate was 0.23 cm/hour. Based on TLC analyses of 

leachate samples, [14C]orthosulfamuron was not found in leachate, whereas several 

transformation products were in leachate. In the [14C-U-phenyl]-labeled orthosulfamuron 

portion of the study, major transformation product, S1, accounted for 44.26–50.56% of the 

applied radioactivity in the leachate. Minor transformation products S9, S2, and S5 accounted 

for 3.59–3.76%, 7.32–8.01%, and 1.33–2.47% of the applied, respectively. Minor 

transformation product S4 was found in soil from one column, comprising 3.71% of the applied. 

In the [14C-5-pyrimidinyl]-labelled orthosulfamuron columns, transformation products S9 and 

S11, accounting for 4.07–4.57% and 0.21–0.24% of the applied radioactivity, respectively, were 

found in the leachate. 

MRID 46578968 (Supplemental) 

The column leaching of unaged [14C-5-pyrimidinyl]-labelled orthosulfamuron was investigated 

in two sandy loam soils (58.25% sand, 36.25% silt, 5.5% clay pH 6.50, organic matter 1.79%; 

60% sand, 32% silt, 8% clay, pH 5.66, organic matter 0.60%) from Arkansas, a sand soil 

(87.25% sand, 11% silt, 1.75% clay, pH 4.70, organic matter 1.77%) from Minnesota, a clay 

loam (24.75% sand, 44.5% silt, 30.75% clay, pH 5.37, organic matter 5.18%) from North 

Dakota, and a silt loam (13.50% sand, 72.5% silt, 14% clay, pH 7.50, organic matter 1.58%) 

from Italy. The columns were continuously leached under saturated conditions for 119 hours 

with 997 mL (equivalent to 508 mm of rainfall) of 0.01M CaCl2 solution, resulting in ca. 5-6 

pore volumes of leachate. The flow rate ranged from 8.42 to 125.11 mL/h, and the infiltration 

rate ranged from 0.43 to 6.37 cm/h. 

For the Ark-1 sandy loam soil, an average of 8.68% of the applied radioactivity was recovered in 

the 1s segment (top 5-cm segment), 16.06% in the 2s (5–10 cm) segment, 26.71% in the 3s (10– 

15 cm) segment, 31.11% in the 4s (15–20 cm) segment, 14.84% in the 5s (20–25 cm) segment, 

and 1.27% of the applied in the 6s (25–30 cm) segment. Based on TLC analysis, 

[

14C]orthosulfamuron comprised 88.51% of the applied, of which 6.18%, 13.08%, 24.35%, 

29.47%, 14.33%, and 1.10% of the applied was recovered in soil segments 1s, 2s, 3s, 4s, 5s, and 

6s, respectively. Transformation product S12 (DOP urea) was found in the top 25 cm of soil and 

totaled 8.22% of the applied radioactivity. Transformation product S13 (DOP amine) was not 

detected. Total extractable [14C]residues accounted for 96.86% of the applied, and unextractable 

residues accounted for 1.81% of the applied. Radioactivity in the leachate samples totaled 

0.63% of the applied. Based on TLC analysis, [14C]orthosulfamuron comprised all of the 

radioactivity recovered in the leachate samples. 

For the Ark-2 sandy loam soil, an average of 31.32% of the applied radioactivity was recovered 

in the 1s segment, 50.13% in the 2s segment, and 15.60% of the applied in the 3s segment. 

Radioactivity was not recovered in the 4s, 5s, and 6s soil segments. Based on TLC analysis, 

[

14C]orthosulfamuron comprised a total of 72.51% of the applied, of which 18.64%, 40.32%, and 

13.55% of the applied was recovered in soil segments 1s, 2s, and 3s, respectively. 

Transformation product S12 (DOP urea) was found in the top 15 cm of soil and totaled 22.22% 

of the applied. Transformation product S13 (DOP amine) was found in the top 5 cm of soil and 

totaled 0.29% of the applied. Total extractable [14C]residues accounted for 95.00% of the 

79
applied, and unextractable residues accounted for 2.05% of the applied. Radioactivity in the 

leachate samples was not detected. 

For the Benson sand soil, an average of 32.60% of the applied was recovered in the 1s segment, 

29.86% in the 2s segment, 22.65% in the 3s segment, 9.26% in the 4s segment, and 0.46% of the 

applied in the 5s segment. Radioactivity was not recovered in the 6s (bottom) soil segment. 

Based on TLC analysis, [14C]orthosulfamuron comprised a total of 52.80% of the applied, of 

which 11.95%, 17.31%, 15.99%, and 7.55% of the applied was recovered in soil segments 1s, 2s, 

3s, and 4s, respectively. Transformation product S12 was found in the top 20 cm of soil and 

totaled 38.16% of the applied. Transformation product S13 was found in the top 15 cm of soil 

and totaled 1.35% of the applied. Total extractable [14C]residues accounted for 92.44% of the 

applied, and unextractable residues accounted for 2.39% of the applied. Radioactivity in the 

leachate samples was not detected. 

For the M-CL clay loam soil, an average of 84.60% of the applied was recovered in the 1s 

segment, 10.94% in the 2s segment, and 0.25% of the applied in the 3s segment. Radioactivity 

was not recovered in the remaining 4s, 5s, and 6s soil segments. Based on TLC analysis, 

[

14C]orthosulfamuron comprised a total of 72.22% of the applied, of which 64.01% and 8.21% of 

the applied was recovered in soil segments 1s and 2s, respectively. Transformation product S12 

was found in the top 10 cm of soil and totaled 18.04% of the applied. Transformation product 

S13 was found in the top 5 cm of soil and totaled 0.67% of the applied. Total extractable 

[

14C]residues accounted for 91.17% of the applied, and unextractable residues accounted for 

4.62% of the applied. Radioactivity in the leachate samples was not detected. 

For the PC-1 silt loam soil, an average of 13.50% of the applied was recovered in the 1s 

segment, 11.16% in the 2s segment, 15.37% in the 3s segment, 20.61% in the 4s segment, 

22.63% in the 5s segment, and 10.08% of the applied in the 6s segment. Based on TLC analysis, 

[

14C]orthosulfamuron comprised a total of 80.99% of the applied, of which 10.78%, 8.39%, 

13.18%, 18.31%, 20.77%, and 9.56% of the applied was recovered in soil segments 1s, 2s, 3s, 

4s, 5s, and 6s respectively. Transformation product S12 was found in all soil segments and 

totaled 9.68% of the applied. Transformation product S13 was not detected. Total extractable 

[

14C]residues accounted for 90.65% of the applied, and unextractable residues accounted for 

2.70% of the applied. Radioactivity in the leachate samples totaled 2.09% of the applied. TLC 

analysis showed that [14C]orthosulfamuron accounted for all of the radioactivity recovered in the 

leachate samples. 

The study is classified as supplemental since only one compound ring was radiolabelled and the 

compound was not aged in soil. This study is valid for orthosulfamuron parent, but does not 

evaluate the leaching potential of major degradates. 

164-2. Aquatic Field Dissipation 

MRID 46578985 (Supplemental) 

Orthosulfamuron (IR5878 50WG, 50% a.i.) was applied once at a target application rate of 375 g 

a.i./ha (0.335 lb a.i./A; which is 500% of the normal use rate) onto a bare ground plot of silt loam 

80
soil (32% sand, 56% silt, 12% clay, pH 6.7, 0.8% organic matter) in Arkansas and a bare ground 

plot of silty clay loam soil (18% sand, 49% silt, 33% clay, pH 7.7, 2.2% organic matter) in 

California. The plots were flooded with water 1–2 days following the test application to 

approximate the timing of herbicide application to rice. Soil (0–60 cm depth), water, and 

sediment (0–5 cm depth) samples were collected for analysis of orthosulfamuron and three 

transformation products. Soil samples were collected through 550–553 days post-treatment and 

water and sediment samples were collected from 3 days to 2 months post-treatment, at which 

time the water was drained from the plots. 

At the Arkansas test site, orthosulfamuron dissipated in the soil, sediment, and water with firstorder half-lives of 4.1 days (r2

 = 0.9119), 6.2 days (r2 = 0.8864), and 6.4 days (r2 = 0.7323), 

respectively. 

Orthosulfamuron was detected in the 0- to 15-cm soil depth at a mean concentration of 0.069 

mg/kg at day 0, which is 33.7% of the theoretical amount (calculated based on a theoretical value 

of 0.205 mg/kg determined for the 0–15 cm soil depth based on the application rate at 0.375 kg 

a.i./ha and the site specific bulk density of 1.22 g/cm3). Orthosulfamuron decreased to 0.046 

mg/kg by 1 day and 0.015 mg/kg by 7 days, and was last detected at 0.006 mg/kg (single 

replicate) at 15 days post-treatment. It was only detected once in the 15- to 30-cm soil depth, at 

0.007 mg/kg (single replicate) at day 0, and was not detected below that depth. The levels of 

orthosulfamuron and three degradation products in soil (0–15 cm depth), sediment, and water are 

shown in Tables B-4 through B-6. 

Table B-4. Mean Concentration of Orthosulfamuron Residues in Arkansas S(soil 0–15 

cm), Expressed as mg/kg Soil. 

Days Posttreatment 

Average Residue in the 0–15 cm Soil Depth (mg/kg) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) 

0 0.069 0.007a ND ND 

1 0.046 0.006a ND ND 

7 0.015 0.026 ND 0.047b 

15 0.006a

 0.026 ND ND 

22 <0.005 0.025 ND 0.025b 

31 <0.005 0.023 ND ND 

60 <0.005 0.026 ND ND 

123 <0.005 0.023a ND – 

186 – 0.049 – – 

273 – 0.033 – – 

364 – 0.018 – – 

462 – 0.037 – – 

81
Table B-4. Mean Concentration of Orthosulfamuron Residues in Arkansas S(soil 0–15 

cm), Expressed as mg/kg Soil. 

Days Posttreatment 

Average Residue in the 0–15 cm Soil Depth (mg/kg) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) 

550 – 0.017 – – 

Orthosulfamuron, S12 and S9: LOD = 0.0006 mg/kg and LOQ = 0.005 mg/kg. S1: LOD = 0.008 mg/kg and LOQ = 0.02 

mg/kg. 

a

 Single replicate value (other replicates <LOQ) b

 Mean of duplicate detects (with the third replicate <LOQ) 

Table B-5. Mean Concentration of Orthosulfamuron Residues in Arkansas Sediment (0-5 

cm), Expressed as mg/kg Soil. 

Sampling Interval 

Concentration in Sediment (mg/kg) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) 

3 days 0.182 0.042 ND 0.061 

7 days 0.055 0.126 <0.005 0.065 

15 days 0.019 0.141 <0.005 ND 

22 days 0.011 0.085 <0.005 0.053 

1 month 0.008 0.062 <0.005 0.031a 

2 months <0.005 0.049 ND ND 

Orthosulfamuron, S12 and S9: LOD = 0.0006 mg/kg and LOQ = 0.005 mg/kg. S1: LOD = 0.008 mg/kg and LOQ = 0.02 

mg/kg. 

a

 Single replicate value (other replicates <LOQ) 

Table B-6. Mean Concentration of Orthosulfamuron Residues in Arkansas Water (mg/L). 

Sampling Interval 

Concentration in Water (mg/L) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) 

3 days 0.024 <0.005 ND 0.006 

7 days 0.012 <0.005 ND 0.009a 

15 days 0.006a <0.005 ND 0.011a 

22 days <0.005 <0.005 ND 0.009 

1 month <0.005 <0.005 <0.005 0.006a 

2 months <0.005 <0.005 ND <0.005 

Orthosulfamuron, S12 and S9: LOQ = 0.005 mg/L. S1: LOQ = 0.02 mg/L. a

 Mean from replicates with a detection 

82
At the California test site, orthosulfamuron dissipated in the soil and sediment with first-order 

half-lives of 2.3 days (r2

 = 0.8678) and 4.3 days (r2 = 0.438), respectively. A half-life for 

orthosulfamuron in water could not be calculated because the chemical was not detected in the 

water. The levels of orthosulfamuron and three degradation products in soil (0–15 cm depth) and 

sediment are shown in Tables B-7 and B-8. 

Table B-7. Mean Concentration of Orthosulfamuron Residues in California Soil (0–15 

cm), Expressed as mg/kg Soil. 

Days Posttreatment 

Average Residue in the 0–15 cm Soil Depth (mg/kg) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) 

0 0.094 <0.005 ND <0.02 

1 0.095 0.008 ND <0.02 

3 0.031a 0.012a ND <0.02 

7 0.013 0.022 ND <0.02 

15 <0.005 0.019 ND ND 

31 <0.005 0.017b ND ND 

62 ND 0.010 ND ND 

122 ND 0.031 ND ND 

194 <0.005 0.040 ND ND 

284 – 0.021 – – 

372 – 0.036 – – 

464 – 0.015a – – 

553 – 0.024 – – 

Orthosulfamuron, S12, and S9: LOD = 0.0006 mg/kg and LOQ = 0.005 mg/kg. S1: LOD = 0.008 mg/kg and LOQ = 0.02 

mg/kg. 

a

 Single replicate value (other replicates <LOQ) b

 Mean of duplicate detects (with the third replicate <LOQ) 

Table B-8. Mean Concentration of Orthosulfamuron Residues in California Sediment (0­

5 cm), Expressed as mg/kg Soil. 

Sampling Interval 

Concentration in Sediment (mg/kg) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) 

3 days 0.062 0.028 ND <0.02 

7 days 0.050 0.100 ND <0.02 

15 days 0.007a 0.033 ND ND 

1 month <0.005 0.023b ND ND 

2 months ND 0.017 ND ND 

Orthosulfamuron, S12 and S9: LOD = 0.0006 mg/kg and LOQ = 0.005 mg/kg. S1: LOD = 0.008 mg/kg and LOQ = 0.02 

mg/kg. 

83
Table B-8. Mean Concentration of Orthosulfamuron Residues in California Sediment (0­

5 cm), Expressed as mg/kg Soil. 

Sampling Interval 

Concentration in Sediment (mg/kg) 

Orthosulfamuron DOP Urea (S12) 

o-Desmethyl 

Orthosulfamuron 

(S9) DBS Acid (S1) a

 Single replicate value (other replicates <LOQ) b

 Mean of duplicate detects (with the third replicate <LOQ) 

The study is classified as supplemental because the storage stability data (from field spikes) 

could not demonstrate stability of the parent and transformation products for the maximum 

storage interval of test samples (with the exception of parent and S12 from the Arkansas water 

samples). Recoveries for S1 from Arkansas soil and sediment and for orthosulfamuron, S1, and 

S12 from California soil and sediment were low, indicating that the compounds were not stable 

for the storage interval. 

165-4 Accumulation in Fish 

MRID 46588507 (Acceptable) 

The bioaccumulation of [14C-5-pyrimidinyl]-labeled orthosulfamuron was studied in bluegill 

sunfish (Lepomis macrochirus) at nominal concentrations of 142 μg/L (low-dose) and 1420 μg/L 

(high-dose) under flow-through conditions. Following the 14-day exposure period, fish from 

each aquarium were transferred to a flow-through system with untreated tap water for a 14-day 

depuration period. Calculated bioconcentration factors (BCFs) in the low dose experiments, 

based on the average amount of residual radioactivity in fish during the entire exposure period, 

were 0.29, 0.34, and 0.32 for edible tissues, non-edible tissues, and whole fish tissues, 

respectively. Lipid content in control fish samples was 11.3–11.8 mg/g in edible tissues, 20.0– 

21.7 mg/g in non-edible tissues, and 16.7–17.7 mg/g in whole fish. Average lipid-BCF values 

ranged from 16–29. In the high dosage experiments, calculated BCFs were 0.72, 1.14, and 0.97 

for edible tissues, non-edible tissues, and whole fish, respectively. Average lipid-BCF values 

ranged from 52–68. 

84
Synonyms and Chemical Structures 

The synonyms, IUPAC names, and chemical structures of orthosulfamuron and its 

transformation products are provided in Table B-9. 

Table B-9. Chemical Structures of Orthosulfamuron and Degradation Products 

Detected in Submitted Environmental Fate Studies. 

Name Structure 

Orthosulfamuron 

S3 

IR5878 

1-(4,6-dimethoxypyrimidin-2-yl)­

3-[2-(dimethylcarbamoyl)phenylsulfa 

moyl]urea 

CAS # 213464-77-8 

N 

O 

NH 

S 

O 

O 

NH 

O 

NH 

N 

N 

O 

O 

DBS acid 

S1 

IR7863 

2-dimethylcarbamoylphenyl sulfamic 

acid 

O 

N 

O 

S O 

OH 

HN 

DBS amide 

S2 

2-sulfmoylamino-N,N-dimethylbenzamide 

O 

N 

O 

S O 

NH2 

HN 

DB amine 

S4 

2-amino-N,N-dimethylbenzamide O 

N 

H2N 

85
Table B-9. Chemical Structures of Orthosulfamuron and Degradation Products 

Detected in Submitted Environmental Fate Studies. 

Name Structure 

O-desmethyl orthosulfamuron 

S9 

IR8181 

1-(4-hydroxy-6-methoxypyrimidin2-yl)-3­

[2-(dimethylcarbamoyl)phenylsulfam 

oyl]urea 

NH 

O 

NH 

O 

S 

O 

NH N 

O 

N 

N 

O 

HO 

DOP urea 

S12 

IR7825 

N-(4,6-dimethoxypyrimidin2-yl)urea 

N 

H 

O 

H2N 

N 

N O 

O 

DOP amine 

S13 

4,6-dimethoxypyrimidin-2-yl amine N 

N 

O 

O 

H2N 

O-desmethyl DOP urea 

S15 

N-(4-hydroxy-6-methoxypyrimidin2-yl)urea 

N 

H 

O 

H2N 

N 

N O 

OH 

86
APPENDIX C. Interim Rice Model Input/Output data. 

1. Interim Rice Model (USEPA, 2002). 

EEC = 109

 x MT / [VT + (msed x Kd)] 

where, 

MT = total mass of pesticide applied per area = 0.0772 kg a.i./ha 

VT = volume of paddy water, including water column and pore water = 1.067 x 106 L/ha 

Kd = mean KOC from nine soils times 2% soil organic carbon content 

= 359 L/kgOC x 0.02 = 7.19 L/kg 

msed = mass of top 1 cm of sediment = 1.30 x 105 kg/ha 

109 = μg/kg conversion for estimate of ppb 

EEC = the dissolved concentration in water (μg a.i./L, ppb) 

Example calculation: 

EEC (μg a.i./L) = (109 μg/kg) x (0.0772 kg a.i./ha) / [1.067 x 106 L/ha + (1.30 x 105 kg/ha 

x 7.19 L/kg)] = 38.6 μg a.i./L (ppb) 

2. Units conversion for semi-aquatic plant calculations: 

EEC (lbs a.i./A) = (38.6 μg a.i./L) x (1.067 x 106 L/ha) x (2.20 x 10-9 lbs a.i./μg a.i.) 

x (0.405 ha/A) = 0.0367 lbs a.i./A 

87
APPENDIX D: Example T-Rex Input and Output for Orthosulfamuron. 

88
89
T-Rex can be found at: 

http://www.epa.gov/oppefed1/models/terrestrial/trex_usersguide.htm 

APPENDIX E: Example Terrplant (v. 1.2.1) Input and Output for 

Orthosulfamuron. 

90
91
APPENDIX F: Ecological Effects Assessment. 

II. Toxicity to Freshwater Aquatic Animals 

a. Freshwater Fish, Acute 

Two freshwater fish toxicity studies using the technical grade active ingredient (TGAI) are 

required to establish the acute toxicity of orthosulfamuron to fish. The preferred test species are 

rainbow trout (a coldwater fish) and bluegill sunfish (a warmwater fish). Acceptable acute 

toxicity studies using orthosulfamuron TGAI have been submitted for rainbow trout (one study) 

and bluegill sunfish (one study). The results are summarized in Table E-1. 

The 96-hour LC50 values reported in these static, acute toxicity studies exceeded 122 mg a.i./L in 

rainbow trout (MRID 46219042; Acceptable) and 142 mg a.i./L in bluegill sunfish (MRID 

46219043; Acceptable) indicating that orthosulfamuron is practically nontoxic to freshwater fish. 

The guideline (72-1) is fulfilled. 

In addition to lethality endpoints, sublethal effects of acute orthosulfamuron TGAI exposure 

were assessed in studies in rainbow trout (MRID 46219042; Acceptable) and bluegill sunfish 

(MRID 46219043; Acceptable). No signs of sublethal toxicity were observed in either study. 

No studies assessing the acute toxicity of orthosulfamuron formulations degradates in fish were 

submitted. 

92
Table E-1. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to Freshwater 

Fish. 

Species 

% 

a.i. LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Rainbow trout 

(Oncorhynchus 

mykiss) 

98.56 96-h LC50: 

>122 mg 

a.i./L 

96-h acute toxicity test in juvenile 

rainbow trout under static test 

conditions. Nominal 

concentrations: 0 (negative control), 

16, 26, 43, 72, and 120 mg a.i./L 

Mean measured concentrations: 0, 

16, 26, 44, 74, and 122 mg a.i./L, 

respectively. 

Practically 

nontoxic 

MRID 46219042 

(Acceptable) 

No mortalities or sublethal effects 

in control group or any treatment 

groups. 

96-h LC50: >122 mg a.i./L (95% 

C.I.: N/A; Probit slope: N/A) 

Bluegill sunfish 

(Lepomis 

macrochirus) 

98.56 96-h LC50: 

>142 mg 

a.i./L 

NOAEC (mortality and sublethal 

effects): 122 mg a.i./L 

LOAEC (mortality and sublethal 

effects): >122 mg a.i. /L 

96-h acute toxicity test in juvenile 

bluegill sunfish under static test 

conditions. Nominal 

concentrations: 0 (negative control), 

16, 26, 43, 72, and 120 mg a.i./L; 

mean measured concentrations: 0, 

18, 34, 46, 84, and 142 mg a.i./L, 

respectively. 

Practically 

nontoxic 

MRID 46219043 

(Acceptable) 

No mortalities or sublethal effects 

in the control group or any 

treatment groups. 

96-h LC50: >142 mg a.i./L 

(95% C.I.: N/A; Probit slope: N/A) 

NOAEC (mortality and sublethal 

effects): 142 mg a.i./L 

LOAEC (mortality and sublethal 

effects): >142 mg a.i./L 

b. Freshwater Fish, Chronic 

A freshwater fish early life-stage test using the TGAI is required for orthosulfamuron because 

end-use products could contaminate surface water through drift or runoff events and may be 

transported to water from the intended use site. 

93
One early life-stage toxicity study with fathead minnow was submitted (MRID 46578953; 

Acceptable). NOAEC and LOAEC values were based on dry weight measurements, the only 

endpoint affected. Study details and results are summarized in Table E-2. In addition to 

lethality, sublethal effects of orthosulfamuron were assessed in the submitted study (MRID 

46578953; Acceptable). No signs of exposure-related sublethal toxicity were observed. The 

guideline (72-4[a]) is fulfilled. 

No chronic toxicity studies of orthosulfamuron formulations or degradates in freshwater fish 

were submitted. 

Table E-2. Chronic Toxicity of Technical Grade Orthosulfamuron (TGAI) to 

Marine/Estuarine Fish. 

Species 

% 

a.i. NOAEC Comments 

Identification 

Number (Study 

Classification) 

Fathead 98.56 NOAEC: 33-day early life-stage toxicity test using fertilized MRID 46578953 

minnow 6.1 mg eggs/embryos under flow-through test conditions. (Acceptable) 

(Pimephales a.i./L Nominal concentrations: 0 (negative control), 0.75, 

promelas) (dry weight) 1.5, 3.0, 6.0, and 12 mg a.i./L.; mean measured 

concentrations: 0, 0.76, 1.5, 3.2, 6.1, and 13 mg 

a.i./L, respectively. 

Endpoints monitored: embryo survival, larval 

survival, terminal length, dry weight, wet weight, 

and clinical signs of toxicity. 

Day 33 (28 days post-hatch), dry weights averaged 

11.7 mg for the control group, 11.4–12.5 mg for the 

0.76 through 6.1 mg a.i./L groups, and 10.2 mg for 

the 13 mg a.i./L group. No other treatment-related 

effects were observed. 

NOAEC (dry weight): 6.1 mg a.i./L 

LOAEC (dry weight): 13 mg a.i./L 

(dry weight) 

c. Freshwater Invertebrates, Acute 

A freshwater aquatic invertebrate toxicity study using the TGAI is required to establish the 

toxicity of orthosulfamuron to freshwater invertebrates. The preferred test species is the water 

flea (Daphnia magna). One acute toxicity study using orthosulfamuron TGAI has been 

submitted for water flea (MRID 46219044; Acceptable). Study details and results are 

summarized in Table E-3. An acute toxicity value (48-hour EC50) greater than 97.3 mg a.i./L 

(the highest concentration tested) was reported for Daphnia magna (MRID 46219044; 

Acceptable). Based on this result, orthosulfamuron TGAI is categorized as not more than 

slightly toxic to freshwater invertebrates on an acute basis. The study did not distinguish 

between mortality and immobility; therefore, the EC50 value of >97.3 mg a.i./L is used as a 

94
surrogate value for lethality to evaluate acute toxic exposure of freshwater invertebrates to 

orthosulfamuron. The guideline (72-2) is fulfilled. 

A 96-hour acute toxicity study with crayfish (Procambarus clarkia) was submitted (MRID 

46578955; Supplemental). Study details and results are summarized in Table E-3. There were 

no deaths or sublethal effects at any of the concentrations tested. The 96-hour LC50 and the 

NOAEC for mortality and sublethal effects were >129 and 129 mg a.i./L, respectively, indicating 

that orthosulfamuron was practically nontoxic to the crayfish on an acute basis. Although this 

study is scientifically sound it is classified as Supplemental because crayfish are not a U.S. EPArecommended species for toxicity testing with freshwater invertebrates, and guidelines do not 

exist for this species. The results of this study, however, are useful for risk assessment purposes. 

No acute toxicity studies of orthosulfamuron formulations or degradates in freshwater 

invertebrates were submitted. 

Table E-3. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to Freshwater 

Invertebrates. 

Species 

% 

a.i. EC50/LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Water flea 98.54 48-h EC50: 

(Daphnia >97.3 mg 

magna) a.i./L 

(mortality and 

immobility) 

48-h acute toxicity in neonate 

daphnids under static test conditions. 

Nominal concentrations: 0 (negative 

control) 6.25, 12.5, 25, 50, and 100 

mg a.i./L; mean measured 

concentrations for control and two 

highest treatment levels (the only 

levels analytically verified) were 

<1.7, 47.0, and 97.3 mg a.i./L. 

48-h mortality: 20% in 97.3 mg a.i./L 

group. No mortality in control or 

other treatment groups. 

48-h EC50: >97.3 mg a.i./L 

95% C.I.: N/A; Probit slope: N/A 

(for mortality and immobility) 

NOAEC: 47.0 mg a.i./L 

(for mortality and immobility) 

LOAEC: 97.3 mg a.i./L 

(for mortality and immobility) 

Slightly MRID 46219044 

toxic (Acceptable) 

95
Table E-3. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to Freshwater 

Invertebrates. 

Species 

% 

a.i. EC50/LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Crayfish, 

(Procambarus 

clarkia) 

98.56 96-h LC50, 

EC50 >129 

mg a.i./L 

96-h acute toxicity study in juvenile 

crayfish under static test conditions. 

Nominal concentrations: 7.5, 15, 30, 

Practically 

nontoxic 

MRID 46578955 

(Supplemental) 

(for mortality 60, and 120 mg a.i./L; mean measured 

and sublethal concentrations: 8.2, 16, 32, 64, and 

effects) 129 mg a.i./L, respectively. 

Endpoints assessed: mortality and 

sublethal effects. 

No mortalities or sublethal effects 

were observed during the study at any 

treatment level. 

This study is scientifically sound, but 

it is classified as Supplemental 

because guidelines do not exist for 

this species. 

96-h LC50: >129 mg a.i./L 

95% C.I.: N/A; Probit slope: N/A 

EC50: >129 mg a.i./L (for sublethal 

effects) 

NOAEC: 129 mg a.i./L 

(for mortality and sublethal effects) 

d. Freshwater Invertebrate, Chronic 

A freshwater aquatic invertebrate life-cycle test using the TGAI is required for orthosulfamuron 

because the end-use product may be transported to water from the intended use site. 

One life-cycle toxicity study with Daphnia magna (MRID 46578956; Acceptable) was 

submitted. Study details and results are summarized in Table E-4. NOAEC and LOAEC values 

of 6.5 and 14 mg a.i./L, respectively, were established based on reductions in mean total length. 

In addition, first generation survival was reduced at the highest dose tested. Reproduction and 

dry weight were not affected at any of the doses tested. . The guideline (72-4[b]) is fulfilled. 

No life-cycle toxicity studies of orthosulfamuron formulations or degradates in freshwater 

aquatic invertebrates were submitted. 

96
Table E-4. Chronic Toxicity of Technical Grade Orthosulfamuron (TGAI) to Freshwater 

Invertebrates. 

Species 

% 

a.i. NOAEC Comments 

Identification 

Number 

(Study 

Classification) 

Cladoceran 

(Daphnia 

98.56 NOAEC: 6.5 

mg a.i./L. 

21-day chronic toxicity in Daphnia magna neonates 

under static renewal conditions. Nominal 

MRID 

46578956 

magna) (total length) concentrations: 0 (negative control), 6.3, 13, 25, 50, (Acceptable) 

and 100 mg/L.; mean measured concentrations: <3.00 

(LOQ, control), 6.5, 14, 26, 52, and 105 mg a.i./L, 

respectively. 

Endpoints assessed: first generation survival, 

reproduction, total length, dry weight, and sublethal 

signs of toxicity. 

Endpoints affected: total length, dry weight, first 

generation survival. Most sensitive endpoint: total 

length. 

Total Length (growth): 

NOAEC: 6.5 mg a.i./L 

LOAEC: 14 mg a.i./L 

Dry Weight (growth): 

LOAEC: >105 mg a.i./L 

NOAEC: 105 mg a.i./L 

First generation survival: 

EC50: >105 mg a.i./L 

LOAEC: 105 mg a.i./L 

NOAEC: 52 mg a.i./L 

Neonate production (reproduction): 

EC50: >105 mg a.i./L 

NOAEC: 105 mg a.i./L 

LOAEC: >105 mg a.i./L 

e. Freshwater Benthic Organisms 

Studies in benthic organisms are not guideline requirements. No toxicity studies of 

orthosulfamuron TGAI, formulations, or degradates in freshwater benthic organisms were 

submitted. 

III. Toxicity to Estuarine and Marine Animals 

97
a. Estuarine and Marine Fish, Acute 

Acute toxicity testing with estuarine/marine fish using the TGAI is required for orthosulfamuron. 

The preferred test species is the sheepshead minnow. One acute toxicity study in 

estuarine/marine fish was submitted for sheepshead minnow (MRID 46578951; Acceptable). 

Study details and results are summarized in Table E-5. 

The submitted study reported an LC50 >123 mg a.i./L, indicating that orthosulfamuron was 

practically nontoxic to estuarine/marine fish on an acute basis (MRID 46578951; Acceptable). 

No sublethal effects were observed in sheepshead minnow exposed up to 123 mg a.i. 

orthosulfamuron/L. The guideline (72-3[a]) is fulfilled. 

No acute toxicity studies of orthosulfamuron formulations or degradates in estuarine/marine fish 

were submitted. 

Table E-5. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to 

Estuarine/Marine Fish. 

Species 

% 

a.i. LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Sheepshead 

minnow 

(Cyprinodon 

variegates) 

98.56 96-h LC50: 

>123 mg 

a.i./L 

96-h acute toxicity test in juvenile 

sheepshead minnow under static test 

conditions. Nominal concentrations: 

control, 16, 26, 43, 72, and 120 mg 

a.i./L; mean measured concentrations: 

16, 27, 45, 75, and 123 mg a.i./L, 

respectively. Control concentrations 

were not reported. 

Practically 

nontoxic 

MRID 46578951 

(Acceptable) 

Endpoints assessed: mortality and 

sublethal effects. 

Endpoints affected: none 

96-h LC50: >123 mg a.i./L 

95% C.I.: N/A; Probit slope: N/A 

Sublethal effects: 

EC50: >123 mg a.i./L 

NOAEC: 123 mg a.i./L 

b. Estuarine and Marine Fish, Chronic 

No life cycle toxicity test with estuarine/ marine fish with orthosulfamuron TGAI, formulations, 

or degradates were submitted. The guideline (72-5) is not fulfilled. 

98
c. Estuarine and Marine Aquatic Invertebrates, Acute 

Acute toxicity testing with estuarine/marine invertebrates using the TGAI is required for 

orthosulfamuron. The preferred test species are eastern oyster (Guideline 72-3[b]) and mysid 

shrimp (Guideline 72-3[c]). 

One acute toxicity study using orthosulfamuron TGAI has been submitted for Eastern oyster; 

study details and results are summarized in Table E-6. No effect on shell deposition was 

observed, yielding a 96-hour EC50 >97 mg a.i./L (MRID 46578957; Acceptable). The study did 

not report any other sublethal effects. An acute toxicity study using orthosulfamuron TGAI was 

submitted for the mysid shrimp; study details and results are summarized in Table E-6. The 

study reported an LC50 >122 mg a.i./L (MRID 46578952; Acceptable). No sublethal effects 

were observed in this study. The EC50 value of >97 mg a.i./L will be used to assess acute risk to 

estuarine/marine mollusks and the LC50 value of >122 mg a.i./L to assess acute risk to 

estuarine/marine shrimp. The guideline (72-3) is fulfilled. 

No acute toxicity studies of orthosulfamuron formulations or degradates in estuarine/marine 

invertebrates were submitted. 

Table E-6. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to 

Estuarine/Marine Invertebrates. 

Species % a.i. EC50/LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Eastern Oyster 98.56% 96-h EC50: 

(Crassotrea >97 mg 

virginica) a.i./L 

(based on 

shell 

growth) 

Saltwater 98.56 96-h LC50: 

mysid >122 mg 

(Americamysis a.i./L 

bahia; 

formerly 

known as 

Mysidopsis 

96-h acute toxicity test in the Eastern 

oyster under flow-through conditions. 

Nominal concentrations: 0 (negative 

control), 6.3, 13, 25, 50, and 100 mg/L; 

mean measured concentrations were 

Slightly 

toxic 

MRID 

46578957 

(Acceptable) 

<3.00 (<LOQ, control), 6.2, 13, 24, 49, 

and 97 mg a.i./L, respectively. 

Endpoints assessed: mortality and shell 

growth. 

No mortality and no exposure-related 

changes in shell growth. 

Shell deposition: 

96-h EC50: >97 mg a.i./L 

NOAEC: 97 mg a.i./L 

96-h acute toxicity test in saltwater 

mysid under static conditions. Nominal 

concentrations: 0 (negative control), 16, 

26, 43, 72, and 120 mg a.i./L; mean 

measured concentrations were <5.0 

Practically 

nontoxic 

MRID 

46578952 

(Acceptable) 

(<LOQ; control), 16, 26, 43, 73, and 122 

mg a.i./L, respectively. 

99
Table E-6. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to 

Estuarine/Marine Invertebrates. 

Species % a.i. EC50/LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

bahia) 

96-h mortality was 5, 5, and 10% in the 

43, 73, and 122 mg a.i./L treatment 

groups, respectively. No sublethal 

effects were observed. 

96-h LC50: >122 mg a.i./L 

95% C.I.: N/A;

Probit slope: N/A

LOAEC: 43 mg a.i./L (mortality) 

NOAEC: 26 mg a.i./L 

(mortality) 

d. Estuarine and Marine Invertebrates, Chronic 

The estuarine/marine aquatic invertebrate life-cycle test using the TGAI of orthosulfamuron is 

required. The preferred test species is the mysid shrimp. 

One life-cycle toxicity study in the mysid shrimp was submitted; the study details and results are 

summarized in Table E-7. NOAEC and LOAEC values of 27 and >27 mg a.i. 

orthosulfamuron/L, respectively, were established for mysid shrimp based on the absence of an 

effect on mortality, reproduction, or growth after 29 days (MRID 46578954; Acceptable). The 

NOAEC of 27 mg a.i./L will be used estimate and characterize chronic risk to estuarine/marine 

invertebrates. The guideline (72-4[c]) is fulfilled although the study is classified as supplemental 

since reproduction of the control treatment was marginally adequate (75% of control produce 8 

or more offspring in two broods). 

No chronic toxicity studies of orthosulfamuron formulations or degradates in estuarine/marine 

invertebrates were submitted. 

Table E-7. Chronic Toxicity of Technical Grade Orthosulfamuron (TGAI) to 

Estuarine/Marine Invertebrates. 

Species 

% 

a.i. NOAEC Comments 

Identification 

Number 

(Study 

Classification) 

Saltwater mysid 98.56 NOAEC: 27 

(Americamysis mg a.i./L 

bahia; formerly (mortality, 

known as growth, 

Mysidopsis reproduction, 

bahia) clinical signs) 

29-day, chronic toxicity test in mysid shrimp MRID

neonates under flow-through conditions. Nominal 46578954

concentrations: 0 (negative control), 1.75, 3.25, 6.5, (Supplemental) 

13, and 26 mg/L; mean measured concentrations

were <0.5, LOQ, negative control, 1.88, 3.56, 6.6,

14, and 27 mg a.i./L, respectively. 

100
Table E-7. Chronic Toxicity of Technical Grade Orthosulfamuron (TGAI) to 

Estuarine/Marine Invertebrates. 

Species 

% 

a.i. NOAEC Comments 

Identification 

Number 

(Study 

Classification) 

Endpoints assessed: first generation survival, 

reproduction, body length, dry weight, and clinical 

signs. 

No effects on survival, growth, reproduction, or 

clinical signs were observed. 

Mortality, reproduction, growth, clinical signs: 

LOAEC: >27 mg a.i./L 

NOAEC: 27 mg a.i./L 

e. Aquatic Field Studies 

No aquatic field studies were submitted. 

IV. Toxicity to Plants Inhabiting Aquatic Environments 

Acute toxicity testing with plants inhabiting aquatic environments using the formulated product 

is required for orthosulfamuron. Eleven acute toxicity studies using orthosulfamuron 

formulations (typical end-use product, TEP) have been submitted for freshwater algae, saltwater 

algae, and aquatic vascular plants. All studies were classified as Acceptable or Supplemental. 

Study details and results are summarized in Table E-8. Studies with algae yielded EC50 values 

ranging from 0.16 mg formulation/L (equivalent to 0.08 mg a.i./L) for reductions in biomass in 

the marine diatom Skeletonema costatum (MRID 46578931) to >108 mg formulation/L 

(equivalent to >54 mg a.i./L) in the freshwater diatom Navicula pelliculosa (MRID 46578932; 

Acceptable), indicating that orthosulfamuron is slightly to highly toxic to algae. Results of 

14-day studies in duckweed (a freshwater vascular plant) yield EC50 values ranging from 1.4 μg 

formulation/L (equivalent to 0.7 μg a.i./L) for decreased from number (MRID 46578939; 

Acceptable) to 1.5 μg formulation/L (equivalent to 0.75 μg a.i./L) for decreased frond number 

(MRID 46578940; Acceptable), indicating that orthosulfamuron is very highly toxic to 

freshwater vascular plants. Based on these results, aquatic macrophytes and marine algae appear 

much more sensitive than freshwater algae to orthosulfamuron. 

The lowest EC50 values will be used to assess acute risks to aquatic plants: EC50 = 1.6 mg 

formulation/L (equivalent to 0.8 mg a.i./L) for decreased biomass in Navicula pelliculosa (MRID 

46578935; Supplemental) for freshwater algae; EC50 = 0.16 mg formulation/L (equivalent to 0.08 

mg a.i./L) for decreased biomass in Skeletonema costatum for marine algae (MRID 46578931; 

Supplemental); EC50 = 1.4 μg formulation/L (equivalent to 0.7 μg a.i./L) for decreased biomass 

in Lemna gibba (MRID 46578939; Acceptable) for freshwater vascular plants. The guideline 

requirement for Tier II growth and reproduction studies (Guideline 123-2) in aquatic plants is 

fulfilled. 

101
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater Algae 

Freshwater 

green algae 

(Selenastrum 

capricornutum) 

49.96 Cell density: 

EC50: 6.2 mg 

formulation/L 

(3.1 mg a.i./L) 

Most sensitive 

endpoints: cell 

density 

96-h acute toxicity study of 

IR5878 50WG (formulation) 

in green algae under static 

conditions. Nominal 

concentrations: 1.9, 3.8, 7.5, 

15, and 30 mg/L; mean 

measured concentrations: 1.9, 

3.7, 7.4, 15, and 30 mg/L, 

respectively. 

Endpoints assessed: cell 

density, biomass, and growth 

rate. 

Cell density:

EC50: 6.2 mg formulation/L

(3.1 mg a.i./L); 95% C.I.: 

5.3–7.2 mg formulation/L 

(2.6–3.6 mg a.i./L) 

EC05: 1.1 mg formulation/L 

(0.55 mg a.i./L); 95% C.I.: 

0.78–1.6 mg formulation/L 

(0.39–0.80 mg a.i./L) 

NOAEC: <1.9 mg 

formulation/L (<0.95 mg 

a.i./L) 

Probit slope: 2.20±0.140 

Growth rate: 

EC50: >30 mg formulation/L 

(>15 mg a.i./L); 95% C.I.: 

N/A 

EC05: 3.7 mg formulation/L 

(1.8 mg a.i./L); 95% C.I.: 

3.0–4.6 mg formulation/L 

(1.5–2.3 mg a.i./L) 

NOAEC: 1.9 mg 

formulation/L (0.95 mg a.i./L) 

Probit slope: 1.63±0.0859 

Biomass: 

EC50: 6.6 mg formulation/L 

(3.3 mg a.i./L); 95% C.I.: 

5.7–7.8 mg formulation/L 

(2.8–3.9 mg a.i./L) 

EC05: 1.1 mg formulation/L 

Moderately MRID 46578931 

toxic (Acceptable) 

102
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater green 

alga (Selenastrum 

capricornutum) 

49.96 Biomass: 

EC50: 2.9 mg 

formulation/L 

(1.4 mg a.i./L) 

Most sensitive 

endpoints: 

biomass 

(0.55 mg a.i./L); 95% C.I.: 

0.74–1.6 mg formulation/L 

(0.37–0.80 mg a.i./L)

NOAEC: <1.9 mg

formulation/L (<0.95 mg

a.i./L) 

Probit slope: 2.08±0.135. 

Most sensitive endpoints: cell 

density 

96-h acute toxicity study of 

IR5878 50WG (formulation) 

in green algae under static 

conditions. Nominal 

concentrations: 0.12, 0.26, 

0.58, 1.3, 2.8, 6.2, 14, and 30 

mg/L; mean measured 

concentrations were 0.13, 

0.27, 0.60, 1.3, 2.8, 6.3, 14, 

and 31 mg/L, respectively. 

Endpoints assessed: cell 

density, biomass, and growth 

rate. 

Significant inhibition of all 

parameters occurred in the 

adjuvant control. 

This toxicity study does not 

satisfy the guideline 

requirement because there 

was significant inhibition in 

the adjuvant control. Thus, 

there is uncertainty associated 

with the effects of the 

adjuvant. 

Biomass:

EC50: 2.9 mg formulation/L

(1.4 mg a.i./L); 95% C.I.: 

2.3–3.8 mg/L (1.1–1.9 mg 

a.i./L) 

EC05: 0.17 mg 

formulation/L (0.08 mg 

a.i./L); 95% C.I.: 0.095–0.32 

mg formulation/L (0.047– 

0.16 mg a.i./L) 

Moderately MRID 46578934 

toxic (Supplemental) 

103
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater green 49.80 Cell density: 

algae EC50: 7.0 mg 

(Pseudokircheriell formulation/L 

a subcapitata) (3.5 mg a.i./L) 

(formerly known 

as Selenastrum Most sensitive 

capricornutum) endpoints: cell 

density 

NOAEC: 0.27 mg 

formulation/L (0.13 mg a.i./L) 

Probit slope: 1.35±0.0936 

Cell density: 

EC50: 3.1 mg formulation/L 

(1.5 mg a.i./L); 95% C.I.: 

2.1–4.4 mg formulation/L 

(1.0–2.2 mg a.i./L) 

EC05: 0.17 mg formulation/L 

(0.08 mg a.i./L); 95% C.I.: 

0.072–0.41 mg formulation/L 

(0.036–0.20 mg a.i./L) 

NOAEC: <0.13 mg 

formulation/L (<0.06 mg 

a.i./L) 

Probit slope: 1.32±0.129 

Growth rate: 

EC50: 30 mg formulation/L 

(15 mg a.i./L); 95% C.I.: 26– 

34 mg formulation/L (13–17 

mg a.i./L) 

EC05: 3.1 mg formulation/L 

(1.5 mg a.i./L); 95% C.I.: 

2.0–4.9 mg formulation/L 

(1.0–2.4 mg a.i./L) 

NOAEC: 0.6 mg 

formulation/L (0.3 mg a.i./L) 

Probit slope: 1.67±0.177 

Most sensitive endpoints: 

biomass 

72-h acute toxicity study of 

IR5878 50WG (formulation) 

in green algae under static 

conditions. Nominal 

concentrations: 0.28, 0.62, 

1.4, 3.0, 6.8, and 15 mg/L; 

mean measured 

concentrations: 0.27, 0.57, 

1.3, 2.9, 6.4, and 15 mg/L, 

respectively. 

Endpoints assessed: cell 

density, biomass, and growth 

rate. 

Moderately MRID 46578959 

toxic (Acceptable) 

104
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater algae 49.96 Cell density: 

The study is scientifically 

sound but does not satisfy the 

guideline requirement; this 

study was conducted for 72 

hours only. 

Cell density:

EC50: 7.0 mg formulation/L

(3.5 mg a.i./L); 95% C.I.: 

4.9–9.8 mg formulation/L 

(2.4–4.9 mg a.i./L) 

EC05: 1.3 mg formulation/L 

(0.65 mg a.i./L); 95% C.I.: 

0.49–3.7 mg formulation/L 

(0.24–1.8 mg a.i./L) 

NOAEC: 0.57 mg 

formulation/L (0.28 mg a.i./L) 

Probit slope: 2.30±0.548 

Growth rate: 

EC50: >15 mg formulation/L 

(>7.5 mg a.i./L); 95% C.I.: 

N/A 

EC05: 3.5 mg formulation/L 

(1.7 mg a.i./L); 95% C.I.: 

2.1–5.6 mg formulation/L 

(1.0–2.8 mg a.i./L) 

NOAEC: 2.9 mg 

formulation/L (1.4 mg a.i./L) 

Probit slope: 1.78±0.299 

Biomass: 

EC50: 8.0 mg formulation/L 

(4.0 mg a.i./L); 95% C.I.: 

5.9–11 mg formulation/L 

(3.0–5.5 mg a.i./L) 

EC05: 1.5 mg formulation/L 

(0.75 mg a.i./L); 95% C.I.: 

0.60–3.9 mg formulation/L 

(0.3–1.9 mg a.i./L) 

NOAEC: 0.57 mg 

formulation/L (0.28 mg a.i./L) 

Probit slope: 2.29±0.523 

Most sensitive endpoints: cell 

density 

96-h acute toxicity study of 

105

Moderately MRID 46578937 
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

(Anabaena flosaquae) EC50: 3.8 mg 

formulation/L 

(1.9 mg a.i./L) 

IR5878 50WG (formulation) 

in algae under static 

conditions. Nominal 

concentrations: 0.091, 0.20, 

Most sensitive 

endpoints: cell 

density 

0.45, 1.0, 2.2, 5.0, and 11 

mg/L; mean measured 

concentrations: 0.082, 0.19, 

0.43, 0.96, 2.2, 4.6, and 10 

mg/L, respectively. 

Endpoints assessed: cell 

density, biomass, and growth 

rate. 

Enlarged cells were observed 

in the 10 mg/L treatment 

group. 

Cell density: 

EC50: 3.8 mg formulation/L 

(1.9 mg a.i./L); 95% C.I.: 

2.5–5.6 mg formulation/L 

(1.2–2.8 mg a.i./L) 

EC05: 1.0 mg formulation/L 

(0.50 mg a.i./L); 95% C.I.: 

0.37–2.8 mg formulation/L 

(0.18–1.4 mg a.i./L) 

NOAEC: 2.2 mg 

formulation/L (1.1 mg a.i./L) 

Probit slope: 2.89±0.750 

Growth rate: 

EC50: 4.7 mg formulation/L 

(2.3 mg a.i./L); 95% C.I.: 

3.7–6.0 mg formulation/L 

(1.8–3.0 mg a.i./L) 

EC05: 1.1 mg formulation/L 

(0.50 mg a.i./L); 95% C.I.: 

0.53–2.1 mg formulation/L 

(0.26–1.0 mg a.i./L) 

NOAEC: 2.2 mg 

formulation/L (1.1 mg a.i./L) 

Probit slope: 2.55±0.444 

Biomass: 

EC50: >10 mg formulation/L 

(>5.0 mg a.i./L); 95% C.I.: 

N/A 

106

toxic (Acceptable) 
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

EC05: 1.8 mg formulation/L 

(0.90 mg a.i./L); 95% C.I.: 

0.91–3.5 mg formulation/L 

(0.45–1.7 mg a.i./L) 

NOAEC: 2.2 mg 

formulation/L (1.1 mg a.i./L) 

Probit slope: 1.89±0.377 

Most sensitive endpoints: cell 

density 

Freshwater algae 49.96 Cell density: 96-h acute toxicity study of Moderately MRID 46578938 

(Anabaena flos- EC50: 4.7 mg IR5878 50WG (formulation) toxic (Acceptable) 

aquae) formulation/L in algae under static 

(2.3 mg a.i./L) conditions. Nominal 

concentrations of 0.091, 0.20, 

Biomass: 0.45, 1.0, 2.2, 5.0, and 11 

EC50: 4.7 mg mg/L; mean measured 

formulation/L concentrations: 0.089, 0.20, 

(2.3 mg a.i./L) 0.45, 0.99, 2.2, 4.9, and 11 

mg/L, respectively. 

Most sensitive 

endpoints: cell Endpoints assessed: cell 

density and density, biomass, and growth 

biomass rate. 

Cell density and biomass 

were equally sensitive. 

Enlarged cells were observed 

in the 11 mg/L treatment 

group. 

Cell density: 

EC50: 4.7 mg formulation/L 

(2.3 mg a.i./L); 95% C.I.: 

3.5–6.5 mg formulation/L 

(1.7–3.2 mg a.i./L) 

EC05: 1.8 mg formulation/L 

(0.90 mg a.i./L); 95% C.I.: 

0.87–3.7 mg formulation/L 

(0.43–1.8 mg a.i./L) 

NOAEC: 2.2 mg 

formulation/L (1.1 mg a.i./L) 

Probit slope: 3.92±0.954 

Biomass: 

EC50: 4.7 mg formulation/L 

(2.3 mg a.i./L); 95% C.I.: 

107
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

3.7–5.9 mg formulation/L 

(1.8–2.9 mg a.i./L) 

EC05: 1.5 mg formulation/L 

(0.75 mg a.i./L); 95% C.I.: 

0.84–2.6 mg formulation/L 

(0.42–1.3 mg a.i./L) 

NOAEC: 2.2 mg 

formulation/L (1.1 mg a.i./L) 

Probit slope: 3.27±0.532 

Growth rate: 

EC50: 12 mg formulation/L 

(6.0 mg a.i./L); 95% C.I.: 10– 

13 mg formulation/L (5.0–6.5 

mg a.i./L) 

EC05: 3.0 mg formulation/L 

(1.5 mg a.i./L); 95% C.I.: 

1.9–4.6 mg formulation/L 

(0.95–2.3 mg a.i./L) 

NOAEC: 2.2 mg 

formulation/L (1.1 mg a.i./L) 

Probit slope: 2.76±0.456 

Most sensitive endpoints: cell 

density and biomass 

Freshwater 49.96 Cell density: 96-h acute toxicity study of Slightly toxic MRID 46578932 

Diatom (Navicula EC50: >108 mg IR5878 50WG (formulation) (Acceptable) 

pelliculosa) formulation/L in diatom under static 

(>54 mg a.i./L) conditions. Nominal 

concentrations: 7.5, 15, 30, 

Growth rate: 60, and 120 mg/L; mean 

EC50: >108 mg measured concentrations were 

formulation/L 7.7, 15, 29, 56, and 108 mg/L, 

(>54 mg a.i./L) respectively. 

Biomass: Endpoints assessed: cell 

EC50: >108 mg density, biomass, and growth 

formulation/L rate. 

(>54 mg a.i./L) 

Cell density: 

Endpoints EC50: >108 mg 

affected: none formulation/L (>54 mg 

a.i./L) 

EC05: >108 mg 

formulation/L (>54 mg 

a.i./L) 

NOAEC: 108 mg 

formulation/L (54 mg a.i./L) 

108
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater 

diatom, (Navicula 

pelliculosa) 

49.96 Biomass: 

EC50: 1.6 mg 

formulation/L 

(0.8 mg a.i./L) 

Most sensitive 

endpoints: 

biomass 

Growth rate: 

EC50: >108 mg formulation/L 

(>54 mg a.i./L) 

EC05: >108 mg formulation/L 

(>54 mg a.i./L) 

NOAEC: 108 mg

formulation/L (54 mg a.i./L) 

Biomass: 

EC50: >108 mg formulation/L 

(>54 mg a.i./L) 

EC05: >108 mg formulation/L 

(>54 mg a.i./L) 

NOAEC: 108 mg

formulation/L (54 mg a.i./L) 

Endpoints affected: none 

96-h acute toxicity study of

IR5878 50WG (formulation)

in diatom under static

conditions. Nominal 

concentrations: 0.31, 0.63, 

1.3, 2.5, and 5.0 mg/L; mean 

measured concentrations: 

0.28, 0.57, 1.1, 2.3, and 4.6 

mg/L.

Endpoints assessed: cell 

density, biomass, growth rate.

Due to 100% inhibition of

cell density in the adjuvant 

control it is impossible to 

discern the effects of the 

adjuvant from the effects of 

orthosulfamuron.

Biomass:

EC50: 1.6 mg formulation/L

(0.8 mg a.i./L); 95% C.I.: 

1.5–1.7 mg formulation/L 

(0.75–0.85 mg a.i./L) 

EC05: 0.87 mg 

formulation/L (0.43 mg 

a.i./L); 95% C.I.: 0.75–1.0 

mg formulation/L (0.37–0.50 

mg a.i./L) 

Highly toxic MRID 46578935 

(Supplemental) 

109
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Marine Algae 

Marine diatom 49.96 Biomass: 

(Skeletonema 

costatum) 

EC50: 0.16 mg 

formulation/L 

(0.08 mg a.i./L) 

Most sensitive 

endpoints: 

biomass 

NOAEC: 0.57 mg 

formulation/L (0.28 mg a.i./L) 

Probit slope: 6.26±0.493 

Cell density: 

EC50: 2.4 mg formulation/L 

(1.2 mg a.i./L); 95% C.I.: 

2.3–2.5 mg formulation/L 

(1.1–1.2 mg a.i./L) 

EC05: 1.6 mg formulation/L 

(0.8 mg a.i./L); 95% C.I.: 

1.5–1.8 mg formulation/L 

(0.75–0.90 mg a.i./L) 

NOAEC: 1.1 mg 

formulation/L (0.55 mg a.i./L) 

Probit slope: 9.98±0.993 

Growth rate: 

EC50: 3.3 mg formulation/L 

(1.6 mg a.i./L); 95% C.I.: 

3.2–3.4 mg formulation/L 

(1.6–1.7 mg a.i./L) 

EC05: >1.1 mg formulation/L 

(>0.55 mg a.i./L); 95% C.I.: 

N/A 

NOAEC: 1.1 mg 

formulation/L (0.55 mg a.i./L) 

Probit slope: could not be 

determined 

Most sensitive endpoints: 

biomass 

96-h acute toxicity study of 

IR5878 50WG (formulation) 

in marine diatom under static 

conditions. Nominal 

concentrations: 0.018, 0.041, 

0.091, 0.20, 0.45, and 1.0 

mg/L; mean measured 

concentrations: 0.019, 0.043, 

0.089, 0.20, 0.43, and 0.97 

mg/L. Both negative and 

adjuvant control were tested 

in this study. Significant 

inhibition of all parameters 

occurred in the adjuvant 

control. 

Highly toxic MRID 46578936 

(Supplemental) 

110
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Marine diatom 49.96 Biomass: 

(Skeletonema EC50: 24 mg 

costatum) formulation/L 

(12 mg a.i./L) 

Endpoints assessed: cell 

density, biomass, and growth

rate. 

Biomass:

EC50: 0.16 mg/L (0.08 mg 

a.i./L); 95% C.I.: 0.11–0.22

mg/L (0.05–0.11 mg a.i./L) 

EC05: 0.059 mg/L (0.029 mg 

a.i./L); 95% C.I.: 0.027–0.13 

mg/L (0.013–0.06 mg a.i./L) 

NOAEC: 0.043 mg/L (0.021 

mg ai/L) 

Probit slope: 3.86±0.921 

Cell density: 

EC50: 0.19 mg/L (0.09 mg 

a.i./L); 95% C.I.: 0.13–0.29 

mg/L (0.06–0.14 mg a.i./L) 

EC05: 0.046 mg/L (0.023 mg 

a.i./L); 95% C.I.: 0.019–0.12 

mg/L (0.009–0.06 mg a.i./L) 

NOAEC: 0.043 mg/L (0.021 

mg ai/L) 

Probit slope: 2.68±0.518 

Growth rate: 

EC50: 0.26 mg/L (0.13 mg 

a.i./L); 95% C.I.: 0.23–0.29 

mg/L (0.11–0.14 mg a.i./L) 

EC05: 0.18 mg/L (0.09 mg 

a.i./L); 95% C.I.: 0.15–0.22 

mg/L (0.07–0.11 mg a.i./L) 

NOAEC: 0.043 mg/L (0.021 

mg ai/L) 

Probit slope: 11.5±1.51 

Endpoints affected: cell 

density, biomass, and growth 

rates. 

Most sensitive endpoints: 

biomass 

96-h acute toxicity study of 

IR5878 50WG (formulation) 

in marine diatom under static 

conditions. Nominal 

Slightly toxic MRID 46578933 

(Acceptable) 

111
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Most sensitive 

endpoints: 

biomass 

concentrations: 3.8, 7.5, 15, 

30, and 60 mg/L; mean

measured concentrations were

3.6, 7.2, 15, 29, and 59 mg/L. 

The test concentrations were 

not corrected for the percent 

active ingredient in the test 

substance. 

Endpoints assessed: cell 

density, biomass (area under 

the curve), and growth rate. 

Aggregation and flocculation 

was observed in the 59 mg/L 

group. 

Biomass:

EC50: 24 mg formulation/L 

(12 mg a.i./L); 95% C.I.: 22–

26 mg formulation/L (11–13

mg a.i./L) 

EC05: 12 mg formulation/L 

(6.0 mg a.i./L); 95% C.I.: 

8.8–17 mg formulation/L 

(4.4–8.5 mg a.i./L) 

NOAEC: 15 mg 

formulation/L (7.5 mg a.i./L) 

Probit slope: 5.56±0.939 

Cell density: 

EC50: 36 mg formulation/L 

(18.0 mg a.i./L); 95% C.I.: 

33–40 mg formulation/L 

(16.5–20.0 mg a.i./L) 

EC05: 23 mg formulation/L 

(11.5 mg a.i./L); 95% C.I.: 

19–28 mg formulation/L 

(9.5–14.0 mg a.i./L) 

NOAEC: 7.2 mg 

formulation/L (3.6 mg a.i./L) 

Probit slope: 8.52±0.943 

Growth rate: 

EC50: 42 mg formulation/L 

(21 mg a.i./L); 95% C.I.: 41– 

43 mg formulation/L (20.5– 

21.5 mg a.i./L) 

112
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater 

vascular plant, 

duckweed (Lemna 

gibba) 

49.96 Frond number: 

EC50: 1.4 μg 

formulation/L 

(0.7 μg a.i./L) 

Most sensitive 

endpoint: frond 

number 

EC05: 7.0 mg formulation/L 

(3.5 mg a.i./L); 95% C.I.: 

1.3–38 mg formulation/L 

(0.65–19.0 mg a.i./L) 

NOAEC: 7.2 mg 

formulation/L (3.6 mg a.i./L) 

Probit slope: 0.805±0.370 

Most sensitive endpoints: 

biomass 

7-d acute toxicity study of 

IR5878 50WG (formulation) 

in freshwater vascular plant 

under static conditions. 

Nominal concentrations: 

0.074, 0.16, 0.36, 0.81, 1.8, 

and 4.0 μg/L; mean measured 

concentrations: 0.074, 0.16, 

0.52, 0.86, 1.9, and 3.9 μg/L, 

respectively. 

Endpoints assessed: number 

of fronds and growth rate. 

Exceedingly high 

concentrations of a.i. (114– 

2450%) were observed. 

Frond number:

EC50: 1.4 μg formulation/L

(0.7 μg a.i./L); 95% C.I.: 1.1– 

1.8 μg formulation/L (0.55– 

0.90 μg a.i./L) 

EC05: 0.28 μg formulation/L 

(0.14 μg a.i./L); 95% C.I.: 

0.15–0.53 μg formulation/L 

(0.07–0.26 μg a.i./L) 

NOAEC: 0.52 μg 

formulation/L (0.26 μg a.i./L) 

Probit slope: 2.36±0.321 

Growth rate: 

EC50: 2.0 μg formulation/L 

(1.0 μg a.i./L); 95% C.I.: 1.7– 

2.5 μg formulation/L (0.85– 

1.2 μg a.i./L) 

EC05: not determined 

NOAEC: 0.52 μg 

Very highly MRID 46578939 

toxic (Acceptable) 

113
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Freshwater 49.96 Frond Number: 

vascular plant, 

duckweed (Lemna 

gibba) 

EC50: 1.5 μg 

formulation/L 

(0.75 μg a.i./L) 

Most sensitive 

endpoint: frond 

number 

formulation/L (0.26 μg a.i./L) 

Probit slope: not reported 

Most sensitive endpoint: 

frond number. 

7-d acute toxicity study of 

IR5878 50WG (formulation) 

in freshwater vascular plant 

under static conditions. 

Nominal concentrations: 

0.028, 0.070, 0.18, 0.44, 1.1, 

2.7, and 6.8 μg/L; mean 

measured concentrations for 

the four highest 

concentrations were 0.45, 

0.978, 2.4, and 5.9 μg/L. 

Because the LOQ was 

0.200 μg/L, lower 

concentrations were not 

analytically determined. 

Endpoints assessed: 

number of fronds and growth 

rate 

Frond Number:

EC50: 1.5 μg formulation/L

(0.75 μg a.i./L); 95% C.I.: 

1.2–1.8 μg formulation/L 

(0.60–0.90 μg a.i./L) 

EC05: 0.24 μg formulation/L 

(0.12 μg a.i./L); 95% C.I.: 

0.14–0.41 μg formulation/L 

(0.07–0.20 μg a.i./L) 

NOAEC: 0.45 μg 

formulation/L (0.22 μg a.i./L) 

Probit slope: 2.11±0.214 

Growth rate: 

EC50: 2.1 μg formulation/L 

(1.0 μg a.i./L); 95% C.I.: 2.1– 

2.2 μg formulation/L (1.0–1.1 

μg a.i./L) 

EC05: not determined 

NOAEC: 0.45 μg 

formulation/L (0.22 μg a.i./L) 

Probit slope: not reported 

Very highly MRID 46578940 

toxic (Acceptable) 

114
Table E-8. Acute Toxicity (Tier II) of Orthosulfamuron formulation (TEP) to Plants 

Inhabiting Aquatic Environments. 

Species 

% 

a.i. EC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Frond number was the most 

sensitive endpoint. 

V. Toxicity to Terrestrial Animals 

a. Birds, Acute and Subacute 

An acute oral toxicity study using the technical grade of the active ingredient is required to 

establish the toxicity of orthosulfamuron to birds. The preferred test species is either mallard 

duck (a waterfowl) or bobwhite quail (an upland gamebird). 

Studies of the acute oral toxicity studies of orthosulfamuron TGAI in mallard duck (MRID 

46260107; Acceptable) and bobwhite quail (MRID 46260108; Acceptable) were submitted. 

Study details and results are summarized in Table E-9. Both studies indicate that 

orthosulfamuron is not more than slightly toxic to mallard ducks or bobwhite quail on an acute 

oral basis. The reported acute oral LD50 of >1960 mg a.i./kg body weight in bobwhite quail and 

mallard duck will be used to evaluate the acute exposure of birds to orthosulfamuron. The 

guideline (71-1) is fulfilled. 

No acute oral toxicity studies of orthosulfamuron formulations or degradates in avian species 

were submitted. 

Table E-9. Acute Oral Toxicity of Technical Grade Orthosulfamuron (TGAI) to Birds. 

Species 

% 

a.i. LD50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Mallard ducks 97.99 LD50: 

(Anas >1960 

platyrhynchos) mg 

a.i./kg-bw 

Bobwhite 97.99 LD50: 

14-d oral toxicity test with mallard ducks. 

Nominal doses: 0 (vehicle control), 500, 

1000, and 2000 mg/kg-bw; mean measured: 

doses: 0, 505, 1005 and 1960 mg a.i./kg-bw, 

respectively. 

Slightly 

toxic 

MRID 46260107 

Acceptable 

No mortality or signs of toxicity in any 

treatment group. No clinical signs of 

toxicity, effects on feed consumption, body 

weight, or gross necropsy findings in control 

or high-dose groups. 

LD50: >1960 mg a.i./kg-bw 

LOAEL: >1960 mg a.i./kg-bw 

NOAEL: 1960 mg a.i./kg-bw 

14-d acute oral toxicity in bobwhite quail. Slightly MRID 46260108 

115
Table E-9. Acute Oral Toxicity of Technical Grade Orthosulfamuron (TGAI) to Birds. 

Species 

% 

a.i. LD50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

quail (Colinus 

virginianus) 

>1960 

mg 

Nominal concentrations: 0 (vehicle control), 

500, 1000, and 2000 mg/kg-bw; mean 

toxic (Acceptable) 

a.i./kg-bw measured doses: <0.3 (LOD, control), 500, 

988, and 1960 mg a.i./kg-bw, respectively. 

No mortality or signs of toxicity in any 

treatment group. No clinical signs of 

toxicity, effects on feed consumption, body 

weight, or gross necropsy findings in control 

or high-dose groups. 

LD50: >1960 mg a.i./kg-bw 

LOAEL: >1960 mg a.i./kg-bw 

NOAEL: 1960 mg a.i./kg-bw 

Endpoints affected: none 

Two acute dietary studies using the TGAI are required to establish the toxicity of 

orthosulfamuron to birds. The preferred test species are mallard duck and bobwhite quail. Acute 

dietary toxicity studies with mallard duck (MRID 46219040; Acceptable) and bobwhite quail 

(MRID 46219041; Acceptable) were submitted. Study details and results of these acute dietary 

studies are summarized in Table E-10. 

In mallard ducks (MRID 46219040; Acceptable) and bobwhite quail (MRID 46219041; 

Acceptable) the acute LC50 values were >4790 and >4980 mg a.i./kg diet (the highest 

concentrations tested), respectively. These results indicate that orthosulfamuron TGAI is not 

more than slightly toxic to birds on an acute dietary basis. The lowest reported acute dietary 

LC50 (>4790 mg a.i./kg diet) in mallard ducks will be used to evaluate the acute dietary exposure 

of birds to orthosulfamuron. The guideline (71-2) is fulfilled. 

No acute dietary toxicity studies of orthosulfamuron formulations or degradates in avian species 

were submitted. 

116
Table E-10. Acute Dietary Toxicity of Technical Grade Orthosulfamuron (TGAI) to Birds. 

Species 

% 

a.i. LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Mallard duck 

(Anas 

platyrhynchos) 

Bobwhite quail 

(Colinus 

virginianus) 

97.99 LC50: >4790 

mg a.i/kg 

diet 

97.99 LC50: >4980 

mg a.i./kg 

diet 

8-d acute dietary toxicity test in mallard 

duck. Nominal dietary concentrations: 0 

(control), 156, 313, 625, 1250, 2500, and 

5000 mg/kg diet; mean measured 

concentrations: 0, 161, 310, 603, 1210, 

2440, and 4790 mg a.i./kg diet, 

respectively. 

No mortality, clinical signs of toxicity, or 

treatment-related effects on body weight 

or food consumption were observed. 

LC50: >4790 mg a.i/kg diet. 

NOAEC (for mortality and toxicity): 

4790 mg a.i./kg diet 

LOAEC (for mortality and toxicity): 

>4790 mg a.i./kg diet 

8-d acute dietary toxicity test in 

bobwhite quail. Nominal concentrations 

of 0 (control), 156, 313, 625, 1250, 2500, 

and 5000 mg/kg diet; mean measured 

concentrations were <7.5 (LOD, 

control), 153, 308, 603, 1210, 2450, and 

4980 mg a.i./kg diet, respectively. 

No mortality was observed during the 

study. No clinical signs of toxicity or 

treatment-related effects on body weight 

or food consumption were observed. 

LC50: >4980 mg a.i./kg diet 

NOAEC: 4980 mg a.i./kg diet 

(mortality and clinical signs) 

LOAEC: >4980 mg a.i./kg diet 

(mortality and clinical signs) 

Endpoints affected: none 

Slightly MRID 

toxic 46219040 

(Acceptable) 

Slightly MRID 

toxic 46219041 

(Acceptable) 

b. Birds, Chronic 

Avian reproduction studies using the TGAI are required for orthosulfamuron because birds may 

be subject to continuous exposure to the pesticide, especially preceding or during the breeding 

season. The preferred test species are mallard duck and bobwhite quail. 

Studies of the reproductive toxicity of orthosulfamuron TGAI in mallard ducks (MRID 

46578949; Acceptable) and bobwhite quail (MRID 46578950; Acceptable) were submitted. 

117
Study details and results are summarized in Table E-11. Results of reproductive studies in 

mallard ducks (MRID 46578949; Acceptable) and bobwhite quail (MRID 46578950; 

Acceptable) show no treatment-related effects on adult bird mortality, food consumption, body 

weight, or reproductive parameters. No clinical signs or treatment-related effects in offspring 

survival or body weight were observed at the highest dietary concentrations tested in these 

studies (1280 mg a.i/kg diet). The NOAEC value of >1280 mg a.i/kg diet will be used to assess 

chronic risk of orthosulfamuron in avian species. The guideline (71-4) is fulfilled. 

No chronic toxicity studies of orthosulfamuron formulations or orthosulfamuron degradates in 

avian species were submitted. 

Table E-11. Chronic Toxicity of Technical Grade Orthosulfamuron (TGAI) to Birds. 

Species 

% 

a.i. NOAEC Comments 

Identification 

Number 

(Study 

Classification) 

Mallard duck 98.56 NOAEC: 

(Anas 1280 mg 

platyrhynchos) a.i./kg diet 

Endpoints 

affected: None 

Northern 98.56 NOAEC: 

bobwhite quail 1280 mg 

(Colinus a.i./kg diet 

virginianus) 

Endpoints 

affected: none 

One-generation reproductive toxicity in mallard MRID 

duck was assessed over approximately 21 weeks. 46578949 

Nominal concentrations: 0 (vehicle control), 200, (Acceptable) 

500, and 1250 mg a.i./kg diet. Mean-measured 

concentrations were <50 (<LOD, control), 195, 

500, and 1280 mg a.i./kg diet, respectively. 

There were no clinical signs of toxicity and no 

effects on parental mortality, food consumption, 

body weight, or reproductive endpoints. Offspring 

showed no signs of toxicity or effects in survival or 

body weight. 

NOAEC: 1280 mg a.i./kg diet 

LOAEC: >1280 mg a.i./kg diet 

One-generation reproductive toxicity in bobwhite MRID 

quail was assessed over approximately 21 weeks. 46578950 

Nominal concentrations: 0 (vehicle control), 200, (Acceptable) 

500, and 1250 mg a.i./kg diet; mean measured 

concentrations: <50 (<LOD, control), 195, 500, and 

1280 mg a.i./kg diet, respectively. 

There were no clinical signs of toxicity and no 

effects on parental mortality, food consumption, 

body weight, or reproductive endpoints. Offspring 

showed no signs of toxicity or effects in survival or 

body weight. 

NOAEC: 1280 mg a.i./kg diet 

LOAEC: >1280 mg a.i./kg diet 

Endpoints affected: none 

118
c. Mammals, Acute 

In an acute oral study (MRID 46219019), five young adult rats/sex (Wistar – SPF, males 230­

350 g, females 200-252 g) were dosed with orthosulfamuron (93.7%). The dose was divided in 

two equal parts in deionized water and given at two hour intervals (10 mg/kg/time). Evaluation 

parameters included signs of gross toxicity and mortality for a subsequent period of 14 days. 

Initial and weekly body weights and necropsy finding were recorded on all animals. The LC50 

is >5000 mg/kg, the highest and only tested concentration (Table E-12). 

Table E-12. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to Rats. 

Species 

% 

a.i. LC50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Laboratory Rat 

(Rattus 

norvegicus) 

93.7 LC50: >5000 

mg a.i/kg 

diet 

No mortality, clinical signs of toxicity, or 

treatment-related effects on body weight 

or food consumption were observed. 

Practically 

non-toxic 

MRID 

46219019 

(Acceptable) 

LC50: >5000 mg a.i/kg diet. 

NOAEC (for mortality and toxicity):

5000 mg a.i./kg diet

LOAEC (for mortality and toxicity): 

>5000 mg a.i./kg diet 

d. Mammals, chronic 

In a two-generation reproduction study (MRID 46219033), IR5878 (98.5% a.i., batch # 

G009/02) was administered in the diet to 24 male and 24 female HanBrl:WIST (SPF) rats/dose at 

concentrations of 0, 350, 1400, or 5600 ppm throughout the study for males and during 

premating, mating, and gestation for females. Concentrations of the test article in the diet were 

reduced to 0, 225, 900, and 3600 ppm during lactation of the F0 and F1 dams. Dietary 

concentrations were selected on the basis of a preliminary one-generation study (MRID 

46260106). One litter was produced in each generation. Premating doses for the F0 parental 

animals were 0, 38.1, 145.3, and 634.5 mg/kg/day, respectively, for males and 0, 47.8, 205.0, and 

764.9 mg/kg/day, respectively, for females. Premating doses for the treated F1 parental animals 

were 0, 41.2, 164.7, and 711.9 mg/kg/day, respectively, for males and 0, 52.4, 214.8, and 888.3 

mg/kg/day, respectively, for females. Due to unrealistically high food consumption data, the 

calculated test item intake in this study is extremely high. This could possibly be due to food 

spillage of the powdered diet. For a more realistic estimation of the actual test item intake, the 

study author used values from a concurrent 2-generation reproduction study (RCC 842842) 

performed with the same rat strain and same diet (although pelleted) to calculate achieved doses. 

At concentrations of 0, 350, 1400, 5600 ppm, the achieved premating doses for the F0 parental 

animals were 0, 22.2, 88.6, and 354.5 mg/kg/day, respectively, for males and 0, 25.6, 102.2, and 

408.89 mg/kg/day, respectively, for females. Achieved premating doses for the treated F1 

parental animals were 0, 24.3, 97.0, and 388.1 mg/kg/day, respectively, for males and 0, 27.8, 

111.2, and 444.6 mg/kg/day, respectively, for females. These values are comparable to those 

calculated using a generic conversion (20:1) of ppm to mg/kg/day. F0 and F1 parental animals 

119
were administered test or control diet for 70 or 120 days, respectively, prior to mating, 

throughout mating, gestation, and lactation, and until sacrifice. At approximately six weeks of 

age, the F1 parental animals were subjected to a Functional Observational Battery (FOB) and 

tested for motor activity. 

No treatment-related deaths or clinical signs of toxicity were observed in any group during the 

study. No treatment-related adverse effects on body weight, body weight gain, or food 

consumption were observed during the premating interval in adult animals of either generation or 

in F0 and F1 dams during gestation and lactation. No abnormalities were observed in the FOB. 

No treatment-related effects on organ weight and no gross lesions were seen in adults of either 

generation. High-dose females of both generations had increased incidences and severity of 

kidney lesions. Tubular mineralization was observed at similar incidence in all groups but the 

mean severity grade was 1.8 in both the high-dose F0 and F1 females compared with 1.0-1.4 in 

the controls. The incidence (severity) of urothelial hyperplasia was 11/24 (1.3) in both F0 and F1 

high-dose females compared with 3-4/24 (1.0) for the control groups. The parental systemic 

LOAEL was 5600/3600 ppm for males and females (354.5-388.1and 408.89-444.6 mg/kg/day, 

respectively), based on kidney lesions in F0 and F1 females. The parental systemic NOAEL was 

1400/900 ppm in males (88.6-97.0 mg/kg/day) and females (102.2-111.2 mg/kg/day). 

No treatment-related differences in estrus cycle or estrus cycle length were observed between the 

treated and control females of either generation and no differences in testicular and epididymal 

sperm counts, sperm motility, or sperm morphology were found between the treated and control 

males of either generation. Mating, fertility, and gestation indices, number of days to mating, 

and gestation length were not affected by treatment of either generation during litter production. 

Mean day of sexual maturation and body weight were not affected in the F1 animals. 

For litters of both generations, live birth, viability, lactation indices, mean litter sizes, and sex 

ratios were similar between the treated and control groups. No treatment-related clinical signs of 

toxicity were observed in the pups during lactation and gross necropsy was unremarkable. Body 

weight throughout lactation, and brain, spleen, thymus, and uterus weights on PND 21 were not 

affected by treatment in either generation. High-dose F1 males had significantly reduced (p ≤

0.01) motor activity at all time points and in total activity. No differences in motor activity were 

observed between treated and control females. 

The offspring toxicity LOAEL was 5600/3600 ppm for males and females (354.5-388.1and 

408.89-444.6 mg/kg/day, respectively), based on decreased motor activity in F1 males. The 

offspring NOAEL is 1400/900 ppm in males (88.6-97.0 mg/kg/day) and females (102.2-111.2 

mg/kg/day) (Table E-13). 

This study is Acceptable/Guideline and satisfies the guideline requirement for a two-generation 

reproduction study (OPPTS 870.3800; OECD 416) in rats. 

Table E-13. Chronic Toxicity of Technical Grade Orthosulfamuron (TGAI) to Birds. 

120
Species 

% 

a.i. NOAEL Comments 

Identification 

Number 

(Study 

Classification) 

Laboratory Rat 98.56 NOAEL: MRID 

(Rattus 88.6mg a.i./kg NOAEC: 1280 mg a.i./kg diet 46219033 

norvegicus) bw/day LOAEC: >1280 mg a.i./kg diet (Acceptable) 

Endpoints 

affected: 

decreased 

motor activity 

in F1 males 

e. Terrestrial Insects, Acute Contact 

A honey bee acute contact study using the TGAI is required because outdoor use of 

orthosulfamuron will result in honey bee exposure. The acute contact LD50, using the honey bee, 

Apis mellifera, is an acute contact, single-dose laboratory test designed to estimate the quantity 

of toxicant required to cause 50% mortality in a test population of bees. The TGAI is 

administered by one of two methods: whole body exposure to technical pesticide in a nontoxic 

dust diluent or topical exposure to technical pesticide via micro-applicator. The median lethal 

dose (LD50) is expressed in micrograms of active ingredient per bee (μg a.i./bee). 

One acute contact study of the orthosulfamuron TGAI in honey bees was submitted (MRID 

46219046; Acceptable). Study details and results are summarized in Table E-14. A 48-hour 

contact LD50 >100 μg a.i./bee was shown in this study, indicating that orthosulfamuron (TGAI) 

is practically nontoxic to honey bees. The guideline (141-1) is fulfilled. One acute oral toxicity 

test of orthosulfamuron TGAI in honey bees was submitted, yielding an acute oral LD50 >109.4 

μg a.i./bee (MRID 46219046; Supplemental). Study details and results are summarized in Table 

E-14. This acute oral study is scientifically sound and is classified as Supplemental because the 

study is a non-guideline study and does not fulfill a guideline requirement. 

No acute contact tests LD50 values in honey bees were submitted for orthosulfamuron 

formulations or degradates. 

Table E-14. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to Honey Bees. 

Species 

% 

a.i. LD50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

Acute Contact Toxicity Test 

Honey bee 

(Apis mellifera) 

98.54 LD50: >100 μg 

a.i./bee 

48-h contact toxicity test in the 

honey bee. Nominal doses: 0 

(negative control), 0 (solvent 

control), and 100 μg/bee. 

Practically 

nontoxic 

MRID 

46219046 

(Acceptable) 

48-h mortality: 0% in negative 

121
Table E-14. Acute Toxicity of Technical Grade Orthosulfamuron (TGAI) to Honey Bees. 

Species 

% 

a.i. LD50 Comments 

Toxicity 

Category 

Identification 

Number 

(Study 

Classification) 

control. 2% in solvent control, 10% 

in the 100 μg a.i./bee group. No 

sublethal effects were reported. 

LD50: >100 μg a.i./bee 

Acute Oral Toxicity Test 

Honey bee 

(Apis mellifera) 

98.54 LD50: >109.4 

μg a.i./bee 

48-h oral toxicity test in the honey 

bee. Nominal doses: 0 (solvent 

control) and 100 μg/bee. 

Practically 

nontoxic 

MRID 

46219046 

(Supplemental) 

48-h mortality: 8% in the solvent 

control, 4% in the 100 μg a.i./bee 

treatment. No sublethal effects. 

LD50: >109.4 μg a.i./bee 

95% C.I.: N/A 

NOAEC: 109.4 μg a.i./bee 

Probit slope: N/A 

This study is classified as 

Supplemental because the study is a 

non-guideline study. 

f. Earthworms, Acute Toxicity 

No acute toxicity studies of orthosulfamuron TGAI, formulations, or degradates in earthworms 

were submitted. 

g. Field Studies on Non-Target Terrestrial Invertebrates 

No field studies of orthosulfamuron TGAI, formulations, or degradates in non-target terrestrial 

invertebrates were submitted. 

VI. Plants Inhabiting Terrestrial Environments 

Terrestrial plant testing (seedling emergence and vegetative vigor) is required for herbicides that 

have terrestrial non-residential outdoor use patterns and/or may have endangered or threatened 

plant species associated with the application site. Seedling emergence and vegetative vigor 

testing of the following plant species and groups should be conducted: (1) six species of at least 

four dicotyledon families, including one soybean species (Glycine max) and one root crop, and 

(2) four species of at least two monocotyledon families, including one which is corn (Zea mays). 

Tier II tests measure the responses of plants at five or more test chemical concentrations relative 

to a control. Tier II studies of the effect of the orthosulfamuron formulation IR5878 50WG on 

seed emergence and vegetative vigor in terrestrial plants were submitted. Study details and 

122
results of these studies are summarized in Table E-13 (for most sensitive species for seedling 

emergence and vegetative vigor), Table E-14 (synopsis for Tier II seedling emergence testing, 

including all endpoints), and Table E-15 (synopsis for Tier II vegetative vigor testing, including 

all endpoints). 

A Tier II seedling emergence study was conducted in monocots: corn (Zea mays), oat (Avena 

sativa), onion (Allium cepa), and rice (Oryza sativa) and; dicots: carrot (Daucus carota), mung 

bean (Phaseolus aureus), oilseed rape (Brassica napus), pea (Pisum sativum), radish (Raphanus 

sativus), and soybean (Glycine max) (MRID 46578941; Acceptable). Rice was the most 

sensitive monocot and dry weight was the most sensitive endpoint affected, with EC05 and EC25 

values of 0.030 lbs a.i./A and 0.078 lbs a.i./A, respectively. Radish was the most sensitive dicot 

and dry weight was the most sensitive endpoint, with an EC05 and EC25 values of 0.017 lbs a.i./A 

and 0.040 lbs a.i./A, respectively. These values will be used to assess the effects of exposure to 

orthosulfamuron on seedling emergence in non-listed and listed terrestrial plants. The guideline 

(23-1[a]) is fulfilled. 

A Tier II vegetative vigor study was conducted in monocots: corn (Zea mays), oat (Avena 

sativa), onion (Allium cepa), and rice (Oryza sativa) and; dicots: carrot (Daucus carota), mung 

bean (Phaseolus aureus), oilseed rape (Brassica napus), pea (Pisum sativum), radish (Raphanus 

sativus), and soybean (Glycine max) (MRID 46578942; Supplemental). Onion was the most 

sensitive monocot and dry weight was the most sensitive endpoint affected, with EC05 and EC25 

values of 0.0013 lbs a.i./A and 0.0048 lbs a.i./A, respectively. Carrot was the most sensitive 

dicot and dry weight was the most sensitive endpoint, with EC05 and EC25 values of <0.0000664 

lbs a.i./A and 0.00012 lbs a.i./A, respectively. This study was found to be scientifically sound, 

but is classified as Supplemental since a NOAEC could not be determined for several species, 

particularly for legume species (MRID 46578942; Supplemental). The guideline (23-1[b]) is 

fulfilled. 

Table E-13. Toxicity of Orthosulfamuron Formulation to Terrestrial Plants — Results of 

Tier II Testing (Seedling Emergence and Vegetative Vigor) for the Most Sensitive Species. 

Species 

% 

a.i. Toxicity Values Comments 

Identification 

Number 

(Study 

Classification) 

Tier II Seedling Emergence 

Monocots: 49.96 Most sensitive 

Corn (Zea monocot: rice 

mays), (dry weight) 

Oat (Avena EC25/IC25: 0.078 

sativa), lbs a.i./A 

Onion (Allium 

cepa), and Most sensitive 

Rice (Oryza dicot: radish 

sativa) (dry weight) 

EC25/IC25: 0.040 

Dicots: lbs a.i./A 

Carrot (Daucus 

Seedling emergence study with IR5878 50WG 

(formulation). Nominal application rates: 0 

(negative and adjuvant controls), 0.00163, 

0.00489, 0.0147, 0.0440, and 0.132 lbs a.i./A. 

Mean measured: 0 (negative and adjuvant 

controls), 0.00174, 0.00517, 0.0150, 0.0436, and 

0.135 lbs a.i./A. 

MRID 

46578941 

(Acceptable) 

Endpoints measured: emergence on days 7, 14 

and 21; plant height and dry weight on day 21. 

Most sensitive monocot: rice 

123
Table E-13. Toxicity of Orthosulfamuron Formulation to Terrestrial Plants — Results of 

Tier II Testing (Seedling Emergence and Vegetative Vigor) for the Most Sensitive Species. 

Species 

% 

a.i. Toxicity Values Comments 

Identification 

Number 

(Study 

Classification) 

carota), 

Mung Bean 

(Phaseolus 

aureus), 

Oilseed rape 

(Brassica 

napus), 

Pea (Pisum 

sativum), 

Radish 

(Raphanus 

sativus), and 

Soybean 

(Glycine max) 

Tier II Vegetative Vigor 

Monocots: 49.96 Most sensitive 

Corn (Zea monocot: onion 

mays), (dry weight): 

Oat (Avena EC25: 0.0048 lbs 

sativa), Onion a.i./A 

(Allium cepa), 

and Rice Most sensitive 

(Oryza sativa) dicot: carrot 

(dry weight) 

Dicots: EC25: 0.00012 lbs 

Carrot (Daucus a.i./A 

carota), Mung 

Bean 

(Phaseolus 

aureus), 

Most sensitive parameter: 

dry weight

EC50/IC50: 0.15 lbs a.i./A; 95% C.I. (0.083–0.28 

lbs a.i./A) 

EC25/IC25: 0.078 lbs a.i./A; 95% C.I. (0.031–

0.20 lbs a.i./A) 

EC05/IC05: 0.030 lbs a.i./A; 95% C.I. (0.0033–

0.27 lbs a.i./A) 

NOAEC: 0.0436 lbs a.i./A 

Probit slope: 2.34±1.66 

Most sensitive dicot: radish 

Most sensitive parameter: 

dry weight 

EC50/IC50: 0.072 lbs a.i./A; 95% C.I. (0.060– 

0.088 lbs a.i./A) 

EC25/IC25: 0.040 lbs a.i./A; 95% C.I. (0.029–

0.055 lbs a.i./A) 

EC05/IC05: 0.017 lbs a.i./A; 95% C.I. (0.010–

0.029 lbs a.i./A) 

NOAEC: 0.0150 lbs a.i./A 

Probit slope: 2.63±0.355

The study authors reported that the occasional 

signs of phytotoxicity did not appear to be doseresponsive and were generally not severe. 

Additionally, some mortality was observed 

during the test but, like the signs of 

phytotoxicity, there was no apparent doseresponse. 

Vegetative vigor study with IR5878 50WG 

(formulation). Nominal application rates: 0 

(negative and adjuvant controls), 0.00163, 

0.00489, 0.0147, 0.0440, and 0.132 lbs a.i./A for 

all species with the exception of carrot and 

radish; mean measured concentrations for rice, 

corn, oat, oilseed rape, and soybean were <1.00 

ppb a.i. (negative and adjuvant controls), 

0.00170, 0.00527, 0.0150, 0.0366, and 0.115 lbs 

a.i./A; mean measured concentrations for onion, 

pea, and mung bean were <1.00 ppb a.i. 

(negative and adjuvant controls), 0.00169, 

0.00514, 0.0143, 0.0337, and 0.125 lbs a.i./A. 

Carrot and radish were tested at nominal 

concentrations of 0 (negative and adjuvant 

MRID 

46578942 

(Supplemental) 

124
Table E-13. Toxicity of Orthosulfamuron Formulation to Terrestrial Plants — Results of 

Tier II Testing (Seedling Emergence and Vegetative Vigor) for the Most Sensitive Species. 

Species 

% 

a.i. Toxicity Values Comments 

Identification 

Number 

(Study 

Classification) 

Oilseed rape 

(Brassica 

napus), Pea 

(Pisum 

sativum), 

Radish 

controls), 0.0000604, 0.000181, 0.000543, 

0.00163, and 0.00489 lbs a.i./A; mean measured 

concentrations were <1.00 ppb a.i. (negative and 

adjuvant controls), 0.0000664, 0.000198, 

0.000587, 0.00169, and 0.00488 lbs a.i./A. 

(Raphanus 

sativus), and 

Soybean 

(Glycine max) 

Endpoints measured: survival, plant height, and 

seedling condition on days 7, 14, and 21; dry 

weight on day 21. 

Most sensitive monocot: onion 

Most sensitive parameter: dry weight 

EC50: 0.012 lbs a.i./A; 95% C.I. (0.0083–0.018 

lbs a.i./A) 

EC25: 0.0048 lbs a.i./A; 95% C.I. (0.0028– 

0.0084 lbs a.i./A) 

EC05: 0.0013 lbs a.i./A; 95% C.I. (0.00055– 

0.0030 lbs a.i./A) 

NOAEC: 0.0143 lbs a.i./A 

Probit slope and standard error: 1.69±0.195 

Most sensitive dicot: carrot 

Most sensitive parameter: dry weight 

EC50: 0.00033 lbs a.i./A; 95% C.I. (0.00024– 

0.00045 lbs a.i./A) 

EC25: 0.00012 lbs a.i./A; 95% C.I. (0.000074– 

0.00019 lbs a.i./A) 

EC05: <0.0000664 lbs a.i./A 

NOAEC: <0.0000664 lbs a.i./A 

Probit slope and standard error: 1.52±0.123 

All species exhibited phytotoxic effects 

throughout the study and all effects appeared to 

be dose-related. 

125
APPENDIX G: 

Federally Listed Species Associated with Orthosulfamuron Use Areas 

Species Listing by State with Use Criteria 

No species were excluded 

Minimum of 1 Acre. 

All Medium Types Reported 

Mammal, Marine mml, Bird, Amphibian, Reptile, Fish, Crustacean, Bivalve, 

Gastropod, Arachnid, Insect, Dicot, Monocot, Ferns, Conf/cycds, Lichen 

rice 

Arkansas ( 13) species: Taxa Critical Habitat 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

Woodpecker, Red-cockaded Endangered Bird No 

(Picoides borealis) Terrestrial 

Fatmucket, Arkansas Threatened Bivalve No 

(Lampsilis powelli) Freshwater 

Mucket, Pink (Pearlymussel) Endangered Bivalve No 

(Lampsilis abrupta) Freshwater 

Mussel, Scaleshell Endangered Bivalve No 

(Leptodea leptodon) Freshwater 

Pearlymussel, Fat Pocketbook Endangered Bivalve No 

(Potamilus capax) Freshwater 

Rock-pocketbook, Ouachita (=Wheeler's pm) Endangered Bivalve No 

(Arkansia wheeleri) Freshwater 

Fruit, Earth (=geocarpon) Threatened Dicot No 

(Geocarpon minimum) Terrestrial 

Harperella Endangered Dicot No 

(Ptilimnium nodosum) Freshwater 

Pondberry Endangered Dicot No 

(Lindera melissifolia) Terrestrial 

Sturgeon, Pallid Endangered Fish No 

(Scaphirhynchus albus) Freshwater 

Bat, Gray Endangered Mammal No 

(Myotis grisescens) Subterraneous, Terrestrial 

California ( 72) species: Taxa Critical Habitat 

Frog, California Red-legged Threatened Amphibian Yes 

(Rana aurora draytonii) Terrestrial, Freshwater 

Salamander, California Tiger Endangered Amphibian No 

(Ambystoma californiense) Terrestrial, Vernal pool 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

126
California ( 72) species: Taxa Critical Habitat 

Murrelet, Marbled Threatened Bird Yes 

(Brachyramphus marmoratus marmoratus) Freshwater, Terrestrial, Saltwater 

Owl, Northern Spotted Threatened Bird Yes 

(Strix occidentalis caurina) Terrestrial 

Pelican, Brown Endangered Bird No 

(Pelecanus occidentalis) Terrestrial 

Plover, Western Snowy Threatened Bird Yes 

(Charadrius alexandrinus nivosus) Terrestrial 

Rail, California Clapper Endangered Bird No 

(Rallus longirostris obsoletus) Terrestrial 

Fairy Shrimp, Conservancy Fairy Endangered Crustacean Yes 

(Branchinecta conservatio) Vernal pool 

Fairy Shrimp, Vernal Pool Threatened Crustacean Yes 

(Branchinecta lynchi) Vernal pool 

Tadpole Shrimp, Vernal Pool Endangered Crustacean Yes 

(Lepidurus packardi) Vernal pool 

Adobe Sunburst, San Joaquin Threatened Dicot No 

(Pseudobahia peirsonii) Terrestrial 

Bird's-beak, Palmate-bracted Endangered Dicot No 

(Cordylanthus palmatus) Terrestrial 

Bird's-beak, Soft Endangered Dicot No 

(Cordylanthus mollis ssp. mollis) Brackish, Saltwater 

Checker-mallow, Keck's Endangered Dicot Yes 

(Sidalcea keckii) Terrestrial 

Clover, Fleshy Owl's Threatened Dicot Yes 

(Castilleja campestris ssp. succulenta) Vernal pool 

Dudleya, Santa Clara Valley Endangered Dicot No 

(Dudleya setchellii) Terrestrial 

Evening-primrose, Antioch Dunes Endangered Dicot Yes 

(Oenothera deltoides ssp. howellii) Terrestrial 

Fiddleneck, Large-flowered Endangered Dicot Yes 

(Amsinckia grandiflora) Terrestrial 

Golden Sunburst, Hartweg's Endangered Dicot No 

(Pseudobahia bahiifolia) Terrestrial 

Goldfields, Burke's Endangered Dicot No 

(Lasthenia burkei) Terrestrial 

Goldfields, Contra Costa Endangered Dicot Yes 

(Lasthenia conjugens) Terrestrial 

Grass, Hairy Orcutt Endangered Dicot Yes 

(Orcuttia pilosa) Vernal pool 

Grass, Sacramento Orcutt Endangered Dicot Yes 

(Orcuttia viscida) Vernal pool 

127
California ( 72) species: Taxa Critical Habitat 

Grass, Slender Orcutt Threatened Dicot Yes 

(Orcuttia tenuis) Vernal pool 

Jewelflower, California Endangered Dicot No 

(Caulanthus californicus) Terrestrial 

Meadowfoam, Butte County Endangered Dicot Yes 

(Limnanthes floccosa ssp. californica) Vernal pool 

Navarretia, Few-flowered Endangered Dicot No 

(Navarretia leucocephala ssp. pauciflora (=N. pauciflora)) Vernal pool, Terrestrial 

Navarretia, Many-flowered Endangered Dicot No 

(Navarretia leucocephala ssp. plieantha) Terrestrial, Vernal pool 

Pussypaws, Mariposa Threatened Dicot No 

(Calyptridium pulchellum) Terrestrial 

Rock-cress, McDonald's Endangered Dicot No 

(Arabis mcdonaldiana) Terrestrial 

Spineflower, Howell's Endangered Dicot No 

(Chorizanthe howellii) Terrestrial 

Spurge, Hoover's Threatened Dicot Yes 

(Chamaesyce hooveri) Vernal pool 

Stonecrop, Lake County Endangered Dicot No 

(Parvisedum leiocarpum) Vernal pool 

Thistle, Suisun Endangered Dicot No 

(Cirsium hydrophilum var. hydrophilum) Brackish, Terrestrial 

Tuctoria, Green's Endangered Dicot Yes 

(Tuctoria greenei) Vernal pool 

Wallflower, Menzie's Endangered Dicot No 

(Erysimum menziesii) Terrestrial 

Woolly-threads, San Joaquin Endangered Dicot No 

(Monolopia (=Lembertia) congdonii) Terrestrial 

Chub, Hutton Tui Threatened Fish No 

(Gila bicolor ssp.) Freshwater 

Goby, Tidewater Endangered Fish Yes 

(Eucyclogobius newberryi) Freshwater 

Salmon, Chinook (California Coastal Run) Threatened Fish Yes 

(Oncorhynchus (=Salmo) tshawytscha) Freshwater, Saltwater, Brackish 

Salmon, Chinook (Central Valley Fall Run) Threatened Fish No 

(Oncorhynchus (=Salmo) tshawytscha) Brackish, Freshwater, Saltwater 

Salmon, Chinook (Central Valley Spring Run) Threatened Fish Yes 

(Oncorhynchus (=Salmo) tshawytscha) Brackish, Saltwater, Freshwater 

Salmon, Chinook (Sacramento River Winter Run) Endangered Fish No 

(Oncorhynchus (=Salmo) tshawytscha) Saltwater, Freshwater, Brackish 

Salmon, Coho (Central California Coast population) Endangered Fish No 

(Oncorhynchus (=Salmo) kisutch) Saltwater, Brackish, Freshwater 

128
California ( 72) species: Taxa Critical Habitat 

Salmon, Coho (Southern OR/Northern CA Coast) Threatened Fish Yes 

(Oncorhynchus (=Salmo) kisutch) Freshwater, Brackish, Saltwater 

Smelt, Delta Threatened Fish Yes 

(Hypomesus transpacificus) Freshwater, Brackish 

Steelhead, (California Central Valley population) Threatened Fish Yes 

(Oncorhynchus (=Salmo) mykiss) Brackish, Freshwater, Saltwater 

Steelhead, (Central California Coast population) Threatened Fish Yes 

(Oncorhynchus (=Salmo) mykiss) Freshwater, Saltwater, Brackish 

Steelhead, (Northern California population) Threatened Fish No 

(Oncorhynchus (=Salmo) mykiss) Saltwater, Brackish, Freshwater 

Sucker, Modoc Endangered Fish Yes 

(Catostomus microps) Freshwater 

Trout, Lahontan Cutthroat Threatened Fish No 

(Oncorhynchus clarki henshawi) Freshwater 

Trout, Little Kern Golden Threatened Fish Yes 

(Oncorhynchus aguabonita whitei) Freshwater 

Trout, Paiute Cutthroat Threatened Fish No 

(Oncorhynchus clarki seleniris) Freshwater 

Beetle, Delta Green Ground Threatened Insect Yes 

(Elaphrus viridis) Vernal pool, Terrestrial 

Beetle, Valley Elderberry Longhorn Threatened Insect Yes 

(Desmocerus californicus dimorphus) Terrestrial 

Butterfly, Behren's Silverspot Endangered Insect No 

(Speyeria zerene behrensii) Terrestrial 

Butterfly, Lotis Blue Endangered Insect No 

(Lycaeides argyrognomon lotis) Terrestrial 

Skipper, Carson Wandering Endangered Insect No 

(Pseudocopaeodes eunus obscurus) Terrestrial 

Fox, San Joaquin Kit Endangered Mammal No 

(Vulpes macrotis mutica) Terrestrial 

Kangaroo Rat, Fresno Endangered Mammal Yes 

(Dipodomys nitratoides exilis) Terrestrial 

Kangaroo Rat, Giant Endangered Mammal No 

(Dipodomys ingens) Terrestrial 

Mountain Beaver, Point Arena Endangered Mammal No 

(Aplodontia rufa nigra) Freshwater, Terrestrial 

Mouse, Salt Marsh Harvest Endangered Mammal No 

(Reithrodontomys raviventris) Terrestrial 

Rabbit, Riparian Brush Endangered Mammal No 

(Sylvilagus bachmani riparius) Terrestrial 

Woodrat, Riparian Endangered Mammal No 

(Neotoma fuscipes riparia) Terrestrial 

129
California ( 72) species: Taxa Critical Habitat 

Grass, Colusa Threatened Monocot No 

(Neostapfia colusana) Vernal pool 

Grass, San Joaquin Valley Orcutt Threatened Monocot Yes 

(Orcuttia inaequalis) Vernal pool 

Grass, Solano Endangered Monocot Yes 

(Tuctoria mucronata) Vernal pool, Terrestrial 

Lizard, Blunt-nosed Leopard Endangered Reptile No 

(Gambelia silus) Terrestrial 

Sea turtle, olive ridley Threatened Reptile No 

(Lepidochelys olivacea) Saltwater 

Snake, Giant Garter Threatened Reptile No 

(Thamnophis gigas) Freshwater, Terrestrial 

Florida ( 24) species: Taxa Critical Habitat 

Salamander, Flatwoods Threatened Amphibian No 

(Ambystoma cingulatum) Freshwater, Vernal pool, Terrestrial 

Caracara, Audubon's Crested Threatened Bird No 

(Polyborus plancus audubonii) Terrestrial 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Kite, Everglade Snail Endangered Bird Yes 

(Rostrhamus sociabilis plumbeus) Terrestrial 

Plover, Piping Endangered Bird Yes 

(Charadrius melodus) Terrestrial 

Scrub-Jay, Florida Threatened Bird No 

(Aphelocoma coerulescens) Terrestrial 

Sparrow, Florida Grasshopper Endangered Bird No 

(Ammodramus savannarum floridanus) Terrestrial 

Stork, Wood Endangered Bird No 

(Mycteria americana) Terrestrial 

Woodpecker, Red-cockaded Endangered Bird No 

(Picoides borealis) Terrestrial 

Mussel, Oval Pigtoe Endangered Bivalve No 

(Pleurobema pyriforme) Freshwater 

Gourd, Okeechobee Endangered Dicot No 

(Cucurbita okeechobeensis ssp. okeechobeensis) Terrestrial 

Jacquemontia, Beach Endangered Dicot No 

(Jacquemontia reclinata) Terrestrial, Coastal (dunes) 

Pawpaw, Four-petal Endangered Dicot No 

(Asimina tetramera) Terrestrial 

Polygala, Tiny Endangered Dicot No 

(Polygala smallii) Terrestrial 

Sturgeon, Gulf Threatened Fish Yes 

(Acipenser oxyrinchus desotoi) Saltwater, Freshwater 

130
Florida ( 24) species: Taxa Critical Habitat 

Cladonia, Florida Perforate Endangered Lichen No 

(Cladonia perforata) Terrestrial 

Panther, Florida Endangered Mammal No 

(Puma (=Felis) concolor coryi) Terrestrial 

Manatee, West Indian Endangered Marine mml Yes 

(Trichechus manatus) Saltwater 

Seagrass, Johnson's Threatened Monocot Yes 

(Halophila johnsonii) Coastal (dunes), Saltwater 

Sea turtle, green Endangered Reptile No 

(Chelonia mydas) Saltwater 

Sea turtle, hawksbill Endangered Reptile Yes 

(Eretmochelys imbricata) Saltwater 

Sea turtle, leatherback Endangered Reptile Yes 

(Dermochelys coriacea) Saltwater 

Sea turtle, loggerhead Threatened Reptile No 

(Caretta caretta) Saltwater 

Snake, Eastern Indigo Threatened Reptile No 

(Drymarchon corais couperi) Terrestrial 

Illinois ( 8) species: Taxa Critical Habitat 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

Mucket, Pink (Pearlymussel) Endangered Bivalve No 

(Lampsilis abrupta) Freshwater 

Pearlymussel, Orange-footed Endangered Bivalve No 

(Plethobasus cooperianus) Freshwater 

Aster, Decurrent False Threatened Dicot No 

(Boltonia decurrens) Terrestrial, Freshwater 

Sturgeon, Pallid Endangered Fish No 

(Scaphirhynchus albus) Freshwater 

Bat, Gray Endangered Mammal No 

(Myotis grisescens) Subterraneous, Terrestrial 

Bat, Indiana Endangered Mammal Yes 

(Myotis sodalis) Subterraneous, Terrestrial 

Louisiana ( 19) species: Taxa Critical Habitat 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Pelican, Brown Endangered Bird No 

(Pelecanus occidentalis) Terrestrial 

Plover, Piping Endangered Bird Yes 

(Charadrius melodus) Terrestrial 

131
Louisiana ( 19) species: Taxa Critical Habitat 

Tern, California Least Endangered Bird No 

(Sterna antillarum browni) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

Woodpecker, Red-cockaded Endangered Bird No 

(Picoides borealis) Terrestrial 

Mucket, Pink (Pearlymussel) Endangered Bivalve No 

(Lampsilis abrupta) Freshwater 

Pearlshell, Louisiana Threatened Bivalve No 

(Margaritifera hembeli) Freshwater 

Chaffseed, American Endangered Dicot No 

(Schwalbea americana) Terrestrial 

Fruit, Earth (=geocarpon) Threatened Dicot No 

(Geocarpon minimum) Terrestrial 

Sturgeon, Gulf Threatened Fish Yes 

(Acipenser oxyrinchus desotoi) Saltwater, Freshwater 

Sturgeon, Pallid Endangered Fish No 

(Scaphirhynchus albus) Freshwater 

Bear, Louisiana Black Threatened Mammal No 

(Ursus americanus luteolus) Terrestrial 

Manatee, West Indian Endangered Marine mml Yes 

(Trichechus manatus) Saltwater 

Sea turtle, green Endangered Reptile No 

(Chelonia mydas) Saltwater 

Sea turtle, hawksbill Endangered Reptile Yes 

(Eretmochelys imbricata) Saltwater 

Sea turtle, Kemp's ridley Endangered Reptile No 

(Lepidochelys kempii) Saltwater 

Sea turtle, leatherback Endangered Reptile Yes 

(Dermochelys coriacea) Saltwater 

Sea turtle, loggerhead Threatened Reptile No 

(Caretta caretta) Saltwater 

Mississippi ( 19) species: 

Frog, Dusky Gopher (Mississippi DPS) Endangered 

Taxa Critical Habitat 

Amphibian No 

(Rana capito sevosa) Terrestrial, Freshwater 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Pelican, Brown Endangered Bird No 

(Pelecanus occidentalis) Terrestrial 

Plover, Piping Endangered Bird Yes 

(Charadrius melodus) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

132
Mississippi ( 19) species: 

Woodpecker, Red-cockaded Endangered 

Taxa Critical Habitat 

Bird No 

(Picoides borealis) Terrestrial 

Pondberry Endangered Dicot No 

(Lindera melissifolia) Terrestrial 

Potato-bean, Price's Threatened Dicot No 

(Apios priceana) Terrestrial 

Quillwort, Louisiana Endangered Ferns No 

(Isoetes louisianensis) Freshwater, Terrestrial 

Sturgeon, Gulf Threatened Fish Yes 

(Acipenser oxyrinchus desotoi) Saltwater, Freshwater 

Sturgeon, Pallid Endangered Fish No 

(Scaphirhynchus albus) Freshwater 

Bat, Gray Endangered Mammal No 

(Myotis grisescens) Subterraneous, Terrestrial 

Bear, Louisiana Black Threatened Mammal No 

(Ursus americanus luteolus) Terrestrial 

Sea turtle, green Endangered Reptile No 

(Chelonia mydas) Saltwater 

Sea turtle, Kemp's ridley Endangered Reptile No 

(Lepidochelys kempii) Saltwater 

Sea turtle, loggerhead Threatened Reptile No 

(Caretta caretta) Saltwater 

Snake, Eastern Indigo Threatened Reptile No 

(Drymarchon corais couperi) Terrestrial 

Tortoise, Gopher Threatened Reptile No 

(Gopherus polyphemus) Terrestrial 

Turtle, Yellow-blotched Map Threatened Reptile No 

(Graptemys flavimaculata) Freshwater, Terrestrial 

Missouri ( 15) species: Taxa Critical Habitat 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

Mucket, Pink (Pearlymussel) Endangered Bivalve No 

(Lampsilis abrupta) Freshwater 

Pearlymussel, Curtis' Endangered Bivalve No 

(Epioblasma florentina curtisii) Freshwater 

Pearlymussel, Fat Pocketbook Endangered Bivalve No 

(Potamilus capax) Freshwater 

Aster, Decurrent False Threatened Dicot No 

(Boltonia decurrens) Terrestrial, Freshwater 

Clover, Running Buffalo Endangered Dicot No 

(Trifolium stoloniferum) Terrestrial 

133
Missouri ( 15) species: Taxa Critical Habitat 

Pondberry Endangered Dicot No 

(Lindera melissifolia) Terrestrial 

Darter, Niangua Threatened Fish Yes 

(Etheostoma nianguae) Freshwater 

Shiner, Topeka Endangered Fish Yes 

(Notropis topeka (=tristis)) Freshwater 

Sturgeon, Pallid Endangered Fish No 

(Scaphirhynchus albus) Freshwater 

Beetle, American Burying Endangered Insect No 

(Nicrophorus americanus) Terrestrial 

Dragonfly, Hine's Emerald Endangered Insect No 

(Somatochlora hineana) Freshwater, Terrestrial 

Bat, Gray Endangered Mammal No 

(Myotis grisescens) Subterraneous, Terrestrial 

Bat, Indiana Endangered Mammal Yes 

(Myotis sodalis) Subterraneous, Terrestrial 

Oklahoma ( 10) species: Taxa Critical Habitat 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Plover, Piping Endangered Bird Yes 

(Charadrius melodus) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

Woodpecker, Red-cockaded Endangered Bird No 

(Picoides borealis) Terrestrial 

Mussel, Scaleshell Endangered Bivalve No 

(Leptodea leptodon) Freshwater 

Rock-pocketbook, Ouachita (=Wheeler's pm) Endangered Bivalve No 

(Arkansia wheeleri) Freshwater 

Darter, Leopard Threatened Fish Yes 

(Percina pantherina) Freshwater 

Beetle, American Burying Endangered Insect No 

(Nicrophorus americanus) Terrestrial 

Bat, Indiana Endangered Mammal Yes 

(Myotis sodalis) Subterraneous, Terrestrial 

Bat, Ozark Big-eared Endangered Mammal No 

(Corynorhinus (=Plecotus) townsendii ingens) Terrestrial, Subterraneous 

Tennessee ( 4) species: Taxa Critical Habitat 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

134
Tennessee ( 4) species: Taxa Critical Habitat 

Sturgeon, Pallid Endangered Fish No 

(Scaphirhynchus albus) Freshwater 

Bat, Indiana Endangered Mammal Yes 

(Myotis sodalis) Subterraneous, Terrestrial 

Texas ( 18) species: Taxa Critical Habitat 

Toad, Houston Endangered Amphibian Yes 

(Bufo houstonensis) Terrestrial, Freshwater 

Crane, Whooping Endangered Bird Yes 

(Grus americana) Terrestrial, Freshwater 

Curlew, Eskimo Endangered Bird No 

(Numenius borealis) Terrestrial 

Eagle, Bald Threatened Bird No 

(Haliaeetus leucocephalus) Terrestrial 

Pelican, Brown Endangered Bird No 

(Pelecanus occidentalis) Terrestrial 

Plover, Piping Endangered Bird Yes 

(Charadrius melodus) Terrestrial 

Prairie-chicken, Attwater's Greater Endangered Bird No 

(Tympanuchus cupido attwateri) Terrestrial 

Tern, Interior (population) Least Endangered Bird No 

(Sterna antillarum) Terrestrial 

Woodpecker, Red-cockaded Endangered Bird No 

(Picoides borealis) Terrestrial 

Dawn-flower, Texas Prairie (=Texas Bitterweed) Endangered Dicot No 

(Hymenoxys texana) Terrestrial 

Phlox, Texas Trailing Endangered Dicot No 

(Phlox nivalis ssp. texensis) Terrestrial 

Beetle, American Burying Endangered Insect No 

(Nicrophorus americanus) Terrestrial 

Bear, Louisiana Black Threatened Mammal No 

(Ursus americanus luteolus) Terrestrial 

Sea turtle, green Endangered Reptile No 

(Chelonia mydas) Saltwater 

Sea turtle, hawksbill Endangered Reptile Yes 

(Eretmochelys imbricata) Saltwater 

Sea turtle, Kemp's ridley Endangered Reptile No 

(Lepidochelys kempii) Saltwater 

Sea turtle, leatherback Endangered Reptile Yes 

(Dermochelys coriacea) Saltwater 

Sea turtle, loggerhead Threatened Reptile No 

(Caretta caretta) Saltwater 

135