3

Table 1. Listed Species Risks Associated with Potential Direct Effects Due to the Applications of Fosthiazate.

Listed Plant Taxon Potential Direct Effects

Terrestrial and semiaquatic plants –

monocots and dicots

No effect

Aquatic plants No effect

Listed Animal Taxon

Potential Direct Effects

Acute Notes Chronic Notes

Terrestrial invertebrates Yes

(see note 1)

1. All potential direct effects identified are 

expected to be limited to the site of application 

(i.e., treated tomato fields).

2. Based on T-REX, screening-level RQ values 

exceed the listed species RQ for birds that 

weigh ≤ 100 g and eat arthropods. None of the 

RQs would exceed the acute LOC for listed 

birds (also surrogate for reptiles and terrestrial 

amphibians) that eat contaminated terrestrial 

invertebrates if the application scenario were 

modified by generally reducing the single 

maximum application rate to 1.0 lb a.i./acre 

(using 1 inch of irrigation water/acre) or to 

~0.5 lb a.i./acre (using 0.5 inches of irrigation 

water/acre)

Based on the Earthworm Fugacity model, 

screening-level RQ values would not exceed 

the acute LOC for listed birds that eat 

contaminated earthworms if the application 

scenario were modified by generally reducing 

ND

4. Based on T-REX, screening-level RQ 

values exceed the chronic LOC for 

mammals that weigh ≤ 35 g and eat 

arthropods. None of the RQs would 

exceed the chronic LOC for listed 

mammals that eat contaminated terrestrial 

invertebrates if the application scenario 

were modified by generally reducing the 

single maximum application rate to 1.0 

lb a.i./acre (using 0.5 inches of irrigation 

water/acre) or keeping the application 

rate at 1.5 lb a.i./acre and using ≥0.75 

inches of irrigation water/acre.

Based on the Earthworm Fugacity model, 

screening-level RQ values would not 

exceed the chronic LOC for listed 

mammals that eat contaminated 

earthworms if the application scenario 

were modified by generally reducing the 

single maximum application rate to 1.3

lb a.i./acre (using a KOC of 285 and a soil 

Mammals No effect See notes 1 

and 4

Birds See notes 1 

and 2 No effect

Reptiles See notes 1, 

2 and 3 No effect

Amphibians See notes 1, 

2 and 3 No effect

Freshwater fish No effect No effect

Freshwater 

invertebrates No effect No effect

Molluscs No effect ND

Estuarine/marine fish No effect No effect
4

Listed Plant Taxon Potential Direct Effects

Estuarine/marine 

invertebrates No effect

the single maximum application rate to 0.75 

lb a.i./acre (using a KOC of 285 and a soil 

depth of 10 cm) or to 0.15 lb a.i./acre (using 

a KOC of 25 and a soil depth of 1.0 cm)

3. To help refine the risk assessment for 

terrestrial-phase amphibians and reptiles that 

may eat invertebrates contaminated with 

fosthiazate, T-HERPS (which uses feeding 

rates based on iguanids instead of birds) was 

used. Based on the T-HERPS analysis, none of 

the RQs for amphibians or reptiles that eat 

terrestrial invertebrates exceed an Agency 

LOC. Currently the Earthworm Fugacity 

model does not calculate RQs for terrestrialphase amphibians or reptiles that eat 

contaminated earthworms. Therefore, the 

potential risk to terrestrial-phase amphibians or 

reptiles that specifically eat earthworms is 

uncertain.

No effect

depth of 10 cm) or to 0.26 lb a.i./acre 

(using a KOC of 25 and a soil depth of 1.0 

cm)
5

Based on this preliminary assessment, there are potential risks of direct effects to listed and nonlisted birds (surrogates for terrestrial-phase amphibians and reptiles), listed and non-listed 

mammals, and terrestrial invertebrates from the use of fosthiazate on tomatoes. Listed species of 

other taxa may also be affected through indirect effects because of the potential direct effects on 

listed and non-listed species. Potential direct effects on birds (surrogates for terrestrial-phase 

amphibians and reptiles), mammals, and terrestrial invertebrates from the use of fosthiazate may 

be associated with modification of primary constituent elements of designated critical habitats, 

where such designations have been made. However, at this current stage of the Registration 

Review process, it is premature to make effects determinations until further refinements are 

conducted. In order to make species-specific effects determinations, useful refinements include 

the use of more detailed; 1) species-specific ecological and biological data, 2) information on use 

patterns for fosthiazate, and 3) sub-county level spatial proximity analyses for the co-occurrence 

of potential areas of effects and listed species/designated critical habitat of concern. Examples of

such refinements are described below.

EFED is currently developing tools that are expected to further refine the assessment and are 

designed to support effects determinations for individual federally listed species and their 

designated critical habitats (where applicable). Scientific information obtained from the U.S. 

Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS), and other 

reliable sources is being collated by EFED to address all currently listed species. The 

information will be stored in an Office of Pesticide Programs Pesticide Registration Information 

SysteM (PRISM) knowledgebase. The listed species knowledgebase will consist of an 

information repository that houses biological and behavioral information relevant to individual 

species (e.g., habitat, diet, and life history, including specific temporal and spatial associations)

and a document repository that contains supporting documents (e.g., USFWS recovery plans) 

and electronic information (e.g., GIS data files). For terrestrial taxa, the biological information 

relevant to risk quotient (RQ) calculations (e.g., diet and body weight) will be used to 

parameterize exposure estimates to derive species-specific RQs using a method consistent with 

currently used methods in the T-REX and T-HERPS models. 

Refinements may also include more detailed analyses of the registered uses and their use patterns 

that result in LOC exceedances for federally listed species in the preliminary assessment. The 

analyses may include more information on where, when, and how fosthiazate is used on 

tomatoes. Actual usage data (when available) and national land-cover datasets that indicate 

potential use sites (e.g., national land cover dataset (NLCD), crop data layer (CDL)) may be used 

to support a more refined analysis of where fosthiazate is reasonably expected to be used. 

Similarly, refinements for the timing of applications and how fosthiazate is used may be based 

on the analysis of additional usage data, beyond what were available at the time of the screeninglevel assessment, and a more in-depth exploration of agronomic practices. 

In addition, a committee of the National Research Council (NRC) has been tasked with 

providing advice on ecological risk assessment tools and scientific approaches under ESA and 

FIFRA (Project Identification Number DELS-BEST-11-01). The committee has been asked to 

review the use of “best available data;” methods for evaluating sublethal, indirect, and 

cumulative effects; the state of the science regarding assessment of mixtures and pesticide inert 

ingredients; the development, application, and interpretation of results from predictive models; 
6

uncertainty factors; and what constitutes authoritative geospatial and temporal information for 

the assessment of individual species and habitat effects. The Agency anticipates that this NRC 

report, tentatively expected in Spring 2013, will provide recommendations to ensure the 

scientific soundness and maximize the utility of risk assessment refinements for listed species.

The refinements based on individual species data; additional, detailed usage information, when 

available; and further recommendations from the NRC report are expected to help to more 

accurately identify potential areas of effect and to better inform effects and habitat 

determinations for listed species and any designated critical habitats. For example, if fosthiazate

is used when a particular species of concern is not present (e.g., it is migratory) or is not colocated in space, then risk of potential direct effects to the species may often be precluded. If 

LOCs are still exceeded for birds (surrogates for terrestrial-phase amphibians and reptiles),

mammals, and terrestrial invertebrates after conducting the refined analyses, further analyses of 

the potential spatial and temporal co-occurrence of listed species of concern (and any designated 

critical habitat) may be conducted. The extent of possible refinement in the analyses of 

spatial/temporal co-occurrence will largely depend on the scale and quality of the available subcounty level use site (e.g., National Land Cover Dataset, Cropland Data Layer) and species 

location data.
7

Ecological Risk Assessment for the Registration Review of Fosthiazate

O-ETHYL-S-(1-METHYLPROPYL)(2-OXO-3-THIAZOLIDINYL)-

PHOSPHONOTHIOATE 

(CAS Reg. No. 98886-44-3; USEPA PC Code: 129022)

Prepared by:

Melissa Panger, Ph.D., Senior Scientist

James Wolf, Ph.D., Environmental Scientist

Reviewed by:

James Hetrick, Ph.D., Senior Advisor

Rosanna Louie-Juzwiak, Risk Assessment Process Leader

Approved by:

Dana Spatz, Branch Chief

Environmental Risk Branch III

Environmental Fate and Effects Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, NW

Washington, D.C. 20460

March 2013
8

Table of Contents

I. EXECUTIVE SUMMARY ................................................................................................ 9

A. Purpose of Assessment ........................................................................................... 9

B. Nature of the Stressor.............................................................................................. 9

C. Summary of Effects and Risk Conclusions ............................................................ 9

II. PROBLEM FORMULATION.......................................................................................... 13

A. Pesticide Type, Class, and Mode of Action.......................................................... 13

B. Overview of Pesticide Use and Usage .................................................................. 13

C. Previous Ecological Risk Assessments................................................................. 14

E. Analysis Plan and Conceptual Models ................................................................. 18

1. Measures to Evaluate Risk Hypotheses.................................................... 18

2. Conceptual Model..................................................................................... 18

3. Risk Hypothesis........................................................................................ 19

III. ANALYSIS....................................................................................................................... 20

A. Measures of Exposure........................................................................................... 20

B. Environmental Fate Characterization and Modeling Input Parameters................ 22

C. Ecological Effects Characterization...................................................................... 26

IV. RISK ESTIMATION........................................................................................................ 28

1. Non-target Aquatic Animals and Plants ................................................... 28

2. Non-target Terrestrial Animals................................................................. 28

3. Probit Slope Response Analysis of LOC Values and Acute RQ Values.. 30

V. RISK DESCRIPTION ...................................................................................................... 31

1. Review of Incident Data ........................................................................... 33

2. Assumptions and Limitations ................................................................... 33

APPENDIX A. REFERENCES................................................................................................... 37

APPENDIX B. BIBLIOGRAPHY .............................................................................................. 39

APPENDIX C. Sample Inputs and Outputs for the Earthworm Fugacity Model........................ 42

APPENDIX D: ECOTOX Run.................................................................................................... 46
9

I. EXECUTIVE SUMMARY

A. Purpose of Assessment

The purpose of this assessment is to evaluate the potential risks of fosthiazates use on non-target 

organisms, including federally listed endangered and threatened (listed) species. This risk 

assessment incorporates the available exposure and effects data and most current modeling and 

risk methodologies. 

B. Nature of the Stressor

Fosthiazate is a systemic organophosphate (OP) nematicide/insecticide used for the control of a 

broad spectrum of nematode species in tomatoes. Although the persistence and mobility of 

fosthiazate are conducive to runoff and leaching, the approved application methods are designed 

to minimize potential transport to surface water. Labels require application through drip 

irrigation under plastic mulch. Therefore, spray drift to surface water is not a concern, and the 

potential for runoff is reduced by the direct soil application and by the protection from 

precipitation. If fosthiazate does reach aquatic environments, it is stable to aquatic photolysis 

and has limited hydrolysis in neutral and acidic conditions, but it hydrolyzes rapidly in alkaline 

conditions.

C. Summary of Effects and Risk Conclusions

The results of this preliminary risk assessment indicate that the registered use of fosthiazate on 

tomatoes has the potential for direct adverse effects to listed and non-listed birds that weigh ≤100 

g and ingest arthropods (acute exposure), listed and non-listed mammals that weigh ≤35 g that 

ingest arthropods (chronic exposure), and terrestrial invertebrates. Risks to terrestrial-phase 

amphibians and reptiles that eat arthropods (in general) are not expected. There is a potential 

risk to listed and non-listed birds, terrestrial-phase amphibians, reptiles, and mammals that 

specifically eat earthworms (risks to amphibians and reptiles could not be precluded). 

The available acute toxicity data on fosthiazate (TGAI) indicate that it is highly toxic to birds, 

terrestrial invertebrates, freshwater invertebrates, and estuarine/marine invertebrates; moderately 

toxic to small mammals; slightly toxic to estuarine/marine fish; and practically non-toxic to 

freshwater fish. Avian reproduction studies showed significant effects on male and female

weight gain, decreased eggshell thickness, and increased cracked eggs were observed in the 

bobwhite quail (NOAEC = 21.7 mg a.i./kg-diet; LOAEC = 42.6 mg a.i./kg-diet). A 2-generation 

rat study yielded a reproductive NOAEL of 10 mg a.i./kg-diet and a LOAEL of 30 mg a.i./kgdiet based on decreased viability index, litter size and pup weight for the f1 generation.

Chronic effects in the freshwater fish early life stage study included reduced dry weight and 

length of young fish (NOAEC = 2.32 mg a.i./L, LOAEC 4.48 mg a.i./L). The freshwater 

invertebrate life-cycle study determined a NOAEC value of 0.061 mg a.i./L and a LOAEC value 

of 0.128 mg a.i./L based on reduced number of offspring produced and parental mortality.
10

Tier I and Tier II terrestrial plant toxicity tests were performed on technical fosthiazate in which 

dicots appear to be more sensitive than monocots [Tier II seedling emergence test: NOAEC and 

EC25 of 0.8 and 1.0 lb a.i./A, respectively (mustard); Tier II vegetative vigor, NOAEC and EC25

of 0.8 lb a.i./A, respectively (buckwheat]. A Tier I test with the green alga (Selenastrum 

capricornatum) found no adverse effects at a concentration equal to 4.5 mg a.i./L. 

Risks to aquatic organisms or terrestrial plants are not expected from the use of fosthiazate on 

tomatoes. Risks are expected for terrestrial invertebrates [both soil-dwelling (from direct 

exposure) and non-soil-dwelling (from ingestion of treated tomato plants)] and federally-listed 

and non-listed birds (acute) and listed and non-listed mammals (chronic) from the ingestion of 

contaminated terrestrial invertebrates (including earthworms). Risks to terrestrial-phase 

amphibians and reptiles that eat arthropods (in general) are not expected. There is a potential 

risk to listed and non-listed terrestrial-phase amphibians and reptiles that specifically eat 

earthworms (risks could not be precluded). Risks to birds (and, thus, reptiles and terrestrialphase amphibians) and mammals from the ingestion of contaminated tomato plants are not 

expected. 
11

Table 1. Listed Species Risks Associated with Potential Direct Effects Due to the Applications of Fosthiazate.

Listed Plant Taxon Potential Direct Effects

Terrestrial and semiaquatic plants –

monocots and dicots

No effect

Aquatic plants No effect

Listed Animal Taxon

Potential Direct Effects

Acute Notes Chronic Notes

Terrestrial invertebrates Yes

(see note 1)

1. All potential direct effects identified are 

expected to be limited to the site of application 

(i.e., treated tomato fields).

2. Based on T-REX, screening-level RQ values 

exceed the listed species RQ for birds that 

weigh ≤ 100 g and eat arthropods. None of the 

RQs would exceed the acute LOC for listed 

birds (also surrogate for reptiles and terrestrial 

amphibians) that eat contaminated terrestrial 

invertebrates if the application scenario were 

modified by generally reducing the single 

maximum application rate to 1.0 lb a.i./acre 

(using 1 inch of irrigation water/acre) or to 

~0.5 lb a.i./acre (using 0.5 inches of irrigation 

water/acre)

Based on the Earthworm Fugacity model, 

screening-level RQ values would not exceed 

the acute LOC for listed birds that eat 

contaminated earthworms if the application 

scenario were modified by generally reducing 

ND

4. Based on T-REX, screening-level RQ 

values exceed the chronic LOC for 

mammals that weigh ≤ 35 g and eat 

arthropods. None of the RQs would 

exceed the chronic LOC for listed 

mammals that eat contaminated terrestrial 

invertebrates if the application scenario

were modified by generally reducing the 

single maximum application rate to 1.0 

lb a.i./acre (using 0.5 inches of irrigation 

water/acre) or keeping the application 

rate at 1.5 lb a.i./acre and using ≥0.75 

inches of irrigation water/acre.

Based on the Earthworm Fugacity model, 

screening-level RQ values would not 

exceed the chronic LOC for listed 

mammals that eat contaminated 

earthworms if the application scenario 

were modified by generally reducing the 

single maximum application rate to 1.3

lb a.i./acre (using a KOC of 285 and a soil 

Mammals No effect See notes 1 

and 4

Birds See notes 1 

and 2 No effect

Reptiles See notes 1, 

2 and 3 No effect

Amphibians See notes 1, 

2 and 3 No effect

Freshwater fish No effect No effect

Freshwater 

invertebrates No effect No effect

Molluscs No effect ND

Estuarine/marine fish No effect No effect
12

Listed Plant Taxon Potential Direct Effects

Estuarine/marine 

invertebrates No effect

the single maximum application rate to 0.75 

lb a.i./acre (using a KOC of 285 and a soil 

depth of 10 cm) or to 0.15 lb a.i./acre (using 

a KOC of 25 and a soil depth of 1.0 cm)

3. To help refine the risk assessment for 

terrestrial-phase amphibians and reptiles that 

may eat invertebrates contaminated with 

fosthiazate, T-HERPS (which uses feeding 

rates based on iguanids instead of birds) was 

used. Based on the T-HERPS analysis, none of 

the RQs for amphibians or reptiles that eat 

terrestrial invertebrates exceed an Agency 

LOC. Currently the Earthworm Fugacity 

model does not calculate RQs for terrestrialphase amphibians or reptiles that eat 

contaminated earthworms. Therefore, the 

potential risk to terrestrial-phase amphibians or 

reptiles that specifically eat earthworms is 

uncertain.

No effect

depth of 10 cm) or to 0.26 lb a.i./acre 

(using a KOC of 25 and a soil depth of 1.0 

cm)
13

II. PROBLEM FORMULATION

A. Pesticide Type, Class, and Mode of Action 

Fosthiazate is a systemic organophosphate (OP) nematicide/insecticide used for the control of a 

broad spectrum of nematode species in tomatoes. Fosthiazate also suppresses insects including 

sweet potato whitefly, tomato pinworm, and beet armyworm in tomatoes. Current labels allow 

application of fosthiazate to the soil prior to receiving transplanted tomatoes at a maximum 

annual rate of 1.5 lb active ingredient (a.i.)/planted acre. It must be applied through drip 

irrigation systems placed under plastic mulch. Fosthiazate is active against invertebrates via 

contact and oral exposure. As an OP, its mode of action is considered to be through acetyl 

cholinesterase inhibition (AchEI), although fosthiazate itself is only a weak inhibitor of AchEI in 

in vitro studies (USEPA, 2009). Fosthiazate is activated as a cholinesterase inhibitor by mixed 

function oxidase or other intracellular oxidation processes.

B. Overview of Pesticide Use and Usage

Fosthiazate is registered for use on tomatoes at a maximum annual rate of 1.5 lb active ingredient 

(a.i.)/planted acre. It must be applied through drip (trickle) irrigation systems placed under 

polyethylene plastic mulch (which is impervious) before seeding or transplanting. Based on 

information in sample state crop profiles (e.g., North Carolina Crop Profile Tomato Plastic 

Mulch, Crop Profile for Tomatoes in Arkansas), the plastic mulch is placed over raised beds and 

remains on the beds until after harvesting (the space between the beds is not treated). Registered 

formulations of fosthiazate include the technical product [Technical Fosthiazate, 96% a.i. (EPA 

Reg. No. 71512-6)], as well as three end use products (all single a.i.), two of which are 

Restricted Use Pesticides (see Table 1). Targeted pests include the control of various nematodes 

[e.g., root-knot nematode (Meloidogyne incognita) and spiral nematode (Helicotylenchus spp.)] 

and the suppression of various insects (i.e., potato whitefly, tomato pinworm and beet 

armyworm).

TABLE 2. Registered Fosthiazate End-Use Products.

PRODUCT 

NAME (EPA 

REG. NO.)

% 

A.I.

USE 

SITE

MAXIMUM 

SINGLE 

APPLICATION 

RATE

MAXIMUM 

ANNUAL 

APPLICATION 

RATE

APPLICATION 

METHOD COMMENT(S)

Fosthiazate 

900EC 

(71512-4)

75 Tomato

1.5 lb a.i./ 

planted acre/ 

crop cycle

Not reported1

Drip irrigation 

under plastic 

mulch

Restricted Use 

Pesticide; do not 

treat more than 25 

acres per day per 

application

Fosthiazate 

75% EC 

(71512-17)

75 Tomato

1.5 lb a.i./ 

planted acre/ 

crop cycle

Not reported1

Drip irrigation 

under plastic 

mulch

Restricted Use 

Pesticide; do not 

treat more than 25 

acres per day per 

application

Nemathorin® 

500EC 

(71512-5)

47.2 Tomato

1.5 lb a.i./ 

planted acre/ 

crop cycle

1.5 lb a.i./planted 

acre/year

Drip irrigation 

under plastic 

mulch

Do not treat more 

than 25 acres per 

day per application

1 The product must be used prior to seeding or transplanting, however, a maximum application rate per year is not 
14

PRODUCT 

NAME (EPA 

REG. NO.)

% 

A.I.

USE 

SITE

MAXIMUM 

SINGLE 

APPLICATION 

RATE

MAXIMUM 

ANNUAL 

APPLICATION 

RATE

APPLICATION 

METHOD COMMENT(S)

specified. Therefore, it is assumed that there will be one application per crop cycle. 

There are no usage data available for fosthiazate [i.e., the use of fosthiazate has not been reported 

in the available usage databases (i.e., United States Department of Agriculture’s National 

Agricultural Statistics Service, private pesticide market research, and California Department of 

Pesticide Regulation Pesticide Use Reporting)]. 

C. Previous Ecological Risk Assessments and Evaluations

Fosthiazate was first registered in 2004. As part of the initial registration, the ecological risks 

associated with several proposed different application methods and rates for the tomato use were 

assessed [USEPA, 2002 (December)]. In that assessment, the EPA found that when fosthiazate 

is applied as a broadcast (3 to 4.5 lb a.i./A) or banded spray (1 to 1.5 lb a.i./A), there were 

concerns for acute risk to birds, mammals and insects (such as honey bees) as well as chronic 

risk to birds and mammals. When fosthiazate is applied as a broadcast (3 to 4.5 lb a.i./A) or 

banded spray (1 to 1.5 lb a.i./A) its use may pose acute and chronic risk to listed birds and 

mammals as well as acute risk to listed terrestrial invertebrates. However, when fosthiazate is 

applied by shank injection or chemigation under plastic mulch, fosthiazate poses minimal acute 

or chronic risk to listed or non-listed, non-target animals and plants. The only RQs for aquatic 

organisms that exceeded EPA levels of concern (LOC) were the acute RQs for freshwater 

aquatic invertebrates based on a 4.5 lb a.i./A broadcast spray, which exceeded the acute listed 

species LOC. Subsequently, only application via chemigation (drip irrigation) under plastic 

mulch of fosthiazate prior to seeding or transplanting tomatoes, was registered. 

The new chemical assessment (USEPA, 2002) identified some data gaps for the broadcast and 

banded uses of fosthiazate (i.e., freshwater invertebrate life-cycle, mysid shrimp life cycle, Tier 

II seedling emergence, Tier II vegetative vigor, and acute honey bee contact); however, the data 

set for the drip irrigation uses was considered complete.

An ecological risk assessment was also conducted for proposed new uses of fosthiazate in 2008 

(USEPA, 2008a). This assessment assessed the risks associated with proposed new uses on 

peanuts (4.0 lb a.i./A) and potatoes (4.5 lb a.i/A) and an increased application rate for tomatoes 

(4.5 lb a.i./A). Fosthiazate was found to present acute risk to birds and mammals and chronic 

risk to endangered birds and mammals. Acute and chronic risk to freshwater and 

estuarine/marine fish and estuarine/marine invertebrates was found to be below the level of 

concern, but there was a potential for acute risk to freshwater invertebrates from the proposed 

uses. Minimal risk was found for terrestrial and aquatic plants. To date, these uses have not 

been registered, and will not be considered further in this preliminary registration review risk 

assessment.

Subsequent to the 2008 new use assessment, a Problem Formulation (PF) was completed for 

Registration Review (USEPA, 2009). The PF addressed the use pattern considered in this 

assessment (tomato use; drip irrigation under plastic mulch; 1.5 lb a.i./A maximum annual 
15

application rate) and is the basis for this risk assessment. The PF concluded the following 

regarding risks to non-target organisms from the use of fosthiazate on tomatoes:

“Due to the application method, aquatic exposure will be low and risk to aquatic 

organisms is minimal. In the new chemical assessment, uses of fosthiazate at twice the 

currently labeled rate applied through broadcast spray did not exceed any aquatic levels 

of concern. With the drip irrigation method required by current labels, drift to surface 

water is not a factor, and because fosthiazate is applied directly to soil in low amounts of 

water and is protected from precipitation by the plastic mulch, runoff is unlikely. 

Therefore, previous assessments concluded that any aquatic exposure from the current 

use on tomatoes will be substantially lower than in those estimated for other uses and so 

there will still be no exceedances.

In the terrestrial environment, there is some potential for dietary exposure to birds and 

mammals who probe beneath the surface for seeds and insects or which feed on emerging 

seedlings containing translocated residues. This exposure is unquantifiable and expected 

to be negligible, so there is minimal risk to terrestrial organisms as well.” (pp. 8 – 9).”

The data set for the drip irrigation use on tomatoes was considered complete. Therefore, no new 

data were requested for fosthiazate in the PF. Since the PF, additional data on the translocation 

of fosthiazate in tomato plants have become available in the open literature (e.g., Mukherjee, et 

al., 2011; Sharma and Kumar, 2011). These studies are considered in this assessment.

D. Assessment Endpoints

The available acute toxicity data on fosthiazate (TGAI) indicate that it is highly toxic to birds, 

freshwater invertebrates, and estuarine/marine invertebrates; moderately toxic to small 

mammals; slightly toxic to estuarine/marine fish; and practically non-toxic to freshwater fish. 

A summary of the toxicity data and the resulting measures of ecological effect selected for each 

taxonomic group are included in Table 3. 

TABLE 3. Summary of the Most Sensitive Measures of Effects (for Each Taxon) of 

Fosthiazate.

STUDY

REGISTRANT SUBMITTED STUDIES

MRID CLASSIFICATION MEASURES OF EFFECTS

Acute Avian Oral 

[Northern Bobwhite Quail 

(Colinus virginianus)]

43916819 Acceptable LD50 = 10.6 mg a.i./kg-bw

Acute Avian Dietary

[Northern Bobwhite Quail 

(Colinus virginianus)]

41381106

Supplemental (the 

birds were not 

randomly assigned to 

treatment groups)

LC50 = 85 mg a.i./kg-diet
16

STUDY

REGISTRANT SUBMITTED STUDIES

MRID CLASSIFICATION MEASURES OF EFFECTS

Avian Reproduction

[Mallard Duck (Anas 

platyrhynchos)]

43916825 Acceptable

NOAEC = 21.7 mg a.i./kg-diet

LOAEC = 42.6 mg a.i./kg-diet (based on reduced 

weight gain, decreased eggshell thickness and 

increased cracked eggs)

Avian Reproduction

[Northern Bobwhite Quail 

(Colinus virginianus)]

43916824 Acceptable

NOAEC = 21.7 mg a.i./kg-diet

LOAEC = 42.6 mg a.i./kg-diet (based on reduced 

weight gain, decreased eggshell thickness and 

increased cracked eggs)

Acute Rat Oral 41347622 Acceptable LD50 = 51 mg a.i./kg-bw (females)

Rat Reproductive 

Development 

41381113; 

44414501 Acceptable

NOAEL = 10 mg a.i./kg-diet

LOAEL = 30 mg a.i./kg-diet (based on decreased 

viability index, litter size for the f1 generation and 

pup weight)

Honey Bee Acute (Apis 

mellifera)

41347636 Acceptable LD50 = 0.247 μg a.i./bee (contact)

Freshwater Fish Acute 

Toxicity [Rainbow Trout 

(Oncorhynchus mykiss)]

43916826 Acceptable LC50 = 111 mg a.i./L

Freshwater Fish Early-Life 

Stage [fathead minnow 

(Pimephales promelas)]

45540404 Acceptable

NOAEC = 2.32 mg a.i./L

LOAEC = 4.48 mg a.i./L (based on reduced dry 

weight and length)

Estuarine/Marine Fish 

Acute Toxicity [Sheepshead 

minnow (Cyprinodon 

variegatus)]

45540403 Acceptable LC50 = 46.5 mg a.i./L

Estuarine/Marine Fish 

Chronic No data available

Freshwater Invertebrate 

Acute Toxicity 

[Daphnid (Daphnia magna)]

43916828 Acceptable EC50 = 0.26 mg a.i./L

Freshwater Invertebrate 

Life-Cycle 

[Daphnid (Daphnia magna)]

43916829

Supplemental (the 

length and weight of 

the offspring were not 

measured)

NOAEC = 0.061 mg a.i./L

LOAEC = 0.128 mg a.i./L (based reduced 

reproduction and parental mortality)

Estuarine/Marine Acute 

Invertebrate [Eastern oyster 

(Crassostrea virginica); 

shell deposition]

45540401 Acceptable EC50 = 14.1 mg a.i./L
17

STUDY

REGISTRANT SUBMITTED STUDIES

MRID CLASSIFICATION MEASURES OF EFFECTS

Estuarine/Marine Acute 

Invertebrate [Mysid 

(Americamysis bahia)]

45540402 Acceptable LC50 = 0.429 mg a.i./L

Estuarine/Marine 

Invertebrate Chronic No data available

Terrestrial Plants (Seedling 

Emergence) 43916839

Supplemental (raw 

data were not 

submitted)

Most Sensitive Dicot1:

Mustard – NOAEC = 0.8 lb a.i./A

EC25 = 1.0 lb a.i./A

Endpoints based on reduced fresh weight

Most Sensitive Monocot:

None – NOAEC = 6.0 lb a.i./A

EC25 > 6.0 lb a.i./A

Terrestrial Plants 

(Vegetative Vigor) 43916840 Acceptable

Most Sensitive Dicot1:

Buckwheat– NOAEC = 0.8 lb a.i./A

EC25 = 3.3 lb a.i./A

Most Sensitive Monocot:

Sorghum – NOAEC = 3.0 lb a.i./A

EC25 > 6.0 lb a.i./A

Endpoints based on reduced shoot weight

Aquatic Plants NonVascular2

[Green Algae 

(Selenastrum 

capricornatum)]

43916821 Acceptable

EC50 > 4.51 mg a.i./L

NOAEC = 4.51 mg a.i./L (the highest 

concentration tested)

Aquatic Plant Vascular No data available

1 Although peppers showed a greater than 25% effect response in the Tier I study, they were not included in the Tier II 

study.

2 Data are only available for one of the four typically required aquatic non-vascular plant species.

Open Literature 

Additional toxicity data were located in the open literature using the ECOTOXicology database, 

however, none of the acceptable studies had endpoints that were more sensitive than those from 

the submitted studies (see Appendix D).

To assess exposure from the uptake of fosthiazate in the tomato plants, data available from the 

open literature are considered for this assessment (Mukherjee, et al. 2011; Sharma and Kumar, 

2011; Wu, et al. 2012) (see the ‘Measures of Exposure’ section below for details). 
18

E. Analysis Plan and Conceptual Models

1. Measures to Evaluate Risk Hypotheses

In the case of fosthiazate, measures of exposure are based on terrestrial models that estimate 

environmental concentrations of fosthiazate using maximum labeled application rates. The 

model used to produce terrestrial EECs on food items is T-REX. For more information on 

EPA’s models, visit http://www.epa.gov/pesticides/science/models_db.htm. The most sensitive 

toxicity endpoints from surrogate test species are used to estimate treatment-related effects on 

growth, reproduction and/or survival. 

Measures of effect are obtained from a suite of studies conducted with a limited number of 

surrogate species. The test species are not intended to be representative of the most sensitive 

species but rather are selected based on their ability to thrive under laboratory conditions. 

2. Conceptual Model

The conceptual model is a graphic representation of the structure of the risk assessment. It 

specifies the fosthiazate release mechanisms, biological receptor types, and effects endpoints of 

potential concern. The conceptual model for terrestrial exposure is shown in Figure 1 (aquatic 

exposures are not expected). For the registered use, fosthiazate is applied to tomatoes via drip 

irrigation under plastic mulch. The only potential exposure pathways to non-target organisms 

are via direct application (for soil-dwelling invertebrates) and ingestion of contaminated 

invertebrates and/or ingestion of tomato plant parts in which fosthiazate has been translocated. 

Dashed lines (such as for spray drift, runoff, leaching, and atmospheric transport) denote 

exposure routes not assessed due to the likelihood of low potential exposure. 
19

3. Risk Hypothesis

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. For fosthiazate, the 

following ecological risk hypothesis is being employed for this national-level ecological risk 

assessment:

Fosthiazate, when used in accordance with current labels, can result in exposure 

to non-target terrestrial animals. Exposure via direct applications (soil-dwelling 

invertebrates) and/or via ingestion of contaminated invertebrates and/or part(s) 

of the treated tomato plant may be above levels where adverse effects upon the 

survival, growth, and reproduction of non-target terrestrial animals (including 

federally-listed threatened and endangered species) would occur. 
20

III. ANALYSIS

A. Measures of Exposure

As discussed in the Registration Review Problem Formulation for fosthiazate, previously 

assessed broadcast uses of fosthiazate that had twice the labeled application rate as the registered 

tomato use did not exceed any aquatic levels of concern. With the drip irrigation method 

required by current labels, drift to surface water is not a concern, and because fosthiazate is 

applied directly to soil in low amounts of water and is protected from precipitation by the plastic 

mulch, any appreciable runoff is unlikely. The persistence and mobility of fosthiazate and the 

MBSo/MBSx and BSA degradates1suggest that the potential exists for leaching to groundwater. 

Previous assessments concluded that any aquatic exposure from the current fosthiazate use on 

tomatoes will be substantially lower than estimated for other previously assessed uses and no 

aquatic LOC exceedances are expected. Therefore, risks to aquatic organisms (plants or 

animals) are not expected from the registered use and aquatic exposure values will not be 

calculated in this assessment. Risk from exposure from groundwater is expected to be less than 

for surface water from previously assessed broadcast uses, and, therefore, additional analysis for 

exposure via groundwater was not done.

The only potential exposures expected from application via drip irrigation (under plastic mulch) 

are to soil-dwelling invertebrates (direct application) and to animals (e.g., terrestrial 

invertebrates, birds, and mammals) that may feed directly on tomato plant parts in which 

fosthiazate has been translocated (e.g., roots, leaves, stems, fruits, flowers, pollen, nectar) or 

contaminated soil-dwelling invertebrates. Therefore, potential exposures are expected to be 

limited to the site of application. Risks to non-target terrestrial plants are not expected due to 

limited exposure potential. Currently, there are no standard methods for quantitatively assessing 

risks to soil-dwelling invertebrates from direct exposure to pesticides via drip irrigation or risks 

associated with systemic pesticides. Therefore, potential risks to non-target terrestrial animals 

will not be assessed using the standard methodology. 

For direct exposure to soil-dwelling invertebrates, information from the labels is used to estimate 

a concentration of the a.i. in the irrigation water that is used to apply fosthiazate that can be 

compared to the available toxicity endpoint for bees (contact). The current labels state that 0.5 to 

1 inch of irrigation water per acre is required for the incorporation of fosthiazate. The highest 

concentration of a.i. in the irrigation water would be with the application of 0.5 inch of irrigation 

water/acre. Therefore, the 0.5 inch of water/acre is used for modeling. One-acre inch of water is 

equal to 27,154 gallons; therefore, 0.5 acre inches of water = 13,577 gallons (which equals 

51,395 L). The maximum allowed application rate for fosthiazate is 1.5 lb a.i./A, which equals 

680,389 mg a.i./acre. This results in a concentration of 13.2 mg a.i./L (i.e., 680,389 mg 

a.i./51,395 L). This concentration is used to assess exposure and potential risks to terrestrial 

invertebrates.

This concentration [i.e., 13.2 ppm (mg/kg)] is also used to calculate the concentration found on 

contaminated arthropods that may be ingested by listed and non-listed birds and mammals that 

 

1 MBSo: sec-butyl methyl sulfone; MBSx: sec-butyl methyl sulfoxide; and BSA: 2-Butanesulfonic acid
21

may probe for arthropod prey under the plastic mulch. To account for the mass of the ingested 

invertebrate(s), the average fresh weight of an adult honey bee of 128 mg (Mayer and Johansen, 

1990) is used as a surrogate for the mass of soil-dwelling arthropods. Adjusting for the weight of 

the bee exposed to 13.2 ppm of fosthiazate, results in a concentration of 1.7 ppm/arthropod (13.2 

mg a.i./L x 0.128 mg). This number can then be used as the estimated environmental exposure 

(EEC) for arthropods in T-REX (v 1.5).

The T-REX model is useful for assessing exposures of terrestrial animals to pesticide residues on 

foliar surfaces of crops and seeds. The model cannot be used to assess pesticide exposures to 

terrestrial animals resulting from consumption of earthworms contaminated with pesticide mass 

present in the soil of the application site. Therefore, in order to explore the potential exposures 

of mammals and birds to pesticides in the soil and earthworms on the treatment site, a simple 

fugacity approach (an ‘earthworm fugacity’ model) was also employed to estimate 

concentrations of the pesticide of interest in earthworms (see APPENDIX C for details). In this 

approach, it is assumed that a pesticide partitions between the soil, the (pore) water and the air 

contained within the soil of the treatment site. It is assumed that earthworms dwelling within the 

soil are exposed to a pesticide via ingestion of contaminated soil. In this model, it is assumed 

that assessed mammals and birds consume only earthworms (i.e., vermivores) from the treatment 

site. The earthworm fugacity model uses the maximum average concentration in the soil 

(modeled using PRZM). A range of both Koc values (25 and 285) and modeled depths (1.0 cm 

and 10.0 cm) were used to bound the potential soil concentrations. In order to assess acute dosebased and dietary-based exposures of vermivores to pesticides, an approach similar to the one 

employed by the T-REX model is used.

To estimate potential exposures for terrestrial animals feeding on parts of tomato plants in which 

fosthiazate has been translocated, we relied on data from fosthiazate uptake studies in tomatoes 

that had been transplanted into treated soil (i.e., Sharma and Kumar, 2011; Sharma and Kumar, 

2011b; and Wu, et al., 2012). Based on these data, a maximum of 0.489% of the applied 

fosthiazate is absorbed by the plant (for fosthiazate applied via drip irrigation with a surfactant). 

Therefore, to estimate the mass of the pesticide in each plant, the application rate (i.e., 1.5 lb 

a.i./A) can be multiplied by 0.00489. This results in a value of 0.007 lb a.i./A of plants (i.e., 

3175 mg a.i./A of plants). To calculate a concentration per plant, the fresh weight of tomato 

plants is needed along with the number of plants per acre. Based on data from Wu, et al. (2012), 

fresh shoot weight of tomato plants at 12 weeks ranged from 3.59 to 2.67 kg/plant. Twelve 

weeks is a time-frame which would allow for uptake – tomato plants are typically transplanted at 

4 – 6 wks old. Using the lower end of the range (i.e., 2.67 kg/plant) and a lower bound number 

of plants per acre [i.e., ~3,700 – 5,000 plants/acre (Crop Profile for Tomatoes in Arkansas; 

Commercial Tomato Production Handbook)] results in 9,879 kg of tomato plants per acre (3,700 

plants x 2.67 kg/plant). Therefore, a peak fosthiazate concentration of 0.32 ppm is expected in 

the tomato plants (3,175 mg a.i./9,879 kg plant) (it is assumed that all parts of the plant have this 

same fosthiazate concentration). This number can then be used as the estimated environmental 

exposure (EEC) via ingestion of plants in T-REX (v 1.5). No data are available for the 

translocation of fosthiazate in plants grown from seed. However, since the soil treatment is 

identical for tomatoes grown from seed and from transplant, we assume that the amount of 

fosthiazate translocated in the plants will be similar.
22

B. Environmental Fate Characterization and Modeling Input Parameters

The physical/chemical properties and environmental fate properties of fosthiazate are listed in 

Table 4. In aerobic soils, measured half-lives were 14.0 to 57.7 days with the appearance of 

slower metabolism in acidic soils (t1/2 = 41.8 to 57.7 days) than in alkaline soils (t1/2 =14.0 to 

20.7 days). Substantial degradation was seen in sterile controls as well, suggesting that some of 

the transformation occurs through abiotic processes. Laboratory studies suggest that persistence 

of fosthiazate in soils will be on the scale of weeks to months, with rates depending on soil pH. 

Terrestrial field dissipation (TFD) half-lives ranged from 7 to 40 days depending upon location 

and formulation. The influence of soil pH on half-life was not observed in the TFD studies. The 

terrestrial field dissipation studies were conducted in soils that are expected to be relatively 

permeable (sand content generally > 50 % - sandy clay loam to loamy sand). Therefore, the 

terrestrial field dissipation half-lives may reflect the differences in leaching between the different 

study site locations. The soil partition coefficients (Kads) ranged between 0.43 and 2.77 mL/g. 

Fosthiazate has low sorption to soil and the sorption of fosthiazate is correlated (p-value = 0.05) 

to soil organic carbon content. Based on Koc, values ranging from 25 to 285.7 mL/goc, 

fosthiazate is classified as mobile to moderately mobile by the FAO classification scheme (FAO, 

2000). Sorption did not appear to be correlated to soil pH. Based upon its vapor pressure, the 

volatility class for fosthiazate from dry non-adsorbing surfaces is between “non-volatile under 

field condition” and “intermediate to high volatility under field condition” (4.20 x 10-6torr).

The persistence and mobility of fosthiazate are conducive to runoff and leaching. However, the 

approved application methods are designed to minimize potential transport to surface water. 

Labels require application through drip irrigation under plastic mulch. Therefore, spray drift to 

surface water is not a concern, and the potential for runoff is reduced by the direct soil 

application and by the protection from precipitation. If any fosthiazate does reach aquatic 

environments, it is stable to aquatic photolysis and has limited hydrolysis in neutral and acidic 

conditions, but it hydrolyzes rapidly in alkaline conditions. It is moderately persistent in watersediment systems, with an average half-life, using linear regression, in aerobic aquatic 

environments of 51 days and in anaerobic aquatic environments of 32 days.

Terrestrial field dissipation (TFD) studies were conducted with 4 lbs a.i./A, applied as 

emulsifiable concentrate (EC) and granular formulations, to bare ground and incorporated 4 to 5 

inches with no plastic mulch. In three sites, calculated half-lives were 9 to 17 days, and in a 

fourth site, the half-life was 40 days for the granular formulation. For the EC formulation the 

calculated half-lives ranged from 7 to 15 days, at the three sites, and at the fourth site 28 days. 

Because the laboratory aerobic metabolism studies suggest that soils with an acidic pH were 

more persistent, all studies were conducted at sites with acidic soils (pH <6.6). Soils were also 

selected to represent soils with higher leaching potentials as all contained 50 percent or more 

sand. In most cases, fosthiazate residues were detected to no more than 15-30 cm below the soil 

surface. In three samples collected at the Georgia site, fosthiazate residues were found at low 

levels (≤0.02 mg/kg) up to 46 cm below the soil surface. Degradates MBSo/MBSx and BSA 

were not detected in samples collected below 0-15 cm.
23

In the registered use, the plastic mulch cover would minimize volatilization and runoff; 

therefore, increasing the amount of the chemical available for leaching. However, with the drip 

irrigation method, a small amount of water is slowly dripped into soils precisely where it is 

needed, thus lessening the amount of water flowing down through the soil past the root zone 

where it cannot be used by the crop. This greatly reduces the potential for the chemical to reach 

ground water. 

Based on the results of the fish accumulation study, the bioconcentration factors were 2.3X for 

edible tissue, 4.5X for non-edible tissue, and 3.2X for whole body tissue after 28 days exposure 

and a 14-day depuration period, suggesting low bioaccumulation potential. By day 14 of the 

depuration period 78%, 81% and 80% of the 14C-residues had been eliminated from the edible, 

non-edible and whole body tissue portions, respectively.

TABLE 4. Physical/chemical Properties and Environmental Fate Properties of 

Fosthiazate.

PARAMETER VALUE(S) SOURCE (Study 

Acceptability 

Classification)a

COMMENTS

Molecular Structure

Chemical Name O-Ethyl S-(1-methylpropyl)(2-oxo-3-thiazolidinyl) 

phosphonothioate

Chemical Class Organophosphate (OP)

Molecular Formula C9H18NOPS2 MRID 47223201 

Molecular Weight 283.36

Solubility 

in water (25 oC)

9880 mg/L@ pH5

9000 mg/L @ pH 7

9460 mg/L @ pH 9

MRID 47223201 

Vapor Pressure (25 oC) 4.20 x 10-6 mm Hg MRID 47223201 

Henry’s Law Constant 

(25 oC) 

1.74 x 10-10 atm m3/mol Calculated Henry’s Law Constant = 

[Vapor Pressure (mm 

Hg)/760 mm Hg)] x [Mole 

Weight (g/mole)/Solubility 

(ppm)]

Hydrolysis Half-life 

(25 oC)

177 days @ pH 5 

104 days @ pH 7

3.2 days @ pH 9

MRID 41347637 (a)

Aqueous Photolysis 

Half-life (pH 4)

stable MRID 43916831(a)
24

PARAMETER VALUE(S) SOURCE (Study 

Acceptability 

Classification)a

COMMENTS

Aerobic Soil Metabolism 

Half-life

LRc T1⁄2 = 41.75, 45.89 days @ 

pH 6.1 

53.3 to 57.7 days @ pH <6.1b

14.0 to 20.7 days @ pH >7.0b

MRID 43916832 (a)

MRID 47098902 (s)

MRID 47098902 (s)

One soil with carbonyl and 

butyl labels

Pantelelis et al.,2006 (this 

publication is included in 

MRID 47098902)

Anaerobic Aquatic Soil 

Metabolism

32 days MRID 43916833 (a) Represents average of 31 

days (carbonyl label)

33 days (butyl label) for one 

soil

Aerobic Aquatic 

Metabolism Half-life

Total System

river sediment (Ohio)

LR T1⁄2 - 72.3 days

Non-LRd T1⁄2 - 70.0 days

river sediment (German)

LR T1⁄2 - 29.5 days

Non-LR T1⁄2 - 39.8 days

MRID 47098903 (s) The LR T1⁄2 is used because 

the fate and transport models 

used by EFED use simple 

first-order kinetic models.

Soil Partition Coefficient 

(Kd) (mL/g)

Kd = 0.43, 1.22, 1.71

1.48 to 2.77 (n=9)

MRID 41347639 (a)

MRID 41347640 (s)

MRID 47098902 (s) Pantelelis et al.,2006 (in 

MRID 47098902)

Organic Carbon Partition

Coefficient (Koc) (mL/goc)

Koc = 45.3, 96.2, 24.8

205.0 to 285.7 (n=9)

MRID 41347639 (a)

MRID 47098902 (s)

-

Pantelelis et al.,2006 

(included in MRID

47098902)

Log Octanol/water partition 

coefficient (Kow )(25◦C) 

1.752 MRID 47223201

Terrestrial Field Dissipation 

Half-life

Study Location: LR T1⁄2 [pHf]

Formulation: EC Granular

WA: 15 d 17 d [≤5.5]

CA: 28 d 40 d [5.6 – 6.6]

GA: 16 d 13 d [<5.5, 

surface sample = 6]

-

NC: 7 d 9 d [<4.6

surface sample = 6.3]

MRID 43952901 (a)

MRID 43952902 (a)

MRID 43952903 (a) &

MRID 43916835 

MRID 43952904 (a)

EC and Granular Formulations 

of fosthiazate were applied to 

bare ground plots at 

~4.5 lb a.i./A 

with no plastic mulch

Analytes in all studies included 

parent and degradates MBS and 

BSAe.

Bioconcentration Factor 

(BCF) in fish

2.3 to 4.5X MRID 41347642 (a)

a

* (a) = acceptable study that fulfills guideline requirement; (s) = supplemental study

b Total of 9 soils, 3 with pH <6.1 and 6 with pH > 7.0

c LR is Single First-Order (SFO) linear regression

d Non-LR is Single First-Order (SFO) non-linear regression

e Degradates: MBS (2-(Methylsulfonyl) butane) and BSA (2-Butanesulfonic acid),

f

Soil pHs for soil increments sampled in the terrestrial field dissipation studies.
25

As summarized in Table 5, carbon dioxide and bound residues were the primary end products in 

most cases. Additionally, six degradation products were identified: (RS)-S-sec-butyl hydrogen 

2-oxo-1,3-thiazolidin-3-ylphosphorothioate (DETO), O-ethyl-2-oxo-1,3-thiazolidin-3-

ylphosphonate (DBTO), 1,2-thiazolidin-2-one (TZO), (RS)-S-sec-butyl O-ethyl hydrogen 

phosphorothioate (DTTO), sec-butyl methyl sulfone (MBSo), sec-butyl methyl sulfoxide 

(MBSx), and 2-Butanesulfonic acid (BSA) were detected along with unidentified organic 

volatiles. Study lengths were not sufficient to determine the pattern of formation and decline for 

all degradates. The only degradates found in terrestrial field dissipation studies were 

MBSo/MBSx which at maximum represented about 1 to 4 % of applied (maximum fosthiazate 

concentration = 2.2 mg/kg). The maximum MBSo/MBSx soil concentration was 0.06 mg/kg and

the maximum BSA soil concentration was 0.1 mg/kg. These degradates were not detected below 

the shallowest sampling increment (0-15 cm). In the column leaching studies, the three major 

degradation products recovered in the leachate were TZO, DTTO, and DEDT ((RS)-S-sec-butylphosphorothioate) at 2.6%, 7.8%, and 42.5% of applied radioactivity, respectively.

Table 5. Major degradates of fosthiazate, as a percentage of applied parent

Degradates bStudy Type (Study Length)a

Hydrolysis Aerobic 

Soil

(150 d)

Aerobic 

Aquatic

(140 d)

Anaerobic 

Aquatic Soil

(120 d)

pH 5

(30 d)

pH 7

(30 d)

pH 9

(14 d)

DETO ~13 % ~13 % up to 10% c minor

DBTO 45%

TZO 40% 32%

(60 d)

DTTO 44% up to 10% c minor

MBSo/

MBSx d

11%

(28 – 35 d)

16.4%

(60 d)

BSA 20%

Unidentified 

organic 

volatiles

~30% 8%

CO2 27 – 67% 31.9% 43%

a Unless otherwise noted, maximum concentrations occurred at study termination.

b DETO: (RS)-S-sec-butyl hydrogen 2-oxo-1,3-thiazolidin-3-ylphosphorothioate; DTTO: (RS)-S-sec-butyl Oethyl hydrogen phosphorothioate; MBSo: sec-butyl methyl sulfone; MBSx: sec-butyl methyl sulfoxide; BSA: 2-

butanesulfonic acid.

c Aerobic aquatic study did not separate DETO/DTTO.

d MBSo/MBSx not separated.

Additional information concerning the environmental fate of fosthiazate is described in the New 

Chemical Assessment for Fosthiazate (USEPA, 2002, D229582).

a) Monitoring Data

Fosthiazate was not included as one of the residues analyzed for in groundwater at the time that 

the Pesticides in Ground Water Data Base was published, in 1992 (USEPA, 1992). This may be 

because very few groundwater samples have been analyzed for fosthiazate residues in the United 

States and because it has limited usage areas and crops. Fosthiazate was not included in the suite 

of analyses conducted in the USEPA's National Survey of Pesticides in Drinking Water Wells 
26

(USEPA, 1990, 1992). Fosthiazate also is not included in the USGS NAQWA program. No 

surface water monitoring was located.

The California Department of Pesticide Regulation (CDPR) surface water database 

(http://www.cdpr.ca.gov/docs/emon/surfwtr/surfcont.htm, USGS NAWQA surface and ground

water database (http://infotrek.er.usgs.gov/apex/f?p=136:1:0::NO:::), Pesticide Data Program 

(http://www.ams.usda.gov/AMSv1.0/ams.fetchTemplateData.do?template=TemplateG&navID=

&rightNav1=&topNav=&leftNav=ScienceandLaboratories&page=PDPDownloadData/Reports&

resultType=&acct=pestcddataprg), and the USGS/EPA Reservoir Data Program (Blomquist et 

al., 2001) were evaluated for available monitoring data, however fosthiazate does not appear to 

be an analyte in these monitoring programs.

C. Ecological Effects Characterization

a) Aquatic Animals

The available acute toxicity data on fosthiazate (TGAI) indicate that it is highly toxic to 

freshwater invertebrates [EC50 = 0.26 mg a.i./L (MRID 43916828)] and estuarine/marine 

invertebrates [LC50 = 0.429 mg a.i./L (MRID 45540402)]; slightly toxic to estuarine/marine fish

[LC50 = 46.5 mg a.i./L (MRID 45540403)]; and practically non-toxic to freshwater fish [LC50 = 

111 mg a.i./L (MRID 43916826)] (see Table 3). 

Chronic effects in the freshwater fish early life stage study using the fathead minnow 

(Pimephales promelas) included reduced dry weight and length of young fish (NOAEC = 2.32 

mg a.i./L, LOAEC 4.48 mg a.i./L) (MRID 45540404). The freshwater invertebrate life-cycle 

study determined a NOAEC value of 0.061 mg a.i./L and a LOAEC value of 0.128 mg a.i./L 

based on reduced number of offspring produced and parental mortality (Daphnia magna; MRID 

43916829). No chronic toxicity data are available for estuarine/marine fish or invertebrates.

b) Aquatic Plants

A Tier I test with the green alga (Selenastrum capricornatum) found no adverse effects at a 

concentration equal to 4.5 mg a.i./L. There are no data available for vascular aquatic plants.

c) Terrestrial Animals

Birds

The available toxicity data on fosthiazate (TGAI) indicate that it is highly toxic to birds on an 

acute [LD50 = 10.6 mg a.i./kg-bw (MRID 43916819)] and sub-acute [LC50 = 85 mg a.i./kg-diet 

(MRID 41381106)] exposure basis.

Both the mallard duck (Anas platyrhynchos) and bobwhite quail (Colinus virginianus) avian 

reproduction studies had the same NOAEC (21.7 mg a.i./kg-diet) and LOAEC values (42.6 mg 

a.i./kg-diet) (MRIDs 43916825 and 43916824, respectively). Significant effects on male and 

female weight gain, decreased eggshell thickness, and increased cracked eggs were observed in 

the bobwhite quail. 
27

Mammals

The available acute toxicity data on fosthiazate (TGAI) indicate that it is moderately toxic to 

mammals [LD50 = 51 mg a.i./kg-bw (MRID 41347622)].

A 2-generation rat study (see MRIDs 41381113 and 44414501) yielded a reproductive NOAEL 

of 10 mg a.i./kg-diet (or 0.91 mg/kg/day for both males and females) and a LOAEL of 30 mg 

a.i./kg-diet (equivalent to 2.09 and 2.60 mg/kg-bw/day males and females, respectively) based on 

decreased viability index, litter size and pup weight for the f1 generation.

Terrestrial Invertebrates

The acute contact honey bee (Apis mellifera) LD50 is 0.247 μg a.i./bee (MRID 41347636). Since 

the LD50 is less than 2 μg a.i./bee, fosthiazate TGAI is categorized as highly toxic to bees on an 

acute contact basis.

d) Terrestrial Plants

Tier I and Tier II terrestrial plant toxicity tests were performed on technical fosthiazate in which 

dicots appear to be more sensitive than monocots. Based on a Tier II seedling emergence test on 

technical fosthiazate, the NOAEC and EC25 for mustard are 0.8 and 1.0 lb a.i./A, respectively 

(MRID 43916839). Although the Tier I test results showed peppers were more sensitive (27 %) 

than mustard (<25 %) (MRID 43916837), no test was conducted with peppers. For Tier II 

vegetative vigor, the most sensitive terrestrial plant is the dicot buckwheat (NOAEC = 0.8 lb 

a.i./A; EC25 = 3.3 lb a.i./A). Sorghum was the only monocot tested (NOAEC = 3.0 lb a.i./A and 

the EC25= > 6.0 lb a.i./A). 
28

IV. RISK ESTIMATION

1. Non-target Aquatic Animals and Plants

Because runoff and spray drift are not expected with the use of fosthiazate on tomatoes via drip 

irrigation under plastic mulch and previous assessments for fosthiazate that modeled higher 

application rates than assessed here found no LOC exceedances for aquatic organisms, risks to 

aquatic organisms are not expected. Exposure may occur via groundwater, but such exposure is 

expected to be less than previously assessed uses. Therefore, risks to aquatic animals are not 

quantitatively estimated.

2. Non-target Terrestrial Animals

Screening-level risk assessments do not typically evaluate risks to terrestrial invertebrates; 

however, toxicity information for beneficial insects is used to develop precautionary label 

language where necessary. Based on the available toxicity data alone, precautionary label 

language for bees is recommended for the fosthiazate labels. 

To estimate risks to soil-dwelling invertebrates from direct application of fosthiazate, a 

concentration of 13.2 ppm is used as the estimated environmental concentration (EEC) (see the 

‘Measures of Exposure’ section). The available contact LD50 for honey bees is used as 

surrogate toxicity data for all arthropods (i.e., LD50 = 0.247 μg a.i./bee). Based on an average 

fresh weight per honey bee of 128 mg (Mayer and Johansen, 1990), the contact LD50 of honey 

bees (μg/bee) can be multiplied by 7.8 to convert the μg/bee value to a ppm value. This results 

in an LD50 for bees of 1.9 ppm (0.247 μg a.i./bee x 7.8). Dividing the EEC (13.2 ppm) by the 

LD50 (1.9 ppm) results in an RQ of 6.9, which exceeds the interim listed species LOC of 0.05 for 

terrestrial invertebrates.

For birds and mammals that may probe the soil for arthropod prey that are contaminated via the 

treated irrigation water, it is assumed that soil-dwelling arthropods have a residue value of 1.7 

ppm (see the ‘Measures of Exposure’ section). When 1.7 ppm is used as the residue on 

arthropods in T-REX, acute dose-based RQs for small and medium-sized birds exceed the acute 

listed species LOC of 0.1 (RQs = 0.25 and 0.11, respectively), and dose-based chronic RQs 

exceed the chronic LOC of 1 for small and medium mammals (RQs = 1.48 and 1.26, 

respectively) (see Table 6).
29

TABLE 6. Acute and Chronic RQs for Birds and Mammals that Ingest Arthropods 

Contaminated with Fosthiazate (1.7 ppm) Via Treated Irrigation Water.

EXPOSURE 

TYPE BODY SIZE BIRDS MAMMALS

Acute Chronic Acute Chronic

DOSE-BASED 

RQs

Small

[20 g (birds); 15 g (mammals)] 0.25

Not 

applicable

0.01 1.48

Medium

[100 g (birds); 35 g (mammals)] 0.11 0.01 1.26

Large

[1,000 g (birds and mammals)] 0.04 0.01 0.68

DIETARYBASED RQs All sizes 0.02 0.08 Not 

applicable 0.17

Bolded numbers exceed an EPA Level of Concern (LOC).

For birds and mammals that may eat earthworms, the earthworm fugacity model was used (based 

on maximum average soil concentrations estimated using PRZM). The avian and mammalian 

RQs are bounded based on two different KOC’s and soil depths. The highest soil concentration 

(and the one resulting in the highest RQs) was based on a KOC of 25 and a soil depth of 1 cm; the 

lowest soil concentration was based on a KOC of 285 and a soil depth of 10 cm (see Table 7). 

The acute RQs for birds exceeded the listed species LOC for both modeled soil concentrations 

and the non-listed species LOC for the highest soil concentration modeled (acute RQs ranged 

from 0.01 to 0.98). All of the chronic RQs for birds were <1. For mammals, none of the acute 

RQs exceeded any LOC; however the chronic LOC was exceeded for both modeled soil 

concentrations (RQs ranged from (0.11 to 5.71).

TABLE 7. Acute and Chronic RQs for Birds and Mammals that Ingest Earthworms

Contaminated with Fosthiazate Via Treated Irrigation Water (Based on the Earthworm 

Fugacity Model).

USING A SOIL 

CONCENTRATION 

BASED ON THE 

FOLLOWING:

EXPOSURE 

TYPE

BIRDS MAMMALS

Acute Chronic Acute Chronic

KOC = 285

Soil Depth = 10.0 cm

DOSEBASED RQs 0.20 N/A 0.01 1.16

DIETARYBASED RQs 0.01 0.05 N/A 0.11

KOC = 25

Soil Depth = 1.0 cm

DOSEBASED RQs 0.98 N/A 0.06 5.71

DIETARYBASED RQs 0.06 0.24 N/A 0.53

Bolded numbers exceed an EPA Level of Concern (LOC).

For animals that may ingest treated tomato plants, a residue value of 0.32 ppm was used to 

model RQs for birds and mammals eating broadleaf plants in T-REX (see the ‘Measures of 

Exposure’ section). The only LOC exceeded is for listed 20 g birds (acute) (the RQ is equal to 

the acute listed species LOC of 0.05) (see Table 8). No other RQ for birds or mammals that eat 

broadleaf plants (acute or chronic) exceed an LOC. 
30

TABLE 8. Acute and Chronic RQs for Birds and Mammals that Ingest Tomato Plants 

(Broadleaf Plants) Contaminated with Fosthiazate (0.32 ppm) Via Uptake from Treated 

Irrigation Water.

EXPOSURE 

TYPE BODY SIZE BIRDS MAMMALS

Acute Chronic Acute Chronic

DOSE-BASED 

RQs

Small

[20 g (birds); 15 g (mammals)] 0.05

Not 

applicable

<0.01 0.28

Medium

[100 g (birds); 35 g (mammals)] 0.02 <0.01 0.24

Large

[1,000 g (birds and mammals)] 0.01 <0.01 0.13

DIETARYBASED RQs All sizes <0.01 0.01 Not 

applicable 0.03

Bolded numbers exceed an EPA Level of Concern (LOC).

There are no acute oral toxicity data available for honey bees and fosthiazate; therefore, risks to 

terrestrial invertebrates that may eat contaminated tomato plants cannot be quantified. Because 

fosthiazate can be used to suppress insects (according to current labels), it is assumed that any 

insect that may feed on contaminated tomato plants is at risk of mortality or other adverse effect.

Risks to non-target plants are not expected due to the relatively low toxicity (relative to the 

application rate) and the low exposure potential from the use of fosthiazate via drip irrigation 

under plastic mulch. Therefore, risks to plants are not quantitatively estimated.

3. Probit Slope Response Analysis of LOC Values and Acute RQ Values

The chance of individual effects for the taxa assessed here using the IECv1.1.xls spreadsheet are 

provided in Table 9. For all of the taxa, the default slope = 4.5 (upper and lower bound = 2 and 

9)] was used to calculate the chance of mortality. The highest RQ for each taxon was used. If 

the highest RQ for a taxon did not exceed an acute LOC, the acute listed species LOC was used 

to calculate the chance of effects. For birds, the chance of mortality (RQ = 0.98; slope = 4.5) is 

~1 in 2 (or 50%); for mammals the chance of mortality at the acute listed species LOC of 0.1 

(slope = 4.5) is ~1 in 294,000; for terrestrial invertebrates, the chance of individual effects is 

100% (RQ = 6.9; slope = 4.5); and for fish and aquatic invertebrates, the chance of mortality at 

the acute listed species LOC of 0.05 (slope = 4.5) is ~1 in 418,000,000 (see Table 9). 
31

Table 9. Chance of Individual Effects for Fosthiazate Use on Tomatoes.

TAXON ACUTE 

RQ or LOC SLOPE CHANCE OF INDIVUAL EFFECTS

Birds RQ = 0.98

4.5 ~1 in 2.07

2 ~1 in 2.03

9 ~1 in 2.13

Mammals LOC = 0.1

4.5 ~1 in 294,000

2 ~1 in 44.0

9 ~1 in 8.86E+18

Terrestrial Invertebrates RQ = 6.9

4.5 ~1 in 1.0

2 ~1 in 1.05

9 ~1 in 1.0

Fish (Freshwater and Estuarine/ 

Marine) LOC = 0.05

4.5 ~1 in 418,000,000

2 ~1 in 216

9 ~1 in 1.75E+31

Aquatic Invertebrates (Freshwater and 

Estuarine/ Marine) LOC = 0.05

4.5 ~1 in 418,000,000

2 ~1 in 216

9 ~1 in 1.75E+31

V. RISK DESCRIPTION

Based on the available data and the registered use pattern for fosthiazate (i.e., drip 

irrigation to tomatoes under plastic mulch), off-site transport is not expected; therefore, 

risks to aquatic organisms are not expected based on the low potential of exposure in 

aquatic environments and the results of previous assessments. Furthermore, risks to 

terrestrial plants are not expected due to the low potential for exposure and the results of 

previous risk assessments. Risks, however, are expected for terrestrial invertebrates [both 

soil-dwelling (from direct exposure) and non-soil-dwelling (from ingestion of treated 

tomato plants)] and federally-listed birds (acute) and listed and non-listed mammals 

(chronic) from the ingestion of contaminated terrestrial invertebrates (including 

earthworms). Risks to birds (and, thus, reptiles and terrestrial-phase amphibians) and 

mammals from the ingestion of contaminated tomato plants are expected to be minimal. 

Therefore, the risk hypothesis is supported: Fosthiazate, when used in accordance with 

current labels, can result in exposure to non-target terrestrial animals. Exposure via 

direct applications (soil-dwelling invertebrates) and/or via ingestion of part(s) of the 

treated tomato plant may be above levels where adverse effects upon the survival, 

growth, and reproduction of non-target terrestrial animals (including federally-listed

threatened and endangered species) would occur (see below for the discussion on listed 

species). 

The only registered use for fosthiazate is for tomatoes under plastic mulch via drip 

irrigation. Therefore, offsite transport from spray drift, runoff, and leaching to 

groundwater are expected to be minimal. For aquatic organisms (i.e., aquatic vertebrates, 

invertebrates, and plants), no LOCs were exceeded in previous risk assessments for 

broadcast fosthiazate uses with higher application rates than assessed here. Additionally, 

because of the low potential for off-site exposure and relative insensitivity of terrestrial 
32

plants to fosthiazate, risks to terrestrial plants are not expected from the registered 

fosthiazate use on tomatoes. Therefore, although not quantitatively assessed, risks to 

aquatic organisms and terrestrial plants are not expected from the use of fosthiazate on 

tomatoes. 

For terrestrial vertebrates that may ingest tomato plants in which fosthiazate has been 

translocated, the only RQ that approaches an LOC is the dose-based acute RQ for listed, 

small birds (the RQ = 0.05). No other RQs (for vertebrates that may eat plants) approach 

or exceed any LOC. Because the EECs are expected to be conservative [due to the 

assumptions made in the modeling (e.g., using the lower end of the range of plant weight 

and a lower bound number of plants per acre)], and the fact that the LOC does not exceed 

but instead matches the LOC, actual risks to listed birds that may ingest treated tomato 

plants are not expected. 

There is, however, a potential for risk to birds (and, thus, reptiles and terrestrial-phase 

amphibians) and mammals that ingest terrestrial invertebrates contaminated with fosthiazate on 

the site of application. Based on T-REX and an EEC of 1.7 ppm for contaminated arthropods, 

the dose-based RQs for small and medium size birds exceed the acute listed species LOC [RQs = 

0.25 (20g bird) and 0.11 (100g bird)]. Additionally, the chronic, dose-based RQs for small and 

medium size mammals exceed the chronic risk LOC [RQs = 1.48 (15g mammal) and 1.26 (35g 

mammal)]. No other RQs based on the T-REX analyses exceed any LOCs. Similar results were 

found for birds and mammals that eat contaminated earthworms (acute RQs for birds ranged 

from 0.01 to 0.98; chronic RQs for mammals ranged from (0.11 to 5.71).

In addition to risks to birds, reptiles, terrestrial-phase amphibians, and mammals that eat 

terrestrial invertebrates, there are potential direct risks to terrestrial invertebrates from the use of 

fosthiazate on tomatoes. Screening-level risk assessments do not typically evaluate risks to 

terrestrial invertebrates; however, toxicity information for beneficial insects is used to develop 

precautionary label language where necessary. Based on the available toxicity data [LD50 = 

0.247 μg a.i./bee (contact)] and the systemic nature of fosthiazate, precautionary label language 

for bees is recommended for the fosthiazate labels. 

For listed terrestrial invertebrates, risks to soil-dwelling invertebrates found on the site of 

application are expected (RQ = 6.9; this RQ exceeds the interim listed species LOC for terrestrial 

invertebrates of 0.05). Additionally, although not quantifiable due to a lack of oral toxicity data 

for invertebrates, risks to listed terrestrial invertebrates that may ingest tomato plant parts in 

which fosthiazate has been translocated are expected. This is based on the contact toxicity data 

for honey bees, the systemic nature of fosthiazate and label information that states that 

fosthiazate can be used to suppress insects; it is, therefore, assumed that any insect that may feed 

on contaminated tomato plants is at risk of mortality or other adverse effect (i.e., risk is 

assumed). 
33

1. Review of Incident Data

Reviews of the Ecological Incident Information System (EIIS, version 2.1), the Avian Incident 

Monitoring System (AIMS)2, and the Incident Data System (IDS) were conducted on August 13, 

2012. There were no reported ecological incidents associated with fosthiazate. Because 

ecological incident data are not systematically collected, an absence of reported incidents should 

not be construed as the absence of incidents.

2. Assumptions and Limitations

a) As required by FIFRA and the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA 

reviews numerous studies to assess potential adverse outcomes from exposure to 

chemicals. Collectively, these studies include acute, subchronic and chronic toxicity, 

including assessments of carcinogenicity, neurotoxicity, developmental, reproductive, 

and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ 

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

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

EPA evaluates acute tests and chronic studies that assess growth, developmental and 

reproductive effects in different taxonomic groups. As part of the Preliminary Problem 

Formulation for Registration Review (DP Barcode D360360), EPA reviewed these data 

and selected the most sensitive endpoints for relevant risk assessment scenarios from the 

existing hazard database. However, as required by FFDCA section 408(p), fosthiazate is 

subject to the endocrine screening part of the Endocrine Disruptor Screening Program 

(EDSP). 

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

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

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

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

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

to identify the potential of a chemical substance to interact with the estrogen, androgen, 

or thyroid (E, A, or T) hormonal systems. Chemicals that go through Tier 1 screening 

and are found to have the potential to interact with E, A, or T hormonal systems will 

proceed to the next stage of the EDSP where EPA will determine which, if any, of the 

Tier 2 tests are necessary based on the available data. Tier 2 testing is designed to 

identify any adverse endocrine-related effects caused by the substance, and establish a 

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

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

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

of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. 

Fosthiazate is not among the group of 58 pesticide active ingredients on the initial list to 

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

future EDSP orders/data call-ins, requiring the submission of EDSP screening assays for 

 

2

http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/login.cfm?CFID=113048231&CFTOKEN=9243482
34

fosthiazate. For further information on the status of the EDSP, the policies and 

procedures, the list of 67 chemicals, future lists, the test guidelines and the Tier 1 

screening battery, please visit our website: http://www.epa.gov/endo/).

b) The primary uncertainties for this risk assessment are related to the fosthiazate use 

pattern (i.e., application via drip irrigation to tomatoes under plastic mulch) and the 

systemic nature of the chemical. Because limited off-site exposure is expected from this 

use pattern, the focus of concern for risks is on the site of application. The primary 

routes of exposure to non-target organisms is expected to be via direct application (to 

soil-dwelling invertebrates), ingestion of contaminated soil-dwelling invertebrates (by 

terrestrial invertebrates), and ingestion of tomato plant parts in which fosthiazate has 

been translocated (by terrestrial vertebrates and invertebrates). There are currently no 

standard methods for assessing exposure or risk to soil-dwelling invertebrates (or things 

that might eat them) or exposure or risk from systemic pesticides. Therefore, attempts 

were made to conservatively quantify risk whenever possible; however, there is 

uncertainty regarding the non-standard methods used. The assumptions made to model 

exposures were largely based on label information (e.g., the amount of water used to 

water in fosthiazate) and data from the open literature (e.g., the amount of chemical that 

is translocated through the treated plants and the weight of tomato plants). Changes in 

any of these assumptions have the potential to alter the risk conclusions. Additionally, 

there is a potential for some organisms (e.g., amphibians) to be attracted to the use sites –

i.e., the dark, moist areas under the plastic mulch. The potential preferential use of such 

sites is beyond the scope of this assessment

Because most of the RQs calculated for birds and mammals are close to the LOCs for 

acute or chronic exposure, some additional modeling was done to see how different use 

assumptions would impact the RQs for birds and mammals that may eat contaminated 

terrestrial invertebrates. The RQs in this assessment, using T-REX, are based on a 

maximum application rate (1.5 lb a.i./acre) and the minimum recommended amount of 

irrigation water (0.5 inch of water per acre), since this results in the highest concentration 

of fosthiazate in irrigation water. However, the concentration of fosthiazate in irrigation 

water could be reduced by increasing the amount of water used per acre (the label states 

0.5 to 1.0 inches of irrigation water per acre should be used) and/or by reducing the 

application rate. 

For birds, using T-REX, the concentration of fosthiazate in irrigation water would need to 

be ≤5.16 ppm for none of the RQs for birds that eat insects to exceed an Agency LOC [a 

concentration of 5.16 ppm in irrigation water would result in an arthropod concentration 

of 0.66 ppm; i.e., 5.16 ppm x 0.128 (the weight of a surrogate honey bee)]. Therefore, 

any increase in the amount of irrigation water used and/or a decrease in the application 

rate that would result in concentrations of fosthiazate ≤5.16 ppm would lead to no LOC 

exceedances for birds using T-REX. The concentration of fosthiazate in irrigation water 

was calculated for various amounts of irrigation water used and application rates (see 

Table 10). Based on this analysis, if the application rate was reduced to 1.0 lb a.i./acre

and was applied using 1 inch of irrigation water/acre, no bird LOCs would be exceeded 

using T-REX. If 0.5 inches of irrigation water were used per acre, the application rate 
35

would need to be reduced to ~0.5 lb a.i./acre for no bird LOCs to be exceeded using TREX.

Table 10. Estimated Concentratoins (in ppm) of Fosthiazate in Irrigation Water 

Based on Various Amounts of Water Used and Application Rates. 

AMOUNT OF 

IRRIGATION 

WATER/ACRE 

(in inches)

APPLICATION RATE/ACRE

0.5 lb

(226,796 mg)

0.75 lb

(340,194 mg)

1.0 lb

(453,592 mg)

1.25 lb

(566,991 mg)

1.5 lb

(680,389 mg)

0.5 (51,395 L) 4.41 6.62 8.83 11.03 13.24

0.75 (77,093 L) 2.94 4.4 5.88 7.35 8.83

1.0 (102,790 L) 2.21 3.31 4.41 5.52 6.62

For mammals, using T-REX, the concentration of fosthiazate in irrigation water would 

need to be ≤8.83 ppm for none of the RQs for mammals that eat insects to exceed an 

Agency LOC [a concentration of 8.83 ppm in irrigation water would result in an 

arthropod concentration of 1.13 ppm; i.e., 8.83 ppm x 0.128 (the weight of a surrogate 

honey bee)]. At an application rate of 1.5 lb a.i./acre, no mammal LOCs would be 

exceeded using T-REX if ≥0.75 inches of irrigation water were used per acre (see Table 

10). If 0.5 inches of irrigation water were used per acre, the application rate would need 

to be reduced to 1.0 lb a.i./acre for no mammal LOCs to be exceeded using T-REX.

For birds and mammals that may eat contaminated earthworms specifically, there were 

some LOC exceedances at the maximum fosthiazate application rate (1.5 lb a.i./acre) 

using the Earthworm Fugacity model (see Table 7). The RQs calculated using the 

Earthworm Fugacity model have a linear relationship with the application rate. 

Therefore, to determine an application rate that would result in an RQ that no longer 

exceeds an LOC, the RQ is divided by the LOC; the application rate can then be divided 

by that number to estimate the application rate that no longer exceeds an LOC (i.e., 

RQ/LOC = x; 1.5 lb a.i./acre ÷ x = the application rate that no longer exceeds the LOC). 

The results of the fugacity model were bound by different KOC and soil depths. Using a 

KOC of 285 and a soil depth of 10 cm resulted in an acute RQ for birds of 0.20. 

Therefore, using this KOC and soil depth, the application rate would need to be ≤0.75 lb 

a.i./acre for the RQ not to exceed the listed species LOC for birds [0.20 (RQ)/0.10 (LOC)

= 2; 1.5 lb a./acre ÷ 2 = 0.75 lb a.i./acre]. With a KOC of 25 and a soil depth of 1 cm, the 

application rate would need to be ≤0.15 lb a.i./acre for the RQ not to exceed the listed 

species LOC for birds using the Earthworm Fugacity model [0.98 (RQ)/0.10 (LOC) = 

9.8; 1.5 lb a.i./acre ÷ 9.8 = 0.15 lb a.i./acre].

For mammals and a KOC of 285 and a soil depth of 10 cm, the application rate would need to be 

≤1.3 lb a.i./acre for the RQ to not exceed the chronic LOC for mammals using the Earthworm 

Fugacity model [1.16 (RQ)/1 (LOC) = 1.16; 1.5 lb a.i./acre ÷ 1.16 = 0.15 lb a.i./acre]. With a 

KOC of 25 and a soil depth of 1 cm, the application rate would need to be ≤0.26 lb a.i./acre for the 

RQ not to exceed the listed species LOC for mammals [5.71 (RQ)/1 (LOC) = 5.71; 1.5 lb 

a.i./acre ÷ 5.71 = 0.26 lb a.i./acre].
36

c) Birds are used as surrogate species for reptiles and terrestrial-phase amphibians. 

Terrestrial-phase amphibians and reptiles are poikilotherms (their body temperature 

varies with environmental temperature). Birds are homeotherms (their temperature is 

regulated, constant, and largely independent of environmental temperatures). As a 

consequence, the caloric requirements of terrestrial-phase amphibians and reptiles are 

markedly lower than birds. Therefore, on a daily dietary intake basis, birds consume 

more food than terrestrial-phase amphibians and reptiles. 

The T-HERPS model is used to allow for further characterization of dietary exposures of 

terrestrial-phase amphibians and reptiles relative to birds (T-HERPS is available at: 

http://www.epa.gov/oppefed1/models/terrestrial/index.htm). To quantify the potential 

risk for listed terrestrial-phase amphibians and reptiles that may eat contaminated 

terrestrial invertebrates, food intake equations for the iguanid lizard in T-HERPS are used 

to replace the food intake equation in T-REX for birds. Unlike T-REX, T-HERPS has 

not been updated to include estimated residues on arthropods as a single dietary item; 

instead T-HERPS includes ‘small insect’ and ‘large insect’ dietary categories. For the 

purposes of this analysis, since the estimated residues on terrestrial invertebrate food 

items are based on the concentration of fosthiazate in the irrigation water used during 

application (instead of estimated residues based on a foliar application), input parameters 

that resulted in residues of 1.7 ppm on ‘small insects’ (i.e., 0.0126 lb a.i./acre application 

rate; one application; 35-day default foliar half-life; Upper Bound Kenaga values) were 

used for calculating RQs.

Based on this analysis, none of the RQs for amphibians or reptiles that eat terrestrial 

invertebrates exceed an Agency LOC (acute RQs range from <0.01 to 0.02; the chronic 

RQ is 0.08). This indicates a low potential for risk to insectivorous terrestrial-phase 

amphibians or reptiles from the use of fosthiazate on tomatoes. Currently, the Earthworm 

Fugacity model does not calculate RQs for terrestrial-phase amphibians or reptiles that 

eat contaminated earthworms. Therefore, the potential risk to terrestrial-phase 

amphibians or reptiles that specifically eat earthworms is uncertain.

d) There are no toxicity data for fosthiazate available from a fish life-cycle study. 

Additionally, data are only available for one of the four species of aquatic non-vascular 

plants typically tested. However, data from such studies would not be expected to alter 

the risk conclusions for aquatic organisms from fosthiazate use on tomatoes using drip 

irrigation due to the limited potential for off-site exposure. 

e) Based on its mode of action and target pests, the risks to terrestrial invertebrates are more 

certain than the potential risks to terrestrial vertebrates that consume contaminated 

arthropods and/or plants. However, based on the available information, there is a 

potential risk to terrestrial invertebrates; listed and non-listed birds (acute) listed and 

non-listed mammals (chronic) that eat arthropods (including earthworms); and terrestrialphase amphibians and reptiles that specifically eat earthworms.
37

APPENDIX A. REFERENCES

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U.S. EPA. 2008a. Moore, K. and Flaherty, C. Memorandum: Section 3 registration for new use 

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Fate and Effects Division, Office of Pesticide Programs. Washington, DC.

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Environmental Fate and Effects Division, Office of Pesticide Programs. Washington, 

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39

APPENDIX B. BIBLIOGRAPHY

MRIDs – Ecotoxicity:

43916819 Turck, P.; Shults, S.; Laveglia, J. (1992) Acute Oral Toxicity (LD50) Study in Bobwhite 

Quail with IKI-1145: Lab Project Number: 3917-91-0240-TX-003: 272-105: 91-0240. 

Unpublished study prepared by Ricerca, Inc. and Wildlife International Ltd. 119 p. 

41381106 Cameron, D. ; Norman, A. (1989) The Dietary Toxicity (LC50) of IKI- 1145 Technical to the 

Bobwhite Quail: Lab Project Number: ISK 34/891274. Unpublished study prepared by 

Huntingdon Research Centre Ltd. 43 p. 

43916821 Turck, P.; Shults, S.; Laveglia, J. (1992) Dietary (LC50) Study in Bobwhite Quail with IKI1145: Lab Project Number: 3917-91-0242-TX-003: 272-107: 91-0242. Unpublished study 

prepared by Ricerca, Inc. and Wildlife International Ltd. 127 p. 

43916824 Turck, P.; Laveglia, J. (1993) Reproduction Study in Bobwhite Quail with IKI-1145: (Final 

Report): Lab Project Number: 3922-91-0259-TX-003: 272-111: 91-0259. Unpublished study 

prepared by Ricerca, Inc. and Wildlife International Ltd. 190 p. 

43916825 Turck, P.; Laveglia, J. (1993) Reproduction Study in Mallard Ducks with IKI-1145: (Final 

Report): Lab Project Number: 3922-91-0258-TX-003: 272-112: 91-0258. Unpublished study 

prepared by Ricerca, Inc. and Wildlife International Ltd. 192 p. 

43916826 Jenkins, C. (1991) IKI-1145 Technical: Acute Toxicity to Rainbow Trout: (Final Report): Lab 

Project Number: 91/ISK177/0015: ISK/177: 91-0015. Unpublished study prepared by Life 

Science Research Ltd. 26 p. 

43916828 Jenkins, C. (1991) IKI-1145 Technical: Acute Toxicity to Daphnia magna: (Final Report): 

Lab Project Number: 91/ISK179/0017: ISK/179: 91/0017. Unpublished study prepared by 

Life Science Research Ltd. 27 p. 

45540401 Boeri, R.; Ward, T. (2001) Technical IKI-1145: Flow-Through Mollusc Shell Deposition 

Test: Lab Project Number: 2118-SK. Unpublished study prepared by T.R. Wilbury 

Laboratories, Inc. 29 p. {OPPTS 850.1025} 

45540402 Boeri, R.; Ward, T. (2001) Technical IKI-1145: Acute Toxicity to the Mysid, Americamysis 

bahia: Lab Project Number: 2117-SK. Unpublished study prepared by T.R. Wilbury 

Laboratories, Inc. 29 p. {OPPTS 850.1035} 

45540403 Boeri, R.; Ward, T. (2001) Technical IKI-1145: Acute Toxicity to the Sheepshead Minnow, 

Cyprinodon variegatus: Lab Project Number: 2119-SK. Unpublished study prepared by T.R. 

Wilbury Laboratories, Inc. 26 p. {OPPTS 850.1075} 

43916829 Bogers, M. (1994) Daphnia magna Reproduction Test with IKI-1145 Technical: Lab Project 

Number: 123468. Unpublished study prepared by NOTOX B.V. 33 p. 

45540404 Boeri, R.; Ward, T. (2001) Technical IKI-1145: Early Life Stage Toxicity to the Fathead 

minnow, Pimephales promelas: Lab Project Number: 2116-SK. Unpublished study prepared 

by T.R. Wilbury Laboratories, Inc. 51 p. {OPPTS 850.1400} 

41347622 Cummins, H. (1989) Acute Oral Toxicity Study in the Rat: IKI-1145 Technical: Lab Project 

Number: 89/ISK093/0846. Unpublished study prepared by Life Science Research Limited. 54 

p. 
40

41381113 McAnulty, P. (1989) IKI-1145: Reproductive Performance Study in Rats Treated 

Continuously through Two Successive Generations: Volume 1: Lab Project Number: 

89/ISK109/0923. Unpublished study prepared by Life Science Research Ltd. 791 p. 

44414501 Lucas, F. (1997) A Rebuttal to an EPA Review of the Study Entitled IKI-1145: Reproductive 

Performance Study in Rats Treated Continuously Through Two Successive Generations: Lab 

Project Number: 97-0148: 7081-97-0148-TX-001. Unpublished study prepared by Ricerca, 

Inc. 10 p. 

43916839 Crosby, K. (1995) Effect of IKI 1145 on Seed Germination/Seedling Emergence (Tier II): Lab 

Project Number: 6362-95-0017-BE-001: 95-0017: 6362-95-0017-BE-000. Unpublished study 

prepared by Ricerca, Inc. 166 p. 

43916840 Crosby, K. (1995) Effect of IKI 1145 on Vegetative Vigor of Plants (Tier II): Lab Project 

Number: 6362-95-0018-BE-001: 95-0018: 6362-95-0018-BE-000. Unpublished study 

prepared by Ricerca, Inc. 122 p. 

41347636 Hoxter, K. (1989) An Acute Contact Toxicity Study with the Honey Bee: IKI-1145 Technical: 

Lab Project Number: 272-101B. Unpub- lished study prepared by Wildlife International Ltd. 

16 p. 

MRIDs – Environmental Fate:

47223201 Shimura, T. (2007) Product Chemistry Studies for Fosthiazate 75%EC. Project 

Number: 1145FI/0706101, 92944653. Unpublished study prepared by Ishihara 

Sangyo Kaisha, Ltd. 43 p.

47223201 Shimura, T. (2007) Product Chemistry Studies for Fosthiazate 75%EC. Project 

Number: 1145FI/0706101, 92944653. Unpublished study prepared by Ishihara 

Sangyo Kaisha, Ltd. 43 p.

47223201 Shimura, T. (2007) Product Chemistry Studies for Fosthiazate 75%EC. Project 

Number: 1145FI/0706101, 92944653. Unpublished study prepared by Ishihara 

Sangyo Kaisha, Ltd. 43 p.

41347637 Kato, Y. (1987) IKI-1145: Hydrolysis in Buffer Solutions at PH 5, 7, and 9: Lab 

Project Number: I-221. Unpublished study prepared by Ishihara Sangyo Kaisha Ltd. 

34 p. 

43916831 Huhtanen, K.; Lentz, N. (1993) A Photolysis Study of Fosthiazate (IKI-1145) in 

Water at pH 5: Lab Project Number: 5287-92-0153-EF-001: 92-0153: 5287-92-

0153-EF-000. Unpublished study prepared by Ricerca, Inc. 106 p. 

43916832 Walsh, K.; Huhtanen, K. (1995) An Aerobic Soil Metabolism Study with IKI-1145 

(Fosthiazate): Lab Project Number: 3378-89-0384-EF-001-001: 89-0384. 

Unpublished study prepared by Ricerca, Inc. 293 p. 

43916833 Hatzenbeler, C. (1995) An Anaerobic Aquatic Soil Metabolism Study with ((carbon 

14)-T)-IKI-1145 and ((carbon 14)-B)-IKI-1145: Lab Project Number: 5163-92-

0023-EF-001: 92-0023: IKI-1145. Unpublished study prepared by Ricerca, Inc. 123 

p. 
41

47098903 Hatzenbeler, C. (1996) [14-Carbon-B]IKI-1145: Degradation and Fate in 

Water/Sediment System. Project Number: 6214/94/0186/EF/001. Unpublished 

study prepared by Ricerca, Inc. 120 p.

41347639 Kato, Y. (1988) IKI-1145: Adsorption and Desorption in Soils: Lab Project 

Number: I-231. Unpublished study prepared by Ishihara Sangyo Kaisha Ltd. 33 p. 

41347640 Arita, H. (1989) IKI-1145: Mobility of Parent Compound and Its De- gradation 

Products in Soil Columns: Lab Project Number: I-228. Unpublished study prepared 

by Ishihara Sangyo Kaisha Ltd. 43 p. 

43916835 Jablonski, J. (1995) Terrestrial Field Dissipation of Fosthiazate Applied to 

Bareground Near Camilla, Georgia (Bridging Report: Effect of Formic Acid on 

Extraction of Residues): Lab Project Number: 5288-92-0159-CR-005: 92-0159: 

ISK-1992-501-03. Unpublished study prepared by Ricerca, Inc. 218 p.

43952901 Jablonski, J. (1995) Terrestrial Dissipation of Fosthiazate Applied to Bareground 

Near Ridgefield, Washington: Lab Project Number: 92-0159: 5288-92-0159-CR001: ISK-1992-501-00. Unpublished study prepared by Ricerca, Inc. 365 p. 

43952902 Jablonski, J.; McFall, D. (1995) Terrestrial Dissipation of Fosthiazate Applied to 

Bareground Near Madera, California: Lab Project Number: ISK-1992-501-01: ISK1992-501-00: 92119. Unpublished study prepared by Ricerca, Inc. 371 p. 

43952903 Jablonski, J. (1995) Terrestrial Dissipation of Fosthiazate Applied to Bareground 

Near Camilla, Georgia: Lab Project Number: 92-0159: ISK-1992-501-03: ISK1992-501-00. Unpublished study prepared by Ricerca, Inc. 507 p. 

43952904 Jablonski, J. (1995) Terrestrial Dissipation of Fosthiazate Applied to Bareground in 

Lucama, North Carolina: Lab Project Number: 92-0159: 5288-92-0159-CR-004: 

5288-92-0159-CR-000. Unpublished study prepared by Ricerca, Inc. 407 p. 

41347642 Fackler, P. (1989) IKI-1145: Bioconcentration and Elimination of ?Carbon 14|-

residues by Bluegill (Lepomis macrochirus): Lab Pro- ject Number: 89-11-3157. 

Unpublished study prepared by Spring- born Laboratories, Inc. 38 p. 

47223201 Shimura, T. (2007) Product Chemistry Studies for Fosthiazate 75%EC. Project 

Number: 1145FI/0706101, 92944653. Unpublished study prepared by Ishihara 

Sangyo Kaisha, Ltd. 43 p.

43916800 ISK Biosciences Corp. (1996) Submission of Product Chemistry, Toxicology, 

Residue, Hazard to Non-Target Organisms, and Environmental Fate Data in 

Support of the Application for Registration of Fosthiazate Technical. Transmittal of 

41 Studies. 

47098902 Doran, T. (2007) Environmental Fate Assessment for Fosthiazate: 

GroundWater/Drinking Water Modeling Estimates. Project Number: 06/001/ISK. 

Unpublished study prepared by North Coast Regsci, LLC. 28 p.
42

APPENDIX C. Sample Inputs and Outputs for the Earthworm Fugacity Model

Use of fugacity approach to estimate exposures to small mammals consuming earthworms 

contaminated with pesticides.

The T-REX model (USEPA, 2008) is useful for assessing exposures of terrestrial animals to 

pesticide residues on foliar surfaces of crops and seeds. The model cannot be used to assess 

pesticide exposures to terrestrial animals resulting from consumption of earthworms 

contaminated with pesticide mass present in the soil of the application site. In order to explore 

the potential exposures of mammals and birds to pesticides in the soil and earthworms on the 

treatment site, a simple fugacity approach can be employed to estimate concentrations of the 

pesticide of interest earthworms. 

Fugacity is most often regarded as the "escaping tendency" of a chemical from a particular 

phase. Fugacity (F) has units of pressure, generally pascals (Pa), and can be related to phase 

concentrations. For any particular environmental phase (e.g., water, soil, air, or biota) there is a 

corresponding "fugacity capacity" with units of mol/m3-Pa and is denoted by Z. The relationship 

between fugacity, fugacity capacity and chemical concentration (C) is defined by Equation 1.

Fugacity capacities for a given chemical are calculated for the phases of interest as part of the 

exposure point estimation methodology (Mackay and Paterson 1981). The following 

calculations of fugacity capacities for soil (ZS) and earthworms (ZE) (Equations 2 and 3, 

respectively) require several chemical-specific parameters and assumptions of system 

temperature (25oC) and steady state equilibrium. Parameter values relevant to Equations 2 and 3 

are defined in Table 1.

Fugacity capacities for a given chemical are calculated for the phases of interest as part of the 

exposure point concentration estimation methodology. By definition, the ratio between Z values 

of different phases (compartments) equals the partitioning coefficient (e.g., Equation 4).

In this approach, it is assumed that a pesticide partitions between the soil, the (pore) water and 

the air contained within the soil of the treatment site. It is assumed that earthworms dwelling 

within the soil are exposed to a pesticide via ingestion of contaminated soil. The concentration 

Equation 1. C Z *F

H

K

Equation Z

d S

S

*

2.

H

L K

Equation Z

O W

E

*

3.

OW

water

oc ol K

Z

Z

Equation tan 4.
43

of a pesticide in earthworm tissues can be calculated according to Equation 5 (see Table 1 for 

parameter definitions). 

Table 1. Summary of parameters relevant to earthworm fugacity model.

Symbol Definition Units

CE Chemical concentration in earthworm tissue mol/m3

CE' Chemical concentration in earthworm tissue g/kg

CS Chemical concentration in soil mol/m3

H Henry’s Law constant m

3

-Pa/mol

Kd Soil partitioning coefficient cm3/g

KOW Octanol to water partition coefficient none

L Lipid fraction of earthworm none

MW molecular weight of chemical g/mol

ZE Fugacity capacity of pesticide in earthworms mol/m3-Pa

ZS Fugacity capacity of pesticide in soil mol/m3-Pa

ρE density of earthworm kg/m3

ρS Bulk density of soil g/cm3

Equation 5 can be redefined using equations 2 and 3 as follows in Equation 6. Equation 6 is used 

to calculate the concentration of a pesticide in earthworms inhabiting the soil of treatment sites.

CS is intended to be representative of the steady-state concentrations of the pesticide of interest in 

soil. This value is calculated using PRZM. Kd and Kow are chemical-specific parameters. Kd 

should be consistent with the value input into PRZM. ρS is dependant upon the soil properties of 

the selected PRZM scenario used to derive CS. L is based on the lipid content of earthworms, 

which was assumed to be 0.01 (Cobb et al. 1995). The resulting CE value is in units of mol/m3. 

This value is converted to units of g/kg using equation 7. The density of the earthworm (ρE) is 

assumed to be 1000 kg/m3 (equivalent to density of water). 

d s

S ow

E

K

C L K

Equation C

*

* *

6.

E

E

E

C MW

Equation C

*

7.

'

S

E

E S

Z

Z

Equation5. C C *
44

MODEL INPUTS AND OUTPUTS:

Characteristics of Fosthiazate.

Parameter (symbol) Value Units

Pesticide Name Fosthiazate none

Molecular weight (MW) 283.36 g/mol

Octanol-water Partition Coefficient (Kow) 194 none

Soil partition coefficient (Kd) 1.789 cm3

/g

Soil parameters.

Parameter (symbol) Value Units

Bulk density of soil (ρs)* 1.30 g/cm3

Concentration of pesticide in soil (estimated using PRZM) 6.3 g/m3

Concentration of Fosthiazate in soil (Cs) 2.22E-02 mol/m3

Earthworm parameters.

Parameter (symbol) Value Units

Lipid fraction of earthworm (L) 0.01 none

Water fraction of earthworm (W) 0.84 none

Density of earthworm (ρE) 1000 kg/m3

Concentration of Fosthiazate in earthworm (CE) 1.86E-02 mol/m3

Concentration of Fosthiazate in earthworm (CE') 0.005 g/kg*

*equivalent to mg/g

Mammalian toxicity data for Fosthiazate.

Endpoint/Parameter (symbol) Value Units

Acute oral LD50 51 mg/kg-bw

Body weight of acute test animal* (TW) 350 g

Chronic NOAEL 0.5 mg/kg-bw

Chronic NOAEC 10 mg/kg-diet

Body weight of chronic test animal* (TW) 350 g

Body weight of assessed animal (AW) 15 g

Food intake of assessed animal (F) 17.9 g/day

Body weight normalized food intake of assessed animal 

(FN)

1192 g/kg-bw-day

*For rats, the default body weight is 350 g, if no other data are available.

Avian toxicity data for Fosthiazate.

Endpoint/Parameter (symbol) Value Units

Acute oral LD50 10.6 mg/kg-bw

Body weight of test animal for LD50* (TW) 178 g

Subacute dietary LC50 85 mg/kg-diet

Chronic NOAEC 21.7 mg/kg-diet

Mineau Scaling Factor** 1.15 none

Body weight of assessed animal (AW) 20 g

Food intake of assessed animal (F) 28.47 g/day

Body weight normalized food intake of assessed animal 

(FN)

1424 g/kg-bw-day
45

*Unless study specific data are available: For bobwhite quail, assume 178 g. For mallard duck, 

assume 1580 g.

**Default value is 1.15. Consult Mineau et al. (1996) to obtain pesticide specific values.

Mammalian and avian risk quotients for Fosthiazate.

Endpoint EEC Toxicity Value RQ

Mammalian, acute dose-based 6.28 112.1 0.06

Mammalian, chronic dose-based 6.28 1.1 5.71

Mammalian, chronic dietary-based 5.27 10.0 0.53

Avian, acute, dose-based 7.50 7.6 0.98

Avian, acute, dietary-based 5.27 85.0 0.06

Avian, chronic, dietary-based 5.27 21.7 0.24

References:

Cobb, G.P., E.H. Hol, P.W. Allen, J.A Gagne, R.J. Kendall. 1995. Uptake, metabolism, and 

toxicity of terbufos in the earthworm (Lumbricus terrestris) exposed to COUNTER-15G 

in artificial soils. Environ. Toxicol. Chem. 14(2):279-285.

Mackay, D. and S. Paterson. 1981. Calculating fugacity. Environ. Sci. Technol. 15: 1006-

1014.

U.S. EPA. 2008. User’s Guide: T-REX Version 1.4.1 (Terrestrial Residue Exposure model). 

United States Environmental Protection Agency. Environmental Fate and Effects 

Division. http://www.epa.gov/oppefed1/models/terrestrial/index.htm#trex
APPENDIX D: ECOTOX Run

Open literature studies identified using EPA’s ECOTOXicology database (ECOTOX) (USEPA, 

2007c), which employs a literature search engine for locating chemical toxicity data for aquatic 

life, terrestrial plants, and wildlife.

Papers that Were Accepted for ECOTOX

Buhler, W. G., Brust, G. E., & Foster, R. E. Control of Striped Cucumber Beetle on Cantaloupe in Vincennes, IN, 

1993. Arthropod Manag.Tests 19, 77-78 (28E). 1994. SOIL,ENV. 

Notes: EcoReference No.: 105074

Chemical of Concern: FTZ,CBF,DZ,ES,IMC,CBL,PMR,EFV,BFT

Grove, I. G., Woods, S. R., & Haydock, P. P. J. Toxicity of 1,3-Dichloropropene and Fosthiazate to Wireworms 

(Agriotes spp.). Ann.Appl.Biol. 137[1], 1-6. 2000. SOIL,ENV. 

Notes: EcoReference No.: 93662

Chemical of Concern: EP,FTZ,13DPE

Lin, K., Zhang, F., Zhou, S., Liu, W., Gan, J., & Pan, Z. Stereoisomeric Separation and Toxicity of the Nematicide 

Fosthiazate. Environ.Toxicol.Chem. 26[11], 2339-2344. 2007. WATER,AQUA. 

Notes: EcoReference No.: 105106

Chemical of Concern: FTZ

Power, K. T., Shetlar, D. J., Niemczyk, H. D., & Belcher, M. G. Control of Billbug Larvae and a Subsequent White 

Grub Population on a Lawn Area in Wayne County, Ohio, 1993. Arthropod Manag.Tests 19, 324 (55G). 

1994. ENV,SOIL. 

Notes: EcoReference No.: 104171

Chemical of Concern: FTZ,IMC

Semtner, P. J. & Wilkinson, W. B. Cutworm and Flea Beetle Control on Flue-Cured Tobacco, 1994. Arthropod 

Manag.Tests 20, 257-258 (135F). 1995. SOIL,ENV. 

Notes: EcoReference No.: 104170

Chemical of Concern: FTZ,CPY,ACP

Target Papers 

Giannakou, I. O., Karpouzas, D. G., Anastasiades, I., Tsiropoulos, N. G., & Georgiadou, A. Factors Affecting the 

Efficacy of Non-Fumigant Nematicides for Controlling Root-Knot Nematodes. Pest Manag.Sci. 61[10], 

961-972. 2005. SOIL,TOP,ENV. 

Notes: EcoReference No.: 86817

Chemical of Concern: OML,FTZ,FMP,CDF

McKenzie, C. L., Cartwright, B., Damicone, J., & Jackson, K. Evaluation of Soil Insecticides for Early Season 

Control of Thrips on Peanuts, 1993. Arthropod Manag.Tests 19, 104-105 (62E). 1994. SOIL,ENV. 

Notes: EcoReference No.: 104176

Chemical of Concern: FTZ,ADC,FMP

Rich, J. R., Dunn, R. A., Thomas, W. D., Breman, J. W., & Tervola, R. S. Evaluation of Fosthiazate for 

Management of Meloidogyne javanica in Florida Flue-Cured Tobacco. J.Nematol. 26[4 Suppl.], 701-704. 

1994. SOIL,ENV. 

Notes: EcoReference No.: 93865

Chemical of Concern: FTZ,FMP,13DPE
47

Papers Not Acceptable for ECOTOX

Gilreath, J. P., Jones, J. P., Santos, B. M., & Overman, A. J. Soil Fumigant Evaluations for Soilborne Pest and 

Cyperus rotundus Control in Fresh Market Tomato. Crop Prot. 23[10], 889-893. 2004. 

SOIL,ENV,MIXTURE. 

Notes: EcoReference No.: 77512

Chemical of Concern: MTAS,DZM,CLP,FTZ,PEB,MB,CLPM