### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

OFFICE OF
CHEMICAL SAFETY AND
POLLUTION PREVENTION



### PC Code: 074801

DP Barcode: D424574

Date: September 3
, 2015

MEMORANDUM

SUBJECT: Transmittal of the Preliminary Environmental Fate and Ecological Risk Assessment for the Registration Review of the Organophosphate Tribufos

TO: Marianne Mannix, Chemical Review Manager Tracy Perry, Team Leader Kelly Sherman , Branch Chief Risk Management and Implementation Branch III
Pesticide Re

- Evaluation Division ( 7508P )

FROM: Katrina White

, Ph.D., Risk Assessment Process Leader Cheryl Sutton, Ph.D.

, Environmental Scientist
Environmental Risk Branch IV
Environmental Fate and Effects Division ( 7507P )

REVIEWED
BY: Thomas M. Steeger, Ph.D., Senior Science Advisor James Carleton, Ph.D., Senior Fate Scientist
Environmental Risk Branch IV Environmental Fate and Effects Division (7507P)

THROUGH: Jean Holmes

, D.V.M., M.P.H., Bran ch Chief
Environmental Risk Branch IV
Environmental Fate and Effects Division ( 7507P )

This memorandum transmits the preliminary ecological risk assessment for the registration
review of tribufos (S,S,S

- tributyl phosphorotrithioate; CAS No.: 78

- 48

- 8; PC C ode 074801). After reviewing the most recent environmental fate and effects data for tribufos, the assessment concludes that registered uses of the defoliant tribufos may result in risks to both federally threatened and endangered (listed) and non

- listed species of wildlife and aquatic vertebrates and
invertebrates.- Page 2 of 116

- 

# Environmental Fate and Ecological Risk Assessment for the Registration Review of Tribufos

Tribufos ( S,S,S

- tributyl phosphorotrithioate ) CAS Registry Number 74

- 48

- 8
PC Code 074801

Prepared b y : Katrina White, Ph.D.

, Biologist Cheryl Sutton, Ph.D.

, Environmental Scientist U.S. Environmental Protection Agency

Office of Pesticide Programs
Environmental Fate and Effects Division (EFED)
Environmental Risk Branch IV 1200 Pennsylvania Ave., NW
Mail Code 7507P Washington, DC 20460 

### Reviewed by: Thomas Steeger, Ph.D., Senior Science Advisor James Carleton, Ph.D., Senior Fate Scientist Jean Holmes, D.V.M., M.P.H., Branch Chief



### September 3
, 201 5- Page 3 of 116

- 

## Table of Contents

1. Executive Summary

................................ ................................ ................................ .............. 5
2. Problem Formulation

................................ ................................ ................................ ......... 10

2.1. Nature of Regulatory Action

................................ ................................ ................................ .................. 10
2.2. Stressor Source and Distribution

................................ ................................ ................................ .......... 11
2.2.1. Nature of the Stressor

................................ ................................ ................................ ........................ 11
2.2.3. Overview of Pesticide Use

................................ ................................ ................................ ................ 11
2.3. Receptors

................................ ................................ ................................ ................................ ................. 12
2.3.1. Aquatic and Terrestrial Effects

................................ ................................ ................................ .......... 12
2.3.2. Ecosystems Potentially at Risk

................................ ................................ ................................ .......... 12
2.4. Assessment Endpoints

................................ ................................ ................................ ............................ 12
2. 5. Conceptual Model

................................ ................................ ................................ ................................ ... 13
2.5.1. Risk Hypotheses

................................ ................................ ................................ ................................ 14
2.5.2. Conceptual Pathways Table

................................ ................................ ................................ .............. 14 2.6. Analysis Plan

................................ ................................ ................................ ................................ ........... 15
2. 6.1. Residues of Concern

................................ ................................ ................................ .......................... 15
2.6.2. Preliminary Identification of Data Gaps and Uncertainties

................................ ............................... 16
2.6.4. Measures of Exposure

................................ ................................ ................................ ....................... 16
2.6.5. Measures of Effect

................................ ................................ ................................ ............................. 18
2.6.6. Integration of Exposure and Effects

................................ ................................ ................................ .. 20 

### 3. Analysis

................................ ................................ ................................ ............................. 21

3.1. Use Characterization

................................ ................................ ................................ .............................. 21
3. 2. Exposure Characterization

................................ ................................ ................................ .................... 22
3.2.1. Environmental Fate and Transport Characterization

................................ ................................ ......... 22
3.2.2. Measures of Aquatic Exposure

................................ ................................ ................................ .......... 27
3.2.3. Measures of Terrestrial Exposure

................................ ................................ ................................ ...... 30
3.3. Ecological Effects Characterization

................................ ................................ ................................ ...... 37 

### 4. Risk Characterization

................................ ................................ ................................ ......... 46
4.1. Risk Quotient (RQ) Values

................................ ................................ ................................ .......................... 46
4.2. Incident Database Review

................................ ................................ ................................ ............................ 54 4.3. Risk Description

................................ ................................ ................................ ................................ ............ 55
4.3.1 Risk to Aquatic Organisms

................................ ................................ ................................ ................ 56
4.3.2. Risk to Terrestrial Organisms

................................ ................................ ................................ ............ 59

Non

- target terrestrial plants

................................ ................................ ................................ .............................. 63
4.4. Uncertainties and Data Gaps

................................ ................................ ................................ ................. 64
4.4.1. Fate and Transport

................................ ................................ ................................ ............................. 64
4.4.2. Effects

................................ ................................ ................................ ................................ ................ 65 

### 5. Endocrine Disruptor Screening Program (EDSP)

................................ ........................... 66
6. Federally Threatened and Endangered (Listed) Species Concerns

............................... 66

7. Conclusions

................................ ................................ ................................ .......................... 67
8. References

................................ ................................ ................................ ............................ 69 8.1 Submitted Product Chemistry and Environmental Fate Studies

................................ ............................. 72 8.2. Submitted Ecotoxicity Studies (Retrieved from OPPIN April 2015)

................................ ....................... 72- Page 4 of 116

- 

## Appendices Appendix A. Selected SWCC Output Files

................................ ................................ ................. 85 Appendix B. Toxicity Categories and Levels of Concern

................................ .......................... 92 Appendix C. Summary of Ecological Toxicity Data

................................ ................................ ... 93 Appendix D. Example T

- REX (v. 1.5.2) Input and Output for Tribufos

................................ .. 100 Appendix E. STIR Results

................................ ................................ ................................ ......... 102 Appendix F. Screening Imbibition Program (SIP) Version 1.0 Inputs and Results

.................. 103 Appendix G. A cce p t ed E C O T O X D a t a Ta b l e (2008 to 2015 Refresh Report)

......................... 104 Appendix H. Ecosar Analysis for Parent and Degradate

................................ ........................... 107 Appendix I. Example KABAM Inputs and Outputs

................................ ................................ .. 111 Appendix J. Aquatic Plant Toxicity Endpoints In the EFED ECOTOX Database

................... 115- Page 5 of 116

- 

### 1. Executive Summary

The Environmental Fate and Effects Division ( EFED ) has completed the preliminary ecological
risk assessment for the Registration Review of tribufos (S,S,S

- tributyl phosphorotrithioate; CAS
No.: 78

- 48

- 8; PC code 074801) and its end

- use product s . The potential for direct effects to federally threatened and endangered (listed) and non

- listed organisms was assessed.

Tribufos is an organophosphate chemical that, when applied to cotton plants

, is taken up by its leaves, resulting in premature abscission of whole gr een leaves. Information was not available to determine whether tribufos is transported in the xylem and phloem of plants. Tribufos is registered for use on cotton, and is used in a ground or aerial spray application prior to harvest.

Th is preliminary ris k assessment examines the potential for adverse effects on non

- target organisms following exposure ( i.e

., ecological ri sks ) associated with this single labeled use of
tribufos based on available scientific and commercial information on the use, environmental fate and transport, and effects of tribufos on nontarget organisms

.

Tribufos is a semi

- volatile, moderately soluble compound that has low mobility in soil. Based on submitted data, it is stable to the abiotic proc esses of hydrolysis and photolysis. It is expected

to rapidly degrade if present in the atmosphere. Tribufos is persistent in aerobic and anaerobic soil, and slightly persistent in anaerobic aquatic environments. Therefore, there is potential for tribufos to accumulate in soil with repeated applications. Tribufos is expected to sorb to soil, and not to appreci ably leach to groundwater or move to surface waters in solution phase via runoff.
S urface water contamination may occur though through spray drift and/or transport of residues
sorbed to sediment in runoff ( i.e ., erosion ) . In either aquatic or terrestrial environments, tribufos may bioaccumulate in organisms exposed to it (BCF=730 L/kg

- whole fish); however,
metabolism and rapid depuration will help to mitigate this exposure pathway

. While residues of
tribufos bioconcentrate in fish

, as indicated by its BCF

, the BCF is not high enough to trigger the Office of Chemical Safety and Pollution Prevention (OCSPP) criteria ( i.e ., BCF >1000) for being considered bioaccumulative 1



### .

Tribufos is the only residue of concern identified for aquatic and terr estrial organisms. Oxon transformation products were not identified in laboratory or field studies. Aquatic exposure
estimates for tribufos are presented for the parent compound as the single residue of concern

. Acute 1

- in

- 10 year estimated environmenta l concentrations (EECs) in surface water for modeled

cotton use of tribuf os ranged from 11 μg/L to 28 μg/L. Tribufos monitoring data are limited. Surface water monitoring conducted by the California Department of Pesticide Regulation ( DPR ) between 1991 and 2003 reported detections (at the limit of quantification [ LOQ ] of 0.01 ppb) in only 2 of 810 surface water samples from 15 counties (DPR, 2004b). However, the DPR data do not reflect targeted monitoring and it is uncertain whether the fr equency and quantity of material in surface water would be higher if sampling w ere conducted at or close to the time/site of application.

Tribufos is characterized as very highly toxic to aquatic invertebrates

, and highly toxic to aquatic

1 http://www.pbtprofiler.net/criteria.asp- Page 6 of 116

- 

### vertebrates (fi sh and aquatic

- phase amphibians) on an acute exposure basis . The compound is highly toxic to mammals on a subacute dietary exposure basis and is moderately toxic to
mammals and birds , reptiles and terrestrial

- phase amphibians on an a cute oral exposure bas is
while it is slightly toxic to birds , reptiles and terrestrial

- phase amphibians on a s ubacute dietary exposure basis

. Chronic effects observed across taxa include effects on survival, growth

, and reproduction. Table 1 summarizes the taxa with a potential for direct adverse effects from exposure to tribufos along with the l ines of evidence used in assessing risk

.

Risk was evaluated at both maximum and average application rates. The average application
rate is derived by dividing the average pounds of active ingredient applied based on proprietary usage survey data by the total area treated (USEPA, 2014). Thus, the average rate may not reflect an actual application rate used in the field and is lower than the rate use d by some.

Table 1 . Potential for Direct Effects on the Use of Tribufos on Cotton 1



### .

Taxa Exposure Duration and Endpoint RQ 2 Potential for Direct
Effects? Data gaps/ Refinements/
Lines of evidence Listed Non

listed Aquatic vascular plants Frond Count 0.02

- 0.21 No

- No

- None

Aquatic non

vascular plants Measures of biomass 0.14

- 0.25 NA Yes* Data gaps on non

- vascular aquatic plants, see text.

Dicot terrestrial plants Measures of biomass 0.21

- 0.53 Yes* Yes* Defoliation observed in plants that form abscission
zones at maximum labeled application rates. Effects
observed for cotton at 0.42
lbs a.i./A

. Monocot terrestrial plants Measures of biomass 0.10

- 0.26 Yes* Yes*

Freshwater
Vertebrates Acute: mortality 0.07

– 0.10 Yes + No

Some LOCs exceeded at average and maximum labeled application rates. Chronic: NOAEC extrapolated using ACR
for E/M fish 4.09

- 7.17 Yes +

Estuarine/ marine
fish Acute: mortality 0.03

- 0.04 No

- No

Chronic: growth, post
hatch survival 1.30

- 2.28 Yes+

Freshwater
invertebrates Acute: mortality 3.9

- 5.5 Yes+ Yes + LOCs exceeded at average
and maximum labeled application rates. Chronic: Reduced number of young/adult/day and reduced growth 10.8

- 17.4 (water column)
3.9

- 24 (benthic) Yes+

Estuarine/ marine
Invertebrates Acute: mortality 1.8

- 2.6 Yes+ Yes + LOCs exceeded at average
and maximum labeled application rates. Chronic: mortality 2.4

- 3.8 (water column)
4.4

- 8.4 (benthic) Yes+

Mammals Acute oral dose: mortality Subacute dietary: mortality < 0.01

- 1.02
0.05

- 2.80, 52.6

- 114 Yes+ Yes + LOCs exceeded at average
and maximum labeled application rates and with

upper

- bound and mean

K enaga EECs. LOCs
exceeded for mammals and Chronic: increased
number of litters with still born pups 0.53

- 14.04, 32.6

- 70.5 Yes+- Page 7 of 116

- Taxa Exposure Duration and Endpoint RQ 2 Potential for Direct
Effects? Data gaps/ Refinements/
Lines of evidence Listed Non

listed

Birds Acute oral dose : mortality
Sub

- Acute dietary: mortality, based on BCF <0.01

- 4.71
0.01

- 0.30, 5.57

- 12.1 Yes+ Yes + birds consuming aquatic organisms using both low and high EECs and BCF
values.

Chronic : egg

- shell thickness, based on BCF 0.19

- 3.00, 32.6

- 70.5 Yes+

Terrestrial
invertebrates Individual survival:
Acute contact: 3% mortality at level <0.21 No

Tier 1 dietary and chronic
data are not available to
evaluate risk. An o pen literature study shows
effects on terrestrial
i nvertebra tes at maximum labeled application rates. Individual survival: Acute and chronic dietary No data

Brood Size and success:
Acute and chronic larval No data

ACR=Acute

- to

- chronic; RQ=risk quotient; LOC=level of concern; E/M=estuarine/marine; NOAEC=No observable adverse effect concentration; BCF=bioconcentration factor; EEC=estimated environmental concentration

1 ‘Taxa’ cells and ‘potential for direct effects’ cells are shaded as follows:

- red and plus sign (+) indicates high confidence in a high likeli hood of direct adverse effects ( e.g ., multiple lines of evidence, RQs exceed LOCs, RQs based on reliable data and exposure estimate);

- yellow and asterisk (*) indicates lower confidence in a high likelihood of direct adverse effects ( e.g ., low confidence in data used to calculate RQs, lack of data, or few lines of evidence support the conclusion); and

- green and minus sign (

- ) indicates a high confidence in a low likelihood of direct adverse effects ( e.g ., full data set, high confidence in exposure estimates and toxicity dataset).

- When data were not available to evaluate risk and there are no lines of evidence suggesting a potential for direct effects, t he cell was
not shaded.

2 The RQ range reflects the RQs for the range of exposure estimates for maximum labeled application rates.



### Lines of Evidence

• Exposure Considerations

o Tribufos is persistent and slightly to hardly mobile. It has the potential to accumulate in soils with repeated applications and be tran s ported into surface water and benthic
sediment s via erosion and spray drift

.

o Tribufos is taken up into leaves

, but it is uncertain whether it is transported in the xylem and phloem or absorbed by roots.

o Based on BCF value of 730 L/kg

- wet weight, tribufos may bioconcentrate and bioaccumulate in aquatic and terrestrial organisms; however, it is metabolized and depurates rapidly in fish. The upper trophic BCF and BAF estimated using the Arnot

Gobas method are 277 and 281 , respe ctively (EPI Suite TM 

### , v.4.11, 2012).

Aquatic Environment

• Freshwater and Estuarine/marine Aquatic Invertebrates :

o There is a potential for acute mortality and reduced shell growth, reduced growth, and reduced number of young following chronic exposure for aquatic invertebrates inhabiting the water

- column and benthic zones ( i.e

., RQs> acute listed, acute non

- listed, and chronic risk LOCs). RQs exceed acute listed and non

- listed and chronic risk LOCs
for freshwater fish and chronic risk LOCs for estuari ne/marine fish for both maximum and average application , with the exception that t he chronic risk LOC for
estuarine /marine invertebrates inhabiting the water column is not exceeded for California and Arizona average application rates simulated with the Cal ifornia cotton- Page 8 of 116

- 

### scenario.

• Freshwater and Estuarine/marine aquatic vertebrates ( in clu ding aquatic

- phase amphibians and reptiles)

o There is a potential for a cute mortality and reduced growth, and reduced survival of

young following chronic exposure for freshwater aquatic vertebrates from use of tribufos on cotton ( i.e

., RQs> acute listed and chronic risk LOCs). Acute and chronic risk LOCs are exceeded for both maximum and average application rates.

o There is a potential for reduced growth, and reduced s urvival of young following chronic exposure for estuarine/marine aquatic vertebrates from use of tribufos on cotton ( i.e

., RQs> chronic risk LOCs). Acute and chronic risk LOCs are exceeded for both maximum and average application rates with the exception that t he chronic risk LOC for
estuarine /marine vertebrates is not exceeded for California and Arizona average application rates simulated with the California cotton scenario.

o There is one incident of a fish kill associated with an approved use of tribufos.

• Aquatic Plants

o RQs do not exceed LOCs for risk to listed or non

- listed aquatic plants. However, a full
dataset is not available to assess the risk to non

- vascular aquatic plants, and based on aquatic plant data for other organophosphates, it is possible that RQs could exceed
LOCs if additional data were available.

• Monitoring data confirm the identified transport pathways. Non

- targeted monitoring data for surface water (peak=0.3 μg/L) and sediment (peak=5.1 μg/kg) are approximately a
factor of 10 lower th an the most sensitive toxicity endpoints for aquatic invertebrates ( Daphnia magna median lethal concentration = 5.4 μg/L; D

. magna 21

- day n o

- observable

adverse

- effect

- concentration, NOAEC=1.56 μ g /L; Hyalella azteca 10

- day sediment NOAEC=71 μg /kg

- sediment) and aquatic vertebrates ( Lepomis macrochirus estimated NOAEC=4.1μg/L

. However, these data are not expected to capture maximum concentrations because the sampling was infrequent and not targeted to an area of trib ufos

use.

• Spray Drift

o The re is a potential for adverse effects to aquatic invertebrates when exposure was estimated for runoff only. Therefore, a spray drift buffer will reduce exposure but will
not eliminate risk from runoff in vulnerable areas.

o When con sidering exposure to spray drift alone, there is a potential for direct adverse effects to listed aquatic invertebrates located in surface waters greater than 1000 feet from the edge of the field for aerial applications and 170 to 577 feet from the edge of the field for ground applications. For non

- listed aquatic invertebrates, adverse effects may

occur up to 262 feet from the edge of the field due to exposure to spray drift

, depending on the application rate and type of application.

Terrestrial Environme nt

• Birds (surrogates for terrestrial

- phase amphibians and reptiles) and Mammals

o There is a potential for acute mortality and reduced egg shell thickness, reduced egg production, reduced survival of hatchlings, reduced growth, and increased number of
femal es with regressed ovaries following chronic exposure for birds consuming short grass, tall grass, broadleaf plants/small insects, and arthropods ( i.e

., RQs> acute listed,

acute non

- listed, and chronic risk LOCs). Some RQs exceed acute and chronic risk- Page 9 of 116

- 

### LOC s for both maximum and average application rates.

o There is a potential for acute mortality and increased number of litters born with stillborn pups, increased pup death through lactation, decreased growth (bodyweight) in F1 and F2, and an increased F1 gestation period following chronic exposure for mammals consuming short grass, tall grass, broadle af plants/small insects, and arthropods ( i.e., RQs> acute listed, acute non

- listed, and chronic risk LOCs). Some RQs exceed acute and chronic risk LOCs for both maximum and average application rates.

o There is a potential for adverse effects due to acute and chronic dietary exposure to birds, reptiles, terrestrial

- phase amphibians and mammals consuming aquatic organisms ( i.e

., RQs>acute listed, acute non

- listed, and chronic risk LOCs). This risk is main ly in
vulnerable areas such as areas where tribufos residues may persist in water through erosion or spray drift

.

• Terrestrial Invertebrates

o Acute

- contact honey bee ( Apis mellifera ) toxicity data indicate that the likelihood of adverse effects from exposure to tribufos following its use on cotton is low ( i.e

., RQ<LOC). Acute and chronic oral toxicity data for young adult bees and acute and chronic larval honey bee toxicity data are not available to fully evaluate the potential for effects to individual adult honey bees or their brood (eggs, larvae, and pupae ).

o Given tribufos is an organophosphate and there is evidence of insect mortality at lower application rates than average and maximum labeled rates, there is a potential for adverse effects to terrestrial invertebrates from exposure to the compound.

• Ter restrial Plants

o There is a potential for adverse effects (defoliation) to non

- target plants that form abscission zones ( e.g ., deciduous shrubs and trees) based on the tribufos being a known defoliant. Data are available showing that effects to non

- target p lants do occur at the maximum labeled application rates.

o There is one incident to terrestrial plants associated with the use of tribufos and diuron. This incident may have been caused by diuron, as it is more toxic to plants than tribufos.

There are fat e and ecotoxicity data gaps discussed in the Section 4.4 . The understanding of the microbial (biotic) metabolism of tribufos and the model estimates for aerobic and anaerobic soil metabolism and anaerobic aquatic metabolism rely on only one study with eac h of these studies testing one soil or sediment to derive model parameters. Consistent with EPA’s model input parameter guidance, the available half

- life for each of these studies is multiplied by an uncertainty factor (3X) to derive the model input value s.

The main uncertainties in the toxicity dataset involve risk to honey bee s , benthic aquatic
invertebrates , and aquatic non

- vascular plants as data are not available for these taxa to fully evaluate the potential for direct effects. There is also some u ncertainty on the risk to freshwater vertebrates from chronic exposure to tribufos.

A ten

- day sediment toxicity study is not available for the freshwater benthic invertebrate midge ( Chironomus dilutus ). There are 10

- day sediment toxicity studies availa ble for the freshwater ( H

. azteca ) and estuarine/marine amphipod ( Leptocheirus plumulosu s ). The midge and amphipod have different life histories, occupy different taxonomic groups (crustaceans versus insects) and generally interact with sediments in different ways. Chironomid larvae are more infaunal- Page 10 of 116

- 

### (submerged in sediment) whereas amphipods are more epibenthic (moving in and out of surficial sediment layer). Additionally, the 10

- day sediment toxicity tests do not examine the potential for reproductive effects, which were observed in toxicity studies where other taxa were exposed to
tribufos. The current risk assessment for sediment may underestimate the potential for risk to benthic aquatic invertebrates.

Pollinator risk assessment guidance has recently been finalized (see Section 3.2.3.4) and recommends the following honey bee data for a T ier I screening

- level risk assessment for honey
bees:

• acute oral toxicity to adult honey bees;

• acute oral toxicity to larval honey bees;

• chronic oral toxicity to adult honey bees; and,

• chronic oral toxicity to larval honey bees.

If Tier I studies identify the potential for a risk concern, additional studies may be requested

. As these data are currently unavailable for tribufos, the potential for adverse effects to individual honey bees and their brood could not be fully assessed.

Toxicity data from chron ic exposure to tribufos are not currently available for the species of freshwater fish that are most acutely sensitive to tribufos ( i.e ., bluegill sunfish; L

. macrochirus ). Therefore, the chronic effects endpoint used in this assessment for freshwater fish is based on an

acute

- to

- chronic ratio (ACR) using toxicity data from the estuarine/marine sheepshead minnow ( Cyprinodon variegatus ). Because the ACR was determined using endpoints from an estuarine/marine species, chronic risks to freshwater fish may be o ver

- or under

- estimated, depending on the relative sensitivity of those species.

2. Problem Formulation

The purpose of problem formulation is to provide the foundation for the environmental fate and ecological risk assessment for the R egistration R eview of the organophosphate pesticide tribufos (S,S,S

- tributyl phosphorotrithioate; CAS No.: 78

- 48

- 8; PC code 074801) and its end

- use products. The problem formulation sets the objectives for the risk assessment, establishes a risk hypothesis and conceptual mo del depicting potential routes of exposure, biological receptors and their measurement endpoints , and it provides a plan for analyzing the data and characterizing the
risk associated with the use of tribufos (USEPA, 1998)

.

2.1. Nature of Regulatory Action

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides distributed or sold in the United States must be registered by the United States Env ironmental Prote ction Agency ( EPA). To determine whether a pes ticide can be registered, the EPA evaluates its safety

to non

- target species based on a wide range of environmental and health effects studies. In 1996, FIFRA was amended by the Food Quality Protection Act (F QPA), and EPA was mandated to implement a new program for the periodic review of pesticides, i.e

., R egistration R eview 2 

### . The

2 http://www.epa.gov/oppsrrd1/registration_review/- Page 11 of 116

- 

### R egistration R eview program is intended to ensure that as the ability to assess risk evolves and as policies and practices change, all registered pesticides continue to meet the statutory standard of no unreasonable adverse effects to human health and the environment. Changes in science, public policy, and pesticide use practices will occur over time. Through the registration review program, the Agency periodically reevaluates pesticides to make sure that as change s occur , products in the marketplace can be used safely.

2.2. Stressor Source and Distribution

2.2.1. Nature of the Stressor

Tribufos, S,S,S

- tributyl phosphorotrithioate, is an organophosphate chemical that, when applied to cotton plants and absorbed by its leaves, injures the cells in the layer immediately beneath the leaf cuticle (via esterase inhibition), causing stress to th e plant, which stimulates the production of ethylene (USEPA, 2000) . The increased ethylene concentrations result in the premature abscission of whole green leaves

. Due to tribufos’ mechanism of action, effects to terrestrial plants that form abscission zones ( e.g ., some woody, deciduous plants) could occur as a consequence of exposure

. Like other organophosphates there is evidence that tribufos inhibits brain, plasma, and erythrocyte acetyl cholinesterase (ChE) activity in animals after acute and chronic exposures (USEPA, 2000)

. Table 2 summaries the chemical/physical characteristics of
tribufos.

Table 2

. Chemical Profile of Tribufos

.

Common name T ribufos

Chemical name S,S,S

- tributyl phosphorotrithioate; CAS No.: 78

- 48

- 8; PC code 074801

Structure (A3 form of the molecule, the most toxic of the 8 homologues)

SMILES Notation O=P(SCCCC)(SCCCC)SCCCC Pesticide type Pre

- harvest cotton defoliant

Chemical class Organophosphate

CAS number CAS No.: 78

- 48

- 8

Molecular mass 314.54 g mol

- 1



### 2.2. 3

. Overview of Pesticide Us e

Tribufos was first registered in the United States in 1961 for use on cotton and is formulated as an emulsifiable concentrate that is applied by ground or aerial spray as a pre

- harvest treatment as a defoliant to facilitate cotton harvesting and to reduce the pieces of dry leaves and other inert
matter in harvested cotton. Three technical products and four end

- use products containing
tribufos a re registered and all products only contain the single active ingredient. This assessment evaluates risk based on currently labeled maximum application rates and average application- Page 12 of 116

- 

### rates. The average application rate is derived by dividing the average p ounds of active ingredient applied by the total area treated (USEPA, 2014). Thus, the average rate may not reflect an actual application rate used in the field

. Additionally, usage at rates higher than the average application

rate does occur. More infor mation on use and usage is available in the analysis plan.

2.3. Receptors

2.3.1. Aquatic and Terrestrial Effects

The receptor is the biological entity that is exposed to the stressor (USEPA , 1998) . Consistent with the process described in the Overview Document (USEPA, 2004a) , this risk assessment uses a surrogate species approach. T oxic ity data generated from surrogate test species, which are intended to be representative of broad taxonomic groups, are used to extrapolate potential effects on a variety of species (receptors) included under these taxonomic groupings.

A cute and chronic tox icity data from studies submitted by pesticide registrants along with the available open literature are used to evaluate potential direct effects to aquatic and terrestrial receptors. The open literature studies are located through EPA’s ECOTOXicity datab ase ( ECOTOX ; http://cfpub.epa.gov/ecotox/ ), which provides a source for locating single chemical toxicity data for aquatic life, terrestrial plants, and wildlife.

2.3.2. Ecosystems Potentially at Risk

The ecosystems potentially at risk are often extensive in scope; therefore, it may not be possible to identify specific ecosystems during the development of a nation

- wide ecological risk assessment. However, in general terms, terrestrial ecosystems potential ly at risk could include
the treated field or tree(s) and immediately adjacent areas that may receive drift or runoff. Areas adjacent to the treated field or tree(s) could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grass lands, woodlands, riparian habitats, and other uncultivated areas.

Aquatic ecosystems potentially at risk include water bodies adjacent to or downstream from use sites, and might include natural or impounded lentic water bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers including all adjacent off

- channel habitats that are permanently or intermittently connected to flowing waters. For uses in coastal areas, aquatic habitat also includes marine ecosystems, includin g estuaries, embayments, and

near

- shore environments such as tidal marshes.

2.4. Assessment Endpoints

Assessment endpoints represent the actual environmental value that is to be protected, defined by an ecological entity (species, community, or other entity) and its attribute or characteristics (USEPA, 1998) . For tribufos , ecological entities of potential concern include the following: birds, terrestrial

- and aquatic

- phase amphibians, reptiles, mammals, freshwater fish and invertebrates, estuarine/marine fish and invertebrates, non

- target t errestrial plants, terrestrial invertebrates, and aquatic vascular and non

- vascular plants. The attributes for each of these entities include gro wth, survival, and reproduction

.- Page 13 of 116

- 

### The assessment endpoints are intended to reflect population sustainability a nd community structure within ecosystems and hence relate back to ecosystems at risk. If risks are expected for given species/taxa based on the screening

- level assessment, then risks might be expected to translate to higher levels of biological organizati on.

2.5. Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the
environment from a source to a n ecological receptor. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposure. The conceptual model is
intend ed to provide a written description and visual representation of the predicted relationships
between tribufos , potential routes of exposure, and the predicted effects for the assessment endpoint. The conceptual model consists of two major components: the risk hypotheses and a conceptual model (USEPA, 1998)

.

The conceptual model used to depict the potential ecological risk associated with the proposed and existing uses of tribufos relies on previous assessments and the Agency’s current understanding of the environmental fate and ecological effects of the chemical

. Consistent with the intended use of tribufos as a defoliant, p otential risk to non

- target terrestrial and aquatic plants is expec ted

. Effects on plants, which represent the primary producers in an ecosystem, may result in secondary effects on consumers which may include a broad range of taxa

.

Based on the Interim Reregistration Eligibility Decision (IRED) (USEPA, 2000) , acute and
chronic risks to birds, mammals, and aquatic invertebrates (both freshwater and estuarine/marine) are expected from the registered use of tribufos on cotton. Acute risks to estuarine/marine fish, but not freshwater fish, were also identified. Neither risks to fish from chronic exposure to tribufos nor risks to plants could be fully evaluated previously due to a lack of data. Several studies were submitted after the IRED was completed. These stu dies were considered by the EPA in an endangered species risk assessment for tribufos and the endangered
California red

- legged frog ( Rana aurora draytonii ) (CRLF) that was submitted to the U.S. Fish and Wildlife Service as part of formal Section 7 consulta tion on October 20, 2008. EPA
determined in its endangered species risk assessment that use of tribufos on cotton in California was likely to adversely affect (LAA) the CRLF . Based on the previous risk assessments, the

current risk hypothesis evaluated i n this assessment is that the use of tribufos on cotton may result in exposure and subsequent adverse effects to terrestrial and aquatic animals.

Due to the potential direct adverse effects to the listed and non

- listed groups of organisms described above, listed species in all taxa may potentially be affected indirectly due to alterations in their habitat ( e.g. , food sources, shelter, and areas to reproduce) if exposure to tribufos occurs.- Page 14 of 116

- 

### 2.5.1. Risk Hypotheses

For tribufos , the following gener ic ecological risk hypotheses are being employed for this risk

assessment:

Given the currently labeled uses of tribuf os and its environmental fate properties, there is a likelihood of exposure to non

- target terrestrial and aquatic organisms.

When used in accordance with the label, tribuf os may result in potential adverse effects upon the survival, growth, and reproduction of non

- target terrestrial and aquatic organisms.

2.5.2. Conceptual Pathways Table

The environme ntal fate properties of tribufos indicate that for foliar applications

, spray drift and
runoff (including of eroded sediment) are potential transport mechanisms to aquatic habitats
where non

- target organisms may be exposed. It is expected that non

- target terrestrial organisms can be exposed via foliar applications of tribufos through consumption of exposed plants and
invertebrates on treated field s . Additionally, tribufos may reach terrestrial environments off the field via spray drift, and via application of irrigation water containing residues of tribufos . A summary of the transport pathways and the models used for those pathways in the assessment are provided in Table 3

.

Tribufos is a semi

- volatile, moderately soluble compound that has low mobility in soil. It is
stable to abiotic degradation and is persistent in soil. It is expected to sorb to soil and sediments,
and is slightly persistent in anaerobic aquatic environments. S urface water contamination may
occur due to spray drift and/or transport of residues sorbed to sediment in runoff ( i.e ., erosion)

. In eith er aquatic or terrestrial environments, tribufos may bioaccumulate in organisms exposed to
it (BCF = 730 L/kg

- wet weight fish); however, it is metabolized and depurates rapidly (71

- 88% of residues depurated over 14

- days) once exposure ends

.

Additionally , the Screening Tool for Inhalation Risk (STIR) version 1.0 (November 23, 2010) indicates that exposure via inhalation is not likely to be a risk concern for birds and mammals ( Appendix G ). Sorption coefficients of tribufos indicate that risk to sediment

- dwelling organisms should be evaluated.

The exposure pathways may result in exposure to various aquatic and terrestrial organisms. With exposure, the following attribute changes have the potential to occur:

• e ffects to individual organisms ;

• e ffects to th e food chain (reduction in prey and food, modification of primary constituent elements (PCE) related to prey availability) ; and

,

• e ffects to habitat integrity (reduction in primary productivity, reduced cover, community change, and modification of PCE relat ed to habitat).- Page 15 of 116

- 

### Table 3 . List of the Various Models and the Related Taxa for which the Models will be
Used to A ssess R isk

.

Environment Taxa of
Concern Exposure
Media Exposure Pathway Model(s) or Pathway Attribute Change

Aquatic Vertebrates/
Invertebrates

(including
sediment dwelling) Surface water and
sediment Runoff and spray
drift to water and
sediment SWCC Individual Organisms
Food Chain Habitat Integrity

Aquatic Plants (vascular and nonvascular) Food Chain
Habitat Integrity

Riparian plants See terrestrial exposure pathways Habitat Integrity

Terrestrial Vertebrate Dietary items Ingestion of
residues in/on dietary items as
a result of direct application T

- REX Individual Organisms
Food Chain Habitat Integrity

Consumption of aquatic organisms Residues taken up by aquatic

organisms KABAM Individual Organisms
Food Chain Habitat Integrity

Plants Spray drift/runoff Runoff and spray drift to plants TERRPLANT

Food Chain Habitat Integrity Surface water Residues in irrigation water Not a major

transport pathway Groundwater

Bees and other
terrestrial
invertebrates 1 Contact Dietary items Spray contact and ingestion of

residues in/on dietary items as
a result of direct application See honey bee
risk assessment guidance (USEPA et al

., 2014) Individual Organisms Colony/Population Integrity

All
Environments All Movement through air to aquatic and
terrestrial media Spray drift AgDRIFT (Spray drift) Individual Organisms
Food Chain Habitat Integrity AgDISP (Spray drift)

Atmospheric

transport Not a major

transport pathway

Text in italics represent transport pathway s that are not of concern.

1 See pollinator SAP white paper for full list of modelling approaches for evaluating exposure used in this

assessm ent (USEPA, 2012b)

.



### 2.6. Analysis Plan

2.6.1. Residues of Concern

The only major degradate observed in the aerobic soil metabolism study was 1

- butane sulfonic acid (1

- BSA), identified at approximately 10% of the applied ra dioactivity 9 months after

treatment. The 1

- BSA degradate was a minor degradate in anaerobic soil , but was a major- Page 16 of 116

- 

### degradate in the anaerobic aquatic ( i.e ., flooded sediment) system, at up to 29.5

- 30.6% of the applied radioactivity 6 to 9 months after treatment. No toxicity data are available on this degradate, but it was determined to be of no toxicological concern in previous risk assessments (USEPA, 2008) . Additionally, 1

- BSA does not retain the organophosphate moiety of the parent compound ; the Ecological Structure Activity Relationship ( ECOSAR ; http://www.epa.gov/oppt/newchems/tools/21ecosar.htm ) tool indicates 1

- BSA will likely be less toxic than parent ( Appendix H )

. Therefore , the degradation product is not considered a residue
of concern. Oxon degradates are often a concern for organophosphates. T ribufos itself is an

oxon and additional oxon transformation products did not occur in laboratory or field studies (the single major degradate was 1

- BSA) . Therefore, only the parent compound is considered the
resi due of concern.

2.6.2. Preliminary Identification of Data Gaps and Uncertainties

This assessment is based upon available data. There are no significant data gaps in the environmental fate database submitted by the registrant. However, there is some uncertainty introduced by the use of single half

- life values. Laboratory metabolism data are only available for single soils or sediments for aerobic and anaerobic soil metabolism, and anaerobic aquatic metabolism. There are no data available for aerobic aquatic metabolism as that data requirement was waived, and tribufos is simply assumed to be stable in aerobic aquatic systems.

Ecotoxic ity data gaps are discuss ed further in the Risk Description . Ecotoxicity data gaps include toxicity data for benthic invertebrates, freshwater fish, honey bee s, and aquatic non

vascular plants.

The main ecotoxicity uncertainties in the risk assessment involve risk to honey bee

, as data are not available to fully assess risk

, and benthic aquatic invertebrate risk may be underestimated based on available data. While the chronic toxicity endpoint for freshwater vertebr ates is estimated, it is consistent with available non

- quantitative results. Finally, a full dataset to assess
risk to non

- vascular aquatic plants is not available

.

2.6.4. Measures of Exposure

Using EFED’s standard suite of models, surface water esti mated environmental concentrations (EECs) were generated for tribufos for the registered use on cotton. The Surface Water Concentration Calculator (SWCC, v 1.106, May, 2014) is used to generate estimated environmental concentrations ( E E C) s that may occur in surface water . The SWCC simulates pesticide transformation on and runoff from an agricultural field (in addition to loadings from spray drift), following applications to crops. The model then simulates resulting concentrations in an adjacent surface w ater body ( i.e ., the standard pond)

. The measure of exposure for aquatic species in surface water bodies receiving runoff and/or spray drift is a return frequency of 1

- in

10 years of the EEC, based on 30

- year simulations. The maximum 1

- in

- 10 year return frequency concentration is used for estimating acute exposures to aquatic organisms (plants and animals);
the 1

- in

- 10 year 21

- day mean concentration is used for assessing aquatic invertebrate chronic exposure; and the 1

- in

- 10 year 60

- day mean concentration is used for assessing chronic exposure for fish (and aquatic

- phase amphibians for which freshwater fish serve as surrogates). EECs for- Page 17 of 116

- 

### tribufos include only the parent compound as the single residue of concern. Additional details on
the model can be fou nd at http://www.epa.gov/oppefed1/models/water/



### .

Terrestrial wildlife are potentially exposed to tribufos via consumption of residues on food items
from spray applications on cotton. For spray applications, the T

- REX model ( T errestrial

R esidue EX posure mode l; v. 1.5. 2 ; June 6, 2013) is used to predict dietary exposure to tribufos
residues on foliar surfaces and insects using the K enaga nomogram as modified by Fletcher (Fletcher et al. , 1994; Hoerger and Kenaga, 1972) . In this assessment, the default foliar dissipation half

- life of 35 days was used for terrestrial m odeling purposes. Additionally , the influence of lower foliar dissipation half

- live values on risk is explored. Estimated exposures of
terrestrial insects to tribufos are evaluated. Additional details on the model may be found at http://www.epa.gov/oppefed1/models/terrestrial/trex/trex_v1_5_webversion.xlsm



### .

The TERRPLANT (v. 1.2.2; October 29, 2009 ) model is used to derive EECs relevant to terrestrial and wetland plants for the proposed new uses of tribufos

. The model assumes that default fractions of the intended application will be transported to an adjacent field through runoff and spray drift. Measures of exposure to terrestrial plants are expressed as a fraction of
the mass of the tribufos applied to a treated field

. Additional details on the model may be found

at http://www.epa.gov/oppefed1/models /terrestrial/index.htm#terrplant



### .

To characte rize potential non

- target animal and plant exposure from spray drift alone, Tier 1 modules in AgDRIFT (v. 2.1.1, December 2011) were used to estimate how far off

- site spray drift exposure might occur at a level kn own to cause adverse effects based on aquatic and terrestrial toxicity endpoints

. Additional details on the model may be found at http://www.agdrift.com/AgDRIFt2/DownloadAgDrift2_0. htm



### .

The Screening Tool for Inhalation Risk (STIR v.1.0, November 19, 2010) was used to calculate

an upper

- bound estimate of wildlife inhalation exposure using tribufos ’ vapor pressure and molecular weight for vapor phase exposure as well as the maximum a pplication rate and method of application for spray drift. STIR incorporates results from several toxicity studies including acute oral and inhalation rat toxicity endpoints obtained from the “six

- pack” of core studies,
which is a series of six guideline studies that are submitted to the Registration Division of the Office of Pesticide Programs for technical and formulated products of a pesticide (LD 50 

### = 192 mg/kg

- bw/day, MRID 41954903 ; and inhalation LC 50 

### > 4.65 mg/L, MRID 41782301

, respectively) as well as the most sensitive acute oral avian toxicity endpoint ( Bobwhite quail ; Colinus virginianus ; LD 50 

### = 151 mg/kg

- bw, MRID 00120771 ). Based on the results of the STIR model ( Appendix E ), exposure through inhalation of spray drift or the vapor phase of tribuf os is

not considered a primary pathway of concern for either avian or mammalian species on an acute
inhalation exposure basis. Additional details on the model may be found at http://www.epa.g ov/oppefed1/models/terrestrial/

.

The analysis of the inhalation route in STIR does not consider that aggregation with other exposure pathways such as dietary, dermal, or drinking water may contribute to a total exposure that has a potential for effects to non

- target animals. However, the Agency does consider the relative importance of other routes of exposure in situations where data indicate that pesticide exposures through other routes may be potentially significant contributors to wildlife risk- Page 18 of 116

- 

### (USEPA, 2004a)

. The risk characterization section ( Section 4.3 ), discusses the impact of consideration of other routes of exposure that have been identified as potentially important and the degree of certainty associated with screening

- level risk assessment conclusions. Detailed information about STIR v.1.0, as well as the tool , can be found on EPA’s website ( http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial ).

The Screening Imbibition Program (SIP v.1.0, released June 15, 2010) wa s used to calculate an

upper

- bound estimate of wildlife drinking water exposure using tribufos ’ solubility ( i.e

., 2.3 mg/L at 20 o 

### C, MRID 41618803 ), and compared to the most sensitive acute and chronic avian and mammalian toxicity endpoints (see Table 19 ). Based on this analysis, d rinking water exposure alone is not considered a primary pathway of concern for birds or mammals on either an acute or chronic exposure basis. For a sample of the output generated by SIP v.1.0, please see Appendix F

. Additional details on the model may be found at http://www.epa.gov/oppefed1/models/terrestrial/

.

Because there is evidence of the potential for bioaccumulation of tribufos in aquatic organisms 3



### , an additional exposure pathway that is considered in this assessment is the consumption of contaminated fish or aquatic invertebrates that have residues of tribufos from uptake from the
water and diet

. The potential risk from this pathway will be evaluated and discussed further in
the “Risk D escription” section of the document. Multiple lines of evidence will be used to evaluate bioaccumulation potential, including measured bioconcentration factors (BCF), bioaccumulation factors (BAF) and a food web bioaccumulation model (K ow 

### - Based Aquatic

Bi oaccumulation Model or KABAM ver sion 1.0 ). The bioaccumulation assessment relies on predicted water and sediment concentrations from SWCC to estimate concentrations of tribufos

in the tissues of aquatic organisms. I n order to evaluate potential risk t hes e estimated tissue concentrations will be compared to toxicity values for various taxonomic groups that may eat aquatic organisms. The current version of KABAM estimates risks only to terrestrial birds and mammals consuming aquatic prey

.

2.6.5. Measures of Effect

Measures of effect are obtained from a suite of registrant

- submitted guideline studies that were conducted with a limited number of surrogate test species ( Table 4 ) . The test species are not intended to be representative of the most sensitive species but rather were selected based on their ability to thrive under laboratory conditions. Toxicity testing reported in this risk assessment utilizes surrogate species to represent all freshwater fish (2000+) and bird (680+) species in the U.S. In addition, t he ECOTOX database (USEPA, 2009a) was searched in March 201 5 to provide more ecological effects data for tribufos. Data were further examined if endp oints were
more sensitive (lower) than endpoints available from submitted studies or were available for amphibians, freshwater mollusks , or reptiles (USEPA, 2011) . Data meeting the OPP’s standard for inclusion in risk assessment ( http://www.epa.gov/pesticides/science/literature

- studies.html )

were available in ECOTOX that showed greater sensitivity than results from submi tted studies

3 The measured BCF values for whole fish was 730 L/kg

- wet weight fish. Additionally, the log octanol

- water partition coefficient of 5.5, indicates that the bioaccumulation pathway should be assessed. However, evidence
indicates that tribufos is metabolize d and accumulates less than expected based on its K OW value and that tribufos rapidly depurates (71

- 88% depurated over 14

- days) once fish are transferred to clean water.- Page 19 of 116

- 

### for freshwater fish (Mayer and Ellersieck, 1986, MRID 40098001, ECOTOX Number 6797) and daphnid s (Brausch et al. , 2010, ECOTOX R ecord Number 156445; Mayer and Ellersieck, 1986, MRID 40098001, ECOTOX Number 6797) . Additionally, ECOTOX data were examined for data on amphibians, freshwater mollusks , and reptiles.

The acute measures of effect used in this screening

- level assessment are the LD 50 

### (Lethal Dose),
LC 50 

### (Lethal Conc entration)

, EC 50 

### (Effects Concentration) , and IC 50 

### (Inhibition Concentration)

. These are measures of acute toxicity which result in 50% of the respective effect in tested organisms. The endpoints for chronic measures of exposure are the NOAEC (No Observe d Adverse Effects Concentration) and the NOAEL (No Observed Adverse Effects Level). Toxicity studies were submitted for freshwater fish and invertebrates, estuarine/marine fish and invertebrates, aquatic and terrestrial plants, birds, mammals, and honey b ees. The endpoints
used for risk characterization were derived from studies which underwent review and were classified as “acceptable” (conducted under guideline conditions and considered to be scientifically valid) or “supplemental” (conditions deviated from guidelines but the results are considered to be scientifically valid).

Table 4 lists the measures of environmental exposure and ecological effects used to assess the potential risks of tribufos to non

- target organisms. The methods used to assess the risk are
consistent with those outlined in the document “ Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs ” (USEPA, 2004a)

.

Table 4

. Measures of Exposure and Measures of Effect Used in Assessing Potential Risks Associated with the Proposed Uses of Tribufos

. Assessment Endpoint Surrogate Species and Measures of Ecological Effect 1 Measures of Exposure

Birds 2 Survival Lowest acute LD 50 (single oral dose test)
and LC 50 (subacute dietary test) Upper

- bound residues on
food items Reproduction
and Growth Lowest NOAEC (21

- week reproduction test)

Mammals Survival Lowest acute LD 50 (single oral dose test)
and LC 50 (subacute dietary test) Reproduction
and Growth Lowest NOAEC (2

- generation reproduction test)

Aquatic Animals (Fish and invertebrates) 3 Survival Lowest tested LC 50 or EC 50 (acute toxicity test) Peak EECs 4

Reproduction
and Growth Lo west NOAEC (early life

- stage, full
life

- cycle tests , 10

- day sediment tests, or chronic sediment tests) 21

- day EECs for invertebrates
and 60

- day EECs for fish 4

Terrestrial plants 5 Survival and growth Lowest EC 25 (for non

- listed plants) and corresponding NOAEC (for listed plants)
(endpoints derived for monocots and dicots from seedling emergence and vegetative vigor studies) Estimates of runoff and spray
drift to non

- target areas

Insects 6 Survival Lowest honey bee LD 50 (acute contact test) Upper

- bound residues on tall

grass 7- Page 20 of 116

- 

### Table 4

. Measures of Exposure and Measures of Effect Used in Assessing Potential Risks Associated with the Proposed Uses of Tribufos

. Assessment Endpoint Surrogate Species and Measures of Ecological Effect 1 Measures of Exposure

Aquatic plants (vascular
and non

- vascular) Survival and growth Lowest EC 50 (for non

- listed plants) and corresponding NOAEC or EC 05 (for listed plants) Peak EECs 4

1 The most sensitive species tested within taxonomic groups is used for screening

- level risk assessments.

2 Birds represent surrogates for terrestrial

- phase amphibians and reptiles.

3 Freshwater fish represent surrogates for aquatic

- phase amphibians.

4 Aquatic EECs are based on modeling described in Section 3.2.2.1

. 5 Four species of two families of monocots

- one is corn, six species of at least four dicot families, of which one is soybeans.

6 Risk to terrestrial invertebrates from tribufos use is quantitatively evaluated against the acute listed terrestrial inverteb rate LOC of 0.4.

7 The tall grass residue value from the T

‐ REX model (v. 1.5.2) is used as a surrogate for pesticide concentration s in nectar and pollen.



### 2.6.6. Integration of Exposure and Effects

The exposure and toxicity effects data are integrated in order to evaluate the risks of adverse ecological effects on non

- target species. For the risk assessment of tribufos , the risk quotient (RQ) method is used to compare estimated exposure and measured toxicity values. The RQ method involves dividing estimated environmental concentrations (EEC) by acute and chronic toxicity values. The resulting RQs are then compared to the Agency ’s Levels of Concern (LOC) (USEPA, 2004a) ( Table 5 ). The LOCs are used to indicate when applications of tribufos , as directed on the label, have the potential to cause adverse e ffects to non

- target organisms from exposure to tribufos

.

Table 5 . Agency Risk Quotient (RQ) Metrics and Levels of Concern (LOC) Per Risk Class.

R isk C lass R isk D escription RQ LOC
Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non

- listed animals from acute

exposures Peak EEC/LC 50 1 0.5

Acute
Restricted Use Potential for effects to animals from acute exposures Risks may be mitigated through restricted use
classification Peak EEC/LC 50 1 0.1

Acute Listed Species Listed species may be potentially affected by acute

exposures Peak EEC/LC 50 1 0.05

Chronic Potential for effects to non

- listed and listed animals from chronic exposures 60

- day EEC/NOAEC (fish)

1 21

- day EEC/NOAEC (invertebrates)

Aquatic Plants

Non

- Listed Potential for effects to non

- listed plants from

exposures Peak EEC/LC 50 1 1

Listed Potential for effects to listed plants from exposures Peak EEC/NOAEC 1

Terrestrial Animals (mammals and birds) 2

Acute Potential for effects to non

- listed animals from acute

exposures EEC/LC 50 (Dietary) 0.5 EEC/LD 50 (Dose)

Acute
Restricted Use Potential for effects to animals from acute exposures Risks may be mitigated through restricted use
classification EEC/LC 50 (Dietary)
0.2 EEC/LD 50 (Dose)- Page 21 of 116

- R isk C lass R isk D escription RQ LOC
Aquatic Animals (fish and invertebrates)

Acute Listed Species Listed species may be potentially affected by acute

exposures EEC/LC 50 (Dietary) 0.1 EEC/LD 50 (Dose)

Chronic Potential for effects to non

- listed and listed animals from chronic exposures EEC/NOAEC 1

Honey bee s

Acute Potential for effects to individual bees or brood due to contact and dietary exposure. Contact EEC/acute contact

LD 50 Diet EEC/ acute oral LD 50

Diet EEC/ Larval LD 50 0.4

Chronic Potential for effects to individual bees or brood due to contact and dietary exposure. Diet EEC/ adult NOAEL
Diet EEC/ larval NOAEL 1.0

Terrestrial and Semi

- Aquatic Plants

Non

- Listed Potential for effects to non

- target, non

- listed plants from exposures EEC/ EC 25 1

Listed Plant Potential for effects to non

- target, listed plants from

exposures EEC/ NOAEC 1 EEC/ EC 05

1 LC 50 or EC 50

. 2 EEC based on upper bound K enaga nomogram values for foliar exposure.



### 3. Analysis

3.1

. Use Characterization

Use patterns



### Tribufos was first registered in the United States in 1961 for use on cotton and is formulated as
an emulsifiable concentrate that is applied by ground or aerial spray as a pre

- harvest treatment as a defoliant to facilitate cotton harvesting and to reduce the pieces of dry leaves and other inert
matter in harvested cotton. Three technical products and four end

- use pr oducts containing tribufos are registered and all products only contain one active ingredient. End

- use p roducts
include F OLEX ® 

### 6EC (70.5% a.i.)

, D ef ® 

### 6 Emulsifiable Defolian t ® 

### (70.5% a.i.), DFT ® 

### 6 EC Cotton Defoliant (70.9% a.i.), and Tribufos ® 

### 6 (70.9% a.i.; liquid). Table 6 provides details on the registered use rates and typical use rates.

The maximum annual label application rate is 1. 8 75 lb a.i./A in California and Arizona, and the maximum annual label application rate is 1.1 25 lb a.i./A in all other states. In all states, two applications are allowed, not to exceed the annual maximum application rate, although it is usually used in a single application (BEAD, 2014). The re application interval is not specified on
the current labels other than as “2

- 6 weeks apart” for rank cotton (CA and AZ). The pre

- harvest
interval is listed as 7

- 10 days for CA and AZ. Applications are limited to fo liar applications via ground and aerial spray equipment; applications via irrigation systems (chemigation) are not allowed. All formulations are liquid formulations.

Table 6 . Tribufos Use on Cotton: Maximum Application Rates On Labels and Average Application Rates Applied in the Field- Page 22 of 116

- Rates Shown Area
Allowed Single App

Rate (lbs a.i./A) Seasonal

Rate 2 (lbs a.i./A) Number of Applications Comment

Maximum Rates
on Labels All except
CA and AZ 1.1 25 1.1 25 1

˗

CA and AZ 1. 875 1. 875 1

˗

Average Rates
Used in the Field
Recommended by BEAD 1 All except
CA and AZ 0.54 Not provided 1 Average over 2008 to
2012

CA 0.64 Not provided 1.2 Average over 2008 to 2012 (excluding 2011)

AZ 0.77 Not provided 1.6 Average over 2008 to
2012

1 Averate rates in the f ield were provided by BEAD (USEPA, 2014)

. 2 Cotton will only be grown once per year on a given production field because it is a warm season crop with a growing cycle of 130 to 160 days (USEPA, 2014) . Therefore, the seasonal rate is equal to the annual rate. Two applications are allowed, as long as the maximum annual application rate is not exceeded. Gener ally tribufos is applied as a single application , but may be used twice such as for rank cotton

. Rank cotton
refers to tall, vegetative cotton growth; often a result of late planting, excessive nitrogen fertilizer, fertile soils, or excessive m oisture. Ra nk growth often renders cotton plants more attractive and susceptible to late

- season insects, more susceptible to boll rot, and more difficult to
defoliate.



### Though labels indicate potential use of tribufos, usage data allow for more accurate
characterizat ion of actual us ag e of tribufos. The Screening Level Usage Analysis (SLUA) prepared by the Biological and Economic Analysis Division (BEAD) , estimated the average percent crop treated as 30% nationally, with a maximum estimate of 35% (USEPA, 2014) . The average annual pounds applied estimated for the SLUA was 2.3 million pounds per year. Tribufos is used throughout the cotton belt which extends from California to Florida and as far

nor th as Missouri, Tennessee, and Virginia (USEPA, 2014).

BEAD used available proprietary data to estimate the average a.i. rate and number of applications both nationally and for California and Arizona. National usage data from 2008

– 2012 show that the average rate for tribufos is 0.5 4 lb a.i. per acre, and the average number of applications per year on acreage is 1 .2 per year. Arizona and California have higher labelled application rates. For Arizona from 2008

- 2012, the average rate for tribufo s is 0.7 7 lbs a.i. per acre, and the average number of applications is 1.6 per year. From 2008

– 2012 (excluding 2011 due to anomalous data), the average rate for California was 0.6 4 pounds a.i. per year, and an average number of applications on treated a creage is 1 .2 per year. BEAD indicated that data for
2011 in California are outliers and should not be considered in the 5

- year average because they

are not considered by BEAD to be representative. BEAD recommended using an average rate of
0.64 lbs a.i./ A for California, which excludes usage data from 2011.

This assessment evaluates exposure and con sequent risk based on currently labeled maximum application rates and average application rates. The average application rate is derived by dividing the aver age pounds of active ingredient applied by the total area treated (USEPA, 2014). Thus, the average rate may not reflect an actual application rate used in the field and is lower than the rate used by some

.

3.2. Exposure Characterization

3.2.1. Environm ental Fate and Transport Characterization

The general physical/chemical properties of tribufos are summarized in Table 7 . Environmental- Page 23 of 116

- 

### fate and transport

- related properties of tribufo s are characterized in further detail in the following
sections. The Agency’s understanding of these properties is limited by the available dataset.

Table 7

. General Physical and Chemical Properties of Tribufos.

Property Value Reference

Molecular mass (molecular formula) 314.54 g/mol MRID 41618803

Vapor press ure (20°C) 1.7 x 10

- 6 T orr MRID 41618803
Water solubility (20 °C) 2.3 mg/L MRID 41618803

Henry’s Law constant (20°C) 3.1 x 10

- 7 atm

- m 3 /mol (calculated)

Octanol

- air partition coefficient (K OA ) 2.6 x 10 10 E PI Suite (v.4.11, 2012) , estimate

Octanol

- water partition coefficient (K ow; Log

K ow ) (20 °C) 3.3 1 x 10 5

5. 5 (log K
ow )

5.7 MRID 41618803

EPI Suite (v.4.11, 2012)

, experimental database

Fish Bioconcentration Factor (35 d) 300X (edible) 1300X (inedible)
730X (whole fish)

71

- 88% depurated after 14 days

113

- 277 (estimated BCFs) MRID 41 618811
MRID 43080401

E PI Suite (v.4.11, 2012), estimate s



### Tribufos is a semi

- volatile, moderately soluble compound that has low mobility in soil. Based on submitted data, tribufos is stable to the abiotic processes hydrolysis and photolysis (MRID s 41618814, 41618816, 41719401). Estimates of atmospheric oxidation (half

- life of 1.6 days) indicate that it would rapidly degrade if present in the atmosphere (EPI Suite, v.4.11, 2012). It is persistent in aerobic and anaerobic soil, and slightly persistent in anaerobic aquatic
environ ments. Therefore, there is potential for tribufos to accumulate in soil with repeated applications if the compound reaches the soil surface and does not dissipate from such through
volatilization . Tribufos is expected to sorb to soil, and not to apprecia bly leach to groundwater or move to surface waters in solution phase via runoff. To the extent that it occurs, surface water contamination may be expected to arise predominantly as a consequence of spray drift and/or transport of residues sorbed to sedime nt entrained in runoff ( i.e ., erosion). In either aquatic or terrestrial environments, tribufos may bioconcentrate and/or bioaccumulate in organisms exposed to it. Additional discussion on the environmental fate of tribufos is presented below.
Table 8 contains the submitted environmental fate data for the pesticide

.

Table 8

. Environmental Fate Data Summary for Tribufos.

Parameter Value Source /Comments

Persistence

Hydrolysis half

- life (50 ° C) No evidence of degradation MRID 41618814- Page 24 of 116

- Parameter Value Source /Comments

Persistence

Aqueous photolysis half

- life (25 ° C) No evidence of degradation MRID 41719401

Soil photolysis half

- life (20 ° C) No evidence of degradation MRID 41618816

Aerobic soil metabolism half

- life (2 5 ° C)
745 d (sandy loam) MRID 4 2007204 Single half

- life
available.

Anaerobic soil metabolism half

- life (2 5 ° C) 389 d (sandy loam) MRID 4 2007205

Aerobic aquatic metabolism half

- life No data Data requirement
waived.

Anaerobic aquatic metabolism half

- life (2 5 ° C) 100 d (flooded silty clay sediment) MRID 43325504

Mobility

Freundlich soil

- water partition coefficients (K F ); 60.6 mL/g ( sandy loam)

66.8 mL/g (sand)

74.3 mL/g (s ilt loam)

106 mL/g (clay loam ) MRID 41618817

Freundlich organic carbon

- normalized coefficients (K FOC ) 1 0

, 465 mL/g ( sandy loam)

12

, 684 mL/g (sand)

4

, 870 mL/g (silt loam)

9

, 115 mL/g (clay loam) MRID 41618817

Do es not follow K
oc

mod el (USEPA, 2008, DP Barcode 357536)

Field Dissipation

Terrestrial field dissipation half

- life 13.9 d (not detected below 15 cm) MRID 45863701



### 3.2.1.1. Transport and Mobility

Tribufos is expected to be relatively immobile in soil, based on Freundlich soil adsorption values that range from 61 to 106 L/kg (MRID 41618817). Because the coefficient of variation (COV) for Freundlich soil adsorption (K F 

### ) values (0.26) is less than that for values normalized for organic carbon (K FOC 

### ) (0.36), tribufos does not conform to the organic carbon partitioning model (USEPA, 2006) . However, surface water contamination may occur via spray drift and/or from the transport o f residues sorbed to sediment that is suspended in runoff ( i.e. , erosion). Based on the tendency of the compound to bind to soil, significant groundwater contamination as a result of tribufos use is not expected.

Tribufos may dissipate in the environme nt partially through volatilization, although th e potential for volatilization from soil and water is expected to be low to moderate. Tribufos’ moderately low vapor pressure (1.7 x 10

- 6 

### torr at 20oC; MRID 41618803) and Henry’s Law constant (calculated to be 3.1 x 10

- 7 atm

- m 3 

### /mol at 20°C) indicate that the compound is semi

- volatile. In a submitted foliar washoff study, 7.6% of the applied tribufos volatilized during the 15 days after foliar application. However, volatilization was not observed in other submitted environmental fate studies. Based on a quantitative structure

- activity relationship (QSAR) estimation method, volatilized (vapor phase) tribufos is predicted to be degraded in the atmosphere by reaction with photochemically

- produced hydroxyl ra dicals, with an estimated atmospheric half

- life of 1.6
hours ( EPI Suite v.4.11, 2012)

.- Page 2 5 of 116

- 

### The potential for moderate volatilization has been reviewed by the California Department of Pesticide Regulation (CDPR) in which a panel reviewed the open li terature on ambient air concentrations of tribufos as of August 1998 (Scientific Review Panel, 1999) . The panel highlighted two monitoring studies in which air concentrations in California Central Valley towns near cotton fields ranged from nondetectable ( i.e ., less than 1.1 ng/m 3 

### ) to 548 ng/m 3



### , indicating that photode gradation in the atmosphere may not consistently remove all of the pesticide . Furthermore, CDPR has found that tribufos is readily photodegraded to the volatile transformation product, n

- butyl mercaptan, and possibly to n

- butyl disulfide (CADPR, 1999)

. However, these photodegradates were not observed in environmental fate studies su bmitted to the Agency. CDPR listed the end

- use product DEF ( i.e ., tribufos) as a Toxic Air Contaminant (TAC) due to a slight carcinogenic ri sk from tribufos in ambient air

.

3.2.1.2. Degradation

Tribufos degraded very slowly (745

- day half

- life) in a single aerobic sandy loam soil (25°C; MRID 42007204). Th us , tribufos is apparently more persistent than is typical for most organophosphate chemicals. The only major degradate observed in the aerobic soil metabolism study was 1

- butane sulfonic acid (1

- BSA), identified at approximately 10% of the applied radioactivity 9 months after trea tment.

A half

- life of 389 days was calculated for tribufos in anaerobic sandy loam soil (MRID 42007205)

, and a half

- life of approximately 100 days was calculated for tribufos in anaerobic flooded silty clay sediment (MRID 43325504). The primary degrada te, 1

- BSA, was a minor degradate in anaerobic soil. However, it was a major degradate in the anaerobic aquatic ( i.e

., flooded sediment) system, at up to 29.5% to 30.6% of the applied radioactivity 6 to 9 months
after treatment. A naerobic aquatic metaboli sm followed a n atypical biphasic pattern, with degrad ation occurring slowly during the first 2 months

, and more rapidly thereafter . The
observed d egrad ation half

- life ( DT 50 

### ) was 4 to 6 months; however, the linearly regressed half

- life
for the duration of the study was approximately 2 months. No explanation was provided for the atypical degradation pattern. A single, nonlinearly regressed half

- life of 100 days was selected

to represent the benthic zone degradation rate in modeling

.

3.2.1.3. Field Studies

In a supplemental terrestrial field dissipation study conducted on a bare ground plot at a single
site in Mississippi (MRID 45863701), the half

- life for dissipation of tribufos in the top 15 cm of sandy loam soil was 13.9 days. The dissipation pattern was biphasic in this study, with an initial rapid decline through approximately 28 days post

- treatment, f ollowed by slower dissipation for the duration of the study period. Tribufos did not leach below the 15

- cm depth. The major route of dissipation of tribufos under terrestrial field conditions was not reported. The patterns of
formation and decline of tr ansformation products were not addressed and the transformation products were not identified in the study; therefore, it could not be determined whether the study duration was adequate to capture such information. In addition, only one site representative of the intended tribufos use site (cotton) was studied. The dissipation half

- life from this study is not consistent with the laboratory fate data and suggests that there are dissipation pathways (such as- Page 26 of 116

- 

### volatilization) that have not been addressed in la boratory fate studies. A cropped plot (with foliar treatment) was not studied.

3.2.1.4. Monitoring Data

M onitoring data are available for tribufos. Groundwater monitoring was conducted by the CDPR, the Department of Health Services and the U.S. Geologic al Survey (USGS) between
1986 and 1994 (CADPR, 2004b)

. All of the samples from 465 wells in 16 California counties yielded non

- detectable residues (< the LOQ of 0.01 ppb).

Surface water monitoring conducted by C DPR between 1991 and 2003 yielded positive detections (at the LOQ of 0.01 ppb) in only 2 of 810 samples from 15 counties (CADPR, 2004a)

. However, data from more recent years ( e.g ., 2007, 2009) from USGS’s National Water Quality Assessment ( NAWQA ) program show multiple detection s in CA surface water samples, at up to 0.3 μg/L; tribufos was also detected in surface water samples from Texas at up to that maximum
level. There are NAWQA surface water monitoring data available for CA, TX, AL, AK

, AZ, CO, CT

, FL, GA

, IA, ID

, IL, IN, KY, MD, MI, MN, MO, MS, NC, NE , NJ, NM, NE, NY, OH, OR, PA, SC, TN, TX, UT , VA and WA. Generally tribufos levels in surface water are <0.035 μg/L, although there are multiple detections greater than that in several states including CA and

TX. NAWQA s edim ent monitoring data are reported for IA , IL , IN, KS , KY, MN, NE , OH, SD,

TX through 2013 . The maximum level reported in sediment is 5.1 μg/kg for a sample from Texas. Generally tribufos levels in sediment are <2.2 μg/kg.

3.2.1.5. Bioconcentration Data

Bioconcentration factors (BCF) for tribufos residues in bluegill sunfish were determined to be 300X for edible tissue, 1300X for inedible tissue, and 730X for whole fish tissues (MRIDs 41618811, 43080401 ). The 730 L/kg BCF value is based on measured radio activity associated with tribufos in the water and tissue with 28 days of exposure. This was the highest BCF value reported in the study for whole fish with a 35

- day exposure period, confirming that equilibration was likely achieved. After 14 days of de puration, 71

- 88% of residues were eliminated from fish tissues. Parent tribufos was the only compound detected in the edible tissue and water samples. In inedible tissue, tribufos parent was the major extractable residue at 33 to 46.2 % of radioactivity. In addition to parent, 47 other metabolites (radio

- labeled compounds) were extracted from the inedible tissue; however, only three were identified, at between 3% and 4% of the measured radioactivity. Unidentified unextracted radioactivity accounted for 1 7 to 20% of the radioactivity extracted from fish tissue. The BCF values indicate that tribufos has some potential to bio concentrate , although this may be limited by the metabolism and excretion of the compound

.

Consistent with these BCF values, an octanol

- water partition coefficient (K OW 

### ) of 3.31 x 10 5 

### (log

K OW 

### of 5.52) was determined for tribufos, indicating that tribufos is ol e ophilic (MRID 41618803). Quantitative structure

- activity relationship (QSAR) estimates for tribufos determined using the Estimation Program Interface ( EPI ) Suite ( http://www.epa.gov/oppt/exposure/pubs/episuite.htm ) yielded an octanol

- air partition coefficient (K OA 

### ) of 2.6 x 10 10 

### (log octanol

- air partition coe fficient, K OA 

### , of 10.41). Kelly and- Page 27 of 116

- 

### Gobas (2003) and Armitage and Gobas (2007) concluded that chemicals with log K OW 

### >2 and log K OA 

### >5 have the potential to biomagnify in organisms in terrestrial habitats. Therefore, tribufos has the potential to biomagnify in organisms in terrestrial habitats.

3.2.1.5. Environmental Degradates

The major degradate resulting from environmental degradation processes is 1

- butane sulfonic acid (1

- BSA; Table 9 ). This transformation product w as identified in at least one of the
environmental fate studies at concentrat ions >10% of the applied radioactivity and would typically be considered in the environmental exposure assessmen t

. However, b ecause it does not retain the organophosphate moiety of the parent compound, 1

- BSA is not expected to be as toxic
as tribufos and the degradate is not included in EECs

.

Table 9

. Table of Transformation Products Formed in the Environmental Fate Studies

Chemical

Name Chemical Structure Study Type MRID (s) Maximum %AR (day) Final %AR (study length
or last interval

detected )

Tribufos

S,S,S

tributyl phosphoro

trithioate Aerobic Soil
Metabolism 42007204

̶ 62.3

- 66.8% (360 days)

Anaerobic Soil

Metabolism 42007205

̶ 73.3

- 84.4% (60 days post

flooding)

Anaerobic

Aquatic
Metabolism 43325504

̶ 0.9% (12 months)

Terrestrial
Field Dissipation 45863701

̶ 0.014 μg a.i./g ( 28 days ; 0

- 15 cm)

1

- BSA

1

- butane
sulfonic

acid Aerobic Soil
Metabolism 42007204 6.9

- 9.9% (272 days) ̶

Anaerobic Soil

Metabolism 42007205 3.4% (31 days
post

- flooding) 3.5% (60 days
post

- flooding)

Anaerobic

Aquatic
Metabolism 43325504 29.5

- 30.6% (6

- 9 months) ̶



### 3.2.2. Measures of Aquatic Exposure

3.2.2.1. Surface Water and Sediment Exposure to Tribufos

Surface Water and Sediment Exposure to Tribufos

Using EFED’s standard suite of models, surface water

, sediment pore water, and bulk sediment
EEC s were generated for tribufos for the registered use on cotton. The Surface Water Concentration Calculator (SWCC, v 1.106, May, 2014) , which incorporates the Pesticide Root- Page 28 of 116

- 

### Zone Model ( PRZM ) and the Exposure Analysis Model System ( EXAMS )

, is used to generat e EEC s that may occur in surface water and sediment . The SWCC simulates pesticide transformation on and runoff from an agricultural field (in addition to loadings from spray drift), following applications to crops. The model then simulates resulting conc entrations in an adjacent surface water body. The EXAMS model simulates pesticide concentrations in water due to loading via runoff, erosion, and spray drift, assuming a standard 1

- ha pond, 2

- m deep (20,000 m 3 

### ) with no outlet that borders a 10

- ha treated field. Simulations are for 30 years, from which the Agency estimates peak values that are expected to recur on average once every ten years, based on time series of daily estimated concentrations. The coupled PRZM and EXAMS
models and user’s manuals are available from the U.S. Environmental Protection Agency Water
Models web

- page ( USEPA, 2011b).

Exposure estimates generated using the standard pond are intended as surrogates for potential concentrations in a wide variety of vulnerable water bodies, includ ing prairie potholes, playa lakes, vernal pools, other wetlands, man

- made and natural ponds, and ephemeral and first

- order

streams. Multiple site

- specific factors will tend to make such water bodies more or less vulnerable than the standard pond. Static water bodies that have larger ratios of pesticide

- treated drainage area to water body volume are generally expected to have higher peak concentrations than the standard pond’s EECs. Such water bodies may be smaller in size, and/or have larger drainage are as. However such water bodies may be more likely to overflow and discharge pesticide in their effluent, whereas the EFED standard pond has no discharge. As watershed size increases, it becomes increasingly unlikely that the entire watershed is planted wi th a single crop that is all treated simultaneously with a pesticide. Headwater streams may have peak concentrations that are higher than those predicted for the standard pond, but such concentrations will likely persist for only short periods of time or distance, as they are carried downstream and diluted with water originating elsewhere.

The general chemical and environmental fate data for tribufos listed in Table 8 and 9 were used for g enerating model input parameter values for SWCC (listed in Table 10 and 1 1 ) . C hemical specific and model input values were chosen in accordance with current divisional guidance (USEPA, 2009 ). M odeling was conducted to generate EECs in surface water of tribu fos following a foliar application to cotton 7 days prior to harvest ( harvest date varies with the standard scenario used)

. M odeling was conducted using SWCC with an application rate of 1.1 25 (for all scenarios except CA) or 1. 875 lb a.i./A ( CA scenario only ), applied as either a single
aerial or single ground spray application. Modeling was also conducted for the average application rates described in Section 2 on Overview of Pesticide Use and Usage. M odeling
results are reported in T able 12

.

Table 10

. SWCC Chemical Specific I nput P arameter V alues for M odeling T ribufos U se on C otton.

INPUT PARAMETER (units) VALUE(S) SOURCE COMMENT

Molecular weight (g/mol) 314.54 g/mol MRID
41618803 −

Henry’s Law Constant (atm

m 3 /mol ; 20oC ) 3.1 x 10

- 7 atm

m 3 /mol MRID
41618803 −- Page 29 of 116

- INPUT PARAMETER (units) VALUE(S) SOURCE COMMENT

Vapor Pressure ( T orr ; @ 2 0 oC ) 1.7 x 10

- 6 T orr MRID
41618803 −

Solubility in Water ( mg/L @ 20oC; pH 7 ) 2.3 MRID
41618803 −

Soil partition coefficient K FD (mL/g) 76.9 mL/g MRID
41618817 Mean K FD (x=4), per EFED guidance. 1 Does not follow K
oc model.

Hydrolysis (t 1⁄2 in days ; pH 7 ) Stable MRID
41618814 −

Aqueous Photolysis (t 1⁄2 in days ; pH 7 ) Stable MRID
41719401 −

Aerobic Soil metabolism half

life ( 25°C; t 1⁄2 in days) 2235 (sandy loam) MRID

4 2007204 Input value is three times the study
half

- life to account for uncertainty in using a single half

- life, per EFED guidance. 1

Anaerobic aquatic metabolism
half

- life ( 25°C, t 1⁄2 in days) 300 MRID
43325504 Input value is three times the study
half

- life (100 days) to account for uncertainty in using a single half

- life, per EFED guidance. 1

Aerobic Aquatic metabolism
half

- life ( 25°C; t 1⁄2 in days) 4470 MRID

4 2007204 Input value is two times the aerobic soil input value, per EFED guidance. 1

1 Input Parameter Guidance found at http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm

.



### Table 11

. SWCC S cenario(s) and In puts for Mo deling Tri bufos U se on Cotton

. Geographic
Area Type of Rate SWCC Scenario Applic. Rate (lbs a.i./A)

[kg/ha] Applic. Date Source/Comments 1

National Max label MS Cotton 1.125 [1.26] Sept. 15 (single application) Aerial spray/foliar Ground spray/foliar

National Max label NC Cotton 1.125 [1.26] Oct. 25 (single application) Aerial spray/foliar Ground spray/foliar

National Max label TX Cotton OP 1.125 [1.26] Sept. 9 (single application) Aerial spray/foliar Ground spray/foliar

California
and Arizona Max label CA Cotton w/irrig 1.875 [2.1] Nov. 4 (single application) Aerial spray/foliar Ground spray/foliar

National Average MS Cotton 0.54 [0.61] Sept. 15 (single application Aerial spray, foliar

California Average (CA rate) CA Cotton w/irrig 0.64 [0.72] Nov. 4 (single application) Aerial spray/foliar

Arizona Average (AZ rate) CA Cotton w/irrig 0.77 [0.86] Nov. 4 (single application) Aerial spray/foliar

1 The aerial spray drift fraction for the EPA pond is 0.125 (USEPA, 2013) . The ground spray drift fraction for the EPA pond is 0.062 (USEPA, 2013)

. 

### The modeled aquatic EECs resulting from the tribufos use on cotton ( listed in Table 12 ) were used for risk estimation in this assessment. Bolded values indicate the maximum EECs for- Page 30 of 116

- 

### maximu m and average application rates, both of which are associated with aerial spray. Selected model input and output files supporting these values are presented in Appendix A

.

Table 12

. Modeled Aquatic Surface Water 1

- in

- 10

- year EECs for Tribufos on Cotton

.

Crop Scenario

(application date) App Rate (lbs a.i./A) 1

- in

- 10 year Surface Water (μg/L0 1

- in

- 10 year Pore

Water 1

- in

- 10 year Bulk

Sediment (μg/kg)

peak daily peak 21

- day

average peak 60

- day

average peak daily peak
21

- day

average peak daily peak
21

- day

average Aerial Spray

- Max Labeled Rate MS Cotton, (9/15) 1.125 29.7 27.1 25.1 22.4 22.4 173 2 173 2

CA Cotton w/Irrigation (11/4) 1.875 21.2 16.8 14.3 11.7 11.7 904 904

Aerial Spray

– Average Application Rates

MS Cotton (9/15) 0.54 14. 2 12.9 11.9 10. 7 10. 6 827 819

CA Cotton
w/ Irrig ., CA
avg. rate (11/4) 0.64 7.3 5 .8 4.9 4.0 4.0 309 309

CA C otton w/Irrig., AZ
avg. rate (9/15) 0.77 8.7 6.9 5.9 4.8 4.8 370 370

Ground Spray

- Max label rate

MS Cotton (9/15) 1.125 29.0 26.1 23.9 21.5 21.5 1662 1662

1.125
runoff only 26.5 24.0 21.8 19.8 19.6 1531 1515

Ground Spray

– Average Application Rate

MS Cotton (9/15) 0.54 14 .0 12.6 11.6 10.4 10.4 804 804



### 3.2. 3

. Measures of Terrestrial Exposure

3.2.3.1

. Ingestion of Surface Residues by Birds and Mammals

Terrestrial wildlife exposure estimates are typically calculated for birds and mammals, emphasizing a dietary exposure route for uptake of pesticide active ingredients. Avian exposures are considered surrogates for exposures to terrestrial

- phase amphibians and reptiles. For exposure to terrestrial organisms, such as birds and mammals, pesticide residues on food items are estimated, based on the assumption that organisms are exposed to pesticide residues in a given exposure use pattern. For tribufos , applic ation methods for the registered uses include foliar spray. For terrestrial animals, the T

- REX model (Version 1.5. 2 ) 4 

### is used to calculate dietary

- and dose

- based EECs of tribufos for mammals and birds feeding on the site of application. Input values for T

- REX include the maximum single application rates, number of applications, and retreatment interval for a given use and are located in Table 13

. In this assessment, EFED uses a default foliar dissipation half

- life of 35 days as an input for terrestrial exposure modeling in T

- REX. Additionally, foliar dissipation half

- life values between 1 and 35

4 http://www.epa.gov/o ppefed1/models/terrestrial/- Page 31 of 116

- 

### days were explored as input s for terrestrial exposure m odeling in T

- REX

.

Upper

- bound Ken a ga nomogram values based on Hoerger and Kena ga (1972) as modified by
Fletcher et al

. (1994) are used to derive EECs for tribufos exposures to terrestrial mammals and birds based on dietary

- and dose

- based exposures from foliar applications of tribufos ( Table 13 )

. A one

- year time period is simulated. Consideration is given to different types of f eeding strategies for mammals and birds, including herbivores, insectivores and granivores. For dose

based exposures, three weight classes of mammals (15, 35, and 1000 g) and birds (20, 100, and 1000 g) are considered. For more information on estimating exposure to terrestrial organisms,
see the T

- REX User’s Guide 5



### . EECs derived based on mean Kenaga nomogram values were
also evaluated.

5 http://www.epa.gov/oppefed1/models/terrestrial/trex/t_rex_user_guide.htm- Page 32 of 116

- 

### Table 13 . T

- REX Calculated EECs as Food Residues for Terrestrial Animals from Tribufos Uses.

Food Type Dietary

- Based
EEC (mg/kg

diet) Dose

- Based EEC (mg/kg

- body weight)

Mammals and
Birds Birds Mammals

All Size s Classes Small (20 g) Medium (100 g) Large (1000 g) Small (15 g) Medium (35 g) Large (1000 g)

Max Label Rate for Cotton Across U.S Except AZ and CA : 1.125 lbs a.i./A, 1 application Short grass 270.0 307.5 175.4 78.51 257.4 177.9 41.25 Tall grass 123.8 140.9 80.37 35.98 118.0 81.54 18.91 Broadleaf plants/small insects 151.9 173.0 98.64 44.16 144.8 100.1 23.20 Fruits/pods/(seeds, dietary only) 16.88 19.22 10.96 4.907 16.09 11.12 2.578 Arthropods 105.8 120.4 68.68 30.75 100.8 69.68 16.16 Seeds (granivore) N/A 4.271 2.435 1.090 3.575 2.471 0.5729

Max Label Rate for Cotton in AZ and CA : 1.875 lbs a.i./A, 1 application Short grass 450.0 512.5 292.3 130.85 429.0 296.5 68.75 Tall grass 206.3 234.9 133.95 59.97 196.6 135.91 31.51 Broadleaf plants/small insects 253.1 288.3 164.39 73.60 241.3 166.8 38.67 Fruits/pods/(seeds, dietary only) 28.13 32.03 18.27 8.178 26.82 18.53 4.297 Arthropods 176.3 200.7 114.47 51.25 168.0 116.14 26.93 Seeds (granivore) N/A 7.118 4.059 1.817 5.959 4.118 0.9549 Average Rate Used on Cotton Across U.S. Except CA and AZ : 0.54 lbs a.i./A, 1 application Short grass 129.6 147.6 84.17 37.68 123.6 85.40 19.80 Tall grass 59.40 67.65 38.58 17.27 56.63 39.14 9.075 Broadleaf plants/small insects 72.90 83.03 47.34 21.20 69.50 48.04 11.14 Fruits/pods/(seeds, dietary only) 8.100 9.225 5.261 2.355 7.723 5.337 1.238 Arthropods 50.76 57.81 32.97 14.76 48.40 33.45 7.755 Seeds (granivore) N/A 2.050 1.169 0.5234 1.716 1.186 0.2750 Average Rate Used on Cotton in CA : 0.6 4 lbs a.i./A, 1 application * Short grass 153.6 174.9 99.76 44.66 146.4 101.21 23.47 Tall grass 70.40 80.18 45.72 20.47 67.12 46.39 10.756 Broadleaf plants/small insects 86.40 98.40 56.11 25.12 82.38 56.93 13.20 Fruits/pods/(seeds, dietary only) 9.600 10.933 6.235 2.791 9.153 6.326 1.467 Arthropods 60.16 68.52 39.07 17.49 57.36 39.64 9.191
Seeds (granivore) N/A 2.430 1.385 0.6203 2.034 1.406 0.3259 Average Rate Used on Cotton in AZ : 0.77 lbs a.i./A, 1 application + Short grass 184.8 210.5 120.02 53.73 176.2 121.77 28.23 Tall grass 84.70 96.46 55.01 24.63 80.75 55.81 12.940- Page 33 of 116

- Food Type Dietary

- Based
EEC (mg/kg

diet) Dose

- Based EEC (mg/kg

- body weight)

Mammals and
Birds Birds Mammals

All Size s Classes Small (20 g) Medium (100 g) Large (1000 g) Small (15 g) Medium (35 g) Large (1000 g) Broadleaf plants/small insects 103.95 118.39 67.51 30.23 99.11 68.50 15.88 Fruits/pods/(seeds, dietary only) 11.550 13.154 7.501 3.358 11.012 7.611 1.765 Arthropods 72.38 82.43 47.01 21.05 69.01 47.69 11.058 Seeds (granivore) N/A 2.923 1.667 0.7463 2.447 1.691 0.3921 * An average of 1.2 applications a year was estimated by BEAD. This estimate gives a lower bound of average exposure. + An average of 1 .6 applications a year was esti m a ted by BEAD. This estimate gives a lower bound of average exposure.

### 34 3.2.3.2. Residues in Aquatic Food Items for Mammals and Birds

The KABAM model (K OW 

### (based) Aquatic BioAccumulation Model) version 1.0 was used to evaluate the potential exposure and risk of direct effects to birds and mammals via bioaccumulation and biomagnification in aquatic food webs. KABAM is used to estimate potential bioaccumulat ion of hydrophobic organic pesticides in freshwater aquatic ecosystems and risks to mammals and birds consuming aquatic organisms which have bioaccumulated these pesticides. The bioaccumulation portion of KABAM is based upon work by Arnot and Gobas (2004) who parameterized a bioaccumulation model based on PCBs and some pesticides ( e.g ., lindane, DDT) in freshwater aqua tic ecosystems (Arnot and Gobas, 2004) . KABAM relies on a
chemical's octanol

- water partition coefficient (K OW 

### ) to estimate uptake and elimination constants through respiration and diet of organisms in different trophic levels. Pesticide tissue residues are
calculated for organisms at different levels of an aquatic food web. The model then uses pesticide tissue conce ntrations in aquatic animals to estimate dose

- and dietary

- based exposures and associated risks to mammals and birds (surrogate for amphibians and reptiles) consuming aquatic organisms. Seven different trophic levels including phytoplankton, zooplankton, benthic invertebrates, filter feeders, small

- sized (juvenile) forage fish, medium

- sized forage fish, and larger piscivorous fish, are used to represent an aquatic food web. Importantly, chemical metabolism by biota is assumed to be zero in KABAM unless ev idence indicates such metabolism is likely to affect the model predictions substantially. Measured BCF values are lower than what would be expected based on tribufos’ log K OW 

### of 5.5 and metabolites were observed in the BCF studies, indicating that tribufos is metabolized in fish. Input scenarios and parameters were chosen to represent the range of exposures from high to low and are presented

in Table 14

. Example output from the bioaccumulation model is provided in Appendix I

.

Table 14

. Bioaccumulation Model Input Values for Tribufos

.

Parameter Input Value Source

Pesticide Name Tribufos

-- Log K OW 5.52 MRID 41618803

K OC 9284 M ean K OC value from MRID 41618817

. Because the coefficient of variation for Freundlich soil adsorption (K F ) values (0.26) is less than that for values normalized for organic carbon (K FOC ) (0.36), tribufos does not conform to the organic carbon partitioning model (USEPA, 2006)

. Therefore , there is uncertainty in the KABAM model output.

Pore water EEC (μg/L) 22.4 Maximum 1

- in

- 10 year 21

- day average value from surface water modeling. The estimated time to reach steady state was 93 days.

Water column EEC (μg/L) 25.1 Maximum 1

- in

- 10 year 60

- day average value surface water modeling. The estimated time to reach steady state was 93 days.



### Based on KABAM results, estimated concentrations of tribufos residues in the tissue of organisms in the different trophic levels following application on cotton range from 35 6 to 2,250

m g/kg

- tissue ( Table 15 ). The measured bioconcentration potential in whole fish of tribufos in bluegill sunfish was 730 L/kg

, and is lower than BCF values estimated in KABAM modeling (Cleveland and Hamilton, 1983) . The maximum BCF from KABAM was 15,912 L/Kg in the
whole fish

, suggesting th at the model estimates exag g erate residues in fish and that fish may be
able to metabolize tribufos

.

### 35 Table 15

. Predicted concentrations of tribufos in aquatic organism tissues at different trophic levels ( μg/kg)

.

Use Scenario Phytoplankton Zooplankton Benthic

Invertebrates Filter

Feeders 1 Small
Fish Medium
Fish Large
Fish

MSCotton (1.1 lbs a.i./A) 355,660 306,175 363,261 238,200 669,880 1,027,363 2,250,493

1 Filter feeders include clams, krill, sponges, whales, and many fish and may be vertebrates or invertebrates.



### Because a reliable metabolism rate constant cannot be generated to parameterize KABAM, the empirical BCF values for fish was used to estimate tribufos concentrations in aquatic organisms.
The e mpirical bioconcentration factors (BCF) for tribufos is 730 L/kg for whole fish. Maximum

1

- in

- 10

- year 60

- day average EECs for the scenarios explored for aquatic modeling ranged from
11.6 to 25.1 μg/L. The estimated concentrations in aquatic organisms resul ting from this range of
EECs are used in combination the measured BCF to bracket the potential concentrations of
tribufos in aquatic vertebrate tissues (at steady state). It should be noted that tissue concentrations in aquatic vertebrates will likely be limited by toxicity of tribufos on these organisms. For instance, the NOAEC for aquatic vertebrates exposed to tribufos is 4.1 μg a.i./L. At this concentration, there were reductions in growth and post

- hatch survival. Given that we expect a range of sens itivit ies in different aquatic invertebrates, some sensitive aquatic
vertebrates would be expected to experience effects at the estimated concentrations while less sensitive species could carry residues in tissue without showing effects. Assuming EECs of 1 1.6 to 25.1 μg a.i./L and a BCF value of 730 L/kg , tribufos concentrations in aquatic vertebrate tissues may range from 8

. 5 to 18 m g a.i./kg (diet ) (BCF x EEC = Concentration in fish).

3.2.3.4. Exposure to Honey bee s

Potential risk to bees is assessed in this document according to the tiering process described in
the Guidance for Assessing Pesticide Risks to Bees (USEPA et al., 2014)

. As part of the Tier I risk assessment, screening

- level exposures are estimated in pollen and nectar using generic residue data generated from other chemicals as well as othe r plant parts as described Table 16

. For dietary exposures resulting from foliar applications, it is assumed that pesticide re sidues on tall grass (from the K enaga nomogram of T

- REX) are a suitable surrogate for residues in pollen and nectar of flowers that are directly sprayed during application. For contact exposure, exposure is based on the work of Koch and Weisser 6 

### (Koch and Weißer, 1997)

. For soil applications, pesticide concentrations in pollen and nectar are assumed to be consistent with chemical concentrations in the xylem of barley (calculated using the Briggs’ model). F or seed treatments, pesticide concentrations in pollen and nectar are based on concentrations in leaves and stems of treated plants (based on the European and Mediterranean Plant Protection Organization (EPPO) default value discussed in the White Paper), a ssumed to be 1 milligram per

6 Koch, H. and P. Weißer. 1997. Exposure of honey bees during pesticide application under field conditions. Apidologie

, 28 : 439

- 447.

### 36 kilogram (mg/kg) or 1 part per million (ppm). More details on these methods are available in the
in the T

- REX User’s Guide 7



### .

The Tier I method is intended to generate “reasonably conservative” estimates of pesticide

exposure to honey bee s which are then refined using available empirical residue data from a variety of crops ; however, these data are not available for tribufos . The Tier I exposure method is intended to account for the major routes of pesticide exposure that are relevant to bees ( i.e

., through diet and contact). Exposure routes for bees differ based on application type. Under the approach used in this assessment, bees foraging in a field treated with a pesticide through foliar spray could potentially be exposed to the pesticide through direct spray, i.e. , contact, as well as through consuming tribufos residues in pollen and nectar. Table 16 summarizes exposure estimates for honey bees for the Tier I assessment.

Table 16 . Screening

- level EECs for honey bee s based on foliar applications

.

Use Exposure
Route Exposure Estimate Calculation 1 Life

stage EEC (μg

a

. i

. /bee/da y)

Max Label Rate for Cotton Across U.S Except AZ and CA: 1.125 lbs a.i./A, 1 application Contact APP*(2.7 μ g a

. i

. /bee) Adults 3.03

Diet APP*(110 μ g a.i /g)*(0.292 g/day) Adults 36.1

Diet APP*(110 μ g a.i /g)*(0.124 g/day) Brood 15.3

Max Label Rate for Cotton in
AZ and CA: 1.9 lbs a.i./A, 1 application Contact APP*(2.7 μ g a.i. /bee) Adults 5.06

Diet APP*(110 μ g a.i /g)*(0.292 g/day) Adults 60.2

Diet APP*(110 μ g a.i /g)*(0.124 g/day) Brood 25.6 Average Rate Used on Cotton

Across U.S. Except CA and AZ: 0.54 lbs a.i./A, 1 application Contact APP*(2.7 μ g a

. i

. /bee) Adults 1.46

Diet APP*(110 μ g a.i /g)*(0.292 g/day) Adults 17.3

Diet APP*(110 μ g a.i /g)*(0.124 g/day) Brood 7.37

Average Rate Used on Cotton in CA: 0.64 lbs a.i./A, 1 application* Contact APP*(2.7 a

. i

. /bee) Adults 1.73

Diet APP*(110 μ g a.i /g)*(0.292 g/day) Adults 20.6

Diet APP*(110 μ g a.i /g)*(0.124 g/day) Brood 8.73 Average Rate Used on Cotton in AZ: 0.77 lbs a.i./A, 1 application+ Contact APP*(2.7 a

. i

. /bee) Adults 2.08

Diet APP*(110 μ g a.i /g)*(0.292 g/day) Adults 24.7

Diet APP*(110 μ g a.i /g)*(0.124 g/day) Brood 10.5
APP = application rate in lbs ai/A * An average of 1.2 applications a year was estimated by BEAD. One application was modeled based on the recommendation from BEAD that more than one application per year is not expected to occur. + An average of 1.6 applications a year was estimated by BEAD. One application was modeled based on the recommendation from BEAD that more than one application per year is not expected to occur.

1 Based on food consumption rates for larvae (0.124 g/day) and adult (0.292 g/day) worker bees and concentration in pollen and nectar.



### 3. 2

. 3.2. Runoff and Spray Drift to Terrestrial and Semi

- Aquatic Plants

TERRPLANT (Version 1.2.2) 8 

### is used to calculate EECs for non

- target plants that inhabit dry
and semi

- aquatic areas. In this assessment, exposure to non

- target plants is calculated based on the potential runoff and spray drift of foliar applications of tribufos and potential runoff after soil and seed treatment applications ( Table 17 ). TERRPLANT does not account for particulate drift.

7 http://www.epa.gov/oppefed1/models/terrestrial/trex/t_rex_user_guide.htm

8 http://www.epa.go v/oppefed1/models/terrestrial/

### 37 Table 17 . EECs for Non

- target Terrestrial and Semi

- aquatic P lants for Tribufos (based on TERRPLANT)

.

Uses App Technique Single Max. App. Rate (lbs a

. i

. /A) EECs (lbs a

. i

. /A)

Semi

- Aquatic Areas (Total) Dry Areas (Total)

Max Label Rate for Cotton Across U.S Except AZ and CA Foliar 1.125 0.16875 0.0675

Max Label Rate for Cotton in AZ and CA Foliar 1.875 0.28125 0.1125

Average Rate Used on Cotton Across U.S. Except CA and AZ Foliar 0.54 0.081 0.0324

Average Rate Used on Cotton in CA* Foliar 0.64 0.096 0.0384

Average Rate Used on Cotton in AZ+ Foliar 0.77 0.1155 0.0462

App = Application * An average of 1.2 applications a year was estimated by BEAD. This estimate gives a lower bound of average exposure. + An average of 1.6 applications a year was estimated by BEAD. This estimate gives a lower bound of average exposure.



### 3.3

. Ecological Effects Characterization

The ecological effects characterization for tribufos is based up on registrant

- submitted toxicity
data for the technical grade active ingredient ( TGAI ) and for formulations

. The ecotoxicity data for tribufos and its associated products have been reviewed previously in multiple ecological risk

assessments (USEPA, 2000) (USEPA, 2008) and in a Preliminary Problem Formulation for Registration Review (USEPA, 2008 , DP Barcode 357536)

. These data are summarized briefly in
Sections 3.3.1 and 3.3.2. Various studies with terrestrial and aquatic plants, birds, and aquatic animals exposed to either the TGAI or formulated tribufos have been received since the Problem
Formulation was issued in 2008 ; the results of these studies are described briefly in this section

.

T he results of a 2015 review of the Ecological Incident Information System (EIIS) are described

in Section 3.3.3 (USEPA, 2012a) . A search of the public ECOTOXicology database in March
2015 and the EFED ECOTOX refresh report (February 2014) , yielded no new data from suitable
studies with more sensitive (lower) toxicity endpoints than those previously used in risk

assessments 9



### . Data meeting the OPP’s standard for inclus ion in risk assessment ( http://www.epa.gov/pesticides/science/literature

- studies.html ) were available in ECOTOX that showed greater sensitivity than results from submitted studie s for freshwater fish (Mayer and Ellersieck, 1986, MRID 40098001, ECOTOX Number 6797) and daphnids (Brausch et al. , 2010,
ECOTOX Record Numb er 156445; Mayer and Ellersieck, 1986, MRID 40098001, ECOTOX Number 6797)

. The Mayer and Ellersick (1986) results for freshwater fish and daphnid were included in previous risk assess m e nts; however, the endpoints were updated in this risk
assessment because the raw data were obtained and statistically analyzed , resulting in the most sensitive toxicity endpoints for freshwater fish and daphnid

. The endpoints from the ECOTOX

catalogued open literature studies are provided in Appendix G , for reference. Tables summarizing registrant

- submitted ecological toxicity data, and open literature results found to be more sensitive to registrant submitted studies or that provided additional informa tion on

9 There were some endpoints that were lower in the ECOTOX report; however, the endpoints were not considered
reliable for use in risk assessment.

### 38 mollusks , amphibians, or reptiles are available in Appendix C

.

3.3.1. Aquatic Toxicity Assessment

A summary of the most sensitive toxicity endpoints for aquatic organisms is shown in Table 18

. These endpoints will be used to calculate risk quotient s.

The available data indicate that tribufos TGAI is highly toxic to freshwater fish and highly toxic

to estuarine/marine fish on an acute exposure basis. Tribufos is very highly toxic to highly toxic

to freshwater invertebrates and highly toxic to estuar ine/marine invertebrates on an acute exposure basis. Acute toxicity s tudies on the toxicity of formulated product DEF6 ® 

### ( 72.3% a.i.)

w ere submitted for freshwater f ish and aquatic invertebrates. The studies conducted with TGAI
resulted in lower (more sensitive) endpoints. Effects o n growth were observed in chronic fish
studies at 19 μg a.i./L and effects on post

- hatch survival were observed at 39 μg a.i./L

. Effects

on reduced number of young/adult/day and reduced adult length were observed in chronic water flea studies at 3.5 μg a.i./L

. Effects on frond count were observed in the v a scular aquatic plant duckweed ( Lemna gibba ; EC 05 

### =140 μg a.i./L) and inhibited growth was observed when
nonvascular freshwater green alga ( Pseudokirchneriella subcapitata ) were exposed to tribufos at 254 μg a.i./L.

Table 18 . Summary of Most Sensitive Toxicity Data for Aquatic Organisms Exposed to Tribufos (TGAI) and Formulations.

Common Name (Species) Study Type

and ( Duration of

Exposure) Test
Substance

(% a.i.) Endpoint (Effect Observed

at Endpoint) Toxicity Value (95% CI)

μ g a.i./L 3 (Acute Toxicity Category) MRID Study
Classification 1

Freshwater Vertebrates

Bluegill sunfish ( Lepomis macrochirus ) Static ( 96

- hour ) TGAI LC 50 (Survival) 283 (136

- 378) Slope=6.23 (highly toxic) 40098001 Supplemental

Quantitative Bluegill sunfish ( Lepomis macrochirus ) Chronic

-- NOAEC 4.1 Estimated 2

Estuarine/Marine Vertebrates Sheepshead minnow (Cyprinodon variegatus ) Acute
Flow

- through

96

- hour TGAI (98.6%) LC 50 (Survival) 767 (560

- 1370) (highly toxic) 41896302 Acceptable

Sheepshead minnow (Cyprinodon variegatus ) Early Life Cycle /
Flow

- through (36

- day) TGAI (99.4%) NOAEC/ LOAEC (growth ) 11/ 19 45863707 Acceptable

Freshwater Aquatic Invertebrates

Water flea (Daphnia magna) Static (48

- hour) TGAI

Not
available EC 50 (Immobility) 5.4 (3.5

- 7.7) Slope=2.5 (very highly toxic) 40098001 Supplemental

Quantitative

Water flea (Daphnia magna) Static

- renewal (21

- days) TGAI (97.2%) NOAEC/ LOAEC (reduced number of

young/adult/day

and reduced adult length) 1.56/

3.23 4 43978201 Acceptable

### 39 Common Name (Species) Study Type

and ( Duration of

Exposure) Test
Substance

(% a.i.) Endpoint (Effect Observed

at Endpoint) Toxicity Value (95% CI)

μ g a.i./L 3 (Acute Toxicity Category) MRID Study
Classification 1

Hyalella ( Hyalella azteca) (Amphipod) Spiked

sediment (10

- day) TGAI (98.2%) NOAEC LOAEC (Growth) 71/ 220 μg a.i./kg

sediment 2.81/8.27 μg/L pore

water 49164802

Acce p t able

Estuarine/marine Aquatic Invertebrates Mysid shrimp ( Americamysis bahia formerly Mysidopsis
bahia ) Flow

- through (96

- hour) TGAI (96.4%) LC 50 (Survival) 11.53* (9.30

- 15.11) (very highly toxic) 41896301 Acceptable

Mysid shrimp ( Americamysis bahia formerly Mysidopsis
bahia ) Flow

- through (96

- hour) TGAI NOAEC/ LOAEC (None) 0.26/ >0.26* 42083201 Acceptable

Marine Amphipod (Leptocheirus plumulosus ) Spiked
sediment (10

- day) TGAI (98.2%) NOAEC/
LOAEC (Mortality) 207 /773 μg/kg

sediment 7.10/22.7 μg a.i./L

pore

- water 49164801 Acceptable

Aquatic Plants

Duckweed ( Lemna gibba ) Static Renewal

14

- day TGAI (99.4%) EC 50 (Frond Count) 1100 (760

- 1700) 45863705 Supplemental

quantitative EC 05 140 (35

- 570)

Freshwater green alga ( Pseudokirchneriella

s ubcapitata 1 ) 7

- day TGAI (99.9%) EC 50 (Percent inhibition) 148 41618813 Acceptable

NOAEC/ LOAEC 118/ 254* 41618813 Acceptable
TGAI=technical grade active ingredient: *Represents the most sensitive toxicity endpoint to be used in RQ calculations.

1 Supplemental studies may or may not be suitable to calculate RQs. Quantitative values are suitable for calculation of RQ. Q ualitative values are not considered suitable for calculation of RQs but may be useful in understanding the weight of evidence for evaluating the likelihood of risk.

2 This NOAEC is based on the acute

- to

- chronic ratio using sheepshead minnow endpoints [767/11=69.7 (ACR)] and the 96

- hour LC 50 of the bluegill sunfish

. 3 Endpoints are for water

- column, unless otherwise stated.

4 The AC R for daphnid is 3.5 (5.4/1.56).



### 3.3.1.1. Toxicity to Aquatic Vertebrates

On an acute exposure basis, tribufos is highly toxic to freshwater fish, with 96

- hour LC 50 

### values ranging from 245 to 920 μg a.i./L across two tested species. Only a single estuarine/marine fish acute study was provided for tribufos on the sheepshead minnow ( Cyprinodon variegatu s ; MRID
41896302 ) , which resulted in a 96

- hour LC 50 

### of 767 μ g a.i. /L

.

Two freshwater fish early

- life cycle studies were submitted; however, the results from the tests are not considered suitable for calculation of risk quotients due to either the presence of tribufos
near the limit of detection in controls or statistic ally significant (p<0.05) effects observed with
the solvent control relative to the negative control

. In orde r to derive a chronic freshwater fish toxicity endpoint for calculation of risk quotients , an acute

- to

- chronic ratio (ACR) based upon

### 40 data from th e sheepshead minnow was applied to the bluegill sunfish acute toxicity endpoint 10 

### resulting in a chronic toxicity value (NOAEC) of 4.1 μg a.i./L. The consistency of the acute toxicity values for saltwater and freshwater species suggests that saltwater species are not considerably more or less sensitive to tribufos than freshwater species.



### Available data ( Appenidix C ) indicate that DEF6 ® 

### is not substantially (more than an order of magnitude) more toxic to freshwater fish as compared to tribufos TGAI on an acute exposure basis.

Chronic toxicity to estuarine/ marine fish was evaluated in a 36

- day early life stage test with the sheepshead minnow (Cyprinodon variegatus ; MRID 45863707 ) , the NOAEC and LOAEC were 11 and 19 μg a.i./L, respectively, based on ef fects observed on growth. For all growth endpoints, statistically significant (p<0.05) differences were observed at the mean

- measured concentration of 19, 39, and 81 μg a.i./L. The percent juvenile survival of 51% at 39 μg a.i./L was significantly differ ent (p<0.05) than the juvenile survival at 19 μg a.i./L of 86%, resulting in a
NOAEC and LOAEC of 19 and 39 μg a.i./L , respectively

.

3.3.1.2. Toxicity to Aquatic Invertebrates

On an acute exposure basis, tribufos is highly to very highly toxic to freshwater invertebrates,
with water

- column 48

- hour LC 50 

### values ranging from 5.4 to 110 μg a.i./L for the water flea ( Daphnia magna ) . Estuarine/marine inver tebrate acute toxicity studi es were provided for tribufos on the mysid shrimp ( Americamysis bahia formerly Mysidopsis bahia ; MRID
41896300 ) and the 96

- hour LC 50 

### value was 11.5 μg a.i/L. The 96

- hour EC 50 

### for inhibition of shell growth for the E astern oyster ( Crassostrea virginica ; MRID 45863702) was 39.6 μg a.i./L. These endpoints indicate that tribufos is very highly toxic to estuarine/marine invertebrates on an acute exposure basis.

Chronic toxicity data are available for the water flea and the mysid shrimp, the most sensitive species based on acute toxicity data. For the water flea, the 21

- day NOAEC/ LOAEC was 1.56
/3.23 μg a.i./L (MRID 43978201) based on statistically significant ( p<0.05) reduction in number of young/adult/day and reduced adult lengt h

. For the mysid shrimp, the 28

- day NOAEC/LOAEC was 0.26/>0.26 μg a.i./L because no treatment related effects were observed in the study.

Sediment toxicity studies were submitted since the previous risk assessments and problem formulations were completed. In a 10

- day spiked sediment test for the freshwater amphipod ( Hyalella azteca )

, NOAEC/ LOAEC for reduced growth were 2.81/8.27 μg a.i./L in pore water
and 71/220 μg a.i./kg

- sediment . There was a 39% reduction in weights at the LOAEC. In a 10

- day spiked sediment test for the marine amphipod ( Leptocheirus plumulosus ), the NOAEC/
LOAEC were 207/ 773 μg a.i./ kg

- sediment and 7.10/ 22.7 μg a.i./L pore water based on mortality . There was 74% survival at 22.7 μg a.i./L pore water, as compared to 89 to 90% survival in other treatments and controls. These endpoints will be used to evaluate risk to

10 The ACR was calculated as the sheepshead minnow 96

- hour LC 50 of 767 μg a.i./L divided by the 35

- day NOAEC for the sheepshead minnow of 11 μg a.i./L resulting in an ACR of 69.7. The chronic bluegill sunfish endpoint was calculated by dividing the bluegill sunfish 96

- hour LC 50 of 283 μg a.i./L divided by the ACR of 69.7.

### 41 sediment

- dwelling freshwater and estuarine/marine invertebrates

. Because a definitive
estuari ne/marine chronic endpoint for aquatic invertebrates is not available in the water

- column, the pore water NOAEC of 7.10 μg a.i./L for the estuarine/marine amphipod, will be used to evaluate risk in the water column for estuarine/marine aquatic invertebrate s.

Typically , sediment data are also recommended for the freshwater midge ( Chironomus dilutus ). The midge , a Dipteran, and Hyalella , an amphipod

, have different life histories, occupy different taxonomic groups (insects versus crustaceans ) and generally interact with sediments in different ways. Chironomid larvae are more infaunal (submerged in sediment) whereas amphipods are more epibenthic (moving in and out of surficial sediment layer). This is an uncertainty in the sediment toxicity dataset.

3.3.1.3. Toxicity to Aquatic Plants

Data on one aquatic vascular plant species and one nonvascular plant species are available. In a 14

- day toxicity study with vascular aquatic plant duckweed, L

. gibba (MRID 45863705 ) exposed

to tribufos TG AI (99.9%)

, statistically significant (p<0.05) effects in frond count were observed.
The 14

- day EC 50 

### was 1100 μg a.i./L and the corresponding EC 05 

### was 140 μg a.i./L

. The percent growth inhibition based on frond count (the most sensitive endpoint) in the treated culture as compared to the control ranged from 26.2 to 69.5%.

In a 7

- day toxicity test, the nonvascular freshwater green alga was exposed to tribufos TGAI ( 99.4%, MRID 41618813 ) , a statistically significant (p<0.05) reduction in percent inhibition was observed at 254 μg a.i./L

. The NOAEC and EC 50 

### /IC 50 

### values based on percent inhibition were
118 and 1 4 8 μg a.i./L, respectively.

Data on a marine diatom ( e.g ., Skeletonema costatum ), freshwater diatom ( e.g ., Navicula pelliculosa ), and cyanobacterium ( e.g ., Anabaena flos

- aquae ) are not available

.

3.3.2. Terrestrial Effects Characterization

A summary of the most sensitive terrestrial animal toxicity data for tribufos , based on a current

EPA review of all submitted data, is provided in Table 19 and is discussed further in Sections
3.3.2.1 to 3.3.2.3. The available data indicate that tribufos TGAI ranges from practically non

toxic to m oderately toxic to five species of birds including passerines and is moderately toxic to mammals on an acute oral exposure basis and highly toxic to mammals on an sub acute

- dietary

exposure basis

. Tribufos is practically nont oxic to young adult honey bees on an acute contact exposure basis.

Bobwhite quail ( Colinus virginianus ) fed diets containing tribufos for 20

- weeks had a reduced eggshell thickness relative to controls at 280 mg a.i./kg

- diet , but no mortality or overt signs of toxicity were observed. L aboratory rats fed diets containing tribufos (260 mg a.i./kg

- diet) had an increased number of litters with stillborn pups relative to controls. Additional endpoints affected include increased pup death through lactation, decreased F1 and F2 pu p body weigh ts, and increased F1 gestation period.

### 42 The available data for terrestrial plants exposed to the formulated product DEF6 ® 

### ( 70.8 % a.i.) provided in Section 3.3.2.4, indicate that tribufos exposure to seeds in treated soils resulted in reduced plant height at application rates equivalent to 0.22 lbs a.i./A and exposure to foliage resulted in reduced plant height and dry weight at application rates equivalent to 0.93 lbs a.i./A

. In a non

- guideline study examining plant defoliation, exposure of deciduous tree saplings and shrubs resulted in a reduction in the number of old leaves left on the plant and an increased weight of fallen leaves at 1.1 25 and 1 .875 lbs a.i./A (NOAEC=0.56 lbs a.i./ A)

.

Table 19 . Summary of the Most Sensitive Toxicity Data for Terrestrial Animals Exposed
to Tribufos.

Common Name (Species) Study Type (Duration of

Exposure) Test
Substance

(% a.i.) Endpoint (Effect at endpoint) Toxicity Value (95% CI) (Acute Toxicity Category) MRID Study
Classification

Birds

Canary ( Serinus canaria) Acute Oral (Oral gavage with 14

- day observation) TGAI (98.2%) ED 50 (Mortality and Regurgitation) 111 mg/kg

- bw (73.7

- 168)* (moderately toxic) 49121303 Supplemental due to regurgitation within one hour of dosing. Bobwhite quail ( Colinus virginianus) Acute Oral (Oral gavage with 14

- day observation) TGAI (92%) LD 50 (Mortality) 151 mg a.i./kg

- bw (128

- 178)* Slope=7.9 (4.3

- 11.5) (moderately toxic) 00120771 Acceptable

Bobwhite quail ( Colinus virginianus) Subacute Dietary (5

- day) TGAI (98.9%) LD 50 (Mortality) 1519 mg a.i./kg

- diet (slightly toxic) 41618804 Acceptable

Bobwhite quail ( Colinus virginianus) Reproduction (20 week) TGAI (98.7%) NOAEC/

LOAEC (egg shell thickness) 150/280 mg a.i./kg

- diet* 40757101 Acceptable

Mammals 2 Laboratory rat (Rattus norvegicus) Acute Inhalation (4

- hour) TGAI LC 50 (Mortality) 4650 mg/m 3 4.65 mg/L 41782301

Laboratory rat (Rattus norvegicus) Acute Oral TGAI LD 50 (Mortality) 192 mg/kg

- bw (practically non

- toxic) 41954903

White footed

mouse ( Peromyscus leucopus ) Sub

- a cute
Diet ary (5

- day) TGAI LC 50 (Mortality) 161 mg/kg

- diet (28.3

- 293.7) Slope=1.73 (0.66

- 2.79) 45863708 Supplemental

Quantitative

Laboratory rat (Rattus norvegicus) Two

- generation Reproduction TGAI NOAEL/

LOAEL (increased
number of
litters with still born pups, see comments) 32 mg/kg

- diet* 1.7 mg/kg/day/

260 mg/kg

- diet 15 mg/kg/day 42040201

Honey bee s

### 43 Common Name (Species) Study Type (Duration of

Exposure) Test
Substance

(% a.i.) Endpoint (Effect at endpoint) Toxicity Value (95% CI) (Acute Toxicity Category) MRID Study
Classification

Honey Bee (Apis mellifera) Acute Contact (48

- hour) Variable.,

Mixed
with pyrolite

dust LD 50 (Mortality) >24.17 μg a.i./bee* (practically nontoxic) 00001999 Acceptable

* Most sensitive endpoint; will be used in RQ calculations.

2 Most m ammalian toxicity endpoints were provided and reviewed by EPA/OCSPP/OPP Health Effects Division



### 3.3.2.1. Toxicity to Terrestrial Animals

A cute oral LD 50 

### values for four bird species (including a passerine species) ranged from 111 to 871 mg/kg

- body weight, indicating that tribufos is moderately to slightly toxic to birds . The 111 mg/kg

- body weight value was based on the effect on both surviv al and regurgitation in the passerine canary ( Serinus canaria)

. Subacute dietary 5

- day LC 50 

### values for two species ranged from 150 to >5000 mg/kg

- diet, indicating that tribufos range d from practically nontoxic to moderately toxic to birds. Clinical signs of toxicity observed in these studies were ruffled feathers, underactivity, incoordination, rec u mbency, body tremors, panting, salivation, and/or regurgitation

.

In 20

- week reproductive toxicity study on the Northern bobwhite quail, the NOAEC and LOAEC were 150 and 280 mg a.i./kg

- diet, based on effects observed on egg shell thickness.
There was also a statistically significant (p<0.05) reduction in egg production (71% reduction) and hatchling survival (56 % reduction ) at 410 mg/kg

- diet relative to controls

.

Available data indicate that tribufos is moderately toxic to laboratory rats ( Rattus norvegicus ) on an acute oral exposure basis, with an LD 50 

### of 192 mg a.i./kg

- bw (MRID 41954903). On a
sub acute

- dietary exposure basis, tribufos is classified as highly toxic based on a 5

- day LC 50 

### of 161 mg/kg

- diet for the white footed mouse ( Peromyscus leucopus ). Chronic exposures to
tribufos during a two

- generation reproduction study in rats (MRID 42040201 ) resulted in a statistical significant (p<0.05) increase in the number of litters with stillborn pups at 260

- mg/kg

diet (15 mg/kg/day) , resulting in a NOAEL of 32 mg/kg

- diet ( 1.7 mg/kg/day)

. Effects on pup death through lactation, decreased F1 and F2 pup weights, and increased F1 gestation period
were also observed at 260 mg/kg

- diet

.

In an acute contact toxicity test , young adult honey bees were exposed to tribufos mixed with pyrolite dust (MRID 00001999 ). There was 3% mortality observed at 24.17 μg a.i./bee

. Based on this limited dataset, tribufos is classified as practically non

- toxic to you ng adult honey bees on

an acute

- contact exposure basis. 11



### As some tier I honey bee toxicity studies are currently unavailable for tribufos, there is
uncertaint y in the risk assessment on the potential for adverse effects on to honey bee s from

11 More information on pollinator data gaps is available in the executive summary.

### 44 exposure to tribufos

.

An additional study identified from the open literature (Greenberg et al. , 2004, ECOTOX Reference Number 92450) i ncludes some i nformation on effects of tribufos on terrestrial invertebrates [specifically boll weevils ( Anthonomus grandis )]. This study is considered supplemental and not adequate for RQ calculation ( e.g ., it is a non

- guideline study; no controls were used in portions of the study; only one concentration was tested). In the laboratory portion of the study, boll weevils sprayed directly with tribufos at an application rate of 0.42 lb a.i./acre (using the DEF ® 

### 6 formulation), which is 22% of the maximum labeled rate, had statistically significantly (p<0.05) higher mortality than controls 72

- hrs post

- spray [42.5% ( standard
deviation ± 2.2) mortality, versus 2.5% ( standard deviation ± 5.0), respectively].

3.3.2.4. Toxicity to Terrestrial Plants

Terrestrial plant toxicity studies are required for pesticides that have terrestrial use patterns or may move off of the application site

. The NOAEL and IC 25 

### (concentration that causes an inhibitory effect in 25% of the population for the binary endpoint s such as survival and emergence or 25% of an effect for continuous endpoints ) values are established for markers of seedling emergence and vegetative vigor.

The submitted Tier II seedling emergence study (MRID 4 5863404) indicated that onion ( Allium cepa) was the most sensitive monocot species tested (NOAEC 0.45 lb a.i./A; EC 25 

### >2.0 lb a.i./A) based on reduced plant height. Soybean ( Glycine max ) was the most sensitive dicot species tested, also based on reduced pl ant height, with a NOAEC of 0.22 lb a.i./A (LOAEC=0.45 lbs a.i./A) and an EC 25 

### of >2.0 lb a.i./A. All other species (monocots and dicots) had NOAEC and
EC 25 

### values at 2.0 lb a.i./A and >2.0 lb a.i./A (the highest rate tested) with the exception of turnip ( Brassica rapa ) , a dicot species with a NOAEC of 0.94 lb a.i./A and LOAEC of 1.9 lbs a.i./A

.

The Tier II vegetative vigor study (MRID 45863704) indicated that corn (monocot ; Zea mays ) and buckwheat (dicot ; Fagopyrum sagiitatum ) were the most sensitive spe cies based on reduced dry weight. The NOAEC and EC 25 

### values for corn were 0.48 lb a.i./A and 1.8 lb a.i./A, respectively. The NOAEC and EC 25 

### values for buckwheat were 0.48 lb a.i./A and 1.3 lb a.i./A, respectively. All other species tested showed that dry weight was the most sensitive endpoint for all species, though ryegrass (monocot ; Lolium perenne ) and sunflower (dicot ; Helianthus

annuus ) did not exhibit effects at any of the rates tested

.

Because tribufos affects the abscission zone in plants, plants that do not form abscission zones are not expected to be as sensitive to tribufos as plants that form abscission zones. While some of the plants tested in guideline vegetative vigor and seedling emergence studies do form abscission zones, the studies may n ot be sensitive to the defoliation endpoint. A non

- guideline plant defoliation study ( MRID 48728101 ) was conducted to better characterize risk to sensitive plant species. The effect of the tribufos formulation Folex ® 

### 6EC (70.5% a.i.) along with an adjuvant (0.1% Activator 90 ® 

### ) on non

- target woody, deciduous shrubs (flowering currant, Ribes sanguineum [ribes], forsythia, Forsythia intermedia , viburnum, Viburnum spp.) and trees (maple,

Acer spp, and oak, Quercus spp) was studied at nomi nal application rates of 0 (negative control), 0.141, 0.281. 0.563, 1.125, and 1.875 lb a.i./acre (0, 0.158, 0.315, 0.63, 1.26, 2.10 kg a.i./ha).

### 45 Both adjuvant and negative controls were run concurrently with treatments.

The study was designed to measure health, growth and survival of woody, deciduous plants exposed to a foliar spray of the formulated product. Eight individually potted shrubs of forsythia, flowering currant

, and viburnum and seven individually potted saplings of maple and oak were
selected for each treatment rate. After treatment, each pot was placed in a sheltered outdoor area.
Plants were bottom

- watered as needed and fertilized once per week. Each day, fallen leaves were collected, counted and dried before being weighed. Each plant was in spected daily over the 28

- day study period for phytotoxicity (chlorosis, necrosis, wilting, leaf and stem deformation) and plant mortality.

Application of the formulated tribufos product Folex ® 

### 6EC at rates of up to 1.875 lb a.i./acre and
in combination with the adjuvant Activator 90 ® 

### (0.1%) resulted in statistically significant (p<0.05) leaf fall in viburnum and maple at treatment rates equivalent to 1.125 and 1.875 lb
a.i./acre a nd in oak at 1.875 lb a.i./acre (NOAEC = 0.563 lbs a.i./A) . These effects w ere accompanied by a reduction in the numbers of old leaves remaining on the plants at the end of
the 28

- day study period. There were no apparent treatment

- related effects on the development of new leaves in the three shrub species, F orsythia, R ibes and V i burnum at any of the treatment rates in comparison to the water

- and adjuvant

- treated controls, or in the limited number of replicates of the two tree species where new growth was recorded.

One study identified from the open literature (Greenberg et al. , 2004, ECOTOX Reference Number 92450) describe s effects (defoliation) to cotton from a tribufos application at a rate of 0.42 lb a.i./acre (using the DEF6 ® 

### ) formulation). At this application rate (which is 22% of the
maximum labeled rate), an average of 80.2% (± SD of 6.1) of the leaves per plant (N = 9) were dropped 7 days post

- application ; whereas

, in the untreated control plot, 3.3% (± SD of 1.6) of the leaves per plant (N = 10) were dropped in the same time period.

Table 20

. Summary of Terrestrial Plants Toxicity Data for Tribufos Formulations.

Crop Formulation (% a.i.) Species E C 25 (lbs a.i./A) NOAEC
or IC 05 / LOAEC (lbs a.i./A) Endpoint
Affected MRID Study Classification

Seedling Emergence

Monocots DEF 6 ® (70.8%) Onion ( Allium

cepa ) >2.0 * 0.45 /0.93* Plant height

45863404 Acceptable

Dicots Soybean ( Glycine

max ) >2.0 * 0.22 /0.46* Plant height

Vegetative Vigor

Monocots DEF 6 ® (70.8%) Corn ( Zea

mays ) 1.8 * 0.48 /0.93* Dry weight, plant height 45863704 Acceptable

Dicots Buckwheat ( Fagopyrum sagiitatum ) 1.3 * 0.48 /0.99* Dry weight

Plant Defoliation Study

Deciduous
shrubs Folex 6EC ®

Cotton
Defoliant Forsythia ( Ribes sanguineum ) Responses not
sufficient to

reliably 1.875 No significant response observed

at highest dose 48728101 Supplemental

### 46 Crop Formulation (% a.i.) Species E C 25 (lbs a.i./A) NOAEC
or IC 05 / LOAEC (lbs a.i./A) Endpoint
Affected MRID Study Classification

Activator90 ®

adjuvant (0.1%) calculate a
dose

- response

curve tested

Viburnum ( Viburnum

spp .) 0.563 */
1.125 Number/weight of
fallen leaves

Deciduous

Tree samplings Maple (Acer spp.) 0.563 */
1.125 Number of old leaves left on plant

Oak (Quercus

Spp.) 0.563 */
1.125 Number of old leaves left on plant

* Most sensitive endpoint used for risk estimation ( i.e. , RQ calculations) or risk description (for non

- definitive endpoints).



### 4. Risk Characterization

4.1. Risk Quotient (RQ) Values

This assessment of the labeled uses of tribufos relies on the deterministic RQ method to provide a metric of potential risks. The RQ provides a comparison of exposure esti mates to toxicity endpoints ( i.e. , estimated exposures divided by acute and/or chronic toxicity endpoints expressed in the same units as exposures, respectively). The resulting unitless RQ values , calculated in the Risk Estimation Section) are compared to the Agency’s LOCs (see Table 5 ) . The LOCs are used by the Agency to indicate when the use of a pesticide, as directed by the label, has the

p otential to result in exposure levels sufficient to cause adverse effects to non

- target organisms. For endangered species, LOC exceedances require an additional in

- depth listed species evaluation to characterize risks for the potential co

- occurrence of li sted species and areas in which crops are grown. In this approach, RQs that exceed non

- listed species LOCs necessarily also exceed the corresponding listed species LOCs. Acute risk LOCs are different for listed and

non

- listed taxa; however, the chronic L OC is 1.0 across all animals

. For plants, unlike for animals, RQ values are not presented for acute versus chronic risk; instead, RQ values are presented for listed and non

- listed species based on a comparison of a given EEC to NOAEL and
EC 25 

### values (for terrestrial plants) and EC 50 

### values (for aquatic plants), respectively. The LOC for all plants is 1.0. A discussion of the RQ values for tribu f os and of other information that provides context for the interpretation of potential risk to various taxa is p resented in the Risk Description in Section 4.2

.

Risk quotients were estimated for maximum labeled rates and for average application rates. Risk
evaluated based on maximum labeled rates reflect s the potential for adverse effects from

exposure if tribuf os is used at the maximum amount allowed on the label. Risk evaluated based on average application rates reflects the potential for adverse effects from exposure if tribufos is used at the average application rate. Some individuals will use tribufos at higher

- than

- average application rates

, and in such cases the risk evaluation based upon average application rates may not be protective for these uses.

### 47 4.1.1

. RQ Values for Aquatic Organisms

The SWCC was used to calculate water

- column, pore water, and bulk sediment 1

- in

- 10

- year peak, 21

- day average, and 60

- day average EECs for aquatic organism s . Toxicity endpoints used to calculate risk quotients are the most sensitive acute and chronic endpoints for each tax o n and are specified in the table showing the RQ value.

Freshwater fish serve as surrogates for aquatic

- phase amphibians. RQ values based on both maximum and average application rates for freshwater fish exposed to tribufos are at or above ( i.e ., exceed) the LOCs (0.05) for acute risk for listed but not non

- listed species LOC (0.5) ( Table 21 ). Similarly, chronic RQ values for freshwater fish exceed the chronic risk LOC (1.0) for both maximum label rates and average application rates

. When the contribution of spray drift to exposure is not simulated and at the maximum labeled rate , RQs still exceed the acute risk to
list ed species LOC and chronic ri sk LOC for freshwater vertebrates.

RQ values based on both maximum label and average application rates for estuarine/marine fish exposed to tribufos are below the LOCs (0.05) for acute risk for listed and non

- listed species (LOC = 0.5) ( Table 21 ). C hronic RQ values for estuarine/marine fish exceed the chronic risk LOC of 1.0 for both maximum label rates and average application rates

, except for averag e application rate simulated using the Califonria cotton scenario and average application rates in
Arizona and California

. When the contribution of spray drift to exposure is not simulated and at the maximum labeled rate, RQs still exceed chronic risk LOC s for estuarine/marine vertebrates.

Table 21 . RQs for Direct Effects to Fish from Tribufos Use on Cotton.

Geographic area and Type of Application App.
Rate (lbs a.i./A) Peak
EECs

(μg a.i./L) 60

- day

average

EECs Risk Quotients

Freshwater Fish Estuarine/Marine Fish

Acute
LC 50 = 283

μg a.i./L Chronic
NOAEC =

4.1 μg a.i./L 1 Acute
EC 50 = 767

μg a.i./L Chronic
NOAEC = 11 μg a.i./L

Maximum Label Rates

– Runoff and Spray Drift Simulated

National Aerial 1.125 29.7 25.1 0.10* 6.12 * 0.04 2.28*

CA and AZ Aerial 1.875 21.2 14.3 0.07* 3.49 * 0.03 1.30*

National Ground 1.125 29.0 23.9 0.10* 5 .83* 0.04 2.17* Average Application Rates

– Runoff and Spray Drift Simulated

National Aerial 0.54 14 11.9 0.05* 2.90* 0.02 1.08*

CA Aerial 0.64 7.3 4.9 0.03 1.20* 0.01 0.45

AZ Aerial 0.77 8.7 5.9 0.03 1.44* 0.01 0.54

National Ground 0.54 14 11.6 0.05* 2.83 * 0.02 1.05*

Maximum Label Rates

– Runoff Only

National Ground 1.125 26.5 21.8 0.09* 5.31 * 0.03 1.98*

CA Ground 1.875 7.53 6.07 0.03 1.48 * 0.01 0.55*

Abbreviations: App.= Application

A bold value with an asterisk indicates that the RQ meets or exceeds the LOC for acute risk ( 0.05) to listed species or meets or exceeds the
chronic risk LOC ( 1) for listed and non

- listed species. The acute risk LOC (0.5) for non

- listed species is not exceeded.

1 Estima ted using the f reshwater fish 96

- hr LC 50 of 283 μg a.i./L and an ACR from estuarine/marine fish.



### All RQ values based on maximum and average application rates for freshwater and a quatic invertebrates exposed to tribufos on an acute exposure basis exceed LOCs for risk to listed

### 48 (LOC=0.05) and non

- listed (LOC=0.5) species ( Table 22 ). All RQ values for freshwater aquatic
invertebrates

, inhabiting both the water

- column and benthic zone, based on chronic exposure to
tribufos

, exceed LOCs for chron ic risk ( Table 22 and 23 )

. When the contribution of spray drift to exposure is not simulated at the maximum labeled rate, RQs still exceed the acute risk to listed
and non

- listed species LOC and chronic LOCs for freshwater invertebrates.

RQ values based on maximum and average application rates for estuarine/marine aquatic invertebrates exposed to tribufos on an acute basis exceed LOCs for risk to listed (LOC=0.05)
and non

- listed (LOC=0.5) species ( Table 22 ). In the chronic water

- column study with estuarine/marine invertebrate mysid s , no effects were observed at the highest concentration tested of 0.26 μg a.i./L. Chronic EECs are higher than the highest level tested. There are two alternative endpoints that could be used to evaluate the potential for effects due to chronic

exposure for estuarine/marine aquatic invertebrates, 1) the benthic estuarine/marine aquatic
invertebrate NOAEC of 7.1 μg a.i./L for pore

- water, or 2) an estimated chronic endpoint using an ACR for the daphnid 12 

### and the 96

- hr EC 50 

### for the mysid, resulting in an est imated NOAEC of 3.3 μg ai./L 13 

### . The toxicity value for the benthic invertebrate was used in RQ calculations.
C hronic RQ values for estuarine/marine aquatic invertebrates, inhabiting both the water

- column
and benth os , exceed the LOC of 1.0 for chronic risk ( Table 22 and 24 ) , except for California and
Arizona average application rate s simulated using the Califonria cotton scenario . When the
contribution of spray drift to exposure is not simulated at the maximum labeled rate, RQs still
exceed the acute risk to listed and non

- listed species LOC and chronic risk LOCs for some aquatic invertebrates

.

Table 22 . RQs for Direct Effects to Aquatic Invertebrates Inhabiting the Water

- c olumn
from Tribufos Use on Cotton.

Geographic area and Type of Application App.

Rate (lbs a.i./A) Peak
EECs (μg a.i./L) 21

- day

average

EECs Risk Quotients

Freshwater
Invertebrates E/M Invertebrates

Acute
EC 50 = 5.4 μg a.i./L Chronic
NOAEC =

1.5 μg
a.i./L Acute
EC 50 = 11.53 μg

a.i./L Chronic
NOAE = 7.1

μg a.i./L 2

Maximum Label Rates

– Runoff and Spray Drift Simulated

National Aerial 1.125 29.7 27.1 5.5* 17.4* 2.6* 3.8*

CA and AZ Aerial 1.875 21.2 16.8 3.9* 10.8* 1.8* 2.4*

National Ground 1.125 29.0 26.1 5.4* 16.7* 2.5* 3.7* Average Application Rates

– Runoff and Spray Drift Simulated

National Aerial 0.54 14.2 12.9 2. 6 * 8. 3 * 1.2* 1. 8 *

CA Aerial 0.64 7.3 5.8 1.4 * 3.7 * 0.6 * 0. 82

AZ Aerial 0.77 8.7 6.9 1.6 * 4.4 * 0 .8* 0.97

National Ground 0.54 14.0 12.6 2.6* 8.1* 1.2* 1.8*

Maximum Label Rates

– Runoff Only

National Ground 1.125 26.5 24.0 4.9* 15.4* 2.3* 3.4*

CA Ground 1.875 7.53 6.51 1.4* 4.2* 0.7 8* 0.9

12 ACR=48

- hr EC 50 /NOAEC=5.4 μg a.i./L/1.56 μg a.i./L=3.5

13 NOAEC = 96

- hr LC 50 / ACR = 11.53 μg a.i./L /3.3 μg a.i./L = 3.3 μg a.i./L

### 49 Abbreviations: App.= Application. ; E/M=estuarine/marine All RQs exceed acute and chronic risk LOCs for listed and non

- listed species. A bold value with an asterisk indicates that the RQ meets or
exceeds the acute non

- listed, acute listed, and chronic ris k LOC.

. 2 The NOAEC used to calculate risk quotient for estuarine/marine invertebrates inhabiting the water column was taken from a 10

- day spiked sediment test with the estuarine/marine amphipod (MRID 49164801). A definitive chronic endpoint from a water

- column study was not
available for estuarine/marine invertebrates

.



### Table 23

. Chronic RQs for Direct Effects to Benthic Invertebrates from Tribufos Use on
Cotton.

Geographic area and Type of Application App.

Rate (lbs a.i./A) 21

- day Average EEC Chronic Risk Quotients

Pore

water (μg a.i./L) Bulk

sediment (μg a.i./kg) Freshwater Invertebrates Estuarine/Marine

Invertebrates

NOAEC = 2.81 μg a.i./L NOAEC = 71 μg a.i./kg NOAEC =
7.10 μg a.i./L NOAEC =
207 μg a .i./kg

Maximum Label Rates

– Runoff and Spray Drift Simulated

National Aerial 1.125 22.4 173 2 7.97* 24* 3.15* 8.36*

CA and AZ Aerial 1.875 11.7 904 4.16* 13* 1.65* 4.37*

National Ground 1.125 21.5 166 2 7.65* 23* 3.03* 8.03* Average Application Rates

– Runoff and Spray Drift Simulated

National Aerial 0.54 10.6 819 3.77* 11.5* 1.49* 3.96*

CA Aerial 0.64 4.00 309 1.42* 4.35* 0.56 1.49*

AZ Aerial 0.77 4.80 370 1.71* 5.21* 0.68 1.79*

National Ground 0.54 10.4 80 4 3.70* 11* 1.46* 3.88*

Maximum Label Rates

– Runoff Only

National Ground 1.125 19.6 1515 6.98* 21 2.76* 7.32*

CA Ground 1.875 5.29 409 1.88* 0.64 0.745* 1.98*

Abbreviations: App.= Application

A bold value with an asterisk indicates that the RQ meets or exceeds the chronic risk LOC (1) for listed and non

- listed species.



### None of the RQ values based on maximum application rates for aquatic vascular and non

vascular plants exposed to tribufos exceeded LOCs (1.0) for risk to listed or non

- listed plant s ( Table 24 ). Therefore, ba sed on these studies the likelihood of adverse effects to aquatic plants from exposure to tribufos in surface water is considered low.

Table 24 . RQ Values for Direct Effects to Aquatic Vascular and Nonvascular Plants from
Tribufos Use on Cotton.

Geographic area and Type of Application App.

Rate (lbs a.i./A) Peak water
EEC (μg a.i./L) Risk Quotients Aquatic Vascular Plants Aquatic Non

- vascular Plants

Listed
EC 05 = 140 μg a.i./L Non

- listed
EC 50 = 1100 μg a.i./ L Listed
NOAEC =
118 μg a.i./L Non

- listed
EC 50 = 148 μg a.i./ L

Maximum Label Rates

– Runoff and Spray Drift Simulated

National Aerial 1.125 29.7 0.21 0.03 0.25 0.20

CA and AZ Aerial 1.875 21.2 0.15 0.02 0.18 0.14

National Ground 1.125 29.0 0.21 0.03 0.25 0.20

Abbreviations: App.= Application RQs do not exceed the aquatic plant risk LOC of 1.



### 4.1.2. RQ Values for Terrestrial Organisms

Exposure estimate s for birds and mammals were calculated using upper

- bound K enaga values calculated using T

- Rex version 1.5.2

, as well as though ingestion of contaminated prey estimated

### 50 using KABAM based on BCF values , and 1

- in

- 10 year 60

- day water

- column concentrations estimated using the SWCC

. As noted previously, b irds are the surrogate species for reptiles an d

terrestr ial

- phase amphibians. Toxicity endpoints used to calculate risk quotients are the most sensitive for the taxa evaluated and are described in the tables showing the RQ values.

For maximum and average applications rates for use of tribufos on cotton , the acute dose

- based RQ values for birds exceed the LOC for acute risk to listed (RQ≥0.1) species for three or more types of dietary items ( Table 25 ). In addition, for maximum label rates , the acute dose

- based RQ values for birds exceed the LOC for acute risk to non

- listed (RQ≥0.5) species for the all size
classes of birds feeding on three or more types of dietary items

. When evaluating risk based on

a ver age application rates, acute

- dose based RQs still exceed LOCs for risk to listed and non

listed birds, but not for as many size classes and dietary categories. The chronic risk LOC (RQ≥1) is exceeded for birds consuming short grass, tall grass, or broadleaf plants/small insects at the maximum label rate in California and Arizona. At the national maximum label rate, the chronic risk LOC is exceeded for birds consuming short grass and broadleaf plants/small insec ts. When evaluating risk based on average application rates, the chronic risk LOC is exceeded for birds consuming short grass in Califor nia and Arizona but not for the average national rate of
0.54 lbs a.i./A.

Table 25 . Acute and Chronic RQ for Birds Exposed to Tribufos as a Result of Use on
Cotton.

Food Type Acute Dose

- Based RQs 1 Subacute Dietary RQs 2 Chronic Dietary

- Based RQs 3 Small (20 g) Medium (100 g) Large (1000 g)

California and Arizona Maximum Label Rate
1.875 lbs a.i./A, 1 application, Foliar Short grass 4.71 * 2.11 * 0.67 * 0.30 * 3.00 * Tall grass 2.16 * 0.97 * 0.31 * 0.14 * 1.38 * Broadleaf plants/small
insects 2.65 * 1.19 * 0.38 * 0.17 * 1.69 * Fruits/pods/(seeds, dietary only) 0.29 * 0.13 * 0.04 0.02 0.19 Arthropods 1.85 * 0.83 * 0.26 * 0.12 * 1.18 * Seeds (granivore) 0.07 0.03 0.01 NA NA

National Maximum Label Rate 1.125 lbs a.i./A, 1 application, Foliar Short grass 2.83 * 1.27 * 0.40 * 0.18 * 1.80 * Tall grass 1.30 * 0.58 * 0.18 * 0.08 0.83 Broadleaf plants/small
insects 1.59 * 0.71 * 0.23 * 0.10 * 1.01 * Fruits/pods/(seeds, dietary only) 0.18 * 0.08 0.03 0.01 0.11 Arthropods 1.11 * 0.50 * 0.16 * 0.07 0.71 Seeds (granivore) 0.04 0.02 0.01 NA NA Arizona Average Use Rate 0.54 lbs a.i./A, 1 application, Foliar Short grass 1.36 * 0.61 * 0.19 * 0.09 0.86 Tall grass 0.62 * 0.28 * 0.09 0.04 0.40 Broadleaf plants/small
insects 0.76 * 0.34 * 0.11 * 0.05 0.49

### 51 Food Type Acute Dose

- Based RQs 1 Subacute Dietary RQs 2 Chronic Dietary

- Based RQs 3 Small (20 g) Medium (100 g) Large (1000 g) Fruits/pods/(seeds, dietary only) 0 .08 0.04 0.01 0.01 0.05 Arthropods 0.53 * 0.24 * 0.08 0.03 0.34 Seeds (granivore) 0.02 0.01 <0.01 NA NA National Average Use Rate 0.77 lbs a.i./A, 1 application, Foliar Short grass 1.93 * 0.87 * 0.27 * 0.12 * 1.23 * Tall grass 0.89 * 0.40 * 0.13 * 0.06 0.56 Broadleaf plants/small
insects 1.09 * 0.49 * 0.15 * 0.07 0.69 Fruits/pods/(seeds, dietary only) 0.12 * 0.05 0.02 0.01 0.08 Arthropods 0.76 * 0.34 * 0.11 * 0.05 0.48 Seeds (granivore) 0.03 0.01 <0.01 NA NA California Average Use Rate 0.64 lbs a.i./A, 1 application, Foliar Short grass 1.61 * 0.72 * 0.23 * 0.10 * 1.02 * Tall grass 0.74 * 0.33 * 0.10 * 0.05 0.47 Broadleaf plants/small
insects 0.90 * 0.41 * 0.13 * 0.06 0.58 Fruits/pods/(seeds, dietary only) 0.10 * 0.05 0.01 0.01 0.06 Arthropods 0.63 * 0.28 * 0.09 0.04 0.40 Seeds (granivore) 0.02 0.01 <0.01 NA NA

NA=not applicable
Bolded values with an asteris k meet or exceed the Level of Concern (LOC) for acute risk to listed (RQ > 0.1) and/or non

- listed (RQ > 0.5) birds or chronic risk to birds (RQ > 1).

1 Acute dose

- based RQ values are based on the bobwhite quail LD 50 value of 151 mg ai/kg

- bw (MRID 00120771 )

. There is an acute dose

- based

ED 50 for the canary of 111 mg a.i./kg

- bw based on both mortality and regurgitation (MRID 49121303) . When you correct for body weight, the RQ values based on the bobwhite quail and canary endpoint are different by 0.01

. 2 Ac ute dietary RQ values are based on the bobwhite quail 5

- day LC 50 value of 1519 mg a.i./kg diet (MRID 41618804)

. 3 Chronic RQ values are based on the bobwhite quail NOAEC value of 15 0 mg a

. i

. /kg diet (MRID 40757101 )

.



### For maximum and average applications rates for use of tribufos on cotton , the acute dose

- based RQ values for all size classes of mammals exceed the LOC for acute risk to listed (RQ≥0.1) species for three or more types of dietary items ( Table 26 ). In addition, for maximum label

rates , the acute dose

- based RQ values for mammals exceed the LOC for acute risk to non

- listed (RQ≥0.5) species for medium and small size classes of mammals for one or more dietary classes

. When evaluating risk based on average application rates, acute dose

- based RQs still exceed
LOCs for risk to listed and non

- listed species for some dietary items. Subacute dietary RQs for
maximum label rates meet or excee d the risk to listed species LOCs for two or more dietary classes. Chronic dietary RQs exceed the chronic risk LOC of 1.0 for at least two dietary classes.

The chronic risk LOC (RQ≥1) is exceeded for mammals consuming short grass, tall grass, broadleaf p lants /small insects , and arthropods for R Qs based on maximum label rates in California and Arizona and for mammals consuming short grass and broadleaf plants/insects for
that national maximum label rate . Chronic risk LOCs for mammals consuming short grass are also exceeded for RQs calculated based on average application rates in California and Arizona but not the national average application rate

.

### 52 Table 26 . Acute and Chronic RQ for Mammals Exposed to Tribufos as a Result of Use on
Cotton.

Food Type Acute Dose

- Based RQs 1 Subacute Dietary RQs 2

Acute Dose Chronic Dietary

- Based RQs 3 Acute Dietary Small (15 g) Medium (35 g) Large (1000 g)

California and Arizona Maximum Label Rate 1.875 lbs a.i./A, 1 application, Foliar
Short grass 1.02* 0.87* 0.47* 2.80* 14.06* Tall grass 0.47* 0.40* 0.21* 1.28* 6.45* Broadleaf plants/small
insects 0.57* 0.49* 0.26* 1.57* 7.91* Fruits/pods/(seeds, dietary only) 0.06 0.05 0.03 0.17* 0.88 Arthropods 0.40* 0.34* 0.18* 1.09* 5.51*
Seeds (granivore) 0.01 0.01 0.01 NA NA

National Maximum Label Rate 1.125 lbs a.i./A, 1 application, Foliar Short grass 0.61* 0.52* 0.28* 1.68* 8.44* Tall grass 0.28* 0.24* 0.13* 0.77* 3.87* Broadleaf plants/small
insects 0.34* 0.29* 0.16* 0.94* 4.75* Fruits/pods/(seeds, dietary only) 0.04 0.03 0.02 0.10* 0.53 Arthropods 0.24* 0.20* 0.11* 0.66* 3.30* Seeds (granivore) 0.01 0.01 <0.01 NA NA Arizona Average Use Rate 0.54 lbs a.i./A, 1 application, Foliar Short grass 0.29* 0.25* 0.13* 0.80* 4.05* Tall grass 0.13* 0.11* 0.06 0.37* 1.86* Broadleaf plants/small
insects 0.16* 0.14* 0.08 0.45* 2.28* Fruits/pods/(seeds, dietary only) 0.02 0.02 0.01 0.05 0.25 Arthropods 0.11* 0.10* 0.05 0.32* 1.59* Seeds (granivore) < 0.0 1 < 0.0 1 < 0.0 1 NA NA

National Average Use Rate 0.77 lbs a.i./A, 1 application, Foliar Short grass 0.42* 0.36* 0.19* 1.15* 5.78* Tall grass 0.19* 0.16* 0.09 0.53* 2.65* Broadleaf plants/small
insects 0.23* 0.20* 0.11* 0.65* 3.25* Fruits/pods/(seeds, dietary only) 0.03 0.02 0.01 0.07 0.36 Arthropods 0.16* 0.14* 0.07 0.45* 2.26* Seeds (granivore) 0.01 <0.01 <0.01 NA NA California Average Use Rate 0.64 lbs a.i./A, 1 application, Foliar Short grass 0.35* 0.30* 0.16* 0.95* 4.80* Tall grass 0.16* 0.14* 0.07 0.44* 2.20* Broadleaf plants/small
insects 0.20* 0.17* 0.09 0.54* 2.70* Fruits/pods/(seeds, dietary only) 0.02 0.02 0.01 0.06 0.30

### 53 Food Type Acute Dose

- Based RQs 1 Subacute Dietary RQs 2

Acute Dose Chronic Dietary

- Based RQs 3 Acute Dietary Small (15 g) Medium (35 g) Large (1000 g) Arthropods 0.14* 0.12* 0.06 0.37* 1.88* Seeds (granivore) <0.01 <0.01 <0.01 NA NA

NA=not applicable
Bolded values with an asterisk meet or exceed the Level of Concern (LOC) for acute risk to listed (RQ > 0.1) and/or non

- listed (RQ > 0.5) birds or chronic risk to birds (RQ > 1).

1 Acute dose

- based RQ values are based on the laboratory rat LD 50 value of 192 mg a.i

. /kg

- bw (MRID 41954903 ).

2 Suba cute dietary RQ values are based on the white footed mouse 5

- day LC 50 value of 161 mg a.i./kg diet (MRID 45863708 )

. 3 Chronic RQ values are based on the laboratory rat NOAEC value of 32 mg a.i./kg

- diet (MRID 42040201 ).

4 Probability of individual mortality based on actual screening

- level RQ value for small mammals. The default acute dose

- response slope of 4.5
and a conc entrati on

- response slope value of 2.79 was used to generate the probability values. A dose

- response slope value was not calculable
from the available acute dose test data (Urban and Cook, 1986; USEPA, 2004b)

. Probability values are shown for the highest and lowest RQ
values.



### No t enough data are available to calculate a reliable metabolism rate constant to parameterize

KABAM ; therefore, the empirical BCF values for fish w ere used to estimate tribufos concentrations in aquatic organisms. The e mpirical BCF value for tribufos is 730 L/kg in whole fish and was measured for the bluegill sun fish ( Lepomis macrochirus ) . Maximum 1

- in

- 10

- year 60

- day average EECs for the scenarios explored for aquatic modeling ranged from 11.6 to 25.1 μg/L. The estimated concentrations in aquatic organisms resulting from this range of EECs are
used with the BCFs to bracket the potential concentrations of tribufos in aquatic vertebrate tissues (at steady state) in areas vulnerable to runoff . It should be noted that tissue concentrations in aquatic vertebrates will likely be bound by toxicity of tribufos on these organisms. For instance, the NOAEC for aquatic vertebrates exposed to tribufos is 4.1 μg a.i./L. At this concentration, there were redu ct ions in growth and post

- hatch survival. Given that we expect a range of sensitivity in different aquatic invertebrates, some sensitive aquatic vertebrates would be expected to have effects at the estimated concentrations while less sensitive species

cou ld carry residues in tissue without showing effects

. Assuming EECs of 11.6 to 25.1 μg a.i./L
and a BCF value of 730 L/kg for whole fish , tribufos concentrations in aquatic vertebrate tissues
may range up to 8.5 to 18 m g a.i./kg (diet) (BCF x EEC = c oncen tration in fish). All of these concentrations are higher than dietary subacute and chronic dietary endpoints for mammals and
birds. Acute RQs range from 5.57 to 12.1 for birds and 52.6 to 114 for mammals. Chronic RQs range from 56.5 to 122 for birds and 32.6 to 70.5 for mammals.

Table 27 . RQ Values for Birds and Mammals Consuming Fish.

Use
Scenario Water

Column
60

- day

average EEC (μg/L) BCF (L/kg) Tribufos

con c in

fish (μg/kg) Subacute Dietary RQ Chronic RQ

Birds
5

- day LC 50 = 1519 mg a.i./kg

diet Mammals
5

- day LC 50 = 161 mg/kg

- diet Birds
NOAEC= 150 mg/kg

diet Mammals
NOAEC= 260 mg/kg

diet

1.875 lbs a.i./A, no
runoff

, California 11.6 730 8468 5.57 52.6 56.5 32.6

1.1 lbs a.i./A, Mississippi 25.1 730 18323 12.1 114 122 70.5

Conc=concentration

### 54 4.1.2.3. Terrestrial Invertebrates

EECs for terrestrial invertebrates were calculated using the equations described in Section
3.2.3.4

. Tribufos is classified as practically non toxic to honey bee s on an acute contact exposure basis

. The only study available to evaluate potential effects to honey bee s is currently an acute contact study where only 3% mortality was observed at the highest dose tested of 24.7 μg a.i./bee. The highest acute contact EECs of 5.06 estimated for the maximum label rate of 1. 875 lbs a.i./A is lower than the highest dose tested where only 3% mortality occurred. Since the acute contact toxicity study for honey bee s exposed to tribufos was non

- definitive ( i.e. , LD 50 

### greater than highest concentration test ed), RQs are not calculated. The risk to insect pollinators is discussed in greater detail in the Risk Description ( Section 4.2 ).

4.1.2.4. Non

- target Terrestrial Plants

EECs for terrestrial plants were calculated using TERRPLANT (Version 1.2.2). RQ values for terrestrial plants are calculated using the most sensitive endpoints for monocot and dicot species in vegetative vigor and seedling emergence tests with tribufos typical end

- use product (TEP) ( Table 28 ). For all label ed uses of tribufos , RQ values for monocot and dicot plants exposed to
runoff are lower than ( i.e ., do not exceed) the risk to non

- listed and listed species LOC (LOC =1).

R Q values are not calculated for non

- listed terrestrial plants due to runoff because definitive
EC 25 

### values w ere not available from the submitted seedling emergence tests with TEP ( i.e. , no dicot species/endpoints were inhibited by 25% or more at the applic ation rates used). The potential for adverse effects to listed and non

- listed species of terrestrial and semi

- aquatic plants from exposure to formulated tribufos is discussed in greater detail in the Risk Description ( Section 4.2 ). In the risk description, the distance from the edge of the field where effects may
occur due to exposure to spray drift is reported based on the results of a non

- guideline defoliation study

.

Table 28 . RQs for Non

- target Terrestri al Plants Adjacent to Tribufos Use on Cotton (Aerial Application).

Plant Type Listed Status Risk Quotients

Dry Semi

- Aquatic

Monocot non

- listed Not calculated* Not calculated*

Monocot listed 0.10 0.26

Dicot non

- listed Not calculated* Not calculated*

Dicot listed 0.21 0.53

* Runoff RQ values for non t arget plants are based on the seedling emergence NOAEC of 0.45 lbs a.i./A for monocots and 0.22 lbs a.i./A for
dicots , corresponding EC 25 values were estimated to be > 2 lbs a.i./A and an RQ was not calculated for non

- listed species . The most sensitive NOAEC for vegetative vigor is 0.48 lbs a.i./A for both monocots and dicots.



### 4. 2. Incident Database Review

The Ecological Incident Information System (EIIS)
, which is maintained by the Agency’s Office of Pesticide Programs, was searched to determine if ecological incidents have been reported for tribufos. Based on a search of EIIS conducted in April 2015. There is only one incident in the

### 55 EIIS database associated wit h tribufos (I016036

- 024). This incident involved damage to 53 acres of lettuce in Riverside, California, in 2004. The damage was described as ‘uniform throughout’ the field, although the specific type of damage to the lettuce was not specified in the incid ent report. Damage was attributed to spray drift of tribufos and diuron that had been legally applied by air to a cotton field adjacent to the damaged lettuce field. The damaged lettuce tested positive for tribufos (50 ppb). No other residue information was provided in the report.

The American Bird Conservancy Avian Incident Monitoring System was searched in April 2015
and returned no records of incidents associated with tribufos 14



### .

Based on a search of the U.S. EPA Office of Pesticide Programs Inciden t Data System (IDS), which compiles aggregate incidents, there were a total of four incidents involving tribufos between 1993and 1997, of which four were associated with minor plant damage and one was associated with a fish kill in a pond. There w ere als o two misuse incidents associated with a fish
kill.

A lack of reported incidents does not necessarily mean that incidents have not occurred. In addition, incident reports for non

- target plants and animals typically provide information on acute mortality events only. Reports for other adverse effects, such as reduced growth or impaired reproduction, are rarely received. Available incident information indicates that use of tribufos on cotton has the potential to result in effects to nontarget plants.

4.3

. Risk Description

This screening

- level ass essment of the labeled uses of tribufos on cotton relies on the deterministic RQ method to provide a metric of potential risks. RQs exceed LOC values for :

• freshwater and estuarine/marine fish (acute list ed and chronic risk LOCs) ;

• freshwater and estuarine/marine invertebrates (acute listed, acute non

- listed , and chronic
risk LOCs) ;

• birds (acute listed, acute non

- listed , and chronic risk LOCs) ; and

,

• mammals (acute listed, acute non

- listed , and chronic LOC s)

.

While RQs for terrestrial plants are not exceeded, incidents for terrestrial plants have been reported and non

- guideline toxicity studies indicate that defoliation may occur in sensitive plants
such as cotton and deciduous trees and shrubs . This will be discussed in more detail in this
section.

Limited a vailab le toxicity data for honey bee s suggest that LOCs wo uld not be exceeded on an

acute

- contact basis; however, there is uncertainty in risk to bees via oral exposure.

RQs for aquatic plants do not exceed LOCs for listed or non

- listed plants. Therefore, the
likelihood o f risk to aquatic plants is considered low.

14 http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/index.cfm

### 56 4.3 .1 Risk to Aquatic Organisms

Aquatic Exposure
Surface water and benthic sediment pore

- water EECs resulting from applications of tri bufos to cotton are estimates of exposure for the use of tribufos as a broadcast herbicide

, i.e ., defoliant

. Application practices were modeled using the maximum annual application rate with a single application and with average application rates assuming a single application

. Exposure estimated for average application rates will produce EECs lower than those that may occur when tribufos is used at a higher rate. Use of tribufos at rates higher than the average rate is e xpected

to commonly occur. Environmental fate data were conservatively represented in keeping with EFED’s Input Parameter Guidance ( http://www.epa.gov/oppefed1/models/wa ter/input_parameter_guidance.htm ) by using an uncertainty factor of 3X applied to the single soil and sediment metabolism half

- life estimates. Finally, scenario selection was conservatively performed by modeling runoff prone soils that drain to a small po nd without an outlet. When EECs were calculated assuming that spray drift would not occur ( e.g ., that the spray drift fraction was zero), EECs were 35 to 89% of the
maximum EECs modeled with spray drift included

. In runoff vulnerable areas, the contribut ion of spray drift to the final EEC was minimal ( i.e ., EECs calculated with and without simulation of spray drift were similar)

.

Aquatic Animals Based on the most sensitive endpoints, one major concern for aquatic organisms in this
assessment is for freshwater and estuarine/marine invertebrates inhab iting both the water

- column
and benthic environments . Tribufos is characterized as highly toxic to very highly toxic to aquatic invertebrates

. Acute risk (listed and non

- listed ) and chronic risk LOCs for freshwater
and estuarine/marine invertebrates a re exceeded for the EECs simulated for maximum label rates and average application rates 15



### . Effects on survival and shell deposition were observe d in acute toxicity studies at concentrations lower than those estimated in the environment from the use of tribufos on cotton. Acute RQ values range from 0.65 to 5.5 for all exposure scenarios simulated (including maximum and average application rates, a nd simulations excluding spray drift). This
indicates a potential for acute mortality to occur among aquatic invertebrates from exposure as a result of the current labeled use of tribufos in areas vulnerable to runoff. With chronic exposure,
a reduced nu mber of young/adult/day (LOAEC=3.23 μg a.i./L for the water flea), reduced, growth ( LOAEC= 8.27 μg a.i./L in pore

- water for the freshwater amphipod), and reduced survival (LOAEC=22.7 μg a.i./L in pore

- water for the estuarine/marine amphipod) were
observed a t concentrations lower than those predicted in vulnerable areas when tribufos is used on cotton ( 21

- day average EECs range from 6.51 to 27.1 μg a.i./L in the water

- column and 5.29 to 22.4 in pore

- water) ( Table 29 )

. Chronic risk LOCs are still exceeded, a fter the contribution of spray drift i s removed from exposure estimates

. While any buffer between an application and aquatic water body is expected to reduce exposure and risk, a methodology is not available to estimate the reduction in EECs due to transport in runoff because channelized runoff may occur.
Therefore

, the re is a potential for adverse effects ( e.g ., mortality, reduced growth, reductions in

15 The chronic risk LOC for esturarine/marine invertebrates inhabiting the water column is not exceeded for average application rates simulated with the California cotton scenario.

### 57 the number offspring, and reduced shell growth ) to aquatic invertebrates (including mollusks 16 

### ) inhabiting both the water

- column and benthic zones from use of tribufos on cotton

.

Table 29 . Comparison of LOAEC Values to the Lowes t and Highest Estimated EECs for Aquatic Invertebrates.

21

- day

average EECs LOAEC Ratio of
EEC
/LOAEC Species Effect Observed at LOAEC

10.4* 3.23 3.22 Water flea 10% reduction in number of young/adult/day,

2

- 6% reduced growth

8.27 1.26 Freshwater amphipod 39% reduction in growth

22.7 0.46 Estuarine/marine amphipod 16% reduction in survival

27.1+ 3.23 8.39 Water flea 10% reduction in number of young/adult/day,

2

- 6% reduced growth

8.27 3.28 Freshwater amphipod 39% reduction in growth

22.7 1.19 Estuarine/marine amphipod 16% reduction in survival

* Lowest 1

- in

- 10 year 21

- day average EEC in pore

- water for 0.54 lbs a.i./A applied via ground application. + Highest 1

- in

- 10 year 21

- day average EEC in the water

- column for 1.125 lbs a.i./A applied via aerial application.



### Based on available information, tribufos is categorized as highly toxic to aquatic vertebrates (fish
and aquatic

- phase amphibians) o n an acute exposure basis

. Risk quotients for freshwater fish

, based on acute exposure and the most sensitive endpoints available, exceed LOCs for risk to listed species but not non

- listed species. Risk quotients for estuarine/marine fish based on acute exposure basis do not exceed acute risk LOCs. Risk quotients based on a chronic exposure exceed chronic risk LOCs for both freshwater and estuarine/marine vertebrates. These LOCs are exceeded when simulating both maximum labeled rates and average application rates and when simulating runoff only in a reas highly vulnerable to runoff

, except for the chronic risk LOC for
estuarine/marine vertebrates for the California and Arizona average application rates simulated using the Califonria cotton scenario

. Effects to growth and post hatch

- survival were obse rved in early life cycle tests with the sheepshead minnow at the 19 μg a.i./L treatment level

. One

- in

- 10

- year 60

- day average EECs for maximum label rates ranged from 14.3 to 25.1 and LOAECs range from 4.83 to 19 μg a.i./L. One

- in

- 10 year 60

- day average EE Cs estimated for average application rates are lower than the LOAECs but still exceed NOAECs. Similar effects to freshwater vertebrates would be expected to occur based on an esti m ated toxicity endpoint. Additionally , there is one incident associated wit h an approved use of tribufos involving a fish kill in a pond , although, diuron 17 

### was also present in the formulation and is also toxic to fish

. Therefore, there is a potential for adverse effects ( e.g., mortality, reduced growth, and reduced
survival of young ) to aquatic vertebrates from use of tribufos on cotton

.

Non

- targeted monitoring data for surface water (peak=0.3 μg/L) and sediment (peak=5.1 μg/kg) confirm the identified transport pathways and are approximately a factor of 10 lower than the

most sensitive toxicity endpoints for aquatic invertebrates ( Daphnid 48

- LC 50

, 

### =5.4 μg/L;

16 Toxicity data are only available for estuarine/marine mollusks. Unless additional data are provided showing that freshwater mollusks are less sensitive than estuarine/marine mollusks, the risk conclusion fo r estuarine/marine
mollusks is also assumed for freshwater mollusks.

17 According to the EFED ECOTOXITY Database, the lowest diruon acute toxicity endpoint for fish is a 96

- hour

LC 50 for the Cutthroat trout ( Oncorhynchus clarkii ) of 0.71 mg/L.

### 58 Daphnid 21

- day No

- observable

- adverse

- effect

- concentration, NOAEC=1.56 μ g /L; Hyalella

azteca 10

- day sediment NOAEC=71 μg a.i./kg

- sediment) and aquatic vertebrates ( Lepomis promelas estimated NOAEC= 4.1 μg/L)

. These monitoring studies are not expected to capture peak concentrations because the sampling was infrequent and not targeted to an area of tribufos

use

. These data add support to the potential for exposure at concentra tions that could result in
adverse effects to aquatic invertebrates and vertebrates.

F ormulation toxicity data for tribufos ( DEF6 ® 

### ) resulted in higher (less sensitive) aquatic toxicity values as compared to tribufos TGAI. Therefore, evaluation of risk based on TGAI, is expected to be protective of risk due to exposure to formulations.

Aquatic Plants Based on available data, t he likelihood for adverse effects to listed and non

- listed vascular plants is considered low, and possible for nonvascul ar aquatic plants. RQ values for non

- listed and listed vascular and nonvascular aquatic plants ranged from 0.02 to 0.25 and were all lower than
LOCs of 1.0. However, there is some uncertainty with this conclusion for non

- vascular plants as data are only available for freshwater green alga e . Data are also required for marine diatom, freshwater diatom, and cyanoba cterium and it is possible that these species could be more sensitive than freshwater green algae. Data from the EFED ECOTOX database on

organop hosphate chemicals was compiled (see Appendix J ) to better understand the potential risk to plants from exposure to tribufos. Results indicate that the EC 50 

### endpoints for organophosphates commonly vary by a factor of 10. Therefore, it is possible additional data for

non

- vascular aquatic plants could change risk conclusions

.

Aquatic Spray Drift Exposure Spray drift exposure to tribufos was determined using AgDRIFT version 2.1.1 (USEPA, 2013)

. The distance to water body from edge

- of

- field was determined for an initial average
concentration of 0.27 μg/L for listed species and 2.7 μg/L for non

- listed species in Tier I Ground and Tier I Aerial aquatic assessments. The default ASAE Fine to Medium droplet size distribution was assumed for aerial applications. For ground applications, a high boom, ASAE very fine to fine drop size distribution, and the 90 th 

### data percent ile was assumed. These are the default spray drift inputs recommended for modeling spray drift (USEPA, 2013)

.

While runoff only EECs exceed LOCs for aquatic organisms and therefore, a spray drift buffer will not eliminate the potential for adverse effects to aquatic organisms from exposure through
runoff (both water and erosion) , it is useful to know how far from the edge of the field spray drift

exposure alone could result in risk to aquatic organisms. Concentrations of 0.27 μg/L in water
exceed the a cute risk to listed s pecies LOC ( based o n the D

. magna acute toxicity endpoint of 5.4 μg/L ). The aquatic spray dr ift distance ( i.e ., the distance from the edge of the field where spray drift exposure could result in RQs that exceed LOC s ) for risk to listed and non

- listed aquatic
invertebrates are summarized in Table 30

. For listed species, the buffer distance for aerial applications is greater than 1000 feet from the edge of the field for the lower average application
rate of 0.54 lbs a.i./A. For ground a pplications, the spray drift distance ranges from 170 to 577 feet from the edge of the field. For non

- listed species , the spray drift distances are lower.

### 59 Table 30 . Aquatic Drift Distance for the Use of Tribufos on Cotton.

Appl ication rate Distance from Edge of Field Where Spray Drift Could R esult in RQs greater than
LOCs for Aquatic Invertebrates (feet) 1 ,2 Listed aquatic invertebrates Non

- listed aquatic invertebrates Aerial Application (Tier I, Fine to Medium DSD)

1.875 > 1000 262

1.125 >1000 131

0.54 >1000 30 Ground Application (Tier I, Very fine to fine DSD, 90 th data percentile, high boom)

1.875 577 30

1.125 374 7

0.54 170 0
DSD=drop size distribution

1 Estimated based on a the 48

- hour LC 50 of 5.4 μg a.i./L for daphnid and the listed (0.05) and non

- listed (0.5) LOCs, initial average concentrations were 270 ng/L for listed species and 2700 ng/L for non

- listed species.

2 Runoff only RQs exceed LOCs, therefore, a spray drift buffer alone will n ot completely eliminate the potential for risk to aquatic invertebrates.



### 4.3.2. Risk to Terrestrial Organisms

Terrestrial Exposure To evaluate the potential for terrestrial exposure from the use of tribufos on c otton, a pplication practices were modeled by using maximum application rates a nd average applications and assuming a single application

. Exposure estimated for average application rates results in EECs that are lower than those that may occur when tribufos is used at a higher rate. Exposure was estimated using upper

- bound and mean Kenaga values , unless otherwise stated, from T

- REX version 1.5.2 and using BCF values. RQs considering T

- REX and BCF values are discussed separately. T he spray drift model AgDrift version 2.1.1 provide s helpful bounds which define the spatial extent of risk concern resulting from off

- field drift at currently registered tribufos application rates.

Birds and Mammals
Tribufos is categorized as being slightly toxic to moderately toxic to birds on an acute oral

exposure basis and practically non

- toxic to slightly toxic birds on a s ubacute dietary exposure
basis. Tribufos is categorized as being moderately toxic to mammals on an acute oral exposure basis and highly toxic on a sub acute dietary exposure basis

.

In this as sessment, RQ s based on acute oral exposure to birds exceed the acute risk to listed species LOC of 0.1 and acute risk to non

- listed species LOC of 0.5 for at least three of the dietary classes for both average application rates and maximum application rate s. Risk to n on

listed species LOCs are exceeded for four dietary classes for small and medium

- sized birds at
maximum label e d rates. RQs calculated based on a sub acute dietary exposure to birds exceed
LOCs for risk to listed birds at the maximum label rates but not for the average application rates. RQs for birds based on chronic dietary exposure exceed the chronic risk LOC for three dietary classes at the maximum application rate of 1. 875 lbs a.i./A, for two dietary classes at 1.125 lbs a.i./A, for one dietary class at 0.64 and 0.77 lbs a.i./A, and there a re no exceedances at the average application rate of 0.54 lb s a.i./A. Bobwhite quail exposed to tribufos in the diet at 280 mg a.i./kg

- diet for 20 weeks, had a redu ced egg shell thickness. At 410 mg/kg

- diet there was a reduced egg production, reduced survival of hatchlings, and reduced growth, an increased

### 60 number of females with a regressed or regressing ovary, and slight to moderate distension of the gastrointestin al tract. Dietary EECs range from 17 6 to 450 mg/kg

- diet for maximum label rates
and are lower th an the LOAEC (280 mg a.i./kg

- diet) for average application rates. Standard RQs are calculated based on upper

- bound K enaga values. When considering EECs based on mean K enaga exposure estimates, some RQs exceed acute risk to listed, acute risk non

- listed , and
chronic risk LOCs at the 1. 875 lbs a.i./A application rate. When considering EECs based on

mean K enaga exposure estimates and the 1.125 lbs a.i./A applica tion rate , some RQs exceed

acute risk listed and acute risk to non

- listed species LOCs but chronic risk LOCs are no t
exceeded

.

For tribufos use on cotton, RQ s based on acute oral exposure to mammals ex ceed the acute risk to listed species LOC of 0.1 and acute non

- listed species LOC of 0.5 for at least three of the dietary classes for both average application rates and maximum application rates. Non

- listed species LOCs are exceeded for short grass for small and medium

- sized mammals at maximum
label ra tes. RQs calculated based on sub

- acute dietary exposure to mammals exceed the acute
risk to listed species and chronic risk LOCs at the maximum label rates and average application rates for at least four dietary forage c ategories

.

Laboratory rats expos ed to tribufos in the diet at 260 mg a.i./kg

- diet in the 2

- generation mammalian reproduction study , had a n increased number of litters with still born pups

, increased pup death through lactation, decrease in F1 and F2 pup body weights, and an increased F1 gestation period. Dietary EECs range from 17 6 to 450 mg/kg

- diet for maximum label rates and are lower than the LOAEC, for average application rates. Standard RQs are calculated based on

upper

- bound K enaga values. When considering EECs based on mean K ena ga dietary exposure estimates, some RQs exceed acute risk to listed and non

- listed species , and chronic risk LOCs at
the maximum labeled application rate s . When considering EECs based on mean K enaga exposure estimates and the 0.54 lbs a.i./A application r ate , some RQs exceed acute risk to listed
and non

- listed species LOCs

, but chronic risk LOCs are no longer exceeded.

The potential for risk to birds and mammals from proposed foliar uses were evaluated in this assessment using the default foliar dissipation half

- life of 35 days, since no additional data w ere available to determine the decline in tribufos residues in dietary items. However, since LOCs for acute risk to listed (RQ≥0.05) and non

- listed (RQ≥0.1) birds and chronic risk (RQ≥1) to

mamma ls are exceeded in this assessment, the impact of different half

- lives on RQs was
examine d for purposes of characterization ( Table 31 ). Based on this analysis, at maximum labeled application rates, both acute and chronic risk LOCs are exceeded even when a half

- life of 1 day is considered. Additionally, at maximum label rates and assuming the default 35 day foliar dissipation rates, LOCs are exceeded fo r 30 to more than 56 days. Therefore, potential risks of
concern to birds and mammals from use of tribufos on cotton would not be precluded based on refinements to the default foliar dissipation half

- life.

### 61 Table 31

. Impact of Different Foliar Dissipation Half

- lives on the Number of Days RQs Based on Dietary Exposure Exceed LOCs.

Application Rate (lbs a.i./A) Number of Days T here is a D ietary LOC exceedance 1

Avian Mammalian

Acute Chronic Acute Chronic 35 day foliar dissipation rate

1.875 56 56 56 56

1.125 30 56 56 56

0.54 56 0 56 55

1 day foliar dissipation rate

1.875 6 2 4 7

1.125 5 1 3 7

0.54 4 0 2 6

1 The analysis is only carried out to a maximum of 56 days based on limitations in T

- REX.



### Based on EECs of 11.6 to 25.1 μg a.i./L and using a BCF value of 730 L/kg, tribufos concentrations in aquatic vertebrate tissues range from 8,468 to 18,323 μg a.i./kg(diet) (BCF x
EEC = c oncentration in fish). Th ese concentrations are higher than acute

- dietary LC 50 

### values and chronic dietary NOAECs for birds and mammals for all scenarios explored in aquatic modeling

. Risk quotients range from 5.57 to 122

. Therefore, there is a potential for adverse
effects to birds and mammals from exposure to aquatic prey items in which residues may have
accumulated/concentrated

. However, tribufos has been shown to rapidly depurate, and once fish are in clean water, 71

- 88% of tribufos residues are expected to dissipate over 14

- days. Additionally, the EECs were estimated for areas vulnerable to runoff and risk is only expected to occur in these areas that would be highly vulnerable to runoff. When evaluating risk using the peak single value from a grab sample, (0.3 μg/L), tribufos c oncentrations in aquatic vertebrate tissues drop to 219 μg a.i./kg

- diet, and only exceed the subacute dietary endpoint for mammals (EEC/NOAEC= 219/161= 1.4) and chronic NOAEC for birds (EEC/NOAEC=219/150=1.5). It would take several days of exposure at 0.3 μ g/L for residues in fish to accumulate concentrations
where effects would be observed.

Although tribufos is characterized as semi

- volatile, t he STIR model output indicates that inhalation is not likely to be a significant exposure pathway of concern for a vian and mammalian species.

Terrestrial Invertebrates In an acute contact toxicity test in which young adult honey bees were exposed to tribufos mixed with pyrolite dust

, t here was 3% mortality observed at 24.17 μg a.i./bee. Based on th ese limited data, tribufos is classified as practically non

- toxic to young adult honey bees on an acute contact exposure basis. The acute dietary exposure EEC for tall grass range from 1.46 to 5.06 μg a.i./bee/day

, the highest ratio of the EEC to the highest level tested with 3% mortality (24.17/5.06=0.21) is l ess than the acute risk LOC (0.4) for individual bees.

Since tribufos is used on cotton and since cotton is used by some beekeepers to produce honey, the proximity of bee colonies to tribufos use areas may be high especially given that cotton is an interderminant blooming crop, i.e. , blooms over a protracted period of time

. I n a survey of pesticide residues in various colony matrices (bees, wax, pollen) from managed migratory be e

### 62 colonies (Mullin et al. , 2010) 18



### , t ribufos residues were reported in 2. 9 % of wax samples, ranging from 7.6 to 59.0 ppb (mean=25.1 ppb) in samples with a positive detection ( Table 32 )

. The l imit of detection was 2.0 ppb. This provides evidence that honey bee s will be exposed in the field
and that residues can be brough t back to the colony where developing brood may in t urn be exposed

. Tribufos is taken up into plants ; however, it is unknown whether it is transported in the xylem and phloem (USEPA, 2008) and whether bees may be exposed to tribufos taken up into plant materials such as pollen, nectar, etc. As tribufos is used close to harvest, the potential for honey bee exposure may be lessened; however, the detectio ns in wa x and pollen samples, indicate that exposure can still occur (either through late blooms on cotton or through exposure

to residues on nontarget blooming plants adjacent to the cotton fields).

Table 32

. Summary of Pesticide Detections in Wax and Pollen Samples from North American Honey Bee Colonies (Reported in Mullin et al .,(2010))

Media Detects Samples % Tribufos concentrations (ppb) High Low 95 %tile Mean

Wax 6 208 2.9 59.0 7.6 51.5 25.1

Pollen 1 350 0.3 3.5 3.5 3.5 3.5



### There are no reported incidents of bee kills for tribufos. However, there are honey bee incidents for other organophosphate insecticides. The absence of bee kill incident data cannot be
construed as the absence of incidents.

Based on the acute contact study , risk to individual honey bee s would be considered low; however, a full dataset is not available to fully evaluate risk to honey bee s. Pollinator risk assessment guidance has recently been finalized and recommends the following honey bee data be available for a Tier I screening level risk assessment for honey bee s:

• acute oral toxicity to adult honey bee s ;

• acute oral toxicity to larval honey bee s ;

• chronic oral toxicity to adult honey bee s ; and

,

• chronic oral toxicity to larval honey bee s.

If Tier I studies identify the potential for a risk concern, additional studies may be requested

.

Until these data are a vailable, the risk to honey bee s cannot be fully evaluated. Risk to
individual adult honey bee s exposed in the ir diet to tribufos could not be evaluated. Additionally, data are not available to evaluate potential eff ects to brood.

Additional informati on from the open literature (Greenberg et al ., 2004; ECOTOX Ref.: 92450) indicates mortality to individuals and population effects in boll weevils exposed to tribufos at an application rate of 0.42 lb a.i./acre (using the DEF 6 formulation), which is 22 to 37 % of the
maximum allowable labeled rate s

. This line of evidence indicates that mortality to similarly
sensitive insects in the field will occur at average and maximum labeled application rates. Additionally, tribufos is an organophosphate (intended for use as a defoliant) and does inhibit acetylcholine esterase (USEPA, 2009b)

. Other organophosphates are commonly used as

in secticides and terrestrial invertebrates may be sensitive to toxicity from acetylcholine esterase

18 http://j ournals.plos.org/plosone/article?id=10.1371/journal.pone.0009754

### 63 inhibition

.

Non

- target terrestrial plants
Based on the available registrant

- submitted toxicity data, RQs do not exceed the Agency’s LOC
for risk to terrestria l plants ( Table 28 ). Because the studies from which these data a re drawn

were not conducted on sensitive plant species ( e.g ., deciduous trees and shrubs) , these data are expected to underestimate the potential toxicity of tribufos to non

- target plants that do form abscission zones ( e.g ., some woody, deciduous plants).

Application of the formulated tribufos product Folex ® 

### 6EC at rates of up to 1. 9 lb a.i./acre and in combination with the adjuvant Activator 90 ® 

### (0.1%) resulted in statistically significant (p<0.05) leaf fall in viburnum and maple at treatment rates equivalent to 1.1 25 and 1. 875 lb a.i./acre and in oak at 1.875 lb a.i./acre (NOAEC = 0.563 lbs a.i./A). These effects were accompanied by a
reduction in the numbers of old leaves remaining on the plants at the end of the 28

- day study period. However, t here were no apparent treatment

- related effects on the development of new leaves in the three shrub species

, F orsythia, R ibes and V iburnum at any of the t reatment rates in comparison to the water

- and adjuvant

- treated controls, or in the limited number of replicates of the two tree species where new growth was recorded. This indicates that there is a potential for
effects to non

- target plants that form abs cission zones to occur at the maximum labeled rates and average application rates. Some plants will be able to replace dropped leaves. Assuming an aerial application, ASAE fine to medium drop size distribution, and 1. 9 lbs a.i./A application
rate, exposu re at 0.56 lbs a.i./A would occur up to 13 feet from the edge of the field. Effects
would not occur off the field at 1.1 25 lbs a.i./A.

One study identified from the open literature ( Greenberg, 2004) describe s effects (defoliation) to
cotton from a trib ufos application at a rate of 0.42 lb a.i./acre using the DEF 6 ® 

### formulation. At this application rate (which is 22 to 37 % of the maximum allowable labeled rate), an average of 80.2% (± SD of 6.1) of the leaves per plant (N = 9) were dropped 7 days post

- application ; whereas

, in the untreated control plot, 3.3% (± SD of 1.6) of the leaves per plant (N = 10) were dropped in the same time period. It is possible that other plants will have a similar sensitivity as

cotton.

One terrestrial plant incident in the EIIS database is associated with tribufos (I016036

- 024). This incident, which damaged 53 acres of lettuce in Riverside, California, also involved the herbicide diuron. Although the damaged lettuce tested positive for tribufos (50 ppb) and no other residues were identified, the fact that an herbicide that is more toxic to plants was also involved in the incident makes it difficult to determine what specific effects, if any, were due to tribufos alone, diuron alone, and/or both chemicals together. T he diuron vegetative vigor EC 25 

### for the dicot tomato ( Lycopersicon esculentum ) is 0.002 lb a.i./A (MRID 44113401) suggests, that diuron may have been the cause of the incident. However, based on the fact that tribufos is a known defoliant, has a mechanism of action that could result in effects to plants ( e.g ., deciduous shrubs and trees), there is a potential for tribufos to directly affect terrestrial plants such as
deciduous shrubs and trees.

### 64 Terrestrial Spray Drift Distance
It is useful to know how far from the edge of the field spray drift exposure alone could result in
risk to terrestrial organisms. Similar to what was done for aquatic organisms, s pray drift exposure to tribufos was determined using AgDRIFT version 2.1.1 (USEPA, 2013)

. The terrestrial spray drift distance was determined using Tier I Ground and Tier I Aerial terrestrial point deposition estimates using a fraction of applied based on the acute

- dose based RQ for birds
and the acute listed and acute non

- listed LOC. The default ASAE Fine to Medium droplet size distribution was assumed for aerial applications. For ground applications, a high boom, ASAE very fine to fine drop size distribution, and the 90 th 

### data percentile was assumed. These are the default spray drift inputs recommended for modeling spray drift (USEPA, 2013)

.

The acute

- dose based RQ value combined with the acute risk to listed and acute risk to non

- listed species LOC s , results in the greatest spray drift distance for terrestrial organisms. The terrestrial spray drift distance ( i.e ., the distance from the edge of the field where spray drift exposure could result in RQs that exceed LOC s ) for risk to listed and non

- listed birds are summarized in Table
33 . For listed species, the terrestrial spray drift distance s for ae r i al applications range from 135
to 460 feet

. For ground applications, the spray drift distance ranges from 170 to 577 feet from the edge of the field. For non

- listed species , the spray drift distances range from 10 to 89 feet

. These spray drift distances are lower for ground applications. The terrestrial spray drift distance estimated for birds is protective of other terres trial organisms from effects due to exposure to spray drift

. These spray drift distances are not protective for birds and mammals that consume aquatic organisms because they are exposed through ingestion of residues in aquatic organisms
rather than dietar y items close to the field

.

Table 33 . Aquatic Drift Distance for the Use of Tribufos on Cotton.

Application rate Distance from Edge of Field Where Spray Drift Could Result in RQs greater than
LOCs for Terrestrial Organisms (feet) 1,2

Listed Birds Non

- listed Birds Aerial Application (Tier I, Fine to Medium DSD)

1.875 460 89

1.125 233 46

0.54 135 10 Ground Application (Tier I, Very fine to fine DSD, 90 th data percentile, high boom)

1.875 125 27

1.125 62 16

0.54 40 7
DSD=drop size distribution

1 Estimated based on acute

- dose based RQ values for the small bird consuming short grass and acute listed LOC (0.1) and acute non

- listed LOC (0.5).



### 4.4

. Uncertainties and Data Gaps

4.4 .1. Fate and Transport

T

- Rex EECs are based on residues on surfaces of dietary items. Tribufos is taken up into leaves
and it is uncertain whether tribufos is taken up by roots and/or distributed in xylem and/or phloem . Exposure based on this exposure route was not assessed.

### 65 Applications were only assumed to occur once per year; however, labels allow for two applications a year and usage data indicate that more than one application may occur in some

cases ( e.g ., for rank cotton) , if the maximum application rate is not used

. T he maximum single application rate and maximum annual application rate are the same. The assumption of one application per year was based on a recommendation from BEAD, stating that c otton will only be grown once per year on a given production field becau se it is a warm season crop with a growing cycle of 130 to 160 days (USEPA, 2014) and tribufos is applied pre

- harvest. The main uncertainty occurs when using the risk estimates based on ave rage application rates, where more than one application could legally occur and do occur based on market survey data

. Additionally, the “average application rate” used to refine EECs is derived by dividing the average pounds of active ingredient applied b y the total area treated (USEPA, 2014). Thus, the average rate modeled may not reflect an actual application rate used in the field.

4.4 .2. Effects

Toxicity data from chronic exposure to tribufos are not currently available for the species of
freshw ater fish that are most acutely sensitive to tribufos ( i.e ., bluegill sunfish). Therefore, the chronic effects endpoint used in this assessment for freshwater fish is estimated based on an

acute

- to

- chronic ratio using toxicity data from sheepshead minnows

. Because the ACR was determined by using endpoints from an estuarine/marine species, chronic risks to freshwater fish may be over

- or under

- estimated, depending on the relative sensitivity of those species. The Agency’s LOCs are intentionally set low, a nd conservative estimates are made in the risk assessment to account for these types of uncertainties. The potential for risk evaluated based on average appli cation rates is not considered to be conservative because it may underestimate exposure under use conditions that are expected to occur.

A ten

- day sediment toxicity study is not available for the freshwater insect C

. dilutus although data are available for the freshwater benthic amphipod Hy alella . The midge and amphipod have different life histories, occupy different ecological niches, belong to different taxonomic groups ( insects versus crustaceans ) and generally interact with sediments in different ways. Chironomid
larvae are more infaun al (submerged in sediment) whereas amphipods are more epibenthic (moving in and out of surficial sediment layer). The 10

- day toxicity study for the C. dilutus is a standard data requirement and lack of this data is an uncertainty that could result in
unde restimating risk. Because RQ values based on the 10

- day sediment tests exceed the chronic
risk LOCs, there is uncertainty whether or not these data are reflective of the sensitivity of organisms which may spend a greater percentage of time within benthic sediments

. Also, t he 10

- day sediment tests do not examine the potential for reproductive effects, which were observed in toxicity studies where other taxa were exposed to tribufos. The current analysis for sediment may underestimate the potential for ris k to benthic aquatic invertebrates.

Pollinator risk assessment guidance has recently been finalized and recommends a suite of laboratory

- based studies extending beyond the acute contact study with adult bees. As these data are currently unavailable for t ribufos, the potential risk to individual honey bee s and brood

### 66 success could not be fully assessed

.

Data on a marine diatom ( Skeletonema costatum ), freshwater diatom ( Navicula pelliculosa ), and cyanobacterium ( Anabaena flos

- aquae ) are not available to evaluate the potential risk to aquatic plants

. As these data are currently unavailable for tribufos, the potential risk to non

- vascular aquatic plants could not be fully assessed

.

5. Endocrine Disruptor Screening Program (EDSP)

Tribufos was not inc luded in the first group of 67 chemicals issued an order to conduct Tier 1 EDSP testing. For additional information on the EDSP, visit http://www.epa.gov/endo/

.

6

. Federally Threatened and Endangered (Listed) Spe cies Concerns

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS) (collectively, the Services) , and the U.S. D epartment of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks to listed species from pesticides. The Interim Approaches were developed jointly by the

a g encies in response to the N ational A cademy of S ciences’ (NAS) recommendations and reflect

a common approach to risk assessment shared by the a gencies as a way of addressing scientific
differences between the EPA and the Services. The NAS report outlines recommendations on specific s cientific and technical issues related to the development of pesticide risk assessments
that EPA and the Services must conduct in connection with their obligations under the Endangered Species Act (ESA) and FIFRA

.

The joint Interim Approaches were releas ed prior to a stakeholder workshop held on November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013

P esticide P rogram D ialogue C ommittee (PPDC) and S tate

- FIFRA Issues Research and Evaluation Group ( SFIREG ) meetin gs, and held a stakeholder workshop in April 2014, allowing additional opportunities for stakeholders to comment on the Interim Approaches. As part of a phased, iterative process for developing the Interim Approaches, the agencies will also consider publi c comments on the Interim Approaches in connection with the development of upcoming Registration Review decisions. The details of the joint Interim Approaches are contained in the white paper “ Interim Approaches for National

- Level Pesticide Endangered Species Act Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report ,” dated November 1, 2013.

Given that the agencies are continuing to develop and work toward i mplementation of the Interim Approaches to assess the potential risks of pesticides to listed species and their designated critical habitat, this preliminary risk assessment for tribufos does not contain a complete ESA analysis that includes effects determ inations for specific listed species or designated critical habitat. Although EPA has not yet completed effects determinations for specific species or habitats, for this preliminary assessment EPA conducted a screening

- level
assessment for all taxa of non

- target wildlife and plants that assumes for the sake of the assessment that listed species and designated critical habitats may be present in the vicinity of the application of tribufos. This screening level assessment will allow EPA to focus its future

### 67 evalua tions on the types of species where the potential for effects exists once the scientific methods being developed by the agencies have been fully vetted. This screening

- level risk
assessment for tribufos indicates potential risks of direct effects to listed dicot terrestrial plants, monocot terrestrial plants, freshwater and estuarine/marine vertebrates and invertebrates, mammals, birds, and terrestrial invertebrates for tribufos use on cotton . Listed species of semi

aquatic plants may also be affect ed through indirect effects because of the potential for direct
effects on listed and non

- listed species upon which such species may rely. Potential direct
effects on listed dicot terrestrial plants, monocot terrestrial plants, freshwater and
estuarine/ma rine vertebrates and invertebrates, mammals, birds, and terrestrial invertebrates from the use of tribufos may be associated with modification of Primary Constituent Elements (PCEs) of designated critical habitats, where such designations have been made. O nce the agencies have fully developed and implemented the scientific methods necessary to complete risk assessments for endangered and threatened (listed) species and their designated critical habitats, these methods will be applied to subsequent analyses for tribufos as part of completing this registration
review.

Table 34

. Preliminary Conclusions for Potential Direct Effects to Federally Listed Taxa Associated with the Registered Uses of Tribufos

.

Listed Plant Taxon Potential Direct Effects

Terrestrial and semi

- aquatic plants

– monocots and dicots Yes , for sensitive plants that form abscission zones

Aquatic vascular plants No

Terrestrial Plants Yes , for plants that form abscission zones

Listed Animal Taxon Potential Direct Effects

Acute Notes Chronic Notes

Terrestrial invertebrates Yes Effects
observed in

open literature No data No data on
chronic
exposure to honey bee s Mammals Yes RQ>LOC Yes RQ>LOC

Birds Yes RQ>LOC Yes RQ>LOC Reptiles Amphibians

Freshwater fish Yes RQ>LOC Yes RQ>LOC

Freshwater invertebrates Yes RQ>LOC Yes RQ>LOC

Mollusks Yes RQ>LOC No data

Estuarine/marine fish No RQ < LOC Yes RQ>LOC

Estuarine/marine invertebrates Yes RQ>LOC Yes RQ>LOC



### 7

. Conclusions

The risk hypothesis identified in the problem formulation stated

,

### 68 Given the currently labeled uses of tribufos and its environmental fate properties, there is a likelihood of exposure to non

- target terrestrial and aquatic organisms.

When used in accordance with the label, tribufos may result in potential adverse effects upon the survival, growth, and reproduction of non

- target terrestrial and aquatic organisms.

After reviewing the most recent environmental fate and effects data for tribufos, the screening

level assessment concludes that registered uses of the defoliant tribufos may result in risks to both
listed and non

- listed species of wildlife and aquatic vert ebrates and invertebrates.

With respect to exposure, t ribufos is characterized as a semi

- volatile, moderately soluble compound that has low mobility in soil. Based on submitted data, it is stable to the abiotic processes hydrolysis and photolysis. Tri bufos is persistent in aerobic and anaerobic soil, and slightly persistent in anaerobic aquatic environments. Therefore, there is potential for tribufos (which is applied to folia ge ) to accumulate in soil with repeated applications if it reaches the soil surface and is not dissipated through volatilization . Tribufos is expected to sorb to soil, and not to appreciably leach to groundwater or move to surface waters in solution phase via runoff. Surface water contamination may also occur due to spray drift and/or transport of residues
sorbed to sediment in runoff ( i.e , erosion) . In either aquatic or terrestrial environments, tribufos may bioaccumulate in organisms exposed to it.

The available data indicate that tribufos TGAI is highly toxic to freshwate r and estuarine/marine fish and invertebrates on an acute exposure basis. Effects o n growth and on post

- hatch survival
were observed in chronic studies with fish while reduced survival and growth were observed in chronic studies of aquatic invertebrates. Effects on frond count were observed in vascular aquatic plants and inhibited growth was observed in nonvascular aquatic plants.

T ribufos TGAI ranges from practically non

- toxic to moderately toxic to birds and is moderately
toxic to mammals on an acute oral exposure basis and highly toxic to mammals on a subacute

dietary exposure basis

. However, t ribufos is practically nontoxic to young adult honey bees on an acute contact exposure basis.

Terrestrial plants exposed to formulated product experienced reduced plant height and dry weight based on guideline studies and in a reduction in the number of old leaves left on the plant and an increased weight of fallen leaves based on a non

- guideline study.

There is a potential for direct adverse effects to th e following taxa based on LOC exceedances :

• Mammals (acute listed, acute non

- listed , and chronic risk LOCs exceeded)

• Birds

, terrestrial

- phase amphibians

, and reptiles (acute listed, acute non

- listed , and
chronic risk LOCs exceeded)

• Freshwater and e stuarine/marine invertebrates (acute listed, acute non

- listed , and chronic
risk LOCs exceeded)

• Freshwater vertebrates ( aquatic

- phase amphibians) (acute non

- listed and chronic risk LOCs exceeded)

• Estuarine/marine vertebrates (chronic risk LOCs exceeded)

### 69 Wh ile RQs do not exceed LOCs for risk to terrestrial plants, tribufos is a defoliant based on its
intended use as well as a non

- guideline study where defoliation was observed ; there fore, there is a potential for direct adverse effects to terrestrial plants t hat form abscission zones such as
deciduous trees and shrubs from exposure to tribufos from its registered use on cott o n

.

Limited available toxicity data for honey bee s suggest that acute risk LOCs are not exceeded on

an acute contact basis; however, data are not available to evaluate potential for effects to
individual bees and their brood exposed via the diet.

RQs for aquatic plants do not exceed LOCs for risk to listed or non

- listed plants. However, a full
dataset is not available to assess the risk to non

- vascular aquatic plants

, and based on aquatic plant data for other organophosphates

, it is possible that these RQs could exceed LOCs if
additional data were available

.

8. R eferences

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- chain bioaccumulation model for
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2343

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at http://www.cdpr.ca.gov/docs/emon/surfwtr/surfdata.htm (Accessed
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-- laboratory
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### 71 Prevention, Pesticides, and Toxic Subs tances. U.S. Environmental Protection Agency.
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USEPA. 2008.DP Barcode 357536. Registration Review: Preliminary Problem Formulation for Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments for Tribufos . DP Barcode 357536. December 10, 2008. Environmental Fate and Effects
Divisi on. Office of Pesticide Programs. U.S. Environmental Protetion Agency.
USEPA. 2008. Risks of Tribufos Use to Federally Threatened California Red

- legged Frog

. Memorandum From to Environmental Fate and Effects Division. Office of Pesticide Programs. U. S. Environmental Protection Agency. Available at http://www.epa.gov/espp/litstatus/effects/redleg

- frog/tribufos/determination.pdf (Accessed March 27, 2015).
USEPA. 2009a. ECOTOXicology Database

, United States Environmental Protection Agency (USEPA) . Available at http://cfpub.epa.gov/ecotox/ (Accessed March 27, 2015).
USEPA. 2009b. Tribufos. Revised Human Health As sessment Scoping Document in Support of Registration Review . D. B. 361529. February 2009. Health Effects Division. Office of Pesticide Programs. U.S. Environmental Protection Agency.
USEPA. 2011. Evaluation for Ecological Toxicity Data in Open Literatu re . May 9, 2011. Environmental Fate and Effects Division. Office of Pesticide Programs. Office of Chemical Safety and Pollution Prevention. U.S. Environmental Protection Agency.
Available at http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_s pecies_reregistration_workgroup/esa_evaluation_open_literature.htm (Accessed April 3, 2015). USEPA. 2012a. Ecological Incident Information System. Environmental Fate and Effects Division. United States Environmental Protection Agency.
USEPA. 2012b. White Paper in Support of the Proposed Risk Assessment Process for Bee s. September 11

- 14, 2012 . September 11, 2012. U.S. Environmental Protection Agency. Pest Management Regulatory Agency. California Department of Pesticide Regulation.
Available at http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 2012

- 0543

- 0004 (Accessed June 22, 2014).
USEPA. 2013. Guidance on Modeling Offsite Deposition of Pesticides Via Spray Drift for Ecological and Drinking Water Assessment . Environm ental Fate and Effects Division. Office of Pesticide Programs. Office of Chemical Safety and Pollution Prevention. U.S. Environmental Protection Agency. Available at
ht tp://www.regulations.gov/#!docketDetail;D=EPA

- HQ

- OPP

- 2013

- 0676 (Accessed April 11, 2014).
USEPA. 2014. Tribufos (074801) Use and Usage Data for Draft Risk Assessment . November 6, 2014. Biological and Economic Analysis Division. Office of Chemical Safety and Pollution Prevention. U.S. Environmental Protection Agency. USEPA, Health Canada PMRA, & California Department of Pesticide Regulation. 2014. Guidance for Assessing Pesticide Risks to Bees . June 23, 2014. U.S. Environmental Protection Agency. Healt h Canada Pest Management Regulatory Agency. California Department of Pesticide Regulation. Available at http://www2.epa.gov/pollinator

protection/pollinator

- risk

- assessment

- guidance (Accessed April 10, 2015).

### 72 8 .1 Submitted P roduct Chemistry and Environmental Fate Studies

MRID 41618803. Talbott, T. 1990. Product Chemistry of DEF Technical: Lab Project Number: 90606: 94500: 94682. Unpublished study prepared by Mobay Corp. 29 p.

MRID 41618811. Cohle, P. 1990. Uptake, Depuration and Bioconcentration of (Carbon 14)

- DEF by Bluegill (Lepomis macrochirus): Lab Project Number: 38466: 100236. Unpublished study prepared by Analytical

Bio

- Chemistry Labo ratories, Inc. 48 p.

MRID 41618814. Schocken, M. and I. Philippson. 1987. Stability of DEF in Sterile Aqueous Buffer Solutions: Lab Project Number: 94918. Unpublished study prepared by Mobay Corp. 23 p.

MRID 41618816. Jackson, S., A. Kesterson, L. Lawrence. 1988. Soil Surface Photolysis of [ 14 C]DEF in Natural Sunlight: Lab Project Num ber: 1153: 206: 95673. Unpublished study prepared by Pharmacology and Toxicology Research Laboratory. 67 p.

MRID 41618817. Daly, D. 1987. Soil Adsorption/Desor ption with [ 14 C]DEF: Lab Project Number: 36356: 95600. Unpublished study prepared by Analytical Bio

- Chemistry Laboratories, Inc. 50 p.

MRID 41719401. Carpenter, M. 1990. Determination of the Aqueous Photolysis Rate of DEF: Lab Project

Number: 38876. Unpublished study prepared by Analytical Bio

- Chemistry Laboratories, Inc. 41 p.

MRID 42007204. Stevenson, T., W. Leimkuehler, A. Mathew. 1991. The Metabolism of Tribufos in Soil Under Aerobic Conditions: Lab Project Number : DE042101: 100338. Unpubl ished study prepared by Mobay Corp., R & D Dept. 33 p.

MRID 42007205. Stevenson, T., W. Leimkuehler. 1990. The Metabolism of Tribufos in Soil Under Anaerobic Conditions: Lab Project Number: 100333. Unpublished study prepared by Mobay Corp., R & D Dep t. 31

p.

MRID 43080401. Leimkuehler, W., K. Moor. 1993. Identification and Characterization of Radioactive Residues of [ 14 C] Tribufos in Bluegill Sunfish (Lepomis m acrochirus): Lab Project Number: DE040301. Unpublished study prepared by Miles Inc. 84 p.

MRID 43325504. Schmidt, J. 1994. Anaerobic Aquatic Metabolism of 14 C

- Tribufos: Lab Project Number: DE042402: 106767. Unpublished study prepared by ABC Lab., Inc. 61 p.

MRID 45863701. Wood, S. 2002. Terrestrial Field Dissipation of Tribufos on Mississippi Soil, 2000: Lab Project Number: DE022102: 110590. Unpublished study prepared by Stoneville R & D, Inc., A & L Great Lakes Laboratories, and Bayer Corporation. 84 p.



### 8 .2. Submitted Ecotoxicity Studies (Retrieved from OPPIN April 2015 )

71

- 1 Avian Single Dose Oral Toxicity

49258 Lamb, D.W.; Jones, R.E. (1972) Acute Oral Toxicity of DEF Technical to Bobwhite Quail and Mallard Ducks: Report No. 35016. (Unpublished study received Mar 22, 1976 under 3125

- 71; submit ted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224114

- P 

### )

### 73 120771 Lamb, D.; Jones, R. (1972) Acute Oral Toxicity of DEF Technical to Bobwhite Quail and Mallard D ucks: Report No. 35016. (Unpub lished study received May 7, 1973 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, MO; CDL:007020

- O 

### )

92034001 Toll, P. (1990) Mobay Corporation Phase 3 Summary of MRID 00049258 and Related MRIDs 00120771. Acute Oral Toxicity of DEF Technical to Bobwhite Quail and Mallard Ducks: Reference No. 72

- 35; Report
No. 35016

- 1. Prepared by Chemagro Div. of Baychem. 12 p.

71

- 2 Avian Dietary Toxicity

41618804 Grau, R. (1990) DEF Technical Grade: 5

- day Dietary LC50 to Bobwhite Quail: Lab Project Number: BV

- 007:

E2950351

- 5: 100223. Unp ublished study prepared by Bayer Ag. 36 p



### .

41618805 Grau, R. (1990) DEF Technical Grade: 5

- day Dietary LC50 to Mallard Duck: Lab Project Number: VE

- 002:

E2970426

- 0: 100224. Unpublished study prepared by Bayer Ag. 43 p



### .

71

- 4 Avian Reproduction

40757101 Beavers, J.; Marselas, G.; Jaber, M. (1988) DEF: A One

- generation Reproduction Study with the Bobwhite ( Colinus virginianus ): Wildlife International Ltd. Project No. 149

- 127. Unpublished study prepared by Wildlife International Ltd. 101 p.

92034002 Toll, P. (1990) Mobay Corporation Phase 3 Summary of MRID 40757101. A One

- generation Reproduction Study with the Bobwhite ( Colinus virginianus ): WIL Project No.149

- 127. Prepared by Wildlife International Ltd.. 16 p.

71

- 5 Simulated or Actual Field Testing

49259 Lamb, D.W.; Jones, R.E. (1972) Toxicity of DEF 6 Lbs/Gal Spray Concentrate to Bobwhite Quail and New Zealand Rabbits Applied under ULV Simulated Field Conditions: Report No. 35030. (Unpublished study
received Mar 22, 1976 under 3125

- 7 1; submitted by Mobay Chemical Corp., Kansas City, Mo.; 

### CDL:224114

- Q)

72

- 1 Acute Toxicity to Freshwater Fish

63387 Howell, J.H. (1963) Letter sent to Lewi s F. Stevens dated Jan 4, 1963 Chemicals related to Bayer 73|: Report No. 11144. (U.S. Fish and Wildlife Service, Burea u of Commercial Fisheries, Ham mond Bay Biological Station; unpublished study; CDL: 

### 130685

- H)

74016 Borash, A.J.; Moorefield, H.H. (1963) The Toxicity of Sodium cis

- 3

- Chloroacrylate (UC 20299) to Goldfish: Project No. 141E41. (Unpublished study received Dec 10, 1963 under unknown admin. no.; submitted by Union Carbide Corp., Arlington, Va.; CDL: 129278

- B)

83208 Borash, A.J.; Moorefield, H.H. (1963) The Toxicity of Sodium cis

- 3

- Chloroacrylate (UC 20299) to Goldfish: Project No . 141E41. (Unpublished study received Dec 11, 1963 under PP0410; submitted by Union Carbide Corp., New York, N.Y.; CDL:090442

- F)

120762 Howell, J. (19??) Toxicity of Chemicals: | 11144. (Unpublished study received May 7, 1973 under 3125

- 71; prepared by U. S. Fish and Wildlife Service, Bureau of Commercial Fisheries, Hammond Bay Biological Station, submitted by Mobay Chemical Corp., Kansas City, MO; CDL:007020

- B)

120764 Walker, C. (1963) Chemical Toxicity to Fish: DEF 12947. (Unpublished study received May 7, 1973 under
3125

- 71; prepared by U.S. Fish and Wildlife Service, Fish Control Laboratory, submitted by Mobay Chemical Corp., Kansas City, MO; CDL: 

### 007020

- D)

### 74 120767 Marking, L. (1967) Concentrations Producing All

- or

- none Effects on a Preliminary Basis at 24 Hours and 12C: ?Various Chemagro Compounds 17363. (Unpublished study received May 7, 1973 under 3125

- 71; prepared by U.S. Fish and Wildlife Service, Fish Control Laboratory, submitted by Mobay Chemical Corp., Kansas City,
MO; CDL:007020

- G 

### )

120770 Lamb , D.; Roney, D. (1972) Acute Toxicity of DEF 6 Lbs/Gal Spray Concentrate to Fish: Report No. 33400. (Unpublished study received May 7, 1973 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, MO; CDL:007020

- N)

41618806 Grau, R. (1990) DEF Techn ical Grade: Acute Toxicity to Bluegill Sunfish in a Flow

- through Test: Lab Project
Number: FB

- 003: E2860137: 100222. Unpublished study prepared by Bayer Ag. 36 p.

41618807 Grau, R. (1990) DEF 6: Acute Toxicity to Bluegill Sunfish in a Flow

- through Test: Lab Project Number: FB

006: E02860355

- 9: 100219. Unpublished study prepared by Bayer Ag. 40 p.

41618808 Grau, R. (1990) DEF Technical Grade: Acute Toxicity to Rainbow Trout in a Flow

- through Test: Lab Project
Number: FF

- 286: E2810136

- 1: 100221. Unpublishe d study prepared by Bayer Ag. 36 p.

41618809 Grau, R. (1990) DEF 6: Acute Toxicity to Rainbow Trout in a Flow

- through Test: Lab Project Number: FF

228: E2510429: 100220. Un

- published study prepared by Bayer Ag. 39 p.

45863706 Kern, M.; Lam, C. (2002) A cute Toxicity of Tribufos Technical to the Fathead Minnow ( Pimpephales promelas ) Under Flow

- Through Conditions: Lab Project Number: DE831202: 200144. Unpublished study prepared by Bayer Corporation. 34 p.

72

- 2 Acute Toxicity to Freshwater Invertebrates

111775 Lowe, J. (1964) Effects of Pesticides: Telodrin and Other Com

- pounds|. (U.S. Fish and Wildlife Service, Bureau of Commercial Fisheries, Biological Laboratory; unpublished study; CDL: 

### 123712

- A)

41689901 Heimbach, F. (1989) Acute Toxi city of DEF (Technical) to Waterfleas ( Daphnia magna ): Lab Project Number: 99630. Unpublished study prepared by Bayer AG. 32 p.

41689902 Heimbach, F. (1990) Acute Toxicity of DEF 6 to Waterfleas ( Daphnia magna ): Lab Project Number:

HBF/ DM96: E 320 0403

- 2: 100208. Un published study prepared by Bayer AG. 33 p.

72

- 3 Acute Toxicity to Estuarine/Marine Organisms

66341 U.S. Environmental Protection Agenc y, Environmental Research Labo ratory (1981) Acephate, Aldicarb, Carbophenothion, DEF, EPN, Ethoprop, Methyl Parathion, and Phorate: Their Acute and Chronic Toxicity, Bioconcentration Potential, and Persistence as Related to Marine Environments: EPA

- 600/4

- 81

- 023. (Unpublished study)

103754 Butler, P. (1966) The Problem of Pesticides in Estuaries. Pages 110

- 115 I n Symposium on Estuarine Fishes |; 1964, At lantic City, NJ. Washington, DC . (Also In unp ublished sub mission received Oct 6, 1969 under unknown admin. no.; submitted by Shell Chemical Co., 

### Washington, DC; CDL:120338

- K)

41896301 Ward, G. (1991) DEF: Acute Toxicity to The Mysid, Mysidopsis bahia, Under Flow

- Through Test Conditions: Lab Project Number: J900802

- 4B: 101245. Unpublished study prepared by Mobay Corp. 45 p.

41896302 Gagliano, G. (1991) Acute Toxicity of DEF Technical to the Sheeps head Min now ( Cyprinodon variegatus )
Under Flow

- Through Condi tions: Lab Project Number: DE831201: 101240. Unpublished study prepared by Mobay Corp. 31 p.

### 75 42083201 Wheat, J.; Ward, G. (1991) DEF Technical: Acute Effect on New Shell Growth of, The Eastern Oyster,

Cr

assostrea virginica : Lab Pro ject Number: 101959: J9008024C. Unpublished study prepared by Toxikon Environmental Sciences. 53 p.

72

- 4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

48320 Butler, P.A. (1963 ) Commercial Fishery Investigations. Pages 5

- 28, In Pesticide

- Wildlife Studies, 1963: A Review of Fish and Wildlife Service Investigations during the Calendar Year. By U.S. Fish and Wildlife Service. Washington, D.C.: U.S. Fish and Wildlife Service. (Circular 199; submitter re port no. 16229h, published study; CDL:226511

- H)

49257 Lamb, D.W.; Roney, D.J. (1972) Acute Toxicity of DEF 6 Lbs/Gal Spray Concentrate to Fish: Report No. 33400. (Unpublished study received Mar 22, 1976 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224114

- O)

51525 Howell, J.H. (1963) Letter sent to Lewis F. Stevens date d Jan 4, 1963 Toxicity of chemicals to fish and larvae|: Report No. 11144. (U.S. Fish and Wild life Service, Bureau of Commer cial Fisheries, Hammond Bay Biologica l Station, unpublished study; CDL:224114

- B)

51526 Walker, C.R. (1963) Letter sent to Lewis F. Stevens dated Apr 24, 1963 Screening results on various compounds|: Report No. 11401. U.S. Fish and Wildlife Service, unpublished study; CDL:224114

- C)

66341 U.S. Environmental Protection Agenc y, Environmental Research Labo ratory (1981) Acephate, Aldicarb, Carbophenothion, DEF, EPN, Ethoprop, Methyl Parathion, and Phorate: Their Acute and Chronic Toxicity, Bioconcentration Potential, and Persistence as Related to Marine Environments: EPA

- 600/4

- 81

- 023. (Unpublished study 

### )

111775 Lowe, J. (1964) Effect s of Pesticides: Telodrin and Other Com pounds|. (U.S. Fish and Wildlife Service, Bureau of Commercial Fisheries, Biological Laboratory; unpublished study; CDL: 123712

- A)

41618810 Heimbach, F. (1990) Influence of DEF Technical on the Reproduction Rate of Water Fleas: Lab Project
Number: HBF/RDM29: E3210393

- 1: 100235. Unpublished study prepared by Bayer Ag. 56 p.

43978201 Bowers, L. (1996) Chronic Toxicity of (ca rbon 14)

- DEF to the Waterflea ( Daphnia magna ) Under Static Renewal Conditions: Lab Project Number: DE840701: 107327. Unpublished study prepared by Bayer Corp. 64

p.

45863702 Blankinship, A.; Kendall, T.; Krueger, H. (2002) Tribufos Technical: A Flow

- Throu gh Life

- Cycle Toxicity Test with the Saltwater Mysid ( Mysidopsis bahia ): Lab Project Number: 149A

- 133A: DE843101: 200363. Unpublished study prepared by Wildlife International, Ltd. 77 p.

45863703 Kern, M.; Lam, C. (2002) Early Life Stage Toxicity of Trib ufos to the Fathead Minnow ( Pimephales promelas ): Lab Project Number: DE841201: 200308. Unpublished study prepared by Bayer Corporation. 79 p.

45863707 Palmer, S.; Kendall, T.; Krueger, H. (2002) Tribufos Technical: An Early Life

- Stage Toxicity Test with the Sheepshead Minnow ( Cyprinodon variegatus ): Lab Project Number: 149A

- 134: DE842801: 200336. Unpublished study prepared by Wildlife International, Ltd. 82 p.

### 76 47958201 Matlock, D.; Lam, C. (2010) Early Life Stage Toxicity of Tribufos Technical to the Fa thead Minnow ( Pimephales promelas ) Under Flow

- Through Conditions. Project Number: EBTRL001, M/360947/01/1. Unpublished study prepared by Bayer CropScience. 96 p.

72

- 6 Aquatic org. accumulation

41618818 Cohle, P. (1990) Uptake, Depuration and Bioconcentration of (Carbon 14)

- DEF by Bluegill ( Lepomis
Macrochirus ): Lab Project Number: 38466: 100234. Unpublished study prepared by Mobay Corp. 45 p.

81

- 1 Acute oral toxicity in rats

45983 Crawford, C.R. (1971) Treatment Studies for DEF Intoxic ation: Report No. 30093. (Unpublished study received Jul 19, 1 971 un der unknown admin. no.; submitted by Chemagro Corp., Kansas City, Mo.;
CDL:103419

- A)

49241 Crawford, C.R.; Anderson, R.H. (1972) The Acute Oral Toxicity of DEF (Special) 6 lbs/gal Spray C oncentrate to Rats: Report No. 33127. (Unpublished study received Mar 22, 1976 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL: 224109

- F)

62031 Dow Chemical Company (1965) Results of Acute Oral Toxicity Testing of Ronnel Insectici de in Paired Combination with Other Cholinesterase Inhibitors When Administered to Female Rats. (Unpublished study received Apr 23, 1969 under 9F0800; CDL:091378

- H)

74871 Schoenig, G. (1966) Report to Chevron Chemical Company: Dibrom Potentiation Studies with Six Organic Phosphates: IBT No. A4629. (Unpublished study received Sep 20, 1966 under 7F0532; prepared by Industrial
Bio

- Test Laboratories, Inc., submitted by Chevron Chemical Co., Richmond, Calif.; CDL:090645

- G)

75911 Shoenig, G. (1966) Report to Ch evron Chemical Company: Desethyl

- phosphamidon

-- Potentiation Studies with Six Organic Phosphates: IBT No. A4734. (Unpublished study received Nov 1, 1966 under 7F0546; prepared by Industrial Bio

- Test Laboratories, Inc., submitted by Chevron Chemical Co., Ri chmond, Calif.;
CDL: 090671

- G)

79900 Connor, N.D. (1965) Letter sent to H.S. Bryan dated Mar 9, 1965: DEF and Banol acute oral potentiation study in rats. (Unpublished study received Feb 3, 1966 under 9156

- 1; submitted by Upjohn Co., Kalamazoo, Mich.;
CDL:100650

- W)

87417 Murphy, S.D.; DuBois, K.P. (1959) Toxicity and anticholinesterase activity of tributyl phosphorotr ithioate (DEF). American Medical Association Archives of Industrial Health 20(Aug):161

- 166. (Submitter 4242; also

In unpublished submission received Jan 18, 1969 under 9F0737; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- J)

87420 DuBois, K.P. (1964) The Acute Toxicity of Two Samples of S,S,S

- Tributyl Phosphorothioate to Adult, Female Rats: 14565. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Dept. of Pharmacology, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- M)

99099 Schoenig, G. (1966) Report to Chevron Chemical Company: Phosphamidon

-- Potentiation Studies with Six Organic Phosphates: IBT No. A4630. (Unpublished study received Nov 1, 1966 under 7F0546; prepared by
Industria l Bio

- Test Laboratories, Inc., submitted by Chevron Chemical Co., Richmond, Calif.; CDL: 090671

- E)

### 77 118756 Connor, N. (1965) Letter sent to H. Bryan dated Mar 9, 1965: DEF and Banol: Acute oral potentiation study in rats. (Unpublished study received Feb 3, 1966 under 9156

- 1; submitted by Upjohn Co., Kalamazoo, MI;
CDL:005694

- W)

142425 Crawford, C. (1971) Treatment Studies for DEF Intoxication: Report No. 30093. Unpublished study prepared by Chemagro Corp. 7 p.

41954903 Sheets, L. (1991) Acute Oral Toxicity Study with Technical Grade Tribufos (DEF) in Rats: Lab Project
Number: 90

- 012

- ES: 100697. Unpublished study prepared by Mobay Corp. 20 p.

42408101 Astroff, A. ; Phillips, S. (1992) Experimental Acute Oral Toxicity Study with HBM Sulfone (a Metabo lite of Tribufos, DEF) in Female Rats: Lab Project Number: 92

- 912

- OD. Unpublished study prepared by Miles, Inc. 18 p.

42682401 Sheets, L.; Phillips, S. (1992) Acute Oral Toxicity Study with DEF 6 in Rats: Lab Project Number: 92

- 012

- NO: 102678. Unpublished study prepared by Miles Inc. 22 p.

45863708 Mach, J. (2002) Tribufos: Acute Dietary Toxicity Test with the White

- Footed Mouse ( Peromyscus leucopus ): Final Report: Lab Project Number: 02005: DE732601: 110770. Unpublished study prepared by Genesis
Laborato ries, Inc. 91 p.

81

- 2 Acute dermal toxicity in rabbits or rats

45978 DuBois, K.P. (1957) The Dermal Toxicity of S,S,S

- Tributyl phosphorotrithioate to Rats (DEF; B

- 1776): Report No. 1990. (Unpublished study received Feb 8, 1960 under unknown admin. no.; pre pared by Univ. of Chicago, Dept. of Pharmacology, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:103421

- D)

49243 Crawford, C.R.; Anderson, R.H. (1972) The Acute Dermal Toxicity of DEF ULV to Rabbits: Report No.

3448 0. (Unpublished study received Mar 22, 1976 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224109

- H)

87420 DuBois, K.P. (1964) The Acute Toxicity of Two Samples of S,S,S

- Tributyl Phosphorothioate to Adult, Female
Rats: 14565. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Dept. of Pharmacology, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- M)

87424 Dubois, K.P.; DiGiacomo, R.; Root, M.; et al. (1966) The Subacute Dermal T oxicity of Tributyl Phosphorotrithioate (DEF) to Rats: 19563. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Toxicity Laboratory, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:
091270

- Q)

41954902 Sheets, L. ; Phillips, S. (1991) Acute Dermal Toxicity Study with Technical Grade Tribufos (DEF) in Rabbits: Lab Project Number: 90

- 025

- FE: 100698. Unpublished study prepared by Mobay Corp. 20 p.

42682402 Astroff, A.; Phillips, S. (1992) Acute Dermal Toxicity Study with DEF 6 in Rats: Lab Project Number: 92

- 022

- NZ: 102679. Unpublished study prepared by Miles Inc. 22 p.

81

- 3 Acute inhalation toxicity in rats

49238 DuBois, K.P.; Meskauskas, J. (1968) The Acute Inhalation Toxicity of a DEF Formulation to Mice: Report No. 23805. (Unpublished study received Mar 22, 1976 under 3125

- 71; prepared by Univ. of Chicago, Toxicity Laboratory, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224109

- C)

### 78 49242 Kimmerle, G.; Lorke, (1972) DEF ULV 6 Lb./Gal. S.C.: Acute Inhalation Toxicity: Report No. 3487; Report No. 34161. (Unpublished study received Mar 22, 1976 under 3125

- 71; prepared by Farbenfabriken Bayer, AG, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224109

- G)

87858 Mobay Chemical Corporation (1981 ) Pulmonary Exposure of Mice to DEF: 54054. (Unpublished study received Sep 10, 1981 under 3125

- 282; CDL:246511

- B)

151227 Thyssen, J. (1978) DEF: Studies on Acute Inhalation Toxicity (Rats): 80

- T

- 014: Report No. 7636. Unpublished Mobay Report No. 66481 prepared by Bayer AG. 6 p.

41782301 Warren, D. (1990) Acute Four

- Hour Inhalation Toxicity Study with Technical Grade DEF in Rats: Lab Project
Number: 90

- 042

- HQ. Unpublished study prepared by Mobay Corp. 33 p.

42682403 Warren, D.; Tran, A. (1992) Acute Four

- Hour Inhalation Toxicity Study with DEF 6 in Rats: Lab Project
Number: 91

- 042

- MD: 102669. Unpublished study prepared by Miles Inc. 35 p.

81

- 4 Primary eye irritation in rabbits

49239 Crawford, C.R. (1971) The Eye and Dermal Irritating Pro perties of DEF 6 Lbs/Gal Spray Concentrate to Rabbits: Report No. 30814. (Unpublished study received Mar 22, 1976 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL: 224109

- D)

49244 Crawford, C.R.; Anderson, R.H. (1972) The Skin and Eye Irritation Properties of DEF Technical to Rabbits: Report No. 35006. (Unpublished study received Mar 22, 1976 under 3125

- 71; submit

- ted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224109

- I)

42441601 Sheets, L.; Phillips, S. (1992) Primary Eye Irri tation Study with Technical Grade Tribufos in Rabbits: Lab Project Number: 91

- 335

- MN. Unpublished study prepared by Miles Inc. 17 p.

92034003 Sheets, L. (1990) Mobay Corporation Phase 3 Summary of MRID 00049244. The Skin and Eye: Irritation Properties of DEF Technical to Rabbits: Project: 72

- 38 (Mobay Report 35006). Prepared by Mobay Corp.. 7 p.

81

- 5 Primary dermal irritation

49239 Crawford, C.R. (1971) The Eye and Dermal Irritating Properties of DEF 6 Lbs/Gal Spray Concentrate to Rabbits: Report No. 30814. (Unpublished study received Mar 22, 1976 under 3125

- 71; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL: 224109

- D)

49244 Crawford, C.R.; Anderson, R.H. (1972) The Skin and Eye Irritation Properties of DEF Technical to Rabbits: Report No. 35006. (Unpublished study received Mar 22, 1976 under 3125

- 71; submit

- ted by Mobay Chemical Corp., Kansas City, Mo.; CDL:224109

- I)

41896303 Sheets, L.; Fuss, M. (1991) Primary Dermal Irritation Study with Technical Grade Tribufos (DEF) in Rabbits:

La b Project Number: 90

- 325

- FS. Unpublished study prepared by Mobay Corp. 16 p.

42289301 Sheets, L.; Phillips, S. (1992) Primary Dermal Irritation Study with DEF 6 in Rabbits: Lab Project Number: 91

- 325

- MG. Unpublished study prepared by Miles Inc. 28 p.

42891202 Zorbas, M. (1993) Primary Dermal Irritation Study with Technical Grade Tribufos (DEF) in Rabbits: Lab Project Number: 90

- 325

- FS; 100694

- 1. Unpublished study prepared by Miles, Inc. 8 p.

81

- 6 Dermal sensitization

41618812 Sheets, L. (1990) Dermal Sensitization Study with Technical Grade Tribufos (DEF) in Guinea Pigs: Lab Project Number: 90

- 324

- GK: 100268. Unpublished study prepared by Mobay Corp. 24 p.

42891201 Zorbas, M. (1993) Dermal Sensitization Study with Technical Grade Tr i bufos (DEF) in Guinea Pigs: Lab Project Number: 90

- 324

- GK: 100268

- 1. Unpublished study prepared by Miles, Inc. 9 p.

### 79 43936601 Warren, D.; Meier, M. (1996) Dermal Sensitization Study with DEF 6 in Guinea Pigs: Lab Project Number:
107182: 95

- 324

- EJ. Unpublished study prepared by Bayer Corp. 25 p.

81

- 7 Neurotoxicity study in hens

144098 Thyssen, J.; Schilde, B.; Kimmerle (1976) DEF: Neuroto xicity stud ies on Dermally Treated Hens: Report No. 6255. Unpublished study prepared by Bayer AG. 17 p.

144940 Thyssen, J.; Mohr, U. (1976) DEF: Neurotoxicity Studies on Hens: Report No. 5948. Unpublished Mobay report 47932 prepared by Bayer Ag and Medizinische Hochschule Hannover, Abteillung fuer Experimentelle Pathologie, W. Ger. 21 p.

146338 Thyssen, J.; Wechsler, W.; Schilde, B. (1977) DEF: Neurotoxicity Studies on Hens: Thirty

- day Feeding Experiments: Report No. 6941. Unpublished study prepared by Bayer AG. 39 p.

151228 Abou

- Donia, M. (1978) Study of the Low Level Effects of Organophosphorus Esters with Specific Refe rences to the Delayed Neurotoxic Syndrome: Quarterly Report 4: Effect of a Single Oral Dose and Subchronic (90

- day) Oral Administration of Technical DEF to Adult Hens. Unpublished study prepared by Duke University Department of Pharmacology. 35 p.

151229 Abou

- Donia, M. (1979) Late acute eff ect of S,S,S

- tributyl phosphor otrithioate (DEF) in hens. Toxicology Letters (4): 231

- 236.

151230 Wilson, B.; Cisson, C.; Randall, W.; et al. (1980) Organophosphate risk assessment: Field testing of DEF with
the scaleles s chicken. Bull. Environm. Contam. Toxicol. (24):921

- 928.

151231 Abou

- Donia, M.; Graham, D.; Timmons, P.; et al. (1979) Delayed neurotoxic and late acute effec ts of S,S,S

tributyl phosphoro trithioate on the hen: Effect of route of administration. Neurotox icology 1:425

- 447.

151232 Abou

- Donia, M.; Graham, D.; Abdo, K.; et al. (1979) Delayed neurotoxic, late acute and cholinergic effects of S,S,S

- tributyl phosphorotrithoate (DEF): Subchronic (90 days) administration in hens. Toxicology 14:229

- 243.

158404 Abdo, K.; Timmons, P.; Abou

- Donia, M. (1983) Effects of a dermal dose of S,S,S,

- Tri

- n

- butyl phosphorotrithioate on brain acetyl

- cholinesterase, acid phosphatase, and 2,3'

- cyclic nucleotide

- 3' phosphohydrolase and plasma butyrlcholinesterase in hens: Repor t No. 88977. P. 499

- 502 in Elsevier Science
Publishers B.V.

- Development in the Science and Practice of Toxicology.

164992 Thyssen, J.; Schilde, B. (1976) DEF: Neurotoxicity Studies on Hens (30

- day Feeding Study): Report No. 6440. Unpublished Mobay Report No. 90493 prepared by Bayer AG. 44 p.

40869201 Baron, R.; Johnson, H. (1964) Neurological disruption produced in hens by two organophosphate esters. Brit. J.
Pharmacol. 23:295

- 304.

40879102 Johnson, M. (1970) Organophosphorus and other inhibitors of brain 'neurotoxic esterase' and the development of delayed neurotoxicity in hens. Biochem. J. 120:523

- 531.

81

- 8 Acute neurotoxicity screen study in rats

44071501 Wu, S.; Casida, J. (1996) Subacute neurotoxicity induced in mice by potent organophosphorus neuropathy target esterase inhibitors. Tox. and Appl. Pharmacol. 139:195

- 202.

45194401 Sheets, L.; Gilmore, R. (2000) An Acute Oral Neurotoxicity Screening Study with Technical Grade Tribufos (DEF) in Wistar Rats: Lab Project Number: 98

- 4 12

- WF: 109802. Unpublished study prepared by Bayer Corporation. 476 p. {OPPTS 870.6200}

### 80 45464601 Sheets, L.; Gilmore, R. (1999) Verification of Personnel Training to Perform a Functional Observational Battery with Rats: (Carbaryl): Lab Project Number: 97

- 962

- LG. Unpublished study prepared by Bayer Corporation. 94 p.

82

- 1 Subchronic Oral Toxicity: 90

- Day Study

87421 Doull, J.; Root, M. (1965) Subacute Oral Toxicity of DEF to Male and Female Dogs: 16422. (Unpublished study received Jan 18, 1969 un der 9F0737; prepared by Univ. of Chicago, Dept. of Pharmacology, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- N)

87423 Root, M.; Taitel, C.; Doull, J. (1965) Subacute Oral Toxicity of DEF to Male and Female Rats: 16823. (Unpublished stu dy received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Dept. of Pharmacology, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- P)

87425 Root, M.; Doull, J. (1967) Effect of Adding DEF in Combination with Malathion to the Diet of Male and Female Dogs: 19773. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Toxicity Laboratory, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- R)

97897 Root, M.S.; Doull, J. (1966) Comparative sub acute oral toxicity of some organic phosphates in rats and dogs. Taken from: Abstracts of Papers of the Fifth Annual Meeting of the Society of Toxicology, 1966. N.P. (Abstract 50). (Submitter 17845; also in unpublished submission received Aug 21, 1972 unde r unknown admin. no.; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:140139

- G)

153410 Hayes, R. (1985) Pilot Study on Technical Tribufos (DEF) with Mice: Study No. 85

- 971

- 01: 90445. Unpublished study prepared by Mobay Chemical Corp. 11 p.

82

- 2 21

- day dermal

- rabbit/rat

42007201 Sheets, L.; Phillips, S. (1991) 21

- Day Dermal Toxicity Study with Technical Grade Tribufos (DEF) in Rabbits: Lab Project Number: 90

- 125

- FP. Unpublished study prepared by Mobay Corp., Toxicology Dept. 445 p.

82

- 3 90

- day dermal

- rodent

87424 Dubois, K.P.; DiGiacomo, R.; Root, M.; et al. (1966) The Subacute Dermal Toxicity of Tributyl Phosphorotrithioate (DEF) to Rats: 19563. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chica go, Toxicity Laboratory, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:
091270

- Q)

82

- 4 90

- day inhal.

- rat

80037 Thyssen, J.; Lorke, D.; Mohr, U. (1978) DEF: Subacute Inhalation Study on Rats: Report No. 7649; 66435. (Unpublished study rec eived Aug 21, 1981 under 3125

- 282; prepared by Bayer AG, West Germany, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:245782

- A 

### )

149213 Thyssen, J.; Mohr, V.; Lorke, D. (1978) DEF: Subacute Inhalation Study on Rats: Report No. 7649. Unpublished study prepared by Bayer AG. 63 p.

41954901 Pauluhn, J. (1991) DEF: Tribufos; Tribufate: Range

- Finding Study of the Subacute Inhalation Toxicity to Rats (Exposure: 10 x 6h): Lab Project Number: 100695: 91

- T

- 036: 19903. Unpublished study prepared by Bayer

A G. 212 p.

### 81 42399801 Pauluhn, J. (1992) DEF (Common Name: Tribufos): Study of the Subchronic Inhalation Toxicity to Rats in Accordance with OECD Guideline No. 413: Lab Project Number: 102697. Unpublished study prepared by Bayer Ag, Wuppertal, Germany. 1050 p.

82

- 5 Subchronic Neurotoxicity: 90

- Day Study

80026 Thyssen, J.; Schilde, B.; Lorke, D. (1978) DEF, Studies of Subacute Dermal Neurotoxic Effects on Poultry: Report No. 8081; 67075. (Unpublished study received Aug 21, 1981 under 3125

- 282; pre

- pared by Bayer AG, West Germany, Submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:245780

- A 

### )

132875 Hansen, L.; Francis, B.; Metcalf, R.; et al. (1982) Effects of Chronic Oral and Dermal Administration of Pesticides on Laying Hens, Including Delaye d Neuropathy: I. Organophosphorus Pesticides: Project No. XX

82

- 275. (Unpublished study received Nov 30, 1983 under 524

- 124; prepared by Univ. of Illinois, College of Veterinary Medicine and Institute of Environmental Studies, submitted by Monsanto Co., Wa shington, DC;
CDL:251840

- C)

151228 Abou

- Donia, M. (1978) Study of the Low Level Effects of Organophosphorus Esters with Specific References to the Delayed Neurotoxic Syndrome: Quarterly Report 4: Effect of a Single Oral Dose and Subchronic (90

- day) Oral Administration of Technical DEF to Adult Hens. Unpublished study prepared by Duke University Department of Pharmacology. 35 p.

151232 Abou

- Donia, M.; Graham, D.; Abdo, K.; et al. (1979) Delayed neurotoxic, late acute and cholinergic effects of S,S,S

- tribu tyl phosphorotrithoate (DEF): Subchronic (90 days) administration in hens. Toxicology 14:229

- 243.

42007202 Sheets, L. (1991) Subchronic Delayed Neurotoxicity Study with Technical Grade Tribufos (DEF) in Hens: Lab Project No: 89

- 428

- CS. Unpublished study prepared by Mobay Corp., Toxicology Dept. 189 p



### .

82

- 7 Subchronic Neurotoxicity

45369101 Sheets, L.; Gilmore, R. (2001) A Subchronic Neurotoxicity Screening Study with Technical Grade Tribufos (DEF) in Wistar Rats: Lab Project Number: 99

- N72

- BB: 110 242: 9465. Unpublished study prepared by Bayer Corp. and Pathology Associates International. 538 p.

83

- 1 Chronic Toxicity

87426 Hibbs, C.; Ne lson, D.L. (Year not reported) C hronic Oral Toxicity of DEF to Male and Female Rats: 20462. (Unpublished st udy received Jan 18, 1969 under 9F0737; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- S)

87428 DuBois, K.P.; Root, M.; Meskauskas, J.; et al. (1967) Chronic Oral Toxicity of DEF to Male and Female Dogs: Submitter| 21556. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Toxicity Laboratory, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:091270

- U)

145268 Root, M.; Meskauskas, J.; Doull, J. (1967) Chronic Oral Toxicity of DEF to Male and Fema le Rats. Unpublished Mobay report 20462 prepared by Univ. of Chicago, Toxicity Laboratory. 18 p.

145868 Root, M.; Meskanskas, J.; Doull, J. (1967) Chronic Oral Toxicity of DEF to Male and Female Rats. Unpublished study prepared by University of Chicago. 1 8 p.

42007203 Christenson, W. (1991) Chronic Feeding Toxicity Study of Technical Grade Tribufos (DEF) with Dogs: Lab Project Number: 88

- 274

- AB. Unpublished study prepared by Mobay Corp., Toxicology Dept. 585 p.

### 82 83

- 2 Oncogenicity

40273801 Hayes, R. (1987) Interim Report on Tribufos (DEF) Mouse Oncogenicity Study: Lab Project No.: 94700. Unpublished study prepared by Mobay Corp. 4 p.

40436001 Hayes, R. (1987) Oncogenicity Study with Tribufos (DEF) in the Mouse: Interim Report: Laboratory Project

ID 86

- 271

- 01. Unpublished study prepared by Mobay Corporation. 5 p.

40611301 Hayes, R. (1988) Oncogenicity Study with Tribufos (DEF) in the Mouse: Study No. 86

- 271

- 01. Unpublished study prepared by Mobay Corp. 5 p.

41171001 Hayes, R. (1989) Oncogenicity Stu dy of Technical Grade Tribufos (DEF) with Mice: Study No. 86

- 271

- 01. Unpublished study pre

- pared by Mobay Corp. 2042 p.

92034004 Christenson, W. (1990) Mobay Corporation Phase 3 Summary of MRID 41171001. Oncogenicity Study with Technical Grade Tribufos ( DEF) with Mice: Project: 86

- 271

- 01 (Mobay Report 99175). Prepared by Mobay Corp.. 25 p.

83

- 3 Teratogenicity

-- 2 Species

40190601 Kowalski, R. (1986) A Teratology Study with DEF Technical in the Rat: Report No. 87320. Unpublished study prepared by Miles Laboratories, Inc. 213 p.

40190602 Clemens, G.; Bare, J.; Hartnagel, R. (1987) Teratology Study in the Rabbit with DEF Technical: Report No. MTD0003. Unpublished study prepared by Miles Laboratories, Inc. 120 p.

40879101 Kasymova, R. (1975) Experim ental Study of the Embryotoxic Effect of Butiphos. A translation of Ekcnepnmehtanbhoe Nyhehne Embpnotok cnheckoto )|enctbnr bytnoca translated by Rainbow Systems, Inc. 9

p.

92034005 Eigenberg, D. (1990) Mobay Corporation Phase 3 Summary of MRID 40190601. A Teratology Study with DEF in the Rat: Project 8536 (Mobay Report 87320). Prepared by Miles Laboratories, Inc.. 27 p.

92034006 Eigenberg, D. (1990) Mobay Corporation Phase 3 Summary of MRID 40190602. Teratology Study in the
Rabbit with DEF Technical: Pro ject 8605 (Mobay Report 94468). Prepared by Miles Laboratories, Inc.. 34 p.

83

- 4 2

- generation repro.

- rat

87427 DuBois, K.P.; Root, M.; DiGiacomo, R.; et al. (1967) Effect of DEF in the Diet on the Reproduction and Lactation on Mice: ?Submitter| 215 43. (Unpublished study received Jan 18, 1969 under 9F0737; prepared by Univ. of Chicago, Toxicity Laboratory, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL: 091270

- T)

144939 Root, M.; DiGiacomo, R.; Meskauskas, J.; et al. (1967) Effect of DEF in the Diet on the Reproduction and Lactation of Mice. Unpublished Mobay report 21543 prepared by Univ. of Chicago, Toxicity Laboratory. 7 p.

42040201 Eigenberg, D.; Elcock, L. (1991) A Two

- Generation Reproduction Study in Rats Using Tribufos (DEF): Lab

P roject Number: 88

- 671

- AK. Unpublished study prepared by Mobay Corp. 1025 p.

83

- 5 Dietary: Combined Chronic Toxicity/Oncogenicity Studies

42335101 Christenson, W. (1992) Technical Grade Tribufos (DEF): A Chronic Toxicity/Oncogenicity/ Neurotoxicity Feeding Study in the Fisher 344 Rat: Lab Project Number: 88

- 271

- AA. Unpublished study prepared by Miles Inc. 3672 p.

### 83 42553601 Christenson, W. (1992) Technical Grade Tribufos (DEF): A Chronic Toxicity/Oncogenicity/Neurotoxicity Feeding Study in the Fischer 344 Rat: A Supplement: Lab Project Number: 88

- 271

- AA: 102675

- 1. Unpublished study prepared by Miles, Inc. 183 p.

45475501 Sheets, L. (2001) A Developmental Neurotoxicity Screening Study with Technical Grade Tribufos (DEF) in Wistar Rats: Lab Proje ct Number: 00

- D72

- AG: 00

- D72

- AS: 110523. Unpublished study prepared by Bayer Corporation. 1281 p.

45499501 Lake, S. (2001) A Developmental Neurotoxicity Screening with Technical Grade Tribufos (DEF) in Wistar Rats: Lab Project Number: 00

- D72

- AG: 00

- D72

- A S. Unpublished study prepared by Bayer Corporation. 1281

p.

121

- 1 Phytotoxicity

102298 Mobay Chemical Corp. (1974) Efficacy of Guthion Preparations and Other Compounds for Insect Control on Cotton|. (Compilation; unpublished study received Aug 9, 1974 under 3125

- 271; CDL:009691

- B)

112032 Mobay Chemical Corp. (1974) Efficacy Study: DEF, Guthion, & Other Specific Insecticides on Selected Grain Crops|. (Compilation; unpublished study received Apr 23, 1974 under 3125

- 71; CDL: 025713

- A)

112149 Olson, T.; Horton, J. (1974) Comparative Drift Study of DEF As ULV and Spray Concentrate in Water: 39400. (Unpublished study received Mar 22, 1976 under 3125

- 282; submitted by Mobay Chemical Corp., Kansas City, MO; CDL:232397

- C)

139286 Mobay Chemical Corp. (1972 ) (Phytotoxicity of DEF and DEF

- Guthion to Sorghum and Other Crops). (Compilation; unpublished study received Mar 22, 1976 under 3125

- 282; CDL:232397

- A)

122

- 2 Aquatic plant growth

45863705 Kern, M.; Lam, C. (2002) Toxicity of Tribufos Technical to Duckweed (Lemna gibba G3): Lab Project Number: DE883701: 200301. Unpublished study prepared by Bayer Corporation. 45 p.

123

- 1 Seed germination/seedling emergence and vegetative vigor

45863704 Bowers, L. (2002) Tier 2 Seedling Emergence and Vegetati ve Vigor Nontarget Phytotoxicity Study Using DEF 6: Lab Project Number: DE451601: DE451602: 200245. Unpublished study prepared by Bayer Corporation. 105 p.

123

- 2 Aquatic plant growth

41618813 Hughes, J. (1990) The Toxicity of DEF Technical to Selanastrum capricornutum (Tier 2 Growth and Reproduction of Aquatic Plant

- s): Lab Project Number: BO59

- 02

- 2: 100230. Unpublished study prepared by Malcolm Pirnie, Inc. 36 p.

141

- 1 Honey bee acute contact

49252 University of California, Agricultur al Extension Service Toxicity of Pesticides and Other Agricultural Chemicals to Honey Bees: Field Study. Riverside, Calif.: UC, ACES. (AXT

- 251; submitter report no. 21052; also in unpublished submission received Mar 22, 1976 under 3125

- 71; submitted by Mob ay Chemical Corp., Kansas City, Mo.; CDL:224114

- I)

165

- 0 Accumulation Studies

-- General

66341 U.S. Environmental Protection Agency, Environmental Research Laboratory (1981) Acephate, Aldicarb, Carbophenothion, DEF, EPN, Ethoprop, Methyl Parathion, and Phorate: Their Acute and Chronic Toxicity, Bioconcentration Potential, and Persistence as Related to Marine Environments: EPA

- 600/4

- 81

- 023. (Unpublished study 

### )

### 84

### 85 Appendix A

. Selected SWCC Output Files

MS Cotton, Aerial Spray , Maximum Application Rate (1.125 lb ai/A)



# Summary of Water Modeling of Tribufos and the USEPA Standard

Pond

Estimated Environmental Concentrations for Tribufos are presented in Table 1 for the USEPA standard pond with the MScottonSTD field scenario. A graphical presentation of the year

- to

- year peaks is presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are summarized in Tables 2 a nd 3. This model estimates that about 5.6% of Tribufos applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by runoff (53.9% of the total transport), followed by erosion (23.8%) and spr ay drift (22.3%). In the water body, pesticide dissipates with an effective water column half

- life of 759.1 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide fr om the complete system.) The main source of dissipation in the water column is volatilization (effective average half

- life = 907.2 days) followed by metabolism (4649.4 days). In the benthic region, pesticide dissipates very slowly (312.0 days). The main so urce of dissipation in the benthic region is metabolism (effective average half

- life = 312 days). The vast majority of the pesticide in the benthic region (99.52%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Conce ntrations (ppb) for Tribufos.

Peak (1

- in

- 10 yr) 29.7

4

- day Avg (1

- in

- 10 yr) 29.1

21

- day Avg (1

- in

- 10 yr) 27.1

60

- day Avg (1

- in

- 10 yr) 25.1

365

- day Avg (1

- in

- 10 yr) 21.6

Entire Simulation Mean 15.4

Table 2. Summary of Model Inputs for Tribufos.

Scenario MScottonSTD

Cropped Area Fraction 1

Kd (ml/g) 76.9

Water Half

- Life (days) @ 20 °C 4470

Benthic Half

- Life (days) @ 20 °C 300

Photolysis Half

- Life (days) @ 40 °Lat 0

Hydrolysis Half

- Life (days) 0

Soil Half

- Life (days) @ 20 °C 2235

Foliar Half

- Life (days)

### 86 Molecular Wt 314.54

Vapor Pressure (torr) 1.7E

- 6

Solubility (mg/l) 2.3

Table 3. Application Schedule for Tribufos.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

9/15 Foliar 1.26 0.95 0.125

Figure 1. Yearly Peak Concentrations



### CA Cotton with Irrigation Standard Scenario , Aerial Spray , Max

. Applic. Rate (1.875 lb ai/A)



# Summary of Water Modeling of Tribufos and the USEPA Standard

Pond

Estimated Environmental Concentrations for Tribufos are presented in Table 1 for the USEPA standard pond with the CAcotton_WirrigSTD field scenario. A graphical presentation of the year

- to

- year peaks is presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values f or the model are summarized in Tables 2 and 3. This model estimates that about 2% of Tribufos applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by spray drift (63.6% of the total

tr ansport), followed by runoff (32.8%) and erosion (3.67%). In the water body, pesticide dissipates with an effective water column half

- life of 830.4 days. (This value does not include dissipation by transport to the benthic region; it includes only processe s that result in removal of pesticide from the complete system.) The main source of dissipation in the water column is volatilization (effective average half

- life = 1005 days) followed by metabolism (4781.1 days). In the benthic region, pesticide dissipates very slowly (320.9 days). The main source of dissipation in the benthic region is metabolism (effective average half

- life = 320.9 days). The vast majority of the pesticide in the benthic region (99.52%) is sorbed to sediment rather than in the p ore water.

### 87 Table 1. Estimated Environmental Concentrations (ppb) for Tribufos.

Peak (1

- in

- 10 yr) 21.2

4

- day Avg (1

- in

- 10 yr) 20.0

21

- day Avg (1

- in

- 10 yr) 16.8

60

- day Avg (1

- in

- 10 yr) 14.3

365

- day Avg (1

- in

- 10 yr) 11.5

Entire Simulation Mean 9.48

Table 2. Summary of Model Inputs for Tribufos.

Scenario CAcotton_WirrigSTD

Cropped Area Fraction 1

Kd (ml/g) 76.9

Water Half

- Life (days) @ 20 °C 4470

Benthic Half

- Life (days) @ 20 °C 300

Photolysis Half

- Life (days) @ 40 °Lat 0

Hydrolysis Half

- Life (days) 0

Soil Half

- Life (days) @ 20 °C 2235

Foliar Half

- Life (days)

Molecular Wt 314.54

Vapor Pressure (torr) 1.7E

- 6

Solubility (mg/l) 2.3

Table 3. Application Schedule for Tribufos.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

11/4 Foliar 2.1 0.95 0.125

Figure 1. Yearly Peak Concentrations

### 88 MS Cotton, Aerial Spray
, Average Application Rate ( 0.54 lb ai/A)



# Summary of Water Modeling of T ribufos and the USEPA Standard

Pond

Estimated Environmental Concentrations for tribufos are presented in Table 1 for the USEPA standard pond with the MScottonSTD field scenario. A graphical presentation of the year

- to

- year peaks is presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 1.1 06). Critical input values for the model are
summarized in Tables 2 and 3. This model estimates that about 5.6% of tribufos applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by runof f (53.9% of the total transport), followed by erosion (23.8%) and spray drift (22.3%). In the water body, pesticide dissipates with an effective water column half

- life of 759.1 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the complete system.) The main source of dissipation in the water column is volatilization (effective average half

- life = 907.2 days) followed by metabolism (4649.4 days).
In the b enthic region, pesticide dissipates very slowly (312.0 days). The main source of dissipation in the benthic region is metabolism (effective average half

- life = 312 days). The vast majority of the pesticide in the benthic region (99.52%) is sorbed to sedime nt rather than in the
pore water.

Table 1. Estimated Environmental Concentrations (ppb) for T ribufos.

Peak (1

- in

- 10 yr) 14.2

4

- day Avg (1

- in

- 10 yr) 13.9

21

- day Avg (1

- in

- 10 yr) 12.9

60

- day Avg (1

- in

- 10 yr) 11.9

### 89 365

- day Avg (1

- in

- 10 yr) 10.3

Entire Simulation Mean 7.34

Table 2. Summary of Model Inputs for T ribufos.

Scenario MScottonSTD

Cropped Area Fraction 1

Kd (ml/g) 76.9

Water Half

- Life (days) @ 20 °C 4470

Benthic Half

- Life (days) @ 20 °C 300

Photolysis Half

- Life (days) @ 40

°Lat 0

Hydrolysis Half

- Life (days) 0

Soil Half

- Life (days) @ 20 °C 2235

Foliar Half

- Life (days)

Molecular Wt 314.54

Vapor Pressure (torr) 1.7E

- 06

Solubility (mg/l) 2.3

Table 3. Application Schedule for T ribufos.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

09/15 Foliar 0.60 .95 .125

Figure 1. Yearly Peak Concentrations

### 90 CA Cotton with Irrigation Standard Scenario , Aerial Spray

, Average Applic. Rate for Arizona (0.77 lb ai/A) 

# Summary of Water Modeling of T ribufos and the USEPA Standard

Pond
Estimated Environmental Concentrations for tribufos are presented in Table 1 for the USEPA standard pond with the CAcotton_WirrigSTD field scenario. A graphical presentation of the

year

- to

- year peaks is presented in Figure 1. These values were generated wi th the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are
summarized in Tables 2 and 3. This model estimates that about 2% of tribufos applied to the field eventually reaches the water body. The main mecha nism of transport from the field to the water body is by spray drift (63.6% of the total transport), followed by runoff (32.8%) and erosion (3.67%). In the water body, pesticide dissipates with an effective water column half

- life of 830.4 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the complete system.) The main source of dissipation in the water column is volatilization (effective average half

- life = 1005 days) followed by metabolism (4781.1 days). In the benthic region, pesticide dissipates very slowly (320.9 days). The main source of dissipation in the benthic region is metabolism (effective average half

- life = 320.9 days). The vast majority of the p esticide in the benthic region (99.52%) is sorbed to sediment rather than in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for T ribufos.

Peak (1

- in

- 10 yr) 8.66

4

- day Avg (1

- in

- 10 yr) 8.20

21

- day Avg (1

- in

- 10 yr) 6.89

60

- day Avg (1

- in

- 10 yr) 5.86

365

- day Avg (1

- in

- 10 yr) 4.70

Entire Simulation Mean 3.88

Table 2. Summary of Model Inputs for T ribufos.

Scenario CAcotton_WirrigSTD

Cropped Area Fraction 1

Kd (ml/g) 76.9

Water Half

- Life (days) @ 20 °C 4470

Benthic Half

- Life (days) @ 20 °C 300

Photolysis Half

- Life (days) @ 40

°Lat 0

### 91 Hydrolysis Half

- Life (days) 0

Soil Half

- Life (days) @ 20 °C 2235

Foliar Half

- Life (days)

Molecular Wt 314.54

Vapor Pressure (torr) 1.7E

- 06

Solubility (mg/l) 2.3

Table 3. Application Schedule for T ribufos.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift

11/04 Foliar 0.86 .95 .125

Figure 1. Yearly Peak Concentrations

### 92 Appendix B

. Toxicity Categories and Levels of Concern

Table B1. Categories of Toxicity for Aquatic Organisms

L C 50 ( p pm) Toxici t y C a t e go r y

< 0

. 1 Very hi g h ly t o xic

> 0

. 1

- 1 Hi g h ly toxic

> 1

- 10 M od e rately t o xic

> 1 0

- 1 0 0 Slightly toxic

> 1 00 Practically n on toxic



### Table B2. Categories of Toxicity for Te r res t rial Organisms

Oral d o se LD 5 0 ( m g/k g
- b w ) Toxici t y C a t e go r y
< 10 Very h ig h ly to x ic

10

- 5 0 Hi g h ly toxic

5 1

- 500 M od e rately t o xic

5 0 1

- 2 0 0 0 Slightly toxic

> 2 0 00 Practically n ont ox ic

Die t ary L C 50 (ppm) Toxici t y C a t e go r y

< 50 Very h ig h ly to x ic

5 0

- 500 H i g h ly t ox i c

5 0 1

- 1 0 0 0 M od e rately t o x ic

1 00 1

- 5 00 0 Slightly toxic

> 5 0 00 Practically n ont ox ic



### Table B3. Categories of Toxicity for Honey Bee

Bee A c ute Contact L D 50 (μg / bee) Toxici t y C a t e go r y <2 Hig h ly t ox ic

2

– 1 0

. 9 9 M od e rately t o x ic

> 11 Practically nontoxic



### Table B4. Levels of Concern for Te rr estrial and Aquatic Organisms

T a xa Acu t e L O C Ch r o nic L O C

Avi a n 1 (t e rres t rial p h ase a m phibia n s) 0

. 1 1

M a m m a lia n 2 0

. 1 1

Terres t rial pla n ts 3 1 Aq u atic A n i m a ls 4 (aq u atic phase

a m phibia n s) 0

. 05 1

Insects 5 0

. 05 1

Used in RQ ca lc ulations:

1 L D 50 and es t i m a ted NOEL

2 L D 50 and NOEC

3 EC25

4 LC / EC 50 and estimated and r e p roducti v e NOEC

5 L D 50 p e r EF E D’s CRLF Steer i ng Co mm ittee

### 93 Appendix C

. Summary of Ecological Toxicity Dat a

Data in this appendix include results from submitted ecological toxicity studies and results from ECOTOX when the test result was more sensitive than those in submitted toxicity data. Submitted studies that are considered invalid include: 41618808, 41618809 (no finalized DER, and 41918810 ).

Table C 1

. Summary of Toxicity Data for Aquatic Vertebrates Ex posed to Tribufos (TGAI) and Formulations.

Common Name (Species) Study Type

and ( Duration of

Exposure) Test
Substance

(% a.i.) Endpoint (Effect
Observed at

Endpoint) Toxicity Value (95% CI)

μ g a.i./L (Acute Toxicity Category) MRID Study
Classification Comments

Freshwater Vertebrates

Bluegill sunfish ( Lepomis macrochirus ) Static ( 96

- hour ) TGAI LC 50 (Survival) 283* (136

- 378) Slope=6.23 (highly toxic) 40098001 Supplemental

Quantitative Some deviations from guidelines requirements.

Bluegill sunfish ( Lepomis macrochirus ) F low

- through ( 96

- hour ) TGAI (96.2%) LC 50 (Survival) 630 (500

- 780) Slope=6.46 (3.18

- 9.74) (highly toxic) 41618806 Acceptable Precipitate in all test solutions. Not filtered prior to analysis . Variation in
measured concentration. Test levels do not overlap but they are close to overlapping. Bluegill sunfish ( Lepomis macrochirus ) F low

- through

96

- hour DEF® 6 (72.3%) LC 50 (Survival) 490 (highly toxic) 41618807 Acceptable Binomial

Rainbow trout (Oncorhynchus mykiss) F low

- through

96

- hour TGAI (96.2%) LC 50 (Survival) -- 41618808 Supplemental

Qualitative Precipitate observed at all test concentrations. Not filtered prior to analysis . Concentrations near solubility.

Fathead Minnow ( Pimephales promelas ) F low

- through

96

- hour TGAI (99.4%) LC 50 (Survival) 920 (highly toxic) 45863706 Acceptable Loss of equilibrium, labored respiration,
at surface and/or bottom of the vessel at

0.59 mg a.i./L and above. Binomial.

Fowlers toad ( Bufo fowleri ) Acute (96

- hr) TGAI LC 50 (Survival) 450 40098001
Not reviewed Included in summary because it is data specific to amphibians.

Fathead Minnow ( Pimephales promelas ) Early Life Cycle (36

- day) TGAI (99.4%) NOAEC/

LOAEC (post hatch survival) 3.35 / 8.38 45863703 Supplemental

Qualitative Tribufos residues in negative control days 0 to 4 near level of quantitation of 0.16 μg/L. Some overlap in concentrations between treatment groups.

### 94 Common Name (Species) Study Type

and ( Duration of

Exposure) Test
Substance

(% a.i.) Endpoint (Effect
Observed at

Endpoint) Toxicity Value (95% CI)

μ g a.i./L (Acute Toxicity Category) MRID Study
Classification Comments

Fathead Minnow ( Pimephales promelas ) Early Life Cycle (3 5

- day) TGAI (96.6%) NOAEC/

LOAEC ( fry survival, length,

dry weight) 2.49/ 4.83 45863703 Supplemental

Qualitative Significant reduction in average dry weight in solvent control. Endpoint may

not be a result of exposure to TGAI.

Bluegill sunfish ( Lepomis macrochirus ) Chronic

-- NOAEC 4.1 * Estimated This NOAEC is based on the acute to chronic ratio using sheepshead minnow endpoints [767/11=69.7 (ACR)]

Estuarine/Marine Vertebrates Sheepshead minnow (Cyprinodon variegatus ) Acute
Flow

- through

96

- hour TGAI (98.6%) LC 50 (Survival) 767* (560

- 1370) (highly toxic) 41896302 Acceptable Binomial method.

Sheepshead minnow (Cyprinodon variegatus ) Early Life Cycle (35

- day) TGAI (99.4%) NOAEC/

LOAEC (growth, post hatch survival) 11/ 19* 45863707 Acceptable

TGAI=technical grade active ingredient *Represents the most sensitive toxicity endpoint to be used in RQ calculations.



### Table C 2 . Summary of Toxicity Data for Aquatic Invertebrates Exposed to TGAI and Formulations Containing Tribufos

.

Species (Common Name) Study Type ( Exposure
Duration ) Test
Substanc e (% a.i.) Endpoint (Effect
Observed at

Endpoint) Toxicity Value [95% CI]

μ g a.i./L (Acute Toxicity Category) MRID Study
Classification 1 Comments

Freshwater Invertebrates

Water flea ( Daphnia magna ) Static (48

- hour) Not
available EC 50 (Immobility) 6.63 (5.50

- 8.01) ( v ery highly toxic) 40098001 Supplemental

Q ualitative A negative control was not included in the study.

Water flea ( Daphnia magna ) Static (48

- hour) Not
available EC 50 (Immobility) 5.4* (3.5

- 7.7) Slope=2.5 (very highly toxic) 40098001 Supplemental

Quantitative --

Water flea ( Daphnia magna ) Static (48

- hour) DEF6 ® (72.3%) EC 50 (Immobility) 61 (highly toxic) 41689902 Acceptable --

### 95 Species (Common Name) Study Type ( Exposure
Duration ) Test
Substanc e (% a.i.) Endpoint (Effect
Observed at

Endpoint) Toxicity Value [95% CI]

μ g a.i./L (Acute Toxicity Category) MRID Study
Classification 1 Comments

Water flea ( Daphnia magna ) Static (48

- hour) TGAI (98.7 %) EC 50 (Immobility) 110 (highly toxic) 41689901 Acceptable --

Water flea Static

renewal (21

- days) TGAI (97.2%) NOAEC/ LOAEC (reduced number
of young/adult/day

and reduced adult length) *1.56/
3.23 43978201 Acceptable

Freshwater amphipod ( Hyalella azteca) S piked
sediment (10

- day) TGAI (98.2%) NOAEC/ LOAEC (Survival) 693/>693 μg a.i./kg

sediment 27,000/ >27,000

μg/kg

- TOC 34.1/>34.1 pore

- water 49164802 Acceptable --

NOAEC LOAEC (Growth) 71/ 220 μg a.i./kg

sediment 2700/ 8500 μg a.i./kg

TOC 2.81/8.27 pore

- water --

Estuarine/Marine Invertebrates

Mysid shrimp ( Mysidopsis
bahia ) F low

through (96

- hour) TGAI (96.4%) LC 50 (Survival) 11.53* (9.30

- 15.11) (very highly toxic) 41896301 Acceptable Calculated using moving average
method. Abnormal physical appearance and mortality observed at

lowest test concentratio n (1.26 μg a.i./L). Eastern Oyster ( Crassostrea virginica ) Flow

through (96.4) TGAI EC 50 (shell deposition) 39.6 (35

- 45) (very highly toxic) 42083201 Acceptable

### 96 Species (Common Name) Study Type ( Exposure
Duration ) Test
Substanc e (% a.i.) Endpoint (Effect
Observed at

Endpoint) Toxicity Value [95% CI]

μ g a.i./L (Acute Toxicity Category) MRID Study
Classification 1 Comments

Mysid shrimp ( Americamysis
bahia ) F low

through (28

- day) TGAI (96.4%) NOAEC/ LOAEC (None) 0.26/ >0.26* 45863702 Supplemental Analytical variation in the measured
test concentrations exceeded the 20%

among replicate results. Minimum control number of offspring produced

was less than one. The minimum mean requirement is 3 offspring per female per day. No treatment related
effec ts observed

. Amphipod ( Leptocheirus plumulosus ) S piked
sediment (10

- day) TGAI (98.2%) NOAEC/
LOAEC (Mortality ) 207 /773 μg a.i./kg

sediment

7.10/22.7 pore

- water 49164801 Acceptable --

TGAI=technical grade active ingredient: *Represents the most sensitive toxicity endpoint to be used in RQ calculations. A risk quotient is not calculated for non

- definitive endpoints, but the information is used in the risk description.

1 Supplemental studies may or may not be suitable to calculate RQs . Quantitati ve values are suitable for calculation of RQ . Qualitative values are not consid ered
suitable for calculation of RQs but may be useful in understanding the weight of evidence for evaluating the likelihood of risk.



### Table C 3

. Summary of Toxicity Data for Vascular and Nonvascular Aquatic Plants Exposed to Tribufos.

Common Name (Species) Type of Test (Exposure Duration) Test Substance (% a.i.) Endpoint (Effect at Endpoint) Toxicity Value (95% CI) μg a.i./L MRID (Study Classification)

Duckweed ( Lemna gibba ) Static Renewal

14

- day TGAI (99.4%) EC 50 (Frond Count) 1100 (760

- 1700)* 45863705 Supplemental EC 05 140 (35

- 570)*

NOAEC <17.2

Freshwater green alga ( Pseudokirchneriella Subcapitata 1 ) 7

- day TGAI (99.9%) EC 50 (Percent inhibition) 148* 41618813 Acceptable NOAEC /
LOAEC 118/ 254*

*Represents the most sensitive toxicity endpoint to be used in RQ calculations

1 Pseudokirchneriella subcapitata are formerly known as Selenastrum capricornutum and also as Raphidocelis subcapitata

.

### 97 Table C 4 . Summary of Toxicity Data for Terrestrial Animals Exposed to Tribufos.

Common Name (Species) Study Type ( Duration of

Exposure ) Test Substance (% a.i.) Endpoint ( Effect at endpoint ) Toxicity Value (95% CI) (Acute Toxicity Category) MRID Study
Cl assification Sublethal effects

Birds

Zebra Finch ( Taeniopygia

guttata ) Acute Oral (Oral gavage
with 14

- day observation) TGAI (98.2%) ED 50 (Mortality and Regurgitation) 397 mg/kg

- bw (265

- 588) assuming regurgitation was equal to mortality (slightly toxic) 49121302 Supplemental due to regurgitation within one hour of dosing Ruffled feathers, underactivity, incoordination, recumbency, body tremors, panting, salivation and/or regurgitation observed at all
treatment levels.

Canary ( Serinus canaria) Acute Oral (Oral gavage
with 14

- day observation) TGAI (98.2%) ED 50 (Mortality and Regurgitation) 111 mg/kg

- bw (73.7

- 168) Assuming regurgitation was equal to mortality (moderately toxic) 49121303 Supplemental due to regurgitation within one hour of dosing Lethargy, unsteadiness,

rec u mb e ncy, body tremors, panting, salivation, hunched posture, and/or emesis were observed at all treatment levels.

Mallard duck (Anas platyrhynchos ) Acute Oral (Oral gavage with 14

- day observation) TGAI (92%) LD 50 (Mortality) 871 mg a.i./kg

- bw (468

- 2892) Slope=1.67 (0.56

- 2.77) (slightly toxic) 00049258 Supplemental due to testing of 8 birds and
no food consumption data Bobwhite quail ( Colinus virginianus) Acute Oral (Oral gavage
with 14

- day observation) TGAI (92%) LD 50 (Mortality) 151 mg a.i./kg

- bw (128

- 178)* Slope=7.9 (4.3

- 11.5) (moderately toxic) 00120771 Acceptable

Mallard duck (Anas platyrhynchos ) Subacute Dietary (5

- day) TGAI (99.8%) LC 50 (Mortality) >5000 mg a.i./kg

- diet (practically non

- toxic) 41618805 Acceptable Reduced body weight gain
observed at all test concentrations (313 to 5000 mg a.i./kg

- diet).

Bobwhite quail ( Colinus virginianus) Subacute Dietary (5

- day) TGAI (98.9%) LD 50 (Mortality) 1519 mg a.i./kg

- bw (slightly toxic) 41618804 Acceptable Reduced body weight gain during exposure period was observed at the three highest test concentrations (lowest was 1135 mg/kg

- bw)

Bobwhite quail ( Colinus virginianus) Reproduction (20 week) TGAI (98.7%) NOAEC/
LOAEC (egg shell thickness) 150/280 mg a.i./kg

diet* 40757101 Acceptable

Mammals 2

### 98 Common Name (Species) Study Type ( Duration of

Exposure ) Test Substance (% a.i.) Endpoint ( Effect at endpoint ) Toxicity Value (95% CI) (Acute Toxicity Category) MRID Study
Cl assification Sublethal effects

Laboratory rat (Rattus norvegicus) Acute
Inhalation (4

- hour) TGAI LC 50 (Mortality) 4650 mg/m 3 4.65 mg/L 41782301

Laboratory rat (Rattus norvegicus) Acute Oral TGAI LD 50 (Mortality) 192 mg/kg

- bw (moderately toxic) 41954903

White footed

mouse ( Peromyscus leucopus ) Acute Diet (5

- day) TGAI LC 50 (Mortality) 161 mg/kg

- diet (highly toxic) Slope=1.73 (0.66

- 2.79) 45863708 Supplemental

quantitative Droopy eyelids, ataxia, hypoactivity, immobility,
moribund condition observed at
all treatment levels.

Laboratory rat (Rattus norvegicus) Two

generation Reproduction TGAI NOAEL/
LOAEL (increased

number of
litters with still born pups) 32 mg/kg

- diet*

1.7 mg/kg/day/

260 mg/kg

- diet 15 mg/kg/day 42040201 Additional endpoints affected include increased pup death through lactation; decrease F1 and F2 pup body weights, increased F1 gestation period.

Honey bee s

Honey Bee (Apis mellifera) Acute Contact (48

- hour) Variable.,
Mixed with pyrolite dust LD 50 (Mortality) >24.17 μg a.i./bee* (practically nontoxic) 00001999 Acceptable 3% mortality at 24.17 μg a.i./bee.

* Most sensitive endpoint; will be used in RQ calculations.

2 Mammalian toxicity endpoints for provided and reviewed by EPA/OCSPP/OPP Health Effects Division



### Table C 5 . Summary of Terrestrial Plants Toxicity Data for Tribufos Formulations.

Crop Formulation (% a.i.) Species E C 25 (lbs a.i./A) NOAEC
or IC 05 / LOAEC (lbs a.i./A) Endpoint
Affected MRID Study Classification

Seedling Emergence

Monocots DEF 6 (70.8%) Onion ( Allium

cepa ) >2.0 * 0.45 /0.93* Plant height 45863404 Acceptable

Dicots Soybean ( Glycine >2.0 * 0.22 /0.46* Plant height

### 99 Crop Formulation (% a.i.) Species E C 25 (lbs a.i./A) NOAEC
or IC 05 / LOAEC (lbs a.i./A) Endpoint
Affected MRID Study Classification

max ) Vegetative Vigor

Monocots DEF 6 (70.8%) Corn ( Zea

mays ) 1.8 * 0.48 /0.93* Dry weight, plant height 45863704 Acceptable

Dicots Buckwheat ( Fagopyrum sagiitatum ) 1.3 * 0.48 /0.99* Dry weight

Plant Defoliation Study

Deciduous
shrubs Folex® 6EC

Cotton
Defoliant

Activator90

® adjuvant

(0.1%) Forsythia ( Ribes sanguineum ) Responses not
sufficient to

reliably
calculate a
dose

- response

curve 1.875 No significant response observed

at highest dose
tested

48728101 Supplemental Viburnum ( Viburnum

spp .) 0.563 Number/weight of
fallen leaves

Deciduous

Tree samplings Maple (Acer spp.) 0.563 Number of old leaves left on plant

Oak ( Quercus

Spp.) 0.563 Number of old leaves left on plant

* Most sensitive endpoint used for risk estimation ( i.e. , RQ calculations) or risk description (for non

- definitive endpoints).

### 100 Appendix D

. Example T

- REX (v. 1.5 .2 ) Input and Output for Tribufos

Table D .1. T

- REX Model Inputs: Chemical Application Scenarios and Body Mass for Assessed Species.

### 101 Table D .2. Avian and Mammalian Toxicity Endpoints for RQ Calculation.

### 102 Appendix E

. STIR Results

### 103 Appendix F

. S creening Imbibition Program (SIP) Version 1.0 Inputs and Results

### 104 Appendix G

. A cce p t ed E C O T O X D a t a Ta b l e (2008 to 2015 Refresh Report)
Th e c od e li st f o r E C O T O X can b e f oun d a t : htt p :// c f p u b

. e p a .gov/ ec otox/ b l ac k b ox/h e l p / c od e li s t. p df

Genus Species Common

Name Effect
Group Effect Meas Endpt1 Endpt2 Dur

Preferred

Mean Dur Unit

Preferred Conc #2 Purity Adjust ed in

Preferred

Unit Mean Conc

Units

Preferred % Purity Ref #

Americamysis bahia Opossum Shrimp MOR MOR MORT LC50 4 d mg/L 95 56755

Americamysis bahia Opossum Shrimp MOR MOR MORT LC50 4 d mg/L 95 56755

Daphnia magna Water Flea MOR MOR MORT LC50 2 d mg/L 100 156445

Penaeus duorarum Northern Pink Shrimp MOR MOR MORT LC50 4 d mg/L 95 56755

Palaemonetes pugio Daggerblade Grass Shrimp MOR MOR MORT LC50 4 d mg/L 95 56755

Penaeus stylirostris Shrimp MOR MOR MORT LC50 4 d mg/L 95 56755

Leiostomus xanthurus Spot MOR MOR MORT LC50 4 d mg/L 95 56755

Leiostomus xanthurus Spot MOR MOR MORT LC50 4 d mg/L 95 56755

Schizaphis graminum Greenbug MOR MOR MORT LC50 0.3333 d ug/eu 100 103314

Oligonychus pratensis Banks Grass

Mite MOR MOR MORT LC50 1 d ug/eu 100 63628

Tetranychus urticae Two

- Spotted Spider Mite MOR MOR MORT LC50 1 d ug/eu 100 63628

Musca domestica House Fly MOR MOR MORT LC50 1 d AI mg/m2 >98 93122

Musca domestica House Fly MOR MOR MORT LC50 1 d AI mg/m2 >98 93122

Lagodon rhomboides Pinfish MOR MOR MORT LC50 4 d mg/L 95 56755

Cyprinodon variegatus Sheepshead

Minnow MOR MOR MORT LC50 4 d mg/L 95 56755

Ceriodaphnia dubia Water Flea MOR MOR MORT LC50 4 d ug/L 98 158065

Ceriodaphnia dubia Water Flea MOR MOR MORT LC50 4 d ug/L 98 158065

Phasianus colchicus Ring

- Necked

Pheasant MOR MOR MORT LD50 14 d mg/kg

bdwt 92 50386

Anas platyrhynchos Mallard Duck MOR MOR MORT LD50 14 d mg/kg

bdwt 92 50386

### 105 Genus Species Common

Name Effect
Group Effect Meas Endpt1 Endpt2 Dur

Preferred

Mean Dur Unit

Preferred Conc #2 Purity Adjust ed in

Preferred

Unit Mean Conc

Units

Preferred % Purity Ref #

Tribolium castaneum Rust

- Red Flour

Beetle MOR MOR MORT LD50 9 d ug/cm2 100 93121

Anthonomus grandis Boll Weevil MOR MOR MORT LD50 2 d ug/org 100 92637

Tribolium castaneum Rust

- Red Flour

Beetle MOR MOR MORT LD95 9 d ug/cm2 100 93121

Varroa jacobsoni Mite MOR MOR MORT NOAEL 2 d nl/org 100 103663

Varroa jacobsoni Mite MOR MOR MORT NOAEL 2 d nl/org 100 103663

Americamysis bahia Opossum Shrimp MOR MOR MORT NOAEL LOAEL 28 d 0.00068 mg/L 95 56755

Penaeus stylirostris Shrimp MOR MOR MORT NR

LETH 3 d mg/L 95 56755

Americamysis bahia Opossum Shrimp MOR MOR MORT NR

LETH 9 d mg/L 95 56755

Cyprinodon variegatus Sheepshead

Minnow MOR MOR MORT NR

ZERO 4 d mg/L 95 56755

Penaeus duorarum Northern Pink Shrimp MOR MOR MORT NR

ZERO 2 d mg/L 95 56755

Blattella germanica German

Cockroach MOR MOR MORT NR

ZERO 14 d ppm 100 68639

Aedes sollicitans Mosquito MOR MOR MORT NR

ZERO 1 d mg/L 100 119693

Aedes sollicitans Mosquito MOR MOR MORT NR

ZERO 1 d mg/L 100 119693

Aedes aegypti Yellow Fever
Mosquito MOR MOR MORT NR

ZERO 0.1667 d mg/L 100 66934

Helicoverpa armigera Old World

Bollworm MOR MOR MORT NR

ZERO 2 d ug/org 99 74861

Culex pipiens ssp. pipiens Mosquito MOR MOR MORT NR

ZERO 1.1667 d mg/L 100 103374

Culex pipiens ssp. pipiens Mosquito MOR MOR MORT NR

ZERO 1.1667 d mg/L 100 103374

Culex pipiens ssp. quinquefasciata Mosquito MOR MOR MORT NR

ZERO 1.1667 d mg/L 100 103374

Helicoverpa armigera Old World

Bollworm MOR MOR MORT NR

ZERO 2.0417 d ug/org 98 119665

### 106 Genus Species Common

Name Effect
Group Effect Meas Endpt1 Endpt2 Dur

Preferred

Mean Dur Unit

Preferred Conc #2 Purity Adjust ed in

Preferred

Unit Mean Conc

Units

Preferred % Purity Ref #

Helicoverpa armigera Old World

Bollworm MOR MOR MORT NR

ZERO 2.0417 d ug/org 98 119665

Heliothis virescens Budworm MOR MOR MORT NR

ZERO 1 d ppm 100 92447

Apis mellifera Honey Bee MOR MOR MORT NR

ZERO 1 d ug/org 98 119503

Listronotus oregonensis Carrot Weevil MOR MOR MORT NR

ZERO 1 d ppm 100 103315

Listronotus oregonensis Carrot Weevil MOR MOR MORT NR

ZERO 1 d ppm 100 103315

Spodoptera frugiperda Fall Armyworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Spodoptera frugiperda Fall Armyworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Helicoverpa zea Corn Earworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Helicoverpa zea Corn Earworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Agrotis ipsilon Cutworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Agrotis ipsilon Cutworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Spodoptera frugiperda Fall Armyworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Helicoverpa zea Corn Earworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Agrotis ipsilon Cutworm MOR MOR MORT NR

ZERO 2 d ug 99 63706

Musca domestica House Fly MOR MOR MORT NR

ZERO 2 d ppm 100 154990

Blattella germanica German

Cockroach MOR MOR MORT NR

ZERO 2 d ppm 100 154990

Oncopeltus fasciatus Large Milkweed Bug MOR MOR MORT NR

ZERO 2 d ppm 100 154990

### 107 Appendix H

. Ecosar Analysis for Parent and Degradate

ECOSAR RUN for Tribufos

ECOSAR Version 1.11 Results Page

SMILES : CCCCSP(=O)(SCCCC)SCCCC
CHEM :
CAS Num:
ChemID1:

MOL FOR: C12 H27 O1 P1 S3
MOL WT : 314.50 Log Kow: 5.748 (EPISuite Kowwin v1.68 Estimate) Log Kow: (User Entered) Log Kow: 5.70 (PhysProp DB exp value

- for comparison only) Melt Pt: (User Entered for Wat Sol estimate)
Mel t Pt:

- 25.00 (deg C, PhysProp DB exp value for Wat Sol est, <

- 25) Wat Sol: 0.5384 (mg/L, EPISuite WSKowwin v1.43 Estimate) Wat Sol: (User Entered) Wat Sol: 2.3 (mg/L, PhysProp DB exp value)

------------------------------------ -- Values used to Generate ECOSAR Profile

-------------------------------------- Log Kow: 5.748 (EPISuite Kowwin v1.68 Estimate) Wat Sol: 2.3 (mg/L, PhysProp DB exp value)

-------------------------------------- ECOSAR v1.11 Class

- specific Estimations

-------------------------------------- Esters Esters (phosphate)
Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

====================== ===== ================== ======== ====== ========== Esters : Fish 96

- hr LC50 0.272 Esters : Daphnid 48

- hr LC50 0.379 Esters : Green Algae 96

- hr EC50 0.089
Esters : Fish ChV 0.009 Esters : Daphnid ChV 0.088 Esters : Green Algae ChV 0.077 Esters : Fish (SW) 96

- hr LC50 0.329 Esters : Mysid 96

- hr LC50 0.051 Esters : Fish (SW) ChV 0.093

Esters : Mysid (SW) ChV 0.00181
Esters : Earthworm 14

- day LC50 253.805 *

Esters (phosphate) : Fish 96

- hr LC50 0.332 Esters (phosphate) : Daphnid 48

- hr LC50 0.000471 Esters (phosphate) : Green Algae 96

- hr EC50 0.203 Esters (phosphate) : Fish ChV 0.005 Esters (phosphate) : Green Algae ChV 0.751

### 108 Esters (phosphate) : Fish (SW) 96

- hr LC50 0.356 Esters (phosphate) : Mysid (SW) 96

- hr LC50 0.002 Esters (phosphate) : Fish (SW) ChV 0.010 Esters (phosp hate) : Mysid (SW) ChV 1.32e

- 005

=========================== ================== ======== ====== ========== Neutral Organic SAR : Fish 96

- hr LC50 0.111 (Baseline Toxicity) : Daphni d 48

- hr LC50 0.089 : Green Algae 96

- hr EC50 0.278
: Fish ChV 0.016 : Daphnid C hV 0.023 : Green Algae ChV 0.157

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect. If the effect level exceeds the
water solub ility by 10X, typically no effects at saturation (NES) are reported.

------------------------------ Class Specific LogKow Cut

- Offs

------------------------------ If the log Kow of the chemical is greater than the endpoint specific cut

- offs

pres ented below, then no effects at saturation are expected for those endpoints.

Esters:

------ Maximum LogKow: 5.0 (Fish 96

- hr LC50; Daphnid LC50, Mysid LC50) Maximum LogKow: 6.0 (Earthworm LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV)

Esters (phosphate):

------------------ Maximum LogKow: 5.0 (LC50) Maximum LogKow: 6.4 (EC50) Maximum LogKow: 8.0 (ChV)

Baseline Toxicity SAR Limitations:

--------------------------------- Maximum LogKow: 5.0 (Fish 96

- hr LC50; Daphnid LC50)
Maximu m LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV)

ECOSAR run for 1

- BSA

ECOSAR Version 1.11 Results Page

SMILES : S(O)(=O)(=O)CCCC
CHEM :
CAS Num:
ChemID1:

MOL FOR: C4 H10 O3 S1
MOL WT : 138.18 Log Kow:

- 0.908 (EPISuite Kowwin v1.68 Estimate)

### 109 Log Kow: (User Entered) Log Kow: (PhysProp DB exp value

- for comparison only) Melt Pt: (User Entered for Wat Sol estimate)
Melt Pt:

- 15.20 (deg C, PhysProp DB exp value for Wat Sol est)
Wat Sol: 1E+006 (mg/L, EPISuite WSKowwin v1.43 Estimate) Wat Sol: (User Entered) Wat Sol: (PhysProp DB exp value)

-------------------------------------- Values used to Generate ECOSAR Profile

-------------------------------------- Log Kow:

- 0.908 (EPISuite Kowwin v1.68 Estimate) Wat Sol: 1E+006 (mg/L, EPISuite WSKowwin v1.43 Estimate)

-------------------------------------- ECOSAR v1.11 Class

- specific Estimations

--------------------------------------

********************************* ********************************************* | Not Related to an Existing ECOSAR Class Definition | | | | Estimates provided below use the Neutral Organi cs QSAR equations which | | represent baseline toxicity potential (minimum toxicity) assuming a simple | | non

- polar narcosis model. Without empirical data on structurally similar | | chemicals, it is uncertain if this substance will present signi ficantly | | higher toxicity above baseline estimates. |

******************************************************************************

Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

=========================== ================== ======== ====== ==========

-- > Acid moeity found: Predicted values multiplied by 10

Neutral Organics

- acid : Fish 96

- hr LC50 4.65e+005 Neutral Organics

- acid : Daphnid 48

- hr LC50 2.02e+005 Neutral Organics

- acid : Green Algae 96

- hr EC50 49493.461 Neutral Organics

- acid : Fish ChV 33084.156 Neutral Organics

- acid : Daphnid ChV 9315.006 Neutral Organics

- acid : Green Algae ChV 7127.344 Neutral Organics

- acid : Fish (SW) 96

- hr LC50 5.75e+005 Neutral Organ ics

- acid : Mysid 96

- hr LC50 3.06e+006 * Neutral Organics

- acid : Fish (SW) ChV 10563.744 Neutral Organics

- acid : Mysid (SW) ChV 6.27e+005 Neutral Organics

- acid : Earthwo rm 14

- day LC50 4811.211

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect. If the effect level exceeds the water solubility by 10X, typically no effects at saturation (NES ) are reported.

------------------------------ Class Specific LogKow Cut

- Offs

### 110 ------------------------------ If the log Kow of the chemical is greater than the endpoint specific cut

- offs presented below, then no effects at saturation are expected for those endpoints.

Neutral Organics:

---------------- Maximum LogKow: 5.0 (Fish 96

- hr LC50; Daphnid LC50, Mysid LC50) Maximum LogKow: 6.0 (Earthworm LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV)

### 111 Appendix I

. Example KABAM Inputs and Outputs

### 112

### 113

### 114

### 115 Appendix J

. Aquatic Plant Toxicity Endpoints In the EFED ECOTOX Database

CHEMICAL PC_CODE MRID COMMONNAME TAXONOMIC % AI STUDY

TIME DOSE

TYPE TGL TOXICITY TOXLEVEL

Naled 034401 42529603 Freshwater diatom Navicula pelliculosa 94.4 5 D EC50 0.012 PPM

Naled 034401 42529602 Marine diatom Skeletonema

costatum 94.4 5 D EC50 0.015 PPM

Coumaphos 036501 48322802 Green algae Pseudokirchneriella subcapitata 95.7 96 hr EC50 > 0.091 PPM

Chlorpyrifos 059101 40228401 Marine algae Isochrysis galbana 92 96 hr EC50 0.14 PPM

Tribufos 074801 41618813 Green algae Selenastrum capricornutum 99.9 7 D EC50 0.148 PPM

Chlorpyrifos 059101 40228401 Diatom Thalassiosira sp. 92 96 hr EC50 0.15 PPM

Coumaphos 036501 48322801 Duckweed Lemna gibba 95.7 7 D EC50 > 0.166 PPM

Chlorpyrifos 059101 40228401 Marine diatom Skeletonema

costatum 92 96 hr EC50 0.3 PPM

EPN (Cancelled in U.S.) 041801 40228401 Marine diatom Skeletonema

costatum 97.2 96 hr EC50 0.34 PPM

Tribufos 074801 40228401 Marine diatom Skeletonema

costatum 95 96 hr EC50 0.37 PPM

Naled 034401 42529604 Bluegreen algae Anabaena flos

- aquae 94.4 5 D EC50 0.64 PPM

Tribufos 074801 45863705 Duckweed Lemna gibba 99.4 14 D EC50 1.1 PPM

Naled 034401 42529601 Duckweed Lemna gibba 94.4 14 D EC50 > 1.8 PPM

Fenthion 053301 40186713 Marine diatom Skeletonema

costatum 96.9 7 D EC50 0.36 PPM

Dicrotophos 035201 00140380 Phytoplankton N.R. 82 4 hr EC50 > 1.0 PPM

Dicrotophos 035201 00140380 Phytoplankton N.R. 82 4 hr EC50 > 1.0 PPM

Terbufos 105001 48939101 Marine diatom Skeletonema grethae 89.3 96 hr EC50 > 1.01 PPM

Fenthion 053301 40186711 Green algae Selenastrum capricornutum 96.9 96 hr EC50 1.1 PPM

Fenthion 053301 40186715 Freshwater diatom Navicula pelliculosa 96.9 7 D EC50 1.1 PPM

### 116 CHEMICAL PC_CODE MRID COMMONNAME TAXONOMIC % AI STUDY

TIME DOSE

TYPE TGL TOXICITY TOXLEVEL

Terbufos 105001 48689902 Green algae Pseudokirchneriella subcapitata 89.3 96 hr EC50 > 1.85 PPM
Oxydemeton

methyl 058702 44657701 Green algae Scenedesmus subspicatus 51.3 96 hr EC50 > 100 PPM

Dichlorvos 084001 40228401 Green algae Dunaliella tertiolecta 98 48 hr EC50 > 100 PPM

Acephate 103301 48879501 Green algae Pseudokirchneriella subcapitata 98.8 96 hr EC50 > 1035 PPM

Acephate 103301 48879503 Duckweed Lemna gibba 98.8 7 D EC50 1038 PPM

Dimethoate 035001 47784001 Green algae Selenastrum capricornutum 96.7 72 Hr EC50 110 PPM

Dichlorvos 084001 40228401 Marine algae Isochrysis galbana 98 48 hr EC50 14 PPM

Dichlorvos 084001 40228401 Marine diatom Thalassiosira pseudonana 98 48 hr EC50 17 PPM

Fenthion 053301 40186714 Duckweed Lemna gibba 96.9 14 D EC50 > 2.8 PPM

Naled 034401 42529605 Green algae Selenastrum capricornutum 94.4 5 D EC50 20 PPM

Dichlorvos 084001 40228401 Marine diatom Skeletonema

costatum 98 48 hr EC50 28 PPM

Diazinon 057801 40509806 Green algae Selenastrum capricornutum 87.7 7 D EC50 3.7 PPM

Fenthion 053301 40186712 Bluegreen algae Anabaena flos

- aquae 96.9 7 D EC50 > 3.8 PPM

Terbufos 105001 48689901 Duckweed Lemna gibba 89.3 7 D EC50 > 4.20 PPM

Acephate 103301 40228401 Marine diatom Skeletonema

costatum 94 96 hr EC50 > 50 PPM