UNITED STATES ENVlRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

PC Code: 036501 

DP Barcode: 409560 

Date: May 1, 2013 

MEMORANDUM 

SUBJECT: Drinking Water Assessment for the Registration Review of Coumaphos 

TO: 

FROM: 

Wilhelmena Livingston, Chemical Review Manager, 

Risk Management and Implementation Branch IV 

Pesticide Re-evaluation Division (7508P!, '\ { ~ T /I j 1 J, 

Environmental 

Faruque Khan, Ph.D.

Risk Branch 

, Senior 

I 

Scienti~ 

Environmental Fate and Effects Division 

BY: 

APPROVED 

Sujatha 

Ed Odenkirchen, 

Sankula, Ph.D., 

Ph.D., 

Lead 

Acting 

Biologist~ Branch ~-

hief 

;~

~ 

~~~ ~ ~ ~ \\\\.3 

Environmental Risk Branch I (7507P) \ -

Environmental Fate and Effects Division 

This memorandum provides the estimated drinking water concentrations (EDWC) of coumaphos 

and its oxygen analog coumaphoxon in surface water and groundwater in support of human 

health risk assessment. Coumaphos (0-[3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7 -yl] 0,0-

diethyl phosphorothioate) is an organophosphate insecticide/acaricide. Currently, coumaphos is 

registered for the control of insects, mites, and ticks on livestock and swine bedding, and to 

control varroa mites and small hive beetles in bee hives. However, the Environmental Fate and 

Effects Division (EFED) believes that the disposal ofbioremidiated coumaphos dip vat solution 

on non-agricultural land would be a major exposure route to drinking water sources for human 

consumptions. Therefore, the coumaphos application rate used in the drinking water assessment 

is based on the proposed disposal of bioremediated coumaphos dip vat solution on nonagricultural lands (US EPA, 1998). The recommended application rate for coumaphos spent 

solution from dip vat operations on non-agricultural land is 10,000 liters of coumaphos spent 

solution containing 10 ppb spread over a one-acre field. The estimated application rate of 

coumaphos is 0.22 lbs/Acre based on above recommendation. 

The residues of concern (ROC) for human health risk assessment and for tolerance expression 

are coumaphos and its oxygen analog coumaphoxon (US EPA, 2007). A maximum conversion 

efficiency of coumaphos to coumaphoxon of 10.2% was derived from available data on 

1 
photodegradation in water. This conversion efficiency was used to estimate a coumaphoxon 

application rate of 0.022 lbs ai/ A for drinking water modeling. The EDWCs of coumaphos and 

coumaphoxon were generated using Tier I FIRST (fQP A Index Reservoir .S.creening Iool) 

model for surface water and Tier I SCIGROW (Screening Concentration in Ground Water 

Program). Pesticide Root Zone Model-Ground Water model (PRZM-GW) was also used for 

ground water based on recent EFED recommendation (US EPA, 2012a). 

The recommended EDWCs for surface water and groundwater are listed in Table 1. FIRST 

model predicted total coumaphos residue concentration (coumaphos + coumaphoxon) in surface 

water are not likely to exceed 5.20 1-1g/L coumaphos equivalent/L for the maximum peak 

concentration (acute) and 0.72 Jlg coumaphos equivalent/L for the average concentration 

(chronic). SCI-GROW and PRZM_GW modeling predicted total coumaphos residue 

concentration in groundwater used as drinking water is not likely to exceed 2.19 Jlg coumaphos 

equivalent/L for the maximum peak concentration (acute) and 0.96Jlg coumaphos equivalent/L 

for the average concentration (chronic). 

The recommended acute surface water concentration of 5.20 Jlg coumaphos equivalent/Lis 

higher than the previously recommended acute concentration of 1.86 1-1g coumaphos equivalent/L 

but chronic concentration of0.72Jlg coumaphos equivalent/Lis lower than the previously 

recommended 1.22 Jlg coumaphos equivalent/L for this chemical (US EPA, 2000a). However, 

GENEEC (GENeric Estimated Environmental Concentration) model was used in the previous 

assessment to estimate concentrations in surface water, which is not a suitable model for 

drinking water assessment. Recommended PRZM_ GW estimated coumaphos equivalent 

concentrations are higher than previously recommended concentrations for groundwater. As a 

screening tool, SCI GROW provides reasonable estimates of pesticide in groundwater but it does 

not have the capability like PRZM-GW to consider variability in leaching potential of various 

soils, weather (including rainfall), cumulative yearly applications or depth to aquifer. 

In addition, PRZM-GW modeling was also performed with the estimated DT50 of2761 days 

based on NAFT A Kinetic modeling procedure (US EPA, 20 12b) and yielded maximum 

concentrations of 11.1 Jlg/L and 4.43 Jlg/L for acute and chronic values respectively for 

groundwater using extended (1 00 yrs) weather data. These concentrations are approximately two 

to three orders of magnitude higher than the estimated acute (0.06 Jlg/L) and chronic (0.005 

Jlg/L) concentrations using 30 year weather data. In addition, there is an uncertainty related to 

the estimated DTso value, which is approximately 7X higher than duration of aerobic soil 

metabolism study and 15 to 23X higher than the reported field dissipation half-lives. Therefore, 

recommended groundwater concentrations based on 3X of duration of aerobic soil metabolism 

study provide reasonable concentrations in groundwater. 

Table 1. Recommended EDWCs for Drinking Water risk assessment for 

Coumaphos and Coumaphoxon 

Source of Drinking Estimated Drinking Water concentration (J.Lg/L) 

Water Acute 

I 

Chronic 

Coumaphos 

Surface Water• 4.80 I 0.70 

2 
Table 1. Recommended EDWCs for Drinking Water risk assessment for 

Coumaphos and Coumaphoxon 

Source of Drinking Estimated Drinking Water concentration (J.lg/L) 

Water Acute Chronic 

Groundwater 2.19 0.96 

Coumaphoxon 

Surface Water 0.40 0.02 

Groundwater 5.72E-05 5.72E-05 

Coumaphos Equivalents (Coumaphos+Coumaphoxon) 

Surface Water 5.20 0.72 

Groundwater 2.19 0.96 

1 EDWCs based on Tier I FIRST model 

2 EDWCs based on PRZM-GW model 

3 EDWCs based on SCIGROW Model 

Modeling Approach and Input Parameters 

The current supported uses for coumaphos include direct application to animals, including dairy 

cattle, beef cattle, swine and bedding, and horses, for the control arthropod pests including ticks, 

scabies mites, lice, flies, fleece worms and screw worms. Coumaphos can be applied by dip vats, 

aerosol can, dustbags, hand-held dusters, hand-held sprayers, backrubber oiler, mechanical 

dusters, shaker can, and squeeze applicator. Based on the above understanding of the uses and 

methods of application on animals, there is a potential for indirect exposure of coumaphos in the 

environment via dislodging of applied chemical from animal hides. However, coumaphos is used 

as a primary tool as dip vat treatment in the USDA Cattle Fever Tick Eradication Program to prevent the 

reintroduction of equine and bovine piroplasmosis into the United States (US EPA 2000b ). A total 

volume of the spent dip vat waste generated annually in the U.S. is estimated to be between 400,000 to 

500,000 Liters (Mulbry et al., 1994 and 1998). Coumaphos is also used in impregnated plastic strips 

in bee hives to control varroa mites and small hive beetles in bee hives. For use in bee hives, 

coumaphos is impregnated on a solid substrate which is placed inside the commercial beehive 

structure. Once in the beehive, the material is sheltered from the elements so that no runoff of 

coumaphos to surrounding environments would likely occur even during precipitation events. 

Therefore, EFED believes that the disposal of treated coumaphos dip vat solution on nonagricultural land would be a major exposure route for drinking water sources. 

A limited environmental fate database for coumaphos indicates that it is a persistent (DT so of> 1 

year in aerobic soil) chemical and slightly mobile to hardly mobile (Koc=1874 to 10297 L/kg) in 

soil according to F AO classification of mobility in soil (F AO, 2000). The major pathway of 

coumaphos degradation appears to be photodegradation in water (DTso of 33 hours). A major 

degradate, oxygen analog, coumaphoxon, was detected in an aqueous photodegradation study at 

a maximum of 10.2% of applied chemical. Limited environmental fate data are available for 

coumaphoxon, which suggests that it is not a persistent compound in the terrestrial environment 

(DTso of0.49 to 2.27 days) and mobile to moderately mobile (K~=767 to 58 10 L/kg) in soil 

according to FAO classification of mobility in soil (F AO, 2000). Since the environmental fate 

3 
data suggest that the fate behavior of coumaphos and coumaphoxon differ in the environment, 

EDWCs were estimated independently for these chemicals. 

Residue of Concern 

The ROC for human health risk assessment and for tolerance expression are coumaphos and its 

oxygen analog coumaphoxon (US EPA, 2007). 

Models 

Surface Water 

Tier 1 EDWCs for surface water were generated using FIRST (v.1.1.0) model, dated August 5, 

2007. FIRST is a screening model to estimate the concentrations found in drinking water from 

surface water sources for use in human health risk assessment. As such, it provides upper bound 

values on the concentrations that might be found in drinking water due to the use of a pesticide. 

FIRST model also uses a Percent Cropped Area (PCA) factor to adjust for the area within the 

watershed that is planted to the modeled crop. The national default for non-agricultural use 

(PCA of 1.0) was applied in this assessment according to the current PCA guidance (US EPA 

2012c). 

Ground water 

Screening Concentration in Ground Water (SCI-GROW v2.3, Jul. 29, 2003) is a regression 

model used as a screening tool to estimate pesticide concentrations found in ground water used 

as drinking water. The SCI-GROW model and user's manual may also be downloaded from the 

EPA Water Models web-page (http://www.epa.gov/oppefed1/models/water/#scigrow). PCAs are 

not used with the SCI-GROW model. 

In addition, Tier 1 groundwater EDWCs for coumaphos and coumaphoxon, resulting from use as 

land farming were also derived using the PRZM-GW model (Pesticide Root Zone Model for 

Groundwater, version 1.0, August 31, 2012), with the GW-GUI (Graphical User Interface, 

version 1.0, August 31, 2012). PRZM-GW is a one-dimensional, finite-difference model that 

estimates the concentrations of pesticides in groundwater. It accounts for pesticide fate in the 

crop root zone by simulating pesticide transport and degradation through the soil profile after a 

pesticide is applied to an agricultural field. PRZM-GW permits the assessment of multiple years 

of pesticide application (up to 100 years) on a single site. Six standard scenarios, each 

representing a different region known to be vulnerable to groundwater contaminations, are 

available for use with PRZM-GW for risk assessment purposes. In PRZM-GW simulations, each 

of these standard scenarios was used. PRZM-GW output values represent pesticide 

concentrations in a vulnerable groundwater supply that is located directly beneath a rural 

agricultural field following many years of pesticide application. Descriptions of all executable 

versions of current models used in drinking water exposure can be obtained from URL link 

(http://www.epa.gov/oppefedl/models/waterQ. 

4 
Input Parameters 

A swnmary of the model input parameter values used in FIRST, SCI-GROW, and the 

PRZM_ GW Models are in Table 2, Table 3, and Table 4 respectively. Input parameters were 

selected in accordance with EFED's "Guidance for Selecting Input Parametet;s in Modeling the 

Environmental Fate and Transport of Pesticides," Version 2.1 (USEPA, 2009). Sample model 

output files are located in Appendix A. 

Table 2. FIRST (V. 1.1.0) input parameten for Coumaphos and Coumaphoxon 

Parameter Value Data Source Comments 

Coumaphos 

Maximum application Estimated application rate based on 

Rate lb a. i.J A (kg 0.22 (0.25) Estimated 10,000 L of solution containing 10 

a.i./ha) Jlg coumaphos/ml is spread over an 

acre field. 

Number of Applications I US EPA, 1998 ---

Depth of Incorporation 0 US EPA, 1998 --- (inches) 

Method of Application Ground spray US EPA, 1998 ---

Spray Drift 0 US EPA 1998 Applied as slurry 

Solubility in Water 0.2 US EPA 1994 --- (mg/L) 

Hydrolysis t112 at pH 7.0 0 NA" Considered stable to hydrolysis @ 

(days) pH7.0 

Aquatic Photolysis t112 1.38 MRID 42764101 Coumaphoxon is a major 

(days) MRID 43103901 degradatre (I 0.2%) 

Aerobic Soil 0 MRID 4051870 I 

Metabolism t 112 (d) 

Aerobic Aquatic 0 Input parameter guidance (USEP A, 

Metabolism t112 (d) 2009) 

Soil Partitioning 5904 

MRID4572140I Represent average Ktoc from 4 soils 

Coefficient (l<oc; mll&,c) 

Wetted in? No --- Assumed 

Percent Crop Area 

US EPA 2012c 

Recommended PCA for non 

1.0 agricultural uses (Decimal) 

Coumaphoxon 

Maximum application Based on application rate of 

Rate lb a.i./ A (kg 0.022 (0.025) Estimatedb coumaphos application on nona.i.lha) agricultural lands. 

5 
Table 2. FIRST (V.l.l.O) input parameters for Coumaphos and Coumaphoxon 

Parameter Value Data Source Comments 

Number of Applications I US EPA, 1998 Based on application rate of 

coumaphos for land farming 

Depth of Incorporation 0 US EPA, 1998 

(inches) 

Method of Application Not applicable --·- Degradation product of coumaphos 

Solubility in Water 31.6 EPISUITE 4.1 Estimated value 

(mg/L) 

Hydrolysis t112 at pH 7.0 0 Not available Assumed stable 

(days) 

Aquatic Photolysis t 112 0 Not available Assumed stable 

(days) 

Aerobic Soil 90th percentile upper confidence 

Metabolism DT50 (d) 4.1 MRID 48705501 bound on the mean half-life of 

coumaphooxon 

Aerobic Aquatic 8.2c --- 2X of Aerobic Soil Metabolism 

Metabolism t 1n (d) DTso (days) 

Percent Crop Area 1.0 US EPA 2012c Recommended PCA for non 

(Decimal) agricultural uses 

a Not available 

b Coumaphos application rate (0.22lb a.i/A) x [(0.102, the maximum conversion rate from aquatic photolytic 

degradation of coumaphos to coumaphoxon in laboratory studies) x (0.96, the molecular weight ratio of 

coumaphos to coumaphoxon)] 

c In absence of aerobic aquatic metabolism study, 2X of aerobic soil metabolism DT50 value was multiplied by 2 

according to Guidance for selecting input parameters in modeling for environmental fate and transport of 

pesticides. Version 2.1 October 22, 2009. 

Table 4. SCI-GROW (v2.3) Input Parameter Values for Coumaphos and Coumaphoxon 

Parameter Value Data Source Comments 

Coumaphos 

Estimated application rate based on 

Application Rate (lbs 0.22 Estimated 10,000 L of solution containing 10 flg 

a. i./acre) coumaphos/ml is spread over an acre 

field. 

Number of 1 US EPA, 1998 See Table 2 applications 

Since there is a threefold difference in 

Kcoc (mL!g) 1870 MRID 45721401 observed values, lowest non-sand Koc 

value used. 

Aerobic soil MRID 45118631 metabolism DT so 0 Stable 

(days) 

Coumaphoxon 

6 
Table 4. SCI-GROW (v2.3) Input Parameter Values for Coumaphos and Coumaphoxon 

Parameter Value Data Source Comments 

Application Rate (lbs 0.022 (0.025) Table2 --- a. i./acre) 

Number of Table2 

applications --- ~(mUg) 2922 MRlD 45721401 Median value 

Aerobic soil 4.1 MRID 48705501 90111 percentile upper confidence bound 

metabolism (DT 50) d on the mean half-life of coumaphoxon 

Table 4. PRZM-GW (vl.O) Input Parameter Values for Coumaphos and Coumaphoxon 

Data Source 

Parameters Va Comments lue 

Application Method Ground Table 2 ---

Application Rate 0.22 (0.25] (lbs. a.i./acre) [kglha] Table2 ---

Application 1 Table2 --- Frequency 

Hydrolysis (DT 50) d Stable --- No study 

Aerobic soil 10951 MRlD 45118631 Stable. Assumed 3X of duration of 

metabolism (DT50) d study 

Kroe 2922 L!Kg MRID 46808411 Average Kroe b 

1 Model requires a numerical value other than 0. DT50 was estimated using the NAFTA degradation kinetics 

procedure and did not have a recommendation for modeling (Figure 1, Appendix B). In addition, the estimated 

Single First Order (SFO) DT50 of2761 days is well beyond the duration of study. 2 EFED input parameter guidance: 

httD://www.eoa.eov/oooefed1/models/water/orzrn ew/wott orzm aw inout guidance.htm 

Results 

Estimated coumaphos concentrations in surface water and ground water used for drinking water 

are summarized in Table 5 and 6. Outputs from the model runs are provided in Appendix A. 

FIRST model concentrations (~giL) represent untreated surface water concentrations. The SCIGR9W 

and PRZM-GW concentrations represent groundwater concentration that might be expected in shallow 

unconfined aquifers under sandy soils. All scenarios run in PRZM-GW required the use of an extended 

weather file, which allows the user to run the simulation for up to 100 years in order to observe 

breakthrough. 

7 
The simulated concentrations provided in this assessment are conservative estimates of concentrations in 

drinking water. If dietary risks require refinement, higher-tiered, crop-specific and location-specific 

models and modeling scenarios can be used. 

Table 5. EDWCs for Coumaphos and Coumaphoxon Based on Bioremediated 

Coumaphos on Non-agriculture Land 

Peak (Acute) Annual Mean 

Drinking Water Source Crop Scenario Exposure (Chronic) 

(Jtg/L) Exposure (Jtg/L) 

Coumaphos 

Surface Water Generic Scenario1 4.80 0.70 

Ground water NC Cotton Scenario• 2.19 0.96 

Generic Scenario~ 3.22E-02 3.22E-02 

Coumaphoxon 

Surface Water Generic Scenario 4.04 0.019 

Ground water FL Citrus Scenario• 8.75E-11 5.7E-11 

Generic Scenario' 5.72E-05 5.72 E-05 

1 EDWCs generated using FIRST model 

2 EDWCs generated using PRZM-GW model 3 EDWCs generated using SCIGROWmodel 

Table 6. PRZM-GW results based on Based on Bioremediated Coumaphos on Nonagriculture 

Application Rate and Highest Post Average Simulation 

Scenario1 Daily Breakthrough Breakthrough Time Frequency Value (~IVL) Avera2e ~IVL) (days) 

0.22 lbs a.i./A x FL citrus 6.15E-02 1.59E-02 Incomplete 

1 applications Coumaphos 

FL Citrus 0.37 0.08 Incomplete 

FL potato 4.21E-04 6.56E-05 Incomplete 

GA peanut 3.54E05 2.27E-06 Incomplete 

NC cotton 2.19 0.96 Incomplete 

Delmarva sweet com 0.43 0.06 Incomplete 

WI com 0.05 0.004 Incomplete 

Couma ~hoxon 

0.22 lbs a.i./A x FL Citrus 8.75E-ll 5.70E-ll 24189 

1 applications FL potato 0 0 Incomplete 

GA peanut 1.21El3 1.83E-14 Incomplete 

NC cotton 2.75E13 1.12E13 19073 

Delmarva sweet com 7.22E-15 2.69E-15 24124 

WI com 3.07E-ll 8.85E-12 30881 1 These scenarios are regional vulnerable sites for groundwater evaluation. 

Monitoring Data 

There were no national-scale monitoring data available for this assessment. 

8 
Drinking Water Treatment 

There is no available information on the drinking water treatment effects on coumaphos and 

coumaphoxon. 

Uncertainties 

The main uncertainty associated with this Tier 1 drinking water assessment is the lack of 

acceptable environmental fate data for coumaphos and its degradate coumaphoxon. Limited data 

available for coumaphos and it's degradate, coumaphoxon. Other uncertainties associated with 

this assessment are the application rate of coumaphos and coumaphoxon and the lack of 

information on the concentration of degradation products in the bioremediated coumaphos 

solutions. Based on EFED guidance on proposed USDA land farming methods (US EPA, 1998), 

coumaphos should be applied at a maximum application rate of0.22lbs ai/A. This application 

rate assumes that 10,000 L of solution containing 10 J.lg coumaphos/ml is spread over an acre 

field. Supplemental photodegradation in water data (MRID 42764101 and 42764102) indicate 

that the maximum coumaphoxon concentration at any sampling time was 10.2% of coumaphos 

application rate. This conversion rate was used to estimate a coumaphoxon application rate of 

0.022 lbs ai/ A. 

In addition, there is an additional uncertainty related to the estimated DTso value, which is 

approximately 7X higher than duration of aerobic soil metabolism study and 15 to 23X higher 

than the reported field dissipation half-lives. Groundwater concentrations was based on 3X of 

duration of aerobic soil metabolism study. 

9 
References 

F AO 2000. Appendix 2. Parameters of pesticides that influence processes in the soil. In F AO 

Information Division Editorial Group (Ed.), Pesticide Disposal Series 8. Assessing Soil 

Contamination. A reference Manual, Rome: Food and Agricultural Organization of the 

United Nations. Available at http://www.fao.org/DOCREP/003/X2570E/X2570E06.htm 

(Accessed April 10, 2013). 

Mulbry, W., E. Ahren, and J. Karns. 1998. Use of a field-scale biofilter for the degradation of the 

organophosphate insecticide coumaphos in cattle dip wastes. Pestic. Sci. 52: 268-274. 

Mulbry, W., P.L. Del Valle, E. Ahren, 1996. Biodegradation ofthe organophosphate insecticide 

coumaphos in in highly contaminated soils and liquids waste. Pestic. Sci. 149-155. 

US EPA. 2012a. Memorandum: Approval ofPRZM-GW for use ofDrinking Water Exposure 

Assessment. Environmental Fate and Effects Division, Office of Chemical Safety and 

Pollution Prevention. U.S. Environmental Protection Agency. 

US EPA. 2012a. Memorandum: NAFTA Guidance for Evaluating and Calculating Degradation 

Kinetics in Environmental Media. Environmental Fate and Effects Division, Office of 

Chemical Safety and Pollution Prevention. U.S. Environmental Protection Agency. 

US EPA. 20 12c. Development and Use of Percent Cropped Area and Percent Turf Area 

Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update 

http:/ /www.epa.gov/oppefed 1/models/water/pca adjustment dwa.html 

US EPA, 2009. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport ofPesticides, Version II. U.S. Environmental Protection Agency. 

Washington, D.C. http://www.epa.gov/oppefed1/models/water/ 

US EPA. 2007. Coumaphos: Human Health Risk Assessment for Proposed Use on Honey and 

Honeycomb. PC Code: 036501; Petition Number: 2E6504; DP Number: D315769. 

US EPA, 2000a. Memorandum: Revised Tier 1 Drinking Water Assessment for Coumaphos. 

Environmental Fate and Effects Division, Office of Prevention, Pesticides, and Toxic 

Substances. United States Environmental Protection Agency. DP Barcode: 0266513. 

US EPA, 2000b. Reregistration Eligibility Decision Addendum and FQPA Tolerance 

Reassessment Progress Report: Coumaphos. Office of Prevention, Pesticides, and Toxic 

Substances. United States Environmental Protection Agency. EPA 738-R-00-010. 

US EPA. 1998. Coumaphos-EFEO Reply to Registrant's Rebuttal. Office of Prevention, 

Pesticides and Toxic Substances, DP Barcodes D230394 and 0239676 

US EPA. 1994. Coumaphos (36501) Reregistration Case No. 0018. Product and Residue 

Chemistry Chapters for the Coumaphos Reregistration Eligibility Decision (RED) 

Document. DP Barcode D207352.Appendix A 

10 
Surface Water 

RUN No. 1 FOR Coumaphos 

RATE (#/AC) 

ONB(MULT) 

.220( .220) 

No . APPS & 

INTERVAL 

1 1 

Model Outputs 

ON Baregrond * INPUT VALUES * 

SOIL SOLUBIL APPL TYPE \CROPPED INCORP 

!toe (PPM ) (\DRIPT) AREA (IN) 

5905.0 0 . 2 GRANUL ( • 0) 100.0 . 0 

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS 

(FIELD) RAIN/RUNOPF (RESERVOIR) (RES.-EFF) 

METABOLIC COMBINED 

(RESER.) (RESER. ) 

.00 2 N/A l. 38- 171.12 .00 171.12 

UNTREATED WATER CONC (MICROGRAMS/ LITER (PPB)) Ver 1.1.0 JAN 1, 2007 

PEAK DAY (ACUTE) 

CONCENTRATION 

4.799 

RUN No. 2 FOR Oxon 

RATE (#/AC) 

ONB(MULT) 

. 022 ( .022) 

No.APPS & 

INTERVAL 

1 1 

ANNUAL AVERAGE (CHRONIC) 

CONCENTRATION 

.704 

ON Bare * INPUT VALUES * 

SOIL SOLUBIL APPL TYPE \CROPPED INCORP 

Koc (PPM ) (\DRIFT) AREA (IN) 

2922 . 0 31.6 GRANUL( .0) 100 . 0 . 0 

FIELD AND RESERVOIR HALPLIFE VALUES (DAYS) 

METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS 

(FIELD) RAIN/RUNOFF (RESERVOIR) (RES. - EFF) 

METABOLIC COMBINED 

(RESER.) (RESER.) 

4 . 10 2 N/A .00 - . 00 8 . 20 8.20 

UNTREATED WATER CONC (NANOGRAMS/ LITER (PPTr) ) Ver 1.1.0 JAN 1 , 2007 

PEAK DAY (ACUTE) 

CONCENTRATION 

404 . 402 

ANNUAL AVERAGE (CHRONIC) 

CONCENTRATION 

19 . 007 

11 
Application 

rate (lb/acre) 

0 . 220 

Ground water 

SCI GROW 

VERSION 2.3 

ENVIRONMENTAL FATE AND EFFECTS DIVISION 

OFFICE OF PESTICIDE PROGRAMS 

U. S. ENVIRONMENTAL PROTECTION AGENCY 

SCREENING MODEL 

FOR AQUATIC PESTICIDE EXPOSURE 

SciGrow version 2 .3 

chemical:Coumaphos 

time is 4/23/2013 16: 3: 4 

Nwnber of 

applications 

Total Use 

(1b/acre/yr) 

Koc 

(ml/g) 

Soil Aerobic 

metabolism (days) 

1.0 0 . 220 1 . 87E+03 365.0 

groundwater screening cond (ppb) = 1. 72E-02 

************************************************************************ 

Application 

rate (lb/acre) 

0 . 022 

SciGrow version 2.3 

chemical : Coumaphoxon 

time is 4/23/2013 16 : 3:53 

Nwnber of 

applications 

Total Use 

(lb/acre/yr) 

Koc 

(ml/g) 

Soil Aerobic 

metabolism (days) 

1 . 0 0 . 022 2 . 56E+03 4.1 

groundwater screening cond (ppb) = 5 . 72E-05 ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 

12 
PRZM-GW 

PR7M GW (Vcrston 1 0 1) ~ Jx! ---- -- -

Hit;tlest O¥yVl!AJe(ppb) ~ 

Sirula6onA.,.ageVl!AJefppb) ~ 

Ave~age Bteoktlvough Tine (&lys) jlncornplete I Thll>u!h>ut. ~ 

Pent 81f!ol<tlvoughAvOfage fppb) llneomple<e I 

2.5,----..,..----------------, 

I SoveGtaph I I Cop)'Gtaph I 

I Run Sindoticn I 1/0F~Aa amo: N~Col1<>n 1(i(lyJs 

1/0 WOJking DrectOI)I: C:\Modeh\pr2mgw\Coumophos\ 

North Carolina 

PRZMGW(Vcmon1.0 ) 1::.1 J'X 

P .. ticide Scenario: Gen01ol Scenario: Horizon C""'96olion S'""'"ary 0Up<Jt L------, 

Note: Tine serie• output is de§veted to the -'<i1g dwectOI)' speclied below. 

Higheot Daly Value (ppb) J B. 7SE • 11 

SirulotionAve~ageValuefppb) j 5.7E·11 

l E-10·,------------------, 

I Save Graph I l Copy Graph I 

110 FqFiloName: FLCitrur_OJ<On...101¥t 

110 Wcxl<ng DrectOI)I: C:\Models~\ 

Florida (Central Ridge) 

13 
Appendix B 

Coumaphos Aerobic Soil metabolism 

Days Percent AR 

0 99.3 

0 99.5 

0 99.7 

1 96.8 

80 

c: 

·

2 60 ~ 

4 

·2 

4 

2 1 99.0 

1 99.0 

c 

Q) 

(.) 

...:__---x---S+- 0 

3 98.0 

3 98.9 

3 97.0 

7 98.9 

7 98.9 

7 96.1 

14 97.8 

14 97.8 

14 98.7 

30 98.5 

60 96.5 

90 91 .3 

120 !=lR R 

§ 40 (_) 

20 

0 100 200 300 0 100 200 300 

Time 

~~~ OT50 DToo -l Co Parameters 

FO 2761 9171 1. 7 98.2 k = 0.000251 

·2 

-2 

:op NA NA 1.4 98.7 f"' 0.4 79, ko • 0.0023, k, = -0.000916 

)RE 1645934 7678 194832180211 048451 0248402846886 1.5 98.8 N = 29.7, k= 4.82e-61 

Figure 1. Aerobic Soil Degradation Kinetics (MRID 48705501) 

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