1

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 060101

Chemical: Thiabendazole

DP Barcode: D410805

DATE: February 24, 2014

MEMORANDUM

SUBJECT: Thiabendazole: Drinking Water Assessment for Proposed New Uses of the 

fungicide Mertect®340-F (EPA Reg. No. 100-889) as a seed treatment.

TO: Tony Kish, PM 22 (7505P)

Rosemary Kearns Reviewer (7505P)

Registration Division, Fungicide Branch

Bonnie Cropp-Kohlligian

Elissa Reaves, Branch Chief

Registration Action Branch 4

Health Effects Division (7509P)

FROM: James K. Wolf, Environmental Scientist

Environmental Risk Branch 3

James A. Hetrick, Ph.D. Senior Scientist

Rosanna Louie-Juzwiak, RAPL

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507C)

Dana Spatz, Branch Chief

Environmental Risk Branch 3

Environmental Fate and Effects Division (7507C)

Syngenta Crop Protection has submitted an application to amend the Mertect®340-F (EPA 

Registration No. 100-889) label with the addition of seed treatment uses on vegetables and small 

grains crops1and amend the label to add a higher rate on soybeans. A Tier 1 drinking water 

 

1 Vegetable, root (except sugarbeet); Subgroup 1B, Onion, bulb, Subgroup 3-07A; Brassica, head and stem, Subgroup 5-A; 

Vegetable, Cucurbit Group 9; Alfalfa; Spinach (including baby); and small grain cereals (wheat, barley, oats, rye, and triticale).
2

assessment was conducted for thiabendazole in surface water using the FIRST model and Tier 1

groundwater using PRZM-GW for the proposed new seed treatment uses and soybean rate 

increase. 

The Estimated Drinking Water Concentrations (EDWC) for the proposed new uses and the 

application rate increase for soybeans are based on the maximum seed treatment use rate of 0.15 

lb a.i./A planted to a depth of 1 inch. For this assessment EFED also assumed that there was only 

1 cropping season per year. These proposed rates are lower than the currently registered wheat 

seed treatment rate of 0.20 lb a.i./A, which results in the highest EDWCs. The highest EDWCs in 

surface water for thiabendazole were previously prepared for the 2002 Reregistration Eligibility

Document (RED)2, using the Tier 1 GENEEC model (which has since been replaced by the 

FIRST model3) and the SCI-GROW model (which has been replaced with PRZM-GW4) for 

groundwater. Input parameters used by the models also followed current model input guidance. 

The surface water and groundwater EDWCs for the proposed new uses and reevaluated here for

the wheat seed treatment rate are presented in this document (Table 1).

Based on the proposed new uses of thiabendazole, the Tier 1 peak (acute) and annual average 

(chronic and cancer) EDWCs in surface source drinking water are 2.85 and 0.35 μg/L, 

respectively. For the wheat seed treatment, the reassessed surface water concentrations are 3.80 

and 0.47 μg/L for peak (acute) and annual average (chronic and cancer), respectively. The peak 

concentrations are higher than previously determined for the RED primarily due to changes in the 

conceptual model (GENEEC vs. FIRST) (e.g., differences of field size and shape and the 

implementation of the Index Reservoir) and difference in fate input values for modeling. The 

chronic EDWCs are lower than before due the inclusion of the Index Reservoir (e.g., size and 

flow through the reservoir).

For groundwater as a source drinking water, the PRZM-GW model-estimated peak concentrations

are 0.46 μg/L and 0.61 μg/L for 100 year simulation, respectively, for the proposed new uses and 

the wheat seed treatment use. Breakthrough average concentrations of thiabendazole in 

groundwater could not be estimated because no breakthrough of thiabendazole into groundwater 

was predicted.

EFED recommends that 3.80 μg/L (peak) and 0.47 μg/L (annual average) concentrations be 

used in the human health dietary risk assessment.

 

2

http://www.epa.gov/oppsrrd1/REDs/thiabendazole_red.pdf, page 33. 

3

http://www.epa.gov/oppefed1/models/water/

4

http://www.epa.gov/oppefed1/models/water/index.htm#przm_gw
3

Table 1.Summary of Tier 1 Estimated Drinking Water Concentrations in Surface and Ground Water for the 

New Uses and Previously Assessed Wheat Use.

New Uses and Reassessment Thiabendazole

Peak Concentration Annual Average

Surface Water Crop (app rate lb a.i./A) Model μg/L

New Uses (0.15) FIRST 2.85 0.35

Wheat (0.20) FIRST 3.80 0.47

From RED Peak Concentration 56-day Average

Wheat (0.20) GENEEC 2.40a1.55a

Groundwater Highest Daily 

Concentration

Average 

Concentration after 

Breakthrough

New Uses (0.15) PRZM-GW 0.46 -

Wheat (0.20) PRZM-GW 0.62 -

a EDWCs reported in the 2002 RED.

USE CHARACTERIZATION

The seed treatment rates for the proposed new uses of thiabendazole are summarized in Table 2. 

Mertect 340-F is applied to seeds as a water-based slurry using standard seed treatment 

equipment. Treated seeds may be planted at any time of the year. While it is assumed that only

one application (i.e., one planting of treated seed) may be made per year, in some regions, more 

than one crop cycle may occur per year. Maximum seed treatment rates as defined by the label are 

given in Table 2.

The proposed use rate for seed treatments are expressed as mg (milligrams) of active ingredient 

(a.i.) per seed with the per seed rates ranging from 0.002 to 0.10 mg a.i. per seed or as fluid 

ounces (fl oz) of product per 100 pounds of seed (or 100 cwt) with rates ranging from 2.6 to 5.8 fl

(fl oz) per 100 cwt (Table 2). 

Table 2. Maximum Application Rates for Proposed New Seed Treatment Uses of Thiabendazolea

Crop or Crop Group Crop Group ID

Max. Seed Treatment Rate

mg a.i./seed fl oz product per 

100 lb seed

lb a.i. per

100 lb seed

Alfalfa NA 0.004 5.8 0.18578

Cereals, Small Grainb

 Barley NA 0.03 2.6 0.08328

 Oat NA 0.03 3.4 0.10891

 Rye NA 0.03 3.2 0.1025

 Triticale NA 0.03 2.6 0.08328

 Wheat NA 0.03 3.1 0.09930

Brassica, head and stem Subgroup 5A 0.002 - -

Cucurbit Group 9 0.1 - -

Onion, bulb Subgroup 3-07A 0.002 - -

Root vegetables 

(except sugar beet) Subgroup 1B 0.002 - -
4

Table 2. Maximum Application Rates for Proposed New Seed Treatment Uses of Thiabendazolea

Crop or Crop Group Crop Group ID

Max. Seed Treatment Rate

mg a.i./seed fl oz product per 

100 lb seed

lb a.i. per

100 lb seed

Spinach NA 0.006 - -

Soybeans (rate increase) NA 0.0302 - 0.020

a Mertect 340-F 889 MAS 0510 AMEND 0313 HiLite-dt/df 3/15/13; 000100-00889.20130318 Mertect_340-F-Amend-0313-

HiLite.PDF. 

b

“Small grains” is not designated as an EPA crop group.

The proposed new use rates, on a per acre basis, vary depending on the crop, the size of seed, seed

treatment rate (mg a.i. per seed), and the seeding rate per acre. To determine the potential 

thiabendazole loading within a given acre, upper bound seeding rates for the available crops were 

used using information from a report prepared by the Biological and Economic Analysis Division 

(BEAD) for some of the proposed crops (Becker and Ratnayake, 20115). Based on the proposed 

wheat use, the maximum seed treatment rate on a pound of active ingredient per acre (lb a.i./A) 

basis would be 0.15 lb a.i./A. The seeding rates for the relevant crops are summarized in Table 3. 

In correspondence from the registrant, Syngenta6, it was indicated that the following would be 

added to the label “regardless of type of application (seed treatment, soil, or foliar), do not apply 

more than 0.15 lb a.i./A (68 g a.i./A) per year.”

Table 3. Proposed use rates for thiabendazole seed treatment for the new uses.

Mertect®340-F EPA Reg. No. 100-889 [e-submission #4085; see Table 2]

Crop Group Representative 

Crops

Seed Treatment Rate

Range of Seeding 

Rates

(# seeds/A)

b

Max. Appl. Rate

(lb a.i./A)

c

fl. oz. 

product/100 

lb seeda

mg 

a.i./seeda

Alfalfa 5.8 0.004 3,405,000 0.030

Cereals (small grains)

Barley 2.6 0.03 1,222,000 to 1,300,000 0.081 to 0.086

Oats 3.4 0.03 1,305,000 0.0863

Rye 3.2 0.03 1,962,000 0.130

Triticale 2.6 0.03 1,744,000 0.115

Wheat

Wheat, winter

Wheat, forage

3.1 0.03 2,250,000d

600,000 to 1,350,000

1,740,000

0.149

0.040 to 0.089

0.115

Brassica, head and 

stem Broccoli 0.002 8,297 to 210,845 0.00004 to 0.0009

Cabbage 0.002 7,260 to 98,010 0.00003 to 0.00043

Bulb Vegetables Onion 0.002 87,120 to 1,254,528 0.00038 to 0.0055

Cucurbit Vegetables

Cucumber

Muskmelon

Squash, 

summer

Squash, winter

0.1 4,840 to 139,392

2,420 to 34,848

1,452 to 15,374

2,723 to 7,260

0.0011 to 0.031

0.00053 to 0.0077

0.00032 to 0.0034

0.00060 to 0.0016

Spinach - 0.006 196,020 to 653,400 0.0026 to 0.0086

Root Vegetables Beet, garden 0.002 261,360 to 2,090,880 0.0012 to 0.0092

 

5 Becker, Jonathan and Ratnayake, Sunil. 2011. Acres Planted per Day and Seeding Rates of Crops Grown in the United States. Biological and 

Economic Analysis Division (BEAD), Office of Pesticide Programs, United States Environmental Protection Agency.

6 E-Mail from P. McCain (Syngenta) to T. Kish (USEPA). (Dated 05/31/13).
5

Table 3. Proposed use rates for thiabendazole seed treatment for the new uses.

Mertect®340-F EPA Reg. No. 100-889 [e-submission #4085; see Table 2]

Crop Group Representative 

Crops

Seed Treatment Rate

Range of Seeding 

Rates

(# seeds/A)

b

Max. Appl. Rate

(lb a.i./A)

c

fl. oz. 

product/100 

lb seeda

mg 

a.i./seeda

(except sugarbeet) Carrot

Horseradish

Radish

Parsley

Parsnip

104,544 to 2,090,880

9,680 to 10,249

418,176 to 1,045,440 

52,272 to 1,568,160

87,120 to 435,600

0.00046 to 0.0092

0.00004 to 0.00005

0.0018 to 0.0046

0.00023 to 0.0069

0.00038 to 0.0019

Soybeans - 0.0302 50,000 to 250,000 0.0033 to 0.017

a Proposed label MERTEC 340-F 889 MAS 0313 HILITE –dt/df 3/15/13 (Density = 4.1 lb a.i./gallon of product; 42.3 % active ingredient (a.i.).[esubmission #4085; MRID 4907800]

b Becker and Ratnayake. 2011.

c mg a.i./seed * seeds/A * (1 lb/453.59 g) * 1 g/1000 mg = lb a.i./A.

d Conservative maximum seeding rate proposed by Syngenta.

e Current label EPA Reg. No. 100-889 April 5, 2013. Maximum rate of soybeans is 0.16 fl oz. per 100 lb of seed = 0.00512 lb a.i./100 lb of seed.

ESTIMATED DRINKING WATER CONCENTRATIONS

Previous Drinking Water Assessments

As part of the Thiabendazole RED7, a drinking water assessment was conducted to predict 

thiabendazole EDWC from seed treatment for dry peas, chickpeas, lentils, wheat, and corn. The 

Tier 1 EDWCs from GENEEC were 2.4 μg/L and 1.55 μg/L for the peak and average 56-day

concentration, respectively, for the maximum wheat seed treatment of 0.20 lb a.i./A [or 3.6 fl oz 

a.i. per 100 pounds of seed and 90 lb of seed per acre]. The Tier 1 SCI-GROW model EDWC

was less than 0.01 μg/L. Section 18s for Brussels sprout, cabbage, and cauliflower in California 

(D326593) and Washington (D327512) assumed the same drinking water exposure concentrations 

as the RED. 

For a new use assessment for seed treatment on dry peas @ 1 inch planting depth (D315436), the

Tier 1 drinking water concentrations using FIRST, which was developed to replace GENEEC for 

drinking water assessment, was 2.0 μg/L for acute and 0.5 μg/L for chronic exposure. For a new 

use on seed treatment on corn at an application rate of 0.0055 lb ai/A and 2 inch seed planting 

depth (D363978), the highest Tier 2 PRZM/EXAMS for thiabendazole were 0.018 μg/L, 0.0048

μg/L, and 0.0034 μg/L, for the peak, annual average and 30 year average concentrations, 

respectively.

ENVIRONMENTAL FATE SUMMARY

There have been no additional environmental fate data submitted since the previous assessments. 

Pertinent physico-chemical and environmental fate and transport properties of thiabendazole are 

summarized in Table 4

 

7

http://www.epa.gov/oppsrrd1/REDs/thiabendazole_red.pdf, page 33. 
6

Environmental fate studies show that thiabendazole is persistent and immobile (Table 4). 

Thiabendazole is stable to hydrolysis and soil photolysis and degrades slowly in aerobic (half-life 

~ 700 days) and anaerobic soil environments (>200 days). Aquatic photolysis, with a half life of 

1.2 days in clear water, appears to be the only significant degradation pathway. Under anaerobic 

aquatic conditions thiabendazole showed no evidence of abiotic or biotic degradation but moved 

rapidly from water phase to the sediment phase. Thiabendazole binds tightly to soil due to its high 

soil/water partitioning coefficients (Kocs > 1,000 mL/goc), thus limiting the amount available for 

leaching into ground water and for solution phase runoff into surface water. With the high 

sorption capacity, thiabendazole would be transported on eroded sediment. Sorption was weakly 

correlated to organic carbon. Terrestrial field dissipation studies showed thiabendazole to be 

extremely persistent with no observable leaching. Vapor pressure and Henry’s Constant indicate 

that thiabendazole has a low potential to volatilize from soil and water.

Table 4. Physical/Chemical Properties, Environmental Fate Parameters and Fish Bioconcentration of 

Thiabendazole.

Parameter Value Description Source

(MRID #)

Selected Physical/Chemical Parameters

Molecular mass 201.1 g/mol -- (Calculated)

Molecular formula C10H7N3S --

Vapor pressure (25°C) 3.45 x 10-9 mm Hg 

4.0 x 10-9 mm Hg

-- 48354601

Thiabendazole 

RED (2002)

Henry’s Law Constant (25°C) 3.26 x10-11 atm-m

3

/mol -- (Calculated)

Dissociation Constants pKa1 = 4.5

pKa2 = 12.01

-- 48354604

40947302

Aqueous solubility Buffered solution (25C) at 

pH 5: 30 mg/L

pH 7: 28 mg/L

pH 9: 28 mg/L

Water: 22.74 mg/L

Buffer solution (20C) at:

pH4: 79.82 mg/L

pH7: 22.77 mg/L

pH10: 23.75 mg/L

-- 40947301

48354601

48354604

Log octanol-to-water partition 

coefficient (log KOW)

1.61 @ Room temperature = 16.6°C 48254601

48354604

Persistence

Hydrolysis half-life (22C) Stable @ pHs 5, 7, 9 Ratesa

of transformation were 

extrapolated resulting in t1⁄2 (198 days

@pH 7) far beyond the length of the 

study (30 days)

41265301

(D245780; 

02/04/99)

Aqueous photolysis half-life

(22.5 to 23.2C)

1.2 days 96 hour study @ pH5 43328305

Soil photolysis half-life (25C) Stable -- 41297301

41397302

Aerobic soil metabolism half-life 

(25°C)

688 days Registration Document D245780

One soil.

41791201
7

Table 4. Physical/Chemical Properties, Environmental Fate Parameters and Fish Bioconcentration of 

Thiabendazole.

Parameter Value Description Source

(MRID #)

Anaerobic soil metabolism half-life 

(25°C)

211 day Only degradate detected was 

benzimidazole in a 90 day study.

(max 13.7 % AR;).

41559601 

Anaerobic aquatic metabolism half-life No evidence of biotic or 

abiotic degradation.

Rapidly moved from water phase to 

the sediment phase.

00122888

00070753

Aerobic aquatic metabolism half-life 

[dissipation half-life ] (25C)

-- Study requirement waived

(D169687; 12/30/92)

41559601

Mobility

Freundlich soil-water partition 

coefficients (KF); organic carbonnormalized Freundlich coefficients 

(KFOC)

KF (mL/g)/ KFoc(mL/goc):

(soil textural class)

2.49/1,104: (sand)

15.97/3,992: (sandy loam)

21.75/1,812: (silt loam)

269.6/22,467: (clay)

Mean = 7,343 mL/goc

Median = 2,902 mL/goc

41170102

Field Dissipation

Terrestrial field dissipation half-life in 

upper 6 inch soil layer; (max. depth of 

observed leaching)

t1⁄2 = 1100 days; (6 inches).

t1⁄2 = 990 and 1444 days; (12 

inches)

t1⁄2= 833 and 1093 days: (6 

inches).

Winter wheat/loamy sand/WA

Soybean and bare ground/sandy 

loam/IL

Soybean and bare ground/sandy 

loam/GA

43187201

43187202

43187201

Octanol/Water Partition Coefficient 

(logPow)

1.61 -- 48354604

Fish Bioconcentration

Fish bioconcentration factors (steadystate); depuration rate86.5 (whole); 19.7 (edible), 

747 (viscera), 3-day 

depuration: 96% in viscera 

and 50% in edible tissue.

Low bioconcentration potential in 

edible tissue, some potential to 

bioaccumulate in viscera but with 

rapid depuration

41631801

42022701

a Transformation rates of thiabendazole: pH 5 (-0.0019 days-1

); pH 7 (-0.0035 days-1); pH 9 (-0.0026 days-1)

Transformation Products

Three degradates were identified in the aqueous photolysis study (benzimidazole-2-carboxamide 

as a major degradate; benzimidazole and benzimidazole-2-carboxylic acid as minor degradates), 

two minor degradates were identified in the aerobic soil metabolism study (benzimidazole and 5-

hydroxythiabendazole (maximum observed 0.33%)), and one major degradate was identified in 

the anaerobic soil metabolism study (benzimidazole) (Appendix 1 Table 1). The metabolite 5-

hydroxythiabendazle and benzimidazole are included in the tolerance dietary exposure for food 

(40 CFR 180.2428), but not included in drinking water. The common name, chemical names, CAS 

No., molecular formula and mass, chemical structure, and maximum and final percent of applied 

radioactivity (AR) of the major degradates are summarized in Appendix 2 Table 1. The only

degradate that was analyzed for in the terrestrial field dissipation studies (TFD) is benzimidazole, 

since it is a major metabolite in a soil study (anaerobic soil metabolism). Results TFD studies 

showed that benzimidazole was not detected in any soil layers. No data were available for the 

other three degradates to verify their presence in the field. However, since they comprised a 

 

8

http://www.gpo.gov/fdsys/pkg/CFR-2005-title40-vol23/xml/CFR-2005-title40-vol23-sec180-242.xml
8

relatively small fraction (less than 10%) of the total applied radioactivity in the laboratory studies, 

EFED believes that any transformation to these degradates in the fields will also be negligible. 

While photodegradation is a route of degradation, the dissipation of thiabendazole is expected to 

be dependent on water conditions (e.g., sediment loading, depth, etc.) affecting sunlight 

penetration. For example, thiabendazole should not persist in clear shallow water bodies, but will 

be more persistent in turbid and/or deeper waters, particularly those with long hydrological 

residence times.

Due the low vapor pressure and burial of treated seeds when planted, volatilization is not 

expected to be an important route of dissipation. Spray drift, foliar dissipation, and wash-off are 

also not expected to be important for seed treatments. It is also assumed that the intent is to bury

all seed, which would reduce the presence of a.i. at the surface and keep losses due to runoff at 

minimum.

Monitoring Data

There are no detections of thiabendazole reported in the California Department of Pesticide 

Regulation (CDPR) Surface Water9 Monitoring Database available and it is not included in CDPR 

Groundwater Protection List10. Thiabendazole is not included in the surface water database 

collected in the USGS National Water Quality Assessment (NAWQA)11 Program. There were no 

detections of thiabendazole reported in groundwater (49 samples from CA, DE, FL,MD, NJ) in 

USGS NAWQA12 data warehouse with limits of detection <0.06 μg/L. 

Simulation Modeling

Surface Water 

This Tier I drinking water assessment utilizes the Tier I FQPA Index Reservoir Screening Tool 

(FIRST, Version 1.1.1, released 03/26/08) to assess surface water. Exposure was estimated for a 

seed treatment application at 0.15 lb a.i./A, which is to be the maximum annual application rate 

allowed on the Mertect®340-F label, and 0.20 lb a.i./A for the wheat seed-treatment use. 

Description of the FIRST model can be found on the EPA’s website at: 

http://www.epa.gov/pesticides/science/models_pg.htm.

Model Inputs 

The fate data used in modeling have been selected (Table 5) according to current modeling 

guidance13. Using current guidance for preparing the environmental fate data for input into the 

EFED water models results in slightly different values from the previous assessments. Previous 

drinking water assessments used the single aerobic soil metabolism half-life value of 688 days 

and the median Koc of 2,903 mL/goc which does not agree with current model input guidance (see 

Table 4). While inputs (average vs. median Koc and aerobic soil metabolism half-life) may have 

 

9

http://www.cdpr.ca.gov/docs/emon/surfwtr/index.htm; searched January 27, 2014.

10 http://www.cdpr.ca.gov/docs/legbills/calcode/040101.htm#a6800; searched January 27, 2014. 

11 http://infotrek.er.usgs.gov/nawqa_queries/jsp/swmaster.jsp; searched January 27, 2014.

12 http://infotrek.er.usgs.gov/nawqa_queries/jsp/gwmaster.jsp; search January 27, 2014.

13 http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm
9

changed due to updated guidelines, the conclusions concerning the fate of thiabendazole does not 

change. For PRZM-GW the application date (i.e., planting date) is assumed to occur 7 days before 

the emergence date as specified in each scenario.

The assessment assumes that 100 percent of the a.i. comes off the seed and is available for runoff 

or leaching (EFED, 199914). Thus, the runoff prediction of thiabendazole is expected to be 

conservative.

Table 5. Summary of environmental fate parameters for thiabendazole and other values used for modeling

FIRST, PRZM-GW, and SCI-GROW. 

Parameter Value or Range Value Used Source

Solubility (water)a28 mg/L 28 mg/L MRID 40947301

Hydrolysis t1/2 stable at pH 7

0 daya- surface water

198 daysb- groundwater

MRID 41265301

Aquatic Photolysisat1/2 29 hours 1.2 daysb MRID 43328305

Aerobic Soil Metabolism t1/2

688 days (single value)

2,064 (3 x 688)

2064 daysa,b MRID 41791201

(DER 2)

Aerobic Aquatic Metabolismat1/2 Stable (0 day)b No data available

Koc See Table 3 Mean = 7,343 mL/goc

a,b

Median = 2,902 mL/goc

c MRID 41170102

Application Method Granular D Model option 

Application Rate

New uses

Wheat rate (RED)

0.15 lb a.i./A

0.20 lb a.i./A

Max rate

Number of Applications per Year - 1 -

Watered In - No -

DEPI (depth of soil incorporation) 1 to 2 inches 1 and 2 inchb Beale, 2007 

Percent Crop Area (PCA)d All agriculture (0.91) 0.91b EFED, 2011d

a

Input for FIRST

b

Input for PRZM-GW c Median Koc value used for SCI-GROW (earlier assessments used median Koc of 2903 mL/goc).

d

http://www.epa.gov/oppefed1/models/water/pca_adjustment_dwa.html

The Tier 1 surface water EDWCs for thiabendazole are summarized in Table 6. Maximum values 

are shown in bold in Table 6. Output from FIRST for the two planting depths are located in 

Appendix 3. A percent crop area (PCA)15 of 0.91 was used.

 

14 EFED, 1999. Standard Method of Determining the Leachability of pesticides from treated seeds. July 30, 1999, USEPA, OPP, EFED, 

Arlington, VA.

15 http://www.epa.gov/oppefed1/models/water/pca_adjustment_dwa.html
10

New Uses

For the proposed new seed treatment rate of 0.15 lb a.i./A, the EDWCs for thiabendazole in 

surface water source of drinking water are 2.85 and 0.35 μg/L, for the peak and annual average 

concentrations, respectively. 

Updated Drinking Water Concentrations for Wheat Use Rate

For the wheat seed treatment rate of 0.20 lb a.i./A, the EDWCs for thiabendazole in surface water 

source of drinking water are 3.80 and 0.47 μg/L, for the peak and annual average concentrations, 

respectively. 

Table 6. FIRST Model Estimated drinking water concentrations (EDWCs) of thiabendazole for proposed 

maximum annual application rate of 0.15 lb a.i./A and two seeding depths and for the Maximum Wheat Rate 

Assessed in the RED (0.20 lb a.i./A). 

Crop Scenario

EDWCs (μg a.i./L)a

Peak Annual Average

All New Uses

0.15 lb a.i./A

Generic granular/seed treatment scenario 

with 1-inch soil incorporation 2.85 0.35

Generic granular/seed treatment scenario 

with 2-inch soil incorporation 1.42 0.18 

Wheat Rate

0.20 lb a.i./A

Generic granular/seed treatment scenario 

with 1-inch soil incorporation 3.80 0.47

Generic granular/seed treatment scenario 

with 2-inch soil incorporation 1.90 0.23

a All agriculture PCA = 0.91

Ground Water

The Tier 1 drinking water assessment used the PRZM-GW and SCI-GROW models for predicting 

thiabendazole concentrations in groundwater source drinking water.

PRZM-GW 

The six standard PRZM-GW scenarios16 used in the groundwater simulations were developed to 

be representative of known vulnerable sites—shallow, unconfined aquifers under an agricultural 

field with leaching prone soil and adequate precipitation and/or irrigation. Output values 

represent pesticide concentrations that may be observed in private drinking water wells resulting 

from the use of groundwater vulnerable to pesticide contamination. The results are expected to 

represent the upper bound values on the concentrations of thiabendazole that might be found in 

drinking water supplied by vulnerable groundwater sources. The selection and procedures for 

selecting model input parameters followed EFED model input guidance. 

 

16 Florida Citrus, Florida Potato, Wisconsin Corn, Georgia Peanuts, North Carolina Cotton, and Delmarva Sweet Corn
11

Groundwater Concentrations

PRZM-GW is a graphical user interface (GUI) for running the Pesticide Root Zone Model

(PRZM) to estimate exposure in a shallow, unconfined, aquifer following pesticide application to 

an agricultural field. PRZM was developed by the U.S. EPA to simulate the vertical movement of 

pesticides in the unsaturated soil, within and below the plant root zone, and extending to the water 

table using generally available input data (Carsel et al., 198417). PRZM is also currently used by 

EFED in combination with EXAMS18 to estimate pesticide concentrations in surface water. 

Groundwater EDWCs with PRZM-GW are simulated for 30 (and 100) years as done with 

PRZM/EXAMS for surface water. Unlike SCI-GROW, estimated groundwater concentrations

using PRZM-GW are influenced by both the soil and hydrology of the specific scenario. 

The inputs for PRZM-GW are summarized in Table 5. In the previous drinking water exposure 

assessment, a single aerobic soil metabolism half-life value of 688 days had been used. EFED 

model input guidance recommends multiplying a single half-life value times 3 (2064 days) to 

account for variability of half-lives among different soils. Also following current model input 

guidance, the mean Koc (7,343 mL/goc) is used with the PRZM-GW. In contrast, the median Koc 

is used in SCI-GROW. The highest daily concentration of thiabendazole in predicted by PRZMGW as groundwater source drinking water is 0.46 and 0.62 μg/L for the proposed new uses and 

the existing wheat use rate, respectively (Table 7). Complete breakthrough was not achieved for 

any of the scenarios with both 30 and 100 years of simulation. Therefore, the average 

concentration after breakthrough was not determined. This modeling shows that the leaching of 

thiabendazole to groundwater is not expected to be a significant dissipation pathway as 

concentrations estimates ranged from essentially 0 to less than 1 μg/L, with a 100 year of 

simulation. Representative output from PRZM-GW is presented in Appendix 3.

Table 7. Thiabendazole EDWC PRZM-GW (version 1.03) and updated 

scenarios.

Scenario Length of 

Simulation

(years)

High Daily 

Valuea

(μg/L)

Avg BT

(μg/L)a

Avg BT time 

(days)

Application Rate 0.15 lb a.i./A

Delmarva 30 <10-8-

b

-

b

“ 100 0.0038 - -

FL citrus 30 0.0029 - -

“ 100 0.46 - -

FL potato 30 <10-10- -

“ 100 2.1x10-5- -

GA Coast Pl 30 <10-16- -

 

17 Carsel, R.F.; Smith, C.N.; Mulkey, L.A.; Dean, J.D; Jowise, P. Users Manual for the Pesticide Root Zone Model (PRZM) Release 1. December 

1984. EPA-600/3-84-109. Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, 

Athens, GA, 227 pp. 

18 Burns, L. A. 2002. EXAMS (Exposure Analysis Modeling System) Version 2.98.04.06. Environmental Research Laboratory. U. S. 

Environmental Protection Agency. Athens, GA.
12

Table 7. Thiabendazole EDWC PRZM-GW (version 1.03) and updated 

scenarios.

Scenario Length of 

Simulation

(years)

High Daily 

Valuea

(μg/L)

Avg BT

(μg/L)a

Avg BT time 

(days)

“ 100 <9.0x10-7- -

NC Coast Pl 30 <6 x 10-7- -

“ 100 0.028 - -

WI Central Sands 30 3.2 x 10-14- -

“ 100 0.00015 - -

Application Rate 0.20 lb a.i./A 

FL citrus 100 0.62 - -

a Hydrolysis half-life @ pH7 = 198 days for all runs.

b Breakthrough not achieved during simulations (30 and 100 years).

SCI-GROW

A SCI-GROW estimate of the thiabendazole concentration in groundwater is also provided as 

required by the implementation of the PRZM-GW model. SCI-GROW (SG23.exe, version 2.3, 

dated 09/10/08) is a Tier I, regression-based model that provides a groundwater screening 

exposure value to be used in determining the potential risk to human health from drinking water 

contaminated with the pesticide. SCI-GROW does not consider multiple years of use.

The SCI-GROW estimate considers the highest rate as a single application, 0.15 and 0.20 lb a.i.

per acre for thiabendazole. The environmental fate values used are listed in Table 5. The 

thiabendazole concentrations were estimated to be 9.43 x 10-3μg/L and 1.26 x 10-2 μg/L, the 

proposed maximum new use rate and the current wheat seed treatment rate, respectively, (Table 

8). SCI-GROW output is given in Appendix 3.

Table 8. SCI-GROW estimated ground water concentration for thiabendazole at the

maximum proposed rate new use rate and the maximum wheat use rate.

Concentration (app rate 0.15 lb a.i./A) 9.43 x 10-3 μg/L 

Concentration (app. rate 0.20 lb a.i./A) 1.26 x 10-2μg/L
13

Appendix 1.

Appendix 1. Table 1. Thiabendazole degradates identified in Environmental Fate Studies.

Degradates Hydrolysis Photolysis 

(water)

Photolysis 

(soil)

Aerobic 

Soil

Anaerobic 

Soil

Terrestri

al Field

Benzimidazole X X X

a

5-hydroxythiabendazole X 

Benzimidazole-2-

carboxamide X

a

Benzimidazole-2-

carboxylic acid X

Unidentified [14C] X X

Unknown 1 X

14CO2 X

a

- major degradates (>10%)
14

Appendix 2. 

Appendix 2. Table 1. Thiabendazole and Its Environmental Degradates

Name

Chemical Name CAS 

No.

Formula

Molecular Mass

Chemical Structure Study Type Maximum %AR 

(day)

Final %AR 

(study length)

PARENT

Thiabendazole 2-(4-thiazolyl)-1Hbenzimidazole

CAS No.: 148-79-8

Formula: C10H7N3S

MW: 201.25 g/mol

Aerobic Soil Metabolism

Anaerobic Soil Metabolism

56.8%

78% (@ day 90)

TRANSFORMATION PRODUCTS

Thiabendazole-5-hydroxy 5-hydroxythiabendazole;

2-(4-Thiazolyl)-5-

benzimidazolol

CAS No.: 948-71-0

Formula: C10H7N3S

MW: 217.25g/mol

Aerobic Soil Metabolism

0.33% max 

observed through 

study

Benzimidazole 1H-Benzimidazole

CAS No.: 962-28-7 

Formula: C7H6N2

MW: 118.05 g/mol

Aq. Photolysis (minor)

Aerobic Soil Metabolism

Anaerobic Soil Metabolism

Terrestrial Field Dissipation

-

2.2%

13.7%

-

6.49% (avg.)

0.17%

5.5% (@ day 90

-
15

Name

Chemical Name CAS 

No.

Formula

Molecular Mass

Chemical Structure Study Type Maximum %AR 

(day)

Final %AR 

(study length)

Benzimidazole carboxylic 

acid

1H-Benzimidazole-2-

carboxylic acid 

CAS No.:

Formula: C8H6N2O2

MW: 162.15 g/mol

Aq. Photolysis (minor) 9.98% @ 96 hrs

Benzimidazole-2-

carboxamide

1H-Benzimidazole-2-

carboxamide

CAS NO. 5805-52-7

Formula: C8H7N3O

MW: 161.16 g/mol

Aq. Photolysis (major) 10.2% @ 96 hrs
16

Appendix 3. Representative Model Output

FIRST OUTPUT

Proposed New Use Maximum Rate of 0.15 lb a.i./A

 RUN No. 1 FOR thiabendazole ON seed treat * INPUT VALUES * 

 --------------------------------------------------------------------

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

 ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

 --------------------------------------------------------------------

 .150( .150) 1 1 7343.0 28.0 GRANUL( .0) 91.0 1.0

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

 --------------------------------------------------------------------

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

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

 --------------------------------------------------------------------

 2064.00 2 N/A 1.20- 148.80 .00 148.80

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

 --------------------------------------------------------------------

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

 --------------------------------------------------------------------

 2.846 .349

 RUN No. 2 FOR thiabendazole ON seed treat * INPUT VALUES * 

 --------------------------------------------------------------------

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

 ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

 --------------------------------------------------------------------

 .150( .150) 1 1 7343.0 28.0 GRANUL( .0) 91.0 2.0

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

 --------------------------------------------------------------------

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

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

 --------------------------------------------------------------------

 2064.00 2 N/A 1.20- 148.80 .00 148.80

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

 --------------------------------------------------------------------

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

 --------------------------------------------------------------------

 1.423 .175

ReRun EDWCs for Wheat Seed Treatment at 0.20 lb a.i./A

 RUN No. 1 FOR Thiabendazole ON Seed Treat * INPUT VALUES * 

 --------------------------------------------------------------------

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

 ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

 --------------------------------------------------------------------

 .200( .200) 1 1 7343.0 28.0 GRANUL( .0) 91.0 1.0
17

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

 --------------------------------------------------------------------

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

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

 --------------------------------------------------------------------

 2064.00 2 N/A 1.20- 148.80 .00 148.80

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

 --------------------------------------------------------------------

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

 --------------------------------------------------------------------

 3.795 .466

 RUN No. 2 FOR Thiabendazole ON seed treat * INPUT VALUES * 

 --------------------------------------------------------------------

 RATE (#/AC) No.APPS & SOIL SOLUBIL APPL TYPE %CROPPED INCORP

 ONE(MULT) INTERVAL Koc (PPM ) (%DRIFT) AREA (IN)

 --------------------------------------------------------------------

 .200( .200) 1 1 7343.0 28.0 GRANUL( .0) 91.0 2.0

 FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

 --------------------------------------------------------------------

 METABOLIC DAYS UNTIL HYDROLYSIS PHOTOLYSIS METABOLIC COMBINED

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

 --------------------------------------------------------------------

 2064.00 2 N/A 1.20- 148.80 .00 148.80

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

 --------------------------------------------------------------------

 PEAK DAY (ACUTE) ANNUAL AVERAGE (CHRONIC) 

 CONCENTRATION CONCENTRATION 

 --------------------------------------------------------------------

 1.897 .233
18

PRZM-GW

1/28/2014 7:52:43 AM; thiabendazole hyd up b HL ave koc; Florida Citrus - FL Central 

Ridge, Polk County - (Tampa) Met File (12842.dvf) - Astatula sand, hrgb A

User Interface Version: PRZM-GW (Version 1.03)

***Record 3 

 0.78 0 0 33 1 1

***Record 6

 0

***Record 8

 1

***Record 9

 1 0.25 200 60 1 10 10 10 0 100

***Record 10

 99

***Record 11

 0101 1 0102 1 3112 1 1

 0101 2 0102 2 3112 2 1

 0101 3 0102 3 3112 3 1

 0101 4 0102 4 3112 4 1

 0101 5 0102 5 3112 5 1

 0101 6 0102 6 3112 6 1

 0101 7 0102 7 3112 7 1

 0101 8 0102 8 3112 8 1

 0101 9 0102 9 3112 9 1

 010110 010210 311210 1

 010111 010211 311211 1

 010112 010212 311212 1

 010113 010213 311213 1

 010114 010214 311214 1

 010115 010215 311215 1

 010116 010216 311216 1

 010117 010217 311217 1

 010118 010218 311218 1

 010119 010219 311219 1

 010120 010220 311220 1

 010121 010221 311221 1

 010122 010222 311222 1

 010123 010223 311223 1

 010124 010224 311224 1

 010125 010225 311225 1

 010126 010226 311226 1

 010127 010227 311227 1

 010128 010228 311228 1

 010129 010229 311229 1

 010130 010230 311230 1

 010131 010231 311231 1

 010132 010232 311232 1

 010133 010233 311233 1

 010134 010234 311234 1

 010135 010235 311235 1

 010136 010236 311236 1

 010137 010237 311237 1

 010138 010238 311238 1

 010139 010239 311239 1

 010140 010240 311240 1

 010141 010241 311241 1

 010142 010242 311242 1

 010143 010243 311243 1

 010144 010244 311244 1

 010145 010245 311245 1

 010146 010246 311246 1
19

 010147 010247 311247 1

 010148 010248 311248 1

 010149 010249 311249 1

 010150 010250 311250 1

 010151 010251 311251 1

 010152 010252 311252 1

 010153 010253 311253 1

 010154 010254 311254 1

 010155 010255 311255 1

 010156 010256 311256 1

 010157 010257 311257 1

 010158 010258 311258 1

 010159 010259 311259 1

 010160 010260 311260 1

 010161 010261 311261 1

 010162 010262 311262 1

 010163 010263 311263 1

 010164 010264 311264 1

 010165 010265 311265 1

 010166 010266 311266 1

 010167 010267 311267 1

 010168 010268 311268 1

 010169 010269 311269 1

 010170 010270 311270 1

 010171 010271 311271 1

 010172 010272 311272 1

 010173 010273 311273 1

 010174 010274 311274 1

 010175 010275 311275 1

 010176 010276 311276 1

 010177 010277 311277 1

 010178 010278 311278 1

 010179 010279 311279 1

 010180 010280 311280 1

 010181 010281 311281 1

 010182 010282 311282 1

 010183 010283 311283 1

 010184 010284 311284 1

 010185 010285 311285 1

 010186 010286 311286 1

 010187 010287 311287 1

 010188 010288 311288 1

 010189 010289 311289 1

 010190 010290 311290 1

 010191 010291 311291 1

 010192 010292 311292 1

 010193 010293 311293 1

 010194 010294 311294 1

 010195 010295 311295 1

 010196 010296 311296 1

 010197 010297 311297 1

 010198 010298 311298 1

 010199 010299 311299 1

***Record 12

Place Holder

***Record 13

 99 1 0 0

***Record 15

Place Holder

***Record 16

 2512 1 0 5 1 0.168 1 0

 2512 2 0 5 1 0.168 1 0

 2512 3 0 5 1 0.168 1 0
20

 2512 4 0 5 1 0.168 1 0

 2512 5 0 5 1 0.168 1 0

 2512 6 0 5 1 0.168 1 0

 2512 7 0 5 1 0.168 1 0

 2512 8 0 5 1 0.168 1 0

 2512 9 0 5 1 0.168 1 0

 251210 0 5 1 0.168 1 0

 251211 0 5 1 0.168 1 0

 251212 0 5 1 0.168 1 0

 251213 0 5 1 0.168 1 0

 251214 0 5 1 0.168 1 0

 251215 0 5 1 0.168 1 0

 251216 0 5 1 0.168 1 0

 251217 0 5 1 0.168 1 0

 251218 0 5 1 0.168 1 0

 251219 0 5 1 0.168 1 0

 251220 0 5 1 0.168 1 0

 251221 0 5 1 0.168 1 0

 251222 0 5 1 0.168 1 0

 251223 0 5 1 0.168 1 0

 251224 0 5 1 0.168 1 0

 251225 0 5 1 0.168 1 0

 251226 0 5 1 0.168 1 0

 251227 0 5 1 0.168 1 0

 251228 0 5 1 0.168 1 0

 251229 0 5 1 0.168 1 0

 251230 0 5 1 0.168 1 0

 251231 0 5 1 0.168 1 0

 251232 0 5 1 0.168 1 0

 251233 0 5 1 0.168 1 0

 251234 0 5 1 0.168 1 0

 251235 0 5 1 0.168 1 0

 251236 0 5 1 0.168 1 0

 251237 0 5 1 0.168 1 0

 251238 0 5 1 0.168 1 0

 251239 0 5 1 0.168 1 0

 251240 0 5 1 0.168 1 0

 251241 0 5 1 0.168 1 0

 251242 0 5 1 0.168 1 0

 251243 0 5 1 0.168 1 0

 251244 0 5 1 0.168 1 0

 251245 0 5 1 0.168 1 0

 251246 0 5 1 0.168 1 0

 251247 0 5 1 0.168 1 0

 251248 0 5 1 0.168 1 0

 251249 0 5 1 0.168 1 0

 251250 0 5 1 0.168 1 0

 251251 0 5 1 0.168 1 0

 251252 0 5 1 0.168 1 0

 251253 0 5 1 0.168 1 0

 251254 0 5 1 0.168 1 0

 251255 0 5 1 0.168 1 0

 251256 0 5 1 0.168 1 0

 251257 0 5 1 0.168 1 0

 251258 0 5 1 0.168 1 0

 251259 0 5 1 0.168 1 0

 251260 0 5 1 0.168 1 0

 251261 0 5 1 0.168 1 0

 251262 0 5 1 0.168 1 0

 251263 0 5 1 0.168 1 0

 251264 0 5 1 0.168 1 0

 251265 0 5 1 0.168 1 0

 251266 0 5 1 0.168 1 0
21

 251267 0 5 1 0.168 1 0

 251268 0 5 1 0.168 1 0

 251269 0 5 1 0.168 1 0

 251270 0 5 1 0.168 1 0

 251271 0 5 1 0.168 1 0

 251272 0 5 1 0.168 1 0

 251273 0 5 1 0.168 1 0

 251274 0 5 1 0.168 1 0

 251275 0 5 1 0.168 1 0

 251276 0 5 1 0.168 1 0

 251277 0 5 1 0.168 1 0

 251278 0 5 1 0.168 1 0

 251279 0 5 1 0.168 1 0

 251280 0 5 1 0.168 1 0

 251281 0 5 1 0.168 1 0

 251282 0 5 1 0.168 1 0

 251283 0 5 1 0.168 1 0

 251284 0 5 1 0.168 1 0

 251285 0 5 1 0.168 1 0

 251286 0 5 1 0.168 1 0

 251287 0 5 1 0.168 1 0

 251288 0 5 1 0.168 1 0

 251289 0 5 1 0.168 1 0

 251290 0 5 1 0.168 1 0

 251291 0 5 1 0.168 1 0

 251292 0 5 1 0.168 1 0

 251293 0 5 1 0.168 1 0

 251294 0 5 1 0.168 1 0

 251295 0 5 1 0.168 1 0

 251296 0 5 1 0.168 1 0

 251297 0 5 1 0.168 1 0

 251298 0 5 1 0.168 1 0

 251299 0 5 1 0.168 1 0

***Record 17

 0 3 0

***Record 19

Place Holder

***Record 20

 400 0 0 0 0 0 2 1 1 0

***Record 26

 0.0 0.0 0.0

***Record 27

 4 0.1 0.90 7.0

***Record 31

 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.97 10.0

***Record 32

 21 21 21 21 21 21 21 21 21 21 21 21

***Record 32A

 2.00 25.0

***Record 33

 8

*** Record 34,36,37 Horizon 1

 1 10 1.35 0.3 0 0 0

 0.00350.000336 0

 1 0.3 0.014 0.14410.57392

 21 96 2.4 0 0

*** Record 34,36,37 Horizon 2

 2 10 1.58 0.25 0 0 0

 0.00350.000317 0

 5 0.25 0.016 0.14410.57392

 21 95 2.8 0 0

*** Record 34,36,37 Horizon 3

 3 20 1.58 0.25 0 0 0
22

 0.00350.000261 0

 20 0.25 0.016 1.44105.7392

 21 95 2.8 0 0

*** Record 34,36,37 Horizon 4

 4 20 1.45 0.33 0 0 0

 0.00350.000187 0

 20 0.33 0.015 0.14410.57392

 21 95 2.8 0 0

*** Record 34,36,37 Horizon 5

 5 20 1.5 0.27 0 0 0

 0.00350.000112 0

 20 0.27 0.015 0.14410.57392

 21 95 2.8 0 0

*** Record 34,36,37 Horizon 6

 6 20 1.5 0.34 0 0 0

 0.00353.73E-05 0

 20 0.34 0.015 0.14410.57392

 21 95 2.8 0 0

*** Record 34,36,37 Horizon 7

 7 200 1.59 0.25 0 0 0

 0.0035 0 0

 50 0.25 0.014 0.14410.57392

 21 96 2.8 0 0

*** Record 34,36,37 Horizon 8

 8 100 1.58 0.3997 0 0 0

 0.0035 0 0

 50 0.3997 0.001 0.14410.57392

 21 87 11 0 0

*** Record 40

 0

*** Record 42

 YEAR 10 YEAR 10 YEAR 10 0

*** Record 45

 5 YEAR

*** Record 46

 DCON1 TAVE 21 22 1.0E3

 INFL TCUM 21 210.000121

 IRRG TSER

 VFLX TSER

 FPVL TSER

Highest Daily Value(ppb) = 0.461 μg/L 

Average Breakthrough Time(days) – Incomplete

Post-Breakthrough Average (ppb) – Incomplete

Throughputs - 0.487

Simulation Period 100 years

Application rate 0.15 lb a.i./A

Application Date (-7 days) since emergence

Hydrolysis half-life – 198 days
23

Surface Soil Half-life – 2064 days

Sorption Coefficient – Koc 7343 (average Koc)
24

SCIGROW 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:thiabendazole

time is 1/23/2014 13:26: 4

------------------------------------------------------------------------

 Application Number of Total Use Koc Soil Aerobic

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------

 0.150 1.0 0.150 2.90E+03 2064.0

------------------------------------------------------------------------

groundwater screening cond (ppb) = 9.43E-03 

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

SciGrow version 2.3

chemical:thiabendazole

time is 2/24/2014 8: 0:23

------------------------------------------------------------------------

 Application Number of Total Use Koc Soil Aerobic

 rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------

 0.200 1.0 0.200 2.90E+03 2064.0

------------------------------------------------------------------------

groundwater screening cond (ppb) = 1.26E-02 

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