### Page 1 of 6 OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460



### July 1 7 , 2012

PC Code: 014019

MEMORANDUM DP Barcode: 37618 4

SUBJECT: Thiacloprid : Update of the Drinking Water Exposure Assessment for Section 3

New Use s on Stone Fruits and Peppers

FROM: Greg Orrick, Environmental Scientist

E nvironmental R isk B ranch II

E nvironmental Fate and Effects Division (7507P)

THRU : R. David Jones, Ph.D. Senior Agrono mist

Brian Anderson

, Chief

Environmental R isk B ranch II

E nvironmental Fate and Effects Division (7507P)

TO: Elizabeth Holman, Chemist

Christina S wartz, Chief

Risk Assessment Branch II

Health Effects Division (7509P)

Andrew Ertman, Risk Manager

Barbara Madden, Minor Use Team Leader, RM Team 5
Risk Integration Minor Use and Emergency Response Branch
Registration Division (7505P)

Marianne Lewis, Risk Manager
Venus Eagle, Product Manager, Team Leader, RM Team 1

Insecticide

- Rodenticide Branch
Regi stration Division (7505P)

This Environmental Fate and Effects Division (EFED) memorandum updates the 2010
drinking water exposure assessment (DP barcode 376181; USEPA, 2010) for proposed Section 3
new use registrations of thiacloprid on the stone fruits crop group (12) and on peppers (both bell

and non

- bell)

. Bayer CropScience (Bayer) submitted comments on the 2010 drinking water
assessment in a position paper titled, “Bayer CropScience Refinement of the EPA Cancer

Assessment for Thiacloprid” (MRID 48658 203). The position paper proposed three refinements
to EFED’s drinking water assessment concerning unextracted residues, water treatment effects

, and perc ent cropped area (PCA) factors.

### Page 2 of 6 EFED concluded the following, based on Bayer’s comments:

1. T hiacloprid and its amide are the only residues of concern in untreated drinking water.
Following drinking water treatment, thiacloprid is the only residue of concern expected to be
potentially present. This is because the study data indicate that 1) coagulation do es not remove thiacloprid or thiacloprid

- amide from source water, 2) a typical oxidant (sodium
hypochlorite) removes thiacloprid

- amide (but not thiacloprid), and 3) HED has determined
that the four major treatment products of thiacloprid

- amide are not resi dues of concern.
Because surface water sourced drinking water is typically treated, thiacloprid is the only
compound of concern for surface water assessment. For assessment of untreated well water,
thiacloprid and its amide are the residues of concern.

2. I t is highly unlikely that any bioavailable unextracted residues included the parent
compound. Also, although it was not well demonstrated that all bioavailable transformation
products were completely extracted, it is unlikely that any unextracted transfo rmation
products were of toxicological concern ( i.e. , containing the thiazolidine ring). Therefore,
exposure estimates of the residues of concern (whether thiacloprid alone or thiacloprid plus

its amide) should not include unextracted residues.

3. D rinking water exposure estimates for current uses may be adjusted by a PCA factor for
cotton and orchards/vineyards, which is 33% (occurring in the Texas Gulf regional basin
where cotton production is concentrated ; USEPA, 2012 ). Because thiacloprid is also

propos ed for use on peppers (and stone fruit, which doesn’t change PCA calculations that
already include orchards) and a pepper

- specific PCA is not available, drinking water
exposure estimates for proposed uses of thiacloprid should be adjusted by the maximum PC A
factor for all agriculture, which is 91% (USEPA, 2012)

.

These conclusions result in the following updated EDWCs of thiacloprid residues of

concern ( Table 1 ) . The ground water EDWCs are unchanged, with the exception that the values
including unextracted residues formerly included for characterization were removed. Treated
ground water EDWCs are expected to be less due to the removal of thiacloprid

- amide. Th e

surface water EDWCs are less than previously reported (see Table 2 ) because the treated
drinking water residues of concern no longer include thiacloprid

- amide.

Table 1 . Total Residue EDWCs in Surface Water and Ground Water for Use in Dietary Risk

Asse ssment Based on the Use Pattern of Maximum Exposure, Pome Fruits

.

Use (maximum

rate) Source PCA

(%) 1

- in

- 10

- year Peak Exposure
(ppb) 1

- in

- 10

- year
Annual Mean
Exposure (ppb) 30

- year Mean
Exposure

(ppb)

Pome fruits

(0. 5 0 lbs a.i./A/year) Surface water (treated) 91 1 8 2.3 1.2

Ground water (untreated) N/A 0.25 0.25 < 0.25

Table 2 . EDWCs Reported in the Previous (2010) Drinking Water Exposure Assessment

Pome fruits

(0. 5 0 lbs a.i./A/year) Surface water (treated) 91 26 6 .8 4.4

Ground water (untreated) N/A 0.25 0.25 < 0.25

### Page 3 of 6 SCI

- GROW model inputs (and outputs) from the 2 010 assessment (see Appendix A )
were not updated:

Table 3

. SCI

- GROW Input Parameters for Thiacloprid Residues of Concern

. Input Parameter Value Source

Application Rate 0. 25 lbs a.i./A Current labels

Applications per Year 2 Current labels

Organic Carbon Partition

Coefficient (K OC ) 166 L/kg OC MRID 44927909

Aerobic Soil Metabolism

Half

- life 69 days MRID 44927916



### PRZM use pattern inputs were not updated :

Table 4

. PRZM Scenarios and Input Parameters Describing Proposed and Current Maximum Use

Patterns of Thiacloprid

.

Use Scenario Date of

Initial
App. App. Rate in

lbs a.i./A
(kg a.i./ha) App.

per

Year App.

Interval

(days) CAM

Input IPSCND

Input Application
Efficiency/
Spray Drift

Pome fruits NC apple Aug. 1

0.25 (0.28) 2 7 2 3 0.95/0.16 PA apple Sep. 1

OR apple Oct. 1

CA fruit May 15

Stone fruits MI cherry Jul. 1 0.25 (0.28)

, 0.13 (0.14) A 2 7 2 3 0.95/0.16 GA peach May 15

CA fruit May 15

Peppers FL pepper Oct. 15 0.094 (0.11 ) 3 7 2 1 0.95/0.16

Cotton MS cotton Sep. 1

0.088 (0.099 ) 3 7 2 1 0.95/0.16 NC cotton Sep. 15

CA cotton Oct. 1

A A second application of 0.13 lbs a.i./A was modeled to reach the labeled seasonal maximum application rate.



### Three PE chemical inputs were updated to represent thiacloprid alone rather than the

residues of concern defined in the previous assessment (tabulated in bold). The aerobic s oil
metabolism and aerobic aquatic metabolism half

- life input values were substantially reduced :

Table 5

. PE Chemical Input Parameters for Thiacloprid.

Input Parameter Value Justification Source

Molecular Mass (g/mol) 252.73 Product chemistry data (Calculated)

Henry’s Law Constant

(atm m 3 /mol) 4.7 x 10

- 15 Ratio of vapor pressure to water
solubility (Calculated from

MRID 44927602)

Solubility in Water
(mg/L) 185 Study value for thiacloprid MRID 44927602

### Page 4 of 6 Input Parameter Value Justification Source

Organic Carbon Partition
Coefficient (K OC )
(L/kg OC ) 572 Mean value for thiacloprid MRID 44927905

Aerobic Soil Metabolism

Half

- life (days) 5.5 (was 144) 90 th percentile confidence bound on the

mean half

- life of thiacloprid in four soils MRID 44927916

Aerobic Aquatic

Metabolism Half

- life
(days) 28 (was 139) 90 th percentile confidence bound on the

mean half

- life of thiacloprid in two sediment systems MRID 44927920

Anaerobic Aquatic

Metabolism Half

- life
(days) 945 (was

stable) 90 th percentile confidence bound on the

mean half

- life of thiacloprid in three
sediment systems MRID 44927935

Hydrolysis Half

- life at pH
7 (days) Stable Study value for thiacloprid MRID 44927917

Aqueous Photolysis

Half

- life (days) 381 Study value for thiacloprid MRID 44927918;

45159309



### Updated thiacloprid surface water exposure estimates per use are listed in Table 6

. Exposure estimates were adjusted by the default national perc ent cropped area (PCA) value

(91 %) that accounts for the maximum area within any watershed that may be in agriculture

( USEPA

, 201 2 )

. Multiple P R ZM scenarios are listed for use on cotton because a single scenario

did not produce maximum values for all three exposure durations. Input and output files are

attached in Appendix B

.

Table 6

. EDWCs in Surface Water from Proposed and Current Uses of Thiacloprid

. A

Use PRZM Scenario 1

- in

- 10

- year Peak Exposure (μg/L ) 1

- in

- 10

- year Annual
Mean Exposure ( μg/L ) 30

- year Mean
Exposure ( μg/L )

Proposed Uses

Stone fruits MI cherry 4.0 0.88 0.59

Peppers FL pepper 8.2 0.62 0.37

Current Uses

Cotton MS cotton/ NC cotton 9.0 0.93 0.51

Pome fruits NC apple 18 2.3 1.2

A M aximum values are in bold

.



### References

USEPA. 2010. Orrick, G. Thiacloprid: Drinking Water Exposure Assessment for Section 3 New

Uses on Stone Fruits and Peppers. DP barcode 376181. U.S. Environmental Protection
Agency, Office of Chemical Safety and Pollution Prevention. Memorandum from the

Environmental Fate and Effects Division to the Health Effects Division and the
Registration Division. Oct. 18, 2010.

### Page 5 of 6 USEPA. 2012. Guidance on Developm ent and Use of Percent Cropped Area and Percent Turf
Area Adjustment Factors in Drinking Water Exposure Assessments: 2012 Update.

Internal Environmental Fate and Effects Division memorandum. U.S. Environmental
Protection Agency, Office of Chemical Safety a nd Pollution Prevention. Mar. 16, 2012.

MRID 48658203. Arthur, E., D. Dyer, R. Heintzelman, and G. Sabbagh. Bayer CropScience
Refinement of the EPA Cancer Assessment for Thiacloprid. Bayer report number
US0250. Position paper prepared and submitted by Bay er CropScience, Research
Triangle Park, NC. Nov 14, 2011. 11 p.

Appendix A . SCI

- GROW Input/Output Data.

SCI

- GROW Input/Output File.

SciGrow version 2.3
chemical:Thiacloprid

time is 10/ 7/2010 15:19:49

--------------------------------------------- --------------------------- Application Number of Total Use Koc Soil Aerobic
rate (lb/acre) applications (lb/acre/yr) (ml/g) metabolism (days)

------------------------------------------------------------------------ 0.2 50 2.0 0.500 1.66E+02 69.0

------------------------------------------------------------------------ groundwater screening cond (ppb) = 2.54E

- 01

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

Appendix B . PE Input /Output Files.

Example Input File (Use on Pome Fruits)

Output File: Thia_pome_NC_p

Metfile: w03812.dvf

PRZM scenario: NCappleSTD.txt

EXAMS environment file: ir298.exv

Chemical Name: Thiacloprid
Description Variable Name Value Units Comments Molecular weight mwt 252.73 g/mol
Henry's Law Const. henry 4.7e

- 15 atm

- m^3/mol

Vapor Pressure vapr torr Solubility sol 185 mg/L

Kd Kd mg/L

Koc Koc 572 mg/L

### Page 6 of 6 Photolysis half

- life kdp 381 days Half

- life
Aerobic Aquatic Metabolism kbacw 28 days Halfife
Anaerobic Aquatic Metabolism kbacs 945 days Halfife

Aerobic Soil Metabolism asm 5.5 days Halfife
Hydrolysis: pH 7 0 days Half

- life

Method: CAM 2 integer See PRZM manual
Incorporation Depth: DEPI cm Application Rate: TAPP 0.28 kg/ha
Application Efficiency: APPEFF 0.95 fraction Spray Drift DRFT 0.16 fraction of application rate applied to pond
Application Date Date 01

- 08 dd/mm or dd/mmm or dd

- mm or dd

- mmm

I nterval 1 interval 7 days Set to 0 or delete line for single app.
app. rate 1 apprate kg/ha

Record 17: FILTRA

IPSCND 3

UPTKF

Record 18: PLVKRT

PLDKRT

FEXTRC 0.5
Flag for Index Res. Run IR Reservoir
Flag for runoff calc. RUNOFF total none, monthly or total(average of entire run)