### Page 1 of 6 U. S. ENVIRONMENTAL PROTECTION AGENCY

Washington, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION



### PC Code: 112602

Parent DP Barcode: 377936

Sub DP Barcode: 395601

MEMORANDUM October 28, 2011

SUBJECT: Tier II Drinking Water Assessment for Trinexapac

- Ethyl use on Turf

TO: Bethany Benbow, Risk Manager Reviewer, RAB2

Kathryn Montague

, Risk Manager, RAB2 Registration Division (7505P)

Felicia Fort, Branch Chief

, Risk Assessment Branch 6 Sheila Piper , C hemist Health Effects Division (7509P)

FROM: Christopher M. Koper, Chemist

Environmental Fate and Effects Division (7507P)

THROUGH: Nancy Andrews

, Branch Chi ef

Sujatha Sankula, Lead Biologist

Environmental Fate and Effec ts Division (7507P)

### Page 2 of 6

EXECU TIVE SUMMARY

This drinking water assessment is an addendum to the previous assessment performed on cereals and sugarcane dated 09 August 2011 (D377936). This assessment includes trinexapac

- ethyl’s

use on turf which was previously registered but a drinkin g water assessment was not performed

since the act ion was a non

- agricultural use . Modeled application rates represent the maximum application rates from the label (Primo® WSB; EPA Reg. No. 100

- 752). The maximum application rate is 2.7 lbs. a.i./acre (8 a pplications at 0.34 lbs. a.i./acre).

The recommended estimated drinking water concentrations (EDWCs) for the human health risk

assessment are based on highest predicted value for surface water and groundwater ( Table 1 ).

The recommended EDWCs in surface water and ground water are based on 8 applications of 0.34 lbs. a.i./acre/year on Pennsylvania turf. Input parameters for the PRZM/EXAMS and SCI

GROW models are listed in Table 2 and Table 3

. Representative PRZM/EXAMS and SCI

GROW model output s with inp ut parameter data are attached in Appendix I

.

For surface water, a foliar ground application to Pennsylvania turf yielded the highest EDWCs.

The 1

- in

- 10 yr annual peak (acute) concentration was 12.61 μg/L, the 1

- in

- 10 yr annual mean
(chronic) concentrati on was 1.56 μg/L and the 30

- year annual mean (cancer chronic)

concentration was 1.04 μg/L. For groundwater, based on the proposed highest annual use rate

for turf , the SCI

- GROW model estimated the trinexa pac ethyl concentration at 0.009 μg/L.

These val ues supersede the previous EDWCs reported for Louisiana sugarcane (D377936). To
summarize, Table 1 compares the recommended EDWCs in bold font to the previously reported

values in italicized font. If additional refinements are necessary, please contact C hris Koper at

703.347.8065 or koper.christopher@epa.gov

.

Table 1. Trinexapac

- Ethyl Estimated Drinking Water Concentrations (EDWC s) 1 

### for

Surface Water and Ground Water based on selected Crop Scenarios

Prop osed

Label Use PRZM/EXAMS

Scenario 1

(first app date) Method 2 Maximum Application Rate (interval between applications) 1

- in

- 10

year

acute

( 

### μg/L ) 1

- in

- 10

year chronic

( 

### μg/L ) 30

- year

average ( 

### μg/L )

Primo ® WSB

Surface Water

Turf FL Turf

( Feb 15

– foliar ) G 8 app @ 0.34 lb a.i./acre 10.16 1.22 0.84

PA Turf ( April 15

– foliar) G 8 app @ 0.34 lb a.i./acre 12.61 (10.92) 1.56

(0.98) 1.04

(0.59)

Ground Water

SCI

GROW Turf

-- 8 app @ 0.34 lb a.i./acre 0.009 (0.001) 0.009

(0.001) 0.009

(0.001)

1 For surfa ce water (PRZM/EXAMS), EDWC values adjusted with a Percent C ropped Area (PCA) factor of 1.0

. For ground water (SCI

- GROW), no PCA adjustment was utilized.

2 G = ground application

. Bold numbers denote maximum EDWC values. Italicized numbers denote maxi mum EDWC values from previous drinking water assessment (D377936).

### Page 3 of 6 Table 2. PRZM/EXAMS Input P arameters for Trinexapac

- Ethyl

Input Parameter : Value : Comment: Source :

Scenario (s): FL Turf

PA Turf representative scenarios for turf

use N A

Maximum S ingle Application Rate

lbs a.i./acre (kg a.i./ha) 0.338 (0.380) maximum single application

rate for residential and

commercial uses 1 P rimo ® WSB label EPA Reg. No. 100

- 752

Applications per Year 8 derived by dividing the maximum yearly application

r ate by the maximum single application rate P rimo ® WSB label EPA Reg. No. 100

- 752

Application Interval (d ays ) 7 Interval was arbitrarily selected to represent actively growing

turf as written on the label P rimo ® WSB label EPA Reg. No. 100

- 752

Date of In itial Application (scenario: day

- month) FL Turf: 15

- 02

PA Turf: 15

- 04 Date of initial application was

based on the maturation date from crop scenarios Crop Scenarios

Application Method Foliar: ground (boom sprayer) l abel directions P rimo ® WSB label

EPA Reg. No. 100

- 752

CAM Input 2 linear foliar based on crop

canopy US EPA, 2005

IPSCND Input 2 remaining pesticide on foliage is completely removed after

harvest US EPA, 2005

Spray Drift Fraction 0.064 (ground) drift fraction for ground boom Input pa rameter guidance (USEPA, 2009 )

Application Efficiency 0.99 (ground)

-- Input parameter guidance (USEPA, 2009 )

Molecular Mass (g/mol) 252.3

-- MRID 41604201

Vapor Pressure at 25°C (torr) 1.62 x 10
- 5

-- MRID 41604203

Henry’s Law Constant
(atm

- m 3 /mol) 5.27 x 10
- 10

-- Calculated from water solubility, vapor pressure and molecular weight

Solubility in Water (mg/L) 10200 at pH 5.5 MRID 41604203

Organic Carbon Partition Coefficient (K OC ) (L/kg OC ) 416 2 r epresents the average K OC from 4 values for the a cid
(CGA

- 163935) MRID 41663937

Aerobic Soil Metabolism

Half

- life (days) 5.2 3 r epresents the 90 th percentile

confidence bound on the mean

half

- life of 3 values MRID 46809303 Appendix II B

Aerobic Aquatic

Metabolism Half

- life (days) 17.4 4 r epresents the 90 th percentile

confidence bound on the mean

half

- life of 2 values MRID 46809304 Appendix II C

Anaerobic Aquatic

Metabolism Half

- life (days) 533 5 r epresents the 90 th percentile

confidence bound on the mean

half

- life of 2 values MRID 48043712 Appendix II D

Hydrolysis Half

- lives (days) 0 (stable) pH 7 MRID 41563930

MRID 46809301

### Page 4 of 6 Table 2. PRZM/EXAMS Input P arameters for Trinexapac

- Ethyl

Input Parameter : Value : Comment: Source :

Aqueous Photolysis

Half

- life (days) 22.8 6 recalculated environmental phototransformation half

- life MRID 46809302 Appendix II A

NA = Not Applicable

1

= The maximum single app lication rate for residential and commercial uses. The edging/banding rate was higher but not utilized because this application is more specialized and does not truly represent turf as the residential and commercial uses.

2

= The average K

oc obtained fro m four values (144, 328, 581 and 609) for the acid (CGA

- 163935)

. This value was modeled because of conversion of

the ester to the acid in the environment.

3

= Following the Total Toxic Residue (TTR) approach, this value represents the 90 th percentile confidence bound on the mean half

- life of 3 values (3.0, 3.6 and 5.2). See Appendix II B

4

= Following the Total Toxic Residue (TTR) approach, this value represents the 90 th percentile confidence bound on the mean half

- life of 2 values (12.3 and 14.8). See Appendix II C

5

= Following the Total Toxic Residue (TTR) approach, this value represents the 90 th percentile confidence bound on the mean half

- life of 2 values (290 and 56). See Appendix II D

6

= Following the Total Toxic Residue (TTR) approach, th is value represents the recalculated environmental phototransformation half

- life. See Appendix II A



### Table 3. SCI

- GROW Input P arameters for Trinexapac Ethyl.

Input Parameter Value Comment Source

Maximum Single Application Rate per growing season (lb s a.i./A) 0.34 maximum single application rate from proposed label P rimo ® WSB label EPA Reg. No. 100

- 752

Applications per Year 8 l abel directions

Organic Carbon Partition Coefficient (K OC ) (L/kg OC ) 144 lowest K OC value of the acid data set because

there was greater than a three

- fold variation among four values MRID 41663937

Aerobic Soil Metabolism

Half

- life (days) 3.9 1 mean half life because there is less than 4 values as directed by SCI

- GROW guidance
(US EPA, 2009) MRID 46809303

1

= Following the To tal Toxic Residue (TTR) approach, this value represents the mean half

- life of 3 values (3.0, 3.6 and 5.2).



### Appendix I :

Model Outputs: PRZM/EXAMS and SCI

- GROW

### Page 5 of 6

Representat ive PRZM/EXAM Output: Pennsylvania Turf

– Ground Application

### Page 6 of 6

SC I

- GROW Output : Turf

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:Trinexapac Ethyl

time is 10/27/2011 15:46:12

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

---------------- -------------------------------------------------------- 0.340 8.0 2.720 1.44E+02 3.9

------------------------------------------------------------------------ groundwater screening cond (ppb) = 8.82E

- 03 or 0.009