UNITED STATES ENV IRONMENTAL PR OTECTION AGENCY WAS HINGTON D. C. , 20460

O FFI O : OF**I~ £1\I** **CAL** SAFETY Al\0 POLLl i T I O;\ PREVE' li ON
PC Code : 128810 DP Barcodes: 422726 MEMORANDUM September 1 1 , 20 14
SUBJECT:
TO:

FROM:

THRU: Drinking Water Exposure Assessment for new use of Azoxystrobin on Ornamental Plants and Vegetable Transplants. Christine Olinger, Branch C hief Kristin Rury , Risk Assessor Risk Assessment Branch III Health Effects Di vis ion (7509P) Ibrahim Abdel-Saheb, Ph.D, Environmental

# Scientist**~~** Cf
- \l

- \ '-\ Environmental Risk Branch VI Environmenta l Fate and Effects Di vis ion (7507P )
Mark Corbin , Branch Chief William P. Eckel , Ph.D. , Senior Science Advisor Env ironmental Risk Branch VI Env ironmental Fate and Effects Di vision (7507P) Office of Pesticide Pro grams Office of Chemical Safety & Pollution Prevention
The Enviro nmental Fate and Effec ts Division (EFED) estima tes drinking water concentrations of a chemical based on the highest rate of application of the chemica l on a ll registered and propo sed use sites. The proposed new product that contains azoxystrobin and difenoconazo le (100-RLNA Alibi Flora) is proposed to control fungal diseases on ornamental plants and vegetable transplants grown in both indoor and outdoor production facilities (the vegetable transplants grown for retail sale to residential consumers only). The proposed maximum single application rate is 0.55 lb a.i./A , with a maximum annual application rate of0.80 lb a.i./A , and an application interval of7-21 days. In the case of azoxyst robin, turf , a previously registered use, has the highest application rate of all currently registered use sites: 0.55 lb a.i./ A with up to 9 applications per year and a 1 0-day interval between app lications. (D 278783 , D279444 , and D279561 ; Feb. 4 , 2002). The model Page 1 of6FIRST was used in th e 2002 drinking water assessment (DWA) cite d above and resulted i n estimated drinking wate r concentrations (EOWCs) fo r peak (ac ute) of 173 pp b , and for annual m ean (chronic) of 0.33 ppb. For groundwater, the mod e l SCI-GROW gave EDWC s for

- acute and chronic of 3. 1 pp b
. Since 2002, EFED has introduced new surface water and gro und water models (i.e Surfac e Wat e r Concentration Calc ul ator (SWCC), and PRZM-GW, respectively]. A comparison was made betwee n output from curre nt EFED mod e ls f or azoxy s trobin for the proposed u se on ornamental s and vegetable tra nsplants with the output from the currently registered use on turf (0.55 lb ai/A, 9x, 10 d). Results are shown in Table 1 (see model input and output in Appendix I). Th e resulting surface w ater EDWCs for ornamental plants and vegetab le transplant s are 24.8 ppb for peak , 7.30 ppb for chroni c, and 4.04 ppb for cancer whil e the maximum s urface water EDW Cs for turf are 70.2 ppb for peak, 48.5 ppb for c hronic , and 38 .5 ppb fo r cancer; a nd groundwater of 3.1 pp b (Acute and c hro nic)
. EDWCs calculated w ith PRZM-GW f o r o rnamental pl ants and vegetab le tran sp lants range from 0.008 ppb (peak) to 0 .001 ppb (post breakthrough average); and for turf ran ge from 0.044 ppb (peak) to 0.007 ppb (post breakthrough ave rage). Thu s , EFED re commends that the Health Effects Divi sio n use th e fo llowin g surface water and groundwater EDWCs resultin g from turf modeling. Please note that the surface water EDW Cs are reduced from th e previous 2 002 DW A due to the us e of th e tier 2 model , SWCC. The groun d water EDWC p resented be low is from the SC I-GROW model , since it p rovi des the more conservative estimate of exposure. 

### Surface water (turf, S WCC): Peak (acute)= Chronic= Cancer= 70.2 ppb, 48.5 ppb, and 38.5 ppb. G r oundwater (turf , S CI-GROW): Acute and chronic 

## = 3
. 1 ppb

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### Table 1. 

### Estimated Drinking Water Concentrations (EDWCs) for drinking water risk assessment use on Ornamental Plants and Vegetable Transplants and Turf. Surface Water (ppb) Groundwater (ppb) 2014 Modeling 2014 Modeling 2014

(SWCC) * (SWCC)* 2014 Modeling** Modeling** (0.55 l b a.i./A, 9x, 10 d) (Max single appl. 0.55 lb PRZM-GW PRZM-GW a. i./A on Orn ame ntal on Turf Max annual appl. 0.8 lb a.i./A on Turf P lants and @7 d) Vrge table Tran sp lant s on O rna mental Plants and

Vegetable Transplant s Peak-ppb 0.044 0.008 P

eak ( 1-in-1 0 yr) 24.8 A verage-ppb 0.007 0.001 70.2 Post breakthrough

Avg
. -ppb In complete In complete¥ Average Incomplete Incomplete 365-day Avg(l-in-10 48.5 7.30 Breakthrou gh yr) Time-day Throughputs 0.283 0.283 Entire Simulation Mean 38.5 4.04

*:For the SWCC mode l The following available NURSERY scenarios were used to repre sent ornamentals in nurseries: CA, FL
. MI, NJ, OR, a nd TN. The TN scenario gave th e highest EDWCs. The following ava ilable TURF scenarios were used: FL , and PA Th e PA sce nario gave the highest EDWCs. **: For the PRZM-GW m odel; th e following available scenarios were u sed to represent ornamentals and turf : FLpotato , GAcoastal , NCcoastal, and Wlsand
. Th e FL sce nario gave the highest EDWCs for both uses. ¥:The chemical did not reach groundwater even after running the model with an extended 100-year weather file



### Page 3 of6

# , Appendix I SWCCModel
Summary of Model Inputs for Azoxystrobin on Ornamental Plants and Vegetable Transplants. Scen ario TNnurserySTD
_ V2 Cropped Area Fraction 1.0 Koc (ml/g) 8.87 Water Half

- Li f e (days ) @ 25 ° C 322. 2 Benthic Half-Life (d a ys ) @ 25 ° C 0 Ph oto lysis Hal f-L ife (days) @ 40 23.23 0 Lat Hydrolysis Hal f-L ife (d ay s) 0 Soil Half-Life (days)@ 22 ° C 161. 2 Foliar Hal f -Lif e (days ) 35 Molecular Wt 403.3 Vapor Pressure (torr) 8.2E

- 13 Solubility (mg/1) 6.7

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## Models Output Ornamental Plants and Vegetable Transplants SWCC Model Estimated Drinking Water Concentrations (ppb) for azoxystrobin Output Scenario

(ppb) CA 

### FL MI 

### NJ OR TN
Peak ( 1-in-1 0 yr) 1 2. 9 17.4 12.2 17
. 5 19.9 24.8 4-day Avg (1-in-10 12. 9 16.9 12.0 17.1 19.6 24.1 yr) 21-day Av g (1-in-10 12.7 14.9 11.3 15.9 18.9 22.5 yr) 60-day A v g (1 -in-1 0 1 2. 2 12.5 10.3 14.5 17.3 20.0 yr) 365-day Avg ( 1-in- 8.63 3.72 5.67 7.85 10.1 

### 7
. 30 10 yr) Entire Simulation 6.14 2
. 13 4.25 4
. 8 3 6.70 4.04 Mean



### Turf SWCC Model Estimated Drinking Water Concentrations (ppb) for azoxystrobin Output Scenario

(ppb) 

### FL PA Peak (l-in-1 0 yr ) 51.2 70.2 4-day A v g ( 1-in-10 yr) 50.7 69.6 21-day Av g (1-in-10 yr) 49.6 68.6 60-day Avg (1-in-10 yr) 47
. 1 66.5 365-da y A vg ( 1-in-1 0 yr) 32.0 48.5 Entire S imulation Mea n 26.6 38
. 5

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# PRZM-GW Model

Ornamental Plants and Vegetable Transplants PRZM-GW Model Estimated Drinking Water Concentrations (ppb) for azoxystrobin
Scenario ID DELMARVA ST D.SCN FLCITR US_STD .SCN FLPOTATO_S TD.S CN GACOASTAL STD.SCN NCCOASTAL

- ST O.SCN WISANDS

_ STO.SCN Peak(p pb) 9.72E-08 0.00766 0.000818 2.48£-09 4 .98£- 10 1.93E- 16 PBT Avg(ppb) In comp l ete Incompl ete Inc om pl ete Incomplete Incompl ete Incomplete



### Turf SimAvg BT(d) Thr oug hputs 7.49E-09 In compl ete 0.1543425 0.00128 In complete 0.2835361 0.000146 In complete 0.3307775 1.97E-10 Incompl ete 0.1934483 4.06E-ll In co mp lete 0.1078497 1.08E-1 7 In co mplete 0.07385527 90-day Avg 9.15£-08 0.00765 0.000817 2.43E-09 4.9£-10 1.93E-16



### PRZM-GW Model Estimated Drinking Water Concentrations (ppb) for azoxystrobin Groundwater Results for Azoxystrobin and the Florida Citrus

- FL Central Ridge Scenario. Peak Concentration (ppb) Post-Breakthrough Mean Concentration (ppb) Entire Simu l ation Mean Concentration (ppb) Average Breakthrough Time (days) Throughputs 0.0441 Incomplete 0.00735 Incomplete 0
. 2835361

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