### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION 

### PC Code: 1 28847 DP Barcode: 390040 

### MEMORANDUM **DATE:** June 2 3 , 2011 **SUBJECT:** The Drinking Water Degradate s Id entification Memorandum for

Difeno conazole **FROM:** Faruque Khan , Ph.D., Senior Scientist

Environmental Risk Branch I Environmental Fate and Effects Division (7507P) **TO:** Christine Olinger , Co - chair

Edward Scollon , Co - chair Residues of Concern Knowledgebase Subcommittee **THRU:** Katrina White , Ph.D., EFED ROCKS Representative

William Shaughness y . , Ph.D, , EFED ROCKS Representative Residues of Concern Knowledgebase Subcommittee Nancy Andrews, Ph.D., Branch Chief Sujatha Sankula, Ph.D., Lead Biologist Environmental Risk Branch I Environmental Fate and Effects Division This memorandum identifies the environmental d egradates of difeno conazole . These data are pro vided to help determine which environmental degradates are of risk concern for conducting a drinking water assessment to support a human health risk assessment. If yo u have questions concerning this memorandum, please contact Faruque Khan at 703 - 3 05 - 6127 . Difenoconazole is a fungicide in the conazole chemical class. Fungicidal activity of the conazole class of compounds is attributed to the inhibition of ergosterol biosy nthesis. There are several active registrations for formulations of difenoconazole (including mixtures) and one for the technical grade product. Based on the field and laboratory studies, the active ingredient difenoconazole is persistent in soil and slightly mobile. Difenoconazole is likel y to reach surface water sources of drinking water via spray drift and runoff

. Detailed description of fate and transport properties of di feno conazole can be obtained from previous section 3 assessment (U.S. EPA, 20 10 ; D 37 8927+).

### 2

**Mobility , Volatility, and Propensity to Move into Surface and**  **Ground Water** Based on a low vapor pressure of 2.5 x 10 - 10 

### mm Hg and a Henry ’s Law constant of 8.9 x 10 - 12 

### atm - m3 

### /mol , difenoconazole has a low propensity to volatilize from application site and surface water . It has a low solubility (15 mg/L) in water . Difenoconazole appears to be slightly

mobile to hardly

mobile in the soil; its Koc 

### values range from 3 , 471 - 11 , 202 L/kg. Difenoconazole has potential to reach surface water via run - off, erosion, and spray drift, and is less likely

to reach ground water except in soils of high sand and low organic matter content. **Degradation** Environmental fate data indicate that difenoconazole is relativel y stable to aerobic and anaerobic soil metabolism s and aerobic and anaerobic aquatic metabolism . When applied at 0. 1 - 0.23 ppm to an aerobic soil, difenoconazole appears to degrade with half - lives ranging from 84.5 to 533 days based on laboratory studies conducted on a variety of foreign and domestic soils . At concentrations of 10 ppm , difenoconazole degraded with the half - lives of 1059 - 1600 days in aerobic, and 947 days anaerobic loam soil , respectivel y. In aquatic environment under aerobic conditions, difenoconazole microbially

degraded with half

- lives ranging from 315 to 565 days at concentrations up to 0.17 mg ai/L, and 860 days in a concentration of 10 mg ai/L. Under anaerobic conditions, difenoconazole degraded in 370 days at a concentration of 0.04 mg ai/L, and 1245 days at concentrations of 10 mg ai/L. The longer half - life values obtained for those higher co ncentration rates may imply that the rate of difenoconazole microbially mediated degradation may be concentration dependent. Inlaboratory studies on difenoconazole a significant amount of radioactivity was nonextractable (14.4 to 48.9%) from soils . Con sidering abiotic degradation, difenoconazole is photoly zed in water (half

- life of 6 to 228 days), but stable in soil. The half - life of 228 days was extrapolated from a 15 - day study in which difenoconazole slowly photolyzed from 100% to 91% under artificial light conditions (MRID 46950105). Also, the compound is stable to hydrol ys is at pH values from 4 to 9. Difenoconazole degraded with half - lives ranging from 139 to 462 days in the terrestrial field dissipation studies. The overall stability of the comp ound in the terrestrial environment suggests that difenoconazole may accumulate in soil with successive application s from year to year. **Bioaccumulation** The octanol water partition coefficient, log Kow of 4.4 , suggest s that defienoconazole has a potential to bioaccumulate. Difenoconazole accumulated rapidly in edible and non edible bluegill sunfish tissues with bioconcentration factors of 170x for edible tissues, 570x for non - edible tissues, and 330x for whole body . Depuration was also ra pid with a

### 3

depuration half

- life of approximately

1 day and 96 - 98% clearance after 14 days of depuration. From both edible and non - edible tissues, one metabolite was recovered, CGA - 205375, and accounted for 51 - 64% of the applied. **Possible Degradates of**  **T oxic and**  **Exposure Concern** Difenoconazole may break down to CGA205375 , (1 - [2 - Chloro - 4 - (4 - chlorophenoxy) - phenyl] - 2 - [1,2,4]triazol - 1 - yl - ethanol), next to triazolyl acetic acid and further to tri azole methanol and triazole. 1,2,4 - triazole and its conjugates (triazole alanine and triazole acetic acid) are common metabolites to the class of compounds known as the triaz ole derivative fungicides ( T - D fungicides, conazoles). A separate drinking water assessment was conducted on 1,2,4 - tri azole degradates ( (U.S. EP A, 20 06 ; D D320682 ) . The majority of the major degradates formed under both abiotic and biotic processes . A summary

of ecotoxicity

data for degradates has been submitted (MRID 453427 - 01) from several submitted studies including data in birds (45284015), earthworms (MRID 45297201), daphnids (MRID 00133381), fish (MRID 45284017), and algae (MRID 00133382). The data suggest that 1,2,4 - triazole may be less toxic than difenoconazole to fish, daphnids, and aquatic plants, but more toxic to earthworms. No toxicity data are available on the other major degradates of difenocozole at this time. Residues of possible exposure concern for drinking w ater include the parent and its degradates. The submitted environmental fate data for difenconazole and its degradates are summarized in **Table 1**  .

### Table **1. Difenconazole**  **and Its Major and Minor**  **Environmental Degradates. Code Nam**  **e/ Synonym**  **Chemical Name Chemical Structure**  **Study Type MRID**  **Maximum %AR (day)**  **Final %AR (study**

**length) PARENT**  **Difenconazole CGA** **- 169374**  **IUPAC Name:** 3 - Chloro - 4 -

[(2RS,4RS ;2RS,4SR) - 4 - methyl - 2 - (1H - 1,2,4 - triazol - 1 - ylmethyl) - 1,3 - dioxolan - 2 - yl]phenyl 4 - chlorophenyl ether. **CAS Name:** 1 - [2 - [2 - Chloro - 4 - (4 - chlorophenoxy)phenyl] - 4 - methyl - 1,3 - dioxolan - 2 - ylmethyl] - 1H - 1,2,4 - triazole. **CAS Number:** 119446 - 68 - 3 **Form ula:**  C 19 H 17 C l2N 3 O 3 **MW:** 406.3 **SMILES:** O1CC(C)OC1(Cn2ncnc2)c3c( Cl)cc(Oc4ccc(Cl)cc4)cc3 Hydrolysis pH 5 42245127 --- 1 Hydrolysis pH 7 --- Hydrolysis pH 9 --- Aqueous Photolysis 42245128 2.50 (30 days) 46950104 1.21±0.5 (30 days) 46950105 94.1 (15 days) Soil Photolysis 46950106 - 46950107 91.4 (30 days) Aerobic Soil Metabolism 4695109 18.4 ±0.1 (293 days) 46950110 13.6 (293 days) 46950111 51.0 (228 days) 46950112 - 46950113 54.2 ± 4.8 (360 days) 46950114 46950115 58.8 ± 1 .1 ( 372 days) Aerobic Aquatic Metabolism 46950116 71.2 (183 days) 46950117 - 46950118 81.53±3.22 (112 days) Anaerobic Aquatic Metabolism 46950119 - 46950120 42.72  0.88 (350 days) Terrestrial Field Dissipation 4695012 6 44 ppb (531 days) 46950127 14 ppb (535 days) 46950129 302 ppb (422 days) **MAJOR (>10%) TRANSFORMATION PRODUCTS CGA** **- 179500**  **[CGA 205375, IUPAC Name:**  4 - [ Not

reported **CAS Name:** alpha - [2 - Chloro Aqueous Photolysis 42245128 2.9 (5 days) 0.1 (30 days) 46950104 2.04 (14 days) 0.96 (30 days) 46950105 NA NA

### 5 **Code Nam e/**  **Synonym Chemical Name**  **Chemical Structure Study Type**  **MRID Maximum**  **%AR (day) Final %AR (study** 

**length) CGA 211391 and**  **M1]** 4 - (4 - chlorophenoxy)phenyl] -

1H - 1,2,4 - triazole - 1 - ethanol. 1 - [2 - Chloro - 4 - (4 - chlorophenoxy)phenyl] - 2 - [1,2,4] - triazol - 1 - yl - ethanol. **CAS Number:** 117018 - 19 - 6 Aerobic Soil metabolism 46950109 5.1± 1.4 (84days) 3.7± 0.1

(293 days) 46950110 4.6± 0.1

(56days) 2 .7± 0.5

(293 days) 46950111 9 .4± 05

(120days) 9.0 (2 28 days) 46950112 - 46950113 14.8±1.8

(360days) 14.8± 1.8

(360 days) 4695114 - 4695115 9.4± 0.1

(372 day) 9.4± 0.1

(372 day) Aerobic Aquatic Metabolism 46950116 11.4 (183 days) 11.4 (183 days) Anaerobic Aquatic Metabolism 46950119 - 46950120 12.60± 0.42

(175days) 6.2 ± 0.76

(350 days) Terrestrial Field Dissipation 46950126 11 ppb (358 days) 6.2ppb (531days) 46950127 12 ppb (123

days) 5.6 ppb (531days) 46950129 18ppb (364

days) 12.0 2ppb

(535days) N N N Cl O Cl O H**Code Nam e/**  **Synonym Chemical Name**  **Chemical Structure** CGA - 71019 **IUPAC Name:** 4 - [ Not

reported **CAS Name:** 1H - 1,2,4 - Triazole **CAS Number:** 288 - 88 - 0

CGA - 142856 **IUPAC Name:** 4 - [ Not

reported **CAS Name:** 1H - 1,2,4 - Triazole - 1 - acetic acid **CAS Number:** 28711 - 29 - 7 CGA - 107069 **IUPAC Name:** 4 - [ Not

reported **CAS Name:** 1H - 1,2,4 - Triazole - 1 - methanol **CAS Number:** 74205 - 82 - 6 **Carbon Dioxide**  **CAS Number** : 124 - 38 - 9

**Form ula:**  CO 2 **MW:** 44.1 g/mol O H



### 6 **Chemical Structure Study Type**  **MRID** Aqueous Photolysis 42245128 46950104 46950105 Aerobic Soil Metabolism 4695110 4695111 4695114 - 4695115 Anaerobic Aquatic Metabolism 46950119 - 46950120 Terrestrial Field Dissipation 46950129 Aqueous Photolysis 46950104 Terrestrial Field Dissipation 46950126 Aqueous Photolysis 46950104

Aqueous Photolysis 46950104 46950105 O H O N N N

C H 2 N N N O 

## C O O **Maximum %AR (day)**  **Final %AR (study**

**length)** 13.4 (9 days) 10.9 (30 days) 12.27 ± 0.7 (30days) 12.27 ± 0.7

(30 days) NA2 NA 20.6 (190 day) 17.8± 2.8

(293 day) 1.6±0.4 (120 day) 0.9

(228day) 7.8± 0.1 (372 day) 7.8± 0.1

(372 day) 25.62± 0.35 (350 day) 25.62± 0.35

(350 day) 3.5 ppb (36 days) < LOQ (535days) 41.83 ±0.9 (30days) 41.83±0.9

(30 days) <LOQ 3 11 ppb

(358 days) Reported as combined residue with CGA 71019

2.01 (30 day) 2.01± 2.5(30 days) 0.01 (3days) <0.1 (15 days)

### 7 **Code Nam e/**  **Synonym Chemical Name**  **Chemical Structure Study Type**  **MRID Maximum**  **%AR (day) Final %AR (study** 

**length)** Soil Photolysis 46950106 46950107 0.02 ( 30 days) 0.2 (30 days) Aerobic Soil Metabolism 46950109 23.4 ± 1.9 (293 days) 23.4 ± 1.9

(293 days) 46950110 4.5 ± 2.4

(293 days) 4.5 ± 2.4

(293 days) 46950111 19.2

(228 days) 19.2

(228 days) 46950112 46950113 15.0 ± 1.3

(360 days) 15.0 ± 1.3

(360 days) 46950114 46950115 4.2 ± 0.1

(372 days) 4.2 ± 0.1

(372 days) Aerobic Aquatic Metabolism 46950116 3. 9 (183 days) 3. 9 (183 days) 46950117 46950118 0.59 ± 0.28

(98 days) 0.29 ± 0.03

(112 days) Anaerobic Aquatic Metabolism 46950119 - 46950120 0.55± 0.33

(245days) 0.25 ± 0.02

(350 days) **Non -**  **extractable Residues**  Soil Photolysis 46950106/ 46950107 0.55± 0.33

(245days) 0.25 ± 0.02

(350 days) Aerobic Soil Metabolism 4695109 38.0 ± 1.3 ( 293 days) 38.0 ± 1.3

( 293 days) 46950110 48.9 ±0.6

(293 days) 48.9 ±0.6

(293 days) 46950111 22.9

(228 days) 22.9

(228 days) 46950112 46950113 14.4 ±1.0

(360 days) 14.4 ±1.0

(360 days) 46950114 46950115 18.4 ±1.0

(3 72 days) 18.4 ±1.0

(3 72 days) Aerobic Aquatic Metabolism 46950116 8.7 (183 days) 8.7 (183 days) 46950117 46950118 8.87 ± 3.04

(112 days) 8.87 ± 3.04

(112 days)

### 8 **Code Nam e/**  **Synonym Chemical Name**  **Chemical Structure Study Type**  **MRID Maximum**  **%AR (day) Final %AR (study** 

**length)** Anaerobic Aquatic Metabolism 46950119 - 46950120 8.06± 1.24

(302days) 7.11 ± 0.32

(350 days) **Unidentified Unknowns**  **4** Aqueous Photolysis 42245128 20.0 (15days) 6.5 (30 days) 46950104 29.02 ± 2.9

(30days) 29.02 ± 2.9

(30days) 46950105 16.7(15 days) 11.1 (15 days) Aerobic Soil Metabolism 4695111 0.4 (228 days) 0.4

(228 days) Aerobic Aquatic Metabolism 46950116 5.5 (127days) 5.7

(183day) 46950117 - 46950118 5.56± 0.03

(98days) 4.26± 1.34

(112days) 46950119 - 46950120 0.77± 0.23

(245 day) <LOQ (350 days) Anaerobic Aquatic Metabolism 46950119 - 46950120 5.69± 0.57

(302 day) 5.21± 0.98

(350 day) **MINOR (<10%) TRANSFORMATION PRODUCTS CGA** **- 205374**  **[CGA176459] IUPAC Name**  : 2 - (4 -

Cyclopropyl - 2,4 - dioxo -butyl) - succinic acid **CAS Name:** 1 - [2 - Chloro - 4 - (4 - chlorophenoxy)phenyl] - 2 - (1H - 1,2,4 - triazol - 1 - yl) - ethanone. **CAS Number:** 136815 - 80 - 0 Aqueous Photolysis 42245128 1.5 (0 day) < LOQ (30 days) 46950104 1.11± 0.11

(14 days) 0.13 ± 0.1

(30 days) 46950105 NA NA Aerobic Soil Metabolism 46950114 - 46950115 2.1 ± 0.4

(272days) 1.4 ± 0.1

(293 days) Anaerobic Aquatic Metabolism 46950119 - 46950120 0.77± 0.23

(245 day) <LOQ (350 days) **M2** Aerobic Soil Metabolism 46950109 1.5 (28days) 1.4 ± 0.1

(293 days) O N N N Cl O Cl

### 9 **Code Nam e/**  **Synonym Chemical Name**  **Chemical Structure Study Type**  **MRID Maximum**  **%AR (day) Final %AR (study** 

**length)** 46950110 2.1± 1.81

(293days) 2.1± 1.81

(293days) 46950111 1.5

(228days) 1.5

(228days) Anaerobic Aquatic Metabolism 46950119 - 46950120 5.79± 1.42

(245 days) < LOQ (350 days) **M4** Aerobic Soil Metabolism 46950109 1.2 (190days) 1.0 ± 0.4

(293 days) 1 = Stable 2 = Not Analyzed 3 = Limit of Quantitation 4 Unidentified unknowns may consists of M4, M5, M6, M7 and several other unidentified components with no zone exceeding 5.68% of applied radioactivity . 

### Reference **s :**  US EPA, 20 11 . Ecological Risk Assessment for the Proposed New Uses of Difenoconazole as a Foliar Spray for Carrot, Chickpea, Soy

bean, Stone Fruit (Group 12), and Strawberry and as a Seed Treatment for Oat and Rye

. February

22 , 20 11 . ( 37 8927+) US EPA, 2006. 1,2,4 - Triazole, Triazole Alanine, Triazole Acetic Acid: Drinking Water Assessment in Support of Reregistration and Registration Actions for Triazole - derivative Fungicide Compounds. February 28, 2006. (D320682)