UNITED STATES ENVIRONMENTAL PROT ECTION AGENCY WASHINGTON D.C., 20460
PC Code: 125601 DP Barcode: D425024 Date: January 15, 2015 

### MEMORANDUM SUBJECT: TO:

FROM: Revised Chronic Mammalian Risk Conclusions for the Paclobutrazol Registration Review Ecological Risk Assessment Khue Nguyen , Chemical Review Manager Neil Anderson, Branch Chief Risk Management and Implementation Branch I Pesticide Re-Evaluation Division Office of Pesticide**Pro~rams** (7508P) Meghan Radtke, Ph.D. , Biologist

# Al**~** I II 

### TO 

### /IS 

## ct r Sujatha Sankula, Ph.D. , Branch Chief

## ~**~~}-..~~** \'- \to:> '., Environmental Risk Branch I ,......-r Environmental Fate and Effects Division (7507P) Office of Pesticide Programs As part of a general data review in support of Registration Review, the Health Effects Division recently revised the endpoints in the two generation rat study (MRID 40734303) that are used to characterize chronic risks for mammals. The ToxStat committee determined that the effects at 23.3 mg aifkg.:bw (increased incidenc¢ of chromodacryorrhea and thickened eye lid s observed in both generations) were generally within the provided historical control ranges, and, thus, not considered a treatment-related effect. Consequently, the NOAEC changed from 2.5 to 23.2 mg ai/kg-b w (250 mg ailkg-diet). In the original Registration Review risk assessment (USEPA 2013, D393895) , the Environmental Fate and Effects Division (EFED) identified potential chronic risk concerns for all uses of paclobutrazol, except the seed treatments. EFED has now re -evaluated chronic risk, based on the revised chronic rat endpoint. Using the new chronic endpoint, all risk quotients (RQs) were lowered, but all uses still exceeded the level of concern. However, chronic risk concerns for mammals were still identified for the following uses: • Turf (all size clas ses of mammals on several food items) • Potted ornamental spray (small and medium sized mammals on short grass) • Tree injection (hardwoods only, all size classes of mammals) • Soi l injection/drench (hardwoods and softwoods, all size classes of mammals)• Potted woody ornamental drench (hardwoods only, small sized mammals) 

### • Potted non-woody ornamental drench (small and m Jctium sized mammals) See Tables I and 2 for th. e RQs based on the new chronic Jarnmalia'n endpoint, which replace those in the original risk assessment. Appendix A contains risk quotient calculations for the drench and injection application methods. Table 1 T -REX upper bound chronic risk quotients for mammals for paclobutrazol turf 

# . and spray applications to potted ornamentals Chronic Dose-Based RQs Risk Quotients Chronic Based Dietaryon Kenaga 15 g 35 g 1000 g Based RQs Upper Bound EEC 

### Profile 2SC on Turf- 3 applications at 0. 75 lb ail A (28 day interval) 1 Short grass 6.41 *** 5.47*** 

## I 2.93*** 1.37*** Tall grass 2.94*** 2.51 *** 1.35*** 0 . 63 Broadleaf plants/small insects 3.61 *** 3.08*** 1.65*** 0 .77 Frui ts/pods/seeds/lg insects 0.40 0.34 0.18 0.09 Granivores 0.09 0.08 0.04 0.09 

### Bonzi II Spra_vfor Potted Ornamentals -1 application at 0 . 26 lb ai/A Short grass 1.17*** 1.00*** 0.53 0.25 Tall grass 0.53 0.46 

## I 0.24 0.11 Broadleaf plants/small insects 0.66 0.56 0.30 0.14 Fruits/pods/seeds/l g insects 0.07 0 .06 0.03 0.02 Granivores 0.02 0.01 0 .01 0 .02 1 3 applications at 0.75 lb ai/A exceeds the maximum seasonal rate of2lb ai/A by 0.25 lb ai/A. A T
- REX scenario was run wit}}. 3 applications at 0.66 lb ai/A. Jitisk quotients were -12% lower, but none of the exceeding risk quotients were reduced below the level of concern. Thus the higher application rate was us ed for this assessment to ensure that it was maximally protective. ***Exceeds the chronic LOC of 1

2Table 2. Chronic risk quotients for mammals for paclobutrazol tree injection, soil injection/drench, potted ornamentals drench, and seed treatment applications (see Appendix A for RQ calculations) Chronic Mammal Dose
- Based RQs 

# I 15 g 3Sg_ 1000 g 

### Tree injection at 0.36lh ai!A Hardwoods 3.9* ** 3.4*** 1.8*** S oftwo ods 0 . 1 8 0 .10 0.08 

### Soil injection/drench at J.9lh ai!A Hardwoods 20*** 17* * * 9*** S0ftwood s 9*** I 8*** 4*** 

### Woody potted ornamental drench at 6.1lh ai!A Hardwoods 1.2*** 0. 95 0.50 Softwoods 0.45 0.39 0.20 

### Non-woody potted ornamental drench at 6.1 lh ai!A Non-woody plants 2.1 *** 1.8*** 0.95 ***Exceed s chronic LOC of 1
References USEPA. 2013. Registration revi ew- ecolo g ica l risk assessment and effects determination of paclobutrazol. Environmenta l Fate and Eff ects Division , Offi ce of Pesticide Pro grams, United States Env ironmental Protection Agency.

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### Appendix A- Risk Quotient Calculations for Drenches and Injections The EECs reported in this appendix are taken from the paclobutrazol regi st ration review ri sk assessment (USEPA 2013, D393895). Please refer to that document for details on the EEC calculations. 

### Clipper 20 UL Ornamental Tree Injection - 1 application at 0.36 lb ail A Risk Quotient= EEC I Toxicological Value Mammals The following definiti ve data are available for mammals: NOEL = 23.2 mg/kg-bw Adjusted toxicity values were calculated for mammal size classes by T
- REX 15 g mammal NOEL = 50.99 mg/kg

-bw 35 g mammal NOEL = 41.26 mglkg

-bw 1000 g mammal NOEL = 17.84 mg/kg-bw Chronic Dose-Based Risk Quotients= EEC/NOEL Hardwoods 15 g mammal= (201 mg ail kg-bw) I (50.99 mg ai!kg-bw) = 

### 3.9 35 g mammal = (140 mg ailkg-bw) I ( 41.26 mg ai/kg-bw) = 3.4 1000 g mammal = (32 mg ai/kg-bw) I (17.84 mg ai/kg-bw) = 1.8 Softwoods 15 g mammal = (9 mg ailkg-bw) I (50.99 m g ai/kg-bw) = 0. 1 8 35 g mammal= (4 .2 mg ai/kg-bw) I (4 1.26 m g ai/kg-bw) = 0.10 1

OOOg mammal = ( 1.4 mg ailkg-bw) I ( 17.84 mg ailkg -bw ) = 0.08

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### Paclobutrazol 2SC Soil Injection/Basal Drench for Ornamental Trees- 1 application at 1.9 lb ail A Risk Quotient= EEC I Toxicological iValue Mammals The following definitive data are available for mammals: NOEL = 23 .2 mg/kg-bw 

### I Adjusted toxicity values were calculated for mammal size classes by T -REX 15 g mammal NOEL = 50.99 mglkg-?w 35 g mammal NOEL= 41.26 mg/kg

-bw 1000 g mamm· al NOEL = 17 . 84 mg/kg

-bw Chronic Dose-Based Risk Quotients = EEC/NOEL Hardwoods ) 15 g mammal = (1005 mg ailkg-bw) 

### J (50 .99 mg ailkg-bw) = 20 35 g mammal= (698 mg ai/kg-bw) I**~4 1.26**  mg ai /kg-bw) = 17 1000 g mammal = ( 159 mg ailkg-bw) I ( 17.84 mg ai/kg

-bw) = 9 Softwoods 15 g mammal= (459 mg ailkg-bw) 

### I**~50 .99**  mg ailkg-bw) = 

### 9 35 g mammal = (319 mg ailkg-bw) I (41 .26 mg ailkg-bw) = 

### 8 1

OOOg mammal= (72 mg ai/kg

-bw) I (17.84 mg ai/kg-bw) = 4 

### Bonzi II Drench for Potted O tinamentals -1 application at 6.llb ail A Woody Potted Ornamentals Risk Quotient= EEC I Toxicological .Value Mammals The following definitive data are available for mammals: NOEL= 23 .2 mg/kg-bw

5Adjusted toxicity values were calculated for mammal size classes by T-REX 15 g mammal NOEL= 50.99 mg/kg

- bw 35 g mammal NOEL = 41.26 mglkg

-bw 1000 g mammal NOEL = 17.84 mg/kg-bw Chronic Dose-Based Risk Quotients = EEC/NOEL Hardwoods 15 g mammal = (59 mg ai/kg-bw) I (50.99 mg ai/kg

-bw) = 

### 1.2 35 g mammal= (39 mg ailkg-bw) I (41.26 mg ai/kg-bw) = 0 .95 1000 g m ammal = (9 mg ailkg-bw) I (17.84 mg ailkg

-bw) = 0.50 Softwoods 15 g mammal= (23 mg ai!kg

- bw) I (50.99 mg ail kg-bw) = OA5 35 g mammal = ( 16 mg ai l kg-bw) I (4 1.26 mg ail kg-bw) = 0.39 1

OOOg mammal = (3 .6 mg ai/kg

-bw) I (17 .84 mg ai/kg-bw) = 0.20 Non-Woody Potted Ornamentals Mammals The fo llowing definitive data are availab le for mamma l s: NOEL= 23.2 mg/kg-bw Adjusted toxicity values were calculated for mammal size classes by T -REX 15 g mammal NOEL = 50.99 mg/kg

-bw 35 g mamm al NOEL = 41.26 mg/kg-bw 1000 g mammal NOEL = 17.84 mg/kg-bw Chronic Dose-Based Ri sk Quotients= EEC/NO EL 15 g mammal = (106 mg ai lkg-bw) I (50.99 mg ail kg-bw) = 2.1 35 g mammal = (74 mg ail kg-bw) 

### I (41.26 mg ai/kg-bw) = 1.8 1

OOOg mammal = (17 mg ailkg-bw) I (17 . 84 mg ailkg-bw) = 0.95



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