UN ITED ST A T ES E NV IR ONM E NTA L P ROTECT I ON AGENCY WAS HI NG T ON D .C., 20460



### P C Co d e: 125601 

### DP Ba r co d e: D427 l 5 l 

### D at e: May 6 , 2015
MEMORAN D UM


### SUBJECT: Amended Terrestrial Plant Risk Quotients for the Pac lobutrazol Registrat i on Rev iew Ecological Risk Assessment 

### TO:

FROM: Khue Nguyen , Chemical Review Manager Tom Moriarty , T earn Leader Nei l Anderson , Branch Chief Risk Management and Imp lementation Branch I Pesticide Re-Evaluat ion Divis ion

# ::::::f:a:,:::d:::o~:i:**:~:: 08P** **) i**  Sujatha Sankula , Ph.D. , Branch Chie

### \J..;- 

## :::>===="'" Environmental Risk Branch I Enviromnental Fate and Effects D ivision (7507P) Office of Pesticide Programs

In the October 9 , 2014 , response to comments document for paclobutrazo l (USEPA 2014, D417019) , the Environmental Fate and Effects Divis ion presented new risk quotients (RQs) for terrestrial plants , based on endpoints from the newly subm itted seedling emergence study (MRID 49300408). Th e text of the document correctly asserted that the RQs for terrestria l p l ants were now higher than those presented in the origina l registration rev iew r i sk assessment (USEPA 2013 , D393895). However , the ter restr i a l plant values presented in the appendix were actually lower , and thus incorrect , for all uses but the seed treatments.
Table l presents the endpoints used in the original registration review risk assessment (based on 5 t h percentile estimates from other structurally similar conazoles) and the empirical va lues from the paclobutrazol seedling emergence study.T bl 1 C a e f di' d

. t ompanson o see mg emergence en pom s 5th P e rce ntile (based on d a ta Emp iri ca l D a ta from ot h e r conazoles) Monocot EC 2s > 0.098 lb 

### ailA EC2s 

### = 0.0824 lb ai / A NOAEL 

### = 0.071 lb a i / A N O AEL 

## = 0.0098 lb 

### ai l A Di cot EC 2s 

### = 0.009 lb a i/A EC2s 

### = 0.0063 1 lb ai/ A NOAEL 

## = 0.00 2 lb 

### a i l A E C os 

### = 0.000567 lb 

### a i l A* *T h e EC os was u se d b eca u se th e N O AEL was ca lculated to be grea ter than th e EC2s.

Table 

### 2 p resen t s the co rr ected RQ s, based on the seedl i ng emergence empirical data. General input parameters for Terr Plant include th e sol u bility of paclobutrazol (27 ppm) , app licati on rat es, inc o rpora ti o n d e pth ( 1 to 3 inche s, dep e n d in g o n use) , and dri f t fraction (0.0 1 fo r s pray applicat io n s and 0 for dre n c h , inj ection , a nd s eed treatm e nt s)

. T h e seed trea tm e nt RQ s re m ai n ed the same (RQs 

### < 0. 1 ); h owever, so me of the o th er RQ s in c reased by a m ax imum of I Ox. Although th e RQs in creased in magnitude , n o n ew ri sk concerns we re identifi ed. There r ema in potenti a l ri s k concern s for non-li s t e d / li s ted dicots and li s t e d monocots for t h e t urf , p otted ornamenta l s pra y, so il injection / ba sa l drench , and potted o rnamental dr e nch u ses. There are ri s k concerns for non-li s ted monocot s for turf , soil injection/ basal drench , and the potted ornamenta l drench.
Tab le 2. Revised terre s tria l p l ant RQ s, ba se d o n n ew see dlin g e mer ge nc e d ata (MRlD 49300408) Plant T y p e Li sted Statu s Dry Sem i- Aq u a tic S pray Drift Turf(1 avo at 0. 75 lb ai lA) Monocot Non-l i s t ed 0

. 27 1.91 *** <0 .1 Monocot L i sted 2.30 *** 16.07 *** 0.77 Di cot Non -li s t ed 3.57*** 24.96 *** 1.19 *** Di cot L i s ted 39.68 *** 277.78 *** 13.23 *** P o tted ornamenta l s pra y (1 app at 0.26 lb ai/A) Monocot Non- li s te d < 0. 1 0.66 <0. 1 Mo n oco t L isted 0.80 5.57* ** 0.27 Di cot Non-listed 1. 24*** 8.65 *** 0.4 1 Di cot Li sted 13.76 *** 96.30 *** 4.59 *** Soi l in je c tio 11 /basa l dre n c h (1 app at 3 in c h es deep at 1.9 lb ai/A ) Mono co t Non- li s t e d 0.15 1.54 *** N I A Monocot Listed 1 .29 *** 12 .93* ** N I A Dicot Non-l i s t ed 2.01 *** 20.07 *** 

## N I A Di cot L i sted 22.34 *** 223.40 *** 

## N I A Potte d o rnam e ntal drenc h (1 arJD at 6. I lb ai l A) Monoc o t No n
- li s ted 1.48 *** 14.81 *** 

## N I A Monoco t Listed 12.45 *** 124.49 *** 

## N I A Di cot Non- li s ted 19.33 *** 1 93.3 4 *** N I A Di cot Li s t ed 215. 1 7 * ** 2 1 51.68 *** 

## N I A Tomato see d treatme nt (1 avo at 3 inch es d ee p at 0

. 0004 lb a i/A)
2

### Plant T y pe L is te d S tatu s Dry S e mi- A quati c Spr ay Drift 

### Monocot Non- listed <0. 1 <0.1 

## N I A Mo nocot Lis t ed <0. 1 <0.1 

## N I A Di co t Non- li sted <0.1 <0.1 

## N I A Di cot Listed <0.1 <0.1 

## N I A P e pp e r seed tre atm e nt (1 

### aoo a t 3 in c h es de e p at 0.000 7 9 lb a i/A) 

### Monocot Non-listed <0.1 <0.1 

## N I A Mo nocot Li s ted <0.1 <0.1 

## N I A Di cot Non-listed <0.1 <0.1 

## N I A Di cot Li s ted <0.1 <0.1 

## N I A C u c urbit seed tre atment (J 

### app at 3 in c h es de ep at 0.00029 lb ai /A ) 

### Monocot No n-lis t ed <0. 1 <0. 1 

## N I A Monocot Listed <0. 1 <0.1 

## N I A Di cot Non- li sted <0.1 <0.1 

## N I A Di cot Listed <0.1 <0.1 

## N I A Br occo li see d tr e atm e nt (J 

### app at 3 incit es d e ep at 0

. 0000 96 lb ai l) 

### Monocot Non-li s ted < 0. 1 <0.1 

## N I A Monocot Listed <0.1 <0.1 

## N I A Di cot Non

- lis t ed < 0

. 1 <0

. 1 

## N I A D i co t Listed < 0 .1 <0 .1 

## N I A Caulifl o we r seed tre atm e nt (1 app at 3 in cites de e p at 0.000064 lb ai /A ) 

### Monocot Non- listed <0.1 < 0. 1 

## N I A Monocot Li ste d <0.1 <0.1 

## N I A Di cot Non-li s ted <0.1 <0.1 

## N I A Di cot Listed < 0. 1 < 0. 1 

## N I A Cabbag e see d treatm e nt (1 

### app at 3 incit es deep at 0.0001 2 l b a i/ A) 

### Monoco t Non- listed <0. 1 < 0

. 1 

## N I A Mo n ocot L isted < 0. 1 < 0. 1 

## N I A D i cot Non-listed <0. 1 <0. 1 

## N I A Di cot Listed <0. 1 <0.1 

## N I A N

I A

- not applicable because spray dr ift does not occur with seed treatment/drench/so i l injection us e s 

## ** *

- exceeds the LOC of I

R e fer e nces 

### US EPA. 20 1 3. Reg i s tr ation rev iew
- eco l og ica l ri sk assess me n t a nd effects dete rm i nat ion of pac lobutrazol. Env ironmenta l Fate and Effects Divis ion, Office of P esticide Programs, United States Env ironmenta l Protection Agency. USEPA. 2014. Response to Public Comments on the Paclobutrazol Regi s tration Review Ecological Ri s k As s essment. Environmental Fate and Effects Divi s ion , Office of P

est ic ide Programs , United States Environmenta l P rotection Age ncy.

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