PC Code: 125601 

DP Barcodes: 395022 

Date: January 05, 2012 

MEMORANDUM 

SUBJECT: 

TO: 

FROM: 

Approved 

By: 

Tier I Drinking Water Assessment for the Registration Review ofPaclobutrazol 

on Turf (commercial, ornamental and golf courses), Ornamental and Shade Trees, 

and Seed Treatment of Tomato, Pepper, and Cucurbit 

Khue Nguyen, Chemical Review Manager 

Laura Parsons, Risk Manager 

Risk Management and Implementation Branch 1 

Pesticide Reevaluation Division (7508P) 

Faruque Khan, Ph.D., Senior Scienti~ { {~ t/J I 12_ 

Environmental Risk Branch I 

Environmental Fate and Effects Division (750~~ /~ /ol; ;;J---. 

Nancy Andrews, Ph.D., Branch Chief ~/ flY'• /' 

Environmental Risk Branch I 

Environmental Fate and Effects Division (7507P) 

Attached is the drinking water exposure assessment for the registration review of 

paclobutrazol use on ornamentals grown in outdoor/indoor nurseries, turf (commercial, 

ornamental, and golf courses) and as seed treatment of tomato, pepper, and cucurbit. If 

additional refinements are necessary, please contact Faruque Khan at 703-305-6127 or 

khan.faruque@epa.gov. 
of P.aclobutrazol on Ornamentals Grown in Outdoor/Indoor 

Nurseries, Turf (commercial, ornamental, and golf courses), and 

Seed Treatment of Tomato, Pepper, and Cucurbit 

Cl 

Paclo butrazol 

CAS Number 76738-62-0 

CAS Name - ( aR,JJR)-rel-JJ-[ ( 4-chlorophenyl)methyl)-a.-(1 ,1-dimethylethyl)-1H-1 ,2,4-triazole-1-ethanol 

2 

Mail 

Washingto1_1 DC 20460 

.J!;. ll.;:.r.l',;:i:?.,1~· :P..>ez6f.~.A-l;..•.!:t~'::~. l 
g

), 

j

, 

j

, 

bulb soak, plug/liner soak, and seed treatment. Tier 1 surface water and groundwater modeling 

were conducted with two highest application rates: 6.1 lbs/ A for nursery production of containergrown ornamentals through soil drench method (US EPA, 2011) and 2.0 lbs/A for foliar ground 

spray. Two major environmental degradates, CGA 149907 (maximum of 40.4%) and 

NOA457654 (maximum of25.1 %) were identified in the environmental fate and terrestrial field 

dissipation studies, and were included into the drinking water exposure assessment. However, 

there is no available recommendati<,m to include these major metabolites from the Residues of 

Concern Knowledgebase Sub-committees (ROCKS) of the Health Effects Division (HED). The 

upper-bound estimated drinking water concentrations (EDWCs) for total residue (paclobutrazol 

plus two major degradates (CGA 149907 and NOA 457654) as well as for paclobutrazol (parent 

only) are provided in Table 1 for the human health risk assessment. 

-Table 1. Tier I EDWCs for Paclobutrazol based on Soil Drench Application to ContainerGrown Ornamentals 

Drinking Water Source Model Use rate Acute Chronic 

(lbs ai/A/season) (Jtg/L) (Jtg/L) 

Total Residue (Paclobutrazol plus CGA 149907 and NOA 457654) 

Surface water FIRST 133.8 46.7 

Groundwater SCI-GROW 2.501 33 .1 33.1 

Parent only 

Surface water FIRST 133.5 43.5 

Groundwater SCI-GROW 2.50 20.0 20.0 

1 Maximum rate of6.llbs/A was normalized with the lowest fraction (0.59) ofpaclobutrazol retained in the soil 

column leaching study. Sample calculation is provided in Table 4. 

2 PROBLEMFORMULATION 

This is a Tier I drinking water assessment that uses modeling and available monitoring 

data to estimate the groundwater and surface water concentrations in drinking water sources 

(pre-treatment) resulting from pesticide use on sites that are vulnerable. This initial tier screens 

out chemicals with low potential risk and allows the Office of Pesticide Programs (OPP) to focus 

resources on more refined risk assessments for chemicals which potentially present more 

significant risks. This drinking water assessment reports potential exposure concentrations for 

3 
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y 

pp

, 

, 

, 

333, 

s a p

a

t 

growth regulator that is currently registered for application to a number of food (seed treatments) 

and non-food crops (ornamentals and turf) to induce compact plant growth. Registered 

application methods for paclobutrazol are foliar spray, soil injection, soil drench, bulb soak, seed 

treatment, plug/liner soak, and tree injections. It is used to control the size of numerous plants 

including turf, trees in right-of-ways, ornamental trees and shrubs, and bulbs (flower trade). Ten 

different companies currently have registered products with paclobutrazol concentrations ranging 

from 0.018 to 50.0 percent. Currently registered uses and rates ofpaclobutrazol are shown in 

Table 2. 

Table 2. Current Registered Uses and Application Rates of Paclobutrazol 

Maximum Application Shortest 

Crop Rate1 Number of Application Application Reg# 2 Applications Method Interval 

(days) 

Cucurbit 6.5 Jlg/seed 1 Seed N/A 000100-01014 

0.00029/bs/A Treatment 

Herbaceous 5.7 mg ailff · NS Spray, Drench, As needed 000 100-00992 

and Bulb Soak, 000100-00996 

ornamentals Spray Application Plug/Liner 000100-01079 

(greenhouse) 0.20 lbs!Afor 6'-8 pot Soak 000400-00515 

0.26/bs/Afor 18"x9" 062097-00011 

propagation trays 080697-00003 

drench application 000228-679 

4.3 lbs!Afor 6" pot 62097-25 

6.1/bs/AforB'pot 

Pepper 16 Jlg/seed 1 Seed N/A 000100-01014 

0. 00079 lbs/A Treatment 

Tomato 12.5 Jlg/seed 1 Seed N/A 000100-01014 

0.00040 lbs!A Treatment 

Trees (shade 0.009 lb ai per inch DBH 1 Soil Injection, 3 years or as 000100-01037 

and Basal Drench, needed 000 100-00991 

ornamental) Tree injection: 0.36/bs/A Tree Injection 000100-00995 

Soil Injection: 1.9/bs/A 000100-01014 

Basel drench: 1.9 lbs!A 067690-00022 

000228-680 

74779-3 

74779-7 

80697-4 

81943-31 

62097-24 

4 
009198-00215 

000100-01014 

067690-00022 

000538-00201 

000538-00199 

000228-680 

80697-4 

81943-31 

NS=not specified on label 

N/A Not Applicable 

1 Italic rates are provided by the Biological and Economic Analysis Division (US EPA, 2011) 2 Application rates represent maximum application rate for a least one of the EPA Reg# listed. Other labels may have slightly 

different application rates. 

3.2 Environmental Fate and Transport Characterization 

Paclobutrazol is a racemic mixture of the (2R, 3R)- and (2S, 3S)-enantiomers but the 

submitted physiochemical and fate properties of each enantiomer were not investigated in the 

submitted studies. Therefore, it is assumed that each enantiomer ofpaclobutrazol has similar 

physiochemical and fate properties based on submitted studies. Paclobutrazol has a low 

solubility (25.9 mg!L) in water. The vapor pressure (1.28 x 10-9 mm Hg @25.0°C) and Henry's 

Law Constant (8.09 x 10-Io atm m3/mol) indicate that the compound is relatively non-volatile 

under field conditions. The log Kow of3.2 indicates the potential for this chemical to 

bioaccumulate in aquatic organisms. 

Paclobutrazol is stable to hydrolysis and photolysis. Under aerobic conditions, 

paclobutrazol appears to be generally quite persistent in acidic soils, with half-lives greater than 

300 days. However in soils with neutral or higher pH, estimated half-lives were as short as 25 

days. In anaerobic aquatic metabolism studies, paclobutrazol variably partitioned to the 

sediment and degraded with a half-life of more than one year in flood loam and silt loam soils. 

Since, the extrapolated half-lives were beyond the duration of experiment, paclobutrazol was 

considered stable in the anaerobic aquatic system. Paclobutrazol residues were persistent and 

mobile in terrestrial field dissipation studies in California, West Virginia, Florida, North 

Carolina, Illinois, and Mississippi Half-lives ofpaclobutrazol residues ranged from 450-950 days 

for orchard soils in California, West Virginia, and Florida, and 175 days to 252 days in 

agricultural soils in Mississippi, North Carolina, and Illinois. Two major environmental 

degradates, ketone analog of parent (CGA 149907,:::; 40.0%) and lH-1,2,4-triazol-3-ol 

(NOA457654,:::; 25.1%) were identified in the environmental fate and terrestrial field dissipation 

studies. 

5 
-- -- ---

. 

j

y 

p

applied) of aged residue did not leach out of the upper 10 em of the treated soil columns. Table 3 

summarizes the physiochemical and environmental fate and transport properties of 

paclobutrazol. 't,a~ltr~ fb.xsic~i, Ch~mi~IH~q!!~i*if.onmental F~te properties of P:.adobutrazch_..,.,. r,i<' • t J:i;i:'t,r;:.,, ' 

.•!;:jil? :a....:·· ) ,tl; . ..:"!: .,:~~~-::,~~~ - '"4? ~''~' Value 1<'\l Refer:ence Cf!miJ!.ents · J-::,.. "-· Parameter ,A!.·.·.,ri :·',:i'-~;t~< -~?' .<#l.,;'t-.'7,~ .Ji: ·:..,.. ~~ \ .~.~1 ,tC' ... ~ ,]C.} • ;- .i,'."'::,\, i;t: . ·;~~~-3 Chemical Paclobutrazol MRID 456625-0 1 

Chemical Class Triazole 

CAS No. 76738-62-0 

Empirical Formula C1sH2oCIN30 MRID 456625-01 

IUPAC (2RS,3RS)-1-(4- MRID 456625-01 

- - chlorophenyl)-4,4-dimethyl- -

2-(1H-1,2,4-triazol-1-

yl)pentan-3-ol 

CAS Name (aR,pR)-rel-P-[(4- MRID 456625-01 

chlorophenyl)methyl]-a.-

(1, 1-dimethylethyl)-1H1 ,2,4-triazole-1-ethanol 

Structure ~\\ MRID 456625-01 Cl '7 

I 

N'N ~ H ~" -·-·~r· ··-~"·'·ru,,~·dffl~f~;~~~~i .i~!s~i~tfci Pii li~ille Wrdi~ii Parameters ... ·n 

· .. ,t~,.,.··rj, < ~'71·, ·•"'··- ~- •··~· •w~~~- -~ ~ t'~~!J,;,JJ'~.ij~',~~~' 

Molecular mass 293.8 g/mol MRID 456625-01 

Solubility (20.0°C) 25.9 mg!L (water) MRID 456625-05 

2.8 g fL (n-Octanol) MRID 456625-03 

79.8 giL (methanol) 22 giL (xylene) 

Vapor pressure (25.0°C) 1.7 x 10'7 Pa 

(1.28 x 10'9 mm Hg) 

MRID 456625-05 

Henry's law constant (25°C) 8.2 X 1 0'7 Pa M3 mor1 

(8.09 x 10-12 atm M3 mol'1) 

MRID 456625-05 

Octanol-water partition coefficient 3.18 MRID 456625-05 

(LogKow) (25°C) :~t~'";,· ... ,~:1.!. 'l,<l;' "Ji Persistence ~-~~N~'~: ;;;~! i': :(_\ ~.i.'izel~-v.~~~. } .... · .. .,._ ;:I!" 

6 
paclobutrazol decrease 

to 86.4 %of applied 

radioactivity 

Aerobic Soil Metabolism Sandy clay loam MRID 40685003 Major metabolite 

(t ~) 19 (21 and 17) months1•2 (CGA 149907 (:::::18.7%) 

[47 (58 and 36) months/ 

\ MRID 47338504 Supplemental Sandy clay loam 

301 days No major metabolites [385 days] detected above 10%. 

Sandy loam Major metabolites 

26 days4 NOA 457654(25.1%) 

[75.3 days] CGA 149907(13.3%) 

Sandy loam Major metabolites 25 days4 

[55.9 days] NOA 457654 (20.5%) CGA 149907(26.3%) 

Anaerobic Soil Metabolism No data 

Anaerobic Aquatic Metabolism (t ~ ) Stable MRID 40685003 After a year of 

incubation, 

paclobutrazol decrease 

to :579% of applied 

radioactivity 

Major transformation 

product: 

(CGA 149907 (:::::16.8%) 

No data --

Aerobic Aquatic Metabolism 

Mobility 

Soil Partition Coefficient AdsorJ!tion Kg (mL/g} MRID 4188113 There was no significant 

9.5 (Clay loam) correlation (i = 0.12) 

10.2 (Sandy Clay loam) between Kct and % 

7.6 (Silty clay loam) 

17.3 (Silt loam)5 organic carbon. 

4.1 (sandy loam) 

2.4 (loamy sand) 

5.8 (Silty clay) 

1.4 (Sand) 

7 
10.4 (loamy sand) 

2.7 (Silty clay) 

6.1 (Sand) 

Adsorution & {mL/2) MRID 47338503 Supplemental 

1. 7 (Sandy loam) 5 

0.8 (Sandy loam) 

2.4 (Silty clay loam) 

1.8 (Clay loam) 

Desorption {mL/gt 

10.9 (Sandy loam) 5 

3.81 (Sandy loam) 

2.66 (Silty clay loam) 

11.7 (Clay loam) 

Leaching Aged methine 14C- labeled MRID 40685004 Major transformation 

paclobutrazol residues were product 

-

relatively immobile CGA 149907 (:::::12.6%) 

Aged trizole 14C-labeled 

paclobutrazol residues were 

mobile in loamy sand and 

clay loam soils and low 

mobility in sands and sandy 

loam soils 

Field Dissipation 

Terrestrial Field Dissipation (t Yz) MRID Supplemental 450 to 973 .days 40685006- Major transformation (CA, WV,FL) 406850012 product CGA 149907 

Supplemental 

88 days (CA) MRID 47338505 Major transformation 133 days (NY) product- CGA 149907 

(40%) 

1 Calculated half-lives are based on 14C labeled oftriazole and methane ofpaclobutrazol 

2 Extrapolated half-lives exceeded beyond the study period except soils with pH> 7.0 

3 Italic half-lives are calculated based on paclobutrazol and its major degradates (CGA 149907 and NOA 457654). 

Calculation can be found in Appendix A. 

4 High Soil 7.0) may have contributed faster degradation rates for aerobic soil metabolism 

5 Japanese soils, excluded during exposure assessment 

6 Reported values are based on second desorption step 

8 
Tier 1 EDWCs for surface water were generated using FIRST, dated August 5, 2001. 

FIRST is a screening model designed by the Environmental Fate and Effects Division (EFED, 

2010a) of the Office of Pesticide Programs to estimate the concentrations found in drinking 

water from surface water sources for use in human health risk assessment. As such, it provides 

upper bound values on the concentrations that might be found in drinking water due to the use of 

a pesticide. FIRST is a single-event model (one runoff event), but can account for spray drift 

from multiple applications. FIRST is hardwired to represent the Index Reservoir, a standard 

water body used by the Office of Pesticide Programs to assess drinking water exposure (Office 

of Pesticide Programs, 2010b). It is based on a real reservoir, Shipman City Lake in illinois, that 

is known to be vulnerable to pesticide contamination. The single runoff event moves a maximum 

of 8% of the applied pesticide into the reservoir. This amount can be reduced due to degradation 

on the field and the effects of binding to soil in the field. FIRST also uses a Percent Cropped 

-Area (PCA) factor to adjust for the area within the watershed that is planted to the modeled crop. 

The national default PCA of 1.0 and 0.87 was applied for turf and nursery assessment, 

respectively. 

Tier 1 EDWCs for groundwater were generated with SCIGROW 2.3, dated July 29,2003 

(20 1 Oa). SCI GROW is a regression model used as a screening tool for ground water used as 

drinking water. SCI GROW was developed by regressing the results of Prospective Ground 

Water studies against the Relative Index of Leaching Potential (RILP), The RILP is function of 

aerobic soil metabolism and the soil-water partition coefficient. The output of SCI GROW 

represents the concentrations that might be expected in shallow unconfined aquifers under sandy 

soils. 

3.3.2 Modeling Approach and Input Parameters 

Tables 4 and 5 summarize the model input parameter values used in FIRST and 

SCIGROW, respectively. These parameters were selected in accordance with EFED's input 

parameter guidance (US EPA, 2010c). Half-lives (rate constants) listed in Table 3 were used for 

exposure modeling. Average soil-water partitioning coefficient was used in FIRST. For total 

residue, half-lives were estimated by accounting the percent of applied parent (paclobutrazol), 

CGA 149907 and NOA 457654 present on each sampling period of fate studies (Appendix A). 

The lowest Koc value was used in SCI GROW because there was greater than 3-fold variability in 

the available data. 

9 
9I% retention of parent column leaching study (MRID 

in soil column 40685004) 

2.0 lbs/A for turf 

Number of Applications I (nursery) Product Label 

3(turf) 

Soil Partitioning 4.5 MRIDs 4I88113 and Mean value 

Coefficient (K.i mVg) 47338503 

Aerobic Soil 1 003.2 (Total residue) MRIDs 40685003 and 90m percentile upper confidence 

Metabolism t112 (d) 444.2 (Parent) 47338504 bound on the mean. 

- - - -· - -

Wetted in? No --- ---

Depth of Incorporation 0 --- ---

(inches) 

Method of Application Drench Paclobutrazollabels -- Ground 

Spray Drift Fractions 0 (drench) Paclobutrazollabels Model input guidance 

6.4 (ground foliar) (US EPA, 2010) 

Percent Cropped Area 0.87 Nursery National Default 

1.0 Turf No PCA established for turf 

Solubility in Water 25.9 MRID 456625-05 ---

(mg!L) 

Aerobic Aquatic 2006.4 (Total Residue) 2X of Aerobic soil Model input guidance 

Metabolism t112 (days) 888.4 (Parent) metabolism half-life (US EPA, 2010) 

Hydrolysis t112 0 MRID OOI32698 Stable to hydrolysis 

Aquatic Photolysis t 112 0 MRID 0013299 Stable to aquatic photolysis 

(days) 

1 Example of application rate calculation: 6.I lbs/A- (6.11bs/A *0.59) 

Where 

6.1lbs/A is application rate for drench application for 8-inch container grown ornamentals (US EPA, 2011) 

0.59 is the minimum fraction of retention of parent (paclobutrazol) in column leaching study (MRID 40685004) 

2 Maximum single application rate of0.67lbs/A was used instead of0.75 lbs/A to account maximum seasonal rate of 

2.0 lbs/ A due to Tier I model limitation. Model accepts only uniform rate for multiple applications. 

10 
M~um Number of 

Applications per Year 

Aerobic Soil 

Metabolism Half-life 

Organic Carbon 

Partition Coefficient 

Koe. LIK 2 

See calculation in Table 4 

1 (Nursery) 

230.2 (Total Residue) 

163.5 (Parent) 

40.4 

Product Label 

MRIDs 40685003 and 

47338504 

MRIDs 4188113 and 

47338503 

median value 

Lowest value; > 1 OX variability in 

data 

There is no significant correlation between 1<.! and organic carbon. Since, model does not have an option to use 1<.!, 

----1 the lowest value ofKoc was used in the model 

3. 3. 3 Modeling Results 

The FIRST and SCI-GROW output files are located in Appendix B. Based on the results 

of these simulations, EFED recommends acute surface water EDWC of 133.8 J.lg/L and a 

chronic EDWC of 46.7 J.lg/L for use in the human health risk assessment. These 

recommendations are based on the use ofp~clobutrazol on various uses at an annual application 

rate of2.50 lb a.i./A/season. The recommended EWDC for groundwater is 33 f.lg/L and is also 

based on the use of paclobutrazol on various uses at the previously stated rate. Modeling results 

are depicted in Table 6. Sample outputs of Tier I FIRST and SCIGROW are provided in 

Appendix B. No drinking water assessment was performed in the past to compare with current 

assessment. 

Total Residue (Paclobutrazol plus CGA 149907 and NOA 457654) 

Nursery: 133.8 46.7 {lapp. X 2.50 lbs ailacre) Drench Surface Water 29.4 10.3 (lapp. X 0.55 lbs ailacre) (FffiST) Turf: 

X 0.0.67lbs ailacre) Ground 126.1 44.6 

11 
y 

p

) 

Nursery: 133.5 (lapp. X 2.50 lbs ai!acre) Drench 29.4 (lapp. X 0.55 lbs ai!acre) 

Turf: Ground 124.4 (3 app. X 0.67 lbs ailacre) 

Groundwater lapp. X 2.50 lbs ailacre) Drench 20.0 (SCI GROW) (lapp. X 0.55 lbs ai!acre) 4.4 

3.4 Monitoring Data 

There were no national-scale monitoring data available for this assessment. 

3.5 Drinking Water Treatment 

There is no available information on the drinking water treatment effects on 

Paclobutrazol. 

3.6 Uncertainties 

43.5 

9.6 

41.1 

20.0 

4.4 

In general, the EDWCs provided in this assessment are upper bound estimates of 

paclobutrazol concentrations in untreated drinking water. A major source of uncertainty is the 

leaching of paclobutrazol from indoor drench application of potted nursery. It is assumed that 

treated pots would be placed outdoors immediately after drench application throughout the 

watershed of the index reservoir. If the treated pots remain indoors and/or the applied 

paclobutrazol is taken up by the potted plants, the· residual paclobutrazol would be less than the 

modeled application rate and consequently exposure in surface water and groundwater would be 

less than the reported values. Additionally, exposure assessments were performed based on one 

seasonal application rate for drench method. Indoor potted plants can be grown several times 

within a year. If this chemical is applied to multiple batches of potted plants and placed outdoors 

during the growing season, exposure would be higher than the reported values in Table 6. In 

addition, exposure would be higher or lower based on residence time of treated potted plants 

remain outdoors before planting or distributing to retailers. 

12 
Treatment and Container-Grown Ornamental Uses ofPaclobutrazol. Biological and Economic 

Analysis Division. November, 2011 

US EPA. 2010a. Water Models. U.S. Environmental Protection Agency, Pesticides: Science 

and Policy. Online at: http://www.epa.gov/oppefed1/models/water/ 

US EPA. 2010b. Development and Use of the Index Reservoir in Drinking Water Exposure 

Assessments. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Environmental Fate and Effects Division, April15, 

201 0. Online at: http:/ /www.epa.gov/oppefed 1/models/water/index.htm 

USEP A. 201 Oc. Guidance for Selecting Input Parameters in Modeling the Environmental Fate 

and Transport of Pesticides, Version 2.1. U.S. Environmental Protection Agency, Office of 

Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fate 

and Effects Division, October 22,2009. 

http://www.epa.gov/oppefedl/models/water/input parameter guidance.htm 

13 
Distribution of residues- 18 Acre loam soil 

Half Life 57.8 Months 

LN of 

%of Total total 

Months Residue residue 

0 87.6 4.47 

1 92.2 4.52 

4 88.8 4.49 

8 81.0 4.39 

12 78.7 4.37 

Chemical: Paclobutrazol 

MRID: 40685003 

PC Code: 125601 

Guideline: 835.4100 

Dissipa_tion of paclobutrazol in 18 Acre loam 

loam soil system (12 Months) 

4.55 

-

"g 

.! 4.50 

Q. 

a. 

<C 

.... 4.45 

0 ~ 4.40 

3 

• y = -0.012x + 4.5088 

R2 = 0.8271 

4.35 -1------.---------,r------ --, 

0 5 10 15 

Months (Post -treatment) 

Distribution of residues- 18 Acre loam,:,..2.so~i!..l ------------------------, 

Half Life 35.5 Months 

LN of 

% ofTotal total 

Months Residue residue 

0 96.1 4.57 

1 91.6 4.52 

4 84.6 4.44 

8 80.1 4.38 

12 75.1 4.32 

Dissipation of paclobutrazol in 18 Acre loam 

- 4.6 ~ 4.55 ·~ 4.5 

:4.45 

0 4.4 

?fl. 4.35 

z 4.3 

_, 4.25 

0 

14 

loam soil system (12 Months) 

y = -0.0195x + 4.5422 

= . 5 

2 4 6 8 10 12 

Months (Post -Treatment) 
0 

0 

7 

7 

22 

22 

35 

35 

so 

so 

70 

70 

91 

91 

120 

120 

Chemical: 

MRID: 

PC Code: 

Guideline: 

Half-Life 

Days 

(Posttreatment) 

0 

0 

7 

7 

22 

22 

35 

35 

so 

so 

70 

70 

91 

91 

120 

120 

90.1 4.5 

80.4 4.4 

92.5 4.5 

92.8 4.5 

87.4 4.5 

88.5 4.5 

74.7 4.3 

74.4 4.3 

62.6 4.1 

65.9 4.2 

54 4.0 

55.6 4.0 

41 3.7 

38.3 3.6 

32.3 3.5 

28.9 3.4 

Paclobutrazol 

47338504 

125601 

835.4100 

75.34 days 

Paclobutrazol, LN Total CGA 149907, 

NOA457654 Residue 

85 4.4 

93.4 4.5 

91.9 4.5 

92.6 4.5 

85.5 4.4 

84.9 4.4 

69.5 4.2 

70.3 4.3 

61.4 4.1 

59.2 4.1 

53.3 4.0 

51.9 3.9 

45.3 3.8 

39.2 3.7 

29.3 3.4 

32.6 3.5 

Dissipation of paclobutrazol in Pappelacker 

sandy loam soil system (0-120 days) 

::g 6.00 y = -0.0124x + 4.5691 ·~ ~ 4.00 1 ~~~== ~._~~~ ~0.... .~98~8~6~~ ~ Q. .... 

<( 

.... 2.00 

0 

e o.oo +-------r-- --- ----. 

3 0 50 

Days 

100 

Dissipation ofpaclobutrazol in Gartenackersandyloam soil system 

(0·120days) 5.00 

wa.. y- uu~ux + 4.5731 ...._.__.. 

:g 4.00 "" R2 = 0.9755 

Q. 

.! --.---. 

a. 3.00 

< 

... ~ 2.00 

3 1.00 

0.00 -

0 so 100 150 

Days 

15 
nt) 

0 0 

7 7 

22 22 

35 

35 

50 50 

70 

70 

91 91 

120 120 

NOA457654 Residue 

87.6 4.47 87.2 4.47 

92.8 4.53 88.1 4.48 93.3 4.54 

. 95.3 4.56 

77.1 4.35 

80.8 4.39 81.1 4.40 

74.6 4.31 76.2 4.33 

70.7 4.26 79.8 4.38 

90.2 4.50 

72.1 4.28 70.0 4.25 

= -0.0018x + 4.4919 ::C 4·60 

4.50 _____ ..... ____ _ 

Cl. Cl. 

<( 4.40 -1---..... 

0 e 4.3o 

3 4.20 -1------.------r-------. 

0 50 100 150 

Days (Post-Treatment) 

16 
RATE (#/AC) 

ONE(MULT) 

No.APPS & 

INTERVAL 

SOIL SOLUBIL 

Kd (PPM ) 

APPL TYPE 

(%DRIFT) 

%CROPPED INCORP 

AREA (IN) 

2.500( 2.500) 1 1 4.5 25 . 9 GRANUL ( . 0) 8 7 . 0 . 0 

METABOLIC 

(FIELD) 

1003 . 20 

FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

DAYS UNTIL 

RAIN/RUNOFF 

2 

HYDROLYSIS 

(RESERVOIR) 

N/A 

PHOTOLYSIS 

(RES. -EFF) 

.00- .00 

METABOLIC 

(RESER.) 

****** 

COMBINED 

(RESER.) 

2006.40 

UNTREATED WATER CONC (MICROGRAMS/LITER (PPB)) Ver 1.1.0 JAN 1, 2007 

Application 

rate (lb/acre) 

2.500 

PEAK DAY (ACUTE) 

CONCENTRATION 

ANNUAL AVERAGE (CHRONIC) 

CONCENTRATION 

133.759 

Ground Water 

SCI GROW 

VERSION 2.3 

46.658 

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:Paclobutrazol 

time is 12/22/2011 14:19:32 

Number of 

applications 

Total Use 

(lb/acre/yr) 

Koc 

(ml/g) 

Soil Aerobic 

metabolism (days) 

1.0 2.500 4.04E+01 230.2 

groundwater screening cond (ppb) = 3.31E+01 

17 
! 

I