UN ITED STATES ENVIRONME NTA L PROTEC TION A GEN CY WASHINGTON D

. C

., 20460



### MEMORANDUM PC Code: 1 25601 DP Barcode: D4170 19

Date: October 9, 2014



### SUBJECT: Response to Public C t mments on the Paclobutra zol Registration Review Ecologi cal Risk Asse smen t



### TO : Khue Nguyen, Chemical Review Manag e r Melissa Grable,

## Actin~ Team Lead er Neil Anderson, Bran ch Chief

j 

### Risk Management and I mplementation Branch I Pe st icide Re-Evaluatien Di vision Office of Pesticide Pr ograms (7508P)



### FROM: Meghan Rad tke, Ph.D.

, Acti n g RAPL Faruque Khan, 

### P h. D.
, Senior**Scientist ..J-.** **1-. ~-""**  

### Sujatha Sanku la

, Ph.D., Branch Chief Env ironm ental Ri sk Branch I E

nvironmental F at e and Effects Division (7507P) Office ofPesticide Programs

In response to the " Registration Review

- Ecological Risk A ss e ss m e nt and Effects D ete rmination of Paclobutrazol " (DJ J 93895), Syngenta Crop Prot ect ion submitted comments durin g the public comment period. 1 he Agency appreciates the feedback, in particular, the nine

a dditi onal ecotoxic it y studies that were submitt ed.

Thi s memo se rves two purposes. Fir l t, i t documents the Agency 's response to t he public
comments tha t were received from Syngenta. Comments that addressed similar topics were combined and s ummarized. Second, when applicable

, it update s the ana l yses and results of the paclobutrazol R eg istration Re view ri s k assessment.

Syngenta Comme11t 

### Syngenta believes t h at the meth o d o f using the 5th percen t ile in conjunction with Monte Carlo simulations (est imating a 5th percentile toxicity va lue u s i n g the m ost se nsi t i ve endpoint from
str u ctura ll y s imilar chemica ls) w as too conserva t ive to generate toxico lo g i cal endpo ints when empirical data were not available. In response, they subm itt ed nine studies that provided ecotoxicity data for acute exposure t 1 es tuarine/marine fi s h

, chronic ex posure to freshwate r inv e rt ebrates, ac ut e exposure to estuarine / marin e inv erteb r ates, expos ur e to terrestrial plan t sUNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460



### PC Code: 125601 DP Barcode: D417019

Date: October 9, 2014

MEMORANDUM

SUBJECT: Response to Public Comments on the Paclobutrazol Registration Review Ecological Risk Assessment

TO: Khue Nguyen, Chemical Review Manager Melissa Grable, Acting Team Leader Neil Anderson, Branch Chief Risk Management and Implementation Branch I Pesticide Re-Evalu ation Division Office of Pesticide Programs (7508P)

FROM: Meghan Radtke, Ph.D., Acting RAPL Faruque Khan, Ph.D., Senior Scientist Sujatha Sankula, Ph.D., Branch Chief Environmental Risk Branch I Environmental Fate and Effects Division (7507P) Office of Pesticide Programs

In response to the “Registr ation Review – Ecological Risk Assessment and Effects Determination of Paclobutrazol” (D393895), Syngenta Crop Protection submitted comments during the public comment period. The Agency appr eciates the fee dback, in particular, the nine additional ecotoxicity studies that were submitted.

This memo serves two purposes. First, it do cuments the Agency’s re sponse to the public comments that were received from Syngenta. Comments that addressed similar topics were combined and summarized. Second, when applicab le, it updates the analys es and results of the paclobutrazol Registration Review risk assessment.

Syngenta Comment Syngenta believes that th e method of using the 5 th 

### percentile in conjunction with Monte Carlo simulations (estimating a 5 th 

### percentile toxicity value usi ng the most sensitive endpoint from structurally similar chemicals) was too conser vative to generate toxicological endpoints when empirical data were not available. In res ponse, they submitted nine studies that provided ecotoxicity data for acute exposure to estuarine/ marine fish, chronic exposure to freshwater invertebrates, acute exposure to estuarine/marine invertebrates, exposure to terrestrial plants

### 2 (seedling emergence), acute contact/oral expos ure to honeybees, and exposure to aquatic vascular plants, cyanobacteria, and aquatic non-v ascular plants. A vegetative vigor study was also cited (as below), but it was not received by the Agency in time to incorporate into the revised Registration Review risk assessment:

Martin, JA. 2013. Paclobutrazol formulation – vegetative vigor test. Smithers Viscient, 790 Main Street, Wareham, MA 02571-1037 USA. Report number: 1781.6907, Study number: 1781.6907, Task number: TK0176295. 294 pgs.

In addition, Syngenta had se veral specific suggestions:

 The acute-to-chronic ratio (ACR) would be an appropriate method to estimate the missing endpoints for chronic estuarine/ma rine fish and invertebrates.

 For aquatic vascular plants, the watermilf oil and hydrilla study endpoints were too conservative, not based on robust endpoint s, and not analytically verified.

 The passerine acute oral toxic ity test was not identified as a data gap in the Problem Formulation or the Data Call-In and that the av ailable acute oral toxicity data for mallard duck and bobwhite quail should be sufficient to assess risk to passerine species.

EFED Response The 5 th 

### percentile method was chosen to estimate missing ecotoxicological endpoints because it was thought to be a conservative approach. Currently, the Agency is moving toward a probabilistic approach for ecotoxicology data.

EFED evaluated the nine new studies that were submitted by Syngenta. Details of the evaluation can be found in USEPA 2014 (D418054). Informati on from “supplemental” and “acceptable” studies is incorporated into the analysis and risk conclusions of the revised Registration Review risk assessment, as described below. Revised risk conclusion summary tables are located in Appendix A (Tables 1-4).

Acute risk to estuarine/marine fish The newly submitted study (MRID 49300405) with sheepshead minnow was classified as “invalid.” Consequently, the results of the original Registration Review risk assessment remain intact. There is the potential for direct ac ute effects to listed estuarine/marine fish from the potted ornamental drench use.

Chronic risk to estuarine/marine fish The acute-to-chronic ratio (ACR) approach that was proposed by Syngenta is inappropriate for two reasons. First, the ratio must be establis hed with acute and chronic data from the same species. The acute data from grass carp and chro nic data from fathead mi nnow cannot be used to generate the ratio. Secondly since the r ecently submitted acute sheepshead minnow study was found to be “invalid”, an acute estuarine/marine fish study with paclobutrazol is not available. Consequently, the results of the original Regi stration Review risk assessment remain in place. There is the potential for direct chronic effects to listed and non-listed estuarine/marine fish from the turf and potted ornamental drench uses.

### 3 Chronic risk to fres hwater invertebrates The original Registration Review risk assessment i ndicated potential direct chronic risk concerns for listed and non-listed freshwater invertebrates for turf and potted ornamental drench uses. The newly submitted waterflea study (MRID 49300406) yielded a NOAEC of 0.32 mg ai/L, which is much less toxic than the endpoint generated by the 5 th 

### percentile approach (NOAEC = 0.009 mg ai/L). Using the new endpoint, only one scen ario (Total Toxic Residues - TTR - Florida ornamentals, 2.5 lb) produced an RQ above th e LOC of 1 (RQ = 1.04) (see Appendix A for RQs, Table 5). The updated risk conclusion is that there is a potential for di rect chronic effects to listed and non-listed freshwater invertebrates only for the potted ornamental drench use.

Acute risk to estuarin e/marine invertebrates The original Registration Review risk assessment c oncluded that there were potential direct acute risk concerns for listed species to turf and orna mental uses, and non-listed species to ornamental uses. The newly submitted studies with P acific oyster larvae (MRID 49300403) and mysid shrimp (MRID 49300404) yielded LC 50 

### s of > 9.9 and > 9.0 mg ai/L, respectively. These values are less toxic than the en dpoint generated by the 5 th 

### percentile approach (LC 50 

### = 0.24 mg ai/L). RQs cannot be calculated with the new endpoints because they are non-definitive (greater than values). Instead, when the highest estimated en vironmental concentration (EEC) (333 μg ai/L – TTR Florida ornamentals, 2.5 lb) is compared directly with > 9000 μg ai/L (mysid shrimp endpoint), the EEC is less than 1/20 th 

### of the LC 50 

### , indicating that direct acute risk is unlikely. The updated risk conclusion is that direct acute risk concerns to estuarine/marine invertebrates are unlikely for all uses.

Chronic risk to estuarine/marine invertebrates Syngenta proposed that an acute-to-chronic rati o (ACR) approach be employed using existing acute and chronic waterflea data and the ne wly submitted mysid shrimp data (MRID 49300404; see above). The NOAEC generated by Syngenta us ing an ACR approach is not substantially different than the tebuconazole NOAEC that was us ed as a surrogate endp oint in the assessment (ACR NOAEC > 0.082 mg ai/L; Tebuconazole NOAEC = 0.035 mg ai/L) and would still result in RQs above the LOC. Consequently, the results of the or iginal Registration Review risk assessment remain in place. There is the potential for direct chronic effects to listed and non-listed estuarine/marine invertebrates fr om the turf and potte d ornamental drench

uses.
Risk to terrestrial plants The original Registration Review risk assessmen t concluded there were potential direct risk concerns for listed and non-listed dicots (turf, potted ornamental spray, soil injection/basal drench, and potted ornamental drench) and listed monocots (turf, soil injection/basal drench, and potted ornamental drench). The newly submitted seedling emergence study (MRID 49300408) yielded paclobutrazol endpoints that were lower than t hose estimated using the 5 th 

### percentile approach (Table 1). Note, a new paclobutr azol vegetative vigor study was submitted shortly before the draft interim decision document was pub lished. The data will be considered in future analyses.

### 4 Table 1. Comparison of s eedling emergence endpoints 5 th 

### Percentile Empirical Data Monocot EC 25 

### > 0.098 lb ai/A NOAEL = 0.071 lb ai/A EC 25 

### = 0.0824 lb ai/A NOAEL = 0.0098 lb ai/A Dicot EC 25 

### = 0.009 lb ai/A NOAEL = 0.002 lb ai/A EC 25 

### = 0.00631 lb ai/A EC 05 

### = 0.000567 lb ai/A* *The EC 05 

### was used because the NOAEL was calcu lated to be greater than the EC 25



### .
Incorporating the new endpoints in to the assessment, the resultant RQs are higher, now resulting in risk concerns for non-listed monocots (turf, soil injection/ba sal drench, and potted ornamental drench) in addition to the risk concerns identified in the original assessment. No risk concerns were identified for any of the seed treatme nts (see Appendix A for RQs, Table 6). Consequently, there is the potential for direct effects to listed and non-listed dicots and listed monocots for the turf, soil injection/ basal drench, potted ornamental spray, and potted ornamental drenches. In addition, the re are potential direct risk concerns for nonlisted monocots for the turf, soil injection/ basal drench, and potted ornamental drench

uses.

Acute risk to terrestrial invertebrates The original Registration Review risk assessmen t concluded that there were no potential direct risk concerns for listed and non-lis ted terrestrial invertebrates. The conclusions were based upon triticonazole (LD 50 

### >24 μg ai/bee), which was used as a surrogate for paclobutrazol. A newly evaluated honeybee acute or al and contact toxicity study (MRID 49300407) yielded less sensitive LD 50 

### s of >237 μg ai/bee (oral) a nd >235 μg ai/bee (contact). Consequently, the conclusions from the original Registration Review risk assessment are unchanged. No direct risk concerns are expected for listed a nd non-listed terrestrial invertebrates for any of the uses.

Risk to aquatic vascular plants The original Registration Review risk assessmen t concluded that there were potential risk concerns for non-listed aquatic vascular plants fr om the turf and ornamental drench uses. The newly evaluated study yielded an endpoint (EC 50 

### = 4.61 μg ai/L) that is lower than the endpoint generated by the 5 th 

### percentile approach (EC 50 

### = 8 μg ai/L). Using the new EC 50 

### endpoint, the RQs are higher, but the risk pi cture does not change. In addition, the new study reported a NOAEC of 1.65 μg ai/L, which was used to calc ulate RQs for listed aquatic vascular plant species (see Appendix A for RQs, Table 5). All of the scenarios exceeded the LOC for listed aquatic vascular plants.

In addition, Syngenta was concerne d that the toxicity informati on from the open literature on watermilfoil and hydrilla was limited in its scope. EFED agrees; the open literature information was only used to qualitatively char acterize risks to aquatic monocot s and dicots, but was not used to calculate RQs.

The conclusions from the origin al Registration Review risk assessment are unchanged for non-listed species, with the exception that th e RQs are higher. There are potential direct

### 5 risk concerns for listed and non-listed aquati c vascular plants for the turf and ornamental drench uses.

Risk to aquatic non-vascular plants The endpoints from the newly submitted studies for blue-green algae (EC 50 

### > 25 mg ai/L) (MRID 49300401) and green algae (EC 50 

### = 6.4 mg ai/L) (MRID 49300402) were lower than the paclobutrazol endpoint used in the risk assessment (green algae EC 50 

### = 40.8 mg ai/L). New RQs were calculated using the most sensitive endpoi nt (6.4 mg ai/L); although the RQs are higher, they do not exceed the non-listed species LOC (see Appendix A for RQs, Table 5). Consequently, the conclusions from the original Registration Review risk assessment are unchanged for non-listed speci es (there are currently no list ed species of aquatic nonvascular plants). Potential risk concerns fo r non-listed aquatic non-vascular plant species are unlikely.

Acute risk to birds Syngenta indicated that mallard duck and bobwhite quail data could be used in place of acute oral passerine data to assess risk to these avian species. The original Registration Review risk assessment adopted this approach and concluded th at there were no potential risk concerns for acute exposures to birds. This conclusion remains unchanged. An acute oral study with a passerine species will remain a data gap, in acco rdance with the data requirements in the Code of Federal Regulations.

Syngenta Comment Syngenta indicated that further refinements are needed beyond the simple deterministic screening-level asse ssment methods that were used in the Registration Review risk assessment. If risk concerns are identifi ed, further information such as community-level effects data, environmental fate and exposure data, monitoring data, geospatial location and proximity data, and species biology data can be in corporated into the assessment . Refined modeling techniques and probabilistic methods can be employed to more accurately characterize the risk.

Specifically, Syngenta recommended that the aquatic exposure numbers could be further refined by predicting exposure concentrations over time and space that are specific to listed species and their habitats, and by distinguishing flowing wate r from static water bodies, as outlined in the National Academy of Sciences re port. For terrestrial plants, Syngenta suggests that Pesticide Root Zone Model (PRZM) output be used to generate RQs for runoff exposures.

EFED Response EFED agrees that further refinements are neede d, particularly for the endangered species portion of the assessment. In conjunction with the Nation al Marine Fisheries Service and the U.S. Fish and Wildlife Service, EPA is developing a suite of tools and a process to more realistically assess risk to listed species. Many of the techniques, tools, and data referenced in Syngenta’s comment are under consideration.

Regarding the suggested refinements for assessing ri sks to terrestrial plants from runoff, EFED is currently developing a model based on PRZM out put for terrestrial plants; however, until the

### 6 model has been fully vetted and approved, TerrPlant will be used as a Tier 1 model for screening risks to plants.

Syngenta Comment Syngenta indicated than an acceptable bioaccu mulation study is available, Study RJ 0321B PP333: Accumulation in Bluegill Sunfish in a Flow-Through System, D. Riley (10/21/83). Of particular note, bluegill sunfish were exposed to 14 

### C triazole labelled PP333 in a flow-through system (~0.5 mg/L). After exposure, fish were transferred to uncontaminated flowing water for 14 days (depuration). During the exposure peri od, the maximum concentration in whole fish, muscle, and viscera were 23.2, 10.7, and 131.4 mg/ kg wet weight respectively which is equivalent to bioconcentration factors of 44, 20, and 248 respectively. There was no significant increase in 14 

### C residues after 3 days of exposure. During the depuration period, the 14 

### C levels fell rapidly and returned to backgroun d levels in all tissues in 7 days.

EFED Response The study (RJ 0321B) author’s conclusion that 14 

### C residues in fish tissue had plateaued was contradicted by the data provided in Table 4 a nd Figure 3 of the submitted study and captured in the Data Evaluation Record. The maximum biocon centration factor in various tissues is not reliable because the study was terminated befo re it was certain that the concentration of 14 

### C residues reached a platea u in the fish tissues.

Syngenta Comment With respect to drift, EPA assesses potentia l drift onto non-target areas using the AgDRIFT model. Tier 1 modelling with AgDRIFT produces a highly conservative estimation of spray drift deposition fractions using default and generic as sumptions that can be refined using realistic model adjustments and alternatives ( e.g., evaporation rate, boom hei ght, droplet size, use of the 50th centile deposition data). Th e only inputs available to the us er in Tier 1 AgDRIFT are boom height, data percentile and dropl et size distribution. No further information about the spray material, equipment or climate conditions is c onsidered. To improve understanding of factors influencing drift, two higher tiered models are proposed; REGDISP for ground application and AGDISP for aerial application. The existing aerial application models take a ‘mechanistic’ approach with consideration of physical and chemical properties wh ile the current ground application models use empirical data (deposition data) and representative curve fits. Accuracy of those drift model performances relies on how well a model predicts up per centile of a biased data set.

EFED Response While EFED has evaluated the spray drift deposition data submitted by Crop Life America ( i.e., REGDISP), issues with the completeness of data prevent EFED from using the information for quantitative purposes. EFED is in the process of evaluating all spray drift data that have been submitted to the Agency and developing a policy for the use of existing and future deposition data in the conduct of its assessments. Until th is policy has been formalized and approved by management, EFED will continue to use methods developed in its Guidance on Modeling Offsite Deposition of Pesticides Via Spray Drift for Ecological and Drinking Water Assessments document in the quantitative assessment of spray drift, while using supplemental data submitted to the Agency for characterization purposes. The only exception woul d be for spray drift

### 7 deposition data, generated specifically for th e active ingredient/for mulated product being assessed. Such data could be used for quantita tive purposes, if found to be acceptable to the Agency.

Syngenta Comment There were a number of minor errors identified in the Registration Revi ew risk assessment. They usually consisted of typos, di fferences in species names, slig ht variations in environmental fate parameters, and other similar issues.

EFED Response EFED appreciates Syngenta’s careful review of th e risk assessment and ag rees that the following errors should be corrected and incorpor ated into future risk assessments:

 Change the chronic early lif e stage species from rainbow trout to fathead minnow.

 Table 5 and Table 6 have been revised (s ee Appendix A) to incorporate Syngenta’s comments related to fate properties.

 Table 7 has been revised to incorporate Syngenta’s comments on model inputs (see Appendix A). All future modeling exercises will be performed with the revised input values listed in the table in conjunction with current EFED guidance and models.

 Data used in generating half- lives for the total to xic residues (TTR) of paclobutrazol were included in the revised Appendix B. The half- life of Pappelacker soil was also modified (see Appendix B).

 The field study subsection of the “Environmen tal Fate and Transport” section has been revised to incorporate Syngenta’s comments and the mobility of paclobutrazol based on MRID 155854 (see Appendix B). The following fi eld dissipation study citations will be incorporated into the fate data bibliography.

146597 Pearson, F.J. (1985) PP333 ketone residue dissipation in U.S. soils. Report –Series TMU1760/B. Unpublished study prepared by IC I Americas Inc., Goldsboro, NC, and Analytical biochemistry Laboratories, Columbia, MO; and submitted by ICI Americas Inc., Goldsboro, NC. 155854 Hendley, P.; Francis, P. (1986) Paclobut razol: Short Term Dissipation and Movement following a Broadcast Spray: TMU1953. Unpub lished study prepared by ICI Americas, Inc.

### 8 References

USEPA. 2013. Registration revi ew – ecological risk assessment and effects determination of paclobutrazol. Environmental Fate and Eff ects Division, Office of Pesticide Programs, United States Environmental Protection Agency.

USEPA. 2014. Review of nine ecotoxicity st udies on ecological effects of paclobutrazol. Environmental Fate and Eff ects Division, Office of Pesticide Programs, United States Environmental Protection Agency.

### 9 

# Appendix A

Tables 1 through 4 summarize the overall risk conclusions for listed and non-listed species. Tables 5 and 6 report revised RQs for a number of aquatic taxa and terr estrial plants, based on newly submitted toxicity data.

Table 1. Revised summary table for potentia l risks to non-listed and listed species associated with direct or indirect effects from paclobutrazol (changes from the original assessment are in bold)

Taxonomic Group Effects Endpoint 1 Direct Effects Indirect Effects from Direct Effects to: 1 Non-listed Listed

Aquatic vascular plants Measures of biomass – EC 50 and NOAEC ( Lemna spp.) Yes May Affect/Likely to Adversely Affect Terrestrial plants

Aquatic nonvascular plants Non-vascular plant –EC 50 (green algae) No; RQs<LOC No Effect; RQs<LOC Currently no listed non-vascular plants

Terrestrial plants - dicots Measures of biomassVegetative vigor EC 25 and NOAEC (tomato) Seedling emergence EC 25 and EC 05 (soybean) Yes May Affect/Likely to Adversely Affect Mammals, birds, terrestrial invertebrates Terrestrial plants -
monocots Measures of biomassVegetative vigor EC 25 (nondefinitive) and NOAEC (corn, onion, ryegrass, wheat) Seedling emergence EC 25 NOAEC (ryegrass) Yes May Affect/Likely to Adversely Affect

Freshwater fish/amphibians Acute: Mortality- LC 50 (grass carp) Mortality – LC 50 (Asiatic toad) No; RQs<LOC No Effect; RQs<LOC Terrestrial invert ebrates, aquatic invertebrates, terrestrial and aquatic plants Chronic: Chronic early life- stage-NOAEC (rainbow trout) Yes May Affect/Likely to Adversely Affect

Estuarine/marine fish Acute: Mortality -LC 50 (sheepshead minnow) (surrogate data) No; RQs<LOC May Affect/Likely to Adversely Affect Terrestrial and aquatic plants, terrestrial invertebrates, birds and/or mammals Chronic: Early-life stage NOAEC (sheepshead minnow) (surrogate data) Yes May Affect/Likely to Adversely Affect

Freshwater invertebrates Acute: Mortality- EC 50 ( D.magna ) Mortality- LC 50 (Chinese mystery snail) No; RQs<LOC May Affect/Likely to Adversely Affect; No Effect (freshwater mollusks only) Terrestrial and aquatic plants

Chronic: Growth and Reproduction- NOAEC ( D.
magna ) (surrogate data) Yes May Affect/Likely to Adversely Affect Estuarine/marine invertebrates Acute: EC 50 (Eastern oyster and mysid shrimp) (surrogate data) No; RQs<LOC No Effect Terrestrial and aquatic plants

### 10 Taxonomic Group Effects Endpoint 1 Direct Effects Indirect Effects from Direct Effects to: 1 Non-listed Listed
Chronic: chronic toxicity NOAEC (mysid shrimp) (surrogate data) Yes May Affect/Likely to Adversely Affect

Mammals Acute: Oral LD 50 (rat) Yes May Affect, Likely to Adversely Affect; Terrestrial invertebrates, birds, reptiles, land-phase amphibians; terrestrial plants Chronic: Growth, survival, and reproduction - Multi-gen rat study Yes May Affect, Likely to Adversely Affect

Birds (surrogate forreptiles and landphase amphibians) Acute: Oral LD 50 (mallard duck) Acute: Dietary LC 50 (bobwhite quail) No; RQs<LOC No; RQs<LOC Terrestrial invertebrates, mammals, terrestrial plants Chronic: Growth, survival, and reproduction- (bobwhite quail) Chronic dietary - Yes May Affect, Likely to Adversely Affect Terrestrial invertebrates Acute: Contact and oral LD 50 (honeybee) No No Terrestrial plants

1 Direct effects to species may result in indirect effects to other species by changing availability of prey and modification to habitat. 

### Table 2. Revised summary of potential direct effects to listed and non-listed terrestrial organisms from exposure to paclobutrazol 1 

### (changes from the original assessment are in bold) Paclobutrazol Listed Terrestrial Sp ecies Non-listed Terrestrial Species
Birds 2 Mammals Plants Inverts. Birds 2 Mammals Plants Inverts.
Acute Chronic Acute Chronic Acute Chronic Acute Chronic

Turf N N Y (S,M) Y (S,M,L) Y N N N N Y (S.M.L) Y N

Potted ornamental
spray N N N Y (S,M,L) N N N N N Y (S,M,L) Y N

Tree injection N N N Y (S,M,L) N/A N N N N Y (S,M,L) N/A N

Soil injection/ basal drench N Y Y (S,M, L) Y (S,M,L) Y N N Y N Y (S,M,L) Y N

Potted ornamental drench N N N Y (S,M,L) Y N N N N Y (S,M,L) Y N

Tomato seed
treatment N N N N N N N N N N N N

Pepper seed
treatment N N N N N N N N N N N N

Cucurbit seed
treatment N N N N N N N N N N N N

### 11 Paclobutrazol Listed Terrestrial Sp ecies Non-listed Terrestrial Species
Birds 2 Mammals Plants Inverts. Birds 2 Mammals Plants Inverts.
Acute Chronic Acute Chronic Acute Chronic Acute Chronic

Broccoli seed
treatment N N N N N N N N N N N N

Cauliflower seed
treatment N N N N N N N N N N N N

Cabbage seed
treatment N N N N N N N N N N N N

1 Y= Potential direct effects (RQ ≥ LOC); N = Potential direct effects not expected (RQ < LOC); N/A = not available (incomplete exposure pathway, thus it was not anal yzed); S, M or L indicate wh ich size class is potentially affected; S = small bird (20 g) or mammal (15 g); M = medium bird (100 g) or mammal (35 g); L = large bird (1000 g) or mammal (1000 g). For mammals, ch ronic size classes are for dose-based exposure only. Dietary-based acute and chronic exposure for birds and mammals is not evaluated using body weights. RQ values were determined for these specific weights only, therefore, it is expected that potential direct effects may exist between two size classes in which the lower size class exceeded th e LOC but the next size class did not. Therefore, for example, if small birds (20 g) exceeded the LOC but medium birds (100 g) did not, th en potential direct effects may exist for all birds less than 100 g at any life stage until can be shown otherwise.

2 Birds are surrogates for terrestrial re ptiles and terrestrial-phase amphibians.



### Table 3. Revised summary of potential direct effects to listed aquatic organisms from exposure to paclobutrazol 1 

### (changes from the original assessment are in bold)

Paclobutrazol
Freshwater Fish Estuarine/Marine Fish Vascular Aquatic Plants Freshwater Invertebrates Estuarine/Marine Invertebrates Acute Chronic Acute Chronic Acute Chronic Acute Chronic

Turf N Y N Y Y Y N N Y

Potted ornamental drench N Y Y Y Y Y Y N Y

1 Y= Potential direct effects; N = Potential direct effects not expected



### Table 4. Revised summary of potential direct effects to non-listed aquatic organisms from exposure to paclobutrazol 1 

### (changes from the origin al assessment are in bold)
Paclobutrazol
Freshwater Fish Estuarine/Marine Fish Vascular Aquatic Plants Non-vascular Aquatic Plants Freshwater Invertebrates Estuarine/Marine Invertebrates Acute Chronic Acute Chronic Acute Chronic Acute Chronic

Turf N Y N Y Y Y N N N Y

Potted ornamental drench N Y N Y Y Y Y Y N Y

### 12 1 Y= Potential direct effects; N = Potential direct effects not expected



### Table 5. Revised aquatic RQs for select groups Aquatic Exposure (model) Use Scenario (modeled rate) Freshwater Invertebrate Chronic RQ (21-Day EEC/ NOAEC) NOAEC = 320 μg ai/L Non-Listed Aquatic Vascular Plant RQ (Peak EEC/EC 50 ) EC 50 = 4.61 μg ai/L Listed Aquatic Vascular Plant RQ (Peak EEC/ NOAEC) NOAEC = 1.65 μg ai/L Non-ListedAquatic NonVascular Plant RQ (Peak EEC/EC 50 ) EC 50 = 6400 μg ai/L

Total Toxic Residue (Paclobutrazol plus CGA 149907and NOA 457654) 1,2

Surface Water (Tier 2 PRZM/ EXAMS) Ornamentals: CA Ornamentals STD FL Ornamentals STD MI Ornamentals STD NJ Ornamentals STD OR Ornamentals STD TN Ornamentals STD(1 app. X 2.5 lb ai/A) <0.01-0.04 0.46 -1.04*** 0.62-0.94 0.45-0.80 0.16-0.32 0.45-0.80 <0.01- 2.8*** 33-72*** 43-65*** 31-54*** 11-22*** 32-56*** 0.02- 7.9*** 88-202*** 120-182*** 87-150*** 32-62*** 88-156*** <0.01-<0.01 0.02-0.05 0.03-0.05 0.02-0.04 0.01-0.02 0.02-0.04

Ornamentals: CA Ornamentals STD FL Ornamentals STD MI Ornamentals STD NJ Ornamentals STD OR Ornamentals STD TN Ornamentals STD (1 app. X 0.56 lb ai/A) <0.01-<0.01 0.10-0.23 0.14-0.21 0.10-0.18 0.04-0.07 0.10-0.18 <0.01-0.61 6.9-16*** 9.5-15*** 6.9-12*** 2.6-5.0*** 6.9-12*** <0.01- 1.7*** 19-45*** 27-41*** 19-35*** 7.3-14*** 19-35*** <0.01-<0.01 0.01-0.01 0.01-0.01 0.01-0.01 <0.01-<0.01 0.01-0.01

Turf: FL Turf STD PA Turf STD (3 app. [2 app. X 0.75 lb and 1 app. X 0.5 lb] ai/A) 0.07-0.12 0.11-0.21 4.6-8.5*** 7.6-15*** 13-24*** 21-41*** <0.01-0.01 0.01-0.01

Parent Paclobutrazol Only 3
FL Ornamentals STD (1 app. X 2.5 lb ai/A) 0.58 41*** 113*** 0.03

PA Turf STD (3 app. [2 app. X 0.75 and 1 app. X 0.5 lb] ai/A 0.16 11*** 31*** 0.01

1 Multiple months were modeled; the range of RQs represents the highest and lowest EECs.

2 Total toxic residue simulation includes two metabolites (CGA 149907and NOA 457654 )

3 Exposure of parent only based on highest exposure scenarios (FL Ornamentals STD and PA Turf STD) identified from total toxic residue simulations. ***Exceeds LOC (1)

### 13 Table 6. Revised terrestrial plant RQs, based on new seedling emergence data (MRID 49300408) Plant Type Listed Status Dry Semi-Aquatic Spray Drift Turf (1 app at 0.75 lb ai/A) Monocot Non-listed 0.27 1.91*** <0.1 Monocot Listed 2.30*** 16.07*** 0.77 Dicot Non-listed 3.57*** 24.96*** 1.19*** Dicot Listed 3.97*** 27.78*** 1.32*** Potted ornamental spray (1 app at 0.26 lb ai/A) Monocot Non-listed <0.1 0.66 <0.1 Monocot Listed 0.80 5.57*** 0.27 Dicot Non-listed 1.24*** 8.65*** 0.41 Dicot Listed 1.38*** 9.63*** 0.46 Soil injection/basal drench (1 app at 1.9 lb ai/A) Monocot Non-listed 0.69 4.84*** N/A Monocot Listed 5.82*** 40.71*** N/A Dicot Non-listed 9.03*** 63.23*** N/A Dicot Listed 10.05*** 70.37*** N/A Potted ornamental drench (1 app at 6.1 lb ai/A) Monocot Non-listed 2.22*** 15.55*** N/A Monocot Listed 18.67*** 130.71*** N/A Dicot Non-listed 29.00*** 203.01*** N/A Dicot Listed 32.28*** 225.93*** N/A Tomato seed treatment (1 app at 0.0004 lb ai/A) Monocot Non-listed <0.1 <0.1 N/A Monocot Listed <0.1 <0.1 N/A Dicot Non-listed <0.1 <0.1 N/A Dicot Listed <0.1 <0.1 N/A Pepper seed treatment (1 app at 0.00079 lb ai/A) Monocot Non-listed <0.1 <0.1 N/A Monocot Listed <0.1 <0.1 N/A Dicot Non-listed <0.1 <0.1 N/A Dicot Listed <0.1 <0.1 N/A Cucurbit seed treatment (1 app at 0.00029 lb ai/A) Monocot Non-listed <0.1 <0.1 N/A Monocot Listed <0.1 <0.1 N/A Dicot Non-listed <0.1 <0.1 N/A Dicot Listed <0.1 <0.1 N/A Broccoli seed treatment (1 app at 0.000096 lb ai/) Monocot Non-listed <0.1 <0.1 N/A Monocot Listed <0.1 <0.1 N/A Dicot Non-listed <0.1 <0.1 N/A Dicot Listed <0.1 <0.1 N/A

### 14 Plant Type Listed Status Dry Semi-Aquatic Spray Drift Cauliflower seed treatment (1 app at 0.000064 lb ai/A) Monocot Non-listed <0.1 <0.1 N/A Monocot Listed <0.1 <0.1 N/A Dicot Non-listed <0.1 <0.1 N/A Dicot Listed <0.1 <0.1 N/A Cabbage seed treatment (1 app at 0.00012 lb ai/A) Monocot Non-listed <0.1 <0.1 N/A Monocot Listed <0.1 <0.1 N/A Dicot Non-listed <0.1 <0.1 N/A Dicot Listed <0.1 <0.1 N/A N/A – not applicable because spra y drift does not occur with seed treatment/drench/soil injection

uses *** – exceeds the LOC of 1

### 15 Revised Table 5. Summary of physical, chem ical, and fate properties of paclobutrazol
Parameter Value Reference Comments

Chemical Paclobutrazol MRID 456625-01 --- Chemical Class Triazole --- CAS No. 76738-62-0 --- Empirical Formula C 15 H 20 ClN 3 O MRID 456625-01 --- IUPAC 

### ( 2 RS, 3 RS )-1-(4- chlorophenyl)-4 ,4-dimethyl2-(1 H -1,2,4-triazol-1- yl)pentan-3-ol MRID 456625-01

---

CAS Name ( α R
, β R )- rel

- β -[(4- chlorophenyl)methyl]- α

- (1,1-dimethylethyl)-1 H

1,2,4-triazole-1-ethanol MRID 456625-01

---

Structure MRID 456625-01

---

Selected Physical/Chemical Parameters Molecular mass 293.8 g/mol MRID 46180501

--- Solubility (20.0°C) 2.29 x 10 -2 (water) 5.67 g/L (xylene) 0.166 g/L (n-Heptane) 72.4 g/L (Acetone) 45.1 g/L (Ethyl Acetate) 29.4 g /L (n-Octanol) 115 g/L (methanol) 51.9 g/l (1,2- Dichloromethane) MRID 468342-02

---

Vapor pressure (20.0°C) 1.9 x 10 -6 Pa (1.43 x 10 -8 mm Hg) MRID 468342-02

--- Henry’s law constant (20°C) 2.36 x 10 -10 atm M 3 mol -1 ) MRID 468342-02

--- Octanol-water partition coefficient (LogK O W ) (25°C) 3.11 MRID 468342-02

---

Persistence

Hydrolysis pH 4: stable pH 7: stable pH 9: stable MRID 00132698

---

Aqueous Photolysis (t 1⁄2 ) Stable MRID 00132699

--- Soil Photolysis (t 1⁄2 ) Stable MRID 40685002 After 33 days paclobutrazol decrease to 86.4 % of applied radioactivity
Aerobic Soil Metabolism (t 1⁄2 ) Sandy clay loam 19 (21 and 17) months 1,2 [47 (58 and 36) months] 3 MRID 40685003 Major metabolite (CGA 149907 ( ≈ 18.7%)

### 16 Parameter Value Reference Comments

Sandy clay loam 301 days [385 days] MRID 47338504 Supplemental

No major metabolites detected above 10%.
Sandy loam 26 days 4 [38.9 days] Major metabolites NOA 457654(25.1%) CGA 149907(13.3%) Sandy loam 25 days 4 [36 days] Major metabolites NOA 457654 (20.5%) CGA 149907(26.3%)

Anaerobic Soil Metabolism No data Anaerobic Aquatic Metabolism (t 1⁄2 ) Stable MRID 40685003 After a year of incubation, paclobutrazol decrease
to ≤ 79% of applied radioactivity Major transformation product: (CGA 149907 ( ≈ 16.8%)

Aerobic Aquatic Metabolism No data --

Mobility
Soil Partition Coefficient Adsorption K d (mL/g) 9.5 (Clay loam) 10.2 (Sandy Clay loam) 7.6 (Silty clay loam) 21.3 (Silt loam) 5 4.1 (sandy loam) 2.4 (loamy sand) 5.8 (Silty clay) 1.4 (Sand) 3.8 (Silt loam) MRID 40685005 There was no significant correlation (r 2 = 0.12) between K d and % organic carbon.

Soil Partition Coefficient Desorption K des (mL/g) 6 14.8 (Clay loam) 17.4 (Sandy Clay loam) 13.5 (Silty clay loam) 33.4 (Silt loam) 5 8.6 (sandy loam) 4.9 (loamy sand) 9.2 (Silty clay) 2.7 (Sand) 5.8 (Silt loam) MRID 40685005

---

### 17 Parameter Value Reference Comments Adsorption K d (mL/g) 1.7 (Sandy loam) 5 0.8 (Sandy loam) 2.7 (Silty clay loam) 2.1 (Clay loam) Desorption K des (mL/g) 6 10.9 (Sandy loam) 5 3.81 (Sandy loam) 14.2 (Silty clay loam) 11.7 (Clay loam) MRID 47338503 Supplemental

Leaching Aged methine 14 C- labeled paclobutrazol residues were relatively immobile

Aged trizole 14 C-labeled paclobutrazol residues were mobile in loamy sand and clay loam soils and low mobility in sands and sandy loam soils MRID 40685004 Major transformation product CGA 149907 ( ≈ 12.6%)

Field Dissipation Terrestrial Field Dissipation (t 1⁄2 ) 450 to 973 days (CA, WV, FL) MRID 40685006- 406850012 Supplemental Major transformation product CGA 149907

88 days (CA) 133 days (NY) MRID 47338505 Supplemental Major transformation product - CGA 149907 (40%)
175 to 224 days (MS, NC, IL) MRID 00146597 Supplemental Transformation product CGA 149907

1 Calculated half-lives are based on 14 C labeled triazole and methane of paclobutrazol

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 B.

4 High Soil pH ( ≥ 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

### 18 Table 6. Selected physical, chemic al, and fate properties of NOA-457654

Parameter Value Reference Comments

Chemical NOA-457654 MRID 473385-01

--- Chemical Class Triazole MRID 473385-01

--- CAS No. 122442-66-4 MRID 473385-01

--- CAS Name 4H-1,2,4-Triazol-3-ol MRID 473385-01

--- IUPAC Name 1H-1,2,4-Triazol-3-ol. MRID 473385-01

--- Synonyms Hydroxytriazole, Triazole hydroxy, J7140/45/2 MRID 473385-01

--- Empirical Formula C 2 H 3 N 3 O MRID 473385-01

--- Molecular Weight 85.07 g/mole MRID 473385-01

---

Aerobic Soil Metabolism (t 1⁄2 ) Sandy clay loam soil 8.2 days MRID 473385-01 No major degradate except CO 2 Silt loam soil 3.8 days Loamy sand soil 10.8 days Sandy loam soil 3.4 days

Soil Partition Coefficient Adsorption K ads (mL/g) 0.13 (Loamy Sand) 0.25 (Loam) 0.19 (Sandy loam) 0.30 (Sandy loam) Adsorption K OC (mL/g) 8.9 (Loamy Sand) 10.7 (Loam) 8.1 (Sandy loam) 13.0 (Sandy loam) MRID 47338502 Calculated r 2 value for K ads vs. % organic carbon content was 0.93and K ads vs. % clay was 0.8

Desorption K des (mL/g) 1.0 (Loamy Sand) 1.7 (Loam) 1.5 (Sandy loam) 1.8 (Sandy loam) Adsorption K OC (mL/g) 72,7 (Loamy Sand) 74.6 (Loam) 72.0 (Sandy loam) 66.5 (Sandy loam) ---

### 19 Revised Table 7. PRZM-EXAMS input parameter values for paclobutrazol

Parameter Value Source Comments

Application Rate (lb ai/A) 2.50 lb ai/A (based on 59% retention of parent in soil

column) 1

0.55 lbs/A (based on

91% retention of parent in soil column

2.0 lbs/A for turf Memo from the Biological and Economic Analysis Division (BEAD) (US EPA, 2011)

Product Label Maximum application rate was estimated based on information provided by BEAD

(US EPA 2011) and adjusted with the retention of paclobutrazol in a soil column leaching study (MRID 40685004)

EPA Reg No. 100-1079

Number of Applications 1 (Nursery) 3 (Turf) Product Label EPA Reg No. 100-1079
Application frequency (days) Drench –None Foliar-14 Product Label EPA Reg No. 100-1079

Scenarios Ornamentals CA Ornamentals STD FL Ornamentals STD MI Ornamentals STD NJ Ornamentals STD OR Ornamentals STD TN Ornamentals STD T urf FL Turf STD PA Turf STD Selected ornamental scenarios were chosen to represent various regions of the Continental United States

Application Date Ornamentals–01 (Mar –Sept) 2 Turf

FL Turf -15 (FebSept) 3PA Turf 15 (AprSept) 4 ---

Spray Drift

Fraction Drench - 0 Ground foliar-0.1 Model input guidance (US EPA, 2010) Application Efficiency Drench- 1.0 Ground Foliar -0.99

### 20 Parameter Value Source Comments

Soil Partitioning Coefficient (K oc ml/g) 144.0 (clay loam) 338.9 (sandy clay loam) 232.8 (silty clay loam) 233.3 (sandy loam) 262.9 (loamy sand)

413.8 (silty clay)

204.0 (sand) 429.9 (silt loam) 263.0 (sandy loam)

106.0 (silty clay loam) 40.4 (clay loam) 242.6 (Mean value) 5 MRIDs 4188113 and 47338503 Mean value: 242.6

Aerobic Soil Metabolism t 1/2 (d) 999.2 (Total residue) 6 444.2 (Parent) 6 MRIDs 40685003 and 47338504 90 th percentile upper confidence bound on the mean.

Method of Application Drench Ground Paclobutrazol labels ---
Solubility in Water (mg/L) 22.9 MRID 468342-02 ---

Aerobic Aquatic Metabolism t 1/2 (days) 1998.4 (Total Residue) 888.4 (Parent) 2X of Aerobic soil metabolism half-life Model input guidance (US EPA, 2010)

Hydrolysis t 1/2 0 MRID 00132698 Stable to hydrolysis

Aquatic Photolysis t 1/2 (days) 0 MRID 0013299 Stable to aquatic photolysis

1 Example of application rate calculation: 6.1 lbs/A- (6.1lbs/A*0.59) Where 6.1 lbs/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 pa rent (paclobutrazol) in column leaching study (MRID 40685004)

2 In absence of application date from the label, model simulations were performed from March to September with date of application first of the month

3 In absence of application date in label, model simulations were performed from February to September with date of application 15 th of the month

4 In absence of application date in label, model simulati ons were performed from April to September with date of application 15 th of the month

5 Coefficients of variations (CV) were lower for organi c carbon normalized solid-wat er distribution coefficients (K OC ; CV=50%) as compared to solid-w ater distribution coefficients (K d ; CV=73%). Therefore, and consistent with the input parameter guidance, the mean K d of 4.5 L/Kg will be revised with mean K oc of 142.6 L/Kg to estimate paclobutrazol concentrations for future aquatic modeling.

6 Some of the estimated half-lives (Table 5) are beyond the study period and can be considered as stable. However, to use 90 th percentile of the degradation rate in the mode ling, all estimated half-lives were considered

### 21 

# Revised A 

# ppendix B – Half-Life Calculat ions of Parent and Total Toxic Residues

Aerobic Soil Metabolism

Chemical: Paclobutrazol MRID: 40685003 PC Code: 125601 Guideline: 835.4100

Mass Balance- 18 Acres loam

Posttreatment Paclobutrazol CGA 149907 Total Toxic Residue Months % of Applied
Triazole 14 C Label 0 87.5 0.1 87.6 1 87.0 5.2 92.2 4 78.7 10.1 88.8 8 66.9 14.1 81.0 12 60.0 18.7 78.7
Methane 14 C Label 0 96.0 0.1 96.1 1 88.0 3.6 91.6 4 74.8 9.8 84.6 8 67.9 12.2 80.1 12 57.9 17.2 75.1

Chemical: Paclobutrazol MRID: 47338504 PC Code: 125601 Guideline: 835.4100

Mass Balance- 18 Acres Sandy clay loam

Posttreatment Paclobutrazol CGA 149907 Total Toxic Residue Days % of Applied

0 86.6 1.0 87.6 0 86.2 1.0 87.2 7 88.8 3.0 91.8 7 84.1 3.1 87.2 22 87.8 4.0 91.8 22 90.5 3.6 94.1

### 22 35 68.9 4.1 73.0 35 72.5 3.9 76.4 50 74.4 3.1 77.5 50 64.8 5.0 69.8 70 69.0 3.7 72.7 70 63.3 3.4 66.7 91 73.3 4.1 77.4 91 83.3 4.2 87.5 120 64.9 4.5 69.4 120 63.2 3.8 67.0

Mass Balance- Pappelacker Sandy loam

Posttreatment Paclobutrazol CGA 149907 Total Toxic Residue Days % of Applied

0 90.1 0.0 90.1 0 80.4 0.0 80.4 7 81.9 9.1 91.0 7 83.1 8.6 91.7 22 58.9 24.8 83.7 22 60.3 24.0 84.3 35 36.0 26.6 62.6 35 36.5 25.9 62.4 50 21.6 24.5 46.1 50 22.4 27.3 49.7 70 11.8 20.9 32.7 70 12.7 23.2 35.9 91 7.8 13.6 21.4 91 6.2 11.1 17.3 120 3.8 9.1 12.9 120 3.7 6.9 10.6

Mass Balance- Gartenacker Sandy loam

Posttreatment Paclobutrazol CGA 149907 Total Toxic Residue Days % of Applied 0 85 0 85 0 93.4 0 93.4 7 85.4 5.7 91.1 7 86.2 5.5 91.7 22 67.3 13.5 80.8 22 66.5 13.1 84.9 35 41.5 12.3 53.8 35 41.2 12.6 53.8 50 30.5 11.8 42.3 50 26.1 11.9 38 70 16.1 10.7 26.8

### 23 70 17.1 11.1 28.2 91 12.9 10.7 23.6 91 9 9.1 18.1 120 3.8 3.7 7.5 120 3.9 6.8 10.7



### Calculations of Half lives

(MRID 40685003) 

## Parent

DT 50 = 21 months

DT 50 = 17 months

### 24 

## Total Toxic Residue

DT 50 = 58 months

DT 50 = 36 months

### 25 

## MRID 47338504

Total Toxic Residue

Half-life = 385 days

### 26 Dissipation of paclobutrazol in Gartenacker sandy loam soil system (0-120 days) 

### 5.00**-,------------------ "'f!"="-=A-f)'l-q.,!l-lr-F--;H;~**  R

2 = 0.9676 

# j 4.00**-1-------= "'"'-<!1~** **-------------------** ii Half life 

## = 36 days**~** 

### 3.00**~** 

### 2.00**-1---------------------- ~~** **--­** 

## '*-



# - z 1.00 +------------------------------------------------


## _. 0.00 -1------,-----,-----,-----,-----,------,-----, 

### 0 

### 20 40 60 

### 80 

### 100 120 140 Days

### 27 Revised section for field studies

c. Field Studies

Paclobutrazol residues were persistent and mobile in terrestrial field dissipation studies in California, West Virginia, Flor ida, North Carolina, Illinois, and Mississippi (Supplemental MRID 00155854, 40685007, 40685009, 40685010, 40685011, 4068512 and 40685006- and146597). Paclobutrazol residues include paclobutr azol and its ketone metabolite. Half-lives of paclobutrazol residues ranged from 450-973 days for orchard soils in California, West Virginia, and Florida, and 25 weeks to 32 week s in agricultural soils in Mississippi, North Carolina, and Illinois. Although it was characteri zed as mobile in some soils in laboratory studies, no significant movement of paclobutrazol was detected in th e agricultural so ils. In the orchard studies, total paclobutrazo l residues were detected at 0.01 to 1.9 ppm in the deepest soil samples that were collected, depths of 48 inches in the California and Florida and 24 inches in the West Virginia study. Note that these depths are the maximum depths sampled at each study. The CGA149907 metabolite was predominately detect ed in the subsurface soil layers, also at insignificant levels. In addition, there is no evidence of paclobutrazol and its ketone analogue movement was observed in an irrigated turf -covered sandy soil plot (MRID 155854). However, the study was terminated after only 30 days, befo re the pattern of dec line of paclobutrazol was established.