UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, 

### D.C. 20460

MEMORANDUM Date: May 7, 2015 OFFI C E OF C HEMI CA L SA FETY A ND P O L L UTION PRE V ENTION

SUBJECT: Oxadiazon. HED 's Response to Public Comments Received on the Pre liminary Work Plan for Registrati on Review.

P C Code: I0900 I D ecis ion No.: 500417 P etition No.: NA R is k Assess m e n t Type: NA T X R No.: NA MRJD Nos.: NA D P Ba r code: 0425885 Reg is trat io n Nos. : NA Reg ul a t o r y Act io n : Reg istration Review Case No.: 2485 CAS Nos. : 19666-30-9 40CFR : NA FROM: Linnea Hansen , Ph.D. , Biologist

### ~**~)\J-_**



### . Cm! Margarita Co ll antes, M.S., Biologist

### ~J )

- . Risk Assessment Branch II H eal th Effects Division (7509P) THROUGH: Christina Swartz, Branch Chief Risk Assessment Branch II Health Effects Division (7509P) TO : Katherine St. Clair, Chemical Review Manager R i sk Management and Implementation Branch II Pesticide Reevaluation Division (7508P)



### CONCLUSI O NS: HED has responded to comments received from the registrant , Bayer Environmental Science (a division of Bayer CropScience, hereafter referenced as " Bayer" ) , on the Preliminary Work P lan (PWP) for registration rev iew of the herbicide oxad i azon. Ba yer has addressed issues raised by HED during registration review scoping regarding data re quirements to support registration review and particulars of the intended use patterns and parameters. The issues, Bayer comments and HED responses are briefly summarized in the table below. A more detailed response to each comment is provided below under the Discussion section of this memorandum.

Pa ge I of6OPP P reliminarv Work Pl a n Baver Comment HEDComment 1 Rat 28-day inhalation toxic ity For expos ure patterns with HED will review the revised st

ud y is required (OPPTS inha lation MOEs < 1000 , AHETF is inhalation assess m e nt when it is 870.3465) unless r isk from use developing data that Bayer will use submitted. A determination will be patterns with MOEs below I 000 to prepare a revised inha lation made at that time as to the need for can be m itigated expos ure assessment, where data a 28-day inhalation study, if Bayer avai labi l ity meets registration has not already initiat e d one. review timelines. The revised assessment may be u sed to determine if a waiver is su pported. If not, the 28-day inhalation study will be co nducted or expos ures of concern will be addressed admin istrativ ely. 2 Oi slodgeable foliar residue (DFR) A DFR study should not be required A DFR study is required. There is and turf transferable re s idu e (TFR) because post-appI ication contact potential for po st-applicatio n foliar st

udi es are required (O PPTS with ornamentals plants, v in es or contact by nursery workers with 875.2100) trees is unlikely. treated plants, vines or trees. A TTR study should not be required HED concurs that the TTR study i s because the HED polic y of not needed to assess golfers and 12

/ 12/2012 states that the study is golf course maintenance workers automatically wa ived when MOEs using a granular formulatio n . based o n defau lt TTRs**are ~**  I 000. Ba sed on current (2012) Resident ial SOPs for turf and lawn, th e previously s ubmitted TTR studies are acceptable and new TTR data are not needed. However, HED will conduct risk assessments for products labelled for parks and non-residential lawns. HED notes that based on a prel iminary assessment using these studies, there is potential for ri sks of concern for adults and chi ldren from u se of oxad iazon on parks and non-res idential lawns

. 3 C lar ification is reque ste d of the Oxadiazon is not int ende d to be a Based on this information , HED i ntent to allow or re stric t the u se of restricted use pesticide and both will conduct handler exposure oxadiazon on turf and lawn for professional and residen ti al hand ler assessments for residentia l as well re side ntial uses. exposure assessments are required. as occupational exposure scenario s For homeowner handler expos ure , using app ropriate app li cation granular and liquid spray methods and labe l directions. formu lations should be assessed

. 4 Clarification of app li cation Details about applica ti on parameters Bayer has s ubmitted adequate parameters for some product labe ls (e

. g . , application rates, intervals, information regarding ap plication is requested for the quantitative frequency , sites, methods and parameters. It will be considered ri s k assessment

- otherwise equipment, applications per season, in assessment of handler exposure. conservative assumpt ions will be formulat ions , and geograph ic Labels s hould be rev ised as used. limit ations on use) are s ubmitted app ropriate to clarify any with the comments on the appl ication parameter. preliminary work p lan.

P

age 2 of6

### INTRODUCTION: EPA req ues ted publi c comments on the PWP for the Registration Review of Ox ad iazo n (Docket Number E PA-HQ -O PP-2014-0782). Bayer, th e reg ist ran t, reviewed th e document entitl e d
" Oxadiazon Preliminary Work Plan: Registration Review: Initial Docket , D ecember 20 14 " and pro v ided comments, as we ll as re levant information that was req ues ted by the Agency. HED was req uested to respond to the comments that are pertinent to t he human h ealth risk assessment. 

### DISCUSSION: The fo ll owing co mm ents from Bayer on t h e Oxadiazon PWP for Registration Review were received and are add resse d by HED: 

### (1) Anticipated Data Needs, GDLN 870.3465, Rat 28-Day Inhalation Toxicity Study Preliminary Work Plan: A 28

- day inhalation tox ici ty study in the rat was requ ired by the Agency, based o n co n cerns for the potential for portal-of-entry tox i c i ty to the respiratory tract and inhalation margins of exposure (MOEs) for certain use p atterns that were below the leve l of concern (LOC) of 1000. If addi tion al mi ti gatio n meas ures are added by th e r eg i strant for the scenar io s with MOEs of concern, the Agency may waive the inhalat ion study require me nt. This data requ ireme nt was reviewed by the HED Hazard and Sc ience Policy Co mmittee (HASPOC , HED TXR N o. 0057091). Bayer Comme n t: B ayer's response is as fo ll ows:

" Bayer has calcu lated inhalation exposure a nd MOEs based on the unit exposures provided in the March 20 1 3 handlers surrogate guid e . Inhalation MOEs l ess than 1000 have been confirmed for certai n u se patterns s u ch as mixing/loading with the WP form ulation and some of the hand held sp ray app li cations. The scenar io s in which the MO Es are l ess than the 1000 req uired for a waiver of the 2 8-da y inhalation s tud y are scenar io s w hich th e Ag ri cu ltural Handlers Exposure Task Force (AHETF) has recently completed data development or has initiated the data deve l opment phase. Bayer intends to incorp orate the revised inh alation unit exposures into a rev i sed assessment for scenarios where the data are avai l ab le consistent with the reg i stration re - evalu ation timeline and determine if a wai ve r is supported. If use sce n arios remain that have MO Es les s than 1000, Bayer wi ll either comm it to co nduct the 28-day inhalation toxicity st ud y or ad mini strative ly address the use patterns with MO Es less than 1000. " E PA R esponse : The Agency wi ll await submiss ion of the revised inhalation exposure assessme nt from Bayer that w ill be based on d ata now being developed for u se patterns with inh alati on risk that c urrently exceed the level of concern (LOC ) of 1000. T h e need for a 28-day inhalation toxicity study w ill b e determined at that time

. 

### (2) Anticipated D ata Needs, GDLN 870.2100, Dislodgeabl e Foliar Residue and Transferable Residues

Page3o f6Preliminary Work P lan : Dislodgeable foliar residue (DFR) and turf transferable residue (TTR) studies are required for oxadiazon, In general , TTR data are required for al I occupational (e

. g .. sod fanns, golf courses, parks , and rec reation a l areas) or residential turf us es that could result in post

- application exposure to turf. In the absence of chemical-specific TTR data, EPA uses default values. Two TTR st udie s were submitted in support of the oxadiazon RED; however, they were found to be unacceptable due to transfer efficiencies l ess than 1 %. Bayer Comment: Bayer's response is as fo ll ows:

" Based on th e us e patterns of oxadiazon , there is not an anticipation of post application foliar contact with ornamental plants, vines, or trees. Therefore , Bayer does not believe that a dislodgeab l e foliar residue study i s required. Post application turf exposure can occur to golfers and to go lf course maintenance workers. Exposure can occur to either the granular formu lation or the li quid sprays. The Health Effects Division issued a policy notice on 12 December 2012 that provides for an automatic waiver of th e turf transferrab le residue (TTR) study if the margins of exposure (MOEs) based on the default TTRs are 1000 or greater. For the granu l ar formu l ations, Ba yer has estimated the post app li cation expos ure to both golfers and golf course maintenance personnel assuming that the highest TTRs are 0.2% of the 4 lb a.i ./ acre app lication rate or 0.089 μg /cm2. Default tran sfer coefficients and durations of exposure as provided in the 20 12 Residential SOPs were used to calculate the dai l y exposure to golfers. The go lf course maintenance worker transfer coefficient of 3700 cm2/hr and an 8

- hour work day were used to estimate the golf course occupational post app li cation exposure. Based on a dermal NOAEL of 12 mg/kg/ day and a dermal absorption of 9% , the MO Es for golfers aged 6 years or older were 4900 and the MOE for maintenance workers was 3500. Therefore , a granular TTR study is not required. Bayer previo u s l y conducted a TTR study for the liquid spray app lication of oxadiazon using the 50 WP formulation in North Carolina. The TTRs expressed as a percentage of the application rate were 3. 7% for non-irrigate d turf and 2

. 0% for irrigated turf based on the hi ghest TTRs sampled. The results from a study (MRID 44995502) conducted in GA with the wettable so luble powder (WSP) formu l atio n are provided in Tab l e D-17 of the Residential SOPs and were 2.6% of the application rate. Based on the existing liquid spray application TTR data, additional TTR data sho uld not be required as a part of the re-evaluation process." EPA Response: DFR s tud y req uirement for ornamental s: There are several Bayer product labels (Reg Nos. 432

- 893 , 432

- 887 , and 432-886) which spec if y use of oxadiazon in commercial ornamental and conifer nurserie s. There is potential for post application foliar contact with ornamenta l plants, vines , or trees by nur se ry workers as a result of direct spray to so ils and over - the-top applications to ornamentals and conifers. Therefore , the Agency continues to conclude that a dislodgeable foliar residue study is required for oxadiazon.

Page 4 of6

### TT R stud y requirements for turf/lawns/parks : The EPA concurs that a TTR study is not needed fo r assess ing go lfers and go lf co urse maintenance workers using a "granu lar" formulation. Furthermore, based on the refinement s made to the revised transfer coefficients in the 2012 Residential SOPs for turf and lawn, the Agency a lso concurs that the previously subm itted TTR studies (MRID # 449955-0land 449955- 02) are acceptable. S in ce the oxadiazon RED , the s upp orting science and gu id ance for developing transfer coefficie nt s (Tc) and their respective TTR transfer efficiencies has significantly evolved. The previously submitted studies incorporated the use of the modified Ca li fornia roller method wh ich resulted in TTR transfer efficiencies of

- 1- 5% (transfer efficiency = % of the app li cation rate) which correspond to the current transfer coeffic ient s used in the 20 12 Re si d e n tial Turf SOPs. In addition, there are currently seve ral Baye r product labels (Reg. Nos 432- 983, 432-887 and 432-886) formulated as liquids and granules which are registered for use on "parks" and "non

residential lawns "

. The Agency continues to support the decision to perform a dermal postapplication exposure assessment fo r these uses. Based on a preliminary assessment using the above mentioned studies , there is potential fo r risks of concern for adults and chil dren resulting from use of oxadiazon on parks and non-residential lawns. 

### (3) Clarification reque ste d by 

### EPA regarding intention for product u se on residential or home lawns/turf

Preliminarv Work Plan: EPA requested that the registrant clarify whether oxadiazon turf and lawn uses would be restricted use or allowed for residential use by residential handlers. Bayer Comment: Bayer ' s response i s as follows: "Handle r exposure assess ments will be necessary for professiona l ap pli cation by vehicle drawn groundboom s prayers , broadcast spreader s , and by profess ional hand-h e ld spray gun application. 

### In addition, homeowner app lication of the granu lar formu lation or the liquid spray formulations w ill be assessed as the oxadiazon formulat ions are general u se pesticides and are not restricted use pesticides. Bayer anticipates that the handler exposure data deve loped by the Agricultural H and l ers Exposure Task Force , the Outdoor Residential Exposure Task Force , or the data in the Pesticide Handlers Exposure Database will address all handler exposure scenarios and will be based on the versio n of the surrogate handler unit exposure guide available at the time that the assessme nt is conducted. Bayer is a member of both task forces." EPA Response: Based on th e registrant 's intent to i nclude homeowner application of granular and liquid spray formu lations , a residential handler exposure assessment w ill be performed for oxadiazon. 

### (4) C larificati o n r eq u ested by 

### EPA reg a rding application p ara m ete r s as pro v ided o n current produ ct lab el s

Page 5 of6Preli minary Work Plan: Th e EPA stated that certai n labels for oxadiazon products were unclear o n some parameters of app li ca tion , including: s ites of a pplicati o n , fo rmulati o n s, application m etho ds and equipment , maximum application rat es, frequency of application , application intervals and maximum numb er of application s pe r seaso n , and geographi c limitations on u se. B ayer Comment: Bayer provided the following informati o n:

Region "Typicall y oxad iazo n is app li ed in the late winter /early spri ng for pre-emergent cont rol of weeds. Ap pli cations are either made as a s ingle spray application at 3

- 4 lb ai/A o r as a granu l ar with 2 applications at the 2 lb a i / A rate. Granular application s to land scape or nursery plant s are made in the Spring o r Fall. Most applications are in the So utheast United States. 73% of all applications were made in seve n states : FL, NC, GA , SC , TX, TN, and AL. Ti min g of the fir st app li cation d epe nd s on weed seed ge rmination in different geographies of the US (shown below). Interval s between app li cat ion s are mad e 30

- 60 days fo r the sp lit application in the spring (2 lb ai/A). First Aoolication Timinq South F l orida January Southeast US February VA

. OK March Northern US March
- snow melt Further inform ation on the applicat i ons for Bayer Labe l s i s provid ed in the attached pd f ( O xa di azo n EFED Tab le 1 Use Patte rn s Bayer Pre -li m Com men t)." [note: see D ocke t fo r this information]. E PA R esponse: B ayer has provided information on application parameter s as requeste d in th e PWP. The Age ncy will use these parame ters in conducting handler exposure assessments. In addition, lab e l directions for these products shou ld be updated as app rop ri ate.

Page 6 of6