UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

DA TE: August 12, 2015 

SUBJECT: Bifenazate. Draft Human Health Risk Assessment in Support of Registration Review. 

FROM: 

PC Code: 000586 

Decision Nos.: 495937 

Petition Nos.: NA 

Risk Assessment Type: Single 

Chemical/ Aggregate 

TXR No.: NA 

MRID No.: NA 

DP Barcodes: 0423 162 

Registration No.: 7267- 1 

Regulatory Action: Registration 

Review 

Case No.: 7609 

CAS No.: 149877-41-8 

40 CFR: § 180.572 

Monica Hawkins, Ph.D., M.P.H., Environmental I lealth Scientist/Risk Assessor ~4-V Risk Assessment Branch VI '//~ Health Effects Division (7509P) 

~ 

THROUGH: Donna S. Davis. Acting Branch Chief lf'J.. £\1111 I\ ~ 

Risk Assessment Branch VI 'fd:JIJVV-A...V r 

Health Effects Division (7509P) 

and 

V e-. , ... h....-t... - Lata Venkateshwara, ExpoSAC Rev~e~ • t / • 1 ·e;. 

Ivan Nieves, ExpoSAC Reviewer f?"1J I -

Exposure Science Advisory Committee (ExpoSAC) I I-IED 

TO: Garland Waleko. Chemical Review Manager 

Cathryn Britton, Team Leader 

Kevin Costello, Branch Chief 

Pesticide Re-Evaluation Division (7505P) 

Risk Management & Implementation Branch 3 (RMIB3) 

1.0 Executive Summary 

As part of Registration Review, the Pesticide-Re-evaluation Division (PRO) of OPP has 

requested that the Health Effects Division (HED) conduct an occupational and residential 

exposure assessment, as needed, to estimate the risk to human health that will result from the 

Page 1 of 4 
currently registered uses of bifenazate. HED recently conducted a human health risk assessment 

for the active ingredient, bifenazate (W. Wassell et al., 0 388228, 6/25/20 14). Since the previous 

risk assessment, no changes were made to the hazard characterization and use profile; therefore 

this document serves as the draft risk assessment for bifenazatc for the purposes of registration 

review. A total aggregated risk index (ARI) was used since the level of concern values for 

dermal exposure (100) and inhalation exposure (30) are different. The target ARl is 1; therefore 

ARls of less than J result in risk estimates of concern. All ARls were greater than 1 and are not 

risks of concern, except for the following scenarios that require single layer of gloves: (I) 

mixing/loading liquids for aerial and chemigation applications and (2) 

mixing/loading/application of liquids via mechanically pressurized handgun (foliar). The most 

recent risk assessment did not include a spray drift exposure and risk assessment; therefore, a 

quantitative spray-drift exposure/risk assessment was conducted for bifenazate and is included 

herein. Bifenazate is a selective miticide/insecticide that controls the motile stage of mites either 

by direct contact or through contact with foliar residues. 

The registered formulations for bifenazate include wettable powders (WP) in water-soluble 

packets (WSP). soluble concentrates (SC), water-dispersible granules (WDG), and flowable 

concentrates (FIC). The maximum application rate is 0.75 lb ai/acre for use on timothy forage 

and hay and 0.5 lb ai/acre for use on pome fruit. Bifenazate is registered for use on various 

agricultura l crops and on ornan1entals and non-bearing fruit crops ( citrns, berries, currants, dates, 

figs, and persimmons). 

Dermal risk estimates were evaluated for adults. Dermal and incidental oral risk estimates were 

evaluated for children (1 to< 2 years old). The risk estimates from exposure to bifenazate 

related to spray drift result in no risks of concern at the field edge for either ground boom, aerial 

applications, or airblast orchard applications. 

2.0 Non-Occupational Spray Drift Exposure and Risk Estimates 

Off-target movement of pesticides can occur via many types of pathways and it is governed by a 

variety of factors. Sprays that are released and do not deposit in the application area end up offtarget and can lead to exposures to those it may directly contact. They can also deposit on 

surfaces where contact with residues can eventually lead to indirect exposures (e.g., children 

playing on lawns where residues have deposited next to treated fields). The potential risk 

estimates from these residues can be calculated using drift modeling onto 50 feet wide lawns 

coupled with methods employed for residential risk assessments for turf products. 

The approach to be used for quantitatively incorporating spray drift into risk assessment is based 

on a premise of compliant applications which, by definition, should not result in direct exposures 

to individuals because of existing label language and other regulatory requirements intended to 

prevent them.

1 Direct exposures would include inhalation of the spray plume or being sprayed 

directly. Rather. the exposures addressed here are thought to occur indirectly through contact 

with impacted areas, such as residential lawns, when compliant applications are conducted. 

Given this premise, exposures for children (1 to 2 years old) and adults who have contact with 

turf where residues are assumed to have deposited via spray drift thus resulting in an indirect 

1 This approach is consistent with the requirements of the EPA 's Worker Protection Standard. 

Page 2 of 4 
exposure are the focus of this analysis analogous to how exposures to turf products are 

considered in risk assessment. 

In order to evaluate the drift potential and associated risks, an approach based on drift modeling 

coupled with techniques used to evaluate residential uses of pesticides was utilized. Essentially, a 

residential turf assessment based on exposure to deposited residues has been completed to 

address drift from the agricultural applications of bifenazate. ln the spray drift scenario, the 

deposited residue value was determined based on the amount of spray drift that may occur at 

varying distances from the edge of the treated field using the AgDrift (v2. l. l) model and the 

Residential Exposure Assessment Standard Operating Procedures Addenda 1: Consideration of 

Spray Drift Policy. Once the deposited residue va lues were determined, the remainder of the 

spray drift assessment was based on the algorithms and input values specified in the recently 

revised (20 12) Standard Operating Procedures For Residential Risk Assessment (SOPs). 

A screening approach was developed based on the use of the AgDrift model in situations where 

specific label guidance that defines application parameters is not available.2

.3 AgDrift is 

appropriate for use only when applications are made by aircraft, airblast orchard sprayers, and 

groundboom sprayers. When AgDrift was developed, a series of screening values (i.e., the Tier 

1 option) were incorporated into the model and represent each equipment type and use under 

varied conditions. The screening options specifically recommended in this methodology were 

selected because they are plausible and represent a reasonable upper bound level of drift for 

common application methods in agriculture. These screening options are consistent with how 

spray drift is considered in a number of ecological risk assessments and in the process used to 

develop drinking water concentrations used for risk assessment. In all cases, each scenario is to 

be evaluated unless it is not plausible based on the anticipated use pattern (e.g .. herbicides are 

not typically applied to tree canopies) or specific label prohibitions (e.g., aeria l appli cations are 

not allowed). Section 2.1. I provides the screening level drift related risk estimates. 

2.1.1 Risk Estimates From Lawn Deposition Adjacent to Applications 

The spray drift risk estimates are based on an estimated deposited residue concentration as a 

result of the screening level agricultural application scenarios. Bifenazate is used on various 

agricultural crops and can be applied via groundboom, aerial, and airblast equipment. Bifenazate 

is also registered on ornamentals and non-bearing fruit crops (citrus, berries, currants, dates, figs, 

and persimmons). The spray drift assessment was conducted using the highest registered 

application rate of 0. 75 lb a i/acre for use on timothy forage and hay for ground and aerial 

application and 0.5 lb ai/acre for airblast application. The recommended drift scenario 

screening level options are I isted below: 

• Groundboom applications are based on the AgDrift<l!> option for high boom height and 

using very fine to fine spray type using the 901

h percentile results. 

• Aerial applications are based on the use of AgDrift® Tier I aerial option for a fine to 

medium spray type and a series of other parameters, which will be described in more 

2http://www.agdrift.com/ 3 otc that for many cases the scenarios outlined in the screening approach represent actual use practice so risk assessors should 

be aware and characterize these appropriately. 

Page 3 of 4 
detail below (e.g., wind vector assumed to be I 0 mph in a downwind direction for entire 

application/drift event). 

• Orchard airblast applications are based on the AgDrift option for Sparse 

(Young/Dormant) tree canopies. 

Dermal risk estimates have been evaluated for adults. Dermal and incidental oral risk estimates 

were evaluated for children (1 to < 2 years old). The total applicable LOC is I 00 so MOEs < 

100 would be of concern. Children's (1 < 2 years old) dermal and incidental oral risk estimates 

from exposure to bifenazatc related to spray drift result in no risks of concern at the field edge 

for either groundboom, aerial, or airblast applications. Adult dermal risk estimates from 

exposure to bifenazate related to spray drift result in no risks of concern at the field edge for 

either groundboom, aerial. or airblast applications. Results are presented in Tables 2. 1. l. and 

2. 1.2. below. 

Table 2.1.1. Adult Risk Estimates (MOEs) Related to Indir ect Ex posure to Spray Drift for Bifenazate fo r 

the Dermal Route of Exposure 

Application Spray Type/ Application Estimated TTR At Edge 

Nozzle Equipment Confo?.uration Rate (lb ai/A) (ug/cm2) Dermal MOE 

Timothy Forage and Hay 

Aerial Fine to Medium 4.400 

Ground boom Higlt Boom Very 0.75 0.0833625 6,100 fine to Fine 

Pome Fruit 

Airblast Sparse 0.5 0.055575 12,000 

Table 2. 1.2. Children (I < 2 years old) Risk Estimates (MO Es) Rela ted to Indirect Exposure to Spray 

Drift for Bifenazate for Dermal and Incidental Oral Route of Exposure 

At Edge At 

Estimated Edge Application Spray Type/ Nozzle Application TTR1 Equipment Configuration Rate (lb ai/A) (ug/cm2) Dermal Incidental Oral MOE MOE 

Timothy Forage and Hay 

Aerial Fine to Medium 2,200 3 10 

Higlt Boom Very 0.75 0.0833625 

Groundboom fine to Fine 3, 100 420 

Pome Fruit 

Airblast Sparse 0.5 0.055575 6,000 820 

Note: This memorandum was reviewed by the Exposure Science Advisory Committee 

(ExpoSAC) on July 23, 20 15. 

Page 4 of 4