Draft for Comment

Version

– November 1 , 2013



# Residential Exposure Assessment Standard

Operating Procedures

Addenda 1: Consideration of Spray Drift

Office of Pesticide Programs

Office of Prevention, Pesticides, and Toxic Substances

U.S. Environmental Protection Agency

Washington, DCU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

1 

## Table of Contents 1



### Section 1 Introduction

................................ ................................ .............................. 2 2



### Section 2 Problem Formulation

................................ ................................ ............... 3 3



### Sect ion 3 Scoping

................................ ................................ ................................ ....... 7 4

3.1 Information Gathering

................................ ................................ ................................ ................... 7 5

3.2 Scenario Development

................................ ................................ ................................ .................. 8 6

3.2.1 Ne eds Screening

................................ ................................ ................................ .............. 8 7

3.2.2 Defining Scenarios

................................ ................................ ................................ .......... 9 8

3.2.3 Characterization of Spray Drift Potential

................................ ................................ ...... 11 9



### Section 4 Method

................................ ................................ ................................ ..... 12 10

4.1 Current Meth od In Residential SOPs For Calculating Dermal Exposure

................................ ... 13 11

4.2 Modification To SOP Method To Account For Spray Drift

................................ ....................... 14 12

4.3 Drift Fraction Values

................................ ................................ ................................ ................... 14 13



### Section 5 Consideration s

................................ ................................ ........................ 18 14

15



### Attachment A Derivation of Drift Fraction Estimates 16

17

18

19U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

2 

# Section 1 Introduction 20

Th is document is as an addendum to the SOPs For Residential Exposure Assessment ( hereafter 21

SOPs) 1 which was developed for the purpose of introducing procedures for a ss essing potential 22

risks to human health associated with spray drift. This effort was undertaken to allow for routine 23

consideration of these types of exposures in risk assessment , based on the current SOP for use of 24

pesticides on turf, whic h is consistent with policy statements made by the Agency in a variety of 25

forums. 2 This document spe cifically provides guidance that define s when quantitative risk 26

assessment s for spray drift are required

, and it also provides the information needed to complete 27

such assessments when needed. 3 Volatilization can also occur during or after application. This 28

document addresses only those exposures associated with spray drift and not volatilization. 29

30

Off

- target movement of pesticides can occur via many types of pathways

, and it is governed by a 31

variety of factors . Sprays (or solid materials) that are released and do not deposit in the 32

application area end up off

- target and can lead to exposure s through direct contact with sprays. It 33

is also clear that incidents due to spray drift occur as noted in an analysis completed based on 34

acute illnesses using 1 998

- 2006 NIOSH SENSOR data. 4 Sprays can also deposit on surfaces 35

where contact with residues can eventually lead to indirect exposure s ( e.g. , children playing on 36

lawns where residues have deposited next to treated fields). The potential risk estimates from 37

these residues can be cal culated using drift modeling coupled with methods employed for 38

residential risk assessments for turf products

. There is a regulatory precedent for this approach 39

as it has been used by the Agency in a number of previous situat ions that include: (1) response to 40

a petition to cancel 14 pesticides , (2) develop ment of buffer zone estimates for two 41

organophosphate insecticides used on orchard crops in the Pacific Northwest , and (3) 42

development of a spray drift risk assessment for an org anophosphate insecticide

. 5 43

44

1 http://www.epa.gov/pesticides/science/residential

- exposure

- sop.html

2 http://www.epa.gov/pesticides/ppdc/2011/april/session4

- ch

- workerrisk.pdf and

http://ww w.regulations.gov/#!docketDetail;D=EPA

- HQ

- OPP

- 2009

- 0889

3 This document is not intended to provide guidance for addressing mosquito adulticide and other ultra low volume

types of applications. These analyses are completed on a case by case basis because label criteria must be accounted

for when parameterizing the model for spray quality and other application parameters (e.g., release height).

4 Lee et al (2011) Acute Pesticide Illnesses Associated with Off

- Target Pesticide Drift from Agricultural

Applica tions

— 11 States, 1998

– 2006 , available at the following:

http://ehp03.niehs.nih.gov/article/info%3Adoi%2F10.1289%2Fehp.1002843

5 http://www.epa.gov/fedrgstr/EPA

- PEST/2004/May/Day

- 26/p11779.htm and

http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 200 8

- 0850

- 0105U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

3 Section 2: Problem Formulation provides a brief discussion of the issues associated with spray 45

drift and their possible implications

. Section 3: Scop ing outlines the criteria risk assessors 46

should use to determine what t ype of assessment is needed in order to properly evaluate and 47

characterize spray drift in risk assessment. Section 4: Method describes the techniques used to 48

calculate risks associated with drift. Section 5: Consideration s describes the factors which 49

s hould be described and/or considered associated with risks from spray drift. 50

51



# Section 2 Problem Formulation 52

Data summarized from 2007 indicate that about 12.4 billion dollars was spent on pesticide 53

products domestically and that resulted in about 1.1 billion pounds of pesticides being applied 54

that year. 6 U.S. Census data from 2010 also indicate that about 90 million people live in areas 55

classified as either rural (~30 million) or in relatively small urban clusters (~60 million) which 56

indicates that there is a wides pread opportunity for spray drift related exposure s if applications 57

are not properly managed. 7 58

59

P esticide application technology to prevent all possible spray drift is not truly feasible except 60

under highly prescribed situations using technologies not ge nerally available . For example, 61

when granular formulations are applied directly into the soil no drift would be expected

. 62

A nother example is that certain types of programmable controllers are used on more 63

sophisticated application equipment to actively m anage drift potential

, but they are not wide ly 64

used . Drift would be greatly minimized in these example situations but th ese type s of 65

application technique s do not work for all crop/pesticide/pest combinations. F oliar applications 66

of sprays and other deli very techniques are prevalent in many areas of agriculture and in these 67

situations drift is difficult to completely eliminate. There is a significant level of effort focused 68

within the agricultural engineering community on drift reduction technologies and the 69

development of best management practices. 8 This document focuses only on evaluating spray 70

drift in application situations that are considered compliant with label statem ents that prohibit 71

application sprays from contacting people directly through drift

. Situations involving direct 72

human contact from spray drift are addressed by the Agency using other types of already existing 73

requirements such as enforcement actions, bas ic requirements for worker protection, or 74

modifying use instructions (e.g., add drift mini mi zation language to all pertinent labels ). 75

76

The EPA has developed a methodology for estimating potential risks from spray drift. This 77

approach is based on drift mod eling coupled with techniques previously designed to evaluate 78

residential turf uses of pesticides . Essentially, a residential turf assessment is conducted but the 79

residue value inputs are adjusted to account for the amount of pesticide residue deposited as a 80

result of spray drift instead of being based on a direct, intentional application onto turf . The 81

6 http://www.epa.gov/opp00001/pestsales/07pestsales/market_estimates2007.pdf (pgs 4 and 8)

7 http://www.census.gov/geo/reference/urban

- rural

- 2010.html , urban clusters are defined as 2,500 and 50,000

people, also see http://www.census.gov/population/www/cen susdata/files/urpop0090.txt

8 Manufacturers of application equipment have widely integrated drift management into their product portfolios. As

an example, refer to information at: http://www.teejet.com/english/home.aspxU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

4 amount of residue which deposits from drift varies with distance from the edge of a treated field. 82

The overall approach is illustrated in Figure 1

. [ Note: In Figure 1 the ter m “buffer” is included 83

and the lawn area is 50 feet wide. These are explained in more detail below.] 84

85

86

87

Figure 1

. Conceptual Model of Exposure Pathway Associated With Spray Drift 88

89

As described by various spray equipment manufacturer s and the Spray Drift Task Force, 9 spray 90

drift levels can be directly impacted by many facto rs including application equipment, 91

environmental conditions, and site characteristics. Figure 1 illustrates an aerial application but 92

drift can occur from the use of other types of application equipment used in agriculture such as 93

groundboom sprayers commonly used in field crops and airblast sprayers commonly used in 94

orchards. Drift profiles differ depending upon the type of equipment used. H ow that equipment 95

is configured ; types of nozzles, operating pressures, ground speed, and release height among 96

other factors c an impact drift results

. Environmental conditions such as wind speed, wind 97

direction, and stability of the atmosphere can also impact the amount of sprays that drift. The 98

higher the windspeed the more drift which occurs based on total mass of pesticide m oving off

99

target but changes in wind direction can lower total drift estimates in a specific area downwind 100

because less mass is moving away from a treatment area in one direction . The characteristics of 101

an application site also have relevance. Flat terra in in some ways can cause more drift especially 102

if it has a low surface roughness ( i.e., essentially the contour of the area that may be bare soil or 103

field stubble) which impacts how much drift can be trapped as spray plumes move across such 104

areas. 105

106

E stima ted e xposures from spray drift are based on the premise that residential areas, or other 107

public areas routinely accessible to the general population such as parks, are near where a 108

pesticide application may occur . Exposures may occur in a variety of ways but for regulatory 109

purposes , as noted above, this document focus es on compliant application events. In compliant 110

application events no individual should be directly sprayed , given existing label language and 111

requirements for worker protection, which means direct dermal and inhalation exposures to 112

9 http://www.agdrift.com/

, http://www.teejet.com/english/home.aspxU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

5 sprays will not be considered. E xposures considered for risk assessment purposes occur solely 113

as a result of contact with a surface that has bee n previously impacted by spray drift such as 114

nearby lawns . There are existing methods for evaluating a variety of exposure pathways in a 115

residential environment as described in the SOPs. Based on the SOPs it is also clear that 116

considering the exposures of chi ldren playing on turf is an appropriate exposure sce nario basis 117

for this method given the magnitude of the resulting exposures and the relevant physical 118

processes (see SOP 3.2)

. The residential turf post

- application SOP provides a standard method 119

for estimating potential dermal doses among adults and child ren 1 < 2 years old from dermal 120

contact with turf that has previously been treated with pesticides. This scenario assumes that 121

pesticide residues are transferred to the skin of adults/children who enter treated lawns for play, 122

recreation, yardwork or other homeowner activities. Considering the strengths and limitations of 123

available data and behavioral characteristics of potentially exposed lifestages

, post

- application 124

dermal exposure is only calculated for adults and children 1 < 2 years old. 125

126

Pesticides us ed to treat turf are typically applied either in a broadcast type of application to 127

ensure complete coverage across an entire lawn or they are completed using a localized approach 128

focus ed only on infested areas (i.e., referred to as spot treatments)

. In b roadcast application s , the 129

intent is to uniformly deliver the chemical so when intentional broadcast l awn application s are 130

evaluated in risk assessment the size of a lawn is not a key issue. This eliminates the need to 131

address time and location factors in risk assessment . W hile a child could be playing anywhere on 132

a treated lawn

, the lawn would have been treated in a uniform manner and thus, exposure 133

potential would be similar throughout any location on the treated area

. When spray drift deposits 134

onto a lawn adjacent to an application site it will also depo sit across an entire lawn similar to a 135

broadcast application with a notable exception as illustrated in Figure 1

. 136

137

When lawns are impacted by spray drift the concentration of deposited residues decrea se s as the 138

distance away from a treated site increases. In order to account for this some assumptions have 139

to be made related to how a chi ld spends their time outdoors on a lawn. It is essentially 140

impossible to define from a regulatory perspective a time /location approach for child ren 141

outdoors. Rather, the spray drift assessment uses an approach similar to that outlined in the 142

SOPs for evaluations of indoor crack and crevice applications where residue profiles change 143

within treated rooms (see pg 7

- 26/Fig ure 7

- 1/SOP 7.2.2.1)

. 144

145

For spray drift risk assessment

, how the amount of deposited residue changes over distance has 146

been integrated over a turf area (e.g., lawn or public areas such as parks/playgrounds) of 147

predefined dimension s (i.e., 50 feet wide)

. A n average residue level over such area s is 148

determined and it is assumed a child could be anywhere in that area while playing and being 149

exposed to deposited residues

. The dimensions of a lawn or public area where children play can 150

impact risk es timates associated with drift because the wider the turf area where a child plays the 151

lower residues that will be available for exposure because more dilution of deposited residues 152

occur s with greater distance from the treated area

. The characteristics of domestic housing 153

indicate a large range of possibilities for establishing a lawn size for risk assessment purposes

. 154

The American Housing Survey completed by the U.S. Census indicates about 30.5 percent of 155

domestic housing is multi

- dwelling while the rema ining are single family houses (62.7%) or 156

manufactured/trailer homes (6.8%). 10 The U.S. Census also provides information on the sizes of 157

10 http://www.census.gov/housing/ahs/files/ahs11/National2011.xlsU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

6 lots relative to housing type which indicates for attached one family houses the average lot size 158

is 4,155 ft 2 and the median is 2956 ft 2 (2008 information presented but similar values are 159

reported for years 1992

- 2008). F or detached one family houses the average lot size is 9,070 ft 2 160

and the median is 19,482 ft 2

. 11 Given this information, the lawn dimensions used as the basis of 161

this methodology are 50 feet wide by 100 feet long (5,000 ft 2 ) as illustrated in Figure 1. Th e 162

5000ft 2 value approximates the mean lot size for at tached housing and also a reasonable 163

representation for detached housing with smaller lots. [Note: Lot size is equated for the 164

purposes of this discussion with lawn size and housing footprints are not accounted for in this 165

methodology

. It should also b e noted that buffer zone distance s are included a t varying 166

distances from adjacent to the field edge to 300 feet downwind from the field edge in this 167

methodology. ] 168

169

Residential risk assessments are conducted based on a premise which requires that they be 170

completed for each specific scenario associated with the product in order to evaluate the potential 171

risks associated with that use pattern. F or products which allow applications to turf, for example, 172

it is assumed that homeowners and their families will be exposed on the day of application 173

through contact with treated turf. How often applications of such products occur and the 174

persistence of resulting residues directly impact the duration of exposure. Analogous to how risk 175

assessments are completed for turf use products, spray drift risk assessments should be 176

completed on a similar premise which assumes impacted individuals are present in areas adjacent 177

to agricultural fields where the pesticide of interest has been sprayed and that they have contact 178

wit h that pesticide on the day of application

. As with o the r residential assessments, t he duration 179

of exposure can be governed by many factors including pest pressure, longevity of a pesticide in 180

the environment, seasonal use relative to the crop , costs, and issues associated with resistance 181

management. The U

. S

. Census also indicates , as described above, that a large percentage of the 182

population lives in areas where the opportunity for drift occurrences may be inherently higher 183

than other areas of the countr y (i.e., ~90 million people live in rural and urban cluster settings)

. 184

Given these factors it is difficult to predict how frequent ly e xposures via spray drift may occur 185

unless such information is available concerning how a pesticide is used

. As with any risk 186

assessment process, there are potential refinements which could occur related to factors 187

associated with use. Data that could refine the conclusions of an assessment include more 188

information on how a particular pesticide is used including application rates, application 189

frequency, the seasonality of its use, and the kinds of application equipment commonly 190

employed. These factors will be considered

, as appropriate

, on an individual case basis. 191

192

In summary, a number of factors can impact the potential f or exposure from spray drift. The 193

remainder of this document describes how the factors have been specifically considered for the 194

purposes of developing human health risk assessments associated with exposures from spray 195

drift. 196

197

198

199

200

201

11 http://www.census.gov/const/C25Ann/medavgsoldlotsize_cust.xls

,U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

7 

# Section 3 Scoping 202

This section outlines the criteria risk assessors should use to determine what type of assessment 203

is needed in order to evaluate and characterize spray drift. These criteria have been developed to 204

assist risk assessors in first defining if there is a need for a quantita tive risk assessment and 205

second for determining what to include in a quantitative assessment if it is required. In cases 206

where a quantitative risk as sessment is not needed

, a qualitative characterization piece should be 207

developed that de scribes the scenarios and why a qua ntitative approach i s not needed. 208

209

Section 3.1: Information Gathering discusses the types of information that are important to 210

know about a pesticide and its use in order to determin e if a quantitative spray drift risk 211

assessment is needed and to guide the development of qualitative characterization

. Section 3.2: 212

Scenario Development provides guidance for risk assessors when deciding what specific types 213

of drift calculations are needed

, if a quantitative risk asse ssment is required. 214

215

3.1 Information Gathering 216

217

I n de termin ing if a quantitative risk assessment is needed it is important to gather the appropriate 218

information. This includes developing an understanding of the types of end

- use products that 219

contain the pesticide and how th e pesticide is used . It is also important to identify any risk 220

assessments that have been previously completed. Proper characterization of how a pesticide i s 221

used will assist in defining which uses should be considered in an assessment and may also help 222

eliminate some uses for further consideration (e.g., certain granular products) . Having an 223

understanding of what risk assessments have been completed is also important because the 224

results of existing risk assessments may be useful in characterizing risks from drift or defining if 225

additional work is required . For example, if a pesticide has existing labels for use on turf

, a risk 226

assessment for that use may be considered protective of any type of exposure that would be 227

associated with spray drift if certain criteria are met

. The following list was created as a 228

framework for reviewers to aid them in the development of the necessary information: 229

230

• What crop(s)/pe st(s) are treated with the pesticide? Is there a seasonality associated with 231

the crop(s)/pest(s) of concern? What are the application rates for each crop/pest 232

complex ? Is information available that details the typical use patterns for the pesticide? 233

234

• Is the formulation a solid or liquid? If a solid, is it applied directly or is it mixed with 235

water or other carrier and then sprayed? 236

237

• What types of equipment are allowable and viable for the application of the pesticide? 238

239

• Are applications soil

- directed or foliar ? Do labels require soil incorporation? 240

241U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

8 • Is there an existing residential turf use? If so, has an up

- to

- date risk assessment utilizing 242

the 2012 Residential Turf SOP been completed for that use? What application rate was 243

assessed for the turf use? What were the findings of the risk assessment? 244

245

• Do product labels contain spe cific language related to application parameters such as 246

specific guidance on spray quality (e.g., types of nozzles to be used or the size of droplets 247

that are allowable ) ? 248

249

• Wh at data /information are available which may inform further refinements in a 250

residential risk assessment that have not been i ncluded ? Have these data/information 251

been reviewed and/or otherwise summarized? Examples include: (1) whether there is an 252

existing turf transferable residue study and whether has it been used in risk assessment, 253

and (2) does the pesticide manifest its efficacy through systemic or contact control which 254

can impact how the pesticide is applied

– systemic compounds may be applied using 255

larger droplets because total coverage is less of a concern ? 256

257

3.2 Scenario Development 258

259

In order to define the scenarios which should be considered in a spray drift risk assessment , a 260

categorization process was developed which provides a series of decision poi nts for de ciding if a 261

quantitative assessment is needed ( Section 3.2.1 ) and second ly, what scenarios should be 262

included ( Section 3.2.2 )

. In all cases there should be a qualitative characterization of the 263

potential for spray drift based on both the informa tion above and the screening process described 264

below ( Section 3.2.3 )

. 265

266

3.2.1 Needs Screening 267

268

This section describe s the process that should be used to de termine if a quantitative risk 269

assessment for spray drift needs to be completed for a particular pesticide. A series of questions 270

to consider are presented below. If the answer to any question below is “ Yes ” then quantitative 271

risk assessment is not required. 12 272

273

• Is the pesticide solely formulated as a granular product or in some other form that would 274

preclude drift (e.g., rodent bait) ? 275

276

• Is the pesticide solely used for direct soil injected or near soil (e.g., in

- furrow) 277

applications that require immediate soil incorporation? 278

279

• Are handheld equipment or stationary devices (e.g., drip irrigation systems) the sole 280

methods of application for the pesticide? 13 281

282

12 A qualitative discussion of spray drift potential needs to be included in every risk assessment even if a quantitative

analysis is not required. The questions should be used as guidance for developing such characterization pieces.

13 Note that quantitative spray drift predictions can only be made based on 3 types of agricultural spray equipment

including groundboom sprayers, airblast sprayers, and aircraft.U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

9 • Does the pesticide have an existing turf use registration? Is there an existing risk 283

assessment for that use? Is the following condition met where the maximum application 284

rate on crops adjusted by drift is less than or equal to existing turf application rates ? 14 285

286

Appl. Rate

max crop (lb ai/A ) x 0.26 ≤ Appl . Rate residential turf (lb ai/A) 287

288

• Is there other information available, which can be documented, that indicate s a 289

quantitative assessment should not be co mpleted? I f so, such information should b e 290

provided in the risk assessment in order to document this conclusion. 291

292

3.2.2 Defining Scenarios 293

294

Deciding wh ich scenarios need to be included in a quantitative spray drift risk assessment is 295

highl y dependent upo n the details provided o n the label, the pests being controlled, the timing of 296

application, the application equipment used, and whether the pesticide act s in a systemic manner 297

or i f it works via contact. Some pesticide labels provide detailed information that describes how 298

spray equipment should be configured for applying the specific product (e.g., the type of noz zle 299

or spray pattern to be used) . Howeve r, more often than no t

, no details are provide d except for 300

defining very basic criteria such as application rate, equipment types, frequency of application or 301

how much carrier (typically water) should be used to make applications. Th e following 302

approaches were deve loped to address each situation. 303

304

Screening Approach : A screening approach was developed based on the use of the AgDrift 305

model in situations where specific label guidance that defines application parameters is not 306

available

. 15

, 16 AgDrift is appr opriate for use only when application s are made by aircraft, airblast 307

orchard sprayers, and groundboom sprayers. These equipment types are commonplace and 308

account for most liquid spray pesticide applications in production agriculture. When AgDrift 309

was de veloped a series of screening values (i.e., Tier 1 option) were incorporated i nto the model 310

and represent each equipment type and use under varied conditions . There are options for 311

considering different spray characteristics such as fine to medium droplet s for aerial applications

, 312

different sprayboom height s and spray characteristics for groundboom sprayers

, and the impacts 313

of crop canopy on orchard airblast sprayers

. The screening options specifically recommended in 314

this methodology were selected because they are plausible and represent a reasonable upper 315

bound level of drift for common application methods in agriculture. These screening options are 316

consistent with how spray drift is considered in a number of ecological risk assessments and in 317

the process used to develop drinking water concentrations used for risk assessment. In all cases, 318

each scenario is to be evaluated unless it is not plausible based on the anticipated use pattern 319

(e.g., herbicides are not typically applied to tree canopies) o r specific label prohibitions (e.g., 320

aerial applications are not allowed). 321

322

14 The value (0.26) represents the maximum fraction of the application rate that can move and deposit on lawns from

spray drift predicted from all application methods. These lawns are in contact with the fi eld edge and are 50 feet

wide.

15 http://www.agdrift.com/

16 Note that for many cases the scenarios outlined in the screening approach represent actual use practice so risk

asse ssors should be aware and characterize these appropriately.U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

10 The screening options that are recommended include: 323

324

• Ground boom a pplications are based on the AgDrift option for high boom height and 325

using ve ry fine to fine spray type using the 9 0 th percentile results

. 326

327

• Orchard a irblast applications are based on the AgDrift option for Sparse 328

(Young/Dormant) tree canopies

. 329

330

• Aerial a pplication s are based on the use of AgDrift Tier 1 aerial option for a f ine to 331

m edium spray type and a series of other parameters which will be described in more 332

detail below (e.g., wind vector assumed to be 10 mph in a downwind direction for entire 333

application/drift event). 17 334

335

If Application Parameters Are Available : When label direction s or other i nformation are 336

av ailable that can be used to refine an assessment , this information should be incorporated into 337

the risk asse ssment to the extent possible (e.g., specific language for a herbicide to be applied 338

using a very coarse spray or airblast applications only on full foliage mature citrus for fruit 339

abscission). T his is a mo re appropriate approach than just using the screening values described 340

above because it allows for assessments to be more reflective of actual label requirements and 341

use practices. To this end, a series of additional scenarios were developed for this SOP. 342

Assessors should match them to the label language as appropriate

. [Note: It is anticipated that in 343

very limited circumstances there may be label language which is not reflected in the available 344

options. In these circumstances, additional analyses using AgDrift may be needed. If this is the 345

case, the additional outputs that are generated will be added to the accompanying calculator and 346

this SOP will be updated with the additional information.] The additional scenarios that are 347

available

, also calculated using the AgDrift model include: 18 348

349

• Groundboom application : 350

o High boom height coupled with fine to medium/coarse spray quality 351

o Low boom heig ht coupled with very fine to fine spray quality 352

o Low boom height coupled with fine to medium/coarse spray quality 353

354

• Orchard airblast application : 355

o Normal canopy (Stone and Pome fruit & vineyards) 356

o Dense canopy (Citrus and tall trees) 357

o Vineyard 358

359

17 AgDrift allows for consideration of even finer spray patterns characterized as very fine to fine. However, this

spray pattern was not selected as the common screening basis since it is used les s commonly for most agriculture. If

assessors identify this use pattern it should be used as the screening criteria and deposition values associated with it

are provided in Table 1 below. Justification for including this spray quality should be included in any assessment

based on specific label directions for its use.

18 For groundboom and orchard airblast applications no further refinements other than the scenarios presented can be

evaluated using AgDrift or other models at this time since the model is ba sed on an empirical evaluation of the

existing data and it is not a mechanistically based model. There are more options available for evaluating

refinements for aerial applications as that model is a mechanistic model that allows for variance of a number of

parameters (e.g., weather, plane type, nozzle numbers and location, spray quality).U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

11 • Aerial applications T he aerial application scenario allows for permutations based on a 360

number of factors. A number of these have been developed and are included as possible 361

options for assessors to consider if label language or other factors indicate that the 362

sc reening level assessment is not appropriate. These include the other scenarios in 363

AgDrift that reflect different spray quality (e.g., coarse and very coarse sprays which may 364

be required for certain pesticides such as some herbicides) and the use of helico pters 365

rather than fixed wing aircraft. 366

367

3.2.3 Characterization of Spray Drift Potential 368

369

The final aspect of scenario development is summarizing the information for risk managers

. 370

When quantitative spray drift risk assessments are required they should be completed as 371

described below in Section 4. These analyses should be based on the criteria outlined above 372

such as the form of the pesticide product(s) in question and how they are a pplied. The 373

information upon which the se decisions are based, including the screening criteria described 374

above, should be described in the risk assessment. 375

376

In m any cases pesticides are marketed and/o r applied in ways that preclude the need for a 377

quanti tative spray drift risk assessment but this does not eliminate the need to describe the 378

rationale for this approach

. Such descriptions should be developed for each risk assessment so 379

impacted stakeholders can clearly understand how the approach was develo ped. Two examples 380

have been compiled to illustrate this issue. 381

382

Example 1: Formulation Type 383

W hen pesticides are applied directly to soil as granules with ground equipment , the drift 384

poten tial is negligible so in a risk assessment context this should be described (e.g., pesticide is 385

sold only as a granular product intended application directly to soil from ground equipment)

. 386

387

Example 2: Application Equipment 388

T he use of handheld equipment also can greatly r educe the potential for off

- target spray drift so a 389

quantitative evaluation of these types of scenarios is not needed. Handheld equipment reduce s 390

the potential for spray drift because the spray quality is usually a coarser type which inherently 391

minimizes drift and users also consciously control drift potential during application since they 392

are holding the nozzle(s) in their hands and directing them during application. In summary, 393

application methods not including groundboom sprayers, aircraft or orchard a irblast sprayers do 394

not require a quantitative assessment of spray drift. However, their use and their characteristics 395

relative to spray drift potential should be characterized in risk assessments. 396

397

398

399

400U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

12 

# Section 4 Method 401

As described above in Section 2: Problem Formu lation , the approach to be used for 402

quantitatively incorporating spray drift exposure into risk assessment is based on an assumption 403

that applications will not result in direct exposures to individuals , since such contact would 404

constitute a misuse. Direct exposures would include inhalation of the spray plume or being 405

directly sprayed. Rather, the exposures addressed here would occur indirectly through contact 406

with impacted areas, such as residential lawns, when compliant applications are conducted. 407

Given this assumption , this methodolog y only presents techniques that estimate exposures for 408

children (1 to 2 years old) and adults who have contact with turf where residues are assumed to 409

have deposited via spray drift thus

, resulting in an indirect exposure. 410

411

The 2012 Residential SOPs prescribe a number of potential scenarios for evaluating residential 412

exposures to pesticides. The highest potential for exposure from spray drift is from contact with 413

outdoor areas such as lawns where drift can directly deposit. Th e residential turf post

414

application SOP provides a standard method for estimating potential exposures to adults and 415

children. The SOPs also indicate that small children (index lifestage of 1

- 2 years old) have the 416

highest exposure potential whe n playing on “treated” turf

. 19 The SOPs estimate dermal 417

exposures for adults and children resulting from playing on lawns as well as oral exposures for 418

children because they exhibit mouthing behaviors which lead to oral exposure during play . The 419

method for calculating quantitative risk estimates associated with spray drift deposition is 420

direct ly based on the existing methodology for turf pesticides with one modification to account 421

for the amount of drift that occurs and thus impacts turf residue levels. 422

423

Dermal exposures are based on the premise that pesticide residues are transferred to the skin of 424

adults and children who play on impacted lawn s. Similar to the evaluation of pesticides 425

intentionally used on residential turf, i t is assumed that children contact turf on the same day a 426

pesticide application is conducted and that spray drift occurs . EPA also assumes that turf does 427

not have residues of the pesticide of concern from other sources. However, the se assessment s can 428

be refined to more accurately reflect exposure over a longer period of time (e.g., a week or 429

month) if toxicological , fate characteristics, or activity information indicate the need for such 430

calculations. 431

432

A description of how risks from spray drift s hould be computed based on the SOP for turf 433

pesticides, with the appropriate adjustment to account for the amount of spray drift, is provided 434

below. It is based on a modification of algorithms provided in SOP 3.2.2 for estimating dermal 435

exposure. [Note: Incorporating this modification will also automatically address spray drift for 436

oral exposures as it is based on estimated dermal exposure

– see equations 3.6 and 3.7 in SOP 437

3.2.3.] 438

439

19 See SOPs at http://www.epa.gov/pesticides/science/USEPA

- OPP

- HED_Reside ntial%20SOPs_Oct2012.pdfU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

13 4.1 Current M ethod In Residential SOPs For Calculating Dermal Exposure 440

441

In the 2012 SOPs dermal e xposure resulting from contacting previously treated turf while 442

performing physical activities is calculated as follows (Equation 3.3 in SOPs) : 443

444

E = TTR * CF1 * T C * E D 445

446

where: 447

E

= exposure (mg/day) 448

TTR

= turf transferable residue (μg/cm 2 ) 449

CF1

= weight unit conversion factor (0.001 mg/μg) 450

T C

= transfer coefficient (cm 2 /hr) 451

E D

= exposure duration (hr/day) 452

453

If chemical

- specific TTR data are available, the TTR on Day 0 (i.e., the day of application) 454

should be calculated because it is assume d that individuals could be exposed to residues 455

immediately after application. However, if data are not available, then TTR can be calculated 456

using the following formula (Equation 3.4 in SOPs) : 457

458

TTR = AR * F * (1

- D) t * CF2 * CF3 459

460

where: 461

TTR

= turf transferable residue (μg/cm 2 ) 462

AR

= application rate (lbs ai/ft 2 or lb ai/acre) 463

F

= fraction of ai as transferable residue following application (unitless) 464

D

= fraction of residue that d issipates daily (unitless) 465

t = post

- application day on for exposure is being assessed (Day 0 in this SOP) 466

CF2

= weight unit conversion factor (4.54 x 10 8 μg/lb) 467

CF3

= area unit conversion factor (1.08 x 10

- 3 ft 2 / cm 2 or 2.47 x 10

- 8 acre/cm 2 ) 468

469

Dermal dose s are calculated as (Equation 3.5 in SOPs) : 470

471

D = E * AF / BW 472

473

where: 474

475

D

= dose rate (mg/kg/day); 476

AF

= absorption factor (dermal); and 477

BW

= body weight (kg) 478

479

480U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

14 4.2 M odification To SOP Method To Account For Spray Drift 481

482

The modification to SOP 3.2.2 that has been made to account for spray drift only alters Equation 483

3.4 from the SOPs. The modified equation is presented below and it should be used to evaluate 484

potent ial risks from spray drift. This equation is the same except that an additio nal term has been 485

included (DF or Drift Fraction) which provides an adjustmen t for the amount of drift that moves 486

into and deposits in a non

- target area such as a lawn. This equation applies to situations where 487

TTR data are not available. 488

489

TTR = AR * DF * F * (1

- D) t * CF2 * CF3 490

491

where: 492

TTR

= turf transferable residue (μg/cm 2 ) 493

DF

= drift fraction of spray drift that deposits on lawns ( unitless ) 494

AR

= application rate (lbs ai/ft 2 or lb ai/acre) 495

F

= fraction of ai as transferable residue following application (unitless) 496

D

= fraction of residue that dissipates daily (unitless) 497

t = post

- application day on for exposure is being assessed (Day 0 in this SOP) 498

CF2

= weight unit conversion factor (4.54 x 10 8 μg/lb) 499

CF3

= area unit conversion factor (1.08 x 10

- 3 ft 2 / cm 2 or 2.47 x 10

- 8 acre/cm 2 ) 500

501

If chemical specific TTR data are available, the residue on Day 0 is used after it is adjusted based 502

on the ratio of the applicable application rate for risk assessment (i.e., ba sed on the crop of 503

concern) and the application rate for the TTR study followed by an additional adjustment for the 504

d rift fraction factor like illustrated above. 505

506

4.3 Drift Fraction Values 507

508

D rift fraction values for different application scenarios and distances from the edge of treated 509

fields ha ve been develop ed for the scenarios described above in Sec tion 3.2. These values were 510

estimated using the AgDrift model as described in Attachment A of this document. They are 511

based on the screening options des cribed above and the alternative options that could be selected 512

if appropriate label language exists and there is adequate justification for applying the alternative 513

options . As noted above, these values are based on the average deposition across 50 feet wide 514

swaths of lawn (Figure 1)

. A range of drift fraction v alues are provided for lawns which are 515

located immediately adjacent to the edge of a treated field and up to distances where the nearest 516

edge is 300 feet from the treated field edge. For all anal yses, values at the immediate field edge 517

should be considered as the basis for risk assessment with the others providing characteri zation 518

of those risks. This range of values can inform risk managers about potential management 519

options (e.g., implementing possible buffer zones

, requiring certain types of application methods 520

to reduce risk levels to acceptable l evels

, or requirement of coarser spray quality compared to 521

recommended screening scenarios ). 522

523U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

15 Drift Fractions For Aerial Applications: The spray d rift deposition curves for selected aerial 524

application scenario s , based on average deposition values at each distance of interest, are shown 525

in Figure 2 (note that the fine to medium (F2M) curve is the recommended screening option for 526

this SOP) . The estimated drift fract ions over a 50’ wide lawn for various distances downwind 527

from the treate d field are provided in Table 1

. The screening level scenario recommended for 528

risk assessment is included in the first row of the table ( Fine to Mediu m ). If label specifications 529

exist values can be selected from other options if justified. 530

531

532

Figure 2 : Aerial Deposition Curves for Various Droplet Sizes From AgDrift 533

534

Table 1 : Average D rift Fractions for a 50’ Wide Lawn Starting at Various Distances 535

Downwind From a Field Treated Using Aerial Equipment 536

Droplet Size + Distance Downwind From Treated Field (feet)

0 10 25 50 75 100 125 150 200 250 300

Fine to Medium* 0.257 0.209 0.169 0.129 0.098 0.076 0.063 0.054 0.041 0.034 0.028

Medium to Coarse* 0.211 0.156 0.115 0.082 0.058 0.044 0.035 0.029 0.021 0.016 0.013

C oarse to Very Coarse* 0.183 0.124 0.082 0.053 0.037 0.028 0.022 0.018 0.013 0.010 0.008

Very Fine to Fine* 0.373 0.340 0.305 0.262 0.226 0.197 0.175 0.155 0.127 0.108 0.095

AT401, M, 10 mph, 34 % SD 0.234 0.183 0.142 0.105 0.078 0.060 0.049 0.042 0.032 0.026 0.021

WASP, M, 1 0 mph, 34 % SD 0.218 0.171 0.129 0.086 0.063 0.049 0.040 0.034 0.026 0.021 0.018

AT401, C, 10 mph, 2 5 % SD 0.198 0.141 0.099 0.067 0.047 0.036 0.029 0.024 0.017 0.013 0.011

WASP, C, 10 mph, 2 5 % SD 0.171 0.121 0.084 0.053 0.038 0.028 0.023 0.018 0.013 0.010 0.009

AT401, VC, 10 mph, 2 0 % SD 0.175 0.115 0.072 0.044 0.031 0.023 0.018 0.014 0.010 0.008 0.006

WASP

, VC, 10 mph, 2 0 % SD 0.138 0.088 0.057 0.036 0.025 0.019 0.014 0.012 0.008 0.007 0.006

*Information is based on the Tier 1 option in the AgDrift model. The fine to medium spray quality is used in this SOP as the

basis for the screening level assessment. These are all based o n fixed wing aircraft.

+ For further options the AT401 is the representative fixed wing aircraft and the Wasp is the representative helicopter. SD =

swath displacement . SD values for non

- Tier I options computed using AgDrift automated adjustment option.

Spray Quality Summaries: Fine to Medium (F2M): D v0.5 = 255 μM ; Medium (M): D v0.5 = 294 μM ; Medium to Coarse

(M2C): D v0.5 = 341 μM ; Coarse (C) D v0.5 = 3 85 μM ; Coarse to Very Coarse (C2VC ): D v0.5 = 439 μM; Very Coarse (V C):

D v0.5 = 478 μM & Very Fine to Fine (VF2F): D v0.5 = 137 μM

– only to be used with labeling justification

537 0.000 0.050 0.100 0.150 0.200 0.250 0.300

0 50 100 150 200 250 300Fraction of Applied



### Distance Downwind From Treated Fields (feet) AgDrift Tier 1

- Fine to Medium

AgDrift Tier 1

- Medium to Coarse

AgDrift Tier 1

- Coarse to Very Coarse

AT401, M, 10 mph, 33% SD

WASP, M, 10 mph, 33% SD

AT401, C, 10 mph, 25% SD

AT401, VC, 10 mph, 20% SDU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

16 Drift Fractions For Groundboom Applications: The spray drift deposition curves for 538

groundboom applica tions , using the 90 th percentile outputs and based on average deposition 539

values at each distance of interest, are shown in Figure 3

. The estimated drift frac tions over a 540

50’ wide lawn for various distances downwind from the treated field are provided in Table 2

. 541

The screening level scenario recommended for risk assessment is included in the first row of the 542

table ( High Boom/Very Fine to Fine ) . If label specifications exist values can be selected from 543

other options if justified. 544

545

546

Figure 3

. Deposition Curves Using Ground boom Equipment 547

548

Table 2 : Average Drift Fractions for a 50’ Wide Lawn Starting at Various Distances 549

Downwind From a Field Treated Using Ground Equipment 550

Boom

Height Droplet Size Distance Downwind From Treated Field (feet)

0 10 25 5 0 75 100 125 150 200 250 300

High Very Fine to

Fine 0.187 0.093 0.056 0.035 0.025 0.020 0.017 0.014 0.011 0.008 0.007

Low Very Fine to

Fine 0.085 0.032 0.020 0.013 0.010 0.008 0.007 0.006 0.005 0.004 0.003

High Fine to

Medium/Coarse 0.049 0.019 0.013 0.009 0.007 0.006 0.005 0.005 0.004 0.003 0.003

Low Fine to

Medium/Coarse 0.033 0.012 0.008 0.006 0.005 0.004 0.003 0.003 0.002 0.002 0.0 02

Low Boom 0.508 m (20 in), High Boom 1.27 m (50 in)

Fine to Medium/Coarse (F2M/C): Avg. Droplet size (D v0.5 ) = 341 μM

551

Drift Fractions For Airblast Applications: The spray drift deposition curves for the orchard 552

airblast sprayers , based on average deposition values at each distance of interest, are shown in 553

Figure 4 . The estimated drift frac tions over a 50’ wide lawn for various distances downwind 554

from the treated field are provided in Table 3

. The screening level scenario which is 555

recommended for risk assessment is included in the first row of the table ( Sparse ). If label 556

specifications exist values can be selected from other options if justified. 557

558 0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140 0.160 0.180 0.200

0 50 100 150 200 250 300Fraction of Applied



### Distance Downwind From Treated Fields (feet) High Boom, Very Fine to Fine

Low Boom, Very Fine to Fine

High Boom, Fine to

Medium/CoarseU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

17 559

560

561

562

Figure 4 : Deposition Curves Using Orchard Blast Equipment in Various Orchard Types 563

564

565

Table 3 : Average Drift Fractions for a 50’ Wide Lawn Starting at Various Distances 566

Downwind From a Field Treated Using Orchard Blast Equipment 567

Crop

Canopy Distance Downwind From Treated Field (feet)

0 10 25 50 75 100 125 150 200 250 300

Sparse 0.1435 0.0834 0.0443 0.0200 0.0110 0.0068 0.0045 0.0032 0.0018 0.0011 0.0008

Normal 0.0030 0.0020 0.0013 0.0009 0.0006 0.0005 0.0004 0.0003 0.0003 0.0002 0.0002

Dense 0.0422 0.0279 0.0175 0.0100 0.0067 0.0049 0.0039 0.0032 0.0023 0.0018 0.0015

Vineyard 0.0080 0.0041 0.0022 0.0012 0.0008 0.0006 0.0005 0.0004 0.0003 0.0002 0.0002

Sparse (Young, Dormant): This composite orchard combines small grapefruit and dormant apple orchards.

Normal (Stone and Pome Fruit, Vineyard): This composite orchard combines grape and orchards

. Dense (Citrus, Tall Trees): This composite orchard combines almond, orange, grapefruit, small grapefruit (mist

blower) and pecan orchards.

Vineyar d: This composite curve combines grape air blast sprayer applications and may not apply to other

application equipment.

Note: AgDrift also contains an “Orchard” scenario which is a composite of results from all tree canopy types. Since

it is a composite it has not been included.

568

569 0.0000 0.0200 0.0400 0.0600 0.0800 0.1000 0.1200 0.1400 0.1600

0 50 100 150 200 250 300Fraction of Applied



### Distance Downwind From Treated Fields (feet) Sparse Normal

Dense VineyardU.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

18 

# Section 5 Consideration s 570

T here ar e a significant number of considerations relevant to risk characterization that should be 571

factored into the interpretation of s pray d rift exposure and risk assessments completed based on 572

this guidance. These include: 573

574

• The risk estimates calculated are based on the premise that spray drift occurs in a manner 575

similar to that predicted and that an exposed person is at the locations and exhibits the 576

behaviors represented in the assessment

. 577

578

• The ae rial drift fraction estimates are based on application to bare ground with no crop in 579

the downwind area as well (i.e., these are referred to as a low surface roughness condition 580

and these conditions are known to have higher drift; this is a convention in A gDrift 581

Tier1)

. It should also be noted that in the drift analyses completed in the assessment, 582

wind vectors were moving from treated areas to the downwind area of the field 100 583

percent of the time at a constant windspeed of 10 mph which would maximize spr ay drift 584

levels under the model conditions. 585

586

• Spray drift values are based on the general application of the Tier I output values from 587

AgDRIFT and the subsequent higher tier analyses that were completed. There are 588

uncertainties associated with all of these approaches which have been discussed 589

extensively during the activities of the SDTF and the development of the AgDrift model

. 590

All of the associated uncertainties apply to the results of this analysis. There are 591

additional analyses that could be completed i n order to elicit how sensitive spray drift 592

levels may be to such changes in how applications are made or the conditions during 593

applications ( e.g. , evaluate impact of alternative aircraft, evaluate nozzle placement, 594

impacts of surface roughness ). 595

596

• AgDISP (another spray drift model similar to AgDrift) c ould also be used if further 597

potential refinements are needed in certain circumstances . For example, the effect that a 598

crop canopy may have on the deposition pattern downwind of a treated field following an 599

aerial application could be investigated . However, such an analysis would be limited 600

because: 1) canopy simulations in AgDISP are theoretical in natu re ; and 2) AgDISP 601

simulations represent uniformly closed canopy structures that are generally not expected 602

for tree crops in an agricultural orchard setting where air movement really occurs through 603

non

- homogeneous canopies more common in agriculture. 604

605

• The residential aspects of the calculation are based on the SOPs that have undergone an 606

extensive review process as cited above. Associ ated with each calculation is a degree of 607

uncertainty which is described in detail in the SOP s. 608

609

• If possible, the prevalence of one application method compared to another should be 610

considered and characterized

. 611

612U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

19 Because it can be demonstrated that spray drift occurs even if applications are compliant with 613

labels, s pray drift is being further examined as described in t his SOP to quantify potential risk 614

estimate s associated with exposure downwind of a tr eated field. There are several actions which 615

could be taken by risk managers that would result in lower risk estimates that should be 616

considered when incorporated into ri sk assessment . The impacts have been considered where 617

feasible. These are described below as a guide for the risk assessors in developing their 618

documents. These include: 619

620

• Reduce maximum application rates to those needed to achieve desired efficacy. 621

622

• Poten tially implement b uffers to alleviate potential human health risks in situations. 623

624

• Implement drift reduction technologies and approaches consistent with possible drift 625

reduction technologies ( DRTs ) that can alleviate risks including: 626

627

o require larger drop lets be used to alter spray patterns and reduce drift ( e.g., 628

perhaps requiring larger nozzle sizes by specifying a droplet size distribution ( i.e.

, 629

D v0.5 ) on the label)) 630

o require larger swath displacement from field edge 631

o require lower boom release heights 632

633

• Other possible approaches, consistent with the spirit of those used recently to manage 634

potential risks for fumigants, may also be appropriate such as: 635

636

o drift management plans for applicators 637

o specialized training for applicators on drift management issues 638

o use of buffer credit system consistent with the concept of DRTs, supported by 639

appropriate data 640

o place restrictions around sensitive areas such as schools 641

o encourage use of technology to manage drift such as GPS for pilots 642

643

• Restrict aerial applications based on risk findings and available mitigation options. 644

645

Data to confirm the efficacy of any DRT measures implemented to reduce the risk estimates 646

associated with spray drift may also be required

. 647

648

649U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

1 

# At tachment A: Derivation of Drift Fraction Estimates 650

651

As described in the text of this document a series of drift fraction values have been incorporated 652

as recommended values. One scenario has been designated as the basis for a screening 653

assessment for eac h type of application equipment and all others represent a potential risk 654

assessment refinement option if the information warrants they should be considered. In order to 655

avoid confusion, because of the nomenclature within AgDrift (e.g., Tier 1 Aerial, etc .), the same 656

terminology has not been used as the basis of this methodology because only one Tier 1 option 657

within AgDrift is considered as a screening estimate in this method. In other words, AgDrift 658

Tier 1 includes both the screening level drift fraction s defined in this methodology and the 659

scenarios which may represent potential refinements (e.g., for larger droplets resulting in a 660

coarser spray quality). For brevity, however, it is easier to describe how the drift fraction values 661

specified in this docu ment were calculated using the typical AgDrift Tier nomenclature even 662

though values within a tier may represent different levels of possible refinement for managing 663

spray drift risk concerns. 664

665

AgDrift Tier 1 Drift Fraction Values: 666

Tier I analysis for defining aerial, ground, and orchard air blast application drift fractions were 667

completed using AgDRIFT 20 (v2.1.1)

. 21 The AgDRIFT spray drift model is a Microsoft 668

Windows

- based computer program provided to the U.S. Environmental Protection Agency’s 669

Office of Pesticide Programs as a product of the Cooperative Research and Development 670

Agreement (CRADA) between EPA’s Office of Research and Development and the Spray Drift 671

Task Force (SDTF)

. AgDRIFT has undergone extensive validation including evaluation by a 672

FIF RA Scientific Advisory Panel. 22

, 23 673

674

Tier I AgDRIFT is a regression model developed from SDTF data including more than 300 675

applications made in 10 field studies covering a range of application practices for each type of 676

application ( i.e. , aerial, ground, a nd orchard air blast applications). AgDRIFT has been formally 677

validated by comparing its predicted outputs to 180 SDTF field trials. These data were generated 678

for aerial applications to a distance of about 800 meters downwind of the application field edge

. 679

These field trials were conducted using pesticide ( i.e. , dissolved or emulsifiable) in a liquid spray 680

and therefore they may not fully represent spray drift resulting from encapsulated or granular 681

based pesticide formulations. If these formulations ( e.g. , dispersible capsules or dispersible 682

granular) are applied using a liquid carrier and the droplet size distribution is the same as those 683

droplet size distribution included in AgDRIFT the resulting spray drift values are assumed to be 684

20 A User’s Guide for AgDRIFT 2.1.1: A Tiered Approach for the Assessment of Spray Drift Pesticides (February

2003). AgDRIFT V2.01 was used to model inhalation exposure concentrations.

21 AgDRIFT and AGDISP models : Models are avail able thr o u gh Harold Thistle, US Forestry, hthistle@fs.fed.us

. 22 U.S. Environmental Protection Agency. Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific

Advisory Panel: Estimating Drinking Water Exposure as a Component of the Dietary Risk Assessment; Spray Drift

Program, December 10

- 11, 1997

. 23 U.S . Environmental Protection Agency. Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) Scientific

Advisory Panel: Burholderia cepacia: Risk Assessment of a Biopesticide with Affinities to a Human Opportunistic

Pathogen; A Consultation on Protocol D esign to Assess Acute Neurotoxicity Studies following Oral Administration

of Pesticides; Higher Tier Ecological Risk Assessment for Chlorfunapyr; Spray Drift

- Review of Proposed Pesticide

Deposition Curves to Adjacent Areas, July 20

- 23, 1999

.U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

2 the same. Granular fo rmulations , applied as solid materials and no liquid spray, have d ifferent 685

drift patterns than liquid sprays, and as such need to be considered in a separate analysis. 686

However, from a human health perspective, off

- site movement of granular products would result 687

in lower risk estimates than those for liquid products ( e.g. , less drift occurs and the re is less 688

exposure uptake for granules). In most cases pesticides also have liquid end

- use products and an 689

analysis for them would be protective of potential risks from granular drift. 690

691

Drift fractions are essentially a representation of the amount of dr ift which occurs relative to a 692

nominal application rate ( i.e.

, they represent how much of the target application rate is predicted 693

to be deposited at various distances downwind of the treated field , averaged over a 50 feet wide 694

lawn in this case )

. Input pa rameters used in the Tier I spray drift analysis are provided in Table 695

A

- 1

. 696

697

Table A

- 1 : Tier I AgDRIFT Input Parameters 698

Parameter Value Comments

Aerial

Equipment Air Tractor AT

- 401 AgDRIFT default for Tier 1

Release Height 10 ft AgDRIFT default for Tier 1

Wind Speed 10 mph AgDRIFT default for Tier 1

Surface Roughness 0.0075 m (0.3 in) Default for Tier 1 (reflects flat terrain)

Temperature Not specified AgDRIFT Tier I ground models are based on regression

equations developed on empirical data.

Swath Displacement 0.372 2 (F2M)

0.2851 (M2C)

0.2191 (C2VC) AgDRIFT default values for Tier 1 (Users cannot alter these

values in Tier 1, taken from User Manual in description of

Tier I curves )

Droplet Size F2M, M2C, C2VC AgDRIFT default f or Tier 1, see note re: F2M

Fine to Medium (F2M): Droplet size (D v0.5 ) = 255 μM

– this option is the basis for the screening value for this SOP

Medium to Coarse (M2C): D v0.5 = 341 μM

Coarse to Very Coarse (C2VC): D v0.5 = 439 μM

Ground 1

Equipment Low Boom (LB)

High Boom (HB) AgDRIFT default options

, The high boom option is the basis

for the screening value for this SOP

Release Height LB: 0.508 m (20 in)

HB: 1.27 m (50 in) AgDRIFT default values

Application Efficiency LB: 99.27

HB: 99.22 AgDRIFT default values

Wind Speed Not specified AgDRIFT Tier I ground models are based on regression

equations developed on empirical data.

Surface Roughness Not specified AgDRIFT Tier I ground models are based on regression

equations developed on empirical data.

Temperature Not specified AgDRIFT Tier I ground models are based on regression

equations developed on empirical data.

Swath Width 13.72 m (45 ft) AgDRIFT default value

Droplet Size Very fine to fine (VF 2 F)

Fine to medium/coarse

(F2M/C) Note: The VF2F option is the basis for the screening value for

this SOP

Orchard Air Blast 1

Equipment Not specified AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.

Release Height Not specified AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

3 Parameter Value Comments

Application Efficiency Normal: 99.85

Dense: 98.01

Sparse: 97.69

Vineyard: 99.73

Orchard: 98.63 AgDRIFT default

Wind Speed Variable AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.

Surface Roughness Not specified AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.

Temperature Variable AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.

Swath Displacement Not specified AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.

Droplet Size Not specified AgDRIFT orchard air blast model are based on regression

equations developed on empirical data.

Orchard Type 2 Normal, Dense, Sparse,

Vineyard, and Orchard AgDRIFT default , the sparse option is the basis for the

screening value for this SOP

1. Regression equations were developed from SDTF field study results with groundboom and orchard blast

equipment. The 90 th percentile groundboom results are used for the purposes of this SOP. There is no higher tier

modeling available for groundboom and orchard applications.

2. Normal (Stone and Pome Fruit, Vineyard): This composite orchard combines grape and apple orchards

Dense (Citrus, Tall Trees): This composite orchard combines almond, orange, grapefruit, small grapefruit (mist

blower) and pecan orch ards.

Sparse (Young, Dormant): This composite orchard combines small grapefruit and dormant apple orchards.

Orchard: This composite orchard combines apple, almond, orange, grapefruit, small grapefruit, pecan, and

dormant apple orchards.

Vineyard: This com posite curve combines grape air blast sprayer applications and may not apply to other

application equipment.

699

Calculation of Drift Fraction Reduction Options : 700

The concept behind the development of the DRTs and the overall guidance of the PR notice for 701

lab eling related to spray drift described above is that p esticide applicators can control drift 702

through the use of specific equipment and application parameters. These parameters include 703

spray nozzle size, application pressure, vehicle type and configuration

, release height, 704

formulation choice, use of additives such as surfactants, and considering terrain as well as 705

atmospheric conditions at the time of application. Additional spray drift modeling was completed 706

for several droplet size distributions to investi gate the impact that the aircraft, wind speed, swath 707

displacement (the horizontal offset distance between the flight line and the target area), and crop 708

canopy have on the deposition pattern of a pesticide downwind of treated fields. These represent 709

implem entable means that applicators could potentially use to reduce drift 710

711

Tier II modeling for ground and orchard applications is not possible as AgDRIFT does not have 712

the capability to refine the spray drift estimates for these application types; however, Tier II 713

spray drift analysis can and was completed using AgDRIFT for aerial applications. As a Tier II 714

assessment tool, AgDRIFT is a parameterized model that can be used to investigate specific 715

aerial application parameters. A erial application parameters that were investigated include: 716

aircraft (fixed and rotary winged)

, different spray quality, and swath displacement (default value s 717

used but altered to correspond to change in droplet size). AgDRIFT input values for the Tier II 718

analyses are provided in Table A

- 2

. 719

720U.S. EPA Office of Pesticide Programs

– Residential Exposure Assessment Standard Operating Procedures , Addenda 1

4 Table A

- 2: Tier II AgDRIFT Input Parameters 721

Parameter Value Comments

Aerial

Equipment Air Tractor AT

- 401

WASP Helicopter One of the two default Tier II options for helicopter (rotary wing)

applications

Release Height 10 ft AgDRIFT default value in Tier II , same as Tier 1 above

Wind Speed 10 mph AgDRIFT default value in Tier II, same as Tier 1 above

Surface

Roughness 0.0075 m (0.3 in) AgDRIFT default value in Tier II, same as Tier 1 above

Temperature 86 °F AgDRIFT default value in Tier II, same as Tier 1 above

Swath

Displacement 0. 3351 (M)

0. 2489 (C)

0.2 005 (VC) Computed values from AgDRIFT Tier II when swath width is

adjusted using the AgDrift function in the drop size distribution

window . All values are based on ASAE option s

. Droplet Size M, C, VC See VMD values below

Nonvolatile Rate 1.49 lb/a Developed based on a typical pesticide

Spray Volume 2 gal/a Minimum required spray volume

Carrier Type Water

Medium (M): D v0.5 = 294 μM

Coarse (C) D v0.5 = 3 85 μM

Very Coarse (V C): D v0.5 = 478 μM

Other parameters were not changed or adjusted based on standard AgDRIFT recommendation via program prompts

except as noted for Swath Displacement adjustment and use of helicopter in Tier II

. 722