Draft for Comment Version

– March 1, 2014



# Human Health Bystander Screening Level

Analysis: Volatilization of Conventional

Pesticides

Office of Pesticide Programs

Office of Chemical Safety and Pollution Prevention

U.S. Environmental Protection Agency

Washington, DC

March 1 , 2014Draft for Comment Version

– March 1, 2014

2 

## Table of Contents 1

2

Section 1.0: Introduction

................................ ................................ ................................ ................. 2 3

Section 2.0: Volatilization Screening Tool Development

................................ .............................. 4 4

Section 3.0: Volatilization Screening Tool Inputs

................................ ................................ .......... 8 5

Section 4.0: Registration Review Chemical Volatilization Screen Results

................................ .. 11 6

Section 5.0: Registration Review Chemical Volatilization Screen Characterization

................... 17 7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

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## Section 1.0: Introduction 27

28

Over many years, the Environmental Protection Agency (the Agency) has been actively engaged 29

in evaluating possible exposures associated with air borne, off

- target movement of pesticides. 30

This has included developing and refining its methodologies for assessing bystander exposures 31

resulting from volatilization of fumigant s as well as exposure to spray drift 1 from the application 32

of conventional pesticides in agricultur al settings . More recently, the Agency has been adaptin g 33

the approaches developed for conducting risk assessments for the fumigants for use in assess ing 34

potential bystander inhalation risk resulting from the volatilization of other conventional 35

pesticide s (i.e., non

- fumigants)

. Notable milestones in this effort include the 2009 FIFRA 36

Scientific Advisory Panel ( SAP ) 2 review of issues related to volatilization of conventional 37

pesticides and the 2013 chlorpyrifos volatility asse ssment 3

. 38

39

The Agency has recently developed a V olatilization S creening T ool that provides a consistent 40

and health protective framework to assess the potential inhalation bystander risks resulting from 41

volatilization of conventional pesticides. In addition

, a Volatilization Screening Tool Guidance 42

Document (see Appendix A) was produced to support the screening tool. Th e screening tool 43

utilizes a number of physical and chemical properties to predict flux ( i. e., the rate at which a 44

chemical volatilizes off of a treated field) ; the AERSCREEN 4 model to estimate air 45

concentrations at different distances from a treated field ; and chemical

- specific human health 46

toxicological data to estimate potential bystander inhalation risks

. This document provides 47

details on the volatilization screening methodology including the development of the screening 48

tool , the guiding principles behind the screening tool, and the various inputs utilized in the 49

screening tool. It also presents the results of the screening analysis that the Agency has recently 50

completed using th is methodology which examine d all of the conventional pesticides being 51

evaluated in the Registration Review 5 process

. The Agency plans to use the results of the 52

screening analysis to determine when volatilization data (i.e., flux studies ) and/or route

- specific 53

inhalation toxicological data (if not already available) should be required fo r a chemical. 54

55

Section 2: Volatilization Screening Tool Development provides a brief discussion of the 56

development of the volatilization screening tool as well as a discussion o f the guiding principles 57

behind the screening tool

. Section 3: Volatilization Screening Tool Inputs outlines the inputs 58

used to populate the volatilization screening tool

. Section 4: Registration Review Chemical 59

Volatilization Screen Results discusses the results of the Agency’s volatilization analysis for the 60

conventional Registration Review chemicals

. Section 5: Registration Review Chemical 61

Volatilization Screen Characterizatio n discusses issues that should be considered when 62

interpreting the volatilization analysis for the Registration Review chemicals

. 63

64

1 Reference Spray Drift Doc once final

2 2009 Volatilization SAP: http://www.regulations.gov/ (EPA

- HQ

- OPP

- 2009

- 0687)

3 2013 Chlorpyrifos Volatility Assessment: http://www.re gulations.gov/ ( EPA

- HQ

- OPP

- 2008

- 0850 )

4 http://www.epa.gov/ttn/scram/dispersion_prefrec.htm

5 http://www.epa.gov/oppsrrd1/registration_review/Draft for Comment Version

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## Section 2.0: Volatilization Screening Tool Development 65

66

In order to assess the potential inhalation bystander risks resulting from volatilization of 67

conventional pesticides in a consistent and health protective manner, a volatilization screening 68

tool has been developed . This screening tool can be used to estimat e upper bound , health 69

protective air concentrations at various distances from a treated field resulting from the 70

volatilization of conventional pesticides. Prior to development of this screening tool, the Agency 71

typically use d the Probab ilistic Exposure and Risk model for FUMigants (PERFUM) for 72

conducting bystander inhalation screening assessments

. U se of PERFUM 6 is resource intensive 73

and require s the input of emission rate profile s (gathered from field volatility studies ) that are not 74

typically available for conventional pesticides

. 75

76

Given the se issues

, a need was identified for a tool that was less resource and data intensive but 77

still resulted in health protective risk estimates. T he volatilization screening tool utilizes three 78

main inputs in assessing the potential inhalation bystander risks from conve ntional pesticides. 79

First, physical and chemical properties are used to predict flux based on the work by Woodrow et 80

al

. (1997) 7 and Woodrow et al

. (2001) 8

. Second, the screening tool uses the estimated flux along 81

with the AERSCREEN 9 model to estimate air concentrations at different distances from the 82

treated field

. [Note: AERSCREEN is used routinely for regulatory air permitting and has 83

undergone extensive review as described in the associated background materials.] Finally, the ai r 84

concentrations are compared to chemical

- specific human health toxicological data to estimate 85

potential bystander inhalation risks

. All of these components are combined into a simple to use 86

Excel workbook. Users must have Microsoft Excel 2007 or higher in order to use the screening 87

tool. In addition, the tool also uses Visual Basic functions, so users must enable macros in order 88

to use the tool. Figure 1 provides a screen shot of the Volatilization S creening T ool. 89

90

6 http://www.exponent.com/ProjectDetail.aspx?project=450

7 Woodrow, J., Seiber, J., Baker, L. 1997. Correlation Techniques for Estimating Pesticide Volatil ization Flux and

Downwind Concentrations . Environ. Sci. Technol., 31:523

- 529

8 Woodrow, J., Seiber, J., Dary, C. 2001. Predicting Pesticide Emissions and Downwind concentrations Using

Correlations with Estimated Vapor Pressures

. J. Agric. Food Chem. 49 : 3841

- 3846

9 http://www.epa.gov/ttn/scram/dispersion_prefrec.htmDraft for Comment Version

– March 1, 2014

5 91

Figure 1

. Input Screen for Volatilization S creening T ool 92

93

More specific details on the use of a modified Woodrow equation and the AERSCREEN model 94

in the Volatilization Screening Tool are presented below. S pecific details on the physical and 95

chemical properties and toxicological inputs used in the Volatilization Screening Tool are 96

presented in Section 3.0. 97

98

Modified Woodrow Equation 99

At the 2009 FIFRA Scientific Advisory Panel (SAP) 10 related to volatilization of conventional 100

pesticides , the Agency presented multiple methods for estimating emissions released from a 101

pesticide

- treated field. The approach defined in Woodrow et al (1997) and Woodrow et al 102

(2001) was one of the methods presented to the Panel. The Panel commented that the Wo odrow 103

approach would be a good starting point for a Tier I, screening level approach. In these two 104

papers, the study authors developed a linear relationship between the natural logarithm of a 105

chemical’s physical and chemical properties to the natural loga rithm of the amount of chemical 106

emitted from soil or a plant surface. However, like all linear relationships, half of the emissions 107

were underestimated when compared to the measured values used to derive the relationship. In 108

order to be conservative and health protective, the Agency used the data provided in the 109

Woodrow et al (1997) to construct an alternative linear model using the 90% lower confidence 110

limit of the slope and 90% upper confidence limit of the intercept as the model parameters. The 111

result s of the regressions are presented in the Volatilization Screening Tool Guidance Document 112

(see Appendix A)

. 113

114

10 2009 Volatilization SAP: http://www.regulations.gov/ (EPA

- HQ

- OPP

- 2009

- 0687)Draft for Comment Version

– March 1, 2014

6 For soil applied pesticides, the following equation can be used to derive a flux rate : 115

116

117

118

119

120

Where: 121

flux

= flux rate (μg/m 2

- s)

, 122

VP

= vapor pressure (Pa)

, 123

AR

= application rate ( lb/A )

, 124

Sol

= solubility (mg/L) , and 125

Koc

= organic carbon sorption coefficient ( ml /g)

. 126

127

For foliar applied pesticides, the following equation can be used to derive a flux rate 128

129

130

131

Where: 132

flux

= flux rate (μg/m 2

- s)

, and 133

VP

= vapor pressure (Pa)

. 134

135

Note: In Woodrow et al (1997), p esticide residues on plant surfaces were assumed to be 136

volatilizing from a non

- interactive surface in the period just after application and a very good 137

correlation between flux and vapor pressure was obtained for a dozen compounds. An attempt 138

was made to develop an equation that incorporates application rate for foliar applied pesticides 139

however the Agency was unable to obtain a good correla tion for this equation. 140

141

142Draft for Comment Version

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7 AERSCREEN Model 143

AERSCREEN is a screening air model based on AERMOD 11 , which is an air quality model that 144

incorporate s air dispersion based on planetary boundary layer turbulence structure and scaling 145

concepts, including treatment o f both surface and elevated sources, and both simple and complex 146

terrain. AERMOD was developed as a joint effort between the A merican Meteorological 147

S ociety and the EPA. In 1998, a formal peer rev iew of the model was performed 12 . An 148

independent model eva luation was also completed in 1998 13

, 14

. AERMOD is currently a 149

recommended EPA air model as per Appendix W 15 of 40 CFR Part 51. 150

151

AERSCREEN produce s estimates of "worst

- case" 1

- hour concentrations for a single source 152

without the need for site specific hourly meteorological data

. The Volatilization Screening Tool 153

was developed using a limited number of AERSCREEN model runs, at a standard flux rate of 154

1x10

- 6 g/m 2

- s, for various field sizes, crop scenarios, seasons of application

, and meteorological 155

conditions

. The results of these AERSCREEN model runs were then import ed into the Excel 156

screening tool

. T he Volatilization Screening Tool Guidance Document details the input 157

parameters used in the AERSCREEN model runs (see Appendix A)

. 158

159

EPA air screening guidance fr om 1992 does not recommend calculation of air concentrations 160

beyond 1 hour periods to different exposure period s for field source emissions ( e.g. , 8

- hour time 161

weighted air concentration) 16

. However, a peak

- to

- mean scaling factor has been developed

, 162

based on runs done in PERFUM, to allow estimation of concentrations for averaging periods 163

longer than one hour, but less than 24 hours in order to match the duration of the potential 164

exposure period to a period similar to that used for defining the toxicological level of concern 165

(e.g., 6 hour inhalation dose administration in a rodent study is typical). The Agency notes that 166

PERFUM received a favorable review by the FIFRA SAP in 2004 17 and since that time the 167

Agency has consistently used it in the assessment of t he fumigants. T he Volatilization Screening 168

Tool Guidance Document details the specifics of the peak

- to

- mean scaling factor (see Appendix 169

A)

. 170

171

In AERSCREEN, air concentrations are directly related to the emission rate from a field. T he 172

Volatilization Scr eening T ool scales the results from the AERSCREEN runs

, using the 173

application rate and physical and chemical properties of the pesticide to estimate flux, to estimate 174

off

- field air concentrations for a variety of crop scenar i os and meteorological condition s. The 175

Volatilization Screening Tool provides estimates of the distance from the edge of the field where 176

air concentrations fall below the concentration of concern for a chemical

. In this way, the 177

11 http://www.epa.gov/ttn/scram/dispersion_prefrec.htm#aermod

12 United States Environmental Protection Agency. Compendium of

http://www.epa.gov/scram001/7thconf/aermod/dockrpt.pdf . Accessed March 2002.

13 Paine, R.J, R.F. Lee, R. Brode, R.B. Wilson, A.J. Cimorelli, S.G. Perry, J.C. Weil, A. Venkatram, and W. Peters.

Model Evaluation Results for AERMOD.

14 Paine. R., R. Lee, R. Brode, R. Wilson, A. Cimorelli, S. Perry, J.Weil, A. Venkatram, W.

Peters. AERMOD: Model Formulation and Evaluation Results. Preprint s, 92th Annual Meeting of Air and Waste

Management Association, Air and Waste Management Association, Pittsburgh, PA. (1999)

15 http://www.epa.gov/ttn/scram/guidance/guide/appw_05.pdf

16 U.S. EPA, 1992: Screening Procedures for Estimating the Air Quality Imp act of Stationary Sources. EPA

- 454/R

92

- 019. U.S. Environmental Protection Agency, Research Triangle Park, NC 27711.

17 http://www.epa.gov/scipoly/sap/meetings/2004/082404_mtg.htmDraft for Comment Version

– March 1, 2014

8 Volatilization Screening Tool can be used to easily eliminate the inhalation pathway for 178

pesticides not posing a risk of concern to bystanders following applications

. 179

180



## Section 3 .0: Volatilization Screening Tool Inputs 181

182

As described in Section 2, the Volatilization Screening Tool consists of three major components, 183

the modified Woodrow Equation, AERSCREEN, and chemical

- specific human health 184

toxicological data. In order to run the screen, a number of input parameters must be utilized (see 185

Figure 1 above). These param eters include a number of physi cal/ chemical properties, 186

application scenarios, application rate, application timing, and human

- health toxicological data. 187

These inputs were obtained or derived from a number of sources. In many cases, 188

physical/ chemical pro perties and toxicological information for individual chemicals wer e 189

publicly available in Agency exposure and risk assessment documents and were defined based 190

on guideline studies intended for this purpose

. However, i n some cases, it was necessary to find 191

or verify the physi cal/ chemical properties of a chemical via other reliable internet resources

. In 192

addition, application scenarios, application rate, and application timing were obtained from 193

pesticide labels. The following sections will discuss the det ails of each specific input parameter 194

for the Volatilization S creening T ool. 195

196

Vapor Pressure (Pa) 197

Vapor pressure is the pressure exerted by a vapor in equilibrium with its solid or liquid state. 198

C hemicals with higher vapor pressure s are more like ly to transform to the gaseous stage and 199

volatilize off o f treated fields. The modified Woodrow e quation utilizes vapor pressure for both 200

the soil and foliar surface flux equations (see Section 2). 201

202

Solubility (mg/L) 203

Solubility is the ability of a substance to dissolve in solution. C hemicals with higher solubility 204

have a greater likelihood to remain in solution and not volatilize . The modified Woodrow 205

equation utilizes solubility only in the soil surface flux equation (see Section 2). 206

207

K

oc (ml/g) 208

K

oc refers to the soil organic carbon

- water partitioning coefficient. It is the ratio of the mass of a 209

chemical that is absorbed in the soil per unit mass of organic carbon in the soil per the 210

equilibrium chemical concentration in the solution. K

oc is usefu l when predicting the mobility of 211

organic soil contaminants ; higher K

oc values correlate to less mobile organic chemicals and lower 212

K

oc values correlate to more mobile organic chemicals . All other parameters being equal, 213

chemicals with l ower K

oc value s ha ve a greater likelihood to volatilize from soil since they have 214

less of an affinity to adsorb to the soil. The modified Woodrow equation utilizes K

oc only in the 215

soil surface flux equation (see Section 2). 216

217Draft for Comment Version

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9 Maximum Single Application R ate (lb ai/A) 218

The modified Woodrow equation utilizes application rate only in the soil surface flux equation 219

(see Section 2). As a result, maximum application rate in the screening tool refers to the 220

maximum labeled application rate for broadcast soil directed applications . The maximum 221

application rate is chosen in order to be protective of all labeled broadcast soil directed 222

application rates. 223

224

Application Timing 225

Application timing refers to when the pesticide is applied during the year

. The screening tool 226

allows for s election of winter, spring, summer, or fall for the timing of application. The 227

application timing impacts the outputs of the AERSCREEN model run s that the Volatilization 228

Screening Tool utilizes. The model runs are impacted by application timing via a var iety of 229

factors such as temperature, albedo, Bowen ratios, surface roughness , and release height. These 230

are discussed in more detail in the Volatilization Screening Tool Guidance Document (see 231

Appendix A) . For the screening analysis, the Agency chose to use s pring as the default 232

application timing because it represents the most likely season of application

. 233

234

Crop Scenario 235

The screening tool generate s results for four different crop height scenarios that are labeled as 236

bare soil, cole, row, and orchards 18

. The crop scenarios in cluded in the screening tool are not a 237

true input

, but rather a built

- in feature of the screening tool. These scenarios are designed to 238

cover the range of potential release heights (i.e., crop canopy heights) that are most commonly 239

associated with semi

- volatile applications. Results for bare soil represent applications to soil 240

prior to or at planting crops. Results for cole crops represent foliar applications to low growing 241

crops (i.e., about 3 feet or less ) such as soybeans, straw berries, cabbage, and some vegetables. 242

Results for row crops represent foliar applications to medium growing crops (i.e., 6 to < 18 feet) 243

such as corn and tomatoes. Results for orchard crops represent foliar applications to orchard 244

crops (i.e., > 18 feet ) such as apples or oranges

. Crop scenario also impacts the potential size of 245

the source field as acres treated can be impacted by the type of crop or application equipment 246

used to treat that crop

. 247

248

Averaging time for concentration (hours) 249

The a veraging time for concentration input is defined based on the toxicological data for a 250

chemical, and refers to the length of time the study animal was exposed in the study used to 251

select the inhalation endpoint. In all cases, the Agency attempts to match the duration over 252

which the estimated air concentrations (i.e., exposure s ) are averaged with the duration the animal 253

was exposed in the toxicological study. For example, if a rat inhalation study is used where the 254

rat was exposed for 4 hours a day, 4 hou rs would be input for the exposure concentration 255

averaging time in the screening tool . As a default, 6 hours (i.e., the typical duration of exposure 256

in many route

- specific toxicological studies as described in Agency guidelines ) was used as the 257

averaging time in all cases where an oral study was used as the basis for the inhalation endpoint. 258

Due to the importance of averaging time, a peak

- to

- mean scaling factor was developed (as 259

discussed in Section 2 above) to allow estimation of concentrations for avera ging periods longer 260

than the one hour AERSCREEN outputs (Appendix A)

. 261

18 Air flow through an orchard is complex and AERSCREEN does not take this complexity into account. Orchard

values should be characterized appropriately.Draft for Comment Version

– March 1, 2014

10 262

Inhalation Point of Departure ( POD) ( μg/m 3 ) 263

Inhalation POD refers to the chemical

- specific human

- health point of departure selected for the 264

inhalation route of exposure in a chemical’s most recent human health exposure or risk 265

assessment . For th is input , there are three options and all three of these were used in the 266

Registration Review chemical volatilization screen ing analysis : 267

• I f, i n the most recent, relevant risk as sessment, a route

- specific inhalation toxicological 268

study was used as the basis for the inhalation endpoint and a human equivalent 269

concentration (HEC) was calculated via use of the Agency’s reference concentration 270

(RfC) methodology

, 19 the Agency used the HE C for the inhalation POD. 271

• I f, i n the most recent, relevant risk assessment, a route

- specific inhalation toxicological 272

study was used as the basis for the inhalation endpoint

, but an HEC was not calculated

, 273

the Agency used the no observed adverse effect lev el (NOAEL) for the inhalation POD. 274

[Note: In the future, HECs could be calculated for these chemicals.] 275

• I f, i n the most recent, relevant risk assessment, a route

- specific inhalation toxicological 276

study is not available and

, thus

, an o ral toxicological study was used as the basis for the 277

inhalation endpoint

, the Agency used the NOAEL fr o m the oral study

, converted to an 278

inhalation equivalent concentration (IEC) via the following equation. 279

280

281

282

283

284

Where: 285

IEC

= inhalation equivalent concentration (μg/m 3 )

, 286

NOAEL

= NOAEL from oral study (mg/kg/day )

, 287

CF1

= conversion factor to convert mg to μg

, 288

A

= absorption ( unitless )

, 289

CF 2

= conversion factor to account for species specific respiratory 290

volume and body weight ( m 3 /hr/kg )

, 291

D

= duration ( hrs/day )

, and 292

AF

= activity factor ( unitless )

. 293

294

Subsequently, the IECs were used for the inhalation POD in the screening tool

. The IECs 295

used in the Registration Review chemical screen can be found in Appendix B

. 296

297

Uncertain ty Factor (UF) (unitless) 298

Uncertainty fac tor refers to the total uncertainty factors applied to an individual chemical. 299

Uncertainty factors can be applied for a variety of reasons including, but not limited to, 300

interspecies factor, intraspecies factor, FQPA (Food Quality Protection Act) factor, LOAEL to 301

NOAEL factor, database uncertainty factor, etc. 302

303

19 U.S. EPA. Methods for Derivation of Inhalation Reference Concentrations (RfCs) and Application of Inhalation

Dosimetry. U.S. Environmental Protection Agency, Office of Resear ch and Development, Office of Health and

Environmental Assessment, Washington, DC, EPA/600/8

- 90/066F.Draft for Comment Version

– March 1, 2014

11 For the Registration Review chemical screening analysis, the following uncertainty factors w ere 304

used: 305

• Route

- specific inhalation study; HEC calculated: 306

o UF for interspecies extrapolation may be reduced to 3X per the RfC methodology; 307

o UF for intraspecies variation wa s retained at 10X ; and 308

o Additional UFs were applied consistent with the most recent, relevant risk 309

assessment for each chemical (e.g., FQPA, LOAEL to NAOEL, etc.)

. 310

• Route

- specific inhalation study; HEC not calculated: 311

o UF for interspecies extrapolation wa s retained at 10X ; 312

o UF for intraspecies variation wa s retained at 10X ; and 313

o Additional UFs were applied consistent with the most recent, relevant risk 314

assessment for each chemical (e.g ., FQPA, LOAEL to NAOEL, etc.). 315

• Oral study; IEC calculated: 316

o UF for interspecies extrapolation wa s retained at 10X ; 317

o UF for intraspecies variation wa s retained at 10X ; 318

o FQPA UF of 10X to address d atabase uncertainty due to lack of an inhalation 319

study wa s app lied consistent with current Hazard and Science Policy Council 320

(HASPOC) policies; and 321

o Additional UFs were applied consistent with the most recent, relevant risk 322

assessment for each chemical (e.g., FQPA, LOAEL to NAOEL, etc.). 323

324



## Section 4 .0: Registration Rev iew Chemical Volatilization Screen 325



## Results 326

327

All pesticides distributed and sold in the United States must be registered by the Agency, based 328

on scientific data showing that they will not cause unreasonable risks to human health, workers, 329

or the environment when used as directed on product labeling. Registration Review is a process 330

that makes sure that, as the ability to assess risk evolv es and as policies and practices change, all 331

registered pesticides continue to meet the statutory standard of no unreasonable adverse effects. 20 332

To ensure that the potential for exposure via volatilization from all impacted pesticides are 333

considered under this process

, the tool s described above were used to perform a bystander 334

inhalation screening analysis for all of the conventional Registration Review chemicals. 335

Appendix C contains the input sheets for the Volatilization Screening Tool for every chemical 336

screened. The Agency plans to use the results of th is screening analysis to determine when 337

volatilization data (i.e., flux studies ) and/or route

- specific inhalation toxicological data (if not 338

already available) should be required fo r a chemical. 339

340

The ana lysis consisted of screening 4 2 7 chemicals. There were three basic outcomes of the 341

screen: no quantitative screen, pass the quantitative screen, and fail the quantitative screen. 342

These outcomes are desc ribed in further detail below. 343

344

345

20 http://www.epa.gov/oppsrrd1/registration_review/index.htmDraft for Comment Version

– March 1, 2014

12 • A q uantitative screen was not performed for 17 4 chemicals

. In all cases, these chemicals 346

have no wide

- scale , agricultural uses. For pesticide s that did not receive a quantitative 347

screen, the Agency has high confidence that use of the pesticide will not result in any 348

me aningful bystander risk due to volatilization of residues based on a variety of specific 349

reasons which are provided in Appendix D

. In general, the categories of reasons f or not 350

performing a quantitative screen include the following: 351

o 22 of these chemicals will have qualitative risk assessments during Registration 352

Review; 353

o 21 of these chemicals either have no currently registered products or have been 354

voluntarily cancelled as part of Registration Review; 355

o 12 of these chemicals have inhalation toxicity studies that show no effects; 356

o 18 of these chemicals are classified as fumigants and thus volatilization is the 357

major route of exposure and is already assessed or will be assessed during 358

Registration Review; 359

o 12 of these chemicals have uses that will result in separ ate post

- application 360

inhalation assessments (e.g., indoor, mosquito adulticide uses); 361

o 6 5 of these chemicals are registered for uses that are not expected to have any 362

significant potential for volatilization : 363

 8 only registered for direct aquatic application uses; 364

 18 are only registered as baits; 365

 6 are only registered for greenhouse use; 366

 5 are only registered for direct animal application uses (e.g., pet, livestock 367

uses); 368

 5 are only registered for seed treatment uses; 369

 6 are only registered for repellent uses; 370

 10 of these chemicals have import tolerances only and thus have no 371

registered uses in the U.S.; 372

 7 are only registered for other unique uses (e.g., post

- harvest treatments, 373

food handling establishments, tree injection, etc.) 374

o 24 of these chemicals have reg istered uses (e.g., residential turf, ornamentals) 375

that cannot be screened with the Volatilization Screening Tool. The potential for 376

these chemicals to volatilize will be dealt with on an individual chemical basis 377

throughout Registration Review. 378

379

• 1 8 5 chem icals passed the quantitative screen . Passing the quantitative screen means that 380

the concentration of concern (i.e., the point of departure divided by the total uncertainty 381

factors or COC ) was not exceeded for any crop scenario at any distance downwind fr om 382

any size field. For a pesticide that passed the screening analysis, the Agency has high 383

confidence that use of the pesticide will not result in any meaningful bystander risk due 384

to volatilization of residues and further data would generally not be requ ired. 385

386

• 6 8 chemicals failed the quantitative screen

. Failing the quantitative screen means that the 387

COC was exceeded for at least one crop scenario at some distance downwind from the 388

field for at least one field size. Of the chemicals that failed the quantitative screen , 2 4 389

have route

- specific inhalation toxico logical data

, while 4 4 do not. There are 5 3 390

occurrences of a foliar application failing the screen and 2 4 occurrences of a soil 391Draft for Comment Version

– March 1, 2014

13 application failing the screen (i.e., some chemicals have multiple crop scenarios that 392

fail). If a pesticide fails the screening analysis, the Agency would examine whether data 393

are available to refine the analysis and whether additional data should be required. 394

Failing the screening analysis does not necessarily mean t hat the pesticide poses a risk 395

of concern due to volatilization. Rather, due to the purposely conservative nature of the 396

screening analysis (see Section 5.0), failing the screen is merely a trigger for the Agency 397

to further investigate the question of exp osure from volatilization of the pesticide. 398

Potential additional data that could help to refine a failing screen include the following: 399

o volatilization data (i.e., flux studies ); 400

o route

- specific inhalation toxicological data if none are available; and/or 401

o va por

- phase dose administration inhalation toxicological data if only aerosol dose 402

administration inhalation toxicological data are available. 403

404

Table 1 presents the details of the 68 chemicals that failed the quantitative screen. In addition, 405

Appendix D provides details on the screen for the entire 4 2 7 chemicals. 406Draft for Comment Version

– March 1, 2014

14 407

Table 1: Registration Review Chemicals that Fail the Quantitative Volatilization Screen Analysis

Chemical Inhalation

Tox Study

Available ? Comments

Acephate Yes Cole and row scenarios exceed COC at 20 acre and larger fields.

Acibenzolar No Cole scenario exceeds COC at 60 acre and larger fields.

Atrazine No Soil scenario exceeds COC at all field sizes.

Bromoxynil and esters No Cole and row scenarios exceed COC at 60 acre and larger fields.

Buprofezin No Cole and orchard scenarios exceed at all field sizes.

Butylate No Soil scenario exceeds COC at all field sizes. All applications soil incorporated, likely conservative.

Captan Yes Cole , row, and orchard scenarios exceed COC at all field sizes.

Chlorethoxyfos Yes Row scenario exceeds COC at all field sizes.

Chlorothalonil Yes Cole , row, and orchard scenarios exceed COC at all field sizes.

Chlorpropham No Cole scenario exceeds COC at all field sizes. Only “agricultural” use is Easter lilies which are only grown in

Norther CA and Southern OR

. Chlorpyrifos Yes Cole , row, orchard scenarios exceed COC at all field sizes.

Daminozide (Alar) No Row scenario exceeds COC at all field sizes.

DCNA No Cole and row scenarios exceed COC at 20 acre field sizes and larger.

Diazinon Yes Cole , row, orchard scenarios exceed COC at all field sizes.

Dicamba No Cole and row scenarios exceed COC at 40 acre field sizes and larger.

Dichlobenil Yes Row and orchard scenarios exceed COC at all field sizes.

Dicrotophos Yes Cole scenario exceeds COC at all field sizes.

Dimethenamid No Cole and soil scenarios exceed COC at all field sizes.

Dimethoate Yes Cole , row and orchard scenarios exceed COC at all field sizes.

Diquat Dibromide Yes Cole and row scenarios exceed COC at all field sizes. Orchard scenario exceeds COC at 80 acre field si zes and

larger.

Emamectin Benzoate No Cole scenario exceeds COC at 60 acre field sizes and larger.

Endothall, and salts No Cole and row scenarios exceed COC at all field sizes.

EPTC Yes Cole and r ow scenarios exceed COC at all field sizes.Draft for Comment Version

– March 1, 2014

15 Table 1: Registration Review Chemicals that Fail the Quantitative Volatilization Screen Analysis

Chemical Inhalation

Tox Study

Available ? Comments

Esfenvalerate No Row scenario exceeds COC at 60 acre field sizes and larger.

Ethalfluralin No Soil, cole , and row scenarios exceed COC at all field sizes.

Ethofumesate No Soil scenarios exceed COC at all field sizes.

Ethoprop No Soil scenario exceeds COC at all field sizes. All applications soil incorporated, likely conservative.

Fenpropathrin No Row scenario exceeds COC at 120 acre field size only.

Ferbam No Cole scenario exceeds COC at 20 acre field sizes and larger.

Flumetsulam No Soil scenario exceeds COC at 20 acres and larger

.

Flumioxazin No Soil, cole , and row scenarios exceed COC at all field sizes.

Fomesafen No Soil scenarios exceed COC at all field sizes.

Formetanate HCl No Row and orchard scenarios exceed COC at all field sizes.

Fosthiazate Yes Row scenarios exceed COC at all field sizes.

Linuron No Soil, cole , and row scenarios exceed COC at all field sizes.

MCPA No Soil and cole scenarios exceed COC at most field sizes.

Metalaxyl No Cole and row scenarios exceed COC at 60 acre field sizes and larger.

Methamidophos Yes Cole and row scenarios exceed COC at all field sizes.

Metolachlor &

s

- Metolachlor No Cole and row scenarios exceed COC at 60 acre field sizes and larger.

Metsulfuron No Row scenario exceeds COC at 40 acre field sizes and larger.

Naled Yes Cole , row, and orchard scenarios exceed COC at all field sizes.

Nitrapyrin No Row scenarios exceed COC at all field sizes.

Paraquat dichloride Yes Cole and row scenarios exceed COC at all field sizes.

PCNB No Cole , row, orchard, and soil scenarios exceed COC at all field sizes

.

Pendimethalin No Soil, cole , row, and orchard scenarios exceed COC at all field sizes

.

Phorate No Soil scenario exceeds COC at all field sizes. Note: Granular products only. All applications soil incorporated,

likely conservative.

Phosmet No Cole and row scenarios exceed COC at all field sizes.Draft for Comment Version

– March 1, 2014

16 Table 1: Registration Review Chemicals that Fail the Quantitative Volatilization Screen Analysis

Chemical Inhalation

Tox Study

Available ? Comments

Pronamide No Soil, cole, and row scenarios exceed COC at all field sizes.

Propachlor No Soil scenarios exceed COC at all field sizes.

Propazine No Soil scenario exceed COC at 60 acre field sizes and larger.

Pyrethrin and derivatives Yes Cole and row scenarios exceed COC at 40 acre field sizes and larger.

Pyridaben Yes Cole scenario exceeds COC at 40 acre field sizes and larger.

Pyrimethanil No Cole scenario exceeds COC at 40 acre field sizes and larger.

Simazine No Soil scenario exceeds COC at 40 acre field sizes and larger.

Tebupirimiphos Yes Soil and row scenarios exceed COC at all field sizes

.

Tefluthrin Yes Soil scenario exceeds COC at all field sizes.

Terbacil No Row scenario exceeds COC at 120 acre field size only.

Terbufos Yes Soil scenario exceeds COC at all field sizes. Note: Granular products only. All applications soil incorporated,

likely conservative.

Tetraconazole Yes Cole , row, and orchard scenarios exceed COC at all field sizes.

Thiazopyr No Soil scenario exceeds COC at all field sizes.

Thiobencarb No Soil scenario exceeds COC at all field sizes.

Thiodicarb Yes Cole and row scenarios exceed COC at all field sizes. Note: Inhalation study is on dust formulation.

Thiophanate

- methyl No Cole and row scenarios exceed COC at 40 acre field sizes and larger.

TPTH (Triphenyltin hydroxide) Yes Cole and row scenarios exceed COC at all field sizes. Orchard exceed COC at 40 acre field sizes and larger.

Triadimefon No Orchard scenario exceeds COC at 80 acre field size only.

Triallate No Soil scenario exceeds COC at all field sizes.

Triclopyr, salts and esters No Row scenario exceeds COC at 80 acre field sizes and larger.

Triflumizole No Cole scenario exceeds COC at 40 acre field sizes and larger.

Trifluralin Yes Soil scenario exceeds COC at 20 acres and larger

.Draft for Comment Version

– March 1, 2014

17 

## Section 5 .0: Registration Review Chemical Volatilization Screen 408



## Characterization 409

410

There are a number of considerations and uncertainties that should be taken into account i n the 411

interpretation of th e results of the Registration Review chemical volatilization screening analysis 412

presented in Section 4

. The Agency acknowledges that there are uncertainties associated with 413

the current knowledge base relating to the processes that govern volatilization of conventional 414

pesticides from soil and foliar surfaces . However, the Agency is confident that the screening 415

analysis uses data and methodologies that results in a consistent and health protective framework 416

to assess whether a pesticide does not pose potential inhalation bystander risks resulting from 417

volatil ization of conventional pesticides. 418

419

Some of the considerations and uncertainties that should be considered in the interpretation of 420

the screening analysis results include the following : 421

422

Modified Woodrow Equation Characterization 423

• Use of the modified Woodr ow equation to predict flux from soil and foliar surfaces is 424

consistent with the recommendations of the December 2009 Federal Insecticide, 425

Fungicide, and Rodenticide Act (FIFRA) Scientific Advisory Panel (SAP) meeting 426

entitled “ Scientific Issues Associated with Field Volatilization of Conventional 427

Pesticides ” 21

. In order to be more health protective, the Agency used the data provided in 428

the Woodrow paper to estimate the 90 % upper confidence limit around the slope and 429

intercept so that 90% of the estimated f lux rates would exceed the measured values. In 430

addition, as more volatilization data for other chemicals become available it may be 431

possible to update this equation. 432

• It is important to note that the Agency used physi cal/ chemical properties for the active 433

ingredient

, or technical chemical

, and these may not reflect the physi cal/ chemical 434

properties of the end

- use product (s)

. Most pesticides are mixed or diluted with water, 435

solvents, and inerts. The addition of these components can impact these 436

physi cal/ che mical properties relative to the active ingredient in its technical form. 437

438

AERSCREEN Characterization 439

• AERSCREEN generates a maximum one

- hour air concentration assuming air flow 440

remains constant and in a single direction . The values reported in the tool are worst case 441

values and should be characterized as such (Appendix A)

. 442

• AERSCREEN models air flow for simple, uniform terrain. Because of the complex 443

topography and air flow patterns in an orchard, use of the results generated for orchards 444

should be chara cterized appropriately

. 22 While the topography for cole or row crops is 445

not completely uniform, it is believed that the differences are not significant enough to 446

impact the air flow regime and concentrations outside the treated field. 447

21 http://www.regulations.gov/ ( EPA

- HQ

- OPP

- 2009

- 0687 )

22 Unlike AERSCREEN, (interactive mode), the refined model AERMOD considers flow around or above complex

mountainous terrain. However, neither AERSCREEN nor AERMOD considers complex flow patterns through

highly localized non

- homogeneous surfaces such as orchard groves.Draft for Comment Version

– March 1, 2014

18 • For simplicity, the fields in AERSCREEN were modeled as squares and the modeled 448

field sizes were limited. While this may not necessarily reflect all real

- world agricultural 449

scenarios , it is consistent with current Agency fumigant assessment methodology. 450

• In most cases, the maximum AERSCREEN concentration at any distance corresponded 451

to the minimum wind speed of 0.5 m/s. In the case of many, but not all, conventional 452

pesticides , the maximum flux rate is likely to occur during the middle of the day when 453

temperatures are highe st and a ir turbulence and wind speed have increased. As a result, 454

for conventional pesticides , matching the maximum flux rate with the minimum wind 455

speed will result in conservative, health protective air concentr ations around a treated 456

field. 457

• Users need appropriate justifica tion for selecting field sizes and crop scenarios used in 458

the modeling runs. Any differences between what was modeled and what is expected to 459

occur in the real world should be characterized. 460

• Although the Agency chose to use spring as the default application timing for the 461

Registration Review chemical screening analysis, if a particular pesticide has a very 462

specific application timing requirement on the label, use of another season may be more 463

appropriate and result in a different outcome

. 464

465

Hazard Characterization 466



## • The Volatilization Screening Tool provides risk estimates for exposure to chemicals in 467

the vapor phase; however, even f or those chemicals that have route

- specific inhalation 468

toxicological data, these studies are typically not performed under vapor phase 469

conditions . The majority of these data are performed with aerosols

, and following 470

Agency guidelines, the particles are typically 2

- 4 μm in size. V apors and particl es have 471

the potential to be different in terms of the site of deposition, absorption, dose, and 472

toxicity. At the 2009 Volatilization SAP, one of the questions asked by t he Agency of 473

the Panel related to the difference in toxicity between vapor s and aeroso l s; however

, t he 474

Panel knew of no studies that have investigated the health impact of exposure to a single 475

chemical using different phases (e.g., vapors and aerosols). Since that time, data 476

conducted using chlorpyrifos indicate that aerosols may be more t oxic than vapors, at 477

least for this specific chemical . More inhalation toxicological data, including direct 478

comparison vapor/aerosol studies, are needed t o further elucidate this issue. 479