Date: 

Subject: 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

June 24, 2014 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

Saflufenacil. Occupational and Residential Exposure Assessment for Proposed 

Uses on Grass Forage/Hay/Grass Grown for Seed and Olives, and an Amended 

Use on Wheat and Barley. 

PC Code: 118203 DP Barcode: 0418586 

Decision No.: 480698,481309 

Petition No.: N/A 

Risk Assessment Type: Occupational/Residential 

Exposure Assessment 

TXRNo.:NA 

MRIDNo.: NA 

Registration No.: 7969-278, 7969-297, 7969-276 

Regulatory Action: Section 3 

Case No.: 7277 

CAS No.: 372137-35-4 

40 CFR: §180.649 

From: Kelly 

Risk 

Health 

Assessment 

M. 

Effects 

Lowe, 

Division 

Environmental 

Branch 

(7509P) 

1 (RAB 

ScientiC---G) 

1) 

~ 

Through: Charles W. Smith, Branch Chief 

Health Effects Division (7509P) 

To: 

and 

Matthew Lloyd, Reviewer 

Kristin Rury, Reviewer ¥J 

Exposure Science Advisory Committee 

Kathryn Montague, RM23 

Bethany Benbow 

Herbicide Branch 

Registration Division (7505P) 

Introduction 

The Registration Division (RD) requested that the Health Effects Division (HED) conduct an 

exposure and risk assessment for three actions related to saflufenacil: 

(1) a new use on grass forage/hay/grass grown for seed; 

(2) a new use on olives; and 

(3) amended uses on barley and wheat. 

Page 1 of22 
Page 2 of 22 

A quantitative assessment of occupational exposure has been conducted for all of the proposed 

uses of saflufenacil; however, it was determined that an updated exposure assessment was not 

necessary for the amended uses on wheat and barley since both are registered use sites and have 

been assessed previously (Memo, K. Lowe, 18-May-2009, D349939). The proposed amendment 

(adding a use pattern for dessication/harvest aid purposes) does not change the maximum 

application rate previously assessed, and would not impact the occupational post-application 

assessment. The only relevant activity occurring at or after harvest would be mechanical 

harvesting, which is expected to result in negligible exposure. The previous assessment provides 

the exposure and risk estimates relevant for the amended uses on wheat and barley. 

It is HED policy to use the best available data to assess exposure. Several sources of generic 

data were used in this assessment as surrogate data in the absence of chemical-specific data, 

including Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1); the Agricultural 

Handler Exposure Task Force (AHETF) database; the Outdoor Residential Exposure Task Force 

(ORETF) database; and the Agricultural Reentry Task Force (ARTF) database. Some of these 

data are proprietary, and subject to the data protection provisions of the Federal Insecticide, 

Fungicide, and Rodenticide Act (FIFRA). 

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

(ExpoSAC) on 27-FEB-2014. 
Page 3 of 22 

Table of Contents

1.0 Executive Summary ............................................................................................................. 4

2.0 Risk Assessment Conclusions and Recommendations ........................................................ 6

2.1 Summary of Risk Estimates ............................................................................................. 6

2.2 Label Recommendations .................................................................................................. 6

2.3 Data Deficiencies and Requirements ............................................................................... 6

3.0 Hazard Characterization ....................................................................................................... 6

4.0 Exposure and Use Profile..................................................................................................... 8

5.0 Residential Exposure and Risk Estimates .......................................................................... 10

5.1 Spray Drift ...................................................................................................................... 10

5.2 Residential Bystander Post-Application Inhalation Exposure ....................................... 10

6.0 Occupational Exposure and Risk Estimates ...................................................................... 10

6.1 Occupational Handler Exposure/Risk Estimates............................................................ 10

6.2 Occupational Post-application Exposure/Risk Estimates .............................................. 16

6.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates ...................... 16

6.2.2 Occupational Post-application Dermal Exposure/Risk Estimates .......................... 16

Appendix A. Summary of Occupational Non-cancer Algorithms ............................................... 20
Page 4 of 22 

1.0 Executive Summary 

Saflufenacil is a pre- and post-emergence herbicide that acts by inhibiting protoporphyrinogen 

IX oxidase, which leads to chlorophyll destruction by photooxidation and causes bleaching of 

emerging foliar tissue. It is currently registered for use on legume vegetables, citrus fruit, pome 

fruit, stone fruit, tree nuts, cereal grains, cotton, sunflowers, grapes, and soybean. BASF 

Corporation is requesting three actions related to saflufenacil: (1) a new use on grass 

forage/hay/grass grown for seed, (2) a new use on olives; and (3) amended uses on barley and 

wheat. While the new uses have been quantitatively assessed in this document, it was 

determined that an exposure assessment was not necessary for the amended uses on wheat and 

barley since both are registered use sites and have been assessed previously (Memo, K. Lowe, 

18-May-2009, D349939). There are no changes to the exposure profile for these uses, therefore, 

the previous assessment provides the exposure and risk estimates relevant for the amended uses 

on wheat and barley. 

Exposure and Proposed Use Profile 

The proposed new uses involve three labels: Sharpen® (EPA Reg. #: 7969-278), HeatTM X 

(EPA Reg. #: 7969-297), and Treevix® Powered by Kixor® Herbicide (EPA Reg. #: 7969-276). 

The proposed uses are on forage grasses grown in pastures and rangeland, or in fields grown for 

forage, silage and hay production, and for postemergence-directed broadleaf weed control in 

olive trees. The grass/forage uses are proposed at a maximum single application rate of 0.089 lb 

ai/A during the dormant season and 0.045 lb ai/A for in-season weed control, to be made to the 

foliage via aerial or groundboom applications; it may also be applied via dry-bulk fertilizer. 

Multiple applications can be made during the dormant season (not to exceed a maximum of 

0.089 lb ai/A) and in season (not to exceed 0.134 lb ai/A), with a retreatment interval of 14 days. 

The olive use is proposed at a maximum application rate of 0.044 lb ai/A, to be made as a postemergence spray directed at the base of the trunk targeting emerged weeds via groundboom or 

handheld equipment. Multiple applications can be made up to four times per year, with a 

retreatment interval of 21 days. Application via aerial equipment is prohibited for the proposed 

olive use. None of the proposed uses allow for application via chemigation. The amended use 

on barley, wheat, and triticale is for the addition of a harvest aid/dessication use pattern to the 

label. The amended use directions recommend a maximum application rate of 0.045 lb ai/A by 

aerial or groundboom equipment. The restricted entry interval for the proposed and amended 

uses is 12 hours. Based on the proposed use pattern, it has been determined that the potential 

exposure scenarios that will need to be assessed include short- and intermediate-term 

occupational exposures (handler and post-application). 

Hazard Profile 

For all occupational risks, the point of departure (POD) for short- and intermediate-term dermal 

and inhalation exposure/risk assessment is a no-observed adverse-effect level (NOAEL) of 5 

mg/kg/day based on decreased fetal body weights and increased skeletal variations at the lowestobserved adverse-effect level (LOAEL) of 20 mg/kg/day in the developmental study in rats. 

Since an oral study was used, a dermal absorption factor of 3% was used for the dermal risk 

assessment derived from a dermal penetration study (MRID 47128214). Since no inhalation 

absorption data are available, toxicity by the inhalation route is considered to be equivalent to the 

estimated toxicity by the oral route of exposure. A 69 kg body weight was used for all adult 
Page 5 of 22 

exposure calculations because the endpoint is from a development study and was observed in the 

fetuses. Chronic exposures are not expected. Saflufenacil was classified as not carcinogenic 

based on the lack of tumors in the mouse and rat carcinogenicity studies and lack of 

mutagenicity. The total uncertainty factor (UF) that was applied to occupational risk 

assessments is 100 for short- and intermediate-term risks (10x interspecies factor, 10x 

intraspecies factor). Since the POD for the dermal and inhalation routes of exposure are based 

on the same effect, the exposures from these routes can be combined to estimate total risk. 

Residential Exposure and Risk 

There are no residential uses proposed or currently registered for saflufenacil. Therefore, 

residential handler and post-application exposure/risk were not assessed. 

Occupational Exposure and Risk 

The occupational handler exposure and risk estimates indicate that the short- and intermediateterm dermal and inhalation combined margins of exposure (MOEs) are not of concern to HED 

(i.e., MOE > 100). At the baseline level of personal protection (i.e., no gloves and no respirator), 

all scenarios result in combined MOEs (dermal + inhalation) ≥ level of concern (LOC; MOEs ≥

470). 

The occupational post-application dermal exposure and risk estimates are greater than the LOC 

of 100 on the day of application, ranging from 6,000 to 10,000 depending on crop and activity. 

Since the post-application assessment is not a concern on Day 0 (12 hours following 

application), the restricted entry interval (REI) is based on the acute toxicity of saflufenacil 

technical material. Saflufenacil is classified as toxicity category III for acute oral, acute dermal 

toxicity, and acute eye irritation. It is classified as toxicity category IV for acute inhalation 

toxicity and acute dermal irritation. It is not a dermal sensitizer. Therefore, the acute toxicity 

categories for this chemical require a 12 hour REI under 40 CFR 156.208 (c) (2) (iii). The 12-

hour REI, which currently appears on the labels, is adequate for the proposed uses. 

Based on the Agency's current practices, a quantitative non-cancer occupational post-application 

inhalation exposure assessment was not performed for saflufenacil at this time. If new policies 

or procedures are put into place, the Agency may revisit the need for a quantitative occupational 

post-application inhalation exposure assessment for saflufenacil. 

Human Studies Review 

This risk assessment relies in part on data from studies in which adult human subjects were 

intentionally exposed to a pesticide or other chemical. These data, which include studies from 

the PHED 1.1, the AHETF database, and the ARTF database are (1) subject to ethics review 

pursuant to 40 CFR 26, (2) have received that review, and (3) are compliant with applicable 

ethics requirements. For certain studies, the ethics review may have included review by the 

Human Studies Review Board. Descriptions of data sources, as well as guidance on their use, 

can be found at the Agency website1

. 

 

1 http://www.epa.gov/pesticides/science/handler-exposure-data.html and 

http://www.epa.gov/pesticides/science/post-app-exposure-data.html
Page 6 of 22 

2.0 Risk Assessment Conclusions and Recommendations 

2.1 Summary of Risk Estimates 

There are no occupational risk estimates of concern for the proposed uses for saflufenacil. At the 

baseline level of personal protection (i.e., no gloves and no respirator), all scenarios result in 

combined MOEs (dermal + inhalation) ≥ LOC (MOEs ≥ 470). The occupational postapplication dermal exposure and risk estimates are greater than the LOC of 100 on the day of 

application, ranging from 6,000 to 10,000 depending on crop and activity. 

2.2 Label Recommendations 

There are no label recommendations based on the proposed uses. 

2.3 Data Deficiencies and Requirements 

There are no data deficiencies based on the proposed or currently registered uses. 

3.0 Hazard Characterization 

Saflufenacil is classified as toxicity category III for acute oral, acute dermal toxicity, and acute 

eye irritation. It is classified as toxicity category IV for acute inhalation toxicity and acute dermal 

irritation. It is not a dermal sensitizer. Table 3.1 presents a summary of the acute toxicity 

information for saflufenacil. 

Table 3.1. Acute Toxicity Profile – Saflufenacil

Guideline No. Study Type MRID(s) Results Toxicity 

Category Purity 

870.1100 Acute oral [rat] 47128101 LD50 was >2000 

mg/kg bw III 93.8% 

870.1200 Acute dermal [rat] 47128102 LD50 > 2000 

mg/kg III 93.8% 

870.1300 Acute inhalation [rat] 47128103 LC50 > 5.3 mg/L IV 93.8% 

870.2400 Acute eye irritation [White New 

Zealand rabbit] 47128105 minimal irritation III 93.8% 

870.2400 Acute eye irritation [White New 

Zealand rabbit] 47128104 minimal irritation III 93.8% 

870.2500 Acute dermal irritation [rabbit] 47128106 Slightly irritating IV 93.8% 

870.2600 Skin sensitization [Guinea Pig] 47128107 Not a Sensitizer N/A 93.8% 

Subchronic and chronic toxicity studies for saflufenacil in rats, mice, and dogs identified the 

hematopoietic system as the primary target of saflufenacil. Decreased hematological parameters 

were seen at about the same dose level across species, except dogs, where the effects were seen 

at a slightly higher dose. These effects occurred around the same dose level from short- through 

long-term exposures without increasing in severity. Effects were also seen in the liver in mice, 

the spleen in rats, and in both these organs in dogs. These effects also occurred around the same 

dose level from short- through long-term exposures without increasing in severity. 
Page 7 of 22 

Increased fetal susceptibility was observed in the developmental toxicity studies in the rat and 

rabbit and in the 2-generation reproduction study in the rat. Developmental effects such as 

decreased fetal body weights and increased skeletal variations occurred at doses that were not 

maternally toxic in the developmental study in rats, indicating increased quantitative 

susceptibility. In rabbits, developmental effects such as increased liver porphyrins were 

observed at doses that were not maternally toxic, indicating increased quantitative susceptibility. 

In the 2-generation reproductive toxicity study in rats, the reported offspring effects were more 

severe than the maternal effects at the same dose level, indicating evidence for increased 

qualitative susceptibility. 

In a 28-day dermal toxicity study in rats, saflufenacil did not induce any type of dermal or 

systemic toxicity up to the limit dose of 1,000 mg/kg/day. The Hazard and Science Policy 

Council (HASPOC) met on July 18, 2013 to discuss the need for a subchronic inhalation toxicity 

study for saflufenacil (TXR 0056720). Based on a weight-of-evidence approach, the HASPOC 

concluded that a subchronic inhalation toxicity study is not needed for saflufenacil at this time 

for the following reasons: 1) the physical/chemical properties of saflufenacil including its low 

volatility (3.4 x 10-17 mmHg, 20°C); (2) its low acute inhalation toxicity (Toxicity Category IV); 

and (3) the use of an oral POD resulting in MOEs that are ≥9,800, and are above the Agency’s 

level of concern. 

 

The toxicity endpoints and the PODs for various exposure scenarios are presented in Table 3.2. 

For all occupational risks, the POD for short- and intermediate-term dermal and inhalation 

exposure/risk assessment is a NOAEL of 5 mg/kg/day based on decreased fetal body weights and 

increased skeletal variations at 20 mg/kg/day (LOAEL) in the developmental study in rats. For 

overall risk, the dermal and inhalation exposures were added together and compared to the same 

NOAEL. Chronic exposures are not expected. 

Table 3.2. Summary of Toxicological Doses and Endpoints for Saflufenacil for Use in Occupational Human Health 

Risk Assessments. 

Exposure/ 

Scenario 

Point of 

Departure 

(POD) 

Uncertainty Factors 

Level of Concern 

for Risk 

Assessment 

Study and Toxicological Effects 

Dermal ShortIntermediate-Term (1-

30 days, 1-6 months, 

and > 6 months, 

respectively) 

NOAEL=5 

mg/kg/day 

UFA = 10X 

UFH = 10X 

Dermal absorption 

Factor = 6% 

Occupational LOC 

for MOE = 100 

Prenatal developmental in (rat) 

Developmental NOAEL= 5 mg/kg/day 

LOAEL = 20 mg/kg/day based on based 

on decreased fetal body weights and 

increase skeletal variations. 

Inhalation ShortIntermediate-Term (1-

30 days, 1-6 months, 

and > 6 months, 

respectively) 

NOAEL=5 

mg/kg/day 

UFA = 10X 

UFH = 10X 

Inhalation-absorption 

assumed equivalent to 

oral 

Occupational LOC 

for MOE = 100 

Prenatal developmental in (rat) 

Developmental NOAEL= 5 mg/kg/day 

LOAEL = 20 mg/kg/day based on based 

on decreased fetal body weights and 

increase skeletal variations. 

Cancer (oral, dermal, 

inhalation) 

Classification: Classification: Not carcinogenic based on the lack of tumors in the mouse and rat 

carcinogenicity studies and lack of mutagenicity. 

Point of Departure (POD) = A data point or an estimated point that is derived from observed dose-response data and used to mark the beginning 

of extrapolation to determine risk associated with lower environmentally relevant human exposures. NOAEL = no observed adverse effect level. 

LOAEL = lowest observed adverse effect level. UF = uncertainty factor. UFA = extrapolation from animal to human (intraspecies). UFH = 

potential variation in sensitivity among members of the human population (interspecies). FQPA SF = FQPA Safety Factor. MOE = margin of 

exposure. LOC = level of concern. 
Page 8 of 22 

The Agency’s LOC for risks (i.e., target level for MOE) is defined by the uncertainty factors that 

are applied to the assessment. The Agency applies a factor of 10X to account for interspecies 

extrapolation to humans from the animal test species and another factor of 10X to account for 

intra-species sensitivity. The total uncertainty factor that has been applied to occupational risk 

assessments is 100 for short- and intermediate-term dermal and inhalation exposures. 

Absorption 

A DAF of 6% was estimated for saflufenacil based on the highest degree of skin penetration at 

the lowest dose tested in a rat dermal absorption study. Immediately after a 10-hour exposure, 

the estimated DAF was 3.4%. However, about 50% of the radioactivity remaining at the end of 

exposure penetrated through the skin during a 120-hour (5-day) observational period, indicating 

that skin-bound residues of saflufenacil are available for dermal absorption. With skin-bound 

residues included, a DAF of 6% should be applied for converting oral doses to dermal equivalent 

doses to assess the potential risk associated with dermal exposures to saflufenacil. 

Body Weight 

Since the dermal and inhalation PODs are based on developmental and/or fetal effects, the body 

weight appropriate for dermal and inhalation assessments is 69 kg.

4.0 Exposure and Use Profile 

Saflufenacil is currently registered for use on legume vegetables, citrus fruit, pome fruit, stone 

fruit, tree nuts, cereal grains, cotton, sunflowers, grapes, and soybean. BASF Corporation is 

requesting new uses on grass forage/hay/grass grown for seed and olive trees. It is also 

requesting amended uses on barley and wheat. As noted above, it was determined that an 

updated exposure assessment was not necessary for the amended uses on wheat and barley since 

both are registered use sites and have been assessed previously (Memo, K. Lowe, 18-May-2009, 

D349939). The proposed amendment, adding a use pattern for dessication/harvest aid purposes, 

could potentially result in occupational handler exposure; however, the amended use pattern does 

not change the maximum application rate previously assessed. In addition, the only relevant 

activity occurring at or after harvest would be mechanical harvesting, which is expected to result 

in negligible exposure. The previous assessment provides the exposure and risk estimates 

relevant for the amended uses on wheat and barley. 

Based on the proposed new uses, it has been determined that the potential exposure scenarios 

that will need to be assessed include short- and intermediate-term occupational exposures 

(handler and post-application). A summary of the proposed and amended use directions are 

included in Table 4.1 below. 

 
Page 9 of 22 

Table 4.1. Summary of Proposed and Amended Use Directions for Saflufenacil. 

Applic. Timing, Type, and Equip. 

Formulation 

[EPA Reg. 

No.] 

Application 

Rate 

Max No. 

Applications 

per Season 

Max Seasonal 

Application 

Rate 

Use Directions 

and Limitations 

Sharpen®1 (7969-278) 2.85 lb ai/gal (29.74% ai) 

HeatTM X1 (7969-297) 2.85 lb ai/gal (29.74% ai) 

Treevix® Powered by Kixor® Herbicide (7969-276) (70% ai) 

Forage Grasses Grown in Pastures and Rangeland, or in Fields Grown for Forage, Silage and Hay Production

Apply as broadcast burn-down spray to 

weeds in the dormant season (i.e., when 

grasses are not actively growing in the 

fall (postharvest), during the winter 

dormancy period, or in the early spring 

before green-up) 

Groundboom, Aerial, or 

Dry Bulk Fertilizer 

Liquid 

(7969-278 and 

7969-297) 

4 fl oz/A = 

0.089 lb 

ai/A 

0.89 lb 

ai/ton 

fertilizer 

Not specified 

0.089 lb ai/A 

(0.134 lb ai/A 

for entire 

season; both 

dormant and in 

season apps) 

Do not apply via 

chemigation. 

REI = 12 hours. 

RTI = 14 days. 

PHI = 7 days 

Apply as broadcast postemergence 

spray to control weeds in season (i.e., 

actively growing cool-season forage 

grasses). Can be made in the spring 

after green-up. 

Groundboom, Aerial, or 

Dry Bulk Fertilizer 

Liquid 

(7969-278 and 

7969-297) 

2 fl oz/A = 

0.045 lb 

ai/A 

0.45 lb 

ai/ton 

fertilizer 

Not specified 

0.045 lb ai/A 

(0.134 lb ai/A 

for entire 

season; both 

dormant and in 

season apps) 

Olive Trees 

Apply as broadcast, banded, or spot 

application directed at the base of the 

tree trunk 

Groundboom, Manually-pressurized 

handwand, Backpack 

Water 

Dispersible 

Granule 

(WDG) or Dry 

Flowable (DF) 

(7969-276) 

1 oz/A = 

0.044 lb 

ai/A 

0.01 oz/gal 

= 0.00044 lb 

ai/gal 

Max of 4 

apps only if 

one or two 

occur during 

the period of 

postharvest 

to the 

beginning of 

bloom; Max 

of 3 apps 

while trees 

are in 

fruiting stage 

until crop 

harvest 

0.131 lb 

ai/A/crop 

season or 0.175 

lb ai/A/crop 

season when 

one or more 

applied during 

postharvest 

period. 

0.175 lb 

ai/A/year 

Do not apply via 

aerial or 

chemigation 

equipment. 

Do not use in 

tree nurseries. 

REI = 12 hours. 

RTI = 21 days. 

PHI = 0 days 

Barley, Wheat, Triticale 

Apply for harvest aid/dessication to 

dessicate the crop and weeds and to 

facilitate crop harvest 

Aerial and Groundboom 

Liquid 

(7969-278) 

2 fl oz/A = 

0.045 lb 

ai/A Not specified 

2 fl oz/A = 

0.045 lb ai/A 

REI = 12 hours 

PHI = 3 days 

1. PPE = long-sleeved shirt and long pants, shoes plus socks, chemical-resistant gloves, protective eyewear such as face shield, goggles, or safety 

glasses. 
Page 10 of 22 

5.0 Residential Exposure and Risk Estimates 

There are no residential uses proposed or currently registered for saflufenacil. Therefore, 

residential handler and post-application exposure/risk were not assessed. 

5.1 Spray Drift 

Spray drift is a potential source of exposure to those nearby pesticide applications. This is 

particularly the case with aerial application, but, to a lesser extent, spray drift can also be a 

potential source of exposure from the ground application methods (e.g., groundboom and 

airblast) employed for saflufenacil. The Agency has been working with the Spray Drift Task 

Force (a task force composed of various registrants which was developed as a result of a Data 

Call-In issued by EPA), EPA Regional Offices and State Lead Agencies for pesticide regulation 

and other parties to develop the best spray drift management practices (see the Agency’s Spray 

Drift website for more information). 2 The Agency is also taking means to qualitatively and 

qualitatively address spray drift as a potential source of exposure in risk assessments for 

pesticides through existing programs such as Ag Drift and chemical specific properties of 

pesticides. The potential for spray drift will be quantitatively evaluated for each pesticide during 

the Registration Review process which ensures that all uses for that pesticide will be considered 

concurrently. 

5.2 Residential Bystander Post-Application Inhalation Exposure 

Based on the Agency's current practices, a quantitative post-application inhalation exposure 

assessment was not performed for saflufenacil at this time primarily because of the low acute 

inhalation toxicity (Toxicity Category IV) and the low vapor pressure (3.4 x 10-17 mmHg, 20°C). 

However, volatilization of pesticides may be a source of post-application inhalation exposure to 

individuals nearby pesticide applications. The Agency sought expert advice and input on issues 

related to volatilization of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act 

Scientific Advisory Panel (SAP) in December 2009, and received the SAP’s final report on 

March 2, 20103

. The Agency is in the process of evaluating the SAP report and may, as 

appropriate, develop policies and procedures to identify the need for and, subsequently, the way 

to incorporate post-application inhalation exposure into the Agency's risk assessments. If new 

policies or procedures are developed, the Agency may revisit the need for a quantitative postapplication inhalation exposure assessment for saflufenacil. 

6.0 Occupational Exposure and Risk Estimates 

6.1 Occupational Handler Exposure/Risk Estimates 

HED uses the term handlers to describe those individuals who are involved in the pesticide 

application process. HED believes that there are distinct job functions or tasks related to 

applications and exposures can vary depending on the specifics of each task. Job requirements 

(amount of chemical used in each application), the kinds of equipment used, the target being 

 

2

 Available: http://www.epa.gov/opp00001/factsheets/spraydrift.htm 3

 Available: http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html
Page 11 of 22 

treated, and the level of protection used by a handler can cause exposure levels to differ in a 

manner specific to each application event. 

Based on the anticipated use patterns, and the current labeling regarding types of equipment and 

techniques that can be used, occupational handler exposure is expected. The quantitative 

exposure/risk assessment developed for occupational handlers is based on the following 

scenarios: 

1) Mixing/loading liquids for aerial and groundboom applications; 

2) Mixing/loading dry flowables for groundboom applications; 

3) Applying sprays via aerial and groundboom equipment; 

4) Flagging for aerial applications; 

5) Mixing/loading/applying dry flowables via backpack or manually-pressurized handwand; 

6) Impregnating liquids onto dry bulk fertilizer in commercial and on-farm settings; and 

7) Applying impregnated dry bulk fertilizer with commercial equipment and grower-owned 

equipment. 

Occupational Handler Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the occupational 

handler risk assessments. Each assumption and factor is detailed below on an individual basis.

Application Rate: 

The application rates used in this assessment are provided in Table 4.1. 

Unit Exposures: It is the policy of HED to use the best available data to assess handler exposure. 

Sources of generic handler data, used as surrogate data in the absence of chemical-specific data, 

include PHED 1.1, the AHETF database, the Outdoor Residential Exposure Task Force 

(ORETF) database, or other registrant-submitted occupational exposure studies. Some of these 

data are proprietary (e.g., AHETF data), and subject to the data protection provisions of FIFRA. 

The standard values recommended for use in predicting handler exposure that are used in this 

assessment, known as “unit exposures”, are outlined in the “Occupational Pesticide Handler Unit 

Exposure Surrogate Reference Table4

”, which, along with additional information on HED policy 

on use of surrogate data, including descriptions of the various sources, can be found at the 

Agency website5

. 

For the dry bulk fertilizer scenarios, HED assumed a closed mixing/loading scenario for 

commercial impregnation of dry bulk fertilizer, and an open mixing/loading scenario for growerowned equipment impregnation of dry bulk fertilizer. For all applications of dry bulk fertilizer, 

HED assumed the use of an open-cab spreader. 

Area Treated or Amount Handled: 

The inputs for area treated were mostly based on information in ExpoSAC Policy 9.1. HED does 

not have data regarding the mixing/loading or the application of saflufenacil-impregnated dry 

 

4

 Available: http://www.epa.gov/opp00001/science/handler-exposure-table.pdf 5

 Available: http://www.epa.gov/pesticides/science/handler-exposure-data.html
Page 12 of 22 

bulk fertilizer. The mixing/loading processing rate for commercial impregnation of dry bulk 

fertilizer has been estimated to be 960 tons of fertilizer processed per 8 hour day based on 

information supplied by a registrant concerning the chemical alachlor (as referenced in its 

reregistration eligibility document (RED) document6

). Mixing/loading for on-farm impregnation 

of dry bulk fertilizer was then assessed using an estimate of 160 acres/day. Application of dry 

bulk fertilizer was assessed assuming application to up to 320 acres/day for commercial 

equipment and 160 acres/day for grower-owned equipment. The following summarizes the 

inputs used for estimating handler exposures: 

 1,200 acres for aerial application to high acreage crops 

 200 acres for groundboom application to high acreage crops 

 80 acres for groundboom application to typical acreage crops 

 350 acres for flaggers 

 40 gallons for backpack and manually-pressurized handwand applications 

 960 tons of fertilizer per day for mixing/loading for commercial impregnation of dry bulk 

fertilizer 

 160 acres/day for mixing/loading for grower-owned equipment impregnation of dry bulk 

fertilizer 

 320 acres/day for commercial application of dry bulk fertilizer 

 160 acres/day for grower-owned equipment application of dry bulk fertilizer 

Exposure Duration: 

HED classifies exposures from 1 to 30 days as short-term and exposures 30 days to six months 

as intermediate-term. Exposure duration is determined by many things, including the exposed 

population, the use site, the pest pressure triggering the use of the pesticide, and the cultural 

practices surrounding that use site. For most agricultural uses, it is reasonable to believe that 

occupational handlers will not apply the same chemical every day for more than a one-month 

time frame; however, there may be a large agribusiness and/or commercial applicators who may 

apply a product over a period of weeks. 

For the proposed use patterns, short- and intermediate-term exposures are anticipated for the 

following reasons: (1) up to three in-season and two dormant season foliar applications can be 

made per crop season 14 days apart; and (2) commercial applicators may apply this product at 

various locations within a region over a period of weeks. In addition, the short- and 

intermediate-term PODs are the same; therefore, short-term risk estimates are protective of 

longer-term exposures. 

Mitigation/Personal Protective Equipment: Estimates of dermal and inhalation exposure were 

calculated for various levels of personal protective equipment (PPE). Results are presented for 

“baseline,” defined as a single layer of clothing consisting of a long sleeved shirt, long pants, 

shoes plus socks, no protective gloves, and no respirator, as well as baseline with various levels 

of PPE as necessary (e.g., gloves, respirator, etc). The saflufenacil product labels direct mixers, 

loaders, applicators and other handlers to wear long-sleeved shirt and long pants, shoes plus 

 

6 http://www.epa.gov/oppsrrd1/REDs/0063.pdf
Page 13 of 22 

socks, chemical-resistant gloves, and protective eyewear such as face shield, goggles, or safety 

glasses. 

Occupational Handler Non-Cancer Exposure and Risk Estimate Equations 

The algorithms used to estimate non-cancer exposure and dose for occupational handlers can be 

found in Appendix A. 

Combining Exposures/Risk Estimates: 

Dermal and inhalation risk estimates were combined in this assessment, since the toxicological 

effects for these exposure routes were similar. Dermal and inhalation risk estimates were 

combined using the following formula: 

Total MOE = Point of Departure (mg/kg/day) ÷ Combined dermal + inhalation dose (mg/kg/day) 

Summary of Occupational Handler Non-Cancer Exposure and Risk Estimates 

The occupational handler exposure and risk estimates indicate that the short- and intermediateterm dermal and inhalation combined MOEs are not of concern to HED (i.e., MOE > 100). At 

the baseline level of personal protection (i.e., no gloves and no respirator), all scenarios result in 

combined MOEs (dermal + inhalation) ≥ LOC (MOEs ≥ 250). 

HED has no data to assess exposures to pilots using open cockpits. The only data available is for 

exposure to pilots in enclosed cockpits. Therefore, risks to pilots are assessed using the 

engineering control (enclosed cockpits) and baseline attire (long-sleeve shirt, long pants, shoes, 

and socks); per the Agency’s Worker Protection Standard stipulations for engineering controls, 

pilots are not required to wear protective gloves for the duration of the application. With this 

level of protection, there are no risk estimates of concern for applicators. 

The Agency matches quantitative occupational exposure assessment with appropriate 

characterization of exposure potential. While HED presents quantitative risk estimates for human 

flaggers where appropriate, agricultural aviation has changed dramatically over the past two 

decades. According the 2012 National Agricultural Aviation Association (NAAA) survey of 

their membership, the use of GPS for swath guidance in agricultural aviation has grown steadily 

from the mid 1990’s. Over the same time period, the use of human flaggers for aerial pesticide 

applications has decreased steadily from ~15% in the late 1990’s to only 1% in the most recent 

(2012) NAAA survey. The Agency will continue to monitor all available information sources to 

best assess and characterize the exposure potential for human flaggers in agricultural aerial 

applications.
Page 14 of 22 

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Saflufenacil. 

Exposure Scenario Crop or Target 

Dermal Unit 

Exposure 

(μg/lb ai)1

Inhalation 

Unit 

Exposure 

(μg/lb ai)1

Maximum 

Application 

Rate (lb 

ai/A)2

Area 

Treated 

(acres)3

Dermal 

(LOC = 100) 

Inh

(LO

Mitigation 

Level 

Mitigation 

Level 

Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day

Mixer/Loader 

Aerial application of liquid 

formulation 

Forage Grasses Grown 

in Pastures and 

Rangeland, or in Fields 

Grown for Forage, 

Silage and Hay 

Production 

220 

(baseline) 

0.219 

(baseline) 0.089 

1200 0.0204 250 0.000339 

Groundboom application of 

liquid formulation 200 0.00341 1,500 0.0000565 

Groundboom application of 

dry flowable formulation Olive trees 227 (baseline) 8.96 (baseline) 0.044 80 0.000695 7,200 0.000457 

Commercial Impregnation 

of Dry Bulk Fertilizers 

(closed system) 

Forage Grasses Grown 

in Pastures and 

Rangeland, or in Fields 

Grown for Forage, 

Silage and Hay 

Production 

8.6 (engineering 

control) 

0.083 

(engineering 

control) 

0.89 lb 

ai/ton 960 tons 0.00639 780 0.00103 

On-farm Impregnation of 

Dry Bulk Fertilizers 

220 

(baseline) 

0.219 

(baseline) 0.089 160 0.00272 1,800 0.0000452 

Applicator 

Aerial spray application 

Forage Grasses Grown 

in Pastures and 

Rangeland, or in Fields 

Grown for Forage, 

Silage and Hay 

Production 

2.08 

(engineering 

control) 

0.0049 

(engineering 

control) 0.089 

1200 0.000193 26,000 0.0000075

Groundboom spray 

application 

78.6 

(baseline) 

0.34 

(baseline) 

200 0.00122 4,100 0.0000877 

Olive trees 0.044 80 0.000241 21,000 0.0000174 

Commercial Impregnation 

of Dry Bulk Fertilizers 

Forage Grasses Grown 

in Pastures and 

Rangeland, or in Fields 

Grown for Forage, 

Silage and Hay 

Production 

9.9 

(baseline) 

1.2 

(baseline) 0.089 

320 0.000245 20,000 0.000496 

On-farm Impregnation of 

Dry Bulk Fertilizers 160 0.000123 41,000 0.000248 
Page 15 of 22 

Table 6.1.1. Occupational Handler Non-Cancer Exposure and Risk Estimates for Saflufenacil. 

Exposure Scenario Crop or Target 

Dermal Unit 

Exposure 

(μg/lb ai)1

Inhalation 

Unit 

Exposure 

(μg/lb ai)1

Maximum 

Application 

Rate (lb 

ai/A)2

Area 

Treated 

(acres)3

Dermal 

(LOC = 100) 

In

(LO

Mitigation 

Level 

Mitigation 

Level 

Dose 

(mg/kg/day)4 MOE5 Dose (mg/kg/day

Flagger 

Flagger for aerial spray 

application 

Forage Grasses Grown 

in Pastures and 

Rangeland, or in Fields 

Grown for Forage, 

Silage and Hay 

Production 

11 

(baseline) 

0.35 

(baseline) 0.089 350 0.000298 17,000 0.000158 

Mixer/Loader/Applicator 

Mixing/loading/applying 

dry flowables via backpack 

applications Olive trees 

(ground-directed) 

8260 2.58 

0.00044 lb 

ai/gallon 40 gallons 

0.000126 40,000 0.00000065

Mixing/loading/applying 

dry flowables via manuallypressurized handwand 

applications 

100,000 30 0.00153 3,300 0.0000076

1 Based on the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (March 2013); Level of mitigation: Baseline, Eng. Controls. 2 Based on proposed labels (Reg. No. 7969-278, 7969-276 and 7969-297). 

3 Exposure Science Advisory Council Policy #9.1 and Registrant information. 4 Dermal Dose = Dermal Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre) × Area Treated (A/day) × DAF (6 %) ÷ BW (69 k5 Dermal MOE = Dermal NOAEL (5 mg/kg/day) ÷ Dermal Dose (mg/kg/day). 

6 Inhalation Dose = Inhalation Unit Exposure (μg/lb ai) × Conversion Factor (0.001 mg/μg) × Application Rate (lb ai/acre) × Area Treated (A/day) ÷ BW (69 kg). 7 Inhalation MOE = Inhalation NOAEL (5 mg/kg/day) ÷ Inhalation Dose (mg/kg/day). 

8 Total MOE = NOAEL (5 mg/kg/day) ÷ (Dermal Dose + Inhalation Dose). 
Page 16 of 22 

6.2 Occupational Post-application Exposure/Risk Estimates 

HED uses the term post-application to describe exposures that occur when individuals are 

present in an environment that has been previously treated with a pesticide (also referred to as reentry exposure). Such exposures may occur when workers enter previously treated areas to 

perform job functions, including activities related to crop production, such as scouting for pests 

or harvesting. Post-application exposure levels vary over time and depend on such things as the 

type of activity, the nature of the crop or target that was treated, the type of pesticide application, 

and the chemical’s degradation properties. In addition, the timing of pesticide applications, 

relative to harvest activities, can greatly reduce the potential for post-application exposure. 

6.2.1 Occupational Post-application Inhalation Exposure/Risk Estimates 

Based on the Agency's current practices, a quantitative post-application inhalation exposure 

assessment was not performed for saflufenacil at this time primarily because of the low acute 

inhalation toxicity (Toxicity Category IV) and low vapor pressure (3.4 x 10-17 mmHg, 20°C). 

However, there are multiple potential sources of post-application inhalation exposure to 

individuals performing post-application activities in previously treated fields. These potential 

sources include volatilization of pesticides and resuspension of dusts and/or particulates that 

contain pesticides. The Agency sought expert advice and input on issues related to volatilization 

of pesticides from its Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory 

Panel (SAP) in December 2009, and received the SAP’s final report on March 2, 20107. The 

Agency is in the process of evaluating the SAP report as well as available post-application 

inhalation exposure data generated by the ARTF and may, as appropriate, develop policies and 

procedures, to identify the need for and, subsequently, the way to incorporate occupational postapplication inhalation exposure into the Agency's risk assessments. If new policies or 

procedures are put into place, the Agency may revisit the need for a quantitative occupational 

post-application inhalation exposure assessment for saflufenacil. 

Although a quantitative occupational post-application inhalation exposure assessment was not 

performed, an inhalation exposure assessment was performed for occupational/commercial 

handlers. Handler exposure resulting from application of pesticides outdoors is likely to result in 

higher exposure than post-application inhalation exposure. Therefore, it is expected that these 

handler inhalation exposure estimates would be protective of most occupational post-application 

inhalation exposure scenarios. 

6.2.2 Occupational Post-application Dermal Exposure/Risk Estimates 

A post-application exposure assessment has not been conducted for the proposed use on olive 

trees since the use directions indicate that the product is to be applied to the base of the tree trunk 

and is not to contact the foliage. Currently, HED has no transfer coefficients or other data to 

assess post-application dermal exposures to soil by occupational workers. In general, such 

exposures are considered to be negligible. Therefore, for the soil-directed uses, post-application 

exposures and risks to occupational workers were not assessed. 

 

7

 Available: http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html
Page 17 of 22 

The proposed uses on grass/forage are not specifically soil directed and, therefore, could result in 

potential post-application exposures. These exposures have been assessed in this memo. 

Occupational Post-application Dermal Exposure Data and Assumptions 

A series of assumptions and exposure factors served as the basis for completing the occupational 

post-application risk assessments. Each assumption and factor is detailed below on an individual 

basis. 

Exposure Duration: HED classifies exposures from 1 to 30 days as short-term and exposures 30 

days to six months as intermediate-term. For saflufenacil, short- and intermediate-term 

exposures are expected since up to three in-season and two dormant season foliar applications 

can be made per crop season 14 days apart. In addition, the short- and intermediate-term PODs 

are the same; therefore, short-term risk estimates are protective of longer-term exposures. 

Transfer Coefficients: It is the policy of HED to use the best available data to assess postapplication exposure. Sources of generic post-application data, used as surrogate data in the 

absence of chemical-specific data, are derived from ARTF exposure monitoring studies, and, as 

proprietary data, are subject to the data protection provisions of FIFRA. The standard values 

recommended for use in predicting post-application exposure that are used in this assessment, 

known as “transfer coefficients”, are presented in the ExpoSAC Policy 38

” which, along with 

additional information about the ARTF data, can be found at the Agency website9. Activities 

such as non-handset irrigation, fertilizing, and mechanical harvesting are expected to occur, but 

are anticipated to result in negligible exposure and, therefore, are not quantitatively assessed. 

Table 6.2.2.1. Summary of Post-Application Activities and Dermal Transfer Coefficients. 

Crop Policy Crop Group 

Category 

Crop 

Height 

Foliage 

Density 

Transfer 

Coefficients 

(cm2/hr)

Activities 

Forage Crop Field / row crop, low / 

medium 

Low/High Full 0 

Irrigation (non 

handset), Fertilizing, 

Mechanical 

Harvesting 

Low Full/Min 1,100 Scouting 

Low Full 1,900 Irrigation (hand set) 

Application Rate: 

The application rate used in this assessment is provided in Table 4.1. Only the in-season rate 

was used to assess post-application activities, since it was assumed that these activities would 

only occur in season. It is not expected that these activities would be occurring during the 

dormant season. 

 

8

 Available: http://www.epa.gov/pesticides/science/exposac_policy3.pdf 9

 Available: http://www.epa.gov/pesticides/science/post-app-exposure-data.html
Page 18 of 22 

Exposure Time: The average occupational workday is assumed to be 8 hours. 

Dislodgeable Foliar Residues: In accordance with 40CFR158, DFR data are required for all 

occupational (e.g., crop, nursery, greenhouse use sites) or residential (e.g., ornamental and 

vegetable gardens, pick your own farms, retail tree farms) uses that could result in postapplication exposure to foliage. In the absence of chemical-specific DFR data, EPA uses default 

values. The 2012 Standard Operating Procedures for Residential Pesticide Exposure 

Assessment includes an analysis of a number of DFR studies, which resulted in the selection of a 

revised default values for the fraction of the application rate available for transfer after a foliar 

application (FAR). These values are based on an analysis of 19 DFR studies. Since that time, the 

Agricultural Re-entry Task Force has submitted information (MRID 49299201) that corrects an 

application rate error made in the original submission of “ARF039 – Determination of Dermal 

and Inhalation Exposure to Reentry Workers During Chrysanthemum Pinching in a Greenhouse” 

(EPA MRID 45344501). As a result, the range of FAR values was revised from 2% - 89% to 2% 

- 47%. In the data, a large range of transferability is observed and this variability can potentially 

be attributable to many factors such as active ingredient; formulation; field conditions in the 

studies; weather conditions (e.g., humidity); or many other difficult to quantify factors. 

Although witnessed across multiple chemicals, this range in FAR values is not expected when 

considering DFR data for a single chemical. At this time, the ARTF submission did not alter the 

selection of 25% as the reasonable, high-end default value. Because DFR data are not available 

for saflufenacil, EPA is using the default value of 25%. Although there may be a small degree of 

uncertainty in the use of the default DFR value for saflufenacil (i.e., there is a small chance that 

the FAR value may exceed the applicable default value), it is likely that the health-protective 

aspects of EPA’s occupational post-application assessment methodology will more than 

compensate for this potential uncertainty. For example, when assessing residential and 

occupational post-application exposure to gardens and ornamentals, EPA assumes the following: 

exposures occur to zero-day (i.e., day of application ) residues every day of the assessed 

exposure duration (i.e., EPA assumes that no dissipation or degradation occurs, it doesn’t rain, 

etc); individuals perform the same post-application activities performed in the transfer 

coefficient study day after day (e.g., weeding, harvesting, pruning, etc.); and individuals engage 

in these post-application activities for a high-end amount of time every day (represented by data 

reflecting time spent gardening based on survey data). 

Given the conservatisms discussed above and the potential compounding nature of these 

conservatisms, EPA is able to rely upon the calculated exposure estimates with confidence that 

exposure is not being underestimated. 

Since the highest estimated occupational post-application exposure using default DFR values for 

saflufenacil is minimal in comparison to the level of concern (i.e., the calculated MOE is greater 

than 2 times higher than the level of concern, MOE = 3,000 compared to the LOC of 100); EPA 

is waiving the 40CFR DFR data requirement. In this instance, it is unlikely that chemicalspecific DFR data would be needed to further refine exposure assessments or would add 

appreciably to our overall understanding of the availability of dislodgeable foliar pesticide 

residues for saflufenacil. 
Page 19 of 22 

Occupational Post-application Non-Cancer Dermal Exposure and Risk Estimate Equations 

The algorithms used to estimate non-cancer exposure and dose for occupational post-application 

workers can be found in Appendix A. 

Occupational Post-application Non-Cancer Dermal Risk Estimates 

The short- and intermediate-term post-application exposure scenarios associated with the 

proposed uses for saflufenacil are summarized in Table 6.2.2.2. All scenarios resulted in MOEs 

greater than the LOC of 100 (ranging from 3,000 to 5,200) on day 0 (12 hours after application) 

and, therefore, are not of concern to HED. 

Table 6.2.2.2. Occupational Post-application Non-Cancer Exposure and Risk Estimates for Saflufenacil.

Crop/Site Activities 

Transfer 

Coefficient 

(cm2/hr) 

Proposed 

Application 

Rate (lb ai/A)

DFR1 Dermal Dose 

(mg/kg/day)2

MOE3

(LOC = 

100) 

Short- and Intermediate-term 

Forage crop 

Scouting 1,100 

0.045 0.13 

0.00097 5,200 

Irrigation (hand set) 1,900 0.00167 3,000 

1 DFR = Application Rate × F × (1-D)t × 4.54E8 μg/lb × 2.47E-8 acre/cm2; where F = 0.25 and D = 0.10 per day. 

2 Daily Dermal Dose = [DFR (μg/cm2

) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption (6%)]  BW (69 kg).

3 MOE = POD (5 mg/kg/day) / Daily Dermal Dose. 

Restricted Entry Interval 

The REI specified on the proposed label is based on the acute toxicity of saflufenacil. 

Saflufenacil is classified as toxicity category III for acute oral, acute dermal toxicity, and acute 

eye irritation. It is classified as toxicity category IV for acute inhalation toxicity and acute dermal 

irritation. It is not a dermal sensitizer. Short- and intermediate-term post-application risk 

estimates were not a concern on day 0 (12 hours following application) for all post-application 

activities. Under 40 CFR 156.208 (c) (2) (iii), ai’s classified as Acute III or IV for acute dermal, 

eye irritation and primary skin irrigation are assigned a 12-hour REI. Therefore, the [156 subpart 

K] Worker Protection Statement interim REI of 12 hours is adequate to protect agricultural 

workers from post-application exposures to saflufenacil. 
Page 20 of 22 

Appendix A. Summary of Occupational Non-cancer Algorithms 

Occupational Non-cancer Handler Algorithms 

Potential daily exposures for occupational handlers are calculated using the following formulas: 

E=UE * AR * A * 0.001 mg/ug

where: 

E = exposure (mg ai/day), 

UE = unit exposure (μg ai/lb ai), 

AR = maximum application rate according to proposed label (lb ai A or lb ai/gal), and 

A = area treated or amount handled (e.g., A/day, gal/day). 

 

The daily doses are calculated using the following formula: 

ADD= 

 E * AF

BW

where: 

ADD = average daily dose absorbed in a given scenario (mg ai/kg/day), 

E = exposure (mg ai/day), 

AF = absorption factor (dermal and/or inhalation), and 

BW = body weight (kg). 

Margin of Exposure: Non-cancer risk estimates for each application handler scenario are 

calculated using a Margin of Exposure (MOE), which is a ratio of the toxicological endpoint to 

the daily dose of concern. The daily dermal and inhalation dose received by occupational 

handlers are compared to the appropriate POD (i.e., NOAEL) to assess the risk to occupational 

handlers for each exposure route. All MOE values are calculated using the following formula: 

MOE= 

POD

ADD

where: 

MOE = margin of exposure: value used by HED to represent risk estimates (unitless), 

POD = point of departure (mg/kg/day), and 

ADD = average daily dose absorbed in a given scenario (mg ai/kg/day). 

Occupational Non-cancer Post-application Algorithms 
Page 21 of 22 

Potential daily exposures for occupational post-application workers are calculated using the 

following formulas: 

DFRt=AR * F* (1-D)t* ቀ4.54E8 ug

lbቁ * ൬2.47E-8

A

cm2൰

where: 

DFRt = dislodgeable foliage residue on day "t" (μg/cm2

), 

AR = application rate (lb ai/acre), 

F = fraction of ai retained on foliage or 25% (unitless), 

D = fraction of residue that dissipates daily or 10% (unitless), and 

t = number of days after application day (days). 

E=TC * DFR t * ET * 0.001 mg

ug

where: 

E = exposure (mg ai/day), 

TC = transfer coefficient (cm2/hr), 

DFRt = dislodgeable foliar residue on day “t” (μg/cm2), and 

ET = exposure time (hours/day). 

 

The daily doses are calculated using the following formula: 

ADD= 

 E * AF

BW

where: 

ADD = average daily dose absorbed in a given scenario (mg ai/kg/day), 

E = exposure (mg ai/day), 

AF = absorption factor (dermal and/or inhalation), and 

BW = body weight (kg). 

Margin of Exposure: Non-cancer risk estimates for each scenario are calculated using a Margin 

of Exposure (MOE), which is a ratio of the toxicological endpoint to the daily dose of concern. 

The daily dermal dose received by occupational post-application workers is compared to the 

appropriate POD (i.e., NOAEL) to assess the risk to occupational post-application workers. All 

MOE values are calculated using the following formula: 

MOE= 

POD

ADD
Page 22 of 22 

where: 

MOE = margin of exposure: value used by HED to represent risk estimates (unitless), 

POD = point of departure (mg/kg/day), and 

ADD = average daily dose absorbed in a given scenario (mg ai/kg/day).