Page 2 of 19

Table of Contents

1.0 Executive Summary............................................................................................................ 3

2.0 Hazard Characterization...................................................................................................... 5

3.0 Use Patterns ........................................................................................................................ 7

4.0 Occupational Exposure/Risk............................................................................................... 8

4.1 Occupational Handler ................................................................................................ 8

4.1.1 Data and Assumptions for Handler Exposure Scenarios............................... 9

4.1.2 Occupational Handler and Exposure Risk Summary................................... 11

4.2 Post-application Exposure ....................................................................................... 16

4.2.1 Data and Assumptions for Post-application Exposure Scenarios................ 16

4.2.2 Post-application Exposure and Risk ............................................................ 18

5.0 Residential (Non-Occupational) Exposure and Risk ........................................................ 18
Page 3 of 19

1.0 Executive Summary

Lactofen is an herbicide used by occupational handlers in agricultural settings. It is typically 

used early in the growing season, before or shortly after the crop has emerged. This 

memorandum presents the results of HED’s review of the potential human health risks from

occupational exposure to lactofen from its use on soybeans, snap beans, conifer seedlings and 

strawberries (non-bearing). 

Use Profile

The end-use products evaluated in this assessment include three emulsifiable concentrate (EC) 

products (EPA Reg. No. 59639-34, 59639-92, and 59639-118) and one wettable powder in

water-soluble packaging (WP in WSP) product (EPA Reg. No. 59639-113). Additionally, four 

SLN labels, under the main label for EPA Reg. No. 59639-34, were evaluated. 

Lactofen may be applied to soybeans as pre-plant, pre-emergent, or post-emergent application,

up to the R6 (full seed) growth stage. The maximum single application rate is 0.2 lb ai/A for 

foliar applications and 0.3 lb ai/A for soil-directed applications. The pre-harvest interval (PHI) is 

45 to 60 days. For snap beans, a single pre-emergent application is made to the soil, no later than 

48 hours after planting, at a maximum rate of 0.25 lb ai/A. The PHI is 55 days. For strawberries 

(non-bearing), a single pre-emergent application is made at a maximum application rate of 0.38 

lb ai/A to the soil before transplanting or to dormant strawberry plants within 48 hours of 

transplanting; the plants should have soil placed over the crown of the plant before the 

application. The PHI is 1 year. For conifers, lactofen may be applied to the soil or seedlings in 

outdoor settings including plantations and nurseries (not forests) at a maximum single 

application rate of 0.25 lb ai/A. Handlers may apply lactofen to soybeans, snap beans, conifer 

seedlings and strawberries (non-bearing) using aerial and groundboom equipment. Applications 

to conifers may also be applied using handgun equipment. 

Based on application rates and label information, exposure is expected to occur for short- (1 to 

30 days) and intermediate-term (1 to 6 months) durations. Long-term (6 months or greater)

occupational exposure is not expected with these use patterns.

Hazard Characterization

Lactofen has a low acute toxicity profile based on its classification in Toxicity Category III via 

the dermal route and Toxicity Category IV via the oral and inhalation routes. It is not a skin 

sensitizer, but it is a very slight dermal irritant. The manufacturing use product is classified as a 

moderate eye irritant.

The point of departure (PoD) selected for regulation of dermal and inhalation risk at short- and 

intermediate-term durations is the lowest observed adverse effect level (LOAEL) of 5 

mg/kg/day, based on decreases in live young per litter accompanied by increases in postimplantation loss and in early embryonic death per litter. A no observed adverse effect level 

(NOAEL) was not established for this study. Since the dermal PoD was selected from an oral 

study, a 20% dermal absorption factor was used to estimate dermal dose. Inhalation doses were 
Page 4 of 19

converted to oral equivalent doses, assuming an absorption factor of 100%. The average body 

weight of an adult (80 kilograms) was used in the exposure assessments. Since the dermal and 

inhalation PoDs were the same, margins of exposure (MOEs) were combined to provide a total 

margin of exposure for handler exposure scenarios.

Lactofen is classified as “Not likely to be carcinogenic to humans.”

HED’s level of concern (LOC) for lactofen short- and intermediate-term dermal and inhalation 

exposures is 300 (i.e., an MOE ≥ 300 is not of concern to HED). The LOC is based on a 10X to 

account for interspecies extrapolation (differences between humans and animals), a 10X to 

account for intraspecies sensitivity (differences among humans), and an additional 3X factor to 

account for the extrapolation of a LOAEL to NOAEL. 

Occupational Handlers

HED has determined that there is potential for short- and intermediate-term dermal and 

inhalation occupational exposure to lactofen during handling activities (e.g., mixing, loading and 

application). None of the occupational handler exposure scenarios assessed result in combined 

dermal and inhalation risks of concern (i.e., an MOE ≥ 300) at either baseline attire, with the 

addition of chemical-resistant gloves, and/or engineering controls.

Occupational Post-application

HED has determined that there is potential for occupational post-application dermal exposure to 

lactofen following use on soybeans and conifer seedlings. Post-application exposures for 

soybean are not assessed in this action, however, because the exposure is anticipated to be 

similar to that previously assessed previously for peanut. Post-application exposures are 

considered to be negligible for the use of lactofen on snap beans and strawberry (non-bearing) 

based on label application instructions (i.e., soil-directed applications); therefore, postapplication exposures and risks to occupational workers for the snap bean and strawberry uses 

were not quantitatively assessed.

Based on a post-application assessment of common agricultural practices anticipated for conifer 

seedlings, risks were not of concern (i.e., MOEs ≥ 300) on Day 0 (12 hours after application) 

using the highest applicable transfer coefficient. 

Since post-application risks are not a concern on day 0 (12 hours following application), the 

restricted entry interval (REI) is based on the acute toxicity of lactofen technical material. 

Lactofen is classified as Toxicity Category III via the dermal route and eye irritation potential 

and Toxicity Category IV for skin irritation potential. Under the Worker Protection Standard for 

Agricultural Pesticides, active ingredients classified as acute toxicity categories III or IV for 

these routes are assigned a 12-hour REI. Therefore, the 12-hour REI that appears on the labels is 

adequate.
Page 5 of 19

Residential Exposure

No residential uses are associated with the uses being evaluated in this action and, therefore, no 

residential handler exposure and risk assessment has been conducted. 

Review of Human Research

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 

PHED 1.1 and the AHETF 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 

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

http://www.epa.gov/pesticides/science/post-app-exposure-data.html.

2.0 Hazard Characterization

Lactofen has a low acute toxicity profile based on its classification in Toxicity Category III via 

the dermal route and Toxicity Category IV via the oral and inhalation routes. It is not a skin 

sensitizer but it is a very slight dermal irritant. The manufacturing use product (MUP), however, 

is classified as a moderate eye irritant. Table 1 presents a summary of the acute toxicity 

information for lactofen.

Table 1. Acute Toxicity Profile – Lactofen

Guideline

No. Study Type Accession #(S). Results Toxicity Category

81-1 Acute Oral 73859 LD50 > 5.96 g/kg IV

81-2 Acute Dermal 73859 LD50 > 2.0 g/kg III

81-3 Acute Inhalation 73859 LC50 > 6.3 m/L IV

81-4 Primary Eye Irritation (MUP) 73859 Moderate eye irritant III

81-5

Primary Skin Irritation

(MUP) 73859 Very slight dermal irritant IV

81-6 Dermal Sensitization 73859 Not a dermal sensitizer

On February 22, 2000 the Health Effects Division (HED) Hazard Identification Assessment 

Review Committee (HIARC) evaluated the toxicology database for lactofen, re-assessed the 

existing reference dose, and selected the doses and toxicological endpoints for dietary and nondietary exposure risk assessments. Additional data and information have been submitted since 

then, including mechanistic data on the carcinogenicity of lactofen (Fricke 2002) and a request to 

waive the rabbit developmental study (Phang 2006). The cancer classification of lactofen should 

be characterized as “not likely to be carcinogenic in humans.”

The toxicological points of departure that were used to complete the occupational risk 

assessment are summarized below and in Table 2. Adverse effects were identified at durations 
Page 6 of 19

of exposure ranging from short-term to intermediate-term durations. No cancer endpoint was 

identified; therefore, cancer risks were not assessed.

Dermal and Inhalation Route (Non-cancer)

The short- and intermediate-term dermal and inhalation risk assessments for lactofen are based 

on a LOAEL of 5 mg/kg/day defined in an oral developmental toxicity study in rabbits. A 

NOAEL was not established for this study. No long-term occupational exposures are expected 

from the uses of lactofen.

Non-cancer Level of Concern (LOC)

HED’s level of concern (LOC) for lactofen short- and intermediate-term dermal and inhalation 

exposures is 300 (i.e., an MOE ≥ 300 is not of concern to HED). The LOC is based on a 10X to 

account for interspecies extrapolation (differences between humans and animals), a 10X to 

account for intraspecies sensitivity (differences among humans), and an additional 3X factor to 

account for the extrapolation of a lowest observed adverse effect level (LOAEL) to NOAEL.

Body Weight

The average adult body weight (80 kg) was used for occupational dermal and inhalation risk 

assessments because the short- and intermediate-term inhalation point of departure was not sexspecific.

Table 2. Summary of Toxicological Doses and Endpoints for Lactofen for Use in 

Occupational Human Health Risk Assessments

Exposure/

Scenario

Point of 

Departure

Uncertainty 

Factors

Level of Concern 

for Risk 

Assessment

Study and Toxicological Effects

Dermal ShortTerm (1-30 

days)

and 

IntermediateTerm (1-6 

months)

LOAEL = 5 

mg/kg/day

UFA=10x

UFH=10x

UFL =3X

Occupational LOC 

is an MOE = 300

Developmental Toxicity Study – Rabbit

LOAEL was 5 mg/kg based on decrease in 

live young per litter accompanied by 

increases in post-implantation loss and in 

early embryonic death/litter.

Inhalation 

Short-Term (1-

30 days) and

Intermediateterm (1-6 

months)

LOAEL = 5 

mg/kg/day

UFA=10x

UFH=10x

UFL =3X

Occupational LOC 

is an MOE = 300

Developmental Toxicity Study – Rabbit

LOAEL was 5 mg/kg based on decrease in 

live young per liver accompanied by 

increases in post-implantation loss and in 

early embryonic death/litter.

Cancer (oral, 

dermal, 

inhalation)

Classification: Not likely to be carcinogenic to humans.

1 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. LOAEL 

= lowest observed adverse effect level. UF = uncertainty factor. UFA = extrapolation from animal to human (intraspecies). UFH
Page 7 of 19

= potential variation in sensitivity among members of the human population (interspecies). UFL = use of a LOAEL to extrapolate 

a NOAEL. FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = chronic). RfD = reference dose. 

MOE = margin of exposure. LOC = level of concern. N/A = not applicable.

3.0 Use Patterns

Table 3 provides a summary of the registered products with uses on soybeans, snap beans, 

conifer seedlings, and strawberries (non-bearing) for lactofen. Four end-use product labels were 

evaluated, including three products formulated as an emulsifiable concentrate (Cobra® Herbicide 

- EPA Reg. No. 59639-34; Stellar® Herbicide - EPA Reg. No. 59639-92; and V-10086

Herbicide EPA Reg. No. 59639-118) and one product formulated as a wettable powder in watersoluble packaging (Cobra® 25 Herbicide - EPA Reg. No. 59639-113). Additionally, four SLN 

labels for Cobra® Herbicide (EPA Reg. No. 59639-34) were evaluated. 

Table 4 provides a summary of the use pattern for each of registered uses of lactofen on 

soybeans, snap beans, conifer seedlings, and strawberries (non-bearing). Maximum single 

application rates are 0.20 lb ai/A for soybean, 0.25 lb ai/A for snap bean and conifer seedlings, 

and 0.38 lb ai/A for strawberries (non-bearing). 

Table 3. Summary of End-Use Products

Product EPA Reg No. Formulation 

Typea % ai lb ai/gal Crop Use

Cobra® Herbicide

59639-34 EC 24 2

Soybean, Snap Bean, Conifer 

Seedlings

IA890002 EC 23.2 2 Soybean

NM980003 and 

TX980006 EC 23.2 2 Snap Bean

OR010006 EC 23.2 2 Strawberries (non-bearing)

Stellar® Herbicide 59639-92 EC 26.6 2.4 Soybean

V-10086

Herbicide 59639-118 EC 24 2 Soybean, Snap Bean

Cobra® 25

Herbicide 59639-113 WP in WSP 25 N/A Soybean

a, EC = emulsifiable concentrate; WP in WSP = wettable powder in water-soluble packaging.

Table 4. Summary of Maximum Application Rates for Lactofen Agricultural Uses

Crop Target Formulation Maximum Single 

Application Ratea

Application 

Equipment

Soybean

Foliage EC; WP in WSP 0.20 lb ai/acre

Aerial

Ground

Soil EC; WP in WSP 0.30 lb ai/acre

Aerial

Ground

Snap Bean Soil EC 0.25 lb ai/acrea Aerial

Ground

Conifers Soil and Seedling EC 0.25 lb ai/acre Ground
Page 8 of 19

Table 4. Summary of Maximum Application Rates for Lactofen Agricultural Uses

Crop Target Formulation Maximum Single 

Application Ratea

Application 

Equipment

Transplants (prior to 

bud break) Handgun

Strawberries (nonbearing)

Soil and Transplants 

(dormant, with soil 

placed over crown)

EC 0.38 lb ai/acre

Aerial

Ground

a. For the SLN label, the maximum application rate is 0.22 lb ai/A.

4.0 Occupational Exposure/Risk

4.1 Occupational Handler

The Agency uses the term “handlers” to describe those individuals who are involved in the 

pesticide application process. The anticipated use patterns and current labeling indicate 

occupational exposure scenarios based on the types of equipment and techniques that can 

potentially be used for lactofen applications. 

Handlers may apply lactofen to all crops using aerial and groundboom equipment. Applications 

to conifers may also be applied using handgun equipment. Application methods, maximum 

application rates, and use sites are summarized in Table 4. Handler exposure is expected to be 

short- or intermediate-term based on information provided on the labels. 

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

exposure scenarios: 

Mixer/Loaders

1. Mixing/loading liquids to support aerial applications,

2. Mixing/loading liquids to support groundboom applications,

3. Mixing/loading wettable powders in water-soluble packaging to support aerial 

applications,

4. Mixing/loading wettable powders in water-soluble packaging to support groundboom

applications,

Applicators

5. Applying sprays with fixed-wing aircraft (enclosed cockpit),

6. Applying sprays with groundboom equipment,

Flaggers

7. Flagging to support aerial spray applications, and

Mixer/Loader/Applicator

8. Mixing/loading/applying using mechanically pressurized handgun sprayer.
Page 9 of 19

4.1.1 Data and Assumptions for Handler Exposure Scenarios

Unit Exposures

Chemical-specific data for assessing exposure during pesticide handling activities 

(mixing/loading, applying, flagging, etc.) were not submitted to the Agency in support of this 

action. 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

the 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, 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 Table” (http://www.epa.gov/opp00001/science/handler-exposuretable.pdf), which, along with additional information on HED policy on use of surrogate data, 

including descriptions of the various sources, can be found at 

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

Risk Mitigation Approach

The baseline clothing level for occupational exposure scenarios represents an individual wearing 

long pants, a long-sleeved shirt, shoes, socks, no chemical-resistant gloves, and no respirator. 

The first level of mitigation applied is personal protective equipment (PPE), which may include

addition of chemical-resistant gloves (as specified on current labeling), an additional layer of 

clothing, and/or a respirator. The next step in mitigation considered in the risk assessment 

process is the use of appropriate engineering controls. Examples of commonly used engineering 

controls include enclosed cockpits or tractor cabs, closed mixing/loading systems, and watersoluble packets.

Occupational handler exposure assessments of lactofen use were completed using baseline 

clothing, baseline clothing plus gloves, closed mixing/loading systems for the EC formulations, 

water-soluble packets for the wettable powder formulation, and enclosed cockpits for aerial 

applications.

Area Treated

Based on HED Exposure Science Advisory Committee SOP No. 9.1, the area treated in a day is

assumed to be:

1,200 acres for aerial treatments for soybean;

350 acres for aerial treatments for snap beans, conifer seedlings, and strawberries (nonbearing); 
Page 10 of 19

200 acres for groundboom applications for soybean;

80 acres for groundboom applications for snap beans, conifer seedlings, and strawberries 

(non-bearing); 

350 acres for flagging for aerial treatments (all crops); and

20 acres for mechanically pressurized handgun sprayer treatments for conifers.

Application Rate

Broadcast foliar applications of lactofen may be applied at a maximum application rate of 0.30 lb 

ai/A for soybean, 0.25 lb ai/A for snap bean and conifer seedlings, and 0.38 lb ai/A for 

strawberries (non-bearing). Application rates are shown in Table 4.

Body Weight

The average adult body weight of 80 kg was used for estimating dermal and inhalation doses, 

since the selected toxicological endpoints are not sex-specific.

Absorption Factors

Since the short- and intermediate-term dermal and inhalation PoD was based on an oral 

developmental study, a dermal absorption factor of 20 % was used to estimate dermal exposure 

for short-and intermediate-term durations. 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. 

Equations and Calculations

Daily Exposure: Daily handler exposures are estimated for each applicable handler task with the 

application rate, the amount of acres treated in a day, and the applicable unit exposure using the 

following formula:

Daily Exposure (mg ai/day) = 

Unit Exposure (mg or μg ai/lb ai) x Application Rate (lb ai/A) x Daily Area Treated (A/day)

Where: 

Daily Exposure = Amount (mg ai/day) deposited on the surface of the skin that is 

available for dermal absorption or amount inhaled that is 

available for inhalation absorption;

Unit Exposure = Unit exposure value (mg or μg ai/lb ai) derived from exposure 

data;

Application Rate = Normalized application rate based on a logical unit treatment, 

such as acres, square feet, or gallons. Maximum values are 

generally used (lb ai/A) and

Daily Area Treated = Normalized application area based on a logical unit treatment 
Page 11 of 19

such as acres (A/day).

Daily Dose: Daily dose (inhalation or dermal) was calculated by normalizing the daily dermal or 

inhalation exposure value by body weight and accounting for dermal and inhalation absorption. 

Average Daily Dose (mg ai/kg/day) = Daily Exposure (mg ai/day) x (Absorption Factor (%/100)

Body Weight (kg)

Where:

Average Daily Dose = Absorbed dose received from exposure to a pesticide in a given

scenario (mg pesticide active ingredient/kg body weight/day);

Daily Exposure = Amount (mg ai/day) deposited on the surface of the skin that is 

available for dermal absorption or amount inhaled that is 

available for inhalation absorption;

Absorption Factor = A measure of the amount of chemical that crosses a biological 

boundary such as the skin or lungs (% of the total available 

absorbed); and

Body Weight = Body weight determined to represent the population of interest in 

a risk assessment (kg).

Margin of Exposure (MOE): The daily dermal dose and daily inhalation dose received by 

occupational handlers were compared to the appropriate point of departure (i.e., NOAEL) to 

assess the risk to occupational handlers for each exposure route. All MOE values were calculated 

separately for dermal and inhalation exposure levels using the following formula:

MOE = NOAEL or LOAEL (mg ai/ (kg/day))

Average Daily Dose (mg ai/ (kg/day))

Where:

MOE = Margin of Exposure, value used by HED to represent risk or how 

close a chemical exposure is to being a concern (unitless);

ADD = Average Daily Dose or the absorbed dose received from 

exposure to a pesticide in a given scenario (mg pesticide active 

ingredient/kg body weight/day); and

NOAEL or LOAEL = Dose level in a toxicity study, where no observed adverse effects 

(NOAEL) or where the lowest observed adverse effects 

(LOAEL) occurred in the study

Combined Risks: Dermal and inhalation risks for short- and intermediate-term risks were 

combined in this assessment, since the toxicological effects for the dermal and inhalations routes 

were the same. Dermal and inhalation risks were combined using the following formula:

Total MOE = 1/ ((1/ Dermal MOE) + (1/Inhalation MOE)) 

4.1.2 Occupational Handler and Exposure Risk Summary

Summaries of the risks for occupational handlers are included in Table 5. The maximum 

application rate for each exposure scenario is presented as the worst-case scenario. None of the 
Page 12 of 19

occupational handler exposure scenarios assessed result in combined dermal and inhalation risks 

of concern (i.e., an MOE ≥ 300) at either baseline attire, with the addition of chemical-resistant 

gloves, and/or engineering controls.
Page 13 of 19

Table 5. Short- and Intermdiate-term Agricultural Handler Risk Estimates for Lactofen

Exposure Scenario Crop or 

Target

Application 

Rate a

(lb ai/A)

Area 

Treated 

Daily b

(acres)

Unit Exposurec,d,e

(μg/lb ai)

Dosef,g

(mg/kg/day) MOEs h,i,j,k

Baseline 

Dermal

PPE-G

Dermal

Baseline 

Inhalation

Baseline 

Dermald,h

PPE-G 

Dermali

Baseline 

Inhalatione

Baseline 

Dermalf

PPE-G

Dermal

Baseline 

Inhalationg

Combined 

Baseline 

Dermal + 

Inhalationj

Combined 

PPE-G

Dermal + 

Inhalationj k

Mixer/Loader

Mixing/Loading Liquids

for Aerial Applications

Soybean 0.30 1,200 220

37.6

[eng. 

control=

8.6]

0.219

[eng. 

control=

0.083]

0.20

0.034

[eng. 

control=

0.0077]

0.00020

[eng. 

control=

0.000075]

25

150

[eng. 

control=

650]

26,000

[eng. 

control =

67,000]

25

150

[eng. 

control=

640]

Snap Bean 

and Conifer 

Seedlings

0.25 350 220 37.6 0.219 0.048 0.0082 0.000048 100 610 100,000 100 610

Strawberries 

(nonbearing)0.38 350 220 37.6 0.219 0.073 0.013 0.000073 70 400 69,000 70 400

Mixing/Loading Liquids 

for Groundboom 

Applications

Soybean 0.30 200 220 37.6 0.219 0.033 0.0056 0.000033 150 890 150,000 150 890

Snap Bean 

and Conifer 

Seedlings

0.25 80 220 37.6 0.219 0.011 0.0019 0.000011 450 2,700 460,000 450 2,700

Strawberries 

(nonbearing)0.38 80 220 37.6 0.219 0.017 0.0029 0.000017 300 1,700 300,000 300 1,700

Mixing/Loading 

Wettable Powders in 

Water-Soluble 

Packaging for Aerial 

Applications

Soybean 0.30 1,200 NA

9.8

(eng. 

control)

0.24

(eng. 

control)

NA

0.088

(eng. 

control)

0.00022

(eng. 

control)

NA

570

(eng.

control)

23,000

(eng. 

control)

NA

570

(eng. 

control)

Mixing/Loading 

Wettable Powders in 

Water Soluble 

Packaging for 

Groundboom 

Applications

Soybean 0.30 200 NA

9.8

(eng. 

control)

0.24

(eng. 

control)

NA

0.0015

(eng. 

control)

0.000036

(eng. 

control)

NA

3,400

(eng. 

control)

140,000

(eng. 

control)

NA

3,400

(eng. 

control)
Page 14 of 19

Table 5. Short- and Intermdiate-term Agricultural Handler Risk Estimates for Lactofen

Exposure Scenario Crop or 

Target

Application 

Rate a

(lb ai/A)

Area 

Treated 

Daily b

(acres)

Unit Exposurec,d,e

(μg/lb ai)

Dosef,g

(mg/kg/day) MOEs h,i,j,k

Baseline 

Dermal

PPE-G

Dermal

Baseline 

Inhalation

Baseline 

Dermald,h

PPE-G 

Dermali

Baseline 

Inhalatione

Baseline 

Dermalf

PPE-G

Dermal

Baseline 

Inhalationg

Combined 

Baseline 

Dermal + 

Inhalationj

Combined 

PPE-G

Dermal + 

Inhalationj k

Applicator

Applying Sprays via 

Fixed-Wing Aerial 

Equipment

(Enclosed Cockpit)

Soybean 0.30 1,200

5.0

(eng. 

control)

No Data

0.068

(eng. 

control)

0.0045

(eng. 

control)

No Data

0.000061

(eng. 

control)

1,100

(eng. 

control)

No Data

82,000

(eng. 

control)

No Data

1,100

(eng. 

control)

Snap Bean 0.25 350

5.0

(eng. 

control)

No Data

0.068

(eng. 

control)

0.0011

(eng. 

control)

No Data

0.000015

(eng. 

control)

4,600

(eng. 

control)

No Data

340,000

(eng. 

control)

No Data

4,600

(eng. 

control)

Strawberries 

(nonbearing)0.38 350

5.0

(eng. 

control)

No Data

0.068

(eng. 

control)

0.0017

(eng. 

control)

No Data

0.000023

(eng. 

control)

3,000

(eng. 

control)

No Data

220,000

(eng. 

control)

No Data

3,000

(eng. 

control)

Applying Sprays via 

Groundboom Equipment

(Open Cab)

Soybean 0.30 200 78.6 16.1 0.34 0.012 0.0024 0.000051 420 2,100 98,000 420 2,100

Snap Bean 

and Conifer 

Seedlings

0.25 80 78.6 16.1 0.34 0.0039 0.00081 0.000017 1,300 6,200 290,000 1,300 6,200

Strawberries 

(nonbearing)0.38 80 78.6 16.1 0.34 0.0060 0.0012 0.000026 840 4,100 190,000 840 4,100

Flagger

Flagging for Aerial 

Sprays Applications

Soybean 0.30 350 11 NA 0.35 0.0029 NA 0.000092 1,700 NA 54,000 1,700 NA

Snap Bean 0.25 350 11 NA 0.35 0.0024 NA 0.000077 2,000 NA 65,000 2,000 NA

Strawberries 

(nonbearing)0.38 350 11 NA 0.35 0.0037 NA 0.00012 1,400 NA 43,000 1,300 NA
Page 15 of 19

Table 5. Short- and Intermdiate-term Agricultural Handler Risk Estimates for Lactofen

Exposure Scenario Crop or 

Target

Application 

Rate a

(lb ai/A)

Area 

Treated 

Daily b

(acres)

Unit Exposurec,d,e

(μg/lb ai)

Dosef,g

(mg/kg/day) MOEs h,i,j,k

Baseline 

Dermal

PPE-G

Dermal

Baseline 

Inhalation

Baseline 

Dermald,h

PPE-G 

Dermali

Baseline 

Inhalatione

Baseline 

Dermalf

PPE-G

Dermal

Baseline 

Inhalationg

Combined 

Baseline 

Dermal + 

Inhalationj

Combined 

PPE-G

Dermal + 

Inhalationj k

Mixer/Loader/Applicator

Mixing/Loading/

Applying Mechanically 

Pressurized Handgun 

Sprayer

Conifer 

Seedlings 0.25 20 1,300 390 3.9 0.016 0.0049 0.0000049 310 1,000 100,000 310 1,000

a. Application rates = maximum application rates from labels.

b. Area treated daily from Science Advisory Council Policy # 9.1. 

c. Unit Exposures are from the “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table,” dated 9/26/11, and located at 

http://www.epa.gov/opp00001/science/handler-exposure-table.pdf. Engineering control unit exposure for mixing/loading liquids = closed system. Engineering control unit 

exposure for applying sprays via aerial equipment = enclosed cockpit. Engineering control unit exposure for mixing/loading wettable powders = water-soluble packaging. 

d. Baseline Dermal = Long-sleeve shirt, long pants, and no gloves; Baseline Inhalation: no respirator.

e. PPE-G = Baseline plus chemical-resistant gloves; 

f. Dermal Dose (mg/kg/day) = daily unit exposure (mg/lb ai) x application rate (lb ai/acre) x acres treated x dermal absorption factor (20%) / body weight (80 kg adult).

g. Inhalation Dose (mg/kg/day) daily unit exposure (μg/lb ai) x application rate (lb ai/acre) x acres treated x inhalation absorption (100%) / body weight (80 kg adult). 

h. Dermal MOE = NOAEL (3.0 mg/kg/day) / dermal daily dose (mg/kg/day). Level of concern = 300. Bold = MOE ≤ 300. 

i. Inhalation MOE = NOAEL (3.0 mg/kg/day) / inhalation daily dose (mg/kg/day). Level of concern = 300. Bold = MOE ≤ 300.

j. Combined Baseline Dermal + Inhalation MOE = 1 / (1/Baseline Dermal MOE) + (1/Baseline Inhalation MOE). Bold = MOE ≤ 300.

k. Combined PPE-G + Baseline Inhalation MOE = 1 / (1/PPE-G Dermal MOE) + (1/Baseline Inhalation MOE). Bold = MOE ≤ 300.
Page 16 of 19

4.2 Post-application Exposure

4.2.1 Data and Assumptions for Post-application Exposure Scenarios

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

exposure assessment was not performed for the uses of lactofen at this time primarily because it 

has low vapor pressure (2.8 x 10-7 mm Hg). However, volatilization of pesticides may be a 

potential source of post-application inhalation exposure to individuals nearby to 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. The Agency received the SAP’s final report on March 2, 2010 

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). 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 put into place, the 

Agency may revisit the need for a quantitative post-application inhalation exposure assessment 

for indaziflam.

Dermal: There is the possibility for agricultural workers to have post-application dermal

exposure to lactofen following use on soybeans and conifer seedlings. Post-application

exposures for soybean are not assessed in this action, however, because the exposure is 

anticipated to be similar to that previously assessed for peanut. Post-application exposures are 

considered to be negligible for the use of lactofen on snap beans and strawberry (non-bearing) 

based on label instructions. For snap beans, lactofen is applied to the soil only and for 

strawberries, lactofen is applied to either to the soil or to dormant seedlings with soil placed over 

the crown prior to application. HED assumes that post-application dermal exposure to treated 

soil by occupational workers is negligible and, therefore, post-application exposures and risks to 

occupational workers for the snap bean and strawberry uses were not quantitatively assessed. 

The assumptions made in assessing the short- and intermediate-term dermal post-application

risks for the use of lactofen on conifer seedlings include the application rate, bodyweight, and 

dermal absorption factor values discussed above in the occupational handler section, and the 

following assumptions below:

Dislodgeable foliar residues

There were no chemical-specific dislodgeable foliar residue data to assess post-application risks 

to workers while performing tasks related to crops treated with lactofen. Occupational postapplication exposures and risks are assessed using HED’s default assumptions that 25 % of the 

initial application is available for transfer on day 0 (i.e., 12 hours after application), and that the 

residue dissipates at a rate of 10 % per day. 

Transfer coefficients

Transfer coefficients numerically represent the post-application exposures one would receive 

(generally presented as cm2/hour). A transfer coefficient is a measure of the residue transferred 
Page 17 of 19

from a treated surface to a person who is doing a task or activity in a treated area. These values 

are the ratio of an exposure for a given task or activity to the amount of pesticide residue on 

treated surfaces available for transfer. 

It is the policy of HED to use the best available data to assess post-application exposure. The TC 

values recommended for use in predicting post-application exposure are presented in the 

“Science Advisory Council for Exposure (ExpoSAC) Policy 3” 

(http://www.epa.gov/pesticides/science/exposac_policy3.pdf), which, can be found at 

http://www.epa.gov/pesticides/science/post-app-exposure-data.html.

HED selects the most appropriate TCs based on the label use patterns for the crops. HED 

assessed post-application exposure to conifers (seedlings and conifers in nurseries) using a 

transfer coefficient of 580 for scouting Christmas trees (low height foliage and minimum density 

foliage). HED did not select a TC for irrigation activities because the only irrigation transfer 

coefficient available for Christmas trees is for full foliage density, which is not representative of 

the use pattern. 

The TC for sod harvesting, 6,700, was selected as it was determined to be most similar to the 

activity of harvesting and bundling conifer seedlings. When using the sod harvesting TC, the 

fraction application rate retained on foliage (DFR) is anticipated to be 1%, which is consistent 

with that recommended for the assessment of liquid formulated turf products. 

Workday

HED assumes an 8 hour workday for post-application workers.

Equations and Calculations

Daily Dermal Exposure: Daily dermal exposures were calculated on each post-application day 

after application using the following equation:

E(t) (mg/day) = (DFR(t) (μg/cm2) x TC (cm2/hr) x Hr/Day)/1,000 (μg/mg)

Where:

E(t) = Daily exposure or amount deposited on the surface of the skin at time (t) 

attributable for activity in a previously treated area;

DFR(t) = Dislodgeable foliar residue at time “t” (μg/cm2);

TC = Transfer Coefficient (cm2/hour); and

Hr/day = Exposure duration meant to represent a typical workday (8 hours).

DFR: Default dislodgeable foliar residue (DFR) values were calculated on each post-application

day after application using the following equation:

DFR (μg/cm2) = AR (lb ai/A) x F x (1- D)tx CF1 x CF2
Page 18 of 19

Where:

AR = Maximum application rate;

F = Fraction of ai retained on the foliage;

D = Fraction of residue that dissipates daily;

t = Post-application day ;

CF1 = 4.54E+8 μg/lb ; and

CF2 = 2.47E-8 A/cm2.

4.2.2 Post-application Exposure and Risk

The post-application exposure associated with conifer seedlings is summarized in Table 6. 

Using HED default assumptions and surrogate DFR data, risks were not of concern (i.e., MOEs 

≥ 300) on Day 0 (12 hours after application) using the highest transfer coefficient.

Table 6. Post-application Exposure and Risk for Lactofen

Crop TCa Days after 

Treatment DFRb

(μg/cm2)

Daily Dermal Dosec

(mg/kg/day) MOEd

Conifer Seedlings

580 

(scouting)

0

(12 hours) 0.63 0.0073 680

6,700

(harvesting)

e

0

(12 hours) 0.025 0.0034 1,500

a. Transfer coefficients from “Science Advisory Council for Exposure (ExpoSAC) Policy 3” 

http://www.epa.gov/pesticides/science/exposac_policy3.pdf)

b. DFR = Dislodgeable Foliar Residue = application rate (lb ai/A) x (1- daily dissipation rate) tx 4.54E8 μg/lb x 2.47E-8 A/cm2x 

25% DFR after initial treatment or 1% turf transferable residue (TTR) after initial treatment (for use with sod harvesting TC)

c. Daily Dermal Dose = [DFR (μg/cm2) x Tc (cm2/hr) x 0.001 mg/μg x dermal absorption (20%) * 8 hrs/day] body weight (80 

kg adult)

d. MOE = LOAEL/Daily Dose (Dermal NOAEL = 5 mg/kg/day) 

e. The TC for sod harvesting was selected from “Science Advisory Council for Exposure (ExpoSAC) Policy 3” which was 

determined to be most similar to the activity of harvesting and bundling conifer seedlings.

Restricted Entry Interval: Since post-application risks are not a concern on day 0 (12 hours 

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

lactofen technical material. Lactofen is classified as Toxicity Category III via the dermal route 

and for eye irritation potential and as Toxicity Category IV for skin irritation potential. Under the 

Worker Protection Standard for Agricultural Pesticides, active ingredients classified as acute 

toxicity categories III or IV for these routes are assigned a 12-hour REI. Therefore, the 12-hour 

REI that appears on the labels is adequate.

5.0 Residential (Non-Occupational) Exposure and Risk

No residential uses are associated with the uses of lactofen being evaluated in this action and, 

therefore, no residential handler exposure and risk assessment has been conducted in this 

document. 

Residential Bystander Post-Application Inhalation Exposure
Page 19 of 19

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

assessment was not performed for lactofen at this time because of the low acute inhalation 

toxicity (Toxicity Category IV), low vapor pressure (3.0 × 10-8 mm Hg at 21 oC), and the low 

application rates (0.20 to 0.38 lb ai/A). However, volatilization of pesticides may be a potential 

source of post-application inhalation exposure to individuals nearby to 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, 2010 

(http://www.epa.gov/scipoly/SAP/meetings/2009/120109meeting.html). 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 post-application inhalation exposure assessment 

for lactofen.

Spray Drift

Spray drift is always a potential source of exposure to residents nearby to spraying operations. 

This is particularly the case with aerial application, but, to a lesser extent, could also be a 

potential source of exposure from the ground application method employed for lactofen. The 

Agency has been working with the Spray Drift Task Force, 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 at 

http://www.epa.gov/opp00001/factsheets/spraydrift.htm). On a chemical by chemical basis, the 

Agency is now requiring interim mitigation measures for aerial applications that must be placed 

on product labels/labeling. The Agency has completed its evaluation of the new database 

submitted by the Spray Drift Task Force, a membership of U.S. pesticide registrants, and is 

developing a policy on how to appropriately apply the data and the AgDRIFT computer model to 

its risk assessments for pesticides applied by air, orchard airblast and ground hydraulic methods. 

After the policy is in place, the Agency may impose further refinements in spray drift 

management practices to reduce off-target drift with specific products with significant risk 

estimates associated with drift.

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

performed as a result of pesticide drift from neighboring treated agricultural fields, an inhalation 

exposure assessment was performed for flaggers. This exposure scenario is representative of a 

worse case inhalation (drift) exposure and may be considered protective of most outdoor 

agricultural and commercial post-application inhalation exposure scenarios.