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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460 

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

MEMORANDUM (DRAFT)

Date: March 24, 2015

SUBJECT: Review of “Determination of Dermal and Inhalation Exposure to Workers during 

Backpack and Handgun Application of Liquid Sprays in Utilities Rights-of-Way” (AHE400)

PC Code: -- DP Barcode: D424153

Decision No.: -- Registration No.: --

Petition No.: -- Regulatory Action: --

Risk Assessment Type: -- Case No.: --

TXR No.: -- CAS No.: --

MRID No.: 49472001 40 CFR: --

 

 

FROM: Matthew Crowley, Biologist

Chemistry and Exposure Branch

Health Effects Division

THROUGH: David J. Miller, Chief

Chemistry and Exposure Branch

Health Effects Division

TO: Richard Dumas

Pesticide Registration Division

This memorandum presents EPA’s review of the analytical and field phase reports for AHE400

(AHETF, 2014), an Agricultural Handler Exposure Task Force (AHETF) study monitoring 

dermal and inhalation exposure for workers making backpack or handgun applications of liquid 

sprays to utility rights-of-way and similar areas. The scenario monographs (Bruce, et al, 2014a 

and 2014b), which incorporate the monitoring data from AHE400 into single/composite datasets

and includes statistical analysis based on pre-defined benchmark accuracy objectives, are

reviewed under separate cover (Crowley, 2015a and 2015b).

This study meets EPA standards for occupational pesticide exposure monitoring and are 

considered acceptable and appropriate for use in occupational exposure assessments for 

backpack and handgun applicators.
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1.0 Executive Summary

The Agricultural Handler Exposure Task Force (AHETF) monitored dermal and inhalation 

exposure for 21 workers using handgun sprayers and 19 workers using backpack sprayers while 

applying liquid spray pesticides to undesirable vegetation such as shrubs, vines, and trees in

areas such as utility rights-of-way (ROW), parks, roadsides, and wildlife refuges across the 

eastern half of the United States. Importantly, the pesticide solution was not prepared by the 

monitored workers; thus, results of monitoring did not include exposures during the pesticide 

mixing process.

Backpack applications in this study were conducted using a handwand attached to a low-volume 

tank worn on a worker’s back. While walking through the target area, the pesticide solution is 

sprayed by manually pressurizing the spray tank with a hand-pump attached to the backpack and 

squeezing the trigger on the wand. Additionally, some of the workers using backpacks also 

performed “hack-and-squirt” applications (a direct/localized spray following a slice/cut to the 

base of a tree or bush).

Handgun applications in this study were conducted with a handgun attached to a hose, which is 

in turn attached, through a mechanical pump, to a vehicle-mounted holding tank. The 

mechanical pump provides the pressure to spray the pesticide solution. The workers often 

sprayed the target vegetation from the vehicles, but at times had to drag the hose and walk in and 

around the targeted areas. 

Table 1 presents a high-level summary of all of the exposure monitoring.

Table 1. AHE400 Summary

Equipment Site State No. Monitored 

Worker-Days

Monitoring Year

(for each Worker-day)

Age

Range

(years)

Backpack

ROW & Park PA 3 2012/-12/-13 29-53

NC 1 2011 33

ROW GA 1 2011 29

SC 1 2012 38

Wildlife Refuge & ROW FL 3 2011/-12/-12 26-48

ROW AR 3 2011/-12/-12 21-31

Pipeline terminal & ROW IN 2 2012/-13 24-34

Park & Drainage ditch MI 2 2012/-13 33-37

ROW TX 3 2011/-12/-12 27-29

Handgun

ROW

PA 2 2012 54-68

WV 1 2012 49

NC 2 2011/-13 34-47

TN 1 2012 48

FL 3 2011/-13/-13 27-54

MN 2 2013/-13 20-48

Fence line & ROW LA 3 2012/-12/-12 20-48

Pipeline terminal & ROW IN 3 2012/-12/-13 19-39

Roadsides MI 1 2012 45

Drainage ditch & ROW TX 3 2011/-11/-12 25-58

Note: all study subjects were male.
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Monitored on actual days of work, backpack applicators handled from 0.03 to 9.65 lbs of active 

ingredient, spraying 4.5 to 64.5 gallons of solution in 2 to 10.7 hours, covering (when recorded) 

less than 1 to approximately 6 acres. Handgun applicators handled from 0.077 to 45.95 lbs of 

active ingredient, spraying 71 to 2900 gallons of solution in 3.3 to 11.4 hours, covering less than 

1 to approximately 20 acres. Applicators wore long-sleeved shirts, pants, shoes/socks and 

chemical-resistant gloves, with a few donning protective leggings and eye protection. No 

applicator wore a respirator.

Dermal exposure was measured using hand washes, face/neck wipes, and whole body dosimeters 

(100% cotton union suits) for the remainder of the body (torso, arms, and legs). Inhalation 

exposure was measured using personal air sampling pumps and OSHA Versatile Samplers 

(OVS) mounted on the shirt collar.

All studies followed the applicable and most up-to-date AHETF standard operating procedures 

(SOPs) and their corresponding protocols with deviations appropriately recorded. No protocol 

deviation is considered to have compromised the overall research. Analytical field and 

laboratory recovery results were acceptable, generally averaging between 70 and 120% recovery, 

with coefficients of variation generally lower than 25%. All field samples were appropriately

adjusted for the corresponding recovery adjustment factors. 

Total dermal exposure1, calculated by summing the results for inner dosimeters, hand washes 

and face/neck wipes, as well as dermal exposure normalized to body weight and also normalized 

to the amount of active ingredient handled are summarized in Table 2 below.

Table 2. Dermal Exposure Summary

Equipment Statistic1 Total Exposure

(μg)

Normalized by Body 

Weight

(μg/kg BW)

Normalized by Amount ai 

Handled

(μg/lb ai)2

Backpack

Minimum 34 0.48 675

Maximum 752,379 8,360 241,923

Mean 73,414 855 31,273

Handgun

Minimum 80 0.88 26

Maximum 112,258 1,467 12,123

Mean 12,431 135 1,868

1 Means are simple averages (i.e., sum of values ÷ n)

2 Though other exposure metrics are shown in this table, exposure normalized to the amount of active ingredient 

handled is typically the format used by EPA as an input in standard handler exposure calculations.

Total inhalation exposure, calculated2assuming a breathing rate of 16.7 L/min3, as well as 

inhalation exposure normalized to body weight and also normalized to amount of active 

ingredient handled are summarized in Table 3 below.

 

1 All dermal exposure values reflect a 2X adjustment on hand rinse and face/neck wipe measurements accounting for 

assumed 50% residue collection method efficiency (see Section 3.3). Non-adjusted values are available in 

associated review spreadsheets.

2

Inhalation exposure (μg) = Residue collected * [Breathing rate (L/min) ÷ Pump rate (L/min)]. Pump rates 

generally were 2 L/min. Note: AHE400 presented the total active ingredient collected (μg), not results adjusted for 

breathing rates as shown here. AHETF monograph submissions, reviewed separately, perform the calculation 

shown here. 

3 NAFTA, 1998. Rate of 16.7 L/min represents light activity.
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Table 3. Inhalation Exposure Summary

Equipment Statistic Total Exposure

(μg)

Normalized by Body Weight

(μg/kg BW)

Normalized by Amount ai 

Handled

(μg/lb ai)

Backpack

Minimum 0.54 0.007 1.74

Maximum 567 7 112

Mean 100 1.22 35

Handgun

Minimum 0.24 0.003 0.18

Maximum 670 8.28 35

Mean 88 1.09 7

Note: Means are simple averages (i.e., sum of values ÷ n)

2.0 Summary of Field Study Characteristics

This section provides summary characteristics for AHE400. While a summary is provided, the 

submitted AHE400 report should be consulted for more specific details (applicable sections, 

tables, and/or page numbers are provided).

2.1 Administrative Summary

AHE400 was sponsored by the AHETF and adequately followed both the protocol and scenario 

construction plan (AHETF, 2010a), the AHETF Governing Document (AHETF, 2008 and 

2010b), and applicable AHETF SOPs. 

The study was conducted in compliance with Good Laboratory Practice Standards (GLPS) (40 

CFR §160) and met the standards in EPA Test Guidelines Series 875 – Occupational and 

Residential Exposure (875.1100 – dermal exposure; 875.1300 – inhalation exposure). 

Deviations from GLPS are noted in AHE400 pages 3-4 – none are considered to have 

substantially impacted the study conduct or results. Signed copies of acceptable Quality 

Assurance and Data Confidentiality statements were provided.

Protocol amendments included: adding additional sources for recruitment; allowance for 

additional clothing such as rubber boots, leggings, and headgear; allowance for sites that are not 

strictly rights-of-way but are similar in terms of vegetation and terrain and would be subject to 

similar pesticide applications; increases to field fortification levels; analytical method 

specifications; and relaxing the “different employer” requirement. The amendments are all

considered reasonable accommodations in order to carry out the study and were appropriately

documented. 

Protocol deviations included: use of analytical methods that were validated but had yet to be 

specified in the protocol; failure to meet monitoring time and load thresholds; potential lack of 

sampling test substance lots; failure to perform a hand wash at a break; use of non-AHETF 

provided gloves; failure to notify potential employers of an introductory letter and phone call; air 

sampling pump issues; and a change to a principal analytical investigator. None are considered 

to have negatively impacted the study conduct or results.
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For a more detailed summary of amendments and deviations, see Section 4.0 below and refer to 

AHE400 pages 11-14 as well as Appendix A (pages 454-538).

2.2 Test Materials

Four potential surrogate active ingredients, all herbicides, were specified in the protocol: 

glyphosate, fosamine, 2,4-D, and imazapyr. Backpack applications utilized 3 of 4 of the 

surrogates, each one spraying either glyphosate, fosamine, or imazapyr. Handgun applications 

utilized all four surrogate herbicides, each one spraying either glyphosate, fosamine, 2,4-D, and 

imazapyr.

Per GLP, AHETF analyzed the test substances for purity. Certificates of Analysis, which 

formally document analysis of the test substances, are provided in AHE400 Appendix F pages 

1400-1430. AHETF determined that analysis of “Pre-Mix” products were suspect due to 

homogeneity concerns and would instead, where applicable, use the label-specified active 

ingredient concentrations to calculate amount of active ingredient handled. Additionally, in 

some cases a sample of the product used was unattainable for analysis, so the nominal 

concentration listed by the manufacturer on the product was used.

AHE400 pages 65-68 and Table B-2 on pages 92-93 provides more specific details on the 

products used and methodologies for calculating amount of active ingredient handled. This is 

also described more in Section 2.7 below.

2.3 Sample Size, Monitored Workers, and Locations

According to the Backpack and Handgun ROW Scenario Construction Plan (AHETF, 2010a) 

and the AHETF Governing Document (AHETF, 2008 and 2010b), a “7 x 3” configuration was 

deemed a reasonable approach for these scenarios. That is, for each of the two scenarios, a total 

of 21 “monitoring units” (MU), obtained by monitoring exposure from 7 spatially distinct study

locations across the eastern U.S., each with 3 workers per location would be likely to satisfy predefined accuracy benchmarks.

Ultimately, 21 separate workers were monitored conducting handgun applications and 19 were 

monitored conducting backpack applications. The AHETF decided to terminate the backpack 

monitoring due to logistical difficulties and because they believed the resulting dataset would be 

adequate to meet scenario benchmarks. Discussion of the sampling design and related issues is 

covered under a separate review (Crowley, 2015a and 2015b).

Monitoring locations were all places where undesirable vegetation such as shrubs, vines, or 

bushes were meant to be controlled. Most of the monitoring was in utility rights-of-ways, such 

as areas through which electric transmission and distribution lines or pipelines run. These are 

areas where controlling vegetation is important so as to not only provide easy access to utility

personnel and vehicles, but also because the vegetation can damage utility distribution 

equipment. Other monitoring areas included parks, drainage ditches, wildlife refuges, fence 

lines, and roadsides where these types of pesticide applications are also conducted. While these 

are not rights-of-way, both the purpose of the application (i.e., controlling undesirable 
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vegetation) and location characteristics such as terrain and vegetation type were similar to the 

right-of-way locations that constituted the bulk of the monitoring.

Table 4 below provides some more detailed characteristics of the workers and locations. The 

AHE400 study report provides additional backpack applicator details in Table BP-3 on pages 94-

97 and handgun applicator details in Table HG-3 on pages 284-287. 

Table 4. Worker and Location Summary

Equipment

Age

Range

(years)

Gender Weight 

(lb)

Work

Experience

(years)

Site/Target State Monitoring 

Years

Backpack 21 -53 All 

male

137 -

351 < 1 to 15

Distribution line 

ROW PA/SC/NC/AR/IN 2011-2013

Transmission

line ROW PA/GA/FL/AR/TX 2011-2013

Wildlife refuge FL 2011

Pipeline ROW IN 2012

Park PA/MI 2012-2013

Drainage ditch MI 2013

Handgun 19 –

68

All

male

127 -

251 < 1 to 34

Distribution line 

ROW

NC/TN/LA/IN/MN/

TX 2011-2013

Transmission 

line ROW

PA/WV/NC/FL/LA/

TX 2011-2013

Dist. and Trans. 

line ROW PA 2012

Drainage ditch TX 2011

Roadsides MI 2012

Fence line LA 2012

Pipeline 

terminal IN 2013

2.4 Environmental Conditions

Temperature (including heat index), humidity, wind speed and direction, cloud cover, and 

rainfall were all reported. The maximum reported temperature was 93° F (Handgun application, 

TX, 2011 and Backpack application, AR, 2012) and the lowest reported temperature was 45° F

(Handgun application, WV, 2012). Rain impacted some of the monitoring. For two handgun 

applications, monitoring was halted during rain and the applicators took shelter and resumed 

applications after the rain stopped. Additionally, for each a backpack and handgun application,

rain halted monitoring, but in each case in terms of time, amount applied, etc. monitoring was 

sufficiently complete when halted. Maximum reported wind speed was approximately 20 miles 

per hour.

In a few instances monitoring was affected or halted because the ambient temperature exceeded

the pre-defined threshold of concern for potential heat-related injury: one backpack application 

in West Virginia in 2012 (heat index = 106° F) and two handgun applications (both in Texas, 

heat indices of 105° F in 2011 and 110° F in 2012). However in all cases in terms of time, 

amount applied, etc. monitoring was sufficiently complete by the time the application was halted.
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For more details on environmental conditions see the AHE400 report tables BP-7 (pages 106-

109) and HG-7 (pages 296-299).

2.5 Clothing and Personal Protective Equipment (PPE)

Per the stated goals of the AHETF, monitoring of backpack and handgun applications to 

undesirable vegetation in rights-of-way or similar areas was conducted to represent exposure for 

workers wearing long-sleeve shirts, pants, shoes/socks, chemical-resistant gloves and no 

respiratory protection. While this was largely the case, because of the nature of the terrain and 

environment nearly all workers wore (company-required) hard hats and some wore additional leg 

coverings (7 backpack applicators, 2 handgun applicators) to protect from thorns or snakes.

So long as the work clothing met the standards of the EPA Worker Protection Standard (WPS), 

monitoring was conducted with the clothing worn by the worker on the scheduled monitoring 

day. In three instances, the AHETF supplied workers with replacement shirts or pants prior to 

study initiation.

Per protocol, new chemical-resistant gloves were supplied by the AHETF to all workers at the 

beginning of the day and were available throughout the day according to WPS requirements. In 

one instance a worker (backpack applicator A27) preferred to wear his own chemical-resistant 

gloves – this was noted as a protocol deviation. Additionally, many workers, either due to 

company policy or worker preference or required by the pesticide label, wore protective 

eyewear. In these cases, the exposure measurements were adjusted (according to AHETF SOP 

9.K) to extrapolate deposited residue to those portions of the face/head covered by the protective 

eyewear.

More specific details on work clothing and PPE can be found in the AHE400 study report in 

Tables BP-4 and BP-5 on pages 98-101 and Tables HG-4 and HG-5 on pages 288-291.

2.6 Application Equipment and Methods

For these studies, as indicated above, only application with either a backpack or handgun was 

monitored – monitoring was not conducted for those workers responsible for mixing and loading 

the pesticide. 

For backpack applications, the worker used a handheld wand/hose/nozzle apparatus attached to a 

3 to 4 gallon spray tank mounted to their backs with shoulder straps. The spray tank solution 

was pressurized manually using a lever. The spray nozzle typically had a dual set-up where 

workers could switch between a straight stream or broad/fan stream. In three instances, in 

addition to the standard backpack applications, workers also conducted “hack-and-squirt” 

applications, also known as “frill” applications. For these, the trunk of a tree or bush is cut with 

a knife or machete, and spray solution applied with a small squirt bottle.

For handgun applications, the worker sprayed with a wand/hose/nozzle apparatus attached to 

vehicle-mounted mechanical pressurizing pump and large spray tank. Vehicle types varied 

including all-terrain vehicles (ATVs), trucks and tractors. Workers sprayed the target vegetation 
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from the vehicles, but also at times got off the vehicle dragging the hose behind them while 

walking through the area. Spray pressures varied, with most less than 100 pounds per square 

inch (psi), though some others used higher-pressure rigs (e.g., 800 psi) that can spray up to 30 

feet.

 

More details on application equipment and methods can be found in the AHE400 study report for 

backpack applications on page 70-71 and Table BP-6 on pages 102-105 and for handgun 

applications on page 259 and Table HG-6 on pages 292-295.

 

2.7 Application Rates

According to the Backpack and Handgun ROW Scenario Construction Plan (AHETF, 2010a) 

and the AHETF Governing Document (AHETF, 2008 and 2010b), the total amount of active 

ingredient applied should be diversified across the scenario and within each study location. 

For backpack applications, small volumes of liquid concentrate products (< 1 gallon up to 15

gallons) were mixed with water (7.5 to 400 gallons) according to label specified dilutions in a 

tank from which workers would load the spray into their backpack. Overall workers sprayed 4.5 

to 64.5 gallons of solution in 2 to 11 hours. 

In two cases (MUs A27 and A16) ready-to-use products (i.e., packaged as diluted solutions) 

were used so the amount of product in the spray is the same as the amount of spray prepared. 

Also, amounts handled reflect the “hack-and-squirt” applications conducted by three workers 

(MUs A1, A2, and A23) in addition to their backpack applications.

Using the product concentration – determined either by purity analysis or labeled concentration –

with the known dilution and amount sprayed, the amount of active ingredient handled can be 

determined. Backpack applicators handled from 0.03 to 9.65 lbs of active ingredient. 

Table 5 below provides more detail on backpack application rates. The submitted AHE400 

study report should also be referenced on page 71 and Tables BP-6 (pages 102-105) and BP-13 

(page 250).

Table 5. Backpack Application Information

MU 

ID Site

Active 

Ingredient 

(ai)

Product 

Conc.

(lb ai / 

gal)

Amt 

Product 

in 

Spray

(gal)a

Amt 

Spray 

Prepared

(gal)

Amt 

Spray 

Applied 

(gal)

Loads 

Sprayed

(#)

Area 

Treated

(acres)

Time 

(hr)

AaiH 

(lb)b

A27c,d Distribution Glyphosate 0.32 5 5 4.5 2

Not 

recorded 3.5 1.44

A33d Transmission Glyphosate 2.67 9.5 160 28.5 10 5.25 9 4.49

A34dPark Glyphosate 3 2 100 13.5 4 3.5 2 0.81

A8 Distribution Fosamine 4.3 5.5 275 12.25 4 4 4 2.11f

A10 Transmission Glyphosate 4.28 14 400 64.5 17 6 6.4 9.65

A20d Distribution Imazapyr 4.19 0.5 210 48 12 0.75 5.1 0.48

A11 Wildlife 

Refuge Imazapyr 0.45 1.5 300 22.5 9 3.3 8.2 0.051

A12 Transmission Glyphosate 4.13 1.35 50 16.5 6 5 5 1.9

A13 Transmission Glyphosate 4.13 1.35 50 20 7 5 5 2.27
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Table 5. Backpack Application Information

MU 

ID Site

Active 

Ingredient 

(ai)

Product 

Conc.

(lb ai / 

gal)

Amt 

Product 

in 

Spray

(gal)a

Amt 

Spray 

Prepared

(gal)

Amt 

Spray 

Applied 

(gal)

Loads 

Sprayed

(#)

Area 

Treated

(acres)

Time 

(hr)

AaiH 

(lb)b

A1d,e Distribution Glyphosate 2.67 11 151 33.25 10 2 10.7 6.65

A23e Distribution Glyphosate 3.9 8 160 14.5 5 0.45 6 3.11

A24 Transmission Imazapyr 2.04 1.25 225 33 10 Not 

recorded 4.3 0.37

A16c,d Pipeline Glyphosate 0.32 30 30 15.875 6 3.25 10.2 5.08

A38d Distribution Glyphosate 2.07 1.92 32 14.75 5 0.75 8.8 1.83

A31 Park Glyphosate 3.02 0.4 16.5 16.5 6 0.6 6.3 1.13

A40 Drainage 

Ditch Glyphosate 4.07 0.15 7.5 7.5 7 0.9 7.8 0.62

A2d,e Transmission Glyphosate 2.67 15 200 16.5 7 0.75 7.5 3.62

A4 Transmission Imazapyr 1.98 0.28 300 16 6 2 6.1 0.03

A25 Transmission Glyphosate 4 10 221 19.5 7 1.6 3.6 3.51

a Amount of product includes any removal of small amounts used for purity analysis.

b Amount active ingredient can be approximated by the calculation: product concentration (lb ai/gal product) * amount of 

product in spray mixture (gal prod) * [amount of spray mixture applied (gallons) ÷ amount of spray mixture prepared (gallons)]. 

Slight differences with the reported value are due to AHETF calculating and summing the amount ai handled for each load.

c

Product was a ready-to-use solution, so gallons of product in spray mixture and gallons of spray mixture prepared are the same.

d

Product was unavailable for sampling or was a “Premix” product – thus, concentration on label was used for calculation 

purposes.

e Worker also made “hack-and-squirt” applications.

f Reflects the addition of a total (across 4 backpack loads) of 0.25 gallons (1 lb ai) of the product to the mixture.

For handgun applications, small volumes of liquid concentrate products (< 1 gallon up to 12 

gallons) were mixed with large volumes of water (~ 100 to 3100 gallons) according to label 

specified dilutions. Workers then sprayed from 80 to 2900 gallons in about 3 to 11 hours. Using 

the product concentration – determined either by purity analysis or labeled concentration – with 

the known dilution and amount sprayed, the amount of active ingredient handled can be 

determined. Handgun applicators handled from 0.077 to 45.95 lbs of active ingredient.

Table 6 below provides more detail on backpack application rates. The submitted AHE400 

study report should also be referenced for handgun applications on pages 259-260 and Tables 

HG-6 (on pages 292-295) and HG-13 (page 449).

Table 6. Handgun Application Information

MU 

ID Site

Active 

Ingredient 

(ai)

Product 

Conc.

(lb ai / 

gal)

Amt 

Product 

in 

Spray

(gal)a

Amt 

Spray 

Prepared

(gal)

Amt 

Spray 

Applied 

(gal)

Loads 

Sprayed

(#)

Area 

Treated

(acres)

Time 

(hr)

AaiH

(lb)b

A28c Trans. + 

Dist. ROW Glyphosate 4 5 500 485 1

Not 

recorded 6.8 19.4

A29c Trans. ROW Glyphosate 2.67 6 600 580 3 6.09 6.7 15.49

A30 Trans. ROW Glyphosate 4.02 5 600 400 2 3 6.6 13.19

A9 Dist. ROW Fosamine 4.3 5.5 275 188 1

Not 

recorded 4.8 16.17

A19 Dist. ROW Imazapyr 2.13 0.75 900 700 3 4.7 8 1.24

A39 Trans. ROW Imazapyr 3.88 0.31 260 260 1 6.2 5.5 1.21

A6 Trans. ROW Imazapyr 1.88 2 250 190 3 40 8.4 2.89

A7 Trans. ROW Glyphosate 4.27 2.7 295 86.5 2 52 9.7 3.54

A36 Trans. ROW Imazapyr 2.06 1.5 200 190 2 9.7 5.9 3.09

A14 Fence Line Imazapyr 1.96 0.46 185 144 4 0.36 7.1 0.71
Page 10 of 22

Table 6. Handgun Application Information

MU 

ID Site

Active 

Ingredient 

(ai)

Product 

Conc.

(lb ai / 

gal)

Amt 

Product 

in 

Spray

(gal)a

Amt 

Spray 

Prepared

(gal)

Amt 

Spray 

Applied 

(gal)

Loads 

Sprayed

(#)

Area 

Treated

(acres)

Time 

(hr)

AaiH

(lb)b

A15 Trans. ROW Glyphosate 4.18d6 755 671 13 Not 

recorded 6.4 21.73

A17 Dist. ROW Glyphosate 4.23 6.3 315 225 2 3 5.2 19.04

A21 Dist. ROW 2,4-D 2.51 1 200 200 4 1.2 6.6 2.51

A22 Dist. ROW 2,4-D 3.76 2.125 635 635 3 2.2 7.4 7.99

A35 Pipeline 

Terminal 2,4-D 2.32 3.9 107.5 104.5 7 1.5 8.1 8.87

A26 Roadsides Glyphosate 4.11 12 3100 2900 2

Not 

recorded 10.4 45.95

A32 Dist. ROW Fosamine 3.99 3.5 350 338 6 6.7 8.6 13.49

A37 Dist. ROW Imazapyr 2.06 0.13 275 80 4

Not 

recorded 11.4 0.077

A3 Trans. ROW Imazapyr 1.98 0.26 300 281 1 3 6 0.52

A5 Drainage 

Ditch Glyphosate 4.10 2.6 140 81e

2 1 3.3 6.84

A18 Dist. ROW Glyphosate 4.24 11 1000 900 2 17 6.9 41.98

a Amount of product includes any removal of small amounts used for purity analysis or for backpack applications.

b Amount active ingredient can be approximated by the calculation: product concentration (lb ai/gal product) * amount of 

product in spray mixture (gal prod) * [amount of spray mixture applied (gallons) ÷ amount of spray mixture prepared (gallons)]. 

Slight differences with the reported value are due to AHETF calculating and summing the amount ai handled for each load.

c

Product was unavailable for sampling or was a “Premix” product – thus, concentration on label used for calculation purposes.

d Represents the average of two product concentrations: 4.16 and 4.19 lb ai/gallon.

e AHE400 incorrectly reports this as 71 gallons.

2.8 Exposure Monitoring and Analytical Methods

Per applicable AHETF SOPs, standard passive dosimetry methods recognized by EPA as 

appropriate for worker exposure monitoring were utilized for all monitoring. No biomonitoring 

samples were collected. Dermal exposure to the hands was measured using a hand rinse method 

administered at the end of the workday as well as at lunch, restroom breaks, or other instances 

where workers would otherwise wash their hands as outlined in AHETF SOP 8.B. Dermal 

exposure to the face/neck was measured using a wipe technique as outlined in AHETF SOP 8.C 

and extrapolated to non-wiped portions of the head according to AHETF SOP 9.K. Thus, for 

those workers who wore eye protection and/or hard hats, the extrapolation to the whole head 

renders the resulting measurement somewhat representative of face/neck/head exposure without 

that additional gear. Generally, 1-2 face/neck wipe samples were collected for each worker then

analyzed as a composite sample.

Dermal exposure to the remainder of the body (torso, arms, and legs) was measured using whole 

body dosimeters (100% cotton union suits), sectioned into six pieces and analyzed separately

according to AHETF SOP 8.A. All these measurements combine to reflect dermal exposure 

underneath a single layer of work clothing (long-sleeve shirt, pants, shoes/socks) and chemicalresistant gloves. Inhalation exposure was measured using OVS tubes mounted on the worker’s 

collar and personal sampling pumps (set at 2 liters per minute) according to AHETF SOP 8.D. 

The concentrations measured represent the chemical available in each worker’s breathing zone. 

The submitted AHE400 study report outlines the passive dosimetry procedures in more details 

on pages 14-18.
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Validated analytical methods specific to each type of monitoring matrix (i.e., inner dosimeters, 

hand rinses, etc.) were used to extract residues. The analytical methods are outlined in the 

analytical reports:

 2.4-D – AHE400 Appendix B, pages 539-647

 Fosamine – AHE400 Appendix C, pages 648-760

 Glyphosate – AHE400 Appendix D, pages 761-1176

 Imazapyr – AHE400 Appendix E, pages 1177-1399. 

Limits of quantification and detection (as defined in AHETF SOP 9.A) are presented in Table 7

below.

Table 7. Analytical Limits (μg/sample) for AHE400

Monitoring 

Matrix

Limit of Detection Limit of Quantification

2,4-D Fosamine Glyphosate Imazapyr 2,4-D Fosamine Glyphosate Imazapyr

Inner 

Dosimeter 0.30 0.1701 0.139 0.041 1.0

Socks 0.060 0.0285 0.011 0.0355 0.25

Hand Rinse 0.30 0.1278 0.179 0.167 1.0

OVS air 

sampler

(per section)

0.0015 0.0008 0.0016 0.0005 0.005

Face/Neck 

Wipe 0.30 0.3123 0.143 0.317 1.0

3.0 Results

This section provides a discussion of quality assurance and quality control sampling and the 

actual field monitoring measurements of workers.

3.1 Quality Assurance

All phases of each study were subject to appropriate quality assurance processes according to 

EPA’s GLPs which included an audit by the AHETF Quality Assurance Unit (QAU) per AHETF 

SOPs (AHETF SOP Chapter 5: A-K). The inspected phases were: Protocol, Field Phase, Field 

Data, Draft Report, Analytical Data, Final Report, and Post-Audit Report. The study contains a 

signed quality assurance compliance statement as required by GLPs. Protocol amendments or 

deviations were addressed appropriately under GLP guidance and are described further in 

Section 4.0.

3.2 Quality Control

AHETF instituted various quality control measures to ensure proper field conduct including 

calibration of sprayers, preparation and handling of exposure measurement matrices, evaluation 

of test material, and field observations (AHETF SOP Chapter 10: A-G). Analytical methods 

were validated appropriately ensuring that all exposure matrices could be measured for the 

surrogate active ingredients proposed. Analytical quality control measures for ensuring the 
Page 12 of 22

integrity of measurements captured in the research were also instituted according to AHETF 

SOP 9.J. 

Exposure monitoring matrices (inner whole body dosimeters, hand washes, face/neck wipes, 

OVS tubes) were fortified with known amounts of active ingredient to assess their stability

during field, transit, and storage conditions according to AHETF SOP 8.E. Laboratory control 

samples were also fortified at the level of quantification and at levels capturing the range of 

expected field exposures for each matrix. Generally, field fortification samples were collected in 

triplicate at each of 3 levels (high, middle, and low) on each sampling day. Travel fortifications 

were generally conducted on each day of sampling in duplicate only at the high fortification 

level. Untreated control samples – included to determine if there are significant background 

sources or contamination during sample processing – were generally conducted in duplicate on 

each day of sampling.

The following sections provide results for all quality control sampling across all exposure 

measurement matrices for all chemicals used. The identified supplemental tables should be 

referenced for chemical-specific results.

3.2.1 Field and Laboratory Control Samples

As expected, most non-fortified (blank) laboratory and field control samples contained no 

detectable residues. For field controls, detectable residues (imazapyr, fosamine, and glyphosate)

were infrequent and found mostly in OVS tubes. For laboratory controls, imazapyr was detected 

in a few inner dosimeter and OVS tubes. Detections in the OVS tube control samples are not 

surprising given the sensitivity of the method – the LOD ≤ 0.0016 ug/sample, and many were 

close to that residue level. For other dosimeters, the detections were all lower than the lowest 

field fortification level tested. In all cases, both the frequency and magnitude of these detections 

did not indicate systematic contamination; thus, per standard AHETF procedure, no correction 

was made to any field monitoring samples based on results of control samples. 

More detailed results can be found in AHE400: Appendix B (2,4-D) Tables 7-11 on pages 578-

582; Appendix C (Fosamine) Tables 7-11 on pages 689-694; Appendix D (Glyphosate) Tables 

11-16 on pages 844-860; Appendix E (Imazapyr) Tables 11-16 on pages 1241-1252.

3.2.2 Field Fortification Recoveries – Applicable to Both Backpack and Handgun 

Exposure Monitoring

Field fortification sampling matrices are spiked with known amounts of chemical, then placed 

under similar conditions and duration as the actual sampling matrices used on the workers

(including drawing air through OVS samplers). The intent of these samples is to quantify

potential residue losses due to the sampling methods used under actual field conditions. 

Additional samples are also fortified to assess degradation of the sample during transit from the 

field to the lab and during sample storage. However, per AHETF protocol, these are only

analyzed if anomalous field fortification recoveries indicate potential degradation during 

transport and sample storage. No storage or transport fortification samples were analyzed since 
Page 13 of 22

field fortification results did not indicate any problems related to excessive degradation of 

residues.

Field fortifications are conducted at 3 levels to capture the expected range of results, with 

triplicate samples taken on each day at each fortification level4. Once analyzed, the average 

recovery results (expressed as a percentage of known amount applied) are used as multipliers to 

adjust, or correct, all measured field samples to 100%. As the fortification samples are 

conducted at levels to capture the range of expected field sample results, adjustments are done 

using the average percent recovery for the fortification level closest to the measured field 

sample5. The mid-point between each fortification level is used as the threshold in determining 

the average recovery percentage for use in adjusting the field sample.

With some exceptions, field fortification averages for each fortification level and each 

monitoring matrix were in the range of 70-120% with coefficients of variation generally less than 

25%. A summary of field fortification results for each matrix is provided below in Sections 

3.2.3.1 – 3.2.3.4.

3.2.2.1 Inner Dosimeters and Socks

Results for inner whole body dosimeter (WBD) and sock field fortification samples were 

acceptable, with average recoveries ranging from 70% to 120% and coefficients of variation less 

than 25%. 

Some atypically high and low average recoveries (~ 9% of all inner dosimeter and sock 

fortifications) were observed (48-66% and 121-153%), mostly for glyphosate fortifications in 

sock dosimeters. However, except for one fortification with a CV=31% (which did not end up 

being applicable to any field sample) all other CVs for these atypical results were less than 25%. 

For more details on field fortification results for inner dosimeters and socks see AHE400 Table 

BP-11 on pages 216-232 and Table HG-11 on pages 413-430.

Adjustments based on results for each surrogate active ingredient at each fortification level were 

applied to field samples falling into the following ranges6. Specific adjustment factors associated 

with each of these ranges can be found in AHE400 in Tables BP-12 on pages 233-249 and HG12 pages 431-448.

 Imazapyr/Glyphosate/Fosamine

o WBD

 Before 2012: ≤ 52.5 μg, > 52.5 to ≤ 2,050 μg, and > 2,050 μg

 

4

In 2012 fortification levels for dermal dosimetry were increased to accommodate field samples that exceeded the 

highest fortification level.

5

Per AHETF standard procedure, if average recovery is > 120% the maximum (“downward”) adjustment value 

applied is 1.2. 

6 During review, EPA identified minor errors in the values used for recovery adjustments for WBD for backpack 

applicators: MU A10 – a value of 1.00 was used instead of 0.784 for the upper leg sample; MU A23 – a value of 

1.00 was used instead of 0.997 for most of the WBD samples; MU A25 – a value of 1.00 was used instead of 0.997 

for some of the WBD samples. EPA decided to note these corrections but, because of the insignificant effect on 

overall results, not require any changes or re-submissions.
Page 14 of 22

 After 2012: ≤ 252.5 μg, > 252.5 to ≤ 25,250 μg, and > 25,250 μg 

o Socks: 

 Before 2012: ≤ 5.5 μg, > 5.5 to ≤ 55 μg, and > 55 μg

 After 2012: ≤ 50.5 μg, > 50.5 to ≤ 2,550 μg, and > 2,550 μg

 2,4-D

o WBD: ≤ 252.5 μg, > 252.5 to ≤ 25,250 μg, and > 25,250 μg 

o Socks: ≤ 50.5 μg, > 50.5 to ≤ 2,550 μg, and > 2,550 μg

3.2.2.2 Face/Neck Wipes

Results for face/neck wipe field fortification samples were acceptable, with average recoveries 

ranging from approximately 70% to 120% and coefficients of variation less than 25%. Very few 

(~ 6%) atypical recoveries (63-68% and 125-149%) were observed, all with CVs less than 25%. 

For more details on field fortification results for face/neck wipes see AHE400 Table BP-11 on 

pages 216-232 and Table HG-11 on pages 413-430.

Adjustments based on results for each surrogate active ingredient at each fortification level were 

applied to field samples falling into the following ranges. Specific adjustment factors associated 

with each of these ranges can be found in AHE400 in Tables BP-12 on pages 233-249 and HG12 pages 431-448.

 Glyphosate/Fosamine/2,4-D/Imazapyr

o Before 2012: ≤ 52.5 μg, > 52.5 to ≤ 1,050 μg, and > 1,050 μg

o After 2012: ≤ 52.5 μg, > 52.5 to ≤ 2,550 μg, and > 2,550 μg

3.2.2.3 Hand Washes

Results for hand wash field fortification samples were acceptable, with average recoveries 

ranging from approximately 70% to 120% and coefficients of variation less than 25%. Very few 

(~ 5%) atypical recoveries (43-64% and 121-124%) were observed (mostly for glyphosate), all 

with CVs less than 25%. For more details on field fortification results for face/neck wipes see 

AHE400 Table BP-11 on pages 216-232 and Table HG-11 on pages 413-430.

Adjustments based on results for each surrogate active ingredient at each fortification level were 

applied to field samples falling into the following ranges. Specific adjustment factors associated 

with each of these ranges can be found in AHE400 in Tables BP-12 on pages 233-249 and HG12 pages 431-448.

 Glyphosate/Fosamine/2,4-D/Imazapyr

o Before 2012: ≤ 52.5 μg, > 52.5 to ≤ 1,050 μg, and > 1,050 μg

o After 2012: ≤ 252.5 μg, > 252.5 to ≤ 5,250 μg, and > 5,250 μg

3.2.2.4 OVS Air Samplers

Results for OVS field fortification samples were acceptable, with average recoveries ranging 

from approximately 70% to 120% and coefficients of variation less than 25%. Very few (~ 5%) 
Page 15 of 22

atypical recoveries (59% and 124-138%) were observed (mostly for glyphosate), all with CVs 

less than 25%. For more details on field fortification results for face/neck wipes see AHE400 

Table BP-11 on pages 216-232 and Table HG-11 on pages 413-430.

Adjustments based on results for each surrogate active ingredient at each fortification level were 

applied to field samples falling into the following ranges. Specific adjustment factors associated 

with each of these ranges can be found in AHE400 in Tables BP-12 on pages 233-249 and HG12 pages 431-448.

 Glyphosate/Fosamine/2,4-D/Imazapyr: ≤ 2.525 μg, > 2.525 to ≤ 252.5 μg, and > 252 μg

3.3 Field Measurements

The following sections summarize the exposure monitoring results, conducted as described in 

Section 2.8. Exposure values reflect total exposure for workers across their monitoring periods, 

not normalized by any exposure metric. All measurements were appropriately adjusted for field 

fortification recoveries (see Section 3.2.2). Face/neck wipe measurements were extrapolated to 

un-wiped portions of the face and head according to AHETF SOP 9.K. For samples below the 

LOQ or LOD, 1⁄2 LOQ or 1⁄2 LOD was used.

Additionally, in order to account for potential residue collection method inefficiencies, EPA 

makes adjustments to hand and face/neck field study measurements as follows7:

 if measured exposures from hands, face and neck contribute less than 20% as an 

average across all workers, no action is required;

 if measured exposure contribution from hands and face/neck represents between 20% 

and 60% of total, the measurements shall be adjusted upward by a factor of 2, or 

submission of a validation study to support the residue collection method

 if measured exposure contribution from hands and face/neck represents is greater than 

60%, a validation study demonstrating the efficiency of the residue collection 

methods is required.

For handgun applicators, the contribution of hands and face/neck exposures averaged 30% while 

for backpack applicators, the contribution averaged 27%. Therefore the results for exposures to 

the hands and head and total dermal exposures outlined in the following sections present the 

aforementioned additional 2x adjustment for hand and face/neck measurements.

3.3.1 Inner Dosimeters and Socks

For backpack applicators, without field fortification adjustments, individual WBD sections 

ranged from < 0.3 (non-detectable) – 259,830 μg. Out of a total of 120 inner dosimeter samples, 

3 were below the LOQ and 1 below the LOD. Sock samples without field fortification 

 

7 This approach was discussed and presented at a meeting of the Human Studies Review Board (June 2007). The 

terminology used to describe this are “method efficiency adjusted” (MEA) or “method efficiency corrected” (MEC). 

Previous AHETF submissions included these adjustments but they have indicated that they will no longer continue 

to do so. Thus these adjustments are instead made by EPA.
Page 16 of 22

adjustments ranged from 0.95 – 3,959 μg. No sock dosimeter sample was below the LOQ or 

LOD. AHE400 Tables BP-14 and BP-15 on pages 251-252 provide more details on these 

samples. After adjusting for field fortification recoveries and summing the six separate body

sections, the total dermal exposure underneath the long-sleeve shirt and pants ranged from 6 –

730,551 μg with an average of 66,760 μg. Sock dosimeters with field fortification adjustments 

ranged from 1 – 3,884 μg with an average of 679 μg.

For handgun applicators, AHE400 presents results for WBD and sock samples without field 

fortification adjustments. Individual WBD sections ranged from < 1.0 (non-detectable) – 49,165 

μg. Out of a total of 126 inner dosimeter samples, 1 was below the LOQ. Sock samples ranged 

from 0.25 – 6,117 μg. Only 1 sock dosimeter sample out of 21 was below the LOQ. AHE400 

Tables HG-14 and HG-15 on pages 450-451 provide more details on these samples. After 

adjusting for field fortification recoveries and summing the six separate body sections, the total 

dermal exposure underneath the long-sleeve shirt and pants ranged from 44 – 98,905 μg with an 

average of 8,497 μg. Sock dosimeters ranged from 0.13 – 6,185 μg with an average of 548 μg.

3.3.2 Face/Neck Wipes

For backpack applicators face/neck wipe samples ranged from < 0.3 (non-detectable) – 549 μg

without field fortification adjustments. Out of 19 face/neck wipe samples, 1 was below the 

LOQ. AHE400 Table BP-15 on page 252 provides more details on these samples. For handgun 

applicators these ranged from 1.6 – 2,160 μg without field fortification adjustments. No 

face/neck wipe sample was below the LOQ or LOD. AHE400 Table HG-15 on pages 451 

provides more details on these samples.

Because some workers wore eye protection and because measurements cannot be easily

conducted on hair, extrapolations from those portions of the face/neck that are wiped need to be 

made to portions of the head that are not measured. Specifics on these adjustment factors can be 

found in AHETF SOP 9.K. Additionally, as previously described, the measurements are further 

adjusted upward by EPA by a factor of 2 to account for potential inefficiencies in residue 

collection by the wipe technique.

For backpack applicators, after adjusting for field fortification recoveries and extrapolating to 

non-wiped portions of the head described above, total head exposure ranged from 0.8 – 943 μg 

with an average of 200 μg. Including the 2X adjustment by EPA for potential method collection 

inefficiencies, total head exposure ranged from 1.6 – 1,886 μg with an average of 399 μg.

For handgun applicators, after adjusting for field fortification recoveries and extrapolating to 

non-wiped portions of the head described above, total head exposure ranged from 3 – 4,347 μg 

with an average of 500 μg. Including the 2X adjustment by EPA for potential method collection 

inefficiencies, total head exposure ranged from 6 – 8,694 μg with an average of 999 μg.

3.3.3 Hand Washes

Per protocol, hand washes were collected at the end of each work day and at points where 

workers would normally wash their hands such as during restroom or lunch breaks. Most 
Page 17 of 22

workers had 2 hand wash samples taken; one handgun applicator had 4 hand washes and one 

backpack applicator had 5 hand washes. A few workers, despite having relatively long work 

days (i.e., 4-8 hours) did not take any breaks and thus only had the 1 hand wash sample 

conducted at the end of their workday. The following table outlines the number of hand wash 

samples broken down by the work duration. 

Table 8. Hand Wash Summary

Work Duration (hours)

< 4 4-6 6-8 ≥ 8

Backpack Percentage of Workers 16% 26% 32% 26%

# of Hand Washes 1-2 1-3 1-2 2-5

Handgun Percentage of Workers 5% 19% 43% 33%

# of Hand Washes 1 1-2 1-4 2-3

For backpack applicators, individual hand wash samples ranged from 3.5 – 8,404 μg without 

field fortification adjustments. No hand wash sample was below the LOQ or LOD. AHE400 

Table BP-15 on page 252 provides more details on these samples. For handgun applicators, 

individual hand wash samples ranged from < 1.0 – 3,042 μg without field fortification 

adjustments. Out of a total of 43 hand wash samples, 1 was below the LOQ. AHE400 Table 

HG-15 on page 451 provides more details on these samples.

For backpack applicators, after adjusting for field fortification recoveries and summing hand 

washes for each worker, the total hand exposure ranged from 13 – 10,776 μg with an average of 

2,788 μg. Including the 2X adjustment by EPA for potential method collection inefficiencies, 

total hand exposure ranged from 26 – 21,552 μg with an average of 5,575 μg. 

For handgun applicators, after adjusting for field fortification recoveries and summing each hand 

wash, the total hand exposure ranged from 4 – 4,473 μg with an average of 1,194 μg. Including 

the 2X adjustment by EPA for potential method collection inefficiencies, total hand exposure 

ranged from 8 – 8,946 μg with an average of 2,387 μg. 

3.3.4 OVS Air Samplers/Inhalation Exposure

Front and back sections of the OVS tube were analyzed separately. Most back section samples 

were less than the LOD, with a few less than the LOQ. All front section samples had detected 

residues. Inhalation exposure results were invalidated for two backpack applicators due to 

sampling pump failure (MU A27) and lack of remaining sample for analysis (MU A1 – sample 

extract was used up from previous analysis with an improper analytical method).

For backpack applicators, OVS front sections ranged from 0.0466 – 59.66 μg without field 

fortification adjustments. AHE400 Table BP-16 on page 253 has more details on these results. 

After adjusting for field fortification recoveries, the total (front section + back section) collected 

active ingredient amounts ranged from 0.07 – 67 μg with an average of 12 μg.

For handgun applicators, OVS front sections ranged from 0.0219 – 77.79 μg without field 

fortification adjustments. AHE400 Table HG-16 page 452 has more details on these results. 

After adjusting for field fortification recoveries, the total (front section + back section) collected 

active ingredient amounts ranged from 0.03 – 80 μg with an average of 11 μg. 
Page 18 of 22

The above described results for the amount of active ingredient collected by the air sampling 

units. The AHE400 report – as it is mainly a presentation of field and analytical results –

presents only total active ingredient collected by the air sampling units. Separate AHETF 

monograph submissions (under separate EPA reviews) present worker inhalation exposures 

applying an assumed breathing rate. To calculate worker inhalation exposures, the measured 

amounts are adjusted based on the pump flow rate (in liters per minute) and a typical worker’s 

breathing rate for this type of activity. For these studies a breathing rate of 16.7 liters per minute 

was used, representing light activities (NAFTA, 1998). The calculation is as follows:

Inhalation exposure = Adjusted residue (μg) * [Breathing rate (LPM) ÷ Pump flow rate (LPM)]

For backpack applicators, worker exposures ranged from 0.54 – 567 μg with an average of 100 

μg. For handgun applicators, worker exposures ranged from 0.24 – 670 μg with an average of 

88 μg. 

3.4 Exposure Calculations

This section provides total exposures (expressed as mass active ingredient), as well as exposures 

normalized to (i.e., dividing by) body weight and amount of active ingredient handled (AaiH).

3.4.1 Dermal Exposures

Total dermal exposure, calculated by summing the results for inner dosimeters, hand washes and 

face/neck wipes, are presented below as well as normalized to body weight and amount of active 

ingredient handled. Results are presented both with and without adjustments for potential 

inefficiencies of the hand wash and face/neck wipe methods (MEA = method efficiency

adjustment).

Table 9. Dermal Exposure Summary

Equipment Statistic

Total Exposure

(μg)

Normalized by Body 

Weight

(μg/kg BW)

Normalized by Amount ai 

Handled

(μg/lb ai)

MEA Non-MEA MEA Non-MEA MEA Non-MEA

Backpack

Minimum 34 20 0.48 0.28 675 400

Maximum 752,379 742,664 8,360 8,252 241,923 238,799

Mean 73,414 70,426 855 819 31,273 30,110

Handgun

Minimum 80 66 1.06 0.88 26 17

Maximum 112,258 108,674 1515 1,467 12,123 11,365

Mean 12,431 10,738 156 135 1,868 1,654

Note: Means are simple averages (i.e., sum of values ÷ n)

3.4.2 Inhalation Exposures

As shown in Section 3.3.4, inhalation exposure is calculated based on the chemical in air over 

the monitoring period, the pump flow rate, and the worker’s breathing rate. Results are 

presented below.
Page 19 of 22

 

Table 10. Inhalation Exposure Summary

Equipment Statistic Total Exposure

(μg)

Normalized by Body 

Weight

(μg/kg BW)

Normalized by Amount ai 

Handled

(μg/lb ai)

Backpack

Minimum 0.54 0.007 1.74

Maximum 567 7 112

Mean 100 1.22 35

Handgun

Minimum 0.24 0.003 0.18

Maximum 670 8.28 35

Mean 88 1.09 7

Note: Means are simple averages (i.e., sum of values ÷ n)

3.5 Field Observations

Field researchers observed each worker and recorded their behavior throughout the work day. 

These can be found in the AHE400 report in Table BP-9 on pages 112-174 and HG-9 on pages 

302-369.

Much of the observations detailed routine application procedures (e.g., MU A27 @ 0815: 

“Sprayed a ~20 ft. section of high brush along side of road.”). Other observations may

potentially provide clues as to determinants of exposure – examples of these types of 

observations include:

 Overhead spraying – e.g., MU A33 @ 0902: “Sprays a birch tree (~5 ft. tall) on 

hillside, which requires overhead spraying. Large visible plume, moderate contact 

with A33”;

 Contact with treated foliage – e.g., MU A10 @ 1102: “A10 observed walking 

directly into just sprayed foliage (below waist high)”;

 Getting off truck to walk and spray target area (handgun) – e.g., MU A22 @ 0918: 

“A22 down from truck, walking along ROW area, spraying into ROW.”

EPA reviewed the field observations for potential clues as to determinants of exposure or 

potential reasons for high exposures. Though difficult to quantify in this fashion, some 

additional analysis where field observations were reviewed in a quantitative fashion, refer to the 

scenario monograph reviews (Crowley, 2015a and Crowley, 2015b). Data users are 

recommended to review the field observations to get a sense of the extent of activities within 

these exposure scenarios. 

4.0 Protocol Amendments and Deviations

Amendments to and deviations from the study protocol are detailed below. For additional 

details, see the AHE400 study report on pages 11-14 as well as Appendix A on pages 504-538. 

The study amendments were reasonable accommodations to accomplish the research and 

deviations did not adversely impact the study conduct or the exposure monitoring results.
Page 20 of 22

Protocol Amendments:

 To increase likelihood of finding workers to monitor, additional employer sources were 

added: the same employer can be used in multiple monitoring areas; referrals from other 

employers; and, employers/companies the AHETF is aware of but not on the “Employer 

Universe List”.

 Because recruitment revealed that workers commonly wear chaps and leggings for 

physical protection, this was removed as an exclusion criterion.

 Because recruitment revealed that workers commonly wear (or are required by their 

employers to wear) hard hats and boots that rise above mid-calf, those were removed as 

exclusion criteria.

 Because recruitment specifically for electric and pipeline utility rights-of-way proved 

limiting, additional areas of similar brush/shrubs, foliage density/height, and terrain such 

as roadsides and wildlife refuges were added as possible sites.

 Amended contact information for Principal Analytical Investigator and Analytical 

Facility

 Amended fosamine and imazapyr analytical methods sections to more accurately identify 

the methods following their complete development and validation.

 Recruitment in the originally specified US states proved limiting, other states will be 

acceptable.

 Field fortification levels for dermal exposure monitoring methods were increased.

 Recruitment proved difficult, so the “same employer” restriction was relaxed – but with 

additional restrictions that if they had the same employer monitoring must occur in a 

separate year, a different job site, and a different application crew.

 Changed glyphosate analytical methods following addition of a derivatization step and 

added additional text specifying how this revised method was validated.

Protocol Deviations

 Field samples for MUs A8 and A9 as well as associated field fortification levels were 

analyzed for fosamine using analytical methods not fully identified in the protocol or by a 

protocol amendment. Though not identified in the protocol or amendment, at the time of 

analysis the method had been validated and finalized.

 Unavailability of test substances for purity analysis. Amount of active ingredient handled 

determined from product label and dilution rates.

 Instances of less than 4 hours of monitoring time. Other application characteristics (tank 

loads, gallons sprayed, etc.) were still adequate and representative of typical workdays.

 Lack of hand wash collection preceding a cigarette break.

 Use of applicator’s own chemical-resistant gloves rather than AHETF-supplied chemicalresistant gloves.

 Failure to inform application company representative that they would receive an AHETF 

introductory letter.

 Inhalation exposure pump off for extended periods of (non-exposure) time such as lunch 

breaks or rain events.

 Lack of documentation of changes to analytical laboratory facilities.
Page 21 of 22

5.0 Conclusion

As the studies followed their corresponding protocols as well as EPA guidelines for occupational 

pesticide exposure monitoring, the results are reliable for assessment of exposure and risk for 

backpack and handgun applications in utility rights-of-ways and other areas where chemical 

control of similar undesirable vegetation is conducted.

Since these exposure data were collected with the intention to populate a generic pesticide 

exposure database, reviewers are directed to the additional information and statistical analyses in 

the AHETF Handgun ROW Scenario Monograph (Bruce, et al, 2014a) and the AHETF 

Backpack ROW Scenario Monograph (Bruce, et al, 2014b). 

Review of those monographs as well as recommendations for use of the data by EPA exposure 

assessors are in a separate review memorandum (Crowley, 2015a and 2015b).

6.0 References

AHETF, (2008). Volume IV AHETF Revised Governing Document for a Multi-Year Pesticide 

Handler Worker Exposure Monitoring Program. Version Number: 1. April 7, 2008. 

Agricultural Handlers Exposure Task Force (AHETF). [MRID 47172401]

AHETF, (2010a). Monitoring Unit Selection and Construction Plan for Scenarios: 1. 

BACKPACK APPLICATION OF LIQUID SPRAYS IN UTILITIES RIGHTS-OF-WAY 2. 

HANDGUN APPLICATION OF LIQUID SPRAYS IN UTILITIES RIGHTS-OF-WAY. June 

4, 2010.

AHETF, (2010b). Governing Document for a Multi-Year Pesticide Handler Exposure 

Monitoring Program, Version 2, August 12, 2010.

Bruce, E. (2014). Determination of Dermal and Inhalation Exposure to Workers during 

Backpack and Handgun Application of Liquid Sprays in Utilities Rights-of-Way. Study Number 

AHE400. Unpublished study sponsored by the Agricultural Handler Exposure Task Force. 1430

p. September 18, 2014. EPA MRID 49472001.

Bruce, E., Holden, L., and Klonne, D. (2014a). Agricultural Handler Exposure Scenario 

Monograph: Handgun Application of Liquid Sprays in Utilities Rights-of-Way. Report Number 

AHE1013. Unpublished study sponsored by the Agricultural Handlers Exposure Task Force. 

218 p. September 29, 2014. EPA MRID 49478602.

Bruce, E., Holden, L., and Klonne, D. (2014b). Agricultural Handler Exposure Scenario 

Monograph: Backpack Application of Liquid Sprays in Utilities Rights-of-Way. Report 

Number AHE1012. Unpublished study sponsored by the Agricultural Handlers Exposure Task 

Force. 224 p. September 29, 2014. EPA MRID 49478601. 
Page 22 of 22

Crowley, M. (2015a). Memorandum: Review of Agricultural Handler Exposure Task Force 

(AHETF) Monograph: “Backpack Application of Liquid Sprays in Utilities Rights-of-Way” 

(AHE1012). D424145. March 24, 2015.

Crowley, M. (2015b). Review of Agricultural Handler Exposure Task Force (AHETF) 

Monograph: “Handgun Application of Liquid Sprays in Utilities Rights-of-Way” (AHE1013). 

D424145. March 24, 2015.

NAFTA - Dept. of Pesticide Regulation (DPR), California EPA, HSM-98014, April 24, 1998.