UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460

MEMORANDUM

Date: January 24

, 2013 OFFI CE OF
C H

E MICAL SAF E TY AND

PO L LUTION PREV E NTI O N

Subject: Glufosinate Ammonium. Human Health Risk Assessment for Registration Review.

PC Code : 1288 50

Decision No.: 471210

Petition No.: NA DP Barcode: 040 6360 Registration No.: NA Regulatory Action: Regi s tration Review

Case No.: NA Risk Assessment Type: Sing l e Chemical Aggregate

TXR No.: NA CAS No.: 77 182 -82-2

40 CFR: 180.437 MRIDNo.: NA



### From:

Through:

To:

# ~~D~ William H. Donovan, Ph.D., Chemist 

# lfd.

CH

... /) nh Ana Rivera

- Lupianez, Chemist

### W~Jl.**t~** 

# F..____

Risk Assessment Branch V (RABV)

H ealth Effects Di v ision (HED) (7509P)

Michael S. Metzger, Branch Chief 

# U' (} (} /}
f**~** Ri sk Assessment Branch V (RABV)**~~** ;{ ' 

# Jl '\.

Health Effects Division (7509P)

Katie Weyrauch, Chemical Review Manager

Ri sk Management and Implementation Branch V

Pesticide Re-evaluation Di vision (P RD) (7508P)

The PRD requested that HED prepare a human-health risk assessment for glufosinate ammonium

in support of registration review. To address this request

, H ED cites the most recent glufosinate

ammonium risk assessment (D3874 13

, W. Donovan, 

### J. Doherty, and A. Rivera-Lupiafiez, 07/25/12) and has prepared this memo, which updates and expands appropriate sect ions of the July 25, 20 12 assessment. Recent changes in occupational assessment policies 

### (e.g.

, unit

exposures
, TC s and new guidance for requiring/waiving Turf Tran sferrable Residue (TTR) and Dislodgeable Foliar Residu e (DF R) studies) have triggered the need for an updated occupational

assessment for gl u fosi nate ammonium. To take into account this new information, the following

sections are provided:

1) Updated occupational handler exposure and risk esti mate s for spot/di r ected treatments to

Page 1 of 10

### Page 2 of 10

citrus, pome, and stone fruits; and olives. 2) New occup ational handler exposure and risk assessment for the representative crops of corn, cotton, sorghum, an d canola. 3) New summary of estimated occupational post

- application risks for application of glufosinate ammonium to representative crops.

HED concludes that , based on currently registered uses, the following studies have been identified as data gaps for glu fosinate ammonium :

Dislodgeable Foliar Residue ( DFR ) studies for corn, canola, cotton

, and soybeans.

Finally, HED reiterat es that all glufosinate ammonium labels allowing residential turf uses or park/recreational field uses must restrict lawn/turf uses to spot treatments only. The maximum application rate for residential lawn treatments should not exceed 4 fl ounces per gallon of water per 1,000 square feet.

No other changes to the July 25, 2012 glufosinate ammonium risk asse ssment are needed.

### Page 3 of 10

Detailed Considerations The updated and new sections of t his document supersede the previous glufosinate

- ammonium

risk assessment ( D387413, W. Donovan, et al., 07/25/12 )

. The present analysis includes a revision to the mixer/loader/applicator (M/L/A) scenario utilizing mechanically

- pressurized handgun for spot/directed treatments on c itrus f ruit, p ome f

ruit, s tone f

ruit, and o lives

, to account for the Exposure Science Advisory Committee (ExpoSA C) revision of the unit exposure value assigned for this particular M/L/A scenario ( ExpoSAC Meeting Minutes, 09/13/2012 ).

Also, a n up dated occupational assessment was performed for registered uses of glufosinate to
account for changes in occupational ass essment policies ( e.g., unit exposures, TCs and new

g uidance for r equiring/ w aiving Turf Transferrable Residue (TTR) and Dislodgeable Foliar Residue (DFR) s tudies ). Several high

- acreage field crops that represent worst

- case scenarios for

exposure to glufosinate

- ammonium were assessed ( i.e., corn , canola, cotton, and soybeans).

1) Revised Occupational Exposure and Risk Estimates for Spot/Directed Treatments on Citrus Fruit, Pome Fruit, Stone Fruit, and Olives The previous assessment ( D387413

, 07/25/1 2 ) identified risk concerns for M/L/A scenarios utilizing mechanically

- pressurized handgun for spot/directed treatments on c itrus f ruit, p ome f ruit, s tone f

ruit, and o lives ; however, results of the current revised assessment indicate that

short

- and intermediate

- term dermal risks are not of concern to the HED (MOE s ≥ 1000) at the level of personal protection recommended on the label (double layer clothing and gloves). Likewise, results from the updated assessment indicate that short

- and i ntermediate

- term
inhalation risks are not of concern to the HED (MOEs ≥ 300) at baseline level s of respiratory protection (i.e., no respirator)

. A summary of short

- and intermediate

- term agricultural handler exposure and risk estimates for glufosinate amm onium for spot/directed spray applications is presented i n Table 1

. This tab le supersedes Table 9.1c from the July 2012 risk assessment.

2) Occupational Exposure and Risk Estimates for Representative Registered Ag ricultural

Uses

Results from the assessment of occupational handler scenarios on representative high

- acreage crops (corn, canola, cotton and soybeans) indicate that short

- and intermediate

- term dermal risks

for mixer/loader scenarios are not of concern to HED (MOE s ≥ 1000) at some level of ris k

miti gation ( e.g., gloves

, or other engineering control measures such as closed systems ). Likewise, results from the assessment of all occupational handler scenarios indicate that short

and intermediate

- term inhalation risks are not of concern to HED (MOEs ≥ 300) at the baseline

level of respiratory protection (i.e., no respirator)

. Aerial and groundboom applicator risks do

not exceed HED’s level of concern (MOEs ≥ 10 00 for dermal exposures and MOEs ≥ 3 00 for

inhalation exposures) at some level of ris k mitigation or engineering control measures ( i.e., gloves, enclosed cockpit

, or closed cab). A summary of short

- /intermediate term agricultural handler exposure and risk estimates for glufosinate ammonium applications on corn, canola, cotton and soybeans is presented i n Table 2.

3) Occupational Post

-

Application Exposure and Risk A summary of post

- application risk estimates for glufosinate ammonium applications on corn, canola, cotton and soybeans is presented i n Table 3.

### Page 4 of 10

Short

- and intermediate

- term post

- application risk estimates were not a concern on day 0 (12 hours following application) following glufosinate treatments on cotton.

F or scouting activities on corn (unspecified type ) , an MOE >1,000 is achieved on d ay 2 af ter

treatment at the highest label rate ( see EPA Reg 264

- 663)

. For irrigation activities

, an acceptable

MOE is not achieved until d ay 4 for sweet corn, d ay 5 for field corn, and d ay 7 for corn (unspecified type at the highest label rate). Therefore, th e s e post

- application activ ities are of

concern to the HED

.

The results of the glufosinate ammonium post

- application exposure and dermal risk assessment

for scouting activities on canola indicate an MOE of 990 on d ay 1; an MOE>1000 is achieved on Day 2 aft er treatment. Likewise

, for scouting activities on soybeans, an MOE >1,000 is achieved on day 4 after glufosinate treatment. Therefore, th e s e post

- application activ ities are of concern

to the HED

.

It should be noted that glufosinate label s indicate an REI of 12 hours . HED recommends that the

REI be revised to address th e risk concerns identified

.

Residue Data Requirements In accordance with the updated Part 158 data requirements (2007), one or more DF R stud ies are required when a pesticide has residential or occupational uses t hat could result in post

application dermal exposure. As part of the recent revision to the Health Effects Division’s 2012 Standard Operating Procedures for Residential Pesticide Exposure Assessment

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

- exposure

- sop.html

, HED analyzed a number

of DFR studies and selected a new default value for the fraction of the application rate available

to be dislodged after a foliar application (F AR 

### ). This default value is 25 % and is based on an analysis of 19 DFR studies where the F AR 

### value ranged from 2% to 89%. This value is recommended for use in both residential and occupational post

- application assessments. Of the analyzed DF R studies, the maximum F AR 

### value seen was 89% or 3.6 times higher than the

default residue transfer value. Therefore, HED has decided that a calculated MOE of approximately 4 times higher than the level of concern ( e.g., an MOE > 4000 if the LOC = 100 0 ) using the default dislodged residue values would provide an adequate margin of safety for any potentially higher residues seen in a chemical

- specific DFR study ( Guidance for Requiring/Waiving Turf Transferrable Residue (TTR) and Dislodgeable Foliar Residue (DFR)

Studies . 6/7/2012, Exposure Science Advisory Council). DFR stud ies for corn, canola, cotton and soybeans are required for glufosinate ammonium since the post

- application dermal MOEs

are lower than 400 0 ( i.e. 4 X LOC) on Day 0 (scouting and or irrigation mature/high foliage plants ) based on default values for the fraction of application rate available for transfer after a

foliar application.

### Page 5 of 10

Table 1. Short

- /Intermediate Term Agricultural Handler Exposure and R isk Estimates for Glufosinate A mmonium ( Updated M/L/A Scenario for Spot/Directed Spray Applications )

Exposure

Scenario App

Rate a (lb ai/ gal ) Acres

Treated Daily b 

### Unit Exposure c , j 

### Dose (mg/kg/Day) MOEs

(Dermal LOC = 1000 Inhalation LOC = 300)

Baseline

Dermal h
(mg/lb ai) PPE

Dermal j
(mg/lb ai) Baseline

I nhalation s (ug/lb ai) Baseline

Dermal d,h PPE

Dermal

j Baseline

Inhalation e Baseline

Dermal f,h PPE

Dermal j Inhalation g ,i

Citrus Fruit, Pome Fruit, Stone Fruit, Olives

Mixer/Loader/Applicator

Mixing/Loading/Applying (MLAP) with Mechanically Pressurized Handgun ( spot/ directed spray ) 1.7 fl oz/gal

0.031 lbai/gal 1,000

gallons 1.3 2.160

0.390 (SL/G)

0.290 (DL/G) 3.9 0.0526 0.0158 (SL/G)

0.0117 (DL/G) 0.00151 270 890 ( SL/G)

1,200 (DL/G) 8,300

Mixing/Loading/Applying (MLAP) with Backpack Sprayer ( spot/ directed spray ) 40 gallons 8.260 8.260 2.58 0.0133 0.0133 0.0004 1,100 1,100 (SL/G) 310,000

a) Application Rates based on proposed uses on label for Glufosinate

- ammonium formulations Liberty Herbicide (EPA Reg. No. 264

- 660) and Liberty 280 SL Herbicide (EPA Reg. No. 264

- 829). Units expressed in lb ai/Acre unless specified otherwise. b) E xposure Science Advisory Council Policy # 9.1 c) Unit Exposures based on Unit Exposures based on “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (PHED) ( http://www.epa.gov/pesticides/science/handler

- exposure

- table.pdf ), dated September 2011. Engineering control unit exposure for applying sprays via aerial equipment = enclosed cockpit. d) Dermal Dose (mg/kg/day) = daily unit exposure (mg/ lb ai) x application rate (lb ai/acre) x acres treated x dermal absorption factor (9%) / body weight (69 kg adult female). e) Inhalation Dose (mg/kg/day) = daily unit exposure (μg/ lb ai) x conversion factor (1 mg/1,000 μg) x application rate (lb ai/acre) x acres treated x inhalation absorption (100%) / body weight (80 kg). f) Dermal MOE = LOAEL (14 mg/kg/day) / dermal daily dose (mg/ kg/ day). Level of concern = 1000. g) Inhalation MOE = LOAEL (12.5) mg/kg/day) / inhalation daily dose (mg/ kg/ day). Level of c oncern = 300. h) Baseline Dermal: Long

- sleeve shirt, long pants, and no gloves; i) Baseline Inhalation: no respirator j) PPE: G ( gloves ), SL (Single Layer), DL (Double Layer),

### Page 6 of 10

Table 2

. Short

- /Intermediate Term Agricultural Handler Exposure and Risk Estimates for Glufosinate Ammonium (Representative crops)

Exposure

Scenario Crop or

Target App

Rate a (lb ai/A) Acres

Treate

d Daily b Unit Exposure c Dose (mg/kg/Day) MOEs (Dermal LOC = 1000 Inhalation LOC = 300)

Baseline

Dermal (mg/lb ai) PPE

Dermal (mg/lb ai) Inhalatio

n (ug/lb ai) Baseline

Dermal d,

h PPE

Dermal i Inhalatio

n e Baselin

e Dermal

f PPE

Dermal Inhalation

g,i

Mixer/Loader

Mixing/Loading to Support

Aerial

treatments (PHED) Sweet Corn 0.365 350

0.220 0.0376 (SL/G) 0.219 0.0367 0.00626 (SL/G)

0.00485 (DL/G) 0.00035 380 2,200 (SL/G) 36,000

Corn (Field), Canola, Soybean 0.6615 1200 0.228 0.0389 (SL/G)

0.0301 (DL/G)

0.00891 (EC) 0.00218 61 360 (SL/G)

470 (DL/G)

1600 (EC) 5,700

Cotton 0.7901 1200 0.273 0.0464 (SL/G)

0.036 (DL/G)

0.0106 (EC) 0.0026 51 3 0 0 (SL/G)

39 0 (DL/G)

1300 (EC) 4,800

Mixing/Loading to Support

Groundboom Applications (PHED) Sweet Corn 0.365 80

0.220 0.0376 (SL/G) 0.219 0.00837 0.00143 (SL/G) 0.000079 1,700 9,800 (SL/G) 160,000

Corn (Field), Canola, Soybean 0.6615 200 0.038 0.00648 (SL/G) 0.000363 370 2,200 (SL/G) 34,000

Cotton 0.7901 200 0.0454 0.00775 (SL/G) 0.000433 310 1,800 SL/G) 29,000

### Page 7 of 10

Table 2

. Short

- /Intermediate Term Agricultural Handler Exposure and Risk Estimates for Glufosinate Ammonium (Representative crops)

Exposure

Scenario Crop or

Target App

Rate a (lb ai/A) Acres

Treate

d Daily b Unit Exposure c Dose (mg/kg/Day) MOEs (Dermal LOC = 1000 Inhalation LOC = 300)

Baseline

Dermal (mg/lb ai) PPE

Dermal (mg/lb ai) Inhalatio

n (ug/lb ai) Baseline

Dermal d,

h PPE

Dermal i Inhalatio

n e Baselin

e Dermal

f PPE

Dermal Inhalation

g,i

Applicator

Applying Sprays

via Aerial Equipment

– Enclosed Cockpit (PHED) Sweet Corn 0.365 350

No Data 0.005 (EC) 0.068

(EC) No Data 0.000833 (EC) 0.000109

(EC) No Data 17,000 (EC) 110,000

(EC)

Corn (Field), Canola, Soybean 0.6615 1200 No Data 0.00518 (EC) 0.000675

(EC) No Data 2,700 (EC) 19,000

(EC)

Cotton 0.7901 1200 No Data 0.00618 (EC) 0.000806

(EC) No Data 2,300 (EC) 16,000

(EC)

Applying Sprays

via Groundboom Equipment Open

Cab Sweet Corn 0.365 80

0.0786 0.0161 (SL/G) 0.34 0.003 0.000613 (SL/G) 0.000124 4,700 23,000 (G) 100,000

Corn (Field), Canola, Soybean 0.6615 200 0.0136 0.00278 (SL/G) 0.000563 1,000 5,000 22,000

Cotton 0.7901 2 00 0.0162 0.00331 (SL/G) 0.000671 860 4,200 19,000

Flagger

Flagging for Aerial Sprays Sweet Corn 0.365

350 0.011 0.012 0.35 .00183 0.0020 0.00064 7,600 7,000 (G) 19,000

Flagging for Aerial Sprays High Acreage

Crops 0.7901 0.00397 NA 0.00121 3,500

- 10,000

### Page 8 of 10 a) Application Rates based on proposed uses on label for Glufosinate

- ammonium formulations Liberty Herbicide (EPA Reg. No. 264

- 660) and Liberty 280 SL Herbicide (EPA Reg. No. 264

- 829). Units expressed in lb ai/Acre unless specified otherwise. b) Exposure Science Advisory Council Policy # 9.1 c) Unit Exposures based on Unit Exposures based on “Occupational Pesticide Handler Unit Exposure Surrogate Reference Table” (PHED) ( http://www.epa.gov/pesticides/science/handler

- exposure

- table.pdf ), dated September 2011. Engineering control unit exposure for applyi ng sprays via aerial equipment = enclosed cockpit. d) Dermal Dose (mg/kg/day) = daily unit exposure (mg/ lb ai) x application rate (lb ai/acre) x acres treated x dermal absorption factor (9%) / body weight (69 kg adult female). e) Inhalation Dose (mg/kg/day) = daily unit exposure (μg/ lb ai) x conversion factor (1 mg/1,000 μg) x application rate (lb ai/acre) x acres treated x inhalation absorption (100%) / body weight (80 kg). f) Dermal MOE = LOAEL (14 mg/kg/day) / dermal daily dose (mg/ kg/ day). Level of c oncern = 1000. g) Inhalation MOE = LOAEL (12.5) mg/kg/day) / inhalation daily dose (mg/ kg/ day). Level of concern = 300. h) Baseline Dermal: Long

- sleeve shirt, long pants, and no gloves; i) Baseline Inhalation: no respirator j) PPE: G ( gloves ), SL ( Single Layer ), DL (Double Layer), PF10 R (respirator) , E.C. (Engineering Control; Closed System).

### Page 9 of 10

Table 3

. Summary of Estimated Post

- application Risks for glufosinate ammonium ( Representative crops)

EPA Reg.

N umber Maximum

Application

Rate a (lb ai/A)

. ExpoSAC

Policy 3 TC Crop Group DAT b DFR c

(μg/cm 2 ) TC d Activity d Short

- /Int

Term MOE e



### C orn ( Sweet )

279

- 3313,

279

- 3108 0.365 

### Field / row crop, tall 0 1.024 

### 1,100 Scouting mature/high foliage plants 

### 1,200

0 1.024 1,900 Irrigation mature/high foliage plants 690

4 0.672 1, 9 00 1,050



### Corn (Field)

264

- 829 0.4042 Field / row crop, tall 0 

### 1.13 1,100 Scouting mature/high foliage plants 

### 1,100

0 

### 1.13 1, 9 00 Irrigation mature/high foliage plants 

### 630

5 

### 0.669 1, 9 00 

### 1,100

Corn ( Unspecified )

264

- 663 0.5218 Field / row crop, tall 0 1.46 1,100 Scouting mature/high foliage plants 

### 830

2 1.46 1,000

0 1.46 1,900 Irrigation mature/high foliage plants 

### 480

7 0.70 1000

Canola

264

- 660 0.4435 Field / row crop, low /

medium 0 

### 1.24 1,100 Scouting mature/high foliage plants 

### 990

1 

### 1.12 1,100 

### 1,100

### Page 10 of 10

Table 3

. Summary of Estimated Post

- application Risks for glufosinate ammonium ( Representative crops)

EPA Reg.

N umber Maximum

Application

Rate a (lb ai/A)

. ExpoSAC

Policy 3 TC Crop Group DAT b DFR c

(μg/cm 2 ) TC d Activity d Short

- /Int

Term MOE e



### Cotton

264

- 829 0.7901 Field / row crop, low /

medium 0 

### 2.22 210 Scouting low/ full foliage plants 

### 2,900

0 

### 2.22 70 Hand weeding low/ full foliage plants 

### 8,600

Soybeans

264

- 829 0.6615 Field / row crop, low /

medium 0 

### 1.86 1,100 Scouting low/ full foliage plants 660

4 

### 1.22 1000

a) Maximum application rate (lb ai/A) indicated on registered labels b) DAT = Days after treatment needed to reach the LOC of 1000; DAT 0 = the day of treatment, after sprays have dried; assumed to be approximately 12 hours. c) DFR (μg/cm 2 ) = Application rate (lb ai/A) x Fraction of ai retained on foliage on day zero (25%) × (1

- fraction of residue that dissipates daily 10%) t × 4.54E8 μg/lb ×

2.47E

- 8 acre/cm 2

. d) TC (cm 2 /hr) = Transfer coefficients and associated activities from ExpoSAC Policy 3 ( http://w ww.epa.gov/pesticides/science/exposac_policy3.pdf ) e) MOE = MOE on the corresponding DAT. MOE = LOAEL / Daily Dose. Daily Dose = [DFR (μg/cm 2 ) × Transfer Coefficient × 0.001 mg/μg × 8 hrs/day × dermal absorption 9 %] body weight (69 kg adult).