OFFICE OF CHEMICAL

SAFETY AND

POLLUTION

PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 114401, 114402

DP Barcode: 431361

Date: March 01 , 201 6

MEMORANDUM

SUBJECT: Addendum to: Registration Review: Preliminary Environmental Fate and

Ecological Risk Assessment Endangered Species Effects Determination for

Acifluorfen

TO: Nathan Sell , Chemical Review Manager

Tracy Perry , Team Leader

Kelly Sherman, Branch Chief

Risk Management and Implementation Branch III

Pesticide Re

- evaluation Division (7508P)

FROM: Brian D. Kiernan, Biologist

Environmental Risk Branch VI

Environmental Fate and Effects Division (7507P )

REVIEWED

BY: Monica Wait, Risk Assessment Process Leader

Environmental Risk Branch VI

Environmental Fate and Effects Division (7507P )

APPROVED

BY: Mark Corbin, Branch Chief

Environmental Risk Branch VI

Environmental Fate and Effects Division (7507P )

The Environmental Fate and Effects Division (EFED) has completed a n addendum to the

preliminary risk assessment for the herbicid al active ingredient acifluorfen (PC Code s 114401,

114402). This addendum corrects the rates used in the TerrPlant model ing , s omewhat altering

the resultant risk quotients (RQs)

. A lso presented is a dditional modeling with AgDRIFT

. Additionally , a correction has been ma d e to the labelin g text in the table of chronic RQs for

mammals

.

In the preliminary risk assessment ( PRA; D 426394 ), TerrPlant modeling was conducted using

the maximum annual label rate for each use site. However, as the risk assessment was nearingcompletion, a minimum retreatment interval of 15 days was specified. As a result, TerrPlant

mod eling should have be en conducted on the maximum single application rate for each use site

in accordance with current protocol. Below are Tables 4.9 and 4.10 (from the assessment)

displaying results for the maximum single application rates. Change in the RQs are most

noticeable for the strawberry use, where the modeled use rate is half that presented in the PRA;

note that no changes are made to the rice use pattern.

Table 4.9. Terrestrial Plant RQs for Ground Spray Applications of Acifluorfen. (Bold

values indicate an LOC exceedance. )

Application

Rate

lbs a

. i

. /A Plant Type Listed

Status Dry Semi

- Aquatic Spray Drift

0. 3 75

Soybean/Peanut /

Strawberry Grass non

- listed ND * ND <0.1

Grass listed ND ND 0.11

Non

- grass non

- listed 1.07 9.11 0.99

Non

- grass listed 1.50 12.75 4.17

0.25

Rice Grass non

- listed ND ND <0.1

Grass listed ND ND <0.1

Non

- grass non

- listed 0.71 6.07 0.66

Non

- grass listed 1.00 8.50 2.78

* Not determined

Table 4.10. Terrestrial Plant RQs for Aerial Spray Applications of Acifluorfen. ( Bold

values indicate an LOC exceedance.

Application

Rate

lbs a

. i

. /A Plant Type Listed

Status Dry Semi

- Aquatic Spray Drift

0. 3 75

. Soybean/Peanut /

Strawberry Grass non

- listed ND * ND 0. 22

Grass listed ND ND 0. 27

Non

- grass non

- listed 1.79 9.82 4.93

Non

- grass listed 2.50 13.75 20.83

0.25

Rice Grass non

- listed ND ND 0.15

Grass listed ND ND 0.18

Non

- grass non

- listed 1.19 6.55 3.29

Non

- grass listed 1.67 9.17 13.89

* Not determined

PRD requested additional AgDRIFT modeling to account for the current droplet size spectrum

on the labels (medium

- coarse) and to illustrate the impact of increasing the droplet size spectrum

on the distance to the level of concern ( i.e. RQ=1 .0). Table A presents selected results for aerial

application. It should be noted that this modeling holds all parameters but droplet size as Tier 1

terrestrial model defaults. These defaults are assumed to be on the label

.

For aerial, standard label s pray drift mitigation is:

• 3

- 10 mph wind speed

• 10 ft release height above canopy

• 1/2 swath offset upwind at the edge of the field• no sprays made during temperature inversions (the 3 mph low wind speed restriction is

essentially equivalent

• spray length 75% o f the wing or rotor length or less

Table A. Distance (in feet) to the LOC for selected plant sensitivity and application rate of 0.375

lbs ai/A, representative of soybean, peanut and strawberry maximum single application rate

. Note

these distances are fo r aerial applications.

Crop Endpoint IC 25 Med ium

coarse Coarse

very

coarse

Corn Dry Weight 0.085 20 16

Onion Dry Weight 0.12 10 3.3

Cabbage Plant Height 0.028 79 49

Radish Dry Weight 0.0038 4 20 269

Soybean Dry Weight 0.087 16 13

Tomato Dry Weight 0.046 43 30

Additionally, in Table 4.5 of the assessment, the label for the soybean and peanut use patterns

indicates a single seasonal application of 0.5 lbs ai/A. This label is incorrect , although the results

presented are correct for the use patterns. The single maximum application rate is 0.375 lbs ai/A

with a seasonal maximum application rate of 0.5 lbs ai/A. Thus, the modeling was actually

conducted for a first application at 0.375 lbs ai/A on day zero and a follow

- up application of

0.125 lbs ai/A on day 15. The RQs in the table are correct for this application scenario.