Document ID: EPA-HQ-OPP-2007-0535-0008
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2008-06-11T04:00Z

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

	

OFFICE OF                  

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES        

MEMORANDUM

DATE:  03/26/2008

SUBJECT:	Registration:  08OR08; Section 18 Exemption For The Use of
Bifenthrin on Orchardgrass Grown for Seed in Oregon.

Registration No.	08OR08	Decision No:	390214

DP No.:	350052	40 CFR:	§180.442

Chemical No.:	128825	Class:	Synthetic Pyrethroid

Trade Name:	Brigade 2EC	EPA Reg. No.: 	279-3313

MRID:	None

From:		William D. Wassell, Chemist

		Registration Action Branch 1 (RAB1)

		Health Effects Division (HED, 7509P)

Through:	Dana Vogel, Branch Chief

		RAB1/HED (7509P)

To:		Daniel Rosenblatt/Andrea Conrath (RM 05)

	Registration Division (7505P) 

Introduction

The Department of Agriculture of Oregon has requested an emergency
exemption for the use of bifenthrin [(2-methyl [1,1'-biphenyl]-3-yl)
methyl-3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropane
carboxylate] on orchardgrass grown for seed for control of billbug. 
This is the seventh year this request has been made.  Capture 2EC,
containing bifenthrin as the active ingredient (ai), is to be applied to
orchardgrass at the rate of 0.10 pounds (lb) ai per acre (A) using
ground equipment.  Up to 2 applications for a total rate of 0.2 lb ai/A
may be made (one in the spring and one after harvest), with a
pre-harvest interval (PHI) of 30 days.  The proposed use period is from
March 25 to November 15, 2008.

Summary

Bifenthrin is a broad-spectrum, non-systemic insecticide/miticide in the
class of synthetic pyrethroids.  It is registered to FMC Corporation for
use as foliar applications on a variety of field, fruit, and vegetable
crops.

Tolerances for residues of bifenthrin are currently expressed in terms
of bifenthrin per se.  Permanent tolerances are established for
bifenthrin residues in/on several food commodities under 40 CFR
§180.442(a)(1).  The established tolerances for plant and livestock
commodities, range from 0.05 ppm (various plant and poultry commodities)
to 25 ppm (coriander, dried leaves).  A tolerance of 0.05 ppm is also
established for residues of bifenthrin in food/feed handling
establishments under §180.422(a)(2).  In addition, time-limited
tolerances for residues of bifenthrin have been established under
§180.422(b) in connection with Section 18 emergency exemptions; these
include tolerances for orchardgrass, forage and hay each at 0.05 ppm
with a 12/31/09 expiration date.

There are no direct human feed items associated with orchardgrass grown
for seed.  Based upon HED’s previous evaluation of secondary residues
of bifenthrin in livestock tissues (Memo, 7/25/07, W.D. Wassell, DP#
335688), residues of bifenthrin in/on forage or hay from orchardgrass
grown for seed will not result in higher residues for livestock
commodities.  

Considering that this Section 18 is not expected it increase human
dietary exposure to bifenthrin, HED concludes that no human-health risk
assessment is needed for this Section 18 use on orchardgrass grown for
seed.  HED's previous risk assessment (Memo, 7/25/07, W.D. Wassell, et
al., DP# 371449) adequately covers the subject use.  

Estimates of handler exposure and risk for the proposed application of
bifenthrin to orchardgrass at 0.1 lb ai/acre are expected to be no
higher than that calculated in HED’s previous risk assessment for
bifenthrin (Memo, 7/25/07, W.D. Wassell, et al., DP# 371449) as rates up
to 0.3 lb ai/A were evaluated.  Provided that mixer/loaders wear
protective gloves, all MOEs are above 100, and, therefore, are not of
concern to HED.

Estimates of post-application exposure and risk for the proposed
application of bifenthrin to orchardgrass are expected to be no higher
than that calculated in HED’s previous risk assessment (Memo, 7/25/07,
W.D. Wassell, et al., DP# 371449).  A restricted-entry interval (REI) of
24 hours is specified on the proposed Section 18 label.  Based on the
lowest acute toxicity of bifenthrin technical (category III for acute
dermal), an REI of at least 12 hours is required by the Worker
Protection Standard.  Currently, 12 hours is the shortest REI appearing
on the Section 3 label.

As concluded in the 7/25/07 human-health risk assessment, aggregate risk
estimates for acute, chronic, short- and intermediate-term exposure are
not of concern to HED.  Provided the rotational crop restrictions on the
Section 18 label are modified (see below), this Section 18 exemption
should not pose an unacceptable aggregate risk to infants, children, or
adults.  HED has no objection to the issuance of the Section 18
emergency exemption for the use of bifenthrin on orchardgrass grown for
seed in OR.  To support this Section 18 use, time-limited tolerances for
residues of bifenthrin per se should be established as follows:

Crop (commodity)	

Tolerance Level (ppm)

Grass, forage	

2.5

Grass, hay	

4.5

The rotational crop restrictions on the current label may be replaced
with the following restrictions:  Crops having bifenthrin tolerances may
be replanted at any time, and all other crops may be replanted 30 days
following the last application of bifenthrin.

Detailed Discussion 

Magnitude of the Residues

The Interregional Research Project No. 4 (IR-4) has conducted field
trial data for residues of bifenthrin in/on orchardgrass.  A very brief
summary of these data were included in the Section 18 submission.  IR-4
expects to submit the data and a petition for tolerances before the end
of 2008.  These data are summarized in Table 1.

Table 1.  Residues of Bifenthrin per se in or on Orchardgrass Forage and
Hay.

Trial ID, Location, Year	NAFTA Growing Region	Variety	Commodity	Total
rate

(lb ai/A)	PHI

(days)	Bifenthrin residues

(ppm)

ID07, Swan Valley ID, 2005	11	Bannock wheat grass	Forage	0.203	29	1.72

	Hay

29	2.93

OR11, Aurora, OR, 2005	12	Adams Valley tall fescue	Forage	0.201	29	0.62

	Hay

38	0.32

OR12, Aurora, OR, 2005	12	Icon rye grass	Forage	0.207	36	0.10

	Hay

43	0.13

OR13, Aurora, OR, 2005	12	Fawn tall fescue	Forage	0.199	30	0.43

	Hay

40	0.10

WA05, Prosser, WA, 2005	11	Pulte orchard

grass	Forage	0.201	29	0.14

	Hay

36	0.15

HED concludes bifenthrin residues in/on orchard grass forage and hay
should not exceed 2.5 ppm and 4.5 ppm, respectively.  These tolerance
levels are as per IR-4 recommendation and were determined using the EPA
MRL calculator.  Therefore, time- limited tolerances for residues of
bifenthrin in/on orchardgrass forage and hay should be established at
2.5 ppm and 4.5 ppm, respectively.

Processed Commodities

There are no processed commodities associated with orchardgrass grown
for seed for which residue data are required.

Meat, Milk, Poultry and Eggs

Although forage and hay from orchardgrass grown for seed are considered
to be livestock feed items, they contribute a minor percentage of
livestock diets compared to the contribution from corn and aspirated
grain fractions (Memo, 7/25/07, W.D. Wassell, DP# 371449).  HED thus
concludes that residues of bifenthrin in/on forage and hay from
orchardgrass grown for seed will not result in higher livestock dietary
burdens and that increased tolerances are not required for residues in
livestock commodities from this Section 18 use.

Rotational Crop Restrictions

The following rotational crop restrictions were included on the label: 
Leafy vegetables and root crops may be rotated 30 days following the
final application of bifenthrin.  Crops for which bifenthrin tolerances
exist may be rotated at any time.  All other crops may be rotated seven
months following the final application of bifenthrin.

Adequate confined and field rotational crop studies are available for
bifenthrin.  Based on these data, HED has previously determined the
following rotational crop restrictions are adequate:  Crops having
bifenthrin tolerances may be replanted at any time, and all other crops
may be replanted 30 days following the last application of bifenthrin. 
No rotational crop tolerances are required.  These restrictions are less
limiting than the rotational crop restrictions included on the proposed
label. A revised label with the approved rotational crop restrictions
may be submitted if the less limiting rotational crop restrictions are
desired.

International Residue Limits

There are no Codex maximum residue limits (MRLs) established for
bifenthrin on grass forage and hay (see Attachment 1).  Therefore, no
compatibility problems exist for the proposed tolerances.

RDI: M. Clock-Rust:  03/26/2008, G.F. Kramer:  03/26/2008

Registration:  08OR08

DP Number:  350052

PC Code:  128825

WDWassell:S10316:Potomac Yard:703-305-6135:7509P:RAB1

ATTACHMENT 1:  IRLS Sheet

INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name:

(2-Methyl [1,1'-biphenyl]-3-yl)
methyl-3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropane
carboxylate	

Common Name:

BIFENTHRIN	

( Proposed tolerance

( Reevaluated tolerance

( Other	

Date:

3/25/08

Codex Status (Maximum Residue Limits)	

U. S. Tolerances

X No Codex proposal step 6 or above

( No Codex proposal step 6 or above for the crops requested	

Petition Number:  08OR08

DP Number:  350052

Other Identifier:

Residue definition: 	

Reviewer/Branch:  W.D. Wassell

	

Residue definition:  bifenthrin per se

Crop (s)	

MRL (mg/kg)	

Crop(s)	

Tolerance (ppm)

	

	

Grass, forage	

2.5

	

	

Grass, hay	

4.0

	

	

	

	

	

	

	

	

	

Limits for Canada	

Limits for Mexico

X No Limits

( No Limits for the crops requested	

X No Limits

( No Limits for the crops requested

Residue definition:

	

Residue definition:

Crop(s)	

MRL (mg/kg)	

Crop(s)	

MRL (mg/kg)

	

	

	

	

	

	

Notes/Special Instructions:

Rev. 1998

 PAGE   

Page   PAGE  2  of   NUMPAGES  5