UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

	OFFICE OF PREVENTION, PESTICIDE

	AND TOXIC SUBSTANCES

  SEQ CHAPTER \h \r 1 MEMORANDUM

Date:  1/7/2009

SUBJECT:	Cyhalofop-butyl.  Tolerance Petition for use on Wild Rice. 
Summary of Analytical Chemistry and Residue Data

PC Code:  082583	DP Barcode:  D352156

Decision No.:  391343	Registration No.:  62719-356

Petition No.:  8E7341	Regulatory Action:  Section 3

Risk Assessment Type:  NA	Case No.:  NA

TXR No.:  NA	CAS No.:  122008-85-9

MRID No.:  N/A	40 CFR:  §180.576

		              									

FROM:	Douglas Dotson, Ph.D., Chemist

		Registration Action Branch II

		Health Effects Division (7509P)

			  SEQ CHAPTER \h \r 1 

THROUGH:	Michael Doherty, Ph.D., Chemist

		Richard Loranger, Ph.D., Senior Scientist

		Registration Action Branch II

		Health Effects Division (7509P)

TO:		Sidney Jackson/Dan Rosenblatt, RM Team 05

		RIMUERB

		Registration Division (7505P)		  SEQ CHAPTER \h \r 1   SEQ CHAPTER \h
\r 1 

		

Executive Summary

Interregional Research Project Number 4 (IR-4), on behalf of the state
of California, has submitted a tolerance petition for the use of the
herbicide cyhalofop-butyl
(R-(+)-n-butyl-2-(4-(4-cyano-2-fluorophenoxy)-phenoxy)propionate) on
wild rice.  Tolerances have been established for cyhalofop-butyl and its
acid and diacid metabolites in/on two commodities only:  rice grain at
0.03 ppm and rice straw at 8.0 ppm (40CFR §180.576).  These tolerances
were time-limited and expired on 6/1/2007.  HED reviewed the residue
data and recommended in favor of these time-limited tolerances in 2002
(Memo, D267558, M. Nelson, 11/13/2001 and Memo, D277695, D. Davis,
4/10/2002).  The tolerances were time-limited because of deficiencies in
the toxicology database.  IR-4 has requested that the rice field trial
data be translated to wild rice, and that a tolerance be established for
residues of cyhalofop-butyl and its acid and diacid metabolites in/on
rice, wild, grain, at 0.03 ppm.  Wild rice straw is not a regulated
commodity; therefore, a tolerance was not proposed for this commodity. 
The end-use product proposed for use on wild rice is Clincher CA (EPA
Registration Number 62719-356).

HED’s Chemistry Science Advisory Council (ChemSAC) decided that rice
grain residue data could be translated to wild rice because similar
cultural practices are used for the two crops (ChemSAC, Meeting Minutes,
7/18/2007).  For cyhalofop-butyl, the proposed use directions are the
same for wild rice as they are for rice.  Clincher CA is proposed for a
maximum of two postemergence applications to wild rice, with a 10-day
retreatment interval, at up to 0.28 lb ai/A per application.  The
maximum allowable seasonal application rate is 0.46 lb ai/A.  The
proposed preharvest interval (PHI) is 60 days.

The residue chemistry aspects of the use of cyhalofop-butyl on rice were
discussed in detail in the residue chemistry review prepared for the
request (Memo, D267558, M. Nelson, 11/13/2001).  This memo discusses all
of the following topics:  the nature of the residue in rice, the nature
of the residue in ruminants and poultry, the residue analytical methods,
storage stability of residues in rice commodities, water/fish/irrigated
crops, field trial studies, rice processing data, residues in
meat/milk/poultry/eggs, and confined and field accumulation in
rotational crops.  HED is translating this information to wild rice.  As
a result, the rice residue chemistry review may be consulted for a
discussion of all topics relevant to wild rice.

GC/MS Method GRM 99.06 is the enforcement method for determining
cyhalofop-butyl residues of concern in/on rice commodities.  The method
has been subjected to a successful ILV and it has also undergone a
successful petition method validation by the Analytical Chemistry Branch
of the Biological and Economic Analysis Divison (ACB/BEAD).  Method GRM
99.06 was also the residue analytical method used in the analysis of
rice commodities collected from the field trial, processing, and storage
stability studies.  The concurrent method recoveries indicate that the
method is adequate for data collection.  

Rice grain field trial residues ranged from below the LOQ of 0.01 ppm to
a maximum of 0.0253 ppm.  Of the 42 field trial samples analyzed, 35 of
them had residue levels that were below the LOQ (i.e., 83% of them). 
For this reason, HED’s Tolerance Generator for NAFTA-Harmonized
Tolerances cannot be used to determine the recommended tolerance for
wild rice grain.  HED recommends in favor of the establishment of a
tolerance of 0.03 ppm for rice, wild, grain.  This tolerance is
equivalent to that established for rice, grain.  No Codex, Canadian, or
Mexican MRLs have been established for cyhalofop-butyl.  As a result,
the translation of the 0.03 ppm tolerance to wild rice grain will not
create international MRL harmonization issues.  

Analytical reference standards for cyhalofop-butyl, cyhalofop-acid, and
cyhalofop-diacid are available at the EPA National Pesticide Standards
Repository.

  SEQ CHAPTER \h \r 1 Regulatory Recommendations and Residue Chemistry
Deficiencies

There are no residue chemistry deficiencies that would preclude the
granting of tolerances for rice, grain and rice, wild, grain.  The
submitted data support the following tolerance for residues of
cyhalofop-butyl and its acid and diacid metabolites in/on:

Rice, grain	0.03 ppm

Rice, wild, grain	0.03 ppm

Although a time-limited tolerance was in effect for rice straw, the
Agency no longer establishes tolerances for this commodity.  As a
result, HED is not recommending in favor of a tolerance for rice straw. 

Background

The chemical structure and nomenclature of cyhalofop-butyl are provided
in Table 1, below.  The physicochemical properties of the technical
grade of cyhalofop-butyl are presented in Table 2.

Table 1.   Cyhalofop-butyl Nomenclature.

Compound

		

 

Common name	Cyhalofop-butyl

IUPAC name	2-(4-(4-cyano-2-fluorophenoxy)phenoxy)propanoic acid, butyl
ester (R)

CAS name	R-(+)-n-butyl-2-(4-(4-cyano-2-fluorophenoxy)-phenoxy)propionate

CAS registry number	122008-85-9

End-use product (EPs) requested for registration	Clincher® CA Herbicide
(29.6% Emulsifiable Concentrate)





TABLE 2	Physicochemical Properties of Cyhalofop-butyl.

Parameter	Value	References

Melting point/range	45.5-49.5ºC	Memo, D277695, D. Davis, 4/10/2002

pH	9.0 

	Relative Density (20ºC)	1.172 g/cm3

	Water solubility (20ºC)	0.44 mg/L at pH 7

	Solvent solubility (g/L)	n-heptane           6.06

n-octanol          16.0

methoanol     >250

acetone          >250

ethyl acetate  >250

acetonitrile    >250

	Vapor pressure (25ºC)	5.3 x 10-8 kPa (4.0 x 10-7 mmHg) 

	Octanol/water partition coefficient, Log(KOW) (25ºC)	3.32 

	

860.1200  Directions for Use

The proposed use directions for wild rice are very comparable to those
in effect for rice.  The use directions for rice and wild rice are
outlined in Table 3, below.  

Table 3.	Summary of Directions for Use of Cyhalofop-butyl on Wild Rice.

Applic. Timing, Type, and Equip.	Formulation	Applic. Rate 

(lb ai/A)

	Max. No. Applic. per Season	

Max. Seasonal Applic. Rate

(lb ai/A)

	PHI

(days)	Use Directions and Limitations

Rice and Wild Rice

Broadcast foliar

Ground or aerial	29.6% Emulsifiable Concentrate

(2.38 lb ai/gallon)	0.24-0.28	2	

0.46

	60	

Applications are to be made with crop oil concentrate at a rate of 2.5%
v/v.  A spray volume of 10-15 gallons per acre should be used. 
Sequential applications must be made at least 10 days apart.  Do not
apply through any type of irrigation system.  Do not allow discharge of
paddy water from treated areas for a minimum of 7 days after the most
recent application.





Conclusions.  The proposed use directions for rice and wild rice are
adequately described and sufficient to allow evaluation of the rice
residue data relative to the proposed uses.

860.1300 Nature of the Residue - Plants

Residue Chemistry Memo D267558, 11/13/01, M. Nelson, (PP# 0F6089)

HED MARC Decision Memo DP# 277192, 11/13/2001

  SEQ CHAPTER \h \r 1 The nature of cyhalofop-butyl residues in rice is
adequately understood based upon acceptable 14C metabolism studies
conducted on rice (Memo, D267558, M. Nelson, 11/13/2001).  HED assumes
that the metabolism in wild rice is the same as that in rice.  The HED
MARC concluded that the combined residue of parent and its acid and
diacid metabolites should be regulated and used for risk assessment
purposes (Memo, D277192, Y. Donovan, 11/13/2001).  These conclusions
apply to wild rice as well.

860.1300 Nature of the Residue – Livestock

Residue Chemistry Memo D267558, 11/13/01, M. Nelson, (PP# 0F6089)

For a discussion of the nature of the residue in livestock, see the
previous residue chemistry review prepared for cyhalofop-butyl (Memo,
D267558, M. Nelson, 11/13/2001).  In that document, the following
conclusion was made:  “For the purpose of this petition only, there is
no reasonable expectation of finite cyhalofop-butyl residues of concern
in egg, milk and edible livestock tissues [Category 3, 40 CFR
§180.6(a)] as a result of the proposed uses on rice.  Therefore, the
requirements for tolerances, analytical methods, and data depicting
magnitude of the residue in eggs, milk and edible livestock tissues are
not required.  The Category 3 situation may not remain applicable if
additional livestock feed items are proposed for tolerances in the
future.”  The proposed use on wild rice does not result in an increase
in residues that are expected to occur in animal commodities.  As a
result, the conclusion that there is no reasonable expectation of finite
cyhalofop-butyl residues of concern in egg, milk and edible livestock
tissues [Category 3, 40 CFR §180.6(a)] continues to be in effect.

860.1340 Residue Analytical Methods

Residue Chemistry Memo D267558, 11/13/01, M. Nelson, (PP# 0F6089)

GC/MS Method GRM 99.06 is the enforcement method for determining
cyhalofop-butyl residues of concern in/on rice commodities.  Method GRM
99.06 quantitates residues of cyhalofop-butyl and cyhalofop-acid as the
acid equivalent, and residues of cyhalofop-diacid and cyhalofop-amide as
the diacid equivalent.  The validated method LOQ for cyhalofop-acid and
cyhalofop-diacid is 0.01 ppm each in all rice matrices, except in straw,
where the LOQ for cyhalofop-diacid is 0.05 ppm.

Method GRM 99.06 has been subjected to a successful ILV.  It has also
undergone a successful petition method validation by ACB/BEAD (Memo,
D272679, E. Kolbe, 3/18/2002).  The method can be obtained from
ACB/BEAD.

    

Method GRM 99.06 was also the residue analytical method used in the
analysis of rice commodities collected from the field trial, processing,
and storage stability studies.  The concurrent method recoveries
indicate that the method is adequate for data collection.

860.1360 Multiresidue Methods

Residue Chemistry Memo D278385, 8/15/03, M. Nelson, (PP# 1F06313)

The results of m  SEQ CHAPTER \h \r 1 ultiresidue methods testing can be
found in the residue chemistry summary document prepared for rice (Memo,
D267558, M. Nelson, 11/13/2001).  Complete recovery of cyhalofop-butyl
was achieved through Protocol D (without Florisil cleanup and using NPD
detection), and through Protocol E.  The acid and diacid metabolites do
not appear to be recovered by any of the FDA multiresidue methods.

860.1380 Storage Stability

The results of storage stability testing for cyhalofop-butyl,
cyhalofop-acid, and cyhalofop-diacid   SEQ CHAPTER \h \r 1  can be found
in the residue chemistry summary document prepared for rice (Memo,
D267558, M. Nelson, 11/13/2001).  The storage stability data are
adequate to support the submitted field trial and metabolism studies for
cyhalofop-butyl.

860.1400 Water, Fish and Irrigated Crops

The proposed label prohibits use of cyhalofop-butyl through irrigation
systems.  It also prohibits fishing or the commercial growing of fish,
shellfish, or crustaceans on treated acres during the year of treatment.
 Based on these label restrictions, residue data pertaining to the
magnitude of cyhalofop-butyl residues of concern in water, fish, and
irrigated crops are not required.

860.1480 Meat, Milk, Poultry, and Eggs

The residue chemistry review for rice stated the following with respect
to the need for tolerances for animal commodities:  “For the purpose
of this petition only, the data requirements for magnitude of
cyhalofop-butyl residues of concern in eggs, milk, and edible tissues of
animals are waived, based on low levels of radioactive residues observed
from the animal metabolism studies.  This is considered to be Category 3
of 40 CFR §180.6(a) with respect to the need for cyhalofop-butyl
tolerances in animal commodities.  In the event that tolerances are
proposed on additional livestock feed items in the future, the Agency
will recalculate the maximum dietary burdens and reassess the need for
animal feeding studies and tolerances.”

As part of the residue chemistry review, a maximum theoretical dietary
burden (MTDB) was calculated for cyhalofop-butyl.  This diet was based
on rice grain, straw, hulls, and bran.  Although wild rice grain and
straw are potential animal feed items, wild rice straw is not a
significant feed item, and HED is not recommending in favor of a
tolerance for this commodity.  Wild rice grain could replace rice grain
in the MTDB; however, the tolerance is the same as the rice tolerance
that was used in the calculation of the MTDB.  As a result, the
inclusion of wild rice grain in the MTDB calculation will have no effect
on it.  Rice straw is no longer considered to be a significant animal
feed item and could be removed from the MTDB calculation.  Removing rice
straw from the calculation would result in a decrease in the MTDB.  As a
result, the use of cyhalofop-butyl on rice and wild rice is still
considered to fall under Category 3 of 40 CFR §180.6(a) with respect to
the need for cyhalofop-butyl tolerances in animal commodities.    

860.1500 Crop Field Trials

The results of the magnitude of the residue studies for cyhalofop-butyl 
 SEQ CHAPTER \h \r 1 can be found in the residue chemistry summary
document prepared for rice (Memo, D267558, M. Nelson, 11/13/2001).  Rice
grain field trial residues ranged from below the combined LOQ of 0.01
ppm to a maximum of 0.0253 ppm.  Of the 42 field trial samples analyzed,
35 of them had residue levels that were below the combined LOQ (0.01
ppm).  

860.1520 Processed Food and Feed

The residue chemistry review for rice stated the following with respect
to processed rice commodities:  “The rice processing study is adequate
for the purpose of this petition.  Residues of cyhalofop
(cyhalofop-butyl and cyhalofop-acid, determined as the acid equivalent)
and cyhalofop-diacid were each less than the method LOQ (<0.010 ppm)
in/on rice grain treated with Clincher( (2.38 lb/gal EC formulation) at
1.40 lb ai/A (5x the maximum proposed single application rate and 3x the
maximum proposed seasonal rate).  Following processing of treated rice
grain according to simulated commercial practices, residues did not
concentrate in bran and polished rice; residues concentrated marginally
(1.1-1.2x) in hulls.  Based on the results of the current processing
study, tolerances for cyhalofop-butyl residues of concern in the
processed commodities of rice are not required.”

There are no processed commodities associated with the use of
cyhalofop-butyl on wild rice for which residue data are required.  As a
result, this guideline topic is not relevant to the proposed use on wild
rice.

  SEQ CHAPTER \h \r 1 860.1650 Submittal of Analytical Reference
Standards

Analytical standards for cyhalofop-butyl, cyhalofop-acid, and
cyhalofop-diacid are currently available in the EPA National Pesticide
Standards Repository (electronic communication, D. Wright, ACB/BEAD,
11/14/2008).  The expiration dates of the standards are as follows: 
cyhalofop-butyl (6-14-2010), cyhalofop-acid (3-31-2012), and
cyhalofop-diacid (3-17-2012).  The analytical reference standards must
be recertified or replenished as requested by the Repository.  The
reference standards should be sent to the Analytical Chemistry Lab,
which is located at Fort Meade, to the attention of Theresa Cole at the
following address:

	USEPA

	National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

	701 Mapes Road

	Fort George G. Meade, MD  20755-5350

(Note that the mail will be returned if the extended zip code is not
used.)

860.1850 and 860.1900 Confined and Field Accumulation in Rotational
Crops

The same cultural practices are followed for rice and wild rice.  For
this reason, the rotational crops would be the same for the two
commodities.  The results of a confined rotational crop study using
spring wheat, leaf lettuce, and radishes were discussed in the residue
chemistry summary document prepared for rice (Memo, D267558, M. Nelson,
11/13/2001).  The confined rotational crop study was deemed adequate for
the purposes of characterizing the nature of the cyhalofop-butyl
residues in rotational crops.  HED concluded that the proposed 3-month
plantback interval for crops other than rice was adequate.  HED further
concluded that field rotational crop studies were not required.  The
proposed label for wild rice specifies a plantback interval of 3 months
for crops other than rice.  HED’s conclusions concerning the
rotational crop studies and the plantback interval apply to the current
petition for wild rice. 

860.1550 Proposed Tolerances

The residue of concern in plants is cyhalofop-butyl, cyhalofop-acid, and
cyhalofop-diacid for the purposes of risk assessment and tolerance
expression.  The rice tolerance is listed in 40 CFR §180.576.  There
are no residue chemistry data deficiencies that would preclude the
establishment of a tolerance of 0.03 ppm for both rice, grain and rice,
wild, grain.

No Codex, Canadian, or Mexican MRLs have been established for
cyhalofop-butyl.  As a result, the translation of the 0.03 ppm tolerance
to wild rice grain will not create international MRL harmonization
issues.

  

A tolerance summary is presented below in Table 4.

Table 4.   Tolerance Summary for Cyhalofop-butyl.

Commodity	Proposed

Tolerance (ppm)	Expired

Tolerance (ppm)	Recommended Tolerance (ppm)	Comments; 

Correct Commodity Definition

Rice, wild, grain	0.03	NA	0.03

	Rice, grain	None	0.03	0.03	Rice, grain

Rice, straw	None	8.0	none	Rice straw is no longer a regulated commodity.
 As a result, a tolerance is not needed.



References

PP#0F06089.  NEW CHEMICAL:  Cyhalofop-Butyl in/on Rice.  Review of
Residue Chemistry, D267558, M. Nelson, 11/13/2008

Cyhalofop-butyl:  Human Health Risk Assessment for Use on Rice, D277695,
D. Davis, 4/10/2002

PP# 0F06089.   NEW CHEMICAL:   Cyhalofop-Butyl in/on Rice, Decision
Memorandum of the HED Metabolism Assessment Review Committee, D277192,
Y. Donovan, 11/13/2008

  



INTERNATIONAL RESIDUE LIMIT STATUS

Chemical Name: 
R-(+)-n-butyl-2-(4(4-cyano-2-fluorophenoxy)-phenoxy)propionate

	Common Name:

Cyhalofop-butyl	X Proposed tolerance

⁪ Reevaluated tolerance

⁪s Other	Date:   11/12/08

Codex Status (Maximum Residue Limits)	U. S. Tolerances

√No Codex proposal step 6 or above

□  No Codex proposal step 6 or above for the crops requested	Petition
Numbers:  PP#8E7341

DP#:  D351856

Other Identifier:  

Residue definition (step 8/CXL): N/A	Reviewer/Branch:  Doug Dotson/RAB2

	Residue definition:  cyhalofop-butyl, cyhalofop acid, and cyhalofop
diacid

Crop (s)	MRL (mg/kg)	Crop(s) 	Tolerance (ppm)

None

Wild rice	0.03















	Limits for Canada	Limits for Mexico

√  No Limits

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Crop(s)	MRL (mg/kg)	Crop(s)	MRL (mg/kg)

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	Notes/Special Instructions:  S.Funk, 11/13/2008.



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