UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF           

PREVENTION, PESTICIDES

AND TOXIC SUBSTANCES

MEMORANDUM

	Date:	12/MAR/2008

	Subject:	Dichlobenil.  Use on Caneberry (Subgroup 13-07A), Bushberry
(Subgroup 13-07B).  Summary of Analytical Chemistry and Residue Data. 
PP#7E7230.

		DP Number: 349398	Decision Number:  380110

		PC Code: 027401	MRID Number:  45572201

		40 CFR 180.231	Chemical Class: nitrile herbicide	 

       From:	Debra Rate, Ph.D., Biologist

Alternative Risk Integration and Assessment (ARIA) Team 

Risk Integration, Minor Use and Emergency Response (RIMUER) Branch 

Registration Division (7505P)

	Through:	William Cutchin, Acting Senior Branch Scientist

		ARIA

		RIMUERB/RD (7505P)

		

		And

		

		George F. Kramer, Ph.D., Senior Chemist

		Registration Action Branch 1 (RAB1)

		Health Effects Division (HED)(7509P)

	To:	Susan Stanton, Environmental Scientist

		RIMUERB/RD (7505P)

Executive Summary

Interregional Research Project No. 4 (IR-4) has requested tolerances for
the use of dichlobenil (2,6-dichlorobenzonitrile) on rhubarb, caneberry,
subgroup 13-07A, and bushberry, subgroup 13-07B commodities. 
Dichlobenil is a nitrile herbicide that acts by inhibiting germination
of actively dividing meristems and acts primarily on growing points and
root tips.  The rhubarb request was previously reviewed by W. Cutchin
(DP Num: 31566, 22/FEB/2006).  Dichlobenil, formulated as the 4%
granular product Casoron® 4G (EPA Reg. No. 400-168), is to be applied
at a maximum seasonal rate of 4 lb ai/A to berry commodities.  The
product is applied directly to soil while the target crop is dormant. 
For berry crop group tolerances, no additional data was submitted. 
Tolerances are currently established for blackberry, blueberry, and
raspberry.  Since the previously reviewed data encompasses the
representative commodities for the requested berry crop groups, the data
may be translated to support the requested berry tolerances.

The qualitative nature of the residue in plants is adequately understood
based on acceptable plant metabolism studies on apples and grapes.  Both
studies indicate that the major residue of concern is
2,6-dichlorobenzamide (BAM).  The parent compound, dichlobenil, was not
detected in either of the studies.  HED concluded that BAM is the major
terminal residue of dichlobenil in plants, and should be added to the
tolerance expression.  Since there are no berry animal feed items of
regulatory concern, a discussion of the nature of the residues of
dichlobenil in livestock commodities is not germane to this action.  

Pesticide Analytical Manual (PAM) Vol. II, Method A is a gas-liquid
chromatography/electroconductivity detector (GLC/ECD) method with a
limit of detection (LOD) of 0.05 ppm, which can be used for
determination of residues of dichlobenil in/on plant commodities.  This
method was judged adequate for tolerance enforcement.  However, the
registrant was required to revise the method or develop an alternative
method using safer solvents.  The revised method is not adequate and
will require additional modification before it can be accepted as a
tolerance enforcement method.  A GLC/ECD method, L 3-53-71, for
determination of residues of BAM in/on fruits and nuts has undergone a
successful independent laboratory validation and has been validated by
the EPA Analytical Chemistry Laboratory (ACL).  However, a revised
method incorporating ACL's comments must be submitted before the
requirements for an analytical method for BAM can be considered
fulfilled.  Dichlobenil is completely recovered using the multiresidue
methods in PAM Vol. I Sections 302 and 304.  BAM is also completely
recovered using Section 302.  Since the multiresidue methods adequately
quantitate dichlobenil and BAM, there is adequate enforcement
methodology for this action.  

The analytical methods SOP# Meth-83, Determination of Dichlobenil
Residues in Cherries and SOP# Meth-84, Determination of
2,6-dichlorobenzamide Residues in Cherries, developed by Morse
Laboratories were used with minor modifications for the analysis of
dichlobenil residues on rhubarb.  Dichlobenil residues were extracted
from the raw agricultural commodity (RAC) by extracting with ethyl
acetate/hexane and clean up using a Florisil column.  BAM residues were
extracted from RAC by extracting with ethyl acetate and clean up using a
Florisil column.  Samples were analyzed using a GLC/ECD in halogen mode.
 The analytical method was validated at 0.05, 0.1, and 0.5 ppm for
dichlobenil and 0.01, 0.02, and 0.1 ppm for BAM.  At the range of the
fortification levels, method recoveries were generally within Agency
standards of 70-120%.  The lower limit of method validation (LLMV) was
reported for dichlobenil and BAM as 0.05 ppm and 0.01 ppm, respectively.
 The LOD was 0.006 ppm for both dichlobenil and BAM.  The method used
for data collection is adequate

There are no processed commodities of regulatory interest resulting from
the requested berry uses.  Berry crops are not rotated on a regular
basis; therefore, inadvertent residues in rotational crops are not a
concern for this action.

Regulatory Recommendations and Residue Chemistry Deficiencies

Pending receipt of the revised Section F, revised Section B and the
forthcoming human health risk assessment, ARIA previously recommended
the tolerances of the combined residues of the herbicide dichlobenil
(2,6- dichlorobenzonitrile) and its metabolite 2,6-dichlorobenzamide
in/on rhubarb at 0.06 ppm (DP Num: 315266, W. Cutchin, 22/FEB/2006) and
recommends the following tolerances for the requested berry commodities
at the levels listed below: 

Caneberry, Subgroup 13-07A	0.10 ppm

Bushberry, Subgroup 13-07B	0.15 ppm

The revised Reregistration Eligibility Decision (RED) (K. Boyle,
31/JUL/1996) recommended deletion of a stone fruit crop group tolerance
which was not being supported by the petitioner and establishment of a
separate tolerance on cherries.  However, as stated in the previous RED,
the stone fruit crop group was included in this dietary exposure
assessment since as long as the tolerance exists commodities containing
BAM residues could be imported (Dichlobenil: The Revised HED Chapter of
the RED, Case 0263, Chemical 027401, 027402 (BAM), K. Boyle,
31/JUL/1996,).

Background

Dichlobenil is a nitrile herbicide that acts by inhibiting germination
of actively dividing meristems and acts primarily on growing points and
root tips.

TABLE 1.  Test Compound Nomenclature.

Compound	Chemical Structure



Common name	dichlobenil

Company experimental name	DCBN

IUPAC name	2,6-dichlorobenzonitrile

CAS name	2,6-dichlorobenzonitrile

CAS #	1194-65-6

End-use product/(EP)	Casoron® 4G (EPA Reg. No. 400-168)



TABLE 2.  Physicochemical Properties of Dichlobenil.  

Parameter	Value	Reference

Melting point/range	145°C	RED Chapter, 6/29/95 

pH	NA

	Density	1.3 g/cm3	IPS Inchem, 4/05

Water solubility ( 25°C)	0.0021g/100mL	RED Chapter, 6/29/95

Solvent solubility (g/100mL at 25°C)	xylene 5.3 

ethanol 1.5 

cyclohexane 0.37   

	Vapor pressure at 20°C	5.5 x 10-4 mmHg	IPS Inchem, 4/05

Dissociation constant (pKa)	NA

	Octanol/water partition coefficient Log(KOW)	2.64	IPS Inchem, 4/05

UV/visible absorption spectrum	NA

	

860.1200  Directions for Use

Table 3.  Summary of Directions for Use of Dichlobenil.



Applic. Timing, Type, and Equip.	

Formulation

[EPA Reg. No.]	

Applic. Rate 

(lb ai/A)	

Max. No. Applic. per Season	

Max. Seasonal Applic. Rate

(lb ai/A)	

PHI

(days)	

Use Directions and Limitations



Bushberry, Subgroup 13-07A (Blueberry, Currant, Elderberry, Gooseberry,
Huckleberry, Aronia berry, Blueberry lowbush, Buffalo currant, Chilian
guava, European barberry, Highbush cranberry, Honesuckle, Jostaberry,
Juneberry, Lingonberry, Native currant, Salal, Sea buckthorn)



Apply only to established plantings using granular applicator

Maybe used on bearing, non-bearing, and nursery stock.  Do not apply
until 4 weeks after transplanting.	

Casoron® 4G [400-168]	

4

6	

1 (assumed)	

4

6	

NA	

Do not apply during new shoot emergence.



Caneberry, Subgroup 13-07B (Blackberry, Raspberry, Boysenberry,
Dewberry, Loganberry, Wild Raspberry)



Apply only to established plantings using granular applicator	

Casoron® 4G [400-168]	

4	

1 (assumed)	

4	

NA	

Do not apply during new shoot emergence.

Do not allow livestock to graze on treated orchards.

* Highlighted areas represent wording of the Section B that differs from
the proposed label.  

Conclusions.  The label is adequate to allow evaluation of the residue
data relative to the proposed uses on caneberry, subgroup 13-07A. 
However, the Section B must be revised for the bushberry, subgroup
13-07B from 6 lbs ai/A to 4 lbs ai/A to match the label use and
submitted data for the bushberry, subgroup 13-07B commodities.  Also,
the label and Section B must be revised to correctly spell the
commodities containing “currant” in the name.  

860.1300 Nature of the Residue - Plants

Dichlobenil RED, October 1998

The qualitative nature of the residue in plants is adequately understood
based on acceptable plant metabolism studies on apples and grapes.  Both
studies indicate that the major residue of concern is BAM.  The parent
compound, dichlobenil, was not detected in either of the studies.  On
June 8, 1992, HED concluded that BAM is the major terminal residue of
dichlobenil in plants, and should be added to the tolerance expression. 
Because dichlobenil plant metabolism studies demonstrate that
2,6-dichlorobenzoic acid (2,6-DCBA) is not a plant metabolite, HED has
recommended removing 2,6-DCBA from the tolerance expression for
dichlobenil.  Therefore, residue data for 2,6-DCBA are no longer
required.  All conclusions specified here regarding the status of
residue chemistry data requirements and the adequacy of the established
tolerances reflect the determination to add BAM to the tolerance
expression and remove 2,6-DCBA from the tolerance expression.

Conclusions.  The residues of concern in plants are the parent
dichlobenil and the metabolite BAM. 

860.1300 Nature of the Residue - Livestock

Since there are no berry animal feed items of regulatory concern, a
discussion of the nature of the residue of dichlobenil is not germane to
this action.

860.1340 Residue Analytical Methods

Dichlobenil RED, 10/98 

45572201.der.doc, W. Cutchin, 22/FEB/2006

PAM Vol. II, Method A is a GLC/ECD method with a detection limit of 0.05
ppm, which can be used for determination of residues of dichlobenil
in/on plant commodities.  This method was judged adequate for tolerance
enforcement; however, Method A uses benzene as a solvent.  The
registrant was required to revise the method or develop an alternative
method using safer solvents.  This method will likely require additional
modification before it can be accepted as a tolerance enforcement
method.  The Dichlobenil Guidance Document (23/MAR/1987), referenced in
the RED document, required the development of an analytical method for
the detection and quantitation of BAM in plant commodities.  The former
basic producer, Solvay Duphar, submitted a GLC/ECD method (L 3-53-71)
for determination of residues of BAM in/on fruits and nuts.  This method
has undergone a successful independent laboratory validation and has
been validated by the EPA Beltsville ACL.  However, a revised method
incorporating ACL's comments must be submitted before the requirements
for an analytical method for BAM can be considered fulfilled.  

The analytical methods SOP# Meth-83, Determination of Dichlobenil
Residues in Cherries and SOP# Meth-84, Determination of
2,6-dichlorobenzamide Residues in Cherries, developed by Morse
Laboratories were used with minor modifications for the analysis of
dichlobenil residues on berry matrices.  Dichlobenil residues were
extracted from the RAC by homogenizing the samples with ethyl
acetate/hexane and rotovaping the supernatant almost to dryness.  The
residue is then redissolved in hexane and cleaned up using a Florisil
column.  The dichlobenil residues are eluted with ethyl acetate/hexane,
rotovaping the eluant almost to dryness, and the sample redissolved in
hexane for analysis.  BAM residues were extracted from the RAC by
homogenizing the samples with ethyl acetate and taking the supernatant
almost to dryness.  The residue is then redissolved in hexane and
cleaned up using a Florisil column.  The BAM residues are eluted with
ethyl acetate/hexane, taking the eluant almost to dryness, and the
sample redissolved in hexane for analysis.  A GLC/ECD in halogen mode
was used for the analysis.  The analytical method was validated at 0.05,
0.1, and 0.5 ppm for dichlobenil and 0.01, 0.02, and 0.1 ppm for BAM. 
At these fortification levels, method recoveries were generally within
Agency standards of 70-120%.  The petitioner presented adequate sample
chromatograms and calibration curves.  The LLMV was reported for
dichlobenil and BAM as 0.05 ppm and 0.01 ppm, respectively.  The LOD was
0.006 ppm for both dichlobenil and BAM.

Conclusions.  The previously submitted methods proposed for tolerance
enforcement for dichlobenil and BAM on plants are not adequate for the
reasons described above.  However, as the multiresidue methods
adequately quantitate dichlobenil and BAM (see, 860.1360, below), there
is no deficiency for this action.  The method used for data collection
is adequate.

860.1360 Multiresidue Methods

Dichlobenil RED, October 1998 

The FDA PESTDATA database dated 1/94 (PAM Vol I, Appendix I) indicates
that dichlobenil is completely recovered (>80%) using multiresidue
methods PAM Vol. I Sections 302 (Luke method) and 304 (Mills fatty food
method), and has partial recovery (50-80%) using Section 303 (Mills,
Onley, Gaither method).  The database also indicates that BAM is
completely recovered (>80%) using Section 302.

860.1380 Storage Stability

DP Num: 179079, C. Olinger, 09/FEB/1993

DP Num:182600, C. Olinger, 05/MAR/1993

Since the representative berry commodity samples were stored for less
than 35 days at -18ºC between harvest and analysis, additional storage
stability data is not required for these RACs.  

860.1480 Meat, Milk, Poultry, and Eggs

Since there are no berry livestock feed items of regulatory concern, a
discussion of dichlobenil residues in livestock commodities is not
germane to this action. 

860.1500 Crop Field Trials

DP Num: 179079, C. Olinger, 09/FEB/1993

DP Num:182600, C. Olinger, 05/MAR/1993

Caneberry, Subgroup 13-07A and Bushberry, Subgroup 13-07B

No additional field trial studies have been submitted.  The petitioner
has requested that current tolerances on blackberry, blueberry, and
raspberry in combination with previously submitted studies be translated
to include tolerances on caneberry, subgroup 13-07A, and bushberry,
subgroup 13-07B.  

Adequate data on blackberry, blueberry and raspberry is available to
support the requested tolerances.  ARIA recommends for the establishment
of tolerances for dichlobenil residues in/on caneberry, subgroup 13-07A
at 0.10 ppm, and bushberry, subgroup 13-07B at 0.15 ppm.  A revised
Section F is required.

860.1520 Processed Food and Feed

Since there are no berry processed food items of regulatory concern, a
discussion of dichlobenil residues in processed commodities is not
germane to this action. 

860.1650 Submittal of Analytical Reference Standards

No analytical reference standards are available in the Agency’s
Pesticide Repository.  However, both dichlobenil and BAM are available
as reference standards in the commercial market place.

860.1850 & 860.1900 Confined and Field Accumulation in Rotational Crops

The requested berry commodities are perennial crops; therefore a
discussion of residues in rotational crops is not germane to this
action.

860.1550 Proposed Tolerances

Dichlobenil residues of concern are parent dichlobenil and the
metabolite BAM (2,6-dichlorobenzamide) as stated in 40 CFR §180.231. 
There are no international harmonization issues associated with this
action.

Table 5.  Tolerance Summary for Dichlobenil



Commodity	

Proposed Tolerance (ppm)	

Recommended Tolerance (ppm)	

Comments (correct commodity definition)

Rhubarb*	0.15	0.06

	Caneberry, Subgroup 13A	0.1	0.10	Caneberry, Subgroup 13-07A

Wild raspberry	0.1	NA	Member of new Caneberry, Subgroup 13-07A.

Bushberry, Subgroup 13B	0.15	0.15	Bushberry, Subgroup 13-07B.

Aronia berry	0.15	NA	Member of new Bushberry, Subgroup 13-07B.

Blueberry, lowbush	0.15	NA 	

Member of new Bushberry, Subgroup 13-07B.

Buffalo currant	0.15	NA

	Chilian guava	0.15	NA

	European barberry	0.15	NA

	Highbush cranberry	0.15	NA

	Honeysuckle	0.15	NA

	Jostaberry	0.15	NA

	Juneberry	0.15	NA

	Lingonberry	0.15	NA

	Native currant	0.15	NA

	Salal	0.15	NA

	Sea buckthorn	0.15	NA

	* Recommended in DP Num: 315266, W. Cutchin, 22/FEB/2006.



INTERNATIONAL RESIDUE LIMIT STATUS



Chemical Name: 2,6- dichlorobenzonitrile	

Common Name:  Dichlobenil	

√ Proposed tolerance

( Reevaluated tolerance

( Other	

Date: 01/22/2008



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:  2E6398, 7E7320

DP Num:  341453, 315266

Other Identifier:  



Residue definition (step 8/CXL): N/A	

Reviewer/Branch: D. Rate

	

Proposed Residue definition:  Combined residues of dichlobenil and
metabolite 2,6-dichlorobenzamide (BAM)



Crop (s)	

MRL (mg/kg)	

Crop(s) 	

Tolerance (ppm)





Rhubarb	0.06



Caneberry, Subgroup 13A	0.1



Wild raspberry	0.1



Bushberry, Subgroup 13B	0.15



Aronia berry	0.15



Buffalo currant	0.15



Chilian guava	0.15



European barberry	0.15



Highbush cranberry	0.15



Honeysuckle	0.15



Jostaberry	0.15



Juneberry	0.15



Lingonberry	0.15



Native currant	0.15



Salal	0.15



Sea buckthorn	0.15



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Residue definition: N/A	

Residue definition: N/A



Crop(s)	

MRL (mg/kg)	

Crop(s)	

MRL (mg/kg)



	

	

	





Notes/Special Instructions:  S. Funk, 01/30/2008.



Dichlobenil	Summary of Analytical Chemistry and Residue Data	DP Num:
349398

 PAGE  8  of  NUMPAGES  8 

