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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND

 POLLUTION PREVENTION

MEMORANDUM

Date: 17-December-2013

Subject: Addendum to DP Barcodes D404359 and D411652: Linuron. Petition for the 

Establishment of Permanent Tolerances and Registration for Use on Coriander, Dill, 

Parsley, Pea (Dry), and Horseradish; and Submission of Residue Analytical Methods 

of Plants and Animal Matrices. Summary of Analytical Chemistry and Residue Data. 

PC Code: 035506 DP Barcodes: D416651

Decision No.: 469722 Registration No.: 61842-23

Petition No.: 2E8083 Regulatory Action: Section 3

Risk Assessment Type: NA Case No.: NA

TXR No.: NA CAS No.: 330-55-2

MRID No.: NA 40 CFR:§180.184

From: Nancy Tsaur, Chemist

Risk Assessment Branch 3 (RAB3)

Health Effects Division (7509P)

Through: Christine Olinger, Branch Chief

Risk Assessment Branch 3 (RAB3)

Health Effects Division (7509P)

To: Kristin Rury, Biologist, Risk Assessor

Risk Assessment Branch 3 (RAB3)

Health Effects Division (7509P)

and

Laura Nollen/Barbara Madden, RM05

Risk Integration Minor Use and Emergency Response Branch (RIMUERB)

Registration Division (7505P)

This document serves as an addendum to the original residue data review from August 14, 2013. 

The addendum updates corrected values for the recommended tolerances, tolerance derivation, 

and input/output values for the Organization for Economic Cooperation and Development 

(OECD) tolerance calculation procedures.
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Table of Contents

1.0 Executive Summary............................................................................................................ 3

2.0 Regulatory Recommendations............................................................................................ 3

2.1 Tolerance Considerations................................................................................................. 3

2.1.1 Recommended Tolerances........................................................................................ 3

2.1.2 Revisions to Petitioned-For Tolerances.................................................................... 4

2.1.3 International Harmonization ..................................................................................... 4

3.0 Residue Data: Crop Field Trials (860.1500).................................................................... 4

4.0 Tolerance Derivation .......................................................................................................... 5

Appendix A. OECD MRL Calculation Procedure Inputs/Outputs................................................ 8
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1.0 Executive Summary

The Interregional Research Project No. 4 (IR-4) has submitted a petition (PP#2E8083) for 

tolerances on coriander, dill, parsley, pea (dry), and horseradish; and has proposed to add these 

uses to the Tessenderlo Kerley label for Lorox® DF (EPA Reg. No. 61842-23). IR-4 has 

submitted crop field trials utilizing comparable formulations, all of which consist of 50% active 

ingredient (ai) in a dry flowable formulation. The residue chemistry database is adequate for 

tolerance assessment of the proposed uses.

2.0 Regulatory Recommendations

HED has examined the residue chemistry database for linuron and concluded that, provided a 

revised label and a revised Section F are submitted, there are no residue chemistry deficiencies 

that would preclude granting Section 3 registration for the requested crop commodity uses of 

linuron, or establishment of tolerances for residues of linuron. The specific tolerance 

recommendations are discussed in Section 2.1.1.

2.1 Tolerance Considerations

2.1.1 Recommended Tolerances

In addition to the recommended tolerances listed below in Table 1, the tolerance with regional 

registration under 40 CFR §180.184(c) for parsley, leaves (0.25 ppm) should be deleted.

Table 1. Tolerance Summary for Linuron.

Commodity Proposed 

Tolerance (ppm)

HED-Recommended 

Tolerance (ppm)

Commentsa

(OECD calculation 

DP404359 DP416651 adjustments to tolerances)

Cilantro, fresh leaves 3.0 1.5 3.0 Corrected OECD Calculation 

Procedure values

Cilantro, dried leaves 27 10 10 9X PF × HAFT of 1.055 ppm

Coriander, seed 0.01 0.05 0.01 LOQ of 0.01 ppm

Dillweed, fresh leaves 1.5 0.6 1.5 Corrected OECD Calculation 

Procedure values

Dillweed, dried leaves 7.1 3.0 5.0 9X PF × HAFT of 0.56 ppm

Dill, seed 0.3 0.5 0.5 5 × Mean of 0.09 ppm

Dill, oil 4.8 2.0 2.0 3.21 PF × HAFT of 0.56 ppm

Horseradish 0.05 0.05 0.05 LOQ of 0.05 ppm

Parsley, leaves 3.0 4.0 4.0 5 × Mean of 0.75 ppm

Parsley, dried leaves 8.3 3.0 9.0 9X PF × HAFT of 1.015 ppm

Pea, dry, seed 0.08 0.06 0.09 Corrected OECD Calculation 

Procedure values

a OECD = Organization for Economic Cooperation and Development. PF = processing factor. HAFT = highest 

average field trial. LOQ = limit of quantitation.
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2.1.2 Revisions to Petitioned-For Tolerances

All of the petitioned-for tolerance levels (except for fresh cilantro, coriander seed, fresh dillweed, 

and horseradish) must be revised to reflect the tolerance levels recommended by HED for linuron 

(3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea) and its metabolites convertible to 3,4-

dichloroaniline (DCA), calculated as linuron, in or on the commodities.

The Organization for Economic Cooperation and Development (OECD) calculation procedures

were used to calculate the tolerance levels for the following three commodities: cilantro, fresh 

leaves; dillweed, fresh leaves; and pea, dry, seed. Based on the OECD calculations, the tolerance 

level for pea, dry, seed should be increased.

Instead of using the OECD calculator due to a limited number of field trials, the formula of 5X 

the mean was used to establish tolerance levels for the following two commodities: dill, seed; 

and parsley, leaves. Based on this calculation method, both tolerance levels should be increased.

For the dried herbs (cilantro, dillweed, and parsley), the formula of the highest average field trial 

(HAFT) multiplied by the herb processing (drying) factor of 9X was used to calculate the 

recommended tolerance levels (the processing factor was derived from dividing the average 

dried cilantro commodity residue by the average fresh cilantro residue). Based on this 

calculation method, the tolerance levels for dried cilantro and dillweed should be decreased, and 

the tolerance for dried parsley should be increased.

For dill oil, the formula of the HAFT multiplied by the herb processing (oil extraction) factor of 

3.21X was used to calculate the recommended tolerance level (the processing factor was derived 

from dividing the average dill oil commodity residue by the average fresh dill residue). Based 

on this calculation method, the dill oil tolerance should be decreased.

2.1.3 International Harmonization

There are no established maximum residue limits (MRLs) for linuron in Codex for any

agricultural commodity. Furthermore, no Canadian or Mexican MRLs have been established for 

linuron. Therefore, there are no harmonization issues that exist with respect to U.S. tolerances.

3.0 Residue Data: Crop Field Trials (860.1500)

DER References: MRIDs 48928501, 48928502, 48928503, 48928504, 45633501, 45633502

All of the field trials were conducted according to the proposed label use directions in the 

appropriate representative geographical regions. Adjuvants were not used in any of the field 

trials. Residue decline studies were not conducted.

The available residue data, as shown in Table 2, are acceptable and reflect the proposed use 

patterns provided in Section B. The number and geographical locations of the field trials are in 

accordance with the test guidelines. Furthermore, an acceptable method was used for residue 

quantitation and the data are supported by adequate storage stability data.
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Table 2. Summary of Residues from Field Trials with Linuron.

Crop Matrix Analyteb Applic. Rate

(lb ai/acre)

PHI 

(days) n

Residuesa,b (ppm)

Min. Max. HAFT Mean SD

Coriander: Proposed Use = 2.0 lb ai/acre total application rate, 21-day PHI.

Fresh Leaves and Stems

Linuron 1.997 - 2.118

19-21 8 0.08 1.14 1.055 0.65 0.4

Dried Leaves and Stems 19 1 8.5 NA NA NA

Seed 155 2 <0.01 NA NA NA

Dill: Proposed Use = 2.0 lb ai/acre total application rate, 21-day PHI.

Fresh Leaves and Stems

Linuron 2.005 - 2.026

20 - 22 7 0.3 0.67 0.56 0.48 0.1

Dried Leaves and Stems 22 2 1.8 3.5 2.65 2.65 1.2

Seed 59 - 85 4 0.06 0.12 0.12 0.09 0.03

Oil 48 1 1.8 NA NA NA

Parsley: Proposed Use = 1.5 lb ai/acre total application rate, 30-day PHI.

Fresh Leaves and Stems Linuron 1.510 29 - 32 4 0.43 1.3 1.02 0.75 0.387

Dried Leaves and Stems 1.511 29 1 2.8 2.8 2.8 NA

Pea (Dry): Proposed Use = 1.0 lb ai/acre total application rate, unspecified PHI.

Pea (Dry) 0.972 - 1.015 65 - 92 12 <0.01 0.052 0.051 0.014 0.018

Horseradish: Proposed Use = 1.5 lb ai/acre total application rate, unspecified PHI.

Roots Linuron 1.43 – 1.55 77 - 100 3 <0.05 NA NA NA

a HAFT = highest average field trial. SD = Standard Deviation. For samples with no detectable residues (< 0.01 ppm) 

the LOQ value (0.01 ppm) was used to calculate the Mean and Standard Deviation.

b Residues were converted to and measured as 3,4-DCA. Values were converted to linuron equivalents.

4.0 Tolerance Derivation

As shown in Appendix A, the statistical goal of the OECD calculation procedures is to produce 

an MRL/tolerance proposal in the region of the 95th percentile of the underlying residues 

distribution. 

Coriander (MRID 48928501)

The dataset used to establish a tolerance for linuron consisted of field trial data on coriander 

representing two applications within -5% to +10% of 1 lb ai/A per application for a total of 2 lb 

ai/A per crop, and 19- to 21-day PHIs. The average residue values used to calculate the 

tolerance are provided below. Combined residues of linuron and its metabolites hydrolyzed to 

3,4-DCA were quantifiable (LOQ = 0.01 ppm) in/on samples. 

For fresh coriander, data from four field trials were used in the OECD tolerance calculation 

procedures for fresh coriander, resulting in a recommended tolerance of 3.0 ppm. (Note that the 

correct commodity term is cilantro, fresh leaves).

For dried coriander, a 9X concentration factor was derived from a single residue field trial 

where the coriander was dried (calculated by dividing the average dried cilantro commodity

residue by the average fresh cilantro residue), resulting in a recommended tolerance of 10 ppm

(calculated by: HAFT of fresh coriander residue 1.055 ppm × processing factor 9). (Note that 

the correct commodity term is cilantro, dried leaves).

For coriander seed, no detectable residues were found, resulting in a recommended tolerance of 

0.01 ppm (at the LOQ 0.01 ppm).
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Dill (MRID 48928502)

The dataset used to establish a tolerance for linuron consisted of field trial data on dill 

representing two applications within -5% to +10% of 1 lb ai/A per application for a total of 2 lb 

ai/A per crop, and 20- to 22- day PHIs. The average residue values used to calculate the 

tolerance are provided below. Combined residues of linuron and its metabolites hydrolyzed 

to3,4-DCA were quantifiable (LOQ = 0.01 ppm) in/on all samples. 

For fresh dill, data from three field trials were used in the OECD tolerance calculation 

procedures for fresh dill, resulting in a recommended tolerance of 1.5 ppm.

For dried dill, the 9X processing factor derived for coriander was used, resulting in a

recommended tolerance of 5.0 ppm (calculated by: HAFT of fresh dill 0.56 ppm × concentration 

factor 9). Since all fresh herbs contain comparable water content, the processing factor for dried 

herbs should be the same. By using the highest processing factor value derived from coriander 

(at 9X), HED is being sufficiently protective that the residues of linuron are not underestimated 

in dried herb commodities.

For dill seed, the OECD calculation procedures could not be used because there were only two 

field trials, thus resulting in a recommended tolerance of 0.5 ppm (calculated by: 5 × mean dill 

oil residue 0.09 ppm).

For dill oil, a 3.21X concentration factor was derived from a single residue field trial (calculated 

by dividing the average dill oil commodity residue by the average fresh dill residue), resulting in 

a recommended tolerance of 2.0 ppm (calculated by: HAFT of fresh dill 0.56 ppm × 

concentration factor 3.21).

Horseradish (MRIDs 45633501 and 45633502)

The dataset used to establish a tolerance for linuron consisted of field trial data on horseradish 

representing one application within -5% to +10% of 1.5 lb ai/A per application, and 76- to 100-

day PHIs. The average residue values used to calculate the tolerance are provided below. An 

LOQ was not statistically calculated in this study, but the Lowest Limit of Method Validation 

(LLMV) was determined to be 0.05 ppm. 

For horseradish, data from three field trials indicated that detectable residues were not found. 

Thus, data consisting of <LOQ values from three field trials were used in the OECD tolerance 

calculation procedures, resulting in a recommended tolerance equivalent to the LOQ of 0.05 

ppm.

Parsley (MRID 48928503)

The dataset used to establish a tolerance for linuron consisted of field trial data on parsley

representing one application of 1.51 lb ai/A and 29- to 32-day PHIs. The average residue values 

used to calculate the tolerance are provided below. Although the LOQ were not statistically

calculated in this study, all combined residues of linuron and its metabolites hydrolyzed to 3,4-

DCA were quantifiable in/on samples above the LLMV (0.05 ppm).
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For fresh parsley, the OECD calculation procedures could not be used because there were only 

two field trials, thus resulting in a recommended tolerance of 4.0 ppm (calculated by: 5 × mean 

fresh parsley residue 0.75 ppm).

For dried parsley, the 9X processing factor derived for coriander was used, resulting in a

recommended tolerance of 9.0 ppm (calculated by: HAFT of fresh parsley 1.015 ppm × 

concentration factor 9). Since all fresh herbs contain comparable water content, the processing 

factor for dried herbs should be the same. By using the highest processing factor value derived 

from coriander (at 9X), HED is being sufficiently protective that the residues of linuron are not 

underestimated in dried herb commodities.

Pea (Dry) (MRID 48928504)

The dataset used to establish a tolerance for linuron consisted of field trial data on peas (dry)

representing one application within -5% to +10% of 1 lb ai/A, and 65- to 92-day PHIs. The 

average residue values used to calculate the tolerance are provided below. Combined residues of 

linuron and its metabolites hydrolyzed to3,4-DCA were quantifiable in/on two of six trials. 

For dry peas, data from all six field trials were used in the OECD calculation procedures, 

resulting in a recommended tolerance of 0.09 ppm.
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Appendix A. OECD MRL Calculation Procedure Inputs/Outputs

Coriander (MRID 48928501) (Cilantro, Fresh)

2.0 lb ai/A; 19-21 day PHIs

Residues (mg/kg)

0.940 1

0.086 1

0.525 1

1.055 1

Compound Linuron

Crop Fresh Coriander

Region / Country CA/OR/TN/TX

GAP

Total number of data (n) 4

Percentage of censored data 0%

Number of non-censored data 4

Lowest residue 0.086

Highest residue 1.055

Median residue 0.733

Mean 0.651

Standard deviation (SD) 0.441

Correction factor for censoring 

(CF) 1.000

Proposed MRL estimate

- Highest residue 1.055

- Mean + 4 SD 2.414

- CF x 3 Mean 1.954

Unrounded MRL 2.414

Rounded MRL 3

High uncertainty of MRL estimate due to small dataset.
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Dill (MRID 48928502)

2.0 lb ai/A; 20-22 day PHIs

Residues (mg/kg)

0.335 1

0.490 1

0.560 1

Compound Linuron

Crop Fresh Dill

Region / Country CA/FL/WA

GAP

Total number of data (n) 3

Percentage of censored data 0%

Number of non-censored data 3

Lowest residue 0.335

Highest residue 0.560

Median residue 0.490

Mean 0.462

Standard deviation (SD) 0.115

Correction factor for censoring 

(CF) 1.000

Proposed MRL estimate

- Highest residue 0.560

- Mean + 4 SD 0.922

- CF x 3 Mean 1.385

Unrounded MRL 1.385

Rounded MRL 1.5

High uncertainty of MRL estimate due to small dataset.
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Pea (Dry) (MRID 48928504)

1.0 lb ai/A; 65-92 day PHIs

Residues (mg/kg)

0.015 1

0.010 *

0.010 *

0.010 *

0.051 1

0.010 *

Compound Linuron

Crop Pea (Dry)

Region / Country ID/ND/WA

GAP

Total number of data (n) 6

Percentage of censored data 67%

Number of non-censored data 2

Lowest residue 0.010

Highest residue 0.051

Median residue 0.010

Mean 0.018

Standard deviation (SD) 0.016

Correction factor for censoring 

(CF) 0.556

Proposed MRL estimate

- Highest residue 0.051

- Mean + 4 SD 0.083

- CF x 3 Mean 0.029

Unrounded MRL 0.083

Rounded MRL 0.09

High uncertainty of MRL estimate due to small dataset and 

high level of censoring.
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Horseradish (MRIDs 45633501 and 45633502)

1.5 lb ai/A; 76-100 day PHIs

Residues (mg/kg)

<0.05 *

<0.05 *

<0.05 *

Compound Linuron

Crop Horseradish

Region / Country MD/WI/NJ

GAP

Total number of data (n) 3

Percentage of censored data 100%

Number of non-censored data 0

Lowest residue 0.050

Highest residue 0.050

Median residue 0.050

Mean 0.050

Standard deviation (SD) 0.000

Correction factor for censoring 

(CF) 0.333

Proposed MRL estimate

- Highest residue 0.050

- Mean + 4 SD 0.050

- CF x 3 Mean 0.050

Unrounded MRL 0.050

Rounded MRL 0.05

High uncertainty of MRL estimate due to small dataset and 

high level of censoring.