OFFICE OF

PREVENTION, PESTICIDES, AND

TOXIC SUBSTANCES

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

MEMORANDUM

DATE: 15 NOV 2005

SUBJECT: Petition Number: 4F6950 -- Human Health Risk Assessment for DichlormidRequest for Establishing Permanent Tolerances for Dichlormid on Corn.

DP Barcode: D321928 Decision #: 357395

PC Code: 900497 Class: Herbicide Safener

Trade Names: SurpassTM EC

Keystone8TM

TopNotchTM

SurpassTM 20G

FulTimeTM

SurpassTM 7 E

KeystoneTM LA

EPA Reg.

Nos.:

62719-367

62719-368

62719-369

62719-370

62719-371

62719-372

62719-373

TO: Keri Grinstead/Dan Rosenblatt

Inerts Team, MUIER Branch

Registration Division (7505C)

FROM: Breann Hanson, Biologist

Technical Review Branch (TRB)

Registration Division(RD) (7505C)

THRU: William Cutchin, Chemist 

Technical Review Branch

Registration Division(RD) (7505C)

Dow AgroSciences, LLC is requesting that current time-limited tolerances of the herbicide

safener dichlormid, N,N-diallyl dichloroacetamide, be converted to permanent tolerances for use

in/on field corn raw agricultural commodities (RACs). Dichlormid is an inert ingredient

(safener) in pesticide formulations and may be applied to corn fields before and after corn plants

emerge from the soil. This is the only registered use. Products containing dichlormid are

conditionally registered in the U.S. under the trade names SurpassTM EC, Keystone8TM,

TopNotchTM, SurpassTM 20G, FulTime, SurpassTM 7 E, and KeystoneTM LA.

This risk assessment incorporates all current, pending, and proposed tolerances for dichlormid as

of November 8, 2005. 
2

TABLE OF CONTENTS
3

1.0. EXECUTIVE SUMMARY .................................................5

2.0. PHYSICAL/CHEMICAL PROPERTIES CHARACTERIZATION ..................9

2.1. Identification of Active Ingredient ........................................9

2.2. Structural Formulae of Dichlormid .......................................9

2.3. Physical and Chemical Properties ........................................9

3.0. HAZARD CHARACTERIZATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.1. Hazard Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2. FQPA Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.2.1. Cumulative Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.2.2. Endocrine Disruption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.3. Dose Response Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.0. EXPOSURE ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.1. Summary of Directions for Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4.2. Dietary Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.2.1. Food Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4.2.1.a. Nature of the Residue - Plants and Livestock . . . . . . . . . . . . . . . . . 20

4.2.1.b. Residue Analytical Method - Plants and Livestock . . . . . . . . . . . . . 23

4.2.1.c. Multiresidue Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.2.1.d. Storage Stability Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.2.1.e. Crop Field Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.2.1.f. Processed Food/Feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2.1.g Water, Fish, and Irrigated Crops . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2.1.h Food Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2.1.i. Meat, Milk, Poultry and Eggs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

4.2.1.j. Confined Accumulation in Rotational Crops . . . . . . . . . . . . . . . . . . 27

4.2.1.k. Field Accumulation in Rotational Crops . . . . . . . . . . . . . . . . . . . . . 29

4.2.1.l. Proposed Tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.1.l. International Harmonization of Tolerances . . . . . . . . . . . . . . . . . . . 29

4.2.2. Dietary Exposure and Risk Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.2.a. Acute Dietary Exposure Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.2.b. Chronic Dietary Exposure Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.2.c. Cancer Dietary Exposure Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.3. Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.3.a. Surface and Ground Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.3.b. Drinking Water Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.3. Occupational/Residential Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.3.1. Summary of Use Patterns and Formulations . . . . . . . . . . . . . . . . . . . . . . . . 33

4.3.2. Occupational Exposure Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.3.2.a. Worker Post-Application Exposure Assumptions and Assessment . 34

4.3.2.b. REI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3.2.c. Incident Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4

4.3.3. Residential Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.4. Non-Occupational Off-Target Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.0. AGGREGATE RISK ASSESSMENTS AND RISK CHARACTERIZATION . . . . . . . . 35

5.1. Acute Aggregate Risk (food + water) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.2. Short + Intermediate-Term Aggregate Risk (food + water + residential) . . . . . . . . . 36

5.3. Chronic Aggregate Risk (food + water) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

6.0. DATA GAPS/LABEL CHANGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6.1. Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6.2. Toxicology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6.3. Occupational/Residential Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.0. ATTACHMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
5

1.0. EXECUTIVE SUMMARY

General Background

Dichlormid is a herbicide safener used in pesticide formulations with the active ingredient,

acetochlor, for the control of grass and broadleaf weeds. Current time-limited tolerances that

Health Effects Division (HED) supports for the use of the herbicide safener, dichlormid, are the

following:

Commodity: ppm 

Corn, field, forage............................. 0.05 

Corn, field, grain.............................. 0.05 

Corn, field, stover............................. 0.05 

Corn, pop, grain................................ 0.05 

Corn, pop, stover............................... 0.05 

Corn, sweet, forage............................. 0.05 

Corn, sweet, grain.............................. 0.05 

Corn, sweet, stover............................. 0.05 

These tolerances are set to expire at the end of the 2005 calendar year. There are no new

tolerances requested in this petition, only the request for the conversion of time-limited

tolerances to permanent tolerances. 

The most recent human health risk assessment for dichlormid was conducted by Registration

Action Branch 1 (RAB1) (PP# 6F3344, DP Barcode: D248305, S. Chun, 09/21/1999) for an

extension of the dichlormid time-limited tolerance use on corn.

Hazard Assessment

In acute toxicity studies, dichlormid exhibits low to moderate toxicity, depending on the route of

exposure. Dichlormid is of moderate toxicity by the oral and dermal routes (III) and low toxicity

by inhalation (IV) in rats. Dichlormid technical is relatively non-irritating to the eye (III) and

causes moderate dermal irritation (toxicity category II) in rabbits. Dichlormid is a mild dermal

sensitizer. 

The toxicology database provides no evidence of carcinogenetic effects based on a combined

chronic toxicity/carcinogenicity study in rats. No DNA synthesis could be induced in

Unscheduled DNA Synthesis studies performed with rats. Dichlormid is mutagenic into the

cytotoxic range based on an in vitro assay in mouse lymphoma cells.

Previously, the HIARC concluded that there is qualitative evidence of increased susceptibility

demonstrated following in utero exposure in the prenatal developmental toxicity study in rabbits,

since fetal effects observed (resorptions, decreased live fetuses per litter, and decreased fetal

body weight) are considered to be more severe than those observed in maternal animals
6

(increased alopecia, decreased body weight gain and food consumption). At this time the

toxicity database was incomplete - there were data gaps for the 2-generation reproduction study

in rats and acute and subchronic neurotoxicity studies. Based on this hazard assessment, with no

consideration of the exposure assessments, the HIARC recommended that the FQPA SF be

retained at 10x for enhanced sensitivity to infants and children since there is qualitative

evidence of increased susceptibility in the rabbit developmental study. Although the data gap

has since been addressed, metabolism studies are still needed to reassess reducing the FQPA SF.

For chronic dietary exposure only, an additional 3x UF was included in the previous dietary risk

assessment due to a data gap for the chronic toxicity study in dogs. Although this study has

since been submitted and reviewed, no determination can be made at this time as to the

appropriateness of the UF. For purposes of the dichlormid dietary risk assessment, the additional

3x UF has been included, but, it can be reevaluated at a later date for the next dichlormid action.

There are still outstanding data gaps for dichlormid including subchronic dermal and inhalation,

neurotoxicity and metabolism studies. Dermal absorption is by default 100% due to neither a

dermal absorption nor a dermal toxicity study (for extrapolation) being available. Chemistry

data that need to be submitted are noted in another TRB memo (DP Barcode: D318075 &

D357398, D. Rate, 09/14/2005).

Dose Response Assessment

The acute dietary endpoint is based on decreased body weight gain and food consumption, noted

in a developmental toxicity study in rats. The short- and intermediate-term incidental oral

endpoints are based on decreased body weight, food consumption, and feed efficiency. Chronic

dietary and long-term endpoints are based on skeletal muscle fiber degeneration and increased

severity and/or incidence of vacuolation of the adrenal cortex, noted in a Chronic Toxicity Study

in Dogs. 

Cancer

Dichlormid has not been classified by the Hazard Identification Assessment and Review

Committee (HIARC) or HED Cancer Assessment Review Committee (CARC) in terms of

potential for carcinogenicity. Therefore, no chronic (cancer) aggregate human health risk

assessment was completed with this action.

Residential Exposure

There are no existing or proposed residential uses for dichlormid.

Occupational Handler Exposure Assessment

The herbicide safener formulations are typically applied as pre-emergence soil or early

post-emergence foliar applications using broadcast ground equipment. The HIARC has
7

identified toxicological endpoints of concern for occupational exposure. Handler exposures

addressing mixer/loaders and applicators have been assessed using surrogate data available in

the Pesticide Handlers Exposure Database (PHED Ver 1.1) Surrogate Table. Since no

potentially significant post-application exposure is expected based on the use pattern, this

exposure assessment was not conducted. Short- and intermediate-term exposures are expected

for workers applying dichlormid. Based on use pattern, long-term exposure is not expected. All

occupational exposure scenarios yielded risk estimates below HED's level of concern for

dichlormid.

Margin of Exposure (MOE)

An MOE of 100 is adequate for occupational exposure risk assessment.

Occupational Post-Application

A post-application exposure assessment was not performed. Cultural activities associated with

the subject corn uses are likely to result in relatively low levels of dermal exposure. Field corn is

planted, cultivated, and harvested mechanically (website: Crop Profiles, USDA, Office of Pest

Management Policy and Pest Impact Assessment Program, updated 8/23/99). Therefore,

potential worker post-application exposures from a herbicide applied pre-emergent or in the

early post-emergent stage are expected to be minimal.

Dietary Risk Estimates

Acute and chronic dietary exposure analyses for dichlormid were performed using the Dietary

Exposure Evaluation Model (DEEM-FCID Version 2.02). Acute dietary risk estimates were

3.4% of the aPAD at the 95th percentile for the general U.S. population and 7.5% of the aPAD

for the highest exposure group, all infants (< 1 year old). Chronic dietary risk estimates were

6.1% of the cPAD for the general U.S. population and 15% of the cPAD for the highest exposure

group, children 3-5 years old. Neither the acute or chronic analyses exceed HED’s level of

concern (PP# 4F6950, DP Barcode: D321927, B. Hanson, 11/07/2005). 

Drinking Water

Drinking water level of comparison’s (DWLOCs) were calculated by TRB for acute and chronic

aggregate exposures to dichlormid. The Environmental Fate and Effects Division (EFED)

provided ground and surface water exposure estimates for the use of dichlormid on corn (DP

Barcode: D258095, A. Clem, 8/3/99). Surface water estimated environmental concentrations

(EEC) for both acute and chronic exposures were calculated to be 27.29 and 8.98, respectively. 

Acute drinking water concentrations in shallow ground water on highly vulnerable sites was

determined to be 0.046 ppb. Chronic concentrations are not expected to be higher than acute

values for ground water exposure.

For acute exposure, TRB calculated DWLOCs for the U.S. population and all infants (< 1 year
8

old) to be 338 ppb and 92 ppb, respectively. For chronic exposure, TRB calculated DWLOCs

for the U.S. population and children (3-5 years old) to be 56 and 15 ppb, respectively. The

maximum estimated concentrations of dichlormid in surface and ground water are less than

HED’s DWLOCs for dichlormid as a contribution to both acute and chronic aggregate

exposure.

Aggregate Exposure and Risk Assessment

Aggregate exposure risk assessments were performed for the following: acute aggregate

exposure (food + water) and chronic aggregate exposure (food + water). There are no residential

uses resulting in non-dietary exposure to infants and children at this time and so a short-

/intermediate-term aggregate risk assessment is not applicable for this dichlormid action. A

cancer aggregate risk assessment was not performed because neither the HIARC or HED CARC

have classified dichlormid in terms of potential for carcinogenicity.

Acute aggregate risk estimates are below HED's level of concern. The acute aggregate risk

assessment takes into account exposure estimates from dietary consumption of dichlormid (food

and drinking water). A Tier 1 acute dietary risk assessment was performed assuming tolerance

level residues, default processing factors for all commodities and 100% CT. For acute dietary

risk, HED’s level of concern is >100% aPAD. Acute dietary risk estimates were 3.4% of the

aPAD at the 95th percentile for the general U.S. population and 7.5% of the aPAD for the highest

exposure group, all infants (< 1 year old). The estimated acute dietary risk associated with the

use of dichlormid on corn RACs is below HED’s level of concern. Additional refinement by

incorporating %CT information may result in even lower exposure estimates.

For acute exposure, TRB calculated DWLOCs for the U.S. population and all infants (< 1 year

old) to be 338 ppb and 92 ppb, respectively. The maximum estimated concentrations of

dichlormid in surface, 27.29, and ground water, 0.046 ppb, are less than HED’s DWLOCs for

dichlormid as a contribution to acute aggregate exposure. Therefore, taking into account the

uses proposed in this action, TRB concludes with reasonable certainty that residues of

dichlormid in drinking water would not result in unacceptable levels of acute aggregate human

health risk at this time. 

A short + intermediate term aggregate risk assessment was not performed because there are

no residential uses for dichlormid.

Chronic aggregate risk estimates are below HED's level of concern. A chronic dietary

analysis was performed assuming tolerance level residues, default processing factors for all

commodities and 100% CT. Chronic dietary risk estimates were 6.1% of the cPAD for the

general U.S. population and 15% of the cPAD for the highest exposure group, children 3-5 years

old. The estimated chronic dietary risk associated with the use of dichlormid on corn RACs is

below HED’s level of concern. Additional refinement by incorporating %CT information may

result in even lower exposure estimates.
9

N

O

Cl

Cl

For chronic exposure, TRB calculated DWLOCs for the U.S. population and children (3-5 years

old) to be 56 and 15 ppb, respectively. The maximum estimated concentrations of dichlormid in

surface, 8.98, and ground water, 0.046 ppb, are less than HED’s DWLOCs for dichlormid as a

contribution to chronic aggregate exposure. Therefore, taking into account the uses proposed in

this action, TRB concludes with reasonable certainty that residues of dichlormid in drinking

water would not result in unacceptable levels of chronic aggregate human health risk at this time.

A cancer aggregate risk assessment was not performed because neither the HIARC or HED

CARC have classified dichlormid in terms of potential for carcinogenicity.

Recommendation for Tolerances and Registration

The toxicology and residue chemistry databases are adequate only to support extending the timelimited tolerances for residues of dichlormid. Tolerance expressions are set in terms of the

parent compound only. Because no other data exists on the associated metabolites, the

recommended time-limited tolerance is based only on the parent compound. For permanent

tolerances to be set for the use of dichlormid, residue chemistry deficiencies need to be

addressed (DP Barcode: D318075 & D357398, D. Rate, 09/14/2005).

2.0. PHYSICAL/CHEMICAL PROPERTIES CHARACTERIZATION

2.1. Identification of Active Ingredient

Chemical Name: N,N-diallyl-2,2-dichloroacetamide

Molecular Formula: C8H11Cl2NO

Common Name: Dichlormid

Trade Names: SurpassTMEC; KeystoneTM; TopNotchTM; SurpassTM20G;

FulTimeTM; SurpassTM 7 E; KeystoneTM LA

Chemical Type: Herbicide safener

PC Code Number: 900497

CAS Registry No.: 37764-25-3

2.2. Structural Formula of Dichlormid 

2.2. Physical and Chemical Properties

Density: 1.1963 g / mL

Vapor Pressure: 6.3 x 10-3

mm Hg at 25 /C

Water Solubility: 4388 mg / L at 25 /C

Octanol/Water Partition Coefficient: log Kow = 1.839
10

3.0. HAZARD CHARACTERIZATION

The toxicology database for dichlormid, for the purpose of establishing permanent tolerances for

field corn (forage, grain, stover), sweet corn (forage, grain, stover) and pop corn (grain, stover)

at 0.05 ppm, is not adequate. There are still outstanding data gaps for dichlormid including

subchronic dermal and inhalation, neurotoxicity and metabolism studies. Dermal absorption is

by default 100% due to neither a dermal absorption nor a dermal toxicity study (for

extrapolation) being available. Chemistry data that need to be submitted are noted in another

TRB memo (DP Barcode: D318075 & D357398, D. Rate, 09/14/2005).

There is high confidence in the quality of existing studies and the reliability of the toxicity

endpoints identified for use in this risk assessment. 

3.1. Hazard Profile

The acute toxicity of dichlormid technical is shown in Table1.

Table 1. Acute Toxicity Data on Dichlormid Technical.

Guideline No./ Study Type MRID No. Results Toxicity

Category

870.1100 Acute oral toxicity 

- rat

44606401 LD50 = male 2816/female

2146 mg/kg

III

870.1200 Acute dermal toxicity

- rat

44606402 LD50 = >2000 mg/kg III

870.1300 Acute inhalation toxicity 

- rat

44606403 LC50 = > 5.5 mg/L (male +

female)

IV

870.2400 Acute eye irritation

- rabbit

44606404 mild irritant IV

870.2500 Acute dermal irritation

- rabbit

42807902 severe irritant II

870.2600 Skin sensitization

- Guinea pig

44606405 mild sensitizer

In acute toxicity studies, dichlormid exhibits low to moderate toxicity, depending on the route of

exposure. Dichlormid is of moderate toxicity by the oral and dermal routes (III) and low toxicity

by inhalation (IV) in rats. Dichlormid technical is relatively non-irritating to the eye (III) and

causes moderate dermal irritation (toxicity category II) in rabbits. Dichlormid is a mild dermal

sensitizer. Dermal absorption is by default 100% due to neither a dermal absorption nor a

dermal toxicity study (for extrapolation) is available.

The toxicology database provides no evidence of carcinogenetic effects based on a combined

chronic toxicity/carcinogenicity study in rats. No DNA synthesis could be induced in
11

Unscheduled DNA Synthesis studies performed with rats. Dichlormid is mutagenic into the

cytotoxic range based on an in vitro assay in mouse lymphoma cells.

Previously, the HIARC concluded that there is qualitative evidence of increased susceptibility

demonstrated following in utero exposure in the prenatal developmental toxicity study in rabbits,

since fetal effects observed (resorptions, decreased live fetuses per litter, and decreased fetal

body weight) are considered to be more severe than those observed in maternal animals

(increased alopecia, decreased body weight gain and food consumption). At this time the

toxicity database was incomplete - there were data gaps for the 2-generation reproduction study

in rats and acute and subchronic neurotoxicity studies. Based on this hazard assessment, with no

consideration of the exposure assessments, the HIARC recommended that the FQPA SF be

retained at 10x for enhanced sensitivity to infants and children since there is qualitative

evidence of increased susceptibility in the rabbit developmental study. Although the data gap

has since been addressed, metabolism studies are still needed to reassess reducing the FQPA SF.

There are still outstanding data gaps for dichlormid including subchronic dermal and inhalation,

neurotoxicity and metabolism studies. Dermal absorption is by default 100% due to neither a

dermal absorption nor a dermal toxicity study (for extrapolation) being available. Chemistry

data that need to be submitted are noted in another TRB memo (DP Barcode: D318075 &

D357398, D. Rate, 09/14/2005).

Dichlormid has not been classified by the HIARC or HED CARC in terms of potential for

carcinogenicity. However, there is no evidence of a positive carcinogenic effect in the rat and

mouse carcinogenicity studies based on evaluation of the studies.

The toxicity profile of dichlormid is listed in Table 2.

Table 2. Toxicity Profile of Dichlormid Technical.

Guideline No./

Study Type

MRID No. (year)/

Classification /Doses

Results

DICHLORMID

Dichlormid

870.3100

90-Day oral toxicity

- rat

44606461 (1989)

Acceptable/guideline

0, 20, 200, 2000 ppm

M 0, 1.4, 14, 140

mg/kg/day

F 0, 1.6, 16, 150

mg/kg/day

NOAEL = 1.4 mg/kg/day (male), 1.6 mg/kg/day (female), 20

ppm

LOAEL = 14 mg/kg/day (male), 16 mg/kg/day (female), 200

ppm based on: minor decreased in body weight gains and

food efficiency in females and on increased liver weight and

a slightly increased (NS) incidence of liver lipidosis in

males.

Dichlormid

870.3150

90-Day oral toxicity

- dog

41419401 (1988)

Acceptable/guideline

capsule

0, 1, 5, 25, 50 mg/kg/day

NOAEL = 5 mg/kg/day (male, female)

LOAEL = 25 mg/kg/day (male/female) based on: decreased

body weight gains, hematological and clinical chemistry

alternations, liver toxicity and voluntary muscle pathological

changes.
Table 2. Toxicity Profile of Dichlormid Technical.

Guideline No./

Study Type

MRID No. (year)/

Classification /Doses

Results

12

Dichlormid

870.3465

Inhalation - 14 week

- rat

00155678 (1983)

Acceptable/guideline

0, 2, 19.9, 192.5

mg/L/day

NOAEL = 2 mg/L/day (male, female)

LOAEL = 19.9 mgL/day (male/female) based on: clinical

signs, gross pathology, opthamology, liver and kidney

weights and non-neoplastic histology.

Dichlormid

870.3700

Develpmental

Toxicity Study

- rat

44606408 (1989)

Acceptable/guideline

0, 10, 40, 160 mg/kg/day

Maternal NOAEL = 10 mg/kg/day

Maternal LOAEL = 40 mg/kg/day based on: decreased mean

absolute body weights, body weight gains, and food

consumption.

Developmental NOAEL = 40 mg/kg/day

Developmental LOAEL = 160 mg/kg/day based on:

marginal increased in skeletal anomalies. 

Dichlormid

870.3700

Develpmental

Toxicity Study

- rabbit

44606407 (1989)

Acceptable/guideline

0, 5, 30, 180 mg/kg/day

Maternal NOAEL = 30 mg/kg/day

Maternal LOAEL = 180 mg/kg/day based on: increased

incidence of alopecia and decreased mean maternal body

weight gains and food consumption.

Developmental NOAEL = 30 mg/kg/day

Developmental LOAEL = 180 mg/kg/day based on:

increases in post-implantation loss accompanied by an

increase number of resorptions/doe (both early and late

resorptions), decreased number of live/fetuses/litter, slightly

decreased mean fetal body weights. 

Dichlormid

870.3800

Reproduction and

fertility effects

- rat

46353801 (2000)

Acceptable/guideline

0, 15, 75, 500 ppm

M0 0, 1.5, 7.4, 48.5

mg/kg/day

M1 0, 1.8, 8.9, 59.4

mg/kg/day

F0 0,1.6, 8.0, 52.1

mg/kg/day

F1 0, 1.9, 9.4, 63.0

mg/kg/day

Parental/Systemic NOAEL = 7.4 mg/kg/day (male), 8.0

mg/kg/day (female), 75 ppm

LOAEL = 48.5 mg/kg/day (male), 52.1 mg/kg/day (female),

500 ppm based on: minimal increased liver weight, minimal

decreased weight gain, minimal decreased in food

consumption.

Reproductive NOAEL = 48.5 mg/kg/day (male),

52.1mg/kg/day (female), >500 ppm

LOAEL = cannot be determined

Offspring NOAEL = 7.4 mg/kg/day (male), 8.0 mg/kg/day

(female), 75 ppm

LOAEL = 48.5 mg/kg/day (male), 52.1 (female), 500 ppm

based on: increased liver weights.

Dichlormid

870.4200

Carcinogenicity -

mouse

44529401 (1998)

Acceptable/guidline

0, 10, 50, 500 ppm

M 0, 1.4, 7.0, 70.7

mg/kg/day

F 0, 18., 9.2, 92.4

mg/kg/day

NOAEL = 7.0 mg/kg/day (male), 9.2 mg/kg/day (female), 50

ppm

LOAEL = 70.7 mg/kg/day (male), 92.4 mg/kg/day (female),

500ppm based on changes in reproductive organs and kidney

changes in males
Table 2. Toxicity Profile of Dichlormid Technical.

Guideline No./

Study Type

MRID No. (year)/

Classification /Doses

Results

13

Dichlormid

870.4300

Feeding/

Carcinogenicity - 

rat

44529402, 44751801

(1998)

Acceptable/guideline

0, 20, 100, 500 ppm

M 0, 1.3, 6.5, 32.8

mg/kg/day

F 0, 1.5, 7.5, 37.1, 

mg/kg/day

NOAEL = 6.5 mg/kg/day (male), 7.5 mg/kg/day (female),

100 ppm

LOAEL = 32.8 mg/kg/day (male), 37.1 mg/kg/day (female),

500 ppm based on decreased BWG, decreased FE, increased

liver weight, and liver histopath.

No evidence of carcinogenicity.

Gene Mutation

Dichlormid

870.5100

Salmonella

typhimurium and

Escherichia coli

41561404 (1987)

Acceptable/guideline

In two independent experiments, dichlormid (97.2% a.i.)

was not mutagenic in 4 strains of S. typhimurium at

concentrations up to 3000 :g/plate in the presence or

absence of S9 activation.

Gene Mutation

Dichlormid

870.5300

In vitro assay in

mammalian

cells/mouse

lymphoma cells 

41561405 (1997)

Acceptable/guideline

In two independent experiments, R-25788 (97.2% a.i.) is

mutagenic in L5178Y mouse lymphoma cells both with and

without S9 activation at doses the extend into the cytotoxic

range. 

Cytogenetics 

Dichlormid

870.5375

in vitro/human

lymphocytes

41561407 (1989)

Acceptable/guideline

The high dose of 1200 :g/ml induced a => 50% decrease in

the mitotic index with or without S9 activation. There was

no evidence of a clastogenic effect at nay non-activated or

S9- activated dose.

Cytogenetics 

Dichlormid

870.5395

In vivo mouse

micronucleus assay

41561403 (1997)

Acceptable/guideline

There was no evidence of a clastogenic or aneugenic effect

at any R-25788 dose or at any harvest time.

Cytogenetics 

Dichlormid

870.5550

Unscheduled DNA

Synthesis 

- rat

44606409 (1988)

Acceptable/guideline

There was no consistent, reproducible evidence that

unscheduled DNA synthesis was induced.

Cytogenetics 

Dichlormid

870.5550

Unscheduled DNA

Synthesis 

- rat

41561408 (1989)

Acceptable/guideline

There was no evidence that dichlormid at the selected doses

increased the frequency of UDS in treated hepatocytes at

either the 2 or 16 hour sacrifice interval.
Table 2. Toxicity Profile of Dichlormid Technical.

Guideline No./

Study Type

MRID No. (year)/

Classification /Doses

Results

14

Dichlormid

870.7600

Dermal penetration

NA 100% by default

3.2. FQPA Considerations

Previously, the HIARC concluded that there is qualitative evidence of increased susceptibility

demonstrated following in utero exposure in the prenatal developmental toxicity study in rabbits,

since fetal effects observed (resorptions, decreased live fetuses per litter, and decreased fetal

body weight) are considered to be more severe than those observed in maternal animals

(increased alopecia, decreased body weight gain and food consumption). At this time the

toxicity database was incomplete - there were data gaps for the 2-generation reproduction study

in rats and acute and subchronic neurotoxicity studies. Based on this hazard assessment, with no

consideration of the exposure assessments, the HIARC recommended that the FQPA SF be

retained at 10x for enhanced sensitivity to infants and children since there is qualitative

evidence of increased susceptibility in the rabbit developmental study. Although the data gap

has since been addressed, metabolism studies are still needed to reassess reducing the FQPA SF.

3.2.1. Cumulative Risk

EPA does not have, at this time, available data to determine whether dichlormid has a common

mechanism of toxicity with other substances or how to include this pesticide in a cumulative risk

assessment. For the purposes of this tolerance action, therefore, EPA has not assumed that

dichlormid has a common mechanism of toxicity with other substances. 

On this basis, the petitioner must submit, upon EPA’s request and according to a schedule

determined by the Agency, such information as the Agency directs to be submitted in order to

evaluate issues related to whether dichlormid shares a common mechanism of toxicity with any

other substance and, if so, whether any tolerances for dichlormid need to be modified or revoked.

3.2.2. Endocrine Disruption

EPA is required under the Federal Food Drug and Cosmetic Act (FFDCA), as amended by

FQPA, to develop a screening program to determine whether certain substances (including all

pesticide active and other ingredients) "may have an effect in humans that is similar to an effect

produced by a naturally occurring estrogen, or other such endocrine effects as the Administrator

may designate." Following the recommendations of its Endocrine Disruptor Screening and

Testing Advisory Committee (EDSTAC), EPA determined that there was scientific bases for

including, as part of the program, the androgen and thyroid hormone systems, in addition to the

estrogen hormone system. EPA also adopted EDSTAC’s recommendation that the Program

include evaluations of potential effects in wildlife. For pesticide chemicals, EPA will use FIFRA
15

and, to the extent that effects in wildlife may help determine whether a substance may have an

effect in humans, FFDCA authority to require the wildlife evaluations. As the science develops

and resources allow, screening of additional hormone systems may be added to the Endocrine

Disruptor Screening Program (EDSP).

When the appropriate screening and/or testing protocols being considered under the Agency’s

EDSP have been developed, dichlormid may be subjected to additional screening and/or testing

to better characterize effects related to endocrine disruption.

3.3. Dose Response Assessment

The doses and toxicological endpoints selected for various exposure scenarios are summarized in

Table 3.

Table 3. Summary of Toxicological Dose and Endpoints for Dichlormid Use in Human Risk Assessment 1.

Exposure

Scenario

(Fipronil)

Dose Used in

Risk

Assessment,

UF

FQPA SF and

Endpoint for Risk

Assessment

Study and Toxicological Effects

Acute Dietary

all populations

including infants

and children

NOAEL= 10

mg/kg

UF = 100

Acute RfD =

0.10 mg/kg/day

FQPA SF = 10

aPAD = acute RfD

 FQPA SF

= 0.010 mg/kg/day

Developmental Toxicity Study - rat

Maternal LOAEL = 40 mg/kg/day based on

decreased body weight gain and food

consumption (most significant on days 7-10

of dosing)

Chronic Dietary

all populations

NOAEL= 5

mg/kg/day

UF = 300

Chronic RfD =

0.017 mg/kg/day

FQPA SF = 10

cPAD = chr RfD

 FQPA SF

= 0.0017 mg/kg/d

90-Day oral toxicity - dog

LOAEL = 25 mg/kg/day (male/female)

based on: decreased body weight gains,

hematological and clinical chemistry

alternations, liver toxicity and voluntary

muscle pathological changes.

Short-Term

Dermal

Oral NOAEL =

10.0

MOE = 100 Developmental toxicity Study - rats

Maternal LOAEL = 40 mg/kg/day based on

decreased body weight gain and food

consumption (most significant on days 7-10

of dosing). This dose/endpoint/study was

used for deriving the aRfD. Dermal

toxicity study is not available. 100%

dermal absorption factor should be used for

this risk assessment.
Table 3. Summary of Toxicological Dose and Endpoints for Dichlormid Use in Human Risk Assessment 1.

Exposure

Scenario

(Fipronil)

Dose Used in

Risk

Assessment,

UF

FQPA SF and

Endpoint for Risk

Assessment

Study and Toxicological Effects

16

Intermediate- and

Long-Term 

(Dermal)

Oral NOAEL = 

6.5 

MOE = 100 2-year study - rat

LOAEL = 32.8 mg/kg/day (%) based on

liver clinical pathology/histopathology and

increased liver weight.

This dose/endpoint/study was used for

deriving the cRfD. 100% dermal

absorption factor should be used for this

risk assessment.

Inhalation

(All Durations)

2 :g/L 14-week inhalation study 

LOAEL = 19.9 :g/L based on clinical

signs, increased liver and kidney weights,

gross pathology and non-neoplastic

histopathology. The route of exposure in

this study is appropriate for this risk

assessment.

Cancer NOAEL = 6.5 LOAEL = 32.8

mg/kg/day based on

decreased BWG,

decreased FE,

increased liver weight,

and liver histopath.

No evidence of

carcinogenicity.

Feeding/

Carcinogenicity Study in rats

1

 UF = uncertainty factor, FQPA SF = FQPA Safety Factor, NOAEL = no observed adverse effect level, LOAEL =

lowest observed adverse effect level, PAD = population adjusted dose (a = acute, c = chronic) RfD = reference dose,

LOC = level of concern, MOE = margin of exposure.

Acute Dietary Endpoint: The aRfD is established at 0.10 mg/kg/day based on the maternal

toxicity no-observed-adverse-effect-level (NOAEL) of 10 mg/kg/day from the developmental

toxicity study in the rat (MRID# 44606408) and an uncertainty factor (UF) of 100 (10x

interspecies extrapolation, 10x intraspecies variation). The NOAEL of 10 mg/kg/day was based

on decreased body weight gains and food consumption (most significant on days 7-10 of dosing)

seen at the maternal toxicity lowest observed adverse effect level (LOAEL) of 40 mg/kg/day. 
17

The FQPA SFC determined that the SF of 10x is applicable for this acute dietary risk

assessment. Thus, the aPAD for the general U.S. population (including infants and children) is

equivalent to the acute RfD/10, 0.010 mg/kg.

Chronic Dietary Endpoint: 

TRB assigned a cRfD for dichlormid of 0.017 mg/kg/day using a NOAEL of 5 mg/kg/day (100

ppm) established from a chronic toxicity study in dogs and an UF of 300 (10x interspecies

extrapolation, 10x intraspecies variation, 3x UF from previous assessment). The LOAEL of 25

mg/kg/day is based on decreased body weight gains, hematological and clinical chemistry

alternations, liver toxicity and voluntary muscle pathological changes.

The FQPA SFC determined that the SF of 10x is applicable for this chronic dietary risk

assessment. Thus, the cPAD for the general U.S. population (including infants and children) is

equivalent to the chronic RfD/10, 0.005 mg/kg.

Carcinogenicity: Dichlormid has not been classified by the HIARC or HED CARC in terms of

potential for carcinogenicity. However, there is no evidence of a positive carcinogenic effect in

the rat and mouse carcinogenicity studies based on evaluation of the studies.

Short-Term Dermal Toxicity: In the developmental toxicity study in rats, the HIARC selected

the maternal toxicity NOAEL of 10 mg/kg/day based on decreased body weight gain and food

consumption at the LOAEL of 40 mg/kg/day in the rat developmental toxicity study for the

short-term dermal toxicity dose/endpoint. This dose was also selected for the aRfD. The

duration of the short-term dermal scenarios for dichlormid are comparable to the duration of

exposure in the rat developmental toxicity study. There were no appropriate dermal toxicity

studies available. Since an oral NOAEL was selected, a dermal absorption factor should be used

for this risk assessment. Therefore, a default factor of 100% was used in the absence of data to

provide a better estimate. This risk assessment is required.

Intermediate- and Long-Term Dermal Toxicity: The HIARC identified the same dose and

endpoint for intermediate- and long-term dermal exposure. The HIARC selected the 2-year

chronic toxicity/carcinogenicity rat feeding study with a NOAEL of 6.5 mg/kg/day (100 ppm)

and a LOAEL of 32.8 mg/kg/day (500 ppm), based on an increased incidence of liver clinical

pathology/histopathology and increased liver weight in the 2-year study in rats (MRID No.
18

44529402). This study/dose were also selected for the cRfD. Since an oral NOAEL was

selected, a dermal absorption factor should be used for this risk assessment. Therefore, a default

factor of 100% was used in the absence of data to provide a better estimate. This risk assessment

is required.

Dermal Penetration: The dermal absorption factor is 100%.

Inhalation (All Durations): The HIARC selected an inhalation NOAEL of 2 :g/L based on

clinical signs, increased liver and kidney weight, gross pathology findings and non-neoplastic

histopathology at the LOAEL of 19.9 :g/L (14-week inhalation study). This risk assessment is

required.

MOE for Occupational/Residential Assessments: The HIARC determined that a MOE of 100 is

adequate for occupational exposure risk assessment (HED Doc. No. 013604, J. Rowland and

Brenda Tarplee, 8/5/99). A MOE of 1000 (including the10x FQPA SF) would be adequate for

residential exposure.

4.0. EXPOSURE ASSESSMENT

4.1. Summary of Directions for Use

Table 4. Summary of Directions for Use of Dichlormid

Formulation

[EPA Reg.

No.]

Applic.

Timing,

Type, and

Equip.

Applic.

Rate 

(lb ai/A)

Max.

No.

Applic.

per

Season

Max.

Seasonal

Applic.

Rate

(lb ai/A)

PHI

(days)

Use Directions and

Limitations

Field Corn, Pop Corn, Sweet Corn and RACs

SurpassTM

EC

[62719-367]

Emulsifiable

Concentrate

Pre-Plant or

preemergence

Postemergence

up to 11'’high

Broadcast

Ground

Equipment

0.216-

0.54

1 - 2 0.54 Within 30

days of

planting: early

pre-plant

within 14 days

of planting:

pre-plant

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 
19

KeystoneTM 

[62719-368]

SuspoEmulsion

Pre-Plant or

preemergence

Postemergence

up to 11'’high

Broadcast

Ground

Equipment

0.275-

0.43

 1 - 2 0.43 Within 30

days of

planting: early

pre-plant

within 14 days

of planting:

pre-plant

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 

TopNotchTM 

[62719-369]

MicroEmulsion

Pre-Plant or

preemergence 

Broadcast

Ground

Equipment

0.26 -0.43 1 - 2 0.43 Within 40

days of

planting: early

pre-plant

within 14 days

of planting:

pre-plant

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 

SurpassTM

20G

[62719-370]

Granular

Pre-Plant or

preemergence 

Broadcast

Ground

Equipment

0.3-0.52 1 - 2 0.52 Within 30

days of

planting: early

pre-plant

within 14 days

of planting

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 

FulTimeTM 

[62719-371]

MicroEncapsulate

Pre-Plant or

preemergence

Postemergence

up to 11'’high

Broadcast

Ground

Equipment

0.25-0.51 1 - 2 0.51 Within 40

days of

planting: early

pre-plant

within 14 days

of planting:

pre-plant

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 

SurpassTM

7E

[62719-372]

Soluble

Concentrate

Pre-Plant or

preemergence

Postemergence

up to 11'’high

Broadcast

Ground

Equipment

0.25-0.43 1 - 2 0.43 Within 30

days of

planting: early

pre-plant

within 14 days

of planting:

pre-plant

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 
20

KeystoneTM

LA

[62719-479]

SuspoEmulsion

Pre-Plant or

preemergence

Postemergence

up to 11'’high

Broadcast

Ground

Equipment

0.20-0.49 1 - 2 0.49 Within 30

days of

planting: early

pre-plant

within 14 days

of planting:

pre-plant

Do not apply to

following soils if

ground water is

below 30ft.: sand

with <3% organic,

loamy sand with <2%

organic, sandy loam

with<1% organic. 

Do not apply through

irritation or aerial. 

The proposed use directions are adequate.

4.2. Dietary Exposure

4.2.1. Food Exposure

Residue chemistry data pertaining to the proposed use of dichlormid on corn were submitted and

reviewed by TRB (DP Barcode: D3318075 & D357398, D. Rate, 9/14/2005).

4.2.1.a. Nature of the Residue - Plants and Livestock

Plants

MRID 46015801, D. Rate, 09/13/04.

A plant metabolism study was conducted using the herbicide safener dichlormid

(N,N-diallyl-2,2-dichloroacetamide, 99.8% a.i., [14C]-labeled at the carbonyl carbon). 

Dichlormid, applied either pre-emergence (on soil) or post-emergence (foliarly) to corn at 10X

the maximum agricultural use rate (5.60 kg a.i./ha), yielded sufficient TRRs in corn matrices

(0.027-0.272 mg/kg) for analysis of residues by solvent extraction and TLC. Extractability of

TRR was substantial for young forage (63.0%) and stover (53.1-53.8%) but was poor for grain

and cobs (6.8-7.8%), and the latter were not further characterized. Identified components in

young forage were dichlormid and the metabolites N,N-diallyl glycolamide and dichloroacetic

acid (4.2%, 4.9%, and 2.5% TRR, respectively), but the rest of the TRR, including metabolite A

(15.0% TRR; 0.16 mg/kg), was not identified. The stover contained dichloroacetic acid

(5.3-5.9% TRR) and unknown metabolite A (14.0-16.6% TRR) and post-emergence stover also

had low levels of dichlormid and N,N-diallyl glycolamide (0.9-1.2% TRR). Enzyme and acid

hydrolysis of stover unextractable debris released residues that were not identified. The results

indicate that dichlormid metabolism is qualitatively similar in all corn matrices and involves two

routes: a de-chlorination followed by oxidation to form N,N-diallyl glycolamide, and loss of an

allyl group followed by oxidation to form dichloroacetic acid.

The residue(s) of concern in corn for dichlormid were not defined with certainty in this study. 

The identified residues represent a small fraction (<12%) of the TRR in each matrix, and a

metabolite (unknown A) that represented >10% TRR in stover and young forage was not

identified. The relatively low residue levels in the 10X samples may have contributed to the low
21

percent identification of residues in the various corn matrices. It is possible that the identified

residues, which each represented #0.010 mg/kg at the 10X treatment rate (unknown A was

#0.045 mg/kg), would not be detected in plants treated at the 1X treatment rate. 

The plant metabolism data are classified as scientifically Unacceptable/Guideline and does not

satisfy OPPTS 860.1300. However, the study may be upgraded if additional metabolites are

identified, including unknown A, to allow a more complete characterization of the nature of the

residue of dichlormid in corn. 

It is notable that the corn matrices had low TRR (#0.27 mg/kg), as did the individual

components (#0.010 mg/kg for identified residues; #0.045 mg/kg for unknown A) at the 10X

treatment rate, and these may not be detectable at the 1X treatment rate. The study is acceptable

for the purpose of extending time-limited tolerances. 

Livestock

MRID 46015802, D. Rate, 09/13/04.

MRID 46015803, D. Rate, 09/13/04.

Lactating Goat:

In a goat metabolism study, the herbicide safener dichlormid

(N,N-diallyl-2,2-dichloroacetamide, 99.8% a.i., [14C]-labeled at the carbonyl carbon)

(14.36-14.88 mg/day; 11.59 - 13.89 ppm) was given to one goat by gavage once/day for 5 days. 

The majority of each dose was excreted within 24 hours of administration; the total excreted

radioactivity 23 hours after the last dose accounted for ~82% of the administered dose. The

milk, liver, kidneys, and muscle each contained <1% of the administered radioactivity, the

majority of which was solubilized by solvent extraction and enzyme hydrolysis. Only 0.6-

22.7% of the radioactive residues present in any given matrix were identified by HPLC,

precluding a complete characterization of the nature of the residues, or residues of concern, of

dichlormid in goat milk and tissues. 

Dichlormid may be extensively metabolized in goats, as dichlormid parent was found in only a

few samples (32 hour milk and liver PES supernatants), where it represented a lower % TRR

(0.2-8.5%) than other components. Its metabolic pathway was not well-defined since only a

small fraction (0.6-22.7%) of the TRR was identified in each matrix. Dichlormid metabolism is

proposed to involve N-dealkylation and dechlorination followed by oxidation, since the

metabolites N-allyl-2,2-dichloro-acetamide and N,N-diallyl glycolamide were found in almost

all matrices (the latter was not found in muscle, which had TRR of only 0.056 ppm). It is

unknown if the metabolic pathway was the same in all tissues because >77% of the TRR was not

identified.

This goat metabolism study (MRID 46015802) did not provide sufficient information to

establish the residues of concern for dichlormid in goat milk and tissues. This is because only a

small fraction (0.6-22.7%) of the TRR was identified in each matrix, and these identities were
22

not confirmed by a second analytical method (as required by OPPTS 860.1300 guidelines). 

Total residue levels in the evaluated tissues and milk were low (<0.001 - 0.064 ppm), which

likely contributed to the inability to identify some unknowns, although the parent and

metabolites R 326590 and R 305588 were identified at similarly low levels (<0.001- 0.040 ppm). 

The livestock metabolism data are classified as scientifically Unacceptable/Guideline for a

metabolism study in ruminants (OPPTS 860.1300) because it did not adequately define the

nature of the residues or the residue(s) of concern for dichlormid, and 84.4% is an inadequate

animal mass balance accounting. It may be upgraded upon further identification of residues

representing $10% TRR and/or 0.05 ppm, and an adequate explanation of the poor mass balance

accounting. The study is acceptable for the purpose of extending time-limited tolerances. 

Laying Hen:

In a hen metabolism study, the herbicide safener dichlormid (N,N-diallyl-2,2-dichloroacetamide,

99.8% a.i., [14C]-labeled at the carbonyl carbon)(1.75 mg/day; 10 ppm) was given to 5 laying

hens by gavage once/day for 14 days. Within 24 hours of administration, the majority of each

dose was excreted and a steady state was achieved for excreted residues. Residues accumulated

somewhat in egg whites and yolks, which attained steady state residue levels after 3 and 8 days,

respectively. After 14 days, 96.91% of the TRR was accounted for, being found in the excreta

(94.38% TRR), cage washes (1.14% TRR), egg yolks and whites, liver, breast and thigh muscle,

fat, and skin with (latter each <1% of the administered radioactivity). Limited identification of

residues was achieved for each matrix using two HPLC methods, varying from 0% TRR (fat) to

15.4% TRR (day 13 egg whites). This precluded a complete characterization of the nature of the

residues, or residues of concern, of dichlormid in hen eggs and tissues. The residue identities

were not confirmed by a second analytical method, as suggested by OPPTS 860.1300 guidelines,

although an unsuccessful attempt was made to use LC-MS with several tissues. The parent

dichlormid and/or metabolites R326590 and R305588 were identified at low levels (<0.001-

0.077 ppm) in all matrices except fat, and could possibly be used to regulate dichlormid residue

levels for tolerance purposes. 

The finding of very little parent dichlormid in tissues (#1% tissue TRR), at levels lower than of

other identified and/or unknown components, indicates that it is extensively metabolized. The

presence of metabolite R326590 (N-allyl-2,2-dichloro-acetamide) and R305588 (N,N-diallyl

glycolamide) in most matrices, and of R336075 (N,N-diallyloxamic acid) and R327940

(N,N-diallylglyoxylamide) in egg yolks and thigh muscle, respectively, indicates that dichlormid

metabolism involves N-dealkylation and dechlorination coupled with various degrees of

oxidation. Because only a small fraction (#15.4%) of the TRR was identified in each matrix,

however, the dichlormid metabolic pathway and similarities among tissues cannot be defined

with certainty. 

This metabolism study is classified Unacceptable/Guideline for a metabolism study in laying

hens (OPPTS 860.1300) because it did not adequately define the nature of the residues or the

residue(s) of concern for dichlormid (0-15.4% TRR was identified in each matrix). It is
23

upgradeable upon further identification of residues representing $10% TRR and/or 0.05 ppm. It

may be possible to use levels of dichlormid, R326590, and/or R305588 to regulate residue levels

in hen tissues for tolerance purposes, since one or more of these was found in all examined

matrices except fat. The study is acceptable for the purpose of extending time-limited

tolerances. 

4.2.1.b. Residue Analytical Method - Plants and Livestock

PP#:6F3344, DP Barcode: D248305, S. Chun, 09/21/99.

An enforcement method has been submitted for the determination of residues of dichlormid in

field corn, grain, fodder, and forage. A petition method validation (PMV) was successfully

completed with minor revisions recommended by the Analytical Chemistry Branch (ACB) (PP#:

6F03344, DP Barcode: D199320, G. Kramer, 08/29/94). The registrant was requested to submit

standards of dichlormid to the EPA repository and submit a revised version of the proposed

analytical enforcement method. The Agency received a pure active ingredient (PAI) standard

(dichlormid) for the EPA Repository from the registrant in August of 2003. Until the receipt of

the revised method, the requirements for analytical enforcement methodology will remain

unfulfilled. However, for the purposes of extending the time-limited tolerance, the method is

adequate.

4.2.1.c. Multiresidue Methods

PP#:6F3344, DP Barcode: D248305, S. Chun, 09/21/99.

A report on multiresidue testing of dichlormid was received and forwarded to FDA (PP#:

6F03344, DP Barcode: D191195, G. Kramer, 9/16/93). Dichlormid was evaluated using

multiresidue method Protocols C, D and E. Protocol C demonstrated dichlormid to be amenable

to detection by electron capture, nitrogen/phosphorous and electrolytic conductivity detectors. 

The recovery from lettuce samples fortified at 0.1 ppm was 79.2% with Protocol D and 41.4%

with Protocol E. The recovery from soybean samples fortified at 0.1 ppm was 38.3% with

Protocol E. 

4.2.1.d. Storage Stability Data

PP#:6F3344, DP Barcode: D248305, S. Chun, 09/21/99.

Storage stability data were submitted for dichlormid in field corn ears (Accession# 005802). 

Twenty-five gram samples were fortified with 0.10 ppm of dichlormid. Samples were kept

frozen at approximately -20/C ± 10/C for up to three years. Periodic analyses of the samples

were completed to determine if dichlormid deteriorated with time during frozen storage. 

Samples were analyzed at day 0 and after storage for 3, 8, 12, 24, and 36 months. At the 24 and

36 month intervals, newly fortified control samples were also analyzed to verify the accuracy of

the analytical procedure. At each interval, 2 fortified samples and 1 unfortified sample were

analyzed. 
24

The samples were analyzed for dichlormid using analytical method RRC-83-64, “Determination

of Residues of Cycloate, R29148, and R25788 in Corn Fodder and Corn Grain by Gas

Chromatography”. The results of this study are presented in Table 5.

Table 5. Percent recovery of Dichlormid in Corn Ears at

Different Time Intervals

Time Interval (days) Corrected % Recovery a

0 93

96 101

240 86

360 99

751 95

1095 73

a Each value is the average of 2 individual determinations.

No dichlormid residues, < 0.05 ppm (LOQ), were detected in the control samples.

The study does not specify what different corn RACs were analyzed and uses the term “corn

ears.” The study does include storage stability data of dichlormid in wheat grain and straw.

These data can be translated to corn RACs. Wheat samples were stored at intervals of 270, 818,

and 1240 days. The wheat data are presented in Table 6.

Table 6. Percent Recovery of Dichlormid in Wheat RACs

at Different Time Intervals

RAC Time Interval

(days)

Corrected %

Recovery a

Wheat Grain 0 93

270 88

818 96

1240 100

Wheat Straw 0 93

270 96

818 96

1240 87

a Each value is the average of 2 individual determinations.
25

The storage stability data are acceptable. The data shows dichlormid to be stable in corn and

wheat for up to 3 years when stored frozen. HED concluded that storage stability had been

demonstrated for the purposes of time-limited tolerances for dichlormid. If other residues are

found to be of regulatory interest, storage stability studies for those residues will be required, as

well.

4.2.1.e. Crop Field Trials

PP#:6F3344, DP Barcode: D248305, S. Chun, 09/21/99.

MRID 46353807, D. Rate, 08/25/05.

Corn field trial data were previously submitted and reviewed in support of the post-emergent use

(PP#: 5F4505, DP Barcode: D214735, G. Herndon, 06/25/96) of acetochlor. A formulation,

designated Acetochlor EC Herbicide, was used in the field trials. Eight field trials were

conducted during the 1993 growing season in IA (Region 5), IL (Region 5), IN (Region 5), MN

(Region 5), NE (Region 5), OH (Region 5), TX (Region 8), and WI (Region 5), 1 trial per state. 

Each treated plot received one post-emergence application of emulsifiable concentrate (EC)

formulation when the corn plants had reached a height of 5-9" at an application rate of 3.0 lbs.

acetochlor/A. The application rate of dichlormid was 0.5 lb. dichlormid/A. Table 7 summarizes

this data. All field trials had residues below the LOQ (0.01 ppm).

Table 7. Summary of Residue Data From Previous Crop Field Trials with Dichlormid

Crop

Matrix

Total

Applic.

[Target]

Rate1

 (lb

a.i./A) 

PHI

(Days)

Residue Levels (ppm)

n2 Min Max. HAFT* Median

(STMdR)

Mean

(STMdr)

Std. Dev.

Std.

Dev.

Dichlormid

Forage 0.5 12-31 8 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 0

Grain 0.5 104-131 8 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 0

Stover 0.5 104-131 19 < 0.01 < 0.01 < 0.01 < 0.01 < 0.01 0

1

 This is the rate of application of dichlormid itself.

2

 Includes duplicate analysis of some samples.

* HAFT = Highest Average Field Trial.

The reviewed field trials were submitted prior to the current OPPTS Test Guidelines, Series 860. 

HED concluded that assuming residues are less than the LOQ, a total of 15 field trials should be

conducted on field corn and analyzed for dichlormid in accordance with OPPTS Test Guideline

860.1500.

In response to the previous HED review, Pyxant Labs Inc. has submitted field trial data for

dichlormid on field corn. Eight additional trials were conducted encompassing EPA Regions 1

(1, PA), 2 (1, VA), 5 (5, IA, IL, IN, OH, WI), and 6 (1, TX) during the 2002 growing season.
26

The number and locations of field trials were chosen in order to satisfy an EPA request for an

additional eight magnitude of residue trials to be conducted in EPA regions 1, 2, 5 and 6.

At each test location, treatment consisted of a single foliar application to field corn when it was

9-12 inches tall of dichlormid at the target rate of 0.48 lb a.i./A (0.54 kg a.i./ha). This mixture

resulted from dissolving the GF-670 Capsule Suspension formulation of TopNotch Herbicide in

water. An adjuvant was not added to the spray mixture in any applications. Forage, grain, and

stover were harvested at pre-harvest intervals (PHIs) of 62-77, 102-135, and 102-135 days,

respectively. Table 8 summarizes this data.

Table 8. Summary of Residue Data From Crop Field Trials with Dichlormid

Crop

Matrix

Total

Applic.

[Target]

Rate1

 (lb

a.i./A) 

PHI

(Days)

Residue Levels (ppm)

n2 Min Max. HAFT* Median

(STMdR)

Mean

(STMdr)

Std. Dev.

Std.

Dev.

Dichlormid

Forage 0.48 62-77 19 < 0.003 < 0.0046 < 0.003 < 0.003 < 0.003 0

Grain 0.48 102-135 20 < 0.003 < 0.033 < 0.003 < 0.003 < 0.003 0

Stover 0.48 102-135 19 < 0.003 < 0.003 < 0.003 < 0.003 < 0.003 0 1

 This is the rate of application of dichlormid itself.

2

 Includes duplicate analysis of some samples.

* HAFT = Highest Average Field Trial.

Residues of dichlormid were quantified using Zeneca Agrochemical’s analytical method

RAM-244/02, which uses gas chromatography with nitrogen phosphorous detection (GC/NPD). 

Satisfactory method performance in detecting residues was demonstrated by concurrent

recoveries. The results from these trials show that maximum residues in forage, grain, and

stover never exceeded the method’s LOQ, which is 0.01 ppm. The petitioner stated that a freezer

storage study is in progress showing that dichlormid is stable for up to four months in all three

matrices. Storage stability of dichlormid is adequate as shown in previously submitted data

(PP#:6F3344, DP Barcode: D248305, S. Chun, 09/21/99). There was no residue decline study.

Though the submitted field trial data report residue levels <0.01 ppm, the enforcement method’s

LOQ is 0.05 ppm. Therefore, the appropriate tolerance level is 0.05 ppm for all corn RACs. If

other residues are found to be of regulatory interest, additional field trials will be required.

The submitted studies reflect the use patterns for dichlormid, and the storage stability studies

support the residue data. The enforcement methods are adequate for detecting the parent

compound, dichlormid. However, because the metabolism studies were not adequate to

determine residues present at levels >10% TRR, residues of concern in addition to the parent

compound have not been identified. Based on the previously submitted data on corn, TRB can

only recommend for an extension to the current time-limited tolerances of 0.05 ppm for the use

of dichlormid on field corn (forage, grain, stover), sweet corn (K+CWHR, forage and stover) and

pop corn (grain, stover).
27

4.2.1.f. Processed Food/Feed

No processing studies are required for field corn.

4.2.1.g. Water, Fish, and Irrigated Crops

Dichlormid is presently not registered, nor is the registrant seeking registration for direct use on

water and aquatic food and feed crops; therefore, no residue chemistry data are required under

these guideline topics.

4.2.1.h. Food Handling

Dichlormid is presently not registered, nor is the registrant seeking registration for use in

food-handling establishments; therefore, no residue chemistry data are required under these

guideline topics.

4.2.1.i. Meat, Milk, Poultry and Eggs

MRID 46015802, D. Rate, 09/13/04.

PP# 3E6676, DP Barcode: D294741, D. Rate, 09/14/04

Currently, there are no registered direct animal treatments of dichlormid to livestock. However,

dichlormid has time-limited tolerances for use on field corn, popcorn, silage corn and production

seed corn, with a request for the addition of sweet corn, which contains animal feedstuffs. Based

on the submitted study on lactating goats, the dichlormid residues found in animal tissues were

between <0.001 - 0.023 ppm when treated at a level ~200X the proposed tolerance level. TRB

does not expect quantifiable residues in animal commodities when fed corn treated by the

proposed use of dichlormid, therefore dichlormid tolerances are not required on animal

commodities.

4.2.1.j. Confined Accumulation in Rotational Crops

MRID 46353807, D. Rate 08/25/05.

In a confined rotational crop study, sandy loam soil was sprayed with the herbicide safener

dichlormid (N,N-diallyl-2,2-dichloroacetamide, 99.8% a.i., [14C]-labeled at the carbonyl

carbon) prepared as an emulsifiable concentrate with the herbicide acetochlor. The single

application was at the maximum seasonal application rate (1X) of 0.56 kg a.i./ha (0.5 lb/acre). 

At 30, 120, and 365 days after application (DAA), spring wheat, carrot, and soybean seeds were

planted in the treated soil.

 

Samples were initially extracted with acetonitrile (ACN), ACN:water, and water, and soybean

grain also with hexane, and the extracts characterized by HPLC. The polar extracts were

subjected to solid phase extraction (SPE) and ACN extracts to acid hydrolysis at 95/C, followed

by HPLC. Post-extraction solids (PES) were extracted with acid, some were partitioned with

dichloromethane, and supernatants analyzed by HPLC. The remaining insolubles were
28

resuspended and the radioactive residues shown to be incorporated into plant cell wall

polysaccharides, starch, monosaccharides, proteins, and lignin by driselase, pullulanase and

amylglucosidase digestion, trichloroacetic acid precipitation, and base hydrolysis, respectively. 

The storage stability study of wheat hay and early forage, and soybean early forage (55-63 weeks

at -20/C) indicated that dichlormid and its metabolites are stable frozen at -20/C for a year. 

Residues in soil were not evaluated, although a natural water sample from an environmental fate

study with [14C]-dichlormid was analyzed by HPLC. 

Total radioactive residues (TRR) at the 30, 120, and 365 DAA wheat samples were: 0.005-0.169

ppm in early forage, 0.017-0.639 ppm in hay, 0.014-0.629 ppm in straw, and 0.017-0.295 ppm in

grain. TRR in carrot shoots were 0.005-0.115 ppm and in 30 DAA roots were 0.038 ppm. TRR

in soybean samples were: 0.005-0.122 ppm in early forage, 0.014-0.331 ppm in hay, 0.010-0.139

ppm in straw, and 0.019-0.039 ppm in grain. In every matrix, maximum residues occurred at 30

DAA, and TRR levels decreased as the DAA increased. TRR recoveries of extracts were

acceptable for all matrices. Radioactive residues were also found in control matrices, which was

likely due to incorporation of 14CO2 released from dichlormid in the soil. 

Dichlormid was extensively metabolized, as the parent was found in only wheat early forage and

hay at low levels (0.01 ppm). Based on their partitioning behavior, most of the known and

unknown metabolites from all three crops were polar. Wheat forage, hay, and/or straw

metabolites included N,N-diallyl-2-hydroxyacetamide, N,N-di-2-propenylacetamide, N,N-diallyl

glyoxylamide, 2-chloro-N,N-di-2-propenylacetamide, N-allyl-2,2-dichloroacetamide,

N-allyl-2,2-glyoxylamide, and dichloroacetic acid (each 0.001-0.024 ppm, 0.3-3.7% TRR). 

Residues were also present in wheat hay and straw cell wall polysaccharides and lignin, and in

starch and cell walls in grain. The 120 DAA carrot shoots contained

N,N-di-2-propenylacetamide (0.001 ppm, 6.3% TRR) and radiolabeled glucose (0.001 ppm,

2.0% TRR) was detected in 30 DAA roots. Identified metabolites in 30 and/or 120 DAA

soybean early forage, hay, and/or straw included N,N-diallyl glyoxylamide,

N,N-diallyl-2-hydroxyacetamide, N-allyl-2,2-dichloroacetamide, and 2-chloro-N,N-di-2

-propenylacetamide (each 0.001-0.013 ppm, 0.9-3.9% TRR). No dichlormid-related metabolites

were identified in soybean grain. The environmental fate study water sample contained

N,N-di-2-propenylacetamide, 2-chloro-N,N-di-2-propenylacetamide, and 

N,N-diallyl-2-hydroxyacetamide (59.7, 33.0 and 7.2% of the applied sample radioactivity,

respectively).

Dichlormid metabolism in all rotational crops is proposed to involve two routes. In one,

dichlormid is first de-chlorinated to form 2-chloro-N,N-di-2-propenylacetamide and

N,N-di-2-propenylacetamide, and in the other, dichlormid first loses an allyl group to form

N-allyl-2,2-dichloroacetamide. The final product of both routes is CO2, which can be

re-assimilated into endogenous plant cell components. This study did not establish the residues

of concern for dichlormid because 12.8% of the TRR was identified in each matrix, although the

low levels of metabolites and the similarities in proposed metabolic pathway with a primary crop

(corn, MRID 46015801) suggest that no new metabolites will be present at levels of concern in

the rotational crops. 
29

Based on this confined rotational crop study, the label crop rotation restriction interval for all

crops is one year, because residues > 0.01 ppm were found at 30 DAA and 120 DAA in all three

rotational crops.

4.2.1.k. Field Accumulation in Rotational Crops

No studies in field accumulation in rotational crops have been submitted. The registrant

should submit a field accumulation in rotational crop study in accordance with OPPTS

Guideline, 860.1900.

4.2.1.l. Proposed Tolerances

Tolerance expressions are set in terms of the parent compound only. Because no other data

exists on the associated metabolites, the recommended time-limited tolerance is based only on

the parent compound. Once additional data is submitted and reviewed, a complete tolerance

expression can be established for the herbicide safener, dichlormid. 

4.2.1.m. International Harmonization of Tolerances

Currently there are no international harmonization issues associated with the use of dichlormid

on corn. 

4.2.2. Dietary Exposure and Risk Analyses

HED conducts dietary (food only) risk assessments using DEEMTM, which incorporates

consumption data generated in USDA’s Continuing Surveys of Food Intakes by Individuals

(CSFII), 1989-1992. For acute dietary risk assessments, one-day consumption data are summed

and a food consumption distribution is calculated for each population subgroup of interest. The

consumption distribution can be multiplied by a residue point estimate for a deterministic

exposure/risk assessment, or be used with a residue distribution in a probabilistic type risk

assessment. Acute exposure estimates are expressed in mg/kg bw/day and as a percent of the

aPAD. For chronic risk assessments, residue estimates for foods or food-forms of interest are

multiplied by the average consumption estimate of each food/food-form of each population

subgroup. Chronic exposure estimates are expressed in mg/kg bw/day and as a percent of the

cPAD.

4.2.2.a. Acute Dietary Exposure Analysis

A Tier 1 acute dietary risk assessment was performed assuming tolerance level residues, default

processing factors for all commodities and 100% CT. For acute dietary risk, HED’s level of

concern is >100% aPAD. For acute dietary risk, HED’s level of concern is >100% aPAD. 

Dietary exposure estimates for the U.S. population and other representative subgroups are

presented in Table 9. 
30

Table 9. Summary of Results from Acute DEEMTM Analysis at 95th Percentile.

Subgroups 1 Exposure

(mg/kg/day) % aPAD

U.S. Population 0.000336 3.4

All infants (<1 year old) 0.000752 7.5

Children (1-2 years old) 0.000597 6.0

Children (3-5 years old) 0.000611 6.1

Children (6-12 years old) 0.000464 4.6

Youth (13-19 years old) 0.000381 3.8

Adults 20-49 years old. 0.000245 2.5

Females (13-49 years old) 0.000257 2.6

Adults (50+ years old) 0.000148 1.5

1

 HED notes that there is a degree of uncertainty in extrapolating exposures for certain

population subgroups which may not be sufficiently represented in the consumption surveys,

(e.g., non-nursing infants, etc.). Therefore, risks estimated for these subpopulations were

included in representative populations having sufficient numbers of survey respondents (e.g., all

infants, females, 13-50 years, etc.).

The results of the acute analysis indicate that the estimated acute dietary risk associated with the

recommended uses of dichlormid is below HED’s level of concern (<100% aPAD). 

4.2.2.b. Chronic Dietary Exposure Analysis

A chronic dietary analysis was performed assuming tolerance level residues, default processing

factors for all commodities and 100% CT. For chronic dietary risk, HED’s level of concern is

>100% cPAD. Dietary exposure estimates for the U.S. population and other representative

subgroups are presented in Table 10. 

Table 10. Summary of Results from Chronic DEEMTM Analysis.

Subgroups 1 Exposure

(mg/kg/day) % cPAD

U.S. Population 0.000104 6.1

All infants (<1 year old) 0.000138 8.1

Children (1-2 years old) 0.000213 13

Children (3-5 years old) 0.000246 15

Children (6-12 years old) 0.000188 11

Youth (13-19 years old) 0.000142 8.4

Adults (20-49 years old) 0.000085 5.0

Females (13-50 years old) 0.000085 5.0

Adults (50+ years old) 0.000049 2.9

1

 HED notes that there is a degree of uncertainty in extrapolating exposures for certain population

subgroups which may not be sufficiently represented in the consumption surveys, (e.g., non-nursing

infants, etc.). Therefore, risks estimated for these subpopulations were included in representative

populations having sufficient numbers of survey respondents (e.g., all infants, females, 13-50 years,

etc.).
31

The results of the chronic analysis indicate that the estimated chronic dietary risk associated with

the recommended uses of dichlormid is below HED’s level of concern (<100% cPAD).

4.2.2.c. Cancer Dietary Exposure Analysis

Dichlormid has not been classified by the HIARC or HED CARC in terms of potential for

carcinogenicity. Therefore, no cancer dietary exposure analysis was completed with this action.

4.2.3. Drinking Water

A DWLOC is a theoretical upper limit on a pesticide’s concentration in drinking water in light of

total aggregate exposure to a pesticide in food, drinking water, and through residential uses. A

DWLOC will vary depending on the toxic endpoint, with drinking water consumption, and body

weights. Different populations will have different DWLOCs.

HED uses DWLOCs internally in the risk assessment process as a surrogate measure of potential

exposure associated with pesticide exposure through drinking water. In the absence of

monitoring data for pesticides, it is used as a point of comparison against conservative model

estimates of a pesticide’s concentration in water.

DWLOC values are not regulatory standards for drinking water. They do have an indirect

regulatory impact through aggregate exposure and risk assessments.

HED does not have monitoring data available to perform a quantitative drinking water risk

assessment for dichlormid at this time. EFED provided ground and surface water exposure

estimates for the use of dichlormid on corn (DP Barcode: D258095, A. Clem, 8/3/99).

4.2.3.a. Surface and Ground Water 

Dichlormid is relatively short-lived in aerobic soil (aerobic soil “half-life” measured in one soil

of approximately 7-12 days). Carbon dioxide was the only major identified aerobic soil

metabolite. Its evolution from the centrally labeled carbonyl position indicates a high degree of

mineralization of the dichlormid molecule. Other unidentified volatiles totaled less than

approximately 3%. Minor amounts of several degradates extracted from the soil by organic

solvents were not identified. Significant amounts of other soil degradates were resistant to

harsher extraction and presumably remain as bound residues. Dichlormid was stable against

hydrolysis and photolysis in soil and water.

Dichlormid’s low sorptivity to soil (median Kd of 0.45 and median Koc of 39 mL/g in four soils)

indicates high mobility. Based on its low sorptivity to soil, high solubility in water (4.4 g/L),

and low octanol to water partitioning ratio (Kow = 69), bioconcentration is not anticipated.

Drinking water exposure estimates are based on degradation and transport factors for dichlormid

coupled with EFED’s current GENEEC (surface water) and SCI-GROW (groundwater)
32

screening models for surface and ground water, respectively. Model results are for an

application rate of dichlormid of 0.5 a.i./A (DP Barcode: D258095, A. Clem, 8/3/99).

Tier 1 GENEEC estimated environmental concentrations (EEC) are summarized in Table 11.

Table 11. EECs for Dichlormid Use on Corn

GENEEC (:g/L)

Parent and Degradate Peak EEC 56-dayEEC

56-day1

EEC

Dichlormid 27.29 26.93 8.98 1

 HED interim policy allows the 56-day GENEEC value to be divided by 3 to obtain a value for chronic risk

assessment calculations. The values in this column have been divided by 3.

Based on the SCI-GROW model, acute drinking water concentrations in shallow ground water

on highly vulnerable sites are summarized in Table 12. 

Table 12. Acute Groundwater EEC for Dichlormid Use on Corn

SCI-GROW :g/L (ppb)

Dichlormid 0.046

Chronic concentrations are not expected to be higher than acute values (DP Barcode: D258095,

A. Clem, 8/3/99).

4.2.3.b. Drinking Water Risk

HED’s default body weights are: males - 70kg, females - 60kg, and children - 10 kg. Drinking

water consumption defaults are: adults - 2 L, children - 1 L

DWLOCs were calculated for the U.S. general population and the children subgroup which had

the highest dietary exposure. To calculate DWLOCs for acute (or chronic) exposure relative to

an acute (or chronic) toxicity endpoint, the acute (or chronic) dietary food exposure (from the

DEEMTM analysis) was subtracted from the aPAD (or cPAD) to obtain the acceptable acute (or

chronic) exposure to dichlormid in drinking water.

The results for both the acute and chronic DWLOC calculations are presented in sections 5.1 and

5.3, respectively. 
33

4.3. Occupational/Residential Exposure

4.3.1. Summary of Use Patterns and Formulations

Dichlormid, N,N-diallyl dichloroacetamide, is a herbicide safener used in pesticide formulations

with the active ingredient, acetochlor, for the control of grass and broadleaf weeds. Products

containing dichlormid are conditionally registered in the U.S. to Dow AgroSciences, LLC under

the trade names Surpass® EC, Keystone®, TopNotchTM, Surpass® 20G, FulTimeTM, Surpass® 7

E, and Keystone® LA. Currently, it is used in the treatment of corn (field, sweet and pop) raw

agricultural comodities (RACs). Dichlormid is an emulsifiable concentrate that was prepared by

blending dichlormid (98.0% purity X 12.04% of formulation) with acetochlor technical. The

herbicide/safener formulations are typically applied as pre-emergence soil or early

post-emergence foliar applications using broadcast ground equipment. The herbicide/safener

may be applied both in the spring and fall, but the total applied must not exceed the maximum

labeled rate for corn in that type of soil. The application must also be made within 14 days of

planting when applied by conventional tillage systems and up to 40 days before planting in

no-till systems. The application rate of dichlormid ranges from 0.30-0.54 lbs a.i./A. 

Proposed Uses

There are many product formulations for dichlormid, each containing a different amount of

dichlormid. The highest application rate from all the formulations is 0.54 lbs dichlormid/A

(Surpass® 100).

Two products, FultimeTM and Surpass® 100, contain atrazine and acetochlor as active ingredients. 

The other four products, TopNotchTM, Surpass® 7E, Surpass® 20-G, and Surpass® EC, contain

only acetochlor as the active ingredient. All products specify use on field corn, production seed

corn, silage corn, and popcorn. In all formulations, soil type and organic matter content

determined the maximum application rate, with fine soil having the highest application rate. No

aerial application is allowed. Application through sprinkler irrigation systems is prohibited. 

Tank mixing with other herbicides such as Atrazine, Bladex, 2,4-D, Accent, Beacon and Banvel

is on the labels.

4.3.2. Occupational Exposure Assessment

HED has identified toxicological endpoints of concern for occupational exposure. Based on the

use pattern, only short- and intermediate-term exposures are expected for workers applying

dichlormid. Chemical specific data for dichlormid are not available. Therefore, handler

exposures (mixer/loaders and applicators) have been assessed using surrogate data available in

the Pesticide Handlers Exposure Database (PHED Ver 1.1, 1998) Surrogate Table. Table 15

summarizes the HED exposure estimates for workers mixing, loading, and applying dichlormid.

HED’s level of concern for occupational exposures to dichlormid is for MOEs that are below

100. The aggregate (dermal and inhalation) MOEs for the groundboom applicator are 240 and

190 for short- and intermediate-term exposures, respectively. The aggregate MOEs for the
34

mixer/loader in support of groundboom applications are 150 and 120 for short- and intermediateterms exposures, respectively. Therefore, all exposure estimates are below HED’s level of

concern.

Table 13. Handler Exposure and Risk from Proposed Uses of Dichlormid

Job

Functionliquid

formulations

Appl.

Rate

(lbs

ai/Acre)

Unit

Exposure 1

(mg/lb ai)

Acres/

Day2

 Dermal

Average

Daily Dose

(ADD) 3

mg/kg/day

Inhalation 

ADD3

mg/kg/da

y

 Shortterm 

MOE4

Intermterm

MOE4

Total

Shortterm

MOE 5

Total 

Intermediat

e- term

MOE5

Open

SystemGroundmixer/loader

0.54

0.023

dermal

190 0.034 0.0018

300

dermal

190

dermal

150 120

0.0012

inhalation

300

inhalation

300

inhalation

Open CabGroundapplicator

0.54

0.014

dermal

190 0.021 0.0011

490

dermal

320

dermal

240 190

0.00074

inhalation

480

inhalation

480

inhalation

1 Source: Pesticide Handlers Exposure Database (PHED) V1.1, Surrogate Exposure Table. All data is rated High

Confidence with the exception of the dermal unit exposure for the ground applicator which is Medium Confidence. 2

 Assumptions regarding acreage treated/day from 1997 Agriculture Census. Average farm size is 190 acres for the

state with the largest acreage of corn (Iowa). Assumes that a commercial applicator can treat an entire farm in 1 day. 3 ADD = Unit exposure(:g/lb ai) x AR x Acres/Day x 1/BW (70kg) x % Absorption (100%-inhalation and dermal) 4 MOE = NOAEL/ADD; (where NOAEL = 10 mg/kg/day for short-term dermal; 6.5 mg/kg/day for intermediateterm dermal; 0.52 mg/kg/day (equivalent to 2ug/L) for inhalation)

5 Total MOE = 1/{1/MOE(dermal in oral equivalents) + 1/MOE(inhalation)}

All occupational risk estimates are below HED’s level of concern (MOE>100).

4.3.2.a. Worker Post-Application Exposure Assumptions and Assessment

A post-application exposure assessment was not performed. Cultural activities associated with

the subject corn uses are likely to result in relatively low levels of dermal exposure. Field corn is

planted, cultivated, and harvested mechanically (website: Crop Profiles, USDA, Office of Pest

Management Policy and Pest Impact Assessment Program, updated 8/23/99). Therefore,

potential worker post-application exposures from a herbicide applied pre-emergent or in the

early post-emergent stage are expected to be minimal.

4.3.2.b. REI

There is no REI associated with dichlormid.
35

4.3.2.c. Incident Reports

There have been no reported incidents of accidental exposure.

4.3.3. Residential Exposure

There are no residential uses resulting in non-dietary exposure to infants and children at this

time.

4.4. Non-Occupational Off-Target Exposure

There are no non-occupational off-target exposure scenarios for dichlormid.

5.0. RISK ASSESSMENTS AND RISK CHARACTERIZATION

Aggregate exposure risk assessments were performed for acute and chronic aggregate exposure

(food + drinking water). DWLOCs were calculated for the U.S. general population and the

children subgroup which had the highest dietary exposure. Ground and surface water estimates

were provided by EFED. There are no residential uses resulting in non-dietary exposure to

infants and children at this time and so a short-/intermediate-term aggregate risk assessment is

not applicable for this dichlormid action. Dichlormid has not been classified by the HIARC or

HED CARC in terms of potential for carcinogenicity. Therefore, no aggregate cancer risk

analysis was completed with this action.

5.1. Acute Aggregate Risk (food + drinking water)

Acute aggregate risk estimates are below HED's level of concern. A Tier 1 acute dietary risk

assessment was performed assuming tolerance level residues, default processing factors for all

commodities and 100% CT. For acute dietary risk, HED’s level of concern is >100% aPAD. 

Acute dietary risk estimates were 3.4% of the aPAD at the 95th percentile for the general U.S.

population and 7.5% of the aPAD for the highest exposure group, all infants (< 1 year old). The

estimated acute dietary risk associated with the use of dichlormid on corn RACs is below HED’s

level of concern. Additional refinement by incorporating %CT information may result in even

lower exposure estimates.

TRB has calculated DWLOCs for acute exposure to dichlormid in surface and ground water for

the U.S. population and all infants (< 1 year old) to be 338 ppb and 92 ppb, respectively. The

maximum estimated concentrations of dichlormid in surface and ground water, 27.29 and 0.046

ppb, respectively, are less than HED’s DWLOCs for dichlormid as a contribution to acute

aggregate exposure. Therefore, taking into account the uses proposed in this action, TRB

concludes with reasonable certainty that residues of dichlormid in drinking water (when

considered along with other sources of exposure for which HED has reliable data) would not

result in unacceptable levels of acute aggregate human health risk at this time. 
36

Table 14. Aggregate Risk Assessment for Acute Dietary Exposure to Dichlormid.

Population

Subgroup1

Acute Scenario

aPAD

mg/kg/day

Acute

Food Exp

mg/kg/day

Max Acute

Water Exp

mg/kg/day2

Ground

Water

EDWC

 (ppb) 3 

Surface

Water

EDWC

(ppb)3

Acute

DWLOC

(ppb)4

 

U.S. Population 0.010 0.000336 0.009664 0.046 27.29 338

All Infants (<1 year

old)

0.010 0.000752 0.009248 0.046 27.29 92

Children 1-2 years old 0.010 0.000597 0.009403 0.046 27.29 94

Children 3-5 years old 0.010 0.000611 0.009389 0.046 27.29 94

Children 6-12 years old 0.010 0.000464 0.009536 0.046 27.29 95

Youth 13-19 years old 0.010 0.000381 0.009619 0.046 27.29 289

Adults 20-49 years old 0.010 0.000245 0.009755 0.046 27.29 341

Females 13-49 years

old

0.010 0.000257 0.009743 0.046 27.29 341

Adults 50+ years old 0.010 0.000148 0.009852 0.046 27.29 296

1

 HED notes that there is a degree of uncertainty in extrapolating exposures for certain population subgroups

which may not be sufficiently represented in the consumption surveys, (e.g., non-nursing infants, etc.). 

Therefore, risks estimated for these subpopulations were included in representative populations having sufficient

numbers of survey respondents (e.g., all infants, females, 13-50 years, etc.). Body weights for subgroups: 70 kg

adult male; 60 kg adult female; 10 kg child.

2 Maximum acute water exposure (mg/kg/day) = [(aPAD (mg/kg/day) - acute food exposure (mg/kg/day)] 3 Drinking water exposure estimates are based on degradation and transport factors for dichlormid coupled with

EFED’s current GENEEC (surface water) and SCI-GROW (groundwater) screening models for surface and

ground water

4

 Acute DWLOC(μg/L) = [maximum acute water exposure (mg/kg/day) x body weight (kg)]

 [water consumption (L) x 10-3 mg/μg]

5.2 Short- + Intermediate-Term Aggregate Risk (food + residential + drinking water)

There are no residential uses resulting in non-dietary exposure to infants and children at this time

and so a short-/intermediate-term aggregate risk assessment is not applicable for this dichlormid

action. 

5.3. Chronic Aggregate Risk (food + drinking water)

Chronic aggregate risk estimates are below HED's level of concern. A chronic dietary

analysis was performed assuming tolerance level residues, default processing factors for all

commodities and 100% CT. Chronic dietary risk estimates were 6.1% of the cPAD for the

general U.S. population and 15% of the cPAD for the highest exposure group, children 3-5 years
37

old. The estimated chronic dietary risk associated with the use of dichlormid on corn RACs is

below HED’s level of concern. Additional refinement by incorporating %CT information may

result in even lower exposure estimates.

TRB has calculated DWLOCs for chronic exposure to dichlormid. The DWLOCs are 56 and 15

ppb for the U.S. population and children (3-5 years old), respectively. The maximum estimated

concentrations of dichlormid in surface and ground water, 8.98 and 0.046, respectively, are less

than HED’s DWLOCs for dichlormid as a contribution to chronic aggregate exposure. 

Therefore, taking into account the uses proposed in this action, TRB concludes with reasonable

certainty that residues of dichlormid in drinking water (when considered along with other

sources of exposure for which HED has reliable data) would not result in unacceptable levels of

chronic aggregate human health risk at this time. 

Table 15. Aggregate Risk Assessment for Chronic (Non-Cancer) Exposure to Dichlormid

Population

Subgroup1

Chronic Scenario

cPAD

mg/kg/day

Chronic

Food Exp

mg/kg/day

Max

Chronic

Water Exp

mg/kg/day2

Ground

Water

EDWC

 (ppb) 3

Surface

Water

EDWC

(ppb)3

Chronic

DWLOC

(ppb) 

U.S. Population 0.0017 0.000104 0.001596 0.046 8.98 56

All Infants (<1

year old)

0.0017 0.000138 0.001562 0.046 8.98 16

Children 1-2

years

0.0017 0.000213 0.001487 0.046 8.98 15

Children 3-5

years

0.0017 0.000246 0.001454 0.046 8.98 15

Children 6-12 0.0017 0.000188 0.001512 0.046 8.98 15

Youth 13-19 0.0017 0.000142 0.001558 0.046 8.98 47

Adults 20-49 0.0017 0.000085 0.001615 0.046 8.98 57

Females 13-49 0.0017 0.000085 0.001615 0.046 8.98 48

Adults 50+ years 0.0017 0.000049 0.001651 0.046 8.98 58

1

 HED notes that there is a degree of uncertainty in extrapolating exposures for certain population subgroups which

may not be sufficiently represented in the consumption surveys, (e.g., non-nursing infants, etc.). Therefore, risks

estimated for these subpopulations were included in representative populations having sufficient numbers of survey

respondents (e.g., all infants, females, 13-50 years, etc.). Body weights for subgroups: 70 kg adult male; 60 kg adult

female; 10 kg child.

2

Maximum Chronic Water Exposure (mg/kg/day) = [Chronic PAD (mg/kg/day) - Chronic Dietary Exposure

(mg/kg/day)]

3

 Drinking water exposure estimates are based on degradation and transport factors for dichlormid coupled with

EFED’s current GENEEC (surface water) and SCI-GROW (groundwater) screening models for surface and ground

water.

4

 Chronic DWLOC(μg/L) = [maximum chronic water exposure (mg/kg/day) x body weight (kg)]
38

 [water consumption (L) x 10-3 mg/μg]

6.0. DATA GAPS/LABEL CHANGES

6.1. Chemistry

For the purpose of establishing permanent tolerances for field corn (forage, grain, stover), sweet

corn (forage, grain, stover) and pop corn (grain, stover) at 0.05 ppm, the studies provided are not

adequate. For permanent tolerances to be set for the use of dichlormid, the following

deficiencies need to be addressed:

1. 860.1300: Nature of the Residue - Plants

The studies submitted (MRID No. 46015801) for the purpose of fulfilling the Guideline

860.1300 is scientifically unacceptable and does not satisfy the requirements. It may be

upgraded if additional metabolites are identified, including unknown A, to allow a more

complete characterization of the nature of the residue of dichlormid in corn.

2. 860.1300: Nature of the Residue - Livestock

The studies submitted (MRID No. 46015802, 46015803) for the purpose of fulfilling the

Guideline 860.1300 are scientifically unacceptable and do not satisfy the requirements. The

studies do not adequately define the nature of the residues or the residue(s) of concern for

dichlormid. They may be upgraded upon further identification of residues representing ?10%

and/or 0.05 ppm. 

3. 860.1340: Residue Analytical Methods

The requested revised method has not yet been received.

4. 860.1900: Field Accumulation in Rotational Crops

No studies in field accumulation in rotational crops have been submitted. The registrant should

submit a field accumulation in rotational crop study in accordance with OPPTS Guideline,

860.1900.

6.2. Toxicology

There are still outstanding data gaps for dichlormid including subchronic dermal and inhalation,

neurotoxicity and metabolism studies. Dermal absorption is by default 100% due to neither a

dermal absorption nor a dermal toxicity study (for extrapolation) being available.

6.3. Occupational/Residential Exposure

No data gaps.

7.0. ATTACHMENTS

Attachment 1: Dietary Exposure Analyses (available electronically).

Attachment 2: IRLS Form.
39

B.Hanson:284:CM#2:(703)305-6891:7509C:TRB
40

Attachment 1: Dietary Exposure Analyses (available electronically).
41

ATTACHMENT 2. IRLS SHEET

Chemical Name:

2,2'-dichloro-N,N’-di-2-prop

enylacetamide

Common

Name:

Dichlormid

: Proposed tolerance

9 Reevaluated tolerance

9 Other

Date:

8/10/05

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

 X No Codex proposal step 6 or above

9 No Codex proposal step 6 or above for the

crops requested

Petition Number: 4F6950

DP #: 318075

Other Identifier:

Residue definition: N/A Reviewer/Branch: Rate /TRB

Residue definition: dichlormid

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

corn, field 0.05

corn, pop 0.05

corn, sweet 0.05

Limits for Canada Limits for Mexico

X No Limits

9 No Limits for the crops requested

X No Limits

9 No Limits for the crops requested

Residue definition: N/A Residue definition: N/A

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

cottonseed 0.010

Notes/Special Instructions: S. Funk, 08/23/2005.