MCPB and Salts RED 

March 27, 2006 
United States Prevention, Pesticides EPA 738-R-06-016 

 Environmental Protection and Toxic Substances March 2006 

 Agency (7508C) 

 

 

Reregistration 

 Eligibility Decision for 

 MCPB, and Salts 

 

(Case 2365) 

 

 

 
Reregistration Eligibility Decision (RED) 

Document for 

MCPB

List B 

Case 2365 

Approved by: /S/ 

Debra Edwards, Ph. D. 

Director 

Special Review and Reregistration 

Division 

Date: March 27, 2006 

2 

Table of Contents 

Executive Summary ........................................................................................................................................... 7


I. Introduction .......................................................................................................................................... 9


II. Chemical Overview ............................................................................................................................ 10


A. Chemical Identification ........................................................................................................ 10


B. Use Profile.............................................................................................................................. 12


III. Summary of MCPB Risk Assessments............................................................................................. 13


A. Human Health Risk Assessment ......................................................................................... 13


1. Toxicity ..................................................................................................................... 13 


2. Dietary Exposure and Risk from Food and Drinking Water ............................ 16


3. Residential and Other Non-occupational Exposure and Risk ........................... 18


4. Aggregate Exposure and Risk ............................................................................... 18


5. Occupational Exposure and Risk Assessment ..................................................... 18


B. Environmental Risk Assessment ......................................................................................... 20


1. Environmental Exposure........................................................................................ 21


2. Environmental Effects (Hazard) ........................................................................... 23


3. Ecological Risk Estimation (RQs) ......................................................................... 27


4. Ecological Incidents ................................................................................................ 30


5. Endangered Species Concerns............................................................................... 30


6. Risk Characterization............................................................................................. 31


IV. Risk Management, Reregistration, and Tolerance Reassessment Decision ................................ 32


A. Determination of Reregistration Eligibility ....................................................................... 32


B. Public Comments and Responses........................................................................................ 32


C. Regulatory Position .............................................................................................................. 33


1. Food Quality Protection Act Findings .................................................................. 33


2. Tolerance Reassessment Summary ....................................................................... 35


D. Regulatory Rationale............................................................................................................ 35


1. Human Health Risk Mitigation ............................................................................. 36


2. Environmental Risk Mitigation ............................................................................. 37


3. Endangered Species Considerations ..................................................................... 37


5. Spray Drift Management ....................................................................................... 38


V. What Registrants Need to Do ........................................................................................................... 38


A. Manufacturing Use Products............................................................................................... 39


1. Additional Generic Data Requirements ............................................................... 39


2. Labeling for Manufacturing-Use Products .......................................................... 40


B. End-Use Products ................................................................................................................. 40


1. Additional Product-Specific Data Requirements ............................................... 40


2. Labeling for End-Use Products ............................................................................ 40


C. Labeling Changes Summary Table..................................................................................... 41


3 
MCPB Reregistration Eligibility Decision Team 

Office of Pesticide Programs: 

Biological and Economic Analysis Assessment 

Elisa Rim 

Jenna Carter 

Alan Halvorson 

Sunil Ratnayake 

Environmental Fate and Effects Risk Assessment 

Marie Janson 

Ed Odenkirchen 

Kevin Costello 

Health Effects Risk Assessment 

Elizabeth Mendez 

Kit Farwell 

Felecia Fort 

Timothy Dole 

Registration Support 

Joanne Miller 

Risk Management 

James Parker 

Demson Fuller 

Thomas Brennan 

Kelly Sherman 

 4 
Glossary of Terms and Abbreviations 

ai Active Ingredient 

ae Acid Equivalent 

AR Anticipated Residue 

CFR Code of Federal Regulations 

cPAD Chronic Population Adjusted Dose 

CSF Confidential Statement of Formula 

CSFII USDA Continuing Surveys for Food Intake by Individuals 

DCI Data Call-In 

DEEM Dietary Exposure Evaluation Model 

DFR Dislodgeable Foliar Residue 

DNT Developmental Neurotoxicity 

DWLOC Drinking Water Level of Comparison 

EC Emulsifiable Concentrate Formulation 

EDWC Estimated Drinking Water Concentration 

EEC Estimated Environmental Concentration 

EPA Environmental Protection Agency 

EUP End-Use Product 

FDA Food and Drug Administration 

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act 

FFDCA Federal Food, Drug, and Cosmetic Act 

FQPA Food Quality Protection Act 

FOB Functional Observation Battery 

GENEEC Tier I Surface Water Computer Model 

IR Index Reservoir 

LC50 Median Lethal Concentration. A statistically derived concentration of a substance that can be 

expected to cause death in 50% of test animals. It is usually expressed as the weight of substance per 

weight or volume of water, air or feed, e.g., mg/l, mg/kg or ppm. 

LD50 Median Lethal Dose. A statistically derived single dose that can be expected to cause death in 50% of 

the test animals when administered by the route indicated (oral, dermal, inhalation). It is expressed as 

a weight of substance per unit weight of animal, e.g., mg/kg. 

LOC Level of Concern 

LOAEL Lowest Observed Adverse Effect Level 

μ g/g Micrograms Per Gram 

μ g/L Micrograms Per Liter 

mg/kg/day Milligram Per Kilogram Per Day 

mg/L Milligrams Per Liter 

MOE Margin of Exposure 

MRID Master Record Identification (number). EPA’s system of recording and tracking submitted studies. 

MUP Manufacturing-Use Product 

NA Not Applicable 

NAWQA USGS National Ambient Water Quality Assessment 

NPDES National Pollutant Discharge Elimination System 

NR Not Required 

NOAEL No Observed Adverse Effect Level 

OPP EPA Office of Pesticide Programs 

OPPTS EPA Office of Prevention, Pesticides and Toxic Substances 

PAD Population Adjusted Dose 

PCA Percent Crop Area 

PDP USDA Pesticide Data Program 

PHED Pesticide Handler’s Exposure Data 

 5 
PHI Preharvest Interval 

ppb Parts Per Billion 

PPE Personal Protective Equipment 

ppm Parts Per Million 

PRZM/EXAMS Tier II Surface Water Computer Model 

Q1 * The Carcinogenic Potential of a Compound, Quantified by the EPA’s Cancer Risk Model 

RAC Raw Agriculture Commodity 

RED Reregistration Eligibility Decision 

REI Restricted-Entry Interval 

RfD Reference Dose 

RQ Risk Quotient 

SCI-GROW Tier I Ground Water Computer Model 

SAP Science Advisory Panel 

SF Safety Factor 

SLN Special Local Need (Registrations Under Section 24©) of FIFRA) 

TGAI Technical Grade Active Ingredient 

USDA United States Department of Agriculture 

UF Uncertainty Factor 

WPS Worker Protection Standard 

6 

Executive Summary 

This document presents the Environmental Protection Agency’s (hereafter referred to as 

the Agency or EPA) decision on the reregistration eligibility of the registered uses of MCPB [4-

(2-methyl-4-chlorophenoxy) butyric acid]. MCPB is a phenoxy herbicide used for postemergence weed control to protect pea crops from a variety of weeds including Canadian thistle, 

common lambsquarters, pigweed, smartweed, sowthistle, and morning glory. 

The Agency made its reregistration eligibility determination based on the required data, 

and the current guidelines for conducting acceptable studies to generate such data. Confirmatory 

studies are required to fulfill some guideline data requirements. However, the Agency has found 

that currently registered uses of MCPB are eligible for reregistration. There is currently one 

MCPB tolerance, which is being reassessed at the current level. 

Dietary Risk 

Acute and chronic dietary risks for food and drinking water do not exceed the Agency’s 

level of concern. No mitigation is required. 

Occupational Risk 

Short- and intermediate-term inhalation risks to occupational handlers are below the 

Agency’s level of concern with baseline clothing (no respirator). Dermal risks associated with 

mixing and loading for groundboom and aerial application are above the Agency’s level of 

concern with baseline clothing, but are below the Agency’s level of concern when chemicalresistant gloves are added. Therefore, chemical-resistant gloves will be required on all MCPB 

product labels. 

Residential Risk 

There are no residential uses of MCPB. Thus, EPA did not conduct a residential 

assessment. 

Aggregate Risk. 

Short-term and chronic aggregate risks posed by the use of MCPB are below EPA’s level 

of concern. No mitigation is required. 

Cumulative Risk 

EPA has not made a common mechanism of toxicity finding for MCPB, and 

therefore the Agency did not conduct a cumulative assessment. 

7 

 8 

Ecological Risk 

EPA’s level of concern is exceeded for acute risk to terrestrial plants, acute risk to small 

birds that consume short grass, and chronic risk to mammals. EPA has determined that the 

appropriate risk mitigation for environmental concerns at this time is to require medium or coarser 

droplet sizes to minimize the potential for spray drift. 

Endangered Species 

The screening level ecological risk assessment results in a determination that the 

use of MCPB will have no direct acute effects on freshwater fish, freshwater 

invertebrates, and insects, and no direct chronic effects to birds. However, the Agency’s 

level of concern for direct acute effects to endangered and threatened birds, and 

terrestrial and semi-aquatic plants, and for direct acute and chronic effects to mammals, 

is exceeded for the use of MCPB. Potential risks to endangered species identified in the 

Environmental Fate and Ecological Risk Assessment and reflected in this 

Reregistration Eligibility Decision (RED) for MCPB are based solely on EPA’s screening 

level ecological risk assessment and do not constitute “may effect” findings under the 

Endangered Species Act. 

Next Steps 

The Agency is issuing this Reregistration Eligibility Decision (RED) document for MCPB 

as announced in a Notice of Availability published in the Federal Register. 

In the future, EPA will issue a generic DCI for additional data necessary to confirm the 

conclusions of this RED for the active ingredient MCPB. EPA will also issue a product-specific 

DCI for data necessary to complete product reregistration for products containing MCPB. 

9 

I. Introduction 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) was amended in 1988 to 

accelerate the reregistration of products with active ingredients registered prior to November 1, 

1984. The amended Act calls for the development and submission of data to support the 

reregistration of an active ingredient, as well as a review of all submitted data to the EPA. 

Reregistration involves a thorough review of the scientific database underlying a pesticide’s 

registration. The purpose of the Agency’s review is to reassess the potential risks arising from the 

currently registered uses of the pesticide, to determine the need for additional data on health and 

environmental effects, and to determine whether or not the pesticide meets the “no unreasonable 

adverse effects” criteria of FIFRA. 

On August 3, 1996, the Food Quality Protection Act (FQPA) was signed into law. This 

Act amends FIFRA and the Federal Food Drug and Cosmetic Act (FFDCA) to require 

reassessment of all existing tolerances for pesticides in food. FQPA also requires that by August 

2006, EPA must review all tolerances in effect on the day before the enactment of the FQPA, 

which was August 2, 1996. FQPA also amends the FFDCA to require a safety finding in tolerance 

reassessment based on factors including aggregate risks from non-occupational sources of 

pesticide exposure, whether there is increased susceptibility to infants and children, and the 

cumulative effects of pesticides with a common mechanism of toxicity. 

Unlike other pesticides for which EPA has followed a cumulative risk approach based on a 

common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as to 

MCPB and any other substances. For the purposes of this tolerance reassessment action, 

therefore, EPA has not assumed that MCPB has a common mechanism of toxicity with other 

substances. For information regarding EPA’s efforts to determine which chemicals have a 

common mechanism of toxicity, and to evaluate the cumulative effects of such chemicals, see the 

policy statements released by EPA’s Office of Pesticide Programs concerning common mechanism 

determinations and procedures for cumulating effects from substances found to have a common 

mechanism on EPA’s website at http://www.epa.gov/pesticides/cumulative/. 

EPA followed a four-phase, modified public participation process for MCPB. 

Consistent with this process, EPA initiated Phase 1 of the process by transmitting the 

human health and ecological risk 

assessments to the technical registrants for a 30-day error-correction review. In Phase 

2, EPA considered the errors that were identified by the registrants and made changes 

in the risk assessments as appropriate. To initiate Phase 3 of the process, EPA 

published a Federal Register notice announcing the availability of the revised risk 

assessments and supporting documents for a 60-day public review and comment 

period. During the 60-day public comment period, EPA received two comments, from 

the MCPB Task Force and a public citizen. 

This document presents EPA’s revised human health and environmental fate and effects 

10 
risk assessment, its progress toward tolerance reassessment, and the reregistration eligibility 

decision for MCPB. The document consists of six sections. Section I contains the regulatory 

framework for reregistration and tolerance reassessment. Section II provides a description of the 

chemical and a profile of the use and usage of the chemical. Section III provides a summary of 

the human health and ecological risk assessments which have been revised based on data, public 

comments, and other information received in response to the preliminary risk assessments. 

Section IV presents the Agency’s risk management, reregistration eligibility, and tolerance 

reassessment decision. Section V summarizes any data requirements necessary to confirm the 

reregistration eligibility decision as well as label changes and language necessary to implement the 

risk mitigation measures outlined in Section IV. Section VI, the Appendices, provides related 

information and supporting documents. The preliminary and revised risk assessment for MCPB 

are available in the public docket EPA-HQ-2005-0263 located on-line in the Federal Docket 

Management System (FDMS) at http://www.regulations.gov. 

II. Chemical Overview 

A. Chemical Identification 

MCPB was first registered by EPA in 1964. Currently, there are five products containing 

MCPB registered under Section 3 of FIFRA. There are two manufacturing use products (MCPB 

Technical Acid and MCPB Technical Grade) and the three end-use formulations (Sodium MCPB 

Herbicide, Thistrol Herbicide, and Sodium MCPB Solution). There are no Special Local Need 

(SLN) registrations. 

MCPB (sodium) 

Chemical Name: [Sodium 4-(2-methyl-4-chlorophenoxy)buytrate] 

Chemical Structure: 

CAS Registry Number: 6062-26-6 

OPP Chemical Code: 019202 

11 

Case Number: 2365 


Molecular Weight: 250.7 g/mol


Vapor Pressure: 4 x 10-7 (torr at 25 degrees Celsius)


Empirical Formula: C11H12ClNaO3


Basic Manufacturers: A. H. Marks & Co. Ltd., Nufarm BV and Nufarm, Inc. 

MCPB (acid)


Chemical Name: [4-(2-methyl-4-chlorophenoxy)butyric acid]

Chemical Structure:


CAS Registry Number: 94-81-5 

OPP Chemical Code: 019201 

Case Number: 2365 

Molecular Weight: 228.6 g/mol 

Vapor Pressure: 4 x 10-7 (torr at 25 degrees Celsius) 

Empirical Formula: C11H13ClO3 

Basic Manufacturers: A. H. Marks & Co. Ltd., Nufarm BV and Nufarm, Inc. 

12 

B. Use Profile 

The following is information on the currently registered MCPB use sites and application 

methods. 

Type of Pesticide: MCPB is a phenoxy herbicide produced as a sodium salt and an acid. 

Summary of Use: MCPB is registered for use on peas (both green and dry peas) before 

flowering. There are no residential uses of MCPB. 

Target Organisms: Post-emergence control of Canadian thistle, buttercup, mustard, purslane, 

ragweed, common lambsquarters, pigweed, smartweed, sowthistle, 

morning glory and other broad leaf weeds 

Use Classification: General Use 

Formulation Types: Liquid 

Application Methods: Methods of application include controlled droplet 

applicator, high volume ground sprayer, low volume ground sprayer, 

hand held sprayer, high volume spray (dilute), low volume spray 

(concentrate), aerial and ground broadcast, and spot treatment. 

Application Rates:	 The maximum label application rate is 1.5 pounds acid equivalent/acre (lb 

ae/A), applied once per year. 

Use Locations:	 MCPB is primarily used in Delaware, Idaho, Illinois, Maine, Maryland, 

Michigan, Minnesota, Montana, New Jersey, New York, Oregon, 

Pennsylvania, Washington and Wisconsin. 

Tolerances:	 There is 1 tolerance, for peas. 

Annual Pounds Used: Less than 15,000 pounds per year 

Percent Crop Treated: Approximately 15 percent of green pea crops are treated with 

MCPB. Less than 2.5 percent of other types of pea crops are treated 

with MCPB. 

13 

III. 

This section summarizes EPA’s human health and ecological risk findings and 

conclusions for MCPB. This information is presented in greater detail in the following 

documents: “MCPB: Revised Occupational and Residential Exposure (ORE) and Risk 

Assessments for the Reregistration Eligibility Decision RED Document” (Dole, 

10/19/2005), “Revised Environmental Fate and Effects Division Preliminary Risk 

Assessment for MCPB” (Janson, 3/07/2006) and MCPB HED Chapter of the 

Reregistration Eligibility Decision (RED) Document” (Mendez, 10/24/2005). 

/

1.

116340 LD50 / III 

144801 LD50 / III 

116342 LD50 / IV 

144799 LD50 / III 

41630001 LC50 /L III 

Summary of MCPB Risk Assessments 

The purpose of this section is to highlight the key features and findings of the risk 

assessments in order to help the reader better understand the risk management decisions reached 

by the Agency. While the risk assessments and related addenda are not included in this document, 

they are available in the OPP Public Docket 

http://www.regulations.gov/fdmspublic-rel11/component main (docket number EPA-HQ-OPP2005-0263). 

A. Human Health Risk Assessment 

Although data do not support and the Agency is not assuming a common mechanism of 

toxicity with other pesticides, MCPB is similar in its toxicity to the structurally related compound 

MCPA. Also, there are similarities in the metabolism of MCPB and MCPA. Thus, studies from 

the MCPA database were used as a surrogate for those lacking in the MCPB database. 

 Toxicity 

MCPB has a low to moderate acute toxicity profile (Toxicity Category III to IV). The 

acute dermal toxicity test indicated low to moderate acute toxicity (Toxicity Category III to IV). 

The acute oral and inhalation toxicity studies showed moderate toxicity (Toxicity Category III). 

MCPB is not a dermal sensitizer nor is it irritating to the skin. However, it does cause moderate 

eye irritation. Please see Table 1, below, for the acute toxicity profile for MCPB. 

Table 1. Acute Toxicity Profile for MCPB 

Guideline No. Study Type MRID # Results Toxicity Category 

870.1100 Acute oral - rat = 1570 mg kg 

870.1100 Acute oral - rat = 4300 mg kg 

870.1200 Acute dermal - rabbit > 10000 mg kg 

870.1200 Acute dermal - rat > 2000 mg kg 

870.1300 Acute inhalation - rat > 1.14 mg

 14 

116343 III 

144797 III 

144798 IV 

144800 IV 

/

Table 1. Acute Toxicity Profile for MCPB 

Guideline No. Study Type MRID # Results Toxicity Category 

870.2400 Acute eye irritation - rabbit Moderately irritating 

870.2400 Acute eye irritation - rabbit Moderately irritating 

870.2500 Acute dermal irritation - rabbit Non-irritating 

870.2600 Skin sensitization - guinea pig Negative 

Kidney and liver effects appear to be the most prevalent hazard concerns for MCPB, 

based on the effects seen throughout the MCPA database. Developmental and reproductive 

toxicity studies did not indicate an enhanced sensitivity or susceptibility to young animals. 

Neurotoxicity effects were noted in studies conducted on MCPA. Therefore, a developmental 

neurotoxicity study is required for MCPB. 

EPA has established an acute reference dose (RfD) of 0.2 mg/kg/day for MCPB, based on 

a No Observed Adverse Effect Level (NOAEL) of 200 mg/kg/day in an acute neurotoxicity study 

of MCPA in rats. The main effect observed at the Lowest Observed Adverse Effect Level 

(LOAEL) was gait impairment in male rats. The RfD was calculated by dividing the NOAEL by 

an uncertainty factor of 1,000 (10x for interspecies variability, 10x for intraspecies variability, and 

10x FQPA database uncertainty to account for the lack of a developmental neurotoxicity study). 

The uncertainty factors are discussed in more detail below. 

EPA has established a chronic RfD of 0.015 mg/kg/day for MCPB, based on a NOAEL of 

4.4 mg kg/day in a chronic toxicity study of MCPA in rats. Effects observed at the LOAEL were 

liver and kidney toxicity. The RfD was calculated by dividing the NOAEL by an uncertainty 

factor of 300 (10x for interspecies variability, 10x for intraspecies variability, and 3x database 

uncertainty to account for the lack of a developmental neurotoxicity study). The uncertainty 

factors are discussed in more detail, below. 

There were no tumor effects observed in any MCPA or MCPB studies, and therefore EPA 

did not conduct a cancer assessment. Mutagenicity tests conducted with MCPB and MCPA were 

negative. 

FQPA Safety Factor 

FQPA directs EPA, in setting pesticide tolerances, to use an additional tenfold margin of 

safety to protect infants and children, taking into account the potential for pre- and post-natal 

toxicity and the completeness of the toxicology and exposure databases. The statute authorizes 

EPA to modify this tenfold FQPA safety factor only if reliable data demonstrate that the resulting 

level of exposure will be safe for infants and children. 

The toxicity database for MCPB, which is bridged from MCPA, includes acceptable 

15 

developmental and reproductive toxicity studies. There is no evidence in the developmental 

(MCPB and MCPA) or reproductive (MCPA) toxicity studies of increased sensitivity or 

susceptibility to newborns. However, EPA has determined that all or part of the FQPA safety 

factor must be retained to account for database uncertainties. 

Neurotoxicity was not seen in the MCPB subchronic studies (clinical signs of 

neurotoxicity in a rabbit developmental study occurred on the day of or day prior to death or 

moribund sacrifice and were attributed to agonal death). However, neurotoxicity was noted in an 

acute and subchronic MCPA rat study (decreased arousal, impaired coordination and gait, 

reduced motor activity, and reduced grip strength). Given that the MCPA database was used to 

evaluate MCPB, signs of neurotoxicity are expected with MCPB. A developmental neurotoxicity 

study is therefore necessary to further characterize the potential for pre- and post-natal 

neurotoxicity. The MCPB and MCPA databases do not include a DNT study, and therefore an 

FQPA database uncertainty factor must be retained for exposure scenarios through which 

exposure to children or pregnant women is expected. 

The size of the FQPA database uncertainty factor is based on an analysis of DNT studies 

previously submitted to the Agency which suggests that NOAELs from a DNT study could be 

lower than the lowest dose tested in the studies currently used in the risk assessment. For MCPB, 

a 10x FQPA database uncertainty factor is retained for the acute dietary risk assessment because 

it is anticipated that the DNT may yield a NOAEL approximately ten times lower than the one 

currently used for the risk assessment. A 3x FQPA database uncertainty factor is retained for the 

chronic dietary risk assessment because it is expected that the DNT could yield a NOAEL 

approximately three times lower than the one currently used for this risk assessment. 

The toxicological endpoints and uncertainty factors used in the human health risk 

assessment for MCPB are listed below in Table 2. 

Table 2. Summary of Toxicological Doses and Endpoints for the MCPB Dietary Risk Assessment 

/ Study ) 

N 0 of 

43562602] 

100x 

10x 

100x 

3x 

Exposure 

Scenario 

Dose 

(mg/kg day) Endpoint 

Uncertainty 

Factor 

FQPA 

Safety 

Factor 

PAD 

(mg/kg/day 

Acute Dietary 

(general 

population) 

OAEL = 20

mg/kg/day 

Clinical signs 

neurotoxicity 

Acute neurotoxicity 

study (MCPA) in rats 

with a LOAEL of 400 

mg/kg/day based on 

gait impairment in 

males 

[MRID No. 

(10x for 

intraspecies 

variation and 

10x for 

interspecies 

extrapolation) 

(for database 

uncertainty) 0.2 

Chronic 

Dietary 

(general 

population) 

NOAEL= 4.4 

mg/kg/day 

Hepatotoxicity 

and 

nephrotoxicity 

Chronic toxicity study 

(MCPA) in rats with a 

LOAEL of 17.6 

mg/kg/day 

[MRID No. 

(10x for 

intraspecies 

variation and 

10x for 

(for database 

uncertainty) 

0.015 

16 

Table 2. Summary of Toxicological Doses and Endpoints for the MCPB Dietary Risk Assessment 

/ Study ) 

40634101] 

Exposure 

Scenario 

Dose 

(mg/kg day) Endpoint 

Uncertainty 

Factor 

FQPA 

Safety 

Factor 

PAD 

(mg/kg/day 

interspecies 

extrapolation) 

Cancer Classification: Not likely to be carcinogenic to humans 

17 

2. 

TM

TM

a. 

th

j

j

/ /

 % 

/ /

2 

b. 

Dietary Exposure and Risk from Food and Drinking Water 

EPA conducted acute and chronic dietary (food and drinking water) risk assessments for 

MCPB using the Dietary Exposure Evaluation Model software with the Food Commodity Intake 

Database (DEEM-FCID , Version 2.03). To conduct the assessments, both food consumption 

data from USDA’s Continuing Survey of Food Intakes by Individuals (CSFII), 1994-1996 and 

1998, and screening-level model results for drinking water exposure were incorporated in the 

DEEM-FCID to estimate combined food and drinking water dietary risks. 

Dietary Exposure and Risk from Food 

The acute and chronic dietary (food only) risk assessments assumed 100% crop treated 

and tolerance-level residues for all commodities. This analysis is known as an unrefined (Tier 1) 

assessment, which provides an upper-bound estimate of potential risks. 

The results of the dietary (food only) exposure and risk estimates for MCPB for the 

general population and the most highly-exposed population subgroup (all infants <1 year old) are 

summarized below in Table 3. The acute assessment shows that at the 95 percentile of 

exposure, the risk estimates are below the Agency’s level of concern (<100% acute Population 

Ad usted Dose [aPAD]) for the general U.S. population and all population subgroups. The most 

highly exposed population subgroup was infants (<1 years old) at 2% of the aPAD. Note that for 

MCPB and other pesticides for which EPA conducts an unrefined Tier 1 analysis, the Agency 

presents acute dietary exposure results at the 95th percentile of exposure, which provides a more 

realistic though still high-end estimate of risk. The chronic risk estimates were also below the 

Agency’s level of concern (<100% of the chronic Population Ad usted Dose [cPAD]) for the 

general U.S. population and all population subgroups. The most highly exposed population 

subgroup was infants (<1 years old) at <4% of the cPAD. 

Table 3. Summary of dietary (food only) exposure and risk for MCPB 

Acute Dietary 

(95th Percentile) Chronic Dietary 

Population Subgroup 

aPAD 

(mg/kg day) 

Exposure 

(mg/kg day) aPAD* 

cPAD 

(mg/kg day) 

 Exposure, 

mg kg/day % cPAD* 

General U.S. Population 0.2 0.000754 0.4 0.015 0.000128 0.9 

All Infants (< 1 yr) 0.2 0.003971 0.015 0.000568 3.8 

* Risks > 100% of the aPAD or cPAD exceed EPA’s level of concern. 

Dietary Exposure from Drinking Water 

Drinking water exposure to pesticides can occur through surface and ground water 

contamination. EPA considers acute (one day) and chronic (lifetime) drinking water risks and 

uses modeling (or monitoring data, if available and of sufficient quality) to estimate those 

exposures. For MCPB, EPA used modeling to calculate Estimated Drinking Water 

18 

Concentrations (EDWCs) for groundwater and surface water sources of drinking water for use in 

the human health risk assessment. 

EPA used the Tier II screening model, Pesticide Root Zone Model and Exposure Analysis 

Modeling System (PRZM-EXAMS), to estimate MCPB residues in surface water. The Agency 

assumed MCPB would be applied once a year at 1.5 pounds of acid equivalent per acre (lb ae/A).

 EPA used the Tier I Screening Concentrations in Ground Water (SCI-GROW) model to estimate 

MCPB concentrations in ground water, assuming a maximum seasonal use rate of 1.5 lb ae/A. 

The EDWCs in surface water and ground water for MCPB are provided below, in Table 4. EPA 

used these EDWCs for the aggregate (food + water) risk assessments. 

Table 4. Surface and Ground Water EDWCs for MCPB 

Exposure Duration Surface Water Concentration a Ground Water Concentration b 

(ppb) (ppb) 

Acute 54.7 0.86 

Chronic (non-cancer) 13.5 0.86 

a

 From the Tier II PRZM-EXAMS - Index Reservoir model. Input parameters are based on use of MCPB on pea 

crops once a year at the rate of 1.5 lbs ae/A. 

b

 From the SCI-GROW model assuming a maximum seasonal use rate of 1.5 lbs ae/A 

c. Dietary Exposure and Risk from Food and Drinking Water 

MCPB concentrations are predicted to be higher in surface water than in ground water, 

and therefore EPA used the surface water EDWCs to calculate exposure and risk from combined 

dietary exposures from food and drinking water. The results of the acute and chronic dietary 

exposure analyses are summarized in Table 5, below. 

At the 95th percentile of exposure, the acute risk estimates are below the Agency’s level of 

concern (<100% aPAD) for the general U.S. population and all population subgroups. The most 

highly exposed population subgroup was infants (<1 years old) at approximately 6% of the aPAD.

 The chronic risk estimates were also below the Agency’s level of concern (<100% cPAD) for the 

general U.S. population and all population subgroups. The highest exposed population subgroup 

was infants (<1 years old) at 10% of the cPAD. 

Table 5. Acute and Chronic Dietary (food plus drinking water from surface water sources) Exposure and 

Risk Estimates for MCPB 

/ /

Acute (95th Percentile) Chronic 

Population Subgroup 

Exposure 

(mg/kg day) 

% aPAD* Exposure 

(mg/kg day) 

% cPAD* 

General U.S. Population 0.003356 1.7 0.00041 2.8 

19 

Table 5. Acute and Chronic Dietary (food plus drinking water from surface water sources) Exposure and 

Risk Estimates for MCPB 

All Infants (< 1 year old) 0.011869 5.9 0.001501 10

* Risks > 100% of the aPAD or cPAD exceed EPA’s level of concern. 

3. Residential and Other Non-Occupational Exposure and Risk 

There are no residential uses of MCPB, and therefore EPA did not conduct a residential 

risk assessment. 

4. Aggregate Exposure and Risk 

The FQPA amendments to the FFDCA (Section 408(b)(2)(A)(ii)) require “that there is a 

reasonable certainty that no harm will result from aggregate exposure to pesticide chemical 

residue, including all anticipated dietary exposures and all other exposures for which there is 

reliable information.” Aggregate exposure will typically include exposures from food, drinking 

water, residential uses of a pesticide, and other non-occupational sources of exposure. In the case 

of MCPB, the aggregate risk estimates are the same as those presented in the dietary (combined 

food and drinking water) risk section of this document (see Table 5), because there are no 

registered residential uses and no residential exposures are expected to occur. 

While the Agency has concluded that MCPB converts to MCPA in the 

environment, and that MCPA may be present in crops, residues of MCPA resulting from 

MCPB use are expected to be negligible, and significantly below analytical method limits 

of detection. These residues will not contribute significantly to the aggregate exposure 

to MCPA from other sources, and therefore EPA did not conduct an aggregate 

assessment combining MCPA exposures from MCPA and MCPB uses. 

5. Occupational Exposure and Risk Assessment 

Workers may be exposed to MCPB while handling, mixing, loading, or applying MCPB, 

and when entering treated sites. Handler and worker risks are measured by a Margin of Exposure 

(MOE) which determines how close the occupational exposure comes to a No Observed Adverse 

Effect Level (NOAEL) taken from animal studies. Generally, MOEs greater than 100 do not 

exceed the Agency’s level of concern. 

For MCPB, only short- and intermediate-term occupational exposures are expected based 

on label-specified use patterns. The Agency determined that pesticide handlers and applicators 

are likely to be exposed during MCPB use resulting in short- (one day to one month) and 

intermediate-term (one to six month) exposures. Chronic exposures (longer than six months) are 

not expected because MCPB is used only once a year. 

20 

For the occupational assessment, the short- and intermediate-term dermal endpoint was 

selected from an MCPA 21-day dermal toxicity study in rabbits. The short- and intermediateterm inhalation endpoint was selected from an MCPB developmental toxicity in rabbits. Table 6, 

below, provides a listing of the toxicological endpoints used in the MCPB occupational risk 

assessment. 

21 

Table 6. MCPB Toxicological Endpoints Used for Occupational Risk Assessment 

/ Study 

N 0 

100x 

100 

100x 

100 

Exposure 

Scenario 

Dose 

(mg/kg day) Endpoint Uncertainty Factor 

Level of 

Concern 

Dermal (Shortand 

Intermediateterm) 

Dermal 

OAEL = 10

mg/kg/day 

Kidney toxicity 

and decreased 

body weight gain 

21-day dermal toxicity 

study (MCPA) in rats 

with a LOAEL of 1,000 

mg/kg/day 

[MRID No. 42715001] 

(10x for intraspecies 

variation and 10x for 

interspecies extrapolation) 

Inhalation 

(Short- and 

IntermediateTerm) 

Oral 

NOAEL = 5 

mg/kg/day* Maternal 

mortality 

Developmental toxicity 

study in rabbits 

(MCPB) with a LOAEL 

of 20 mg/kg/day 

[MRID No. 40865401] 

(10x for intraspecies 

variation and 10x for 

interspecies extrapolation) 

* Inhalation absorption is assumed to be equivalent to oral absorption (100 percent default value). 

a. Short- and Intermediate-Term Handler Risk 

EPA has determined that there are potential short- and intermediate-term exposures to 

workers who handle MCPB. The four major occupational handler exposure scenarios are as 

follows: 

2. Mixing/loading liquid formulations; 

3. Performing aerial applications; 

4. Performing groundboom applications; and 

5. Flagging for aerial applications. 

For MCPB, the target MOE for occupational exposures is 100, which includes the default 

uncertainty factors for interspecies extrapolation and intraspecies variation. The MOEs for 

handlers are summarized in Table 7. All of the MOEs for dermal exposure are greater than 100 

(and therefore do not exceed the Agency’s level of concern) if single layer PPE (i.e., baseline 

clothing with chemical resistant gloves) is worn. All inhalation MOEs are greater than 100 at 

baseline (i.e., respirators not needed), and therefore do not exceed the Agency’s level of concern. 

Table 7. MCPB MOEs for Handlers 

350 580 560 

200 1000 970 

Exposure Scenario 

Application Rate 

(lb ae/acre) Acres/Day 

Dermal MOE 

(Single Layer 

PPE) 

Inhalation MOE 

(Baseline) 

Mixing and Loading Liquids for 

Aerial Application 1.5 

Mixing and Loading Liquids for 

Groundboom Application 1.5 

22 
Table 7. MCPB MOEs for Handlers 

350 9800 

200 1700 1600 

350 1100 1900 

Exposure Scenario 

Application Rate 

(lb ae/acre) Acres/Day 

Dermal MOE 

(Single Layer 

PPE) 

Inhalation MOE 

(Baseline) 

Applying Aerially 1.5 N/A 

Applying via Groundboom 

Equipment 1.5 

Flagging for Aerial Applications 1.5 

b. Short- and Intermediate-Term Postapplication Risk 

Post-application exposures to MCPB can occur when workers enter pea fields recently 

treated with MCPB to conduct tasks such as scouting and irrigation. 

Since no chemical-specific data were available for MCPB, standard values and 

assumptions were used to evaluate post-application risks (e.g., maximum application rates, default 

dislodgeable foliar residue value of 20 percent). 

A summary of worker risks for post-application exposures is presented in Table 8. All of 

the MOEs are above 100 on Day 0 (12 hours after application) for all activities which indicates 

that the risks are below the Agency’s level of concern. 

2

Day 0 

100 2600 

Table 8. MCPB Post-Application Worker Risks 

Crop 

Application Rate 

(lb ae/acre) Task 

Transfer 

Coefficient 

(cm /hr) 

Dermal 

MOE 

Peas 1.5 Irrigation, scouting, immature plants 

B. Environmental Risk Assessment 

A summary of the Agency’s environmental risk assessment for MCPB is 

presented below. The complete environmental risk assessment may be accessed in the 

OPP Public Docket (EPA-HQ-OPP-2005-0263) at www.regulations.gov and on the 

Agency’s website at www.epa.gov/pesticides/reregistration/status.htm. 

MCPB is a phenoxy herbicide that disrupts hormone (auxin) and protein synthesis within 

various sites in sensitive plants to cause growth abnormalities in addition to non-lethal effects 

(such as brown leaf tips, necrosis, decrease in size, leaf curling, chlorosis, and stem tumors). The 

use of MCPB produces potential risks to non-target plants within close proximity to target areas 

23 

and along streams and/or ponds near sprayed fields. 

The environmental fate database is sufficient to characterize the environmental 

exposure associated with MCPB use. However, EPA does intend to issue a DCI as part 

of this RED to require submission of additional data for the parent compound to 

address areas of uncertainty. Studies on environmental fate, aquatic invertebrates, and 

marine/estuarine fish will help provide the Agency with data to refine the 

environmental risk assessments and to confirm the conclusions reached in this RED. 

As previously discussed, MCPB has similiar effects as MCPA. Therefore, EPA took into 

consideration both MCPB and MCPA data for the purpose of this environmental assessment. 

1. Environmental Exposure 

a. Environmental Fate and Transport 

MCPA and the CHPA-hexose conjugate are byproducts of MCPB detected in fate studies.

 MCPA, MCPB, and the CHPA-hexose conjugate have similar fate characteristics as evidenced by 

fate studies and chemical structure. The inclusion or exclusion of these metabolites had little 

influence on the overall risk assessment because of their relatively minor presence and lack of 

persistence. However, the Agency has included both metabolites in combination with parent 

MCPB as total toxic residues with a combined half-life of 26 days. The Agency assumed that the 

toxicity and environmental fate properties for the two metabolites are equivalent to parent MCPB.

 Based on laboratory studies and physicochemical properties, MCPB is not volatile, not 

persistent, and not likely to bioconcentrate. Its acidic/anionic nature, physicochemical properties, 

and relatively low sorption to soil (average soil sorption coefficient of 0.85 mL/g) indicate that 

MCPB is prone to leaching and runoff. 

MCPB is essentially stable to hydrolysis, but photolyzed in laboratory water under optimal 

light exposure conditions with half-lives of approximately 2 to 3 days. Phototransformation 

products included 4 -(4-hydroxy-o-tolyloxy)butyric acid, 2,4-dihyroxyphenyl formate, o-cresol, 

benzoic acid, and 2-hydroxyphenyl formate. Specific study information is not available 

concerning the fate of these products, and the Agency has not included any potential effects of 

aqueous photolysis products in the risk assessment based on their expected toxicity and 

persistence. 

b. Aquatic Organism Exposure 

EPA used the PRZM 3.12 and EXAMS 2.98 models in tandem to estimate aquatic 

exposure concentrations for MCPB. PRZM/EXAMS is a Tier II screening model 

designed to estimate pesticide concentrations found in water at the edge of a treated 

field. As such, it provides high-end values of the pesticide concentrations that might be 

found in ecologically sensitive environments following pesticide application. The acute 

risk assessments were performed using 1-in-10-year peak estimated environmental concentration 

24 

(EEC) values for single applications of MCPB. EPA performed chronic risk assessments for 

aquatic invertebrates and fish using the average 21-day and 60-day EECs, respectively. 

To simulate field application of MCPB to peas, EPA selected a California lettuce 

scenario and an Oregon snap bean scenario based on similarity in agricultural practices and 

usage areas. The EECs from the two scenarios are provided in Table 9. The Oregon scenario 

represents the typical use of MCPB application to peas, and the California scenario represents a 

reasonable upper bound estimate. 

Table 9. Estimated Environmental Concentrations (μg ae/L) of MCPB + Metabolites (MCPA and 

CHPA/CHPA-hexose) in Surface Water (PRZM-EXAMS) 

μg ae/

Rate 

21-Day 60-Day 

/

/

Simulation Scenario Concentration ( L) 

Crop and Location 

Application 

Method Peak Average Average 

Lettuce (CA) 

(Surrogate for Peas) 

1.5 lbs ae/acre 

(1.68 kg ae ha) 

Ground spray 

Aerial spray 

40.4 

43.2 

39.0 

41.7 

36.4 

38.9 

Snap Beans (OR) 

(Surrogate for Peas) 

1.5 lbs ae/acre 

(1.68 kg ae ha) 

Ground spray 

Aerial spray 

29.5 

 33.1 

29.0 

32.5 

28.1 

31.5 

Surface water and groundwater monitoring data were not available for evaluation in this 

risk assessment. 

c. Terrestrial Organism Exposure 

(1) Exposure to Terrestrial Birds and Mammals 

EPA estimated exposure to birds and mammals by first predicting the amount of 

MCPB residues found on animal food items, and then using information on typical food 

consumption by various species of birds and mammals to determine the amount of 

pesticide consumed. The amount of residues on animal feed items are based on the 

Fletcher nomogram, which is a model developed by Hoerger and Kenaga (1972) and 

modified by Fletcher (1994), and the current maximum application rate for MCPB (1.5 

lb ae/acre). 

EPA used the terrestrial exposure (T-REX) model Ver. 1.1 to predict mean EECs 

from a single application of MCPB. The predicted EECs are provided in Table 10, below. 

EPA calculated acute and chronic RQs using these EECs and appropriate toxicity data. 

Table 10. Mean EECs on Terrestrial Food Items from Use of MCPB on Peas 

Simulation Scenario Concentration (ppm ae) 

Crop Food item Mean 

25 
 26 

 

Table 10. Mean EECs on Terrestrial Food Items from Use of MCPB on Peas Simulation Scenario Concentration (ppm ae) Crop Food item Mean 

Short Grass 127.5 

Tall Grass 54 

Broadleaf Plants/Small Insects 67.5 

Peas 

 

 

Fruits/Pods/Seeds/Large Insects 10.5 

 

 

(2) Exposure to Non-target Insects 

 

There is a potential for exposure to non-target insects as a result of spray drift 

from aerial and ground applications of the liquid formulation. 

 

(3) Exposure to Non-target Terrestrial Plants 

 

Exposure to non-target terrestrial plants is most likely to occur as a result of 

spray drift from aerial and ground applications of the liquid formulation. Spray drift is 

an important factor in characterizing the risk of MCPB to non-target plants. EPA used 

the TerrPlant model (Ver.1.0) to predict EECs for terrestrial plants located adjacent to 

the treated field. MCPB applied according to label directions as a liquid for ground or 

aerial applications may impact non-target plants for some distance from the application 

site depending on droplet size, wind speed, and other factors. In addition, the Agency 

used the AgDrift model (Ver. 2.0.1) to estimate drift dispersion and deposition as a 

result of ground and aerial spray droplet and nozzle size, wind speed, and distance from 

the treated field. 

 

2. Environmental Effects (Hazard) 

 

a. Toxicity to Aquatic Organisms 

 

(1) Freshwater and Estuarine/Marine Fish 

 

Available acute toxicity data, listed below in Table 11, indicate that MCPB is 

slightly to moderately toxic to freshwater fish. The median lethal concentration (LC50) 

value from the rainbow trout study (the more sensitive species) was used to evaluate 

acute risk to freshwater fish. 

 

Table 11. Freshwater Fish Acute Toxicity for MCPB Sodium 
 27 

 Species 

 

 

96-hour 

LC50 

(mg ae/L) 

(nominal

) Toxicity Category MRID Number Bluegill sunfish (Lepomis macrochirus) 12.7 Slightly toxic 42532601 Rainbow trout (Oncorhynchus mykiss) 3.9 

Moderately toxic 42532608 

 

No chronic data for freshwater fish are available. These studies were not 

previously required by the Agency. 

 

No acute or chronic data for estuarine/marine fish are available. These studies 

were not previously required by the Agency. A study with the degradate MCPA 

indicates that MCPA is practically non-toxic to estuarine/marine fish for acute exposures. 

However, a comparison between freshwater fish acute exposure studies with MCPB and 

MCPA indicates that MCPB is potentially more toxic to fish than MCPA. 

 

(2) Freshwater and Estuarine/Marine Invertebrates 

 

A toxicity study with the test species Daphnia magna demonstrated that MCPB 

is slightly toxic to freshwater invertebrates under acute exposure. The study results are 

provided below, in Table 12. 

 

Table 12. Freshwater Invertebrate Acute Toxicity for MCPB Sodium 

 Species 

 48-hour EC50 

(mg ae/L) Toxicity category MRID Number Waterflea 

(Daphnia magna) 50 Slightly toxic 42532602 

 

 

No freshwater aquatic invertebrate life-cycle studies or estuarine/marine 

invertebrate toxicity studies are available. These studies were not previously required 

by the Agency. 

 

Studies with the degradate MCPA indicate that MCPA is practically non-toxic to 

freshwater and estuarine/marine invertebrates. However, a comparison between 

freshwater invertebrate acute exposure studies with MCPB and MCPA indicates that 

MCPB is potentially more toxic to aquatic invertebrates than MCPA. 

 

(3) Aquatic Plants 

 

EPA has reviewed several aquatic plant toxicity studies to establish the toxicity of 

MCPB to aquatic plants. The results of these studies are provided in Table 13, below. 

 
 28 

 

Table 13. Non-target Aquatic Plant Toxicity for MCPB 

 Species 

[Study Type] 

 EC50/NOEC 

(mg ae/L) Endpoints Affected MRID Number Duckweed 

(Lemna gibba) [Tier I] 

 0.21/<0.01 

1.55/0.15 

 Frond production 

Frond biomass 42532604 Green Algae 

(Selenastrum capricornutum) 

[Tier I] 0.38/<0.31 Cell density 42532605 Blue-green Algae 

(Anabaena flos-aquae) 

[Tier I] >1.9/1.9 Cell density 42532603 Diatom 

(Navicula pelliculosa) 

[Tier I & II] 0.65/0.044 Cell density 42532609 Diatom 

(Skeletonema costatum) 

[Tier I & II] 1.36/0.10 Cell density 42532606 

 

 

b. Toxicity to Terrestrial Organisms 

 

(1) Birds 

 

MCPB is classified as moderately toxic to birds on an acute oral basis, based on a 

gavage study with bobwhite quail with a median lethal dose (LD50) of 257 mg ae/kg. 

MCPB is classified as practically non-toxic to avian species on an acute dietary basis, 

based on an 8-day acute dietary LD50 of greater than 4,550 ppm ae for both mallard 

duck and bobwhite quail. Table 14, below, summarizes the data that support the acute 

toxicity endpoints used in assessing acute risks to birds. 

 

Table 14. Avian Toxicity Studies for MCPB 

 

Acute Oral Gavage 

 

Species 

 

LD50 (mg ae/kg) 

 

Toxicity 

Category 

 

MRID No. 

 

Northern bobwhite quail (Colinus 

virginianus) 

 

257 

 

Moderately toxic 

 

42560801 

 

 Acute Dietary Species 

8-Day LD50 (ppm 

ae) 

 

 Toxicity 

Category 

 

MRID No. 

 Northern bobwhite quail (Colinus 

virginianus) 

 > 4,550 

Practically nontoxic 

 

42560802 

 

Practically non- 
 Acute Dietary 

Species 8-Day LD50 (ppm Toxicity MRID No. 

ae) Category 

Mallard duck (Anas platyrhynchos) > 4,550 toxic 42560803 

No chronic avian data on MCPB are available. These data were not previously 

required by the Agency. A chronic avian reproduction study with the degradate MCPA 

resulted in a no observed adverse effect concentration (NOAEC) of 1,000 mg ae/kg-diet (the 

highest dose tested). No negative effects were observed in that study. EPA used the MCPA 

chronic avian study to estimate chronic avian risks from MCPB. The MCPA study is an 

appropriate surrogate because MCPB is expected to rapidly dissociate to MCPA in a bird’s gut 

due to the chemical properties of MCPB. Further, a comparison of the MCPB and MCPA avian 

acute toxicity studies with bobwhite quail indicates that the two compounds have an 

approximately equivalent acute toxic potential to birds. 

(2) Mammals

MCPB is classified as slightly toxic to practically non-toxic to small mammals on 

an acute oral basis (LD50 values range from 912 to 7,400 mg ai/kg/day). However, 

adverse effects were demonstrated in the mammalian subchronic and developmental 

toxicity studies. See Table 15, below, for a summary of the data. 

Table 15. Summary of Mammalian Toxicity Endpoints for MCPB 

Species Purity Test Type Dose 

Affected 

Endpoints 

MRID 

No. 

Rat 

Technic 

al Acute oral 

LD50 = 912-2700 mg/kg/day (males) 

LD50 = 969-2981 mg/kg/day 

(females) Mortality 116340 

Rabbit 97.6% Developmental 

NOAEL = 5 mg/kg/day 

LOAEL = 20 mg/kg/day 

Maternal 

toxicity; 

developmental 

effects 

4086540 

1 

(3) Non-Target Insects 

There is a potential for exposure to non-target insects from the use of MCPB. In 

particular, MCPB’s foliar application will result in honey bee exposure. Available data 

from a honey bee acute toxicity study indicated that technical MCPB is practically nontoxic to the honey bee (with an LD50 greater than 23 micrograms per bee). 

29 

 30 

(4) Non-target Terrestrial Plants 

 

MCPB is an herbicide, and therefore plant toxicity is expected. Terrestrial plant 

toxicity studies indicate that the most sensitive monocot species in seedling emergence 

tests is the onion with the lowest EC25 of 0.02 lb ae/acre based on shoot length. This 

value represents 0.093% of the maximum application rate for MCPB. The most 

sensitive dicot species is cabbage with an EC25 of 0.016 lb ae/acre in the seedling 

emergence study based on shoot length. The most sensitive monocot in the vegetative 

vigor test is onion, with an EC25 of 0.016 lb ae/acre based on shoot weight. The most 

sensitive dicot species in the seedling emergence study is tomato with an extrapolated 

EC25 of 0.0017 lb ae/acre based on shoot weight. The observed non-lethal effects 

included brown leaf tips in cabbage, corn, onion, ryegrass, radish, and soybean; necrosis 

in corn, radish, onion, and soybean; chlorosis in onion, cucumber, and lettuce; stem 

tumors in soybean and tomato; leaf curl in tomato, and decreased size in cabbage, 

cucumber, lettuce, onion, and ryegrass. 

 

 
 31 

3. Ecological Risk Estimation (RQs) 

 

The Agency’s ecological risk assessment compares toxicity endpoints from 

ecological toxicity studies to EECs which are based on environmental fate 

characteristics and pesticide use data. To evaluate the potential risk to non-target 

organisms from the use of MCPB products, the Agency calculates a Risk Quotient (RQ), 

which is the ratio of the EEC to the most sensitive toxicity endpoint values, such as the 

median lethal dose (LD50) or the median lethal concentration (LC50). These RQ values 

are then compared to the Agency’s levels of concern (LOCs), shown in Table 16, which 

indicate whether a pesticide, when used as directed, has the potential to cause adverse 

effects to non-target organisms. When the RQ exceeds the LOC for a particular 

category, the Agency presumes a risk of concern to that category. These risks of concern 

may be addressed by further refinements of the risk assessment or mitigation. Use, 

toxicity, fate, and exposure are considered when characterizing the risk, as well as the 

levels of certainty and uncertainty in the assessment. EPA further characterizes 

ecological risk based on any reported incidents to non-target terrestrial or aquatic 

organisms in the field (e.g., fish or bird kills). 

 

Table 16. EPA’s Levels of Concern and Associated Risk Presumptions 

 

Risk Presumption 

 

LOC for 

Terrestrial 

Animals 

 

LOC for 

Aquatic 

Animals 

 

LOC for 

Plants 

 

Acute Risk - there is potential for acute risk; regulatory 

action may be warranted. 

 

0.5 

 

0.5 

 

1 

 

Acute Endangered Species - endangered species may be 

adversely affected; regulatory action may be warranted. 

 

0.1 

 

0.05 

 

1 

 

Chronic Risk - there is potential for chronic risk; regulatory 

action may be warranted. 

 

1 

 

1 

 

N/A 

 

 

a. Risk to Aquatic Organisms 

 

(1) Fish and Aquatic Invertebrates 

 

No acute risks are predicted for freshwater fish and invertebrates at the 

maximum predicted estimated concentration of MCPB in water bodies. All acute 

freshwater fish and invertebrate RQs are less than 0.01. 

 

There are no LOC exceedences for acute risks to estuarine/marine fish and 

chronic risks to freshwater fish, freshwater invertebrates, and estuarine/marine fish for 

MCPB based on RQ values calculated using acute-to-chronic ratios derived from MCPA 

data. 
 32 

 33 

(2) Aquatic Plants 

 

For MCPB acid runoff/drift, there are no exceedances of the acute risk LOCs for 

the pea scenarios that were modeled. The RQs range from 0.08 to 0.21. 

 

b. Risk to Non-target Terrestrial Organisms 

 

(1) Birds 

 

Assuming mean predicted residues at the maximum application rate (1.5 lb 

ae/A), there are potential acute risks to small (20 gram) birds that consume short grass 

(RQ is 0.80). All other avian RQs are below the Agency’s level of concern. The avian 

acute risk quotients are presented in Table 17, below. 

 

No chronic avian risks are predicted for MCPB. Chronic RQs for MCPB were 

calculated using the NOEC of 1,000 mg/kg-diet from an MCPA avian reproduction 

study. The chronic RQs range from 0.02 to 0.36, which is below EPA’s level of concern. 

 

 

Table 17. Avian Acute Risk Quotients (RQs) 

 Food type 

Weight class (g) 

 RQs at Predicted Mean 

Residues 20 0.8 100 0.36 short grass 1000 0.11 20 0.34 100 0.15 tall grass 1000 0.05 20 0.42 100 0.19 broadleaf forage, small insects 1000 0.06 20 0.07 100 0.03 fruit, pods, seeds, 

large insects 1000 0.01 

 

(2) Mammals 

 

Assuming mean residue levels at the maximum MCPB application rate of 1.5 lb 

ae/A, there are no exceedances of any acute LOCs for mammals (RQs range from <0.01 

to 0.07). However, chronic LOCs are exceeded for mammals of all weight classes that 
 34 

consume grasses, broadleaf forage, and small insects (RQs range from 1.23 to 6.44). 

Table 18, below, provides the mammalian chronic RQs. 

 

Table 18. Mammalian Chronic Risk Quotients (RQs) based on NOAEC of 91.2 mg/kg-diet 

 Food type Weight class (g) 

 RQs at Predicted Mean 

Residues 15 6.44 35 5.53 

Short grass 1000 2.91 15 2.73 35 2.34 

Tall grass 1000 1.23 15 3.41 35 2.93 

Broadleaf forage, small insects 1000 1.54 15 0.53 35 0.46 

Fruit, large insects 100 0.24 

 

15 

 

0.12 

 

35 

 

0.1 

 

Seeds, pods 

1000 

 

0.08 

 

 

(3) Non-Target Insects 

 

EPA does not currently quantify risks to terrestrial non-target insects. RQs are 

therefore not calculated for these organisms. Since MCPB is practically non-toxic to 

bees on a contact exposure basis (LD50 of >23 μg/bee), the potential for MCPB to have 

adverse effects on pollinators and other beneficial insects is low. 

 

(4) Non-Target Terrestrial Plants 

 

EPA used the most sensitive seedling emergence values (0.02 and 0.016 lb 

ae/acre, respectively) for monocots and dicots, to calculate RQs for exposure to 

terrestrial plants near MCPB-treated fields. Exposure is expected due to runoff and 

spray drift. The acute LOCs for non-target terrestrial plants are exceeded for nonendangered monocots and dicots in dryland and semi-aquatic areas located near treated 

areas. Acute LOCs are also exceeded for monocots and dicots due to exposure from 

spray drift. Table 19, below, provides the terrestrial plant risk quotients. 
 35 

 

 

 

Table 19. Terrestrial Plant Risk Quotients (RQs) 

 

Acute Non-Endangered RQs 

 

Acute Endangered RQs 

 

Scenario 

 

Adjacent 

to 

treated 

sites 

 

SemiAquatic 

areas 

 

Drift 

 

Adjacent 

to 

treated 

sites 

 

SemiAquatic 

areas 

 

Drift 

 

Ground spray application (1.5 lbs ae/acre) 

 Monocot 

 

4.50 

 

38.25 

 

0.94 

 

9.00 

 

76.50 

 

-- 

 Dicot 

 

5.63 

 

47.81 

 

2.08 

 

9.00 

 

76.50 

 

-- 

 

Aerial spray application (1.5 lbs ae/acre) 

 Monocot 

 

6.00 

 

26.25 

 

4.69 

 

12.00 

 

52.50 

 

-- 

 Dicot 

 

7.50 

 

32.81 

 

10.42 

 

12.00 

 

52.50 

 

– 

 

 

4. Ecological Incidents 

 

The Agency has not received any ecological incident reports for MCPB. 

 

5. Endangered Species Concerns 

 

The screening level ecological risk assessment results in a determination that the 

use of MCPB will have no direct acute effects on freshwater fish, freshwater 

invertebrates, and insects, and no direct chronic effect to birds. However, the Agency’s 

level of concern for direct acute effects to endangered and threatened birds, and 

terrestrial and semi-aquatic plants, and for direct acute and chronic effects to mammals, 

is exceeded for the use of MCPB. Further, potential indirect effects to any species 

dependent upon a species that experiences effects from use of MCPB can not be 

precluded based on the screening level ecological risk assessment. 

 

a. Risk to Endangered Species 

 

The screening level risk assessment for listed species indicates that MCPB 

exceeds the acute endangered species LOCs for birds that feed on grasses, broadleaf 

forage, and small insects (RQs range up to 2.26 at maximum predicted residues) and 

terrestrial and semi-aquatic plants (RQs range up to 77). Also, the chronic LOC of 1.0 is 

exceeded for mammals foraging on grasses, broadleaf forage, small insects, fruit, and 

large insects (RQs range up to 20 at maximum predicted residues). In addition to 
potential direct effects, there may be potential for indirect effects to listed species that 

are dependent upon a taxa that may experience effects from the use of this pesticide. 

The Agency can not quantitatively predict potential acute direct effects to 

endangered and threatened estuarine/marine fish or aquatic vascular and non-vascular 

plants; nor direct chronic effects to endangerd and threatened fresh water fish and 

invertebrates, and estuarine/marine fish and invertebrates and therefore the potential 

for effects can not be precluded based on EPA's screening level ecological risk 

assessment. In the case of the current lack of effects thresholds for listed aquatic plants, 

the potential for indirect effects on listed species with obligate relationships on a given 

species of aquatic plant cannot be discounted because definitive RQs for comparison to 

the listed species LOCs are unavailable. Potential risks to endangered species identified 

in the Environmental Fate and Ecological Risk Assessment and reflected in this RED 

for MCPB are based solely on EPA’s screening level ecological risk assessment and do 

not constitute “may effect” findings under the Endangered Species Act. 

6. Risk Characterization 

The risk assessment for MCPB is a conservative, screening-level assessment conducted 

with the maximum application rate of 1.5 lb ae/A. 

Freshwater and estuarine/marine fish and aquatic invertebrates do not appear to be at 

acute risk from exposure to MCPB, and there are no risk concerns for non-endangered aquatic 

plants for the pea scenarios that were modeled. 

EPA’s level of concern is exceeded for chronic risk to mammals that consume grasses, 

broadleaf plants, and small insects, although the exceedances are relatively small (RQs range from 

1.23 to 6.44; chronic LOC is exceeded if RQ > 1.0). This screening-level assessment assumes 

that 100 percent of the diet is comprised of single food types foraged only from treated fields. 

The assumption of 100 percent diet from a single food type may not be realistic for chronic 

exposures from the single annual application of MCPB to peas because diets are likely to be more 

variable over longer periods of time depending on size and forage range of animals. 

EPA’s level of concern is also exceeded for acute risk to small birds that consume short 

grasses, although the exceedances are relatively small (RQs range from 0.34 to 0.80). The 

screening-level assessment assumes that 100 percent of the diet is comprised of single food types.

 This assumption may be more realistic for acute risks than chronic risks. MCPB is categorized as 

moderately toxic to avian species on an acute oral basis, but it is practically non-toxic to avian 

species on an acute dietary basis. Based on these acute toxicity data, there is a large differential in 

the acute lethality when MCPB is administered as a single gavage for acute oral studies, as 

compared to when MCPB is mixed in the feed for acute dietary studies. There are limitations to 

both the dose-based and dietary-based method of calculating risk quotients; however, for many 

compounds a gavage dose represents a very short-term, high-intensity exposure, whereas dietary 

exposure may be of a more prolonged nature. The disparity in mortality between the two types of 

36 

studies suggests that the dietary matrix may have a lowering effect for the toxicity of MCPB. 

EPA’s level of concern is exceeded for terrestrial plants, which is expected based on 

MCPB’s herbicidal properties. Risks are expected if exposure occurs, but there is very limited 

use of MCPB. It is only registered for use on pea crops, and it is approved for use only once per 

year, at a maximum rate of 1.5 lb ae/acre. Total annual use is less than 15,000 pounds. 

IV. Risk Management, Reregistration, and Tolerance Reassessment Decision 

A. Determination of Reregistration Eligibility 

Section 4(g)(2)(A) of FIFRA calls for the Agency to determine, after submission of 

relevant data concerning an active ingredient, whether products containing the active ingredient 

are eligible for reregistration. The Agency has previously identified and required the submission 

of the generic (i.e., active ingredient-specific) data to support reregistration of products 

containing MCPB as an active ingredient. 

The Agency has completed its review of submitted data and its assessment of the human 

and ecological risks associated with the use of pesticide products containing the active ingredient 

MCPB. Based on a review of these data, the Agency has sufficient information on the human 

health and ecological effects of MCPB to make decisions as part of the tolerance reassessment 

process under FFDCA and the reregistration process under FIFRA, as amended by FQPA. The 

Agency has determined that MCPB-containing products are eligible for reregistration provided 

that: (i) required product-specific data are submitted; (ii) the risk mitigation measures outlined in 

this document are adopted; and (iii) label amendments are made to reflect these measures. Label 

changes are described in Section V. Appendix A summarizes the uses of MCPB that are eligible 

for reregistration. Appendix B identifies the generic data that the Agency reviewed as part of its 

determination for reregistration eligibility of MCPB, and lists the submitted studies that the 

Agency found acceptable. 

Based on its evaluation of MCPB, the Agency has determined that MCPB products, 

unless labeled and used as specified in this document, would present risks inconsistent with 

FIFRA and FFDCA. Accordingly, should a registrant fail to implement any of the risk mitigation 

measures identified in this document, the Agency may take regulatory action to address the risk 

concerns from the use of MCPB. If all changes outlined in this document are incorporated into 

the product labels, then all current risks for MCPB will be adequately mitigated for the purposes 

of this determination under FIFRA. Once the Endangered Species assessment is completed, 

further changes to these registrations may be necessary as explained in Section IV.D.3. 

B. Public Comments and Responses 

37 
Through the Agency’s public participation process, EPA worked extensively with 

stakeholders and the public to reach the regulatory decisions for MCPB. During the public 

comment period on the risk assessments, which closed on January 3, 2006, the Agency received 

comments from one private citizen, and the MCPB Task Force. These comments in their entirety 

are available in the public docket (EPA-HQ-OPP-2005-0263) at http://www.regulations.gov. A 

detailed Response to Comments document is available in the public docket as well. 

The RED and technical supporting documents for MCPB are available to the public 

through EPA’s electronic public docket and comment system, EPA Dockets, under docket 

identification (ID) number EPA-HQ-OPP-2005-0263. The public may access EPA Dockets at 

http://www.regulations.gov/fdmspublic-rel11/component/main. In addition, the MCPB RED may 

be downloaded or viewed through the Agency’s website at 

http://www.epa.gov/pesticides/reregistration/status.htm. 

C. Regulatory Position 

1. Food Quality Protection Act Findings 

a. “Risk Cup” Determination 

As part of the FQPA tolerance reassessment process, EPA assessed the risks associated 

with MCPB. An aggregate assessment was conducted for exposures through food and drinking 

water. (Residential exposures were not aggregated because MCPB is not registered for 

residential use.) EPA has determined that risk from dietary (food and water sources) exposure to 

MCPB is within its own “risk cup.” The Agency has determined that the human health risks from 

these combined exposures are within acceptable levels. In other words, EPA has concluded that 

the tolerances for MCPB meet FQPA safety standards. In reaching this determination, EPA has 

considered the available information on the special sensitivity of infants and children, as well as 

aggregate exposure from food and water. 

b. Determination of Safety to the U.S. Population 

The Agency has determined that the established tolerances for MCPB meet the safety 

standards under the FQPA amendments to Section 408(b)(2)(D) of the FFDCA, and that there is 

a reasonable certainty no harm will result to the general population or any other population from 

the use of MCPB. In reaching this conclusion, the Agency has considered all available 

information on the toxicity, use practices and exposure scenarios, and the environmental behavior 

of MCPB. As discussed in Chapter 3, the total acute and chronic dietary (food plus water) risks 

are below the Agency’s level of concern (< 100% of the PAD) for the general population and all 

subgroups. The highest exposed population subgroup was infants (<1 years old) at < 4% of the 

aPAD and 10% of the cPAD. 

c. Determination of Safety to Infants and children 

38 
The Agency has determined that the established tolerances for MCPB meet the safety 

standards under the FQPA amendments to Section 408(b)(2)(C) of the FFDCA, and that there is 

a reasonable certainty that no harm will result to infants and children. The safety determination 

for infants and children considers the toxicity, use practices, and environmental behavior noted 

above for the general population, but also takes into account the possibility of increased dietary 

exposure due to the specific consumption patterns of infants and children, as well as the possibility 

of increased susceptibility to the toxic effects of MCPB residues in this population subgroup. 

In determining whether infants and children are particularly susceptible to toxic effects 

from MCPB residues, the Agency considered the completeness of the database for developmental 

and reproductive effects, the nature of the effects observed, and other information. The FQPA 

safety factor for MCPB has been retained for acute exposures and partially retained for chronic 

exposures due to uncertainty in the toxicology database (lack of a DNT study). However, the 

toxicity database for MCPB, which is bridged from MCPA, includes acceptable developmental 

and reproductive toxicity studies and there is no evidence in the developmental or reproductive 

toxicity studies of sensitivity or susceptibility to newborns. 

As discussed in Chapter 3, the total acute and chronic dietary (food plus water) risks are 

below the Agency’s level of concern (< 100% of the PAD) for the general population and all 

subgroups. The highest exposed population subgroup was infants (<1 years old) at < 4% of the 

aPAD and 10% of the cPAD. 

d. Endocrine Disruptor Effects 

EPA is required under the 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 endocrine effects as the Administrator may designate.” Following recommendations of its 

Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC), EPA determined 

that there was a scientific basis 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 EPA include evaluations of potential effects in wildlife. For pesticides, EPA 

will use FIFRA 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. Furthermore, 

as the science develops and resources allow, screening of additional hormone systems may be 

added to the Endocrine Disruptor Screening Program (EDSP) and MCPB may be subject to 

additional screening. 

e. Cumulative Risks 

Risks summarized in this document are those that result only from the use of 

MCPB. The Food Quality Protection Act (FQPA) requires that the Agency consider 

available information concerning the cumulative effects of a particular pesticide’s 

39 

residues and “other substances that have a common mechanism of toxicity.” The 

reason for consideration of other substances is due to the possibility that low-level 

exposures to multiple chemical substances that cause a common toxic effect by a 

common toxic mechanism could lead to the same adverse health effect as would a 

higher level of exposure to any of the substances individually. Unlike other pesticides 

for which EPA has followed a cumulative risk approach based on a common mechanism 

of toxicity, EPA has not made a common mechanism of toxicity finding for MCPB. For 

information regarding EPA’s efforts to determine which chemicals have a common 

mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the 

policy statements released by EPA’s Office of Pesticide Programs concerning common 

mechanism determinations and procedures for cumulating effects from substances 

found to have a common mechanism on EPA’s website at 

http://www.epa.gov/pesticides/cumulative/. 

2. Tolerance Reassessment Summary 

a. Tolerances Currently Listed Under 40 CFR § 180.318 

Tolerances are currently established under 40 CFR §180.318 for residues of MCPB [4-(2-

methyl-4-chlorophenoxy)butyric acid)] per se in/on peas at 0.1 ppm. The Agency has concluded 

that the residue of concern for both tolerance enforcement and for dietary risk analysis consists of 

MCPB and MCPA, free and conjugated. The tolerance expression will be revised accordingly, 

once all data have been submitted (see Table 20). EPA notes that although additional data are 

required, there are no dietary risks associated with the tolerance for peas and EPA considers it 

reassessed at the current level. 

No maximum residue limits (MRLs) for MCPB have been established by Codex for any 

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

MCPB. 

Table 20. Tolerance Reassessment Summary for Registered MCPB Uses 

Commodity 

Current 

Tolerance 

(ppm) 

Range of 

Residues (ppm) 

Tolerance 

Reassessment 

(ppm) Comment 

Tolerances Listed Under 40 CFR §180.318 

Pea 0.1(N)* <0.05 0.1 

Residue studies must be submitted 

depicting the magnitude of both MCPB 

and MCPA residues in/on peas. 

* The “(N)” designation indicates negligible residues and EPA will propose to remove the “(N)” designation 

from all entries to conform to current Agency administrative practice. 

D. Regulatory Rationale 

40 
The Agency has determined that MCPB is eligible for reregistration provided that risk 

mitigation measures outlined in this document are adopted, and label amendments are made to 

reflect these measures. 

The following is a summary of the rationale for managing risks associated with the use of 

MCPB. Where labeling revisions are warranted, specific language is set forth in the summary 

tables of Section V of this document. 

41 

1. Human Health Risk Mitigation 

a. Dietary (Food) Risk Mitigation 

The Agency’s unrefined Tier 1 (100% crop treated) acute and chronic dietary (food only) 

risk assessments for MCPB indicated that acute and chronic risk estimates are below the 

Agency’s level of concern. Therefore, no dietary risk reduction measures are required. 

b. Drinking Water Risk Mitigation 

Estimated environmental concentrations (EECs) of MCPB and its degradates for both 

ground water and surface water sources of drinking water are below the Agency’s level of 

concern. Therefore, no mitigation is needed for drinking water. 

c. Aggregate Risk Mitigation 

EPA must consider and aggregate (add) pesticide exposures and risks from three major 

sources: food, drinking water, and residential. MCPB has no residential uses. Therefore, the 

aggregate exposure risk assessments for MCPB only incorporate exposures and risks from food 

and drinking water. 

(1) Acute Aggregate Risk 

The Agency’s acute dietary (food plus water) risk assessment indicated that acute dietary 

risks are below the Agency’s level of concern. Therefore, no mitigation is required. 

(2) Chronic Aggregate Risk 

The Agency’s chronic dietary (food plus water) risk assessment indicated that chronic 

dietary risks are below the Agency’s level of concern. Therefore, no mitigation is required. 

d. Occupational Risk Mitigation 

(1) Handler Exposure 

EPA completes handler exposure assessments by using a baseline (long-sleeved shirt and 

long pants) exposure scenario and, if required, increasing levels of mitigation such as Personal 

Protective Equipment (PPE) or engineering controls to achieve an adequate margin of exposure 

(MOE). For MCPB, short- and intermediate-term inhalation risks to occupational handlers are 

below the Agency’s level of concern (i.e., MOE ≥100) at baseline (i.e., no respirator) for mixers, 

loaders, and applicators. For dermal risks associated with mixing and loading for groundboom 

and aerial application, MOEs are above the Agency’s level of concern (i.e., MOE < 100) at 

baseline, but are below EPA’s level of concern (i.e., MOE ≥100) when chemical-resistant gloves 

42 

are added. To mitigate the potential dermal risks to mixers and loaders, chemical-resistant gloves 

will be required. 

(2) Post-Application Risk Mitigation 

EPA assessed short/intermediate-term post-application risks to workers who enter pea 

fields recently treated with MCPB to conduct tasks such as scouting and irrigation. EPA did not 

assess long-term post-application exposure risks because MCPB is used only once per season. 

Using the maximum application rate of 1.5 lb ae/A and the default dislodgeable foliar residue 

value of 20 percent, post-application risks are below the Agency’s level of concern (i.e., MOEs 

≥100) on day zero, or 12 hours after application. EPA has determined that a 12-hour restricted 

entry interval is appropriate for MCPB. 

2. Environmental Risk Mitigation 

EPA’s levels of concern are exceeded for acute risk to small-sized birds and terrestrial 

plants, and chronic risk to mammals. EPA has determined that the risk mitigation that is 

appropriate for environmental concerns at this time is to require medium or coarser droplet sizes 

to minimize the potential for spray drift. 

3. Endangered Species Considerations 

From the screening-level assessment, RQs exceeded the LOCs for endangered 

species for some of the exposure scenarios. Chronic RQs exceed the LOCs for 

endangered mammals (RQs range from 2 to 20 at maximum residue levels), acute RQs 

exceed LOCs for endangered birds (RQs range from 0.2 to 2.26 at maximum residue 

levels), and acute RQs exceed the endangered terrestrial plant LOCs for monocots and 

dicots (RQs range from 9 to 77). 

The Agency has developed the Endangered Species Protection Program to 

identify pesticides whose use may cause adverse impacts on endangered and threatened 

species, and to implement mitigation measures that address these impacts. The 

Endangered Species Act (ESA) requires federal agencies to ensure that their actions are 

not likely to jeopardize listed species or adversely modify designated critical habitat. To 

analyze the potential of registered pesticide uses that may affect any particular species, 

EPA uses basic toxicity and exposure data developed for the REDs and considers it in 

relation to individual species and their locations by evaluating important ecological 

parameters, pesticide use information, geographic relationship between specific 

pesticide uses and species locations, and biological requirements and behavioral aspects 

of the particular species, as part of a refined species-specific analysis. When conducted, 

this species-specific analysis will take into consideration any regulatory changes 

recommended in this RED that are being implemented at that time. 

43 

Following this future species-specific analysis, a determination that there is a 

likelihood of potential impact to a listed species or its critical habitat may result in 

limitations on the use of MCPB, other measures to mitigate any potential impact, or 

consultations with the Fish and Wildlife Service or the National Marine Fisheries 

Service, as necessary. If the Agency determines use of MCPB “may affect” listed species 

or their designated critical habitat, EPA will employ the provisions in the Services 

regulations (50 CFR Part 402). Until that species-specific analysis is completed, the 

risk mitigation measures being implemented through this RED will reduce the 

likelihood that endangered and threatened species may be exposed to MCPB at levels of 

concern. EPA is not requiring specific MCPB label language at the present time relative 

to threatened and endangered species. If, in the future, specific measures are necessary 

for the protection of listed species, the Agency will implement them through the 

Endangered Species Protection Program. 

4. Spray Drift Management 

The Agency has been working with the Spray Drift Task Force, EPA Regional Offices, 

State Lead Agencies for pesticide regulation, and other parties to develop the best spray drift 

management practices. The Agency has completed its evaluation of the new database submitted 

by the Spray Drift Task Force, a membership of U.S. pesticide registrants, and is developing a 

policy on how to appropriately apply the data and the AgDRIFT computer model to its risk 

assessments for pesticides applied by air, orchard airblast, and ground hydraulic methods. After 

the policy is in place, the Agency may impose further refinements in spray drift management 

practices to reduce off-target drift and risks associated with aerial as well as other application 

methods where appropriate. 

Spray drift is a potential source of MCPB non-target exposure near spraying operations. 

This is particularly the case with aerial application, but spray drift exposure may also result from 

ground application of MCPB. To minimize the potential for spray drift, the Agency is requiring 

medium or coarser droplet sizes for all MCPB end-use products. Additionally, the Agency 

encourages the inclusion of best management practices on labels to reduce spray drift. In the 

future, MCPB labels may need to be revised to include additional or different drift label 

statements. 

V. What Registrants Need to Do 

The Agency has determined that MCPB is eligible for reregistration provided that 

product-specific data are submitted and the mitigation measures stated in this document are 

included in upcoming label submissions. In the near future, the Agency intends to issue Data CallIn (DCI) notices requiring product-specific data and generic confirmatory data. Generally, 

registrants will have 90 days from receipt of a DCI to complete and submit response forms or 

request time extensions and/or waivers with a full written justification. For product-specific data, 

44 

the registrant will have eight months to submit data and amended labels. For generic data, due 

dates can vary depending on the specific studies being required. Listed below are the additional 

generic data that the Agency intends to require. 

45 

F. Manufacturing Use Products 

1. Additional Generic Data Requirements 

The generic database supporting the reregistration of MCPB for the above eligible use has 

been reviewed and determined to be substantially complete based on bridging from MCPA data. 

However, the data listed below, in Tables 21 and 22, are necessary to confirm the reregistration 

eligibility decision documented in this RED. 

Table 21. Toxicology and Residue Chemistry Data Requirements 

Study Required Guideline Number Comment 

Confined Accumulation in Rotational Crops 

Study 860.1850 Must be conducted with MCPB 

Magnitude of Residues in Plants 860.1300 

Must be conducted with MCPB and 

MCPA 

Enforcement Analytical Methods 860.1340 

Must be conducted with MCPB and 

MCPA 

Reserved pending outcome of 

Developmental neurotoxicity study in rats developmental neurotoxicity study in rats 

[Reserved] 870.6300 with MCPA 2-EHE 

28-day Inhalation Study (abbreviated 90-day Reserved pending outcome of 28-day 

protocol) [Reserved] 870.3465 Inhalation Study with MCPA 

Table 22. Environmental Fate and Ecological Toxicity Data Requirements 

Study Required Guideline Number Comment 

Terrestrial Field Dissipation 835.1600 

Estuarine/marine invertebrate acute EC50 

(eastern oyster) 

850.1025 

Estuarine/marine fish acute LC50 

(sheepshead minnow) 

850.1075 

Freshwater fish early life stage 

(fathead minnow) 

850.1400 

Freshwater invertebrate life cycle (daphnia) 

[Reserved] 

850.1300 Reserved pending the outcome of acute 

estuarine/marine fish and invertebrate studies. 

Estuarine/marine life cycle (mysid) [Reserved] 850.1350 Reserved pending the outcome of acute 

estuarine/marine fish and invertebrate studies. 

Estuarine/marine life cycle (fish) [Reserved] 850.1400 Reserved pending the outcome of acute 

estuarine/marine fish and invertebrate studies. 

Reserved pending the outcome of acute 

46 
Study Required Guideline Number Comment 

Freshwater fish full life cycle [Reserved] 850.1500 estuarine/marine fish and invertebrate studies. 

2. Labeling for Manufacturing-Use Products 

To ensure compliance with FIFRA, manufacturing use product (MUP) labeling should be 

revised to comply with all current EPA regulations, PR Notices, and applicable policies. The 

MUP labeling should bear the labeling contained in Table 23 at the end of this section. 

B. End-Use Products 

1. Additional Product-Specific Data Requirements 

Section 4(g) (2) (B) of FIFRA calls for the Agency to obtain any needed productspecific data regarding the pesticide after a determination of eligibility has been made. 

The registrant must review previous data submissions to ensure they meet current EPA 

acceptance criteria and if not, commit to conduct new studies. If a registrant believes 

that previously submitted data meet current testing standards, then the study MRID 

numbers should be cited according to the instructions in the Requirement Status and 

Registrations Response Form provided for each product. The Agency intends to issue a 

separate product-specific Data Call-In outlining specific data requirements. 

2. Labeling for End-Use Products 

Labeling changes are necessary to implement measures outlined in Section IV 

above. The specific changes and language required are presented in Table 23 below. 

Existing stocks time frames will be established case-by-case, depending on the 

number of products involved, the number of label changes, and other factors. Please 

refer to “Existing Stocks of Pesticide Products; Statement of Policy,” Federal Register, 

Volume 56, No. 123, June 26, 1991. 

47 

C. Labeling Changes Summary Table 

In order to be eligible for reregistration, registrants must amend all product labels to incorporate the risk m

outlined in Section IV. The following table describes how language on the labels should be amended. 

Table 23: Summary of Labeling Changes for MCPB 

Description Amended Labeling Language 

Manufacturing Use Products 

One of these statements may be added to a label to allow reformulation of the product for a specific use or all additional uses supported by a formulator or user group 

“Only for formulation into an herbicide for use on peas.” 

“This product may be used to formulate products for specific use(s) not listed on the MUP labeformulator, user group, or grower has complied with U.S. EPA submission requirements regardsupport of such use(s).” “This product may be used to formulate products for any additional use(s) not listed on the MP formulator, user group, or grower has complied with U.S. EPA submission requirements regardsupport of such use(s).” 

Environmental Hazards Statements Required by the RED and Agency Label Policies 

“Do not discharge effluent containing this product into lakes, streams, ponds, estuaries, oceans 

unless in accordance with the requirements of a National Pollutant Discharge Elimination Syste(NPDES) permit and the permitting authority has been notified in writing prior to discharge. Ddischarge effluent containing this product into sewer systems without previously notifying the setreatment plant authority. For guidance, contact your State Water Board or Regional Office of tEnvironmental Protection Agency.” 

End Use Products Intended for Occupational Use (WPS) 

PPE Requirements Established by the RED1 

“Personal Protective Equipment (PPE) 

48 

for liquid formulations Some materials that are chemical-resistant to this product are (registrant inserts correct chemic

resistant material). If you want more options, follow the instructions for category [registrant in

B, C, D, E, F, G, or H] on an EPA chemical-resistance category selection chart. Mixers, loaders, and other handlers must wear: · Long-sleeved shirt · Long pants · Shoes plus socks · Chemical-resistant gloves when mixing, loading or exposed to the concentrate. ” 

User Safety Requirements “Follow manufacturer’s instructions for cleaning/maintaining PPE. If no such instructions for w

exist, use detergent and hot water. Keep and wash PPE separately from other laundry.” 

Engineering Controls “Engineering Controls: 

Pilots must use an enclosed cockpit that meets the requirements listed in the Worker Protection (WPS) for agricultural pesticides [40 CFR 170.240 (d)(6)].” 

User Safety Recommendations 

“User Safety Recommendations Users should wash with plenty of soap and water before eating, drinking, chewing gum, using tusing the toilet. Users should remove clothing/PPE immediately if pesticide gets inside. Then wash thoroughly on clean clothing. Users should remove PPE immediately after handling this product. Wash the outside of gloves removing. As soon as possible, wash thoroughly and change into clean clothing.” 

Environmental Hazards “Environmental Hazards 

49 

Avoid spray drift as this product may injure susceptible crops and plants such as cotton, beans, 

tomatoes and ornamentals. (Course sprays are less likely to drift.) Do not use same spray equipother purposes unless thoroughly cleaned prior to use. Do not apply this product through any tyirrigation system.” 

Restricted-Entry Interval “Do not enter or allow worker entry into treated areas during the restricted-entry interval (REI) 

hours.” 

Early Re-entry Personal “PPE required for early entry to treated areas that is permitted under the Worker Protection StaProtective Equipment that involves contact with anything that has been treated, such as plants, soil, or water, is: established by the RED. 

Coveralls, Shoes plus socks, Chemical-resistant gloves made of any waterproof material” 

General Application Restrictions 

“It is a violation of Federal Law to use this product in a manner inconsistent with its labeling. Rlabel before using this product.” “Do not apply this product in a way that will contact workers or other persons, either directly or drift. Only protected handlers may be in the area during application. For any requirement speciState or Tribe, consult the agency responsible for pesticide regulations.” 

Spray Drift Label Language for Products Applied as a Spray 

“Apply only as a medium or coarser spray (ASAE standard 572) or a volume mean diameter omicrons or greater for spinning atomizer nozzles.” “A variety of factors including weather conditions (e.g., wind direction, wind speed, temperaturhumidity) and method of application (e.g., ground, aerial, airblast, chemigation) can influence pdrift. The applicator and grower must evaluate all factors and make appropriate adjustments wapplying this product. WIND SPEED: Do not apply at wind speeds greater than 10 mph at the application site.” DROPLET SIZE: “Apply as a medium or coarser spray (ASAE standard 572).” RELEASE HEIGHT (GROUND APPLICATION): 

50 

1

“Apply using a nozzle height of no more than 4 feet above the ground or crop canopy.” RELEASE HEIGHT (AERIAL APPLICATION): “Do not release spray at a height greater than 10 feet above the ground or crop canopy.” 

 PPE that is established on the basis of Acute Toxicity of the end-use product must be compared to the active ingredient PPE in this documen

must be placed in the product labeling. For guidance on which PPE is considered more protective, see PR Notice 93-7. 

Instructions in the Labeling section appearing in quotations represent the exact language that should appear on the l

Instructions in the Labeling section not in quotes represents actions that the registrant should take to amend their laregistrations. 

51 

VI. Related Documents and How to Access Them 

This interim Reregistration Eligibility Document is supported by documents that are presently 

maintained in the OPP docket under docket number EPA-HQ-2005-0263. The OPP docket is 

located in Room 119, Crystal Mall #2, 1921 Jefferson Davis Highway, Arlington, VA. It is open 

Monday through Friday, excluding legal holidays from 8:30 am to 4 pm. The documents are also 

available on-line in the Federal Docket Management System (FDMS) at http://www.regulations.gov. 

The docket initially contained preliminary risk assessments and related documents as of 

November 2, 2005. Sixty days later, on January 3, 2006, the public comment period closed. The 

EPA then considered the comments received, revised the risk assessments as necessary. EPA then 

added formal “Response to Comments” documents, the Reregistration Eligibility Decision (RED) 

document, and the revised risk assessments to the docket on July 21, 2006. 

All documents, in hard copy form, may be viewed in the OPP docket room or downloaded or 

viewed via the Internet at http://www.regulations.gov. 

52 

Appendix A: 

Use Patterns Eligible for Reregistration for use on Peas 

Table 1. MCPB use on Peas 

Application Type, 

Equipment 

Formulation Max. Single 

App. Rate 

(lbs ae/A) 

Seasonal Max. 

(lbs ae/A/Yr) 

PHII 

(Days) 

REI 

(Hours) 

Restrictions/Comments 

Spray/ground and 

Aerial 

Thistrol Herbicide 

(71368-5) and 

Sodium MCPB 

Solution (71368-7) 

1.5 1.5 1 24 Use single layer PPE 

53 
Appendix B:


Data Supporting Guideline Requirements of the Reregistration of MCPB


Table 1. Product Chemistry 

New Guideline 

Number 

Old Guideline 

Number 

Requirement Use Citation(s) 

860.1400 171-4H Magnitude of Residue in Irrigated Crops Peas 44754101 

Table 2. Ecological Effects 

New Guideline 

Number 

Old Guideline 

Number 

Requirement Use Citation(s) 

850.2100 71-1 Bobwhite Quail Peas 42560801 

850.2200 71-2A Avian Acute Dietary Toxicity Test, Bobwhite quail Peas 42560802 

850.2200 71-2B Avian Acute Dietary Toxicity Test, Mallard Peas 42560803 

850.1075 72-1C Fish Acute Toxicity Test Rainbow Trout Peas 42532608 

850.1075 72-1A Fish Acute Toxicity Test, Bluegill Sunfish Peas 42532601 

850.1010 72-2A Invertebrate Acute Toxicity Test, Freshwater 

Daphnids 

Peas 42532602 

850.1100 82-1 Acute Oral Toxicity Test, Rat Peas 144801, 116340 

870.3100 82-1A Subchronic Oral Toxicity Test, (90-day Feeding, 

rodent) 

Peas 42883602, 42883601 

870.3150 82-1B Subchronic Oral Toxicity Test, (90day - Feeding, 

non-rodent) 

Peas 116345, 116344, 

42883603 

870.3700 83-3A Prenatal Developmental Toxicity (Teratogenicity), 

RAP 

Peas 40865402 

870.3700 83-3B Prenatal Developmental Toxicity (Teratogenicity), 

Rabbit 

Peas 40865401 

870.3800 83-4A (MCPA) 2-generation Reprodution and Fertility Peas 40041701 

850.4150 122-1B Terrestrail Plant, Tier 1 (Vegetative Vigor) Peas 42560804, 43083205 

(MCPA) 

850.5400 122-2A Algal Toxicity, Tier 1 Peas 42532605,42532603,4 

2532609, 42532606 

850.5400 122-2B Algal Toxicity, Tier 2 Peas 42532605, 42532609, 

42532603, 42532606 

54 
850.4225 123-1A Seedling Germination and Seedling Emergence, 

Tier 2 

Peas 42560804 

850.4250 123-1B Vegetative Vigor, Tier 2 Peas 42560804 

850.4400 123-2 Aquatic Plant Toxicity Test Using Duckweed 

Lemma 

Peas 42532604 

850.3020 141-1 Honey Bee Acute Contact Toxicity Peas 42532607 

Table 3. Toxicology 

New Guideline 

Number 

Old Guideline 

Number 

Requirement Use Citation(s) 

870.1100 81-1 Acute Oral Toxicity-Rat Peas 116340, 144801 

870.1200 81-2 Acute Dermal Toxicity-Rabbit/Rat Peas 116342, 144799 

870.1300 81-3 Acute Inhalation Toxicity-Rat Peas 41630001 

870.2400 81-4 Primary Eye Irritation- Rabbit Peas 116343, 144797 

870.2500 81-5 Primary Skin Irritation - Rabbit Peas 144798 

870.2600 81-6 Dermal Sensitization, Guinea Pig Peas 144800 

870.3100 82-1A Subchronic Oral Toxicity Test (90 Day Feeding ­

Rodent) 

Peas 42883602 

870.3150 81-1B Subchronic Oral Toxicity Test (90 Day Feeding -

Non-Rodent) 

Peas 42883603 

870.3200 82-3 Repeated Dose Dermal Toxicity Test (21 Day), 

Rabbit 

Peas 116346 

870.3700a 83-3A Prenatal Developmental Toxicity, (Teratogenicity), 

Rat 

Peas 40865402 

870.3700b 83-3B Prenatal Developmental Toxicity, (Teratogenicity), 

Rabbit 

Peas 40865401 

870.5100 84-2 Bacterial (Escherichia Coll Wp2 and Wp2 uvrA) 

Reverse Gene Mutation Assay Test 

Peas 40564302, 40564303 

870.5375 84-2B In Vitro Mammalian Cytogenetics Tests (Structural 

Chromosomal Aberration Test) 

Peas 40564301 

870.5550 84-2 Unscheduled DNA synthesis in Mammalian Cells 

in Culture 

Peas 40564304 

870.7485 85-1 Metabolism and Pharmacokinetics (General 

Metabolism) 

Peas 44818101 

 55 
Table 4. Environmental Fate 

New Guideline 

Number 

Old Guideline 

Number 

Requirement Use Citation(s) 

835.2120 161-1 Hydrolysis of Parent and Degradates as a Function 

of pH at 25°C (Hydrolysis) 

Peas 42574301 

835.2240 161-2 Direct Photolysis Rate of Parent and Degradates in 

Water (Photodegradation in water) 

Peas 42574302 

835.2410 161-3 Photodegradation of Parent and Degradates in Soil 

(Photodegradation in soil) 

Peas 43829901 

835.4100 162-1 Aerobic Soil Metabolism Study Peas 43247601 

835.4200 162-2 Anaerobic Soil Metabolism Study Peas 43015501 

835.1230 163-1 Sediment (Leaching) and Soil 

Absorption/desorption for Parent and Degradates 

Peas 42693701, 43466401 

 56 
Appendix C:


Technical Support Documents


Additional documentation in support of this RED is maintained in the OPP docket, located in 

2777 Crystal Drive (One Potomac Yard) Arlington, VA 22202. It is open Monday through Friday, 

excluding legal holidays, from 8:30 AM to 4:30 PM. 

The docket initially contained preliminary human health and ecological effects risk 

assessments and related documents that were published November 2, 2005. The public comment 

period closed sixty days later, on January 3, 2006. The EPA then considered the comments received 

and revised the risk assessments where appropriate. Revised ecological risk assessments, as well as 

additional supporting documents will be published in the docket with this RED. 

57 

Appendix D: 

Citation Considered to be Part of the Database Supporting the Reregistration 

Eligibility Decision (Bibliography) 

Open Literature 

Books 

Howard, P.H. and W.M. Meylan. 1997 Handbook of Physical Properties of Organic Chemicals. 

Lewis Publishers, New York. Page 121. 

Podall, H. 2002. CBI Product Chemistry Review, March 8, 2002 

Tomlin, C.D.S., ed. 1997. The Pesticide Manual #65 MCPB Sodium Salt, British Corp Protection 

Council, 11th ed, Farnham, Surrey, UK. Page 254. 

WSSA (Weed Science Society of America). 1994. Herbicide Mode of Action and Sugarbeet Injury 

Symptoms. North Dakota State University of Agriculture and Applied Science Fargo, ND. 

Ferrell, J.A., G.E. Mac Donald, B.J. Brecke, A.C. Bennett, and J. Tredaway Ducar. 2005. Florida's 

Organo-Auxin Herbicide Rule-2005. University of Florida, Institute of Food and Agricultural 

Sciences, Gainesville, FL. 

Heimann, M.F. and R.C. Newman. 1997. Plant injury due to turfgrass broadleaf weed herbicides. 

University of Wisconsin - Cooperative Extension, Madison, WI. 

Lingenfelter, D.D. and N. L. Hartwig. 2003. Introduction to Weeds and Herbicides. Penn State 

Colloge of Agricultural Sciences - Agricultural Research and Cooperative Extension Page 1-20. 

Bibliography 

PC Code: 019201 

MRID CITATION 

116340 Holsing, G. (1969) Acute Oral--Rats: MCPB Technical: Project No. 517-102. Final rept. (Unpublished study received on un- known date under 1F1051; 

prepared by TRW, Inc., submitted by Rhodia, Inc., New Brunswick, NJ; 

CDL:091885-B) 

116342 Holsing, G. (1969) Acute Dermal--Rabbits: MCPB Technical: Project No. 517-103. Final rept. (Unpublished study received on un- known date under 

58 

 59 

1F1051; prepared by TRW, Inc., submitted by Rhodia, Inc., New Brunswick, 

NJ; CDL:091885-D) 

 

116343 

 

Holsing, G. (1969) Draize Eye--Rabbits: MCPB Technical: Project No. 517- 105. Final rept. (Unpublished study received on un- known date under 

1F1051; prepared by TRW, Inc., submitted by Rhodia, Inc., New Brunswick, 

NJ; CDL:091885-E) 

 

116345 

 

Holsing, G.; Ferrell, J. (1970) 13-week Dietary Administration-- Dogs: MCPB: Project No. 517-107. Final rept. (Unpublished study received on 

unknown date under 1F1051; prepared by TRW, Inc., submitted by Rhodia, 

Inc., New Brunswick, NJ; CDL: 091885-G) 

 

116346 

 

Weatherholtz, W.; Voelker, R. (1970) Three-week Repeated Dermal-- Rabbits: MCPB: Project No. 517-104. Final rept. (Unpublished study 

received on unknown date under 1F1051; prepared by TRW, Inc., submitted 

by Rhodia, Inc., New Brunswick, NJ; CDL: 091885-H) 

 

144797 

 

Liggett, M.; Parcell, B. (1985) Irritant Effects on the Rabbit Eye of MCPB Technical Acid: 841198D/AHM 19/SE. Unpublished study prepared by 

Huntingdon Research Centre plc. 7 p. 

 

144798 

 

Liggett, M.; Parcell, B. (1984) Irritant Effects on Rabbit Skin of MCPB Technical Acid: 841126D/AHM 18/SE. Unpublished study pre- pared by 

Huntingdon Research Centre plc. 6 p. 

 

144799 

 

Kynoch, S. (1985) Acute Dermal Toxicity to Rats of MCPB Technical Acid: 85150D/AHM 16/AC. Unpublished study prepared by Hunting- don 

Research Centre plc. 7 p. 

 

144800 

 

Seaber, J. (1985) Delayed Contact Hypersensitivity in the Guinea- Pig with MCPB Technical Acid: 85119D/AHM 20/SS. Unpublished study prepared 

by Huntingdon Research Centre plc. 14 p. 

 

144801 

 

Kynoch, S. (1985) Acute Oral Toxicity to Rats of MCPB Technical Acid: 85131D/AHM 15/AC. Unpublished study prepared by Hunting- don 

Research Centre plc. 12 p. 

 

40564301 

 

SanSebastian, J. (1987) 2-Methyl-4-chlorophenoxybutyric Acid (MCPB Acid): In vitro Chromosome Aberration Analysis in Chinese Hamster Ovary 

(CHO) Cells: Laboratory Project ID PH 320-RP-001- 87. Unpublished 

study prepared by Pharmakon Research Interna- tional, Inc. 34 p. 
 60 

 

40564302 

 

Stankowski, L. (1987) 2-Methyl-4-chlorophenoxybutyric Acid (MCPB Acid): Ames/Salmonella Plate Incorporation Assay: Laboratory Project ID 

PH 301-RP-001-87. Unpublished study prepared by Pharmakon Research 

International, Inc. 22 p. 

 

40564303 

 

Stankowski, L. (1988) @-Methyl-4-chlorophenoxybutyric acid (MCPB Acid): CHO/HPRT Mammalian Cell Forward Gene Mutation Assay: 

Laboratory Project ID PH 317-RP-001-87. Unpublished study pre- pared by 

Pharmakon Research International, Inc. 67 p. 

 

40564604 

 

Barfknecht, T. (1987) @-Methyl-4-chlorophenoxybutyric Acid (MCPB Acid): Rat Hepatocyte Primary Culture/DNA Repair Test: Laboratory 

Project ID PH 311-RP-001-87. Unpublished study pre- pared by 

Pharmakon Research International, Inc. 68 p. 

 

40865401 

 

Tyl, R.; Neeper-Bradley, T. (1988) Developmental Toxicity Evaluati- on of MCPB Administered by Gavage to New Zealand White Rabbits: Laboratory 

Project ID 51-547. Unpublished study prepared by Bu- shy Run Research 

Center. 241 p. 

 

40865402 

 

Tyl, R. (1988) Developmental Toxicity Evaluation of MCPB Administe- red by Gavage to CD (Sprague Dawley) Rats: Laboratory Project ID 51-532. 

Unpublished study prepared by Bushy Run Research Cente- r. 299 p. 

 

41630001 

 

Jackson, G.; Hardy, C.; Lewis, D.; et al. (1985) MCPB Technical Acid Acute Inhalation Toxicity Study in Rats 4-Hour Exposure: Lab Project Number: 

AHM17/85188. Unpublished study prepared by Hungtindon Research 

Centre, Ltd. 47 p. 

 

42574301 

 

Das, Y. (1992) Hydrolysis of (carbon 14)MCPB in Aqueous Solutions Buffered at pH 5, 7 and 9: Lab Project Number: 92010: 92-06. Unpublished 

study prepared by Innovative Scientific Services, Inc. 77 p. 

 

42574302 

 

Das, Y. (1992) Photodegradation of (carbon 14)MCPB in Aqueous Solutions Buffered at pH 5, 7 and 9 under Artificial Sunlight: Lab Project Number: 

92011: 92-07. Unpublished study prepared by Innovative Scientific 

Services, Inc. 174 p. 

 

42693701 

 

Robson, M. (1993) Determination of Adsorption/Desorption Characteristics of 4-(2-Methyl,4-Chlorophenoxy) Butyric Acid (MCPB) in Soil: Final 

Report: Lab Project Number: 68/127: 7414. Unpublished study prepared by 
 61 

Hazleton UK. 81 p. 

 

42883601 

 

Trutter, J. (1993) Range-Finding Dietary Toxicity Study with MCPB in Rats: Final Report: Lab Project Number: HWA 656-173. Unpublished study 

prepared by Hazleton Washington, Inc. 275 p. 

 

42883602 

 

Trutter, J. (1993) 13-Week Dietary Toxicity Study with MCPB in Rats: Final Report: Lab Project Number: HWA 656-174. Unpublished study prepared 

by Hazleton Washington, Inc. 439 p. 

 

42883603 

 

Dalgard, D. (1993) 13-Week Dietary Toxicity Study with MCPB in Dogs: Final Report: Lab Project Number: HWA 656-172. Unpublished study 

prepared by Hazleton Washington, Inc. 406 p. 

 

43015501 

 

Goodyear, A. (1993) Carbon 14-MCPB: Anaerobic Soil Metabolism: Final Report: Lab Project Number: 68/131-1015: 68/131: 200352. Unpublished 

study prepared by Hazleton UK. 90 p. 

 

43247601 

 

John, A.; Jones, M.; Lowden, P.; et al. (1994) MCPB: Aerobic Soil Metabolism: Lab Project Number: P/93/194. Unpublished study prepared 

by Rhone-Poulenc Agriculture Ltd. 108 p. 

 

43466401 

 

John, A.; Jones, M.; Lowden, P. (1994) MCPB: Fresh and Aged Leaching Study in Five Soils: Lab Project Number: P 92/333: 200724: RPAL 

P92/333. Unpublished study prepared by Rhone-Poulenc Agriculture Ltd. 

142 p. 

 

 

43829901 

 

Ferreira, E.; John, A.; Lowden, P.; et al. (1995) MCPB Soil Photolysis Study: Amended Report: Lab Project Number: P92/126 Unpublished study 

prepared by Rhone-Poulenc Agriculture Ltd. 75 p. (Amended version of 

42519101). 

 

44754101 

 

Corley, J.; Kunkel, D. (1999) MCPB: Magnitude of Residue on Pea (Reregistration): Lab Project Number: 05470.94-CAR23: 05470.94-CA52: 

05470.94-NY17. Unpublished study prepared by University of California. 

423 p. 

 

44818101 

 

Thornley, K. (1998) (Carbon-14)-MCPB: A Study of Adsorption, Distribution, Metabolism, and Excretion Following Oral Administration to 

the Rat: Final Report: Lab Project Number: 785/10-D1141. Unpublished 

study prepared by Covance. 195 p. 
PC Code: 019202 

MRID CITATION 

42532601 Bettencourt, M. (1992) MCPB Sodium--Acute Toxicity to Bluegill Sunfish (Lepomis macrochirus) under Flow-through Conditions: Final Report: Lab 

Project Number: 92-8-4363: 10566.0392.6226.105. Unpublished study 

prepared by Springborn Labs, Inc. 64 p. 

42532602 Putt, A. (1992) MCPB Sodium--Acute Toxicity to Daphnids (Daphnia magna) under Flow-through Conditions: Final Report: Lab Project 

Number: 92-7-4351: 10566. 0392. 6228. 115. Unpublished study prepared 

by Springborn Labs, Inc. 2 p. 

42532603 Hoberg, J. (1992) MCPB Sodium--Toxicity to the Freshwater Blue-green Alga, Anabaena flos-aquae: Final Report: Lab Project Number: 92-8-4381: 

10566.0392.6230.420. Unpublished study prepared by Springborn Labs, 

Inc. 54 p. 

42532604 Hoberg, J. (1992) MCPB Sodium--Toxicity to the Duckweed Lemna gibba: Final Report: Lab Project Number: 92-8-5368: 10566. 0392.6229.410. 

Unpublished study prepared by Springborn Labs, Inc. 61 p. 

42532605 Hoberg, J. (1992) MCPB Sodium--Toxicity to the Freshwater Green Alga, Selenastrum capricornutum: Final Report: Lab Project Number: 92-8-

4361: 10566.0392.6232.430. Unpublished study prepared by Springborn 

Labs, Inc. 58 p. 

42532606 Hoberg, J. (1992) MCPB Sodium--Toxicity to the Marine Diatom, Skeletonema costatum: Final Report: Lab Project Number: 92-8-4372: 

10566.0392.6233.450. Unpublished study prepared by Springborn Labs, 

Inc. 59 p. 

42532607 Maggi, V. (1992) Acute Contact Toxicity of MCPB Sodium Salt to Honey Bees (Apis melliflora L.): Lab Project Number: CAR 169-92. Unpublished 

study prepared by California Agricultural Research, Inc. 22 p. 

42532608 Bettancourt, M. (1992) MCPB Sodium--Acute Toxicity to Rainbow Trout (Oncorrhynchus mykiss) under Flow-through Conditions: Final Report: 

62 
Lab Project Number: 92-7-4338: 10566.0392.6227. 108. Unpublished 

study prepared by Springborn Labs, Inc. 64 p. 

42532609 Hoberg, J. (1992) MCPB Sodium--Toxicity to the Freshwater Diatom, Navicula pelliculosa: Final Report: Lab Project Number: 92-10-4448: 

10566.0392.6231.440. Unpublished study prepared by Springborn Labs, 

Inc. 60 p. 

42560801 Pedersen, C.; Helsten, B. (1992) MCPB Sodium: 14-day Acute Oral LD50 Study in Bobwhite Quail: Lab Project Number: 108-016-03. Unpublished 

study prepared by Bio-Life Associates, Ltd. 59 p. 

42560802 Pedersen, C.; Helsten, B. (1992) MCPB Sodium: 8-day Acute Dietary LC50 Study in Bobwhite Quail: Lab Project Number: 108-014-01. Unpublished 

study prepared by Bio-Life Associates, Ltd. 103 p. 

42560803 Pedersen, C.; Helsten, B. (1992) MCPB Sodium: 8-day Acute Dietary LC50 Study in Mallard Ducklings: Lab Project Number: 108-015-02. 

Unpublished study prepared by Bio-Life Associates, Ltd. 103 p. 

42560804 Christensen, K. (1992) MCPB Sodium: Determination of Effects on Seed Germination, Seedling Emergence and Vegetative Vigor of Ten Plant 

Species: Final Report: Lab Project Number: 92-8-4377. Unpublished study 

prepared by Springborn Labs, Inc. 208 p. 

44754101 Corley, J.; Kunkel, D. (1999) MCPB: Magnitude of Residue on Pea (Reregistration): Lab Project Number: 05470.94-CAR23: 05470.94-CA52: 

05470.94-NY17. Unpublished study prepared by University of California. 

423 p. 

PC Code: 030501 

40041701 MacKenzie, K. (1986) Two-Generation Reproduction Study with MCPA in Rats: Final Report: Study No. 6148-100. Unpublished study pre- pared by 

Hazleton Laboratories America, Inc. 1304 p. 

43083205 Hoberg, J. (1993) MCPA Acid--Determination of Effects on Seed Germination, Seedling Emergence and Vegetative Vigor of Ten Plant 

MRID CITATION 

 63 
 64 

Species: Final Report: Lab Project Number: 10566.0493. 6280.610: 93-8-

4888. Unpublished study prepared by Springborn Laboratories, Inc. 246 p. 

106595 Reuzel, P.; Hendriksen, C.; Feron, V.; et al. (1980) Subchronic (13-week) Oral Toxicity Study of MCPA in Beagle Dogs: Report No. R 6478. Final rept. 

(Unpublished study received Jul 6, 1982 under unknown admin. no.; 

prepared by Centraal Instituut Voor Voedingsonderzoek, TNO, Neth., 

submitted by Diamond Shamrock Agricultural Chemicals, Cleveland, OH; 

CDL:247854-A; 247855; 247856) 

165471 Kirsch, P. (1985) Report on the Study of the Toxicity of MCPA in Rats after 3 Months Administration in the Diet: [Range-finding Study for 2-year 

Oncogenicity Study in Rats]: Project No. 31S0046/8302. Unpublished 

study prepared by BASF Ag. 381 p. 

42723801 Hellwig, J.; Hildebrand, B. (1993) Study of the Prenatal Toxicity of MCPA- Acid in Rats after Oral Administration (Gavage): Lab Project Number: 

30R0374/91096. Unpublished study prepared by BASF Aktiengesellshaft. 

302 p. 

42723802 Hellwig, J.; Hildebrand, B. (1993) Study of the Prenatal Toxicity of MCPA- Acid in Rabbits after Oral Administration (Gavage): Lab Project No. 

40R0374/91095. Unpublished study prepared by BASF Aktiengesellshaft. 

230 p. 

43562601 Mellert, W.; Deckardt, K.; Kaufmann, W.; et al. (1994) MCPA-Acid-- Subchronic Oral Dietary Toxicity and Neurotoxicity Study in Wistar Rats: 

Lab Project Number: 50C0374/91133. Unpublished study prepared by 

BASF Aktiengesellschaft. 723 p. 
Appendix E: 

Generic Data Call-In 

The Generic Data Call-In will be posted at a later date. See Chapter V of the MCPB RED for a list 

of studies required. 

65 

Appendix F: 

Product Specific Data Call-In 

The product specific Data Call-In will be posted at a later date. 

66 
Appendix G: 


EPA's Batching of MCPB Products for Meeting Acute Toxicity Data


Requirements for Reregistration


EPA'S BATCHING OF MCPB PRODUCTS FOR MEETING ACUTE TOXICITY DATA 

REQUIREMENTS FOR REREGISTRATION 

In an effort to reduce the time, resources and number of animals needed to fulfill 

the acute toxicity data requirements for reregistration of products containing MCPB as the 

active ingredient, the Agency has batched products which can be considered similar for 

purposes of acute toxicity. Factors considered in the sorting process include each 

product's active and inert ingredients (identity, percent composition and biological 

activity), type of formulation (e.g., emulsifiable concentrate, aerosol, wettable powder, 

granular, etc.), and labeling (e.g., signal word, use classification, precautionary labeling, 

etc.). Note that the Agency is not describing batched products as "substantially similar" 

since some products within a batch may not be considered chemically similar or have 

identical use patterns. 

Using available information, batching has been accomplished by the process 

described in the preceding paragraph. Notwithstanding the batching process, the Agency 

reserves the right to require, at any time, acute toxicity data for an individual product 

should the need arise. 

Registrants of products within a batch may choose to cooperatively generate, 

submit or cite a single battery of six acute toxicological studies to represent all the 

products within that batch. It is the registrants' option to participate in the process with all 

other registrants, only some of the other registrants, or only their own products within a 

batch, or to generate all the required acute toxicological studies for each of their own 

products. If a registrant chooses to generate the data for a batch, he/she must use one of 

the products within the batch as the test material. If a registrant chooses to rely upon 

previously submitted acute toxicity data, he/she may do so provided that the data base is 

complete and valid by today's standards (see acceptance criteria attached), the formulation 

tested is considered by EPA to be similar for acute toxicity, and the formulation has not 

been significantly altered since submission and acceptance of the acute toxicity data. 

Regardless of whether new data is generated or existing data is referenced, registrants 

must clearly identify the test material by EPA Registration Number. If more than one 

confidential statement of formula (CSF) exists for a product, the registrant must indicate 

the formulation actually tested by identifying the corresponding CSF. 

In deciding how to meet the product specific data requirements, registrants must 

follow the directions given in the Data Call-In Notice and its attachments appended to the 

RED. The DCI Notice contains two response forms which are to be completed and 

submitted to the Agency within 90 days of receipt. The first form, "Data Call-In 

67 

 68 

Response," asks whether the registrant will meet the data requirements for each product. 

The second form, "Requirements Status and Registrant's Response," lists the product 

specific data required for each product, including the standard six acute toxicity tests. A 

registrant who wishes to participate in a batch must decide whether he/she will provide 

the data or depend on someone else to do so. If a registrant supplies the data to support a 

batch of products, he/she must select one of the following options: Developing Data 

(Option 1), Submitting an Existing Study (Option 4), Upgrading an Existing Study (Option 

5) or Citing an Existing Study (Option 6). If a registrant depends on another's data, he/she 

must choose among: Cost Sharing (Option 2), Offers to Cost Share (Option 3) or Citing an 

Existing Study (Option 6). If a registrant does not want to participate in a batch, the 

choices are Options 1, 4, 5 or 6. However, a registrant should know that choosing not to 

participate in a batch does not preclude other registrants in the batch from citing his/her 

studies and offering to cost share (Option 3) those studies. 

 

Five products were found which contain MCPB as the active ingredient. These products 

have been placed in one batch and a no batch group in accordance with the active and 

inert ingredients and type of formulation.. 

 

Batching Instructions: 

 

No Batch: Each product in this Batch should have its own data generated. 

 

 

NOTE: The technical acute toxicity values included in this document are for informational 

purposes only. The data supporting these values may or may not meet the current 

acceptance criteria. 

 

 

 

 

Batch 1 

 

EPA Reg. No. 

 

% Active Ingredient 

 

15440-28 

 

95.5 

 

 

 

71368-8 

 

97 

 

 

 

 No 

Batch 

 

EPA Reg. No. 

 

% Active Ingredient 

 

15440-38 

 

23.5 

71368-5 

 

23.5 

 

 

 
 69 

 

 No 

Batch 

 

EPA Reg. No. 

 

% Active Ingredient 

71368-7 43.85 
Appendix H: 

List of Registrants Sent This Data Call-In 

A list of registrants sent this Data Call-In will be posted at a later date 

A H MARKS & CO LTD 

Richard J. Otten 

Official Address: 

PMB 239, 7474 Creedmoor Road 

Raleigh, North Carolina 27613 

United States 

Agent Phone: (919) 846-7860 

NUFARM, INC. 

Theodore D. Head 

Official Address 

150 Harvester Drive Suite 200 

Burr Ridge, Illinois 60527 

United States 

Agent Phone: (630) 455-2000 

70 

Appendix I:


List of Available Related Documents and Electronically Available Forms


Pesticide Registration Forms are available at the following EPA internet site: 

http://www.epa.gov/opprd001/forms/ 

Pesticide Registration Forms (These forms are in PDF format and require the Acrobat reader) 

Instructions 

1.	 Print out and complete the forms. (Note: Form numbers that are bolded can be filled 

out on your computer then printed.) 

2.	 The completed form(s) should be submitted in hardcopy in accord with the existing 

policy. 

3.	 Mail the forms, along with any additional documents necessary to comply with EPA 

regulations covering your request, to the address below for the Document Processing 

Desk. 

DO NOT fax or e-mail any form containing 'Confidential Business Information' or 'Sensitive 

Information.' 

If you have any problems accessing these forms, please contact Nicole Williams at (703) 308-5551 

or by e-mail at williams.nicole@epa.gov. 

The following Agency Pesticide Registration Forms are currently available via the internet: 

at the following locations: 

Application for Pesticide http://www.epa.gov/opprd001/forms/857 

8570-1 Registration/Amendment 0-1.pdf 

8570-4 Formula 

Confidential Statement of http://www.epa.gov/opprd001/forms/857 

0-4.pdf 

Notice of Supplemental 

8570-5 

Registration of Distribution of a http://www.epa.gov/opprd001/forms/857 

Registered Pesticide Product 0-5.pdf 

8570-1 

7 Use Permit 

Application for an Experimental http://www.epa.gov/opprd001/forms/857 

0-17.pdf 

8570-2 Application for/Notification of http://www.epa.gov/opprd001/forms/857 

71 
5 State Registration of a Pesticide 0-25.pdf 

To Meet a Special Local Need 

8570-2 Formulator's Exemption http://www.epa.gov/opprd001/forms/857 

7 Statement 0-27.pdf 

8570-2 Certification of Compliance with http://www.epa.gov/opprd001/forms/857 

8 Data Gap Procedures 0-28.pdf 

8570-3 

0 

Pesticide Registration http://www.epa.gov/opprd001/forms/857 

Maintenance Fee Filing 0-30.pdf 

8570-3 

2 

Certification of Attempt to Enter 

into an Agreement with other 

Registrants for Development of 

Data 

http://www.epa.gov/opprd001/forms/857 

0-32.pdf 

Certification with Respect to 

8570-3 

4 

Citations of Data (PR Notice http://www.epa.gov/opppmsd1/PR_Notice 

98-5) s/pr98-5.pdf 

8570-3 

5 

http://www.epa.gov/opppmsd1/PR_Notice 

Data Matrix (PR Notice 98-5) s/pr98-5.pdf 

8570-3 Summary of the http://www.epa.gov/opppmsd1/PR_Notice 

6 Physical/Chemical Properties (PR s/pr98-1.pdf 

Notice 98-1) 

8570-3 Self-Certification Statement for http://www.epa.gov/opppmsd1/PR_Notice 

7 the Physical/Chemical Properties s/pr98-1.pdf 

(PR Notice 98-1) 

Pesticide Registration Kit www.epa.gov/pesticides/registrationkit/ 

Dear Registrant: 

For your convenience, we have assembled an online registration kit which contains the 

following pertinent forms and information needed to register a pesticide product with the U.S. 

Environmental Protection Agency's Office of Pesticide Programs (OPP): 

1.	 The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal 

Food, Drug and Cosmetic Act (FFDCA) as Amended by the Food Quality Protection 

Act (FQPA) of 1996. 

2.	 Pesticide Registration (PR) Notices 

a.	 83-3 Label Improvement Program--Storage and Disposal Statements 

b.	 84-1 Clarification of Label Improvement Program 

c.	 86-5 Standard Format for Data Submitted under FIFRA 

72 
d.	 87-1 Label Improvement Program for Pesticides Applied through Irrigation 

Systems (Chemigation) 

e.	 87-6 Inert Ingredients in Pesticide Products Policy Statement 

f.	 90-1 Inert Ingredients in Pesticide Products; Revised Policy Statement 

g.	 95-2 Notifications, Non-notifications, and Minor Formulation Amendments 

h.	 98-1 Self Certification of Product Chemistry Data with Attachments (This 

document is in PDF format and requires the Acrobat reader.) 

Other PR Notices can be found at http://www.epa.gov/opppmsd1/PR_Notices 

3.	 Pesticide Product Registration Application Forms (These forms are in PDF format 

and will require the Acrobat reader). 

a.	 EPA Form No. 8570-1, Application for Pesticide Registration/Amendment 

b.	 EPA Form No. 8570-4, Confidential Statement of Formula 

c.	 EPA Form No. 8570-27, Formulator's Exemption Statement 

d.	 EPA Form No. 8570-34, Certification with Respect to Citations of Data 

e.	 EPA Form No. 8570-35, Data Matrix 

4.	 General Pesticide Information (Some of these forms are in PDF format and will 

require the Acrobat reader). 

a.	 Registration Division Personnel Contact List 

b.	 Biopesticides and Pollution Prevention Division (BPPD) Contacts 

c.	 Antimicrobials Division Organizational Structure/Contact List 

d.	 53 F.R. 15952, Pesticide Registration Procedures; Pesticide Data 

Requirements (PDF format) 

e.	 40 CFR Part 156, Labeling Requirements for Pesticides and Devices (PDF 

format) 

f.	 40 CFR Part 158, Data Requirements for Registration (PDF format) 

g.	 50 F.R. 48833, Disclosure of Reviews of Pesticide Data (November 27, 1985) 

Before submitting your application for registration, you may wish to consult some additional 

sources of information. These include: 

1.	 The Office of Pesticide Programs' website. 

2.	 The booklet "General Information on Applying for Registration of Pesticides in the 

United States", PB92-221811, available through the National Technical Information 

Service (NTIS) at the following address: 

National Technical Information Service (NTIS)


5285 Port Royal Road 


Springfield, VA 22161 


The telephone number for NTIS is (703) 605-6000. 

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3.	 The National Pesticide Information Retrieval System (NPIRS) of Purdue University's 

Center for Environmental and Regulatory Information Systems. This service does 

charge a fee for subscriptions and custom searches. You can contact NPIRS by 

telephone at (765) 494-6614 or through their website. 

4.	 The National Pesticide Telecommunications Network (NPTN) can provide 

information on active ingredients, uses, toxicology, and chemistry of pesticides. You 

can contact NPTN by telephone at (800) 858-7378 or through their website: 

ace.orst.edu/info/nptn. 

The Agency will return a notice of receipt of an application for registration or 

amended registration, experimental use permit, or amendment to a petition if the 

applicant or petitioner encloses with his submission a stamped, self-addressed 

postcard. The postcard must contain the following entries to be completed by OPP: 

· Date of receipt;


· EPA identifying number; and 


· Product Manager assignment.


Other identifying information may be included by the applicant to link the 

acknowledgment of receipt to the specific application submitted. EPA will stamp the 

date of receipt and provide the EPA identifying file symbol or petition number for the 

new submission. The identifying number should be used whenever you contact the 

Agency concerning an application for registration, experimental use permit, or 

tolerance petition. 

To assist us in ensuring that all data you have submitted for the chemical are properly 

coded and assigned to your company, please include a list of all synonyms, common 

and trade names, company experimental codes, and other names which identify the 

chemical (including "blind" codes used when a sample was submitted for testing by 

commercial or academic facilities). Please provide a chemical abstract system (CAS) 

number if one has been assigned. 

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Documents Associated with this RED 

The following documents are part of the Administrative Record for this RED document and 

may be included in the EPA's Office of Pesticide Programs Public Docket. Copies of these 

documents are not available electronically, but may be obtained by contacting the person listed on 

the respective Chemical Status Sheet. 

1.	 Health Effects Division and Environmental Fate and Effects Division Science 

Chapters, which include the complete risk assessments and supporting documents. 

2.	 Detailed Label Usage Information System (LUIS) Report. 

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