### Data Gaps

The fate database is incomplete based on the environmental fate data requirements outlined in the Code of Federal Regulations Title 40 Part 158 (40CFR158) Subpart N. Data are needed for environmental chemistry methods (with independent laboratory validations; 850. 61 00), and laboratory volatility study (835.1410) in low moisture soil and under high temperature. Additionally, a fish BCF study (850.1730) is necessary for the EHE formulation. The log K

ow 

### MCPA EHE is 5.87, indicating a strong potential for bioaccumulation. While EFED believes that this potential will be mitigated by metabolism in the receptors, a BCF study that achieves a reliable metabolic rate constant (K

m 

### ) is necessary to confirm this assumption.

The e cological database is also incomplete based on the ecological effects data requirements. At this time an avian acute toxicity study (850.2100) with a passerine species is necessary for risk assessment. Additionally, only one of the required avian reprodu ction studies has been submitted for MCPA. A study (850.2300) conducted with a water fowl, preferably mallard duck

, is necessary for risk assessment.

In keeping with the Agency’s proposed new paradigm for determining potential adverse effects

to insect pollinators from conventional pesticides (USEPA 2012), two additional studies are being requested. An acute oral toxicity study (followin g OECD 213 ) and a larval toxicity study (followin g OECD 237 ) are necessary to evaluate the potential for MCPA to adve rsely affect bees and other pollinators

.

MCPA products are not the only source of MCPA in the environment. Another source is the phenoxy herbicide, MCPB, which degrades to MCPA. Previously

, EFED conducted analysis of

MCPA and MCPB use patterns (2003b) from the data collected by Thelin and Gianessi (USGS Open

- File Report 00

- 250) . These data indicated that while MCPB is not used in the highest MCPA use areas, there was geographic overlap between the use s of these two groups of

chemi cals . It is likely that some percentage of the MCPA detected in surface water and groundwater monitoring data may result from degradation of MCPB to MCPA. Therefore EFED seeks relevant usage data to determine what impact the degradation of MCPB to MCPA h as on an evaluation of monitoring data, estimated drinking water concentration and aquatic EECs, to

reduce the uncertainty from the previous risk assessment.

### 1. Introduction

MCPA is an herbicide in the phenoxyaceticacid (aka phenoxy) family that is used postemergence

for selective control of broadleaf weeds. The purpose of the Problem Formulation is to broadly review the registered uses of MCPA, MCPA salts and ester, and iden tify potentially complete environmental exposure pathways that will be assessed during the comprehensive Registration Review process. This document specifically addresses the following four forms of MCPA: MCPA acid, MCPA sodium salt, MCPA dimethylamine s alt (MCPA DMAS), and MCPA 2

- ethylhexyl ester (MCPA 2

- EHE). There is a Section 3 registration for MCPA isooctyl ester

which will also be assessed.

a. Previous Ecological Risk Assessment

The most recent ecological risk assessment on 2

- methyl

- 4

- chloropheno xyacetic acid (MCPA) is the EFED Preliminary Risk Assessment for MCPA Reregistration Eligibility Decision (RED) Document (US EPA, 2003, D286079). The RED assessment served as the basis for this problem

formulation document.

At th e time of the previous as sessment, EPA identified ecological risk of concern (Table 1) to plants and terrestrial animals from MCPA uses and particularly to mammals from maximum application rates for rice and sorghum.

Table 1

. Summary of Risk Concerns Identified for MCPA in Previous Assessments

Birds Mammals Terr.

Plants Terr.

Inverts Fish BCF Aquatic

Inverts Aquatic

Plants Groundwater

Contamination Persistence Degradates

of Concern √ a √ b √

-- -- -- √ c √ d √

-- ??

--

a Insufficient chronic data

b Chronic

c Listed species from EHE

d Vascular only except for rice use



### b. Drinking Water Exposure Assessments

The latest drinking water assessment was completed on April 9, 2003 (D286079). An addendum

to this assessment was issued on June 24, 2003 to include a use on rice (D286079). Since that

time the MCPA task force has voluntarily cancelled the use on rice and sorghum in response to the RED (2004).

In the last drinking water assessment , the PRZM/EXAMS generated surfac e water
concentrations were recommended for use in the human health risk assessment because monitoring data available for MCPA were not specific to areas of use of MCPA. The maximum acute concentration was 45.9 μg acid equivalents ( ae ) /l for the Minnesota pasture scenario, while the highest chronic concentrations were 2.1 μg ae/l for the 1 in 10 year annual mean concentration and 1.3 μg ae/l for the 30 year annual mean for the Pennsylvania pasture scenario modeled at 2 lbs ae/acre applied twice at an inter val of 30 days. These model estimates were approximately double the peak (acute) concentration of 18.58 μg ae/l detected in the monitoring

### data and roughly equivalent to the maximum time weighted annual mean (TWM) concentration of 1.49 μg ae/l.

c. Clean Water Act Programs

MCPA does not have Primary Drinking Water Standards and does not have a set Maximum Contaminant Level (MCL) under the Safe Drinking Water Act (SDWA), but its non

- cancer lifetime limit Health Advisory Levels for a 70

- kg adult is set at 0.01 mg/l. The chemical is

classified Group E

, “no evidence of carcinogenicity in at least two adequate animal tests in different species or in adequate epidemiologic and animal studies”.

MCPA is not identified as a cause of impairment for any water bodie s listed as impaired under section 303(d) of the Clean Water Act 1 

### . No Total Maximum Daily Load (TMDL) criteria have been developed for MCPA . Aquatic benchmarks have been established for all registered forms

of MCPA and are available at http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm . Any data submitted or otherwise located as part of the registration review process may be used to update aquatic life benchmarks if applicable.

2. Stressor Source and Distribution

Registered agricultural use sites of MCPA include: barley, flax, grass es grown for seed, oats, pastureland, peas, rye, and wheat. The registered non

- agricultural use sites of MCPA include: nonagricultural areas, uncultivated areas/so il s, ornamental lawns and turf. (BEAD Chemical Profile, 2013). Single Application rates of up to 2.0 lbs ae/A are allowed by labels.

There are four primary active ingredients associated with MCPA (Table 2) : MCPA acid, MCPA sodium salt, MCPA dimethylamine salt (MCPA DMAS), and MCPA 2

- ethylhexyl ester (MCPA

2

- EHE). A fifth active ingredient, MCP A isooctyl ester will also be assessed. Formulation types

for registered products include solids, soluble concentrate/solid, water dispersible granules (dry flowable), and wettable powder. MCPA is usually applied in combination with other phenoxy

class c hemicals, such as 2,4

- D, 2,4DB, MCPP

- p, and MCPB (2004). According to product labels, MCPA can be applied anytime of year , but for best efficacy application is recommended in early spring and early fall.

1 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885Table 2. MCPA, MCPA Salt, Amine Salt, and Ester

PC Code Name s (CAS and IUPAC) 1 Abbreviation

Acid

030501 2

- methyl

- 4

- chlorophenoxyacetic acid (MCPA) Acid /MCPA

Salts

030502 Sodium salt of MCPA : Na

Amine Salts

030516 Dimethylamine salt of MCPA : DMAS

Esters

030564 2

- ethylhexyl ester of MCPA : 2

- ethylhexyl 2

- (4

- chloro

- 2

- methylphenoxy)acetate (RS)

- 2

- ethylhexyl 4

- chloro

- o

- tolyloxyacetate 2

- EHE

1 Selected physico

- chemical properties of MCPA forms can be obtained from Appendix A



### Various phenoxy herbicides are known contain dioxin/furan impurities as a result of manufacturing processes (Holt, et. al. 2010). Data pertaining to dioxin/furan impurities in

MCPA formulations (up to 17 known dioxin/furan congeners) will be considered in the upcoming environmental risk assessment. Previously s ubmitted dioxin/furan data for MCPB were below levels of quantitation (LOQ) (MRIDs 45524105 and 47374801). However, the Agency is aware that lower limits of quantitation of dioxins/furans by one or more orders of magnitude are now achievable through techn ological advances in analytical chemistry. Therefore, the Agency requests any additional information on the presence of dioxins/furans impurities in MCPA formulated products that may be available based on currently achievable LOQs. In absence of addition al information, the Agency will use best available information (including appropriate assumptions related to reported LOQs) for determining the potential for exposures of concern at the time of risk assessment.

3. Environmental Fate and Transport

The agency established a strategy for bridging the environmental fate data requirements for the MCPA ethylhexyl ester (EHE) and MCPA dimethylamine salt (DMAS) to the MCPA acid. Bridging data verified that MCPA DMAS and MCPA EHE will be rapidly converted t o the free acid in the environment. A selection of environmental fate and transport properties of MCPA is

summarized in Table A.2 of the Appendix A

.

### In aqueous environments, MCPA

- DMAS will completely dissociate to form MCPA (USEPA 2004b) while MCPA EHE will hydrolyze to MCPA acid. MCPA EHE hydrolysis appears to be pH dependent

. It hydrolyzed with half

- life <117 hours at pH 9, much slower at pH 7, and was stable at pH 5. In a non

- sterile soil:CaCl 2 

### system at pH 5.6 and 6.8, MCPA EHE was initially

adsorbe d to the soil particles, and then available for degradation to MCPA acid with a half

- life of less than 12 hours. A soil microbial degradation study, conducted under OECD GLP guidelines and called soil hydrolysis, indicated that MCPA EHE underwent microbial degradation to

MCPA with half

- lives ranging from 4.5 to 12 hours in two tested soil s under 50% or 70% of the maximum water holding capacity (MWHC).

There may be environments, however, where this bridging strategy is not applicable, such as dry

soils whic h may limit the dissociation of the MCPA DMAS and acid environments which may limit the abiotic hydrolysis of the MCPA EHE. There is also evidence for the phenoxy esters as a class to suggest that the conversion of MCPA EHE to MCPA acid may not be rapid u nder all conditions. For example, according to Smith and Hayden (1980) data, MCPA EHE which was surface applied to soils in Saskatchewan was rapidly converted to MCPA acid, but under dry conditions (15% of field capacity) the ester persisted for days with greater than 90% present after 48 hours. In a typical setting a farmer will irrigate to add moisture to the soil or abandon the crop. Therefore, EFED believes the available data support the environmental fate bridging strategy for MCPA DMAS and MCPA EHE with the exception of environmental conditions previously described.

MCPA acid is moderately stable in the natural environment and mobile. Based on the available data, MCPA in soil degrades mainly through aerobic soil metabolism, and in aquatic

envir onment s through photodegradation and aerobic aquatic metabolism. It can enter surface water via spray drift during application and run off after rainfall event. In the field it showed a low potential for leaching as it was not detected at soil depths great er than six inches. MCPA has been shown to be stable in the anaerobic soil and in aerobic aquatic environment.

MCPA acid did not hydrolyze in sterile, buffered solutions at pH's ranging from 5 to 9 (MRID 42665301) . In sterile buffer solution at pH 5 when irradiated with natural sunlight MCPA acid photodegraded with a half

- life of approximately 25 days; forming one degradate, 4

- chloro

- o

cresol (4

- CC). 4

- CC comprised up to 12% of the initial radioactivity. MCPA acid photodegraded slowly when applied to soi l surfaces and irradiated with natural sunlight; the

calculated half

- life was 67 days. In the aerobic soil metabolism study MCPA acid degraded with

a half

- life of 24 days (MRID 41586001) . No major degradates were present, but 14 

### CO 2 

### accounted

for 64% of th e initial applied radioactivity after 209 days of aerobic incubation. Under aerobic aquatic conditions MCPA acid degraded with an observed degradation half

- life of >30 days in

the water

- sandy clay loam sediment system, and half

- life values of 13 to 15 day s in water

- loamy sand sediment system. The observed degradation half

- life of MCPA acid in the water

- light clay sediment system was >100 days in the total system. In another aerobic aquatic biodegradation study MCPA acid degraded in a ditchwater/sediment s ystem from the Netherlands with a whole system half life of 16.3 days and in a river water/sediment system from Netherlands with whole system half life of 16.8 days. MCPA acid did not degrade anaerobically in either an anaerobic

soil metabolism or an anae robic aquatic metabolism study.

### Three laboratory batch equilibrium studies indicated that MCPA acid is mobile (overall

K f

- ads 

### = 0.021

- 1.2 and K foc 

### = 8.9

- 59 mL/g). MCPA Freundlich K ads 

### values ranged from 0.45 to 1.20 mL/g in clay loam, silt loam, sandy l oam soils, in a sandy loam aquatic sediment and in a beach sand in one study (MRID 42596903). In second study Freundlich K ads 

### values ranged from 0.0212 to 1.11 mL/g and corresponding K f

- oc 

### values were from 9.6 to 46 in clay, silt loam, sandy

loam and loam soils (MRID 40555801). In the last study, uniformly phenyl ring

- labeled [ 14 

### C]MCPA acid was studied in sand (0.7% o.m.), sandy loam, loam and silty clay loam soil:solution slurries and sandy clay loam sediment:solution slurries (1.7% o.m.) and its

Freundlic hK ads 

### values ranged from 0.21 to 0.55. Corresponding Koc values ranged from 31 to 59 mL/g (MRID 44239601). The study also shown that MCPA adsorption could not be correlated with soil organic matter, pH, or clay content.

In various terrestrial field di ssipation studies (TFD), MCPA dissipated with half

- lives ranging from 3.3 to 23 days with a median half

- life of 5.6 days. When the product was applied as MCPA EHE, the parent dissipated with half

- lives of 4 to 9 days (MRID 43815701) while MCPA isooctyl est er dissipated with half

- lives of 9 and 23 days (MRIDs 42134001 and 42134101). When the product was applied as MCPA DMAS, the parent dissipation half

- lives ranged from 3 to 10 days (MRIDs 43883001 and MRID 43697501). T otal MCPA residues dissipated in the

g rass and tha tch with registrant

- calculated half

- lives of 8.5to 15.5 days on grass and 9.6 to 11 days on thatch following the second application of MCPA DMAS to CA, FL, and NY plots (MRID 43883001). Sodium salt of MCPA dissipated with a half

- life of 15 days from a barley plot in Washington State (MRID 42133901). All concentrations in the TFD studies were reported as total MCPA residues. There was no obvious leaching of MCPA observed below 6 inches of soil depth in any of the mentioned studies with the except ion of the single replicates as indicated by data in the Table A.2.

Aged column leaching studies and bioconcentration in fish studies are not available. Based on physico

- chemical properties (log K

ow 

### = 2.83) MCPA itself has low potential for bioaccumulation

hence fish bioconcentration studies a re not requested at this time. However, a fish BCF study (850.1730) is necessary for the EHE formulati on. The log K

ow 

### for MCPA EHE is 5.87, indicating a strong potential for bioaccumulation. While EFED believes that this potential will be mitigated by metabolism in the receptors, a BCF study that achieves a reliable metabolic rate constant (K

m 

### ) is necessary to confirm this assumption.

a) Atmospheric Transport

It is known that the various phenoxy ester forms are volatile to various degrees depending on the ester and will potentially volatilize both during and after their application. The degree of volatility of the phenoxy ester varies depending on the molecula r weight of the alcohol used to make the ester. The overall rule is the heavier molecules are less volatile than lighter molecules. Current open literature will be researched further to address the knowledge gap of potential MCPA atmospheric transport. The search emphasis will be placed on the short term transport, droplet drift at time of application, and long term transport, evaporation from the droplet and from the surface of the soil and plants after the spray has landed after application.

### A volatilit y study indicated that MCPA does not have potential to volatilize of f soil surface. In the laboratory study conducted on MCPA 2

- EHE applied to sandy clay loam soil (pH 6.7, organic carbon 2.2%) that was microbially active and adjusted to 40

- 60% of 0.33 bar moisture, no volatile organics were produced during the 15

- day study (MRID 47075203). Based the study, the majority of radioactivity (ca. 97

- 100%) of MCPA 2

- EHE converted to MCPA acid. Since the study was conducted at 25°C and the relative humidity was 95

- 100%, the conditions are favorable to abiotic and/or microbial hydrolysis of the ester form to acid. There is evidence for the phenoxy esters as a class to suggest that the conversion of MCPA EHE to MCPA acid may not be rapid under all conditions; e. g. l ow moisture soils, as discussed previously. Microbial mediated hydrolysis rates in soils may be dependent on clay mineralogy, organic carbon content, temperature, and moisture content (Wolfe, et al, 1989 and Wolfe, 1990). Although, the open

literature dat a suggest that under normal environmental conditions MCPA EHE will be expected to rapidly convert to MCPA acid, analysis of terrestrial field dissipation data collected for 2,4

- D

EHE indicates that the ester remains in the field with half lives between one and 14 days. That increases the time when the chemical can be available for evaporation of the soil surface.

a. Transformation Products

Several degradates were detected in the laboratory fate studies. The degradates detected were 4

- chloro

- o

- cresol (4

- CC) , 5

- chlorosalicylaldehyde, and 14 

### CO 2 

### . 4

- chloro

- 2

- methylanisole (4

- MCA) was postulated by the registrant to be a potential degradate of MCPA but was not detected/identified in any of the laboratory or field studies. At the time of completion of the RED in 2004, the Metabolite Assessment Rev iew Committee (MARC) has determined that none of these degradates are of toxicological concern, therefore, no degradates were included in the previous risk assessments. The potential inclusion of degradates may be revisited at the time of

risk assessment b ut it is not expect that our previous conclusion will change.

Note that 4

- CC is a common degradate for MCPA and 2,4

- D. The chemical is also used in synthesis of phenoxy herbicides; i.e. MCPA, MCPB, MCPP (EUR, 2002). In addition, MCPA is a major degradat e of MCPB formed in soil. The chemical structures for 4

- CC, 5

- chlorosalicylaldehyde, and 4

- chloro

- 2

- methylanisole (4

- MCA) are provided in Table A.3 of Appendix A. In addition, v arious phenoxy herbicides are known contain dioxin/furan impurities

as a resu lt of manufacturing processes (Holt, et. al. 2010).

4. Receptors

Table 3 and Table 4 p rovide a summary of the most sensitive aquatic and terrestrial acute an d chronic endpoints that will be used in the risk assessment. In addition, the tables provide a preliminary overview of the potential acute toxicity of MCPA by providing the acute toxicity classifications. There are no submitted data on the potential tox icity of the degradates on either aquatic or terrestrial organisms.

### 4.1. Effects to Aquatic Organisms

In the available studies for fish and invertebrates, most of the toxicity endpoints are within one order of magnitude when restricted to evaluating the MCPA acid, sodium salt and DMAS. The toxicity of MCPA EHE tends to be two to three orders of magnitude greater than the toxicity of the acid and salts. No EHE studies regarding chronic exposure are available; in the absence of these data, EFED will cons ider the use of acute

- to

- chronic ratios when possible. As expected with an herbicide, effects to vascular and nonvascular plants are evident in the available studies.

In the RED risk assessment , EFED hypothesized that the primary reason for the differences in the levels of toxicity between the ester formulation relative to the salts and acid is because of the fact that esters have a greater affinity for uptake through cell wall membranes. The i ncreased toxicity, coupled with the fact that MCPA EHE may be more stable in acidic aquatic environments is explanation for the inclusion of the ester drift scenario in the ecological risk assessment. EFED assumes that this scenario only applies to acute exposure because biotic processes should result in conversion of MCPA EHE to MCPA acid after an initial acute

exposure.

The most sensitive of the available endpoints from the acid, salt or DMAS and the endpoint for the EHE (if available) are presented in Table 3

. For the isooctyl ester, toxicity will be considered equivalent to the EHE where data are lacking.

No studies have been submitted for degradates of MCPA. However, a risk assessment conducted by the EU is available for the 4

- CC degradate (2002), which indicates there is potential toxic effects to aquatic organisms for this degradate. The current thinking is that exposure to this degradate will be below the toxic thresholds indicated in the report, but EFED will explore this potential exposure in the risk assessment.

The aquatic effects dataset for MCPA is largely complete and further data are not being requested at this time.

Table 3 . Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for MCPA

. Taxonomic

Group Study Type Sur rogate Species Toxicity

Value Acute Toxicity

Classification Source (Study classification)

Freshwater fish 1 Acute Rainbow trout ( Oncorhynchus mykiss )

Bluegill Sunfish ( Lepomismacrochirus ) LC 50 = 96 mg

a e /L (DMAS)

LC 50 = 0.76 mg

a e /L (EHE) Practically

non toxic

Highly toxic 40062005 (Acceptable)

42624404 (Acceptable)Taxonomic Group Study Type Sur rogate Species Toxicity

Value Acute Toxicity

Classification Source (Study classification)

Chronic (Early

Life

Stage) Fathead Minnow ( Pimephalespromelas ) NOAEC = 12 mg ai/L

LOAEC = 29 mg ai/L Endpoint:

reduction in growth (DMAS) -- 44407202 (Acceptable)

Freshwater

invertebrates Acute Water Flea ( Daphnia magna ) EC 50 > 8 2 mg

a e /L (DMAS)

EC 50 > 0.18 mg

ae/L (EHE) Slight ly toxic

Highly toxic 41800906 (Acceptable)

42613601 (Acceptable)

Chronic Water Flea NOAEC = 11

mg a e /L

LOAEC = 22

mg a e /L Endpoint: reproduction -- 44 407201 (Acceptable)

Estuarine/marine

fish Acute Atlantic silverside ( Menidia menidia )

Sheepshead Minnow ( Cyprinodon variegatus ) LC 50 = 179 mg

a e /L (Acid)

LC 50 > 2.7 mg

ae/L (EHE) Practically

nontoxic

Moderately

toxic 40062002 (Acceptable)

43086501 (Acceptable)

Chronic No data

Estuarine/marine

invertebrates Acute Eastern Oyster ( Cassostrea virginica ; shell deposition)

Mysid ( Americamysi

sbahia ) EC 50 = 4.9 mg ae/L (Salt)

LC 50 = 4.2 mg ai/L (EHE) Moderately

toxic

Moderately

toxic 41939506 (Acceptable)

43086502 (Acceptable)

Chronic No data

Aquatic plants Vascular Duckweed ( Lemna gibba ) NOAEC =

0.0 16 mg a e /L

IC 50 =0.1 3 mg

a e /L (DMAS)

NOAEC =

0.007 mg ae/L

IC 50 =0.02 mg ae/L (EHE) -- 44903501 (Acceptable)

43083214 (Acceptable)Taxonomic Group Study Type Sur rogate Species Toxicity

Value Acute Toxicity

Classification Source (Study classification)

Non

vascular Green algae ( Pseudokirchneriella subspicatus )

D iatom ( Skeletonema

costatum ) NOAEC <

0.027 mg ae/L

IC 50 =0.16 mg ae/L (DMAS)

NOAEC < 0.0019 mg ae/L

IC 50 =0.0 56 mg ae/L (EHE) -- 42461301 (Supplemental)

44287310 (Supplemental)

1 Freshwater fish may be surrogates for aquatic

- phase amphibians.



### 4.2. Effects to Terrestrial Organisms

For terrestrial organisms, there does not appear to be differentiation in the toxicity levels for MCPA among the acid, salts, and ester based on the available data. Within an organism group ( i.e. , birds, mammals, honey bee, monocot plants, and dicot plants), the variation in the toxicity endpoints is less than two orders of magnitude, and for some groups, the variation is less than one order of magnitude. For those o rganism groups for which toxicity data were submitted to the Agency for MCPA EHE, there does not appear to be an increase in the toxicity relative to the

acid and salts.

Across all forms, MCPA is classified as moderately toxic to birds, slightly toxic to mammals on an acute exposure basis and practically nontoxic to honey bees on an acute contact basis. As expected with an herbicide, MCPA adversely affects plants. Effects were seen in both the seedling emergence and vegetative vigor studies and in both m onocots and dicots well below the

maximum label rates.

The most sensitive available endpoint s across all studies for each taxon are reported in Table 4

.

Table 4 . Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for Propazine

Taxonomic

Group Study Type Surrogate Species Toxicity Value Acute Toxicity

Classification Source (Study classification)

Birds Acute a Bobwhite quail ( Colinusvirginianus ) LD 50 = 221 mg

a e /kg

- bw Moderately

toxic 4 00192 0 2 (Acceptable)

Sub

- acute dietary Mallard duck ( Anasplatyrhynchos ) LC 50 > 4608 mg

a e /kg

- diet Practically

non

- toxic 40555802

40555803 (Acceptable)

Chronic b Bobwhite quail NOAEC = 1000 mg

a e /kg

- diet

LOAEC > 1000 mg

a e /kg

- diet -- 43505201 (Acceptable)Taxonomic Group Study Type Surrogate Species Toxicity Value Acute Toxicity

Classification Source (Study classification)

Mammals Acute Oral Laboratory rat ( Rattusnorvegicus ) LD 50 = 1383 mg

a e /kg

- bw Slightly toxic Acc. 21972 (Acceptable)

Chronic Laboratory rat NOAEL = 150 mg

a e /kg

- diet

LOAEL = 450 mg ae/kg

- diet Endpoint: ovary weights and decreased pup weight gain -- 40041701 (Acceptable)

Insects Acute

contact Honey bee ( Apismellifera ) LD 50 > 17 μg ai/bee Practically

non

- toxic 42197801 (Acceptable)

Terrestrial plants Seedling Emergence Dicot ( Cabbage ; Brassica oleracea ) IC 25 = 0. 0 08 lb ae /A

NOAEC = 0. 00 27

lbs ae /A --
43083205 (Acceptable) Monocot (Onion; Allium cepa ) IC 25 = 0. 0 28 lb ae /A

NOAEC = 0. 01 2

lbs ae /A --

Vegetative Vigor Dicot (Lettuce;

Lactuca sativa IC 25 = 0. 0 4 lb a e /A

NOAEC = 0. 0004

lb ae /A --
47216806 ( in review ) Monocot (Onion; Allium cepa ) IC 25 = 0.35 lb ae/A

NOAEC = 0.09 lbs

ae/A --

a data for passerine necessary

b no data for mallard duck; therefore endpoint remains uncertain



### 4.3. Ecological Incidents

The ecological incident information system (EIIS) is an OPP database that houses ecological incidents that have been reported to the Agency. When available, EIIS includes date and location of an incident, type and magnitude of effects observed in various species, use(s) of pesticides known or suspected of contributing to the incident, and results of any chemical residue analysis or other analyses conducted during incident investigation. EIIS incidents are categorized according to the certainty that the incident resulted from pesticide exposure. The Avian Monitoring System (AIMS) is a database administered by the American Bird Conservancy that contains publicly available data on reported avian incidents involving pesticides. Many of

the inciden ts listed in this database are also in the EIIS. Further, some incidents may be reported as ‘aggregate incidents’; these are contained in a separate database.

As of 01/08/2014, there are 60 reported incidents in EIIS for MCPA; seven for MCPA (under PC

Co de 030501), 20 for MCPA DMAS (under PC Code 030516) and 33 for MCPA EHE (under PC Code 030564). All of the reported incidents involved damage to plants and most are ascribed to registered uses. Incidents were reported for agricultural, residential and ve getative

### management uses. Additionally, 68 incidents (across all forms) are reported in the aggregate incident database, all for plant damage.

As of 01/08/2014, AIMS identified no ecological incidents involving any form of MCPA.

5. Exposure Pathways of Con cern

The environmental fate and toxicity profile for MCPA suggests that direct spray, spray drift, leaching and runoff represent the likely exposure pathways for terrestrial and aquatic non

- target organisms. Drinking water and inhalation exposure pathway s were screened using the SIP (Screening Imbibition Program) and STIR (Screening Tool for Inhalation Risk) screening methods and were found to be exposure pathways of low concern (no LOC exceedances are expected). SIP and STIR are described in detail at: http://www.epa.gov/oppefed1/models/terrestrial/index.htm

.

Risk Hypothesis

The Registration Review ecological risk assessment will test the following risk hypothesis:

Based on the application methods, mode of action, fate and transport, and the sensitivity of non

- target aquatic and terrestrial species, MCPA has the potential to reduce survival, reproduction, and/or growth in non

- target terrestrial and aquatic organisms as well as ne gatively affect the structure, productivity, and function of plant communities when used in accordance with the current labels. These non

target organisms include Federally

- listed threatened and endangered species as well

as non

- listed species.

6. Analysis Plan

This analysis plan may be revised depending upon a full review of the data available in the open literature and the information submitted by the public in response to the opening of the registration review docket.

a. Stressors of Concern

The stressor s of ecological concern for terrestrial and aquatic organisms are the four forms of MCPA. MCPA acid and salts are classified as practically non

- toxic to moderately toxic, while the ester formulation of MCPA is classified as moderately toxic to highly toxi c. Consequently, the esters will be considered separately for aquatic organisms, as has been done in the past risk assessment (USEPA 2003b). For terrestrial scenarios, the most sensitive endpoint, regardless of the MCPA form (ester, salt, acid) will be u sed in the risk assessment.

There are few toxicity data on degradates of MCPA. Previous assessments have considered the likelihood of exposure to MCPA degradates in significant quantities to be minimal. However,

### any information regarding the toxicity of MCPA degradates will be considered for the risk assessment. Information in this regard will reduce uncertainty in risk conclusions. EFED will consider the toxicity of the 4

- CC degradate, as indicated the European risk assessment cited earlier, relative to the potential exposure to aquatic organisms in the risk assessment.

b. Measure of Exposure

EFED will use standard available models to evaluate potential exposures to aquatic and terrestrial organisms as described at http://www.epa.gov/pesticides/science/models_db.htm

.

c. Measure of Effect

Toxicity data presented in Section 3 of this problem formulation will be used to calculate risk quotients. Any additional information submitted by the registrant or found in the open literature prior to conduct of the risk assessment will also be consider ed. The open literature studies are identified using EPA’s ECOTOXicology database ( ECOTOX) (USEPA, 2007 c ), which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The evaluation of both sources of data can also provide insight into the direct and indirect effects of pesticides on biotic commun ities from loss of species that are sensitive to the chemicals and from changes in structure and functional characteristics of the affected

communities.

d. Drinking Water Assessment

The drinking water assessments conducted to support future human health ris k assessments of MCPA will incorporate modeling of MCPA acid form in surface and ground water. Since the last drinking water assessment was conducted, EFED has updated its models (PRZM

- EXAMS), the drinking water modeling input parameters, and the percent c rop area (PCA) guidelines. For all modeling, the input parameters will be selected according to the current input guidelines, and where in question a conservative approach will be taken in the selection of half

- lives. In addition, the newly available PRZM

- GW model will be utilized to obtain estimated drinking water concentrations ( EDWCs ) from ground water source. Descriptions of all executable versions of current models for drinking water exposure can be obtained from the following URL link: http://www.epa. gov/oppefed1/models/water/

EFED will consider all ground and surface water monitoring data available to us, and will conduct a comprehensive evaluation of the data for the risk assessment. The data that may be considered include the United States Geologi cal Survey (USGS) National Water

- Quality Assessment (NAWQA) Program monitoring data.

It is likely that some unknown percentage of the MCPA detected in surface water and groundwater monitoring data may result from degradation of MCPB to MCPA. Therefore, in the event of uncertainties regarding MCPA and MCPB use pattern overlap, EFED will assess an impact the degradation of MCPB to MCPA on monitoring data, EDWCs , and aquatic EECs, in a

conservative manner.

### 7. Endangered Species Assessment

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to federally listed species from registered uses of pesticides in registration review . The process for evaluating potential risks to listed species is further

described at http://www.epa.gov/oppfead1/endanger/litstatus/riskasses.htm

.

8. Preliminary Identification of Data Gaps

a. Environmental Fate

Table 5 identifies environmental fate studies by MRID that offer data for each guideline requirement, as well as study classifications and whether or not further data are needed to support the risk assessment.

Table 5 . Submitted Environmental Fate Data for MCPA

, MCPA sodium, MCPADMAS, and MCPAEHE

.

OCSPP

Guideline Data Requirement Submitted

Studies (MRID) Study

Classifications Sufficient

for

EFED? Rationale for Additional Data Need

Not

available Dissociation 42457101 Acceptable Not Applicable

835.2120 Hydrolysis 42693901A

42671501

42665301A Acceptable Supplemental Acceptable Yes Not Applicable

835.2240 Aqueous photolysis 42928101 Acceptable Yes Not Applicable

835.2410 Soil photolysis 43225801 Acceptable Yes Not Applicable

835.4100 Aerobic soil

metabolism 41586001

47744901 Acceptable Supplemental Yes Not Applicable

835.4200 Anaerobic soil

metabolism 41586001 Acceptable Yes Not Applicable

835.4300 Aerobic aquatic

metabolism 44732401A/

44192701

44732401B

45889303 Acceptable Acceptable Acceptable Yes Not Applicable

835.4400 Anaerobic aquatic

metabolism 40461901 Acceptable Yes Not ApplicableTable 5 . Submitted Environmental Fate Data for MCPA

, MCPA sodium, MCPADMAS, and MCPAEHE

.

OCSPP

Guideline Data Requirement Submitted

Studies (MRID) Study

Classifications Sufficient

for

EFED? Rationale for Additional Data Need

835.1230

835.1240 Adsorption/ desorption 42596903

40555801

44239601

47075204 Acceptable Supplemental Supplemental Supplemental A Yes No Applicable

Leaching

835.1410 Volatility

laboratory 47075203 Supplemental A No In the study o nly moist soil at 25 ± 2 ° C was tested, dry soil, with sufficient moisture to

still maintain microbial activity , and mo st soil in a higher temperature are

recommended to be tested.

835.8100 Volatility Field Reserved

835.6100 Terrestrial field dissipation 42133901

42134001

42134101

42134201

43815701

43883001

43697501 Supplemental Supplemental Supplemental Unacceptable Acceptable Acceptable Acceptable Yes Not Applicable

835.6200 Aquatic field dissipation 46875802 Waived Yes Not Applicable

850.6100 Analytical

method in soil 42134 0 01 06/05/1990 No The environmental chemistry method (EMC) for soil is from 1990 (GC/Hall Detector) and at that time an independent laboratory validation method (ILV) was

not submitted. A current ECM and ILV for

MCPA residues in water and sediment are required to support current monitoring for

MCPA residues and to evaluate the newly

submitted environmental fate and ecologica l effects data.

Analytical

method in water

and sediment

. 44192701 12/06/1996 No E xternal Validation of a Method for the

Determination of 4

- Chloro

- 2

- methylphenoxyacetic Acid Dimethylamine Salt(MCPA DMAS) as its Acid Equivalent, 4

- Chloro

- 2

- methylphenoxyacetic Acid (MCPA), and

4

- chloro

- 2

- methylphenoxyacetic Acid 2

- Ethylhexyl Ester(MCPA 2

- EHE) in Water Samples by Gas Chromatography with Mass Selective Detection (GC/MCD).

The EMC and ILV for water are

from 1996 . T he updated ECM and ILV for

MCPA residues in water and sediment are required to support current monitoring fo r MCPA residues and to evaluate newly

submitted environmental fate and ecological effects data.Table 5 . Submitted Environmental Fate Data for MCPA

, MCPA sodium, MCPADMAS, and MCPAEHE

.

OCSPP

Guideline Data Requirement Submitted

Studies (MRID) Study

Classifications Sufficient

for

EFED? Rationale for Additional Data Need

165

- 4 (850.1730) Fish

bioconcentration --- ---- No A fish BCF study is necessary for the EHE formulation. The log Kow MCPA EHE is 5.87, indicating a strong potential for

bioaccumulation. While EFED believes that this potential will be mitigated by metabolism in the receptors, a BCF study

that achieves a reliable me tabolic rate constant (K

m ) is necessary to confirm this assumption.

A After further review the studies were downgraded from acceptable to supplemental.



### Volatility

- Laboratory:

Guideline 835.1410 In the available study (MRID 47075203) only moist soil at 25±2 o 

### C was tested . D ry soil, with sufficient moisture to still maintain microbial activity, and mo i st soil at a higher temperature are

recommended to be tested. The processes by which pesticides may be transported away from the target site include spray dr ift at the time of application and volatilization. Transport resulting from volatilization is highly dependent on the properties of the active ingredient ( e.g. vapor pressure) and as well as a number of environmental parameters. Two of those parameters are temperature and soil moisture. The magnitude and impact of potential transport of MCPA esters via volatilization or long range drift away from the target site was an uncertainty in the previous assessment (US EPA, 2004). Reported evidence in the public literature suggests concern for impact to non

- target organisms due to drift and volatilization of the ester formulations of the phenoxy herbicides (2003 c ). In th e submitted study, the majority of radioactivity (ca. 97

- 100%)

of MCPA 2

- EHE converted to MCPA acid. Open literature data (US EPA, 2003 c ) suggests that thephenoxy herbicide esters may not convert rapidly under dry soil conditions to the acid form.

In absen ce of the data it is assumed that MCPA has potential to volatilize of soil surface.

Environmental Chemistry Methods and Associated Independent Laboratory Validation:

Guideline 850.6100 The environmental chemistry method for MCPA residues of concern in so il, water, and sediment as well as independent laboratory validation of the methods are required to support monitoring for MCPA residues and to evaluate newly submitted environmental fate and ecological effects data. Independently validated analytical meth ods for residues in soil, water, and sediment, and plant material (environmental chemistry methods) submitted by the registrant are used to evaluate analyses described in submitted environmental fate and ecological effects studies. Submitted analytical me thods are also used by various federal, state, tribal, and local agencies to detect and monitor residues that are or are suspected to be in environmental compartments from outdoor uses and accidental releases. Independent laboratory validations for submit ted analytical methods are necessary to confirm that the methods are functional and to confirm the levels of detection and quantitation reported in registrant

- prepared validations. Presently, the available

methods from 1990 and 1996 do not fulfill the abov e requirements.

### An independent validation of environmental chemistry method for MCPA residues in soil has not been submitted by the registrant. The original methods for water and soil were submitted in 1994 and 1990. An independent validation performed for water method by Wildlife International Ltd. in 1996 used only 2 reps for the MCPA 2

- EHE. This is lower than the four typically requested for an ILV.

Fish BCF: Guideline 850.1730

A fish BCF study is necessary for the EHE active ingredient . The log K

ow 

### for MCPA EHE is 5.87, indicating a strong potential for bioaccumulation. While EFED believes that this potential will be mitigated by metabolism in the receptors, a BCF study that achieves a reliable metabolic rate constant (K

m 

### ) is necessary to confirm this assumption.

b. Effects

The effects database for MCPA formulations is not complete based on the ecological effects data requirements. At this time an avian acute toxicity study (850.2100) with a passerine species is necessary for risk assessment. Additionally, only one of the required avian reproduction studies has been submitted for MCPA. A study (850.2300) conducted with a waterfowl species ( e.g. mallard duck) is necessary for risk assessment. The endpoints presented in Table s 3 and 4
represent the most sensitive currently available, not necessarily those that will be used in the risk

assessment.

In keeping with the Agency’s proposed new paradigm for determining potential adverse effects to insect pollinators from conventional pesticides (USE PA 2012) , two additional studies are being requested. An acute oral toxicity study ( followin g OECD 213 ) and a larval toxicity study ( followin g OECD 237 ) are necessary to evaluate the potential for MCPA to adversely affect bees and other pollinato rs . Although the mode of action and acute contact toxicity would not suggest substantial toxicity to adult and larval bees via oral routes, it may not be the only mode of action

relevant to non

- target species. Also, several the target crops are considered attractive to honey bees and this is a systemic chemical that is transported throughout the plant. Thus, MCPA residues may be available to pollinators via pollen and/or nectar.

Due to the large number of studies regarding effects of MCPA formulations to various taxa, please see Appendix B for a complete summary of available studies and their classifications.

Avian Acute Toxicity: Guideline 850.2100

Data regarding the acute toxicity of MCPA to a passerine species is necessary for risk

assessment. A proposed protocol should be submitted for review prior to conducting the study.

Avian Reproduction: Guideline 850.2300

Data from an avian reproduction study with a waterfowl species ( e.g. mallard duck) is necessary for risk assessment. Although data fro m bobwhite is available, it remains unknown whether mallard, a required test species, is more sensitive to MCPA than bobwhite quail.

### 9. References

EUR (2002).4

- CHLORO

- O

- CRESOL European Union Risk Assessment Report, Valium 1.

Office for Official Publications of the European Communities, ISBN 92

- 894

- 0809

- X.

Holt. E., Weber, R., Stevenson, G., and Gaur, C. 2010. Polychlorinated Dibenzo

- p

- Dioxins and Dibenzofurans (PCDD/Fs) Impurities in Pesticides: A Neglected Source of Contemporary

Relevance. Environ. Sci. T echnol. 44, 5409

- 5415.

Smith, A.E. and Hayden B.J. (1980). Hydrolysis of MCPA Esters and the Persistence of MCPA in Saskatchewan Soils. Bull. Environm. Contam. Toxicol., 25, 369

- 373.

US EPA (2003 a ). MCPA

– Drinking Water Assessment for the Health Effects Division (HED) Reregistration Eligibility Decision Document.April 9, 2003.D286079

US EPA (2003 b ). Addendum to the Drinking Water Assessment for MCPA Transmitted to the Health Effects Division (HED) to Account for Use on Rice. June 24, 2003.D286079

US EPA (2003 c ). Environmental Fate and Effects Division Preliminary Risk Assessment for

the 2

- methyl

- 4

- chlorophenoxyacetic acid (MCPA) Reregistration Eligibility Decision Document. September 5, 2003. D286079

US EPA (2004). Reregistration Eligibility Decision (RED) for MCPA (2

- methyl

- 4

- chlorophenoxyacetic acid) List A Case 0017. September 30, 20 04.

USEPA. 2012. White Paper in Support of the Proposed Risk Assessment Process for Bees. Submitted to the FIFRA Scientific Advisory Panel for Review and Comment September 11

– 14,

2012. Office of Chemical Safety and Pollution Prevention Office of Pesti cide Programs Environmental Fate and Effects Division, Environmental Protection Agency, Washington DC; Environmental Assessment Directorate, Pest Management Regulatory Agency, Health Canada, Ottawa, CN; California Department of Pesticide Regulation http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 2012

- 0543

- 0004

USEPA (2013). BEAD Chemical Profile (BCP) for Registration Review: MCPA Case (030501, 030511, 030502,030516,030563 and 030564). December 12, 2013

### Appendix A. Physical Parameters of MCPA and its Forms, and MCPA Degradates

Table A.1. Selected physical chemical properties of various forms of MCPA 1

PC Code

Active Ingredient Molecular

Formula and weight (g/mol) Solubility Density (g/cm3) Log K

ow Vapor Pressure (mm Hg@ ≈25°C)

030501

MCPA acid C 9 H 9 ClO 3 2 00.6 0.03g/100g 1.18

- 1.21 2.82 8 7.7 x 10 - 6 mbar at 20°C

3.12E

- 4 torr 2

030502

MCPA Na

Salt C 9 H 8 ClNaO 3 2 22.6 Water soluble NA Na salt dissociate to acid

030516

MCPA DM A S C 1 1 H 1 6 ClNO 3 245.7 NA 1.181 1.415 (25 o C) NA

030564

MCPA 2

- EHE C 1 7 H 2 5 ClO 3 312. 8 69 x 10 - 6 g/L (pH 5) 4

57 x 10 - 6 g/L (pH 7) 4

110 x 10 - 6 g/L(pH 9) 4 1.06 5.37 1.77 x10 - 5 mbar

8.43 E

- 6 mm Hg 3

2E

- 06 mm Hg at 18°C 5

1E

- 04 mm Hg a t 45 ° C 5

1 Data assembled for RED (USEPA, 2004)

2 Product Chemistry

3 Estimated by EpiSuite Software

4 Values at 20 ° C; MRID 47075204

5 MRID 47075203

NA Not available



### Table A.2. Physical Chemical and Environmental Fate Properties of MCPA.

Parameter Value Source
Selected Physical/Chemical Parameters

Chemical Structure 1 TOXNET

IUAPC Name 4

- chloro

- o

- tolyloxyacetic acid U.S. EPA, 2003 b

CAS Name (4

- chloro

- 2

- methylphenoxy)acetic acid U.S. EPA, 2003 b

CAS No. 94

- 74

- 6 U.S. EPA, 2003 b Molecular Weight (molecular formula) 200.6 g/mol (C 9 H 9 ClO 3 ) U.S. EPA, 2003 b

Smiles Code Clc1cc(c(OCC(=O)O)cc1)C IUPAC web site Physical state colorless crystal Vapor pressure (25°C) 0.000312 mm Hg U.S. EPA, 2003 b
Aqueous solubility (20 ° C) 1500 ppm U.S. EPA, 2003 b
Dissociation constants (pKa ) 3.73 (weak acid) in water (25°C) IUPAC Web Site Henry’s Law Constant (25°C) 0.000549 atm

- m 3 /mol U.S. EPA, 2003 b Log octanol

- to

- water partition coefficient(log K OW ) 2.828 U.S. EPA, 2003 b

Persistence

### Table A.2. Physical Chemical and Environmental Fate Properties of MCPA.

Parameter Value Source

Dissociation MCPA

- DMA completely dissociated MRID 42457101 Hydrolysis half

- life MCPA

- EHE in buffer pH 9: 75

- 117 hrs pH 7: 76 days pH 5: Stable

MCPA

- EHE in soil:0.01 M CaCl 2 (1:5) systems After 12 hrs of incubation, MCPA

- acid accounted for an avg. of 83.9% of in the silt loam soil system and 71.5% of the applied in the sandy loam soil system.

MCPA pH 9,7, 5: Stable MRID 42693901

MRID 42671501

MRID 42665301 Aqueous photolysis half

- life 25.4 days MRID 42928101 Soil photolysis half

- life irradiated with natural sunlight 67.3 days on sandy loam soil

incubated in the dark 121.6 days on sandy loam soil MRID 43225801

Aerobic soil metabolism half

- life (days) Sandy loam

– 24 days

MCPA 2

- EHE (OECD GLP:viable soil hydrolysis study) Sandy loam soil (pH 5.6

- 6.3) 4.5 hrs (50% MWHC) 7.5 hrs (70% MWHC) Clay loam soil (pH 5.5

- 6.3) 0.4 days (DT50 ca 8 hrs, DT90 48 hrs) (50% MWHC) 0.7 days (DT50 12 hrs, DT90 96 hrs) (70% MWHC) Degradate : 4

- CC (2 %) MRID 41586001

MRID 47744901

Anaerobic soil metabolism half

- life Stable (>62 days) MRID 41586001 Anaerobic aquatic metabolism half

life (total system) Stable MRID 40461901

Aerobic aquatic metabolism half

- life (total system) MCPA DMAS in water

- sandy clay loam sediment 236 days (extrapolated value) Degradates

4

- CC(1.9% at 30 d in sediment)

15 days total, 13 days water, 7 days sediment (water

- loamy sand sediment system) >100 days in total system, water and sediment (water

- light clay sediment system) Degradates

4

- CC: 44 days in total system

The Netherlands 16.3 days (TNO ditch water

- sediment) 16.8 days (Kromme Rijn river water

- sediment) MRID 44732401A

/44192701

MRID 44732401B

MRIDs 45889303

Mobility

### Table A.2. Physical Chemical and Environmental Fate Properties of MCPA.

Parameter Value Source
Adsorption/desorption

K foc

- ads / (mL/g) MCPA only Adsorption Freundlich adsorption K f

- ads values ranged from 0.45 to 1.20 mL/g for clay loam, silt loam, sandy loam soils, in a sandy loam aquatic sediment Adsorption Freundlich adsorption K f

- ads values : from 0.0212 to 1.11 mL/g

K foc values: 9.6

- 46 mL/g fo r clay, silt loam, sandy loam and loam soils MRID 42596903

MRID 44239601

Adsorption/desorption

K foc

- ads / (mL/g) MCPA and Degradate Adsorption : Freundlich adsorption K fads values 0.21 sand soil (0.7% o.m.), 0.26 sandy loam soil, 0.55 loam soil, 0.50 silty clay loam soil, and 0.36 sandy clay loam sediment (1.7% o.m.); Corresponding K f

- oc values ranged from 31 to 59 mL/g Desorption : K f

- des = 0.45

- 1.5 corresponding K

oc

- des = 71

- 305 mL/g.

4

- chloro

- o

- cresol (4

- CC) Adsorption: FreundlichK ads values 0.81 sand soil (0.7% o.m.), 1.6 sandy loam soil, 3.1 loam soil, 2.7 silty clay loam soil, and 2.1 sandy clay loam sediment (1.7% o.m.); corresponding K

oc : 198, 199, 330, 266, and 238 mL/g. Desorption: Freundlich K des values 0.87 to 4.2

Corres ponding K f

- oc : 212, 311, 543, 418, and 302 mL/g.

4

- MCA Adsorption : Freundlich K ads values 2.4 for the sand soil (0.7% o.m.), 4.8 for the sandy loam soil, 7.1 for the loam soil, 6.2 for the silty clay loam soil, and 5.5 for the sandy clay loam sediment (1.7% o.m.); Corresponding K

oc : 588, 580, 755, 623, and 628 mL/g. Desorption : Freundlich K des = 1.4 to 8.5 Corresponding Koc = 346

- 904 mL/g. MRID 40555801

Adsorption/desorption

K d / (mL/g)

MCPA 2

- EHE Adsorption Single K d valuesat 0, 24, and 48 hours:

9.22

- 178 (clay loam; pH=6.6)

3.52

- 103 (sandy loam; pH=6.9)

3.66

- 106 (loam; pH=7.9)

5.39

- 57.9 (loamy sand; pH=7.4, oc=0.3%) Respective single K

oc values at 0, 24, and 48 hours:

396

- 7661 (clay loam; pH=6.6)

155

- 4514(sandy loam; pH=6.9)

87.4

- 2531(loam; p H=7.9)

1546

- 16585(loamy sand; pH=7.4, oc=0.3%) MRID 47075204

Field Dissipation
Terrestrial field dissipation half

- life The first order half

- lives ranged from 3 to 23 days with a

median half

- lif e of 5.6 days.

MCPA

- Na salt dissipated with a half

- life of 14.6 days from the top 6 inches of a sandy loam soil in Othello, Washingtonwhen applied to barley. MRID 42133901

### Table A.2. Physical Chemical and Environmental Fate Properties of MCPA.

Parameter Value Source

Total MCPA residues (reported as MCPA

- isooctyl ester) dissipated with a half

- life of 9.08 days from the top 6 in ches of a loam soil in Californiawhen applied to barley.

MCPA isooctyl

- ester (reported as total MCPA residues) dissipated with a half

- life of 23 days from the top 6 inches of a sandy loam soil (pH 7.8) when applied to bareground in

Montana.

MCPA EHE diss ipated (based on total MCPA residues) from loamy sand soil in Georgia with half

- lives of 6.2 days on bareground and 4.1 days on the wheat plot, and from loam soil in Kansas 8.9 days on bareground and 4.1 days on the wheat plot.

Following the 2 nd applicati on of MCPA DMAS,total MCPA residues (as MCPA equivalent) dissipated

in California (sandy loam soil) with half

- life of 3.9 days on the bareground plot 5.6 days on the grass plot.

in Florida with half

- life of 3.5 days on bareground 5.3 days on grass

in New Y ork with half

- life of 10.4 days on bareground 3.3 days on grass Degradates : In CA and FL, 4

- CC and 4

- MCA were not detected above the LOQ. In New York, 4

- CC was detected

twice at 0.010

- 0.012 ppm (0

- to 6

- inch depth; 1 of 3 replicates each) from 0 to 1 day p osttreatment, and was not

detected below the 0

- to 6

- inch depth. The degradate 4

- MCA was not detected above the LOQ.

MCPA DMAS dissipated in

CA with t 1/2 3.8 days on baregroundand 3.2 days on wheat,

In Kansas with t 1/2 5.6 days on baregroundand 6.6 days on the wheat plot, Degradates : 4

- CC was detected once at 0.010 ppm (1 of 3 replicates at 0

- to 6

- inch depth, in Kansas) at 28 days
posttreatment; Wheat plants were not analyzed for MCPA residues. MRID 42134001

MRID 4213 4101

MRID 43815701

MRID 43883001

MRID 43697501

Table A.3. Environmental Degradates of MCPA and its forms.
Degradate/

Molecular formula Max Percent Formation in %AR (Study) Source/Study

MRID Chemical Structure

4

- chloro

- o

- cresol (4

- CC)

4

- chloro

- 2

- methylphenol (PCOC )

C 7 H 7 ClO 11.6% (aq. photolysis) 2.1% (at 3 hrs, aerobic soil metabolism) A
1.7% (at 48 hours, aerobic soil metabolism) B
5.6% (soil photolysis) 16.7% (aerobic aquatic) 42928101

47744901

47744901

MRID MRID5

- chlorosalicylaldehyde 1.2% (aq. photolysis) 42928101

4

- chloro

- 2

- methylanisole (4

- MCA) analyzed for and

not detected

4

- Chloro

- 2

- hydroxymethylphenoxyacetic

acid (HMCPA) C analyzed for and not detected 47744901

A Detected once in single replicate of clay loam soil under aerobic conditions at 50% MWHC,

B Detected once in single replicate of sandy loam soil under aerobic conditions at 50% MWHC,

C Another abbreviation seen is CHPA

### 279 Appendix B. Summary Tables of Ecological Effects Studies

Table G

- 2: Ecological Effects Data Requirements for MCPA

Guideline # Data 030501 030502 030516 030564

Requirement MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n

71

- 1 850.21 Avian Oral L D 50 bobwhite

400192

- 01 core bobwhite

400192

- 01 core

71

- 2 850.22 Avian Dietary

LC 50 bobwhite

405558

- 03

m a llard

405558

- 02 core

core

71

- 4 850.23 Avian Reproduction bobwhite

435052

- 01 core

72

- 1 850.1075 Freshwater Fish

LC 50 bluegill

418009

- 01

rainbow

418009

- 02 core TEP

core TEP bluegill

400620

- 04

bluegill

426244

- 02

bluegill

418009

- 04

rainbow

400620

- 05

rainbow

418009

- 05 core

core

core TEP

core

core TEP bluegill

426244

- 03

rainbow

426244

- 04 core

core

72

- 2 850.101 Freshwater

Invertebrate

Acute LC 50 daphnid

418009

- 03 core TEP daphnid

424122

- 01 daphnid

418009

- 06 core

core TEP daphnid

426136

- 01 core

72

- 3(a) 850.1075 Estuarine/Marine

Fish LC 50 Atlantic silverside

400620

- 02 core sheepshead 419395

- 04 core TEP sheepshead

430832

- 10 sheepshead

419395

- 01 core

core TEP sheepshead

430865

- 01 core

### 280 Table G

- 2: Ecological Effects Data Requirements for MCPA

Guideline # Data 030501 030502 030516 030564

Requirement MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n

72

- 3(b) 850.1025 Estuarine/Marine

Mollusk EC 50 Eastern o y ster
larvae

400620

- 03 core Eastern o y ster sh ell

419395

- 06 core TEP Eastern o y ster
shell 430932

- 09

Eastern o y ster
shell 432521

- 01

Eastern o y ster
shell 419395

- 03 core

core TEP

supp TEP (no

definitive NOAEC)

72

- 3(c) 850.1035

850.1045 Estuarine/Marine Shrimp EC 50 pink shrimp

400620

- 01 core m y s i d

419395

- 05 core TEP m y sid

419395

- 02 pink shrimp

400620

- 06 core TEP

core m y si d

430965

- 02 core

72

- 4(a) 850.14 Freshwater Fish Early Life

- Stage fathead minnow

444072

- 02 core

72

- 4(b) 850.1300

850.1350 Aquatic

Invertebrate Life

C y cle daphnid

444072

- 01 core

72

- 5 850.15 Freshwater Fish

Full Life

- C y c le

### 281 Table G

- 2: Ecological Effects Data Requirements for MCPA

Guideline # Data 030501 030502 030516 030564

Requirement MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n

123

- 1(a) 850.4100 S eedling Emergence 430832

- 05 (ten species) core 426987

- 08 (eight species)

432579

- 01 (two species) Together,

these two

studies

contain core data for ten

sp ecies

. 426693

- 01 (ten species) core

123

- 1(b) 850.4150 Vegetative Vigor 430832

- 05 (ten species) core 47216808 Under review 426693

- 04 (five species)

437882

- 01 (five species) Together,

these two

studies

contain core data for ten

sp ecies

. 426693

- 02 (ten species) core

### 282 Table G

- 2: Ecological Effects Data Requirements for MCPA

Guideline # Data 030501 030502 030516 030564

Requirement MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n

123

- 2 850.44 Aquatic Plant

Growth Lemna gibba

431265

- 01

Selan. capricornitum

430632

- 03

Navic. pelliculosa

430932

- 02

Ana. flos

- aquae

430832

- 04

Skel. cos t atum

430832

- 01 supp (no

definitive NOAEC)

core

core

core

core Lemna gibba

431265

- 02

Lemna gibba

449035

- 01

Selan. capricornitum

424613

- 01

Selan. capricornitum

449035

- 02

Selan. capricornitum

453131

- 01

Selan. capricornitum

455544

- 03

Navic. pelliculosa

430832

- 07

Navic

. pelliculosa

449035

- 04

Ana. flos

- aquae

430832

- 08

Ana. flos

- aquae

449035

- 03

Skel. cos t atum

430832

- 06

Skel. cos t atum

449035

- 05 supp (no

definitive NOAEC)

core

core

core

supp (insufficient replicates )

supp (no

definitive NOAEC)

core

supp (no

definitive NOAEC)

core

core

core

core Lemna gibba

430832

- 14

Selan. capricornitum

424612

- 01

Navic. pelliculosa

430832

- 11

Ana. flos

- aquae

430832

- 13

Skel. cos t atum

430832

- 12 core

core

core

core

core

141

- 1 850.302 Honey Bee Acute

Contact L D 50 honey bee 421503

- 01 core hone y bee

421978

- 01 core

### Table G

- 2: Ecological Effects Data Requirements for MCPA

Guideline # Data 030501 030502 030516 030564

Requirement MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n MRI D Study

Cl a ssific a ti o n

141

- 2 850.303 Honey Bee

Residue on

Foliage