### Page 1 of 40 risk assessments and for the purposes of this problem formulation are considered equivalent as well and will be referred to collectively here as 2 ,4

- DB unless otherwise noted

. According to the Office of Pesticide Programs’ ( OPP ) Reregistration Eligibility Decision (RED) document completed in 2005 (USEPA 2005a), EPA has not made a common mechanism of toxicity finding for 2,4

- DB and any other substances

. However, 2,4

- DB produces the transformation product 2,4

- D (PC Code 030001) , w hich is a registered active ingredient. Risks posed to the environment from 2,4

- D are addressed separately in the 2,4

- D RED, and will be addressed as part of the currently ongoing Registration Review process for 2,4

- D. The EFED problem formulation for 2, 4

- D was drafted in April 2013 ( D 402410).

Th is problem formulation describes the methods planned to be used during the completion of drinking water and ecological risk assessments in support of registration review and provides an overview of the environmen tal fate, ecological effects, and potential risks associated with the use of 2,4

- DB as well as uncertainties unique to risk assessment of 2,4

- DB. This document also identifies additional studies that would be beneficial to the conduct of an ecological ris k assessment. Major findings include:

• 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 1 . Data are needed for aerobic soil metabolism (835 .4100) , aerobic and anaerobic aquatic metabolism (835.4300 & 835.4400)

, bioconcentration in fish (850.1730 )

, and environmental chemistry methods (with independent laboratory validations ; 850. 6100 ).

• The ecological database is also incomplete based on the ecological effects data requirements outlined in the 40CFR158 Subpart G 2 . The required studies are listed below. U se of either 2,4

- DB or 2,4

- DB

- DMAS is adequate to fulfill guideline requirements.

o Data are needed for acute studies on one est uarine/marine mollusk and one estuarine/marine shrimp (Guidelines 850.1025, 850.1035, 850.1045, 850 .1055 ).

o Saltwater invertebrate life cycle (Guideline 850. 1350)

. o Saltwater and f reshwater fish early

- life stage (Guideline 850.1400). EFED recommends testi ng on the rainbow trout (Oncorhynchus mykiss ) for the freshwater species since this species resulted in the lowest 96

- hour L C 50 among tested species. If the test species for this data requirement is different from the species used for the freshwater and estuarine/marine fish acute toxicity test s , a 96

– hour LC 50 on th at species must also be provided.

o Passerine acute toxicity study. (Guideline 850.2100).

o Avian reproduction study (Guideline 850.2300). An avian reproduction study is required for an upland an d game bird species.

o Aquatic non

- vascular plant (a lgal toxicity ; Guideline 850.4500). Current guidelines require a minimum of three species; freshwater green algae, marine diatom, and freshwater diatom. The available study (MRID 41407803) only includes t he green alga Raphidocelis subcapitata ( formerly Pseudokirchneriella subcapitata )

. o Cyanobacteria toxicity (Guideline 850. 4550). Current Part 158 Guideline requirements include the cyanobacteria toxicity test in addition to the algal toxicity study previously cited.

1 CFR. 2013. Title 40 (Protection of the Environment), Chapter 1 (Environmental Protection Agency), Subchapter E (Pesticide Programs), Part 158 (Data Requirements for Pesticides), Subpart N (Environmental Fate) http://www.ecfr.gov/cgi

- bin/text

idx?c=ecfr&SID=ff5c7fef3645e7cd5abceca0b597bccb&tpl=/ecfrbrowse/Title40/40cfr158_main_02.tpl
2 CFR. 2013. Title 40 (Protection of the Environment), Chapter 1 (Environmental Protection Agency), Subchapter E (Pesticide Programs), Part 158 (Data Requirements for Pesticides), Subpart G (Ecological Effects) http://www.ecfr.gov/cgi

- bin/text

idx?c=ecfr&SID=ff5c7fef3645e7cd5abceca0b597bccb&rgn=div6&view=text&node=40:25.0.1.1.9.7&idno=40

### Page 2 of 40 o EFED has received the following studies and they are currently under review. Once the data evaluations are completed, a determination will be made whether they fulfill the associated data requirements

.

 Acute toxicity with the Sheepshead Minnow (Guideline 850.1075)

 Seedling emergence, Tier II (Guideline 850.4225)

 Vegetative vigor, tier II (Guideline 850.4250)

1. Introd uction

The herbicide 2,4

- DB is a systemic pesticide and belongs to the chlorophenoxy class of herbicides. It is a synthetic plant auxin hormone and has a mode of action like indole acetic acid, a natural plant growth regulator that controls the rate of plant growth (USEPA 2013). The compound has been registered for use in controlling annual and perennial broadleaf weeds since 1958 (USEPA 2005a). Currently, there are seven active Section 3 registrations for 2,4

- DB products and 13 active Section 3 registrations for 2,4

- DB

DMAS.

EFED evaluated the most recent ecological risk assessments for 2,4

- DB in association with any avail able updated toxicity, exposure, and usage information to determine if sufficient data are available and if further updates are needed to support Registration Review. Recent risk assessments include the 2004 EFED risk assessment of 2,4

- DB (USEPA 2004a; DP Barcode 291209 ) in support of the 2,4

- DB RED (USEPA 2005a). No new uses have been assessed since that time. In addition, EFED considered the latest Agency science policies and risk assessment methodologies.

2. Use Characterization

Based on information provided in the chemical profile created by the OPP Biologic and Economic Analysis Division (BEAD; USEPA 2013) for Registration Review, 2,4

- DB is formulated as a liquid (emulsifiable, flowable or soluble concentrate) in multiple end

- us e products and can be applied as a ground broadcast application or a directed spray by ground or aerial application. The herbicide 2,4

- DB is used on alfalfa, wheat, clover (pasture) , peppermint, spearmint, peanuts, soybeans and birdsfoot trefoil, while 2,4

- DB

- DMAS is used on alfalfa, peanuts, and soybeans ; 2,4

- DB and 2,4

- DB

- DMAS have no non

agricultural use sites registered. The Screening Level Usage Analysis (SLUA; USEPA 2012 b ) conducted by BEAD estimates the following agricultural uses during 2003

- 2010: p eanuts at 200,000 lbs acid equivalent (a.e.) ; alfalfa at 60,000 lbs a. e .; pasture at 40,000 lbs a. e .; soybeans at 20,000 lbs a. e.; and wheat at 20,000 lbs a.e . Use on peanuts has a percent crop treated range of 40

- 60%, while the range is

< 1

- 2.5% for all other crops listed.

The chemical profile produced by BEAD, located in the docket, lists the use patterns associated with the active registrations of 2,4

- DB. EFED will rely on the BEAD chemical profile when estimating environmental exposur e s that result from these registered uses. Additionally, in order to be protective, EFED will utilize the use information that result s in maximum exposure estimates for a given use pattern for the drinking water and ecological risk assessment s

. If the la bels (and consequently the BEAD chemical profile) do not include information needed to estimate exposure, such as the maximum single application rate, the application interval, the annual maximum rate allowed (lbs a.i./year), and application method, EFED w ill make conservative assumptions.



### One of the major degradates of 2,4

- DB, 2,4

- D, is a registered phenoxy herbicide and is also one of the most highly used herbicides in the US. Since 2,4

- D is a major degradate of 2,4

- DB, there is the potential for incre ased environmental loading of 2,4

- D through the use of 2,4

- DB. However, the relative amounts applied makes this unlikely. In all, 29 million pounds 2,4

- D were

### Page 3 of 40 applied to agricultural crops in the United States annually between 2006 and 2010. An addition al 5 million pounds were estimated average annual use on lawns, turf, nurseries, etc. in commercial settings. Homeowner and aquatic weed control uses have remained fairly constant with average annual uses of 9 to 9.5 million pounds per year (USEPA 2012a). In contrast, the use estimates for 2,4

- DB combine for approximately 340,000 lbs between 2003

- 2010, less than 1% of the total amount of 2,4

- D applied annually. Because 2,4

- D is a degradate of 2,4

- DB and the amount of 2,4

- DB used is less 1% of the total a mount of 2,4

- D, it is not likely that the use 2,4

- DB will significantly contribute to the overall environmental loading of 2,4

- D.

3. Conclusions from Previous Risk Assessments

a. Ecological Risk Assessment

The Agency issue d a Reregistration Eligibility Decision ( USEPA 2005a ) for 2,4

- DB that serve s as a basis for this problem formulation . The RED concluded that 2,4

- DB presents the greatest potential risks to: 1) terrestrial non

- target plants th r ough spray

- drift and runoff in to adjacent are a s where these plants are present; 2) small and medium

- sized mammals through direct application to treated fields; 3) small and medium

- sized birds; and 4) Federally endangered or threatened species (hereafter referred to as “listed”) freshwa ter fish through spray drift and runoff from use on alfalfa.

Because 2,4

- DB

- DMAS dissociates rapidly in water to form 2,4

- DB, and ecotoxicity data were similar for 2,4

- DB and 2,4

- DB

- DMAS, EFED bridged the ecotoxicity data studies for 2,4

- DB

- DMAS with 2,4

- DB. No ecotoxicity data were available to directly assess potential risks to aquatic vascular plants, or chronic toxicity to birds and estuarine/marine organisms for either 2,4

- DB

- DMAS or 2,4

- DB. Risk quotients for terrestrial and aquatic organisms were calculated on an “acid equivalents (ae) ” basis accounting for molecular weight differences between 2,4

- DB and 2,4

- DB

- DMAS. EFED has considered available information on all formulations of 2,4

- DB for toxicity, potential use areas, fate properties, and appl ication methods in characterizing ecological risks related to labeled use.

Based on a n acute contact honey bee study (Accession Number 00018842), previous risk assessments have concluded that the potential for 2,4

- DB to have direct adverse effects on poll inators and other beneficial insects was low. Similarly, modeling results did not indicate potential concerns for freshwater invertebrates and freshwater fish. However, the acute risk Level of Concern (LOC) for listed fish was exceeded using the maximum application rate and minimum application interval.

The major environmental fate and ecological risk conclusions identified in the RED are summarized in Table 1

.

Table 1 . Summary of Risk Concerns Identified for 2,4

- DB in Previous Assessments

Birds Mammals Terr. Plants Terr. Inverts Fish BCF Aquatic Inverts Aquatic Plants Groundwater Contamination Persistence Degrad at es of Concern Yes a Yes Yes No Yes b No No c Yes Yes Yes Yes

a No reproduction data were available to allow for a chronic risk assessment
b A cute risk LOC for listed fish was exceeded using the maximum application rate and minimum application interval

c Acute and chronic data are currently not available for estuarine /marine invertebrates and fish Yes = at least one LOC has been exceeded in previous assessments; “No“= LOCs have not been exceeded in previous assessments; NA = R Qs have not been calculated previously.

### Page 4 of 40 **b. Drinking Water Exposure Assessments** 

A drinking water exposure assessment was conducted for 2,4

- DB in 2004 (USEPA, 2004a) as part of the RED process. Exposure estimates of 2,4

- DB from labeled uses at that time produced maximum exposures (for alfalfa in TX), on an acid

- equivalents basis, of 318.7 μg ae/L (1

- in

- 10

- year peak), 72.4 μg ae/L (1

- in

- 10

- year annual mean), and 39.9 μg ae/L (30

- year mean) for surface water and 0.51 μg ae/L for groundwater. At that time, estimated drinking water concentrations (EDWC) of 2,4

- DB for drinking water from surface and groundwater for human health risk assessment were well below the level of

concern [ 1 % of the a cute population adjusted dose (a PAD ) , and < 2% of the c hronic one (c PAD )] for the most highly exposed population subgroups for e ither acute or chronic exposures for the general U.S. population or any subgroups. Currently, the Health Effects Division (HED) does not anticipate updating the dietary exposure estimates from food, given that it is not likely to have a significant impact on aggregate risk (7/12/13 email from Wade Britton, HED, to Katherine St. Clair, PRD)

. Thus, an updated drinking water assessment will not be needed as part of the Registration Review process. Because 

### EFED recently implemented revised percentage crop a rea (PCA) factors as well as introduced a PRZM

GW model to determine EDWCs in groundwater, in the event that HED does need to update dietary exposure estimates from food, new EDWCs for surface and groundwater will be determined.

In 2005, a drinking water exposure assessment was conducted as part of the RED for the 2,4

- DB degradate of concern, 2,4

- D (USEPA 2005b), which is a registered active ingredient in the same family as 2,4

- DB

.

**c. Clean Water Act Programs** 

The herbicide 2,4

- DB is not specifically iden tified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Act. No Total Maximum Daily Load (TMDL) criteria have been developed for 2, 4

- DB. Aquatic benchmarks have been established for 2,4

- DB; 2,4

- DB

DMAS; and the 2,4

- DB degradate 2,4

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

4. Environmental Fate and Transport



### In aqueous environments

, 2,4

- DB

- DMAS will rapidly dissociate to form 2,4

- DB (acid form) and dimethyl ammoni um (USEPA 2004a). Steady

- state conductance was atta ined for 2,4

- DB

- DMAS in water i n approximately 1.3 minutes (<80 seconds) at 85 μ Ω . Therefore, studies conducted with the acid provide “surrogate data” for 2,4

- DB

- DMA S

.
Based on submitted data, 2,4

- DB dissipates in the environment mainly through aqueous photolysis (half

life of 6

- 17 days), aerobic soil metabolism (half

- life of 25 days) and leaching/runoff ; plant uptake is also expected to be a major factor in dissipation given that the pesticide works in the plants following uptake

. The major degradates of 2,4

- DB in aerobic soil are 2,4

- dichlorophenoxyacetic acid (2,4

- D acid ; resulting from beta

- oxidation ) and 2,4

- dichlorophenol (2,4

- DCP) ; 2,4

- DB does not photodegrade on soil and only metabolizes slowly in anaerobic soil. Thus, it may persist in subsurface soil, aquatic systems, and sediment, although uncertainties exist due to a lack of aquatic metabolism data. Although 2,4

- DB

- DMAS rapidly dis s ociates to 2,4

- DB

, the co mpound 2,4

- DB is stable to hydrolysis. In the environment, because it is an ionizable compound (pK a of approximately 4.6 , indicating that half of the 2,4

- DB molecules will

### Page 5 of 40 be ionized at a pH of 4.6, with increasing percentage of the anion ic form as pH inc reases ), the fate of 2,4

- DB will be dependent on the pH of the soil or aquatic systems in which it is present. Adsorption (and mobility), solubility, and volatility may vary between soil and aquatic systems due to differences in pH and other soil properti es that affect adsorption. At higher pH values, when the compound is present in greater proportions as an anion, the solubility of 2,4

- DB will be greater. Also at higher pH values, the compound will be more hydrophilic and any potential hydrophobic adsor ption to the soil will be lower. Because 2,4

- DB will be present primarily as an anion in soil at environmental pH value s, there is a potential for both surface runoff and leaching to groundwater , and therefore there is a potential groundwater concern for 2,4

- DB . It is uncertain whether 2,4

- DB will bioaccumulate in fish , although it is not expected due to its hydrophilicity at most environmental pH values

. A selection of environmental fate and transport properties of 2,4

- DB is summarized in Table 2

.

Table 2

. Chemical Properties and Environmental Fate Parameters of 2,4

- DB ( and 2,4

- DB

- DMAS as noted, if a vailable )
Parameter Value Description /Comments Source Selected Physical/Chemical Parameters Molecular mass (molecular formula) 249.1 g/mol for 2,4

- DB acid (C 10 H 10 Cl 2 O 3 )

294.2 g/mol for 2,4

- DB

DMAS ( C 12 H 17 C l2 N O 3 ) --

MRID 00153216

Vapor pressure (20°C) 7.1 x10 - 5 Torr Not expected to volatilize from dry surfaces . Will vary with pH. USEPA 2004a

Aqueous solubility (25 ° C ; pH 7 ) 46 mg/L Soluble , but level will vary with pH. MRID 00153216

Henry’s Law Constant (20°C ; pH 7 ) 3.14 x 10 - 9 atm.m 3 /mol Not expected to volatilize from water or moist/wet soil surfaces. Will vary with pH. USEPA 2004a

Dissociation Constant pKa (25 o C) 4. 56 (2,4

- DB) 4.2

- 4.6 (2,4

- DB

- DMAS) Compound is a weak acid and will exist mainly in the dissociated form at most environmental pH value s. As an ion, it will behave differently at various pH levels. MRID 42741501 ; 45512401

Log octanol

- to

- water partition coefficient (Log K OW ) 3.91 -- MRID 00153216

Persistence Hydrolysis half

- life (22 ° C) Stable at pH 5, 7, 9 Does not hydrolyze. MRID 41101101

### Page 6 of 40 Parameter Value Description /Comments Source Aqueous photolysis half

- life (25 ° C) pH 5: 6.3 days pH 7: 17.2 days pH 9: 6.9 days May photolyze slowly in clear, shallow waters. Adjusted for sunlight intensity at 40 ° N latitude. MRID s 41101102

, 42067801

Soil photolysis half

- life (25 ° C) Stable -- MRIDs 41101103, 41101104, 42678401
Aerobic soil metabolism half

life (2 5 °C) 24.5 days Slightly persistent * in a single aerobic soil. MRID 41325501

Ana erobic soil metabolism half

life (2 5 °C) 269.2 days Not a rapid degradation pathway (persistent * ). MRID 41325501

Anaerobic aquatic metabolism half

- life (20

- 2 5 ° C) No data. -- --

Aerobic aquatic metabolism half

- life ( 20

- 25 ° C) No data. -- --

Mobility

Freundlich soil

- water partition coefficients (K F ); organic carbon

- normalized Freundlich coefficients (K FOC ) Adsorption K

F = 0.80 (sand), 0.46 (silt loam), 1.5 (sandy loam), 3.3 (clay loam)

Desorption K

F = 1.0 (sand), 0.90 (silt loam), 2.1 (sandy loam), 4.7 (clay loam) Compound will exist primarily in dissociated form (as an anion) at most environmental pHs , and mobility m ay vary greatly with pH and other soil properties.

1/n range: 0.79

- 0.95

K oc values not reported, but are not meaningful due to the ionizable propert y of the pesticide. MRIDs 41101105, 41617201

Field Dissipation

Terrestrial field dissipation half

life; leaching depth GA: t 1/2 = 3.5 days ( max depth of leaching 0

- 6” ) IA: t 1/2 = 2.0 days ( max depth of leaching 6

- 12”; leached mainly to 0

- 6” depth) NY: t 1/2 = 6.7 days ( max depth of leaching 0

- 6” ) GA: peanut cropped plot IA: soybean cropped plot NY: alfalfa cropped plot MRIDs 44660502, 44660503,44680701

Fish Bioconcentration

### Page 7 of 40 Parameter Value Description /Comments Source

Fish bioconcentration factors (steady

- state ); depuration rate No data.

-- -- *Goring et al. 1975 scale was used to describe persistence. Nonpersistent: t1⁄2 < 15 days; slightly persistent t1⁄2 15

- 45 days; moderately persistent t1⁄2 45

- 180 days; persistent t1⁄2 >180 days.

**a. Transformation Products** 

The major organic degradates of 2,4

- DB in submitted environmental fate studies were 2,4

- D and 2,4

- DCP in aerobic soil and field studies. Multiple minor degradates (not identified) were observed in the aqueous photolysis study. Table 3 summarizes the transformation products of 2,4

- DB and their maximum amounts formed.

A recent problem formulation (DP barcode 402410; 4/12/2013) conducted for 2,4

- D details the environmental fate propertie s of that compound. Similar to 2,4

- DB, 2,4

- D is primarily degraded through microbially

- mediated metabolism and aqueous photolysis, although it also degrades in aerobic aquatic environments, forming 2,4

- DCP and chlorohydroquinone (CHQ). Mobility data on t he degradates of 2,4

- D were not available.

In all three terrestrial field dissipation studies, the degradates 2,4

- D and 2,4

- DCP were present at their maximum detected concentrations within a week of the final applications, and were not detected in surfac e soil by the end of the studies (approximately 1 year)

.Page 8 of 40 Table 3. 2,4

- DB (and 2,4

- DB

- DMAS) and Its Major Environmental Degradates

Code Name/ Synonym Chemical Name Chemical Structure Study Type Ref. (MRID) Maximum %AR (day) A Final %AR (study length)
PARENT

2,4

- DB 4

- (2,4

- dichlorophenoxy) butyric acid (IUPAC)

or 4

- (2,4

- dichlorophenoxy) butanoic acid (CAS)

2,4

- DB

- DMAS Dimethylamine 4

- (2'4

- dich1orophenoxy) butyrate

MAJOR TRANSFORMATION PRODUCTSPage 9 of 40 Code Name/ Synonym Chemical Name Chemical Structure Study Type Ref. (MRID) Maximum %AR (day) A Final %AR (study length)

2,4

- D 2,4

- dichlorophenoxyacetic acid 835.2410 42678401 <1% 835.4100 41325501 835.4200 41325501 TFD (GA) 44660502 15% (3) n.d. TFD (IA) 44660503 9.1% (1) n.d.

TFD (NY) 44680701 5% (7) n.d.

2,4

- DCP 2,4

- dichlorophenol TFD (GA) 44660502 10% (3) n.d. TFD (IA) 44660503 27.3% (7) n.d.

TFD (NY) 44680701 5% (3) n.d.

CO 2 carbon dioxide 834.4100 41325501

n.d. means “not detected”. Terrestrial field study percentages represent the ratio of degradate concentration to the maximum parent concentration, both in the top layer of soil.Page 10 of 40 5. Receptors

Table 4 and Table 5 provide a summary of the most sensitive acute and chronic toxicity values for 2,4

- DB and 2,4

- DB

- MAS across aquatic and terrestrial taxonomic groups, respectively. Base d on the available ecotoxicity information

, freshwater aquatic and terrestrial plants appear to be the most sensitive taxa

, which is expected for an herbicide. Among the other taxa, 2,4

- DB is only slightly to moderately toxic to freshwater fish and aquati c invertebrates, slightly toxic to birds on an acute basis, and practically nontoxic via dietary exposure to birds, mammals, and terrestrial insects. 2,4

- DB and 2,4

- DB

- D MAS have roughly equivalent acute toxicity to the waterflea ( D. magna )

, 

### likely owing to the rapid hydrolysis of the MAS

. Since no data are available specific to aquatic

- phase amphibians, freshwater fish are used as surrogate.

There are no data available examining the effect of either 2,4

- DB or 2,4

- DB

- DMAS on estuarine/marine species.

For terrestrial animals, 2,4

- DB and 2,4

- DB

- D MAS are practically nontoxic to birds ( birds also serve as surrogates for reptiles and terrestrial

- phase amphibians) based on acute studies. There are no 2 ,4

- DB chronic or reproductive studies available for bird s. The registrant submitted a waiver request for an a vian reproduction study

. At the time of the RED, the Agency elected to hold the conduct of the avian reproduction study in reserve b ased on potential exposure through repeated dosing and potential persis tence of the chemical in certain environments

.
2,4

- DB is slight ly to moderately toxic to freshwater fish and aquatic invertebrates in acute studies

. Chronic studies are not available to assess the chronic toxicity of 2,4

- DB or 2,4

- DB

- D MAS in either fish

or aquatic invertebrates

. EFED has recently received t wo new terrestrial plant toxicity studies for 2,4

- DB [ seedling
emergence / growth (MRID 481033

- 01) and vegetative vigor (MRID 481033

- 02) ]

, as well as an estuarine/ m arine acute toxicity study with sheepshead minnows (MRID 479304

- 01). These studies are under review in EFED, and will be used to inform the risk assessment for 2,4

- DB.

**a. Effects to Aquatic Organisms** 

Table 4 . Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for 2,4

- DB and 2,4

- DBMAS (Test material is acid form unless otherwise noted.)

Taxonomic Group Study Type Test Species Toxicity Value (all units in

terms of

acid equivalents ) Acute Toxicity Classification Source (MRID)

Freshwater fish 1 Acute Rainbow Trout ( Oncorhynchus mykiss ) LC 50 = 2 mg/L Moderately toxic 03503 (Accession number)

Chronic (none)

--

Freshwater invertebrates Acute Stonefly ( Pteronarcys sp. ) EC 50 = 15 mg/L Slightly toxic 40094602Page 11 of 40 Taxonomic Group Study Type Test Species Toxicity Value (all units in

terms of

acid equivalents ) Acute Toxicity Classification Source (MRID)

Acute Waterflea ( Daphnia
magna ) EC 50 = 25 mg/L Slightly toxic 41407801

Acute * Waterflea ( Daphnia
magna ) EC 50 = 20.3 mg/L Slightly toxic 41642701

Chronic (none)

--

Estuarine/marine fish Acute (none)

Chronic (none)

Estuarine/marine shrimp Acute (none)

Estuarine/marine mollusk Acute (none)

Estuarine/marine invertebrate Chronic (none)

Aquatic plants and algae Vascular (none)

Non

vascular Green Alg a e ( 

### Pseudokirchneriella subcapitata formerly Selenastrum

c apricornutum ) LOAEC = 1.1 mg/L 41407803

1 f

reshwater fish act as surrogates for aquatic phase amphibians *Study conducted with 2,4

- DB

- DMASPage 12 of 40 **b. Effects to Terrestrial Organisms** 

Table 5 . Summary of the Most Sensitive Endpoints from Terrestrial Toxicity Studies for 2,4

- DB and 2,4

- DB

- D MAS. (Test material is acid form unless otherwise noted.)

Taxonomic Group Study Type Test Species Toxicity Value

(all units in terms of measured acid equivalents ) Acute Toxicity Classification Source

Birds 1 Acute Bobwhite quail ( Colinus virginianus ) LD 50 = 1536 mg/kg

- bw Slightly toxic 41370102

Sub

- acute

dietary Bobwhite quail LC 50 >5,000 mg/kg diet Practically

non

- toxic 41370102, 41370103

Bobwhite quail

, Mall ard Duck & Ring

necked Pheasant LC 50 >5,000 mg/kg diet Practically

non

- toxic 22923

Chronic (none)

--

Mammals Acute Oral Laboratory rat ( Rattus norvegicus ) LD 50 = 1470 mg/kg

- bw Slightly

- toxic 41224401

Acute Inhalation Laboratory rat ( Rattus norvegicus ) LD 50 = >2.3 mg/L Toxicity Category IV 41774001

Chronic Laboratory rat ( Rattus norvegicus ) NOAEL = 3 mg/kg bw /day LOAEL = 30 mg/kg bw /day

Endpoint: decreased body weight gain and food consumption -- 40257501

Insects Acute Honey bee ( Apis mellifera L. ) LD 50 = 14.5 μg/bee Practically

non

- toxic 00018842

Terrestrial plants * Seedling Emergence Dicot

– carrot ( Daucus
carota ) NOAEC = 0.0028 lbs/A EC 25 = 0.0032 lb/A Endpoint: shoot dry weight -- 41605401Page 13 of 40 * Seedling Emergence Monocot

– Onion ( Allium cepa ) NOAEC = 0.043lb/A EC 25 = 0.07 lbs/A Endpoint: shoot dry weight -- 41605401

1 Birds a re surrogates for terrestrial

- phase amphibians and reptiles. *Study conducted with 2,4

- DB

- DMAS

**c. 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 in cident 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 incidents listed i n this database are also in the EIIS.

There was a single incident reported in the EIIS database involving 2,4

- DB. The incident was classified as highly probable to have been caused by 2,4

- DB and involved a misuse of the application to soybean. The inc ident occurred in Iowa in 1991 and resulted in plant damage to honeysuckle and vegetable (species unknown ; ID# 1000077

- 001). As of 15 July, 2013, AIMS identified no ecological incidents involving 2,4

- DB nor were there any incidents reported by the registr ants. The lack of incident reports cannot be considered as evidence of lack of hazard.

In comparison, there were several incident reports for 2,4

- D. As of August 6, 2012, EIIS database returned more than 400 inciden t s between 1949 and the present. The majority of incidents were repor t ed for 2,4

- D acid and involved plants (although one involved the death of a single bird, and was classified as highly certain that 2,4

- D caused the death) . Many of the plant incidents appeared to result from over

- app lication of 2,4

- D products to lawns or application of 2,4

- D products to types of grass that are sensitive to 2,4

- D. Other plant incidents were the result of spray drift in agricultural settings. The larger number of reports compared to 2,4

- DB is likely a reflect ion of the more extensive use of 2,4

- D. For more details on the 2,4

- D incident reports, see the EFED Registration Review Problem Formulation for 2,4

- D (D402410).

6. Exposure Pathways of Concern

The environmental fate properties and use patterns of 2 ,4

- DB indicate that direct spray, spray drift, leaching through soil (to groundwater or in subsurface lateral flow) , and runoff represent potential transport mechanisms of 2,4

- DB to non

- target aquatic and terrestrial organisms. Drinking water and inhalati on exposure pathways were screened using the SIP (Screening Imbibition Program) and STIR (Screening Tool for Inhalation Risk) screening m odels . STIR indicated the inhalation pathway was of low concern (no LOC exceedances are expected) for birds and mammals . SIP indicated exposure through drinking water alone was of low concern for acute risk to birds and mammals. However, drinking water alone is a potential chronic concern for mammals. The data are insufficient to determine if expos ure through drinking water is a potential chronic risk for birds, and therefore risk cannot be precluded. SIP and STIR are described in detail at http://www.epa.gov/oppefed1/models/ter restrial/index.htm

. Potential exposure through sediment was screened using EPI Suite TM v4.11 ( http://www.epa.gov/opptintr/exposure/pubs/episuitedl.htm ). Although t here is a reasonable expectation of exposure in freshwater and marine water bodies as a result of spray drift and runoff and the half

- life of 2,4

-Page 14 of 40 DB in aerobic soil metabolism studies >10 d (MRID 41325501)

, residues in sediment are expected to be negligible ( i.e. , <1% ) . See Appendix B for EPI Suite model results

.

7. Analysis Plan

**a. Stressors of Concern** 

i. Ecological Risk Assessment

The stressors of ecological concern for terrestrial organisms are 2,4

- DB, 2,4

- DB

- DMAS, and the major degradates 2,4

- D and 2,4

- DCP

, for terrestrial and aquatic species. B oth 2,4

- D and 2,4

- DCP were identified in aerobic soil and field studies conducted with 2,4

- DB. 2,4

- DCP is also a major degradate in 2,4

- D anaerobic aquatic studies , and a product impurity of both 2,4

- DB and 2,4

- D. There are some toxicity data for 2,4

- DCP available in the ECOTOX ( http://cfpub.epa.gov/ecotox/ ), which suggest that it is more toxic than 2,4

- D to selected aquatic organisms. EFED will use a total toxic residues appro ach for assessing 2,4

- DB and the degradate 2,4

- DCP unless sufficient data exist to determine EECs separately. The degradate 2,4

- D will be assessed using submitted data for the pesticide, with the determination of separate EECs.

ii. Formulation Impurities

Another possible source of toxicity from the use of 2,4

- DB products is the presence of impurities that may be present as a result of the manufacturing process. Dioxin/furan congeners and other possible organochlorine contaminants have been found in 2,4

- DB products (Holt et. al., 20 10 )

. The term “dioxins” is used to represent polychlorinated dibenzo

- p

- dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). T here are 210 different congeners of dioxins (75 PCDDs and 135 PCDFs); however, only 17 congeners are considered to be of toxicological concern (listed in Table 6 ). For these 17 congeners, evidence is sufficient to conclude that a common mechanism of actio n, involving binding of the chemicals to the aryl hydrocarbon receptor (AHR) as the initial step, underlies 2,3,7,8

- TCDD

- like toxicity elicited by these PCDDs, PCDFs, and Polychlorinated biphenyls (PCBs) (Van den Berg et al ., 1998, 2006). It is

w orth noti ng here that not all of the 17 dioxins identified in Table 6 were found in the 2,4

- DB formulations. 2,4

- DB impurities are limited to a small subset of the toxic dioxin congeners listed below

.

Table 6 . Dioxin Congeners of Toxicological Concern and Toxicity Equivalency Factors for Mammals, Birds and Fish

Congener* Toxicity Equivalency Factors from U.S. EPA 2008b

Mammal TEF Bird TEF Fish TEF

2378

- TCDF 0.1 1 0.05 12378

- PeCDF 0.03 0.1 0.05 23478

- PeCDF 0.3 1 0.5 123478

- HxCDF 0.1 0.1 0.1 123678

- HxCDF 0.1 0.1 0.1 234678

- HxCDF 0.1 0.1 0.1 123789

- HxCDF 0.1 0.1 0.1 1234678

- HpCDF 0.01 0.01 0.01 1234789

- HpCDF 0.01 0.01 0.01 OCDF 0.0003 0.0001 <0.0001Page 15 of 40 Congener* Toxicity Equivalency Factors from U.S. EPA 2008b

Mammal TEF Bird TEF Fish TEF

2378

- TCDD 1 1 1 12378

- PeCDD 1 1 1 123478

- HxCDD 0.1 0.05 0.5 123678

- HxCDD 0.1 0.01 0.01 123789

- HxCDD 0.1 0.1 0.01 1234678

- HpCDD 0.01 <0.001 0.001 OCDD 0.0003 0.001 <0.001 *Abbreviations are as follows: TCDD = tetrachlorodibenzodioxin; PeCDD = pentachlorodibenzodioxin; HxCDD = hexachlorodibenzodioxin; HpCDD = Heptachlorodibenzodioxin; OCDD = Octachlorodibenzodioxin; TCDF = Tetrachlorodibenzofuran; PeCDF = Pentachlorodibenzof uran; HxCDF = Hexachlorodibenzofuran; HpCDF = Heptachlorodibenzofuran; OCDF = octachlorodibenzofuran

2 ,3,7,8

- TCDD and other similar

- acting PCDD, PCDF and PCB congeners have been shown to adversely affect reproduction, development, endocrine functions

, wasting syndrome

, immunotoxicity

, and mortality in fish, birds, and mammals . The EPA (U S EPA 20 10 ) and the World Health Organization (Van Den Berg
et

. al. 1998, 2006) have established toxicity equivalency factors (TEFs) for dioxins as they relate to mammals, birds and fish ( Table 6 ). In the TEF approach, the toxicities of individual congeners are

norm alized to 2,3,7,8

- TCDD . For example, 2,3,7,8

- TCDD has a TEF of 1 and 23478

- PeCDF , which is 1/3 as toxic to mammals, has a TEF of 0.3 ( Table 6 ) . For each PCDD and PCDF, the concentration (or mass) of the chemical is multiplied by its TEF. The sum of the pr oduct s for each PCDD and PCDF represents the toxicity equivalent (TEQ) concentration relative to 2,3,7,8

- TCDD (Equation 1; USEPA 20 10 ).

Equation 1

.

For risk assessment, a TEQ approach may be used to evaluate the toxicity of the dioxin impurities found in the 2,4

- DB formulations. Findings will be included in the overall risk conclusions.

ii. Drinking Water

Currently, HED does not anticipate updating the dietary exposure estimates from food, given that it is not likely to have a significant impact on agg regate risk. Additionally, EFED believes recent changes in the drinking water exposure models will not impact the previously estimated EDWCs in a way that would significantly impact the human dietary risk picture. Thus, an updated drinking water assessmen t will not likely be needed as part of the Registration Review process.

**b. Measures of Exposure** 

EFED will use standard available models (identified in Table 7 ) to evaluate potential exposures to aquatic and terrestrial organisms as described at http://www.epa.gov/pesticides/science/models_db.htm

. Aquatic exposure estimates will be based on estimated environmental concentrations (EECs) generated using the Pesticide Root Zone Model (PRZM 3.12.2 dated May 12, 2005) coupled with the Exposure Analysis Model System (EXAMS 2.98.04.06 dated April 25, 2005) to simulate a waterbody that is considered representative of vulnerable aquatic environments ( e.g ., ponds and streams in headwater
wate rsheds). Terrestrial exposure will be estimated using a model (T

- REX version 1.5) that assumes direct application to a variety of avian, mammalian and reptilian food items. Exposure to terrestrial plants will be estimated using a model (TerrPlant; versio n 1.2.2) that assumes 2,4

- DB drifts or moves with runoff toPage 16 of 40 adjacent habitats. For more information on the various models that will be used in the risk assessment see the links as outlined in Table 7

. Two spray drift models, AgDISP and/or AgDRIFT, will b e used to assess exposures of aquatic and terrestrial organisms to 2,4

- DB deposited in terrestrial and aquatic habitats by spray drift. AgDRIFT (version 2.1.1; dated 03/07/2012) is the model most commonly used by EFED to simulate spray drift into
terrestr ial and aquatic environments. AgDISP (version 8.26; dated 03/07/2012) is used when a parameter needs to be modeled that is not available in AgDRIFT. Spray drift analysis will be an important part of the analysis in defining the potential area of effects for listed species.

Table 7 . List of the various models and the related taxa for which the models will be used.

Environment Taxa of Concern Model(s) Link

Aquatic Fish/ Invertebrates/ Plants PRZM, EXAMS http://www.epa.gov/oppefed1/models/wate r/

Terrestrial Vertebrate T

- REX (dietary item) http://www.epa.gov/oppefed1/models/terre strial/trex/trex_v1_5_webversion.xlsm

AGDISP (Spray drift) http://www.continuum

- dynamics.com/pr

agdisp.html
SIP (imbibition) 

### http://www.epa.gov/oppefed1/models/t errestrial/
STIR (Inhalation) 

### http://www.epa.gov/oppefed1/models/t errestrial/

Plant TerrPlant (Run

- off) http://www.epa.gov/oppefed1/models/terre strial/index.htm#terrplant AgDRIFT (Spray drift) http://www.agdrift.com/AgDRIFt2/Downl oadAgDrift2_0.htm AGDISP (Spray drift) http://www.continuum

- dynamics.com/pr

agdisp.html

Screening

- level calculations using SIP have suggested that drinking water exposure alone may be significant for chronic risks in mammals . This exposure pathway may be further considered at the time of the risk assessment

. The STIR model i ndicated that inhalation i s not likely to be a significant pathway for
exposure. ( Appendix B ).

i. Available Monitoring Data

The Agency is aware of monitoring conducted by federal and state agencies and this information will be considered in the assessment to the extent that data on 2,4

- DB or other residues of concern are available.Page 17 of 40 **c. Measures of**  **Effect**

The most sensitive toxicity endpoints presented in Section 6 of this problem formulation will be used to calculate risk quotients for the respective taxa. Any additional information submitted by the registrant or found in the open literature prior to conduct of the risk assessment will also b e considered. The open literature studies will be identified using EPA’s ECOTOXicology database ( ECOTOX ; http://cfpub.epa.gov/ecotox/ ) , which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. D ata that meet the Agency’s standard for inclusion in risk
assessments can also provide insight into the direct and indirect effects of pesticides on biotic communities . Such effects could include loss of species that are sensitive to the chemicals and from changes in structure and functional characteristics of the affected communities.

**8. Endangered Species Assessments** 

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), t he Agency will evaluate risks to 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

.

**9. Endocrine Disruptor Screening Program** 

Under Federal Food Drug and Cosmetic Act (FFDCA) section 408(p), the Agency must screen all pesticide chemicals for potential endocrine disruptor activity. Between October 2009 and February 2010, EPA issued test orders/data call

- ins for the first group of 67 chemicals, which comprises 58 pesticide active ingredients and 9 inert ingredients. The herbicide 2,4

- DB is not among the group of 58 pesticide active ingredients on the initial list to be screened under the EDSP. For further information on the statu s of the EDSP, the policies and procedures, the list of 67 chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our website: http://www.epa.gov/endo/

.

**10. Preliminary Identification**  **of Data Gaps**

a. Environmental Fate

Table 8 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 in order to support risk assessment.Page 18 of 40 Table 8 . Environmental Fate Data and Study Classifications for 2,4

- DB

.

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct risk assessment? Justification and Assumptions EPA will Make in Absence of Data

835.2120 Hydrolysis 41101101 Acceptable No

--

835.2240 Aqueous photolysis 41101102, 42067801 Supplemental No

--

835.2410 Soil photolysis 42678401 Supplemental No

-- Photodegradation in Air 41479702 Supplemental No

--

835.4100 Aerobic soil metabolism 41325501 Supplemental Yes . Data are needed for three additional soils. The single available half

- life is inadequate for risk assessment. In the absence of additional data, the value will be increased (3x) for the purposes of modeling to account for uncertainty associated with using a single value.

835.4200 Anaerobic soil metabolism 41325501 Supplemental No

--

835.4300 Aerobic aquatic metabolism No data.

-- Yes The assumption of compound stability will be made in the absence of acceptable data.

835.4400 Anaerobic aquatic metabolism No data.

-- Yes The assumption of compound stability will be made in the absence of acceptable data.

835.1230 835.1240 Adsorption/ desorption and leaching 41101105 Acceptable No

--

835.1410 Volatility

– laboratory No data.

-- No Not expected to be volatile under normal use conditions based on low vapor pressure and Henry’s Law Constant.

835.6100 Terrestrial field dissipation 44660502 Acceptable
No

-- 44660503 Acceptable 44680701 Acceptable

850.6100 Analytical method in soil 44660501 Acceptable No

--

Analytical method in water No data.

-- Yes Environmental chemistry method (ECM) and independent laboratory validations (ILV) are required.

850.1730 Fish bioconcentration No data.

-- Yes Based on a K ow = 3.91.Page 19 of 40 Environmental chemistry methods (ECM) for 2,4

- DB residues of concern in soil, water, and sediment as well as independent laboratory validation (ILV) of the methods are required to support monitoring for 2,4

- DB residues and to evaluate newly submitted environmental fate and ecological effects data. I LV methods submitted by the registrant are used to evaluate analyses described in submitted environment al fate and ecological effects studies. Submitted analytical methods 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 acc idental releases. Independent laboratory validations for submitted 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. Currently, ECMs hav e only been submitted for soil; ECMs and ILVs for water and sediment have not been submitted.

b. Effects

The database for the 2,4

- DB is incomplete. There are a number of studies, including several estuarine/marine studies for fish and invertebrates, which are required for risk assessment. Studies may be 

### performed with 2,4

- DB salt or ester. The rationale for requiring chronic aquatic studies includes the following points:

• 2,4

- DB is mobile and persistent under some conditions such that aquatic exposure is likely to

occur

• The RED identified risk to non

- target terrestrial plants through spray drift or runoff to areas adjacent to or near treated fields. Therefore, use sites in close proximity to marine/estuarine environments can expect to generate residues in sufficient quantity to result in risks of concern to marine/estuarine plants and animals

.

In the absence of acc eptable stud ies , EPA will make conservative assumptions to estimate an LC 50 /EC 50 using data such as QSAR 3 estima tes, open literature data, or data from other, similar chemicals ( e.g

. , 2,4

- D)

. If no such data exist for a taxon , risk will be presumed.



### The following aquatic and terrestrial toxicity data are needed for the 2,4

- D B ecological effects
assessment:

• Data are needed for acute studies on one estuarine/marine mollusk and one estuarine/marine shrimp (Guidelines 850.1025, 850.1035, 850.1045, 850 .1055 ). The RED identified risk to non

target terrestrial plants through spray drift or runoff to areas adjacent to or near treated fields. Therefore, use sites in close proximity to marine/estuarine environments can expect to generate residues in sufficient quantity to result in risks of concern to marine/estuarine plants and animals.

• Saltwater invertebrate life cycle (Guideline s 850.1300 and 850.1350). Test s on the freshwater and saltwater species are being recommended at this time

. Although 2,4

- DB is only slightly toxic to freshwater invertebrates, 2,4

- D is moderately toxic to freshwater invertebrate species b ut very highly toxic to marine/estuarine species. Without an adequate acute study to determine the chronic toxicity to freshwater and estuarine/marine species to freshwater invertebrates, risk is presumed. In addition, chronic exposure can be expected th rough drift or runoff and persistence in soils

.

• Saltwater and freshwater fish early

- life stage (Guideline 850.1400). EFED recommends testing on the rainbow trout (Oncorhynchus mykiss ) for the freshwater species since this species resulted in

3 Q SAR Quantitative Structure

- Activity Relationship a quantitative re lationship between an endpoint (biological activity, e.g. , toxicity) and one or more descriptors associated with the endpoint/activity. For more information on QSARs, see: http://www.epa.gov/oppfead1/international/naftatwg/guidance/qsar

- guidance.pdf

.Page 20 of 40 the lowest 96

- hour L C50 among tested species. If the test species for this data requirement is different from the species used for the freshwater fish acute toxicity test , a 96

– hour LC 50 on that species must also be provided. Testing is required at this time for the freshwater fish because the RED indicated potential risk and the absence of a chronic fish study to establish an RQ. Testing is also required on a n estuarine/marine species at this time. One of the triggers for the estuarine/marine fish early

- life stage test is an LC 50 < 1mg/L in the saltwater fish acute toxicity. The acute LC50 in the fre s hwater rainbow trout for 2,4

- DB is 2 mg/L (Accession No. 03503)

, which is greater than the trigger value stated. However, EFED has only recently received and is

curr ently reviewing an acute study for an estuarine/marine species . Due to the relatively small difference between the trigger v alue of 1 mg/L and the LC 50 for the trout of 2 mg/L, and the reasonable assumption of chronic exposure , the estuarine/marine early

- life stage toxicity is currently being required.

• Avian Acute Oral Toxicity Test (Passerine Species; Guideline 850.2100). Acute avian oral toxicity data are required for either one waterfowl or one upland game species and one passerine species under the 40 CFR Part 158 (2010) data requirements for conventional pesticides with outdoor uses. The lowest endpoint from submitted acute oral avian effects data shows an LD 50 of 1536 mg ae/kg

- bw for the bobwhite quail (MRID 41370102 ). Given that passerine species have higher metabolic rates because of their smaller sizes than either waterfowl or upland game bird species and because they may utilize different metabolic pathways, they may be more or less sensitive to 2,4

- D B . A passerine study protocol should be submitted for review by the Agency prior to initiation of the study.

• Avian Reproduction (Guideline 850.2300). In the bobwhite quail, 2,4

- DB is only slightly toxic after an acute exposure (MRID 41370102) and practically non

- toxic in a subacute study (MRID 41370102, 41370103). However, a guideline study compliant with the avian reproduction study for an upland and a game species is require d. 2,4

- DB may be persistent under certain conditions such that chronic terrestrial exposure is likely to occur. In the absence of an appropriate avian reproduction study, 962 mg ae/kg diet, taken from the 2,4

- D reproduction study in bobwhite quail (MRID 45336401) may be used for risk assessment. 2,4

- D appears to be more toxic to birds based on the results of the acute studies, i.e. 2,4

- D LC 50 = 218 mg/kg bw compared to 2,4

- DB which showed no effects at 1536 mg/kg bw. Therefore, the use of the value from the 2,4

- D avian reproduction study is likely protective for 2,4

- DB effects. Furthermore, subacute studies in both 2,4

- D and 2,4

- DB resulted in no effects at the highest doses tested, indicating that dietary exposures are likely to result in significantly lower toxicity compared to acute oral studies. Therefore, the absence of this study is not likely to impact the overall risk.

• Aquatic non

- vascular plant (algal toxicity; Guideline 850.4500). Current guidelines require a minimum of three species; freshwa ter green algae, marine diatom, and freshwater diatom. The available study (MRID 41407803) only includes the green alga Raphidocelis subcapitata (formerl y Pseudokirchneriella subcapitata ). This data gap is critical since plants are the most sensitive tax a and therefore are the main drivers in the risk assessment.

• Cyanobacteria toxicity (Guideline 850. 4550). Current Part 158 Guideline requirements include the cyanobacteria toxicity test in addition to the algal toxicity study previously cited.

Table 9 and 10 identify ecological effects studies by MRID that provide data for each guideline requirement, as well as study classifications and whethe r or not further data are needed in order to support risk assessment. Additional r ationale for the required studies is also presented

.Page 21 of 40 Table 9 . Aquatic Ecological Effects Data and Study Classifications for 2,4

- DB and 2,4

- DB

- D MAS

.

OCSPP Guideline Data Requirement Study Type Submitted Studies (MRID) Study Classification Are data needed to conduct risk assessment Justification and Assumptions EPA will Make in Absence of Data

- Some Example texts are include

850.1010 Freshwater invertebrate

toxicity Acute 40094602 Acceptable

No -- 4140 7801 Acceptable

-- 41642701 (2,4

- DB

DMAS) Acceptable

--

850.102 5 850.1035 850.1045 850.1055 Saltwater invertebrate

toxicity Acute Yes A guideline study compliant to saltwater invertebrate acute toxicity is required. Data are required on one estuarine/marine mollusk and one estuarine/marine shrimp

.

850.1075 Freshwater fish Acute 00050682 Supplemental

No -- 40762601 Acceptable

-- 40762602 Acceptable

-- 41370104 (2,4

- DB

DMAS) Acceptable

--

40094602 Acceptable

-- 41407802 (2,4

- DB

D MAS) Acceptable

--

850.10 75 Saltwater fish Acute 47930401

-- Under Review Study is currently u nder review

850.1300 Freshwater invertebrates

life cycle Chronic (None) (N/A) Yes A study compliant with the freshwater invertebrate guideline is required

850.1350 Saltwater invertebrates life cycle Chronic (None) (N/A) Yes A study compliant with the saltwater invertebrate life cycle guideline is required for the reasons listed above the current table.Page 22 of 40 850.1400 Freshwater fish early

- life stage Chronic (None) (N/A) Yes A study compliant with the freshwater fish early life

- stage guideline is required. P revious risk assessments indicated risks ab ove the LOC for listed species.

850.1400 Saltwater fish early

- life stage Chronic (None) (N/A) Yes Current study under review by EFED

850.1500 Fish life cycle Chronic (None) (N/A) No This study is not currently required. There ar e currently no labels which allow for direct application of 2,4

- DB to water bodies

. Furthermore, the required early life

- stage toxicity studies will likely account for toxicity to the sensitive life stages.

850.1735 850.1740 10

- day Sediment Toxicity Test Subacute (None) NA No There is a reasonable expectation of residue in freshwater and marine water bodies as a result of spray drift and runoff. In addition, the half

- life of 2,4

- DB is aerobic soil metabolism studies >10 d (MRID 41325501 )

. Therefore, the sediment toxicity test is required.

850.4400 Aquatic plant Toxicity Test using Lemna minor. -- 46395501 supplemental No Lemmna gibba is the recommended test species. Although the current study is classified as supplemental. EFED has determined that the current study is sufficient for risk assessment and is not requiring an additional study with Lemna gibba (D290495).Page 23 of 40 850.4500 Algal toxicity

-- 41407803 (2,4

- DB

MAS) Supplemental Yes A nonvascular plant guideline study compliant with the algal toxicity guideline is required. Current guidelines require a minimum of 3 species; freshwater green algae, marine diatom, freshwater diatom. The available study (MRID 41407803) only includes the green alga 

### Pseudokirchneriella sub capitata ( formerly Selenastrum

c apricornutum )

.

850.4550 Cyanobacteria none Yes There are no studies available which satisfy this guideline requirement.

Table 10. Terrestrial Ecological Effects Data for 2,4

- DB and 2,4

- DB

- DMAS.

OCSPP Guideline Data Requirement Study Type Submitted Studies (MRID) Study Classifications Are data needed for risk assessment Current Additional Data Need

850.2100 Avian oral toxicity Acute 41370102 Acceptable No

--

41767112 (2,4

- DB

DMAS) Supplemental

--

Passerine Acute (None) (NA) Yes 

### Acute avian oral toxicity data are required for either one waterfowl or one upland game species and one passerine species under the 40 CFR Part 158 (2010) data requirements for conventional pesticides with o utdoor

uses

850.2200 Avian dietary toxicity subacute 00036935 Supplemental No

--

00092162 Supplemental

--Page 24 of 40 OCSPP Guideline Data Requirement Study Type Submitted Studies (MRID) Study Classifications Are data needed for risk assessment Current Additional Data Need

41370103 (2,4

- DB

DMAS) Acceptable

--

41767113 (2,4

- DB

DMAS) Supplemental

--

41767114 (2,4

- DB

DMAS) Supplemental

--

850.2300 Avian reproduction Chronic ( N one ) (NA) Yes A guideline study compliant with the avian reproduction test guideline is required. 2,4

- DB may be persistent under certain

con d itions such that chronic terrestrial exposure is likely to

occur.

Non

guideline Avian inhalation Acute (None) (NA) No 2,4

- DB has a vapor point of 7.1 x10 - 5 Torr and is
not expected to volatilize

. EFED’s S TIR model further indicated that inhalation is not likely to be a significant pathway for exposure. Therefore, this study is
not required at this time.

850.3020 Honey bee
acute contact toxicity Acute 00018842 Acceptable No

--Page 25 of 40 OCSPP Guideline Data Requirement Study Type Submitted Studies (MRID) Study Classifications Are data needed for risk assessment Current Additional Data Need

850.3030 Honey bee residue on

foliage -- (None) (NA) No The LD 50 for the honey bee acute contact study was 14.5 μg/bee, just slightly above the trigger for the honey bee residue on foliage study of 11 μg/bee. However, 2,4

- DB has not been highlighted as a pervasive pesticide in bee colonies and oral exposure will be

ne gligible based on the use pattern. Therefore, this study is not being required at this time.

850.3040 Field testing for pollinators -- (None) (NA) No See explanation for Honey bee residue on foliage.

Non

Guideline Honeybee Foraging -- 00071149 Supplemental

--

Non

Guideline Honeybee development -- 00111490 Supplemental

--

850.4225 Seedling Emergence -- 48103301

-- Under Review Currently Under Review

850.4100 Seedling Emergence and Seedling Growth -- 41605401 (2,4

- DB

DMAS) Invalid DER not retrievable

850.4250 Vegetative vigor

-- 48103302

-- Under Review Currently Under R eview

850.4225 850.4250 Seedling Emergence and Vegetative Vigor

-- 43054001 (2,4

- DB

DMAS) Invalid The study was determined to be invalid due to flaws in the study methodology ( e .g

. , dry Petri dishes in the seed germination study and a lack of criterion for seed germination) along with other more minor deviations.

1 QSAR Quantitative Structure

- Activity Relationship a quantitative relationship between an endpoint (biological activity, e.g. , toxicity) and one or more descriptors associated with the endpoint/activity. For more information on QSARs, see: http://www.epa.gov/oppfead1/international/naftatwg/guidance/qsar

- guidance.pdf

.Page 26 of 40 11. References

Food and Agriculture Organization of the United Nations. 2000. FAO PESTICIDE DISPOSAL SERIES 8. Assessing Soil Contamination: A Reference Manual. Appendix 2. Parameters of pesticides that influence processes in the soil. Editorial Group, FAO Information Division. Rome.

Goring, C.A.I., D.A. Laskowki, J.H. Hamaker, and R. W. Meikle. 1975. Principles of pesticide degradation in soil. Pages 135

- 172 in (R. Haque and V.H. Freed, eds.) Environmental dynamics of pesticides

. Plenum Press, New York.

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. Technol. 4 4 : 5409

- 5415.

USEPA. 2002a. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides, Version II (February 28, 2002). Office of Pesticide Programs, Environmental Fate and Effects Division, U.S. Environmental Protection Agency. Arlington, VA.

U.S. EPA. 2002b. Pesticide Root Zone Model (PRZM) Field and Orchard Crop Scenarios: St andard Procedures for Conducting Quality Control and Quality Assurance. Office of Pesticide Programs, Environmental Fate and Effects Division, U.S. Environmental Protection Agency. Arlington, VA.

USEPA. 2004a. Environmental Fate and Effects Division Revi sed Risk Assessment 2 for 4

- (2,4

- dichlorophenoxy) Butyric Acid (2,4

- DB) and Dimethylamine 4

- (2,4

- dichlorophenoxy) Butyrate (2,4

- DB DMAS) Reregistration Eligibility Document. DP Barcode 291209. United States Environmental Protection Agency (USEPA). Environm ental Fate and Effects Division. Office of Pesticide Programs. December 13, 2004.

USEPA. 2004b. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs

. United States Environmental Protection Agency (USEPA). Environmental Fa te and Effects Division. Office of Pesticide Programs. Available at http://www.epa.gov/espp/consultation/ecorisk

- overview.pdf

. USEPA. 2005a. Reregistration Eligibility Decision (RED) for 2,4

- DB. United States Environmental Protection Agency (USEPA). Office of Chemical Safety and Pollution Prevention (OCSPP) formerly Prevention, Pesticides and Toxic Substances. EPA 738

- R

- 05

- 001. January 2005.

USEPA. 2005b. Reregistration Eligibility Decision for 2,4

- D. Office of Prevention, Pesticides and Toxic Substances, (7508C) EPA 738

- R

- 05

- 002 June 2005.

USEPA . 2010

. Recommended Toxicity Equivalence Factors (TEFs) for Human Health Risk Assessments of 2,3,7,8

- Tetrachlorodibenzo

- p

- dioxin and Dioxin

- Like Compounds. Risk Assessment Forum, Washington, DC. EPA/600/R

- 10/005.

USEPA. 20 12a . Reregistration Review Problem Formulation for 2,4

- D. United States Environmental Protection Agency (USEPA). Office of Chemical Safety a nd Pollution Prevention (OCSPP). D#402410. November 15, 2012.Page 27 of 40 USEPA. 2012 b . 2,4

- DB (0 30801) Screening Level Usage Analysis (SLUA). United States Environmental Protection Agency (USEPA). Biological and Economic Analysis Division. Office of Pesticide Programs. August 3, 2012.

USEPA. 2013. BEAD Chemical Profile for Registration Review: 2,4

- DB Case (includes 2,4

- DB which is manufactured as an acid and the dimethylamine salt, 2,4

- DB

- DMAS( 030801, 030819)

. Memorandum From M. Kaul, S. Haddad, and D. Berwald to Jill Bloom. Biological and Economic Analysis Division to Pesticide Re

- evaluation Divis ion. February 19, 2013.

Van den Berg, et

. al. ,1998. Toxic Equivalency Factors (TEFs) for PCBs, PCDDs, PCDFs for Humans and Wildlife. Environ Health Perspect 106 (12): 775

- 792.

Van den Berg, et. al., 2006. The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin

- like compounds. Toxicol Sci 93 (2):223

- 41.Page 28 of 40 Appendix A. Bibliography of Submitted Studies

Environmental Fate

161

- 1 Hydrolysis

41101101 2060107

2021630 Rustum, A. (1988) Hydrolysis of Carbon 14|

- 2,4

- DB in Buffered Aqueous Solutions: Laboratory ID: HLA 6015

- 395. Unpublished study prepared by Hazleton Laboratories America, Inc. 77 p.

41888001 2010427 Ruzo, L.; Ewing, A. (1989) Determination of the pK a Value for 2,4

- DB: Lab Project Number: 167

- 1: 167. Unpublished study prepared by Pharmacology and Toxicology Research Lab. 24 p.

41890601

or 41888001 2010427 Ruzo, L.; Ewing, A. (1989) Determination of the pK a Value for 2,4

- DB (Environmental Fate Data): Lab Project Number: 167

- 1: 167. Unpublished study prepared by Pharmacology and Toxicology Research Lab. 24 p.

45512401 Ruzo, L.; Ewing, A. (2001) Determination of the (pKa) Value for 2,4

- DB: Lab Project Number: 167

- 1: 167W. Unpublished study prepared by Pharmacology and Toxicology Research Laboratory West, Inc. 24 p.

161

- 2 Photodegradation

- water

41101102 2021630 Rustum, A. (1988) Artificial Sunlight Photodegradation of ? carbon 14|

- ,4 DB in a Buffered Aqueous Solution: Project ID: HLA 6015

- 396. Unpublished study prepared by Hazleton Laboratories America, Inc. 146 p.

42067801 Supplemen t to MRID 41101102 Obrist, J. (1989) Artificial Sunlight Photodegradation of (Carbon 14) 2,4

- DB in a Buffered Aqueous Solution: (Supplement to MRID 41101102): Lab Project Number HLA 6015

- 396. Unpublished study prepared by Hazleton Labs America, Inc. 39 p.

161

- 3 Photodegradation

- soilPage 29 of 40 41101103 2014639 Saxena , A. (1988) Artificial Sunlight Photodegradation of ? \ carbon 14|

- 2,4

- DB on Soil: Project ID: HLA 6015

- 397. Unpublished study prepared by Hazleton Laboratories America, Inc. 90 p.

41101104 2014639 Saxena, A. (1988) Artificial Sunlight Photodegradation of carbon 14|

- 2,4

- DB in Soil: HLA 6015

- 397. Unpublished study prepared by Hazleton Laboratories America, Inc. 39 p.

42678401 2021630 Lawrence, B.; Mobley, S.; Kesterson, A. (1993) Soil Surface Photolysis of (carbon 14)2,4

- DB in Artificial Sunlight: Lab Project Number: 729: 1499. Unpublished study prepared by PTRL East, Inc. 69 p.

162

- 1 Aerobic soil metabolism

38385 Open lit MacRae , I.C.; Alexander, M. (1965) Microbial degradation of selected herbicides in soil. Journal of Agricultural and Food Chemistry 13(1):72

- 76. (Also in unpublished submission received Oct 2, 1967 under 8F0643; submitted by Stauffer Chemical Co., Richmond, Cali f.; CDL:091118

- S)

41325501 2022165

2021630 Saxena , A. (1989) Aerobic and Aerobic/Anaerobic Soil Metabolism of Carbon

- 14|

- 2,4

- DB in a Sandy Loam Soil: Lab Project Number: HLS/6015/398. Unpublished study prepared by Hazleton Laboratories Americas, Inc. 108 p.

162

- 2 Anaerobic soil metabolism

41325501 2022165 2021630 Saxena, A. (1989) Aerobic and Aerobic/Anaerobic Soil Metabolism of Carbon

- 14|

- 2,4

- DB in a Sandy Loam Soil: Lab Project Number: HLS/6015/398. Unpublished study prepared by Hazleton Laboratories Americas, Inc. 108 p.

163

- 1 Leach/adsorp/desorption

143294 2014639 Hormby, T. (1978) Alanap Soil Persistence Study: PL No. 8PL

- 21

- A. Unpublished study prepared by Biospherics Inc. 55 p.

41101105 2058228 2058532 2021630

- Rustum , A. (1987) The Adsorption and Desorption of ?carbon 14|

- 2, 4

- DB on Representative Agricultural Soils: Project ID: HLA 6015

- 394. Unpublished study prepared by Hazleton Laboratories America, Inc. 59
p.Page 30 of 40 41617201

or 41101105 2058228 2014639 Rustrum, A. (19 87) The Adsorption and Desorption of (Carbon 14)

- 2, 4

- DB on Representative Agricultural Skills: Desorption Coefficient Data: Lab Project Number: HLA 6015

- 394. Unpublished study prepared by Hazleton Laboratories America, Inc. 8 p. supplemental data

164

- 1 Terrestrial field dissipation

41325502 2021630

- Norris, F. (1989) A Small Scale Field Soil Dissipation Study with 4

- (2,4

- Dichlorophenoxy)Butyric Acid (2,4

- DB) the Active Ingredient of Butyrac Brand Herbicide: Lab Project Number: 40643.4

- 1 Unpublished study prepared by Rhone

- Poulenc Ag Co. in cooperation with A & L Eastern Agricultural Laboratories, Inc. and CYAL. 100 p.

44660502 2021630

- White, J.; Taulbee, L.; Horn, W. et al. (1998) Terrestrial Dissipation of 2,4 Dichlorophenoxy Butyric Acid Applied to Peanuts: Lab Project Number: 1007: 2010. Unpublis hed study prepared by PTRL East, Inc. and Hickey's Agri

- Services Laboratory, Inc. 1007 p.

44660503 2021630

- White, J.; Taulbee, L.; Horn, W. et al. (1998) Terrestrial Dissipation of 2,4 Dichlorophenoxy Butyric Acid Applied to Soybeans: Lab Project Number: 1008: 2007:. Unpublished study prepared by PTRL East, Inc. and Easton Agri

- Consulting, Inc. 526 p.

44680701 2021630

- White, J.; Horn, W.; Johnson, T. (1998) Terrestrial Dissipation of 2,4

- Dichloro

- phenoxy Butyric Acid Applied to Alfalfa: Lab Project Number: 1009: 2004. Unpublished study prepared by PTRL East, Inc., A.C.D.S. Research, Inc., and A & L Great Lakes Laboratories, Inc. 395 p.

165

- 4 Fish accumulation

2010407 2021630

- waiver request

Non Guideline or possibly Bridging Data

42741501 2021630

- Andrews, K. (1993) Dissociation of 2,4

- DB Dimethyl Amine Salt (DMAS) in Water: Lab Project Number: SC920205. Unpublished study prepared by Battelle Columbus Operations. 60 p.

43779601 2021630

- Reynolds, J. (1995) Aerobic Aquatic Metabolism of (Carbon

- 14)

- Dimethylamine: Lab Project Number: XBL95031: RPT00231: 8437. Unpublished study prepared by XenoBiotic Labs, Inc. 118 p. PC Code 030019

43908301 2021630

- Reynolds, J. (1995) Anaerobic Aquatic Metabolism of (Carbon 14)

- Dimethylamine: Lab Report No. RPT00246; Study No. XBL95032. Unpublished study prepared by XenoBiotic Labs., Inc. 128 p. PC CodePage 31 of 40 030019

41479702 2021630

- Shepler, K.; Chari, S.; Ruzo, L. (199 0) Vapor Phase Photolysis of (Carbon 14)4

- (2,4

- Dichlorophenoxy) Butyric Acid (2,4

- DB Acid}: PTRl Report No.: 201W: 201W

- 1. Unpublished study prepared by Pharmacology & Toxicology Research Laboratories

- West. 77 p. PC Code 030853Page 32 of 40 Ecological Effects

2 ,4

- DB PC Code 030801

71

- 1 Avian Single Dose Oral Toxicity

36395 2010395 Atkins, E.L.; Greywood, E.A.; Macdonald, R.L. (1975) Toxicity of Pesticides and Other Agricultural Chemicals to Honey Bees: Laboratory Studies. By University of California, Dept. of Entomology.: UC, Cooperative Extension. (Leaflet 2287; published study.) CALLED HILL et al.

92162 2010395 2010399 Weatherholtz, W.M. (1969) Final Report: Acute Toxicity Study

— Duck

lings: Project No. 656

- 113. (Unpublished study received Dec 16, 1970 under 1F1089; prepared by TRW, Inc., submitted by Rhodia, Inc., New Brunswick, N.J.; CDL:090849

- E)

41370102 2010401 Pederson, C. (1989) 2,4

- DB Technical Acid: 21

- Day Acute Oral LD50 Stu dy in Bobwhite Quail: Final Report: Lab Project ID: # 89 QD 132. Unpublished study prepared by Bio

- Life Associates, Ltd. 33 p.

41767112 2039718 Pedersen, C. (1991) Hinder: 21

- Day Acute Oral LD50 Study in Bob

white Quail: Lab Project Number: 109

- 003

- 03. Unpublished study prepared by Bio

- Life Associates, Ltd. 32 p

71

- 2 Avian Subacute Dietary

41767113 2039718 Pedersen, C. (1991) Hinder: 8

- Day Acute Dietary LC50 Study in Bobwhite Quail: Lab Project Number: 109

- 001

- 01. Unpublished study prepared by Bio

- Life Associates, Ltd. 27 p.

41767114 2039718 Pedersen, C. (1991) Hinder: 8

- Day Acute Dietary LC50 Study in Mallard Ducklings: Lab Project Number: 109

- 002

- 02. Unpublished study prepared by Bio

- Life Associates, ltd. 29 p.

71

- 4 Avian Reproduction

46395401 2022164 Pigott, G. (2004) Request for a Waiver for a 2,4

- DB Avian Reproduction Study. Project Number: DBTF/102604/1. Unpublished study prepared byPage 33 of 40 2,4

- DB Task Force. 5 p.

72

- 1 Acute Toxicity to Freshwater Fish

50682 2010400 Bentley, R.E. (1974) Acute Toxicity of Three Anchem Compounds to Bluegill ( Lepomis macrochirus ) and Rainbow Trout ( Salmo gairdneri ). (Unpublished study received Sep 13, 1974 under 264

- 143; prepared by Bionomics EG&G, Inc., submitted by Union Carbide Agricultural Products Co., Inc., Ambler, Pa.; CDL: 131083

- A)

40762601 2010398 McCann, J. (1976) Biological Report of Analysis of Amchem Technical 2,4

- DB: Rainbow Trout (Salmo gairdneri): Static Jar Test 928. Unpublished study prepared by Ter restrial and Aquatic Biology Laboratory. 2 p.

40094602 2010396 Johnson, W.; Finley, M. (1980) Handbook of Acute Toxicity of Chemicals to Fish and Aquatic Invertebrates: Resource Publication 137. US Fish and Wildlife Service, Washington, D.C. 106.

407626 02 2010397 McCann, J. (1976) Biological Report of Analysis of Amchem Technical 2,4

- DB: Bluegill ( Lepomis macrochirus ): Static Jar Test 938. Unpublished study prepared by Terrestrial and Aquatic Biology Laboratory. 1 p.

72

- 2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

41407801 2010404 McNamara, P. (1990) 2,4 DB

- acid

-- Acute Toxicity to Daphnids ( Daphnia
magna ) during a 48

- hour Flow

- through Acute Exposure: Final Report: Lab Report # 89

- 7

- 3031; Study # 10566.0289.6125.115. Unpublished study prepared by Springborn Laboratories, Inc., Environmental Sciences Div. 39 p.

122

- 1 Seed Germination/Seedlin g Emerge nce and Vegetable Vigor

41605401 2101406 Hoberg, J. (1990) 2,4 DB Amine

- Determination of Effects on Seedling Germination, Seed Emergence and Vegetative Vigor of Ten Plant Species: Lab Project Number: 10566

- 0289

- 6130

- 610: 90

- 4

- 3280. Unpublished study prepared by Springborn Laboratories, Inc. 150 p.

123

- 1 Seed germination/seedling emergence and vegetative vigorPage 34 of 40 43359001 Hoberg, J. (1994) 2,4

- DB Amine

-- Determination of Effects on Seedling Germination, Shoot Emergence and Vegetative Vigor of Ten Plant Species: Supplement: Lab Project Number: 90

- 4

- 3280: 93

- 6

- 4820. Unpublished study prepared by Springborn Laboratories, Inc. 94 p.

850.1075 Fish acute toxicity test, freshwater and marine

47930401 Warbritton, R. (2005) Butoxone 200: Flow

- Through Acute Toxicity Test with the Sheepshead Minnow, Cyprinodon variegatus . Project Number: 49718. Unpublished study prepared by ABC Laboratories, Inc. 46 p.

850.2300 Avian reproduction test

46395401 2022164 Pigott, G. (2004) Request for a Waiver for a 2,4

- DB Avian Reproduction Study. Project Number: DBTF/102604/1. Unpublished study prepared by 2,4

- DB Task Force. 5 p.

850.4000 Plants Aquatic Vascular

46395501 2022962 2022963 Mattock, S. 1999. 2,4

- DB Sodium 400 g/L: Toxicity to Lemna minor

. Unpublished study performed by Covance, North Yorkshire, England. Laboratory Project ID No . 78.516 1

- D2 145. Study submitted by 2,4

- DB Task Force, Richard J. Otten, EPA Liason, Raleigh, North Carolina. Study initiated November 11, 1998 and completed February 1999.

850.???? Plants Aquatic Growth and Reproduction

41407803 2080565 Giddings, J.M. 1990. 2,4 DB Amine

- Toxicity to the Freshwater Green Alga Selenastrum caricornutum . Report No. 90

- 1

- 3196. Conducted by Springborn Laboratories, Inc., Wareham, MA. Submitted by 2,4 DB Task Force, c/o Rhone

- Poulenc Ag Company, Research Triang le Park, NC.Page 35 of 40 PC Code 030819 2,4

- DBMAS

71

- 1 Avian Acute Toxicity

41407802 2010437 Sousa, J. (1990) 2,4 DB Amine

-- Acute Toxicity to Bluegill ( Lepomis macrochirus ) under Flow

- through Conditions: Final Report: Lab Report # 89

- 6

- 3059; Study # 10566.0289.6126.105. Unpublished study prepared by Springborn Laboratories Inc., Environmental Sciences Div. 38 p.

71

- 2 Avian Dietary Toxicity

108367 Fink, R. (1974) Final Report: Eight

- day Dietary LC50

-- Bobwhite Quail: Butyrac 175|: Project No. 113

- 105. (Unpublished study received Apr 17, 1974 under unknown admin. no.; prepared by Truslow Farms, Inc., submitted by Union Carbide Agricultural Products Co ., Inc., Research Triangle Park, NC; CDL:131724

- A)

108368 Fink, R. (1974) Final Report: Eight

- day Dietary LC50

-- Mallard Ducks: Butyrac 175|: Project No. 113

- 106. (Unpublished study received Mar 20, 1974 under unknown admin. no.; prepared by Truslow Farm s, Inc., submitted by Union Carbide Agricultural Products Co., Inc., Research Triangle Park, NC; CDL:131724

- B)

126694 Ross, D.; Burroughs, S.; Roberts, N. (1974) The Acute Toxicity (LC50) of Mecoprop Formulated to Japanese Quail: BTS63/74875. (Unpublished study received Apr 1, 1983 under 2217

- EX

- 3; pre

- pared by Huntingdon Research Centre, Eng., submitted by PBI

- Gordon C orp., Kansas City, MO; CDL:071502

- B)

126695 Ross, D.; Burroughs, S.; Roberts, N. (1974) The Acute Toxicity (LD50) of Mecoprop Formulated to Mallard Duck: BTS64/74664. (Unpublished study received Apr 1, 1983 under 2217

- EX

- 3; pre

- pared by Huntingdon Rese arch Centre, Eng., submitted by PBI

- Gordon Corp., Kansas City, MO; CDL:071502

- C)

41370103 2010402 Pedersen, C. (1989) Butyrac 200: 8

- Day Acute Dietary LC50 Study in Bobwhite Quail: Final Report: Lab Project ID: # 89 QC 130; HLA 6012

- 273. Unpublished stu dy prepared by Bio

- Life Associates, Ltd. and Hazleton Laboratories, America, Inc. 71 p.

72

- 1 Acute Toxicity to Freshwater Fish

92168 Syracuse University Research Corporation (1970) Report on the Acute Toxicity of Butoxone Amine, Butoxone Ester and Cantrol to the Fathead Minnow ( Pimephales promelas Rafinesque) and the Rain

- bow TroutPage 36 of 40 (?~Salmo guairdneri ~?sic|). (Unpublished study, including published data, received Dec 16, 1970 under 1F1089; submitted by Rhodia, Inc., New Brunswick, N.J.; CDL:090849

- L)

116347 Syracuse Univ. Research Corp. (1970) Report on the Acute Toxicity of Butoxone Amine, Butoxone Ester and Can

- Trol to the Fathead Minnow ( Pimephales promelas Rafinesque) and the Rainbow Trout (Salmo guairdneri). (Unpublished study received on unknown date under 1F1051; submitted by Rhodia, Inc., New Brunswick, NJ; CDL: 091885

- I)

41370104 2 010403 Sousa, J. (1989) 2,4

- DB Amine Acute Toxicity to Rainbow Trout ( Oncorhynchus mykiss ) under Flow

- through Conditions: Final: SLS Report # 89

- 6

- 3003; Study 1056.0289.6126.108. Unpublished study prepared by Springborn Laboratories, Inc. Environmental Sci ences Div. 39 p.

41407802 2010405 Sousa, J. (1990) 2,4 DB Amine

-- Acute Toxicity to Bluegill ( Lepomis macrochirus ) under Flow

- through Conditions: Final Report: Lab Report # 89

- 6

- 3059; Study # 10566.0289.6126.105. Unpublished study prepared by Springborn L aboratories Inc., Environmental Sciences Div. 38 p.

41642701 2010432 2010436 Putt, A. (1990) 2,4 DB Amine: Acute Toxicity to Daphnids ( Daphnia
magna ) During a 48

- hour Flow

- through Exposure: Final Report. Lab Project Number: Report 90

- 8

- 3451; STUDY 10566. 0289.6127.115. Unpublished study prepared by Springborn Labs, Inc. 63 p.

72

- 4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

54668 Davis, J.T.; Hardcastle, W.S. (1960) Biological assay of herbicides for fish toxicity. Weeds 7:397

- 404. (Also in unpublished submission received Aug 26, 1977 under 4581

- EX

- 30; submitted by Pennwalt Corp., Philadelphia, Pa.; CDL:231831

- J)

122

- 2 Aquatic plant growth

41407803 Giddings, J. (1990) 2,4

- DB Amine

-- Toxicity to the Freshwater Green Alga Selenastrum capricornutum: Final Report: Lab Report # 90

- 1

- 3196; Study # 10566

- 0289

- 6129

- 430. Unpublished study prepared by Springborn Laboratories, Inc., Environmental Sciences Div. 29 p.

123

- 1 See d germination/seedling emergence and vegetative vigor

43054001 2010435 Hoberg, J. (1993) 2,4 DB Amine

-- Determination of Effects on Seed Germination and Seedling Emergence of Several Plant Species: Supplemental Report: Lab Project Number: 93/6/4820:Page 37 of 40 10566/0289/6130/610: 90/4/3280. Unpublished study prepared by Springborn Labs, Inc. 93 p.

41605401 2010434 2010428 2010429 Hoberg, J. (1990) 2,4 DB Amine

- Determination of Effects on Seedling Germination, Seed Emergence and Vegetative Vigor of Ten Plant S pecies: Lab Project Number: 10566

- 0289

- 6130

- 610: 90

- 4

- 3280. Unpublished study prepared by Springborn Laboratories, Inc. 150 p

850.1075 Fish acute toxicity test, freshwater and marine

47930401 Warbritton, R. (2005) Butoxone 200: Flow

- Through Acute Toxicity Test with the Sheepshead Minnow, Cyprinodon varietgatus. Project Number: 49718. Unpublished study prepared by ABC Laboratories, Inc. 46 p.

850.4225 Seedling emergence, Tier II

48103301 Aufderheide, J. (2005) Butoxone 200: Effects on the Seedling Emergence and Growth of Non

- Target Terrestrial Plants (Tier II). Project Number: 49715. Unpublished study prepared by ABC Laboratories, Inc. 82 p.

850.4250 Vegetative vigor, Tier II

48103302 Aufderheide, J. (2006) Butoxone 200: Effects on the Vegetative Vigor of Non

- Target Terrestrial Plants (Tier II). Project Number: 49716. Unpublished study prepared by ABC Laboratories, Inc. 79 p.Page 38 of 40 Appendix B. Ecological Model Results

A. SIP (version 1.0)

Table 1. Inputs Parameter Value Chemical name 2,4

- DB Solubility (in water at 25°C; mg/L ) 46

Mammalian L D 50 ( mg/kg

- bw ) 1470 Mammalian test species laboratory rat Body weight (g) of "other" mammalian

Mammalian NOAEL ( mg/kg

- bw ) 3 Mammalian fest species laboratory rat Body weight (g) of "other" mammalian i Avian L D 50 ( mg/kg

- bw ) 1536 Avian test species northern bobwhite quail Body weight (g) of "other" avian species Mineau scaling factor 1.15

Mallard NOAEC ( mg/kg

- diet ) 0 Bobwhite quail NOAEC ( mg/kg

- diet ) 0 NOAEC (mg/kg

- diet) for other bird species 0 Body weight (g) of other avian species NOAEC (mg/kg

- diet) for 2nd other bird i Body weight (g) of 2nd other avian species

Table 2. Mammalian Results Parameter Acute Chronic Upper bound exposure ( mg/kg

- bw ) 7.91 7.9120 Adjusted toxicity value ( mg/kg

- bw ) 1130.6660 2.3075 Ratio of exposure to toxicity 0.0070 3.4288
Conclusion* Drinking water exposure alone is NOT a potential

concern for mammals Exposure through drinking water alone is

a potential concern for mammals

Table 3

. Avian Results Parameter Acute Chronic Upper bound exposure ( mg/kg

- bw ) 37.2600 37.2600

Adjusted toxicity value ( mg/kg

- bw ) 1106.5797 0.0000

Ratio of exposure to acute toxicity 0.0337 0. 0000

Conclusion* Drinking water exposure alone is NOT a potential

concern for birds Due to insufficient data, risk cannot be precludedPage 39 of 40 STIR (version 1.0)Page 40 of 40 

### EPI Suite TM 

### v4.11 Results

Level III Fugacity Model (Full

- Output):

=======================================

Chem Name : 2,4

- Dichlorophenoxybutyric acid Molecular Wt: 249.1 Henry's LC : 3.14e

- 009 atm

- m3/mole (user

- entered) Vapor Press : 7.1e

- 005 mm Hg (u ser

- entered) Log Kow : 3.91 (user

- entered) Soil Koc : 98.4 (KOCWIN MCI method)

Mass Amount Half

- Life Emissions (percent) (hr) (kg/hr) Air 0.0261 18 1000 Water 17.6 900 1000 Soil 82.3 1.8e+003 1000 Sediment 0.117 8.1e+003 0

Fugacity Reaction Advection Reaction Advection (atm) (kg/hr) (kg/hr) (percent) (percent) Air 1.18e

- 012 47 12.2 1.57 0.407 Water 5.18e

- 014 634 823 21.1 27.4 Soil 1.01e

- 012 1.48e+003 0 49.5 0 Sediment 5.12e

- 014 0.468 0.109 0.0156 0.00364

Persistence Time: 1.56e+003 hr Reaction Time: 2.16e+003 hr Advection Time: 5.61e+003 hr Percent Reacted: 72.2 Percent Advected: 27.8

Half

- Lives (hr), (based upon Biowin (Ultimate) and Aopwin): Air: 18.02 Water: 900 Soil: 1800 Sediment: 8100

Biowin estimate: 2.542 (weeks

- months)

Advection Times (hr):

Air: 100 Water: 1000 Sediment: 5e+004