OFFICE OF
PESTICIDE PROGRAMS UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

PC Code: 114402

DP Barcode: 370340

March 24, 2010

MEMORANDUM

Subject: Registration Review – Preliminary Problem Formulat ion for the Ecological Risk and

Drinking Water Exposure Assessments for Sodium Acif luorfen

To: Christina Scheltema, Chemical Review Manager (RM5 3) Risk Management and Implementation Branch III

Pesticide Re-Evaluation Division (7508P)

From: Donna Judkins, Biologist Stephanie Syslo, Environmental Scientist/RAPL Dana Spatz, Branch Chief

Environmental Risk Branch 3 (ERB3) Environmental Fate and Effects Division (7507P)

The Environmental Fate and Effects Division (EFED) has completed the preliminary problem formulation (attached) for the ecological risk and drinking water exposure assessments to be conducted as part of the Registration Review of the herbicide, sodium acifluorfen. This document is intended to provide an overview of what is currentl y known regarding the environmental fate and ecological effects associated with sodium acifluorf en and its degradation products and outlines uncertainties regarding attributes of the parent co mpound and its transformation products. It describes the preliminary ecological risk hypothesi s and the processes that will be used during the completion of drinking water and ecological risk as sessments in support of Registration Review.1 OFFICE OF
CHEMICAL SAFETY AND
POLLUTION PREVENTION



# Problem Formulation for the Ecological Risk and Drinking Water Exposure Assessments In Support of the Registration Review of

Sodium Acifluorfen

Sodium acifluorfen (CAS 62476-59-9) Sodium 5-(2-chloro-a,a,a-trifluoro-p-tolyloxy)-2-ni trobenzoate 5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenz oic acid, sodium salt

Prepared by: Donna Judkins, Ph.D. Biologist Stephanie Syslo, Environmental Scientist

Reviewed by: Dana Spatz, Branch Chief

Date March 24, 2010 U. S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division

Environmental Risk Branch III 1200 Pennsylvania Ave., NW

Mail Code 7507P Washington, DC 204602 

### Table of Contents

I. Purpose........................................

................................................... ................................................. 3 II. Nature of Regulatory Action....................

................................................... .................................. 3

A. Conclusions from Previous Risk Assessments......

................................................... ..............4

III. Stressor Source and Distribution..............

................................................... ............................... 5

A. Mechanism of Action ............................

................................................... ................................5 B. Overview of Pesticide Usage....................

................................................... .............................5 C. Environmental Fate and Transport ...............

................................................... .....................9 A. Physical and Chemical Properties...............

................................................... ........................9 B. Environmental Fate Summary .....................

................................................... .......................9

1. Environmental Fate .............................

................................................... ........................ 9

2. Transformation Products........................

................................................... .................. 11 3. Environmental Transport .....................

................................................... .................... 11 Monitoring Data

................................................... ................................................... ................... 12 IV. Receptors.....................................

................................................... ............................................ 13 A. Effects on Aquatic Organisms ...................

................................................... ........................14 B. Effects on Terrestrial Organisms...............

................................................... ........................17 D. Ecosystems at Risk.............................

................................................... .................................18 V. Assessment Endpoints...........................

................................................... ................................... 20 VI. Conceptual Model...............................

................................................... ..................................... 20 A. Risk Hypotheses ................................

................................................... ..................................20 B. Diagram........................................

................................................... ........................................20

Direct Terrestrial Uses ............................

................................................... .............................. 20 VII. Analysis Plan Options.........................

................................................... ................................... 21 A. Ecological Risk Assessment.....................

................................................... ...........................22 C. Drinking Water Assessment......................

................................................... .........................23

D. Clean Water Act................................

................................................... ..................................23 E. Endocrine Disruptor Screening Program...........

................................................... ..............24 F. Anticipated Data Needs ..........................

................................................... ............................243



### I. Purpose

The purpose of this problem formulation is to provi de a better understanding of the environmental fate and ecological effects of the registered uses of sodium acifluorfen (s odium 5-(2-chloro-a,a,atrifluoro-p-tolyloxy)-2-nitrobenzoate). Sodium acifluorfen is a non-selective, postemerge nt contact
herbicide used to control annual broadleaf weeds an d some grasses in soybean, peanuts, rice and strawberries. This document will provide a plan fo r analyzing data relevant to sodium acifluorfen and for conducting updated ecological risk and drin king water exposure assessments for its registered uses. Additionally, this problem formul ation is intended to identify remaining data gaps, uncertainties and potential assumptions used to add ress those uncertainties relative to characterizing the ecological risk associated with the registered uses of sodium acifluorfen.

The problem formulation is based on a bridging stra tegy linking the dissociation of sodium

acifluorfen salt to the formation of acifluorfen an d sodium ions. The active ingredient is acifluorfe n acid and application rates will be referred to in t his problem formulation in terms of acid equivalent s (ae). Acifluorfen acid is also a break-down produc t of lactofen, a herbicide used on agricultural crops and in forestry. Because lactofen will degra de to acifluorfen in the environment, the EFED drinking water assessment for sodium acifluorfen wi ll aggregate the potential exposure to acifluorfen from both pesticides.



### II. Nature of Regulatory Action

The Food Quality Protection Act of 1996 mandated th e EPA to implement a new program for assessing the risks of pesticides, i.e ., registration review. 1 All pesticides distributed or sold in the United States generally must be registered by EPA. The decision to register a pesticide is based on

the consideration of scientific data and other fact ors showing that it will not cause unreasonable ris ks to human health, workers, or the environment when u sed as directed on product labeling. The Registration Review program is intended to ensure t hat, as the ability to assess risk evolves and as policies and practices change, all registered pesti cides continue to meet the statutory standard of no

unreasonable adverse effects to human health and th e environment. Changes in science, public policy, and pesticide use practices will occur over time. Through the new Registration Review program, the Agency periodically reevaluates pestic ides to ensure that as change occurs, products in the marketplace can be used safely.

As part of the implementation of the new Registrati on Review program pursuant to Section 3(g) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is beginning its

evaluation to determine whether sodium acifluorfen continues to meet the FIFRA standard for registration. This problem formulation for the ecol ogical risk assessment chapter in support of the registration review is intended for the initial doc ket opening for the public phase of the review

process.

1 http://www.epa.gov/oppsrrd1/registration_review/4

A. Conclusions from Previous Risk Assessments

The Agency has conducted previous ecological risk a ssessments on sodium acifluorfen that serve as a basis for this problem formulation. Each of the previous risk assessments is briefly discussed

below

.

Sodium acifluorfen was first registered in the Unit ed States in 1980 for post-emergent weed control on agricultural crops and was subsequently register ed for residential spot treatment. Four data call

ins (DCIs) were issued in June 1991, March 1995, Oc tober 1995 and January, 2006.

• Re-registration Eligibility Decision (RED)

A RED for sodium acifluorfen was completed in 2003. EPA conducted an aggregate drinking water

assessment for lactofen and sodium acifluorfen beca use they share an environmental degradate, acifluorfen. Because lactofen was first registered after 1984, it was not subject to reregistration un der FIFRA; however, under The Federal Food, Drug and Co smetic Act (FFDCA), as amended by the Food Quality Protection Act (FQPA), it was necessar y to reassess the lactofen tolerances.

The Agency conducted a screening level ecological r isk assessment using modeling to determine the potential impact of sodium acifluorfen use on non-t arget terrestrial and aquatic organisms. The Agency had some concerns for chronic risk to birds that feed on short grasses. The Agency had no concerns for the impacts of sodium acifluorfen on m ammalian species or aquatic organisms.

The Agency determined that sodium acifluorfen will have “no effect” on threatened and endangered aquatic organisms, mammals, and birds. Although chr onic RQs for birds that eat short grass exceeded the level of concern, the only listed enda ngered species that consumes short grass is the Hawaiian goose, which resides on golf courses in Ha waii. Because sodium acifluorfen was not used in or around this bird’s habitat, the Agency conclu ded that there was “no effect” to endangered birds.

Limited plant information was available about the t oxicity of sodium acifluorfen, so the Agency was unable to conduct a risk assessment for non-target plants. Because sodium acifluorfen is an herbicide, there may be some risk to nontarget plan ts exposed via drift. The Agency was unable to

conduct a risk assessment for insects due to a data gap for the honey bee acute contact study.

As part of the RED, the Agency required several lab el amendments to limit the potential for drift. In addition, the Agency required confirmatory plant to xicity data (the vegetative vigor and seedling emergence studies), and the honey bee acute contact study. In addition, since sodium acifluorfen belongs to a class of compounds known to have a pho totropic mode of action in plants and animals,

and there is evidence that such chemicals have incr eased toxicity in the presence of light, a confirmatory phototoxicity study was required. In 2006, a DCI was issued for testing the lightdependent peroxidizing herbicide (LDPH) effects of sodium aciflourfen. See Section: Data required for existing DCIs , for more detailed information.5



### III. Stressor Source and Distribution

A. Mechanism of Action

Sodium acifluorfen (CAS number 62476-59-9) [ Sodium 5-(2-chloro-a,a,a-trifluoro-p-tolyloxy)-2-

nitrobenzoate ] belongs to the nitrophenyl ether class of herbici des. Compounds in this group cause rapid disruption of cell membranes and very rapid k ill. Acifluorfen penetrates into the cytoplasm, and causes the formation of peroxides and free elec trons (light is required) that destroy the cell membranes almost immediately. Rapid destruction of cell membranes prevents translocation to other regions of the plant. Partial coverage of a plant with spray results in spotting and/or partial shoot kill, and new growth on surviving plants will be no rmal in appearance.

B. Overview of Pesticide Usage

Sodium acifluorfen is labeled for use as a non-sele ctive herbicide on the agricultural crops soybeans, peanuts, rice, and strawberries, and as a spot trea tment in residential areas. Based on usage data provided by the Biological and Economic Analysis Di vision (BEAD), on average, roughly 300,000 pounds of sodium acifluorfen are applied annually t o agricultural crops (Table 1) . Sodium acifluorfen usage is highest on soybeans, with annu al average applications of 200,000 lbs a.i. applied (representing >50% of the total use on agricultural crops). The crop with the highest average percent crop treated with sodium acifluorfen is peanuts (20 %), followed by rice and soybeans (5% each). No data were provided for the strawberry use.

Table 1. Screening Level Estimates of Agricultural Uses of Acifluorfen (Source: BEAD SLUA report dated June 5, 2009) Crop Lbs. A.I. Percent Crop Ttd. Avg. Max. Fallow, Summer+ 1,000 <1 5 Peanuts 50,000 10 20 Peas, Green+ <500 <1 <2.5 Rice 20,000 5 5 Soybeans 200,000 <2.5 5

All numbers rounded. <500 indicates less than 500 lbs. of active ingredi ent. <2.5 indicates less than 2.5 percent of crop is tr eated. <1 indicates less than 1 percent of crop is tre ate + These crops were not known to be listed on activ e end use product registrations when this report wa s run. SLUA data sources include: USDA-NASS (United State s Department of Agriculture's National Agricultural Statistics Service; use years 2001-2007); Private Pesticide Ma rket Research, 2001-2007; NPUD 2002 (National Pesti cide Use Database) of the CropLife America Foundation; and C alifornia DPR data. These results reflect amalgama ted data developed by the Agency and are releasable to the p ublic.

As shown in Figure 1 , based on U.S. Geological Survey (USGS) National W ater Quality Assessment Program (NAWQA) data from 2002, acifluor fen is used on agricultural crops only east of the Rocky Mountains, predominantly in the Missis sippi Delta region, the Corn Belt, and Southeastern states from Maryland to Florida. In 2 002, the use of acifluorfen on soybeans represented about 75% of the national use (out of r oughly 400,000 pounds applied).6

Figure 1. Map of Estimated Annual Agricultural Use of Sodium acifluorfen in 2002

(Source: http://water.usgs.gov/nawqa/pnsp/usage/maps/ ).

NAWQA data for the years 1997 and 1992 ( Figures 2 and 3 , respectively) reported substantial use in Nebraska, South Dakota, North Dakota, Minnesota, and Michigan. Approximately 1.7 and 1.25 million pounds active ingredient (a.i.) of sodium a cifluorfen were used in those years, respectively, with approximately 90% used on soybeans. Apparentl y, use of sodium acifluorfen has been declining in recent years with the availability of Roundup Ready ® soybeans.

Formulations used in sodium acifluorfen products in clude liquid (20.1% single active ingredient; 13.4% active ingredient, co-formulated with bentazo n), liquid ready-to-use (0.12% active ingredient, co-formulated with glyphosate), and soluble concent rate (44% active ingredient, manufacturers use product).7

Figure 2. Map of Estimated Annual Agricultural Use of Sodium acifluorfen in 1997

(Source: http://water.usgs.gov/nawqa/pnsp/usage/maps/ ).8

Figure 3. Map of Estimated Annual Agricultural Use of Sodium acifluorfen in 1992

(Source: http://water.usgs.gov/nawqa/pnsp/usage/maps/ ).

Sodium acifluorfen is applied by aircraft and by br oadcast and band treatment using ground equipment for agricultural crops, and by trigger sp ray bottle for spot treatments. It can be applied to peanuts both pre- and post emergence and at crackin g; for rice, from the tiller through boot stage; fo r soybeans both preplant and foliar; and for strawber ries at dormant, pretransplant, and postharvest. Single application rates for agricultural crops ran ge from 0.25 to 0.375 pounds active ingredient/acre (lbs a.i./A) and seasonal application rates are up to 0.75 lbs a.i./A. Applications intended for spot treatment are to be made until the foliage is wet, so in these cases the application rate is estimated

. Sites that can be treated are: fencerows/hedgerows ; mulch; ornamental and shade trees; ornamental lawns and turf; ornamental wood shrubs and vines; p aths/patios; and paved areas (private roads/sidewalks).9

C. Environmental Fate and Transport

A. Physical and Chemical Properties

Common name: Sodium acifluorfen

CAS No.: 62476-59-9 Chemical name: Sodium 5-(2-chloro-a,a,a-trifluoro-p -tolyloxy)-2-nitrobenzoate or

5-(2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenz oic acid, sodium salt Trade name(s): Blazer TM , Storm TM , Ultrablazer TM, Kleeraway Grass and Weed Killer TM

Table 2. Summary of Physical and Chemical Properti es of Flurprimidol

Parameter Value Reference/Comments

Molecular formula C 14 H 7 ClF 3 NO 5 RED* Molecular weight 361.66 g/mol RED Physical state Light yellow powder RED Melting point 274-279oC (with decomposition) RED Vapor pressure (25oC) <1.33 x 10 -5 Pa RED Water Solubility ( 20°C) 62.07 g/ 100 mL RED Henry's Law Constant 7.65 x 10 -10 atm m 3 /mol Reviewer-calculated Dissociation constant (pK

a ) 3.5 RED

Octanol/Water Partition Coefficient (K

ow ; pH 7) 1.55 RED

* http://www.epa.gov/oppsrrd1/REDs/acifluorfen_red.p df

B. Environmental Fate Summary

1. Environmental Fate

The dominant dissipation mechanism for sodium acifl uorfen in the environment is dissociation to the negatively charged acifluorfen anion. The acifluor fen anion is persistent in soil (aerobic soil metabolism half life 170 days) and in aerobic aquat ic environments (estimated aerobic half-life 117 days); it is less persistent in anaerobic condition s (aquatic half-life estimated to be 2.75 days). T he acifluorfen ion is relatively mobile; K d s range from 0.148 to 3.10 g/mL. Adsorption and desorption were strongly correlated with soil clay content. Acifluorfen undergoes photolytic degradation in wat er with a half-lives ranging from 21.7 hours to 352 ho urs depending on the pH and buffer systems used. Thus acifluorfen may degrade rapidly in surface wat er bodies with clear and/or shallow water that is able to transmit adequate light. It is stable to h ydrolysis, and photodegradation on soil is not a ma jor degradation route in the environment. Volatilizati on does not appear to be a significant dissipation pathway for acifluorfen (vapor pressure is <1.33 x 10 -5 Pa; Henry's Law constant is 7.65 x 10 -10 atm

m 3 /mol). Acifluorfen is not expected to bioaccumulat e in aquatic organisms because of the low K

ow .

The environmental fate data shown in the following Tables are taken from required studies submitted in support of registration of sodium acif luorfen.10

Table 3. Environmental Fate Laboratory Data for Sod ium acifluorfen

1 Major degradates are defined as those which reach >10% of the applied. 2 OM = Organic matter content of soil

Study Value Major Degradates 1

, Comments MRID #

Abiotic Hydrolysis Half-life Stable at pHs 3, 6, an d 9 (at up to 40°C for 28 days)

Stable at pHs 4.5, 7.2, and 9.7 (at 25°C) None 00071584,

00122757

00107479

Direct Aqueous Photolysis 21.7 to 352 hours Numerou s polar photoproducts;

none >6.5% of total radioactive residues (TRR) 41891208, 42793502, 44195001,

44195002

Soil Photolysis Half-life > 15 days Degradation in dark control was comparable to that in irradiated samples 44412901

Aerobic Soil Metabolism

Half-life 170 days 6 month incubation period Degradates < 5% TRR each 00143572

Anaerobic Aquatic

Metabolism

Half-life 2.75 days (Water- clay soil system

under N 2 atmosphere) Degradation of parent determined during incubation of 10 days;

incubation for formation and decline of degradates conducted for 375 days. Amino acifluorfen persisted through the incubation period. 43155201

Aerobic Aquatic Metabolism

Half-life 114 days (extrapolated; r 2
0.728) (at 25°C for 35 days in well water - clay soil mixtures) Acifluorfen decreased to 81.8% of TRR by 35 days; sum of 10 minor components and CO 2 approximately

5% each 42330601

Study Value MRID #

Soil K F 1/n K Foc

sand 0.148 0.82 50

sandy loam 0.346 0.89 74

loam 1.51 0.85 57

clay (1.6%

OM 2 ) 1.87 0.79 199 Batch Equilibrium for parent acifluorfen (mL/g)

clay (3.2% OM) 3.10 0.75 165 42793501

Soil K F 1/n K Foc

loamy sand 47.01 0.94 7368

loam 19.34 0.89 741

clay 12.11 0.87 625 Batch Equilibrium

For amino acifluofen degradate (mL/g)

sand 1.25 0.80 431 4441290211

Table 4. Environmental Fate Field Study Data for So dium acifluorfen

2. Transformation Products

The primary degradate of acifluorfen under anaerobi c conditions was the corresponding amine from the reduction of the nitro group (amino acifluorfen (5- [2-chloro-4(trifluoromethyl) phenoxy]-2- aminobenzoic) acid). When samples were incubated under anaerobic conditions for up to 375 days, the degradates amino acifluorfen, acifluorfen aceta mide (5-[2-chloro-4-(trifluoromethyl) phenoxy]- 2-acetamidobenzoic acid), and desnitro acifluorfen (3-[2-chloro-4-(trifluoromethyl)phenoxy]- benzoic acid) were identified in the soi1:water sys tems . Amino acifluorfen averaged 64 -71% of the radioactivity applied at 25 through 375 days; maxim um concentrations of the other degradates were < 5% throughout the study. These same three degradat es were seen in the other metabolism studies; however, none were present at greater than 5% of th e applied radioactivity.

The amino acifluorfen degradate is less mobile than the parent; K d s range from 1.25 to 47 g/mL. Adsorption and desorption were strongly correlated between K ads and soil pH, with an increase in sorption with a decrease in pH. For sand, clay and loam a correlation existed between K ads and % organic matter; however, this relationship did not hold for loamy sand soil. The loamy sandy, however, had the highest level of sorption and the lowest pH value. This indicates that soil pH may have a stronger effect on sorption than organic mat ter. A correlation was not observed for % clay.

3. Environmental Transport

A small-scale prospective ground water monitoring s tudy conducted on soybeans in the central sands of Wisconsin addressed both field dissipation and l eaching potential for sodium acifluorfen. Although acifluorfen and two degradates were monito red, only the parent was detected. Residues Study Value MRID #

Terrestrial Field Dissipation

Half-life 15 days

59 days Estimated as part of limited prospective ground water study After 2 months, residue levels were

near detection levels

Mississippi silt loam; leaching below 3-in depth negligible during 179 days of study 42152201

00137756,

00143573

Aquatic Field Dissipation Half-life 2.2-17.2 days In unvegetated rice fields in Mississippi and Loiusiana 43270801

Small scale prospective ground water study Acifuorfen residues detected in suction lysimeters and in ground

water Soybeans in Wisconsin Detected in ground water at up to 46 ppb 41172801

Small scale retrospective ground water study Residues leached through soil

profile and under certain

conditions were detected in ground water Five states: North Carolina, North Dakota, Indiana, Tennessee, and Virginia 41160001, 41409501, 41458901, 41644901,
41833202,

4215220112

were detected in 56 out of 283 samples in soils to depths of 0.6 m and were detected in ground water at up to 46 ppb. Residues were also found in soil-w ater lysimeters. The ground water detects were uniformly distributed in the field and pesticide re sidues appear to have been transported down gradient. Residues were detected until 10 months a fter application. Results of the prospective monitoring study indicate that pesticide residues r eached ground water by typical mechanisms, and not by preferential flow.

In addition to the results of the small-scale prosp ective groundwater monitoring study

conducted for sodium acifluorfen in a vulnerable ar ea of Wisconsin discussed above,

information on acifluorfen movement in soil is avai lable from a small-scale prospective groundwater monitoring study for lactofen conducted in Mi chigan. Low level concentrations of acifluorfen (lactofen degradate) were detected during the lacto fen PGW in soil-water at several depths (3- and 6- feet) (acifluorfen LOD in soil water = 0.035 ppb), but there were no detections in the ground water (acifluorfen LOD in ground water = 0.035 ppb). The concentrations of acifluorfen observed in the lactofen PGW study were much lower than in the Wisc onsin sodium acifluorfen PGW study; however, several factors contribute to this differe nce. The sodium acifluorfen rate applied (0.75 Ib a.i./ac) in the Wisconsin PGW study is almost twice the seasonal application rate for lactofen (0.4 Ib a.i./ac per season); the sodium acifluorfen was app lied in a single application, while the lactofen application was split into 2 applications at 0.2 Ib a.i./ac with a minimum 12 day interval; sodium acifluorfen dissociates to acifluorfen very rapidly (less than 1 day), but it takes longer for lactofe n to transform to acifluorfen (half-life 3 to 7 days); a nd the maximum amount of acifluorfen that can be derived from lactofen is approximately 60 percent.

When acifluorfen reaches ground water the compound will persist due to its stability to abiotic hydrolysis. Sodium acifluorfen may reach surface wa ter from runoff events, or from discharge of acifluorfen-contaminated ground water into surface water. Acifluorfen reaching surface waters may persist for some time, unless there is some photode gradation. Sodium acifluorfen would not be expected to bioaccumulate in fish because of the lo w K

ow value. Acifluorfen is not expected to be
transported in the vapor phase, but it could be a t hreat to nontarget plants if it moves off-site via spray drift.

Monitoring Data

Acifluorfen (which can be formed from lactofen or s odium acifluorfen) has been detected in surface water and ground water. Degradates of acif luorfen (amino acifluorfen and desnitroacifluorfen) have generally not been includ ed in monitoring studies.

In Small Scale Retrospective Ground Water Monitorin g studies conducted in five states (NC, ND, IN, TN, VA), acifluorfen was persistent and mobile in permeable soils (i.e., sands, loamy sands, sandy loams) low in clay content. However, survey monitoring studies (where existing water sources are sampled) are generally "non-targeted st udies", so specific pesticide use is not known.

Acifluorfen has been detected in both surface and g round water samples collected by the USGS in the National Water Quality Assessment (NAWQA) pr ogram. Results from 13,524 samples13

collected in the United States over the years 1993 -2007 showed quantifiable residues (estimated and measured) in 173 samples (1.28 %); 10 were from gro und water (out of 6092 samples; 0.16%); 163 were from surface water (out of 7432 samples; 2.19% ). Maximum measured residues found in ground water were 0.33 μg/L (from agricultural land in North Carolina in April 2002); the maximum estimated residues in surface water were 2.2 μg/L ( from agricultural land in Indiana in June 1994);

maximum measured residues in surface water were 1.1 μg/L (from agricultural land in North Carolina in June 1993).

Acifluorfen residues in ground water were reported in the Pesticides in Ground Water Data Base, PGWDB (USEPA, 1992), a summary of other groun dwater monitoring studies. The PGWDB (USEPA, 1992) reports four of 1185 wells samp led with concentrations ranging from

0.003 to 0.025 μ g/L. Because the studies summarized in the PGWDB w ere conducted with many objectives and study designs, the results may reflect conditions where no lactofen or

acifluorfen had been used or where there is a low s usceptibility to ground water contamination. Therefore, EFED has low confidence that the monitor ing reflects the potential contamination of ground water from acifluorfen.

The highest measured levels of acifluorfen in groun d water were from the small-scale prospective groundwater study in Wisconsin. This t argeted study was conducted in a vulnerable area with maximum use rates. This study provided information with the highest degree of confidence, because the hydrology and aci fluorfen use were known ( e.g., the detection came from a known use). What is not as w ell known is how this site compares to other use sites in the US. Although the EPA is con fident that the prospective study was conducted at a vulnerable site, the other monitorin g studies were not specifically conducted for acifluorfen (excluding the retrospective study). S ome sampling or study sites were probably in vulnerable areas, but the relationship between acif luorfen use and the monitoring sites, sampling dates, and so on are not well known (or no t known). Use rates were not known.

There is no Maximum Contaminant Level (MCL) establi shed for acifluorfen; Health Advisories (for a 10-kg child) are 2 mg/L (1-day and 10-day), with a Reference Dose (RfD) of 0.01 mg/kg/day, and a Drinking Water Equivalent Level (DWEL) of 0.4 mg/ L. The cancer descriptor for acifluorfen is L/N (Likely to be carcinogenic above a specified do se but not likely to be carcinogenic below that dose because a key event in tumor formation does no t occur below that dose).



### IV. Receptors

Consistent with the process described in the Overvi ew Document (U.S. Environmental Protection Agency, 2004. Overview of the Ecological Risk Asse ssment Process in the Office of Pesticide Programs. Office of Prevention, Pesticides, and To xic Substances. Office of Pesticide Programs. Washington, D.C. January 23, 2004), the risk asses sment for sodium acifluorfen will rely on a surrogate species approach. Toxicological data gen erated from surrogate test species, which are intended to be representative of broad taxonomic gr oups, are used to extrapolate to potential effects on a variety of species (receptors) included under these taxonomic groupings.14

Acute and chronic toxicity data from studies submit ted by pesticide registrants along with the available open literature are used to evaluate the potential direct and indirect effects of sodium acifluorfen on aquatic and terrestrial receptors. T oxicity studies for the technical grade active ingredient (TGAI) and the typical end-use product ( TEP) will all be considered in the ecological risk assessment. Open literature studies are identified using EPA’s ECOTOX database 2 , which employs a literature search engine for locating chemical to xicity data for aquatic life, terrestrial plants, a nd wildlife. Research papers accepted into the ECOTOX database are screened using standard procedures to ensure consistent, high quality infor mation; these studies will be considered during the ‘Analysis’ phase of risk assessment process. The In cident Data System (IDS), which tracks incident reports submitted to EPA, is used to identify suppo rtive, line of evidence information on exposure of aquatic and terrestrial receptors. Data from all o f these sources can also provide insight into the

direct and indirect effects of sodium acifluorfen o n biotic communities from loss of species that are sensitive to the chemical and from changes in struc ture and functional characteristics of the affected

communities.

A. Effects on Aquatic Organisms

A fair amount of acute aquatic toxicity data is ava ilable for consideration in this ecological risk assessment for sodium acifluorfen, but not very muc h chronic data. Table 5 provides a summary of the taxonomic groups and the surrogate species test ed to characterize the potential acute and chronic aquatic effects of sodium acifluorfen. Sodium acif luorfen is classified as slightly toxic, on an acut e basis, to freshwater and saltwater fish and freshwa ter invertebrates, and moderately toxic to

estuarine/marine invertebrates.

The LC 50 was 17 ppm a.i. for the rainbow trout using techni cal grade sodium acifluorfen (MRID 000122752). For estuarine/marine fish, the Sheeps head minnow LC 50 was 39 ppm a.i., also using technical grade (MRID 00122753). Two datasets were submitted of freshwater fish early life stage (ELS) tests using the Fathead minnow ( Pimephales promelas ). Reduced larval weight was reported at 1.5 ppm (the lowest level tested) in MRID 001242 22. The study was supplemental since no

NOEAC was found. There are no data from estuarine and marine fish early life-stage or life-cycle

studies. No freshwater or saltwater fish ELS studi es were required in the RED because 1) none of the criteria were exceeded except reproductive impa irment in birds and 2) the 21-day PRZM/EXAMS value was less than 21 ppb a.i., which i s below 1/100 of the lowest LC 50 of 17 and 39 ppm a.i., respectively.

The most sensitive acute endpoint for freshwater in vertebrates was the Daphnia magna LC 50 of 28.1 ppm a.i. using technical grade sodium acifluorfen ( MRID 071901). No freshwater invertebrate lifecycle study was required in the 2003 RED for sodium acifluorfen because 1) none of the criteria were exceeded except reproductive impairment in bir ds and 2) the 21-day PRZM/EXAMS value was less than 21 ppb a.i., which is below 1/100 of the lowest LC 50 of (28 ppm a.i.). Sodium acifluorfen was categorized as moderately toxic to estuarine/ma rine invertebrates. The most sensitive endpoint was from a mysid shrimp study (MRID, 122755), with an LC 50 of 3.8 mg/L. Sodium acifluorfen

2 http://www.epa.gov/ecotox15

was slightly toxic to practically nontoxic to estua rine mollusks on an acute basis. The Eastern oyste r LC 50 was 74 ppm ai for the technical grade (MRID 111964 ).

Since the only aquatic sublethal endpoint found for sodium acifluorfen (MRID 00124222) did not produce an NOAEC, it is not possible to calculate a n acute-to-chronic ratio (ACR) to estimate the chronic toxicity of sodium acifluorfen to aquatic o rganisms. However, using data from a closely related compound, lactofen 3 (acifluorfen is a major degradate of lactofen and sodium acifluorfen readily dissociates into sodium and acifluorfen in water), when the ACR from lactofen fish data (349) is applied to the mysid acute sodium acifluor fen data, the resulting estimated mysid chronic endpoint is 12 ppb. When this estimated chronic en dpoint is used to calculate a risk quotient (using the 60-day PRZM/EXAMS value), EPA’s level of concer n is exceeded (RQ = 1.8). Therefore, EPA cannot preclude risk to aquatic invertebrates from chronic exposure to sodium acifluorfen.

There are no toxicity data available to assess the potential risk of major degradates to fish or aquat ic invertebrates; this is a major source of uncertaint y in the ecological risk assessment. The breakdown products of sodium acifluorfen include: acifluorfen , amino acifluorfen acid, acifluorfen acetamide

and desnitro acifluorfen. As mentioned in the Envi ronmental Fate and Transport section, for this assessment, acifluorfen acid and sodium acifluorfen (also a breakdown product of lactofen) will be assumed to be equivalent and called sodium acifluor fen.

3 EFED Problem Formulation for Lactofen Registration Review, December 13,2006; DP

Barcode: 323196.16Table 5. Aquatic toxicity profile for sodium acifluorfenTaxonExposureDurationGuidelineMost SensitiveSpecies TestedToxicity ValueAcute ToxicityCategory1ClassificationData GapYes/NoMRIDAcute 850.1075Rainbow trout,Oncorhynchus mykissLC50=17 mga.i./LSlightly toxic AcceptableNo00122752Freshwater FishChronic850.1400Fathead minnow,Pimephales promelasNOAEC = <3.4mg a.i./L (<1.5mg/L Blazer at44.1% a.i.)N/A Supplemental2Outstanding DCI200124222Acute 850.1075Sheepshead minnow,CyprinodonvariegatusLC50= 39 mga.i./LSlightly toxic AcceptableNo00122753Estuarine/ MarineFishChronic 850.1400No DataNANoAcute 850.1010Water Flea,Daphnia magnaLC50=28.1 mga.i./LSlightly toxic AcceptableNo00071901FreshwaterInvertebratesChronic 850.1300No DataNANo3AcuteMysid shrimp,Americamysis bahiaLC50= 3.8 mga.i./LModeratelytoxicAcceptableNo00122755Estuarine/ MarineInvertebratesChronic 850.1350No DataYes3Tier I 850.5400Anabaena flos-aquaeEC50= >355ppmPracticallynontoxicAcceptableNo41680702Non-vascularplantTier II 850.5400Green algae,SelenastrumcapricornutumNOAEC =>265 ppmNA AcceptableNo41680702Tier I 850.4400Duckweed,Lemna gibbaEC50= 378ppmPracticallynontoxicAcceptableNo41680702Vascular plantTier II 850.4400L. gibbaNOAEC = 180ppmNA AcceptableNo416807021Categories ofacute toxicity for aquatic organismsbased on LC50(mg/L): < 0.1 very highly toxic; 0.1-1 highly toxic; >1-10 moderately toxic; >10-100 slightly toxic;>100 practicallynontoxic.2LDPH (light-dependent peroxidizing herbicide) fishearly life-stage testing has been requested; Data Call-in was issued for this chemical on January 25,2005 (GDCI-114402-20870).3EPA’s level of concernis exceeded when an Acute:Chronic ratio (ACR) fromlactofen fish data is applied to the mysid acute data and the resulting mysid chronic endpoint is usedto calculate arisk quotient. Therefore, EPA requests chronic saltwater invertebrate data. This data will, in turn,be used to calculate an invertebrate ACR for sodium aciflourfen, which will be applied to thefreshwater invertebrate data to calculate a more refined chronic freshwater invertebrate toxicity endpoint.17

Toxicity to Aquatic Plants

Since the aquatic concentration that is equivalent to the maximum label rate (355 μg/L) caused no reduction in growth after 120 hours, sodium acif luorfen is considered to be practically nontoxic to algae at the Tier I level.

Aquatic Tier II studies are required for all low do se herbicides (those with the maximum use rate of 0.5 lbs a.i./A or less) (maximum currently- registered application rate for sodium acifluorfen is 0.375 lbs a.i./A) and any pesticide showing a negative response equal to or greater than 50% in Tier I studies. In the Tier II studies, Duckweed, with an EC 50 of 378 ppb, was the most sensitive aquatic vascular plant. Non vascular aquatic plants were not sensitive to

sodium acifluorfen at maximum label rates. The Tie r II results show that Selenastrum capricornutum is the most sensitive nonvascular aquatic plant.

B. Effects on Terrestrial Organisms

Laboratory and field toxicity studies are available for characterization of the effects of sodium acifluorfen to birds (also surrogate for terrestria l-phase amphibians and reptiles), mammals, and

terrestrial invertebrates. Table 6 provides a summary of the most sensitive species te sted for each terrestrial taxonomic group.

Sodium acifluorfen is categorized as moderately tox ic to birds and slightly toxic to mammals, based on quail and rat acute oral tests (LD 50 = 325 and 1540 mg/Kg, respectively; MRIDs 122747 a nd 071887). Acceptable acute avian oral toxicity data were not submitted for a passerine species, which is now required under the 40 CFR Part 158 (CFR 40 2 008) data requirements for conventional pesticides.

Sub-acute and chronic studies, available for birds show sodium acifluorfen to be practically nontoxic via the dietary route (quail and mallard LC 50 >10,000 ppm; MRID 083059 and 083060); however,

sodium acifluorfen reduced the number of viable emb ryos (quail NOAEC = 20 ppm; MRID 107491) at 100 ppm. Studies done on laboratory rats were s ubstituted for wild mammal testing in the last RED. In a rat developmental study (MRID 0122743) t he NOAEC was 20 mg/kg/day (400 ppm) based on decreased fetal body weight.

Terrestrial invertebrate toxicity data are required to quantitatively assess the potential impacts on this group of organisms. Data are especially needed fro m the honey bee acute contact study due to wide spread use and possible drift to off site vege tation in bloom. A honey bee acute contact study (GLN 850.3020; MRID 46650202) has been submit ted and is currently under review.

Phytotoxic effects ( i.e. , plant kills) have been demonstrated in the field (see Incidents section below)

and we anticipate that there may be a risk to offsite, nontarget plants, although the magnitude is

uncertain

. Previous data (MRID 41680701) for vegetative toxi city of sodium acifluorfen to nontarget terrestrial plants were not scientificall y sound because the sodium acifluorfen solution applied to the experimental plants was too dilute and the water may have washed the18

chemical away from the plant. This caused uncertai nty about the exposure. A new vegetative vigor study (GLN 123-2/850.4250; MRID 46431401) was submitted but was classified invalid

because the EC 25 for cucumber dry weight was less than the lowest t reatment level. Since cucumber is likely the most sensitive plant tested, this data is needed to make an assessment of risk to sensitive plants.

C. Adverse Ecological Incidents

A preliminary review of the Ecological Incident Inf ormation System (EIIS) 4 maintained by the Agency’s Office of Pesticide Programs (OPP) produce d only one incident (I003654-012), a fish kill (unknown number) in 1993 caused by runoff with sodi um acifluorfen as the probable cause. A search of the American Bird Conservancy database on the same date revealed no incident data. Lactofen, of which sodium acifluorfen is the chief breakdown product, had four incidents occurring between 1995 and 1998 (3 plant, 1 fish; incidents I 007776-006, I002969-061, I003062-004 and I002969-054, respectively). In 1995, an adjacent f ield sprayed with lactofen resulted in stunted snapbean growth in one incident and in stunted gree nbean and snapbean growth in another. In 1998, soybeans were reportedly damaged by lactofen. The fish kill (unknown species and number) was possibly from over-spraying a product containing la ctofen. Overall, the incident data that are available indicate that exposure pathways for sodiu m acifluorfen are complete and that exposure

levels are sufficient to result in field-observable effects.

D. Ecosystems at Risk

Sodium acifluorfen may be applied as an aerial or g round spray herbicide to terrestrial habitats for agricultural uses, and as a spot treatment for non- agricultural and residential areas. The ecosystems potentially at risk are often extensive in scope; t herefore, it may not be possible to identify specif ic ecosystems during the development of a nation-wide ecological risk assessment. However, in general terms, terrestrial ecosystems potentially a t risk could include the treated field and immediately adjacent areas that may receive drift o r runoff. Areas adjacent to the treated field coul d include cultivated fields, fencerows and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats, and other uncultivate d areas.

Sodium acifluorfen has the potential to contaminate surface water at application from spray drift and runoff. In general terms, aquatic ecosystems poten tially at risk include water bodies adjacent to, or down stream from, the treated field and might inclu de impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, including estuarie s.

4 EIIS was accessed on October 29, 200919Table 6. Terrestrial toxicity profile for sodium acifluorfenTaxonExposureDurationMost SensitiveSpecies TestedGuidelineToxicity ValueAcute ToxicityCategoryClassificationData GapYes/NoMRIDAcuteRatRattus norvegicus850.2400LD50= 1540 mg/kg bw Slightly toxicAcceptable No00071887MammalsChronicRatR. norvegicus850.2400NOAEC = 400 ppm(20 mg/Kg/d)LOAEC = 1800 ppm(90 mg/Kg/d)N/AAcceptable No00122743AcuteOralNorthernbobwhite quailColinusvirginianusMallardAnasplatyrhynchosPasserine850.2100LD50= 325 mg/Kg bwLD50= 4187 mg/Kg bwData GapModerately toxicPractically nontoxic--AcceptableAcceptable--NoNoYes10012274700083059--Sub-acuteDietaryQuail and mallardC. virginianuandA. platyrhynchoss850.2200 >10,000 ppmPractically nontoxic Acceptable No0008305900083060BirdsChronicReproductionQuailC. virginianus850.2300NOAEC = 20 ppmLOAEC = 100 ppmN/A Acceptable No00107491TerrestrialInvertebratesAcuteHoney BeeApis mellifera850.3020 ----In ReviewPending 46650202Tier I2--850.4100850.4150-- -- -- -- --SeedlingEmergenceVegetative Vigor850.4100850.4250Dicot EC25= 0.021 lba.i./A------Seedling EmergenceAcceptableVegetative VigorUnacceptable3NoDCI stillout-standing41680701TerrestrialPlantsTier IIVegetative Vigor 850.4250 ----Vegetative VigorUnacceptable3464314011All pesticides with exposure routes with consumption by passerine birds must be tested on a passerinespecies using guideline 850.2100; this is a newrequirement.2Not required for herbicides; go directly to Tier II3Cucumber, most sensitive dicot, data unacceptable;study may be upgraded with acceptable cucumber rerun20



### V. Assessment Endpoints

The most sensitive toxicity endpoints are used from surrogate test species to estimate treatmentrelated direct effects on acute mortality and chron ic reproductive, growth, and survival assessment endpoints. Surrogate aquatic animals include fresh water and estuarine/marine fish and invertebrates, and surrogate terrestrial animals include birds and mammals. These tests include short-term acute, subacute, and reproduction studies and are typicall y arranged in a hierarchical or tiered system that progresses from basic laboratory tests to applied f ield studies.

The most sensitive toxicity endpoints from surrogat e species are also used for plants. Nonvascular (i.e., algae) and vascular (e.g., duckweed) plant m ortality; growth and reproduction impairment endpoints are used. For plants in terrestrial and semi-aquatic environments, the screening assessment endpoint is the perpetuation of populati ons of non-target species (crops and non-crop plant species). When data are available, endpoints assessed include emergence of seedlings and vegetative vigor.



### VI. Conceptual Model

A. Risk Hypotheses

Risk hypotheses are specific assumptions about pote ntial adverse effects (i.e., changes in assessment endpoints) and may be based on theory and logic, em pirical data, mathematical models, or probability models. For this assessment, the risk is stressor-initiated, where the stressor is the re lease

of sodium acifluorfen to the environment. The foll owing risk hypothesis is presumed for this screening-level assessment:

When used in accordance with current labels for ter restrial use patterns, acifluorfen can move off-site via runoff (in the dissolved phase) a nd spray-drift and expose non-target organisms. Application to foliar surfaces and soil may also result in exposure to non-target organisms. Monitoring data indicate detections of sodium acifluorfen in surface waters and near field sites from use areas presumably due to c urrent uses. These potential exposure pathways may result in adverse effects on the survi val, growth, and/or reproduction of nontarget terrestrial and aquatic organisms, including Federally-listed threatened and endangered species.

B. Diagram

Direct Terrestrial Uses

The environmental fate properties of sodium acifluo rfen along with monitoring data identifying its presence in surface waters indicate that runoff via dissolved phase and spray drift represent potentia l transport mechanisms of sodium acifluorfen to aquat ic and terrestrial organisms. As depicted in21

Figure 4 , these transport mechanisms ( e.g ., sources) for spray (ground, aerial) applications may result in the movement of sodium acifluorfen into a quatic (water) and terrestrial (soil and foliage) habitats. The movement away from the site of appli cation represents exposure pathways for a broad range of biological receptors of concern (non-targe t animals) and the potential attribute changes, i.e.

, effects such as reduced survivals, growth, and repr oduction in the receptors.

Figure 4. Conceptual model for effects of sodium ac ifluorfen on non-target aquatic and terrestrial organisms



### VII. Analysis Plan Options

In Registration Review, pesticide ecological risk a ssessments will follow the Agency’s Guidelines for Ecological Risk Assessment, will be consistent with the paper titled “Overview of the Ecological

Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency” (“Overview Document”) (USEPA, 2004), and wi ll be done in accordance with Section 7 of the Endangered Species Act. Stressor Sodium acifluorfen applied as ground/aerial spray i n agricultural and residential settings.

Source/ Transport Pathways Volatilization/ Wind Suspension Direct Deposition Spray

Drift Runoff Leaching (infiltration/ percolation)

Source/ Exposure
Media Terrestrial Food Residues (foliage, fruit, insects) Upland Foliage/Soil Riparian/

Wetland Foliage/Soil Water

Column/
Sediment Groundwater

Exposure
Point Ingestion Direct contact Direct contact Gill/ Integument Uptake

Receptors

Attribute Changes Terrestrial Vertebrates

Birds, Small Mammals, Reptiles, Terrestrial

Insects Terrestrial Upland

Plants

Individual Animals
Reduced survival Reduced growth Reduced reproduction Aquatic Invertebrates Aquatic Vertebrates Amphibians Aquatic Plants Wetland/ Riparian

Plants

Individual Plants Seedling emergence Vegetative vigor Individual
Vertebrates and

Invertebrates

Reduced

survival

Reduced growth

Reduced reproduction Food Web Exposure (bioconcentration)

Piscivorous

Vertebrates Birds,

Mammals

Individual
Animals

Reduced survival, growth, and reproduction Plant Population

Reduced population growth22

A. Ecological Risk Assessment

Previously completed risk assessments and exceedanc es of Agency levels of concern indicate that acute effects are not expected for terrestrial anim als, freshwater and estuarine animals, or aquatic plants. Chronic risk is anticipated for herbivorou s and insectivorous birds but not for mammals.

Insectivorous birds would be at chronic risk at max imum exposure levels. No data are available to

assess the risk of sodium acifluorfen to the Passer ine group of birds.

Chronic risk is uncertain for freshwater and estuar ine animals. Sodium acifluorfen is classified as a light-dependent peroxidizing herbicide (LDPH). LDP Hs may be more toxic to animals exposed to natural light than would be predicated from guideli ne toxicity data generated from standard EFED toxicity guideline studies (72 series), which are n ot conducted under lighting conditions with the same wavelength or intensity as sunlight. Evidence for this comes from a preliminary phototoxicity study with another LDPH (carfentrazone-ethyl) which showed a nearly 20-fold increase in toxicity when natural wavelength light was used.

Terrestrial plant risk assessment could not be cond ucted due to lack of adequate data. Since sodium acifluorfen is an herbicide, an assumption has been made that risk exists to nontarget plants. The magnitude of this risk is unknown.

The potential impact to water quality from the use of sodium acifluorfen and its degradates also

considers the herbicide lactofen. Lactofen and sod ium acifluorfen have many of the same degradates or break-down products including acifluo rfen and amino acifluorfen. The likelihood of water contamination by acifluorfen from uses of sod ium acifluorfen or lactofen is high due to the low sorption of acifluorfen and its long persistenc e under many conditions. The likelihood of water

contamination from lactofen is low. Lactofen has a high binding potential. Thus, it will sorb to soi l or sediment. Lactofen breaks down rapidly to form acifluorfen and other degradates.

The potential for acifluorfen to contaminate water is confirmed by monitoring studies that found acifluorfen residues in ground water and surface wa ter. Generally, there was inadequate usage

information at the time of the 2003 RED to determin e whether the detections resulted from the use of sodium acifluorfen or lactofen, so modeling was used (GENEECx, PRZM/EXAMS, and SCIGROW). The estimated concentrations correspond rea sonably well with the maximum concentrations seen in NAWQA monitoring data. Fate data for lactofen show that it has a high binding potential and that it rapidly is transforme d to acifluorfen. It is not clear whether bound lactofen can be degraded and released as acifluorfe n. The ultimate fate of the acifluorfen degradation products in soil and water cannot be de termined. Uncertainties remaining from previous assessments and potential paths forward ar e described below.

B. Endangered Species

Consistent with the Agency’s responsibility under t he Endangered Species Act (ESA), EPA will evaluate risks to Federally-listed threatened and/o r endangered (listed) species from registered uses23

of sodium acifluorfen. This assessment will be con ducted in accordance with the Overview Document, provisions of the ESA, and the Services’ Endangered Species Consultation Handbook (U.S. Fish and Wildlife Service and National Marine Fisheries Service, 1998. Endangered Species Consultation Handbook: Procedures for Conducting C onsultation and Conference Activities Under Section 7 of the Endangered Species Act. Final Dra ft. March 1998)

.

The assessment of effects associated with registrat ions of sodium acifluorfen is based on an action

area. The action area is considered to be the area directly or indirectly affected by the federal action, as indicated by the exceedance of Agency Le vels of Concern (LOCs) used to evaluate direct or indirect effects. The Agency’s approach to defi ning the action area under the provisions of the

Overview Document considers the results of the risk assessment process to establish boundaries for that action area with the understanding that exposu res below the Agency’s defined LOCs constitute a no-effect threshold. For the purposes of this as sessment, attention will be focused on the footprin t of the action ( i.e. , the area where sodium acifluorfen application occ urs), plus all areas where offsite transport ( i.e. , spray drift and runoff) may result in potential e xposure that exceeds the Agency’s LOCs. Specific measures of ecological effect that define the action area for listed species include any direct and indirect effects and/or potential mo dification of its critical habitat, including reduction in survival, growth, and reproduction as well as the full suite of sublethal effects availab le in the effects literature. Therefore, the action a rea extends to a point where environmental exposures are below any measured lethal or subletha l effect threshold for any biological entity at the whole organism, organ, tissue, and cellular level o f organization. In situations where it is not possible to determine the threshold for an observed effect, the action area is not spatially limited a nd

is assumed to be the entire United States.

C. Drinking Water Assessment

The drinking water assessment will be based on the PRZM-EXAMS model with the Index Reservoir and Crop Area Factors. In addition, an u pdated drinking water assessment will include any monitoring data that may be available. Both so dium acifluorfen and a related pesticide, lactofen, will degrade to the degradate acifluorfen in the environment. Therefore, EPA will conduct an aggregate drinking water assessment that will in clude the degradate acifluorfen from both

lactofen and sodium acifluorfen sources.

Ground water EDWCs for acifluorfen will be derived from a Tier I screening-level model (SCI-GROW), which estimates the maximum ground wate r concentrations from the application of a pesticide to crops. The ground water EEC for a cifluorfen derived from lactofen will be derived from a prospective groundwater monitoring study for lactofen, which monitored for both compounds.

D. Clean Water Act

Sodium acifluorfen is not identified as a cause of impairment for any water bodies listed as impaired under section 303(d) of the Clean Water Ac t, based on information provided at http://iaspub.epa.gov/tmdl_waters10/attains_nation_ cy.cause_detail_303d?p_cause_group_id=885

. In addition, no Total Maximum Daily Loads (TMDL) ha ve been developed for sodium acifluorfen, based on information provided at http://iaspub.epa.gov/tmdl_waters10/attains_nation. tmdl_pollutant_detail?p_pollutant_group_id=885&p_po l lutant_group_name=PESTICIDES

. More information on impaired water bodies and TMD Ls can be

found at http://www.epa.gov/owow/tmdl/

.24

The Agency invites submission of water quality data for this pesticide. To the extent possible, data should conform to the quality standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management Process (see:
http://www.epa.gov/oppfead1/cb/ppdc/2006/november06 /session1-sop.pdf ), in order to ensure they can be used quantitatively or qualitatively in pesticide r isk assessments.

E. Endocrine Disruptor Screening Program

As required under FFDCA section 408(p), EPA has dev eloped the Endocrine Disruptor Screening Program (EDSP) to determine whether certain substan ces (including pesticide active and other ingredients) may have an effect in humans or wildli fe similar to an effect produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator may designate.” The EDSP employs a two-tiered approach to making the statuto rily required determinations. Tier 1 consists of a battery of 11 screening assays to identify the po tential of a chemical substance to interact with th e estrogen, androgen, or thyroid (E, A, or T) hormona l systems. Chemicals that go through Tier 1 screening and are found to have the potential to in teract with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA wil l determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 t esting is designed to identify any adverse endocrine related effects caused by the substance, and establish a dose-response relationship between the dose and the E, A, or T effect.

Between October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 chemicals, which contains 58 pesticide active in gredients and 9 inert ingredients. This list of chemicals was selected based on the potential for h uman exposure through pathways such as food and water, residential activity, and certain post-a pplication agricultural scenarios. This list shoul d not be construed as a list of known or likely endoc rine disruptors.

Sodium acifluorfen is not among the group of 58 pes ticide active ingredients on the initial list to be screened under the EDSP. Under FFDCA sec. 408(p) t he Agency must screen all pesticide chemicals. Accordingly, EPA anticipates issuing fu ture EDSP test orders/data call-ins for all pesticide active ingredients.

For further information on the status of the EDSP, the policies and procedures, the list of 67 chemicals, the test guidelines and the Tier 1 scree ning battery, please visit our website: http://www.epa.gov/endo/.

F. Anticipated Data Needs

The following tables summarize the studies needed t o reduce the amount of uncertainty in the ecological risk assessment. The passerine acute to xicity requirement is a recent decision within EPA that originated from a realization that passeri ne species may be more sensitive than bird species traditionally tested. EPA also requests ch ronic saltwater invertebrate toxicity data, which are provided by the saltwater aquatic invertebrate life cycle study. This data will, in turn, be used to
calculate an invertebrate ACR for sodium acifluorfe n, which will be applied to the freshwater

invertebrate data to calculate a more refined chron ic freshwater invertebrate toxicity endpoint.25

Guideline Number: 850.2100

Test Substance: Sodium acifluorfen Study Title: Avian Acute Oral Toxicity Test Species: Passerine Species Rationale for Requiring the Data

Acute risk to passerines as a result of exposure to sodium acifluorfen has not been considered in prev ious assessments since there are no acute oral toxicity data available. Current Part 158 data requirements (CFR 40 2007) specify that acute avian oral toxicity dat a be submitted for either mallard duck or bobwhite quail AND a passerine species. (A protocol for the acute oral toxicity test with a passerine species should be submitted to the Agency prior to test initiation.) Without this study, the Agency would have to presum e risk to listed and non-listed passerines, but would not be able to quantify the risk. Practical Utility of the Data

How will the data be used? Acute oral avian toxicity data will be used to quan titatively estimate the risk of sodium acifluorfen to birds (and terrestrial-phase amphibians and reptiles) and to define an action area for endangered species an d explore risk mitigation strategies. These toxicity data will reduce uncertainties associated with the risk assessment for passerines. In the absence of data o n sodium acifluorfen, quantitative risk estimation will not be possible. Therefore, determination of the d istance from a treated field to which risk may exte nd and application rate reductions resulting in no LOC exc eedances cannot be quantified without these data.

How could the data change the Agency’s decision or impact the Agency’s future decision-making? The value of these acute oral toxicity studies woul d be in quantifying and potentially refining risks to passerine birds. Defining an action area for endang ered species and exploring risk mitigation strategi es cannot be evaluated without these data. If future endangered species risk assessments are performed without these data, the Agency will assume that sod ium acifluorfen “may affect” passerines directly, a nd use of sodium acifluorfen may need to be restricted in areas where listed species could be exposed. T he lack of these data will limit the flexibility the A gency and registrants have in coming into complianc e with the Endangered Species Act and could result in use restrictions for sodium acifluorfen that are unnecessarily severe.26

Guideline Number: 850.1350
Test Substance: Sodium acifluorfen Study Title: Aquatic Invertebrate Life-Cycle (saltwater) Test Species: Mysid shrimp, Americamysis bahia Rationale for Requiring the Data

The acute toxicity of sodium acifluorfen to estuari ne/marine invertebrates indicates the potential

for chronic risk to this taxon. The chronic toxici ty tests for both freshwater and estuarine/marine invertebrates were described as "conditionally requ ired" in 40 CFR part 158 when the RED was signed, but sodium acifluorfen meets both the acute toxicity and exposure conditions for requirement of this study.

Since the only aquatic sublethal endpoint found for sodium acifluorfen did not produce a noobserved effects concentration (Table 5), no sodium acifluorfen acute to chronic ratio (ACR) was available to estimate chronic toxicity to aquatic o rganisms. Using data from a closely related compound, lactofen 5 (sodium acifluorfen is a major degradate of lactof en), EPA’s level of concern (LOC = 1 for chronic risk to aquatic animal s) is exceeded when the ACR from lactofen fish data (349) is applied to the mysid acute sodiu m acifluorfen data and the resulting mysid chronic endpoint (12 ppb) is used to calculate a ri sk quotient (1.8). Therefore, EPA cannot preclude risk to aquatic invertebrates from chronic exposure.

Without this study, the Agency would have to presum e chronic risk to listed and non-listed estuarine/marine invertebrates, but would not be ab le to quantify the risk.
Practical Utility of the Data

How will the data be used? The aquatic invertebrate life-cycle toxicity study using a saltwater species would allow the Agency to refine the screening level risk assessmen t for Registration Review. The study would allow the Agency to analyze chronic effects, includ ing effects on reproductive success and growth, to saltwater invertebrates. The effects da ta would be used to determine the likelihood that the chronic risks can potentially impact aquat ic communities, either by direct effects on invertebrates or by indirect effects on fish and ot her organisms that feed on saltwater

invertebrates.

This data will, in turn, be used to calculate an in vertebrate ACR for sodium acifluorfen, which will be applied to the freshwater invertebrate data to calculate a more refined chronic freshwater invertebrate toxicity endpoint.

How could the data impact the Agency’s future decis ion-making? If future endangered species risk assessments are p erformed without these data, the Agency would have to assume that sodium acifluorfen "may a ffect" saltwater invertebrates directly and other taxa that feed on saltwater invertebrates, in directly. The use of sodium acifluorfen might need to be restricted in areas where these species could be exposed. The lack of these data would limit the flexibility the Agency and registrants ha ve and could result in unnecessarily severe use

restrictions for sodium acifluorfen.

In addition, environmental chemistry methods and in dependent laboratory validation of those methods are required to support registration of pro ducts containing sodium aciflourfen. The following table summarizes the needed studies.

5 EFED Problem Formulation for Lactofen Registration Review, December 13,2006; DP

Barcode: 323196.27

Guideline Number: 835.6100 Study Title: Environmental Chemistry Methods (ECM ) and Independent Laboratory Validation (ILV) for Soil Rationale for Requiring the Data According to the data requirements in 40 CFR Part 1 58, ECMs are currently required along with successful confirmatory method trials (validation) by an independent laboratory ( i.e. ILVs). Acceptable ECMs for the residues of concern (parent and its tr ansformation products) should have levels of quantitation that are adequate to address risk conc erns or that are at levels below the toxicological endpoints for the relevant aquatic organisms. The ECMs should include parent and those residues found in the laboratory studies that exceeded 10% of the applied. Practical Utility of the Data

How will the data be used? The data will be used to verify the suitability of the methods. Subsequently the methods could be use d by states or other enforcement agencies, department s or entities, to monitor concentrations of the residues of concern. Validated analytical methods in environmental media ( a.k.a. , ECMs) are useful for conducting and evaluating submitted environmental f ate and toxicity field and monitoring studies and for addressing potential risks to the environment p osed by the use and/or accidental release of pestic ides.

How could the data impact the Agency’s future decis ion-making? If monitoring of the chemical is required or perfor med, the Agency could be able to determine if the chemical is present in the environment at concentra tions that are threatening to wildlife (or to human s, in the case of drinking waters), according to the leve ls of concern (LOCs). If that is the case, measure s to prevent these concentrations to occur could be take n. The data could also be used by enforcement entities like the states or government agencies or departments. Without these data, the potential for the

determination of residues of sodium acifluorfen in soil, water and sediment is restricted.

Guideline Number: 835.6200 Study Title: Environmental Chemistry Methods (ECM ) and Independent Laboratory Validation (ILV) for Water and Sediment Rationale for Requiring the Data According to the data requirements in 40 CFR Part 1 58, ECMs are currently required along with successful confirmatory method trials (validation) by an independent laboratory ( i.e. ILVs). Acceptable ECMs for the residues of concern (parent and its tr ansformation products) should have levels of quantitation that are adequate to address risk conc erns or that are at levels below the toxicological endpoints for the relevant aquatic organisms. The ECMs should include parent and those residues found in the laboratory studies that exceeded 10% of the applied. Practical Utility of the Data

How will the data be used? The data will be used to verify the suitability of the methods. Subsequently the methods could be use d by states or other enforcement agencies, department s or entities, to monitor concentrations of the residues of concern. Validated analytical methods in environmental media ( a.k.a. , ECMs) are useful for conducting and evaluating submitted environmental f ate and toxicity field and monitoring studies and for addressing potential risks to the environment p osed by the use and/or accidental release of pestic ides.

How could the data impact the Agency’s future decis ion-making? If monitoring of the chemical is required or perfor med, the Agency could be able to determine if the chemical is present in the environment at concentra tions that are threatening to wildlife (or to human s, in the case of drinking waters), according to the leve ls of concern (LOCs). If that is the case, measure s to prevent these concentrations to occur could be take n. The data could also be used by enforcement entities like the states or government agencies or departments. Without these data, the potential for the

determination of residues of sodium acifluorfen in soil, water and sediment is restricted.28

Data required for existing DCIs

Non-target Area Phytotoxicity (Tier II) Seedling Em ergence and Vegetative Vigor studies were submitted in 1990 (MRID 41680701). The study was r eviewed and the seedling emergence portion of the study was acceptable. However, the vegetati ve vigor portion of the study was found to be unacceptable. A new Vegetative Vigor study (MRID 4 6431401) was submitted, and was found partially acceptable, but the data were unacceptabl e for the most sensitive dicot (cucumber, NOAEL not determined. Acceptable data establishing the NOAEL for cucumber are still required.

In January 2006, a DCI was issued to a group of reg istrants who hold technical registrations for the LDPHs requiring submission of Guideline number 850. 1400, fish early life-stage toxicity test, to measure how sunlight (particularly ultraviolet) aff ects the toxicity of the LDPHs on aquatic organisms. United Phosphorus, the technical regist rant for sodium acifluorfen, has joined a work group which submitted a modified protocol for Guide line 850.1400, as required by EPA, to detect potential enhanced toxicity in fish in the presence of the LDPHs and ultraviolet lighting. The protocol has been reviewed by EPA, and the Agency h as instructed the work group to proceed with pilot testing. An initial pilot test was initiated in November 2009, with an additional pilot study currently being conducted (March 2010) after modifi cations to the test design. Submission of the definitive toxicity data is expected in late 2010.

Other Information Needs

There is specific information that will assist the Agency in refining the ecological risk assessment, including any species-specific effects determinatio ns. The Agency is very much interested in obtaining the following information:

1. confirmation on the following label information a. sites of application

b. formulations c. application methods and equipment d. maximum application rates e. frequency of application, application intervals, and maximum number of applications

per season f. geographic limitations on use 2. use or potential use distribution (e.g., acreage and geographical distribution of relevant crops) 3. use history

4. median and 90 th percentile reported use rates (lbs ai/acre) from u sage data – national, state, and county 5. application timing (date of first application an d application intervals) by crop – national, state, and county 6. sub-county crop location data 7. usage/use information for non-agricultural uses (e.g., forestry, residential, rights-of-way) 8. directly acquired county-level usage data (not d erived from state level data) a. maximum reported use rate (lbs ai/acre) from usa ge data – county b. percent crop treated – county

c. median and 90 th percentile number of applications – county29 d. total pounds per year – county e. the year the pesticide was last used in the coun ty/sub-county area f. the years in which the pesticide was applied in the county/sub-county area 9. typical interval (days)

10. state or local use restrictions 11. ecological incidents (non-target plant damage a nd avian, fish, reptilian, amphibian and mammalian mortalities) not already reported to the Agency 12. monitoring data

The analysis plan will be revisited and may be revi sed depending upon the data available in the open literature and the information submitted by th e public in response to the opening of the Registration Review docket.