### Page 2 of 12 Executive Summary

Dibromodicyanobutane (DBDCB) is an orga no-cyanobromine compound registered for use as an algicide, bactericide, fungicide, slimic ide, and microbicide/microbistat in industrial process and water systems such as gas/oil drill ing muds/packer fluids, completion and workover fluids, water floods, gas/oil recove ry injection systems, enhanced oil recovery systems, oil field water, polymer of micellar floods, water-disposal systems or other oil field water systems, cooling water tower systems, paper mills, pulp, paper and paperboard systems and as a material preservative. Pesticide products containing the active i ngredient DBDCB were first registered in the United States in 1980. Currently there are 16 registered products with active ingredient declarations of 23.725 to 99.9 percent. All pr oduct chemistry data requirements have been satisfied for this active ingredient DBDCB.

The submitted environmental fate studies demonstrate that parent DBDCB is generally hydrolytically less persiste nt than its degradates, trans 1-bromo-2,4-dicyanobutene (BDCB, once-debrominated parent) and 2-methylenegluta ronitrile (MGN, twice debrominated parent), under alkaline conditions. They also demonstrat e that the degradate BD CB (trace levels present only) biodegrades aerobically fa ster than the parent (half-lif e 0.87 days) or MGN (4.6 days). Given that all residues of DBDC B and its major degradates have limited sorption to soil and sediment, the primary residues that can reach surface and ground water are DBDCB and its degradate MGN. The overall degradation of DBD CB appears to lead to stable degradates that have not been identified, but the remaining portio n of the compound is a st raight-chain aliphatic hydrocarbon which can become part of the organic ma tter of soil or biosolids. The registrant has submitted environmental fate studies that were considered to be “supplemental, upgradeable” and “not completely acceptable”. However, the in formation is of sufficient quality to use in the ecological risk assessment. To address fate of the more stable degradate MGN through the waste water treatment plant process, biodegradability in sewage sludge is n eeded and an activated sludge respiration inhibition study are anticipated. Based on the environmental fate information, drinking water consumption from ground or surfa ce water is likely to be limited for parent DBDCB but is more likely for the metabolite MGN.

The aquatic organism toxicity data base for DBDCB contains acute and chronic freshwater fish and invertebrate data and acute estuarine/marine fish and invertebrate data for DBDCB and avian acute oral and subacute diet ary data. DBDCB is moderately toxic to freshwater and estuarine/marine animals and sli ghtly toxic to birds and mammals. In order to perform an ecological risk assessment, includi ng an endangered species determination, the Agency anticipates needing algal (Tier II) to xicity studies using fr eshwater green alga, freshwater diatom, marine diatom, and cyanobact erium, and; an aquatic plant toxicity study using Lemna spp. If the IC 50 

### is >1000 ppb a.i. for freshwater gr een alga, then freshwater diatom, marine diatom, cyanobacterium and aquatic plant t oxicity studies can be waived. No toxicity data is available for the MGN degradate, toxicity of this degradate will be assumed to be as toxic as the parent.

### Page 3 of 12 Introduction

DBDCB was first registered in the United States in 1980. Currently 16 products are registered for use as an algicide , bactericide, fungicide, slimicide, and microbicide/microbistat in industrial process and water systems such as ga s/oil drilling muds/packer fluids, completion and workover fluids, water floods, gas/oil recovery inj ection systems, enhanced oil recovery systems, oil field water, polymer of micellar floods, wate r-disposal systems or other oil field water systems, cooling water tower systems, paper mills, pulp, paper and paperboard systems and as a material preservative in such products as adhesives, glues and tackifiers (nonfood contact), aqueous paints and coatings, dispersed pigments, latex emulsions, paper and paper additives, paints, coatings and stains, metalworking cutting fl uids, fiber processing fluids, joint cement, as well as dishwashing liquids, furniture and floor waxes and polishes, cleaners and treatment products and over-the counter i nks. A Reregistration Eligibilit y Decision (RED) was issued by EPA for DBDCB in June 1996 1



### .

A. Product Chemistry Summary of DBDCB (99.9% TGAI)

Common Name: Dibromodicyanobutane Methyldibromoglutaronitrile Bromothalonil Chemical Name: 1-bromo-(bromoethyl)-1,3-propanedicarbonitrile 1,2-dibromo-2,4-dicyanobutane 1,2-dibromo-2,4-dicyanobutan e (dibromodicyanobutane) Pentanedinitrile, 2-bromo-2-(bromomethyl) Trade and Other Names: Tektamer 38; Metacide 38; Merck 48051 1-Bromo-1-(bromomethyl)-1,3-propanedicarbonitrile 2-Bromo-2-(bromomethyl)glutaronitrile 2-Bromo-2-(bromometh yl)pentanedinitrile Merguard 1105 OPP Chemical Code: 111001 CAS Registry Number: 35691-65-7 Molecular Formula: C 6 

### H 6 

### Br 2 

### N 2 

### Molecular weight: 265.9340 g/mole Molecular Structure:

Color: Yellowish white; off-white to light tan. Physical State: Granular solid at 21.72° C; crystalline solid

1 http://www.epa.gov/oppsrrd1/REDs/2780red.pdf

### Page 4 of 12 Odor: Slightly sweet at room te mperature; mildly pungent. Stability: The chemical was found to be stable when subjected to aluminum, tin, nickel, iron, thermal and photosensitivity tests. Stable for one y ear at room temperature. pH: 4.9 UV/Visible absorption: Maximum at 290 nm. No UV absorbance above 290 nm. Melting point: 51-53°C Density: 0.970 g/ml at 24.28°C Dissociation Constant: Not applicable. Chemical does not ionize. Log K o/w 

### : 1.022 Solubilities: Water: 0.212 g/100 ml at 20°C Organic solvents: It is soluble in diethyl ether, ethanol, and methanol and very soluble in acetone, benzene, chloroform, dimethylformamide, ethyl acetate. Vapor Pressure: 5.0 × 10 -5 

### mm Hg at 25°C Henry's Law Constant: 8.25 x 10 -9 

### atm-m 3 

### /mole (Calculated) Enforcement Analytical Mass Spectrometry; Infra-red spectrometry Method: Gas Chromatography

All product chemistry data requirements have been satisfied for the active ingredients DBDCB (Source: RED).

B. Environmental Fate Summary

The registrant has submitted environmental fate studies that were considered to be “supplemental, upgradeable” and “not completely acceptable”. However, there are no environmental fate data gaps for DBDCB. Th e dissipation of DBDCB should be controlled by rapid alkaline-catalyzed hydrolysis and microbial-mediated degr adation in aquatic systems. The overall degradation appears to lead to stable degradates that ha ve not been identified, but the remaining portion of the compound is a straight-c hain aliphatic hydrocarbon which can become part of the organic matter of soil. The parent compound is very mobile in soil with Freundlich K ads 

### values of <1.

The hydrolysis (MRID 00055032) and aer obic aquatic metabolism (MRID 41883902) studies both demonstrated degrad ation of parent DBDCB. In th e hydrolysis study, the half-lives at 25 o 

### C were 190, 24, and 13 days at pH 5, 7, and 9, respectively. The only degradate that reached significant (> 10 % of applied parent) concentr ations at pH 5 and 7 was oncedebrominated parent compound (BDCB, trans 1-bromo-2,4-dicyanobutene), which increased until the end of the study. The degradate MGN (2-methylenegluaronitrile, twice-debrominated parent compound) reached significant concentrations at pH 9 and increased until the end of the study. In the aerobic aquatic metabolism study, the to tal system half-life of parent DBDCB was 0.87 days, and the only significant degradate was MGN which reached up to 34 % of applied parent compound by 3 days, and declined to 0.1 % by 30 days (end of study). MGN biodegraded with a half-life of 4.6 days. Carbon dioxide (CO 2 

### ) was also formed. Table 1 below contains a summary table of the environmental fate of parent DBDCB and its primary degradates.

### Page 5 of 12 The leaching-adsorption-desorption study was al so considered to contain “supplemental, upgradeable” information because the desorption was greater than the adsorption. However, these issues do not invalidate the studies because the term inal significant degradates ( cis and

trans isomers of parent compound minus a bromine) are more water soluble and sorbed to a lower degree. Radiolabel ed DBDCB, at 0.1 to 1.0 μ g/ml, had Freundlich coefficients of 0.26 (K oc 

### =528; Freundlich 1/n=1.33) in a sand, 0.35 (K oc 

### =88; 1/n=1.05) in a sandy loam soil, 0.47 (K oc 

### =73; 1/n=0.99) in a clay loam soil, and 0.70 (K oc 

### =33; 1/n=1.09) in a silt loam soil. DBDCB degradation was observed during a 2 hour equilibration period. The cis and trans isomers of BDCB were detected (6-75% of applied) by high performance liquid ch romatography (HPLC). Desorption coefficients were not reported. However, the mean percent desorption of DBDCB was 125% for a sand, 107% for a sandy loam soil, 148% for a clay loam soil, and 126% for a silt loam soil. The material balance is off because of rapid degradation to biodegradation products with less sorption than the pa rent compound. The reported data indicate DBDCB should be mobile in aquatic and soil environments. Base d on the above environmental fate information, drinking water consumption from ground or surfa ce water is likely to be limited for parent DBDCB but is more likely for the MGN biodegradate.

To address fate of DBDCB and its MGN de gradate through the waste water treatment plant process, biodegradability in sewage sludge is needed and an activated sludge respiration inhibition study are anticipated.

Table 1. Summary Table of Environmenta l Fate Data for DBDCB and Degradates

Parameters Parent Degradates

Source/
CommentsDibromodicyanobutane (DBDCB) trans 1-bromo-2,4- dicyanobutene (BDCB) (parent compound minus one bromine) 2-methylene glutaronitrile (MGN)

(parent compound minus two bromines)

Structures 41883901

Dissociation Constant (pK
a ) Not applicable,

chemical does not

ionize Not applicable, chemical

does not ionize Not applicable,

chemical does not ionize

Hydrolysis halflife (835.2120) pH 5, 190 days pH 7, 21 days pH 9, 13 days Slowly degrades 1 Significant (>10 % of applied), increased until end of study; terminal significant degradate. Slowly degrades 2 Did not reach significant (>10 %) concentrations at pH 5 and 7, but did so at pH 9; terminal significant degradate at pH 9. 00055032 (10 ppm @ 25 o C)

### Page 6 of 12 Parameters Parent Degradates

Source/
CommentsDibromodicyanobutane (DBDCB) trans 1-bromo-2,4- dicyanobutene (BDCB) (parent compound minus one bromine) 2-methylene glutaronitrile (MGN)

(parent compound minus two bromines)

Hydrolysis halflife (835.2120) pH 5, 96 days pH 7, 14 days pH 9, 0.6 days Slowly degrades 1 Significant (>10 % of applied), increased until end of study; terminal significant degradate. Slowly degrades 2 Did not reach significant (>10 %) concentrations at pH 5 and 7, but did so at pH 9; terminal significant degradate at pH 9. 00055032 (10 ppm @ 45 o C)

Hydrolysis halflife (835.2120) pH 5, 198 days pH 7, 73 days pH 9, 14 days Slowly degrades 1 Significant (>10 % of applied), increased until end of study; terminal significant degradate. Slowly degrades 2 Did not reach significant (>10 %) concentrations at pH 5 and 7, but did so at pH 9; terminal significant degradate at pH 9. 00055032 (40 ppm @ 25 o C)

Hydrolysis halflife (835.2120) pH 5, 122 days pH 7, 11 days pH 9, 0.8 days Slowly degrades 1 Significant (>10 % of applied), increased until end of study; terminal significant degradate. Slowly degrades 2 Did not reach significant (>10 %) concentrations at pH 5 and 7, but did so at pH 9; terminal significant degradate at pH 9. 00055032 (40 ppm @ 45 o C)

Aerobic aquaticmetabolism halflife (835.4300) 0.87 day Trace levels detected (<10% of parent) 4.6 days 4 41883901

Soil absorption constant, K ads (835.1230) K ads values of 0.26-0.7 ml/g

K oc 33-528 ml/g Present at 6-75 % of applied parent compound by equilibrium (more mobile than parent). 3 No data 41883902

1 No half-life could be calculated because it increased until the end of the study. The formation was faster than the decline, which defines this as a terminal degradate.

2 No half-life could be calculated at pH 9 because it increased until the end of the study. The formation was faster than the decline, which defines this as a terminal degradate.

3 Because biodegradation was so rapid, no meaningful K ads value could be obtained.

4 Leads to stable degradates that have not been identified, but the remaining portion of the compound is a straightchain aliphatic hydrocarbon which can become part of the organic matter of soil.



### Water Quality

DBDCB is not identified as a cause of impair ment for any water bodies listed as impaired under section 303(d) of the Clean Water Act, ba sed on information provided at the Agency’s National Pesticides Cause of Impairment of Waters we bsite (searched March 29, 2012) 2 

### . In addition, no Total Maximum Daily Loads (TMDL) have been developed for DBDCB, based on

2 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885

### Page 7 of 12 information provided at the Agency’s National Pesticide TMDL web site (searched, March 29, 2012) 3 

### . More information on impaired water bodies and TMDLs can be found at http://www.epa.gov/owow/tmdl/ . 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: Inclusi on of Impaired Water Body and Other Water Quality Data in OPP’s Registration Revi ew Risk Assessment and Management Process (see: http://www.epa.gov/oppfead1/cb/p pdc/2006/november06/session1-sop.pdf ), in order to ensure they can be used quantitatively or qual itatively in pesticide risk assessments.

C. Ecological Effects Summary

No quantitative ecological risk assessment was performed for DBDCB at the time of the reregistration. Available ecotoxicity guide line studies for DBDCB and the results are summarized in Table 2 below. An acute-to-chronic ratio (ACR) is 2.33 4 

### for freshwater fish based on rainbow trout data and 1.57 5 

### for freshwater inve rtebrates based on Daphnia magna data. In the D. magna acute and chronic high purity active ingredient studies, the acute NOAEC was lower than the chronic NOAEC, which may i ndicate that the organisms used in the acute study were potentially more sensitive than those used in the chronic, or that the ability to detect differences from the control was not as high in the chronic study as compared to the acute. The ACR may be underestimated to some degree in eith er case. There is no toxicity data for the major degradate MGN. This degradate will be assumed to be as toxic as the parent compound.

Table 2. Ecotoxicity Data Summary for DBDCB

MRID NOs. COMMON NAME TAXONOMIC NAME GUIDE LINE TYPE % a.i. STUDY TIME DOSE TYPE TOXI CITY TOX LEVEL NOEL STUDY STATUS TOX CATEGORY/ Avian Acute Oral Toxicity

00077315 Mallard duck Anas platyrhynchos 850.2100 71-1 O Tech 14 D LD 50 1038 mg/kgbw <215 Supplemental Slightly Toxic Avian Subacute Dietary Toxicity

00077317 Mallard duck Anas platyrhynchos 850.2200 71-2b D Tech 8 D LC 50 >10000 ppm N.A. Acceptable Practically Non-toxic

00077316 Bobwhite quail Colinus virginianus 850.2200 71-2a D Tech 8 D LC 50 4042 ppm 2150 Acceptable Slightly Toxic Freshwater Invertebrate Acute Toxicity

00063851 Water flea Daphnia

magna 850.1010 72-2 S 98.0 48 hr EC 50 2.2 ppm 0.75 Acceptable Moderately Toxic

70890 00026469 Water flea Daphnia

magna 850.1010 72-2 S 10 48 hr EC 50 3.1 ppm 1.8 Supplemental Moderately toxic Freshwater Fish Acute Toxicity 00063850 Bluegill sunfish Lepomis macrochirus 850.1075 72-1 S 98 96 hr LC 50 4.1 ppm 3.2 Acceptable Moderately Toxic

00063850 Rainbow

trout Oncorhynchus mykiss 850.1075 72-1 S 98.0 96 hr LC 50 1.75 ppm 1.4 Acceptable Moderately Toxic Estuarine/Marine Fish Acute Toxicity

3 http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl _pollutant_detail?p_pollutant_group_id=885&p_pollutant_ group_name=PESTICIDES

4 ACR rainbow trout = Chronic NOAEC/96-hr LC 50 = 1.75 ppm/0.75 ppm = 2.33

5 ACR Daphnia magna = Chronic NOAEC/96-hr LC 50 = 2.2 ppm/1.4 ppm = 1.57

### Page 8 of 12 MRID NOs. COMMON NAME TAXONOMIC NAME GUIDE LINE TYPE % a.i. STUDY TIME DOSE TYPE TOXI CITY TOX LEVEL NOEL STUDY STATUS TOX CATEGORY/ 41885301 Sheepshead minnow Cyprinodon variegatus 850.1075 72-3 F 99.85 96 hr LC 50 8.3 ppm 6.7 Acceptable Moderately Toxic 00150032 Sheepshead minnow Cyprinodon variegatus 850.1075 72-3 S 98.0 96 hr LC 50 17 ppm 7.5 Acceptable Moderately Toxic Freshwater Fish Early-Life Stage Toxicity

41986701 Rainbow

trout Oncorhynchus mykiss 850.1400 72-4a S 99.85 21 D LOEC 1.0 ppm 0.75 Acceptable N/A for chronic

Freshwater Invertebrate Chronic Toxicity

41885304 Water flea Daphnia

magna 850.1300 72-4b F 99.85 21 D LOEC 2.6 ppm 1.4 Acceptable Percent survival Estuarine/Marine Acute Toxicity – Invertebrates, Crustaceans 41885303 Opossum shrimp Americamysis bahia 850.1035 72-3 F 99.85 96 hr LC 50 2.7 ppm 1.5 Acceptable Moderately Toxic

00150034/ 46006403 Daggerblade grass shrimp Palaemonetes pugio 850.1045 72-3 S 98.0 96 hr LC 50 45 ppm <10 Acceptable Moderately Toxic

Estuarine/Marine Acute Toxici ty – Invertebrates, Mollusks

41885302 Eastern oyster(embryolarvae) Crassostrea virginica 850.1055 72-3b S 99.85 48hr EC 50 2.67 ppm 1.4 Acceptable Moderately Toxic

Mammalian Acute Oral Toxicity

41885501 Rat Rattus norvegicus 870.1100 81-1 O 99.9 14 D LD 50 770(M) 515(F) mg/kgbw ------ Acceptable Slightly Toxic III

Test Type —O: oral; D: dietary; F: flow-through; S: Static; Tox Level —mg/kg-bw: milligrams per kilogram-body weight; ppm: parts per million (equivalent to milligrams per kilogram-diet (mg/kg-diet) for dietary exposure and milligrams per liter (mg/L) for aquatic exposures) Categories of acute toxicity for aquati c organisms (U.S. EPA, 2004) based on EC 50 /LC 50 (mg/L): < 0. 1 very highly toxic; 0.1-1 highly toxic; >1- 10 moderately toxic; >10-100 slightly toxic; >100 practically nontoxic. Categories of acute toxicity to terrestrial an imals, avian and mammalian (U.S. EPA, 2004). LC 50 (ppm): < 50 very highl y toxic; 50 - 500 highly toxic; 501 – 1000 moderately t oxic; 1001-5000 slightly toxic; >5000 practically non-toxic. LD 50 (mg/kg bw): < 10 very highly toxic; 10 - 50 highly toxic; 51 - 500 moderately toxic; 501-2000 slightly toxi c; >2000 practically non-toxic.



### Adverse Ecological Incidents

There are no reported incidents in the Agency 's Ecological Incident Information System (EIIS) regarding DBDCB. The absence of documen ted incidents does not necessarily mean that such incidents did not occur.

Ecological Effects Risk Assessment

An ecological risk assessment was not c onducted on the DBDCB’s use patterns described in this document. The Agency needs to conduc t an environmental fate and ecological risk assessment for material preservatives discharges and industrial process and water system uses and consumer product uses ( e.g ., dish washing liquids) that may di scharge directly into terrestrial and aquatic environments or which may reach those environments after passing through waste water treatment plants (WWTPs). For this eco logical risk assessment, including an endangered species assessment, the Agency anticipates need ing the ecotoxicity data outlined on page 9 of this document.

### Page 9 of 12 The Agency has not conducted a risk asse ssment for DBDCB that supports a complete endangered species effects determination. Th e ecological risk assessment planned during registration review will allow th e Agency to determine whether DBDCB’s use has “no effect or “may affect” federally listed threatened or enda ngered species (listed sp ecies) or their designed critical habitats. When an assessment conclude s that a pesticide’s use “may affect” a listed species or its designated critical habitat, the Ag ency will consult with the U.S. Fish and Wildlife Service and/or National Marine Fisheries Se rvices (the Services), as appropriate.

Environmental Fate and Ecotoxicity Data Gaps and Anticipated Work

• The Agency anticipates needi ng the following data to conduct a complete environmental fate assessment for the DBDCB degradate MGN because it is the primary and terminal degradate in many of the environmental fate studies:

o Activated Sludge Respiration Inhi bition (OCSPP 850.6800 or OECD 209);

o One of four activated sl udge biodegradability stud ies (Ready biodegradability [OCSPP 835.3110], or Porous Pot Test [O CSPP 835.3220], or Simulation Tests to Assess the Biodegradability of Chemical s Discharged to Wastewater [OCSPP 835.3280], or Simulation Test – Aerobic Se wage Treatment: A. Activated Sludge Units [OCSPP 835.3240] 6 

### :

• The Agency anticipates needing the followi ng ecotoxicity data in order to conduct a complete ecological risk assessment, including an endangered species assessment:

o Algal toxicity (Tier II) us ing freshwater green alga, Selenastrum capricornutum (OCSPP 850.5400);

o Algal toxicity (Tier II) using freshwater diatom, Navicula pelliculosa (OCSPP 850.5400) (If the IC 50 

### is > 1000 ppb a.i. for Selenastrum capricornutum this data can be waived;

o Algal toxicity (Tier II) using marine diatom, Skeletonema costatum (OCSPP 850.5400) (If the I C50 

### is > 1000 ppb a.i. for Selenastrum capricornutum this data can be waived;

o Algal toxicity (Tier II) using cyanobacterium, Anabaena flos-aquae (OCSPP 850.5400) (If the IC 50 

### is > 1000 ppb a.i. for Selenastrum capricornutum this data can be waived;

o Aquatic vascular plant toxicity (Tier II) using Lemna spp. (OCSPP 850.4400) (If the IC 50 

### is > 1000 ppb a.i. for Selenastrum capricornutum this data can be waived).

6 The results of the Activated Sludge Inhibition Test (A SRI) determine which of these biodegradation tests are required. If the ASRI test EC 50 is less than or equal to 20 mg/L, then either the (i) Biodegradation in Activated Sludge Study or (ii) Simulation Test – Aerobic Sewage Trea tment: A. Activated Sludge Units or the (iii) Porous Pot Test is required. If the ASRI test EC 50 is greater than 20 mg/L, then the applicant must choose either: (i) Ready Biodegradability or (ii) Biodegradation in Activated Sludge or (iii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units or (iv) the Porous Pot Test. If the antimicrobial passes the Ready Biodegradability study, then no further testing is required. If, however, the an timicrobial fails the Ready Biodegradability study, then the (i) Biodegradation in Activated Sludge or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or (iii) the Porous Pot study is required.

### Page 10 of 12 

## Appendix A. Environmental Fate Guideline Study Justifications

Study Title: Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals or Activated Sludge Respiration Inhibition Test Guideline Number: OCSPP 850.6 800 or OECD 209, respectively Test Substance: 2-methylene glutaronitrile (MGN) Rationale for Requiring the Data An activated sludge, respiration inhibition te st (ASRI) is needed to identify whether 

### MGN, which is expected to reach waste treatment facilities based on the use pattern, could harm activated sludge microorganisms found in biological wastewater treatment systems. The Agency will use these data to determine the potential impact of this degradate on waste water treatment plants (WWTPs) as a result of respiration inhibition of activated sludge microorganisms. This test is also necessary to enable the EPA

to establish correct concentrations for use in the biode gradability test, if that test is determined to be adequate for assessing biodegradation potential. Furthermore, the results of the ASRI determine which biodegradation test is required. If the ASRI test EC 50 is less than or equal to 20 mg/L, then either the Biodegradation in Activated Sludge Study or the Porous Pot Test is required. If the ASRI test EC 50 is greater than 20 mg/L, then the applicant must choose either: (i) Ready Biodegradability or (ii) Biodegradation in Activated Sludge or the Porous Pot Test. If the antimicrobial passes the ready biodegradability study, then no further testing is requi red. If, however, the antimicrobial fails the ready biodegradability study, then the Biodegradation in Ac tivated Sludge or the Porous Pot study is required. Practical Utility of the Data 1. How will the data be used? The results of this study will identify the inhibitory effect of MGN on treatment plant microorganisms’ respiration at various concentrations as well as the EC 50 , the effective concentration at which the respiratory rate is reduced by 50%. EPA will use the data to determine the potential for MGN to adversely impact activated sludge microorganisms present in a WWTP whic h, in the event that microorganisms are adversely impacted, could result in the subsequent release of less th an fully treated or marginal ly treated wastewaters. Additionally, eliciting or not eliciting such releases ar e important considerations in characterizing impacts to the quality of the aquatic environment and sub sequent effects to federa lly listed endangered and threatened species and their critical habitat and to non-ta rget non-listed species and their habitat. The data will also determine suitable non-inhibitory concentr ations to be used in biodegradability tests.

2. How could the data impact th e Agency’s future decision-making? If concentrations of MGN reaching the influent of the WWTP are expected to be below the level of concern identified by the ASRI test, then th e Agency can conclude that there is no concern for adverse impacts to activated sludge microorganisms, or for release of less than fully treated or marginally treated wastewaters that would result from such impacts. If the data indicate a high degree of activated sludge respiration inhibition for 

### MGN , a more rigorous test for biodegradation in wastewater treatment will be required than the ready biodegradability test. Additionally, if these da ta indicate that MGN can be inhibitory to activated sludge microorganisms at concentrations that may be possible in WWTP influent from antimicrobial uses, this may result in the Agency requiring label or use r estrictions that would be necessary to meet the “no unreasonable adverse effects” requirement of FIFRA.

### Page 11 of 12 Study Titles: Ready Biodegradability, Poro us Pot Test, Simulation Tests to Assess the Biodegradability of Chemicals Discharged to Wastew ater (particularly Biodegradation in Activated Sludge), or Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, respectively Guideline Numbers: OCSPP 835.3110, 835. 3220, 835.3280, or 835.3240, respectively 

### Test Substance: 2-methylene glutaronitrile (MGN) Rationale for Requiring the Data 

### MGN is a significant abiotic and biotic degradate of DBDCB and waste water treatment process systems are expected to be exposed to this degr adate based on use patterns of DBDCB and known fate information. As part of its screening-level envir onmental fate assessment, EPA will analyze the potential impact of the use of DBDCB on the microorganisms in the biological treatment processes of a WWTP. For DBDCB, the residue of interest and concern for this analysis is 

### MGN, the twice-debrominated parent compound. Results from an activated sewage sludge st udy are expected to supply information on the rate of biological breakdown and the completeness of the degr adation to carbon dioxide and water. One of four studies can be used to supply the information needed . The results of the Activated Sludge Respiration Inhibition Test (ASRI) determine which of these four bi odegradation tests are required. If the ASRI test EC 50 is less than or equal to 20 mg/L, then either the (i) Biodegradation in Activated Sludge Study or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activa ted Sludge Units or the (iii) Porous Pot Test is required. If the ASRI test EC 50 is greater than 20 mg/L, then the applicant must choose either: (i) Ready Biodegradability or (ii) Biodegradation in Activated Sludge or (iii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units or (iv) the Poro us Pot Test. If the antimicrobial passes the Ready Biodegradability study, then no further testing is requi red. A ready biodegradability study would allow the Agency to determine whether or not the chemical achieves ‘‘pass levels’’ for ready biodegradability ( e.g ., 70% removal of dissolved organic carbon). If, however, the antimicrobial fails the Ready Biodegradability study, then the (i) Biodegradation in Activated Sludge or (ii) Simulation Test – Aerobic Sewage Treatment: A. Activated Sludge Units, or (iii) the Porous Pot study is required. Practical Utility of the Data 1. How will the data be used? The data from a biodegradation study with MGN will be used to determine the percent removal of this degradate as a result of biodegradation by activat ed sludge microorganisms. Percent removal via biodegradation is a key input used to determine c oncentrations of MGN in surface water immediately downstream of wastewater treatment plants. The con centrations of antimicrobial pesticide and degradates immediately downstream of wastewater treatment plants are used to assess exposure and risk to non-target endangered and non-endangered species. Exposure da ta are integral parts of the risk equation for determining the impact of pesticides to beneficial non- target organisms through direct exposure from their food sources and habitat.

In addition, the data will be used to determine whether or not additional studies and/or label restrictions are needed. If the chemical does not achieve a ‘‘pass level’’ for ready biodegradability, then the Agency would determine that the chemical has the potentia l to pass through the WWTP and therefore may be discharged in to the aquatic environment potentially resulting in exposure to non-target species. This determination would trigger furthe r data requirements to assess the chemical’s impact on the aquatic environment upon release.

2. How could the data impact th e Agency’s future decision-making? If the chemical is found to be readily biodegrade d, then activated sludge microorganisms would be identified as highly biodegradable (90% removal via bi odegradation). This result would be used in conjunction with wastewater treatment plant infl uent volume and measurem ent endpoints for aquatic organisms to determine concentrations of antimicro bial pesticide downstream of wastewater treatment plants. If high inhibition of activated sludge microorganisms ( i.e ., EC 50 less than or equal to 20 mg/L) is determined in an activated sludge respiration inhibiti on test, then higher-tiered wastewater treatment plant

### Page 12 of 12 (WWTP) biodegradation studies and/or an activated sludge sorption isotherm study may be triggered. If results of higher-tier WWTP biodegradation tests indicat e low or negligible removal by biodegradation, the risk assessments for this chemical would reflect the ma gnitude of potential risk derived from the chemical’s lack of biodegradability. The risk assess ment may result in the Agency requiring label restrictions that would be necessary for the products to meet the “ no unreasonable adverse effects” requirements of FIFRA (e.g., changes to the directions for disposal).

In addition, EPA is required by section 7(a)(2) of the ESA to ensure that any action it authorizes or takes “...is not likely to jeopardize the continued existence of any endangered or threatened species or result in the destruction or adverse modification of critical habita t” and to use the best scientific data available” in carrying out this obligation. The data EPA intends to call in are necessary to inform the determination required by the ESA as to whether continued registra tion of a pesticide is not likely to jeopardize the species or its critical habitat. Absent this data EPA may not be able to conclude that this pesticide will not harm endangered species and may theref ore need to consider other limitati ons on the use of the pesticide in order to fulfill the Agency’s statutory obligations under the ESA. The lack of these data will limit the flexibility that the Agency and registrants have in co ming into compliance with the ESA and could result in use restrictions which are unnecessarily severe.