Page 2 of 23 EXECUTIVE SUMMARY

Dibromodicyanobutane (DBDCB) is registered fo r use in materials preservation, industrial recirculating cooling water treatment, oil produ ction, and paper mill water treatment. The material preservation uses include adhesives, caulks, household cleaning solution, paints and coatings, metal working fluids and non-apparel textiles. The RED for DBDCB was completed in 1996 and all of the existing uses were found to be eligible for registration. No additional uses

have been added since the RED. There are 15 end use antimicrobial pr oducts that contain DBDCB as an active ingredient.

Dietary (food) exposure to DBDCB is likely because it is used as a slimicide in food contact paper and paperboard production and to preserve paper-making chemicals. Migration of DBDCB from paper packaging to the food contents may occur. The material preservative uses of DBDCB are likely to result in waste water being di scharged, which may lead to contamination of human and livestock drinking water. DBDCB a nd/or its degradation products could also potentially pass through wastewater treatment plants. Therefore, the Agency anticipates needing certain environmental fate data which will be used during the risk assessment stage of registration review to determine the potential for drinking water exposures.

Occupational and residential de rmal and inhalation exposures to DBDCB could occur during open pouring of liquids and wetta ble powders for material pres ervation and during the use of treated paints, metal working fluids, and househ old cleaners. Resident ial incidental oral exposures could occur for toddlers playing on fl oors cleaned with treated cleaning solutions.

The following toxicology studies will be needed for registration review:

• 90 day Inhalation Toxicity Study in Rats

• 2- Generation Reproduction Study in Rats

The following exposure data will be needed for registration review:

• Indoor exposure studies (dermal and inhala tion) during open pouring of liquids and

wettable powders for material preservation a nd during the use of tr eated paints, metal working fluids, and household cleaners.

• Surface residue dissipation studies on count ertops and household floors cleaned with

household cleaning solution.

• Migration studies on paper packaging.

• Product use informationPage 3 of 23 1.0 BACKGROUND

1.1 Chemical Identity

The chemical identity of 1,2-Dibromo-2,4-dicy anobutane (DBDCB) is listed in Table 1.

Table 1 - Chemical Identity of 1,2 -Dibromo-2,4-dicyanobutane (DBDCB)

Chemical Name 1,2-Dibromo-2,4-dicyanobutane Common Name Dibromodicyanobutane (DBDCB) Synonym 1-bromo-1-(bromomethyl )-1,3-propanedicarbonitrile

PC Code 111001 CAS Registry Number 35691-65-7

Case No. 2780 Empirical Formula C 6 H 6 Br 2 N 2 Structure

1.2 Chemical and Physical Properties

The physical and chemical properties of DBDCB that are relevant for human health risk

assessment are listed in Table 2.

Table 2 - Physical and Chemical Properties of DBDCB

Property Value Reference

Molecular Weight 265.8 Based on formula

Physical State Yellowish White Granular Solid US EPA, 1996

Melting Point 52.2 – 53.2 C US EPA, 1996
Water Solubility 0.212 grams per 100 ml US EPA, 1996 Vapor Pressure 6.7 x 10 -3 Pascal @ 25 C (5.0 x 10 -5 mm hg) US EPA, 1996

2.0 USE AND USAGE INFORMATION

2.1 Product Types

There are 15 end use antimicrobial products that contain DBDCB as an active ingredient (ai). The concentration of DBDCB in these products ranges from 10 to 99.9 percent. The liquid formulations include emulsifiable concentrates, r eady to use solutions or soluble concentrates (11 products), and the solid products include wettab le powder (3 products) an d pellets/tablets (1Page 4 of 23 product). Only one wettable powder product (59106- 2) is packaged in water soluble packaging (WSP) while the other two products (39967-32 and 67869-35) are not packaged in WSP.

2.2 Summary of Registered Uses

DBDCB is registered for a variety of antim icrobial uses as listed in Table 3.

Table 3 – DBDCB Antimicrobial Uses

Use Application Rate (In Terms of ai) Label with Highest

Rate

Materials Preservation Adhesives, Glues and Tackifiers 600 – 5900 ppm 67869-35 Household Products (Cleaning Solutions) 600 – 1520 ppm 39967-39 Joint Cements, Caulks and Plasters 480 - 3920 ppm 67869-35 Latex Emulsions 240 -1960 ppm 67869-35 Paints, Coatings and Stains 360 – 2940 ppm 67869-35 Paper Additives 1700 ppm 67869-45 Pigments 250-12000 ppm 39967-28 Polymer dispersions and emulsions 600 ppm 67869-45 Printing Fluids and Inks 380 – 1000 ppm 39967-40 Textiles, Non– Apparel (Fiber Processing Solu tions used for canvas) 1440 – 11760 ppm 67869-35

Waxes and Polishes 120-1000 ppm 39967-40 Industrial Cooling Water and Process Preservation Cooling Water Systems, Industrial Recirculating 9.5 to 1898 ppm 39967-38 Metal Working Fluids 50- 3920 ppm 67869-35 Oil Production (Drilling Muds, Packer Fluids etc) 8.0-127 ppm 59106-2 Paper Mill Water Systems 0.05 – 0.4 lbs/ton 39967-40

The RED for DBDCB was completed in 1996 and a ll of the existing uses were found to be eligible for registration. No additional uses have been added since the RED.

2.3 Usage Information

According to the Kline Biocid es Report for 2004/2005 (Kline, 2006)

, the most important uses for

DBDCB are adhesives and sealants (57% of DBDCB sales value), paints and coatings (33%) and synthetic latex polymers (11%). According to the report, DBDCB is not used in metal working fluids, oil production or paper production.

3.0 TOXICOLOGY

At the time of the RED, the toxicology database for DBDCB was considered to be complete and no additional studies were required. In addition to the studies th at were included in the RED, several studies (MRID 48767301) have recently been conducted by the National Toxicology Program (NTP) to evaluate the hazards of DBDCB us e in cosmetics. These include 2 week, 3 month and 2 year dermal toxicity studies in mice and rats and genetic studies in Salmonella typhimurium

, Escherichia coli , and mouse peripheral bl ood erythrocytes.Page 5 of 23 3.1 Acute Toxicity

A summary of the acute toxicity findings is included in Table 4. DBDCB is of low acute oral toxicity (Toxicity Category III), low dermal t oxicity (Toxicity Category IV) and low inhalation toxicity (Toxicity Category IV). DBDCB is a se vere dermal and eye irritant (Toxicity Category I). It is not a dermal sensitizer in animals but it is a dermal sensitizer in humans.

Table 4 - Acute Toxicity Values for DBDCB Test (species) MRID (% ai) Result Toxicity Category
81-1 Oral Toxicity (rat) 41885501 (99.9) LD50 (males) = 770 mg/kg LD50 (females) = 515 mg/kg III

81-2 Dermal Toxicity (rabbit) 00027554 (98) LD50 (combined) > 5000 mg/kg IV 81-3 Inhalation Toxicity (rat) 00025846 (98) 42526401 (99.9) LC50 (combined) > 5.09 mg/l LC50 (combined) > 13.09 mg/l IV

IV 81-4 Eye Irritation (rabbit) 0025848 (98) Severe Irritant I 81-5 Dermal Irritation (rabbit) 0025847 (98) 41885502 (98) Severe Irritant I

81-6 Dermal sensitization (guinea pig) 00105188 (98) Not a sensitizer N/A 81-6 Dermal sensitization (human) 43183801 (98) A skin sensitizer. Tested at 2000 ppm using repetitive occlusive patchings. The effect was independent of UV exposure. N/A

When conducting risk assessments in the past, EP A relied in part on some human studies, such

as the human skin sensitizati on study mentioned above, which may have involved intentional exposure to pesticides. In the course of regist ration review, EPA will reconsider these studies, as well as any other research involvi ng intentional exposur e of human subjects to pesticides, such as DBDCB, brought to its attenti on. If EPA decides to rely on any of these studies, EPA will ensure that all applicable re gulatory requirements are met, including but not limited to the requirements for EPA ethics revi ew and Human Studies Review Bo ard (HSRB) review of certain research involving intentional exposure of human subjects.

3.2 Subchronic and Chronic Toxicity

The following is a brief summary of the currentl y available toxicology studies for DBDCB.

More detailed information is included in D397608.

3.2a Subchronic Toxicity

Oral Administration Route

Subchronic Oral Study in Dogs (MRID 43540501) - DBDCB was administered to beagle dogs (4-6/sex/dose group) in the di et at dose levels of 0, 10, 100, or 4000 ppm (0, 0.29, 3.1, or 100 mg/kg/day for males and 0, 0.33, 3.1 or 120 mg/kg/da y for females) for three months followed with a 3-month recovery phase using 2 dogs/sex at doses of 0, 100, or 4000 ppm of the test material. No mortality was reported; one male was euthanized in extremis on Day 40.Page 6 of 23 No effects were observed at the 10 ppm dose level. At the 100 ppm dose le vel, the incidence of treatment-related clinical signs of toxicity we re slightly increased, and these effects included diarrhea, soft stool, emesis, and thin appearance. These effects were observed more consistently in the females, and were only marginally increase d in the males. No clear test compound-related effects were shown in body weight and/or food consumptions in this dose group.

At the 4000 pm dose level, a treatment-relate d much higher and progressively increased

incidence of decreased body mass, hindlimb ataxia, and pale oral mucosa was reported in both

sexes. Treatment-related eff ects also included decreases in food consumption and body weights; changes in hematology, clinical chemistry, urol ogical parameters, and gross and microscopic pathology. Treatment-related effect s were also observed on the thyr oid glands in both males and females. These effects included significantly decreased serum T 4 , T 3 , and reverse T 3 at most or all of the monitoring time points, enlargement of the thyroid, increased absolute and relative thyroid weights, and hypertrophy (a ll males and females)/hyperplas ia (all males and one female) in the thyroid glands. The severity of hist opathological changes was greater in males than

females.

Additional findings at the 4000 ppm dose level were green discol oration of the kidneys; brown pigmentation in the liver; axonal degeneration in the brain and spinal cord; anemia triggered bone marrow response; seminifer ous tubule degeneration in th e testis with concurrent hypospermia and giant cell formation; prostatic at rophy; histopathological changes in spleen; and lymphoid depletion of the thymus. After the 3- month recovery period, a less severe form of axonal degeneration was seen; however, an increa sed thyroid/parathyroi d/body weight ratio was

found in the females.

The NOAEL is 0.33 mg/kg/day (10 ppm) for females and 3.1 mg/kg/day (100 ppm) for

males. The LOAEL is 3.11 mg/kg/day (100 ppm) fo r females and 102 mg/kg/day (4000 ppm, the highest dose tested [HDT]) for males base d on treatment-related significant decreases in

serum T 4 , T 3 , and reverse T 3 , enlargement of the thyroid, increa sed absolute and relative thyroid weights, and hypertrophy/hyperplasia in the thyr oid glands, and gross an d microscopic pathology changes in other system/organs including kidneys , liver, the brain and sp inal cord, anemic bone marrow response, the testis, pros tatic atrophy, spleen, and thymus, as well as treatment-related decreases in food consumption and body weights and changes in hematology, clinical chemistry, and urological parameters.

Subchronic Oral Study in Dogs (MRID 92199020) - DBDCB was administered to beagle dogs, (4 dogs/sex/group) in the diet at 0, 4.8, 28.9, or 101.5 mg/kg/day for males and 0, 5.3, 37.7 or 109.8 mg/kg/day for females for three mont hs. Thyroid follicula r cell hyperplasia was observed at the high dose in both sexes, in addition to decreased weight gains and food consumption; altered hematological paramete rs; decreased alkaline phosphatase; enlarged thyroid; marked increases in organ/body weight ratios for several organs and extramedullary hematopoiesis in spleen and liver. A NOAEL was not established. The LOAEL was 4.8/5.3 mg/kg/day (the lowest dose tested [LDT]) base d on a dose-related significant increase in absolute and relative thyroid weights in ma les (4.8 mg/kg/day) and in relative ovary weights in females (5/3 mg/kg/day).Page 7 of 23 Thyroid Hormone Study in Dogs (MRID 41858401) - A special subchronic feeding study was

conducted to determine the effect of the exposure to DBDCB on the thyroid hormones triiodothyronine (T 3 ) and thyroxine (T 4 ) in dogs. In this study, DBDCB was administered to beagle dogs (4/sex/group) in the diet at a single dose of 4.8 mg/kg/day for three months. The dose used in this study was the low dose of th e 3-month dietary study in dogs (MRID 92199020). Both sexes of animals showed enlarged thyroids and increased levels of T 3 and T 4 after being stimulated with thyroid stimulating hormone (T SH). Thyroid weights and organ/body weight ratios were significantly increased in females.

Dermal Administration Route

NTP 2-Week Study in Rats: Groups of five male and female rats received dermally

administered DBDCB in acetone at concen trations of 0, 37.5, 75, 150, 300, or 600 mg/mL, 5 days per week, for 16 days. The dose formula tions were applied at constant volume of 0.5 mL/kg to yield doses of 0, 37.5, 75, 150, 300, or 600 mg/kg/day. No mortality or effects on body weights were reported. The thyr oid gland weights of males in the 600 mg/kg/day group were significantly less than th ose of the controls, while the liver and kidney weights of 300 and 600 mg/kg/day females were significantly increase d. Dermal reactions were observed including irritation, thickened skin, and ulce rs at the site of applicati on in most dosed animals.

NTP 2-Week Study in Mice: Groups of five male and female mice were dermally administered DBDCB in acetone at concentrations of 0, 37.5, 75, 150, 300, or 600 mg/mL, 5 days per week, for 16 days. The dose formulations were app lied at 2.0 mL/kg to yield doses of 0, 75, 150, 300, 600, or 1,200 mg/kg/day. No mortality was re ported. The final mean body weight of 300 mg/kg/day males was significantly lower than thos e of the controls. Hyperactivity was observed in all dosed groups. The organ weights (liver, hear t, and kidneys) were significantly increased in the groups of 600 and 1,200 mg/kg/day animals (k idneys weight increased in males at 150 mg/kg/day). The thymus weight s were significantly decreased in males dosed 300 mg/kg/day and beyond and in all dosed female groups. All dermal reactions seen in the 2-week rat study were also observed in this 2-week mouse study.

NTP 3-Month Study in Rats: Groups of 10 male and 10 female rats were dermally

administered DBDCB in acetone at concentrations of 0, 0.4, 1.2, 4, 12, or 36 mg/mL, 5 days per week, for 14 weeks. The dose formulations were applied at 0.5 mL/kg to yield doses of 0, 0.2, 0.6, 2, 6, or 18 mg/kg/day. One 2 mg/kg/day female died on day 91, while all males survived the study. No effects on the body weights were reported for either males or females. Clinical findings included thin hair coat in both male and female animals and skin irritation at the site of application in males. All dermal reactions obser ved in the 2-week studies were also reported for this 3-month study at the doses of 0.6 mg/kg/day (1.2 mg/mL) or beyond in dosed animals.

NTP 3-Month Study in Mice: Groups of 10 male and 10 female mice received dermal

administration of DBDCB in acetone at concentr ations of 0, 0.1, 0.3, 1, 3 or 9 mg/mL. The dose formulations were applied at 2.0 mL/kg to yield doses of 0, 0.2, 0.6, 2, 6, or 18 mg/kg/day. All animals survived the study and no effects were reported on the body weights of dosed animals. The liver and lung weights of dosed females were si gnificantly lower than t hose of the controls.Page 8 of 23 Dermal findings were similar as those of in the 3-month rats study, and generally seen at the doses of 2 mg/kg/day (1 mg/mL) and beyond.

Inhalation Administration Route

No inhalation studies ar e available for DBDCB.

3.2b. Chronic Toxicity/Carcinogenicity

Oral Administration Route

No chronic or carcinogenicity oral studies are available for DBDCB.

Dermal Administration Route

NTP Two Year Study in Rats: Groups of 50 male and 50 female rats were dermally

administered DBDCB in 95% ethanol at concentr ations of 0, 4, 12, or 36 mg/mL, 5 days a week,

for 104 to 105 weeks. The dose formulations were applied at constant volume of 0.5 mL/kg to yield doses of 0, 2, 6, or 18 mg/kg/day. Survival of 18 mg/kg/day males was significantly higher than that of the controls; however, body weights of this dose group of both sexes were 7% lower than those of the controls after 1 year. No increases in the incidences of neoplasms were

observed in dosed animals. The combined incidence of mammary gland fibroadenoma, adenoma, or adenocarcinoma showed a negative trend, and significantly decreased incidence was observed in 6 mg/kg/day females. Dermal adverse reactions such as epidermal hyperplasia were

observed in males and females dosed at 6 or 18 mg/kg/day and the incidences of hyperkeratosis of the epidermis were significantly increased in all dosed groups. The incidences of inflammation of the nose were reported to be significantly higher in all dosed male rats.

NTP Two Year Study in Mice: Groups of 50 male and 50 female mice were dermally

administered DBDCB in 95% ethanol at concentr ations of 0, 0.3, 1, or 3 mg/mL, 5 days a week,

for 105 weeks. The dose formulations were a pplied at constant volume of 2.0 mL/kg to yield doses of 0, 0.6, 2, or 6 mg/kg/day. No effects were re ported on the survival rate or body weight. No clinical findings were attributed to the test material, and no increases in the incidences of neoplasms were observed in the doses animals. At the site of application, significantly increased

incidences of minimal to mild hyperplasia of the epidermis were reported in 2 and 6 mg/kg/day

males and all dosed females. Female mice also showed significantly increased incidences of

minimal to mild chronic active inflammation in the dermis at all doses.

3.2c. Developmental Toxicity

Developmental Study in Rats (MRID 92199012) - DBDCB was administered by gavage to rats at doses of 0, 25, 100, or 175 mg/kg/day on gestat ion days (GD) 6 through 15. Surviving dams were sacrificed on GD 20; necropsied a nd reproductive status recorded. The maternal NOAEL is 25 mg/kg/day and the LOAEL is 100 mg/kg/day based on significant decrease in body weightPage 9 of 23 change. There were no mortali ties among dams. Clinical signs were observed in high-dose dams including dyspnea, hypoactivity, and staining of mouth. No change in mean fetal weight with respect to dose was reported. There were no compound-related external, visceral or skeletal

variations or malformations in th e treated fetuses in comparison to controls on either a litter or

fetal basis. The developmental toxicity NOAEL is 175 mg/kg/day (HDT) . The resorptions observed in the treated groups were considered to be the result of significant maternal toxicity at the mid- and high-dose levels because of (1) a lack of statistically significant decrease in litter size accompanying the increased resorptions; (2) marginally significant pairwise difference in the number of litters with one or more resorption in each group; and (3) no statistically significant dose-related trend

Developmental Study in Rabbits (MRID 43540502) - DBDCB was administered by gavage to presumed pregnant New Zealand white rabbits (2 0/dose) at 0, 10, 30, or 60 mg/kg/day from GD 6 through GD 18. One animal in the mid-dose group was found dead on GD 25, and one animal in the high-dose group was sacrificed moribund due to intubation error. Two animals from the control group aborted on GD’s 24 and 28. None ofthese findings were considered to treatmentrelated. No clinical and necrops y findings were considered to be treatment-related in these animals or in those surviving the treatment a nd sacrificed at termination. Although decreased maternal body weight gain occurred during GD 6- 9 and decreases in feed consumption were observed during GDs 6-9 and 9-12 (both were at th e high dose group), there were no statistically significant decreases when the entire dosing interv al (GD 6-18) for each was compared to those of the controls. Therefore, these effects we re not considered to be treatment-related . The maternal and developmental toxicity NOAEL is 60 mg/kg bw/day (HDT).

3.2d. Reproductive Toxicity

There were no reproductive toxici ty studies in the RED. Th e 90-day feeding study in rats exposed in utero (MRID 00055028) summarized below was included in the RED as an acceptable subchronic study. This study was review ed and found to be unacceptable as a onegeneration reproduction study for the follo wing reasons as noted in D213921:

1. The number of animals used (10/sex/group wa s too low to properly measure reproductive

indices.

2. The lack of day zero data, i.e., accurate pup count prevents a determ ination of potentially dose related decreases in pups born.

3. The report indicated that only healthy F1 pups were randomly selected for the 90 day portion of the study. The report stated that “obviously dise ased” pups were removed but the report did not clearly stat e nature of disease and when and how many “diseased” pups

were removed.

4. No data were provided on mate rnal weight during pregnancy and weight and count of the number of pups born to determine resorption.Page 10 of 23 90 Day Feeding Study in Rats Exposed in Utero ( MRID 00055028) - DBDCB was administered to rats (10 animals/sex/dose gr oup) in the diet at 6.3, 37, or 275 mg/kg/day for males and 7.5, 43, or 360 mg/kg/day for females se ven days before mating and throughout the 14-day mating, gestation, and lactation periods. Forty (20/sex) of the weanling offspring (F 1 rats) receiving each dosage level we re randomly selected for use in the 90-day phase of the study. After 13 weeks, the F 1 animals were necropsied and tissues preserved. Effects seen at the high-dose group in both sexes of the F 1 animals included significan t decrease in body weight, decrease in brain weight, increa se in pituitary weight, increase in pituitary to body weight ratio and pituitary to brain weight ratio, increase in spleen to body weight ratio, and splenic hematopoiesis. Additionally, males showed a si gnificant increase in liv er to body weight ratio and significant decrease in testes with epididymides weight and testes with epididymides to brain weight ratio, and females showed an increase in thyroid weight and thyroi d to body weight ratio. The weight gain in both sexes were much lower (32-36%) than controls in the high-dose group, although they were higher than controls in bot h sexes in the low- and mid-dose groups (20-25% and 10%, respectively) on days 1-21. The NOAEL is 6.3 mg/kg/day for males and 7.5 mg/kg/day for females , and the LOAEL is 37 mg/kg/day for males and 43 mg/kg/day for females based on increased severity in sp lenic extramedullary hematopoiesis in F 1 males and increased pituitary weight and pi tuitary to body weight ratio in F 1 females.

3.2e Mutagenicity

The DBDCB RED included six submitted mutage nicity studies. DBDCB was negative for mutagenic effects except in an in vitro Chinese hamster ovary (CHO) assay. However, the in

vivo cytogenetics assay in rats was negative. The study results are summarized in Table 5.

Table 5 – Mutagenicity Studies Included in the DBDCB RED

MRID Test Results 25091 Bacterial Mutagenicity (Ames Assay) Not mutagenic up to viability limits with and without S9

activation. 128134 Chinese Hamster Ovary (CHO) Assay Produced significant frequencies of chromosomal aberrations ( i.e. it was mutagenic ) in CHO at 11 μg/ml without S9 activation and 190 μg/ml with S9 activation.

125850 In Vivo Mammalian Erythrocyte Micronucleus Assay (Rat) Not mutagenic in rat erythrocytes when tested up to 50 mg/kg/day.

144412 In Vitro Mammalian Cell Gene Mutation Assay Not mutagenic in Chinese hamster lung fibroblasts up to cytotoxicity limits with and without S9 activation.

137288 Unscheduled DNA Synthesis (UDS) Assay Did not induce UDS in human embryonic lung fibroblasts

with and without S9 activation.

55029 Dominant Lethal Mutation Assay (Mouse) Did not produce dominant lethal mutations in male mice (10/dose) administered dietary doses of 0, 12.5 , 75.0, and 450 mg/kg/day for 8 weeks prior to mating.

In addition, DBDCB was negative in the Ames Assay and the In Vivo Mammalian Erythrocyte Micronucleus Assay (Mouse) conducted by NTP.Page 11 of 23 3.2f Absorption, Distribution, Metabolism and Excretion (ADME)

One metabolism study has been submitted to the Agency and one study was found in the

literature.

In the submitted metabolism study (MRID 55031), male CD rats were administered a single oral dose of 50 mg/kg radiolabeled 14 C-DBDCB. Total recovery of radioactivity during the 7 day collection period in the urine, feces, and respired air was 84-91%, 6-10%, and 0.5% of the administered dose, respectively, and most of th e radioactivity in the urine was found during the first 24 hours post-administration. Tissue assay 7 days post-admi nistration indicated that the lung, liver, kidneys and spleen contained 2.7, 2.5, 2.3 and 2.3 ppm, respectively. Maximum blood concentration (71μg/ml) of DBDCB e quivalent was attained at 5 hours postadministration. On the basis of percent dose pe r whole organ, each of these retentions is

calculated to be less th an 0.1%, except for liver at 0.3%. This study provides supplemental

information on metabolism of DBDCB despite deficiencies identified.

A study on the metabolism of DBDCB was locat ed in the open literature (MRID 48767302).

Radiolabeled 14 C-DBDCB was administered to male Fischer 344 rats at doses of 8 mg/kg, 80 mg/kg, and 25 mg/kg by the IV, oral, and derm al routes, respectively. Radiolabeled 14 CDBDCB was absorbed greater than 60%, approxima tely 85%, and less than 12% of dosed parent compound following IV, oral, and dermal administ ration. No parent compound was detected in the blood regardless of route of administration (including the 1-min time point for IV route); however, 2-methylene-glutaroni trile (CAS No. 1572-52-7), a debrominated metabolite of DBDCB, was identified following IV and oral administration but not dermal administration. Despite its relatively high levels, 2-methylen e-glutaronitrile declined rapidly and was not

detectable within one hour of IV administration. A small amount of the dose for IV, oral and

dermal route was retained in tissues 72 hours post-administration and distributed evenly among tissues including liver and the GI tract (for oral route). However, 12.5% of the dose was bound to the erythrocyte fraction of the bloo d following IV route of administration. 14 C-DBDCB was primarily excreted in urine followed by feces and exhaled air. Urinary metabolite profiles were

almost identical for each route of ad ministration; the primary metabolite was N -acetyl- S -(2,4- dicyanobutane)- L- cysteine which is a mercapturate conjuga te of 2-methyleneglutaronitrile. The authors concluded that DBDCB is totally debrominat ed prior to systemic di stribution; therefore, tissues exposure to intact DBDC B was expected to be exceedingl y low regardless of the routes

of administration. This conc lusion will be further evaluated during registration review.

3.2g Neurotoxicity

No neurotoxicity studies are available for DBDCB.Page 12 of 23 3.3 Toxicology Endpoints

Dietary exposures were not assessed in the RE D because indirect food additive tolerances had

been established for the DBDCB indirect food uses in adhesives and paper/paperboard and dietary exposures from these uses were expected to be minimal. Occupational and residential exposures to DBDCB were not assessed in th e RED because no endpoints of concern were identified for short and intermediate term expos ures and no chronic exposures were anticipated (US EPA, 1996). No additional toxicology data were required in the RED; however, two additional studies (two generation reproduction and 90 day inhalation) will be needed for registration review and endpoints may need to be selected based on the outcome of these studies.

4.0 DIETARY ASSESSMENT

Information regarding dietary exposures is taken from DP397607, Summ ary of Dietary and Drinking Water Exposures for the 1,2-Dibr omo-2,4-dicyanobutane (DBDCB) Registration Review Scoping Document.

4.1 Dietary Exposure

DBDCB is regulated by the FDA as an indirect f ood additive. Tolerances have been established for DBDCB as a preservative in food grade adhe sives (see 21 CFR § 175.105) and as a slimicide in the manufacture in food grade paper and pape rboard at a maximum level of 0.005% of dry weight fiber (see 21 CFR § 176.300). Dietary (food) exposure to DBDCB is likely because it is used as a slimicide in food contact paper and paperboard production a nd to preserve papermaking chemicals. Migration of DBDCB from paper packaging to the food contents may occur. A migration study is anticipated to be needed as will a dietary (food source) risk assessment to support the antimicrobial uses of DBDCB as a part of this registration review case.

4.2 Drinking Water Exposure

The fate of DBDCB in water is discussed in the Product Chemistry, Environmental Fate, and Ecological Effects Scoping Document in Support of Registration Review of DBDCB (D397530).

The submitted environmental fate studies demonstrat e the relative lack of persistence of parent DBDCB and more persistent degr adates. They also show that all residues of DBDCB have limited sorption to soil and sediment, indicating th at the primary residues that can reach surface and ground water are the metabolites. The registra nt has submitted environmental fate studies that were considered to be “supplemental, upg radeable” and “not comp letely acceptable”. However, the information is of sufficient quality to use in the ecological risk assessment. The hydrolysis half-life of DBDCB is pH dependent and ranges from 13 days in alkaline conditions to 190 days in acidic conditions at 25 o C. Two major degradates are formed, including trans 1- bromo-2,4-dicyanobutene (BDCB) and 2-methylen eglutaronitrile (MGN). The aerobic aquatic half-life of MGN is on the order of 4.6 days. Th e overall degradation of DBDCB appears to lead to stable degradates that have not been identi fied, but the remaining por tion of the compound is a straight-chain aliphatic hydro carbon which can become part of the organic matter of soil. Limited sorption to soil and sediment for all re sidues was demonstrated by the near quantitativePage 13 of 23 partitioning to water in the aquatic metabolism study and the limited Freundlich Kads values of 0.26-0.70 ml/g.

To address the fate of the degradate BDCB in th e waste water treatment plant process, studies on biodegradability in sewage sludge and activated sludge respirati on inhibition are anticipated to

be needed. Based on the above environmental fate information, drinking water consumption from ground or surface water is likely to be lim ited for parent DBDCB at environmental pH values (+ pH 7) but is more likely for the metabolites. The available fate data and the requested studies will be used during the risk assessment stage of registration review to determine the potential for discharged residue s to result in human dietary e xposure via drinking water and, if needed, to trigger a drinking water assessment.

5.0 OCCUPATIONAL AND RE SIDENTIAL EXPOSURES

If endpoints of concern are id entified from the toxicology st udies that are required for registration review, then exposures to DBDCB will need to be assessed during registration review. The exposure routes could include de rmal and inhalation for occupational exposures and dermal, inhalation and incident al oral for residential exposure s. A listing of the exposure

scenarios for DBDCB is included in Table 6.

Table 6 – Occupational and Residential Exposure Scenarios for DBDCB

Scenario Exposure Route(s) Duration
Occupational Exposures Open pour liquids Dermal and Inhalation Short and Intermediate

Term Open pour wettable powder Dermal and Inhalation Short and Intermediate

Term Using treated metal working fluids Dermal and Inhalation Short, Intermediate and Long Term Painting with treated paints (Airless spray and brush/roller) Dermal and Inhalation Short and Intermediate

Term Residential Exposures Using treated cleaning solutions Dermal and Inhalation Short and Intermediate

Term Painting with treated paints (Airless spray and brush/roller) Dermal and Inhalation Short Term

Toddlers playing on floors cleaned with treated cleaning solutions Dermal and Incidental Oral Short and Intermediate

Term

6.0 AGGREGATE AND CUMULATIVE EXPOSURE

The DBDCB RED does not include a human health assessment, as no endpoints of concern had

been identified. The RED also assumed that resi dential handler exposures from treated products were not expected to pose a si gnificant risk because of the lo w concentrations used. For registration review, upon an eval uation of toxicological studies requested for DBDCB and if endpoints of concern are identified from these studies, then aggregate exposures to DBDCB will need to be assessed. The exposure routes could in clude dermal, inhalation and incidental oral forPage 14 of 23 residential exposures; all of wh ich may be appropriate to aggr egate with dietary and drinking

water exposures.

7.0 INCIDENTS

There are no human incidents repo rted in the OPP incident database that are associated with DBDCB exposure.

8.0 TOLERANCES

Indirect food additive tolerances have been established for DBDCB as a preservative in food grade adhesives (see 21 CFR § 175. 105) and as a slimicide in the manufacture in food grade paper and paperboard at a maximum level of 0.005% of dry weight fiber (see 21 CFR § 176.300).

9.0 ENDOCRINE DISRUPTION EFFECTS

As required by FIFRA and FFDCA, EPA reviews num erous studies to asse ss potential adverse outcomes from exposure to chemicals. Collectiv ely, these studies includ e acute, subchronic and chronic toxicity, including asse ssments of carcinogenicity, ne urotoxicity, developmental, reproductive, and general or systemic toxicity. These studies include endpoints which may be susceptible to endocrine influe nce, including effects on endocri ne target organ histopathology, organ weights, estrus cyclicity, sexual maturatio n, fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. As part of the re-registration elig ibility decision in 1996, EPA reviewed the available toxicology data and determined that ther e were no endpoints of concern for the existing use patterns. However, as required by FFDCA section 408(p), DBDCB is subject to the endocrine screeni ng part of the Endocrine Disrup tor Screening Program (EDSP).

EPA has developed the EDSP to determine whet her certain substances (including pesticide active and other ingredients) may have an effect in humans or wildlife similar to an effect produced by a “naturally occurring estrogen, or ot her such endocrine effect s as the Administrator may designate.” The EDSP employs a two-tiered approach to making th e statutorily required

determinations. Tier 1 consists of a battery of 11 scr eening assays to identify the potential of a chemical substance to interact with the estrog en, androgen, or thyroid (E, A, or T) hormonal systems. Chemicals that go th rough Tier 1 screening and are found to have the potential to interact with E, A, or T hormonal systems will proceed to the next stag e of the EDSP where EPA will determine which, if any, of th e Tier 2 tests are necessary base d on the available data. Tier 2 testing is designed to identify a ny adverse endocrine-related eff ects caused by the substance, and establish a dose-response relations hip between the dose and the E, A, or T effect. Under FFDCA section 408(p), the Agency must screen all pe sticide chemicals. 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 ingr edients and 9 inert ingredients. DBDCB is not among the group of 58 pesticide active ingredients on the initial li st to be screened under the EDSP. For furtherPage 15 of 23 information on the status of the EDSP, the polic ies and procedures, the list of 67 chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our website: http://www.epa.gov/endo/

.

10.0 ANTICIPATED DATA NEEDS

10.1 Toxicology Studies

Additional studies are needed to assess the hazards of DBDCB. These studies are listed in Table 7 and detailed justifications ar e provided in Appendix A.

Table 7 –Toxicology Studies Needed for DBDCB
Study Needed Guideline Applicable Uses 90 day Inhalation Toxicity 870.3465 1. All uses involving open pour applications 2. Metal working fluids

3. Paints 4. Cleaning solutions 2- Generation Reproduction 870.3800 All uses that can result in dietary and drinking water exposures.

10.2 Exposure Studies

Several dietary and occupational and residentia l exposure studies are needed to assess the

antimicrobial uses of DBDCB. These studies are listed in Table 8 and detailed justifications are provided in Appendix A.

Table 8 –Dietary and Occupational Reside ntial Exposures Studies Needed for DBDCB
Study Needed Guideline Applicable Exposure Scenarios Indoor Exposure, Dermal Indoor Exposure, Inhalation Data Reporting/Calculations 875.1100

875.1300

875.1600 1. Open pour liquids A,C

2. Open pour wettable powder B,C
3. Application of preserved paints - brush/roller or airless spray C
4. Use of treated metal working fluids C
5. Trigger sprayer and mop application of preserved cleaning solutions C
Surface Residue Dissipation 875.2300 1. Residential post application dermal and incidental oral exposure to floors cleaned with preserved household cleaning solutions.

Nature of Residue on Surfaces Migration N/A

N/A 1. Dietary exposures from countertops cleaned with preserved household cleaning solution. 2. Dietary exposures from DBDCB treated paper products used in food packaging.

Product Use Information 875.1700 All above scenarios A. If the labels are amended to require closed mixing/loading, the exposure study can be waived. B. If the labels are amended to require water so luble packaging, the exposure study can be waived. C. It may be possible to use proprietary surrogate exposure data if data compensation issues can be addressed.Page 16 of 23 11.0 REFERENCES

Kline, 2006. Specialty Biocides Nort h America 2004/2005, Kline and Company, Inc.

MRID 48767301. Toxicology and Carcinogenesis Studies of 1,2-Dibr omo-2,4-Dicyanobutane (CAS No. 35691-65-7) in F344/N Rats and B6C3F1 Mice (Dermal Studies). NTP TR 555, NIH

Publication No. 10-5896. National Toxicology Program, June 2010. http://ntp.niehs.nih.gov/nt p/htdocs/LT_rpts/TR555.pdf )

MRID 48767302. Sauer, JM, Smith, RL, and Bao, J, et al. (1998). Metabolic and Dispositional Fate of 1,2-Dibromo-2,4-Dicya nobutane in the Male Fischer 344 Rat. Drug Metabolism and Disposition. 26:429-36. http://dmd.aspetjournals .org/content/26/5/429.long

US EPA, 1996. Registration Eligibility Decisi on (RED) for 1,2-Dibromo-2,4-dicyanobutane, United States Environmental Protection Agency, August 1996

D213921. Toxicology Review for the Registration Eligibility Decision Do cument on Tektamer (1,2-dibromo-2,4-dicyanobutane) , Pa ul Chin, EPA Office of Pesticide Programs, Health Effects Division, Toxicology Branch, February 5, 1996.

D397530. Product Chemistry, Environmental Fate, and Ecological Effects Scoping Document in Support of Registration Review of Dibromodicyanobutane. Srin i Gowda, David Bays, Ph.D., James Breithaupt, EPA Office of Pesticide Pr ograms, Antimicrobials Division, Risk Assessment and Science Support Branch.

D397607. Summary of Dietary and Drinking Water Exposures for the 1,2-Dibromo-2,4- dicyanobutane (DBDCB) Registration Review Scoping Document, Talia Lindheimer, EPA Office of Pesticide Programs, Antimicrobials Division, Risk Assessment and Science Support

Branch.

D397608. Dibromodicyanobutane : Summary of Mammalian Toxicology Data for the Registration Review Scoping Document, Jenny Tao, EPA Office of Pesticide Programs, Antimicrobials Division, Risk Assess ment and Science Support Branch.Page 17 of 23 

# Appendix A –

Justification for the

Studies Needed for the Human Health Registration Review of DibromodicyanobutanePage 18 of 23 Study Title: 90-Day Inhalation Toxicity (Rat)

Guideline Numbers: 870.3465

Rationale for Requiring the Data
Occupational (i.e. worker) inhalation exposures to dibromodicyanobutane are expected during the open pour addition of liquids and wettable powders during materials preser vation, paper production operations and oil field treatments. Occupational and residential (i.e. homeowner or consumer) inhalation exposures are also expe cted during the use of preserved products such as paints, metal working fluids and household cleaning solutions. Given that dibromodicyanobutane has a fairly low vapor pressure of 5.0 x 10 -5 mm hg, the exposures will be primarily to aerosols rather than vapors.

Practical Utility of the Data
1) How did the Agency make its earlier regulatory decision without these data?

Inhalation risk has never been assessed for di bromodicyanobutane even t hough inhalation exposures are expected. There is no rout e-specific study availa ble to appropriately use in a quantitative assessment of inhalation exposures.

2) How would the data be used?

The data would be used to prope rly evaluate inhalation hazards a nd risks to occupational workers during open pour addition of dibromodicyanobut ane liquids and wettable powder products during industrial treatment operations such as materials preservation and wh en working with treated paints and metal working fluids. This data would also be used to evaluate risks to residential adults during painting and when using household surface cleaners.

3) How could the data impact the Agency’s future decision making?

In the absence of inhalation toxicity data, the Agency would have to estimate inhalation risks using an oral toxicity study and rely on th e assumption that absorption and toxicity of dibromodicyanobutane

are the same via the oral and inhala tion routes of exposure. Note that absorption of pes ticides into the bloodstream via the lungs is often hi gher than that via the oral rout e and often many times higher than

via the dermal route. Paired with the requested inhalation exposure data, the route-specific 90-day inhalation toxicity study on dibromodicyanobutan e will permit EPA to conduct occupational and

residential risk assessments that are refined and in which there is a high degree of confidence.Page 19 of 23 Study Title: Two-Generation Reproduction Study

Guideline Numbers: 870.3800

Rationale for Requiring the Data
The two-generation reproduction study is conditi onally required for non-direct food contact use pesticides, such as material pres ervatives like dibromodicyanobutane, under the data requirements of

40 CFR 161.340. In this case, the trigger for this requi rement is the chronic (>6 months) human exposure to dibromodicyanobutane via indirect-f ood and drinking water sources. There is no reproduction toxicity study or othe r alternative informa tion (e.g., SAR), surrogate data, or weight-ofevidence available to be utilized to evaluate the potential for reproduction a nd fertility effects.

The existing 90-day feeding study in rats exposed “in utero” is not ad equate and acceptable to address reproductive toxicity due to a lack of reproductive parameters that are required by the guideline. These parameters include fertilit y, birth, viability, offspring sex ra tio, parental (P) females cycle pattern and mean estrous cycle length, implantati on data and postimplantation loss for P parental females, as well as total cauda epididymal sper m number, homogenization-resi stant testis spermatid number, number and percent of progressively motil e sperm, number and pe rcent of morphologically normal sperm, and number and percent of sperm with each identified anomaly.

This study will provide informati on of potential reproductive hazards of dibromodicyanobutane. In addition, the data generated may al so provide a toxicity endpoint ap plicable to risk assessment for occupational and residential exposures.

Practical Utility of the Data

1) How did the Agency make its earlier regulatory decision without these data?

The Agency has never characterized and quantified the potential reproduction a nd fertility hazard and risks associated with the regist ered uses of dibromodicyanobutan e due to a lack of the study.

2) How would the data be used?

The data would be used to characterize and quant ify the hazard and risks of dibromodicyanobutane

via the oral route to the U.S. general population including infants a nd children as required by the FQPA. The data would allow the Agency to concl ude more definitively whether or not there would be any concerns for reproduction and fertility. A t oxicity endpoint may be sele cted from this study for use in quantitative risk assessments.

3) How could the data impact the Agency’s future decision making?

This study may result in a change in how risks are quantified and would greatly increase the Agency’s confidence in the hazard profile of dibromodicyanobutane which increases the confidence in future risk assessments and, hence, regulato ry decisions. This study could be used as the source for selection of toxicity endpoints for use in th e assessment of human risks.Page 20 of 23 Study Titles: Indoor Exposure Dermal, Indoor Exposure Inha lation, Data Reporting and Calculations

Guideline Numbers: 875.1100, 875.1300, 875.1600 Rationale for Requiring the Data

Dermal and inhalation exposures to dibromodi cyanobutane are expected during the open pour

addition A of liquids and wettable powders B during materials preservation , paper production operations and oil field treatments. These exposures were not assessed in the RED because no endpoints of

concern were identified. If additional toxicol ogical studies for dibromodicyanobutane are required during registration review and e ndpoints of concern are identified from these studies, then the exposures to dibromodicyanobutane will need to be assessed during registration review.

Dermal and inhalation exposures are also expected during the use of pres erved products such as paints, metal working fluids and household cleani ng solutions. These exposures also were not

assessed in the RED.

Dermal and inhalation exposures from these scenarios are evident in exposure studies in the Pesticide Handlers Exposure Database (PHED). The existing Chemical Manufacturer Association (CMA) data

base and PHED for these scenarios are limited in sc ope for QA/QC and the number of replicates (i.e., number of times a worker is monitored for a specific activity). EPA presented the need for additional handler exposure data to the Ja nuary 2007 Science Advisory Panel (S AP) as well as to the April 2007

Human Studies Review Bo ard (HSRB) and both groups agreed th at additional data are warranted.

Practical Utility of the Data

1) How would the data be used?

The data would be used to assess dermal and i nhalation exposures that result from the open pour addition of liquids A and wettable powders B and during the use of treated materials C including paints, metal working fluids and household surface cleaners.

2) How could the data impact the Agency’s future decision making? The exposure data would be used to assess the ri sks of exposure and to determine if mitigation measures, such as closed system loading, water so luble packaging, decreased application rates or use of PPE are needed to reduce these risks. If expos ure data are not available, these assessments will have to be made using models which might lead to the overestimation of risk and the requirement for excessive and onerous mitigation measures.
A. If the labels are amended to require closed mixing/load ing, the study for the open pour scenario can be waived. B. If the labels are amended to require water soluble packaging, the exposure study can be waived. C. There are proprietary studies that can be used as surroga te data for these exposure scenarios if data compensation

issues are addressedPage 21 of 23 Study Title: Surface Residue Dissipation (Floors and Carpets)

Guideline Numbers: 875.2300 Rationale for Requiring the Data

Dermal and incidental oral exposures to dibrom odicyanobutane are expected for toddlers who sit or play on household floors after they are cleaned with household cleani ng solutions that are preserved with dibromodicyanobutane. These exposures were not assessed in the RED because no endpoints of

concern were identified. If additional toxicol ogical studies for dibromodicyanobutane are required during registration review and e ndpoints of concern are identified from these studies, then the exposures to dibromodicyanobutane will need to be assessed during registration review.

Practical Utility of the Data

1) How would the data be used?

The surface residue data would be used to assess dibromodicyanobutane exposures that result from the use of household cleaning solutions pr eserved with dibromodicyanobutane.

2) How could the data impact the Agency’s future decision making? The surface residue data will be used during regist ration review to decide if the exposures to dibromodicyanobutane from its use in household cleani ng solutions generate a risk of concern that requires mitigation. This mitigation could include re duction of the application rate or elimination of

the use. If surface residue data are not availa ble, then the standard assumption of 100 percent

transferable surface residue will be used which might overestimate the risk and require excessive mitigation.Page 22 of 23 Study Titles: Nature of Residue on Surfaces, Migration Study

Guideline Numbers: No Guidelines Rationale for Requiring the Data These residue chemistry studies will allow the Agen cy to conduct chemical-specific, quantitative dietary risk assessments that utilize the meas ured quantities of DBDC B and/or degradation products that will be available for dietary consum ption when food contact su rfaces that have been freshly cleaned with preserved prod ucts or preserved with DBDCB itself. In the past, the Agency did not assess exposures to residue s on counter tops or from treated pulp and paper. Furthermore, no consideration was given to dissipation/loss of surface residues via volatilization, identity of degradates, or preferential migr ation of residues to certain ty pes of food depending on porosity, water or fat content, etc. The Nature of the Residue on Surfaces study will determine whether residues persist on treated food-cont act surfaces, the identity of those residues, and a measured upper limit on total surface residue level. The Mi gration Studies are automatically required but may be waived depending on the outcome of th e Nature of the Residue on Surfaces study. Migration Studies determine the concentrations of specific residues of toxicological concern

transferred from treated food-c ontact surfaces to various types of food coming in contact with

these surfaces. Data from these studies will re place any default leaching and migration rates used

in earlier risk assessments.
Practical Utility of the Data

1. How will the data be used?

The Nature of the Residue on Surfaces study will be used to determine whether the active ingredient remains on the treated food-contact surf ace, whether it degrades, to what it degrades, and the upper limit on total food-contact surface re sidues. This study may negate the need for a dietary risk assessment, may be used as an upper (yet more refined) exposure limit, and may be used to either waive or provide direction for the Migration Studies. Migr ation Studies determine the concentrations of specific residues of toxicologi cal concern transferre d from treated foodcontact surfaces to various types of food coming in contact with these surfaces.

2. How could the data impact the Agency’s future decision-making?

If residues of DBDCB and/or de gradation products transfer from treated surfaces to food, human exposure will occur. These studi es will permit the conduct of ch emical-specific, quantitative dietary risk assessments that are much more re fined than earlier assessments and in which the Agency has higher confidence. This information will permit a determination of which use patterns are expected to result in exposures le ss than the Agency’s level of concern, which ones must be supported by additional data, and which ones are likely to have risks of concern and, therefore, must be mitigated. In addition, these data will permit a more realistic estimate of human aggregate risk.Page 23 of 23 Study Title: Product Use Information

Guideline Numbers: 875.1700 Rationale for Requiring the Data

Product use information serves as the basis for determining what exposure scenarios should be assessed and what assumptions a nd exposure data are needed to perform these assessments in a

manner that does not over or underestimate the actual risk.

Practical Utility of the Data

1) How would the data be used? The product use information will be used to define and characterize the exposure scenarios that will be

assessed in the risk assessment.

2) How could the data impact the Agency’s future decision making? A complete description of product us e would ensure that the risk asse ssment is inclusive of the types of exposures occurring during use and that these exposures are accu rately assessed. Without product use information the Agency will have to use default assumptions that might over estimate the actual

risk.