Page 2 of 7

Table 1. Registered Active Product of Dimethoxane

Registration # Registration Name Company

Name Formulation

Type % of Active

Ingredient

464

- 682 BIOBAN DXN

Antimicrobial The Dow

Chemical Co. Ready

- to

- use

solution 87

Science Findings

The Agency has conducted a review of the available product chemistry, environmental

fate, and ecotoxicity data for dimethoxane . The findings are summarized below.

P roduct Chemistry Summary

Common Name: Dimethoxane

Chemical Name: 2, 6

- dimethyl

- m

- dioxan

- 4

- ol acetate

CAS Registry Number: 828

- 00

- 2

OPP Chemical Code: 001001

Case: 3064

Molecular Formula: C 8 O 4 H 14

Trade and Other Names: Dimethoxane, Acetomethoxane

Molecular weight : 174.2 g/mol

Molecular Structure:

Color: Clear yellow to light amber

.

Physical Sta te: Liquid

Odor: Strong odor

- Characteristic halide odor. Mustard

- like odor.

Stability: Stable after exposure to Zinc foil (a reducing agent). Not

stable at:

(a) low temperatures (

- 2 to 9 o C) after 48 hours

(b) high temp. (53

- 54 o C) for 2 weeks.

( c) simulated sunlight (Xenon lamp ) for 24 hours

.

Oxidation/Reduction: N/A

Flammability

- Flash Point : 87 o C/189 o F (T ag C losed C up )

Explodability : N/APage 3 of 7

Storage Stability : Stable during the storage period of 17. 72 months at ambient temp

.

Miscibility : N/ A

Corrosion Characteristics : Corrosion rate of zinc coupons

- 3.06 mm ± 0.266 per year

Dielectric breakdown voltage : N/A

pH: 5.8 at 25 o C

UV/Visible absorption : NR

Viscosity : 8.5 cPs at 25 o C

Melting point : N/A

Freezing Point: Below 25 o C /77 o F

Boiling Point: 66

- 68 o C at 3 mm Hg

Density: 1.060

- 1.075 g/ml at 25 o C

Specific Gravity: 1.0704 (25 o C/25 o C)

Dissociation Constant : N/A. Hydrolyses in aqueous solution to produce acetic acid and the

corresponding free alcohol

.

log P (octanol

- wa ter) : N/A. Hydrolyz es in water.

Solubility: > 2 gm /ml @ 25 o C in Methanol, Hexane & Water. Not stable

in water. The approximate saturation point of test sample:

Methanol: 3.11 x 10 3

Hexane: 2.25 x 10 3

Water: 2.38 x 10 3

Vapor Pressure : 0.111 mm Hg at 23 o C

Henry's Law Constant : 1.24E

- 07 atm

- m3/mole 25 o C EST (EPI Suite)

Enf. Analytical Method: Gas Chromatograph

All product chemistry data requirements have been satisfied for the active ingredient

dimethoxane

.Page 4 of 7

Environmental Fate Summary

The Agency co uld not conduct a meaningful fate assessment because of limited data.

The hydrolysis study was not adequate because it was not in compliance with OPPTS guideline

835.2120 and no data were available on the acti vated sludge sorption isotherm o r the ready

bi odegradability.

For h ydrolysis (MRID Nos. 43326901 & 43797301) t he available data indicate that the

major route of degradation is abiotic hydrolysis aided by microbial mediated degradation.

Further more , the data indicate that dimethoxane is highly unstabl e in water with over 50% of the

compound hydrolyzed in 2 hours. Dimethoxane is appear ing to react with water to form acetic

acid and a transient intermediate, dioxinol. The dioxinol then breaks down into acetaldehyde and

aldol (aldehyde + alcohol dimer) . T he breakdown into acetic acid and dioxinol is completed in

14 hours

. T he study is classified as supplemental and provides useful in formation for risk

assessment. A new study is not required.

In an acceptable Activated Sludge Respiration Inhibition study ( OECD 209; MRID

45560901) dimethoxane was shown to be essentially non

- toxic to activated sludge respiration

inhibition with an EC 50 value of 1, 060 mg/ l

. The study is acceptable.

The Agency did not conduct an environmental fate assessment for dimethoxane be cause

of lack of data

. However, the Agency needs to conduct an environmental fate assessment for

material preservatives (including dimethoxane) that may potentially pass through waste water

treatment plants (WWTPs) and may be discharged into terrestrial a nd aquatic environments. For

this assessment the Agency anticipates needing those data outlined on page 6 of this document

.

Water Quality

Dimethoxane is not identified as a cause of impairment for any water bodies listed as

impaired under section 303(d) of the Clean Water Act, based on information provided at

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=8 8

5

. In addition, no Total Maximum Daily Loads (TMDL) have been developed for dimethoxane

, based on information provided at

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id

=885&p_pollutant_group_name=PESTICIDES

. 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: Inclusion of Imp aired

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/november 06/session1

- sop.pdf ), in order to ensure they can be used quantitatively or qualitatively in pesticide risk

assessments.Page 5 of 7

Ecological Effects Summary

The registrant has submitted ecological effects studies for both terrestrial and aquatic

animals. These data are adequate to provide the Agency with sufficient information to determine

appro priate label precautions, and may be seen in Table 2 below.

a. Toxicity to Terrestrial Animals

(1) Birds, Acute and Subacute

Dimethoxane is slightly toxic to practica lly nontoxic to avian species on an acute

oral and subacute dietary basis.

b. Toxicity to Aquatic Animals

(1) Freshwater Fish

Dimethoxane is not more than slightly toxic to both cold and warm water fish.

(2) Freshwater Invertebrates

Dimethoxane is not more than slightly toxic to aquatic invertebrates.

c. Toxicity to Plants (Algae)

Dimethoxane was toxic to freshwater alga at 3.4 ppm.

Table 2 . Ecotoxicity Data Summary for Dimethoxane

GUIDE

LINE COMMON

NAME TAXONOMIC

NAME TEST

TYPE %

AI STUDY

TIME DOS E

TYPE TOXI

CITY TOX

LEVEL NOEL STUDY

STATUS TOX

CATEGORY MRID

Avian Acute Oral Toxicity

71

- 1

850. 2100 Bobwhite

quail Colinus

virginianus O 92 14 D LD 50 1585 MGK 810 Acceptable S lightly

toxic 41962502

Avian Subacute Dietary Toxicity

71

- 2b

850. 2200 Ma llard

duck Anas

platyrhynchos D 92 8 D LC 50 >5620 PPM 5260 Acceptable P ractically

nontoxic 41962503

71

- 2a

850. 2200 Bobwhite

quail Colinus

virginianus D 92 8D LC 50 >5620 PPM >5620 Acceptable P ractically

nontoxic 41962504

Freshwater Fish Acute Toxicity

7 2

- 1c

850. 1075 Rainbow

trout Oncorhynchus

mykiss F 88.5 96 hr LC 50 >37 PPM 10 S uppl S lightly

toxic 41936701

Freshwater Invertebrate Acute Toxicity

7 2

- 2

850. 1010 Water

flea Daphnia

magna F 88.5 48 hr EC 50 >24 PPM 13 S uppl S lightly

toxic 41962501

Algal To xicity (Aquatic (Algal) Plant Growth Tier II)

123

- 2

850. 5400 Green

algae Selenastrum

capricornutum S 94.3 96 hr EC 50 3.4 PPM 2.39 S uppl Toxic 45664601

45828001Page 6 of 7

Ecological Effects Risk Assessment

The Agency has not conducted a risk assessment that s upports a complete endangered

species determination. The ecological risk assessment planned during registration review will

allow the Agency to determine whether d imethoxane’s use has “no effect or “may affect”

federally listed threatened or endangered sp ecies (listed species) or their designed critical

habitats. When an assessment concludes that a pesticide’s use “may affect” a listed species or its

designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service

and/or Nation al Marine Fisheries Services (the Services), as appropriate.

Environmental Fate and Ecotoxicity Data Gaps and Anticipated Work

Environmental fate and ecological risk assessments have not been conducted for

dimethoxane. The Agency needs to conduct enviro nmental fate and ecological risk assessments for

material preservatives that potentially pass through waste water treatment plants (WWTPs) and may

be discharged into terrestrial and aquatic environments. Therefore, the Agency anticipates needing

the propo sed environmental fate data for dimethoxane and/or any of its major degradation products

that are of potential concern for all registered uses of dimethoxane. The following environmental

fate data are needed to conduct an environmental fate and ecological risk assessment:

The Agency anticipates needing the following data to conduct a complete

environmental fate assessmen t for material preservative uses :

o (GLN 835.1110) A ctivat ed Sludge Sorption I sotherm; and

o (GLN 835.3110) R eady B iodegradability.Page 7 of 7



## Appendi x A. Environmental Fate Guideline Study J ustifications

Guideline Number: 835.1110

Study Title: Activated Sludge Sorption Isotherm

Practical Utility of the Data

1) What is the value of the study?

The results from activated sludge sorption study would a llow EPA to assess the distribution of the

antimicrobial among the solid, aqueous, and vapor phases of WWTPs. Specifically, this study identifies

those chemicals which sorb to sludge biomass.

2) How would the data be used?

The data would be used to deter mine the sorption potential of d imethoxane to activated sludge biomass

and in biological wastewater treatment systems.

3) How could the data affect the risk assessment?

If d imethoxane is not sorbed or biodegraded then, it would pass through a biological t reatment system

unaffected and it may contaminate surface and drinking waters and also may have potential adverse

effects to nontarget organisms.

4) What is triggering the need for this data?

Studies are needed to conduct environmental fate assessment and to determine the sorption potential of

activated sludge for the removal of specific chemical compounds in biological wastewater treatment

systems.

Guideline Number: 835.3110

Study Title: Ready Biodegradability

Practical Utility of the Data

1) What is the value of the study?

The ready biodegradability study would enable the Agency to determine the likelihood that the

antimicrobial pesticide of biodegrading in aquatic environments under aerobic conditions.

2) How would the data be used?

The results fro m the data would be used to determine the rate and extent of aerobic biodegradation of

dimethoxane when it is released into aquatic environments and would help establish if d imethoxane is

stable or not stable under real environmental conditions.

3) How co uld the data affect the risk assessment?

If the result shows low biodegradability then, d imethoxane would occur in significant quantities in

WWTP effluents (water and biosolids) and in environmental compartments (e.g., surface waters) such

that potential a dverse effects to nontarget organisms, found in such environmental compartments, may

occur.

4) What is triggering the need for this data?

Data are needed to conduct environmental fate assessment and to determine the ready biodegradability of

d imethoxane

.

Sign

- off Date: 11/23/10 DP Barcode No.: D382303