UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

                                                                        
                                    PREVENTION, PESTICIDES AND 

                                                                        
                                             TOXIC SUBSTANCES

					

July 31, 2006

MEMORANDUM  

                                                                        

	

SUBJECT:	Environmental Fate Assessment of Didecyl dimethyl ammonium
chloride (DDAC) for the Reregistration Eligibility Decision (RED)
Document

Case No.: 3003	DP Barcode: 323302

FROM:	Srinivas Gowda, Microbiologist/Chemist

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

TO:			Mark Hartman, Branch Chief

Diane Isbell, Team Leader

Najm Shamim, Risk Assessor

Regulatory Management Branch II

Antimicrobials Division (7510P)

Tracy Lantz, Chemical Review Manager

Regulatory Management Branch I

Antimicrobials Division (7510P)

THRU:	Siroos Mostaghimi, Team Leader, Team one

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Norman Cook, Branch Chief

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Chemical Name				PC Code	CAS#		Common Name

Didecyl dimethyl ammonium chloride	069149	7173-51-5	DDAC

	

Environmental Fate Science Chapter and Fate Assessment on DDAC is
submitted for Reregistration Eligibility Decision (RED).

1-DECANAMINIUM, N-DECYL-N,N-DIMETHYL-, CHLORIDE (DDAC)

ENVIRONMENTAL FATE SCIENCE CHAPTER

EXECUTIVE SUMMARY

	DDAC is used primarily as a disinfectant, sanitizer, or as a
microbiocide/microbiostat.  It also serves as an algaecide,
bacteriocide/bacteriostat, fungicide/fungistat, insecticide, miticide,
virucide, and tuberculocide.  Use sites for DDAC include agricultural
premises and equipment, food handling, commercial, industrial and
institutional settings, residential areas or areas of public access,
pets and kennels, medical facilities, swimming pools, aquatic areas, and
industrial water systems.   DDAC is also used as a wood preservative. 
As an agricultural pesticide, DDAC is used for ornamental plants,
shrubs, and vines.  Some of the required guideline studies for an
environmental fate assessment have been submitted.  The Agency is using
these environmental fate studies for fate assessment of DDAC to fulfill
the reregistration requirements.  However, field dissipation and aquatic
field dissipation studies as well as a long-term study on accumulation
on soils are still needed.

	DDAC has been shown to be hydrolytically stable under abiotic and
buffered conditions over the pH 5-9 range.  DDAC is stable to
photodegradation in pH 7 buffered aqueous solutions; even in the
presence of a photosensitizer (acetone), degradation is minimal.  DDAC
is not subject to photodegradation in soil.

	Aquatic metabolism studies under aerobic and anaerobic conditions
indicate that DDAC is stable to microbial degradation.  The calculated
aerobic and anaerobic half-lives of 14C-DDAC in flooded river water are
180 days and 261 days, respectively.  Similarly, DDAC was found to be
stable with very little degradation in aerobic soils during a year-long
metabolism study.  Based on the results of a biodegradability test
conducted using the CO2 evolution procedure, DDAC is not considered to
be readily biodegradable, although biodegradation was observed during
the 28-day test.  However, a report on the biodegradability of DDAC
prepared by the Registrant concluded that the degree of DDAC
biodegradability is variable and is influenced by the chemical
concentration, alkyl chain length, the presence of anionic moieties and
the quantity and characteristics of the microbial population.  
According to this report, DDAC is biodegradable and environmentally
acceptable.  This report was based on information from the open
literature, unpublished sources, and meeting proceedings and has not
been reviewed by the Agency.  

	DDAC is immobile in soil. A soil mobility study reviewed by the Agency
shows that DDAC has a strong tendency to bind to sediment/soil with
Freundlich Kads values of 1,095, 8,179, 32,791, and 30,851 in sand,
sandy loam, silty clay loam, and silt loam soils, respectively.  Because
of its strong adsorption to soils, DDAC is not expected to contaminate
surface and ground waters.

	Bioaccumulation of DDAC in freshwater fish is not likely to occur. 
Mean steady state bioconcentration factors for DDAC were determined to
be 38X, 140X, and 81X in the edible, nonedible, and whole body fish
tissue, respectively.  DDAC is not expected to pose a concern for
bioconcentration in aquatic organisms.

	Information on the aqueous availability of DDAC from wood indicates
that the use of DDAC as a wood preservative may result in minimal
releases to the environment.

I.	Environmental Fate Assessment

Abiotic

μg/ml, was stable in sterile aqueous buffer solutions adjusted to pH 5
(0.2 M acetate), pH 7 [tris(hydroxymethyl)aminomethane- (TRIS)], pH 7
[N-2-hydroxyethyl-piperazine-N’-2-ethanesulfonic acid (HEPES)], and pH
9 (0.2 M borate) that were incubated in darkness at 25C ± 1C for
30 days.  Of the recovered radioactivity throughout the 30-day
monitoring period, DDAC residues comprised 92.0 to 95.9% (pH 5), 89.9 to
94.5% (pH 7, HEPES), 93.1 to 97.9% (pH 7, TRIS), and 92.0 to 96.7% (pH
9).  The calculated half-lives for DDAC (extrapolated beyond the
experimental timeframe) were 368 days at pH 5, 194 days at pH 7 (TRIS),
175 days at pH 7 (HEPES), and 506 days at pH 9.  The hydrolysis
guideline requirements (OPP 161-1) have been fulfilled by this study
(MRID No. 411758-01).

μg/ml, was relatively stable in nonsensitized sterile aqueous buffer
solutions that were continuously irradiated with a xenon light source at
25C ± 1C for 30 days.  DDAC concentrations ranged from 91.2 to
103% of the applied radioactivity with no discernible pattern of
decline.  In the dark controls, DDAC concentrations ranged from 93.5 to
100% of the applied radioactivity throughout the 30-day monitoring
period.  In a similar experiment using acetone-sensitized buffer
solutions, DDAC was also found to be relatively stable.   DDAC declined
from 100% of the applied radioactivity immediately post treatment to
93.1% at the end of 30-day monitoring period.  DDAC concentrations
ranged from 96.2 to 102 percent of the applied radioactivity with no
discernible pattern of decline in the dark sensitized controls.  The
calculated half-life of DDAC (extrapolated beyond the experimental
timeframe) was 227 days based on results for the sensitized irradiated
solutions.  The photodegradation in water guideline requirements (OPP
161-2) have been fulfilled by this study (MRID 411758-02).

	

	B.	Biotic

The aerobic aquatic biotransformation of DDAC was studied in a pond
water/sediment system (water - pH of 8.7, sediment - pH of 8, sandy loam
texture, organic carbon content of 1.6%) from Northwood, North Dakota
treated with methyl-labeled [14C]DDAC at a nominal concentration of 10
parts per million (ppm).  The treated water/sediment system was
incubated in the dark for 365 days at 25C.   The calculated
half-lives of 14C-DDAC in water, sediment, and in the entire system were
180 days, 22,706 days (60.5 years), and 8,366 days (22.9 years),
respectively.  At test termination, 101% of the applied radioactivity
was partitioned from water to sediment.  Transformation products were
not present in any significant amounts in the water or sediment.  The
aerobic aquatic metabolism guideline requirements (OPP 162-4) have been
fulfilled by this study (MRID 422538-03).

A study of the anaerobic aquatic metabolism of DDAC in lake water and
sediment was also conducted.  Samples of lake water and sediment were
incubated at 25 C in a dark environment for 365 days.  In this study,
DDAC was shown to be stable to microbial degradation.  The calculated
half-lives, based on first-order degradations of 14C-DDAC in anaerobic
water, sediment and in the entire system were 261, 4,594, and 6,217
days, respectively.  Transformation products were not present in any
significant amounts in the water or sediment.  This study satisfies the
anaerobic aquatic metabolism guideline requirements (OPP 162-3) (MRID
No. 422538-02).

The aerobic soil metabolism of DDAC was investigated in a sandy loam
soil, which is a representative agricultural soil.  The soil was treated
with [14C]DDAC to achieve a concentration of 10 ppm and incubated in
darkness at 25C for up to 365 days.  DDAC was found to be stable with
very little degradation during the year-long study.  Transformation
products were not present in any significant amounts.  The calculated
half-life for degradation was 1,048 days.  This study is acceptable and
satisfies guidelines (OPP 162-1) for aerobic soil metabolism (MRID No
422538-01).

	A 28-day biodegradability study based on the CO2 evolution method (OECD
Test Guideline 301B) was conducted to determine the biodegradability of
DDAC in an aerobic aqueous medium.  DDAC at concentrations of 5 mg total
organic carbon (TOC)/L (BTC® 1010-E) and 10 mg TOC/L (MAKON® NF-5),
mineral nutrients, activated sludge from a local wastewater treatment
plant, and soil were incubated together in closed vessels and placed on
a magnetic stirrer under controlled conditions.  The quantity of carbon
dioxide emitted at various intervals during the study was used as a
measure of the rate of degradation.  The amount of carbon dioxide
produced by the microbial population during biodegradation of the test
substance (corrected for the value in the blank control) was expressed
as a percentage of the maximum theoretical quantity (ThCO2).   By the
4th day of observation, the degradation of both test compounds exceeded
10% of ThCO2.  However, the degradation of the test compounds was below
60% of ThCO2 within the 10-day window of reaching 10% biodegradation
(day 14).  Since the degradation of the test compounds did not meet the
“pass” criteria specified in the OECD 301B guidelines, the test
compounds are not considered to be readily biodegradable.   This study
was reviewed by the Agency and was found to be scientifically valid and
acceptable (MRID No. 468657-01).

A review of information from the open literature, unpublished sources
and meeting proceedings prepared by the Registrant indicates that DDAC
is aerobically biodegradable.  The report author noted that the aerobic
and anaerobic aquatic metabolism studies conducted on DDAC were designed
to assess the environmental fate of DDAC based on outdoor applications
of agricultural chemicals but not the direct biodegradability potential
of DDAC as a result of its use as an antimicrobial.  Other limitations
of the tests were noted such as loss of microbial activity during air
drying of soil material, limited gas exchange in the aerobic test, and
the use of unacclimated microbial systems.   According to this report,
the degree of DDAC’s biodegradability is variable and is influenced by
the chemical concentration, alkyl chain length, the presence of anionic
moieties and the quantity and characteristics of the microbial
population. 

A mechanism of biodegradation for DDAC in which several bacterial
species are needed for ultimate biodegradation of this compound is also
described.  This report has not been reviewed by the Agency. 

 

In an adsorption/desorption study reviewed by the Agency, DDAC was found
to be immobile in four representative agricultural soils (sand, sandy
loam, silt clay loam, and silt loam).  Freundlich Kads values were 1,095
for the sand, 8,179 for the sandy loam, 32,791 for the silty clay loam,
and 30,851 for the silt loam soils.  Respective Koc values were 437,805,
908,757, 1,599,564, and 1,469,081.  Freundlich Kdes values were 591 for
the sand soil, 2,074 for the sandy loam soil, 8,309 for the silty clay
loam soil, and 7,714 for the silt loam soil.  Respective Koc values were
236,473, 230,498, 405,328, and 367334.  This study (MRID No. 413853-01)
partially fulfills the adsorption/desorption data requirements for DDAC
(OPP 163-1) by providing information on the mobility (batch equilibrium)
of unaged 14C-DDAC in sodium azide-sterilized sand, sandy loam, silty
clay loam, and silt loam soils.  However, additional data are required
on the mobility of aged 14C-DDAC residues in soil.

	A 46-day study (28-day bioconcentration and 18-day depuration period)
was conducted to evaluate the bioconcentration of DDAC in bluegill
sunfish under flow-through aquarium conditions (MRID No. 458341-01).  In
this study, the levels of 14C residues in the edible, nonedible and
whole body fish tissue reached steady state by day 10 of exposure.  Mean
steady state bioconcentration factors for DDAC were 38X, 81X, and 140X
in the edible tissue, whole body fish tissue, and nonedible tissue,
respectively.  These bioconcentration factors are considered relatively
low and indicate that DDAC would not be expected to bioaccumulate in
fish tissue.  By day 14 of the depuration period, 57%, 67%, and 71% of
the 14C residues present on the last day of exposure in the edible,
whole body, and nonedible tissue, respectively, had been eliminated.
DDAC was found to bind significantly to the non-edible segments of the
bluegill, especially the skin and scales.  14C residue levels were
approximately 2 to 6 times higher in skin tissue than those observed for
the corresponding edible tissue.  The half-life of DDAC was determined
to be between 7 and 14 days of depuration.  Study results also indicated
that the half-life of DDAC in edible tissue is significantly shorter
than that of the nonedible segments.  The Agency noted that the
concentration of DDAC in the treatment aquarium was continuously above
nominal and was not consistently maintained within ± 20% of the mean
measured value. In addition, the temperatures ranged between 17-18 °C,
which is below the recommended temperature of 20-25 °C.   However, the
study was found by the Agency to be acceptable and provided useful
information on the bioaccumulation of DDAC residues in bluegill sunfish.
 It satisfies the bioaccumulation in fish data requirements for DDAC
(OPP 165-4/850.1730).

	A photolysis study was conducted with DDAC on soil treated at a nominal
concentration of 10 ppm.  The study consisted of two test systems: an
exposed test system that was continuously irradiated with a xenon arc
light source for 30 days and a non-exposed test system.  In the exposed
system, the photolysis rate constant and half-life of DDAC were reported
as 5.26 x 10-3 days-1 and 132 days, respectively.   The photolysis rate
constant and half-life of DDAC in the non-exposed system were determined
to be 4.11 x 10-3 days-1 and 169 days, respectively.   This study is
acceptable and meets guidelines for the fulfillment of data requirements
for DDAC on photodegradation on soil (OPP 161-3) (MRID No. 424807-01).

	An aqueous availability study (MRID No. 455243-05), performed according
to the American Wood Preservers’ Association Standard, Method E11-97,
evaluated the leachability of didecylmethyl ammonium carbonate
(DDACarb), a related compound, from treated wood.  Wood samples were
vacuum-treated with 0.85 percent (0.5X retention level), 1.7 percent
(1X), and 3.4 percent (2X) of DDACarb, and placed in deionized water for
14 days.  Leachate was collected from the sampling unit at intervals of
6, 24, and 48 hours, and 4, 6, 8, 10, 12, and 14 days following the
start of the leaching period.  The corrected amount of DDACarb recovered
from the leachate ranged from 186.1 µg to 764.7 µg (0.5X retention
level), from 218.9 µg to 1152.9 µg (1X), and from 446.2 µg to 2101.1
µg (2X).  The total recovery from the leachate over the 14-day period
was 3464.7 µg, 4483.0 µg and 7444.7 µg for the 0.5X, 1X and 2X
retention levels, respectively.  

APPENDIX

Environmental Fate Data for DDAC

A.	Environmental Fate Guideline Studies

	1.	Hydrolysis (OPP Guideline Number 161-1, MRID No. 411758-01)

	This hydrolysis study was reviewed by the Agency and was found
acceptable.  The hydrolysis data requirements for DDAC have been
fulfilled.

	In this study, methyl-labeled [14C]DDAC (didecyldimethylammonium
chloride, radiochemical purity 99.2%, specific activity 9.01 mCi/mmol),
in deionized, sterile-filtered water, was added to sterile pH 5
(acetate), pH 7 (TRIS), pH 7 (HEPES)  and pH 9 (borate) aqueous buffer
solutions at concentrations of 8.47-8.69 μg/ml.  Aliquots of the
treated buffer solutions were added to sterile, foil-covered culture
tubes and incubated in the dark at 25 ± 1C for 30 days.  Samples
were removed for analysis at 0, 4, 7, 14, 22, and 30 days post
treatment.

	At each sampling interval, duplicate aliquots of the buffer solutions
were analyzed for total radioactivity by liquid scintillation counting
(LSC).  An additional aliquot of the test solution was analyzed by
one-dimensional TLC on silica gel plates developed in
chloroform:methanol:formic acid (60:40:2, v:v:v).  Radioscanning was
used to locate and quantify radioactive areas.  TLC plates from the 0-
and 30-day sampling intervals were analyzed by autoradiography.

	Study results indicate that methyl-labeled [14C]DDAC was relatively
stable in sterile  pH 5, pH 7 (TRIS and HEPES), and pH 9 buffer
solutions incubated in the dark at 25 ± 1C for 30 days.  In the pH 5
buffer solution, the parent was present at 92.0% of the recovered
radioactivity at 30 days posttreatment (range during the study: 92.0 -
95.9% of the recovered radioactivity); total [14C]DDAC residues during
the study ranged from 8.22 μg/mL to 8.95 μg /ml with no discernible
pattern.  The parent comprised 89.9 - 94.5% and 93.1 - 97.9% of the
recovered radioactivity in the pH 7(HEPES) and pH 7 (TRIS) buffer
solutions, respectively.  Total [14C]DDAC residues during the study
ranged from 7.93 μg /ml to 9.02 μg /ml in the pH 7 (HEPES) buffer
solution and from 7.83 μg /ml to 8.90 μg /ml in the pH 7 (TRIS) buffer
solution .  In the pH 9 buffer solution, total [14C]DDAC residues ranged
from 8.00 μg /ml to 8.67 μg /ml with no discernible pattern; parent
[14C]DDAC comprised 92.0 - 96.7% of the recovered radioactivity.   The
material balances were 95.6 - 104% for the pH 5 solution, 93.6 - 106%
for the pH 7 (HEPES) solution, 90.1 - 102% for the pH 7 (TRIS) solution,
and 92.3 - 100% for the pH 9 solution.   

	The calculated half-lives for [14C]DDAC were 368 days at pH 5, 194 days
at pH 7 (TRIS), 175 days at pH 7 (HEPES), and 506 days at pH 9.  It was
noted that these statistical estimates are of limited value because the
calculations involve extrapolation considerably beyond the experimental
time limits of the study.  

	TLC analysis of the pH 7 (HEPES) solution at day 30 indicated a slight
decrease (approximately 10%) in the size of the parent peak; the
material appeared to form a shoulder on the parent peak.  However, given
the apparent half-life of 175 days and a low correlation coefficient (r2
= 0.575), the authors concluded that this observation did not indicate
significant degradation.  

	2.	Photodegradation in Water (OPP Guideline No. 161-2, MRID No.
411758-02)

	This photodegradation study was reviewed by the Agency and was found to
be acceptable.  The photodegradation in water data requirements for DDAC
have been satisfied.

	In this study, methyl-labeled [14C]DDAC (didecyldimethylammonium
chloride, radiochemical purity ≥ 98.5%, specific activity 9.01
mCi/mmol), in deionized water, was added to sterile pH 7 (TRIS) buffer
solution at a concentration of 8.58 µg/ml.  [14C]DDAC was also added at
a concentration of 8.59 µg /ml to a sterile pH 7 (TRIS) buffer solution
that had been photosensitized with 1% acetone.  Aliquots of the treated
solutions were transferred to borosilicate glass culture tubes with
Teflon-lined screw tops.  Some of the vials containing the test
solutions were covered with aluminum foil and stored inside a closed box
(dark control samples).  The box was placed along with unwrapped tubes
(12) in a photolysis apparatus.  A xenon lamp was used to continuously
irradiate the samples for 30 days.  The temperature in the photolysis
chamber was maintained at 25 ± 1C.  

	Aliquots of the test solutions were analyzed immediately post treatment
and duplicate samples of irradiated and dark control solutions were
removed for analysis at 1.03, 2.02, 7.03, 14.0, 21.0, and 29.9 days post
treatment.  At each sampling interval, duplicate aliquots of irradiated
and dark control solutions were analyzed for total radioactivity by
liquid scintillation counting (LSC).  Additional aliquots of each test
solution were analyzed by one-dimensional TLC on silica gel plates
developed in chloroform:methanol:formic acid (60:40:2, v:v:v). 
Radioactive areas were located and quantified by radioscanning.  In
addition, TLC plates from the 0- and 30-day sampling intervals were
autoradiographed.  The volatilization of [14C]  residues from the
irradiated and dark control samples was also measured. 

C ± 1C for 30 days.  In the irradiated samples, [14C]DDAC was
present at 100% of the applied radioactivity immediately post treatment 
and ranged from 91.2 to 103% of the applied radioactivity throughout the
study period (1.03 – 29.9 days).   [14C]DDAC was 93.5-98.9% of the
applied radioactivity from 1.03 – 29.9 days and was present at 100% of
the applied radioactivity immediately post treatment in the dark control
samples.

	In the irradiated sensitized samples, [14C]DDAC was present at 100% of
the applied radioactivity immediately post treatment and declined to
93.1% at 29.9 days.  An unidentified degradate was detected, but not
quantified.  In the dark controls, [14C]DDAC was 100% of the applied
radioactivity immediately post treatment  and 96.2-102% of the applied
radioactivity from 1.03 – 29.9 days.  The calculated photolytic
half-life was 227 days.

	Material balance ranged from 90.4 to 102%.  Results of the volatility
experiments indicated little or no volatilization of [14C]DDAC from the
test solutions.

	3.	Aerobic Soil Metabolism (OPP Guideline No. 162-1, MRID No.
422538-01)

	This aerobic soil metabolism study was reviewed by the Agency and found
to be acceptable.  The study meets guidelines for the fulfillment of
data requirements for DDAC on aerobic soil metabolism.  However, the
Agency stated that the Registrant must provide evidence that aerobic
conditions were maintained throughout the experiment.  

	In this study, samples of sandy loam soil (collected from Northwood,
North Dakota, 78% sand, 10% silt, 12% clay, 1.8% organic carbon, pH 6.3,
CEC 0.7 meq/100 g) were treated with methyl-labeled [14C]DDAC
(didecyldimethylammonium chloride, radiochemical purity 90%, specific
activity 9.01 mCi/mmol), at a nominal concentration of 10 parts per
million (ppm).  

The treated soil samples were incubated in darkness at 24-26C for up
to 365 days; soil moisture levels were maintained between 70% and 75% of
field moisture capacity by the addition of water as needed.  The test
system consisted of a standard tall form 3,000 ml resin-pot as the
incubation vessel and included an ethylene glycol trap, a sulfuric acid
trap and two potassium hydroxide traps vessels for trapping CO2 and
volatile organics.  Samples were analysed at 0, 1, 3, 7, 14, 31, 61, 92,
123, 182, 273, and 365 days of incubation. The soil samples were
extracted with 30 ml of 80:20 (v:v) dimethylformamide:acetic acid and
then shaken for 1 hour, followed by centrifugation for 10 minutes. 
Total radioactivity in the samples was determined by liquid
scintillation counting (LSC). Quantification and identification of the
14C-DDAC residues was performed using TLC and/or HPLC.  

Material balance averaged 100.5 ± 4.1% of the applied amount. The
concentration of the parent compound decreased from a mean of 93.7% of
the applied amount at day 0, to a mean of 72.85% of the applied amount
at the end of the study period. However, no biotransformation of the
parent compound was reported.  The calculated half-life of 14C-DDAC in
aerobic soil was 1,048 days.  

	Extractable 14C-residues decreased from a mean of 98.55% of the applied
amount at day 0 to a mean of 74.87% of the applied amount at the end of
study period.  Non-extractable 14C-residues increased from a mean of
1.45% of the applied amount at day 0 to a mean of 17.74% of the applied
at the end of the incubation period.  At study termination, an average
of 1.95% of the applied radioactivity was present as volatile organics.
CO2 was not present in any significant amount.  Transformation products
were not present in any significant amounts in the water or sediment.

	4.	Anaerobic Aquatic Metabolism (OPP Guideline No. 162-3, MRID No.
422538-02)

	This anaerobic aquatic metabolism study was reviewed by the Agency and
was found acceptable.  It fulfills the anaerobic aquatic metabolism data
requirement for DDAC; however the Agency noted that the Registrant must
submit information describing how anaerobic conditions were assured and
maintained.

	The anaerobic aquatic metabolism of DDAC was studied using subsamples
(10 g dry weight) of sieved (2 mm) sandy loam sediment from Northwood,
ND (62% sand, 22% silt, 16% clay, pH 8, CEC 16.3 meq/100g, organic
carbon 1.6%) flooded with 20 ml of lake water from the same site (pH
8.1).   The sediment water samples were treated with a sufficient amount
of methyl-labeled [14C]DDAC (didecyldimethylammonium chloride,
radiochemical purity 90%, specific activity 9.01 mCi/mmol), to achieve a
nominal concentration of 10 parts per million (ppm).  The test tubes
were incubated in the dark at a temperature of 25 °C for 365 days; the
test system consisted of a standard tall form 3000-ml resin-pot as the
metabolism vessel.  An ethylene glycol trap, a sulfuric acid trap and
two potassium hydroxide traps were attached for the collection of carbon
dioxide (CO2) and volatile organic compounds.  Sediment, water and
volatile traps were sampled at 0, 1, 3, 7, 14, 31, 61, 92, 123, 182,
273, and 365 days of incubation.  Volatile traps were also sampled at
151, 212, 243, 304 and 335 days of incubation. 

At each sampling interval, sediment:water samples were centrifuged and
the aqueous phase decanted.  The water samples were extracted via mixing
with an equal volume of 80:20 (v:v) dimethylformamide:acetic acid and
then run through a 0.2- filter to remove any suspended solids.  The
sediment samples were extracted with 30 ml of 80:20 (v:v)
dimethylformamide:acetic acid and then shaken for 1 hour, followed by
centrifugation for 10 minutes.  Quantification and identification of the
14C-DDAC residues was performed using TLC and/or HLPC.

Material balance averaged 103.1 ± 3.5 % of the applied amount for the
year-long study.  The test conditions outlined in the study protocol
were maintained throughout the study.  Extractable [14C]residues in
sediment increased from a mean of 84.87 % at day 0, to a mean of 92.22 %
of the applied amount, at study termination.  Non-extractable
[14C]residues in sediment decreased from a mean of 12.21 % at day 0, to
a mean of 10.39 %  of the applied amount, at study termination.  At the
end of the study, 0.30 % of the applied radioactivity was present as
volatile compounds, and this activity was later confirmed to be
14C-carbon dioxide via precipitation with barium chloride.

The concentration of 14C-DDAC in water decreased from a mean of 100 % at
day 0 to a mean of 68.65 % of the applied amount, at study termination. 
The concentration of 14C-DDAC in the sediment increased from a mean of
93.85 % at day 0 to a mean of 97.45 % of the applied amount, at the end
of the study period.  The study authors noted that transformation
products were not present in any significant amounts in the water or
sediment.

The calculated half-life of 14C-DDAC (for the entire system), based on a
first-order degradation, was 6,218 days.  The Agency’s calculated
half-lives, based on first-order degradations of 14C-DDAC in anaerobic
water, sediment and in the entire system were 261, 4,594, and 6,217
days, respectively.  No biotransformation of the parent compound was
reported.

	5.	Aerobic Aquatic Metabolism (OPP Guideline No. 162-4, MRID No.
422538-03)

	This aerobic aquatic metabolism study was reviewed by the Agency and
was found to be acceptable.  It satisfies the aerobic aquatic metabolism
data requirements for DDAC.  However, the Agency noted that the
Registrant must submit information describing how aerobic conditions
were assured and maintained.

	In this study, subsamples (10 g dry weight) of sieved (2 mm) sandy loam
sediment from Northwood, ND (62% sand, 22% silt, 16% clay, pH 8, CEC
16.3 meq/100g, organic carbon 1.6%) were weighed into culture tubes and
flooded with 20 ml of lake water from the same site (pH 8.7).   The
sediment was treated with a sufficient amount of methyl-labeled
[14C]DDAC (didecyldimethylammonium chloride, radiochemical purity 98.5
± 0.04%, specific activity 9.01 mCi/mmol), to achieve a nominal
concentration of 10 parts per million (ppm).  The test tubes were
incubated in the dark at 25C for 365 days; the test system consisted
of a standard tall form 3000-ml resin-pot as the metabolism vessel.  An
ethylene glycol trap, a sulfuric acid trap and two potassium hydroxide
traps were attached for the collection of carbon dioxide (CO2) and
volatile organic compounds.  Sediment, water and volatile traps were
sampled for analysis at 0, 1, 3, 7, 14, 31, 61, 92, 123, 182, 273, and
365 days of incubation.  Volatile traps were also sampled at 151, 212,
243, 304 and 335 days of incubation. 

	At each sampling interval, sediment:water samples were centrifuged and
the aqueous phase decanted.   Before analysis by thin layer
chromatography (TLC), the 6-, 9-, and 12-month water samples were
concentrated by evaporating aliquots to dryness and redissolving in
methanol.  The other water samples were not concentrated prior to
analysis.  The sediment samples were extracted with 30 ml of 80:20 (v:v)
dimethylfomamide (DMF):acetic acid and then shaken for 1 hour, followed
by centrifugation for 10 minutes.  Quantification and identification of
the 14C-DDAC residues was performed using TLC and/or high performance
liquid chromatography (HLPC).

The material balance averaged 105 ± 2.8 % of the applied amount for the
year long study.  The mean total recovery of the radiolabelled material
applied was 1.5 ± 0.9% for water and 101.9 % for sediment (93.0 ± 4.4%
for extractable residues and 8.9 ± 3.3% non-extractable residues).  
The concentration of 14C-DDAC in water decreased from 2.20 % at day 0,
to 0.83% of the applied at study termination. The concentration of
14C-DDAC in the sediment increased from 86.0% at day 0 to 87.8% of the
applied, at the end of the study period.  At test termination, 101% of
the applied radioactivity was partitioned from water to sediment. 
Transformation products were not present in any significant amounts in
the water or sediment.

Extractable [14C]residues in sediment decreased from an average of 90.0
% at day 0, to 89.9 % of the applied amount at the end of incubation
period.  Non-extractable [14C]residues in sediment increased from 7.8%
at day 0,  to 11.3%  of the applied amount, at study termination.  At
the end of the study, 4.5 % of the recovered radioactivity was present
as volatiles.  The volatiles were determined to be 14C-carbon dioxide
via precipitation with barium chloride. 

As determined by the Agency, the half-lives of 14C-DDAC in water,
sediment, and in the entire system were 180 days, 22,706 days (60.5
years), and 8,366 days (22.9 years), respectively.  The Registrant
calculated a half-life of 8,365 days for 14C-DDAC in the entire system. 
The pathway of aerobic biotransformation of 14C-DDAC in water-sediment
system was not described.

	6.	Adsorption/Desorption (OPP Guideline No. 163-1, MRID No. 413853-01)

	This adsorption/desorption study was reviewed by the Agency and found
scientifically valid.  This study partially fulfills the
adsorption/desorption data requirements for DDAC by providing
information on the mobility (batch equilibrium) of unaged 14C-DDAC in
sodium azide-sterilized sand, sandy loam, silty clay loam, and silt loam
soils.  Additional data are required on the mobility of aged 14C-DDAC
residues in soil.

C, the soil:solution slurries were centrifuged and triplicate
aliquots of the supernatant were analyzed for total radioactivity by
liquid scintillation counting (LSC).

	For the desorption phase of the study, pesticide-free 0.01N CaCl2
solution (equal to the volume removed in the adsorption phase) was added
to the soil pellets from the adsorption phase of the study.  The
soil:solution slurries were again equilibrated for 24 hours at
approximately 25 ± 1C in the dark.  Following equilibration, the
soil:solution slurries were centrifuged and triplicate aliquots of the
supernatant were analyzed for total radioactivity by LSC.   

	The sandy loam, silty clay, and silt loam samples were dried and
analyzed for total radioactivity by LSC following combustion.  The sand
soil samples were extracted three times with dimethylformamide:acetic
acid (80:20).  Following extraction, the samples were centrifuged and
aliquots of the supernatant were analyzed by LSC.  Subsamples of the
extracted soil were analyzed by LSC following combustion.  

C ± 1C for 24 hours.  Freundlich Kads values were 1,095 for sand,
8,179 for the sandy loam, 32,791 for the silty clay loam, and 30,851 for
the silt loam soils.  Respective Koc values were 437,805, 908,757,
1,599,564, and 1469081.  

	Study results for the desorption phase indicate that 16.26 to 39.33% of
the absorbed radioactivity was desorbed from the sand soil, 2.20 to
12.60% was desorbed from the sandy loam soil, 0.20 to 1.40% was desorbed
from the silty clay loam soil, and 0.20 to 1.66% was desorbed from the
silt loam soil.  Freundlich Kdes values were 591 for the sand soil,
2,074 for the sandy loam soil, 8,309 for the silty clay loam soil, and
7,714 for the silt loam soil.  Respective Koc values were 236,473,
230,498, 405,328, and 367334.  

	Material balances were 88.5 - 108.1% for the sand soil, 91.6 - 108.5%
for the sandy loam soil, 78.3 - 106.5% for the silty clay loam soil, and
80.8 - 118.0% for the silt loam soil.

	7.	Field dissipation study on soil (OPP Guideline No. 164-1)

	A field dissipation study on soil is required for DDAC.  No data have
been submitted to the Agency.

Aquatic field dissipation study (OPP Guideline No. 164-2) 

	

An aquatic field dissipation study is required for DDAC.  No data have
been submitted to the Agency.

9.	Long-term study on accumulation on soil (OPP Guideline No. 164-5).

 	A long-term study on accumulation on soil is required for DDAC if
pesticide residues do not readily dissipate in soil.  No data have been
submitted to the Agency.

.

	10.	Bioaccumulation in Fish (OPP Guideline No. 165-4, MRID No.
458341-01)

	This bioaccumulation study was reviewed by the Agency and found
scientifically valid.  It satisfies the bioaccumulation in fish data
requirements for DDAC.  

	In this study, Bluegill (220) were continuously exposed to a nominal
concentration of 59 μg/L of DDAC for 28 days in an exposure aquarium. 
A control aquarium was also used which had the same conditions as the
treatment aquarium.   Water samples were collected from a central point
in the treatment aquarium on days 0, 3, 4, 10, 11, 17, and 24 of
exposure.  Five fish were collected for tissue analysis from the
treatment aquarium on days 4, 10, 17, 24, and 28 of exposure.  Water
samples and fish were collected from the control aquarium for
14C-residues on days 0 and 28 of exposure.  

	Following a 28-day exposure period, 40 of the fish remaining in the
exposure aquarium were transferred to an aquarium containing untreated
dilution water for an 18-day depuration period.  Water samples were
collected during the depuration period on days 3, 7, 12, and 18.   Five
fish were collected on days 3, 7, 14, and 18 of the depuration phase. 
Water samples and fish were collected from the control aquarium on day
18 of depuration for 14C-residues. 

μg/L (± 32) DDAC.  Concentrations of 14C-residues present in the
depuration aquarium remained at <11 μg /L throughout the 18 days.  The
levels of 14C-residues in the edible, non-edible, and whole tissue of
bluegill exposed to DDAC reached steady state by day 10.  The mean
steady state bioconcentration factor for DDAC in the edible, nonedible
and whole body tissue of the bluegill were determined by the authors to
be 38X, 140X and 81X, respectively.  The half-life of the 14C-residues
present in all tissue portions of the bluegill were found to be between
7 and 14 days.  The elimination of 14C-residues for edible, nonedible
and whole body tissue was 38%, 66% and 56%, respectively. Of the
accumulated 14C-residues in the edible tissue of bluegill exposed 28
days to DDAC, 65.5% was extractable with a polar solvent (methanol),
8.1% was extractable with a non-polar solvent (hexane), and 25.9% was
not extractable with either solvent.  Analysis of skin tissue after 28
days of exposure displayed that 14C-residue levels were approximately 2
to 6 times higher than those observed for the corresponding edible
tissue.  Analytical results for QA samples analyzed concurrently with
water samples during the exposure and depuration period resulted in a
mean recovery (standard deviation) of 91 ± 5.93 percent.  Analyses of
the QA samples analyzed with the tissue samples during exposure and
depuration resulted in a mean recovery (standard deviation) of 88.7 ±
6.29 percent.

μg /L).  The temperature recommended for testing bluegill is 20-25 °C.
 In this study, the temperatures ranged between 17-18 °C. 

	The study authors concluded that 14C-residues reached steady state by
day 10 of exposure.  They found that the bioconcentration factor of
14C-residues in edible tissue of bluegill was much lower (38X) than that
of the nonedible tissues (140X) and also found that DDAC binds
significantly to the non-edible segments of bluegill, and especially to
the skin and scales.  The study results indicated that the half-life of
DDAC in the edible tissue of the bluegill is significantly shorter than
that of the nonedible segments.

	11.	Photolysis Rate on Surface of Soil (OPP Guideline No. 161-3, MRID
No. 424807-01)

	This study was reviewed by the Agency and was found to be
scientifically valid and acceptable.   The study meets guidelines for
the fulfillment of data requirements for DDAC on photodegradation on
soil.

C.  The rest of the vials were not exposed to the xenon arc light
source.   One exposed and one non-exposed test sample were removed from
the photolysis chamber on days 1, 3, 7, 14, 21, and 30.  Each vial was
extracted with aliquots of 80:20 (v:v) dimethylformamide:acetic acid. 
Thin layer chromatography (TLC)/autoradiography/liquid scintillation
counting (LSC) were used to measure 14C-DDAC and potential photolysis
products.  

	For both exposed and non-exposed test systems, the mean 14C-mass
balance was 104%.  The parent compound was the only radioactive
component obtained in the test samples when analyzed by TLC and HPLC. 
In the exposed system, the photolysis rate constant and half-life of
DDAC were reported by the study authors as 5.26 x 10-3 days-1 and 132
days, respectively.   The photolysis rate constant and half-life of DDAC
in the non-exposed system were determined to be 4.11 x 10-3 days-1 and
169 days, respectively.   

	Soil bound residues increased from 9.48% of the dose at day 0 to 25.5
and 20.9% in the exposed and non-exposed test systems, respectively. 
The nature of these bound residues was investigated by HPLC analysis of
the extracts from composites of reserve day 30 soil samples from both
systems.  The analytical results indicated the presence of the parent
compound and no significant degradation products.  

	12.	Ready Biodegradability (CO2 Evolution Test) (OECD Procedure 301 B,
MRID No. 468657-01)

	This study was reviewed by the Agency and was found to be
scientifically valid and acceptable.  

	The purpose of this study was to determine the biodegradability of DDAC
(BTC® 1010-E and MAKON® NF-5) in water by the carbon dioxide evolution
method using OECD Test Guideline 301B.  Mineral nutrients, activated
sludge from a local wastewater treatment plant, soil, and the test
material were incubated together in closed vessels and placed on a
magnetic stirrer under controlled conditions for 28 days.  Nine test
vessels were used: 2 for each test substance, two blank controls, one
sodium benzoate procedural (positive) control and two toxicity controls.
 The test substance concentration was 5 mg C/L in the BTC® 1010-E test
substance vessels and 10 mg C/L in the MAKON® NF-5 test substance
vessels.  Sodium benzoate stock solution was also added to the toxicity
control replicate vessels for a total fortification concentration of 20
mg C/L (10 mg C/L test substance and 10 mg C/L reference substance) for
the MAKON® NF-5 toxicity control vessel and 15 mg C/L (5 mg C/L test
substance and 10 mg C/L reference substance) for the BTC® 1010-E
toxicity control vessels.  The procedural control was fortified with the
sodium benzoate stock solution for a final concentration of 10 mg C/L. 
The quantity of carbon dioxide emitted was used as a measure of the rate
of degradation.  Measurements were taken on days 2, 4, 7, 7, 10, 14, 18
and 22.  The amount of carbon dioxide produced by the microbial
population during biodegradation of the test substance (corrected for
the value in the blank control) was expressed as a percentage of the
maximum theoretical quantity (ThCO2).   

	The reported mean cumulative CO2 for the BTC® 1010-E test vessels and
toxicity control at day 28 was 52.42 and 79.93 mg/L respectively.  The
cumulative net percent CO2 production (blank control values subtracted)
or percent ultimate biodegradation for BTC® 1010-E and toxicity control
was calculated to be 82.89 and 77.64%, respectively. The reported mean
cumulative CO2 value calculated for MAKON® NF-5 test vessels and
toxicity control at day 28 was 51.65 and 79.82 mg/L, respectively.  The
cumulative net percent CO2 production (production from blank subtracted)
or percent ultimate biodegradation for MAKON® NF-5 and toxicity control
was calculated to be 39.35 and 58.08%, respectively.  

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㄀Ĥ摧䋦#ᄀdegradation for BTC® 1010-E and MAKON® NF-5 was 31.55%
and 11.38% on day 4, respectively.  On day 14, the mean percent
biodegradation for BTC® 1010-E and MAKON® NF-5 was 52.23% and 26.76%,
respectively.  Since the guidelines specify that the test material must
exhibit greater than 60% biodegradation within a 10-day window (the 10
days immediately following the attainment of 10% biodegradation), the
test compounds are not considered to be readily biodegradable.  

	13.	Aqueous Availability (Leachability) (American Wood-Preservers’
Association Standard Method E11-97 “Standard Method for Determining
the Leachability of Wood Preservatives, MRID No. 455243-05) 

	This study was reviewed by the Agency based on the standards specified
by the American Wood-Preservers’ Association Standard Method E11-97
and found to be acceptable.  The study was submitted by Lonza Inc. to
fulfill the requirements for registration of the product, Bardac 22C50,
EPA File Symbol 6836-EGA.  Bardac 22C50 consists of two active
ingredients: didecylmethyl ammonium carbonate (DDACarb) and didecyl
ammonium bicarbonate, both of which are similar in structure to DDAC. 

The test material used in the study was Bardac 22C, which contained
51.7% of the active ingredient DDACarb.  The purpose of this study was
to determine the leach rate of DDACarb from a sample of treated wood in
deionized water using high performance liquid chromatography (HPLC).  

	Southern pine wood blocks (19.0 ± 0.2 mm) were vacuum treated with
0.85 percent, 1.7 percent, and 3.4 percent of Bardac 22C (based on the
active ingredient DDACarb).  After treatment, the blocks were subjected
to a post-treatment fixation for 7 days followed by conditioning for 28
days in an environment producing a moisture content of 9 to 10 percent. 
After conditioning, the blocks were vacuum-treated with deionized water
and placed in additional deionized water for 14 days.

	Leach rates of DDACarb from wood blocks were determined by removing the
leachate from the sampling unit at intervals of 6, 24, and 48 hours, and
4, 6, 8, 10, 12, and 14 days following the start of the leaching period.
 The leachate was extracted with aqueous tetramethylammonium chloride
(TMAC) and methylene chloride and analyzed by HPLC.  After 14 days of
leaching, the wooden blocks were extracted with acetonitrile and aqueous
TMAC and analyzed by HPLC.

	The corrected amount of DDACarb recovered from the leachate ranged from
186.1 µg to 764.7 µg (0.5X retention level), from 218.9 µg to 1152.9
µg (1X), and from 446.2 µg to 2101.1 µg (2X).  The total recovery
from the leachate over the 14-day period was 3464.7 µg, 4483.0 µg and
7444.7 µg for the 0.5X, 1X and 2X retention levels, respectively.  For
all three retention levels, the leachability of DDACarb declined
continuously over the 14-day period with the exception of the leaching
rate of the 2X retention level, which began lower than the other two
retention levels (160.4 µg), significantly increased at Day 1 (2101.1
µg), and decline gradually through Day 14 (496.8 µg).  The total
amount of DDACarb recovered from the leachate and the wood blocks
combined were 176,983.0 µg (101.8%), 286,606.6 µg (99.5%), and
542,370.3 µg (104.9%) for the 0.5X, 1X and 2X retention levels,
respectively.  

	American Wood Preservers’ Association Standard, Method E11-97:
“Standard Method of Determining the Leachability of Wood Preservatives
was generally followed; however, an issue of concern was that the study
did not report running spike samples along with the test samples during
HPLC analysis.  Rather, the samples were corrected using average
validated extraction recoveries of 92.1 percent from three different
fortification levels with seven replicates per level.

BIBLIOGRAPHY

   MRID                                                    Citation     
                                                                     	  
                  

411758-01	Dykes, J. and M. Fennessy. 1989.  Hydrolysis of  
Didecyldimethylammonium chloride (DDAC) as a function of pH at 25 °C. 
Final Report #37004.  Unpublished study prepared by Analytical
Bio-chemistry Laboratories, Inc.  

411758-02	Dykes, J. and M. Fennessy. 1989.  Determination of the
Photolysis Rate of Didecyldimethylammonium chloride (DDAC) in pH 7
Buffered solution at 25 °C.  Final Report #37005.  Unpublished study
prepared by Analytical Bio-chemistry Laboratories, Inc.  

413853-01	Daly, D.  1989.  Soil/Sediment Adsorption-desorption of
[14C]Didecyldimethylammonium chloride (14C-DDAC).  Lab Project Number
37009.  Unpublished study prepared by Analytical Bio-Chemistry
Laboratories.

422538-01	Cranor, W.  1991.  Aerobic Soil Metabolism of
[14C]Didecyldimethylammonium chloride (14C-DDAC).  Final Report.  Lab
Project Number 37006.  Unpublished study prepared by ABC Laboratories.

422538-02	Cranor, W.  1991.  Anaerobic Aquatic Metabolism of
[14C]Didecyldimethylammonium chloride (14C-DDAC).  Final Report.  Lab
Project Number 37007.  Unpublished study prepared by ABC Laboratories.

422538-03	Cranor, W.  1991.  Aerobic Aquatic Metabolism of
[14C]Didecyldimethylammonium chloride (14C-DDAC).  Final Report.  Lab
Project Number 37008.  Unpublished study prepared by ABC Laboratories.

424807-01	1992.  Schmidt, J.  Determination of the Photolysis Rate of
Didecyldimethylammoniumchloride on the Surface of the Soil.  Final
Report # 39505.  Unpublished study prepared by ABC Laboratories.  

455243-05	2001.  Bestari, K.  Determination of the Leachability of
Bardac 22C from Treated Wood.  Centre for Toxicology, University of
Guelph, Guelph, Ontario N1G 2W1, Canada. 

458341-01	1990.  Fackler, P.H., E. Dionne, D.A. Hartley, and S.P.
Shepherd.  Bioconcentration and Elimination of 14C- Residues by Bluegill
(Lepomis macrochirus) Exposed to Didecyldimethylammonium Chloride
(DDAC).  Final Report.  Study No.  11696.0887.6104.140. Unpublished
study prepared by Springborn Laboratories, Inc.

468657-01	Gledhill, W. E.  2006.  BTC® 1010-E and MAKON® NF-5 –
Determination of the Biodegradability of a Test Substance Based on OECD
Method 301 B (CO2 Evolution Test).  Laboratory Study No. 13039.6128. 
Unpublished study performed by Springborn Smithers Laboratories,
Wareham, Massachusetts.   

	Lee, C.  1992.  Assessment of the Biodegradability of ADBAC and DDAC. 
Unpublished report prepared by Roy F. Weston, Inc.   Contractor’s Fate
Summary 

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