  SEQ CHAPTER \h \r 1 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF

PREVENTIN, PESTICIDES AND 

TOXIC SUBSTANCES



									PC Code: 069105, 069149

DP Barcodes: 325482, 325483

									

									Date: January 23, 2006

MEMORANDUM					

SUBJECT:	Tier I Drinking Water Assessment for alkyl* dimethyl benzyl
ammonium chloride *(50%C14, 40%C12, 10%C16) (ADBAC) and didecyl dimethyl
ammonium chloride (DDAC)

TO:		Jacqueline McFarland, Chemical Review Manager

		Regulatory Management Branch I

	Antimicrobials Division (7510C)

		

		Tracy Lantz, Chemical Review Manager

		Regulatory Management Branch I

	Antimicrobials Division (7510C)

		

		Matthew Lloyd, Risk Assessor

		Re-Registration Branch I

		Health Effects Division

FROM:	Marietta Echeverria, Environmental Scientist

		Environmental Risk Branch IV

		Environmental Fate and Effects Division

THROUGH:	R. David Jones, PhD, Senior Agronomist

		Environmental Risk Branch IV

		Environmental Fate and Effects Division

APPROVED	

BY:		Elizabeth Behl, Branch Chief

		Environmental Risk Branch IV

		Environmental Fate and Effects Division

Attached is the drinking water exposure assessment for the agricultural
uses ADBAC and DDAC for the re-registration eligibility decision.  If
additional refinements are necessary, please contact Marietta Echeverria
at 703-305-8578 or echeverria.marietta@epa.gov.	



								

Tier I Drinking Water Exposure Assessment for the Outdoor Uses for the
Re-registration of ADBAC and DDAC

						

						

Alkyl* dimethyl benzyl ammonium chloride *(50%C14, 40%C12, 10%C16)
(ADBAC) 

CAS No. 68424-85-1; 

Didecyl dimethyl ammonium chloride (DDAC) CAS No. 7173-51-5

Prepared by:

	Marietta Echeverria, Environmental Scientist

Environmental Risk Branch IV

	U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch IV

1200 Pennsylvania Ave., NW

Mail Code 7507C

Washington, DC 20460

Reviewed by:

R. David Jones, PhD, Senior Agronomist

Elizabeth Behl, Branch Chief

Environmental Risk Branch IV

Environmental Fate and Effects Division

	

Executive Summary	

	This document reports the drinking water exposure assessment for ADBAC
and DDAC that has been conducted to support the human health risk
assessment for the reregistration of ADBAC and DDAC outdoor uses.  As an
outdoor pesticide, ADBAC is used on nursery ornamentals, turf, and for
mosquito control in ponds and puddles and as an algaecide in decorative
pools.  The only DDAC outdoor use is as an algaecide in decorative
pools.  For the mosquito control use and the algaecide use on decorative
pools, the labels suggest that the use sites (water bodies) are
ornamental and periodic in nature and as such disconnected from the
larger watershed.  Therefore, for the purposes of this assessment these
uses were not considered potential sources of drinking water exposure. 
This assessment only considered the labeled turf and nursery uses for
ADBAC.  Foliar spray, drench and “dribble” applications are allowed.
 

	Tier 1 surface water and groundwater modeling was conducted for the
labeled nursery ornamental use (EPA Reg. No. 58044-3, 53642-1), which
represents the highest use rate of all labeled uses with an application
rate of 302 lbs. a.i./A and a maximum of 3 applications per year.  Since
the tier I models are not dependent on “crop” type, the EDWCs
determined for the nursery ornamental use are also protective of all
other uses with lower application rates.  The recommended estimated
drinking water concentrations (EDWCs) for the human health risk
assessment are in Table 1 and are based on the nursery ornamental use
pattern.  There were no major degradates of ADBAC in the laboratory
studies. 

Table 1. Tier I Estimated Drinking Water Concentrations (EDWCs) based on
aerial application of ADBAC on nursery ornamentals

Drinking Water Source (Model)	Use rate (lbs ai/A/year)	EDWC (ppb)

Surface water (FIRST)

Acute (peak)

Chronic (annual average)	906	

13,129

331

Groundwater (SCIGROW)	906	5.4



Problem Formulation

	This is a Tier I drinking water assessment that uses modeling and
available monitoring data to estimate the groundwater and surface water
concentrations in drinking water source water (pre-treatment) resulting
from pesticide use on sites that are highly vulnerable.  This initial
tier screens out chemicals with low potential risk and allows OPP to
focus resources on more refined risk assessments for chemicals which
potentially present more significant risks. This drinking water
assessment will report potential exposure concentrations for the human
health dietary risk assessment and provide a clear and transparent
description of how those concentrations were determined. 

Analysis

Use Characterization

ADBAC and DDAC are used primarily as antimicrobial agents; evaluation of
these uses can be found in the AD RED.  Additionally, ADBAC is used on
ornamental plants and shrubs, residential lawns and commercial turf and
golf course greens, tees and fairways.  Both ADBAC and DDAC are labeled
for use in puddles and decorative pools to control algae.  ADBAC is also
labeled for use as a mosquito larvicide in standing waters, including
decorative ponds and pools, inactive spas and hot tubs, as well as
‘old tires, empty tin cans, puddles and water drains around
buildings’ (RD 20 label).  Only the ADBAC/DDAC uses which could result
in potential environmental exposures to drinking water sources are being
evaluated in this assessment.  The target water bodies for the algaecide
and the mosquito control uses were assumed, as suggested on the label,
ornamental or periodic and disconnected from the larger watershed. 
Therefore, there were no DDAC uses considered in this assessment.  The
remaining ADBAC uses considered in this assessment are described below.

Turf and Golf Courses

Two ADBAC products are labeled for use on residential lawns, commercial
turf and golf courses, Consan and RD 20.  These uses control algal
build-up, and fungal diseases such as fusarium blight (Fusarium spp.),
brown patch (Rhizoctonia spp.), etc.  Smaller use sites, such as
residential lawns, are labeled for a rate of 790 ppm, one gallon of
solution per 40 sq. ft of lawn, which is equivalent to 6.8 lb ai/A. 
This rate is also allowable for golf courses and commercial
(nonagricultural) turf unless a commercial power sprayer is used.  If a
commercial power sprayer is used, the application rate is reduced to 512
ppm (1 pint of product in 50 gallons for 0.25 A), a rate of 0.82 lb
ai/A.  Presumably, as implied on the labels, smaller areas would be
treated at the higher rate, while larger-scale applications would be
treated at the lower rate.  

The product labels do not specify seasonal or yearly limits on the
number of applications or pounds per acre.  The label does specify 10-14
days between applications.  The label states applications should be made
during the warm growing season, so the number of applications may vary
depending on the geographic area where it is used.  Without a limit, a
hypothetical Florida golf course could apply ADBAC every ten days all
year long.  Without data indicating otherwise, this seems plausible
given the wide range of target organisms for which ADBAC controls
(semi-terrestrial alga species, numerous species of fungi).  However,
these organisms are generally only a big problem under warm wet
conditions, so some use sites may need appreciably fewer applications to
achieve desired control.  

Nursery Uses (bedding plants, ornamental shrubs and trees)

The products Timsen, Consan and RD 20 are all labeled for nursery uses
for the control of various fungal and bacterial pathogens that can cause
damage to ornamental plants.  In 2002, there were 68,214 acres of
floriculture (bedding/garden plants, cut flowers and cut florist greens,
foliage plants, and potted flowering plants) grown in open nurseries in
the US, on 14,579 nurseries (  HYPERLINK
"http://www.nass.usda.gov/census/"  www.nass.usda.gov/census/ ).  The
labels allow for use on a variety of herbaceous annuals, such as fuchsia
and snapdragons, as well as larger perennials such as ash and sycamore
trees.  Because different ornamental species have different pathogen
pressures, different rates are recommended for each pathogen targeted. 
For instance, palms needing protection from heart rot and penicillium
leaf base rot are treated with Consan at a concentration of 1563 ppm
while crepe myrtle and fruit trees being treated for fireblight are
treated at a concentration of 781 ppm.  Differences in amount of product
that will potentially be available for exposure to drinking water
sources depends on the quantity of solution applied.  The palm treatment
uses a small amount of solution poured into the ‘cup’ formed at the
base of the leaves, repeated weekly until control is achieved.  For
fireblight control, the entire tree is sprayed at two-week intervals,
with some phenological limitations (e.g., early spring and fall after
harvest; Consan label only).  For some larger ornamentals, such as ash
or sycamore, the label states that 50-60 gallons of solution (528 ppm)
may be required to achieve full coverage.  These applications can be
repeated up to three times, at intervals determined by leaf emergence
and development.  These treatments are equivalent to application of
0.004 lbs ai/gallon/treatment.  For this assessment, the maximum 60
gallons was assumed to be required per tree per treatment (0.25 lbs
ai/tree/treatment).  It was also assumed that the trees required 6’ x
6’ spacing.  Therefore, based on these assumptions the application
rate used in this assessment was 302 lbs ai/A (0.25 lbs
ai/tree/treatment x 1,210 trees/A).   

Environmental Fate and Transport Characterization

  SEQ CHAPTER \h \r 1 ADBAC is cationic and immobile in soil.  The
available soil mobility study shows that ADBAC has a strong tendency to
bind to sediment/soil with Freundlich Kads values were 6,172 for the
sand soil, 10,797 for the silt loam, 5,123 for the sandy loam soil, and
32,429 for the clay loam (MRID 424148-01).  There is no guideline data
for aerobic soil degradation of ADBAC.  Based on ADBAC’s vapor
pressure (3.5 x 10-12 torr) volatility is not expected.  Because of its
strong adsorption to soils, the potential to reach aquatic water bodies
via runoff or leaching is limited.  ADBAC may, however, be transported
off-site to aquatic water bodies as entrained sediment or via spray
drift during aerial, or ground spray applications.  Once in aquatic
environments, ADBAC is hydrolytically stable under abiotic and buffered
conditions over the pH 5-9 range (MRID 408356-02).  ADBAC is also stable
to photodegradation in pH 7 buffered aqueous solutions (MRID 408356-03).
 

	Aquatic metabolism studies under aerobic and anaerobic conditions
indicate that ADBAC is stable to microbial degradation.  ADBAC did not
degrade in flooded sand loam soil that was incubated at 24-27°C in the
dark for up to 30 days in an aerobic aquatic metabolism study (MRID
408356-04).  Under anaerobic conditions, ADBAC was found to be very
resistant to degradation with a calculated half-life of 1,815 days (MRID
424151-01).  However, a report on the biodegradability of ADBAC prepared
by the Registrant concluded that the degree of ADBAC 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.  This report was based on
information from the open literature, unpublished sources, and meeting
proceedings and has not been reviewed by the Agency.    

	

	Major degradates were not identified in any of the available studies. 
The environmental fate and physical-chemical properties, based on
submitted guideline studies, are summarized in Table 3.1.  Details of
individual studies can be found in the ADBAC Environmental Fate
Assessment conducted by the AD.  

Table 3.1 General fate and physical-chemical data for ADBAC.

Parameter	Value	Source

Molecular Weight	368.05	Product chemistry

Solubility (25º C)	18.44 mg/L	Product chemistry

Vapor Pressure (25º C)	3.53 x 10-12	Product chemistry

Hydrolysis Half-life (25º C)

  pH 5

  pH 7

  pH 9	

150 d

183 d

379 d	MRID 42242601

Aqueous Photolysis Half-life	stable	MRIDs 408356-03, 424152-01

Soil Photolysis Half-life	no data

	Aerobic Soil Metabolism Half-life	no data

	Aerobic Aquatic Metabolism Half-life	stable (sand loam)	MRIDs
408356-04, 424149-01

Anaerobic Aquatic Metabolism Half-life	1,815 d (sandy loam)	MRIDs
424151-01, 424150-02

Organic Carbon Partitioning Coefficient (Koc, L/kgoc)	  SEQ CHAPTER \h
\r 1 6.2 x 106, 2.2 x 106, 6.4 x 105, 1.7 x 106	MRID 424148-01

Soil Partitioning Coefficient (kd, L/kg)	  SEQ CHAPTER \h \r 1 6,172,
10,797, 5,123, 32,429	MRID 424148-01



Drinking Water Exposure Modeling			

Tier 1 modeling was used to estimate the drinking water exposure for use
in the dietary risk assessment of ADBAC/DDAC.  Following is a
description of the models used, the selection of the model input
parameters and a characterization of the output from these simulations. 

Models

	

	Tier 1 EDWCs for surface water were generated using FIRST, dated August
5, 2001.  FIRST is a screening model designed by the Environmental Fate
and Effects Division (EFED, 2001a) of the Office of Pesticide Programs
to estimate the concentrations found in drinking water from surface
water sources for use in human health risk assessment.  As such, it
provides upper bound values on the concentrations that might be found in
drinking water due to the use of a pesticide.  FIRST is a single event
model (one runoff event), but can account for spray drift from multiple
applications.  Spray drift (resulting in direct deposition of the
pesticide into the reservoir) is assumed to be 16% of the applied active
ingredient for aerial application, 6.3% for orchard air blast
application, and 6.4% for other ground spray application.  FIRST is
hardwired to represent the Index Reservoir, a standard water body used
by the Office of Pesticide Programs to assess drinking water exposure
(Office of Pesticide Programs, 2002).  It is based on a real reservoir,
Shipman City Lake in Illinois, that is known to be vulnerable to
pesticide contamination. The single runoff event moves a maximum of 8%
of the applied pesticide into the reservoir.  This amount can be reduced
due to degradation on the field and the effects of binding to soil in
the field.  FIRST also uses a Percent Cropped Area (PCA) factor to
adjust for the area within the watershed that is planted to the modeled
crop.  No PCA was used in this assessment since there are no standard
PCAs for non-agricultural crops such as nursery ornamentals.

	Tier 1 EDWCs for groundwater were generated with SCIGROW 2.3, dated
July 29, 2003 (EFED, 2001b).  SCIGROW is a regression model used as a
screening tool for ground water used as drinking water.  SCIGROW was
developed by regressing the results of Prospective Ground Water studies
against the Relative Index of Leaching Potential (RILP).  The RILP is
function of aerobic soil metabolism and the soil-water partition
coefficient.  The output of SCIGROW represents the concentrations that
might be expected in shallow unconfined aquifers under sandy soils.

Modeling Approach and Input Parameters

	A summary of the model input parameter values used in FIRST and SCIGROW
are presented in Tables 3.2 and 3.3, respectively.  These parameters
were selected in accordance with EFED’s input parameter guidance
(Environmental Fate and Effects Division, 2002).

	For the surface water and groundwater assessments, the application
rates for ornamental trees (302 lb a.i./A/application) was used, which
represents the maximum label rate across all uses.   This rate assumes a
tree spacing of 6’ x 6’ and a maximum application of 60 gallons per
tree (i.e., 0.25 lbs ai/tree/application and 1,210 trees/A).  Because
the Tier I models are not dependent on crop type, the EDWCs determined
for ornamentals are also protective of all other uses with lower
application rates (turf; golf courses).  

	Based on registrant-submitted data for ADBAC, aqueous photolysis,
aerobic soil metabolism and aerobic aquatic metabolism were assumed
stable for surface water modeling with FIRST.  The soil partitioning
coefficient used in FIRST was 5,123 L/kg, the lowest non-sand Kd of four
values and hydrolysis half-life was 183 d.  For groundwater modeling
with SCIGROW, aerobic soil metabolism was also assumed stable and the
median organic carbon partitioning coefficient, 1.95 x 106 L/kgoc, was
used.  This value for Koc is well outside the range for which SCIGROW
was developed.

Table 3.2 FIRST (v 1.0) input parameter values for ADBAC applied to
ornamentals by aerial application.

Parameter	Value	Source	Comments

Application Rate (lb a.i./A)	302	EPA Reg. No. 58044-3	Application rate
for ornamentals

Number of Applications	3	EPA Reg. No. 58044-3

	Interval between Applications (days)	7	EPA Reg. No. 58044-3

	Soil Partitioning Coefficient (Koc; L/kgoc)	6.4 x 105	MRID 42148901	
lowest non-sand value of four values

Aerobic Soil Metabolism Half-life (days)	0	no data	stable to aerobic
soil metabolism

Wetted in?	No	Aerially applied

	Depth of Incorporation (inches)	0	Aerially applied

	Method of Application	aerial spray	EPA Reg. No. 58044-3

	Percent Cropped Area (fraction)	1	Default	No PCA for nursery
ornamentals

Solubility in Water (mg/L)	18.4	Product chemistry

	Aerobic Aquatic Metabolism Half-life (days)	0	MRIDs 408356-04,
424149-01 	stable to aerobic aquatic metabolism

Hydrolysis Half-life (days)	183	MRID 42242601

	Aquatic Photolysis Half-life (days)	0

	MRIDs 46438203, 42419001	stable to aquatic photolysis

 			

Table 3.3  SCIGROW 2.3 input parameter values for ADBAC applied to
ornamentals.

Parameter	Value	Source	Comments

Maximum Application Rate (lb a.i./A/application)	302	EPA Reg. No.
58044-3

	Maximum Number of Applications per Year	3	EPA Reg. No. 58044-3

	Aerobic Soil Metabolism Half-life (days)	10,000	no data	stable to
aerobic soil metabolism

Organic Carbon Partition Coefficient (Koc, L/kgoc)	1.95 x 106	MRID
42148901	 median koc



Modeling Results

The FIRST and SCI-GROW output files are located in Appendix A.

	For use in the human health risk assessment, EFED recommends an acute
(peak) surface water EDWC of 13,129 µg/L and a chronic (annual mean)
EDWC of 331 µg/L, both based on the use of ADBAC on ornamentals at a
annual application rate of 906 lb a.i./A/year.  The recommended EWDC for
groundwater, also based on the use of ornamentals at the previously
stated rate, is 5.4 µg/L.  Because of ADBAC’s relative persistence
there is a potential for accumulation in water bodies with long
residence times.

	

Monitoring Data

There were no national-scale monitoring data available for this
assessment.  

Drinking Water Treatment

There is no available information on treatment effects on ADBAC in
drinking water.  ADBAC’s high sorption potential suggests that
treatment by flocculation/sedimentation and activated carbon could
result in decreased residues of ADBAC in treated drinking water.

Conclusions

	For groundwater, the empirical model, SCIGROW, was used.   SCIGROW is
based on 13 prospective groundwater studies performed in areas of high
leaching potential with chemicals with low Koc.  Because the Koc of
ADBAC is well outside the range of SCIGROW, the model simply returns a
default value concentration (5.4 µg/L).  For compounds with Koc values
over 10,000 ml/g, SCIGROW assumes 0.006 µg/L for every pound per acre
applied.  Because of ADBAC’s high partitioning coefficient, relative
non-persistence in aerobic soils, and demonstrated fate and transport in
the field, leaching to groundwater is not expected to be a major route
of dissipation. 

	The estimated concentrations provided in this assessment for are
conservative estimates of ADBAC concentrations in drinking water.  Major
sources of uncertainty include the assumptions used in deriving the
application rate and the appropriate percent cropped area for nursery
ornamentals.  The application rate was derived from the label-prescribed
maximum concentrations used for treatments, the maximum volumes of
product required for treatments, and an assumed tree spacing of 6’ x
6’.  Since there is no standard PCA for nurseries, this assessment is
based on the assumption that an entire 178-ha watershed consists of
nursery ornamentals (spaced 6’ x 6’) all of which are treated
simultaneously with ADBAC.  This is unlikely. 

	If dietary risks require refinement, higher tiered crop-specific and
location-specific models and modeling scenarios can be utilized upon
request.

Appendix A:   Input/Output Modeling Files

FIRST File

   RUN No.   1 FOR ADBAC            ON   ornamental    * INPUT VALUES * 

   --------------------------------------------------------------------

   RATE (#/AC)   No.APPS &   SOIL  SOLUBIL   APPL TYPE  %CROPPED INCORP

    ONE(MULT)    INTERVAL     Kd   (PPM )    (%DRIFT)     AREA    (IN)

   --------------------------------------------------------------------

302.000(906.000)   3   7    5123.0   18.4   AERIAL(16.0) 100.0      .0

   FIELD AND RESERVOIR HALFLIFE VALUES (DAYS) 

   --------------------------------------------------------------------

   METABOLIC  DAYS UNTIL  HYDROLYSIS   PHOTOLYSIS   METABOLIC  COMBINED

    (FIELD)  RAIN/RUNOFF  (RESERVOIR)  (RES.-EFF)   (RESER.)   (RESER.) 

   --------------------------------------------------------------------

       .00        2         183.00     .00-     .00     .00     183.00

   UNTREATED WATER CONC (MILLIGRAMS/LITER (PPM))    Ver 1.0 AUG 1, 2001

   --------------------------------------------------------------------

        PEAK DAY  (ACUTE)      ANNUAL AVERAGE (CHRONIC)      

          CONCENTRATION             CONCENTRATION            

   --------------------------------------------------------------------

             13.129                       .331

SCIGROW File 

                           SCIGROW

                          VERSION 2.3

            ENVIRONMENTAL FATE AND EFFECTS DIVISION

                 OFFICE OF PESTICIDE PROGRAMS

             U.S. ENVIRONMENTAL PROTECTION AGENCY

                        SCREENING MODEL

                FOR AQUATIC PESTICIDE EXPOSURE

 

 SciGrow version 2.3

 chemical:SDBAC

 time is  1/25/2006   9:28: 7

 -----------------------------------------------------------------------
-

  Application      Number of       Total Use    Koc      Soil Aerobic

  rate (lb/acre)  applications   (lb/acre/yr)  (ml/g)   metabolism
(days)

 -----------------------------------------------------------------------
-

    302.000           3.0         906.000      6.40E+05    10000.0

 -----------------------------------------------------------------------
-

 groundwater screening cond (ppb) =   5.44E+00*

 *Estimated concentrations of chemicals with Koc values greater than
9995 ml/g

 are beyond the scope of the regression data used in SCI-GROW
development.

 If there are concerns for such chemicals, a higher tier groundwater
exposure

 assessment should be considered, regardless of the concentration
returned

 by SCI-GROW.

 ***********************************************************************
*

References

Environmental Fate and Effects Division.  2001a.  FIRST (F)IFRA (I)ndex
(R)eservoir (S)creening (T)ool. Tier 1 Model for Drinking Water
Exposure: User's Manual.     HYPERLINK
"http://www.epa.gov/oppefed1/models/water/first_users_manual.htm" 
http://www.epa.gov/oppefed1/models/water/first_users_manual.htm 

Environmental Fate and Effects Division.  2001b.  SCI-GROW - (S)creening
(C)oncentration (I)n (GRO)und (W)ater: User's Manual.     HYPERLINK
"http://www.epa.gov/oppefed1/models/water/scigrow_users_manual.htm" 
http://www.epa.gov/oppefed1/models/water/scigrow_users_manual.htm 

Environmental Fate and Effects Division.  2002.  Guidance for Selecting
Input Parameters in Modeling the Environmental Fate and Transport of
Pesticides, Version II. U. S. Environmental Protection Agency.
Washington, D.C.      HYPERLINK "http://www.epa.gov/oppefed1/models/" 
http://www.epa.gov/oppefed1/models water/input_guidance2_28_02.htm/ 

Office of Pesticide Programs. 2000.  Part A. Guidance for Use of the
Index Reservoir in Drinking Water Assessments.     HYPERLINK
"http://www.epa.gov/oppfead1/trac/science/reservoir.pdf" 
http://www.epa.gov/oppfead1/trac/science/reservoir.pdf 

         

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