	UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

	WASHINGTON, D.C.  20460

						

                                                                        
     

						

					

					

	

					September 30, 2007

										

MEMORANDUM

SUBJECT:		Revised Environmental Exposure Assessment for Releases of
BUSAN 77 from Once-through Cooling Water Systems 

From:				Siroos Mostaghimi, Senior Scientist

					Risk Assessment and Science Support Branch (RASSB)

					Antimicrobials Division (7510P)

			

		

To:				Norm Cook, Chief

					Risk Assessment and Science Support Branch (RASSB)

					Antimicrobials Division (7510P)

Chemical Name:  Poly [oxyethylene(dimethylminino)
ethylene(dimethyliminio)ethylene dichloride]

Cas Registry Number:  31512-74-0

Pesticide Chemical No.: 069183

Registrant: Buckman Laboratories	

																

 

	This memorandum presents an environmental exposure assessment for
releases of Poly [oxyethylene(dimethylminino)
ethylene(dimethyliminio)ethylene dichloride] (BUSAN 77) used for control
of mollusks in once-through cooling water systems.  The Probabilistic
Distribution Model (version 4) was used to estimate the number and
percentage of days per year with BUSAN 77 concentrations exceeding
ecotoxicity benchmarks of concern.   Analyses were performed for six
BUSAN 77 treatment scenarios derived from product label information. 
The approach used for this assessment is based on the methodology
developed in support of the environmental exposure assessment for
bromonitrostyrene.

1. 	Methodology

	Components of the methodology described in this section include the
probabalistic distribution model (PDM), BUSAN 77 application rates,
environmental exposure concentrations of concern (COCs), model
facilities and flow data, and modeling scenarios.

1.1 	PDM Model

PDM is a screening-level exposure assessment tool developed by EPA to
model chemical releases from point sources to flowing surface waters. 
For this analysis, the PDM component within EPA’s Exposure and Fate
Assessment Screening Tool Version 2.0 (E-FAST2) were used.   

PDM uses detailed U.S. Geological Survey (USGS) stream flow data and
facility-specific data from National Pollutant Discharge Elimination
System (NPDES) permits to model chemical releases from actual
facilities.  For a modeling period of a given number of days, PDM
calculates probability distribution of the chemical concentration in the
receiving stream, and then estimates the number of days during which the
in-stream chemical concentration is expected to exceed a COC.  PDM
counts a day as having an exceedence of a COC if the COC is exceeded for
any part of a 24-hour day.  As a screening-level model, PDM outputs do
not include the duration, location, or aerial extent of exceedences.

Inputs to PDM include facility NPDES number, pretreatment release (i.e.,
loading rate), post-treatment release, number of release days, and COCs.
 Input values and assumptions used for this analysis are discussed
below.  

1.2 	BUSAN 77 Application Rates

Product labels were reviewed to identify application rates for the
analysis.  Application instructions were identified specifically for
mollusk control in once-through industrial cooling water systems. 
Treatment instructions from the product labels are summarized in Table
1.  Control of mollusks may be achieved by either an intermittent or a
continuous application.  A single application scenario based on the
highest dosage provided on the product labels was developed.  The
application scenario consisted of continuous treatment using the highest
product dosage.  For both products listed in Table 1, the maximum
application rate of active ingredient (ai) is 12 ppm.

The number of release days assumed for this analysis was 250.  This
approach assumes that BUSAN 77 is not applied on weekends and holidays. 


Table 1

Poly[oxyethylene)(dimethylimino)ethylene(dimethylimino)ethylenedichlorid
e] Dosage Information for Once-through Cooling Water Systems

Product	Percent Active Ingredient	Label Directions	Application Rate for
Analysis

BUSAN 77	60 percent

	Add BUSAN 77 at dosage rates of 2 to 20 ppm.  Additions should be made
continuously or intermittently to the intake water.  Continuous addition
is required for noticeably fouled systems.  Intermittent feeding is used
to maintain control.	Continuous application at 12 ppm ai (i.e., 20 ppm
product * 60%)



Bio/Tec 112	20 percent

	Add Bio/Tec 112 at dosage rates of 6 to 60 ppm.  Additions should be
made continuously or intermittently to the intake water.  Continuous
addition is required for noticeably fouled systems.  Intermittent
feeding is used to maintain control.	Continuous application at 12 ppm ai
(i.e., 60 ppm product * 20%)





1.3 	COCs

COCs for this analysis were identified from ecological effects
information for BUSAN 77 provided by EPA. At least one COC was chosen
for each of the following study types:  acute toxicity to freshwater
fish, acute toxicity to freshwater invertebrates, life-cycle toxicity to
freshwater invertebrates, and acute toxicity to estuarine and marine
organisms.  The chosen COCs are shown in Table 2 along with text
species, endpoint types, study types and references.  With the exception
of the three COCs for acute toxicity to estuarine and marine organisms,
the available studies did not satisfy study guidelines.  For details
about the ecological effects studies referenced in Table 2, see the
ecological effects chapter identified in Footnote 3.    

1.4 	Modeled Facilities and Flow Data

	The modeling consists of BUSAN 77 releases for 30 steam electric power
plants (SIC 4911) that were identified by EPA during development of the
exposure assessment methodology for Alkyl Dimethyl Benzyl Ammonium
Chloride (ADBAC).  Although this sample of facilities was chosen to
include a range of receiving stream flow rates and includes facilities
located throughout the U.S., it is not necessarily statistically
representative of all facilities with once-through cooling water
systems.   

Table 2

Concentrations of Concern Selected for the Environmental Exposure
Assessment of BUSAN 77

COC	Test Species	Endpoint Type	Study Type	Referencea

12 µg/Lb	Waterflea (Daphnia magna)	NOEC	Life-cycle toxicity to
freshwater invertebrates	Putt et al. 1992 (MRID NR 42479601)

130 µg/Lb	Waterflea (Daphnia magna)	NOEC	Acute toxicity to freshwater
invertebrates	LeLievre et al. 1990 (MRID 41352003)

140 µg/L	Quahog clam (Mercenaria mercenaria)	NOEC	Acute toxicity to
estuarine and marine organisms	Surprenant 1987c (MRID 40334201)

260 µg/Lb	Rainbow trout (Salmo gairdneri)	LC50	Acute toxicity to
freshwater fish	Knott 1970 (ID 0522-010-09)

7,800 µg/L	Mysid shrimp (Mysidopsis bahia)	NOEC	Acute toxicity to
estuarine and marine organisms	Surprenant 1987b (MRID 40139203)

360,000 µg/L	Sheepshead minnow (Cyprinodon variegates)	NOEC	Acute
toxicity to estuarine and marine organisms	Surprenant 1987a (MRID
40139202)



a For full reference information and further study details, see the
source referenced in footnote 3.

b COC is based on a study that does not fulfill the study guideline
requirements.

Table 3 lists the stream flow data and modeled effluent discharge rates
for the 30 facilities used in the analysis.  The mean and 7Q10 flows of
receiving stream reaches are available in the PDM model and were used
for the analysis.  Facility-specific effluent discharge rates also are
available in PDM.  For the analysis, the modeled effluent discharge
rates were based on either facility-specific effluent discharges or the
7Q10 flows of the receiving streams.  Specifically, the modeled effluent
discharge rate for each facility was the lower of these two values.  The
7Q10 flow rate represents the rate that could be maintained continuously
by an electric steam generating plant to ensure a steady supply of
cooling water.  

2. 	Results

PDM was run once for each facility.  The numbers of days exceeding each
COC were copied electronically from the PDM output files into a
Microsoft ® Excel workbook where averages and standard deviations were
calculated.  In addition, the percent of days per year above COCs were
calculated.  Because the number of release days per year was 250, the
highest possible percent of days per year above COCs was 68 percent. 
The percent of days during the release period above COCs (maximum 100
percent) were also calculated.  Standard deviations also were calculated
for all average percent of day’s calculations.

The results are presented in Table 4.  The table shows the average
numbers of days when downstream concentrations of BUSAN 77 were
predicted to exceed each of the COCs.  The average numbers of days were
calculated from the modeling results for the 30 individual facilities. 
Because the numbers of days with exceedences varied among the
facilities, standard deviations are presented with each of the averages.
 Also Tables 4 presents the averages and standard deviations of the
percentage of days per year as well as the percentage of the 250 release
days with exceedences of the COCs.  

For a one year period that includes continuous releases during 250 days,
the lowest COC (12 µg/L) was exceeded on 57 percent of the days (or 83
percent of the 250 release days).  The lowest COC based on a study that
fulfilled the study guidelines (140 µg/L) was exceeded on 42 percent of
the days.  The highest COC (360 mg/L) was exceeded on less than one
percent of the days on average.  Table 5 shows the percentage of
facilities that had exceedences at least once (i.e., on at least one
day) for each COC.  For example, the highest COC (360 mg/L was exceeded
only at three (10 percent) of the 30 facilities.  All other COCs were
exceeded at least once at least 57 percent of the facilities.  The
lowest COC was exceeded at least once at 29 (97 percent) of the 30
facilities.  

Table 3

Effluent Discharge and Stream Flow Data for Modeled Facilities

Facility NPDES Number	Mean Stream Flow (MGD)	7Q10 Stream Flow (MGD)
Modeled Effluent Discharge (MGD)a

FL0025526	401.26	263.63	117.20

GA0004341	1047.42	221.25	0.14

IA0000108	521.26	16.19	0.46

IA0033235	47.81	1.94	0.03

IL0002186	960.51	308.89	308.89

IL0036919	635.87	635.88	635.879

IL0048321	88.85	25.64	12.259

IN0032948	146.03	36.18	0.019

IN0038806	170.59	35.54	0.089

IN0041246	279.79	115.66	23.78

KS0079057	277.85	18.74	18.74

LA0003042	101.33	11.77	0.68

LA0036145	0.78	0.06	0.06

MA0004367	417.42	91.11	5.62

MI0038172	21.322	6.46	6.46

MN0000906	462.212	7.64	0.98

NC0005088	975.75	214.63	43.67

NH0001431	296.59	73.02	7.99

NM0000108	520.519	1.56	1.15

OH0010421	486.089	15.80	9.21

OK0002682	95.91	1.23	1.23

PA0002054	473.50	30.37	30.37

PA0002062	103.30	13.73	13.73

PA0008443	88.90	7.64	7.64

SC0001104	964.98	13.27	0.97

TX0001163	86.58	10.34	10.34

TX0054500	5.88	1.55	1.55

UT0000116	126.00	82.71	0.16

WA0003280	704.31	213.23	34.20

WV0005525	33.60	5.94	5.94



a If the effluent discharge value from PDM was less then the receiving
stream 7Q10, the 7Q10 was used as the modeled effluent discharge.

Table 4

Number and Percent of Days with Downstream 

BUSAN 77 Concentrations Exceeding COCs

COC

(µg/L)	Number of Days With Exceedences	Percent of Days with Exceedences
per Year	Percent of Release Days with Exceedences

	Average Days COC Exceeded	Standard Deviation	Average Days COC Exceeded
Standard Deviation	Average Days COC Exceeded	Standard Deviation

12 µg/La	207	72	57%	20%	83%	29%

130 µg/La	152	94	42%	26%	61%	37%

140 µg/L	149	94	41%	26%	60%	37%

260 µg/La	129	92	35%	25%	51%	37%

7,800 µg/L	12	18	3%	5%	5%	7%

360,000 µg/L	1	5	<1%	2%	<1%	2%

a COC is based on a study that does not fulfill the study guideline
requirements.

Table 5

Percent of Facilities with Downstream BUSAN 77

Concentrations Exceeding COCs on at Least One Day (n = 30)

COC

(µg/L)	Percent of Facilities with at Least One Day with an Exceedence 

12 µg/La	97%

130 µg/La	87%

140 µg/L	87%

260 µg/La	87%

7,800 µg/L	57%

360,000 µg/L	10%

a COC is based on a study that does not fulfill the study guideline
requirements.

3. 	Limitations and Potential Next Steps

	This analysis is a screening level evaluation of the potential for
discharges from once-through cooling water systems to exceed BUSAN 77
ecotoxicity COCs in receiving streams.  The methodology involves the
following potential limitations:

Because exceedences predicted by the PDM do not necessarily occur on
consecutive days the analysis may overestimate the actual potential for
ecological toxicity impacts.  The numbers of days with exceedences of
COCs have not been compared to the numbers of days of exposure used in
the studies from which the COCs were obtained.

Downstream concentrations of BUSAN 77 are considered to exceed a COC on
any given day if the COC is exceeded for any portion of the day.  PDM
does not identify the duration of the exceedences, and the daily scale
results may overestimate the actual potential for BUSAN 77 releases to
result in ecological risks.

The estimated numbers of days with downstream concentrations of BUSAN 77
above COCs are average calculated from the results for individual
facilities.  Facility level results varied considerably, as shown by the
standard deviations presented with the averages.  Thus, this analysis
may under or overestimate the potential for the exceedences at specific
facilities.

The analysis used an assumed release period of 250 days.  This
assumption is likely to overestimate the number of release days for
BUSAN 77 treatment, especially for initial control.  Thus, the results
of the analysis may overestimate the number of days with downstream
BUSAN 77 concentrations above COCs.  

The scenario used for this analysis was based on the maximum application
rate (i.e., 12 ppm) identified on product labels.  It may be possible to
control of target organisms with application rates below the maximum. 
In addition, continuous dosing was assumed throughout the release
period.  This assumption may overestimate the daily treatment duration
that would be required for effective mollusk control.

For this analysis, effluent discharge rates were assumed to equal the
lower of either facility-specific effluent flow rates or the 7Q10 flows
of the receiving streams.  This approach may over or underestimate
average actual effluent discharges.    

The analysis used flow and discharge data for a sample of 30 steam
electric generating facilities.  This sample is not necessarily
statistically representative of the national population of facilities
with once-through cooling water systems where BUSAN 77 may be used.

Three of the COCs evaluate were based on ecotoxicity endpoints from
studies that did not fulfill the applicable study guideline
requirements.

Potential next steps include the following:

Compare the average numbers of days with exceedences of COCs to the
numbers of days of exposure used in the studies from which the COCs were
obtained.  In addition, ICF could calculate the probabilities of COCs
being exceeded on specified numbers of days.

Analyze additional scenarios.  For example, scenarios could be prepared
based on application rates below the maximum product label application
rates or fewer release days.  In addition, scenarios could be developed
to analyze different assumptions about effluent discharge rates (e.g.,
using facility-specific effluent discharge data).

 “Environmental Exposure Assessment for Releases of Bromonitrostyrene
from Once-through Cooling Water Systems,” memorandum to David Bays,
EPA OPP/AD, from Joshua Cleland and Keith Drewes, ICF International,
April 26, 2007. 

 The E-FAST2 model is available from EPA at   HYPERLINK
"http://www.epa.gov/opptintr/exposure/pubs/efastdl.htm" 
http://www.epa.gov/opptintr/exposure/pubs/efastdl.htm  and documentation
is available at   HYPERLINK
"http://www.epa.gov/opptintr/exposure/pubs/efast2man.pdf" 
http://www.epa.gov/opptintr/exposure/pubs/efast2man.pdf .

 “Ecological Effects Chapter for Busan 77 – Action Number CJM 32
(TAF 1-5-11),” memorandum to Najm Shamim, EPA, from Ron Lee, Kathy
Coon, Chris Greene, and Pat Wood, Versar, Inc., December 1, 2002.

 Petrie, R. and K. Montague.  2006.  “Ecological Hazard And
Environmental Risk Assessment Chapter, Alkyl Dimethyl Benzyl Ammonium
Chloride (ADBAC).”  PC Code 069105, CASE No.: 0350, U.S. Environmental
Protection Agency, Office of Pesticide Programs, Antimicrobials
Division.  August, 2, 2006. 

 A 7Q10 stream flow is the lowest seven-day average stream flow over a
ten year period.

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