UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

MEMORANDUM 

Date: September 30,2013 

SUBJECT: 2-(Decylthio) Ethanamine Hydrochloride (DTEA·HCI), Human Health and 

Ecological Preliminary Risk Assessment for Registration Review. 

PC Code: 128963 DP Barcode: 410614, 410615 

Decision No.: NA Registration Nos.: 464-619 

Petition No(s).: NA Regulatory Action: Registration Review PRA 

Risk Assessment Type: Single chemical Case No.: 5029 

TXRNo.:NA CAS No.: 36362-09-1 

MRID Nos.: See PP 11, 12, 15, 38, 66, Tables 6 & 7 40 CFR: None 

TO: Seiichi Murasaki, Chemical Review Manager 

ShaRon Carlisle, Acting Branch Chief Regulatory Management Branch 2 

Antimicrobial Division (751 OP) 

Office of Pesticide Programs 

FROM: William Hazel, Chemist A:/c~ . .,~ ....... Nathan Mottl, Biologist t 

/./ Najm 

Jonathan 

Shamim, 

Chen, 

Chemist 

Toxicologist 

5eL ~ 

~ ~ 

, 

Pat Jennings, Environmental Engineer ~ oJ:- 9-eu..-\...J~.$- David Bays, Biologist / iZ ~ / U 

~<9.J Donna Randall, Senior Scfe;_tist- ~ ~~ 

Risk Assessment and Science Support Branch, Antimicrobial Division (751 OP) 

Office of Pesticide Programs 

THROUGH: Laura Parsons, Acting Associate ~ranch Ch:-~ Ll A1.{_ f tcf~ Steven Weiss, Branch Chief ~u);;:r_J y--· 

Risk Assessment and Science Support Branch, Antimicrobial Division (751 OP) 

Office of Pesticide Programs 

This document provides the preliminary risk assessment (PRA) conducted in support of 

registration review for DTEA-HCl (PC Code 128963) and DTEA (PC Code 128555). 

Information for this registration review case (5029) can be found in the public docket: EPA-HQOPP-2009-0336. 
Page 2 of 68

DTEA-HCl is registered for use to control bacterial, fungi and algae in industrial cooling towers. 

The PRA concludes no risks of concern for human health, but potential risks of concern for 

aquatic organisms from environmental releases of treated water from cooling towers. 
Page 3 of 68

Table of Contents

EXECUTIVE SUMMARY ............................................................................................................ 9

1.0 INTRODUCTION ................................................................................................................ 10

1.1 Case Overview ............................................................................................................... 10

1.2 Recent Regulatory Actions ............................................................................................. 10

1.3 Work Plan Modifications ............................................................................................... 11

2.0 ENVIRONMENTAL FATE ASSESSMENT ...................................................................... 11

3.0 HUMAN HEALTH RISK ASSESSMENT .......................................................................... 11

3.1 Human Health Hazard .................................................................................................... 11

3.1.1 Subchronic Toxicity ................................................................................................ 11

3.1.2 Developmental Toxicity.......................................................................................... 12

3.1.3 Mutagenicity ........................................................................................................... 12

3.1.4 Literature Search Results: ....................................................................................... 12

3.2 Dietary Assessment ........................................................................................................ 12

3.2.1 Dietary (Food) Exposure......................................................................................... 13

3.2.2 Drinking Water Exposure ....................................................................................... 13

3.3 Residential Assessment .................................................................................................. 14

3.4 Aggregate and Cumulative Exposure ............................................................................. 14

3.4.1 Aggregate Exposures .............................................................................................. 14

3.4.2 Cumulative Exposures ............................................................................................ 14

3.5 Occupational Assessment ............................................................................................... 14

3.6 Endocrine Disruptor Screening Program (EDSP) .......................................................... 15

4.0 ECOLOGICAL RISK ASSESSMENT ................................................................................ 16

4.1 Selected Ecological Toxicity Endpoints ........................................................................ 16

4.2 Summary of Exposures .................................................................................................. 17

4.2.1 Exposure of Aquatic Organisms to DTEA Downstream of Recirculating Cooling 

Towers 17

4.2.2 Analysis of Influence of Ratios of Plant Flow to Stream Flow Distributions on 

Estimates of Numbers of Days per Year of Exceedance of COCs ....................................... 20

4.2.3 Estuarine/Marine Organisms .................................................................................. 20

4.2.4 Residue Levels in Aquatic Biota ............................................................................. 21

4.3 Risk Estimation .............................................................................................................. 21

4.4 Risks to Freshwater Fish and Aquatic Invertebrates. ..................................................... 22

4.4.2 Risks to Estuarine/Marine Organisms .................................................................... 24

4.4.3 Risks to Piscivorous Birds and Mammals .............................................................. 24

4.5 Risk Characterization ..................................................................................................... 24

4.5.1 Effect of Exposure Assumptions ............................................................................ 27

4.5.2 Uncertainties ........................................................................................................... 29

4.6 Endangered Species Assessment .................................................................................... 30

4.6.1 Action Area ............................................................................................................. 30

4.6.2 Taxonomic Groups Potentially at Risk ................................................................... 31

4.6.3 Listed Species Occurrence Associated with DTEA-HCl Use ................................ 31

5.0 SUMMARY OF RISKS ....................................................................................................... 32

APPENDIX A: Environmental Fate ............................................................................................. 33

APPENDIX B: Summary of Ecotoxicity Data for DTEA ........................................................... 37
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APPENDIX C: Risk Estimation Methods ................................................................................... 47

APPENDIX D: Estimation of Potential Risks from Exposure of Aquatic Organisms to DTEA 

Downstream of Recirculating Cooling Towers ............................................................................ 49

APPENDIX E: Estimated Sediment Exposure Concentrations ................................................... 65

APPENDIX F: Estimated Exposure Concentrations in Aquatic Biota ........................................ 66

List of Tables

Table 1 Ecological Effects Endpoints Selected for Assessing Risks from Use in Recirculating 

Cooling Systems ............................................................................................................... 16

Table 2 Application Rates from the Product Label ..................................................................... 18

Table 3 Application Rates from Label Adjusted for Density and DTEA Equivalents ................ 18

Table 4 Estimated Local Sediment Concentrations for With and Without Wastewater Treatment 

of Blowdown Water Prior to Discharge ............................................................................ 20

Table 5 Comparison of Number of Days per Year of Exceedance of COCs: Steam Electric 

Power Plants SIC Code versus Industrialized POTWs SIC Code (2.8 kg/site/day and 93% 

Removal During WWT and 360 Days of Release per Year) ............................................ 20

Table 6. Physical/Chemical Characteristics and Environmental Fate Studies and Results .......... 33

Table 7 Ecotoxicity Data for DTEA·HCl and DTEA .................................................................. 38

Table 8 Freshwater Benthic Invertebrate Toxicity ...................................................................... 42

Table 9. Risk Presumption Categories ......................................................................................... 47

Table 10 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Large-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment (No 

Removal) ........................................................................................................................... 49

Table 11 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes no treatment and no 

removal ............................................................................................................................. 50

Table 12 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No 

Treatment and No Removal .............................................................................................. 50

Table 13 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No 

Treatment and No Removal .............................................................................................. 51

Table 14 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Large-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent removal 

during WWT ..................................................................................................................... 51

Table 15 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent removal 

during WWT ..................................................................................................................... 52
Page 5 of 68

Table 16 Average Case Scenario Estimates of Number of Days per Year of Exceedance of COCs 

for Aquatic Organisms Downstream of Large-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent removal 

during WWT ..................................................................................................................... 52

Table 17 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT ....................................................................................................... 53

Table 18 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Large-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment (No 

Removal) ........................................................................................................................... 54

Table 19 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes no treatment and no 

removal ............................................................................................................................. 54

Table 20 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No 

Treatment and No Removal .............................................................................................. 55

Table 21 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No 

Treatment and No Removal .............................................................................................. 55

Table 22 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Large-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent removal 

during WWT ..................................................................................................................... 56

Table 23 High-End Scenario Estimates of Number of Days per Year of Exceedance of COCs for 

Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on Facilities 

Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent removal 

during WWT ..................................................................................................................... 57

Table 24 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT ....................................................................................................... 57

Table 25 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT ....................................................................................................... 58

Table 26 BCFBAF Program (v3.01) Results from EPI Suite (v4.11) ......................................... 67

 
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TERMS, ABBREVIATIONS AND SYMBOLS

°C degrees Celsius 

% percent 

% w/w percent weight per weight 

μg microgram 

μg/g microgram per gram 

μg/L microgram per liter 

AD Antimicrobials Division 

Ae acid equivalents 

AI or ai active ingredient 

aPAD acute population adjusted dose 

ASRI activated sludge respiration inhibition 

atm-m3

/mole atmospheric pressure-cubic meter per mole 

BCF bioconcentration factor 

CaSO4 calcium sulfate 

CaSO3 calcium sulfite 

CAS Chemical Abstracts Service 

CCA chromated copper arsenate 

CFR Code of Federal Regulations 

CHO Chinese hamster ovary 

CMA Chemical Manufacturers Association 

CSF Confidential Statement of Formulation 

CO2 carbon dioxide 

COC concentration-of-concern 

cPAD chronic population adjusted dose 

CS2 carbon disulfide 

DCI data call-in 

DTEA 2-(decylthio) ethanamine

EC50 median (or 50 percent) effect concentration

EC05 5 percent effect concentration

ECOTOX ECOTOXicology 

EDI estimated daily intake 

EDSP Endocrine Disruptor Screening Program 

EEC estimated environmental concentration 

E-FAST Exposure and Fate Assessment Screening Tool 

EP End-use product 

EPI Suite Estimation Program Interface Suite 

EPA Environmental Protection Agency 

FDA Food and Drug Administration 

FFDCA Federal Food, Drug, and Cosmetic Act 

FGD flue-gas desulfurization 

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act 

FQPA Food Quality Protection Act 

FWP Final Work Plan 
Page 7 of 68

g gram 

g/mol grams per mole 

GLN guideline number 

HPV high production volume 

IDS Incident Data System 

KDDC potassium dimethyldithiocarbamate 

Koc organic carbon normalized soil-water partition coefficient 

Kd soil-water partition coefficient 

Kow octanol-water partition coefficient 

L liter 

LC50 median (or 50 percent) lethal concentration 

LD50 median (or 50 percent) lethal dose 

LOAEC lowest-observed-adverse-effect-concentration 

LOC level of concern 

LOD limit of detection 

LOEC lowest-observed-effect-concentration 

LOAEL lowest-observed-adverse-effect-level 

Log Kow logarithm of the octanol-water partition coefficient

ml/g milliliter per gram 

mg/kg milligram per kilogram 

mg/kg/day milligram per kilogram per day 

mg/L milligram per liter 

mm Hg millimeter of mercury 

MOE margin of exposure 

MRID Master Record Identification (number) 

MRL maximum residue limit 

MUP manufacturing use product 

NA not applicable 

nm nanometers 

NOAEC no-observed-adverse-effect-concentration 

NOAEL no-observed-adverse-effect-level 

NPDES National Pollutant Discharge Elimination System 

Oc organic carbon 

OCSPP Office of Chemical Safety and Pollution Prevention 

OECD Organization for Economic Co-operation and Development 

OPP Office of Pesticide Programs 

PAD population adjusted dose 

PAI pure active ingredient 

PDM Probabilistic Dilution Model 

PC Code Pesticide Chemical Code 

PCF pounds per cubic foot 

pH power of hydrogen or power of the concentration of the hydrogen ion 

PHED Pesticide Handler’s Exposure Data 

PIS primary irritation score 

pKa power of the acid dissociation constant or negative base-10 logarithm of the acid 

dissociation constant of a solution 

ppb parts per billion 
Page 8 of 68

PPE Personal Protective Equipment 

ppm parts per million 

PWP Preliminary Work Plan 

QSAR quantitative structure-activity relationship 

RED Reregistration Eligibility Decision 

RfD reference dose 

RQ risk quotient 

SAR structure activity relationship 

SF safety factor 

SLN Special Local Need (Registrations under Section 24(c) of FIFRA) 

SSTS Section Seven Tracking System 

SO2 sulfur dioxide 

TEP typical end-use product 

TGAI technical grade active ingredient 

TMDL total maximum daily loads 

TMTDS tetramethylthiuram disulfide (Thiram) 

TMTMS tetramethyl thiomonosulfide 

TMTU tetramethyl thiourea 

UF uncertainty factor 

UV/VIS ultraviolet/visible light absorption 

WP wettable powder 

WPS Worker Protection Standard 

WWTPs wastewater treatment plants 
Page 9 of 68

EXECUTIVE SUMMARY

The Environmental Protection Agency (referred to as the “EPA”, “USEPA”, or “the Agency”) 

has evaluated the risks from the registered uses of 2-(decylthio) ethanamine hydrochloride 

(DTEA·HCl). Since DTEA-HCl is currently not marketed in the US, exposures predicted in this 

document are not occurring at this time and are theoretical only. However, the Agency assumes 

that DTEA-HCl could be used at some time in the future. Therefore, the risk assessment covers 

any potential future exposure if the product becomes active. 

Since DTEA very rapidly dissociates from DTEA·HCl in aqueous solution, this assessment 

focuses on DTEA. EPA has determined that there are unreasonable adverse effects to non-target 

aquatic and terrestrial organisms that may result from exposure to DTEA. 

Based on the label requiring closed-loading, no quantitative occupational human health risk 

assessment was conducted as this label requirement minimizes occupational exposure. For the 

human health risk assessment, no dietary risk assessment is necessary because dietary (food and 

drinking water) exposures are expected to be minimal based on use patterns and water treatment. 

A theoretical quantitative ecological risk assessment was conducted. Exposure levels were 

modeled in a variety of ways including incorporation of wastewater treatment prior to discharge 

and no wastewater treatment, the risk results indicated exceedance of levels of concern for 

exposure of aquatic organisms for both federally listed endangered (listed) species and non-listed 

species in the water column and exceedance of levels of concern for aquatic benthic 

invertebrates. Aquatic food chain transfer and bioaccumulation of DTEA was identified to 

potentially pose risks to mammals and birds. 
Page 10 of 68

1.0 INTRODUCTION

 This document is the United States Environmental Protection Agency’s (USEPA, EPA or 

“the Agency”) Preliminary Risk Assessment (PRA) for 2-(decylthio) ethanamine hydrochloride 

(DTEA·HCl). The PRA document explains what type of exposure analysis was conducted for 

humans and nontarget aquatic and terrestrial organisms, provides exposure estimates used to 

assess human health and ecological risks, characterizes the uncertainties of the risk assessments 

conducted and draws conclusions. 

 The registration review process was designed to include a public participation component 

to solicit input from interested stakeholders. The Agency intends, by sharing this information in 

the docket, to inform the public of what it knows about the risks from the registered DTEA·HCl 

uses and what types of new data or other information would be helpful for the Agency to receive 

as it moves toward a decision on DTEA·HCl. The Agency encourages all interested stakeholders 

to review the PRA and to provide comments and additional information that will help the 

Agency’s decision-making process for this chemical. 

1.1 Case Overview

 The docket for the DTEA·HCl Case (5029) was established at 

http://www.regulations.gov in docket number EPA-HQ-OPP-2009-0366. 

 DTEA·HCl is a liquid, organic industrial biocide commonly known by the trade name 

DTEA. The manufacturing-use product, Antimicrobial DTEA Technical (99.8%), is registered 

for formulation of pesticide products for use in re-circulating cooling water systems. These 

systems include evaporative condensers, heat exchange water systems, commercial and industrial 

cooling towers, influent systems such as flow-through filters and lagoons, industrial water 

scrubbing systems and brewery pasteurizers. The end-use product contains 15% DETA and is 

registered to control bacterial, fungal, and algal slimes. 

 DTEA·HCl was first registered in the United States in 1993 for use in recirculating water 

process systems. Since DTEA-HCl is currently not marketed in the US, exposures predicted in 

this document are not occurring at this time and are theoretical. However, the Agency assumes 

that DTEA-HCl could be used at some time in the future. Therefore, the risk assessment covers 

any potential future exposure if the product becomes active. A Reregistration Eligibility 

Decision (RED) was not issued by the Agency for DTEA·HCl. A summary of product 

chemistry, environmental fate and ecotoxicity data for DTEA·HCl registration review decision 

document was issued in December 2009. 

1.2 Recent Regulatory Actions

 The docket for DTEA·HCl was opened June 24, 2009 and the final work plan (EPA-HQOPP-2009-0366-0007) was posted December 16, 2009 after public comments were addressed. 
Page 11 of 68

No actions have occurred with this chemical since the posting of the final work plan in 2009. A 

registration review generic DCI was issued in August 2011. All data which were required in that 

DCI have been submitted, reviewed and were found acceptable. Those data were used to inform 

this risk assessment. 

1.3 Work Plan Modifications

 A generic data call-in (GDCI) was sent to registrants with products August 17, 2011 

(EPA-HQ-OPP-2009-0366-0007-0010). Two fate studies (835.1110 Activated Sludge Sorption 

Isotherm and 835.3110 Ready Biodegradability) and an ecological effects study (Algal toxicity 

Tier II definitive study with the freshwater green alga, Selenastrum capricornutum) were 

required. All of these studies were submitted and reviewed. 

 Since the final work plan (FWP) was posted, the Agency practice for evaluating 

ecological risks from recirculating cooling process water systems has expanded to include 

evaluation of sediment exposure pathways and bioaccumulation up the aquatic food chain to 

terrestrial wildlife. Therefore, not all the data needed to address these exposure pathways was 

requested in the FWP. The Agency has used alternative methods to address these data gaps, and 

these are addressed in appropriate sections. 

2.0 ENVIRONMENTAL FATE ASSESSMENT

 In aqueous solution DTEA is persistent under abiotic conditions at pH 5, 7, and 9. Its 

solubility is low in water. The Henry’s law constant value indicates that DTEA has a moderate 

tendency to volatilize from water surfaces to air. Its half life in air is about 3 hours, and it is not 

likely to persist in air. It is immobile on soil surfaces, and sludge surfaces. It is not ready 

biodegradable. Its Log Kow is high which indicates that it is likely to be bioaccumulative. The 

dissipation pathway appears to be binding to soil/sediments and therefore, the possibility of 

adverse effects on benthic organisms exists. 

3.0 HUMAN HEALTH RISK ASSESSMENT

3.1 Human Health Hazard

 For DTEA, the registrant submitted the acute toxicity studies, a 90-day dermal toxicity 

test, a developmental test and the mutagenicity studies. 

3.1.1 Subchronic Toxicity

 An acceptable 90-day dermal study (MRID 40634003) was conducted with Fisher 344 

rats. The rats were treated for 13 weeks with pure solid DTEA·HCl and the dose levels were 0, 

1, 5 and 25 mg/kg/day. The dose was administered on weekdays for a total of 65 applications. 

The test material was spread over the skin of rats with a syringe. The tested area was occluded 

for 6 hours with a gauze patch under an elastic bandage. The mean weight of the male and 
Page 12 of 68

female rat was 262.5 gm and 171.6 gm, respectively. Approximately 20 rats were tested for each 

dose level. The systemic NOAEL was 25 mg/kg/day (highest dose tested) and the NOAEL 

for skin irritation was <1 mg/kg/day based on skin thickening, focal erythema, and 

multifocal crust formation at a LOAEL of 1 mg/kg/day was established. Dermal irritation 

was seen between 8 to 12 weeks after dosing. 

3.1.2 Developmental Toxicity

 A developmental toxicity study (MRID 40634002) was conducted using female Fisher 

344 rats with dose levels 0, 2.5, 15, 25 mg/kg/day of DTEA·HCl given by gavage on gestation 

days 6-15. This study was upgraded to acceptable in 1992 (TXR009621). The maternal 

NOAEL was 2.5 mg/kg/day. The maternal LOAEL of 15 mg/kg/day was based on 

decreased body weight and body weight gain as well as suggestive decrease in food and 

water consumption. There did not appear to be any fetotoxicity or teratogenic effect at any 

dose levels. Therefore the NOAEL for developmental toxicity is 25 mg/kg/day or the highest 

dose tested. 

3.1.3 Mutagenicity

 In a test of unscheduled DNA synthesis in primary rat hepatocytes, DTEA did not 

demonstrate mutagenic potential (MRID 40126410). No evidence of mutagenicity or genetic 

toxicity was found in an in vivo mouse bone marrow micronucleus assay (MRID 40126410). 

DTEA did not exhibit mutagenic potential in a Chinese hamster ovary cell forward mutation 

study (MRID 40126409). 

3.1.4 Literature Search Results:

 Searches of the following databases using the key words 2-(Decylthio)Ethanamine 

Hydrochloride and 2-(Decylthio)Ethanamine on 07/21/2013 resulted in no DTEA-HCl studies 

being located that is useful for human health risk assessment: 

 Hazardous Substances Data Bank (HSDB); 

 Toxicology Literature Online (TOXLINE); 

 ChemIDPlus Advance; and 

 Toxicology Data Network (ToxNET). 

 As the DTEA-HCl label requires that the product be added via closed mixing/loading 

systems, no additional toxicology studies are required for occupational risk assessment. 

Similarly, additional toxicology studies are not required to conduct dietary risk assessments as 

dietary exposure is not expected to occur at this time. 

3.2 Dietary Assessment

 DTEA-HCl is registered for use in recirculating cooling water systems (evaporative 

condensers, heat exchangers, cooling towers, influent systems such as flow-through filters and 
Page 13 of 68

lagoons, industrial water scrubbing systems, and brewery pasteurizers). In the Preliminary and 

Final Workplans of the DTEA Registration Review, waste water from these uses of DTEA-HCl 

was considered to be rarely discharged. However, the Agency has recently revisited the extent of 

wastewater discharges associated with various types of commercial and industrial water systems. 

It has been determined that recirculating cooling water systems do, indeed, discharge significant 

volumes of waste water into natural water bodies. Regarding properties that are likely to affect 

its behavior, aqueous solutions dissociate into DTEA and HCl. Once DTEA is released into the 

environment, DTEA has a low water solubility (0.0035 g/100 g water), fairly high log Kow 

(3.27), fairly high vapor pressure (1.8 x 10-4 mmHg), moderate Henry’s Law Constant (2.79 x 

10-5 atm-m3/mole), resistance to hydrolysis, high tendency to adsorb to organic matter and 

sludge, instability in air, and low bioavailability (see fate section of this memorandum). The use 

sites, frequency of discharge, and physical, chemical, and environmental fate properties of 

DTEA-HCl have made it necessary for the agency to consider the need to conduct human dietary 

(food and drinking water) risk assessments. 

3.2.1 Dietary (Food) Exposure

 A dietary (food) risk assessment was not performed for DTEA-HCl in the past because 

there were not considered to be any direct or indirect food uses of DTEA-HCl. No tolerance or 

exemption from tolerance has been established by EPA. As noted above, waste water discharges 

of the dissociated DTEA from recirculating cooling water systems are expected. DTEA has a 

number of properties indicating that it has the potential to bioconcentrate in fish and shellfish. 

However, DTEA-HCl is not currently being marketed; therefore, dietary exposure via fish and 

shellfish is not occurring. In the event DTEA-HCl is marketed, the Agency has determined that 

dietary exposure due to consumption of DTEA-contaminated fish will be minimal despite the 

uncertainties noted above. Humans rarely rely on fish and shellfish from an isolated area in the 

vicinity of a recirculating water system as a major source of animal protein. Additionally, any 

discharged DTEA is expected to become diluted in the receiving water body. Therefore, a dietary 

assessment is not required at this time. 

3.2.2 Drinking Water Exposure

 A dietary (drinking water) risk assessment was not performed for DTEA-HCl in the past 

because recirculating cooling water systems were considered to be rarely discharged. However, 

as noted above, waste water discharges of the dissociated DTEA from recirculating cooling 

water systems are expected. 

Surface water concentrations estimated using General Population Exposures and Industrial 

Releases module of E-FAST assume that water releases can occur up to 360 days per year 

without wastewater treatment and that all DTEA released to surface water could be present in the 

dissolved phase in the water column. These estimates are very conservative and do not account 

for DTEA’s propensity to partition from water into sediment, the effect of wastewater or 

drinking water treatment. The best management practice for operation of recirculating cooling 
Page 14 of 68

water systems is to perform waste water treatment prior to discharge and, as indicated by the 

Activated Sludge Sorption Isotherm study, 93-98% of the DTEA is removed via waste water 

treatment prior to being discharged to surface water (MRID 49004201). Additionally, any 

discharged DTEA will rapidly be adsorbed to particulates that will eventually become part of the 

sediment. Finally, methods of drinking water treatment such as flocculation and sedimentation 

will further lower DTEA residues from potential drinking water. For these reasons, EPA has 

determined that no further human health drinking water assessment is necessary for DTEA. 

3.3 Residential Assessment

 Because the existing DTEA-HCl label uses will not result in residential exposures, 

residential handler and postapplication assessments will not be required. 

3.4 Aggregate and Cumulative Exposure

3.4.1 Aggregate Exposures

 As no dietary (food or drinking water) or residential exposures are associated with the 

registered uses of DTEA-HCl, there are no human health risks to aggregate. 

3.4.2 Cumulative Exposures

 With respect to cumulative exposure, unlike other pesticides for which EPA has followed 

a cumulative risk approach based on a common mechanism of toxicity, EPA has not made a 

common mechanism of toxicity finding as to DTEA-HCl and any other substances and DTEAHCl does not appear to produce a toxic metabolite produced by other substances. For the 

purposes of this preliminary risk assessment, therefore, EPA has not assumed that DTEA-HCl 

has a common mechanism of toxicity with other substances. For information regarding EPA’s 

efforts to determine which chemicals have a common mechanism of toxicity and to evaluate the 

cumulative effects of such chemicals, see http://www.epa.gov/pesticides/cumulative/. 

3.5 Occupational Assessment

An occupational and/or residential exposure assessment is required for an active 

ingredient if (1) certain toxicological criteria are triggered and (2) there is potential exposure to 

handlers (mixers, loaders, applicators, etc.) during use or to persons entering treated sites after 

application is complete. 

The Agency received product use information (MRID 49004204) for the ready-to-use 

product Antimicrobial DTEA 15% (EPA Reg # 464-619) which was submitted by the Dow 

Chemical Company in response to the DTEA·HCl Generic Data Call-In. EPA has reviewed the 

study (D407660) and determined that it is acceptable according to the requirements of 

OPPTS/OCSPP guideline 875.1700 [Applicator Exposure Product Use Information]. 
Page 15 of 68

 The Agency believes that closed mixing/loading systems can be an effective risk 

mitigation measure when required on pesticide labels to reduce risks identified for open 

mixing/loading procedures. The end use product (EPA Reg# 464-619) restricts the loading to 

closed systems. Therefore, the handler exposure is minimal and not quantified. 

 A post application assessment is not required based on the dilution of the product in the 

water systems, and therefore would reduce the vapor pressure to below 1 x 10-4 (the cutoff for 

assessing inhalation exposure to vapors of DTEA). 

3.6 Endocrine Disruptor Screening Program (EDSP)

 As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential 

adverse outcomes from exposure to chemicals. Collectively, these studies include acute, 

subchronic and chronic toxicity, including assessments of carcinogenicity, neurotoxicity, 

developmental, reproductive, and general or systemic toxicity. These studies include endpoints 

which may be susceptible to endocrine influence, including effects on endocrine target organ 

histopathology, organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, 

reproductive loss, and sex ratios in offspring. For ecological hazard assessments, EPA evaluates 

acute tests and chronic studies that assess growth, developmental and reproductive effects in 

different taxonomic groups. As part of the reregistration decisions for DTEA-HCL beginning in 

1993, EPA reviewed these data yet never selected the most sensitive endpoints for relevant risk 

assessment scenarios from the existing hazard database presumably because the hazard database 

was very limited and only occupational exposure was expected. However, as required by 

FFDCA section 408(p), DTEA-HCL is subject to the endocrine screening part of the Endocrine 

Disruptor Screening Program (EDSP). 

 EPA has developed the EDSP to determine whether certain substances (including 

pesticide active and other ingredients) may have an effect in humans or wildlife similar to an 

effect produced by a “naturally occurring estrogen, or other such endocrine effects as the 

Administrator may designate.” The EDSP employs a two-tiered approach to making the 

statutorily required determinations. Tier 1 consists of a battery of 11 screening assays to identify 

the potential of a chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or 

T) hormonal systems. Chemicals that go through Tier 1 screening and are found to have the 

potential to interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP 

where EPA will determine which, if any, of the Tier 2 tests are necessary based on the available 

data. Tier 2 testing is designed to identify any adverse endocrine-related effects caused by the 

substance, and establish a dose-response relationship between the dose and the E, A, or T effect. 

 Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. DTEA-HCL is 

not among the group of 58 pesticide active ingredients on the initial list to be screened under the 
Page 16 of 68

EDSP. Accordingly, as part of registration review, EPA will issue future EDSP orders/data callins, requiring the submission of EDSP screening assays for DTEA-HCL. 

 For further information on the status of the EDSP, the policies and procedures, the list of 

67 chemicals, future lists, the test guidelines and the Tier 1 screening battery, please visit our 

website: http://www.epa.gov/endo/. 

 

4.0 ECOLOGICAL RISK ASSESSMENT

4.1 Selected Ecological Toxicity Endpoints

 All registered uses of the DTEA manufacturing-use product are for the formulation of 

pesticide products for use in re-circulating cooling water systems. The DTEA Technical is 

diluted to concentration of 15% and this formulation is used to treat the water systems. In the 

past the cooling tower use was considered an “indoor use” and exposure to non-target organisms 

was not expected. Under the newly revised 158W guidelines, this use is now subject to an 

evaluation to determine if exposure to non-target organisms is occurring and if so, should be 

subject to risk mitigation measures. Ecological effects endpoints selected for assessing risks 

from use in recirculating cooling systems are presented in Table 1. 

Table 1 Ecological Effects Endpoints Selected for Assessing Risks from Use in 

Recirculating Cooling Systems 

Receptor 

Group Surrogate Species Risk Scenario Toxicity Endpoint Reference 

Freshwater fish Fathead minnow 

Acute 96-h LC50 = 220 ppb 40126416, 

42482901 

Chronic NOAEC = 36.5 ppb 

41198302, 

41198304, 

41512601, 

41779902 

Freshwater 

invertebrates 

Acute 48-h EC50 = 34 ppb 

41198303, 

41198305, 

41512602, 

41779901 

Chronic NOAEC > 7.8 ppb 

41198303, 

41198305, 

41512602, 

41779901 
Page 17 of 68

Receptor 

Group Surrogate Species Risk Scenario Toxicity Endpoint Reference 

Freshwater benthic 

invertebrates 

Subchronic/ 

Chronic 

At Koc of 9810 L/kg 

NOAEC (1% oc) = 0.77 mg/kgsediment 

NOAEC (4% oc) = 3.1 mg/kgsediment 

NOAEC (5% oc) = 3.8 mg/kgsediment 

At Koc of 21,566 L/kg 

NOAEC (1% oc) = 1.68 mg/kgsediment 

NOAEC (4% oc) = 6.7 mg/kgsediment 

NOAEC (5% oc) = 8.4 mg/kgsediment 

Modeled using 

EqP method see 

Appendix E, see 

Table 8 

Estuarine/marine fish Acute Not requiredA -- 

Chronic Not requiredA -- 

Estuarine/marine 

invertebrates 

Mollusk Acute Not requiredA -- 

Shrimp Acute Not requiredA -- 

Chronic Not requiredA -- 

Estuarine/marine 

benthic invertebrates 

Subchronic/ 

Chronic Not requiredA -- 

Algae Nonlisted IC50 >11.7 ppm 49004203 Listed NOAEC > 11.7 ppm 

Aquatic vascular 

plants Duckweed 

Nonlisted IC50 = No data 

Listed NOAEC = No data 

Seedling Emergence Nonlisted IC25 = No data 

Listed NOAEC = No data 

Vegetative vigor Nonlisted Not requiredB

 -- 

Listed Not requiredB -- 

Birds 

Mallard duck Acute LD50 > 2250 mg/kg-bw 40126412 

Mallard duck Subacute dietary LC50 > 5620 ppm 

(30% mortality at highest dose) 

40126414, 

40126413 

 Chronic NOAEC = No data 

Mammals Acute LD50 = 2272mg DTEA/kg-bw 40126405 

Chronic NOAEL = No data 

Nontarget terrestrial 

insects Honey bee Acute Not requiredC

 -- 

A The label specifically prohibits the direct flushing of the coolant to estuarine/marine waters. 

B For cooling tower use pattern, spray drift and irrigation is not considered to be a pathway of concern. 

C For cooling tower use pattern, exposure of terrestrial beneficial insects is not considered to be a pathway of 

concern. 

4.2 Summary of Exposures

4.2.1 Exposure of Aquatic Organisms to DTEA Downstream of Recirculating Cooling Towers

 The general population and ecological exposures for industrial releases module 

(hereinafter referred to as the Industrial Releases Module) of the Exposure and Fate Assessment 
Page 18 of 68

Screening Tool (E-FAST) was used to estimate exposure of aquatic organisms to DTEA, the 

dissociation product of the active ingredient DTEA HCl, downstream of recirculating cooling 

towers. According to the product label (EPA Reg. No. 464-619), DTEA·HCl is present in the 

product, Antimicrobial DTEA·HCl 15%, as 15% of the formulation. The corresponding acid 

equivalent of DTEA is 12.8% of this formulation. 

 According to the product label, there are two methods of treatment for control of bacteria, 

fungi, and algae in recirculating cooling water systems: (1) intermittent or slug method and (2) 

continuous feed method. For both methods of treatment, the label specifies application rates of 

Antimicrobial DTEA 15% for both initial treatment of fouled systems and maintenance 

treatment. Maintenance treatments can range from 0.5 to 25 fluid ounces of product per 1000 

gallons of water for the intermittent or slug method of application and 0.5 to 2 fluid ounces of 

product per 1000 gallons of water for the continuous feed method. Initial treatment of fouled 

systems can range from 6 to 41 fluid ounces of product for both intermittent/slug and continuous 

feed methods. Application rates recommended on the product label are tabulated in Table 2. 

Table 2 Application Rates from the Product Label 

INTERMITTENT OR SLUG METHOD 

Initial treatment of fouled systems 6-41 fluid ounces per 1000 gallons of water in the system 

Maintenance treatment 0.5-25 fluid ounces per 1000 gallons of water in the system 

CONTINUOUS FEED METHOD 

Initial treatment of fouled systems 6-41 fluid ounces per 1000 gallons of water in the system 

Maintenance treatment 0.5-2 fluid ounces per 1000 gallons of water in the system 

 Potential exposures to aquatic organisms were estimated for applications of 41, 25, 6, 2, 

and 0.5 fluid ounces of product applied per 1000 gallons of water. Adjusting for product density 

of 8.5 lbs per gallon, the corresponding amounts of product applied would be slightly higher. 

 Table 3 presents the application rates of Antimicrobial DTEA 15% adjusted for density 

and the corresponding concentrations in parts per million (ppm) expressed as DTEA equivalents 

(12.8%). The table also presents corresponding environmental releases of DTEA to surface 

water from large-size (recirculation rate of 100,000 gallons per minute) and moderate-size 

(recirculation rate of 2000 gallons per minute) recirculating cooling towers. 

Table 3 Application Rates from Label Adjusted for Density and DTEA Equivalents 

Product 

Application rate 

Application rate adjusted 

for product density of 8.5 

pounds per gallon 

DTEA Concentration 

(ppm acid equivalents) 

Environmental 

Release: 

Large-Size 

Cooling Tower 

(kg/site/day) 

Environmental 

Release: 

Moderate-Size 

Cooling Tower 

(kg/site/day) 

41 fluid ounces 41.8 fluid ounces 40 140 2.8 

25 fluid ounces 25.4 fluid ounces 24.4 84 1.7 

6 fluid ounces 6.1 fluid ounces 5.9 20.4 0.41 

2 fluid ounces 2.0 fluid ounces 1.95 6.7 0.13 

0.5 fluid ounces 0.5 fluid ounces 0.5 1.7 0.03 
Page 19 of 68

 Potential exposures and risks to DTEA from releases of blowdown water from 

recirculating cooling towers to surface water were examined for the following circumstances: 

 maintenance treatments versus initial treatments for fouled systems; 

 large-size versus moderate-size recirculating cooling towers; 

 high-end versus average case scenarios from E-FAST; and 

 wastewater treatment versus no wastewater treatment prior to discharge of 

blowdown water to surface water 

 In the case where no treatment of blowdown water is assumed, the industrial releases 

module of E-FAST is run assuming no removal. In the case where it is assumed that blowdown 

water undergoes wastewater treatment prior to discharge, the industrial releases module of EFAST is run assuming 93 percent removal based on activated sludge sorption isotherm data that 

indicate that from 93 to 98 percent of DTEA is removed during wastewater treatment via 

sorption to activated sludge. Surface water concentrations are estimated based on the 

distribution of plant flows and stream flows from the Steam Electric Power Plants SIC code. 

Model results are expressed as days per year of exceedance of concentrations of concern for 

aquatic organisms downstream of recirculating cooling towers. 

4.2.1.1 Sediment EECs

 The general population and ecological exposures for industrial releases module of EFAST used to estimate exposure in surface waters downstream of recirculating cooling water 

systems does not provide estimates of sediment concentrations. Local sediment concentrations 

were modeled using an equilibrium partitioning (EqP) to sediment approach, estimated surface 

water concentrations from E-FAST output for the maintenance scenarios, and Koc values for 

sediment and activated sludge. A description of the method is provided in Appendix E. 

Estimated exposure concentrations in local sediments for high-end conditions, under wastewater 

treatment and no wastewater treatment conditions using the natural sediment Koc and activated 

sludge Koc values (which assumes local sediment is predominated by WWTP oc output) are 

provided in Table 4. An additional analysis based on the 10% 30Q5, which is more reflective of 

everyday inputs using the activated sludge Koc was included in the table, as was an analysis of 

the potential for sorbed oc from a WWTP which was exposed to higher concentrations in 

influent to contribute to sediment exposure. 
Page 20 of 68

Table 4 Estimated Local Sediment Concentrations for With and Without Wastewater 

Treatment of Blowdown Water Prior to Discharge 

Scenario Cw (mg/L 

solution) 

Koc (mg/kg-oc 

per mg/L 

solution) 

Cs (mg/kg-sediment) for foc (kg-oc/kgsediment) 

0.002 0.01 0.02 0.04 0.05 

84 kg/site/day, Large-Size Facility, High-End Scenario 

 w/WWTP, 10% 7Q10 0.569 9,810 11.2 55.8 112 223 279 

 w/WWTP, 10% 7Q10 0.569 21,566 24.5 123 245 490 613 

 w/o WWTP, 10% 

7Q10 8.1 9,810 160 798 1,595 3,191 3,989 

 WWTP effluent oc 8.1* 21,566 351 1,754 3,507 7,015 8,769 

 w/ WWTP, 10% 

30Q5 0.335 21,566 14.4 72.2 144 289 361 

0.03 kg/site/day, Medium-Size Facility, Average Scenario 

 w/WWTP, 10% 7Q10 0.0002 9,810 0.004 0.020 0.039 0.078 0.098 

 w/WWTP, 10% 7Q10 0.0002 21,566 0.009 0.043 0.086 0.172 0.216 

Cs = DTEA sediment concentration; Cw = DTEA dissolved surface water concentration; w/ = with; w/o = without 

* An estimate of DTEA sorbed to effluent oc which may potentially contribute to sediment where influent DTEA 

concentration (8.1 mg/L) is set to the discharge level without wastewater treatment. 

4.2.2 Analysis of Influence of Ratios of Plant Flow to Stream Flow Distributions on Estimates of

Numbers of Days per Year of Exceedance of COCs

 The General Population Exposures and Industrial Releases module of E-FAST was run 

using the distribution of plant flows to stream flows for the Industrialized POTWs SIC code. A 

sample comparison of estimates of number of days of exceedance of COCs out of 360 days per 

year of release of DTEA for the Steam Electric Power Plants SIC code and the Industrialized 

POTWs SIC code is presented in Table 5 assuming that 2.8 kg/site-day of DTEA is released to 

water and 93 percent is removed via sorption to activated sludge during wastewater treatment. 

Table 5 Comparison of Number of Days per Year of Exceedance of COCs: Steam Electric 

Power Plants SIC Code versus Industrialized POTWs SIC Code (2.8 kg/site/day and 93% 

Removal During WWT and 360 Days of Release per Year) 

SCENARIO COC = 110 ppb COC = 17 ppb COC = 10 ppb COC =1.7 ppb 

HIGH-END SCENARIO 

Steam Electric Power Plants SIC Code 18 91 126 270 

Industrialized POTWs SIC Code 4 88 144 314 

AVERAGE CASE SCENARIO 

Steam Electric Power Plants SIC Code 2 9 13 37 

Industrialized POTWs SIC Code 0 12 23 91 

4.2.3 Estuarine/Marine Organisms

 No exposure modeling was conducted specifically for estuarine/marine environments. 

There are no estuarine/marine toxicity data. See Section 4.4.2 for discussion of potential risks. 
Page 21 of 68

4.2.4 Residue Levels in Aquatic Biota

 There were no fish or shell fish bioconcentration studies submitted to the Agency or 

found in the open literature for DTEA. EPI Suite (version 4.11), which includes the BCFBAF 

Program (version 3.01), was used to estimate bioconcentration and bioaccumulation factors 

(BCF and BAF, respectively) for DTEA. Results are provided in Appendix F. Bioaccumulation 

factors (BAFs) range from 210.3 L/kg ww (log BAF 2.329) in the lower trophic level to 239.3 

L/kg ww (log BAF 2.379) for the upper trophic level assuming biotransformation occurs. 

Assuming no biotransformation, the upper trophic level BAF is 927 L/kg ww (log BAF 2.967). 

The BAFs and estimated exposure concentrations in water were used as described in Appendix F 

to estimate residues in aquatic organisms. 

 Residue levels for the maintenance use applications were estimated under conditions of 

no wastewater treatment prior to discharge and wastewater treatment prior to discharge. The 

fouled system treatment was assumed to occur infrequently and therefore unlikely to result in 

residue levels in the aquatic system of concern. At the assumed one time annual use rate for a 

fouled system, daily maintenance would be expected to control exposure concentrations. 

Mitigating factors such as proportion of population exposed on the day of release, proportion of 

diet these organisms would constitute, growth dilution, sediment burial, etc. all make it unlikely 

to result in any detectable residues of concern. 

4.2.4.1 Cooling Tower Maintenance Use with Wastewater Treatment Prior to Discharge

 At the high end (10% 7Q10) estimated dissolved water concentration of 0.569 mg 

DTEA/L, under maintenance use of DTEA·HCl, and using the upper trophic level log BAF 

estimate of 2.967 (assumption of no biotransformation) results in an estimated residue level of 

527 mg DTEA/kg-tissue ww. Assuming biotransformation the upper trophic level log BAF 

estimate of 2.379 results in an estimated residue level of 136 mg/kg-tissue ww. At the lowest 

label application rate for maintenance the tissue residue levels for this case (0.185 mg/kg-tissue 

ww and 0.048 mg/kg-tissue ww without and with biotransformation, see Appendix F). 

4.2.4.2 Cooling Tower Maintenance Use with No Wastewater Treatment Prior to Discharge

 Setting the water concentration to the high end (10th percentile 7Q10) estimated dissolved 

water concentration of 8.132 mg DTEA/L and using the upper trophic level log BAF estimate of 

2.967 (assumption of no biotransformation) results in an estimated residue level of 7,537 mg 

DTEA/kg-tissue ww. Assuming biotransformation occurs, the upper trophic level log BAF 

estimate of 2.379 results in an estimated residue level of 1,946 mg/kg-tissue ww. 

4.3 Risk Estimation

 Risk estimation integrates the results of the exposure and ecotoxicity data to evaluate the 

likelihood of adverse ecological effects. There are generally two approaches used in assessing 

risks from industrial process and water systems, a risk quotient (RQ) method and a probabilistic 
Page 22 of 68

method. In this assessment RQ values were not calculated because of limitations in exposure 

modeling and/or toxicity data. However, information was used semi-quantitatively and 

references to these values are made within the document and therefore this information is 

provided to aid understanding of the comparisons and conclusions drawn. Details of these 

methods are described in Appendix C. 

4.4 Risks to Freshwater Fish and Aquatic Invertebrates.

4.4.1.1 Risks to Freshwater Organisms based on Maintenance Treatment Scenarios

Water Column

 The amount of product containing DTEA used for maintenance treatment can range from 

0.5 to 2.0 fluid ounces for continuous feed methods and 0.5 to 25 fluid ounces based on 

intermittent or slug methods. For the purpose of assessing exposures to aquatic organisms from 

maintenance applications, it is assumed that environmental releases via cooling tower blowdown 

water to surface water can occur 360 days per year. Results from the industrial releases module 

of E-FAST based on maintenance applications are presented in Appendix D in Tables 10 through 

17. Tables 10 through 13 present results based on the assumption that there is direct discharge to 

surface water (no removal of DTEA via wastewater treatment prior to discharge of blowdown 

water to surface water). Tables 14 through 17 present results based on the assumption that 

blowdown water undergoes wastewater treatment prior to discharge and that 93 percent is 

removed based on activated sludge sorption isotherm data that indicate that from 93 to 98 

percent of DTEA is removed during wastewater treatment via sorption to activated sludge. 

 In summary, the estimated numbers of days of exceedance of concentrations of concern 

for aquatic organisms increase as environmental releases increase for maintenance treatment and 

are: 

 higher for large-size cooling towers than for moderate-size cooling towers; 

 higher for recirculating cooling towers that discharge blowdown water without treatment than 

those that discharge blowdown water following wastewater treatment; and 

 higher for the high-end scenario than the average case scenario. 

 It is important to note that there are exceedances of concentrations of concern for aquatic 

organisms for all scenarios examined, including the scenario that predicts the lowest number of 

days of exceedance of concentrations of concern: the average case scenario for a moderate-size 

cooling tower that discharges blowdown water following wastewater treatment (See Table 17). 

At the lowest environmental release for moderate-size cooling towers of 0.03 kg/site/day (0.5 

ppm), however, the only COC exceeded is that for endangered freshwater invertebrates (1.7 

ppb), and that exceedance is only for one day of 360 days per year of release. 
Page 23 of 68

Benthic Invertebrates

 Under the high end use scenario for both the 7Q10 and 30Q5 flow conditions and with 

wastewater treatment prior to discharge, estimated DTEA concentrations in sediments (11.2 to 

613 mg/kg-sediment, Table 4) under a range of organic carbon levels exceed the chronic DTEA 

NOAEC values for benthic organisms (0.15 to 8.4 mg/kg-sediment, Table 1). This indicates the 

potential for chronic effects to the aquatic benthic organisms under the maximum label use rate. 

For the no wastewater treatment scenario prior to discharge, the risks are indicated to be greater 

(estimated sediment concentrations range from 160 to 3,989 mg/kg-sediment compared to 

NOAEC values of 0.15 to 8.4 mg/kg-sediment). 

 At the lowest maintenance application rate, for medium-size facilities, and average 

conditions, estimated DTEA sediment concentrations (0.004 to 0.216 mg/kg-sediment) do not 

exceed the chronic DTEA NOAEC values for benthic organisms (0.15 to 8.4 mg/kg-sediment, 

respectively, Table 1). This indicates under these conditions, unacceptable adverse effects to 

benthic invertebrates due to DTEA are not likely. 

4.4.1.2 Estimates of Exposures and Risks Based on Initial Treatment of a Fouled System Scenarios

Water Column Exposure

 According to the product label, the amount of product containing DTEA used for initial 

treatment can range from 6 to 41 ounces for both continuous feed and intermittent/slug methods. 

In the case of the continuous feed method, the recommended application rate range of 6-41 fluid 

ounces for initial treatment is always higher than the recommended application rate range of 0.50 

to 2.0 fluid ounces for maintenance treatment. In the case of the intermittent or slug method, the 

recommended application rate range of 6-41 ounces for initial treatment is not always higher 

than the recommended application rate range of 0.5-25 fluid ounces for maintenance treatment. 

The annual frequency and duration of initial treatment applications is uncertain. For the purpose 

of assessing exposures to aquatic organisms from initial treatment applications, it is assumed that 

environmental releases of DTEA to surface water via cooling tower blowdown water occur for 

one day. Tables 18 through 25 present information on whether or not concentrations of concern 

for aquatic organisms are exceeded for one day of release to surface water. 

 Surface water concentrations estimated using General Population Exposures and 

Industrial Releases module of E-FAST assume that all DTEA released to surface water is present 

in the dissolved phase in the water column. Based on the log Kow value of 3.7 for DTEA, as a 

result of the potential for DTEA to sorb to suspended solids and aquatic sediments, 

concentrations in the dissolved phase of the water column would be expected to be somewhat 

lower than modeling results indicate; consequently, the number of days per year of exceedance 

of concentrations of concern would also be expected to be somewhat lower than values based on 

model estimates. 
Page 24 of 68

4.4.2 Risks to Estuarine/Marine Organisms

 For use in facilities discharging to estuarine/marine environments the DTEA-HCl label 

requires treatment through a WWTP which would reduce the amount of DTEA released to the 

environment by over 90%. However, based on the results for freshwater systems after treatment, 

potential risks for freshwater aquatic organisms were identified. EPA does not have toxicity data 

for estuarine/marine organisms to show that they would be less sensitive to exposure to DTEA 

than freshwater organisms. In the absence of data. EPA assumes that the use and release of 

DTEA to estuarine and marine systems would result in risks of concern for estuarine and marine 

aquatic organisms. 

4.4.3 Risks to Piscivorous Birds and Mammals

4.4.3.1 Cooling Tower Maintenance Use with Wastewater Treatment Prior to Discharge

 No definitive acute risk quotients (RQs) can be calculated for birds because the acute oral 

LD50 (>2250 mg/kg-bw) and subacute dietary LC50 (>5620 mg/kg-diet; 30% mortality at this 

dietary level) were greater than the highest dose and concentration tested, respectively. 

However, what is evident is that on a dietary basis the potential DTEA residues in the upper 

trophic level, even under the high-end scenario and for an assumption of no biotransformation, 

are more than 10 times lower than the residue levels tested. Residue levels at the middle and 

lower trophic levels are expected to be even lower than the upper trophic level. Therefore, the 

potential for listed and nonlisted acute levels of concern (LOCs) for birds to be exceeded are 

considered unlikely. There are no chronic toxicity data for avian species, therefore no chronic 

RQ could be calculated. 

4.4.3.2 Cooling Tower Maintenance Use with No Wastewater Treatment Prior to Discharge

 Estimated upper trophic residue levels assuming no biotransformation (7,537 mg/kgtissue ww exceeds the subacute dietary level tested with mallard ducks (5620 mg/kg-diet). 

Because this exposure level in the subacute dietary test resulted in 30% mortality, acute levels of 

concern would be expected to be exceeded for listed and nonlisted avian species. Under the high 

end exposure conditions estimated surface water concentrations exceed acute and chronic levels, 

therefore, while residue levels can be calculated based on this estimate the food chain is likely to 

disrupted and impacted by acute effects. Estimated residues in the upper trophic level are not 

likely reasonable in this case. 

4.5 Risk Characterization

 DTEA-HCl is registered for use in re-circulating process water systems to control 

bacterial, fungal and algal slimes. DTEA-HCl is not marketed at this time, so predicted 

exposures are theoretical. Since this use could have a potential for environmental exposure to 

non-target organisms, a risk assessment was conducted. This is particularly important since the 

studies included in this assessment indicate that DTEA is highly to very highly toxic to aquatic 

organisms on both an acute and chronic basis. 
Page 25 of 68

 The results of the risk assessment indicate that DTEA could potentially adversely affect 

non-target aquatic organisms, and wildlife that ingest fish and shellfish. The risk assessment 

evaluated exposure and risks to aquatic organisms in the water column, in the benthic 

compartment, and to wildlife from bioaccumulation in the aquatic food chain. This section 

characterizes these potential risks and uncertainties. 

 Potential exposures and risks to DTEA from releases of blowdown water from 

recirculating cooling towers in the dissolved phase of the water column were estimated for the 

following circumstances: 

 Initial treatments for fouled systems (1 day event) versus maintenance treatments (360 days per

year);

 Large‐size (1.7 – 84 kg/site/day DTEA to surface water ) versus moderate‐size (0.03 – 1.7

kg/site/day DTEA to surface water) recirculating cooling towers;

 High‐end versus average case scenarios from E‐FAST; and  

 Wastewater treatment (93 percent removal of DTEA via sorption to activated sludge) versus no

wastewater treatment prior to discharge of blowdown water to surface water.

The influence of these factors on estimates of potential exposures and risks to DTEA is 

discussed in 4.4.1.1. A probabilistic approach that estimates the number of days of exceedance 

of concentrations of concern (COCs) for aquatic organisms was used to estimate exposures and 

risks to key receptor groups. 

 Based on probabilistic modeling results, if the acute COC (one-half of theLC50 or EC50) 

determined for any key aquatic receptor group is exceeded for one day or more based on results 

from the high-end scenario (i.e., the 10th percentile of the ratio of stream flows to plant flows), 

then potential acute risks to such receptor groups are indicated. In addition, if the endangered 

COC (one-twentieth of the LC50 or EC50 ) determined for any key aquatic receptor group is 

exceeded for one day or more based on results from the high-end scenario, then potential acute 

risks to endangered aquatic organisms in such receptor groups are indicated. Furthermore, if the 

chronic COC (NOAEC or NOAEL) for any key aquatic receptor group is exceeded for 20 days 

or more based on results from the high-end scenario, then potential chronic risks for such 

receptor groups are indicated. 

 For maintenance applications at large-size cooling towers, assuming 360 days per year of 

release of blowdown water to surface water, the potential for acute risks to endangered and nonendangered freshwater fish and invertebrates and chronic risks to freshwater fish and 

invertebrates based on the high-end scenario is predicted at all application rates proposed on the 

product label whether or not discharges undergo wastewater treatment (See Tables 10 and 14, 

Appendix D). 
Page 26 of 68

 For maintenance applications at moderate-size cooling towers, assuming 360 days per 

year of release of blowdown water to surface water and discharge of blowdown water untreated 

(Table 11, Appendix D), results based on the high-end scenario indicate: 

 The endangered and acute COCs for freshwater invertebrates are exceeded one day or more at all 

application rates proposed on the product label. 

 The endangered freshwater fish COC is exceeded one day or more at all application rates 

proposed on the product label and the acute COC for freshwater fish is exceeded for one day or 

more for all but the lowest application rate (0.5 ppm DTEA ae) proposed on the product label. 

 The chronic COC for freshwater invertebrates (COC = 7.8 ppb) is exceeded for 20 days or more 

at the two highest application rates modeled (5.9 and 24.4 ppm DTEA ae). 

 The chronic COC for freshwater fish (COC = 36.5 ppb) is exceeded for 20 days or more at the 

highest application rate (24.4 ppm DTEA ae) proposed on the product label. 

 For maintenance applications at moderate-size cooling towers, assuming 360 days per 

year of release of blowdown water to surface water and discharge of blowdown water following 

wastewater treatment (93% removal of DTEA via sorption to activated sludge during wastewater 

treatment) (Table 15, Appendix D, results based on the high-end scenario indicate: 

 The endangered and acute COCs for freshwater invertebrates are exceeded one day or more at all 

application rates proposed on the product label. 

 The endangered freshwater fish COC is exceeded one day or more at all application rates 

proposed on the product label and the acute COC for freshwater fish is exceeded for one day or 

more for all but the lowest application rate (0.5 ppm DTEA ae) proposed on the product label. 

 The chronic COC for freshwater invertebrates (COC= 7.8 ppb) is exceeded for 20 days or more at 

all but the lowest application rate (0.5 ppm DTEA ae) proposed on the product label. 

 The chronic COC for freshwater fish (COC = 36.5 ppb) is exceeded for 20 days or more at the 

highest application rate (24.4 ppm DTEA ae) proposed on the product label. 

 As a result of initial applications to fouled systems, releases to surface water are expected 

to be episodic and occur for one day per initial application. In the case of initial treatment 

scenarios, modeling was performed to determine whether or not there would be exceedance of 

COCs for one day of discharge. All high-end scenarios modeled for initial treatment predicted 

exceedances of at least some COCs for one day. For the high-end scenario for large-size cooling 

towers with no treatment, all COCs were predicted to be exceeded for the one day of discharge at 

all application rates proposed on the product label.. For the high-end scenario for large-size 

cooling towers with 93 percent removal during wastewater treatment, all COCs were exceeded at 

all application rates proposed on the label with the exception of the acute COC for freshwater 

fish at the lowest application rate (20.4 kg/site/day). For the high-end scenario for moderate-size 

cooling towers with 93 percent removal during wastewater treatment, only the COC for the 

endangered freshwater invertebrate was exceeded at the higher two of three application rates 

proposed on the product label. Of the four average case scenarios modeled for initial treatment, 
Page 27 of 68

only for the scenario for the large-size cooling tower with no wastewater treatment were 

exceedances of COCs predicted for one day for some aquatic organisms. 

 There is a potential for acute and chronic risks to terrestrial wildlife that ingest fish and 

shellfish from bioaccumulation under the high end use with no pretreatment prior to discharge. 

There is a large degree of uncertainty in this portion of the assessment because the 

concentrations of DTEA expected under this scenario would be acutely lethal to a wide variety 

of species, which would impact actual levels of DTEA in the food chain. With wastewater 

treatment prior to discharge acute risks to terrestrial wildlife are not likely. There is some 

uncertainty regarding chronic effects. 

4.5.1 Effect of Exposure Assumptions

4.5.1.1 Exposures and Risks to Aquatic Organisms to DTEA in the Dissolved Phase of the Water

Column

 Potential exposures and risks to DTEA from releases of blowdown water from 

recirculating cooling towers to surface water were examined for the following circumstances: 

 Initial treatments for fouled systems versus maintenance treatments; 

 Large-size versus moderate size recirculating cooling towers; 

 High-end versus average case scenarios from E-FAST; and 

 Wastewater treatment versus no wastewater treatment prior to discharge of blowdown water to 

surface water. 

The magnitude of exposure of aquatic organisms to releases of recirculating cooling tower 

blowdown water to surface water is directly correlated with the product application rate. The 

application rate of DTEA proposed on the product label can be higher for initial treatment of 

fouled systems than for maintenance treatment: 6 to 41 fluid ounces of product per thousand 

gallons for initial treatment compared with 0.5 to 25 fluid ounces per thousand gallons for 

maintenance treatment. The duration of exposure to aquatic organisms from releases to surface 

water from initial treatment of fouled systems, however, would be expected to be much shorter 

than that for maintenance treatment. For modeling purposes, releases from blowdown water 

following initial treatment applications were assumed to be one day per initial treatment episode, 

whereas releases from blowdown water following maintenance treatment applications were 

assumed to occur on a daily basis (360 days per year). The annual frequency of initial treatment 

applications is expected to vary from site to site depending upon the rate at which a system can 

become fouled; this annual frequency can generally be expected to be considerably less than that 

for maintenance treatment. 

 For the maintenance treatment levels (discharge of 360 days per year), there are some 

exceedances of concentrations of concern for aquatic organisms for all scenarios examined. In 

summary, with regard to maintenance treatment the estimated number of days of exceedance of 
Page 28 of 68

concentrations of concern (COCs) for aquatic organisms increase as environmental releases 

increase for maintenance treatment and are: 

 Higher for large-size cooling towers than for moderate-size cooling towers; 

 Higher for recirculating cooling towers that discharge blowdown water without treatment than 

those that discharge blowdown water following wastewater treatment; and 

 Higher for the high-end scenario than the average case scenario. 

 These same trends are observed when estimating whether or not concentrations of 

concern for aquatic organisms are exceeded for one day of release of blowdown water to surface 

water following initial treatment of fouled systems. In the case of initial treatment scenarios, 

modeling was performed to determine whether or not there would be exceedance of COCs for 

one day of discharge. Of the four average case scenarios modeled for initial treatment, only for 

the scenario for the large-size cooling tower with no wastewater treatment were exceedances of 

COCs predicted for one day for some aquatic organisms. All high-end scenarios modeled for 

initial treatment predicted exceedances of at least some COCs for one day. For the high-end 

scenario for large-size cooling towers with no treatment, all COCs were predicted to be exceeded 

for the one day of discharge at all application rates proposed on the product label.. For the highend scenario for large-size cooling towers with 93 percent removal during wastewater treatment, 

all COCs were exceeded at all application rates proposed on the label with the exception of the 

acute COC for freshwater fish at the lowest application rate (20.4 kg/site/day). For the high-end 

scenario for moderate-size cooling towers with 93 percent removal during wastewater treatment, 

only the COC for the endangered freshwater invertebrate was exceeded at the higher two of three 

application rates proposed on the product label. 

 Exposures to aquatic organisms from releases of blowdown water from large-size 

recirculating cooling towers were predicted to be higher than those for moderate-size cooling 

towers as a result of the much higher recirculation rates assumed for large-size recirculating 

cooling towers than for moderate-size cooling towers. The standard scenario developed by the 

Chemical Engineering Branch of the Office of Pollution Prevention and Toxics (OPPT/CEB) 

assumes that the recirculation rate is 2000 gallons per minute for moderate-size cooling towers 

and 100,000 gallons per minute for large-size cooling towers. Consequently, environmental 

releases to surface water from recirculating cooling tower blowdown water are estimated to be 

much higher for large-size cooling towers than for moderate-size cooling towers. Environmental 

releases of DTEA from maintenance treatments can range from 1.7 to 84 kg/site/day for largesize cooling towers compared to 0.03 to 1.7 kg/site/day for moderate-size cooling towers. 

 The Industrial Releases module of E-FAST was also used to examine the influence of the 

selection of Standard Industrial Classification (SIC) code on the modeling results (See Table 5). 

The selection of SIC code influences the distribution of the ratio of stream flows to plant flows. 

The estimated number of days per year of exceedance of COCs for steam electric power plants 

were compared with those for industrialized POTWs at an environmental release of 2.8 
Page 29 of 68

kg/site/day assuming 93 percent removal during wastewater treatment and 360 days per year of 

release for both average case and high-end scenarios. The Industrialized POTWs SIC code 

might be considered to be more representative of the ratio of stream flows to plant flows for 

moderate-size recirculating cooling towers. The results of this comparison predict that for both 

high-end and average case scenarios, the numbers of days per year of exceedance are fewer for 

the Industrialized POTWs SIC code than for the Steam Electric Power Plants SIC code at higher 

COCs (e.g., COC=110 ppb) modeled and greater for the Industrialized POTWs SIC code than 

for the Steam Electric Power Plants SIC code at lower COCs (e.g., COC = 10 and 1.7 ppb). 

4.5.2 Uncertainties

4.5.2.1 Estimated Benthic Invertebrate Toxicity Values

 Sediment toxicity values were estimated using the EqP approach. Since the water 

column testing used in the EqP approach does not include food that has accumulated DTEA, the 

estimated sediment toxicity values using the EqP approach will potentially underestimate this 

exposure pathway. Sediment ingestion for benthic invertebrates is a critical exposure pathway 

for the guideline sediment tests. The result of this pathway not being included may result in 

underestimation of risk. Because the high-end scenarios were greatly over the estimated 

sediment toxicity values, this uncertainty does not impact risk conclusions. 

4.5.2.2 Bioaccumulation/Bioconcentration in Fish and Shellfish

 Bioconcentration and bioaccumulation in fish and shellfish were estimated because of the 

lack of a fish and mollusk bioconcentration study. Biotransformation can play a major role in 

the mitigating estimations of bioconcentration and bioaccumulation. The degree of this impact is 

unknown in this case. EPI Suite provided some estimates of biotransformation for the BAF and 

BCF values used in the assessment and these were used in assessing risks. 

4.5.2.3 Aquatic Plant Toxicity Data

 For this use pattern a battery of three algal species (green algae, freshwater diatom, 

saltwater diatom), in addition to a cyanobacteria, a floating macrophyte (duckweed), and a 

seedling emergence test for an emergent, rooted macrophyte (rice) representing different 

sensitivities and environmental habitats are used to assess risk for the recirculating process water 

system use pattern. Only a green algae study was submitted and no public literature studies were 

found. Because DTEA is the only member of this class structure currently registered in the U.S., 

there was no possibility of using submitted toxicity data from closely-related surrogate chemicals 

to fill in these data gaps. The availability of just the green algae data may result in 

underestimation of risks for aquatic plants. For the high-end exposures evaluated the lack of this 

data does not change the risk conclusions. However, at the lower use rates this potentially 

introduces a large degree of uncertainty where COCs are not exceeded for aquatic plants. 
Page 30 of 68

4.6 Endangered Species Assessment

 Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2), requires all 

federal agencies to consult with the National Marine Fisheries Service (NMFS) for marine and 

anadromous listed species, and/or the United States Fish and Wildlife Service (USFWS) for 

listed wildlife and freshwater organisms, if they are proposing an "action" that may affect listed 

species or their designated critical habitat. Each federal agency is required under the Act to 

ensure that any action they authorize, fund, or carry out is not likely to jeopardize the continued 

existence of a listed species or result in the destruction or adverse modification of designated 

critical habitat. To jeopardize the continued existence of a listed species means "to engage in an 

action that reasonably would be expected, directly or indirectly, to reduce appreciably the 

likelihood of both the survival and recovery of a listed species in the wild by reducing the 

reproduction, numbers, or distribution of the species" (50 C.F.R. § 402.02). 

 To facilitate compliance with the requirements of the Endangered Species Act 

(subsection (a)(2)), the Office of Pesticide Programs has established procedures to evaluate 

whether a registration action may directly or indirectly appreciably reduce the likelihood of both 

the survival and recovery of a listed species in the wild by reducing the reproduction, numbers, 

or distribution of any listed species (USEPA, 2004). After the Agency’s screening level risk 

assessment is conducted, if any of the Agency’s listed species’ LOCs are exceeded for either 

direct or indirect effects, an analysis is conducted to determine if any listed or candidate species 

may co-occur in the area of the pesticide use or areas downstream or downwind that could be 

contaminated from drift or runoff/erosion. If listed or candidate species may be present in the 

proposed action area, further biological assessment is undertaken. The extent to which listed 

species may be at risk is considered, which then determines the need for the development of a 

more comprehensive consultation package, as required by the Endangered Species Act. 

 The federal action addressed herein is the proposed registration review of DTEA-HCl for 

use in recirculating cooling towers and it is expected that its use could occur nationwide. 

4.6.1 Action Area

 For listed species assessment purposes, the action area is considered to be the area 

affected directly or indirectly by DTEA-HCl use and not merely the immediate area where it is 

applied. At the initial screening-level, the risk assessment considers broadly described 

taxonomic groups and conservatively assumes that listed species within those broad groups are 

co-located with the pesticide treatment area. This means that listed terrestrial plants and wildlife 

are assumed to be located on or adjacent to the treated site (cooling tower) and listed aquatic 

organisms are assumed to be located in a surface water body adjacent to the treated site (cooling 

tower). The assessment also assumes that the listed species are located within an assumed area, 

which has the relatively highest potential exposure to the pesticide, and that exposures are likely 

to decrease with distance from the treatment area. 
Page 31 of 68

4.6.2 Taxonomic Groups Potentially at Risk

 The screening level COCs provided in this assessment would indicate a potential for a 

"may affect" conclusion for direct effects on aquatic listed species and may extend to indirect 

effects upon listed species that depend upon that a particular taxonomic group as a resource. In 

such cases, additional information on the biology of listed species, the locations of these species, 

and the locations of use sites are considered to determine the extent to which screening 

assumptions regarding an action area apply to a particular listed organism. These subsequent 

refinement steps will consider how this information would impact the action area for a particular 

listed organism and potentially include areas of exposure that are downwind and downstream of 

the pesticide use site. 

4.6.3 Listed Species Occurrence Associated with DTEA‐HCl Use

 The screening-level risk assessment for DTEA-HCl assumes that it may be applied 

nationwide, including U.S. territories and possessions, unless spatially limited by label. 

Therefore, no federally listed species are excluded from the screening level analyses, unless 

otherwise indicated (e.g., if only listed due to Similarity of Appearance to another listed species). 

A spatial co-occurrence analysis that compares the best available data regarding DTEA-HCl 

potential and documented use areas and listed species occurrence is needed to more explicitly 

address potential risk to listed species of concern. 

 At this stage of the Registration Review process, it is premature to make effects 

determinations for listed species until further refinements are conducted. In order to make 

effects determinations for individual species, useful refinements may include analyses of 1) more 

detailed, species-specific ecological and biological data; 2) more detailed and accurate 

information on DTEA-HCl use patterns; and 3) sub-county level spatial proximity data for the 

co-occurrence of potential effects areas and listed species and any designated critical habitat. 

 Refinements may include more detailed analyses of the registered uses and their use 

patterns that result in LOC exceedances for federally listed species in the screening-level 

assessment. The analyses may include more information on where, when, and how DTEA-HCl 

is used. 

 In addition, On April 30, 2013, the National Academy of Sciences’ National Research 

Council (NRC) released their recommendations for assessing risks from pesticides to listed 

species under the Endangered Species Act (ESA) and the Federal Insecticide, Fungicide, and 

Rodenticide Act (FIFRA). The Environmental Protection Agency, the U.S. Department of 

Agriculture, the U.S. Fish and Wildlife Service, and the National Marine Fisheries Service are 

working collaboratively to identify improvements in the current scientific procedures used in 

evaluating the potential impacts of pesticides to endangered and threatened species. 
Page 32 of 68

5.0 SUMMARY OF RISKS

DTEA-HCl is currently not marketed in the US and therefore, all estimated exposures 

are theoretical. However, if DTEA-HCl is marketed in the future, EPA believes that risks to 

human health from the use of DTEA-HCl are expected to be minimal based on current labels. 

Risks to non-target birds and mammals are also expected to be minimal. There is a 

potential risk to birds that consume fish that are exposed to releases from large towers treated at 

the maximum treatment rate without wastewater treatment prior to release. This risk is highly 

uncertain. 

There are potential risks to all aquatic organisms from releases of cooling tower waters 

including releases of water which has been treated in a wastewater treatment facility prior to 

release. Aquatic invertebrates and algae are more sensitive to DTEA than are freshwater fish, 

but all aquatic organisms would be affected if a release occurs. Maintenance treatments which 

result in daily releases are expected to result in greater risks than initial treatments that result in 

single (one time) release. 

Benthic organisms would be exposed to DTEA as it sorbs to sediment. Chronic risks 

are estimated for treatments of large towers and high rates with no chronic risks for benthic 

organisms from moderate size towers treated at low rates. 

There are several uncertainties associated with this risk assessment. On the hazard 

assessment, EPA made conservative assumptions based on the lack of definitive toxicity data on 

benthic organisms, estuarine and marine organisms, aquatic plants and chronic data for birds. 

For the exposure assessment, lack of aquatic metabolism data and bioaccumulation data on fish 

and shellfish resulted in conservative exposure assumptions. 
Page 33 of 68

APPENDIX A: Environmental Fate

 When DTEA·HCl is added to water, it dissociates into DTEA and HCl. Table 6 

summarizes studies on DTEA·HCl and its major reaction product DTEA which were submitted 

and reviewed prior to the FWP, and those submitted and reviewed in response to the GDCI. The 

studies requested as part of GDCI were a ready biodegradability study and an activated sludge 

respiration inhibition (ASRI) study. Both were reviewed and accepted. Changes in models used 

to estimate some property and fate characteristics in the FWP have been updated, so the latest 

model versions were run and these values have also been updated in Table 6. 

 Since the FWP, additional exposure pathways have been identified for the recirculating 

cooling system use pattern which needed to be considered in this assessment given DTEA 

properties and fate in the aquatic system. Bioaccumulation was identified as a potential exposure 

route as log Kow values for DTEA are above 3 and DTEA is not rapidly degraded. Because no 

bioconcentration study was required at the time of the FWP, bioconcentration factors (BCFs) and 

bioaccumulation factors (BAFs) were estimated for DTEA and are included in Table 6. 

Sediment exposure of benthic invertebrates to DTEA was identified as a potential exposure route 

of concern based on estimated soil organic carbon-water partition coefficient (Koc) and soil 

sorption (Kd) values. The Agency used this information to characterize concentrations in 

sediment below recirculating cooling water systems in Section 4.2.1.1. 

Table 6. Physical/Chemical Characteristics and Environmental Fate Studies and Results 

GLN: Study Type MRID#: Reference Study Summary Results, Conclusions, and 

Study Classification 

835.2110: Hydrolysis 

of DTEA as function of 

pH 

MRID# 40126404: Fate of 

N-decythioethylamine in 

the environment by 

Gonsoir S (1986) 

Report# ES-DR 0065-

5425-1; prepared, 

submitted by Dow Chem. 

Co. 

Percent purity of the active 

ingredient: 99.8. Study was 

conducted under sterile, and 

buffered medium at pH 

5(acetate), pH 7 (phosphate), 

and pH 9 (borate). The active 

ingredient in acetonitrile was 

added @ 3.8 ppm level and 25 

± 0.5 o

C. Samples were 

collected, diluted and analyzed 

by using reverse phase ion 

exchange HPLC. The detection 

limit was 0.1 ppm 

Hydrolytic half life was 

estimated at 66 days (pH 5), 

480 days (at pH 7) and 360 

days (at pH 9). 

The study is classified as 

ACCEPTABLE for pH 5, and 

7, but as SUPPLEMENTAL 

for pH 9. The data at pH 9 

was ambigous, and a second 

study was requested, and the 

registrants submitted a 

separate study on pH 9, as 

discussed below. 

DTEA is persistent at these 

pHs under abiotic conditions. 
Page 34 of 68

GLN: Study Type MRID#: Reference Study Summary Results, Conclusions, and 

Study Classification 

835.2110: Hydrolysis 

of DTEA as a function 

of pH 

MRID# 41198301: 

Gonsior, S, 1989) study 

submitted by Dow Chem 

Co. : Hydrolysis at pH 9 

on the Ndecylthioethaneamine 

hydrochloride with C-14 

radiolabeled at position 2 

Study ID: ES-DR-0224-

8182-2 

The solution was buffered at 

pH 9 and ai at 6.8 ppm with ai 

being at 92% purity. 

Percent recovery: 93% of the 

C-14 activity after 28 days 

means that there was no loss 

due to adsorption on the walls, 

or possible formation of 

volatiles. 

DTEA undergoes 

transformation at pH 9, in 

0.01 M borate solution. Half 

life estimated at 30 days. 

Thus at pH 9, the half life is 

considered borderline stable 

in water under abiotic 

conditions. Study is 

classified as ACCEPTABLE. 

835.1110: Activated 

Sludge Sorption 

Isotherm for DTEA 

MRID# 49004201: 

Submitted by Dow Chem. 

Co. Study ID# 120010; 

conducted by Schaefer, 

EC, and Ponizovsky, AA. 

Samples of the ai (DTEA) 

were prepared with the 

activated sludge solids at 

concentrations of 0.05, 0.10, 

0.30, 0.50 and 0.90 g/L in 

phosphate buffer and at pH 7.3. 

The concentrations of the 

activated solids ranged from 

0.05 to 0.92g/L. The inoculum 

of the activated sludge was 

collected from the wastewater 

treatment plant in Cambridge, 

MD. The sludge was 

pretreated and in the final 

stage, and consisted of 37.78% 

organic carbon. 

The active (DTEA) adsorbed 

to the activated sludge ranged 

from 93.2-98.5% of the 

applied. The Kd (av) = 8148 

ml/g; Koc = 21566 ml/g 

The Koc and or Kd values 

strongly indicate that DTEA 

is immobile and will stay on 

activated sludge surfaces. 

The microbes present are not 

affected by this active. 

The study is classified as 

ACCEPTABLE. 

OECD Test guideline 

No. 209: Activated 

Sludge Respiration 

Inhibition Test for 

DTEA 

MRID# 41198306: 

Conducted by Davis, JW, 

and Madsen, SS, 1989: 

Activated Sludge, 

Inhibition Test for 2-

decylthioethaneamine. 

Submitted by Dow 

Chem.Co. 

The study measures the 

concentration of the active at 

which oxygen consumption is 

inhibited at a 50% rate. The 

IC50 in this study was 

determined to be 27 ppm for 

the active. 

The IC50 for the reference 

substance (3,5-dichlorophenol) 

was measured to be 17 mg/L. 

The IC50 for the reference 

material should be between 5-

30 mg/L. Also if the active has 

an IC50 value above 30 mg/L, 

then this substance would be 

highly toxic. 

The IC50 value measured was 

27 mg/L, thus it within the 

safe limit of IC50 for conduct 

of a ready biodegradability 

study. 

The study was deemed 

SUPPLEMENTAL as some 

raw data were missing. 

OECD Guideline 

301D: BOD Closed 

Bottle TEST for Ready 

Biodegradability 

(Equal to: 835.3110) 

for DTEA 

MRID# 49004202: 

Submitted by Dow Chem. 

Co; Study ID# 121050; 

Study conducted by 

Gonsior, S and Holzheur, 

WB. 

Closed Bottle Test was 

conducted on the ai in the 

presence and absence of silica 

gel, over a period of 28 days. 

The microbial inoculum was a 

secondary effluent from a 

wastewater treatment plant 

which was preconditioned by 

filtration and dilution with 

mineral medium. The 

temperature was maintained at 

The test material did not reach 

pass levels of 60% of 

theoretical oxygen demand as 

the degradation was 43.5% 

and 29.3 % for samples of 

DTEA at 1.6 mg/L and 3.1 

mg/L respectively after 28 

days o f the study. 

DTEA is NOT ready 

biodegradable. Thus under 
Page 35 of 68

GLN: Study Type MRID#: Reference Study Summary Results, Conclusions, and 

Study Classification 

21 ± 0.5 oC and the samples 

were kept in darkness. 

biotic conditions too, it is 

stable. 

The study was classified as 

ACCEPTABLE. 

835.1230: Log soil 

organic carbon-water 

partition coefficient 

(Log Koc) for DTEA 

Estimated using EPI Suite, 

version 4.11) Not applicable. 

3.992 (Koc = 9,810) 

The value shows that the 

DTEA has a strong tendency 

to bind to soils. 

The high value of Log Koc 

for soils and activated sludge 

(see above) is a strong 

indication that DTEA remains 

on soil surfaces and not 

migrate to ground water. (It is 

immobile). 

Kd for DTEA 

Equilibrium Partitioning 

Sediment Benchmarks 

(EPA 600/R-02- 2012) 

Kd = Koc x foc where foc = 

mass fraction of soil 

organic carbon content. 

Not applicable. 

0.02% foc Kd = 19.62 

1% foc Kd = 98.1 

5% foc Kd = 490 

The Koc and Kd values mean 

DTEA is expected to partition 

to suspended particles and 

sediment in an aquatic 

system. 

Henry Law Constant 

for DTEA 

Estimated using EPI Suite 

(version 4.11); no test 

guidelines; it is calculated 

based on the vapor 

pressure and the solubility 

of a substance in water 

Not applicable. 

2.76 x 10-5 atm-m3

 / mole 

Borderline value indicates the 

possibility of volatilizing 

from water surfaces is 

moderately high. 

Volatilization from water 

surfaces will reduce the 

surface water concentration of 

DTEA. 

830.7950: Vapor 

pressure for DTEA EPI Suite, version 4.11 Not applicable. 

7.97 x 10-4 mm Hg 

Considered moderately 

volatile. Will volatilize from 

water surfaces in moderate 

measures into the atmosphere.

Non-Guideline: Half 

life in air for DTEA 

Estimated using EPI Suite 

version 4.11, estimated 

against the hydroxyl 

radical reaction 

4.1 hours 

Will degrade quickly and not 

persist in air. No data is 

available on the possible 

degradate formed and or the 

identity of the degradate in 

the air. DTEA is NOT stable 

in air. 

830.784: Water 

solubility for DTEA 40126403 The Kow determinations, along with the solubility of 

0.0035 g/100 g at 25 oC. (30.5 

mg/L at 25 o

C) 
Page 36 of 68

GLN: Study Type MRID#: Reference Study Summary Results, Conclusions, and 

Study Classification 

830.1755: Log wateroctanol partition 

coefficient (Log Kow) 

for DTEA·HCl and 

DTEA. 

DTEA·HCl and DTEA were 

done by using shake flask and 

generator column methods as 

suggested in the test guideline. 

Kow measurements were done 

in HPLC grade water, and also 

in buffered water (pH 7). 

DTEA·HCl: 

2.35 (approx.) using HPLC 

grade water 

DTEA: 

3.72 (mean) using HPLC 

grade water 

3.05 (mean) using pH 7 

buffered water 

Indicates potential for 

bioaccumulation of DTEA in 

aquatic organisms. 

850. 1730 Fish 

Bioconcentration 

Factor (BCF) and 

Bioaccumulation 

Factor (BAF) in units 

of L/kg-wet-weight for 

DTEA 

EPISuite v4.11 

Arnot-Gobas BCF & BAF 

Methods 

Not applicable 

Assumes a biotransformation 

rate of zero: 

BCF (upper trophic) = 2264 

BAF (upper trophic) = 8863 

Includes estimated 

biotransformation: 

BCF (upper trophic) = 516.5 

BAF (upper trophic) = 518 

BCF (mid trophic) = 572.3 

BAF (mid trophic) = 585.9 

BCF (lower trophic) = 575.8 

BAF (lower trophic) = 623.3 

APPENDIX A REFERENCES

EPI Suite, version 4.11 

MRID# 40126404: Gosnoir, S, 1986. Fate of N-decylthioethylamine in the Environment; Test 

Guideline 835.2110, Hydrolysis as a function of pH, Submitted by Dow Chemical Co. 

MRID # 41198301: Gosnoir, S, 1989. Hydrolysis of DTEA at pH 9, Test guideline 835.2110, 

submitted by Dow Chemical Co. 

MRID#: 41198301, Gonsoir, S, 1989: Hydrolysis at pH 9 on N-decylthioethanemaine 

hydrlochloride with C-14 radiolabeled at position 2; submitted by Dow Chem. Co 

MRID#: 49004202: BOD Closed Bottle Test for Ready Biodegradability, Test guideline # 301D, 

submitted by Dow Chemical Co. 
Page 37 of 68

APPENDIX B:  Summary of Ecotoxicity Data for DTEA

Terrestrial Studies: DTEA was found to be practically non–toxic to birds based on acute 

toxicity testing of Mallard Duck (LD50 = >2250 mg/kg), and dietary toxicity testing of both 

Bobwhite Quail (LC50=>5620 mg/kg) and Mallard Duck (LC50=>5620 mg/kg). 

Aquatic Studies: DTEA was found to be highly toxic to rainbow trout (LC50 = 770 ppb), 

bluegill sunfish (LC50 = 700 ppb), and flathead minnow (LC50 = 220 ppb). Daphnid toxicity 

testing indicated that DTEA is very highly toxic to freshwater aquatic invertebrates (LC50 = 34 

ppb). Chronic toxicity testing indicated that DTEA was very highly toxic to both freshwater 

invertebrates (LOAEC = 13.4 ppb) and fathead minnow (LOEAC = 36.5 ppb) (Table 7). 

 There was aquatic plant study submitted, a green algae study (MRID 49004203) and it 

does not provide a definitive IC50 or NOAEC value. At all tested treatment levels the % 

inhibition was <50% and there was no affect at the highest treatment level as compared to 

controls. All DTEA degraded below detection limit by end of test so a weighted average, 

assuming exponential decay cannot be calculated. The study contains only sufficient information 

to identify that the IC50 based on initial measured exposure concentrations is expected to be > 

11.7 ppb. The Agency uses initial exposure concentration for algae tests under such conditions. 

The NOAEC can be stated as >11.7 ppb. 

 For this use pattern a battery of three algal species (green algae, freshwater diatom, 

saltwater diatom), a cyanobacteria and a floating macrophyte (duckweed), representing different 

morphological characteristics and environmental habitats are used to assess risk for the 

recirculating cooling system use pattern. Because DTEA is the only member of the class of 

currently registered in the U.S., there is no possibility of using submitted toxicity data from 

closely-related surrogate chemicals to fill in potential data gaps. 
Page 38 of 68

Table 7 Ecotoxicity Data for DTEA·HCl and DTEA 

Guideline No./ 

Study Type

MRID No./ 

Reference Information/ 

Study Classification

Dosing and Animal 

Information Results

Aquatic Fauna 

850.1010 

Aquatic 

invertebrate acute 

toxicity test, 

freshwater 

daphnids 

and 

850.1300 

Daphnia sp. Life 

Cycle

MRID 41198303, 

41198305, 41512602, 

41779901 

Gersich, F.; Milazzo, D.; 

Voos-Esquivel, C. (1988) 

An Invertebrate LifeCycle 

Study of the Toxicity of 

2-(Decylthio)-ethanamine 

Hydrochloride 

(DTEA·HCL) to 

Daphnia magna Straus: 

Project Study ID: ES-DR0065-5425-6. 

Unpublished study 

prepared by Dow 

Chemical Co. 23 p. 

Supplemental 

Purity 100.6% of ai 

Daphnia magna used 

were < 24 hours old. 

5 neonates/ replicates, 4 

replicates/test 

concentration. 

Test durations were 21 

day life cycle, flowthrough system and a 48 

hours study. 

Measured test 

concentrations were 7.8, 

13.4, 24.8, 44.8, 84 μg/l 

Nominal test 

concentrations were 1, 

2, 3, 4, and 5 μg/l 

21-day LC50 = 0.033 mg/l 

48–hour LC50 = 0.028 

mg/l (mean measured 

concentrations) 

Maximum Acceptable 

Toxicant Concentration 

(MATC) for 21-days > 

7.8 and < 13.4 μg/l mean 

measured concentrations; 

Geometric mean MATC = 

10.2 μg/l.

850.1010 

Aquatic 

invertebrate acute 

toxicity test, 

freshwater 

daphnids 

MRID 40126416, 

42482901 

Dill, D.; Milazzo, D.; 

Barlett, E.; et al. (1985) 

Evaluation of the Toxicity 

of N-decylthioethylamine 

to Representative Aquatic 

Organisms: Report No. 

ES-805. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. 27 p. 

Supplemental 

Purity 99.8% of ai 

Daphnia magna 

10 daphnids/ replicate, 

3 replicates/test 

concentration. 

Test measured 

concentrations were 

0.0078, 0.013, 0.022, 

0.036, 0.06, and 0.1 

mg/l. 

48 – hours LC50 (95% 

C.I.) = 0.034 (0.030 -

0.038) mg/l 

(measured concentration) 

850. 1075 

Fish acute toxicity 

test, freshwater 

and marine

MRID 40126416, 

42482901 

Dill, D.; Milazzo, D.; 

Barlett, E.; et al. (1985) 

Evaluation of the Toxicity 

of N-decylthioethylamine 

to Representative Aquatic 

Organisms: Report No. 

ES-805. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. 27 p. 

Supplemental 

Purity 99.8% of ai 

Bluegill Sunfish 

(Lepomis macrochirus) 

10 fishes/test 

concentration 

Test concentrations 

were 0.08, 0.13, 0.22, 

0.36, 0.6, and 1 mg/l. 

96 – hours LC50 (95% 

C.I.) = 0.70 mg/l (0.36– 1 

mg/l) 
Page 39 of 68

Guideline No./ 

Study Type

MRID No./ 

Reference Information/ 

Study Classification

Dosing and Animal 

Information Results

850. 1075 

Fish acute toxicity 

test, freshwater 

and marine 

MRID 40126416, 

42482901 

Dill, D.; Milazzo, D.; 

Barlett, E.; et al. (1985) 

Evaluation of the Toxicity 

of N-decylthioethylamine 

to Representative Aquatic 

Organisms: Report No. 

ES-805. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. 27 p. 

Supplemental 

Purity 99.8% of ai 

Rainbow trout (Salmo 

gairdneri) 

10 fishes/test 

concentration 

Test concentrations 

were 0.08, 0.13, 0.22, 

0.36, 0.6, and 1 mg/l. 

96 – hours LC50 (95% 

C.I.) = 0.77 (0.60 – 1) 

mg/l 

850. 1075 

Fish acute toxicity 

test, freshwater 

and marine 

MRID 40126416, 

42482901 

Dill, D.; Milazzo, D.; 

Barlett, E.; et al. (1985) 

Evaluation of the Toxicity 

of N-decylthioethylamine 

to Representative Aquatic 

Organisms: Report No. 

ES-805. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. 27 p. 

Supplemental 

Purity 99.8% of ai 

Fathead minnow

(Pimphales promelas) 

10 fishes/test 

concentration 

Test concentrations 

were 0.08, 0.13, 0.22, 

0.36, 0.6, and 1 mg/l. 

96 – hours LC50 (95% 

C.I.) = 0.22 (0.13 – 0.36) 

mg/l

850.1400 

Fish early-life 

stage toxicity test 

MRID 41198302, 

41198304, 41512601, 

41779902 

Dill, D.; Mayes, M.; 

Bartlett, E.; et al. (1988) 

2-(Decylthio)ethanamine 

Hydrochloride: EmbryoLarval Toxicity Test with 

Fathead Minnow, 

Pimephales promelas

rafinesque: Project Study 

ID: ES-DR-0065-5425-7. 

Unpublished study 

prepared by Dow 

Chemical Co. 26 p. 

Core 

Purity 100.6% of ai 

Embryos of fathead 

minnow (Pimphales 

promelas) 

35 embryos (< 24 hours 

old) were impartially 

distributed to each 

incubation cup; 140 

embryos/test. 

31 day embryo-larval 

flow through test. 

Test concentrations 

were 12, 18, 27, 42, 65, 

and 100 μg ai/l 

Mean measured 

concentrations were 

14.5, 23.3, 38.8, 58.4, 

and 93.1 μg ai/l. 

NOEL = 0.0233 mg/l. 

Maximum Acceptable 

Toxicant Concentration 

(MATC), based on body 

weight, mean measured 

concentration lies 

between 0.0233 and 

0.0383 mg/l. 

Geometric mean MATC = 

0.0301 mg/l.
Page 40 of 68

Guideline No./ 

Study Type

MRID No./ 

Reference Information/ 

Study Classification

Dosing and Animal 

Information Results

Terrestrial Wildlife 

850.2100 

Avian acute oral 

toxicity test

MRID 40126412 

Beavers, J. (1986) Ndecylthioethylamine: An 

Acute Oral Toxicity 

Study with the 

Mallard: Dow Report No. 

ES-DR-0065-5425-5: 

Contract Project No. 103-

243. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. in 

cooperation with Wildlife 

International Ltd. 20 p. 

Core 

Purity 99.8% of ai 

Mallard duck (Anas 

platyrhynchos) were 17 

weeks old. 

Groups of 10 birds/per 

concentration. 

Test duration was 14 

days. 

Test concentrations 

were 2250, 1350, 810, 

486, 292 ppm via 

intubation. 

LD50 > 2250 mg/kg. 

NOEL = 292 mg/kg 

At 810, 1350, and 2250 

mg/kg groups birds 

exhibited eye irritation 

and clouding which 

cleared up in all groups 

by the end of the third 

day. 

850.2200 

Avian dietary 

toxicity test 

MRID 40126414, 

40126413 

Beavers, J. (1986) Ndecylthioethylamine: A 

Dietary LC50 Study with 

the Mallard: Dow Report 

No. ES-836: Contract 

Project No. 103-242. 

Unpublished 

study prepared by Dow 

Chemical U.S.A. in 

cooperation with Wildlife 

International 

Ltd. 20 p. 

Core 

Purity 99.8% ai 

Mallard Duck (Anas 

platyrhynchos) were 10 

days old. 

Groups of 10 ducklings 

were randomly assigned 

to each of the five 

control and five 

treatment groups. 

Test duration was 8 

days 

Test concentrations 

were 562, 1000, 1780, 

3160, and 5620 ppm via 

diet. 

DTEA is non-toxic to 

Mallard ducklings. 

LC50 > 5620 ppm. 

NOAEC = 1780 ppm 

At 3160 ppm, lethargy 

was observed on days 4 

and 5. 

At 5620 ppm, signs of 

toxicity reported were 

lethargy, reduced reaction 

to external stimuli, loss of 

coordination, prostrate 

posture, loss of righting 

reflex, and lower limb 

weakness. 

850.2200 

Avian dietary 

toxicity test 

 MRID 40126415, 

40126413 

Beavers, J. (1986) Ndecylthioethylamine: A 

Dietary LC50 Study with 

the 

Bobwhite: Dow Report 

No. ES-DR-0065-5425-3: 

Contract Project No. 103-

241. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. in 

cooperation with Wildlife 

International Ltd. 19 p. 

Core 

Purity 99.8% ai 

Bobwhite quail 

(Colinus virginianus) 

were 10 days old 

Groups of 10 chicks 

were randomly assigned 

to each of the five 

control and five 

treatment groups. 

The duration of test was 

8 days. 

Test concentrations 

were 389, 1000, 1780, 

3160, 5620 ppm via 

diet.

DTEA is non toxic to 

bobwhite quail chicks. 

LC50 > 5620 ppm. 

NOAEC = 3160 ppm 

At 5620 ppm, slight 

reduction in body weight 

gain was observed. 
Page 41 of 68

Guideline No./ 

Study Type

MRID No./ 

Reference Information/ 

Study Classification

Dosing and Animal 

Information Results

Acute oral rat 

study 

MRID 40126405 

Jeffrey, M.; Schuetz, D.; 

Lomax, L. (1986) 2-

(Decylthio)ethanamine: 

Acute Oral Toxicity 

Study in Fischer 344 

Rats: Report No. HET 

DR-0065-5425-001A. 

Unpublished study 

prepared by Dow 

Chemical U.S.A. 17 p.

Purity 99.8% DTEA 

7 wk-old Fischer 344 

rats 

6 rats/sex/dose; 

Dose levels: 1300, 2500 

or 5000 mg/kg-bw; 

Single dose gavage 

using corn oil carrier 

LD50 = 2272 mg 

DTEA/kg-bw (females) 

LD50 = 3940 mg 

DTEA/kg-bw (males) 

Benthic Invertebrates

 No benthic invertebrate sediment toxicity data for DTEA was submitted or found in the 

open literature. Neither was any sediment toxicity data for a chemical from the same chemical 

structural activity group submitted or found. Therefore, an equilibrium partitioning (EqP) 

approach was used to derive a bulk sediment toxicity value from water-only DTEA toxicity data. 

This method will not account for uptake and exposure from ingestion of the sediment, and may 

therefore underestimate sediment toxicity to some degree. The EqP approach is based on an 

assumption of chemical equilibrium between the solid phase of sediment and the sediment pore 

(interstitial) water and that the effect concentration in water-only exposure will be similar to the 

effect concentration in the sediment pore water. In this method any water-only toxicity data 

value can be used; the approach is not limited to any single effect endpoint. The derived 

sediment toxicity data is expected to be commensurate with the given level of protection of the 

species, exposure, and endpoint (e.g., acute or chronic). The EqP model used is described in 

Equations 1 through 4. The EqP method is applicable to sediments with foc >0.2% but not 

<0.2%. Factors controlling second-order partitioning (e.g., particle size, sorption to nonorganic 

mineral fractions) become relatively more important than organic carbon content at foc <0.2%. A 

sediment invertebrate NOAEC, expressed as milligram of chemical per kilogram of sediment 

(mg/kgsed), is estimated from a water-only chronic value for an invertebrate using Equations 1 

through 3, results are provided in Table 8. 

NOAEC s  K p  NOAEC wo Equation 1

where: 

NOAECwo = water-only chronic NOAEC value for an invertebrate in units of mg/L; 

p oc Koc K  f  = organic carbon binding of a chemical in sediment; Equation 2

foc = weight or mass fraction of organic carbon in the sediment (kg organic carbon (oc)/kg of 

bulk sediment); and 
Page 42 of 68

Koc = organic carbon normalized soil-water partition coefficient (ratio of the concentration in 

water to the concentration in soil organic carbon (oc)) in units of mg/kg-sediment oc per mg/L 

solution or L solution/kg-sediment oc), which is expected to be a constant for each chemical. 

The sediment Koc for DTEA is estimated as 9,810 L/kg (see Table 6). The activated sludge Koc 

was measured to be 21,566 L/kg (Table 6). 

 The sediment toxicity value will differ based on the organic carbon content of sediment. 

The expression of the sediment toxicity value can be normalized on a sediment organic carbon 

basis, expressed in units of milligrams of chemical per gram of sediment organic carbon and 

normalizing to 1 gram of oc (0.001 kg/g): 

NOAECs oc  Koc  001 NOAECwo 0. , . Equation 3 

Table 8 Freshwater Benthic Invertebrate Toxicity 

Chronic Invertebrate 

NOAECwo

Koc (L/kg) 

Chronic 

Invertebrate 

NOAECs,oc

Chronic Invertebrate NOAECs (mg/kgsed) at foc of: 

0.2% 1% 4% 5% 

0.0078 mg/L 

(lowest value, see Table 

1and Table 7) 

9810 0.0765 mg/goc 0.15 0.77 3.1 3.8 

21, 566 0.168 mg/goc 0.34 1.68 6.7 8.4 

REFERENCES

Fuchsman PC. 2003. Modification of the equilibrium partitioning approach for volatile organic 

compounds in sediment. Environ Toxicol Chem 22:1532-1534. 

United States Environment Protection Agency (USEPA). 2003. Technical basis for the 

derivation of equilibrium partitioning sediment benchmarks (ESBs) for the protection of 

benthic organisms: nonionic organics. EPA-600-R-02-014. Office of Research and 

Development, Washington, DC, USA. (draft). 

USEPA. 2007. Environmental Monitoring and Assessment Program (EMAP). Office of 

Research and Development, Washington, DC, USA (www.epa.gov/emap). 

USEPA, 2008. Procedures for the Derivation of Equilibrium Partitioning Sediment Benchmarks 

(ESBs) for the Protection of Benthic Organisms: Compendium of Tier 2 Values for 

Nonionic Organics. EPA/600/R-02/016. 

http://www.epa.gov/nheerl/download_files/publications/ESB_Compendium_v14_final.pd

f

USEPA, 2009. Summary of Product Chemistry, Environmental Fate, and Ecotoxicity Data for 

the 2-(Decylthio) ethanamine hydrochloride Registration Review Decision Document. 

(Memo from Srinivas Gowda). 18 pp. 
Page 43 of 68

DTEA Literature Studies Not Included in ECOTOX: June 2013

 1. Brady, Bonnie M. F. and Havel, James J. Formulations of 2-(decylthio)ethanamine. 1993 Dec 7-(US1265H): 

11 pp. 

 2. Dahanayake, Manilal and Paterson, Donald J. Formulation of stable water-based suspensions of mixtures of 

trihaloalkyl sulfone. 1991 Jan 27-(CA2000282A1): 22 pp. 

 3. Donofrio, Deborah K. and Whitekettle, Wilson K. Synergistic bactericidal mixtures of 2-

(decylthio)ethanamine hydrochloride and 2-bromo-2-nitropropane-1,3-diol for Klebsiella 

pneumoniae. 1990 Apr 3-(US4914134A): 5 pp. 

 4. Elsmore, Richard and Houghton, Mark Phillip. Bactericide combinations in detergents. 2001 Apr 4-

(GB2354771A): 53 pp. 

. 

 5. Gerhold, Robert M.; Labine, Paul U.; Hwa, Chih M., and Fan, Grace L. Synergistic biocidal combinations for 

pulp and paper mills, petroleum operations, and cooling tower waters. 1996 May 17-

(WO9614092A1): 34 pp. 

 6. Kumar, Pritesh Prakash. Searching for Novel Ligands for the Cannabinoid and Related Receptors. 2011. 

 7. Lazonby, Judy G.; McCarthy, Robert E., and Casselman, Nancy L. Method and compositions for inhibiting 

growth of microorganisms in wastewater. 1997 Aug 19-(US5658467A): 10 pp., Cont.-in-part of U.S. 

5,494,588. 

 8. LaZonby, Judy G.; McCarthy, Robert E., and Casselman, Nancy L. Method and compositions for inhibiting 

growth of microorganisms including peracetic acid and a nonoxidizing biocide. 1997 May 21- 

 9. Ludensky, Michael; Hill, Christopher, and Lichtenberg, Florian Christof Albrecht. Synergistic biocidal 

composition comprising a triamine. 2003 Jul 31-(WO2003062149A2): 18 pp. 

 10. McCoy, William F. and Hoots, John E. Method for use of compositions of biocides and fluorescent indicators 

to control microbial growth. 1997 Dec 30-(US5702684A): 14 pp., Cont.-in-part of U.S. Ser. No. 

236,945, abandoned. 

 11. Petrille, Joseph C. III; Werner, Michael W., and Whitekettle, Wilson K. Detoxification of 

alkylthioalkylamines with swelling type natural or synthetic clays. 1997 Jan 21-(CA2174170A1): 12 

pp. 

 12. Rimmer, Karen and Jamieson, Andrew Stephen. Stable biocidal solutions of dithiolane derivative mixtures 

with thioalkylamines. 1992 Jun 17-(GB2250737A): 14 pp. 

 13. Robertson, Linda R. Synergistic product selection test for biocides for industrial water treatment. 1994 Dec 

20-(US5374536A): 11 pp. Cont.-in-part of U.S. Ser. No. 670,858, abandoned. 
Page 44 of 68

 14. Toropov, A. A. and Benfenati, E. QSAR Models for Daphnia Toxicity of Pesticides Based on Combinations 

of Topological Parameters of Molecular Structures. 2006; 14, 2779-2788. 

 15. Unhoch, Michael Joseph; Choi, Sungmee; Roberts, Katherine P., and O'Malley, Leon Peter. Biocidal 

composition and method for treating recirculating water systems. 2008 Jun 19-(US20080142453A1): 

15 pp. 

 16. Walter, Richard W. Jr.; Johnson, Robert L., and Relenyi, Attila G. Control of biofouling in aqueous systems 

with certain alkylthioalkylamines. 1988 May 11-(EP266828A1): 11 pp. 

 17. Whitekettle, Wilson K. and Lyons, Larry A. Controlling macroinvertebrates utilizing decylthioethylamine. 

1990 Nov 13-(US4970239A): 5 pp. 

. 

 18. Whitekettle, Wilson Kurt; Tafel, Gloria Jean; Reynolds, Dorothy G.; Frail, Paul Robert; Wang, Linna; Jiang, 

Juan, and Zhao, Qing. Methods and vesicles for controlling protozoa in aqueous systems. 2011 Mar 

3-(US20110052655A1): 8pp., Cont.-in-part of U.S. Ser. No. 835,717. 

 19. Whitekettle, Wilson Kurt; Tafel, Gloria Jean, and Zhao, Qing. Method for controlling microbial biofilm in 

aqueous systems. 2009 Feb 12-(WO2009020694A1): 21pp.; Chemical Indexing Equivalent to 

150:221519 (US). 

 20. Whitekettle, Wilson Kurt; Tafel, Gloria Jean; Zhao, Qing; Wang, Linna; Reynolds, Dorothy; Frail, Paul; 

Jiang, Juan, and Polizzoti, David M. Methods and liposome carriers for controlling biofilms in 

aqueous systems. 2012 Apr 5-(WO2012044409A1): 27pp. 

 21. Whitekettle, Wilson Kurt; Tafel, Gloria Jean; Zhao, Qing; Wang, Linna; Reynolds, Dorothy; Frail, Paul; 

Jiang, Juan, and Polizzotti, David M. Methods and liposome carriers for controlling biofilms in 

aqueous systems. 2011 Mar 3-(US20110052656A1): 10pp., Cont.-in-part of U.S. Ser. No. 835,722. 

 22. Yin, Bei and Tinetti, Sheila M. Synergistic biocidal effect of 2-(decylthio)ethanamine and tetrakis 

(hydroxymethyl) phosphonium sulfate against Desulfovibrio. 2013 Mar 21-(WO2013039769A1): 

13pp. 

 23. Yu, F. Philip and McCoy, William F. Use of the linear alkylbenzene sulfonate as a biofouling control agent. 

1997 Sep 23-(US5670055A): 5 pp. 

Referenced DTEA MRID Studies: 

71-1 Avian Single Dose Oral Toxicity 
Page 45 of 68

MRID Citation Reference 

40126412 

(reviewed) 

Beavers, J. (1986) N-decylthioethylamine: An Acute Oral Toxicity Study with the Mallard: Dow 

Report No. ES-DR-0065-5425-5: Contract Project No. 103-243. Unpublished study 

prepared by Dow Chemical U.S.A. in cooperation with Wildlife International Ltd. 20 p. 

71-2 Avian Dietary Toxicity 

MRID Citation Reference 

40126413 Gonsior, S. (1985) Investigation of the Stability of N-decylthioethylamine in Game Bird Starter 

Ration: Report No. ES-DR-0065- 5425-3,4. Unpublished study prepared by Dow Chemical 

U.S.A. 13 p. 

40126414 Beavers, J. (1986) N-decylthioethylamine: A Dietary LC50 Study with the Mallard: Dow Report No. 

ES-836: Contract Project No. 103-242. Unpublished study prepared by Dow Chemical 

U.S.A. in cooperation with Wildlife International Ltd. 20 p. 

40126415 Beavers, J. (1986) N-decylthioethylamine: A Dietary LC50 Study with the Bobwhite: Dow Report 

No. ES-DR-0065-5425-3: Contract Project No. 103-241. Unpublished study prepared by 

Dow Chemical U.S.A. in cooperation with Wildlife International Ltd. 19 p. 

72-1 Acute Toxicity to Freshwater Fish 

MRID Citation Reference 

40126416 Dill, D.; Milazzo, D.; Barlett, E.; et al. (1985) Evaluation of the Toxicity of N-decylthioethylamine 

to Representative Aquatic Organisms: Report No. ES-805. Unpublished study prepared by 

Dow Chemical U.S.A. 27 p. 

42482901 Dill, D.; Milazzo, D.; Bartlett, E. (1985) Supplemental Data Requested by EPA for Evaluation of the 

Toxicity of N-Decylthioethylamine to Representative Aquatic Organisms (MRID No. 

40126416): Lab Project Number: ES-805. Unpublished study prepared by Dow Chemical 

Co. 32 p. 

72-2 Acute Toxicity to Freshwater Invertebrates 

MRID Citation Reference 

40126416 Dill, D.; Milazzo, D.; Barlett, E.; et al. (1985) Evaluation of the Toxicity of N-decylthioethylamine 

to Representative Aquatic Organisms: Report No. ES-805. Unpublished study prepared by 

Dow Chemical U.S.A. 27 p. 

42482901 Dill, D.; Milazzo, D.; Bartlett, E. (1985) Supplemental Data Requested by EPA for Evaluation of the 

Toxicity of N-Decylthioethylamine to Representative Aquatic Organisms (MRID No. 

40126416): Lab Project Number: ES-805. Unpublished study prepared by Dow Chemical 

Co. 32 p. 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 

MRID Citation Reference 

41198302 Dill, D.; Mayes, M.; Bartlett, E.; et al. (1988) 2-(Decylthio)ethanamine Hydrochloride: EmbryoLarval Toxicity Test with Fathead Minnow, Pimephales promelas rafinesque: Project 

Study ID: ES-DR-0065-5425-7. Unpublished study prepared by Dow Chemical Co. 26 p. 

41198303 Gersich, F.; Milazzo, D.; Voos-Esquivel, C. (1988) An Invertebrate Life-Cycle Study of the 

Toxicity of 2-(Decylthio)ethanamine Hydrochloride (DTEA.HCL) to Daphnia magna

Straus: Project Study ID: ES-DR-0065-5425-6. Unpublished study prepared by Dow 

Chemical Co. 23 p. 
Page 46 of 68

41198304 Voos-Esquivel, C.; Murphy, P. (1988) 2-(Decylthio)Ethanamine Hydrochloride : Determination in 

Standard Dilution Water for Acute and Chronic Flow-through Aquatic Toxicity Test with 

the Fathead Minnow Using High Performance Liquid Chromatography: Project Study ID: 

ES-DR-0065-5425-7. Unpublished study prepared by Dow Chemical Co. 35 p. 

41198305 Voos-Esquivel, C. (1988) 2-(Decylthio)Ethanamine Hydrochloride: Determination in Standard 

Dilution Water for Chronic Flow- Through Aquatic Toxicity Test with the Daphnia magna

Straus Using High Liquid Chromatography: Project Study ID: ES-DR-0065-5425-6-A. 

Unpublished study prepared by Dow Chemical Co. 30 p. 

41512601 Dill, D.; Mayes, M.; Bartlett, E.; et al. (1988) Supplemental Data Requested by EPA for 2-

(Decylthio)Ethanamine Hydrochloride: Embryo-Larval Toxicity Test with Fathead 

Minnow, Pimephales promelas Rafinesque: Lab Project Number: ES-DR-0065-5425-7. 

Un- published study prepared by The Dow Chemical Co. 14 p. 

41512602 Gersich, F.; Milazzo, D.; Voos-Esquivel, (1988) Supplemental Data Requested by EPA for an 

Invertebrate Life-Cycle Study of the Toxicity of 2-(Decylthio)Ethanamine Hydrochloride 

(DTEA.HCL) to Daphnia magna Straus: Lab Project Number: ES-DR-0065-5425. 

Unpublished study prepared by Dow Chemical Co. 8 p. 

41779901 Gersich, F.; Milazzo, D.; Voos-Esquivel, C. (1988) Supplemental Data Requested by EPA for an 

Invertebrate Life-Cycle Study of the Toxicity of 2-(Decylthio) Ethanamine Hydrochloride 

(DTEA HCL) to Daphnia magna Straus--Final Report (Supplement to MRIDs 41198302, 

41512601): Lab Project Number: ES-DR-0065-5425-6. Unpublished study prepared by 

Dow Chemical Co., Mammalian and Environmental Tox. Research Lab. 21 p. 

41779902 Dill, D.; Mayes, E.; Bartlett, E.; et al. (1988) Supplemental Data Requested by EPA for 2-

(Decylthio) Ethanamine Hydrochloride: Embyro-Larval Toxicity Test with Fathead 

Minnow, Pimephales promelas Rafinesque--Final Report (Supplement to MRIDs 41198-

02, 41512601): Lab Project Number: ES-DR-0065-5425-7. Unpublished study prepared by 

Dow Chemical Co., Mammalian and Environmental Tox. Research Lab. 31 p. 

850.5400 Algal toxicity, Tiers 1 and II 

MRID Citation Reference 

49004203 Lehman, C.; Hutchison, K.; Malowinski, N. et al. (2012) DTEA: Growth Inhibition Test with the 

Green Alga, Pseudokirchneriella subcapitata. Project Number: 121042. Unpublished study 

prepared by Dow Chemical Company. 51p. 

 Non-Guideline Study 

MRID Citation Reference 

42441401 Gersich, F.; Milazzo, D.; Voos-Esquivel. (1988) Supplemental Data Requested by EPA for an 

Invertebrate Life-cycle Study of the Toxicity of 2-(Decylthio) Ethanamine Hydrochloride 

(DTEA HCL) to Daphnia magna Straus: Lab Project Number: ES-DR-0065-5425-6. 

Unpublished study prepared by The Dow Chemical Company. 59 p. 
Page 47 of 68

APPENDIX C:  Risk Estimation Methods

 Risk estimation integrates the results of the exposure and ecotoxicity data to evaluate the 

likelihood of adverse ecological effects. There are generally two approaches used in assessing 

risks from industrial process and water systems, a risk quotient (RQ) method and a probabilistic 

method. 

Risk Quotient (RQ) Method

 In the RQ method, estimates of exposure are divided by ecotoxicity endpoint values. 

These RQs are then compared to presumptive levels of concern (LOCs) to identify potential risk 

to nontarget organisms and the need to consider regulatory action. These LOCs are standards 

used by the EPA to indicate potential risk to non-target organisms and the need to consider 

regulatory action; the development of these LOCs are discussed in detail in the Agency’s 

Overview Document1

. Types of RQs (e.g., acute versus chronic), RQ equations, and 

corresponding LOCs and risk presumptions are tabulated in Table 9.

Table 9. Risk Presumption Categories 

Risk Presumption for Terrestrial Animals RQ LOC 

Acute: Presumption of high acute risk for nontarget animals EECA/LC50 or EECB/LD50 > 0.5 

Acute Restricted Use: Presumption of acute risk for nontarget animals, 

but potentially may be mitigated through restricted use EECA/LC50 or EECB

/LD50 > 0.1 

Acute Endangered Species: Endangered species may be affected acutely EECA/LC50 or EECB/LD50 > 0.05 

Chronic Risk: Presumption of chronic risk to nontarget animals, 

endangered species may be affected chronically EECA/NOAEC > 1.0 

Risk Presumption for Aquatic Animals RQ LOC

Acute: Presumption of high acute risk for nontarget animals EECC

/LC50 or EECC/EC50 or 

EECC/IC50

> 0.5 

Acute Restricted Use: Presumption of acute risk for nontarget animals, EECC/LC50 or EECC/EC50 or > 0.1

Acute Endangered Species: Endangered species may be affected acutely EECC

/LC50 or EECC/EC50 or C > 0.05 

Chronic Risk: Presumption of chronic risk to nontarget animals, 

endangered species may be affected chronically 

Water: EECC

/NOAEC > 1.0 

Sediment: EECD/NOAEC >1.0 

Risk Presumption for Aquatic Plants RQ LOC 

Non-Endangered Species: Presumption of high risk to all nontarget 

aquatic plants EECC

/IC50 > 1.0 

Endangered Species: Endangered plants may be affected EECC/NOAEC or EECC/IC05E > 1.0 

Risk Presumption for Terrestrial Plants RQ LOC 

Non-Endangered Species: Presumption of high risk to all nontarget 

plants EECC

/IC25 > 1.0 

Endangered Species: Presumption of high risk to all nontarget aquatic 

plants EECC

/NOAEC or EECC/IC05E > 1.0 

A Dietary exposure in parts per million (ppm) of the pesticide in/on dietary items. 

 

1

 http://www.epa.gov/espp/consultation/ecorisk-overview.pdf 
Page 48 of 68

B Dietary exposure dose in mg/kg-bw/day. 

C Concentration in water in parts per million (ppm). 

D Concentration in mg/kg-sediment. 

E An IC05 can be used in lieu of an NOAEC, if one cannot be determined or if it is above the IC25. 

Probabilistic Method

 For use patterns that result in antimicrobials entering surface water by way of industrial 

wastewater treatment plants or direct discharge from the industrial site without treatment, the 

Agency relies upon estimating loadings of antimicrobials to industrial wastewater treatment 

plants and using the General Population Exposures from Industrial Releases module of E-FAST 

to estimate number of days of exceedance of concentrations of concern (COCs) for aquatic 

organisms. COCs for acute effects on non-listed aquatic vertebrates and invertebrates were 

determined by dividing LC50 (or EC50) values from acute toxicity tests on aquatic vertebrates and 

invertebrates, respectively, by 2. COCs for chronic effects for non-listed aquatic vertebrate and 

invertebrate species were based on chronic NOAEC values from tests on aquatic vertebrates and 

invertebrates, respectively. Acute COCs for listed endangered and threatened aquatic vertebrates 

and invertebrates were determined by dividing acute LC50 (or EC50) values from acute toxicity 

tests on aquatic vertebrates and invertebrates, respectively, by 20. COCs for nonlisted aquatic 

vascular plants and algae are based on IC50 values. COCs for endangered algae and aquatic 

vascular plants are based on NOAEC values. 

 Based on probabilistic modeling results, if the acute COC (one-half of theLC50 or EC50) 

determined for any key aquatic receptor group is exceeded for one day or more based on results 

from the high-end scenario (i.e., the 10th percentile of the ratio of stream flows to plant flows), 

then potential acute risks to such receptor groups are indicated. In addition, if the endangered 

COC (one-twentieth of the LC50 or EC50 ) determined for any key aquatic receptor group is 

exceeded for one day or more based on results from the high-end scenario, then potential acute 

risks to endangered aquatic organisms in such receptor groups are indicated. Furthermore, if the 

chronic COC (NOAEC or NOAEL) for any key aquatic receptor group is exceeded for 20 days 

or more based on results from the high-end scenario, then potential chronic risks for such 

receptor groups are indicated. 
Page 49 of 68

APPENDIX D:  Estimation of Potential Risks from Exposure of Aquatic Organisms

to DTEA Downstream of Recirculating Cooling Towers

This appendix is divided into two sections. The first section is a complete listing of the tabulated 

results of the modeling runs. The second section is a discussion of the methodology and step 

wise approach for the Exposure and Fate Assessment Screening Tool (E-FAST) . 

Section 1:  Estimates of Exposures and Risks to Freshwater Organisms based on

Maintenance Treatment Scenarios

Table 10 presents estimates of numbers of days per year of exceedance of concentrations of 

concern for aquatic organisms downstream of large-size cooling towers based on a high-end 

scenario and application rates for maintenance treatment proposed on the product label. These 

estimates assume no treatment of blowdown water, hence no removal of DTEA prior to 

discharge to surface water. 

Table 10 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment 

(No Removal) 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

84 24.4 352 360 359 360 360 360 360 

20.4 5.9 302 359 180 356 360 301 359 

6.7 1.95 218 348 302 337 360 353 350 

1.7 0.5 110 291 195 258 355 312 297 

 Table 11 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of moderate-size cooling towers based on a highend scenario and application rates for maintenance treatment proposed on the product label. 

These estimates assume no treatment of blowdown water, hence no removal of DTEA prior to 

discharge to surface water. 
Page 50 of 68

Table 11 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes no treatment 

and no removal 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

1.7 24.4 11 87 33 64 229 109 93 

0.41 5.9 3 27 8 17 116 37 29 

0.13 1.95 1 9 3 6 51 12 10 

0.03 0.5 0 3 1 2 15 4 3 

 Table 12 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of large-size cooling towers based on an average 

case scenario and application rates for maintenance treatment proposed on the product label. 

These estimates assume no treatment of blowdown water, hence no removal of DTEA prior to 

discharge to surface water. 

Table 12 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment 

and No Removal 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

84 24.4 89 211 143 187 293 228 216 

20.4 5.9 46 131 77 109 233 151 137 

6.7 1.95 26 80 46 66 174 94 84 

1.7 0.5 11 42 22 34 100 50 44 

 Table 13 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of moderate-size cooling towers based on an 

average case scenario and application rates for maintenance treatment proposed on the product 

label. These estimates assume no treatment of blowdown water, hence no removal of DTEA 

prior to discharge to surface water. 
Page 51 of 68

Table 13 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment 

and No Removal 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

1.7 24.4 11 42 22 34 100 50 44 

0.41 5.9 4 20 9 15 52 24 21 

0.13 1.95 1 9 4 7 30 12 10 

0.03 0.5 0 3 1 2 12 4 3 

 Table 14 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of large-size cooling towers based on a high-end 

scenario and application rates for maintenance treatment proposed on the product label. These 

estimates assume 93 percent removal of DTEA during wastewater treatment based on activated 

sludge sorption isotherm data that indicate that from 93 to 98 percent of DTEA is removed 

during wastewater treatment via sorption to activated sludge. 

Table 14 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

84 24.4 207 345 293 332 360 352 347 

20.4 5.9 98 278 180 244 353 301 285 

6.7 1.95 42 188 98 152 323 217 196 

1.7 0.5 11 88 34 65 231 110 94 

 Table 15 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of moderate-size cooling towers based on a highend scenario and application rates for maintenance treatment proposed on the product label. 

These estimates assume 93 percent removal of DTEA during wastewater treatment based on 
Page 52 of 68

activated sludge sorption isotherm data that indicate that from 93 to 98 percent of DTEA is 

removed during wastewater treatment via sorption to activated sludge. 

Table 15 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

1.7 24.4 11 87 33 64 229 109 93 

0.41 5.9 3 27 8 17 116 37 29 

0.13 1.95 1 9 3 6 51 12 10 

0.03 0.5 0 3 1 2 15 4 3 

 Table 16 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of large size cooling towers based on an average 

case scenario and application rates proposed on the product label. These estimates assume 93 

percent removal of DTEA during wastewater treatment based on activated sludge sorption 

isotherm data that indicate that from 93 to 98 percent of DTEA is removed during wastewater 

treatment via sorption to activated sludge. 

Table 16 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb ae) 

Endangered 

Freshwater 

Fish (COC =

11 ppb ae) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb 

ae) 

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb ae) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb ae) 

Aquatic 

Plants 

(COC = 

10 ppb ae)

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

84 24.4 24 76 43 62 167 88 79 

20.4 5.9 10 39 20 31 93 46 41 

6.7 1.95 4 21 10 16 56 26 23 

1.7 0.5 1 9 3 6 28 11 10 
Page 53 of 68

 Table 17 presents estimates of numbers of days per year of exceedance of concentrations 

of concern for aquatic organisms downstream of moderate size cooling towers based on an 

average case scenario and application rates proposed on the product label. These estimates 

assume 93 percent removal of DTEA during wastewater treatment based on activated sludge 

sorption isotherm data that indicate that from 93 to 98 percent of DTEA is removed during 

wastewater treatment via sorption to activated sludge. 

Table 17 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC = 

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Number of Days per Year of Exceedance of COCs out of 360 Days Release 

1.7 24.4 1 9 3 6 28 11 9 

0.41 5.9 0 3 1 2 12 4 3 

0.13 1.95 0 1 0 1 5 1 1 

0.03 0.5 0 0 0 0 1 0 0 

Estimates of Exposures and Risks to Freshwater Organisms based on Scenarios for Initial

Treatment of Fouled Systems

 Table 18 presents results indicating whether or not concentrations of concern for 

freshwater aquatic organisms are downstream of large-size cooling towers would or would not 

be expected to be exceeded for assuming one day of application and release based on a high-end 

scenario and application rates for initial treatment proposed on the product label. These 

estimates assume no treatment of blowdown water, hence no removal of DTEA prior to 

discharge to surface water. 

 For all initial application rates proposed on the product label, all COCs for aquatic 

organisms are predicted to be exceeded. 
Page 54 of 68

Table 18 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment 

(No Removal) 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

140 40 1 1 1 1 1 1 1 

84 24.4 1 1 1 1 1 1 1 

20.4 5.9 1 1 1 1 1 1 1 

 Table 19 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of moderate-size cooling towers would or would not be expected to be 

exceeded assuming one day of application and release based on a high-end scenario and 

application rates for initial treatment proposed on the product label. These estimates assume no 

treatment of blowdown water, hence no removal of DTEA prior to discharge to surface water. 

At 2.8 and 1.7 kg/site/day, COCs for all aquatic organisms except for acute freshwater fish are 

exceeded for one day. At 0.41 kg/site/day COCs for aquatic plants, chronic freshwater 

invertebrates, and endangered freshwater invertebrates are exceeded for one day. 

Table 19 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes no treatment 

and no removal 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

2.8 40 0 1 1 1 1 1 1 

1.7 24.4 0 1 1 1 1 1 1 

0.41 5.9 0 0 0 0 1 1 1 

 Table 20 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of large-size cooling towers would or would not be expected to be 

exceeded assuming one day of application and release based on an average case scenario and 
Page 55 of 68

application rates for initial treatment proposed on the product label. These estimates assume that 

blowdown water is discharged directly to surface water without undergoing wastewater 

treatment. At 2.8 and 1.7 kg/site/day, COCs for all aquatic organisms except for acute 

freshwater fish are exceeded for one day. At 0.41 kg/site/day, COCs for aquatic plants, chronic 

freshwater invertebrates, and endangered freshwater invertebrates are exceeded for one day. 

Table 20 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment 

and No Removal 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm ae) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

140 40 0 1 0 1 1 1 1 

84 24.4 0 1 0 1 1 1 1 

20.4 5.9 0 0 0 0 1 0 0 

 Table 21 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of moderate-size cooling towers would or would not be expected to be 

exceeded assuming one day of application and release based on an average case scenario and 

application rates for initial treatment proposed on the product label. These estimates assume that 

blowdown water is discharged directly to surface water without undergoing wastewater 

treatment. No COCs examined would be expected to be exceeded for the one-day of release. 

Table 21 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes No Treatment 

and No Removal 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

2.8 40 0 0 0 0 0 0 0 

1.7 24.4 0 0 0 0 0 0 0 

0.41 5.9 0 0 0 0 0 0 0 
Page 56 of 68

 Table 22 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of large-size cooling towers would or would not be expected to be 

exceeded assuming one day of application and release based on a high-end scenario and 

application rates for initial treatment proposed on the product label. These estimates assume 93 

percent removal of DTEA during wastewater treatment based on activated sludge sorption 

isotherm data that indicate that from 93 to 98 percent of DTEA is removed during wastewater 

treatment via sorption to activated sludge. For all environmental releases examined, COCs are 

exceeded for one day with the exception of the COC for acute freshwater fish for an 

environmental release of 20.4 kg/site/day (5.9 ppm). 

Table 22 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

140 40 1 1 1 1 1 1 1 

84 24.4 1 1 1 1 1 1 1 

20.4 5.9 0 1 1 1 1 1 1 

 Table 23 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of moderate-size cooling towers would or would not be expected to be 

exceeded assuming one day of application and release based on a high-end scenario and 

application rates for initial treatment proposed on the product label. These estimates assume 93 

percent removal of DTEA during wastewater treatment based on activated sludge sorption 

isotherm data that indicate that from 93 to 98 percent of DTEA is removed during wastewater 

treatment via sorption to activated sludge. Only the COC for endangered freshwater 

invertebrates would be exceeded for one day of release at environmental releases of 2.8 

kg/site/day (40 ppm) and 1.7 kg/site per day (24.4 ppm). 
Page 57 of 68

Table 23 High-End Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

2.8 40 0 0 0 0 1 0 0 

1.7 24.4 0 0 0 0 1 0 0 

0.41 5.9 0 0 0 0 0 0 0 

 Table 24 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of large-size cooling towers would or would not be expected to be 

exceeded assuming one day of application and release based on an average case scenario and 

application rates for initial treatment proposed on the product label. These estimates assume 93 

percent removal of DTEA during wastewater treatment based on activated sludge sorption 

isotherm data that indicate that from 93 to 98 percent of DTEA is removed during wastewater 

treatment via sorption to activated sludge. Only the COC for endangered freshwater 

invertebrates would be exceeded for one day of release at an environmental release of 

140kg/site/day (40 ppm). 

Table 24 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Large-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

140 40 0 0 0 0 0 0 0 

84 24.4 0 0 0 0 0 0 0 

20.4 5.9 0 0 0 0 0 0 0 

 Table 25 presents results indicating whether concentrations of concern for aquatic 

organisms downstream of large-size cooling towers would or would not be expected to be 
Page 58 of 68

exceeded assuming one day of application and release based on an average case scenario and 

application rates for initial treatment proposed on the product label. These estimates assume 93 

percent removal of DTEA during wastewater treatment based on activated sludge sorption 

isotherm data that indicate that from 93 to 98 percent of DTEA is removed during wastewater 

treatment via sorption to activated sludge. No COCs for any aquatic organisms are exceeded at 

any of the environmental releases considered. 

Table 25 Average Case Scenario Estimates of Number of Days per Year of Exceedance of 

COCs for Aquatic Organisms Downstream of Moderate-Size Cooling Towers based on 

Facilities Belonging to the Steam Electric Power Plants SIC Code – Assumes 93 percent 

removal during WWT 

Environmental 

Release 

(kg/site/day) 

DTEA 

Concentration 

(ppm 

acid 

equivalents) 

Acute 

Freshwater 

Fish 

(COC = 

110 ppb) 

Endangered 

Freshwater 

Fish (COC =

11 ppb) 

Chronic 

Freshwater 

Fish (COC 

= 36.5 ppb)

Acute 

Freshwater 

Invertebrate 

(COC = 17 

ppb) 

Endangered 

Freshwater 

Invertebrate 

(COC = 

1.7 ppb) 

Chronic 

Freshwater 

Invertebrate 

(COC = 7.8 

ppb) 

Aquatic 

Plants 

(COC = 

10 ppb) 

Exceedance of COCs Based on 1 Day of Release 

2.8 40 0 0 0 0 0 0 0 

1.7 24.4 0 0 0 0 0 0 0 

0.41 5.9 0 0 0 0 0 0 0 

Section 2:  GENERAL METHODOLOGY

 The General Population and Ecological Exposure from Industrial Releases module of EFAST (Exposure and Fate Assessment Screening Tool) was used to estimate potential risks from 

exposure of aquatic organisms to DTEA downstream of recirculating cooling towers. Key input 

parameters required to run this module of E-FAST include: 

 Environmental release of DTEA to surface water (kg/site/day); 

 Concentrations of concern (COC) for aquatic organisms (ug/L); 

 Standard Industrial Classification (SIC) code(s) selected to represent recirculating 

cooling tower facilities; 

 Wastewater treatment removal of DTEA (percent); 

 Annual number of days of release to surface water (days per year); and 

 Selection of high-end or average case scenario. 

A discussion of the basis of high-end and average case scenario results is included at the end of 

this Appendix. The approach used to estimate aquatic exposures to DTEA from release of 

blowdown water from recirculating cooling towers can be described in four steps: 


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 Step 1: Estimate environmental release to surface water from recirculating cooling tower 

blowdown water from recirculating cooling tower blowdown water (kg/site/day); 

 Step 2: Determine percent removal during wastewater treatment; 

 Step 3: Derive concentrations of concern (COC) for aquatic organisms from LC50 and 

NOAEC values; and 

 Step 4: Estimate aquatic exposures from releases of recirculating cooling tower 

blowdown water to surface water using the general population exposures from industrial 

releases module of E-FAST. 

STEP 1: Estimate Environmental Release to Surface Water from Recirculating Cooling Tower

Blowdown Water (B) in kilograms per site per day

 A generic scenario developed by OPPT/CEB (Office of Pollution Prevention and 

Toxics/Chemical Engineering Branch) for recirculating cooling towers (USEPA, undated) was 

used to estimate daily releases to surface water of DTEA in blowdown water in kilograms per 

site per day. 

 The following equation is used to estimate releases of antimicrobial pesticide to surface 

water from blowdown: 

B = (0.6%) (XR) (R) (5760 x 10-06 min-kg/day-gal) 

where: 

B = release of antimicrobial pesticide via blowdown water to surface water (kg/site/day); 

 XR = concentration of antimicrobial pesticide in recirculating water (ppm); and 

 R = recirculation rate of cooling water (gallons per minute). 

 The conversion factor, 5760 x 10-06 min-kg/day-gal is derived from: 

(1440 min/day) (4 kg/gal) (10-06 ppm) in which the blowdown water is assumed to have a 

specific gravity of 1.0, thus 1 liter weighs 1 kilogram, and the conversion of 3.78 liters per gallon 

is expressed in kilograms per gallon and rounded up to the nearest significant figure. The value, 

0.6% is the percentage of cooling tower water that is assumed to be released to surface water via 

blowdown. 

 The following input values were used in this calculation: 

 XR: concentration of DTEA in recirculating cooling tower water – 0.5 to 40 ppm DTEA acid 

equivalents (derived from information on the label for “Antimicrobial DTEA 15%” (EPA 

Reg. No. 464-619) based on the range of product application rates (0.5 to 41 fluid ounces per 

1000 gallons of water) adjusted for product density (8.5 pounds per gallon) and expressed as 

DTEA acid equivalents (12.8%) 
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 R:recirculation rate of cooling water– 2000 gallons per minute for a moderate-size 

cooling tower (default value based on standard scenario developed by OPPT/CEB)) 

and 100,000 gallons per minute for a large-size cooling tower (default value based on 

standard scenario developed by OPPT/CEB). 

 The table that follows presents values of environmental releases of DTEA modeled for 

large-size and moderate-size cooling towers according to product application rate, product 

density, and DTEA concentration in acid equivalents. 

Product 

Application rate 

per 1000 gallons 

of water 

Application rate 

adjusted for product 

density of 8.5 pounds 

per gallon 

DTEA 

Concentration (ppm 

acid equivalents) 

Environmental 

Release: 

Large-Size 

Cooling Tower 

(kg/site/day) 

Environmental 

Release: 

Moderate-Size 

Cooling Tower

(kg/site/day) 

41 fluid ounces 41.8 fluid ounces 40 140 2.8 

25 fluid ounces 25.5 fluid ounces 24.4 84 1.7 

6 fluid ounces 6.1 fluid ounces 5.9 20.4 0.41 

2 fluid ounces 2.0 fluid ounces 1.95 6.7 0.13 

0.5 fluid ounces 0.5 fluid ounces 0.5 1.7 0.03 

STEP 2: Determine Percent Removal During Wastewater Treatment

 Data from an activated sludge sorption isotherm test (OCSPP Guideline 835.1110) that 

were submitted to the Agency for review indicate that from 93.2-98.5 percent of DTEA is 

removed via its sorption to activated sludge (MRID 49004201). For the purpose of this exposure 

and risk assessment, it was assumed that removal during wastewater treatment would result from 

sorption to activated sludge and that 93 percent DTEA would be removed during wastewater 

treatment. 

 There is no information on the product label to indicate that blowdown water must be 

treated prior to discharge to surface water. Consequently, exposures and risks to aquatic 

organisms were also estimated assuming that blowdown water could be discharged directly to 

surface water without treatment. In this case, it was assumed that there would be no removal of 

DTEA from blowdown water prior to its discharge to surface water. 

STEP 3: Estimate Concentrations of Concern (COC) for Aquatic Organisms

 The results of the DtD module are expressed as number of days of exceedance of COCs 

for aquatic organisms. The Agency uses the most sensitive ecotoxicology endpoints for 

surrogate species to assess risk to each aquatic receptor group, such as freshwater fish, 

freshwater invertebrate, sediment-dwelling invertebrate, and aquatic plants. COCs for acute 

effects were determined by dividing LC50 values from acute toxicity tests on aquatic vertebrates 

and invertebrates by 2. COCs for chronic effects for non-listed species were based on No 

Observed Adverse Effects Concentration (NOAEC) values from tests on aquatic vertebrates and 
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invertebrates. COCs for listed endangered and threatened aquatic organisms were determined by 

dividing LC50 values from acute toxicity tests on aquatic vertebrates and invertebrates by 20. 

Acute COCs for aquatic vascular plants and algae are based on EC50 values. COCs for 

endangered algae and aquatic vascular plants are based on NOAEC values. 

STEP 4: Estimate General Population and Ecological Exposure from Industrial Releases

 E-FAST, version 2.0, was used to determine the magnitude and frequency of exposure of 

aquatic organisms from releases of DTEA via blowdown water from recirculating cooling 

towers. For detailed information on the features, data, and methods on which the models in EFAST, version 2.0, are based, refer to the latest version of the Documentation Manual for EFAST, version 2.0 (USEPA 2007). This discussion is limited to summarizing the steps required 

to estimate exposure of aquatic organisms to blowdown water from industrial use of DTEA in 

recirculating cooling towers using the General Population and Ecological Exposure from 

Industrial Releases module of E-FAST with the PDM (probabilistic dilution model) option. The 

user is guided through a series of menus or pages that provide prompts indicating where the user 

should input data. Key input parameters needed to run this module and option include: 

 Environmental release to surface water in kg/site/day (estimated from Step 1); 

 Percent removal of DTEA during wastewater treatment (from Step 2); and 

 Concentrations of Concern (COC) for aquatic organisms (estimated from Step 3). 

 One of the first screens that appears when running the General Population and Ecological 

Exposure from Industrial Releases module of E-FAST is the physical/chemical and fate inputs 

screen; Upon accessing this screen, the user must enter the following information: 

 Chemical identification (e.g., CAS number); 

 Chemical name or abbreviation; 

 Bioconcentration factor (measured or estimated) (used to estimate human exposure from 

ingestion of fish); 

 Percent wastewater treatment removal (measured or estimated); 

 Percent adsorption to wastewater treatment sludge (measured or estimated); and 

 Percent drinking water treatment removal (in the absence of data, assume no removal). 

 The user must also select the appropriate models for estimating exposure to aquatic 

organisms. (In this instance, the appropriate model to use is the general population and 

ecological exposure from industrial releases to surface water model with the option to also run 

the probabilistic dilution model.) Next, the user accesses the “Release Information Page”. This 

page consists of three sub-pages including: 

 general release information; 

 select a facility; and 
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 select an SIC code. 

 The “select a facility” subpage, which accesses a database of site-specific information for 

manufacturing facilities, is not applicable for estimating exposures from processing and 

industrial use. To estimate exposures to aquatic organisms from surface water releases from 

processing or industrial use, the user must provide input values for the “general release 

information” subpage and the “select an SIC code” subpage. On the general releases 

information subpage, the user must input the following: 

 type (media) of release (i.e., surface water, landfill, and/or ambient air); in this case, 

the user would select “surface water”. 

 amount of release in kg/site/day, based on the results from CEB’s generic scenario 

(from Step 1 of this appendix) ; 

 days per year of release, based on results from CEB’s generic scenario; the default 

value for the recirculating cooling towers scenario is 360. 

 Upon being present with a choice of selecting “SIC code analysis” or “facility 

analysis”, select SIC code analysis. A menu of SIC code descriptions will appear on 

the screen and the user will be prompted to select one; in this instance, the appropriate 

SIC code description would be “Steam Electric Power Plants”. 

 Input the number of cooling tower sites; since there is no production volume 

information available for DTEA used in recirculating cooling towers that can be used 

to derive this input, no value is entered. 

 In the box, “enter release activity”, the user has the option to enter a description of the 

release; in this case, an apt description might be “indirect release of cooling tower 

blowdown”. 

 Place a check in the box, “include PDM run”. 

 Enter three values for concentrations of concern. 

 Select results for high end or average exposure. 

 Finally, check the box, “Release activities completed? Continue to Exposure Factors 

page.” Upon checking this box, the Exposure Factors page will appear. 

 The information in the exposure factors page is not used to estimate exposures to aquatic 

organisms, but is used to quantify human exposures from ingestion of drinking water and fish. 

This page includes default values for body weight, exposure duration, averaging time, and acute 

and chronic drinking water and fish ingestion rates. These values are automatically selected 

unless the user changes them. 

DESCRIPTION OF HIGH‐END VERSUS AVERAGE CASE SCENARIO

 The General Population and Ecological Exposure from Industrial Releases module of EFAST uses environmental releases estimated in Step 1 of this Appendix, stream dilution factors 

(i.e., the ratio of stream flow to industrial wastewater treatment plant flows), and wastewater 

treatment removal efficiency to provide both high-end and median time-averaged surface water 
Page 63 of 68

concentrations of a chemical substance immediately downstream of a discharge point. Stream 

flows are not single point estimates since streams have a highly variable seasonal flow pattern. 

PDM uses probability distributions as inputs and calculates the resulting probability distribution 

of the stream concentration. 

 To determine stream dilution factors for industrial uses of chemical substances such as 

DTEA used in recirculating cooling towers, a representative SIC code must be selected. The 

model will develop a distribution of stream dilution factors based on the ratio of stream flows to 

plant flows for facilities that belong to a specified SIC code. The distribution of stream flow 

values used are those immediately downstream of the facilities that belong to a specified SIC 

code. Stream dilution factors (SDFs) for recirculating cooling towers were based on the ratio of 

receiving stream flows to facility effluent flows for those facilities included in the steam electric 

power plants SIC code. For the high-end scenario, results of the number of days per year that 

COCs are exceeded is based on the upper 10th percentile of SDFs. For the average case scenario, 

results of the number of days per year that COCs are exceeded is based on the 50th percentile of 

SDFs. For the upper 10th percentile SDFs, or high-end scenario, the stream flow to plant flow 

ratio is relatively low since this part of the stream flow distribution represents the lower stream 

flows; consequently, plant flows can contribute considerable volume to the flow of the stream 

and resulting surface water concentrations can be relatively high. For the 50th%ile SDF, the 

stream flow to plant flow ratio is more typical. 

CONVERSION OF APPLICATION RATES FROM OUNCES PER THOUSAND GALLONS TO PPM

 DTEA expressed in units of ppm acid equivalents is one of the input values that is used to 

determine the loading of DTEA in kilograms per site per day. This loading is used as an input to 

the General Population and Ecological Exposure to Industrial Releases module of E-FAST. 

DTEA expressed in units of ppm acid equivalents can be determined from the product 

application rates proposed on the product label for “Antimicrobial DTEA 15%. In deriving 

DTEA in units of ppm acid equivalents, one must adjust for the product density and for the 

percent of DTEA acid equivalents (ae) in the product. The density of the product is 8.5 

lbs/gallon and the percent of DTEA acid equivalents in the product is 12.8%. 

 An example of the steps used to convert application rates proposed on the label for the 

product, “Antimicrobial DTEA 15%”, to DTEA in ppm acid equivalents is presented for the 

proposed application rate on the product label of 6 fluid ounces of product per thousand gallons 

of water. 

STEP 1 – Use information on product density to account for the difference of the density of the 

product relative to the density of water. The density of product is 8.5 pounds per gallon and the 

density of water is 8.34 pounds per gallon. 

6 fluid ounces of product x (8.5 lb/8.34 lb) = 6.11508 ounces product 
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STEP 2 – Determine the number of ounces of product per gallon of water. 

6.11508 ounces product / 1000 gallons water = 0.00611508 ounces product per gallon of water 

STEP 3 - Determine ounces of DTEA acid equivalents per gallon of water. 

0.00611508 ounces product per gallon water x 0.128 DTEA = 0.0007827 ounces DTEA 

STEP 4 – Convert ounces of DTEA ae per gallon of water to grams DTEA ae per gallon of 

water. 

0.0007827 ounces DTEA ae per gallon water x 28.3495 grams per ounce = 0.02219 grams 

DTEA ae per gallon water 

STEP 5 – Convert grams of DTEA ae per gallon of water to grams of DTEA as per liter of water. 

0.02219 grams DTEA ae per gallon of water x (1 gallon water / 3.785411 liters) = 0.005862 

grams DTEA ae per liter of water 

STEP 6 – Convert grams of DTEA ae per liter of water to mg of DTEA ae per liter of water. 

0.005862 g DTEA ae per liter of water x 1000 mg/g = 5.861981 mg DTEA ae per liter of water 

Since mg/L = ppm, with rounding the concentration of DTEA ae in ppm is 5.9 ppm. 

REFERENCES

USEPA. 2007. Exposure and Fate Assessment Screening Tool (E-FAST). Version 2.0. 

Documentation Manual. http://www.epa.gov/opptintr/exposure/pubs/efastdl.htm. 

USEPA. Undated. Generic Scenario for Recirculating Water-Cooling Tower. Office of 

Polllution Prevention and Toxics, Chemical Engineering Branch (OPPT, CEB). 
Page 65 of 68

APPENDIX E:  Estimated Sediment Exposure Concentrations

 Screening estimates of local sediment concentrations may be obtained by multiplying the 

concentration of dissolved DTEA in the discharge water by the organic carbon to sediment 

partition coefficient (Koc) and the fraction of organic carbon in the sediment as follows: 

Cs = Koc x foc x Cw; 

where 

Cs is the concentration in bulk sediment in units of mg/kg-sediment;

Koc is the ratio of the concentration associated with sediment oc to bulk sediment concentration 

(mg/kg-oc per mg/kg-sediment); 

foc is the fraction of organic carbon present in sediment in kg-oc/kg-sediment; and

Cw is the DTEA concentration in water in units of mg/L solution. 

 The estimated sediment Koc is 9,810 (L/kg) whereas the measured Koc for activated 

sludge is 21,566 (L/kg). Because the oc in sediments around a WWTP discharge are likely to 

predominately contain oc reflective of the WWTP process rather than natural sediment oc, 

sediments in these locations may have a higher sorption rate than predicted from the laboratory 

studies using natural sediments. Estimated exposure concentrations in local sediments for highend conditions, under wastewater treatment and no wastewater treatment conditions using the 

natural sediment Koc and activated sludge Koc values (which assumes local sediment is 

predominated by WWTP oc output) are provided in Table 4. An additional analysis based on the 

10% 30Q5, which is more reflective of everyday inputs using the activated sludge Koc was 

included in the table, as was an analysis of the potential for sorbed oc from a WWTP which was 

exposed to higher concentrations in influent to contribute to sediment exposure. Estimates for 

medium-size facilities, at the lowest maintenance rate of 0.03 kg/site/day was also included. 
Page 66 of 68

APPENDIX F:  Estimated Exposure Concentrations in Aquatic Biota

 There were no fish or shell fish bioconcentration studies submitted to the Agency or 

found in the open literature for DTEA. EPI Suite (version 4.11), which includes the BCFBAF 

Program (version 3.01), was used to estimate bioconcentration and bioaccumulation factors 

(BCF and BAF, respectively) for DTEA. Results of the BCFBAF Program run are provided in 

Table 26. The inputs to EPI Suite included the measured log Kow of 3.72, water solubility of 

0.0035 g/100 g, and the SMILES code for DTEA. 

 The highest estimated BAF, estimated using the Arnot-Gobas BCF & BAF Methods with 

an assumption of no biotransformation, was 3.0 (rounded) for the upper trophic level. Assuming 

biotransformation the BAF for the upper trophic level was estimated as 2.4 (rounded). 

 Estimates of the residues in aquatic organisms may be obtained by multiplying the BAF 

by the concentration of DTEA in the water as follows: 

Cdiet = BAF x Cw; 

where 

Cdiet = concentration or residue in aquatic organism in units of mg/kg-tissue wet-weight (ww);

BAF is the ratio of the concentration of a chemical in the aquatic organism (due to exposure to 

water and diet) to the concentration in water in units of mg/kg-tissue wet-weight to mg/L 

solution; and

Cw is the DTEA concentration in water in units of mg/L solution. 

Cooling Tower Maintenance Use with Wastewater Treatment Prior to Discharge

 Setting the water concentration to the high end (10th percentile 7Q10) estimated dissolved 

water concentration of 0.569 mg DTEA/L (Appendix C) and using the upper trophic level log 

BAF estimate of 2.967 (assumption of no biotransformation) results in an estimated residue level 

of 527 mg DTEA/kg-tissue ww. Assuming biotransformation occurs, the upper trophic level log 

BAF estimate of 2.379 results in an estimated residue level of 136 mg/kg-tissue ww. At the 

lowest label application rate for maintenance the estimated 10% 7Q10 is 0.0002 mg/L for a 

medium-size facility. The tissue residue levels for this case are 0.185 mg/kg-tissue ww and 

0.048 mg/kg-tissue ww. 

Cooling Tower Maintenance Use with No Wastewater Treatment Prior to Discharge

 Setting the water concentration to the high end (10th percentile 7Q10) estimated dissolved 

water concentration of 8.132 mg DTEA/L (Appendix C) and using the upper trophic level log 

BAF estimate of 2.967 (assumption of no biotransformation) results in an estimated residue level 
Page 67 of 68

of 7,537 mg DTEA/kg-tissue ww. Assuming biotransformation occurs, the upper trophic level 

log BAF estimate of 2.379 results in an estimated residue level of 1,946 mg/kg-tissue ww. 

Table 26 BCFBAF Program (v3.01) Results from EPI Suite (v4.11) 

BCFBAF Program (v3.01) Results: 

============================== 

SMILES : CCCCCCCCCCSCCN 

CHEM : 

MOL FOR: C12 H27 N1 S1 

MOL WT : 217.42 

--------------------------------- BCFBAF v3.01 -------------------------------- 

Summary Results: 

 Log BCF (regression-based estimate): 2.12 (BCF = 132 L/kg wet-wt) 

 Biotransformation Half-Life (days) : 1 (normalized to 10 g fish) 

 Log BAF (Arnot-Gobas upper trophic): 2.38 (BAF = 239 L/kg wet-wt) 

 

Log Kow (experimental): not available from database 

Log Kow used by BCF estimates: 3.72 (user entered) 

 

Equation Used to Make BCF estimate: 

 Log BCF = 0.6598 log Kow - 0.333 + Correction 

 

 Correction(s): Value 

 No Applicable Correction Factors 

 

 Estimated Log BCF = 2.121 (BCF = 132.3 L/kg wet-wt) 

 

=========================================================== 

Whole Body Primary Biotransformation Rate Estimate for Fish: 

=========================================================== 

------+-----+--------------------------------------------+---------+--------- 

 TYPE | NUM | LOG BIOTRANSFORMATION FRAGMENT DESCRIPTION | COEFF | VALUE 

------+-----+--------------------------------------------+---------+--------- 

 Frag | 1 | Linear C4 terminal chain [CCC-CH3] | 0.0341 | 0.0341 

 Frag | 1 | Aliphatic amine [-NH2 or -NH-] | 0.4067 | 0.4067 

 Frag | 1 | Methyl [-CH3] | 0.2451 | 0.2451 

 Frag | 11 | -CH2- [linear] | 0.0242 | 0.2661 

 L Kow| * | Log Kow = 3.72 (user-entered ) | 0.3073 | 1.1433 

 MolWt| * | Molecular Weight Parameter | | -0.5575 

 Const| * | Equation Constant | | -1.5371 

============+============================================+=========+========= 

 RESULT | LOG Bio Half-Life (days) | | 0.0007 

 RESULT | Bio Half-Life (days) | | 1.002 

 NOTE | Bio Half-Life Normalized to 10 g fish at 15 deg C | 

============+============================================+=========+========= 

 

Biotransformation Rate Constant: 

 kM (Rate Constant): 0.692 /day (10 gram fish) 

 kM (Rate Constant): 0.3891 /day (100 gram fish) 

 kM (Rate Constant): 0.2188 /day (1 kg fish) 

 kM (Rate Constant): 0.123 /day (10 kg fish) 

 

Arnot-Gobas BCF & BAF Methods (including biotransformation rate estimates): 

 Estimated Log BCF (upper trophic) = 2.379 (BCF = 239.3 L/kg wet-wt) 

 Estimated Log BAF (upper trophic) = 2.379 (BAF = 239.4 L/kg wet-wt) 

 Estimated Log BCF (mid trophic) = 2.345 (BCF = 221.4 L/kg wet-wt) 

 Estimated Log BAF (mid trophic) = 2.347 (BAF = 222.2 L/kg wet-wt) 

 Estimated Log BCF (lower trophic) = 2.323 (BCF = 210.3 L/kg wet-wt) 

 Estimated Log BAF (lower trophic) = 2.329 (BAF = 213.5 L/kg wet-wt) 

 

Arnot-Gobas BCF & BAF Methods (assuming a biotransformation rate of zero): 
Page 68 of 68

 Estimated Log BCF (upper trophic) = 2.742 (BCF = 552.1 L/kg wet-wt) 

 Estimated Log BAF (upper trophic) = 2.967 (BAF = 926.6 L/kg wet-wt)