Draft 

Toxic Weighting Factor Development 

in Support of 

CWA 304(m) Planning Process 

Prepared for: 

U.S. Environmental Protection Agency 

Engineering and Analysis Division 

Office of Water 

1200 Pennsylvania Avenue, NW 

Washington, D.C. 20460 

Prepared by: 

Eastern Research Group, Inc. 

110 Hartwell Avenue 

Lexington, MA 02421 

July 29, 2005 

EPA Contract No. 68-C01-073 

Work Assignment 4-17 
CONTENTS 

Page 

SECTION 1 INTRODUCTION .................................................. 1-1

1.1 Introduction ........................................................ 1-1

1.2 References ......................................................... 1-3

SECTION 2 CURRENT METHODOLOGY ....................................... 2-1

2.1 Addition of Human and Aquatic Health Values ............................ 2-1

2.2 Human Health Criteria ................................................ 2-2

2.2.1 Effects and Risk Levels ....................................... 2-2

2.2.2 Hierarchy of Data Sources ..................................... 2-3

2.2.3 Deriving Ambient Water Quality Criteria for the Protection Of

Human Health—1980 Methodology and 2000 Revisions ............. 2-4

2.2.3.1 BCFs and BAFs ....................................... 2-7

2.2.3.2 Relative Source Contribution Factors ...................... 2-7

2.2.4 Water Quality Criteria Updates Since 2000 ........................ 2-8

2.3 Chronic Aquatic Life Values .......................................... 2-10

2.3.1 National Chronic Freshwater Criteria ........................... 2-10

2.3.2 Lowest Reported Measured Maximum Allowable Toxicant

Concentration, Lowest-Observed-Effect Concentration, or

 No-Observed-Effect Concentration ............................ 2-11

2.3.3 Lowest Chronic or Reproductive Test Concentration ............... 2-11

2.3.4 Estimated Chronic Toxicity Concentration from a Measured

Acute: Chronic Ratio for a Less Sensitive Species, Quantitative

Structure-Activity Relationship Model, or Default

Acute: Chronic Ratio of 10:1 .................................. 2-13

2.4 References ........................................................ 2-14

SECTION 3 DIOXIN AND CONGENERS ......................................... 3-1

3.1 Slope Factors and TEFs .............................................. 3-1

3.2 BAFs .......................................................... 3-2

3.3 References ......................................................... 3-6

SECTION 4 DEVELOPMENT OF TWF DATABASE ............................... 4-1

4.1 Database Overview .................................................. 4-1

4.2 Quality Control Reviews .............................................. 4-2

4.3 References ......................................................... 4-3

i 
Page 

SECTION 5 UPDATE TWF DATABASE .......................................... 5-1

5.1 Reference5-1 

SECTION 6 TWF DEVELOPMENT ............................................. 6-1

6.1 Fall 2004 List of Chemicals ............................................ 6-1

6.2 Methylmercury ...................................................... 6-1

6.2.1 Water Quality Criterion for Methylmercury as a Concentration

in Water ................................................... 6-2

6.2.2 Conversion of RSC from a Value to be Subtracted to a Percentage ..... 6-3

6.3 Polycyclic Aromatic Compounds (PACs) ................................. 6-4

6.3.1 Background ................................................ 6-4

6.3.2 Human Health .............................................. 6-4

6.3.3 Aquatic Life Criteria ......................................... 6-6

6.3.4 Remaining Chemicals ........................................ 6-7

6.3.5 Summary and Proposed PAC TWFs ............................. 6-8

6.4 Nitrogen ......................................................... 6-10

6.4.1 Sodium Nitrite ............................................. 6-11

6.4.2 Nitrogen Cycle Components .................................. 6-12

6.4.2.1 Ammonia ........................................... 6-13

6.4.2.2 Nitrate ............................................. 6-13

6.4.2.3 Nitrite .............................................. 6-14

6.4.2.4 Extrapolation to Other Forms of Nitrogen ................. 6-14

6.4.2.5 Forms for Which There Is Insufficient Information ........... 6-15

6.4.3 Nitrogen TWF Summary ..................................... 6-15

6.5 Drinking Water Contaminants ......................................... 6-16

6.5.1 Alachlor ESA and Other Acetanilide Pesticide Degradation

Products .................................................. 6-17

6.5.2 Organotins ................................................ 6-18

6.5.3 Perchlorate ................................................ 6-18

6.5.4 Triazines and Degradation Products ............................ 6-19

6.5.5 Summary ................................................. 6-20

6.6 Nicotine ......................................................... 6-21

6.6.1 Human Health ............................................. 6-21

6.6.2 Aquatic Health ............................................. 6-22

6.7 References ........................................................ 6-22

ii 
Page

ATTACHMENT A TWF DATA WORKSHEETS ................................ A-1

iii
LIST OF TABLES 

Page

2-1 Comparison of 1980 and 2000 Methodologies for Calculating Human Health Criteria Based 

on Slope Factors .......................................................... 2-5

2-2 Comparison of 1980 and 2000 Methodologies for Calculating Human Health Criteria Based 

on Reference Doses ......................................................... 2-6

2-3 Uncertainty Factors and Relative Source Contributions ............................. 2-9

3-1 Dioxins and Their Equivalency Factors .......................................... 3-2

3-2 National Default Values for Lipid Fractions by Trophic Level ........................ 3-3

5-1 Comparison of August and December 2004 TWF Values Changes Due to

Shift to 2000 Methodology ................................................... 5-2

5-2 Changes in TWFs Due to Updates .............................................. 5-3

6-1 Weighted-average National BAF for Methylmercury ............................... 6-3

6-2 Conversion of RSC from Amount Subtracted to Percentage .......................... 6-3

6-3 Chemicals Included in the EPCRA Section 313 PAC Category ....................... 6-5

6-4 Changes to Aquatic Life Health Data ............................................ 6-7

6-5 Aquatic Health Data for PAC Chemicals ......................................... 6-8

6-6 Proposed TWF Summary For Various Forms of Nitrogen .......................... 6-16

6-7 Drinking Water Candidate Contaminants Needing TWFs ........................... 6-17

6-8 Human and Aquatic Health Data for Triazines and Degradation Products .............. 6-19

6-9 Drinking Water Candidate Contaminants Needing TWFs ........................... 6-20

iv 
SECTION 1 

INTRODUCTION 

1.1 INTRODUCTION 

In 1981, EPA’s Office of Water convened a Cost-Effectiveness (C-E) Task Force. Once 

developed, the Task Force’s methodology (called C-E methodology) has been applied to all subsequent 

rulemaking efforts and has basically withstood the test of time, Office of Management and Budget (OMB) 

review, and the courts (Ehrensberger and Rico, 1988). All cost-effectiveness calculations are deflated to 

1981 dollars—the year of the Task Force. The Task Force selected the Engineering News Record 

Construction Cost Index (CCI) as the index to be used when deflating the costs to 1981 dollars. 

C-E methodology is an approach to evaluating a series of pollution control technology trains 

within an industry, subcategory, or segment of an industry. In particular, C-E compares the incremental 

costs of moving from one technology train option to another with the incremental removals associated 

with that change. The procedure identifies “inefficient” options that cost more but remove less pollutants. 

When the options are ranked by increasing pollutant removals and plotted against cost, the investigator 

can visually identify the “elbow in the curve,” where it becomes much more expensive to remove fewer 

additional pollutants. 

Because each pollutant has its own level of toxicity, it was necessary to develop toxic weighting 

factors (TWFs). Without such a factor, a pound of tetrachloro-dibenzo-p-dioxin, 2,3,7,8 would have the 

same “value” (in terms of removal) as a pound of copper. TWFs were developed to be protective of both 

human and aquatic life. Section 2 summarizes the TWF methodology. 

By converting chemical discharges to a “toxic-weighted pounds-equivalent” basis, TWFs provide 

a mechanism by which discharges containing different mixtures of chemicals can be compared. For 

effluent guideline development, the comparison is the relative efficiency of different technology train 

options in removing chemicals within a given industry or industry segment. The comparison is the C-E 

methodology described in the paragraph above. For planning purposes, such as the 304(m) process, the 

discharges from different industries can be compared on a toxic-weighted pounds-equivalent basis 

1-1
(TWPE) to identify industries, subcategories, or segments of an industry for which additional pollution 

controls might be beneficial. 

The initial list of pollutants considered in a C-E analysis focused on priority pollutants.1

 As 

effluent limitations guidelines were developed for more and more industries, the number of pollutants for 

which EPA developed TWFs also increased. At present, EPA has developed TWFs for approximately 

1,900 chemicals. 

The C-E methodology was originally intended as a “within-an-industry” analytical tool to 

evaluate different technology train options. EPA routinely reviewed and updated TWF data at various 

points in the rulemaking schedule (e.g., option selection), but at any given point in time, all pollutants 

within an industry were compared with the same set of TWFs. EPA might not have had cause to update a 

pollutant that was detected in wastewater discharges from an industry regulated in the early 1980s if it 

was not detected in wastewater discharges from industries regulated after that time. 

Section 304(b) of the Clean Water Act requires EPA to review effluent guidelines for existing 

direct dischargers each year and to revise the regulations as appropriate. Section 304(b) also specifies 

factors that EPA must consider when deciding whether to revise an effluent guideline. Section 304(m) 

supplements the core requirement of Section 304(b) by requiring EPA to publish a plan every two years 

announcing its schedule for this annual review, as well as its schedule for any guideline revision that 

results from the review. EPA has published a final Plan under Section 304(m), every even-numbered year 

since 1990, that describes these activities. For the 2004 Plan, EPA developed and proposed a draft 

Strategy for National Clean Water Industrial Regulations (“National Strategy”) (EPA, 2002) to outline 

how EPA would address the factors outlined in Section 304(b). The first factor in the strategy considers 

the amount and toxicity of the pollutants remaining in an industrial category’s discharge. TWFs were 

used with discharges reported in the Toxics Release Inventory (TRI) and the Permit Compliance System 

(PCS) to generate preliminary rankings by industry (EPA, 2004). 

With the National Strategy, TWFs underwent a change in role and were used in “industry-toindustry” comparisons. Accordingly EPA decided to develop a TWF database that serves as a self1

These pollutants are discussed in the Clean Water Act (33 USC 1317) Section 307a and Code of 

Federal Regulations, Title 40, Part 423, Appendix A. 

1-2 
contained reference for TWF development. The initial version of the database is the source of the “August 

2004” TWF values. EPA developed a list of updates and revisions (Zipf, 2003) that it then incorporated in 

the database. After revisions and updates, the set of about 1,900 TWFs was called the “December 2004” 

TWF values. 

Section 2 presents EPA’s methodology for developing TWFs as well as the revisions and updates 

to the August 2004 values. Section 3 presents the TWF development for the special case of dioxin and its 

congeners. The database is described briefly in Section 4 while Section 5 compares the August and 

December values. As EPA’s development of effluent limitations guidelines continues, there is an ongoing 

need for TWFs for new pollutants or groups of pollutants. Ongoing efforts are summarized in Section 6. 

1.2 REFERENCES 

Ehrensberger, K., and R. Rico. 1988. Cost-effectiveness analysis for effluent guidelines. United States 

Environmental Protection Agency, Office of Water Regulations and Standards, Economic Analysis 

Branch. May. 

EPA. 2004. Notice of availability of 2004 effluent guidelines program plan. Fed. Reg. 69:53,705–53,721. 

September 2. 

EPA. 2002. Draft strategy for national clean water industrial regulations. Fed. Reg. 67:71,665–71,169. 

November 29. 

Zipf, L. 2003. Revisions to EAD’s toxic weighting factor methodology parameters. Memorandum to 

304(m) record (EPA docket number OW-2003-0074). December 3. 

1-3
SECTION 2 

CURRENT METHODOLOGY 

This section provides a brief overview of the methodology for calculating TWFs and is drawn 

from Zipf (2003). The methodology was first established in 1981 by EPA’s Cost-Effectiveness Task 

Force. One modification to the methodology occurred when the water quality criterion for copper was 

updated in 1985 (Ehrensberger and Rico, 1988). This is noted in the text below. 

The discussion works backward from the TWF (Section 2.1) into its component human health 

and aquatic health components. Sections 2.2 and 2.3 provide additional information for the human and 

aquatic health values, respectively, including the preference order for data sources. All effluent guidelines 

promulgated under the 1992 Consent Decree used the methodology described in this section in the C-E 

analyses. These values are discussed in the Development Document as the “August 2004” TWF values 

(EPA, 2005a). During the latter part of 2004, EPA incorporated updates and revisions to the 

methodology and basic data values; these are the “December 2004” TWF values. 

2.1 ADDITION OF HUMAN AND AQUATIC HEALTH VALUES 

TWFs are derived from chronic aquatic life criteria (or toxic effect levels) and human health 

criteria or toxic effect levels established for the consumption of fish. For carcinogenic substances, EPA 

sets the human health risk level at 10-5 (i.e., protective to a level allowing 1 in 100,000 excess lifetime 

cancer cases over background). In the TWF method for assessing water-based effects, these toxicity levels 

of pollutants of concern are compared to a benchmark value that represents the toxicity level of a 

specified pollutant. EPA selected copper, a toxic metal commonly detected and removed from industrial 

effluent, as the benchmark pollutant. EPA had used copper in previous TWF calculations for the costeffectiveness analysis of effluent guidelines; although EPA revised the water quality criterion for copper 

in 1998 (to 9.0 micrograms per liter, or :g/L), the TWF method uses the former criterion (5.6 :g/L) to 

facilitate comparisons with cost-effectiveness values calculated for other regulations. This was considered 

valid because all CE measures are relative (Ehrensberger and Rico, 1988). The former criterion for copper 

(5.6 :g/L) was reported in the 1980 Ambient Water Quality Criteria for Copper document (EPA, 1980). 

2-1
To calculate TWF values, EPA adds TWFs for aquatic life effects and human health effects for 

each pollutant of concern. EPA uses chronic effects on aquatic life and human health effects from 

ingesting contaminated organisms (HHOO) as the basis for TWFs. To make the calculation, EPA divides 

aquatic life and human health criteria (or toxic effect levels) for each pollutant, expressed as a 

concentration in :g/L, into the former copper criterion of 5.6 :g/L: 

TWF = 5.6 + 5.6

AQ HHOO 

where:

TWF = toxic weighting factor

AQ = chronic aquatic life value (:g/L)

HHOO = human health value (organisms only) (:g/L)

2.2 HUMAN HEALTH CRITERIA 

EPA calculates the human health component of a TWF based on consumption of contaminated 

organisms. Therefore, EPA envisioned a scenario in which a person would fish or harvest shellfish for 

consumption. The water body in this scenario would not necessarily be a drinking water source. Even if it 

were, EPA reasoned, treatment at the drinking water plant would address any contamination. 

2.2.1 Effects and Risk Levels 

As stated in Section 2.4 of the 2000 Methodology for Deriving Ambient Water Quality Criteria 

for the Protection of Human Health, “EPA believes that both 10-6 and 10-5 may be acceptable for the 

general population....adoption of a 10-6 or 10-5 risk level...represents a generally acceptable risk 

management decision” (EPA, 2000). 

For chemicals that (1) have both a reference dose (RfD) value for non-carcinogenic effects and a 

slope factor (SF) value for carcinogenic effects and (2) draw those RfD and SF values from sources in the 

same level of the hierarchy (see below), the human health values are calculated using the SF, which is 

always the more stringent value of the two. When a chemical has both an RfD and SF but these values are 

from different levels of the hierarchy, the value from the source higher on the hierarchy is used. 

2-2
2.2.2 Hierarchy of Data Sources 

EPA follows a hierarchy of data sources to determine human health values. This hierarchy is 

based on Section 2.4.6 of the Technical Support Document for Water Quality-Based Toxics Control 

(EPA, 1991), which recommends using the most current risk information from EPA’s Integrated Risk 

Information System (IRIS) when estimating human health risks. The hierarchy is: 

# Calculated human health criteria using IRIS (EPA, 2005b) oral RfDs or oral cancer 

potency SFs in conjunction with adjusted 3 percent lipid bioconcentration factor (BCF) 

values derived from Ambient Water Quality Criteria Documents published during the 

1980s (EPA, 2005c). Three percent is the mean lipid content of fish tissue reported in the 

study from which the average daily fish consumption rate of 6.5 grams per day (g/day) 

was derived (EPA, 1991). 

# Calculated human health values using current IRIS RfDs or SFs and representative 

unadjusted BCF values for common North American species of fish or invertebrates or 

estimated BCF values. 

# Calculated human health values using RfDs or SFs from EPA’s Health Effects 

Assessment Summary Tables (HEAST) or EPA’s Region III Risk-Based Concentration 

(RBC) Table (EPA, 2004) used in conjunction with adjusted 3 percent lipid BCF values 

derived from Ambient Water Quality Criteria Documents. 

# Calculated human health criteria using current RfDs or SFs from HEAST or EPA’s 

Region III RBC table and representative BCF values for common North American 

species of fish or invertebrates or estimated BCF values. 

# Criteria from the Ambient Water Quality Criteria Documents. 

# Calculated human health values using RfDs or SFs from data sources other than IRIS, 

HEAST, or the Region III RBC Table. 

2.2.3 Deriving Ambient Water Quality Criteria for the Protection of Human Health— 

1980 Methodology and 2000 Revisions 

In 2000, EPA published revisions to its “2000 methodology” for deriving ambient water quality 

criteria for the protection of human health (EPA, 2000a and 2000b). Zipf (2003) identified the need to 

update the TWF calculations to reflect these revisions: 

2-3
# Change average daily fish consumption rate from 6.5 grams to 17.5 grams/day to 

adequately protect the general population of fish consumers. 

# Change from bioconcentration factors (BCFs) to bioaccumulation factors (BAFs). 

Section 2.2.3.1 discusses how this change is incorporated into the model. 

# Incorporate a relative source contribution (RSC) to account for non-water sources of 

exposure. Section 2.2.3.2 discusses how this change is incorporated into the model. 

Tables 2-1and 2-2 present the equations for calculating human health criteria with both the 1980 and 2000 

methodologies. The equation accounts for effect (cancer or non-cancer) and pathway (organism only or 

water and organism). 

The August 2004 TWF database is based on the 1980 methodology. The December 2004 TWF 

database is based on the 2000 methodology and subsequent water quality criteria updates for specific 

chemicals (see Section 2.2.4 below). 

2-4
Table 2-1

Comparison of 1980 and 2000 Methodologies for Calculating Human Health Criteria Based on Slope 

1980 Methodology 2000 Methodology 

Carcinogenicity Protection 

( )

( )

( ) HHOO ug / L 

Risk level 10 

q1* 70 kg 1,000 ug / mg 

0.0065 kg / day BCF L / kg 

5 

=

⎛

⎝⎜ ⎞⎠⎟ × ×

×

−

Ingestion of Organisms Only 

( )

( )

( ( 

HHOO ug / L 

Risk level 10 

q1* 

 0.0175 kg / day BCF 

5 

=

⎛

⎝⎜ ⎞⎠⎟ × 

×

−

Ingestion of Organisms Only 

( ) ( ) ( ) [ [ ( )]] HHWO ug / L Risk level 10 70 kg 1,000 ug / mg q1 mg / kg day 2 L / day + 0.0065 kg / day BCF L / kg 5 * = × × − × × −

Ingestion of Water and Organisms 

( )

( )

[ [ [ 

HHWO ug / L 

Risk level 10 

q1* 7

2 L / day + 0.0175 kg / day B

5 

=

⎛

⎝⎜ ⎞⎠⎟ × 

×

−

Ingestion of Water and Organisms 

where: 70 kg = body weight 2 L/day = daily drinking water intake 0.0065 kg/day = daily fish intake (1980) 0.0175 kg/day = daily fish intake (2000) RfD = reference dose q1* = cancer potency factor or cancer slope factor RSC = relative source contribution BAF = bioaccumulation factor BCF = bioconcentration factor 2-5 
Table 2-2

Comparison of 1980 and 2000 Methodologies for Calculating Human Health Criteria Based on Refere

1980 Methodology 2000 Methodology 

Toxicity Protection 

( ) ( ) HHOO ug / L RfD mg / kg / day 70 kg 0.0065 kg / day BC = × ×

Ingestion of Organisms Only 

( )

 1,000 ug / mg 

F L / kg 

× ( ) ( ) ( ( 

HHOO ug / L RfD mg / kg / day RSC 

0.0175 kg / day BCF 

= × 

×

Ingestion of Organisms Only 

( ) ( ) [ HHWO ug / L RfD mg / kg / day 70 kg 2L / day 0.0065 kg / day = × +

Ingestion of Water and Organisms 

( )]

 1,000 ug / mg 

BCF L / kg 

×

×

( ) ( ) [ [ 

HHWO ug / L RfD mg / kg / day 70 

2L / day 0.0175 kg / day B

= × 

+ ×

Ingestion of Water and Organisms 

where: 70 kg = body weight 2 L/day = daily drinking water intake 0.0065 kg/day = daily fish intake (1980) 0.0175 kg/day = daily fish intake (2000) RfD = reference dose q1* = cancer potency factor or cancer slope factor RSC = relative source contribution BAF = bioaccumulation factor BCF = bioconcentration factor 2-6 
2.2.3.1 BCFs and BAFs 

Bioconcentration is the uptake and retention of a chemical by an aquatic organism from water 

only. Bioaccumulation is the uptake and retention of a chemical from all surrounding media (e.g., water, 

food, and sediment). For some chemicals, e.g., those that are highly persistent and hydrophobic, 

bioaccumulation can be far larger than bioconcentration. EPA (2000a) recommends shifting from BCFs to 

BAFs in the calculation of water quality criteria for human health. 

EPA 2000a outlines separate procedures for deriving national BAFs depending on the type of 

chemical, such as nonionic organic, ionic organic, inorganic, and organometallic. It also recommends the 

use of a weighted-average BAF that incorporates four trophic levels, e.g.: 

4 

BAF = ∑ FIi × BAF i 

i 2=

where: 

FIi = fish intake at trophic level I where I = 2, 3, and 4 

BAFi = bioaccumulation factor at trophic level I where I = 2, 3, and 4 

The time- and resource-intensive nature of estimating national BAFs is cited as the reason why 

EPA did not include BAFs in the human health criteria in the National Recommended Water Quality 

Criteria: 2002 (EPA 2002a). To keep the TWF model as flexible as possible, it is structured to use a BAF 

value if one exists and a BCF value if one does not. 

2.2.3.2 Relative Source Contribution Factors 

The TWF model is structured to calculate a human health criterion based on the 2000 

methodology including an RSC factor. The model is populated with the RSC values where they are 

reported in the National Recommended Water Quality Criteria: 2002 (EPA, 2002a) and in Bell (2000).2 

The values reported by Bell are listed in Table 2-3. 

2

The default value for an RSC is 1. 

2-7 
2.2.4 Water Quality Criteria Updates Since 2000 

EPA updated the TWF models with the data presented in National Recommended Water Quality 

Criteria: 2002 (EPA, 2002a). The values for the components for calculating human health criteria were 

taken from the support document (EPA, 2002b). For some chemicals, however, EPA (2002a) continues to 

calculate water quality criteria based on the 1980 methodology. The TWF model is programed to select 

the human health component as calculated by the 2000 methodology for organism only ingestion. A 

separate variable was added to the model to flag when the TWF should use the 1980 methodology for 

calculating the human health component. This was done in order to make the TWF model consistent with 

EPA (2002a) unless superceded by a later EPA publication. 

On the last day of 2003, EPA published updated national water quality criteria for human health 

for 15 chemicals (EPA, 2003a).3

 EPA incorporated the updated RfD, q1*, RSC, and BCFs into the TWF 

database for the December 2004 version. 

3

Chlorobenzene; cyanide; dichlorobenzene, 1,2; dichlorobenzene, 1,4; dichloroethylene, 1,1; 

dichloropropene, 1,3; endrin; ethylbenzene; hexachlorocyclopentadiene; lindane; thallium; toluene; 

transdichloroethylene, 1,2; trichlorobenzene, 1,2,4; and vinyl chloride. 

2-8 
Table 2-3

Uncertainty Factors and Relative Source Contributions

Chemical 

Uncertainty Factors 

Regular Carcinogenic RSC (%) 

antimony 1000 — 40 

atrazine 100 10 20 

barium 3 — NA 

beryllium 100 10 20 

cadmium 10 — 25 

carbofuran 100 — 20 

chromium 100 — 71 

chlorobenzene 1000 — 20 

copper 2 — NA 

cyanide 100 — 20 

2,4-D 100 — 20 

dalapon 100 — 20 

p-dichlorobenzene 1000 10 20 

o-dichlorobenzene 1000 10 20 

di(2-ethylhexyl) adipate 100 10 20 

1,1-dichloroethylene 1000 10 20 

cis-1,2-dichloroethylene 3000 — 20 

trans-1,2-dichloroethylene 1000 — 20 

dinoseb 1000 — 20 

diquat 100 — 20 

endrin 100 — 20 

ethylbenzene 1000 — 20 

endothall 100 — 20 

glyphosate 100 — 20 

hexachlorocyclopentadiene 1000 — 20 

lindane 1000 10 20 

methoxychlor 1000 — 20 

mercury 1000 — 20 

oxamyl 100 — 20 

picloram 100 — 20 

2-9
Table 2-3

Uncertainty Factors and Relative Source Contributions

Chemical 

Uncertainty Factors 

Regular Carcinogenic RSC (%) 

simazine 1000 10 20 

styrene 1000 10 20 

2,4,5-TP 100 — 20 

thallium 1000 — 20 

toluene 1000 — 20 

1,2,4-trichlorobenzene 1000 — 20 

1,1,2-trichloroethane 1000 10 20 

1,1,1-trichloroethane 1000 — 20 

xylenes 100 — 20 

NA: not appropriate, usually for uncertainty factors and/or RSCs with respect to maximum contaminant 

level goals and lifetime health averages set on the basis of human data, not animal research data. 

Source: Bell, 2000. 

2.3 CHRONIC AQUATIC LIFE VALUES 

When selecting chronic aquatic toxicity values, EPA uses national water quality criteria, when 

available. When these criteria are not available, other values representative of the chemical’s chronic 

toxicity are used. Sections 2.3.1 through 2.3.4 list various data sources for aquatic life values in the same 

order as those sources appear in EPA’s hierarchy. 

2.3.1 National Chronic Freshwater Quality Criteria 

National chronic water quality criteria are the first choice for values because they represent a 

consideration of a chemical’s toxicity to wide range of aquatic life and have been published by EPA. The 

EPA Office of Water describes the derivation of criteria values in documents for specific pollutants (EPA, 

2005c). A national chronic water quality criterion is defined as the 4-day average concentration of a 

toxicant at which a wide range of aquatic organisms should not be unacceptably affected, provided that 

average is not exceeded more than once every 3 years. 

2-10
2.3.2 Lowest Reported Measured Maximum Allowable Toxicant Concentration, 

Lowest-Observed-Effect Concentration, or No-Observed-Effect Concentration 

The term “chronic” refers to a stimulus that continues over time, often for periods of several 

weeks to years, depending on the affected organism’s reproductive life cycle. The biological response to 

the exposure typically progresses slowly and lasts a long time. Chronic aquatic tests measure the effects 

of long-term exposure to a chemical; citing rapid developments in test methodology, EPA recommends 

several 7-day, short-exposure-duration test methods (EPA, 1989). Test endpoints include such variables 

as survival percentage, hatchability, and normal larva weight and length. Chronic tests of longer exposure 

duration measure endpoints such as growth and reproduction. 

EPA uses chronic aquatic test data to identify three concentration levels of potential significance: 

the no-observed-effect concentration (NOEC), the lowest-observed-effect concentration (LOEC), and the 

maximum allowable toxicant concentration (MATC). The NOEC—the highest toxicant concentration to 

which test organisms have been exposed with no observed adverse effects—can be statistically 

determined using hypothesis testing or derived from the inhibition concentration. This inhibition 

concentration is an estimate of the toxicant concentration that will cause a given percentage reduction in 

biological measurement of the test organisms. The LOEC is the lowest toxicant concentration at which a 

chronic effect on a test organism has been observed. The MATC is the geometric mean of the NOEC and 

LOEC and is meant to represent the threshold level where chronic effects will begin to occur. MATC 

values are selected first, followed by LOEC values and then NOEC values for use in calculating TWFs. 

2.3.3 Lowest Chronic or Reproductive Test Concentration 

For chemicals that do not have chronic aquatic life criteria, MATCs, LOECs, or NOECs, EPA 

obtains chronic effect concentrations from readily available sources of chronic toxicity test data. The 

preferred information source is EPA’s Assessment Tools for the Evaluation of Risk (ASTER), which 

combines the Aquatic Toxicity Information Retrieval database (AQUIRE), the EPA Environmental 

Research Laboratory–Duluth (ERL-Duluth) fathead minnow database, and tables of toxicity test results 

from water quality criteria documents (EPA, 2005d).4

 The ASTER system differentiates between 

4

Access to ASTER is restricted as of January 2004 (see 

http://www.epa.gov/med/Prods_Pubs/aster.htm, downloaded September 15, 2004). ASTER technical 

2-11
AQUIRE test data that are likely to be of good quality and AQUIRE test data that are of unknown quality, 

according to the following criteria: 

# Test pH within the range of 6.5 to 8.5. 

# Review code 1 (methodology section cites published or well-documented procedures; 

satisfactory control; measured concentration; temperature, pH, dissolved oxygen, and 

hardness are reported) or code 2 (one or more of the following may occur: control 

mortality not reported; no solvent control when a solvent is used in the test; unmeasured 

concentration; water chemistry variables not reported or incomplete). 

# No use of formulations or carriers. 

# Measured values and flow-through exposure only for tests on fish (no static exposure). 

# Measured values only for invertebrates or plants (exposure may be static or 

flow-through). 

Test results from the ERL-Duluth fathead minnow database are assumed to be of good quality. However, 

test results reported in water quality criteria documents are assumed to be of unknown quality. 

EPA selects the lowest reported concentration—from a chronic growth or reproductive test on a 

North American native fish or invertebrate or from a biologically significant EC50 test for an algal species 

(e.g., chlorophyll production)—from the pool of test data likely to be of good quality or, alternatively, 

from the pool of data of unknown quality. If appropriate test data are not available from ASTER, other 

primary or secondary information sources are consulted. 

2.3.4 Estimated Chronic Toxicity Concentration from a Measured Acute: Chronic Ratio 

for a Less Sensitive Species, Quantitative Structure-Activity Relationship Model, or 

Default Acute: Chronic Ratio of 10:1

 EPA uses estimated chronic toxicity concentrations when measured values are unavailable. The 

first option for estimating a chronic toxicity concentration is to use acute toxicity concentrations and a 

measured acute:chronic ratio (ACR). ACRs are based on measured acute and chronic pollutant 

concentration values for the same species. The calculated ACR is applied to the acute aquatic toxicity 

support staff conduct ASTER searches for EPA projects. The public has access to AQUIRE data through 

EPA’s ECOTOX database at http://www.epa.gov/ecotox/, but the ECOTOX database does not screen the 

data. 

2-12 
criterion or toxic effect level selected for the pollutant of concern. EPA uses this method when an ACR is 

available for a species that has a measured chronic toxicity concentration greater than the acute criterion 

or the representative acute toxic effect level for the selected pollutant. These instances arise when chronic 

toxicity test data are available for less sensitive species only. The acute aquatic toxic effect level (used if 

national acute water quality criteria are not available) is typically the lowest reported acute aquatic 

bioassay test concentration (24- to 96-hour median lethal concentration, or LC50) for a North American 

resident species of fish or invertebrate. As with chronic toxic effect levels, a test result of good quality is 

selected ahead of a test result of unknown quality. 

The second option for estimating a chronic toxicity test concentration is to use ERL-Duluth’s 

quantitative structure-activity relationship (QSAR) model. QSAR derives statistically based relationships 

between physical-chemical properties and biological activity. The QSAR model uses measured toxicity 

test results for compounds with similar chemical structures and properties to estimate MATC values for 

compounds whose chemical structure and properties are known or may be estimated. 

The final option for estimating a chronic toxicity concentration is to apply an assumed ACR of 

10:1 to the acute aquatic toxic effect concentration. The ACR of 10:1 is based on a recommendation in 

the EPA Office of Water’s Technical Support Document for Water Quality-based Toxics Control (EPA, 

1991) for estimating chronic toxicity when no data are available. The recommendation assumes that the 

chronic toxicity value is 10 times lower than the acute value. 

2.4 REFERENCES 

EPA. 2005a. 2005 annual screening-level analysis: supporting the annual review of existing effluent 

limitations guidelins and standards and identification of potential new categories for effluent limitations 

guidelines and standards. EPA-821-B-05-003. August 2005. http://epa.gov/guide/304m/sla_report.pdf 

Also located in Public Record for the 2006 Effluent Guidelines program Plan, EPA Docket Number OW2004-0032-017, see http://www.epa.gov/edockets. 

EPA. 2005b. IRIS database for risk assessment. http://www.epa.gov/iris/. 

EPA. 2005c. Ambient water quality criteria documents for various chemicals published during the 1980s. 

http://www.epa.gov/waterscience/criteria/1980docs.htm. 

EPA. 2005d. ECOTOX data base. http://www.epa.gov/ECOTOX/. 

2-13
EPA. 2004. Risk-based concentration table. Region 3. October 19. 

http://www.epa.gov/reg3hwmd/risk/human/index.htm. Downloaded October 27, 2004. (Contains IRIS, 

HEAST, EPA-NCEA provisional values and EPA peer-reviewed values.) 

EPA. 2000. Methodology for deriving ambient water quality criteria for the protection of human health. 

EPA-822-B-00-004. October. 

EPA. 1999. National recommended water quality criteria—correction. EPA-822-Z-99-001. April. 

EPA. 1991. Technical support document for water quality–based toxics control. EPA-505-2-90-001. 

March. 

EPA. 1989. Short-term methods for estimating the chronic toxicity of effluent and receiving waters to 

freshwater organisms. Office of Research and Development. Cincinnati, Ohio. EPA-600-4-89-001. 

EPA. 1980. Ambient water quality criteria for copper. EPA-440-5-80-036. October. 

http://www.epa.gov/ost/pc/ambientwqc/copper80.pdf. Downloaded May 17, 2005. 

Ehrensberger, K., and R. Rico. 1988. Cost-effectiveness analysis for effluent guidelines. United States 

Environmental Protection Agency, Office of Water Regulations and Standards, Economic Analysis 

Branch. May. 

Zipf, L. 2003. Revisions to EAD’s toxic weighting factor methodology oarameters. Memorandum to 

304(m) Record (EPA Docket Number OW-2003-0074). December 3. 

2-14
SECTION 3 

DIOXIN AND CONGENERS 

EPA updated the TWFs for dioxin and its congeners to be consistent with EPA’s ongoing 

assessment (EPA, 2003b). The revisions incorporate World Health Organization (WHO) Toxicity 

Equivalency Factors (TEFs) to adjust the cancer slope factors (q1*s) and a derivation of BAFs. These are 

discussed in detail below. 

3.1 SLOPE FACTORS AND TEFS 

The Engineering and Analysis Division (EAD) continues to use the 1985 slope factor for 

tetrachlorodibenzo-p-dioxin, 2,3,7,8 (TCDD) in calculating TWFs. The 1985 slope factor of TCDD is 

160,000 (mg/kg/d)-1 (EPA, 1985). The slope factors of the other congeners are estimated by multiplying 

the slope factor of TCDD by the respective TEF. In accordance with EPA (2003b), EAD used the 1998 

WHO TEFs to adjust the 1985 slope factors (Van den Berg et al., 1998). Table 3-1 gives the CAS 

numbers, names, and TEFs for the 17 congeners. 

The revised slope factors are used to calculate updated human health values and the 

corresponding TWFs. The toxic equivalency value is calculated as follows:

 = 1.6x10e5 (slope factor) × TEF 

For example, for hexachlorodibenzo-p-dioxin,1,2,3,7,8,9, the toxic equivalency value is calculated as 

follows:

 = 1.6x10e5 (slope factor) × 0.1 (TEF)

 = 1.6x10e4 

3-1
Table 3-1 

Dioxins and Their Toxic Equivalency Factors

CAS 

Number Chemical Name Abbreviated Name 

Toxic Equivalency 

Factor 

CDDs 

1746-01-6 tetrachlorodibenzo-p-dioxin, 2,3,7,8 TCDD, 2,3,7,8 1 

40321-76-4 pentachlorodibenzo-p-dioxin, 1,2,3,7,8 PeCDD, 1,2,3,7,8 1 

39227-28-6 hexachlorodibenzo-p-dioxin, 1,2,3,4,7,8 HxCDD, 1,2,3,4,7,8 0.1 

57653-85-7 hexachlorodibenzo-p-dioxin, 1,2,3,6,7,8 HxCDD, 1,2,3,6,7,8 0.1 

19408-74-3 hexachlorodibenzo-p-dioxin, 1,2,3,7,8,9 HxCDD, 1,2,3,7,8,9 0.1 

35822-46-9 heptachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8 HpCDD, 1,2,3,4,6,7,8 0.01 

3268-87-9 octachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8,9 OCDD, 1,2,3,4,6,7,8,9 0.0001 

CDFs 

51207-31-9 tetrachlorodibenzofuran, 2,3,7,8 TCDF, 2,3,7,8 0.1 

57117-41-6 pentachlorodibenzofuran, 1,2,3,7,8 PeCDF, 1,2,3,7,8 0.05 

57117-31-4 pentachlorodibenzofuran, 2,3,4,7,8 PeCDF, 2,3,4,7,8 0.5 

70648-26-9 hexachlorodibenzofuran, 1,2,3,4,7,8 HxCDF, 1,2,3,4,7,8 0.1 

57117-44-9 hexachlorodibenzofuran, 1,2,3,6,7,8 HxCDF, 1,2,3,6,7,8 0.1 

72918-21-9 hexachlorodibenzofuran, 1,2,3,7,8,9 HxCDF, 1,2,3,7,8,9 0.1 

60851-34-5 hexachlorodibenzofuran, 2,3,4,6,7,8 HxCDF, 2,3,4,6,7,8 0.1 

67562-39-4 heptachlorodibenzofuran, 1,2,3,4,6,7,8 HpCDF, 1,2,3,4,6,7,8 0.01 

55673-89-7 heptachlorodibenzofuran, 1,2,3,4,7,8,9 HpCDF, 1,2,3,4,7,8,9 0.01 

39001-02-0 octachlorodibenzofuran, 1,2,3,4,6,7,8,9 OCDF, 1,2,3,4,6,7,8,9 0.0001 

Source: Van den Berg, et al., 1998. 

3.2 BAFs 

For dioxin and its congeners, EPA estimated BAFs based on the work done for the Great Lakes 

Water Quality Initiative (EPA, 1995). The BAFs in Table 10 of EPA’s document are lipid normalized and 

freely dissolved based BAFs, also known as “Baseline BAFs,” and were developed according to the 

methodology in EPA (2003c). This process of lipid-normalization and freely dissolved adjustment 

essentially “converts” the “site-specific” BAFs (derived from salmonids in the Great Lakes that have 

specific lipid and organic carbon content) into values that are ready for extrapolation to other 

conditions—that is, a national BAF. 

3-2
The first step is to convert the BAFs from EPA (1995) to “Baseline BAFs” using the national 

defaults for fR (fraction lipid) and f fd (fraction dissolved) and the following equation: 

National BAF TL n = [( Final Baseline BAF)TL n × (fR

) TL n + 1] × f fd

 where: 

Final Baseline BAF TL n = mean baseline BAF for trophic level (TL) n 

(fR) TL n = fraction of tissue that is lipid in aquatic organisms at trophic level n 

f fd = fraction of the total concentration of chemical in water that is freely 

dissolved 

The national default trophic level–specific lipid fractions (fR

) TL n (where fR = fraction lipid at TL n) 

are taken from EPA (2003c). These are shown in Table 3-2. 

Table 3-2

National Default Values for Lipid Fractions by Trophic Level

Trophic Level National Default Value 

2 1.9% 

3 2.6% 

4 3.0% 

Source: EPA, 2003c. 

The ffd (fraction freely dissolved) is calculated as follows: 

f fd = 1 

1 + POC × Kow + DOC × 0.08 × Kow 

where: 

f fd = fraction of the total concentration of chemical in water that is freely dissolved 

POC = concentration of particulate organic carbon in water (kilograms of particulate 

organic carbon per liter of water) 

3-3
DOC = concentration of dissolved organic carbon in water (kilograms of dissolved 

organic carbon per liter of water) 

Kow = n-octanol-water partition coefficient 

The national default values for POC and DOC are 0.5 mg/L and 2.9 mg/L, respectively. The derivation of 

these values is explained in Section 6.3 of EPA (2003c). 

For example, the BAF for TCDD, 2,3,7,8 is 9.00x10e+06 for TL 4 (salmonids); and the log Kow is 

7.02 (EPA, 1995). Given these two parameters, we can calculate the national BAF for a given trophic 

level. The first step is to calculate the fraction of the total concentration of TCDD, 2,3,7,8 that is freely 

dissolved: 

f fd = 1 

1 + POC × Kow + DOC × 0.08 × Kow 

where:

POC = 5.0 × 10e-7 kg/L (national default values)

DOC = 2.9 × 10e-6 kg/L (national default values)

Log Kow = 7.02 (that is, Kow = 107.02, which, in turn, equals 10,471,285)

so: f fd = 1 

1 + 5.0 x10e-7 kg/L × 1.05e+7 + 2.9 × 10e-6 kg/L × 0.08 × 1.05e+7 

f fd = 1.1541x10e-1 

The next step is to insert this value for the freely dissolved fraction of TCDD, 2,3,7,8 into the 

following equation: 

National BAF TL n = [( Final Baseline BAF)TL * (fR

) TL n + 1] * f fd

 where: 

Final Baseline BAF TL n = 9.00e+6 for TL 4 

3-4
(fR

) TL n = 0.03 for TL 4 

f fd = 1.1541x10e-1 

so: 

National BAF TL 4 = [(9.00x10e+06)4 × (.03)4 + 1] × 1.1541x10e-1 

National BAF TL 4 = 3.1160x10e+4 

EPA did not have BAF data for TLs 2 and 3 for dioxin. Therefore, all of the 17.5 grams/day fish 

consumption was apportioned to TL 4. 

Using the equation shown in Table 2-1 for carcinogenicity protection (organism only), we obtain: 

−5 

HHOO (ug / L ) =

⎛

⎝

⎜

(10 )

160,000

⎞

⎟

⎠ × 70 kg× 1,000 ug / mg

 0.0175 kg / day × (3.1160e + 4 × (L / kg) )

or 

HHOO (ug/L) = 8.02e-9 

The toxic weighting factor would be calculated using the following equation: 

TWF = 5.6

1.0e - 6 + 5.68.02e - 9 

or TWF for TCDD, 2,3,7,8 is 7.04e+8. 

3.3 REFERENCES 

Bell, F. 2000. Report on uncertainty factors (UF) and relative source contributions (RSC) for chemicals in 

the six year review. Memorandum to Cindy Roberts and Joyce Donahue, EPA, from Frank Bell, NCBA, 

EPA. September 26. 

EPA. 2003a. National recommended water quality criteria for the protection of human health. Fed. Reg. 

68:75,507–75,515. December 31. 

3-5
EPA. 2003b. Exposure and human health reassessment of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) 

and related compounds. EPA-600-P-00-001Cb. NAS review draft. 

http://www.epa.gov/NCEA/PCDFs/dioxin/nas-review. 

EPA. 2003c. Methodology for deriving ambient water quality criteria for the protection of human health 

technical support document volume 2: development of national bioaccumulation factors. EPA-822-R-03­

030. December. http://www.epa.gov/waterscience/criteria/humanhealth/method/tsdvol2.pdf. 

EPA. 2002a. National recommended water quality criteria: 2002. EPA-822-R-02-047. November. 

EPA. 2002b. National recommended water quality criteria: 2002. Human health criteria calculation 

matrix. EPA-822-R-02-012. November. 

EPA. 2000a. Methodology for deriving ambient water quality criteria for the protection of human health 

(2000) Final. EPA-822-B-00-004. October. 

EPA. 2000b. Revisions to the methodology for deriving ambient water quality criteria for the protection 

of human health (2000); notice. Fed. Reg. 65:66,444–66,482. November 3. 

EPA. 1995. Great Lakes Water Quality Initiative technical support document for the procedure to 

determine bioaccumulation factors. EPA-820-B-95-005. 

EPA. 1985. Health assessment document for polychlorinated dibenzo-p-dioxins. Office of Health and 

Environmental Assessment. EPA-600-8-84-814F. 

ERG. 2004. Fixes to toxic weighting factor (TWF) database. Memorandum to TWF database project file 

by Eastern Research Group, Inc. November 1. 

Van den Berg, et al., 1998. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and 

wildlife. Environ. Health Perspect. 106:775-792.

Zipf, L. 2003. Revisions to EAD’s toxic weighting factor methodology parameters. Memorandum to

304(m) Record (EPA Docket Number OW-2003-0074). December 3.

3-6
SECTION 4 

DEVELOPMENT OF TWF DATABASE 

4.1 DATABASE OVERVIEW 

In May 2004, EPA decided to develop a database to support the transparency, reproducibility, 

and documentation of TWF values. The database is in ExcelTM and can be found in the docket. 

The overall organization of the individual sheets within the file is as follows: 

# Read First: Instructions on using the model. 

# Data Dictionary: List of variable names, with definitions and sources for the data. 

# TWFs: Master list of TWFs. Human health values based on carcinogens are converted to 

a 10-5 risk level, human and aquatic health values are standardized to the value for copper 

(5.6 :g/L), preferred human and aquatic health values are identified and added. 

# HH_CALC: Calculated human health value for carcinogens and non-carcinogens for 

organisms only and water and organisms. All variables are linked to data sheets by 

Chemical Abstracts Service (CAS) number. 

# AQ_FRESH_ACUTE: What the acute aquatic health values for freshwater species are 

based on (e.g., LC50, species, and citation). If the data are taken from ASTER, the original 

reference is included. Separate columns track the source date, last reviewed date, and last 

update date. 

# AQ_FRESH_CHRONIC: Counterpart to AQ_FRESH_ACUTE for chronic exposures. 

# AQ_SALT_ACUTE: Counterpart to AQ_FRESH_ACUTE for saltwater species. 

# AQ_SALT_CHRONIC: Counterpart to AQ_SALT_ACUTE for chronic exposures. 

# BCF_BAF: Data sheet for BCFs and BAFs, study duration, species, and citation. 

Separate columns track the source date, last reviewed date, and last update date. 

# Cancer_Potency_Factor: Cancer potency factor values—also called cancer slope factors, 

slope factors, or q1*—and citations. Separate columns track the source date, last reviewed 

date, and last update date. 

# Reference Dose: Contains each RfD’s value, citation, and three columns tracking the date 

of the source, last review, and last update. 

4-1
# Relative Source Contribution: A parameter that adjust the human health value for 

ingestion of aquatic organisms to account for exposure from other sources. Contains 

value, citation, and three columns tracking the date of the source, last review, and last 

update. 

# Constants: For example, fish intake for calculating the human health criteria. 

The purpose of the database is to duplicate the TWFs in use by EPA in a self-contained database whose 

reader can track the data from the original sources through all of the calculations to the final TWF value. 

As mentioned in Section 1, the set of approximately 1,900 TWF values grew over the course of several 

decades. The output of the August 2004 database was compared against a master list of TWF values and 

no discrepancies were found. EPA proceeded with its industry analysis for the 304(m) process with the 

August 2004 data while it began an overall review and update of the database according to the needs 

outlined in Zipf (2003). These updates are discussed in Section 5. 

4.2 QUALITY CONTROL REVIEWS 

EPA used the structure of the new TWF database to facilitate a series of quality control reviews. 

These included searching for: 

# Missing references for any of the parameters.

# Unknown codes for any of the parameters.

# Missing species for any of the aquatic health values.

# No adjustment on the carcinogenicity risk values to 10-5 risk level (i.e., values that should

have been adjusted from a 10-6 risk level to a 10-5 risk level but were not). 

# Acute:chronic ratios for aquatic health not adjusted to 1991 value of 10. 

# Corrections to references. 

# Pollutants whose TWFs were calculated on either the human health or aquatic health data 

when EPA had data for both parameters. 

# Pollutants for which no TWF was calculated when EPA had data for at least one of the 

human or aquatic health parameters. 

The results of the quality control reviews were summarized in a memo to the project files (ERG, 2004). 

4-2
4.3 REFERENCES 

ERG. 2004. Fixes to toxic weighting factor (TWF) data. Memorandum to Lynn Zipf, EPA, from Eastern 

Research Group, Inc. November 1. 

Zipf, L. 2003. Revisions to EAD’s toxic weighting factor methodology parameters. Memorandum to 

304(m) Record (EPA Docket Number OW-2003-0074). December 3. 

4-3
SECTION 5 

UPDATED TWF DATABASE 

The updates to the TWF database were completed in December 2004. EPA then compared the 

August and December TWF values. Of the approximately 1,900 pollutants, about 1,450 showed no 

change between the August and December databases. Another 372 TWFs registered as showing a change 

in value due to a shift to the 2000 human health methodology (“2000 methodology”), but the differences 

were so small (10e-7 to 10e-19 in value) as to be negligible. Table 5-1 lists TWFs for 26 pollutants for 

which the change to the 2000 methodology resulted in a change of at least 1 percent in the value of the 

TWF. An additional 54 TWFs changed due to updated data. This group includes dioxin and its congeners; 

the group is presented in Table 5-2. 

When comparing the August and December 2004 values, EPA noticed that one 

pollutant—manganese—no longer had a value. Manganese is anomalous in that EPA (2002) provides a 

recommended human health value but does not provide any of the underlying components used to 

calculate it. For manganese, then, the human health value is hard-wired instead of being calculated from 

its component parts. 

5.1 REFERENCE 

EPA. 2002. National recommended water quality criteria: 2002. Human Health Criteria Calculation 

Matrix. EPA-822-R-02-012. November. 

5-1
Table 5-1

Comparison of August and December 2004 TWF Values

Changes Due to Shift to 2000 Methodology

Pollutant CAS Number 

TWF Values 

Difference 

Difference 

December August as a Percent

Dichloropropene, trans-1,3­ 10061026 2.30e-02 2.33e-02 -3.97e-04 -1.73% 

Dichloropropene, cis-1,3­ 10061015 2.30e-02 2.33e-02 -3.97e-04 -1.73% 

Dichloropropene, 1,3­ 542756 5.65e-01 5.42e-01 6.57e-03 1.16% 

Thallium 7440280 1.03e+00 1.00e+00 2.53e-02 2.47% 

Allyl chloride 107051 3.35e-03 2.91e-03 1.16e-04 3.47% 

Chlorine 7782505 5.09e-01 4.87e-01 2.21e-02 4.35% 

Tribromomethane 75252 4.57e-03 1.75e-03 2.10e-04 4.59% 

Trichloroethene 79016 1.91e-02 6.44e-03 8.82e-04 4.62% 

Simazine 122349 6.42e-01 5.61e-01 3.01e-02 4.68% 

BHC, gamma-/lindane 58899 7.03e+01 4.69e+01 8.56e+00 12.18% 

Dinitrotoluene, 2,4­ 121142 4.45e-01 2.81e-01 6.05e-02 13.57% 

Arsenic 7440382 4.04e+00 3.47e+00 5.72e-01 14.15% 

Nitrosopyrrolidine, – 930552 1.62e-02 3.28e-03 2.73e-03 16.88% 

Chrysene 218019 3.10e+01 2.10e+00 9.63e+00 31.07% 

Indeno(1,2,3-cd)pyrene 193395 3.07e+01 1.14e+00 1.02e+01 33.43% 

Tetrachloroethene 127184 2.34e-01 1.26e-02 8.12e-02 34.72% 

Atrazine 1912249 2.31e+00 9.44e-02 8.23e-01 35.60% 

Pentachloronitrobenzene/ 

Quintozene 

82688 3.85e+01 7.41e-01 1.39e+01 36.13% 

Alachlor/Lasso 15972608 1.78e+00 1.57e-02 6.49e-01 36.52% 

Aldrin 309002 1.11e+04 5.02e+01 4.10e+03 36.84% 

Parachlorometacresol 59507 1.33e+00 4.33e-03 4.93e-01 37.02% 

Chlorobenzilate 510156 7.92e+01 1.56e-01 2.93e+01 37.03% 

Trichloropropane, 1,2,3­ 96184 5.26e+00 1.96e-03 1.95e+00 37.11% 

Hydrofluoric acid 7664393 5.60e-06 0.00e+00 2.08e-06 37.14% 

Aflatoxins 4402682 1.79e+04 0.00e+00 6.64e+03 37.14% 

Azinphos methyl/

 Guthion, methyl86500 5.61e+01 2.80e+01 2.80e+01 49.93% 

Cadmium 7440439 2.31e+01 2.61e+00 1.99e+01 85.89% 

Ethoprophos 13194484 8.89e+01 3.81e-01 8.85e+01 99.57% 

Source: EPA estimates. 

5-2
Table 5-2

Changes in TWFs Due to Updates

Pollutant 

CAS 

Number 

TWF 

December August Reasons for Diffe

Tetrachlorodibenzo-p-dioxin, 2,3,7,8­ 1746016 7.04E+08 4.22E+08 Dioxin congener: change from BCPentachlorodibenzo-p-dioxin, 1,2,3,7,8­ 40321764 6.93E+08 2.15E+08 Dioxin congener: change from BCHexachlorodibenzo-p-dioxin, 1,2,3,7,8,9­ 19408743 1.06E+07 4.31E+07 Dioxin congener: change from BCHexachlorodibenzo-p-dioxin, 1,2,3,4,7,8­ 39227286 2.35E+07 4.31E+07 Dioxin congener: change from BCHexachlorodibenzo-p-dioxin, 1,2,3,6,7,8­ 57653857 9.56E+06 4.18E+07 Dioxin congener: change from BCPentachlorodibenzofuran, 2,3,4,7,8­ 57117314 5.57E+08 3.29E+07 Dioxin congener: change from BCTetrachlorodibenzofuran, 2,3,7,8­ 51207319 4.38E+07 6.70E+06 Dioxin congener: change from BCHexachlorodibenzofuran, 1,2,3,7,8,9­ 72918219 4.73E+07 6.67E+06 Dioxin congener: change from BCHexachlorodibenzofuran, 1,2,3,6,7,8­ 57117449 1.41E+07 6.67E+06 Dioxin congener: change from BCHexachlorodibenzofuran, 1,2,3,4,7,8­ 70648269 5.76E+06 6.66E+06 Dioxin congener: change from BCHexachlorodibenzofuran, 2,3,4,6,7,8­ 60851345 5.12E+07 6.66E+06 Dioxin congener: change from BCHeptachlorodibenzo-p-dioxin, 1,2,3,4,6,7,8­

35822469 4.11E+05 4.18E+06 Dioxin congener: change from BC

Pentachlorodibenzofuran, 1,2,3,7,8­ 57117416 7.63E+06 3.29E+06 Dioxin congener: change from BCHeptachlorodibenzofuran, 1,2,3,4,7,8,9­ 55673897 3.03E+06 6.67E+05 Dioxin congener: change from BCHeptachlorodibenzofuran, 1,2,3,4,6,7,8­ 67562394 8.58E+04 6.66E+05 Dioxin congener: change from BCOctachlorodibenzo-p-dioxin 3268879 6.59E+03 4.24E+05 Dioxin congener: change from BCOctachlorodibenzofuran 39001020 2.02E+03 6.74E+04 Dioxin congener: change from BCDieldrin 60571 1.06E+04 5.67E+04 BCF changed; new value taken frBenzo(a)pyrene 50328 1.01E+02 4.28E+03 BCF changed; new value taken frDibenzo(a,h)anthracene 53703 3.07E+01 1.69E+03 BCF changed; new value taken frBenzo(b)fluoranthene 205992 3.07E+01 4.21E+02 BCF changed; new value taken frBenzo(a)anthracene 56553 3.63E+01 1.81E+02 BCF changed; new value taken frMercury 7439976 1.17E+02 1.17E+02 BCF changed; new value taken frBenzo(k)fluoranthene 207089 3.07E+01 4.21E+01 BCF changed; new value taken frNitrosodi-n-butylamine, – 924163 2.56E+00 4.77E+00 BCF changed; new value taken fr

5-3
Table 5-2

Changes in TWFs Due to Updates

Pollutant 

CAS 

Number 

TWF 

December August Reasons for Diffe

Nitrosodi-n-propylamine, – 621647 1.11E+00 2.29E+00 BCF changed; new value taken frAniline 62533 6.86E-03 1.41E+00 BCF changed; new value taken frPentachlorobenzene 608935 3.77E+00 2.26E+00 BCF changed; new value taken frVanadium 7440622 3.50E-02 6.22E-01 Aquatic health value changed; new 

ASTER 

Dibromochloromethane 124481 4.45E-02 1.27E-01 BCF changed; new value taken frTrichlorophenol, 2,4,6­ 88062 4.98E-01 4.44E-01 BCF changed; new value taken frBromodichloromethane 75274 3.29E-02 7.42E-02 BCF changed; new value taken frTrichlorobenzene, 1,2,4­ 120821 2.55E-02 8.21E-02 BCF changed; new value taken frManganese 7439965 1.44E-02 7.04E-02 TWF database will be updated to 

values 

Chloroethene 75014 8.55E-02 1.16E-01 q1* changed; new value taken froPyrene 129000 9.32E-02 1.11E-01 BCF changed; new value taken frTrichlorophenol, 2,4,5­ 95954 1.78E-02 2.62E-02 BCF changed; new value taken frEthylenethiourea 96457 1.56E-01 6.71E-02 q1* changed, see memo “Fixes to 

Factor (TWF) Data” from MaureeLynn Zipf, EPA, dated November 

Beryllium 7440417 1.06E+00 1.06E+00 BCF changed; new value taken frNitrophenol, 4­ 100027 4.89E-03 9.44E-03 BCF changed; new value taken frFluorene 86737 7.01E-01 7.04E-01 BCF changed; new value taken frChloronaphthalene, 2­ 91587 2.16E-02 2.23E-02 BCF changed; new value taken frAnthracene 120127 2.55E+00 2.55E+00 BCF changed; new value taken frAmmonia as N 7664417 1.35E-03 1.83E-03 Fresh acute value changed; value 

update of ambient water quality fo

5-4
Table 5-2

Changes in TWFs Due to Updates

Pollutant 

CAS 

Number 

TWF 

December August Reasons for Diffe

Dichloroethene, 1,2­ 540590 1.46E-03 1.27E-03 Oral reference dose changed; see 

Weighting Factor (TWF) Data” frERG, to Lynn Zipf, EPA, dated N

Bromomethane 74839 5.98E-02 5.77E-02 BCF changed; new value taken frDichloropropane, 1,2­ 78875 3.94E-02 1.55E-02 BCF changed; new value taken frHexachlorobutadiene 87683 6.33E-01 6.14E-01 BCF changed; new value taken frBenzene 71432 3.17E-02 1.84E-02 BCF changed; new value taken frDimethylphenol, 2,4­ 105679 9.41E-03 5.29E-03 BCF changed; new value taken frDichloromethane 75092 1.01E-03 4.23E-04 BCF changed; new value taken frDinitrophenol, 2,4­ 51285 8.14E-03 7.48E-03 BCF changed; new value taken frDichloroethene, trans-1,2­ 156605 9.20E-05 9.25E-05 BCF changed; new value taken frBis(2-chloroisopropyl) ether 108601 2.54E-02 1.26E-03 BCF changed; new value taken fr

Source: EPA estimates. 

5-5
SECTION 6 

TWF DEVELOPMENT 

As EPA continues to study different industries and their discharges as reported to TRI and PCS, 

there is a periodic need to review, update, and/or develop TWFs for specific chemicals or groups of 

chemicals. Appendix A contains the data sheets developed for summarizing the information available. 

After EPA’s internal review, these will be incorporated in the next release of the TWF database. Section 

6.1 discusses updates requested in the fall of 2004. Sections 6.2 through 6.5 provide background 

information on the development of TWFs for methylmercury, polycyclic aromatic compounds (PACs), 

nitrogen, and the second list of drinking water contaminants published by EPA on February 24, 2005 

(EPA, 2005a). 

6.1 FALL 2004 LIST OF CHEMICALS 

In October 2004, EPA decided to review, update, and/or develop TWFs for: 

# Hydrogen fluoride, CAS 7664393

# Chlorine dioxide, CAS 10049044

# 1,3-phenylenediamine, CAS 108452

# Benzo(a)pyrene, CAS 50328

# Aniline, CAS 62533

# Vanadium, CAS 7440622

The worksheets are shown in Appendices A-2 through A-7. 

6.2 METHYLMERCURY 

EPA (2002a) presents a human health water quality criterion for methylmercury expressed as a 

fish and shellfish tissue concentration. The criteria for all other contaminants are expressed as water 

column concentrations. EPA also presented the RSC for methylmercury as an amount subtracted from the 

RfD, rather than as a percentage as is done with the other contaminants. 

6-1
For the TWF database, however, EPA needs to convert water quality criterion from a 

methylmercury concentration in fish tissue to a methylmercury concentration in water. EPA also needs to 

convert the RSC to a percentage for use in the TWF database. The first conversion is discussed in Section 

6.2.1 while the second is presented in Section 6.2.2. The data sheets for mercury and methylmercury are 

located in Appendix A-8 and A-9, respectively. 

6.2.1 Water Quality Criterion for Methylmercury as a Concentration in Water 

In a Federal Register notice (EPA, 2001a), EPA provided three approaches to relate the 

methylmercury fish tissue water quality criterion to a concentration of methylmercury in the water 

column. The first approach is to collect site-specific BAFs based on water and fish collected in the 

waterbody of concern. This approach is not appropriate for a national-level analysis. The second approach 

is to use a bioaccumulation model with site-specific parameters. Again, the site-specific nature of the 

approach is not appropriate for a national-level analysis. 

The third approach is to use empirically derived draft BAFs.5

 These are national estimates. The 

Federal Register notice’s data for fish intake (FI) by trophic level and BAF by trophic level were used to 

create a weighted-average national BAF for methylmercury for the purpose of estimating a TWF for the 

304(m) process. Table 6-1 reproduces the calculations. For each trophic level, the product of the BAF and 

the FI are used. For example, for trophic level 2, the product of 1.6x10e5BAF and .0038 (kg/day) FI is 

608. The calculation is repeated for trophic levels 3 and 4. The final column in Table 1 is the sum of the 

FIs (0.0175 kg/day) and the product of the BAFs (21,438). Dividing 21,438 by the total FI (0.0175) 

estimates the weighted-average BAF value of 1.225029x10e6. 

5

Final methylmercury BAFs were not found in the Federal Register for 2001 through 

November 2004 . 

6-2 
Table 6-1

Weighted-Average National BAF for Methylmercury

Parameter 

Trophic Level 

2 3 4 Sum

Bioaccumulation factor 1.60e+05 6.80e+05 2.70e+06 

Fish intake (kg/day) 3.80e-03 8.00e-03 5.70e-03 1.75e-02 

Product: BAF(trophic level) × FI(trophic level) 6.08e+02 5.44e+03 1.54e+04 2.14e+04 

Weighted average BAF 1.23e+06 

Source: EPA, 2001. 

6.2.2 Conversion of RSC from a Value to be Subtracted to a Percentage 

EPA (2001a) presents the RSC as an amount to be subtracted rather than a percentage. The 

equations in the TWF model assume the RSC is a percentage. Table 6-2 shows the conversion 

calculations. The RfD for methylmercury is 0.1 :g/kg/day (66 FR 1353), or 0.0001 mg/kg/day. The RSC 

in the subtraction approach is 2.7 × 10-5, or 0.000027 mg/kg/day (66 FR 1354). The difference between 

the RfD and the RSC, i.e., the amount to be multiplied by body weight in the water quality criterion 

calculations, is 7.25 × 10-5, or 0.0000725. Dividing 0.0000725 by 0.0001 equals 0.725. The equivalent 

value for RSC is 73 percent. 

Table 6-2

Conversion of RSC from Amount Subtracted to Percentage

Parameter Value 

RfD (mg/kg BW-day) 0.0001000 

RSC (mg/kg BW-day) 0.0000275 

Difference 0.0000725 

(RfD-RSC)/RfD = RSC as a percentage of RfD 0.7250000 

Source: EPA estimates. 

6-3
6.3 POLYCYCLIC AROMATIC COMPOUNDS 

6.3.1 Background 

Table 6-3 lists the 21 chemicals considered to be PACs, based on the Emergency Planning and 

Community Right-To-Know Act guidance as of August 2001 (EPA, 2001b). Most of these compounds 

are the product of incomplete combustion or are from fossil fuels. Two of these 

chemicals—dimethylbenz(a)anthracene, 7, 12 and methylcholanthrene, 3—have been produced in small 

quantities as research chemicals. They are listed in EPA (2001b) as formed during combustion. 

Understandably, no human health or aquatic life data are available for these two chemicals and they are 

excluded from further discussion in this memorandum. 

Section 6.3.2 reviews the chemicals for which EPA has already developed human health water 

quality criteria using the 2000 methodology. Section 6.3.3 summarizes the availability of aquatic life 

values for the PACs listed in Section 6.3.2. Section 6.3.4 discusses the human and aquatic health data 

available for the remaining chemicals. Section 6.3.5 summarizes the findings and proposes a general PAC 

TWF. Worksheets for each chemical are located in Appendix A-5 and A-10 through A-27. 

6.3.2 Human Health 

EPA (2002a) published water quality criteria for: 

# Benzo(a)anthracene

# Benzo(a)phenanthrene (chrysene)

# Benzo(a)pyrene

# Benzo(b)fluoranthene

# Benzo(k)fluoranthene

# Benzo(j,k)fluorene (fluoranthene)

# Dibenzo(a,h)anthracene

# Indeno(1,2,3-cd)pyrene 

EPA (2002b) also noted that the IRIS value for benzo(b)fluoranthene (CAS 205992) was used to derive 

the value presented for benzo(a)anthracene, benzo(a)phenanthrene (chrysene), benzo(k)fluoranthene, 

6-4
Table 6-3

Chemicals Included in the EPCRA Section 313 PAC Category

Chemical Name CAS Number 

Benzo(a)anthracene 56553 

Benzo(a)phenanthrene (chrysene) 218019 

Benzo(a)pyrene 50328 

Benzo(b)fluoranthene 205992 

Benzo(j)fluoranthene 205823 

Benzo(k)fluoranthene 207089 

Benzo(j,k)fluorene (fluoranthene) 206440 

Benzo(r,s,t)pentaphene 189559 

Dibenz(a,h)acridine 226368 

Dibenz(a,j)acridine 224420 

Dibenzo(a,h)anthracene 53703 

Dibenzo(a,e)fluoranthene 5385751 

Dibenzo(a,e)pyrene 192654 

Dibenzo(a,h)pyrene 189640 

Dibenzo(a,l)pyrene 191300 

7H-dibenzo(c,g)carbazole 194592 

7,12-dimethylbenz(a)anthracene 57976 

Indeno(1,2,3-cd)pyrene 193395 

3-methylcholanthrene 56495 

5-methylchrysene 3697243 

1-nitropyrene 5522430 

Source: EPA, 2001b. 

6-5
dibenzo(a,h)anthracene, and indeno(1,2,3-cd)pyrene. As such, data are truly only available for three 

chemicals: 

# Benzo(a)pyrene

# Benzo(b)fluoranthene

# Benzo(j,k)fluorene (fluoranthene)

6.3.3 Aquatic Life Criteria 

EPA (2002a) did not publish corresponding aquatic life criteria for the eight PACs listed in 

Section 6.3.2. ASTER data were reviewed in order to identify appropriate studies and values for deriving 

aquatic life criteria. ASTER sometimes reports studies in two separate sections—the first section includes 

studies that pass ASTER’s filter for data of the highest quality and the second section includes studies that 

do not pass the filter for data quality but are included in the AQUIRE (now ECOTOX) database. A 

researcher with access only to ECOTOX would not have identified better data sources. 

Where possible, data that passed the ASTER filter were used. In addition, data were not 

used—even if they passed the filter—if the citation was a personal communication. With these two 

criteria, higher concentrations than those cited in the earlier TWF data were identified. That is, both 

citations appear in ECOTOX, but the study that ASTER identified as being of higher quality was used. 

Table 6-4 summarizes these changes. 

6-6
Table 6-4

Changes to Aquatic Life Health Data

Chemical Aquatic Life Category 

Values (:g/L) 

Old New 

Benzo(a)anthracene Fresh-acute 10 1,599 

Benzo(a)anthracene Fresh-chronic 1 160 

Benzo(a)phenanthrene chrysene Fresh-acute 592 1,599 

Benzo(a)phenanthrene chrysene Fresh-chronic 16 160 

Benzo(j,k)fluorene 

(fluoranthene) 

Fresh-chronic 7.1 4.5 

Dibenzo(a,h)anthracene Fresh-acute NA 496 

Dibenzo(a,h)anthracene Fresh-chronic NA 50 

Source: ASTER, 2004. 

6.3.4 Remaining Chemicals 

The remaining PACS for which no water quality criteria were available are: 

# Benzo(j)fluoranthene

# Benzo(r,s,t)pentaphene

# Dibenz(a,h)acridine

# Dibenz(a,j)acridine

# Dibenzo(a,e)fluoranthene

# Dibenzo(a,e)pyrene

# Dibenzo(a,h)pyrene

# Dibenzo(a,l)pyrene

# 7H-dibenzo(c,g)carbazole

# 5-methylchrysene

# 1-nitropyrene

No human health criteria were found for these 11 chemicals in IRIS, the EPA Region 3 RBC Table, 

ATSDR toxicological profiles, the EPA 2000 Water Quality Standards, or the EPA 1995 Final Water 

Quality Guidance for the Great Lakes System. ASTER data were examined for these chemicals, and only 

data for 7H-dibenzo(c,g)carbazole were found. 

6-7
6.3.5 Summary and Proposed PAC TWFs 

For the human health component of the PAC TWF, values were identified for three chemicals: 

benzo(a)pyrene, benzo(b)fluoranthene, and benzo(j,k)fluoranthene. The first two are carcinogens and 

have the same cancer slope value (q1* = 7.3 mg/kg/day). The third is a non-carcinogen with a RfD of 

0.04 mg/kg/day. After adjusting the cancer risk factor to 10-5 and standardizing the PACs to copper, the 

human health, organism-only component for the TWF range is nearly three orders of magnitude, as 

follows: 

# benzo(a)pyrene: 30.7 

# benzo(b)fluoranthene: 30.7 

# benzo(j,k)fluoranthene: 0.0403 

Aquatic life data were identified for 6 of the 21 PACs. These data are summarized in Table 6-5. 

Table 6-5

Aquatic Health Data for PAC Chemicals

Chemical 

Fresh Salt 

Chronic Acute Chronic Acute 

Benzo(a)anthracene 160 1,599 7.5 75 

Benzo(a)phenanthrene (chrysene) 160 1,599 

Benzo(a)pyrene 0.08 5 100 1,000 

Benzo(j,k)fluorene (fluoranthene) 4.5 45 

7H-dibenzo(c,g)carbazole 185 1,852 

1-nitropyrene 215 2,149 

Dibenzo(a,h)anthracene 496 496 5 50 

Geometric Mean (:g/L) 29.2 379.6 15.5 155.4 

Toxic Weighting Factor 

Component Value 0.19 0.01 0.36 0.04 

Source: ASTER, 2004. 

EPA identified three approaches to developing TWFs for PACs. First, where the composition of 

the PAC discharge is known, EPA could separate the discharge into its constituents and calculate toxicweighted pound-equivalents using the chemical-specific TWFs. Second, EPA could use the highest TWF 

6-8
for any constituent within the PAC discharge—usually benzo(a)pyrene—as an upper-bound estimate of 

relative toxicity. The second approach, however, could mask a difference between two industrial 

discharges when one discharge is 100 percent benzo(a)pyrene and the second discharge is a PAC with a 

substantial fraction of benzo(j,k)fluoranthene. 

The third approach is to estimate a TWF for a generalized PAC. The 304(m) screening process is 

just that: a nation-wide screening process, not a site- or discharge-specific risk assessment. In this case, 

EPA does not know the composition of the PAC discharge (e.g., 50 percent benzo(a)pyrene, 10% 

benzo(j,k)fluoranthene). There is no single known or suspected common mode of action shared by the 

class of compounds, that is, some PACs have a cancer mode of action while others are non-carcinogenic. 

This means that PACs do not meet the minimum data requirements for developing a relative potency 

factor (EPA, 2000). 

Strictly for the purposes of ranking discharges for the 304(m) process, EPA considered 

developing a generalized PAC TWF. EPA considered several distributions and measures of central 

tendency and noted that: 

# A three-order-of-magnitude range in human health values suggests that a logarithmic 

distribution might be the most appropriate assumption for the distribution of human 

health values. 

# Logarithmic transformations are used to stabilize the variance if the standard deviation in 

the original scale varies with the mean (Snedcor and Cochrane, 1980). That is, the effects 

are proportional. 

# Both modes of operation (cancer and non-cancer) use the same risk level (10-5). 

The geometric mean for the copper-standardized human health component for benzo(a)pyrene, 

benzo(b)fluoranthene, and benzo(j,k)fluoranthene is the cube root of (30.7 × 30.7 × 0.0403), or 3.36. The 

geometric mean for the copper-standardized chronic aquatic health criterion for fresh water is 0.19 (see 

Table 6-5). The proposed TWF for PACs is, therefore, 3.57—that is, the sum of 3.36 and 0.19. 

6-9
6.4 NITROGEN 

EPA decided to perform a comprehensive review of aquatic and human health data for nitrogen in 

various forms in order to provide a consistent and documented basis for the proposed TWFs. TRI and 

PCS report discharges for: 

# Sodium nitrite

# Ammonia

# Nitrogen, total (as N)

# Nitrogen, Kjeldahl total (as N)

# Nitrogen oxides (as N)

# Nitrogen, organic total (as N)

# Nitrogen, nitrite total (as N)

# Nitrogen, inorganic total

# Nitrogen, Kjeldahl total (TKN)

# Nitrite nitrogen, dissolved (as N)

# Nitrogen, nitrite total (as NO2)

# Nitrogen (as NO3) sludge solid

For nitrogen, the sensitive population is an infant or small child and the major pathway is 

drinking water. Nitrite reacts with the ferrous iron in hemoglobin to form methemoglobin with iron in the 

ferric valence state. Ferric iron is unable to transport oxygen, leading to shortness of breath, skin turning 

blue, and oxygen deprivation in the brain. Although humans convert ingested nitrate into nitrite in the gut, 

the amount converted depends on several factors. The pH of the gut is normally higher in infants than in 

older children and adults, and the higher pH enhances nitrate-to-nitrite conversion. In addition, fetal 

hemoglobin is oxidized more readily by nitrite to methemoglobin, making infants and children the 

sensitive subpopulation (ATDSR, 2001; IRIS, 2004, 2005a). 

The human health component of a TWF , however, is based on the exposure of an adult via 

organism only (not drinking water and organism; see Table 2-1 and Section 2.2). As IRIS (2005a) notes, 

nitrate is a normal component of the human diet. In addition, there is no oral RfD for ammonia reported in 

IRIS (IRIS, 2005b). For these reasons, no human health component is calculated for the various forms 

of nitrogen. The TWFs are based on aquatic health only. 

6-10
6.4.1 Sodium Nitrite 

Sodium nitrite is not included in the forms of organic nitrogen listed in APHA et al., 1995. It 

should not be surprising, then, that its TWF might differ substantially from those for components of the 

nitrogen cycle. Sodium nitrite was added to the list of chemicals reported in TRI in 1994 under the 

Emergency Planning and Community Right-to-Know Act (EPCRA) section 313(d)(2)(B) based on 

chronic hematological and developmental toxicity data from mouse and rat studies (EPA, 1994). 

The ASTER report for sodium nitrite CAS 7632-00-0 references more than 120 studies. Only the 

studies that passed the ASTER filter were considered for the TWFs. The median acute data are: 

# Rainbow trout, 96-hr LC50: 150 :g/L 

# Cutthroat trout, 96-hr LC50: 560 :g/L

# Fathead minnow, 96-hr LC50: 2,990 :g/L

The median chronic data are: 

# Channel catfish, 31-day exposure, growth: 1,620 :g/L

# Channel catfish, 31-day exposure, mortality: 1,250 :g/L

What is apparent is that there is a wide range of sensitivity according to the species examined. 

Channel catfish are far less sensitive than rainbow trout; the median chronic values for catfish are about 

10 times higher than the median acute value for rainbow trout. The sensitivity of salmonids is apparent 

for ammonia as well as sodium nitrite; see EPA (1999a) Figure 8, where the graphs for salmonids have a 

maximum value of 200 mg N/L, while the maximum values for other species range from 400 mg N/L to 

2,000 mg N/L for catfish. See also EPA (1999a), Figure 11 and pages 40–41, concerning the sensitivity of 

salmonids to pollutants. 

Within the acute data, a study of fathead minnows reported a 96-hour LC50 acute value of 2,990 

:g/L, a factor of 20 times higher than the 96-hour LC50 acute value reported for rainbow trout of 150 

:g/L. 

6-11
EPA has four options for the sodium nitrite TWF. If EPA uses the lowest 96-hour LC50 acute 

value for a species and reduces it by an order of magnitude to produce the chronic value, the options are 

15 :g/L (rainbow trout), 56 :g/L (cutthroat trout), and 299 :g/L (fathead minnow). If EPA uses the 

chronic data for channel catfish, the value is 1,250 :g/L. EPA is proposing to use the 15 :g/L value to 

protect the most sensitive species. 

Finally, sodium nitrite is reported to TRI as pounds of sodium nitrite released. The aquatic health 

data are reported in :g/L of sodium nitrite (not nitrogen). The discharges reported in TRI and the TWF 

for sodium nitrite are on the same basis. 

6.4.2 Nitrogen Cycle Components 

This discussion is based primarily on the information in Standard Methods (APHA et al., 1995). 

In order of increasing oxidation state, the forms of nitrogen in the cycle are: 

# Organic nitrogen (organically bound nitrogen in the tri-negative oxidative state—includes 

urea, nucleic acids, peptides, and proteins) 

# Ammonia 

# Nitrite 

# Nitrate 

Some analyses are reported in terms of “Kjeldahl nitrogen”or TKN. TKN refers to ammonia plus 

organic nitrogen identified in a single analysis. It is named after J. Kjeldahl, who invented the analytic 

methods. The analysis results do not measure nitrogen in the form of nitrate, nitrite, nitrile, nitroso, 

onime, azide, aszine, azo, hydrazone, or semi-carbazone. “Total oxidized nitrogen” is the sum of nitrate 

and nitrite. 

Nitrite is an intermediate oxidation state of nitrogen. Certain bacteria can oxidize ammonium to 

nitrite and then to nitrate. This happens rather quickly in aerobic environments such as receiving streams 

and dry soils. On the other hand, in an anoxic (reducing) environment such as bottom waters and 

saturated soils, certain bacteria can convert nitrate to nitrite and then further convert the nitrogen into 

gaseous forms (APHA et al., 1995; EPA, 2005b, 2005c). 

6-12
6.4.2.1 Ammonia 

EPA’s 1999 Update of Ambient Water Quality Criteria for Ammonia (EPA, 1999a) states that the 

limits are given “in terms of nitrogen, i.e., as mg N/L, because most permit limits for ammonia are 

expressed in terms of nitrogen.” In aqueous solutions, ammonia exists in equilibrium in two forms—unionized ammonia (NH3) and ammonium ion (NH4

+

).6 Un-ionized ammonia is the more toxic component. 

TRI guidance for reporting discharges of aqueous ammonia recommends that total aqueous ammonia be 

calculated in terms of un-ionized ammonia equivalents (TRI, 2000a). 

The criteria vary as a function of pH, temperature, and whether early life stages are present. For 

the purpose of evaluating the toxicity of industrial wastewater discharges, we assumed that early life 

stages were present, pH = 7, and temperature = 20 degrees Celsius. The chronic criterion under these 

circumstances is 4,150 :g N/L. If we change the assumed pH to 8, the criterion drops to 1,710 :g N/L. 

The ammonia-as-NH3 criterion needs to be adjusted so that the nitrogen as measured in the 

discharge corresponds to the form used in the TWF. To do this, we need to convert the ammonia-asnitrogen water quality criterion to an ammonia-as-NH3 basis by multiplying by the ratio of the molecular 

weights, i.e. 4,150 × (17/14) = 5,039. Therefore, there will be slight differences between the TWFs for 

ammonia depending on whether the discharges are reported as nitrogen or as un-ionized ammonia. 

6.4.2.2 Nitrate 

None of the ecotoxicologial studies for nitrate as CAS 14797558 pass the ASTER filter. In fact, 

the ASTER report lists only one study for freshwater aquatic animals.7

 EPA reviewed the citation (Lewis 

et al., 1995). They report no statistically significant response at nitrate concentrations up to 75,000 :g/L. 

6

The water quality criterion is under review but the 1999 Update is the most recent available 

published criterion. 

7

Another study is listed in EPA’s ECOTOX database. It dates to 1973, and its absence from the 

ASTER listing indicates that it might not be the best information source for a TWF. 

6-13 
Accordingly, we propose to use an acute freshwater criterion of 75,000 :g/L and a chronic freshwater 

criterion of 7,500 :g/L to reflect the upper range at which no effect was seen. 

TRI guidance, however, indicates that releases of water-dissociable nitrate compounds are 

reported in terms of the nitrate ion (TRI, 2000b). The concentrations in Lewis et al. (1995) are reported as 

NO3-N, indicating that the aquatic component of the TWF and the TRI pounds are both in terms of the 

nitrate ion. 

6.4.2.3 Nitrite 

A search of the ASTER database for “nitrite CAS 14797650” turned up no ecotoxicological 

studies. Nitrite is an intermediate product in the nitrogen cycle and its relative instability might indicate 

that it is inappropriate to scale the nitrate TWF by the relative weights of NO2 and NO3 to estimate the 

toxicity for nitrite. EPA (2005b) notes that nitrite is toxic to aquatic species. At the moment, EPA does 

not believe it can estimate an aquatic health component of the TWF for nitrite regardless of the form in 

which it is measured and/or reported. 

6.4.2.4 Extrapolation to Other Forms of Nitrogen 

For undifferentiated components of the nitrogen cycle, EPA proposes to use the average of the 

ammonia-as-N and nitrate-as-N values. To place the nitrate aquatic health criterion on a nitrogen basis, 

we would multiply 7,500 :g/L by the ratio of atomic weights for N/NO3 ( i.e., 0.233). The resulting value 

is 1,748 :g/L, which, when normalized to copper, provides an aquatic health TWF component of 3.20e-3. 

This is similar to the value for the much more studied ammonia-as-N of 1.35e-3. The average of the two 

values is 2.28e-3. EPA proposes that the 2.28e-3 aquatic health component for nitrate/nitrite mixtures be 

used for all measures that have been converted to nitrogen-equivalents. 

TRI has an entry reported as “Nitrogen (as NO3) Sludge Solid.” It is illogical that a facility would 

go through the effort to de-water a sludge to produce a solid only to discharge the end product to the 

water. Unless the engineers have a better understanding of this discharge, EPA assumes that the facility 

generated a process sludge that they tested for nitrate content and reported the discharge in terms of 

6-14
pounds of nitrate. Presumably, the Kjeldahl method was not used; otherwise the discharge would have 

been reported as Kjeldahl nitrogen, either as TKN or nitrogen. APHA et al. (1995) describe other methods 

for determining nitrates. For this entry, then, we propose to use the original NO3 basis for the aquatic 

health criterion, that is, 7.47e-4. Because it is a single entry in the discharge data base, whatever value for 

nitrogen is used will have minuscule effect on the industry rankings. 

6.4.2.5 Forms for Which There Is Insufficient Information 

As mentioned above, the Kjeldahl methods measure organic nitrogen and ammonia. When a 

discharge is measured in terms of TKN, EPA knows neither the make-up of the organic material nor the 

proportion of ammonia. Without this knowledge, EPA cannot estimate a TWF for TKN.8 

Similarly, EPA cannot estimate a TWF for the entry reported as “Nitrogen, Inorganic Total” 

because it is not known whether the results are reported as the total mass, the nitrite/nitrate portion, or the 

nitrogen portion. 

6.4.3 Nitrogen TWF Summary 

Table 6-6 summarizes the TWFs for various forms of nitrogen. Sodium nitrite has the highest 

TWF (3.73e-1). As noted above, this value is for rainbow trout, a very sensitive species. The TWFs for 

components of the organic nitrogen cycle are two or more orders of magnitude lower. 

Two observations arise from the review of nitrogen data. First, it is necessary to verify whether 

discharges of sodium nitrite in TRI are sodium nitrite (for which we have numerous studies in ASTER 

and a proposed TWF) or an unspecified form of nitrite (for which we either have a much lower TWF or 

no TWF). Second, TWFs measure toxicity. They do not measure the possible eutrophication impacts of 

nutrients. An alternative measure for eutrophication effects should be developed for nutrients. 

8

We presume that discharges identified as “Nitrogen, Kjeldahl Total (as N)” were converted to 

this basis according to the composition of the discharge. 

6-15 
Table 6-6

Proposed TWF Summary for Various Forms of Nitrogen

Chemical 

Freshwater Chronic 

Aquatic Health Criteria 

(:g/L) 

Normalized 

to Copper (TWF) 

Sodium nitrite 1.50e+01 3.73e-01 

Ammonia (as N) 4.15e+03 1.35e-03 

Ammonia (as NH3) (a) 1.11e-03 

Nitrate (as NO3) 7.50e+03 7.47e-04 

Nitrate (as N) (a) 3.20e-03 

Nitrogen, total (as N) 

Nitrogen, Kjeldahl total (as N) 

Nitrogen oxides (as N) 

Nitrogen, organic total (as N) (a) 2.28e-03 

Nitrogen (as NO3) sludge solid 7.50e+03 7.47e-04 

Nitrogen, nitrite total (as N) 

Nitrite nitrogen, dissolved (as N) 

Nitrogen, nitrite total (as NO2) 

N/A N/A 

(a) Blank cells for criteria indicate that the normalized values are either averages or involve a conversion

based on the form in which the nitrogen is measured.

Source: EPA estimates.

6.5 Drinking Water Contaminants 

On February 24, 2005, EPA published its second list of contaminant candidates for drinking 

water (EPA, 2005a). The list has 9 microbiological contaminants and 42 chemical contaminants or 

contaminant groups. Of the chemical contaminants, the TWF database needs information for those listed 

in Table 6-7. That table’s third column identifies chemicals for which neither human nor aquatic health 

data can be found on which to base a criterion. Sections 6.5.1 through 6.5.4 discuss chemicals for which 

TWFs can be estimated. Section 6.5.5 summarizes the TWFs for the drinking water candidate 

contaminants. 

6-16
Table 6-7

Drinking Water Candidate Contaminants Needing TWFs

CHEMICAL CAS Information Available 

1,1-dichloropropene 563586 No 

2,2-dichloropropane 594207 No 

Acetochlor 34256821 Yes 

Alachlor ESA and other acetanilide 

pesticide degradation products 

N/A See Section 6.5.1 

Bromobenzene 108861 Yes 

Organotins N/A See Section 6.5.2 

Perchlorate 14797730 See Section 6.5.3 

RDX 121824 

Triazines and degradation products of 

triazines 

Including, but not limited to, 

cyanazine 21725-46-2 and 

atrazine-desethyl 6190-65-4 

See Section 6.5.4 

DCPA mono-acid degradate 887547 No 

DCPA di-acid degradate 2136790 Yes 

Source: EPA estimates. 

6.5.1 Alachlor ESA and Other Acetanilide Pesticide Degradation Products 

The Pesticide Action Network database (2005) identifies four breakdown products for alachlor: 

# 2,6 diethylaniline, CAS 579-66-8

# 2-hydroxy alachlor (no CAS number)

# Alachlor ethanesulfonic acid (ESA) (no CAS number)

# Alachlor oxanilic acide (no CAS number)

EPA searched Chemfinder for CAS numbers for the last three chemicals and did not find any. ASTER 

searches need to have the CAS number or chemical formula in SMILES format, so EPA could not request 

a search on the last three chemicals. ASTER contained data for diethylaniline, 2,6 (CAS 579-66-8). EPA 

named the entry for this group of chemicals by the name of the chemical for which it has data (i.e., 

6-17
diethylaniline, 2,6 CAS 579-66-8). EPA updated the entry for alachlor (CAS 15972-60-8) with the 

ASTER data for that chemical. 

6.5.2 Organotins 

Organotins are compounds containing at least one bond between tin and carbon. EPA (1999b) 

lists cyhexatin, fenbutatin oxide, and fentin hydroxide (TPTH) under organotins. All three examples are 

triorganotin compounds, meaning that each contains three tin-carbon bonds. From this, we assume that 

the drinking water list means triorganotin compounds when it simply lists “organotins.” Triorganotin 

compounds are used as biocides and pesticides while mono- and diorganotin compounds tend to be used 

in stabilizer, catalyst, and glass-coating applications (Batt, 2005). EPA (2003) notes that the toxicity to 

aquatic organisms generally increases as the number of organic components increases from one to three 

and decreases with the addition of a fourth organic component. That is, the triorganotin compounds are 

more toxic. 

However, EPA (1999b) does not list tributyltin (TBT, CAS 688-73-3) or tributyltin oxide (TBTO, 

CAS 56-35-9) among the organotins even though they have been widely used and studied. EPA published 

ambient aquatic life water quality criteria in 2003 for tributyltin as TBT (EPA, 2003). EPA adjusted all 

the chemicals tested to TBT. Because the newly published study incorporates many organotins in the 

estimation of water quality criteria for organic health for TBT, EPA proposes to use the tributyltin TWF 

for the organotins TWF. Tributyltin is already in the TWF database but will be updated. 

6.5.3 Perchlorate 

EPA recently published an IRIS profile for perchlorate and perchlorate salts (IRIS, 2005c). EPA 

requested ASTER data for perchlorate as well as four perchlorate salts (ammonium, lithium, potassium, 

and sodium); ASTER has data for potassium and sodium perchlorate. Chronic data exist for potassium 

perchlorate for freshwater sea lampreys: hormonal effects were seen at 100,000 :g/L during a 122-day 

exposure. An older study for the effects of 96-hour exposure of trout to sodium perchlorate showed 100 

percent mortality at 3,000,000 :g/L. Neither study passed the ASTER filter on quality. EPA used the data 

for potassium perchlorate for the aquatic health criteria for perchlorate. 

6-18
6.5.4 Triazines and Degradation Products 

EPA has traditionally used the term “triazines” to refer to atrazine, simazine, and cynanizine. 

EPA (2002c) identifies desisopropyl s-atrazine (DIA), desethyl s-atrazine (DEA) and 

diaminochlorotriazine (DACT) as metabolites with a common mechanism. It is presumed that the TWF 

for triazines and degradation products should reflect available information for these six chemicals. 

Unfortunately, no human or aquatic health data could be located for the three metabolites. Table 6-8 

summarizes the human health and aquatic life criteria for atrazine, simazine, and cyanazine. It is 

suggested that EPA use the geometric mean of the three values for a triazine TWF. The human health 

component will be calculated on the basis of the cancer slope factor (q1*). 

Table 6-8

Human and Aquatic Health Data for Triazines and Degradation Products

Chemical 

Human Health 

BCF 

Aquatic-Fresh Aquatic-Salt 

RfD q1* Chronic Acute Chronic Acute 

Atrazine 3.50e-02 2.20e-01 31 65 6,700 2,600 

Simazine 5.00e-03 1.20e-01 18 1,000 124,875 

Cyanazine 2.00e-03 8.40e-01 4.0 3.5 

Geometric Mean 

(:g/L) 7.00e-03 2.80e-01 13 61 29,000 2,600 

Toxic Weighting 

Factor 

Component Value 7.95e+02 1.99e+01 0.0918 0.0002 0.0022 

Source: ASTER, 2005. 

6-19
6.5.5 Summary 

Table 6-9 lists the proposed TWFs for drinking water contaminants. The worksheets are located 

in Appendix A-28 through A-43. 

Table 6-9

Drinking Water Candidate Contaminants Needing TWFs

Chemical CAS Proposed TWF 

1,1-dichloropropene 563586 0 

2,2-dichloropropane 594207 0 

Acetochlor 34256821 1.48e-2 

Alachlor (update) 15972608 1.52e+0 

2,6-diethylaniline 

(alachlor degradation product) 

579668 5.38e-4 

Bromobenzene 108861 7.58e-3 

Tributyltin (organotins) 688733 7.78e+1 

Perchlorate 14797730 2.00e-3 

RDX 121824 4.15e-3 

Triazines N/A 2.46e+0 

Atrazine 1912249 1.04e+0 

Simazine 122349 3.08e-1 

Cyanazine 21725462 4.70e+0 

DCPA mono-acid degradate 887547 0 

DCPA di-acid degradate 2136790 4.10e-4 

Source: EPA estimates. 

6-20
6.6 NICOTINE 

6.6.1 Human Health 

Nicotine is a poison with a lethal dose in adults of 0.5 to 1.0 mg/kg of body weight, or a total 

dose of 30 to 60 mg (Boulton et al., 2003). In 2003, Michigan officials arrested a person for 

contaminating 200 pounds of ground beef with Black Leaf 40—a pesticide containing 40 percent 

nicotine—and thereby affecting about 100 people. EPA canceled its product registration of Black Leaf in 

1992 because of its toxicity (Boulton et al., 2003). In 2002, EPA revoked Federal Food, Drug, and 

Cosmetic Act tolerances for residues of nicotine-containing compounds on agricultural products except 

cucumber, lettuce, and tomato (EPA, 2002d). EPA plans to publish a Reregistration Eligibility Decision 

(RED) on nicotine in fiscal year 2008. In the Notice, nicotine is listed as a pesticide with no associated 

tolerance (EPA, 2004). 

Dermal exposure to nicotine can result in “green tobacco sickness” (GTS) marked by nausea, 

vomiting, weakness, dizziness, and sometimes fluctuations in blood pressure or heart rate. During a 

particularly wet harvesting season in 1992, Kentucky reported an outbreak of 27 cases of GTS severe 

enough that emergency room treatment was sought. A review of hospital records identified 55 possible 

cases of GTS in Kansas between May and October of 1992. Dew from tobacco leaves often saturated 

workers’ clothing within minutes of beginning field work (Boylan et al., 1993). Because it is connected to 

factory workers, this exposure route lies more in OSHA’s purview than EPA’s, but it is indicative of the 

toxicity of nicotine. 

However, EPA checked its traditional sources9

 for a RfD or a cancer slope and did not identify 

either for nicotine. In other words, the TWF for nicotine will be underestimated due to the absence of data 

for calculating a human health component. 

9

IRIS; April 2005 Region 3 Risk Based Concentration/HEAST tables; ATSDR toxicological 

profiles; California Environmental Protection Agency, Proposition 65 list (where nicotine was not placed 

on the candidate list in a March 2004 carcinogenicity evaluation); NIH/NIEHS/Center for Evaluation of 

Risks to Human Reproduction (which deferred a review in 2000 for chemicals with higher priorities); and 

Toxicity and Chemical Specific Factors Data Base, Risk Assessment Information System, located at 

http://risk.lsd.ornl.gov. 

6-21 
6.6.2 Aquatic Health 

A search of the ASTER database identified one study for nicotine that passed the ASTER filter 

(Passino-Reader et al., 1995). The tested species is freshwater rainbow trout and the concentration levels 

are: 

# 60-day LC50: 5,000 :g/L

# 60-day LOEC: 4,200 :g/L

# 60-day NOEC: 2,900 :g/L

We calculate a maximum allowable toxicant concentration (MACT) by taking the geometric mean of the 

NOEC and LOEC values, i.e., 2 4200 × 2900 or 3,490. In accordance with Zipf (2003) the MACT is 

the preferred value for the aquatic health criterion. Normalizing this to copper, i.e., 5.6/3,490, results in an 

aquatic health TWF component of 1.6 e-3. The worksheet for nicotine is located in Appendix A-44. 

6.7 REFERENCES 

APHA (American Public Health Association, American Water Works Association, and Water 

Environment Association. 1995. Standard methods for the examination of water and wastewater. 

Washington, D.C.: American Public Health Association. 19th edition. 

ASTER. 2005. Assessment tools for the evaluation of risk database. Results of data request for chemicals 

in the Drinking Water Contaminant Candidate List 2 category. U.S. Environmental Protection Agency, 

National Health and Environmental Effects Research Laboratory. March. 

ASTER. 2004. Assessment tools for the evaluation of risk database. Results of data request for 21 

chemicals in the PAC category. U.S. Environmental Protection Agency, National Health and 

Environmental Effects Research Laboratory. November. 

Batt, J.M. 2005. The world of organotin chemicals: applications, substitutes, and the environment. 

www.ortepa.org/WorldofOrganotinChemicals.pdf. Downloaded March 29. 

Boulton, M., M. Stanbury, D. Wade, J. Tilden, D. Bryan, J. Payne, and B. Eisenga. 2003. Nicotine 

poisoning after ingestion of contaminated ground beef—Michigan, 2003. MMWR Weekly 52(18):413­

416. May 9. Available at http://www.cdc.gov/mmwr/. 

6-22
Boylan, B., V. Brandt, J. Muehlbauer, M. Auslander, C. Spurlock, and R. Finger. 1993. Green tobacco 

sickness in tobacco harvesters —Kentucky 1992. MMWR Weekly 42(13):237-240. April 9. Available at 

http://www.cdc.gov/mmwr/. 

EPA. 2005a. Drinking water contaminant candidate list 2; final notice. Fed. Reg. 70:9,071-9,077. 

February 24. 

EPA. 2005b. Ag 101. Nitrate. http://www.epa.gov/agriculture/ag101/impactnitrate.html. Downloaded 

February 17. 

EPA. 2005c. Consumer factsheet on: nitrates/nitrites. http://www.epa.gov/safewater/dwh/cioc/nitrates.html. Downloaded February 17. 

EPA. 2004. Pesticide reregistration performance measures and Goals. Notice. Fed. Reg. 69(87):25,082­

25,092. May 5. 

EPA. 2003. Ambient aquatic life water quality criteria for tributyltin (TBT)—final. EPA-822-R-03-031. 

December. 

EPA. 2002a. National recommended water quality criteria: 2002. EPA-822-R-02-047. November. 

EPA. 2002b. National recommended water quality criteria: 2002. Human health criteria calculation 

matrix. EPA-822-R-02-012. November. 

EPA. 2002c. OPP office director memo on grouping triazines. A common mechanism of toxicity 

determination for a series of triazine pesticides. Memorandum from Marcia E. Mulkey dated March 31. 

www.epa.gov/pesticides/cumulative/triazines/triazinestransmittalmemo.htm. Downloaded March 29, 

2005. 

EPA. 2002d. Nicotine: tolerance revocations. Final rule. Fed. Reg. 67(99):35,912-35,915. May 22. 

EPA. 2001a. Water quality criteria: notice of availability of water quality criterion for the protection of 

human health: methylmercury. Fed. Reg. 66:1,344-1,359. January 8. 

EPA. 2001b. Emergency Planning and Community Right-to-Know Act—section 313: guidance for 

reporting toxic chemicals: polycyclic aromatic compounds category. EPA-260-B-01-03. August. 

EPA. 2000. Supplementary guidance for conducting health risk assessment of chemical mixtures. EPA630-R-00-002. August. 

EPA. 1999a. 1999 update of ambient water quality criteria for ammonia. EPA-822-R-99-014. December. 

EPA. 1999b. Pesticides: topical and chemical fact sheets. New data will help ensure protection of 

children. www.epa.gov/pesticides/factsheets/neurotoxicdata.htm. Downloaded March 28, 2005. 

EPA. 1994. Addition of certain chemicals; toxic chemical release reporting; community right-to-know. 

Fed. Reg. 59:61,465. November 30 . 

6-23
IRIS. 2005a. Integrated Risk Information System. Nitrate (CAS 147-55-8). 

http://www.epa.gov/iris/subst/0076.htm. Downloaded February 21 . 

IRIS. 2005b. Integrated Risk Information System. Ammonia (CAS 7664-41-7). 

http://www.epa.gov/iris/subst/0422.htm. Downloaded February 21. 

IRIS. 2005c. Integrated Risk Information System. Perchlorate and perchlorate salts (CAS 7790-98-9 

ammonium perchlorate, CAS 7791-03-9 lithium perchlorate, CAS 7778-74-7 potassium perchlorate, and 

CASRN 7601-89-0 sodium perchlorate). Last revised 2/18/2005. http://www.epa.gov/iris/subst/1007.htm. 

Downloaded March 24. 

IRIS. 2004. Integrated Risk Information System. Nitrite (CAS 147-65-0). 

http://www.epa.gov/iris/subst/0078.htm. Downloaded November 17. 

Lewis, J.W., A.N. Kay, and N.S. Hanna. 1995. Responses of electric fish (family Mormyridae) to 

nonorganic nutrients and tributyltin oxide. Chemosphere 31:3753-3765. 

Passino-Reader, D.R., W.H. Berlin, and J.P. Hickey. 1995. Chronic bioassays of rainbow trout fry with 

compounds representative of contaminants in Great Lakes fish. Journal of Great Lakes Research 

21(3):373-383. 

Pesticide Action Network. 2005. PAN pesticides database—chemicals. Alachlor. 

www.pesticideinfo.org/List_Chemicals.jsp? Downloaded March 21. 

Snedcor, G.W., and W.G. Cochrane. 1980. Statistical methods. Ames, Iowa: The Iowa State University 

Press. 7th edition. 

TRI. 2000a. Emergency Planning and Community Right-to-Know Act Section 313: guidance for 

reporting aqueous ammonia. EPA-745-R-00-005. U.S. Environmental Protection Agency, Office of 

Environmental Information. December. 

TRI. 2000b. List of toxic chemicals within the water dissociable nitrate compounds category and 

guidance for reporting. EPA-745-R-00-006. U.S. Environmental Protection Agency, Office of 

Environmental Information. December. 

Zipf, L. 2003. Revisions to EAD’s toxic weighting factor methodology parameters. Memorandum to 

304(m) Record (EPA Docket Number OW-2003-0074). December 3. 

6-24
ATTACHMENT A

TWF DATA WORKSHEETS

A-1
Pollutant: Hydrogen Fluoride CAS: 7664393 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 

Carcinogen flag Y/N N 

RfD mg/kg-day 0.05 Value is for Fluoride. ATSDR, 2003. Toxicological 

Profile for Fluorides, Hydrogen Fluoride, and Fluorine. 

September. IRIS, 2004; 0.06 mg/kg-day for fluorine 

(soluble fluoride, CAS 7782414) RfD verification date, 

1985. 

Code NOAEL 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L no hits in ASTER or ECOTOX 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-2
Pollutant: Chlorine Dioxide CAS: 10049044 

Variable Units Value Source 

Human Health 

q1* mg/kg-day IRIS, 2004; Carcinogen assessment consensus date, 

2000. Class: D not classifiable because of 

inadequate data. Carcinogen flag Y/N N 

RfD mg/kg-day 0.03 IRIS, 2004; RfD consensus date, 2000. 

Code NOAEL with uncertainty 

factor 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 35 ASTER, 2004; Ref. 17656. Matisoff, G, G Brooks, 

and BI Borland. Toxicity of Chlorine Dioxide to 

Adult Zebra Mussels. J. Am. Water Works Assoc. 

88:93-106. 1996. 

Code Estimated From Acute Value 

Using Acute-Chronic Ratio of 10; 

See U.S. EPA. Technical Support 

Document for Water Qualitybased Toxics Control. EPA 

505/2-90-001. March 1991. 

Species Zebra Mussel 

Aquatic—Freshwater—Acute 

AWQC :g/L 350 ASTER, 2004; Ref. 17656. Matisoff, G, G Brooks, 

and BI Borland. Toxicity of Chlorine Dioxide to 

Adult Zebra Mussels. J. Am. Water Works Assoc. 

88:93-106. 1996. 

Code lowest reported 96-hr LC50 

Species Zebra Mussel 

Aquatic—Saltwater—Chronic 

AWQC :g/L 50,000 ASTER, 2004; Ref. 906. Portmann, JE and KW 

Wilson. The Toxicity of 140 Substances to the 

Brown Shrimp and Other Marine Animals. Shellfish 

Information Leaflet No. 22 (2nd ed.) Ministry of 

Agric. Fish. Food, Fish. Lab. Burnham-on-Crouch, 

Essex and Fish Exp. Station, Conway, North Wales, 

12p. 1971. 

Code Estimated From Acute Value 

Using Acute-Chronic Ratio of 10; 

See U.S. EPA. Technical Support 

Document for Water Qualitybased Toxics Control. EPA 

505/2-90-001. March 1991. 

Species Green Crab 

Aquatic—Saltwater—Acute 

AWQC :g/L 500,000 ASTER, 2004; Ref. 906. Portmann, JE and KW 

Wilson. The Toxicity of 140 Substances to the 

Brown Shrimp and Other Marine Animals. Shellfish 

Information Leaflet No. 22 (2nd ed.) Ministry of 

Agric. Fish. Food, Fish. Lab. Burnham-on-Crouch, 

Essex and Fish Exp. Station, Conway, North Wales, 

12p. 1971. 

Code lowest reported 48-hr LC50 

Species Green Crab 

A-3
Pollutant: 1, 3-Phenylenediamine CAS: 108452 

Variable Units Value Source 

Human Health 

q1* mg/kg-day IRIS, 2004; no data. 

Carcinogen flag Y/N N 

RfD mg/kg-day 6e-3 IRIS, 2004; RfD verification date, 1986. 

Code NOEL with uncertainty 

factor 

BCF L/kg 1 ASTER, 2004; QSAR estimate. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 38,009 ASTER, 2004; QSAR estimate. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Channel Catfish 

Aquatic—Freshwater—Acute 

AWQC :g/L 380,089 ASTER, 2004; QSAR estimate. 

Code lowest reported 96-hr 

LC50 

Species Channel Catfish 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-4
Pollutant: Benzo(a)pyrene CAS: 50328 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 EPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

Carcinogen flag Y/N Y 822-R-02-012.

RfD mg/kg-day 

Code 

BCF L/kg 30 EPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 0.08 ASTER 2004; Ref. 10412. Hannah, JB, JE hose, ML 

Landolt, BS Miller, SP Felton, WT Iwaoka. 

Benzo(a)pyrene-induced Morphological and 

Developmental Abnormalities in Rainbow Trout. Arch. 

Environ. Contam. Toxicol. 11(6):727-734. 1982. 

Code lowest reported growth 

effect 

Species Rainbow Trout 

Aquatic—Freshwater—Acute 

AWQC :g/L 5 ASTER 2004; Ref. 15337. Trucco, RG, FR Englehart, B 

Stacey. Toxicity, Accumulation and Clearance of 

Aromatic Hydrocarbons in Daphnia pulex. Environ. 

Pollut. Ser. A Ecol. Biol. 31(3):191-202. 1983, 

Code lowest reported 96-hr 

LC50 

Species Water Flea 

Aquatic—Saltwater—Chronic 

AWQC :g/L 100 ASTER 2004; Ref. 5053. Rossi, SS and JM Neff. 

Toxicity of Polynuclear Aromatic Hydrocarbons to the 

Polychaete Neanthes arenaceodentata, Mar. Pollut. Bull. 

9(8):220-223. 1978. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Polychaete Worm 

Aquatic—Saltwater—Acute 

AWQC :g/L 1,000 ASTER 2004; Ref. 5053. Rossi, SS and JM Neff. 

Toxicity of Polynuclear Aromatic Hydrocarbons to the 

Polychaete Neanthes arenaceodentata, Mar. Pollut. Bull. 

9(8):220-223. 1978. 

Code lowest reported 96-hr 

LC50 

Species Polychaete Worm 

A-5
Pollutant: Aniline CAS: 62533 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 5.7e-3 IRIS, 2004; Carginogenicity assessment verifications 

date, 1987. Class: B2 probable human carcinogen Carcinogen flag Y/N Y 

RfD mg/kg-day 

Code 

BCF L/kg 7 ASTER, 2004; Arithmetic average of seven studies. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 4,400 ASTER, 2004; Ref. 538. Birge, W.J., JA Black, JE 

Hudson, and DM Bruser. Embryo-Larval Toxicity Tests 

with Organic Compounds. In LL Marking and RA 

Kimerle (eds.) Aquatic Toxicology and Hazard 

Assessment, 2nd Symposium, ASTM STP 667, 

Philadelphia, PA;131-147. 1979 

Code lowest LC50 

Species Largemouth Bass 

Aquatic—Freshwater—Acute 

AWQC :g/L 68,630 ASTER, 2004; Ref. 3910. Marchinie, S, ML Tosato, TJ 

Norberg-King, DE Hammermeister, and MD Holund. 

Lethal and Sublethal Toxicity of Benzene Derivatives to 

the Fathead Minnow, Using a Short-Term Test. 

Environ. Toxicol. Chem 11(2):187-195. 1992. 

Code lowest 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L 2,940 ASTER, 2004; Ref. 5810. McLeese, DW, V Zitko, and 

MR Peterson. Structure-Lethality Relationships for 

Phenols, Anilines, and Other Aromatic Compounds in 

Shrimp and Clams. Chemosphere 8(2):53-57. 1979. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Bay Shrimp/Sand Shrimp 

Aquatic—Saltwater—Acute 

AWQC :g/L 29,400 ASTER, 2004; Ref. 5810. McLeese, DW, V Zitko, and 

MR Peterson. Structure-Lethality Relationships for 

Phenols, Anilines, and Other Aromatic Compounds in 

Shrimp and Clams. Chemosphere 8(2):53-57. 1979. 

Code lowest 96-hr LC50 

Species Bay Shrimp/Sand 

Shrimp 

A-6
Pollutant: Vanadium CAS: 7440622 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 

Carcinogen flag Y/N N 

RfD mg/kg-day 1e-3 EPA-NCEA provisional value from Region III, RiskBased Concentration Table, dated 10/8/2004. Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 160 ASTER, 2004; Ref. 4943. Birge, JW, JA Black, and AG 

Westerman. Evaluation of Aquatic Pollutants Using 

Fish and Amphibian Eggs as Bioassay Organisms. In 

SW Nielsen, G. Migaki, and DG Scarpelli (Eds.) Symp. 

Animals Monitors Environ. Pollut. 1977, Storrs, CT 

12:108-118. 1979 

Code lowest LC50 

Species Rainbow Trout 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 5 ASTER, 2004; Ref. 6761. Ballester, A and J Castellvi. 

Contribution to the Study of V and Ni Uptake in Marine 

Organisms (Contribucion al Estudio de la Biocenetica 

de V y Ni en Organismos Marinos). Invest, Pesq. 

43(2):49-478 (Spanish, English abstract). 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Common bay mussel 

Aquatic—Saltwater—Acute 

AWQC :g/L 50 ASTER, 2004; Ref. 6761. Ballester, A and J Castellvi. 

Contribution to the Study of V and Ni Uptake in Marine 

Organisms (Contribucion al Estudio de la Biocenetica 

de V y Ni en Organismos Marinos). Invest, Pesq. 

43(2):49-478 (Spanish, English abstract). 

Code lowest reported residue 

effects 

Species Common bay mussel 

A-7
Pollutant: Mercury CAS: 7439976 

Variable Units Value Source 

Human Health 

q1* mg/kg-day IRIS, 2004: Carcinogenicity Assessment Verification 

date, 1994. Class: D - not classifiable as to human 

Carcinogen flag Y/N N carcinogenicity (inadequate data). 

RfD mg/kg-day 1.00e-4 IRIS, 2004, not available. 

EPA. 2002. National Recommended Water Quality 

Criteria: 2002 - Human Health Criteria Calculation 

Matrix. EPA-822-R-02-012. November. Based on 1997 

IRIS value. 

Code 

BCF L/kg 7342.6 EPA. 2002. National Recommended Water Quality 

Criteria: 2002 - Human Health Criteria Calculation 

Matrix. EPA-822-R-02-012. November 

BAF 

RSC 1 EPA. 2002. National Recommended Water Quality 

Criteria: 2002 - Human Health Criteria Calculation 

Matrix. EPA-822-R-02-012. November. 1998 Value 

calculated with 1980 methodology. 

FI 18.7 EPA. 2002. National Recommended Water Quality 

Criteria: 2002 - Human Health Criteria Calculation 

Matrix. EPA-822-R-02-012. November 

Aquatic—Freshwater—Chronic 

AWQC :g/L 0.77 EPA. 2002. National Recommended Water Quality 

Criteria: 2002. EPA-822-R-02-047. November Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L 1.4 EPA. 2002. National Recommended Water Quality 

Criteria: 2002. EPA-822-R-02-047. November Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 0.94 EPA. 2002. National Recommended Water Quality 

Criteria: 2002. EPA-822-R-02-047. November Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 1.8 EPA. 2002. National Recommended Water Quality 

Criteria: 2002. EPA-822-R-02-047. November Code 

Species 

A-8
Pollutant: Methylmercury CAS: 22967926 

Variable Units Value Source 

Human Health 

q1* mg/kg-day IRIS, 2004; Carcinogenicity Assessment date 1995. 

Classification = C; possible human carcinogen but 

systemic affects would likely been seen at exposures 

lower than those required for tumor formation. Carcinogen flag Y/N Y 

RfD mg/kg-day 1.00e-4 IRIS, 2004; Oral RfD consensus date 2001. 

Code BMDL50 

benchmark dose, lower 

limit 95% 

BCF 

BAF 1,225,029 Methylmercury Water Quality Criteria. Jan 8, 2001. 66 

FR 1344-1359. Calculated as weighted average of fish 

intake and BAF for fish intake of 17.5 grams/day. See 

memo to Lynn Zipf, EPA, dated 14 December 2004. 

RSC 73% Methylmercury Water Quality Criteria. Jan 8, 2001. 66 

FR 1344-1359. RSC presented as an amount to subtract. 

Converted to percentage. See memo to Lynn Zipf, EPA, 

dated 14 December 2004. 

Aquatic—Freshwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-9
Pollutant: Benzo(a)anthracene CAS: 56553 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. Carcinogen flag Y/N Y 

RfD mg/kg-day 

Code 

BCF L/kg 30 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 160 ASTER. 2004. QSAR est., Ref. 15823. Veith, GD, 

DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. 

Fish. Aquat. Sci. 40(6):743-748. 1983. 

Code Estimated From Acute Value 

Using Acute-Chronic Ratio of 10; 

USEPA. Technical Support 

Document for Water Qualitybased Toxics Control. EPA 

505/2-90-001. March 1991. 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 1599 ASTER. 2004. QSAR est., Ref. 15823. Veith, GD, DJ 

Call, and LT Brooke. Structural-Toxicity Relationships 

for the Fathead Minnow, Pimephales promelas: Narcotic 

Industrial Chemicals. Can J. Fish. Aquat. Sci. 40(6):743­

748. 1983. 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L 7.5 ASTER. 2004. Ref. 3511. 

A.E. McElroy. Polycyclic Aromatic Hydrocarbon 

Metabolism in the Polychaete Nereis virens. Aquat. 

Toxicol. 18(1):35-50. 1990. 

Code Estimated From Acute Value 

Using Acute-Chronic Ratio of 10; 

USEPA. Technical Support 

Document for Water Qualitybased Toxics Control. EPA 

505/2-90-001. March 1991. 

Species Polychaete worm 

Aquatic—Saltwater—Acute 

AWQC :g/L 75 ASTER. 2004. Ref. 3511. 

A.E. McElroy. Polycyclic Aromatic Hydrocarbon 

Metabolism in the Polychaete Nereis virens. Aquat. 

Toxicol. 18(1):35-50. 1990. 

Code lowest reported biological 

effect 

Species Polychaete worm 

A-10
Pollutant: Benzo(a)phenanthrene 

(Chrysene) 

CAS: 218019 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. Carcinogen flag Y/N Y 

RfD mg/kg-day 

Code 

BCF L/kg 30 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 160 ASTER. 2004. QSAR est., Ref. 15823. 

Veith, GD, DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. Fish. 

Aquat. Sci. 40(6):743-748. 1983. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; USEPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 1599 ASTER. 2004. QSAR est., Ref. 15823. 

Veith, GD, DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. Fish. 

Aquat. Sci. 40(6):743-748. 1983. 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-11
Pollutant: Benzo(b)fluoranthene CAS: 205992 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

Carcinogen flag Y/N Y 822-R-02-012.

RfD mg/kg-day 

Code 

BCF L/kg 30 USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-12
Pollutant: Benzo(k)fluoranthene CAS: 207089 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. Carcinogen flag Y/N Y 

RfD mg/kg-day 

Code 

BCF L/kg 30 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-13
Pollutant: Benzo(j,k)fluoranthene 

(fluoranthene) 

CAS: 206440 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 

Carcinogen flag Y/N N 

RfD mg/kg-day 0.04 USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

Code 822-R-02-012.

BCF L/kg 1150 USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 4.5 ASTER. 2004. Ref. 3590. 

Oris, JT, RW Winner, and MV Moore. A Four-Day 

Survival and reproduction Toxicity Test for 

Ceriodaphnia dubia. Environ. Toxicol. Chem. 10(2): 

217-224. 1991. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; USEPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Water flea 

Aquatic—Freshwater—Acute 

AWQC :g/L 45 ASTER. 2004. Ref. 3590. 

Oris, JT, RW Winner, and MV Moore. A Four-Day 

Survival and reproduction Toxicity Test for 

Ceriodaphnia dubia. Environ. Toxicol. Chem. 10(2): 

217-224. 1991. 

Code lowest 48-hr LC50 

Species Water flea 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-14
Pollutant: Dibenzo(a,h)anthracene CAS: 53703 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. Carcinogen flag Y/N Y 

RfD mg/kg-day 

Code 

BCF L/kg 30 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 50 ASTER. 2004. Ref. 17714. 

Wernersson, AS and G Dave. Phototoxicity 

Identification by Solid Phase Extraction and 

Photoinduced Toxicity to Daphnia magna. Arch. 

Environ. Contam. Toxicol. 32(3):268-273. 1997. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; USEPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Water Flea 

Aquatic—Freshwater—Acute 

AWQC :g/L 496 ASTER. 2004. Ref. 17714. 

Wernersson, AS and G Dave. Phototoxicity 

Identification by Solid Phase Extraction and 

Photoinduced Toxicity to Daphnia magna. Arch. 

Environ. Contam. Toxicol. 32(3):268-273. 1997. 

Code lowest EC50 

Species Water Flea 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-15
Pollutant: Indeno(1,2,3-cd)pyrene CAS:193395 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 7.3 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. Carcinogen flag Y/N Y 

RfD mg/kg-day 

Code 

BCF L/kg 30 Value for benzo(b)fluoranthene (CAS 205992). 

USEPA. 2002. National Recommended Water Quality 

Criteria: 2002 Human Health Calculation Matrix. EPA 

822-R-02-012. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-16
Pollutant: Benzo(j)fluoranthene CAS: 205823 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-17
Pollutant: Benzo(r,s,t)pentaphene CAS: 189559 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

A-18
Pollutant: Dibenz(a,h)acridine CAS: 226368 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-19
Pollutant: Dibenz(a,j)acridine CAS: 224420 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No animal data. 

Code 

Species 

A-20
Pollutant: Dibenzo(a,e)fluoranthene CAS: 5385751 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-21
Pollutant: Dibenzo(a,e)pyrene CAS: 192654 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-22
Pollutant: Dibenzo(a,h)pyrene CAS: 189640 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-23
Pollutant: Dibenzo(a,l)pyrene CAS: 191300 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-24
Pollutant: 7H-dibenzo(c,g)carbazole CAS: 194592 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 185 ASTER. 2004. QSAR est., Ref. 15823. 

Veith, GD, DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. Fish. 

Aquat. Sci. 40(6):743-748. 1983. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; USEPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 1852 ASTER. 2004. QSAR est., Ref. 15823. 

Veith, GD, DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. Fish. 

Aquat. Sci. 40(6):743-748. 1983. 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. Results in fish tissue concentration only. 

Code 

Species 

A-25
Pollutant: 5-Methylchrysene CAS: 3697243 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-26
Pollutant: 1-Nitropyrene CAS: 5522430 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000, USEPA 1995) Carcinogen flag Y/N 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 215 ASTER. 2004. QSAR est., Ref. 15823. 

Veith, GD, DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. Fish. 

Aquat. Sci. 40(6):743-748. 1983. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 2149 ASTER. 2004. QSAR est., Ref. 15823. 

Veith, GD, DJ Call, and LT Brooke. Structural-Toxicity 

Relationships for the Fathead Minnow, Pimephales 

promelas: Narcotic Industrial Chemicals. Can J. Fish. 

Aquat. Sci. 40(6):743-748. 1983. 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER. 2004. No data. 

Code 

Species 

A-27
Pollutant: 1,1-dichloropropene CAS: 563586 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L No ASTER data specifically for 1,1, dichloropropene. 

Reference is to 1980 EPA WQC Document for 

dichloropropanes and dichloropropenes. Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-28
Pollutant: 2,2-dichloropropane CAS: 594207 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L No ASTER data specifically for 2,2 dichloropropane. 

Reference is to 1980 EPA WQC Document for 

dichloropropanes and dichloropropenes. Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-29
Pollutant: Acetochlor CAS: 34256821 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 

Carcinogen flag Y/N N 

RfD mg/kg-day 2.0e-2 IRIS 2005. 1993 revision. 

Code 

BCF L/kg 1 assumption. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 38 ASTER. 2005. Ref.: 344. EPA. Office of Pesticide 

Programs. Environmental Effects Database. 1995. Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Rainbow Trout 

Aquatic—Freshwater—Acute 

AWQC :g/L 380 ASTER. 2005. Ref.: 344. EPA. Office of Pesticide 

Programs. Environmental Effects Database. 1995. Value 

cited: 0.38 ppm. 

ppm = mg/L 

Code 96hr LC50 

Species Rainbow Trout 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-30
Pollutant: Alachlor CAS: 15972-66-8 UPDATE

Variable Units Value Source 

Human Health 

q1* mg/kg-day 8.0e-2 Region 3. Risk Based Concentration Table. 2004. 

HEAST Carcinogen flag Y/N Y 

RfD mg/kg-day 1.0e-2 Region 3. Risk Based Concentration Table. 2004. IRIS. 

Code 

BCF L/kg 132 ASTER, 2005. Ref: 7. Veith, G.D. and Kosian. Estimating 

Bioconcentration Potential from Octanol/Water Partition 

Coefficients. In D. Mackay et. al. (Eds.), Physical Behavior of 

PCBs in the Great Lakes. Ann Arbor Sci. Publ., Ann Arbor, 

MI:269-282. 1983. (Former value 158) 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 140 ASTER, 2005. Ref: 10635. Call,D.J., L.T. Brooke, R.J. 

Kent, S.H. Poirier, M.L. Knuth, P.J. Shubat, and E.J. 

Slick. Toxicity, Uptake, and Elimination of the 

Herbicides Alachlor and Dinoseb in Freshwater Fish. J. 

Environ. Qual. 13(3):493-498 1984. 

(Former value 747) 

Code 64-day lowest recorded 

growth effect 

Species Fathead minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 5000 ASTER, 2005. Ref: 15031. Broderius, S.J., M.D. Kahl, 

and M.D. Hoglund. Use of Joint Toxic Response to 

Define the Primary Mode of Toxic Action for Diverse 

Industrial Organic Chemicals. Environ. Toxicol. Chem. 

14(9):1591-1605. 1995. 

Code 96-hr LC50 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-31
Pollutant: 2, 6-Diethylaniline 

(Alachlor degradation product) 

CAS: 579668 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 1042 ASTER. 2005. Ref. 3537. Veith, G.D. and Broderius. 

Structure-Toxicity Relationships for Industrial 

Chemicals Causing Type (II) Narcosis Syndrome. In 

KLE Kaiser (ed.) QSAR in Environmental ToxiciologyII, D. Reidel Publ. Co. Dordrecht, Holland:385-391. 

1987. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 10417 ASTER. 2005. Ref. 3537. Veith, G.D. and Broderius. 

Structure-Toxicity Relationships for Industrial 

Chemicals Causing Type (II) Narcosis Syndrome. In 

KLE Kaiser (ed.) QSAR in Environmental ToxiciologyII, D. Reidel Publ. Co. Dordrecht, Holland:385-391. 

1987. 

Code 96-hr LC-50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-32
Pollutant: Bromobenzene CAS: 108861 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 

Carcinogen flag Y/N N 

RfD mg/kg-day 2.00e-2 Region 3. Risk-based Concentration Table. Oct. 8, 

2004. EPA provisional peer-reviewed value. Code 

BCF L/kg 94 ASTER. 2005. Ref. 7. Veith, GD and P Kosian. Estimating 

Bioconcentration Potential from Octanol/Water Partition 

Coefficients. In D. Mackay et al. (Eds.) Physical behavior of 

PCBs in the Great Lakes. Ann Arbor Scie. Publ. Ann Arbor, 

MI:269-282. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 560 ASTER. 2005: Ref. 4343. Marchini, S, MD Hoglund, 

S.J Borderius, and ML Tosato. Comparison of the 

Susceptibility of Daphnids and Fish to Benezene 

Derivatives. Sci. Total Environ. Suppl:399-808. 1993. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

73Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 5600 ASTER. 2005: Ref. 4343. Marchini, S, MD Hoglund, 

S.J Borderius, and ML Tosato. Comparison of the 

Susceptibility of Daphnids and Fish to Benezene 

Derivatives. Sci. Total Environ. Suppl:399-808. 1993. 

Code lowest LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L Nothing in ASTER. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L ASTER data cites one reference that used body burden 

(mmol/kg), and did not pass filter. Code 

Species 

A-33
Pollutant: tributyltin (TBT) 

(Organotins) 

CAS: 668-73-3 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 501 Tsuda T, Nakanishi, S. Aoki, and S. Takebayashi. Bio 

concentration and metabolism of butyltin compounds in 

carp. Water Res. 22: 647-651. 1988. in EPA. 2003. 

Ambient Aquatic Life Water Quality Criteria for 

Tributyltin (TBT)-Final. EPA 822-R-03-031. 

December. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 0.072 EPA. 2003. Ambient Aquatic Life Water Quality 

Criteria for Tributyltin (TBT)-Final. EPA 822-R-03­

031. December. Code EPA Criteria 

Species None listed. 

Aquatic—Freshwater—Acute 

AWQC :g/L 0.46 EPA. 2003. Ambient Aquatic Life Water Quality 

Criteria for Tributyltin (TBT)-Final. EPA 822-R-03­

031. December. Code EPA Criteria 

Species None listed. 

Aquatic—Saltwater—Chronic 

AWQC :g/L 0.0074 EPA. 2003. Ambient Aquatic Life Water Quality 

Criteria for Tributyltin (TBT)-Final. EPA 822-R-03­

031. December. Code EPA Criteria 

Species None listed. 

Aquatic—Saltwater—Acute 

AWQC :g/L 0.42 EPA. 2003. Ambient Aquatic Life Water Quality 

Criteria for Tributyltin (TBT)-Final. EPA 822-R-03­

031. December. Code EPA Criteria 

Species None listed. 

A-34
Pollutant: Perchlorate CAS: 14797730 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 

Carcinogen flag Y/N N 

RfD mg/kg-day 7.0e-4 IRIS. 2005. 2005 revision. For perchlorate and 

perchlorate salts. Code 

BCF L/kg 1 assumption 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 1.0e5 Data for potassium perchlorate. ASTER. 2005. Ref.: 

16030. Youson, JH, JA Holmes, and JF Leatherland. 

Serum Concentrations of Thyroid Hormones in KClO4­

treated Larval Dea Lampreys (Petromyzon marinus K.) 

Comp. Biochem. Physiol. 111c(2):265-270. 1995. 

Code 122-day exposure, hormonal 

effect 

Species Sea Lamprey 

Aquatic—Freshwater—Acute 

AWQC :g/L Only 100% mortality concentration after 96-hr 

exposure; cannot adjust to LC50. Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L No data 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L No data 

Code 

Species 

A-35
Pollutant: RDX CAS: 121824 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 1.1e-1 IRIS. 2005. 1993 revision. C: possible human 

carcinogen. Carcinogen flag Y/N Y 

RfD mg/kg-day 3.0e-3 IRIS. 2005. 1993 revision. 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 1350 ASTER, 2005. Ref: 17503.Burton, D.T., S.D. Turley, 

and G.T. Peters. The Acute and Chronic Toxicity of 

Hexahydro-1,3,5-Trinitro-1,3,5-Triazine (RDX) to the 

Fathead Minnow (Pimephales promelas). Chemosphere 

29(3):567-579. 1994 B 

Code 32-day NOEC 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 12700 ASTER, 2005. Ref: 17503.Burton,D.T., S.D. Turley, 

and G.T. Peters. The Acute and Chronic Toxicity of 

Hexahydro-1,3,5-Trinitro-1,3,5-Triazine (RDX) to the 

Fathead Minnow (Pimephales promelas). Chemosphere 

29(3):567-579. 1994 B 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L no data 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L no data 

Code 

Species 

A-36
Pollutant: atrazine-desethyl CAS: 6190654 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L no ASTER data. 

Code 

Species 

A-37
Pollutant: Triazines CAS: 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 1.3e-1 Geometric mean of values for atrazine, cyanazine, and 

simazine. IRIS. 2005. 

Carcinogen flag Y/N Y 

RfD mg/kg-day 7.0e-3 Geometric mean of values for atrazine, cyanazine, and 

simazine. Region 3. Risk Based Concentration Table. 

Code 2004. HEAST

BCF L/kg 13 Geometric mean of values for atrazine, cyanazine, and 

simazine. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 61 Geometric mean of values for atrazine, cyanazine, and 

simazine. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L 29,000 Geometric mean of values for atrazine and simazine. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L . 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 2,600 Value for atrazine. 

Code 

Species 

A-38
Pollutant: Atrazine CAS: 1912249 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 2.2e-1 IRIS. 2005. 

Carcinogen flag Y/N Y 

RfD mg/kg-day 2.5e-2 Region 3. Risk Based Concentration Table. 2004. 

HEAST 

Code 

BCF L/kg 31 ASTER. 2005. Ref. 7. Veith, GD and P Kosian. 

Estimating Bioconcentration Potential from 

Octanol/Water Partition Coefficients. In D. Mackay et 

al. (Eds.) Physical behavior of PCBs in the Great Lakes. 

Ann Arbor Scie. Publ. Ann Arbor, MI:269-282. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 65 ASTER. 2005. Ref. 631. Macek, KJ KS Buxton, S 

Sauter, S Gnilka, and JW Dean. Chronic Toxicity of 

Atrazine to Selected Aquatic Invertebrates and Fishes. 

Ecol. Res. Serv. EPA 600/3-76-047. Environ. Res. Lab., 

U.S., EPA, Duluth:MN 50 pp. 1976. 

Code mortality 

Species Brook Trout 

Aquatic—Freshwater—Acute 

AWQC :g/L 6,700 ASTER. 2005. Ref. 17138. Brooke. LT. Results of 

Freshwater Exposures with the Chemicals Atrazine, 

Biphenyl, Carbaryl, Carbazole, Dibenzofuran, 3,3­

dichorobenzidine... Center for Lake Superior 

Environmental Studies, University of Wisconsin, 1991. 

Code 96-hr LC50 

Species Stone Fly 

Aquatic—Saltwater—Chronic 

AWQC :g/L . 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 2,600 ASTER. 2005. Ref. 14715. Hall, LW Jr., MC 

Zeigenfuss, RD Anderson, TD Spittler, and HC 

Leichtweis. Influence of Salinity on Atrazine Toxicity 

to a Chesapeake Bay Copepod (Eurytemora affinis) and 

Fish (Cyprindon variegatus). Estuaries 17(1B):181-186. 

1994. 

Code 96-hr LC50 

Species Calanoid copepod 

A-39
Pollutant: Simazine CAS: 122349 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 1.2e-1 Region 3. Risk Based Concentration Table. 2004. 

HEAST 

Carcinogen flag Y/N Y 

RfD mg/kg-day 5.00e-3 IRIS. 2005. 1994 revision. 

Code 

BCF L/kg 18 ASTER, 2005. Ref. 7. Veith, GD and P Kosian. 

Estimating Bioconcentration Potential from 

Octanol/Water Partition Coefficients. In D. Mackay et 

al. (Eds.) Physical behavior of PCBs in the Great Lakes. 

Ann Arbor Scie. Publ. Ann Arbor, MI:269-282. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 1000 ASTER. 2005. Ref. 10969. McGinty, AS. Effects of 

Periodic Applications of Simazine on the Production of 

Tilapia nilotica Fingerlings. J. Agric. Univ. P.R. 

68(4):467-469. 1984. 

Code mortality 

Species Nile Tilapia 

Aquatic—Freshwater—Acute 

AWQC :g/L 124,875 ASTER. 2005. Ref. 15823. Veith GD, DJ Call, and LT 

Brooke. Structure-Toxicity Relationships for the 

Fathead Minnow, Pimephales promelas: Narcotic 

Industrial Chemicals. Can. J. Fish. Aquat. Scie. 

40(6):743-748. 1983. 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L . 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-40
Pollutant: Cyanazine CAS: 2125462 

Variable Units Value Source 

Human Health 

q1* mg/kg-day 8.4e-1 Region 3. Risk Based Concentration Table. 2004. 

HEAST 

Carcinogen flag Y/N Y 

RfD mg/kg-day 2.0e-3 Region 3. Risk Based Concentration Table. 2004. 

HEAST 

Code 

BCF L/kg 4 ASTER, 2005. Ref. 7. Veith, GD and P Kosian. 

Estimating Bioconcentration Potential from 

Octanol/Water Partition Coefficients. In D. Mackay et 

al. (Eds.) Physical behavior of PCBs in the Great Lakes. 

Ann Arbor Scie. Publ. Ann Arbor, MI:269-282. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 3.5 ASTER. 2005. Ref. 4442. Davies, PE, LSJ Cook, and D 

Goenarso. Sublethal Responses to Pesticides of Several 

Species of Australian Freshwater Fish and Crustaceans 

and Rainbow Trout. Environ. Toxicol. Chem. 

13(8):1341-1354. 1994. 

Code 10-day LC50 

Species Rainbow Trout 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L . 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-41
Pollutant: DCPA mono-acid 

degradate 

CAS: 887547 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Freshwater—Acute 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L no ASTER data. 

Code 

Species 

A-42
Pollutant: DCPA di-acid degradate CAS: 2136790 

Variable Units Value Source 

Human Health 

q1* mg/kg-day No data (IRIS, USEPA Region RBC Table, ATSDR 

toxicological profiles, USEPA 2000 [California], Carcinogen flag Y/N USEPA 1995[Great Lakes]). 

RfD mg/kg-day 

Code 

BCF L/kg 179 ASTER, 2005. Ref. 7. Veith, GD and P Kosian. 

Estimating Bioconcentration Potential from 

Octanol/Water Partition Coefficients. In D. Mackay et 

al. (Eds.) Physical behavior of PCBs in the Great Lakes. 

Ann Arbor Scie. Publ. Ann Arbor, MI:269-282. 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 1364 ASTER, 2005. Ref: 15823. Veith GD, DJ Call, and LT 

Brooke. Structure-Toxicity Relationships for the 

Fathead Minnow, Pimephales promelas: Narcotic 

Industrial Chemicals. Can. J. Fish. Aquat. Scie. 

40(6):743-748. 1983. 

Code Estimated From Acute 

Value Using Acute-Chronic 

Ratio of 10; See U.S. EPA. 

Technical Support 

Document for Water 

Quality-based Toxics 

Control. EPA 505/2-90-001. 

March 1991. 

Species Fathead Minnow 

Aquatic—Freshwater—Acute 

AWQC :g/L 13644 ASTER, 2005. Ref: 15823. Veith GD, DJ Call, and LT 

Brooke. Structure-Toxicity Relationships for the 

Fathead Minnow, Pimephales promelas: Narcotic 

Industrial Chemicals. Can. J. Fish. Aquat. Scie. 

40(6):743-748. 1983. 

Code 96-hr LC50 

Species Fathead Minnow 

Aquatic—Saltwater—Chronic 

AWQC :g/L no ASTER data. 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L no ASTER data. 

Code 

Species 

A-43
Pollutant: Nicotine CAS: 54115 

Variable Units Value Source 

Human Health 

q1* mg/kg-day none identified 

Carcinogen flag Y/N 

RfD mg/kg-day none identified 

Code 

BCF L/kg 4 ASTER, 2005. Ref. 7. Veith, G.D. and Kosian. Estimating 

Bioconcentration Potential from Octanol/Water Partition 

Coefficients. In D. Mackay et. al. (Eds.), Physical Behavior of 

PCBs in the Great Lakes. Ann Arbor Sci. Publ., Ann Arbor, 

MI:269-282. 1983. (QSAR.) 

BAF 

RSC 

Aquatic—Freshwater—Chronic 

AWQC :g/L 3490 ASTER, 2005. Ref. 16362. Passino-Reader, DR, WH 

Berlin, and JP Hickey. Chronic Bioassays of Rainbow 

Trout Fry with Compounds Representative of 

Contaminants in Great Lakes Fish. J. Great Lakes Res. 

21(3):373-383. 1995. Geometric average of 

LOEC=4200 and NOEC=2900. 

Code MATC 

Species Rainbow Trout 

Aquatic—Freshwater—Acute 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Chronic 

AWQC :g/L 

Code 

Species 

Aquatic—Saltwater—Acute 

AWQC :g/L 

Code 

Species 

A-44