EPA RESPONSE 

TO EXTERNAL PEER REVIEW COMMENTS

on the

DRAFT AQUATIC LIFE AMBIENT WATER QUALITY 

CRITERIA FOR CADMIUM – 2015

November 19, 2015

Office of Water

U.S. Environmental Protection Agency

Washington, DC
ii

TABLE OF CONTENTS

1 INTRODUCTION................................................................................................................................... 1

1.1 Background...................................................................................................................................... 1

1.2 Peer Reviewers................................................................................................................................ 1

1.3 Review Materials Provided.............................................................................................................. 1

1.4 Charge Questions............................................................................................................................. 1

2 EXTERNAL PEER REVIEWER COMMENTS AND EPA RESPONSES, ORGANIZED BY 

CHARGE QUESTION ..................................................................................................................................... 2

2.1 Charge Question 1........................................................................................................................ 3

2.2 Charge Question 2...................................................................................................................... 10

2.3 Charge Question 3...................................................................................................................... 27

2.4 Charge Question 4...................................................................................................................... 37

2.5 Other Comments Provided ......................................................................................................... 46

3 REFERENCES CITED BY REVIEWERS......................................................................................... 48
1

1 INTRODUCTION

EPA submitted its Draft Aquatic Life Ambient Water Quality Criteria (AWQC) for Cadmium – 2015 for 

contractor-led independent, external peer review from August 25 to September 14, 2015. The external peer 

reviewers provided their independent responses to EPA’s charge questions. This report documents the EPA’s 

response to the comments provided to EPA. 

This report presents the four peer review charge questions and individual reviewer comments (verbatim) in 

Sections 2.1 through 2.4. Section 2.5 presents additional minor comments provided by one reviewer. New 

information (e.g., references) provided by reviewers is presented in Section 3. EPA separated each reviewer’s 

comments by charge question into distinct topics and responded to each topic individually, and also indicated

how the draft cadmium criteria document was revised in response to peer reviewer comments.

1.1 BACKGROUND

EPA’s Office of Water is charged with protecting ecological integrity and human health from adverse 

anthropogenic, water-mediated effects, under the purview of the Clean Water Act (CWA) Section 304(a)(l). 

The Agency has been working to update water quality criteria to protect aquatic life and aquatic-dependent 

wildlife from the presence of cadmium in freshwater and estuarine/marine environments in order to reflect the 

latest scientific knowledge.

EPA’s AWQC for cadmium presents draft acute and chronic criteria expressed as concentrations of cadmium 

in fresh and estuarine/marine waters (dissolved). The 2015 draft cadmium criteria document is an update to 

the 2001 cadmium criteria. The 2015 draft incorporates additional toxicological data for cadmium, while 

using the same criteria derivation process that was used in 2001. 

1.2 PEER REVIEWERS

An EPA contractor identified and selected five reviewers who met the technical selection criteria provided by 

EPA and who had no conflict of interest in performing this review.

The EPA contractor provided reviewers with instructions, the review document (including appendices), the 

charge to reviewers) prepared by EPA, and supporting reference materials as described in the charge. 

Reviewers worked individually to develop written comments in response to the charge questions. 

1.3 REVIEW MATERIALS PROVIDED

 Internal Draft Cadmium AWQC_ 042115 (081315).pdf

 Internal Draft Cadmium AWQC_Appendicies_7 1 15 (081315).pdf

 Appendix K Issue Summary Regarding Test Conditions and Methods...H. Azteca.pdf

 Internal Draft Cadmium AWQC_References_11 4 14 (081315).pdf

Background/Supplemental Material (not for review, reference only)

 Cadmium Risks to Freshwater (Mebane 2010).pdf

1.4 CHARGE QUESTIONS

1. Please comment on the overall clarity of the document and construction as it relates to the derivation 

of each criterion.

2. Please comment on the technical approach used to derive the draft cadmium criteria; is it logical, does 

the science support the conclusion, and is it consistent with the protection of freshwater and 
2

estuarine/marine aquatic life from acute, chronic, and bioaccumulative effects? Are the methods 

described in the document scientifically sound?

3. Please comment on the data used to derive the revised criteria, including data 

adequacy/comprehensiveness, and the appropriateness of the data selected and/or excluded from the 

derivation of the draft criteria. Is the data used correctly for the intended purpose? Are there other 

relevant data that you are aware of that should be included? If so, please provide the data along with 

supporting information. 

4. Are the derived criteria appropriately protective of listed species and commercially and recreationally 

important species, particularly as the criteria relates to salmonids?

2 EXTERNAL PEER REVIEWER COMMENTS AND EPA RESPONSES, ORGANIZED BY 

CHARGE QUESTION

The following tables list the charge questions submitted to the external peer reviewers, the external peer 

reviewers’ comments regarding those questions (broken into distinct topics), and EPA’s responses to the peer 

reviewers’ comments. EPA revised the 2015 draft considering the external peer review comments, and noted 

in the table where the document was edited.
3

2.1 CHARGE QUESTION 1

1. Please comment on the overall clarity of the document and construction as it relates to the derivation of each criterion.

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

Reviewer 1 This report makes for very dull reading, but it is well-written 

and it is usually clear what the author is trying to say. There 

are no insightful comments or new ideas presented in this 

report, but the report is laid out in a clear, logical fashion.

Thank you for your comment. No edit needed.

Reviewer 2 Overall the document is relatively clear with formatting in a 

risk assessment format which allows the reader to evaluate 

each criteria. Of minor concern was the lack of inclusion of 

emerging materials as sources of cadmium such as quantum 

dots which do make up photovoltaic substances (mentioned). 

However, the increased use of these materials as “inorganic” 

Cd sources and the uncertainties surrounding the potential 

absorption and effects of these materials to aquatic organisms 

needs some discussion.

Information regarding quantum dots has been added to the 

document.

Section 2.1

Reviewer 2 In addition, some inconsistencies were noted with regard to 

sub-lethal effects mentioned in the Estuarine/Marine Acute 

section. While present in this section, discussions of sublethal 

effects were largely omitted in the Freshwater sections and 

chronic sections of both water types.

The Estuarine/Marine Acute section was revised to remove 

inconsistencies. Additionally, information about sublethal 

effects in other media was added to the appropriate sections 

of the document. 

Section 5.1

Section 5.2

Section 5.4

Section 5.5
4

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

Reviewer 2 There was also inconsistencies with regard to the use of flowthrough vs. static exposures and whether more or less 

uncertainty is involved in utilization of the values. For 

example, flow-through methods were stated for Salmo trutta, 

but methods for Morone were static or static-renewal. One 

would clearly suggest the flow through values should be 

given greater weight with regard to uncertainty assessments. 

As it reads right now, it appears there are no differences 

between using static or flow-through exposures.

Data selected to calculate the SMAV for each species 

follows 1985 Guidelines recommendations. Specifically, 

flow-through measured exposures are preferred and selected 

for use over static and static-renewal exposure studies. If 

only static or static renewal exposure studies are available, 

EPA considers the study data and determines whether the 

study is acceptable for inclusion considering factors, such as 

known compound stability and other relevant information 

presented by the study author. EPA’s goal is to consider and 

include as much high quality, scientifically defensible data 

in its assessments as possible in order to characterize

potential response in a broad array of aquatic organisms. For 

example, if a species of concern had only static renewal data 

for acute studies, and EPA knew the compound was stable 

in water during the test duration, the data would be 

considered for inclusion if it met with the other data quality 

screens EPA. 

No edits needed.
5

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

Reviewer 2 The inability to determine salinity relationships to toxicity is 

also a concern but it is likely due to varied salinity regimes 

confounded with temperature and solute constituents in 

experimental designs (see comments below). It is noteworthy 

that a 1ppt value is considered “estuarine” for the Morone

value, when there are “freshwater” systems that likely have 

higher conductance than this value. There should also be 

some statement or better clarity documenting the lack of a 

standard salinity value being utilized to compare toxicity 

values. It appears that the most sensitive toxicity value is 

being used regardless of the salinity.

The current statement in the Executive Summary about the 

salinity relationship addresses this comment:

"Available data suggest the acute toxicity of cadmium may 

be influenced by salinity, with a trend of decreasing 

sensitivity to cadmium with increasing salinity. However, 

this trend could not be definitively characterized and a 

mathematical relationship could not be described to define 

the dependency (See Section 5.4.1)." Text has been added to 

elaborate on why a salinity normalization approach is not 

being used in criteria development.

The estuarine/marine value is intended to be applicable to

the broad range of salinities present in non-freshwater 

systems. EPA will accordingly continue to use 1 ppt as the 

lowest salinity level for a salt water test. This salinity is 

consistent with Mitsch and Gosselink (1986) who classify a 

waterbody with a salinity of 0.5-5.0 ppt is oligohaline.

Mitsch, W.J. and J.G. Gosselink. 1986. Wetlands. Van 

Nostrand Reinhold, New York. 539 pp.

Section 2.3.1 

Section 5.4.1

Reviewer 2 Overall, the uncertainty analysis section should be extended 

to include aspects of uncertainty with the data used for the 

derivation of the criteria. As it stands presently, the emphasis 

seems to be more on justification of data not utilized for the 

derivations.

Data selection is consistent with the procedures presented in 

the 1985 Guidelines. The Effects Characterization section

was revised to include further discussion about uncertainty 

in the criteria calculations.

Section 5.1

Section 5.2

Section 5.4

Section 5.5

Reviewer 3 In general, the document language is reasonably clear. 

However, throughout the document, there are several 

instances where certain decisions are made that appear to be 

rather arbitrary without sufficient justification as to how or 

why these decisions were made (see details below).

Thank you for your comment. Please see responses to 

specific comments.

No edits needed.
6

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

Reviewer 3 Minor comments:

p. 8 and elsewhere: use mass units rather than ppm, ppb etc.

These values are mineral deposit concentrations in units

reported by the author(s), but were changed to mg/kg based 

on the comment. There are no other uses of ppm or ppb in 

the document.

Section 2.1

Reviewer 3 p. 9: quantify concentrations found in impaired water 

(“several micrograms per liter” is vague)

The text has been revised to give a definitive value. Section 2.1

Reviewer 3 p. 10: is the suggestion that precipitated/particulate forms of 

Cd that ultimately end up in sediments are not bioavailable?

Text was added to clarify that particulate forms of cadmium

are potentially available to benthic feeders and sediment 

dwellers. 

Section 2.2

Reviewer 3 p. 19: do data exist for any other salts of Cd that has been 

excluded?

The 1985 Guidelines note specific salts to test for metals;

only these salts were used. According to the Manual of 

Instruction for Preparing Aquatic Life Water Quality 

Criteria Document, Stephan 1985, Section III. Defining the 

Pollutant, "for metals such as cadmium, chromium (III), and 

zinc, only data from tests on chloride, nitrate, and sulfate 

salts (either anhydrous or hydrated) should be used", 

therefore, other data for other cadmium salts were not 

included in the evaluation. Thus, studies conducted with 

cadmium acetate and cadmium borate salts were not used, 

nor were tests with nanoparticles and quantum dots.

Stephan, C.E. 1985. Manual of instructions for preparing 

aquatic life water quality criteria documents. Draft report 

dated 12-12-85. U.S. EPA. Environmental Research 

laboratory, Duluth, MN. 49 pp.

No edits needed.
7

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

Reviewer 3 P.63: Please be explicit about how the constants in the 

equations are derived for both the CMC and CCC.

The reviewed draft contained explicit information about 

how the constants in the equations for the CMC and CCC 

were derived:

The CMC=e(1.103 x ln(hardness)-4.247)

Where, 1.103 is the acute pooled slope and;

-4.247 is calculated as 

=ln(CMC at 100 hardness) - (Pooled Acute Slope x 

(ln(100)))

=ln(2.3)-(1.103 x 4.605)

Similarly, the CCC=e(0.8161 x ln(hardness)-3.663)

Where, 0.8161 is the chronic pooled slope and;

-3.663 is calculated as

=ln(CCC at 100 hardness) - (Pooled Chronic Slope x 

(ln(100)))

=ln(1.1)-(0.8161 x 4.605) 

No edits needed.

Reviewer 3 P. 67: Define the values listed under the two tables: (S2, L, A) Footnotes were added to the document to define the terms S, 

L and A. These terms are refer to the following: S = slope; L 

= intercept; A = lnFAV. FAV = Final Acute Value.

Section 4.3.1

Section 4.3.2

Section 4.4.1.

Reviewer 3 Major comments:

p. 12: “Mebane (2014) conclude that, although there were not 

adequate data to establish acceptable tissue effects 

concentrations for aquatic life, cadmium is unlikely to 

accumulate in tissue to levels that would result in adverse 

effects to aquatic invertebrates or fish. The evaluation of 

direct exposure effects is therefore considered to be more 

applicable to the development of criteria for aquatic life.”

This line of reasoning is questionable on many levels. 

Establishing critical tissue effects thresholds that work across 

species is problematic, especially in invertebrates, because 

species vary in their abilities to store/sequester Cd in 

EPA concurs with the reviewer about the difficulty in 

characterizing dietary exposure and establishing critical 

tissue effects thresholds for bioaccumulated metals. 

Text has been added to discuss these points and incorporate

the work of other researchers, such as Mebane (2006), who 

discuss cadmium bioaccumulation and dietary exposure in 

detail and the uncertainties currently associated with its 

evaluation. In particular, text was added to detail how 

cadmium can bioaccumulate in aquatic organisms through 

multiple exposure routes including ingestion and direct 

exposure, and how total uptake depends on the cadmium 

Section 5.6.1
8

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

physiologically inert forms. However, this does not mean that 

bioaccumulated metals are non-toxic as is implied by the 

language in this document. I think Mebane is being grossly 

misquoted here (aside from the fact that there is no 2014 

reference). Here are some quotes from his 2010 document that 

directly refute the underlined text above:

“Thus the consequences of elevated tissue residues or effects 

of dietary exposures may be important when estimating 

protective thresholds for cadmium and other pollutants 

(McCarty and Mackay, 1993; Meyer and others, 2005).” P. 32

“A diet of cadmium-contaminated green algae Chlorella sp

caused reduced growth in the amphipod Hyalella azteca in a 

recent study (Ball and others, 2006).” P. 38

“Dietary cadmium exposures appear to be an important risk 

for at least some invertebrates. The data reviewed on dietary 

effects of cadmium to invertebrates indicated that adverse 

effects could occur at concentrations realistic in cadmiumpolluted waters”. P. 38

“Toxicity to mayflies from feeding on cadmium-contaminated 

algal mats at environmentally realistic concentrations was 

observed (Irving and others, 2003). P. 38

I understand that dealing with dietary exposures is incredibly 

inconvenient in the context of the 1985 Guidelines, but 

pretending that they are not important in 2015 is irresponsible 

because we know better. The Irving et al., 2003 study 

referenced above provides direct evidence that diet derived 

Cd can be problematic in this aquatic insect example.

concentration, exposure route and the duration of exposure.

Text was also added to clarify that there does not appear to 

be a consistent relationship between body burden and 

toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of

aquatic life.
9

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 1

EPA Response Revision Location

in 2015 Draft 

Cadmium Criteria 

Document

Reviewer 4 I found the overall clarity of the document to be quite good. I 

especially appreciated the document being generally 

organized in a risk assessment format. I think this is very 

useful, particularly the Problem Formulation section that 

outlines various sources, potential exposure pathways and 

receptors. I hope EPA will use this overall structure for future 

criteria documents as well. I also like all of the comparisons 

to previous Cd criteria documents. This makes key changes to 

the criteria very transparent.

Thank you for your comment. No edits

Reviewer 4 My only significant criticism of the overall format is that 

there are a number of redundancies where information is 

presented multiple times, often the exact same wording (for 

example, Section 5.4.1 is redundant of earlier text in the 

document). I encourage EPA to consider consolidating and 

reducing these redundancies.

The document was reviewed and revised to minimize 

redundant text.

Various locations

Reviewer 4 An additional minor point is that it is unclear how the data 

tables in the appendices are organized. They don’t seem to be 

listed alphabetically by either common or scientific name. It 

would be useful if they were.

Data tables are organized as recommended by the 1985 

Guidelines (phylogenetically) and text was added to each 

table in the Appendices to clarify this.

Appendices

Reviewer 5 Generally sufficient. Problem formulation section seemed a 

bit of a forced fit, as if added to satisfy a new stylist protocol.

Thank you for your comment. No edits needed.
10

2.2 CHARGE QUESTION 2

2. Please comment on the technical approach used to derive the draft cadmium criteria; is it logical, does the science support the conclusion, 

and is it consistent with the protection of freshwater and estuarine/marine aquatic life from acute, chronic, and bioaccumulative effects? Are the 

methods described in the document scientifically sound?

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 2

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 1 This report is rather antiquated in its thinking. It basically 

assumes that Cd is accumulated only from the aqueous phase 

rather than from both the aqueous phase and ingested food. 

Over the past 10-15 years, it has been shown that many 

toxicants, including Cd and other metals, can be 

bioaccumulated from food as well as from the aqueous phase. 

Indeed, a number of laboratory, field, and modeling studies 

have shown that diet can be the dominant source of metals for 

marine invertebrates and fish. The relative importance of diet 

has been shown to vary with species, but it is rarely a minor 

source and sometimes (for some fish species, for example) the 

predominant source. Moreover, once accumulated from diet, 

Cd can reach sensitive organs within animals that are not 

reached by Cd taken up from the aqueous phase. Therefore, 

the toxic response of an animal to either ambient Cd or body 

burden Cd can vary considerably, depending on whether the 

source is ingested food or solute in ambient water. Thus, 

dissolved metal may be sorbed onto exoskeletons in 

crustacean zooplankton (often the most sensitive species, as 

the author points out) but this does not directly affect the 

animal because the metal (Cd in this case) bound to chitosan 

on the exoskeleton does not interact with metabolic processes, 

whereas metal assimilated from ingested food can enter into 

internal tissues where it may interfere with a variety of 

metabolic and reproductive processes. I saw no 

acknowledgement of the possible significance of dietary Cd 

on aquatic (freshwater or marine) animals in this report, and 

EPA concurs with the reviewer about the multiple potential 

exposure routes and the complexity of characterizing these 

routes and establishing critical tissue effects thresholds for

bioaccumulated metals.

Text has been added to discuss these points and incorporate

the work of other researchers, such as Mebane (2006), who 

discuss cadmium bioaccumulation and dietary exposure in 

detail and the uncertainties currently associated with its 

evaluation. In particular, text was added to detail how 

cadmium can bioaccumulate in aquatic organisms through 

multiple exposure routes including ingestion and direct 

exposure, and how total uptake depends on the cadmium 

concentration, exposure route and the duration of exposure.

Text was also added to clarify that there does not appear to be 

a consistent relationship between body burden and 

toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.

Section 5.6.1
11

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 2

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

yet numerous papers describing such effects appeared in the 

reference section. In looking over appendices, many of these 

reports were not used, often for what appear to be spurious 

reasons or misinterpretations of studies. In some cases, dietary 

metals could be 1-2 orders of magnitude more toxic than 

dissolved metals to freshwater cladocerans and marine 

copepods, for example. In the case of Cd, an EC50 value of 5 

nM (~0.5 μg/L) was observed in copepods in a study by Hook 

& Fisher (cited in this report) if the animal had been fed food 

exposed to that Cd concentration, whereas the measured LC50

value based on a dissolved Cd source was 200 times greater. 

Also, measuring growth or mortality, as is often the case in 

simple toxicity tests, would have missed the effect—rather the 

reproductive capability of the copepods was affected by the 

dietary Cd, but no mortality was observed at environmentally 

realistic concentrations. Because dissolved Cd concentrations 

are typically at very low concentrations in natural waters (at 

least 10-fold lower in surface seawater, for example), the lower 

EC50 value derived from dietary rather than dissolved sources 

still indicates that Cd is unlikely to cause toxic effects in most 

natural waters.

Reviewer 2 With a few notable exceptions, the technical approach for the 

freshwater acute and chronic derivations appear valid. 

Incorporation of hardness normalization is warranted given the 

likelihood that Cd and Ca compete for similar biological and 

abiotic sites. In addition, the increased number of species 

extending the SSDs is also an excellent step forward in 

confirming proposed criteria.

Thank you for your comment. No edits needed.

Reviewer 2 Of concern is the approach utilized for the chronic 

estuarine/marine values. Utilization of ACRs with freshwater 

fish or other organism to derive estuarine/ marine values is not 

appropriate, especially when the criteria concentrations are 

increased. It is also unclear why freshwater salmonid values 

The use of a freshwater ACR to derive estuarine/ marine 

values is described as an acceptable approach in the 1985 

Guidelines, and was used in the draft criterion document 

reviewed by the external peer reviewers.

Section 2.7.3

Section 4.4.2

Section 5.5.1
12

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 2

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

were not utilized for the ACRs, as many reside in 

estuarine/marine environments (see salmonid comments 

below).

Based on the peer reviewer comment, the estuarine/marine 

ACR approach was re-examined and revised for the 2015 draft 

proposal for public comment. The revised FACR incorporates

data for seven genus-level ACRs and was derived using data 

for marine species and a diversity of freshwater species, many 

of which have taxonomically-related marine species. ACRs 

used to derive the FACR incorporate data for five freshwater 

fish species, three freshwater invertebrate species, and two 

acutely sensitive estuarine/marine mysids.

Reviewer 3 Bioaccumulative effects of Cd are largely ignored in this 

document.

Text has been added to discuss these points and incorporate

the work of other researchers, such as Mebane (2006), who 

discuss cadmium bioaccumulation and dietary exposure in 

detail and the uncertainties currently associated with its 

evaluation. In particular, text was added to detail how 

cadmium can bioaccumulate in aquatic organisms through 

multiple exposure routes including ingestion and direct 

exposure, and how total uptake depends on the cadmium 

concentration, exposure route and the duration of exposure.

Text was also added to clarify that there does not appear to be 

a consistent relationship between body burden and 

toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.

Section 5.6.1
13

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 2

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 3 My comments for this section are divided into 2 parts: 1. The 

technical approach according to the 1985 Guidelines, and 2. 

The technical approach in light of our current understanding of 

cadmium bioaccumulation, effects, and deficiencies in the 

traditional testing approaches. 

The technical approach according to the 1985 Guidelines

A. What is the rationale for use of EC20 values for the chronic 

toxicity assessment? I understand that a MATC approach 

(based on NOEC and LOECs) has its issues, and I’m generally 

in favor of more statistically robust approaches such as the use 

of an EC level based on entire datasets. But why is a 20% 

effect level chosen here? This value seems rather high. There 

should be some rationale for choosing this value, and this 

rationale should be clearly articulated in the text. How do we 

know that a 20% effect level has no impacts at the population 

level?

The endpoint for chronic exposure is the EC20, which 

represents a 20 percent effect/inhibition concentration. This is 

in contrast to a concentration that causes a low level of 

reduction in response, such as an EC5 or EC10, which is rarely 

statistically significantly different from the control treatment. 

U.S. EPA selected an EC20 to estimate a low level of effect 

that would be statistically different from control effects, but 

not severe enough to cause chronic effects at the population 

level (see U.S. EPA 1999c). Reported NOECs (No Observed 

Effect Concentrations) and LOECs (Lowest Observed Effect 

Concentrations) were only used for the derivation of chronic 

criterion when an EC20 could not be calculated for the genus. 

A NOEC is the highest test concentration at which none of the

observed effects are statistically different from the control. A 

LOEC is the lowest test concentration at which the observed 

effects are statistically different from the control. When 

LOECs and NOECs are used, a Maximum Acceptable 

Toxicant Concentration (MATC) is calculated, which is the 

geometric mean of the NOEC and LOEC. 

Regression analysis was used to characterize a concentrationeffect relationship and to estimate concentrations at which 

chronic effects are expected to occur. For the calculation of 

chronic criterion, point estimates were selected for use as the 

measure of effect over a MATC, as MATCs are highly 

dependent on the concentrations tested. Point estimates also 

provide additional information that is difficult to determine 

with an MATC, such as a measure of effect level across a 

range of tested concentrations. 

U.S. EPA. 1999c. 1999 Update of ambient water quality 

criteria for ammonia. EPA-822-R-99-014. National Technical 

Information Service, Springfield, VA.

No edits needed.
14

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 2

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 3 Only 3 species (all fish) were used to generate the hardness 

correction for the freshwater chronic toxicity data set. D. 

magna and P. promelas data were not used because only 

MATCs were available and not EC20s. Is it not possible to 

estimate EC20’s from these datasets? The use of only 3 

species to make this very important hardness adjustment 

would seem to add a significant level of uncertainty to the 

final analysis, especially since 2 of species used have 

divergent slopes. ANCOVA (p=0.08) based on data from 3 

species was used to say that the slopes 0.32, 1.46 and 1.08 are 

not different and can be pooled. Is this defensible? Shouldn’t a 

conservative slope estimate be chosen here.... especially in 

light of the fact that a 20% effect level is much higher than an 

MATC or EC05 would be?

EC20s were not estimated for species other than the three fish 

species because the data necessary to calculate EC20 point 

estimates were not provided by the authors. EC20 point 

estimates were preferentially selected for use over a NOEC or 

LOEC as the measure of effect, as NOECs and LOECs, which 

are the basis of the MATCs, are highly dependent on the test 

concentrations selected. Furthermore, point estimates provide 

additional information that is difficult to determine using 

NOEC and LOEC effect measures, such as a measure of effect 

level across the range of tested concentrations, and the 

confidence intervals around those measures of effect.

Correspondence has been sent to the authors who did not 

provide raw data for their studies, so EC20s can be calculated if 

the data are available. Additional EC20s were calculated based 

on their responses.

An additional analysis was conducted to determine if the 

inclusion of 3 MATCs from the Chapman Manuscript for D. 

magna could be included in the hardness relationship along 

with the new EC20s. This additional data supported the same 

conclusion that a pooled slope could be generated with a 

slightly different slope of 0.7977. Values were edited to reflect 

this new pooled slope.

Section 3.1.2

Appendix C

Reviewer 3 The most acutely sensitive marine genus, Tigriopus was not 

used in the analysis. The rationale was that it falls below the 

5th percentile of the distribution. Isn’t the whole point of the 

SSD to determine what is protective of 95% of the species? 

(Not 95% of the remaining taxa after sensitive taxa are 

arbitrarily removed from the dataset). Shouldn’t all of the data 

be used here?

The 1985 Guideline recommendations were followed in that 

the four GMAVs closest to the 5th percentile are used to 

estimate the FAV. 

Section 2.5

Section 2.7.2
15

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 2

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 3 The use of 2 ACRs from freshwater species in the 

development of a marine chronic criterion is dubious on many 

fronts. The justification for doing this needs to be articulated. 

If justifiable, the authors should then justify their choices as to 

why these 2 species were chosen. The reason given in the text 

is that the freshwater species were chosen on the basis of 

being acutely sensitive. However the purpose of ACRs is to 

evaluate the potential for the chemical to cause chronic 

toxicity. Use of an acutely sensitive species for ACR choice 

should theoretically result in species with low ACRs, and in 

this case, this is borne out. The freshwater invertebrate L. 

silquoidea has a reported ACR of 2.727, suggesting that is 

chronically not very toxic. However, the ACRs for most 

species are considerably higher: (see below) 

Mebane (2010) list ACRs for freshwater invertebrates:

Ephemerella: 158.67

Physa: 47.6

Aplexa: 28.5 and 47.87

Ceriodaphnia: 12.41 and 31.5

Daphnia: 65, 155, 112, 13

Hyalella: 17.5 

This document lists the following freshwater invertebrate 

ACRs:

Aplexa: 49.7

Lymnea: 12.81

Ceriodaphnia: 19.82

Daphnia: 57.3

With all of these values to choose from, 2.727 is clearly not a 

representative ACR for freshwater invertebrates. Since the use 

of a “mean ACR” is being applied across taxa, shouldn’t the 

The use of a freshwater ACR to derive estuarine/ marine 

values is consistent with the1985 Guidelines. However, based 

on the peer reviewer comment, the estuarine/marine ACR 

approach was re-examined and revised in the 2015 draft 

proposal for public comment. The revised FACR incorporates 

data for seven genus-level ACRs and was derived using data 

for both marine species and a diversity of freshwater species, 

many of which have taxonomically-related marine species. 

The revised FACR of 8.291 was derived from a geometric 

mean of genus-level ACRs for the following:

 Estuarine/marine mysids, Americamysis bahia and A. 

bigelowi

 Cladocerans, Ceriodaphnia dubia and Daphnia (D. 

magna and D. pulex)

 Mottled sculpin, Cottus bairdii

 Salmonids, Oncorhynchus (O. mykiss, O. 

tshawytscha) and Salmo (S. trutta)

 Fathead minnow, Pimephales promelas

The seven ACRs differ by a factor of < 11.95, which 

approximates the factor of 10 or less recommended by the 

1985 Guidelines. The ACRs for salmonids were less than

2.0 and were therefore raised to 2.0 to be consistent with 

the 1985 Guidelines. The ACRs for the other freshwater 

species were not used for the revised FACR because they 

have no taxonomically-related marine species (e.g., 

pulmonate snails) and/or the ACRs appear to be outliers.

The description of and rational for the new estuarine/marine 

ACR approach is provided in the post-peer review 2015 draft 

document.

Section 2.7.3

Section 4.4.2

Section 5.5.1
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values be representative? Would it make sense to have higher 

ACRs apply to invertebrates and lower ACRs apply to fish 

since fish generally have low ACRs and inverts generally have 

high ACRs?

Reviewer 3 Technical approach based on what we understand about the 

world post 1985:

Cadmium has been demonstrated to be toxic to practically 

every in vitro system it has been tested in. We strive to limit 

human dietary exposures in part because it is a known 

carcinogen and is nephrotoxic after dietary exposure. Effects 

of Cd on antioxidant physiology are well described in several 

species including aquatic insects. What evidence can we point 

to suggest that bioaccumulated Cd is not toxic to aquatic 

organisms? This is a fundamental flaw in this document.

Text has been added to discuss these points and incorporate

the work of other researchers, such as Mebane (2006), who 

discuss cadmium bioaccumulation and dietary exposure in 

detail and the uncertainties currently associated with its 

evaluation. In particular, text was added to detail how 

cadmium can bioaccumulate in aquatic organisms through 

multiple exposure routes including ingestion and direct 

exposure, and how total uptake depends on the cadmium 

concentration, exposure route and the duration of exposure.

Text was also added to clarify that there does not appear to be 

a consistent relationship between body burden and 

toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.

Section 5.6.1

Reviewer 3 We have a major and important disconnection between what 

traditional laboratory tests (using only direct aqueous 

exposures) and what field ecologists tell us about metal effects 

in aquatic insects. Because insects are such important players 

in freshwater ecosystems, and are the focus of CWA-driven 

biomonitoring programs, we have numerous examples of 

stream community structure being impaired by metal 

Criteria were derived considering lab water-based exposures 

using procedures that are consistent with the 1985 Guidelines. 

Additional discussion has been added to address the 

uncertainty of using lab-based tests to determine protective

field concentrations and the importance of dietary exposures 

to this faunal group.

Section 2.5

Section 5.1.3

Section 5.6.1
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exposures. Yet lab (aqueous) tests generally suggest that 

insects are insensitive to Cd. Work in our laboratory has used 

Cd uptake and depuration kinetics to clearly demonstrate that 

96 hour exposures are insufficient to elicit toxicity in aquatic 

insects are ecologically relevant concentrations (Buchwalter et 

al. 2007, Buchwalter et al. 2008, Poteat and Buchwalter 2014, 

Poteat and Buchwalter 2014). We have also shown that 

periphyton is a major sink for Cd, and is readily 

bioaccumulated in insects (Xie et al. 2010). We have also 

showed that Cd exposure does not negatively affect Ca 

transport in insects (Poteat and Buchwalter 2014) (as it is 

known to do in acutely sensitive taxa), and Ca provides little 

protective effects on Cd uptake (Poteat et al. 2012). Finally, 

we show that diet derived (but not water derived) Cd affects 

antioxidant physiology suggesting that dietary exposures may 

be more challenging to aquatic insects that aqueous exposures 

(Xie and Buchwalter 2011). These findings mirror those of 

Irving et al., 2003. All of these findings point towards shortterm, water-only exposures are insufficient for evaluating 

metal toxicity in this important faunal group (see (Poteat and 

Buchwalter 2014) for discussion of these findings).

In addition, generally good agreement has been reported for 

microcosm studies/whole effluent toxicity test results with 

corresponding field observed effects (Clements and Kiffney 

1996; Clements et al. 2002; Norberg-King 1986). Mebane 

(2006) compared chronic criterion values and apparent effects 

values from ecosystem studies and field surveys and 

concluded that the data showed mostly good agreement 

between the laboratory-based predictions and effects observed 

in the field surveys or ecosystem experiments.

EPA concurs with the reviewer about the importance of 

considering the dietary exposure route. Text has been added to 

discuss this and incorporate the work of other researchers, 

such as Mebane (2006), who discuss cadmium 

bioaccumulation and dietary exposure in detail and the 

uncertainties currently associated with its evaluation. In 

particular, text was added to detail how cadmium can 

bioaccumulate in aquatic organisms through multiple exposure 

routes including ingestion and direct exposure, and how total 

uptake depends on the cadmium concentration, exposure route 

and the duration of exposure. Text was also added to clarify 

that there does not appear to be a consistent relationship 

between body burden and toxicological effect, and an 

acceptable tissue effect concentration cannot be defined for 

aquatic life at this time. Bioaccumulation and effect level data 

that are available indicate that cadmium is unlikely to 

accumulate in tissue to levels that would result in adverse 

effects to aquatic invertebrates or fish at the calculated chronic 

criterion concentrations. For this reason, the evaluation of 

direct exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.
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Reviewer 4 Overall yes, I think the technical approach is scientifically 

sound and consistent with the protection of aquatic life. I do, 

however, have some specific significant comments for EPA to 

consider which I list below.

Thank you for your comment. No edits needed

Reviewer 4 Page 15: EPA concludes that most changes in Cd toxicity can 

be explained by changes in hardness and therefore 

incorporation of the BLM into this revision is not necessary. I 

strongly disagree with this statement. Every study I’m aware 

of in which a range of DOC and pH have been measured has 

shown that these parameters strongly influence Cd toxicity. 

Just because the majority of laboratory studies are conducted 

in laboratory waters with low DOC and do not measure 

dissolved organic carbon (DOC), does not provide a valid 

rationale for not using the BLM (biotic ligand model). 

Obviously, in the natural environment, DOC varies widely. I 

would think the objective of the criteria is to ensure that they 

are protective/predictive of toxicity in the natural 

environment, not in artificial laboratory waters. 

EPA revised the text to indicate that hardness is a critical 

factor in determining toxicity, and additional water quality 

parameters such as DOC, alkalinity, and pH may also 

influence cadmium toxicity. As the external peer reviewer 

noted, the objective of the criteria is to ensure that they are 

protective and predictive of toxicity in the natural 

environment. The addition of consideration of DOC would 

generally yield higher criteria values. Thus the focus on 

hardness only in this draft is expected to be protective. The 

EPA may consider the applicability of the BLM including 

parameters such as DOC in future revisions of the cadmium 

criteria.

Criteria were derived considering lab water-based exposures 

using procedures that are consistent with the 1985 Guidelines. 

Additional discussion has been added to address the 

uncertainty of using lab-based tests to determine safe field 

concentrations and the importance of dietary exposures to this 

faunal group.

In addition, generally good agreement has been reported for 

microcosm studies/whole effluent toxicity test results with 

corresponding field observed effects (Clements and Kiffney 

1996; Clements et al. 2002; Norberg-King 1986). Mebane 

(2006) compared chronic criterion values and apparent effects 

values from ecosystem studies and field surveys and 

concluded that the data showed mostly good agreement 

between the laboratory-based predictions and effects observed 

in the field surveys or ecosystem experiments.

Section 2.3.1

Section 2.5

Section 5.1.3
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Reviewer 4 Page 34: Following up on the previous comment regarding not 

using the BLM, why did EPA only consider a multiple linear 

regression with alkalinity? Why not pH and/or DOC? It is 

quite possible that pH autocorrelates with hardness as well 

given this is the case for most artificial laboratory waters 

(though not as consistent for natural waters), but there will not 

be an autocorrelation with DOC. This is a really important 

water quality parameter that EPA is ignoring.

Text relating directly to alkalinity was removed from the 

document and replaced with the text discussed in the previous 

response to comment. EPA notes that integrating DOC into 

the analysis would be expected in most cases to make the 

criteria less stringent. Thus, while recognizing the need to 

consider applicability of the BLM in future cadmium criteria 

updates, it is notable that the inclusion of DOC in the BLM 

approach will likely not make the criteria more stringent or 

conservative.

Section 2.3.1

Section 2.5

Section 5.1.3

Reviewer 4 Page 50-51: Is the study by Voyer et al. (1974), the only study 

where the effects of salinity on Cd toxicity was not consistent 

or are there multiple studies with this problem? If it’s only this 

one study, it’s not clear why the general trend would be 

ignored. I don’t think EPA would ignore the hardness 

relationship in freshwater if only a single study was 

inconsistent with the general trend. It is a concern that there is 

an obvious and significant salinity effect for the Neomysis 

integer data (p. 51), which is one of the four taxa used for the 

criteria derivation, and yet this obvious effect is ignored and 

the geometric mean is used to develop the species mean acute 

values (SMAV). Does EPA consider a test performed at a 

salinity of 1 ppt to be a marine test?

Based on the peer reviewer’s comments, additional analysis of 

the relationship between salinity and cadmium toxicity was 

conducted. As discussed in a previous comment, text has been 

added detailing why a salinity normalization approach was not 

used in the criteria development. A salinity-toxicity trend 

could not be definitively characterized and a mathematical 

relationship could not be described to define the dependency.

EPA will continue to use the 1 ppt as the lowest salinity level 

for a saltwater test, consistent with the development of 

estuarine/marine criteria, which is applicable to the broad 

range of salinities characterized by these habitats. This salinity 

is also consistent with Mitsch and Gosselink (1986) who 

classify a waterbody with a salinity of 0.5-5.0 ppt as 

oligohaline.

Note that for the salinity in the 1ppt Morone exposure, the 

conductance in this experiment was 1,600 uS/cm at 25C. This 

was approximately three times the conductance compared to 

fresh hard water.

Mitsch, W.J. and J.G. Gosselink. 1986. Wetlands. Van 

Nostrand Reinhold, New York. 539 pp.

Section 2.3.1

Section 5.4.1
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Reviewer 5 Unfortunately some aspects of the document lead to answering 

both parts of the charge question 2 with answers of “no.” I am 

only commenting on aspects which to me did not follow the 

available science, deviate from the principles of the 1985 

“Guidelines” or otherwise have logical problems. While 

Stephan et al. (1985) Guidelines for derivation of aquatic life 

criteria are 30 years old and aspects of the science have 

progressed such that some details may not fit, they include 

solid principals that should continue to guide the approach. 

Key among Stephan et al. guiding concepts is from their p. 3: 

“The guidelines were intended to provide the same level of 

protection as would an (infeasible) approach of conducting 

field tests on a wide variety of unpolluted bodies of water, 

adding various amounts of the material to each body of water 

in order to determine the highest concentration that would not 

cause any unacceptable long-term or short-term effects on the 

aquatic organisms or their uses.” Further (p. 10), These 

National Guidelines have been developed on the theory that 

effects which occur on a species in appropriate laboratory 

tests will generally occur on the same species in comparable 

field situations. All North American bodies of water and 

resident aquatic species and their uses are meant to be taken 

into account.” Not bodies of water for which conditions are 

optimal – all bodies of water. 

Thus, a key concept behind the logic of criteria derivation is 

that criteria be suitable for diverse, natural water bodies, and 

laboratory data should attempt to encompass comparable field 

situations. The draft document instead moves towards a very 

different concept of only using data from an idealized 

aquaculture setting, without regard to whether the species 

occurs in the wild in waters with “suboptimal” conditions.

We concur that an objective of the 1985 Guidelines is to 

provide for the development of criteria that are applicable to a 

variety of field conditions. The testing procedures must, 

however, be conducted with organisms that are determined to 

be fundamentally healthy and with tests that meet with a 

consistent set of standards in order to evaluate test 

acceptability and develop criteria that are not impacted by 

testing artifacts and that are applicable on a national basis. 

This approach is consistent with internationally-recognized 

and broadly applied approaches for developing effects 

analyses for toxicants, relying on such reproducible laboratory 

data because they are designed to be as free from confounding 

influences as possible, in order to permit for robust, 

unconfounded consideration of risk for a given chemical, and 

relative risk across chemicals. States, tribes, and other end 

users can then consider site-specific conditions and variables 

in the development of standards that are applicable to their 

specific end use, such as the application to a particular water 

body or region. A further discussion of uncertainty regarding 

differences between laboratory and field conditions and 

implications for criteria has been added to the document. 

Section 2.5

Section 5.1.3
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Reviewer 5 Drilling down on Hyalella

Most fundamentally, by throwing out all long-term test 

endpoints for the most sensitive genus (Hyalella) this 

document strays from a guiding principle of the Guidelines 

that criteria are to protect diverse natural waters. Criteria are 

indeed developed using laboratory data, but they are not 

intended to apply to laboratory waters; they are intended to 

apply to natural waters. This disconnect between laboratorybased derivation of numeric water quality criteria and 

application to natural waters has repeatedly debated in the 

literature, with me chiming in specifically with cadmium 

(Mebane 2010).

In essence, optimal aquaculture conditions are defined for 

culturing Hyalella azteca, and chronic tests in which less than 

15 mg/L chloride was present in dilution waters, or control 

growth, survival, and reproduction did not meet expectations. 

These were control growth (≥0.35 mg at 28 days and ≥0.5 mg 

at 42 days), survival (80% at 42d) and reproduction (≥6 per 

young). No explanation was found in the document why 

researchers were tasked to drill down on Hyalella, as any 

commonly used test organism could have been similarly 

scrutinized. Absent explanation, the inference is that Hyalella 

must have been chosen because it was the most sensitive 

organism, and there was a desire to exclude data if this 

heightened sensitivity could be shown to be an artifact of 

stressful laboratory culture conditions. In essence this logic 

requires the following implicit assumptions. Since only 

Hyalella data obtained from laboratory test waters >15 mg/L 

are to be used for criteria development, it follows that:

In ambient waters, Hyalella (and presumably other freshwater 

amphipods) are only expected to occur in waters with >15 

mg/L chloride; Alternatively if Hyalella do in fact occur in 

In addition to the response to the previous comment, 

additional text has been added to further detail the decision 

process that was used, based on the recently-completed 

evaluation, to determine which Hyalella tests were included in 

the evaluation. The basic premise behind the selection of 

specific Hyalella tests, based on the consideration of test 

conditions, is that in order to develop robust comparative 

toxicity tests, animal husbandry conditions should be optimal 

and provide for low control mortality and optimal control

growth to decrease control noise, increase the ability to 

capture low level effects, and thus understand the implications 

of introducing a toxicant into the system even at low levels.

EPA developed this test condition/husbandry analysis for 

Hyalella after repeatedly observing extremely high variability 

in Hyalella test results for the same compound under different 

lab/husbandry conditions (e.g., chloride concentrations in test 

water) and considering less than optimal control survival, 

growth and reproduction. These analyses led to the 

determination of conditions under which repeatable results 

could be obtained by minimizing interfering confounders, 

such as water chemistry and diet. 

These analyses were not developed to exclude sensitive tests. 

EPA’s analyses are developed with the goal of generating high 

quality and scientifically defensible predictions of 

concentrations, that if not exceeded beyond the specified 

frequency and duration, will be protective of aquatic life. 

Section 2.5

Section 5.1.3

Section 5.2.1
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waters with lower chloride concentrations, the criteria are 

only intended to apply to waters with >15 mg/L. 

Chloride is an important factor affecting the toxicity of 

cadmium to Hyalella (and presumably other related but less 

well studied amphipods or freshwater crustaceans). If so, then 

it follows that:

Chloride should be included in the criteria derivation and 

factored into the criteria. Per the Guidelines (p32), “when 

enough data are available to show that the chronic toxicity is 

similarly related to a water quality characteristic, the 

relationship should be taken into account .... If two or more 

factors affect toxicity, multiple regression analysis should be 

used.”

Alternatively, while not specifically mentioned in the 

guidance, if data were insufficient for the covariance or 

multiple regression analyses endorsed, it would seem 

reasonable to establish different criteria in brackets, such as 

waters ≤15 mg/L chloride or >15 mg/L chloride.

Alternatively, if chloride is not an important factor affecting, 

then there is no reason to factor it into the criteria 

development.

However, Appendix K does not address the question of 

whether chloride is a factor affecting cadmium toxicity, all 

that has been established is that Hyalella growth and 

reproductive output is greatest in waters with chloride >15 

mg/L. This is not unexpected. Freshwater environments 

usually have an osmolarity far less than blood plasma, and 

energy requirements to maintain hydromineral balance 

increase in more dilute waters (e.g., Wendelaar Bonga and 

Lock 2008). Fish in dilute waters don’t grow well either. For 

instance, about 80% of the restaurant/retail rainbow trout sold 

in the United States come from a 30 mile stretch known as the 
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Thousand Springs area of southern Idaho. There the constant 

chloride of about 20 mg/L, hardness of about 180 mg/L and 

temperature of 15°C provide optimal energy conversions and 

growth per unit feed. It would follow just as logically that only 

rainbow trout data that were generated from waters with 

chloride >15 mg/L or so should be used, because that 

optimizes growth? Why would it not follow that only acute 

data in which organisms were fed should be used, because 

starvation stresses organisms? This seems to be internally 

inconsistent logic.

Reviewer 5 The reason why Appendix K was requested was never stated. 

It should be. I assume the reason must be a presumption that if 

organisms do not grow and reproduce at high rates, then they 

will “too sensitive” or not represent responses expected in 

natural conditions. It is not obvious that this is the case. 

McNulty et al. (1999) showed that starved amphipods exposed 

to low levels of cadmium survived better than controls. 

However, even if optimal diets do produce higher (less 

sensitive) growth and reproduction effects with Cd and 

Hyalella, the universal use of optimal diets could lead to 

underestimation of the toxicity risks experienced by wild 

populations, which may experience limited food availability. 

In the wild, organisms don’t live in optimal conditions. Even 

in the center of their ranges, conditions are seldom optimal all 

of the time. Organisms also live in marginal conditions, for 

they tend to expand their ranges to the limits of their 

physiological tolerances. See for example France’s (1996) 

description of Hyalella living on the margins of lakes with 

tolerable mineral content (France 1996). Similarly, Gibbons 

and Mackie (1991) showed that increasing reproductive output 

of H. azteca was associated with increasing sulfate, calcium 

hardness, sediment particle size, conductivity, alkalinity, 

seston, and the organic matter of the fine sediment. This 

The basic premise behind the selection of specific Hyalella

tests, based on the consideration of test conditions, is that in 

order to develop robust comparative sensitivity analyses, 

animal husbandry conditions should be optimal and provide

for low control mortality and optimal control growth to 

decrease control noise, increase the ability to capture low level 

effects, and thus understand the implications of introducing a 

toxicant into the system even at low levels.

EPA developed this test condition/husbandry analysis for 

Hyalella after repeatedly observing extremely high variability 

in Hyalella test results for the same compound under different 

lab/husbandry conditions (e.g., chloride concentrations in test 

water) and considering less than optimal control survival, 

growth and reproduction. These analyses led to the 

determination of conditions under which repeatable results 

could be obtained by minimizing interfering confounders, 

such as water chemistry and diet. 

These analyses were not developed to exclude sensitive tests. 

EPA’s analyses are developed with the goal of generating high 

quality and scientifically defensible predictions of 

concentrations that if not exceeded beyond the specified 

Section 2.5

Section 5.1.3

Section 5.2.1

Section 5.6.1
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consistent with Appendix K, but begs the question, what are 

effects of Cd in these suboptimal waters? Why assume that if 

Cd criteria are needed, they should only be developed from 

exposures in high hardness, but then blindly extrapolate results 

to low chloride, low hardness conditions using tests with other 

organisms? This is further logical problem with Appendix K’s 

rationale – as noted in appendix K, waters with hardness less 

than 80 mg/L tend to have chloride less than 10 mg/L. Does 

the hardness-toxicity relation predict safe conditions for 

Hyalella at low hardness? No way to know. 

frequency and duration will be protective of aquatic life. 

We concur that an objective of the 1985 Guidelines is to 

provide for the development of criteria that are applicable to a 

variety of field conditions. The testing procedures must, 

however, be conducted with organisms that are determined to

be fundamentally healthy and with tests that meet with a 

consistent set of standards in order to evaluate test 

acceptability and develop criteria that are not impacted by 

testing artifacts and that are applicable on a national basis. 

Reviewer 5 I’ve poked around a bit the literature on Hyalella life histories 

under different environmental stresses in an effort to include 

extrapolate organism-level effects of Cd to potential 

population-level effects (Mebane 2010). While by no means 

exhaustive, and by now a bit dated, this leads to some other 

thoughts on the expected control survival, growth, and 

reproduction in long term tests in Appendix K. With control 

survival, in at least some wild populations, I estimated halfmonth survival rates for juveniles of about 0.9, or close to a 

5% decline per week (Mebane 2010, Table II). This is higher 

than the 2-3% noted in Appendix K, and suggests that in the 

wild, survival to 42-days would likely be less than 80%. With 

regards to growth, while some wild populations grew as much 

as those in the laboratory settings discussed in Appendix (>0.5 

mg at sexual maturity), this cannot be assumed in all natural 

waters. Cooper (1965) reported average dry weights of adults 

Hyalella were 0.2 mg in a population in a warm, shallow lake 

in Michigan. Gibbons and Mackie (1991) reported mean 

weights of Hyalella at maturity were only 0.1 mg, and weights 

of all Hyalella were only 0.3 mg. Thus the 0.35 at day 28 and 

0.5 mg at day 42 may be higher than that expected in some 

natural settings. Gibbons and Mackie (1991) reported ranges 

The basic premise behind the selection of specific Hyalella

tests, based on the consideration of test conditions, is that in 

order to develop robust comparative sensitivity analyses, 

animal husbandry conditions should be optimal and provide 

for low control mortality and optimal control growth to 

decrease control noise, increase the ability to capture low level 

effects, and thus understand the implications of introducing a 

toxicant into the system even at low levels.

EPA developed this test condition/husbandry analysis for 

Hyalella after repeatedly observing extremely high variability 

in Hyalella test results for the same compound under different 

lab/husbandry conditions (e.g., chloride concentrations in test 

water) and considering less than optimal control survival, 

growth and reproduction. These analyses led to the 

determination of conditions under which repeatable results 

could be obtained by minimizing interfering confounders, 

such as water chemistry and diet. 

These analyses were not developed to exclude sensitive tests. 

EPA’s analyses are developed with the goal of generating high 

quality and scientifically defensible predictions of 

Section 2.5

Section 5.1.3

Section 5.2.1

Section 5.6.1
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of brood per female ranged from 6 – 15, which is consistent 

with appendix K. However, Strong (1972), his fig 4, showed 

sometimes natural brook sizes may be as low as 3 per female.

In sum, the logical problems of how Appendix K’s analyses 

are used in the document are analogous to the metaphor of not 

seeing the forest because of all the trees. Some trees were 

examined in great detail (lab performance of Hyalella) but it 

misses the point that the comparisons of acceptable conditions 

should be again performance in the wild. 

concentrations that if not exceeded beyond the specified 

frequency and duration will be protective of aquatic life. 

We concur that an objective of the 1985 Guidelines is to 

provide for the development of criteria that are applicable to a 

variety of field conditions. The testing procedures must, 

however, be conducted with organisms that are determined to

be fundamentally healthy and with tests that meet with a 

consistent set of standards in order to evaluate test 

acceptability and develop criteria that are not impacted by 

testing artifacts and that are applicable on a national basis.

Reviewer 5 Other items:

Problem formulation: It is germane to note that in natural 

waters, Cd is always in association with Zn, usually at about 

mass ratios of 1:200 (Wanty et al. 2009).

This information was added to Section 2.1 of the document. Section 2.1

Reviewer 5 p. 12, I was not quoted quite accurately. “Mebane (2014 2006) 

concluded that, although there were not adequate data to 

establish acceptable tissue effect concentrations for aquatic 

life, cadmium is unlikely to accumulate in tissue to levels that 

would result in adverse effects to aquatic invertebrates or fish, 

at calculated chronic criterion concentrations, which were 

lower than that chronic criterion concentration derived here. “

This report is variously cited as Mebane (2006), Mebane 

(2010), or Mebane (2014). The suggested citation is, 

“Mebane, C.A. 2006. Cadmium risks to freshwater life: 

derivation and validation of low-effect criteria values using 

laboratory and field studies. U.S. Geological Survey Scientific 

Investigation Report 2006-5245 (2010 rev.). 

http://pubs.usgs.gov/sir/2006/5245/.” 

The 2010 revision only corrected minor mistakes, and did not 

include any updated literature reviews.

Text was added as suggested and the citation was fixed. References and 

various locations 

in document

Section 2.3

Section 5.6.1
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Reviewer 5 p. 28, the approach of requiring data used in the hardnesstoxicity regressions to have a 3X spread and 100 mg/L 

absolute difference between the highest and lowest value was 

indeed used in the 2001 version, but was not really presented 

as policy. In contrast, my colleagues and I found that 

hardness-toxicity relations were more reliable from test series 

that concurrently tested the same cohort of organisms in 

waters with different hardness, than were ad hoc collections of 

found data tested under different conditions at different 

hardness levels (Mebane et al. 2012). 

Where available, giving concurrent test series data obtained at 

different hardnesses precedence over general hardness-toxicity 

compilations would be warranted.

The approach of requiring data used in the hardness-toxicity 

regressions to have a 3X spread and 100 mg/L absolute 

difference between the highest and lowest value was 

established when updating the cadmium document in 2001. 

This practice has been followed for all subsequent criteria 

document updates because it was found that the variability 

associated with different test conditions that are associated 

with multiple studies can sometimes be so great that it masks 

the hardness/toxicity relationship.

Data for each species are first reviewed to determine if they 

are potentially suitable for use in the hardness-toxicity 

evaluation. The data are initially considered regardless of 

source/test condition (laboratory, dilution water, temperature, 

etc.). However, if the hardness/toxicity data are widely 

scattered, we then attempt to decrease uncertainty introduced 

by the differing test conditions by focusing on those studies 

specifically evaluating the toxicity relationship. In addition, 

studies are excluded when only a single acute toxicity value 

was available and where multiple tests were conducted at the 

same hardness. When different life stages were used at test 

initiation, only data for the same life stage is evaluated. The 

end result is that the most defensible data are used to develop 

the hardness-toxicity slope.

No edits
27

2.3 CHARGE QUESTION 3

3. Please comment on the data used to derive the revised criteria, including data adequacy/comprehensiveness, and the appropriateness of the 

data selected and/or excluded from the derivation of the draft criteria. Is the data used correctly for the intended purpose? Are there other relevant 

data that you are aware of that should be included? If so, please provide the data along with supporting information. 

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 1 As noted above, the author chose to ignore many relevant 

studies that did not conform with standard EPA toxicity 

protocols. But the problem is that these protocols basically 

ignore the fact that animals eat, hardly a realistic scenario and 

are too simplistic in looking only at growth and mortality. 

Typically, the test organisms are exposed to dissolved Cd at 

varying concentrations, but in the absence of food. 

Occasionally, some artificial food (fish flakes or the like) is 

presented once every several days (sometimes never!) to keep 

the animals alive. But these studies are hardly representative 

of what happens in natural waters.

Studies that were determined not to be acceptable were 

presented in Appendix J, along with a rationale for their 

exclusion. However, the exclusion of food in acute tests is 

standard practice in EPA, ASTM and internationallyharmonized toxicity test protocols. This is based on the 

potential for food to alter the exposure concentration and/or 

bioavailability of the chemical. This approach is consistent 

with procedures stated on page 14 of the 1985 Guidelines: 

“Except for test with saltwater annelids and mysids, results of 

acute tests during which the test organisms were fed should 

not be used, unless data indicate that the food did not affect 

the toxicity of the test material”. 

No edits needed.

Reviewer 2 The use of additional species for SSD reduced uncertainty and 

greatly improved criteria assessments for freshwater. The QA 

evaluations of data usefulness was adequate and the data 

selected for the acute responses was correctly used for the 

intended purpose. The mechanistic assumption that adverse 

effects are primarily related to calcium uptake at the gill, is 

accurate for acute effects. Consequently, the data used for 

derivation of the criteria for acute effects is valid.

Thank you for your comment. No edits needed.
28

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 2 However, with regard to chronic effects, there are other targets 

once absorption of cadmium occurs, particularly the kidney, 

brain and gonad. In addition to specific interactions with 

signaling proteins, Cd clearly binds sulfhydral groups of 

proteins within targets disrupting cellular maintenance. The 

latter two tissue targets above are likely involved in the 

reproductive effects observed with chronic exposures. Cd 

clearly disrupts the Hypothalmic Pituitary Gonadal axis and 

gonadal function in fish (Vetillard, and Bailhache 2005). It 

reduces vitellogenin in females and accumulates in kidney 

upon chronic exposures either via diet or water (Szczerbik et 

al. 2006; Thomann et al. 1997). 

It is understood that tissue data from these organs are limited, 

but studies that have these data, or the fact that these data are 

limited should be discussion points of the uncertainty analysis. 

Clearly, discussions of uncertainty regarding accumulation are 

needed, particularly in light of limited data for chronic effects 

in estuarine/marine organism. The statement “Aquatic 

organisms are considered to be more susceptible to cadmium 

from direct aqueous exposure than through bioaccumulation 

and the development of criteria protective of direct exposure 

effects are considered more applicable to the development of 

criteria for aquatic life” is clearly biased toward acute toxicity 

and should be re-visited with particular emphasis on 

reproductive effects of cadmium which likely result from 

accumulation and not direct exposure.

EPA recognizes the difficulty in characterizing dietary 

exposure and establishing critical tissue effects thresholds 

associated with bioaccumulated metals. 

The information provided regarding tissue targets has been 

added to the Uncertainty section along with additional 

discussion about limitations in the organ data. 

Text has been added to discuss these points and incorporate

the work of other researchers, such as Mebane (2006), who 

discuss cadmium bioaccumulation and dietary exposure in 

detail and the uncertainties currently associated with its 

evaluation. In particular, text was added to detail how 

cadmium can bioaccumulate in aquatic organisms through 

multiple exposure routes including ingestion and direct 

exposure, and how total uptake depends on the cadmium 

concentration, exposure route and the duration of exposure.

Text was also added to clarify that there does not appear to be 

a consistent relationship between body burden and 

toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.

Section 5.6.1
29

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 2 With regard to reproduction, it is unclear what endpoint data is 

being used to determine the effect values in the Appendices. 

Tests are provided in terms of exposure duration, but it is 

unclear whether growth, survival or reproduction is being 

utilized as the endpoint. Again, given the potential for 

reproductive effects upon chronic exposure, reproduction 

would be expected to be the most sensitive endpoint. If other 

endpoints were used then the uncertainties inherent to these 

endpoints should be discussed. Clearly growth and survival 

effects have likely difference mechanisms and targets than that 

of reproduction.

The most sensitive acceptable endpoint is used for each study. 

The endpoint for each exposure concentration was added for 

each study in the table.

Appendix C

Reviewer 2 It is also significantly disappointing that data from the same 2 

species in 1980s are still the only two species being used to 

derive the 2015 values. In addition, it is puzzling how criteria 

values can be raised for estuarine/marine organisms when the 

same degree of uncertainty exists (only 2 species) in each year 

criteria were assessed. To add in data from freshwater 

organisms for ACR estimates increases uncertainty and does 

not reduce it. Therefore, the 2001 value should stay as is, or be 

reduced because of the uncertainty associated with its 

derivation.

Additional acceptable estuarine/marine chronic data were not 

found based on an extensive literature search that was 

conducted in 2014. The CCC was calculated using the 

saltwater FAV and FACR as recommended in the 1985 

Guidelines.

The use of a freshwater ACR to derive estuarine/ marine 

values is described as an acceptable approach in the 1985 

Guidelines, and was used in the draft criterion document 

reviewed by the external peer reviewers.

Based on the peer reviewer comment, the estuarine/marine 

ACR approach was re-examined and revised for the 2015 draft 

proposal for public comment. The revised FACR incorporates

data for seven genus-level ACRs and was derived using data 

for marine species and a diversity of freshwater species, many 

of which have taxonomically-related marine species. ACRs 

used to derive the FACR incorporate data for five freshwater 

fish species, three freshwater invertebrate species, and two 

acutely sensitive estuarine/marine mysids.

Section 2.7.3

Section 4.4.2

Section 5.5.1
30

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 3 Practically all relevant work related to bioaccumulated Cd and 

the importance of dietary exposures is ignored. (see (Barata et 

al. 2002, Barata et al. 2002, Buchwalter et al. 2008, Cain et al. 

2004, Croteau et al. 2003, Hare et al. 2001, Hare et al. 2003, 

Irving et al. 2003, Klaassen et al. 1999, Luoma and Rainbow 

2005, Luoma et al. 2009, Luoma and Carter 1991, Martin et 

al. 2007, Timmermans et al. 1992, Wallace et al. 2003, Xie et 

al. 2010, Xie and Buchwalter 2011, Xie et al. 2008) for some 

examples)

The referenced materials were evaluated and added, as 

applicable, to the bioaccumulation uncertainty section.

Section 5.6.1

Reviewer 3 I suspect that there are other reviewers who can comment 

more directly on the issues with Hyalella data, so I will refrain 

from doing so here. 

Thank you for your comment. No edits needed.

Reviewer 4 Overall, I found the data used by EPA to derive the criteria to 

be comprehensive and generally sound. There are a few 

specific data where I have concerns that EPA should consider 

as described below.

Thank you for your comment. No edits needed.

Reviewer 4 Page 51: I’m very concerned that EPA is still allowing studies 

in which test concentrations were unmeasured as being 

acceptable for WQC derivation. This is particularly 

concerning when they are for one of the four taxa used to 

calculate the criteria. In my opinion, these studies should not 

be included.

The use of unmeasured acute test study results is an acceptable 

approach in the 1985 Guidelines under specific conditions. 

The lack of measured exposure concentrations in an acute 

toxicity test does not invalidate the results if there is a 

demonstration that the material tested is stable during the 

testing period. Only if there were observed solubility problems 

(e.g., precipitant present) would the data be suspect and 

therefore potentially not acceptable.

No edits needed.
31

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 4 Page 68: I agree with EPA’s use of freshwater ACRs to 

supplement the limited marine ACRs for the purpose of 

deriving a final marine ACR. However, I question whether use 

of the ACR for Lampsilis siliquoidea is appropriate. There are 

obviously a number of factors that influence the ACR, but a 

major factor is the life history of the organism and the life 

stage selected for the acute toxicity test used to derive the 

ACR. It seems to me that freshwater mussels have a unique 

life history with no real analog in marine systems (marine 

bivalves have a different life history). Consequently, use of 

this of the ACR for this species to derive a marine ACR seems 

inappropriate. I think use of an ACR for daphnids would be 

more appropriate and representative of the life history of the 

most acutely sensitive taxa in marine systems, the copepod 

Tirgriopus.

Based on peer reviewer comments, calculation of the FACR 

was revised and does not include Lampsilis. The revised 

FACR incorporated data for seven genus-level ACRs and was 

derived from data for marine species and a diversity of 

freshwater species, many of which also have taxonomicallyrelated marine species. ACRs used to derive the FACR 

incorporate data for five freshwater fish species, three 

freshwater invertebrate species (including applicable data for 

daphnids), and two acutely sensitive estuarine/marine mysids.

Section 2.7.3

Section 4.4.2

Section 5.5.1

Section 5.5.2

Reviewer 4 Table 17: Why is the pH 6.0 test for H. azteca excluded? This 

is within the range of test pH values (6.0-9.0) normally 

considered by EPA. Additionally, earlier in the document it 

was stated that hardness was the only water quality parameter 

that mattered for normalizing Cd toxicity data. I disagree with 

that statement, but if EPA is going to argue other water quality 

parameters are not important, then I don’t see how it can then 

exclude data for this reason.

In addition to the pH being below the level accepted by EPA 

for tests (6.5-9.0), Br and Clconcentrations were not provided 

and the dilution water was comprised of well water that was 

significantly diluted from a hardness of 380 mg/L to 15.3 

mg/L (Mackie 1989). The Hyalella memo found in Appendix 

K of the draft criteria document states that "Natural waters 

with hardness less than 80 mg/L typically have <10 mg Cl/L". 

The rationale for the exclusion of this study from the criteria 

derivation was clarified in the document table.

Table 17
32

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 4 Table 18: I agree with EPA’s re-evaluation of the Hyalella 

data and their application of water quality and performance 

criteria for test acceptability. However, I’m concerned about 

the study EPA retained for purposes of criteria derivation for 

several reasons. First, I do not believe use of a 10-d survival 

endpoint constitutes a chronic study as defined in Stephan et 

al. (1985). EPA has excluded a number of other studies from 

use in criteria derivation for this reason (e.g., the 21-d survival 

study on the sea starlet anemone, p. 81) in this document that 

creates a major internal inconsistency. Having said that, it 

could be argued that inclusion of this sub-chronic data is 

warranted given that it is the lowest toxicity value in the data 

set and exclusion of the data would be non-conservative in 

terms of environmental protection (as opposed to including 

sub-chronic data for insensitive species). However, using this 

logic why would the 7-d survival/growth data with the 

fountain darter then be excluded? 

In response to peer reviewers’ comments, a further 

examination of this issue was conducted. Thus, after further 

evaluation, the full-life cycle study by Ingersoll and Kemble 

(2001) was found to satisfy the acceptability criteria for H. 

azteca and was used to replace the 10d study used in the 

previous draft of the document. This change is based on 

consultation with the study author, where it was determined 

that techniques used to measure length data are likely to more 

accurately reflect growth than the originally-reported direct 

weight measurements. Since the original study was conducted, 

this laboratory has developed a robust empirical relationship 

between amphipod length and weight. Applying the formula, 

the 28-d average control length translates into a weight that is

above the minimum control performance values listed in 

Appendix K of the draft criteria document. The average 

control reproduction for this study also met minimum 

performance values. Although the feeding rate used in this test 

was below that recommended for H. azteca, the finding that 

control organisms met the performance criteria of tests using a 

higher feeding rate supports retaining these data for use in 

deriving the AWQC.

Section 3.1.2

Section 5.2.1
33

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 4 My second concern is whether the sensitivity of H. azteca is 

real? Given that these 10-d data come from a 42-d study that 

fails to meet control performance criteria, how does EPA 

know that these animals weren’t already stressed at 10 d and 

inappropriately sensitive? Given both the duration and 

performance issues associated with these data, in my opinion 

they should not be used for WQC derivation. However, I 

strongly encourage EPA to conduct a 28- or 42-d Hyalella

study that meets the necessary performance criteria. Finally, 

after Table 18, EPA has descriptions of each of the chronic H. 

azteca studies and rationale for their rejection but did not 

include a description of the Ingersoll and Kemble study that 

was accepted and the rationale for use of the 10-d survival 

endpoint. This should be added to the document.

Please see response to previous comment. As indicated in the 

response, the full-life cycle study by Ingersoll and Kemble 

(2001) was found to satisfy the acceptability criteria for H. 

azteca and was used to replace the 10d study used in the 

previous draft of the document.

The Agency is interested in obtaining information regarding 

new toxicity tests on H. azteca as noted in the Federal Register 

Notice to be issued announcing the availability of the 2015 

draft cadmium criteria document for public comment.

Section 3.1.2

Section 5.2.1
34

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 5 As noted in the response above, the exclusion of most Hyalella

data is doubtfully justifiable, because the criteria for doing so 

are questionable. However, even with these Appendix K 

criteria as they are, the Ingersoll and Kemble data 

reproductive data should not have been excluded. The 42d 

reproductive endpoint from that test met the Appendix K 

criteria for control survival and brood size (6.35 per female). 

The 28 day endpoint was presumably excluded because of low 

growth as weight. However, the organisms were not weighed, 

but rather lengths were measured and weights were inferred 

from lengths. Regardless, by the stated logic, it would follow 

to exclude the 28-day endpoint with low (estimated) weight. 

But to then pick an acute survival endpoint (10-day) instead of 

the 42-day reproductive endpoint is inexplicable.

The entry for this test in Table 2 is misleading. Saying the test 

was a life cycle test, but then using an acute endpoint, is 

misleading. I estimated the EC20 for reduced reproduction to 

be about 1.2 μg/L using logistic regression, or the MATC 

(geomean of LOEC and NOEC) would be 0.98 μg/L. 

In response to peer reviewers’ comments, a further 

examination of this issue was conducted. Thus, after further 

evaluation, the full-life cycle study by Ingersoll and Kemble 

(2001) was found to satisfy the acceptability criteria for H. 

azteca and was used to replace the 10d study used in the 

previous draft of the document. This change is based on 

consultation with the study author, where it was determined 

that techniques used to measure length data are likely to more 

accurately reflect growth than the originally-reported direct 

weight measurements. Since the original study was conducted, 

this laboratory has developed a robust empirical relationship 

between amphipod length and weight. Applying the formula, 

the 28-d average control length translates into a weight that is

above the minimum control performance values listed in 

Appendix K of the draft criteria document. The average 

control reproduction for this study also met minimum 

performance values. Although the feeding rate used in this test 

was below that recommended for H. azteca, the finding that 

control organisms met the performance criteria of tests using a 

higher feeding rate supports retaining these data for use in 

deriving the AWQC. 

Section 3.1.2

Section 5.2.1
35

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 5 Other specific points on data used or not used. 

Durations of tests

If 30-day tests with salmonids that started with fry consistently 

yield more sensitive results than 60-day tests that started with 

eggs or embryos, why ignore all the shorter, more sensitive 

tests. The Guidance counsels to beware of tests in which 

acclimation probably occurred during resistant states. 

Chapman (1985) recently described this problem. It would 

make more sense to exclude the less sensitive data, rather 

exclude the more sensitive data.

Use of the life cycle (LC) tests over the early life stage (ELS) 

tests in the draft reviewed by the external peer reviewers was 

consistent with the 1985 Guidelines. It was noted that there 

was no consistent pattern of early life stage tests being more 

sensitive than life cycle tests for salmonids 

Subsequently, based upon peer reviewer comments, use of 

sensitive salmonid tests was reconsidered and changes in the 

approach were made for the 2015 draft criteria. Specifically,

ELS tests were used to calculate the revised SMCV in 

instances where they were more sensitive than the LC tests 

(e.g., Salmo trutta).

Section 3.1.2

Section 5.2.2

Appendix C

Reviewer 5 Likewise with Mottled Sculpin, there’s doubtfully anything 

special about 28-day exposures over 21-day exposures. Besser 

et al. (2007) ran two tests, one 28-day and one 21-day test. 

The 28-day was less sensitive, and it was used with the other 

ignored. There is no established ASTM protocol for Mottled 

Sculpin, and the ASTM (1998) mention of “28 to 120-day 

(depending on species) continuous exposure” tests for earlylife stage tests refers back to their species-specific appendices. 

The SMCV/GMCV for the most sensitive fish species, Cottus 

bairdii, is from the results of one 28-d ELS test (Besser et al. 

2007). The other study reported in the same paper, a 21-d ELS 

study, was not used quantitatively for the criteria derivation 

because there is a lack of guidance on the most appropriate 

duration for ELS tests with this species. U.S. EPA and ASTM 

guidance implies that ELS tests should last at least 28 days, so 

these data were not added to Appendix C. However, it is 

noteworthy that incorporating these data would only change 

the CCC slightly; the SMCV would change from 1.721 to 

1.470 μg/L, and the criteria would only change by onehundredth of a microgram, from 0.80 to 0.79 μg/L total 

cadmium. 

Section 5.2.2

Reviewer 5 Other data

(Calfee et al. 2014) and (Wang et al. 2014) report acute and 

chronic data with White Sturgeon and Rainbow Trout. The 

same data are reported in Environmental Toxicology and 

Chemistry, but Wang is paywalled, so I would use the open 

access USGS report version.

The cited papers were reviewed and the additional acceptable 

data were added to the appropriate tables and appendices.

Appendix A

Appendix C

Table 7

Table 20

Sections 5.1 

Section 5.8.1
36

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 3

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 5 An acute test with Mottled Sculpin, (Cottus bairdi) and Cd 

was attributed to Mebane et al. (2012). We tested Shorthead 

Sculpin, Cottus confusus.

This was an error. The species name will be corrected, as 

appropriate.

Various locations
37

2.4 CHARGE QUESTION 4

4. Are the derived criteria appropriately protective of listed species and commercially and recreationally important species, particularly as the 

criteria relates to salmonids?

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 1 I agree with the author that marine animals are less at risk than 

freshwater animals, and this is primarily due to the strong 

chloro-complexation of Cd in seawater, thereby reducing the 

bioavailability of Cd. Consequently, marine bioconcentration 

factors are often 1-2 orders of magnitude higher in freshwater.

Thank you for your comment. No edits needed.

Reviewer 1 I also agree that plants (e.g., phytoplankton) are less sensitive 

to Cd than animals, and thus it is appropriate to focus on the 

animals.

Thank you for your comment. No edits needed.
38

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 1 I think that the criteria that the author generated for dissolved 

Cd have taken into consideration many of the key issues 

influencing this (e.g., water hardness) are probably ok, but by 

missing the effects of dietary Cd, the report is missing a large 

part of the overall story. This is not to suggest that ambient Cd 

concentrations are unsafe for animals, but the derived criteria 

are probably over-estimates of the safe levels of Cd.

Text has been added to discuss dietary exposure and 

incorporate the work of other researchers, such as Mebane 

(2006), who discuss cadmium bioaccumulation and dietary 

exposure in detail and the uncertainties currently associated 

with its evaluation. In particular, text was added to detail how 

cadmium can bioaccumulate in aquatic organisms through 

multiple exposure routes including ingestion and direct 

exposure, and how total uptake depends on the cadmium 

concentration, exposure route and the duration of exposure.

Text was also added to clarify that there does not appear to be 

a consistent relationship between body burden and 

toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.

Section 5.6.1

Reviewer 1 Another complicating issue is the influence of dissolved 

organic carbon and its effect on Cd bioavailability. Thus, 

expressing Cd toxicity as a function of body burden is 

appropriate; the caveats associated with this approach have 

been appropriately discussed in the report.

EPA revised the text to indicate that in addition to hardness, 

which is a critical factor in determining toxicity, other water 

quality parameters such as DOC, alkalinity, and pH may also 

influence cadmium toxicity. EPA notes that integrating DOC 

into the analysis would be expected in most cases to make the 

criteria less stringent. Thus, while recognizing the need to 

consider the applicability of the BLM in future cadmium 

criteria updates, which would incorporate DOC, the inclusion 

of DOC in a BLM would be unlikely to make the criteria more 

stringent or conservative.

Section 2.3.1

Section 2.5

Section 5.1.3
39

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 2 Salmonids are clearly one of the more sensitive species with 

regard to Cd toxicity. Not only are they very sensitive, they 

are commercially important, and possess several species that 

are listed as endangered and threatened in the US. The 

proposed criteria are appropriate for freshwater conditions 

since many of the studies used to derive the criteria focused on 

freshwater treatments to rainbow trout. However, only one 

study evaluated Cd toxicity in coho salmon smolts in saltwater 

conditions, and this was at nearly full seawater strength (28 

ppth). Of concern is the fact that many salmonids including 

strains of O. mykiss (steelhead) are anadromous and often 

come in contact with Cd at lower salinities (5-15 ppth). While 

the agency should be applauded for normalizing toxicity to 

hardness to improve freshwater criteria, there is a critical need 

to understand the impacts of salinity on Cd toxicity 

particularly in anadromous salmonid species. Of additional 

concern is the lack of discussion of sublethal impacts of Cd 

particularly to olfaction (Williams and Gallagher 2013) which 

significantly alters return rates of salmon (Baldwin et al. 

2009). Return metrics are population level endpoints that 

should supersede standard repro/survival/growth. These 

should also be topics of discussion with regard to uncertainty. 

Additional acceptable estuarine/marine toxicity data were not 

available for salmonids. Additional text (and references) was 

added to the appropriate uncertainty sections to emphasize the 

absence of these data.

Section 5.4.1

Section 5.5.2

Reviewer 2 Lastly, the issue of climate change is largely missing from the 

document. Acidification (particularly with metal availability) 

and temperature issues are also likely to impact sensitive 

species (e.g. salmonids). Sea level rise will also cause 

saltwater intrusion into salmonid spawning habitats and affect 

“estuarine/marine” criteria. Evaluation of these stressors 

should be focal points for future criteria assessment 

particularly for salmonids. Overall, while the values for 

freshwater are likely safe for salmonids, the values for 

estuarine/marine are highly uncertain and deserve further 

evaluation.

Thank you for your comment. EPA revises the criteria 

documents based on the best available scientific information at 

the time of development and based on current conditions in 

the environment. Criteria documents are then periodically

revised to incorporate the latest scientific information based 

on toxicity and consideration of applicable environmental 

conditions.

No edits
40

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 3 This seems to be the case if we assume that only aqueous 

exposures matter. Evidence for dietary toxicity is less 

compelling than for invertebrates, so for these fish species, the 

criteria are likely more protective for these species than they 

are for invertebrates. 

EPA concurs with the reviewer about the difficulty of

characterizing dietary exposure and establishing critical tissue 

effects thresholds for bioaccumulated metals. 

Text has been added to discuss dietary exposure and 

incorporate the work of other researchers, such as Mebane 

(2006), who discuss dietary exposure and cadmium 

bioaccumulation in detail and the uncertainties currently 

associated with its evaluation. In particular, text was added to 

detail how cadmium can bioaccumulate in aquatic organisms 

through multiple exposure routes including ingestion and 

direct exposure, and how total uptake depends on the 

cadmium concentration, exposure route and the duration of 

exposure. Text was also added to clarify that there does not 

appear to be a consistent relationship between body burden 

and toxicological effect, and an acceptable tissue effect 

concentration cannot be defined for aquatic life at this time. 

Bioaccumulation and effect level data that are available 

indicate that cadmium is unlikely to accumulate in tissue to 

levels that would result in adverse effects to aquatic 

invertebrates or fish at the calculated chronic criterion 

concentrations. For this reason, the evaluation of direct 

exposure effects to organisms via water is considered 

applicable to the development of criteria that is protective of 

aquatic life.

Section 5.6.1
41

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 4 Yes, I think the criteria as derived will be protective of 

salmonids. However, I’m concerned about the exclusion of the 

fountain darter data from the derivation. EPA argues that the 

acute data should be excluded because the test was fed and 

that the chronic data should be excluded because the study 

was only 7 d in duration (i.e., not true chronic). Generally, I 

agree with both of these decisions, but from my perspective, 

these rules are in place to prevent the inclusion of data 

indicating organisms are insensitive due to inappropriate test 

conditions (i.e., food reducing metal bioavailability, short test 

durations missing sensitive endpoints). However, this is not 

the case with the darter data, which indicate this species is 

very sensitive despite test conditions that would tend to reduce 

their sensitivity. EPA also seems to infer (p. 86) that the 

fountain darter data has limited applicability because this 

species has a limited distribution. However, the genus 

Etheostoma is widespread throughout central and eastern U.S. 

with a number of listed species at both the state and federal 

level. Hence these data a representative for a genus that is 

under considerable threat. Given this, I think it would be 

important to assess how inclusion of these data would impact 

derivation of the freshwater Cd WQC.

Text has been added to clarify that data eliminated were not 

used in criteria derivation because the test organisms were fed 

and the duration was too long for an acute test and too short 

for a true ELS test. EPA also added text indicating the genus 

Etheostoma is widespread, with some of species representing 

those of special concern. It is important that states evaluate the 

potential occurrence of these species when establishing sitespecific standards. 

Section 5.8.1

Section 5.8.2
42

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 4 Page 87: I don’t think the statement that dividing the LC50 by 

two is expected to result in a concentration with effects no 

different than the control is correct. Dividing the LC50 by two 

will result in an “LC-low”. I agree that across a range of 

species and toxicants, dividing by two equates to a values that 

approximates the NOEC. However, it does not equate to an 

LC0, which is inferred by this statement. Please clarify.

Dividing the FAV by a factor of two to derive a CMC is the 

standard approach used by the Agency to derive its 304(a) 

acute criterion recommendations, consistent with the 1985 

Guidelines. The FAV is a statistical estimate of the 5th 

percentile of a set of LC50s. The LC50 is defined as the 

concentration that kills 50% of the exposed organisms. Thus, 

by definition, the FAV, as defined in the 1985 Guidelines, is a 

concentration that would be lethal to 50% of organisms with a 

sensitivity greater than 95% of genera. Since the FAV is a 

concentration that may affect 50 percent of the 5th percentile 

or 50 percent of a sensitive species, this value cannot be 

considered to be protective of that percentile or that species. 

Therefore, per the 1985 Guidelines, to derive the CMC EPA 

divides the FAV by a factor of 2 with the intention of defining 

a concentration that will not affect the majority of organisms. 

The rationale for adjusting the FAV to derive the CMC is 

explained in item 6 on page 17 of the 1985 Guidelines. The 

basis for this adjustment factor is an analysis of data from 219 

acute toxicity tests showing that the mean concentration lethal 

to 0-10% of the test population was 0.44 times the LC50 or the 

LC50 divided by 2.27. The data and analysis on which the 

2.27 value is based is described in the Federal Register on 

May 18, 1978 (43 FR 21506-21518). Best professional 

judgment was used to round the FAV “adjustment factor” of 

2.27 to 2 in revisions of the Guidelines that occurred 

subsequent to the 1987 Federal Register notice. The use of the 

factor became final EPA guidance in the 1985 Guidelines.

Section 5.1.3
43

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 5 Not necessarily, although to definitively answer this would 

take a considerably more thorough review to determine than 

was presented in the document, or could be done 

independently in the time available. I note that NMFS (2012) 

in Oregon concluded the 2001 CMC of 2.0 μg/L could 

jeopardize some salmonids and that the CCC of 0.25 μg/L 

would not jeopardize listed salmonids under their prevue. 

Thus the draft 2015 criterion of 2.2 μg/L would presumably be 

a concern. Conversely, NMFS (2011) concurred with EPA 

that Idaho acute and chronic criteria of 1.34 and 0.55 μg/L 

respectively would not jeopardize listed anadromous 

salmonids. I did not attempt to reconcile the three documents. 

However, I think part of the discrepancies may be in the 

manner of analyses. In the draft document, data from longterm exposures to salmonids that began with sensitive fry life 

stage are excluded in favor of data from tests that began with 

eggs or alevins. While all fish have some life stage-sensitivity 

interaction, with at least salmonids sensitivity increases with 

size up to at least 0.4g ww, and maybe up to 1g or more 

(Hansen et al. 2002; Mebane et al. 2012). With other fish, the 

newly hatched stage may be more sensitive, or life events such 

as the onset of exogenous feeding may be related to a stressful 

and sensitive stage (Wang et al. 2014).

Use of the life cycle (LC) tests over the early life stage (ELS) 

tests is consistent with the 1985 Guidelines. Furthermore, 

there is no consistent pattern of early life stage tests being 

more sensitive than life cycle tests for salmonids However, to 

account for this discrepancy, ELS tests were used to calculate 

revised SMCV in instances where they were more sensitive 

than the LC tests (e.g., Salmo trutta).

Section 3.1.2

Section 5.2.2
44

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 5 There are some instances of inappropriate averaging using 

resistant life stages. Bull trout at the most sensitive (~1g) were 

averaged with results of test with yearling brook trout to 

produce a nonsense genus mean acute value of 126 μg/L.

Stephan et al. advise against pooling species mean values 

when they differ by more than a factor of 10; these differed by 

a factor of 1000X.

This issue was re-examined ion depth based on the peer 

reviewer’s comments. The SMAVs for bull trout and brook 

trout do differ by more than a factor of 10 (factor of 708X), 

most likely due the different sensitivities of the fish used to 

initiate the tests. The freshwater and estuarine/marine acute 

databases also include several genera where two or more 

widely different SMAVs (>10x factor) are available for 

estimating the GMAV. In this case the 1985 Guidelines 

recommend that some or all of the values probably should not 

be used in calculations. To resolve this issue, only the more 

sensitive SMAV (primarily due to a more sensitive life stage 

tested) was used to calculate the GMAV, thereby ensuring 

protection of the genus. It is important to note that the FAV 

can be lowered to protect the most sensitive SMAV for a 

commercially or recreationally important species to be 

conservative. This was the case for the acute freshwater value 

for both the 2001 AWQC and the current 2015 draft criteria 

update.

Table 7

Table 10

Section 5.1.3

Section 5.4.1
45

Reviewer External Peer Reviewer Comments Regarding Charge 

Question 4

EPA Response Revision 

Location in 2015 

Draft Cadmium 

Criteria 

Document

Reviewer 5 The draft document evaluates protection of listed species by 

rolling up species data to a hardness-normalized species mean 

acute value (SMAV) and comparing that with the criteria. 

Because the accuracy of hardness-normalization is uncertain, 

but the criteria values can be calculated with certainty for any 

hardness, a more informative way to evaluate the data with 

listed species is to compare the criteria values for the 

conditions of each test of interest with listed species to the 

effects magnitude of effects to listed species at a given criteria. 

If the test concentrations causing an adverse effect are close to 

criteria concentrations, such as if the EC50s were within a 

factor of 2 (or maybe 2.5 to 3 to be on the safe side), then 

evaluate the actual adverse effects observed at the criteria 

concentrations. The SMAV approach involves a lot of data 

manipulation and may lose sensitive life stages or strains.

The criteria document provides the available toxicity data for 

listed species. A separate document is in development that 

addresses the detailed analyses of protection of Listed 

salmonid species. Additionally, states and tribes have the 

opportunity to use the toxicity data provided in this document, 

as appropriate, to their address their specific situation.

Section 5.8
46

2.5 OTHER COMMENTS PROVIDED

Reviewer Comments EPA Response Revision 

Location

Reviewer 4 Additional Minor Comments

Page 11: Note that Cd does not form complexes with Ca as 

stated, but rather competes with Ca for uptake and Ca 

channels. Please correct.

Text was revised as suggested. Section 2.3

Reviewer 4 Page 11: While Atli and Canli did observe a reduction in NKA 

activity in their study, it's a significant overstatement to say 

disruption of Na homeostasis is a mechanism of action for Cd. 

To the best of my knowledge, it hasn’t been observed in any 

other study that has investigated this potential mechanism.

Text was revised as suggested. Section 2.3

Reviewer 4 Page 11: If Cd inhibits catalase, glutathione reductase, SOD, 

etc., it seems to me this is direct inhibition of anti-oxidant 

processes, not indirect as stated.

Text was revised as suggested. Section 2.3

Reviewer 4 Page 12: Regarding the relationship between Cd tissue 

burdens and toxicity, see also the analysis by Adams et al. 

(2011).

EPA recognizes the difficulty in characterizing dietary 

exposure and establishing critical tissue effects thresholds 

associated with bioaccumulated metals (the identified paper 

has been reviewed and text has been added to the document). 

Section 5.6.1

Reviewer 4 Page 50: Tigriopus is a copepod, not a mysid, as indicated in 

the second paragraph.

Text was revised as suggested. Section 3.2.1

Reviewer 4 Page 58: Please specific at the top of p. 58 which two 

freshwater ACRs were used in the calculation of the marine 

ACR.

Text was revised to be clearer in the selection of ACRs used to 

calculate the FACR.

Section 3.2.2

Section 5.5.1

Reviewer 4 Table 18: Change the test duration for the Borgmann studies 

to 42 d rather than 6 w to make the units consistent with the 

rest of the table.

Text was revised as suggested. Table 18

Reviewer 4 Page 83: It should be mentioned that both BCFs and BAFs are 

inversely related to exposure concentration which explains 

much of the variation in BCFs/BAFs (McGeer et al. 2003, 

DeForest et al. 2007).

Text was revised as suggested. Section 5.6
47

Reviewer Comments EPA Response Revision 

Location

Reviewer 4 Table 21: Taking a final look through Table 21 I note that 

EPA has included several species that are not resident to N. 

America (Oreochromis spp., Danio rerio, Xenopus laevis). 

Unless this requirement has changed, they should be removed 

from the data set.

Naturally/wild reproducing North American species 

populations are considered for inclusion in the document. 

Each has been verified as such. Please see the following links 

for the species mentioned:

http://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=67

http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=505

http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=468

http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=466

No edits

Reviewer 5 Unfortunately, the compressed time period for this review (2 

weeks, which works out to several hours on evenings and 

weekends for volunteer reviewers), makes a comprehensive 

review of a document of this length and complexity infeasible.

Thank you for your comment. EPA appreciates the comments 

that were provided during the time available for review.

No edits
48

3 REFERENCES CITED BY REVIEWERS

Adams, W.J., R. Bluet, K. V. Brix, D. K. DeForest, A. S. Green, J. S. Meyer, J. C. McGeer, P. R. Paquin, P. 

S. Rainbow and C. M. Wood (2011). "Utility of tissue residues for predicting effects of metals on aquatic 

organisms." Integr. Environ. Assess. Manag. 7(1): 75-98.

ASTM. 1998. Standard guide for conducting early life-stage toxicity tests with fishes. Method E1241-98. 

Pages 29 in Annual Book of ASTM Standards, volume 11.04. American Society for Testing and Materials, 

West Conshohocken, PA.

Baldwin, DH, Spromberg, JA, Collier, TK and NL Scholz. 2009. A fish of many scales: extrapolating 

sublethal pesticide exposures to the productivity of wild salmon populations. Ecological Applications 

19:2004-2015.

Barata, C., D. J. Baird, S. E. Mitchell, and A. M. V. M. Soares. 2002. Among- and within-population 

variability in tolerance to cadmium stress in natural populations of Daphnia magna: implications for 

ecological risk assessment. Environ. Toxicol. Chem. 21:1058-1064.

Barata, C., S. J. Markich, D. J. Baird, and A. M. V. M. Soares. 2002. The relative importance of water and 

food as cadmium sources to Daphnia magna Straus. Aquat. Toxicol. 61:143-154.

Besser, JM, Mebane, CA, Mount, DR, Ivey, CD, Kunz, JL, Greer, EI, May, TW, and Ingersoll, CG. 2007. 

Relative sensitivity of mottled sculpins (Cottus bairdi) and rainbow trout (Oncorhynchus mykiss) to toxicity 

of metals associated with mining activities. Environ Toxicol Chem 26:1657–1665.

Buchwalter, D. B., D. J. Cain, C. A. Martin, L. Xie, S. N. Luoma, and T. Garland, Jr. 2008. Aquatic insect 

ecophysiological traits reveal phylogenetically based differences in dissolved cadmium susceptibility. Proc. 

Nat. Acad. Sci. 105:8321-8326.

Buchwalter, D. B., D. J. Cain, W. H. Clements, and S. N. Luoma. 2007. Using biodynamic models to 

reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects. Environ. 

Sci. Technol. 41:4821-4828.

Cain, D. J., S. N. Luoma, and W. G. Wallace. 2004. Linking metal bioaccumulation of aquatic insects to their 

distribution patterns in a mining-impacted river. Environ. Toxicol. Chem. 23:1463-1473.

Calfee, RD, Little, EE, Puglis, HJ, Beahan, E, Brumbaugh, WG, and Mebane, CA. 2014. Acute Sensitivity of 

White Sturgeon (Acipenser transmontanus) and Rainbow Trout (Oncorhynchus mykiss) to Cadmium, Copper, 

or Zinc in Laboratory Water-Only Exposure. Pages 5-34 in Ingersoll, CG, and Mebane, CA, editors. Acute 

and chronic sensitivity of white sturgeon (Acipenser transmontanus) and rainbow trout (Oncorhynchus 

mykiss) to cadmium, copper, lead, or zinc in laboratory water-only exposures. U.S. Geological Survey 

Scientific Investigations Report 2013–5204.

Chapman, GA. 1985. Acclimation as a factor influencing metal criteria. Pages 119–136 in Bahner, RC, and 

Hansen, DJ, editors. Aquatic Toxicology and Hazard Assessment: Eighth Symposium (STP 891-EB), volume 

STP 891. American Society for Testing and Materials (ASTM), Philadelphia.

Cooper, WE. 1965. Dynamics and production of a natural population of a fresh-water amphipod, Hyalella 

azteca. Ecol Monogr 35:377-394.
49

Croteau, M.-N., L. Hare, and A. Tessier. 2003. Difficulties in relating Cd concentrations in the predatory 

insect Chaoborus to those of its prey in nature. Can. J. Fish. Aquat. Sci. 60:800-808.

DeForest, D. K., K. V. Brix and W. J. Adams. 2007. "Assessing metal bioaccumulation in aquatic 

environments: the inverse relationship between bioaccumulation factors, trophic transfer factors and exposure 

concentration." Aquat. Toxicol. 84: 236-246.

France, RL. 1996. Biomass and production of amphipods in low alkalinity lakes affected by acid 

precipitation. Environ Pollut 94:189-193.

Gibbons, WN, and Mackie, GL. 1991. The relationship between environmental variables and demographic 

patterns of Hyalella azteca (Crustacea: Amphipoda). J N Am Benthol Soc 10:444-454.

Hansen, JA, Welsh, PG, Lipton, J, Cacela, D, and Dailey, AD. 2002. Relative sensitivity of bull trout 

(Salvelinus confluentus) and rainbow trout (Oncorhynchus mykiss) to acute exposures of cadmium and zinc. 

Environ Toxicol Chem 21:67–75.

Hare, L., A. Terrier, and L. Warren. 2001. Cadmium accumulation by invertebrates living at the sedimentwater interface. Environ. Toxicol. Chem. 20:880-889.

Hare, L., A. Tessier, and U. Borgmann. 2003. Metal sources for freshwater invertebrates: pertinence for risk 

assessment. Human Ecol. Risk Assessment 9:779-793.

Irving, E. C., D. J. Baird, and J. M. Culp. 2003. Ecotoxicological responses of the mayfly Baetis tricaudatus

to dietary and waterborne cadmium: implications for toxicity testing. Environ. Toxicol. Chem. 22:1058-1064.

Klaassen, C. D., J. Liu, and S. Choudhuri. 1999. Metallothionein: An intracellular protein to protect against 

cadmium toxicity. Annu. Rev. Pharmacol. Toxicol. 39:267-294.

Luoma, S. N. and J. L. Carter. 1991. Effects of trace metals on aquatic benthos, pp. 261-300 In M. C. 

Newman and A. W. McIntosh (eds.), Metal Ecotoxicology Concepts & Applications. Lewis Publishers, Inc., 

Chelsea, Michigan.

Luoma, S. N. and P. S. Rainbow. 2005. Why is metal bioaccumulation so variable? Biodynamics as a 

unifying concept. Environ. Sci. Technol. 39:1921-1931.

Luoma, S. N., D. J. Cain, and P. S. Rainbow. 2009. Calibrating Biomonitors to Ecological Disturbance: a 

New Technique for Explaining Metal Effects in Natural Waters. Integrated Environmental Assessment and 

Management 6:199-209.

Martin, C. A., D. J. Cain, S. N. Luoma, and D. B. Buchwalter. 2007. Cadmium ecophysiology in seven 

stonefly (Plecoptera) species: Delineating sources and susceptibility. Environ. Sci. Technol. 41:7171-7177.

McGeer, J.C., K.V. Brix, J.M. Skeaff, D.K. DeForest, S.I. Brigham, W.J. Adams and A.S. Green. 2003. "The 

inverse relationship between bioconcentration factor and exposure concentration for metals: implications for 

hazard assessment of metals in the aquatic environment." Environ. Toxicol. Chem. 22(5): 1017-1037.

McNulty, EW, Dwyer, FJ, Ellersieck, MR, Greer, EI, Ingersoll, CG, and Rabeni, CF. 1999. Evaluation of 

ability of reference toxicity tests to identify stress in laboratory populations of the amphipod Hyalella azteca. 

Environ Toxicol Chem 18:544-548.
50

Mebane, CA, Dillon, FS, and Hennessy, DP. 2012. Acute toxicity of cadmium, lead, zinc, and their mixtures 

to stream-resident fish and invertebrates. Environ Toxicol Chem 31:1334–1348.

Mebane, CA. 2010. Relevance of risk predictions derived from a chronic species-sensitivity distribution with 

cadmium to aquatic populations and ecosystems. Risk Anal 30:203-223.

Poteat, M. D. and D. B. Buchwalter. 2014. Calcium uptake in aquatic insects: influences of phylogeny and 

metals (Cd and Zn). J. Exp. Biol. 217:1180-1186.

Poteat, M. D. and D. B. Buchwalter. 2014. Four reasons why traditional metal toxicity testing with aquatic 

insects is irrelevant. Environ. Sci. Technol. 48:887-888.

Poteat, M. D. and D. B. Buchwalter. 2014. Phylogeny and Size Differentially Influence Dissolved Cd and Zn 

Bioaccumulation Parameters among Closely Related Aquatic Insects. Environ. Sci. Technol. 48:5274-5281.

Poteat, M. D., M. Diaz-Jaramillo, and D. B. Buchwalter. 2012. Divalent metal (Ca, Cd, Mn, Zn) uptake and 

interactions in the aquatic insect Hydropsyche sparna. J. Exp. Biol. 215:1575-1583.

Stephan, C. E., D. I. Mount, D. J. Hansen, J. H. Gentile, G. A. Chapman and W. A. Brungs. 1985. Guidelines 

for deriving numerical national water quality criteria for the protection of aquatic organisms and their uses. 

Duluth, U.S. Environmental Protection Agency, Environmental Research Laboratory: 98 pp.

Stephan, CE, Mount, DI, Hansen, DJ, Gentile, JH, Chapman, GA, and Brungs, WA. 1985. Guidelines for 

deriving numerical national water quality criteria for the protection of aquatic organisms and their uses. U.S. 

Environmental Protection Agency, EPA 822-R-85-100, NTIS PB85 227049, Duluth, Narragansett, and 

Corvallis. 

Strong, DR, Jr. 1972. Life history variation among populations of an amphipod (Hyalella azteca). Ecology 

53:1103-1111.

Szczerbik, P, Mikolajczyk, T, Sokolowska-Mikolajczyk, M, Socha, M, Chyb, J and P. Epler. 2006. Influence 

of long-term exposure to dietary cadmium on growth, maturation and reproduction of goldfish (subspecies: 

Prussian carp Carassius auratus gibelio B.) Aquatic Toxicology 77:126-135.

Thomann, RV, Shkreli, F. and S. Harrison. 1997. A pharmacokinetic model of cadmium in rainbow trout. 

Environmental Toxicology and Chemistry 16:2268-2274.

Timmermans, K. R., E. Spijkerman, and M. Tonkes. 1992. Cadmium and zinc uptake by two species of 

aquatic invertebrate predator from dietary and aqueous sources. Can. J. Fish. Aquat. Sci. 49:655-662.

Vetillard, A. and T. Bailhache. 2005. Cadmium: An endocrine disrupter that affects gene expression in the 

liver and brain of juvenile rainbow trout. Biology of Reproduction 72:119-126.

Wallace, W. G., B.-G. Lee, and S. N. Luoma. 2003. The subcellular compartmentalization of Cd and Zn in 

two bivalves. I. The significance of metal-sensitive fractions (MSF) and biologically-detoxified metal (BDM). 

Mar. Ecol. Prog. Ser. 249:183-197.
51

Wang, N, Ingersoll, CG, Dorman, RA, Kunz, JL, Hardesty, DK, Brumbaugh, WG, and Mebane, CA. 2014. 

Chronic Sensitivity of White Sturgeon (Acipenser transmontanus) and Rainbow Trout (Oncorhynchus 

mykiss) to Cadmium, Copper, or Zinc in Laboratory Water-Only Exposure. Pages 35-76 in Ingersoll, CG, and 

Mebane, CA, editors. Acute and chronic sensitivity of white sturgeon (Acipenser transmontanus) and rainbow 

trout (Oncorhynchus mykiss) to cadmium, copper, lead, or zinc in laboratory water-only exposures. U.S. 

Geological Survey Scientific Investigations Report 2013–5204.

Wanty, RB, Verplanck, PL, San Juan, CA, Church, SE, Schmidt, TS, Fey, DL, DeWitt, EH, and Klein, TL. 

2009. Geochemistry of surface water in alpine catchments in central Colorado, USA: Resolving host-rock 

effects at different spatial scales. Appl Geochem 24: 600-610.

Wendelaar Bonga, SE, and Lock, RAC. 2008. The osmoregulatory system. Pages 401-416 in Di Giulio, RT, 

and Hinton, DE, editors. Toxicology of Fishes. CRC Press, Boca Raton, Florida.

Williams CR and EP Gallagher. 2013. Effects of cadmium on olfactory mediated behaviors and molecular 

biomarkers in coho salmon (Oncorhynchus kisutch) Aquatic Toxicology 140-141:295-302.

Xie, L. and D. B. Buchwalter. 2011. Cadmium exposure route affects antioxidant responses in the mayfly 

Centroptilum triangulifer. Aquat. Toxicol. 105:199-205.

Xie, L. T., D. Lambert, C. Martin, D. J. Cain, S. N. Luoma, and D. Buchwalter. 2008. Cadmium biodynamics 

in the oligochaete Lumbriculus variegatus and its implications for trophic transfer. Aquat. Toxicol. 86:265-

271.

Xie, L., D. H. Funk, and D. B. Buchwalter. 2010. Trophic transfer of Cd from natural periphyton biofilms to 

the grazing mayfly Centroptilum triangulifer in a life cycle test. Environmental Pollution. 158:272-277.