United States Office of Water EPA-822-R-98-007
Environmental Protection 4304 September 1998
Agency
&EPA Report on the Peer
Consultation Workshop on
Selenium Aquatic Toxicity
and Bioaccumulation
-------
nil ill. .IN in ii
lull
-------
REPORT ON THE
PEER CONSULTATION WORKSHOP ON
SELENIUM AQUATIC TOXICITY AND BlOACCUMULATION
September 1998
Office of Water
U.S-. Environmental Protection Agency
Washington, DC
-------
-------
' • •• ' . NOTE ,
This report was prepared by Eastern Research Group, inc., a contractor to the U.S.
Environmental Protection Agency (EPA), as a general record of discussion during the peer
consultation workshop. As requested by EPA, this report captures the main.points of scheduled
presentations and discussions, and a summary of comments offered by observers attending the
workshop; the report is not a complete record of all details discussed, nor does it embellish,
interpret, or enlarge .upon matters that were-incomplete or unclear. This report will be used by
EPA as an early scientific assessment of technical issues associated with selenium aquatic
toxicology and bioaccumulation and will serve as a technical resource during EPA's review of
freshwater selenium aquatic life criteria. The information in this document does not necessarily
reflect the policy of the U.S. Environmental Protection Agency and no official endorsement
.should be inferred. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
ACKNOWLEDGMENTS
This document summarizes the proceedings and presentations made at a 2-day workshop
sponsored by the U.S. Environmental Protection Agency (EPA) to discuss selenium aquatic
toxicology and bioaccumulation. The meeting was chaired by Anne Fairbrother of ecological
planning and tofxicity, inc., who wrote the overall meeting summary section and led one of the
--discussion-sessions. Other discussion leaders included William, Adams (Kennecott Utah Copper
Corporation), Steven Hamilton (U.S. Geological Survey) and William Van Derveer (Colorado
Springs Utilities). Technical presentations were made by A. Dennis Lemly (Virginia Tech
University) and George Bowie (Tetra Tech, Inc.). Keith Sappington of EPA's Office of Water
served as the Work Assignment Manager for this task. Kate Schalk, Rebekah Lacey, Lauren
Lariviere, and Beth O'Connor of Eastern Research Group provided support services to plan arid
coordinate the workshop and prepare a summary report for task 98-09 under EPA Contract No.
68-D5-0028.
OBTAINING COPIES OF THIS DOCUMENT
Copies of this document may be obtained by contacting the U.S.-EPA, National Center for ,
Environmental Publications and Information (NCEPI), 11029 Kenwood Road, Cincinnati, Ohio,
45242, phone (513) 489-8190. In addition, the document will soon be published on the world
wide web at http://www.epa.gov/ost/selenium. " • ' , ' -
-------
-------
CONTENTS
PREFACE .................... -. :. ..ii
I. INTRODUCTION 1
, Background , * 1
Summary of Opening Remarks .......... 2
Opening Presentations ....'. 3
; Chair's Charge to the Experts and Highlights of Premeeting Comments A .... 8
II. CHAIR'S SUMMARY OF WORKSHOP DISCUSSIONS ............................ 9
III. TECHNICAL DISCUSSION SESSIONS ............:........................:... 14
DISCUSSION SESSION 1:
Technical Issues Associated With a Water-Column-Based Chronic Criterion 14
DISCUSSION SESSION 2:
Technical Issues Associated With a Tissue-Based Chronic Criterion 23
DISCUSSION SESSION 3: -= .
Technical Issues Associated With a Sediment-Based Chronic Criterion .........: 31
DISCUSSION SESSION 4: . ,
Cross-Cutting Issues Associated With a Chronic Criterion ... 39
rv. OBSERVER COMMENTS ... .: ;• 52
V. REFERENCES '..,.55
APPENDIX A Workshop Materials
APPENDDCB Technical Charge to Experts and Background Materials
•- - ',-••• • . f
. APPENDIX C Premeeting Comments
APPENDDCD ' Additional References Provided by Experts
APPENDDCE - Presentation Materials
APPENDIX F Observer Presentations '
-------
PREFACE
Under section 304(a) of the Clean Water Act, the U.S. Environmental Protection Agency (EPA)
publishes ambient water quality criteria which serve as guidance to States and Tribes for setting
enforceable water quality standards. Water quality standards form the basis for establishing
pollutant discharge limits under the National Pollutant Discharge Elimination System (NPDES)
and for setting Total Maximum Daily Loads (TMDLs). Given the importance of 304(a) criteria
to the regulation of pollutant discharges to the Nation's waters, these criteria must be reviewed
and revised periodically to reflect the latest scientific information.
Selenium is one chemical for which 304(a) aquatic life criteria have been derived, but which is
currently undergoing review by EPA. Selenium exhibits a number of chemical and toxicological
properties that complicate the derivation of numeric aquatic life criteria. Among these are: (1) its
existence in at least four different oxidation states in the aquatic environment, (2) its propensity
to bioaccumulate in aquatic food webs, and (3) its ability to convert between different chemical
forms.
On May 27 and 28,1998, EPA sponsored a workshop entitled: Peer Consultation Workshop on
Selenium Aquatic Toxicity and Bioaccumulation. The goal of this peer consultation was to
obtain early assessment of the state of the science on various technical issues associated with
deriving aquatic life criteria for selenium. This document presents the proceedings from this
•workshop and is considered by EPA to be a valuable technical resource for future refinement of
EPA's aquatic life criteria for selenium.
n
-------
I. INTRODUCTION
Background
Selenium, a metalloid that is released.to water'from both natural and anthropogenic sources, can
be highly toxic to aquatic life at relatively low concentrations. Selenium is also an essential trace
nutrient for many aquatic and terrestrial species. Derivation of aquatic life criteria for selenium
is complicated by its complex biogeochemistry in the aquatic environment. Specifically,
selenium can exist in several different oxidation states in water, each with varying toxicities, and
can undergo biotransformations between inorganic and organic forms. The biotransformation of
selenium can significantly alter its bioavailability and toxicity to aquatic organisms. Selenium
also has been shown to bioaccumulate in aquatic food webs, which makes dietary exposures to
selenium a significant exposure pathway for aquatic organisms. ••
The most recent aquatic criteria for selenium were derived by the U.S. Environmental Protection
Agency (EPA) in 1987. At the time of their publication, these criteria could not be conveniently
adjusted to account for the combined toxicities of different selenium forms. Since then, a
substantial body of literature has accumulated on the aquatic toxicity of different selenium forms
(in combination and in isolation). In response to this and other new information, EPA has
initiated an effort to evaluate and revise acute and chronic aquatic life criteria, and site-specific
criteria guidelines for selenium. • .
) . . f
As part of this effort, EPA sponsored a Peer Consultation Workshop on Selenium Aquatic
Toxicity and Bioaccumulation ori May 27-28,1998. This workshop brought together nine
experts on the aquatic chemistry and biology of selenium to discuss technical issues underlying
the freshwater aquatic life chronic criterion. The discussion among the experts was guided by
questions posed in a technical charge written by EPA. While focusing on issues related to the
chronic criterion, the charge also touched on technical questions pertinent to acute criteria,
wildlife criteria, and site-specific criteria guidelines. The output from this meeting
(recommendations in response to the technical charge) will be considered by an EPA-established
work group that will be responsible for revising freshwater selenium criteria and for developing
guidance for site-specific criteria. .
Before the workshop, the experts submitted individual responses to the questions in the technical
charge. At the workshop, the experts heard presentations by two leading selenium researchers;
they then collectively discussed the questions in the technical charge and related issues. This
report presents the results of this peer consultation. Section II of this report presents the chair's
summary of the overarching themes and recommendations that emerged from the workshop.
Section III summarizes the discussions and specific conclusions concerning each question in the
technical charge. Section IV summarizes comments presented by observers at the meeting.
Section V lists the references cited in the report.
Workshop materials, including the agenda and lists of experts, presenters, and observers, are
-------
provided in Appendix A. Appendix B includes the technical charge to the experts and
background materials. Appendix C presents the experts' premeeting comments. Additional
references provided by experts, presentation materials, and observer presentations are included in
Appendices D, E, and F respectively.
Summary of Opening Remarks
Dr. Jeanette Wiltse, director of the Health and Ecological Criteria Division of EPA's Office of
Water, opened the meeting and welcomed participants. She said that the peer consultation
process allows EPA to benefit from the knowledge and experience of experts in the field,
obtaining better understanding of the problem and new perspectives. She thanked the experts for
their time and effort.
Dr. Wiltse commented that metals present a technically complex problem when developing water
criteria. One key issue is the balance between sufficiency and toxicity: Many metals (including
selenium) are required by organisms in small amounts, but are toxic in larger amounts. She
predicted that the experts would find the selenium discussion challenging and thanked them
again for participating in the consultation.
Keith Sappington, also of the Health and Ecological Criteria Division, then presented an
overview and background of the revision of EPA's freshwater aquatic life criteria for selenium.
He said thatthe purpose of the consultation was to provide an early assessment of the science on
a number of the technical issues associated with the criteria, and that EPA would use this
information as a basis for moving forward through the criteria revision process. He explained •
that the impetus for EPA's review of the selenium criteria included:
• New data and concern over the level of protection (too high or too low?).
• Ecological importance (as selenium is both an essential trace nutrient and a
toxicant).
• The need to address the toxicity and bioavailability of different selenium forms.
• The need for site-specific criteria modification procedures (taking into account
bioaccumulation and food-web exposure).
He added that some fundamental issues EPA is facing in the development of the new criteria
include determining in which environmental compartment to express the criteria, establishing the
duration of the averaging period, and identifying the key factors affecting the toxicity and
bioaccumulation of selenium.
Mr. Sappington emphasized that the focus of the peer consultation would be on technical issues
underlying the freshwater aquatic life chronic criterion. He reminded the experts that discussion
-------
of risk management or policy decisions would not be appropriate to this forum. He discussed the
key steps that EPA would undertake in its criteria review process and concluded by presenting a
rough timeline for the development of the revised criteria. (See Appendices B and E for more ,
detail.)
Dr. Anne Fairbrother, the workshop chair, then discussed the workshop structure and objectives,
reminding experts again to focus only on reviewing the state of the science; she added that
waterbirds would not be considered in the discussion. (See Appendix E for presentation
materials.) •
Opening Presentations
Belews Lake:. Lessons Learned
Dr. A. Dennis Lemly of the Department of Fisheries and Wildlife at Virginia Tech University
gave, a presentation entitled "Belews Lake: Lessons Learned." (See Appendix E for presentation
materials.) Belews Lake is a reservoir in the northwestern Piedmont area of North Carolina. The
reservoir is hydrologically divided by a highway crossinginto a main lake and the "158-Arm."
The main lake received selenium input from disposal of waste ash from a coal-fired power plant.
Inputs occurred over a 10-year period, stopping in 1985. The combination of a period of ongoing
inputs and a period of declining selenium concentrations has allowed researchers to obtain a
—great deal of information on tissue residue levels and effects. Dr. Lenity's summary of the key
.information gained from research at Belews Lake is as follows:
Main Lake Studies: ,
' , A concentration of ~ 10 ug/L dissolved selenium (about 80-90% selenite as it entered the
lake) can bioaccumulate in aquatic food chains and cause massive reproductive failure in
warm-water fish. Centrarchids (e.g., largemouth bass, bluegill, crappie, sunfish) are
among the most sensitive to elevated selenium; forage species such as red shiners, fathead
minnows, and mosquitofish are relatively tolerant (Cumbie and Van Horn, 1978; Lemly, .
1985).
Once ecosystem equilibration to ~ 10 ug/L has occurred in this type of a reservoir setting,
natural removal/cleansing processes operate very slowly. Elevated residues and toxic
(teratogenic) effects in fish were evident 10 years.after selenium inputs stopped and
waterborne concentrations dropped below 1 ug/L (Lemly, 1997); consumption advisories
are still in effect because of public health concerns. Complete recovery can be on the
order of decades. . ;
Dietary selenium was the most important source leading to effects in fish. Across years,
the sediment/detrital route of exposure delivered the most consistent dose to fish (i.e.,
residues in benthos were consistently high). However, within a given year, residues in the
waterborne/planktonic route of exposure were occasionally as high as in the benthic
-------
pathway (70-90 ng/g dry weight, especially in summer). Thus, each route of exposure
delivered a toxic dose to fish. Planktivores, omnivores, insectivores, and piscivores were
all similarly affected.
158-Arm Studies:
Concentrations of 0.2-4 ug/L dissolved selenium in the 158-Arm bioaccumulated to levels
that caused teratogenic deformities and chronic selenosis (pathological lesions) in
sensitive fish species (e.g., bluegill and green sunfish) (Sorensen et al., 1984; Lemly,
1993a, 1997).
Concentrations of 0.2-4 ug/L dissolved selenium bioaccumulated to >25 ug/g dry weight
in aquatic food-chain organisms. This concentration is over five times the chronic dietary
toxicity threshold for freshwater fish and aquatic birds, as determined in laboratory studies
(Le., 3-5 ug/g; Lemly 1993b).
\
Selenium concentrations in fish (especially bluegill) reached levels equal to or greater than
those that caused reproductive failure in artificial crosses of bluegill from a sister lake
(Hyco Reservoir; 38-54 ug/g dry weight whole body concentrations in fish; Cumbie and
Van Horn, 1978; Holland, 1979; Gillespie and Baumann, 1986), and reproductive failure
in laboratory feeding experiments with bluegill (13 and 33 ug/g dry weight in fish diets;
Woock et al., 198/; Coyle et al., 1993).
Related Laboratory Studies:
Exposure to waterborne (only) selenium (selenite) at concentrations of 10 ug/L does not •
affect survival of juvenile bluegill. Although some bioconcentration occurs, residues in
tissues do not reach the toxic threshold (Lemly, 1982).
Conditions mimicking those in the Belews 158-Arm (4-5 ug/L dissolved selenium; 5 ug/g
dry weight dietary selenium) can induce physiological and metabolic stress in young
centrarchids, resulting in significant mortality during cold weather due to Winter Stress
Syndrome (Lemly, 1993c, 1996). Thus, time of year may be ah important factor in the
toxicity process when concentrations are near the current EPA criterion for chronic
exposure (5 ug/L).
Conclusions:
Because of the extensive and rapid collapse offish populations, the main body of Belews
Lake has received most of the research focus and notoriety. However, the 158-Arm
provides valuable information on selenium bioaccumulation and effects when waterborne
concentrations are below the EPA national criterion for chronic exposure (5 ug/L).
Historic and current reference to the 158-Arm as "unaffected" (e.g., EPA 1998 Draft Field
Study Summary) are incorrect. Multiple lines of evidence from this field site, (diagnostic
residues, tissue pathology, teratogenic deformities) as well as associated laboratory studies
-------
(simultaneous water/diet exposures), indicate that selenium can become toxic to fish when
waterborne concentrations are 4 ug/L of less. The affected taxa include widely
distributed, economically and recreationally important species such as largemouth bass
and bluegill. In this type of field setting, the threshold for detrimental impacts is well .
below 5 ug/L.
.The most sensitive biological endpoint for detecting toxicity in fish (that has demonstrated
.impacts at a population and community level) is reproductive failure (i.e., teratogenic
deformities and associated, embryomortality that occur shortly after hatching). Winter
Stress Syndrome may be a more sensitive indicator but it has not been confirmed in field
studies. -
From a toxicity perspective, the point of effect is the fish's reproductive tissue (i.e., eggs).
; The toxic threshold for selenium in eggs (10 ug/g dry weight) is consistent regardless of
the source or chemical form of selenium in an aquatic system. Pairing water and egg
concentrations gives a direct source-fate, cause-effect linkage that integrates all aspects of
the selenium cycle. The existing national field database suggests that a single water-tissue
method for setting criteria can be applied equally to both selenate and selenite dominated
systems.
The practice of allowing exceedances in meeting water quality criteria is not supported by
field evidence of effects. For example, current EPA guidelines allow up to 20 ug/L as an
. ", ambient (lake-wide) concentration once every 3 years. The concentration of waterborne
selenium in Belews Lake reached this level only once in 10 years, yet 17 species offish '
were eliminated. ""••
In response to a question on the origin of the 4 jig/L of selenium in the uplake arm, Dr. Lerhly
replied that it must have come from backflow from the main lake,, because he doubted that there
was significant contribution from atmospheric deposition. Dr. Teresa Fan asked whether it had
actually been determined that selenium was incorporated into proteins in the species with which
Dr. Lemly was working. Dr. Lemly said there had been some speciation work done, but that he
did not know if there were differences between mosquitofish and bluegill in terms of selenium
incorporation into protein. He Said that this was one possible explanation for why mosquitofislhi
accumulate higher tissue levels of selenium than bluegills yet show fewer effects. Dr. Steven
Hamilton asked about Dr. Lemly's statement that 10 ug/g of selenium in fish eggs is correlated
with 5 ug/g in the food chain and 2 ug/L in the water column. Dr. Lemly replied that this
statement was based on both data from the Belews recovery period and data from other lakes.
Modeling Selenium in Aquatic Ecosystems ,
Dr. George Bowie of TetraTech gave a presentation entitled "Modeling Selenium in Aquatic
Ecosystems," and referred to the paper "Assessing Selenium Cycling and Accumulation in
Aquatic Ecosystems" (Bowie et al., 1996). (See Appendix E for.presentation materials.) The
-------
model was sponsored by the Electric Power Research Institute (EPRI) and was developed in
conjunction with a major research program. The research had two major components: toxicology
andbiogeochemical processes. Dr. Bowie's presentation focused on three of the five major
components of the model: cycling processes in the water column and in the sediments, and
accumulation in tissues of organisms.
For each of these areas, Dr. Bowie described the processes in the model, discussed areas of
uncertainty or limitations in our understanding of these processes, and showed the results for an
example application to Hyco Lake to illustrate which processes are most important. He used
these results plus some of his experimental results to discuss the response tunes of aquatic
organisms to changes in selenium exposure and the effects of water quality variables on selenium
uptake. Since the model description, Hyco application, and conclusions are covered in the paper,
Dr. Bowie listed the main points concerning uncertainty, pharmacokinetics, and water quality
effects on uptake' that are not included in the paper.
1 ' >. '
Water-Column Uncertainty:
Organic selenides represent a lumped selenium pool that includes many different selenium
Compounds which are poorly understood and most of which cannot be measured with
current analytical techniques. Some, such as selenomethionine, may be very biologically
reactive while others may be much more refractory. Most of the organic selenide pool is
not selenomethionine since the high uptake rates measured in the lab are not consistent
with'accumulation levels and organic selenide turnover times observed in the field.
Sediment Uncertainty:
Sediment selenium accumulation depends-on settling of particulate selenium (plankton,
suspended organic detritus, elemental selenium, selenite adsorbed on clays), diffusion of
water column inorganic selenium into sediment porewaters followed by rapid reduction to
elemental selenium hi anaerobic sediments, and decomposition of organic detrital
selenium in the sediments. In lakes where sediments are usually anaerobic below a thin
oxidized microzone, diffusion of inorganic selenium and subsequent reduction to
elemental selenium is one of the most important processes. However, in other types of
systems where the sediments are aerobic or anaerobic at much greater depths, other
accumulation processes would be more important. Selenium speciation data in other types
of systems are currently lacking, which limits an assessment of accumulation mechanisms
in these systems. Sediment selenium concentrations depend not only on the selenium
fluxes into the sediments, but also on the sediment deposition rates (and sediment
transport rates in flowing systems). This makes sediment selenium concentrations very
dependent on site-specific conditions.
Food Web! Accumulation Uncertainty:
Most research on selenium accumulation in aquatic organisms has focused on planktonic
food webs. Benthic invertebrates can be an important source of selenium accumulation in
fish, and since the sediments contain most of the historical.selenium loadings in aquatic
-------
ecosystems, detrital and sediment pathways to benthic organisms could be extremely
important Bacteria accumulate selenium to levels several times higher than algae, so
sediment bacteria associated with organic detritus could be an important source of
selenium accumulation in benthos. Much of the sediment selenium in lakes is elemental
selenium, which was recently shown to be bibavailable to benthos (though organic
selenium assimilation efficiencies are several times higher). The selenium concentrations
in organic detrital particles, associated bacteria, and the amount of elemental selenium
ingested during feeding are what determine selenium accumulation in benthos, not the
selenium concentrations in the bulk sediments. Systems with high sediment deposition
rates or high sediment transport rates could dilute selenium concentrations in bulk -
sediments, even though the selenium content of the organic food particles remained the
same: ',•'..
Response Rates of Organism Tissue Concentrations to Changes in Exposure:
Uptake and depuration experiments, as well as other studies in the literature, indicate that
the time it takes to reach equilibrium starting from no previous selenium exposure is on
the order of a few days to a week for algae and bacteria, 1 week for microzooplankton, 1
to 2 weeks for zooplankton and benthic invertebrates, and 3 to 10 months for fish. Since
most fish experiments are conducted with small fish in the laboratory, larger fish in the
field could respond more slowly. Food is generally the primary route of selenium
accumulation in cpnsumer organisms, and since the sediments respond much more slowly
to changes in selenium loadings than the water column, the benthic food web can continue
to provide exposure to fish long after the planktonic food web levels drop.
Water Quality Effects on Selenium Accumulation:
Since most selenium accumulation occurs at the bottom of the food web and then moves
, to higher trophic components through food exposure, water quality factors that influence
accumulation in primary producers can be very important. In experimental research with
phytoplankton, three water quality variables had a significant effect on selenium Uptake
rates (Riedel and Sanders, 1996), Low pH and low phosphate increased selenite uptake by
a factor of about 4 or 5, and low sulphate increased selenate uptake by a factor of 2.
Dr. Fan asked Dr. Bowie if the elemental selenium data he was using for sediments involved
analytical confirmation. Dr. Fan cautioned that her group could not confirm using extraction
.methods that the red amorphous material secreted from algae was elemental selenium; this
material contained <10% Se and >90% carbonaceous material, possibly polysaccharides. She
suggested a particular analytical technique that should be used for elemental selenium. Dr.
Bowie replied that he was using results from Dr. Greg Cutter's work (Cutter, 1991), but that Dr.
Terry Layton's work (not yet published) at the University of California at Berkeley used the
analytical technique referred to by Dr. Fan and found that a significant portion of the sediment
selenium was elemental selenium.
-------
Chair's Charge to the Experts and Highlights of Premeeting Comments
Dr. Fairbrpther summarized the technical charge given to the experts by EPA, and the experts'
premeeting responses to the questions in the charge. (See Appendix E for presentation
materials.) She noted that the leaders of each discussion session would present the premeeting
comments in more detail.
Dr. Pah-brother repeated that the charge to the experts was to address .and comment on technical
issues. She asked the experts to identify the rationale behind their comments and conclusions,
assess the level of confidence in data cited, and discuss data quality,
Dr. Fairbrother first addressed the question "What do we know about the relationship between
water-column measurements of selenium and biological effects?" She said that the experts
generally agreed that looking at this relationship alone is not a good approach for a
bioaccumulative compound like selenium. Many of the experts noted that the most sensitive
fully aquatic species are fish species and that diet is the primary exposure route. Also, there
seemed to be a need to discuss selenium chemistry.
Next, Dr. Fairbrother discussed the experts' comments on the relationship between tissue
concentrations and either sediment or water concentrations. She said that there had been mixed
responses on this issue. There was disagreement on the state of the science; some of the experts
said that the-science base was good, while others said that there was too little data. The experts
also disagreed somewhat in what form of selenium to measure in which tissue. There was some
agreement that water-tissue correlations are poor, and that diet-tissue-effects correlations are
, better.
Concerning the link between sediment concentrations and both water concentrations and effects,
Dr. Fairbrother said that there had been disagreement on several aspects of this question. Experts
disagreed about the ability to relate sediment concentrations to either water-column
concentrations or effects in fish. Finally, Dr. Fairbrother said that some of the cross-cutting
issues brought up included selenium geochemistry, selenium kinetics within and between
ecosystem compartments, and the differences between lotic and lentic systems.
-------
II. CHAIR'S SUMMARY OF WORKSHOP DISCUSSIONS
The following summary was written by the Workshop Chair, Anne Fairbrother, based on the
experts' discussion arid premeeting comments. Details of the experts' discussions are provided
.. in Section HI. ' .
The technical sessions initiated discussions among the experts by first reviewing the questions
provided in the premeeting comments and then allowing conversation to develop around a
general theme. General themes were: relationship of effects to water, sediment, or tissue
concentrations and a session on cross-cutting issues to capture ideas on chemistry, system
variability, and other topics brought forward by individual experts.
Water-Effects Relationships
This session began with a discussion of the scientific validity of predicting chronic effects of
selenium from water concentrations. The experts quickly agreed that waterborne exposure to
selenium in all its various forms is less important than dietary exposure in determining the
potential for chronic effects. Therefore, predictions of ecological effects cannot be based on
studies that use water-only exposures. Factors that modify the relationship between water
concentration and effects include the types of organisms constituting the food web, speciation
and rates of transformation of selenium, and rates of exchange of selenium between water,
sediment, and organisms. It was noted that selenium speciation may be sensitive to salinity, thus
altering bioaccumulation potential, but this has not yet been proven.
There were differences of opinion about what to measure in the water column for assessing the
level of selenium contamination of an aquatic system. However, it was agreed that, at a
minimum, dissolved (i.e., in the water phase) versus particulate (i.e., attached to particles of :
inorganic substances or to .bacteria or phytoplankton) selenium be differentiated and that selenate
and selenite .(two oxidation states of selenium) be determined in both fractions. Peptide- and
protein-bound forms of selenium are critically related to the potential for occurrence of chronic
effects. The protein-bound forms should be specifically included in the analysis of selenium in
the particulate fraction, as this is the primary step for the major route of bioaccumulation. The
current definition of the dissolved fraction is the portion of the sample that passes freely through
a 0.4 /urn filter. One expert suggested that an 0.2 /urn filter might be more appropriate in order to
catch the smaller phytoplankton and bacteria in the particulate fraction, as these organisms are
very important hi the first step of bioaccumulation of selenium.
Experts concluded that insufficient information exists to quantitatively correlate water quality
characteristics (such as sulfate, pH, and TOC) with chronic toxicity. Finally, the experts
emphatically agreed that toxicity relationships derived from acute toxicity studies cannot be used
to predict chronic toxicity, as the dietary route of concentration and exposure is so important for
selenium. This also implies that bioconcentration factors (i.e., concentration in tissues divided
by concentration in water) are not appropriate for use with this compound. ,In summary, water
-------
concentrations are related to effects, but it is a nonlinear (and site-specific) relationship.
Tissue - Effects Relationships
Discussion then turned to technical issues associated with a tissue-based criterion. The experts
agreed that tissue integrates all exposures, whether from food or water. The best tissue in which
to measure selenium is fish ovaries or eggs as concentrations have been linked to reproductive
effects in some species. There was some discussion, however, that pointed out the need to
develop a larger data set encompassing interspecies variability in the ovary concentration -
reproductive effects relationship. If fish ovaries are not available (i.e.,.sampling needs to be done
during the wrong time of year), then larval stages are the next-best tissue to measure as older life-
stages are less sensitive to selenium effects. Liver tissue was mentioned as a third tissue for
possible monitoring of residue concentrations. Muscle-plug biopsy techniques have been
suggested for use with endangered species, but do not seem to correlate well with effects.
It was also pointed out that concentrations of selenium in benthic invertebrates could be
measured in order to determine the potential for effects to the lower order organisms as well as to
establish potential dietary exposure values for fish. Discussion highlighted the need to
standardize this method, in order to be sure that sediment is removed from the organisms guts
prior to measurement. A discussion ensued about the ability of selenium to alter community
relationships of phytoplankton with ramifications throughout the entire food web. However, it
-was agreed-that fish are the most sensitive to the chronic effects of selenium and therefore fish
tissue continues to be the choice for a tissue-based toxicological threshold.
Further discussion centered on the form of selenium that is most appropriate to measure in tissue.
To date, nearly all of the studies have measured total selenium, but it was agreed that a more
accurate representation of selenium-effect relationships could be obtained through measuring
protein- or peptide-bound forms of organoselenium. The incorporation of selenium into protein
is the trigger for biological effects.
Finally, it may be difficult to correlate water column concentrations with tissue concentrations.
There are many examples of sites where water levels are low and tissue levels are high, as a
result of previous sediment loading with current reductions in water-column selenium. Sediment
(and subsequent dietary) concentrations will decline over time if water levels are kept low, but
there is a considerable lag from the time when water concentrations are reduced to the time when
sediment concentrations reach low levels. Therefore, if the history of a site is not known, a
single measurement of water and tissue (or sediment) concentrations may provide a misleading
picture and inconclusive relationships.
Sediment-Effects Relationships
Sediment is the dominant sink for selenium, and sedimentary organic materials (detritus) are an
important dietary resource for aquatic invertebrates. The literature relating sediment-based
10
-------
criteria is sparse; most participants relied on three key references in their cpmments, A.positive
relationship between sedimentary selenium concentrations and effects in fish or bioaccumulation
in invertebrate larvae has been-shown in a few studies; 'However, one expert cautioned that a no-
effects determination in field studies must always be tempered with an assertion that the test was
powerful enough to have detected effects if they were there, albeit at low levels.
An analysis of data focusing only on fish indicates that toxic effects may occur when total
sedimentary selenium concentrations exceed 4 ^ug/g (dry weight). Elemental,and organic
selenium forms predominate in sediments. The process is affected by redox conditions, and
selenium tends to associate with the organic detritus. In streams, total sedimentary selenium is
related to water-column concentrations through normalization to total organic carbon. It was
suggested that sedimentary aluminum concentrations might be useful as a marker for inorganic
sediment composition, in an effort to further separate the detrital-bound selenium from ':.'.-'
inorganic-bound forms. Foraccumulation in sediments of lentic systems (i.e., lakes and slow
moving water), consideration of residence time and use of a mass balance approach could relate.
sediment selenium to waterbome selenium."
Because waterborne selenium concentrations tend to exhibit large temporal variations, the -
strength of the water-to-sediment correlation is affected by the averaging period selected. The
issue of spatial heterogeneity of benthic invertebrates as well as selenium deposition and
speciation is very important. Other parameters that might affect the relationship of sediment
-concentrations and ecological effects include water retention time, volatilization rates, the type of
benthic phytoplankton community, and whether of not the system is at equilibrium. Habitat
selection by different types of aquatic biota and preferential feeding habits of higher organisms
also modifies selenium exposure. Various experts made the points that redox potential (i.e.,
amount of oxygen in the system) affects selenium speciation and that improved analytical
methods for sediments are needed. Two experts advocated .the expansion of the use of liquid
chromatography for sediment selenium analysis.
Cross-Cutting Issues
. The cross-cutting session captured issues that did not fit neatly into one of the above themes, as
well as other comments or ideas. Spatio-temporal variability was addressed again, as it applies
to water column, sediments, and tissues, although in different scales for each. Water
concentrations may change rapidly (within days), whereas fish-tissue residue and sediment ,
concentrations take months or years to change. The rate-limiting step may be the rate of
conversion of the inorganic form of selenium to the organic form, which is a function of the
species of selenium in the water column and the types of microorganisms present in the
sediment. , , . ''
There was agreement that the type, of ecosystem has a large effect on selenium cycling in the
system. Lentic and lotic (fast-flowing) systems, ephemeral or perennial waterbodies, saline
systems, and northern (cold) streams, may differ in response to selenium input. Retention time
•'• :. . .' •••"• 11' ' : • ' . ' " ' ....
-------
of carbon, rate of sediment accumulation, rates of conversion of inorganic to organic forms of
selenium, and tolerances of local species all differ among these types of systems. Bacteria and
phytoplankton species differ between the two ecosystem types, which may cause differences in
bioaccumulation rates. Also, lentic systems have higher primary productivity. Open (rather than
closed) fish populations in lotic systems make changes in recruitment more difficult to
document While there was argument about the relative importance of considering one or both of
these types of systems, there was agreement that their interconnections are important.
Two methods using existing field data were suggested for differentiating non-affected sites, areas
with, definite effects, and sites requiring a site-specific determination of effects. The apparent
effects threshold (AET) method categorizes previously studied areas based on sediment or water
concentrations. The sediment/water concentration above which effects always occurred would be
identified, as would the concentration below which effects never occurred. New sites with
sediment/water concentrations that fall between these two values (where effects sometimes
occurred or sometimes did not)'would require a site-specific assessment; otherwise, the site
would be categorized as affected or not. A second method is based on fish tissue concentrations
as a function of water concentrations. The empirical data from field studies that exist in the
literature would be used to develop the bioaccuinulation correlation on a global basis. Sites
where measured fish tissue concentrations were statistically significantly different from what
would be predicted based on water concentrations and the global bioaccumulation factor, would
require a site-specific assessment of potential effects.
It was suggested that the Aquatic Toxicity Model presented by George Bowie could be used to
make a priori predictions of whether a concentration of selenium in water would result in effects
to the fish. Site-specific input parameters include !selenium input (amount, rate, and species),
flow rates, water depth, and a few other hydrological parameters as well as food-web species.
The more site-specific data that are used in the model, the more likely it is to accurately predict
effects.
Selenium has the potential to interact with other metals, causing either greater or lesser responses
than predicted from selenium alone. Furthermore, exposure to selenium may reduce an
organism's ability to respond to other environmental stresses, such as has been shown for fish
similar to those found in Belews Lake that were exposed to cold temperatures during laboratory
studies. These types of interactions might confound the global empirical data set relating effects
to selenium concentrations in water, sediment, or food.
Selenium is a required micronutrientfor both plants and animals. Therefore, there is an exposure
concentration below which insufficiency effects are seen and a different concentration above
which toxicity occurs. The area in between is the Optimal Effects Concentration. In general,
there is at least a 10-fold difference between insufficient and toxic concentrations and, on a
practical basis, it does not appear to be of particular concern in field situations. However, this
issue may be important in laboratory studies where appropriate minimum concentrations of
selenium must be provided to maintain colonies of test species.
12
-------
Analytic methods for detection of selenium in water, sediment, or tissue are technically complex.
However, due to their importance in carefully and critically describing the systems at risk, a
significant amount of time was devoted to discussion of this issue. Desired minimum detection
limits, sample preparation requirements, cost, and laboratory capability all affect the selection of
which method to use. A detailed summary of available methods, as well as sample collection
and retention procedures, is included in the report.
One expert stated that at the national level, median background concentrations of selenium in
aquatic systems do not vary greatly, being at about 0.1 /J-gfL.' However, there was disagreement
on this value and particularly on the variability in background, which is dependent upon the
spatial scale of the analysis as well as on site:specific geology. Methods are being developed for •
differentiating between natural and anthropogenic inputs of selenium into aquatic systems, but
there remains a great deal of uncertainty.
Observer comments reinforced the recommendation to develop methods for setting site-specific
criteria, as a universal numeric chronic criterion for selenium is highly unlikely to be predictive
of effects for any particular site. • ,„'
13
-------
HI. TECHNICAL DISCUSSION SESSIONS
Generally, discussion leaders organized the discussions according to the questions provided in
the technical charge. Each leader opened the discussion on each question by presenting an
overhead summarizing the relevant premeeting comments. The following discussion session
summaries include the presentation of the premeeting comments, followed by an account of the
discussion for each question of the technical charge. Overall conclusions, which were written by
the discussion leaders and reviewed by the other experts, are presented at the end of the
discussion summary for each session.
DISCUSSION SESSION 1:
Technical Issues Associated With a Water-Column-Based Criterion
Question 1: Besides selenite and selenate, which other forms of selenium in water are
toxicologically important with respect to causing adverse effects on freshwater aquatic
organisms under environmentally realistic conditions?
Discussion leader's summary of premeeting comments:
Dr. William Adams presented his summary of the experts' premeeting comments concerning this
question as-follows: Selenate, selenite, seleno-cyanate, arid organo-forms (seleno-methionine) are
the key forms of interest. Selenate and selenite are the predominant forms derived from mining,
agricultural practices, fly ash,, and natural shales. Organo-selenium compounds produced from '
these inorganic forms are of most ecological relevance on a chronic basis; seleno-methionine is
thought to be a key chemical form. Little is known, however, about environmental exposures of
organo-forms, especially seleno-methionine; there is a general lack of analytical procedures for
measuring organo-forms. Dr. Adams then asked the experts for any comments concerning his
summary or question 1.
• , J
Discussion:
Dr. Gregory Cutter, disagreeing with the statements concerning seleno-methionine, said that free
seleno-methionine is not important in water and is easy to measure. Dr. Fan expressed
skepticism about the measurement of seleno-methionine, because most methods do not involve
structure confirmation. She also pointed out that seleno-methionine is abundant in
macromolecules and emphasized that macromolecular seleno-methionine may be important,
although this hypothesis has been neither disputed nor confirmed by the literature. Dr. Cutter
agreed and also stated that, based on his analysis using acid hydrolysis and ligand-exchange
chromatography, the vast majority of organic selenium in unpolluted waters is peptide-bound.
Dr. Fan mentioned the possibility of the selenonium form, a cation, being present, as shown by
Cooke and Bruland (1987). She added that, based on her work, salinity can drive speciation; she
14
-------
has found that one phytoplankton accumulates dimethyl selenonium propionate in a euryhaline
environment. Dr. Cutter agreed that selenonium can be present in highly contaminated systems.
Returning to the discussion of seleno-methionine, Dr. Chapman asked whether laboratory tests
using seleno-methionine are irrelevant to environmental exposures, given the small amounts of
free seleno-methionine found in water. Other experts agreed that water-only exposures to
seleno-methionine are of questionable relevance, but seleno-methionine may be important in
food-chain transfer of selenium. , ,
Question 2: Which form (or combination of forms) of selenium in water are most closely
correlated with chronic effects on aquatic life in the field? (In other words, given current
or emerging analytical techniques, which forms of selenium in water would you measure
for correlating exposure with adverse effects in the field?) Note: Your response should
include consideration of operationally defined measurements of selenium (e.g., dissolved
and total recoverable selenium), in addition to individual selenium species.
Discussion leader's summary of premeeting comments:
Dr. Adams summarized the experts' premeeting comments for this question as follows: Total
recoverable selenium is a useful form to measure. This would include all forms of selenium in
the water except a limited amount of non-bioavailable selenium that might be tied up in the
-crystalline structure of suspended solids. There are no identified actual correlations between
selenium forms and chronic effects. Future efforts should focus on proteinaceous forms
(especially seleno-methionine). Dr. Adams then asked for the other experts' reactions to this
question.
Discussion:
Dr. Fan asked for the other experts' opinions on making correlations between waterborne
particulate selenium and accumulation of selenium in the food chain. She said that she had seen
a couple of papers that indicated that there was a correlation (e.g., Saiki et al., 1993). Dr.
Gerhardt Riedel replied that he thought that gathering data from multiple lakes would result hi a
correlation that was positive but would have large confidence limits. .
Dr. Cutter advocated separating total recoverable selenium into the dissolved and particulate
fractions, because those pools are available to different organisms. He said that this should be
done by filtration using as small i pore size as possible, preferably 0.2 microns. Dr. Riedel and
Dr. Adams agreed that separating the dissolved and particulate fractions is useful.
Dr. Gary Chapman raised the issue of the operational definition of dissolved selenium, which Dr.
Cutter had mentioned in his premeeting comments. He asked Dr. Cutter to discuss this issue.
Dr. Cutter replied that there is some work on colloidal selenium in estuaries, including a paper by
Takayanagi and Wong (1984). He thinks that, based on these papers and his Work, in most
- ' • . • ' • ' 15' '•' ' '.'' • v.
-------
systems colloidal selenium represents a small fraction of "dissolved" (sO.^m) selenium. Thus,
in his opinion, 0.4 microns is not a bad filter pore size for most systems, but he advocates 0.2
microns to ensure that the smaller phytoplankton and bacteria are included in the particulate
fraction. Although Dr. Riedel suggested that cross-flow filtration could be used to get down to
very small size ranges, Dr. Cutter replied that this technique is laborious. Dr. Cutter and Dr.
Riedel agreed that the very small size range is not that important for selenium, although it is
important for some other metals. Dr. Adams concluded this discussion by pointing out that the
operational definition of "dissolved" is a topic currently under debate, particularly in respect to
data collection by the United States Geological Survey (USGS).
Dr. Adams asked whether the experts thought it accurate to state that no forms of selenium in
water have been correlated with chronic effects; he added that the science is uncertain, but it is
probably a polypeptide/protein-bound form of selenium.
Dr. Chapman asked how much of particulate selenium is actually organic and how much is
bound up in a mineral matrix. Dr. Fan agreed that this was an important question for thinking
about bioavailability. Dr. Cutter agreed and listed the possible forms of particulate selenium:
adsorbed selenate or selenite (probably on clays), elemental selenium, and organic forms. He
said that Luoma et al. (1992) have looked at the speciation of selenium on particles. Dr.
Fairbrother responded that the separation of organic from mineralized selenium needs further
research. Dr. Fan suggested that standard biochemical procedures could be used to determine
•what fraction of particulate selenium is bound to proteins. Dr. Adams observed that most of the
previous discussion related to possible areas of future research, rather than currently practical
techniques.
Dr. Joseph Skorupa asked the biochemists present if they felt that any form of selenium was
lexicologically unimportant. Dr. Fan and Dr. Cutter responded that they did not, because all
forms of selenium may eventually interconvert.
Question 3A: In priority order, which water quality characteristics (e.g., pH, TOC, sulfate,
* interactions with other metals such as mercury) are most important in affecting the chronic
toxicity and bioaccumulation of selenium to freshwater aquatic life under environmentally
realistic exposure conditions?
Discussion leader's summary ofpremeeting comments:
Dr. Adams summarized the experts' premeeting comments for this question.as follows: It is not
possible to rank these water quality characteristics with reasonable certainty due to insufficient
information on their effects on expression of chronic toxicity. Overall, the Eh
(oxidative/reductive) state of an ecosystem is most important in determining the potential for
chronic toxicity to occur, because it significantly influences the formation of organo-forms of
selenium. One could predict that, at the extremes and as a function of Eh, pH would be
important due to speciation changes, but chronic data are not available to assess this. pH would
16 • 1
-------
be expected to have the most impact on selenite across typical environmental pH values. Sulfate
appears unimportant in terms of the expression of chronic toxicity except potentially for primary
producers. Arsenic and molybdenum are also mobilized under similar conditions as selenium
and appear to be additive with seleriate. ,
Discussion: •
Dr. Cutter agreed that redox state is important for precipitating elemental selenium and removing
dissolved selenium. He argued, however, that photosynthesis has more influence on the
formation of organo-selenium. Dr. Adams and Dr. Fan pointed out that non-photosynthetic
microbial processes are also important, particularly in sediments; these,processes are somewhat
coupled to redox state. , •;
Dr. Fan added that the presence of sulfate or nitrate in a reducing environment encourages a
certain type of microbial community (sulfate or nitrate reducers), which would have, a major
impact on selenium speciation. She cited evidence of hydrogen selenide and methaneselenol
release into the marine atmosphere via phytoplankton activities (Amoroux and Donard, 1996).
Dr. Cutter expressed skepticism about this possibility. Dr. Fan, Dr. Cutter, and Dr. Adams did
agree, however, that the microbial loop is very important and that the presence of sulfate and
nitrate reducers would affect selenium speciation, resulting primarily in the reduction of
selenium to the elemental form. . , -
Dr. Cutter commented that arsenic and molybdenum behave differently from selenium; in a ,
reducing environment, arsenic is mobilized while selenium is immobilized.
Question 3B: Of these, which have been (or can be) quantitatively related to selenium
chronic toxicity or bioaccumulation in aquatic organisms? How strong and robust are
these relationships?
Discussion leader's summary of'premeeting comments:
i . • ' " • _ ' i '
Dr. Adams summarized the experts' premeeting comments for this question as follows:
Insufficient information exists to quantitatively correlate water quality characteristics with
chronic toxicity across multiple species and trophic levels. Sulfate, phosphate, and temperature
have been shown to correlate with seleriate for some species (i.e., primary producers).
> . - ' • • ' -
Discussion: ' ,
Dr. Riedel amended Dr. Adams's comment by saying that, for primary producers, phosphate
does not affect selenate uptake, but rather high phosphate concentrations appear to suppress
selenite uptake.
17
-------
Question 3C: How certain are applications of toxicity relationships derived from acute
toxicity and water quality characteristics to chronic toxicity situations in the field?
Discussion leader's summary ofpremeeting comments:
Dr. Adams summarized the experts' premeeting comments for this question as follows: The
applications of relationships derived from acute toxicity and water quality characteristics do not
apply to chronic toxicity for most aquatic life (an exception to this might be the relationship
between selenate and sulfate for algae). The primary reason for this is that acute toxicity is most
often the result of water exposures, whereas chronic effects are the result of selenium being
incorporated into the diet where the predominant form of selenium is no longer an inorganic
form. .
Discussion:
None of the experts had any objections to this summation.
^ ^
General Comments:
Discussion leader's summary of premeeting comments:
Dr. Adams offered for discussion the following statements taken from various premeeting
comments: 1) Laboratory studies provide reasonable estimates of acute toxicity. 2) It seems
imperative that chronic criteria include consideration of tissue residue and dietary route of
uptake. 3) Fish eggs may represent a reasonably sensitive tissue to use as an endpoint for
assessing the potential for species-level risk. 4) A useful approach might be to develop a generic
criterion which also allows for site-specific approaches. Toxicity and bioconcentration factors
(BCFs) are a function of time and exposure level. 5) Organic forms are thought to be produced
in response to inorganic selenium enrichment and probably represent a net reduction in potential
for toxicity.
Discussion:
Dr. Adams displayed graphs showing data from an experiment he performed concerning toxicity
as a function of time with rainbow trout fingerlings and fathead minnows (Figures 1-3). Because
the LC50 changed over time in this experiment (i.e., uptake rates are slow), he postulated that the
96-hour assay may not be the right test for acute toxicity. Dr. Cutter questioned the relevance of
a water-only exposure. Dr. Skorupa pointed out that a short-term spike in selenium may have
long-lasting food-chain implications, as shown by a paper by Maier et al. (1998). In this paper, a
short-term 10 u.g/L spike in a Sierra Nevada stream resulted in a concentration of 4 u.g/g in the
food chain for over a year. Dr. Chapman replied that a tissue-based criterion would require
modeling with rate and fate functions and that in such a situation there would be no reason to
18
-------
draw an arbitrary timeline to separate acute closings from chronic effects. Dr. Fairbrother said
that that issue would be addressed in the discussion of averaging times during the cross-cutting
session.
o
in
O
a
o
e
o
O
1.0
0.8
0.6
O.4
20 40 60 80 100
Time Idays]
Figure 1. The effect of time on the toxicity of sodium selenite to
fingerling rainbow trout. The line was fitted by eye.
(Adams, 1976.) *
11
i&
9
_ 8
« 7
E
6
> '
b
w 4
O
_J
i
a
tn 3
10
15
20
.30
40 SO
Time Idaysl
Figure 2. The effect of time on the toxicity of
sodium selenite to juvenile fathead minnows. :
The line was fitted by eye. (Adams, 1976.)
O.5
O.3
• O.OS-
CO
o O.03-
c •
O
«
I 0.01
o
c
o
°O.OOS-
Expo«ur«
Concentrations
• sous/I '
' o 25 ug/l
y - • 10 ug/l
30 4O
Time Idayal
SO 65 9.6
Figure 3., The accumulation of selenium in the muscle of adult
fathead minnows. (Adams, 1976.) ,
. 19
-------
Dr. Adams then initiated discussion on the last point, concerning organic selenium forms. Dr.
Fan pointed out that methylated forms are less toxic and can volatilize out of the system, but that
they can also bioaccumulate. Dr. Cutter stated that a paper by Gobler et al. (1997) showed that
dissolved organic selenium was less bioavailable to primary producers than inorganic forms,
such as selenite. Dr. Riedel made the distinction between selenite, which is essentially nontoxic
to phytoplankton, and selenate, which is moderately toxic. He agreed that concentrations of
organic selenium in real waters are probably less toxic to algae than selenate. Dr. Fan pointed
out that particulate organic forms may be more bioavailable to organisms such as small
protozoans, which can ingest them; Dr. Cutter agreed. Overall, however, Dr. Riedel and Dr.
Cutter bom stated that dissolved (not particulate) organic selenium in most waters is probably
fairly persistent and refractory, and not very bioavailable. (It is taken up poorly and broken
down slowly.) Dr. Cutter referred to a paper his group has published, which looks at the lifetime
of dissolved organic selenium in the North Atlantic (Cutter and Cutter, 1998).
Dr. Adams directed the experts' attention to the comment concerning bioconcentration factors,
which he defined as not including diet. (Bioaccumulation factors would include diet.) He
showed a graph of bioconcentration factors observed at various intervals for fathead minnows
exposed to four concentrations of selenium (Figure 4). Dr. Adams argued that, because there is a
body of literature showing (as did his data) that BCF is inversely related to water concentration
for selenium and many other metals, reporting a BCF for a given species at a given site is of
questionable value. Dr. Chapman replied that he
thought the experts could agree that BCFs were
not relevant for selenium, as food chain is the
key; Dr. Cutter agreed and said that this point
should be emphasized.
o 0.013 no/I
10.0 ug/l
25.0 ug/l
50.0 ug/l
Days
Figure 4. A comparison of the bioconcentration factors
observed at various intervals for fathead minnows exposed
to four concentrations of selenium. (Adams, 1976.)
Dr. Fan remarked that the emphasis on water-
column concentration has led mitigators to focus
on driving down those concentrations, which is
not in fact the aspect of the system that is directly
correlated with ecosystem effects. Dr.
Fairbrother replied that EPA is struggling with
this issue, because water quality criteria have
been set using water column numbers. Dr,
Adams postulated that the mass of selenium in
the sediments may be more important than the
concentration of selenium in the water. Dr.
Cutter replied that water concentrations are
related to effects but that it is a nonlinear
relationship. Dr. Fan gave an example of two
agricultural drainage ponds she has studied.
Water concentrations of selenium differ by an
order of magnitude between the two ponds, but
20
-------
sediment concentrations are similar. Dr. Adams speculated that one site might have more
volatilization, and Dr. Fan agreed. Some of the experts discussed volatilization. Dr. Adams said
he had seen papers that found that volatilization increases in reservoirs which have alternating
drawdown and refill cycles (Hansen etal., 1998; Frankenberger and Karlson, 1994). The experts
discussed the residence time of volatilized selenium hi the atmosphere; Dr. Cutter said that it
lasts a day or two at most, although Dr. Fan said it could be longer if the selenium attaches to
particles and/or aerosols. ^
. Dr. Skorupa asked if the apparent lack of correlation between" water and sediment selenium
concentrations in Dr. Fan's evaporation ponds could be due to sediment heterogeneity and small
sampling size. Dr. Fairbrother replied that this question Could be discussed during the sediment
session.'
Wrap-Up • -* .' ---';-• _ "'• • ,• ' •; '• • '..
Dr. Adams summarized the discussion session as follows: Dietary uptake is criticalto
determining chronic effects. The incorporation of waterbome selenium into the diet is key; -
factors that should be taken into account include transformations, rates of transformation,
chemical species, and types of organisms (e.g., microbes, invertebrates). Peptide/protein-bound
forms are important. Free seleno-methionine is typically nonexistent or at low levels.
5 ~ .. -..'-.. , *
-Dr. Adams-asked what form(s) of selenium hi water should be measured relative to assessing
chronic toxicity and water quality standard pompliance. Dr. Cutter said that, at a minimum,
selenite, selenate, and total dissolved selenium should be measured. Another expert added that •
particulate should be measured as well. The experts discussed this question but did not come to
agreement. Experts with opinions on this topic were asked to write summaries of their opinions.
Dr. Fan gave the following summary of her opinion regarding the significance of differentiating
the protein-bound fraction of particulate selenium in the water column: .
'"= • ' _ ; , -_ *
Particulate selenium can originate from live planktonic organisms, organismal
debris/waste, and soil/sediment particles. The bioavailability of selenium associated with
these different sources can vary. Presumably, selenium associated with organisms and
biodebris represents a dietary route of exposure for aquatic consumers, and this fraction of
selenium may be more concentrated and bioavailable. Since selenium bioaccumulation
and toxic effects are mainly expressed through dietary, exposure, it is important to
distinguish me fraction of particulate selenium that is more representative of the
. consumers' diets. However, it would be a difficult task to speciate all of the. selenium in
,-• particulate matter that is of biological origin. The fraction of biogenic selenium associated
with soluble proteins may be convenient, because it may also be the most significant
selenium sink in planktonic organisms exposed to environmentally relevant waterborne '
selenium concentrations. Major incorporations of selenium into bulk algal proteins have
. been documented for several categories of algae (Wrench, 1978; Fan etal., in press; Fan et
• •''.'.", ' • 21 • • ••'. '•; • • '' '
-------
al., 1998). Based on known selenium biochemistry (e.g., the propensity of selenium to
substitute in sulfur arnino acids), similar incorporations may well be applicable to other
planktonic organisms. Therefore, monitoring protein-bound selenium in particulate matter
may provide a more representative linkage from water to aquatic consumers in terms of
selenium exposure. •
Dr. Adams gave the following summary of his opinion regarding total recoverable selenium
measurements: ,
Total recoverable selenium is recommended as one of several measurements that could be
made to correlate with adverse effects in the field. This measurement includes all of the
forms of selenium present in a water sample (both dissolved and particulate) except those
tied-up in the crystalline structure of suspended solids. This recommendation is based on
the need to identify a measurement that can be performed routinely and reliably across
multiple laboratories. Additionally, many of the existing relationships between water,
sediment and tissue have been developed around either total recoverable selenium or
dissolved selenium. Ultimately, what form(s) of selenium should be measured depends
upon the use of the data.
Dr. Cutter gave the following summary of his opinion regarding selenium measurements:
Additional •measurements that are recommended for water include dissolved (defined as
^0.4 jum) and particulate selenium. Dissolved measurements would be measured as total
dissolved selenium, selenate, and selenite. Se"2 (selenides) would be determined by
subtracting Se+4 + Se*6 from total dissolved selenium (Cutter 1982). Particulate selenium
(defined as selenium associated with particles >0.4 //m) could be measured as total
selenium as well as Se"14 and Se+6. Elemental selenium would be determined separately by
direct analysis for Se° (Velinsky and Cutter 1990). Se'2 would be determined by difference
(i.e., subtracting [elemental + Se+4 + Se*6] from total particulate selenium). As an
approach to reduce costs one could consider speciating samples, especially the particulate
fraction, only on a periodic basis.
Conclusions: The following summary of the entire discussion session was written by the
discussion leader and reviewed by the other experts.
1. Waterbome exposure to selenium in all its various forms is much less important than
dietary exposure in determining the potential for chronic effects in aquatic organisms hi
general and for fish in particular.
2. The relationship between selenium hi water and sediment relative to the aquatic organisms
that live in these compartments and constitute the diet of fishes is key to understanding the
• food chaui transfer of selenium. Factors that are important in understanding these
relationships include rates of transformation and speciation of selenium, rates of exchange
• 22 '
-------
of selenium between sediment and water and organism tissues, and types of organisms
constituting the food web.
3. Peptide- and protein-bound forms of selenium in the diet of aquatic organisms are
emerging as critical factors .in assessing the potential for chronic effects in aquatic
organisms. Free seleno-methionine appears to exist only at very low levels in tissues and
in water. .. .,
4. Bioconcentration and bioaccumulation factors are inversely related to water exposure
levels, which complicates their use hi developing water quality criteria.
- • ' "'.-'' * " .
5. To evaluate selenium hi the water compartment of aquatic ecosystems it is recommended
that at a minimum dissolved versus particulate selenium be differentiated and that selenate
and selenite be determined in the dissolved fraction, Additionally, it appears useful to
determine selenite, selenate, and protein-bound and total selenium in the particulate
fraction of natural surface waters. The latter may be of less importance for industrial
discharges. > .
DISCUSSION SESSION 2:
Technical Issues Associated With a Tissue-Based Chronic Criterion . '.
> ','.''.
Dr. Hamilton opened the session by remarking that tissues integrate all exposures an organism
experiences and represent the biological effects that water quality criteria are intended to prevent.
Question 4: Which forms of selenium in tissues are toxicologically important with respect
to causing adverse effects on freshwater aquatic organisms under environmentally realistic
conditions and why? .
Discussion leader's summary of premeeting comments:
Dr. Hamilton presented a brief summary of each individual's comments on this question. He
said there was general agreement that the form of selenium of concern in tissues was an organic,
or protein-bound, form. He asked for any comments or concerns.
Dr. Chapman asked whether this'question included organisms fed on by fish, pointing out that, if
so, it would be important to think about the issue of gut contents and to specify whether
organisms should be depurated. Dr. Fairbrother asked the other experts to clarify whether fish
were the only organisms in which effects were to be discussed, or whether anyone would say that
selenium affects other organisms. Dr. Fan replied that, based on her review of the literature,
there are not mortality or direct toxic effects on phytoplankton or invertebrates, but there may be
community change. Dr. Riedel agreed. Dr. Fan and Dr. Riedel submitted additional comments
on this point
. . . ' . 23 - :' • •.••."
-------
Dr. Fan submitted the following comments on the potential effect of selenium on community
structure:
It is clear that selenium, regardless of the form, is less toxic to lower trophic organisms
including primary and secondary producers, zooplankton, and benthic invertebrates.
Selenium contamination, however, can have an effect on the competitiveness of different
components of a given community, leading to an alteration of the community structure.
For example, in San Francisco Bay in the 1980s, a shift from a diatom-dominated to a
green algal community occurred. This shift preceded an explosive growth of the Asian
clam, Potamocorbula amurensis, which is an extremely efficient accumulator of selenium
(Brown and Luoma, 1995). It is unclear whether selenium contamination contributed to
the change in the algal community, nor can we draw conclusions about the role of
selenium in the abundance of the Asian clam. However, selenium is interacting with this
new trophic system, and a selenium bioaccumulation factor of over 100,000 from water to
the1 clam has been observed. In addition, the Asian clam is an important food source for
the indigenous sturgeon. There is some evidence that the sturgeon population in the Bay is
not actively reproducing and that field-collected sturgeon eggs exhibit high parts per
million (ppm) selenium concentrations, particularly in certain protein fractions (Kroll and
Doroshov, 1991). Unfortunately, the relationship between high selenium egg content and
sturgeon reproduction problems has not been clearly established. It remains a real
possibility, however, that selenium plays an important role in the impact of altered lower
trophic community structure on fish reproduction.
Dr. Riedel submitted the following comments on selenium toxicity and algal communities:
Although most of the discussion of selenium toxicity has focused on fish reproductive
effects, selenium toxicity can exert other effects on aquatic ecosystems. In some cases,
environmental concentrations of selenium can also exceed the acute toxicity thresholds for
a variety of algal species. The toxicity of selenium to algae is dependent both on the
species of algae and the form of selenium. Of the two predominant forms of inorganic
selenium in water, selenate has been generally observed to be more toxic to algae than
selenite. For example, selenate concentrations from 50 to greater than >10,000 |o.g Se/L
have been observed to inhibit growth of three species of phytoplankton from three
different taxa. A diatom, Cydotella meneghiania, was observed to be the most sensitive
(EC50 « 200 ug/L). A green alga, Chlamydomonas reinhardtii, was the next most
sensitive (EC50 - 2,000 jig/L), while the cyanophyte Anabaena flos-aquae was the least
sensitive, with an ECSO of >10,000 ug/L. 'None of these species were inhibited by
concentrations of selenite up to 10,000 ug/L (Sanders et al., 1989). Similar toxicity results
have been reported by Wheeler et al. (1982). Other authors, notably Kumar and Prakash
(1971) and Moede et al. (1980), have observed that selenate and selenite have similar
effects on several algal species. At least one green algae, Ankistrodesmusfalcatus, may be
unusually sensitive to selenite; Dr. Riedel has observed near complete growth inhibition in
cultures spiked with 10 ug/L selenite, but not selenate (Riedel, unpublished observation).
24
-------
Dr. Riedel has-observed at least one "field" case of selenium toxicity at concentrations
representative of mildly contaminated sites. Riedel et al. (1996) made 10 \igfL additions
of both selenate and selemie to natural phytoplankton cultures collected from Hyco Lake,
as part of a biotrarisformation experiment. The selenate cultures showed a mild reduction
in growth rate and maximum yield (~10%) compared to the control and selenite cultures.
To -verify me study, a series of selenate and selenite additions were made to another
natural collection from the same site one month later; in this case, 10 ^ig/L selenate
showed no inhibition, 20 jig/L decreased growth more than 10%, and inhibition was
complete at 200 ug/L. Selenite did not show inhibition in these experiments either.
If selenium toxicity to a particular species or group of species were to occur in the field, it
would be very difficult to observe from the existing community; the absence of some
subset of possible species; would not readily be detected (unlike the situation, of fish in
Belews where some 13 of 17 possible fish species were eliminated, there .are hundreds of
possible phytoplankton species, and rapid changes in species composition is the rio'rm).
Even a relatively small decrease in growth rate by an individual species could lead to a
very rapid decline in its abundance relative to unaffected species. Nevertheless, the lack
of these species could be significant in the food web, or as links in the chain of selenium
bioaccumulation and biotransformation. If the sensitive species are truly randomly
distributed among taxa, size classes, edibility to higher trophic levels, etc., differential
selenium toxicity to phytoplankton is probably not a significant influence on aquatic
ecosystems. It is unlikely, however, that the effects are truly random, and the net effect of
selenium toxicity to phytoplankton may be to inhibit large cells to a greater extent than
small cells (e.g., Munwar et al. 1987), diatoms to a greater extent than blue-greens (e.g., •
Sanders et al., 1989), and so on. .
To return to the original question about lexicologically important selenium forms in tissue, Dr.
Fan said that she did not believe that all selenium in tissue is in the protein-bound form. She
cited a study of her group's, currently in press, which found that the percent allocation of -
selenium into protein in algae varies with varying selenium concentration (Fan et al., in press).
Dr. Cutter, referencing his dissertation work (Cutter, 1982), said that the remaining selenium
could be going into selenium esters, found in membranes. 'Dr. Hamilton asked the experts:
whether the bottom line of the discussion was still that incorporation of selenium into protein
was the trigger for biological effects. The other experts agreed that this is at least "a" bottom
line. . .
Question 5: Which form (or combination of forms) of selenium in tissues are most closely
correlated with chronic effects on aquatic life in the field? (In other words, given current
or emerging analytical techniques, which forms of selenium in tissues would you measure
for correlating exposure with adverse effects in the field?)
25
-------
Discussion leader's summary ofpremeeting comments:
Dr. Hamilton summarized the experts' premeeting comments for this question as follows: There
were a variety of answers and agreement on some points. The experts agreed that there has been
little speciation work in fish tissue. The forms suggested for measurement were largely total
selenium or protein-bound selenium. William Van Derveer said that he would measure total
selenium only if the exposure was a field exposure.
Discussion:
Dr. Hamilton asked Mr. Van Derveer to elaborate on his premeeting comments. Mr. Van
Derveer replied that his concern is that, in laboratory studies, when diets are dosed with a specific
selenium form, the residues that accumulate in the tissues may differ from the full
biogeochemical spectrum that is found in the field. Dr. Hamilton replied that he had done a
study in which fish were fed diets either spiked with seleno-methionine or made up of selenium-
contaminated organisms from the field. He found mirror-image effects between the two diets
(Hamilton et al., 1990). He added that there has been at least one other study that indicated that
seleno-methionine is a good model for selenium present in the food chain (Bryson et al., 1985).
Dr. Skorupa said that there is fairly strong consensus in the scientific literature that food-chain
selenium, even though it is derived from different forms in water, exerts the same toxicity on a •
gram per gram basis. Besser et al. (1993) showed that seleno-methionine, selenate, and selenite
bioaccumulate to different levels, but exert the same toxicity at the same levels. However, the
various forms will move differently from water into the food chain; for, example, compare
Chevron Marsh to Kesterson (Skorupa, 1998). Dr. Cutter pointed out that the Bryson et al. study
related to water exposure, not selenium added to the diet.
Dr. Hamilton summarized that the form of selenium in the tissue most closely associated with
biological effects is an organic form. Dr. Fairbrother reminded the other experts that the original
question was what to measure in tissues. She added that, historically, total selenium is what has
been measured in tissues to relate to effects, but that in the future more measurement of protein-
bound selenium should be done. Dr. Hamilton agreed, but Dr. Riedel said that, from a
monitoring perspective, total selenium is adequate for tissues. Dr. Fairbrother pointed out that
the morning's discussion indicated that there is not always a good correlation between total
concentrations and effects. She speculated that these differences could be related to different
amounts, or different types, of protein-bound selenium. The experts discussed the implications
of the variation in the correlation between tissue levels of selenium and effects. Some argued
that this variation mostly results from individual and interspecies variation in metabolism and
fitness, whereas others said it may result from different forms of selenium in the tissues. The
latter group thus argued for unproved speciation of selenium forms in tissue.
Question 6: Which tissues (and in which species of aquatic organisms) are best correlated
with overall chronic toxicological effect thresholds for selenium?
26
-------
Discussion leader's summary ofpremeetingcomments:
Dr. Hamilton summarized the experts' premeeting comments as follows: Almost all of the
experts said that reproductive tissue is best correlated with effect thresholds. Some suggested
that whole-body residue measurements would also be acceptable; whole fish are easier to obtain
and much of the data in the literature is on .whole-body residues. Dr. Fairbrother and Dr.
Chapman suggested sampling benthic invertebrates; Dr. Cutter recommended the, cytosol fraction,.
of prey organisms. ,
i • ., , ', -
Discussion: ---.'. , ' •
Dr. Hamiltontasked the experts whether they could recommend the ovaries as the tissue of
choice, even though ovaries are not available all year. After a brief discussion, the experts agreed
that fish ovaries are the tissue of choice in which to measure selenium levels. This agreement,
however,,was followed by further discussion. • -•
• - ' ," " ' "<• . ' - '
Dr. Adams said that there needs to be a great deal more data on the variability of thresholds of
effect among various species, habitat types, and environments. Dr. Hamilton agreed. Dr. Adams
said that it would be important to characterize the distribution of sensitivity among organisms of
interest, as is currently done for the water-column criteria. Dr. Fairbrother asked whether the
variability is based mostly on species sensitivity, or whether the type of selenium measured and
-the problem of gut contents contribute to the variability. Dr. Hamilton said that a lot of the
variability in the current data set is due to life stage, as older organisms are more resistant. He
said that, if whole-body residues are used, larval fish should be sampled. . •
Dr. Fairbrother asked Dr. Skorupa to comment based on his experience with the agricultural
drainwater study. He replied that that type of dataset would be useful for taking a probabilistic
approach to the criterion. The National Irrigation Water Quality Program (NIWQP) dataset
(Seiler, 1996) has a large amount of data relating water concentrations to fish tissue levels
(almost exclusively whole-body). Dr. Skorupa said that this data could be used, along with good
measures of tissue effect levels, to develop, a water column number that was associated with a
certain probability of exceedance of effect thresholds. He agreed that more work would need to
be done on effect-level variability among species. Dr. Fairbrother said that, if this type, of
analysis were done, it would be important to look at all the relevant parameters, such as what,
type of selenium is measured, whether the gut content is included, etc. -
Dr. Fan asked how endangered species could be sampled for regulatory purposes. Dr. Hamilton
replied that a muscle-plug technique has been developed, in which a biopsy is analyzed by
neutron activation. Unfortunately, muscle tissue does not seem to correlate well with effects,
based on his research (Hamilton, unpublished). Dr. Fan asked if blood sampling is an option; Dr.
Riedel replied that it is, although it is hard to get blood from the smaller fish. Dr. Hamilton said
that he has seen sampling of gills, blood, heart, and liver, but that are few data on these tissues.
Dr. Riedel responded that his group had sampled various tissues in fathead minnows. They
27 • - '..'."'
-------
found that selenium concentrations increased more slowly in muscle tissues than in other tissues.
Selenium concentrations in livers, however, mirrored concentrations hi ovaries (Dr. Denise
Breitburg, unpublished research for the EPRI project). Dr. Riedel noted that, unlike ovaries,
livers are available all year.
Dr. Adams said that he thinks gonadal tissue is by far the first choice, because it is where the
most sensitive effect is expressed; it is worth waiting to sample this tissue when it is available.
Other experts agreed, although it was pointed out that there are additional sampling difficulties;
some fish bear their young live, and sometimes it is difficult to get gonadal tissue even during the
reproductive season. Dr. Lemly said a good approach would be to target a sensitive species that
is widespread, such as a salmonid or a centrarchid, depending on the water body. Other experts
reiterated that assessing data sensitivity across species would be'crucial to the establishment of a
tissue-based criterion.
Question 7: How certain are we in relating water-column concentrations of selenium to
tissue-residue concentrations in top trophic-level organisms such as fish? What are the
primary sources of uncertainty in this extrapolation?
Discussion leader's summary ofpremeeting comments:
Dr. Hamilton summarized the experts' premeeting comments as follows: Experts expressed that
ihey were '!not very certain" about making these correlations.
Discussion:
Dr. Hamilton made the point that there are many situations in which the water-column
concentration of selenium is low but tissue levels are high (Hamilton et al., 1990; Schroeder et
al., 1988; Skorupa and Ohlendorf, 1991; Zhang and Moore, 1996). Loading to tissue can come
from the sediments and biota as well as from the water. Dr. Hamilton also asked whether it is
possible that seleno-methionine is found hi such low concentrations in the water column because
it is highly bioavailable and taken up immediately when cells lyse. Dr. Cutter said that his group
is working on this question.
The experts discussed using the MWQP dataset to develop an empirical probabilistic approach
to correlating water-column to tissue concentrations of selenium. Dr. Adams did not have great
success in an initial attempt to make these correlations (Adams, unpublished), but he plans to
redo his analysis. Dr. Hamilton said that better correlations could probably be achieved by taking
site-specific factors into account. Dr. Adams agreed; he said that some of the published studies
say that selenium transfer from the water to the food chain can be predicted well within a small
site, but attempts to extrapolate to a regional or national scale fall apart.
Dr. Cutter raised the issue of detection limits, which he said are often not low enough for
researchers to adequately make the correlations that are attempted. He recommends 0.01 ppb,
.28
-------
because most uncontaminated waters are below 0.1 ppb total selenium. He and Dr. Skorupa
discussed this issue. Dr. Skorupa questioned whether such a low detection limit is necessary if
the effects threshold is much higher. Dr. Cutter responded that the lower the detection limit, the
more useful, the data will be for future uses and for looking at sublethal effects. Dr. Fairbrother
agreed that a low detection limit was a good idea when trying to establish water-tissue
' correlations. Some experts objected to the characterization of the natural background
concentration of selenium as 0.1'ppb, but this discussion was tabled until the cross-cutting
session. , ' .-'...-
Dr. Hamilton then asked whether the other experts thought there would be more certainty hi
relating dietary concentrations to tissue residue in fish, and then in the two-step process of
relating water to food organisms to fish. The experts agreed that there would be more certainty
in these relationships, but that they still would be difficult to quantify. Many of the experts
mentibned the difficulty caused by spatial and temporal variability in water-column selenium
concentrations. Dr. Fan also questioned how to define diet. She mentioned Saiki's work in the
San Joaquin River and San Luis drain (Saiki and Lowe, 1987; Saiki et al., 1993), which showed a
good correlation between benthic invertebrates and detrital selenium. She emphasized, however,
that it is crucial to determine what organisms are actually eating when trying to model food-chain
transfer. Dr. Hamilton added that this point brought up the issue of sediments, which can be a
source of loading to the food chain, and thus should potentially be included- in correlation
models. Dr. Fan said that migration of organisms in and out of the system poses another problem
for correlations.
Wrap-Up:
-" • , ' - • ' ' •
Dr. Hamilton summarized the discussion from this session. He said that he thought the experts
had come to agreement that tissue integrates all exposures, whether different food types or water.
Issues that had been raised included community change and variability in the sensitivity of the
reproduction endpoint across fish species, and sometimes within species; there are limited data
on both of these topics. He said that the group had riot thoroughly discussed which eridpoint was
appropriate to examine (e.g., mortality, growth, deformities). "Dr. Fan responded that this is why
she thought the blood idea would be interesting. Selenium may reduce blood's oxygen-carrying
capacity, and this endpoint would respond fairly quickly to ingestion of selenium. Dr. Hamilton
replied that an important question to ask in considering an endpoint is whether the effect is
reversible. If so, the effect may not be truly adverse; it may not have effects at the .population
' level. ' . . '•'.'.-'
Dr. Hamilton said that the experts had largely agreed that the ovary is the best tissue in which to
measure residues; larval fish are a second choice if ovaries are not available. He reiterated that
the issue of sensitive species is key. He said that information on linking sediments or water back
to tissue is a data gap; too few data exist to build a good model. Dr. Adams said that he thinks
the data exist, but that gathering sufficient data to encompass variability within and across sites
would be a large task. He added that EPA should make a broad effort to compile these data sets.
••"' ;' ••''•'.'"'"• -29 '- :< • '
-------
Dr. Fairbrother put in a cautionary note that the empirical approach of using large data sets to
look at correlations is a useful starting point, but the real goal should be to understand
mechanistically how selenium moves through the different compartments in different systems.
Dr. Hamilton agreed, and said the data set should be built around reproductive studies in a series
of fish species.
Dr. Hamilton said that some of the experts had suggested sampling benthic invertebrates because
they are a key component of the food chain. He agreed that this is a good idea, and added that
tissue concentrations in these organisms will be less variable than other components of the
ecosystem. Dr. Riedel pointed out that selenium concentrations in benthic invertebrates are
highly affected by gut contents, but other experts replied that this problem can be solved by
depurating the organisms. Dr. Adams said that which compartment is most variable can be site-
specific; sediments can be very heterogeneous and may therefore be highly variable. Other
experts responded that this problem could be addressed by sampling in multiple locations.
Dr. Adams made the final point that, when looking at sensitive species, it is important to look at
species that actually occur in the region under study. Dr. Hamilton agreed and added that, in the
west, one may want to differentiate between native and introduced species.
Conclusions: The following summary of the entire discussion session was written by the
discussion leader and reviewed by the other experts.
s
There was an unexpected, readily reached agreement on the four issues concerning the possibility
of a tissue-based chronic criterion. The experts agreed that the selenium form in tissue that is •
toxicologically important with respect to causing effects on freshwater aquatic organisms under
environmentally realistic conditions is protein-bound selenium. By "protein-bound," experts
meant all organic selenium forms as a group. It was acknowledged that different forms of
selenium can exist in tissue, but analysis of tissue selenium is typically as total selenium and not
by speciated forms. In general, the organisms of concern were fish, which is the group usually
emphasized in consideration of adverse effects on aquatic life. However, aquatic invertebrates
were mentioned as another tissue of concern, because they represent an important link in food-
chain transfer of selenium in the aquatic environment.
Protein-bound selenium, measured as total selenium, is the selenium form related to chronic
toxicity. The major concern was organo-selenium forms bound by proteins rather than free
organo-selenium or inorganic forms. One concern raised was that the form of selenium to which
organisms are exposed might influence the resulting tissue residue; thus, emphasis should be on
use of data from environmental field studies rather than laboratory studies in establishing a
tissue-based criterion. The key tissues identified by experts were fish gonads, ovaries, or eggs.
Due to the limited availability of ripe gonads/eggs, however, newly hatched larvae analyzed for
whole-body residues were recognized as a possible alternative. Most data are on whole-body
fish, but for a variety of life stages rather than the preferred, sensitive larval life stage. The
dataset for gonads, ovaries, and eggs are more limited. Liver tissue was mentioned as a third
• 30
-------
tissue for possible monitoring of residue concentrations. .
Referring back to the dietary route for selenium, benthic invertebrates were recognized as a
possible group of organisms to monitor in assessing adverse effects on^quatic environments,
especially from the standpoint of shifts in the composition of a community and the resultant ,
effects on higher trophic levels which might also shift in composition. One concern with benthic
invertebrates was possible errors in residue concentrations due to gut contents.
' '-' ~~ '•''"' m~" » • .''.*'•
Even though tissues were readily embraced as a possible component for establishing a criterion
for selenium, the relation to water concentrations was questionable. Experts readily .
acknowledged that there was a lot of uncertainty in modeling the relation between concentrations
in fish tissue and water. However, the level of uncertainty was less for the relation of selenium
in water to that in aquatic invertebrates, and concomitantly, from selenium in dietary organisms
to fish tissue.
Data gaps were identified including the limited number offish reproductive studies where
exposures included water and dietary routes using realistic water characteristics and food
organisms and where meaningful endpoints were measured such as egg and larvae residues along
with biological effects on offspring^ These reproductive fish studies should include several
representative families of fish.
DISCUSSION SESSION 3:
Technical Issues Associated With a Sediment-Based Chronic Criterion •
Mr. Van Derveer opened the session by making some general observations based on the
premeeting comments. First, sediment is the dominant sink for selenium. Second, sedimentary
organic materials (detritus) are an important dietary resource for aquatic invertebrates, and
selenium tends to accumulate in detritus. He added that the literature applicable to sediment-
based criteria is sparse; most participants relied on two to three references in their comments.
Finally, he said that there was a range of opinions expressed in the comments regarding the
potential merit of a sediment-based criterion. ,
" . '• **"
Question 8: Which forms of selenium in sediments are toxicologically important with
respect to causing adverse effects on freshwater aquatic organisms under environmentally
realistic conditions? :
Discussion leader's summary ofpremeeting comments: <
Mr. Van Derveer presented a brief summary of each individual's comments on this question.
Experts expressed a range of different opinions. Forms suggested included total selenium,
elemental and organic selenium,'and detrital selenium. Various experts made the points that
redox affects jspeciation and that improved analytical methods are needed.
...-'•- .'...•- . 31 . ' •
-------
Discussion:
The issue of sediment heterogeneity was raised and discussed by some of the experts. They
agreed that selenium can be distributed very heterogeneically in sediments, and that this should
be considered in sampling and modeling. Dr. Skorupa added that the spatial heterogeneity of
benthic invertebrate distribution should also be noted. He said that this distribution often maps
onto the spatial heterogeneity of selenium; both are found in areas of fine organic matter. In his
opinion, sampling that does not concentrate on these areas misrepresents the toxicological risk.
Dr. Riedel agreed and said that normalization to total organic carbon (TOC) is one way to solve
this problem. Mr. Van Derveer said that he would later present some data showing that
depositional zone selenium concentrations can fairly well predict concentrations in riffle-
dwelling midges.
Mr. Van Derveer asked Dr. Adams to elaborate on his call for improved analytical methods for
sedimentary selenium. Dr. Adams replied that he sees variability among analytical laboratories
in determining sediment selenium speciation. Dr. Cutter responded that the techniques are
established, but that better training may be needed. Dr. Skorupa said that he agreed with Dr.
Adams, and added that it is important that all analytical data be evaluated. Dr. Riedel agreed that
there is a problem with analysis for selenate. He and Dr. Fan advocated the expansion of the use
of liquid chromatography for selenium analysis.
»
"Mr. Van Derveer asked if there were any other.issues related to question 8, recognizing that the
literature relating sediment concentrations to toxicity is sparse. Dr. Cutter replied that, because
of the lack of literature, the conclusion should be that the experts had low confidence in
answering the question; Dr. Riedel
agreed.
Reanalysis of Sedimentary Selenium Toxicity Data from
Van Derveer and Canton (1997) Using Only Effects
Data for Fish
Observed
Predicted
None
• Observed Effects Level
• Predicted Effects Level
(n = 6)
(n = 3)
0.5 10 15 20 25
Total Sedimentary Se (ug/g)
Figure 5. Reanalysis of sedimentary selenium toxicity data using only effects
data for fish. (Van Derveer and Canton, 1997.)
Mr. Van Derveer presented a
graph using data from'a
publication of his (Van Derveer
and Canton, 1997) (Figure 5). The
graph showed the relationship
between sedimentary selenium
concentration and effects in fish,
using data from a variety of
sources, including NIWQP,
Belews Lake, Hyco, and others.
Mr. Van Derveer said that there
appears to be a clear
concentration-response ratio, but
that more data are needed. Dr.
Skorupa cautioned that the power
of the study should be kept in
32
-------
mind when there is a finding of "no effect," as many studies lack the necessary power to detect
. effects. •.-.-•..
! '
i ' ' ' ' - - '" .
Question 9: Which form (or combination of forms) in sediment are most closely correlated
with chronic effects on aquatic life hi the field? (In other words, given current or emerging
analytical techniques, which forms of selenium in sediments would you measure for
correlating exposure with adverse effects in the field?)
Discussion leader's summary ofpremeeting comments:
Mr. Van Derveer presented a brief summary of each individual's comments on this question as
follows: He himself said to measure total selenium and mentioned his unpublished data
indicating high sediment-to-benthos correlation in lotic (flowing-water) systems. Dr. Fairbrother
said to measure total selenium and to consider lotic vs. lentic (standing water) differences. Dr.
Adams said to measure total selenium, because individual species have not been correlated with
benthos. Dr. Fan said to measure proteinaceous selenium and seleno-methionine in benthos and
detritus. Dr. Riedel said that better analytical methods are needed, and Dr. Skorupa said that a
matched sediment and benthos study is needed. • _ '
Discussion: .
Dr. Adams clarified that the, lack of correlation between selenium species and benthos results
from the lack of data on the subject. Dr. Fan said that her recommendation to measure
proteinaceous selenium was based on an educated guess that detrital selenium is probably
concentrated in peptides or proteins. Dr. Cutter agreed that this is a reasonable assumption. Dr.
Fan added that her group
performed an experiment in which
they compared detrital material
captured in a sediment trap to
cored sediments. The material
that settled in the trap (rich in
detritus) contained an order of
magnitude more selenium than did
the cored sediments (Fan,
unpublished).
Relationship Between the Concentrations of Selenium
in Bulk Sediment and Chironomidae Larvae in Streams
of the Middle Arkansas River Basin, CO
100.0
80.0
60.0
40.0
-------
'He pointed out that there seemed to be a positive relationship. The experts discussed the
possibility of relating this information to the effects information in the previous graph to estimate
a threshold of dietary selenium associated with effects hi fish. Mr. Van Derveer agreed that this
was a useful direction for research, but he stressed that far more data would be needed. Dr.
Skorupa added that, to perform such an analysis, it would be important to know what the fish
were actually eating. The experts discussed the possibility of using assimilation efficiencies and
protein-normalized selenium values in food-chain modeling. The variety of food chains present
in different habitats was also discussed; not only do lotic and lentic systems differ, but lotic
systems have high-and low-energy areas.
Question 10: In priority order, which sediment quality characteristics (e.g., TOC, etc.) are
most important in affecting the chronic toxicity and bioaccumulation of selenium to
freshwater aquatic life under environmentally realistic conditions? Of these, which have
been (or can be) quantitatively related to selenium chronic toxicity or bioaccumulation in
aquatic organisms?
Discussion leader's summary ofpremeeting comments:
/
Mr. Van Derveer gave a brief summary of each individual's comments on this question. He said
there was a reasonable level of agreement among those who responded. Everyone who
responded mentioned TQC may be important, although Mr. Van Derveer pointed out that they all
'Cited the same reference (Van Derveer and Canton, 1997). Other characteristics mentioned
included Eh, pH, gram size, sulfate, sulfide, iron, and temperature. Dr. Fan mentioned detrital
selenium and noted the issue of spatial variability. Dr. Cutter warned to beware of
pseudocorrelation when looking at the effects of TOC.
Discussion:
Dr. Adams asked Dr. Cutter if the pseudocorrelation information was published. Dr. Cutter
replied that it is (Velinsky and Cutter, 1991). He explained that high carbon deposition drives
high microbial populations, which leads to anoxia in the sediment; elemental selenium is
precipitated under anoxic conditions.
Dr. Fan said that there is a correlation between detrital selenium levels and accumulation of
selenium by benthos. She cited Saiki's work in the San Joaquin River (Saiki and Lowe, 1987;
SaiM et al, 1993), as well as the data presented by Mr. Van Derveer. She said that detritus
should be looked at as a separate sediment component, using detrital selenium, rather than
selenium in whole sediments, to relate back to the water column. In lentic systems, detritus may
be sampled by putting out sediment traps; the top layer will be detrital. Dr. Adams responded
that TOC was a good measure of detrital content. Dr. Fan replied that TOC is relevant, but that
she was looking for a more direct correlation; the value of TOC can be false if the sediment
contains a significant amount of carbon such as carbonate. Other experts brought up the
difficulties in sampling detritus, but this discussion was deferred to the cross-cutting session.
34
-------
Question 11: How certain are we in relating water-column concentrations of selenium to
sediment concentrations? What are the primary sources of uncertainty in this
extrapolation? ,
Discussion leader's summary ofpremeeting comments:
Mr. Van Derveer summarized each individual's comments on this question. He noted that many
of the experts referenced his paper (Van Derveer and Canton 1997), which argued that TOC is a
variable that may determine sedimentary selenium accumulation. He also cited lentic data
obtained by Birkner (1978). Dr. Riedel said that we are very uncertain hi relating sediments ,to
water, and that this relationship is affected by many processes. Dr. Cutter said that water .
residence':time determines sedimentary selenium accumulation, which can be calculated. Dr. Fan
said that the sediment-water relationship is confounded by variability among sites, and she listed
many possible sources of uncertainty. V ,
Discussion: ..•
Dr. Fan said that microbes may greatly affect the sediment-water relationship, because elemental s
selenium is an important sink, and also because microbes can volatilize a large amount of
selenium. She noted that this has been shown under laboratory or microcosm conditions
(Karlson and Frankenberger, 1990; Zhang and Moore, 1997). Dr. Cutter reiterated that hi a lake
-system, the longer the residence time in the water, the more selenium accumulates in the
sediments; this can be modeled relatively easily.. He said that he did not know if this could be
done for lotic systems. Mr. Van Derveer added that Birkner (1978) looked at selenium in many'
different compartments hi lakes and reservoirs in Colorado and Wyoming and that this could be
used to generate a lentic model similar to his lotic one. Dr. Fan brought up the problem of
sediment heterogeneity and asked whether a selenium water/sediment ratio is a
pseudocorrelation. Dr. Riedel responded that it is a real correlation; but a poor and confused one,
affected by many poorly understood processes. Dr. Adams said that the relationship comes down
to mass, balance and rates of transfer. He said that he had only moderate success in attempting a
sediment-water correlation for> lentic systems, using 204 water-sediment pairs from 15 water ;
bodies (Adams, unpublished). The correlation coefficient was 0.66 overall. Correlating water
with the fine-grained fraction of sediments yielded a coefficient of 0.68; with the coarse-grained
fraction the coefficient was,0.73. Dr. Riedel pointed out that, as with fish,,temporal variability
affects correlation; because water is highly temporally variable and sediments are well buffered,
it is not surprising that thei correlation is poor. '
'••-.'-• ~ i
Mr. Van Derveer showed another graph from his work to stimulate more conversation (Figure 7).
This graph showed the product of dissolved selenium and sedimentary TOC on the x-axis and
sedimentary selenium on the y-axis. He noted that, at .least in streams of the western United
States, there is a fairly predictable relationship. Dr. Cutter suggested revisiting the data with a
normalization to aluminum in the low-TOC range (i.e., normalize to "TOC or alumuium"):
Other experts said that it is important to consider whether systems are at equilibrium or not. (For •
. - .' ' .- ,35 ' '" '• --'••"•'-.'.•-.
-------
example, is there an ongoing input?)
Western Streams Model from Van Derveer and
Canton (1997)
100
£
"O
I
0)
CO
0)
V)
10
0 1 10 100 1000
Dissolved Se (pg/L) x Sedimentary TOO (% dw)
Figure 7. Western Streams Model. (Van Derveer and Canton, 1997.)
Research Needs
Dr. Fairbrpther moved the conversation to the issue of research needs. Dr. Fan said there is a
need to test the relationship among waterborne selenium, TOC, detrital selenium, total sediment
selenium, and biota selenium for all abundant sediment species. Dr. Riedel said that it would be
important to obtain the assimilation coefficients for different bentiiic organisms and to examine
how the different types of selenium in the food affect these coefficients. Mr. Van Derveer said
that the issue of whether or not organisms are depurated should be addressed. Dr. Cutter said
that a coupled examination of the ecosystem and the biogeochemical cycle should be performed
at a site. Mr. Van Derveer said that he would like to see a more mechanistic understanding of
what affects selenium accumulation in the sediments. Dr. Skorupa said he would like to see
more data linking the biology of the most sensitive species to the heterogeneity of the sediments;
some species may feed preferentially in high-selenium areas (because of other characteristics of
these areas). Dr. Fan.agreed that she would like to see if selenium accumulation by benthos can
be correlated with selenium levels in organic-rich sediments. Dr. Hamilton mentioned the issue
of differential accumulation of selenium by closely related species (e.g., flannelmouth vs.
razorback suckers). Mr. Van Derveer said that it would be useful to do some.controlled
laboratory studies using field-collected sediments, perhaps running EPA's Lumbriculus
bioaccumulatipn test. Dr. Adams said he would like to see examination of the sites that have
relatively high levels of selenium but no effects seen; he said that these sites should help shed
Light on mechanistic understanding of processes. Dr. Fan said it is important to understand the
mechanism of toxicity; she cited a review article from the biomedical field (Spallholz, 1994),
which she urged the other experts to read.
36
-------
Wrap-Up
Mr. Van Derveer summarized the preceding discussion. After some further discussion, the -
experts agreedthat the following was an accurate summary: '
\ " ' - • ' • ' i
Elemental and organic selenium predominate in sediments. The process is somewhat redox
driven, depending on the system type and the characteristics of the sediments! Selenium tends to
be located in detritus. Total selenium may predict toxicity; there are some questions about
relating selenium concentrations to TOC, the possibility of carbon-to-nitrogen (C:N) ratio
normalization, normalization to proteins, and direct measurements of detritus vs. whole
sediment. Spatial heterogeneity is an issue, as is preferential feeding (some species feeding hi
certain areas with high selenium concentrations). In addition, there are some issues with the
power of biological assessments to detect effects. Concerning the question of what should be
measured,' there is some argument that total selenium in surficial sediments should be measured
and it was also pointed out that multiple dietary pathways should be considered when they exist.
Direct correlations of specific selenium forms to effects are lacking, but an overall causal1
relationship tends to exist, where high selenium in sediments tends to co-occur with effects at the
population and community level. Some examples might be (1) effects seen in Belews Lake after
the cessation of selenium input and (2) microbial community changes.
",..'/••
Which sediment characteristics appear to.be most important? TOC seems to be important, but
-may be inappropriate for anoxic sediments where redox conditions are driving selenium
accumulation; there may be some pseudocorrelation or a simple biogeochemical process moving
selenium and .sequestering it in sediment. Quantity of detritus may be important, and it may be '
important to measure that directly. In lentic systems, the residence time appears to be important;
selenium accumulation can be calculated based on residence time and some other factors.
Aluminum should be considered as a. marker for inorganic sediment composition, to help
differentiate detrital matter from inorganic material. Efflux from sediment to the water column is
important. Sulfate may be important to sedimentary microbial communities, affecting selenium
•speciation. (Dr. Fairbrother noted that most items on this list reflect, not results reported in the
literature, but things some or all of the experts think should be important, based on their
understandings of the relevant processes.)
Finally, relating .sediment to water^ a TOC model exists for western streams. Residence time is
important for both lentic and lotic systems. Whether the system is at equilibrium or not should
be considered. Uncertainty is moderate overall for relating sediment to water, based on the small
number of publications specifically addressing this relationship.
Conclusions: The following summary of the entire discussion session was written by the
discussion leader and reviewed by the other experts.
Sediment is the dominant sink for selenium in aquatic ecosystems. Elemental and organic
selenium tend to predominate in sediment, with elemental selenium dominating under reducing
• - ' ' ' : - • ' 37 :" '.•'•. '' • ''••".-..
-------
conditions. Organic selenium is believed to be markedly more bioavailable than elemental
selenium. Sedimentary organic materials (detritus) are an important dietary resource for aquatic
invertebrates. Selenium tends to accumulate in detritus, thereby entering the benthic-detrital
food web.
The literature regarding the lexicological effects of sedimentary selenium is sparse, and most
workshop participants relied upon two to three publications for preparing their premeeting
comments. Several participants cited a paper by Van Derveer and Canton (1997), which
concluded that the total sedimentary selenium concentration is a reliable predictor of chronic
toxicity in fish and birds. A reanalysis of those data (Van Derveer, premeeting comments),
focusing only on fish, indicated that toxic effects may occur when total sedimentary selenium
concentrations exceed 4 /ug/g (dry weight). The field data that were collected from Belews Lake
after curtailment of fly ash input demonstrate the importance of sedimentary selenium in
bioaccumulation and toxic effects on fish. Although waterbome selenium concentrations
declined rapidly, Se concentrations in sediment and biota declined very slowly and teratogenic
effects in fish populations persisted even 10 years later. Effects data for particular selenium
forms in sediment are lacking in the literature; thus, preventing interpretation of sedimentary
selenium speciation data.
The relationship between sedimentary selenium and toxicological effects may be affected by
factors such as spatial heterogeneity in sedimentary selenium concentrations, habitat selection by
•different types of aquatic biota, and preferential feeding habits of aquatic biota. Moreover,
efforts to relate toxicological effects to sedimentary selenium concentrations, or selenium
concentrations in any environmental compartment, should consider the statistical power of the •
effects assessment. It was hypothesized that prediction of food web bioaccumulation and
subsequent chronic effects on higher trophic levels might be improved by measuring detrital
selenium, proteinaceous selenium in sediment, or seleno-methionine in sediment.
Unpublished data (Van Derveer, premeeting comments) were presented which indicate that a
significant positive relationship exists between total selenium in surficial sediment (ca. 0-3 cm)
and selenium accumulation in depurated Chironomidae larvae from streams of the middle
Arkansas River basin, Colorado. These data suggest that, at least for some systems, total
sedimentary selenium is well correlated with bioaccumulation in benthic organisms.
The following sediment quality characteristics were identified as potentially relevant to chronic
selenium toxicity:
• Sedimentary TOC (possibly inappropriate for anoxic sediments where redox processes
predominate);
• Quantity of sedimentary detritus present;
• Water residence time (longer residence time promotes greater sedimentary selenium
accumulation);
• Normalization of sedimentary selenium to sedimentary carbon:nitrogen ratio;
38
-------
• Normalization of sedimentary selenium to sedimentary protein content;
• Efflux of selenium from sediment to water; and .
« Sulfate concentrations (may affect the composition of sedimentary microbial communities
and thus the speciation of sedimentary selenium)., '
Sedimentary selenium can be related to waterborne selenium using two approaches, with a
moderate degree of uncertainty. For streams of the western United States,,a TOC-based model
can be applied (Van Deryeer and Canton, 1997). Sedimentary selenium accumulation in lentic
and lotic systems can be calculated by considering residence time and applying a mass balance
approach (Gutter, 1991). Because waterborne selenium concentrations tend to exhibit large
temporal variations, the strength of the water-to-sediment correlation is affected by the averaging
period selected. If is also important to consider whether the regime of waterborne selenium input
to a system is relatively consistent over time (e.g., a stream receiving selenium from surrounding
geological sources) or recently altered (e.g., Belews Lake after curtailment of fly ash input).
The following research issues were identified as being relevant to developing a more complete
understanding of the role of sediment in chronic selenium toxicity:
• Assessing the relationship between detrital selenium and food web bioaccumulation;
• Understanding factors that may cause variability in selenium accumulation in benthic
invertebrates, such as interspecific differences, assimilation rates, and effect of sedimentary,
selenium speciation;
• Evaluating the potential merit of depurating specimens prior to correlation with sediment, or
any other environmental compartment; •
• Correlating sedimentary selenium concentrations at preferred feeding sites with particular
species of interest (e.g., endangered fish); ;
• Defining the mechanisms of selenium accumulation in sediment; and.
• Performing laboratory studies of sedimentary selenium accumulation by invertebrates.
DISCUSSION SESSION 4:
Cross-Cutting Issues Associated With a Chronic Criterion
Dr. Fairbrother explained that the cross-cutting session was intended to capture issues that did
not fit neatly in one compartment, as well as any other comments or ideas that any of the experts
had not yet had a chance to raise. She listed the following issues to be discussed during the
session: spatio-temporal variability and averaging'times; ecosystem type (including lentic vs.
lotic); site-specific approaches; analytical methods; sufficiency vs. toxicity; natural background;
and interactions with other stressors.
Question 12: How does time variability in ambient concentrations affect the
bioaccumulation of selenium in aquatic food webs and, in particular, how rapidly do
residues in fish respond to increases and decreases in water concentrations?
. • " • ' • .39 ; .. -
-------
Discussion leader's summary ofpremeeting comments:
Dr. Fairbrother summarized the experts' premeeting comments on this question as follows:
Water concentrations can change by ten-fold in 1 month. Bioaccumulation in fish tissues
changes over months. Phytoplankton and bacteria accumulate selenium rapidly (5-6 days), with
turnover in 2 weeks. The rate-limiting step is the conversion of the inorganic form to the organic
form. The 11/2 for sediments depends on the form of selenium.
Discussion: , . .
Dr. Cutter suggested that averaging time should be a function of retention time (the physics of
the system), which varies greatly between lentic and lotic systems. Dr. Fan said that the
biological component of a system can also have an effect on averaging time. Dr. Skorupa again
raised the issue that a short-term spike can have long-term food-chain implications, based on the
Maier et al. (1998) study. Dr. Fairbrother summarized that, in addition to the physics of the
system, the biology of the system has to be considered, because organisms will have different
effects on the residence time of selenium in the various compartments. Both physics and biology
should be looked at when examining the relationship of water fluxes to responses or to fish tissue
changes.
Question 13: To what extent would the type of ecosystem (e.g., lentic, lotic) affect the
chronic toxicity of selenium?
Discussion leader's summary of premeeting comments:
Dr. Fairbrother summarized the experts' premeeting comments on this question as follows: There
was general agreement that the type of ecosystem has a large effect on selenium cycling in the
system. Lotic systems have a slower rate of conversion of inorganic to organic selenium, shorter
retention time of carbon and decreased storage potential, and less accumulation of selenium in
sediments. The modeling approach differs between lotic and lentic systems. Bacteria and
phytoplankton species differ between the two ecosystem types, which may cause differences in
bioaccumulation factors. Also, lentic systems have higher primary productivity. Open (rather
than closed) fish populations make changes in recruitment more difficult to document.
Discussion:
Dr. Riedel added that lotic systems have a larger contribution of terrigenous detritus, which tends
to dilute the selenium concentration. Dr. Fan replied that if the allochthonous input is through
seleniferous soils, the reverse could be true. Dr. Skorupa said that another way in which lotic
and lentic systems differ is that lotic systems are more likely to provide the source water for
lentic rather than vice versa. Dr. Fairbrother replied that the reverse could also be true. Dr.
Riedel said that the key point is not to consider parts of systems in isolation. Dr. Hamilton
agreed that the interconnection of lentic and lotic systems is important. He cited a study by
40 ,
-------
Radtke et al. (1988) on the Lower Colorado River, which showed that selenium in the backwaters
was coming from the river's main stem. Conversely, a study by Engberg (currently in review)
showed that only 18 percent of the selenium entering Lake Powell stays hi the lake.
Dr. Adams said that there are other ecosystem types that should be considered, such as the Great
Salt Lake, saline streams, ephemeral streams, and cold northern streams. ..He added that .
indigenous biology in each of the different environments should be taken into account
Dr. Fairbrother questioned the statement that modeling approaches vary for different systems.
She said that, in her opinion, the major components of the model are conceptually the same for
different systems and that what varies are the rate processes. She asked for 'comments from the
other experts. Dr. Fan replied that components other than rates vary (e.g., food-web
composition). Dr. Cutter replied that food-web composition is taken into account by Dr. Bowie's
model. Dr. Bowie agreed.
Dr. Fan asked Dr. Bowie what was the minimum amount of information required to use his
model for" a site. Dr. Bowie said that one can use very little information and make guesses, but
that the more actual data that are included, the better the model is. He said that the hydrology of
the system and the selenium loadings would be the most important information, followed by the
food web structure and some hiformation on sediments. Dr. Fan replied that it is difficult to get a
good mass balance for a dynamic system. She mentioned volatilization as an importarit
componerit-that is difficult to measure. Dr. Bowie replied that he didn't think volatilization was
a major-factor in most systems; further, the model takes into account factors which affect
volatilization, such as me volatile fractions of bacterial and algal excretions. During the
discussion, it was also clarified that the main purpose of the model is to be able to tie biological
effects to water concentrations resulting from loadings, and possibly predict outcomes in
hypothetical future situations.
Site-Specific Approaches:
Dr. Fairbrother summarized suggestions Dr. Adams made about different approaches for doing
site-specific assessments. These were: (1) Empirical database of fish tissue concentration as a
function of water concentrations (develop for a variety of species and couple with reproductive
effect concentrations); (2) Apparent Effects Threshold (AET - use it to identify areas where site-
specific effects measurements should be done); and (3) Modeling approach (parameterize for the
ecosystem of concern). .
Discussion: ,
Dr. Adams elaborated further on the AET approach. He explained that it is the approach shown
in the graph Mr. Van Derveer presented earlier (Figure 5). For multiple sites, concentrations of
selenium in various compartments are coupled with mformatibn on the presence or absence of
biological effects at the site. This approach identifies three ranges of concentrations: a range in
• 41 "• '. '":••''; - :
-------
which, effects were never seen, one in which effects were sometimes seen, and one in which
effects were always seen. This approach helps to establish rough effect thresholds and to identify
sites for which more site-specific data are needed (i.e., those in the middle range). The AET
approach has been articulated for marine sediments (Barrick et al., 1989). Dr. Bowie said that,
for such an approach, using total selenium measurements might not be desirable for sediments,
because detrital selenium is what gets into the food web. Dr. Fairbrother agreed that, in the
sediments discussion session, there had been suggestions to normalize to TOC or protein. Dr.
Fairbrother emphasized that, for the AET approach, it would be crucial to consider whether the
studies used had adequate power to detect effects.
Dr. Fairbrother then asked Dr. Adams to discuss the idea of an empirical database. Dr. Adams
said that this idea was based on various papers (e.g., Skorupa and Ohlendorf, 1991; Ohlendorf
and Santolo, 1994). He said that, basically, this approach would again use information from
multiple sites. Relationships between, for example, water concentrations and levels in fish
reproductive tissue could be graphed and used to create a regression line. The strength of the
regression's predictive power could be evaluated; hi addition, as with the AET approach, sites
with strong site-specific influences could be identified.
Dr. Riedel asked Dr. Adams how he would modify the water-to-fish regression if it did not fit
well. Dr. Adams replied that his first step would be to remove sites like Belews Lake, in which
there is not an ongoing selenium discharge. Dr. Skorupa said that it should not be too hard to
•separate out the sites causing the "noise" in the data, based on knowledge of site-specific factors.
He expressed optimism that it would be possible to create a good global relationship between
water-column and fish-tissue selenium. Dr. Cutter added that another factor to consider would •
be the amount each site is elevated above background for its region.
Dr. Fairbrother said that the experts seemed to be contradicting their conclusions from the
previous day, in which most of them had said that water concentrations could not be used to
predict fish tissue concentrations. Dr. Adams said that part of the reason for that conclusion was
that, to date, efforts to build global models had not been very successful. Dr. Skorupa said that
two different scales of analysis were being discussed. During the water session, the experts
addressed the question of what confidence they would have hi predicting fish-tissue selenium
concentrations from water selenium concentrations. He said that that was a different question
from the current issue, which was looking globally at relationships between water and fish and
trying to identify sites that are over or under the regression line. Dr. Cutter agreed. Dr. Adams
said that, even if tissue levels are considered to have the best predictive power of effects, they
still must be related back to water concentrations, or the tissue-based approach leads only to site-
specific assessments for every site. Dr. Fan added that picking apart the variables that make
some sites deviate from the global relationship would lead to a better understanding of the
relationship between tissue concentrations and water concentrations.
' , : : , . '
Dr. Fairbrother commented that what the two approaches under discussion would mainly show is
which sites need site-specific studies. Dr. Riedel asked whether a "site-specific study" means
42
-------
anything beyond analyzing selenium in the discharge and the receiving body. Dr. Skorupa
replied that, in his opinion, site-specific analysis usually boils down to developing rigorous
effects data to assess whether effects are occurring at a particular site.
Analytical Methods:
Dr. Cutter presented the following remarks:
' ' " • ' - ' ' ' "
The Chemical Forms of Selenium in Natural Waters
DISSOLVED
Se(VI) Selenate (SeO42-)
Se(TV) Selenite(HSeO3- + SeO32-)~
Se(0) Elemental selenium (insoluble, but may be colloidal and pass through a
0.4umfilter)
Se(JT) Selenide, primarily in the form of organic selenides such as seleno- amino
. . acids (e.g., seleno-methionine,,CH3Se(CH2)2CH(NH3)CO2H) in dissolved
peptides, and dimethyl selenide ((CH3)2Se))
- PARTICULATE ' / ,
Se(lV+VI) Adsorbed to mineral or biogenic phases
Se(VI) Selenate esters in membranes
Se(0) Elemental Se precipitated from water column or produced in sediments
Se(0/-II) Metal selenides (pyrite-Uke compounds)
Se(-II) Organic selenides (primarily seleno-amino acids in proteins)
Factors to Consider for Selecting Appropriate Analytical Methods far Determining Selenium
in Natural Waters
1. Accuracy. For obvious reasons, systematic errors must be eliminated. Standard additions
method of calibration should be used and appropriate (i.e., same matrix type) standard
reference materials should be analyzed (although only limited speciation data for these are
available). . .
2. Precision. The analytical precision must be much less than the environmental variability in
order to discern it.
3. Low detection limits. Natural concentrations of dissolved selenium can be as low as 2 ng
Se/L, necessitating low detection limits. In this respect, for determining loadings, etc. a lack
of data (i.e., below detection limits) should be avoided. Moreover, low detection limits allow
43 ;' -' - ' • '
-------
potential interferences to be minimized via dilution. As a general rule, the detection limits
should be approximately lOx lower than the expected concentrations.
4. Ability to determine dissolved and particulate speciation. The speciation of selenium in
both the dissolved and particulate phases has been shown to affect its bioavailability and/or
toxicity.
Analytical Techniques for Selenium Determinations in Natural Waters
Method
SHGAAS
SHG
ICP-MS
Deriv.-
fluorimetry
Deriv.-
GC
1C
IC-ICP-MS
Speciation
Dissolved
• yes •
yes
yes
yes
*
yes
yes
Particulate
yes
yes
no
no
no
no
Interferences
few
few
many
few
many
many
Detection
Limit
2pptr
<2pptr
Spptr
Spptr
Ippb
<2pptr
Relative
Cost
$
4>4>4>
$
$$
$
-------
selective hydride generation, because a very acidic waste is generated for which disposal can be
expensive. She added that her laboratory has had problems with their nebulizer becoming
clogged. Dr. Cutter replied that a nebulizer is not necessary for his AA-hydride method.
Dr. Fan noted that selenonium can be analyzed for by spiking whole water with base and
analyzing the resulting head space. She asked Dr. Cutter if he had tried using the copper chelex
method to analyze for seleno-methionine in sediments, and he replied that he had not. Dr. Riedel
said that his group, after dosing algae with selenium-75, had detected small amounts of free .
seleno-methionine in. water (in the parts per trillion range) using copper chelex. Dr. Skorupa
asked Dr. Cutter to comment on neutron activation. Dr. Cutter replied that this method does not
do speciation and that special attention must be paid to sample preparation.
Dr. Cutter presented further remarks: .
Water-Column Sampling '
Sample . , -
—> 0.4 um filter (immediate) .
-> "dissolved" (pH <2 with HCl, borosilicate glass) •
' --> suspended particles (freeze; dry at low temp)
Why? -Dissolved and particulate represent different "pools" available to different parts of
food web. ^ •
Sediment Sampling •/ •
Box core (or equivalent) '
—> "squeeze" and filter
—> dissolved ,
—> particulate (dry at low temp)
Why? Dissolved and particulate availability; fluxes; selenium changes with depth; preserve
flocculent matter at surface.
References for sediment sampling: Bender et al., 1987; Blomqvist, 1985; Blomqvist, 1991;
Jahnke, 198,8; Zhang et al., 1998.
. • • *• •'* , -
For determination of selenium in sediments, Dr. Fan brought up benchtop x-ray fluorescence
spectrometry. She said that it has the advantage of not requiring digestion, which minimizes
sample handling and thus the potential for technician error, Dr. Cutter replied that the detection
limits for this method are very high. Dr. Fan agreed, saying they are currently around 2 ppm, but
she said the method could be useful for more highly contaminated sediments. She added that this
technique determines other metals at the same time, which can be useful for looking at
-------
interactions. Dr. Cutter replied that it is an expensive instrument. Dr. Fan responded that it is
not more expensive than other instruments he had referred to and that it results in large savings in
labor costs.
Dr. Adams commented that Dr. Cutter's chart of analytical methods was a summary of the state
of the art, rather than the methods commonly used. He said he thought a detection limit of 2 pptr
was a stretch for some of the methods and was certainly a stretch for contract laboratories. Most
contract laboratories, he added, are struggling to do a good quantitative analysis at the 2 ppb
level. Dr. Riedel replied that EPA is currently publishing and validating a method for arsenic
and that the selenium method will come hi time. Dr. Cutter replied that, in hi? opinion, it is
crucial that detection limits be ten times below the concentrations being analyzed. He added,
however, that he understands the situation faced by a contract or utility lab analyzing large
quantities of samples in short time periods. He said that, with EPRI funding, he had developed a
methods "cookbook" currently used by many utility labs. He said that the approach he
recommends for these labs is to analyze for total selenium, making sure that their method is
accurate and precise, and to speciate a subset of samples.
Sufficiency vs. Toxicity:
Dr. Fairbrother introduced'this topic by saying that selenium is a required micronutrient; the
question, then, is whether the range between sufficiency and toxicity levels is large enough that
jwe need not worry about sufficiency. Dr. Riedel responded that there are regions, such as places
on the Canadian Shield, in which selenium concentrations are so low (in the low pptr in the water
column) that algae respond to selenium administration. Dr. Fan added that she found that she .
needed to add selenium to an algal culture in her laboratory that she had isolated from an
evaporation pond. Algal growth had been diminished, but was ameliorated when she added 10
ppb of selenium to the culture. Dr. Fairbrother pointed out that these algae were adapted to a
high-selenium environment. She reiterated the question of how wide the zone between
sufficiency and toxicity is, and Dr. Riedel replied that for plants and algae it is quite wide.
For fish, Dr. Hamilton cited a study in which a selenite-spiked diet was fed to rainbow trout
(Hilton et at, 1980). The researchers determined that between 0.15 and 0.38 (ig/g dry weight
selenium in the diet was the sufficiency level;.they estimated that the toxicity level was about 3
ug/g. Dr. Hamilton pointed out that this was only a'ten-fold difference, which is fairly narrow.
Mr. Van Derveer said that spiking with selenite did not realistically mirror an environmental
exposure.
Dr. Cutter said that, in his opinion, one would not have to worry about making a system too
clean. He pointed out that low-selenium environments would have an assemblage of species that
were adapted to the lack of selenium. Dr. Skorupa agreed; he said that, in 10 years of research,
he has never found selenium levels in a waterbird egg in the wild that were below the level of
selenium sufficiency determined for chickens.
46
-------
Dr. Adams said that published papers have established a selenium requirement for daphnids in
the range of 0.5 to 1 fig/L added to the algal culture that is fed to the daphnids. He also
commented that European researchers have started to develop sufficiency-toxicity curves for
metals and said that this is interesting, because it allows one to look at the gradations of effect.
He added that, in the Netherlands, water criteria for metals are adjusted for natural background
concentrations. Dr. Fan-brother then turned the discussion to the topic of natural background.
Natural Background:
'••_'• •. ' • • /•...'•
Dr. Fan-brother asked Dr. Cutter to elaborate on his assertion that 0.1 ppb is the natural
background for selenium in ILS. freshwaters. He replied that the data he based this on were
presented hi a chapter he wrote on selenium in freshwater systems, which he had provided to the
group (Gutter, 1989). He said that he only included data he considered to have been produced
using sound analytical methods; he acknowledged that the western United States was not
adequately represented. He also cited another reference he provided (Cutter and San Diego-
McGlone, 1990), detailing variability in selenium concentrations over 2 years in the Sacramento
arid San Joaquim rivers. He added, however, that concentrations in the San Joaquim are affected
by agricultural input, and that headwater data would be necessary to estimate natural background.
Dr. Riedel said that using headwater data ignores the natural selenium inputs that occur as one
moves downstream. Dr. Fan said that researchers had addressed thi's issue in the San Joaquim by
looking at tracers; they determined that approximately,90% of the selenium inputs were
-agricultural. Dr. Fairbrother asked if this method could be used to determine natural background
in systems with anthropogenic inputs. Dr. Fan replied that some researchers are trying to do this,
but it is not yet a proven method. Dr. Adams questioned how one defines a number for
"background," since there is a range of values; he cited some examples of water bodies with
natural selenium levels much higher than 0.1 ppb.
Dr. Cutter turned the discussion to the natural background selenium level for U.S. freshwater
sediments, which he said is about 1 ppm. Dr. Adams agreed. 'Dr. Cutter said there is not much
regional variation. Dr. Skorupa said that the USGS study of surficial soils in the United States
found little regional variation hi selenium soil levels. Dr. Fairbrother questioned how numbers
were averaged in this study, agreeing with Dr. Adams's comment that one must look at the
distribution as well as the median, She summarized the discussion by saying that there is still
debate about natural background and that more work must done to allow good determinations to
be made of whether sites\ selenium concentrations are at natural background or elevated;
Interactions with Other Stressors:
Dr. Fairbrother raised the issue of the interaction of selenium with other stressors, asking the
experts whether they had confidence that effects seen in the empirical data set are due just to
selenium. Dr. Cutter said that he did not have confidence that this was the case, because when
there is an excess of selenium, there is often an excess of something else. .Dr. Hamilton said that
the literature is fairly limited on many other elements. He cited an example from his research; in
• ' • '•• 47 . ' - '..'•. .'•':..•
-------
a study he did on the Green River, vanadium was somewhat elevated and may have been a
confounding factor, but he could only find one relevant study about vanadium. Dr. Fairbrother
and other experts pointed out the additional problem of extrapolating from the laboratory to the
field. Dr. Fan said that, as broad element scans are becoming easier to do, she is hopeful that
more field data will soon be available. Dr. Skorupa said that he feels there are sufficient data
establishing that effects attributed to selenium are actually caused by selenium alone. His group
has done studies in reservoirs that have a suite of pollutants excluding selenium, and they have
not seen the effects typically associated with selenium.
Clarification Requested by EPA:
At this point, Mr. Sappington asked the experts to clarify a couple of issues. First, he pointed out
that, during the cross-cutting session, experts had discussed possible global approaches in
relating tissue concentrations to water concentrations; however, during the water-column issues
session the day before, experts had expressed skepticism about performing water-to-tissue
correlations. He asked them to clarify this, and also to state some of the factors that they think
might make the correlation poor. He asked whether the experts considered loading from
sediments and spatio-temporal variability in the water column to be important factors.
Dr. Fan replied that the problem might be more complex than that and cited an example of an
irrigation pond in California in which large changes in selenium load in bird eggs were observed
with only a minor dilution of waterbome selenium concentrations, for unknown reasons. Dr.
Fairbrother asked the experts to also clarify whether the form of selenium that is discharged to
receiving waters changes the temporal or magnitudinal dynamics of what happens in the food •
chain. Dr. Cutter replied that it does; for example, the uptake rate of selenate is slow compared
to selenite. Dr. Fairbrother said that part of the problem in trying to establish relationships is that
the systems under study are generally non-equilibrium, dynamic systems.
Dr. Adams responded to Mr. Sappington's original question by agreeing that both mass in the
sediments and spatio-temporal variability in the water column are important. He added that fish
behavior is also important, including what fish feed on and where they forage.
Mr. Sappington asked whether the experts would expect tissue residue effect levels to differ
between the laboratory and the field, or whether laboratory data are in fact useful for generating
effect-level information. Dr. Hamilton replied that when he did laboratory studies, with both
water-only and dietary exposure to selenium, he found the residue effect level to be very similar
between the two; in other words, how the selenium got into the tissue did not affect the effect
level. Dr. Riedel agreed that this is probably generally true, but that there are exceptions. He
pointed out that there are many unknowns in the field, while organisms in the laboratory are kept
under optimal conditions. Dr. Hamilton agreed.
48
-------
Conclusions: The following summary of the entire discussion session was written by the
discussion leader and reviewed by the other experts.
1. Spatio-temporal variability .
There is a large amount of variability in selenium concentrations within compartments of an
ecosystem (e.g., water, sediment, biota) across both time and space. The relationships between
the compartments are not linear, however. Water concentrations may change rapidly (within
days) whereas sediment concentrations take months or years to change, particularly in lentic
systems. Fish tissue residues .integrate all compartments and theoretically may change in
response to alterations in any of them although food-chain exposures tend to dominate.
Therefore, fish tissue residues also change over a period of months, and do not reflect the faster
fluctuations of water. ';'....
The major factors influencing spatio-temporal variability are water residence time and biological
processing (i.e., the type of organisms in the food web). The rate-limiting step may be the rate of
conversion of inorganic form to organic form, which is a function of the form of selenium and
species of microorganisms in the sediment. ' - ,.
2. Ecosystem type . • .
Ecosystems can be divided into lentic or lotic systems. Further subdivisions include ephemeral
-or perennial, highly saline, and northern (cold) streams. Differences in these systems that may
lead to different responses to similar selenium input include retention time of carbon, rate of
sediment accumulation, rates of conversion of inorganic to organic forms of selenium, and > •
tolerance of local species. In addition, rates of allochthonous inputs (i.e., input of selenium
materials from outside the aquatic system) versus autochthonous inputs (i.e., from within the
system) differ. Most lotic systems are biologically open systems which makes it more difficult
to measure ecologically-relevant effects on fish species that may move through the system, rather
than being resident.
3. Site-specific approaches
Three approaches to site-specific assessments were proposed:
• Apparent effects threshold: This method would use existing field data to categorize systems
as affected or not affected relative to selenium concentrations in sediment or water. The
sediment/water concentration above which effects always occurred would be identified, as
would the concentration below which effects never occurred. The concentrations in-between
(where effects sometimes occurred or sometimes did not) would identify sites where a site-
specific assessment would be needed.
• Fish tissue concentrations as a function of water concentrations: The empirical data from
field studies that exist in the literature would be used to develop this bioaccumulatipn
correlation on a global basis. Sites where measured fish tissue concentrations were different
• ; ' - ' . ' - , 49 ';-..- : :, •' • •'••••••>
-------
from the predicted concentrations, based on the amount of selenium in the water, would
require a site-specific approach. If fish tissue - effects relationships are known for the
species of concern, then sites could be further characterized as those with potentially higher
than predicted effects or those with potentially lower effects.
• Modeling approach: The Aquatic Toxicity Model presented by George Bowie could be used
to make a priori predictions of whether a concentration of selenium in water would result in
effects to the fish. Site-specific input parameters include selenium input (amount, rate, and
species), flow rates, water depth, and a few other hydrological parameters as well as food
web species. The more site-specific data that are used in the model, the more likely is it to
accurately predict effects.
4. Analytical methods
There are several methods for analyzing selenium in water, sediment, or tissue. No one method
is the best for all media. Important considerations are desired minimum detection limits (ideally,
should be ten-fold lower than the concentrations of interest), sample preparation requirements,,
and laboratory capabilities. Cost may be a factor as well. While methods are available mat can
achieve very low detection limits, many (if not most) contract laboratories are not set up to
conduct these methods with appropriate accuracy or precision.
In addition to analytical methodology, appropriate sample collection and storage are required.
-Water samples should be acidified (with HC1) and kept cool; solid matrices should be kept
frozen. Selenium may volatilize when a sample is heated and provide an incorrectly low value.
Box core samplers are preferred for sediment sampling as they preserve the depth structure of the
sediment, allowing measurements to be made on the upper flocculent (organic) material versus
the lower inorganic portions.
5. Sufficiency versus toxicity
Since selenium is a required micronutrient for both plants and animals, there is an exposure
concentration below which insufficiency effects are seen and a different concentration above
which toxicity occurs. The area in-between is the Optimal Effects Concentration. For algae,
there is a wide sufficiency zone and the required amount may differ depending on the amount of
selenium in the system from which the test colony was derived (due to adaptation to a higher
selenium environment). Fish have at least a ten-fold difference between required and toxic
amounts. In general, there does not appear to be any naturally deficient systems, with the
exception of some lakes in the Laurentian Shield area in Canada that may be deficient for algae.
Furthermore, on a practical basis, it does not appear that source reduction of site remediation
would result in systems with insufficient selenium concentrations. However, this issue may be
important in laboratory studies where appropriate minimum concentrations of selenium must be
provided to maintain colonies of test species.
50
-------
6. Natural background
On the national level, the median background concentration of selenium in aquatic systems is
about 0.1 ug/L. However, there is disagreement about this value and about the variability and
range of natural background concentrations. Areas of highly seleniferous soils in the western
U.S. may have naturally higher background concentrations either through movement of soils into
waterbodies or into groundwater. Methods are being:deveioped for differentiating between
natural and anthropogenic inputs of selenium into an aquatic system, but there remains a great
deal of uncertainty in the follow-on calculation of what a resulting natural background
concentration would be.
7. Interactions with other stressors
Selenium has the potential to interact with other metals, causing either greater or lesser responses
than predicted from selenium alone. Furthermore, exposure to selenium may reduce an
organisms' ability to respond to other environmental stresses, such as has been shown for fish
similar to those found in Belews Lake that were exposed to cold temperatures during laboratory
studies (Lemly, 1993c, 1996). These types of interactions might confound the global empirical
dataset relating effects to selenium concentrations in water, sediment, or food. Examples where
this may have occurred include interactions between vanadium and selenium in afield study of
' fish reproduction. On the other hand, another study showed that effects were correlated only
with the selenium concentration in the food, and that additional elements had no discernible
-effects. The endpoint of interest also may affect the potential for interactive effects to occur.
51
-------
IV. OBSERVER COMMENTS
At the end of each day of the meeting, Dr. Fairbrother opened the floor to comments from
observers. These comments are summarized below. In addition, observer presentation materials
may be found in Appendix F. •
Peter Chapman. EVS Consultants ,
This observer (speaking on the first day of the meeting) noted that discussions to date had mostly
focused on standing-water systems. In contrast, his interest is flowing cold-water streams,
particularly in Alaska and southeast British Columbia, with inputs of selenium from hard-rock
mining and coal mining. He pointed out that these systems are quite different in many aspects
from the systems under discussion by the experts. To date, his group's studies have found no
adverse effects in streams in British Columbia with concentrations of selenium as high as 65
ug/L. He urged the experts and EPA to, consider three key points:
t .
• Flowing-water systems are very different from standing-water systems; much higher
concentrations can be tolerated without adverse effects.
• Site-specific factors are incredibly important.
• Not all waters or biota require the same level of protection. '
Philip Pom. Shell Development Company
This observer questioned the need for a revision of the national freshwater chronic water quality
criterion for selenium. He argued that no compelling field effects have been demonstrated hi
waters with selenium levels below the existing 5 ug/L chronic criterion. In addition, analytical
methods for compliance testing are limited below 10 ug/L. Finally, there is large uncertainty in
making correlations at the national scale between water-column selenium concentrations,
selenium concentrations in the food chain, and selenium concentrations hi bird eggs. He urged
EPA to move toward developing site-specific residue- or effects-based criteria. He also noted
that the cost per pound to remove selenium from discharge is quite high and that the removal
process generates a large volume of sludge which must be* disposed of He asked EPA to ensure
that future regulations are developed upon fact-based science.
52
-------
Rob Reash. American Electric Power
'• • ' • ' *
'• • - • - ^ '
This observer made comments on behalf of the Utility Water Act Group (UWAG), an association
of electric utility companies and trade associations. UWAG is interested in EPA's reevaluation
of the freshwater chronic aquatic life criterion for selenium because selenium is a natural trace
element in coal and many of UWAG's members use coal as the primary fuel for electrical
generation. The observer said that UWAG views a universal numeric chronic criterion for
selenium as inappropriate. He urged EP. A to consider the following issues: . ^
• Stratification by waterbody type; , . ,
• Accurate accounting of site-specific factors affecting selenium toxicity; and
• Development of site-specific criteria technical guidance. ,'. .
In addition, he offered the opinion that fish liver is a good tissue in which to measure residues if
ovaries are unavailable; in his work, he has found that fish liver tissue mirrors water-column
selenium concentrations.
.Walter Kuit Cominco. Ltd.
Speaking on behalf of Cominco Alaska, this observer said that selenium is a key issue at his
company's Red Dog Mine in northern Alaska. An impending NPDES permit will lower the
mine's selenium discharge limit to a level that the company cannot meet. He said that flowing
streams should be considered separately from standing water and urged EPA to move quickly in
developing site-specific guidance. He also asked EPA to provide preliminary guidance on
possible changes in sampling procedures (e.g., implementation offish ovary sampling), so that
affected parties can start gathering relevant data as soon as possible.
William Wrieht Montgomery Watson
This observer, an ecologist, is managing the Southeast Idaho Phosphate Resource Area Selenium
Project. This project involves the evaluation of a 1,200-square-mile area containing 14 mines,
where selenium is leaching from interburden waste shales. Receiving waters are typically
intermittent tributaries of montane trout streams and are generally sulfate rich. Sampling to date
has found water-column concentrations of selenium ranging from below detection limits to 2,000
ppb. Ninety percent of the selenium is in the selenate form. His group does not have definitive
results yet, but has .seen no adverse effects so far. Healthy populations have been found in areas
with high .concentrations of selenium. =He echoed Peter Chapman's comments, saying that site-
..'.-.'-'•. 53 •:•'•"' : ' .
-------
specificity is important, and beneficial use should be taken into account.
Chris Stanford. JD Consulting
This observer expressed the opinion that we have a long way to go in regard to quantifying the
behavior and effects of selenium in the environment. He added that although revising the
chronic criterion is a good goal, we do not yet have enough information to be able to develop a
new nationwide criterion that is a definite improvement over the existing one. The solution to
this in the short term, he said, is to develop site-specific standards, including guidance on
sampling and data analysis and interpretations. In addition, he asked EPA to establish standards
that can serve as guidance to contract laboratories.
John Goodrich-Mahonev- EPRI Environment Division
This observer said that EPRI will be coming out with their Selenium Aquatic Toxicity Model
this fall. He invited experts and observers to be beta testers for the model. He can be contacted
at . He added that EPRI encourages EPA to develop site-specific
guidance and is willing 1p offer any assistance it can.
Judith Schofield. DvnCorp
This observer stated that DynCorp has been providing support to EPA hi the development of
1600-series analytical methods; she updated the attendees on the status of the two methods that
apply to selenium. EPA Draft Method 1638 is an ICP-MS method with an estimated detection
limit of 0.45 ug/t. EPA Draft Method 1639 is a gas fumace-AA method with an estimated
detection limit of 0.3 ug/L. The methods and their detection limits will be tested in upcoming
interlaboratory validation studies. Formal proposal of the methods will probably occur in early
1999. She added that EPA is also working on a streamlining rule, which is a performance-based
measurement system approach to analytical methods.
54
-------
'•'•'-.• ' • • V. REFERENCES - ' '• '
Adams, WJ. 1976. Thetoxicity and residue dynamics of selenium in fish and aquatic
invertebrates. Ph.D. Dissertation, Michigan State University, E. -Lansing, ML
Amouroux, D. and O.F.X. Donard. 1996. Geophys. Res. Lett. 23:1777-1780.
Barrick, R.C., H. Seller, D.S. Becker, and T.C. Ginn. 1989. Use of the Apparent Effects
Threshold (AET) in classirying contaminated sediments. In. Contaminated Marine
Sediments — Assessment and Remediation. National Academy Press, Washington, DC.
Bender, M., W. Martin, J. Hess, F. Sayles, and L. Ball. 1987. A whole-core squeezer for
interfacial pore-water sampling. Limnol. Oceanogr. 32:1214-1225.
Besser, J.M., T. Canfield, and T. LaPoint. 1993. Bioaccumulation of organic an
-------
Cutter, G.A. 1982. Selenium in reducing waters. Science 217:829-831.
Cutter, G.A. 1985. Determination of selenium speciation in biogenic particles and sediments.
Anal. Chem. 57:2951-2955.
i
Cutter, G.A. 1989. Freshwater systems. In M. Ihnat, ed., Occurrence and Distribution of
Selenium. CRC Press, Boca Raton, FL, pp. 243-261.
Cutter, G. A. 1991. Selenium Biochemistry in Reservoirs. Volume 1: Time Series and Mass
Balance Results. EN-7281, Volume 1, Research Project 2020-1. Electric Power
Research Institute, Palo Alto, CA.
Cutter, G.A. and L.S. Cutter. 1998. Metalloids in the high latitude North Atlantic: sources and
internal cycling. Mar. Chem. 61:25-36.
Cutter, G.A. and M.L.C. San Diego-McGlone. 1990. Temporal variability of selenium fluxes in
the San Francisco Bay. Sci. Total Environ. 97:235-250.
Engberg, R.A. 1998. Selenium budgets for Lake Powell and the upper Colorado River basin. J.
, Amer. Water Res. Assoc. (in review).
Fan, T.W.-M., R.M. Higashi, and A.N. Lane. 1998. Biotransformations of selenium oxyanion
by filamentous cyanophyte-dominated mat cultured from agricultural drainage waters.
Environ. Sci. TechnoL, in press.
Fan, T.W.-M., A.N. Lane, D. Martens, and R.M. Higashi. 1998. Synthesis and structure
characterization of selenium metabolites. Analyst 123:875-884.
Frankenberger, W.T. and U. Karlson. 1994. Microbial volatilization of selenium from soils and
sediments. In W.T. Frankenberger and S. Benson, eds., Selenium in the Environment.
Marcel Dekker, New York, pp. 369-387.
Gillespie, RJB. and P.C. Baumann. 1986. Effects of high tissue concentrations of selenium on
reproduction by bluegills. Trans. Am. Fish. Soc. 115:208-213.
Gobler, C.J., D.A. Hutchins, N.S. Fisher, E.M. Cosper, and S.A. Sanudo-Wilhelmy. 1997.
Release and bioavailability of C, N, P, Se, and Fe following viral lysis of marine
chrysophyte. Limnol. Oceanogr. 42:1492-1504.
Hamilton, S J., KJ. Buhl, F.A. Bullard, and S.F. McDonald. 1996. Evaluation of toxicity to
larval razorback suckers of selenium-laden food organisms from Ouray NWR on the
Green River, Utah. Final Report. Colorado River Recovery Implementation Program,
Denver, CO. 79pp.
Hansen, D., P.J. Duda, A. Zayed, and N. Terry. 1998. Selenium removal by constructed
wetlands: Role of biological volatilization. Environ. Sci. TechnoL 32:591-597.
Hilton, J.W., P.V. Hodson, and SJ. Slinger, 1980. The requirement and toxicity of selenium in
rainbow trout (Salmo gairdneri). J. Nutri. 110:2527-2535.
Holland, E.A. 1979. Arsenic and selenium in the water,.sediments, and biota near a coal-fired
power plant — Belews Lake, North Carolina. M.S. Thesis, School of Public Health,
56
-------
Department of Environmental Sciences and Engineering, University of North Carolina,
Chapel Hill, NC. ;
Jahnke,R.A. 1988. A simple, reliable, and inexpensive pore-water sampler. Limnol. Oceanogr.
33:483-487.
Karlson, U. and W.T. Frankenberger, Jr. 1990. Volatilization of selenium from agricultural
evaporation pond sediments. iStz. Toto/£"nvz>o/2. 92:41-54.
Kroll, K.J. and S.I. Doroshov. 1991. Vitellogenin: Potential vehicle for selenium ,
bioaccumulation in oocytes of the white sturgeon (Acipenser transmontanus). In P.
Williot, ed., Acipenser, Cemagref Publishers, pp. 99-106.
Kumar, H.D. and G. Prakash. 1971. Toxicity of selenium to the blue-green algae, Anacystis
nidulans and Anabaena variabilis.Ann. Bot. (Lond.) 35:687-705.
Lemly, A.D. 1982. Response of juvenile centrarchids to sublethal concentrations of waterbome
: selenium. 1. Uptake, tissue distribution, and retention. Aqiiat. Toxicol. 2:235-252.
Lemly, A.D. 1985. Toxicology of selenium in a freshwater reservoir: Implications for
environmental hazard evaluation and safety. EcotoxicoL Environ. Saf. 10:314-338.
Lemly, A.D. 1993a. Teratogenic effects of selenium in natural populations of freshwater fish.
Ecotoxicol.^Environ. 5(2/26:181-204. , ,
Lemly, A.D. 1993b. Guidelines for evaluating selenium data from aquatic monitoring and
assessment studies. Environmental Monitoring and Assessment 28:83-100.
Lemly, A.D. 1993c. Metabolic stress during winter increases the toxicity of selenium to fish.
Aquat. Toxicol. 27:133-158.
Lemly. A.D. 1996. Winter Stress Syndrome: An important consideration for hazard assessment
of aquatic pollutants. EcotoxicoL Environ. Saf. 34:223-227. ,
Lemly, A.D. 1997. Ecosystem recovery following selenium contamination in,a freshwater
reservoir. Eeotoxicol. Environ. Saf. 36:275-28.
Luoma, S.N., C. Johns, N.S. Fisher, N.S. Steinberg, R.S. Oremlans, and J.R. Reinfelder. 1992.
Determination of selenium bioavailability to a benthic bivalve from particulate and solute
pathways. Environ. Sci. Technol. 26:485-491.
Maier, K.J., C.R. Nelson, F.C. Bailey, S.J. Klaine, and A.W. Knight. 1998. Accumulation of
selenium by the aquatic biota of a watershed treated with seleniferous fertilizer. Bull
Environ. Contam. Toxicol.^60:409-416. -
Moede, A., R.W. Greene, and D.F. Spencer. 1980. Effects of selenium on the growth and
" phosphorus uptake of Scenedesmus dimorphus and Anabaena cylindrica. Environ. Exp.
Bot. 20:207-212. '
Munwar, M., I.F. Munwar, P.E. Ross, and C.I. Mayfield. 1987. Differential sensitivity of
natural phytoplankton size assemblages to metal mixture toxicity. Ergeb. Limnol.
25:123-139.
57
-------
Ohlendorf, H.M. and G.M. Santolo. 1994. Kesterson Reservoir — past, present, and future: an
ecological risk assessment. In W.T. Frankenberger and S. Benson, eds., Selenium in the
Environment. Marcel Dekker, New York, pp. 69-118.
Radtke, D.B, W.G. Kepner, and RJ. Effertz. 1988. Reconnaissance investigation of water
quality, bottom sediment, and biota associated with irrigation drainage in the lower
Colorado River Valley, Arizona, California, and Nevada, 21986-87. Water-Resources
Investigations Report No. 88-4002, U.S. Geological Survey, Tucson, Arizona.
Riedel, G.F. and J. G. Sanders. 1996. The influence of pH and media composition on the uptake
'of inorganic selenium by Chlamydomonas reinhardtii. Environ. Toxicol. Chem. 15:1577-
1583.
Riedel, G.F., J.G. Sanders, and C.C. Gilmour. 1996. Uptake, transformation and impact of
selenium in freshwater phytoplankton and bacterioplankton communities. Aquat
Microbiol. Ecol. 11:43-51.
Saiki, M.K., M.R. Jennings, and W.G. Brumbaugh. 1993. Boron, molybdenum, and selenium in
aquatic food chains from the lower San Joaquin River and its tributaries, California.
Arch. Environ. Contam. Toxicol. 24:307-319.
Saiki, M.K. and T.P. Lowe. 1987. Selenium in aquatic organisms from subsurface agricultural
drainage water, San Joaquin Valley, California. Arch. Environ. Contam. Toxicol 16:657-
670.
-Sanders, J.-G., R.P. Gallagher, C.C. Gilmour, R.W. Osman, and G.F. Riedel. 1989. Selenium
Cycling and Impact in Aquatic Systems. Annual Progress Report for 1989, Prepared for
Electric Power Research Institute. November 1989.
Schroeder, R.A., D.U. Palawski, and J.P. Skorupa. 1988. Reconnaissance investigation of water
quality, bottom sediment, and biota associated with irrigation drainage in the Tulare Lake
Bed Area, southern San Joaquin Valley, California, 1986-88. Water-Resources
Investigations Report 88-4001, U.S. Geological Survey, Sacramento, CA..
Seiler, R.L. 1996. Synthesis of data from studies by the National Irrigation Water-Quality
Program. J. Am. Water Res. Assoc. 32:1233-1245.
Skorupa, J.P. 1998. Selenium poisoning of fish and wildlife in nature: Lessons from twelve
real-world examples. In W.T. Frankenberger and R.A. Engberg, eds., Environmental
Chemistry of Selenium. Marcel Dekker, New York, pp. 315-354.
Skorupa, J.P. and H.M. Ohlendorf. 1991. Contaminants in drainage water and avian risk
thresholds. In A. Dinar and D. Zilberman, eds., The Economics and Management of
Water and Drainage in Agriculture. Kluwer Academic Publishers, Boston, MA, pp. 345-
368.
Sorensen, E.M.B., P.M. Cumbie, T.L. Bauer, J.S. Bell, and C.W. Harlan. 1984.
Histopathological, hematological, condition-factor, and organ weight changes associated
with selenium accumulation in fish from Belews Lake, North Carolina. Arch. Environ.
Contam. Toxicol. 13:153-162.
58
-------
Spallholz, I.E. 1994. On the nature of selenium toxicity and carcinostatic activity. Free Radical
Biology'andMedicine 17'(l):45-64. , " , ,
Takayanagi, K. and G.T.F. Wong. 1984. Organic and colloidal selenium in southern
Chesapeake Bay and adjacent waters. Mar. Chem. 14:141-148.
Van Derveer, W.D. and S.P. Canton. 1997. Sediment selenium toxicity thresholds and
derivation of water-quality criteria for freshwater biota of western streams. Environ:
Toxicol. Chem. 16:1260-1268. ,
Velinsky, DJ. and G. A. Cutter. 1990. Determination of elemental selenium and pyrite-
selenium in sediments. Anal. Chim. Acta 235:419-425.
Velinsky, D J. and G.A. Cutter. 1991. Geochemistry and selenium in a coastal salt marsh.
Geochim. Cosmochim. Acta 55:179-191.
Wheeler, A.E., R.A. Zingaro, and K. Irgolic. 1982. The effect of selenate, selenite, an4 sulfate
on six species of unicellular algae. J. Exp. Mar. Biol. Ecol57:181-194.
Woock, S.E., W.R. Garrett, W.E. Partin, and W.T. Bryson. 1987. Decreased survival and
teratogenesis during laboratory selenium exposures to bluegill, Lepomis macrochirus.
Butt. Environ. Contam. Toxicol. 39:998-1005.
Wrench, JJ. 1978. Selenium metabolism in the marine phytoplankters Tetraselmis tetrathele
andDunatiella minuta. Marine'Biol. 49:231-236.
Zhang, L., R.S. .Walsh, andG.A. Cutter. 1998. Estuarine cycling of carbonylsulfide: Production
and sea-air flux. Mar. Chem. 61:127-142.
Zhang, Y., and J.N. Moore. 1996. Selenium fractionation and speciation in a wetland system.
Environ. Sci. Technol. 30:2613-2619. -
Zhang, Y. and J.N. Moore. 1997. Environmental conditions controlling selenium volatilization
from a wetland system. Environ. Sci. Technol. 31:511-517.
59
-------
-------
APPENDIX A
WORKSHOP MATERIALS
-------
-------
United States
Environmental Protection Agency
Office of Water
Peer Consultation Workshop on Selenium
Aquatic Toxicity and Bioaccumulation
Radisson Barcelo Hotel
Washington, DC
May 27-28, 1998
Agenda
Workshop Chair:
Anne Fairbrother
ecological planning & toxicology, inc.
WEDNESDAY, MAY 27, 1998
8:OOAM Registration/Check-ln
9:OOAM Welcome Remarks ,
Jeaneffe Wiltse, Director, Health and Ecological Criteria Division, Office of Water,
U.S. EPA, Washington, DC
9:1 OAM Overview and Background
Keith Sappingtqn, Health and Ecological Criteria Division, Office of Water,
U.S. EPA, Washington, DC . .
9:25AM Workshop Structure and Objectives
Anne Fairbrother, Workshop Chair
9:40AM Introduction of Invited Experts
9:55AM Presentation: Belews Lake—Lessons Learned
A. Dennis Lemly, Department of Fisheries and Wildlife, Virginia Tech University, Blacksburg, VA
10:1 SAM Presentation: Modeling Selenium in Aquatic Ecosystems
George Bowie, TetraTech, Lafayette, CA
10:30AM BREAK ,
10:45AM Charge to the Panel/Highlights of Premeeting Comments
Anne Fairbrother ,
11:15AM Discussion on Issue #1: Water Column-Based Criterion
Discussion Leader: William Adams, Kennecott Utah Copper Corporation, Magna, UT
I Printed on Recycled Paper
(over)
A-l
-------
WEDNESDAY, MAY 27, 1998 (continued)
12:30PM LUNCH
1:30PM Summary of Discussions on Issue #1
2:OOPM Discussion on Issue #2: Tissue-Based Criterion
Discussion Leader: Steven Hamilton, U.S. Geological Survey, Yankton, SD
3:30PM BREAK
3:45PM Summary of Discussions on Issue #2
4:15PM Observer Comments
4:45PM Review of Charge for Day Two
Anne Fairbrother
- Writing Assignments
5:OOPM ADJOURN
THURSDAY, MAY 28, 1998
8:30AM Planning and Logistics
Anne Fairbrother
> - -
8:40AM Discussion on Issue #3: Sediment-Based Criterion
Discussion Leader: William Van Derveer, Colorado Springs Utilities,
Colorado Springs, CO
10:OOAM BREAK
10:1 SAM Summary of Discussions on Issue #3
10:45AM Discussion on Issue #4: Crosscutting Concerns
Discussion Leader Anne Fairbrother
Analytical Chemistry Natural Background
Lentic vs. Lotic Systems Sufficiency vs. Toxicrty
Interaction with Other Metals Loss Through Volatilization
12M5PM LUNCH
1:30PM Summary of Discussions on Issue #4
2:30PM Observer Comments
3:OOPM Closing Remarks
Anne Fairbrother
3:30PM ADJOURN
.A-2
-------
EPA
United States.
Environmental Protection Agency
Office of Water
Peer Consultation Workshop on Selenium
Aquatic Toxicity and Bioaccumulation
Radisson Barcelo Hotel
Washington, DC
May 27-28, 1998
List of Experts
William Adams A
Director, Environmental Science
Kennecott Utah Copper Corporation
8315 West 3595 South
Magna, UT 84044
801-252-3112
Fax:801-252-3125
E-mail: adamsw@kennecott.com
»
Gary Chapman
Proprietor
Paladin Water Quality Consulting
3725 Northwest Polk Avenue
Corvallis.OR 97330
541-754-6088
Fax:541-758-6338
E-mail: chapman@proaxis.com
Gregory Cutter
Professor of Oceanography
Department of Ocean, Earth,
and Atmospheric Sciences
Old Dominion University
4600 Elkhorn Avenue
Norfolk, VA 23529-0276
757-683-4929
Fax:757-683-5303
E-mail: gcutter@odu.edu
= Workshop Chair
= DiscussionLeader
Anne Fairbrother *
Senior Ecotoxicologist
ecological planning and toxicity, inc.
501 OSWHout Street
Corvallis, OR 97333
541-752-3707
Fax:541-753-9010
E-mail: fairbroa@aol.com '
Teresa Fan .
Research Biochemist
Department of Land, Air,
and Water Resources
University of California - Davis
One Shields Avenue
.Davis, CA 95616-8622
530-752-1450
Fax:530-752-1552 .
E-mail: twfan@ucdavis.edu
Steven Hamilton A
Project Leader
U.S, Geological Survey
31247-436th Avenue
Yankton, SD 57078-6364
605-665-9217
Fax:605-665-9335
E-mail: steve_hamilton@usgs.gov
Gerhardt "Fritz" Riedel
Assistant Curator
Academy of Natural Sciences
Estuarine Research Center
10545 Mackall Road
St. Leonard, MD 20685
410-586-9700
Fax:410-586-9705
E-mail: friedel@acnatsci.org
Joseph Skorupa
Senior Biologist
Sacramento Fish arid Wildlife Service
U.S. Fish and Wildlife Service
3310 El Camino Avenue, Suite 130
Sacramento, CA 95821
916-979-2100, Ext: 409
Fax:916-979-2128
E-mail; joseph_skorupa@mail.fws.gov
William Van Derveer A
Aquatic Biologist
Water Resources Department
Colorado Springs Utilities
703 East Las Vegas Street
Colorado Springs, CO 80903
719-448-4533
Fax:719-448-4514
E-mail: vwanderveer@csu.org
) Printed on Recycled Paper
A-3
-------
v>EPA
United States
Environmental Protection Agency
Office of Water
Peer Consultation Workshop on Selenium
Aquatic Toxicity and Bioaccumulation
Radisson Barcelo Hotel
Washington, DC
May 27-28, 1998
List of Presenters
George Bowie
Senior Environmental Engineer
TetraTech
3746 Mount Diablo Boulevard
Suite 300
Layfayette, CA 94549
510-283-3771
Faxi510-283-0780 '
E-mail: bowieg@tetratech.com
A. Dennis Lemly
Professor of Fisheries
Department of Rsheries and Wildlife
Virginia Tech University
Blacksburg, VA 24061
540-231-6663
Fax: 540-231-7580
E-mail: dlemly@vt.edu
) Printed on Recycled Paper
A-4
-------
Unfed States
Environments Protection Agency
Office of Water
Peer Consultation Workshop on Selenium
Aquatic Toxicity and Bioaccumulation
Radisson Barcelo Hotel
Washington, DC
May 27-28, 1998
Final List of Observers
Al Alwan
Chemist
Standards and Applied Sciences
Office of Water
U.S. Environmental
Protection Agency
77 West Jackson Boulevard WT-15J
Chicago, IL 60604
312-353-2004 »
Fax:-312-886-0168
E-mail: alwan.al@epa.gov
Ray Arnold
Exxon Biomedical Sciences
Mettlers Road (CN 2350)
East Millstone, NJ 08875-2350
732-873-6305
Fax:908-873-6009
Steve Canton
Senior Aquatic Ecologist
Chadwick Ecological
Consultants, Inc.
5575 South Sycamore Street
Suite 101
Littleton, CO 80120
303-794-5530
Fax: 303-794-5041
E-mail: chadco@aol.com
Richard Carlton
Project Manager
Ecology, Biogeochemistry, Aquatic
Toxics Environment Division
Electric Power Research Institute
3412 Hillview Avenue
Palo Alto, CA 94304-1395
650-855-2115
Fax:650-855-2619
E-mail: rcarfton@epri.com ,
Peter Chapman
EVS Consultants
195 Pemberton Avenue
North Vancouver, BC V7P 2R4
Canada
604-986-4331 -
Fax:604-662-8548
E-mail: pchapman@ibm.net
Jon Cherry
Remediation Project Manager
Kennecott Utah Copper
P.O. Box 6001
Magna, UT
801-252-3126-
Doug Davis '
Tulare Lake Drainage District
P.O. Box 985
Corcoran, CA 93212
209-992-3145
Fax:209-992-2267
Philip Dorn
Senior Staff Research
Environmental Toxicologist
Shell Development Company
Westhollow Technology Center
3333 Highway 6 South
Houston, TX 77082 .
Milton Friend
Chair, Salt & Sea Science Committee
U.S. Geological Survey
8505 Research Way '
Middleton.WI 53562
608-821-3859
Fax: 608-821-3817
E-mail: mitton_friend@usgs.gov
Dan Glaze
Shell Martinez Refining Company
P.O. Box 711
Martinez, CA 94553
510-313-3348 •-.;,-
Sudha Goei
Research Associate
Rifkin and Associates
World Trade Center
401 East Pratt Street - Suite 2332
Baltimore, MD 21202
410-962-1401
Fax: 410-962-1065
E-mail: rifkin@access.digex.net
I Printed on Recycled Paper
A-5
-------
John Goodrich-Mahoney
Program Manager
Electric Power Research Institute
2000 L Street, NW
Washington, DC 20036
202-293-7516
Fax: Fax: 202-293-2697
E-mail: jmahoney@epri.com
Karen Gourdine
Engineer
Water Quality Standards Branch
Standards and Applied
Sciences Division
U.S. Environmental
Protection Agency
401 M Street, SW (4305)
Washington, DC 20460
202-260-1328
Fax: 202-260-9830
E-mail: gourdine.karen@.epa.gov
Alan Hais
Health and Ecological
Criteria Division
U.S. Environmental
Protection Agency
401 M Street, SW (4304)
Washington, DC 20460
202-260-7579 '
Fax:202-260-1036
David Hall
Senior Water Quality Specialist
Central and Southwest Services
P.O. Box 660164
Dallas, TX 75266-0164
214-777-1072
Fax:214-777-1380
E-mail: dahall@csw.com
Walter Kuit
Cominco, Ltd.
500-200 Burrard Street
Vancouver, BC V6C3L7
Canada
604-685-3011
Fax: 604-685-3019
Joel Lusk
Environmental Specialist
New Mexico Ecological
Services Field Office
Environmental Contaminants
U.S. Fish and Wildlife Service
2105Osuna, NE
Albuquerque, NM 87113
505-761-4525, Ext: 109
Fax: 505-761-4542
E-mail: joeljusk@iws.gov
Al Middleton
Exxon Company
Benicia Refinery
3400 East Second Street
Benicia, CA 94510
707-745-7764
Tom Mongan
Consulting Engineer
84 Mann Avenue
Sausalito, CA 94965
415-332-1506
Fax:415-332-1513
E-mail: jtm@cri.com
Robert Pepin
Life Scientist
U.S. Environmental
Protection Agency
77 West Jackson Boulevard
(WT-15J)
Chicago, IL 60604
312-886-1505
Fax:312-886-0168
E-mail: pepin.robert@epa.gov
Jim Pietl
Environmental Scientist
HRSD
1436 Air Rail Avenue
Virginia Beach, VA 23455-
757-460-4246
Fax: 757-460-2372
E-mail: jpletl@hrsd.dstva.us
Rob Reash
Senior Environmental Specialist
American Electric Power
1 Riverside Plaza
Colurjnbus, OH 43215
614-223-1237
Fax:614-223-1252
E-mail: robin_j._reash@aep.com
Mary Reiley
Biologist
Office of Science & Technology
U.S. Environmental
Protection Agency
401 M Street, SW (4304)
Washington, DC 20460
202-260-9456
Fax:202-260-1036
E-mail: reiley.mary@epa.gov
Michael Remington
Supervisor, Environmental Compliance
Imperial Irrigation District
333 East Barioni Boulevard
Imperial, CA 92251
760-339-9149
Fax:760-339-9191
E-mail: michelr@quix.net
Cindy Roberts
Environmental Scientist
Health and Ecological
Criteria Division
U.S. Environmental
Protection Agency
401 M Street, SW (4304)
Washington, DC 20460
202-260-2787
Fax:202-260-1036
E-mail: roberts.cindy@epa.gov
Keith Sappington
Office of Water
Office of Science and Technology
U.S. Environmental Protection Agency
401 M Street, SW (4304)
Washington, DC 20460
202-260-9898
Fax:202-260-1036
Roy Schroeder
Research Hydrologist
Water Resource Division
U.S. Geological Survey
5735 Kearny Villa Road - Suite O
San Diego, CA 92123
619-637-6824
Fax:619-637-9201
Judith Schofield
Environmental Scientist
Consulting Services
Dyn Corp
300 North Lee Street
Suite 500
Alexandria, VA 22314 •
703-519-1391
Fax:703-684-0610
A-6
-------
E-mai(: schofiej@dyncorp.com
Jackie Sincere
Senior Regulatory Analyst
HPI
1220 L Street, NW
Washington, DC 20005
202^682-8326
Fax: 202-682-8031
E-mail: sincorej@api.org
Terri Spanogle
Toxicologist
Jellinek, Schwartz & Connolly, Inc.
1525 Wilson Boulevard - Suite 600
Arlington, VA 22209
703-312-8573
Fax: 703-527-5477'
E-mail: terri@jscinc.com
Chris Stanford
Senior Consultant
JD Consulting
19509 Sterling Creek Lane
Rockville, VA 23146
804-749-3187
Fax:804-749-3187
E-mail: cstanford@jdconsult.com
Richard Thiery
Laboratory Director
Coachella Valley Water District
P.O. Box 1058
Coachella, CA 92236
760-398-2651, Ext: 326 ,
Fax:760-398-3711
E-mail: rgthiery@compuserve.com
Ed Thompson
President , • ,
Phelps, Dodge Refining Corporation
P.C5. Box20001
El Paso, TX 79998
915r775-8871
Jeanette Wiltse
Division Director
Health and Ecological
Criteria Division
Office of Water
U.S. Environmental
Protection Agency .
401 M Street, SW (4304)
Washington, DC 20460
202-260-7317
Fax:202-260-1036
William Wright
Principal Ecologist
Northwest Program
Industrial/Federal Operations
Montgomery Watson
2375 130 Avenue, NE - Suite 200
Bellevue, WA 98005-1758
425-881-1100 Ext: 376 ,
Fax:425-867-1970
E-mail: william.e.wright@us.mw.com
' A-7
-------
-------
APPENDIXB
TECHNICAL CHARGE TO EXPERTS AND BACKGROUND
> MATERIALS
-------
-------
Premeeting Documents Provided to Experts
1. Overview of EPA's Review of Selenium Aquatic Life Criteria (included in this appendix)
2. Technical Charge to Experts (included in this appendix)
' I ,-.-•' '
3. Selected References (list of references included in this appendix)
" , - . " ) . . -
4. EPA's Existing Aquatic Life Criteria Document for Selenium.
U.S. EPA. 1987. Ambient Water Quality Criteria for Selenium. EPA-440/5-87-006.
Washington, DC. (Available through the National Technical Information Service (NTIS)
5258 Port Royal Road, Springfield, VA 22161. Order number: PB88-142237).
s'
5. Draft Field Study Summary and Bibliography from EPA's 1997 Literature Review.
(Available from: U.S. EPA, Office of Water, Health and Ecological Criteria Division,
Mail Code 4304,401 M St., S.W., Washington, DC 20460. Contact: Keith Sappington,
E-mail: sappington.keith@epamail.epa.gov). " . ,
6. Proposed Acute Criteria for Selenium Under the Great Lakes Water Quality Initiative
Guidance (Available in the Federal Register). .
Proposed Selenium Criterion Maximum Concentration for the Water Quality Guidance
for the Great Lakes System; Proposed Rule. Federal Register. Vol. 61, No. 221,
November 14,1996, p. 58444-58449. "
B-l
-------
B-2
-------
EPA's REVIEW OF FRESHWATER AQUATIC LIFE CRITERIA FOR SELENIUM
OVERVIEW AND BACKGROUND
Background Material for U.S. EPA's Peer Consultation Workshop on Selenium
. Aquatic Toxicity and Bioaccumulation
May 27-28,1998
Washington, D.C.
> U.S. Environmental Protection Agency
Office of Science and Technology
Office of Research and Development, Risk Assessment Forum
401MSt,SW
Washington, D.C. 20460
B-3
-------
BACKGROUND
Selenium, a metalloid which occurs in water from both natural and anthropogenic sources, can be highly
toxic to aquatic life at relatively low concentrations. Selenium is also an essential trace nutrient for many
aquatic and terrestrial species. Derivation of aquatic life criteria for selenium is complicated by its complex
bfogeochemistry in the aquatic environment. Specifically, selenium can exist in several different oxidation
states in water, each with varying toxicities, and can undergo biotransformations between inorganic and
organic forms. The biotransformation of selenium can significantly alter its bioavailability and toxicity to
aquatic organisms. Selenium also has been shown to bioaccumulate in aquatic food webs, which makes
dietary exposures to selenium a significant exposure pathway for aquatic organisms.
The most recent aquatic criteria for selenium were derived by EPA in 1987. At the time of their publication,
these criteria could not be conveniently adjusted to account for the combined toxicities of different selenium
forms. Since this time, a substantial body of literature has accumulated on the toxicrty of different forms (in
combination and in isolation) of selenium to aquatic life. In response to this and other new information, EPA
has initiated various activities for evaluating and revising acute and chronic freshwater selenium criteria.
GOALS OF EPA's REVIEW OF FRESHWATER SELENIUM CRITERIA
EPA envisions three main products emerging from its review of freshwater selenium criteria.
1. Revised freshwater acute aquatic life criteria (called the Criterion Maximum Concentration or CMC)
2. Revised freshwater chronic aquatic life criteria (called the Criterion Continuous Concentration or
CCC)
3. Development of Site-specific Aquatic Life Criteria Guidelines for Selenium
_EPA recognizes the need td review saltwater aquatic life criteria for selenium. However, EPA's original and
updated literature reviews indicate that the availability of data concerning selenium effects on saltwater
organisms is much more limited compared to freshwater (i.e., sufficient data appear to be available for only
one oxidation state of selenium (selenite). Thus, at this time, EPA has decided to focus its review on the '
freshwater criteria. EPA is also considering the development of wildlife criteria for selenium following the
development of aquatic fife criteria. It is expected that some of the work being undertaken in the revision of
the aquatic life criteria would be applicable to wildlife criteria (i.e., issues dealing with bioaccumulation in
aquatic food webs).
SUMMARY AND STATUS OF EPA's CRITERIA REVIEW PROCESS
Figure 1 illustrates the major components of EPA's review of freshwater criteria for selenium. EPA has
initiated work on several projects that relate to both the acute and chronic freshwater criteria (e.g., draft
updates of the literature review, additional acute toxicity testing, proposed additivity approach for the CMC
under the Great Lakes Water Quality Initiative Guidance, analysis of new data from the Monticello
experimental stream). However, the first major step in the revision process is viewed as being the conduct
of the Peer Consultation Workshop on Selenium Aquatic Toxicity and Bioaccumulation. The output from
this meeting (recommendations in response to the technical charge) will be considered by an EPA-
established work group that will be responsible for revising both the national acute and chronic aquatic life
criteria. The work group would also be charged with developing guidance for site-spe.eific criteria for
selenium. Other inputs to this work group include the results from the various tasks summarized below
(e.g., literature review, Monticello stream data, additional toxicHy tests).
The draft national criteria and site-specific criteria guidance woufd then undergo external peer review and
revision prior to being noticed in the Federal Register. Ideally, all three products (national acute, chronic,
and site-specific criteria guidance) would be produced and published at the same time. However, it
appears likely that EPA might first revise the acute criteria (National and GLI), then revise the chronic and •
B-4 - •
-------
-«. ' • = '. . ' -
site-specific criteria guidance. The sequence of products is being discussed further at EPA-
In terms of time lines, setting precise dates is difficult at this point because EPA does not know how much
work will be required to complete these products and will need to consider the Panel's recommendations
on some technical issues. For example, one paramount technical issue is whether or not EPA will attempt
to develop a chronic criterion that is extrapolated from critical tissue residues in aquatic,organisms or one
that is derived directly from water column-based field data as in the past. However, it is likely that the
development of draft national acute and chronic criteria would require 9-12 months of work after the expert
panel meeting, perhaps longer. Peer review and publishing final criteria might require an additional 4-6
months. .
Listed below is the status of various components of the criteria revision process.
Updated Literature Review for Selenium
. Purpose: This project is being conducted to update both the acute and chronic aquatic toxicity
database for selenium; This is necessary for revising the national and GLI criteria and may also be
useful in the development of site-specific criteria guidance for selenium.
Status: Draft literature review corhpleted by the contractor in August, 1997 (reflecting literature
collected up to early 1997). The draft document (and some of the underlying data) has been
reviewed and comments have been compiled. This draft literature review will be revised based on
these comments and made current prior to the publication of revised selenium criteria.
Review and Analysis of Monticello Stream Data '
Purpose: This project is being conducted to review and revise (if necessary) the statistical analysis
of toxjcdlogical data from an unpublished EPA study of selenium effects in outdoor experimental
sfrea'ms. This study is considered to be important because it fills a data gap on the selenium
: effects on aquatic organisms in stream systems under field conditions and is directly relevant to the
freshwater, chronic criterion. It may also be useful in the development of site-specific criteria
modification guidance. ,
Status: Re-analysis of these data is nearly completed: EPA is.planning to produce a revised draft
manuscript by August.
' * > ^ . • • =,-'-" •
Peer review of Revised Monticello Stream Study
Purpose: Once the revised Monticello study manuscript is completed, EPA plans to have it peer
reviewed externally. Since the peer review process in scientific journals can be lengthy and may
not be conducted at the desired level of detail, EPA is planning to have the draft manuscript peer
reviewed by experts external to the Agency. , .
Status: The contract is in place and work will begin after the draft document is completed.
Region V Acute Toxicity Testing
Purpose: This project is being performed to confirm and expand Upon the results from acute toxicity
tests previously conducted with several sensitive freshwater species. These tests are important to
the development of acute, freshwater criteria for selenium (National and GLI). It is being funded by
Region V, with technical assistance from both ORD and OW.
Status: The toxicity tests and chemistry analyses have been completed. The data have been
reviewed and extensive comments have been prepared. EPA Region V is in the process of
responding to the comments.
E-5
-------
Averaging Period and Site-Specific Guidance
Some work on the averaging period and site-specific guidance for selenium has been conducted by
staff at ORD. Additional work on selenium food web modeling is being considered to help in the
evaluation of different averaging periods on the level of protection of chronic criteria.
B-6
-------
Figure 1. EPA's Review of Freshwater Selenium Aquatic Life Criteria
Site-Specific Criteria
Guidelines Activities
Acute Criteria Activities
(CMC)
Chronic Criteria Activities
(CCC)
Se Peer
Consultation
Workshop
EPA-Established Selenium Criteria Workgroup
Draft Site-
Specific
Criteria
Guidelines
Final CMC
(National & GLI)
Final CCC
(National & GLI)
Final Site Specific
Criteria Guidelines
B-7
-------
B-8
-------
AEPA
United States
Environmental Protection Agency
Office of Water
Peer Consultation Workshop on Selenium
Aquatic Toxicity and Bioaccumulation
\, - • • "" • ' *
TECHNICAL CHARGE TO EXPERTS
BACKGROUND
The U.S. Environmental Protection Agency's (EPA's) national aquatic Ijfe criteria for selenium were last
updated in 1987. EPA's current freshwater chronic criterion of 5 ug/L is based on the results from field
studies conducted on Belews Lake, North Carolina (in addition to laboratory information), because
available data indicate that selenium is more toxic under field conditions than in standard laboratory
toxicity tests. One reason for the increased toxicity observed in the field is the greater exposure of
aquatic organisms to dietary selenium, which results from selenium accumulation in aquatic food webs.
Dietary (food web) exposure is typically not addressed by standard chronic toxicity tests and, therefore,
results from laboratory tests can be underprotective when applied to field settings.
Over the past decade, additional data have been collected on the toxicity and bioaccumulation of
selenium under both laboratory and field conditions. EPA< has received comments that suggest the
current chronic aquatic life criterion (5 ug/L) might not provide adequate protection.to some sensitive
aquatic organisms under some conditions. EPA has also received comments that suggest the criterion
of 5 ug/L might be overly protective under some conditions. As discussed in EPA's national guidelines
for deriving aquatic life criteria (U.S. EPA, 1985), the chronic criterion (officially called the Criterion
Continuous Concentration or CCC) is considered to be a long-term, continuous concentration that, if not
exceeded beyond a specified duration and frequency, would not be expected to result in unacceptable
effects on the vast majority of aquatic organisms (i.e., 95% of tested aquatic species) under the vast
majority of environmental conditions. ••-.»••
Although EPA has established procedures for calculating site-specific modifications to its national criteria
(e.g., recalculation procedure, water-effect ratio procedure), such procedures are generally not
applicable to the selenium chronic criterion. This is because to be adequately protective, site-specific
adjustments of the chronic selenium criterion must address food web exposure to fish under field
conditions. However, for practical reasons, the site-specific procedures listed previously are typically
oriented toward data generated by standard laboratory tests, which usually do not fully address exposure
through the food web. EPA has initiated work on developing site-specific procedures for selenium.
Review and revision of the national chronic criterion for selenium is further complicated by the fact that
selenium exists in several inorganic and organic forms in the aquatic environment, which might undergo
biotransformations and exert differential toxicities to aquatic organisms.
EPA acknowledges concerns and issues associated with the risks, to semi-aquatic terrestrial wildlife from
waterbome exposure to selenium. Historically, criteria to protect semi-aquatic wildlife have been
established using different procedures and for only one region of the country (the Great Lakes). EPA is
aware of other approaches that might be useful for establishing wildlife criteria for selenium (e.g., tissue-
based methods). However, EPA belieyes that significant effort will be required to adapt these
methodologies on a national or multi-regional basis and that this is beyond the scope of this workshop
EPA recognizes that several issues addressed in this technical charge which pertain to aquatic life
criteria (e.g., bioaccumulation issues) would also be applicable to the derivation of wildlife criteria for -
selenium, should such efforts be conducted.
B-9
-------
fn its ongoing review of the freshwater chronic criterion for selenium, EPA anticipates taking the
following actions and making several key decisions:
f . ' . ••
1. Gathering and determining the acceptability of all relevant chemical, toxicological, and
bioaccumulation data.
2. Deciding which environmental compartments) (e.g., water, tissue, sediment) provide(s) the
most reliable expression of the chronic criterion.
3. Deciding in which form(s) to express the chronic criterion (e.g., dissolved, total).
4. Deciding whether sufficient data exist to warrant expression of the criterion as a function of
some other environmental parameter (e.g., pH, DOC, sulfate).
5. Deciding on the appropriate magnitude, averaging period, and excursion frequency for the
chronic criterion.
6. Developing guidelines for conducting site-specific adjustments to the national chronic selenium
criterion.
OVERRIDING ISSUES
The technical charge for this workshop emerged from several overriding issues, which EPA will need to
address in its review and revision of the freshwater chronic criterion for selenium. These issues are
described in the following to provide additional context to the specific questions presented in the
technical charge.
Environmental Compartment. Of the issues listed previously, issue 2 (deciding which environmental
compartments) provide(s) for the most reliable expression of a chronic criterion) is of primary concern to
EPA in relation to selenium. In considering this issue, EPA must not only assess the level of confidence
in the expression of toxicological effect levels but also the level of confidence in any extrapolations that
may be needed between selenium concentrations in different environmental compartments (e.g., from
tissue residues to water, from sediments to water). EPA expects that regardless of which environmental
compartment(?) is (are) eventually selected for expressing the chronic criterion, the criterion will
ultimately need to be related to potential or actual selenium loads to water and hence will involve some
type of translation to the water column.
Averaging Period. Selecting the appropriate averaging period (i.e., the amount of time over which
water concentrations can be averaged to determine an excursion above the chronic criterion) is also of
concern to EPA. Although EPA has generally used a generic averaging period of 4 days for chronic
aquatic life criteria, the agency will likely determine a selenium-specific averaging period based in part on
considerations of the toxicokinetics and the bioaccumulation of selenium to aquatic organisms.
Site-Specific Criteria Guidelines. Finally, a number of the questions in the technical charge also pertain
to the development of site-specific guidelines for adjusting selenium aquatic life criteria. EPA envisions
that site-specific criteria guidelines for selenium could theoretically involve at least two possible
approaches: (1) a calculation-based approach in which the criterion is adjusted based on calculated
differences in bioavailability and bioaccumulation; or (2) a field measurement-based approach in which
appropriate data (e.g., tissue residues) are collected from the sites of concern to document any
differences in bioavailability or bioaccumulation. "" '
EPA intends to consider the experts' responses to the technical charge during its forthcoming evaluation
B-10
-------
and revision of the chronic criterion.
TECHNICAL CHARGE ,
Considering his or her knowledge of the available data on selenium aquatic toxicity and bioaccumulation
each expert on the panel is charged with addressing and commenting on the following technical issues.'
In responding to the various technical questions, each expert must make clear the rationale for his or her
conclusions. In addition, each expert should assess the level of confidence (or, conversely, the degree
of uncertainty) associated with each response (e.g., low, medium, high) and provide an appropriate
explanation. This is especially important when assessing the strength of causal associations from field
studies. EPA further requests that when discussing or presenting specific data to justify a response,
each expert qualify this data to indicate its acceptability and quality (e.g., whether these data have been
peer reviewed, the extent of QA/QC). Finally, as part of .this peer consultation workshop, EPA is asking
for each expert's scientific comment on these technical issues. EPA is not seeking input on policy or risk
management issues.
B-ll
-------
!. Technical Issues Associated with a Water-Column-Based Chronic Criterion
1. Besides selenite and selenate, which other forms of selenium in water are lexicologically
important with respect to causing adverse effects on freshwater aquatic organisms under
environmentally realistic conditions?
2. Which form (or combination of forms) pf selenium in water are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in water would you measure for correlating exposure with
adverse effects in the field?) Note: Your response should include consideration of operationally
defined measurements of selenium (e.g., dissolved and total recoverable selenium), in addition
to individual selenium species. -
3. A) In priority order, which water quality characteristics (e.g., pH, TOC, sulfate, interactions with
other metals such as mercury) are most important in affecting the chronic toxicity and
bioaccumulation of selenium to freshwater aquatic life under environmentally realistic exposure
conditions? .
B) Of these, which have been (or can be) quantitatively related to selenium chronic toxicity or
bioaccumulation in aquatic organisms? How strong and robust are these relationships?
y
C) How certain are applications of toxicity relationships derived from acute toxicity and water
quality characteristics to chronic toxicity situations in the field?
II. Technical Issues Associated with a Tissue-Based Chronic Criterion
4. Which forms of selenium in tissues are toxicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions and
why?
5. Which form (or combination of forms) of selenium in tissues are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in tissues would you measure for correlating exposure
with adverse effects in the field?)
6. Which tissues (and in which species of aquatic organisms) are best correlated with overall
chronic toxicological effect thresholds for selenium?
7. How certain are we in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish? What are the primary sources of
uncertainty in this extrapolation?
B-12
-------
III. Technical Issues Associated with a Sediment-Based Chronic Criterion
8. Which forms of selenium in sediments are lexicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions?
9. Which form (or combination of forms) in sediment are most closely correlated with chronic
effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in sediments would you measure for correlating exposure
with adverse effects in the field?)
t • • , - ' . - • ' > '
10. In priority order, which sediment quality characteristics (e.g., TOC, etc.) are most important in
affecting the chronic toxicity and bioaccumulation of selenium to freshwater aquatic life under
environmentally realistic exposure conditions? Of these, which have been (or can be)
quantitatively related to selenium chronic toxicity or bioaccumulation in aquatic organisms?
11. How certain are we in relating water-column concentrations of selenium to sediment
concentrations? What are the primary sources of uncertainty in this extrapolation?
IV. Cross-Cutting Technical Issues associated with Chronic Criterion
12. How does time variability in ambient concentrations affect the bioaccumulation of selenium in
aquatic food webs and, in particular, how rapidly do residues in fish respond to increases and
decreases in water concentrations?
13. To what extent would the type of ecosystem (e.g., lenticjotic) affect the chronic toxicity of
selenium?
B-13
-------
B-14
-------
Premeeting References Provided to Experts
Besser, J.M., T.J. Canfield, and T.W. La Point. 1993. Bioaccumulation of organic and inorganic
selenium in a laboratory food chain. Environ. Toxicol. Chem. 12:57-72.
Bowie, G.L., IG. Sanders, G.F. Riedel, C.C. Gilmour, D.L. Breitburg, G.A. Cutter, and D.B.
Porcella. 1996. Assessing selenium cycling and accumulation in aquatic ecosystems.
Water, Air and Soil Pollution 90:93-104. -
Brasher, A.M. and R.S. Ogle. 1993. Comparative toxicity of selerute and selenate to the
amptipod Hyalella azteca. Arch. Environ. Contam. Toxicol. 24:182-186,
Buhl, K.J. and S.J. Hamilton. 1996. Toxicity of inorganic contaminants, individually and in
environmental mixtures, to three endangered fishes (Colorado squawfish, bonytail, and
razorback sucker). Arch. Environ. Contam. Toxicol. 30:84^-92.
Pobbs, M.G., D.S. Cherry, and J. Cairns, Jr. 1996. Toxicity and bioaccumulation of selenium to
a three-trophic level food chain. Environ. Toxicol. Chem. 15:340-347.
Hamilton, S.J: and K.J. Buhl. 1990. Acute toxicity of boron, molybdenum, and selenium to fry of
chinook salmon and coho salmon. Arch. Environ. Contam. Toxicol. 19:366-373
> ' '".•'.,
Hermanutz," R.O., K. Allen, T.H. Roush, and S.F. Hedtke. 1991. Effects of elevated selenium
concentrations on bluegills (Lepomis macrochirus) in outdoor experimental streams.
Environ. Toxicol. Chem. 11:217-224.
Ingersoll, C.G., F.J. Dwyer, and T.W. May: 1990. Toxicity of inorganic .and organic selenium to
DaphniaMagna(CladocQra)andChironomusriparius(piptQra). Environ. Toxicol.
Chem. 9:1171-1181. '. ,
Lemly, A.D. 1996. Evaluation of the hazard quotient method for risk assessment of selenium.
Ecotoxicol. Environ. Sctf. 35:156-162.
Lemly, A.D. 1995. A protocol for aquatic hazard assessment of selenium: Ecotoxicol Environ
Sqf. 32:280-288.
Lemly, A.D. 1992. Teratogenic effects of selenium in natural populations of freshwater fish.
Ecotoxicol. Environ. Sqf. 26:181-204. '
Lemly, A.D. 1993. Metabolic stress during winter increases the toxicity of selenium to fish.
Aquatic Toxicol. 27:133-158.
Maier, K.J. and A.W. Knight. 1993. Comparative acute toxicity and bioconcentratioh of
. . ' '.. • ," , • ' /B-15 .-" -'• ' . ' "' ••" .
-------
selenium by the midge Chironomus decorus exposed to selenate, selenite, and seleno-
DL-methionine. Arch. Environ. Contam. Toxicol. 25:365-370.
Naddy, R.B., T.W. La Point, and SJ. Klaine. 1995. Toxicity of arsenic, molybdenum and
selenium combinations to Ceriodaphnia dubia. Environ. Toxicol. Chem. 14:329-336.
Ogle, R.S. and A.W. Knight. 1996. Selenium bioaccumulation in aquatic ecosystems: 1. Effects
of sulfate on the uptake and toxicity of selenate in Daphnia magna. Arch. Environ.
Contam. Toxicol. 30:274-279.
Riedel, G.F., D.P. Ferrier, and J.G. Sanders. 1991. Uptake of selenium by freshwater
phytoplankton. Water, Air and Soil Pollution 57-58:23-30.
Riedel, G.F., J.G. Sanders, and C.C. Gilmour. 1996. Uptake, transformation, and impact of
selenium in freshwater phytoplankton and bacterioplankton communities. Aquatic
Microb.Ecol 11:43-51.
RiedeL, G.F. and J.G. Sanders. 1996. The influence of pH and media composition on the uptake
of inorganic selenium by Chlamydomonas reinhardtii. Environ. Toxicol. Chem.
15:1577-1583.
Rosetta, T.N. and A.W. Knight. 1995. Bioaccumulation of selenate, selenite, and seleno-DL-
methionine by the brine fly larvae Ephydra cinerea Jones. Arch. Environ. Contam.
Toxicol. 29: 351-357.
Sanders, R.W. and C.C. Gilmour. 1994. Accumulation of selenium in a model freshwater
microbial food web. Applied and Environmental Microbiology 60:2677-2683.
Wang, W.-X., N.S. Fisher, and S.N. Luoma. 1996. Kinetic determinations of trace element
bioaccumulation in the mussel Mytilus edulis. Marine Ecology Progress Series 1,40:91-
113.
B-16
-------
APPENDIXC
PREMEETING COMMENTS
-------
-------
; CONTENTS
William Adams ........... . C-l
Gary Chapman C-l 1
, Gregory Cutter • •••-••••"•-•...................;....,. C-I7
Anne Fairbrother .....:...... C-27
Teresa Fan ...... C_35
Steve Hamilton ......... C-49
Gerhardt Riedel ......;...... C-67
JosephSkorupa '..•.'..................._...;............... C-81
William Van Derveer , .......................... ... ;. C-97
C-i
-------
C-ii
-------
William Adams
c-i
-------
C-2
-------
William Adams
I. Technical Issues Associated with a Water-column-Based Chronic Criterion
1. Besides selenite and selenate, which other forms of selenium in water are
toxicologically important with respect to causing adverse effects oh freshwater
aquatic organisms under environmentally realistic conditions?
The only form other than selenate and selenite in water (not sediment) that
appears to be toxicologically important is selenocyanate. Uttle is known about the
toxicity of this form, but it is found in petroleum and a limited number of mining
discharges. Selenate and selenite are the predominant forms derived from mining,
agricultural practices, fly ash, and natural shales. However, ft is the conversion of
these forms to qrgano-selenium compounds that are of most ecological relevance.
Organo-tforms are rarely found in water at detectable levels. However, it should be
pointed out that the analytical methods for measuring these forms are not well
, developed. ' -.
^ . i •
2. .. Which form (or combination of forms) of selenium in water are most closely
correlated with chronic effects on aquatic life in the field? (In other words, given
, current or emerging analytical techniques, which forms of selenium in water would
you measure for correlating exposure with adverse effects in the field?) Note:
Your response should include consideration of operationally defined
measurements of selenium (e.g., dissolved'and total recoverable selenium), in
addition to individual selenium species.
Given the state-of-the-art for measuring selenium in. water and given that organo-
forms of selenium are rarely found in the water column- the most relevant form of
selenium to measure in water to correlate with adverse effects would be total
recoverable selenium. This would include all forms of selenium in the water except
a limited amount of non-bioavailable selenium that might be tied up in the •
crystalline structure of suspended solids. However; it should be pointed out that
the body of literature is growing which shows that chronic effects in aquatic as well
as terrestrial systems are primarily due to the conversion of inorganic forms to
organic forms which are then taken up via the diet. This simply points to the fact •
, that the diet is important and that chronic toxicity may not be principally due to
waterbome selenium. Exceptions to this might be for primary producers. .
3. A) In priority order, which water quality characteristics (e.g., pH, TOG, sulfate,
interactions with other metals such as mercury) are most important in affecting the
\ chronic toxicity and bioaccumulation of selenium to freshwater aquatic life under .
environmentally realistic exposure conditions?
C-3 '
-------
William Adams
Overall, the eh (oxidative/reductive) state of an ecosystem is most important in
determining the potential for chronic toxicity to occur because it significantly influences
the formation of organo-forms of selenium. I do not believe we can prioritize these water
quality characteristics due to insufficient information of their effects on expression of
chronic toxicity. One could predict that, at the extremes, pH would be important due to
speciation changes, but chronic data are not available to assess this. Sulfate appears
unimportant in terms of the expression of chronic toxicity except potentially for primary
, producers. . • "
" .... j , ','.'•
B) Of these, which have been (or can be) quantitatively related to selenium chronic
toxicity or bioaccumulation in aquatic organisms? How strong and robust are these
relationships?
None, if one looks fora water quality characteristic which crosses all trophic levels.
Sulfate would most likely correlate well with chronic toxicity ofselenate to primary
producers. , '
C) How certain are applications of toxicity relationships derived from acute toxicity and
water quality characteristics to chronic toxicity situations in the field?
> '
The applications of relationships derived from acute toxicity and water quality
characteristics do not apply to chronic toxicity for most aquatic life (an exception to this
might be the relationship between selenate and sulfate for algae). This is primarily due to
the fact that acute toxicity is most often the result of water exposures whereas chronic
effects are the result of selenium being incorporated into the diet where the predominant
form of selenium is no longer an inorganic form.
II. Technical Issues Associated with a Tissue-Based Chronic Criterion
4. Which forms of selenium in tissues are toxicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic
conditions and why?
Protein-bound (reduced forms) of selenium (i.e., most likely seleno-methionine orseleno-
cysteine). Due to the lack of analytical methodologies to actually measure organo-forms .
of selenium little actual information on specific forms is available. However, there is a
growing body of evidence that points to the fact that chronic toxicity is the result of the
conversion of inorganic forms to organic forms either by plants or animals in the water
column or by microbes in the sediments under reducing conditions. These organo-
selenium compounds enter the food chain and are transmitted to receptors where they
mimic their sulfur analogs and interfere with normal metabolic processes. The
conversion of inorganic forms to organic forms occurs through several rate limiting steps
and at different rates under different environmental conditions. Understanding (and
C-4
-------
William Adams
predicting) the factors controlling these rate limiting processes is the challenge of the next
decade.
5. Which form (or combination of forms) of selenium in tissues are most closely correlated
with chronic effects on aquatic life in the field? (In other words, given current or emerging
analytical techniques, which forms of selenium in tissues would you measure for
correlating exposure with adverse effects in the field?)
-At present, in spite of emerging techniques for organp-seleriium forms, the best measure
of selenium in tissues is total selenium. Measures of protein bound and organo-selenium
would help advance the science.
6. . Which tissues (and in which species of aquatic organisms) are best correlated with
overall chronic toxicological effect thresholds for selenium?
Measuring total selenium in fish ovaries (eggs) from gravid females (pre-spawning)
appears to be a potentially useful monitoring tool. Certainty (uncertainty) in the threshold
is unknown due to the lack of multiple data set. Values in the range of 8-12 ug/g have
been proposed as a threshold.
> . '-..•' •' • ' ".•
- ' i
7. How certain are we in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish? What are the primary sources
of uncertainty in this extrapolation?
Over the past few months my colleagues and I have endeavored to -relate water-column
concentrations of selenium to bird egg concentrations and tissue-residue concentrations
.in fish. For the water to bird egg analysis, we have developed a model based on a one
step regression from mean water selenium to mean egg selenium concentration (Adams
et al, 1997). This model represents the mean relationship over many sites, and the
overall uncertainty and variability in applying a single model to different sites. The
database we used was based on selenium egg and water concentrations from USFWS
and USGS reports for 15 lentic sites in the western U. S. The sites covered a broad range
of physical and ecological conditions. We believe this heterogeneity appropriately
encompassed much or all of the uncertainty in applying such a model to any given site.
Data for each site included different areas (e.g., Kesterson Reservoir within San Joaquin
Valley) and different ponds (e.g., Pond #2 at Kesterson Reservoir) within an area. Our
model allows us to quantify the uncertainty in relating water column selenium
concentrations of mean egg residues. For purpose of example, we've run our model to
predict the water concentration that would be protective of bird eggs with a selenium
threshold of 8 - 20 mg/kg. Our analysis found that the 10th to 90th percentile range on the
water concentration that would be protective of this endpoint, for lentic sites in the
Western U.S., is 3-173 ug/L). Thus, the max:min uncertainty factor for the egg
threshold is 2.5, whereas the 90:10 uncertainty factor for water is 58, or more than 20
. ••- ' • • . e-5 - . •• • ' •
-------
William Adams
times higher. This indicates that site variability is an important factor in extrapolating from
water column selenium concentrations to tissue residue concentrations. Our model
estimates that a water concentration of 5 ug/L is over-protective of 83% of sites of the
sites examined (for the uncertain selenium threshold of 8-20 mg/kg). A water
concentration of 2 ug/L would be over-protective of 94% fthe sites for this uncertain egg
threshold.
Our efforts torelate water column and fish tissue selenium concentrations has met without
much success, due to the absence of suitable data. The idea was to correlate the tissue
concentrations (say fish eggs) to their diet and to the water column concentration of total
recoverable selenium. This would be patterned after the approach used by Skorupa and
Ohlendorf (1991) for birds. Our modeling efforts indicated a rather low degree of
correlation due to the lack of good data sets where the appropriate information on dietary
and selenium composition existed along with tissue and water selenium concentrations.
This approach requires an extensive amount of data. For this approach to be useful it
would have to be performed at several sites so the variability in the relationship could be
assessed.
111. Technical Issues Associated with a Sediment-Based Chronic Criterion
. 8. Wbjch forms of selenium in sediments are toxicologically important with respect to
causing adverse effects on freshwater aquatic organisms under environmentally realistic
conditions? . -
For the most part total selenium in bulk sediments has been used to relate sediment
concentrations to possible effects. Recently, Van DerVeerand Canton (1997)
demonstrated the importance of considering total organic carbon in sediments as a
potential ligand for binding selenium, controlling its bioavailability or as a surrogate
measure for the potential for inorganic forms to be converted to organic forms, (actual
mechanism was not explained in the publication). In general, it is thought that inorganic
selenium is converted to organic forms in sediments by microorganisms under reducing
conditions and that these organic forms are incorporated in the diet and are responsible
for toxicity to higher trophic level organisms. It is also known the vegetation brings
organic forms of selenium to the sediment and hence into the diet of higher trophic level
organisms.
Selenium chemistry is very complex in sediments and not well understood due to. the lack '
of analytical tools to measure specific chemical forms. The following is an abbreviated
list of some of the forms of selenium reported to be present in sediments under reducing
conditions: elemental selenium, selenium hydrogen sulfide (SeH2S), Hydrogen selenide
(H2Se), dimethyl and trimethyl selenide [(CH^Se & (CHJSeJ, dimethyl diselenide
(CH^zSe-2, seleno-diglutathione, seleno-methionine and other organo-forms, copper and
several other metal selenides (CuSe-2). A critical factor in assessing the selenium
chemistry is the eh of the sediment environment. In aerobic sediments, such as the
surficial layers in flowing waters or low organic carbon environments, the reduced forms
C-6
-------
William Adams
(and organic forms) will not predominate in sediments. -./-.',
9. Which form (or combination of forms) in sediment are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging
analytical techniques, which forms of selenium in sediments would you measure for
correlating exposure with adverse effects in the field?)
/ would measure total selenium; there are no speciated forms of selenium which have
been closely correlated with benthic organism or water column effects. Effects that are
seen in the field are typically on higher trophic level species such as fish and birds.
Effects are not often observed on sediment benthos.
\ • • :
10. In priority order, which sediment quality characteristics (e.g., TOG, etc.) are most
important in affecting the chronic ioxicity and bioaccumulation of selenium to freshwater
aquatic life under environmentally realistic exposure conditions? Of these, which have
been (or can be) quantitatively related to selenium chronic toxicity or bioaccumulation in
aquatic organisms?
The list is very short. To date, only total organic carbon (TOO) has been closely
correlated with total selenium in the sediment and the potential for chronic effects. These
data are limited to flowing waters (lotic systems) and to the Arkansas River system (Van
DerVeerand Canton 1997). This research does suggest that there is merit in further
•' ' understanding the role of carbon in controlling bioavailability or as a surrogate measure for
the potential for inorganic forms to be converted to organic forms and hence, a surrogate
measure for the potential for chronic toxicity. This is somewhat analogous to carbon
: normalization for non-polar organics although in this case it does not appear to be due to
soption of selenium to carbon in the sediment. Direct correlations of TOO or other
sediment quality characteristics with chronic toxicity are lacking. Temperature could be an
important factor for Northern aquatic systems where the conversion of inorganic forms to
organic forms would be expected to be slower than Southern warm water environments.
11. How certain are we in relating water-column concentrations of selenium to sediment
concentrations? What are the primary sources of uncertainty in this extrapolation?
Once again, the most definitive work in this area has been done by Van DerVeer and
Canton (1997) relating total recoverable water-column selenium with total sediment
selenium. A correlation coefficient of 0.79 was obtained without sediment carbon
correction and with carbon correction a correlation coefficient of 0.93 was obtained.
Earlier work done by Lemly related sediment concentrations to observed biological effects
in various aquatic systems, but did not correlate sediment selenium with water-column
concentrations of selenium.
C-7
-------
William Adams
•IV. Cross-Cutting Technical Issues Associated with Chronic Criterion
12. How does time variability in ambient concentrations affect the bioaccumulation of selenium
in aquatic food webs and, in particular, how rapidly do residues in fish respond to
increases and decreases in water concentrations?
In general, variability in ambient concentrations slowly affects the bioaccumulation of
selenium in higher trophic level systems. By slow, I mean over a period of months as
opposed to days. The principal reasons for this is due to the fact that there are several
rate limiting steps in the conversion of inorganic forms of selenium to organic forms
followed by uptake and food-chain transfer of the selenium to higher trophic levels. This
approach assumes a dietary pathway. Exceptions to this do occur where there are
severely elevated levels of selenium in a given discharge and where the primary route of
uptake by the fish is via the gill. In this case, laboratory experiments have shown that the
rates of uptake and depuration can be somewhat faster and tissue levels can vary by an
order of magnitude over a period of a month in fish. Selenium is an essential element for
fish and at low levels of selenium 'in the water (1 ppb or less) fish (and other aquatic
organisms) conserve selenium to meet their needs. Hence, tissue levels remain
somewhat constant at environmentally relevant concentrations. Experiments with very
low concentrations of selenium (<0.01 ppb) result in very large bioconcentration factors for
selejiium. In summary, bioconcentration factors for selenium and other essential metals
are inversely related to the water concentration.
13. To what extent would the type of ecosystem (e.g., lentic, lotic) affect the chronic toxicity of
selenium?
The type of ecosystem and specific ecosystem components appears to play a major role
in controlling the potential for chronic toxicity to be expressed in both aquatic and avian
species. The work of Van DerVeer and Canton (1997), Canton and Van DerVeer (1997)
and Bowie et al (1995) support this conclusion. Lotic systems appear to lack the
necessary anaerobic zone(s) and standing vegetation to result in a significant conversion
of inorganic forms of selenium to organic forms with subsequent food-chain transfer of the
organo-forms to higher trophic levels where embryonic effects are observed. Other factor
distinguishing lotic from lentic environments are hydraulic retention time and retention of
carbon in the system. Lotic environments have shorter hydraulic retention times and they
have much less carbon in the sediments and thereby lack the storage and potential for
conversion 'of inorganic forms to organic forms relative to lentic systems. This is an area
where more research is needed. However, there is mounting field collected data
supporting the idea that site specific conditions are important in controlling the potential for
chronic toxicity to aquatic life from selenium.
Sfte-specific approaches for determining water quality criteria for aquatic organisms:
Several approaches were considered as to how one might derive a site specific water quality
criterion (WQC) for aquatic organisms. First the use of indigenous species and or a water effects
C-8
-------
• William Adams
ratio (WER) approach were considered. The WER ratio approach does not look promising
because selenium bioavailability in the water column is not significantly altered by site conditions
such as suspended solids, dissolved organic carbon, hardness or other factors thought to
influence the bioavailability of copper, cadmium and other divalent metals (however, this has not
been thoroughly investigated). The use of indigenous species probably would not alter the
existing WQC because it is based on a single study in Belews Lake and is not derived from the
standard EPA Guidelines for WQC. However, exceptions to this conclusion would be ecosystems
for which the Belews Lake data (and WQC) are not applicable; for example the Great Salt Lake,
Salton Sea or ephemeral streams. These are clear examples where one would question the
applicability of existing WQC and the use of indigenous species could be appropriate. Following
this line of thinking, one would have to ask how applicable a WQC derived from a Southern lentic
lake (Belews Lake) applies to Western/Northern lotic systems?
Second, if sufficient data were available a generic or global model could be developed for
the relationship between water-borne selenium and tissue-residue selenium which
incorporated a dietary component in the model. This would be patterned after the
approach that Skorupa and Ohlendorf (1991) presented for birds. Site -specific data could
then be used to determine whether or not site conditions result in significantly more or less
accumulation of selenium. The site to global model ratio could be used to provide a site-
specific modification of the WQC. This approach can be done, but requires a lot of data.
Third, another alternative which might provide a practical and near-term approach to
setting site-specific WQC would be, to adopt an approach similar to that developed by
Barrick et a/. (1988) - Apparent Effect Threshold approach or the Threshold Effects Level-
approach published by Long and Morgan. This approach to developing a threshold where
effects can be seen ts(kes advantage of field data and compares the concentration where
effects are never seen versus the concentration where effects are always observed. In
between these two values lies the apparent effects threshold. A casual review of the
' literature for flowing water systems versus lentic systems suggests that there are
significant differences in the levels of selenium in the water where effects are observed.
Compilation of the existing data should allow for developing lotic and lentic threshold
values. Site modifications could potentially be made by adjusting the existing WQC by a
factor based on the aforementioned approach to accommodate lotic systems:
C-9
-------
William Adams
C-10
-------
Gary Chapman
c-n
-------
Gary Chapman
C-12
-------
Gary .Chapman
will be away from my office all of next week and the following week through May 13. As a result,
I have to submit my remarks and recommendations now, without further study of the materials. ' '
As an expert on water quality criteria, their site-specific modifications, and criteria guidelines, but
with only a nodding acquaintance with past selenium studies, I base my comments regarding
selenium primarily upon my reading to date of the materials provided. The main points that I wish
to emphasize are in bold, and represent my stronger opinions.
Environmental Compartment. Because of the complex nature of selenium (Se) chemistry and
its close relationship to toxicity and bioaccumulation, it is difficult to establish a simple water
column concentration criterion. Even in the relatively simple case of mercury, EPA was
compelled to establish a criterion that used tissue residues to trigger further site studies of
mercury concentrations. In the case of mercury, water concentration exceedence triggers tissue
residue investigations targeting FDA action levels. The more complex nature of selenium
chemistry probably will require a similar approach with at least some dependency upon thejevels
of selenium in resident organisms. In addition, Se concentrations below simple detection levels
could lead to adverse tissue levels, so that it may be impractical to use water concentration as a
trigger for tissue residue investigations. Finally, there is no FDA action level to trigger a residue-'
based regulation. ,
''••'. -
Laboratory toxicity studies have provided reasonable estimates for acute toxicity of inorganic
forms of selenium as well as selenomethionine. Laboratory studies that included food-chain
organisms allowed to accumulate selenium provide additional effect level estimates for chronic
toxicity, but even these studies are usually much less complex than the situation in the field.
Considering that, in nature, chronic toxic effects will almost always include a food-chain
component, it seems imperative that chronic criteria include consideration of tissue residues in •
arriving at any chronic water column criterion. EPA's current selenium criterion indirectly utilized
this route of uptake by relying upon effect data from the field in establishing a link between water
column concentrations and apparently "safe" and toxic conditions. It is well known that the time-
course of exposure from various environmental compartments can be very different, with water
being the most variable and sediment concentrations being much slower to change. Tissue
residues can variably reflect changes in either or both of these sources, as well as spatial
variability in water, sediment, and food chain contamination.
I have relied for the following upon the paper by Lemly (1996), describing his evaluation of the
hazard quotient (HQ) method for selenium risk assessment as a general basis for my comments.
This paper considers eleven sites-having various levels of contamination, and the method rates
each, of five compartments for hazard with a summation of an overall hazard score. I have
tended to ignore the bird egg compartment in my comments because they generally appear the
same as that for fish eggs, because they may be considered under a separate wildlife criterion,
and because of the potential that the site of collection may not represent the site of
contamination (depending upon the species involved and its relative migratory habits).
Without consideration of the original studies from which the data were taken, it is difficult to fully
comprehend the significance of the ranges of concentrations indicated for each site. These
ranges may reflect variance due to temporal, spatial, or individual organism/sample differences.
If we assume that the hazard rating score for each site is a good indication of the hazard
involved, it appears to me that the best correlation between individual compartments and •
-. ' ' ' C-13 . '• . ...'•"• '"..
-------
Gary Chapman
overall hazard score is achieved by the invertebrates and fish egg component. Indeed, if
one considers only these two components, and then takes the higher of the two hazard ratings, -
they are the same as the overall score for nine of the eleven sites. For the other two sites
(Stillwater WMA and La Plata River) either the rating for fish eggs or invertebrates is one
category higher (more severe) than the overall rating. This pair of compartments represents a
reasonably good surrogate for the overall score, and is conservative.
These eleven sites probably do not represent all types of aquatic habitats at risk, so that
generalizations that might work with this data set may be inapplicable to other habitats. Never-
theless, criteria are always established using data with various degree of limitation. Regardless
of how well the hazard protocol method appears to work to characterize potential toxicity
problems, there are very clear limitations (even with just these eleven cases) with respect
to setting a water column criterion. This is apparent by inspection of the data sets for the three
WMAs where tissue residues are high but neither water column nor sediment appear heavily
contaminated. The suggestion that this situation is due to very toxic seleno-organic materials is
germane, but not particularly instructive with respect to quantification or characterization of the
molecule(s) involved. This data does generate considerable prejudice against the Great Lakes
approach of treating seleno-organics as toxicologically proportionate to selenate and selenite.
In summary, I believe that it is currently unwise to set any chronic criterion for selenium
that does not take into account tissue residue data. It appears that there may be little data
upon which to establish dose-response relationships with seleno-organics common to the field.
_One could .assume that all seleno-organics had bioconcentration factors and toxicity similar to
"selenomethionine, at least in situations where tissue residues are high but selenate, selenite,
and total seleno-drganics are low. The apparent bioconcentration factors reported by Besser et
al. (1993) for selenomethionine at O.i ug Se/L for algae (36,300) and daphnids (382,000) would
easily account for the range of invertebrate and fish tissue levels reported for the three WMAs
from water concentrations of <1 ug Se/L. To a lesser extent, the data of Rosetta and Knight
(1995) and Maier and Knight (1993) suggest relatively high selenomethionine bioconcentration
for midge and brine fly. Each of these three studies was short-term and might not represent a
reasonable steady-state bioaccumulation, especially for longer lived organisms.
The basic problem with applying the tissue residue approach is defining a safe level on the
basis of laboratory and field studies. In this regard it would be very instructive to have Lemly
discuss the technical basis for his hazard profile categories for macroinvertebrates and fish eggs
(from citations in Fig. 1 of his 1995 paper outlining the protocol). I assume that this will be a
component of his presentation to the panel; if not, it really must be addressed at the meeting.
Averaging Period. It is generally recognized that the current averaging periods being used by
EPA are generally conservative (short) periods intended to apply to a few rapidly toxic chemicals
and a few taxa with relatively short life-cycles. The use of toxicokinetics, at least for mortality, is
an attractive and reasonably practical approach. In order to implement this approach with any
chemical criteria, the data base requirements would be broader than those necessitated by
current methods for criteria development. These include more frequent observations of mortality,
especially during the first day or two of the test, and consideration of changing sensitivity or
modes of action at critical life stages or as exposures lengthen. Another area of data need
(generally ignored in current EPA criteria) is the effect of temperature on acute toxicity and
toxicokinetics.
C-14
-------
Gary Chapman
It is possible that the toxicokinetic approach will essentially due away with averaging periods, per
se, and simply declare a particular exposure regime as either acceptable or unacceptable.
Assuming that the exposure period for acute toxicity will be rather short, and the exposure
essentially constant, the Mancini model considered recently by EPA can provide
reasonable acute toxicity criteria (Keith Sappington: what is the status of this evaluation?).
Regardless of the current status of this approach, its application to selenium is complicated by
the several chemical forms that may nefed to be considered in the model. For this reason alone,
the approach may need to be site-specific. '
Site-Specific Criteria Guidelines. There are two major considerations under this topic. The
more common one is how to modify national criteria to apply to a specific location; the less
common one, but perhaps more attractive with selenium, is to have no national criterion, or only
a narrative criterion or a default criterion, and then establish "site" criteria where problems are
expected. . ,
In this regard, it may be possible to classify sites by type. Forexample, there may be wetland,
stream, or lake/pond habitats that have different, but type-specific, exposure patterns regarding
chemistry, chemical and hydrological dynamics, and food-chain types. There may be
recognizable differences seen with the source of the material (e.g. fly ash, agricultural drain
water, normal geological sources). An approach might be generated that would be followed on a
regional or a more local basis to establish a criterion for a specific site, for a specific habitat,
and/or a specific source. This could be used for problem areas and a generic national criterion
apply elsewhere. Obviously such an approach would require state-of-the-art chemical analysis,
biocriteria monitoring, and perhaps toxicity tests (at least using ambient water and food organism
samples and perhaps using/n situ exposures). " ''_
In practice, site-specific approaches are often considered too data intensive (meaning too
resource intensive), too subject to subjective outcomes, and too often only as either the regulator
or the regulated using delaying tactics. Also, in practice, initially using less intensive and quicker
procedures only delays the activity ultimately necessary for site-specific approaches, because the
technical shortcomings of the easy approach only too quickly become obvious and there is a
clamor to "fix" the problem. One way around this issue would be to establish a generic
criterion, but establish a concurrent site-specific approach that would almost automatically
be used in problem areas. Although these comments perhaps appear non-technical (policy), it
is important that we determine the best use of today's technical knowledge, and that may include
both the best way to seta site-specific criterion where there are known pr suspected problems,
plus the best way to develop a generic criterion that is relatively risk-free, but, at the same time,
generally attainable. To accomplish this requires a reasonable knowledge of selenium sources
and ambient levels, not only in water, but in biota (e.g. if we were to recommend that tissue-
residues should trigger a requirement for site-specific studies).
C-15
-------
Gary Chapman
C-16
-------
Gregory Cutter
C-17
-------
-------
Gregory A. Cutter
Premeeting Comments
Gregory A. Cutter
Dept. of Ocean, Earth, and Atmospheric Sciences, Old Dominion University,
Norfolk, VA 23529-0276
Preface
Before addressing the specific questions on this topic; and as the only biogeochemist on
the panel, I think it appropriate to briefly review what we know about the aquatic cycle of
selenium, both in fresh and marine waters (indeed the cycles are essentially the same). Such a
review is needed since understanding the cycle allows one to rationally evaluate toxicological
data and decisions. In the water column selenium can exist as the dissolved inorganic ions
selenate (SeVI) and selepite (SelV), as dissolved organic selenide in which Se-II is covalently
"bonded to carbon moieties, and as particulate selenium (i.e., In "suspended particulate matter")
that includes organic selenide, adsorbed selenite + selenate; and elemental selenium (SeO). In •
uncontaminated, fresh waters, dissolved organic selenide and selenate are usually the
predominant forms (i.e., nearly equimolar), with seienite being a minor species (see Cutter, 1989;
Cutter, 1991; Cutter and San Diego-McGlone, 1990). The chemical "identity0 of organic selenide
is very relevant to bioavailability questions, but elusive. It is definitely not the free selerio-amino
acids (seleno-methionine or-cysteine; Cutter, 1982; Cutter, 1991), but it probably is these
seleno-amino acids bound in soluble peptides/proteins (Cutter, 1982; Cutter, 1991; Cutter and
. Cutter, 1995). In contaminated fresh waters, particularly those associated.with fossil fuel
combustion or refining, selenite tends to be the predominant dissolved form of selenium (Cutter,
1989; Cutter, 1991; Cutter and San Diego-McGlone, 1990), although in systems such as the San
Luis Drain/Kesterson Reservoir in the Central Valley of California selenate was the predominant
form (Cobke and Bruland, 1987; Cutter, 1989). This then leads into the biogeochemical cycle of
selenium in the water column and the interconversiqns of dissolved selenium species that I
believe makes it very difficult to set criteria based on water column concentrations or speciation.
In the water column, removal of dissolved selenium is driven by phytoplankton uptake,
which js selective, with the rate of selenite uptake being greater than that for selenate or organic
C-19 '. , :
-------
Gregory A. Cutter
selenide. With respect to the latter, the work of Gobler et al. (1997) is the only definitive study of
which I am aware that follows uptake of more "realistic" organic selenide (derived from the lysis
of phytoplankton) rather than seleno-methionine; it's uptake by a marine diatom is far slower than
that for selenite. In spite of the original dissolved oxidation state, the selenium taken up by
phytoplankton is reductively incorporated to organic selenide, primarily seleno amino acids in
proteins (e.g., Wrench, 1978; Cutter, 1985; Cutter and Bruland, 1984). While it is possible that
selenite or selenate are adsorbed to phytoplankton tissues, solid phase speciation data do not
indicate that this is a significant fraction (i.e., > 20% of the total; Cutter, 1985; Cutter and
Bruland, 1984; Cutter, 1991). Thus, selenium is transferred to the next trophic level largely as
organic selenide (Reinfelder and Fisher, 1991) in spite of the original water column speciation,
and this appears to hold with further steps in the food web (Fisher and Reinfelder, 1995). The
regeneration of particulate selenium in detritus to the dissolved state is a multi step process
where particulate organic selenide is regenerated during bacterial respiration/degradation of
organic matter to dissolved organic selenide, which then oxidizes to selenite and then to
selenate; the rate of the latter step is extremely slow, accounting for the persistence of
thermodynafnically unstable selenite in all natural waters (Cutter, 1982; Cutter and Bruland,
1984; Cutter, 1991; Cutter, 1992). The net result is that any form of selenium can be taken up, •
but at different rates, and it will be regenerated to the biologically-preferred form, selenite, during
* '""'',
the cycle.
This cycle can be put into an entire ecosystem context as depicted in the attached figure.
This figure is for an estuary and is the model currently under investigation by our lab, and those
of Nick Fisher (SLJNY, Stony Brook), Sam Luoma (USGS, Menlo Park),.and David Hinton (UC
Davis) with funding from NSF and the State of California. I'd suggest that it is just as viable in
rivers and streams, where the horizontal advective/diffusive transport terms are large and
unidirectional, or in lakes (horizontal transport minimal). In this model, biotic uptake from the
\ ','/'.>
dissolved state (SelV, SeVI, or org Se-ll) is accomplished by the primary producers, and the
n
resulting organic selenide (or adsorbed SelV+VI) are transferred to the next trophic levels
("consumer organisms"). However, some consumer organisms, in particular for this model,
bivalves, can also take up selenium from sediments, which, in addition to organic selenide and
adsorbed SelV+VI (largely from detritus, but also produced in situ), contain elemental Se from
the dissimilatory reduction of selenite and selenate (Oremland et al., 1989; Velinsky and Cutter,
C-20 ..
-------
, Gregory A. Cutter
1991; Cutter, 1992). This is another biotic uptake vector and there is some effect by solid phase
speciation on selenium's assimilation into bivalves (organic Se-il>SeO; Luoma et al., 1992), but
the selenium still resides in organic matter after uptake. For trophic transfer, the work of Fisher
and his colleagues (see Fisher and Reinfelder, 1995 for a review) shows that the primary control
on selenium's trophic transfer (as measured by assimilation efficiency) is really its phase
speciation...whether it is in a cell's cytosol or tissues. Thus, the important parameters influencing
the concentration; of selenium in a higher organism are: selenium speciation in the, water column
and sediments, rates of uptake of the various selenium forms by primary producers (and
i . '
consumers) relative to the rates of physical transfer in the system (i.e., residence times), and the
assimilation efficiency and net rate of trophic transfer (uptake - depuration) between the various
trophic levels! It is a whole ecosystem problem that requires quantitative information on the
physical setting (advection/diffusion), the biogeochemical cycle controlling the water column and
sediment speciation (dynamics between primary producers and the microbial loop; aquatic
chemistry of selenium), and the trophic structure/interactions of the ecosystem.
' i • ' . • ••''•- • ' '
One other important topic concerning any criteria for selenium is its analytical chemistry.
Because kinetics play such a dominant role in the environmental behavior of this element (Cutter,
1992), one should avoid assumptions and instead make empirical observations. This requires
analytical methods that are precise (random errors in the analysis have to be far less than the
environmental variability), accurate (minimize systematic errors; are you measuring the chemical
form you think you are?), and able to determine speciation in both the dissolved and particulate
phases. Related to this, when examining literature on uptake, etc. one must question whether the
selenium form added was correct (e.g., selenite contamination is-pervasive in selenate .
standards) and remained in that form during the experiment (i.e., the recycling of selenium
changes its chemical speciation). Furthermore, radiotracers only tell us that it is selenium, but not
what chemical form it is. .-"'-,.
Water Column-Based Chronic Criterion
1. As noted in the review above, all forms of dissolved selenium are important since they all can
be taken up (they are all bioavailable), albeit at different rates, and then recycled to other forms.
2.1 do not believe that a legitimate correlation between dissolved form and chronic effects can be
'• . • ' - C-21 ' .
-------
Gregory A. Cutter
made. Perhaps the best examples are Kesterson Reservoir where selenate (and organic
selenide in the last ponds in the flow scheme) predominated and waterfowl mortality was clearly
a problem, and the power plant cooling reservoirs in North Carolina, Hyco (Carolina Power and
Light) and Belews (Duke Power), where selenite predominated and complete collapses of their
fisheries occurred. In terms of measurements, it is essential to separate dissolved and
particulate forms of selenium via filtration, and each should be determined uniquely, not by
difference (i.e., filter the sample through a 0.2 urn membrane filter, determine dissolved selenium
speciation in the filtrate, and determine selenium speciation on the filtered material). The key
here is dissolved selenium is that fraction available to primary producers, while particulate
selenium (which includes the primary producers in the water column) is that available for trophic
transfer to higher organisms.
3.1 can find no compelling reason to rank any water quality parameter as being important to
selenium's bioavailability without resorting to site-specific cases. In the case of sulfate, if sulfate
inhibits dissolved selenate uptake, then oceanic phytoplankton which live in waters with 26
mmol/L sulfate and less than 0.4 nmol/L selenate (8 orders of magnitude difference) would never
take up selenate, but they do. A similar situation occurred in Kesterson Reservoir. Riedel and
Sanders (1996) suggest that phosphate may be important for one green alga, but it would be
difficult to separate this effect from simple growth stimulation.
Tissue-Based Chronic Criterion
4-5. As noted in my review, essentially all tissue selenium is in proteins as selenide. Thus, there
is little to differentiate. ,
6. There may be subtle differences in the types of tissues/location of selenium (so called "phase
speciation") that effects selenium's assimilation efficiency and trophic transfer. Again, Reinfelder
and Fisher (1991) found selenium in soluble peptides of the cytosol more bioavailable.
7. As noted in my review above, the concentration of selenium in tissues of higher organisms
such as fish may be correlated with water column concentrations, but there are many factors
(rate constants, assimilation efficiencies) that would create considerable error in the estimate (I
say this even though I have been involved in such estimates and co-authored papers on
simulation models that seek to make these calculations).
C-22
-------
Gregory A. Cutter
1 Sediment-Based Chronic Criterion
8-9. Again referring to the review above, all forms of selenium are found in sediments, although
the primary ones are organic selenide (most bioavaiiable for trophic transfer) and .elemental
selenium (less available), depending on the redox state of the sediment arid overlying water (see
Cutter, 1991). There have been no definitive studies of toxicity and sedimentary selenium
speciation to my knowledge, with the work of Luoma et al. (1992) being the best in terms of
analytical methods (accuracy of speciation) and environmental relevance (concentrations,
speciation, organisms). •
10. Like the water column, it is probably unwise to seek pseudo correlations/factors influencing
selenium's bioavailability. There may also be some irrelevant correlations since TOC will drive
sediment anoxia which preserves sedimentary selenium (Velinsky and Cutter, 1991; Cutter,
1992), making high Se correlate with high TOG. ,
11. By knowing the residence time of water in a system, the concentration of sedimentary
.selenium can be accurately calculated from the water column concentrations (see Cutter, 1991 -
for an example). This is derived from mass balance calculations, where selenium introduced to a
lake either is removed to the sediments via biotic uptake/detrital flux or by precipitation of Se(0) •
during hypolimnetic anoxia, or lost by volatilization (minor)i or removed by water outflow (i.e.,
relative rates of water removal vs. removal to the sediments). Thus, the longer the water
residence time (less outflow), the more is found in the sediments. The primary errors here are in
the rate constants for removal and sediment regeneration. "
Cross-Cutting Issues
12. Time variability is a crucial factor, and as noted in the sediment comment above, it is a
relative rate problem. Using primary producers as an example, if the water column ;
concentrations of selenium vary faster than the uptake rates, then the concentration of organic
selenide in the phytoplankton will be controlled by the average water column concentration,
whereas slow water column variations will make the phytoplankton concentrations represent the
instantaneous concentrations. This effect will be diminished with each step in the food web, but
other terhporal variations will be then included. Overall, at the top of the food chain, fish should
average out the water column behavio'r of selenium. . :
' . ". C-23 - '• ' -.'-.'".:
-------
Gregory A. Cutter
13. The type of ecosystem/food web will strongly control the effects of selenium. In a lentic
system, more selenium can accumulate in the sediments, affecting any benthic food web, and
relatively slow rates of reactions will become more important (e.g., the slow rate of selenate
uptake by phytoplankton will manifest itself, whereas in a lotic system it would be
inconsequential). As a result, the modeling approaches to simulating these systems, and
therefore predicting selenium concentrations and bio-effects in the upper trophic levels, would be
substantially different.
C-24
-------
Gregory A. Cutter
References ,
Cooke, T.D. and K.W. Bruland. 1987. Aquatic chemistry of selenium: evidence of biomethylation.
Environ. Sci. Technol. 21: 1214-1219.
Cutter, G.A. 1982. Selenium in reducing waters! Science 217: 829-831.
Cutter, G.A. 1985. Determination of selenium speciation in biogenic particulate material and .
sediments. Anal. Chem. 57: 2951-2955.
i •> i ' • - »•
Cutter, G.A. 1989. Selenium in fresh water systems. In: Occurrence and Distribution of Selenium
(M. Ihnat, ed.).CRC Press, Florida, Chap. 10.
Cutter, GA. 1.991. Selenium biogeochemistry in reservoirs. EPRI EN-7281, Vol 1, Project 2020-1,
Final report. Electric Power Research Institute, Palo Alto, CA, 147pp.
Cutter, G.A. 1992. Kinetic controls on the speciation of metalloids in seawater. Mar. ChemM 40:
65-80. , -'-•-
Cutter, G.A. and K.W. Bruland. 1984. The marine biogeochemistry of selenium: a re-evaluation.
Limnol. Oceanogr. 29: 1179-1192. '
Cutter, G.A and LS. Cutter. 1995. Behavior of dissolved antimony, arsenic, and selenium in the
Atlantic Ocean. Mar. Chem., 49: 295-306.
Cutter,'G A and M.L.C. San Diego-McGlone. 1990. Temporal variability of selenium fluxes, in
the San Francisco Bay. Sci. Total Environ. 97: 235-250.
Fisher, N.S. and J.R. Reinfelder. 1995. The trophic transfer of metals in marine systems. In Metal
speciation and bioavailability in aquatic systems, A. Tessier and D.R. Turner, Eds:, Wiley and/
Sons, Chichester, pp. 363-406,
C-25
-------
Gregory A. Cutter
Gobler, C.J., D.A. Hutchins, N.S. Fisher, E.M. Cosper, and S.A. Sanudo-Wilhelmy. 1997.
Release and bioavailability of C, N, P, Se, and Fe following viral lysis of marine chrysophyte.
LJmnol. Oceanogr. 42: 1492-1504. .
Luoma, S.N., C. Johns, N.S. Fisher, N.S. Steinberg, R.S. Oremland, and J.R. Reinfelder. 1992.
Determination of selenium bioavailability to a benthic bivalve from particulate and solute
pathways. Environ. Sci. Technol. 26: 485-491.
Oremland, R.S., J.T. HoIIibaugh, A.S. Maest, T.S. Presser, L.G. Miller, and C.W. Culbertspn.
1989. Selenate reduction to elemental selenium by anaerobic bacteria in sediments and culture:
biogeochemical significance of a novel sulfate-dependent respiration. Appl Environ. Microbiol. 55:
2333-2343.
Reinfelder, J.R. and N.S. Fisher. 1991. The assimilation of elements ingested by marine .
copepods. Science 251:794-796.
Riedel, G.F. and J.G. Sanders. 1996. The influence of pH and media composition on the uptake •
i v 1
of inorganic selenium by Chlamydomonas Reinhardtii. Environ. Toxicol. Chem. 15:1577-1583.
Velinsky, D.J. and G.A. Cutter. 1991. Geochemistry of selenium in a coastal salt marsh.
Geochim. Cosmochim. Ada 55: 179-191.
Wrench. J.J. 1978. Selenium metabolism in the marine phytoplankters Tetraselmis tetrathele and
Dunfella minufa. Mar. Biol. 49: 231-236.
C-26
-------
Anne Fair-brother
C-27
-------
C-28
-------
Anne Fairbrother
Anne Fairbrother, D.V.M., Ph.D.
. ecological planning and toxicology, inc.
Corvallis, Oregon
I. Technical Issues Associated with a Water-Column-Based Chronic Criterion
' ' - . ' . . '•
Selenate (Se*6) and selenite (Se*4) are the two most common forms of selenium in the water column, with
Se^ more prevalent under strongly oxidizing conditions of fast moving waters and So*4 likely to be more
prevalent in lentic systems. Organic forms of selenium (e.g., the biological forms of seleno-DL-
methionine and seleno-DL-cysteine or selenocystine) are toxicologically more important than the
inorganic forms, but generally are found at very low concentrations in water (see.Bowie et al 1996 or
Scott 1991). Elemental selenium is very insoluble and selenide (Se"2) generally cannot exist in the
natural aqueous environment because reducing conditions cannot be met (Scott 1991).
- • >. • . ~ ' ' . ' '
The relative toxicological importance of selenate and selenite may vary by species, although selenite
appears to generally be more toxic to aquatic organisms than selenate. Selenite is 2-4 times more toxic to
Hyallela azteca than is selenate (Brasher and Ogle 1993). Similarly, selenite is more toxic than selenate
to.chinopk salmon (Oncorhynchus tshdwytschd) and coho salmon (O. kisutch) in short-term (acute)
studies (Hamilton and Buhl, 1990). However, Chironomus decorus larvae are more sensitive to
selenate, then selenite in a water-only'exposure (Maier and Knight 1993), although the water column is
not likely to be the primary exposure medium for benthic invertebrates or fish (food selenium is a more
important exposure route). The acute toxicity of the two forms of selenium appears to be additive, but
this is not known for chronic exposures. Therefore, until such studies are performed with chronic toxicity
studies I would recommend that both selenate and selenite be measured in the water column, rather than
assuming additivity and measuring only total selenium.
The following water quality characteristics, listed in order of priority, are most important in affecting the
chronic toxicity and bioaccumulation of selenium to freshwater aquatic life: dissolved oxygen (DO), Eh,
pH, sulfate, TOC, iron, other metals (especially mercury and copper).
C-29
-------
Anne Fairfarother
Toxicity relationships derived from acute toxicity and water quality characteristics are not very
applicable to chronic toxicity situations in the field for organisms other than phytoplankton and bacteria.
Only the primary producers are affected mainly by water-borne selenium; all pther organisms receive
most of their exposure from food or sediment (e.g., Bowie et al. 1996). Therefore, acute toxicity studies
that look at water-only exposures are likely to underestimate chronic toxicity to benthos and fish.
In addition, uptake of selenium by benthic macroinvertebrates is not very predictable from water-only
selenium concentrations (Adams et al. 1998). This is due to differences in selenium species in the wafer
(generally reported as total selenium), differences in water and sediment physical parameters, whether the
system is oxic or anoxic, and volatilization rates of selenium, that may be as high as 25-35% in shallow
systems (Hanarmef al. 1996).
II. Technical Issues Associated with a Tissue-Based Chronic Criterion ,
Within organisms, the most lexicologically important forms of selenium are the amino acid-substituted
forms, selenomethionine, selenocysteine, and selenocystine. Selenium causes adverse biological effects
by substituting for sulfur in these amino acids and, subsequently, in various protein enzymes such as
glutothione peroxidase (GPx). The loss of function of GPx results in a decreased antioxidant ability and
subsequent destabilization of cell membranes. Selenium also interiors with cell division, thereby causing
the terata associated with selenium-induced reproductive disorders. The inorganic forms of selenium
must be converted to these organic forms prior to exerting their effects. However, nearly all studies that
correlate tissue selenium concentrations with either biological effects or with water or food
concentrations have measured only total selenium. Even this measure has a relatively reasonable
correlation with effects (see below).
Tissues best correlated with overall chronic toxicological effects thresholds for selenium in aquatic
organisms are gravid fish ovaries and whole body concentrations in benthic invertebrates (Lemly 1996).
Whole body residues in fish are not correlated with incidence of effects if all species are considered
together; however, by considering each species separately, a reasonable fit of an exponential function is
expressed (Lemly 1993). Muscle tissue plugs (or fillets) also have been correlated with effects. Note
that all tissue concentrations should be expressed on a dry-weight basis when making these types of
correlations.
C-30
-------
Anne Fairbrother
.We are not very certain in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish. This is because fish receive their primary
exposure through food (i.e., greater amounts of selenium but also the selenium is in the more toxic form
of amino-acid substituted selenides) not frpm the water. The amount of exposure from food is, dependent
, upon the physical conditions of the water column (see above) as well as the sediments (see below).
Moreover, the types offish prey items present will affect how much selenium has been accumulated into
the fish diet. For example, the organoselenium forms are accumulated more rapidly by behthic
invertebrates than are the two inorganic forms (Maier and Knight 1993; Rosetta and Knight 1995; Reidel
et dl., 1991). Both selenomethionine and selenate uptake from water by phytoplankton seem to be active
physiological processes, whereas selenite is merely mechanical binding kinetips although over the long
term uptake rates of the two inorganic forms are similar (Bowie et al 1996), For bacteria, uptake of
selenite is more rapid, even over the long term, than is selenate (Bowie et al 1996). '
Therefore, in order to use tissue-to-effect correlations for setting a water-based criterion, we need to be
able to predict what water concentrations will result in tissue concentrations that are known to be
correlated to adverse effects. This means first understanding what food concentrations (i.e., invertebrate
i ., . - , "
tissue concentrations) cause effects in fish - this we can do with a fair amount of success. The next step
is 'to predict what sediment or phytoplankton concentrations result in the various tissue concentrations in.
invertebrates. This we can do with lesser success. For sediment - benthos relationships, the variability
in sediment .selenium species and benthic community composition confound the relationship (see below).
The phytoplankton.-. benthos relationship has not been measured. Direct correlations of water - benthos
concentrations are not very good (Adams et al. 1998), so the final step is correlating water concentrations
with sediments or phytoplankton. This we can do with some degree of certainty, at least for a few
systems. Bowie et al. (1996) and Van Derveer and Conton (1997) have attempted to mathematically
model these relationships and have been fairly successful for particular systems. The challenge, now, is
to see how this model can be parameterized for a larger variety of systems.
III. Technical Issues Associated with a Sediment-Based Chronic Criterion
The dominant selenium species in sediments are elemental selenium and organic selenium (Van Derveer
and Canton 1997), although this likely is dependent upon the type of sediment (oxic versus anoxic).
, For sediments, measurement of total selenium may be sufficient, without the need to speciate the types of
' . . ' . .' ' C-31 . ' '•" '
-------
Anne Fairbrother
selenium present (Van Derveer and Canton 1997). However, this probably needs to be investigated
further with particular emphasis on comparing lotic versus lentic systems.
The following sediment characteristics, listed in order of priority, are most important in affecting the
chronic toxicity and bioaccumulation of selenium to freshwater aquatic life: TOC, texture, Eh, pH,
sulfate, iron.
(
. Of these, total organic carbon (TOC) is by far the most important factor, with texture and Eh close
behind. Van Derveer and Canton (1997) have developed an empirical model of water-to-sediment
selenium transfer in lotic systems (western streams) that predicts sediment accumulation as a function of
dissolved selenium in the water column and sediment TOC.
IV. Cross-Cutting Technical Issues Associated with Chronic Criterion
Fish tissue residues respond relatively slowly to changes in water selenium concentrations (Lemly 1996).
This is partly because fish are exposed primarily through their food source (benthic invertebrates) which,
in turn, are exposed thrpugh sediments and through phytoplankton which take up selenium from the
water column. Phytoplankton and bacteria accumulate selenium rapidly, reaching maximum levels within
5 to 6 days or less (Sanders and Gilmour 1994). If the assumption were made that depuration rates are '
no greater than uptake rates, turnover time for these organisms would be about two weeks. Benthos and
fish respond much more slowly to changes in water column selenium due to the retention of selenium in
sediments (Bowie et al. 1996). The rate of loss of selenium from sediments depends upon volatilization
rates (from 5 - 35%, depending upon the type of bacteria present which are a function of the redox
potential of the sediments), the amount of binding to sulfides and iron, and the reducing environment of
the sediments (and consequent sequestration as elemental or reduced forms of selenium). Half-lives of
sediment selenium also depend upon the species of selenium. For example, in microcosm studies, half-
lives were measured at 7 days for selenomethionine, 20 days for selenite, and 33 days for selenate (Besser
et al. 1989). While these relative relationships probably hold for field systems, it is unlikely that the
absolute numbers would be the same.
The type of ecosystem (lentic or lotic) will have a large influence on the chronic toxicity of selenium to
aquatic organisms. This is due to the differences in speciation of selenium in the water column and, more
importantly, in the sediments as a result of different amounts of oxygen. In addition, different types of
C-32
-------
Anne Fairbrother
bacteria and phytoplankton will be present Since these organisms are responsible for the majority of the
bioaccumulation of selenium into the food web (with BCFs up to 3 orders of magnitude), as well as for
the amount of methylation and subsequent volatilization out of the system, they will have a large
influence on the flux of selenium through the aquatic biota. Different species take up the various forms
of selenium at different rates and to different concentrations. It is likely that lotic systems can have
higherwater concentrations, of selenium than can lentic systems, prior to causing overt effects tofish.
This has not be systematically studied, however, although the system model of Bowie et al. (1996) might
be useful for examining such predictions and identifying key relationships in more detail.
References Cited >
Adams, WJ. K.V. Brix, K.A. Cothern, L.M. Tear, R.D. Cardwell, A. Fairbrother, and J.E. Toll. 1998.
Assessment of selenium food chain transfer and critical exposure factors for avian wildlife species: need
for site-specific data. In E. E. Little, A. J. DeLonay, andB. M. Greenberg (eds.). Environmental
Toxicology and Risk Assessment: Seventh Volume. ASTMSTP1333, American Society for Testing and
Materials, Philadelphia, PA . •,.•".'•..
Bowie, G.L., J.G. Sanders, G.F. Fiedel, C.C. Gilmour, D.L. Breitburg, G.A. Cutter, and D.B. Porcella.
1996. Assessing selenium cycling and accumulation in aquatic ecosystems. Water, Air and Soil
Pollution 90:93-104.
Brasher, A.M. and R. S> Ogle. 1993. Comparative toxicity of selenite and selenate to the amphipod
Hyalella azteca. Archives of Environmental Contamination and Toxicology. 24:182-186.
Hamilton, S.J. and K.J. Buhl, 1990. Acute toxicity of boron, molybdenum, and selenium to fry of
chinook salmon and coho salmon. Archives of Environmental Contamination and Toxicology. 19:366-
373. . , ' ,
Hanarm, D., P. J. Duda, A. Zayed, and N. Terry. 1998, Selenium removal by consturcted wetlands: role
of biological volatilization. Environmental Science and Technology. 32:591-597. •
Lemly, A. D. 1996. Selenium in aquatic organisms. In: Beyer, W.N., G.H. Heinz, and Am.W. Redrhon-
Norwood (eds.). Environmental contaminants in wildlife: interpreting tissue concentrations. Lewis
Publishers, Boca Raton, Fl. Pp. 427-445.
Lemly, A.D. 1993. Teratogenic effects of selenium in natural populations of freshwater fish.
Ecotoxicology and Environmental Safety. 26:181-204.
Maier, K.J. and A.W. Knight. 1993. Comparative acute toxicity and biococnetration of selenium by the
:.••'-'• ' C-33: ' •-'. •'''-•• . ' ' • '
-------
Anne Fairbrother
midge Chironomus decorus exposed to selenate, selenite, and seleno-DL-methionine. Archives of
Environmental Contamination and Toxicology. 25:365-370.
Riedel, G.F., D.P. Ferrier, and J.G. Sanders. 1991. Uptake of selenium by freshwater phytoplankton.
Water, Air, and Soil Pollution. 57-58:23-30.
Rosetta, T.N. and A.W. Knight 1995. Bioaccumulation of selenate, selenite, and seleno-DL-methionine
by the brine fly larvae Ephydra cinerea Jones. Archives of Environmental Contamination and
Toxicology. 29:351-357.
Sanders R.W. and C.C. Gilmour. 1994. Accumulation of selenium in a model freshwater microbial food
web. Applied and Environmental Microbiology. 60:2677-2683.
Scott, M. 1991. Kinetics of adsorption and redox processes on iron and manganese oxides:
Reactions of As (HI) andSe (JV) at goethite and bimessite surfaces. ,EQL Report No. 33,
Environmental Quality Laboratory, California Institute of Technology, Pasadena, CA.
Van Derveer, W.D. and S. P. Canton. 1997. Selenium sediment toxicity thresholds and derivation of
water quality criteria for freshwater biota of western streams. Environmental Toxicology and
Chemistry. 16:1260-li68.
C-34
-------
Teresa Fan
C-35
-------
C-36
-------
Teresa Fan
COMMENTS TO TECHNICAL CHARGE ASSOCIATED WITH EPA Se WORKSHOP
Teresa Fan, Pept of Land, Air & Water Resources, UC-Davis
I. Technical Issues Associated with a Water-Column-Based Chronic Criterion
1. Besides selenite and selenate, which other forms of selenium in water .are lexicologically
important with respect to causing adverse effects on freshwater aquatic organisms under
environmentally realistic conditions?
It appears that dissolved organoselenium form(s) including those in dissolved organic
matter may be very important in highly productive systems in terms of foodchain transfer and
toxicological relevance. However, there is little information regarding the chemical nature of .
these forms. Based on known stability of different organoselenium compounds,
selenomethionine may be one of the more persistent forms that should be investigated.
In addition to dissolved form(s), particulate Se form(s) derived from planktonic organisms
and detritus are also important to investigate because these forms are ingested by aquatic
invertebrates and fish, which represent a major route for Se bioaccumulation and transfer
through the foodcahin (e.g. Hermanutz et al., 1992; Wang et al., 1996). There is also evidence
that particulate Se responds to changes in waterborne Se concentration rapidly (Bowie et al.,
1996). As such, it may be a good short-term integrative indicator of waterborne Se status.
C-37
-------
Teresa Fan
2. Which form (or combination of forms) of selenium in water are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in tissues would you measure for correlating exposure with
adverse effects in the field?)
Note: Your response should include consideration of operationally defined measurements of
selenium (e.g. dissolved and total recoverable selenium), in addition to individual selenium
species.
The literature data on this issue is very limited. However, I believe proteinaceous Se
form(s) both as total and as specific form(s) such as selenomethionine warrant measurements
for the reasons given in Point #4. In addition, the analysis for these forms is now practical to
perform.
3. A) in priority order, which water quality characteristics (e.g. pH, TOC, sulfate, interactions
with other metals such as mercury) are most important in affecting the chronic toxicity and
bioaccumulation of selenium to freshwater aquatic life under environmentally realistic exposure
conditions?
I could not rank these characteristics based on available literature data but it is clear
that pH (e.g. Riedel and Sanders, 1996), TOC, salinity (particularly sulfate salinity, e.g. Riedel
and Sanders, 1996; Ogle and Knight, 1996), temperature (e.g. Lemly, 1993), and presence of
other metal/metalloid ions such as mercury, cadmium, copper, arsenic, and molybdenum (e.g.
Naddy et al., 1995) would have significant effects on Se impact on aquatic life. The importance
of each characteristics will depend on the site conditions, foodweb, and biogeochemistry. Some
1 .,'''' ^
of these effects appear to be antagonistic and some are synergistic, depending on a number of
factors (e.g. category of organisms, life stages of organisms, concentration range, specific forms,
etc.)
C-38
-------
Teresa Fan
B) Of these, which have been (or can be) quantitatively related to selenium chronic toxicity
or bipaccumulation in aquatic organisms? How strong and robust are these relationships?
'•' ~ Temperature have been related to fish chronic toxicity (Lemly, 1993) while sulfate,
phosphate, and pH have been related to Se bioaccumulation in phytoplankton (Riedel and
Sanders, 1996). There have been other studies pf the influence of sulfate on Se
bioaccumulation but they were conducted as acute toxicity testing. Since the temperature,
sulfate, and pH effect was demonstrated on only a few species, it is difficult to conclude whether
the observed relationships are generally applicable.
C) How certain are applications of toxicity relationships derived from acute toxicity and
water quality characteristics t6 chronic toxicity situations in the field?
The acute toxicity tests for Se are generally conducted using water exposure at
environmentally unrealistic concentrations and in very short time periods. There is a general
consensus from the literature that Se exposure to aquatic consumers is mainly mediated through
diet and that reproductive failure is a key toxic effect resulting from Se exposure. Neither is
addressed with the established acute toxicity assay. In addition, there are indications that Se
bioaccumulation, biotransformation pathways, and therefore toxic actions depend on exposure
concentrations and length pf exposure, and that extraploating effects expressed at high/short to
low/long exposure would be difficult and complicated. For example, both bioconcentration factor
and toxicity (e.g. LC50) of Se depend on Se exposure concentration and length (e.g. Brasher and
Ogle, 1993; Besser et al., 1993); this dependence does not appear to be easily defined.
Biotransformation pathways in microorganisms change with Se treatment concentrations (e.g.
Fan et al., 1997; Fan et al., submitted to ES&T). In particular, the extent of Se incorporation into
proteins and proteinaceous Se, forms are dependent on Se treatment concentrations, which may
have important implications in regard to adverse effects (see also. Point 4).
II. Technical issues Associated with a Tissue-Based Chronic Criterion
G-39
-------
Teresa Fan
4. Which foms of selenium in tissues are lexicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions and
why?
Total tissue Se burden does not appear to be a reliable indicator of adverse effect since there
are many cases where normal and adversely affected organisms have comparable Se burden
(e.g. the normal and deformed fish from Belews Lake had equivalent whole body Se
concentrations, Lemly, 1993). Tissue burden of Se may not be indicative of foodchain transfer
and bioaccumulation potential either since Se retention by a given organisms depends on many
factors such as predator/prey relationship, ingestion rate, assimilation efficiency, depuration rate,
Se forms, and environmental conditions (e.g. Wang et al., 1996; Saiki et al., 1991.). Moreover,
tissue burden does not explain the differential sensitivity of aquatic organisms to Se exposure.
No direct information is available regarding the form(s) of Se in tissues that are toxicologically
relevant in aquatic systems. However, there are hints from the literature that selenomethionine
may be a key. Selenomethionine is generally bioconcentrated to a greater extent and more toxic
to aquatic life than selenite and selenate (e.g. Besser et al., 1993; Woock et al., 1987; Ingersoll
et al., 1990). Dietary selenomethionine toxicity in laboratory trials closely approximates that of
field-collected organisms (e.g. Hamilton et al., 1990; Heinz et al., 1996; Woock et al., 1987). On
i /
the other hand, it is unclear whether FREE selenomethionine in tissue is relevant since none of
these studies measured the free selenomethionine concentration in tissues. In the tissues that
we have surveyed (micralgae, vascular plants, mushroom, and bird blood), there is very little free
selenomethionine. It is also difficult to rationalize selenomethionine toxicity because its selenol
group is blocked by methylation. Indeed, selenomethionine does not catalyze the production of
superoxide anion and its in vivo toxicity is low compared with other Se compounds that catalyze
this reaction (Spallholz, 1998)
It is more likely that selenomethionine in tissue proteins (prbteinaceous Se-Met) may be most
toxfcologically relevant based on the following observations. Free selenomethionine
concentration in algae isolated from agricultural drainwaters is very low (e.g. Fan et al., 1997),
while proteinaceous Se-Met is a significant fraction of biomass Se in these algae and aquatic
birds (Fan et al., submitted to ES&T & unpublished results). Although free Se-Met has been
C-40
-------
Teresa Fan
reported in some other algae (e.g. Bottino et al., 1984), the identity of Se-Met has not been
structurally confirmed in these studies. This is a problem since we could not find GC-MS
evidence of Se-Met in an HPLC peak assumed to be Se-Met based on retention time.
There are also indirect evidence that Se present in the protein fraction of aquatic organisms is
very relevant to Se bioaccumulatidn and adverse effect. Bioconcentration factors of Se in
aquatic invertebrates decrease with increasing Se dose from their algal diet (e.g. Besser et al.,
1993; Knight, 1988). This is consistent with a decreasing allocation of Se and Se-Met into algal
proteins with increasing algal Se burden (Fan et al., submitted to ES&T). A Chlorella agla with a
much lower % Se allocation into proteins exhibited a much higher tolerance towards Se
treatment than a filamentous cyanophyte (Fan et al., in press; Fan et al., submitted to ES&T),
Most Se in fish tissues is associated with protein-rich organs (Lemly, 1993) and aquatic
microorganisms contain significant amounts of selenoproteins (Wrench, 1978; Weiss et al.,
1965). Se depuration from tissues is consistent with a two-compartment model (Wang et al.,
1996); the less depuratable compartment may represent the protein compartment. Regardless
of the forms of Se fed to aquatic algae or invertebrates, the tissue Se burden in their consumers
such as fish exhibit a linear relationship with the food-borne Se dose, which suggests conversion
to a common metabolic pool by the diet organisms (Besser et al., 1993), such as proteins. Acute
toxicity to aquatic invertebrates and fish increases with length of exposure (Brasher and Ogle,
1993; Hamilton and Buhl, 1990) regardless of the forms of Se exposure and that different Se
forms appear to have a common mode of toxic action in fish (Hamilton and Buhl, 1990). Based
on known Se biochemistry, this toxic action may be related to proteinaceous Se.
5. Which form (or combination of forms) of selenium in tissues are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in tissues would you measure for correlating exposure with
adverse effects in the field?)
Proteinacious Se and proteinacious selenomethionine, in particular, should be relevant and
practical to measure (see Point 4). Other selenocompounds with free selenol and/or diselenide
groups may also be important, but they are unstable to extraction and their analysis is more
difficult at the present time.
C-41 '
-------
Teresa Fan
6. Which tissues (and in which species of aquatic organisms) are best correlated with overall
chronic toxicological effect thresholds for selenium?
Since reproductive disturbance of higher trophic organisms is a key toxic expression of chronic
Se exposure, fish and bird reproductive organs and eggs should be a good choice (Hermanutz et
al., 1992). However, in case of difficulty in obtaining these tissues, blood samples collected
during reproductive season may be a good surrogate.
7. How certain are we in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish? What are the primary sources of
uncertainty in this extrapolation?
I don't think we can be certain in relating waterborne Se concentrations to tissue residue
concentrations in fish because there are cases where Se concentrations in fish eggs do not
correlate with waterborne Se concentrations based on the data compiled by Lemly, "1996. These
deviations are to be expected since the pathway from water through foodweb could vary among
different aquatic ecosystems.
C-42
-------
Teresa Fan
III. Technical Issues Associated with a Sediment-Based Chronic Criterion *
8. Which forms of selenium in sediments are lexicologically important with respect to causing
adverse effects on freshwater organisms under environmentally realistic conditions?
Again, the literature information regarding this issue is very limited. However, it can be reasoned
that Se forms in detritus and possibly sediment organic matter would be toxicblogically important
since there is evidence that Se is highly concentrated in detritus (e.g. Saiki and Lowe, 1987) and
that these are important food source for bentnic organisms.
9. Which form (or combination of forms) in sediment are most closely correlated with chronic
effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, Which forms 5of selenium in sediment would you measure for correlating exposure
with adverse effects in the field?)
Proteinaceous Se and selenomethionine in benthic organisms, detritus, and sediment organic
matter would stand a good chance in correlating with chronic effects on aquatic life.
10. In priority order, which sediment quality characteristics (e.g. TOO, etc.) are most important in
affecting the chronic toxicity and bioaccumulation of selenium to freshwater aquatic life under
environmentally realistic exposure conditions? Of these, which have been (or can be)
quantitatively related to selenium chronic toxicity or bioaccumulation in aquatic organisms?
Organoselenium forms in benthic organisms and sediment > total Se in benthic organisms and
sediment organic matter > total sediment Se > TOC. Total sediment Se have been related to
effects on fish and birds (e.g. Van Derveer and Canton, 1997). However, this correlation is only
tentative since there are uncertainty associated with the sediment Se data and the effect
assessment. I should also point out that sediment Se distribution and possibly TOC can be
.••••'.' C-43 •'• " •- ' . '..'.'
-------
Teresa Fan
highly heterogenous, varying with location and depth. This issue would need to be resolved ,
before these parameter can be used reliably.
11. How certain are we in relating water-column concentrations of selenium to sediment
concentrations? What are the sources of uncertainly in this extrapolation?
I don't think we can relate waterbome to sediment Se concentrations due to a highly variable
relationship observed in the field (e.g. Saiki and Lowe, 1987). For example, the waterbome Se
concentration could differ by an order of magnitude in two of the California's agricultural drainage
ponds, and yet the sediment Se concentrations for the two ponds are comparable. The sources
of uncertainty could be sediment characteristics in terms of Se sorption, particulate deposition
from water column, Se speciation in water and sediment, algal and microbial community and
activity, etc.
IV. Cross-Cutting Technical Issues Associated with Chronic Criterion
12. How does time variability in ambient concentrations affect the bioaccumulation of selenium in
aquatic food webs, in particular, how rapidly do residues in fish respond to increases and
decreases in water concentrations?
C-44
-------
Teresa Fan
It appears that Se residues in fish do not respond rapidly to changes in ambient concentrations
as exemplified by the cases of Beiews Lake and Hyco Lake (Lemly, 1993; Bowie et al., 1996).
Se status in plantonic organisms including microalgae, bacteria, and protozoans tends to be
more reflective of ambient concentrations.
13. To what extent would the type of ecosystem (e.g. lentic, lotic) affect the chronic toxiciiy of
selenium?
Se biogeochemistry and foodweb differ among ecosystems, particuarly between lentic and lotic
systems'. As such, the chronic toxicity of Se is expected to vary with ecosystem type. For
example, primary productivity is generally much lower in fast-flowing river than reservoirs and
lakes with long residence time, this difference would greatly influence Se biotransformation and
bioaccumulation through the foodchain, and therefore chronic toxicity. Other factors such as
sulfate could alter the behthic microbial community (e.gr dominance of sulfate reducers), which in
turn would affect Se transformations in the sediment. However, it is difficult to quantitatively
assess these effects based on existing literature information. '
.Literature ,
Besseretal., 1993. Bioaccumulation of organic and inorganic>selenium in a laboratory food
chain. Environ. Toxicol. Chem. 12:57-72.
Bottinoetal., 1984. Phytochemistry 23:2445-2452. /
Bowie et al., 1996. Assessing selenium cycling and accumulation in aquatic ecosystems. Water
Air Soil Pollut. 90:93-104. .•'... .
C-45
-------
'•••'. Teresa Fan
Brasher and Ogle, 1993. Comparative toxicity of selenite and selenate to the Amphipod Hyalella
azteca. Arch. Environ. Contam. Toxicol. 24:182-186.
Fan et ai., 1997. Selenium biotransformations by a euryhaline microalga isolated from a saline
evaporation pond. Environ. Sci. Technol. 31:569-576.
Hamilton et al., 1990. Toxicity of selenium in the diet to chinook salmon. Environ. Toxicol. Chem.
9:347-358.
i ' • " '
Hamilton and Buhl, 1990. Acute toxicity of boron, molybdenum, and selenium to fry of Chinook
salmon and Coho Salmon. Arch. Environ. Contam. Toxicol. 19:366-373.
Hefnz et al., 1996. Toxicity of seleno-L-methionine, seleno-DL-methibnine, high selenium wheat,
and selenized yeast to mallard ducklings. Arch. Environ. Contam. Toxicol. 30:93-99.
Hermanutz et al., 1992. Effects of elevated selenium concentrations on bluegills (Lepomis
macrochirus) in outdoor experimental streams. Environ. Toxicol. Chem. 11:217-224.
> . "
Ingersoll et al., 1990. Toxicity of inorganic and organic selenium to Daphnia magna (Cladocera)
and Chironomus riparius (Diptera). Environ. Toxicol. Chem. 9:1171-1181.
Knight, A.W. 1988. Determination of the toxicity and biomagnification of agricultural drainwater
contaminants in aquatic food chains. Technical Progress Report. Project 86-9, Salinity/Drainage
Task Force, University of California, Davis, pp. 82-90.
Lemly, A.D., 1993. Teratogenic effects of selenium in natural populations of freshwater of fish.
Ecotox. Environ. Safety 26;181-204.
J ' " , • {
Lemly, A.D., 1993. Metabolic stress during winter increases the toxicity of selenium to fish.
Aquat. Toxicol. 27:133-158.
Naddy et al., 1995. Toxicity of arsenic, molybdenum, and selenium combinations to Ceriodaphnia
dubia. Environ. Toxicol. Chem. 14:329-336.
C-46
-------
Teresa Fan
Ogle and Knight, 1996. Selenium bibaccumulation in aquatic ecosystems: 1. Effects of sulfate on
the uptake and toxicity of selenate in Daphnia magna. Arch. Environ. Contam. Toxicol.
30:274-279.
Riedel and Sanders, 1996. The influence of pH and media composition on the uptake of
inorganic selenium by Chlamydomonas reinhardtii. Environ. Toxicol. Chem. 15:1577-1583.
Saiki et al., 1994. Preliminary assessment of the effects of selenium in agricultural drainage on
fish in the San Joaquin Valley. In: The Economics and Management of Water arid Drainage in
Agriculture, A. Dinar & D. Zilberman, eds., KJuwer Academic Publishers, pp.369-385.
Saiki and Lowe, 1987. Selenium in aquatic organisms from subsurface agricultural drainage
water, San Joaquin Valley, California. Arch. Environ. Contam. Toxicol. 16:657-670. ,
Van Derveerand Canton, 1997. Selenium sediment toxicity thresholds and derivation of water
quality criteria for freshwater biota of western streams. Environ^ Toxicol. Chem. 16:1260-1268.
Wang et al., 1996. Kinetic determinations of trace element bioaccumulation in the mussel Mytilus
edulis. Mar.-Ecol. Prog. Ser. 140:91-113. /
, ^ " • •
Weiss et al., 1965. Inhibitory action of selenite on Escherichia coli, Proteus vulgaris and
Salmonella thompson. J. Bacteriql 90:857-862.
Woock et al., 1987. Decreased survival and teratogenesis during laboratory selenium exposure
to bluegill, Lepomis macrochirus, Bull. Contam. Toxicol. 39:998-1005.
Wrench, J.J., 1978. Selenium metabolism in the marine phytoplankton Tetraselmis tetrathele and
Dunaliella minuta. Mar. Biol. 49:231-236.
C-47
-------
C-48
-------
Steve Hamilton
C-49
-------
C-50
-------
Steven J. Hamilton
\ • •
Technical Charge To Experts
I. Technical Issues Associated with a Water-Column-Based Criterion.
1. Organic forms of selenium such as selenomethionine and selenocysteine may be
important to consider in evaluating the toxicological effects in water, and through the food
chain. Several studies have shown these organic forms are readily taken up in the food
chain and bioaccumulated to concentrations toxic to higher trophic levels (Besser et al.
1993). Several investigators have shown selenomethionine was the most toxic of the two
most commonly tested forms to cyanobacteria (Kiffney and Knight 1990), aquatic
invertebrates (Maier et al. 1993), and fish (Niimi and LaHam 1976). Maier et al. (1993)
cited three papers that demonstrated that upto 60% of the total selenium in aquatic
ecosystems may be.in the organic form (Robberecht and Van Griekert 1982, Takayanagi
/ and Wong 1985, Cooke and Bruland 1987).
Nevertheless, the practicality of measuring organic forms of selenium as part of a
criterion would be difficult due to the lack of a relatively accessible method for widespread
use. •."..-
2. Most studies do not speciate selenium into its forms as part their analytical measurement.
Some work has been done to differentiate dissolved versus total (participate) selenium.
Graham et al. (1992) compared the cycling of selenomethionine and selenite in a
freshwater experimental pond and showed that little difference between filtered (0.45 /^m)
and unfiltered water samples using radio-labelled compounds.
Part of the problem -in measuring organic selenium compounds in water is that they can
be taken up by biota at a rate an order of magnitude faster than selenite (Graham et al.
1992). ' '
C-51
-------
Steven J. Hamilton
3A. My priority order would be 1) interaction with other elements, 2) total organic carbon
(TOC), 3) sulfate, 4) pH. I am not aware of any affects on selenium toxicity due to pH.
Sulfate does not seem important because in high sulfate aquatic environments,
selenium effects do not seem to be ameliorated (Skorupa 1998). Skorupa (1998, p.
345) gives several examples of low and high sulfate aquatic environments where
selenium toxicity to biota was not confounded by the presence of sulfate at high
concentrations.
TOC has been identified as a component relatively closely associated with selenium
concentrations (Stephens et al. 1992 [pages 96-99], Peltz and Waddell 1991) reported a
positive relation between concentrations of selenium in pond sediments at Ouray national
Wildlife Refuge (NWR), Utah, and concentrations of organic material in sediment.
3B.
3C.
4. Selenomethionine seems to be the most toxjcologically important form in tissues followed
by selenite, and seienate. However, because of the rapidity that Selenomethionine is
removed from the water by biota and sediments, it would be difficult to quantify it in water
in a meaningful manner. Once selenium is incorporated into the tissues of biota, it's
many potential forms would make it difficult to measure (see response to item 5 below).
C-52
-------
Steven J. Hamilton
5. The form ,of selenium in tissues related to toxic effects is apparently organic in nature
based on the work of Stadtman (1974, 1980) who identified selenoproteins in
microorganisms and demonstrated that selenium is essential for certain enzymes. If
present at greater than essential amounts, selenium saturates the sulfur metabolic
pathways, forming deleterious amounts of selenorganic compounds, which can form
i ",'.'.',-• - ; , • • • t '
selenoproteins, but may disrupt whole-animal functions such as growth, behavior, and
eventually survival. Stadtman (1974) stated "Because of the greater reactivity and lower
' stability of selenium compounds compared to the corresponding sulfur compounds, the
cell may encounter metabolic problems which eventually can lead to death of the
organism." ' .
For tissue, the most useful approach would be to measure total selenium because of
the multitude of organoselen forms that could be present. Several investigators have .
identified a variety selenium containing amino acids and proteins (Bottino et al. 1984,
Stadtman 1980, Wrench 1978). Consequently, trying to quantify selenium residues in
tissue based on one form or another would not fruitful.
6. Most of the literature is based on whole-body residues. There is limited information on
concentrations in various tissues including gills, skin, liver kidney, spleen, heart, muscle,
eggs, blood, plasma, and other tissues. Because he majority of information is in whole-
body tissues, I recommend that whole-body residues should be the basis for a tissue-
based criterion. Some of the other tissues such as liver, kidney, and eggs may have
higher residues of selenium, but the small amount of tissue available from small fish
would make analysis impractical. Composites of whole-body would be necessary for
aquatic and benthic invertebrates and plants.
A tissue-based criterion for selenium would be better than an water or sediment-based
criterion because tissues integrate all exposures and results in the biological effect that
criterion are established to protect, i.e., aquatic life. Several studies have documented
.adverse effects in aquatic life and linked adverse effects with either waterbome, dietary,
or combined water and dietary exposure to selenium (Table 1). Examining these studies
.*• shows a convergence of whole-body residues in the 4-5 ywg/g dry weight range,
C-53
-------
Steven J. Hamilton
regardless of exposure route. In general, background selenium residues in fish typically
fall in the <2 ^g/g range, with a few exceptions.
C-54
-------
, Steven J. Hamilton
Table 1. Selenium concentrations in young fish exposed to selenium in the diet or water and adverse effects
observed. ,
Exposure
route,
species,
weight (g),
age
Diet
Rainbow trout
79 (NG)
, 1.3 (NG)
0.6 (NG)
.
Chinook salmon
4.2 (NG)
~1 (swimup)
~-l (swimup)
~1- (swimup)
~1 (swimup)
Fathead minnow
-0.12 (60 day)
0.0001 (sw-up)
Striped bass
251(NG)
Bluegill
2.8 (NG)
'• ' ' Treated ' Control/Reference
' ,Se . ' • '
form
Selenite2
Selenite4
Selenite4
,SLD7
SLD7
SEM9
SLD7
SEM9
' '
Mix10
Rotifer11
Fish12
Mayfly14
Exp.
period
(day)
294,
140
112
34
90
90
90
90
98
7-9
80
44
, 0.2 (3 mo), SEM9 60
Seexp.
cone. W-B
Og/g; Se
9
13
11-12
26s
9.6
9.6
• 5.3
18.2
15
NG3
5.2s
4.0-4.56 -
8.4s
6.5
5.4
4.0
10.8
. 5.4
55-70 43-61
39
54
6'.6
158-13
318-13
'4.216
Seexp.
cone. , W-B
O^g/g; Se
Effect jug/L) (/wg/g)
Mortality
Mortality &~
reduced weight
Kidney damage &
reduced growth
Reduced migration
Mortality
Mortah'ty
Reduced growth
Reduced growth
Reduced weight
Reduced weight
Mortality
1 J
Mortality
Mortality
NG
0.07
0.6-0.7
2.08
1.0
1.0
1.0
1.0
•
0.4
NG
1.38
2.415
0.7
NG
0.35
0.26
1.2s
0.8
0.8
0.8
0.8
2.7
NG
4.48
Ref.1
1
2
3
4
5
5
5
5
6
7
8
7.6 9
1,01610
C-55
-------
Steven J. Hamilton
Table 1. Continued.
Exposure
route,
species,
weight (g),
age
Exp.
Se period
form (day)
Treated Control/Reference
Seexp. Seexp.
cone. W-B cone. W-B
C"g/g; Se Cwg/g; Se
Mg/L) (/^g/g) Effect //g/L) Cwg/g) Ref.1
Razorback sucker
-0.005 (5 day)
Water
Rainbow trout
0.08(sacfty)
Chinook salmon
0.3 (NG)
03 (NG)
Egg/alvin21
Bluegill
0.3 (5 mo)
Razorback sucker
NG(7day)
NG(7day)
Bonytail
NG(6day)
NG(6day)
Zooplt17 30
Selenite 60
i
Mix19 60
Mix20 60
Mix22 60
Mix23 60
Mix24 60
Mix24 60
Mix24 60
Mix24 60
2.4-5.1 3.6-8.7 Mortality 2.3-2.5 3.7-14.318 11
•
47 5.28 Mortality & <0.4 2.3s 12
reduced length
69 3.8 Mortality 0.9 1.2 4,13
143 4.9 Reduced growth 0.9 1.2 4,13
67 . 4.5 Mortality & 1.4 2.0 4,13
, reduced growth
640 5.1 Mortality 20 1.0 10
480 21 Mortality <3 1.2 14
252 12 Reduced growth. <3 1.2 14
1232 28 Mortality <3 1.1 14
532 17 Reduced growth <3 1.1 14
Diet and Water
Bluegill
NG(2yr)/ SEM9 140 ad/ 33.3D/10W 18.7
NG(swimup) SOlar 33.3D/9W -6.0
None
Mortality
0.8D/0.6W 1.0 15
0.8+2.725 3.326
C-56
-------
Steven J. Hamilton
References: 1 Goettl & Davies 1978; 2 Hilton et al. 1980; 3 Hilton & Hodson 1983; 4 Hamilton et al. 1986;
5 Hamilton et al. 1990; 6 Ogle & Knight 1989; 7 Bennett et al. 1986; 8 Coughlan & Velte 1989; 9 Finley
1985; 10 Cleveland et al. 1993; 11 Hamilton et al. 1996; 12 Hunn et al. 1987; 13 Hamilton & Wiedmeyef
1990; 14 Hamilton etal. 1998; 15 Coyleetal. 1993.
2Selenite incorporated in standard Colorado trout diet.
^NG: not given.
4Selenite incorporated in a casin-torula yeast trout diet.
5Derived from figure 2 in Hilton etal. (1980). .
6Carcass. '•'_.••'..' •
7SLD: western mosquitofish (Gambusia afflnis) collected from San Luis Drain, CA, used as fish meal
portion in an Oregon moist pellet diet.
Reported as wet weight and converted to dry weight assuming 75% moisture.
9SEM: selenomethionine incorporated into an Oregon moist pellet diet
10Mix: 25% selenomethionine, 25% selenate, and 50% selenite incorporated in a fish food diet.
"Rotifer: rotifers fed selenium-laden algae.
~ 12Fish: red shiners (Notropis lutrensis) weighing about 1 g each were sieved weekly from Belews Lake, NC,
where they were chronically exposed to 10 //g/L selenium and food-chain selenium under natural conditions.
13MuscIe tissue.
14Mayfly: burrowing mayfly nymphs (Hexagenia limbatd) collected from Belews Lake, NC. '
15Meal worm (Tenebrio molitor).
, 16Derived from figure 3 in Cleveland et al. (1993).
17Zooplankton: zooplankton collected from Sheppard Bottoms pond at Ouray NWR, UT, water <2 jUg/L,
18100% mortality. ,
19Mix: 3,023 ywg/L boron, 96 //g/L molybdenum, 69 //g/L selenium, and water simulating the San Joaquin River, CA.
20Mix: 6,046 A*g/L boron, 193 ,ug/L molybdenum, 143 ^g/L selenium, and water simulating the San Joaquin River, CA.
21 Exposed eyed egg 2 weeks before hatch and alevins 90 days posthatch.
ix: 2,692 ^§/L boron, 92 jUg/L molybdenum, 67 //g/L selenium, and well water at Yankton, SD.
ix: 6:1 mixture of selenate:selenite (measured 550 yug/L selenate, 90 jUg/L selenite).
C-57
-------
Steven J. Hamilton
MMix: ratio of environmental concentrations: 2 jUg/L As, 630 //g/L B, 10 y^g/L Cu, 5 ^g/L Mo, 59 jUg/L Se (6:1
selenaterselenite), 33 yug/L U, 2 ^g/L V, 20 //g/L Zn.
"Dry diet contained 0.8 fj.g/g and brine shrimp nauplii contained 2.7 jWg/g; water exposure was 9 yUg/L (10:1
selenate:selenite).
mortality.
C-58
-------
Steven J. Hamilton
7. As can be observed in Table 1, a wide range of dietary and water borne concentrations have been used n
exposures and some exposures have involved mixtures with other trace elements that would have
contributed to the observed toxicity. The selenium concentrations in the waterborne exposures are very
• • • ' v •
high relative to the current standard. The main point of the table is that the whole-body residues of
selenium, regardless of the exposure route, associated with adverse effects is consistently at 4-5
Likewise, the whole-body concentration in control or reference fish is consistently at 2 fj,g/g. hi the
four exceptions shown in the table, one study had control fish mat were very old and large (25 1 g
subadults) that were able to accumulate selenium without adverse effects (see reference 8), a second study
had relatively large juveniles (2.8 g) that also accumulated selenium without effects (reference 9), a third
study very young control fish that had 75% mortality (reference 1 1), and a fourth study had reference fish
that had 100% mortality (reference 12). hi each of these studies selenium concentrations were sufficiently
elevated to potentially cause adverse effects based on tissue residue concentrations of selenium - in the
studies with older fish, no effects were observed as would be expected, but in the two studies with younger
fish, adverse effects were observed. . .
The difficulty in pursuing a tissue-based criterion is linking water concentrations to food organism
(plant, animal, or detritus) to adverse effects on aquatic life. I believe it would be fruitless to try to relate
waterborne toxicity studies to a tissue-based criterion because of the great disparity between waterborne
and dietary toxicities of selenium. The problem, then is in relating water concentrations to food chain
concentrations to whole-animal residues.
Several studies have shown that water concentrations of selenium can be below 2 //g/L, yet food chain
concentrations can be elevated to toxic concentrations. Hamilton et al. (1996) reported that water and
zooplankton concentrations at four sites at Ouray NWR, UT, over a 4-week period contained were as
follows:
C-59
-------
Steven J. Hamilton
Site
SI
S3
S4
S5
Water Zooplankton
a g/L ' we/g
0.7-<1.1 2.3r3.7
0.4-<1.1 4.5-6.7
0.3-O.6 2.4-5.0
0.6-3.1 12.0-25.7
The selenium concentrations in zooplankton from sites SI, S3, and S4 contain sufficient selenium to
be of concern, and based on other biological effect studies, should probably have caused effects. Fish fed
these zooplanktoa had 100 % mortality in less than 2 weeks. The concentrations in zooplankton from S5
are extremely elevated and yet the waterbome concentration was less than the current criterion.
As long as 20 years ago, lakes in Colorado were identified with low waterbome concentrations of
selenium from 0.7 to 2.2 A*g/L, but high selenium concentrations in aquatic invertebrates of 4.2 to 28.4
j^g/g (Birkner 1978). More recently, others have reported situations where waterbome concentrations of
selenium were <3 jUg/L, but aquatic invertebrates contained potentially toxic concentrations of selenium >3
yug/g (Hallock et al. 1993, Skorupa and Ohlendorf 1991, Zhang and Moore 1996), based on the proposed
toxic dietary threshold (Lemly 1993). Consequently, low waterbome concentrations of selenium may be
misleading in predicting potential adverse effects on aquatic organisms. A tissue-based criterion would
integrate both water, sediment, and dietary exposures, and would be directly relatable to adverse effects on
aquatic organisms.
C-60
-------
Steven J. Hamilton
• '• '^ • - . • • ' '
8. There may not be a major difference in uptake rates in sediments for selenium species. Graham et al.
(1992) showed that sediments took up radio-labelled selenite and selenomethionine in a similar rapid
manner, but during the growing season was lost from the sediment back to the water. Other components of
me freshwater experimental ponds where they conducted their study also rapidly taken up by periphyton,
pond wed, snails, and Gambusia; the most rapid uptake in the selenomethionine pond. They concluded
that sediments may at first act as a sink for selenium, but can be remobilized and taken up by biota and the
water column (they reported a two-fold increase in organic and/or cation fraction in the water column).
9. ; . ' •"•••'•""..•••"'
13. Ecosystem type can have a major bearing on the chronic toxicity of selenium to aquatic organisms.
However, identifying effects in a lotic (flowing) system may be very difficult compared to measuring
effects in a lentic (still) system because of demographically open fish populations (populations that can
have recruitment by immigration of individuals from outside an area affected by ,a toxic stress). Skorupa
(1998) has discussed this point, and also emphasized the importance of considering offstream impacts
from instream sources of selenium. Identifying adverse effects in lotic environments from environmental
degradation is possible if the appropriate approach is used such as (1) indicator taxa or guilds, (2) indices
of species richness, diversity, and evenness, (3) multivariate methods, and (4) the index of biotic integrity
OBI); these methods were reviewed by Fausch et al. (1990). They repeated for each of the approaches the
necessity of appropriate reference sites and the setting of a priori values, such as expected fish community
for a relatively unperturbed stream in a specific ecoregion by a competent fish
ecologist/biologist/ichthyologiest. These methods have been intensively used in Ohio (Ohio EPA 1988)
and the Midwest, but elsewhere. " '
Two recent papers (Canton and Van Derveer 1997, Van Derveer and Canton 1997) argued for a site-
specific sediment-based criterion for selenium in lotic ecosystems and used as part of their justification the
presence of healthy fish populations in the streams they were concerned about. Hamilton and Lemly
(1998) noted in their review of the two papers that no methodology was given to substantiate that "
environmental stresses had not altered the fish community or demonstrate that the presence fish
community was actually healthy! Hamilton and Lemly (1998) also discuss the problem of allowing high
instream selenium standards and the high potential for offstream, i.e., backwater, oxbow, or reservoir,
. C-61
-------
Steven J. Hamilton
effects from bioaccumulation through the food chain.
C-62
-------
Steven J. Hamilton
References
Bennett, WN, AS Brooks, and ME Boraas. 1986, Selenium uptake and transfer in an aquatic food chain and its
effecb on fathead minnow larvae. Archives of Environmental Contamination and Toxicology 15:513-517.
Besser, JM, TJ Canfield, and TW LaPoint. 1933. Bioaccumultation of organic and inorganic selenium in a
laboratory food chain. Environmental Toxicology and Chemistry 12:57-72.
Birkner, JH. 1978. Selenium in aquatic organisms from seleniferous habitats. PhD Dissertation, Colorado State
University, Ft. Collins, CO.
i ''."'- ' '
Bottino, NR> CH Banks, KJ Irgolic, P Micks, AE Wheeler, and RA Zingaro. 1984. Selenium containing amino
acids and proteins in marine algae. Phytochemistry 23:2445-2452
Canton, SP, and WD Van Derveer. 1997. Selenium toxicity to aquatic life: An argument for sediment-based water
quality criteria. Environmental Toxicology and Chemistry 16:1255-1259.
> - •• • ••'••',
Cleveland, L, EE Little, DR Buckler, and RH Wiedmeyer. 1993. Toxicity and bioaccumulation of waterborne and
dietary selenium in juvenile bluegiil (Lepomis macroehirus). Aquatic Toxicology 27:265-280. >-
Cooke, TD, and KW Bruiand. 1987. Aquatic chemistry of selenium: Evidence of biomethylation Environ Sci
Technol 21:2114-2119.
Coughlan, DJ, and JS Velte. 1989, Dietary toxicity of selenium-contaminated red shiners to striped bass.
Transactions of the American Fisheries Society 118:400-408. ,
Coyle, JJ,DR Buckler, CQ IngersoU, JF Fairchild, and TW May. 1993. Effect of dietary selenium on the
reproductive success of bluegills (Lepomis macrochinis). Environmental Toxicology and Chemistry 12:551-565.
Fausch, KD, J Lyons, JR Karr, and PL Angerneier. 1990. Fish communities as indicators of environmental
degradation. American Fisheries Society Symposium 8:123-144. ' •
C-63
-------
Steven J. Hamilton
Finley, KA 1985. Observations of bluegills fed selenium-contaminatedHexagenia nymphs collected from Belews
Lake, North Carolina. Bulletin of Environmental Contamination and Toxicology 35:816-825.
Goettl, JP, and PH Davies. 1978. Water pollution studies. Job Progress Report Federal Aid Project F-33-R-13.
Colorado Division of Wildlife, Ft Collins, CO.
Graham, RV, BG Blaylock, FO Hoffman, and ML Frank. 1992. Comparison of selenomethionine and selenite
cycling in freshwater experimental ponds. Water, Air, and Soil Pollution 62:25-42.
• ' • ; ' '-.',' I : '
Hallock, RJ, HL Burge and PL Tuttle. 1993. Biological pathways: Movement of selenium and mercury. Pages 39-
53 in Detailed Study of Irrigation Drainage in and near Wildlife Management Areas in West-Central Nevada, 1987-
90, RJ Hallock and LL Hallock, editors. U.S. Geological Survey, Water-Resources Investigations Report 92-4024B,
Carson City, NV.
*i ' • :
Hamilton, SJ, KJ Buhl, FA Bullard, and EE Little. 1998. Chronic toxicity of an inorganic mixture simulating
irrigation drainwater to razorback sucker and bonytail. Aquatic Toxicology (in review).
. .' * , ' • ,
•Hamilton, SJ, KJ Buhl, FA Bullard, and SF McDonald. 1996. Evaluation of toxicity to larval razorback sucker of
selenium-laden food organisms from Ouray NWR on the Green River, Utah. National Biological Survey, Yankton,
SD. Final Report to Recovery Implementation Program for the Endangered Fishes of the Upper Colorado River
Basin, Denver, CO. 79 pages.
Hamilton, SJ, KJ Buhl, NL Faerber, RH Wiedmeyer, and FA Bullard. 1990. Toxicity of organic selenium in the diet
to chinook salmon. Environmental Toxicology and Chemistry 9:347-358.
Hamilton, SJ, and AD Lemly. 1998. Do not let sediment muddy up the water quality criteria for selenium.
Environmental Toxicology and Chemistry (in review).
Hamilton, SJ, AN Palmisano, GA Wedemeyer, and WT Yasutake. 1986. Impacts of selenium on early life stages
and smoltification of fall chinook salmon. Transactions of the North American Wildlife, and Natural Resources
Conference 51:343-356. .
Hamilton, SJ, and RH Wiedmeyer. 1990. Concentrations of boron, molybdenum, and selenium in chinook salmon.
Transactions of the American Fisheries Society 119:500-510.
C-64
-------
Steven J. Hamilton
Hilton, JW, and PV Hodson. 1983. Effect of increased dietary carbohydrate on selenium metabolism and toxicity in
rainbow trout (Sdlmo gairdnerf). Journal of Nutrition 113:1241-1248.
. Hilton, JW, PV Hodson, and S J Slinger. 1980. The requirement and toxicity of selenium in rainbow trout (Salmo
gairdneri). Journal of Nutrition 110:2527-2535.
Hunn, 18, SJ Hamilton, and DR Buckler. 1987. Toxicity of sodium selenite to rainbow trout fry. Water Research
.21:233-238. s
Kiffhey, P, and A Knight. 1990. The toxicity and bioaccumulation of selenate, selenite and seleno-L-methionine in
the cyanobacterium Anabaenaflos-aquae. Archives of Environmental Contamination and Toxicology 19:488-494.
Maier, KJ, CG Foe, and AW Knight. 1993. Comparative toxicity of selenate, selenite, seleno-DL- methionine and
seleno-DL-cystine to Daphnia magna. Environmental Toxicology and Chemistry 12:755-763.
Niimi, AJ, and QN LaHam. 1976. Relative toxicity of organic arid inorganic compounds of selenium to newly
hatched zebrafish (Brachydaniorerio). Canadian Journal of Zoology 54:501-509.
Ogle, RS, and AW Knight. 1989. Effects of elevated foodborne selenium on growth and reproduction of the fathead
minnow (Pimephales prbmelas). Archives of Environmental Contamination and Toxicology 18:795-803.
Ohio EPA (Environment Protection Agency). 1988. Biological criteria for the protection of aquatic life, volumes 1-
3, OEPA, Columbus, OH. -.-'.•
Peltz, LA, and B Waddell. 1991. Physical, chemical, and biological data for the detailed study of irrigation drainage
in the middle Green River basin, Utah, 1988-89, with selected data for 1982-871 Open-File Report 91-530. U.S.
Geological Survey, Salt Lake City, UT. '. -,
Robberecht, H, and R Van Griekert. 1982. Selenium in environmental waters: Determination, speciation and
concentration levels. Talanta 29:823-844.
Skorupa, JP. 1998. Selenium poisoning offish and wildlife in nature: Lessons from twelve real-world examples.
Pages 315-354 in Environmental Chemistry of Selenium, WT Frankenberger and RA Engberg, editors, Marcel
Dekker,NewYork,NY. ;
C-65
-------
Steven J. Hamilton
Skorupa, JP, and HM Ohlendorf. 1991. Contaminants in drainage water and avian risk thresholds. Pages 345-368
in The Economics and Management of Water and Drainage in Agriculture, A Dinar and D Ziberman, editors.
Kluwer Academic Publishers, Boston, MA
Stadtman, TC. 1974. Selenium biochemistry. Science 183:915-922.
Stadtman,TC. 1980. Biological functions of selenium. Trends in Biochemical Sciences 5:203-206.
Stephens, DW, B Waddell, LA Peltz, and JB Miller. 1992. Detailed study of selenium and selected elements in
water, bottom sediment, and biota associated with irrigation drainage in the middle Green River basin, Utah, 1988-
90. Water-Resources Investigations Report 92-4084. U.S. Geological Survey, Salt Lake City, UT.
H ^ ' ' , •
Takayanagi, K, and GTF Wong. 1985. Dissolved inorganic and organic selenium in the Orca Basin. Geochim.
Cosinochim. Acta 49:539-546. .
Van Derveer, WD, and SP Canton. 1997. Selenium sediment toxicity thresholds and derivation of water quality
criteria for freshwater biota of western streams. Environmental Toxicology and Chemistry 16:1260-1268.
Wrench, JJ. 1978. Selenium metabolism in the marine phytoplankters Tetraselmis tetrathele and Dunaliella
minuta. Marine Biology 49:3231-236.
Zhang, Y and JN Moore. 1996. Selenium fractionation and speciation in a wetland system. Environ. Sci. Technol
30:2613-2619.
C-66
-------
Gerhardt Riedel
C-67
-------
Gerhardt F. Riedel
C-68
-------
Gerhardt F. Riedel
-1) Besides selenite and selenate, which other forms of selenium in water are toxicologically
. important with respect to causing adverse effects on freshwater aquatic organisms under
environmentally realistic conditions?
At present, selenate and selenite are the only forms of selenium for which enough combined field
analytical data and laboratory toxicity and bioaccumulation work exist to determine that adverse effects
are being caused at environmentally realistic conditions. This is not to deny the existence of organic
forms of selenium are present in water. A wide variety of organic Se compounds undoubtedly exist in
fresh waters, including individual seleno-amino acids such as selenomethlonine and selenocysteine,
polypeptides of various lengths containing seleno-amino acids, transformation products such as
selenonium compounds and dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe) (Cooke and
Bruland, 198?;) , and possibly complexes of selenium with dissolved organic matter (DOM). While the
seleno-amino acids have been detected in impacted fresh waters, and these compounds are often
' 4 ' . ' ' ' ' ' '
-observed to be highly^accumulative and toxic (Kiffhey and Knight, 1990; Riedel et al., 1991), these
compounds are present in vanishingly small concentrations, are difficult to determine, and are extremely
labile. These compounds are also formed biologically in response to enrichment with selenate and
selenite (Besser, et al., 1994), and are thus closely linked to the concentrations of the inorganic species,
thus regulating their concentrations should also regulate the formation of the ammo-acids as well. Other
known dissolved species such as, selenonium compounds, and (DMSe) and (DMDSe), are likely to be
less toxic than the inorganic species, although to my knowledge, this has not been tested in aquatic
systems. . ,
Confidence level: High
C-69
-------
Gerhardt F. Riedel
1-2) Which form (or combination of forms) of Se in water are most closely correlated with chronic
effects)
Since both selenate and selenite can be present essentially separately, or combined in mixtures
depending on the source of the selenium and subsequent transformations, and because the two forms
have substantially different patterns of bioaccumulation and toxicity (e.g.Kifihey and Knight, 1990;
Riedel et al., 1991, Maier and Knight, 1993) , it is imperative that analytical methods used to evaluate Se
in aquatic systems be capable of separating selenate, selenite (Cutter 1978). In most cases, the
concentration of Se in particles is snlall with respect to the concentration of Se in the dissolved phase,
and the difference between total dissolved and total recoverable Se is unimportant, and may be difficult
to resolve analytically. Furthermore, it is of greater interest whether Se in the suspended particles is
elevated compared to total particle mass or organic carbon (Cutter, 1985). However, it also is important
to distinguish between the inorganic forms which are likely the primary forms for uptake (at the lower
»
"trophic levels) and toxicity, and the myriad organic forms which have been produced in response to
inorganic Se enrichment, and probably represent a net reduction in toxicity (e.g. Yu et al., 1997). • This
separation can also be done within the analytical framework of Cutter (1978), At this time it is unlikely
that the organic Se species will be better resolved analytically at a regulatory level, although this should
be an area of continued research. , .
Confidence level: High
I-3A) In priority order, which water qualify characteristics (e.g. pH, TOC, sulfate, interactions
with other metals such as Hg) are most important in affecting the chronic toxicity and
bioaccumulation of Se to freshwater aquatic life under environmentally realistic conditions?
The answers differ for selenate and selenite. For selenate, sulfate appears to act as a competitive
inhibitor of both uptake and toxicity in a variety of plants and animals (Wheeler et al., 1982, Riedel et al
i
and Sanders, 1996; Ogle and Knight, 1996) . Given that areas where selenate is mobilized (e.g.
C-70 :
-------
Gerhardt F. Riedel
' ,. _ " ,• • , , . - , • ',..•-,. /
agricultural drain water, and various types of geology) are also generally sites where sulfate is enriched
as well, sulfate should be considered important in the environmental toxicity of selenate. Arsenic (As)
and molybdenum (Mo), which are also mobilized under similar conditions, appear to produce additive
toxicity with selenate, and should also be considered important (e.g. Naddy et al., 1995). TOC, DOC,
pH and other common water quality characteristics do not appear to significantly influence the
environmental toxicity of selenate.
It appears likely, based on simple chemical principals, that pH has a significant effect on the
speciation of selenite over the environmentally reasonable pH range, and thus is likely to exert strong
influences on the uptake and toxicity of selenite in a variety of organisms (Riedel and Sanders, 199,6).
Unfortunately, fairly little work has been done on this relationship, and some additional work would be
necessary to show its (generality across species. For algae, there is some evidence that selenite
bioaccumuiation can be affected by phosphate concentrations (Riedel and Sanders, 1996). This is both
an environmental concern, as the phosphate status of a freshwater system can be quite variable, as well
as in evaluating reports of selenite accumulation and toxicity to algae in the laboratory, which is
commonly done at environmentally unrealistic concentrations of phosphate. Again, as with pH, the
evidence for this effect is limited, and it should be further verified. It is likely that other similar elements
(arsenate, molybdate etc) and possibly mercury can influence selenite uptake and toxicity under
environmentally realistic conditions although this work has focused on selenate dominated systems.
Other water quality parameters, such as TOC, hardness, sulfate, have not beep shown to substantially
influence selenite accumulation and toxicity. „
Confidence level: medium
C-71
-------
' Gerhardt F. Riedel
I-3B) Of these which have been or can be quantitatively related to selenium chronic toxicity or
bioaccumulation in aquatic organisms. How strong or robust are these relationships?
The relationship between sulfate and selenate is at least semi-quantitative and relatively robust
(particularly at the algal level). However, at higher trophic levels, this relationship is likely to be not a
strong, and to be expressed indirectly through the food web.
Confidence level: medium
I-3C) How certain are applications of toxicity relationships derived from acute toxicity and water
quality characteristics to chronic toxicity situations in the field?
Relatively poor. Although algae appear to have relatively uniform responses to concentrations, within a
>
"Species or group, there are always algae that grow under extreme conditions and thus it is difficult to
determine that high selenium concentrations have any toxic effect on algae in the field. Toxicity to algae
is more likely to show as changes in the species composition of algal communities rather than changes in
growth or biomass. The influence of sulfate on the uptake and toxicity of selenate in Crustacea
(cladocera and midge larvae) is somewhat variable, and there appears to be no systematic effect with
fish-
Confidence level: medium
n. - 4) Which forms or selenium in tissues are toxicologically important with respect to causing
adverse effects of freshwater organisms under environmentally realistic conditions and why?
It is widely held that the accumulation of selenium in selenoamino acids and selenoproteins is the
predominant form of Se in tissues and that they are responsible for most of the effects of selenium
observed in organisms, either good or ill. Although I do not actively collect that literature, I know of no
* '. X ,
C-72 ' ' * .
-------
,-''•' Gerhardt F. Riedel
evidence of different forms of selenium within tissues that act in different manners. However, it is a
reasonable presumption that selenate and selenite that had recently entered a tissue and had not yet been
converted to an organic form might have different effects. Similarly, degradation products such as
selenonium compound and DMSe and DMDSe are likely to have substantially different toxicological
properties than their parent organic compounds; but tissue measurements of these compounds are
virtually unavailable. Unfortunately, speciation analysis of selenium in a tissue matrix is very difficult.
Confidence level: low
n - 5) Which form (or combination of forms) of selenium in tissues are most closely correlated
with chronic effects on aquatic life in the field?
Following the answer above, I am unaware of any correlations of Se tissue speciation with chronic
effects of Se. However, reasoning from chemical principals, I would prefer analytical techniques that
could 1) separate inorganic Se (particularly selenite) from "incorporated" Se; 2) determine S,e
incorporated into proteins, and preferably which seleno-amino acids were incorporated into which
proteins, in which tissues, and 3) separate and identify-the "breakdown" products, selenonium
compounds, DMSe and DMDSe. . .
Confidence level: low
n - 6) Which tissue (and in which species of aquatic organisms) are best correlated with overall
chronic toxicological effect thresholds of selenium?
Liver and gonad tissue are relatively responsive to Se concentrations in fish, while muscle tissue
responds relatively slowly. Although I am not aware of any such research one would suspect that the
hepatopancreas of larger crustaceans would also be relatively responsive. Observed chronic Se toxicity
• ' •' ' ' '•':•'' C-73 ".- . '.•.-'
-------
Gerhardt F. Riedel
in natural aquatic systems has been largely restricted to fish, and among fish, largely restricted to
centrarchids, although some suckers and salmonids may be affected as well.
Confidence level: medium •
EC- 7) How certain are we. in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish? What are the primary sources of
uncertainty in this extrapolation?
* ,'„',, <.,,„'',
We are fairly uncertain in predicting Se in fish tissues from water column Se concentrations. Given that
we can make a rough projection of phytoplankton and zooplankton concentrations from form specific
water column data, and other water quality data, (and that projection is likely to be quite rough, see
attached Fig. 1), the transfer of that Se to fish can vary with the type offish, the feeding behavior of the
fish at any particular time. When you also consider a variable benthic food chain for most of the
important fish (centrarchids, salmonids arid suckers) I believe it will become quite difficult to predict fish
tissue concentrations without a significant modeling effort.
Confidence level: medium
in - 8) Which forms of selenium in sediment are toxicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions?
In aerobic sediment, most of the Se is likely to be present as either adsorbed
11 • ' • . . " , ' •
selenite or as organic Se present in the microbial compartment. Se in the organic form is likely have a
higher assimilation efficiency, and thus be more available for toxicity than inorganic Se adsorbed to
particles. Furthermore, in aerobic sediments, pore water concentrations of Se may be high enough that
direct uptake of selenite and selenate by benthic organisms could be a significant route. In anaerobic
' • "' ' ' , .," -C-74 ' , ' • ' '
-------
Gerhardt F. Riedel
sediment, elemental Se (Se°) is likely to be the predominant form, and pore water Se is likely to be
vanishingly small. While there is evidence that Se° is available to molluscs (Luoma et al., 1992), it seems
likely that it is less available than organic, Se, and it is also likely to be much less available to benthic
animals with short digestion times, such as chironomids, and oligochaetes.
Confidence level: high
HI - 9) Which form or forms in sediment are most closely correlated with chronic effects on
aquatic life in the field?
Following the discussion above, I would like to see analytical techniques for Se in sediment to separate
organically bound Se, adsorbed selenate and selenite, and Se°.
> . • . . -
"Confidence level: high .
- 10) In priority order, which sediment quality characteristics (e.g. TOC) etc. are most
important in affecting the chronic toxicity and bioaccumulation of selenium to freshwater aquatic
life und environmentally realistic conditions? Of these, which have been (or can be)
quantitatively related to selenium chronic toxicity or bioaccumulation in aquatic organisms?
In priority order, oxidation state (Eh, presence of sulfide, etc), TOC, pH, grain size. Indirectly, the
redox condition can be linked to the concentrations of Se in fish hi Hyco reservoir, which in turn links to
the chronic toxicity of Se. TOC in sediment has been quantitatively linked to accumulation of Se in fish
in riverine systems.
Confidence level: medium
C-75
-------
Gerhardt F. Riedel
in - 11) How certain are we in relating water-column concentrations of selenium to sediment
concentrations? What are the primary sources of uncertainty in this extrapolation?
Very uncertain. Water column concentrations of Se can fluctuate over a wide range in a relatively short
" " ' lv *"
period of time, where sediment accumulation integrates Se inputs over a very long period. Furthermore,
the processes that transfer Se from the water column to the sediment and vice versa can operate at very
different directions and rates depending on (roughly in order of importance) selenium form, redox
conditions, productivity, benthic fauna, temperature.
Confidence level: High
IV - 12) How does time variability in ambient concentrations affect the bioaccumulation of
selenium in aquatic food webs, and in particular, how rapidly do residues in fish respond to
increases and decreases in water concentrations?
The effect time variability of ambient concentrations of Se on bioaccumulation can be expected to
depend on the time constants of individual steps. For a water column-based food chain, phytoplankton
and zooplankton would respond relatively quickly to changes in water column Se concentrations, and
fish would respond to changes in prey concentrations according to their own assimilation and depuration
kinetics (on the order of months). Large piscivores would presumably have a longer response time due
to the lag in their prey. Once a substantial component of benthic food is assumed, the link between
ambient water concentrations and fish accumulation is seriously compromised, since high concentrations
of Se in the sediment can lead to substantial accumulation in fish despite relatively low water column
concentrations of Se.
Confidence level: medium
C-76
-------
Gerhardt F. Riedel
r '! ' ' 'I • ' ' ' .
, . ' \ . ' ' '
IV -13) To what extent would the type of ecosystem (e.g. lentic, lotic) affect the chronic toxicity of
selenium?
~i' " * ' "'.. --
The type of ecosystem could have a dramatic effect on the chronic effect of Se loadings. In a relatively
quickly moving body of water, such as a stream, river, or short residence time lake, the rapid overturn of
water and sediment could prevent the accumulation of substantial quantities of Se in the sediment. In a
long-term residence time lake, particularly one with a seasonally anoxic hypolimnion, Se could be
extensively trapped by the sediment, which could be a continuing source for chronic toxicity through the
benthic food web, and seasonal releases of Se to the water column.
Confidence level: medium '
C-77
-------
Gerhardt F. Riedel
References
Besser, J. M., J.N. Huckins and R.C. Clark. 1994. Separation of selenium species released from Se-
exposed algae. Chemosphere 29: 771-780.
Cooke, T.D. and K. W. Bruland. 1987. Aquatic chemistry of selenium: evidence of biomethylation
Environ. Sci. Technol 21 1214-1219.
Cutter, G.A. 1978. Species determination of selenium in natural waters. Anal. Chim. Acta 98: 59-66.
Cutter, G.A. 1985. Determination of selenium speciation in biogenic particles and sediments. Anal.
Chem. 57: 2951-2955.
' ' • i
Kifihey, P. and A. Knight. 1990. The toxicity and bioaccumulation of selenate, selenite and seleno-1-
methionine in the cyanobacterium Anabaena flos-aquae. Arch. Environ. Contain. Toxicol. 19, 488-
494.
Luoma, S.N., C. Johns, N.S. Fisher, N. A Steinberg., R. S. Oremland and J. R. Reinfelder. 1992.
Determination of selenium bioavailability to a benthic bivalve from particulate and solute pathways.
Environ. Sci. Technol. 26:485-491.
Maier, K. J. and A.W. Knight. 1993. Comparitive acute toxicity and bipconcentration of selenium by the
midge Chironomus decorus exposed to selenate, selenite and seleno-dl-methionine. Arch. Contamin.
Toxicol. 25: 365-370.
Naddy, R. B., T.W. La Point and S. J. Kline. 1995. Toxicity of arsenic, molybdenum, and selenium
combinations to Ceriodaphnia dubia. Environ.. Toxicol & Chem. 14:329-336.
i
Ogle, R. S. and A. W. Knight. 1996. Selenium bioaccumulation in aquatic ecosystems: 1. Effects of
sulfate on the uptake and toxicity of selenate in Daphnia magna. Arch. Contamin. Toxicol. 30:274-
C-78
-------
GerhardtF. Riedel
•279. , -. : - . !'"-'• "'."•'. "'•
Riedel, G.F., D.P. Ferrier, and J.G. Sanders. 1991. Selenium uptake by freshwater phytoplankton.
Water Air Soil Poll. 57-58:23-30.
Riedel G. F., J. G. Sanders and C. C. Gilmour. 1996. Uptake, transformation and impact of selenium in
freshwater phytoplankton and bacterioplankton communities! Aquat. Microb. Ecol. 11:43-51
Wheeler, A. E., R. A. Zingaro, K. Irgolic andKR. Bottino. 1982.. The effect.of selenate, selenite and
sulfete on the growth of six unicellular marine algae. J. Exp. Mar. BioL Ecol. 57:181-194.
Yu, r., J. P; CofBnan, V. Van Fleet-Stalder and T.G. Chasteen. 1997. Toxicity of oxyanions of selenium
and of a proposed bioremediation intermediate, dimethyl selenone. Environ. Toxicol. Chem. 16:
140-145. - '
C-79
-------
03
o
_o
- o
n
o
o
o
I""'
o
o
I"
o
o
•o
_o
O)
LLJ
LU
CO
O
CO
CO
o
(B/6n)
1V91V
te
S3
£•!•
2 £
•8 8
tj ^%
CO UH
OH O
S 13
8 o
8 3-
o
00
1
0
03 C
-S H
o £
V3 a)
'St
" o
I 8
11
I*
o
S
-------
Joseph Skorupa
C-81
-------
SKORUPA
C-82
-------
....... ' . SKORUPA
Peer Consultation Workshop on Selenium Aquatic Toxicity
and Bioaccumulation
Premeetino Written Comments
1. Besides selenite and selenate, which other forms of selenium in water are toxicologically
important with respect to causing adverse effects on freshwater aquatic organisms under
environmentally realistic conditions?
Another form of selenium in water that appears to be toxicologically important is selenomethipnine (and
perhaps other selenoamino acids). Se-meth has repeatedly been demonstrated to exhibit order-of-
magnitude higher bioaccumulation dynamics (e.g., Riedel et al. 1991; Graham et al. 1992; Besser et al.
1993; Rosetta and Knight 1995) and toxicity (e.g., Ingersoll et al. 1990; Kiffney and Knight 1990; Maier
and Knight 1993; Maier dt al. 1993) than se|enite or selenate. Maier and Knight (1993) caution,
however, that species-specific exceptions to the general trend also occur.
Ingersoll et al. (1990) reported a chronic geometric mean-maximum acceptable toxicant concentration
(GM-MATC)for Se-meth of 0.16 ug Se/L for Daphnia magna. Furthermore, based on observations that
fish foods containing 3-20 mg Se/kg, on a dry weight basis, are sufficiently contaminated to cause toxic
effects (depending on the life stage and species offish being considered) (e.g., Hamilton et al. 1990;
Lemly 1993a, 1997a), and based on a bioconcentration factor of 382,000 for Se-meth from water to
zooplankton (at 0.1 ug Se/L; Besser et al. 1993), as little as 0.008-0.052 ug Se/L in the form of Se-meth
appears sufficient to produce a toxic diet for fish. Because bioconcentration factors are inversely
proportional to waterbbme concentrations (e.g., Besser et al. 1993), the bioconcentration factor for Se-
meth at 0.008-0.052 ug Se/L may actually be greater than the 382,000 observed at 0.1 ug Se/L and
therefore waterbome'concentrations of less than 0.008-0.052 ug Se/L may actually be sufficient to
result in .toxic diets for fish.
C-83
-------
, SKORUPA
Given such evidence that Se-meth concentrations in water on the order of parts per trillion are sufficient
to be toxicologicaliy significant, it is important to assess how commonly, and under what conditions,
such concentrations would be met or exceeded in the field? That's a question I would need more time
to research the literature on. I suspect that other panel members are probably already familiar with that
segment of the selenium literature and can address that issue.
2. Which form (or combination of forms) of selenium in water are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in water would you measure for correlating exposure with
adverse effects in the field?) Note: Your response should include consideration of operationally
defined measurements of selenium (e.g., dissolved and total recoverable selenium), in addition to
individual selenium species. ,
I am not aware of sufficient research on this topic, with regard to aquatic life, to provide a definitive, or
even putative, answer.
_ Conceptually, waterbome selenium concentrations are useful for predicting chronic effects only to the
extent that they consistently covary with the partitioning of selenium into the aquatic food chain. .
Although consistent covariation of waterbome selenium and foodchain selenium has been reported on
a local scale for physically uniform and biotically simple aquatic systems (e.g., Birkner 1978; Skorupa
and Ohlendorf 1991), at a national scale any form of waterbome selenium (or combination of forms)
likely would be relatively unreliable for predicting chronic effects. This is because at a national scale the
immense variety of environmental permutations and site histories would commonly include cases where
waterbome selenium concentrations and food chain selenium concentrations .are discordant (e.g.,
Luoma et al., 1992; Lemly 1997b; Setmire and Schroeder 1998; Maier et al., In Press). For example,
waterbome concentrations of selenium can be low either because of low mass loading into a water
body (in which circumstance foodchain selenium will also be low and nonhazardous) or because of
efficient and rapid partitioning of elevated mass loads out of the water column and into other
compartments, including the food chain (a potentially hazardous situation). Thus, a priori, a low
" ' ' ' .^ '
waterbome concentration of selenium isn't necessarily safe or hazardous. -
AlthougH measures of total selenium on both a filtered (dissolved) and unfiltered (total recoverable)
,i' . ,
C-84
-------
SKORUPA
basis will be uncertain predictors of chronic effects at a national scale, based on first principles it can be
deduced logically that unfiltered values (total recoverable) should usually be better predictors than
filtered (dissolved) values. It is selenium contamination of the aquatic food chain that most directly
causes chronic effects in sensitive aquatic taxa (such as fish; e.g:, Hermanutz et al. 1992), and since a
substantive part of the particulate load in a water column is often composed of foodchain tissues (living
and decaying), it logically follows that including particulates in measures of waterbbrne selenium should
usually increase the linkage between such measures and the probability of chronic effects.
3. A) In priority order, which water quality characteristics (e.g., pH, TOO, sulfate, interactions
with other metals such as mercury) are most important in affecting the chronic toxicity and
bioaccumulation of selenium to freshwater aquatic life under environmentally realistic exposure
conditions?
B) Of these, which have been (or can be) quantitatively related to selenium chronic toxicity or
bioaccumulation in aquatic organisms? How strong and robust are these relationships?
- •' - •"'*', • •. •' • .•
C) How certain are applications of toxicity relationships derived from acute toxicity and water
quality characteristics to chronic toxicity situations in the field? .
A) I am unaware of any studies that have simultaneously partitioned the relative proportions of variance
in selenium bioaccumuiation explained by pH, TOG, sulfate concentration, and chemical interactions
effects. Birkner (1978) simultaneously examined several water quality parameters such as dissolved
sulfate, hardness, and conductivity and found that none of those parameters explained a significant
amount of variation in foodchain bioaccumulation of selenium across thirty field sites surveyed in
Colorado and Wyoming. Foodchain selenium did, however, significantly covary with water and ,
sediment concentrations of selenium. I suspect that there is insufficient basis in the scientific literature,
to conclusively establish a priority order for water quality characteristics that influence selenium toxicity.
There is increasing evidence, however, that interaction effects with mercury may rank prominently
among the factors influencing selenium toxicity. For example, Heinz and Hoffman (1998) recently
':'•"-.' C-85 .-.•'. •
-------
SKORUPA
demonstrated that the most environmentally relevant forms of dietary selenium and mercury
(selenomethionine and methyl-mercury) caused highly synergistic reproductive toxicity to an egg-laying
vertebrate. Similarly, studies at a set of mercury-contaminated lakes in Sweden provided circumstantial
field evidence for severe toxic effects on fish populations at unexpectedly low levels of experimental
selenium additions (3-5 ug Se/L as sodium selenite; Paulsson and Lundbergh 1991).
B) Concentrations of dissolved sulfate have been demonstrated in short-term bench top experiments to
strongly inhibit bioconcentration and bioaccumulation of dissolved selenate by algae and aquatic
invertebrates (e.g., Hansen et al. 1993; Maier et al. 1993; Williams et al. 1994; Ogle and Knight 1996).
These studies have demonstrated that such inhibition can be quantitatively related to selenium
bioaccumulation and toxicity, at least within the context of biotically and chemically simplistic
experimental conditions.
_C) The berjch top studies of sulfate interaction effects cited above, however, do not appear to translate
very well to observed patterns of selenium bioaccumulation (and therefore chronic effects) in the field.
As already mentioned, Birkner (1978) found no significant effect of dissolved sulfate concentrations (5
to 9,611 mg/L) on foodchain bioaccumulation in the field. Likewise, very strong correlations between
waterbome selenium and aquatic foodchain selenium (correlation coefficients > 0.9 for most foodchain
taxa) were observed across multiple field sites in California's Tulare Lake Basin despite widely varying
concentrations of dissolved sulfate ranging from 2,000 to 100,000 mg/L (Skorupa and Ohlendorf 1991;
Skorupa 1998). This pronounced discrepancy between lab and field observations may be related to the
fact that although selenate and sulfate compete for a common uptake pathway, bioaccumulation of
selenite and selenomethionine occurs via separate pathways from sulfate (e.g., Maier et al. 1993).
Even in the presence of high sulfate concentrations, uptake of selenate and its biotransformation to
reduced forms of selenium such as selenite and selenomethionine by algae and other primary
producers is only depressed, not eliminated. Also, selenate-reducing bacteria in sediments and water
can function independently of sulfate concentrations (e.g., Oremland et al., 1989; Gerhardt et al., 1991).
Bacteria play a critical role in the foodchain cycling of selenium (e.g., Bowie et al., 1996). Thus, over
C-86
-------
SKORUPA
time, even, if the original form of selenium entering an aquatic system was virtually pure selenate,
reduced forms of selenium that are not inhibited by sulfate (e.g., selenite, selenomethionine, etc.)
increasingly become available and increasingly dominate the process of foodchain bioaccumulation.
For example, drainage water in' the San Joaquin Valley of California was found to contain selenium as
selenate, selenite, and selenomethionine (Se-Meth) in a ratio of approximately 18:3:1 (Besseret al.
1989). Bioconcentration factors for periphyton, however, showed a reverse ratio of about 1:6:120
(Besser et al. 1989). Thus, the approximate ratio of selenium uptake from selenate, selenite, and Se-
. Meth would be 18:18:120. Therefore, only about 11 % (18/156) of bioaccumulated selenium in the
: • - - i \
periphyton would be taken up directly from the inventory of dissolved selenate. Under these
circumstances, even if a sulfate-interference effect as high as 50% assimilative inhibition were
occurring it would cause only about a 5% (0.5 x 0.11) reduction in overall bioaccumulation of selenium.
At toxic threshold exposures in the region of 2-5 ug/L waterborne selenium, a 5% reduction would be
very negligible in absolute terms. Even this example probably overestimates the contribution of
jselenate to_ overall bioaccumulation of selenium because it does not account for the cumulative loading
of predominantly non-selenate species of selenium into aquatic sediments, which is another major
bioaccumulation pathway that further devalues the relative importance of dissolved selenate selenium.
It is quite plausible that in biologically and chemically complex aquatic environments, even where
concentrations of dissolved sulfate are low, only a minute proportion of selenium bioaccumulation is
due to direct uptake of selenate selenium. Recently, Milne (1998) has similarly noted that because of
the vast differences in assimilatory dynamics of selenate versus reduced forms of selenium (unrelated
to uptake inhibition by sulfate)"...selenate is often a spectator in living systems."
It appears that 48-hr to 96-hr bench top experiments may be too short in duration and too biotically
simplified to mimic the typicaj real-world progression from a selenate-dominated water to a complex
mixture of multiple chemical species of selenium metabolically dominated by reduced forms of selenium
whose cycling is independent of dissolved sulfate concentrations. In summary, for whatever reasons,
field data for aquatic organisms do not support the notion that foodchain bioaccumulation of selenium is
sulfate-dependent. Sixty years ago, Beath (1937) concluded that the "...sulfur-selenium antagonism
theory has not been found generally applicable to farm and range practices [for ameliorating selenium
"•','' :, ''C-87 : ' • ••'.'' .'
-------
SKORUPA
toxicity to range animals] of the Rocky Mountain region."
C-88
-------
/ SKORUPA
4. Which forms of selenium in tissues are toxicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions and
why?
Several studies have concluded that the most common forms of dissolved selenium all appear to be
metabolically transformed to a common pool of selenium (a uniform toxicological currency) in foodchain
biota (e.g., Gissel-Nielsen 1987; Zayed and Terry 1992; Besser et al. 1993; Milne 1998). Several
studies have also indicated that the putative universal foodchain currency is either selenomethionine or
one or more forms of selenium with toxicological profiles functionally equivalent to selenomethionine
(e.g., Woock et al. 1984; Hamilton et al. 199Q; Heinz 1996). Thus, it appears that one or more
selenoarnino acids, possibly including selenomethionine, are the toxicologically important forms of
selenium in biotic tissues.
It has been suggested that selenoarnino acids are toxicologically important because of their propensity
to substitute for the analogous sulfuramirio acids and thereby alter the normal structure and function of
proteins (e.tl-, Rosetta and Knight 1995; Lemly 1997a; Martens and Suarez 1998).
5. Which form (or combination of forms) of selenium in tissues are most closely correlated with
chronic effects on aquatic life in the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in tissues would you measure for correlating exposure with
adverse effects in the field?)
This question is still largely unaddressed in the scientific literature. Much of my response provided
above for question number 4 is also relevant here. Therefore, it is likely that prediction of chronic
effects in the field could be improved by examining the relationship of specific selenoarnino acids to
chronic effects. Nonetheless, even on the basis of undifferentiated total selenium concentrations in
tissues, exposure-response relationships strong enough to provide good predictive value for chronic
effects in the field have been delineated (e.g., Lemly 1993b, 1997a). In some respects, the crucial
question is not what specific form of selenium to measure in tissues, but rather what's the most
appropriate tissue to focus on for measures of total selenium or specific forms of selenium.
Reproductive tissues, such as fish ovaries or eggs, have clearly been established as the answer to the
latter question (e.g., Lemly 1993c, 1995, 1996a), as has been established for aquatic birds also(Heinz
/ ' • - ' ' C-89' " , .
-------
SKORUPA
• .. • • (•;'••' '
1996; Skorupa 1998).
6. Which tissues (and in which species of aquatic organisms) are best correlated with overall
toxicological effect thresholds for selenium?
Reproductive tissues of sensitive species offish, such as centrarchids arid salmonids (e.g., Lemly
1996b, 1997b).
7. How certain are we in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish? What are the primary sources of
uncertainty in this extrapolation?
It is much easier to reliably relate foodchain concentrations of selenium to fish tissue residues .than to
reliably relate water-column concentrations because water-column selenium occurs in several
"toxicological currencies, whereas foodchain selenium occurs in a reasonably universal toxicological
currency (see response provided above for question number 4). It should be possible with reasonable
certainty to experimentally determine levels of foodchain selenium that result in toxicological threshold
levels of tissue selenium in fish (e.g., Woock et al., 1987; Hamilton et al., 1990; Cleveland et al., 1993;
Coyle et al., 1993). Then for various forms and mixtures of water-column selenium the partitioning
dynamics into aquatic foodchain compartments would have to be determined. Ultimately this would
- „ , i ...••• . ... . .
identify waterbome concentrations that have the potential to result in toxicological threshold levels of
foodchain selenium. When and where such experimentally determined potentials for chronic effects
would be realized in the field would still depend on a complex interactive combination of site-specific
environmental conditions.
Alternatively, field data systematically collected on a national scale, or at least on a regional scale,
could be analyzed to characterize the realized probabilities of exceeding threshold tissue concentrations
in fish that are associated with a range of water-column selenium concentrations. Existing databases
such as the National Water Quality Assessment Program (NAQWA), or National Irrigation Water Quality
«' ' '' "'"''' - '' ''•'"',,",'," '!' :, ' - ' ' ' - '
Program (NIWQP) might provide the basis for a preliminary investigation of this nature. This has
C-90
-------
SKORUPA
already been done for eggs of aquatic birds (Adams et al., In Press) associated with irrigation projects
in the western United States, revealing that only when waterborne concentrations of dissolved selenium
(primarily as selenate) are near or below 1 ug/L is the probability of toxic threshold exceedance below
10%.
Until more experimental data are generated for fish, or probability analyses are conducted on
geographically extensive field-collected databases for fish, the relationship between waterborne
selenium concentrations and selenium concentrations in fish tissues should be viewed as poorly
Characterized and therefore relatively uncertain^
Questions 8-12.
I defer on these question's to other committee members, in my view, most issues associated with
developing a sediment-based chronic criterion are largely unaddressed in existing scientific literature.
As far as I am aware there has yet to be published even a single set of field data reporting selenium
concentrations in carefully matched samples of sediment and benthic foodchain fauna, which seems to
me like a logical first step toward developing sediment criteria. In any case, I look forward to other
committee members'comments on sediment issues.
13. To what extent would the type of ecosystem (e.g., lentic, lotic) affect the chronic toxicity of
selenium?
The type of ecosystem would affect the chronic toxicity of selenium to the extent that categorical
differences in ecosystems either alter the dynamics of selenium bioaccumulation in the aquatic
foodchain, alter the form of selenium incorporated into foodchain tissues, or alter the relative exposure
of upper trophic level organisms (i.e., fish) to different foodchain compartments (e.g., benthic versus
water-column biota, fauna versus flora, etc.). There are several sound conceptual bases for expecting
\ C-91
-------
SKORUPA
lotic ecosystems to be less prone to chronic toxicity than lentic ecosystems (Skorupa 1998)> however,
unless lotic and lentic ecosystems are sufficiently isolated from one another hydrologically, criteria
protective of the more sensitive of the two systems would have to be applied to both ecosystems.
For example, in a normal water year, the entire flow of the Colorado River is diverted offstream, thus,
criteria applied to the Colorado River (lotic) ecosystem would also have to be protective of offstream
(lentic) ecosystems such as the Salton Sea (Skorupa 1998). As another example, many rivers now
have large onstream reservoirs that create direct hydrologic linkages of lotic and lentic ecosystems,
thus, any criteria implemented for the river would also have to be protective of onstream reservoirs.
Because of extensive anthropogenically created linkages of lotic and lentic ecosystems, ecosystem
affects on chronic toxicity may be largely a moot technical issue except for identifying baseline criteria
that are appropriately protective of the most sensitive ecosystem link.
LITERATURE CITED
Besser, J.M., T.J. Canfield, and T.W. La Point. 1993. Bioaccumulation of organic and inorganic
selenium in a laboratory food chain. Environ. Toxicol. Chem., 12:57-72.
Birkner, J.H. 1978. Selenium in aquatic organisms from seleniferous habitats. Ph.D. thesis, Colorado
State University, Fort Collins, CO.
Graham, R.V., B.C. Blaylock, F.O. Hoffman, and M.L Frank. 1992., Comparison of selenomethionine
and selenite cycling in freshwater experimental ponds. Water Air Soil Pollut, 62:25-42..
C-92
-------
SKORUPA
Hamilton, S.J., K.J. Buhl, N.L. Faerber, R.H. Wiedmeyer, and F.A. Bullard. 1990. Toxiclty of organic
selenium in the diet to Chinook salmon. Environ. ToxicoL Chem., 9:347-358.
Hansen, L.D., K.J. Maier, and A.W. Knight. 1993. The effect of sulfate on the bioconcentration of
selenate by Chironomusdecorus and Daphnia magna. Arch. Environ. Contain. ToxicoL, 25:72-78.
Heinz, G.H;, and D.J. Hoffman. 1998. Methylmercury chloride and selenomethionine interactions on
health and reproduction in mallards. Environ. ToxicoL Chem., 17:139-145.
Hermanutz, R.O., K.N. Allen, T.H. Roush, and S.F. Hedtke. 1992. Effects of elevated selenium
concentrations on bluegills (Lepomis macrochirus) in outdoor experimental streams. Environ.
ToxicoL Chem., 11:217-224. ;
Ingersoll, C.G., F.J. Dwyer, and T.W. May. 1990. Toxicity of inorganic and organic selenium to
Daphnia magna (Cladocera) and Chironomus riparius (Diptera). Environ. ToxicoL Chem., 9:1171-
1181.
Kiffney, P., and A.W, Knight. 1990. The toxicity and bioaccumulation of selenate, selenite and seleno-
L-methionine in the Cyanobacterium Anabaena flos-aquae. Arch, Environ. Contam. ToxicoL,
19:488-494.
Lemly, A.D. 1993a: Metabolic stress during winter increases the toxicity of selenium to fish. Aquatic
ToxicoL, 27:133-158.
Lemly, A.D. 1997a. A teratogenic deformity index for evaluating impacts of selenium on fish
. C-93,
-------
. SKORUPA
populations. Ecotoxicol. Environ. Safety, 37:259-266.
Lemly, A.D. 1997b. Ecosystem recovery following selenium contamination in a freshwater reservoir.
Ecotoxicol. Environ. Safety, 36:275-281.
Luoma, S.N., C. Johns, N.S. Fisher, N.A. Steinberg, R.S. Oremland, and J.R. Reinfelder. 1992.
Determination of selenium bioavailability to a benthic bivalve from particulate and solute pathways.
1992. Environ. Sci. Technol., 26:485-491.
Maier, K.J., and A.W. Knight. 1993. Comparative acute toxicity and bioconcentration of selenium by
the midge Chironomus decorus exposed to selenate, selenite, and seleno-DL-methionine. Arch.
Environ. Contam. Toxicol., 25:365-370.
' '
Maier, K.J., C.R. Nelson, F.C. Bailey, S.J. Klaine, and A.W. Knight. In Press. Accumulation of '
selenium by the aquatic biota of a watershed treated with seleniferous fertilizer. Bull. Environ.
Toxicol. Chem., 00:000-000.
Maier, K.J., C.G. Foe, and A.W. Knight. 1993. Comparative toxicity of selenate, selenite, seleno-DL-
methionine and seleno-DL-cystine to Daphnia magna. Environ. Toxicol. Chem., 12:755-763.
Ogle, R.S., and A.W. Knight. 1996. Selenium bioaccumulation in aquatic ecosystems: 1. Effects of
sulfate on the uptake and toxicity of selenate in Daphnia magna. Arch. Environ. Contam. Toxicol.,
30:274-279.
Paulsson, K., and K. Lundbergh. 1991. Treatment of mercury contaminated fish by selenium addition.
C-94
-------
SKORUPA
Water Air Soil Pollut, 56:833-841. .
Riedel, G.F., D.P. Ferrier, and J.G. Sanders. 1991. Uptake of selenium by freshwater phytoplanktbn.
Water Air Soil Pollut., 57/58:23-30.
Rosetta, T.N., and A.W. Knight. 1995. Bioaccumulation of selenate, selenite, and seleno-DL-
methionine by the brine fly larvae Ephydra cinerea Jones. Arch. Environ. Contam. Toxicol.,
29:351-357.
Setmire, J.G., and R.A- Schroeder. 1998. Selenium and salinity concerns in the Salton Sea area of
California. Pp. 205-221 in: W.T. Frankenberger, Jr., and R.A. Engberg (eds.), Environmental
Chemistry of Selenium. Marcel Dekker, Inc., New York, NY. ,,
Skorupa, J.P. 1998. Selenium, poisoning offish and wildlife in nature: Lessons from twelve real-world
examples. Pp. 315-354 in: W.T. Frankenberger, Jr., and R.A. Engberg (eds.), Environmental
Chemistry of Selenium. Marcel Dekker, New York, NY.
Skorupa, J.P., and H.M. Ohiendorf. 1991. Contaminants in drainage water and avian risk thresholds.
Pp. 345-368 in: A. Dinar and D. Zilberman (eds.), The Economics and Management of Water and
Drainage in Agriculture, Kluwer Academic Publishers, Boston, MA.
Williams, M.J.-, R.S. Ogle, A.W. Knight, and R.G. Burau. 1994. Effects of sulfate on selenate uptake
and toxicity in the green alga Selenastrum capricomutum. Arch. Environ. Contam. Toxicol.,
27:449-453.
C-95
-------
C-96
-------
William Van Derveer
C-97
-------
William D. Van Derveer
C-98
-------
. William D. Van Derveer
EER CONSULTATION WORKSHOP ON SELENIUM AQUATIC TOXICITY AND
BIOACCUMULATION: PREMEETING COMMENTS
William D. Van Derveer .
Colorado Springs Utilities-Water Resources Department
703 East Las Vegas Street •
Colorado Springs, CO 80903-4348
INTRODUCTION
In preparation for the Peer Consultation Workshop, the U.S. Environmental Protection
Agency (EPA) requested that the workshop participants comment on a series of issues
related to the aquatic toxicity and bioaccumulation of selenium (Se). The EPA issues and my
Comments (in italics) are provided below. Regardless of how the revised chronic water
quality criteria are ultimately expressed: water-column, tissue, or sediment; I hope that it is
based upon sound science and is amenable to site-specific modification where appropriate.
ISSUES AND COMMENTS
I. Technical Issues Associated with a Water-Column-Based Chronic Criterion
1. Besides selenite and selenate, which other forms of selenium in water are lexicologically
important with respect to causing adverse effects on freshwater aquatic organisms under
environmentally realistic conditions?
C-99
-------
. William D. Van Derveer
Comments: Organic Se compounds such as selenomethionine have been shown to be
toxicologically important is some laboratory experiments (e.g., Maier and Knight 1993);
however, I am unaware of any studies that have shown these specific organic Se forms to
occur in the water column of the natural environment. Some studies (e.g., Cutter 1991;
Zhang and Moore 1996) suggest that naturally occurring organic Se forms can be found in
the water column; however, the chemical identity and potential toxicity of these compounds
are largely unknown. .
2. Which form (or combination of forms) of selenium in are most closely correlated with
chronic effects on aquatic life in the field?) (In other words, given current or emerging
analytical techniques, which forms of selenium in water would you measure for correlating
exposure with adverse effects in the field?) Note: Your response should include
_consideration of operationally defined measurements of selenium (e.g., dissolved and total
recoverable selenium), in addition to individual selenium species.
Comments: Waterborne Se concentration alone, regardless of its method of measurement,
appears to correlate poorly with chronic effects on aquatic life in the field. Chronic toxicity
under field conditions does not result from direct waterborne Se exposure, rather, it results
from the propensity for Se to cycle through the food web, the dominant exposure route, and
cause reproductive impairment in fish and wildlife. A review of the literature by Lemly
(1993a) found that "the consensus of research studies is that most of the Se in fish tissues
results from Se in the diet rather than in the water". Limitations in the ability to extrapolate Se
concentrations from water to tissue are discussed in my comments for question 7.
If new water-column-based chronic criteria are ultimately developed, they should account for
C-100
-------
William D. Van Derveer
selenite and selenate individually as their relative toxicity and bioaccumulative potential
differ. Bioaccumulation and subsequent reproductive effects on warmwater fish populations
observed at Belews Lake, NC were the result of selenite discharge from fly ash. The current
chronic criterion for Se is based on studies conducted at that site and thus is based only on
selenite. Studies of outdoor experimental streams in central Minnesota (Hermanutz 1992;
Hermanutz et al. 1992; Schultz and Hermanutz 1990) have been cited as validation for the
current chronic criterion. In these studies, effects on fathead minnow (Pimephales promelas)
and bluegill (Lepomis macrochirus) reproduction and adult survival were observed using
waterborne selenite concentrations of 10 and 30 //g/L. Criteria based upon and validated by
the BeJews Lake and experimental streams studies fail to acknowledge the fact that most
waterborne Se in the western U.S. occurs as selenate. In this region, Se entering aquatic
ecosystems is primarily derived from weathering of selenate from geologic materials (i.e.,
Cretaceous marine shale) not industrial discharges.
With respect to operationally defined measurements of waterborne Se, there seem to be only
small differences between total and dissolved analyses for most field samples. Seiler (1996)
summarized U.S. Department of Interior data from 26 investigations that were conducted
throughout the western U.S. and found that total and dissolved Se concentrations were
approximately equal at concentrations in excess of 10 ^g/L and that moderate variability
exists at concentrations below 10 jjg/L Seiler (1996) concluded that the likely source of the
observed variability was Se-bearing suspended particuiates and cautioned that the difference
' • ' • i " '
between total and dissolved Se concentrations may be greatest in highly productive waters
where large algal populations are present.
3-A) In priority order, which water quality characteristics (e.g., pH, TOC, sulfate, interactions
with other metals such as mercury) are most important in affecting the chronic toxicity and
C-101
-------
William D. Van Derveer
bioaccumulation of selenium to freshwater aquatic life under environmentally realistic
exposure conditions?
Comments: The only water quality characteristic/of which I am aware, that may modify
chronic Se toxicity is sulfate. There is some evidence to suggest that the chemical
similarities of selenate and sulfate allow sulfate to reduce the acute toxicity of selenate in
laboratory exposures. High dissolved sulfate concentrations can substantially reduce the
acute toxicity of selenate to aquatic invertebrates (Ingersoll et al. 1990; Maier et al. 1993;
Ogle and Knight 1996). Since sulfate appears to reduce the short-term bioavailability of
selenate it is plausible that a similar effect may occur during long-term field exposures.
_3-B) Of these, which have been (or can be) quantitatively related to' selenium chronic toxicity
or bioaccumulation in aquatic organisms? How strong and robust are these relationships?
Comments: I am not aware of any studies that have specifically focused on the potential
interaction of sulfate and selenate from the standpoint of chronic toxicity or bioaccumulation
during long-term exposures.
3-C) How certain are applications of toxicity relationships derived from acute toxicity and
water quality characteristics to chronic toxicity situations in the field?
Comments: Extrapolation from acute toxicity data to chronic toxicity situations in the field is
inappropriate for Se. Acute Se toxicity is caused by direct waterborne exposure whereas
C-102
-------
. William D. Van Derveer
chronic Se toxicity under field conditions is caused by excessive dietary (food web) exposure.
These two exposure pathways are sufficiently distinct as to prohibit valid extrapolation
between acute and chronic toxicity data. Moreover, the degree of dietary contamination at a
given site is a function of many site-specific factors, which affect the fate and bioavailabjlity of
waterborne Se, thus application of a single chronic criterion to all sites may be inappropriate.
II. Technical issues Associated with a Tissue-Based Chronic Criterion
4. Which forms of selenium in tissues are toxicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions
and why?
Comments: Selenium in the tissues of aquatic organisms is customarily reported as total Se
and is generally considered to be "organic Se" rather than a specific chemical form such as
selenomethionine or selenocysteine. The lack of published information regarding the ;
chemical forms of Se in tissues indicates that significant research would be needed to
develop a full understanding of this issue.
C-103
-------
William D. Van Derveer
5. Which form (or combination of forms) of selenium in tissues are most closely correlated
with chronic effects on aquatic life in the field? (In other words, given current or emerging
analytical techniques, which forms of selenium in tissues would you measure for correlating
exposure with adverse effects in the field?
Comments: As noted above, Se in the tissues of aquatic organisms is commonly reported as
total Se. Use of total Se data may be appropriate for criteria-setting provided the tissue
concentrations that are used to derive the criteria are also based on field exposures.
However, it is plausible that the composition of Se forms in the tissues of field exposed
organisms may vary depending upon the form of Se that was initially released to the
'!,„ ' , ' • • ' ', •'".,,.'"'' ' • . "' ' ' ' " •
environment (i.e., selenate, selenite, or organic Se compounds). Thus, aggregating data
without respect to the released Se form may increase the level of uncertainty associated with
.tissue-based criteria, ^Moreover, tissue concentration data developed from chronic laboratory
or experimental stream exposures (e.g., Besser et al. 1993; Coyle et al. 1993; Dodds et al.
1996; Hermanutz et al. 1992) may not represent the true composition of Se forms that occur
in organisms that are exposed to Se the natural environment. Thus, data derived from these
types of studies should not be used for criteria development unless there is a reasonable
demonstration that the Se forms that accumulated in tissues of the test organisms were
comparable to those found in the natural environment. ,
C-104
-------
William D. Van Derveer
6. Which tissues (and in which species of aquatic organisms) are best correlated with overall
chronic toxicological effect thresholds for selenium?
Comments: The literature pertaining to this issue is varied, suggesting that under certain
conditions, the Se concentrations in an organism's diet, muscle or whole-body, hepatic
tissues, and eggs all can serve as reliable predictors of chronic effects on aquatic life. Other
workshop participants are better qualified to provide an in-depth response to the issue of
specifically which tissues should be measured.
Although it is common practice, the use of whole-body samples to assess Se accumulation is
problematic because it assumes that all of the Se contained within an organism has been
.assimilated. This is not necessarily true because an organism's gut contents can be a
mixture of bioavailable and non-bioavailable materials. The true magnitude'of Se
bioaccumulatipn can be overstated by assuming that these non-bioavailable materials, some
of which may contain Se,;have been assimilated by the organism. This issue can be
alleviated by clearing an organism's gut through depuration or mechanical means prior to
analysis.
In terms of which species of organisms best reflect toxic effects, fish generally appear to be
more sensitive to Se exposure than invertebrates. The fish species that are most susceptible
to Se toxicity belong to the families Gentrarchidae, Clupeidae, Percichthyidae, Percidae, and
Catostomidae as indicated by their elimination from Belews Lake, NC shortly after the
addition of Se-enriched effluent, whereas, species belonging to the family Cyprinidae were
largely unaffected (Lemly 1985a, 1985b, 1993b). It is important to note that gamefish do not
occur in all waters and that tissue-residue thresholds derived for gamefish may not be
C-105 -
-------
William D. Van Derveer
applicable to more tolerant nongame species. Water quality criteria should account for the
relative sensitivity of the biota that are to be protected.
7. How certain are we in relating water-column concentrations of selenium to tissue-residue
concentrations in top trophic-level organisms such as fish? What are the primary sources of
uncertainty in this extrapolation?
Comments: The relationship between waterborne concentration and tissue-residue
concentrations is complicated by site-specific influences on bioaccumulation. Peterson and
Nebeker (1992) observed that the ratio of waterborne Se to tissue Se (i.e., bioaccumulation
factors) tended to be similar within a given study site but markedly different among study
_sites. This may be a result of site-specific factors, such as the waterborne Se form and
concentration and food web structure, that affect the degree of bioaccumulation.
The effect of waterborne Se concentration may be significant as Peterson and Nebeker
(1992) and Zhang and Moore (1996) noted that there is a negative correlation between
waterborne Se and water-to-tissue bioaccumulation factors. As waterborne Se
concentrations increase, the proportion of the Se that is taken up by the exposed organisms
decreases—the relationship is nonlinear.
In terms of criteria-setting, the implications of among-site variability and non-linear uptake
rates are that the use of a single bioaccumulation factor for extrapolation from water to tissue
would yield erroneous results.
C-106
-------
William D. Van Derveer
III. Technical issues Associated with a Sediment-Based Chronic Criterion
Note: The comments in this section are based extensively upon two publications: Canton
and Van Derveer (1997) and Van Derveer and Canton (1997), which discuss the aquatic
chemistry, fate, and biological effects of sedimentary Se. Citations are provided for
information that is not contained within these publications. ''.-'
8. Which forms of selenium in sediments are toxicologically important with respect to causing
adverse effects on freshwater aquatic organisms under environmentally realistic conditions?
Comments: Dissolved 'Se has three potential fates in aquatic systems: remaining in solution,
absorption by organisms, or association with particulate matter and sedimentation. Sediment
is clearly the dominant repository for Se in aquatic ecosystems and sedimentary Se is in the
organic fraction (detritus). Detritus can account for >50% of the aquatic ecosystem energy .
.base and, consequently, the sediment to biota pathway is the most important for long-term Se
cycling. Particulate Se, as sedimentary, detrital, or suspended Se, has been repeatedly
implicated as a causal or contributing factor for food web contamination at sites throughout,
the U.S.
In reference to development of appropriate water quality criteria for Se, Luoma et al. (1992)
reported that "selenium clearly requires a protective criterion based on particulate
concentrations or food web transfer". Likewise, Presser et al. (1994) in summarizing 20
irrigation drainage studies conducted throughout the western U.S., concluded that "the
degree of development of organic-rich sediments (i.e., detrital layers), which is known to
C-107
-------
William D. Van Derveer
accelerate the entrance of Se biologically into the detrital food chain, and anaerobic and
reducing conditions for geochemically sequestering it in bottom sediments, must be taken
into account for determining the potential for bioaccumulation".
Van Derveer and Canton (1997) reported that the concentration of total sedimentary Se is a
reliable predictor of chronic effects upon fish and semi-aquatic birds. Based on a review of
25 study sites located throughout the U.S., they identified 2.5 ^g/g as a predicted effects
level and 4.0 jug/g as an observed effects level (all sediment concentrations reported herein
are expressed on a dry weight basis). Total sedimentary Se concentrations of <1.8 yug/g
were consistently associated with an absence of adverse ecological effects (n=i 1). Total
sedimentary Se concentrations of >4.0 ^g/g were consistently associated with observed
ecological effects (n=7) or predicted effects (n=4). Ecological effects associated with total
.sedimentary Se concentrations of >1.8 to <4.0 jug/g were variable, ranging from no effect to
predicted effects (n=5).
For the purpose of this workshop, which focuses solely on aquatic toxicity, these data were
reanalyzed, using the approach described in the original publication, to include only fish.
This reanaiysis revealed a predicted effect level of 2.4 y^g/g and an observed effect level of
4.5 ^g/g (Figure 1). These effect levels are consistent with the "low" and "high" hazard levels
for reproductive effects in fish and birds proposed by Lemly (1996). The six-month average
concentration of sedimentary Se for the central Minnesota experimental streams that were
dosed with 10 /zg/L of seienite was 2.85 //g/g (Allen 1991). This concentration, which is
between the predicted and observed effect levels, corresponded to reduced bluegill survival
(Hermanutz et al. 1992) and developmental abnormalities in fathead minnow (Schultz and
Hermanutz 1990; Hermanutz 1992).
C-108
-------
William D. Van Derveer
The clear delineation between no effects and observed effects concentrations suggests that
total sedimentary Se is a powerful predictor of adverse effects on fish. Little, if any, data on
the direct toxicity of sedimentary Se to aquatic invertebrates are present in the literature.
This may not be an impediment to sediment-based criteria-setting, as invertebrates appear to
be relatively tolerant of Se exposure, largely serving as a conduit for Se transport through the
food web. , '.-.'•'
Figure 1. Reanalysis of Sedimentary Selenium Toxicity Data from Van Derveer and Canton
(1997) Using Only Effects Data for Fish.
9. Which form (or combination of forms) in sediment are most closely correlated with chronic
-effects on,aquatic life fn the field? (In other words, given current or emerging analytical
techniques, which forms of selenium in sediments would you measure for correlating
exposure with adverse effects in'the field?)
Comments: The dominant Se species in sediment are elemental and organic Se, which
typically constitute most of the total sedimentary Se burden. Van Derveer and Canton (1997)
reported that about 85% (n=8) of the total sedimentary Se content was present in the
elemental (mean=42%) and organic species (mean=43%) in streams of the middle Arkansas
River basin, CO. Similar sedimentary Se speciation has been reported at Se-contaminated
coal-fired power plant reservoirs (i.e., Belews Lake, NC; Hyco Reservoir, NC; and Martin
Creek Lake, TX) and irrigation drainage sites (Kesterson National Wildlife Refuge, CA and
Benton Lake National Wildlife Refuge, MT. Comparable speciation has also been reported
at uncontaminated freshwater lakes/reservoirs (Phillpott Lake, VA and Lake Murval, TX), a
salt marsh (Great Marsh, DE), and National Bureau of Standards (NBS) Standard Reference
C-109 . '
-------
William D. Van Derveer
Material (SRM) river and estuarine sediments (SRM 1645 and 1646).
My Graduate research (Van Derveer 1997) examined the relationship between sedimentary
Se concentration and Se accumulation by Chironpmidae larvae (midges) inhabiting streams
of the middle Arkansas River basin, CO. Larval Chironomidae were used to represent
detritivorpus benthic invertebrates because of their abundance, wide distribution, importance
in aquatic food webs, and demonstrated capacity to accumulate high concentrations of Se.
Paired sediment and Chironomidae samples were collected at ten lotic sites along a
sedimentary selenium concentration gradient. Surficial sediment samples were characterized
through Se and total organic carbon (TOC) analyses of bulk and <63-vm size fractions.
Samples of depurated Chironomidae larvae were analyzed for Se concentration as well as
taxonomic and functional feeding group composition. Step-wise linear regression determined
that bulk sedimentary Se explained the highest proportion of the variance in larval
Chironomidae Se accumulation (R2 = 0.817, p = 0.0003, standard error of estimate ±1.6
A*g/g)(Figure 2).
C-llO
-------
William D. Van Derveer
Figure 2. Relationship Between the Concentrations of Selenium in Bulk Sediment and
Chironomidae Larvae in Streams of the Middle Arkansas River Basin, CO.
following is the regression model that was developed for Chironomidae Se on bulk
sedimentary Se, after correction for transformation bias:
Chironomidae Se = 12.3716 (bulk sedimentary Se)0.7799 * 1 10. :
Chironomidae samples were structurally and functionally, similar across all sites except one.
Collector-gatherers and shredders were the co-dominant functional feeding groups at all sites
.except one site where'predators were dominant. The co-dominance of fine and coarse
particulate detritus feeding taxa may have resulted in the superior predictive capacity of bulk
i - .
sedimentary Se relative to fine sedimentary Se. •
A common issue encountered in field-observational studies, such as this, is ascribing
causation to correlative relationships. A case for causation can be advanced based on
knowledge that (1) Se in sediment is generally associated with detritus (Van Derveer and
Canton 1997), (2) most Se in consumer organisms is derived from their diet (Lemly 1993a),
and (3) a majority of Chironomidae larvae; including those collected in this study, are benthic
detritivores. Thus, the cycling behavior of Se arid the feeding ecology of the study organisms
support the validity of the empirically derived model of Se accumulation by Chironomidae
from bulk sediment.
C-lll
-------
William D. Van Derveer
The quality assurance/quality control information associated with these unpublished data are
provided below. Limits of detection for Se in sediment and Chironomidae ranged from 0.1 to
0.2 yug/g and 0.3 to 1.0 //g/g, respectively. Procedural blank Se concentrations (n=11) were
below the limit of detection for all but one blank, which was less than 5% of the lowest
measured concentration for any field sample or SRM. Selenium recoveries for SRM 1646
(estuarine sediment)(n=7) and SRM 1577a (bovine liver)(n=4) were within the reported or
certified ranges. Duplicate sedimentary TOC analyses (n = 2) yielded identical results and
recoveries for laboratory control standards (n = 2) were 112.9 and 120.0%.
In priority order, which sediment quality characteristics (e.g., TOC, etc.) are most important in
affecting the chronic toxicity and bioaccumulation of selenium to freshwater aquatic life under
environmentally realistic exposure conditions? Of these, which have been (or can be)
. quantitatively related tb selenium chronic toxicity or bioaccumulation in aquatic organisms?
Comments: A positive relationship between sedimentary Se and organic carbon or carbon-
containing materials (i.e., detritus) has been reported under a broad range of environmental
conditions including microcosms; lake enclosures; and numerous studies of freshwater,
marine, and estuarine environments. This correlation may be due to many factors including
deposition of biogenic particles (detritus) with associated organic Se compounds, uptake of
Se by surface biofilms on organic matter, and dissimilatory reduction of waterborne selenate
to elemental Se by sedimentary.
Total organic carbon appears to be the most important sediment characteristic affecting
chronic toxicity and bioaccumulation of Se because it is highly correlated with the
concentration of sedimentary Se, which in turn is a powerful predictor of bioaccumulation and
• C-112
-------
William D. Van Derveer
subsequent effects upon aquatic biota (see comments for question 8). In my Graduate
research (Van Derveer 1997, summarized above) sedimentary TOG did not explain a
statisticallysignificant proportion (p = 0.4 and 0.6 for bulk and fine sediment regressions,
respectively) of the Chironomidae Se variance. This may. have resulted from the high degree
of collinearity between sedimentary Se and TOG—both variables were not required to explain
the Chironomidae Se variance. This phenomenon, where sedimentary Se accumulation is.
_x • ' -
determined by the amount of sedimentary organic carbon present, is apparently widespread.
With respect to criteria development, sedimentary TOG need not be addressed directly.
Rather, the criteria should in some way account for the quantity of sedimentary organic
carbon present at a given site.
How certain are we in relating water-column concentrations of selenium to sediment
..concentrations? What are the primary sources of uncertainty in this extrapolation?
Comments: Van. Derveer and Canton (1997) developed an empirical relationship between
sedimentary Se and an interaction term of waterborne Se (as mean dissolved) and
sedimentary TOG for streams of the western U.S. This model was derived through stepwise
regression analysis of dissolved Se, sedimentary TOG, and. the interaction term of dissolved
Se x sedimentary TOG for streams of Colorado. The resultant model was validated using
data for streams in Wyoming, South Dakota, and Nevada. Comparison of the actual and
modeled data for the validation sites revealed that the model is a sound empirical
representation of the sedimentary Se accumulation process in western U.S. streams. There
is a high degree of certainty associated with the ability to predict sedimentary Se
accumulation in streams of the western U.S. based on the dissolved Se x sedimentary TOC
model.
C-113
-------
William D. Van Derveer
The sources of uncertainty associated with this relationship include the following:
Specific data for determining the appropriate period of record to be used when averaging
dissolved Se data for relating it to sedimentary Se data do not exist. All available data from
each study was used in model development.
, In some instances, Se and TOC data for bulk or <2.0-mm and <0.063-mm sediment size
fractions were expressed as grand mean concentrations due to sample size limitations in the
available data sets. Addition of data published since mid-1996 may sufficiently increase the
sample size to permit separate models to be developed for each sediment size fraction.
Given the information provided above (see question 8 comments) a model that predicts Se
accumulation in bulk sediment would likely be of greatest utility for criteria development.
This relationship is not necessarily applicable to streams of the eastern U.S., systems where
selenate is not the dominant waterbome Se form, or lentic ecosystems.
Despite the presence of a modest degree of uncertainty, the model described by Van
Derveer and Canton (1997) would be suitable for derivation of site-specific chronic water
quality standards for western streams or possibly for regional chronic criteria for streams of
the western U.S. The uncertainty associated with this approach can be reduced substantially
by collecting site-specific dissolved Se, sedimentary TOC, and sedimentary Se data to test
model applicability.
With respect to lentic ecosystems, Birkner's (1978) empirical relationship between
waterbome Se and organic-carbon-normalized sedimentary Se in lentic systems of Colorado
and Wyoming may be suitable for extrapolating between waterborne Se and sedimentary Se.
C-114
-------
William D. Van Derveer
Cross-Cutting Technical Issues Associated with Chronic Criterion
How does time variability in ambient concentrations affect the bioaccumulation of selenium in
aquatic food webs and, in particular, how rapidly do residues in fish respond to increases and
decreases in water concentrations?
Comment: The effect of time variability in ambient waterborne Se concentrations on food
web bioaccumulation is difficult to assess and I am unaware of studies that specifically
address this issue. Several published studies examine the uptake rates between water and
dietary organisms (e.g., algae and invertebrates) and between dietary and consumer
)'-.''. • ..
organisms (e:g., fish). Data from these types of studies cannot simply be linked together to
-form a composite response timeline for Se transfer from water to diet to fish. Food web
bioaccumulation is most likely a parallel process whereby Se is concurrently accumulating in
or depurating from dietary and consumer organisms in response to the Se concentration in
the environment. It may be possible to determine a permissible chronic exposure period by
reviewing the available literature pertaining to the rate of Se transfer from water to dietary
organisms. Consideration should be given to thfe differential rates at which particular
waterborne Se forms (i.e., selenate, selenite, or organic Se compounds) accumulate in
dietary organisms (Besseretal. 1989, 1993). ,
To what extent would the type of ecosystem (e.g., lentic, lotic) affect the chronic toxicity of
, selenium?
Comments: Inherent differences in Se accumulation and transformation between standing
' F
... .'.--.. . , ' ' C-115 • . •'•':. •
-------
William D. Van Derveer
and flowing waters systems suggest that criteria developed to protect aquatic organisms of
one habitat type may be over- or under-protective of the other habitat type. Lemly (1985a) in
discussing the 1980 EPA Se criteria criticized the EPA because "...they did not adequately
consider differences in the dynamics of Se cycling and the exposure regimes of organisms
between lotic and lentic systems...". .
In contrast to standing or slow moving waters, fast-flowing waters have several
characteristics that make them less efficient at accumulating Se (Lemly and Smith 1987).
These characteristics include the rarity of organic sediment deposits (due to continuous
flushing), lower primary productivity, and a greater dependence on terrestrial carbon inputs.
As a result, the food web of flowing waters have a reduced accumulation efficiency relative to
standing waters.
C-116
-------
William D. Van Derveer
It can be argued that the connectivity between lotic and lentic systems renders the distinction
trivial from a chronic Se toxicity standpoint. Clearly, these types of systems are
interconnected; however, there are instances where Se-enriched streams flow into Se-poor
streams thus dilution occurs before the Se-enriched water enters a downstream lentic
system. In instances where Se-enriched streams do flow directly into lentic systems, it may
be feasible to use the Total Maximum Daily Load (f MDL) process to protect a sensitive
downstream point.
LITERATURE CITED ,
Allen, K.N. 1991. Seasonal variation of selenium in outdoor experimental stream-wetland
• systems. Journal of Environmental Quality 20: 865-868.
_ Besser, J.M., J.N. Huckins, E.E. Little, and T.W. La Point. 1989. Distribution and
bioaccumulation of selenium in .aquatic microcosms. Environmental Pollution 62: 1-12.
Besser, J.M., T.J.Canfield, and T.W. La Point. 1993. Bioaccumulation of organic and
inorganic selenium in a laboratory food chain. Environmental Toxicology and Chemistry 12:
57-72.
Birkner, J.H. 1978. Selenium in Aquatic Organisms from Seleniferous Habitats. Ph.D.
Dissertation, Colorado State University, Fort Collins, CO.
Canton, S.P. and W.D. Van Derveer. 1997. Selenium toxicity to aquatic life: an argument for
sediment-based water quality criteria. Environmental Toxicology and Chemistry 16:1255-
1259.
Coyle, J.J., D.R. Buckler, C.G. Ingersoll, J.F. Fairchild, and T.W. May. 1993. Effect of
dietary selenium on the reproductive success of bluegills (Lepomis macrochirus).
Environmental Toxicology and Chemistry 12: 551-565.
' - ",' C-117 . : ,'••'..
-------
William D. Van Derveer
Cutter, G.A. 1991. Selenium Biochemistry in Reservoirs. Volume 1: Time Series and Mass
Balance Results, EN-7281, Volume 1, Research Project 2020-1. Electric Power Research
Institute, Palo Alto, CA.
Dodds, M.G., D.S. Cherry, and J. Cairns, Jr! 1996. Toxicity and bioaccumulation of selenium
to a three-trophic level food chain. Environmental Toxicology and Chemistry 15: 340-347..
Hermanutz, R.O. 1992. Malformation of the fathead minnow (Pimephales promelas) in an
ecosystem with elevated selenium concentrations. Bulletin of Environmental Contamination
and Toxicology 49: 290-294.
Hermanutz, R.O., K.N. Allen, T.H. Roush, and S.F. Hedtke. 1992. Effects of elevated
selenium concentrations on bluegills (Lepomis macrochirusj in outdoor experimental streams.
Environmental Toxicology and Chemistry 11:217-224.
~lngersoll,-C.A. F.J. Dwyer, and T.W. May. 1990. Toxicity of inorganic and organic selenium
to Daphnia magna (Cladocera) and Chironomus tentahs (Diptera). Environmental Toxicology
and Chemistry 9:1171-1181.
Lemly, A.D. 1985a. Ecological basis for regulating aquatic emissions from the power
industry: the case with selenium. Regulatory Toxicology and Pharmacology 5: 465-486.
Lemly, A.D. 1985b. Toxicology of selenium in a freshwater reservoir: Implications for
environmental hazard evaluation and safety. Ecotoxicology and Environmental Safety 10:
314-338.
Lemly, A.D. 1993a. Guidelines for evaluating selenium data from aquatic monitoring and
assessment studies. Environmental Monitoring and Assessment 28: 83-100.
Lemly, A.D. 1993b. Teratogenic effects of selenium in natural populations of freshwater fish.
Ecotoxicology and Environmental Safety 26: 181-204.
C-118
-------
; • William D. Van Derveer
Lemly, A.D. 1996. Assessing the threat of selenium to fish and aquatic birds. Environmental
Monitoring and Assessment 43: 19-35.
Lemly, A.D. and G.J. Smith. 1987. Aquatic Cycling of Selenium: Implications for Fish and
Wildlife. Fish and Wildlife Leaflet 12. U.S. Fish and Wildlife Service, Washington, DC.
Luoma, S.N., C. Johns, N.S. Fisher, N.A. Steinberg, R.S. Oremland, and J.R. Reinfelder.
1992. Determination of selenium bioavailability to a benthic bivalve from particulate and
solute pathways. Environmental Science and Technology 26: 485-491.
Maier, K.J. and A.W. Knight. 1993. Comparative acute toxicity and bioconcentration of
selenium by the midge Chirdnomus decorus exposed to selenate, selenite, and seleno-DL-
methionine. Archives of Environmental Contamination and Toxicology 25:365-370.
Maier, K.J., C.G. Foe, and A.W. Knight. 1993. Comparative toxicity of selenate, selenite,
..seleno-DL-methionine' and seleno-DL-cystine to Daphnia magna. Environmental Toxicology
and Chemistry 12: 755-763!
Ogle, R.S. and A.W. Knight. 1996. Selenium bioaccumulation in aquatic ecosystems: 1.
Effects of sulfate on the uptake and toxicity of selenate in Daphnia magna! Archives of
Environmental Contamination and Toxicology 30: 274-279, : -
Peterson, J.A. and A.V. Nebeker. 1992. Estimation of waterborne selenium concentrations
that are toxicity thresholds for wildlife. Archives of Environmental Contamination and
Toxicology 23: 154-162.
C-119
-------
William D. Van Derveer
Presser, T.S., M.A. Sylvester, and W.H. Low. 1994. Bioaccumulatjon of selenium from
natural geologic sources in western states and its potential consequences. Environmental
Management 18: 423-436.
Schultz, R. and R. Hermanutz. 1990. Transfer of toxic concentrations of selenium from
1 - , ' {• ' - '.- • , ' ' v; • : ., ' - . : ';,„, .•.',.,
parent to progeny in the fathead minnow (Pimephales promelas). Bulletin of Environmental
Contamination Toxicology 45: 568-573.
f ' r *
Seller, R.L. 1996 Synthesis of data from studies by the National Irrigation Water-Quality
Program. Water Resources Bulletin 32:1233-1245. .
Van Derveer, W.D. 1997. Bioavailability of Sedimentary Selenium to Lotic Chironomidae
Larvae of the Middle Arkansas River Basin, Colorado. M.S. Thesis, University of Southern
Colorado, Pueblo, CO. . ,
Van Derveer, W.D. and S.P. Canton. 1997. Sediment selenium toxicity thresholds and
derivation of water-quality criteria for freshwater biota of western streams. Environmental
Toxicology and Chemistry 16:1260-1268.
Zhang, Y. And J.N. Moore. 1996. Selenium fractionation and speciation in a wetland
system. Environmental Science and Technology 30: 2613-2619.
William Van Derveer
C-120
-------
APPENDIXD
ADDITIONAL REFERENCES PROVIDED BY EXPERTS
-------
-------
Adams, W.J., K.V. Brix, K.A. Cothern, L.M. Tear, R.D. Cardwell, A. Fairbrpther, and J.E. Toll.
1998, Assessment of selenium food chain transfer and critical exposure factors for avian
wildlife species: Need for site-specific data. In E.E. Little, A.J. DeLonay, and B.M.
Greenberg, eds., Environmental Toxicology and Risk Assessment: Seventh Volume
AS7MSIP J333. pp. 312-336.
Besser, J.M., J.N. Huckins, E.E. Little, and T.W. La Point. 1989. Distribution and
bioaccumulation of selenium in aquatic microcosms. Environ. Pollut.62:1-12.
Canton, S.P. and W.D. Van Derveer. 1997. Selenium toxicity to aquatic life: An argument for
sediment-based water quality criteria. Environ. Toxicol. Chem. 16:1255-1259.
Cutter, G.A. 1989. Freshwater systems. In M. Binat, ed., Occurrence and Distribution of
Selenium. Boca Raton, FL: CRC Press, Inc. pp. 243-262!
Cutter, G,A. 1991. Selenium Biogeochemistry in Reservoirs. Volume 1: Time Series and Mass
Balance Results. EN-7281, Volume 1, Research Project 2020-1.
Cutter, G.A. 1992. Kinetic controls on metalloid speciatioh in seawater. Mar. Chem. 40:65-80.
- " ' J ' '"
Cutter, G.A. and L.S. Cutter. 1994. Behavior of dissolved antimony, arsenic, and selenium in the
Atlantic Ocean. Mar. Chem. 49:295-306.
Cutter, G.A. and M.L.C. San Diego-McGlone. 1990. Temporal variability of selenium fluxes in
San Franciscp Bay. Sci. Tot. Environ. 97/98:235-250. ;
Fan, T.W.-M. and R.M. EBgashi. Biochemical fate of selenium hi microphytes: Natural
bioremediation by volatilization and sedimentation in aquatic environments.
Bioremediation in Aquatic Environments, pp. 545-562.
Fan, T.W-M., A.N. Lane, and R.M. EGgashi. 1997. Selenium biotransformations by a euryhaline
microalga isolated from a saline evaporation pond. Environ. ScLTechnol 31:569-576.
Fan, T.W-M., A.M. Lane, D. Martens, aiid R.M. Higashi. 1998. Synthesis and structure
characterization of selenium^metabolites. Analyst 123:875-884.
Gobler, C.J., D.A, Hutchins, N.S. Fisher, E.M. Cosper, and S.A. Sanudo-Wilhelmy. 1997.
Release and bioavailability of C, N, P, Se, and Fe following viral lysis of a marine
chrysophyte. Limnol. Oceanogr. 42(7): 1492-1504.
Lemly, A.D. and GJ. Smith. 1987. Aquatic Cycling of Selenium: Implications for Fish and
Wildlife. United States Department of the Interior, Fish and Wildlife Service Leaflet 12.
v. Washington, DC. Document Number 149.13/5:12.
••''.'. . D-r • •" •' ,-.'•.
-------
Maier, K.J., C.R. Nelson, F.C. Bailey, SJ. Klaine, A.W. Knight. 1998. Accumulation of selenium
by the aquatic biota of a watershed treated with seleniferous fertilizer. Bull Environ.
Contain. Toxicol 60:409-416.
Presser, T.S., M.A. Sylvester, and W.M. Low. 1994. Bioaccumulation of selenium from natural
geologic sources in western states and its potential consequences. Environmental
Management 18:423-436. .
Spallholz, IE. 1994. On the Nature of selenium toxicity and carcinostatic activity. Free Radical
Biology &Medicine 17:45-64.
Van Derveer, W.D. and S.P.Canton. 1997. Selenium sediment toxicity thresholds and derivation
of water quality criteria for freshwater biota of western streams. Environ. Toxicol. Chem.
16:1260-1268.
Zhang, Y. and J.N. Moore. 1996. Selenium fractionation and speciation in a wetland system.
Environ. Sci., Technol. 30:2613-2619. . ' .
D-2
-------
APPENDIX E
-. . • / ••• • '•/
PRESENTATION MATERIALS
-------
-------
•I
li
3
ivision
!
a
ater
« ^
|i
ou
>.
5s O
^ ..
a w ««
ee • o
'CO CO o>
«- ^ «
•5 i-3
Offi
^^^
C8'
W T^
*53o g
o -S
•§•?
Ed '£
•g.a-
C3
W
•I
»:
^>
O
« '
^
•**
;aq
•^
«•
«
£>
•**
o
•<•*
X
.£
'*«
5-
*M
C
•js
ea
C
OJ
&
«
• «
^
^
1
•**••
1
*.'
00
ON
2
oo
f^l
tf-
s
I
1
i
s
I
05
I
•s
3
O
a
v
g
CQ
M
E-l
-------
OS
0
0"
.g
«
s->
«
^
J=
&H4
O
i
-B
ss
o
TO
CJ
.S
=
'S
Of)
s
o
I g
o 8
e3
JH
> s-*
- «
"3 -a
£ fi
o o
&
G6
s
o
o
d
o
S3
O
S-
eS
S
*3
«*H
O
S3
o
-4->
3
pQ
«
ns
«
>
cs
o
• PN
^
^
=
eg
53
O
5S
•PN
T5
O
S
•S
0>
53
*
-d
1
W)
O
o
TS
T3
C5
O
13
il a
3
1S
A
a.
o
o
I-N &D O
•= i
^N "
2 fl T3
riMM - — • r^^l
ues
ronmen
M •£
05 ^>
•^ S3
13 ^
"S 'S
^ .£
SJ3
>.
TO ^
•§ '
3
^
•'•N A
WD ^
S UO
^ S3
S «
TO ^
^H pV
o sa
S3 *
O QC
•pN X—i
11
0 TO
P fo
E-2
-------
Review
ss
o
O
o
*->
=
^
E
TS
CS
S3
cr
&£
S3
S
C
0
fi
O
-M
cs
I-H
53
%
•s
o
o
-
S3
S3
E-3
-------
" a
i
i
i
o
0
o
V3
CJ
o
fa
fi
o
eg
P
cr
eg
^^v
1
je
lu
« a
•S I
a *C
•5 -I
ST »i^
M
00
ON
\
ss
u
u
u
^^
1
w-
agnitude
CJ
o
.2 -
£ $u
^j !^
^ fc,
•80 st
s: ^
•s »t^
feC &
5* fe
^ '8
^ r^
^ ^
r\
C3
CJ
C5
e
11
'•g • w>
5S *C
cc O
s a
cs *s
o 3
•PM ^
fl
e tec
o
C/J
E'-4
-------
O
£
d
o
'S
^^j
^^^j
r
•I-*
d
o
U
d
G
O
d
vi
d
05
05
Q
O
8
d
05
d
o
E
t;
05
O
•p*
»5
QC
O
S-
ON
S
2
So
S!
O
05
0
^ 05
PPN 05
0> -M
P* 05
Q ^
•s S
X3 O
.•« *^2
5 *
^1
W5 d
^ S
o ^
-S 2
* 1
rh-S-
G
E
o
"3.
'd
Decide which environ
criterion
f
feX
c
05
05
o
^
•PN
T3
o
E
05
e
Decide on the chemica
ssess factors affecting
•
agnitude
the
o
CJ
ency
s
c.
"M _i
o d
v« o^
IS .g-
cc «b
E-5
-------
j£
42
s->
M
o>
£
riteria Review Activities:
U
Cu
jjl
O
(DD
•a
o
•S
fe
^
CJ
^^
&
§
Formation of EPA seleni
rH
•
&5
su
S
•8
a
**>
i$*
"8
&
j.
•^jf
•»•*
'a
S
t
I
&
S
0
00
ON
ON
"3
^^j
^^^j
^^S
j*5
'S
M
e •
i
.2
•p
^3
MH
a
Complete Acute Criterio
r
-------
fl
O
u
O
13
0
O
s
cc
c
o
1^
feil O
% ^
^sa
ON
.ON
•S2
s
fc-
• •
Review Activities
cs
•c-
o
^»
•c
^•^
fl
o
*C
PN
O
•c
u
o
•IM
c
2
^=
u
«
s
•"ft
=
O
7- \
u
o
0
O'
73
o
•«• ^
ature review
«
•15
^
g.
^
««.
^
v^
consultation work
Is
•$
•§>
|
^
I
GT5
1
1
0
42'
Si
i
• .
>*
.^,
•»^
&^
.- draft m anusci
•^
*««*
.«.
***
^
t
^
s
S-
6
^
^
i
r activities
<&
i
s»
§
k^^
^3
f
1
t for peer review
^
i
review/final draft
1
^
E-7.
-------
Figure 1. EPA's Review of Freshwater Selenium Aquatic Life Criteria
Acute Criteria Activities I
(CMC) j
t
DRWTCMC
Aoocnvrrr
APPROACH (GU)
Chronic Criteria Activities
(CCC)
PROPOSED GU
CMC APPROACH
(I 1/96)
LIT. REVIEW
Se Peer
Consultation
Workshop
Site-Specific Criteria
Guidelines Activities
AND ACUTE ^v
Tbxicmr ./
V TfcSTINO .S
W 1
s
f
MONTIC
E*PERIM
STREAM
1
gi tit B
ENTAL I
STUDT i
' t
r
EPA-Established Selenium Criteria Workgroup
Draft Site-
Specific
Criteria
Guidelines
FinarcMC
(National & GLI)
Final CCC
(National & GLI)
Final Site Specific
Criteria Guidelines
E-8
-------
O
CO
CO
o
o
0
CD
o
o
C5)
CD
4—»
CO
CD
0
CO
0 ^
CO O
03
D
CD
f
1
"
1
s
E-9
-------
o
0
O
i—*
CD
t
E-10
-------
03
-i—*
C
0
C/)
0
Q_
0
CO
CO
0
0
CD
O
0
CO
0
••HIM
CO
o
CO
CO
CD
I
CO
E
xo
E
zj
'c
CO -t ^
CO
0
CO
o
o
S ro
B.g
o
ro •£
£.' O
c
o
CO
CD CO
CD o
»1
CD
0
o ^
0
i E
CO
0
CO
co
0
0
CO
O
o
xo
o
CO
o
Q_
Q.
CO
T5
0
CO
CO
^5
(D
CO
CO
£ £
I . I
CO
0
3
CO
tco
E
5
'c
0
0
CO
c:
0
E
0
CO
1
CO
0
CO
*7Z O)
O
i
CO
CO
Q
o
l
CO
•i—I
c
0
£
o
5 O
CD
£
0
CO
Oi
s
E-ll
-------
o
CO
o
CO
CO
0
o
o
CO
co
£
0
D)
"0
CO
0
o
CO
c
~ o
CO
03
0
CO
-c
0
0.
X
0
CO
CO
Z5
O
CO
Q I " I Q
CO
0
O
O
D)
0
0
Q.
0
summ
f
I
K
c—
0
CO
CO
— «
_.J
o
CO
a)
"£
0
E
c
O)
• ^mmm
CO
CO
05
D)
C-
T"
I I
E-12
-------
CO
4—»
o
O
c
CO
O
GL
LU
o
a.
CD
CO
0.
CO
E
3
CO
c
o
^*—»
CO
•*—»
c
0
CO
CO
CO
CO
13
O
CO
O
O
0
ormato
I I I
CO
"»—»
c:
0
£
o
o
O)
0
0
£
Q.
1
I
1
S!
E-13
-------
E-14
-------
BELEWS LAKE:
LESSONS LEARNED
A. Dennis Lemly
Department of Fisheries and Wildlife
> Virginia Tech University
Blacksburg, VA 24061-0321
E-15
-------
• Xctolurtdoo
-Contrarehldao
——I—Catostomldao
—Porclehlhyldao
\ Ctupoldao
Pcreldoo
\
I
Cyprfntdao. -
• Poocilildao >
1973 ' t ' 75t' 77
linltl Units
1 79 ' '81 '83
E-16
-------
BELEWS LAKE
0 -1 Z
KWSKETES
E-17
-------
• •*••*•«*• If *'*• * * * "
E-18
-------
100:
10-
Z
2
Ul
«n
*
a:
1-
MlL
Jl-HH~r
O V/alor
• Scdlmonl
A Bonthos
* Plankton
O Flnhoo
I973 ' f ' 75 I
Unit I '
75 |' 77' ' 79 ' ' 81
YEAR
E-19
-------
E-20
-------
M
e E
c o
.23
ex
0) M
0 8
.i» v
00 y
V
« 2
S3-
I<
1
e
s?
o
o
i!
f JSi
I ^
2 o
tt 4)
II
(0 Q)
T5 *
2-£
O u
^'S
•o tS
•« -s
c uj
o
Q
s?
3
£
«
8
u
1
S °£
•— 1 m
O S W
rt **
rt » w
»W M *^M
« II
'Ml
u i«
-s?u> 3
OJ *J U
"o fe c
« 8 .2
2-§5
•wee!?
"S c S
rt « 3
•El|
032
Gregory Cutter
d Dominion UniVers
*•? t
S^L§
q,
E-21
-------
Experimental Research
Benedict Estuarine Research Center
Philadelphia Academy of Natural Sciences
Dr James G. Sanders (Principal Investigator)
Uptake
Elimination
Toxicity
Biogeochemical
Processes
Bacteria (natural communities,
pure culture)
Phytoplankton (natural communities,
green, diatom, blue-green)
Protozoan (ciliate)
Zooplankton (daphnid, copepod)
Benthic invertebrate
Fish (fathead minnow)
Oxidation
Reduction
Volatilization
Organic particle
regeneration
Sediment fluxes
ill: 5;
Different Se Forms
Food Exposure
Water Exposure
Water Chemistry Effects
(pH, SO4, nutrients, ions)
Fish Tissue Kinetics
Fish Reproduction..
E-22
-------
Relationships Between
Model Components
Toxicants (h Water*
and Sediments
BIOGEOCHEM1CAL
i MODEL
PHARMACOKINETIC
MODEL
Uptake and
Elimination
Fluxes
Tissue
Concentrations
Toxicants In Water Toxicants
and Sediments in Food
Uptake and
Elimination Rates
Population Densities,
Biological Process
Fluxes
TOXIC EFFECTS
MODEL
ECOSYSTEM EFFECTS
MODEL
Effects on Growth,
Reproduction, Mortality
E-23
-------
'it
E-24
-------
Water Quality Effects on
Algal Uptake
c
o
Selenite
05 L
I I II I
3 5 6 7 8 9
£ pH
3 . ' . •-- ••
O
O
E
3 ,
•••i
c
"o
> ' "
'V- : ;. Selenite
H ' •
^*^^^*sw ^^v • ^ '
*" ^^^*!!*S:SS!Bne=as«S!»SSTSs^^ v.^V
|— t I I - I . J
-= 0 20 40 60 80 100
Co '
*W • • < «^^^ t • M\
O) PO4((lM)
< v v:. • . v" -.-
Selenate
0 200 400 600 800 1000
E-25
-------
E-26
-------
E-27
-------
E-28
-------
Fathead Minnow
Selenium Accumulation
Foodborne selenomethionine
Waterborne selenite
50 T Liver
30 food (jig/g-dry)
+ 30 water (jig/I)
30 food
13 food + 13 water
13 food
30 water
13 water
0 28 56 84 112 140
50 n Muscle
30 food
30 food + 30 water
13 food + 13 water
13 food
30 water
13 water
0 28 56 84112 140
Time (days)
E-29
-------
E-30
-------
Total Dissolved Selenium, 1985-1987
Epilimnion
20
16-
12-
8-
4-
0
'85
'86
'87
Hypolimnion
20-,
16-
12-
8-
4
'85
'86
'87
Data from CP&L
E-31
-------
'ill
Selenium Speciation
in Epilimnion
12-j
10-
8
6
4
Selenite
6
4-
2-
0
'85
Organic Selenides
'86
'87
'85
'86
'87
Data from Cutter, 1991
E-32
-------
Selenium
in Hypolimnion
12-, Selenite
'87
6 n Organic Selenides
1
2n Selenate
'85
'86
'87
E-33
Data from Cutter, 1991
-------
, ";;, I1'!.:1- i iff .i1;1!*: • ' 4
total Dissolved Selenium, 1985-1992
Epilimnion
20-1
16-
12-
8H
Dry ash disposal
started Jan. 1990
'85 '86
'8?' '88' '89' '90 '91 '92'
Hypolimnion
20-1
16-
12-
'85 '86 '87 '88 '89 '90 '91 '92
DatafromCP&L
,E-34
-------
00
O
u
I
1
a.
I
CM
CM
•o
o
o
Ik
1?
£
.0
CM
O>
O)
•^
O
O)
CO
CO
».
E5
•s
~tO
00
•k
"in
CO
1
o o o o o o o
CM O CO <0 «* CM
1 1 1 r
O O O O O
CM O CO CO *T
O O
CM
Ajp-6/Brl
A4p-B/6ri
E-35
-------
i
CM
,2
_o>
o)
V)
•O
O
o
t»
M
CO
0
in
CM
o^
O>
••••••i
3
O
u
o
"35
•"••••••• ^^^^
Q Q>
U)
c
«*
z =
C6 o
CO
o
o
CO
£
o
Q.
CD
CO
£
o
X
5 "fi
o
P
CO
*-l
O
0)
CO
0
CO
CO
O
CD
CO
CO
Q.
0)
CO
x
o
o
CO
E-36
-------
LO
00
01
G)
M
O
|
UL
|
CM
CM
c
o
"o
-a
CD
BO
"co
O)
(1)
CO
0)
CO
0)
g
o
O
s
0)
CO
0)
o
a.
0)
CO
0)
o
a.
0)
CO
!=
O
CO
H- 0)
0
CO
O
Q.
O
O
CD
•o
i
0
O
a.
o
CO
i
o
a.
-------
JS
3
LO
o
CO
E-38
-------
(0
H s
Vl CD
O
£
I
01
CO
£
^
O
O
S
13
JQ
0
"•5
0
E-39
-------
DJO
3
"w
e
o
u
0 flj .2*
> fS
O Q.
u C
u C
o •=
•? i
M
^^
fd
"2 c
c o
*-l
f'i
•^ a.
^ M
^ O
rt ^
i ^
3 %
* a
"3 .£
•^ S
wO i>
O O
II
ation
3
U
^
0>
U)
V)
0)
•D
£•
11
« S
•s £
-Q ^
2'
2 &
z £
rt o
S |
0) fc
fe^
en
% £
ȣ
Cc
(\J
.2 d
IS I
= z
f •?
CO
E-40
-------
0
X
0
o
0
D)
CO
O
CD
o
0
0
o
o
CO
CO
CO
0
0
CO
0
en
g
o
o
4—
o
"0
CO
CO
0
CO
CO
CO
I I
03
c
03
••MM*
Q.
X
0
0
O
-= 0 -^
0
E
13
O
CO
T3
I
0
"o
O
O
= a
s -
°"--i
co 5
« |
p^
CO
to
0
-------
CM
CO
X
0
O
0
O>
O
CD
CD O..C
CO Q
C CD
CD CO "O
Q o co
.g
0
+-»
O
"cc
c:
O
4—»
03
C
03
O
CO
03
O
O
E
1
I
i
5
E-42
-------
CO
CD
ZJ
CO
CO
g>
X
t± 0
CO
0 05
CO C
CO
-I-J
0
^H
•^
•^
I
CO
E
CD
O
2
'c
.0
CD
CO
CO
CO
Q. O
«... .22
0
0
f
E-43
-------
CO
0
CO
CO
C
o
Q)
(Q
-Q
-------
^^ *•
issues... [2
-
*
fi
^
^..^
^
o
O^
^^•^
c
.0
c
^>
'5
* k.
issue based c
/
^py
^^•^
• •
c
o
Disagreement
•v*
ii
•••^^^^
Hh-*
0
"S)
1
0
Z3
CO
L—
£
0
o
c
0
"o
CO
*1
o
i
-5
to
I
^
<;
'
correlations
--J
, • JL
1*X1
¥
0
CO
CO
JD
JO
lo
-o
- sufficiency of
0
13
CO
CO
•^^ w
_o
lc
>
c
0
^•^^
CO
CO
' ~ \0
0
£
o
-1— »
E
Z5
"c
0
0
CO
^
E
£
i
• .
Agreement on
b
0
o
a**tm>
0
CO
CO
c
.2
'co
0
&_
0
o
0
Z3
CO
_co
1
0
CO
£
1
3
H— '
0
o
MfltaiM
0
CO
CO
_g
'co
0
L_
O
o
CO
^* +
13
0
i
0
13
CO
_co
1
]0
1
i
I
•»••*
I
s
E-45
-------
CO
CD
CO
CO
c
o
CD
<0
TO
c
CD
.i
•o
0)
to
O :=
g
)—>
CD
o
O
O
s
0
o
0
CO
CO
0 CD
Q.
CO
CD
"2
0
0
CO
0
0
2
O)
CD
CO
Q
CO
£
0
CO
CO
c
g
+—*
CO
0
o
c
o
o
0
~" CO
0
0 =
CO CO
*-' c
i i
o
o
1 fl i
\ \
£
0
o
0
0
CO
I
.1
s
.
E-46
-------
es
ss
Q)
0)
05
CO ±±
i i
CD
q> .£
O -^ -=i
see
c/)
O C/)
8 !-•§
o
CD
*—»
CO
CO
o
CO
i I i S
I
*
1
E-47
-------
E-48
-------
APPENDIXF
OBSERVER PRESENTATIONS
-------
-------
^
*>
5 ^
Q £-•
*XJ
Co <^>
Q
SS
<^>
-^
^
>*A
«
^
^•^
'**««*
^S
s
^
^
QJ
«
»^«
^
&
m
Co
.8.
«
.^
•-s
•r-o
S
^
^^^^^X
"^4
^j
CO
;?-
K
• R"-s
O
• *^ ^
^^*
co
•*^a •
2J
cS
^
o •»
^ o
1 OT
8 "g
§< ••$
£4
-------
F-2
-------
o
o
o
o
o
St
S
:S
0)
(6H/6UJ) uiniusiag 663
•S'3
•T—I 5?
> .2
cfl O
a- s £ 'S'
° *s o -a
Cd t ^H |H
o
o o
s: a
o
C/)
13
'o
CD
O
c«
1
> t ''
§ '3
° §•&
S.i
§!
••8-
F-3
-------
^ TJ *> $2
-------
CO
a
.2
1
Mandated red
i
O
• 1— 1
•s
s-
CD
!
CO
CD
•a
/o
*o
1
CD
O
Selenium rem
CD
W)
CO
a
• o -• •..
o
10
o
-8 -•
2
CO
CO
O
0
Environmenta
w
CD
O
a.
-B-
CD
00
generated /Ib
0
I
00
£
o
o
o^
-------
F-6
-------
COMMENTS SUBMITTED BY
THE UTILITY WATER ACT GROUP
DURING EPA'S PEER CONSULTATION WORKSHOP
ON SELENIUM AQUATIC TOXICTTY AND BIO ACCUMULATION
May27,1998
Good afternoon. My name is Robin Reash. I am employed as an aquatic biologist with
American Electric Power Company in Columbus, Ohio. I present these comments on behalf of the
Utility Water Act Group, or UWAG for short. UWAG is an association of 95 individual electric
utility companies and three national trade associations of electric utilities. UWAG is interested in
EPA's re-evaluation of the freshwater chronic aquatic life criterion for selenium because selenium
is a natural trace element in coal and many of UWAG's members use coal as the primary fuel for
electrical generation. .
As a starting point, UWAG commends EPA for this new process of revising a water quality
criterion. The establishment of an external expert panel is a positive step in assuring that the
scientific and technical issues are discussed thoroughly. UWAG appreciates the opportunity for
interested_stakeholders to voice comments at this early stage.
UWAG's primary concern is that the Agency may be considering establishment of a
universal numeric criterion value for selenium mat would be used for the protection of all designated
uses among States. This is of particular concern to UWAG members that use wet ash disposal of
coal fly ash and bottom ash, wastewaters that are discharged to all types of waterbodies. Potential
water quality-based effluent limits for selenium, applied to such treated wastewaters, would be based
on EPA's revised chronic criterion. In short, UWAG views a universal numeric chronic criterion
for selenium as wholly inappropriate. ,
UWAG encourages the Agency to recognize that site-specific factors drive the potential
chronic toxicity of selenium. The Agency's existing chronic aquatic life criterion of 5 parts per
billion was based on implicit assumptions of bioaccumulation within one type of waterbody setting
(i-e., a significant waste water discharge in a relatively closed system). However, the potential for
bioaccumulation and/or direct water column toxicity is clearly not the same for all waterbodies.
Receiving streams have a wide variety of physical and chemical properties that can affect the
potential for toxicity. Hydrological retention time may substantially affect the potential for
bioaccumulation of selenium. While Belews Lake, which EPA primarily relied upon to establish
the existing chronic criterion, has a retention time of about 4 1A years, Lake Erie is a relatively
"open" system, having a hydrological retention time of only 2.6 years. Running waterbodies such
F-7
-------
as streams and rivers have retention times in periods of hours or days. UWAG urges the Agency to
consider distinctions in applicable criteria by waterbody types.
UWAG urges the Agency to focus carefully on the factors affecting the propensity of ^
selenium to bioaccuniulate on a site-specific basis. UWAG cautions the Agency that use of a.
bioaccumulation factor, as in the Great Lakes Water Quality Guidance rulemaking, is not an
appropriate mechanism to measure the bioaccumulative potential of a pollutant. Indeed, recent
technical papers (e.g.. the February issue of Environmental Toxicology and Chemistry) have been
highly critical of the BAF approach to characterize the relative risks of mercury bioaccumulation. .
In UWAG's comments on the GLI Guidance, we explained at length our concern that the proposed
bioaccumulation factor did not adequately characterize variability over time. UWAG refers the
Agency to those comments for further discussion of this issue.
UWAG is aware that some researchers advocate a low parts per billion chronic criterion that
would serve as a suitable "safety net" for all possible exposure settings. Bioaccumulation-induced
effects to fish and/or wildlife have been documented, or have been projected to occur, .in cases where
water column selenium concentrations were lower than 5 parts per billion. Thus, in some settings,
a low parts per billion*criterion would be appropriate. While promulgating a generic, one-
"concentratibn-fits-all criterion that protects the most sensitive ecological receptors in the most highly
exposed setting sounds good theoretically, such an approach ignores the significant advances in bur
understanding of selenium cycling and the site-specificity of selenium toxicity. It ignores the role
of sediments, food web structure, and differential bioavailability of the various inorganic and organic
forms.
UWAG also would like to comment on the issue of whether certain toxic effects can be
expected to occur in fish when tissue levels of selenium reach pre-established thresholds. UWAG
notes that bioaccumulation is a process, which may or may not be synonymous with adverse
population-level effects. UWAG would like to emphasize the point that in the three well-studied
power plant cooling lakes - Belews Lake, Hyco Reservoir and Martin Reservoir - seleniuni was the
only trace metal elevated in biotic and abiotic components. Fly ash discharges typically contain
highly variable mixtures of trace metals, with relative proportions dependent on numerous factors.
Recent studies at fly ash pond receiving streams in Ohio and West Virginia showed an absence of
population crashes in sunfish populations that had elevated levels of several trace metals. (Reash,
etaL manuscript submitted for publication.) Thus, UWAG strongly urges EPA to avoid usage of
a rigid "tissue threshold" in setting a national criterion or reviewing a site-specific criterion request.
If tissue levels are used, they must be interpreted in conjunction with several population-level
parameters.
F-8
-------
As a final comment, UWAG notes mat, for the chronic selenium criterioiL, there is an absence
of EPA technical guidance for site-specific criteria development UWAG believes that technical
guidance on site-specific criteria development for adjustments of the applicable chronic criterion
should be a necessary parallel objective of the criterionTrevision process.
In summary, UWAG has no numeric criterion value that we can recommend to EPA at this
time. In order to arrive at that point we feel that the issues just mentioned first need to be carefully
discussed by EPA and the expert panel. These issues, again, are:
•1. stratification by waterbody type; -
2. accurate accounting of site-specific factors affecting selenium toxicity; and
3. development of site-specific criteria technical guidance.
UWAG appreciates the opportunity to present these comments. We Welcome the opportunity
to work with EPA and the expert panel, if the situation arises, to provide constructive input.
Thank you.
Doc #: 213314; V.I
F-9
-------
------- |