# T ECHNICAL 

# M EMORANDUM 

# 3:

N ORTH 

# S AN 

# F RANCISCO 

# B AY 

# S ELENIUM 

# T OXICOLOGICAL 

# A SSESSMENT

DRAFT
April 2008

Prepared for Regional Water Quality Control Board San Francisco Bay Region 1515 Clay Street Oakland, CA 94612

Prepared by Tetra Tech, Inc. 3746 Mt. Diablo Blvd., Suite 300 Lafayette, CA 94549North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. i 

### T ABLE OF 

### C ONTENTS

Abbreviations .............................................................................................................................. vii

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

2 Invertebrate toxicity review................................................................................................ 2-1

2.1 Discussion................................................................................................................ 2-4

2.2 Conclusions.............................................................................................................. 2-4

3 Fish toxicity review ...........................................................................................................

. 3-1

3.1 Methods.................................................................................................................... 3-2

3.2 Results ..................................................................................................................... 3-4

3.3 Discussion.............................................................................................................. 3-13

3.4 Conclusions............................................................................................................ 3-18

4 Avian toxicity review.......................................................................................................... 4-1

4.1 Methods.................................................................................................................... 4-3

4.2 Results ..................................................................................................................... 4-5

4.3 Improved performance studies................................................................................. 4-9

4.4 Discussion................................................................................................................ 4-9

4.5 Conclusions............................................................................................................ 4-18

5 Marine mammal toxicity review ......................................................................................... 5-1

5.1 Methods.................................................................................................................... 5-1

5.2 Results ..................................................................................................................... 5-1

5.3 Discussion................................................................................................................ 5-2

5.4 Conclusions.............................................................................................................. 5-5

6 Issues Affecting The Choice of Screening Values ............................................................ 6-1

7 Issues Affecting Implementation ....................................................................................... 7-1

8 References........................................................................................................................ 8-1

Appendix A Wet Weight to Dry Weight Conversions ................................................................ A- 1

Appendix B Threshold Values for Selenium in Great Salt Lake................................................ B- 1

Appendix C Allometric Adjustment of Dietary Concentrations .................................................. C- 1North San Francisco Bay Selenium Toxicological Assessment April 2008

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### L IST OF 

### F IGURES
Figure 1-1 Ranked freshwater genus mean acute values for copper .................................. 1-4

Figure 1-2 Health vs. dietary selenium concentration.......................................................... 1-5

Figure 1-3 Weight gain in fingerling channel catfish as a function of dietary selenium....... 1-5

Figure 3-1 Biphasic regression analysis of the data from Hamilton et al. (1990)................. 3-5

Figure 3-2 Biphasic regression based on simulated data from Hamilton et al. (1990) ........ 3-6

Figure 3-3 Effect thresholds for centrarchids from the selected studies grouped by life history stage. .................................................................................................... 3-11

Figure 3-4 Effect thresholds for rainbow trout from the selected studies grouped by life history stage. .................................................................................................... 3-11

Figure 3-5 Effect thresholds for centrarchids after relaxing the selection criteria. ............. 3-12

Figure 3-6 Effect thresholds for rainbow trout after relaxing the selection criteria............. 3-13

Figure 4-1 Logistic regression of mallard dietary selenium concentration vs. proportion of eggs hatching. .............................................................................................. 4-11

Figure 4-2 Hockey stick regression of mallard dietary selenium concentration vs. proportion of eggs hatching.............................................................................. 4-12

Figure 4-3 Logistic regression of mallard egg selenium concentration vs. proportion of eggs hatching. .............................................................................................. 4-12

Figure 4-4 Hockey stick regression of mallard egg selenium concentration vs. proportion of eggs hatching.............................................................................. 4-13North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. v 

### L IST OF 

### T ABLES
Table 2-1 Summary of Results from Hyne et al. (2002) ..................................................... 2-3

Table 2-2 Effect thresholds for invertebrates exposed to dietary or sediment-bound

selenium ............................................................................................................. 2-4

Table 3-1 Selenium toxicity studies evaluated in this review.............................................. 3-3

Table 3-2 The EC10 and EC20 from 10 simulated experiments and 95% confidence limits (CLs) on salmon survival at the EC10 and EC20...................................... 3-7

Table 3-3 Summary of selenium toxicity studies evaluated in this review.......................... 3-9

Table 3-4 Species mean chronic values calc ulated from the toxicity studies evaluated

above................................................................................................................ 3-10

Table 3-5 Whole body fish tissue screening levels (mg/kg-dw) published in the

scientific literature............................................................................................. 3-14

Table 4-1 Selenium toxicity studies evaluated in this review.............................................. 4-5

Table 4-2 Summary of dietary selenium toxi city studies evaluated in this review. ............. 4-7

Table 4-3 Summary of additional selenium toxicity studies from the NRC (1980).............. 4-8

Table 4-4 Summary of additional selenium toxicity studies from the NRC (1994).............. 4-8

Table 4-5 Summary of additional selenium toxicity studies from the NRC (2005).............. 4-8

Table 4-6 Studies evaluating improved performance in poultry from selenium supplementation. ................................................................................................ 4-9

Table 4-7 Summary of NOAELs and LOAELs (mg/kg-dw) reported in this section grouped by whether the effects were measured in chicks/ducklings, adult birds, or in terms of reproductive success........................................................ 4-10

Table 4-8 Selenium screening values for teratogenesis in bird eggs . ............................. 4-14

Table 4-9 Allometrically adjusted dietary selenium screening values............................... 4-15

Table 4-10 Selenium nutritional requirements for commercially reared birds..................... 4-15

Table 5-1 Dietary toxicity studies on pigs from NRC (1980, 2005)..................................... 5-2

Table 5-2 Dietary toxicity studies on dogs from NRC (1980).............................................. 5-2

Table 5-3 Selenium nutritional requirement s for commercially reared pigs by body weight ................................................................................................................. 5-3

Table C-1 Body weights and ingestion rates...................................................................... C- 3

Table C-2 Allometric adjust factors and allometrically adjusted dietary thresholds............ C- 3North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. vii 

### A BBREVIATIONS


### AET apparent effects threshold

ANOVA Analysis of variance

CDH California Department of Health

DFG Department of Fish and Game

dw dry weight

EC01 concentration at which an effect is observed in 1% of the population (i.e., effect concentration 1%)

EC10 concentration at which an effect is observed in 10% of the population (i.e., effect concentration 10%)

LC50 concentration lethal to 50% of test subjects

LOAEL lowest observed adverse effects level

MBTA Migratory Bird Treaty Act

Na 2 

### SeO 3 

### sodium selenite

NRC National Research Council

NIWQP National Irrigation Wa ter Quality Control Program

NOAEL no observed adverse effect level

Se selenium

SeMet selenomethionine

SFEI San Francisco Estuary Institute

SMCV Species mean chronic values are cal culated by taking the geometric mean of the effect thresholds (e.g., NOAEL and LOAEL) for a particular species.

TMDL total maximum daily load

UCL95 95% upper confid ence limit on the mean

USDOI U.S. Department of the Interior

USEPA U.S. Environmental Protection Agency

USFWS U.S. Fish and Wildlife ServiceApril 2008 North San Francisco Bay Selenium Toxicological Assessment

viii Tetra Tech, Inc. 

### USGS U.S. Geological Survey

ww wet weightNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 1-1 

### 1 I NTRODUCTION


### This technical memorandum provides a review of the available information on the toxicity

of selenium to invert ebrates, fish, birds, and marine mammals. This information has been developed to support the Regional Water Qual ity Control Board, San Francisco Bay Region (Water Board) in determining numeric target s for the selenium TMDL for the North San Francisco Bay (North Bay). The review of th e selenium toxicity data was conducted in several steps. First, the available toxicity da ta from the published scientific literature and unpublished reports were compiled. These documents were identified from on-line searches

of scientific references and the literature-cite d sections of these repor ts were reviewed to identify unpublished reports. We estimate that greater than 95% of the relevant Englishlanguage literature has been reviewed. Next, the reported toxicity values were screened to identify those data that were most relevant to setting a numeric target for North Bay fish and wildlife. Screening criteria included:

• Chronic exposure to single chemical (selenium)

• Controlled experimental conditions

• Dietary exposure

• Tissue concentrations repor ted for exposed animals

The reported toxicity values ( tissue concentrations) for indivi dual species can exhibit a wide range due to differences in the corresponding toxicity e ndpoint of the test. Th erefore, the test endpoint merits special attenti on in interpreting the reported to xicity values. The tables in this report, summarizing the selenium toxicity studies evaluated, report both the toxicity value and the test endpoint.

The focus of this report is on the compilation of relevant toxicity values. Some of the key issues to consider in interpreting the results of the laboratory tests and data analyses are also

identified.

1.1 B ACKGROUND I NFORMATION



### The current EPA and California state freshwat er water chronic quality criterion for the protection of aquatic life (5 μg/L) has been cri ticized as inadequately representative of the toxic risks of selenium to aquatic life. Recent studies on selenium toxicity in aquatic food chains have generally reached th e conclusion that a water-based criterion is not suitable due to “...temporal [and spatial] changes in conc entrations, speciation, a nd rates of transfer between water, sediment and organisms...” (Hamilton 2004). Since the primary route of exposure to selenium is via the diet, and selenium is highly bioaccumulative, these

differences can mean that a concentration of sele nium in water that results in adverse effects in one location may not result in adverse eff ects to the same species in another location. Thus, the current recommendation (USEPA 2004, Chapman 2007, Hamilton 2002, 2004) for the appropriate media for regulati on of selenium in the aquatic environment is not water, but

rather tissue.April 2008 North San Francisco Bay Selenium Toxicological Assessment

1-2 Tetra Tech, Inc. 

### In 1987 in the North San Francisco Bay (hereinaft er referred to as the “North Bay”), “...the California Department of Health (CDH) issued a health advisory for the consumption of three [sic] species of diving ducks in Suisun Bay, near San Francisc o. These diving ducks (i.e., surf scoter, lesser an d greater scaup) feed on bo ttom-dwelling animals (clams, mussels), which concentrate selenium from sediment and phytoplankton. In a study by the California Department of Fish and Game, the m ean selenium levels in the muscle of duck were as follows: scoters, 3.6 ppm Se, wet weight; scaups, 2.2 ppm Se, wet weight. These levels were up to 5 times higher than mean Se levels in similar species in control areas (i.e., Humboldt Bay near the borde r of Oregon and California). The CDH recommended limiting the consumption of scoters to 4 oz/2 wk a nd of scaups to 4 oz/wk. Because of the known effects of selenium on the reproduction of birds, the CDH recommended that women of child-bearing age and children, 15 years old not consume th ese ducks” (Barceloux 1999).

In addition to the CDH health advisories for the consumption of diving ducks, the North Bay including Suisun Bay, Carquinez Strait, San Pa blo Bay and Central Bay were listed in 1998, 2002, and 2006 under section 303(d) of the Clean Water Act due to impairments to both wildlife and human-health beneficial uses (A bu-Saba and Ogle 2002). It is on the basis of these listings that the Regional Water Quality Control Board, San Francisco Region (Water Board) is developing the Total Max imum Daily Load for the North Bay.

1.2 R ELEVANT T OXICITY D ATA 

### Several approaches have been used to deve lop screening values in the scientific and regulatory literature. Th ese approaches include:

• LOAELs

• Effect thresholds

• Species mean chronic values

• EC01 or EC10

• Species sensitivity distributions

In the literature on selenium toxicity to fish, th e approach that has generally been used is to set the screening value equal to the lowest LOAEL (i.e., the lowest observed adverse effect

level ) that has been reported (e.g., Hamilton 2003, 2004). When there is a large body of literature, with many reported LOAELs, this approach is likely to come close to the concentration at which effects first appear. Howe ver, when there are only a few studies, it is likely that effects begin at a level below the lowest LOAEL reported. For that reason, it may be advisable to use an SMCV, EC10, or effect threshold (see below) instead.

Effect thresholds are calculated as the geometric mean of the NOAEL (i.e., the highest no observed adverse effect level ) and LOAEL reported for the sa me effect in an individual study. Since toxicity tests do not generally test many differen t concentrations, and effects may occur at concentrations below the LOA EL, calculating the geometric mean of the NOAEL and the LOAEL is one way to add a marg in of safety to the LOAEL. That is,North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 1-3 

### effects are likely to occur somewhere between the NOAEL and the LOAEL. The USEPA (1985, 2003) has made the decision that the ge ometric mean of the NOAEL and LOAEL is representative of where those e ffects are likely to occur.

Species mean chronic values (SMCVs) are used by USEPA in the calculation of water quality criteria (USEPA 1985). An SMCV is cal culated by taking the geometric mean of the effect thresholds for a particular species. When there is only one study available, the results of that study are regarded as the SMCV.

Another approach that can be used to find th e concentration at which effects are likely to occur between the NOAEL and LOAEL is to pool the data from similar studies and perform a regression (e.g., biphasic, hockey-stick, or logistic) on the response data. The data is generally only from a single species. This approach has been used in State of Utah (Ohlendorf 2007) by pooling the data from 6 st udies on mallards and performing regressions

on the concentration of selenium in feed and eggs vs. reproductive success. The State of Utah derived an EC10 (i.e., the effect concentration 10% or the concentration at which an

effect is observed in 10% of the population) for selenium in mallard diets and eggs protective of reproductive success. This same a pproach can also be used to calculate an EC01 (i.e., effect concentration 1% ), which will be lower, but protective of a greater proportion of individuals.

Species sensitivity distributions are another approach that have been used to derive screening values. In this approach, the probabi lity distribution of some measure of toxicity (e.g., NOAEL, LOAEL, effect threshold, SMCV, LC 50 

### , etc.) for multiple animal species is calculated. From the probability distribution, a screening value is then calculated that is protective of a certain proportion of the species (e.g., 95%). USEPA calculates percentiles of species sensitivity distributions for use in the derivation of water quality criteria (Posthuma et al. 2002). This approach is similar to th e EC10 approach describe d above, except that it always uses data from multiple species, with each data point representative of a single species, and uses probability distributions instea d of regressions to derive screening values. For the recent acute criterion for copper, USEPA compared their calculated value to a species sensitivity distribution (Figure 1-1) and found that it was protec tive of 95% of the genera making up the acute copp er toxicity database (USEPA 2007a). The species sensitive distribution (Figure 1-1) contains the genus mean acute value (GMAV) for 27 genera, including 15 species of invertebrates, 22 sp ecies of fish, and 1 amphibian species. Each GMAV was calculated as the as the geometric mean of the species mean acute values (SMAV) for the species within that genera and the SMAV was calculated as the geometric

mean of the individual value. The selected final acute value of 4.67 ug/L exceeds only one of 27 GMAVs (Figure 1-1); i.e., the GMAV for that cladoceran (an invertebrate) Daphnia

.April 2008 North San Francisco Bay Selenium Toxicological Assessment

1-4 Tetra Tech, Inc. Figure 1-1 Ranked freshwater genus mean acute values (GMAVs) for copper (USEPA 2007a).



### Effect thresholds and SMCVs will be calculat ed for the toxicity data presented in the following chapters. The lowest LOAEL will also be noted. Where an EC01, EC10, or species sensitivity distribution has been report ed, that will also be noted. However, the

calculation of these other m easures of toxicity is not included in this review.

Selenium is an essential micro-nutrient. Adverse effects occur both when selenium concentrations are too low and too high in the di et (see Figure 1-2). At low concentrations,

selenium is an essential micro-nutrient in anim als. If the concentration of selenium in the diet is not adequate, selenium deficiency may result. The symptoms of selenium deficiency include edema, white muscle disease, reduced growth, reduced disease resistance, liver necrosis, morbidity, and increased mortality (National Research Council 1980, 2005, Ullrey 1992). At high concentrations, however, sele nium can cause toxic effects, including emaciation, hair/feather loss, reduced reproduct ive success, reduced growth, developmental deformities, and mortality (Nationa l Research Council 1980, 2005, Ohlendorf 2003).North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 1-5 Figure 1-2 Health vs. dietary selenium c oncentration (adapted from NRC 2005).



### The occurrence of effects in fish from low dietar y selenium concentrations is seen in one of the toxicity studies examined in this report. In a study on fingerling channel catfish, Gatlin and Wilson (1984) were able to show that dietary selenium concentrations below approximately 0.3 mg/kg resulted in reduced weig ht gain. Above that, there was a plateau in the response (i.e., the optimal level) in whic h increased selenium concentrations did not have an adverse effect. However, the plat eau ends at approximately 10 mg/kg, with

concentrations above that also resulting in reduced weight gain (Figure 1-3). This has also been observed for calcium, magnesium, ma nganese, molybdenum, phosphorus, potassium, sodium, sulfur, and zinc (NRC 2005).

Figure 1-3 Weight gain in fingerling channel cat fish as a function of dietary selenium (Gatlin and Wilson 1984).



### Thus, screening values for dietary selenium c oncentrations should be set above the dietary requirement. When dietary concentrations ar e below the dietary requirements, adverse effects could theoretically occur from deficien cy. Further, when dietary concentrations are near the requirements, a proportion of the popul ation may also be adversely affected by selenium deficiency. In turn, th ese effects could lead to the ve ry reduction in fish and birdApril 2008 North San Francisco Bay Selenium Toxicological Assessment

1-6 Tetra Tech, Inc. 

### populations that the selenium TMDL sought to avoid by reduci ng selenium concentrations. The dietary requirements of fish, birds, pigs, and other mammals have been determined by the NRC (1993, 1994, 1998) and will be presented in each of the sections evaluating the toxicity to the biot a of the North Bay.North San Francisco Bay Selenium Toxicological Assessment April 2008

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### 2 I NVERTEBRATE TOXICITY REVIEW


### Invertebrates are an integral part of many food chains in the North Bay, supporting many species of fish and birds, including species of recreational interest as well as threatened and endangered species. This suggests that if selenium negatively impacts the aquatic invertebrates in the North Bay, the result may be reduced food availability for the fishes and birds of the North Bay. Ultimately, this may l ead to a reduction in the population sizes of those fishes and birds, even in the absenc e of direct impacts to the fishes and birds themselves from selenium. This suggests that the potential impacts of selenium on aquatic invertebrates in the North Bay should be part of the TMDL process.

While there is a large amount of literature on the toxicity of se lenium to fishes, birds, and mammals, the chronic toxicity literature is very sparse for aquatic invertebrates. Thus, there is very little literature that may help the Water Board to determine whether the aquatic invertebrates in the North Bay are impact ed by selenium. Similarly, the paucity of information on the toxicity of selenium to aquatic invertebrates means that are very few published sources of selenium screening values; e.g., no “Consensus-Based Sediment Quality Guidelines” (MacDonald et al. 2000), no California sediment quality objectives (SWRCB 2007), and only an apparent effect threshold in the NOAA SQuiRTs (Buchman 1999).

Despite the paucity of selenium toxicity data for aquatic invertebrates, there are a few chronic toxicity studies that may be informa tive to the Water Board. These studies are listed and briefly described below:

• Alaimo et al. (1994)

• Bielmeyer et al. (2005)

• Brasher and Ogle (1993)

• Debruyn and Chapman (2007)

• Hyne et al. (2002)

• Ingersoll et al. (1990)

• Jensen et al (2007)

• Malchow et al (1995)

• Naddy et al (1995)

• NOAA SQuiRTs (Buchman 1999)

Alaimo et al. (1994) 

### The authors performed chronic toxicity in a laboratory on the larvae of the midge

Chironomus decorus . Chironomids are a major component of fish and waterfowl diet.April 2008 North San Francisco Bay Selenium Toxicological Assessment

2-2 Tetra Tech, Inc. 

### Midge eggs were placed in “moderately hard ” water and, after hatching, were fed with powdered plants that were collected from ev aporation ponds in California with varying

concentrations of selenium. The authors found th at increased selenium concentrations in the powdered food resulted in lower body weight s of the growing midges with a NOAEL and LOAEL of approximately 0.5 and 1.6 mg/kg-dw, respectively, in the powdered food (effect threshold of 0.9 mg/kg-dw); the NOAEL and L OAEL for selenium in midge tissues were both below the detection limit of approximately 0.5 mg/kg-dw. In this experiment, selenium was only added via the food, but that also led to increases in selenium in the water column

over time.

Bielmeyer et al. (2005) 

### The authors performed chronic t oxicity tests in a laboratory on the larvae of sea urchins. Although the species tested, Diadema antillarum , does not occur in the North Bay, the

authors state that “ sea urchin larvae have been shown to be highly sensitive to metals and therefore have been extensively used in marine pollution bioassays ” (Bielmeyer et al. 2005). Therefore, their results should be applicable to the North Bay in a general sense. The authors examined the development of larval sea ur chins by exposing them to 0, 5, 10, 20, 36, 73

μ g/L selenium as Na 2 

### SeO 4 

### for 40 hours in sea water. The au thors found that selenium cause abnormal development with an EC50 of 26 μ g/L. However, there were no apparent adverse effects at up to 20 μ g/l (i.e., the NOAEL was 20 μ g/L). The experiments design that the authors used did not expose the parents to se lenium, but only the larvae. In the North Bay, both the parents and the offspr ing will be exposed, which may potentially increase selenium sensitivity.

Brasher and Ogle (1993) 

### The authors performed chronic toxicity test s in a laboratory on the freshwater amphipod Hyallela azteca . Separate experiments were conducted using sodium seleni te at 0, 50, 100, 200, 300, and 400 μ g/L and sodium selenate at 0, 100, 250, 350, 500, and 700 μ g/L for 24 days. Reproduction was reduced at 200 μ g/L selenite but no eff ects were observed for

selenate.

Debruyn and Chapman (2007) 

### The authors compiled existing toxicity data on ma jor effects (i.e., toxic effects that are likely to affect a species at the popul ation level, including reproduc tion and growth) that included water, dietary, or tissue selenium concentra tions associated with toxic effects to 29 macroinvertebrate species. Studies reporting di etary and tissue concen trations were pooled across freshwater benthic, freshwater planktoni c, and terrestrial inve rtebrate groups. For chronic waterborne exposures, th e authors found that the amphipod Hyallela was the most sensitive with a median lethality reported at 100 μ g/L selenite, 200 μ g/L selenate, and a >50% reduction in reproduction at 100 μ g Se/L selenate. Sublethal effects from dietary exposures were found to range from 1 to 80 mg/kg-dw. Sublethal effects for tissue

concentrations of selenium were found to range from 1 to 30 mg/kg-dw. Although the

authors used the data collected to construct a percentile based species sensitivity distribution (not a probability), they did not use the distri butions to calculate values protective of a percentage of the species observed.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 2-3 Hyne et al. (2002) 

### The authors performed chronic to xicity tests in a laboratory on juveniles and adults of the estuarine amphipod Corophium sp. Amphipods exposed to sediments spiked with seleno-Lmethionine to give final con centrations of 0, 0.3, 1, 3, and 10 mg/kg-dw. Selenium was not added to either the water or the food given to the amphipods and all experiments were conducted using seawater. The only response m easured in the amphipods was mortality. The results of these experiments are summarized in the Table 2-1 below (from Hyne et al. 2002).

Table 2-1 Summary of Results from Hyne et al. (2002)

Lifestage Test conditions of overlying water 10-day LC 50 sediment (dry wt) μg Se/g (95% CL) 10-day NOAEL sediment μg Se/g (dry wt) 10-day LOAEL sediment μg Se/g (dry wt)

Juvenile No renewal 1.6 (1.3-1.9) 0.84 2.0

Juvenile Daily renewal 6.3 (5.5-7.2) 1.7 5.0

Adult No renewal 7.6 (6.8-8.4) 4.6 11.0



### These results indicate that si gnificant mortality was observed at concentrations as low as approximately 2 mg/kg-dw. An effect threshol d was calculated for juvenile mortality in waters without renewal of 1.3 mg/kg-dw. However, it should be noted that since the authors only measured mortality, sublethal effect s may be expected at lower sediment

concentrations.

Ingersoll et al. (1990) 

### The authors performed chronic toxicity tests in a laboratory on the freshwater arthropods Daphnia magna and Chironomus riparius . Chironomids are a major component of fish and waterfowl diet. The experiments produced LOA ELs for inorganic selenium in waterborne exposures of 85 μ g/L for Daphnia and 837 μ g/L for Chironomus

.

Jensen et al. (2007) 

### The authors performed freshwater chronic toxicity tests in a laboratory on the larvae of the southern house mosquito Culex quinquefasciatus. Culex spp. are algal and bacterial feeders and are important as food for many organism s. The larvae were exposed to 2, 4, 8, 16, and 32 mg/L selenate. The experiments produced a LOAEL for reduced growth of 2 mg/L.

Malchow et al. (1995) 

### The authors performed freshwater acute toxicity tests in a laboratory on the larvae of the midge Chironomus decorus. Chironomids are a major component of fish and waterfowl diet. The experiments consisted of feeding th e midge larvae with a diet of algae ( Selenastrum capricornutum ) cultured in three concentrations of selenite (0, 10, and 40 μ g/L) or four concentrations of selenate (0, 4, 10, and 40 μ g/L). The experiments produced a NOAEL and LOAEL for reduced body weight of 1.10 and 2.11 mg/kg-dw, respectively, in algae (effect threshold of 1.5 mg/kg-dw); or a NOAE L and LOAEL of <0.25 and 2.55 mg/kg-dw, respectively, in the midges (effect thre shold of 0.8 mg/kg-dw, assuming the NOAEL was 0.25). Although this was an acute toxicity test, this is one of the few studies where invertebrates were exposed to selenium in th e diet. Chronic tests ma y result in toxicity

observed at lower concentrations.April 2008 North San Francisco Bay Selenium Toxicological Assessment

2-4 Tetra Tech, Inc. Naddy et al (1995) 

### The authors performed freshwater chronic (9 day) toxicity tests in a laboratory using Ceriodaphnia dubia . The daphnia were exposed to <170, 510, 610, and 870 μ g/L selenate. No effects on survival or reproduction were observed at any concentration.

NOAA SQuiRTs (Buchman 1999) 

### The National Oceanic and Atmospheric Admini stration has published a set of screening values called the Screening Quick Referen ce Tables (SQuiRTs). The SQuiRTs contain a marine sediment apparent effects threshold (AET) protective of am phipods of 1 mg/kg-dw. AETs are described as “...the concentration above which adverse biological impacts would always be expected... Conversely, adverse impact s are known to occur at levels below the AET... AET values were developed fo r use in Puget Sound (Washington)...”

2.1 D ISCUSSION 

### “Selenium toxicity is greater in laboratory te sts in which organisms are fed than in water only tests, because food accumulates Se from th e aqueous phase, adding substantially to the test organism’s total exposure” (Debruyn an d Chapman 2007). Therefore, the results of water only tests can result in apparently high t oxicity thresholds for invertebrates; e.g., 26

μ g/L for sea urchins (Bielmeyer et al. 2005) and 2,000 μ g/L for Culex quinquefasciatus (Jensen et al. 2007). Similarly, for sediment dwe lling invertebrates, exposures to selenium in sediments appears to result in adverse effects at relatively low levels.

From the few studies presented above that ha ve been performed using either dietary or sediment exposures, the followi ng Table 2-2 was constructed:

Table 2-2 Effect thresholds for invertebrates exposed to dietary or sediment-bound selenium

Exposure Effect Threshold (mg/kg-dw) Organism route Diet Sediment Organism Reference midge diet 0.9 - <0.5 Alaimo et al. (1995) amphipod sediment - 1.3 - Hyne et al. (2002) midge diet 1.5 - 0.8 Malchow et al. (1995)



### These data indicate that invertebrates ma y be affected by relatively low selenium concentrations, when exposed to selenium in dietary items or in se diments (for sediment dwelling biota).

Nutritional requirements 

### Selenium is a micro-nutrient (see Section 1). When animals do not have enough selenium in their diet, selenium deficiency results (NRC 1993, 1994). While the NRC (1993, 1994, 1998) has not established seleni um nutritional requirements for invertebrates, it has established nutritional requirements for animals that potentially feed on invertebrates: 0.25- 0.3 mg/kg for fish (NRC 1993), 0.17-0.33 for pigs (NRC 1998), and 0.16-0.22 mg/kg for birds (NRC 1994).

2.2 C ONCLUSIONS



### The effect thresholds shown in the table a bove are similar to the few published lower bound values available; i.e., the AET for selenium in marine sediment s of 1 mg/kg is very close toNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 2-5 

### the effect threshold of 1.3 mg /kg-dw observed by Hyne et al. (2002); and the lower bound dietary and organism selenium concentra tions published by Debruyn and Chapman (2007) of 1 mg/kg-dw each are close to the effect thresholds reported for midges above (0.9-1.5 mg/kg-dw for diet and <0.5-0.8 mg /kg-dw for organism). All of these values are above the dietary requirements for fish, birds, and pigs (NRC 1993, 1994, 1998), although some are

close.

Based upon the data presented here, there are seve ral options for screenin g values protective of invertebrates. Those options are as follows (all in units of mg/kg-dw):

1. Dietary items

a. Lowest effect threshold: 0.9

b. Lowest LOAEL: 1.6

2. Sediment

a. Lowest effect threshold: 1.3

b. Lowest LOAEL: 2.0

c. AET: 1.0

3. Organism (excluding non-detects)

a. Lowest effect threshold: 0.8

b. Lowest LOAEL: 2.55North San Francisco Bay Selenium Toxicological Assessment April 2008

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### 3 F ISH TOXICITY REVIEW


### The North Bay supports a diverse fish biota. The fish supported include both sportfish and threatened and endangered fish species. The five most common sportfish in the North Bay are (SFEI 2000; listed in order catch frequency):

1. Striped bass ( Morone saxatilis )

2. Halibut ( Paralichthys californicus )

3. Jacksmelt ( Atherinopsis californiensis )

4. White sturgeon ( Acipenser transmontanus )

5. White croaker ( Genyonemus lineatus )

In addition to the sportfish listed above, the North Bay supports the following threatened and endangered fishes (USFWS 2007):

1. Chinook salmon ( Oncorhynchus tshawytscha )

2. Delta smelt ( Hypomesus transpacificus )

3. Green sturgeon ( Acipenser medirostris )

4. Longfin smelt ( Spirinchus thaleichthys )

5. Sacramento perch ( Archoplites interruptus )

6. Sacramento splittail ( Pogonichthys macrolepidotus )

7. Steelhead trout ( Oncorhynchus mykiss )

8. Tidewater goby ( Eucyclogobius newberryi )

Selenium in the North Bay may adversely im pact these fish by causing reduced production of viable eggs, post-hatch mortality, deformitie s in growing larvae, and various pathological effects in the kidneys, liver, heart, and ovaries (Hamilton 2003, 2004; Lemly 2002a). These identified effects may lead to population declin es of both the sportfish and the threatened and endangered fishes in the North Bay. Theref ore, as part of the selenium TMDL for the North Bay, selenium screening values will be developed that are protective of the species

listed above.

As stated in the Introduction (s ee Section 1), the potential scr eening values that are proposed here are tissue concentrations. For fish, measur ing the concentration of selenium in dietary items poses a logistical challenge. Mainly, the challenge lies in that many fish feed on a wide array of small prey items. Collecting th e right kind of prey items, and a sufficient number for analysis, can be ve ry time consuming. Instead, it is generally recommended that

selenium be measured in the fish of concern (Hamilton 2002, 2003, 2004, USEPA 2004). Additionally, it is recommended that these meas urem ents be made in whole fish due to

“... practical reasons of sampling and because a sufficient data base containing chronic effects based on whole-body tissue is present in the literature ” (USEPA 2004). The amount

of data for chronic effects ba sed on other tissue types (e. g., ovary, liver, kidney , and muscle) is not as extensive and, therefore, not amenable to deriving screening values. Further, although “ ovaries may be the best tissue to lin k selenium to reproductive effects...April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### ovarian tissue is also only available seasona lly and sometimes difficult to extract in quantities sufficient for analysis ...” (USEPA 2004). Therefore, whole body concentrations in fish are recommended for use as screening values.

3.1 M ETHODS 

### Selenium toxicity data for the fishes that occu r in the North Bay would be the most relevant for developing selenium fish tissue screening values for the North Bay. However, for the fishes in the North Bay, there is very limited toxicity data and almost no toxicity data for fishes at all in the salinity range that occurs in the North Bay; i.e., 1 to 33.5 ppt. Therefore, this review is largely limited to the evalua tion of the freshwater toxicity literature.

Selenium toxicity studies on fish es were gathered from the scientific literature, as well as reports and other “grey literature. ” The studies collected were ev aluated to select those that provided fish tissue concentrations at which t oxic effects from chronic selenium exposures were observed. To ensure that screening values were not influenced by other variables (e.g., other contaminants), only studies with contro lled experimental designs were selected.

The criteria used to identify studies with usable toxicity information are as follows:

A. provide a NOAEL and/or a LOAEL

B. chronic

C. exposed to selenium only

D. only treatment was selenium exposure level

E. contained tissue data

F. fish (and their food) were raised in the laboratory under controlled conditions

G. used a dietary exposure scenario; mesoco sm experiments in which selenium was

added to the water column meet this requirement

All studies that were reviewed are listed in Table 3-1. Studies that were determined to be

unsuitable are noted in Tabl e 3-1 using the designations from the list above.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-3 Table 3-1 Selenium toxicity studies evaluated in this review. Studies that were excluded from review are indicated (see text above for an explanation of the criteria).

Study Reference Evaluation

criteria failed Study Reference Evaluation

criteria

failed 1 Bennett et al. (1986) A 41 Hilton and Hodson (1983)
2 Bertram and Brooks (1986) A 42 Hodson et al. (1980) E
3 Brandão et al. (1992) A 43 Hodson et al. (1986) A
4 Chapman (1992) B 44 Holm et al. (2005) F
5 Cleveland et al. (1993) 45 Hunn et al (1987) G
6 Coughlan and Velte (1989) F 46 Kennedy et al. (2000) F
7 Coyle et al. (1993) 47 Kimball (1978) E
8 de Rosemond et al. (2005) A 48 Klaverkamp et al. (1983) E
9 Dobbs et al. (1996) 49 Kleinow (1984) A
10 Doroshov et al. (1992) 50 Kleinow and Brooks (1986a) A
11 Finger and Bulak (1988) C,D 51 Kleinow and Brooks (1986b) A
12 Finley (1985) F 52 Lawler et al. (1981) E
13 Gatlin and Wilson (1984) 53 Lemly (1993a)
14 Gillespie and Baumann (1986) F 54 Lemly (1993b) F

15 Gissel-Nielsen and Gissel-Niels en (1978) E 55 Linville (2006)
16 Goettl and Davies (1977) E 56 Mehrle et al. (1982) C,D
17 Goettl and Davies (1978) E 57 Muscatello et al. (2006) F
18 Hall et al. (1984) C 58 Ogle and Knight (1989)
19 Hall et al. (1985) B,C,D 59 Pyron and Beitinger (1989) A
20 Hall et al. (1987) B,C,D 60 Saiki et al. (1992) E
21 Halter et al. (1980) B 61 Saiki et al. (2004) C
22 Hamilton et al. (1986) C 62 Schultz and Hermanutz (1990)
23 Hamilton et al. (1990) 63 Schlenk et al. (2003) B
24 Hamilton and Wiedmeyer (1990) C 64 Sorensen and Bauer (1983) E
25 Hamilton et al. (2000) C 65 Sorensen and Bauer (1984) A
26 Hamilton et al. (2002a) C 66 Sorensen et al. (1982a) A,E
27 Hamilton et al. (2002b) C,D 67 Sorensen et al. (1982b) A
28 Hamilton et al. (2005a) C,D 68 Sorensen et al. (1983) A
29 Hamilton et al. (2005b) C 69 Sorensen et al. (1984) F
30 Hamilton et al. (2005c) C 70 Sorensen (1988) F
31 Hamilton et al. (2005d) C 71 Tashjian et al. (2006)
32 Harrison et al. (1990) A 72 Tashjian et al. (2007) E
33 Hardy (2003) F 73 Teh et al. (2002) B,E
34 Hartwell et al. (1987a) A 74 Teh et al. (2004)
35 Hartwell et al. (1987b) A 75 Vidal et al (2005)
36 Hermanutz (1992) E 76 Watenpaugh and Beitinger (1985a) A
37 Hermanutz et al. (1992) 77 Watenpaugh and Beitinger (1985b) B
38 Hicks et al (1984) 78 Watenpaugh and Beitinger (1985c) A
39 Hilton et al. (1980) 79 Woock et al. (1987) E
40 Hilton et al. (1982) A 80 Wise et al. (1993) E



### The reported effects from each study were grou ped into one of two categories: major and minor effects. Major effects are those that have the potential to impact fish at the organism and/or population level (e.g., incr eased mortality, reduced fecund ity, reduced growth, etc.). Minor effects are those that are measurable, but are unlikely to result in population level effects and/or the long-term impacts on indi vidual fish performance was unclear (e.g., a change in an enzyme concentration). Where bo th major and minor effects were observed at the same concentration, the effects was assu med to be major. Only major effects were considered in development of screening values.April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### Effect thresholds were calculated as th e geometric mean of the NOAEL and LOAEL reported for the same effect in an indivi dual study, as is recommended in USEPA water quality criteria development guidance (USEPA 1985). Additionally, species mean chronic values (SMCVs) were calculated as the geomet ric mean of the effect thresholds (USEPA 1985). Studies that did not repor t a NOAEL were excluded from th e calculation of an effect

threshold and the SMCV. Note that excludi ng studies in which a NOAEL was not reported

from the calculation of the SMCV results in lower SMCVs. USEPA (1985) provides the following rationale for the use of ge ometric means to calculate SMCVs:

“Geometric means rather than arithmetic means are used here because the distributions of individual organisms’ sensitivities in toxicity tests on most materials, ... are more likely to be lognormal than normal.”

The calculated SMCVs can then be used to eval uate the relative sensitivity of each species of fish to selenium and help determine the appropriate threshold for use.

In studies where selenium was not measured in whole fish (e.g., selenium was measured in liver or muscle), measured concentrations were converted to whole body concentrations using the equations presented by USEPA (20 04). Additionally, tissu e values based upon wet-weight values were convert ed to dry-weight values usi ng either the %moisture values presented in the same study or default valu es from USEPA (2004). A ll conversion methods are described in detail in Appendix A.

3.2 R ESULTS 

### The toxicity studies from Table 3-1 that were included in the evalua tions below included 18 studies on the following fish species:

• Bluegill

• Channel catfish

• Chinook salmon

• Fathead minnows

• Rainbow trout

• Sacramento splittail

• White sturgeon

Bluegill 

### Five suitable studies were found on bluegills. Whole body effect thresholds ranged from 3.0 to 13.8 mg/kg-dw (Table 3-3).

Channel catfish 

### Two suitable studies were identified; i.e., Doroshov et al. (1992) and Gatlin and Wilson (1984). In the study by Doroshov et al. (19 92), the exposure route was intramuscularNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-5 

### injection of selenomethionine. The degree of correlation between intramuscular injection and dietary exposures for selenium is unknow n. In the study by Gatlin and Wilson (1984), selenium exposure was dietary. From these studies, we calculated whol e body effect thresholds of 2.7 and 3.3 mg/kg-dw , respectively (Table 3-3).

Chinook salmon 

### A single suitable study was identified (Hamilt on et al. 1990). That st udy evaluated selenium toxicity in both brackish and freshwaters, th e whole body effect thresholds calculated from this study were 7.6 mg/kg-dw for freshwater and 17.1 mg/kg-dw for brackish water (Table 3-3) for fishes fed SeMet. These results indicate that selenium may be less toxic to salmon in

brackish than in fresh waters.

Beckon (2007) also anal yzed the data from Hamilton et al . (1990) but included the data from salmon that were fed field-collected mosquito fish. In our analyses, we excluded the data from salmon fed mosquitofish caught in the field as this exposed the salmon to multiple contaminants simultaneously which might have negatively influenced survival. Instead of calculating an effect thres hold from the LOAEL and NOAEL from Hamilton et al. (1990), Beckon (2007) performed a regression of seleni um concentration vs. survival and estimated an EC10 and EC20 of 1.84 and 2.5 mg/kg-dw, resp ectively. The analysis in shown in the figure below.

Figure 3-1 Biphasic regression analysis of the data from Hamilton et al. (1990)



### It should be noted that perf orming a regression on the treatm ent means, instead of the raw

data from individual test organisms, masks the true va riation associated with the experimental data; i.e., the confidence limits associated with the regression line in Figure 3-April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### 1 could be much larger. Further, the nature of the relationship betw een fish survival and whole-body selenium concentratio ns (i.e., the EC10) may cha nge when using the raw data. To examine the effects of using the data for th e individual test organisms in the analysis, we

used the treatment means and standard errors for the same 11 treatments that Beckon (2007) used to create the regression analysis in Figur e 3-1 and repeated the experiment 10 times in a Monte Carlo simulation analysis. Assuming a normal distribution, we generated 2 data points per treatment (i.e., the number of data points collected by Hamilton et al. (1990)) and performed the same regression analysis. An example graph from one of the simulation experiments is provi ded in Figure 3-2.

Figure 3-2 Biphasic regression based on simulated data from Hamilton et al. (1990)



### From this simulated data set (Figure 3-2), it can be seen that performing a regression analysis on the (simulated) raw data (vs. the treatment means) leads to wider confidence intervals on the regression line. For example, th e confidence limits on the regression line at the lowest treatment level are approximate ly 48-97% survival, as opposed to the approximately 57-80% survival that was cal culated using only the treatment means.

The EC10 and EC20 derived from all 10 simula ted experiments are presented in Table 3-2. The graphically derived confiden ce limits are also presented.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-7 Table 3-2 The EC10 and EC20 from 10 simulated experiments and 95% confidence limits (CLs) on salmon
survival at the EC10 and EC20

EC10 EC20(mg/kgdw) LCL for salmon
survival at EC10 a UCL for salmon
survival at EC10 a (mg/kgdw) LCL for salmon
survival at EC20 a UCL for salmon
survival at EC20 a

1.91 52 83 2.47 47 73

2.03 55 88 2.61 49 79

1.59 57 76 2.38 50 68

1.82 51 74 2.50 46 70

1.60 47 72 2.26 41 64

1.88 46 71 2.52 41 64

1.82 50 77 2.46 45 68

1.94 48 75 2.74 43 67

2.42 55 72 3.33 49 64

1.85 49 74 2.65 44 66

Notes: a - Confidence limits are graphically derived UCL – upper confidence limit
LCL – lower confidence limit



### Further, from Figure 3-2 and Table 3-2, it appears that th e EC10 and the EC20 derived by Beckon (2007) may not significantly different from each other and that both may not significantly different from the no effect level in the regression; i.e., 70% survival. Testing for significant differences among the no effect level, the EC10, and the EC20 requires the ability to set 95% confidence limits. For non-linea r regression analyses, the likelihood-ratio method is recommended for calculating confiden ce limits (see Moerbeek et al. 2004, Sand et al. 2006). However, we have not yet taken this next step to calculate confidence limits on the

EC10 and EC20.

Fathead minnows



### Three suitable studies were identified for fathead minnows. Whole body effect thresholds ranged from 6.0 to 73 mg/kg-dw (Table 3-3).

Rainbow trout



### Four suitable studies were identified for ra inbow trout (Table 3- 3). Whole body effect thresholds for selenium ranged from 1.7 to 53.1 mg/kg-dw (Table 3-3). Using the treatment means from one of the suitable studies (i.e., Hi lton et al. 1980; see study 38 in Table 3-3) Beckon (2007) derived an EC 20 for juvenile rainbow trout of 2.15 mg/kg-dw based on a 20% reduction in body weight. Ho wever, this approach is s ubject to the same limitations

discussed above for chinook salmon.

It should also be noted that Beckon (2007) used the raw data from a study that did not meet our selection criteria (i.e., Ho lm et al. 2005) to derive an EC20 of 2.93 mg/kg-dw for adult rainbow trout, based on a 20% reduction in th e survival of fry from tout exposed to

selenium.

Sacramento splittail 

### A single suitable study was identified (Teh et al . 2004). In that study, an effect threshold of 12.3 mg/kg-dw (muscle) was determined. Using the equations in USEPA (2004) to convertApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### muscle concentrations to whole body concentr ations, an effect threshold of 10.8 mg/kg-dw (whole body) was calcula ted (Table 3-3).

White sturgeon 

### Two suitable studies were identified which evaluated the toxicity of selenium to white sturgeon (i.e., Linville 2006, Tash jian et al. 2006). Linville ( 2006) performed two sets of experiments: 1) injecting selenium into stur geon eggs and 2) expos ing adult sturgeon to dietary selenium. Only the results from the di etary exposure experiment are used in the evaluations presented here. We calculated wh ole body effect threshol ds of 6.2 mg/kg-dw from Linville (2006) and 18.2 mg/kg-dw from Ta shjian et al. (2006) (Table 3-3). William Beckon (2008) of the USFWS analyzed the data in Linville (2006) and derived an EC10 for

selenium in muscle tissue which he then c onverted to a whole body concentration of 7.50 mg/kg-dw using a linear regre ssion relating the two tissue types. The regression that Beckon (2008) used to convert selenium muscle concentrations to whole body

concentrations was derived from the treatment means in Tashjian et al . (2006). Tetra Tech

obtained the raw data from Tash jian et al. (2006) and used that to derive a linear regression relating muscle to whole body co ncentrations (see Appendix A) . Using that regression,

Tetra Tech converted the muscle tissue EC 10 derived by Beckon (2008) into a whole body concentration of 11.9 mg/kg-dw. However, it should be noted that there were few data points available for the calculation of the EC10, making this value somewhat uncertain. The regression derived from the raw data from Tash jian et al. (2006) was also used to convert Linville’s (2006) muscle NOAEL and LOAEL into whole body concentrations (Table 3-3).North San Francisco Bay Selenium Toxicological AssessmentApril 2008Tetra Tech, Inc.3-9Table 3-3Summary of selenium toxicity studies evaluated in this review.Liver1Muscle1WholeBodyEffect Threshold(mg/kg-dw)Fish StudyWaterType Life stageNOAEL(mg/kg-dw)LOAEL(mg/kg-dw)NOAEL(mg/kg-dw)LOAEL(mg/kg-dw)NOAEL(mg/kg-dw)LOAEL(mg/kg-dw) Liver Muscle Whole BodyEndpointbluegill 5freshJuvenile16.824.55.18.4 4.7 7.6 20.3 6.5 6.0 BW,Lbluegill 7freshAdult30.149.111.121.5 10.0 19.0 38.4 15.4 13.8 Rbluegill 10freshAdult 12.3 26.0 5.8 10.45.59.3 17.9 7.8 7.1 Dbluegill 37freshAdult 6.0 37.2 1.2 7.21.36.714.9 2.9 3.0BW, R, Sbluegill 53freshJuvenile6.319.91.46.3 1.3 7.8 11.2 2.9 3.2 S,BW,Lchannel catfish10 fresh Adult 7.312.52.13.82.03.6 9.6 2.8 2.7Schannel catfish13 fresh Fingerling --3.03.53.13.5 - 3.3 3.3BWchinook salmon 23 fresh Larvae218.831.95.912.0 5.4 10.8 24.5 8.4 7.6BW, Lchinook salmon 23 brackish Juvenile235.957.214.126.4 12.6 23.2 45.3 19.3 17.1BW, L, Sfathead minnow 9 fresh Larvae -121.0 -72.8 - 62.0 - - -BWfathead minnow 58 fresh Juvenile18.821.9 5.7 6.6 5.4 6.6 20.36.1 6.0BWfathead minnow 62 fresh Egg----1.619.6- -5.5Drainbow trout75 fresh Larvae6.19.91.32.5 1.2 2.3 7.8 1.8 1.7BW, Lrainbow trout38 fresh Juvenile 153.2 197.2--46.860.3 173.8 - 53.1BW, FG, Srainbow trout39 fresh Juvenile 42.095.0--12.628.9 63.2 - 19.1BW, S, FGrainbow trout41 fresh Juvenile321.0 71.71.04.3 1.0 4.0 38.8 2.1 2.0BW, FGSacramento splittail 74 fresh Juvenile 23.026.810.115.19.012.9 24.8 12.3 10.8Dwhite sturgeon55 fresh Adult 1.410.41.312.13.112.3 3.9 4.0 6.2Dwhite sturgeon71 fresh Juvenile 22.037.422.9 36.814.7 22.528.7 29.0 18.2BW, SANotes:1 - shaded cells represent concentrations predicted from measurements in other tissues (see Appendix A)2 - only results from the SeMet dietary exposure part of the study are used here3 - data from the low carbohydrate diet were not used as the authors reported that reduced weight of fish on this diet was likely due to food avoidance, not toxicityBW = Body WeightD = DeformitiesFG = Feed:Gain ratioL = LengthR= ReproductionS = SurvivalSA = Swimming ActivityApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### Using the data presented in Table 3-3, SMCVs were calculated for each fish species. For species where only one toxicity study was re ported, the SMCV is equal to the effect threshold from that study. The SMCVs are shown in the Table 3-4.

Table 3-4 Species mean chronic values calculated from the toxicity studies evaluated above.

SMCV (mg/kg-dw) Fish Species Water Type Liver Muscle Whole body Bluegill Lepomis macrochirus fresh 18.8 5.8 5.6

Channel catfish Ictalurus punctatus fresh 9.6 3.0 3.0

Chinook salmon Oncorhynchus tshawytscha fresh 24.5 8.4 7.6

Chinook salmon Oncorhynchus tshawytscha brackish 45.3 19.3 17.1

Fathead minnow Pimephales promelas fresh 20.3 6.1 6.0

Rainbow trout Oncorhynchus mykiss fresh 42.7 1.9 7.6 Sacramento splittail Pogonichthys macrolepidotus fresh 24.8 12.3 10.8 White sturgeon Acipenser transmontanus fresh 10.5 10.8 10.6

Note: shaded cells are based (at least partl y) on regressions, not measurements

Life History differences



### To determine whether there is a trend in the sensitivity to selenium over the lifespan of a fish, the data gathered were segregated by lif e-history stage (e.g., adul t, juvenile/fingerling, fry/larvae, egg). There were little data for fish larvae/eggs, and the majority of the available data are for effects on juveniles and adults. From the available data (Figures 3-3, 3-4) there does not appear to be a relationship between age and selenium sensitivity. A relationship may be present, but there is insufficient data available to adequately evaluate the existence of a pattern.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-11 Centrarchids

Juvenile Adult

Stage 2 4 6 8 10 12 14 16Selenium (mg/kg dw) in Centrarchids (whole body) Major effects

Figure 3-3 Effect thresholds for centrarchids (i.e., bluegill, green sunfish, and redear sunfish) from the selected studies grouped by life history stage.

Fry/larvae Juvenile

Stage 10 20 30 40 50 60 70Selenium (mg/kg dw) in Rainbow Trout (whole body) Minor effects
Major effects

Figure 3-4 Effect thresholds for rainbow tr out from the selected studies grouped by life history stage.April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### Since there were too few suitable studies to eval uate the potential effect of life history stage on selenium toxicity to fish, some of the criter ia that had been used to exclude studies were relaxed. Specifically, criteria F and G of Tabl e 3-1 were relaxed to increase our ability to evaluate life history stage. However, this mean s that studies that were included where fishes

were either fed food that wa s not reared under controlled conditions or where fishes were exposed to selenium in water on ly. The results are shown in Fi gures 3-5 and 3-6. Note that the studies that were added by relaxing the selection criteria were not included in the

calculation of SMCVs or screening values.

egg Fry/larvae Juvenile Adult

Stage 0 5 10 15 20 25 30 35Selenium (mg/kg dw) in Centrarchids (whole body) Major effects

Figure 3-5 Effect thresholds for centrarchids after relaxing the selection criteria.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-13 Egg Fry/larvae Juvenile Adult

Stage 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0Selenium (mg/kg dw) in Rainbow Trout (whole body) Minor effects
Major effects

Figure 3-6 Effect thresholds for rainbow trout after relaxing the selection criteria.



### Although the range of effect thresholds in Figure 3-5 overl ap, the mean effect threshold for juvenile centrarchids is 1.7 times lower than fo r adults. No trend was apparent in the data available for rainbow trout. Overall, it does not appear that eggs are more sensitive than juvenile or larval fish. There are several potenti al reasons that the available data do not show that eggs are more sensitive th an juvenile/larval fish: 1) the endpoints measured were not sensitive enough, 2) the type of selenium e xposure was not conducive to observing effects on eggs (e.g., waterborne exposures), or 3) fish eggs may indeed be less sensitive to toxic

chemicals than other life hi story stages (Finn 2007).

3.3 D ISCUSSION 

### 80 selenium toxicity studies were reviewed in an effort to de rive selenium sc reening values for species representative of fishes in the North Bay (Table 3-1). Based on this review, species which are appropriate for use in deve loping a fish tissue scre ening values for the North Bay, and for which usable selenium toxi city data are available, include: bluegill ( Lepomis macrochirus ), fathead minnow ( Pimephales promelas ), rainbow trout ( Oncorhynchus mykiss ), Chinook salmon ( Oncorhynchus tshawytscha ), Sacramento splittail ( Pogonichthys macrolepidotus ), and white sturgeon ( Acipenser transmontanus ).

With the exception of the study on the impact s of selenium on Chinook salmon in fresh and brackish water (Hamilton et al. 1990 ), all usable studies performed to date on the effects of selenium on fish have been performed in fres hwater. In addition to these species, selenium toxicity data was sought for striped bass, flounder, and delta smelt. However, no usable selenium toxicity data were available for thes e fish, nor were data available for any other closely related species (e.g., pond smelt, Hypomesus olidus ).April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### Based on the available data, it appears that the species of concern in the North Bay for which toxicity data are available (i.e., Sacram ento splittail and white sturgeon) are less sensitive to selenium than bluegill (Table 3- 4), a species that has been observed to be particularly sensitive to selenium in a number of studies (e.g., Lemly 1993a) and was selected by USEPA as the basis of the curren t draft water quality criterion for selenium (USEPA 2004). Further, channel ca tfish appear to be even more sensitive to selenium than bluegill. However, with only one dietary and one injecti on toxicity study available on catfish, confidence in the sensitivity of channel catfish to selenium is limited.

Other selenium screening values 

### The selection of an appropriate selenium fish tissue screening value, protective of toxic

effects in both individual fish and populations, is an area of active debate (Chapman 2007; Hamilton 2003, 2004; Lemly and Skorupa 2007; McDonald and Chapman 2007; Skorupa et al. 2004; USEPA 2004). Numerous screening values for selenium in fish tissues have been proposed in the past. These values are summarized in Table 3-5.

Table 3-5 Whole body fish tissue screening levels (mg/kg-dw) published in the scientific literature.

Reference No effect a Level of concern b Toxicity Threshold c
Lemly and Smith (1987) 12 Henderson et al (1995) 4 4-12 12 Stephens et al. (1997) 2-3 4 4 USDOI (1998) 2-3 2-4 4 DeForest et al (1999) 6 (cold water) DeForest et al (1999) 9 (warm water) Lemly (1993c, 1996, 2002b) 4 Hamilton (2003) 4 Ohlendorf (2003) 4 USEPA (2004) 7.9

Notes: a - Concentrations less than this value produce no discernible adverse effects on fish or wildlife and are typical of background concentrations in uncontaminated environments (USDOI 1998). b - Concentrations in this range rarely result in discernib le adverse effects on some fish or wildlife species (USDOI 1998). c - Concentrations greater than this value may result in adverse effects on some fish or wildlife species (USDOI 1998).



### The earliest screening values were 12 mg/kg-dw (see Le mly and Smith (1987), Henderson et al. (1995)) (Table 3-5). However, as more da ta became available, most authors generally recommended a screening value of 4 mg/kg-dw (T able 3-5). In part, those screening values were derived to be protective of the lowest concentration at which selenium exposures resulted in toxicity in a singl e study. Thus, the approach used to derive the screening values in the scientific literature has generally been to use the lowest whole body values from Table 3-3. Further, the approach in the scientific li terature has been to derive a screening value protective of all fish species across the entire United States and not just the North Bay.

There have also been several critiques of the USEPA (2004) draf t that have noted statistical and interpretational errors in the draft that potentially affect the draft screening value (Lemly and Skorupa 2007, Skorupa et al. 2004).North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-15 

### Presser and Luoma (2006) also reviewed the to xicity literature and concluded that wholebody fish tissue concern levels range from 1.5 to 6 mg/kg-dw.

Warm water vs. cold water screening values 

### One of the major topics of discussion in the recent past has been whether cold water fish are

more sensitive to selenium that warm water fish. Recent reviews have not found support for

the cold vs. warm water distinct ion (e.g., Hamilton 2003, Chapman 2007).

Effect of sulfate on selenium toxicity 

### Acute toxicity tests have shown that sulfate reduces the potential for bioaccumulation and toxicity of selenium to algae, aquatic invertebrates, and fish (see Brix et al. 2001, Schlenk et al. 2003, USEPA 2004). USEPA (2004) provides th e following discussion on the effects of sulfate on selenium toxicity:

“The toxicity of a number of metals (e.g., c opper and cadmium) to aquatic organisms is

related to the concentrat ion of hardness in the water. The to xicity of these metals to many different aquatic species has been shown to decrease as the hardness concentration increases. A similar relationship also has been recognized between selenate and dissolved sulfate in freshwater (a similar relationship is not evident between selenite and sulfate or between either form of selenium and hardness ). The studies reviewed in this document indicate that, as the concentration of sulfate increases, the acute toxicity of selenate is reduced (less toxic). Selenate ac ute toxicity tests c onducted at different l evels of dissolved sulfate are available with C. dubia, D. magna, H. azteca

, G. pseudolimnaeus , chinook salmon and fathead minnows (Table 1a [of USEPA 2004] ). These data indicate that, in general, selenate is more toxic to these species in low sulfate water than in higher sulfate

water.”

Since sulfate levels should be higher in brack ish and marine waters than in freshwaters, screening values based on freshwater selenium toxicity studies are likel y to be protective of potential impacts to fishes in estuarine and marine environments. Th ere are several possible reasons why sulfate may reduce th e toxicity of selenate, includi ng 1) the ability of sulfate, calcium, or magnesium to prevent the inte raction of selenomethi onine with critical subcellular proteins by maintaining the cellular redox potential (Schlenk et al. 2003) and 2) direct competition at the cell uptake site as sele nate and sulfate are structurally similar group VI oxyanions of the form XO 4 

### ; experiments with bacteria indicate that selenate and sulfate

have a common membrane carrier and that active transport by this carrier is the only means by which selenate may enter a cell (Brix et al. 2001).

Potential screening values for the North Bay 

### The objective of this review of the selenium to xicity information available for fishes is to provide a technical basis for th e selection of an appropriate selenium fish tissue screening value for in the North Bay. Since there are limite d selenium toxicity da ta available for fish of concern for the North Bay (e.g., no suitable sele nium toxicity data for delta smelt, halibut, jacksmelt, striped bass, Tidewater goby, or white croaker), it is not possible to develop screening values that take into account the effect s of selenium on all fish species of potential concern in the North Bay.April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### The SMCVs for species such as Chinook salmon, rainbow trout, Sacramento splittail, and white sturgeon indicate that these species are less sensitive to selenium than bluegill and channel catfish (Table 3-4), which appear to be fairly sensitive to selenium. Thus, using a screening value for the North Bay based on either bluegill (e.g., SMCV of 5.6 mg/kg-dw whole body) or channel catfish (e.g., SMCV of 3.0 mg/kg-dw w hole body) should be protective of most (if not all) fish species, wh ile not setting an unrea listically low threshold for potential effects.

The single study that evaluate d the effects of selenium in both brackish and freshwater (Hamilton et al. 1990), indicated that Chinook sa lmon were more than twice as sensitive to

selenium in freshwater as in brackish water. However, this study ex amined the effects of

selenium on larvae in fresh wa ter and juveniles in brackish wa ter. Therefore, the greater sensitivity observed in freshwater with larvae could also be due to life history differences in selenium sensitivity.

Table 3-4 also presents SMCV s for selenium in liver and muscle. Liver concentrations respond rapidly to changes in the environment and may be useful in detecting short term

selenium fluctuations. Muscle concentratio ns may be non-destructively measured in relatively large fishes by collec ting and analyzing muscle plugs. This may be desirable as it reduces the impact of selenium monitoring on fish populations, which is especially important for special status species. However, it should be noted that the regressions used

here to convert selenium concentrations measur ed in one tissue type to another tissue type are not specific to the species and populations considered here, with the exception of white sturgeon (see Appendix A). Therefore, using scre ening values that were calculated using the regressions from USEPA (2004) in corporates some uncertainty.

Beckon (2007) 

### In contrast to the approach used here (i.e ., calculating effect thresholds and SMCVs), Beckon (2007) derived an EC10 and an EC20 (of 1.84 and 2.5 mg/kg-dw, respectively) for the survival of salmon fry by performing a re gression on the treatment means in Hamilton (et al. 1990) (see above). However, it should be noted that performing a regression on the treatment means artificially reduces the varia tion. Further, the shape of the relationship may change when using the raw data. Thus, the EC10 and EC20 derived by Beckon (2007) should be viewed as approximations. It is also unknown whether the EC10 and EC20 are significantly different from each other.

Nutritional requirements 

### Selenium is a micro-nutrient (see Section 1). When animals do not have enough selenium in their diet, selenium deficiency results (N RC 1993, 1994). For fish, nutrient requirements are given in terms of the concentration in their feed, not in fish tissue, as is being used here to derive screening values. Nonetheless, the nutri tional requirements of two species of fish have been established and are provided here for reference: 0.25 mg/kg for channel catfish and 0.3 mg/kg for rainbow trout (NRC 1993). These concentrations are gi ven in an “as fed basis.” Fish feed is usually in the form of dr y pellets and probably ha s a moisture content of approximately 10%, meaning the dietary requir ements listed above in mg/kg-as fed do not differ substantially from mg/kg-dw.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 3-17 Additional considerations



### Issues to be considered in the collec tion and interpretation of samples include:

• tissue concentrations in fishes may vary with the time of year sampled

• tissue concentrations may vary by geographic location

• if sampling dietary items of birds, seleni um concentrations may also differ among their prey items

• number of samples to collect

• the frequency of collections

• whether samples should be composited

• how to compare measured concen trations to screening values

These issues are discussed in greater detail in Section 6.

The studies used in the determination of the screening value presented above, and all screening values obtained from the literature, were not derive d using the populations of fish that occur in the North Bay nor using the e nvironmental conditions in the North Bay. This means that there is some uncertainty as to whether any screening criteria are actually applicable. Similarly, McDonald and Chapma n (2007), recommend that screening values only be used to determine if further evaluati on is necessary. They recommend that if fish tissue concentrations exceed an appropriate sc reening value that 1) reproductive toxicity testing be conducted for the species of concern and that if reproductive toxicity testing indicates that the species has been negatively affected by selenium th at 2) fish population surveys be conducted. McDonald and Chapma n (2007) provide recommendations on how both reproductive toxicity test ing and fish population survey s can be integrated into a selenium monitoring program.

Future research and data gaps 

### Several data gaps and areas wh ere further research may be be neficial to the Water Board were identified during the evaluation of seleni um toxicity to fish in the North Bay, as

follows:

1. Although it is believed that selenium should be less toxic to fish in marine and estuarine systems than freshwater systems, the data to show this are lacking. Toxicity experiment performed with representative fish species in using multiple salinities over the range that occurs in the North Bay would provide valuable

information.

2. Toxicity studies have not been performed on most of the species of concern (which includes endangered species) in the North Bay. Thus, this report has assumed that toxicity studies on bluegill, rainbow tr out, chinook salmon, channel catfish, andApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### fathead minnows are representative of th e species of concern. The species of concern may be more or less sensitive.

3. Channel catfish appear to be one of the most sensitive species. However, only two

studies were available. If the Water Board believes that channel catfish are representative of the fish in the North Ba y, additional toxicity studies using channel

catfish would be warranted.

4. The existing toxicity data suggests th at younger life history stages are more sensitive to selenium, but most selenium toxicity studies have focused on only a single life history stage. Thus, it is po ssible that some species may be more

sensitive to selenium than shown here.

5. Species-specific regressions to convert selenium concentrations from one tissue type to another are lacking for all of the fish species evaluated here, except white sturgeon. Therefore, the re gressions from USEPA (2004) for bluegill were used for most species. Since the applicability of these regressions to other species is unknown, screening values derived using the bluegill tissue rela tionships should be viewed as approximations and may need to be revisited as new data becomes available. Further, if the Water Board deci des to monitor fish tissue concentrations by collecting muscle plugs, it would be beneficial to deve lop species-specific regressions.

6. A detailed re-analysis of the published toxi city data using, for example, biphasic regressions (Beckon 20 07, Beckon et al. 2008) would pr ovide a greater level of

confidence in estimates of the threshold fo r toxic effects of selenium vs. a LOAEL, NOAEL, or effect threshold. However, if on ly the treatment means are available for the analyses, it should be remembered that th is type of analysis will mask the true variability in the data.

3.4 C ONCLUSIONS 

### Exposure to elevated levels of selenium can cau se adverse effects in fish. Two of the species that occur in the North Bay that have been tested (i.e., Sacramento splittail and white sturgeon) appear to be less sens itive than other freshwater fi sh. While it has generally been believed that bluegill are one of the more sensitive fish species , the two studies available on channel catfish indicates that they may be more sensitive than bluegill. However, one of the most important concerns for selenium toxicity to fish remains an open question at the end of

this review: is selenium less toxic to fish in marine and brackish waters than freshwater? The available data supports the asser tion that selenium should be less toxic to fish in marine and brackish waters, but it is not possible to quantify the difference at this point.

Numerous selenium screening values protectiv e of fish have been proposed. For whole body fish selenium concentrations, the recommended screening values are usually in the range of 2-4 mg/kg-dw (Table 3-5). Additionally, it has been proposed that separate screening values

be used for cold water fish vs. warm wate r fish, although recent reviews have not found support this distinction (e.g., Hamilton 2003, Chapman 2007).

Based upon the data presented here, there are several options for selenium fish tissue screening values. Those options are as follo ws (all in units of mg/kg-dw whole body):North San Francisco Bay Selenium Toxicological Assessment April 2008

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### 1. The lowest SMCV: 3.0 (Table 3-4)

2. The salmon EC20 from Beckon (2007) of 2.5

3. Lowest concentration at which advers e effects were reported (Table 3-3)

a. LOAEL of 2.3

4. The lowest LOAELs for fish in the North Bay (Table 3-3)

a. 12.9 for Sacramento splittail

b. 12.3 for white sturgeon

5. The lowest effect thresholds for fi sh in the North Bay (Tables 3-3, 3-4)

a.10.8 for Sacramento splittail

b.6.2 for white sturgeon

6. The lowest SMCVs for fish in the North Bay (Table 3-4)

a.10.8 for Sacramento splittail

b.10.6 for white sturgeon

7. The white sturgeon EC10 calculated by Beckon (2008) from the data in Linville (2006)

of 11.9

The choice of using an SMCV, LOAEL, or effe ct threshold is dependent upon both the level of risk and uncertainty the Water Board wishes to accept. This issue was discussed in more

detail in the Introduction. It is worth noting that of thes e values, only the LOAELs represent concentration at which effects have been demonstrated. However, since only a few concentrations have been tested, effects may actually occur at lower concentrations.North San Francisco Bay Selenium Toxicological Assessment April 2008

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### 4 A VIAN TOXICITY REVIEW


### The waters of the North Bay s upports a diverse avian biota. So me birds are residents in the Bay all year round, while many others rely on the North Bay as part of their annual migrations. The birds supported include both ga me birds as well as and threatened and endangered species. The North Bay supports th e following threatened and endangered bird species (USFWS 2007):

• American bittern ( Botaurus lentiginosus )

• American peregrine falcon ( Falco peregrinus anatum )

• American white pelican ( Pelecanus erythrorhynchos )

• bald eagle ( Haliaeetus leucocephalus )

• black tern ( Chlidonias niger )

• California black rail ( Laterallus jamaicensis coturniculus )

• California brown pelican ( Pelecanus occidentalis californicus )

• California clapper rail ( Rallus longirostris obsoletus )

• California least tern ( Sterna antillarum browni )

• double-crested cormorant ( Phalacrocorax auritus )

• marbled murrelet ( Brachyramphus marmoratus )

• mountain plover ( Charadrius montanus )

• northern harrier ( Circus cyaneus )

• osprey ( Pandion haliaetus )

• prairie falcon ( Falco mexicanus )

• tricolored blackbird ( Agelaius tricolor )

• western least bittern ( Ixobrychus exilis hesperis )

• western snowy plover ( Charadrius alexandrinus )

• white-faced ibis ( P legadis chihi )

• white-tailed kite ( Elanus leucurus )April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### The North Bay supports a number of birds that are not classified as threatened and endangered but are covered under the Migrat ory Bird Treaty Act (MBTA), including (USFWS 2007):

• Aleutian Canada goose ( Branta canadensis leucopareia )

• black scoter ( Melanitta nigra )

• Caspian tern ( Sterna caspia )

• greater scaup ( Aythya marila )

• lesser scaup ( Aythya affinis )

• surf scoter ( Melanitta perspicillata )

• white-winged scoter ( Melanitta fusca )

Lastly, the North Bay supports seve ral species of water fowl that are of recreational interest. While the California Department of Fish and Game (DFG) does not provide any information on which species are harvested in the North Ba y, they do provide limits (i.e., “bag limits”) on how many can be harvested at one time (D FG (2007). These limits, which indicate which water fowl species are of recreati onal interest, are provided below:

• canvasback ( Aythya valisineria ): 1

• American coot ( Fulica americana ): 25

• Ross’s goose ( Chen rossii ): 4

• snow goose ( Chen caerulescens ): 4

• white-fronted goose ( Anser albifrons ): 4

• cackling goose ( Branta hutchinsii ): 6

• Aleutian goose ( Branta canadensis leucopareia ): 6

• Canada goose ( Branta canadensis ): 4

• mallard ( Anas platyrhynchos ): 7 but not more than 2 hens

• common moorhen ( Gallinula chloropus ): 25

• pintail ( Anas acuta ): 1

• redhead ( Aythya america na ): 2North San Francisco Bay Selenium Toxicological Assessment April 2008

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### • scaup ( Athya affinis and Athya marila ): 3

• merganser ( Mergus spp. and Lophodytes cucullatus ): 7

The USFWS (2007) evaluated th e bird species found in the North Bay that are covered

under the MBTA as well as the threatened and endangered species and determined that the following species were most at risk from potential exposures to selenium:

• bald eagle ( Haliaeetus leucocephalus )

• black scoter ( Melanitta nigra )

• California clapper rail ( Rallus longirostris obsoletus )

• greater scaup ( Aythya marila )

• lesser scaup ( Aythya affinis )

• surf scoter ( Melanitta perspicillata )

• white-winged scoter ( Melanitta fusca )

Among birds, exposures to elevated levels of selenium can induce gross abnormalities during development, egg inviability, chick mort ality (Adams et al. 2003), reduced weight gain, reduced adult condition, and reduced adult survival (N RC 2005, Ohlendorf 2003). When the selenium concentrations are high enough in a large enough area, these effects can lead to population declines fo r the most affected species.

The step in the effort to determine whether bi rds may be adversely impacted by selenium in the North Bay is to evaluate the toxicity of se lenium to the marine mammals. Next, potential selenium screening values for the species in the North Bay are proposed. Lastly, the screening values are compared to nutritional requirements.

4.1 M ETHODS 

### Selenium toxicity data for the bird species that the USFWS (2007) ha s identified as being most at risk from selenium in the North Bay (s ee list above) would be the most relevant for the Water Board’s development of a TMDL. Howe ver, selenium toxicity studies have not been performed for any of the species identified by the USFWS ( 2007) as being most at risk from selenium in the North Bay. Therefore, in this section of the report, we review the

available avian selenium toxicity literature.

For birds, selenium studies have generally fo cused on 1) determining a toxic concentration in the diet, 2) determining a toxic concentrati on in eggs, or 3) improving bird “performance” on a poultry farm. We reviewed papers published in the scientific literature for all three types of data. Studies were excluded from the consideration for the selection of a screening value (see Table 4-1) if they:

A. did not provide a LOAELApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### B. were not chronic

C. exposed birds to multiple contaminants simultaneously

D. exposed birds to multiple treatments simultaneously

E. field studies

Using the filtering criteria above, only studies where the re ported effects can unambiguously

be attributed to selenium were reviewed. So me of the poultry perfor mance studies were not performed using dietary concentrations high enough to cause toxic ef fects. These studies will be used to set a lower bound on screening values. Most of the studies describing the early laboratory work on th e effects of selenium on poultry species are no longer readily accessible. When the original studies are not re adily available, the reviews that summarize the results of the original studies are cited.

The reported effects from each study were grou ped into one of two categories: major and minor effects. Major effects are those that have the potential to impact birds at the organism and/or population level (e.g., incr eased mortality, reduced fecund ity, reduced growth, etc.). Minor effects are those that are measurable, but are unlikely to result in population level effects and/or the long-term impacts on indi vidual bird performance was unclear (e.g., a change in an enzyme concentration). Where bo th major and minor effects were observed at the same concentration, the effects was assu med to be major. Only major effects were considered in development of screening values.

All studies that were reviewed are listed in Table 4-1. Studies that were determined to be

unsuitable are noted in Table 4-1 using the designations from the list above. The 21 suitable studies selected are pr esented in Table 4-2.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 4-5 Table 4-1 Selenium toxicity studies evaluated in this review. Studies that were excluded from review are indicated in the table (see text above for an explanation of the criteria).

Study Reference Evaluation

criteria failed Study Reference Evaluation

criteria failed 1 Albers et al. (1996) 24 Latshaw et al. (2004) 2 Anteau et al. (2007) A,C,E 25 Lowry and Baker (1989) 3 Biswas et al. (2006) A 26 Ort and Latshaw (1978) 4 Elzubier and Davis (1988) 27 O'Toole and Raisbeck (1997) 5 Fairbrother et al. (1994) C, E 28 Pappas et al. (2005) A 6 Franson et al. (2007) 29 Paton et al. (2002) A 7 Green and Albers (1997) 30 Payne et al. (2005) A 8 Harding (2007) E 31 Ratti et al. (2006) A,E 9 Heinz and Hoffman (1996) 32 Rattner et al (2000) A,C,E 10 Heinz and Hoffman (1998) 33 Ryu et al. (2005) A 11 Heinz et al. (1987) 34 Sahin and Kucuk (2001) A 12 Heinz et al. (1988) 35 Santolo et al. (1999) A 13 Heinz et al. (1989) 36 Stanley et al. (1994) 14 Heinz et al. (1996) 37 Stanley et al. (1996) 15 Hoffman and Heinz (1998) 38 Stoewsand et al. (1978a) A,C 16 Hoffman et al. (1991) 39 St oewsand et al. (1978b) A,C 17 Hoffman et al. (1992a) 40 Surai et al. (2006) A 18 Hoffman et al. (1992b) 41 Takekawa et al. (2002) A,C,E 19 Hoffman et al. (1996) 42 Wa yland et al. (2002) A,C,E 20 Hoffman et al. (1998) C,E 43 Wiemeyer and Hoffman (1996) 21 Hoffman et al. (2002) C,E 44 Wilson et al. (2007) A,C,D,E 22 Jensen (1975) 45 Yamamoto and Santolo (2000) A 23 Kinder et al. (1995) D 46 Yamamoto et al. (1998) A



### To be consistent with the approach used fo r developing screening va lues for fish, effect thresholds were calculated as the geometri c mean of the NOAEL and LOAEL reported for

the same effect in an indivi dual study. Additionally, species mean chronic values (SMCVs) were calculated as the geometri c mean of the effect thres holds (USEPA 1985). Studies in which a zero concentration was reported in th e control were assumed to have used 0.2 mg/kg-dw, as this is the di etary requirement for birds (N RC 1984). Studies that did not report a NOAEL were excluded from the calculation of an effect threshold and the SMCV. Note that excluding studies in which a NOAEL was not reported from the calculation of the

SMCV results in lower SMCVs.

Conversions from dry weight to wet weight are detailed in Appendix A.

4.2 R ESULTS Toxicity studies 

### The toxicity studies from Tabl e 4-1 that were included in the evaluations below included the following bird species:

• Chickens

• Eiders

• Kestrels

• PheasantsApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### • Mallards

• Screech owls

In contrast to the studies on fish, where whole body selenium concentrations are usually measured, the toxicity studies performed on birds have usually measured the selenium content of the feed given to the bird. Therefor e, the screening values derived here are for dietary selenium concentrations.

Chickens



### Four studies were identified for domestic ch ickens (Table 4-2). On ly one study (Ort and Latshaw 1978) examined the effect of seleni um on the most sensitive endpoint; i.e., egg hatchability. It is also worth noting that Ort and Latshaw (1978) review two earlier studies

not available to us that show 1) “egg weight, fertility and hatchability were all significantly decreased by 8 ppm [dietary] selenium,” and 2) “Embryonic development was adversely affected by 10 ppm dietary se lenium but not by 5 ppm.”North San Francisco Bay Selenium Toxicological AssessmentMarch 2008Tetra Tech, Inc.4-7Table 4-2Summary of dietary selenium toxicity studies evaluated in this review.(mg/kg-dw) EffectBird Study Lifestage DietaryformNOAEL LOAEL Effect threshold Major MinorEndpointChicken 4Chick selenite 0.15 10 1.2 X BWChicken 22Chick selenite 0.9 4.3 2.0 X BWChicken22 Chickselenite4.313.57.6XBW, SChicken 25Chick selenite;SeMet 0.2 15 1.7 X BWChicken 26Adult selenite 3 5 3.9 X RCommon eider6 AdultSeMet20.657.734.5XBWMallard 1Adult SeMet 22.3 44.7 31.6 X CMallard 7Adult SeMet 11.2 22.3 15.8 X SMallard 9Adult SeMet 0.6 10.6 2.6 X RMallard 10Adult SeMet 0.4 9.8 2.1 X RMallard 11Adult selenite 10.9 27.3 17.3 X BW,RMallard 11Adult SeMet 0.2 10.9 1.5 X RMallard 12Duckling selenite 10.9 21.6 15.3 X BWMallard 12Duckling SeMet 10.9 21.6 15.3 X BWMallard 13Adult SeMet 4.6 9.0 6.4 X RMallard 14Duckling SeMet 17.0 33.7 24.0 X BWMallard 15Adult SeMet 0.4 11.6 2.3 X EMallard 16Duckling SeMet;lowprotein0.2 16.9 1.9 XBWMallard 16Duckling SeMet 16.9 66.9 33.6 X BW,SMallard 17Duckling SeMet 0.2 16.9 1.9 X BWMallard 18Duckling SeMet 0.2 16.5 1.9 X EMallard 18Duckling SeMet 16.5 65.4 32.9 X BWMallard 18Duckling SeMet;lowprotein16.5 65.4 32.9 X SMallard 18Duckling SeMet;lowprotein0.2 16.5 1.9 X EMallard 18Duckling SeMet;highprotein0.2 16.5 1.9 X BWMallard19 DucklingSeMet, Se yeast,Se in wheat0.2 16.9 1.9 X EMallard 27Flightling SeMet 13.8 33.8 21.6 X BW,SMallard 36Adult SeMet 0.37 6.5 1.6 X RMallard 37Adult SeMet 3.9 7.8 5.5 X BW,RPheasant124 Adult unknown 0.4 9.3 1.9 X R,SScreech owl43 adultSeMet8.83016.2XBW, RScreech owl43 adultSeMet0.38.81.6XENotes: 1 - Although the concentration at the NOAEL was not measured, the lead investigator on this study said that he believes it was probably 0.4 mg/kg.BW = Body WeightC = ConditionD = DeformitiesE = EnzymesFG = Feed:Gain ratioL = LengthR= ReproductionS = SurvivalSA = Swimming ActivityApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### In addition to the studies summarized in Table 4-2, the NRC (1980, 1994, 2005) provide summaries of additional dietary selenium toxic ity studies on domestic chickens that were

not available to the authors of this report. These data are pr esented in Tables 4-3 through 4- 5, respectively.

Table 4-3 Summary of additional selenium toxi city studies from the NRC (1980).

Concentration (mg/kg) Age Chemical Form NOAEL LOAEL Effect Reference Adult Se in corn, barely, wheat 2.5 5 increased chick mortality Moxon (1937)

Adult Na 2 SeO 3 - 6.5 deformed embryos Moxon (1937) 1 day Na 2 SeO 3 4 8 decreased weight gain Moxon (1937) 1 day selenous acid 2 8 increased ch ick mortality Thapar et al (1969) 1 day SeO 2 - 5 increased mortality Hill (1979)

Adult Na 2 SeO 3 - 8 embryo necrosis Gruenwald (1958)

Table 4-4 Summary of additional selenium toxi city studies from the NRC (1994).

Age Chemical Form Concentration (mg/kg) Effect Reference

Immature Na 2 SeO 3 + Se in wheat 10 Reduced growth Carlson and Leitis (1957) Laying hen Se in wheat 10 Reduced hatchability Moxon and Wilson (1944)

Table 4-5 Summary of additional selenium toxi city studies from the NRC (2005).

Concentration (mg/kg) Age Chemical Form NOAEL LOAEL Effect Reference

Adult selenite 5 10 reduced growth Jensen and Chang (1976) 1 day selenite 1 5 reduced growth Jensen (1986)



### For all of the studies on chic kens presented above, it is unclear whether the dietary concentrations are provided as ww or dw. It is likely that the dietary concentrations are ww

but that the %moisture is relati vely low (e.g., 10%) as chicken feed is usually in the form of dry pellets. So, there is some uncertainty abou t the exact concentration of selenium in the studies above on chickens, but it is likely to be a small effect; e.g., 5 mg/kg-ww with a %moisture of 10% is equi valent to 5.6 mg/kg-dw.

Eiders 

### A single suitable study was identified (Franson et al. 2007). That study provided both a NOEAL and LOAEL for weight loss (i.e., a ma jor effect) in diet, but did not examine reproductive success (Table 4-2).

Kestrels



### Three studies have been conducted on the toxicity of dietary sele nium to kestrels (Santolo et al. 1999, Yamamoto et al. 1998, Yamamoto and Sa ntolo 2000). The first two studies (i.e., Santolo et al. 1999, Yamamoto et al. 1998) did not show an effect at up to 12 mg/kg-dw. In the third study (Yamamoto and Santolo 2000), th e authors state that kestrels fed 12 mg/kgdw selenium had a lower “normalized body fat” than the kestrels in the other treatments.North San Francisco Bay Selenium Toxicological Assessment April 2008

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### However, the difference wa s not significant (i.e., p = 0.173) and was, therefore, excluded

from Table 4-2 and consideration in th e development of a screening value.

Mallards 

### Mallards are the bird species for which the most information is available. Fourteen suitable

studies were identified on mallards. The studi es examined effects on adults, ducklings, and reproductive success (Table 4-2).

Pheasants 

### A single suitable study was identified (Latsh aw et al. 2004). That study provided a NOAEL and LOAEL based on mortality and reduced egg laying (Table 4-2).

Screech owls 

### A single suitable study was identified (Wie meyer and Hoffman 1996). That study provided

both a NOAEL and LOAEL for selenium in the diet and eggs base d on weight loss and reduced reproductive success. A NOAEL and L OAEL was also provided for minor effects; i.e., changes in enzyme concentrations (Table 4-2).

4.3 I MPROVED PERFORMANCE STUDIES 

### Among birds that are raised on poultry farms, there has been extens ive research in an attempt to balance the beneficial effects of se lenium supplementation against the toxicity of selenium. These studies generally provide NOA ELs only and do not necessarily examine the effects of selenium on reproductive success. Th e available studies are summarized in Table

4-6 below.

Table 4-6 Studies evaluating improved performance in poultry from selenium supplementation.

Effects

Bird Study Life stage Dietary

form NOAEL (mg/kg) dw/ww Survival Weight Egg output Reproductive

success Chicken 24 Adult selenite 2.6 ? X

Chicken 24 Adult Seyeast 2.9 ? X

Chicken 27 1 day selenite 8.17 dw X Japanese quail 3 1 day selenite 1.2 ? X X

Japanese quail 28 10 day selenite 0.2 dw X



### The most sensitive endpoint for selenium eff ects in birds is reproductive success (i.e., egg hatchability and chick survival). However, since none of the performance studies examined the potential effects of selenium on reproductive success, these studies should not be used to put a lower bound on the acceptable level of dietary selenium for birds.

4.4 D ISCUSSION 

### More than 40 selenium toxicity studies were reviewed in an effort to determine dietary selenium screening values for species represen tative of birds in the North Bay (Table 4-1). Based on this review, species which are appropri ate for use in developing screening criteria for the North Bay, and for which usable seleni um toxicity data are available, include:April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### chickens ( Gallus gallus ), common eiders ( Somateria mollissima ), mallards ( Anas platyrhynchos ), pheasants ( Phasianus colchicus ), and screech owls ( Otus asio ).

The data presented above (Tab les 4-2 through 4-5; regardle ss of selenium type) were grouped into effects on immature birds (i.e., ch icks and ducklings), adults, and reproductive success (i.e., egg hatchability, chick survival, e gg fertility, etc.) and are presented in Table 4-

7 below.

Table 4-7 Summary of NOAELs and LOAELs (mg/kg-dw) reported in this section grouped by whether the

effects were measured in chicks/ducklings, adul t birds, or in terms of reproductive success. Studies using all selenium species are shown here.

Chick/Duckling Adult Reproductive success

NOAEL LOAEL Effect

Threshold NOAEL LOAEL Effect

Threshold NOAEL LOAEL Effect

Threshold

0.15 10 1.2 5 10 7.1 2.5 5 3.5

0.2 15 1.7 3 5 3.9

0.9 4.3 2.0 5 10 7.1

1 5 2.2 - 6.5 -

2 8 4.0 - 8 -

4 8 5.7 - 8 -

4.3 13.5 7.6 - 10 -

- 5 -

- 10 - Chicken

SMCV 2.9 SMCV 7.1 SMCV 4.6

Eider 20.6 57.7 34.5

0.2 16.5 1.9 11.2 22.3 15.8 0.2 10.9 1.5

0.2 16.9 1.9 13.8 33.8 21.6 0.37 6.5 1.6

0.2 16.9 1.9 22.3 44.7 31.6 0.4 9.8 2.1

10.9 21.6 15.3 0.6 10.6 2.6

10.9 21.6 15.3 3.9 7.8 5.5

16.5 65.4 32.9 4.6 9.0 6.4

16.5 65.4 32.9 10.9 27.3 17.3

16.9 66.9 33.6

17.0 33.7 24.0 Mallard

SMCV 10.4 SMCV 22.1 SMCV 3.6

Pheasant 0.4 9.3 1.9

Screech

owl 8.8 30 16.2



### From the data presented in Table 4-7, it woul d appear that immature chickens are more

sensitive to selenium than immature malla rds, although there was some variation among chicken strains (see Table 4-2). The availabl e studies on reproductive success appear to

indicate that mallards are a little more sensitive than chickens but that screech owls are less

sensitive than either chickens or mallards. Fo r pheasants, the small amount of available data indicates that reproductive success is affect ed at relatively low concentrations.

State of Utah 

### The State of Utah is also deriving dietary se lenium screening values protective of birds feeding at the Great Salt Lake (Ohlendorf 2007, provided as Appendix B). To develop a selenium screening value for the Great Sa lt Lake, the Great Salt Lake Science Panel compiled the concentration of selenomethionine in feed, total selenium in eggs, and mean hatching success per treatment from 6 studi es on mallards (i.e., Heinz et al. 1987, 1989, Heinz and Hoffman 1996, 1998, Stanley et al. 1994, 1996; all of these studies are included in Tables 4-1, 4-2, and 4-7) and examined the data using both a logistic regression and aNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 4-11 

### hockey-stick regression. The regre ssions were used to derive concentrations at which 10% of the population would be affected (EC10) for both dietary and egg selenium

concentrations. The results for mean hatc hing success are as follows (mg/kg-dw):

• Dietary selenium

o Logistic regression: 4.9

o Hockey stick-regression: 4.4

• Egg selenium

o Logistic regression: 12.5

o Hockey stick-regression: 11.5

Figure 4-1 Logistic regression of mallard dietary selenium concentration vs. proportion of eggs hatching. From Ohlendorf (2007).April 2008 North San Francisco Bay Selenium Toxicological Assessment

4-12 Tetra Tech, Inc. Figure 4-2 Hockey stick regression of mallard dietary selenium concentration vs. proportion of eggs hatching. From Ohlendorf (2007).

Figure 4-3 Logistic regression of mallard egg selenium concentration vs. proportion of eggs hatching. From Ohlendorf (2007).North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 4-13 Figure 4-4 Hockey stick regression of mallard egg selenium concentration vs. proportion of eggs hatching. From Ohlendorf (2007).



### The logistic regressions were previously re ported in Ohlendorf (2003) and the hockey-stick regression for egg selenium was previously re ported in Adams et al. (2003). The paper by Adams et al. (2003) is the third paper publishe d by the same group of authors on this topic; i.e., Fairbrother et al. (1999, 2000) used the data from fewer studies (i.e., Heinz et al. 1989 and Stanley et al. 1994) to derive an EC10 for eggs of 16 mg/kg-dw.

As discussed above for the regression approach used by Beckon (2007) to analyze fish data, the State of Utah (Ohlendorf 2007) performed regressions on the treatment means, instead of the raw data from each individual, which artificially reduces the variation; i.e., the confidence limits on the regre ssion lines in Figures 4-1 th rough 4-4 may be much larger. Further, the shape of the relationship may change when using the raw data. Thus, the EC10 and EC20 presented in Figures 4-1 through 4-4 should be viewed as approximations. Lastly, the data used in the logistic regressions (O hlendorf 2003) was also normalized against the controls. This may have obscured a biphasi c relationship (see Beckon et al. (2008)).

There are a few minor problems with the data used by the St ate of Utah (Ohlendorf 2007) that should be kept in mind. First, the concentrat ion of selenomethionine used in the logistic regressions was assumed by the State of Ut ah (see Ohlendorf 2003) to be dry weight (Ohlendorf 2007) but the concentrations were actu ally presented as wet weight. The State of Utah (Ohlendorf 2007) acknowledged this by stating that the values derived in the logistic regressions for dietary concentr ations should be increased by 11 percent (i.e., to 5.4 mg/kgdw). Further, the State of Utah (see Oh lendorf 2003) used the “nominal” selenium concentrations added to feed in their analys es and not the measured concentrations. This adds an additional layer of uncertainty to th e thresholds reported by the State of Utah (Ohlendorf 2007) as the actual concentration can differ from the nominal concentration either positively or negatively, de pending upon the individual treatment.April 2008 North San Francisco Bay Selenium Toxicological Assessment

4-14 Tetra Tech, Inc. Other selenium screening values 

### The National Irrigation Water Quality Control Program (NIWQP) recommends a lower screening value for selenium in bird eggs than the State of Utah; i.e., 6 mg/kg-dw (NIWQP 1998). The USGS (Seiler et al. 2003) used l ogistic regressions to derive threshold concentrations for selenium induced teratogenici ty (a less sensitive endpoint than hatching success) in bird eggs collected from several selenium-impacted field sites across California (Table 4-8). The NIWQP also recommends a screening value for di etary selenium of 3 mg/kg-dw. Presser and Luoma (2006) also review ed the toxicity literature and concluded that dietary “concern levels range fr om 2 to 7” mg/kg-dw for birds.

Table 4-8 Selenium screening values for teratogenesis in bird eggs (mg/kg-dw) (Seiler et al. 2003).

Bird EC01 EC10

Ducks 15 23

Black-necked stilts 14 37

American avocets 41 74

Allometric adjustment for dietary concentrations 

### The species of concern in the North Bay identified by USFWS (2007) have not been examined in selenium toxicity studies. On e approach for applying screening values developed for one species to another species is to allometrically adjust the screening values (Sample and Arenal 1999). This adjusts for differences in body weight, metabolism, pharmacokinetics, and sensitivity to provide the best available estimates of species-specific toxicity. The equations use to perform the allo metric adjustments, and parameter values, are provided in Appendix C.

Allometric adjustments were applied to predict dietary selenium screening values for the species of concern in the North Bay identified by USFW S (2007) from three example dietary toxicity values prot ective of reproductive success:

1. the EC10 for mallards fed selenomethi onine derived using a hockey-stick regression by Adams et al. (2003) and used by the Great Salt Lake Science Committee (Ohlendorf 2007);

2. the effect threshold (Table 4-2) derive d from the study by Ort and Latshaw (1978) for chickens, and;

3. the effect threshold (Table 4-2) de rived from the study by Wiedemeyer and Hoffman (1996) for screech owls.

These studies were chosen as the most representative of the available toxicity data although other toxicity values may also be used (e.g., the SMCV fo r chicken reproductive studies). However, since reproductive success is th e most sensitive endpoint in birds, it is

recommended that the allometric ally adjust dietary threshold all be based on that endpoint. The allometrically adjusted screening va lues are presented below in Table 4-9.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 4-15 Table 4-9 Allometrically adjusted dietary selenium screening values.

Dietary Screening Value (mg/kg-dw) Allometrically Adjusted from Bird species Mallard a Chicken b Screech Owl c
Bald eagle 9.7 4.0 104.3 California clapper rail 2.2 0.9 - Greater scaup 3.9 1.6 - Lesser scaup 3.2 1.3 - White-winged scoter 5.6 2.3 - Surf scoter 4.1 1.7 - Black scoter 3.9 1.6 - Notes: a - EC10 for reduced hatching success from Adams (2003) and Ohlendorf (2007) of 4.4 mg/kg-dw b - effect threshold for reduced hatching success of 3.9 mg/kg-dw from Ort and Latshaw (1978) (Table 4-2) c - effect threshold for reduced hatching success of 17.3 mg/kg-dw from Wiemeyer and Hoffman (1996) (Table 4-2)



### Note that allometric adjustments are used to adjust dietary screening values (Sample and Arenal 1999) and are not used to adjust screenin g values for selenium in eggs. Further, there is some uncertainty associated with the use of allometric scaling as the allometric scaling factor used here was developed for acute toxicity data its “... applicability to chronic toxicity data is unknown. The modes of action for acute and chronic effects differ for many chemicals. As a consequence, it is likely that scaling factors based on chronic toxicity data will also differ from those based on acute toxicity data ” (Sample and Arenal 1999). It should also be noted that the allometric scaling factor used here is not spec ific to selenium, but a

mean value for other contaminants.

Allowable limits in bird feed 

### The FDA has approved the use of sodium selena te, sodium selenite, and selenium yeast at up to 0.3 mg/kg for chickens, swine, turkey s, sheep, cattle, and ducks (21CFR573.920). The major (i.e., 60-80%) form of selenium in seleni um yeast is selenomethionine (Capelo et al. 2004, McSheehy et al. 2005, Polatajko et al. 2005).

Nutritional requirements



### Selenium is a micro-nutrient. When animal s do not have enough selenium in their diet, selenium deficiency results; i.e., poor gr owth, muscular dystrophy, and chick mortality (Ullrey 1992, NRC 1994). Due to the economic importance of the poultry industry, the nutritional requirements to maintain an adequa te growth rate and normal metabolism of some of the more widely raised species have been established by th e NRC (1994; see Table 4-10 below).

Table 4-10 Selenium nutritional requirements for commercially reared birds (mg/kg-dw).

Age (weeks) Species Strain 0-2 2-4 4-6 6- Chicken Leghorn white egg- laying 0.17 0.17 0.17 0.17 Chicken Leghorn brown egg-la ying 0.16 0.16 0.16 0.11

Chicken Broiler 0.17 0.17 0.17 0.17 Turkey - 0.22 0.22 0.22 0.22

Duck - 0.22 - - - Quail Japanese 0. 22 0.22 0.22 0.22 Source: NRC (1994)April 2008 North San Francisco Bay Selenium Toxicological Assessment

4-16 Tetra Tech, Inc. Maximum tolerable limits 

### The NRC (2005) defines the maximum tolerable level as the concentration “...of a mineral is the dietary level that, when fed for a define d period of time, will not impair animal health and performance.” The NRC (2005) has set th e following maximum tolerable levels for selenium in bird diets: a) 3 mg/kg for poultry and b) 2 mg/kg- dw for aquatic birds. Poultry includes chickens, turkeys, grous e, and pheasants, as well as ducks and geese (which are water birds). It should also be noted that the studies on kestrels did not produced adverse effects at up to 12 mg/kg-dw (Santolo et al. 1999, Yamamoto et al. 1998, Yamamoto and Santolo 2000).

Additional considerations



### Issues to be considered in the collec tion and interpretation of samples include:

• tissue concentrations in fishes may vary with the time of year sampled

• tissue concentrations may vary by geographic location

• if sampling dietary items of birds, seleni um concentrations may also differ among their prey items

• number of samples to collect

• the frequency of collections

• whether samples should be composited

• how to compare measured concen trations to screening values

These issues are discussed in greater detail in Section 6.

A point worthy of consideration is whethe r the type of food consumed affects the bioavailability and/or toxicity of selenium. The bird toxicity studies reviewed above would likely have used a feed that ma inly consisted of cereal grai ns and oilseed meals (NRC 1994), whereas many of the bird species of concer n in the North Bay are at least partially carnivorous. Among pigs, “ animal Se sources generally have a lower (<25%) absorption rate than Se from plant tissue. However, Se abs orption is influenced by the type of animal product being fed. For example, the absorption of Se from bovine milk is high and equivalent to that of selenite , whereas Se in meat and bone meal or poultry by-products is

≤

20% ” (Mahan 2001). This implies that the bioavail ability of selenium is likely to be lower in the diets of the birds in the North Bay than in the diets used in the toxicity studies reviewed here. Thus, dietary scr eening levels for selenium may need to be adjusted upwards when they are based on studies where the test animal was fed mainly vegetable matter.

The toxicity values presented above were not derived using the populations and species of birds that occur in the North Bay nor using th e environmental conditions in the North Bay. This means that there is some uncertainty as to whether any screening criteria are actually applicable. Similarly, McDonald and Chapma n (2007) recommend that screening values only be used to determine if further evaluati on is necessary. They recommend that if sampleNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 4-17 

### concentrations exceed an appropriate screening value that actual impacts on the species of concern be assessed. Since reprodu ctive success is the most sensitive endpoint in birds, it may be relatively easy to determine whether reproductive success of aquatic birds is being adversely impacted in the North Bay. This woul d require that an egg monitoring program be designed and implemented.

Future research and data gaps 

### Several data gaps and areas wh ere further research may be be neficial to the Water Board were identified during the evaluation of seleni um toxicity to birds in the North Bay, as

follows:

1. The logistic regressions developed by the State of Utah (Ohlendorf 2007) to derive a dietary effect threshold for selenium should be redone using the correct data.

2. Toxicity studies have not b een performed on most of the species of concern in the North Bay (USFWS 2007). Thus, this report has assumed that toxicity studies on mallards, chickens, pheasants, and screech ow ls are representative of the species of concern. The species of concern may be more or less sensitive.

3. If toxicity testing is not performed for the species of concer n in the North Bay, another approach may be to develop seleni um-specific allometric scaling factors for organic selenium in avian diets.

4. Species-specific regressions to convert di etary selenium concentrations to egg concentrations are lacking. If the Water Board decides to use the protection of egg hatching as a numeric criterion, this will be an important data gap.

5. The selenium toxicity studies perfor med to date have used selenite, selenomethionine, and selenized yeast. The degree to which the dietary formulations used in the toxicity studies reflects the speciation of selenium speciation in the food of bird s of concern in the North Bay is not very well known. Since the speciation of selenium affects its toxicity, this ma y be an important

consideration.

6. Toxicity experiments are une ven in assaying the actual amount of selenium in the experimental feeds. Many studies only report the estimated concentration added. Thus, the reported amount of selenium provided to birds in selenium toxicity studies is subject to some error. The e rror can be either pos itive or negative, depending upon the individual treatment.

7. Many toxicity studies performed to date report their concentration data in wet weight and do not provide a %moisture. A lthough a default %moisture can be used to estimate dry weight concentrations, this adds an additional layer of uncertainty as the actual %moisture will vary from sample to sample, at the very least.

8. A detailed re-analysis of the published toxi city data using, for example, biphasic regressions (Beckon 20 07, Beckon et al. 2008) would pr ovide a greater level of

confidence in estimates of the threshold fo r toxic effects of se lenium vs. a LOAEL, NOAEL, or effect threshold. However, if on ly the treatment means are available for the analyses, it should be remembered that th is type of analysis will mask the true variability in the data.April 2008 North San Francisco Bay Selenium Toxicological Assessment

4-18 Tetra Tech, Inc. 4.5 C ONCLUSIONS 

### Exposure to elevated levels of selenium can cause adverse effects in birds. Raptors, such as screech owls and kestrels, appear to be less sensitive to dietary exposures to selenium than ducks and chickens. While it has generally b een recognized that reproductive success is the most sensitive endpoint in mallards, a review of the toxicity data available for chickens indicates that the growth/survi val of young is a more sensitive endpoint in chickens. Thus, it is an open question as to which endpoint will be more sensitive for the birds of concern in the North Bay.

Numerous selenium screening values protective of birds have been proposed. For dietary selenium, the recommended screening values ar e usually in the range of 3-5 mg/kg-dw. For bird eggs, the range of recommended screening va lues is considerably larger, ranging from 6 to 74 mg/kg-dw.

Based upon the data presented here, there are se veral options for selenium screening values protective of birds. Those options are as presen ted below (all in units of mg/kg-dw). All of the screening values are well above the dietary requirements for birds of approximately 0.2 mg/kg-dw (Table 4-10), with the exception of so me of the allometrically adjusted dietary thresholds, which are close to the dietary requirements.

1. The lowest dietary SMCV of 2.9 (Table 4-7)

2. Lowest dietary concentration at which a dverse effects were reported (Table 4-7)

a. LOAEL of 4.3

3. The effect concentrations protective of reproductive success in mallards derived by the State of Utah (Ohlendorf 2007):

a. Dietary selenium

i. Logistic regression: 5.4

ii. Hockey stick-regression: 4.4

b. Egg selenium

i. Logistic regression: 12.5

ii. Hockey stick-regression: 11.5

4. Allometrically adjusted dietary thresholds for the species of concern in the North Bay (Table 4-9)

a. Note that allometric adjustment predicts that smaller birds will have lower dietary thresholds, with the lowest being approximately 1 mg/kg-dw for California clapper rails

The choice of using an SMCV, LOAEL, effect threshold, an EC01, or an EC10 is dependent upon both the level of risk and un certainty the Water Board wishes to accept. This issue was presented in more detail in the Introduction. It is worth noting that of these values, only the LOAEL represents concentrations at which effe cts have been demonstrated. However, since only a few concentrations have been test ed, effects may actually occur at lower

concentrations.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 5-1 

### 5 M ARINE MAMMAL TOXICITY REVIEW


### Although some whale and dolphin species may o ccasionally enter the waters of the North Bay, they are generally consid ered infrequent visitors. The three marine mammal species that are considered to be resident in the North Bay include (DFG 2007, USFWS 1992):

• River otter ( Lontra canadensis )

• Harbor seal ( Phoca vitulina )

• California sea lion ( Zalophus californianus )

Radio telemetry data indicates that harbor seal s and sea lions venture in and out of the North Bay (USFWS 1992). None of the three marine mammal species found in the North Bay are special status species.

Among mammals exposure to elevated levels of selenium can cause reduced growth, emaciation, hair loss, lesions, paralysis, re duced conception rates, reduced litter size, increased stillbirths, and mortality (M ahan 2001, NRC 1980, 2005, Ohlendorf 2003). When selenium concentrations are high enough in a large enough area, these effects can lead to population declines for the most affected species.

The step in the effort to determine whether marine mammals may be adversely impacted by selenium in the North Bay is to evaluate the toxicity of selenium to the marine mammals. Next, potential selenium screening values fo r the species in the North Bay are proposed. Lastly, the screening values are compared to nutritional requirements.

5.1 M ETHODS 

### No toxicity studies have been performed on the effects of selenium on any marine mammal. Among mammals, selenium toxicity studies have been performed on cows, dogs, goats, hamsters, mice, pigs, and rats. However, “ due to the reduction of selenite and selenate, and the formation of insoluble par ticles in the rumen, cattle and sh eep have [a] lower absorption of selenium... than non-ruminant species ” (NRC 2005). Therefore, toxicity studies where selenium has been fed to cows, sheep, and goat s are probably not repr esentative of marine

mammals. Herbivorous and semi-herbivorous rode nts (e.g., hamsters, mice, and rats) have reducing conditions in their inte stines (as opposed to the stomach of ruminants) and also engage in coprophagy. Therefore, dietary toxicity studi es on hamsters, mice, and rats are not likely to be reflective of carnivores, includi ng marine mammals. Thus, it was assumed that dietary toxicity studies on pigs and dogs are likely to be representative of marine mammals.

Dietary selenium toxicity st udies using pigs have been reviewed by the NRC (1980, 2005) and Mahan (2001). Studies on dogs have also been reviewed by the NRC (1980). The

studies included in those reviews are summarized below in the Results section.

5.2 R ESULTS 

### As stated above, no selenium toxicity studies on marine mammals were found. However, it was assumed that dietary toxicity studies on pigs and dogs are representative of marineApril 2008 North San Francisco Bay Selenium Toxicological Assessment

5-2 Tetra Tech, Inc. 

### mammals as all three groups are carnivor ous mammals. The studies on pigs and dogs reviewed by the NRC (1980, 2005) are provided in Tables 5-1 and 5-2 below, respectively.

Table 5-1 Dietary toxicity studies on pigs from NRC (1980, 2005).

Concentration (mg/kg) Age Chemical Form NOAEL LOAEL Effect Reference "growing" Na 2 SeO 3 4 8 reduced weight gain Goehring et al. (1984) "growing" Na 2 SeO 3 5 15 reduced weight gain Mahan and Magee (1991)

8-10 wk Na 2 SeO 3 and SeMet 0.4 25 reduced weight gain, paralysis Panter et al. (1996)

24.7 kg Na 2 SeO 3 or Se-yeast 5 10 reduced weight gain Kim and Mahan (2001a)

Adult Na 2 SeO 3 4 8 offspring with reduced weight Poulsen et al. (1989)

25 kg Na 2 SeO 3 or Se-yeast 3 7 lower number of live

born Kim and Mahan (2001b) 5 kg Na 2 SeO 3 and SeMet 10 20 reduced weight gain Herigstad et al. (1973) 35 kg Seleniferous corn 5 10 toxicosis Schoening (1936) 15 kg Na 2 SeO 3 - 7 reduced weight gain Wahlstrom et al. (1956) 14 kg Na 2 SeO 3 - 10 reduced weight gain Wahlstrom et al. (1956) 13 kg Na 2 SeO 3 - 11 reduced weight gain Wahlstrom et al. (1956) 15 kg Na 2 SeO 3 - 10 reduced reproductive

success Wahlstrom and Olson (1959) 16-19 kg Na 2 SeO 3 - 24 Anorexia, death Miller and Schoening (1938)

Table 5-2 Dietary toxicity studies on dogs from NRC (1980).

Concentration (mg/kg) Age Chemical Form NOAEL LOAEL Effect Reference 60 days Seleniferous corn - 7.2 Decreased weight gain Rhian and Moxon (1943) 150 days Na 2 SeO 3 - 10 Decreased weight gain Rhian and Moxon (1943) 72 days Seleniferous corn - 20 Decreased weight gain Rhian and Moxon (1943) "young" Na 2 SeO 3 - 20 Decreased weight gain Moxon (1937) "young" Seleniferous corn - 20 Decreased weight gain Moxon (1937)



### For all of the studies on presented above, it is unclear whether the dietary concentrations are provided as ww or dw. Thus, the units are given only as mg/kg.

Mahan (2001) summarizes the existing studies on pigs by stating that “chronic selenosis generally occurs when diets or f eedstuffs contain 5 to 20 ppm Se.”

5.3 D ISCUSSION 

### No selenium toxicity studies have been performed on marine mammals. Therefore, it was assumed that toxicity studies on other mamm als would be representative of marine mammals. Among the mammals that have been st udied, it was assumed that pigs and dogs are more likely to be representative of the marine mammals of concern in the North Bay than studies using ruminants and rodents. This is because ruminants and rodents have reducing conditions in their gastro-intestinal tr acts that may reduce the bioavailability of selenium relative to the gastrointestinal tract s of pigs, dogs, seals, sea lions, and otters.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 5-3 

### The studies reviewed by the NRC (1980, 2005) i ndicate that effects in pigs were not observed at dietary concentrations of less than 7 mg/kg (Table 5-1). In Nutrient Requirements of Swine (NRC 1998), a study that wa s not reviewed in the Mineral Tolerance of Animals (NRC 1980, 2005) was cited as causing adverse effects in pigs at 5 mg/kg. Mahan (2001) also states that effects have been observed in pigs at f eed concentrations at 5 mg/kg. Thus, it appears that th e lowest reported dietary concentration at which selenium has been shown to affect pigs is approximately 5 mg/kg.

The studies reviewed by the NRC (1980) on dogs did not administer dietary concentrations below 7.2 mg/kg. Since adverse effects were obser ved at that dietary concentration, it is not possible to determine the an act ual effect threshold in dogs.

A point worthy of consideration is whethe r the type of food consumed affects the bioavailability and/or toxicity of selenium. The pig studies reviewed above would likely have used a feed that mainly consisted of corn and soybean s (NRC 1998), whereas seals, sea lions, and river otters are enti rely carnivorous. Among pigs, “ animal Se sources generally have a lower (<25%) absorption rate than Se fr om plant tissue. However, Se absorption is influenced by the type of animal product being fed. For example, the absorption of Se from bovine milk is high and equivalent to that of selenite, wherea s Se in meat and bone meal or poultry by-products is ≤ 20% ” (Mahan 2001). This implies that the bioavailability of selenium is likely to be lower in the diets of marine mammals than pigs and that the dietary screening level for selenium may need to be adjusted up wards of 5 mg/kg for marine

mammals.

Allowable limits in feed 

### “In 1982, the FDA approved the addition of 0.3 ppm of selenium to diets for pigs up to 20 kg, because 0.1 ppm of added selenium does not always prevent deficiency signs in weanling pigs. The current regula tion allows up to 0.3 pp m of selenium in the diet for all pigs” (NRC 1998).

Nutritional requirements



### It should also be remembered that selenium is a micro-nutrient. Wh en mammals do not have enough selenium in their diet, selenium deficiency results; i.e., edema, hepatic necrosis, poor growth, white muscle disease, mulberry heart disease, impaired repr oduction, reduced milk production, impaired immune response, and mortality (NRC 1998). Due to the economic importance of the pig farming industry, the nutrit ional requirements to ma intain an adequate growth rate and normal metabolism of pigs have been established by the NRC (1998; see Table 5-3 below) and Mahan (2001).

Table 5-3 Selenium nutritional requirements for commercially reared pigs (mg/kg-dw) by body weight (kg).

NRC (1998) Mahan (2001) Body weight (kg) 3-10 10-20 20-120 125+ 5-20 20-60 60+ - growing pigs 0.33 0.28 0.17 0.30 0.20 0.15 gestating female 0.17 0.3 lactating female 0.17 0.3 Sexually active boars 0.17April 2008 North San Francisco Bay Selenium Toxicological Assessment

5-4 Tetra Tech, Inc. Maximum tolerable limits 

### The NRC (2005) defines the maximum tolerable level as the concentration “...of a mineral is the dietary level that, when fed for a define d period of time, will not impair animal health and performance.” The NRC (2005) has set a maxi mum tolerable level of selenium in feed for pigs of 4 mg/kg (wet weight vs. dry weight not specified). The NRC (1998) also provides the following discussion of the maximum tolerable limit for selenium in pig feed:

“When fed to growing swine as sodium sele nite, sodium selenate, selenomethionine, or seleniferous corn, selenium doe s not produce toxicity at levels of less than 5 ppm. In some cases, however, a level of 5 ppm and levels from 7.5 to 10 ppm have produced toxicity. Signs of toxicity include anorexia, hair loss, fatty in filtration of the liver, degenerative changes in the liver and kidney, edema, o ccasional separation of hoof and skin at the coronary band, and symmetrical, focal areas of vac uolation and neuronal necrosis.”

Future research and data gaps 

### Several data gaps and areas wh ere further research may be be neficial to the Water Board were identified during the evalua tion of selenium toxicity to marine mammals in the North Bay, as follows:

1. Toxicity studies have not been perform ed on any of the marine mammals that reside in the North Bay. Thus, this report has assumed that toxicity studies on pigs and dogs are representative of harbor seals, sea lions, an d river otters. The marine mammals in the North Bay may be more or less sensitive than pigs and dogs.

2. Toxicity studies on pigs have used a diet based on vegetable matter. The bioavailability of selenium in such diets is higher than in animal matter based diets. This means that the bioavailability of se lenium in the diets of marine mammals may be lower than the in th e toxicity studies that have been performed on pigs.

3. For this report, only the secondary literature was reviewed. A thorough examination of the primary literature (as was done for fish and birds) may prove

more informative.

4. A detailed re-analysis of th e published toxicity data fo r pigs using, for example, biphasic regressions (Beckon 2007, Beckon et al. 2008) would pr ovide a greater

level of confidence in estimates of the thre shold for toxic effects of selenium vs. a LOAEL, NOAEL, or effect threshold. Ho wever, if only the treatment means are available for the analyses, it should be reme mbered that this type of analysis will mask the true variability in the data.

5. For harbor seals and sea lions, the coll ection and analysis of blood, hair, and blubber samples appears to be fairly r outine. These types of samples can be collected without killing th e seal/sea lion. It might pr ove useful to examine the dietary toxicity literature for pigs and develop rela tionships between dietary selenium levels and blood, fat, and/or hair levels in pigs that may be used to evaluate data collected from seals and sea lions in the North Bay.

6. The selenium toxicity studies perfor med to date have used selenite, selenomethionine, and selenized yeast. The degree to which the dietary formulations used in the toxicity studi es reflects the speciation of seleniumNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 5-5 

### speciation in the food of marine mammals of concern in the North Bay is not very well known. Since the speciation of selenium affects its toxicit y, this may be an important consideration.

7. The secondary reviews do not detail whethe r the toxicity studie s performed on pigs

measured the selenium concentration in f eed as ww or dw. This adds an additional layer of uncertainty.

5.4 C ONCLUSIONS 

### Exposure to elevated levels of selenium can cause adverse effects in mammals. Based upon the data presented here, there are several options for selenium screening values protective of marine mammals. Those options are as follows (all in units of mg/kg):

1. The maximum tolerable limit recommended by that NRC (2005): 4

2. Lowest concentration at which adve rse effects have been reported: 5

These proposed screening values are well in excess of the dietary requirements for pigs (which are assumed here to be representati ve of marine mammals) of approximately 0.3 mg/kg-dw (Table 5-3).North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. 6-1 

### 6 I SSUES 

### A FFECTING 

### T HE 

### C HOICE OF 

### S CREENING 

### V ALUES


### This report has presented seve ral options for screening valu es protective of different receptor groups. Here, we discuss issues related to selecting a screening value for use in the TMDL process.

Derivation of screening values 

### In Section 1, multiple methods were identified that have been used in th e toxicity literature to derive screening values, including:

• LOAELs

• Effect thresholds

• Species mean chronic values

• EC01 or EC10

• Species sensitivity distributions

Further, there are multiple means of calculating an effect concentrations (i.e., an EC01 or EC10) or a species sensitivit y distribution. This means th at different mathematical techniques can be applied to the same da ta to derive different screening values.

Determining which method is the best is no easy matter, as each method has its own limitations. Most of the selenium toxicity data examined in this review was collected from experiments designed to be analyzed using an ANOVA; i.e., there are several groups of animals in an experiment and each group is e xposed to a different selenium dose. These types of experiments produce a NOAEL and a L OAEL; i.e., the highest selenium dose at

which no adverse effects were observed and th e lowest selenium dose at which adverse

effects were observed.

Some authors have re-analyzed the treatment means from these kind of experiments using a regression analysis (e.g., logist ic, hockey stick, or biphasic) to obtain a better understanding

of the threshold for toxic effects than is provided by the NOAEL and LOAEL (e.g., Adams 2003, Ohlendorf 2003, 2007, Beckon 2007, 2008). Howeve r, in analyzing only the treatment means, significant variation is lost and the toxicity thresholds derived are uncertain.

Toxicity experiments designed to be analyzed using regression analyses have the potential to be much more powerful than toxicity tests de signed to be analyzed using an ANOVA; i.e., “the purposes of accurately determining risk and maximizing benefit are more efficiently served by the allocation of limite d experimental resources to a greater range of dose levels rather than to multiple replicates at a small number of dose levels. The latter, a legacy of traditional hypothesis testing, is relatively poorly suited for fitting and comparing

mathematical models of the dose-response relationship” (Bec kon et al. 2008). Therefore, it is recommended that future toxicity studies be designed with a regre ssion analysis in mind.April 2008 North San Francisco Bay Selenium Toxicological Assessment

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### When using an effect concentration (EC) or a species sensitivity dist ribution, one must also decide on what level to protect in order to deri ve the screening value. For effect thresholds, it is common to set the threshold at a 1, 10, or even 20% effect. For species sensitivity distributions, it is common to choose a value that is protective of 95% of the species evaluated. Choosing what threshold to use sh ould be related to wh at level may actually impact populations in the field, yet information on that is scant. Further, when comparing screening values derived using either of these methods, one must also consider the confidence limits; e.g., is an EC10 of 1.8 signi ficantly different from an EC20 of 2.5?

Uncertainties in toxicity testing 

### There are some additional sources of uncertainty associated with toxicological studies reviewed here that should be considered when interpreting the results to set regulatory standards, including the following:

• Responses to selenium differ among sp ecies and life-stage within the same species. However, results for one species of life-history stage are used to assess the effects on other species and life stages . For example, the only toxicity data available for white sturgeon were deri ved from short-term chronic (8-week) exposures to juvenile fish, but this fish is long-lived and does not reach sexual maturity until they are 10 years of age or more.

• In short-term toxicity tests performed on fi sh in the laboratory, the concentrations in the tissue may not have reached steady state. Thus, screening values derived

from short term studies where tissue concentrations have not yet reached equilibrium may underestimate the tissue level that causes t oxicity. However,

current recommendations are to use fish ti ssue concentrations as screening values (Hamilton 2002, 2003, 2004, USEPA 2004).

• There is a lack of data linking the results of laboratory toxicity data to selenium

concentrations and effects observed in th e field. Even though effects have been demonstrated in the laboratory, it is unknown whether these effects will translate to population level eff ects in the field; i. e., population declines.

Current selenium toxicity testing efforts 

### At a recent meeting of the North American Industry Selenium Working Group (November 16, 2007) several new selenium toxicity studies were announced. Thes e studies include the following:

• J.R. Simplot will spend approximately $500K for selenium toxicity testing with brown trout, Yellowstone cutthroat tr out, and possibly a third species.

• USEPA has performed a repeat of the bluegill toxicity te st done by Lemly (1993a) upon which the USEPA (2004) base d its draft ambient water quality criterion. Toxicity was found at higher c oncentrations that observed by Lemly (1993a). These results have not yet been published.North San Francisco Bay Selenium Toxicological Assessment April 2008

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### • The North American Industry Seleni um Working Group may be funding relatively small studies on “site-specific assessments of selenium bioaccumulation in aquatic systems” and “tissue endpoint assessment.” Howeve r, the details of

these studies are unknown.

• Cameco is performing “water bird research in Saskatchewan including assessing food, productivity, and egg [S e] for tree swallows.”

The research that is currently in progress de scribed above is all on freshwater ecosystems. So, although the research is of general interest, it will not ad dress the issues of greatest concern to the Board; i.e., the toxicity of selenium of brackish/marine ecosystems and the toxicity of selenium to the species of concern in the North Bay. Further, the current research does not appear to have been designed for use with regression analyses, meaning the NOAELs and LOAELs will be prov ided and deriving an EC20 will still be associated with some uncertainty.

Conclusions 

### Ultimately, given importance of selenium to the water resources of California, and the history of its effects, it is surp rising that so little toxicity data on the species of concern in

California is available. The met hods used in selenium toxicity testing to date do not provide regulatory entities with a high de gree of confidence in deriving toxicity thresholds and/or screening values. Lastly, fiel d validation of selenium toxi city studies should also be performed to increase confidence in any screening levels derive d from the existing toxicity

literature.North San Francisco Bay Selenium Toxicological Assessment April 2008

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### 7 I SSUES 

### A FFECTING 

### I MPLEMENTATION 

### When sampling invertebrates, fish, bird eggs, or other biological media to compare to the selenium screening values proposed in the earlie r sections of this re port, there are several

issues that should be considered to maximize th e use of the data. This section of the report provides a brief discussion of some of the more important issues . Some of these issues have been considered by various authors (e .g., Lemly and Skorupa 2007, McDonald and Chapman 2007, USEPA 2000, 2006).

Spatial variability



### The concentration of selenium in the waters of the North Bay is expected to differ depending upon where samples are collected. Near selenium inputs (e.g., refineries, some creeks, and the San Joaquin River), selenium concentratio n in the water column are expected to be higher. This should result in hi gher concentrations for the bi ota that inhabit that area, providing that they have a relatively small ra nge. For example, a clam may move only a few feet within its lifetime, but a s ea lion may travel thousands of mile s. Therefore, if there is an area where there is a localized input of selenium, elevated selenium levels would be expected in biota with a small range (e.g., the cl am) but not necessarily in biota with a large range (e.g., the sea lion). This suggests that sa mples should be collected from areas near known selenium inputs from biota that are most likely to be impacted. To determine the extent of impacts, a number of locations shou ld be sampled, not just areas near selenium inputs.

Background 

### Since selenium is a naturally occurring elemen t, it is expected to be present at some concentration in all waters, soils, and sediment s in the North Bay. Therefore, in addition to examining the spatial variability of selenium in the North Bay, it may be desirable to establish an area (or areas) that are represen tative of unimpacted (or reference) conditions. Then, biota may be sampled from that area an d selenium concentrations in the tissues of biota from the background location can be co mpared to the samples collected from the North Bay to determine what areas are impacted. If this technique is used, it is advised that statistically robust techniques be used to compare sample lo cations, such as the t-test, ANOVA, or Kruskall-Wallis test.

Temporal variability



### Concentrations of selenium in tissues ma y vary with the time of year. USEPA (2006) recommends that fish samples be collected dur ing the same time of y ear during each sample event to avoid potential temporal effect.

Comparing measured concentrations to screening values 

### USEPA (2006) ”... recommends using the [one sample] t-test to determine whether the mean concentration of mercury in composite fish tissue samples exceeds the screening value. This involves a statistical comparison of the mean of all fish tissue data to the criterion. EPA recommends that this procedure also be used for determining impairment.” This technique is also app licable to selenium (without the compositing). To use a onesample t-test, the screening value is compared against the mean concen tration for all of the biota samples of the same species collected from the location/tim e being evaluated. TheApril 2008 North San Francisco Bay Selenium Toxicological Assessment

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### results of the test can be used to determine whether the measured concentrations significantly exceed the screening value or not.

Another approach that can also be used is to compare the 95% upper confidence limit on the mean (UCL 95 

### ) to the screening value. If the calculated UCL 95 

### does not exceed the screening value, then no action is necessa ry. USEPA (2007b) provides free st atistical software that can

be used to calculate a UCL 95 

### s for selenium data in biological samples.

Lastly, it is also possible to simply compare measured concentrations to the screening values. This method is likely to result in more exceedances than using a one sample t-test or

a UCL 95 

### . In that respect, comparing individual concentrations to the screening value may be more “sensitive” but it is not statistically valid.

Food webs 

### It has been demonstrated that among the fish sp ecies in the North Bay that those that feed on clams, or are part of a food web that starts with clams, have higher selenium tissue concentrations (Stewart et al. 2004). This is because the concentr ations of selenium in one of the more abundant clams in the North Bay, Potamocorbicula amurensis , are much higher than many of the other invertebrates that fi sh feed on (Stewart et al. 2004). Similarly, it would be expected that birds that feed on this species of clam have higher selenium exposures than other bird species . In addition, it is generally exp ected that fish and birds that feed on biota in the sediments of the Bay woul d have greater selenium exposures than fish and birds that feed in the ope n water column; i.e., the Delta smelt only feed on zooplankton near the top of the water column and would, ther efore, be expected to be exposed to less selenium than fish that feed in the sediments, such as sturgeon. Howeve r, it is possible that species that have a lower poten tial for exposure may be more sensitive to selenium. Thus, the other species in the North Bay should not be ignored.

Size of specimens 

### Data collected by the USGS indi cate that as the size of Sacr amento splittail increases over their lifetime, the fish’s dietary habits change and that this affects their bioaccumulation of selenium. In addition, the concentrations of many metals increase with the size of the specimen sampled. For selenium, this does no t always appear to be the case, but the potential effect of body size s hould be accounted for when collecting biota samples. Thus, body size (i.e., length and weight) should always be measured and data should be corrected for any relationship with size/wei ght (Tremblay et al. 1998, Wente 2004).

Frequency of collection 

### USEPA (2006) recommends that fish samples be collected at least once every two years to determine compliance with the fish tissue criterion for methylmercury. If a monitoring strategy for the North Bay is implemented, it may be appropriate to collect samples annually, at least initially.

Compositing 

### When collecting fish samples to support fish consumption advisories, USEPA (2000, 2006) recommends the collection of composite samples. What this means in that samples are collected from several fish individuals, but then the samples are homogenized and the laboratory analyzes only the single composite sample. This approach is designed toNorth San Francisco Bay Selenium Toxicological Assessment April 2008

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### minimize costs and to provide an indicatio n of the average concentration. However, compositing biota samples makes evaluating relati onships between 1) age, sex, size, time of year and 2) selenium concentra tion more difficult. Further, the costs for low level selenium analyses in tissues have fallen in recent ye ars. Therefore, it is recommended that biota samples should not be composited, at least fo r organisms where it is possible to obtain samples large enough for analysis from a single individual (i.e., 2 g).

Sample size



### If the Water Board elects to use the statis tical techniques recommended above, then it is recommended that a minimum of eight samples be collected for a species during each sampling event. This will provide the necessary sample size to perform both background comparisons and the calculation of a UCL 95 

### . This is consistent with USEPA (2007b)

recommendations.

Fish tissue screening value protective of human health 

### The State of California (OEHHA 2006) has calculated a screeni ng value for selenium in fish tissue that is protective of fi shermen (i.e., the human consump tion fish). The screening value was calculated using toxicity data from USEPA (2007c). It should be noted that the

calculations that the State of California (OEHHA 2006) used assume a 100% bioavailability of selenium in fish tissues to humans. However, as stated in the section on the toxicity of selenium to marine mammals, the bioavailability of selenium in animal tissues is generally lower (<25%) (Mahan 2001). This may need to be evaluated in more detail prior to implementing the fish tissue screening value protective of human health in the North Bay.North San Francisco Bay Selenium Toxicological Assessment April 2008

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Tetra Tech, Inc. A-1 

### A PPENDIX 

### A

W ET 

### W EIGHT TO 

### D RY 

### W EIGHT 

### C ONVERSIONS



### Concentrations of selenium in tissues and an imal feed are reported in either wet weight (ww) or dry weight (dw). Un fortunately, the two measurements are not equivalent. The

selenium concentrations that were used in the analyses presented earlier in this report are presented in their original units in Table A-1. All of the selenium concentrations reported in Table A-1 were converted to dry weight using either the percent mois ture reported in the original publication or the default percent mo isture of 75% (USEPA 1993) for studies on fish where the percent moisture was not reported. The percent moisture used in the calculations is presented in Table A-1 and the dry weight selenium concentrations are reported in Table A-2. The formula used to cove rt wet weight to dry weight is as follows:

moisture percent 100 100 wet weight Dry weight

− × =

Additionally, not all stud ies measured selenium in all tis sue types. USEPA (2004) provides equations to convert selenium concentratio ns in fish muscle and liver to whole body concentrations. The data that USEPA (2004) presented was also used to derive linear regression equations to convert selenium concentrations meas ured in one tissue type to another tissue type for all fish, except whit e sturgeon. The equati ons used are provided below and are given in order of preferen ce used to estimate tissue concentrations.

1. Selenium in fish muscles to whole body (USEPA 2004):



## ( ) ( ) 

## [ ]

muscle wholebody 

### Se Se ln8937.01331.0exp × + =

2. Selenium in fish liver to whole bo dy (USEPA 2004):



## ( )

liver wholebody 

### Se Se × +

− = 3071.02609. 0

3. Selenium in whole fish bodies to fish livers (p < 0.0001, r 2 

### = 0.73): 

# ( ) ( ) 

# [ ]

wholebody liver 

### Se Se ln7628.06475.1exp × + =

4. Selenium in whole fish bodies to fish muscle (p < 0.0001, r 2 

### = 0.96): 

# ( ) ( ) 

# [ ]

wholebody muscle 

### Se Se ln031.10324.0exp × + =

For white sturgeon, TetraTech obtained the raw data from the study co nducted by Tashjian et al. (2006) and used that data to calculate the fo llowing regression equation (F 1,22 

### = 222.42, Adjusted R2 = 0.91, p < 0.00001):



## ( ) ( ) 

## [ ]

muscle wholebody 

### Se Se ln6206.09586.0exp × + =April 2008 North San Francisco Bay Selenium Toxicological Assessment

A-2 Tetra Tech, Inc. 

### This regression equation was used to conve rt the muscle EC10 derived by Beckon to a whole body concentration as well as the mu scle NOAEL and LOAEL from Linville (2006) to whole body concentrations.

For the selenium toxicity studie s on birds, only the concentrat ion in the feed given to the birds was converted from wet weight to dry weight. That is presen ted in Table A-4 for toxicity studies and A- 5 for production studies.

References 

### U.S. Environmental Protection Agency (USEPA). 1993. Wildlife Exposure Factors

Handbook. Office of Research and Development. EPA/600/R-93/187.Table A-1Fish Tissue Concentration DataMeasured Selenium Concentrations (mg/kg or ug/g)WaterExposureKidney Se (mg/kg)Liver Se (mg/kg)Muscle Se (mg/kg)Whole Body Se (mg/kg)EffectUsed inFishStudyTypeLife stageRouteNOAELLOAELNOAELLOAELNOAELLOAELNOAELLOAELdw/ww%moisture1NotesMajorMinorSMCVBluegillCleveland (1993)freshJuvenileWater------3.03.4dw-2XBluegillCleveland (1993)freshJuvenileDiet------4.77.6dw-2XXBluegillCoyle et al. (1993)freshAdultWater/Diet------1019dw-2,4XXBluegillCoyle et al. (1993)fresheggWater/Diet------2341dw-2,4XBluegillDoroshov et al. (1992)freshAdultDiet--12.326.05.810.4--dw--XXBluegillFinley (1985)freshadultDiet--5.08.52.065.10--ww75-XBluegillGillespie and Baumann (1986)freshFry/larvaeNatural------3.128.2dw--XBluegillGillespie and Baumann (1986)freshAdultNatural------0.45.9ww75-XBluegillHermanutz et al. (1992)freshadultWater/Diet--1.59.30.31.8--ww75-XXBluegillLemly (1993a); Skorupa et al. 2004freshJuvenileWater/Diet------1.35.8dw--XXBluegillSorensen et al. (1984)freshAdultNatural--1.37.01.32.3--ww75-Xchannel catfishDoroshov et al. (1992)freshAdultInjection--7.312.5----dw--channel catfishGatlin and Wilson (1984)freshfingerlingDiet----3.03.5--dw--XXchinook salmonHamilton et al. (1990)freshlarvaeDiet------5.410.8dw-6XXchinook salmonHamilton et al. (1990)brackishjuvenileDiet------12.623.2dw-6XXfathead minnowDobbs et al. (1996)freshlarvaeWater/Diet-------62dw--XXfathead minnowOgle and Knight (1989)freshjuvenileDiet----5.76.65.46.6dw--XXfathead minnowSchultz and Hermanutz (1990)fresheggWater/Diet------0.33.9ww80-XXgreen sunfishLemly (1993b)freshAdultNatural------12.414.7dw--Xrainbow troutHicks et al (1984)freshjuvenileDiet3.010.738.349.3----ww75-XXrainbow troutHilton and Hodson (1983)freshjuvenileDiet0.73.80.621.0--0.21.0dw-3, 4Xrainbow troutHilton and Hodson (1983)freshjuvenileDiet3.87.721.071.7--1.04.0dw-3, 4XXrainbow troutHilton et al. (1980)freshjuvenileWater/Diet93742.095.0----dw-2XXrainbow troutHolm et al. (2005)freshadultNatural-----1.8--ww75-Xrainbow troutHolm et al. (2005)fresheggNatural-------3.5ww61-Xrainbow troutHunn et al (1987)freshFry/larvaeWater------0.50.9dw-4Xrainbow troutHunn et al (1987)freshFry/larvaeWater------0.61dw-4Xrainbow troutVidal et al (2005)freshFry/larvaeDiet------0.30.6ww75-XXRedear sunfishSorensen et al. (1988)freshAdultNatural2.17.6--0.35.0--ww755XSacramento splittailTeh et al. (2004)freshjuvenileDiet--23.026.810.115.1--dw--XXStriped BassCoughlan and Velte (1989)freshAdultDiet----1.13.5--ww75-Xwhite sturgeonLinville (2006)freshAdultDiet--1.410.41.312.1--dw--XXwhite sturgeonTashjian et al. (2006)freshjuvenileDiet30.951.722.037.422.936.814.722.5dw--XXNotes:1 - a value of 75% is the default assumpttion (USEPA 199302 - concentration estimated from figures3 - data from the low carbohydrate diet were not used as the authors reported that reduced weight of fish on this diet was likely due to food4 - dry weight assumed. Not explicilty stated whether dw or ww5 - muscle concentration calculated using regression equation from Sorensen et al. (1982); i.e., muscle concentation = kidney concentration x 0.835 -1.3756 - excludes treatment where fish were exposed to water from the San Luis DrainTable A-2Wet Weight to Dry Weight Conversion for Fish Tissue Concentration DataSelenium Concentrations in Dry Weight (mg/kg-dw or ug/g-dw)WaterExposureKidney Se (mg/kg)Liver Se (mg/kg)Muscle Se (mg/kg)Whole Body Se (mg/kg)EffectUsed inFishStudyTypeLife stageRouteNOAELLOAELNOAELLOAELNOAELLOAELNOAELLOAELMajorMinorSMCVBluegillCleveland (1993)freshJuvenileWater------3.03.4XBluegillCleveland (1993)freshJuvenileDiet------4.77.6XXBluegillCoyle et al. (1993)freshAdultWater/Diet------10.019.0XXBluegillCoyle et al. (1993)fresheggWater/Diet------23.041.0XBluegillDoroshov et al. (1992)freshAdultDiet--12.326.05.810.4--XXBluegillFinley (1985)freshadultDiet--20.033.98.220.4--XBluegillGillespie and Baumann (1986)freshFry/larvaeNatural------3.128.2XBluegillGillespie and Baumann (1986)freshAdultNatural------1.523.6XBluegillHermanutz et al. (1992)freshadultWater/Diet--6.037.21.27.2--XXBluegillLemly (1993a); Skorupa et al. 2004freshJuvenileWater/Diet------1.35.8XXBluegillSorensen et al. (1984)freshAdultNatural--5.228.05.29.2--Xchannel catfishDoroshov et al. (1992)freshAdultInjection--7.312.5----XXchannel catfishGatlin and Wilson (1984)freshfingerlingDiet----3.03.5--XXchinook salmonHamilton et al. (1990)freshlarvaeDiet------5.410.8XXchinook salmonHamilton et al. (1990)brackishjuvenileDiet------12.623.2XXfathead minnowDobbs et al. (1996)freshlarvaeWater/Diet-------62.0XXfathead minnowOgle and Knight (1989)freshjuvenileDiet----5.76.65.46.6XXfathead minnowSchultz and Hermanutz (1990)fresheggWater/Diet------1.619.6XXgreen sunfishLemly (1993b)freshAdultNatural------12.414.7Xrainbow troutHicks et al (1984)freshjuvenileDiet12.042.8153.2197.2----XXrainbow troutHilton and Hodson (1983)freshjuvenileDiet0.73.80.621.0--0.21.0Xrainbow troutHilton and Hodson (1983)freshjuvenileDiet3.87.721.071.7--1.04.0XXrainbow troutHilton et al. (1980)freshjuvenileWater/Diet9.037.042.095.0----XXrainbow troutHolm et al. (2005)freshadultNatural-----7.2--Xrainbow troutHolm et al. (2005)fresheggNatural-------9.0Xrainbow troutHunn et al (1987)freshFry/larvaeWater------0.50.9Xrainbow troutHunn et al (1987)freshFry/larvaeWater------0.61.1Xrainbow troutVidal et al (2005)freshFry/larvaeDiet------1.22.3XXRedear sunfishSorensen et al. (1988)freshAdultNatural8.230.5--1.320.0--XSacramento splittailTeh et al. (2004)freshjuvenileDiet--23.026.810.115.1--XXStriped BassCoughlan and Velte (1989)freshAdultDiet----4.414.0--Xwhite sturgeonLinville (2006)freshAdultDiet--1.410.41.312.1--XXwhite sturgeonTashjian et al. (2006)freshjuvenileDiet30.951.722.037.422.936.814.722.5XXTable A-3Conversion of Fish Tissue Concentration Data Among Tissue TypesSelenium Concentrations in Dry Weight (mg/kg-dw or ug/g-dw)WaterExposureKidney Se (mg/kg)Liver Se (mg/kg)Muscle Se (mg/kg)Whole Body Se (mg/kg)EffectUsed inFishStudyTypeLife stageRouteNOAELLOAELNOAELLOAELNOAELLOAELNOAELLOAELMajorMinorSMCVBluegillCleveland (1993)freshJuvenileWater--12.013.23.23.63.03.4XBluegillCleveland (1993)freshJuvenileDiet--16.824.55.18.44.77.6XXBluegillCoyle et al. (1993)freshAdultWater/Diet--30.149.111.121.510.019.0XXBluegillCoyle et al. (1993)fresheggWater/Diet------23.041.0XBluegillDoroshov et al. (1992)freshAdultDiet--12.326.05.810.45.59.3XXBluegillFinley (1985)freshadultDiet--20.033.98.220.47.516.9XBluegillGillespie and Baumann (1986)freshFry/larvaeNatural--12.366.33.332.33.128.2XBluegillGillespie and Baumann (1986)freshAdultNatural--7.058.01.526.91.523.6XBluegillHermanutz et al. (1992)freshadultWater/Diet--6.037.21.27.21.36.7XXBluegillLemly (1993a); Skorupa et al. 2004freshJuvenileWater/Diet--6.319.91.46.31.35.8XXBluegillSorensen et al. (1984)freshAdultNatural--5.228.05.29.25.08.3Xchannel catfishDoroshov et al. (1992)freshAdultInjection--7.312.52.13.82.03.6XXchannel catfishGatlin and Wilson (1984)freshfingerlingDiet----3.03.53.13.5XXchinook salmonHamilton et al. (1990)freshlarvaeDiet--18.831.95.912.05.410.8XXchinook salmonHamilton et al. (1990)brackishjuvenileDiet--35.957.214.126.412.623.2XXfathead minnowDobbs et al. (1996)freshlarvaeWater/Diet---121.0-72.8-62.0XXfathead minnowOgle and Knight (1989)freshjuvenileDiet--18.821.95.76.65.46.6XXfathead minnowSchultz and Hermanutz (1990)fresheggWater/Diet------1.619.6XXgreen sunfishLemly (1993b)freshAdultNatural--35.440.313.816.512.414.7Xrainbow troutHicks et al (1984)freshjuvenileDiet12.042.8153.2197.2--46.860.3XXrainbow troutHilton and Hodson (1983)freshjuvenileDiet0.73.80.621.00.21.00.21.0Xrainbow troutHilton and Hodson (1983)freshjuvenileDiet3.87.721.071.71.04.31.04.0XXrainbow troutHilton et al. (1980)freshjuvenileWater/Diet9.037.042.095.0--12.628.9XXrainbow troutHolm et al. (2005)freshadultNatural-----7.2-6.7Xrainbow troutHolm et al. (2005)fresheggNatural-------9.0Xrainbow troutHunn et al (1987)freshFry/larvaeWater--3.24.70.50.90.50.9Xrainbow troutHunn et al (1987)freshFry/larvaeWater--3.75.50.71.10.61.1Xrainbow troutVidal et al (2005)freshFry/larvaeDiet--6.19.91.32.51.22.3XXRedear sunfishSorensen et al. (1988)freshAdultNatural8.230.5--1.320.01.516.6XSacramento splittailTeh et al. (2004)freshjuvenileDiet--23.026.810.115.19.012.9XXStriped BassCoughlan and Velte (1989)freshAdultDiet----4.414.04.312.1Xwhite sturgeonLinville (2006)freshAdultDiet--1.410.41.312.13.112.3XXwhite sturgeonTashjian et al. (2006)freshjuvenileDiet30.951.722.037.422.936.814.722.5XXNote:shaded cells represent predicted concentrations. See text for explanation.Table A-4Wet Weight to Dry Weight Conversion for Bird Dietary Concentration DataMeasured Selenium Concentrations (mg/kg or ug/g)wMeasured Diet Se (mg/kg)Diet Se (mg/kg-dw)EffectBirdStudyLife stageChemical formNOAELLOAELdw/w%moistureNOAELLOAELMajorMinorChickenElzubier and Davis (1988)Chickselenite0.1510??0.1510XChicken (Hubbard)Jensen (1976)Chickselenite0.94.3dw-0.94.3XChicken (leghorn)Jensen (1976)Chickselenite4.313.5dw-4.313.5XChickenLowry and Baker (1989)Chickselenite; SeMet015??015XChickenOrt and Latshaw (1978)Adultselenite35??35XCommon eiderFranson et al. (2007)AdultSeMet20.657.7dw-20.657.7XMallardAlbers et al. (1996)AdultSeMet2040ww10.522.344.7XMallardGreen and Albers 1996AdultSeMet1020ww10.511.222.3XMallardHeinz and Hoffman, 1998AdultSeMet0.48.8ww100.49.8XMallardHeinz et al., 1987Adultselenite1025ww8.510.927.3XMallardHeinz et al., 1987AdultSeMet010ww8.50.010.9XMallardHeinz et al., 1988Ducklingselenite10.120.1ww710.921.6XMallardHeinz et al., 1988DucklingSeMet10.120.1ww710.921.6XMallardHeinz et al., 1989AdultSeMet4.18.1ww104.69.0XMallardHeinz et al., 1989AdultSeCysteine10.1-ww1011.2-XMallardHeinz et al. (1996)DucklingSeMet15.3430.34ww11017.033.7XMallardHoffman and Heinz (1998)AdultSeMet0.410.4ww100.411.6XMallardHoffman et al. (1991)DucklingSeMet; low protein0.215.2ww100.216.9XMallardHoffman et al. (1991)DucklingSeMet15.260.2ww1016.966.9XMallardHoffman et al. (1992a)DucklingSeMet0.215.2ww100.216.9XMallardHoffman et al., 1992bDucklingSeMet0.215.2ww80.216.5XMallardHoffman et al., 1992bDucklingSeMet15.260.2ww816.565.4XMallardHoffman et al., 1992bDucklingSeMet; low protein15.260.2ww816.565.4XMallardHoffman et al., 1992bDucklingSeMet; low protein0.215.2ww80.216.5XMallardHoffman et al., 1992bDucklingSeMet; high protein0.215.2ww80.216.5XMallardHoffman et al. (1996)DucklingSeMet, Se yeast, Se in wheat0.215.2ww1100.216.9XMallardO'Toole and Raisbeck (1997)FlightlingSeMet10.3225.32ww2513.833.8XMallardStanley et al. (1994)AdultSeMet0.376.5dw-0.376.5XMallardStanley et al. (1996)AdultSeMet3.57ww103.97.8XPheasantLatshaw et al. (2004)Adultunknown-9.3dw--9.3XScreech owlWiemeyer and Hoffman (1996)AdultSeMet8.830dw-8.830XScreech owlWiemeyer and Hoffman (1996)AdultSeMet0.38.8dw-0.38.8XNotes:1 - a %moisture of 10 was assumed based on other studies by the same authors where a %moisture was specified.Table A-5Summary of Chicken Enhanced Production StudiesMeasured Selenium Concentrations (mg/kg or ug/g)Measured NOAELNOAELEffectsBirdStudyLife stageDietary form(mg/kg)dw/ww%moisture(mg/kg-dw)SurvivalWeightEgg outputReproductive successChickenPayne et al. (2005)Adultselenite2.6?-2.6XChickenPayne et al. (2005)AdultSe-yeast2.9?-2.9XChickenRyu et al. (2005)1 dayselenite8.2dw-8.2XJapanese quailBiswas et al. (2006)1 dayselenite1.2?-1.2XXJapanese quailSahin and Kucuk (2001)10 dayselenite0.2ww10.320.2XNorth San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. B-1 

### A PPENDIX 

### B

T HRESHOLD 

### V ALUES FOR 

### S ELENIUM IN 

### G REAT 

### S ALT 

### L AKEES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 1 **F I**  **N A**  **L T**  **E C**  **H N**  **I C**  **A L**  **M E**  **M O**  **R A**  **N D**  **U M** 



# Thre **s ho**  **ld V**  **a l**  **ue s for S**  **e le**  **niu m**  **in Gr**  **e a**  **t**

**S a**  **lt L**  **a ke**  **: Se**  **le c**  **tio ns**  **by th**  **e S**  **ci e**  **nce P**  **a n**  **e l** 

**PR EPA**  **R ED**  **F OR**  **:** Gre at Sal t La k e Sc i ence P a nel

**PR EPA**  **R ED**  **B Y:**  Har ry Ohl endorf

**C OPI**  **ES:** J ef f D enBle y k er Earl By ron Gary Santol o
D an Moore

Pri nci p al I nve s ti g ator s

**D A**  **T E:**  F eb ruary 28, 2007

**PR OJEC**  **T N**  **U M**  **B ER**  **:** 341055. P P. Q C

The p urp o s e of t his tec hn i c al m e m orandu m i s to p rovi de a s um m ary and doc um entation

of the Sc i ence P anel’s di s c u s s i on s rel ati ve to to xic i ty thre s hold s f or e xp o s ure of b i rds to

s el enium at the Gre at Sal t La k e

. I t i s g eneral l y rec og nized t hat t he m os t s i g nif i c ant

exp os ure of b i rds oc c urs throu g h their di et, and th at the b es t­ doc um e nted a nd m os t
read i l y

­ m onito red ef f ec ts are tho s e o n reprod ucti ve s ucc es s ( p arti c ularl y eg g hatchab i l i ty )

. Thus, mu c h of the f oc us of thi s tec h nic al m em ora n dum i s o n tho s e exp o s ure s and endp oi nts, b ec aus e they c an b e m o s t read i l y a p p l i ed tow ard e s tab l i s hm e nt of a s i te­ s p ec i f i c

w ater qu al i ty s ta ndard f or s el eniu m i n the open w aters of the Gre at Sal t La k e

.

Bef ore the Sc i ence P anel m eeti ng on No vem b er 29

­ 30, 2006

, I p repared a tec hn i c al

m em orand um ( Sub ject: Thres hold Val ue s f or Sel e nium i n Gre at Sal t La k e; dated

No vem b er 28) to p rovi de the f ol l ow i ng :

· a s um m ary of p ot ential thre s hold val ues ide ntif i ed b y Sc i ence P anel m em b ers f or

c ons i der ati on i n e s tab l i s hin g a w ater q uali ty s tand ard for s el eniu m i n the ope n w ater s of

the Gre at Sal t La k e, and

· s up p orti ng doc um e ntation and l i terature p rovi de d b y Pan el m em b er s to b e u s ed as the

b as i s of di s c ussion b y the Pa nel.

Bi l l Adam s , An ne F ai rb rother, There s a Pres s er, an d J oe Skor up a p rovi ded in p ut c onc erni ng thres hold val ues to b e c ons i der ed and s ent s up p or ti ng l i terature ( ei ther as c i tati ons or co p i es of p ubl i c ati ons )

, i n addi ti on to p rovi di ng their vi ew s on the thre s hold val ue s the m s el ve s

. The entir e Pan el di s c ussed t hat m ateri al a nd rel ate d i nfor m ati on f ro m other s ourc es on
No vem b er 30. F rom the avai l ab l e i nfor m ati on, t he Pan el narrow ed th e ran g e s of v al ues for

b i rd die ts and eg g s to t hos e l i s ted i n Tab l es 1 a nd 2 ( Attachm e nt A [ tab l es m odi f i ed f rom the

c omp i l ati on of f i el d and l ab orato ry data p re s ented i n Tab l e 15 of Pre s s er and Luo m a, 2006] )

and the n i dentif i ed “w orkin g v al ues ” f or th e ran g es of ac c ep tab l e s el eniu m c onc entrati on s
i n b i rd die ts a nd i n b i rd eg g s ( thos e s haded i n the tab l es )

. I t i s u nders tood that the val ue s

w i l l l i k el y b e ref i ned duri ng f utu re p has e s of w ork ( i ncl uding c ons i der ati on of s i te­ s p ec i f i cT HR ESHO LD VALUES F O R SELENI UM I N G REAT SALT LAKE: S ELECT I O NS BY T HE SCI ENCE PANEL

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 2 data c urrently b ei ng g enerat ed b y the Gre at Sal t L ak e re s earc h ef f ort) and di s c u s s i on rel ated

to es tab l i s hin g a s i te­ s p ec i f i c s tandard f or Great Sa l t Lak e.

A p revi ou s draf t of t his tec h nic al m em ora ndu m ( dated D ec e m b er 8) p rovi ded a b ri ef

s um m ar y of t he t hres hold val ue s t hat w ere s el ec te d b y t he Pan el d uring thos e di s c u s s i ons

. F or bo th d i et and eg g s , the ra ng e s of s el eniu m c on c entrati ons s el ec ted b y the Pan el are t he

l ow er an d u p p er 95 p erc ent c onfi denc e i nt erval s ( 95% C I s ; al s o ref err ed to as the 5 p erc ent
l ow er conf i denc e l i m i t [ LCL] and the 95 p erc ent u p p er conf i denc e l i m i t [ UC L] ) f or t he m ean

s el enium c onc entrati on t hat i s a s s oc i ated w i th a 1 0 p erc ent red ucti on ( i

. e

. , the 10 p erc ent
ef f ec t c onc entrati on or EC 1 0 ) i n the hatch ab i l i ty of m al l ard eg g s

. Tho s e val ues wer e re p orte d

b y Ohl endorf ( 2003)

, b as e d on the anal y s i s of data f rom s i x l ab orato ry s t udies ( He i nz et al

. 1987, 1989; He i nz a nd Ho f f m a n 199 6, 1998 ; Stanl e y et al

. 1994, 1996)

. E s s e ntial l y , t here i s 95 p erc ent c onfi denc e that the m ea n di etar

y or eg g s el enium c onc entrati on that c aus e s a 10 p erc ent red ucti on of eg g hatchab i l i ty i s w i thin t he i dentif i ed ran g es , w hic h are il l us trated

i n the f i g ures b el ow

.

The Pa nel ag reed b y c ons e nsus that the 95% C I s o n m e an seleni u m c onc entrati on s i n

m al l ard die t and eg g s a s s oc i ated w i th the EC 1 0 f or eg g hatchab i l i ty w ould b e re as on ab l y

p rote c ti ve f or bi rds ne s ti n g at the Gre at Sal t Lak e , and that the ran g es of val u es repre s ented

b y the 95% C I s i ncl uded t he c onc entrati on s p ropo s ed b y vari ou s P anel m em b ers f or

c ons i der ati on. Rational e s u p p orti n g s el ec ti on of th e 95% C I s i s p rovi ded b y t he p revi ous

tec hn i c al m em orand um ( dated Nove m b er 28) and throu g h di s c ussion at t he P anel m eeti ng

.

Pan el m em b ers p rovi ded c omm e nts on the D ec e m

b er 8 draf t ver s i on of this tec hn i c al

m em orand um s um m ari zi ng thre s hold val ue s ( Att ac hm ent B)

, and Bi l l Ada m s p rovi ded

f urth er data analy s e s of ef f ec t l evel s i n di et s a nd e g g s of m al l ards that are incl uded i n thi s
revi s ed draf t. Addi ti onal co n s i der ati ons and qu al i f i c ati ons ab out the s el ec ted di etary and

eg g c onc entrati ons are p rese nted b el ow i n the D i s c us s i on s ec ti on

.

All c onc entrati ons i n b i rd die ts or e g g s m entio ned b el ow are ex p res s ed o n dr

y

­ w ei g ht b a s i s

.



## Sel **e niu**  **m in**  **B ird**  **D ie**  **t s** 

The di etary s el eniu m E C 1 0 f or m al l ards w as report ed as 4. 87 m g / k g

, w i th 95 % C I s of 3. 56 to

5. 74 m g /k g b a s ed on reprod ucti ve toxic i ty ( eg g h atc habi l i ty ) ( Ohl endorf 2003)

. The EC 1 0 of

4. 87 m g /k g w a s e s ti m ated b y f i tti ng a l og i s ti c re g ress i on m odel ( F i g ure 1)

. I t s hou l d b e noted, howeve r, that the m al l ard s tudie s us ed a “ dry di et” t hat had ab ou t 10 p erc ent

m oi s ture

. O hlendor f ( 2003) u s ed the reported di etary seleni um c onc entrati ons w i thou t adju s t m ent f or th at m oi s ture c onten t

, b ut an u p w a rd adj u s tm e nt of the val ues (b y
11 p erc ent) w o uld be a p p ropri ate to ac c oun t f or t h e m oi s t ure c onte nt of the duck di et.

I n Adam s et al

. ( 2003)

, hoc k e y

­ s ti c k regre s s i on w a s u s ed to m odel rel ati ons hips b etw een e g g

s el enium c onc entrati ons and adver s e ef f ec ts i n or der to der i ve to xic i ty thre s hold s , s uch a s EC 1 0 val ue s

. Ho c k ey

­ s ti c k re g res s i on i s a m odel th at ha s b een u s ed el s ew here to def i ne a thres hold w hen an underl y i n g b ac k g round l evel o f resp o ns e i s un rel ated to t he do s e ( s ee Adam s c om m ent s i n Attach m ent B)

. Thu s , s uch a m odel m a y b e rel evant to na turall y

oc c urri ng el em ent s t hat ar e e s s e ntial to b i rds and a w i de vari ety of other orga nis m s and

p arti c ularl y usef ul f or eleme nts suc h a s s el eniu m , w hic h has a narr ow ran g e b etw een l evel s that are es s ential a nd t hos e that are t o xic to b i rds s o that vari ance arou nd t he i nfl ec ti on

p oi nt ( thre s hold ) i n the m odel i s s m al l

. A s s hown i n F i g ure 2 b el ow , a thres hold c l earl yT HR ESHO LD VALUES F O R SELENI UM I N G REAT SALT LAKE: S ELECT I O NS BY T HE SCI ENCE PANEL

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 3 **0 %**  **1 0**  **% 2**  **0 %**  **3 0**  **% 4**  **0 %**  **5 0**  **% 6**  **0 %**  **7 0**  **% 8**  **0 %**  **9 0**  **% 1**  **0 0**  **%**

**0 .1**  **1 1**  **0 1**  **0 0** 

**Die t**  **a ry**  **S e**  **, m**  **g/k g d**  **ry w**  **t**

**. D** **uc k** **li ng** **M ort** **a li** **t y** **, %**  E m p i r ic a l d a ta

P r e d icte d m o r ta li ty

9 5 % co n f ide n c e in te r va l

In f lect ion p o i n t = 3 .9 m g /kg

E C 1 0 ( p r e d ict e d ) = 4 .4 m g /k g
E C 1 0 ( L C L ) = 3 .8 m g / kg

E C 1 0 ( U CL) = 4 .8 m g /k g

**Fi gure**  **2**

**. H**  **oc k**  **e y**  **s t**  **i c**  **k r**  **e gr**  **e s**  **s i**  **on of l**  **a bora**  **t ory**  **m a**  **ll a**  **rd duc k**  **l i**  **ng**

**m ort**  **a li**  **t y**  **v e**  **rs us**  **di e**  **t a**  **ry s**  **e l**  **e n**  **i um** 

**.**T HR ESHO LD VALUES F O R SELENI UM I N G REAT SALT LAKE: S ELECT I O NS BY T HE SCI ENCE PANEL

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 4 ap p ear s to exis t w hen di etary s el eni um i s p l otted vers u s duc k l i ng m ortal i ty ( w hic h

i nco rporated th e c um ulati ve ef f ec ts of f erti l i zati on s ucc es s and hatchab i l i ty )

. The i nfl ec ti on

p oi nt oc c urs at a di etary s el e nium c onc entrati on o f 3. 9 m g /k g

. ( The D i s c u s s i on s ec ti on b el ow des c ri b es un c ertai nty arou nd th e i nfl ec ti on p oi nt. ) T he p red i c ted EC 1 0 i s 4

. 4 m g /k g ( ju s t s l i g htl y ab ove the i nfl ec ti on p oi nt) and the 95 % C I around the p red i c ted E C 1 0 ran g e s f rom 3. 8 to 4. 8 m g / k g

. Th e p red i c ted EC 1 0 of 4. 4 m g /k g i s s l i g htly l ow er t han Ohl endorf ’ s ( 2003) EC 1 0 of 4. 9 m g / k g , a nd t he 95 % C I i s narro w er u s i n g hoc k ey s ti c k regre s s i on tha n

w hen u s i ng l og i s ti c re g res s i on.



## Sel **e niu**  **m in**  **B ird**  **Egg s** 

Si m i l ar to the di etary v al ues cal c ulated by O hlend orf ( 2003) f or rep rod ucti ve to xic i ty f or

m al l ards, th e EC 1 0 i n e g g s w a s re p orte d a s 1 2. 5 m g /k g

, w i th 95% C I s of 6

. 4 to 16

. 5 m g /k g ( F i g ure 3)

. The E C 1 0 of 12

. 5 m g /k g w a s e s ti m ated b y f i tti ng a l og i s ti c re g res s i on m odel to
the res ults of the s i x l ab orato ry stu di e s w i th m al l a rds

.

As noted i n Tab l e 2

, the E C 1 0 f or du c k l i ng m ortal i ty

, as reported i n Adam s et al

. ( 2003)

, rang ed f ro m 12 to 16 m g / k g ( s ee Ada m s c om m en ts i n Attach m ent B)

. Thes e E C 1 0 val ue s are b as ed on a s y nth e s i s of l ab orato ry stu di e s i n w hic h the f i nal end p oi nt w a s d uckli ng m ortal i ty ( the s a m e ef f ec ts data u s ed i n the di etary EC 1 0 eva l uation w i th hoc k ey

­ s ti c k regre s s i on ab ove)

and the ran g e of EC 1 0 val ues refl ec ts di f f erent s tati s ti c al ap p roac he s f or analyzin g t he dat a.
An ada p tati on f rom F i g ure 3 i n Ada m s et al

. ( 2003 ) i s p rovi ded bel ow ( F i g ure 4)

, w i th the

95% C I i ncl uded. A s s hown

, t he i nfl ec ti on p oi nt o c c urs at a n e g g s el enium c onc entrati on of 9. 8 m g /k g , w i th a p red i c ted E C 1 0 c om p arab l e to that der i ved b y Ohl endorf ( 2003)

. ( See D i s c u s s i on f or co m m ent s c onc erni n g un c ertai nty around the i nfl ec ti on p oi nt. ) Ho w ever, the 95 % C I u s i ng hoc k e y

­ s ti c k regre s s i on i s m uch narrow er (9. 7 to 13

. 6 m g /k g ) tha n t hat

der i ved b y Ohl endorf us i n g l og i s ti c regre s s i on ( 6. 4 to 16

. 5 m g /k g )

. Gi ven t hat there i s a c l ear

eg g

­ s el eni um thre s hold at w hic h ef f ec ts b e g i n to b e ob s erved

, a un i m odal m odel

, s uch as l og i s ti c regres s i on, m ay res ult i n e xag g erated c onfi denc e i nterval s , p arti c ularl y i n the tai l s

.



## D **is c**  **u s**  **s ion** 

Addi ti onal discus s i on i s p resen t ed b el ow c onc erni ng t he b a s i s f or s el ec ti on of thres hold

val ues , u ncer tai nty s urro un di ng the hoc k e y

­ s ti c k regres s i on i nfl ec ti on p oi nt s , hor m eti c ef f ec ts of s el eniu m , and other q uali f i c ati ons and p oi nts di s c u s s ed d uring the Pan el m eeti n g
i n No vem b er, as ref l ec ted i n c om m ent s f rom Pan e l m em b er s ( Attach m ent B)

.



### B **as i**  **s for S elect**  **i on**  **of Threshold V**  **a l**  **ues**

The Sc i ence P an el c an c hoo s e a s c i entif i c al l y

­ b as ed thres hold val ue or acc ep tab l e “b enchm ark” c onc entrati on b a s ed o n t he c on s en s us c onfi denc e l i m i t s de s c ri b ed b y an al y s i s of avai l ab l e data ( p rese nted ab ove)

, b ut ulti m atel y , a c hoic e of n um b ers f rom w i thin the

c ons en s us conf i denc e l i m i ts f or reg ulator y p ur p os es i s not a s c i entif i c dec i s i on. C hoic es of a

s p ec i f i c nu m b er or n um b ers f rom w i thin tho s e c o nfi denc e rang e s are p hil os oph i c al /legal

dec i s i ons th at de p end on how p rec autionary the S tate of Ut ah w a nts to b e ( a m atter of

p hil os oph y ) a nd o n how m uch p otential f or legal l i ab i l i ty the St ate i s c omfor tab l e w i th

exp os i n g i t s el f to. The k e y dec i s i on the State m u s t m ak e i s w heth er they w ant to re g ulate to

a “NE C ” ( no ef f ec ts c onc entrati on, w hic h i s not th e s a m e a s a NO E C [ no ob s erved ef f ec tsT HR ESHO LD VALUES F O R SELENI UM I N G REAT SALT LAKE: S ELECT I O NS BY T HE SCI ENCE PANEL

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 5 **0 %**  **1 0**  **% 2**  **0 %**  **3 0**  **% 4**  **0 %**  **5 0**  **% 6**  **0 %**  **7 0**  **% 8**  **0 %**  **9 0**  **% 10**  **0 %** 

**0 .1**  **1 1**  **0 1**  **0 0** 

**E gg**  **S e**  **, mg**  **/k g d**  **ry w**  **t**

**. Du** **c kl** **ing Mo** **rta lity** **, %** E m p i r i c a l da ta

P r ed i c t ed m o r ta l i ty

9 5% c o nf i d e nc e i n te r v a l

I nf l e c ti on p o i n t = 9. 8 m g/k g
E C 10 (p r e d i c te d ) = 1 1. 5 m g/k g
E C 10 (L CL ) = 9 .7 m g/ k g
E C 10 (U C L) = 1 3.6 m g /k g

**Fi gure**  **4**

**. H**  **oc k**  **e y**  **s t**  **i c**  **k r**  **e gr**  **e s**  **s i**  **on of l**  **a bora**  **t ory**  **m a**  **ll a**  **rd duc k**  **l i**  **ng**

**m ort**  **a li**  **t y**  **v e**  **rs us**  **e gg s**  **e l**  **e ni**  **u m** 

**.**T HR ESHO LD VALUES F O R SELENI UM I N G REAT SALT LAKE: S ELECT I O NS BY T HE SCI ENCE PANEL

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 6 c onc entrati on]) s tandard or to s o m e v ersion of a “t ol erab l y toxic ” s tand ard s uch as an EC 1 0 ,

an EC 2 0 , or an EC 0 5 , etc

.

C onc ep tuall y , a b ench m ark c onc entrati on i s def i n ed as the l oc ati on on the exp o s ureresp on s e c urv e th at i s the thre s hold b etw een ab s e nce an d p re s ence of a g i ven ef f ec t or endp oi nt ( i

. e

. , the thre s hold b etw een an EC 0 0 and an EC 0 1 c onc entrati on [ s ee:

w w w

. ep a. g ov/ec otox/eco s s l /p df /ec o s s l _attac h m ent_3­2

. p df

; p

. A­6] )

. Benc h m ar k

c onc entrati ons are es ti m ated a s the l ow er 95 p erc ent c onfi denc e b oun dar

y o n t he E C 1 0 ( s ee :
M ei s ter and Va n Den Bri nk [ 2000]

, p p

. 114­ 116 i n p arti c ular; and USE PA [ 2000] )

.



### U **nce rt**  **ainty S**  **urroundi ng**  **t he Hoc**  **ke y­**  **S t**  **i ck**  **R egre**  **ss i**  **on I**  **nflect i**  **on P**  **o i**  **nts**

To deter m i ne the i nfl ec ti on p oi nt b etw een the hoc k ey

­ s ti c k “b l ade” and “ha ndle”, or a ny

p arameter i n t he m odel

, i niti al p arameter val ue s a re inp ut to the s of tw are p rogra m SPl u s ®

and an i terati ve tec h niqu e i s us ed to s earc h f or m o re ex ac t p arameter val ue s t hat w i l l

m i nimize th e s u m of s q uared devi ati on s b etw een the ob s erved ef f ec ts data and ef f ec ts
val ues p red i c ted b y the m odel

. Var i ance in the es t i m ate of t he i nfl ec ti on p oi nt val ue i s af f ec ted b y the s p ac i ng of the m ea s ured X val ue s a s w el l as the s c atter or tre nd i n Y val ue s
i n the vi c i nity of the e s ti m ated i nfl ec ti on p oi nt. I f

, f or ex am p l e, there are f ew m eas ured

di etary s el eni um c onc entrati ons near the p red i c te d i nfl ec ti on p oi nt, th e un c ertai nt

y i n the

l oc ati on of the i nfl ec ti on p oi nt w i l l b e g reater b ec aus e i t w i l l b e di f f i c ult to deter m i ne t he

exact c onc entrati on at w hic h t he i nfl ec ti on p oi nt o c c urs ( i

. e. , i t c ould b e b etw een tw o of t he

m eas ured val ue s )

. Un c ertai nt y aro un d the p red i c ted Y ( EC) val ue s at t he p red i c ted

i nfl ec ti on p oi nt i s af f ec ted b y t he n um b er of Y val ues an d the s c atter of the Y val ues at that

p arti c ular X v al ue ( w hic h, when c al c ulati ng th e c o nfi denc e i nterval around Y

, i s a s s um ed to
b e es ti m ated w i thou t err or)

. Th us, b oth the s p ac i n g of t he m ea s ured X val ues an d the

vari ance in the res p on s e vari ab l e af f ec ts the un c ert ai nty aro un d t he i nfl ec ti on p oi nt. The

ti g hter s p ac i ng and l es s a m b i g uou s ef f ec ts re s p on s e af ter the i nfl ec ti on p oi nt c au s e s th e 95% C I arou nd the di etary s el e nium

­ b as ed i nfl ec ti on p oi nt ( 3. 0 to 4. 9 m g / k g ) to b e n arr ow er than t hat f or the eg g s el enium

­ b as ed i nfl ec ti on p oi

nt ( 6. 4 to 14. 9 m g / k g )

.

Ho w ever, al thou g h there i s un c ertai nty s urroundi ng t he i nfl ec ti on p oi n t, u s e of t he b e s t

es ti m ate of the i nfl ec ti on p oi nt resu l t s i n the b es t f i t of the re g res s i on m odel to the data

. I n
F i g ure 4, f or ex a m p l e , i f th e i nfl ec ti on p oi nt oc c urred at ei ther end of the 95 % C I of e g g

s el enium c onc entrati on ( 6

. 4 to 14

. 9 m g /k g dr

y w t

. ) one c an ea s i l y vi s uali ze that the f i t of the

regres s i on to the data p oi nts abo ve t he i nfl ec ti on p oi nt w ould not p a s s thro ug h th e

m eas ured val ue s i n the s am e w ay

.



### H **orm et**  **i c E**  **f f**  **ec t**  **s of S eleni**  **um**

C ons i der ati on of the hor m eti c ef f ec ts of s el eniu m m ay res ult i n l ow eri ng of thre s hold s ( f or horm eti c s ubs tance s a nd e ndp oi nt s on e ha s to di s t i ng uis h b etw een val i d c ontrol res p on s es and hor m eti c def i c i ency res p ons e s b ef ore a val i d b as el i ne to c om p are to xic res p on s es

ag ai ns t c an b e i dentif i ed)

. The horm eti c b i as i n t he data us ed f or th e Ohl endorf ( 2003)

regres s i ons ha s not y et b een f ull y c on s i der ed b y t he Sc i ence P a nel. I f s uch c ons i der ati on

w ere to res ult i n c han g es , t hos e c han g es c ould onl y b e i n the di rec ti on of a dow nwar d

s hif ti ng of the thre s hold c onfi denc e l i m i ts

. ( F or ex am p l e, p rel i m i nar y un p ubl i s hed a nalys e s that adj us ted f or horm eti c ef f ec ts i n the m al l ard d ata y i el ded a revi s ed EC 1 0 f or die t ofT HR ESHO LD VALUES F O R SELENI UM I N G REAT SALT LAKE: S ELECT I O NS BY T HE SCI ENCE PANEL

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) 7 4. 1 m g /k g , w i th a 95% C I of 1. 3 to 5. 8 m g / k g

, a nd a revi s ed E C 1 0 f or e g g s of 9. 22 m g / k g

,

w i th a 95 % C I of 4

. 11 to 13

. 07 m g /k g

. )

.



### Ot **her Qual i**  **f i**  **ca t**  **i ons and**  **P oi**  **nts D**  **i sc**  **uss ed** 

The Pa nel al s o di s c u s s ed the f ol l ow i ng addi ti onal qu al i f i c ati ons and p oi nts rel ati ve to

toxic i ty thres hold val ue s :

· Ap p l i c ab i l i ty of l ab orato ry data to f i el d s i tua ti ons i s not c ertai n ( note that f i el d data w ere
retai ned i n c om p i l ati on of e g g

­ s el enium c onc entra ti ons i n Tab l e 2)

, and i t i s i m p orta nt to

c ol l ec t s i te­ s p ec i f i c f i e l d data on s el eniu m c onc en t rati ons i n b i rd eg g s ( e. g

. , c urrent data

g atheri ng ef f ort at the Gre at Sal t Lak e)

.

· Ap p l i c ab i l i ty of m al l ard data to s p ec i es at Gre at S al t Lak e i s un c ertai n, bec aus e rel ati ve

s en s i ti vi ty of al l s p ec i es ne s ti ng there i s not k now n.

· Thres hold val ues discu s s ed are for the hatchab i l i ty end p oi nt ( b a s ed on di et a nd avi a n

eg g ) b ut no n­reprod ucti ve adver s e ef f ec ts end p oi nts (e. g

. , avi an b l ood endp oi nt) al s o

m ay b e i m p ortant

. Ho w ever, i nterp reti ve val ue s f or s el eniu m i n avi an b l ood are n ot

avai l ab l e; al thou g h s el enium c onc entrati ons i n b l ood i ndic ate exp o s ure of t he b i rds, tha t endp oi nt i s not c on s i der ed u s ef ul f or s etti n g a w at er q uali ty s ta ndard.

· Ph al aropes are s ea s onall y nu m ero u s at the Gre at Sal t Lak e and s ho uld be added to the

l i s t of s p ec i es to b e m onito red b ec au s e t hey repre s ent s p ec i es w i th a f eedi ng rat e th at i s a l arge p erc enta g e of b ody w ei g ht ( af f ec ti ng e nerg

y c ons i der ati on i n det ermini ng w i l dl i f e

c ri teri on).



## R **e c**  **om m**  **e nd**  **e d**  **N e**  **x t St**  **e ps** 

The i s s ue s s u m m ari zed i n thi s tec h nic al m em ora n dum s ho uld be dis c u s s ed/c ons i der ed

f urth er by the Pan el

, p arti c ularl y to ref i ne the s el e c ti on of thres hold val ue s f or bi rd die t s a nd

eg g s w i th res p ec t to ef f ec ts doc um e nted el s ew her e ( i n f i el d and l ab orato ry s t udies) and

c ons i der i ng t he re s ults b ei ng devel oped throu g h researc h at the Gre at Sal t Lak e

. I n p aral l el

, i t w i l l b e i m p ortant to k now what l evel of p rote c ti venes s t he State and EP A w i l l ap p l y i n the

devel opm ent of th e s i te­ s p ec i f i c s tandard f or s el en i um on the Gre at Sal t La k e ( i

. e

. , EC 2 0 , EC 1 0 , E C 0 5 , etc

. ) s o that the Sc i ence P anel c an mos t ef f ec ti vel y m ak e rec omm e ndatio ns th at

c an b e ap p l i ed tow ard t hat pu rpo s e

.



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. V. Bri x, M

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, L

. M

. Tear

, D

. K

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. An al y s i s of f i el d and l ab orato ry data to der i ve s el e nium to xic i ty thre s hold s f or bi rds.

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. , M

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En vir o n

. C o n t a m. To xic o l

. 26 : 4 44­ 451.

Stanl ey , J r. , T. R., G

. J

. Smith

, D

. J

. Ho f f m a n, G. H

. H ei nz, a nd R. R o s s c oe. 1996

. Ef f ec ts of

b oro n and s el eniu m on m al l ard rep rod ucti on a nd duckli ng g row th a nd s urvival

. En v ir o n

. To xic o l. C hem

. 15: 1, 1 24­ 1, 132

.

U. S. Envir on m ental Protec ti on A g ency ( USEP A). 2 000. Be nchm ar k D os e Tec hn i c al Guid ance
D oc um en t. [ External Review D raf t]

. EP A/ 630/ R­ 00/001. U

. S. Envir on m ental Protec ti on Ag ency , Was hing to n, D C

.

Y am a m oto, J

. T

. , and G. M

. Santol o

. 2000

. Bod y c on di ti on ef f ec ts i n Am eri c an kes trel s f ed

s el enom et hioni ne. J

. W il dl

. Di s

. 36 : 646­ 652.**A TT**  **A C**  **HM E**  **NT A** 



# Tabl **e s** AT T ACHMENT A: T ABLES

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) A­1 **TA B**  **LE 1** 
Di et Conc en t r ati on s

**mg/ k**  **g A**  **pp roach**  **or S**  **i t**  **e E**  **f**

**f ec**  **t s**  **S pe**  **ci es**  **R efer**  **en ce(s**  **)**

4. 87 **( C**  **I 3.**  **5 6** 

**­ 5** 

**. 74**  **)** S ynt he si s o f l ab
D at a H at chab i l i t y i n m a l l ards ( 10 % e f

f e ct l e ve l / 95% co nf i de nce bou nda r i e s) M al l a r d O h l e ndo r f 200 3

4. 4 ( C I 3. 8

­ 4

. 8 ) S ynt he si s o f l ab

data E C 10 f o r duck l i ng m o r

t al i t y M al l a r d B i l l A da m s ana l yse s

pre se nt e d i n A t t ach m e n t B

3. 85

­ 7. 7 ( di e t base d
on 10 % m o i s t ure ) Lab R e duce d hatchi ng succe ss i n m al l a r ds ( 3 3% a t 7

. 7 μg / g) ;

r e duce d grow t h an d w e i gh t i n ha t ch l i ngs M al l a r d S t an l e y e t a l

. 199 6

7. 7 ( d i e t ba se d on 10% m o i s t u r e ) Lab R e ducti on i n nu m be r of su r v i v i ng m a l l ar

d du ck l i n gs produce d pe r f e m a l e M al l a r d S t an l e y e t a l

. 199 6

8. 8 4. 4 / 6

. 2 ( d i e t ba se d
on 10 % m o i s t ure ) Lab 8. 8

­ L O A E L, 4

. 4

­ N O A E L

, 6. 2

­ G e o m e t r i c M e an

R e ducti on ( 1 7% ) i n su r v i va l o f m a l l ar d du ck l i n gs; m e an de cr e ase ( 43%) i n n u m be r of 6

­ day

­ o l d d uck l i ngs M al l a r d H e i nz e t al

. 198 9

6 Lab A dve r se e f

f e ct on bod y co ndi t i on of m al e A m e r i can ke st r e l s A m e r i ca n K e st r e l s Y a m a m o t o a nd Sa nt o l o

, 2 000

7. 7

­ 8. 8 ( di e t base d
on 10 % m o i s t ure ) Lab D i e t ary t hre shol d o f t e r at oge ni c e f

f e ct s i n m a l l a r ds ; abo ve upp e r t hre sho l d, r at e o f de f o r m i t y r i se s s harp l y M al l a r d S t an l e y e t a l

. 199 6

7. 7

­ 8. 8 ( di e t base d
on 10 % m o i s t ure ) Lab D i e t ary t hre shol d o f m a l l ar

d du ck l i n g m o r t a l i t y ( pare nt a l

ex posu r e ) M al l a r d S t an l e y e t a l

. 199 6

N o t e : H igh li g h t e d c e ll s a r e t h e t h r e s h o ld v a lu e s f o r b i r d d ie ts i d e n ti fi e d b y

c o n s e n s u s o f th e S c ien c e P a n e l o n N o v e m b e r 3 0

, 2 0 0 6

.AT T ACHMENT A: T ABLES

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) A­2 **TA B**  **LE 2**  Egg Conce ntra t i on s

**mg/ k**  **g (**  **dry w**  **t**

**. )**  **A pp**  **roach or**  **S i**  **t e**  **E f** 

**f ec**  **t s**  **S pe**  **ci es**  **R efer**  **en ce(s**  **)**

12.5 **( C**  **I 6.**  **4**

**­ 16** 

**. 5**  **)** S ynt he si s o f l ab

data H at chab i l i t y i n m a l l ards ( 10 % e f

f e ct l e ve l / 95% co nf i de nce bou nda r i e s) M al l a r d O h l e ndo r f 200 3

10 S ynt he si s o f l ab
data N O A E L M al l a r d A da m s e t a l

. 20 03

12 ­ 16 S ynt he si s o f l ab

data E C 10 f o r duck l i ng m o r

t al i t y M al l a r d A da m s e t a l

. 20 03

9 S ynt he si s o f l ab

data I m p ai r e d c l ut ch vi a bi l i t y ( 8. 2 % e f

f e ct s l e ve l ) M al l a r d La m e t a l

. 200 5

8. 2 ( o r 7

. 3 ) ( e gg base d
on 73 % m o i s t ure ) Fi e l d 16% de pre ssi on i n e gg v i ab i l i t y **( 7** 

**. 3**  **i n p**  **ap er**  **)** S pott e d S a ndp i pe r H ardi ng e t al

. 200 5

6 S ynt he si s o f f i e l d

data Th r e shol d ( 3% e f

f e ct l e ve l ) of ha t cha bi l i t y S t i l t s S korupa

, 199 8 ; S korup a, 199 9

5. 1 ( e gg ba se d on 78.4 % m o i s t ure ) Fi e l d 15% de pre ssi on i n e gg v i ab i l i t y A m e r i ca n d i ppe r H ardi ng e t al

. 200 5

N o t e : H igh li g h t e d c e ll s a r e t h e t h r e s h o ld v a lu e s f o r b i r d e g g s i d e n ti f ied b y

c o n s e n s u s o f t h e S c ien c e P a n e l o n N o v e m b e r

3 0

, 2 0 0 6

.**A TT**  **A C**  **HM E**  **NT B**  

# Co **mme nt**  **s on De**  **c e**  **mbe r**  **8**

**, 2**  **0 0**  **6**

**, Draft**  **Tec hnic**  **a l**  **Memor a**  **ndum**ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­1 **A TT**  **A C**  **HM E**  **NT B**  

# Co **mme nt**  **s on De**  **c e**  **mbe r**  **8**

**, 2**  **0 0**  **6**

**, Draft**  **Tec hnic**  **a l**  **Memor a**  **ndum**

**C o**  **m m**  **ents o**  **f B**  **ill A**  **d ams** 

F ol l ow i ng are com m ent s o n Har r y Ohl e ndorf ’s draf t tec hn i c al m e m orandu m to the Gre at
Sal t Lak e Sc i ence Pan el e ntitl ed Threshold Va lu es fo r S e le n iu m i n Gr

ea t S a lt L a k e: S el e ctions by

t he S c ie n ce Pa n el ( D ec em b er 8

, 2006)

.



## Sel **e niu**  **m in**  **B ird D**  **ie t**  **s**

As noted i n the draf t m em ora ndu m , the m al l ard s tudies us ed i n O hlendor f ( 2003) a s t he

b as i s f or a di etary s el eniu m E C 10 i n b i rds w as b as ed on a “dr

y di et” c ontaini ng ab out
10% m oi s ture

. Althou g h the m oi s t ure c onte nt of t he m al l ard die t w as l ow , w e rec omm e nd

that stan dard c onven ti on s hou l d b e us ed to p rope rl y adju s t the di etary seleni u m

c onc entrati ons to a dr y w ei g ht b a s i s

. The eq uation f or th e w et w ei g ht­to­ dry w ei g ht

c onvers i on i s i ncl uded i n Attach m ent 1 to thi s m e m orandu m

.

I n Adam s et al

. ( 2003)

, hoc k e y

­ s ti c k regre s s i on w a s u s ed to m odel rel ati ons hips b etw een e g g

s el enium c onc entrati ons and adver s e ef f ec ts i n or der to der i ve to xic i ty thre s hold s , s uch a s EC10 val u es

. Ho c k e y

­ s ti c k regre s s i on i s a m odel t hat ha s b een us ed to def i ne a t hres hold

w hen an u nderl y i ng b ac k g ro un d l evel of res p on s e i s un rel ated to the dos e. Thu s , s uch a

m odel m a y b e rel evant to na turall y oc c urri ng el e m ent s th at are es s ential to b i rds a nd a w i de

vari ety of ot her org anis m s and p arti c ularl y us ef ul f or elemen ts s uch as s el eniu m , w hic h has

a narrow ran g e b etw een l evel s that are e s s ential a nd l evel s that are to xic to b i rds so that

vari ance aroun d the i nfl ec ti on p oi nt ( thre s hold ) i n the m odel i s s m al l

. A s s hown i n
F i g ure 1 b el ow , a thre s hold c l earl y ap p ears to e xis t w hen di etary seleni u m i s p l otted vers us duckli ng m ortal i ty ( w hic h i nco rporated the c um ulati ve ef f ec ts of f erti l i zati on s ucc es s and

hatchab i l i ty )

. The i nfl ec ti on p oi nt oc c urs at a di eta ry seleni um c onc entrati on of 3. 9 m g / k g dry w t. ( p l eas e s ee di s c ussion at end of c om m ent s c onc erni ng u ncer tai nty around the

i nfl ec ti on p oi nt). The p red i c ted E C 10 i s 4

. 4 m g /k g dry w t. (

j us t s l i g htly ab ove the i nfl ec ti on

p oi nt) and the 95% c onfi denc e i nterval aro un d the p red i c ted EC 10 ran g e s f rom 3. 8 to

4. 8 m g /k g dr y w t. The p red i c ted E C 10 of 4. 4 m g / k g dry w t. i s s l i g htly l ow er th an Har ry Ohl endorf ’s E C 10 of 4. 9 m g / k g dry w t.

, b ut the 95 % c onfi denc e i nterval i s narrow er u s i ng hoc k ey s ti c k regre s s i on

.



## Sel **e niu**  **m in**  **B ird Egg**  **s**

As noted i n Tab l e 2 of the draf t m em ora ndu m

, the EC10 f or du c k l i n g m ortal i ty

, as reported

i n Ada m s et al

. ( 2003)

, ran g ed f ro m 12­ 16 m g / k g dry w t. The s e E C 10 val ues are b as ed o n a

s y nt hes i s of l ab orato ry s t udies i n w hic h the f i nal e ndp oi nt w a s d uckli ng m ortal i ty ( the s a m e ef f ec ts data us ed i n t he di etar y E C 10 ev al uation a b ove) and the ran g e of EC10 val ue s ref l ec ts
di f f erent s tati s ti c al ap p roac hes f or an al y zi ng the d ata. An adaptation f rom F i g ure 3 i n Adam s et al

. ( 2003) i s p rovi ded bel ow , w i th the 95 % c onfi denc e i nterval i ncl uded

. AsAT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­2 s hown

, th e i nfl ec ti on p oi nt oc c urs at a n e g g s el eni um c onc en trati on of 9

. 8 m g /k g w i th a

p red i c ted EC10 c omp arab l e to that der i ved b y Ha rr y Ohl endorf ( p l eas e s ee di s c u s s i on at
end of c om m ent s c onc erni n g un c ertai nty arou nd t he i nfl ec ti on p oi nt). Ho w ever, the

95% c onfi denc e i nterval u s i ng hoc k e y s ti c k re g res s i on i s m uch narrow er (9. 7 to 1 3. 6 m g / k g dry w t. ) than that der i ved b y Har ry u s i ng l og i s ti c regres s i on ( 6. 4­ 16. 5 m g /k g dr

y w t

. )

. Gi ven that there i s a c l ear e g g s el eniu m t hres hold at w hic h ef f ec ts b e g i n to b e ob s erved

, a

un i m odal m odel

, s uch a s l og i s ti c regre s s i on

, m ay resu l t i n exa g g erated c onfi denc e i nterval s , p arti c ularl y i n th e tai l s

.



## U **nc e**  **r tai**  **nty S**  **ur r**  **oundi ng**  **the H**  **o c**  **k e**  **y ­S**  **tic k**  **R e**  **gr e**  **s s**  **ion Infl**  **e c**  **ti on**  **Po ints** 

To deter m i ne the i nfl ec ti on p oi nt b etw een the hoc k ey

­ s ti c k “b l ade” and “ha ndle”, or a ny

p arameter i n t he m odel

, i niti al p arameter val ue s a re inp ut to the s of tw are p rogra m SPl u s ®

and an i terati ve tec h niqu e i s us ed to s earc h f or m o re ex ac t p arameter val ue s t hat w i l l

m i nimize th e s u m of s q uared devi ati on s b etw een the ob s erved ef f ec ts data and ef f ec ts
val ues p red i c ted b y the m odel

. Var i ance in the es t i m ate of t he i nfl ec ti on p oi nt val ue i s af f ec ted b y the s p ac i ng of the m ea s ured X val ue s a s w el l as the s c atter or tre nd i n Y val ue s
i n the vi c i nity of the e s ti m ated i nfl ec ti on p oi nt. I f

, f or ex am p l e, there are f ew m eas ured

di etary s el eni um c onc entrati ons near the p red i c te d i nfl ec ti on p oi nt, th e un c ertai nt

y i n the

l oc ati on of the i nfl ec ti on p oi nt w i l l b e g reater b ec aus e i t w i l l b e di f f i c ult to deter m i ne t he

exact c onc entrati on at w hic h t he i nfl ec ti on p oi nt o c c urs ( i

. e. , i t c ould b e b etw een tw o of t he

m eas ured val ue s )

. Un c ertai nt y aro un d the p red i c ted Y ( EC) val ue s at t he p red i c ted

i nfl ec ti on p oi nt i s af f ec ted b y t he n um b er of Y val ues an d the s c atter of the Y val ues at that

p arti c ular X v al ue ( w hic h, when c al c ulati ng th e c o nfi denc e i nterval around Y

, i s a s s um ed to
b e es ti m ated w i thou t err or)

. Th us, b oth the s p ac i n g of t he m ea s ured X val ues an d the

vari ance in the res p on s e vari ab l e af f ec ts the un c ert ai nty aro un d t he i nfl ec ti on p oi nt. The

ti g hter s p ac i ng and l es s a m b i g uou s ef f ec ts re s p on s e af ter the i nfl ec ti on p oi nt c au s e s th e 95% c onfi denc e i nterval around the di etary s el eni um

­ b as ed i nfl ec ti on p oi nt ( 3

. 0 to

4. 9 m g /k g dr y w t. ) to b e narrow er t ha n t hat f or th e eg g s el enium

­ b a s ed i nfl ec ti on p oi nt ( 6. 4 to 14. 9 m g / k g dry w t. )

.

Ho w ever, al thou g h there i s un c ertai nty s urroundi ng t he i nfl ec ti on p oi n t, u s e of t he b e s t

es ti m ate of the i nfl ec ti on p oi nt resu l t s i n the b es t f i t of the re g res s i on m odel to the data

. I n
F i g ure 2, f or ex a m p l e , i f th e i nfl ec ti on p oi nt oc c urred at t he ei ther end of the 95 % c onfi denc e
i nterval of eg g s el eniu m c onc entrati on ( 6. 4 to 14

. 9 m g / k g dry w t. ) o nce can eas i l y vi s u al i ze that the f i t of t he re g res s i on to the data p oi nt s ab o ve the i nfl ec ti on p oi nt w o uld n ot p a s s throug h the m eas ured val ue s i n the s am e w ay

.AT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­3 **F i**  **g u**  **re 1** 

**. Ho**  **c k**  **e y**  **s ti**  **c k**  **reg r**  **e s**  **s io**  **n o**  **f la**  **b o**  **ra to**  **ry m**  **a ll**  **a rd**  **d uc**  **k l**  **in g**  **m o**  **rta l**  **it y**  **v e**  **rs u**  **s d**  **ie t**  **a ry** 

**s e**  **l e**  **n iu**  **m**

**.**

**0 %**  **1 0**  **% 2**  **0 %**  **3 0**  **% 4**  **0 %**  **5 0**  **% 6**  **0 %**  **7 0**  **% 8**  **0 %**  **9 0**  **% 1**  **0 0**  **%**

**0**

**. 1**  **1 1**  **0 1**  **0 0** 

**D ie**  **ta ry**  **Se**

**, m**  **g /k**  **g d**  **r y**  **w t.** **D u** **c k** **l in** **g M** **o rta** **l it** **y ,** **%** Em p i ri c a l d a t a

Pr e d i c t e d m o rt a l i t y

9 5 % c o n f i d e n c e i n te rv a l

In f l e c t i o n p o i n t = 3

. 9 m g /k g
EC 1 0 (p re d i c t e d ) = 4

. 4 m g /k g
EC 1 0 (L CL ) = 3

. 8 m g /k g
EC 1 0 (UC L ) = 4 .8 m g / k g

**F i**  **gu re**  **2. H**  **oc key**  **sti ck r**  **e g**  **res si**  **on of**  **l ab**  **or a**  **t ory**  **m a**  **l l**  **ard du**  **ckl i**  **n g m**  **ort a**  **l i**  **t y**  **versus eg**  **g**

**seleni um** 

**.**

**0% 10%**  **20% 30%**  **40% 50%**  **60% 70%**  **80% 90%**  **100%**

**0. 1**  **1 10**  **100**

**E g**  **g Se, mg/**  **kg dry**  **w t** 

**. D** **uc kl** **i ng** **M ort** **al i** **t y,** **%** E m pi r i cal dat a

P r edi ct ed m ort al i t y

95% confide nce inter val

I nf l ect i on poi nt = 9. 8 m g/ k g
E C 10 ( pr ed i ct ed) = 11. 5 m g / k g
E C 10 ( LC L) = 9. 7 m g/ k g
E C 10 ( U C L ) = 13. 6 m g/ k gAT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­4 **AT T**  **ACH MEN**  **T 1** 

**WET WE**  **IGH T** 

**­ T**  **O D**  **RY WEIG**  **H T**  **CO N**  **VERSIO N**  **F O**  **R DIE T**  **ARY SEL**  **EN IU**  **M**

**CO N**  **CE N**  **T RAT**  **ION S**  **IN MALLARD**  **STU D**  **IES**

s o l i d s f io n C o n c e n t ra t W e ig h t W e t io n C o n c e n t ra t D ry W e ig h t
=

Where: f sol i ds = f rac ti on s ol i ds i n di et ( i

. e

. , 0

. 9 i n a di et c ont ai ning

10% m oi s ture)AT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­5 

# C **o m**  **m ents**  **o f**  **A n**  **n e Fairb**  **ro t**  **h er** 

I real i ze t hat I a m l ate ( the l as t? ) on p rovi di ng c om m ent s a nd f eedb ac k o n t he re p ort y ou

p ull ed tog et her f rom our l as t Sal t La k e C i ty m eeti ng o n t hres hold val ue s

. I w as s ort of hop i ng to s ee the data f ro m Bi l l Ada m s ’ re­ analy s i s of t he do s e­ res p on s e b ef ore repl y i ng

. . . Absen t that

, h ere are m y t hou g hts an d c om m ent s

.

I thin k y ou di d a n a p p ropri ate job p ull i ng to g ethe r w hat w a s di s c u s s ed at the m eeti ng i n regard to di et and eg g thres hold l evel s

. Ho w ever, the m ore I l ook at the d ata i n regard to

s el enium u p tak e and ef f ec ts

, the m ore c onvinc ed do I bec ome th at w e are deali ng w i th a thres hold p he nom eno n, li k el y b ec aus e of the es s e ntial natu re of the el em e nt. I do b el i eve that the m ean val ue f or the EC10 that w as s el ec ted f or bo th e ndp oi nt s i s l i k el y to re m ai n

p retty m uch the s am e regardl e s s of w hat dose­re s p ons e m od el i s used

, b ut t he s tandard

err or abo ut the m ean m a y b e di f f erent. Li k el y i t w i l l b e s m al l er when u s i ng a thres hold

m odel s i nce a l og i s ti c m odel te nds to s p read ou t t he C I ’ s a t i ts tai l s

. So

, f or now, I am w i l l i ng

to ap p rove t he doc u m ent as a report of w hat w a s di s c us s ed at the m eeti n g , b ut not as a f i nal

s ay on w hat w e have ag reed to f or th e EC10 and i t s c onfi denc e i nterval s

.AT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­6 

# C **o m**  **m ents**  **o f**  **T h**  **ere sa**  **Pres se**  **r**

Sug g e s ted addi ti ons to thre s hold di s c ussion w ri te

­ up of 1 2/8/06 :

1) Pag e 1: No te t hat c om p i l ati on of data f or co n s i der ati on w as adapted f rom Pres s er and

Luom a ( 2006)

, t ab l e 15.

2) Pag e 1: No te t hat i n addi ti on to l ab orato ry data

, a c omp i l ati on of f i el d data f or eg g

c onc entrati ons w a s retai ned

. 3) Pag e 1: No te t hat a ny f i nal deter m i na ti on m u s t ta k e i nto ac c oun t s i te­ s p ec i f i c data

c urrently b ei ng g e nerated b y the Gre at Sal t La k e r es earc h ef f ort.

4) Pag e 2 w ord i ng : “T he p anel ag reed b y c on s en s u s t hat the 95 % C I s o n mean s el eni um

c onc entrati ons i n m al l ard die t and eg g s w ould b e reason ab l y p rote c ti ve f or bi rds nes ti n g

at the Gre at Sal t Lak e , a nd t he ra ng e of val ue s i ncl uded the c onc entrati on s p ropos ed b y
vari ous p anel m em b er s f or co n s i der ati on. Rationa l s u p p orti n g s el ec ti on of the 95 % C I s i s

p rovi ded by t he p revi ou s tec hn i c al m em ora ndu m and thro ug h di s c u s s i on at the p an el

m eeti ng

. ”

a) D i d y o u mean here the 95% C I s on the m ea n E C 10 f or h atc habi l i ty ?

b ) The p hras e “w ould b e rea s onab l y p rote c ti ve f or b i rds ne s ti n g at the Gre at Sal t Lak e”

does no t ade qu atel y c onvey al l p arts of the exte ns i

ve di s c u s s i on that took p l ac e. I di d

not p erc ei ve t hat a co n s en s u s had b een reac hed a s to p rote c ti venes s , only that a

c ons en s us h ad b een reac hed a s to the i nterp reta ti on of data f rom m al l ard lab

exp eri m ent s

. Theref ore , I s u g g e s t i nco rporati n g i n to the w ord i ng of a s u m m ar

y

s tatem e nt t he f ol l ow i ng qu al i f i c ati ons and p oi nt s t hat w ere di s c ussed a t the m eeti ng :

1) Ap p l i c ab i l i ty of l ab data to f i el d s i tuation s ( note re tention of c om p i l ati on of f i el d

data i n tab l e 2 and c urrent data g at heri ng ef f ort at the Gre at Sal t La k e; p oi nt s
2 and 3 l i s ted ab ove)

2) Ap p l i c ab i l i ty of m al l ard data to s p ec i es at Gre at S al t Lak e ( s en s i ti vi ty i s s ue)

3) Ap p l i c ab i l i ty of hatchab i l i ty endp oi n t ( di et a nd av i an eg g ) and no n­reprod ucti ve adver s e ef f ec ts end p oi nts (e. g

. , avi an b l ood end p o i nt)

4) Level of p rote c ti on a nd p rec autionary reg ulati on a s e xem p l i f i ed b y b enchm ar k

c onc entrati on regu l ati on

. S p ec i f i c al l y add ex c erpt f rom p a g e 8 of 11 /28/06

m em o as c l ari f i c ati on of 95% C I : “ C onc ep t uall y , a b enchm ark c onc entrati on i s def i ned as the l oc ati on on t he e xp o s ure­r es p on s e c urve that i s the thre s hold

b etw een ab s ence and p rese nce of a g i ve n ef f ec t or endp oi nt, i. e

. , the thre s hold

b etw een an E C 00 and an EC01 c onc entrati on ( s ee:

w w w

. ep a. g ov/ec otox/eco s s l /p df /ec o s s l _attac h m ent_3­2

. p df

; p

. A­6)

... . . Benc hm ark c onc entrati on s are es ti m ated a s the l ow er 95% c onfi denc e b oun dary

on the EC1 0 ( s ee : M ei s ter, R

. , and P. J

. Va n Den Bri nk

. 2000

. T he a nalys i s of

l ab orato ry toxic i ty ex p eri m ent s

. Pa g es 99­ 118 i n T

. Spark s ( ed. )

, Stati s ti c s i n
Ec otoxi c ol og y

. J ohn Wi l ey & Sons

, LT D

, New Y or k

, NY: [ p p 114­ 116 i n

p arti c ular] ; and s ee : USEPA

. 2000. Benc h m ark D o s e Tec hn i c al Guid anceAT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­7 D oc um en t. [ External Review D raf t]

. EP A/ 630/ R­ 00/001. U

. S. Envir on m ental

Protec ti on Ag e ncy, Wa s hin g ton

, D C )

. ”

5) Addi ti on of p halar ope to l i s t of s p ec i es to b e m oni tore d to re p resen t s p ec i es w i th

a f eedi ng rate t hat i s a l arge perc entag e of b ody w ei g ht ( ener g y c ons i der ati on i n deter m i ning w i l dl i f e c ri ter i on).

6) Potent i al l ow eri ng of t hres hold s t hrou g h c on s i der ati on of hor m es i s data ( f or horm eti c s ubs tance s a nd e ndp oi nt s on e ha s to di s t i ng uis h b etw een val i d c ontrol

res p on s es and hor m eti c def i c i ency res p ons es b ef ore a val i d b a s el i ne to c o m p are
toxic resp o ns e s a g ai n s t c an b e i dentif i ed)

. 5) Refere nces: A dd Pre s s er and Luo m a, 2006

. 6) Tab l e 1: ”Bi l l Adam s s u g g e s ti on” need s to b e doc u m ented as how his entry di f f ers f rom entry #1 i n tab l e 1.AT T ACHMENT B: CO MM ENT S O N DECEM BER 8, 20 06

, DR AF T T ECHN I CAL M EM O RAND U M

ES022 00 70 0 4SAC/341 05 5/07 03 8 00 0 1 (DO CU ME NT 1) B­8 

# C **o m**  **m ents**  **o f**  **J o**  **e S koru**  **p a** 

I n Tab l e 1 I don ’t b el i eve the s c i ence p anel w anted the val ue of 4. 87 to b e p re s ented i n b ol d
ty p e , onl y t he c onfi denc e l i m i ts ( f or co m p ari s on s ee Tab l e 2 w here I thin

k y ou have i t t he

w ay the s c i ence p anel i nten ded)

. Adj u s ti ng f or 10 % m oi s ture w ould re s ult i n an 11 % i ncr eas e i n the di etar

y val u es , not an

up w ard ad ju s tm ent of 10 % as s ta ted.

I di dn’ t f eel l i k e y our draf t w ri te­ up adequ atel y c o nvey ed our ( s c i

. p anel’ s ) di s c u s s i on

c onc erni ng the f ac t tha t, ulti m atel y , a c hoic e of n u m b ers f rom w i thin t he c on s en s u s

c onfi denc e l i m i ts i s not a s c i entif i c dec i s i on. That c onfi denc e rang e i s as f ar a s s c i ence can b ri ng u s

. . . c hoos i n g a s p ec i f i c nu m b er or nu m b ers f rom w i thin tho s e c onfi denc e rang e s are

p hil os oph i c al /legal dec i s i on s t hat de p end on how p rec autionar

y t he State of U tah w a nts to
b e ( a m atter of p hil os op hy ) a nd o n how m uch p ot ential f or legal l i ab i l i ty the State i s

c omfor tab l e w i th exp o s i ng i ts el f to

. The k e y dec i s i on the State m u s t m a k e i s w het her t hey

w ant to re g ulate to a “NE C ” ( no ef f ec ts c onc entrat i on.

. . w hic h i s not t he s am e a s a NO EC)

s tandard or to s o m e ver s i on of a “tol erab l y toxic ” s tandard s uch a s a n E C

­ 10, or E C

­ 20, or
EC­05 etc

.

F i nall y , I thin k on the s c i entif i c s i de of thing s w e w ould b e remis s i n our dut

y a s exp ert s

not to i ncl ude s o m e di s c ussion i ndic ati ng that the i s s ue of hor m eti c b i as i n the data u s ed f or the Ohl endorf ( 200 3) regre s s i on s ha s not y et b een f ull y c ons i der ed b y the s c i ence p anel ( at

Bi l l Adam s reque s t to def er it s o that he c ould p re vi ew Bec k on’ s SET A C p rese ntation b ef ore
I p resen ted a ny of i t to the p a nel.

. . al thou g h i t s ee m ed to b e ac c ep tab l e to everyon e to s ee
K enn ec ott’s U

. of Wy o m i ng p re s entation w i thou t any o p p ort un i ty f or an

y one other than

Bi l l A. to p revi ew i t.

. . s eem s l i k e a do ubl e s ta ndar d to m e)

, and that i f s uch c on s i der ati on

w ere to res ult i n c han g es , t hos e c han g es c ould onl y b e i n the di rec ti on of a dow nwar d

s hif ti ng of the thre s hold c onfi denc e l i m i ts

.

F or ex a m p l e , re m em b er t hat the analy s i s that Brad Sam p l e re­ ran to adj us t f or h or m eti c ef f ec ts i n the m al l ard data y i el ded a revi s ed E C

­ 10 f or die t of 3

. 7 p p m w w [ 4. 1 p p m dw ]

w i th a 95 % c onfi denc e i nterval of 1

. 15

­ 5. 18 p p m w w [ 1. 3

­ 5

. 8 p p m dw ] and a revi s ed

EC­10 f or e g g s of 9. 22 p p m dw w i th a 95 % c onfi denc e i nterval of 4

. 11

­ 13

. 07 p p m dw

.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. C-1 

### A PPENDIX 

### C

A LLOMETRIC 

### A DJUSTMENT OF 

### D IETARY 

### C ONCENTRATIONS


### The Appendix explains the approach used to allo metrically adjust dietary toxicity threshold for birds. In ecological risk assessments fo r bids, dose-based toxicity reference values (TRVs) are used to estimate toxic effects. Toxi city reference values ar e calculated using the following equation:

BW AFFCIREPC TRV

t 

### × × ×

=



### where:

TRV t 

### = Toxicity reference value for the test species.

EPC = Exposure point concentration; i.e., the dietary concentration of a chemical that produced the toxic e ffects measured in the toxicity study (mg/kg-dw).

IR = Food ingestion rate (mg/day-dw).

FC = Fraction contacted ( unitless; assumed to be 1).

AF = Assimilation fraction (unitless; assumed to be 1).

BW = Body weight (kg).

Toxicity reference values are allometrically adjusted using the follo wing equation (Sample and Arenal 1999):

)b1(

a t a 

### BW BW TRV TRV − 

### ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

×= t



### where:

TRV

a 

### = Allometrically adjusted toxicity reference value.

TRV t 

### = Toxicity reference value for the test species.

BW t 

### = Body weight of the test species.

BW

a 

### = Body weight of species for whic h the allometric adjustment is being performed.

b = Allometric scaling factor (unitless).April 2008 North San Francisco Bay Selenium Toxicological Assessment

C-2 Tetra Tech, Inc. 

### The )b1(

a 

### BW BW − 

### ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

t 

### term in the equation above is also re ferred to as an “allo metric adjustment

factor”. Combining the above two equations, an d eliminating the variables assumed to equal 1, produces the following equation:

)b1(

a t a 

### BW BW

BW IREPC

BW IREPC − 

### ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

× ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ×

= × t

t t

a a



### By re-arranging the equation above, it is possible to derive an allometrically adjusted dietary concentration protective of specific toxic eff ect. The re-arranged equation is as follows:

)b1(

a t

a a

a 

### BW BW

BW IREPC

IR BW EPC − 

### ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛

× ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ ×
× ⎥ ⎦ ⎤ ⎢ ⎣ ⎡

= t

t t



### Allometrically adjusted dietary thresholds we re calculated for the av ian species of concern in the Bay identified by USFWS (2007):

• Bald eagle

• California clapper rail

• Greater scaup

• Lesser scaup

• White-winged scoter

• Surf scoter

• Black scoter

The test species from which the TRVs were allometrically adjusted include:

• Leghorn chicken

• Mallard

• Screech owl

The body weights for all of these birds are provid ed in Table C-1 below. Ingestion rates for each bird species were calculated from th eir body weights using the equations provided by Nagy (2001). The ingestion rate equations and cal culated ingestion rate s are also shown in

Table C-1 below.North San Francisco Bay Selenium Toxicological Assessment April 2008

Tetra Tech, Inc. C-3 Table C-1 Body weights and ingestion rates.

Bird species Body Weight (g) Ingestion Rate Equation f Ingestion Rate (mg/day-dw) Bald eagle a 5,275 Carnivorous birds y = 0.849*(x)^0.663 249,311 California clapper rail a 346 Marine birds y = 0.880*(x)^0.658 41,228 Greater scaup a 959 Marine birds y = 0.880*(x)^0.658 80,634 Lesser scaup a 663 Marine birds y = 0.880*(x)^0.658 63,247 White-winged scoter a 1,917 Marine birds y = 0.880*(x)^0.658 127,189

Surf scoter b 1,047 Marine birds y = 0.880*(x)^0.658 85,429

Black scoter a 987 Marine birds y = 0.880*(x)^0.658 82,198

Mallard c 1,214 Marine birds y = 0.880*(x)^0.658 94,167

Chicken d 1,800 Galliformes y = 0.088*(x)^0.891 69,973

Screech Owl e 186 Carnivorous birds y = 0.849*(x)^0.663 27,139

Notes: a - female body weight from USFWS (2007) b - female body weight from BNA (2007) c - body weight is from Heinz et al. (1989) and is average of females at time of sacrific e in all treatments except 16 mg/kg d - egg laying leghorn chickens average 1, 800 g (National Research Council 1994) e - body weight is from Wiemeyer and Hoffman (1996) and is average of females at time of sacrifice in all treatments f - from Nagy (2001)



### The body weights and ingestion ra tes from Table C-1were used to calculate allometric adjustment factors and allometrically adjusted dietary threshold concentrations for the species of concern in the Bay (Table C-2).

Table C-2 Allometric adjust factor s and allometrically adjusted dietary thresholds.

Allometric Adjustment Factor (-) for Dietary Screening Values from Dietary Screening Value (mg/kg-dw) Adjusted from Bird species Mallard Chicken Screech Owl Mallard a Chicken b Screech Owl c
Bald eagle 1.34 1. 24 1.95 9.7 4.0 104.3 California clapper rail 0.78 0.72 - 2.2 0.9 - Greater scaup 0.95 0.88 - 3.9 1.6 - Lesser scaup 0.89 0.82 - 3.2 1.3 - White-winged scoter 1.10 1.01 - 5.6 2.3 - Surf scoter 0.97 0.90 - 4.1 1.7 - Black scoter 0.96 0.89 - 3.9 1.6 -

Notes: a - EC10 for reduced hatching success from Adams et al. (2003) Ohlendorf (2007) of 4.4 mg/kg-dw b - effect threshold for reduced hatching succe ss of 3.9 mg/kg-dw from Ort and Latshaw (1978) c - effect threshold for reduced hatching success of 17.3 mg/kg-dw from Wiemeyer and Hoffman (1996)

References 

### Adams WJ, Brix KV, Edwards M, Tear LM, Defo rest DK, Fairbrother A. 2003. Analysis of field and laboratory data to de rive selenium toxicity thres holds for birds. Environmental Toxicology and Chemistry 22:2020–2029.

Birds of North America Online. 2007. Corne ll Laboratory of Ornithology, Ithaca, NY. Available online at: http://bna.birds.cornell.edu/BNA/.

Heinz GH, Hoffman DJ, Gold LG. 1989. Impaired reproduction of mallards fed an organic

form of selenium. Journal of Wildlife Management 53:418–428.April 2008 North San Francisco Bay Selenium Toxicological Assessment

C-4 Tetra Tech, Inc. 

### Nagy KA. 2001. Food requirements of wild animals: Predictive equa tions for free-living mammals, reptiles, and birds. Nutrition Abstract s and Reviews, Series B: Livestock Feeds and Feeding 71:2R-12R.

National Research Council. 1994. Nutrient Requir ements of Poultry. Ninth Edition. National Academy Press, Washington, D.C.

Ohlendorf HM. 2007. Threshold Values for Seleni um in Great Salt Lake: Selections by the Science Panel. Submitted to Great Salt Lake Science Panel. February 28, 2007.

Ort JF and Latshaw JD. 1978. The toxic level of sodium selenite in the diet of laying

chickens. Journal of Nutrition 108:1114-1120.

Sample BE and Arenal CA. 1999. Allometric models for interspecies extrapolation of wildlife toxicity data . Bulletin of Environm ental Contamination and Toxicology 62:653-663.

USFWS (U.S. Fish and Wildlife Service). 2007. Sp ecies at Risk from Selenium Exposure in the San Francisco Estuary.

Wiemeyer SN and Hoffman DJ. 1996. Reproducti on in eastern screech-owls fed selenium. Journal of Wildlife Management 60:332-341.