SDMS DocID 2102891

Golder Associates Inc. . ^ i i S ^ ^ ^

200 Century Parkway, Suite C M ^ m 3 ^ C T O I H I ^ I * Mt. Laurel, NJ 08054 V K ^ M ' k . ^ ^ ^ * M ^ - ^ Tel: (856)793-2005 ^ ^ ^ A S S O C i a t e S Fax: (856)793-2006 www.golder.com

May 6, 2009 Project No.: 963-6333

Mr. Frank Klanchar Remedial Project Manager U.S. Environmental Protection Agency Western PA Remedial Section (3HS22) 1650 Arch Street Philadelphia, PA 19103-2029

RE: OPERABLE UNIT 2 FEASIBILITY STUDY CENTRE COUNTY KEPONE SITE, STATE COLLEGE, PA

Dear Frank:

Following our recent telephone conversation, and on behalf of RUTGERS Orgajiics Corporation (ROC), this letter supplements the Operable Unit 2 Feasibility Study (OU-2 FS) for the Centre County Kepone site (Site).

USEPA's letter to ROC dated December 22, 2008 approved the OU-2 FS subject to ROC's response to USEPA comments contained in e-mail correspondence dated March 25 and August 26, 2008. USEPA's comments and ROC's approved responses entailed the adjustment of certain parameters in the derivation of soil concentration thresholds presented in Appendix D of the OU-2 FS, as well as specifying the methodology for calculating a surface soil preliminary remediation goal (PRG) for kepone. As requested, we are enclosing a revised version of Appendix D, which reflects the required changes, for inclusion in the Administrative Record. In addition, consistent with USEPA's comments, the surface soil PRG for kepone has been re-calculated based on the geometric mean of the LOAEL and NOAEL based concentration tlvesholds for the two lower trophic level receptors (shrew and robin). The resulting surface soil PRG for kepone is 190 ug/kg (geometric mean of 130, 26, 890 and 440 ug/kg from the enclosed Appendix D) and this value should be included in the upcoming Record of Decision.

If you have any questions regarding this matter, please do not hesitate to call.

Very truly yours,

GOLDER ASSOCIATES INC.

P. Stephen Finn, C.Eng. Principal

PSF/bjb g:\projects\1992 - 1999 projects\963-6333 roc centre count>'\prg revision draft.docx

cc: Rainer Domalski, ROC

OFFICES ACROSS ASIA, AUSTRALIA, EUROPE, NORTH AMERICA, SOUTH AMERICA

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APPENDIX D

DERIVATION OF SOIL CONCENTRATION THRESHOLDS

L Introduction

The following analysis derives ecologically based threshold levels of mirex, photomirex and kepone (MPK) in soil for Operable Unit 2 of the Centre County Kepone Site.

Literature derived parameters are used in food chain models to determine soil levels that correspond to lowest observed adverse effect level (LOAEL) and no observed adverse effect level (NOAEL) Hazard Quotients (HQs) of unity for the American Robin, the Short-tailed Shrew, and the Red Fox.

jjj-. _ Dietary Intake Chronic Toxicologi cal Ingestion Benchmark

Dietary Intake and Ingestion Benchmarks are expressed in terms of the mass of chemical consumed (from all sources) per unit of body weight per day (|ig/kg-BW/day). In the case of both the Robin and the Shrew, dietary intake comprises terrestrial plants, terrestrial invertebrates (principally earthworms) and incidental direct soil ingestion. The fox consumes small mammals in addition to plants, invertebrates, and incidental soil. In the following sections, MPK concentrations are derived for terrestrial plant tissue, earthworm tissue, and small mammal tissue as a function of soil concentration. These concentrations are then used to derive expressions for the total dietary intake, also as a function of soil concentration. Finally, the dietary intakes are combined with ingestion benchmarks to determine the soil concentrations corresponding to a HQ of unity.

Ingestion benchmarks are not available for photomirex and so the combined concentrations of mirex and photomirex are used in the calculations.

2. Terrestrial Plant Tissue Concentrations

Terrestrial Plant Tissue Concentration on a wet weight basis (PTC) is given by the following expression:

PTC= S X BCFsp X (dw/ww)

Where: S = Soil concentration (|Ag/kg)

BCFsp = Bioconcentration factor from soil to plants = 0.04 for Kepone (Scheunert, 1981) = 0.34 for Mirex and Photomirex (de la Cruz & Rajama, 1975)

(dw/ww) = Dry weight/Wet Weight ratio for terrestrial plant tissue = 0.15 (Cruz & Rajama, 1975)

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Thus: PTCk = .0006 Sk (for Kepone)

PTCmp = 0.051 (S„,+ Sp)(for Mirex and Photomirex)

3. Earthworm Tissue Concentrations

Earthworm Tissue Concentration on a wet weight basis (ETC) is given by the following expression (from USEPA, 2005):

Where: Cw = Concentration in soil pore water (ng/L)

Kww ~ Bioconcentration factor from soil pore water to earthworms

Kww is calculated using the following empirical equation (Jager, 1998) based on data for 69 lipophilic chemicals (with log KQW values ranging from 2 to 8) as recommended in USEPA, 2005:

log(/:„,J = 0.87 x log(^„J-2 .0

where: Kow = octanol-water partition coefficient (see below)

The concentration in soil pore water, Cw, is calculated based on the concentration in soil and the soil to water partitioning coefficient as shown below;

C = ^

where: Kd = soil to water partitioning coefficient (L soil pore water/ kg dw

soil) S = concentration in soil (|ig/kg)

The soil to water partitioning coefficient is estimated by the following equation:

where:

Koc = organic carbon partifion coefficient (see below)

foe = fraction of organic carbon in soil 6.176 X 10'' (mean based on OU-2 investigation results)

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The following values for the partition coefficients are available from the literature:

Kepone:

Thus:

Mirex:

Photomirex:

K„ K„ K„

And:

C c c

ETCk

ETC„

ETC„

logKo logKo logKo logKo logKo logKo

= 408.3 = 9869.6 = 237.7

= 0.0269 Sk = 6.75x10"^ S„ = 0.00186 Sn

= l lSk

= 0.067 S„

= 0.44 S„

5.30 (USEPA, 1995a) 3.78 (Ziegenflissetal., 1986) 6.89 (USEPA, 1995a) 7.38 (Bombergeretal, 1983) 5.03 (USEPA, 1995a) 4.94 (Calculated using USEPA, 1996)

(for Kepone) (for Mirex) (for Photomirex)

(for Kepone) (for Mirex) (for Photomirex)

(for Kepone)

(for Mirex)

(for Photomirex)

4. Small IMammal Tissue Concentration

Small Mammal Tissue Concentration on a wet weight basis (MTC) is determined by the following expression:

MTC= BAF„>i HFR.v^v)(Ci)(PDi)_+(FR,J(S)(PDJ

F R ^ + ( F R d J ( P D J

where: MTC BAF„

r i^ww

FRdw Ci S PD, PD,

Small Mammal Tissue Concentration (|ig/kg) Whole body bioaccumulation factor from food to small mammal tissue wet-weight food ingestion rate (g food/day ww) dry-weight food ingestion rate (g food/day dw) concentration of chemical in food item i (|ig/kg) concentration of chemical in soil (|.ig/kg) proportion of food item i in diet proportion of incidental soil ingestion in diet

Measured diet to whole-body tissue BAF values were not available from the literature for the chemicals of concern and were therefore estimated based on BAF values for specific tissues (e.g., fat and muscle).

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There are three long-term studies in the literature that can be used to estimate a diet-to-fat BAF for mirex for small mammals; all data are for the rat. Chu et al (1981a) reports values for diet exposures to two doses of mirex over 21 months. The mean diet-to-fat BAF is 38.2. In a second study, Chu et al (1981b) reports values for three exposures conducted for about four and one-half months. The mean diet-to-fat BAF is 49.0. The third study (Ivie et al 1974) reports values for three dietary exposures over 16 months. The mean diet-to-fat BAF is 122.7. The average of the mean diet-to-fat BAF values from the three studies is 70.0. Using this average value of 70.0 and a measured total body fat content of 10.2 percent for the rat (Geyer et al. 1993), the estimated diet to whole-body BAF for mirex is 7.14.

A diet-to-fat BAF for photomirex can be estimated using the two studies reported by Chu et al (1981a and 1981b). In the first study, four doses were fed to rats for 21 months; the mean diet-to-fat BAF was 42.1. In the second study, five doses were fed to rats for about four and one-half months; the mean diet-to-fat BAF was 47.5. The average of the mean diet-to-fat BAF values from both studies is 44.8. Multiplying this value by a total body fat content of 10.2 percent for the rat (Geyer et al. 1993), the estimated diet to whole-body BAF for photomirex is 4.6.

For Kepone, diet-to-fat BAFs have been reported for the mouse (range of 0.7 to 2.1, mean of 1.4, n = 2; Bell et al. 1978) and the rat (range of 1.5 to 4.8, mean of 2,8, n = 5; Epstein 1978). Using the mean diet-to-fat BAFs and a measured total body fat content of 13 percent for the mouse and 10.2 percent for the rat (Geyer et al. 1993), the estimated diet to whole-body BAF for Kepone is 0.18 and 0.29 for the mouse and rat, respectively. Bell also reports Kepone diet to muscle tissue BAFs for the rat (range of 0.28 to 0.65, mean of 0.47, n = 2). Since this muscle tissue BAF of 0.47 is higher than either of the two BAFs based on fat, and since there is considerable muscle mass in the body, it was used as a conservative whole body BAF for Kepone.

Species-specific values for the dietary composition are summarized below based on the data provided in USEPA (1993) and other sources where noted:

Receptor Species

Short-tailed Shrew American Robin

Red Fox

FR

(g food/ day)

9.3 132.2 444'

FRdw

(g food/ day)

2.2 18.2

126 '

Dietary Composition (%)

Plants/ Fruits 13.1 37.5 17.4'

Earthworms/ Invertebrates

86.9 62.5 4.3=

Small Mammals

0 0

78.3'''

Soil

3.0' 15.12' 2.80'

Body Weight

(g)

15.0 83.2

4690"

1 90* percentile value from USEPA (2005), Attachment 4-1. ^ Based on 90"' percentile American Woodcock data from USEPA (2005), Attachment 4-1, factored by the relative consumption of earthworms by the two species •' Based on average (mean) for breeding and non-breeding adults in North Dakota. The ingestion rate is considered to be conservative since the mean places equal weighting on pregnant females, nursing females (which consume twice as much as non-nursing foxes), and the rest of the adult fox population. * Dry weight ingestion rate determined by using moisture contents specified in USEPA (2005) along with the dietary composition fractions from Illinois data and the wet weight ingestion rate. ^ Dietary fraction listed as "unspecified/other" was equally distributed to the other four components of the diet. ^ Small mammal ingestion for the fox includes the ingestion of birds since no bioaccumulation factors for bird tissue were available for food chain modeling.

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The small mammal tissue concentrations are therefore:

MTCk =4.45Sk (for Kepone)

MTCn, =0.48S„ (for Mirex)

MTCp =1.80Sp (for Photomirex)

5. Dietary Intake

Dietary intake (Dl) is calculated from the following equation (after Ma et al, 1991 and USEPA, 1993):

DI L|FRww)(C,)(P^)_+(FR,J(S)(PD3)

BfV (FI)

Where: DI FR FRdw Ci s PD, PD, BW Fl

dietary intake of chemical (|ig/kg-BW/day) wet-weight food ingestion rate (g food/day ww) dry-weight food ingestion rate (g food/day dw) concentration of chemical in food item i (ug/kg) concentration of chemical in soil (| g/kg) proportion of food item i in diet proportion of incidental soil ingestion in diet body weight (g) fraction ingested from contaminated source (0.5 for migratory robin, 1.0 for all other receptors)

Using the dietary composition data presented in the preceding section. Dietary Intakes for each chemical and receptor are as follows:

Shrew

Robin

Dlk Dl mp

Dlk Dl, mp

5.9 Sk 0.042 S,n+0.24 So

5.48 Sk 0.065 S„+0.25 So

(for Kepone) (for Mirex and Photomirex)

(for Kepone) (for Mirex and Photomirex)

Red Fox Dlk DI mp

0.38 Sk (for Kepone) 0.037 S„, + 0.14 Sp (for Mirex and Photomirex)

''From Beyer 1994. * Mean body weight for adult males and females in spring in Illinois.

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6. Chronic Toxicological Ingestion Benchmarks

Shrew

Based upon a review of available subchronic and chronic toxicity data for mammals, the following reproducfive toxicity studies were selected as the basis for the ingestion benchmarks:

Kepone: Good etal (1965) LOAEL = 640 pg/kg-BW/day for mouse The NOAEL value is assumed to be equal to 20% of the LOAEL value.

Adjusting for body weight as recommended by Sample et al (1996):

T>i25

LOAEL,,, ,., = LOAEL ^ K mouse ,

^ ^ shrew ^->

where: BW^ e = 0.032 kg BWshrew = 0 . 0 1 5 kg

Thus: Ingestion Benchmark LOAEL = 775 ftg/kg-BW/day (for Kepone) Ingestion Benchmark NOAEL = 155 fig/kg-BW/day (for Kepone)

Mirex and Photomirex: Chu et al (1981b) LOAEL = 500 pg/kg-BW/day for rat

Adjusting for body weight (BW t = 0.2 kg):

Thus: Ingestion Benchmark LOAEL = 955 fxg/kg-BW/day (for Mirex and Photomirex) Ingestion Benchmark NOAEL = 191 jug/kg-BW/day (for Mirex and Photomirex)

Robin

Based upon a review of available subchronic and chronic toxicity data for birds, the following reproductive toxicity studies were selected as the basis for the ingestion benchmarks:

Kepone: The most conservative lowest observed adverse effect concentration (LOAEC) found in the literature was from studies published by DeWitt et al (1962, 1963). However, the DeWitt studies have a number of deficiencies that make them unreliable for quantitative ecological risk assessment:

• The studies did not present testing protocol, study conditions, study data, or sample sizes. • The studies did not employ controls or conduct or present statistical analyses of the study

data. • There were internal inconsistencies in the reporting of the study results between text and

tables.

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• The data suggest that reduced reproduction occurs at levels that are below those shown to be associated only with subtle changes in germ cell and gonad characteristics in other higher quality studies.

There are, however, two well-designed and implemented studies on the effects of Kepone that can be used. The first study, by Eroschenko and Hackmann (1981) was performed on the Japanese quail. LOAEC and NOAEC values were reported in this study to be 160 mg/kg and 80 mg/kg respectively. To convert these concentrations in diet to LOAEL and NOAEL values, they must be multiplied by the dry-weight food ingestion rate and divided by the body weight. The food ingestion rate (wet weight) was found in USEPA (2003) to be 77.75 grams per gram body weight (the mean of adult males and females year-round in Texas) for the northern bobwhite quail which was used as a surrogate for the Japanese quail since exposure parameters for the Japanese quail were not available. Using a mean body weight of 157.25 grams' the daily food ingestion rate was calculated to be 12.2 g/day (wet weight) for the northern bobwhite. To convert this wet weight ingestion rate to a dry weight ingestion rate, the dietary composition of northern bobwhite quails in Texas was used from USEPA (2003). The dietary composition in the Texas study was reported in dry-weight, so they were first converted to appropriate wet-weight fractions using the following equation:

P D ' " ' =

where: PDj"™ = Proportion in diet of food item i (wet weight basis) PDj"™ = Proportion in diet of food item i (dry weight basis) DFj = Dry fraction of food item i

The dry fraction of each food item was determined from USEPA (2005) and after determining the wet weight proportions, the overall dry weight ingestion rate was calculated as follows:

FR,,^=Y^j,FR^^.„xPDrxDF,)

The dry weight food ingestion rate was therefore determined to be 0.0048 kg/day for the northern bobwhite quail. The NOAEC and LOAEC were multiplied by this ingestion rate and divided by the body weight of 157.25 grams to yield LOAEL and NOAEL values of 4,860 pg/kg-BW/day and 2,430 |ig/kg-BW/day respectively.

The second study, by Naber and Ware (1965) was performed on white leghorn hens. Only a LOAEC value of 75 mg/kg (dry weight) was reported in this study. By using a chicken feed ingestion rate (dry weight) of 0.2 kg/day (USEPA, 1995b) and a body weight of 1.44 kg (Thirunavukkarasu P. et al., 2006), the LOAEC was converted to a LOAEL of 10,417 pg/kg-BW/day.

' Based on Texas data.

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Accordingly, Eroschenko and Hackmann (1981) provides the more conservative (lower) LOAEL and NOAEL values and is also the highest quality study available:

LOAEL Ingestion Benchmark = 4,860 jug/kg-BW/day (for Kepone) NOAEL Ingestion Benchmark = 2,430 jug/kg-BW/day (for Kepone)

Mirex and Photomirex: Kendall et al (1978) NOAEL = 40 mg/kg in the diet Anticipated LOAEL = 40/0.2 = 200 mg/kg (Calabrese & Baldwin, 1993)

Based on a body weight of 0.154 kg and a food consumpdon rate of 0.0143 kg/day for bobwhite quail:

Ingestion Benchmark LOAEL = 18,600 g/kg-BW/day (for Mirex and Photomirex) Ingestion Benchmark NOAEL = i, 720 fxg/kg-BW/day (for Mirex and Photomirex)

Red Fox

Based upon a review of available subchronic and chronic toxicity data for mammals, the following reproductive toxicity studies were selected as the basis for the ingestion benchmarks:

Kepone: Good et al (1965) LOAEL = 640 pg/kg-BW/day for mouse The NOAEL value is assumed to be equal to 20% of the LOAEL value.

Adjusting for body weight (BW^^se = 0.032 kg and BW dfox = 4.69 kg):

Thus: Ingestion Benchmark LOAEL = 184 /Jg/kg-BW/day (for Kepone) Ingestion Benchmark NOAEL = 36.8 fig/kg-BW/day (for Kepone)

Mirex and Photomirex: Chu et al (1981b) LOAEL = 500 pg/kg-BW/day for rat The NOAEL value is assumed to be equal to 20% of the LOAEL value.

Adjusting for body weight (BWrat = 0.2 kg):

Thus: Ingestion Benchmark LOAEL = 227 fig/kg-BW/day (for Mirex and Photomirex) Ingestion Benchmark NOAEL = 45.4 fig/kg-BW/day (for Mirex and Photomirex)

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7. Soil Concentration Thresholds

Combining the dietary intake and ingestion benchmarks derived above with a HQ of unity, yields the following soil concentration thresholds'":

Receptor

Shrew

Robin

Red Fox

Chemical

Kepone Mirex + 5.8 Photomirex

Kepone Mirex + 3.85 Photomirex

Kepone Mirex + 3.7 Photomirex

LOAEL-Based Soil Screening Concentration

130 22,000

890 290,000

490 6,100

NOAEL-Based Soil Screening Concentrafion

t R kg 26

4,500 440

57,000 100

1,200

8. References

Baes et al (1984). A review and analysis of parameters for assessing transport of environmentally released radionuclides through agriculture. Oak Ridge National Laboratory Report ORNL-5786. 148 pp.

Bell et al (1978). Reviews of the environmental effects of pollutants: I. Mirex and kepone. EPA/600/1-78/013.

Beyer, W. Nelson eL al. (1993). Estimates of Soil Ingestion by Wildlife. Journal of Wildlife Management, 58(2):375-382.

Bomberger, D.C., J.L. Gwinn, W.R. Mabey, D. Tuse, and T.W. Chou (1983). Environmental fate and transport at the terrestrial-atmosphere interface. Pages 197-214 In Fate of chemicals in the environment. Compartmental and multimedia models for predictions. ACS Symposium Series 225. American Chemical Society, Washington DC.

Calabrese & Baldwin (1993). Performing ecological risk assessments. Lewis Publishers, Chelsea, Michigan. 257 pp.

Chu, I., D.C. Villeneuve, V.E. Valli, V.E. Secours, and G.C. Becking. (1981a). Chronic toxicity of photomirex in the rat. Toxicology and Applied Pharmacology. 59:268-278.

Chu et al (1981b). Effects of photomirex and mirex on reproduction in the rat. Toxicology and Applied Pharmacology. 60:549-556.

Connell, D.W. and R.D. Markwell (1990). Bioaccumulation in the soil to earthworm system. Chemosphere. 20:91-100.

de la Cruz & Rajama (1975). Mirex incorporation in the environment: uptake and distribution in crop seedlings. Bull Environ. Contam. Toxicol. 14:38-42. (as cited in Bell et al. 1978).

DeWitt et al (1962). Effects of pesticides on fish and wildlife: a review of investigations during 1960. Circular 143. U.S. Department of the Interior, Bureau of Fish and Wildlife, Washington DC. (as cited in Bell et al. 1978).

Epstein, S.S. (1978). Kepone - hazard evaluation. Science of the Total Environment. 9:1-62. Eroschenko VP, Hackmann NL (1981) Continuous ingestion of different chlordecone (kepone)

concentrations and changes in quail reproduction. Toxicol Environ Hlth 8:659

'" The fmal results have been rounded based on the rules of significant digits to show the precision of the analysis based on the parameters used.

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French, C.E., Liscinsky, S.A., and Miller, D.R. (1957). Nutrient composifion of earthworms. Paper No. 2131 in the Journal Series of the Pennsylvania Agricultural Experiment Station.

Geyer, H.J., I. Scheunert, K. Rapp, I. Gebefugi, C. Steinberg, and A. Kettrup. (1993). The relevance of fat content in toxicity of lipophilic chemicals to terrestrial animals with special reference to dieldrin and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Ecotoxicology and Environmental Safety. 26:45-60.

Gish, CD. and D.L. Hughes (1982). Residues of DDT, dieldrin, and heptachlor in earthworms during two years following application. U.S. Fish and Wildlife Service Special Scientific Report-Wildlife No. 241. Washington, D.C. 15 pp.

Good et al (1965). Effects of insecticides on reproduction in the laboratory mouse. I. Kepone. J. Econ. Entromol. 58:754-757.

Ivie, G.W., J.R. Gibson, H.E. Bryant, J.J. Begin, J.R. Bamett, and H.W. Dorough. (1974). Accumulation, distribution, and excretion of mirex-14C in animals exposed for long periods to the insecticide in the diet. J. Agr. Food Chem. 22:646-653. (as cited in Waters etal. 1977)

Jager, T (1998). Mechanistic approach for estimating bioconcentration of organic chemicals in earthworms (oligochaeta). Envr. Toxic, and Chem. 17:2080-2090.

Kendall et al (1978). Toxicological studies with mirex in bobwhite quail. Poult. Sci. 57:1539-1545.

Lord, K.A., G.C. Briggs, M.C. Neale, and R. Manlove (1980). Uptake of pesticides from water and oil by earthworms. Pesticide Science. 11:401-408.

Ma et al (1991). Hazardous exposure of ground-living small mammals to cadmium and lead in contaminated terrestrial ecosystems. Archives of Environmental Contamination and Toxicology. 20:266-270.

Naber, E.G. and Ware, G.W. (1965). Effect of kepone and mirex on reproducfive performance in the laying hen. Poult Sci. 44:875-80.

Sample et al (1996). Toxicological benchmarks for wildlife: 1996 revision. Environmental Restoration Division, ORNL Environmental Restoration Program. ES/ER/TM-86/R3.

Scheunert (1981). Results of long-term studies on the behavior of foreign substances in plant-soil systems. GSR-Ber. 5:85-93.

Thirunavukkarasu P. et al. 2006. Body Weight and Egg Production Performance of Induced Moulted White Leghorn Layers. International Journal of Poultry Science 5 (10): 996-1000.

USEPA (1993). Wildlife exposure factors handbook Volume 1 of I I EPA/600/R-93/187a. USEPA (1995a). Internal report on summary of measured, calculated, and recommended log Kg^

values. Prepared for E. Southerland, Chief of the Risk Assessment and Management Branch, Standards and Applied Science Division, Office of Water by S.W. Karickoff and J.M. Long, Environmental Research Laboratory - Athens. April 10, 1995.

USEPA (1995b). Further Studies for Modeling the Indirect Exposure Impacts from Combustor Emissions. Memorandum from Matthew Lorber, Exposure Assessment Group, and Glenn Rice, Indirect Exposure Team, Environmental Criteria and Assessment Office, Washington D.C, January 20.

USEPA (1996). Ecotox thresholds. Eco Update, Volume 3, Number 2. EPA/540/F-95/038. 12 pp.

USEPA, (1999). Memorandum: Issuance of Final Guidance: Ecological Risk Assessment and Risk Management Principals for Superfund Sites. OSWER Direcfive 9285.7-28P.

USEPA (2005). Guidance for Developing Ecological Soil Screening Levels (Eco-SSLs) Attachment 4-1. OSWER Directive 9285.7-55. Revised February 2005.

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van Gestel, C and V. Ma. (1988). Toxicity and bioaccumulation of chlorophenols in earthworms, in relation to bioavailability. Ecotoxicol Environ Safety 15: 289-297.

Ziegenfuss, P.S., W.J. Renaudette, and W.J. Adams (1986). Methodology for assessing the acute toxicity of chemicals sorbed to sediments: testing the equilibrium partitioning theory. Pages 479-493 In Aquatic Toxicology and Environmental Fate, ASTMSTP 921.

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