Body Residues Research Articles

Whole-body and body-part-specific bioconcentration of explosive compounds in sheepshead minnows

Sheepshead minnows (Cyprinodon variegatus) were exposed to radiolabeled isotopes of the explosives 2,4,6-trinitrotoluene (TNT), exahydro-1,3,5-trinitro-1,3,5-triazine (commonly known as RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (commonly known as HMX), yielding the bioconcentration factors (BCF) of 3.3, 0.7, and 0.1Lkg−1, respectively. For TNT, the body residue of transformation product exceeded that of the parent compound by factors of 1, 8, and 16 for total aminonitrotoluenes, total extractable compounds, and total transformation products, respectively, with substantial bioaccumulation of both non-identified extractable and unextractable (i.e., tissue-bound), compounds. In comparison, the sum body residues of RDX and HMX transformation products were <4 times higher than for parent compounds. The concentrations of RDX and HMX and their transformation products were similar among liver, viscera (excluding liver), gills, and body remains (integument and muscles), while 46% of the TNT transformation products resided in the liver, and 64% of the parent compound was in the viscera.

Chemical techniques for assessing bioavailability of sediment-associated contaminants: SPME versus Tenax extraction

The traditional approach for predicting the risk of hydrophobic organic contaminants (HOCs) in sediment is to relate organic carbon normalized sediment concentrations to body residues or toxic effects to organisms. However, due to the multiple variables controlling bioavailability, this method has limitations. A matrix independent method of predicting bioavailability needs to be used in order to be universally applicable. Both chemical activity (freely dissolved chemical concentrations) measured by solid-phase microextraction (SPME) and bioaccessibility (rapidly desorbing fraction) estimated by Tenax extraction have been developed to predict bioavailability of sediment-associated HOCs. The objectives of this review are to summarize a number of studies using matrix-SPME or Tenax extraction to estimate bioavailability and/or toxicity of different classes of HOCs and evaluate the strengths and weakness of these two techniques. Although the two chemical techniques assess different components of the matrix, estimates obtained from both techniques have been correlated to organism body residues. The advantages of SPME fibers are their applicability for use in situ and their potential usage for a wide array of contaminants by selection of appropriate coatings. Single time-point Tenax extraction, however, is more time- and labor-effective. Tenax extraction also has lower detection limits, making it more applicable for highly toxic contaminants. This review also calls for additional research to evaluate the role of sequestrated contaminants and ingestion of sediment particles by organisms on HOC bioavailability. The use of performance reference compounds to reduce SPME sampling time and linking chemical based bioavailability estimates to toxicological endpoints are essential to expand the applications of these methods.

The tissue residue approach for toxicity assessment: Findings and critical reviews from a Society of Environmental Toxicology and Chemistry Pellston Workshop

Over the past few years, the "critical body residue" approach for assessing toxicity based on bioaccumulated chemicals has evolved into a more expansive consideration of tissue residues as the dose metric when defining dose-response relationships, evaluating mixtures, developing protective guidelines, and conducting risk assessments. Hence, scientists refer to "tissue residue approach for toxicity assessment" or "tissue residue-effects approach" (TRA) when addressing ecotoxicology issues pertaining to tissue (or internal) concentrations. This introduction provides an overview of a SETAC Pellston Workshop held in 2007 to review the state of the science for using tissue residues as the dose metric in environmental toxicology. The key findings of the workshop are presented, along with recommendations for research to enhance understanding of toxic responses within and between species, and to advance the use of the TRA in assessment and management of chemicals in the environment.

A review of the tissue residue approach for organic and organometallic compounds in aquatic organisms

This paper reviews the tissue residue approach (TRA) for toxicity assessment as it applies to organic chemicals and some organometallic compounds (Sn, Hg, and Pb) in aquatic organisms. Specific emphasis was placed on evaluating key factors that influence interpretation of critical body residue (CBR) toxicity metrics including data quality issues, lipid dynamics, choice of endpoints, processes that alter toxicokinetics and toxicodynamics, phototoxicity, species- and life stage-specific sensitivities, and biotransformation. The vast majority of data available on TRA is derived from laboratory studies of acute lethal responses to organic toxicants exhibiting baseline toxicity. Application of the TRA to various baseline toxicants as well as substances with specific modes of action via receptor-mediated processes, such as chlorinated aromatic hydrocarbons, pesticides, and organometallics is discussed, as is application of TRA concepts in field assessments of tissue residues. In contrast to media-based toxicity relationships, CBR values tend to be less variable and less influenced by factors that control bioavailability and bioaccumulation, and TRA can be used to infer mechanisms of toxic action, evaluate the toxicity of mixtures, and interpret field data on bioaccumulated toxicants. If residue-effects data are not available, body residues can be estimated, as has been done using the target lipid model for baseline toxicants, to derive critical values for risk assessment. One of the primary unresolved issues complicating TRA for organic chemicals is biotransformation. Further work on the influence of biotransformation, a better understanding of contaminant lipid interactions, and an explicit understanding of the time dependency of CBRs and receptor-mediated toxicity are all required to advance this field. Additional residue-effects data on sublethal endpoints, early life stages, and a wider range of legacy and emergent contaminants will be needed to improve the ability to use TRA for organic and organometallic compounds.

A single dose of DNA vaccine based on conserved H5N1 subtype proteins provides protection against lethal H5N1 challenge in mice pre-exposed to H1N1 influenza virus

BackgroundHighly pathogenic avian influenza virus subtype H5N1 infects humans with a high fatality rate and has pandemic potential. Vaccination is the preferred approach for prevention of H5N1 infection. Seasonal influenza virus infection has been reported to provide heterosubtypic immunity against influenza A virus infection to some extend. In this study, we used a mouse model pre-exposed to an H1N1 influenza virus and evaluated the protective ability provided by a single dose of DNA vaccines encoding conserved H5N1 proteins.ResultsSPF BALB/c mice were intranasally infected with A/PR8 (H1N1) virus beforehand. Six weeks later, the mice were immunized with plasmid DNA expressing H5N1 virus NP or M1, or with combination of the two plasmids. Both serum specific Ab titers and IFN-γ secretion by spleen cells in vitro were determined. Six weeks after the vaccination, the mice were challenged with a lethal dose of H5N1 influenza virus. The protective efficacy was judged by survival rate, body weight loss and residue virus titer in lungs after the challenge. The results showed that pre-exposure to H1N1 virus could offer mice partial protection against lethal H5N1 challenge and that single-dose injection with NP DNA or NP + M1 DNAs provided significantly improved protection against lethal H5N1 challenge in mice pre-exposed to H1N1 virus, as compared with those in unexposed mice.ConclusionsPre-existing immunity against seasonal influenza viruses is useful in offering protection against H5N1 infection. DNA vaccination may be a quick and effective strategy for persons innaive to influenza A virus during H5N1 pandemic.

Endosulfan and its metabolite, endosulfan sulfate, in freshwater ecosystems of South Florida: a probabilistic aquatic ecological risk assessment

Endosulfan is an insecticide-acaricide used in South Florida and is one of the remaining organochlorine insecticides registered under the Federal Insecticide Fungicide and Rodenticide Act by the U.S.EPA. The technical grade material consists of two isomers (alpha-, beta-) and the main environmental metabolite in water, sediment and tissue is endosulfan sulfate through oxidation. A comprehensive probabilistic aquatic ecological risk assessment was conducted to determine the potential risks of existing exposures to endosulfan and endosulfan sulfate in freshwaters of South Florida based on historical data (1992-2007). The assessment included hazard assessment (Tier 1) followed by probabilistic risk assessment (Tier 2). Tier 1 compared actual measured concentrations in surface freshwaters of 47 sites in South Florida from historical data to U.S.EPA numerical water quality criteria. Based on results of Tier 1, Tier 2 focused on the acute and chronic risks of endosulfan at nine sites by comparing distributions of surface water exposure concentrations of endosulfan [i.e., for total endosulfan (summation of concentrations of alpha- and beta-isomers plus the sulfate), alpha- plus beta-endosulfan, and endosulfan sulfate (alone)] with distributions of species effects from laboratory toxicity data. In Tier 2 the distribution of total endosulfan in fish tissue (whole body) from South Florida freshwaters was also used to determine the probability of exceeding a distribution of whole body residues of endosulfan producing mortality (critical lethal residues). Tier 1 showed the majority of endosulfan water quality violations in South Florida were at locations S-178 followed by S-177 in the C-111 system (southeastern boundary of Everglades National Park (ENP)). Nine surface water sampling sites were chosen for Tier 2. Tier 2 showed the highest potentially affected fraction of toxicity values (>10%) by the estimated 90th centile exposure concentration (total endosulfan) was at S-178. At all other freshwater sites there were <5% of the toxicity values exceeded. Potential chronic risk (9.2% for total endosulfan) was only found at S-178 and all other sites were <5%. Joint probability curves showed the higher probability of risk at S-178 than at S-177. The freshwater fish species which contain tissue concentrations of endosulfan (total) with the highest potential risk for lethal whole body tissue residues were marsh killifish, flagfish and mosquitofish. Based on existing surface water exposures and available aquatic toxicity data, there are potential risks of total endosulfan to freshwater organisms in South Florida. Although there are uncertainties, the presence of tissue concentrations of endosulfan in small demersal fish, is of ecological significance since these fish support higher trophic level species, such as wading birds.

Toxicity and bioconcentration evaluation of RDX and HMX using sheepshead minnows in water exposures

Lethal effects of the explosives RDX and HMX were assessed using ten-day water exposures to juvenile sheepshead minnows ( Cyprinodon variegatus). For RDX, maximum mortality occurred during the first two days of exposure with a 10-d median lethal concentration (LC50) of 9.9 mg L −1. The RDX 10-d median lethal residue (LR50) was 9.6 mg kg −1 (34.9 μmol kg −1) wet weight (ww), the first RDX critical body residue reported for fish. Previous investigations reported that RDX body residues in marine amphipods up to 96 μmol kg −1 ww and in marine mussels up to 86 μmol kg −1 ww failed to result in significant mortality. The highest HMX concentration tested, corresponding to its apparent solubility limit in seawater (2.0 mg L −1), and the associated mean body residue (3 mg kg −1 or 14 μmol kg −1 ww) resulted in no significant mortality for exposed minnows. The mean 10-d bioconcentration factors for RDX (0.6–0.9 L kg −1) and HMX (0.3–1.6 L kg −1) were typically lower than 1, reflecting the low bioaccumulative potential for these compounds.

Acute toxicity and related metabolism of pyridalyl in Chironomus yoshimatsui and Hyalella azteca

Acute toxicity and metabolism of a new insecticide pyridalyl were examined in the larval midge Chironomus yoshimatsui and adult amphipod Hyalella azteca using 14C-labeling. The median lethal concentrations (LC50) of pyridalyl were determined to be 1.1 (48 hr) and 0.015 (96 hr) mg/l for midges and amphipods, respectively, based on its mean measured concentrations in water. Pyridalyl taken up by these organisms underwent ether cleavage at 3,3-dichloroallyloxy moiety followed by conjugation to a significantly higher extent in C. yoshimatsui. The similar acute median lethal body residues (LR50) of pyridalyl estimated for both species from its body residues indicated an insignificant difference in its potential toxicity and therefore, uptake and metabolism behaviors were most likely to play a great role in the apparent toxicity.

Chronic, dietary polybrominated diphenyl ether exposure affects survival, growth, and development of Rana pipiens tadpoles

Levels of polybrominated diphenyl ethers (PBDEs) in the environment have been increasing rapidly over the past two decades; however, the toxicology of these compounds to aquatic organisms is poorly understood. Because amphibians play a role in both aquatic and terrestrial food webs, and are currently undergoing worldwide population declines, it is of interest to determine how PBDEs may affect amphibian health. This is the first study that reports chronic, dietary effects of environmentally relevant levels (7-277 ng/g wet food) of PBDEs in amphibians throughout larval development. Beginning at the free-swimming stage (Gosner Stage [GS] 25), Rana pipiens tadpoles were orally exposed to a technical pentabromodiphenyl ether mixture (DE-71) through metamorphic climax (GS 42). On exposure day 43, a subset of tadpoles was removed for body residue analysis. Sum PBDEs in whole-body tissue correlated linearly to dietary concentrations with BDE-99 represented as the highest contributing congener in both diet and tissue. Survival among all treatments compared to the control was decreased by DE-71 exposure. Further, growth and development were delayed in all but the highest treatment, perhaps indicating greater PBDE tolerance among those individuals that survived the highest treatment. Time to metamorphic climax was delayed, on average, 22 to 36 d in DE-71-treated tadpoles compared to control tadpoles. Additionally, size at metamorphosis was smaller in the highest treatment, suggesting that individuals that survived and metamorphosed similarly to the controls did so with a trade-off in size. At environmentally relevant levels, PBDEs induced mortality as well as sublethal effects on developing tadpoles through dietary exposure.

Bayesian multilevel discrete interval hazard analysis to predict dichlorodiphenyldichloroethylene mortality in Hyalella azteca based on body residues

We exposed Hyalella azteca to p,p'-dichlorodiphenyldichloroethylene for intervals of 1 to 4 d and followed mortality out to 10 d. Mortality was determined as the cessation of heartbeat; dead organism body residue was determined daily. To model mortality probability, body residues of the living organisms were estimated using published kinetic data with concentration-dependent rate constants. The estimated residues compared favorably with measured residues in the dead organisms (predicted body residue = 1.302 ± 0.142 measured body residue + 10.351 ± 15.766, r² = 0.64, n = 50). The response data were collected at discrete intervals; thus, it was not possible to determine the exact time of death for organisms. Consequently, we analyzed the mortality data using discrete interval analysis, in a Bayesian hierarchical framework, with body residue as the dose metric. The predicted body residues to produce mortality were similar across the duration of exposure when postexposure mortality was considered. The concentration for 50% mortality was 0.47 μmol/g (148.6 tg/g, range 0.32-0.66 μmol/g), and predictions of response indicted 95% (range 73-99.9%) mortality at 0.79 μmol/g (250 μg/g) and 4% (range 1.2-9.6%) mortality at 0.16 μmol/g (50 μg/g). The lethal residue for 50% mortality based on interval analysis for short-term exposures with postexposure mortality resulted in values similar to long-term continuous exposures for exposure durations of more than 600 h.

Reproductive performance in East Greenland polar bears ( Ursus maritimus) may be affected by organohalogen contaminants as shown by physiologically-based pharmacokinetic (PBPK) modelling

Polar bears ( Ursus maritimus) feed mainly on ringed seal ( Phoca hispida) and consume large quantities of blubber and consequently have one of the highest tissue concentrations of organohalogen contaminants (OHCs) worldwide. In East Greenland, studies of OHC time trends and organ system health effects, including reproductive, were conducted during 1990–2006. However, it has been difficult to determine the nature of the effects induced by OHC exposures on wild caught polar bears using body burden data and associated changes in reproductive organs and systems. We therefore conducted a risk quotient (RQ) evaluation to more quantitatively evaluate the effect risk on reproduction (embryotoxicity and teratogenicity) based on the critical body residue (CBR) concept and using a physiologically-based pharmacokinetic (PBPK) model. We applied modelling approaches to PCBs, p, p′-DDE, dieldrin, oxychlordane, HCHs, HCB, PBDEs and PFOS in East Greenland polar bears based on known OHC pharmacokinetics and dynamics in laboratory rats ( Rattus rattus). The results showed that subcutaneous adipose tissue concentrations of dieldrin (range: 79–1271 ng g −1 lw) and PCBs (range: 4128–53 923 ng g −1 lw) reported in bears in the year 1990 were in the range to elicit possible adverse health effects on reproduction in polar bears in East Greenland (all RQs ⩾ 1). Similar results were found for PCBs (range: 1928–17 376 ng g −1 lw) and PFOS (range: 104–2840 ng g −1 ww) in the year 2000 and for dieldrin (range: 43–640 ng g −1 lw), PCBs (range: 3491–13 243 ng g −1 lw) and PFOS (range: 1332–6160 ng g −1 ww) in the year 2006. The concentrations of oxychlordane, DDTs, HCB and HCHs in polar bears resulted in RQs < 1 and thus appear less likely to be linked to reproductive effects. Furthermore, sumRQs above 1 suggested risk for OHC additive effects. Thus, previous suggestions of possible adverse health effects in polar bears correlated to OHC exposure are supported by the present study. This study also indicates that PBPK models may be a supportive tool in the evaluation of possible OHC-mediated health effects for Arctic wildlife.

Use of (Eco)toxicity data as screening criteria for the identification and classification of PBT/POP compounds

Characterization of "significant adverse ecotoxicological effects" of persistent organic pollutants (POPs) presents particular challenges. In the various international conventions on POPs and persistent, bioaccumulative, and toxic substances, guidance on classification is not detailed and, in some cases, is unclear. This paper focuses on several key issues in relation to selection of assessment endpoints, use of appropriate effect measures, and uncertainty in the face of limited data. Because POPs are persistent and bioaccumulative, measures of effect should be based not on concentrations in environmental matrices but rather on residues in the body of the organism or in tissues that are causally linked to adverse responses. To obtain these data, currently used toxicity testing methods may need to be modified or substantiated by toxicokinetic information to ensure that substances with POP-like properties are adequately characterized. These data can be more easily matched to environmental monitoring measurements of body or tissue residues for the purposes of assessing whether adverse effects occur in the environment. In the face of persistence and accumulation in the food chain, and considering the extent and suitability of available data, a suitable policy on the use of uncertainty factors may need to be applied when making judgments about toxicity. This paper offers guidance that can be used to identify candidate POPs that have the potential to cause significant adverse effects in the ecosystem.

Evaluation of Bioaccumulation Using In Vivo Laboratory and Field Studies

A primary consideration in the evaluation of chemicals is the potential for substances to be absorbed and retained in an organism's tissues (i.e., bioaccumulated) at concentrations sufficient to pose health concerns. Substances that exhibit properties that enable biomagnification in the food chain (i.e., amplification of tissue concentrations at successive trophic levels) are of particular concern due to the elevated long-term exposures these substances pose to higher trophic organisms, including humans. Historically, biomarkers of in vivo chemical exposure (e.g., eggshell thinning, bill deformities) retrospectively led to the identification of such compounds, which were later categorized as persistent organic pollutants. Today, multiple bioaccumulation metrics are available to quantitatively assess the bioaccumulation potential of new and existing chemicals and identify substances that, upon or before environmental release, may be characterized as persistent organic pollutants. This paper reviews the various in vivo measurement approaches that can be used to assess the bioaccumulation of chemicals in aquatic or terrestrial species using laboratory-exposed, field-deployed, or collected organisms. Important issues associated with laboratory measurements of bioaccumulation include appropriate test species selection, test chemical dosing methods, exposure duration, and chemical and statistical analyses. Measuring bioaccumulation at a particular field site requires consideration of which test species to use and whether to examine natural populations or to use field-deployed populations. Both laboratory and field methods also require reliable determination of chemical concentrations in exposure media of interest (i.e., water, sediment, food or prey, etc.), accumulated body residues, or both. The advantages and disadvantages of various laboratory and field bioaccumulation metrics for assessing biomagnification potential in aquatic or terrestrial food chains are discussed. Guidance is provided on how to consider the uncertainty in these metrics and develop a weight-of-evidence evaluation that supports technically sound and consistent persistent organic pollutant and persistent, bioaccumulative, and toxic chemical identification. Based on the bioaccumulation information shared in 8 draft risk profiles submitted for review under the United Nations Stockholm Convention, recommendations are given for the information that is most critical to aid transparency and consistency in decision making.

Joint toxicity of fluoranthene and pentachlorobenzene to Hyalella azteca and Chironomus dilutus

Nonpolar organic chemicals such as polycyclic aromatic hydrocarbons and chlorobenzenes are expected to act additively when exposed as a mixture. The present study examined the toxicity of fluoranthene (FLU) and pentachlorobenzene (PCBz) individually and in a binary mixture using the whole-body residue as the dose metric. Body residues were based on the toxic equivalent body residue, which included the parent compound plus the organically extractable metabolites for FLU and the parent compound only for PCBz. Using a toxic unit (TU) approach, the binary mixtures of FLU and PCBz following 4- and 10-d water-only exposures acted additively. The lethal residue (LR50) values for mixtures of the compounds for Hyalella azteca were 1.26 (1.19–1.33) TU and 1.27 (1.20–1.34) TU for 4- and 10-d exposures, respectively. For Chironomus dilutus, the 4-d and 10-d values were 0.93 (0.90–0.97) TU and 1.01 (0.96–1.06) TU. Additionally, the total molar sum of PCBz and FLU whole-body residues in a mixture were compared to residues from single compound exposures. For both species tested, the LR50 values based on the total molar sum fell within the range of those determined from the single compound tests; providing additional support for molar additivity for nonpolar narcotic compounds. Assuming that residue-effects data among narcotic compounds (e.g., LR50) are similar, applying the molar sum methodology to narcotic compounds in tissues determined from routine biomonitoring programs and risk specific sampling may be a valuable tool to assess potential effects to biota in the field.

Ecological risks of an old wood impregnation mill: application of the Triad approach.

Although many studies deal with the distribution and mobility of chromated copper arsenate (CCA) metals in soil, the ecotoxicity of CCA-contaminated soils is rarely studied. The Triad approach was applied to determine the ecological risks posed by a CCA mixture at a decommissioned wood impregnation mill in southern Finland. A combination of (1) chemical analyses; (2) toxicity tests with plants (aquatic: Lemna minor; terrestrial: Lactuca sativa), earthworms (Lumbricus rubellus), and enchytraeids (Enchytraeus albidus) conducted on contaminated soils, their aqueous extracts, and well water collected from the site; and (3) determination of the abundance of enchytraeids and nematodes and the bioaccumulation of metals in plants (horsetail) collected from the field were used to assess the actual risk. Although metal concentrations were low, L. minor growth appeared to be reduced by As contamination of the well water. In soil, metals were heterogeneously distributed with total concentrations of 14.8 to 4360 mg As/kg, 15.2 to 1740 mg Cr/kg, and 4.83 to 790 mg Cu/kg. In several samples, concentrations were above Finnish regulatory guideline values and exceeded the half maximal effective concentration (EC50) or 50% lethal concentration (LC50) values for the toxicity of the individual metals to earthworms and enchytraeids, indicating hazards to the ecosystem. (Bio)availability of metals was high, as indicated by weak electrolyte extractions and body residues in L. rubellus and E. albidus exposed in bioassays. Earthworm survival correlated significantly with body metal concentrations, but not with soil total metal concentrations. Enchytraeid responses in the soil bioassays were less sensitive to CCA metal exposure. Plant growth was affected by CCA pollution, with L. sativa root elongation correlating significantly with total and available As concentrations and L. minor development being significantly reduced in H2O extracts of the most contaminated soil sample. Abundance of enchytraeids and nematodes in the field was much lower than in nonpolluted Finnish soils but did not significantly correlate with CCA contamination. Arsenic accumulation in horsetail did not correlate with As concentrations in soil. Overall, the results of the 3 lines of evidence of the Triad approach indicate possible increased risks to the ecosystem at the most contaminated sites of the CCA treatment area.

Survival, Growth, and Body Residues of Hyalella azteca (Saussure) Exposed to Fipronil Contaminated Sediments from Non-Vegetated and Vegetated Microcosms

We assessed chronic effects of fipronil and metabolite contaminated sediments from non-vegetated and Thallia dealbata vegetated wetland microcosms on Hyalella azteca during wet and dry exposures. Mean sediment concentrations (ng g(-1)) ranged from 0.72-1.26, 0.01-0.69, 0.07-0.23, and 0.49-7.87 for fipronil, fipronil-sulfide, fipronil-sulfone, and fipronil-desulfinyl, respectively. No significant differences in animal survival or growth were observed between non-vegetated and vegetated microcosms during wet or dry exposures. Mean animal body residue concentrations (ng g(-1)) ranged from 28.4-77.6, 0-30.7, and 8.3-43.8 for fipronil, fipronil-sulfide, and fipronil-sulfone. Fipronil-desulfinyl was not detected in any animal samples.

Agricultural Pesticides in Mississippi Delta Oxbow Lake Sediments During Autumn and Their Effects on Hyalella azteca

Agricultural pesticide contamination of sediments from five Mississippi Delta oxbow lakes and their effects and bioavailablity to Hyalella azteca were assessed during a low-application season-autumn. Three reference oxbow lakes were located in the White River National Wildlife Refuge (WRNWR), Arkansas and two impaired lakes, according to the US Environmental Agency Sect. 303 (d) Clean Water Act, were located in Mississippi. Surface sediment (top 5 cm) was collected at three sites within each lake and analyzed for 17 current and historic-use pesticides and metabolites. Chronic 28-day H. azteca sediment bioassays and pesticide body residue analyses were completed to determine the degree of biological responses and bioavailability. The greatest number of detectable pesticides in WRNWR and 303 (d) sediment samples was 9 and 12, respectively, with historic-use pesticide metabolite, p,p'-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] ubiquitous. No significant (p > 0.05) differences in animal survival were observed among sites. Animal growth was significantly (p < 0.05) less at only one site in a 303 (d)-listed lake (Macon Lake). Only six pesticides were observed in H. azteca with current-use pesticides detected at three sites; historic-use pesticides and metabolites detected at 11 sites. Animal body residues of a historic-use pesticide (dieldrin) and metabolite (p,p'-DDE) were associated with observed growth responses. Results show limited current-use pesticide contamination of sediments and H. azteca body tissues during autumn and that historic-use pesticides and metabolites are the primary contributors to observed biological responses.

The physicochemical basis of QSARs for baseline toxicity

The physico-chemical properties relevant to the equilibrium partitioning (bioconcentration) of chemicals between organisms and their respired media of water and air are reviewed and illustrated for chemicals that range in hydrophobicity. Relationships are then explored between freely dissolved external concentrations such as LC50s and chemical properties for one important toxicity mechanism, namely baseline toxicity or narcosis. The ‘activity hypothesis’ proposed by Ferguson in 1939 provides a coherent and compelling explanation for baseline toxicity of chemicals in both water- and air-respiring organisms, as well as a reference point for identifying more specific toxicity pathways. From inhalation studies with fish and rodents, narcosis is shown to occur at a chemical activity exceeding approximately 0.01 and there is no evidence of narcosis at activities less than 0.001. The activity hypothesis provides a framework for directly comparing the toxic potency of chemicals in both air- and water-breathing animals. The activity hypothesis is shown to be consistent with the critical body residue concept, but it has the advantage of avoiding the confounding effect of lipid content of the test organism. It also provides a theoretically sound basis for assessing the baseline toxicity of mixtures. It is suggested that since activity is readily calculated from fugacity, observed or predicted environmental abiotic and biotic fugacities can be used to evaluate the potential for baseline toxicity. Further, models employing fugacity or activity can be used to improve the experimental design of bioassays, thus possibly reducing unnecessary animal testing.

Sublethal toxicity and biotransformation of pyrene in Lumbriculus variegatus (Oligochaeta)

The aim of this work was to study the toxicity and biotransformation of polyaromatic hydrocarbon (PAH) pyrene in the oligochaete aquatic worm, Lumbriculus variegatus. PAHs are ubiquitous environmental pollutants that pose a hazard to aquatic organisms, and metabolizing capability is poorly known in the case of many invertebrate species. To study the toxicity and biotransformation of pyrene, the worm was exposed for 15 days to various concentrations of water-borne pyrene. The dorsal blood vessel pulse rate was used as a sublethal endpoint. Pyrene biotransformation by L. variegatus was studied and the critical body residues (CBR) were estimated for pyrene toxicity. The toxicokinetics of pyrene uptake was evaluated. A combination of radiolabeled (14C) and nonlabeled pyrene was used in the exposures, and liquid scintillation counting (LSC) and high-pressure liquid chromatography were employed in both water and tissue residue analyses. The results showed that L. variegatus was moderately able to metabolize pyrene to 1-hydroxypyrene (1-HP), thus demonstrating that the phase-I-like oxidizing enzyme system metabolizes pyrene in L. variegatus. The amount of the 1-HP was 1-2% of the amount of pyrene in the worm tissues. The exposure to pyrene reduced the blood vessel pulse rate significantly (p<0.05), showing that pyrene had a narcotic effect. The estimated CBRs remained constant during the exposure time, varying from 0.120 to 0.174 mmol pyrene/kg worm wet weight. The bioconcentration factors (BCF) decreased as exposure concentration increased. It was suggested that the increased toxicity of pyrene accounted for the decrease in BCFs by lowering the activity of the organism.

Uptake and elimination of hydrophobic organic contaminants in estuarine copepods: An experimental study

Polycyclic aromatic hydrocarbons (PAHs) are considered to be rapidly biotransformed by organisms, whereas polychlorinated biphenyls (PCBs) are strongly bioaccumulated. In the present study, the estuarine copepod Eurytemora affinis was exposed in a continuous flow-through system to dissolved PAH (500 ng/L) and PCB (300 ng/L) mixtures for 86 h, whereas control groups were placed in a continuous flow-through system with clean water. Both PCB and PAH body residues were measured and compared in exposed and in nonexposed copepods to assess the uptake and the elimination of these two contaminant classes in this copepod species. After the exposure, exposed copepods exhibited concentration factors, based on a dry-weight basis, of 25, 750, and 1,200, respectively, for total PCBs and PAHs. The lower concentrations of PAHs in the nonexposed versus exposed copepods in contrast to small differences for PCBs suggest a higher rate of metabolism of PAHs compared with PCBs and could explain the differences observed in the accumulation. Furthermore, uptake as well as elimination of both PCBs and PAHs were compound selective in E. affinis. Therefore, higher-molecular-weight PCBs and PAHs were preferentially accumulated, while lower-molecular-weight compounds were preferentially eliminated. These results suggest the importance of copepods in the biogeochemical cycles of hydrophobic organic contaminants in estuarine ecosystems.