Overview and comparison of lipid-containing semipermeable membrane devices and oysters (Crassostrea gigas) for assessing organic chemical exposure

We performed 20-d, flow-through exposures of lipid-containing semipermeable membrane devices (SPMDs) and Pacific oysters (Crassostrea gigas) to three concentrations (nominally 10, 100, and 250 ng/L) of a diverse mixture of polycyclic aromatic hydrocarbons (PAHs). Exposure water was seawater free of particulates larger than 0.1 microm. The results of these controlled laboratory studies demonstrated that SPMDs and oysters concentrate the same chemicals but that the relative amounts accumulated are different. For oysters, the 20-d mean (across treatments) concentration factors (CFs) of test compounds with log Kow < or = 4.8 were much lower (4.0- to 20-fold lower) than those of the same compounds in SPMDs. In contrast, the 20-d CFs of PAHs with log Kow > or = 5.6 in oysters from the low-level treatment were higher than the corresponding CFs for SPMDs. The CFs of these compounds in oysters from the low-level treatment ranged from approximately 3.0- to 13-fold higher than those in oysters from the high-level treatment. This physiologically mediated difference in oyster CFs appears to be linked to active feeding in the low-level treatment and to apparent toxicity-induced cessation of feeding (i.e., valve closure) in the high-level treatment. Because CFs for these compounds in oysters were not independent of exposure concentrations, it follows that tissue levels were not proportional to exposure concentration. However, both sampling approaches have advantages and disadvantages, and the appropriateness of their use depends on the goals of a given study.     

Using Semipermeable Membrane Devices, Bioassays, and Chemical Analysis for Evaluation of Bioavailable Polycyclic Aromatic Hydrocarbons in Water

Meiliang Bay is a sublake of Taihu Lake and has been polluted by domestic and industrial effluents. As part of a comprehensive risk assessment project in this region, semipermeable membrane devices (SPMDs) were applied to evaluate the levels and potential toxic potency of polycyclic aromatic hydrocarbons (PAHs) in lakewater, in combination with chemical analysis and in vitro bioassay using H4IIE rat hepatoma cells. In addition, induction of hepatic ethoxyresorufin-O-deethylase (EROD) activity, in crucian carp (Carassius auratus), caged in the vicinity of SPMD sampling sites was also used as a biomarker of exposure to PAHs and related chemicals. The caged crucian carp accumulated similar PAH profile patterns (p < 0.001) but at lower levels compared with SPMDs on a wet-weight basis. Total concentrations of PAHs in crucian carp muscle tissues ranged from 35.6 to 69.1 ng/g after the 32-day exposure, whereas total PAHs in SPMDs ranged from 716.9 to 1007.8 ng/g. Dialysates from SPMDs exposed to Meiliang Bay water caused marked EROD activity in H4IIE cells. Toxic potency of dialysates expressed as bioassay-derived 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ) ranged from 3.8 to 6.2 pg TCDD-EQ/g SPMD for 32-day exposure samples. A linear correlation of total amount of PAHs and in vitro TCDD-EQ of SPMD dialysates yielded an R ² of 0.82. Empirical evidence suggests that aryl hydrocarbon receptor-active PAHs can account for about 42–56% of the potency observed. Significant induction of liver EROD activity was also observed in crucian carp caged alongside SPMDs and there was a good correlation between the results of EROD assays in vivo and in vitro (R ² = 0.62, p = 0.02). It is, therefore, suggested that the SPMD technique in connection with chemical analysis and specific in vitro bioassays might be a valuable tool to assess the levels and effects of bioavailable hydrophobic pollutants in water.     

Synthetic Musks in the Environment. Part 2: Enantioselective Transformation of the Polycyclic Musk Fragrances HHCB,AHTN, AHDI,and ATII in Freshwater Fish

A method for the enantioselective separation of the chiral polycyclic musks HHCB, AHTN, AHDI, and ATII is presented. Eighteen fish samples (rudd, tench, crucian carp, eel) and one pooled zebra mussel sample from the pond of a municipal sewage treatment plant were investigated with regard to their concentrations and the enantiomeric ratios (ERs) of polycyclic musks. In addition, three water samples taken at the effluent of the sewage plant, as well as two water samples and two series of semipermeable membrane devices (SPMDs) consisting of six samples each from the pond were included in the present study. This comprehensive data set allowed a reliable evaluation of species-dependent metabolization processes. The pattern of the polycyclic musks in the chromatograms obtained by enantioselective gas chromatography seems to be typical of each species, like a fingerprint. The highest deviations from the racemic ER were found for trans-HHCB and trans-ATII in crucian carp with values of or below 0.1. Calculations showed that enantioselective transformation seems to be the most important process, resulting in the observed lower concentrations in crucian carp compared to tench. Consequences for a risk assessment are discussed. Received: 12 June 2001/Accepted: 1 December 2001     

Bioaccumulation of polycyclic aromatic compounds: 2. Modeling bioaccumulation in marine organisms chronically exposed to dispersed oil

Within the frame of a large environmental study, we report on a research program that investigated the potential for bioaccumulation and subsequent effect responses in several marine organisms exposed to chronic levels of dispersed crude oil. Body burden can be estimated from kinetic parameters (rate constants for uptake and elimination), and appropriate body burden-effect relationships may improve assessments of environmental risks or the potential for such outcomes following chronic discharges at sea. We conducted a series of experiments in a flow-through system to describe the bioaccumulation kinetics of polycyclic aromatic hydrocarbons (PAH) at low concentrations of dispersed crude oils. Mussels (Mytilus edulis) and juvenile turbot (Scophthalmus maximus) were exposed for periods ranging from 8 to 21 d. Postexposure, the organisms were kept for a period of 9 to 10 d in running seawater to study elimination processes. Rate constants of uptake (k1) and elimination (k2) of the PAHs during and following exposure were calculated using a first-order kinetic model that assumed a decrease of the substances in the environment over time. The estimated bioconcentration factor was calculated from the ratio of k1/k2. The kinetic parameters of two-, three-, and four-ring PAHs in mussel and fish are compared with estimates based on hydrophobicity alone, expressed by the octanol-water partition coefficient, Kow (partitioning theory). A combination of reduced bioavailability of PAHs from oil droplets and degradation processes of PAHs in body tissues seems to explain discrepancies between kinetic rates based on Kow and actual kinetic rates measured in fish. Mussels showed a pattern more in compliance with the partitioning theory.     

Accumulation and elimination of 16 polycyclic aromatic compounds in the earthworm (Eisenia fetida)

Accumulation and elimination of different polycyclic aromatic compounds (PACs) were studied in earthworms (Eisenia fetida) exposed to contaminated soil from an old gasworks site. In total, 12 polycyclic aromatic hydrocarbons (PAHs), two N- and S-heterocyclic PACs, and two PAC-quinones were included in the study. Peak-shaped accumulation curves were found for many of the compounds. After 19 d of exposure, the ratio between concentrations in worm lipids and soil organic matter was 0.02 on average. The half-lives of the PACs were relatively long, between 2 and 11 d. The elimination rate constants, k2, correlated both with literature-derived octanol-water partition coefficients (Kow) for PAHs (r2 = 0.93) and the computed polarizability (r2 = 0.88) of all the compounds. The elimination rate constants of PAHs are comparable to those of PCBs found in earlier studies, and the linear regression coefficient, r2, of k2 against Kow for PAHs and PCBs together was 0.93.     

Investigating the Spatial Trends in the Level of Organic Contaminants in the Ethiopian Rift Valley Lakes Using Semipermeable Membrane Devices

Organic pollutants in the Ethiopian Rift Valley Lakes are the major factors that contribute to severe environmental problem. SPMDs were deployed for the analysis of selected organic pollutants for 1?month at 2 sites in Lakes Hawassa, Ziway and Koka, Ethiopia. From SPMDs placed in the three lakes, the predominant OCPs were DDT which comprise 67% and followed by endosulfan 23% of the total organochlorine pesticides (OCPs) retrieved. The highest level of OCPs, in general, was found in the SPMDs deployed in Lake Ziway with the mean concentration of 308.5 ng/SPMD. However, the concentrations of polychlorinated biphenyls (PCBs) were the highest in the SPMDs deployed in Lake Hawassa with mean concentration of 50.2 ng/SPMD. Spatial variation on the accumulation of OCPs and PCBs among the lakes depends on the shoreline activities, distance of the lakes from point and non-point sources, and the biofouling factors.     

In situ biomonitoring of PAH-contaminated sediments using juvenile coho salmon (Oncorhynchus kisutch)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous marine and freshwater sediment contaminants. Extensive data exist to confirm that PAHs are toxic to aquatic receptors. However, limited information is available regarding the bioavailability and genotoxicity of sediment PAHs to aquatic organisms. This study investigated an integrated biomonitoring approach using chemical analyses and biomarkers to characterize the bioavailability and genotoxicity of a complex PAH mixture in freshwater lake sediments associated with a former manufactured gas plant (MGP). Sediment PAH genotoxicity was assessed by flow cytometry (FCM), DNA adduct (32)P-postlabeling, and erythrocyte micronuclei in juvenile coho salmon (Oncorhynchus kisutch) caged in the water column. Significant PAH-induced genotoxicity was observed with FCM and (32)P-postlabeling, but not with erythrocyte micronuclei. Chromosome damage in peripheral blood and hepatic DNA adducts correlated with sediment, but not water column PAH concentrations. Total hepatic DNA adducts in salmon caged nearest the former MGP facility was 39+/-6.5 (RALx10(9)), while salmon caged in a reference lake had 28+/-2.3 total hepatic DNA adducts per 10(9) nucleotides. These results indicate that in situ biomonitoring using biomarkers and caged fish can be a sensitive indicator of genotoxic PAHs in sediments.     

Bioconcentration, biotransformation, and elimination of polycyclic aromatic hydrocarbons in sheepshead minnows (Cyprinodon variegatus) exposed to contaminated seawater

Sheepshead minnows (Cyprinodon variegatus) were continuously exposed to two concentrations of polycyclic aromatic hydrocarbons (PAHs) dissolved in seawater (sigma PAH = 7.57 and 72.31 microg/L) for 36 d, followed by 8 d of depuration. The PAHs studied were naphthalene (NPH or C0-NPH), phenanthrene (PHE or C0-PHE), pyrene (PYR), 2-methylnaphthalene (C1-NPH), 1,3-dimethylnaphthalene (C2-NPH), 2-isopropylnaphthalene (C3-NPH), 9-methylphenanthrene (C1-PHE), and 9-ethylphenanthrene (C2-PHE). Uptake rate constants (k1) for NPHs increased with increasing degree of alkylation and log value of the octanol/water partition coefficient (Kow), whereas k1 values for three- and four-ring PAHs were lower despite their high log Kow values. Elimination rate constants (k2) for the homologue series of NPHs and PHEs generally increased with decreasing degree of alkylation and log Kow values. However, the depuration time did not directly correlate with the molecular size for nonalkylated PAHs. Bioconcentration factors (BCFs) were estimated from the ratio of k1 to k2 and also directly from PAH concentrations in fish tissue and water samples, and the factors generated by the two methods were very similar. A significant positive correlation was determined between log BCFs and log Kow values for the series of C0- through C3-NPH at both low (r2 = 0.985, p = 0.0077) and high (r2 = 0.956, p = 0.022) exposures, although this correlation was not determined for all the PAHs studied. As a result of increased metabolism and/ or reduced bioavailability with increasing lipophilic character, the estimated BCFs for C0- through C2-PHE and PYR were generally lower than those for C0- through C3-NPH. The two exposure levels revealed minor variations in k1 and k2 values for parent PAHs and in the temporal pattern of PAH metabolite concentrations in bile. The present results indicate that the presence and nature of alkyl groups have a significant influence on the kinetics and metabolism of PAHs in fish.     

Uptake and depuration of nonionic organic contaminants from sediment by the oligochaete,Lumbriculus variegatus

Uptake of sediment-associated contaminants by the oligochaete Lumbriculus variegatus was evaluated after 1, 3, 7, 14, 28, and 56 d of exposure to a field-collected sediment contaminated with DDT and its metabolites, dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE), or to a field-collected sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). Depuration of contaminants by oligochaetes in a control sediment or in water was also evaluated over a 7-d period after 28 d of exposure to the field-collected sediments. Accumulation of PAHs with a log octanol-water partitioning coefficient (log Kow) <5.6 typically reached a peak at day 3, followed by a lower plateau between days 7 and 56 of the sediment exposure. Similarly, 4,4'-DDT exhibited a peak in accumulation at day 14 followed by a decline at days 28 and 56. In contrast, accumulation of PAHs with a log Kow >5.6 or DDD and DDE typically exhibited a steady increase from day 1 to about day 14 or 28, followed by a plateau. Therefore, exposures conducted for a minimum of 14 to 28 d better reflected steady-state concentrations for DDT and its metabolites and for PAHs. Depuration rates for DDT and its metabolites and high-Kow PAHs were much higher in organisms held in clean sediment relative to both water-only depuration and model predictions. This suggests that depuration in clean sediment may artificially accelerate depuration of hydrophobic compounds. Comparisons between laboratory-exposed L. variegatus and oligochaetes collected in the field from these sediments indicate that results of laboratory tests can be extrapolated to the field with a reasonable degree of certainty.     

Predicting the toxicity of neat and weathered crude oil: toxic potential and the toxicity of saturated mixtures

The toxicity of oils can be understood using the concept of toxic potential, or the toxicity of each individual component of the oil at the water solubility of that component. Using the target lipid model to describe the toxicity and the observed relationship of the solubility of oil components to log (Kow), it is demonstrated that components with lower log (Kow) have greater toxic potential than those with higher log (Kow). Weathering removes the lower-log (Kow) chemicals with greater toxic potential, leaving the higher-log (Kow) chemicals with lower toxic potential. The replacement of more toxically potent compounds with less toxically potent compounds lowers the toxicity of the aqueous phase in equilibrium with the oil. Observations confirm that weathering lowers the toxicity of oil. The idea that weathering increases toxicity is based on the erroneous use of the total petroleum hydrocarbons or the total polycyclic aromatic hydrocarbons (PAHs) concentration as if either were a single chemical that can be used to gauge the toxicity of a mixture, regardless of its makeup. The toxicity of the individual PAHs that comprise the mixture varies. Converting the concentrations to toxic units (TUs) normalizes the differences in toxicity. A concentration of one TU resulting from the PAHs in the mixture implies toxicity regardless of the specific PAHs that are present. However, it is impossible to judge whether 1 microg/L of total PAHs is toxic without knowing the PAHs in the mixture. The use of toxic potential and TUs eliminates this confusion, puts the chemicals on the same footing, and allows an intuitive understanding of the effects of weathering.     

Impact of sediment manipulation on the bioaccumulation of polycyclic aromatic hydrocarbons from field-contaminated and laboratory-dosed sediments by an oligochaete

The accumulation kinetics of polycyclic aromatic hydrocarbons (PAHs) by the freshwater oligochaete Lumbriculus variegatus were measured for field-contaminated and laboratory-dosed sediment. In addition, sediment manipulations typically used for homogenization and dosing in bioaccumulation assays were compared. Rather than an asymptotic approach to steady state, both resident and dosed PAH accumulation exhibited a peak during the 14-d assays, with steeper declines being noted for the lower-molecular-weight compounds. Lack of evidence of a peak for higher-molecular-weight PAHs may be due to slower kinetics and the short length of the assay. Relative to minimally mixed sediment, slurried sediment enhanced the accumulation of less-soluble resident PAHs, did not affect moderately soluble PAHs, and reduced the uptake of the more-soluble PAHs, fluorene and phenanthrene. Aging sediment after mixing reduced the availability of highly to moderately soluble resident PAHs but had no effect on less-soluble PAHs. A similar effect was noted for dosed PAHs, though a larger reduction in bioavailability was observed. Dosed PAH uptake clearance coefficients (ks) exceeded those of minimally mixed resident PAHs by factors of 3 to 4 for pyrene and 26 for benzo[a]pyrene. These results demonstrate that sediment manipulations and contamination history need to be considered when measuring PAH bioaccumulation.     

河北省淡水鱼香港海鸥型菌分布及耐药性研究

目的了解河北省淡水鱼中香港海鸥型菌的分布现状及耐药性。方法含头孢哌酮32μg/ml的血平板进行分离,API20NE和VITEK GNI+进行生化鉴定,药敏试验采用K-B琼脂纸片扩散法。结果 429份鱼类样本中,检出8株香港海鸥型菌,总检出率为1.86%(8/429),其中草鱼的检出率为5.43%(5/92),鲤鱼为0.53%(1/189),鲫鱼为2.08%(2/96),其他淡水鱼未检出(0/52)。药敏结果显示8株香港海鸥型菌对万古霉素、头孢哌酮、克林霉素、甲硝唑耐药,对多粘菌素B、替卡西林/克拉维酸、红霉素、庆大霉素、阿米卡星、四环素、环丙沙星、磺胺、氯霉素敏感。结论河北省淡水鱼存在香港海鸥型菌的污染并显示一定程度的耐药,应加强监测和预警,防止香港海鸥型菌病在河北省的流行和传播。     

3,4-dichloroaniline-induced oxidative stress in liver of crucian carp (Carassius auratus)

3,4-dichloroaniline (DCA) and its analogs are widely used as chemical intermediates in the synthesis of herbicides, azo dyes, and pharmaceuticals. They bring danger to growth, development, and propagation of aquatic organisms. The purpose of this study was to show DCA-induced oxidative stress response in liver of crucian carp (Carassius auratus). Superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO), and NO synthase (NOS) in liver were measured in crucian carp after exposure to DCA solution (0.2, 0.4, and 0.8 mg/L, respectively) for 15 days and compared with the control. DCA significantly induced SOD activity and enhanced MDA concentration in liver of crucian carp. Compared with the control, GSH and NO concentrations decreased and NOS activity was inhibited in crucian carp liver 15 days after DCA treatment. The data suggested that DCA-induced free radical generation and antioxidant depletion, and caused oxidative stress and lipid peroxidation in liver of crucian carp.     

Similarities in bioaccumulation patterns of polychlorinated dibenzo-p-dioxins and furans and polychlorinated diphenyl ethers in laboratory-exposed oligochaetes and semipermeable membrane devices and in field-collected chironomids

Sediment and chironomid samples were collected from a river in the vicinity of and downstream from a closed chlorophenol production plant, and they were analyzed for polychlorinated dibenzo-p-dioxins and furans (PCDD/F) and polychlorinated diphenyl ethers (PCDE). Bioaccumulation of these compounds from the sediments by the oligochaeta, Lumbriculus variegatus, and semipermeable membrane devices (SPMDs) was studied in a 28-d bioaccumulation test. The sum concentrations of PCDD/Fs and PCDEs in sediments varied spatially, peaking at the site below the production plant, but the congener composition remained fairly constant throughout the river. The sum concentrations of chironomids, oligochaetes, and SPMDs all varied independently of sediment concentrations. Both invertebrates accumulated more PCDEs, whereas PCDD/Fs dominated in sediments and SPMDs. Despite the variable sum concentrations, similarities were observed in concentrations and compositions of individual congeners. A significant correlation was found between sediments and oligochaetes, and between oligochaetes and chironomids, for both PCDD/Fs and PCDEs. These results suggest that bioaccumulation of PCDD/Fs and PCDEs in invertebrates is nonselective. Furthermore, the laboratory bioaccumulation tests seem to yield relevant results. The SPMDs were found to give good predictions of the PCDD/F concentrations of sediments and oligochaetes. For PCDEs, the estimates were slightly poorer, but still useful for preliminary concentration assessments.     

Influence of lake characteristics on the biomagnification of persistent organic pollutants in lake trout food webs

The biomagnification of polychlorinated biphenyls (PCBs) and major organochlorine pesticides (OCPs) was studied using lake trout (Salvelinus namaycush) and other food web organisms collected from 17 lakes in Canada and the northeastern United States between 1998 and 2001. Whole lake trout (n = 357) concentrations of the sum (Sigma) of 57 PCB congeners ranged between 1.67 and 2,890 ng/g wet weight (median 61.5 ng/g wet wt). Slimy sculpin had the highest mean concentrations of SigmaPCB of all forage fish (32-73 ng/g wet wt). Positive relationships between log (lipid wt) concentrations of PCB congener 153, PCB congener 52, p,p'-dichlorodiphenyldichloroethylene, hexachlorobenzene, cis-chlordane, trans-nonachlor, or dieldrin and trophic level (determined using stable nitrogen isotope ratios) were found for most of the 17 food webs, indicating biomagnification of these PCBs and OCPs. The p,p'-dichlorodiphenyldichloroethylene had the highest trophic magnification factors (TMFs) of the 14 individual compounds studied, averaging 4.0 +/- 1.8 across the 17 lakes, followed by trans-nonachlor (3.6 +/- 1.5) and PCB congener 153 (3.4 +/- 1.2). Average TMFs for 14 individual PCBs or OCPs were significantly correlated with log octanol-water partition coefficient, implying that the rate of accumulation along the food web is dependent on hydrophobicity and recalcitrance. Significant correlations (p < 0.05) were found between TMFs of SigmaPCBs, hexachlorobenzene, alpha-hexachlorocyclohexane, and lindane and lake area, latitude, and longitude, but not for 11 other PCBs or OCPs. Overall, the results of the present study show that biomagnification of PCBs and most OCPs, as measured by TMFs, is only weakly influenced by such factors as latitude and longitude. Exceptions are hexachlorocyclohexane isomers and hexachlorobenzene, which had generally greater TMFs in northern lakes, possibly due to lower rates of elimination and biotransformation in the food web.     

The changes of serum testosterone level and hepatic microsome enzyme activity of crucian carp (Carassius carassius) exposed to a sublethal dosage of pentachlorophenol

Pentachlorophenol (PCP), which was reported to be a typical persistent organic pollutant and environmental endocrine disruptor, may cause threat to aquatic species. In this study, serum testosterone concentration, activity of liver microsome ethoxyresorufin O-deethylase (EROD) and glutathione S-transferases (GST) of crucian carp (Carassius carassius) exposed to PCP for 7 and 15 d, respectively, were examined. The results showed that testosterone concentration was induced remarkably after 7 d (P<0.05), and the testosterone concentrations in 15 d treatment crucian carp were higher than those in 7 d treatment. It was found that there were significant effects on activities of EROD and GST after crucian carp were exposed to PCP for 7 and 15 d (P<0.05), compared to the controls. EROD and GST activities increased with increase in PCP concentration and also with increase in time on exposure. The results indicated that serum testosterone, EROD and GST were sensitive endpoints to PCP. PCP may have endocrine disrupting activities and may affect the reproductive success of this species. It is possible that the changes of hepatic microsome enzyme activities may result in alterations of serum testosterone levels in crucian carp.     

Use of polynomial expressions to describe the bioconcentration of hydrophobic chemicals by fish

For the bioconcentration of hydrophobic chemicals by fish, relationships have been previously established between uptake rate constants (k1) and the octanol/water partition coefficient (Kow), and also between the clearance rate constant (k2) and Kow. These have been refined and extended on the basis of data for chlorinated hydrocarbons, and closely related compounds including polychlorinated dibenzodioxins, that covered a wider range of hydrophobicity (2.5 less than log Kow less than 9.5). This has allowed the development of new relationships between log Kow and various factors, including the bioconcentration factor (as log KB), equilibrium time (as log teq), and maximum biotic concentration (as log CB), which include extremely hydrophobic compounds previously not taken into account. The shape of the curves generated by these equations are in qualitative agreement with theoretical prediction and are described by polynomial expressions which are generally approximately linear over the more limited range of log Kow values used to develop previous relationships. The influences of factors such as hydrophobicity, aqueous solubility, molecular weight, lipid solubility, and also exposure time were considered. Decreasing lipid solubilities of extremely hydrophobic chemicals were found to result in increasing clearance rate constants, as well decreasing equilibrium times and bioconcentration factors.     

Net trophic transfer efficiencies of polychlorinated biphenyl congeners to lake whitefish (Coregonus clupeaformis) from their food

Lake whitefish (Coregonus clupeaformis) were fed rainbow smelt (Osmerus mordax) in four laboratory tanks over a 133-d experiment. At the start of the experiment, 10 to 14 of the fish in each tank were sacrificed, and the concentrations of 40 polychlorinated biphenyl (PCB) congeners within these fish were determined. Polychlorinated biphenyl congener concentrations were also determined in the 15 lake whitefish remaining in each of the four tanks at the end of the experiment as well as in the rainbow smelt fed to the lake whitefish. Each lake whitefish was weighed at the start and the end of the experiment, and the amount of food eaten by the lake whitefish during the experiment was tracked. Using these measurements, net trophic transfer efficiency (gamma) from the rainbow smelt to the lake whitefish in each of the four tanks was calculated for each of the 40 PCB congeners. Results showed that gamma decreased exponentially as log K(OW) for the congeners increased from 6 to 8. Further, gamma averaged 0.70 for the tetrachloro congeners but averaged only 0.45 for the higher chlorinated congeners.     

Determination of polychlorinated biphenyl and polycyclic aromatic hydrocarbon elimination rates in adult green and leopard frogs

The purpose of the present study was to quantify elimination kinetics of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in adult green frogs (Rana clamitans) and leopard frogs (Rana pipiens). Three experiments were conducted: PCB elimination rate constants were determined for both frog species, and PAH elimination rate constants were determined for leopard frogs only. In green frogs, significant PCB elimination rate constants ranged from 0.013 to 0.04 d(-1) (time for frogs to achieve 90% steady state with water [t90] = 57.8-178.2 d). In leopard frogs, significant PCB elimination rate constants ranged from 0.004 to 0.047 d(-1) (t90 = 48.8-657.9 d). Polycyclic aromatic hydrocarbon elimination in leopard frogs was faster than PCB elimination in either frog species: Significant PAH rate constants ranged from 0.069 to 0.188 d(-1) (t90 = 12.2-33.5 d). In both species, and for both PCBs and PAHs, a significant inverse relationship was found between the chemical elimination rate constant and Kow. These results show that adult anurans have relatively low elimination rates of PCBs but exhibit a small capacity for metabolic biotransformation of PAHs that is comparable to that of invertebrates but lower than that of fish. These findings suggest that adult amphibians have the potential to be used as biomonitors for persistent organic chemicals.     

Organochlorine Pesticides in Consumer Fish and Mollusks of Liaoning Province, China: Distribution and Human Exposure Implications

Fish and mollusk samples were collected from markets located in 12 cities in Liaoning province, China, during August and September 2007, and 22 organochlorine pesticides (OCPs) were detected. DDT, HCH, endosulfan, chlordane, and HCB were the dominating OCPs, with mean concentrations and ranges of, respectively, 15.41 and 0.57 to 177.56 ng/g, 0.84 and below detection limit (BDL) to 22.99 ng/g, 1.31 and BDL to 13.1 ng/g, 1.05 and BDL to 15.68 ng/g, and 0.63 and BDL to 9.21 ng/g in all fish and mollusk samples. The concentrations of other OCPs generally were low and were detectable in a minority of samples, reflecting the low levels of these OCPs in the study region. In general, OCP concentrations were obviously higher in fish than in mollusks, and higher in freshwater fish than in marine fish, which indicated, first, that freshwater fish are more easily influenced than seawater fish and mollusks by OCP residues in agricultural areas and, second, that there are different biota accumulation factors for OCPs between fish and mollusk. To learn the consumption of fish and mollusk, 256 questionnaires were sent to families in 12 cities of Liaoning province. Using the contamination data, average estimated daily intakes of OCPs via fish and mollusk consumption were calculated, which were used for exposure assessment. The public health risks caused by exposure to OCPs in the course of fish and mollusk consumption were compared to noncancer benchmarks and cancer benchmarks.