Solid-phase microextraction (SPME) with stable isotope calibration for measuring bioavailability of hydrophobic organic contaminants.

Solid-phase microextraction (SPME) is a biomimetic tool ideally suited for measuring bioavailability of hydrophobic organic compounds (HOCs) in sediment and soil matrices. However, conventional SPME sampling requires the attainment of equilibrium between the fiber and sample matrix, which may take weeks or months, greatly limiting its applicability. In this study, we explored the preloading of polydimethylsiloxane fiber with stable isotope labeled analogs (SI-SPME) to circumvent the need for long sampling time, and evaluated the performance of SI-SPME against the conventional equilibrium SPME (Eq-SPME) using a range of sediments and conditions. Desorption of stable isotope-labeled analogs and absorption of PCB-52, PCB-153, bifenthrin and cis-permethrin were isotropic, validating the assumption for SI-SPME. Highly reproducible preloading was achieved using acetone-water (1:4, v/v) as the carrier. Compared to Eq-SPME that required weeks or even months, the fiber concentrations (Cf) under equilibrium could be reliably estimated by SI-SPME in 1 day under agitated conditions or 20 days under static conditions in spiked sediments. The Cf values predicted by SI-SPME were statistically identical to those determined by Eq-SPME. The SI-SPME method was further applied successfully to field sediments contaminated with PCB 52, PCB 153, and bifenthrin. The increasing availability of stable isotope labeled standards and mass spectrometry nowadays makes SI-SPME highly feasible, allowing the use of SPME under nonequilibrium conditions with much shorter or flexible sampling time.

[Human biomonitoring and variation of haematic parameters in a population exposed to PCB and dioxin near a steel plant in the lower Susa Valley]. / Biomonitoraggio umano e variazione dei parametri ematici in una popolazione esposta a PCB e diossine presso un'acciaieria in bassa Val di Susa.

OBJECTIVE: to evaluate the degree of exposure to PCB in a population resident in the lower Susa Valley and its effects on general and endocrine homeostasis. DESIGN, SETTING, PARTICIPANTS AND MAIN OUTCOME MEASURES: in the lower Susa Valley (Piedmont, Italy), there is a steel secondary casting plant (i.e. by fusion of scrap iron), active since the '50s. The emissions of PCB and dioxin coming from the furnace were found in samples of herb, pulse and ground in a preliminary environmental characterisation study. During 2005-2006 we run an epidemiologic study of biomonitoring (measuring as outcome common haematochemical parameters, hormonal parameters, haematic PCB) on a sample of subjects resident in the municipalities with higher levels of PCB and dioxin contamination (exposed subjects), that was compared with another sample (unexposed) of subjects residing in other areas of the Susa Valley. RESULTS: the final sample consisted of 244 subjects (119 unexposed and 125 exposed), balanced by gender, age, education and representative of the Susa Valley population. The greater part of hormonal and toxic parameters showed worse values among exposed than among unexposed, including PCB median value (2.30 µg/l among exposed vs. 1.90 µg/l among unexposed). The difference however was not statistically significant and the values were lower than the population reference values (7.2 µg/l). Haematic PCB values were significantly and positively correlated with age and alcohol consumption and not significantly with male gender. The distribution of the principal haematochemical parameters (hemochrome, total, LDL and HDL cholesterol, triglycerides, glucose, creatinine, bilirubin, transaminases, gamma-glutamiltranspeptidase, proteine electrophoresis) showed also, on the whole, worse values among exposed compared to unexposed, even if the difference was not statistically significant for single values. CONCLUSIONS: the exposed population showed higher values of PCB haematic values and alterations of the hormonal and common heamatochemical parameters compared to unexposed population, even if within reference limits.

Bioavailability of hydrophobic organic contaminants in sediment with different particle-size distributions.

Few studies have been conducted examining the distribution of different-sized particles in sediment and its potential impact on bioavailability of sediment-associated contaminants. In the current study, three sediments composed of different particle sizes, i.e., fine (0-180 µm), combined (0-500 µm), and coarse (180-500 µm), were used to evaluate the bioaccumulation potential and toxicokinetic rates of four hydrophobic organic contaminants (HOCs) including two polychlorinated biphenyls (PCB-101 and PCB-118), a metabolite of an organochlorine insecticide (p,p'-DDE), and a polybrominated diphenyl ether (BDE-47) to the benthic oligochaete Lumbriculus variegatus. Two chemical approaches, Tenax extraction and matrix-solid phase microextraction (SPME), were also used to measure bioavailability of the sediment-associated HOCs. The uptake and elimination rates of HOCs by L. variegatus from coarse sediment were greater than those from fine sediment, although the biota-sediment accumulation factors (BSAFs) were not significantly different among sediments with different particle sizes. The freely dissolved HOC concentrations measured by matrix-SPME were greater in coarse sediment, however, no difference was found in uptake and desorption rates for the matrix-SPME and Tenax extraction measurements. Although BSAFs in L. variegatus were the same among sediments, kinetic rates of HOCs for organisms and freely dissolved HOC concentrations were lower in fine sediment, suggesting that sediment ingestion may also play a role in organism uptake, especially for HOCs in fine sediment.

PCDDs, PCDFs, PCBs, OC pesticides and mercury in fish and osprey eggs from Willamette River, Oregon (1993, 2001 and 2006) with calculated biomagnification factors.

The osprey (Pandion haliaetus) population nesting along the main stem Willamette River and lower Santiam River was first studied to evaluate contaminants and reproductive rates in 1993 when 78 occupied nests were present. By 2001, the population increased to 234 occupied nests, a 13.7% annual rate of population increase. A sample egg was collected from each of a series of nests along the Upper River (river mile 55-187) in 1993, 2001 and 2006 to evaluate trends of persistent contaminants (organochlorine [OC] pesticides, polychlorinated biphenyls [PCBs], polychlorinated dibenzo-p-dioxins [PCDDs], and polychlorinated dibenzofurans [PCDFs]). Nearly all OC pesticide residues decreased significantly, e.g., p, p'-DDE (DDE) from 2,350 to 1,353 to 210 microg/kg wet weight (ww). PCBs followed a similar pattern over time, e.g., SigmaPCBs 688 to 245 to 182 microg/kg ww, while PCDDs and PCDFs showed a more precipitous decline (often 85-95%) between 1993 and 2001, with no egg analyses warranted in 2006. During 2001-2002, sample osprey eggs were also collected from nests at three Headwater Reservoirs and two lower reaches (Newberg Pool and Tidal Portland) of the Willamette River, as well as the lower portion of the Santiam River to evaluate spatial residue patterns. Significant differences were seldom detected among the different sampling areas for OC pesticides (probably due to small sample sizes), although higher concentrations were often seen in the lower reaches, e.g., DDE 901 microg/kg ww (Headwater Reservoirs), 1,353 (Upper River), 1,384 (Newberg Pool) and 2,676 (Tidal Portland). PCB congener concentrations in eggs were usually higher in the Tidal Portland reach than at other locations and often significantly higher than at the Headwater Reservoirs or Upper River. Mercury (first analyzed in eggs in 2001), PCDDs and PCDFs were extremely low in 2001/2002 with no significant spatial patterns. Whole fish composite samples of largescale sucker (Catastomus macrocheilus) and northern pikeminnow (Ptychocheilus oregonensis), which account for about 90% of the biomass in the diet of this osprey population, were also collected from the Willamette River in 1993 and 2001 and analyzed for the same contaminants as osprey eggs. Contaminant residues in fish from the Upper River decreased between 1993 and 2001, paralleling findings for osprey eggs. Likewise, spatial patterns for fish residues paralleled findings for osprey eggs from the different reaches in 2001. A second empirical estimate of biomagnification factors (BMFs) from fish to osprey eggs for OC pesticides, PCBs, PCDDs and PCDFs (ww and lipid weight [lw] basis) was calculated based on residue data collected in 2001. The two independent BMF estimates (1993 and 2001) for each contaminant from the Upper River provide a measure of consistency, e.g., DDE (ww) 87 and 79, (lw) 103 and 112; SigmaPCBs (ww) 11 and 8.4, (lw) 13 and 12. Mercury did not biomagnify from fish to osprey eggs (BMF = 0.60). Legacy contaminants investigated had limited (perhaps only DDE), if any, effects on reproductive success of the increasing osprey population nesting along the Willamette River by 2001.

Development and use of real-time reverse transcription-polymerase chain reaction assay to quantify cytochrome P4501A1 expression in American mink.

The distribution of natural populations of American mink is restricted to locales that are in proximity to aquatic ecosystems. Because of the lipophilicity and persistence of polychlorinated biphenyls (PCBs) and reliance of mink on aquatic-based diets, mink at contaminated locales often bioacccumulate high levels of PCBs. In addition, in controlled laboratory studies, mink are highly sensitive at reproductive and developmental end points to the toxic effects of environmental PCB mixtures. It is believed that most, if not all, toxic effects of PCBs occur through activation of the aryl hydrocarbon receptor (AHR) pathway. Transcription of cytochrome P4501A1 (CYP1A1) by PCBs is also mediated through activation of AHR. Thus, levels of CYP1A1 mRNA provide a quantitative assay of exposure to and early biologic effect of PCBs on mink and may be predictive of toxicity at higher levels of biologic organization. We developed polymerase chain reaction (PCR) primers to amplify CYP1A1 as well as identified a housekeeping gene from mink cDNA. We used real-time reverse transcription-PCR to quantify and compare levels of hepatic CYP1A mRNA among groups of ranched mink kits and juveniles, which were fed diets or exposed in utero to fish that were low in PCBs (Atlantic herring) or to diets that were contaminated with three different levels of PCBs (carp) from Saginaw Bay, Lake Michigan. We found significant differences in CYP1A1 mRNA expression between mink fed the control diet and those fed a PCB-contaminated carp diet at all three treatment levels and exposure times. CYP1A1 mRNA was significantly induced 5.3- to 6.6-fold and 3.7- to 4.7-fold at 6 and 27 weeks, respectively. In previous studies, dietary exposures to PCB-contaminated carp were shown to cause mild to moderate lesions in the mandible and maxilla of these animals. This study demonstrates that hepatic CYP1A1 mRNA may be a sensitive biomarker of exposure of mink to environmentally relevant levels of PCBs and may be predictive of their effects in natural populations.

Persistent organic pollutants in fat of three species of Pacific pelagic longline caught sea turtles: Accumulation in relation to ingested plastic marine debris.

In addition to eating contaminated prey, sea turtles may be exposed to persistent organic pollutants (POPs) from ingesting plastic debris that has absorbed these chemicals. Given the limited knowledge about POPs in pelagic sea turtles and how plastic ingestion influences POP exposure, our objectives were to: 1) provide baseline contaminant levels of three species of pelagic Pacific sea turtles; and 2) assess trends of contaminant levels in relation to species, sex, length, body condition and capture location. In addition, we hypothesized that if ingesting plastic is a significant source of POP exposure, then the amount of ingested plastic may be correlated to POP concentrations accumulated in fat. To address our objectives we compared POP concentrations in fat samples to previously described amounts of ingested plastic from the same turtles. Fat samples from 25 Pacific pelagic sea turtles [2 loggerhead (Caretta caretta), 6 green (Chelonia mydas) and 17 olive ridley (Lepidochelys olivacea) turtles] were analyzed for 81 polychlorinated biphenyls (PCBs), 20 organochlorine pesticides, and 35 brominated flame-retardants. The olive ridley and loggerhead turtles had higher ΣDDTs (dichlorodiphenyltrichloroethane and metabolites) than ΣPCBs, at a ratio similar to biota measured in the South China Sea and southern California. Green turtles had a ratio close to 1:1. These pelagic turtles had lower POP levels than previously reported in nearshore turtles. POP concentrations were unrelated to the amounts of ingested plastic in olive ridleys, suggesting that their exposure to POPs is mainly through prey. In green turtles, concentrations of ΣPCBs were positively correlated with the number of plastic pieces ingested, but these findings were confounded by covariance with body condition index (BCI). Green turtles with a higher BCI had eaten more plastic and also had higher POPs. Taken together, our findings suggest that sea turtles accumulate most POPs through their prey rather than marine debris.

Bioaccumulation of PCBs from microplastics in Norway lobster (Nephrops norvegicus): An experimental study.

Plastic debris acts as a sorbent phase for hydrophobic organic compounds like polychlorinated biphenyls (PCBs). Chemical partitioning models predict that the ingestion of microplastics with adsorbed chemicals in the field will tend not to result in significant net desorption of the chemical to the organism's tissues. This is expected due to the often limited differences in fugacity of the chemical between the indigestible plastic materials and the tissues, which are typically already exposed in the same environment to the same chemicals as the plastic. However laboratory trials validating these model predictions are scarce. In this study, PCB-loaded microplastics were offered to field-collected Norway lobsters (Nephrops norvegicus) during in vivo feeding laboratory experiments. Each ingestion experiment was repeated with and without loading a mixture of ten PCB congeners onto plastic microspheres (MS) made of polyethylene (PE) and polystyrene (PS) with diameters of either 500-600 µm or 6 µm. We observed that the presence of chemicals adsorbed to ingested microplastics did not lead to significant bioaccumulation of the chemicals in the exposed organisms. There was a limited uptake of PCBs in Nephrops tail tissue after ingestion of PCB-loaded PE MS, while almost no PCBs were detected in animals exposed to PS MS. In general, our results demonstrated that after 3 weeks of exposure the ingestion of plastic MS themselves did not affect the nutritional state of wild Nephrops.

Body burdens of polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls and their relations to estrogen metabolism in pregnant women.

Polychlorinated dibenzo-p-dioxins (PCDDs, dioxins), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) are environmental endocrine disruptors that have half-lives of 7-10 years in the human body and have toxicities that probably include carcinogenesis. A high ratio of 4-hydroxyl estradiol (4-OH-E2) to 2-hydroxyl estradiol (2-OH-E2) has been suggested as a potential biomarker for estrogen-dependent neoplasms. In this cohort study of maternal-fetal pairs, we examined the relationship of PCDD/PCDF and PCB exposure to levels of estrogen metabolites in the sera of 50 pregnant women 25-34 years of age from central Taiwan. Maternal blood was collected during the third trimester, and the placenta was collected at delivery. We measured 17 dioxin congeners, 12 dioxin-like PCBs, and 6 indicator PCBs in placenta using gas chromatography coupled with high-resolution mass spectrometry. Estrogen metabolites in maternal serum were analyzed by liquid chromatography tandem mass spectrometry. The ratio of 4-OH-E2:2-OH-E2 decreased with increasing exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (beta=-0.124, p=0.004 by the general linear regression model, R=0.4). Meanwhile, serum levels of 4-OH-E2 increased with increasing concentrations of high-chlorinated PCDFs (i.e., 1,2,3,4,6,7,8-hepta-CDF: beta=0.454, p=0.03, R=0.30). Altered estrogen catabolism might be associated with body burdens of PCDDs/PCDFs. Our study suggests that exposure to PCDDs/PCDFs significantly affects estrogen metabolism. Therefore, PCDD/PCDF exposure must be considered when using the OH-E2 ratio as a breast cancer marker.

Seasonal variation of the distribution of PCBs in sediments and biota in a PCB-contaminated estuary.

To elucidate the effects of seasonal variation of precipitation on the distribution of polychlorinated biphenyls (PCBs) in estuarine sediments and benthic feeders, PCB concentrations of river surface sediments and mullet fish (Liza macrolepis) were investigated in the estuary of Er-Jen River near former PCB contamination sites before and after each wet season from 2002 to 2004. Analyses of grain size distribution and organic matter revealed that the pre-existing surface sediments were covered by and mixed with the soil particulates brought by surface runoff after each wet season. Obvious increment of PCB content and significantly elevated fraction (p<0.005) of light PCBs of the river mouth's sediments after each wet season indicated that the invading particles were rich in un weathered PCBs. PCBs previously buried in the surface soil of heavily contaminated sites were flushed into this estuary through surface runoff. The precipitation altered the PCB patterns in sediment organic matter, the dietary source of mullet, and consequently changed that of mullets accordingly, which all possessed significant greater fraction of light PCBs. In this study, it was demonstrated that seasonal summer precipitation affected the distribution of PCBs on surface sediments and the mullets of this estuary. PCB residuals retained in this region still pose potential threats to biota resided here.

Availability of polychlorinated biphenyls (PCBs) and lindane for uptake by intestinal Caco-2 cells.

Children may ingest contaminated soil from hand to mouth. To assess this exposure route, we need to know the oral bioavailability of the contaminants. Two determining steps in bioavailability of soil-borne contaminants are mobilization from soil during digestion, which is followed by intestinal absorption. The first step has been investigated in previous studies that showed that a substantial fraction of PCBs and lindane is mobilized from soil during artificial digestion. Furthermore, almost all contaminants are sorbed to constituents of artificial human small intestinal fluid (i.e., chyme), whereas only a small fraction is freely dissolved. In this study, we examine the second step using intestinal epithelial Caco-2 cells. The composition of the apical exposure medium was varied by addition of artificial chyme, bile, or oleic acid at similar or increasing total contaminant concentrations. The uptake curves were described by rate constants. The uptake flux seemed to be dose-dependent. Furthermore, different exposure media with similar total contaminant concentrations resulted in various uptake rates. This can be attributed to different freely dissolved concentrations and carrier effects. In addition, the large fractions of contaminants in the cells indicate that PCBs and lindane sorbed to bile, oleic acid, and digestive proteins contributed to the uptake flux toward the cells. These results can be extrapolated qualitatively to in vivo conditions. Because the sorbed contaminants should be considered available for absorption, the first step of mobilization from soil is the most important step for oral bioavailability of the presently investigated soil-borne contaminants.

Application of chitosan for treatment of wastewaters.

Research has clearly demonstrated that the biopolymer chitosan (deacetylated chitin) can be used as an effective coagulating agent for organic compounds, as a chelating polymer for binding toxic heavy metals, as well as an adsorption medium for dyes and small concentrations of phenols and PCBs present in various industrial wastewaters. In these specific applications, chitosan appears more effective than other polymers such as synthetic resins, activated charcoal, and even chitin itself. In addition, the amino group in chitosan is an effective functional group that can be altered chemically for production of other chitinous derivatives with specific useful characteristics as effective absorptive agents. Chitosans exhibiting different physicochemical characteristics, i.e., molecular weight, crystallinity, deacetylation, particle size, and hydrophilicity, differ in their effectiveness as waste treatment agents. The specific relationship between methods and the particular crustacean species used in preparation of chitosan for wastewater treatment needs further examination. Use of bioremediation approaches, combined with immobilization of specific microorganisms on immobilized chitinous columns, is an extremely promising area of current research and actual plant operation.

Bioconcentration of lipophilic organochlorines in ovine dentine.

The bioconcentration of lipophilic organochlorines in ovine dentine in comparison to adipose tissue was examined. Sheep were given a single dose (0.2-1.4 mg/kg body wt) of individual polychlorobiphenyl (PCB) congeners (tetrachlorobiphenyls IUPAC Nos. 54 and 80, and hexachlorobiphenyls IUPAC Nos. 155 and 169) and organochlorine pesticides 1,1-bis(4-chlorophenyl)-2,2-dichloroethene) (4,4'-DDE) and hexachlorobenzene (HCB). They were killed 2 months after the dose and teeth and adipose tissue were collected. For the extraction of organochlorines, dentine was treated ultrasonically with sulfuric acid and hexane. The concentration of organochlorines in dentine and adipose tissue was determined by high-resolution gas chromatography with electron-capture detection. The bioconcentration of 'planar' compounds (PCB-169, HCB) in dentine, compared to adipose tissue, was lower than that of 'non-planar' (PCB-155, 4,4'-DDE). Ratios of the non-planar to planar compounds PCB-155/-169 and 4,4'-DDE/HCB in dentine were 1.4 and 7.2, and in adipose tissue 0.5 and 2.4, respectively. The dentine:adipose tissue bioconcentration ratios (on a lipid basis) of PCB-54, -80, -155, -169, 4,4'-DDE and HCB were 47, 16, 0.3, 0.1, 3.2 and 1.0, respectively. The results indicate that the bioconcentration of organochlorines in different tissues cannot be based on lipid content only. It is suggested that the physicochemical properties of individual organochlorines, i.e. lipophilicity (K(ow)), diffusivity, metabolism and tissue-specific interactions, play a part in the different bioconcentrations of individual organochlorine pollutants in dentine compared to adipose tissue.

Risk assessment of dioxin contamination in human food.

Dioxins are highly toxic by-products of incineration processes and of production of chloro-organic chemicals. Accidental poisonings have occurred repeatedly. The main human exposure is via the dietary route. Species comparisons of toxic effects on the basis of ingested doses are not possible because of the highly differing toxicokinetics between humans and experimental animals. On the basis of internal doses or body burdens acute toxic and tumorigenic responses are observed at similar levels in humans and rats. PCB/PCDD/F contamination at levels which have been reported of marketed chicken meat and eggs in 1999 in Belgium may have increased body burdens by approximately 10%. However, it is estimated that a several hundred-fold higher uptake would be necessary to reach body burdens leading to overt toxicity in normal human subjects.

Toxicological consequences of feeding PCB congeners to infant rhesus (Macaca mulatta) and cynomolgus (Macaca fascicularis) monkeys.

In a study designed to minimize interspecies extrapolation of toxicological data, nine rhesus (Macaca mulatta) and 15 cynomolgus (M. fascicularis) day-old infant monkeys were separated from their dams following parturition and hand-reared using a liquid non-human primate formulation. The infants were randomly divided into a control and a treated group which received a mixture of polychlorinated biphenyl (PCB) congeners analogous to those found in breast milk from Canadian women. The concentration of congeners in the dosing media resulted in each infant receiving a total of 7.5 microg PCB congeners/kg body weight/day. The congeners were added either to the liquid formulation or to corn oil and administered to the back of the monkey's mouth for 20 weeks. Monthly blood and adipose specimens were obtained during the dosing period and then periodically until the monkey was necropsied or taken off test (minimum of 66 weeks on test) for congener analysis. Parameters such as body weight, formula consumption, tooth eruption, somatic measurements, haematology and serum biochemistry were monitored throughout the study. In addition, a qualitative evaluation of the absorption and depletion of the various congeners was undertaken as was an immunological evaluation. For the monitored parameters, very few differences were found to be statistically significant. For the immunological parameters, the only statistically differences found were a reduction over time for immunoglobulins M and G antibodies to sheep red blood cells (cyno, P = 0.025; rhesus, P = 0.002) and a treatment-related reduction in the levels of the HLA-DR cell surface marker (mean percent, P = 0.016; absolute levels, P = 0.027). There were some qualitative differences regarding absorption and depletion rates for the various congeners, but it could not be definitely ascertained whether these differences were due to species differences or dosing mode. However, statistically significant differences were found for treatment (P = 0.0293) as well as for species and vehicle regarding the concentration of PCB in blood (species;--P = 0.0399; treatment--P = 0.0001) and adipose tissue (species--P = 0.0489; treatment--P = 0.0001).

Contaminant levels in sediments and asteroids (Asterias rubens L., Echinodermata) from the Belgian coast and Scheldt estuary: polychlorinated biphenyls and heavy metals.

The Southern Bight of the North Sea is particularly exposed to anthropogenic contamination, due to heavy urbanisation and industrialisation of its catchment area. The present work focuses on polychlorinated biphenyl (PCB) and metal contamination of the marine environment along and off the Belgian coast. Its objectives were to compare the concentrations of seven PCB congeners and four heavy metals in the sediments (a repository for anthropogenic contaminants) and in the asteroid Asterias rubens (a recognized bioindicator species). Nineteen sampling stations were considered between the mouth of the Scheldt Estuary and the southern limit of the Belgian coast (asteroids were found in 10 out of the 19 stations). PCB and metal concentrations measured in sediments and asteroids were in the range of values reported in previous studies. Stations under direct influence of the Scheldt were the most impacted by the considered contaminants. Metal concentrations varied according to the grain-size fraction considered. In asteroids, PCBs and metals were found to be selectively distributed among body compartments, and pyloric caeca were found to most efficiently discriminate between sampling stations contamination levels. PCB and metal analysis of sediments provided a physicochemical evaluation of the contamination, whereas analysis of asteroids introduced a biological dimension to the approach by taking into account bioavailability of the contaminants.

Approach to risk assessment of chlorinated dioxins from Yusho PCB poisoning.

A Japanese was estimated to ingest 3 and 11 pg/kg/day of TEQ from PCDD/PCDFs and coplanar PCBs respectively through foods. A Japanese baby was calculated to consume 100-530 pg/kg/day level of TEQ through breast milk feeding, more than 60% being attributed to TEQ of coplanar PCBs. These intakes of TEQ were compared to the average (154 ng/kg/day) and minimum (28 ng/kg/day) intakes of Yusho, a PCB posioning occurred in Japan in 1968. There are three or four orders of magnitude difference between the daily TEQ intakes of general population and Yusho patients. However, the TEQ intakes by breast milk-fed babies of general population are at least 53 times less than the minimum intake of Yusho patients.

Investigating the role of desorption on the bioavailability of sediment-associated 3,4,3',4'-tetrachlorobiphenyl in benthic invertebrates.

Only a fraction of all sediment-associated hydrophobic organic contaminants are bioavailable, and a simple Tenax extraction procedure may estimate this fraction. Bioavailability is assumed to coincide with the rapidly and, possibly, slowly desorbing sediment-associated contaminant. River sediment was spiked with radiolabeled (14C) and nonradiolabeled (12C) 3,4,3',4'-tetrachlorobiphenyl (TCBP), and desorption kinetics using Tenax extraction were obtained at 10 degrees C and 22 degrees C. Bioaccumulation was measured in Lumbriculus variegatus, Chironomus tentans, and Hyalella azteca. Desorption of TCBP was triphasic at 22 degrees C and slowed at 10 degrees C to show only biphasic kinetics. The rapidly desorbing fractions decreased with increasing TCBP sediment concentration. The biota sediment accumulation factors, biota accumulation factors, and sediment clearance coefficients (ks) also decreased with increasing sediment TCBP concentration. The rapidly plus slowly desorbing fractions and the total TCBP desorbed when 99.9% of the rapidly desorbing fraction had desorbed were used to estimate bioavailable TCBP. These Tenax-based fractions did not explain the decreasing bioavailability with increasing TCBP load. Several factors, such as animal behavior and TCBP water solubility limitations, were evaluated to explain the concentration effect, but the most likely cause was severe diffusion limitations in whole sediment that were not predicted by the fully mixed Tenax extraction. Therefore, desorbing fractions determined by Tenax extraction overestimated the bioavailable fractions in sediments.

Tenax extraction mimics benthic and terrestrial bioavailability of organic compounds.

Biota to sediment accumulation factors (BSAFs) are widely used to describe the potential accumulation of organic contaminants in organisms. From field studies it is known that these BSAFs can vary dramatically between sediments of different origin, which is possibly explained by the variation in bioavailability of organic contaminants in sediments. In the present study it is shown that the variability in BSAF values for different sediment samples obtained at two Dutch freshwater sites could largely be explained by the variation in Tenax-extractable concentrations in these sediments. Variations of a factor of about 50 could be explained. The ratio between concentrations in biota and Tenax-extractable concentrations in sediment varied slightly between sediments and contaminant class, but was close to the theoretically expected value of 2. This is a strong indication that Tenax-extractable concentrations of contaminants in sediments are an excellent indicator of available concentrations.

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.

[Stimulation of the fecal excretion of polychlorinated biphenyls (KC-600) by diets containing rice bran fiber and cholestyramine].

Among the eight kinds of dietary fiber tested, rice bran fiber (RBF) mostly bound Kanechlor 600 (PCB) in vitro. The PCB bound to dietary fiber was in proportion to the lignin content in dietary fiber. We investigated whether RBF, lignin, cholestyramine and their combination stimulate the fecal excretion of PCB in rats. In the group fed a diet containing 10% (w/w) RBF, fecal excretion of PCB was stimulated. In the group fed a diet containing 10% (w/w) RBF and 5% (w/w) cholestyramine, more PCB was excreted in the feces. However, the group fed a diet containing 10% (w/w) RBF and 5% (w/w) lignin excreted the same amount of PCB as the group fed a diet containing 10% (w/w) RBF. The total PCB excreted into the feces for 21 days in the groups fed 10% (w/w) RBF, 10% (w/w) RBF and 5% (w/w) lignin, 5% (w/w) cholestyramine and 10% (w/w) RBF and 5% (w/w) cholestyramine diet was 3.4, 3.8, 2.3 and 5.7 times, respectively, that of the control. The stool transit time of rats fed 10% (w/w) RBF and 5% (w/w) cholestyramine diet was one hour faster than that of rats fed a 5% (w/w) cholestyramine diet. Therefore, we concluded that RBF has the greatest effect when administered in combination with cholestyramine on the fecal excretion of PCB.