Integrating data gap filling techniques: A case study predicting TEFs for neurotoxicity TEQs to facilitate the hazard assessment of polychlorinated biphenyls.

The application of toxic equivalency factors (TEFs) or toxic units to estimate toxic potencies for mixtures of chemicals which contribute to a biological effect through a common mechanism is one approach for filling data gaps. Toxic Equivalents (TEQ) have been used to express the toxicity of dioxin-like compounds (i.e., dioxins, furans, and dioxin-like polychlorinated biphenyls (PCBs)) in terms of the most toxic form of dioxin: 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). This study sought to integrate two data gap filling techniques, quantitative structure-activity relationships (QSARs) and TEFs, to predict neurotoxicity TEQs for PCBs. Simon et al. (2007) previously derived neurotoxic equivalent (NEQ) values for a dataset of 87 PCB congeners, of which 83 congeners had experimental data. These data were taken from a set of four different studies measuring different effects related to neurotoxicity, each of which tested overlapping subsets of the 83 PCB congeners. The goals of the current study were to: (i) evaluate an alternative neurotoxic equivalent factor (NEF) derivations from an expanded dataset, relative to those derived by Simon et al. and (ii) develop QSAR models to provide NEF estimates for the large number of untested PCB congeners. The models used multiple linear regression, support vector regression, k-nearest neighbor and random forest algorithms within a 5-fold cross validation scheme and position-specific chlorine substitution patterns on the biphenyl scaffold as descriptors. Alternative NEF values were derived but the resulting QSAR models had relatively low predictivity (RMSE ∼0.24). This was mostly driven by the large uncertainties in the underlying data and NEF values. The derived NEFs and the QSAR predicted NEFs to fill data gaps should be applied with caution.

Polychlorinated biphenyls: New evidence from the last decade.

Millions of pounds of polychlorinated biphenyl (PCB) compounds have been produced in multiple countries for industrial applications over the last several decades. PCB exposure induces various adverse health effects in animals and humans. Environmental and occupational exposures to PCBs have been associated with liver, kidney, endocrine, and neurodevelopmental adverse effects. We have collected and reviewed animal and human data cited in the US National Library of Medicine from 2000 to 2010. In brief, our review shows new evidence, that is, in animal studies, exposure to one of the PCBs, A1221, induces a significant alteration of serum luteinizing hormone. The effects were more profound in the F2 generation, particularly with respect to fluctuations in hormones and reproductive tract tissues across the estrous cycle. Morphological analyses of brain tissue from rats exposed to A1254 confirmed the results of an earlier work which showed that the relative size of the intra- and infrapyramidal (II-P) mossy fibers was smaller than that in the controls and also reduction in growth was selective for the II-P mossy fibers. PCB exposure increased anogenital distance and prostate size but decreased epididymal weight, epididymal sperm count, and motile epididymal sperm count. No effects were observed on testicular weight or size. The epidemiological data showed an association between diabetes mellitus prevalence and elevated concentrations of PCB 153. Additionally, prenatal PCB exposure studies were associated with a smaller thymic index at birth and could adversely affect immune responses to childhood vaccinations and resistance to respiratory infections. PCB exposure was also reported to adversely affect enamel development in children in a dose-dependent manner. Because PCBs and their metabolites are potential health hazards, understanding the risk factors associated with individual PCBs, PCB mixtures, and PCB metabolites is important. PCB exposures of vulnerable populations (pregnant women, fetuses, infants, and children) are of particular concern because of heightened sensitivity during this period of brain development.

Experimental study of catalytic hydro-dechlorination (HDC) of Aroclor 1232.

Polychlorinated biphenyls (PCBs) is a group of persistent organic pollutants that still requires remediation and reduction long after the production is discontinued. Aroclor 1232 is a commercial PCB mixture that has been much less studied. To address this void, this paper presented catalytic hydro-dechlorination (HDC) of Aroclor 1232 using palladium on activated carbon (Pd/AC) at atmospheric pressure. Experimental variables studied including three mild temperatures, 22.5 °C, 50 °C, and 80 °C, and four different co-catalyst loadings. This batch of Aroclor 1232 constituted of more than 83% of mono-, di-, and tri-, chlorinated biphenyls (CB), in addition to biphenyl, tetra- and penta CBs. HDC efficiency increased with temperature, and reached 99.9% within 4 h of reaction at 80 °C. HDC efficiency also increased with co-catalyst loading. HDC efficiencies followed the trend of para > meta > ortho positions among isomers. The increase of temperature and Et3N dosage are especially effective in dechlorination at ortho and meta positions. The apparent activation energy of Aroclor 1232 HDC was estimated as 25.57 kJ/mol based on pseudo-first order assumption, indicating that the reaction may be diffusion limited. Given the modest reaction conditions used, the HDC of Aroclor 1232 can potentially be a low-cost process.

Transfer and toxicokinetic modeling of non-dioxin-like polychlorinated biphenyls (ndl-PCBs) into accidentally exposed dairy cattle and their calves - A case report.

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that accumulate in tissues of exposed animals and humans. This case report refers ton=3 dairy cows accidentally exposed to non-dioxin-like PCBs (ndl-PCBs) of unknown origin on a German farm. At study start they had a cumulative total of 122-643 ng/g fat in milk and 105-591 ng/g fat in blood, consisting mainly of PCBs 138, 153, and 180. Two cows calved during the study and their calves were raised on their mothers' milk, resulting in cumulative exposure until slaughter. A physiologically based toxicokinetic model was developed to describe the fate of ndl-PCBs in the animals. The toxicokinetic behavior of ndl-PCBs was simulated in individual animals, including transfer of contaminants into calves via milk and placenta. Both the simulations and experimental data indicate that contamination via both routes is significant. In addition, the model was used to estimate kinetic parameters for risk assessment.

Concentrations of Persistent Organic Pollutants in Women's Serum in the European Arctic Russia.

Persistent organic pollutants (POPs) are heterogeneous carbon-based compounds that can seriously affect human health. The aim of this study was to measure serum concentrations of POPs in women residing in the Euro-Arctic Region of Russia. A total of 204 women from seven rural settlements of the Nenets Autonomous Okrug (NAO) took part in the study. We measured serum concentrations of 11 polychlorinated biphenyls (PCBs) and 17 organochlorine pesticides (OCPs) across the study sites and among Nenets and non-Nenets residents. Measurement of POPs was performed using an Agilent 7890A gas chromatograph equipped with an Agilent 7000 series MS/MS triple quadrupole system. The concentrations of all POPs were low and similar to findings from other Arctic countries. However, significant geographic differences between the settlements were observed with exceptionally high concentrations of PCBs in Varnek located on Vaygach Island. Both ΣDDT (p = 0.011) and ΣPCB (p = 0.038) concentrations were significantly lower in Nenets. Our main findings suggest that the serum concentrations of the legacy POPs in women in the Euro-Arctic Region of Russia are low and similar to those in other Arctic countries. Significant variations between settlements, and between Nenets and non-Nenets residents, were found. Arctic biomonitoring research in Russia should include studies on the associations between nutrition and concentrations of POPs.

A new marine sediment certified reference material (CRM) for the determination of persistent organic contaminants: IAEA-459.

A new marine sediment certified reference material (IAEA 459) with very low concentrations (µg kg-1) for a variety of persistent organic contaminants (POPs) listed by the Stockholm Convention, as well as other POPs and priority substances (PSs) listed in many environmental monitoring programs was developed by the IAEA. The sediment material was collected from the Ham River estuary in South Korea, and the assigned final values were derived from robust statistics on the results provided by selected laboratories which demonstrated technical and quality competence, following the guidance given in ISO Guide 35. The robust mean of the laboratory means was assigned as certified values, for those compounds where the assigned value was derived from at least five datasets and its relative expanded uncertainty was less than 40% of the assigned value (most of the values ranging from 8 to 20%). All the datasets were derived from at least two different analytical techniques which have allowed the assignment of certified concentrations for 22 polychlorinated biphenyl (PCB) congeners, 6 organochlorinated (OC) pesticides, 5 polybrominated diphenyl ethers (PBDEs), and 18 polycyclic aromatic hydrocarbon (PAHs). Mass fractions of compounds that did not fulfill the criteria of certification are considered information values, which include 29 PAHs, 11 PCBs, 16 OC pesticides, and 5 PBDEs. The extensive characterization and associated uncertainties at concentration levels close to the marine sediment quality guidelines will make CRM 459 a valuable matrix reference material for use in marine environmental monitoring programs.

Genomic instability in adult men involved in processing electronic waste in Northern China.

BACKGROUND: Managing and recycling electronic waste (e-waste), while useful and necessary, has resulted in significant contamination of several environments in China. The area around Tianjin, China has become one of the world's largest e-waste disposal centers, where electronics are processed by manually disassembly or burning, which can result in serious exposure of workers to a multitude of toxicants. OBJECTIVE: The present study assessed potential genomic damage in workers involved in recycling e-waste. METHODS: To detect cytogenetic and DNA damage, chromosomal aberrations (CA), cytokinesis blocking micronucleus (CBMN) and the comet assay were performed. Concentrations of some trace elements, markers of oxidative stress and polychlorinated biphenyls (PCBs) in whole blood or serum were measured, and relationships among the markers described above, age, and duration of exposure were analyzed. The profiles of expression of genes in lymphocytes in peripheral blood were assessed to determine the status of the regulation of genes involved in genome stability. RESULTS: Concentrations of 28 PCB congeners in the whole blood of the exposed group were significantly (P<0.001) greater than those in the control individuals. Frequency of CA (8.01%) and CBMN (26.3‰) in lymphocytes and the level of DNA damage in the lymphocytes and spermatozoa of the exposed men were also significantly (P<0.0001) greater than those of the controls. There were significant relationships between CA, CBMN, DNA damage and duration of exposure. Concentrations of malondialdehyde (MDA) and lead (Pb) in the blood serum were significantly greater, but activities of superoxide dismutase (SOD), glutathione (GSH) and concentrations of calcium (Ca) and magnesium (Mg) were lower in the serum of the exposed men. MDA, Pb, Ca and Mg were associated with the duration of exposure to handling e-waste. In males involved in handling of e-waste, there were 13 genes - ATM, ATR, ABL1, CHEK1, CHEK2, GADD45A, CDK7, GTSE1, OGG1, DDB1, PRKDC, XRCC1 and CCNH - for which expression of mRNA was up-regulated and 7 genes - BRCA1, GTF2H1, SEMA4A, MRE11A, MUTYH, PNKP and RAD50 - for which the expression of mRNA was down-regulated. CONCLUSIONS: A strong correlation between indicators of damage of DNA, which could result in instability of the genome, and duration of processing e-waste was observed. If proper procedures are not followed, there are significant risks to the health of the individuals involved in such activities.

Polychlorinated biphenyls (PCBs) in adult and juvenile mallards (Anas platyrhynchos) from the Hudson River, New York, USA.

The Hudson River, NY, USA is contaminated for over 300 km with polychlorinated biphenyls (PCBs) released from two General Electric (GE) capacitor plants. We collected adult and juvenile mallards (Anas platyrhynchos) from four different areas of the river; an area upstream of the GE plants (n = 38), two areas directly downstream of the GE plants (n = 41, n = 38), and an area more than 100 km downstream in the freshwater tidal river (n = 20). Collections occurred during July and August (2008) when ducks were flightless to ensure ducks were "resident" and exposures were local. Fat and muscle tissue were analyzed for PCBs. PCBs were detected in all samples, and mallards below the GE plant sites on the Hudson River had orders of magnitude higher concentrations of PCBs than those above the plants. Juvenile mallards from areas directly downstream of the GE plant sites tended to have higher PCB concentrations in fat than adults. The patterns of PCB congeners and homolog groups varied across the study areas, with areas directly downstream of the GE plants dominated by tetra-chloro biphenyls whereas samples from upstream and the freshwater tidal river tended towards higher chlorinated congeners. Congener patterns between male and female and juvenile and adult mallards were generally similar within study areas, with the exception of one area downstream of the GE plants where adult birds exhibited different patterns than juveniles. Evidence of PCBs from the GE plant sites was detected in the tidal Hudson River, more than 100 km downstream of the plant sites. More than 90% of the ducks collected in areas downstream of the GE plants but above the tidally influenced river exceed the USFDA tolerance level for PCBs in poultry, which should be a concern for consumers of waterfowl taken in proximity to the upper Hudson River.

Polychlorinated biphenyls (PCBs) in sediments/soils of different wetlands along 100-year coastal reclamation chronosequence in the Pearl River Estuary, China.

PCBs (polychlorinated biphenyls) were determined in sediment/soil profiles to a depth of 30 cm from three different wetlands (i.e., ditch wetlands, riparian wetlands and reclaimed wetlands) of the Pearl River Estuary to elucidate their levels, distribution and toxic risks along a 100-year chronosequence of reclamation. All detected PCB congeners and the total 15 PCBs (∑15 PCBs) decreased with depth along sediment/soil profiles in these three wetlands. The ∑15 PCBs concentrations ranged from 17.68 to 169.26 ng/g in surface sediments/soils. Generally, old wetlands tended to have higher PCB concentrations than younger ones. The dominant PCB congeners at all sampling sites were light PCB homologues (i.e., tetra-CBs and tri-CBs). According to the sediment quality guideline, the average PCB concentrations exceeded the threshold effects level (TEL, 21.6 ng/g) at most of the sampling sites, exhibiting possible adverse biological effects, which were dominantly caused by light PCB congeners. The total toxic equivalent (TEQ) concentrations of 10 dioxin-like PCBs (DL-PCBs) detected at all sampling sites ranged from 0.04 to 852.7 (10(-3) ng/g), mainly affected by PCB126. Only DL-PCB concentrations in ditch and riparian wetland sediments with 40-year reclamation histories (i.e., D40 and Ri40) exhibited moderate adverse biological effects according to SQGQ values. Principal component analysis indicated that PCBs in three wetland sediments/soils mainly originated from Aroclor 1016, 1242, and 1248. Correlation analysis showed that sediment/soil organic carbon content had a significant correlation with the concentrations of several PCB congeners (P < 0.05), whereas no significant correlations were observed between any PCBs congeners and grain size or aggregate content (P > 0.05).

Analysis of 19 PCB congeners in catfish tissue using a modified QuEChERS method with GC-MS/MS.

A simple approach to determine 19 PCB congeners in catfish tissue was presented. A modified QuEChERS method employing high solvent to sample ratio 10:1 was used to improve the extraction recovery of 19 PCB congeners. After salting out by shaking with anhydrous magnesium sulfate and sodium chloride, 1 mL of acetonitrile extract was pipetted into a 2-mL centrifuge tube containing anhydrous magnesium sulfate, primary secondary amine sorbent, and C-18 sorbent. The tube was then shaken and centrifuged to absorb fat and fatty acid residue present in the acetonitrile extract. The acetonitrile extract was analyzed by GC-MS/MS. The excellent sensitivity of GC-MS/MS allows for the direct injection of the samples to detect the low level of the PCB congeners. The method therefore is high throughput, uses fewer consumable lab supplies, and provides excellent sensitivity with an LOQ below 1 ng/g.

Polychlorinated biphenyls and organochlorine pesticides in human milk samples from two regions in Croatia.

We analyzed 20 polychlorinated biphenyls (PCBs) and seven organochlorine pesticides (OCPs) in milk samples collected during 2009-2011 from primiparae living in two different regions in Croatia. p,p'-DDE is the dominant organochlorine pesticide. α-HCH/γ-HCH and p,p'-DDE/p,p'-DDT ratios indicate that there is fresh input of γ-HCH in investigated population on both locations, while this is not applicable to p,p'-DDT. The PCB profile was dominated by higher chlorinated congeners. Non-ortho PCB congeners which have the highest TEF values were not detected in any of individual samples. Toxic equivalents for mono-ortho substituted PCB congeners indicated higher exposure to toxic PCBs in Zadar, but estimated daily intakes for both locations indicate that infants consuming mother's milk are not at risk of adverse effects caused by PCBs and OCPs. Our study builds on the previous research of human milk samples collected in Zagreb and reveals that over 10-year period, levels of investigated organochlorine compounds decreased significantly.

Polychlorinated biphenyls still pose significant health risks to northwest Atlantic harbor seals.

Polychlorinated biphenyls (PCBs) have been detected at relatively high concentrations in harbor seals, apex predators in the northwest Atlantic. As part of an ongoing assessment of the effects of PCBs on population health, we analyzed tri- to deca-PCBs in the liver of 56 harbor seals (6 adult males, 50 pups) and in 11 blubber samples (4 adult males, 7 pups) and examined tissue-specific accumulation patterns, biomagnification potential, and toxic implications of current PCB concentrations. Hepatic ∑30PCB concentrations (overall mean±standard deviation: 76,860±111,800 ng/g lipid weight, lw) were higher than blubber concentrations (48,180±69,420 ng/g lw). Regional trends were suggestive of fresh PCB inputs from the industrialized, densely populated southern coast of New England versus the rural north. The lack of temporal trends confirmed that tissue concentrations of PCBs have plateaued since the early 1990s. Tissue distribution of PCBs varied significantly by age and, surprisingly by gender among the pups. Principal Component Analysis (PCA) revealed that lighter PCBs are selectively transferred from mother to pup blubber in relation to lipid solubility (log Kow), but heavier PCBs may be efficiently transferred during late lactation from mother to pup liver. Biomagnification factors (BMFs) for ∑6PCBs from prey fish to adult male seals ranged from 90 to 547 in the liver and 88 to 532 in the blubber, and suggested that molecular structure and metabolic capacity were more important influences than log Kow on the retention of PCBs. Blubber concentrations of ∑30PCBs in 87% of the pups were an order of magnitude higher than recent toxic reference values (TRVs) calculated for ∑154PCBs in nursing harbor seals, suggesting that the pups are at risk for PCB-mediated toxicity at a vulnerable stage of development. Given the recurring pattern of epizootics in these seals, the health of the population is of concern.

Polychlorinated biphenyl (PCB) concentrations and congener composition in masu salmon from Japan: a study of all 209 PCB congeners by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS).

We collected two subspecies of masu salmon: Oncorhynchus masou masou from four localities (southern Sea of Japan northward to Hokkaido) and O. masou ishikawae from upstream from Ise Bay close to a heavy industrial area. All 209 PCB congeners were analyzed using HRGC/HRMS. PCA ordination of congener concentrations divided data into three groups: (i) ssp. masou from Hokkaido, (ii) ssp. masou from the other regions and (iii) ssp. ishikawae. The highest ∑ PCB concentration (40.39 ng/wet wt) was in ssp. ishikawae followed by ssp. masou from southern waters; however the TEQdioxin-like PCBs was highest in ssp. masou from southern water (1.96 pg-TEQdioxin-like PCBs/g wet wt.) due to the high proportion of congener #126 in its complement (#126 has the highest toxic equivalency factor among congeners). There is likely a contamination source offshore in the southern Sea of Japan and/or along the migratory route of ssp. masou.