Polychlorinated Biphenyls in Imported Fish

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) which have been described as organohalogenic and legacy contaminants that are hazardous to both wildlife and man. The paucity of ecotoxicological data on the PCB content in commercially important fish in Benin Metropolis, Nigeria, warranted this research. In this stead, the PCB profile in the Atlantic Herring (Clupea harengus, Family: Clupeidae, mean length=31.59 cm; Mean weight=274.98 g) marketed in Benin Metropolis, was determined via Gas Chromatographic technique in order to evaluate its suitability for human consumption and to provide baseline data for this contaminant in commercially important fish species. The summary statistics for the mean concentrations of detectable PCBs in C. harengus ranged from 0.019 mg/kg (PCB 118, 156) to 0.434 mg/kg (PCB 126), with a total of 0.581 mg/kg (w/w) while the mean concentrations of PCBs in C. harengus by market ranged from 0.012 mg/kg (PCB 118) at Santana market to 0.526 mg/kg (PCB 126) at New Benin market with no observed significant difference (p>0.05) in the mean concentrations of PCBs in fish between markets. The toxicity quotient (TQ) values for PCBs in C. harengus ranged from 0.0095 (PCB 118, 156) to 0.217(PCB 126) while the estimated daily intake (EDI) values in mg/person/day for PCBs ranged from 0.00076 (PCB 118, 156) to 0.017 (PCB 126). A toxic equivalency (TEQ) value of 0.04342 while the total PCB content in C. harengus according to market ranged from 0.469 mg/kg (Santana market) to 0.658 mg/kg (Uselu market). The total toxicity of mixtures (TTM) index was 0.291. The PCB levels in fish decreased below International threshold values suggesting suitability for human consumption. Continous monitoring of this fish species for toxic concentrations of PCBs was proferred.

Residual Levels of Polychlorinated biphenyls (PCBs) in the Atlantic Mackerel (Scomber scombrus, Linnaeus, 1758) Marketed within a Niger Delta Community

The residual levels of polychlorinated biphenyls (PCBs) in the Atlantic Mackerel, Scomber scrombrus (mean length 44.87 cm, mean weight 478.35 g) marketed in Asaba, Delta State, Nigeria, were determined by Gas Chromatographic (GC) technique in order to ascertain its suitability for human consumption. The summary statistics for the mean concentrations of detectable PCBs in S. scrombrus ranged from 0.04 mg/kg (PCB 153) to 0.65 mg/kg (PCB 126), with a total of 0.93 mg/kg while the mean concentrations of PCBs in S. scrombrus by market ranged from 0.02 mg/kg (PCB 153) at Cable market to 0.82 mg/kg (PCB 126) at Abraka market with no observed significant difference (p>0.05) in the mean concentrations of PCB 153 and PCB 169 in fish between markets. The toxicity quotient (TQ) values for PCBs in S. scrombrus ranged from 0.02 (PCB 153) to 0.33(PCB 126) while the estimated daily intake (EDI) values in mg/person/day for PCBs ranged from 0.00072 (PCB 138) to 0.026 (PCB 126). A toxic equivalency (TEQ) value of 0.0656 was recorded with PCB 126 having the highest Sub-TEQ value of 0.065 while the total PCB content in S. scrombrus according to market ranged from 0.67 mg/kg (Cable market) to 1.20 mg/kg (Abraka market). The observed PCB levels in fish fell below International threshold values indicating suitability for human consumption. However constant monitoring of this aquatic species for hazardous levels of PCBs was highly recommended.

Bioaccumulation Kinetics and Bio Concentration Factors of Few Polychlorinated Biphenyls: A Study on Freshwater Fish Puntius ticto

The present work aims to understand the bioaccumulation kinetics and bioconcentration factors (BCF) of the Polychlorinated Biphenyls (PCBs) PCB 126 and PCB 169 in tissues of fish Puntius ticto. A continuous fed system was used to carry out the study. Bioconcentration in the tissues of the fish has been summarised using a first order uptake model. Fish were exposed to the PCBs continuously for a period of 30 days and this exposure has been used to calculate the steady state of BCF. The gill tissue of P. ticto showed a maximum rate of bioaccumulation of 30.61 μg g-1 wet weight for PCB 169 and 19.91 μg g-1 wet weight for PCB 126 respectively. In this study, the regression coefficients (R2), were found to vary between 0.736 and 0.97. This is indicative of a good to high correlation between the PCB concentration and exposure time. Prediction of the Octanol water partition coefficient (Kow) has been carried out to demonstrate the hydrophobic property of PCB compounds and their attraction towards lipid. The actual calculated BCF values have been used to predict the Kow values. Results indicate that it is possible to correlate the Kow values with both the lipid content of the tissue and the exposure time, in case of either PCB, and that the burden of PCB differs from one tissue to another.

Skeletal Toxicity of Coplanar Polychlorinated Biphenyl Congener 126 in the Rat Is Aryl Hydrocarbon Receptor Dependent

Epidemiological evidence links polychlorinated biphenyls (PCBs) to skeletal toxicity, however mechanisms whereby PCBs affect bone are poorly studied. In this study, coplanar PCB 126 (5 μmol/kg) or corn oil vehicle was administered to N = 5 and 6 male and female, wild type (WT) or AhR −/− rats via intraperitoneal injection. Animals were sacrificed after 4 weeks. Bone length was measured; bone morphology was assessed by microcomputed tomography and dynamic histomorphometry. Reduced bone length was the only genotype-specific effect and only observed in males (p < .05). WT rats exposed to PCB 126 had reduced serum calcium, and smaller bones with reduced tibial length, cortical area, and medullary area relative to vehicle controls (p < .05). Reduced bone formation rate observed in dynamic histomorphometry was consistent with inhibition of endosteal and periosteal bone growth. The effects of PCB 126 were abolished in AhR −/− rats. Gene expression in bone marrow and shaft were assessed by RNA sequencing. Approximately 75% of the PCB-regulated genes appeared AhR dependent with 89 genes significantly (p < .05) regulated by both PCB 126 and knockout of the AhR gene. Novel targets significantly induced by PCB 126 included Indian hedgehog (Ihh) and connective tissue growth factor (Ctgf/Ccn2), which regulate chondrocyte proliferation and differentiation in the bone growth plate and cell-matrix interactions. These data suggest the toxic effects of PCB 126 on bone are mediated by AhR, which has direct effects on the growth plate and indirect actions related to endocrine disruption. These studies clarify important mechanisms underlying skeletal toxicity of dioxin-like PCBs and highlight potential therapeutic targets.