Evidence of elevated levels of polychlorinated biphenyl congeners in commonly consumed fish from Eleyele Reservoir, Southwestern Nigeria

Role of niche and micro-habitat preferences in per- and polyfluoroalkyl substances occurrence in the gills of tropical lake fish species

The present study has investigated per- and poly-fluoroalkyl substances (PFAS) in the gill tissues of various fish species inhabiting different trophic levels within Eleyele Lake, a tropical freshwater lake in Nigeria. The mean concentrations of PFAS congeners were determined, and their trends and patterns were analyzed across different trophic species. The results revealed variations in congener abundance and species-specific patterns that was influenced by habitat and niche preferences. Multivariate associations using canonical-correlation analysis (CCA) revealed distinct trends in the relationships between gill concentrations of specific PFAS congeners and different trophic groups. The strongest congener relationships were observed in the pelagic omnivore (Oreochromic niloticus: ON) with positive associations for 4:2 FTS, 9CL-PF3ONS, PFTDA, MeFOSA and PFHxS. The differences in congener profiles for the two herbivorous fish (Sarotherodon melanotheron (SM) and Coptodon galilaeus (CG)) reflect possible divergence in microhabitat and niche preferences. Furthermore, the congener overlaps between the herbivore (CG), and benthic omnivore (Clarias gariepinus: ClG) indicate a possible niche and microhabitat overlap. Our study provides valuable insights into the congener dynamics of PFAS at Eleyele Lake. However, the dissimilarity and overlapping PFAS congener profile in fish gills reflects the interplay of species niche preference and microhabitat associations. The present study highlights the need for further research to assess ecological risks and develop effective PFAS management strategies.

Organochlorine pesticides and polychlorinated biphenyls in city drains in Makurdi, central Nigeria: Seasonal variations, source apportionment and risk assessment

A study of seasonal variation, sources and potential risks of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in open city drains in Makurdi, Central Nigeria was carried out. OCPs and PCBs were quantified using gas chromatograph-mass spectrometer. The total (∑₈OCPs) concentrations (ngL^-1) of OCPs in water was 2.99 with a mean ± SD of 0.75 ± 0.12 during wet season, while during dry season, the values were 11.43 and 2.86 ± 1.54 respectively. In sediment, the total concentration (ngg^-1) of OCPs was 5270.66 with a mean ± SD of 1756.89 ± 450.01 during wet season and a total concentration of 5837.93 and the mean ± SD of 1945.98 ± 646.04, during dry season. Source apportionment of OCPs suggested historic application of the pollutants. The total (∑₇PCBs) concentration (ngL^-1) of PCBs in water was 0.24 with a mean ± SD of 0.03 ± 0.02 during wet season and a total concentration of 0.61 with a mean ± SD of 0.09 ± 0.11 during dry season. The total concentration (ngg^-1) of PCBs in sediment was 37.88, mean ± SD of 5.41 ± 5.93 during wet season and a total of 47.07 and mean ± SD of 6.72 ± 7.27 during dry season. Ecological risk assessment based on effect range low (ERL) and effect range median (ERM) or threshold effect level (TEL) and probable effect level (PEL) that ecological risks were possible for some OCPs in this study, which calls for source control and remediation of the affected sites. Toxicity equivalency (TEQ) of PCB-118, the dioxin-like congener, indicated that it was most harmful to humans/mammals followed by birds, then fish.

Utility of cockroach as a model organism in the assessment of toxicological impacts of environmental pollutants

Environmental pollution is a global concern because of its associated risks to human health and ecosystem. The bio-monitoring of environmental health has attracted much attention in recent years and efforts to minimize environmental contamination as well as to delineate toxicological mechanisms related to toxic exposure are essential to improve the health conditions of both humans and animals. This review aims to substantiate the need and advantages in utilizing cockroaches as a complementary, non-mammalian model to further understand the noxious impact of environmental contaminants on humans and animals. We discuss recent advances in neurotoxicology, immunotoxicology, reproductive and developmental toxicology, environmental forensic entomotoxicology, and environmental toxicology that corroborate the utility of the cockroach (Periplaneta americana, Blaptica dubia, Blattella germanica and Nauphoeta cinerea) in addressing toxicological mechanisms as well as a sensor of environmental pollution. Indeed, recent improvements in behavioural assessment and the detection of potential biomarkers allow for the recognition of phenotypic alterations in cockroaches following exposure to toxic chemicals namely saxitoxin, methylmercury, polychlorinated biphenyls, electromagnetic fields, pharmaceuticals, polycyclic aromatic hydrocarbon, chemical warfare agents and nanoparticles. The review provides a state-of-the-art update on the current utility of cockroach models in various aspects of toxicology as well as discusses the potential limitations and future perspectives.

Bioaccumulation of Polychlorinated Biphenyls (PCBs) in Fish Host-Parasite Bentho-Pelagic Food Chain in Epe Lagoon, Lagos, Nigeria

This paper investigates the concentrations of PCBs in the water and sediment media and its bio-concentration in the fish host-parasite bentho-pelagic food chain in Epe lagoon. Samples of water, sediment, plankton, mollusks, fish and intestinal helminth parasites were collected from three stations (Oriba, Imode and Ikosi) in Epe Lagoon. Concentration of total PCBs in the surface water and sediment across the stations ranges from 3.20 to 6.00 ppb and 405.50-860.70 ppb respectively. Imode had the highest concentrations. The plankton bio-concentrates most PCBs in Ikosi (286.70 ppb) followed by Imode concentration (165.40 ppb), then Oribo (92.60 ppb) with total bio-concentration of 544.60 ppb. Surface water temperature negatively and strongly correlates with PCBs in the plankton. The planktons bio-concentrates total PCBs 44 times than that in the surface water. Chrysichthys nigrodigitatus bio-concentrates total PCBs 48 times than that in the surface water. Bioaccumulation of PCBs in human food chain could pose health risk.

Enantioselective Toxicity in Adult Zebrafish ( Danio rerio) Induced by Chiral PCB91 through Multiple Pathways

This study aimed to further investigate the toxic mechanism of chiral polychlorinated biphenyl (PCB) 91 in adult zebrafish ( Danio rerio) exposed to racemic (rac-), (+)-, or (-)-PCB91 for 63 days. The enantioselective mortalities of adult zebrafish exposed to rac-/(+)-/(-)-PCB91 were 95.86, 50.08, and 81.50%, respectively. Tubular necrosis and cellular hypertrophy occurred in the kidneys of (-)-PCB91-treated groups, whereas demyelination and immune cell infiltration occurred in brains of the rac-, (+)-, and (-)-PCB91-treated groups. Additionally, exposure to chiral PCB91 enantioselectively induced neurotoxicity, apoptosis, and inflammation in brain tissues owing to perturbations of gene expression, protein content and sphingolipid levels. The high mortality after rac-/(+)-PCB91 exposure might be due to toxic effects on brain tissue, while the high mortality after (-)-PCB91 exposure might be due to toxic effects on kidney as well as brain tissues. Thus, our findings offer an important reference for elucidating the enantioselective toxicological mechanism of chiral PCBs in aquatic organisms.

Assessment of the Pollution Status of Eleyele Lake, Ibadan, Oyo State, Nigeria

BACKGROUND

Lakes are a vital water resource, but are adversely affected by pollutants such as heavy metals and polychlorinated biphenyls (PCBs) from urban, agricultural and industrial activities. This can give rise to potential pollution-related health problems such as cancer and infectious diseases. Risk assessments are necessary to determine the degree of pollution and its effects on human health and ecological systems.

OBJECTIVES

This study assessed the pollution status and a risk assessment was calculated to determine the degree of the pollution and its effects on the human health and the ecological system of Eleyele Lake in Ibadan, Nigeria.

METHODS

Physical and chemical parameters, heavy metals and PCBs were determined in the lake water using standard methods from December 2013 to February 2014 at ten different sites of anthropogenic activity.

RESULTS

Water pH ranged from 6.00-7.50, while electrical conductivity ranged from 205.00-221.00 μs/cm³. Dissolved oxygen ranged from 0.30-6.00 mg/L and total dissolved solids ranged from 105.00-113.00 mg/L. Phosphate levels ranged from 13-0.99 mg/L. Nitrate and sulphate in the dry season ranged from (3.10-3.80 and 35.81-40.97 mg/L) and (0.12-0.37 and 6.10-10.30 mg/L) in the wet season. Heavy metal concentrations were in the order cadmium (Cd) > zinc (Zn) > copper (Cu) > chromium (Cr) > lead (Pb) for the dry season and Cd > Zn > Cr > Pb > Cu for the wet season. Total PCBs ranged from 493.90-732.55 μg/L and 52.00-390.03 μg/L for the dry and wet seasons, respectively. All determined physical and chemical parameters were within permissible levels, while heavy metals and PCB concentrations were higher than permissible levels.

DISCUSSION

The hazard quotients and carcinogenic risk values were greater than acceptable limits, indicating that PCBs in Eleyele lake water pose adverse health effects to the local population. It was observed in this study that lower chlorinated PCBs were more prevalent than higher chlorinated PCBs. This may be attributed to the fact that the lower chlorinated PCBs are influenced by atmospheric deposition as a result of their volatility, and they are more susceptible to atmospheric transport than highly chlorinated PCBs.

CONCLUSIONS

PCBs possess serious health risks to the population that depends on the lake as a source of domestic water and its aquatic organisms. Efforts are needed to reduce anthropogenic influence on the lake through strict environmental controls.

Chiral PCB 91 and 149 Toxicity Testing in Embryo and Larvae (Danio rerio): Application of Targeted Metabolomics via UPLC-MS/MS

In this study, we aimed to investigate the dysfunction of zebrafish embryos and larvae induced by rac-/(+)-/(-)- PCB91 and rac-/(-)-/(+)- PCB149. UPLC-MS/MS (Ultra-performance liquid chromatography coupled with mass spectrometry) was employed to perform targeted metabolomics analysis, including the quantification of 22 amino acids and the semi-quantitation of 22 other metabolites. Stereoselective changes in target metabolites were observed in embryos and larvae after exposure to chiral PCB91 and PCB149, respectively. In addition, statistical analyses, including PCA and PLS-DA, combined with targeted metabolomics were conducted to identify the characteristic metabolites and the affected pathways. Most of the unique metabolites in embryos and larvae after PCB91/149 exposure were amino acids, and the affected pathways for zebrafish in the developmental stage were metabolic pathways. The stereoselective effects of PCB91/149 on the metabolic pathways of zebrafish embryos and larvae suggest that chiral PCB91/149 exposure has stereoselective toxicity on the developmental stages of zebrafish.

Concentration of polychlorinated biphenyl (PCB) congeners in the muscle of Clarias gariepinus and sediment from inland rivers of southwestern Nigeria and estimated potential human health consequences

The distributions of polychlorinated biphenyl (PCB) congeners were determined in sediment and muscle of the African sharptooth catfish (Clarias gariepinus) from the Ogun and Ona rivers, southwest Nigeria. In addition, the effect of PCB congeners on condition factor (CF) and associated human health risk was assessed using muscle levels for a noncarcinogenic hazard quotient (HQ) calculation. Elevated concentrations of high-molecular-weight (HMW) PCB congeners were detected in sediment and fish downstream of discharge points of both rivers. A significant reduction in fish body weight and CF was observed to correlate with high PCB congener concentrations in the Ona River. A principal component (PC) biplot revealed significant site-related PCB congener distribution patterns for HMW PCB in samples from the Ogun River (71.3%), while the Ona River (42.6%) showed significant PCB congener patterns for low-molecular-weight (LMW) congeners. Biota-sediment accumulation factor (BSAF) was higher downstream for both rivers, presenting PCB congener-specific accumulation patterns in the Ona River. Significant decreases in fish body weight, length and CF were observed downstream compared to upstream in the Ona River. The non-carcinogenic HQ of dioxin-like congener 189 downstream in both rivers exceeded the HQ = 1 threshold for children and adults for both the Ogun and Ona rivers. Overall, our results suggest that industrial discharges contribute significantly to PCB inputs into these rivers, with potential for significant health implications for neighboring communities that utilize these rivers for fishing and other domestic purposes.

Enantio-alteration of gene transcription associated with bioconcentration in adult zebrafish (Danio rerio) exposed to chiral PCB149

Enantioselective enrichment of chiral PCB149 (2,2’,3,4’,5’,6-hexachlorobiphenyl) was analysed in adult zebrafish (Danio rerio) exposed to the racemate, (−)-PCB149, and (+)-PCB149. Greater enrichment of (−)-PCB149 compared to (+) PCB149 was observed following 0.5 ng/L exposure; however, as the exposure time and concentration increased, racemic enrichment was observed in adult fish exposed to the racemate. No biotransformation between the two isomers was observed in fish exposed to single enantiomers. When zebrafish were exposed to different forms of chiral PCB149, enantioselective expression of genes associated with polychlorinated biphenyls (PCBs) was observed in brain and liver tissues and enantioselective correlations between bioconcentration and target gene expression levels were observed in brain and liver tissues. The strong positive correlations between expression levels of target genes (alox5a and alox12) and PCB149 bioconcentration suggest that prolonged exposure to the racemate of chiral PCB149 may result in inflammation-associated diseases. Prolonged exposure to (−)-PCB149 may also affect metabolic pathways such as dehydrogenation and methylation in the brain tissues of adult zebrafish. Hepatic expression levels of genes related to the antioxidant system were significantly negatively correlated with bioconcentration following exposure to (+)-PCB149.