Microplastic particles in river sediments and water of southwestern Nigeria: insights on the occurrence, seasonal distribution, composition, and source apportionment.

Microplastics (MPs) are globally recognized as an emerging environmental threat, particularly in the aquatic environment. This study presents baseline data on the occurrence and distribution of MPs in sediments and surface water of major rivers in southwestern Nigeria. Microplastics were extracted by density separation and polymer identification using Fourier transformed infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR). The abundance of MPs in surface sediment and water samples across all locations ranged from 12.82 to 22.90 particle/kg dw and 6.71 to 17.12 particle/L during the dry season and 5.69 to 14.38 particle/kg dw and 12.41 to 22.73 particle/L during the wet season, respectively. On average, fiber constituted the highest percentage of MP in sediments (71%) and water (67%) while foam accounted for the lowest values of 0.6% and 1.7%, respectively. Polypropylene (PP) and polyethylene (PE) were the main MPs across all locations based on Fourier transform infrared spectroscopy (FTIR). MPs of size < 1 mm were the most abundant (≥ 55%) on average in both water and sediments. The study identified run-off from human activities and industrial wastewater as potential sources of MP exposure based on positive matrix factorization. The study suggests assessing the impact of different land-use activities on MPs occurrence and distribution in addition to quantifying MPs in seafood as a way forward in food safety management systems for further studies. This study confirmed the occurrence and widespread distribution of MPs in surface water and sediments and provides a database on MP pollution in Nigeria.

Occurrence and probabilistic risk assessment of polycyclic aromatic hydrocarbons in blood and urine of auto-mechanics in Akure Metro, Nigeria.

This study provides baseline data on the concentration of polycyclic aromatic hydrocarbons (PAHs) in blood and urine samples of auto-mechanics, using Nigeria as a case study. Eighteen auto-mechanics participated in the study excluding two controls. The concentrations for the ΣPAHs across all participants (excluding control) ranged from 1.67 to 3.30 (2.17 ± 0.58) in blood with a significantly higher (P < 0.05) range of 7.61 to 10.76 (8.69 ± 1.00) in urine. The high molecular weight PAHs (4-6 rings) dominated the PAH profile in both blood (≥ 92%) and urine (≥ 87%) across all locations. Dibenz(a)anthracene was the most distributed PAH, while acenaphthene and indeno(1,2,3-cd)pyrene were the least distributed. The dermal route constituted approximately 99% of the total chronic exposure, followed by ingestion, and the least via inhalation. The hazard index (HI) was below the safe thresholds (HI = 1), suggesting non-carcinogenic PAH effects. However, all the participants including control samples had carcinogenic risk (CR) values above the acceptable level of 10-6 in both blood and urine samples. The carcinogenic and mutagenic potencies were higher in urine than in blood. The results suggest less acute toxicity and more potential chronic effects. The computed elimination ratio (> 1) suggests low excretion in urine and a potentially harmful trend. Molecular diagnostic ratios and principal component analysis suggest mixed PAH sources. The study revealed biomonitoring solely dependent on blood analysis may greatly underestimate health risks due to PAH exposure. To the best of our knowledge, this study is the first to provide levels of PAHs in the blood and urine of Nigerian mechanics. Findings herein will support policymakers at all levels in re-focusing attention to the less prioritized professions that pre-disposes people to PAHs and other emerging pollutants in society.

Concentrations and Toxic Equivalency of Polycyclic Aromatic Hydrocarbons (PAHs) and Polychlorinated Biphenyl (PCB) Congeners in Groundwater Around Waste Dumpsites in South-West Nigeria.

Polyaromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in groundwater and leachate around selected waste dumpsites from two southwestern states of Nigeria were investigated. Samples were Soxhlet-extracted using hexane/methylene chloride mixture and cleaned-up with preconditioned solid-phase extraction cartridges. The ∑PAHs (PCBs) (all in µg/L) in the boreholes, leachate, and hand-dug well across all locations ranged from below detection limit (BDL) to 0.62 (BDL to 0.067), 1.16 to 9.96 (0.003 to 0.041), and BDL to 0.01 (0.001-0.031), respectively. Low molecular weight-PAHs accounted for ≥61% of ∑PAHs detected across all locations. The highly chlorinated hexa-PCBs [2,2',3,4,4',5'-HeCB(#180), 2,2',3,4',5',6-HeCB(#34) and 2,2',4,4',5,5'-HeCB(#153)] dominated the entire congener profiles. Pyrene and 2,3',4,4',5-PeCB(#118) constituted 56% and 58% of the ∑PAHs and ∑PCBs, respectively. Sampled water is not adequately safe for drinking and may pose cancer risk. This study should be sustained for health risk and sustenance of an enduring ecological integrity.

Bioaccumulation and toxic potencies of polycyclic aromatic hydrocarbons in freshwater biota from the Ogbese River, Nigeria.

Samples of fish and shellfish (periwinkles, mussel, and snail) collected from the rapidly contaminated Ogbese River, Ondo State, Nigeria, were analyzed for their polycyclic aromatic hydrocarbon (PAH) levels by gas chromatography-mass spectrometry after cleanup using solid-phase extraction. The rank order of concentration of ΣPAHs in fish follows: gills >> eggs >>> muscle. The dry weight concentrations (µg/g) of total PAHs ranged from < 0.001 to 2.06, 0.01 to 18.67, 0.01 to 9.56, and 0.01 to 8.28 in fish muscle, periwinkle, snail, and mussel respectively. Accumulation levels of PAHs in the biota were used to calculate biota-sediment (or porewater) accumulation factors (BSAF (BPwAF)) and bioaccumulation factor (BAF). The lower molecular weight PAHs constitute major components (≥ 87% in each case) of PAH congener profiles. Bioaccumulation was greatest for PAHs with log Kow values between 5.0 and 5.6. However, the study did not show a good correlation between log Kow of individual PAH and the corresponding BSAFs/BPwAF for the biota. The study indicates that significantly greater (p < 0.05) BSAFs for ΣPAHs were observed in the three bottom dwellers than in fish muscle which suggests that the sediment-feeding behavior largely affected the extent of PAH bioaccumulation in the aquatic organisms. The calculated potency equivalent concentration (PEC) of total PAHs was above the recommended screening value (SV) in US EPA guidelines, suggesting great concern for human consumption. However, estimated excess cancer risk (ECR) induced by dietary exposure only suggests potential cancer risk. The study suggests urgent remediation of the river to safeguard public health.