Toxicity and Risks Assessment of Polycyclic Aromatic Hydrocarbons in River Bed Sediments of an Artisanal Crude Oil Refining Area in the Niger Delta, Nigeria

Human health risks of PAHs in soil and vegetables from Tiga, Kano State, Nigeria

This study evaluates the concentrations of seventeen polycyclic aromatic hydrocarbons (PAHs) in soil and selected vegetable samples (onions, tomatoes, hot peppers, sweet peppers, and garden eggs) from Tiga agricultural locations in Kano State, Nigeria. Soil samples were collected from ten plots (depth profiles of 0-10 cm, 10-20 cm, and 20-30 cm) and combined at each depth to create composite samples. Additionally, 20 g of each vegetable were collected and divided into fruit, stem, and root components. Standard procedures were used for the extraction and clean-up of PAHs from both soil and vegetable samples, and instrumental analysis was conducted using SHIMADZU GC-MS (GC-17A). PAH levels in soil ranged from 1.20E-02 mg/kg to 3.80E-02 mg/kg, while vegetables showed concentrations from 1.00E-03 mg/kg to 8.90E-02 mg/kg. The 0-10 cm soil samples displayed higher PAH concentrations among all the depths studied, while the vegetables with the highest PAH concentration followed the trend: Onions > Sweet Pepper > Tomatoes > Hot Pepper > Garden Egg. Overall, total PAH concentrations in vegetables exceeded those in soil. Estimated daily PAH doses were below the Tolerable Daily Dose Limit set by FAO, indicating low health risks. Incremental lifetime cancer risk values also fell below US EPA acceptable levels (10E-06), suggesting negligible cancer risk while the hazard index was less than 1, implying no appreciable non-cancer health risks. PAH pollution was attributed to both petrogenic and pyrogenic sources. The findings of this study indicate that under the assessed conditions, the five vegetables evaluated from Tiga pose no significant risk and are considered safe for consumption.

PAHs in sediments and shrimps: Levels, sources, and risk estimation in a tropical coastal lagoon system near oil industry

Anthropogenic activities in the surrounding the Tehuantepec Isthmus Lagoon System (Mexican South Pacific) region are related to the emission of polycyclic aromatic hydrocarbons (PAHs), such as the Salina Cruz oil refinery, the combustion of fossil fuels, and the traditional agricultural method of "slash and burn." Therefore, PAHs have impacted shrimp fishery resources and increased human health risks of Indigenous communities such as Huaves and Zapotecos, increasing their vulnerability. PAHs were quantified in sediments and shrimp in dry, rainy, and cold front seasons; sources, ecotoxicological risk, and the bioconcentration factor in shrimp were estimated. Σ16PAHs in sediments were 166-5286.8 ng g-1 (dw) and for shrimp were 100.9-8155.8 ng g-1. Seasonal factors and Tehuano winds were essential in the PAHs distribution. Pyrogenic PAHs were dominant during the dry and the cold front seasons from industrial sources; meanwhile, petrogenic PAHs were dominant in the rainy season from river runoff and oil-fuel spill sources. PAHs levels were not correlated with organic matter in sediments (Spearman r = 0.1368, p = 0.4964). Petrogenic and pyrogenic PAHs sources were identified. The most concerning findings are the high bioaccumulation factor levels found in shrimp (553 for dibenzo[a,h]anthracene) and the identified environmental medium-high risk found in the fishery areas estimated by the Mean Maximum Permissible Concentration Quotient, which suggest a possible high health risk Indigenous communities in the region. This study could help to have better public policies in environmental management for tropical coastal ecosystems affected by the oil industry worldwide.

Seasonal variations, source apportionment, and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in sediments from Klip River, Johannesburg, South Africa

The widespread occurrence of polycyclic aromatic hydrocarbons (PAHs) in water bodies is a significant cause of concern due to their persistence and toxicity. This study aimed at assessing the qualitative and quantitative profile of 16 EPA PAHs present in sediment collected from nine sites along the Klip River, Johannesburg, South Africa. The target compounds were extracted from sediment by microwave-assisted extraction (MAE). The extraction method accuracy was evaluated by analyzing certified reference material of sediment (CRM-104). The total concentration of PAHs detected in sediment samples ranged from 1.46 to 7.41 mg/kg. High molecular weight (HMW) PAHs were found to be in higher concentrations for both low flow (24.5 mg/kg) and high flow (19.4 mg/kg) seasons compared to the lower molecular weight (LMW) PAHs, which had 11.1 mg/kg for low flow and 5.63 mg/kg for high flow seasons. For identification of source of PAHs in sediments, the diagnostic ratio was employed, which revealed the PAHs were from petrogenic and pyrogenic sources. Toxicity test using zebrafish embryo development test (ZFET) resulted in high mortality, low hatch rate, and high malformations, which indicated the contamination of sediments from the Klip River. These findings suggest that exposure to this water system poses risks to the environment, aquatic life, and humans who depend on it.

Long-term effects of petroleum mulch on concentration, health, and ecological risks of polycyclic aromatic hydrocarbons in sand dune soils of Khuzestan province, Iran

Environmental consequences of petroleum mulch application are crucial in regions prone to wind erosion and desertification. This study aimed to assess the long-term effects of petroleum mulching on soil polycyclic aromatic hydrocarbon (PAH) concentrations and the associated human and ecological risk indices. These indices include incremental lifetime cancer risk (ILCR), hazard index (HI), toxic equivalent concentration (TEQBaP), toxic unit (TU), and risk quotient (RQ) in soil samples from Khuzestan province, Iran. Soil samples were collected from two depths: surface soil (0-10 cm) and deep soil (10-50 cm) across four regions with varying durations of petroleum mulch application: less than 5 years (T5), 5-20 years (T20), 20-30 years (T30), and 30-40 years (T40), and a control sample without mulching. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the concentrations of 19 PAHs and 23 groups of alkylated PAHs (alkyl PAHs) in the soil. Petroleum mulching significantly impacted heavily contaminated soil samples (T5 and T20) with PAH levels ranging from 2.03 to 2.08 mg kg-1. Older samples (T30 and T40) showed lower contamination levels (0.29 and 0.41 mg kg-1), primarily due to the alkylated compounds. ILCR, HI, TEQBaP, TU, and RQ indices were highest in T5 and T20 surface samples, indicating high risk in T5 surface soil from RQ and moderate risk in the others, despite low cancer and non-carcinogenic risks. Although the risk from the compounds, particularly alkyl PAHs, has decreased over time, they could still adversely affect the ecosystem, emphasizing the use of environmentally friendly alternative mulches in such areas.

Distribution, levels, sources and risk assessment of polycyclic aromatic hydrocarbons in the bottom sediments of a Mediterranean river under multiple anthropopressures (Soummam River), Algeria

The Soummam River, a vital watercourse in Algeria is threatened by anthropogenic activities despite its protected wetland status. This study is the first to assess sediment pollution in the Soummam River, examining levels, compositions, sources of 16 PAHs and their effects on the environment and human health. Analysis employing Principal Component Analysis (PCA) and molecular diagnostic ratios pointed to petrogenic sources, likely stemming from petroleum leaks originating from aging pipeline and vehicles, as well as pyrogenic sources arising from vehicle exhaust and biomass combustion. Environmental and health risks were assessed through risk quotients (RQ), Sediments Quality Guidelines (SQG) and Total Lifetime Cancer Risk (TLCR). Ecological risk was found to range from moderate to high, with anticipated biological impacts, while cancer risk was deemed low. Toxicity assessment, measured by TEQ, revealed that the majority of monitoring stations exceeded safe levels. Consequently, urgent action by local authorities is warranted to implement ecosystem rehabilitation measures.

Polycyclic aromatic hydrocarbons in fish (fresh and dried) and public health in Nigeria: a systematic review

In Nigeria, environmental pollution linked with PAHs has been increasing, and PAHs in fish pose a threat to all, especially those that rely upon fish. This systematic review aimed at evaluating human health effect of PAHs concentration in dried and fresh fish in Nigeria. A systematic literature search was carried out on PubMed, MedLine, Web of Science and Science Direct, etc. From the total of 31 articles reviewed, 19 studies reported on fresh fish and 9 on dried fish. 54.8% of the selected research reported on high-level PAH accumulation in fresh fish. PAH contamination was mainly from petrogenic and pyrogenic sources. The major health outcomes from this study were cancer and non-carcinogenic risks, skin irritations, gastrointestinal, child deformities, respiratory disorders, emotional distresses, neurological and haematological effects. It is recommended that regulations be made to abate and monitor the environmental exposure of humans to PAHs to ameliorate the public health effects.

Risk assessment of polycyclic aromatic hydrocarbon infested sediments along the coast of Goa, India

Goa, a small state in India, is a tourist hotspot known for its coastline and beaches. Anthropogenic activities lead to pollution in the environment. Amongst many other pollutants, polycyclic aromatic hydrocarbons represent a major class of contaminants owing to their widespread distribution and protracted environmental persistence. No information is available about the levels of Polycyclic aromatic hydrocarbon (PAH) contamination in the sediments along the coastline of Goa. The study aimed to establish a baseline for PAH concentrations in the sediments along the shoreline to help comment on the pollution levels caused and thereby understand the risk and their impact on the marine life therein. The total concentration of PAHs along the selected sampling sites of the Goa coastline was 1.00 to 875 μg g-1. Maximum PAH concentrations were detected in the Divar island mangrove (875 μg g-1); the least was observed at Galgibaga beach (365 μg g-1). The results revealed that the sediment of the Goa coastline is heavily contaminated with PAH. Source apportionment of PAHs was analysed based on diagnostic ratios, and results exhibited that petroleum products and their combustion were primarily responsible for their generation. The results of risk quotients showed that the values are way above effect range median (ER-M), indicating these could pose a high risk to the ecosystem.

Outstanding Separation Performance of Oil-in-Water Emulsions with TiO2/CNT Nanocomposite-Modified PVDF Membranes

Membrane filtration is an effective technique for separating micro- and nano-sized oil droplets from harmful oil-contaminated waters produced by numerous industrial activities. However, significant flux reduction discourages the extensive application of this technology; therefore, developing antifouling membranes is necessary. For this purpose, various titanium dioxide/carbon nanotube (TiO₂/CNT) nanocomposites (containing 1, 2, and 5 wt.% multi-walled CNTs) were used for the modification of polyvinylidene fluoride (PVDF) ultrafilter (250 kDa) membrane surfaces. The effects of surface modifications were compared in relation to the flux, the filtration resistance, the flux recovery ratio, and the purification efficiency. TiO₂/CNT_2% composite modification reduced both irreversible and total filtration resistances the most during the filtration of 100 ppm oil emulsions. The fluxes were approximately 4-7 times higher compared to the unmodified PVDF membrane, depending on the used transmembrane pressure (510, 900, and 1340 L/m²h fluxes were measured at 0.1, 0.2, and 0.3 MPa pressures, respectively). Moreover, the flux recovery ratio (up to 68%) and the purification efficiency (95.1-99.8%) were also significantly higher because of the surface modification, and the beneficial effects were more dominant at higher transmembrane pressures. TiO₂/CNT_2% nanocomposites are promising to be applied to modify membranes used for oil-water separation and achieve outstanding flux, cleanability, and purification efficiency.

Legacy PAHs in effluent receiving river sediments near a large petroleum products depot in Enugu, Nigeria: Human health risks and economic cost of pollution

This study assessed the human health risk of exposure to legacy PAHs in the Nwaenebo River sediments that received effluents for over two decades from the Nigeria National Petroleum Corporation (NNPC) petroleum product Depot in Emene, Enugu, Nigeria. The study went further to estimate economic costs of the sediment PAHs pollution based on the human health risk of exposure. The human health risks were determined by estimating carcinogenic and mutagenic risks via Benzo[a]pyrene total potential equivalent (BaP TPE) and mutagenic equivalent quotient (MEQ). The economic costs of the sediment pollution comprised costs due to mortality and those due to morbidity and were estimated using the value of statistical lives (VSLs) and cost of illness (CoI), respectively. The study, with an appropriate selection of sampling points established that the NNPC petroleum Depot was responsible for the Nwaenebo River sediment PAHs pollution with ƩPAHs concentration 14.3-163 mg/kg. The carcinogenic and mutagenic risks varied from 1.3*10^-5 to 4.7*10^-5 and 1.4*10^-5 to 6.0*10^-5 respectively. Based on risk threshold of 10^-6, these risks were high. The long term economic costs of pollution of the sediments by the PAHs were estimated at 60.5 million USD and 0.46 million USD for mortality and morbidity costs, respectively.

Ecological risk assessment of priority PAHs pollutants in crude oil contaminated soil and its impacts on soil biological properties

Polycyclic aromatic hydrocarbons (PAHs) are one of the major toxic constituents of crude oil and therefore, an understanding on PAHs associated risks and their relationship with soil biological parameters are necessary for adopting effective risk-based and site specific remediation strategies in the contaminated soil. Here, risks evaluation of eight detected PAHs in terms of toxic equivalent concentration (TEQ_C), benzo(a)pyrene equivalent (BaPeq), contamination factor (CF), pollution load index (PLI), hazard quotient (HQ), hazard index (HI), toxic unit for individual PAHs (TU) and PAHs mixture (TU_m) have been evaluated. Besides, the effect of PAHs contamination on soil biological properties has also been investigated and correlated with PAHs concentrations. The TEQc of eight PAHs was recorded in the range of 0.06-5.0 mg kg^-1 soil_, whereas the BaPeq value was 25.3 mg kg^-1 soil which exceed the permissible limit. Similarly, CF (85.5-1668.2), PLI (322.8), HQ (311.7-8340.9), HI (26,443.8), TU (227.9-3821.6) and TU_m(7916.2) also exceed the permissible values for non-toxic conditions indicating carcinogenic risk for humans. Besides, activities of soil dehydrogenase, urease, alkaline-phosphatase, catalase, amylase and cellulase were decreased by 1.5-2.3 folds in the contaminated soil than control. The results of Pearson's correlation matrix also established negative impact of PAHs on the soil's biological properties.

Investigation of Indoor Polycyclic Aromatic Hydrocarbons (PAHs) in Rural Northeast China: Pollution Characteristics, Source Analysis, and Health Assessment

Due to the low winter temperatures in rural areas of Northeast China, biomass fuels are widely used for heating and cooking, resulting in increased concentrations of PAHs in rural indoor areas during the heating period and threatening human health. Therefore, exploring the pollution characteristics, source localization, and risk assessment of indoor PAHs in rural Northeast China is of great significance for improving rural indoor air quality. In this study, PAHs were collected from a residential building in rural Northeast China for one consecutive year (January 2020–December 2020), and their concentrations were determined to explore the distribution patterns and sources of PAHs to further assess the carcinogenic risk of PAHs to humans. The results of the study showed that the average concentration of indoor PAHs in rural areas during the heating period (93.02 ng/m3) was about 1.81 times higher than that of the non-heating period (51.26 ng/m3). The main sources of PAHs were mixed combustion of biomass and coal, motor vehicle emissions, and domestic waste combustion. The level of indoor PAHs pollution has posed a carcinogenic risk to the health of the rural population in the Northeast.