Levels and health risk assessment of polycyclic aromatic hydrocarbons in protein foods from Lagos and Abeokuta, Southwestern Nigeria

Occurrence of BTX and PAHs in underground drinking water of coking contaminated sites: Linkage with altitude and health risk assessment by boiling-modified models

The safety of underground drinking water has received widespread attention. However, few studies have focused on the occurrence and health risks of pollutants in underground drinking water of coking contaminated sites. In this study, the distribution characteristics, sources, and human health risks of benzene, toluene, xylene (BTX) and polycyclic aromatic hydrocarbons (PAHs) in underground drinking water from a typical coking contaminated site in Shanxi of China were investigated. The average concentrations of BTX and PAHs in coking plant (CP) were 5.1 and 4.8 times higher than those in residential area (RA), respectively. Toluene and Benzene were the main BTX, while Acenaphthene, Fluorene, and Pyrene were the main PAHs. Concentrations of BTX/PAHs were negatively correlated with altitude, revealing altitude might be an important geological factor influencing spatial distribution of BTX/PAHs. PMF model demonstrated that the BTX/PAHs pollution in RA mainly originated from coking industrial activities. Health risk assessments were conducted by a modified US EPA-based model, in which environmental concentrations were replaced by residual concentrations after boiling. Residual ratios of different BTX/PAHs were determined by boiling experiments to be 9.4-93.8 %. The average total carcinogenic risks after boiling were decreased from 2.6 × 10-6 to 1.4 × 10-6 for adults, and from 4.3 × 10-6 to 2.1 × 10-6 for children, suggesting boiling was an effective strategy to reduce the carcinogenic risks from BTX/PAHs, especially for ingestion pathway. Monte Carlo simulation results matched well with the calculated results, suggesting the uncertainty was acceptable and the risk assessment results were reliable. This study provided useful information for revealing the spatial distribution of BTX/PAHs in underground drinking water of coking contaminated sites, understanding their linkage with altitude, and also helped to more accurately evaluate the health risks by using the newly established boiling-modified models.

Occurrence, source delineation, and health hazard of polycyclic aromatic hydrocarbons in tissues of Sarotherodon melanotheron and Chrysichthys nigrodigitatus from Okulu River, Nigeria

Polycyclic aromatic hydrocarbons (PAHs) are mistakenly consumed by people through their diet, including food and water. The occurrence, source, and health hazards of 16 PAHs in 36 tilapia (Sarotherodon melanotheron) and silver catfish (Chrysichthys nigrodigitatus) samples from Okulu River, Nigeria were investigated in this study. The total PAH concentration ranged from 11.70-24.20 to 13.40-19.60 µg/kg, being statistically different between the two species. The values were higher than the European Commission limits of 12 µg/kg and within the World Health Organization limit of 20 µg/kg. The 16 PAHs were detected in both fish species. The diagnostic ratio revealed that petroleum, fossil fuel, and incomplete combustion of biomass wastes were the sources of PAHs in the fishes. Pearson's correlation showed that the PAHs can come from diverse sources. The non-carcinogenic risk quotients (HQs) and hazard index (HI) in both fish species were 1, an indication of no adverse health effects. Among the 9 PAHs that were used to calculate the HI, BaP and BgP accounted for 31% and 62%, respectively, for Chrysichthys nigrodigitatus, and 25% and 69%, respectively, for Sarotherodon melanotheron. The carcinogenic hazard of the 7 PAHs assessed was within the acceptable range of 10^-6-10^-4. But the sum of the carcinogenic hazard was on the order of 10^-3 in both species of fish, an indication of carcinogenic health effects. 79% and 75% of the total carcinogenic risk for Chrysichthys nigrodigitatus and Sarotherodon melanotheron, respectively, are from DaA and InP. The consumption of PAHs by residents of the study area and other population groups through fish foods from the studied river underlines the importance of checking PAHs in aquatic foods for health concerns on a frequent basis.

A Review of Chemical Contaminants in Marine and Fresh Water Fish in Nigeria

Pollutants in aquatic food are a major global concern for food safety and are a challenge to both national and international regulatory bodies. In the present work, we have reviewed available data on the concentrations of polycyclic aromatic hydrocarbons (PAH), persistent organic pollutants, metals, and microplastics in freshwater and marine fish in Nigeria with reference to international maximum levels for contaminants in food and the potential risk to human health. While most of the contaminant levels reported for fish do not imply any health issues, iron and lead may represent potentially toxic levels in fish from specific areas. Studies on PAHs in marine fish are scarce in Nigeria, and the main focus is on the environmental pollution caused by PAHs rather than on their presence in food. The findings suggest that the consumption of smoked Ethmalosa fimbriata poses a higher potential carcinogenic risk than the other fish species that were investigated. Most of the other studies on PAHs in smoked fish are focused on the smoking method, and little information is available on the initial level of PAHs prior to the smoking process. Metal contamination in fish appeared to be affected by mineral deposits in the environment and industrial effluents. In general, heavy metal levels in fish are below the maximum levels, while there is limited data available on POPs of relevance to food safety in fish from Nigeria, particularly in terms of dioxins, brominated flame retardants, and fluorinated compounds. Furthermore, there is currently limited information on the levels of microplastics in fish from Nigerian waters. This work revealed the need for a more systematic sampling strategy for fish in order to identify the most vulnerable species, the hot spots of contaminants, and applicable food safety control measures for fish produced and consumed in Nigeria.

Quantitative versus qualitative risk assessment of meat and its products: what is feasible for Sub-Saharan African countries?

Prevalent risks in meat value-chains of sub-Saharan African (SSA) countries are increasingly attributed to microbial rather than chemical hazards. Resource constraints and lack of capacity has limited the utilization of risk assessment tools in the instituting of food controls to mitigate the risks. The review sought to bring to light the focus of risk assessment studies in SSA while generating evidence of feasible options to further the contribution of this component in risk mitigation. The informal street vending sector emerges as a priority in the meat value chain with a vendor population that are unwilling to abandon it. Campylobacter and Staphylococcus aureus are prevalent risks that have bedeviled this sector. However, limited risk assessment studies with capacity to inform proper food controls for the sector have been done. Evidence in place indicate that the incorporation of qualitative aspects in quantitative approaches serve as less-costly and effective ways of generating risk estimates. Limitations of capacity and gaps in epidemiological data are also circumvented. Considering that the street-vending sector is robust and its dynamics of operation are not fully in the picture of policy actors; incorporation of a participatory approach that combines qualitative and quantitative aspects of risk assessment is highly recommended.

Degradation of tricyclic polyaromatic hydrocarbons in water, soil and river sediment with a novel TiO2 based heterogeneous nanocomposite

Polycyclic aromatic hydrocarbons (PAHs), pervasive and precedence pollutants have potential to decimate the bionetwork and human health. Therefore, photocatalytic degradation of toxic three membered PAHs, namely acenaphthene (ACN), phenanthrene (PHN) and fluorene (FLU) was explored in water and soil. Titanium dioxide based zinc hexacyanoferrate framework (TiO₂@ZnHCF) nanocomposite was synthesized via a two step A. indica mediated co-precipitation method. Under sunlight, fall in concentration of PAHs (Water- 93%-96%, soil- 82%-86% and river sediment- 81.63%-85.43%) with time revealed superior activity of nanocomposite (TiO₂@ZnHCF) as compared to the bared one. Slower degradation in soil and sediment could be attributed to the reduced diffusion caused by the interaction between the organic content of soil/sediment with PAHs. Doping caused an increase in surface area (118.15 m²g^-1) with decrease in band gap energy (1.65 eV) and photoluminescence intensity. PAHs removal (X_m = 9.48 mg g^-1 of ACN, 9.35 mg g^-1 of PHN and 8.96 mg g^-1 of FLU) involved role of "cation- π" interaction with nanocomposite. Besides, it reduced t_1/2 values of ACN (1.88 h), PHN (2.09 h) and FLU (2.86 h) and resulted into smaller by-products. Smaller by-products like (Z)-prop-1-ene-1,2,3-triol (m/z = 91) and (E)-3-hydroxyacrylaldehyde (m/z = 71) identified in GC-MS, evidently braced e^- excitement from encapsulated nanocatalyst followed by OH (active species) based oxidation of PAHs. Lower photoluminescence intensity indicates the least charge carrier recombination with highest photocatalytic activity of nanocomposites. Inclusive of the present study provides promising photocatalyst with greater surface activity, low quantum yield with charge separation, reusable up to ten cycles deprived of substantial loss of its action and suppressing the cost of process.