Human health risks associated with consumption of fish contaminated with trace elements from intensive mining activities in a peri-urban region

Element contamination of the Orange-Vaal River basin, South Africa: a One Health approach

Numerous low-income groups and rural communities depend on fish as an inexpensive protein source worldwide, especially in developing countries. These communities are constantly exposed to various pollutants when they frequently consume polluted fish. The largest river basin in South Africa is the Orange-Vaal River basin, and several anthropogenic impacts, especially gold mining activities and industrial and urban effluents, affect this basin. The Department of Environment, Forestry and Fisheries in South Africa has approved the much-anticipated National Freshwater (Inland) Wild Capture Fisheries Policy in 2021. The aims of this study were (1) to analyze element concentrations in the widely distributed Clarias gariepinus from six sites from the Orange-Vaal River basin and (2) to determine the carcinogenic and non-carcinogenic human health risks associated with fish consumption. The bioaccumulation of eight potentially toxic elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) was assessed in C. gariepinus from sites with different anthropogenic sources. The human health risks were determined to assess the potential risks posed by consuming contaminated C. gariepinus from these sites. Carcinogenic health risks were associated with fish consumption, where it ranged between 21 and 75 out of 10,000 people having the probability to develop cancer from As exposure. The cancer risk between the sites ranged between 1 and 7 out of 10,000 people to developing cancer from Cr exposure. A high probability of adverse non-carcinogenic health risks is expected if the hazard quotient (HQ) is higher than one. The HQ in C. gariepinus from the six sites ranged between 1.5 and 5.6 for As, while for Hg, it was between 1.8 and 5.1. These results highlight the need for monitoring programs of toxic pollutants in major river systems and impoundments in South Africa, especially with the new fisheries policy, as there are possible human health risks associated with the consumption of contaminated fish.

Distribution characteristics of microorganisms in sediments of Dagu River and their biological indicator function for evaluating eco-environmental quality of rural river

The microorganisms in sediments play a crucial role in biogeochemical cycle processes, and numerous studies have shown that microbial community is closely related to environmental factors. However, the usability of sediment microorganisms to evaluate the eco-environment quality of rural rivers has not been adequately explored. This study investigated the distribution characteristics and response of sediment microorganisms to environmental parameters and benthic organisms. Based on the environmental parameters and benthic community indices, the 12 stations were divided into high-polluted group A, moderate-polluted group B and low-polluted group C. Station DG01 and DG02 in group A had the highest level of As and Ni pollution and nutrient concentration, and DG09 in group A had the lowest benthic diversity. Correspondingly, group A had the lowest abundance of Proteobacteria, which has a higher requirement for the environment than Planctomycetes. Group B had the highest sulfide level (97.45 mg/kg), and bacteria (Thiobacillus, Sulfurisoma and Sulfuritalea) with genes involved in sulfur cycling were more enriched in this group. Group C had the lowest level of total nitrogen (243.36 mg/kg), and Rhodanobacteraceae in Xanthomonadales might be a key bioindicator for low nitrogen. In addition, Chlorophyta was found to be more susceptible to heavy metals, and moreover co-occurrence networks showed that microeukaryotes were more sensitive to heavy metal pollution compared to benthic animals and prokaryotes. Therefore, this study suggested that benthic microorganisms especially microeukaryotes could be used as good indicators for evaluating the eco-environmental quality of rural rivers.

Assessment of metals (Ni, Ba) deposition in plant types and their organs at Mersin City, Türkiye

The increase in heavy metal concentrations in the air, especially after the Industrial Revolution, is notable for the scientific world because of the adverse effects that threaten environmental and human health. Among the trace elements, nickel (Ni) is carcinogenic, and all barium (Ba) compounds are toxic. Trace elements are critical for human and environmental health. Their threat further increases, especially in the urban areas and surroundings with a high population. In urban areas, the trace element contamination in the airborne can be reduced using plants. However, which plant and plant organs absorb trace elements could not be determined. In the present study, Ni and Ba concentrations in the branch, wood, and leaf samples of 14 species collected from the city center of Mersin province were determined. As a result, broad-leaved species' Ni and Ba concentrations in their leaf sample were generally higher than other species. Almost all species had the lowest Ni and Ba concentrations in their wood samples. Among these 14 species, it was found that Ni concentration was very high, especially in non-washed leaves of Platanus orientalis, Photinia serrulata, and Citrus reticulate, and Ba concentration was very high in Citrus reticulata, Chamaecyparis lawsoniana, Laurus nobilis, and Acer hyrcanum. Using broad-leaved species in urban areas where pollution is at high levels will significantly contribute to reducing Ni and Ba pollution. It is recommended that these points be considered in future urban landscaping projects.

Mining wastewater treatment technologies and resource recovery techniques: A review

Mining wastewater can have adverse effects on the ecosystem; thus, treatment before discharging into the environment is of utmost importance. This manuscript reports on the effect of mining wastewater on the environment. Moreover, the currently used, effective and commercialised mine wastewater treatment technologies such as SAVMIN®, SPARRO®, Biogenic sulphide, and DESALX® are reported in this study. These technologies integrate two or more separation processes, which have been proven to be effective for the high recovery of salts and water for reuse. Some of the technologies reported can significantly recover salts and >95% of water. Modern pilot-stage and laboratory-scale treatment systems used for the recovery and removal of metals are also reported herein. Since some treatment technologies can generate highly toxic sludge and other waste products, the management of the generated waste was also considered. Some studies have focused on the treatment of wastewater at the laboratory level using the adsorption process. Most adsorbents exhibit promising results; however, there is insufficient research on reusability, toxic sludge management, and the economic analysis of the systems. Moreover, the implementation of adsorption systems in wastewater is necessary. Furthermore, the integration of treatment systems to recover precious metals at low concentrations is desirable in addition to water reclamation to achieve circular mine water.

Bioaccumulation of trace elements and hydrocarbons in chondrichthyans of the western Arabian Gulf: Environmental and human health risk assessment and implications for conservation

This is a first attempt to assess the levels of trace elements, PAHs, and TPHs in six elasmobranch species (Carcharhinus dussumieri, C. sorrah, Chiloscyllium arabicum, Gymnura poecilura, Sphyrna lewini, S. mokarran) from the Arabian Gulf. The chemical analysis showed that the concentrations of contaminants differed significantly between liver and muscle samples with both pelagic and benthic species and all families. For all species, contaminant concentrations were significantly higher in the liver than in the muscle. While muscle contaminant concentrations differed significantly with respect to species' lifestyles and families, those of liver showed no significant differences between pelagic and benthic species, neither between the four families nor between the six species. None of the analysed contaminants exceeded the internationally recognized standards in all studied species. These results enrich the knowledge on the bioaccumulation of contaminants in elasmobranchs and allow to assess the environmental status of the Arabian Gulf.

Element Concentrations in Muscle and Liver Tissue of Two Eel Species from the Incomati River, Mozambique

Many rural communities in Mozambique get their income from fisheries, as well as consume fish as an inexpensive source of protein. In Mozambique, fish consumption from small-scale fisheries dependent families can range between 60 and 150 kg/person/year. Anguillid eels have important social value to vulnerable local communities in the Incomati Basin. Anguillid eels in the lower Incomati Basin are targeted for consumption, as well as cultural rituals by traditional healers. The aim of the present study was to determine trace element concentrations in environmental matrices, bioaccumulation patterns in muscle and liver tissue of two Anguilla species (Anguilla mossambica and Anguilla marmorata), as well as the chronic health risk these elements pose to regular consumers in the lower Incomati River. Bioaccumulation of elements from the water had a higher effect on both muscle and liver tissues, where only the bioaccumulation of Pb in the sediments played a major role. From the human health risk assessment, Hg pose non-carcinogenic risk, whereas As, Cr, and Ni pose carcinogenic risks.

Variation in the burden and chemical forms of thallium in non-detoxified tissues of tilapia fish (Oreochromis niloticus) from waterborne exposure

Thallium (Tl) is highly toxic to aquatic ecosystems, but information about its concentration and distribution characteristics in different fish tissues is limited. In this study, juvenile tilapia (Oreochromis niloticus) were exposed to Tl solutions with different sub-lethal concentrations for 28 days, and the Tl concentrations and distribution patterns in the fish non-detoxified tissues (gills, muscle, and bone) were analyzed. The Tl chemical form fractions, Tl-ethanol, Tl-HCl, and Tl-residual, corresponding to easy, moderate, and difficult migration fraction, respectively, in the fish tissues were obtained by sequential extractant approach. The Tl concentrations of different fractions and total burden were determined using graphite furnace atomic absorption spectrophotometry. Exposure-concentration effect determined the Tl burden in the fish tissues. The average Tl-total concentration factors were 360, 447, and 593 in the bone, gills, and muscle, respectively, and the limited variation during the exposure period indicates that tilapia have a strong ability to self-regulate and achieve Tl homeostasis. However, Tl fractions varied in tissues, and the Tl-HCl fraction dominated in the gills (60.1%) and bone (59.0%), switchover Tl-ethanol fraction dominated in the muscle (68.3%). This study has shown that Tl can be easily taken up by fish during 28-days-period and largely distributed in non-detoxified tissues especially muscle, in which concurrent risks of high Tl-total burden and high levels of Tl in the form of easy migration fraction, posing possible risks to public health.

Mitochondrial DNA Corroborates the Genetic Variability of Clarias Catfishes (Siluriformes, Clariidae) from Cameroon

The airbreathing walking catfish (Clariidae: Clarias) comprises 32 species that are endemic to African freshwater systems. The species-level identification of this group is challenging due to their complex taxonomy and polymorphism. Prior to this study, the biological and ecological studies were restricted to a single species, Clarias gariepinus, resulting in a biased view of their genetic diversity in African waters. Here, we generated the 63-mitochondrial Cytochrome c oxidase subunit 1 (COI) gene sequences of Clarias camerunensis and Clarias gariepinus from the Nyong River in Cameroon. Both C. camerunensis and C. gariepinus species maintained adequate intra-species (2.7% and 2.31%) and inter-species (6.9% to 16.8% and 11.4% to 15.1%) genetic distances with other Clarias congeners distributed in African and Asian/Southeast Asian drainages. The mtCOI sequences revealed 13 and 20 unique haplotypes of C. camerunensis and C. gariepinus, respectively. The TCS networks revealed distinct haplotypes of C. camerunensis and shared haplotypes of C. gariepinus in African waters. The multiple species delimitation approaches (ABGD and PTP) revealed a total of 20 and 22 molecular operational taxonomic units (MOTUs), respectively. Among the two Clarias species examined, we found more than one MOTU in C. camerunensis, which is consistent with population structure and tree topology results. The phylogeny generated through Bayesian Inference analysis clearly separated C. camerunensis and C. gariepinus from other Clarias species with high posterior probability supports. The present study elucidates the occurrence of possible cryptic diversity and allopatric speciation of C. camerunensis in African drainages. Further, the present study confirms the reduced genetic diversity of C. gariepinus across its native and introduced range, which might have been induced by unscientific aquaculture practices. The study recommends a similar approach to the same and related species from different river basins to illuminate the true diversity of Clarias species in Africa and other countries.

Bioaccumulation of trace metals in Neoechinorhynchus buttnerae and in its fish host tambaqui (Colossoma macropomum) from fish farms

Fish parasites are excellent bioindicators of environmental contamination because they respond quickly to water pollutant chemicals, and they can accumulate high concentrations of trace metals compared to their hosts. Here, we investigated the bioaccumulation pattern of the following: Cd, Ca, K, Na, Mg, Fe, Al, Zn, Ba, Mn, Cu, Pb, Cr, Ni, and Co. We investigated the presence of trace metals in the acanthocephalan parasite Neoechinorhynchus buttnerae, and the bioaccumulation factors (BAFs) of metals were tested in the food, muscle, and liver of its host fish Colossoma macropomum (tambaqui). We used samples from four commercial fish farms that also conduct other agribusiness activities. Tissues of the fish along with their parasites were subjected a trace metal concentration analysis by inductively coupled plasma optical emission spectrometry. Most of metals showed significantly higher presence in N. buttnerae than in tambaqui (p < 0.05), with increased level of Na, Pb, Ca, Mn, Zn, Al, and Fe in fish muscle and that of Cr, Ni, Zn, Al, Ca, and Ba in fish liver. Considering all the fish farms, the highest values of BAF were observed for Fe, Al, Zn, and Mn with concentrations up to 35.63, 26.88, 14.12, and 6.66 times higher in acanthocephalan tissues than in the fish muscle, respectively. Moreover, Ba, Ca, and Al showed concentrations up to 18.11, 12.18, and 11.77 times higher in acanthocephalan than in the liver of tambaqui. Our results indicate that the higher the levels of these metals in the parasite, the lower their concentrations in the muscular and hepatic tissues of the fish. Therefore, we suggest that N. buttnerae can directly influence the concentrations of trace metals in the fish tissues and accumulate both essential trace (Fe, Zn, Mn, and Ca) and toxic elements (Al, Pb, and Ba) in the host.

Mitochondriomics of Clarias Fishes (Siluriformes: Clariidae) with a New Assembly of Clarias camerunensis: Insights into the Genetic Characterization and Diversification

The mitogenome of an endemic catfish Clarias camerunensis was determined from the Cameroon water. This circular mitogenome was 16,511 bp in length and comprised 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNAs, and a single AT-rich control region. The heavy strand accommodates 28 genes, whereas the light strand is constituted by ND6 and eight transfer RNA (tRNA) genes. The C. camerunensis mitochondrial genome is AT biased (56.89%), as showcased in other Clarias species. The comparative analyses revealed that most of the Clarias species have 6 overlapping and 11 intergenic spacer regions. Most of the PCGs were initiated and terminated with the ATG start codon and TAA stop codon, respectively. The tRNAs of C. camerunensis folded into the distinctive cloverleaf secondary structure, except trnS1. The placement of the conserved domains in the control region was similar in all the Clarias species with highly variable nucleotides in CSB-I. Both maximum likelihood and Bayesian-based matrilineal phylogenies distinctly separated all Clarias species into five clades on the basis of their known distributions (South China, Sundaland, Indochina, India, and Africa). The TimeTree analysis revealed that the two major clades (Indo-Africa and Asia) of Clarias species might have diverged during the Paleogene (≈28.66 MYA). Our findings revealed the separation of Indian species (C. dussumieri) and African species (C. camerunensis and Clarias gariepinus) took place during the Paleogene, as well as the South Chinese species (Clarias fuscus) and Sundaland species (Clarias batrachus) splits from the Indochinese species (Clarias macrocephalus) during the Neogene through independent colonization. This pattern of biotic relationships highlights the influence of topography and geological events in determining the evolutionary history of Clarias species. The enrichment of mitogenomic data and multiple nuclear loci from their native range or type locality will confirm the true diversification of Clarias species in African and Asian countries.

Health Risk Assessment for Human Exposure to Heavy Metals via Food Consumption in Inhabitants of Middle Basin of the Atrato River in the Colombian Pacific

The Atrato river basin is one of the world's most biodiverse areas; however, it is highly impacted by mercury gold mining, which generates air, water, and soil pollution. (1) Background: The concentrations of persistent heavy metal pollutants, mercury (Hg), lead (Pb), cadmium (Cd), and arsenic (As) in the fish, fruits, and vegetables most consumed by the riverside inhabitants of the middle basin of the Atrato river represent a danger to public health; (2) Methods: A total of 154 samples of different fruits and vegetables and 440 samples of fish were analyzed by atomic absorption spectroscopy. A sample of 446 people were surveyed to evaluate food consumption and carcinogenic and non-carcinogenic risk; (4) Conclusions: High concentrations of As, Hg, Pb, and Cd were identified in fish, fruits-tubers, and vegetables-stems commonly consumed by inhabitants of the middle basin of the Atrato River, which exceeded the Codex limits and the limits established by the WHO/FAO, especially for carnivorous fish species. A high carcinogenic and non-carcinogenic risk was evidenced amongst inhabitants of the middle basin of the Atrato River due to the consumption of fish contaminated with high concentrations of As, MeHg, and THg. The risk due to the consumption of vegetables was very low.

High element concentrations are not always equivalent to a stressful environment: differential responses of parasite taxa to natural and anthropogenic stressors

Environmental parasitology developed as a discipline that addresses the impact of anthropogenic activities related to the occurrence and abundance of parasites, subsequently relating deviations of natural parasite distribution to environmental impact. Metals, often considered pollutants, might occur under natural conditions, where concentrations might be high due to a natural geogenic release rather than anthropogenic activities. We specifically investigated whether naturally occurring high levels of elements might negatively affect the parasite community of the intertidal klipfish, Clinus superciliosus, at different localities along the South African coast. Parasite communities and element concentrations of 55 klipfish (in muscle and liver) were examined. Our results show that parasites can disentangle anthropogenic input of elements from naturally occurring high element concentrations. Acanthocephala, Cestoda and Isopoda were associated with higher concentrations of most elements. Environmental parasitology, applicable to a wide range of systems, is scarcely used on marine ecosystems and can contribute to environmental monitoring programs.