Risk of heavy metal ingestion from the consumption of two commercially valuable species of fish from the fresh and coastal waters of Ghana

Heavy Metal Bioaccumulation in Highly Consumed Pelagic and Benthic Fish and Associated Health Risk

The present study investigated the levels of Manganese (Mn), Cadmium (Cd), Copper (Cu), Zinc (Zn), Lead (Pb) and Iron (Fe) in the tissues of a benthic fish (Clarias gariepinus) and a pelagic fish (Oreochromis niloticus), which are highly consumed in Ghana. The fish were collected from the Weija reservoir, which is an important source of fishery and potable water in Accra, Ghana. The results indicate heavy metal accumulation in all the tissues (gills, liver and muscles) analyzed. The bioaccumulation of all the metals was lowest in the muscles compared to the liver and gills in both species. The bioaccumulation of the metals was generally higher in the tissues of the catfish, except for Fe and Zn. Fe was higher in the gills and liver of the tilapia, and Zn was higher in the liver of the tilapia. The analysis of relationships between metal levels in the different tissues and the size of the fish showed a few significant correlations. The results also showed that all metals showed no potential health risk to consumers, as THQs and TTHQs in tilapia and catfish were less than one, and the metal levels in both species were all below the FAO/WHO maximum permissible limits.

Trace metal load of two urban wetlands with varied catchment activities in Ghana

This study compared Lead (Pb), Chromium (Cr), Copper (Cu), Zinc (Zn), Mercury (Hg), Arsenic (As) and Cadmium (Cd) concentrations in sediment, water, and biota at Vaughan Dam which receives limited sewage effluent discharge from residential areas, and Korle Lagoon which receives industrial effluents, electronic waste, garages-spill oil and a host of others in addition to residential sewage effluent discharge. Samples were analyzed with Atomic Absorption Spectrometer. The results showed that concentrations of trace metals were generally higher in the sediment, water, and plants from the Korle Lagoon but only Cu in the sediment of Korle Lagoon showed a significantly high concentration. The similarities in the rank orders of the metal concentrations together with the dominance of Zn and Pb in most compartments of the wetlands indicated major differences did not exist in the contaminant input to the two wetlands except electronic waste recycling and disposal that resulted in significantly high copper concentrations in the sediment of Korle Lagoon. No evidence of biomagnification was determined along the food chains of the Vaughan Dam and the Korle Lagoon for all the metals studied.The Tilapia zilli from Vaughan Dam, the only biota that is regularly consumed from the wetlands, had Cr, Cu, Pb, Cd, Hg, and As concentrations above FAO/WHO permissible limits and therefore pose a health risk to consumers.

Contamination of selected heavy metals in Limnothrissa miodon (Boulenger, 1906) in the four strata of Lake Kariba Zambia: are the consumers at risk?

Pollution of aquatic ecosystems is one of the major challenges affecting many countries of the world. Heavy metal pollutants, in particular, threaten the life of aquatic organisms (fauna and flora) and, more importantly, humans who consume aquatic products as a critical source of proteins. In the present study, the concentrations of selected heavy metals (cobalt- Co, Chromium-Cr, nickel- Ni and manganese- Mn) in Limnothrissa miodon, locally known as 'Kapenta' were assessed using the Microwave Plasma Atomic Emission Spectrometer (MP AES) 4200 at the Zambia Agricultural Research Institute (ZARI). The fish was collected from Lake Kariba, Zambia, which is divided into four fisheries management strata (I, II, III, and IV). The health risks to consumers were evaluated using the Estimated Daily Intake (EDI), Target Hazard Quotient (THQ) and Hazard Index (HI). Analysis of variance (ANOVA) was used to assess the difference in the means of heavy metal concentration across the four strata for each element. The concentrations of all the heavy metal elements were within the permissible limits considered to be safe for human consumption based on the Food and Agriculture Organization (FAO) standards. However, the concentration of individual heavy metal elements varied significantly across the strata with stratum I and II showing higher levels in general except for Mn which was highest in stratum II and III compared with the other strata. Furthermore, Mn concentration was the highest in all the strata and the highest concentration was observed in the fish from stratum II. The EDIs, THQs and HIs of each heavy metal element did not show any threat to consumers of the fish from the lake. Further studies are required to better understand the potential sources of heavy metals and to regularly monitor existing activities that may elevate the concentration levels.

The development of decontamination methods in coastal marine habitats by transplantation of the mussel Mytilus galloprovincialis (Lamarck, 1819): Comparison between in vivo and in situ investigations

The health status of Mytilus galloprovincialis native from a polluted habitat was surveyed before and after 30 and 60 days of in situ transplantation and in vivo experiments. The results showed a reduction in filtration rate by 24 % and 45 %, respectively, after 60 days of in vivo and in situ experiments compared to the rates at polluted sites. The respiration rate reached a minimum of 0.081 ± 0.05 mg O₂.L^-1 after 60 days of in situ transplantation. Moreover, the antioxidant activities were changed in a time-dependent manner for both transplantation conditions. The highest superoxide dismutase and catalase activities corresponded to the stressed mussels and declined by 76 % and 54 %, respectively, after 60 days of in situ transplantation. Changes in lipid peroxidation and acetylcholinesterase activity were observed in internal organs following 60 days of transplantation. At this time slot, the lowest content of metals and microplastics was also noticed.

Evaluation and Association of Heavy Metals in Commonly Used Fish Feed with Metals Concentration in Some Tissues of O. niloticus Cultured in Biofloc Technology and Earthen Pond System

For successful aquaculture, the primary need is the quality of fish feed, which determines fish flesh quality. The current study was conducted to evaluate the number and concentration of heavy metals in commonly used fish feeds and fish gills, liver, and muscle of biofloc technology and earthen pond systems. Besides this, the correlation between heavy metals in fish feeds with detected metals in the gills, liver, and muscle of fish was also determined. Results revealed that heavy metals concentration, including Cu and Cd, in feed B was significantly greater than in feed A, but the Zn level in feed A was significantly higher than in feed B. Furthermore, the concentration of heavy metals in fish of both aquaculture systems was significantly higher in the liver than in the gills and muscle. The metal concentration in fish feeds and fish edible parts (muscle) was lower than the WHO standard level; however, the amount of Pb was higher in the fish muscle, which is harmful for human consumption. Though the correlation test revealed that all of the metals from the feeds were positively correlated to the metals detected in the fish, but most of the estimated correlation was insignificant. From the current study, it can be concluded that the fish feed producers need to measure feed quality adequately to avoid hazardous contamination by heavy metals in the feed. The ultimate consumer, fish and humans, may, otherwise, be predisposed to assimilate and accumulate these heavy metals.

Assessment of environmental degradation in two coastal communities of Ghana using Driver Pressure State Impact Response (DPSIR) framework

In this study, a qualitative research method using Driver Pressure State Impact Response (DPSIR) framework was employed to assess the drivers of environmental degradation and their implications on Anlo and Sanwoma coastal communities in the Western Region of Ghana. Pollution Index (PI) and Environmental Risk Factor (ERF) were estimated in Pra and Ankobra estuaries, respectively, in Anlo and Sanwoma communities to complement the qualitative assessment in the studied coastal communities. The state and condition of the coastal ecosystems are critical to the well-being and livelihood of the residents of the two coastal communities. Therefore, it was important to assess the drivers of environmental degradation and their consequences on the coastal communities. The findings showed that the coastal communities were severely degraded and were in a vulnerable state due to the impact of drivers such as gold mining, farming, improper waste disposal, and illegal fishing that pressurize the environment. Also, PI and ERFs showed that the estuaries in Anlo and Sanwoma coastal communities were contaminated with metals such as arsenic, lead, zinc, and iron. Some of the impacts of the environmental degradation on the communities included reduction in fish catch and health-related ailments among the residents of the two communities. Unfortunately, regulatory policies by government and efforts of non-governmental organisations and members of the two coastal communities to address the environmental issues have not yielded the desired results. It is recommended that there should be urgent interventions by policymakers to stop further degradations in the coastal communities to enhance the well-being and livelihoods of the residents of Anlo and Sanwoma.

What about the Arsenic? Health Risk Assessment in Canned Tuna Commercialized in Northern Spain

The incorrect labeling, as well as the bioaccumulation of heavy metals in seafood, represent a recurring problem worldwide, not only for natural resources but also for the consumers’ health. Heavy metals can be accumulated through the food chain and transferred to the final human consumer. Despite its toxicology, arsenic does not have a concentration limit on food, unlike other heavy metals like cadmium, mercury, and lead. Tuna species, with a worldwide distribution and high per capita consumption, represent a well-known toxicological issue caused by heavy metals. In this context, 80 samples of canned tuna were analyzed to check if the information contained in the label was correct and complete. Genetic identification was made by sequencing a fragment of 16S rDNA from 80 samples. For the heavy metal quantification, only those samples with the complete FAO fishing area information on the label were analyzed. Only 29 out of 80 samples presented enough information on the labels for the analysis. Some of the canned tuna commercialized in Spanish markets surpassed the safety standard levels established by the Joint FAO/WHO Expert Committee on Food Activities (JECFA) under the consumption rates of 300 g and 482 g per week. However, the carcinogenic risk (CRlim) for arsenic in all cans and all scenarios was higher than the safety levels.

Heavy metal exposure risk associated with ingestion of Oreochromis niloticus and Coptodon kottae harvested from a lacustrine ecosystem

Lacustrine ecosystems have not been widely assessed for heavy metal contamination and associated health risks; yet, they could be accumulating these contaminants to the detriment of aquatic organisms and communities relying on them for various aspects. The water quality index (WQI) and concentrations of heavy metals including As, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, and Zn in water, sediment, Oreochromis niloticus, and in the endemic and endangered Coptodon kottae in Lake Barombi Kotto in Cameroon were determined to evaluate fish heavy metal bioaccumulation, and heavy metal exposure risk posed to communities consuming these fish species. The WQI of the lake was found to be excellent with heavy metal concentrations that were lower than what was obtained in the sediments and fish samples. Mean heavy metal concentrations in sediment ranged from 0.86 ± 0.03 mg/kg for Cd to 560.1 ± 11.15 mg/kg for Fe. In both fish species, Fe, Mn, and Cu had the highest concentrations. Though the heavy metal concentrations in the lake water were low, heavy metal bioconcentration factors for both fish species were very high ranging from 1.6 for Fe to 1568 for Mn. The concentration patterns of heavy metals in the organs of both fish species followed the order bones > gut > muscle. Consumption of these two fish species contributes less than 1.0% of the permissible tolerable daily intake (PTDI) and provisional tolerable weekly intake (PTWI) of these metals with lead (Pb) having the potential to exceed permissible exposure levels when high amounts of these fish are consumed by adults.

Selenium Content in Freshwater and Marine Fish from Southern Brazil Coastal Plain: a Comparative Analysis on Environmental and Dietary Aspects

The coastal plain of Rio Grande do Sul is considered to be a Se-deficient region in terms of its population dietary habit, making it the focus of this study. Selenium dietary deficiency is a concern when we consider its potential critical health effects on the local population. Therefore, this study contributes new information on the levels of Se in several species of marine and freshwater fish in the region of the Patos-Mirim Lagoon system, coupled with a comparative analysis of the metalloid contents between both fish groups. The Se contents in the fish species ranged from 88 ± 13 to 688 ± 19 μg.kg^-1. The average Se concentration in the muscle tissue of the freshwater species (251 ± 96 μg kg^-1) was significantly lower than that of the marine species (412 ± 143 μg kg^-1). Likewise, no evidence of Se biomagnification was found among the fish from both the marine and freshwater environments, suggesting the absence of trophic transfer of Se. We note that to ensure that the RDA (Recommended Daily Allowance, 55 μg day^-1) of Se dietary intake for adults is met, at least 134 g of freshwater or 82 g of marine fish fillet could be incorporated into the diet of the population of Rio Grande do Sul. According to target hazard quotients (THQ) and the permissible safety limits, consumption of the fish species analyzed is safe for human health.

Potential human health risks associated with ingestion of heavy metals through fish consumption in the Gulf of Guinea

Heavy metal pollution of the marine environment has toxic implications for both the aquatic biota and human health. We examined the levels of Zinc (Zn), Lead (Pb), Copper (Cu), Cadmium (Cd), Arsenic (As) and Mercury (Hg) in muscles of Sardinella maderensis, Dentex angolensis, Sphyraena sphyraena and Penaeus notialis caught from the coastal waters of Ghana using inductively coupled plasma mass spectrometry method. Penaeus notialis recorded the highest concentrations of all the metals (Cu:12.08 ± 1.46 µg/g, Zn: 19.20 ± 2.27 µg/g, As: 8.46 ± 2.42 µg/g, and Cd: 0.03 ± 0.01 µg/g) except Hg. Mercury was relatively high in D. angolensis (0.14 ± 0.03 µg/g). Apart from As, all metals were within globally permissible daily limits for consumption by human per meal. The estimated Target Hazard Quotient due to the intake of Hg through D. angolensis consumption exceeded the threshold value across all age categories. Carcinogenic risks due to As intake through P. notialis consumption far exceeded the 10^-6 threshold for all age groups in Ghana. It is recommended that the consumption of these fish species particularly, the shrimp P. notialis be done cautiously to avoid possible future health challenges.

Risk of Heavy Metal Poisoning From Consuming Grasscutter Digesta in Ghana

Grasscutter (cane rat/Thryonomys swinderianus) digesta is used as a spice in Ghana. Research shows that heavy metals from the environment may accumulate in the internal organs of grasscutters, which raises concerns about the possible contamination of grasscutter digesta, too, with heavy metals. Although grasscutter meat in Ghana has been described as safe for consumption, information is lacking on the health risks associated with ingesting the digesta. This study, therefore, aimed to assess the knowledge and perceptions of a merchant and a consumer about the safety of ingesting grasscutter digesta and to evaluate potential health risks from exposure to heavy metals from the spice. A total of 12 digesta samples were analyzed to evaluate potential health risks from exposure to Cd, Fe, Hg, and Mn using a Varian AA240FS Atomic Absorption Spectrometer. The levels of Cd, Hg, and Mn were below the detection limit of 0.01 mg/kg digesta. Also, the estimated daily intake of Fe (0.02 mg/kg) was less than the maximum allowable dose recommended by the US EPA (0.7 mg/kg). The hazard indices of Fe for daily and weekly consumption were <1, suggesting that the consumers may be safe from iron poisoning. Because grasscutter digesta is a relatively expensive spice, it is unlikely to be consumed daily by the average Ghanaian. Moreover, if 10 g of digesta is consumed daily, it can be safely ingested about 971 times in a month. Domestication of grasscutters may be a useful approach to monitor their diet and consequently the quality of their digesta.

Existence of a novel heavy metal-tolerant Pseudomonas aeruginosa strain Zambia SZK-17 Kabwe 1: the potential bioremediation agent in the heavy metal-contaminated area

Bacterial biomass may serve as an important environmental cleaning agent to toxic heavy metal ions at the expense of chemical processes which are not environmentally friendly. This study aimed at characterizing bacterial agents which could serve as a potential in situ bioremediation agent at the site of isolation. The characterization was performed using both phenotypic and molecular approaches. A novel Pseudomonas aeruginosa strain Pseudomonas aeruginosa Zambia SZK17 Kabwe1 was successfully isolated, identified, and characterized. The strain showed a promising tolerance to heavy metals such as copper (2 mM), zinc, nickel (2 mM), cobalt (1 mM), and cadmium (0.5 mM) at the laboratory level. The bacterium has shown the bioaccumulation of at least 60% of copper (II) sulfate (0.3655 mg/l) with R = 69.75%, cadmium (II) chloride (0.0241 mg/l) with R = 69.98%, zinc (II) chloride (0.1389 mg/l) with R = 69.91%, nickel (II) chloride (0.1155 mg/l) with R = 69.92%, and cobalt (II) chloride (0.593 mg/l) with R = 69.92%. The highest bioaccumulation has been observed in heavy metals cadmium, zinc, nickel, and cobalt. Characterization of the bacterium on pH has revealed that at a very high pH (≥ 9) and lower (≤ 5.5) pH, the bacterium tended to have reduced growth with optimum growth at pH 8. The high temperature at around 40 °C had a negative effect on the growth performance of the bacterium while optimum growth was observed at 28 °C. This novel P. aeruginosa strain has shown the phenotypic attributes to become a potential bioremediation agent; however, further investigation needs to be done to understand the genes and or molecular mechanisms that drive their tolerance to multiple heavy metals.

Investigating fish contamination scenario and community willingness to adopt consumption advice proposing an advisory option

Consumption advice to ensure the health and safety of fish consumers remains urgent to handle the ever-increasing panic over heavy metal toxicity. Moreover, studies of fish consumption rarely focus on the perceptions and awareness of consumers. Considering this, the present study examines the factors determining the willingness to follow fish consumption advice as well as calculate the risk-benefit ratio and produce the vulnerability map followed by formulating fish consumption advice for consumers of two commercially important fish species, tilapia (Oreochromis niloticus) and mudfish (Ophiocephalus striatus), in the Laguna de Bay area of the Philippines. Primary data on consumers' perceptions were collected through a questionnaire, whereas heavy metal contamination data were compiled from the best available literature. We concluded that people's willingness to adopt consumption advice is mostly dependent on their existing level of fish consumption (P = 0.000). There was no discernible difference in the mean concentration of heavy metals in fish between the dry and wet seasons, with the exception of As concentrations in the samples (t15.75 = 3.72, p < 0.001). The hazard quotient (risk-benefit ratio) for fish consumption (HQefa) was an order of magnitude higher in the mudfish samples (0.05 and 28.28) compared to tilapia (0.04 to 16.02). Binangonan and Taguig from the Northern West Bay (1A, 1B) were clearly recognised on the vulnerability map as the most vulnerable regions in the lake. In general, it was determined that As and Pb were the elements causing consumption restrictions on tilapia collected from various parts of Laguna Lake. As with tilapia, locations with a high-risk advisory for mudfish were identified as the Northern West Bay and Central Bay, with a consumption limit of five meals per month due to excessive mercury pollution. This empirical study can serve as an option for the future development of fish consumption advice in the region.

Heavy metals in fish nearby electronic waste may threaten consumer's health. Examples from Accra, Ghana

Electronic waste sites are rich in heavy metals contained in electronic and electric equipment waste and pose a risk of pollution if metals enter in the environment nearby. The Korle lagoon, located in the center of Accra, is receiving waste effluents from industries, households and the adjacent e-waste burning site Agbogbloshie which is the biggest in the country. Thus, the risk of heavy metal contamination of the water body and subsequent uptake in the aquatic food chain is particularly relevant. Small-scale fishing, not entering the commercial chain, occurs in the lagoon despite its consideration of biologically dead. We assessed if the exposure to heavy metals through these fish consumption is posing higher health risks than fish sold on Ghanaian markets. Using ICP-MS technology, we quantified concentrations of As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn in fish caught from the Korle Lagoon (Trachinotus ovatus, Mugil curema and Mugil cephalus) and compared them to fish from the Tema Newtown fishing market (Scomber colias, Pseudotolithus senegallus). Cobalt and lead concentrations, typical e-waste metals, were higher in fish from the Korle lagoon, even though they were of lower trophic level. Calculated risk indices revealed risk of elevated arsenic and mercury exposure, particularly through T. ovatus from the Korle lagoon, if consumed daily as it is common in the region. This study suggests the need of monitoring programs of Ghanaian catch, with a special focus in environmental risk areas like Korle lagoon to ensure human food safety.

Occurrence of heavy metals and their removal in Perna viridis mussels using chemical methods: a review

Despite the nutritional benefits, bivalves like mussels are also an excellent aquatic heavy metal biomonitoring agent due to their high tolerance to varying levels of temperature, salinity and oxygen, as well as pollutants. Although the accumulated toxic heavy metals may not exert direct negative impacts on the mussels, such toxicants in mussel tissues can give harmful effects on human body when consumed in toxic quantities and/or over prolonged period. The booming of urban and industrial activities, and consequently the increment of runoffs, as well as wastewater effluents and leaching, further exacerbated the magnitude of this issue. Hence, continuous monitoring of heavy metal contents in mussels is vital to ensure its compliance with food safety regulations, protecting consumers at large. This review paper discusses the occurrence of heavy metals in mussels especially that of Perna viridis in Malaysia and other parts of the world since year 2000 until 2021. Heavy metal concentration data and patterns from various coastal and/or estuaries were compared. Where applicable, statistical data that indicate variations between sampling sites, sampling months or years and chemical treatments for heavy metal removal were critically reviewed. Health risk assessment findings were also discussed. More importantly, related chemical-based interventions to minimize and/or eliminate toxic heavy metals from mussels are also reviewed.

Health Risk Assessment and Levels of Heavy Metals in Farmed Nile Tilapia (Oreochromis niloticus) from the Volta Basin of Ghana

Heavy metals (Pb, Cd, As, Mn, Fe, Zn, Cu, Ni, and Cr) are some of the most toxic elements that can bioaccumulate from sources linked to human activities, such as industry and agriculture. This study quantifies the concentrations of several heavy metals in caged tilapia found in Ghana’s Volta Basin and assesses the associated health risks. The levels of heavy metals in the tissues of Oreochromis niloticus from three cage farms (N = 52) were determined using Atomic Absorption Spectrometry (AAS). The implication for human health was assessed using several risk assessment techniques. Fe (50.11 ± 10.22 mg/kg) and Cr (0.31 ± 0.07 mg/kg) had the highest and lowest accumulated metal concentrations, respectively. Heavy metal concentrations in tilapia tissue from fish farms were ordered as follows: Fe > Mn > Zn > Ni > Cr (farm A), Fe > Zn > Ni > Mn (farm B), and Fe > Mn > Zn > Ni > Cr (farm C). All metals had an estimated daily intake (EDI) below the threshold, and mean differences between sample farms were not statistically significant. Similarly, the values of target hazard quotients (HQs) and hazard indices (HIs) were less than one. According to the risk assessment results, eating tilapia from farms posed no risk to human health. The presence of Mn, Fe, and Ni concentrations above the maximum level in the fish, on the other hand, suggests that they may affect fish health.

Fish Nutritional Value as an Approach to Children's Nutrition

Fish is a relatively cheap and accessible source of animal protein for human consumption even in rural communities. It is critical for global food and nutrition security, and its consumption continues to increase. As a highly nutritious food, fish consumption is highly recommended for children and expectant mothers for normal growth and development. The present paper explores the nutritional value of fish as approach to nutrition in children and its benefits. The findings reveal that fish is a valuable source of essential amino acids (EAA) and polyunsaturated fatty acids (PUFAs) that play important physiological functions for maintenance and development of fetuses, neonates, and infant brains. Therefore, it could be a valuable tool in the fight against food insecurity and malnutrition. However, fish and fish products are also highly susceptible to contamination by various organic and inorganic compounds that threaten public health. Particularly, heavy metals and biogenic amines (BAs) have shown adverse effects when contaminated fish is consumed, and the effects in children have been worse. Hence, while fish consumption is highly recommended for children's nutrition, the safety and quality of the product should always be checked to safeguard public health.

Human health risk assessment from heavy metals in three dominant fish species of the Ankobra river, Ghana

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Anthropogenic activities along the banks of the Ankobra river affect quality of fish consumed.

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Concentrations of Mn, Zn and Hg in fish species from the Ankobra river exceed recommended limits for human consumption.

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Concentrations of Cd, Ni, Cr, As and Co in fish species were lower than the permissible limits for human consumption.

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Assessment of non-carcinogenic risk suggests that consumption of fish from the Ankobra river pose a low risk to consumers.

This study assessed heavy metal contamination of fish and its associated health risk to communities around the Ankobra River in the Western Region of Ghana. Species of fish randomly collected from different sections of the river were analyzed for Cd, Ni, Zn, Pb, Mn, Hg, As, Co and Cr using Atomic Absorption Spectrophotometry. Three commonly consumed fish species, Clarias gariepinus, Sarotherodon melanotheron and Pseudotolithus senegalensis, were analyzed. The health risks were assessed based on the potential non-carcinogenic effect associated with the daily consumption of fish by communities around the river. Concentrations of all the metals were higher in gills than the muscles of all three species. On average, levels of Mn (6.65 ± 7.30 mg.kg⁻¹), Zn (2.24 ± 1.99 mg.kg⁻¹) and Hg (3.06 ± 1.53 mg.kg⁻¹) in all three species were above the permissible limits recommended by the Wealth Health Organization. The health risk estimated for all the heavy metals was < 1, significantly below the ≥ 1 index associated with the incidence of cancer. This suggests that fish species examined in this study pose no significant non-carcinogenic risk and are safe for human consumption.

Bioaccumulation of trace elements in liver and kidney of fish species from three freshwater lakes in the Ethiopian Rift Valley

The objective of the present work was to obtain scientific information on the ecological health of three freshwater lakes (Awassa, Koka, and Ziway) situated in the Ethiopian Rift Valley by investigating possible trace element contamination accumulated in fish. Accordingly, fish liver and kidney samples were collected from three commercially important fish species (Barbus intermedius, Clarias gariepinus, and Oreochromis niloticus) in the lakes to determine the concentrations of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb), using ICP-MS. Trace element concentrations were generally higher in O. niloticus compared with concentrations in B. intermedius and C. gariepinus. Compared to background values of most freshwater fish species, higher liver concentrations of Cu in C. gariepinus and O. niloticus, Mn in O. niloticus, Co in all except B. intermedius, and Zn in C. gariepinus from Lakes Ziway and Awassa were found. Cr, Co, Ni, Cd, and Pb were enriched in kidney, while Mn, Cu, Zn, As, and Se seems retained in the liver tissues. Assessment of transfer factors indicated that bioaccumulation from water and diet occurred, while uptake from sediments was low. Furthermore, the transfer factor values were generally higher for essential elements compared to the non-essential elements. Multivariate statistical analyses showed that the differences between the trace element levels were generally not significant among the lakes (p = 0.672), while significant differences were found between the fish species (p = 0.042), and between accumulation in kidney and liver (p = 0.002).

Trace metal(loid)s contamination in paddy rice (Oryza sativa L.) from wetlands near two gold mines in Côte d'Ivoire and health risk assessment

This study examined the concentrations of arsenic (As), cadmium (Cd), and mercury (Hg) in rice grains grown in wetlands associated with gold mining in central-southern of Côte d'Ivoire to evaluate potential health risks exposure via rice consumption. In total, 30 rice grains were sampled around Agbaou and Bonikro gold mines. Arsenic and cadmium concentrations were determined using an inductively coupled plasma-optical emission spectrometer (ICP-OES), while atomic absorption spectrometry (AAS) was used for mercury. Results showed that As and Hg average concentrations in rice were above the permissible limits, while Cd average concentrations were below the permissible limit established by FAO/WHO in both sites. Except for Hg at Agbaou, no significant (p < 0.05) difference was found between trace metal concentrations in the two sites. The average daily intake (ADI) of As via rice consumption exceeded the USEPA reference dose (RfD) of 0.0003 μg g^-1 day^-1, indicating that rice ingestion is a pathway of As exposure for adults and children in the area. The average values of non-carcinogen (HQ) for As and carcinogen (CR) for As and Cd risks index suggest that potential health risks exist for both adults and children due to rice consumption at Agbaou and Bonikro. The maximum safe weekly consumption (MSWC) of rice relative to As, Cd, and Hg was estimated for the study area. Overall, this study provides strong evidence that As could threaten local population health in Côte d'Ivoire regions where gold mine extraction is occurring through rice ingestion.

Assessing the Potential Health Risk from Mercury Through Consumption of the Most Popular and Preferable Fish Species, Rutilus frisii kutum, on the Northern Coast of Iran

Due to the importance of Caspian kutum (Rutilus frisii kutum) in the nutrition and health of consumers, a study was conducted to evaluate the concentration of mercury and its associated health risk for this species, its predators, and the people. Samples were collected from the fish at the four best-selling stations, Bandar Torkaman, Bander Anzali, Fereydunkenar, and Chalos, with mean mercury concentrations in the samples from the stations being 49.4, 132.6, 103.6, and 107.6 μg/g respectively. Mercury in the muscle tissue of the collected samples increased from east to west in the southern Caspian Basin. The mercury concentrations at all stations were below the permissible international levels for this heavy metal, suggesting no or low potential health risk. However, due to the toxicity and other harmful properties of mercury, it is necessary to monitor the values of this element as well as other pollutants in fish species to assess the health risk.

Composition of nutrients, heavy metals, polycyclic aromatic hydrocarbons and microbiological quality in processed small indigenous fish species from Ghana: Implications for food security

The triple burden of malnutrition is an incessant issue in low- and middle-income countries, and fish has the potential to mitigate this burden. In Ghana fish is a central part of the diet, but data on nutrients and contaminants in processed indigenous fish species, that are often eaten whole, are missing. Samples of smoked, dried or salted Engraulis encrasicolus (European anchovy), Brachydeuterus auritus (bigeye grunt), Sardinella aurita (round sardinella), Selene dorsalis (African moonfish), Sierrathrissa leonensis (West African (WA) pygmy herring) and Tilapia spp. (tilapia) were collected from five different regions in Ghana. Samples were analyzed for nutrients (crude protein, fat, fatty acids, several vitamins, minerals, and trace elements), microbiological quality (microbial loads of total colony counts, E. coli, coliforms, and Salmonella), and contaminants (PAH4 and heavy metals). Except for tilapia, the processed small fish species had the potential to significantly contribute to the nutrient intakes of vitamins, minerals, and essential fatty acids. High levels of iron, mercury and lead were detected in certain fish samples, which calls for further research and identification of anthropogenic sources along the value chains. The total cell counts in all samples were acceptable; Salmonella was not detected in any sample and E. coli only in one sample. However, high numbers of coliform bacteria were found. PAH4 in smoked samples reached high concentrations up to 1,300 μg/kg, but in contrast salted tilapia samples had a range of PAH4 concentration of 1 μg/kg to 24 μg/kg. This endpoint oriented study provides data for the nutritional value of small processed fish as food in Ghana and also provides information about potential food safety hazards. Future research is needed to determine potential sources of contamination along the value chains in different regions, identify critical points, and develop applicable mitigation strategies to improve the quality and safety of processed small fish in Ghana.

Trace metals contamination potential and health risk assessment of commonly consumed fish of Perak River, Malaysia

The rapid growth of industrial and agricultural activities in Malaysia are leading to the impairment of most of the rivers in recent years through realising various trace metals. This leads to toxicity, particularly when the toxic has entered the food chain. Perak River is one of the most dynamic rivers for the Malaysian population. Therefore, in consideration of the safety issue, this study was conducted to assess the concentration of such metals (Cd, Cu, Zn, Fe, and Pb) in the muscles of most widely consumed fish species (Barbonymus schwanenfeldii, Puntius bulum, Puntius daruphani, Hexanematichthys sagor, Channa striatus, Mystacoleucus marginatus, and Devario regina) from different locations of Perak River, Malaysia by employing inductively coupled plasma optical emission spectroscopy (ICP-OES). Among the trace metals, Fe and Cd were found to be the highest (29.33–148.01 μg/g) and lowest (0.16–0.49 μg/g) concentration in all of the studied species, respectively. Although the estimated daily intakes (μg/kg/day) of Cd (0.65–0.85), Fe (79.27–352.00) and Pb (0.95–12.17) were higher than their reference, the total target hazard quotients values suggested that the local residents would not experience any adverse health effects from its consumption. In contrast, the target cancer risk value suggested that all fish species posed a potential cancer risk due to Cd and cumulative cancer risk values, strongly implying that continuous consumption of studied fish species would cause cancer development to its consumers.

Determination of heavy metals and selenium contents in fish meat sold at Erbil City, Kurdistan Region, Iraq

Food contamination with heavy metals may pose a serious threat to human health. Fishes are the most common seafood globally. This study aimed to evaluate the levels of heavy metals in different fishes sold in Erbil city markets. The targeted heavy metal elements were cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), mercury (Hg), manganese (Mn), nickel (Ni), selenium (Se), and zinc (Zn). Seventeen dorsal meat samples were digested and subjected to metal analysis by Inductively Coupled Plasma Optical Emission Spectrometry. Co, Mn, Cu and Se were detected in all samples, while cadmium was below the detectable level in all samples. The average concentrations of targeted trace elements were 0.03±0.016, 0.02±0.03, 0.07±0.08, 0.10±0.08, 0.03±0.03, and 2.90±3.33 mg/kg for cobalt, chromium, copper, manganese, nickel, and zinc, respectively. Lead was only found in one sample (5.88%). On the contrary, mercury was detected in all samples but in low concentration (0.14±0.07). All detected heavy metals with specified permissible limits by FAO/WHO were significantly lower than the permissible limits. Based on detected levels of targeted heavy metals, consumption of such fish has no potential risks to human.

Levels of heavy metals, total petroleum hydrocarbons, and microbial load in commercially valuable fish from the marine area of Tripoli, Lebanon

The present study aimed at evaluating the levels of microbiological contamination, total petroleum hydrocarbons (TPHs), and heavy metals (As, Cd, Hg, and Pb) in the edible tissues of commonly consumed fish (8 species) collected from the marine area of Tripoli, Northern Lebanon. Total coliform levels in all sampled fish, and Escherichia coli levels in Liza ramada only, exceeded the permissible limits set by FAO/WHO 2002. Staphylococcus aureus counts were within the recommended thresholds, while sulfate-reducing bacteria levels were the highest in fish of the genus Liza. Salmonella species and Listeria monocytogenes were not detected in all fish analyzed. Analysis of heavy metals levels showed that arsenic exhibited the highest levels among the assessed metals in all genera. Levels of As in Epinephelus, Diplodus, Oblada, and Liza were above the acceptable limits, while Cd levels were below the permissible limits set by the European Commission. Significant negative correlation was found between levels of As and Hg in muscle tissues and fish size (length). Levels of TPHs were the highest in fish of the genus Epinephelus. Significant difference in TPHs contamination was found within three fish genera, with Epinephelus being the most contaminated.

Bioaccumulation of mercury in Haemulopsis elongatus and Pomadasys macracanthus from the SE Gulf of California: condition indexes and health risk assessment

Mercury (Hg) was measured in the muscle, liver, and gonads of Haemulopsis elongatus and Pomadasys macracanthus from Mazatlán (SE Gulf of California) to determine the relationships of the hepatosomatic index (HSI) and gonadosomatic index (GSI) of fish with Hg concentrations in the corresponding tissues. Health risk to consumers was assessed by using the hazard quotient (HQ), considering the average rate of fish consumption in Mexico and Hg concentration in the edible tissue. In H. elongatus, the highest Hg levels were measured in the liver (3.748 μg g^-1); in P. macracanthus, the highest Hg concentration was quantified in the muscle (0.574 μg g^-1). In P. macracanthus, the HSI was negatively correlated with Hg concentration in the liver; in H. elongatus, there was also a negative relationship between Hg levels in gonads and the GSI. Mean HQ values in Haemulopsis elongatus (0.005) and Pomadasys macracanthus (0.002) were below the value (HQ ≥ 1) of concern. The significant reduction of HSI and GSI with Hg increase in the liver and gonads may suggest that Hg bioaccumulation in these fish shows adverse physiological effects. Though HQ values in both species were below the unit, i.e., the consumption of the muscle from this species does not represent a health risk, it is necessary to carry out surveys of fish consumption rates in coastal areas of Mexico to do a more precise health risk assessment associated to Hg intake.

Loss of food nutrients orchestrated by cooking pots: a common trend in developing world

Six types of cooking pots with five different food stuffs were used to investigate the influence of cooking pots on macro and micronutrients of cooked foods. A general trend observed was that cooking pot forged from titanium offered best protection (retention) of micronutrients while pitted aluminum pot offered the lowest irrespective of the food sample cooked. Titanium and enamel coated cooking pots required less quantity of water to get food done resulting into a low (68.67%) moisture content for food cooked in such pots in contrast to values as high as 77.89% when other pots were used. Our research evidenced that cooking pot may have impact on people's morbidity since steady consumption of food cooked in some pots may aggravate, micronutrient malnutrition. Our findings suggest a contrary view to the previous idea of using pressure pot to cook food. Pots that offered low-pressure cooking (82 °C/0.53 bar) was found to preserve the most heat liable nutrients. Our recommendation, therefore, is the use of titanium and enamel coated cooking pots which offered better retention of food nutrients. Cooking may cause changes to food nutrient depending on foodstuff, materials used in forging the pot as well as the fitness of the pot lid.

Bioaccumulation of Metals/Metalloids and Histological and Immunohistochemical Changes in the Tissue of the European Hake, Merluccius merluccius (Linnaeus, 1758) (Pisces: Gadiformes: Merlucciidae), for Environmental Pollution Assessment

Pollution and other types of environmental stress do not spare marine environments, especially those affected by high industrial pressure. Fish, especially coastal species, are used for monitoring the marine environment because they are particularly efficient as bioindicators thanks to their ability to bioaccumulate and biomagnify along the trophic chain. The aim of this research is to evaluate the bioaccumulation and the indirect bioindication ability of the European Hake, Merluccius merluccius (Linnaeus, 1758), one of the most important commercial fish species of the Mediterranean Sea. Morphological and histological alterations of the main target organs, such as liver and gills, have been investigated and the results showed a steatosis in the hepatic tissue. The accumulation of heavy metals has been analyzed by inductively coupled plasma mass spectrometry and for several metals it was showed a different concentration in the two sexes. Moreover, the expression of metallothioneins 1 and Heat Shock Protein 70 has been assessed by immunohistochemistry and did not show high level of expression. We underline the importance of contamination evaluation in commercial fish species and the utilization of the ichthyofauna as bioindicator of environmental quality.

Health Risk Assessment for Human Exposure to Trace Metals Via Bushmeat in Ghana

Consumption and trade in bushmeat are entrenched in sub-Saharan Africa amid growing land degradation and environmental pollution that raise safety concerns, yet sustainability of bushmeat extraction and zoonoses considerations have been the focus of bushmeat research. Here, we evaluated the health risk of trace metals in the skeletal muscle, bone, liver, and skin of the black duiker (Cephalophus niger), brush-tailed porcupine (Atherurus africanus), bushbuck (Tragelaphus scriptus), cane rat (Thryonomys swinderianus), and Maxwell's duiker (Cephalophus maxwelli) being the five most hunted and consumed species of bushmeat in Ghana. Sample tissues of the five species were analyzed for Cu, Zn, Se, Cd, As, Pb, and Hg. Targeted hazard quotient (THQ) of Se for black duiker, bushback, and Maxwell's duiker as well as that of Pb for black duiker, Brush-tailed porcupine, and Maxwell's duiker were concerning (> 1) for individuals foraging daily on bushmeat. Thus, cane rat was the only species that recorded both estimated daily intake (EDI) and THQ of Se and Pb within safe limits for daily consumption. In respect of Cu, Zn, Cd, As, and Hg, EDI and THQ values indicated no perceived risk to consumers for all five species. Lifetime cancer risk (CR) of As was negligible for all species. At the rate of bushmeat consumption in sub-Saharan Africa (0.104 kg per day), the cane rat was the only species considered safe for daily consumption among the five species.

Assessment of Potential Health Risks Associated with the Intake of Heavy Metals in Fish Harvested from the Largest Estuary in Colombia

This study assesses the potential human health risks posed by six heavy metals (Hg, As, Pb, Cd, Cu, and Zn) found in five of the most consumed fish species (Mugil incilis, Centropomus undecimalis, Cathorops mapale, Eugerres plumieri, and Elops smithi) collected by the riverine population living in Ciénaga Grande de Santa Marta (CGSM), the largest estuary in Colombia. Metal concentrations were low compared with those reported in other regions around the world and the maximum value established by international monitoring organizations. The estimation of the potential risk (HQ) indicated that Cu and Hg could generate negative effects in groups of women of childbearing age (WCA) and the remaining population (RP), because they exceeded their related reference doses, with HQ values > 1; however, Cu and Hg concentrations were not high in fish and EWI, MFW, or MeHgPSL values shows that there is no evidence of a potential health risk from MeHg exposure in the study population. Therefore, the recommendations are to establish continuous monitoring of heavy metals together with strategies that address the high fish consumption, as well as to implement mechanisms for the mitigation of contamination of the watershed, to ensure the safety of organisms in the ecosystem and human health, not only of populations who depend on aquatic resources in the area but also of those that market and consume these resources in the Colombian Caribbean.

Health risk assessment and levels of toxic metals in fishes (Oreochromis noliticus and Clarias anguillaris) from Ankobrah and Pra basins: Impact of illegal mining activities on food safety

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Toxic metals analysis revealed that there were appreciable concentrations of Cadmium, Arsenic, Lead and Mercury in the fish samples (Oreochromis niloticus and Clarias anguillaris) and water samples from both rivers.

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All the examined fish species had toxic mineral concentrations within the E.U set limits except for Mercury (Hg) which exceeded the set limits of WHO.

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Human health risk assessment from lifetime metal exposure through fish consumption from the two rivers for both children and adults showed no significant non-carcinogenic adverse health risk to humans.

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Target Hazard Quotient (THQ) values calculated for both children and adult exposure to Cadmium and Mercury were >1 which implied a likely cause of adverse effects during such a person’s lifetime.

Arsenic (As), mercury (Hg), Cadmium (Cd) and lead (Pb) are toxic heavy metals that naturally occur in the ecosystem. Their levels are on the rise due to anthropogenic activities posing threat to aquatic wildlife and humans. In Ghana, pollution of some water bodies has led to unsafe consumption of riverine fishes as well as a shortage of treated potable water principally because the cost of treating polluted water has become expensive across the country. This study aimed to assess the As, Hg, Pb and Cd concentrations in water and fishes from rivers Pra and Ankobrah where activities of artisanal gold mining were carried out resulting in gross pollution of the water bodies.

An experimental study was performed to ascertain the levels of As, Hg, Pb and Cd in fish species of Nile tilapia (Oreochromis noliticus) and mudfish (Clarias anguillaris) and aquatic media (water) from the Pra and River Ankobrah basins using the Atomic Absorption Spectrophotometer (AAS) (Varian AA240FS).

Both river water samples recorded ranges of 0- 0.0040, 0.0060- 0.0387, 0 - 0.0020, 0.006-0.0093 mg/l for Cadmium, Lead, Arsenic and Mercury respectively. For Cadmium and Arsenic, their levels were comparable (p > 0.05). However, detected values for Lead and Mercury were no comparable (p < 0.05). Toxic metals concentrations in the rivers decreased in the order of Hg > Pb > Cd > As. For the fish samples, values ranged 0-0.08, 0.04-0.42, 0-0.04, and 0.40- 0.60 mg/kg for Cadmium, Lead, Arsenic and Mercury respectively. Generally, appreciably high values were obtained for Mercury. Toxic metals concentrations in the rivers decreased in the order of Hg > Pb > Cd > As.

Human health risk assessment from heavy metal exposure through fish consumption from the Rivers for both children and adults showed no significant non-carcinogenic adverse health risk to humans since all calculated values for Hazard Quotient (HQ) were <1. Nonetheless, Target Hazard Quotient (THQ) values calculated for children and adult exposure to Cadmium and Mercury were>1 which implied a likely cause of adverse effects during a person's lifetime.

Elemental distribution in urban sediments of small waterbodies and its implications: a case study from Kolkata, India

The impacts of elemental pollution in sediments of freshwater bodies are of particular concern in rapidly urbanizing cities of the developing world and have been extensively studied in rivers and lakes. The current study is an attempt to highlight the importance of smaller waterbodies, which happen to form a natural network in cities, for assessing the contamination status of sediments. The distribution of elements (Al, Ca, Fe, K, Mg, S, Si, Ti, Ba, Mn, Sr, V, As, Cr, Cu, Ni, Pb and Zn) in sediments of 15 ponds and 6 canals was studied to understand the overall pollution status and the associated ecological risk to aquatic organisms. Geochemical indices revealed Cr, Cu, Pb and Zn to be the principal elements of concern. The mean concentration of Cr, Cu, Pb and Zn was 308, 174, 76.9 and 446 mg kg^-1, respectively. Ecological risk assessment revealed that Cr in 86% sites, Ni in 52% sites, Cu and Zn in 28% sites and Pb in 10% sites were associated with possible ecological toxicity. The findings suggest that multielemental concentration in sediments of ponds and canals could effectively distinguish between pristine and polluted sites and suitably identify the main elements of concern to support cost-efficient waste management solutions customized to both the sites and elements of concern.

Levels of Some Heavy Metals and Health Risks Assessment of Three Different Species of Catfishes in Ikoli Creek, Bayelsa State, Nigeria

Heavy metals are the most common form of aquatic pollutants and are of great health risk to consumers of contaminated sea food. This study investigated the level of heavy metals in three species of catfishes Chrysichthys nigrodigitatus (marine catfish), Clarias gariepinus (African catfish), and Schilbe mystus (silver catfish) in Ikoli Creek, Bayelsa State. The potential human health risks to consumers in the study area were investigated. The heavy metal concentration in the three species of catfishes was found in the following order: Fe > Zn > Cr > Pb > Cd. The levels were below WHO/FAO guideline, except for Fe having the highest value of 88.23 ± 0.09 mg/kg in C. gariepinus, 85.54 ± 0.26 mg/kg in S. mystus, and 66.36 ± 0.10 mg/kg in C. nigrodigitatus, which were above the acceptable regulatory limits in the fishes. The Chronic Daily Intake (CDI) values of all the metals were lower than the USEPA-recommended limits except for Cd in C. nigrodigitatus, C. gariepinus, and S. mystus. The Target Hazard Quotient for C. nigrodigitatus, C. gariepinus, and S. mystus was > 1. Life Cancer Risk from the consumption of Cr in C. nigrodigitatus and S. mystus was 1.65E-03 and 8.11E-04, indicating a probable risk of one chance of cancer for the populace that consumed fishes obtained from Ikoli creek. Heavy metal contamination of fishes caught in Ikoli creek may pose a health risk to the local populace via consumption of fishes.

Levels of heavy metals in the straightfin barb Enteromius paludinosus (Peters 1852) from River Malewa, Naivasha, Kenya

There have been several studies on heavy metals in Lake Naivasha. However, none of them has reported the levels of mercury (Hg), arsenic (As), and chromium (Cr). Moreover, there are no studies on the heavy metals' concentrations in the straightfin barb (Enteromius paludinosus, Peters 1852), a fish species that hosts a parasite (Ligula intestinalis), the latter having been reported to have a high ability to absorb heavy metals from its host. This paper therefore addresses the accumulation of heavy metals, namely arsenic (As), chromium (Cr), lead (Pb), and mercury (Hg) in the tissues of straightfin barb, Enteromius paludinosus (Peters 1852) from the mouth of River Malewa in Lake Naivasha, Kenya. A total of 1307 fish were collected during the month of November 2017. Water samples, sediment samples, 25 fish muscle tissues, and its endoparasite, the cestode Ligula intestinalis, were isolated, and heavy metal concentrations were determined using the thermal-electron atomic absorption spectrophotometer at the Lake Nakuru Water Quality Testing Laboratory. The concentrations of heavy metals in the sediment were below the lowest effect level in sediment, threshold effect concentration in sediment, severe effect concentration in sediment, and the shale values of sedimentary rocks thus showing no sign of pollution. In the muscle tissues of the fish, As, Cr, Pb, and Hg showed high levels with mean concentrations of 5.0696, 22.0854, 45.2108, and 1.5458 mg/kg ww, respectively. Bioconcentration factors further supported the observation that trace element accumulation was higher in fish compared with sediment and water. The target hazard quotients of As, Cr, Pb, and Hg obtained for both the female and male were > 1 indicating a possible health risk associated with the consumption of E. paludinosus. The bioaccumulation factors (BAFs) for L. intestinalis were 2.4093, 2.1873, 5.8601, and 5.1395 for As, Cr, Pb, and Hg, respectively, indicating the potential of the cestode in the accumulation of heavy metals from the host; hence, it can be used as an accumulation bioindicator.

Mercury, silver, selenium and other trace elements in three cyprinid fish species from the Vaal Dam, South Africa, including implications for fish consumers

The levels of Cr, Cu, Zn, Se, Ag, Cd, Hg, and Pb were determined in muscle and liver samples from 30 specimens of fish belonging to the species Labeobarbus aeneus, Labeobarbus kimberleyensis, and Labeo umbratus from the Vaal Dam. Health risks for human fish consumers were estimated using the target hazard quotient (THQ), the Se:Hg-ratio, and Se health benefit value (Se HBV). This is the first comprehensive report on Hg levels in fish from this lake. Mean concentrations ranging from 0.247-0.481 mg/kg dw in muscle and from 0.170-0.363 mg/kg dw in liver clearly show a contamination with this element. Although levels in muscle did not exceed maximum allowances for human consumption, a calculated THQ of 0.12 and 0.14 for the two Labeobarbus species, respectively, showed a potential risk due to additive effects. All Se:Hg-ratios as well as Se HBVs clearly suggested positive effects for fish consumers. Levels of Cu were remarkably high in the liver of L. umbratus, calling for further investigation on this species. Cadmium levels were above the maximum allowances for fish consumption in the liver of all three species (means between 0.190 and 0.460 mg/kg dw), but below the LOD in all muscle and intestine samples. This is also the first report of Ag in fish from South Africa. Levels were below the LOD in muscle, but well detectable in liver; they varied significantly between the two Labeobarbus species (0.054 ± 0.030 and 0.037 ± 0.016 mg/kg dw) compared to L. umbratus (1.92 ± 0.83 mg/kg dw) and showed a positive correlation with Cu levels (63.7 ± 17.0; 70.3 ± 9.0 and 1300 ± 823 mg/kg dw), possibly due to similar chemical affinities to metallothioneins. The detected Ag levels can serve as a basis to monitor the development of this new pollutant in aquatic environments in South Africa and worldwide.