Metal Contamination Research Articles

Assessment of heavy metal contamination in the surface sediments, seawater and organisms of the Pearl River Estuary, South China Sea

Coastal heavy-metal contamination poses significant risks to marine ecosystems and human health, necessitating comprehensive research for effective mitigation strategies. This study assessed heavy-metal pollution in sediments, seawater, and organisms in the Pearl River Estuary (PRE), with a focus on Cd, Cu, Pb, Zn, As, Hg, and Cr. A notable reduction in heavy metal concentrations in surface sediments was observed in 2020 compared to 2017 and 2018, likely due to improved pollution management and COVID-19 pandemic restrictions. Spatial analysis revealed a positive correlation between elevated heavy-metal concentrations (Cu, Pb, Zn, Cd, and As) and areas with significant human activity. Source analysis indicated that anthropogenic activities accounted for 63 % of the heavy metals in sediments, originating from industrial effluents, metal processing, vehicular activities, and fossil fuel combustion. Cd presented a high ecological risk due to its significant enrichment in surface sediments. Organisms in the PRE were found to be relatively enriched with Hg and Cu, with average As concentrations slightly exceeding the Chinese food-health criterion. This study identified high-risk ecological zones and highlighted Cd as the primary pollutant in the PRE. The findings demonstrate the effectiveness of recent pollution control measures and emphasize the need for ongoing monitoring and mitigation to safeguard marine ecosystems and human health.

Heavy metals (Pb, Cd, Ni) in insect-based products for human consumption sold by e-commerce in the EU market: Occurrence and potential health risk associated with dietary exposure

Ensuring the safety of insect-based products (IBPs) is essential considering their potential as food source in the future. Among food contaminants, heavy metals represent a concern for food safety. In this study, the concentrations of lead (Pb), cadmium (Cd), and nickel (Ni) in 52 IBPs marketed on European e-commerce were assessed. The analyses were conducted with Graphite Furnace Atomic Absorption Spectrometry. The impact of consuming IBPs on the toxicological reference values for each analyzed heavy metal was also assessed, to characterize the potential human health risks. Results showed a statistically significant higher concentration of Pb in products containing a percentage greater than 50% of insects compared to those with lower percentage of inclusion. Specifically, 70% of samples containing 100% insect powder exceeded the Pb levels established by regulation, while 10% exceeded the Cd limits. The Ni values, higher respect to other studies, were compared with the mean values reported by the EFSA monitoring plan on foodstuff, showing that our data mainly fell between grain and other vegetables products, which have a greater nickel content respect to products of animal origin. According to EFSA, the health risk assessment conducted suggests that consuming products containing A. diaperinus, A. domesticus, L. migratoria, and T. molitor as proposed does not significantly contribute to overall dietary exposure to heavy metals. However, 4.24% of the Margins of Exposure for Pb were above 1 but below 10, suggesting a very low health risk, while 12.30% of the Margins of Exposure for Ni were lower than 30, indicating potential health risks for sensitized individuals. The importance of rigorous monitoring of heavy metal contamination to ensure the safety of IBPs and the need for continued research to mitigate potential health risks associated with their consumption were highlighted.

NZVI@BC as a Soil Amendment and Its Effects on Potted Rice Growth and Soil Properties

This study investigated the effects of nano zero-valent iron-modified biochar (nZVI@BC) as a soil amendment on potted rice growth, soil properties, and heavy metal dynamics. Seven treatments with varying amounts of soil conditioner, biochar, and nZVI@BC were applied to potted rice. Results showed that nZVI@BC application significantly improved rice agronomic traits, with the 15 g·kg−1 treatment increasing the panicle formation rate by 15% and 100-grain weight by 8% compared to the control. Soil fertility was enhanced, with available phosphorus increasing from 137 to 281 mg·kg−1 in the most effective treatment. Heavy metal analysis revealed that nZVI@BC application did not increase soil heavy metal content, with Cd levels remaining below 0.3 mg·kg−1 across treatments. Notably, the 10 g·kg−1 nZVI@BC treatment showed potential for slight Cd immobilization, reducing its concentration from 0.32 to 0.26 mg·kg−1. Microbial community analysis showed that nZVI@BC altered soil microbial diversity and composition, with the 10 g·kg−1 treatment resulting in the highest fungal diversity (Chao1 index: 294.219). The relative abundance of the beneficial fungal class Agaricomycetes increased from 40% to 55% with optimal nZVI@BC application. These findings suggest that nZVI@BC has potential as an effective soil amendment for improving rice cultivation while maintaining soil health, microbial diversity, and potentially mitigating heavy metal contamination.

Evaluating washing techniques to eliminate external contamination of trace elements in bat fur and bird feathers

Non-invasive proxies, such as fur and feathers, are likely to be increasingly used to assess the potential exposure of chemicals, including trace metals and metalloids. However, the amount of external contamination is usually unknown, and there is no standard method for removing external contamination of trace metals in fur or feathers. To date, 40 % of studies published related to the measurement of trace metal levels in fur or the hair of non-human mammals and 24 % of studies in feathers do not state any washing methods or did not wash the samples before analysis. We assessed three washing techniques to remove external contamination of arsenic (As), lead (Pb), and zinc (Zn) from bat fur. We selected the three most frequently used fur washing methods from literature. To test these methods, fur samples from great flying foxes (Pteropus neohibernicus neohibernicus, n=15 individuals) from Papua New Guinea preserved over eight decades (AMNH, USA) were used. Percentages of trace metal removed are 87.19 % (SD= 12.28), 92.99 % (SD= 5.5) and 88.57 % (SD= 9.33) for As, 54.72 % (SD= 31.64), 55.89 % (SD= 37.87), and 53.93 % (SD= 41.28) for Pb, and 74.03 % (SD= 22.96), 22.93 % (SD= 73), and 24.95 % (SD= 49.5) for Zn using M2, M3, and M4, respectively. We also assessed four washing techniques to remove external contamination of arsenic (As), mercury (Hg), and zinc (Zn) from bird feathers. We identified the four most prevalent washing techniques in the literature used for feathers. We used feathers from the great horned owl (Bubo virginianus) and the great blue heron (Ardea herodias) to test these methods. Percentages of trace metal removed are 34.35 % (SD= 44.22), 69.22 % (SD= 36.5), 62.59 % (SD= 48.37), and 80.89 % (SD= 14.54) for As, 66.97 % (SD= 13.26), 29.4 % (SD= 67.06), 49.68 % (SD= 42.33), and 28.88 % (SD= 69) for Hg, and <0 % (SD= 80.1), 0 % (SD= 29.55), 11.23 % (SD= 47.73), and 57.09 % (SD= 21.2) for Zn using M2, M3, M4, and M5, respectively. This study shows the importance of washing fur and feather samples prior to trace metals analyses in ecotoxicology and biomonitoring studies.

Use of phytoextraction with Noccaea caerulescens to limit the transfer of cadmium and zinc to subsequent rocket crops

Soil trace metal (TM) contamination is a worldwide issue and threatens food production and security. Remediation of cadmium (Cd) and zinc (Zn) contaminated soils by phytoextraction with the Zn/Cd hyperaccumulator Noccaea caerulescens is widely studied but few studies have investigated the efficiency of this technique to reduce Cd and Zn soil-to-crop transfers to subsequent vegetable crops. The vegetable biomonitor rocket Diplotaxis tenuifolia was grown in pots on 13 moderately contaminated soils that had previously been cropped with N. caerulescens. Using mixed-effects models, we show the drivers of rocket biomass, Cd and Zn concentrations.Our models show, for our study soils, the benefit of previous N. caerulescens uptake of Cd and Zn in decreasing Cd and Zn concentrations in a subsequent rocket crop. We also show a slight positive impact of N. caerulescens biomass (and therefore uptake) on rocket growth. Our data show that exchangeable soil concentrations are major drivers of Cd and Zn rocket concentrations. Other soil variables negatively driving rocket Cd and Zn concentrations are NO3− content, organic matter content, cation exchange capacity, and soil manganese which stimulate rocket biomass and/or influence TM bioavailability. Rocket D. tenuifolia seems to be a good biomonitor for contaminated soils as it is tolerant to relatively high TM soil concentrations. We demonstrate that 40 % of rockets grown on soils below 2 mg total Cd kg−1 dry soil have foliar Cd concentrations above the European maximum allowed level confirming the need to review soil legal thresholds to protect consumers' health.In conclusion, our study suggests promising use of N. caerulescens phytoextraction for bioavailable contaminant stripping which is all the more interesting given the increasing demand for urban growing spaces.

Assessment of Heavy Metal Contamination of Groundwater in Rural Areas of Duhok City, Iraq

This study investigates the quality of groundwater sources in the rural areas of Duhok City, Iraq, with a particular focus on heavy metal contamination, chemical composition, and properties of water. Water samples from 14 wells, serving as the main water source for the surrounding areas, were collected and analyzed. Water quality parameters including calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl⁻), potassium (K⁺), and sulfate (SO₄²⁻) values ranged from 24 to 105.6 mg/L, 6.832 to 50.752 mg/L, 18 to 34 mg/L, 1 to 7 mg/L, and 3.4 to 38 mg/L respectively. Common heavy metals like manganese (Mn), lead (Pb), copper (Cu), and cobalt (Co) exhibited varying concentrations. Most parameters meet the WHO standards, except for the elevated potassium in one sample, requiring attention. Additionally, 50% of the sampled wells showed elevated cadmium (Cd) levels. Possible sources of contamination include industrial activities, agricultural runoff, and geological factors, highlighting the importance of ongoing monitoring and targeted interventions to ensure access to clean and safe water.

TXRF capability of metallic contamination analysis on rough silicon wafers

TXRF capability of metallic contamination analysis on rough silicon wafers

First Assessment of Water Quality Impact from a New Landfill in Tangier, Morocco – Microbial and Metal Contamination

First Assessment of Water Quality Impact from a New Landfill in Tangier, Morocco – Microbial and Metal Contamination

Chitosan-based modalities with multifunctional attributes for adsorptive mitigation of hazardous metal contaminants from wastewater

The increase in population and industrialization has intensified water scarcity and stress, and contaminated water bodies. Therefore, the development of advanced water and wastewater treatment technologies has gained global attention from researchers. Adsorption, using natural materials (nano, polymer, and bio) is one of the most cost-effective, less challenging, and well-known technologies for wastewater treatment and improving water quality. Among them, chitosan (CS) has demonstrated a set of unique features, such as biodegradability, eco-friendliness, availability, low cost, and biocompatibility. Hence, this review provides an overview of some recent advancements in the removal of heavy metals, including As (III) and (V), Cd (II), Cu (II), Cr (VI), and Pb (II) by CS-based adsorbents, and their potential effects on human health. It also covers the synthesis of CS-based adsorbents for the elimination of mentioned contaminants in recently reported studies. In addition, this study recommends encountering potential drawbacks by enhancing the adsorption capacity by incorporating functional groups, nanoparticles, and other materials. These modifications may help increase selectivity for specific metal contaminants and synthesize adsorbents that can perform better over a wide range of pH. Insights gained from this study will guide researchers in the future toward optimal water treatment and pollutant elimination strategies.

Fortifying casein phosphopeptides and calcium in wheat reduce the cadmium, arsenic, and lead bioavailability based on a mouse model: Calcium and phosphate transporters and gut microbiota

Reducing the oral bioavailability of metal contaminants including cadmium (Cd), arsenic (As), and lead (Pb) in foods can protect human health. Studies showed reduced metal bioavailability with elevated calcium (Ca) and iron (Fe) intake; however, the effectiveness of enhancing food Ca and Fe bioavailability remains unknown. Based on a mouse bioassay and using metal accumulation in tissues (kidneys and liver) as the bioavailability endpoint, this study investigated the roles of casein phosphopeptides (CPP, food nutrition fortifier) in lowering the Cd, As, and Pb bioavailability from consuming a metal-contaminated wheat. The CPP amendment at 0.10–0.50% in wheat promoted its Ca bioavailability, causing 33–62% and 59–80% decreases of the gene expression encoding for duodenal Ca and phosphate transporters in mice. This limited transcellular transport of Cd2+ and inorganic arsenate via Ca and phosphate transporters respectively, thus leading to 27% and 34% decreases in Cd and As contents in mouse kidneys fed with wheat at 0.50% CPP amendment. In addition, CPP promoted the colonization of Feacalibaculum and Bifidobacterium in mouse gut, likely promoting As excretion in feces by 81–112%. In contrast to Cd and As, CPP failed to reduce Pb contents in mouse tissue after consuming CPP-amended wheat, probably by elevating wheat-Pb solubility in the intestinal fluid by 48–136%. However, co-amendment of 0.30% CPP and 500 μg g–1 Ca as Ca gluconate lowered the Cd, As, and Pb contents in mouse kidneys by 38–71%. The data indicate that fortifying Ca together with CPP in wheat can reduce human exposure to multi-metals via dietary intake.

Generalized Richards model of slow sand filtration to remove lead pollutant from polluted waters: study of velocity effect

In Morocco, numerous regions face water scarcity. To address water shortages in the arid Marrakech region, agricultural reuse of wastewater can be a viable solution, provided that accessible and cost-effective methods, such as slow sand filtration, are employed to reduce pollutant levels. In the vicinity of the Mine Draa Lasfar, wastewater discharged into the Tensift River has led to significant contamination by metallic trace elements, including lead (Pb). This contamination spreads from the water to the soil, plant cover, and living organisms, with severe Pb contamination observed in children, leading to serious neurological diseases. Addressing this critical issue, our study explores the application of slow sand filtration for water treatment. This method is reliable and environmentally friendly, particularly effective at lower water velocities, ensuring optimal contaminant removal. We introduced the Generalized Richards model, a versatile mathematical tool, which outperformed the standard logistic model by providing a more accurate fit to our experimental data. In conclusion, slow sand filtration, when implemented in areas like Mine Draa Lasfar, offers a promising solution for mitigating metallic trace elements contamination in water sources, with the Generalized Richards model enhancing our understanding and optimization of the filtration process.

Hazard assessment of microplastics and heavy metals contamination in Levant frogs (Pelophylax bedriagae): A bioindicator in Western Iran

The increasing pollution of aquatic ecosystems caused by microplastics (MPs) and heavy metal ions worldwide threatens the life of aquatic organisms, including amphibians. In this study, we investigated the presence and accumulation of MPs and heavy metal ions in the upper gastrointestinal tract (GIT) of the Levant frog (Pelophylax bedriagae) as a bioindicator in contaminated sites of Western Iran. A total of 192 adult frogs from 16 locations in the west and northwest of Iran were collected. We measured the accumulation of MPs and heavy metal ions in the collected frogs and determined the characteristics of MPs in the samples. Our findings revealed widespread MPs and heavy metal ions contamination in the frog GIT across all sampled stations. We found 742 MP particles in the digestive system of frogs, with the highest (7.09 MP/individual) and lowest (2.37 MP/individual) number observed in stations 10 and 9, respectively. Fibers were the most common MPs and polyester (PES) (42.5%) and polyethylene terephthalate (PET) (17.2%) were found to be the most common polymers in the GIT of frogs. The average accumulation of heavy metal ions showed significant differences (P < 0.05) among 16 sampling stations, and zinc (II) and mercury (II) showed the highest and lowest concentrations in frogs. We also found moderate to strong positive correlations between the detected MPs and heavy metal ions in the frog samples across all sampling stations. Our findings confirm the contamination of frogs by MPs and heavy metal ions and the potential capacity of MPs to increase the toxicity of heavy metals in P. bedriagae as a bioindicator in contaminated sites.

Application of Batch Electrocoagulation with Aluminium Electrodes for Simultaneous Removal of Organic and Heavy Metal Contaminants from Borneo Urban Rivers

The challenges of sludge management and complex water treatment systems hinder the effectiveness of chemical coagulation in treating heavily contaminated urban river water. Realizing these issues, this study aims to develop a batch electrocoagulation system using aluminum electrodes to generate in-situ aluminum hydroxide coagulants for simultaneous removal of organic contaminants and heavy metals from Borneo urban river water. Subsequent, the treatment system achieves a reduction of 91.67% of turbidity, 98.29% of color, 95.16% of total suspended solids (TSS), 97.78% of iron, 94.21% of lead, 21.94% of pH, and 98.58% of chemical oxygen demand (COD) with an electric current of 5A and a residence time of 25minutes. Besides, the treated water meets the Malaysia National Water Quality Standards for Class I which making it suitable for domestic consumption. The energy consumption cost for the treatment is only RM 1.48 (USD 0.31) per cubic meter of treated water. Additionally, the analysis of the electrocoagulation flocs reveals the presence of carbon, iron, lead, and various dissolved minerals which indicates effective contaminant removal from urban river. Overall, this study demonstrates the potential of the batch electrocoagulation treatment system as an effective and cost-efficient solution for treating urban river water in Borneo industrial areas.

Efficient removal and stepwise recovery of various heavy metals from water by using calcium carbonate with different activity

Heavy metals in wastewater have caused serious environmental contamination in the world. However, a key challenge with the most effective solution through chemical precipitation is the high pH of in the effluent by the use of lime. Herein, we propose a strategy using highly active calcium carbonate (HACC) for enhancing its slow-release activity, which efficiently removes heavy metal contamination while avoiding high pH of the effluent. The HACC demonstrate a removal of more than 99 % for Cd(II), Cu(II), Zn(II) and Pb(II) from the composite contaminated water within 50 min, while maintaining the pH of the effluent close to neutral. In addition, mechanistic analyses unveil that the free heavy metals in different solutions combine with OH– and CO32– released from HACC in different precipitation behaviors to form their respective precipitates, thereby discovering the mechanism of regulating the precipitation rates of different heavy metals by controlling the activity of calcium carbonate. Based on it, the stepwise recovery of heavy metals was realized by adjusting the calcium carbonates with different activity. The present work provides guidance for gentle and efficient removal of heavy metal pollution in water bodies and inspires the future development of recovery of heavy metals.

Response of benthic assemblages to heavy metal contamination from shipbreaking operations in a tropical coastal area

The response of macrobenthic communities to both environmental and anthropogenic pressures serves as a valuable indicator of ecosystem integrity. This study aimed to unravel the benthic community structure, examine the heavy metal contamination status, and explore the response of the microbenthic community to heavy metals in a tropical shipbreaking region. For this, sediment and benthos samples were taken from different sampling stations of the shipbreaking area and the non-shipbreaking sites. The results showed the benthic community consisted of 23 taxa, including Polychaeta, Oligochaeta, Amphipoda, Decapoda, Gastropoda, Bivalvia, and Priapulida, with polychaetes being the predominant group. The benthic community and diversity values were significantly varied between the two sampling sites (p <0.05). Taxa richness was lower in the shipbreaking area, primarily characterized by the dominance of opportunistic benthic groups, particularly Capitella sp. The concentrations of heavy metals (µg. g-1) in the sediment varied within the following ranges: 35.54-258.021 for Zn, 4.84-132.08 for Pb, 22.82-75.25 for Cu, 198.74-764.16 for Mn, 14.57-42.13 for Cr, 4.03-42.23 for Ni, and 3.82-14.85 for Co. Based on concentration levels, Zn, Pb, and Cu were identified as major contaminants with moderate to high potential for adverse effects, particularly evident in the shipbreaking area compared to non-shipbreaking areas. Pollution indices, including enrichment factors and contamination factors, also highlighted contamination by Zn, Pb, and Cu. Among the benthic taxa, Polychaeta demonstrated a high degree of tolerance to elevated concentrations of these heavy metals. Amphipoda density was significantly negatively correlated with Zn, Pb, and Cu concentrations, with significant coefficients of determination (r2= 0.38, p <0.10; r2= 0.64, p <0.01 and r2 = 0.63, p <0.01, respectively). Multivariate analyses (cluster analyses, MDS and CCA) demonstrated both positive and negative relationships among heavy metals and benthic groups. Canonical Correspondence Analysis (CCA) showed the benthic community was negatively correlated with Zn, Pb, and Cu. This finding provided critical insights into the ecological health of aquatic ecosystems, aiding in the development of informed conservation and management strategies.

Distribution, sources, impact factors and ecological risks of sediment heavy metals from typical estuarine wetlands in tropical islands

Heavy metal contamination in the estuarine wetlands of tropical islands is becoming increasingly severe. This study focused on four typical estuarine wetlands of Hainan Island, including the mangrove and seagrass areas in Lingshui County, the mangrove and seagrass areas in Xinying Port, the mangrove area in Sibi Wan, and the seagrass area in Huachang Wan. By analyzing the heavy metal content in the surface sediments of these wetlands, we investigated the distribution characteristics and levels, explored their influencing factors, and assessed ecological risk of heavy metals in these areas. It was found the accumulation of heavy metals was high from obvious sampling sites of human activities, the type of sediment could affect the adsorption of heavy metals, with silty mudflats accumulating more. TOC/TN indicated that the organic sources of mangroves were diverse, included environmental impacts and human interference. According to the soil accumulation index and potential ecological risk index in these areas, almost all heavy metals were unpolluted except for As, which showed moderate pollution levels. The overall ecological risk in these areas was relatively low. The results of principal component analysis and correlation analysis indicated that Pb, Cu, and As were primarily sourced from human activities, while Cr was mainly of natural origin. Moreover, the distribution of heavy metals in the study areas was principally affected by TOC and salinity.

Evaluation of physical and heavy metal contamination and their distribution in waters around Maddhapara Granite Mine, Bangladesh

The Maddhapara Granite Mine is a significant contributor to Bangladesh's economy, causing considerable environmental concern due to the discharge of untreated mine water. This water presents possible hazards to local ecosystems, agriculture, and public health. For this investigation, we obtained water samples from 15 distinct places in the vicinity of the granite mine. A comprehensive analysis of the physicochemical properties was conducted including pH, turbidity, electrical conductivity (EC), total dissolved solids (TDS), and dissolved oxygen (DO) and an Atomic Absorption Spectrometer to quantify the heavy metals’ levels, specifically Ni, Zn, Fe, Pb, Cu, and Cr, following the requirements set by the World Health Organization (WHO), Food and Agriculture Organization (FAO), and Department of Energy (DoE) in Bangladesh. The study was carried out on various pollution indices i.e., Heavy Metal Pollution Index (HPI), Heavy Metal Evaluation Index (HEI), and Degree of Contamination (Cd). The pH of the samples varied from 6.27 to 8.86. Furthermore, the samples’ TDS and EC ranged from 36 mg/l to 392.56 mg/l and 102.78 μS/cm to 611.51 μS/cm, respectively. The HPI values exhibited substantial variation, with the highest HPI-a (WHO) measuring 52215.6, indicating a severe level of heavy metal contamination. Similarly, the HEI-a (WHO) reached a maximum value of 1252.45, while the highest contamination degree (Cd-a, WHO) was 1248.45 and these results are beyond the acceptable limits for human consumption and ecological balance. Immediate actions are required to develop treatment technologies and management strategies to prevent the potential health risks associated with using untreated mine wastewater.

Alleviation of arsenic stress in pakchoi by foliar spraying of engineered nanomaterials.

Addressing heavy metal contamination in leafy vegetables is critically important due to its adverse effects on human health. In this study, we investigated the inhibitory effects of foliar spraying with four nanoparticles (CeO2, ZnO, SiO2, and S NPs) on arsenic (As) stress in pakchoi (Brassica rapa var. Chinensis). The findings reveal that foliar application of ZnO NPs at 1 ~ 2.5 mg plant-1 and CeO2 NPs at 5 mg plant-1 significantly reduces As in shoots by 40.9 ~ 47.3% and 39.4%, respectively. Moreover, 5 mg plant-1 CeO2 NPs increased plant height by 6.06% and chlorophyll a (Chla) content by 30.2% under As stress. Foliar spraying of CeO2 NPs at 0.2-5 mg plant-1 also significantly enhanced superoxide dismutase (SOD) activity in shoots by 9.4 ~ 13.9%, lowered H2O2 content by 42.4 ~ 53.25%, and increased root protein contents by 79 ~ 109.2%. CeO2 NPs regulate the As(III)/As(V) ratio, aiding in As efflux from roots and thereby reducing As toxicity to plants. In vitro digestion experiments reveal that the consumption of CeO2 NPs carries the lowest health risk of As. In addition, foliar spraying of ZnO NPs at 1 ~ 2.5 mg plant-1 can suppress plant As uptake by modulating enzyme activity, reducing leaf damage, and enhancing chlorophyll content. The study demonstrates that high CeO2 NP concentrations and suitable ZnO NP concentrations can alleviate As toxicity in pakchoi, consequently reducing human health risks.

Assessment of heavy metal concentration in the water of major carp breeding River Halda, Bangladesh

Heavy metal contamination in river water is a result of anthropogenic sources like industrial waste, tanneries, used fertiliser, and sewage discharge. Bioaccumulation and toxicity of heavy metals are alarming concerns for the natural carp breeding ground of the one and only river Halda of Bangladesh. Seven heavy metals (Fe, Mn, Cu, Co, Ni, Zn, and Cr (VI)) were assessed in this study following standard methods by gathering data from 36 sampling points that are situated along the area between the origin of Halda and Kalurghat confluence point of Halda and Karnofuli. An atomic absorption spectrophotometer was used for the measurement of the heavy metals, and the correlation between the parameters was determined using principal component analysis (PCA). The concentration of heavy metals ranged from 0.316 to 3.216 mg/L for Fe, 0.023–0.236 mg/L for Mn, 0.022–0.044 mg/L for Cu, 0.022–0.051 mg/L for Co, 0.002–0.008 mg/L for Ni, 0.037–0.282 mg/L for Zn, and 0.013–0.146 mg/L for Cr (VI), respectively. Cu and Mn values in some points were above the permissible limit, but other metal contents were within the permissible limit.

Is the concentration of heavy metals in sun-dried Engraulicypris sardella (Günther, 1868) in Malawi, a human health risk?

The effects of trophic cascades have made small-size pelagic fish species, such as Engraulicypris sardella, from Lake Malawi an important ecological and food system. However, human-induced activities can potentially pollute Lake Malawi exposing E. sardella to heavy metals contamination. This could pose a food system health risk to the population of Malawians and neighboring countries, which heavily rely on fish as a source of animal protein. Therefore, this study investigated the concentration levels of Lead (Pb), Cadmium (Cd), Zinc (Zn), Copper (Cu), Manganese (Mn), and Iron (Fe) in sun-dried E. sardella and conducted a health risk assessment associated with its consumption. E. sardella samples were collected from Karonga, Nkhata Bay, Nkhotakota, Salima, and Mangochi districts in Malawi between December 2023 and February 2024. The results revealed significant variations in Cd, Zn, Cu, Mn, and Fe concentrations among the sampled sites while Pb contamination was not detected. The concentrations of Zn, Cu, Mn, and Fe in E. sardella were within acceptable consumption limits set by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO) in 2012. However, the fish's average Cd levels (0.17 mg kg−1 ww) were slightly above the recommended threshold of 0.1 mg kg−1 ww by FAO/WHO (2012) but remained below the limit of 0.5 mg kg−1 ww set by FAO in 1983. Furthermore, none of the analyzed heavy metals posed a health risk effect to people. Therefore, there is a need for regular monitoring of heavy metal concentrations in E. sardella and other mostly consumed fish species from Lake Malawi, both fresh and processed, for a sustained guarantee of the safety of the fish consumers.