Carcinogenic and non-carcinogenic health risk of arsenic ingestion via drinking water in Langat River Basin, Malaysia

Examining carcinogenic and noncarcinogenic health risks related to arsenic exposure in Ethiopia: A longitudinal study

Background

The carcinogenic properties of arsenic make it one of the most hazardous chemicals globally. Nevertheless, the exact level of human exposure to arsenic and the associated risks of cancer and non-cancer effects through different pathways in Ethiopia are still uncertain.

Objective

The primary aim of this study was to evaluate the risk of both cancer and non-cancer outcomes among children and adults who have been exposed to arsenic through drinking water in the Adami Tulu Jido Kombolcha district of Ethiopia.

Methods

For this study, a longitudinal study design was employed. A total of 45 groundwater sources were sampled using the census sampling method. The concentrations of total arsenic were measured using Agilent 7900 series inductively coupled plasma mass spectrometry. Carcinogenic and noncarcinogenic risk assessments were conducted by calculating lifetime cancer risk and hazard quotients. Microsoft Office Excel was utilized to calculate human health risk indices, and descriptive statistical analysis were performed using SPSS software.

Results

Our findings revealed that during the dry season, the mean arsenic concentration in the groundwater samples was 11.15 ± 9.38 µg/L, while during the rainy season, it was 10.67 ± 8.16 µg/L. The total cancer risk for children, resulting from oral ingestion and skin contact, was 1.15 × 10-2 and 1.07 × 10-2 during the dry and rainy seasons, respectively. For adults, the total cancer risk from oral ingestion and skin contact during the dry and rainy seasons was 4.95 × 10-3 and 4.59 × 10-3, respectively. Furthermore, the total hazard quotients for children via oral ingestion and skin absorption were 25.9 and 24.0 during the dry and rainy seasons, respectively. For adults, the total hazard quotients from ingestion and dermal contact during the dry and rainy seasons were 11 and 10, respectively.

Conclusions

The findings indicate that the risks of cancer and non-cancer effects resulting from arsenic exposure through ingestion and dermal exposure were found to exceed the acceptable thresholds in both seasons. These results emphasize the urgent need for focused attention on the study population in the study area due to the high likelihood of experiencing adverse health outcomes.

Trophic transfer patterns of arsenic in freshwater ecosystem layers in arsenic-endemic Ganges Delta and its potential human health risk

Arsenic (As) is a toxic environmental contaminant with global public health concern. In aquatic ecosystems, the quantification of total As is restricted chiefly to the individual organisms. The present study has quantified the total As in different trophic layers (sediment-water-phytoplankton-periphyton-zooplankton-fish-gastropod-hydrophytes) of lentic freshwater ecosystems. As transfer pathways quantifying the transmission rate across trophic-level compartmental route were delineated using a novel model-based approach along with its potential contamination risk to humans. Lentic water bodies from Indo-Gangetic region, a core area of groundwater As, were selected for the present investigation. The study revealed that among the lower biota, zooplankton were the highest accumulator of total As (5554-11,564 µg kg-1) with magnification (rate = 1.129) of the metalloid, followed by phytoplankton (2579-6865 µg kg-1) and periphytic biofilm (1075 to 4382 µg kg -1). Muscle tissue of zooplanktivore Labeo catla is found to store higher As (80-115 µg kg-1 w.w.) compared to bottom-dwelling omnivore Cirrhinus mrigala (58-92 µg kg-1 w.w.). Whereas, Amblypharyngodon mola has accumulated higher As (203-319 µg kg-1 w.w.) than Puntius sophore (30-98 µg kg-1 w.w.) that raised further concern. The hepatic concentration indicated arsenic-mediated stress based on As stress index (threshold value = 1). Mrigal and Mola showed significant biomagnification among fishes while biodiminution was observed in Catla, Bata, Rohu and Punti. All the studied fishes were under the arsenic mediated stress. In the 'sediment-water-periphytic biofilm-gastropod' compartment, the direct grazing accumulation was higher (rate = 0.618) than the indirect path (rate = 0.587). Stems of edible freshwater macrophytes accumulated lesser As (32-190 µg kg-1 d.w.) than roots (292-946 µg kg-1 d.w.) and leaves (62-231 µg kg-1 d.w.). The target cancer risk (TCR) revealed a greater concern for adults consuming edible macrophyte regularly. Similarly, the varied level of target hazard quotient and TCR for adults consuming fishes from these waterbodies further speculated significant health concerns. The trophic transfer rate of environmental As in soil-water-biota level at an increasing trophic guild and consumer risk analysis have been unravelled for the first time in the Indo-Gangetic plains, which will be helpful for the strategic mitigation of As contamination.

Phytoremediation capability of Typha latifolia L. to uptake sediment toxic elements in the largest coastal wetland of the Persian Gulf

The present study evaluated the status of sediment toxicity and pollution, and the phytoremediation capability of Typha latifolia L. (TlL) within the largest coastal wetland in the southwest of Iran, the Shadegan International Wetland. In eight sampling sites, covering the entire wetland, the concentration of six toxic elements (As, Cr, Cu, Ni, Pb, and Zn) in the surface sediment, root, and stem of TlL were measured. The results indicated that mean concentrations of Cr, Cu, Pb, and Zn were found to be higher than those in the local background, which likely indicates anthropogenic sources of these elements. Due to the presence of a nearby landfill, the results of modified pollution index (MPI) and aggregate toxicity index (ATI) indicated a moderately-heavily polluted level and moderate to high toxic degree, respectively. However, the medium-low level of toxicity toward living of organisms (21 % probability) was detected based on the assessment of the Sediment Quality Guidelines (SGQ). The results of our study indicate that the root and stem tissues of TlL are capable of acting as an indicator of Cu/Pb/Zn and Zn pollution in sediment, respectively. Considering the potential of phytoremediation, TlL represented both phytostabilization and phytoextraction capabilities for Pb and Zn and a significant increase was observed in the phytoremediation capability by increasing the distance from the landfill area. According to the results of the metal accumulation index (MAI) and comprehensive bioconcentration index (CBCI), TlL grown in the study area showed an acceptable performance in the accumulation of multiple toxic elements compared to that in Turkey, India, and Poland. Overall, TlL is a good candidate for the phytoremediation of sediments contaminated by Pb and Zn.

Embryonic Arsenic Exposure Triggers Long-Term Behavioral Impairment with Metabolite Alterations in Zebrafish

Arsenic trioxide (As2O3) is a ubiquitous heavy metal in the environment. Exposure to this toxin at low concentrations is unremarkable in developing organisms. Nevertheless, understanding the underlying mechanism of its long-term adverse effects remains a challenge. In this study, embryos were initially exposed to As2O3 from gastrulation to hatching under semi-static conditions. Results showed dose-dependent increased mortality, with exposure to 30-40 µM As2O3 significantly reducing tail-coiling and heart rate at early larval stages. Surviving larvae after 30 µM As2O3 exposure showed deficits in motor behavior without impairment of anxiety-like responses at 6 dpf and a slight impairment in color preference behavior at 11 dpf, which was later evident in adulthood. As2O3 also altered locomotor function, with a loss of directional and color preference in adult zebrafish, which correlated with changes in transcriptional regulation of adsl, shank3a, and tsc1b genes. During these processes, As2O3 mainly induced metabolic changes in lipids, particularly arachidonic acid, docosahexaenoic acid, prostaglandin, and sphinganine-1-phosphate in the post-hatching period of zebrafish. Overall, this study provides new insight into the potential mechanism of arsenic toxicity leading to long-term learning impairment in zebrafish and may benefit future risk assessments of other environmental toxins of concern.

Delineating the controlling mechanisms of arsenic release into groundwater and its associated health risks in the Southern Loess Plateau, China

The mechanisms controlling arsenic (As) enrichment and mobilization associated with human health risk assessment of groundwater in the Longdong Basin, located in the southern part of the Loess Plateau, China, have been yet unexplained. This uncertainty is partly attributed to a poor understanding of groundwater arsenic management. To address this problem, this study investigated the occurrence and spatial distribution of As in unconfined groundwater (UG) and confined groundwater (CG) in the study area, integrated Self-Organizing Maps (SOM) and geochemical modeling to elucidate the mechanisms controlling As release and mobilization in groundwater, and conducted a health risk assessment of groundwater As. The results showed that 13.6% of UG samples (n = 66) and 22.4% of CG samples (n = 98) exceeded the WHO guideline limit of As (10 μg/L). The detailed hydrogeochemical studies showed that As-enrichment groundwater is dominated by Cl-Na type, and Gaillardet diagram indicated that evaporites weathering may contribute to As mobilization in CG. The SOM analysis combined with Spearman's correlation coefficient quantified the negative correlation between As and redox potential, dissolved oxygen, SO₄^2-, NO₃^-, and the positive correlation between As and HCO₃^-, Mn in UG. In CG, As is positively correlated to pH and negatively to electrical conductivity, SO₄^2-, Fe and Mn. The saturation indices of the mineral phases indicates an insignificant relationship between As and Fe. We conclude that under oxidizing conditions, evaporative controls and the desorption of Fe-oxides under alkaline and high salinity conditions are the dominant mechanisms controlling As release and mobilization in groundwater. In addition, exposure to groundwater As through drinking water posed potential risk of carcinogenic and non-carcinogenic effects on children and adults. This study contributes to groundwater As management and sustainable safe groundwater supply.

Identification of Water Pollution Sources for Better Langat River Basin Management in Malaysia

The shutdown of drinking water treatment plants (DWTPs) at the Langat River Basin, Malaysia, which provides drinking water to almost one-third population in the basin, is very frequent, especially due to chemical pollution in the river. This study explored the pollution sources in the Langat River based on eight specific water intake points of the respective DWTPs to suggest an integrated river basin management (IRBM). Analysis of Al (250.26 ± 189.24 µg/L), As (1.65 ± 0.93 µg/L), Cd (1.22 ± 0.88 µg/L), Cr (0.47 ± 0.27 µg/L), and Pb (9.99 ± 5.38 µg/L) by ICP-MS following the Chelex® 100 column resin ion exchange method found that the mean concentrations except Al were within the water quality standard of the Ministry of Health (MOH) as well as the Dept. of Environment (DOE) Malaysia. However, the determined water quality index based on physicochemical parameters (2005–2015) at the midstream of Langat River was Class III, which needs substantial treatment before drinking. The linear regression model of Al, As, Cd, and Pb suggests that water quality parameters are significantly influencing the increase or decrease in these metal concentrations. Moreover, the principal component analysis (PCA) and the hierarchical cluster analysis (HCA) also support the regression models that the sources of pollution are both natural and man-made activities, and these pollution sources can be clustered into two categories, i.e., upstream (category 1) and mid to downstream (category 2) in the Langat River. The degraded water quality in the midstream compared to up and downstream of the river is mainly due to human activities apart from the natural weathering of minerals. Therefore, the implementation of policies should be effective at the local level for pollution management, especially via the proactive leadership roles of local government for this transboundary Langat River to benefit from IRBM.

Cortex metabolome and proteome analysis reveals chronic arsenic exposure via drinking water induces developmental neurotoxicity through hnRNP L mediated mitochondrial dysfunction in male rats

Lots of people are at the risk of arsenic-contaminated drinking water. Arsenic exposure was confirmed to be closely linked to neurocognitive deficits, particularly during childhood. The multi-omics approaches are known be well suitable for toxicological research. Thus, this study aimed to explore the molecular mechanisms of arsenic-induced learning and memory function impairments through the integrative proteome and metabolome analysis of cortex in rats. The weaned rats were exposed to arsenic-contaminated drinking water for six months to mimic the developmental exposure. 220 differential proteins and 19 differential metabolites were identified in the cortex, and nine potential biomarkers were found to be related to impaired Morris water maze (MWM) indicators. Chronic arsenic exposure affected the cognitive function by inducing the overproduction of amyloid-β (Aβ) peptides and the redox imbalance in the mitochondria. Glycolysis and tricarboxylic acid (TCA) cycle enhancement driven by the increased heterogeneous nuclear ribonucleoprotein L (hnRNP L) is a low-dose protective mechanism against arsenic-induced ATP deficiency and oxidative stress. Moreover, apoptosis is another important pathway of arsenic-induced neurotoxicity. This study provides new evidence about the alterations of proteins and metabolites in the cortex of the exposed rats under arsenic toxicity. These findings suggest hnRNP L could be a potential target for the treatment of arsenic-induced neurotoxicity.

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.

Shallow groundwater environmental investigation at northeastern Cairo, Egypt: quality and photo-treatment evaluation

Groundwater represents the primary source of freshwater for more than 35% of world people, and its contamination became a worldwide challenge. Egypt is suffering from water quantity and quality, especially in desert areas. El Obour city and environs Northeast Cairo face waterlogging owing to the elevated-shallow groundwater table. In the present research work, the water quality of the shallow groundwater aquifer was studied. The remediation efficiency of polluted water using photocatalytic treatment technique in the presence of modified nano-titania and solar radiation has also been investigated. Twenty-eight representative samples have been collected from different locations, and their microbial, physical, and chemical characteristics were determined. The average contents of Pb (214.96 µg/L), As (1517 µg/L), Cd (8.79 µg/L), total bacterial count (2.22 × 10⁵ CFU/ml), and bacterial indicators (MPN-index/100 ml): total coliform (497.4), fecal coliform (358.3), and fecal streptococci (115.9) were higher than WHO permissible limits for drinking water, possibly due to higher industrialization, agricultural, and urbanization rates. The organic pollutants reached critical concentrations (chemical oxygen demand up to 960.8 mg O₂/L). Most of the studied samples contained acceptable concentrations of the major ions, (e.g., K⁺, Mg²⁺, HCO₃^-), for drinking and irrigation purposes. The statistical analyses (e.g., principal component analysis and cluster analysis) pointed out the control of water-rock interaction and anthropogenic activities in water composition. The hydrochemical data show that most of the water samples (96.4%) are Na₂SO₄ and NaHCO₃ type, indicating its meteoric origin. The contamination with human and animal fecal substances, NO₃^¯, and NH₄⁺ was identified in all samples, which pointed out the control of anthropogenic activities in water pollution. The photocatalytic technique efficiently eliminated more than 82-95% of organic contents and microbial pollutants, respectively, but it was inefficient in reducing heavy metal levels. According to the current results, shallow groundwater injection into the deep aquifer must be constrained and reusable after treatment. Finally, more studies are imperative to disseminate the applied treatment techniques to elude bacteria and organic pollutants from water at a pilot scale.

Enabling simultaneous redox transformation of toxic chromium(VI) and arsenic(III) in aqueous media-A review

Simultaneous conversion of most harmful As(III) and Cr(VI) to their less toxic counterparts is environmentally desirable and cost-effective. It has been confirmed that simultaneous oxidation of As(III) to As(V) and reduction of Cr(VI) to Cr(III) can occur via free radical or mediated electron transfer processes. While Cr(VI) is reduced by reacting with H^•, e_aq^-, photoelectron directly or undergoing ligand exchange with H₂O₂ and SO₃^2-, As(III) is oxidized by HO^•, SO₄^•-, O₂^•-, and holes (h⁺) in free radical process. The ability to concentrate Cr and As species on heterogeneous interface and conductivity determining the co-conversion efficiency in mediated electron transfer process. Acidity has positive effect on these co-conversion, while mediated electron transfer process is not much affected by dissolved oxygen (O₂). Organic compounds (e.g., oxalate, citrate and phenol) commonly favor Cr(VI) reduction and inhibit As(III) oxidation. To better understand the trends in the existing data and to identify the knowledge gaps, this review elaborates the complicated mechanisms for co-conversion of As(III) and Cr(VI) by various methods. Some challenges and prospects in this active field are also briefly discussed.

Predicting Arsenic (As) Exposure on Human Health for Better Management of Drinking Water Sources

Chemical pollution in the transboundary Langat River in Malaysia is common both from point and non-point sources. Therefore, the water treatment plants (WTPS) at the Langat River Basin have experienced frequent shutdown incidents. However, the Langat River is one of the main sources of drinking water to almost one-third of the population in Selangor state. Meanwhile, several studies have reported a high concentration of Arsenic (As) in the Langat River that is toxic if ingested via drinking water. However, this is a pioneer study that predicts the As concentration in the Langat River based on time-series data from 2005-2014 to estimate the health risk associated with As ingestion via drinking water at the Langat River Basin. Several time-series prediction models were tested and Gradient Boosted Tree (GBT) gained the best result. This GBT model also fits better to predict the As concentration until December 2024. The mean concentration of As in the Langat River for both 2014 and 2024, as well as the carcinogenic and non-carcinogenic health risks of As ingestion via drinking water, were within the drinking water quality standards proposed by the World Health Organization and Ministry of Health Malaysia. However, the ingestion of trace amounts of As over a long period might be detrimental to human health because of its non-biodegradable characteristics. Therefore, it is important to manage the drinking water sources to minimise As exposure risks to human health.

Household Water Filtration Technology to Ensure Safe Drinking Water Supply in the Langat River Basin, Malaysia

Populations in the Langat River Basin, Malaysia, frequently experience water supply disruption due to the shutdown of water treatment plants (WTPs) mainly from the chemical pollution as well as point and non-point sources of pollution. Therefore, this study investigated the aluminium (Al), arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) concentrations in the drinking water supply chain at the basin because of its prolonged persistence and toxic characteristics in the aquatic environment. Three replicates of water samples were collected from the river, outlets of WTPs, household tap and filtered water, respectively, in 2015, for analysis by Inductively Coupled Plasma Mass Spectrometry. Higher concentration of these metals was found in household tap water than in the treated water at the WTPs; however, the concentration of these metals at the four stages of the drinking water supply chain conformed to the drinking water quality standard set by the World Health Organization. The Mann-Whitney and Kruskal-Wallis tests also found that metal concentration removal significantly varied among the eight WTPs as well as the five types of household water filtration systems. With regards to the investigated household filtered water, the distilled filtration system was found to be more effective in removing metal concentration because of better management. Therefore, a two-layer water filtration system could be introduced in the Langat River Basin to obtain safe drinking water supply at the household level.

Investigating the Status of Cadmium, Chromium and Lead in the Drinking Water Supply Chain to Ensure Drinking Water Quality in Malaysia

Prolonged persistence of toxic cadmium (Cd), chromium (Cr) and lead (Pb) in the aquatic environment are due to its nonbiodegradable characteristic. A few studies have reported higher concentrations of these metals in the transboundary Langat River, Malaysia. This study determined the spatial and temporal distributions of Cd, Cr and Pb concentrations (2005–2015) in the Langat River along with assessing the status of these metals in the drinking water supply chain at the basin. Water samples were collected once in 2015 from the drinking water supply chain, i.e., from the river, treated water at plants, taps and filtration water at households. Determined mean concentrations of Cd, Cr and Pb by inductively coupled plasma mass spectrometry in the Langat River were within the drinking water quality standard of Malaysia and the WHO, except for the Pb (9.99 ± 1.40 µg/L) concentration, which was at the maximum limit, 10 µg/L. The spatial and temporal distribution of these metals’ concentrations indicate dilution of it downstream, along with the increasing trend in rainfall and water flow, especially during the northeast monsoon. Significant correlation and regression analysis of the Cd, Cr and Pb concentrations also indicate that the sources of this metal pollution are mainly the natural weathering of minerals along with anthropogenic activities in the basin. The determined overall water quality of the Langat River is categorized Class IIA (i.e., clean), which requires conventional treatment before drinking; however, the maximum removal efficiency of these metals by the plants at the basin was about 90.17%. Therefore, the proactive leadership roles of the local authorities will be appropriate to reduce the pollution of this river as well as introducing a two-layer water filtration system at the Langat River Basin to accelerate the achievement of a sustainable drinking water supply.