Arsenic health risk assessment in drinking water and source apportionment using multivariate statistical techniques in Kohistan region, northern Pakistan

Spatial distribution of physicochemical parameters and drinking and irrigation water quality indices in the Jhelum River, Pakistan

Sustainable management of river systems is a serious concern, requiring vigilant monitoring of water contamination levels that could potentially threaten the ecological community. This study focused on the evaluation of water quality in the Jhelum River (JR), Azad Jammu and Kashmir, and northern Punjab, Pakistan. To achieve this, 60 water samples were collected from various points within the JR Basin (JRB) and subjected to a comprehensive analysis of their physicochemical parameters. The study findings indicated that the concentrations of physicochemical parameters in the JRB water remained within safety thresholds for both drinking and irrigation water, as established by the World Health Organization and Pakistan Environmental Protection Agency. These physicochemical parameters refer to various chemical and physical characteristics of the water that can have implications for both human health (drinking water) and agricultural practices (irrigation water). The spatial variations throughout the river course distinguished between the upstream, midstream, and downstream sections. Specifically, the downstream section exhibited significantly higher values for physicochemical parameters and a broader range, highlighting a substantial decline in its quality. Significant disparities in mean values and ranges were evident, particularly in the case of nitrates and total dissolved solids, when the downstream section was compared with its upstream and midstream counterparts. These variations indicated a deteriorating downstream water quality profile, which is likely attributable to a combination of geological and anthropogenic influences. Despite the observed deterioration in the downstream water quality, this study underscores that the JRB within the upper Indus Basin remains safe and suitable for domestic and agricultural purposes. The JRB was evaluated for various irrigation water quality indices. The principal component analysis conducted in this study revealed distinct covariance patterns among water quality variables, with the first five components explaining approximately 79% of the total variance. Recommending the continued utilization of the JRB for irrigation, we advocate for the preservation and enhancement of water quality in the downstream regions.

A Bayesian benchmark concentration analysis for urinary fluoride and intelligence in adults in Guizhou, China

Environmental fluoride exposure has been linked to numerous cases of fluorosis worldwide. Previous studies have indicated that long-term exposure to fluoride can result in intellectual damage among children. However, a comprehensive health risk assessment of fluorosis-induced intellectual damage is still pending. In this research, we utilized the Bayesian Benchmark Dose Analysis System (BBMD) to investigate the dose-response relationship between urinary fluoride (U-F) concentration and Raven scores in adults from Nayong, Guizhou, China. Our research findings indecate a dose-response relationship between the concentration of U-F and intelligence scores in adults. As the benchmark response (BMR) increased, both the benchmark concentration (BMCs) and the lower bound of the credible interval (BMCLs) increased. Specifically, BMCs for the association between U-F and IQ score were determined to be 0.18 mg/L (BMCL1 = 0.08 mg/L), 0.91 mg/L (BMCL5 = 0.40 mg/L), 1.83 mg/L (BMCL10 = 0.83 mg/L) when using BMRs of 1 %, 5 %, and 10 %. These results indicate that U-F can serve as an effective biomarker for monitoring the loss of IQ in population. We propose three interim targets for public policy in preventing interllectual harm from fluoride exposure.

Integrated Approach to Hydrogeochemical Assessment of Groundwater Quality in Major Industrial Zone of Punjab, Pakistan

Groundwater contamination with arsenic (As) is a significant concern in Pakistan's Punjab Province. This study analyzed 69 groundwater samples from Faisalabad, Gujranwala, Lahore, and Multan to understand hydrogeochemistry, health impacts, contamination sources, and drinking suitability. Results revealed varying as concentrations across districts, with distinctive cation and anion orders. Faisalabad exhibited Na+ > Mg2+ > Ca2+ > K+ > Fe2+ for cations and SO42- > Cl- > HCO3- > NO3- > F- for anions. Gujranwala showed Na+ > Ca2+ > Mg2+ > K+ for cations and HCO3-  > SO42- > Cl- > NO3-  > F- for anions. In Lahore, demonstrated: Na+ > Ca2+ > Mg2+ > Fe > K+ for cations and HCO3-  > SO42- > Cl- > NO3-  > F- for anions. Multan indicated K+ > Ca2+ > Mg2+ > Na+ > Fe for cations and HCO3-  > SO42- > Cl- > F- > NO3- ) for anions. Hydrochemical facies were identified as CaHCO3 and CaMgCl types. Principal Component Analysis (PCA), highlighted the influence of natural processes and human activities on groundwater pollution. Water Quality Index (WQI) result reveal that most samples met water quality standards. The carcinogenic risk values for children exceeded permissible limits in all districts, emphasizing a significant cancer risk. The study highlights the need for rigorous monitoring to mitigate (As) contamination and protect public health from associated hazards.

Geospatial quality assessment of locally available ice for heavy metals and metalloids and their potential risks for human health in Karachi, Pakistan

Extreme hot conditions during summers, high poverty rate and continuous electricity load shedding affect commercial manufacturing and sale of ice in many countries. The vendors prepared ice using untreated piped water, tanker water and ground water. These waters may contain hazardous pollutants and ice made from them will pose a potential human health risk. Thus, it is important to regularly monitor the chemical composition of water sources and the quality of the manufactured ice. A contemporary examination was carried out to evaluate the physico-chemical properties and heavy metals and metalloids in the ice sold in all the districts of Karachi, Pakistan. This pioneering study was an innovative effort to assess the ice quality in relation to potential pollutant hazards to human health; with concomitant geospatial information. The geospatial distribution of ice quality and major constituents were among the measured parameters; carefully associated with further geospatial information, determined using GIS (Geographic Information Systems) and PCA (Principal Component Analysis) techniques. Interestingly, the physico-chemical analyses revealed that the ice quality was marginally adequate and the total mean metal-metalloid contents were in the sequence of Pb > Ni > Zn > Fe > Cr > As. The concentrations of these metals were above the upper allowable limits with reference to the recommended WHO guidelines. We observed that 57.1% and 35.7% ice samples had good physico-chemical properties assessed using the Ice Quality Index (IQI). Conversely, the IQI for metals showed that the ice was unsafe for human consumption. In terms of health risk assessment, the overall mean CDI (Chronic Daily Intake) and HQ (Hazard Quotient) values were in the order of Pb () > Ni (3.2) > Zn (2.3) > Fe (2.1) > Cr (1.6) > As (0.5) and Pb (7.4) > As (1.7) > Cr (0.5) > Ni (0.4 > Zn (0.008) > Fe (0.003), respectively. This study highlighted that routine monitoring of the water supplies available for making ice is required to protect public health.

Potentially toxic element contamination and health risk assessment in bottled mineral waters consumed in Turkey

This study aimed to evaluate the human health risk posed by potentially toxic elements (PTEs) in 59 bottled mineral water (BMW) samples of 25 different brands marketed in Turkey. The concentrations of Ag, Al, As, Cd, Cr, Co, Cu, Fe, Mn, Ni, and Pb in the BMW samples were analyzed using an ICP-OES and compared with maximum allowable concentrations (MACs). A higher concentration of As than MAC was detected in five BMW samples. The concentrations of Cd, Pb, Cr, Ni, and Al in the majority of BMW samples are higher than the MACs. The human health risk was evaluated for adults estimating non-carcinogenic risk index (HI), incremental lifetime cancer risk (ILCR) and total cancer risk (TCR). All HI values estimated for PTEs in BMW samples are less than one, except for one sample. ILCR values for Cd in approximately half of the BMW samples are above the upper limit.

Combined Multivariate Statistical Techniques and Water Quality Index (WQI) to Evaluate Spatial Variation in Water Quality

In present study, Water Quality Index (WQI) has been assessed of the Rawal Lake which is a major source of drinking water for people in the Federal Capital, Islamabad, and its adjacent city Rawalpindi in Pakistan. For this, the principal component analysis (PCA) and WQI were applied as an integrated approach to quantitatively explore difference based on spatial variation in 11 water quality parameters of the five major feeding tributaries of the Rawal Lake, Pakistan. The results of temperature in water, total dissolved solids, pH, electrical conductivity, chlorides and sulfates were well within the allowable World Health Organisation's (WHO) limits. However, the heavy metals like cadmium and lead were above permissible limits by the WHO in tributaries of Bari Imam and Rumli. Moreover, this has been proven by the Pearson correlation which suggested strong positive correlation (0.910*) between lead and cadmium. The results of present study were subjected to statistical analysis, i.e., PCA which gave three major factors contributing 96.5% of the total variance. For factor 1, pH, TDS, alkalinity, chlorides, sulfates and zinc have highest factor loading values (>0.60) and presented that these parameters were among the most significant parameters of first factor. As per the WQI results, the water was categorised in two major classes indicating that water of Bari Imam and Rumli is highly contaminated with heavy metals and totally unsuitable for drinking purposes. Based on the results of the present study, it is suggested to make heavy metals consideration as an integrated component in future planning for maintaining water quality of the Rawal Lake and its tributaries.

Distribution, geochemical behavior, and risk assessment of arsenic in different floodplain aquifers of middle Gangetic basin, India

The present study interprets the distribution and geochemical behavior of As in groundwaters of different regions along the floodplains of Ganga river (Varanasi, Ghazipur, Ballia), Ghaghara river (Lakhimpur Kheri, Gonda, Basti), and Rapti river (Balrampur, Shrawasti) in the middle Gangetic basin, India for risk assessment (non-carcinogenic and carcinogenic). The concentration of As in groundwaters of these floodplains ranged from 0.12 to 348 μg/L (mean 24 μg/L), with around ~ 37% of groundwater samples exceeding the WHO limit of 10 μg/L in drinking water. Highest As concentration (348 μg/L) was recorded in groundwater samples from Ballia (Ganga Floodplains), where 50% of the samples had As > 10 μg/L in groundwater. In the study area, a relatively higher mean concentration was recorded in deep wells (28.5 μg/L) compared to shallow wells (20 μg/L). Most of the high As-groundwaters were associated with the high Fe, bicarbonate and low nitrate and sulfate concentrations indicating the release of As via reductive dissolution of Fe oxyhydroxides. The saturation index values of the Fe minerals such as goethite, hematite, ferrihydrite, and siderite showed the oversaturation to near equilibrium in groundwater, suggesting that these mineral phases may act as source/sink of As in the aquifers of the study area. The health risk assessment results revealed that a large number of people in the study area were prone to carcinogenic and non-carcinogenic health risks due to daily consumption of As-polluted groundwater. The highest risks were estimated for the aquifers of Ganga floodplains, as indicated by their mean HQ (41.47) and CR (0.0142) values.

Appraisal of groundwater quality with WQI and human health risk assessment in Karamık wetland and surroundings (Afyonkarahisar/Turkey)

Groundwater in Karamık wetland and surroundings, which is one of the important wetlands in Turkey, was examined and the chemical properties and quality of groundwater were determined in the present study. In addition, the possible risks to human health as a result of groundwater usage were investigated along with spatial analyses carried out using Geographic Information Systems (GIS). Physicochemical analyses were carried out on 25 samples taken from groundwater. The dominant ions in the study area are Ca, Mg, and HCO₃. When the results are compared with the limit values in the valid drinking water guidelines such as TSI-266 (Standards for drinking waters, 2005) and WHO (Guidelines for drinking-water quality, 2011), the groundwaters were not suitable for use as drinking water in terms of NO₃, Fe, Pb and As. The analysis results were evaluated together with GIS and Water Quality Index (WQI) methods. In the evaluations with the WQI method, 76% of the samples were in the "poor water" class. The groundwater in the study area is polluted by both geogenic and anthropogenic sources. For this reason, health risk assessment was performed due to the use of groundwater in the region by the local people in different areas, especially as drinking water, and the negative effects of water quality. Accordingly, there are non-carcinogenic negative effects on health in terms of NO₃, As, Pb and Fe parameters from the use of groundwater by children. In addition, Pb and As concentrations are at carcinogenic levels for both children and adults in all groundwater samples collected from the study area. Therefore, it is not recommended to use groundwater as drinking water without treatment.

Characterization and health risk assessment of arsenic in natural waters of the Indus River Basin, Pakistan

The elevated concentrations of arsenic in natural water are one of the major environmental threats to human health. However, the existing characteristics, controlling mechanisms, and associated risks of arsenic in natural waters in the Indus River Basin (IRB), Pakistan, are yet to be unequivocally understood. In this study, a total of 203 samples of surface water (SW), shallow groundwater (SGW), and deep groundwater (DGW) were collected from the IRB to assess the geochemical characteristics of arsenic and its associated health risks, as all three kinds of waters are the main sources of drinking and domestic usage. The results revealed that the arsenic concentrations in the SW, SGW, and DGW were in the ranges of 1.1-26.45, 1.05-44.44, and 0.67-41.09 μg L^-1, respectively. Furthermore, the predominance of As (V) (97 %) over As(III) (3 %) confirmed that the desorption of As in oxidizing environments with elevated pH and Eh is the controlling mechanism. The hazard quotient of 11-45 % and 20-60 % samples and cancer risk of 26-64 % and 26-68 % samples indicated high health risks for the adults and children, respectively, suggesting an immense need for appropriate measures of reducing natural water arsenic concentrations in IRB from the human health perspectives.

Health risk assessment and geospatial analysis of arsenic contamination in shallow aquifer along Ravi River, Lahore, Pakistan

The exposure variation of arsenic from different ground and surface water sources has remained unpredictable which may cause severe human health problems. The current study is, therefore, designed to analyze the spatial variability of arsenic contamination in shallow aquifer and assess the potential human health risks. For this purpose, a total of 55 groundwater, 10 drain water, 4 river water, and 6 sediment samples were collected along zero to 5 km stretch of the River Ravi, Lahore. All water samples were tested for As, pH, and total dissolved solids (TDS), whereas sediments were only tested for As. Health risk models were used to predict cancer and non-cancer risk in adults and children. Among water samples, highest median (minimum-maximum) concentrations (µg/L) of As were recorded 53.32 (1.98-1555) in groundwater, followed by 53.04 (1.58-351.5) in drain water, and 4.80 (2.13-8.67) in river water, respectively, whereas As concentration (mg/kg) in river sediments was 6.03 (5.56-13.92). Variation of As in groundwater was non-significant (P > 0.05) among every 1-km stretch from the Ravi River. However, maximum median concentrations (µg/L) of 60.18 and 60.08 were recorded between 2-3 and 0-1 km from River Ravi, respectively, reflecting possible mixing of river water with shallow aquifers. A very high cancer and non-cancer risk (HI > 1.0 × 10^-4) through groundwater As exposure was predicted for both children and adults. The current study concluded that prevalence of As above WHO prescribed limits in shallow aquifer along the urban stretch of the River Ravi is posing serious health risk to the exposed population.

Contamination and Human Health Risk Assessment of Toxic Trace Elements in Drinking Water of Gilgit-Baltistan, Pakistan

This study investigated the contamination level and risk associated with toxic trace elements in springs’ water from Gilgit-Baltistan, Pakistan. Toxic trace elements, including Hg, As, and Zn, were analyzed by metalyzer, HM 2000 serial no. MY-011-006, while elements such as Cr, Al, B, Ni, Cu, Mn, and Fe were analyzed using Metalometer HM 2000 serial no. MM005-007, the United Kingdom. The mean concentrations of TTEs in water samples from Skardu were ordered as, Mn < Cu < Fe < Zn < Al < Cr < As < Ni < Hg, in Gilgit, Mn < Cu < Zn < Ni < B < Cr < Fe < As < Hg, in Ghizer Cu < Mn < Zn < Ni < Cr < Fe < As < Hg, while in Nagar the concentration of TTEs in water samples were ordered as Cu < Mn < Fe < Ni < Al < Cr < Zn < As < Hg. Results obtained from this study showed that the concentrations of As, Hg, Ni, Cr, Al, and Mn in some water samples were higher than the limits recommended by WHO and Pak-NDWQS. However, the chronic daily intake indices (CDIs) and health risk index (HRI) in all samples were found below the US-EPA standards. The correlation analysis revealed a positive association among different elements, which revealed that the sources of TTES in water samples were mainly geological strata and anthropogenic activities.

Evolution Mechanism of Arsenic Enrichment in Groundwater and Associated Health Risks in Southern Punjab, Pakistan

Arsenic (As) contamination in groundwater is a worldwide concern for drinking water safety. Environmental changes and anthropogenic activities are making groundwater vulnerable in Pakistan, especially in Southern Punjab. This study explores the distribution, hydrogeochemical behavior, and pathways of As enrichment in groundwater and discusses the corresponding evolution mechanism, mobilization capability, and health risks. In total, 510 groundwater samples were collected from three tehsils in the Punjab province of Pakistan to analyze As and other physiochemical parameters. Arsenic concentration averaged 14.0 μg/L in Vehari, 11.0 μg/L in Burewala, and 13.0 μg/L in Mailsi. Piper-plots indicated the dominance of Na⁺, SO₄^2-, Ca²⁺, and Mg²⁺ ions in the groundwater and the geochemical modeling showed negative saturation indices with calcium carbonate and salt minerals, including aragonite (CaCO₃), calcite (CaCO₃), dolomite (CaMg(CO₃)₂), and halite (NaCl). The dissolution process hinted at their potential roles in As mobilization in groundwater. These results were further validated with an inverse model of the dissolution of calcium-bearing mineral, and the exchange of cations between Ca²⁺ and Na⁺ in the studied area. Risk assessment suggested potential carcinogenic risks (CR > 10^-4) for both children and adults, whereas children had a significant non-carcinogenic risk hazard quotient (HQ > 1). Accordingly, children had higher overall health risks than adults. Groundwater in Vehari and Mailsi was at higher risk than in Burewala. Our findings provide important and baseline information for groundwater As assessment at a provincial level, which is essential for initiating As health risk reduction. The current study also recommends efficient management strategies for As-contaminated groundwater.

Geochemical Modeling Source Provenance, Public Health Exposure, and Evaluating Potentially Harmful Elements in Groundwater: Statistical and Human Health Risk Assessment (HHRA)

Groundwater contamination by potentially harmful elements (PHEs) originating from the weathering of granitic and gneissic rock dissolution poses a public health concern worldwide. This study investigated physicochemical variables and PHEs in the groundwater system and mine water of the Adenzai flood plain region, in Pakistan, emphasizing the fate distribution, source provenance, chemical speciation, and health hazard using the human health risk assessment HHRA-model. The average concentrations of the PHEs, viz., Ni, Mn, Cr, Cu, Cd, Pb, Co, Fe, and Zn 0.23, were 0.27, 0.07, 0.30, 0.07, 0.06, 0.08, 0.68, and 0.23 mg/L, respectively. The average values of chemical species in the groundwater system, viz., H+, OH−, Ni2+, Mn2+, Mn3+, Cr3+, Cr6+, Cu+, Cu2+, Cd2+, Pb2+, Pb4+, Co2+, Co3+, Fe2+, Fe3+, and Zn2+, were 1.0 × 10−4 ± 1.0 × 10−6, 1.0 × 10−4 ± 9.0 × 10−7, 2.0 × 10−1 ± 1.0 × 10−3, 3.0 × 10−1 ± 1.0 × 10−3, 1.0 × 10−22 ± 1.0 × 10−23, 4.0 × 10−6 ± 2.0 × 10−6, 4.0 × 10−11 ± 2.0 × 10−11, 9.0 × 10−3 ± 1.0 × 10−2, 2.0 × 10−1 ± 2.0 × 10−3, 7.0 × 10−2 ± 6.0 × 10−2, 5.0 × 10−2 ± 5.0 × 10−2, 2.0 × 10−2 ± 1.5 × 10−2, 6.0 × 10−2 ± 4.0 × 10−2, 8.0 × 10−31 ± 6.0 × 10−31, 3.0 × 10−1 ± 2.0 × 10−4, 4.0 × 10−10 ± 3.0 × 10−10, and 2.0 × 10−1 ± 1.0 × 10−1. The mineral compositions of PHEs, viz. Ni, were bunsenite, Ni(OH)2, and trevorite; Mn viz., birnessite, bixbyite, hausmannite, manganite, manganosite, pyrolusite, and todorokite; Cr viz., chromite and eskolaite; Cu viz., CuCr2O4, cuprite, delafossite, ferrite-Cu, and tenorite; Cd viz., monteponite; Pb viz, crocoite, litharge, massicot, minium, plattnerite, Co viz., spinel-Co; Fe viz., goethite, hematite, magnetite, wustite, and ferrite-Zn; and Zn viz., zincite, and ZnCr2O4 demarcated undersaturation and supersaturation. However, EC, Ca2+, K+, Na+, HCO3−, Cr, Cd, Pb, Co, and Fe had exceeded the WHO guideline. The Nemerow’s pollution index (NPI) showed that EC, Ca2+, K+, Na+, HCO3−, Mn, Cd, Pb, Co, and Fe had worse water quality. Principal component analysis multilinear regression (PCAMLR) and cluster analysis (CA) revealed that 75% of the groundwater contamination originated from geogenic inputs and 18% mixed geogenic-anthropogenic and 7% anthropogenic sources. The HHRA-model suggested potential non-carcinogenic risks, except for Fe, and substantial carcinogenic risks for evaluated PHEs. The women and infants are extremely exposed to PHEs hazards. The non-carcinogenic and carcinogenic risks in children, males, and females had exceeded their desired level. The HHRA values of PHEs exhibited the following increasing pattern: Co > Cu > Mn > Zn > Fe, and Cd > Pb > Ni > Cr. The higher THI values of PHEs in children and adults suggested that the groundwater consumption in the entire region is unfit for drinking, domestic, and agricultural purposes. Thus, all groundwater sources need immediate remedial measures to secure health safety and public health concerns.

Concentrations of Lead in Groundwater and Human Blood in the Population of Palosai, a Rural Area in Pakistan: Human Exposure and Risk Assessment

Lead (Pb) is a toxic environmental contaminant, which enters water bodies from natural and anthropogenic activities. The present study investigates the Pb concentration in groundwater sources and evaluates their potential health risks in Palosai area, Peshawar, Khyber Pakhtunkhwa, Pakistan. Groundwater samples were collected from different groundwater sources in the area where the human blood samples were from the dependent residents. Pb concentration was analyzed using an atomic absorption spectrophotometer and compared with the permissible limits set by Pakistan Environmental Protection Agency and World Health Organization (WHO). The levels of physicochemical parameters were observed within the said safe limits, while the levels of Pb in different groundwater sources (tube wells and wells) showed a little bit variation. Health risk indicators such as chronic daily intake (CDI) and hazard quotient (HQ) were calculated for Pb. The calculated value of CDI and HQ for Pb via groundwater consumption was 0.001 mg/kg·day and $2.8E-02$  mg/kg·day, respectively; however, the overall HQ values of Pb in the groundwater were less than 1, indicating no health risk to the local depending community.

Spatial distribution and health risk assessment of As and Pb contamination in the groundwater of Rayong Province, Thailand

This study investigates the presence of arsenic (As) and lead (Pb) in groundwater and their spatial distribution in Ban Khai District, Rayong Province, Thailand. Forty groundwater samples were collected at different locations in the dry and wet seasons during March and August of 2019, respectively. The hydrochemical facies illustrate that the major groundwater types in both seasons mainly consisted of Ca-Na-HCO_3, Ca-HCO₃-Cl and Na-HCO₃ types. The concentration of As ranged from <0.300 to 183.00 μg/L, accounting for 22% (18 of 80 samples), exceeding the WHO guidelines of 10 μg/L. The spatial distribution of As was distinctly predominant as a hot spot in some areas during the wet season. The wells may have been contaminated from human activity and thus constituted a point source in the adjacent area. For Pb, its concentration in all the wells were not exceeded 10 μg/L of the WHO guidelines, appearing as a background concentration in this area. Most of the wells were shown to be in an oxidation state, supporting As^V mobility. Moreover, the area also had a nearly neutral pH that promoted As^V desorption, while the presence of undissolved Pb in the aquifers tended to increase. Furthermore, chemical applications to agricultural processes could release the As composition into the groundwater. The health risk resulting from oral consumption was at a higher risk level than dermal contact. The non-carcinogenic risk affecting the adult population exceeded the threshold level by approximately 27.5% of the wells, while for the children group, the risk level was within the limit. Total cancer risk (TCR) of adult residents exceeded the acceptable risk level (1 × 10^-6) in all wells, causing carcinogenic health effects. Therefore, health surveillance is important in monitoring the toxic effects on the local residents who use groundwater from these contaminated wells. Furthermore, a sanitation service and an alternative treatment of the water supply will be needed, especially in wells with high As levels.

How does arsenic speciation (arsenite and arsenate) in groundwater affect the performance of an aerated electrocoagulation reactor and human health risk?

Arsenic (As) occurrence in water resources has become one of the most critical environmental problems worldwide. The detrimental health impacts on humans have been reported due to the consumption of As-contaminated groundwater resources. Consumption of As-containing water over the long term can cause arsenicosis and chronic effects on human health due to its toxicity. Several treatment processes are available for As removals such as coagulation, ion exchange, adsorption, and membrane technologies but they have various major drawbacks. In the present work, therefore, an aerated electrocoagulation (EC) system with aluminum anodes was operated for simultaneous arsenate (As(V)) and arsenite (As(III)) removal to overcome the disadvantages of other processes such as, sludge formation, difficulties in operation, high operating costs, high energy consumption, and the requirement of pre-treatment process and to enhance the conventional EC process. The combined effects of the applied current (0.075-0.3 A), aeration rate (0-6 L/min), pH (6.5-8.5), and As speciation (As(V)-As(III)) were studied on As removal efficiency. The findings revealed that As removal mostly depended on the airflow rate and the applied current in the EC system. The highest As removal efficiency (99.1%) was obtained at an airflow rate of 6 L/min, a pH of 6.5, an initial As (V) concentration of 200 μg/L, and a current of 0.3 A, with an energy consumption of 2.85 kWh/m³ and an operating cost of 0.66 $/m³. The human health risk assessment of treated water was also examined to understand the performance of the EC system. At most of the experimental runs, the chronic toxic risk (CTR) and carcinogenic risk (CR) of As were within the permissible limits except for an airflow rate of 0-2 L/min, an initial pH of 8.5, and a current of 0.075-0.15 A for high initial As (III) concentrations. Overall, the As removal performance and groundwater risk assessment show that the EC process is a promising option for industrial applications.

Health risk assessment induced by trace toxic metals in tap drinking water: Condorcet principle development

Acute exposure to trace metals (TMs) in water is hazardous to human health. The average concentrations (C_avg.) and carcinogenic (CAR) and non-carcinogenic (non-CAR) risks of eight TMs to World Health Organization's (WHO) guidelines and national standard limits (NSLs)were determined. The C_avg. and (the range) of As, Hg, Cd, Pb, Co, Cr, Ni, and Zn were measured as 4.29 ± 0.57 μg L^-1 (1.12-10.27 μg L^-1), 0.22 ± 0.10 μg L^-1 (ND-1.05 μg L^-1), 0.31 ± 0.18 μg L^-1 (ND-1.80 μg L^-1), 4.66 ± 0.32 μg L^-1 (0.10-14.22 μg L^-1), 24.61 ± 4.65 μg L^-1 (3.11-67.25 μg L^-1), 16.86 ± 5.54 μg L^-1 (5.12-34.61 μg L^-1), 14.07 ± 4.37 μg L^-1 (3.79-31.39 μg L^-1), and 268.42 ± 75.82 (87.29-561.22 μg L^-1), respectively. The C_avg. of Co and Hg exceeded the WHO and NSLs. The non-CAR risk assessment was used to order the TMs according to the total target hazard quotient (TTHQ) As > Pb > Cr > Co > Zn > Hg > Ni > Cd. None of the investigated age groups are at risk As there is a low C_avg of all trace metals (i.e., the THQ is > 1). The age groups were ranked based on THQ and incremental lifetime cancer risk (ILCR) As < 1 year, >1-10 years, > 11-19 years, and > + 20 years. The ILCR of As for all the age groups was >10^-4, whereas for Pb it was <10^-6. Cumulative carcinogenic risk (CCR) for As and Pb was at a safe threshold risk (>10^-4) for all the age groups.

Arsenic-contaminated groundwater and its potential health risk: A case study in Long An and Tien Giang provinces of the Mekong Delta, Vietnam

The occurrence of arsenic (As) in groundwater (drilled well water) that were used for drinking, cooking, and personal hygiene and its risks to human health in Long An and Tien Giang provinces (Mekong delta, Vietnam) were evaluated in this study. The average As concentrations were 15.92 ± 11.4 μg/L (n = 24, Long An) and 4.95 ± 4.7 μg/L (n = 24, Tien Giang). The average concentrations of As in Long An had not reached the WHO and QCVN 01: 2009/BYT healthy drinking water standard (10 μg/L). When used as a source of water for drinking and daily activities, arsenic-contaminated groundwater may have a direct impact on human health. The risk assessment from groundwater established by the US Environmental Protection Agency (USEPA) was conducted. The risk assessment showed that the average cancer risk (CR) values were 8.68 × 10^-4 (adults) and 2.39 × 10^-3 (children) for Long An, and 2.70 × 10^-4 (adults) and 7.43 × 10^-4 (children) for Tien Giang. These results were significantly higher than the CR (1 × 10^-4) proposed by the USEPA. The adverse health effect was therefore specifically warned by the use of arsenic-contaminated groundwater. This research offers valuable knowledge for efficient water management approaches to guarantee local communities' health protection.

Assessment of groundwater quality and human health risk related to arsenic using index methods and GIS: A case of Şuhut Plain (Afyonkarahisar/Turkey)

In this study the spatial variation of groundwater quality and the potential health risk situation arising were evaluated determining Water Quality Index (WQI and IWQI) for drinking and irrigation water in Şuhut Plain (Afyonkarahisar, Turkey). A total of 27 groundwater samples were collected from wells in May-2019 and physicochemical analysis results were evaluated. According to analysis results of the water samples, the orders of anion and cations are HCO3>SO4-2>Cl- > CO3-2 and Ca+2 > Mg+2 > Na+>K+, respectively. It has been determined that groundwater samples are generally in "excellent" and "good" water class according to the WQI and IWQI assessment. At the same time, groundwater in the study area is suitable for agricultural irrigation water. However, many water samples cannot be used as drinking water in terms of TDS, Mg, NO₃ and As_T according to limit values of TSI-266 (2005) and WHO (2011). Health risk assessment indicate that, the risk of developing cancer due to arsenic exposure in healthy adults or children is very low. But, arsenic has a high non-carcinogenic and carcinogenic potentially harmful effect.

The Fenton-like reaction for Arsenic removal from groundwater: Health risk assessment

In this paper, the heterogeneous Fenton like-reaction for Arsenic-contaminated groundwater remediation based on the performance of FeSO₄ as an efficient and green catalyst and CaO₂ as a source of H₂O₂ was investigated. To intensify the heterogeneous Fenton process, three oxidants were tested: sodium percarbonate (SPC), sodium persulfate (SPS), and calcium peroxide (CP). The results showed that CP and SPC had a synergetic effect on the rate of Arsenic degradation, while SPS had an antagonistic effect. On the other hand, inorganic ions such as Na⁺, Mg²⁺ have a very low impact on the Arsenic removal efficiency, while the anions Cl^- and NO₃^- exhibited significant inhibition of Arsenic degradation. This effect may be imputed to the reaction and conversion of hydroxyl (HO^•) radicals to less reactive. Thus, HCO₃^- and humic acid dramatically raised the degradation rate. Also, the response Surface method based on Box-Behnken design was applied to examine the suitable modeling, and optimized condition of the Fenton like-reaction process, the maximum Arsenic removal efficiency of 94.91% is obtained when [Fe³⁺]₀ = 1.97 mM, [CaO₂]₀ = 1.74 mM and initial pH = 4.67. The obtained results showed that the Fenton-like reaction is an effective and reliable process for arsenic removal from groundwater with low non-carcinogenic risk (HQ) and carcinogenic risk (CR) values.

The impact of cow dung augmentation on soil restoration and bio-accumulation of metals (Lead and Cadmium) in Pheretima posthuma (Annelida: Clitellata)

To investigate the role of cow dung in soil reclamation and bio assimilation along with bio accumulation of heavy metals in earthworm (P. posthuma) (N=900) earthworms were used and treatment groups of CD-soil mixture of different proportion of cow dung were designed. Nonlethal doses of lead acetate and cadmium chloride were added in treatment groups. Mature P. posthuma were released in each experimental pot maintaining the favorable conditions. The pH, carbon, nitrogen, phosphorus, exchangeable cations, and heavy metal level of each mixture was evaluated. The results indicated that bio-assimilation of Pb and Cd by P. posthuma were significantly (P ˂ 0.01) higher in different soil-CD treatments compared to control. Highest bio-assimilation of both metals was observed in T1 of both groups (Pb = 563.8 mg/kg and Cd = 42.95 mg/kg). The contents of both metals were significantly (P ˂ 0.05) lowered in casting. The nutrient concentration in the final castings of all soil-CD treatments were also equally transformed from less or insoluble to more soluble and available for plants, except for carbon level which increased with CD proportion. It is concluded that cow dung as organic matter has a positive effect on soil reclamation and bio-assimilation of metals by P. posthuma.

Microbial transformation of biogenic and abiogenic Fe minerals followed by in-situ incubations in an As-contaminated vs. non-contaminated aquifer

Fe(III) minerals play a crucial role for arsenic (As) mobility in aquifers as they usually represent the main As-bearing phases. Microbial reductive dissolution of As-bearing Fe(III) minerals is responsible for the release of As and the resulting groundwater contamination in many sites worldwide. So far, in most studies mainly abiogenic iron minerals have been considered. Yet, biogenic minerals that possess different properties to their abiogenic counterparts are also present in the environment. In some environments they dominate the iron mineral inventory but so far, it is unclear what this means for the As mobility. We, therefore, performed an in-situ aquifer Fe(III) minerals exposure experiment i) to evaluate how different biogenic and abiogenic Fe(III) minerals are transformed in a strongly reducing, As-contaminated aquifer (25 m) compared to As-free moderately reducing aquifer (32 m) and ii) to assess which microbial taxa are involved in these Fe(III) minerals transformations. We found that higher numbers of bacteria and archaea were associated with the minerals incubated in the As-contaminated compared to the non-contaminated aquifer and that all Fe(III) minerals were mainly colonized by Fe(III)-reducing bacteria, with Geobacter being the most abundant taxon. Additionally, fermenting microorganisms were abundant on minerals incubated in the As-contaminated aquifer, while methanotrophs were identified on the minerals incubated in the As-free moderately reducing aquifer, implying involvement of these microorganisms in Fe(III) reduction. We observed that biogenic Fe(III) minerals generally tend to become more reduced and when incubated in the As-contaminated aquifer sorbed more As than the abiogenic ones. Most of abiogenic and biogenic Fe(III) minerals were transformed into magnetite while biogenic more crystalline mixed phases were not subjected to visible transformation. This in-situ Fe(III) minerals incubation approach shows that biogenic minerals are more prone to be colonized by (Fe(III)-reducing) microorganisms and bind more As, although ultimately produce similar minerals during Fe(III) reduction.

Assessment of groundwater quality and usability of Salda Lake Basin (Burdur/Turkey) and health risk related to arsenic pollution

PURPOSE

In this study the aim was to analyze the seasonal concentration, groundwater quality, usage areas and arsenic-related health risk of major ions and heavy metals in groundwater samples collected from the Salda Lake basin.

METHODS

In this study, 42 groundwater samples were collected from springs and wells in dry and wet seasons in 2015. Hydrogeochemical evaluations were made using different diagrams such as Piper and Gibbs diagrams. Groundwater quality was determined by the water quality index method (WQI) and different diagrams. Finally, health risk assessments related to arsenic were performed.

RESULTS

The dominant water types are Mg-Ca-HCO3 and Mg-HCO3 in the wet season and Mg-HCO3 and Mg-HCO3-CO3 in the dry season. According to calculated WQI values ranged from 24.14 to 56.93 in the wet season ranged from 25.27 to 145.87 in dry season. This situation indicates that the quality of water samples is mostly good both seasons. AsT concentrations were between 2.1-6.3 μg/L in the dry season and 2.9-10.5 μg/L in the wet season. The risk of developing cancer due to arsenic exposure in healthy adults or children is very low. But arsenic has high non-carcinogenic and carcinogenic potentially harmful effect in the study area. In addition, water samples are not appropriate for use as drinking water in terms of fertilizers and trace element concentrations. Also, MH will be an important problem in waters that will be used as irrigation water. The use of some samples is not recommended as it may cause crusting on metal surfaces in industrial areas.

CONCLUSIONS

According to the results obtained, the quality of groundwater in the study area should be monitored and the usage areas should be determined accordingly.

Heavy metals drinking water contamination and health risk assessment among primary school children of Pakistan

The purpose of this study was to characterize the concentrations of lead (Pb), cadmium (Cd), manganese (Mn), and Fe (Fe) in drinking water sources in primary schools in Sindh Province, Pakistan and to quantify potential health risks among those school children. We conducted a representative, cross-sectional study among 425 primary schools in Sindh province of Pakistan. We used risk assessment models to estimate the metal index, pollution index, lifetime cancer risk, and hazard quotient index. Across the 425 sampled schools, the levels of heavy metals in the drinking water often exceeded the WHO permissible limits (67% of schools exceeded Pb limit, 17% for Cd, 15% for Fe). The average incremental lifetime cancer risk (ILCR) for Pb exceeded tolerable limits in all of the districts under study. The findings, particularly for Pb, are of concern, as Pb may negatively influence children's growth, development, school performance, and long-term health.

Potentially toxic elements' occurrence and risk assessment through water and soil of Chitral urban environment, Pakistan: a case study

This study investigated the concentrations of potentially toxic elements (PTE) including copper (Cu), chromium (Cr), cobalt (Co), cadmium (Cd), nickel (Ni), iron (Fe), zinc (Zn), lead (Pb), molybdenum (Mo) and manganese (Mn) in water and soil of the Chitral city, Pakistan. For this purpose, water (n = 66) and soil (n = 48) samples were collected from various locations of the Chitral city and analyzed for the PTE concentrations. Determined PTE concentrations were evaluated for the human and ecological potential risk. Results revealed that hazard quotient through water consumption was less than the threshold limit (1). However, for soil, the Fe mean hazard index (HI > 1) value for children only surpassed the threshold limits. The mean cancer risk index values via soil exposure were higher (RI > 1 × 10^-4) through consumption of Co, Ni and Cd for children and only Co for adults. Contamination factor (CF) values for Mo, Cd and Fe were found very high, considerable and moderate for 79%, 8% and 77% of sampling sites, respectively. Geoaccumulation index (I_geo) showed that soils were moderately-heavily polluted due to Mo. Potential ecological risk index (PERI) values exhibited considerable risk with an average risk index value in the range 190 < RI < 380. Higher values of CF, I_geo and PERI revealed the presence of pollution and pose risk to ecological environment.

Risk assessment of heavy metal(loid)s via Spinacia oleracea ingestion after sewage water irrigation practices in Vehari District

The use of sewage water as an irrigation source can be beneficial in agricultural practices, however, it may result in human health risks due to the consumption of heavy metal(loid)-contaminated food. This study evaluated the suitability of using sewage water (SW), freshwater (FW), and groundwater (GW) for vegetable irrigation in District Vehari. Spinach (Spinacia oleracea) plants were grown in pots irrigated with FW, GW, and SW in different proportions and combinations. The results indicated the substantial lesser buildup of heavy metal(loid)s (As (- 0.8%), Cd (- 38%), Cr (- 6.2%), Cu (- 20%), Fe (- 9.2%), Mn (- 13%), Ni (- 16%), Pb (- 19%), and Zn (-15%)) in soil after S. oleracea cultivation compared to unirrigated soil possibly due to high metal(loid) uptake by S. oleracea. Irrigation with all types of waters resulted in metal(loid) accumulation in S. oleracea predominantly in roots. The combinations of FW, GW, and SW resulted in high metal(loid) accumulation (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the edible S. oleracea leaves than their alone application. Owing to high metal(loid) buildup, plants showed a linear trend in physiological imbalance in terms of reduced pigment content, induction of peroxidation, and oxidation of lipids. The severe oxidative stress was observed in S. oleracea plants under FW and GW irrigation due to high metal(loid) accumulation. The risk indices showed possible carcinogenic risk (CR > 0.0001) and non-carcinogenic risk (HI > 1) from the consumption of metal(loid)-contaminated S. oleracea leaves. Results revealed unsuitability of all waters and their combinations for S. oleracea irrigation. Moreover, this study does not encourage the use of mixed water for vegetable irrigation in Vehari District. Therefore, it is of utmost importance to monitor the quality of irrigation waters to ensure food safety and prevent chronic health risks to the exposed population.

Synthesis and Characterization of Magnetic Nanomaterials with Adsorptive Properties of Arsenic Ions

A new synthesis method of hybrid Fe₃O₄/C/TiO₂ structures was developed using microwave-assisted coprecipitation. The aim of the study was to examine the effect of the addition of glucose and titanium dioxide on adsorptive properties enabling removal of arsenic ions from the solution. The study involved the synthesis of pure magnetite, magnetite modified with glucose and magnetite modified with glucose and titanium dioxide in magnetite: glucose: titanium dioxide molar ratio 1:0.2:3. Materials were characterized by XRD, FT-IR, and BET methods. Magnetite and titanium dioxide nanoparticles were below 20 nm in size in obtained structures. The specific surface area of pure magnetite was approximately 79 m²/g while that of magnetite modified with titanium dioxide was above 190 m²/g. Obtained materials were examined as adsorbents used for removal As(V) ions from aqueous solutions. Adsorption of arsenic ions by pure magnetite and magnetite modified with titanium dioxide was very high, above 90% (initial concentration 10 mg/L), pH in the range from 2 to 7. The preparation of magnetic adsorbents with a high adsorption capacity of As(V) ions was developed (in the range from 19.34 to 11.83 mg/g). Magnetic properties enable the easy separation of an adsorbent from a solution, following adsorption.

Assessing the Adsorptive and Photodegradative Efficiencies of ZSM-11 Synthesized from Rice Husk Ash

Rice husk was used to synthesize zeolite (ZSM-11). FTIR and X-ray diffraction methods were used to characterize the product. The synthesized zeolite was used to treat underground water from some communities in Cape Coast considering parameters such as total dissolved solids, total hardness, conductivity, nitrate, and phosphate. The percentage reduction in PO43− was 96.1% in Ebubonko and 92.5% in Apewosika. Similarly, the NO3− levels also decreased significantly in Kwaprow. The adsorption capability was also determined by using it to remove Pb2+ and Zn2+ from laboratory prepared solutions with varying masses. The percentage reduction recorded 90.57% and 86.61% for the 1.0 g whilst the 1.5 g showed 93.26% and 89.36%, respectively. It was also realized that the adsorption process followed a pseudo-first-order rather than the pseudo-second-order process with their R2 values of 0.9929 and 0.8503 for the pseudo-first-order and 0.9662 and 0.6912 for the second-order for Pb2+ and Zn2+, respectively. The adsorption capacity also favored the Freundlich isotherm with R2 values of 0.7578 and 0.642 rather than Langmuir isotherm with R2 values of 0.1742 and 0.3856 for Pb2+ and Zn2+, respectively. The photodegradation ability of the synthesized zeolite was analyzed using rhodamine blue (RhB) and methyl orange (MO). The process was realized to favor the pseudo-second-order with R2 values of 0.9986 and 0.0007 and a constant K2 of 0.035 and 0.021 for RhB and MO, respectively, whereas the pseudo-first-order showed an R2 value of 0.9376 and 0.9757 with K1 values of 0.03 and 0.02.

Arsenite removal from groundwater by aerated electrocoagulation reactor with Al ball electrodes: Human health risk assessment

The application of conventional electrocoagulation (EC) process for removal of As(III) from groundwater suffers from the need of external oxidation agent for oxidation of As(III) to As(V). To tackle this limitation, an aerated EC reactor for the removal of As(III) from groundwater was evaluated in this study. The effect of initial pH_i, air flow rate, applied current, and electrode height in the EC reactor was examined. The experimental results showed that removal of arsenic mostly dependent on the applied current, electrode height in EC reactor, and air flow rate. The As(III) removal efficiency (99.2%) was maximum at pH_i of 7.5, air flow rate of 6 L min^-1, applied current of 0.30 A, and electrode height in EC reactor of 5 cm, with an total operating cost of 0.583 $ m^-3. Furthermore, the carcinogenic risk (CR) and non-carcinogenic risk of arsenic (As) was in the range of tolerable limits at all operating conditions except applied current of 0.075 A at the end of the aerated EC process to remove As from groundwater. The present EC reactor process is able to remove As(III) from groundwater to below 10 μg L^-1, which is maximum contaminant level of arsenic in drinking water according to the World Health Organization (WHO).

Scenario, perspectives and mechanism of arsenic and fluoride Co-occurrence in the groundwater: A review

Arsenic (As) and fluoride (F^-) are the two most conspicuous contaminants, in terms of distribution and menace, in aquifers around the world. While the majority of studies focus on the individual accounts of their hydro-geochemistry, the current work is an effort to bring together the past and contemporary works on As and F^- co-occurrence. Co-occurrence in the context of As and F^- is a broad umbrella term and necessarily does not imply a positive correlation between the two contaminants. In arid oxidized aquifers, healthy relationships between As and F^- is reported owing desorption based release from the positively charged (hydr)oxides of metals like iron (Fe) under alkaline pH. In many instances, multiple pathways of release led to little or no correlation between the two, yet there were high concentrations of both at the same time. The key influencer of the strength of the co-occurrence is seasonality, environment, and climatic conditions. Besides, the existing primary ion and dissolved organic matter also affect the release and enrichment of As-F^- in the aquifer system. Anthropogenic forcing in the form of mining, irrigation return flow, extraction, recharge, and agrochemicals remains the most significant contributing factor in the co-occurrence. The epidemiological indicate that the interface of these two interacting elements concerning public health is considerably complicated and can be affected by some uncertain factors. The existing explanations of interactions between As-F are indecisive, especially their antagonistic interactions that need further investigation. "Multi-contamination perspectives of groundwater" is an essential consideration for the overarching question of freshwater sustainability.

Evaluation of groundwater contamination in Chandigarh: Source identification and health risk assessment

The major objective of the current study is to estimate the groundwater quality and identify the likely sources of contamination in Chandigarh, India. Total 80 groundwater samples were collected from different locations and at various depths. Further, physcio-chemical analysis was done to estimate pH, electrical conductivity (EC), total dissolved solids, total hardness (TH), total alkalinity (TA), Na⁺, K⁺, Cl^-, SO₄^2-, PO₄^3- and NO₃^-. The groundwater samples collected from shallow water sources contain higher concentration of total dissolved salts. EC, TA, Cl^-, TH, Na⁺, and K⁺ were found relatively higher in the shallow aquifer (<150 ft). Based on the location of pollution sources at the surface and consecutive geo-statistical distribution of physicochemical characteristics, this study suggests that non-scientific disposal of municipal solid waste, dumping of industrial waste and agricultural activities, in the nearby areas lead to the deterioration of groundwater of shallow aquifer. These observations were also confirmed using various water quality indices and outcomes of multivariate modeling, including principal component analysis. Health risk assessment for nitrates indicated that 29 groundwater samples pose non-carcinogenic health risk for children due to dermal and oral exposure. Hence, there is a need to establish a system for regularly assessing the groundwater quality to minimize public health risks.

Arsenic contamination, subsequent water toxicity, and associated public health risks in the lower Indus plain, Sindh province, Pakistan

Arsenic (As) contamination in drinking water is a global public health risk. The present study highlighted the geological and anthropogenic causes of As contamination in groundwater (GW) and surface water (SW) and assessment of their potential health risks in Sindh province of Pakistan. Upon analyzing 720 GW and SW samples from 18 different sites, the estimates of As in groundwater and surface water was observed in the range of 0 to 125 and 0 to 35 μg/L with mean values of 46.8 and 15.43 μg/L respectively. Majority of the samples exceeded WHO permissible limit of As (10 μg/L) with higher concentration detected in groundwater samples compared to surface water. Moreover, both of these sample sources were found not potable based on physicochemical characteristics. The results of statistical analysis (correlation analysis, principal component analysis (PCA), and hierarchy cluster analysis (HCA)) indicate that natural mobilization of As in groundwater is believed to be enhanced by the pH-based reductive dissolution of iron hydroxide (FeOH) and competitive sorption of bicarbonate minerals in the presence of microorganisms along with evaporative enrichment while water logging, coal mining, and excessive use of pesticides are believed to be the anthropogenic causes of As enrichment. Furthermore, enormous health risk was associated with As in terms of chronic daily intake (CRI), hazard quotient (HQ), and cancer risk probability (CR) in GW and SW. Mean HQ values in GW were 4.47 mg/kg/day in adults and 3.89 mg/kg/day in children (standard HQ ≤ 1) and was 1.43 and 1.28 mg/kg/day in SW. Mean CR value in both GW and SW was found higher than the safe limit (10^-6) having a mean of 2 × 10^-3 in GW and 7 × 10^-4 (mg/kg/day) in SW. These findings suggest that majority of the sampling sites carry serious public health risk due to high As values and hence demands exigent remedial and management measures.

Molecular identification of biological contaminants in different drinking water resources of the Jazan region, Saudi Arabia

Drinking water quality plays a remarkable role in human infections and diseases. This study used polymerase chain reaction (PCR) techniques to detect bacterial pathogens. In addition, a physicochemical analysis was performed on drinking water samples from several sources. A total of 123 drinking water samples were collected from different areas in the Jazan region in Saudi Arabia: ground water (40 samples), bottled water (15 samples), tap water (52 samples), and water purification shops (16 samples). To isolate the bacterial pathogens, the water samples were spread on Nutrient and MacConkey agar media, and the grown pathogens were then identified by the 16S ribosomal RNA technique. In 87 (70.7%) of the 123 drinking water samples, there was no pathogen growth on the two-culture medium. However, 36 (29.3%) of the samples were found to be contaminated with bacteria. The physicochemical analysis indicated that the water samples were within the Saudi drinking water standards. The bacteria were resistant to Cefotaxime, Cefotaxime/Clavulanic acid, Erythromycin, Penicillin G, Rifampin and Sulfamethoxazole-Trimethoprim, respectively. The findings suggest that in Jazan, bottled water is a safer source of potable water than tap water. The contamination in the water may be occurring at the reservoirs rather than the water sources.

Titanium-based nanocomposite materials for arsenic removal from water: A review

Arsenic is highly carcinogenic element and less concentration of this chemical element makes natural water unsafe for human consumption. Versatile techniques including adsorption method have been established to remove the arsenic from water. However, adsorption is found to be one of effective method for the remediation of arsenic from contaminated water. Different types of natural adsorbents i.e. clays, waste materials, carbon based material have been studied widely for the adsorption of arsenic. Recently, nanotechnology is considered to be one of the best technology for waste water treatment. Therefore researchers have synthesized several types of nanoadsorbents and investigated them for the removal of various pollutants including arsenic from water. Now days, attention is paid on development of nanocomposite materials which are proven as competent arsenic adsorbent candidate as compared to other adsorbents due to dominant structural and surface features. Various metal/metal oxide based nanocomposites have been developed and studied for arsenic removal from aqueous media. It has been reported that TiO2 based nanocomposite exhibit stong affinity for both inorganic form of arsenic. Therefore, in this review numerous metal or metal oxide based titania nanocomposites i.e. TiO2-αFe2O3, NHITO, Ce-Ti oxide, Zr-TiO2, RGO-MFT etc. have been discussed in details for the water treatment containing arsenic. This review also presents an overview of low cost adsorbents, titania based nanoadsorbent and hybrid titania nanostructures for the removal of arsenic. In this review paper the particle size, surface area and adsorption efficiency of these titania based materials at different pH are also been presented in tabulated form. It provides the opportunity to choose best titania based nanocomposites for the treatment of arsenic polluted water.

A comprehensive review on current status, mechanism, and possible sources of arsenic contamination in groundwater: a global perspective with prominence of Pakistan scenario

Arsenic(As)-mediated contamination of groundwater resources in different parts of the world is a consequence of natural or anthropogenic sources, leading to adverse effects on the environment and human health. Millions of people from different countries are unfortunately consuming groundwater contaminated with alarming levels of As. Exposure to the high concentration of As for an extended period of time can cause devastating effects on human health such as skin lesions, cardiac disorders, discolouration and cancer. Until 2018, about 11 districts of Sindh and Punjab provinces in Pakistan had been found with As contamination in groundwater beyond the national defined permissible level, i.e. 50 µg/L. Tharparkar and Hyderabad (in Sindh province) along Indus river and Lahore and Kasur (in Punjab province) are well-known hotspots sites of natural geogenic As contamination in groundwater. Higher levels of Sulfates (SO₄^2-), Chloride (Cl^-) and Carbonate (CO₃^2-) along with the elevated values of electrical conductivity and basic pH, as well as augmented presence of "As V" species, were all an indication of oxidizing condition in groundwater, and these oxidizing conditions are identified as the primary mechanism of As contamination into aquifers of Pakistan via oxidative dissolution. The main aim of this review is to summarize and discuss the current contamination status of As in groundwater water globally with a special focus on Pakistan scenario, isotopic evidence to track sources of groundwater recharge and its effects on As contamination in groundwater with various redox conditions prevailing in Pakistan. In addition, public health consequences of As contamination and mitigation strategies for As removal from water resources have been also highlighted. In this review, the data were extracted from various cutting edge studies published in national and international journals.

Health risk assessment of phreatic water based on triangular fuzzy theory in Yinchuan plain

Groundwater quality relating closely to human health has become a great concern to the whole society, especially in heavily polluted areas. Yinchuan Plain, located in the arid and semi-arid region of Northwestern China, where people rely heavily on groundwater resource. However, due to the improper groundwater exploitation and negative effect of human activities in recent years, groundwater quality in Yinchuan plain become deteriorated. For the sustainable utilization and protection of groundwater resources, health risk assessment (HRA) of phreatic water is conducted in this paper. On the basis of model recommended by EPA, triangular fuzzy number is applied to establish risk assessment model for health risk assessment of adults and children in wet and dry seasons, respectively. Results of HRA indicate that carcinogenic risk of arsenic is highest among the risk from components in phreatic water, and the highest risk from arsenic to adults and children in wet and dry season are 6.48 × 10^-6a^-1 and 9.56 × 10^-6a^-1, 1.08 × 10^-5a^-1 and 1.59 × 10^-5a^-1, respectively. This study also states that in Yinchuan Plain carcinogenic risk from drinking groundwater can be 3-4 times magnitude higher than the noncarcinogenic risk. Also it is found that the health risk to children is as 1.5-2 times as to adults, while the uncertainties of adults' health risk are higher than that of children.

A meta-analysis of the distribution, sources and health risks of arsenic-contaminated groundwater in Pakistan

Globally, millions of people who rely on groundwater for potable purposes and agriculture have been inadvertently exposed to toxic arsenic (As) because of its natural occurrence in groundwater in several countries of Asia, Europe and America. While the presence of As in groundwater and its impacts on human health have been documented in many countries, there is little information on As contamination in Pakistan. This review highlights, for the first time, the extent and severity of As-induced problems in Pakistan based on relevant published papers; discusses possible sources of As contamination of aquifers; and estimates As-induced potential health hazards in the country in relation to global data. Data from 43 studies (>9882 groundwater samples) were used to describe As variability in groundwater of Pakistan and for comparison with global data. The mean groundwater As content reported in these studies was 120 μg/L (range: 0.1-2090 μg/L; SD: ±307). About 73% of the values for mean As contents in the 43 studies were higher than the World Health Organization (WHO) permissible limit (10 μg/L) for drinking water, while 41% were higher than the permissible limit of As in Pakistan (50 μg/L). It was observed that groundwater samples in some areas of Punjab and Sindh provinces contained high As concentrations which were almost equal to concentrations reported in the most contaminated areas of the world. We predicted that the mean values of ADD, HQ and CR were 4.4 μg kg^-1day^-1 (range: 0-77 μg kg^-1day^-1), 14.7 (range: 0-256) and 0.0029 (range: 0-0.0512), respectively, based on mean As concentrations reported in Pakistan. In addition, this article proposes some integrated sustainable solutions and future perspectives keeping in view the regional and global context, as well as the on-ground reality of the population drinking As-contaminated water, planning issues, awareness among civil society and role of the government bodies. Based on available data, it is predicted that almost 47 million people in Pakistan are residing in areas where more than 50% of groundwater wells contain As concentrations above the WHO recommended limit of As in drinking water.

Associations of potentially toxic elements (PTEs) in drinking water and human biomarkers: a case study from five districts of Pakistan

Potentially toxic elements (PTEs) are hazardous contaminants with great global environmental/ecological concerns due to their toxic, persistence, and bio-accumulative nature. This study investigates the concentrations of PTEs (Cd, Co, Cu, Fe, Ni, Mn, Pb, and Zn) in drinking water sources and consumers' biomarkers such as hair, nails, urine, and blood. For this purpose, drinking water (n = 190) and consumer biomarker (n = 60) samples were collected from five districts of the Southern Khyber Pakhtunkhwa, Pakistan. Samples were extracted and analyzed for selected PTEs concentrations using an inductively coupled plasma mass spectrometer (ICP-MS, PerkinElmer Optima 7000 DV, USA). The concentrations of PTEs were observed within the drinking water guidelines set by the World Health Organization (WHO), except for Fe, Mn, and Pb. The determined concentrations of PTEs were used to evaluate the health risk through exposure, particularly hazard quotient (HQ) and hazard index (HI). The PTEs contamination of drinking water has led to the highest mean ADI values (39.0 and 91.8 μg/kg/day) and HQ values (0.306 and 0.130) for Zn in adults and children, respectively. The mean values of HQ and HI for selected PTEs were observed within the safe health limits (< 1). Among studied biomarkers, hair showed the highest concentrations for Mn, Zn, Cd, and Pb, plasma for Co and Cu, nails for Ni, and red blood cells (RBCs) for Fe only. This study concluded that chronic exposure of PTEs through drinking water consumption has led to their bioaccumulation in human biomarkers.

Prevalent fecal contamination in drinking water resources and potential health risks in Swat, Pakistan

Fecal bacteria contaminate water resources and result in associated waterborne diseases. This study assessed drinking water quality and evaluated their potential health risks in Swat, Pakistan. Ground and surface drinking water were randomly collected from upstream to downstream in the River Swat watershed and analyzed for fecal contamination using fecal indicator bacteria (Escherichia coli) and physiochemical parameters (potential of hydrogen, turbidity, temperature, electrical conductivity, total dissolved solid, color, odor and taste). The physiochemical parameters were within their safe limits except in a few locations, whereas, the fecal contaminations in drinking water resources exceeded the drinking water quality standards of Pakistan Environmental Protection Agency (Pak-EPA), 2008 and World Health Organization (WHO), 2011. Multivariate and univariate analyses revealed that downstream urbanization trend, minimum distance between water sources and pit latrines/sewerage systems, raw sewage deep well injection and amplified urban, pastures and agricultural runoffs having human and animal excreta were the possible sources of contamination. The questionnaire survey revealed that majority of the local people using 10-20years old drinking water supply schemes at the rate of 73% well supply, 13% hand pump supply, 11% spring supply and 3% river/streams supply, which spreads high prevalence of water borne diseases including hepatitis, intestinal infections and diarrhea, dysentery, cholera, typhoid fever, jaundice and skin diseases in children followed by older and younger adults.

Potential health risk assessment through ingestion and dermal contact arsenic-contaminated groundwater in Jianghan Plain, China

Groundwater contamination with high arsenic (As) levels has caused serious health problem in Jianghan Plain. This study presents a framework to evaluate the results and their probable influencing factors of non-carcinogenic risk and carcinogenic risk in Shahu Village. An appropriate health risk assessment for residents exposing to As through ingestion and dermal contact pathways is also discussed in the paper. Hazard quotient (HQ) and target cancer risk (TR) are adopted to compute the non-carcinogenic and carcinogenic effects for residents, respectively. Monte Carlo simulation technique is used to quantify the uncertainty of the risk assessment. The assessment results show that the HQs and TRs of 10-m-deep and 25-m-deep wells exhibit seasonal variations with higher values in rainy season and lower values in dry season. The HQ values exceeding 1 at the depths of 10 (from 0.09 to 23.21 m) and 25 m (from 0.29 to 130.55 m) account for 61 and 94%, respectively, which associate with the As contents distribution in the aquifer sediments. The estimated TR values at the depths of 10 (from 3.86E-05 to 1.04E-02) and 25 m (from 1.32E-04 to 5.87E-02) exceeding the highest acceptable standard (10^-4) account for 95 and 100%, respectively. Comparison of the two exposure pathways, the ingestion exposure contributes much more than the dermal contact exposure for both non-carcinogenic risk and carcinogenic risk. The results of sensitivity analysis indicate that a more accurate measurement and better definition of probability distributions for As concentration in the groundwater can increase the accuracy of health risk assessment in Jianghan Plain. The findings demonstrate the importance of the drinking water safety, and the government should take measures to ensure the drinking water safety.

Hydrogeochemistry, water quality and health risk assessment of water resources contaminated by agricultural activities in Korkuteli (Antalya, Turkey) district center

Groundwater is a major water source for drinking, domestic and agricultural activities in the Korkuteli district. However, the intensive agricultural activities in the region negatively affect the groundwater quality. In this study, 30 water samples were collected from springs, wells, and tap waters in dry and wet seasons. Ca-Mg-HCO₃ and Mg-Ca-HCO₃ were dominant water types in the study area. According to the Gibbs diagrams, which were prepared to determine the mechanism controlling the groundwater geochemistry, samples from both seasons fell in the rock-dominance zone. The water quality index indicates the increase of ion concentrations due to the agricultural effect along with the rainwater in the region. Also, according to WHO standards, water samples are not appropriate to use as drinking water in terms of the heavy metal and fertilizers analysis results. In terms of the irrigation usage, most groundwater samples are suitable in dry and wet seasons. According to HCO₃ and SO₄ results, the mentioned samples can induce incrustation on metal surfaces and therefore are not recommended for industrial use. Groundwater chemistry in the study area is affected with water-rock interaction and dense agricultural activities. In conclusion, the study area is at high risk in terms of the health risk assessment.

A review of global outlook on fluoride contamination in groundwater with prominence on the Pakistan current situation

Several million people are exposed to fluoride (F^-) via drinking water in the world. Current review emphasized the elevated level of fluoride concentrations in the groundwater and associated potential health risk globally with a special focus on Pakistan. Millions of people are deeply dependent on groundwater from different countries of the world encompassing with an elevated level of fluoride. The latest estimates suggest that around 200 million people, from among 25 nations the world over, are under the dreadful fate of fluorosis. India and China, the two most populous countries of the world, are the worst affected. In Pakistan, fluoride data of 29 major cities are reviewed and 34% of the cities show fluoride levels with a mean value greater than 1.5 mg/L where Lahore, Quetta and Tehsil Mailsi are having the maximum values of 23.60, 24.48, > 5.5 mg/L, respectively. In recent years, however, other countries have minimized, even eliminated its use due to health issues. High concentration of fluoride for extended time period causes adverse effects of health such as skin lesions, discoloration, cardiovascular disorders, dental fluorosis and crippling skeletal fluorosis. This review deliberates comprehensive strategy of drinking water quality in the global scenario of fluoride contamination, especially in Pakistan with prominence on major pollutants, mitigation technologies, sources of pollution and ensuing health problems. Considering these verities, health authorities urgently need to establish alternative means of water decontamination in order to prevent associated health problems.