Contamination level, source identification and health risk assessment of potentially toxic elements in drinking water sources of mining and non-mining areas of Khyber Pakhtunkhwa, Pakistan.

Accelerated mining activities have increased water contamination with potentially toxic elements (PTEs) and their associated human health risk in developing countries. The current study investigated the distribution of PTEs, their potential sources and health risk assessment in both ground and surface water sources in mining and non-mining areas of Khyber Pakhtunkhwa, Pakistan. Water samples (n = 150) were taken from selected sites and were analyzed for six PTEs (Ni, Cr, Zn, Cu, Pb and Mn). Among PTEs, Cr showed a high mean concentration (497) μg L-1, followed by Zn (414) μg L-1 in the mining area, while Zn showed the lowest mean value (4.44) μg L-1 in non-mining areas. Elevated concentrations of Ni, Cr and a moderate level of Pb in ground and surface water of Mohmand District exceeded the permissible limits set by WHO. Multivariate statistical analyses showed that the pollution sources of PTEs were mainly from mafic-ultramafic rocks, acid mine drainage, open dumping of mine wastes and mine tailings. The hazard quotient (HQ) was the highest for children relative to that for adults, but not higher than the USEPA limits. The hazard index (HI) for ingestions of all selected PTEs was lower than the threshold value (HIing < 1), except for Mohmand District, which showed a value of HI >1 in mining areas through ingestion. Moreover, the carcinogenic risk (CR) values exceeded the threshold limits for Ni and Cr set by the USEPA (1.0E-04-1.0E-06). In order to protect the drinking water sources of the study areas from further contamination, management techniques and policy for mining operations need to be implemented.


Introduction
Water is one of the essential natural resources for human life and development, and an important part of the biological system. Less than 3% of the total water resources are freshwater resources, and only less than 1% is usable for human use (Saleh et al. 2019). In sustaining aquatic and terrestrial life, freshwater resources play an unavoidable role and are directly linked to drinking, agriculture, and aquaculture (Pilotto et al. 2019). Water resources could be vulnerable to potentially toxic elements (PTEs) contamination in the environment (Ciazela et al. 2018). In fresh water ecosystems, PTEs have become one of the most toxic chemicals due to their persistence in nature (Strungaru et al. 2018). PTEs are released to environment by anthropogenic activities including mining, smelting, metallurgical and industrial beneficiation processes, excavation, and transportation lead to further contaminate the surrounding environment (Santana et al. 2020;Nawab et al. 2017Nawab et al. , 2019Vinod et al. 2019;Oyebamiji et al. 2018;Li et al. 2014).
Natural processes also result in occurrence of PTEs due to complex physiochemical reactions by weathering of parent rocks, oxidation, minerals dissolution, and migration of acid mine drainage containing high contents of PTEs that could extremely affect and deteriorate the geochemical surrounding environment, and reach to the groundwater by erosion or leaching process (Nawab et al. 2018a;Kefeni et al. 2017;Moye et al. 2017), as well as natural geochemical impacts created by mining operations, could alters and affect the surface and groundwater quality for decades on regional basis, even after closing the mining activities (Baeten et al. 2018). Freshwater resources are mostly susceptible to the direct impacts of mining in the environment (Santana et al. 2020).
Mining operations are considered as the most influential anthropogenic activities which could damages the natural habitats, and degrade the land resources, result in soil and water contamination with PTEs (Shifaw 2018). For instance, the mine tailings are exposed to the agriculture lands of 3 non-mining areas, resulting to serious pollution by dispersion and mobilization of PTEs (Zhu et al. 2018). As a result, the PTEs including Pb, Cd, As, Cu and Zn could discharge to rivers due to surface runoff by wastewater or excess of rainwater, leading to contaminate the waterbodies and aquatic ecosystem (Mohammadnejad et al. 2018). In spite of these natural processes, improper treatment of abandoned old mines as well as mine tailings may pose more PTEs pollution in adjacent (non-mining) regions of agricultural soils, surface water and groundwater Sun et al. 2018;Queiroz et al. 2018). Numerous studies have been conducted on PTEs contamination in mining and adjacent non-mining surrounding areas (Santana et al. 2020;. Previous studies of abandoned mines, and tailing ponds showed the high contents of PTEs in mining areas and lead to contaminate the local soil, and rivers water due to mobilization of mining wastes (Shen et al. 2019). Due to these factors, mining is perceived to be one of human activities with the biggest detrimental effects on the environment (Paraguassú et al. 2019). Therefore, a comparative study is needed to conduct the assessment of PTEs distribution in mining and non-mining areas, by identifying their potential sources contributed to contaminate the surface and groundwater sources.
Groundwater pollution has been recognized as an actual route to transfer pollutants to surface water sources (Xiao et al. 2019;Adyasari et al. 2018). The pollutants such as PTEs can migrate more readily through water sources and drastically decrease the consistency of water in rivers, reservoirs and groundwater (Northey et al. 2016). Elevated concentrations of PTEs could deteriorate water quality and pose significant public health risks due to their toxicity, persistence and bio-accumulative nature Alves et al. 2018;Muhammad et al. 2011), and adversely impact human health (Rehman et al. 2018). For instance, high concentration of toxic PTEs in surface and groundwater may have unforeseeable adverse effects on people of all age classes, particularly in children (Yang et al. 2013). Further, it has been well known that long-term exposure to toxic PTEs can result in adverse effects on the nervous, immune, and endocrine systems , and lead to cancer or disability in both children and adults (Wu et al. 2018;Patlolla et al. 2012). And other health problems such as stomach and heart diseases, hypertension, and anorexia (Qian et al. 2020). Chronic PTEs toxicity has adverse effects on human health, such as lung disease, renal failure, bone fracture, and may lead to hypertension, fertility and hormonal, immune, liver function, and endocrine system deficiency (Yuanan et al. 2020). To understand this kind of threat, it is important to evaluate the surface and groundwater quality by means of PTEs distribution in disaster prone mining and non-mining areas and their associated health risk.

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In Pakistan, most of the mining sites are located in high mountainous and rural regions where people are illiterate, poor, and mostly unaware of the health impacts of mining. The open dumping practices of mine-wastes are common in Pakistan, leading to impact the agricultural soils by surface runoff, erosion and landslides (Nawab et al. 2018b). Major developments were made in recent times in the evaluation of the threat and effect of mine-impacted water and even in the remediation technological tools to minimize the burden of point source pollution of mining water on groundwater and surface water . Significant environmental evaluation of water resources is still required as water contamination of PTEs contributes to over-exploitation of groundwater and surface water. The local inhabitants have been using drinking water from both the (surface and groundwater) sources in Khyber Pakhtunkhwa (KPK) newly merged districts of Pakistan. In the previous administrative system, the newly merged districts were termed as agencies and had separate laws and regulations. For this reason, the quality and exposure assessment of contaminated surface water and groundwater are important before its utilization in mining and nonmining regions of three newly merged districts including (Mohmand, Bajaur and Khyber) in KPK province. Therefore, the primary objectives of the present study were (i) to investigate the PTEs distribution in surface, and groundwater of mining and non-mining areas (ii) to identify the potential sources of PTEs by multivariate statistical methods, and (iii) to evaluate the health risks assessment of PTEs for inhabitants of the study area. Our findings would provide a solid framework for further decision-making to take the appropriate steps to manage contamination in order to protect the quality of drinking water and to prevent public health hazards from the source of drinking water.

Study Area Description
The study area of Mohmand, Khyber and Bajaur Districts is located in Khyber Pakhtunkhwa province of Pakistan. Mohmand District is located in Peshawar division at latitude of 34° 22' 20" N and longitude 71° 27' 26" E, and the region is geographically made up of mountainous ranges with rocky hills and scattered along the sides of the Kabul River. The Lower Mohmand region is very fertile, while the Upper area is generally less productive. Much farmlands are rain-fed with adequate rainfall. Mohmand chromite reserves are primarily located within harzbergite and dunite system containing metagabbro minerals, which extend through Dargai across Skhakot to Mohmand DistrictDistrict as linear chain of approximately 60 km in width and 2-6 km in length. Almost all 5 of the dunite sandstones are barren, but chromites mostly occur in lowest layer in areas and bands are well known in the region. The entire ultramafic complex is sporadically crossed by a thin pyroxenite dyke. In locations tremolite veins and talc-carbonate and quartz are common (Rafiq et al. 1984;Uppal 1972).
The Bajaur District is situated in Malakand division at 34° 41′ 0′ N, 71° 30′ 0′ E in the northern region of Khyber Pakhtunkhwa province (Fig. 1) The Khyber District is located at 34.02° N latitude and 71.28° E longitude with total elevation of 1070 m, and area of 2.567 km 2 . The temperature ranges from 25°C (77°F) to over 40°C (104°F) in summer and from 4°C to 18.35°C in winter. Its boundaries Peshawar to the east, Afghanistan to the west, Orakzai to the south and Kurram to the southwest. It has an area of 2,576 sq km with a population of 8, 45,309 people. Sedimentary rocks at the Khyber District contain granite tiles, granite, dolomite, sand, barite, malachite, graphite and quartz. Mullagori marble is among the largest deposits in the study field, and soapstone is the second largest element in the area (Khan 2001). The region has a very small manufacturing base, oil mills, tobacco factories, steel plants and marble factories in Barra, Shakas Jamrud and Mullagori are the main industries in the district.

Samples Collection
A total (n=150) of drinking water samples were collected from Mohmand, Bajaur and Khyber (50 each from these Districts) in January 2018, from the surface water and groundwater sources. All the water samples were collected from different sources including water pumps, bore wells, dug wells, tap water, hand pumps, and spring water. Sampling sites were chosen on the basis of mining 6 operations in the surrounding areas and non-mining areas. All the water samples were collected in pre-washed high density 500 mL polyethylene bottles, containing 10% nitric acid (HNO3) solutions.
Before water sampling, water from water pumps, bore wells, and tap water were allowed to continuously run for few minutes, according to procedure adopted by . The geographical location of the samples was recorded using the GPS coordinates. Water samples were acidified with HNO3 to pH <2 to minimize microbial growth, precipitation and solubility of PTEs in container walls. While sampling, every bottle was labelled and then were immediately transported to the laboratory and stored at 4 °C for further analyses (Ullah et al. 2019).

Analytical Procedure
The water samples were analyzed for selected PTEs such as Ni, Cr, Zn, Cu, Pb and Mn by graphite furnace atomic absorption spectrophotometer (PerkinElmer, USA, ASS-PEA-700) through the standard conditions. The acids and reagents used in the study were 99.9 % analytical grade with spectroscopic purity (Merck Darmstadt, Germany). For the study of PTEs, the samples were transformed to a pH standard of <2 with conc. HNO3 as a preservative for further analysis. The standard solutions of PTEs were prepared by diluting 1000 mg/L standard certified solution (Fluka Kamica, Buchs, Switzerland).

Data Precision and Accuracy
The atomic absorption spectrometry (AAS) was calibrated to a validated level from Fluka Kamica (Buchs, Switzerland) with a dilution of 1000 mg/L of DI water after each 10 samples. Each sample was determined in triplicate under normal optimum AAS conditions with error >0.999. The findings of the AAS were verified by examining standard blanks and replicating them as unknown samples at intervals of every 10 samples. Reproducibility and recovery of these findings was detected at confidence levels of 93±6 and 91±5, overall. Mean results were used for the analysis of the data.
Analytical grade reagents (Merck, Germany) were used to ensure quality data, and glassware and new plastic items were washed with 10% HNO3 solution with water and dried in the oven.

Health Risk Assessment
Oral absorption and dermal contact are known to be the main pathway (over 90%) of human exposure to PTEs (Ullah et al. 2019). The chronic and cancer risks associated with the ingestion of PTEs in drinking water sources were analyzed. The persistent vulnerability was measured by exposure risk assessment. The average daily intake (ADI) shows the PTEs consumption and is calculated by ingestion and dermal contact using the given equations. Exposure can be measured by multiplying the PTEs concentration by the duration of the contact. The average daily dose (ADD) (mg/kg/day), reflecting the average dose dosage over the duration of treatment, occurred.

Average Daily Intake
The calculation of ADI through ingestion for selected PTEs was calculated by the following Eq.
Where, Cs is the concentration of selected PTEs in the sample, IR is the ingestion rate, ED is the exposure duration, EF is the exposure frequency and BW is the body weight of child ren and adults given (Table S1). AT is the average time for both adults and children.
The ADI dermal values calculations were performed using the Eq. (2), adopted by (Ngo et al. 2020).
Where Cs is the concentration of selected PTEs in the sample, SA is the surface area of the skin exposed to PTEs, Kp is the permeability coefficient, ET is the exposure time, CF is the conversion factor, and ABS is dermal absorption factor (USDOE 2011)

Hazard Quotient
Hazard quotient (HQ) indicates non-carcinogenic risk of PTEs via ingestion and dermal contact and were calculated Eq. (3), as the ratio of ADI by the reference dose (RfD) (mg/kg/ day): Where, RfD is the oral reference doses of PTEs as shown in (Table S2). HQ < 1 means that the metal has a potential non-carcinogenic health risk in the assessment system (Qiao et al. 2020).
HQderm is non carcinogenic risk, calculated by the following Eq. (4).
Where ADI is the average daily intake via dermal contact, and RfD is the dermal reference dose provided in (Table S2). Reference doses for dermal absorption have been calculated by multiplying the water ingestion reference doses with gastrointestinal absorption (GIABS) variables as indicated by USDOE-RAIS (Eq. 12) (USDOE 2011).
Where HQ ing/dermal of the selected PTEs were calculated to find HI values. HI < 1 shows the non-carcinogenic risk due to a particular route of exposure or chemical is assumed to be insignificant.

Cancer Risk
Cancer risk through consumption of selected PTEs in drinking water was calculated for oral ingestion and dermal contact (USEPA 2005).
Where CSFing is a slope factors of Ni, Cr and Pb as shown in (Table S2).
Where CSFderm in s dermal factors given in (Table S2)

Statistical Analysis
Analytical tools such as MS-Excel 2019 has been used for statistical analysis of mean, range and standard deviation of PTEs. The principal component analysis (PCA) was used for PTEs source identification and Pearson's correlation analysis for metals correlations, using OriginPro (2018 9 version) and SPSS (17) version. The geo statistical analysis and spatial distribution maps was identified by ArcGIS 10.1.

PTEs Distribution in Mining and Non-mining Areas
The descriptive results of PTEs concentrations in ground and surface water of mining and nonmining areas are summarized in Table 1 Cu, Pb and Mn in groundwater and surface water respectively, and were comparatively lower than the Mohmand District, and Bajaur District of mining regions.

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The overall results showed that Cr had high concentrations in ground and surface water sources of mining areas, followed by Zn, and Mn. The high Cr concentration could be associated to chromite ore deposits and ultramafic rocks in the region, that could be transfer from old mine tailings to the groundwater system through leaching from the surface waterbodies (Dhakate and Singh, 2008).
Mafic and ultramafic rocks deposits and mining wastes are primary source of high levels of PTEs release to the environment (Nawab et al. 2015). Peru (Custodio et al. 2020), respectively as shown in (Table S3).
In non-mining areas, there is moderate variation observed in mean concentrations of PTEs as presented in Table 1. The results showed that mean concentrations of Mn had high mean concentration (227 μg L -1 ), followed by Zn (203 μg L -1 ) in groundwater. Whereas, Mn also showed high mean concentration (254 μg L -1 ), followed by Zn (225 μg L -1 ) in surface water sources of Mohmand District. For Bajaur and Khyber Districts, the concentrations of PTEs were comparatively lower than the Mohmand District, with high mean values of Cu (23.1 μg L -1 ), and Mn (18 μg L -1 ) in surface water, and low mean value of (5.11 μg L -1 ) for Zn in groundwater, and (4.44 μg L -1 ) for Zn in surface water, respectively. The high enrichment levels of Cr, Ni, and Pb (except Zn) in the present study were found lower than the previous study of non-mining site of 11 agriculture soils near the mining-impacted northern areas of Pakistan (Nawab et al. 2016 were relatively lower than the previous studies reported by (Qin et al. 2014) and (Huang et al. 2013).
In addition, the Cr, Zn, Cu, Mn had comparatively high concentrations among PTEs in all three districts of non-mining areas. However, the elevated values of PTEs in both water sources of nonmining areas could be associated to mafic and ultramafic rocks and open dumping of chromite mining wastes that could be dispersed through runoff by rainfall and wind erosion, and thereby accumulated in surrounding areas (Nawab et al. 2015). In addition, numerous studies showed high PTEs concentrations in the surrounding mining areas and ore deposits as well as in terrestrial ecosystems (Rashed 2010).

Correlation Matrix of PTEs in Surface Water and Groundwater
Pearson's correlation coefficient values of PTEs in surface water and groundwater parameters for mining and non-mining sites are shown in Table 2 Table 3. Overall, three loading factors (F1 and F2) were obtained with eigenvalues of (> 1) for the surface water and groundwater of mining and non-mining agencies. The two principal components F1, and F2 described 95.9 % and 97.1 % variance with the eigenvalues of 5.76 and 6.18 for mining and nonmining areas, respectively as shown in (Fig. 2). First two significant factors were observed for mining and non-mining areas are presented in Fig. 3. PTEs are associated to their high concentration in the study area. The elevated PTEs concentration in both water resources could be attributed to mine tailings, and acid mine drainage wastes, released from mining sites and deposited to the underlying bedrocks (Taylor 2007). Thus F1 showed the mixed sources of anthropogenic and natural sources in the study area.
Factor 2 (F2) accounted for 30.7 %, and 6.74 % of total variability with the eigenvalues of 1.85, and 0.75. The significant correlation coefficient (r) values of surface water and groundwater 13 variables were Zn (r = 0.96), and negative loading of Pb (r = -0.93) for mining site. Whereas, the significant positive correlation coefficient (r) value of F2 was Cu (r = 0.82), and also a negative loading of Pb (r = -0.52) for the surface water and groundwater of non-mining areas. The high loadings of PTEs demonstrate the origin of open dumping of mine-wastes, resulting to contaminate the environment by surface runoff, erosion and landslides (Nawab et al. 2018b). Hence, F2 is assumed to show the mixed sources of both natural geo-genic and anthropogenic sources in mining and non-mining sites.

Average Daily Intake Dose
The ADI ingestion and dermal contact values of selected PTEs for both the adults and children are summarized in contribute to a number of problems in the exposed human population. Based on the drinking water quality in mining areas, the ADI ingestion values for Mohmand District, Bajaur District and Khyber District were observed in decreasing order of; Cr>Mn>Ni>Zn>Pb>Cu, Cr>Pb>Zn>Cu>Mn>Ni, and Zn>Cr>Cu>Mn>Ni>Pb in mining areas via both the surface water and groundwater consumption for adults and children, respectively.
The results of ADI ingestion values of non-mining water sources were varied and lower, as compared to mining water sources as shown in Comparatively, the ADI ingestion values of PTEs were found in order of; Mn>Zn>Cr>Cu>Ni>Pb, Cu>Cr>Mn>Pb>Zn>Ni, and Zn>Cu>Mn>Cr>Ni>Pb in non-mining areas of three agencies, respectively. As a result, mining areas via water sources consumption showed relatively higher ADI ingestion values as compared to non-mining areas for children and adults. Children showed high ADI ingestion values in both mining and non-mining areas due to their high consumption rate and low body weight. However, the ADI ingestion values of all PTEs were observed within the safe limits (<1). In addition, several ADI intake levels of PTEs are significantly similar to their respective reference dosage limits, suggesting whether the use of these polluted drinking water supplies tends to have an effect over the lifespan of both adults and children.
Among the source classification of water in mining areas, the Bajaur District showed the lowest ADI dermal value 4.81E-08 of Pb in groundwater for adults. High ADI dermal value of Cr (2.35E-05) was observed for children in surface water of mining areas in Mohmand District, as listed in Table 4. Likewise, Zn was observed with ADI dermal values (1.61E-05, and 2.19E-05) for adults in the groundwater and surface water of Khyber District, respectively. Based on the ADI dermal values calculation, it was observed that the children were more exposed to PTEs as compared to adults. Similarly, Custodio et al. (2020) also reported high ADI values for children in drinking water sources due to elevated PTEs concentration level resulted in mining activities. For non-mining areas of Mohmand District, Pb was observed for low ADI dermal value (8.02E-08) for adults, via surface water consumption, whereas the highest ADI dermal value (1.80E-04) was observed for Zn through surface water consumption for children (Table 5). Furthermore, the highest Zn ADI dermal value (1.56E-05), followed by Cu (1.08E-05) were recorded for children in Bajaur District through groundwater and surface water consumption, respectively. Whereas, the lowest Pb ADI values of 3.09E-08, and (2.62E-08) were observed for adults through ground water, in in Bajaur District and Khyber District, respectively. Overall, the ADI dermal values were frequently low among all agencies for the adults and children in non-mining areas. Although, high ADI dermal contact values for children were highly recorded followed by adults. And consumption of PTEs-contaminated drinking water and by dermal contact could thus be high enough to require action to reduce adverse health threats to the exposed public (Rajeshkumar et al. 2018).

Non Carcinogenic Health Risk
HQs of ingestion and dermal contact were calculated for individual PTEs in three agencies of mining and non-mining areas, presented in Table 6   , and in groundwater and surface water by Lim et al. (2008). and groundwater consumption in three agencies of mining and non-mining areas. In addition, HI values for both the adults and children exposed to all PTEs via ingestion and dermal contact, indicating low non-carcinogenic risks (Table 6 and 7). However, the total HI values in both mining and non-mining areas of Mohmand District were found higher for children indicating that there may be potential non-carcinogenic risk via ingestion continually. Finally, more analysis related to the analyzed HQ, HI and CR supports this study by showing that intake or contact with water polluted with toxic PTEs presents a risk to human health.

Carcinogenic Risk
The carcinogenic risk (CR) associated with selected PTEs (Ni, Cr and Pb) were calculated via ingestion and dermal contact for both the adults and children in mining and non-mining areas.
Based on the ingestion exposure, the CR ingestion values for Ni was found lower 8.92E-07 in Bajaur District via surface water consumption, as listed in ( and its exposure to high toxicity could be potentially harmful in their early stages of growth and may affect the immune, digestive, reproductive and nervous systems of children (Peek et al. 2018).
Thus, high approximate CR of Cr, and Ni via surface and groundwater consumption in mining regions could pose carcinogenic risk to children, and require high enough treatment of water sources to minimize the adverse health threats to the exposed public in study area. According to (WHO), children are more prone to health hazards because of high drinking water consumption, ingest more calories and breathe more air in comparison with adults. The results of present study were found consistent with related previous studies of drinking water sources, conducted in mining areas (Ewusi et al. 2017;Dorleku et al. 2018;Bhattacharya et al. 2012).
All the calculated CR dermal values of selected PTEs were low for all districts of mining areas as listed in (  (Table 9). In children, increased ingestion and dermal contact of these PTEs had shown the negative effects in development of intestinal system, kidney disorders and lung function in early stages of growth (Plum et al. 2010). As a result, the CR values of PTEs were found in order of Ni>Cr>Pb through surface and ground water in all three agencies of non-mining areas. The CR dermal contact results were also below the permissible standard (1×10 −4 ), suggested by the (USEPA 2011), indicating that carcinogenic risk could be appropriate for both adults and children in the study area by dermal contact, except that Ni in the study area exceeded the threshold limits (1.0E−04) set by the (USEPA 2011). The present study proposed that effective purification enhancement systems should be introduced to protect the health of people in the study area, particularly in the Mohmand District.

Conclusions
The distribution levels of PTEs were investigated in surface and groundwater sources of mining and non-mining areas of the newly merged districts (Mohmand, Bajaur and Khyber). In this study, the PTEs concentrations were varied in mining and non-mining water sources. Among PTEs, Cr showed highest concentrations, followed by Zn and Mn in surface water and groundwater sources, while Pb showed the lowest concentration in surface water sources of non-mining areas. The concentrations of Ni, Cr and Pb in the ground and surface water of Mohmand District were exceeded the permissible limits of WHO. The Pearson's correlation matrix and PCA results showed 18 that pollution sources of PTEs were mainly originated from common geogenic sources of maficultramafic rocks, acid mine drainage released to the regions by erosion, leaching and surface runoff.
The anthropogenic sources such as open dumping of mine-wastes and mine tailings in the study area were highly contributed towards water contamination. Drinking water consumption was the primary route of metal exposure for the Mohmand District, followed by a dermal contact route. For both target classes, the daily intake of PTEs from water consumption was at least four to ten times higher than dermal interaction. In the case of dermal exposure, the non-carcinogenic and carcinogenic risk threshold for PTEs indicates no health risk hazard for both adults and children.
However, the risk assessment revealed that there is a non-carcinogenic risk to children at the Mohmand District by ingestion exposure. Risk assessment of exposure to PTEs has shown that the carcinogenic risk from drinking water use ingestion in mining areas is relatively high, in comparison with protection standard of US-EPA risk; thus, people in this study area may be at greater risk and serious attention needs to be paid to this area. Exposure assessments performed by children, resulted in more carcinogenic and non-carcinogenic risks through ingestion, and residents of the Mohmand District were more exposed to Ni and Cr. More research work is required to reduce the levels of PTEs in drinking water sources of these regions. In addition, appropriate management measures for mine waste must be set in place to protect the local population and reduce public health threats.
Further research on the dynamics of other PTEs in mining and non-mining regions should also be undertaken to determine long-term health risks. Figure 1 Location map of the study area showing the sampling Districts Note: The designations employed and the presentation of the material on this map do not imply the expression of any opinion whatsoever on the part of Research Square concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. This map has been provided by the authors.

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