Assessing the Arsenic Contents and Associated Risks in Groundwater of Vehari and Lodhran Districts, Pakistan

Abstract

Exposure to arsenic (As) can induce numerous lethal diseases, such as cancer, cardiovascular issues, skin diseases, and diabetes in humans. The major route of human and animal exposure to As is through drinking As-rich groundwater. This study assessed As occurrence in the groundwater of two districts in the Punjab (Vehari and Lodhran) provinces of Pakistan. Groundwater analysis revealed an average As concentration of 7.7 µg/L (n = 79) in the study area, with a maximum As concentration up to 41.4 µg/L (33% of samples exceeding the WHO limit of 10 µg/L). Arsenic traces were found in animal milk (n = 15, mean: 0.79 µg/L, 17% exceeding 2.0 µg/L), human hair (n = 12, mean: 0.36 µg/g, 17% exceeding 1.0 µg/g), and human nails (n = 8, mean: 0.03 µg/g, none of the samples exceeded 1.0 µg/g). Health risk assessment indices revealed that about 33% of the hazard quotient and 54% of the cancer risk factor exceeded their thresholds. Despite the low–moderate As concentration in groundwater and the accumulation of As in a few biological samples, there is a possibility of potential As poisoning via the long-term and continuous use of groundwater for drinking. Monitoring and blanket testing of wells for As in well water can provide baseline data to minimize the threat of As-mediated arsenicosis in As-affected areas of Pakistan. Moreover, a detailed study of potential As accumulation in biological samples with a higher number of samples is recommended in the area.

1. Introduction

Geogenic groundwater contamination with arsenic (As) exceeding the World Health Organization (WHO) limit of 10 μg/L is a major environmental and public health issue globally (please see the references in Table 1). This issue is threatening the safe water supply of >200 million people worldwide [1,2]. The occurrence of high As concentrations in groundwater is mainly reported in South and Southeast Asian and South American countries with substantial spatial variation [1,3].

The previous literature has revealed that As is released into the groundwater by various geogenic activities [4]. The As-bearing minerals (such as As-containing sulfides, iron oxides) found in the Earth’s crust are considered the main source of As in groundwater [5]. These minerals occur in abundance in the alluvial floodplain of the Indus Basin, which have been mainly transported from Himalayan mountains. Weathering due to the oxidation–reduction of these As-bearing minerals/rocks releases As to the aquifers. Some studies have revealed the role of organic matter contents, climate change, microorganisms, and carbon–iron–sulfur–arsenic cycling in governing the release of As in groundwater.

Numerous reports have delineated several-fold high As concentrations > the WHO’s limit in groundwater aquifers. Table 1 summarizes the studies reporting As concentrations > 1000 µg/L in the groundwater of different regions. Many studies have revealed that >90% of the analyzed groundwater samples showed As contents > 10 µg/L. For example, As contents > 10 µg/L have been reported in 99% of the groundwater samples from Matlab Upazila, Bangladesh [6], 98% of the groundwater samples from Muridke, Pakistan [2], 93% of the groundwater samples in the Jashore district of Bangladesh [7], 100% of the groundwater samples from Sharq-pur, Pakistan [2], and 91% of the groundwater samples from West Bengal, India [8].

Table 1. Arsenic concentrations (µg/L) above 1000 µg/L reported in different areas of world, especially South Asia.

Study Area	Water	Remarks	Reference
Bihar, India	Max 1466	Total of 61% > 10 μg/L and 44% > 50 μg/L. Total of 9.7% with arsenical skin lesions.	[9]
Kandal Province, Cambodia	454 (5–1543)	1.1 million people (2 in 1000) are at risk of cancer	[10]
Ganga River Basin, India	71 (Max 4730)	Up to 3947 µg/kg in food	[11]
Lahore and Kasur districts, Pakistan	32–1900	--	[12]
West Bengal, India	82–1180	91% > 10 μg/L and 63% > 50 μg/L	[8]
Villages in Pakistan	3090 (57.55 median)	63% > 10 μg/L	[13]
District of Nadia, West Bengal, India	1362	Total of 23% > 100 μg/L. Chronic lung disease in 13% and peripheral neuropathy I in 16%.	[14]

Table 1. Arsenic concentrations (µg/L) above 1000 µg/L reported in different areas of world, especially South Asia.

Study Area	Water	Remarks	Reference
Bihar, India	Max 1466	Total of 61% > 10 μg/L and 44% > 50 μg/L. Total of 9.7% with arsenical skin lesions.	[9]
Kandal Province, Cambodia	454 (5–1543)	1.1 million people (2 in 1000) are at risk of cancer	[10]
Ganga River Basin, India	71 (Max 4730)	Up to 3947 µg/kg in food	[11]
Lahore and Kasur districts, Pakistan	32–1900	--	[12]
West Bengal, India	82–1180	91% > 10 μg/L and 63% > 50 μg/L	[8]
Villages in Pakistan	3090 (57.55 median)	63% > 10 μg/L	[13]
District of Nadia, West Bengal, India	1362	Total of 23% > 100 μg/L. Chronic lung disease in 13% and peripheral neuropathy I in 16%.	[14]

Continuously drinking As-contaminated groundwater (>10 µg/L) for long periods causes As buildup in the human body and triggers health concerns [15]. Even recent reports revealed that long-term exposure to As in drinking water (<10 µg/L) can induce toxic health effects. Based on the data of 1,042,413 liveborn children, Richter et al. [16] reported that maternal exposure to As (between 0.5 and 0.9 μg/L) in drinking water enhanced congenital heart risk. Therefore, some of the European countries have set an As threshold limit <10 µg/L (such as 5 µg/L by Denmark and 1 µg/L by The Netherlands) [17]. Hence, it is highly imperative to monitor As contents in groundwater before using it for drinking purposes.

Numerous reports have reported As buildup in human and animal tissues due to drinking As-rich water. The normal As accumulation ranges in human tissues are <100 μg/L for urine, 20–200 μg/kg for hair, and 20–500 μg/kg for nails [9]. However, As accumulations up to 8.5 and 9.7 μg/g in human nails and hair, respectively, have been reported in As-contaminated regions of India [8]. Studies have reported that > 90% of human biological samples (hair or nails) analyzed contained As contents above the normal range or permissible concentration of As. For example, 100% of human hair, nail, and urine samples contained As above the permissible concentration in Bihar, India [9]. Similarly, 100% of hair, 97% of nail, and 90% of urine samples contained As above the normal range in Brahmaputra, India [18].

Moreover, studies have also traced strong correlations between As contents in water and biological samples, implying groundwater As-mediated hazards in people. For example, Gault et al. [19] revealed that As groundwater contents were strongly linked with As levels in hair (r = 0.86) and nails (r = 0.74). Hence, assessing As accumulation in human biological samples and the transfer correlation between As concentrations in water and biological samples can better predict the health hazards of As in the local community. Therefore, the current study aimed to assess the spatial dispersion of As in the groundwater aquifers of Vehari and Lodhran District. Moreover, possible As buildup in human tissues and animal milk was explored for their potential correlations with human health risks. In fact, despite considerable research regarding As occurrence in the groundwater of Pakistan, there is very limited data about As accumulation in human and animal tissues. Therefore, the data of the current study can be of great importance regarding arsenicosis and implementing water treatment strategies.

2. Materials and Methods

2.1. History of Study Area

Groundwater and biological samples were obtained from three sub-areas (Tibba Sultanpur, Kehror Pakka, and Lodhran) of two districts (Vehari and Lodhran) in Punjab, Pakistan. These study areas were selected due to the non-availability of As data in groundwater and biological samples. Several studies have reported As contamination in adjacent areas to the sampling area. The study area is located about 50 km east of the Multan division in the Punjab province (29.9807° N, 71.8868° E) (Tibba Sultanpur), 29.6214° N, 71.9164° E (Kehror Pakka), and 29.5467° N, 71.6276° E (Lodhran). The sampling area spans over an area of >2000 km², with an estimated population of >2.0 million. The study site, part of the Indus Plain, has fertile land with a plain area. The soil of the area is considered ideal for cotton and wheat cultivation. Additionally, several other crops, vegetables, and fruits are also cultivated in this area. The sampling area lies on the banks of the river Sutlej, which mainly governs the recharge of groundwater.

The sampling area has a very dry and hot climate. The winter season (mid-November to mid-March) is the coolest in December-January, with a temperature range of 8–22 °C. The summer season (April to October) is the hottest in May-July with a temperature range of 42–48 °C. During summer, dust and hot winds are common in the area. Rainfall mainly occurs during the monsoon season (July–September). The alluvium of the area mainly contains unconsolidated sand, silt, gravel, and clay. These sediments were mainly deposited by the Indus River.

2.2. Geology and Land Use and Land Cover of Sampling Area

The soil of the region is fine silt mixed with hyperthermic fluventic halpocambids. It is characterized by large reserves of wind-blown sand, which usually forms crisscrossed unstable layers. Fine and coarse sediment mixtures are found in alluvial deposits crafted by a high-energy perennially flowing river, Sutlej. These soils are considered good for agricultural activities; however, the occurrence of As or other heavy metals could contaminate the food. The groundwater in this region is the main source of drinking, crop irrigation, and other domestic activities.

The land use/land cover change between 1987 and 2017 in Vehari District is classified into four main classes of land categories, which are vegetation, buildings, water, and barren soil. Overall, the study area is an agricultural area. There are limited industrial units in the area. The main industrial units include rice and seed factories. A decrease in vegetation cover (from 91.7% to 88.5%) attributed to deforestation and urbanization has been shown in this area. In contrast, the settlement areas are noticeably larger (2.5% of land cover expanded to 9.6%), illustrating rapid building development. There was some fluctuation in the bare soil area, and water bodies have remained largely similar.

2.3. Groundwater, Human Hair, Nails, and Animal Milk Sample Collection

In this study, a total of 79 groundwater, 15 hair, 8 nail, and 12 animal milk samples were obtained from the sampling area (Table S1). The location of each sample was marked using a geographic information system (GIS) (Figure 1). In the case of groundwater samples, the water was collected from households that use it for drinking purposes. These groundwater samples were mainly collected from electric pumps and tubewells. The groundwater sampling depth generally varies from 25 to 35 m for electric pumps and 100–120 m for tubewells. Groundwater normally found at depths less than 30 m and over 30 m represents shallow and deep groundwater, respectively [4]. It is reported that with increasing sampling depth (30–90 m), the As level in groundwater increased from 32.5 to 61.5 μg/L, while decreasing to 50.5 μg/L for a >90 m depth [4].

Each groundwater sample was collected in two distinct plastic bottles (carefully prewashed with deionized water and dried), one for an As analysis and the other for a physicochemical parameter analysis. A few drops of nitric acid (about 1 mL) were added to water samples that were used for the As analysis.

For hair and nail sampling, a few barbershops were selected randomly in the study area. From each barbershop, one composite sample of each hair and nail, representing roughly 4–8 individuals, was collected. The trimmed hair samples were collected for analysis. Hence, each biological sample (hair or nail) was a combination of roughly 4–8 subsamples. For milk samples, chillers were selected, which were animal milk collection centers. One sample was collected from each chiller. Hence, each animal milk sample was a mixture of milk from numerous animals, primarily cows. After sampling, all the samples (groundwater, animal milk, and human tissues) were transported in an ice cooler and stored in dark and dry conditions at 4 °C.

2.4. Analyses of Samples

The groundwater samples were analyzed for pH, total dissolved solids (TDSs), carbonates (CO₃), magnesium (Mg), chloride (Cl), electrical conductivity (EC), and bicarbonates (HCO₃). The Senso-Direct-200 pH-meter, LovibondSenso-Direct Con110 EC meter, and 98,302 model TDS meter were used to record pH, EC, and TDSs of water samples. The recommended titration methods were used for Cl, CO₃, and HCO₃ analyses.

The HG-AAS, Perkinelmer, pinAAcle-900F, San Diego, CA, USA (hydride generation atomic absorption-spectrophotometer) was employed for As concentration in water, animal milk, and biological samples. All the samples were analyzed using double deionized water and analytical-grade chemicals (MERCK, Darmstadt, Germany). The As standards were prepared by its stock solution that was used for the calibration of HG-AAS. Furthermore, analysis accuracy and precision were maintained using three reagent blanks. Furthermore, the As standard solution was run after every 10th reading of AAS to maintain accuracy.

2.5. Risk Assessment and Statistical Analysis

Continuously drinking As-rich water on a daily basis causes its accumulation in human tissues. Therefore, the EDI (estimated daily intake) of As was predicted as follows [20]:

EDI = C × EF × IR × ED/AT × BW

The description and values used for each parameter (C, EF, IR, ED, AT, BW, EDI) are presented in Table S2.

Drinking As-rich water can present carcinogenic and non-carcinogenic hazards to humans. Arsenic-mediated non-carcinogenic hazards (HQ; hazard quotient) were predicted as follows [20]:

HQ = EDI/RfD

The description and values used for each parameter (EDI, RfD) are presented in Table S2.

The As-mediated carcinogenic hazards (CR; cancer risk) were predicted as follows [20]:

CR = EDI × CSF

The description and values used for each parameter (CR, EDI, CSF) are presented in Table S2.

Microsoft Excel (ver. 2016), XLSTAT (ver. 2018), and Arc. GIS (ver. 10.4.1) were used for descriptive analyses of data, a multivariate analysis, and a geostatistical analysis, respectively.

3. Results and Discussions

3.1. Arsenic Concentration in Water

The average As concentration (7.7 µg/L) in the 79 groundwater samples was below the WHO limit (10 µg/L) (Figure 2). The As concentration varied from below detection limit (BDL) to 41.4 µg/L. The mean As concentration was also below the WHO limit for Tibba Sultanpur (2.7 µg/L) and Lodhran (8.4 µg/L). The maximum As concentrations in Tibba Sultanpur and Lodhran were 16.1 and 35.8, respectively. Conversely, the mean As concentration was above the WHO limit (15.0 µg/L) for Kehror Pakka, with a range of BDL of −41.4 µg/L. These results revealed that the groundwater of Tibba Sultanpur and Lodhran is less contaminated with As than Kehror Pakka.

Arsenic groundwater contamination has appeared as a global concern. Numerous reports have revealed the occurrence of high concentrations of As in groundwater. Studies have reported more than 100-fold higher concentrations of As in groundwater aquifers, with 4743 µg/L in the Ganga River Basin of India [11], 1900 µg/L in the Lahore and Kasur districts, Pakistan [12], 1466 µg/L in the Ganga plain of India [9], and 1543 µg/L in Kandal Province, Cambodia [10] (Table 1). These literature data highlight the serious concerns of groundwater As contamination and the possible transfer to human tissues after the continuous use of As-rich water for drinking.

Studies in Pakistan have also revealed groundwater As contamination in different areas of the country. However, the majority of the studies revealed comparatively lower As concentrations in the groundwater of Pakistan [21] than India and Bangladesh [9]. For example, Iqbal et al. [22] reported that none of the water samples from 40 colonies of Bahawalnagar, Pakistan, had As contents above 10 µg/L, with a range from 2.5 to 7.9 µg/L. Similarly, Riaz et al. [21] reported that the average As concentration in groundwater (n = 200) of household areas, roadsides, and small residential and industrial areas in Lodhran, Pakistan, were, respectively, 3.8, 4.8, 3.3, and 4.4 µg/L. Contrarily, there are reports of high As concentrations in the groundwater of Pakistan, with up to 1900 µg/L in Lahore and Kasur districts, Pakistan [12], and about 3000 µg/L in some villages of Pakistan [13].

In order to evaluate the spatial dispersion of high concentrations of As, the groundwater As concentrations were compared with limit values of different health-related organizations (5 µg/L for the New Jersey Department of Environmental Protection (DEP-NJ), 10 µg/L for the WHO, and 50 µg/L for the EPA-Pak). Average As concentrations in 26 (33%) and 38 (48%) water samples were above the WHO and DEP-NJ limits, respectively (

Table 2. Number and percent of water (A), human hair (B), human nails (C), and animal samples (D) exceeding limit values of different health-related organizations. Obs indicates observations.

(A)
Area	n	Number of obs. > limits			% obs. > limits
		WHO	DEP-NJ	EPA-Pak	WHO	DEP-NJ	EPA-Pak
Tibba Sultanpur	30	3	7	0	10	23	0
Kehror Pakka	17	10	14	0	59	82	0
Lodhran	32	13	17	0	41	53	0
Total	79	26	38	0	33	48	0
(B)
Area	n		Number of obs. > limits		% obs. > limits
Tibba Sultanpur	5		1		20
Kehror Pakka	5		1		20
Lodhran	5		0		0
Total	15		2		13
(C)
Area	n		Number of obs. > limits		% obs. > limits
Tibba Sultanpur	2		0		0
Kehror Pakka	4		0		0
Lodhran	2		0		0
Total	8		0		0
(D)
Area	n		Number of obs. > limits		% obs. > limits
Tibba Sultanpur	5		0		0
Kehror Pakka	2		0		0
Lodhran	5		2		40
Total	12		2		17

). However, none of the water samples in all three areas contained an As concentration above 50 µg/L (EPA-Pak limit). Kehror Pakka contained the maximum number of water samples > the WHO limit (n = 10, 59%) and the DEP-NJ limit (n = 14, 82%). However, the respective number and percentages were lower for Tibba Sultanpur (n = 3, 10% for the WHO and n = 7, 23% for the DEP-NJ) and Lodhran (n = 13, 41% for the WHO and n = 17, 53% for the DEP-NJ). The Krigging map of the area also showed some patches of As contamination (Figure 3).

Numerous reports have revealed that a certain percentage of groundwater samples had As content higher than the WHO limit in the groundwater of Pakistan. For example, As content > 10 µg/L have been reported in 9% of groundwater samples in Lodhran [22], 17% in Vehari [23], 21% in Hasilpur [21], 98% in Muridke, Pakistan [2], and 100% in Sharq-pur [2]. Hence, contrasting data are available regarding As concentrations in the groundwater of Pakistan. Several reports have recommended the analysis of well water before its utilization for drinking in the Indus Basin of Pakistan.

3.2. Arsenic Concentration in Human Nails and Hair

The mean As concentration in all 15 hair samples was 0.36 µg/g (range 0–0.82 µg/g) (Figure 2). Comparing three areas, As concentration in hair samples was 0.33, 0.20, and 0.56 µg/g, respectively, for Tibba Sultanpur, Kehror Pakka, and Lodhran. A total of two hair samples (13%) contained As contents above the permissible limit of 1 µg/g (Table 2). One hair sample each from for Tibba Sultanpur (1.32 µg/g) and Kehror Pakka (1.02 µg/g) exceeded the permissible limit. In the case of human nails, As content was detected only in one nail sample from Tibba Sultanpur (0.31 µg/g). None of the nail samples had an As concentration above 0.5 µg/g (Table 2). The correlation data for As content in groundwater and its transfer to human tissues revealed a very weak correlation (R² values of 0.0154 and <0.00, respectively, for human nails and hair) (Figure S1). This can be due to a low number of samples or the pooling of hair and nail samples. Therefore, a detailed study comprising a higher number of individual samples can better explain these potential correlations in the study area.

Numerous reports have reported As buildup in human and animal tissues due to drinking As-rich water. The normal As accumulation range in human tissues is 20–200 μg/kg and 20–500 μg/kg, respectively, for human hair and nails [9]. However, As accumulation up to 8.5 and 9.7 μg/g in human nail and hair, respectively, have been reported in As-contaminated regions of India [8]. Studies have reported that > 90% of human biological samples (hair or nail) analyzed contained As content above the normal range or permissible concentration. For example, 100% of human hair, nail, and urine samples contained As above the permissible content in Bihar, India [9]. Similarly, 100% of hair, 97% of nail, and 90% of urine samples contained As above the normal range in Brahmaputra, India [18]. There are rare data regarding As accumulation in human tissues. Previously, Kazi et al. [24] showed As accumulation in human tissues in the Sheikhupura district (2.77 and 2.68 μg/g, respectively, for females and males).

3.3. Arsenic Content in Animal Milk

The mean As concentration in animal milk samples (n = 12) was 0.79 µg/L, spanning from 0 to 6.6 µg/L (Figure 2). Arsenic was not found in all the samples obtained from Tibba Sultanpur and Kehror Pakka. However, two animal milk samples collected from Lodhran showed As content (2.8 and 6.6 µg/L) (Table 2). In contrast to human hair and nails, a moderate correlation was found between As content in groundwater and animal milk (R² = 0.76) (Figure 4). Therefore, a comprehensive study comprising a high number of individual samples from different types of animals is necessary in the area.

Rare data show As content in animal milk in Pakistan, as well as globally. Chirinos-Peinado et al. [25] reported that the average As content in 19 milk samples was 0.010 ± 0.004. They also reported that the values of QH and HI for As were >1 in <11 years children, implying possible health hazards. Kharkwal et al. [26] evaluated health hazards due to the consumption of As and heavy metals via animal milk (n = 150) in Bathinda and Ludhiana of India. They reported that 25% of rural children and 50% of urban males and 86% of urban females were at risk of cancer due to As in milk samples.

3.4. Risk Assessments

To predict the potential As-mediated health risks via drinking groundwater, the risk assessment indices were measured for the study area. The average ADD values were 0.00022, 0.00008, 0.00043, and 0.00024 µg kg⁻¹ day⁻¹ in adults, respectively, for the study area, Tibba Sultanpur, Kehror Pakka, and Lodhran (

Table 3. Risk index values for adults of study area.

Risk Indices	Mean	SD	Min	Max
Total
ADD	0.00022	0.00027	0.00000	0.00118
HQ	0.7	0.9	0.0	3.9
CR	0.0003	0.0004	0.0000	0.0018
Tibba Sultanpur
ADD	0.00008	0.00012	0.00000	0.00046
HQ	0.3	0.4	0.0	1.5
CR	0.0001	0.0002	0.0000	0.0007
Kehror Pakka
ADD	0.00043	0.00033	0.00000	0.00118
HQ	1.4	1.1	0.0	3.9
CR	0.0006	0.0005	0.0000	0.0018
Lodhran
ADD	0.00024	0.00027	0.00000	0.00102
HQ	0.8	0.9	0.0	3.4
CR	0.0004	0.0004	0.0000	0.0015

). The mean HQ value was below 1.0 for the study area (0.7), Tibba Sultanpur (0.3), and Lodhran (0.8), implying no non-carcinogenic risks to local inhabitants. Meanwhile, Kehror Pakka had a HQ value > 1.0, indicating possible potential hazards. In the case of CR, all the areas had mean values above 10–4, indicating potential carcinogenic risk in the local people. The maximum HQ values calculated were >1 for all the areas (1.5, 3.9, and 3.4, respectively, for Tibba Sultanpur, Kehror Pakka, and Lodhran). Similarly, the maximum CR values were higher than 10–4 for all three areas (0.0007, 0.0018, and 0.0015, respectively, for Tibba Sultanpur, Kehror Pakka, and Lodhran). The levels of calculated risk indices were even higher for children (Tables S3 and S4).

The current study also compared and assessed the number and percentage of groundwater samples with levels of risk indices exceeding limit values for children and adults (

Table 4. Water samples having risk index values higher than limit values.

Area	n	HQ		CR
		Number of Obs. > 0.0001	% Obs. > 0.0001	Number of Obs. > 1.0	% Obs. > 1.0
Tibba Sultanpur	30	3	10	11	37
Kehror Pakka	17	10	59	14	82
Lodhran	32	13	41	18	56
Total	79	26	33	43	54

and Table S4). Overall, 43 samples (54%) surpassed the CR limit, while 26 samples (33%) were above the HQ limit (Table 4). Comparing three areas, Kehror Pakka had the maximum percentage (59% for HQ and 82% for CR) of risk indices exceeding limit values for adults. The respective percentages were 10% and 41% for the HQ and 37% and 56% for CR, respectively, for Tibba Sultanpur and Lodhran. The number and percentage of water samples with risk indices above limit values were even higher for children. These comparisons delineated potential carcinogenic and non-carcinogenic hazards in the children and adults of the study area, especially Kehror Pakka. Hence, monitoring and remediation approaches are needed in the area to avoid the long-term consumption of As-rich water.

Numerous studies in Pakistan have highlighted potential health risks due to the presence of As in groundwater. For example, Rehman et al. [2] delineated that the HQ was >1.0 for 87% of water samples (mean 3.654 and range 0.043–8.546). Similarly, Murtaza et al. [23] reported that HQ values were >1.0 in water samples of all health facilities in the Vehari district, representing possible non-carcinogenic risks. These results indicated potential high risks to the people living in different areas of Pakistan. However, numerous reports in Pakistan also revealed risk index values below threshold limits [21,22].

Globally, even higher values of risk indices have been reported based on the As concentration in groundwater. For example, Sthiannopkao et al. [10] reported a HQ of 5.12, with very high chances of non-carcinogenic risks. The cancer risk can be even more severe in the study area [10]. Recently, Mouttoucomarassamy et al. [27] reported that As-based HQ values of 44% of water samples in the Majha Belt were higher than 4.0, signifying severe health risks. Meanwhile, the CR values were above 10–4 both in children (5.69) and adults (4.07) [27]. Wang et al. [28] revealed that As-mediated HQ values in Jiangsu Province, China, were higher than 1.0 for 21.4%, 28.6%, 21.4%, and 21.4% of children, infants, males, and females, respectively. The respective values of CR were higher than 10–4 for 21.4%, 0%, 28.6%, and 28.6% for children, infants, males, and females, respectively. Similarly, the values of risk indices (HQ and CR) revealed that 100% of people in the middle Gangetic plain were at carcinogenic risk and 35% at non-carcinogenic risk, children being at maximum risk [29].

3.5. Physical and Chemical Parameters of Water

This study also evaluated the physicochemical properties of groundwater and compared them with limit values of the WHO and EPA-Pak (

Table 5. Data of water samples having physicochemical values greater than limits of EPA-Pak and WHO.

Exceeding Limit	pH	EC	TDS	CO3	HCO3	Cl
	All
Number of obs. > limit	0	2	2	0	3	3
% > obs. > limit	0	7	7	0	4	4
	Tibba Sultanpur
Number of obs. > limit	0	2	2	0	0	3
% > obs. > limit	0	7	7	0	0	10
	Kehror Pakka
Number of obs. > limit	0	0	0	0	2	0
% > obs. > limit	0	0	0	0	12	0
	Lodhran
Number of obs. > limit	0	0	0	0	1	0
% > obs. > limit	0	0	0	0	3	0

). Overall, the values of physicochemical properties for most of the groundwater samples were within the optimum range recommended by the EPA-Pak and the WHO (Table S5). For example, pH (6.6 to 8.2) was within the recommended range of 6.5–8.5 for drinking. The variation in the EC value (mean 1133 µS/m and range 150–2270 µS/m) was mainly less than the threshold limit of 2000 µS/m. However, a few water samples (n = 2, 7%) had EC above the limit. Both samples having a higher EC than the limit were collected from Tibba Sultanpur. The trend in TDSs was the same as EC. Only two water samples (both from Tibba Sultanpur) had TDSs above 1000 mg/L. In the case of CO₃, all the samples were fit for drinking (maximum up to 8.0 meq/L with permissible level of 8.19 meq/L). However, the maximum concentration of HCO₃ was >8.19 meq/L. Overall, three water samples (4%) had HCO₃ contents above the limit. The Cl contents for three water samples (4%) were also above the limit value (250 mg/L). These findings revealed that the physicochemical parameters of water samples in the study area mainly fall within the optimum range. Numerous previous reports also revealed that the physicochemical properties of groundwater samples in Pakistan are with optimal ranges [21,22,23].

3.6. Principal Component Analyses (PCAs)

The PCA divided the data of water samples into five component factors (Table S6). The individual contributions of these factors were 35%, 23%, 15%, 12%, and 8%, respectively. The EC (0.77), TDSs (0.77), Ca + Mg (0.44), and Cl (0.50) were the main major contributors of F1. While, pH (0.4), CO3 (0.45), and HCO3 (0.75) contributed mainly to F1. Arsenic was the only main contributor to F4. Henceforth, the PCA revealed that there was no significant correlation between As and other water characteristics. These values do not confirm the same source of As and other water variables.

The PCA diagram also grouped As separately from other groundwater characteristics, thus validating a weak interaction between different water characteristics and As (Figure 5). The correlation matrix (−0.1 to 0.3) was very weak between different water characteristics and As (Table S7). Thus, the PCA showed that the origin of As does not correlate with other water characteristics.

4. Conclusions

Arsenic in groundwater is a global issue and its spatial distribution greatly varies well-to-well. Arsenic content in the study area varied from below the detection limit to 41.4 µg/L (mean 7.7 µg/L). Importantly, 33% of water samples exceeded the 10 µg/L limit. However, none of the samples surpassed the EPA-Pak limit of 50 µg/L. There is a possibility of As-mediated lethal diseases due to high values of the hazard quotient (33% of samples above 1.0) and cancer risk factor (54% of samples above 10-4). Thus, there is a possibility of As poisoning in the inhabitants of the study area via the long-term and continuous use of groundwater for drinking. Thus, the well-to-well monitoring of As content and using only As-free well water for drinking can fully avoid the arsenicosis threat in the study area.

Despite low As content in groundwater, As traces were detected in animal milk (n = 15, 17% above 1.0 µg/L), human hair (n = 12, 13% above 1.0 µg/g), and human nails (n = 8, none of the samples above 1.0 µg/g), possibly due to the continuous and long-term use of groundwater for drinking. However, these As contents in biological samples are based on a low number of biological samples. Moreover, each biological sample was a mixture of >5 nail/hair samples or >25 animal milk samples. Therefore, a comprehensive study with a high number of individual biological samples can better predict the possible As transfer from groundwater to humans.