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This study aimed to investigate the levels of heavy metals in surface and groundwater sources within the vicinity of a gold mine in Iran, as well as to evaluate the associated health and carcinogenic risks. A total of 45 water samples were collected from the mine effluent, the downstream of a river receiving the effluent of the mine, and downstream water resources. Subsequent to laboratory digestion of the samples, arsenic levels were determined using atomic fluorescence spectrophotometry, while other heavy metals were quantified using inductively coupled plasma mass spectrometry (ICP-MS). Data analysis was conducted utilizing IBM SPSS software (Version 22). The health risks and carcinogenic potentials associated with arsenic, lead, cadmium, chromium, cobalt, manganese, mercury, nickel, copper, and zinc were assessed for both pediatric and adult populations. The findings revealed that, in most instances, heavy metal concentrations exceeded the recommended standards for drinking water quality. Furthermore, the health and carcinogenic risks posed to both children and adults were found to surpass the maximum acceptable levels.

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  • We assessed the health and carcinogenic risk of surface and groundwater resources in a gold mine area.

  • The concentration of heavy metals in most cases was higher than the standard recommended for drinking, environment, and animals.

  • Health and carcinogenic risks for children and adults were higher than the maximum acceptable risk.

gold mine, heavy metals, risk assessment, water pollution
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Heavy metal pollution has received a great deal of attention on a local, regional, and global scale. This problem has been addressed through studies on groundwater pollution in Bangladesh, drinking water pollution in Bolivia, Hong Kong, and Iran (Hadzi et al. 2018; Saleh et al. 2019), river pollution in some parts of China and Iran (Gong et al. 2014; Poshtegal & Mirbagheri 2019; Jafarzadeh et al. 2020; Zare Khosheghbal et al. 2020), and groundwater pollution by heavy metals in India, China, and Iran have been reported (Saleh et al. 2019; Akhtar et al. 2020; Qiao et al. 2020).

Human activities such as mining cause the entry of various types of heavy metals in high amounts into the environment and pollution of water resources, soil, and air (Gong et al. 2014; Rehman et al. 2020). One of the most important economic mines in the world is gold mines; the extraction of metals from gold ores eventually leads to the production of large amounts of waste. In fact, more than 99% of the extracted ore is released as waste into the environment (Fashola et al. 2016). Infiltration of water into sulfide-containing ponds and accumulated masses of ore waste leads to the leaching of large amounts of heavy metals such as nickel, zinc, lead, arsenic, copper, and sulfate ions into surface water (Frempong et al. 2008; Edwards et al. 2000). Drainage of mines on the ground causes the infiltration of heavy metal effluents into groundwater aquifers and ultimately contaminates freshwater sources for drinking and irrigation uses and meets the daily demands (Gong et al. 2014). Non-essential heavy metals such as lead, cadmium, arsenic, silver, mercury, and so on are not biologically important for living organisms and in high amounts, only lead to environmental pollution, including water (Fashola et al. 2016). Chronic exposure to heavy metals leads to a wide range of health problems such as liver, kidney, lung, and carcinogenic problems. One of the ways of chronic exposure to heavy metals is through drinking water. One of the water resources used for drinking and irrigation is groundwater, which has faced a very high consumption rate in recent years. Therefore, it is crucial to measure the concentration of heavy metals in water sources in order to the maximum allowable concentration (Jordaan et al. 2018). The health risk assessment is a valuable tool for quantitatively evaluating the connection between the environment and human health in terms of the level of hazard (Emmanuel et al. 2022). The data gathered through the risk assessment serves as a vital resource to assist decision-makers in environmental and health management (Abedi Sarvestani & Aghasi 2019).

Groundwater is a very important water source for arid and semi-arid regions such as Iran, where it is essential for drinking and agriculture practices. Pollution and reduction of groundwater quality bring about the destruction of these water resources, where groundwater is a vital need and commodity (Tahmasebi et al. 2018). One of the potential causes of groundwater pollution in Iran is mines. Iran is located in the Alpine-Himalayan orogenic and metallurgical belt and has a high potential for gold and copper reserves, and this has caused groundwater pollution in Iran's mineral areas. Hence, measuring the amount and type of groundwater chemical pollution in the areas around the mine is very important (Feizi & Mansuri 2013; Jahanshahi & Zare 2015).

Zarshuran is in many ways very similar to the gold deposits of Carlin-type deposits in the western United States. This gold is mainly found in combination with arsenic, pyrite, and sphalerite. Nevertheless, iron, manganese, arsenic, antimony, zinc, lead, silver, and barium are enriched during the extraction of gold ore, which indicates the presence of these elements in the ore (Asadi Haroni & Hale 1999; Fazel et al. 2023). So far, studies have been conducted on the contamination of sediments, plants, and water around the Zarshuran mine with arsenic, which indicates that the area is contaminated with arsenic (Bakhshinezhad et al. 2019). Zarshuran water flow is the main tributary of the Sarooq River; the river is one of the most important water sources of Zarrineh Reservoir, one of the most important reservoirs in northwestern Iran, which provides drinking water to several cities and more villages. The Sarooq River supplies one-third of the reservoir's total storage. During the long years of mining activity, the ore residue has been dumped a lot, which can be a potential factor in the pollution of surface and groundwater in the study area (Bakhshinezhad et al. 2019). Accumulation of metals such as zinc, iron, manganese, nickel, and other metals in the body can lead to serious damage to human health (Low et al. 2015). However, heavy metals such as chromium, lead, cadmium, mercury, and arsenic, even in small amounts, lead to serious problems in human health and must be constantly monitored and evaluated (Rahman & Singh 2019). Risk assessment is a method for determining the level of risk and threat of a toxic element to human health, which will be measured according to the method of exposure such as oral, inhalation, and skin exposure to water, food, soil, and air sources; it must be measured at a specific time to ensure safe exposure (EPA 2004a; Prasad et al. 2020).

Considering that no study has been conducted to investigate the level of heavy metals in the waters of the Zarshuran region, this study aimed to determine the concentration of heavy metals and sanitation and carcinogenicity risk assessment of surface and groundwater resources of the Zarshuran gold mine in Iran.

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Study area

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Zarshuran mine is located next to Zarshuran village between Zanjan-West and East Azarbaijan provinces, 35 km north of Takab in northwestern Iran, with an area of 37 km2 in the catchment area of Lake Urmia. It is located in the geographical area of 36° 44′ to 36° 47′ north latitude and 47° 07′ to 47° 05′ east longitude (Figure 1). It is a mountainous region with a semi-arid climate, an average annual temperature of 9 °C, an average annual rainfall of 400 mL, and low vegetation. The altitude of this area is 2,300 m above sea level. This region is one of the most important gold mining areas in Iran and the largest gold reserves in the Middle East and includes an active arsenic mine (Zarshuran), two known gold deposits (Zarshuran and Aq Darreh), the largest lead and zinc mine in Iran (Angoran), another lead mine (Alamkandy), and a large copper mine (BaicheBagh). Moreover, evidence of ancient mining activities for gold, arsenic, antimony, and basic metals is observed (Abbasi et al. 2017; Bakhshinezhad et al. 2019). The Zarshuran gold deposit, containing 155 tons of gold with an average grade of 2.63 g/t, is situated within the Lower Cambrian black shale and siltstone layers of the Zarshuran unit, as well as the Fe-rich carbonates of the Chaldagh unit, which serve as the host rocks for the deposit. The primary host minerals for gold within this deposit are as-sulfides, such as realgar and orpiment, along with arsenian pyrites playing a significant role (Heshmatnia et al. 2022).
Figure 1
Location of the study area (Zarshuran gold mine).
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Location of the study area (Zarshuran gold mine).

Figure 1
Location of the study area (Zarshuran gold mine).
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Location of the study area (Zarshuran gold mine).

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Sampling

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A total of 135 samples (45 samples with three repetitions) were collected from available points in the areas around the mine (10 samples from the mine area, 10 samples from rivers and running water in the mine-Takab area, 6 samples from springs, 1 sample from a fish aquaculture pond, 2 samples from the rainwater collected behind the earthen reservoir, 2 samples of mine piping water, 1 sample from drainage water, and 13 samples from effluent pond water) (Figure 2). At each sampling site, eight batches of water samples were collected and combined to provide a sample at that water point. Samples were collected in 250 mL high-density polyethylene (HDPE) bottles, which were prewashed and rinsed with distilled water. At the site, the bottles were further rinsed three times with the sampled water before collecting the actual samples. The bottles had tight, leak-proof lids, and were pre-labeled. Groundwater samples were collected after pumping for 7–10 min in order to remove stagnant water stored in the well and obtain more reliable samples. In the case of surface water, samples were collected below the surface. The pH of each sample was adjusted to 2.0 using concentrated nitric acid for metal analysis before transferring from the sampling point to the laboratory. The samples were kept in the refrigerator at 4 °C for further analysis (Hadzi et al. 2018; Jordaan et al. 2018).
Figure 2
Location of the sampling station.
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Location of the sampling station.

Figure 2
Location of the sampling station.
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Location of the sampling station.

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Sample digestion and analysis

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The water microwave digestion was conducted for 52 min following the method proposed by Brady et al. (2015). The water samples were acidified using 1 mL of HNO3 (70%), centrifuged for 15 min at 3,500 rpm, and filtered using 0.45 μm cellulose acetate filters, then each sample was analyzed for 10 metals (As, Pb, Cd, Cr, Mn, Hg, Co, Ni, Cu and Zn) using Inductively coupled plasma mass spectrometry (ICP-OES) with flared end EOP Torch 2.5 mm and a pump rate of 30 rpm (Spectro arcos, Germany). According to the literature, the detection limit for ICP-OES is in the range of 0.0026 to 0.0042 mg/L (Hadzi et al. 2018). The data were analyzed using IBM SPSS software (Ver. 22).

Quality control

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Prior to utilization, each sample container was subjected to a meticulous cleaning procedure that included washing them with diluted HNO3 and then rinsing them with deionized water. Blank samples were inspected after every group of five samples, and this sequence was repeated three times to confirm the accuracy and precision of the analytical technique employed. Additionally, standard reference materials were employed for each element as a standard to evaluate the accuracy and precision of the concentration analysis of the specific heavy metals targeted (Badeenezhad et al. 2023). Tables 1 and 2 present further information about the instrument used for heavy metal analysis.

Table 1

ICP-OES ICP-OES, Spectro arcos, Spectro arcos properties

Parameter
RF generator (W) 1,400 
Plasma, auxiliary, and nebulizer gas Argon 
Plasma gas flow rate (l/min) 14.5 
Auxiliary gas flow rate (l/min) 0.9 
Nebulizer gas flow rate (l/min) 0.85 
Sample uptake time (s) 240 total 
Delay time (s) – 
Rinse time (s) 45 
Initial stabilization time (s) Preflush:45 
Time between replicate analysis (s) – 
Measurement replicate 3 
Element (λ/nm) As below 
Frequency of RF generator (MHz) resonance frequency: 27.12 MHz 
Type of detector solid state CCD 
Type of spray chamber cyclonic Cross flow 
Parameter
RF generator (W) 1,400 
Plasma, auxiliary, and nebulizer gas Argon 
Plasma gas flow rate (l/min) 14.5 
Auxiliary gas flow rate (l/min) 0.9 
Nebulizer gas flow rate (l/min) 0.85 
Sample uptake time (s) 240 total 
Delay time (s) – 
Rinse time (s) 45 
Initial stabilization time (s) Preflush:45 
Time between replicate analysis (s) – 
Measurement replicate 3 
Element (λ/nm) As below 
Frequency of RF generator (MHz) resonance frequency: 27.12 MHz 
Type of detector solid state CCD 
Type of spray chamber cyclonic Cross flow 
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Table 2

Limit of detection, limit of quantification, and wave length of ICP-OES, Spectro arcos for the elements studied

SampleAsPbCdCrCuHgZnNiCoMn
LOD 0.3 0.9 0.3 0.3 0.1 0.45 1.3 0.3 0.38 0.002 
LOQ 1 1.2 1 1 0.3 0.68 4 1 0.53 0.009 
WL (nm) 189.042 220.353 228.802 267.716 324.754 184.9 213.856 231.604 240.725 257.9 
SampleAsPbCdCrCuHgZnNiCoMn
LOD 0.3 0.9 0.3 0.3 0.1 0.45 1.3 0.3 0.38 0.002 
LOQ 1 1.2 1 1 0.3 0.68 4 1 0.53 0.009 
WL (nm) 189.042 220.353 228.802 267.716 324.754 184.9 213.856 231.604 240.725 257.9 
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Human health risk assessment

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Health risk assessment for heavy metals through intake and dermal contact was performed according to the USEPA risk assessment method (EPA 2004b; Hu et al. 2019). The detailed information on risk assessment parameters in children and adults is represented in Table 3.

Table 3

Risk assessment parameters in children and adults

Age groupExposure duration (year)Mean body weight (kg)Mean daily water intake (mL)Skin surface area (cm2)Event Time (h/day)At
CarcinogenicNoncarcinogenic
Child 6 15 453 6,600 0.33 ED (day) 70 year × 365 days/year 
Adult 30 70 1,090 18,000 0.25 
Age groupExposure duration (year)Mean body weight (kg)Mean daily water intake (mL)Skin surface area (cm2)Event Time (h/day)At
CarcinogenicNoncarcinogenic
Child 6 15 453 6,600 0.33 ED (day) 70 year × 365 days/year 
Adult 30 70 1,090 18,000 0.25 
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Exposure assessment, the average daily dose (ADDing) for heavy metals was calculated according to the following equation.
(1)
where ADDing is the average daily dose of heavy metal consumed per kilogram of body weight per day (mg/kg·day), C is the concentration of toxic metals in drinking water (mg/L), IR is the water intake per unit time (l/day), ED is the exposure time (day), BW is the body weight (kg), and AT is the average life (days). In this study, drinking water intake was the main route of risk assessment because surface and groundwater sources are potential sources of drinking water.
In addition, dermal contact is another important route, because residents sometimes swim in these waters, take a shower, etc. Therefore, they may have dermal contact with heavy metals. The average daily dose of dermal contact (ADDderm) was calculated using the following equation (Hadzi et al. 2018).
(2)
where Cx is the concentration of the chemical in water (mg/L), Sa is the total skin area (cm2), Et is the exposure duration (h/day), Pc is the constant chemical permeability of skin (cm/h), Ef is the exposure frequency (365 days/years), Ed is the exposure duration (years), Cf is the conversion factor that was considered equal to 0.001 (l/cm3) and Bwt is the body weight. The hazard quotient (HQ)was obtained using the following equation.
(3)
where HQ indicates the amount of risk through oral or dermal contact (dimensionless) and RFD is the oral and dermal reference dose (mg/kg·day).
The carcinogenic risk (CR) of heavy metals was estimated through ingestion (Equation (4)) and dermal contact (Equation (5)) to assess a person's lifetime risk of cancer as a result of exposure to potentially carcinogenic heavy metals. Slope factor (SF) is a toxicity value that quantitatively defines the relationship between dose and response. The range of CR accepted by EPA (2004a) is 1 × 10−6 to 1 × 10−4.
(4)
(5)
where CRing and CRderm show the CR through ingestion and dermal contact, respectively. SF is in mg/kg/day.

Heavy metal concentrations were used to calculate health, oral, and skin carcinogenesis risks. The detailed reference doses and cancer slope factors for different metals are summarized in Table 4.

Table 4

Reference doses (RfD) and cancer slope factors (CSF) for the different metals

MetalsOral CSFDermal CSFOral RfDDermal RfDPcReference
As 1.5 1.5 3 × 10−4 1 × 10−4 0.001 Hu et al. (2019), Kamunda et al. (2016), Hadzi et al. (2018), Zeng et al. (2015), Wang et al. (2019), Tay et al. (2019), × 10PA (2004b)  
Pb 8 × 10−3 – 3 × 10−3 5 × 10−4 0.004 
Cd 6 × 10−2  5 × 10−4 5 × 10−4 0.001 
Cr (VI) 5 × 10−1  3 × 10−3 6 × 10−5 0.002 
Mn –  1 × 10−1 2 × 10−3 0.001 
Hg – – 3 × 10−4 2 × 10−5 1.00 
Co   2 × 10−2 6 × 10−6 0.0004 
Ni 9 × 10−1  2 × 10−2 6 × 10−3 0.0002 
Cu   4 × 10−2 1 × 10−2 0.001 
Zn   3 × 10−1 6 × 10−2 0.0006 
MetalsOral CSFDermal CSFOral RfDDermal RfDPcReference
As 1.5 1.5 3 × 10−4 1 × 10−4 0.001 Hu et al. (2019), Kamunda et al. (2016), Hadzi et al. (2018), Zeng et al. (2015), Wang et al. (2019), Tay et al. (2019), × 10PA (2004b)  
Pb 8 × 10−3 – 3 × 10−3 5 × 10−4 0.004 
Cd 6 × 10−2  5 × 10−4 5 × 10−4 0.001 
Cr (VI) 5 × 10−1  3 × 10−3 6 × 10−5 0.002 
Mn –  1 × 10−1 2 × 10−3 0.001 
Hg – – 3 × 10−4 2 × 10−5 1.00 
Co   2 × 10−2 6 × 10−6 0.0004 
Ni 9 × 10−1  2 × 10−2 6 × 10−3 0.0002 
Cu   4 × 10−2 1 × 10−2 0.001 
Zn   3 × 10−1 6 × 10−2 0.0006 

CSF, cancer slope factor, RfD, dermal reference dose (mg/kg·day), Pc, dermal permeability coefficient (cm/h).

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Oral and skin health risks for As, Pb, Cd, Cr(VI), Mn, Hg, Co, Ni, Cu, and Zn in children and adults were calculated based on the average concentration of metals in different water sources. In addition, the oral and skin health risk for the collection of these metals (HI) was calculated by considering the sum of the average of each metal in the relevant water sources, for children and adults, based on Equations (6) and (7).

Total health risk was calculated for children and adults, taking into account the total set of oral and dermal health risks and based on Equation (8) for the collection of metals in each water source. Moreover, the oral and dermal cancer risks for As, Pb, Cd, Cr(VI), and Ni in children and adults were calculated based on the average concentration of metals in different water sources. Nevertheless, the total oral cancer risk and total dermal cancer risk were calculated by considering the total average of each metal in the relevant water sources, for children and adults and based on Equations (9) and (10). Total cancer risk was calculated for children and adults, taking into account the total risk of oral and dermal cancer and based on Equation (11) for the collection of metals in each water source.
(6)
(7)
(8)
(9)
(10)
(11)
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Water quality analysis in situ

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Tabulating maximum, minimum, and mean concentration of heavy metals, Table 5 compares the values of heavy metals measured with different national and international standards recommended for drinking water and environmental discharge permission. In most cases, the concentrations of the measured heavy metals were much higher than the standard level recommended for drinking as well as discharging to the environment, indicating the unsafe water resources available for human consumption and the life of other organisms. The high concentration of heavy metals could be attributed to the fact that ores contain impurities of various metals; the mining process causes the introduction of heavy metals in ores wastes to the environment, especially soil and water (Gong et al. 2014; Rehman et al. 2020).

Table 5

Mean concentration of heavy metals existing in different water resources (mg/L)

LocationAsPbCdCoCrMnHgNiCuZn
Mine water Mean 1,900 17 8 5 6 464 0.3 44 6.5 5,379 
N 10 10 10 10 10 10 10 10 10 10 
SD 3,068 47 17 7 6 518 0.5 55 6 11,702 
Minimum 8 0.5 0.05 0.2 0.8 3 0.1 7.63 1.05 10.10 
Maximum 8,025 151 53 21 16 1,372 1 157 16 37,607 
River and surface water Mean 358 18 0.1 3 3 30 0.7 6 2.7740 27.0800 
N 10 10 10 10 10 10 10 10 10 10 
SD 982 53 0.04 5 3 30 0.7 2 1.4 16 
Minimum 8 0.50 0.05 0.3 1 3.95 0.1 3 0.8 12 
Maximum 3,152 169 0.15 16 10 103 1.8 9 5 60 
Water fountain Mean 46 1.2 0.11 0.6 1.7 4.3 0.3 4 6 41 
N 6 6 6 6 6 6 6 6 6 6 
SD 32 0.8 0.06 0.5 0.9 5 0.4 3 5.2 28 
Minimum 2 0.5 0.05 0.3 1 1 0.1 1 0.8 8 
Maximum 85 2.9 0.2 1.5 3.4 14 0.9 8.8 15 90 
Pond Mean 23 1 0.06 0.4 1 29 0.1 2 1 15 
N 1 1 1 1 1 1 1 1 1 1 
SD 0.000 0.000 0.0000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Minimum 23 1 0.06 0.4 1 28 0.1 2 1 15 
Maximum 23 1 0.06 0.4 1 29 0.1 2 1 15 
Drinking water Mean 175 0.8 1.6 0.4 1 111 1.6 7 3.6 491 
N 2 2 2 2 2 2 2 2 2 2 
SD 22 0.2 0.2 0.3 0.0 38 2.2 0.7 2.8 179 
Minimum 160 0.7 1.5 0.2 1 85 0.1 6.8 1.6 364 
Maximum 191 0.9 1.8 0.6 1 138 3.2 7.8 5.6 618 
Drainage Mean 6,564 18 7 786 5.5 5.6 1.3 93 18 65 
N 1 1 1 1 1 1 1 1 1 1 
SD 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Minimum 6,564 18 7 786 5.5 5.6 1.3 93 18 65 
Maximum 6,564 18 7 786 5.5 5.6 1.3 93 18 65 
Effluent pond Mean 99 6 2 240 6.9 39 8.4 213 4,170 67 
N 13 13 13 13 13 13 13 13 13 13 
SD 128 10 0.4 44 2 60 13 86 3,113 15 
Minimum 14 0.5 1.5 180 3 1 0.1 79 74 46 
Maximum 430 40 3 309 11 146 30 373 9,060 90 
Rain Mean 4,880 0.7 0.3 16 1 123 0.3 14 17 15 
N 2 2 2 2 2 2 2 2 2 2 
SD 2,266 0.08 0.3 8.1 0.0 166 0.2 13 3 5 
Minimum 3,277 0.6 0.1 10 1 5.3 0.2 5 15 11 
Maximum 6,480 0.8 0.5 22 1 240 0.4 24 20 19 
Total Mean 907 10 3 89 4 133 3 76 1,209 1,250 
N 45 45 45 45 45 45 45 45 45 45 
SD 2,078 33 8 150 4 300 8 104 2,507 5,745 
Minimum 2 0.5 0.05 0.2 0.8 1 0.1 1 0.8 7.7 
Maximum 8,025 169 53 786 16 1,370 30 370 9,060 37,607 
Drinking water standard Iran 0.01 0.01 0.003 0.05 0.05 0.4 0.006 0.07 2 3 
WHO 0.01 0.01 0.003 0.002* 0.07 0.1–0.4 0.006 0.07 2 3* 
EPA 0.01 0.015 0.005 – 0.1 0.05 0.002 0.1 1.3 2 
Environmental standard I 0.2 0.1 0.05 1 1 – 0.01 1 0.5 24 
II 0.1 1 0.1 1 0.5–2 1 0.01 2 1 2 
III 0.1 1 0.1 1 1–2 1 0.01 2 1 2 
LocationAsPbCdCoCrMnHgNiCuZn
Mine water Mean 1,900 17 8 5 6 464 0.3 44 6.5 5,379 
N 10 10 10 10 10 10 10 10 10 10 
SD 3,068 47 17 7 6 518 0.5 55 6 11,702 
Minimum 8 0.5 0.05 0.2 0.8 3 0.1 7.63 1.05 10.10 
Maximum 8,025 151 53 21 16 1,372 1 157 16 37,607 
River and surface water Mean 358 18 0.1 3 3 30 0.7 6 2.7740 27.0800 
N 10 10 10 10 10 10 10 10 10 10 
SD 982 53 0.04 5 3 30 0.7 2 1.4 16 
Minimum 8 0.50 0.05 0.3 1 3.95 0.1 3 0.8 12 
Maximum 3,152 169 0.15 16 10 103 1.8 9 5 60 
Water fountain Mean 46 1.2 0.11 0.6 1.7 4.3 0.3 4 6 41 
N 6 6 6 6 6 6 6 6 6 6 
SD 32 0.8 0.06 0.5 0.9 5 0.4 3 5.2 28 
Minimum 2 0.5 0.05 0.3 1 1 0.1 1 0.8 8 
Maximum 85 2.9 0.2 1.5 3.4 14 0.9 8.8 15 90 
Pond Mean 23 1 0.06 0.4 1 29 0.1 2 1 15 
N 1 1 1 1 1 1 1 1 1 1 
SD 0.000 0.000 0.0000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Minimum 23 1 0.06 0.4 1 28 0.1 2 1 15 
Maximum 23 1 0.06 0.4 1 29 0.1 2 1 15 
Drinking water Mean 175 0.8 1.6 0.4 1 111 1.6 7 3.6 491 
N 2 2 2 2 2 2 2 2 2 2 
SD 22 0.2 0.2 0.3 0.0 38 2.2 0.7 2.8 179 
Minimum 160 0.7 1.5 0.2 1 85 0.1 6.8 1.6 364 
Maximum 191 0.9 1.8 0.6 1 138 3.2 7.8 5.6 618 
Drainage Mean 6,564 18 7 786 5.5 5.6 1.3 93 18 65 
N 1 1 1 1 1 1 1 1 1 1 
SD 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Minimum 6,564 18 7 786 5.5 5.6 1.3 93 18 65 
Maximum 6,564 18 7 786 5.5 5.6 1.3 93 18 65 
Effluent pond Mean 99 6 2 240 6.9 39 8.4 213 4,170 67 
N 13 13 13 13 13 13 13 13 13 13 
SD 128 10 0.4 44 2 60 13 86 3,113 15 
Minimum 14 0.5 1.5 180 3 1 0.1 79 74 46 
Maximum 430 40 3 309 11 146 30 373 9,060 90 
Rain Mean 4,880 0.7 0.3 16 1 123 0.3 14 17 15 
N 2 2 2 2 2 2 2 2 2 2 
SD 2,266 0.08 0.3 8.1 0.0 166 0.2 13 3 5 
Minimum 3,277 0.6 0.1 10 1 5.3 0.2 5 15 11 
Maximum 6,480 0.8 0.5 22 1 240 0.4 24 20 19 
Total Mean 907 10 3 89 4 133 3 76 1,209 1,250 
N 45 45 45 45 45 45 45 45 45 45 
SD 2,078 33 8 150 4 300 8 104 2,507 5,745 
Minimum 2 0.5 0.05 0.2 0.8 1 0.1 1 0.8 7.7 
Maximum 8,025 169 53 786 16 1,370 30 370 9,060 37,607 
Drinking water standard Iran 0.01 0.01 0.003 0.05 0.05 0.4 0.006 0.07 2 3 
WHO 0.01 0.01 0.003 0.002* 0.07 0.1–0.4 0.006 0.07 2 3* 
EPA 0.01 0.015 0.005 – 0.1 0.05 0.002 0.1 1.3 2 
Environmental standard I 0.2 0.1 0.05 1 1 – 0.01 1 0.5 24 
II 0.1 1 0.1 1 0.5–2 1 0.01 2 1 2 
III 0.1 1 0.1 1 1–2 1 0.01 2 1 2 

*p<0.05. SD, Standard deviation.

Recommended levels (not determined by the Iran Department of Environment but adopted from literature as mentioned in Iran Department of Environment Guideline).

I Proposed Iranian standard for the use of effluents and returned water for drinking livestock and poultry.

II Proposed Iranian standard for discharging effluents and waters returned to surface waters.

III Proposed Iranian standard for discharging effluents and waters returned to cesspool.

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The content of heavy metals contained in the mineral water was measured and shown in Figure 3. The content of As and Zn was the highest in mine water, followed by Mn, Pb, Ni, and Cu. The WHO drinking water standards for As and Zn are 0.01 and 3 ppm, respectively. In mineral water, As and Zn exceed the WHO standards by 190 times and 1,800 times, respectively, and extremely high concentrations were specified. All heavy metals measured in mine water exceeded WHO and EPA drinking water standards. In particular, high excess concentrations of 2,610 times for Cd, 2,310 times for Co, and 1,698 times for Pb were measured. Also, Cr and Hg were measured at 81 times and 54 times higher concentrations, respectively. The water quality of the river and surface water around the mine was high in the order of As > Zn > Mn and Pb, just like mine water (Figure 3(b)). The highest concentration of AS was measured in the mine water at the outflow point, and although it gradually decreased as it went downstream, the concentration was still significantly higher than the WHO standard by 48,000 times or more. Moreover, in the water foundation and pond, As, Zn, and Mn were measured exceeding the standard values. The measured heavy metal content was highest in the following order: Drainage > Rain > Mine water > Surface water > drinking water > Effluent pond > Water fountain > pond (Figure 3(c)). These high concentrations of heavy metals not only seriously adversely affect the natural environment, such as rivers and lakes around the mine, but also seriously adversely affect human health.
Figure 3
(a) Mine water quality, (b) river and surface water quality, and (c) heavy metal concentration near Zarshuran gold mine (n = 10).
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(a) Mine water quality, (b) river and surface water quality, and (c) heavy metal concentration near Zarshuran gold mine (n = 10).

Figure 3
(a) Mine water quality, (b) river and surface water quality, and (c) heavy metal concentration near Zarshuran gold mine (n = 10).
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(a) Mine water quality, (b) river and surface water quality, and (c) heavy metal concentration near Zarshuran gold mine (n = 10).

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In a study conducted by Adewumi & Laniyan (2020), the concentration of metals measured in water sources around a mine was higher than the standard level recommended by WHO and NSDWQ. Moreover, the concentration of all metals in the water samples around the mine area was relatively higher due to the direct entry of rock waste into the waters around the mine, which gradually decreased the concentration of metals in the downstream water. However, sometimes the concentration of a metal in distant waters may be relatively high, which could be due to informal and illegal mining and commercial activities around distant water sources (Hadzi et al. 2018). For example, the highest concentration of As was related to the beginning of runoff around the mine with the amount of 8 mg/L. The highest measured amount of lead was 169 mg/L, which was found at the beginning of the river that flowed from the mine to Takab City. The highest level of Zn was 3,761 mg/L, which was found in a three-way effluent accumulation around the mine. Hadzi et al. (2018) reported that the concentration of most metals measured in the water resources around the gold mine in Ghana was higher than the standard level recommended. In another study by Adewumi & Laniyan (2020) on the water resources around the Nigeria gold mine, the levels of Cu, Pb, As, Ni, Cr, and Zn were higher than the recommended standard for drinking. The level of metals measured in this study was higher than the concentration of heavy metals measured in the abovementioned studies, which could be due to the extent and level of extraction of Zarshuran ores as one of the largest gold mines in the world (Gong et al. 2014; Bortey-Sam et al. 2016; Hu et al. 2019).

Health and cancer risk analysis

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Health and cancer risks were assessed for six water categories (out of eight categories) including water resources of the mine area, surface waters, springs, ponds, drinking water sources, and rainwater collected behind the earthen dam, which could be drunk and had skin contact. According to Table 6, the highest health and oral and dermal cancer risks were related to As due to its concentration and risk factor, and the lowest oral and dermal health risk was related to Zn, Cu, and Ni. In the study of Hadzi et al. (2018), the highest oral health risk was related to As, and the lowest was related to Cu. The highest health risk and oral and dermal cancer risk for the collection of metals (As, Pb, Ka, Cr, Mn, Hg, Co, Ni, Cu, and Zn) were related to rainwater collected behind the earthen dam due to the accumulation of ore waste in the earthen dam and the entry of metals into the earthen dam and the lowest health and oral and dermal cancer risks for the metal collection were related to the pool, as it is located in an area far away from the mine waste and also the insulation of the floor and walls of the pool.

Table 6

Health, cancer, digestion, and dermal risk assessment in different age groups and different water source

MetalsWater sourceMetal concentration (mg/L)Age groupOral health RFD (mg/kg·day)Oral health riskDermal health RFDDermal health riskOral CSFOral cancer riskDermal CSFDermal cancer risk
As Mine water 1,900 Child 3 × 10−4 1.9 × 10+5 1.2 × 10−4 2.2 × 10+3 1.5 7.4 × 10+0 1.5 2.1 × 10−2 
Adult 9.9 × 10+4 9.9 × 10+2 1.9 × 10+1 4.7 × 10−2 
River and surface water 358 Child 3.6 × 10+4 4.2 × 10+2 1.4 × 10+0 4 × 10−3 
Adult 1.9 × 10+4 1.9 × 10+2 3.6 × 10+0 8.9 × 10−3 
Water fountain 46 Child 4.6 × 10+3 5.4 × 10+1 1.8 × 10−1 5.1 × 10−4 
Adult 2.4 × 10+3 2.4 × 10+1 4.6 × 10−1 1.1 × 10−3 
Pond 23 Child 2.4 × 10+3 2.8 × 10+1 9 × 10−2 2.6 × 10−4 
Adult 1.2 × 10+3 1.2 × 10+1 2.3 × 10−1 6 × 10−4 
Drinking water 175 Child 1.77 × 10+4 2 × 10+2 7 × 10−1 2 × 10−3 
Adult 9 × 10+3 9 × 10+1 1.8 × 10+0 4.4 × 10−3 
Rain 4,880 Child 4.91 × 10+5 5.8 × 10+3 1. 9 × 10+1 5.5 × 10−2 
Adult 2.5 × 10+5 2.5 × 10+3 4.9 × 10+1 1.2 × 10−1 
Pb Mine water 17 Child 3.5 × 10−3 1.5 × 10+2 5.3 × 10−4 1.9 × 10+1 8.5 × 10−3 3.7 × 10−4 N/A N/A 
Adult 7.5 × 10+1 8.3 × 10+0 9.6 × 10−4 
River and surface water 18 Child 1.5 × 10+2 2 × 10+1 4 × 10−4 
Adult 8 9 1 × 10−3 
Water fountain 1 Child 1 1 2.6 × 10−5 
Adult 5 6 × 10−1 7 × 10−5 
Pond 1 Child 9 1 2 × 10−5 
Adult 5 5 × 10−1 6 × 10−5 
Drinking water 0.8 Child 7 9 × 10−1 2 × 10−5 
Adult 4 4 × 10−1 5 × 10−5 
Rain 0.7 Child 6 8 × 10−1 1.5 × 10−5 
Adult 3 3 × 10−1 4 × 10−5 
Cd Mine water 7.8 Child 5 × 10−4 5 × 10+2 5 × 10−4 2 6 × 10−2 1 × 10−3 N/A N/A 
Adult 2 × 10+2 1 3 × 10−3 
River and surface water 0.1 Child 5 × 10+0 3 × 10−2 1 × 10−5 
Adult 3 × 10+0 1 × 10−2 4 × 10−5 
Water fountain 0.1 Child 6 × 10+0 3 × 10−2 2 × 10−5 
Adult 3 × 10+0 1 × 10−2 4 × 10−5 
Pond 0.06 Child 4 × 10+0 2 × 10−2 9 × 10−6 
Adult 2 × 10+0 8 × 10−3 2 × 10−5 
Drinking water 1.6 Child 10 × 10+1 5 × 10−1 3 × 10−4 
Adult 5 × 10+1 2 × 10−1 7 × 10−4 
Rain 0.27 Child 2 × 10+1 8 × 10−2 4 × 10−5 
Adult 9 4 × 10−2 1 × 10−5 
Cr (VI) Mine water 5.7 Child 3 × 10−3 60 6 × 10−5 30 5 × 10−1 7 × 10−3 N/A N/A 
Adult 3 10 2 × 10−2 
River and surface water 2.7 Child 30 10 4 × 10−3 
Adult 10 6 9 × 10−3 
Water fountain 1.7 Child 20 8 2 × 10−3 
Adult 9 4 6 × 10−3 
Pond 1 Child 1 5 1 × 10−3 
Adult 5 2 3 × 10−3 
Drinking water 1 Child 1 5 1 × 10−3 
Adult 5 2 34 × 10−3 
Rain 1 Child 1 5 1 × 10−3 
Adult 5 2 3 × 10−3 
Mn Mine water 464 Child 1 1 2 × 10−3 3 N/A N/A N/A N/A 
Adult 5 2 
River and surface water 30 Child 7 2 
Adult 3 1 
Water fountain 4 Child 9 3 × 10−1 
Adult 5 × 10−1 1 × 10−1 
Pond 28 Child 6 2 
Adult 3 1 
Drinking water 111 Child 2 9 
Adult 1 4 
Rain 122 Child 3 10 
Adult 1 4 
Hg Mine water 0.3 Child 3 × 10−4 3 3 × 10−4 2 × 10+2 N/A N/A N/A N/A 
Adult 2 7 
River and surface water 0.68 Child 6.8 3 × 10+2 
Adult 4 1.5 × 10+2 
Water fountain 0.34 Child 3 1.6 × 10+2 
Adult 2 72 
Pond 0.0 Child 10 48 
Adult 5 21 
Drinking water 1.6 Child 165 794 
Adult 9 350 
Rain 0.3 Child 31 150 
Adult 16 66 
Co Mine water 4.7 Child 2 × 10−2 7 6 × 10−6 48 N/A N/A N/A N/A 
Adult 4 21 
River and surface water 3 Child 5 31 
Adult 2 14 
Water fountain 0.57 Child 9 × 10−1 6 
Adult 4 × 10−1 3 
Pond 0.4 Child 6 × 10−1 4 
Adult 3 × 10−1 2 
Drinking water 0.4 Child 6 × 10−1 4 
Adult 3 × 10−1 2 
Rain 16 Child 24 1.6 × 10+2 
Adult 13 72 
Ni Mine water 44 Child 2 × 10−2 67 6 × 10−3 2 × 10−1 9 × 10−1 1 × 10−1 N/A N/A 
Adult 34 1 × 10−1 2. 7 × 10−1 
River and surface water 5.8 Child 9 3 × 10−2 1 × 10−2 
Adult 5 1 × 10−2 4 × 10−2 
Water fountain 4 Child 6 2 × 10−2 10 × 10−3 
Adult 3 10 × 10−3 3 × 10−2 
Pond 2 Child 3 1 × 10−2 5 × 10−3 
Adult 2 5 × 10−3 1 × 10−2 
Drinking water 7 Child 11 4 × 10−2 2 × 10−2 
Adult 6 2 × 10−2 4 × 10−2 
Rain 14 Child 22 7 × 10−2 3 × 10−2 
Adult 11 3 × 10−2 9 × 10−2 
Cu Mine water 6.5 Child 4 × 10−2 5 1 × 10−2 8 × 10−2 N/A N/A N/A N/A 
Adult 3 4 × 10−2 
River and surface water 2.8 Child 2 3 × 10−2 
Adult 1 1 × 10−2 
Water fountain 5.7 Child 4 7 × 10−2 
Adult 2 3 × 10−2 
Pond 1 Child 8 × 10−1 1 × 10−2 
Adult 4 × 10−1 6 × 10−3 
Drinking water 3.6 Child 3 4 × 10−2 
Adult 1 2 × 10−2 
Rain 17 Child 13 2 × 10−1 
Adult 7 9 × 10−2 
Zn Mine water 5,379 Child 3 × 10−1 540 6 × 10−2 8 N/A N/A N/A N/A 
Adult 280 3 
River and surface water 27 Child 3 4 × 10−2 
Adult 1 2 × 10−2 
Water fountain 41 Child 4 6 × 10−2 
Adult 2 3 × 10−2 
Pond 15 Child 1.5 2 × 10−2 
Adult 8 × 10−1 10 × 10−3 
Drinking water 490 Child 49 7 × 10−1 
Adult 26 3 × 10−1 
Rain 14.75 Child 1 2 × 10−2 
Adult 8 × 10−1 9 × 10−3 
HI (Hazard Index) Mine water  Child HI oral 192,400 HI dermal 2,537 Total oral cancer risk 7 Total dermal cancer risk 2 × 10−2 
  Adult 99,340 1,125 19 5 × 10−2 
River and surface water  Child 36,280 817 1.4 4 × 10−3 
 Adult 18,744 362 4 9 × 10−3 
Water fountain  Child 4,695 234 0.2 5 × 10−4 
 Adult 2,414 103 0.492 1 × 10−3 
Pond  Child 2,395 88 0.1 3 × 10−4 
 Adult 1,233 39 0.25 6 × 10−4 
Drinking water  Child 18,068 1,020 0.7 2 × 10−3 
 Adult 9,300 451 1.8 4 × 10−3 
Rain  Child 491,150 6,088 19 5 × 10−2 
 Adult 253,078 2,695 50 1 × 10−1 
Total risk Mine water  Child Total Health Risk = HIOral+ HIDermal 2 × 10+5 Total cancer risk = Total oral cancer risk +Total dermal cancer risk 7.5 
 Adult 1 × 10+5 1.9 
River and surface water  Child 3.7 × 10+4 1.4 
 Adult 2 × 10+4 3.6 
Water fountain  Child 5 × 10+3 2 × 10−1 
 Adult 2.5 × 10+3 4.9 × 10−1 
Pond  Child 2 × 10+3 10 × 10−2 
 Adult 1 × 10+3 2.5 × 10−1 
Drinking water  Child 2 × 10+4 7 × 10−1 
 Adult 10 × 10+3 2 
Rain  Child 5 × 10+5 19 
 Adult 3 × 10+5 50 
MetalsWater sourceMetal concentration (mg/L)Age groupOral health RFD (mg/kg·day)Oral health riskDermal health RFDDermal health riskOral CSFOral cancer riskDermal CSFDermal cancer risk
As Mine water 1,900 Child 3 × 10−4 1.9 × 10+5 1.2 × 10−4 2.2 × 10+3 1.5 7.4 × 10+0 1.5 2.1 × 10−2 
Adult 9.9 × 10+4 9.9 × 10+2 1.9 × 10+1 4.7 × 10−2 
River and surface water 358 Child 3.6 × 10+4 4.2 × 10+2 1.4 × 10+0 4 × 10−3 
Adult 1.9 × 10+4 1.9 × 10+2 3.6 × 10+0 8.9 × 10−3 
Water fountain 46 Child 4.6 × 10+3 5.4 × 10+1 1.8 × 10−1 5.1 × 10−4 
Adult 2.4 × 10+3 2.4 × 10+1 4.6 × 10−1 1.1 × 10−3 
Pond 23 Child 2.4 × 10+3 2.8 × 10+1 9 × 10−2 2.6 × 10−4 
Adult 1.2 × 10+3 1.2 × 10+1 2.3 × 10−1 6 × 10−4 
Drinking water 175 Child 1.77 × 10+4 2 × 10+2 7 × 10−1 2 × 10−3 
Adult 9 × 10+3 9 × 10+1 1.8 × 10+0 4.4 × 10−3 
Rain 4,880 Child 4.91 × 10+5 5.8 × 10+3 1. 9 × 10+1 5.5 × 10−2 
Adult 2.5 × 10+5 2.5 × 10+3 4.9 × 10+1 1.2 × 10−1 
Pb Mine water 17 Child 3.5 × 10−3 1.5 × 10+2 5.3 × 10−4 1.9 × 10+1 8.5 × 10−3 3.7 × 10−4 N/A N/A 
Adult 7.5 × 10+1 8.3 × 10+0 9.6 × 10−4 
River and surface water 18 Child 1.5 × 10+2 2 × 10+1 4 × 10−4 
Adult 8 9 1 × 10−3 
Water fountain 1 Child 1 1 2.6 × 10−5 
Adult 5 6 × 10−1 7 × 10−5 
Pond 1 Child 9 1 2 × 10−5 
Adult 5 5 × 10−1 6 × 10−5 
Drinking water 0.8 Child 7 9 × 10−1 2 × 10−5 
Adult 4 4 × 10−1 5 × 10−5 
Rain 0.7 Child 6 8 × 10−1 1.5 × 10−5 
Adult 3 3 × 10−1 4 × 10−5 
Cd Mine water 7.8 Child 5 × 10−4 5 × 10+2 5 × 10−4 2 6 × 10−2 1 × 10−3 N/A N/A 
Adult 2 × 10+2 1 3 × 10−3 
River and surface water 0.1 Child 5 × 10+0 3 × 10−2 1 × 10−5 
Adult 3 × 10+0 1 × 10−2 4 × 10−5 
Water fountain 0.1 Child 6 × 10+0 3 × 10−2 2 × 10−5 
Adult 3 × 10+0 1 × 10−2 4 × 10−5 
Pond 0.06 Child 4 × 10+0 2 × 10−2 9 × 10−6 
Adult 2 × 10+0 8 × 10−3 2 × 10−5 
Drinking water 1.6 Child 10 × 10+1 5 × 10−1 3 × 10−4 
Adult 5 × 10+1 2 × 10−1 7 × 10−4 
Rain 0.27 Child 2 × 10+1 8 × 10−2 4 × 10−5 
Adult 9 4 × 10−2 1 × 10−5 
Cr (VI) Mine water 5.7 Child 3 × 10−3 60 6 × 10−5 30 5 × 10−1 7 × 10−3 N/A N/A 
Adult 3 10 2 × 10−2 
River and surface water 2.7 Child 30 10 4 × 10−3 
Adult 10 6 9 × 10−3 
Water fountain 1.7 Child 20 8 2 × 10−3 
Adult 9 4 6 × 10−3 
Pond 1 Child 1 5 1 × 10−3 
Adult 5 2 3 × 10−3 
Drinking water 1 Child 1 5 1 × 10−3 
Adult 5 2 34 × 10−3 
Rain 1 Child 1 5 1 × 10−3 
Adult 5 2 3 × 10−3 
Mn Mine water 464 Child 1 1 2 × 10−3 3 N/A N/A N/A N/A 
Adult 5 2 
River and surface water 30 Child 7 2 
Adult 3 1 
Water fountain 4 Child 9 3 × 10−1 
Adult 5 × 10−1 1 × 10−1 
Pond 28 Child 6 2 
Adult 3 1 
Drinking water 111 Child 2 9 
Adult 1 4 
Rain 122 Child 3 10 
Adult 1 4 
Hg Mine water 0.3 Child 3 × 10−4 3 3 × 10−4 2 × 10+2 N/A N/A N/A N/A 
Adult 2 7 
River and surface water 0.68 Child 6.8 3 × 10+2 
Adult 4 1.5 × 10+2 
Water fountain 0.34 Child 3 1.6 × 10+2 
Adult 2 72 
Pond 0.0 Child 10 48 
Adult 5 21 
Drinking water 1.6 Child 165 794 
Adult 9 350 
Rain 0.3 Child 31 150 
Adult 16 66 
Co Mine water 4.7 Child 2 × 10−2 7 6 × 10−6 48 N/A N/A N/A N/A 
Adult 4 21 
River and surface water 3 Child 5 31 
Adult 2 14 
Water fountain 0.57 Child 9 × 10−1 6 
Adult 4 × 10−1 3 
Pond 0.4 Child 6 × 10−1 4 
Adult 3 × 10−1 2 
Drinking water 0.4 Child 6 × 10−1 4 
Adult 3 × 10−1 2 
Rain 16 Child 24 1.6 × 10+2 
Adult 13 72 
Ni Mine water 44 Child 2 × 10−2 67 6 × 10−3 2 × 10−1 9 × 10−1 1 × 10−1 N/A N/A 
Adult 34 1 × 10−1 2. 7 × 10−1 
River and surface water 5.8 Child 9 3 × 10−2 1 × 10−2 
Adult 5 1 × 10−2 4 × 10−2 
Water fountain 4 Child 6 2 × 10−2 10 × 10−3 
Adult 3 10 × 10−3 3 × 10−2 
Pond 2 Child 3 1 × 10−2 5 × 10−3 
Adult 2 5 × 10−3 1 × 10−2 
Drinking water 7 Child 11 4 × 10−2 2 × 10−2 
Adult 6 2 × 10−2 4 × 10−2 
Rain 14 Child 22 7 × 10−2 3 × 10−2 
Adult 11 3 × 10−2 9 × 10−2 
Cu Mine water 6.5 Child 4 × 10−2 5 1 × 10−2 8 × 10−2 N/A N/A N/A N/A 
Adult 3 4 × 10−2 
River and surface water 2.8 Child 2 3 × 10−2 
Adult 1 1 × 10−2 
Water fountain 5.7 Child 4 7 × 10−2 
Adult 2 3 × 10−2 
Pond 1 Child 8 × 10−1 1 × 10−2 
Adult 4 × 10−1 6 × 10−3 
Drinking water 3.6 Child 3 4 × 10−2 
Adult 1 2 × 10−2 
Rain 17 Child 13 2 × 10−1 
Adult 7 9 × 10−2 
Zn Mine water 5,379 Child 3 × 10−1 540 6 × 10−2 8 N/A N/A N/A N/A 
Adult 280 3 
River and surface water 27 Child 3 4 × 10−2 
Adult 1 2 × 10−2 
Water fountain 41 Child 4 6 × 10−2 
Adult 2 3 × 10−2 
Pond 15 Child 1.5 2 × 10−2 
Adult 8 × 10−1 10 × 10−3 
Drinking water 490 Child 49 7 × 10−1 
Adult 26 3 × 10−1 
Rain 14.75 Child 1 2 × 10−2 
Adult 8 × 10−1 9 × 10−3 
HI (Hazard Index) Mine water  Child HI oral 192,400 HI dermal 2,537 Total oral cancer risk 7 Total dermal cancer risk 2 × 10−2 
  Adult 99,340 1,125 19 5 × 10−2 
River and surface water  Child 36,280 817 1.4 4 × 10−3 
 Adult 18,744 362 4 9 × 10−3 
Water fountain  Child 4,695 234 0.2 5 × 10−4 
 Adult 2,414 103 0.492 1 × 10−3 
Pond  Child 2,395 88 0.1 3 × 10−4 
 Adult 1,233 39 0.25 6 × 10−4 
Drinking water  Child 18,068 1,020 0.7 2 × 10−3 
 Adult 9,300 451 1.8 4 × 10−3 
Rain  Child 491,150 6,088 19 5 × 10−2 
 Adult 253,078 2,695 50 1 × 10−1 
Total risk Mine water  Child Total Health Risk = HIOral+ HIDermal 2 × 10+5 Total cancer risk = Total oral cancer risk +Total dermal cancer risk 7.5 
 Adult 1 × 10+5 1.9 
River and surface water  Child 3.7 × 10+4 1.4 
 Adult 2 × 10+4 3.6 
Water fountain  Child 5 × 10+3 2 × 10−1 
 Adult 2.5 × 10+3 4.9 × 10−1 
Pond  Child 2 × 10+3 10 × 10−2 
 Adult 1 × 10+3 2.5 × 10−1 
Drinking water  Child 2 × 10+4 7 × 10−1 
 Adult 10 × 10+3 2 
Rain  Child 5 × 10+5 19 
 Adult 3 × 10+5 50 
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The oral and dermal health risk of As is higher than 1 in all water sources for children and adults; therefore, it has a potential risk of developing non-cancerous diseases. In addition, the risk of oral and dermal cancer risk in all water sources is higher than 10−6–10−4, indicating a potential risk of cancer due to drinking and dermal contact. Considering a water sample from each of the water resources used for drinking and washing (contact), taking into account the metal contents inside it, and accumulating the health risk of all metals and their CR, the water samples with drinking and dermal health risk were much higher than 1 and the cancer risk was much higher than 10−4 for children and adults. Therefore, drinking and daily dermal contact with any of the mentioned water sources can cause different types of cancerous and non-cancerous complications. The consumption of water containing high concentrations of heavy metals has a high cancer risk so drinking and dermal contact with water resources causes cancer (Adewumi & Laniyan 2020). In addition, according to Table 6, oral and dermal health risks for children were higher than for adults and the reason was lower weight in children than adults; hence, the ratio of daily intake of metals to body weight (1 kg) was higher in children. Adewumi & Laniyan (2020) reported higher health risk rates for children than adults.

The risk of oral and dermal cancer was higher in adults than in children, due to longer-term exposure of adults to cancer-causing metals. In its explanation, it can be said that although the daily intake of dermal contact for metals (RfDDermal) is lower than the daily oral intake limit of metals (RfDOral), the daily intake rate of metals through drinking compared to dermal contact was so high that it neutralizes the effect of RFD. However, in the case of Hg and Co metals, RFDDermal was so low compared with RFDOral that overall the health risk of dermal contact due to exposure to these two metals is higher than the health risk of drinking. Also, in a study conducted by Hadzi et al. (2018), health risks for metals Al, V, Cr, Mn, Fe, Ni, Cu, Zn, As, and Pb were more likely to be associated with drinking than health risks caused by dermal contact. High health risks and carcinogenicity of heavy metals in water resources are potential threats to ecological conditions. In addition, it is not only impossible to use these water resources for drinking and dermal contact such as washing and showering, but also it is not possible to use them for cultivation, entering the environment and watering animals and animals, causing diseases and problems (Adewumi & Laniyan 2020).

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The concentration of metals in the water resources of the Zarshuran region exceeded the standard levels recommended for drinking, environmental discharge, and aquaculture purposes. The elevated metal levels, in comparison to national and international standards, pose health and carcinogenic risks to both humans and organisms in the region through daily exposure to these specific water sources. The extensive analysis of water resources in the region revealed high metal concentrations and associated health hazards and carcinogenic potential, placing a significant portion of the population, as well as the local ecosystem, at risk of various diseases. Consequently, stringent monitoring of mining activities is imperative. Proper management of ore extraction and waste disposal is essential to prevent metal contamination of the environment and water sources. Implementing effective purification methods to decontaminate water resources and prevent recontamination is recommended. The provision of alternative, uncontaminated water sources, such as water tankers, for drinking and domestic use is essential for individuals relying on polluted resources. Lastly, the enforcement of strict governmental regulations to prevent pollution and ensure remediation is strongly advised.

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This study was supported by the Basic Science Research Program through the National Research Foundation (NRF) of Korea, funded by the Ministry of Education, Science and Technology (2021R11A3059243/2022RIS-005).

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

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Informed consent was obtained from all individual participants included in the study.

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P. Y. B. and I. N. rendered support in formal analysis, wrote the original draft, helped in data processing and analysis, prepared the original draft and and wrote the article. H. S. Rendered support in formal analysis, collected the data, processed the data,and analyzed the data. H.-J. C. wrote the review & edited the article, reviewed the article, and edited and revised the article. B. S. conceptualized the data, wrote the review and edited the article, reviewed the data, edited them, and revised them. All authors contributed to the interpretation of the results and rendered support in paper writing.

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All relevant data are included in the paper or its Supplementary Information.

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The authors declare there is no conflict.

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