Abstract
The daily intake of trace elements through water resources and their adverse health effects is a critical issue. The purpose of this research was to assess the carcinogenic and non-carcinogenic risks of exposure to iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), chromium (Cr), lead (Pb), and arsenic (As) in groundwater resources of Sari city, Iran. The concentrations of the trace elements in a total number of 66 samples from the groundwater sources were measured using inductively coupled plasma mass spectrometry (ICP-MS). The hazard index (HI) levels of exposure to the trace elements from the groundwater sources for adults, teenagers, and children were 0.65, 0.83, and 1.08, respectively. The carcinogenic risk values of Cr and As in the groundwater sources for children, teenagers, and adults were 0.0001, 0.00009, 0.00007, 0.0003, 0.0002, and 0.0001, respectively, causing a total carcinogenic risk value higher than the acceptable range, and removing Cr and As from the groundwater resources is recommended for safe community water supply.
HIGHLIGHTS
The most important goals of the current research are to (1) determine the concentration of heavy metals in the drinking water and (2) assess the carcinogenic and non-carcinogenic risks of heavy metals through water ingestion by adults, teenagers, and children in the study areas.
Total carcinogenic risk value of the heavy metals in drinking water was higher than the acceptable range.
INTRODUCTION
Groundwater is one of the most important sources of fresh water for industrial, agricultural, and drinking purposes, and it is essential for humans and all living organisms. The entry of various pollutants (agricultural effluent and industrial and municipal wastewater discharge) into the groundwater has decreased its quality (Leung & Jiao 2006). The quantity and quality of groundwater are directly related to the health of organisms. The chemical properties of groundwater depend on factors such as geological characteristics of the region, human activities, evaporation, and hydrogeological conditions. For this reason, various chemicals, such as heavy metals, anions, and cations, are found in groundwater. However, most of these compounds are naturally present in water sources. They are necessary for the survival of all living organisms. Still, many of these compounds have increased their concentration in water due to human activity and have many unhealthy effects on humans (Atamaleki et al. 2021; Hu et al. 2021; Maleki & Jari 2021). Large amounts of heavy metals in water have adverse effects on human health, and the density of heavy metals is five times that of water. Heavy metals in water enter the human body through dermal absorption, inhalation, and mainly through swallowing (Kavcar et al. 2009; Sardar et al. 2013). Heavy metals in water sources can exist in solution, particulate or colloidal phases. Heavy metals such as iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) are necessary and valuable for the body in small doses and play the role of catalysts for body enzymes. However, these metals, in high amounts, are harmful and toxic to the human body (Adepoju-Bello et al. 2009). Touching metals, such as mercury and lead, cause autoimmune diseases. In this disease, the body's immune system destroys the body's cells (Barakat 2011).
Arsenic (As) exists in different concentrations in groundwater. The inorganic form of arsenic is much more dangerous than its organic form. Long-term exposure to the high concentration of arsenic causes nervous system problems, blood circulation disorders, severe vomiting, bladder cancer, skin cancer, lung cancer, and death. High concentrations of arsenic have been observed in the groundwater of many countries, such as Chile, India, Saudi Arabia, Thailand, Mexico, and Iran (Alidadi et al. 2019; Ramsay et al. 2021; Niknejad et al. 2023). Chromium (Cr) is a dangerous metal that enters the groundwater through natural or artificial sources. Among chromium compounds, hexavalent chromium has more toxic effects. Long-term exposure to chromium causes damage to the immune system, respiratory system, blood, skin, and eyes (Amjad et al. 2020; Niknejad et al. 2023).
However, water sources containing high concentrations of heavy metals threaten human health and other living organisms. For example, 1.5 million children die yearly in developing countries due to a lack of safe drinking water (Kavcar et al. 2009; Rossiter et al. 2010). Studies by scientists show that the cause of 33% of deaths and 80% of diseases in developing countries is due to the consumption of contaminated water (Zarif Gharaati Oftadeh et al. 2019). Anyway, determining the concentration of metals in water sources and assessing their risk are very important for the health of organisms. Risk assessment is a suitable method to determine the unhealthy effects of pollutants on living organisms and humans who are exposed to these pollutants (Duggal et al. 2017). The primary source of drinking water supply in Mazandaran province is groundwater. Also, due to the presence of fertile soil in this province, various agricultural activities are using organic poisons and fertilizers in this region. There are studies (Hourieh Fallah et al. 2022; Tarviji et al. 2022) on the quality of water resources in this province due to the special conditions of this province in terms of soil texture, agricultural activities, as well as the high level of groundwater, and the contamination of these waters with agricultural effluents and other pollutants, There is always the possibility of contamination of these waters with heavy metals.
Several studies have been conducted on the geochemical characteristics of the soil of Sari city in Mazandaran province (Iran). According to the latest study conducted by Rahmani and his colleagues in 2022, Cd, P, and Mg of samples in this area were in the class of non-contaminated to moderate contamination. Also, the concentrations of Al, As, Ca, Fe, and Mn, were in the class of moderate contamination and in the class of moderate to high contamination. Also, Cr, Cu, Ni, Va, and Zn were in the high contamination class, and Ba was in the high to extreme contamination class (Rahmani et al. 2022). Based on this study, it is possible that the concentration of heavy metals in the water sources of this area is high.
Because heavy metals accumulate in living organisms’ bodies and cause many unhealthy effects, continuous monitoring of water resources in terms of heavy metals is very important. The findings of this study provide valuable information about the concentration and health risks associated with heavy metals in the water sources of Sari city (Mazandaran, Iran). The aim of this study was to (1) determine the concentration of heavy metals in the drinking water of Sari city and (2) assess the carcinogenic and non-carcinogenic risks of these pollutants for adults, teenagers, and children.
MATERIALS AND METHODS
Area specifications
Geological location of the study area, Sari city.
Sampling and analysis of heavy metals
In this study, 66 samples were prepared from the groundwater sources of Sari city. The sampling points were from 27 groundwater wells and six points were selected randomly from the distribution network. All the samples were taken twice a year (dry and wet seasons), and the tests were repeated three times from each point and then the average data were used. The samples were collected in polyethylene containers to measure heavy metals such as Mn, Zn, Cu, Fe, Pb, Cr, and As. The water samples were filtered with a 0.45 μm membrane filter, and about 2 mL of 65% HNO3 was used to prevent the sedimentation of metals. Then the samples were sent to the laboratory at a temperature of 4 °C. The time interval between preparing and transferring the samples to the laboratory was 6 h. Double distilled water was used to analyze the samples. Finally, the concentration of pollutants was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) (X-Series II; Thermo-Fisher Scientific Inc., Waltham, MA, USA) equipped with an autosampler (Cetac ASX-520 with 4 × 60 place sample racks). The operation conditions of ICP-MS were (radio frequency (RF) power: 1,500 W, RF matching: 1.7 V, carrier gas: 0.9 L/min, makeup gas: 0.27 L/min).
Health risk assessment
CSF values, RfD, and other assumptions for exposure to heavy metals through drinking water (Tirkey et al. 2017; Mohammadi et al. 2019; Radfarda et al. 2019; Lorestani et al. 2020; Maleki & Jari 2021)
| Exposure factors | Unit | Values | ||
|---|---|---|---|---|
| Adults | Teenager | Children | ||
| ED | years | 40 | 13 | 4 |
| EF | days/year | 365 | 365 | 365 |
| IR | L/day | 2.5 | 2 | 0.78 |
| AT for carcinogens | years | 25,550 | 25,550 | 25,550 |
| AT for non-carcinogens | days | 14,600 | 4,745 | 1,460 |
| BW | kg | 80 | 50 | 15 |
| RfD | mg/kg/day | Fe = 0.7, Cu = 0.04, Mn = 0.024, Zn = 0.3, Cr = 0.003, Pb = 0.0035, As = 0.0003 | ||
| CSF | mg/kg/day | Cr = 0.19, As = 1.5 | ||
| Exposure factors | Unit | Values | ||
|---|---|---|---|---|
| Adults | Teenager | Children | ||
| ED | years | 40 | 13 | 4 |
| EF | days/year | 365 | 365 | 365 |
| IR | L/day | 2.5 | 2 | 0.78 |
| AT for carcinogens | years | 25,550 | 25,550 | 25,550 |
| AT for non-carcinogens | days | 14,600 | 4,745 | 1,460 |
| BW | kg | 80 | 50 | 15 |
| RfD | mg/kg/day | Fe = 0.7, Cu = 0.04, Mn = 0.024, Zn = 0.3, Cr = 0.003, Pb = 0.0035, As = 0.0003 | ||
| CSF | mg/kg/day | Cr = 0.19, As = 1.5 | ||
Statistical analysis
The Monte Carlo simulation (MCS) method was used to evaluate the variability and uncertainty in the risk calculation method. To assess the variability and uncertainty in the risk calculation method, the MCS method was used using the Crystal Ball software provided by Oracle Company (Oracle® Crystal Ball Software). In a recent study, the Monte Carlo method with 10,000 repetitions was used to determine the carcinogenic and non-carcinogenic risks of heavy metals (Fe, Cu, Mn, Zn, Cr, Pb, and As) for different age groups (Kaur et al. 2020; Rafiee et al. 2022).
RESULTS
Concentration values of heavy metals in drinking water samples
Table 2 shows the average, minimum, and maximum concentration values of heavy metals in the groundwater samples of Sari city. Then, in order to determine the status of water resources for drinking purposes, the concentration of each heavy metal was analyzed based on the WHO and U.S. EPA standards. The results showed that the concentration of Fe in water samples was in the range of 10–450 μg/L, with an average value of 110 ± 12 μg/L. The concentration of Cu in water samples was in the range of 1–44 μg/L, with an average value of 12.0 ± 0.5 μg/L. The concentration of Mn in water samples was in the range of 10–290 μg/L, with an average value of 39.0 ± 1.4 μg/L. The concentration of Zn in water samples was in the range of 1–43 μg/L, with an average value of 8.9 ± 0.8 μg/L. The concentration of Cr in water samples was in the range of 0.01–44.30 μg/L, with an average value of 13.76 ± 1.03 μg/L. The concentration of Pb in water samples was in the range of 1–7 μg/L, with an average value of 1.66 ± 0.02 μg/L. The concentration of As in water samples was in the range of 1–23 μg/L, with an average value of 4.26 ± 0.12 μg/L. Table 2 also shows that the average concentration of all seven heavy metals in all water samples was lower than the standard concentration recommended by the U.S. EPA and the WHO.
Concentrations of heavy metals in drinking water samples (μg/L) and comparison with the WHO and U.S. EPA (World Health Organization 2008; Iqbal & Shah 2013)
| Metals | Min | Mean | Max | U.S. EPA | WHO |
|---|---|---|---|---|---|
| Fe | 10 | 110 | 450 | 300 | 300 |
| Cu | 1 | 12 | 44 | 1,300 | 2,000 |
| Mn | 10 | 39 | 290 | 50 | 100 |
| Zn | 1 | 8 | 43 | 5,000 | 3,000 |
| Cr | 0.01 | 13 | 44 | 100 | 50 |
| Pb | 1 | 1.6 | 7 | 15 | 10 |
| As | 1 | 4 | 23 | 50 | 10 |
| Metals | Min | Mean | Max | U.S. EPA | WHO |
|---|---|---|---|---|---|
| Fe | 10 | 110 | 450 | 300 | 300 |
| Cu | 1 | 12 | 44 | 1,300 | 2,000 |
| Mn | 10 | 39 | 290 | 50 | 100 |
| Zn | 1 | 8 | 43 | 5,000 | 3,000 |
| Cr | 0.01 | 13 | 44 | 100 | 50 |
| Pb | 1 | 1.6 | 7 | 15 | 10 |
| As | 1 | 4 | 23 | 50 | 10 |
Health risk assessment
Non-carcinogenic risk assessment of exposure to trace elements
Probability estimation of HQ due to heavy metal exposure in drinking water
| Trace element | Age groups | Mean | Min | Max | SD | 10% | 30% | 60% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Fe | Children | 8.15 × 10−3 | − 2.49 × 10−3 | 4.55 × 10−2 | 4.91 × 10−3 | 2.90 × 10−3 | 5.25 × 10−3 | 8.38 × 10−3 | 1.44 × 10−3 |
| Teens | 6.30 × 10−3 | − 1.59 × 10−3 | 3.14 × 10−2 | 3.74 × 10−3 | 2.20 × 10−3 | 4.05 × 10−3 | 6.59 × 10−3 | 1.11 × 10−2 | |
| Adults | 4.90 × 10−3 | − 1.41 × 10−3 | 2.18 × 10−2 | 2.94 × 10−3 | 1.75 × 10−3 | 3.11 × 10−3 | 5.06 × 10−3 | 8.75 × 10−3 | |
| Cu | Children | 1.96 × 10−2 | 7.86 × 10−6 | 1.27 | 4.86 × 10−2 | 9.99 × 10−4 | 3.01 × 10−3 | 9.48 × 10−3 | 4.46 × 10−2 |
| Teens | 1.53 × 10−2 | 1.67 × 10−3 | 1.28 | 3.90 × 10−2 | 7.27 × 10−4 | 2.25 × 10−3 | 7.44 × 10−3 | 3.47 × 10−2 | |
| Adults | 1.14 × 10−2 | 1.57 × 10−5 | 9.38 × 10−1 | 3.09 × 10−2 | 5.82 × 10−4 | 1.82 × 10−3 | 1.82 × 10−3 | 2.49 × 10−2 | |
| Mn | Children | 4.57 × 10−2 | − 9.04 × 10−1 | 8.49 × 10−1 | 1.46 × 10−1 | − 1.28 × 10−1 | − 2.17 × 10−2 | 7.54 × 10−2 | 2.22 × 10−1 |
| Teens | 3.58 × 10−2 | − 5.86 × 10−1 | 6.37 × 10−1 | 1.11 × 10−1 | − 9.66 × 10−2 | − 1.41 × 10−2 | 5.94 × 10−2 | 1.69 × 10−1 | |
| Adults | 2.76 × 10−2 | − 6.30 × 10−1 | 5.22 × 10−1 | 8.69 × 10−2 | − 7.37 × 10−2 | − 1.13 × 10−2 | 4.53 × 10−2 | 1.32 × 10−1 | |
| Zn | Children | 1.60 × 10−3 | 7.50 × 10−6 | 5.66 × 10−2 | 2.73 × 10−3 | 1.80 × 10−4 | 4.29 × 10−4 | 1.07 × 10−3 | 3.56 × 10−3 |
| Teens | 1.22 × 10−3 | 8.94 × 10−6 | 5.92 × 10−2 | 2.06 × 10−3 | 1.35 × 10−4 | 3.30 × 10−4 | 8.31 × 10−4 | 2.85 × 10−3 | |
| Adults | 9.68 × 10−4 | 5.10 × 10−6 | 3.12 × 10−2 | 1.61 × 10−3 | 1.01 × 10−4 | 2.47 × 10−4 | 6.43× 10−4 | 2.21 × 10−3 | |
| Cr | Children | 2.19 × 10−1 | − 3.50 | 1.34 | 3.55 × 10−1 | − 2.41 × 10−1 | 9.43 × 10−2 | 3.50 × 10−1 | 6.10 × 10−1 |
| Teens | 1.70 × 10−1 | − 2.12 | 9.50 × 10−1 | 2.72 × 10−1 | − 1.78 × 10−1 | 7.52 × 10−2 | 2.66 × 10−1 | 4.67 × 10−1 | |
| Adults | 1.33 × 10−1 | − 2.34 | 7.46 × 10−1 | 2.11 × 10−1 | − 1.31 × 10−1 | 5.79 × 10−2 | 2.09 × 10−1 | 3.61 × 10−1 | |
| Pb | Children | 2.51 × 10−2 | 1.98 × 10−6 | 2.86 × 10−1 | 2.59 × 10−2 | 2.61 × 10−3 | 8.93 × 10−3 | 2.25 × 10−2 | 5.79 × 10−2 |
| Teens | 1.92 × 10−2 | 4.46 × 10−6 | 1.77 × 10−1 | 1.96 × 10−2 | 1.99 × 10−3 | 6.65 × 10−3 | 1.75 × 10−2 | 4.42 × 10−2 | |
| Adults | 1.49 × 10−2 | 3.34 × 10−7 | 1.39 × 10−1 | 1.53 × 10−2 | 1.43 × 10−3 | 5.17 × 10−3 | 1.34 × 10−2 | 3.46 × 10−2 | |
| As | Children | 7.56 × 10−1 | 1.06 × 10−1 | 2.88 × 101 | 1.71 | 1.54 × 10−1 | 1.76 × 10−1 | 2.27 × 10−1 | 1.81 |
| Teens | 5.78 × 10−1 | 7.37 × 10−2 | 2.10 × 101 | 1.32 | 1.18 × 10−1 | 1.35 × 10−1 | 1.74 × 10−1 | 1.34 | |
| Adults | 4.53 × 10−1 | 6.23 × 10−2 | 3.07 × 101 | 1.09 | 9.16 × 10−2 | 1.05 × 10−1 | 1.33 × 10−1 | 1.03 | |
| HI (Mean) | Children = 1.08; Teen = 8.26 × 10−1; Adult = 6.46 × 10−1 | ||||||||
| Trace element | Age groups | Mean | Min | Max | SD | 10% | 30% | 60% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| Fe | Children | 8.15 × 10−3 | − 2.49 × 10−3 | 4.55 × 10−2 | 4.91 × 10−3 | 2.90 × 10−3 | 5.25 × 10−3 | 8.38 × 10−3 | 1.44 × 10−3 |
| Teens | 6.30 × 10−3 | − 1.59 × 10−3 | 3.14 × 10−2 | 3.74 × 10−3 | 2.20 × 10−3 | 4.05 × 10−3 | 6.59 × 10−3 | 1.11 × 10−2 | |
| Adults | 4.90 × 10−3 | − 1.41 × 10−3 | 2.18 × 10−2 | 2.94 × 10−3 | 1.75 × 10−3 | 3.11 × 10−3 | 5.06 × 10−3 | 8.75 × 10−3 | |
| Cu | Children | 1.96 × 10−2 | 7.86 × 10−6 | 1.27 | 4.86 × 10−2 | 9.99 × 10−4 | 3.01 × 10−3 | 9.48 × 10−3 | 4.46 × 10−2 |
| Teens | 1.53 × 10−2 | 1.67 × 10−3 | 1.28 | 3.90 × 10−2 | 7.27 × 10−4 | 2.25 × 10−3 | 7.44 × 10−3 | 3.47 × 10−2 | |
| Adults | 1.14 × 10−2 | 1.57 × 10−5 | 9.38 × 10−1 | 3.09 × 10−2 | 5.82 × 10−4 | 1.82 × 10−3 | 1.82 × 10−3 | 2.49 × 10−2 | |
| Mn | Children | 4.57 × 10−2 | − 9.04 × 10−1 | 8.49 × 10−1 | 1.46 × 10−1 | − 1.28 × 10−1 | − 2.17 × 10−2 | 7.54 × 10−2 | 2.22 × 10−1 |
| Teens | 3.58 × 10−2 | − 5.86 × 10−1 | 6.37 × 10−1 | 1.11 × 10−1 | − 9.66 × 10−2 | − 1.41 × 10−2 | 5.94 × 10−2 | 1.69 × 10−1 | |
| Adults | 2.76 × 10−2 | − 6.30 × 10−1 | 5.22 × 10−1 | 8.69 × 10−2 | − 7.37 × 10−2 | − 1.13 × 10−2 | 4.53 × 10−2 | 1.32 × 10−1 | |
| Zn | Children | 1.60 × 10−3 | 7.50 × 10−6 | 5.66 × 10−2 | 2.73 × 10−3 | 1.80 × 10−4 | 4.29 × 10−4 | 1.07 × 10−3 | 3.56 × 10−3 |
| Teens | 1.22 × 10−3 | 8.94 × 10−6 | 5.92 × 10−2 | 2.06 × 10−3 | 1.35 × 10−4 | 3.30 × 10−4 | 8.31 × 10−4 | 2.85 × 10−3 | |
| Adults | 9.68 × 10−4 | 5.10 × 10−6 | 3.12 × 10−2 | 1.61 × 10−3 | 1.01 × 10−4 | 2.47 × 10−4 | 6.43× 10−4 | 2.21 × 10−3 | |
| Cr | Children | 2.19 × 10−1 | − 3.50 | 1.34 | 3.55 × 10−1 | − 2.41 × 10−1 | 9.43 × 10−2 | 3.50 × 10−1 | 6.10 × 10−1 |
| Teens | 1.70 × 10−1 | − 2.12 | 9.50 × 10−1 | 2.72 × 10−1 | − 1.78 × 10−1 | 7.52 × 10−2 | 2.66 × 10−1 | 4.67 × 10−1 | |
| Adults | 1.33 × 10−1 | − 2.34 | 7.46 × 10−1 | 2.11 × 10−1 | − 1.31 × 10−1 | 5.79 × 10−2 | 2.09 × 10−1 | 3.61 × 10−1 | |
| Pb | Children | 2.51 × 10−2 | 1.98 × 10−6 | 2.86 × 10−1 | 2.59 × 10−2 | 2.61 × 10−3 | 8.93 × 10−3 | 2.25 × 10−2 | 5.79 × 10−2 |
| Teens | 1.92 × 10−2 | 4.46 × 10−6 | 1.77 × 10−1 | 1.96 × 10−2 | 1.99 × 10−3 | 6.65 × 10−3 | 1.75 × 10−2 | 4.42 × 10−2 | |
| Adults | 1.49 × 10−2 | 3.34 × 10−7 | 1.39 × 10−1 | 1.53 × 10−2 | 1.43 × 10−3 | 5.17 × 10−3 | 1.34 × 10−2 | 3.46 × 10−2 | |
| As | Children | 7.56 × 10−1 | 1.06 × 10−1 | 2.88 × 101 | 1.71 | 1.54 × 10−1 | 1.76 × 10−1 | 2.27 × 10−1 | 1.81 |
| Teens | 5.78 × 10−1 | 7.37 × 10−2 | 2.10 × 101 | 1.32 | 1.18 × 10−1 | 1.35 × 10−1 | 1.74 × 10−1 | 1.34 | |
| Adults | 4.53 × 10−1 | 6.23 × 10−2 | 3.07 × 101 | 1.09 | 9.16 × 10−2 | 1.05 × 10−1 | 1.33 × 10−1 | 1.03 | |
| HI (Mean) | Children = 1.08; Teen = 8.26 × 10−1; Adult = 6.46 × 10−1 | ||||||||
Probability estimation of CDI due to heavy metal exposures in drinking water.
Histogram of HQ levels of trace elements in the groundwater resources of Sari city for children.
Histogram of HQ levels of trace elements in the groundwater resources of Sari city for children.
Histogram of HQ levels of trace elements in the groundwater resources of Sari city for teenagers.
Histogram of HQ levels of trace elements in the groundwater resources of Sari city for teenagers.
Histogram of HQ levels of trace elements in the groundwater resources of Sari city for adults.
Histogram of HQ levels of trace elements in the groundwater resources of Sari city for adults.
Carcinogenic risk assessment of exposure to trace elements
Probability estimation of LTCR due to heavy metal exposure in drinking water.
Histogram of LTCR levels for heavy metals in different age groups of Sari city.
DISCUSSION
Contamination of drinking water sources with heavy metals
One of the most common occupations in this city is agriculture, which causes soil and groundwater pollution due to the excessive use of chemical fertilizers in agricultural lands (Kazemi et al. 2021). Table 2 shows the concentration of heavy metals in the drinking water sources of Sari city. The results showed that the average concentration of heavy metals in all drinking water samples in the present study was lower than U.S. EPA and WHO standards. As a result, according to these standards, drinking water sources in the city of Sari had few health risks for the city's people. However, some scientists believe that to evaluate the effects and health risks of exposure to heavy metals, more is needed to pay attention to the amount and concentration of these pollutants, and drinking water sources should be examined with other indicators (Dashtizadeh et al. 2019). In a study, Barzegar et al. investigated the concentration of heavy metals (Pb, Al, Cr, Fe, Ni, As, Cu, Zn, and Mn) for 29 samples of drinking water sources in western Iran. The results of their research showed that the average concentration of some trace elements such as As, Pb, and Zn was higher than the standards announced by the WHO (Barzegar et al. 2019). In another study, Dashtizadeh et al. evaluated the levels of heavy metals in the groundwater sources of Zahedan city (south of Iran). Their research showed that the average levels of total trace metals were lower than the limits declared by U.S. EPA and the WHO. They also believed that based on these guidelines and standards, the drinking water sources in Zahedan city lack health risks (Dashtizadeh et al. 2019).
Non-carcinogenic risk assessment index
According to Table 3, the average values of HQ for all age groups were in the order of As > Cr > Mn > Pb > Cu > Fe > Zn. The average non-carcinogenic risk of all heavy metals for children is higher than other age groups due to shorter life spans and lower weight in children compared to teenagers and adults (Wu et al. 2020). Also, the mean values of HQ for all age groups were less than one. According to these findings, HQ values for all age groups have an acceptable amount of non-carcinogenic risks (Lu et al. 2015). Also, according to Table 3, the average values of HI for adults, teenagers, and children were 6.46 × 10−1, 8.26 × 10−1, and 1.08, respectively. In the research area, HI levels for children were higher than other age groups. These results show that children are more sensitive to exposure to heavy metals through water sources, which indicates that they consume more drinking water. In a study, Khalid et al. investigated the concentration of heavy metals (Mn, Fe, Cu, Ni, Cd, Zn, Cr, and Pb) for 129 samples of drinking water sources in the Vehari region of Pakistan. The results of their research showed that the amounts of elements such as Fe, Pb, and Cd in 100, 93, and 68% of the samples were higher than the recommended levels of the WHO, respectively. Also, HQ levels were less than one for all heavy metal results, but for Pb, HQ values were greater than one. In this study, Mn (0.02) and Pb (10.3) showed the lowest and highest levels of HQ, respectively (Khalid et al. 2020). Figure 3 shows the histogram of HQ due to exposure to trace elements through groundwater sources in children; the highest and lowest 90th percentiles were related to As (1.81) and Zn (3.56 × 10−3). Also, Figures 4 and 5 show the histogram of HQ due to exposure to metal elements through groundwater sources in teenagers and adults, respectively. The highest and lowest 10th percentiles were related to As and Mn. In a study, Malkutian et al. investigated the concentrations of heavy metals (Cd, Zn, Ni, and Pb) in drinking water sources in Iran. The results of their study showed that the non-carcinogenic risk for the 5th and 95th percentiles for Cd, Zn, Ni, and As was 1.12 to 3.10, 5.61 × 10−3 to 1.55 × 10−2, 2.50 × 10−2 to 7.07 × 10−2, and 1.6 to 4.59, respectively (Malakootian et al. 2020).
Carcinogenic risk assessment index
According to Figure 6, the average carcinogenic risk of Cr for children was higher than other age groups. Based on this, the risk of carcinogenesis in children is 1 in 10,000. The findings show that the carcinogenic risk of Cr for all age groups is in the accepted range of 10−4 to 10−6. In a study, Mirzabeygi et al. concluded that the carcinogenic risk of chromium and cadmium in the groundwater resources of Sistan and Baluchistan province (Iran) was more than the acceptable range (Mirzabeygi et al. 2017). The findings of this research were consistent with the results of Niknejad et al., who stated that the carcinogenic risks of trace elements were in the range of 10−4 to 10−5 and were higher than the EPA limit (Niknejad et al. 2023).
The carcinogenic risk of arsenic for children, teenagers, and adults was 3.28 × 10−4, 2.61 × 10−4, and 1.99 × 10−4, respectively. The levels of LTCR for different groups were children > teenagers > adults, respectively, and it was consistent with the results of Niknejad et al. (2023). LTCR levels were greater than 10−4 and showed that in all age groups, arsenic values were not in the acceptable range. According to the LTCR classification by the U.S. EPA, it can be stated that the presence of arsenic in the drinking water of the city of Sari can have many unhealthy risks for people (U.S. EPA 2007). These findings confirmed the risk of carcinogenesis caused by exposure to arsenic through water sources, but no specific cancer related to the the consumption of contaminated drinking water was reported in this article.
CONCLUSIONS
In this study, the concentration of trace elements (Fe, Cu, Mn, Zn, Cr, Pb, and As) in drinking water sources of Sari city was investigated. Then, the levels of these metals were compared with U.S. EPA and WHO standards, which were lower than the permissible concentration recommended by these organizations. Mean HQ levels due to exposure to trace elements through drinking water were less than one in all age groups. The non-carcinogenic risk analysis for all metals showed that HQ values were higher in children than in other age groups. The overall non-carcinogenic risk assessment (HI > 1) indicates an increased risk for children. Also, the carcinogenic risk for chromium and arsenic was higher than the U.S. EPA recommended limit for all age groups. Measures such as sanitary disposal of urban sewage and control of agricultural effluents should be carried out to reduce the concentration of heavy metals in the water sources of Sari city.
ACKNOWLEDGEMENTS
The authors would like to thank the authorities of the Shahid Beheshti University of Medical Sciences for their comprehensive support of this study.
DATA AVAILABILITY STATEMENT
Data cannot be made publicly available; readers should contact the corresponding author for details.
CONFLICT OF INTEREST
The authors declare there is not conflict.
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