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03 2023
:17;
105592
doi:
10.1016/j.arabjc.2023.105592

Contamination and health risk assessment of potentially toxic elements in agricultural soil of the Al-Ahsa Oasis, Saudi Arabia using health indices and GIS

, ,
 Geology and Geophysics Department, College of Science, King Saud University, Saudi Arabia

⁎Corresponding author. P.O Box: 2455, Riyadh 11451, Saudi Arabia. asmohamed@ksu.edu.sa (Abdelbaset S. El-Sorogy)

Received: , Accepted: ,
© The Author(s) 2023
Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

The current work aimed to assess contamination and human health risk of potentially toxic elements (PTEs) in agricultural soil of the Al-Ahsa Oasis, Saudi Arabia. For the purpose of evaluating the potential risks to human health associated with ingestion, skin contact, and inhalation, the chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), cancer risk (CR), and total lifetime cancer risk (LCR) were calculated in 30 soil samples. The spatial distribution and possible sources of HMs were investigated using GIS and multivariate analysis. The descending order of PTE averages (dw, µg/g) was Fe (11790) > Mn (176.43) > Zn (54.43) > Cr (28.67) > Ni (14.53) > V (12.33) > Cu (10.83) > Pb (5.23) > Co (2.87) > As (2.27). The average CDI for all PTEs from ingestion pathway in children indicates an increase of approximated 9 times compared to adults. The HI values varied from 1.969 × 10-4 to 2.318 × 10-2 for Adults, and from 1.835 × 10-3 to 2.158 × 10-1 for children, suggesting there is no significant non-carcinogenic risk to the people inhabiting the Al-Ahsa Oasis. The CRs and LCR for Cr, As, and Pb in children was found to be significantly greater than that of adults. LCR values for As, Pb, and Cr varied from lower than 1 × 10-6 to 1 × 10-4, indicating no significant health hazards to acceptable carcinogenic risk.

Keywords

Hazard index
Chronic daily intake
Lead
Arsenic
Chromium
Saudi Arabia
1

1 Introduction

In the last decade, enormous increase in industrialization, rapid urbanization and population growth have resulted in the production of huge quantities of solid and liquid waste including emission of potentially toxic elements (PTEs) in various ecological compartments that drastically deteriorated water quality and threatened aquatic life and human health (El-Sorogy et al., 2016, 2021, 2023; Al-Hashim et al., 2022; Kahal et al., 2023). Agricultural soil is essential for food safety and has a direct impact on human health (Praveena et al., 2015; Agyeman et al., 2021, Alarifi et al., 2023). Unfortunately, dumping of domestic and industrial effluents ultimately contaminate soil with huge quantities of PTEs and become a hazard for the animals and human being (Hashem et al., 2017; Mishra et al., 2019).

Generally, both natural and anthropogenic factors add PTEs to soils and crops. Above-normal concentrations of PTEs can be found in agricultural soils as a result of rock weathering, and volcanic activity. The primary human sources include land amendments made from sewage sludge, livestock manure, wastewater irrigation, metal-based insecticides and herbicides, and fertilizers based on phosphate (El-Kady and Abdel-Wahhab, 2018). Agriculture is severely affected mainly due to usage of industrial wastewater for irrigation resulting in increased contamination of Cd, Pb, Cr, As and other metals in crops (Ilyas et al., 2019).

PTEs are the most hazardous contaminants for human being causing severe complications due to their build-up in crops (Zhang et al., 2018). Children are more vulnerable to HMs due to additional pathways of exposure such as placental exposure, nursing, early-life hand-to-mouth activities, and larger comparative uptakes (Dissanayake and Chandrajith, 2009; Rahman et al., 2021). Of all the metal pollutants major threats to human health emanate from exposure to non-essential PTEs such as As, Cd, Pb and Hg. These metals can enter the human body primarily through ingestion, inhalation, and skin adsorption and can be found in a variety of environmental compartments, including food, water, and air. Consuming tainted food items, including fruits, vegetables, shellfish, fish, and drinking water and beverages, is the primary method by which humans are exposed to metals. The effects of metal poisoning on the human body are well-established and have been linked to numerous diseases, including mental illness, harm to the kidneys, liver, lungs, and other essential organs, as well as changes to the components of blood (Jaishankar et al., 2014; Alharbi et al., 2023a, b; Al-Kahtany et al., 2023a).

Al-Ahsa is the largest oasis in Saudi Arabia’s Eastern Province, covering ∼ 12,000 ha. The soil composition in Saudi Arabia displays a diversity of types determined by their mineralogical properties and the underlying rocks. In the eastern region, the soils vary from Torrifluvents to Gypsiorthids, characterized by coarse texture and elevated levels of salt, gypsum, and carbonate contents (Shadfan et al., 1987). The farming of primarily dates, leafy green plants, vegetables, and fruits is performed in this region (Al Tokhais and Rausch, 2008). Al-Ahsa's groundwater levels have steadily declined over time as a result of overusing water resources to irrigate large areas of farmland. Therefore, part of the sewage water produced by the Saudi Aramco plant, the Hofuf, Al-Ayoun, and Al-Omran sewage treatment facilities, is used to meet the water needs of industry and agriculture. These plants treat residential and industrial sewage as well as agricultural drainage water. To avoid health risks, sewage water must be effectively treated before its reuse in agricultural practices (Chowdhury and Al-Zahrani, 2015). The objectives of this study are threefold: (i) to document the characteristics of Al Ahsa soils and their Ni, Fe, Mn, Zn, Cu, As, Pb, Cr, V, and Co contents; (ii) to compare the PTEs levels in the study area with those reported from local and regional soils and backgrounds; and (iii) to assess the human health risk of PTEs associated with ingestion, skin contact, and inhalation in the study area.

2

2 Materials and methods

2.1

2.1 Study area

Al-Ahsa is situated 320 km away from Riyadh and 75 km away from the Arabian Gulf shore. The study region is located between N25°21′00–N25°37′00 and E49°33′00–E49°46′00 (Fig. 1). Al-Ahsa is an arid region with long and scorching summers that exhibits a wide range of annual fluctuations in temperature, humidity, evaporation, and precipitation. The average temperature and evaporation rates are extremely high at 43 °C and 12 mm, respectively, and humidity decreases to a minimum of 20 %. On the other hand, winters are quite chilly, with daytime highs of 20–28 °C and evening lows of 8–10 °C. The average annual precipitation is 147 mm, the average humidity is 71 %, and the average evaporation rate is 5 mm.

Location map of the sampling sites at Al-Ahsa Oasis.
Fig. 1
Location map of the sampling sites at Al-Ahsa Oasis.

Al-Ahsa is located on a sedimentary succession comprising carbonates, evaporates, and subordinate marl and shale, with a total thickness of 800–2,500 m, which increases and slopes toward the Arabian Gulf. The sedimentary strata are interrupted by several north–south anticlines and synclines, which are the main tectonic elements in Saudi Arabia’s Eastern Province. Four partially interconnected aquifers compose the groundwater system in this area (Assubaie, 2015): from top to bottom, i) karstified fractured bedrock and unconsolidated porous classics of the Neogene aquifer complex with a depth of up to 180 m, ii) partly karstified fractured bedrocks of the Dammam aquifer complex with depths of 180–250 m, and iii) and iv) karstified fractured bedrocks of the Umm Er Radhuma and Aruma aquifers with depth of 240–280 m.

2.2

2.2 Sampling and analytical procedures

From palm farms in the Al-Ahsa Oasis, thirty soil samples were taken (Fig. 1). Samples were collected using a plastic hand trowel at a depth of less than 5 cm from the soil's surface (3 replicates from each site). Subsequently, the samples were placed in plastic sample bags and stored in an icebox. The collected samples underwent sieving and were then left to air dry. A prepared sample (0.50 g) with a fraction of < 63 μm was incubated with a HNO3–HCl aqua regia for 45 min in a graphite heating block. After cooling, the resultant solution was diluted to 12.5 mL using deionized water, mixed, and analyzed. Ni, Fe, Mn, Zn, Cu, As, Pb, Cr, V, and Co were analyzed in terms of linearity, limit of detection, limit of quantification, accuracy, and precision using inductively coupled plasma-atomic emission spectrometry (ICP–AES) in the ALS Geochemistry Lab, Jeddah, Saudi Arabia. Plotting the peak size of the ideal emission line as a function of a standard or spike solution concentration for standard addition curves allowed graphs representing the calibration curves of each element to be created. Excellent linearity was displayed by each calibration curve.

2.3

2.3 Data analysis

The Environmental Protection Agency of the United States assessed the health hazards associated with ingestion, inhalation, and skin contact pathways for both adults and children (US EPA, 2002). To define the CDI for the three pathways (mg/kg. day) the following equations were utilized: (Luo et al., 2012; Mondal et al., 2021; Agyeman et al., 2021; Ahmad et al., 2021): CD I ingest . = ( C s o i l × I n g R × E F × E D ) / ( B W × A T ) × C F CD I inhal . = ( C s o i l . × I n h R × E F × E D ) / ( P E F × B W × A T ) CD I dermal = ( C s o i l . × S A × A F × A B F × E F × E D ) / ( B W × A T ) × C F

C represents the concentration of PTEs in mg/kg. IngR denotes the ingestion rate in mg/day, with a value of 200 for children and 100 for adults. EF represents exposure frequency in days/year (1 8 0), while ED is the exposure duration (6 years for children and 24 years for adults). BW stands for the average body weight, set at 15 kg for children and 70 kg for adults. AT corresponds to the average time (365 × ED). InhR signifies the inhalation rate in mg/cm2 (20 for both adults and children), and PEF is the particle emission factor in m3 kg (1.36 × 109 for both adults and children). SA denotes the surface area of exposed skin in cm2 (2145 for adults and 1150 for children), AF is the skin adherence factor for the soil in mg cm2 (0.2 for adults and 0.07 for children), and ABF represents the dermal absorption factor (0.03 for As and 0.001 for other metals).

Cr, Pb and As were selected to estimate the carcinogenic health risks (IARC, 2012), whilst, V, Fe, As, Co, Ni, Zn, Cr, Pb, and Cu were also estimated for their non-carcinogenic risk. The hazard index (HI) is estimated by summing up all the hazard quotients (HQs), and gives the total risk of being non-carcinogenic for a single element as follows (Chonokhuu et al., 2019): HI = Σ H Q E = H Q ing + H Q dermal + H Q inhal HQE = C D I / R f D where RfD is the reference dose for each PTE (Table 1). HI values less than one indicate no significant risk of non-carcinogenic effects, and HI values exceeds one indicate there is a probability that non-carcinogenic risk effects may occur, and the probability increases with increasing HI (USEPA, 2001; IRIS, 2020). The total lifetime cancer risk (LCR) was determined using the following equations: Cancerrisk = C D I × C S F LCR = Σ C a n c e r R i s k = C a n c e r r i s k ing + C a n c e r r i s k dermal + C a n c e r r i s k inhal where CSF is the carcinogenic slope factor values (mg/kg/day) for Cr, Pb and As (0.5, 0.0085 and 1.5, respectively) (IRIS, 2020). LCR values lower than 1 × 10-6 indicate no significant health hazards, LCR value between 1 × 10-6 and 1 × 10-4 indicates acceptable carcinogenic risk, and LCR value higher than 1 × 10-4 means the risk is unacceptable (USEPA, 1989; Mondal et al., 2021).

Table 1 Elemental analysis by ICP–AES (dw, µg/g) of sampling sites at Al-Ahsa Oasis.
S.N. As Co Cr Cu Fe Mn Ni Pb V Zn
S1 4.00 3.00 23 9.00 11,200 188 18.00 5.00 16.00 42.00
S2 3.00 3.00 25 9.00 13,800 194 20.00 5.00 17.00 46.00
S3 2.00 3.00 45 17.00 12,300 219 16.00 5.00 13.00 62.00
S4 2.00 3.00 20 12.00 10,800 164 13.00 3.00 11.00 53.00
S5 1.00 3.00 28 15.00 13,500 216 20.00 6.00 16.00 54.00
S6 4.00 6.00 54 17.00 19,800 327 38.00 11.00 31.00 100.00
S7 3.00 4.00 50 10.00 11,600 178 19.00 11.00 15.00 30.00
S8 2.00 4.00 26 9.00 12,000 162 18.00 8.00 15.00 33.00
S9 2.00 3.00 26 7.00 11,600 159 14.00 4.00 11.00 16.00
S10 4.00 4.00 59 10.00 10,300 166 21.00 6.00 15.00 28.00
S11 2.00 2.00 17 5.00 8400 115 8.00 5.00 7.00 17.00
S12 1.00 3.00 22 18.00 14,600 222 11.00 3.00 10.00 55.00
S13 2.00 3.00 26 17.00 11,300 192 13.00 4.00 10.00 68.00
S14 2.00 3.00 43 7.00 9500 134 17.00 6.00 18.00 12.00
S15 1.00 2.00 63 18.00 11,100 152 17.00 7.00 15.00 447.00
S16 1.00 1.00 12 6.00 7000 100 8.00 4.00 8.00 21.00
S17 2.00 3.00 24 10.00 10,200 147 16.00 6.00 13.00 31.00
S18 2.00 3.00 22 9.00 14,200 194 16.00 4.00 11.00 43.00
S19 2.00 4.00 77 14.00 11,600 198 24.00 10.00 19.00 45.00
S20 2.00 2.00 13 10.00 11,300 141 6.00 3.00 7.00 19.00
S21 3.00 4.00 26 10.00 12,800 196 18.00 7.00 16.00 21.00
S22 2.00 2.00 15 9.00 11,700 187 10.00 5.00 8.00 44.00
S23 2.00 1.00 11 4.00 10,500 131 5.00 2.00 5.00 19.00
S24 1.00 2.00 16 6.00 9000 139 9.00 3.00 10.00 45.00
S25 4.00 3.00 18 8.00 13,800 173 14.00 4.00 12.00 23.00
S26 5.00 3.00 23 14.00 11,300 186 10.00 5.00 9.00 58.00
S27 2.00 2.00 21 7.00 9600 139 10.00 4.00 9.00 16.00
S28 2.00 2.00 24 6.00 10,100 140 9.00 3.00 7.00 25.00
S29 1.00 3.00 15 25.00 15,600 274 8.00 4.00 7.00 126.00
S30 2.00 2.00 16 7.00 13,200 160 10.00 4.00 9.00 34.00
Min. 1.00 1.00 11 4.00 7000 100.00 5.00 2.00 5.00 12.00
Max. 5.00 6.00 77 25.00 19,800 327.00 38.00 11.00 31.00 447.00
Std. Dev. 1.05 1.01 16.77 4.89 2427 45.89 6.62 2.30 5.18 78.28

3

3 Results and discussion

3.1

3.1 Soil characteristics and distribution of PTEs

The process of land classification and survey in Saudi Arabia commenced in 1986, as documented by MEWA (1986) and Al-Dosary (2022). In the Al Ahsa Oasis, the soil can be categorized into Haplaquepts and Eutrochrepts (28 samples), Torripsamments and Gysiorthids (one sample), and Gysiorthids and Calciorthids (one sample) as illustrated in Fig. 2. A significant 93.33 % of soil samples from the study area were identified as Haplaquepts and Eutrochrepts (Sheta, 2004). Haplaquepts and Eutrochrepts, classified as Inceptisols, exhibit only minimal alteration of the parent material due to soil-forming processes. These soils are found and cultivated in the eastern province of Saudi Arabia, particularly in low-lying areas with abundant natural springs. Haplaquepts, specifically, are poorly drained Inceptisols originating in deep, loamy deposits in the lower landscape regions, with the water table either at or near the surface unless drainage is implemented. Their texture primarily ranges from sandy loam to loam, and they vary in salinity from slightly saline to strongly saline.

Soil types in Al Ahsa Oasis.
Fig. 2
Soil types in Al Ahsa Oasis.

Eutrochrepts belong to the Inceptisols category and exhibit better drainage compared to Haplaquepts. These soils form in deep, loamy deposits and can vary in salinity from slightly to strongly saline. Gysiorthids and Calciorthids fall under the Aridisols classification, characterized by dry conditions with limited available moisture. Gysiorthids feature a gypsic or petrogypsic horizon within 1 m of the soil surface. They have a loamy or loamy skeletal texture, predominantly sandy loam, fine sandy loam, or loam, with corresponding gravely and very gravely variations. Calciorthids, also Aridisols, accumulate secondary carbonates to create a calcic horizon. They range from shallow to deep and have a sandy to loamy texture. Torripsamments are Entisols, forming on well-sorted sandy deposits in stream terraces, are categorized as having a torrid moisture regime and are mostly nonsaline.

The concentration of PTEs in the study area is shown in Table 1. Table 2 shows the average values of PTEs in the study area and compares them to those found in the sediment quality recommendations, the earth's crust, and some Saudi soil. The descending order of PTEs averages (dry weight, micrograms per gram) was Fe (11790) > Mn (176.43) > Zn (54.43) > Cr (28.67) > Ni (14.53) > V (12.33) > Cu (10.83) > Pb (5.23) > Co (2.87) > As (2.27). The highest levels of PTEs were recorded in S6 (Co, Fe, Mn, Ni, Pb, and V), S15 (Zn), S19 (Cr), S26 (As), and S29 (Cu). Our average values of Ni, Zn, Pb, Cr, V were less than those reported in Table 2 for several continental earth crust and Saudi Arabian soils (Yaroshevsky, 2006; Rudnick and Gao, 2003; Turekian and Wedepohl, 1961; Taylor, 1964; Al-Boghdady and Hassanein, 2019; Alharbi and El-Sorogy, 2021).

Table 2 The average values of PTEs (µg/g) in the study area and the comparison with those reported in the earth’s crust and international backgrounds.
Location and reference Ni Zn Cu As Pb Cr V Co Fe Mn
Study area 14.53 54.43 10.83 2.27 5.23 28.67 12.33 2.87 11,790 176.43
Al-Ammariah, Saudi Arabia (Alarifi et al., 2022) 26.94 52.16 11.36 3.78 5.08 19.97 18.94 3.89 11,581 179.61
Al Uyaynah–Al Jubailah soil, Saudi Arabia (Alharbi and El-Sorogy, 2021) 19.25 64.33 10.56 13.8 28.48 30.18 ND 2.45 35,667 ND
Wadi Jazan, Saudi Arabia (Al-Boghdady and Hassanein, 2019) 48.66 75.80 72.85 14.13 19.41 77.22 122.03 7722 23,811 583.58
Worldwide soils (Kabata-Pendias (2011) 29 70 38.9 6.83 27 59.5 129 11.3 35,000 488
Earth’s crust (Yaroshevsky, 2006) 58 83 47 1.7 16 83 90 18 46,500 1000
Continental crust (Rudnick and Gao, 2003) 47 67 28 4.8 17 92 97 17.3 50,400 1000
Earth’s crust (Turekian and Wedepohl, 1961) 68 95 45 13 20 90 130 19 47,200 850
Continental crust (Taylor, 1964) 75 70 55 1.8 12.5 100 135 25 56,300 950
Maximum allowable concentrations Kabata-Pendias (2011) 60 300 150 20 300 200 150 50 ND ND

3.2

3.2 Health risk assessment

Many PTEs are known to be nutritionally essential and are required in minimal quantities. For example, chromium participates in the carbohydrate and lipid metabolism in the body, cobalt is the main constituent of cobalamin, manganese regulates many enzymes in the body, iron is a constituent of hemoglobin and myoglobin, nickel is required for the active synthesis of urease in plant cells, zinc is a cofactor for certain enzymes (Häder et al., 2021; Khaleeq et al., 2022). Overexposure to them can be hazardous and can cause a number of serious illnesses. For instance, an excessive amount of iron can cause a number of grave health issues, including diabetes, cancer, heart disease, and neurological abnormalities (Abbaspour et al., 2014, Al-kahtany et al., 2023b). Exposure to nickel in the workplace results in ailments such as kidney disorders, cardiovascular diseases, lung fibrosis and respiratory tract cancer. Excessive levels of manganese lead to ailments of the nervous system (Neal and Guilarte, 2013; Nour et al., 2022). Comparably, occupational exposure to chromium (VI) compounds in the chromate industry can result in lung cancer, irritated and ulcerated skin, burns in sensitive workers, and asthma and other respiratory distresses (Wilbur et al., 2012).

3.2.1

3.2.1 Chronic daily intake (CDI) and hazard index (HI)

Table 3 presents the average values of the CDI, HQ and HI for non-carcinogenic risk of PTEs from ingestion, inhalation, and dermal contact pathways on adults and children. The CDI values for adults and children took the order of CDI Ing. > CDI Der. > CDI Inh. The maximum CDI values (mg/kg/day) for adults were 1.615 × 10-2, 7.215 × 10-5, and 2.375 × 10-7 through the ingestion, dermal and inhalation pathways, respectively, while in children, the maximum CDI were 1.507 × 10-1, 3.367 × 10-4, and 1.108 × 10-6, respectively. In contrast, the average CDI (mg/kg/day) from ingestion pathway in children for all PTEs shows a rise approximated nine times compared to adults, suggesting that children were at higher risk of non-carcinogenic exposure than adults. The higher CDI due to ingestion of soil by the children may be attributed to the sensitivity of children to the exposure and absorb toxic PTEs during their outdoor play activities in sediments than adults (Gevorgyan et al., 2017). However, the children’s computed hazard quotient (HQ) appears to be higher than the adult's HQ (Table 3).

Table 3 The CDI (mg/kg/day), HQ, and HI for non-carcinogenic risk in adults and children.
HMs Adults
CDI Ing. CDI Dermal CDI Inhal. HQ Ing. HQ Demal HQ Inhal. HI
As 3.105 × 10–6 1.093 × 10–8 4.566 × 10–11 1.035 × 10–2 3.644 × 10–5 1.522 × 10–7 1.039 × 10–2
Cr 3.927 × 10–5 8.745 × 10–8 5.775 × 10–10 1.309 × 10–2 2.915 × 10–5 1.925 × 10–7 1.312 × 10–2
Pb 7.169 × 10–6 2.186 × 10–8 1.054 × 10–10 2.048 × 10–3 6.247 × 10–6 3.012 × 10–8 2.055 × 10–2
V 1.690 × 10–5 4.919 × 10–8 2.485 × 10–10 1.877 × 10–3 5.466 × 10–6 2.761 × 10–8 1.883 × 10–3
Cu 1.484 × 10–5 3.826 × 10–8 2.182 × 10–10 4.000 × 10–4 1.031 × 10–6 5.882 × 10–9 4.010 × 10–4
Ni 1.991 × 10–5 5.466 × 10–8 2.928 × 10–10 9.703 × 10–4 2.733 × 10–6 1.427 × 10–8 9.731 × 10–4
Zn 7.457 × 10–5 1.858 × 10–7 1.097 × 10–9 2.486 × 10–4 6.195 × 10–7 3.655 × 10–9 2.492 × 10–4
Co 3.927 × 10–6 1.093 × 10–8 5.775 × 10–11 1.963 × 10–4 5.466 × 10–7 2.888 × 10–9 1.969 × 10–4
Fe 1.615 × 10–2 7.215 × 10–5 2.375 × 10–7 2.307 × 10–2 1.031 × 10–4 3.393 × 10–7 2.318 × 10–2
Mn 2.417 × 10–4 8.745 × 10–7 3.554 × 10–9 1.726 × 10–3 6.247 × 10–6 2.539 × 10–8 1.733 × 10–3
HMs Children
CDI Ing. CDI Dermal CDI Inhal. HQ Ing. HQ Demal HQ Inhal. Hi
As 2.898 × 10–5 5.101 × 10–8 2.131 × 10–10 9.660 × 10–2 1.700 × 10–4 7.103 × 10–7 9.677 × 10–2
Cr 3.665 × 10–4 4.081 × 10–7 2.695 × 10–9 1.222 × 10–1 1.360 × 10–4 8.983 × 10–7 1.223 × 10–2
Pb 6.691 × 10–5 1.020 × 10–7 4.912 × 10–10 1.912 × 10–2 2.915 × 10–5 1.406 × 10–7 1.915 × 10–2
V 1.577 × 10–4 2.296 × 10–7 1.159 × 10–9 1.752 × 10–2 2.551 × 10–5 1.288 × 10–7 1.755 × 10–2
Cu 1.385 × 10–4 1.785 × 10–7 1.018 × 10–9 3.733 × 10–3 4.813 × 10–6 2.745 × 10–8 3.738 × 10–3
Ni 1.858 × 10–4 2.551 × 10–7 1.366 × 10–9 9.291 × 10–3 1.275 × 10–5 6.831 × 10–8 9.304 × 10–3
Zn 6.960 × 10–4 8.672 × 10–7 5.117 × 10–9 2.320 × 10–3 2.891 × 10–6 1.706 × 10–8 2.323 × 10–3
Co 3.665 × 10–5 5.101 × 10–8 2.695 × 10–10 1.833 × 10–3 2.551 × 10–6 1.347 × 10–8 1.835 × 10–3
Fe 1.507 × 10–1 3.367 × 10–4 1.108 × 10–6 2.153 × 10–1 4.890 × 10–4 1.583 × 10–6 2.158 × 10–1
Mn 2.256 × 10–3 4.081 × 10–6 1.659 × 10–8 1.611 × 10–2 2.915 × 10–5 1.185 × 10–7 1.614 × 10–2

The HI values varied from 1.969 × 10-4 to 2.318 × 10-2 for Adults, and from 1.835 × 10-3 to 2.158 × 10-1 for children (Table S1). The hazard index for PTEs was higher among children for 9 to 9.5 times than adults. The results demonstrated that the most likely way for individuals to be exposed to PTEs in the study area was by ingestion (Chonokhuu et al., 2019). The contribution of HQing to HI for adults and children accounted 99.60 % and 99.80 % of the total risk, respectively. The HI values showed the following descending order for both adults and children: Fe > Cr > As > Pb > V > Mn > Ni > Cu > Zn > Co (Table 3, Fig. 3). The PTEs in the study area had HI values less than 1.0, indicating that residents of Al-Ahsa Oasis are not at significantly non-carcinogenic risk (Bello et al., 2019; Tian et al., 2020; Ahmad et al., 2021). However, the value of HI for Fe was greater than 0.2 for children, indicating the need to protect their health. Children are more vulnerable to the health impacts and appear to be highly susceptible to PTEs due to oral and finger practice (Agyeman et al., 2021a, b).

The HI for non-carcinogenic risk in adults and children.
Fig. 3
The HI for non-carcinogenic risk in adults and children.

The spatial distribution of the HI of the PTEs per sample location for both children and adults showed similar color patterns and hotspots in S1, S2, S6, and S7 in southeastern part of the study area, and S10, S25, and S26 in the northwestern part (Figs. 4 and 5). S7 collected from palm fields irrigated with treated sewage water, while S1, S2, S6, S10, S25, and S26 were irrigated with groundwater. Alharbi and El-Sorogy (2023) indicated that the Al-Ahsa soils were moderately severe enriched with As and minor to negligibly enriched with the remaining PTEs.

Spatial distribution of hazard index (HI) of As, Co, Cr, Cu, and Fe per sampled location.
Fig. 4
Spatial distribution of hazard index (HI) of As, Co, Cr, Cu, and Fe per sampled location.
Spatial distribution of hazard index (HI) of Mn, Ni, Pb, V, and Zn per sampled location.
Fig. 5
Spatial distribution of hazard index (HI) of Mn, Ni, Pb, V, and Zn per sampled location.

3.2.2

3.2.2 Carcinogenic risks (CRs) and total lifetime cancer risk (LCR)

Hazardous consequences may arise from an excessive build-up of toxic PTEs in human bodies. Several investigations have demonstrated that the accumulation of PTEs negatively affects immune system, central nervous system, endocrine, cardiovascular, and urogenital systems, as well as normal cellular metabolism (Wang, 2013; Wang et al., 2015; Agyeman et al., 2021). PTEs cause various health issues in children, including poor respiratory function, cardiovascular disease, reproductive toxicity, cognitive deficits, and bone damage (Madrigal et al., 2018). The CRs for Cr, As, and Pb in children was found to be significantly greater than that of adults (Table 4, Fig. 6). Average CR values in ingestion, dermal, and inhalation pathways of the adults varied from 6.094 × 10-8 to 1.963 × 10-5, from 1.858 × 10-10 to 4.373 × 10-8, and from 8.961 × 10-13 to 2.887 × 10-10, respectively, while in children the CRs varied from 5.687 × 10-7 to 1.833 × 10-4, from 8.672 × 10-10 to 2.041 × 10-7, and from 4.182 × 10-12 to 1.348 × 10-9, respectively. Children's CR values for Cr, As, and Pb are higher than those for adults, suggesting that children are still more likely to be exposed to PTEs due to their behavioral habits that enhance their tendency for skin contact, especially with hands (Agyeman et al., 2021; Alzahrani et al., 2023).

Table 4 Average CRs and LCR for PTEs in the study area.
HMs Adults Children
CR Ing. CR Dermal CR Inhal LCR CR Ing. CR Dermal CR Inhal LCR
As 4.658 × 10-6 1.640 × 10-8 6.849 × 10-11 4.67 × 10-6 4.347 × 10-5 7.652 × 10-8 3.196 × 10-10 4.35 × 10-5
Cr 1.963 × 10-5 4.373 × 10-8 2.887 × 10-10 1.97 × 10-5 1.833 × 10-4 2.041 × 10-7 1.348 × 10-9 1.83 × 10-4
Pb 6.094 × 10-8 1.858 × 10-10 8.961 × 10-13 6.11 × 10-8 5.687 × 10-7 8.672 × 10-10 4.182 × 10-12 5.70 × 10-7
Carcinogenic risks (CRs) for or As, Cr, and Pb, in adults and children.
Fig. 6
Carcinogenic risks (CRs) for or As, Cr, and Pb, in adults and children.

LCR values for Cr, As, and Pb in all studied sites were higher in children than that of the adult (Table S2). LCR values varied between adults and children from 1.97 × 10-5 to 1.83 × 10-4 (Cr), from 4.67 × 10-6 to 4.35 × 10-5 (As), and from 6.11 × 10-8 to 5.70 × 10-7 for Pb, respectively (Table 4, Fig. 7). Carcinogenic risk of the ingestion pathway was the principal contributor to the total lifetime cancer risk. It reached 99.70 % for the three PTEs in adults, while in children it reached 99.93 % for As, 99.78 % for Pb, and approximated 100 % for Cr. The spatial distribution of the LCR for the As, Cr, and Pb per sample location suggested similar color patterns for both children and adults with increase values in children (Fig. 8). LCR values of Cr in 25 samples (83.30 %) reported values slightly greater than 1 × 10-4 for children, indicating the risk is unacceptable compared to the other two HMs, which were between 1 × 10-4 and 1 × 10-6, and lower than 1 × 10-6, indicating acceptable or tolerable carcinogenic risk and no significant health hazards, respectively (Mondal et al., 2021; Al-Kahtany and El-Sorogy, 2023; Ahmad et al., 2023a, b).

The total carcinogenic risk (LCR) for or As, Cr, and Pb, in adults and children.
Fig. 7
The total carcinogenic risk (LCR) for or As, Cr, and Pb, in adults and children.
Spatial distribution of LCR for As, Cr, and Pb per sampled location.
Fig. 8
Spatial distribution of LCR for As, Cr, and Pb per sampled location.

4

4 Conclusions

The health risks associated with Fe, Mn, Zn, Cr, Ni, V, Cu, Pb, Co, and As in soil collected from palm farms in Al-Ahsa oasis were highlighted in this study. For every PTE, children's CDI and HI values were higher than those of adults. HI values were less than 1.0, suggesting there is no significant non-carcinogenic risk to the people inhabiting the Al-Ahsa Oasis. Moreover, the CRs and LCR for Cr, As, and Pb in children were significantly greater than those of adults, indicating that children are more susceptible than adults to health concerns associated with PTEs. LCR values for As, Cr, and Pb ranged from no significant, acceptable to tolerable carcinogenic risk health hazards, with few higher values for Cr in children. This study could be used to track any improvements or additional deterioration over time by establishing baseline PTE hazards related to Al-Ahsa oasis.

Author contributions

[TA] and [ASE] collecting samples, preparing samples for chemical analysis; [TA], [ASE], and [KA] writing manuscript and interpreting chemical analysis. All authors read and approved the final manuscript.

Acknowledgments

The authors extend their appreciation to Researchers Supporting Project number (RSPD2024R791), King Saud University, Riyadh, Saudi Arabia.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Appendix A

Supplementary material

Supplementary data to this article can be found online at https://doi.org/10.1016/j.arabjc.2023.105592.

Appendix A

Supplementary material

The following are the Supplementary data to this article:

Supplementary data 1

Supplementary data 1


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