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The study was conducted in Markazi Province located in the west of Iran at a latitude of 34° 05′ 30.26″ N and a longitude of 49° 41′ 20.98″ E. As Markazi Province is a developed, industrial, and agricultural region, heavy pollution can be found on most of the days in a year. Six different sites (cities) of Markazi Province, namely, Saveh, Khondab, Khomein, Mahallat, Tafresh, and Delijan, were selected for this study due to their fewer distances from industrial zones (Figure 1). The mean annual precipitation was 278 mm/year with a relative humidity of 46%, and the mean temperature is approximately 12.8 °C, with the minimum and maximum annual temperature being approximately −13 °C to −35 °C and 36–49 °C, respectively. The population of this region is about 1.43 million habitants.
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All chemicals and standards and stock standard solutions of As, Cd, Hg, and Pb of analytical grade (purity > 99%) were purchased from Merck (Darmstadt, Germany). Double-deionized water was used in the preparation of all dilutions.
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Different summer fruits such as peach (Prunus persica) (n = 15), apple (Malus domestica) (n = 15), grape (Vitis vinifera) (n = 15), nectarine (Prunus persica) (n = 15), and golden plum (Prunus domestica subsp. Syriaca) (n = 15) in three replicates (n = 3) were collected (a total of 90 samples) randomly from six agricultural sites in Markazi Province (1 kg of each sample). All fruit samples were collected from June to July 2018 and prepared according to the procedure recommended by previous studies[42, 44].
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Based on previously described methods[42, 45, 46], a total of 18 soil samples were collected from around the plant (6 agricultural sites × 3 sample plots; soil samples from each site were collected by excavating 1.5-m radial distance from the plant center) and were prepared for analysis.
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A total of 18 irrigation water samples (1 L of each sample) were collected from the experimental sites (6 agricultural sites × 3 sample plots) and stored in precleaned high-density polyethylene bottles, which were washed with 10% HNO3 overnight and then with deionized water and were dried before use. The water samples were filtered and acid-stabilized, and approximately 20 mL HCl was added to the sample [42, 47, 48]. The samples can be introduced into a plasma directly.
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The ICP-OES method was used for analyzing all samples based on the method described in our previous investigation[42].
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A calibration curve was used to check the linearity of the method. Individual stock standard solutions (10 µg/mL) were prepared as follows: 2.5, 5, 10, 100, 200, 300, 500, and 1,000 μL. Then, the mixed standard stock solutions were added to 10 g of blank samples[39, 46].
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The sensitivity of the analytical methods was investigated by the limit of detection (LOD) (signal-to-noise; S/N ratios of 1/3) and the limit of quantification (LOQ) (10 times more than that of background noise in spiked samples at lowest levels).
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For investigation of the recovery, spiked fruit, soil, and water blank samples at concentration levels of 25, 75, 150, 250, 500, and 750 µg/mL of PTEs (As, Cd, Hg, and Pb) were prepared in triplicates and then treated according to the procedure described in the original sample preparation[42, 49].
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The transfer factor (TF) is defined as the ratio of PTEs in the soil to their ratio in plant tissues, which indicates internal PTE transportation or transfer of PTEs from the soil to the fruits. Soil to plant transfer is the primary pathway of human exposure to PTE contamination[50]. A higher TF level of > 1 reflects the high ability of the plant to absorb each PTE.
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The EDI was estimated using the following Equation[51-54]:
$$\text{EDI} = \frac{{\text{C} \times \text{IR} \times \text{EF} \times \text{ED}}}{{\text{BW} \times \text{AT}}} $$ (Equation (1)) In this equation, C (µg/L) is the concentration of the PTE, IR (kg/n·day) is the ingestion rate of fruit (in Iran, it is 0.012 kg/n·day for children and 0.030 kg/n·day for adults)[55], EF (days/year) is the exposure frequency (350 days/year), ED (year) is the exposure duration (children = 6 years and adults = 30 years), BW (kg) is the bodyweight (children = 15 kg and adults = 70 kg), and AT (days) is the average lifespan time (for noncarcinogenic risk, it is 2,190 days in children and 10,950 days in adults, and for carcinogenic risk, it is 25,550 days in children and 25,550 days in adults).
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The noncarcinogenic risk due to the ingestion of fruit content of PTEs was evaluated using the THQ[51, 56, 57] as follows:
$$ TH{Q_i} = \frac{{EDI}}{{RfD}} $$ (Equation (2)) In this equation, EDI [µg/(kg·d)] is the amount of PTE intake per kilogram BW that is presented as EDI and RfD [mg/(kg·d)], the reference dose of PTEs through the oral pathway. The oral RfD values for As (inorganic), Cd, and Hg (methylmercury) are 0.0003, 0.001, and 0.0001 [mg/(kg·d)] and unavailable, respectively[58]. According to the World Health Organization (WHO) report, the tolerable daily intake (TDI) for Pb is 0.0036 [mg/(kg·d)][59].
To calculate the total THQ (TTHQ), the sum of THQ for each PTE was calculated using the following equation[60, 61]:
$$ TTHQ = \mathop \sum \nolimits_{i = 1}^n THQi $$ (Equation (3)) -
The carcinogenic risk (CR) was evaluated using the following equation[62-64]:
$$ \text{CR} = \text{EDI} \times \text{CSF} $$ (Equation (4)) In this equation, CSF is the cancer slope factor [mg/(kg·d)]−1, which is defined as a probable increase in cancer risk due to one substance through the oral pathway[65, 66].
According to EPA, the CSF through the oral pathway for As is 1.5 [mg/(kg·d)]−1[67]. The CSF values for Cd, Hg, and Pb are not available.
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Uncertainties can occur during a health risk assessment[68]. If the used single-point value of PTE concentration for health risk assessment, high uncertainty can be observed. Therefore, a Monte Carlo simulation model was used as a probabilistic model to decrease uncertainties[69, 70]. The probabilistic risk assessment was conducted using the Crystal Ball software (version 11.1.2.4, Oracle, Inc., USA). The 95th percentile of THQ and CR was considered as a benchmark value that could endanger the health of consumers, and the number of repetitions was 10,000[71].
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Two-way analysis of variance (ANOVA) was performed to assess the effect of different variables on the toxic element concentrations in the tested fruits. ANOVA for each fruit was performed separately using variables such as the study site. A significant level of contamination in different fruits and water and soil of regions of sampling (P ≤ 0.05). All statistical analyses were performed using SPSS v.24 (SPSS Inc., Chicago, IL). Each sample was analyzed three times (n = 3) for each PTE.
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Good linearity was noted according to the calibration curves plotted for four forms of PTEs in five types of fruits. The correlation factors for all the fruits were found to be in the range of 0.9975–0.9996 (Table 1). Figure 2 shows the spiked calibration curve for Hg in nectarine as a representative. Furthermore, an ICP-OES chromatogram of Hg analyzed in nectarine is depicted in Figure 3.
Fruit samples Metal Equation Regression coefficient Nectarine As y = 0.0005x - 0.008 0.9985 Cd y = 0.003x - 0.0248 0.9995 Hg y = 0.0009x - 0.0112 0.9993 Pb y = 0.0009x -0.0048 0.9996 Grape As y = 0.003x + 0.0275 0.9979 Cd y = 0.001x - 0.0123 0.9993 Hg y = 0.0003x - 0.0047 0.9993 Pb y = 0.0014x + 0.0178 0.9975 Plum As y = 0.0012x - 0.0181 0.9987 Cd y = 0.0028x - 0.0362 0.9992 Hg y = 0.0016x - 0.0017 0.9977 Pb y = 0.0003x + 0.0005 0.9992 Peach As y = 0.001x - 0.0136 0.9993 Cd y = 0.0002x - 0.002 0.9984 Hg y = 0.0008x - 0.0062 0.9986 Pb y = 0.0008x - 0.0106 0.9992 Apple As y = 0.0008x - 0.0073 0.9977 Cd y = 0.0007x - 0.0081 0.9978 Hg y = 0.0019x - 0.0056 0.9994 Pb y = 0.0002x - 0.0024 0.9985 Table 1. Linear equations and regression coefficient of the calibration curves for PTEs (range 2.5-1,000 μg/kg)
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Table 2 show the average recoveries (%), relative standard deviations (%), LODs, and LOQs (μg/kg) obtained by ICP-OES analysis at six spiking levels (n = 3) in fruit, soil, and water samples. Using this method, the LODs for As, Cd, Hg, and Pb were calculated as 1, 0.05, 0.35, and 2 µg/kg, and the LOQs were 3.25, 0.42, 1.13, and 6.5 µg/kg in all types of samples, respectively. In addition, the recovery of PTEs at these six spiking levels was in the range of 89.01%–126.65% in fruit, 89.11%–114.07% in soil, and 101.2%–132.8% in water samples. Regarding repeatability, all samples gave an RSD of < 20% with n = 3 at each spiking level (Table 2).
Metal Samples Recovery (n = 18), Mean ± SD (95% CI) Range of RSDr (n = 6) LOD LOQ As Fruits 105.06 ± 8.09 (93.7-116.2) 6.9−14.1 1 3.25 Soil 98.78 ± 2.58 (93.8-103.7) 10.62−19.21 Water 115.7 ± 4.24 (111.2-128.3) 12.1−16.71 Cd Fruits 102.26 ± 5.21 (93.8-112.5) 9.3−15.4 0.05 0.42 Soil 99.71 ± 3.64 (94.2-108.7) 11.86−17.32 Water 110.36 ± 6.3 (101.2-119) 11.9−15.12 Hg Fruits 106.6 ± 8.81 (102.13-126.65) 8.1−16.8 0.35 1.13 Soil 106.6 ± 4.54 (99.43-114.07) 10.86−18.11 Water 121.85 ± 3.24 (119.54-132.8) 9.3−12.11 Pb Fruits 100.4 ± 8.21 (89.01-111.55) 9.1−17.5 2 6.5 Soil 94.37 ± 2.87 (89.11-99.55) 9.86−17.12 Water 110.54 ± 4.5 (105.64-123.17) 13.3−14.3 Table 2. Average recoveries (%), relative standard deviations (RSD) (%), LOD and LOQ (μg/kg) obtained by ICP-OES analysis at 6 spiking levels (n = 3) in fruit, soil and water samples
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The concentration of PTEs showed a wide variation in the fruit samples as indicated by the average level of each PTE in Table 3. The order of mean concentration of PTEs in grape, peach, and nectarine was as follows: Pb > As > Hg > Cd. An almost similar order was found for plum (Pb > Hg > Cd > As) and apple (Pb > Hg > As > Cd). These findings indicate that the lowest and highest mean levels of As (0.085 ± 0.057 and 1.2 ± 0.087 μg/kg, respectively) correlated with nectarine and grape samples, whereas for Cd, the corresponding values were 0.0096 ± 0.005 and 0.3 ± 0.007 μg/kg for golden plum and grape, respectively. For Hg, the corresponding values were 0.03 ± 0.005 and 0.91 ± 0.008 μg/kg for golden plum and grape, and for Pb, the corresponding values were 1.2 ± 0.35 and 6.3 ± 1.11 μg/kg for nectarine and apple, respectively.
Location Plum Apple Grape As Cd Hg Pb As Cd Hg Pb As Cd Tafresh 0.21±0.08a 0.02±0.010ab 0.09±0.006a 4.01±1.62a 0.15±0.03b 0.01±0.000a 0.05±0.007b 1.99±0.70a 0.23±0.10ab 0.03±0.006a Delijan 0.18±0.04a 0.02±0.002ab 0.09±0.010a 3.42±1.14a 0.29±0.06a 0.20±0.003c 0.11±0.005a 2.53±1.15a 0.18±0.05a 0.02±0.001a Saveh 0.30±0.02a 0.03±0.003ab 0.13±0.005b 3.85±0.90a 0.17±0.03ab 0.02±0.004ab 0.06±0.005bc 2.55±1.12a 0.45±0.05b 0.05±0.002b Khomein 0.26±0.06a 0.02±0.080b 0.10±0.017a 4.69±1.23a 0.28±0.05a 0.03±0.007b 0.10±0.009a 3.78±1.22a 1.20±0.08c 0.30±0.006c Mahallat 0.14±0.02a 0.01±0.004a 0.03±0.005c 2.70±1.08a 0.19±0.04ab 0.02±0.004ab 0.08±0.006c 6.27±1.10b 0.51±0.09b 0.11±0.017d Khondab 0.22±0.08a 0.03±0.010ab 0.09±0.007a 4.37±1.20a 0.15±0.03b 0.01±0.004a 0.06±0.005b 1.25±0.29a 0.35±0.06ab 0.03±0.002ab Location Grape Peach Nectarine Hg Pb As Cd Hg Pb As Cd Hg Pb Tafresh 0.10±0.006a 2.49±0.86a 0.14±0.01a 0.01±0.001a 0.06±0.005a 2.77±0.84b 0.22±0.025bc 0.05±0.004c 0.07±0.005b 2.95±0.83b Delijan 0.09±0.005a 1.71±0.56a 0.22±0.05ac 0.02±0.002ab 0.10±0.005b 5.64±1.10a 0.16±0.015a 0.02±0.003a 0.06±0.005a 1.70±0.30a Saveh 0.19±0.005b 6.01±0.83b 0.18±0.03ab 0.02±0.004a 0.06±0.005a 1.57±0.32b 0.10±0.005bc 0.01±0.001b 0.04±0.005c 1.23±0.34b Khomein 0.91±0.008c 2.98±0.53a 0.29±0.07bc 0.03±0.005b 0.12±0.005c 4.53±0.68ab 0.14±0.034ac 0.01±0.005a 0.05±0.005ab 1.61±0.31a Mahallat 0.32±0.032d 2.55±0.55a 0.34±0.07c 0.04±0.004b 0.14±0.005d 5.11±0.78a 0.22±0.060a 0.02±0.004a 0.10±0.005a 2.89±0.78a Khondab 0.16±0.018b 2.50±0.32a 0.19±0.06ac 0.02±0.007a 0.07±0.009a 1.67±0.31b 0.12±0.015ab 0.01±0.002ab 0.04±0.005b 1.97±0.46a Note. Different letters in the same column indicate significant differences (P < 0.05). Table 3. The mean level and standard deviation of different PTEs in different fruits in various sites of Markazi Province, Iran (µg/kg·dw)
A significant difference was observed in the concentration of PTEs among fruit samples collected from different regions (Table 3), and the levels of PTEs in the investigated samples were in the range form 0.10 ± 0.005 to 1.20 ± 0.08 µg/kg for As, 0.01 ± 0.004 to 0.30 ± 0.006 µg/kg for Cd, 0.03 ± 0.005 to0.91 ± 0.008 µg/kg for Hg, and 1.23 ± 0.34 to 6.27 ± 1.10 µg/kg for Pb.
In general, the highest concentration of PTE was associated with apple samples, and the lowest one was noted among plum samples. The highest concentration of Pb was found in apple (6.27 ± 1.10 µg/kg) in Mahallat, and the highest levels of As, Cd, and Hg (1.20 ± 0.08, 0.303 ± 0.006, and 0.910 ± 0.008 µg/kg, respectively) were observed in grape samples in Khomein. However, the levels of Pb, Hg, As, and Cd was below the standard limit recommended by the WHO/Food and Agricultural Organization (FAO). The nectarine fruit samples collected from Saveh were contaminated with the lowest concentrations of As, Cd, and Pb (0.10 ± 0.005, 0.01 ± 0.001, and 1.23 ± 0.34 µg/kg, respectively). Plum samples also contained the lowest concentration of Hg, 0.030 ± 0.005 µg/kg, in Mahallat. According to the Institute of Standards and Industrial Research of Iran (ISIRI), the maximum limit of Pb in fruits is 100 µg/kg, whereas a limit of 200 µg/kg was proposed for grape[72]. Therefore, the level of this toxic element in fruits is lower than the recommended ISIRI limit.
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The analysis results of water and soil samples collected from different sites in Markazi Province are presented in Table 4. The order of PTE levels in the soil and water samples can be summarized as Pb > As > Hg > Cd. There was a significant difference in the concentration of PTEs between fruits as well as soil and water samples collected from different regions. The levels of Pb, As, Hg, and Cd in the soil were in the range of 146.01 ± 6.7 to 318.72 ± 1.43, 79.17 ± 1.07 to 263.9 ± 9.95, 0.71 ± 0.06 to 2.13 ± 0.014, and 0.20 ± 0.009 to 0.20 ± 0.01 µg/kg, respectively, and those in the water samples were 92.40 ± 3.66 to 102.9 ± 5.6, 53.76 ± 6.7 to 171.4 ± 57.6, 11.01 ± 1.11 to 44.4 ± 0.50 µg/kg, respectively. This implies that the concentrations of Pb and As in the soil were higher than those in the water samples, whereas those of Cd and Hg were higher in the water samples than in the soil samples.
Location Water (mean ± SD) Soil (mean ± SD) As Cd Hg Pb As Cd Hg Pb Khomein 55.5 ± 9.5a 5.09 ± 0.16a 20.13 ± 0.22ab 101.6 ± 3.3ab 95.80 ± 6.4b 0.207 ± 0.012a 0.81 ± 0.015a 246.62 ± 1.29b Khondab 54.16 ± 7.2a 5.30 ± 0.53a 20.27 ± 0.45ac 102.9 ± 5.6a 181.32 ± 6.5ab 0.2 ± 0.012a 2.13 ± 0.014b 318.72 ± 1.43c Tafresh 54.09 ± 8.8a 5.27 ± 0.47a 20.27 ± 0.47bc 101.06 ± 2.39ab 181.54 ± 1.24ab 0.2 ± 0.014a 0.81 ± 0.013a 281.93 ± 6.7a Delijan 54.06 ± 6.4a 5.26 ± 0.46a 20.29 ± 0.42a 101.7 ± 3.6ab 237.1 ± 1.01a 0.2 ± 0.011a 1.41 ± 1.04b 166.87 ± 3.5d Saveh 53.7 ± 6.7a 5.28 ± 0.48a 44.4 ± 0.50e 101.2 ± 2.7ab 79.17 ± 1.07b 0.2 ± 0.005a 0.80 ± 0.009a 146.01 ± 6.3e Mahallat 171.4 ± 57.6a 4.22 ± 1.34a 11.01 ± 1.11d 92.4 ± 3.6b 263.9 ± 9.95a 0.2 ± 0.008a 0.71 ± 0.062d 271.23 ± 4.4a Note. Different letters in the same column indicate significant differences (P < 0.05). Table 4. The mean level of different PTEs contamination in water and soil samples in different place of Markazi province (µg/L or kg)
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The TF and the total mean TF in the fruits collected from the study sites are shown in Table 5. The order of the ability of all examined fruits to absorb PTEs was Cd > Hg > Pb > As. Although fruits can uptake the highest levels of Cd from the soil, they can also absorb the lowest level of As from the soil. Among the fruits, grape showed the highest TF level for Cd and Hg, whereas the lowest TF level was found for As in plum, apple, peach, and nectarine.
Fruits As Cd Hg Pb Plum 0.001 0.113 0.074 0.016 Apple 0.001 0.238 0.063 0.013 Grape 0.003 0.439 0.242 0.013 Peach 0.001 0.118 0.083 0.015 Nectarine 0.001 0.114 0.050 0.009 Table 5. The level of transfer factor for different PTEs in fruit samples (µg/kg)−1
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EDI values in adults due to contamination with As, Cd, Hg, and Pb were 1.32 × 10−7, 2.84 × 10−8, 9.45 × 10−8, and 5.34 × 10−9 µg/kg·d, respectively. EDI values in children due to the ingestion of As, Cd, Hg, and Pb through fruit consumption were 2.45 × 10−7, 5.29 × 10−8, 1.76 × 10−7, and 9.97 × 10−9 µg/kg·d, respectively (Table 6). EDI values in both adults and children were lower than the TDI for As (2 µg/kg·d), Cd (1 µg/kg·d), Hg (0.71 µg/kg·d), and Pb (3.6 µg/kg·d) recommended by the FAO/WHO/ food safety agency (FSA)[56].
Consumer group Heavy metal EDI Adults As 1.32 × 10−7 Cd 2.84 × 10−8 Hg 9.45 × 10−8 Pb 5.34 × 10−9 Children As 2.45 × 10−7 Cd 5.29 × 10−8 Hg 1.76 × 10−7 Pb 9.97 × 10−9 Table 6. EDI in the adults and children due to ingestion fruits content of PTEs (µg/kg·d)
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When the THQ and/or the TTHQ is > 1, there could be adverse health effects, but when the THQ is ≤ 1, adverse health effects are not probable[6, 38]. The total mean value of THQ and HQ of PET and also, RfD are presented in Table 7.
As Cd Hg Pb HQ 0.6782 0.0329 0.3215 0.6962 THQ 0.7459 0.0380 0.3236 0.6914 RfD 0.0003 0.0010 0.0003 0.0035 Table 7. The RfD and total mean value of THQ and HQ of metals
In this context, the 95th percentiles of THQ in adults due to the ingestion of PTEs (As, Cd, and Hg) through the consumption of fruits were 7.75 × 10−7, 4.46 × 10−8, and 1.46 × 10−6, respectively (Figure 4A-C); however, the corresponding values for the same PTEs in children were 1.38 × 10−6, 8.02 × 10−8, and 2.60 × 10−6, respectively (Figure 5A-C). The rank order of PTEs based on their THQ in both adults and children was Hg > As > Cd. The THQ of Hg was higher than that of other PTEs primarily due to the lower assigned RfD for Hg[60]. The THQ in children was 1.78 times higher than that of adults due to their lower BW[51-53]. Moreover, the TTHQ values in adults and children due to the ingestion of As, Cd, and Hg were 9.00 × 10−6 and 4.06 × 10−6, respectively. The 95th percentiles of THQ and TTHQ in both adults and children were much lower than 1 (Figures 5 and 6) because of the low concentration of PTEs[51-53] and the low ingestion rate of fruits[55].
Potentially Toxic Element Concentration in Fruits Collected from Markazi Province (Iran): A Probabilistic Health Risk Assessment
doi: 10.3967/bes2019.105
- Received Date: 2019-03-26
- Accepted Date: 2019-08-26
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Key words:
- Fruits /
- Soil /
- Water /
- Toxic elements /
- Target Hazard Quotient (THQ) /
- Estimated Hazard Index (HI)
Abstract:
Citation: | Mohammad Rezaei, Bahareh Ghasemidehkordi, Babak Peykarestan, Nabi Shariatifar, Maryam Jafari, Yadolah Fakhri, Maryam Jabbari, Amin Mousavi Khaneghah. Potentially Toxic Element Concentration in Fruits Collected from Markazi Province (Iran): A Probabilistic Health Risk Assessment[J]. Biomedical and Environmental Sciences, 2019, 32(11): 839-853. doi: 10.3967/bes2019.105 |