The health risk of potentially toxic elements (PTEs) via contamination of the food chain has attracted widespread concern. The aim of this study is to evaluate the effects of PTEs in environment and human body (fingernail, hair, and blood) of people living in agricultural soil near arsenic coal mining areas in Xingren County (Guizhou, southwest China). 89 crop samples which included vegetables, rice, maize, and coix seed and their corresponding soils and 17 local surface water and biological tissue samples (41 × 3) in near arsenic coal mining areas were collected, and the concentrations of potentially toxic elements (As, Cd, Cu, Cr, and Pb) in all the samples were determined. The health risk assessment methods developed by the United States Environmental Protection Agency were employed to explore the potential health hazards of PTEs in soils growing crops. Results showed that 4 toxic elements, Cd, Cu, As, and Cr, were found to have different degrees of contamination in soils in the studied area. The total concentration of toxic elements (As, Cr, Cu, and Pb) in fingernail, hair, and blood samples were 90.50, 69.31, and 6.90 mg·kg−1, respectively. Fingernail samples from females were more likely to show exposure to trace metals compared to males. As the age of the subject increased, the concentration of As also increased in all three biological samples. The risk assessment for the mean hazard index value from the consumption of local food crops was 14.81, indicating that consumers may experience adverse, noncarcinogenic health effects. The estimated mean total cancer risk value of was 5.3 × 10−3, which was approximately 10 to 1000 times higher than the acceptable range of 10−6–10−4, indicating serious carcinogenic risks for local people consuming crops from the area. This study provides evidence that local residents in this study area may be at a high risk of disease caused from toxic element exposure.
Although coal mining creates economic benefits, it can also result in significant contamination to the environment [
Potentially toxic elements present an environmental hazard within the vicinity of coal mining. The metals’ uptake by vegetation is dependent on the soil characteristics, including chemical and physical characteristics, as well the species of vegetation grown [
Several methods have been established to evaluate the potential health risks of pollutants, which are divided into carcinogenic and noncarcinogenic effects [
Our study focuses on assessing the potential health risks of PTEs exposure to multiple targets in the environment (local surface water, soil, and crops) and examining biological indicators in humans for assessing multiple exposures to metals in the local population of Xingren, Guizhou. Particular emphasis is placed on the determination of heavy metals in blood, fingernail, and scalp hair samples and the comparison and assessment of the potential health risks of heavy metal exposure across multiple sites in the mining area. This data could be used to control the environmental hazards to human health in the mining area [
This study was carried out in Xingren (104°54′33″E-105°33′46″E, 25°15′49″N-25°46′58″N), a typical county located in Qianxi Prefecture in central Guizhou Province (China). In the 1980s and 1990s, a large number of coal mining activities were carried out in this area. The coal reserves exceeded 45 million tonnes, and the coal mining activities in Xingren contaminated the soil. A large number of abandoned mines, mine and coal gangue reactors, leaching from rain, and the discharge of acidic wastewater have caused harmful substances to be deposited in the surrounding environment. The soils in this area are primarily loess and dark brown soils. The food crops cultivated in the area are primarily rice, maize, coix seed, and vegetables.
A total of 89 soil samples and corresponding crop samples (edible parts only), including 22 rice (
Each fresh soil sample was approximately 1 kg in dry weight and was a composite of 3 subsamples from nearby sites, taken at a depth of 0 to 20 cm in and around paddy fields, maize, coix seed, and vegetable cultivation areas. After sampling, the crop and soil samples were sealed in polyethylene bags and transported to the laboratory. The soil samples were dried, ground, passed through a100 mesh sieve [
The crop samples were first washed with tap water and then with distilled water, cut into small pieces with a plastic knife, dried in an oven at 50°C, and finally powdered in a grinder to be conserved in polyethylene bags [
A questionnaire based on analysis was collected about gender, age, and living habits for local residents during the sampling period. We had collected and analyzed biological tissue samples (41×3) from local residents. The blood, fingernail, and hair samples of the residents of the coal mining areas were assessed to determine the current status of PTE exposure. The ages and gender of each resident were recorded during sampling. The young generation was out to work early, resulting in little research on children or young people. The concentrations of trace elements in the blood, fingernail, and hair samples taken from residents in the mining areas were divided into 3 age groups, 15–30, 31–50, and ≥50 years (Table
The numbers of males and females in each age group.
Ages (years) | Females | Males |
---|---|---|
15–30 |
|
|
31–50 |
|
|
≥50 |
|
|
Soil pH was measured in using a 1 : 2.5 soil-to-water ratio with a pH meter (PHS-3C, Shanghai INESA Scientific Instrument Co., China). Levels of heavy metals (Cd, Cr, Cu, and Pb) in the soil, crops, water, fingernail, blood, and hair samples were measured using atomic absorption spectrometry (ZEEnit700P, Analytikjena, Germany) and As was determined using atomic fluorescence spectrometry (AFS-933, Beijing Titan, China).
The reagents used in these studies were of guaranteed or analytical grade, and experimental water was ultrapure water (18.2 MΩ·cm). The laboratory analysis process used the national standard reference materials (GBW-07456 (soil), GBW-07409 (soil), GBW07603 (plant)), a reagent blank, and 20% duplicate samples, to control quality. Precision, which was ascertained by replicate analysis, was less than 5% relative standard deviation (RSD). In addition, accuracy expressed as recovery of the reference material was 96.31–105.27% for all metals, and the determination of results of all samples were in the range of the accepted error [
The target hazard quotient (THQ) and hazard index (HI) were used to determine the noncarcinogenic health risks caused by the consumption of vegetables by local people. The measure was provided by USEPA (2005) [
TTHQ indicates the total of crop THQ for an individual crop of selected elements using the equation above. For assessing the overall potential of noncarcinogenic risks across more than one crop, a hazard index (HI) was calculated based on the Guidelines for Health Risk assessment of Chemical Mixtures of USEPA [
Carcinogenic risks to humans associated with crop consumption can be assessed as a cancer risk (CR). CR was determined using following equation:
The data were processed, analyzed, and plotted using Excel (2013), SPSS (19.0), and Origin 8.5, respectively.
The pH range of soil samples is 3.95–6.37 which may be related to the acidification of the surface soil of the mine surrounding the acid mine drainage produced by the mining process. The range of TOC is 13.47–52.36 g·kg−1, and the average value is 26.33 g·kg−1. There is a lot of focus on PTE levels in farmland soil. Statistics on soil samples containing 5 kinds of PTEs are illustrated in Figure
Box-plots of concentrations of As, Cd, Cr, Cu, and Pb (mg·kg−1) in soil samples from the Xingren district.
In addition to Pb, 4 other toxic elements, Cd, Cu, As, and Cr, were found to have different degrees of contamination in the 4 soils in the studied area. Cadmium is considered as an agronomic element and primarily exists in soils through the use of chemical fertilizers, livestock manure, and ground water [
The concentrations of As and other heavy metals in the edible parts of different plant samples were found to be significantly different (Figure
The concentration of As, Cd, Cr, Cu, and Pb in grains and vegetables.
The mean values of the chemical and biological characteristics of pH, K+, Na+, Ca2+, and Mg2+ in the water samples were 7.13, 1.64, 5.22, 62.51, and 18.27 mg·L−1, respectively. Primary descriptive statistics of parameters in water samples are presented in Table
Statistical parameters for trace element concentrations in water samples.
Parameters | Minimum | Maximum | Mean | SD | Cv (%) | Skewness | Kurtosis | GB5749-2006 |
---|---|---|---|---|---|---|---|---|
Pb ( |
49 | 1328 | 611 | 0.462 | 75.68 | −0.10 | −1.59 | 10 |
As ( |
16 | 1583 | 766 | 0.527 | 68.85 | −0.20 | −1.21 | 10 |
Cu ( |
6.619 | 23.200 | 12.499 | 6.115 | 48.92 | 0.82 | −0.83 | 1000 |
Cd ( |
0.001 | 0.579 | 0.184 | 0.221 | 120.11 | 0.77 | −1.14 | 5 |
Cr ( |
0.130 | 3.843 | 1.568 | 1.350 | 86.07 | 0.76 | −1.18 | 50 |
In Figure
Levels of PTEs in nail, hair, and blood samples of inhabitants in Xingren, Guizhou, China (mg·kg−1).
Table
Pearson’s correlation of PTEs contents in human nail, hair, and blood samples.
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|
Nail As | Nail Pb | Nail Cu | Nail Cr | Hair As | Hair Pb | Hair Cu | Hair Cr | Blood As | Blood Pb | Blood Cu | Blood Cr | |
1 | 1 | 0.834 |
0.627 |
0.759 |
0.067 | 0.23 | -0.074 | 0.015 | -0.09 | -0.187 | -0.016 | -0.196 |
2 | 1 | 0.722 |
0.942 |
−0.034 | 0.239 | −0.027 | −0.036 | 0.029 | −0.177 | 0.071 | −0.091 | |
3 | 1 | 0.783 |
0.030 | 0.196 | −0.062 | −0.055 | −0.100 | −0.201 | 0.124 | −0.041 | ||
4 | 1 | 0.042 | 0.230 | −0.005 | 0.056 | 0.086 | −0.231 | 0.059 | −0.145 | |||
5 | 1 | 0.644 |
−0.010 | 0.567 |
0.115 | −0.181 | −0.038 | −0.145 | ||||
6 | 1 | −0.006 | 0.401 |
−0.049 | 0.147 | 0.107 | 0.016 | |||||
7 | 1 | 0.104 | 0.021 | −0.219 | −0.057 | −0.073 | ||||||
8 | 1 | 0.092 | −0.011 | 0.058 | 0.012 | |||||||
9 | 1 | −0.159 | 0.191 | 0.149 | ||||||||
10 | 1 | 0.319 |
0.363 |
|||||||||
11 | 1 | 0.793 |
||||||||||
12 | 1 |
The total concentration of individual elements (As, Cr, Pb, and Cu) in human nail, hair, and blood for males and females living in the mining area is shown in Figure
Concentration of Cr, Pb, Cu, As (mg·kg−1) for the nail (a), hair (b), and blood (c) samples for females and males in local residents from mining areas.
Figure
Concentrations of Cr, Pb, Cu, and As (mg·kg−1) for the nail (a), hair (b), and blood (c) samples across different age groups (15–30, 31–50, >50 years).
As the staple food (rice, coix seed, and maize) and vegetables of the local people are grown in the area, their consumption contributes a large part of their daily intake of PTEs. The above results indicate that toxic metals are found in high concentrations in local crops, indicating a health risk assessment is essential. Assessment of potential health effects of human contamination of toxic metals through the consumption of food includes carcinogenic and noncarcinogenic risks.
The noncarcinogenic risk from the consumption of vegetables, rice, coix seed, and maize by local people were calculated based on the EDI and the THQ values. The THQ is a ratio of a defined dose of a pollutant to a reference dose level, which is calculated using EDIs to indicate the pollution level due to contaminant exposure. If the ratio is greater than 1, the exposed population is likely to experience health effects; otherwise, the exposed population is considered to be not at risk, and levels of contaminants are acceptable (USEPA, 2005; FAD/WHO, 2001) [
Noncarcinogenic risk assessment including THQ for As, Cd, Cu, Pb, and Cr through the consumption of vegetables, rice, coix seed, and maize grown in the mining affected areas.
Noncarcinogenic risk (TTHQ, HI) and carcinogenic risk (TCR, TTCR) of PTEs due to food crop consumption in the Xingren mine affected area.
Health risk assessment | Crop types | ||||
---|---|---|---|---|---|
Vegetable | Rice | Coix seed | Maize | ||
Noncarcinogenic risk | TTHQ | 7.78 | 3.00 | 2.7 | 1.33 |
HI | 14.81 | ||||
Carcinogenic risk | TCR | 2.40 × 10−3 | 1.16 × 10−3 | 9.14 × 10−4 | 4.57 × 10−4 |
TTCR | 5.3 × 10−3 |
The 3 metals, Cd, As, and Pb, are generally accepted as being carcinogenic. The CR, TCR, and TTCR for local people in the affected mine area were calculated and shown in Figure
Carcinogenic risks including CR for As, Cd, and Pb through the consumption of vegetables, rice, coix seed, and maize in the mine affected areas.
A large daily intake of these crops by local people will cause high carcinogenic and noncarcinogenic risks. Moreover, it has also been reported that the exposure to 4 or more contaminants may result in additive or interactive effects, which increase the potential risk of adverse health effects for residents in this area.
The THQs in crops are ranked As > Cd > Cu > Pb > Cr. The mean HI value through food crop consumption was 14.81, indicating that consumers of the studied food crops may experience adverse health effects. Some effective measures are essential to reduce the PTE contamination levels in soil and metal migration from the soil to the edible parts of crops grown in the area. The TCRs are ranked in order As > Cd > Pb. The mean TTCR values for the consumption of selected food was 0.0053, which is about 10 to 1000 times greater than the acceptable range of 10−6–10−4 (UA EPA, 2010). This suggests serious carcinogenic risks for local people consuming crops from the area. A large daily intake of these crops by the local people will cause carcinogenic and noncarcinogenic risks. Although various types of commonly consumed crops were collected from the study area, they are not representative of all vegetables and grains consumed by populations in other mining areas. The daily intake of other elements from other food sources needs to be evaluated to determine the actual exposure to As and other elements and to better evaluate the health risks of this section of the population. Total trace metals (As, Pb, Cu, and Cr) for fingernail, hair, and blood samples were 90.50 mg·kg−1, 69.31 mg·kg−1, and 6.90 mg·kg−1, respectively. Females were more likely to be exposed to trace metals (As, Pb, Cu, and Cr) in fingernail samples compared to males. This study included small sample sizes for soils and vegetables. Future studies should include larger sample sizes and additional food components. In addition, other elements need to be monitored regularly in the mining area.
The authors declare that there are no conflicts of interest regarding the work described in this paper.
This research received funding from the National Science and Foundation of China, “The characteristics of heavy metal pollution in the high arsenic coal mine area of Guizhou province” (21467005), which was held by Fan-xin Qin.