Characterization of soil heavy metal contamination and potential health risk in metropolitan region of northern China

Spatial distribution of heavy metal abundance at distance gradients of roadside agricultural soil from the busiest highway in Bangladesh: A multi-index integration approach

Bangladesh is currently experiencing significant infrastructural development in road networking system through the construction or reconstruction of multiple roads and highways. Consequently, there is a rise in traffic intensity on roads and highways, along with a significant contamination of adjacent agricultural soils with heavy metals. The purpose of this study was to evaluate the ecological risk, health risk and the abundance of seven heavy metals (Cu, Mn, Pb, Cd, Cr, As, and Ni) in three distance gradients (0, 300, and 500 m) of agricultural soil along the Dhaka-Chattogram highway. The concentration of heavy metals was measured with an Atomic Absorption Spectrophotometer (AAS) on a total of 36 soil samples that were taken from 12 different sampling sites. Based on the findings, Cd had a high contamination factor for all distance gradients, whereas Cr had a moderate contamination factor in 67% of the study areas. According to the Pollution Load Index (PLI), Cd, Cr, and Pb were the predominant pollutants. Principal component analysis (PCA) result shows these metals mainly came from anthropogenic sources. The considerable positive correlations between Cu-Pb, Cu-Cd, Pb-Cd, and Cr-Ni all pointed to shared anthropogenic origins. As per Potential Ecological Risk Assessment (PERI) analysis, Pb, Cd, Cr, and Ni each contribute significantly and pose a moderate threat. The Target Hazard Quotient (THQ) values for all pathways of exposure to Pb and Cr in soils were more than 1, which would pose a significant risk to human health in the following order: THQadult female > THQadult male > THQchildren. This study will help to evaluate the human health risk and develop a better understanding of the heavy metal abundance scenario in the agricultural fields adjacent to this highway.

Soil Quality Assessment of Different Land Use Types Based on TOPSIS Method in Hilly Sandy Area of Loess Plateau, Northern China

In order to combat land desertification and to evaluate the soil quality of different cover land types, and thereby determine the best land use strategy for vegetation restoration, this research comprehensively analyzed the soil quality of different land use/cover types in the hilly sandy area of the Loess Plateau by using the Kruskal-Wallis test (K-W test) and principal component analysis (PCA) technique for order preference by the similarity to ideal solution (TOPSIS), and the potential ecological risk index (RI). The result indicated that the cropland abandonment over a period of time could improve the soil quality to a certain extent; however, the process of natural restoration was very slow compared with that of the planted mixed shrubs. The soil quality of all land use/cover types in the hilly sandy area of Youyu County clearly improved after 10-25 years of revegetation, but the degree of improvement varied greatly with the different planted species and their combinations. The low levels of soil organic matter, total nitrogen and available phosphorus were the major limiting factors affecting soil quality improvement under different land use/cover types, not metal toxicity. Pioneer species of H. rhamnoide, C. korshinskii and Pinus sylvestris var. mongolica, etc. are vital to vegetation restoration of the study area. Revegetation using these species is therefore recommended to combat future desertification in this area.

Spatial distribution characteristics and evaluation of soil pollution in coal mine areas in Loess Plateau of northern Shaanxi

The ecological environment in Loess Plateau of Northern Shaanxi is fragile, so the soil pollution caused by the exploitation of coal resources cannot be ignored. With Shigetai Coal Mine in Loess Plateau of Northern Shaanxi as the object of study for field survey and sampling, the content of heavy metals in soil is analyzed, the environmental pollution in the research area is evaluated by the single factor pollution index method, comprehensive pollution index method and potential ecological risk index method, and the spatial distribution characteristics of heavy metals are discussed by the geostatistics method. According to the study results, the average contents of heavy metals Hg, Cd, Pb and Cr are 2.03, 1.36, 1.11 and 1.23 times of the soil background values in Shaanxi Province respectively and the average contents of other heavy metals are lower than the soil background values in Shaanxi Province; Hg and Cd show moderate variation while As, Pb, Cr, Zn, Ni and Cu show strong variation; the skewness coefficients and kurtosis coefficient of Cd, As and Cu in the soil within the research area are relatively high, and these elements are accumulated in large amounts. Single factor pollution index (Pi) and potential ecological risk index (E) indicate that heavy metal Hg is the main pollution factor and mainly distributed in the east and north of the research area. The comprehensive index of potential ecological risk (RI) of the research area is 1336.49, showing an extremely high ecological risk, and the distribution characteristics of potential ecological risk are consistent with that of potential ecological risk index (E) of Hg. The results of ecological risk warning show that Hg is in a slight warning status, while Cd, Pb and Cr are in a warning status. The areas with high ecological risk warning values are mainly distributed in the east and north, and the whole research area shows relatively obvious zonal distribution law. The soil is disturbed greatly during the coal mining, so the ecological governance of the mine area shall adapt to the local natural conditions and regional environmental characteristics and follow the principle of “adjusting governance measures based on specific local conditions and classifications”. An environmentally sustainable governance manner shall be adopted to realize the protection of the ecological environment and high-quality development of coal resources.

Multivariate geo-statistical perspective: evaluation of agricultural soil contaminated by industrial estate's effluents

Present study was carried out to explore heavy metals pollution and potential ecological risk factors associated with agriculture soil irrigated with industrial effluents of Hayatabad industrial estate, Peshawar (HIEP) and Gadoon industrial estate, Sawabi (GIES) of Khyber-Pakhtunkhwa, Pakistan through multivariate geo-statistical tools. Diverse statistical tools like cluster analysis (HC) and principal component analysis (PCA), along with geo-statistical approaches were applied to highlight the geogenic and anthropogenic sources of pollution. The results indicated that concentration of heavy metals in target areas was significantly higher than control. Both soils had significant to moderate enrichment of heavy metals, while Gadoon soil had moderate to considerable ecological risk factor. The geo accumulation indices (Igeo) tendency for heavy metals in both target soil (Gadoon and Hayatabad) were the same. The Pb concentration of both target areas falls in the extremely severely polluted category because of the excessive presence of industries producing lead-containing products. Hence, this study indicated that the majority of toxic heavy metals contributed to soil pollution in the studied areas are coming from industrial and commercial activities.

Effect of minerals and heavy metals in sand samples of Ponnai river, Tamil Nadu, India

River sand samples have been collected from Ponnai river, Tamil Nadu, India for characterization of minerals and heavy metals by different spectroscopic techniques. Initially, the samples were subjected by Fourier Transform-Infra Red (FT-IR) spectroscopic technique and infra-red absorption bands values are observed in the range of 515–520, 695–700, 775–780 cm⁻¹ which shows the presence of quartz in all the samples. Similarly, infra-red peaks were absorbed for feldspar, kaolinite, calcite, gibbsite and organic carbon and confirmed by X-Ray diffraction (XRD) technique. Additionally, zircon, aragonite, magnetite and kyanite minerals were identified in the samples using only the XRD method. The concentration of heavy metals such as Pb, Cr, Zn, Ni, Hg, As, Mn, Cu has been determined by flame atomic absorption spectrometry (FAAS). An average metal concentration measured in mg kg⁻¹ were: Pb 0.12, As 0.15, Hg 0.13, Cu 2.80, Zn 10.15 Cr 12.70, Ni 2.86 and Mn 104.94 and hence found in the order of Mn > Cr > Zn > Ni > Cu > As > Hg > Pb. These average values do not exceed the world average value and hence potentially do not affect the quality of sand in the river. In addition to that, presences of heavy metals are confirmed by scanning electron microscope equipped with energy dispersive X-ray spectrometry (SEM/EDS) analysis. In order to understand the possible natural and anthropogenic sources of heavy metals, multivariate statistical techniques such as Pearson correlation, principal component and cluster analysis were performed. Results obtained from the statistical techniques were good agreement with each other.

Identifying Influencing Factors of Agricultural Soil Heavy Metals Using a Geographical Detector: A Case Study in Shunyi District, China

Identifying influencing factors of heavy metals is essential for soil evaluation and protection. This study investigates the use of a geographical detector to identify influencing factors of agricultural soil heavy metals from natural and anthropogenic aspects. We focused on six variables of soil heavy metals, i.e., As, Cd, Hg, Cu, Pb, Zn, and four influencing factors, i.e., soil properties (soil type and soil texture), digital elevation model (DEM), land use, and annual deposition fluxes. Experiments were conducted in Shunyi District, China. We studied the spatial correlations between variables of soil heavy metals and influencing factors at both single-object and multi-object levels. A geographical detector was directly used at the single-object level, while principal component analysis (PCA) and geographical detector were sequentially integrated at the multi-object level to identify influencing factors of heavy metals. Results showed that the concentrations of Cd, Cu, and Zn were mainly influenced by DEM (p = 0.008) and land use (p = 0.033) factors, while annual deposition fluxes were the main factors of the concentrations of Hg, Cd, and Pb (p = 0.000). Moreover, the concentration of As was primarily influenced by soil properties (p = 0.026), DEM (p = 0.000), and annual deposition flux (p = 0.000). The multi-object identification results between heavy metals and influencing factors included single object identification in this study. Compared with the results using the PCA and correlation analysis (CA) methods, the identification method developed at different levels can identify much more influencing factors of heavy metals. Due to its promising performance, identification at different levels can be widely employed for soil protection and pollution restoration.

Effectiveness of naturally occurring Aphis gossypii on tomato plants as a bio-indicator for heavy metals in Riyadh and Hafar Al-Batin, Saudi Arabia

Although certain pollutants can be biologically degraded by microorganisms, rendering their impact short-term, others can not be impaired, such that their effect persists. The present study evaluates the effectiveness of using a field-collected aphid, Aphis gossypii, as a bio-indicator for heavy metals in tomato farms in Riyadh and Hafar Al-Batin, Saudi Arabia. Heavy metals were selected (Cd, Cu, Zn, and Pb) and measured for comparative screening in field-collected plants, soil, and aphids using inductively coupled plasma-mass spectrometry (ICP-MS). Field-collected aphids from both studied regions were identified as Aphis gossypii. In Riyadh, there was no significant difference observed for Cd, Cu, and Zn for all experimental samples, while, Pb was showed differences among samples especially tomato leaves None of the studied samples in Hafar Al-Batin were showed statistically significant differences in Cd, in reverse to significant differences in the other heavy metals. Comparing concentrations of selected heavy metals between the two studied regions was showed that neither region showed a significant difference in heavy metals except for Cu. This study demonstrates that tomato leaf samples showed the highest concentrations of most studied heavy metals, followed by soil, then aphids. Aphids were utilized as a bio-indicator of heavy metals in the studied regions.

Are heavy metals in urban garden soils linked to vulnerable populations? A case study from Guelph, Canada

With increasing population, there is growing concern for food security in urban areas. Though, urban gardening has gained popularity, several studies have found higher concentrations of contaminants in urban soils, especially heavy metals, often at toxic levels, which pose a potential risk for human health. Moreover, heavy metal polluted sites have been strongly associated with areas populated by low-income families, newcomers and racial minorities. In this study, heavy metals in the soils of community gardens in the city of Guelph, ON were examined as a case study and their relationship with vulnerable populations. We analyzed soil samples at two depths for a range of heavy metals and characterized their spatial patterns to see if they were related to disadvantaged communities. We estimated the pollution levels using two index-based approaches and assessed their potential risk for human health, although concentrations of most heavy metals were below the limits established by Canadian regulations, metals like Cd, Pb, Se and Zn exhibited a mild degree of pollution, whereas As exhibited a severe degree. Their association with vulnerable populations were weak, but hotspots were mainly located in low-income areas. This case study provides scientific evidence that could help to expand our understanding around the interconnection between pollution and poverty/racial inequality. Also the importance of generating strategies for the protection of human health and sustainable soil management practices in urban areas where food for human consumption is grown.

Contamination assessment and source apportionment of heavy metals in agricultural soil through the synthesis of PMF and GeogDetector models

Heavy metal pollution in soils has attracted great attention worldwide in recent decades. Selecting Hangzhou as a case study location, this research proposed the synthesis application of positive matrix factorization (PMF) and GeogDetector models for quantitative analysis of pollution sources, which is the basis for subsequent soil pollution prevention and remediation. In total, 2150 surface soil samples were collected across the study area. Although the mean concentrations of As, Cd, Cr, Hg, and Pb in the soils were lower than the National Environmental Quality Standards for Soils in China, the mean contents of As and Cd were higher than their corresponding local background values by approximately 1.31 and 1.59 times, respectively, indicating that heavy metals have been enriched in topsoil. Agricultural activities, industrial activities, and soil parent materials were the main sources of heavy metal pollution in the soils, accounting for 63.4%, 19.8%, and 16.8% of the total heavy metal accumulation, respectively. Cr was derived mainly from soil parent materials (80.72%). Cd was closely associated with agricultural activities (73.68%), such as sewage irrigation and application of fertilizer. Mercury was mainly attributed to industrial activities (92.38%), such as coal mining and smelting. As was related to agricultural (57.83%) and natural (35.56%) sources, and Pb was associated with industrial (42.42%) and natural (41.83%) sources. The new synthesis models are useful for estimating the source apportionment of heavy metals in soils.

Concentration, Spatial Distribution, Contamination Degree and Human Health Risk Assessment of Heavy Metals in Urban Soils across China between 2003 and 2019-A Systematic Review

This study provides an overview of the studies of heavy metal pollution regarding As, Cd, Cr, Hg, Pb, Cu, Zn and Ni in the urban soils throughout 71 cities of China, based on data from online literature, during the period 2003-2019. The concentrations, spatial distributions, contamination degrees and health risks of heavy metals in the urban soils were evaluated. The results demonstrated that the mean values of eight heavy metals all exceeded the soil background values in China, and the kriging interpolation method showed that the hot-spot cities with heavy metal contamination in urban soils were mainly concentrated in the southwest, southcentral, southeast coast, northcentral and northwest regions of China. The geoaccumulation index (Igeo) indicated that Hg and Cd were at moderate contamination levels and that the levels of the other six metals did not appear contamination. The pollution index (PI) showed that Cd and Hg reached high contamination levels, and the other metals reached moderate contamination levels. The integrated pollution index (IPI) and potential ecological risk index (PRI) indicated that the integral urban soils in the study areas ranked high contamination levels and moderate ecological risk degree, respectively, and Cd and Hg should be labeled as priority metals for control in the urban soils around China. The human health risk assessments for the heavy metals indicated that ingestion was the dominant exposure pathway for having adverse effects on human health. The mean Hazard index (HI) values of eight heavy metals all showed that adverse effects on human health were unlikely, and the mean carcinogenic (CR) values of As, Cr and Ni for children and adults all suggested an acceptable carcinogenic risk to human beings. In addition, children exposed to these heavy metals faced more serious non-carcinogenic and carcinogenic health threats compared to adults. The results could provide valuable information for demanding the better control of heavy metal pollution and mitigation of the adverse effects on residents by environmental regulators in national urban regions.

A partition computing-based positive matrix factorization (PC-PMF) approach for the source apportionment of agricultural soil heavy metal contents and associated health risks

Apportion soil heavy metal sources across large-scale regions is a challenging task. The present study developed a modified receptor model to estimate the contributions of various sources to soil heavy metals and the associated health risks at a large scale. A positive matrix factorization model based on a partition computing approach was employed; the entire study area was divided into several zones for the source apportionment and then calculated together, termed partition computing-PMF (PC-PMF). The agricultural soil in Tianjin, China, was chosen for the case study. The PC-PMF results showed that irrigation, atmospheric deposition and sludge application were the main anthropogenic sources, with contributions of 26.60 %, 19.56 % and 2.86 %, respectively. We subsequently combined PC-PMF with a human health risk assessment model (HHRA) to obtain the human health risk of every source category. The natural background was regarded as a major factor influencing human health in the study area, with contributions of 38.03 % for the noncarcinogenic risk and 28.68 % for the carcinogenic risk. The results indicated that PC-PMF performed better at the source apportionment of soil heavy metals than PMF. This study provides a good example of how the spatial variability can be utilized to reduce the uncertainty in source apportionment.

A critical prospective analysis of the potential toxicity of trace element regulation limits in soils worldwide: Are they protective concerning health risk assessment? - A review

Trace elements (TEs) may have toxic effects to plants and humans; thus, countries and organizations impose maximum allowable regulation limits of their concentrations in soils. Usually such limits are placed in different categories according to soil use, soil properties or based on both attributes. However, some countries have regulation limits irrespective of differentiation in soil properties. In this review, we aimed at collecting TE regulation limits in soils from major countries and organizations around the globe, and critiquing them by assessing potential human health risks in the case of soils attaining the maximum allowable values. We explored the soil-to-human pathway and differentiated among three major exposures from TEs, i.e., residential, industrial and agricultural. We observed the existence of problems concerning TE regulation limits, among which the fact that limits across countries do not regulate the same TEs, not even a minimum number of TEs. This indicates that countries do not seem to agree on which regulation limits of TEs pose a high risk. Also, these regulation limits do not take into account TE mobility to neighbouring environment interphases such as plant, especially edible, and water matrices. Moreover, limits for same TEs are vastly diverse across countries; this indicates that those countries have conflicting information concerning TE-related health risks. Subsequently, we addressed this problem of diversity by quantifying resultant risks; we did that by calculating human health risk indices, taking into consideration the cases in which the highest allowable TE limits are attained in soil. Arsenic limits were found to generate a relatively high hazard quotient (HQ_i, accounting for human intake over the maximum allowable oral reference dose for that same TE), indicating that its risk tends to be underestimated. Other TE limits, such as those of Cd, Cu, Ni, Pb, and Zn typically result in low HQ_i, meaning that limits in their cases are rather overprotective. Our approach reveals the need of reducing diversity in regulation limits by drafting soil legislations of worldwide validity, since risks are common across countries. We suggest that new directions should strategically tend to (a) reduce limits of TEs with underestimated contribution to health risk (such as As), (b) cautiously increase limits of TEs that currently cause minor health risks, (c) quantify TE risks associated with uptake to edible plants and potable water, and (d) consider multi-element contamination cases, where risks are cumulatively enhanced due to TE synergism.

The association between heavy metal soil pollution and stomach cancer: a case study in Hangzhou City, China

Stomach cancer (SC) is a severe health burden, with nearly half of the world's cases found in China. Noticeably, the emissions of heavy metals into the environment have increased alongside rapid urbanization and industrialization in China. However, as regards carcinogenic associations, the relationship between heavy metals and SC is yet unclear. Based on 9378 newly diagnosed SC cases in Hangzhou City from 2009 to 2012, this work is concerned with the quantitative characterization of the spatial distribution pattern of SC incidence and its geographical association with soil heavy metals by means of a novel geographical model. The results show that (a) Cd is one of the severe soil pollutants in Hangzhou; (b) higher SC incidence clusters are in central Hangzhou, whereas lower clusters are found in the northeast and southwest with a male to female incidence ratio about 2.2:1; (c) although when considered separately, the heavy metals in this work do not have a considerable impact on the distribution of SC incidence in Hangzhou City, nevertheless, the joint effects of multiple heavy metals have significant impacts on SC risk. The present work calls for a rigorous quantitative assessment of the integrated heavy metal soil pollution and its effects on SC incidence.

Distribution of Arsenic and Risk Assessment of Activities on Soccer Pitches Irrigated with Arsenic-Contaminated Water

The aim of this research was to estimate the risk of human exposure to arsenic due to sporting activities in a private soccer club in Mexico, where arsenic-contaminated water was regularly used for irrigation. For this purpose, the total concentration in the topsoil was considered for risk assessment. This was accomplished through three main objectives: (1) measuring arsenic concentrations in irrigation water and irrigated soils, (2) determining arsenic spatial distribution in shallow soils with Geographical Information Systems (GIS) using geostatistical analysis, and (3) collecting field and survey data to develop a risk assessment calculation for soccer activities in the soccer club. The results showed that the average arsenic concentrations in shallow soils (138.1 mg/kg) were 6.2 times higher than the Mexican threshold for domestic soils (22 mg/kg). Furthermore, dermal contact between exposed users and contaminated soils accounted for a maximum carcinogenic risk value of 1.8 × 10⁻⁵, which is one order of magnitude higher than the recommended risk value, while arsenic concentrations in the irrigation water were higher (6 mg/L) than the WHO’s permissible threshold in drinking water, explaining the contamination of soils after irrigation. To the best of our knowledge, this is the first risk study regarding dermal contact with arsenic following regular grass irrigation with contaminated water in soccer pitches.

Application of a combined approach including contamination indexes, geographic information system and multivariate statistical models in levels, distribution and sources study of metals in soils in Northern China

The purpose of this study is to recognize the contamination characteristics of trace metals in soils and apportion their potential sources in Northern China to provide a scientific basis for basic of soil environment management and pollution control. The data set of metals for 12 elements in surface soil samples was collected. The enrichment factor and geoaccumulation index were used to identify the general geochemical characteristics of trace metals in soils. The UNMIX and positive matrix factorizations (PMF) models were comparatively applied to apportion their potential sources. Furthermore, geostatistical tools were used to study the spatial distribution of pollution characteristics and to identify the affected regions of sources that were derived from apportionment models. The soils were contaminated by Cd, Hg, Pb and Zn to varying degree. Industrial activities, agricultural activities and natural sources were identified as the potential sources determining the contents of trace metals in soils with contributions of 24.8%-24.9%, 33.3%-37.2% and 38.0%-41.8%, respectively. The slightly different results obtained from UNMIX and PMF might be caused by the estimations of uncertainty and different algorithms within the models.

Cadmium-Induced Oxidative Stress Impairs Glycemic Control in Adolescents

Experimental evidence suggests that cadmium (Cd) boosts oxidative stress that may result in toxicity on the endocrine system also in humans. The aim of this study was to investigate the glycemic control and oxidative stress markers in male adolescents with increased urinary levels of cadmium. We investigated 111 males, aged 12–14 years, living in a polluted area of Sicily and a control age-matched population (n = 60) living 28–45 km far from the polluted site. Malondialdehyde (MDA), total antioxidant activity (TAC), metallothionein-1A (MT-1A) gene expression, insulin resistance by the homeostatic model assessment (HOMA-IR), and urinary cadmium were investigated. Cd levels were significantly higher in adolescents living in the polluted area than in control age-matched subjects. Adolescents with elevated Cd levels had a significant increase in MDA, MT-1A, and HOMA-IR and reduced TAC compared to the control group. A robust correlation was found between urinary cadmium and MT-1A, HOMA-IR, and MDA whereas an inverse correlation was identified between urinary cadmium and TAC. This study indicates that cadmium burden alters glycemic control in adolescents and suggests that oxidative stress plays a key role in cadmium-induced insulin resistance, increasing the risk of developing metabolic disorders.

Multivariate statistical and GIS-based approaches for toxic metals in tropical mangrove ecosystem, southeast coast of India

The heavy metal concentrations in water and sediment samples were investigated in the tropical Muthupet mangrove ecosystem, southeast coast of India. The results demonstrated that, ranges of metals in water comprise of Cd-0.05 to 3.72; Cu-0.5 to 4.43; Pb-6.31 to 17.87; Zn-0.0 to12.91 ppm and sediment comprises of Cd-0.06 to 0.57; Cu-4.46 to 20.59; Pb-2.90 to 21.35; Zn-4.41 to 39.18 ppm. In all the three sites, heavy metals in sediment exhibited significant higher concentrations compared to water, except Cd. The spatial distribution of metals in water and sediment samples followed a similar pattern except Cd with the preponderance of Zn (75% of total metals) followed by Cu and Pb. Muller's Geoaccumulation indexes (Igeo) showed Cd is a potent pollutant in the ecosystem and moderately contaminated the study area. The aquaculture and agricultural culture practices follow improper disposal of municipal wastages, and idol immersion activities are the potent metallic sources for heavy metal pollution were identified by performing principle component analysis. In order to protect the ecosystem from further contamination, regular monitoring is needed to in order to control the anthropogenic discharges. Graphical abstract.

Heavy Metal Contamination in Soil and Brown Rice and Human Health Risk Assessment near Three Mining Areas in Central China

BACKGROUND

Metal mining and waste discharge lead to regional heavy metal contamination and attract major concern because of the potential risk to local residents.

METHODS

This research was conducted to determine lead (Pb), cadmium (Cd), arsenic (As), manganese (Mn), and antimony (Sb) concentrations in soil and brown rice samples from three heavy metal mining areas in Hunan Province, central China, and to assess the potential health risks to local inhabitants.

RESULTS

Local soil contamination was observed, with mean concentrations of Cd, Pb, Sb, and As of 0.472, 193.133, 36.793, and 89.029 mg/kg, respectively. Mean concentrations of Cd, Pb, Sb, Mn, and As in brown rice were 0.103, 0.131, 5.175, 6.007, and 0.524 mg/kg, respectively. Daily intakes of Cd, As, Sb, Pb, and Mn through brown rice consumption were estimated to be 0.011, 0.0002, 0.004, 0.0001, and 0.0003 mg/(kg/day), respectively. The combined hazard index for the five heavy metals was 22.5917, and the total cancer risk was 0.1773. Cd contributed most significantly to cancer risk, accounting for approximately 99.77% of this risk.

CONCLUSIONS

The results show that potential noncarcinogenic and carcinogenic health risks exist for local inhabitants and that regular monitoring of pollution to protect human health is urgently required.

Assessment of Heavy Metal Pollution in Topsoil around Beijing Metropolis

The topsoil around Beijing metropolis, China, is experiencing impacts of rapid urbanization, intensive farming, and extensive industrial emissions. We analyzed the concentrations of Cu, Ni, Pb, Zn, Cd, and Cr from 87 topsoil samples in the pre-rainy season and 115 samples in the post-rainy season. These samples were attributed to nine land use types: forest, grass, shrub, orchard, wheat, cotton, spring maize, summer maize, and mixed farmland. The pollution index (PI) of heavy metals was calculated from the measured and background concentrations. The ecological risk index (RI) was assessed based on the PI values and toxic-response parameters. The results showed that the mean PI values of Pb, Cr, and Cd were > 1 while those of Cu, Ni, and Zn were < 1. All the samples had low ecological risk for Cu, Ni, Pb, Zn, and Cr while only 15.35% of samples had low ecological risk for Cd. Atmospheric transport rather than land use factors best explained the seasonal variations in heavy metal concentrations and the impact of atmospheric transport on heavy metal concentrations varied according to the heavy metal types. The concentrations of Cu, Cd, and Cr decreased from the pre- to post-rainy season, while those of Ni, Pb, and Zn increased during this period. Future research should be focused on the underlying atmospheric processes that lead to these spatial and seasonal variations in heavy metals. The policymaking on environmental management should pay close attention to potential ecological risks of Cd as well as identifying the transport pathways of different heavy metals.

Distribution and assessment of heavy metals in the surface sediment of Yellow River, China

Large amounts of heavy metals discharged by industrial cities that are located along the middle reach of Yellow River, China have detrimental impacts on both the ecological environment and human health. In this study, fourteen surface sediment samples were taken in the middle reach of the Yellow River. Contents of Zn, Pb, Ni, Cu, Cr, Cd, As were measured, and the pollution status was assessed using three widely used pollution assessment methods, including the single factor index method, Nemerow pollution index method and potential ecological risk index. The concentrations of the studied heavy metals followed the order: Zn>Cr>Cu>Ni>Pb>As>Cd. Nearly 50% of sites had Cu and Cr accumulation. The concentration of Cu at the Yiluo River exceeded the secondary standard value of the Environmental quality standard for soils. Comparison of heavy metal concentrations between this study and other selected rivers indicated that Cu and Cr may be the major pollutants in our case. The single factor index indicated that many samples were at high levels of pollution for Cu and Cd; the Nemerow pollution index indicated that the Yihe River, Luohe River, Yiluo River and Huayuankou were polluted. According to the results of potential ecological risk assessment, Cd in the tributaries of Luo River, Yihe River, and Yiluo River showed high risk toward the ecosystem and human health, Cd in Huanyuankou and Cu in Yiluo River showed a middle level of risk and other samples were at a low level of risk.

Use of statistical and GIS techniques to assess and predict concentrations of heavy metals in soils of Lahore City, Pakistan

Soils from different land use areas in Lahore City, Pakistan, were analyzed for concentrations of heavy metals-cadmium (Cd), chromium (Cr), nickel (Ni), and lead (Pb). One hundred one samples were randomly collected from six land use areas categorized as park, commercial, agricultural, residential, urban, and industrial. Each sample was analyzed in the laboratory with the tri-acid digestion method. Metal concentrations in each sample were obtained with the use of an atomic absorption spectrophotometer. The statistical techniques of analysis of variance, correlation analysis, and cluster analysis were used to analyze all data. In addition, kriging, a geostatistical procedure supported by ArcGIS, was used to model and predict the spatial concentrations of the four heavy metals-Cd, Cr, Ni, and Pb. The results demonstrated significant correlation among the heavy metals in the urban and industrial areas. The dendogram, and the results associated with the cluster analysis, indicated that the agricultural, commercial, and park areas had high concentrations of Cr, Ni, and Pb. High concentrations of Cd and Ni were also observed in the residential and industrial areas, respectively. The maximum concentrations of both Cd and Pb exceeded world toxic limit values. The kriging method demonstrated increasing spatial diffusion of both Cd and Pb concentrations throughout and beyond the Lahore City area.

Cadmium delays puberty onset and testis growth in adolescents

OBJECTIVE

Cadmium (Cd) has been shown to impair pubertal development in experimental animals. However, no data are available for male adolescents with increased urinary cadmium levels.

DESIGN

The aim of this cross-sectional study was to evaluate pubertal onset and pituitary-gonadal axis hormones in male adolescents with increased urinary levels of Cd.

SUBJECTS

We studied 111 males, aged 12-14 years living in the Milazzo-Valle del Mela area. A control age-matched population (n = 60) living 28-45 km far from the industrial site was also enrolled.

MEASUREMENTS

Pubertal stages were assessed by clinical examination according to Tanner's score. Mean testicular volume was also investigated by ultrasound examination. Urinary Cd concentration and blood levels of FSH, LH, testosterone and inhibin B were also investigated.

RESULTS

Cd levels were significantly higher in adolescents living in the Milazzo-Valle del Mela area, compared to both age-matched subjects living far from the industrial plants and the reference values. Our population showed also a delayed onset of puberty, a smaller testicular volume and lower testosterone levels. An inverse correlation was found between urinary Cd and testicular volume (r = -0·25; P = 0·0008), testosterone levels (Spearman's r = -0·0·37; two-tailed P < 0·0001) and LH levels (Spearman's r = 0·048; P < 0·05). Testosterone levels were positively correlated with testicular volume (Spearman's r = 0·48; P < 0·0001).

CONCLUSIONS

This study, for the first time, suggests that increased Cd burden is associated with delayed onset of puberty in male adolescents and impaired testicular growth.

Application of sewage sludge and sewage sludge biochar to reduce polycyclic aromatic hydrocarbons (PAH) and potentially toxic elements (PTE) accumulation in tomato

The effects of sewage sludge (SS) and its derived biochar (SSBC) on the availability and uptake of polycyclic aromatic hydrocarbons (PAHs) and potential toxic elements (PTEs) by Solanum lycopersicum (tomato) fruits grown in contaminated urban soil were investigated. Increasing application rates of SS and SSBC (2, 5, and 10%) decreased PAH availability and, correspondingly, PAH accumulation (22-39 and 48-62%, respectively) into tomato. SSBC was more effective in this regard. The available concentrations of PAHs (Σ16PAH) in the SSBC treatments were significantly reduced (from 30.0-47.3%) as compared to the control treatment. The availability of high-molecular-weight PAHs (containing four to six benzene rings) was greatly affected, while low-molecular-weight PAHs (containing two to three benzene rings) was less affected by SSBC amendments. The addition of SSBC showed the least effect on bioaccumulation of naphthalene (two-ring PAH; 24.5-32.6%), while the highest effect was observed for benzo(b)fluoranthene (five-ring PAH; 3.1-86.8%) and benzo(g,h,i)perylene (six-ring PAH; 51.8-84.2%). In contrast, increasing application rates of SS successively increased PTE (As, Cd, Cu, Pb, and Zn) availability and accumulation (15-139%) into tomato while SSBC successively decreased PTE availability and accumulation (17-91%). Changes in accumulation varied with PTE and the extent to which PTE concentrations in soil was elevated.

Contaminants in surface water and sediments near the Tynagh silver mine site, County Galway, Ireland

A former silver mine in Tynagh, Co. Galway, Ireland is one of the most contaminated mine sites in Europe with maximum concentrations of Zn, As, Pb, Mn, Ni, Cu, and Cd far exceeding guideline values for water and sediment. The aims of this research were to 1) further assess the contamination, particularly metals, in surface water and sediment around the site, and 2) determine if the contamination has increased 10 years after the Environmental Protection Agency Ireland (EPAI) identified off-site contamination. Site pH is alkaline to neutral because CaCO3-rich sediment and rock material buffer the exposed acid generating sulphide-rich ore. When this study was compared to the previous EPAI study conducted 10 years earlier, it appeared that further weathering of exposed surface sediment had increased concentrations of As and other potentially toxic elements. Water samples from the tailings ponds and adjacent Barnacullia Stream had concentrations of Al, Cd, Mn, Zn and Pb above guideline values. Lead and Zn concentrations from the tailings pond sediment were 16 and 5 times higher, respectively, than concentrations reported 10 years earlier. Pb and Zn levels in most sediment samples exceeded the Expert Group (EGS) guidelines of 1000 and 5000 mg/kg, respectively. Arsenic concentrations were as high as 6238 mg/kg in the tailings ponds sediment, which is 62 and 862 times greater than the EGS and Canadian Soil Quality Guidelines (CSQG), respectively. Cadmium, Cu, Fe, Mn, Pb and Zn concentrations in water and sediment were above guideline values downstream of the site. Additionally, Fe, Mn and organic matter (OM) were strongly correlated and correlated to Zn, Pb, As, Cd, Cu and Ni in stream sediment. Therefore, the nearby Barnacullia Stream is also a significant pathway for contaminant transport to downstream areas. Further rehabilitation of the site may decrease the contamination around the area.

Assessment of heavy metal contents in surface soil in the Lhasa-Shigatse-Nam Co area of the Tibetan Plateau, China

Eight important heavy metals (As, Cr, Cu, Ni, Pb, Zn, Mn, and Hg) were investigated in surface soil samples collected from the Lhasa-Shigatse-Nam Co region, Tibetan Plateau, China. The mean contents of As, Cr, Cu, Ni, Pb, Zn, Mn, and Hg in the samples were 39.5, 57.4, 28.5, 48.2, 15.7, 79.2, 637 and 0.0175 mg/kg, respectively. All metals were divided into three clusters by cluster analysis. The results of geoaccumulation index indicated that no samples were polluted by Cr, Pb, Zn, and Mn, and samples were polluted with As, Cu, Ni, and Hg to different degrees. All surface soils had a low ecological risk with potential ecological risk index below 150, indicating a low ecological risk. As, Pb, and Hg were the primary contributors to potential ecological risk.

Distribution of arsenic and risk assessment of activities on a golf course fertilised with arsenic-containing Ascophyllum nodosum seaweed

The use of seaweed fertilisers in sports green maintenance has become a common practice across the globe due to its image as an "eco-friendly" alternative to chemical fertilisers. The aim of this study was to characterise the risk of human exposure to arsenic (As), via dermal absorption, from golfing activities on a private golf course in the UK, where As contaminated seaweed fertiliser (~100mg/kg d.wt.) is applied. This was fulfilled by, 1) determining As concentrations in shallow soils with GIS geo-statistical analysis, 2) measuring As concentrations from an on-site borehole groundwater well, and (3) developing a risk assessment calculation for golfing activities based on field and questionnaire data. Total As concentrations in shallow soils were less than the UK threshold for domestic soils, however, frequent and sustained dermal contact between site-users and surface soil attributed to a maximum carcinogenic risk value of 2.75×10(-4), which is in the upper limit of the acceptable risk range. Arsenic concentrations in underlying groundwater exceeded the WHO's permissible drinking water standard, demonstrating the risk of groundwater contamination following the application of seaweed fertiliser to golf course soils. This is the first risk study on dermal As absorption via the application of a seaweed fertiliser.

Oxidative stress and DNA repair and detoxification gene expression in adolescents exposed to heavy metals living in the Milazzo-Valle del Mela area (Sicily, Italy)

BACKGROUND

The area of Milazzo-Valle del Mela (Sicily, Italy) is considered at high risk of environmental crisis by regional authorities.

OBJECTIVE

To measure oxidative-stress, DNA repair and detoxification genes in school children living near the industrial area and in age-matched controls.

METHODS

The parent study was a biomonitoring investigation evaluating heavy metal urine levels in 226 children aged 12-14 years, living in the high risk area, and in 29 age-matched controls living 45 km far from the industrial site. In the present study 67 exposed adolescents and 29 controls were included. Samples were analyzed for urinary 8-hydroxydeoxyguanosine (8OHdG) levels, and gene expression of OGG1 (DNA repair gene), NQO1, ST13, and MT1A (detoxifying genes).

RESULTS

Urinary cadmium was higher (p = 0.0004) in exposed [geometric mean, 0.46 µg/L; 25th-75th percentile: 0.3-0.56] than in control adolescents [geometric mean, 0.26 µg/L; 25th-75th percentile: 0.2-0.3]. Chromium was also significantly elevated in exposed [geometric mean, 1.52 µg/L; 25th-75th percentile: 1.19-1.93] compared with controls [geometric mean, 1.25 µg/L; 25th-75th percentile: 1.05-1.48; p = 0.02]. Urinary 8-OHdG concentration was greater in exposed than in controls (71.49 vs 61.87 µg/L, p = 0.02), and it was correlated with cadmium levels (r = 0.46, p < 0.0001), and with the combined exposure index (r = 0.43, p < 0.0001). Moreover, cadmium levels showed a robust correlation with OGG1 and MT1A gene expression levels (r = 0.44, p < 0.0001; r = 0.39, p < 0.0001, respectively). Finally, OGG1 and MT1A were over-expressed in adolescents from Milazzo-Valle del Mela area compared with controls (p = 0.0004; p < 0.0001, respectively).

CONCLUSIONS

Continuous exposure at relatively low concentrations of heavy metals is associated with increased oxidative DNA damage and impaired expression of DNA repair and detoxification genes in adolescents.

Potential ecological risk of heavy metals and metalloid in the sediments of Wuyuer River basin, Heilongjiang Province, China

The spatial distribution, sources, and potential ecological risk of heavy metals and metalloid were evaluated in sediments of the Wuyuer River and its tributaries. Metal and metalloid concentrations and chemical speciation (Cr, Cu, Ni, Pb, Cd, As, Zn and Hg) in 187 surface sediment samples were measured using inductively coupled plasma mass spectrometry. Metals and metalloid in the sediments of the Wuyuer River were greater than the background values of the Songnen Plain, and mean heavy metal concentrations were greater in downstream segments of the river than in upstream segments. Speciation results indicated that Cd was chemically mobile and Cu, Pb, Zn, Cr, and Ni were potentially bioavailable. Mercury and As existed mainly in the residual fraction. Hakanson's potential risk index indicated that the total potential ecological risk of these elements was moderate in the Wuyuer River. Among the selected metals and metalloid, Hg and Cd were the most potentially toxic and mainly distributed near the cities of Keshan, Yi'an and Fuyü. Because the speciation of Cd in the river sediments is highly bioavailable, the concentrations of Cd should be closely monitored. This research provides managers with information needed to better regulate the environment of the Wuyuer River.

Multivariate-statistical assessment of heavy metals for agricultural soils in northern China

The study evaluated eight heavy metals content and soil pollution from agricultural soils in northern China. Multivariate and geostatistical analysis approaches were used to determine the anthropogenic and natural contribution of soil heavy metal concentrations. Single pollution index and integrated pollution index could be used to evaluate soil heavy metal risk. The results show that the first factor explains 27.3% of the eight soil heavy metals with strong positive loadings on Cu, Zn, and Cd, which indicates that Cu, Zn, and Cd are associated with and controlled by anthropic activities. The average value of heavy metal is lower than the second grade standard values of soil environmental quality standards in China. Single pollution index is lower than 1, and the Nemerow integrated pollution index is 0.305, which means that study area has not been polluted. The semivariograms of soil heavy metal single pollution index fitted spherical and exponential models. The variable ratio of single pollution index showed moderately spatial dependence. Heavy metal contents showed relative safety in the study area.

Trace metals content in soils along the state road 51 (northeastern Poland)

The aim of the study was to determine concentrations of some trace elements (lead, cadmium, chromium, and nickel) in soils along State Road 51 leading from Olsztyn to Olsztynek, northeastern Poland. The traffic flow had a significant effect on the content of heavy metals in soils lying along the road. Further away from the road, and under a lower traffic flow intensity, the amounts of contaminants originating from the motor traffic decreased. There was a pine forest growing by the road near Olsztyn, which served as a buffer zone for all the analyzed heavy metals. At all the sampling locations, the content of chromium was approximately the same as its natural concentration. The statistical analysis demonstrated that there was a strong negative correlation between the concentrations of nickel, lead, chromium, and cadmium in soils and the distance from the road. The biggest differences in the content of an individual element were determined for lead and the smallest ones--for cadmium. Emissions of trace elements depended on the differences in the traffic flow intensity, number, type, and speed of vehicles and on the atmospheric conditions as well as the distribution of buildings.

Potential health risks of heavy metals in cultivated topsoil and grain, including correlations with human primary liver, lung and gastric cancer, in Anhui province, Eastern China

Environmental exposure to heavy metals is a well-known risk factor for cancers. To evaluate potential health risks of heavy metals (Cr, Cd, Pb, As and Hg) and Se in cultivated topsoil and grains, we investigated the concentrations of Hg, As and Se using atomic fluorescence spectrometry and Cr, Cd and Pb using inductive coupled plasma emission spectrometry (ICP-MS). We also analyzed human cancer tissues for heavy metals. Potential health risks for local residents were evaluated by calculating the hazard index (HI) and the total carcinogenic risk (TCR) for soil heavy metals and the target hazard quotient (THQ) and the carcinogenic risk (CR) for grain heavy metals. A bioconcentration factor (BCF) was applied to quantify the bioaccumulation of heavy metals. Our results demonstrated that the mean concentrations of heavy metals in soil were all within the safety limits set by FAO/WHO and Chinese regulations; however, the mean concentrations of Cr and Hg in grain exceeded the safety limits. HI and TCR for soil heavy metals were all within acceptable levels, but the THQ for four grain heavy metals exceeded the target value of 1 (Cr, 2.64; Pb, 1.41; As, 1.24; Hg, 1.07; Cd, 0.39). The grain CR for Cr, Pb and As exceeded the accepted risk level of 10(-6). BCF values indicated that the bioaccumulation capacity decreased in the following sequence: Hg>Se>Cd>Cr>Pb>As. We also observed statistically significant correlations of topsoil Pb concentration with human gastric cancer and grain Hg with human liver cancer. Therefore, long-term low dose exposure of heavy metals may play a key role in tumorigenesis, and it may not be necessary to accumulate a high concentration of heavy metals in the human body for those metals to induce tumorigenesis.

Effect of long-term human exposure to environmental heavy metals on the expression of detoxification and DNA repair genes

The present study was designed to evaluate the influence of long-term environmental human exposure to three heavy metals, lead (Pb), cadmium (Cd), and mercury (Hg), on the expression of detoxifying, xenobiotic metabolizing, and DNA repair genes in Mahd Ad-Dahab city. The study groups consisted of 40 healthy male residents (heavy metal-exposed) and 20 healthy male from Riyadh city, 700 km away, and served as control group. The heavy metal-exposed group with high exposure to Pb, Cd, or Hg was divided into three subgroups Pb-, Cd-, and Hg-exposed groups, respectively. The mRNA expression levels of detoxifying, NQO1, HO-1, GSTA1, MT-1, and HSP70, were significantly decreased in all heavy metal-exposed group as compared to control group. This was accompanied with a proportional decrease in the expression of xenobiotic metabolizing gene, cytochrome P4501A1. On the other hand, the DNA repair gene OGG1 and the 8-OHdG level were dramatically inhibited in Cd-exposed group only.

Assessing the combined risks of PAHs and metals in urban soils by urbanization indicators

We quantitatively describe the impacts of urbanization on the accumulation of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in urban soils as well as their health risks to residents. Residential building age, population density, road density, and distance from urban center were used as urbanization level indicators. Significant correlations were found between those urbanization indicators and the amounts of PAHs, Cu, Cd, Pb, Zn and As in residential soils. The exposure time of soils to urban air was the primary factor affecting soil pollution, followed by local road density and population density. Factor analysis suggested that 59.0% of the elevated pollutant concentrations were caused by citywide uniform deposition, and 15.3% were resulted from short-range deposition and/or non-combustion processes. The combined health risks posed by soil PAHs and HMs were aggravated with time and can be expressed as functions of residence age, road density, and other urbanization indicators.

Comparison of human exposure pathways in an urban brownfield: reduced risk from paving roads

Risk assessments often do not quantify the risk associated with soil inhalation. This pathway generally makes a negligible contribution to the cumulative risk, because soil ingestion is typically the dominant exposure pathway. Conditions in northern or rural centers in Canada characterized by large areas of exposed soil, including unpaved roads, favor the resuspension of soil particles, making soil inhalation a relevant risk pathway. The authors determined and compared human exposure to metals and polycyclic aromatic hydrocarbons (PAHs) from soil ingestion and inhalation and analyzed the carcinogenic and noncarcinogenic risks before and after roads were paved in a northern community. To determine the inhalation exposure, three size fractions of airborne particulate matter were collected (total suspended particulates [TSP], particulate matter with an aerodynamic diameter less than 10 µm [PM10], and particulate matter with an aerodynamic diameter less than 2.5 µm [PM2.5]) before and after roads were paved. Road paving reduced the concentration of many airborne contaminants by 25 to 75%, thus reducing risk. For example, before paving, the carcinogenic risk associated with inhalation of Cr was 3.4 excess cancers per 100,000 people exposed, whereas after paving, this risk was reduced to 1.6 in 100,000. Paving roads reduced the concentrations of total suspended particulates (TSP; p < 0.1) and PM10 (p < 0.05) but not PM25. Consequently, the ingestion of inhaled soil particles was substantially reduced. The authors conclude that resuspended soil is likely an important source of risk for many northern communities and that paving roads is an effective method of reducing risk from the inhalation of soil particles.