Health risk associated with dietary co-exposure to high levels of antimony and arsenic in the world's largest antimony mine area

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.

Antimony as a global dilemma: Geochemistry, mobility, fate and transport

Elevated concentrations of antimony (Sb) in environmental, biological and geochemical systems originating from natural, geological and anthropogenic sources are of particular global concern. This review presents a critical overview of natural geochemical processes which trigger the mobilization of Sb from its host mineral phases and related rocks to the surrounding environments. The primary source of Sb contamination in the environment is geogenic. The geochemical characteristics of Sb are determined by its oxidation states, speciation and redox transformation. Oxidative dissolution of sulfide minerals and aqueous dissolution are the most prevalent geochemical mechanisms for the release of Sb to the environment. Transformation of mobile forms of Sb is predominantly controlled by naturally occurring precipitation and adsorption processes. Oxyhydroxides of iron, manganese and aluminum minerals have been recognized as naturally occurring Sb sequestrating agents in the environment. Antimony is also immobilized in the natural environment via precipitation with alkali and heavy metals resulting extremely stable mineral phases, such as schafarzikite, tripuhyite and calcium antimonates. Many key aspects, including detection, quantification, and speciation of Sb in different environmental systems as well as its actual human exposure remain poorly understood. Identification of global distribution of most vulnerable Sb-contaminated regions/countries along with aquifer sediments is an urgent necessity for the installation of safe drinking water wells. Such approaches could provide the global population Sb-safe drinking and irrigation water and hinder the propagation of Sb in toxic levels through the food chain. Hence, raising awareness through the mobility, fate and transport of Sb as well as further transdisciplinary research on Sb from global scientific communities will be a crucial stage to establish a sustainable Sb mitigation on a global scale.

Metals and Metalloids in Wild Asparagus at Uncontaminated and Mining-Contaminated Sites

Wild edible plants are often considered healthier than crops because they are unaffected by fertilizers, herbicides, and pesticides. However, the occurrence of potentially toxic elements in wild plants is poorly known and needs to be assessed. In this study, 22 elements were determined by inductively coupled plasma mass spectrometry in wild asparagus ( L.). Asparagus shoots were collected in uncontaminated environments (20 sites) and in areas contaminated by past mining (15 sites) in Sardinia, Italy. Beryllium, Bi, Te, Tl, and U were not detected in asparagus (<0.03 μg g); Ag, As, Co, Cd, Li, and Sb were detected at very low levels (median, 0.01-0.05 μg g); B, Cu, Fe, Mn, Rb, and Zn were relatively abundant (median, 10-58 μg g); and Ba, Mo, Ni, Pb, and Sr showed large variations (median, 0.4, 0.3, 3, 0.1, and 0.5 μg g, respectively). Median concentrations of detected elements were similar in asparagus collected in uncontaminated environments or previously mined areas. An exception was Cd in asparagus collected in mined areas (median, 1.4 μg g), whose levels were much higher than in asparagus from uncontaminated environments (median, 0.01 μg g), indicating that high Cd in bedrocks affect contents in asparagus shoots. Also, Sb- and As-rich substrates in mined areas resulted in asparagus with Sb and As concentrations much higher than asparagus samples from areas mined predominantly for Pb and Zn. Results of this study indicate potential health hazards to residents living worldwide in areas affected by past mining.

Interaction of As and Sb in the hyperaccumulator Pteris vittata L.: changes in As and Sb speciation by XANES

Arsenic (As) and antimony (Sb) are chemical analogs that display similar characteristics in the environment. The As hyperaccumulator Pteris vittata L. is a potential As-Sb co-accumulating species. However, when this plant is exposed to different As and Sb speciation, the associated accumulating mechanisms and subsequent assimilation processes of As and Sb remain unclear. A 2-week hydroponic experiment was conducted by exposing P. vittata to single AsIII, AsV, SbIII, and SbV or the co-existence of AsIII and SbIII and AsV and SbV. P. vittata could co-accumulate As and Sb in the pinna (>1000 mg kg(-1)) with high translocation (>1) of As and Sb from the root to the pinna. P. vittata displayed apparent preference to the trivalent speciation of As and Sb than to the pentavalent speciation. Under the single exposure of AsIII or SbIII, the pinna concentration of As and Sb was 84 and 765 % higher than that under the single exposure of AsV or SbV, respectively. Despite the provided As speciation, the main speciation of As in the root was AsV, whereas the main speciation of As in the pinna was AsIII. The Sb in the roots comprised SbV and SbIII when exposed to SbV but was exclusively SbIII when exposed to SbIII. The Sb in the pinna was a mixture of SbV and SbIII regardless of the provided Sb speciation. Compared with the single exposure of As, the co-existence of As and Sb increased the As concentration in the pinna of P. vittata by 50-66 %, accompanied by a significant increase in the AsIII percentage in the root. Compared with the single exposure of Sb, the co-existence of Sb and As also increased the Sb concentration in the pinna by 51-100 %, but no significant change in Sb speciation was found in P. vittata.

The risk of overestimating the risk-metal leaching to groundwater near contaminated glass waste deposits and exposure via drinking water

This study investigates metal contamination patterns and exposure to Sb, As, Ba, Cd and Pb via intake of drinking water in a region in southeastern Sweden where the production of artistic glass has resulted in a large number of contaminated sites. Despite high total concentrations of metals in soil and groundwater at the glassworks sites properties, all drinking water samples from households with private wells, located at a 30-640m distance from a glassworks site, were below drinking water criteria from the WHO for Sb, As, Ba and Cd. A few drinking water samples showed concentrations of Pb above the WHO guideline, but As was the only element found in concentrations that could result in human exposure near toxicological reference values. An efficient retention of metals in the natural soil close to the source areas, which results in a moderate impact on local drinking water, is implied. Firstly, by the lack of significant difference in metal concentrations when comparing households located upstream and downstream of the main waste deposits, and secondly, by the lack of correlation between the metal concentration in drinking water and distance to the nearest glassworks site. However, elevated Pb and Cd concentrations in drinking water around glassworks sites when compared to regional groundwater indicate that diffuse contamination of the soils found outside the glassworks properties, and not only the glass waste landfills, may have a significant impact on groundwater quality. We further demonstrate that different mobilization patterns apply to different metals. Regarding the need to use reliable data to assess drinking water contamination and human exposure, we finally show that the conservative modelling approaches that are frequently used in routine risk assessments may result in exposure estimates many times higher than those based on measured concentrations in the drinking water that is actually being used for consumption.

Relationship between e-waste recycling and human health risk in India: a critical review

Informal recycling of waste (including e-waste) is an emerging source of environmental pollution in India. Polychlorinated biphenyls (PCBs), polychlorinated diphenyl ethers (PBDEs), and heavy metals, among other substances, are a major health concern for workers engaged in waste disposal and processing, and for residents living near these facilities, and are also a detriment to the natural environment. The main objective of this review article was to evaluate the status of these impacts. The review found that, huge quantity of e-waste/waste generated, only a small amount is treated formally; the remainder is processed through the informal sector. We also evaluated the exposure pathways, both direct and indirect, and the human body load markers (e.g., serum, blood, breast milk, urine, and hair), and assessed the evidence for the association between these markers and e-waste exposure. Our results indicated that the open dumping and informal e-waste recycling systems should be replaced by the best available technology and environmental practices, with proper monitoring and regular awareness programs for workers and residents. Further and more detailed investigation in this area is also recommended.

Uptake, translocation and transformation of antimony in rice (Oryza sativa L.) seedlings

Antimony (Sb), as a toxic metalloid, has been gaining increasing research concerns due mainly to its severe pollution in many places. Rice has been identified to be the dominant intake route of Sb by residents close to the Sb mining areas. A hydroponic experiment was conducted to investigate the difference in uptake, translocation and transformation of Sb in rice seedlings of four cultivars exposed to 0.2 or 1.0 mg/L of Sb(V). The results showed that mass concentration of iron plaque (mg/kg FW) formed at the root surfaces of cultivar N was the highest among all tested cultivars at both low and high exposure levels of Sb(V). The accumulated Sb concentration in iron plaque significantly increased with an increase in mass concentration of iron plaque formed at the rice root. The total amount of iron plaque (mg/pot) at rice root generally increased with increasing exposed Sb(V) concentration, which was closely associated with the increasing lipid peroxidation in roots. Concentration percentage of Sb in rice root significantly reduced as the corresponding value in the iron plaque increased, suggesting that iron plaque formation strongly suppressed uptake of Sb by rice root. Sb concentration in rice tissues followed an order: root > stem, leaf. The japonica rice (cultivars N and Z) exhibited a stronger translocation tendency of Sb from root to stem than indica hybrid rice (cultivars F and G). Translocation of Sb from root of cultivar F to its stem and leaf was sharply enhanced with increasing Sb exposure concentration. Sb(V) could be reduced to Sb(III) in rice tissues, especially in stems (10-26% of the total Sb). For the sake of food safety, the difference in uptake, translocation and transformation of Sb in rice species planted in Sb-contaminated soils should be taken into consideration.

Comparison of arsenic and antimony biogeochemical behavior in water, soil and tailings from Xikuangshan, China

Although similar geochemical behaviors of arsenic (As) and antimony (Sb) in the environment has been assumed and widely reported, growing evidence suggests the two elements cannot, under some conditions, be assumed to behave similarly. In this four-year study (samples collected in each year), comparative investigation of the biogeochemistry of As and Sb in water/fish, soil/vegetable, tailings/plant samples were carried out at the world's largest active Sb mine area (Xikuangshan, China). Depending on duration the tailings had been stacked, significant differences in spatial distributions between As and Sb were found, and these were associated with change in pH over time. Bio-accumulation factors (BAFs) of As were approximately 10-fold greater than those of Sb in fish/water, plant/tailing, and vegetable/soil systems. Sb had higher BAF in non-fatty tissues such as gills of fishes and shells of crabs. BAFs of Sb in vegetable/soil exhibited insignificantly, but different from As, positive correlation with pH in soil.

Treatment of antimony mine drainage: challenges and opportunities with special emphasis on mineral adsorption and sulfate reducing bacteria

The present article summarizes antimony mine distribution, antimony mine drainage generation and environmental impacts, and critically analyses the remediation approach with special emphasis on iron oxidizing bacteria and sulfate reducing bacteria. Most recent research focuses on readily available low-cost adsorbents, such as minerals, wastes, and biosorbents. It is found that iron oxides prepared by chemical methods present superior adsorption ability for Sb(III) and Sb(V). However, this process is more costly and iron oxide activity can be inhibited by plenty of sulfate in antimony mine drainage. In the presence of sulfate reducing bacteria, sulfate can be reduced to sulfide and form Sb(2)S(3) precipitates. However, dissolved oxygen and lack of nutrient source in antimony mine drainage inhibit sulfate reducing bacteria activity. Biogenetic iron oxide minerals from iron corrosion by iron-oxidizing bacteria may prove promising for antimony adsorption, while the micro-environment generated from iron corrosion by iron oxidizing bacteria may provide better growth conditions for symbiotic sulfate reducing bacteria. Finally, based on biogenetic iron oxide adsorption and sulfate reducing bacteria followed by precipitation, the paper suggests an alternative treatment for antimony mine drainage that deserves exploration.

Effect of iron plaque on antimony uptake by rice (Oryza sativa L.)

Although iron (Fe) plaque has been shown to significantly affect the uptake of toxic antimony (Sb) by rice, knowledge about the influence of iron plaque on antimony (Sb) (amount, mechanisms, etc) is, however, limited. Here, the effect of Fe plaque on Sb(III) and Sb(V) (nominal oxidation states) uptake by rice (Oryza sativa L.) was investigated using hydroponic experiments and synchrotron-based techniques. The results showed that iron plaque immobilized Sb on the surface of rice roots. Although the binding capacity of iron plaque for Sb(III) was markedly greater than that for Sb(V), significantly more Sb(III) was taken up by roots and transported to shoots. In the presence of Fe plaque, Sb uptake into rice roots was significantly reduced, especially for Sb(III). However, this did not translate into decreasing Sb concentrations in rice shoots and even increased shoot Sb concentrations during high Fe-Sb(III) treatment.

Trace elements in two staple cereals (rice and wheat) and associated health risk implications in Bangladesh

Concentrations of fourteen trace elements (Cd, As, Pb, Cr, Ni, Zn, Se, Cu, Mo, Mn, Sb, Ba, V and Ag) in the composite samples of most frequently consumed two staple foods, i.e. rice and wheat (collected from 30 different agroecological zones for the first time in Bangladesh) were measured by ICP-MS. The mean concentrations (mg/kg fresh weight) of Cd, As, Pb, Cr, Ni, Zn, Se, Cu, Mo, Mn, Sb, Ba, V and Ag were found as 0.088, 0.321, 0.713, 0.183, 0.213, 13.178, 0.0256, 1.985, 0.102, 4.654, 0.0033, 0.144, 0.081 and 0.007 and 0.011, 0.281, 0.221, 0.352, 0.145, 15.472, 0.245, 1.894, 0.209, 22.077, 0.0012, 3.712, 0.023 and 0.0013 in rice and wheat samples, respectively. Dietary risk of human health (non-carcinogenic and carcinogenic risks) was assessed by USEPA deterministic approaches. Total target hazard quotient (THQ) values for As and Pb were higher than 1, suggesting that people would experience significant health risks from consuming rice and wheat. However, the THQ of other metals were all less than 1. Also, the estimation showed that the target carcinogenic risk (TR) of As and Pb exceeded the accepted risk level of 1 × 10(-6). Moreover, concerning the nutritional requirements of essential elements for a sound health, the recommended doses for the daily intake of Mn was conveniently supplied by the studied cereals; however, Cr, Zn, Se, Cu and Mo were below the recommend daily allowances (RDAs). Thus, the carcinogenic and non-carcinogenic risk of As and Pb with lower supplementation of essential elements via staple foods for Bangladeshi people is a matter of concern.

Comparative proteomic analysis in Miscanthus sinensis exposed to antimony stress

To explore the molecular basis of Sb tolerance mechanism in plant, a comparative proteomic analysis of both roots and leaves in Miscanthus sinensis has been conducted in combination with physiological and biochemical analyses. M. sinensis seedlings were exposed to different doses of Sb, and both roots and leaves were collected after 3 days of treatment. Two-dimensional gel electrophoresis (2-DE) and image analyses found that 29 protein spots showed 1.5-fold change in abundance in leaves and 19 spots in roots, of which 31 were identified by MALDI-TOF-MS and MALDI-TOF-TOF-MS. Proteins involved in antioxidant defense and stress response generally increased their expression all over the Sb treatments. In addition, proteins relative to transcription, signal transduction, energy metabolism and cell division and cell structure showed a variable expression pattern over Sb concentrations. Overall these findings provide new insights into the probable survival mechanisms by which M. sinensis could be adapting to Sb phytotoxicity.

Antimony bioavailability: knowledge and research perspectives for sustainable agricultures

The increasing interest in urban agriculture highlights the crucial question of crop quality. The main objectives for environmental sustainability are a decrease in chemical inputs, a reduction in the level of pollutants, and an improvement in the soil's biological activity. Among inorganic pollutants emitted by vehicle traffic and some industrial processes in urban areas, antimony (Sb) is observed on a global scale. While this metalloid is known to be potentially toxic, it can transfer from the soil or the atmosphere to plants, and accumulate in their edible parts. Urban agriculture is developing worldwide, and could therefore increasingly expose populations to Sb. The objective of this review was in consequences to gather and interpret actual knowledge of Sb uptake and bioaccumulation by crops, to reveal investigative fields on which to focus. While there is still no legal maximal value for Sb in plants and soils, light has to be shed on its accumulation and the factors affecting it. A relative absence of data exists about the role of soil flora and fauna in the transfer, speciation and compartmentation of Sb in vegetables. Moreover, little information exists on Sb ecotoxicity for terrestrial ecosystems. A human risk assessment has finally been reviewed, with particular focus on Sb bioaccessibility.

Levels and risk factors of antimony contamination in human hair from an electronic waste recycling area, Guiyu, China

The primitive electronic waste (e-waste) recycling has brought a series of environmental pollutants in Guiyu, China. Antimony is one of the important metal contaminants and has aroused the global concerns recently. We aimed to investigate concentrations of antimony in human hair from Guiyu and compared them with those from a control area where no e-waste recycling exists, and assessed the potential risk factors. A total of 205 human hair samples from Guiyu and 80 samples from Jinping were collected for analysis. All volunteers were asked to complete a questionnaire including socio-demographic characteristics and other possible factors related to hair antimony exposure. The concentrations of hair antimony were analyzed using atomic absorption spectrophotometer. Our results indicated that the level of hair antimony in volunteers from Guiyu (median, 160.78; range, 6.99-4412.59 ng/g) was significantly higher than those from Jinping (median, 61.74; range, 2.98-628.43 ng/g). The residents who engaged in e-waste recycling activities in Guiyu had higher hair antimony concentrations than others (P < 0.001). There was no significant difference of hair antimony concentrations among different occupation types in e-waste recycling. Multiple stepwise regression analysis indicated that hair antimony concentrations were associated with education level (β = -0.064), the time of residence in Guiyu (β = 0.112), living house also served as e-waste workshop (β = 0.099), the work related to e-waste (β = 0.169), and smoking (β = 0.018). The elevated hair antimony concentrations implied that the residents in Guiyu might be at high risk of antimony contamination, especially the e-waste recycling workers. Work related to e-waste recycling activities and long-time residence in Guiyu contributed to the high hair antimony exposure.

Association of urinary metal profiles with altered glucose levels and diabetes risk: a population-based study in China

BACKGROUND

Elevated heavy metals and fasting plasma glucose (FPG) levels were both associated with increased risk of cardiovascular diseases. However, studies on the associations of heavy metals and essential elements with altered FPG and diabetes risk were limited or conflicting. The objective of this study was to evaluate the potential associations of heavy metals and essential trace elements with FPG and diabetes risk among general Chinese population.

METHODS

We conducted a cross-sectional study to investigate the associations of urinary concentrations of 23 metals with FPG, impaired fasting glucose (IFG) and diabetes among 2242 community-based Chinese adults in Wuhan. We used the false discovery rate (FDR) method to correct for multiple hypothesis tests.

RESULTS

After adjusting for potential confounders, urinary aluminum, titanium, cobalt, nickel, copper, zinc, selenium, rubidium, strontium, molybdenum, cadmium, antimony, barium, tungsten and lead were associated with altered FPG, IFG or diabetes risk (all P< 0.05); arsenic was only dose-dependently related to diabetes (P< 0.05). After additional adjustment for multiple testing, titanium, copper, zinc, selenium, rubidium, tungsten and lead were still significantly associated with one or more outcomes (all FDR-adjusted P< 0.05).

CONCLUSIONS

Our results suggest that multiple metals in urine are associated with FPG, IFG or diabetes risk. Because the cross-sectional design precludes inferences about causality, further prospective studies are warranted to validate our findings.

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi (AMF) have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony (Sb). The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE). Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis (PCA) indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis (RDA) showed that Sb contamination was the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Glomus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.

Bioaccumulation of Antimony and Arsenic in Vegetables and Health Risk Assessment in the Superlarge Antimony-Mining Area, China

Heavy metal pollution in soils caused by mining and smelting has attracted worldwide attention for its potential health risks to residents. This paper studies the concentrations and accumulations of Sb and As in both soils and vegetables and the human health risks of Sb and As in vegetables from Xikuangshan (XKS) Sb mine, Hunan, China. Results showed that the soils were severely polluted by Sb and As; Sb and As have significant positive correlation. Sb and As concentrations in vegetables were quite different: Coriandrum sativum L. was the highest in Sb, Allium fistulosum L. was the highest in As, and Brassica pekinensis L. was the lowest in both Sb and As; Daucus carota L. and Coriandrum sativum L. showed advantage in accumulating Sb and As; Coriandrum sativum L. had higher capacity of redistributing Sb and As within the plant. Health risk assessment results showed that the hazard quotient (HQ) values of Sb and As in vegetables were in the ranges of 1.61-3.33 and 0.09-0.39, respectively; the chronic daily intake (CDI) and hazard quotient (HQ) values of Sb were over the safe limit recommended by FAO and WHO, indicating that long-term consumption of vegetables from the surrounding soils of XKS mine may bring health risks to residents.

Antimony in the Soil-Plant System in an Sb Mining/Smelting Area of Southwest China

The distribution, bioavailability, and accumulation of antimony (Sb) at the interface of rhizospheric soils and indigenous plants from a large Sb mining/smelting area in Southwest China were explored. Results showed that the local soil was severely polluted by Sb, and the aluminum magnesium silicate minerals and the carbonate fraction may mainly contribute to bound Sb. The sequential extraction results of soil samples revealed that the portion of bioavailable Sb was low, but the bioavailable Sb concentration was up to 67.2 mg/kg, due to high total Sb concentrations in the soil. The Sb content in local plants showed a wide range, from 21 to 21148 mg/kg. The species of Chenopodium album Linn., Sedum emarginatum Migo, and Sedum lineare Thunb showed high accumulation of Sb at levels of above 1000 mg/kg. The Sb contents in the tissues for most plants decreased with the order of root > leaf > stem. The bioaccumulation coefficients and/or the biological transfer factors for most plants were less than 1. All of the studied plant species were not identified as Sb-hyperaccumulators, but the species of Chenopodium album Linn., Sedum emarginatum Migo, and Sedum lineare Thunb could be applied as alternative plants for phytoremediating Sb-polluted soils.

Elemental bioimaging of tissue level trace metal distributions in rice seeds (Oryza sativa L.) from a mining area in China

Rice is a staple food and major source of nutrients, but it also bioaccumulates toxic elements. In this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine tissue-level trace metal spatial distribution in rice (Oryza sativa) seeds from the active Xikuangshan Sb mine area in China. Whole grain quantified elemental bioimages showed the highest concentration of Zn (1755 mg/kg) in the embryo andmicro zones of elevated Sb, As, Pb, Cd as high as 280, 57, 31 and 830 mg/kg, respectively on the husk/bran/endosperm tissues. Bioimages suggest that both Sb and Cd may be competing with Zn for binding sites. Both Sb(III) and Sb(V) species were detected in seeds from upstream and downstream fields indicating the presence of toxic Sb(III). Brown rice is a good source of Zn, but white rice is a safer option if rice is grown in a polluted area.

Bioaccessibility of antimony and arsenic in highly polluted soils of the mine area and health risk assessment associated with oral ingestion exposure

In this study, the bioaccessibility and the human health risks of Sb and As in soils from Xikuangshan (XKS) Sb mine, Hunan, China were investigated using two commonly used in vitro extraction methods, Simplified Bioaccessibility Extraction Test (SBET) and Physiologically Based Extraction Test (PBET). Soils in the XKS Sb mine area were mainly co-contaminated by Sb (74.2-16,389; mean: 3061mgkg(-1)) and As (7.40-596; mean: 216mgkg(-1)). The bioaccessibility values of Sb and As in most cases were less than 30%, and the average bioaccessibility values of Sb and As were 5.89±6.44% and 2.13±2.55% for the SBET extraction; 7.83±9.82% and 6.62±6.37% for the PBET (Gastric) extraction; and 3.03±3.53% and 2.40±2.01% for the PBET (Intestinal) extraction, respectively. The bioaccessible Sb and As were significantly positively correlated with the total concentrations, but negatively correlated with the Fe, Al, Mn and organic matter (OM) contents in soils. Risk assessment results based on total concentrations might overestimate the risk existing in the studied area. After considering the bioaccessibility, the Hazard Quotient (HQ) values of Sb for most of the sampling sites and of As for all of the sampling sites became lower than 1. The Carcinogenic Risk (CR) values of As were also significantly reduced, 8.77E-06 and 1.74E-05 on average for the SBET and PBET methods, respectively. Considering the bioaccessibility can provide more applicable guidelines for risk assessments and more rational suggestions in the management of the soils contaminated with Sb and As.

Pollution characteristics and possible sources of seldom monitored trace elements in surface sediments collected from Three Gorges Reservoir, China

A geochemical study of Three Gorges Reservoir (TGR) sediments was carried out to analyze the concentrations, distribution, accumulation, and potential sources of the seldom monitored trace elements (SMTEs). The mean concentrations of Li, B, Be, Bi, V, Co, Ga, Sn, Sb, and Tl were 47.08, 2.47, 59.15, 0.50, 119.20, 17.83, 30.31, 3.25, 4.14, and 0.58 mg/kg, respectively. The concentrations of total SMTEs, together with their spatial distribution, showed that the SMTEs were mainly due to anthropogenic inputs in the region of TGR. The assessment by Geoaccumulation Index indicates that Tl, Be, V, Co, and Fe are at the unpolluted level; Bi, Li, Ga, and Sn were at the "uncontaminated to moderately contaminated" level. However, B was classified as "moderately contaminated" level and Sb was ranked as "strongly contaminated" level. The pollution level of the SMTEs is Sb > B > Bi > Li > Ga > Sn > Tl > Be > V > Co > Fe. The results of Correlation Analysis and Principal Component Analysis indicated Be, V, Co, Ga, Sn, Tl, Bi, and Fe in sediments have a natural source. B and Li were positively correlated with each other and mainly attributed into similar anthropogenic input. In addition, Sb has less relationship with other SMTEs, indicating that Sb has another kind of anthropogenic source.

Antimony uptake, translocation and speciation in rice plants exposed to antimonite and antimonate

Antimony (Sb) accumulation in rice is a potential threat to human health, but its uptake mechanisms are unclear. A hydroponic experiment was conducted to investigate uptake, translocation, speciation and subcellular distribution of Sb in rice plants exposed to antimonite (SbIII) and antimonate (SbV) at 0.2, 1.0 or 5.0 mg/L for 4h. More Sb was accumulated in iron plaque than in the plant, with both the roots (~10-12 times) and Fe plaque (~28-54 times) sequestering more SbIII than SbV. The presence of iron plaque decreased uptake of both SbV and SbIII. SbIII uptake kinetics fitted better to the Michaelis-Menten function than SbV. Antimonate (56 to 98%) was the predominant form in rice plant with little methylated species being detected using HPLC-ICP-MS. Cell walls accumulated more Sb than organelles and cytosol, which were considered as the first barrier against Sb entering into cells. Sb transformation and subcellular distribution can help to understand the metabolic mechanisms of Sb in rice.

Study on association between spatial distribution of metal mines and disease mortality: a case study in Suxian District, South China

Metal mines release toxic substances into the environment and can therefore negatively impact the health of residents in nearby regions. This paper sought to investigate whether there was excess disease mortality in populations in the vicinity of the mining area in Suxian District, South China. The spatial distribution of metal mining and related activities from 1985 to 2012, which was derived from remote sensing imagery, was overlapped with disease mortality data. Three hotspot areas with high disease mortality were identified around the Shizhuyuan mine sites, i.e., the Dengjiatang metal smelting sites, and the Xianxichong mine sites. Disease mortality decreased with the distance to the mining and smelting areas. Population exposure to pollution was estimated on the basis of distance from town of residence to pollution source. The risk of dying according to disease mortality rates was analyzed within 7–25 km buffers. The results suggested that there was a close relationship between the risk of disease mortality and proximity to the Suxian District mining industries. These associations were dependent on the type and scale of mining activities, the area influenced by mining and so on.

Removal of antimony (Sb(V)) from Sb mine drainage: biological sulfate reduction and sulfide oxidation-precipitation

Antimony (Sb(V)) in Sb mine drainage has adverse effects on the receiving water environments. This study for the first time demonstrated the feasibility of using sulfate-reducing bacteria (SRB) to convert sulfate ions in SMD into sulfides that reduce Sb(V) to Sb(III) and to form complex with Sb(III) as precipitate. The principal compound in the precipitate was stibnite (Sb2S3) at pH 7 and pH 9. The Sb(V) removal mechanism is sulfate-reduction and sulfide oxidization-precipitation, different from the conventional SRB-precipitation processes for heavy metals. The Sb(V)/sulfate ratio is noted an essential parameter affecting the Sb removal efficiency from SMD.

Changes in Sb speciation with waterlogging of shooting range soils and impacts on plant uptake

A pot experiment was conducted to investigate the solubility and redox species of antimony (Sb) in a relocated shooting range soil and its uptake by Lolium perenne L. and Holcus lanatus L. under different water regimes. After 1-week waterlogging, the total Sb concentration in soil solution decreased from ∼110 μg L(-1) to <20 μg L(-1), and slowly increased over the following 4 weeks, with the dissolution of Fe and Mn (hydr)oxides. In this process, half of the Sb in soil solution was reduced to Sb(III), which greatly affected the plant uptake of Sb. Waterlogging increased shoot Sb concentrations of L. perenne by ∼10 fold but decreased uptake in H. lanatus by 80%. Results indicate that Sb might primarily be taken up as Sb(III) by L. perenne and as Sb(V) by H. lanatus. Temporary waterlogging of soil may increase the risk of trace elements entering the food chain.

Proximity to mining industry and cancer mortality

Mining installations are releasing toxic substances into the environment which could pose a health problem to populations in their vicinity. We sought to investigate whether there might be excess cancer-related mortality in populations residing in towns lying in the vicinity of Spanish mining industries governed by the Integrated Pollution Prevention and Control Directive, and the European Pollutant Release and Transfer Register Regulation, according to the type of extraction method used. An ecologic study was designed to examine municipal mortality due to 32 types of cancer, across the period 1997 through 2006. Population exposure to pollution was estimated on the basis of distance from town of residence to pollution source. Poisson regression models, using the Bayesian conditional autoregressive model proposed by Besag, York and Molliè and Integrated Nested Laplace Approximations for Bayesian inference, were used: to analyze risk of dying from cancer in a 5-kilometer zone around mining installations; effect of type of industrial activity; and to conduct individual analyses within a 50-kilometer radius of each installation. Excess mortality (relative risk, 95% credible interval) of colorectal cancer (1.097, 1.041-1.157), lung cancer (1.066, 1.009-1.126) specifically related with proximity to opencast coal mining, bladder cancer (1.106, 1.016-1.203) and leukemia (1.093, 1.003-1.191) related with other opencast mining installations, was detected among the overall population in the vicinity of mining installations. Other tumors also associated in the stratified analysis by type of mine, were: thyroid, gallbladder and liver cancers (underground coal installations); brain cancer (opencast coal mining); stomach cancer (coal and other opencast mining installations); and myeloma (underground mining installations). The results suggested an association between risk of dying due to digestive, respiratory, hematologic and thyroid cancers and proximity to Spanish mining industries. These associations were dependent on the type of mine.

Multi-trace element levels and arsenic speciation in urine of e-waste recycling workers from Agbogbloshie, Accra in Ghana

To understand human contamination by multi-trace elements (TEs) in electrical and electronic waste (e-waste) recycling site at Agbogbloshie, Accra in Ghana, this study analyzed TEs and As speciation in urine of e-waste recycling workers. Concentrations of Fe, Sb, and Pb in urine of e-waste recycling workers were significantly higher than those of reference sites after consideration of interaction by age, indicating that the recycling workers are exposed to these TEs through the recycling activity. Urinary As concentration was relatively high, although the level in drinking water was quite low. Speciation analysis of As in human urine revealed that arsenobetaine and dimethylarsinic acid were the predominant As species and concentrations of both species were positively correlated with total As concentration as well as between each other. These results suggest that such compounds may be derived from the same source, probably fish and shellfish and greatly influence As exposure levels. To our knowledge, this is the first study on human contamination resulting from the primitive recycling of e-waste in Ghana. This study will contribute to the knowledge about human exposure to trace elements from an e-waste site in a less industrialized region so far scantly covered in the literature.

Antimony (Sb) and arsenic (As) in Sb mining impacted paddy soil from Xikuangshan, China: differences in mechanisms controlling soil sequestration and uptake in rice

Foods produced on soils impacted by antimony (Sb) mining activities are a potential health risk due to plant uptake of the contaminant metalloids (Sb) and arsenic (As). Here we report for the first time the chemical speciation of Sb in soil and porewater of flooded paddy soil, impacted by active Sb mining, and its effect on uptake and speciation in rice plants (Oryza sativa L. cv Jiahua). Results are compared with behavior and uptake of As. Pot experiments were conducted under controlled conditions in a climate chamber over a period of 50 days. In pots without rice plants, flooding increased both the concentration of dissolved Sb (up to ca. 2000 μg L(-1)) and As (up to ca. 1500 μg L(-1)). When rice was present, Fe plaque developing on rice roots acted as a scavenger for both As and Sb, whereby the concentration of As, but not Sb, in porewater decreased substantially. Dissolved Sb in porewater, which occurred mainly as Sb(V), correlated with Ca, indicating a solubility governed by Ca antimonate. No significant differences in bioaccumulation factor and translocation factor between Sb and As were observed. Greater relative concentration of Sb(V) was found in rice shoots compared to rice root and porewater, indicating either a preferred uptake of Sb(V) or possibly an oxidation of Sb(III) to Sb(V) in shoots. Adding soil amendments (olivine, hematite) to the paddy soil had no effect on Sb and As concentrations in porewater.

High levels of antimony in dust from e-waste recycling in southeastern China

Environmental contamination due to uncontrolled e-waste recycling is an emerging global issue. Antimony (Sb) is a toxic element used in semiconductor components and flame retardants for circuit board within electronic equipment. When e-waste is recycled, Sb is released and contaminates the surrounding environment; however, few studies have characterized the extent of this problem. In this study, we investigated Sb and arsenic (As) distributions in indoor dust from 13 e-waste recycling villages in Guiyu, Guangdong Province, southeastern China. Results revealed significantly elevated concentrations of Sb (6.1-232 mg/kg) in dust within all villages, which were 3.9-147 times higher than those from the non e-waste sites, indicating e-waste recycling was an important source of Sb pollution. On the contrary, As concentrations (5.4-17.7 mg/kg) in e-waste dusts were similar to reference values from the control sites. Therefore, dusts emitted from e-waste recycling may be characterized by high Sb/As ratios, which may help identify the contamination due to the e-waste recycling activities.