Endemic Arsenicosis Research Articles

Occurrence and behavior of arsenic in groundwater-aquifer system of irrigated areas.

Groundwater arsenic pollution has received much attention worldwide for decades as a serious threat to public health, but the mechanisms responsible for arsenic mobilization are not fully understood. Groundwater and bore drilling sediment samples from Qiji county, a small geographical agricultural area with endemic arsenicosis, are collected for demonstrating the occurrence and speciation of arsenic in groundwater and sediments, and arsenic release between solid-liquid phase influenced by human activities. Results show that arsenic concentrations in groundwater vary from 5 μg/L to 19.6 μg/L, with 80% exceeding the maximum permissible limits required by WHO (10 μg/L) for drinking water and therefore constituting a health risk for humans. In a weak oxidizing environment (oxidation-reduction potential (ORP): 12.9 mV-151 mV), inorganic As(V) accounts for 85% of total dissolved As, which to some extent alleviates the harm of As pollution on humans. Total As content in the sediments is in the range of 6.98 mg/kg and 14.34 mg/kg (median of 10.71 mg/kg), three times higher than the average value of many countries. Sequential chemical leaching indicates that 11% of arsenic in sediments is labile bound and may be closely related to the arsenic in groundwater. Additionally, irrigation intensity contributes to arsenic release with diverse As3+/As5+ by dissolving weakly bound arsenic rapidly. Subsequently part of As(III) is oxidized to As(V). Competitive and/or alkaline desorption of As(V), which had been adsorbed by FeMn (hydrous)-oxides and carbonates in the unsaturated zone and the aquifer, exerts a significant role in releasing arsenic into the groundwater. Our study indicates that systematic management and regulation of irrigation intensity are required to prevent further deterioration of groundwater resources.

Histone demethylase JHDM2A participates in the repair of arsenic-induced DNA damage in L-02 cells by regulating DDB2.

Arsenic is widely present in nature and is a class I carcinogen confirmed by the World Health Organization and the International Agency for Research on Cancer. The liver is responsible for biotransformation in the body and is one of the major organs where arsenic accumulates in the body, but the mechanisms of arsenic-induced abnormal DNA damage repair pathways in the liver are still unclear. Recent studies have revealed that epigenetic mechanisms play an important role in arsenic-induced lesions. In this study, an in vitro model was established using human normal hepatocytes L-02 to investigate the mechanism of the specific demethylase JHDM2A of H3K9me2 in the repair of arsenic-induced DNA damage in L-02 cells. The results showed that with the increase of arsenic concentrations, the extent of DNA damage in L-02 cells showed an increasing trend and total intracellular H3K9me2 expression was downregulated. In addition, the enrichment level of H3K9me2 in the promoter region of DBB2, a key factor of nucleotide repair (NBR), increased, while protein and mRNA expression levels showed a decreasing trend. Thereafter, we overexpressed and repressed JHDM2A and found a close association between JHDM2A and arsenic-induced DNA damage. DDB2 protein and mRNA expression was downregulated with JHDM2A overexpression and upregulated with JHDM2A repression, while DBB2 promoter region H3K9me2 enrichment levels remained at a high level, although they were affected after JHDM2A overexpression or knockdown to some extent. These results suggest a potential mechanism by which JHDM2A may regulate DDB2 gene expression, participate in the NBR process, and play a role in arsenic-induced DNA damage in L-02 cells, which is not the result of JHDM2A exerting demethylation on H3K9me2 in the DDB2 promoter region. Our results provided an epigenetic mechanism for endemic arsenicosis, as well as a scientific basis for potential prevention and control measures.

Ginkgo biloba extract attenuates the disruption of pro-and anti-inflammatory T-cell balance in peripheral blood of arsenicosis patients.

Endemic arsenicosis is a public health problem that affects thousands of people worldwide. However, the biological mechanism involved is not well characterized, and there is no specific treatment. Exposure to arsenic may be associated with immune-related problems. In the present work, we performed an investigation to determine whether the Th17/Treg balance was abnormal in peripheral blood mononuclear cells (PBMCs) of patients with arsenicosis caused by burning coal. Furthermore, we investigated the effect of Ginkgo biloba extract (GBE) on the Th17/Treg imbalance in patients with arsenicosis. In this trial, 81 arsenicosis patients and 37 controls were enrolled. The numbers of Th17 and Treg cells, as well as related transcription factors and serum cytokines, were determined at the beginning and end of the study. Patients with arsenicosis exhibited higher levels of Th17 cells, Th17-related cytokines (IL-17A and IL-6), and the transcription factor RORγt. There were lower levels of Treg cells, a Treg-related cytokine (IL-10), and the transcription factor Foxp3 as compared with controls. There was a positive correlation between the levels of Th17 cells and IL-17A and the levels of arsenic in hair. Arsenicosis patients were randomly assigned to a GBE treatment group or a placebo group. After 3 months of follow-up, 74 patients completed the study (39 cases in the GBE group and 35 in the placebo group). Administration of GBE to patient upregulated the numbers of Treg cells and the level of IL-10 and downregulated the numbers of Th17 cells and the levels of cytokines associated with Th17 cells. The mRNA levels of Foxp3 and RORγt were increased and decreased, respectively. These results indicated that exposure to arsenic is associated with immune-related problems. The present investigation describes a previously unknown mechanism showing that an imbalance of pro- and anti-inflammatory T cells is involved in the pathogenesis of arsenicosis and that a GBE exerts effects on arsenicosis through regulation of the pro- and anti-inflammatory T cell balance.

Iron-Anode Enhanced Sand Filter for Arsenic Removal from Tube Well Water.

Sand filters are widely used for well water purification in endemic arsenicosis areas, but arsenic (As) removal is difficult at low intrinsic iron concentrations. This work developed an enhanced sand filter by electrochemically generated Fe(II) from an iron anode. The efficiency of As removal was tested in an arsenic burdened region in the Jianghan Plain, central China. By controlling a current of 0.6 A and a flow rate of about 12 L/h, the filter removed total As in the tube well water from 196 to 472 μg/L to below 10 μg/L, whereas the residual As was about 110 μg/L without electricity. Adsorption and subsequent oxidation on the surface of Fe(III) precipitates are the main processes controlling the removals of As and Fe. During a 30-day intermittent operation, both effluent As concentration and electrical energy consumption decreased progressively. Although filter clogging was observed, it can be alleviated by replacing the top layer of sand. Our findings suggest that dosing Fe(II) by an iron anode is an effective means to enhance As removal in a sand filter.

Aberrant methylation of nucleotide excision repair genes is associated with chronic arsenic poisoning

Objective: To define whether aberrant methylation of DNA repair genes is associated with chronic arsenic poisoning.Methods: Hundred and two endemic arsenicosis patients and 36 healthy subjects were recruited. Methylight and bisulfite sequencing (BSP) assays were used to examine the methylation status of ERCC1, ERCC2 and XPC genes in peripheral blood lymphocytes (PBLs) and skin lesions of arsenicosis patients and NaAsO2-treated HaCaT cells.Results: Hypermethylation of ERCC1 and ERCC2 and suppressed gene expression were found in PBLs and skin lesions of arsenicosis patients and was correlated with the level of arsenic exposure. Particularly, the expression of ERCC1 and ERCC2 was associated with the severity of skin lesions. In vitro studies revealed an induction of ERCC2 hypermethylation and decreased mRNA expression in response to NaAsO2 treatment.Conclusion: Hypermethylation of ERCC1 and ERCC2 and concomitant suppression of gene expression might be served as the epigenetic marks associated with arsenic exposure and adverse health effects.

Coupling predicted model of arsenic in groundwater with endemic arsenism occurrence in Shanxi Province, Northern China

Statistical modeling has been used to predict high risk area of arsenic (As) hazard, but information about its application on endemic arsenism is limited. In this study, we aim to link the prediction model with population census data and endemic arsenicosis in Shanxi Province, Northern China. 23 explanatory variables from different sources were compiled in the format of grid at 1km resolution in a GIS environment. Logistic regression was applied to describe the relationship between binary-coded As concentrations data and the auxiliary predictors. 61 endemic arsenism villages were geo-located and combined with output maps of the prediction model. Linear regression was used to identify the relationship between arsenicosis occurrence rate and predictive As probability at village level. Our results show that 6 explanatory environmental variables were significantly contributed to the final model. Area of 3000km2 was found to have high risk of As concentrations above 50μgL−1. The linear regression indicates that 13% of the variation in arsenicosis occurrence rate can be predicted using predictive probability of As concentration above 50μgL−1 in Shanxi Province. These results suggest that As prediction model may be helpful for identifying As-contaminated area and endemic arsenism village.

Metagenomic exploration reveals high levels of microbial arsenic metabolism genes in activated sludge and coastal sediments

Arsenic contamination in a water system is an urgent environmental problem that has caused severe endemic arsenicosis in south and southeast Asian countries. It is well known that microbially mediated arsenic metabolism can enhance arsenic mobility, bioavailability, and toxicity. Here, for the first time, we applied the Illumina high-throughput metagenomic and metatranscriptomic approaches to study the distribution, diversity, abundance, and expression of microbial arsenic metabolism genes in activated sludge and five coastal sediments. An average depth of ~2.6 Gb clean data for each sample was finally obtained for BLAST analysis after quality filtration and normalization. The results revealed that: (1) highly diverse arsenic metabolism-like genes were found and the overall abundance varied from 0.18 % to 0.26 % in the six metagenomic data sets; (2) arsenic metabolism-like genes were expressed with extremely low levels or no expression at all in activated sludge; and (3) the distribution, diversity, and abundance of aioA-like, arrA-like, arsB-like, ACR3-like, and arsM-like genes varied significantly in the six surveyed environments. This study provided a novel perspective on understanding the ecology of arsenic metabolism in different water environments using high-throughput sequencing technique.

Predicting the risk of arsenic contaminated groundwater in Shanxi Province, Northern China

Shanxi Province is one of the regions in northern China where endemic arsenicosis occurs. In this study, stepwise logistic regression was applied to analyze the statistical relationships of a dataset of arsenic (As) concentrations in groundwaters with some environmental explanatory parameters. Finally, a 2D spatial model showing the potential As-affected areas in this province was created. We identified topography, gravity, hydrologic parameters and remote sensing information as explanatory variables with high potential to predict high As risk areas. The model identifies correctly the already known endemic areas of arsenism. We estimate that the area at risk exceeding 10μgL−1 As occupies approximately 8100km2 in 30 counties in the province.

The Arsenic Concentration in Saliva, Urine and Drinking Water in Endemic Arsenicosis Area in Shanyin County of Shanxi Province, China

Biological monitoring for arsenic(As) is usually based upon a determination of urine, blood, nail and hair arsenic concentration, however, saliva has been suggested as a non-invasive biological matrix for assessing exposure. To further evaluate the potential utility of saliva for arsenic biomonitoring, Atomic Fluorescence Spectrometry(AFS-230) and Inductively Coupled Plasma Mass Spectrometer (ICP-MS) were used to evaluate the concentration of arsenic in drinking water, saliva and urine in endemic arsenicosis area in Shanyin County of Shanxi Province. The results showed that the arsenic concentration in drinking water was 0.55-720.0ug/L, and there were 66.67% samples above the arsenic level (50μg/L) of standards for drinking water quality. The median value of arsenic in drinking water was 127.22 μg/L. The salivary and urinary arsenic both can reflect the exposure of arsenic in drinking water. Additionally, there was a significant positive association of salivary arsenic compared with arsenic in drinking water (r=0.674, P<0.05)and urinary arsenic(r=0.794, P<0.05). These results demonstrated that, similar to urinary arsenic, salivary arsenic also can be used as a biomarker for assessing human exposue to arsenic.

Health effects of exposure to natural arsenic in groundwater and coal in China: an overview of occurrence.

Between 2001 and 2005, 21,155 of 445,638 wells in 20,517 villages in 292 counties in 16 provinces from China, or 5% of wells, were found to contain > 50 μg/L arsenic (As) by field testing with the Merck As kit. We achieved quality assurance of analysis of at least 10% of the wells containing > 50 μg/L As using hydride generation atomic fluorescence spectrometry and silver dithiodicarbomate spectrometry. Our best estimate of the population exposed to > 50 μg/L As in drinking water was 582,769. This is probably an underestimate for China because of the limited area surveyed. In a survey of 135,492 individuals in eight provinces, we used the National Diagnosis Standard for Endemic Arsenicosis and identified 10,096 cases of arsenicosis with various degrees of skin lesions. The arsenicosis occurrence rate of 7.5% is likely an overestimate, because the survey focused more on known and suspected endemic areas of arsenicosis. The occurrence of arsenicosis correlates positively with the percentage of wells containing > 50 μg/L As, or at a ratio of 1 to 5%. Based on both the amount of As in well water and the rate of occurrence of arsenicosis, Shanxi province, Inner Mongolia autonomous region, and Jilin province are the top three areas in China as of 2005 for exposure to endemic As from drinking water. Our survey also identified exposure to high levels of As from wells in several provinces and from the indoor burning of coal containing high levels of As in Shaanxi province. These areas, however, have not had any reports of previous arsenicosis endemics. In the endemic areas, the average rate of occurrence of arsenicosis at advanced stages was 1.2%, possibly because of a long exposure time of > 20 years; the rate of occurrence increased to 2.7% when we included a high dose of As exposure from the indoor burning of coal. Mitigation to reduce As exposure remains a challenge in rural China.

Arsenic: In Search of an Antidote to a Global Poison

Arsenic. No other element has such a complex and variegated past. As early as 500 B.C. the ancients knew about arsenic, whose name comes from the Greek word for potent. Through the centuries, this “king of poisons” was a common means of homicide. And yet, arsenic’s image has not always been so morbid. People in the Middle Ages wore arsenic amulets around their necks to ward off the bubonic plague, and women in Victorian times applied arsenic compounds to their faces to whiten their complexions. Hippocrates, the father of western medicine, recorded arsenic’s usefulness as a topical remedy for skin ulcers.

Humic Acids from Endemic Arsenicosis Areas in Inner Mongolia and from the Blackfoot-Disease Areas in Taiwan: A Comparative Study

The physical and chemical properties of humic acids (HA) extracted from drinking waters from the endemic arsenicosis areas in Inner Mongolia and from the Blackfoot disease (BD) areas in Taiwan are studied by using AAS (atomic absorption spectrophotometry), ICP-MS (inductively coupled plasma emission-mass spectrometry), IR (Infrared spectroscopy), FR (fluorescence spectrometry) and TLS (total luminescence spectroscopy) in order to shed light on the pathogenesis of BD with the concern as to whether the disease may eventually occur in arsenicosis-affected areas in the Mainland of China. Ames test and lipid peroxidation experiments were also conducted on these HA samples. It is found that water samples from the two regions are high in arsenic (As) with strong fluorescence and apparent positive correlations between As content, fluorescence, pH and total dissolved solids (TDS). The water samples are similar in fluorescence spectra but differ somewhat in IR and TLS between the two regions. The difference may be a reflection of the difference in radicals and structure of the HA owing to different hydrogeological conditions, and may also be related to the difference in their biological effects, i.e., HA from Inner Mongolia have a stronger ability to cause lipid peroxidation while HA from Taiwan exhibits a more prominent effect of mutation with respect to TA98(±S9).