In vitro assessment of the toxicity of metal compounds

A review of in vitro mutagenesis assessment of metal compounds in mammalian and nonmammalian test systems has been compiled. Prokaryotic assays are ineffective or inconsistent in their detection of most metals as mutagens, with the notable exception of hexavalent chromium. Mammalian assay systems appear to be similarly inappropriate for the screening of metal compounds based upon the limited number of studies that have employed those compounds having known carcinogenic activity. Although of limited value as screening tests for the detection of potentially carcinogenic metal compounds, the well-characterized in vitro mutagenesis systems may prove to be of significant value as a means to elucidate mechanisms of metal genotoxicity.     

Arsenic Bioaccumulation in Freshwater Fishes

The arsenic ambient water quality criterion (AWQC) for protection of human health via ingestion of aquatic organisms is currently 0.14 μ g/L. This AWQC is derived using a bioconcentration factor (BCF) of 44, which is a consumption-weighted average based on two data points for oysters and fish that was proposed by the U.S. Environmental Protection Agency in 1980 for broad application to freshwater and marine environments. This BCF is based on the assumption that bioaccumulation is a simple linear function of the exposure concentration. In the nearly quarter of a century since this BCF was promulgated, there have been additions to the arsenic bioaccumulation database and a broader scientific understanding of bioaccumulation mechanisms and how they can be applied to estimating tissue concentrations in aquatic organisms. From this database, we identified 12 studies of arsenic bioaccumulation in freshwater fishes in order to explore differences in laboratory-generated BCFs and field-generated bioaccumulation factors (BAFs) and to assess their relationship to arsenic concentrations in water. Our analysis indicates that arsenic concentrations in tissue and arsenic BAFs may be power functions of arsenic concentration in water. A power function indicates that the highest BCF values may occur at low background levels and may decrease as environmental concentrations increase above the ambient range.     

Arsenate reductase activity in roots from the arsenic hyperaccumulator Pteris vittata utilizes both glutathione and dithiothreitol as reductants

Abstract

The role of glutathione and dithiothreitol as reductants supporting arsenate reductase activity in root extract from the arsenic hyperaccumulator Pteris vittata was examined. The two reductants in combination enhanced arsenate reduction in vitro more than glutathione alone. The implications of these results for in vivo arsenate reduction are discussed.     

Validation of chemical speciation model of inorganic arsenic in river waters with mobilisation processes

Abstract

The thermodynamic model of inorganic arsenic (acid–base, complexation, precipitation and redox equilibria) was validated with results obtained in arsenic mobilisation processes taking place in several river sediment samples of the Basque Country (North of Spain). Natural waters in contact with the sediment were collected at each sampling point, together with the sediment samples. These waters were analysed and then used as the extractant in the mobilisation studies. Considering pH, redox potential and total concentration values of the main cations and anions, the stoichiometric equilibrium constant were computed for each river water situation. The activity coefficient values of the inorganic arsenic species were estimated by means of the Modified Bromley Methodology (MBM). Both water and sediment for each sampling site were used in the mobility experiments, and the results were compared with the theoretical predictions of the thermodynamic model extrapolated to the chemical conditions of the sampling point. Moreover, a correlation analysis was also performed taking into account all the data and sampling sites; these results were also discussed and compared with the theoretical speciation obtained from the basic model of inorganic arsenic.     

Isolation and Characterization of Arsenic-Resistant Bacteria from Contaminated Water-Bodies in West Bengal,India

Bengal Basin is known for severe arsenic contamination. In the present study, we have isolated six bacteria from the arsenic contaminated surface water of Bengal Basin. 16S rDNA sequence analysis identified them as Microbacterium oleivorans, Acinetobacter soli, Acinetobacter venetianus, Acinetobacter junii, Acinetobacter baumannii, Acinetobacter calcoaceticus. All the isolates possess arsenic accumulation potential and high molecular weight plasmid (>10 kb). PCR amplification indicated the presence of arsenic-resistance genes (arsB and aoxB) either in the genome or plasmid or in both in the isolated bacteria (except in Acinetobacter venetianus). Exposure to arsenic affected bacterial growth and induced alteration in cytoplasmic membrane integrity.     

Ecological Risk Assessment of Arsenic and Metals in Surface Sediments from Estuarine and Coastal Areas of the Southern Bohai Sea,China

Distribution and magnitude of arsenic and metals in surface sediments collected from the coastal and estuarine areas of the southern Bohai Sea, China, were investigated. Sediments from the estuarine and coastal areas of the Jie and Xiaoqing Rivers contained highest concentrations of arsenic, cadmium, copper, mercury, and zinc. Mean concentrations of Cu, Zn, Cr, Pb, and Cd were higher than background concentrations determined for the areas. The magnitude of both enrichment factors (EF) and geoaccumulation indices (I_geo) suggested that pollution with As and metals was occurring along estuarine and coastal areas of the southern Bohai Sea. Risk analysis also suggested that concentrations of As and metals were sufficiently elevated as to cause adverse biological effects in the study area. According to the ecological risk index (RI) values, the upstream of the Jie River has a very high ecological risk for the waterbody. The data provided in this study are considered crucial for controlling and remediation of As and metals’ pollution of the southern Bohai Sea.     

络合型含铁材料对砷胁迫下水稻生理生化特性及砷累积的影响

土壤重金属与农产品质量息息相关.本研究通过设置砷胁迫条件下水稻种植盆栽试验,分析络合型含铁材料不同施用时期和不同施用量对水稻SPAD值、抗氧化酶(SOD、POD、CAT)活性以及水稻砷吸收、累积的影响.结果表明,砷胁迫对水稻SOD、POD、CAT活性有着不同程度的抑制作用,添加络合型含铁材料可以降低水稻MDA含量,缓解砷对水稻光合作用和SOD、POD、CAT活性的抑制;同时能减少水稻对土壤砷的吸收和累积.与移栽前添加络合型含铁材料相比,选择水稻孕穗期前添加络合型含铁材料,水稻砷吸收的抑制效果较好;水稻植株地上部砷含量与络合型含铁材料的添加浓度呈显著负相关,孕穗期前添加0.2 g·kg-1络合型含铁材料对水稻植株砷的吸收抑制效果最好,水稻植株地上部砷含量降低59.22%.     

Concentration of arsenic in groundwater,vegetables, human hair and nails in mining site in the Northern Thai Nguyen province,Vietnam: human exposure and risks assessment

This study was aimed to examine the risk of chronic arsenic (As) exposure for the residents living in Nui Phao, Thai Nguyen in the northern Vietnam. Groundwater, vegetables, human hair, and nail samples were collected from volunteers living in Nui Phao. The results revealed that 75% of the groundwater samples had As exceeding the World Health Organization (WHO) drinking water guideline of 10 µg L^?1. The result of As concentration for most of the vegetable samples was greater than the WHO/FAO safe (0.1?mg kg^?1). The result of hair and nail samples in this study showed that 3.5 and 20% of the samples had As concentration exceeding the level of As toxicity in hair and nails, respectively. The result of health risks indicated that the potential health risk of As contamination is greater for groundwater than vegetables. The total hazard quotient (HQ) value through vegetables ingestion and drinking water exceeded 1.0 suggesting potential health risk for local residents. The calculation of potential carcinogenic risk through both consumption of vegetables and drinking water was low cancer risk in adults. Other food sources and the exposure pathways are needed to exactly assess health risks in this area.