Species-level study on arsenic availability from dietary components

Arsenic (As) contaminated water and foodstuffs are of major concern. Samples of drinking–cooking water (n = 50), raw rice (n = 50), common vegetables (eight types), and common pulses (three types) were collected from households in the endemic region. The study found up to 70% As reduction by using safe water for cooking of rice and vegetables. Speciation study reflected more arsenate than arsenite and other organic arsenicals in all the types of samples. Male intake of 293 μg As through drinking water contained 38 μg arsenite and 246 μg arsenate, and female intake of 199 μg As contained 167 μg arsenate and 25 μg arsenite. In cooked rice, 108 μg As contained 69 μg arsenate and 17 μg arsenite with 9 μg dimethylarsonic acid (DMA). Total As consumption from cooked vegetables was 45 μg with 34 and 4 μg of arsenite and arsenate, respectively, and 5 μg of DMA. Data indicate that cooking with As-free water removes arsenic in already contaminated foodstuffs but without interconversion of the As species, from toxic inorganic to less toxic organic forms.     

A review of arsenicals in biology

The most toxic form of arsenic is arsine gas. Arsenite is also highly toxic and arsenate is moderately toxic. Arsine gas will lyse red blood cells, arsenite inactivates particular enzymes and arsenate uncouples oxidative phosphorylation. Arsenic does not appear to be a significant mutagen. Epidemiological studies have implicated arsenic as a cause of lung cancer and skin cancer, but arsenic generally does not induce cancer in laboratory animals. Arsenic may bioaccumulate in some plants and marine organisms. Bacteria can be resistant to arsenic by preventing arsenate from entering the cell (chromosomal resistance) or pumping arsenic out of the cell (plasmid resistance). Many different organisms, including mammals, have the ability to methylate inorganic arsenic. Biomethylation seems to be a mechanism of arsenic detoxification.     

Health importance of arsenic in drinking water and food

Arsenic is a toxic metalloid of global concern. It usually originates geogenically but can be intensified by human activities such as applications of pesticides and wood preservatives, mining and smelting operations, and coal combustion. Arsenic-contaminated food is a widespread problem worldwide. Data derived from population-based studies, clinical case series, and case reports relating to ingestion of inorganic arsenic in drinking water, medications, or contaminated food or beverages show the capacity of arsenate and arsenite to adversely affect multiple organ systems. Chronic arsenic poisoning can cause serious health effects including cancers, melanosis (hyperpigmentation or dark spots, and hypopigmentation or white spots), hyperkeratosis (hardened skin), restrictive lung disease, peripheral vascular disease (blackfoot disease), gangrene, diabetes mellitus, hypertension, and ischemic heart disease.     

Metabolism and disposition of inorganic arsenic in laboratory animals and humans

The carcinogenicity of inorganic arsenic in humans, particularly in the lung and skin, has been reasonably well established through epidemiological investigations. However, there is no substantial experimental evidence for carcinogenicity in animals to support the human studies. Studies of metabolism and disposition of inorganic arsenic in various animal species are particularly relevant to determining the factors that might account for the lack of an animal model. Numerous studies of this type have been reported, but there do not appear to be clear qualitative or quantitative differences in the overall fate and disposition of inorganic arsenic in most animalsversus humans, although little is known at the cellular and subcellular level.Sulphur chemistry, especially thiol status, is emerging as an important regulating factor in the overall fate and distribution of inorganic arsenic in the body, playing a role in the initial reduction of arsenate to arsenite and subsequent methylation, and possibly in determining tissue affinity and distribution properties. The metabolism of inorganic arsenic can be viewed as a redox cycle in which thiol compounds such as glutathione (GSH) possibly function as reducing agents and methyl donors as oxidising agents. One explanation for the possible sensitivity of certain malnourished human populations to the carcinogenic effects of inorganic arsenic may be related to the reduced availability of nonprotein sulphhydryl compounds such as GSH needed to drive the redox cycle and facilitate arsenic detoxification. Future carcinogenicity studies of inorganic arsenic in animals could be designed to address directly this aspect of the problem.Disclaimer: Although the research described in this article has been supported by the United States Environmental Protection Agency, it has not been subjected to Agency review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. Mention of trade names or commercial products does not constitute endorsement or recommendalion for use.     

集胞藻(Synechocystis sp. PCC6803)对砷吸收转化特性的初步研究

砷是一种广泛存在于环境中的有毒物质.集胞藻属于单细胞藻类,广泛分布在淡水生态环境中.采用营养液培养的方法探讨了集胞藻(Synechocystis sp.PCC6803)对砷的累积和转化特性.当集胞藻分别暴露于2和100 μM的无机As(Ⅲ)和As(Ⅴ)14 d后,体内的砷形态均以As(Ⅴ)为主,并且在100 μM浓度处...     

Toxicology of arsenic in fish and aquatic systems

Arsenic (As) is found in waters such as seawater, warm springs, groundwater, rivers, and lakes. In aquatic environments, As occurs as a mixture of arsenate and arsenite, with arsenate usually predominating. The unrestricted application of As pesticides, industrial activities, and mining operations has led to the global occurrence of soluble As above permissible levels of 0.010 mg/L. Continuous exposure of freshwater organisms including fish to low concentrations of As results in bioaccumulation, notably in liver and kidney. As a consequence As induces hyperglycemia, depletion of enzymatic activities, various acute and chronic toxicity, and immune system dysfunction. Here we review arsenic chemistry, the occurrence of arsenic in aquatic system, the transformation and metabolism of arsenic; arsenic bioaccumulation and bioconcentration; behavioral changes; and acute and other effects such as biochemical, immunotoxic, and cytogenotoxic effects on fish.     

Higher sorption of arsenate versus arsenite on amorphous Al-oxide, effect of ligands

Arsenic pollution is currently a major health issue because As is toxic for human beings, animals, and plants. Knowledge of As mobility is therefore important to assess health risk. The sorption of arsenite and arsenate on metal oxides in the presence of various anionic ligands is closely linked to the mobility, bioavailability, and risk. It was reported that the sorption mechanisms and characteristics of arsenite and arsenate on Al-oxides were different from that on Fe-oxides. Previous work reports the sorption of arsenite and arsenate on Fe-oxides in the presence of ligands. Whereas there is few knowledge on the sorption of arsenite and arsenate by Al-oxides in the presence of ligands. Here, we studied the sorption of arsenite and arsenate on amorphous Al-oxide by batch experiments. We tested the effect of organic ligands: oxalate, malate, tartrate, citrate; and inorganic ligands: sulfate, phosphate, selenate, selenite. Results show that amorphous Al-oxide has more sorption affinity for arsenate than arsenite. The inhibition of As sorption by ligands at pH 6 is higher for arsenite than arsenate. For arsenite, the As sorption inhibition decreases in the order phosphate, citrate, malate, selenite, oxalate, tartrate, sulfate, and selenate. For arsenate, the As sorption inhibition decreases in the order phosphate, malate, citrate, selenite, tartrate, oxalate, sulfate, and selenate.     

The removal of arsenic from water with natural and modified clinoptilolite

The presence of increased arsenic concentrations in Eastern Croatia is a consequence of the geological composition of the soil. Because of its known harmful effects, arsenic removal is of high importance and adsorption represents an attractive and economically efficient approach to arsenic removal. The use of zeolites obtained from the Donje Jesenje deposit, Croatia (CZ) and the Zlatokop deposit in Vranjska Banja, Serbia (SZ) in Na- and Fe–Na-modified forms was investigated in order to effectively remove arsenate and arsenite from aqueous solutions. The adsorption kinetics of arsenic was studied as a function of the initial arsenate and arsenite concentrations (30–300 μg · L^?1), equilibration time (3–48 h), pH (5–10) and in the presence of sulfate and phosphate at initial concentrations of 0.2–0.5 mg · L^?1. In order to estimate sorption constants designating the sorption capacity and affinity of the zeolites samples, the experimental results were fitted to the Langmuir and Freundlich sorption isotherms. Desorption tests conducted with 1–3 mol · L^?1 HCl indicated that arsenate sorption was irreversible. The results obtained indicated that use of the Serbian zeolite in the Fe–Na-modified form (Fe–Na-SZ) was favourable for arsenate removal from water containing up to 30 μg As · L^?1.     

Arsenic species in the well water and sediments of the blackfoot disease area in Taiwan

The blackfoot disease (BFD) observed in southwestern Taiwan is due to drinking high arsenic concentrations in well water. This paper presents some results concerning the distributions of arsenic species in water and sediments collected in the BFD (well, river and coastal) area and the background (lake and ocean) area for comparison. The results show that the concentrations of arsenate (870 ± 26 ug/L) and arsenite (70.2 ± 2.6 ug/ L) in well waters, and the contents of arsenic (1640 ug/g) with high percentage of easily reducible (Fe and Mn oxides, 91.7%) and exchangeable and carbonate (4.6%) phases in well sediments were much higher than those in river, lake and coastal samples. Low arsenic (3.46–31.8 ug/g) with high percentages (73.8–97.3%) of detritus and minerals phase with low percentages (0.4–9.8%) of total carbonate and exchangeable phases were found in the river and coastal samples in the BFD area as well as the lake and ocean samples in background area. It might suggest that the higher concentrations of toxic As(III) in well water and arsenic with higher values of easily reducible, carbonate and exchangeable phases in the well sediments, combined with the higher values of dissolved organic carbon, humic and fulvic acids and aromatic carbon as well as the higher fluorescence indensity in the well water are the key factors to cause the BFD in Taiwan.     

Arsenic metabolism in marine bacteria and yeast

Arsenic metabolism was studied for two marine microorganisms, a facultative anaerobic bacterium, Serratia marinorubra, and an obligately aerobic yeast, Rhodotorula rubra. Both were cultivated in media with (⁷⁴As) arsenate (As V), and the products of arsenate metabolism were determined qualitatively. Both the bacterium and the yeast produced arsenite (AS III) and methylarsonic acid [CH₃AsO(OH)₂]. In addition to the foregoing, only the yeast produced dimethylarsinic acid (CH₃)₂AsO(OH) and volatile alkylarsines. In contrast, the bacterium growing anaerobically with cobalamine as a cofactor did not synthesize gaseous forms of arsenic such as methylarsines. Neither organism synthesized arsoniumphospholipids such as those produced by marine phytoplankton or terrestrial fungi. The yeast did not accumulate arsenite, but instead transported some of it into the culture medium and methylated the remainder first to methylarsonic acid and then to dimethylarsinic acid. Finally, the latter compound was methylated further and volatile alkylarsines were formed. In contrast, the bacterium retained all products of arsenate metabolism intracellularly. Both the bacterium and the yeast, therefore, converted relatively toxic arsenate, the most abundant arsenic compound in seawater, to products that were presumably less toxic.     

砷形态在湖水中垂直分布的研究

本文以天津水上公园湖泊作为研究现场，通过采样分析，研究了湖水中砷酸盐、亚砷酸盐、一甲基胂酸盐和二甲基胂酸盐的垂直分布及其影响因素。结果表明水上公园湖泊中砷酸盐是溶解态砷的主要存在形式，其垂直分布与悬浮物、叶绿素ａ、磷酸盐的浓度、水文等诸因素密切相关；一甲基胂酸盐含量保持相对稳定；光致转化是影响水中亚砷酸盐垂直分布差异的一个因素。     

Arsenic adsorption on lignocellulosic substrate loaded with ferric ion

We loaded a lignocellulosic substrate extracted from wheat bran with ferric ions. This new low-cost adsorbent was prepared for the adsorption and removal of arsenate and arsenite ions from aqueous systems. The loading process of Fe in this biomaterial was done by hydrolization of a ferric salt while an alkaline solution was added dropwise. The new material obtained has a high sensivity to arsenite and arsenate species. Here, we investigated the effect of contact time, pH, and Fe content on the adsorption of both arsenic ions on the new material. This adsorption was found to be highly pH-dependent, which can be explained on the basis of electrostatic interactions between ionic species in solution and the ≡FeOH surface groups. The maximum adsorption capacity of arsenite and arsenate species vary linearly with the amount of Fe loaded on the lignocellulosic substrate.     

Inorganic arsenic compounds: are they carcinogenic,mutagenic, teratogenic?

This review examines and evaluates the literature on the ability of inorganic arsenic compounds to cause cancer in humans and laboratory animals. The epidemiological data that supports the position that inorganic arsenical derivatives are carcinogenic in humans is convincing and difficult to deny because of their consistency. These data are from studies of different occupational exposures such as smelter and pesticide workers, as well as from studies of drinking water, wines and medicinal tonics that contained or were contaminated with inorganic compounds of arsenic. Indeed, positive dose-response relationships between cancer incidence or mortality with many inorganic arsenical substances have been shown. Despite the presence of data which confuse the interpretation and evaluation of epidemiological data, associated neoplasms of the lungs, skin and gastrointestinal systems have been observed as a result of exposure to inorganic arsenic compounds.The mechanism of carcinogenicity of inorganic arsenical substances in humans is unknown. Inorganic arsenic compounds are not carcinogenic in laboratory animals by most routes of administration. However, further studies (subchronic, chronic, carcinogenic) using intratracheal and other conventional routes in other animal species would appear to be warranted. Moreso, especially since there is no evidence that organic arsenic compounds are carcinogenic in numerous mammalian species. Inorganic derivatives of arsenic are not mutagenic but may be teraiogenic. This latter conclusion is dependent on the method of administration and size of the dose, as well as on the species of animal used for the study.     

In vitro development of resistance to arsenite and chromium-VI in Lactobacilli strains as perspective attenuation of gastrointestinal disorder

Inadvertent intake of inorganic arsenic and chromium through drinking water and food causing their toxic insults is a major health problem. Intestinal bacteria including Lactobacilli play important regulatory roles on intestinal homeostasis, and their loss is known to cause gastrointestinal (GI) disorders. Probiotic Lactobacilli resistance to arsenite and chromium-VI could be an importantfactorfor the perspective attenuation of Gl-disorders caused by these toxic metals/metalloid. In the present study resistance of arsenite (up to 32 ppm), Cr-VI (up to 64 ppm), and arsenite plus Cr-VI (32 ppm each) were developed under in vitro condition following chronological chronic exposures in Lactobacilli strains. Comparative study of biochemical parameters such as membrane transport enzymes and structural constituents; dehydrogenase and esterase activity tests, which are respective indicators for respiratory and energy producing processes, and the general heterotrophic activity of cells, of resistant strains showed similarities with their respective normal parent strains. The resistant strains were also found to be sensitive to antibiotics. Findings indicate that these resistant probiotic Lactobacilli would be useful in the prophylactic interventions of arsenic and chromium GI-toxicity.     

Uptake of arsenate, trimethylarsine oxide, and arsenobetaine by the shrimp Crangon crangon

Common shrimp, Crangon crangon (L.), were exposed to inorganic arsenic (arsenate), trimethylarsine oxide, or arsenobetaine in sea water (100 μg As l⁻¹) or in food (1 mg As g⁻¹ wet wt) for up to 24 d, followed by 16 d depuration in clean sea water with undosed food, in order to determine the efficiency of uptake and retention of the compounds. Accumulation of arsenic in the tail muscle, gills, midgut gland, exoskeleton, and remaining tissues was found to depend on the chemical form of the arsenic and the route of exposure. No arsenic was accumulated by C. crangon exposed to arsenate or trimethylarsine oxide in sea water. Shrimps exposed to waterborne arsenobetaine initially accumulated a small amount of arsenic in their tail muscle and gills. After 16 d, C. crangon fed arsenate, trimethylarsine oxide, or arsenobetaine had accumulated arsenic in their tail muscle to levels ∼2-, 2-, or 40-times, respectively, that of the control group. A roughly linear rate of accumulation was shown by shrimps fed trimethylarsine oxide or arsenobetaine, but C. crangon fed arsenate accumulated arsenic for 16 d, then lost arsenic such that their concentration on Day 24 was not significantly different from that of the control group. Patterns of arsenic accumulation in the gills of shrimps fed the compounds were similar to those seen in the tail muscle. On a whole animal basis, C. crangon retained ∼1.2% of the arsenate, 1.6% of the trimethylarsine oxide, and 42% of the arsenobetaine consumed over the first 16 d of exposure, with roughly half present in the tail muscle in each case. Data obtained support the view that the direct uptake of arsenobetaine from sea water does not make a significant contribution to the relatively high concentrations of this compound in marine crustaceans, and that food is the primary source. Naturally occurring arsenic compounds in C. crangon and possible transformations of the administered arsenic compounds were examined by high performance liquid chromatography using an inductively coupled plasma mass spectrometer as the arsenic-specific detector. Control C. crangon contained arsenobetaine as the major arsenic compound (>95% of total arsenic); tetramethylarsonium ion (0.7%) and an unknown arsenic compound (1.7%) were also present as minor constituents. Shrimp ingesting arsenobetaine accumulated it unchanged. Shrimp ingesting arsenate did not form methylated arsenic compounds; they appeared to contain their accumulated arsenic as unchanged arsenate only, although the possibility that some of the arsenic was reduced to arsenite could not be excluded. C. crangon ingesting trimethylarsine oxide biotransformed the compound predominantly to dimethylarsinate. Received: 9 October 1997 / Accepted: 11 February 1998     

植物砷吸收与代谢的研究进展

砷(As)作为一种植物非必需的类金属元素广泛存在于自然界中,砷过量摄人不仅会对植物生长产生毒害作用,而且在植物的可食部位累积并通过食物链对人体健康构成威胁.生长介质中的砷酸盐(五价砷)一般是通过磷酸盐转运蛋白被植物吸收的,而亚砷酸(三价砷)和没有解离的甲基化砷则主要是通过质膜上的水通道蛋白被植物吸收的.在植物体内五价砷...     

Arsenic and fluoride in the groundwater of Mexico

Concentrations of arsenic and fluoride above Mexican drinking water standards have been detected in aquifers of various areas of Mexico. This contamination has been found to be mainly caused by natural sources. However, the specific processes releasing these toxic elements into groundwater have been determined in a few zones only. Many studies, focused on arsenic-related health effects, have been performed at Comarca Lagunera in northern México. High concentrations of fluoride in water were also found in this area. The origin of the arsenic there is still controversial. Groundwater in active mining areas has been polluted by both natural and anthropogenic sources. Arsenic-rich minerals contaminate the fractured limestone aquifer at Zimapán, Central México. Tailings and deposits smelter-rich fumes polluted the shallow granular aquifer. Arsenic contamination has also been reported in the San Antonio-El Triunfo mining zone, southern Baja California, and Santa María de la Paz, in San Luis Potosí state. Even in the absence of mining activities, hydrogeochemistry and statistical techniques showed that arsenopyrite oxidation may also contaminate water, as in the case of the Independencia aquifer in the Mexican Altiplano. High concentrations of arsenic have also been detected in geothermal areas like Los Azufres, Los Humeros, and Acoculco. Prevalence of dental fluorosis was revealed by epidemiological studies in Aguascalientes and San Luis Potosí states. Presence of fluoride in water results from dissolution of acid-volcanic rocks. In Mexico, groundwater supplies most drinking water. Current knowledge and the geology of Mexico indicate the need to include arsenic and fluoride determinations in groundwater on a routine basis, and to develop interdisciplinary studies to assess the contaminant's sources in all enriched areas.     

Antioxidant enzymes and compounds complement each other during arsenic detoxification in shoots of Isatis cappadocica Desv.

Isatis cappadocica has been reported to be an arsenic (As) hyperaccumulator. Antioxidant enzymes and compounds have been proposed to play an important role in the detoxification and tolerance of As. In the present study, As-induced oxidative stress and antioxidant responses were investigated on I. cappadocica grown hydroponically in response to application of arsenate (0–1200?μmol). As accumulation increased with an increase in arsenate concentration in the medium. Along with a significant increase in arsenate concentration, a build up in hydrogen peroxide, indicators of oxidative stress, was observed. The activity of superoxide dismutase and peroxidase was induced after arsenate treatment, reached a maximal value at 800?μmol arsenate and then declined at the highest arsenate treatment. Glutathione reductase activity and contents of non-enzymatic antioxidants (carotenoids, flavonoids and anthocyanins) increased significantly as arsenate concentration augmented. These results indicated that high efficient antioxidant system may play significant roles in As detoxification and improve I. cappadocica tolerance against As toxicity.     

Arsenic accumulation in root and shoot vis-a-vis its effects on growth and level of phytochelatins in seedlings of Cicer arietinum L

Arsenic (As) contamination of water and soil has become a subject of prime interest due to its direct effect on human health through drinking water and food. In present study two varieties (CSG-8962 and C-235) of chickpea, Cicer arietinum L., which is a major supplementary food in many parts of India and a valuable source of protein, has been selected to estimate the level of arsenate in root and shoot of five day old seedlings vis-à-vis effect of arsenate on seedling growth and induction of thiols including glutathione (GSH) and phytochelatins (PCs) and their homologues. Both varieties accumulated arsenate to similar levels and most of the metalloid was confined to roots, only about 2.5% was translocated to shoot. Plant growth was also not affected significantly in both the varieties. Arsenate exposure significantly induced the levels of thiols including PCs and homophytochelatins (hPCs). The induction of thiols was much higher in roots than shoots and was greater in var C-235 between the two tested ones. Thus, both varieties tolerated and detoxified arsenic through chelation with GSH, PCs and hPCs, primarily in roots, however var C-235 performed better