Chronic exposure to arsenic (As) causes significant human health effects, including various cancers and skin disorders. Naturally elevated concentrations of As have been detected in the groundwater of Bangladesh. Dietary intake and drinking water are the major routes of As exposure for humans. The objectives of this study were to measure As concentrations in rice grain collected from households in As-affected villages of Bangladesh where groundwater is used for agricultural irrigation and to estimate the daily intake of As consumed by the villagers from rice. The median and mean total As contents in 214 rice grain samples were 131 and 143 μg/kg, respectively, with a range of 2–557 μg/kg (dry weight, dw). Arsenic concentrations in control rice samples imported from Pakistan and India and on sale in Australian supermarkets were significantly lower (p < 0.001) than in rice from contaminated areas. Daily dietary intake of As from rice was 56.4 μg for adults (males and females) while the total daily intake of As from rice and from drinking water was 888.4 and 706.4 μg for adult males and adult females, respectively. From our study, it appears that the villagers are consuming a significant amount of As from rice and drinking water. The results suggest that the communities in the villages studied are potentially at risk of suffering from arsenic-related diseases.

Arsenic levels in rice grain and assessment of daily dietary intake of arsenic from rice in arsenic-contaminated regions of Bangladesh--implications to groundwater irrigation

• Biotransformation of arsenic includes oxidation, reduction, methylation, and conversion to more complex organic arsenicals. Members of the class of arsenite (As(III)) S-adenosylmethyltransferase enzymes catalyze As(III) methylation to a variety of mono-, di-, and trimethylated species, some of which are less toxic than As(III) itself. However, no methyltransferase gene has been identified in plants. • Here, an arsM gene from the soil bacterium Rhodopseudomonas palustris was expressed in Japonica rice (Oryza sativa) cv Nipponbare, and the transgenic rice produced methylated arsenic species, which were measured by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). • Both monomethylarsenate (MAs(V)) and dimethylarsenate (DMAs(V)) were detected in the roots and shoots of transgenic rice. After 12 d exposure to As(III), the transgenic rice gave off 10-fold greater volatile arsenicals. • The present study demonstrates that expression of an arsM gene in rice induces arsenic methylation and volatilization, theoretically providing a potential stratagem for phytoremediation.

Arsenic biotransformation and volatilization in transgenic rice

Groundwater contaminated with arsenic (As), when extensively used for irrigation, causes potentially long term detrimental effects to the landscape. Such contamination can also directly affect human health when irrigated crops are primarily used for human consumption. Therefore, a large number of humans are potentially at risk worldwide due to daily As exposure. Numerous previous studies have been severely limited by small sample sizes which are not reliably extrapolated to large populations or landscapes. Human As exposure and risk assessment are no longer simple assessments limited to a few food samples from a small area. The focus of more recent studies has been to perform risk assessment at the landscape level involving the use of biomarkers to identify and quantify appropriate health problems and large surveys of human dietary patterns, supported by analytical testing of food, to quantify exposure. This approach generates large amounts of data from a wide variety of sources and geographic information system (GIS) techniques have been used widely to integrate the various spatial, demographic, social, field, and laboratory measured datasets. With the current worldwide shift in emphasis from qualitative to quantitative risk assessment, it is likely that future research efforts will be directed towards the integration of GIS, statistics, chemistry, and other dynamic models within a common platform to quantify human health risk at the landscape level. In this paper we review the present and likely future trends of human As exposure and GIS application in risk assessment at the landscape level.

Human arsenic exposure and risk assessment at the landscape level: a review

World Health Organization classifies pesticides with arsenic compounds as active ingredients to be highly hazardous. Arsenic (As)-containing pesticides are thus banned in Sri Lanka since 1995 and it has been officially notified in the extraordinary gazette notification no 1190/24 of the Democratic Republic of Sri Lanka of 6 th June, 2001. Arsenic is not even prescribed to include as an inert ingredient, except for six types of pesticides in which it is allowed (within limits) as an impurity and in Sri Lanka, copperbased pesticides only are legally allowed to contain (within limits) arsenic. Present study is an attempt to test the pesticides available in the Sri Lankan market for presence of arsenic. Despite the fact that importation of Ascontaining pesticides is illegal, results of the present study revealed that twenty nine (29) out of the 31 available pesticide brands belong to 20 active ingredients in the local market tested, contained As in the range of 180±14 2586±58 μg/kg and it varied depending on the type of active ingredient, brand, batch of pesticides, importer and the area that it is used. Using arsenicals in augmenting toxicity of pesticides is speculated a potential means through which As enters the natural environment, especially in the areas where rice

/pdf/presence-of-arsenic-in-pesticides-used-in-sri-lanka-40xncz4hz5.pdf

Presence of Arsenic in pesticides used in Sri Lanka

A hydroponic experiment with barley seedlings (Hordeum vulgare L. cv. Minorimugi) grown in iron (Fe)-depleted medium in the presence of added arsenic (As) at the rates of 0, 0.67, 6.7 and 67 µmol L−1 (equivalent to 0, 0.05, 0.5 and 5 mg L−1 As, respectively) showed that increasing the As concentration in the medium lowered the release of phytosiderophores (PS) and their concentration in the roots. This Fe-depleted experiment was conducted to clarify the effect of As on the release and concentration of PS in roots and on the phosphorus (P) and Fe concentrations in plants. The chlorophyll index increased substantially in the 67 µmol L−1 As treatment compared with the other treatments. This result indicated that higher concentrations of As might interrupt the appearance of Fe chlorosis in plants grown in Fe-depleted medium. Arsenic at a level of 67 µmol L−1 increased the Fe concentration and accumulation in shoots disappearing the whitish chlorosis. An increased concentration of Fe in the shoot migh...

https://www.tandfonline.com/doi/pdf/10.1111/j.1747-0765.2009.00360.x

Effect of arsenic on phytosiderophores and mineral nutrition of barley seedlings grown in iron-depleted medium

Arsenic contamination of Bangladesh rice.

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Arsenic contamination of Bangladesh rice.