1、 1 外文 文献 ： Arsenic in the environment: Biology and Chemistry Abstract： Arsenic (As) distribution and toxicology in the environment is a serious issue, with millions of individuals worldwide being affected by As toxicosis. Sources of As contamination are both natural and anthropogenic and the scale o
2、f contamination ranges from local to regional.There are many areas of research that are being actively pursued to address the As contamination problem. These include new methods of screening for As in the field, determining the epidemiology of As in humans, and identifying the risk of As uptake in a
3、griculture.Remediation of As-affected water supplies is important and research includes assessing natural remediation potential as well as phytoremediation. Another area of active research is on the microbially mediated biogeochemical interactions of As in the environment. In 2005, a conference was
4、convened to bring together scientists involved in many of the different areas of As research. In this paper, we present a synthesis of the As issues in the light of long-standing research and with regards to the new findings presented at this conference. This contribution provides a backdrop to the
5、issues raised at the conference together with an overview of contemporary and historical issues of As contamination and health impacts.Crown Copyright . 2007 Published by Elsevier B.V. All rights reserved. 1. Introduction 1.1. Location and scale of problem Arsenic (As) has been detected in groundwat
6、er in several countries of the world, with concentration levels exceeding the WHO drinking water guideline value of 10 g/L (WHO, 2001) as well as the national regulatory standards (e.g. 50 g/L in India and Bangladesh, Ahmedet al., 2004； Mukherjee et al., 2006). Arsenic in groundwater is often associ
7、ated with geologic sources, but in some locations anthropogenic inputs can be extremely important. Ingestion of geogenic As from groundwater sources is manifested as chronic health disorders in most of the affected regions of the world (BGS & DPHE, 2001； Bhattacharya et al.,2002a,b； Smedley and Kinn
8、iburgh, 2002； Welch and 2 Stollenwerk, 2003； Bundschuh et al., 2005； Naidu et al., 2006). In Asia, the impact of As toxicity is particularly alarming. For example, in the Bengal Basin of Bangladesh and West Bengal, India (Bhattacharya et al., 1997, 2002a,b, 2004, 2006a； Mukherjee and Bhattacharya, 2
9、001), As in groundwater has emerged as the largest environmental health disaster putting at least 100 million people at risk of cancer and other As-related diseases. Recent studies indicate the occurrence of geogenic As in the Central Gangetic Plains of Uttar Pradesh, Bihar, Jharkhand and the Brahma
10、putra valley in Assam, and several regions of Madhya Pradesh and Chattisgarh, India (Chakraborti et al., 2004； Mukherjee et al., 2006). During the past few years, As has also been detected in groundwaters of the sedimentary aquifers of the Terai Belt in Southern Nepal (Bhattacharya et al., 2003； Tan
11、dukar et al., 2006), Pakistan (Nickson et al., 2005), the Red River Delta and Mekong Basin of Vietnam and Cambodia (Berg et al., 2001, 2007), raising severe constraints on its use as a drinking water resource. However, few reports are available on the epidemiology and prevalence of Asrelated disease
12、s in these areas. Arsenic is also reported in groundwaters of Australia (Smith, 2005； OShea, 2006； Smith et al., 2003, 2006), where the concentrations levels are well above the drinking water standard of 7 g/L recommended by the National Health and Medical Research Council and the Natural Resource M
13、anagement Ministerial Council of Australia (NHMRC/NRMMC, 2004). In addition, As from anthropogenic sources is also reported in groundwaters of Guam (ATSDR, 2002； Vuki et al., 2007-this volume), a small island in Western Pacific Ocean. Arsenic is also found in widely scattered geographical areas in t
14、he United States and Canada as well as in many other countries of Latin America such as Mexico, Argentina, Bolivia, Brazil andNicaragua,where the sources of As are geogenic as well as anthropogenic sources (Matschullat, 2000； Nordstrom, 2002； Smedley et al., 2002； 2005； Barragner-Bigot, 2004； Bundsc
15、huh et al., 2005； Bhattacharya et al., 2006b； Nriagu et al., 2007). 1.2. Field screening for arsenic Following the discovery of As in the Bengal Basin, there is now an urgent need to address the public health implications due to exposure from drinking water sources. In order to do this and initiate
16、appropriate mitigation measures, there is an urgent need to identify the As-contaminated tubewells (TW) that supply most of this drinking water (Chowdhury and Jakariya, 1999). This involves screening of water in millions of TW, and 3 raising community awareness about the health problems related to c
17、hronic As exposure from drinking water. An overall risk assessment including a component of mitigation for As contamination should be based on accurate determination of As levels in TW water using economically viable methods for As screening. Field test kits offer a more practical tool than laborato
18、ry measurements within the time frame and financial resources available for screening and assessment of the As-contaminated wells as well as their monitoring. Simple, low-cost methods for As determination, such as the field test kits have proved to be most suitable for performing the TW screening qu
19、ickly. Several commercial field test kits are available for determination of As in TW water (Rahman et al., 2002； Khandaker, 2004； Deshpande and Pande, 2005； van Geen et al., 2005； Steinmaus et al., 2006). Field kits provide semiquantitative results and the reliability of several field kits are ques
20、tioned because of poor accuracy (Rahman et al., 2002). Thus, there is a need for further evaluation of the screening results by the field kit, prior to its recommendation for wide scale use in Bangladesh and elsewhere in the world. 1.3. Epidemiology Ingestion of groundwater with elevated As concentr
21、ations and the associated human health effects are prevalent in several regions across the world. Arsenic toxicity and chronic arsenicosis is of an alarming magnitude particularly in South Asia and is a major environmental health disaster (Chakraborti et al., 2004； Kapaj et al., 2006). Arsenic is pe
22、rhaps the only human carcinogen for which there is adequate evidence ofcarcinogenic risk by both inhalation and ingestion (Centeno et al., 2002； Chen and Ahsan, 2004). Most ofthe ingested As is rapidly excreted via the kidney within a few days (Tam et al., 1979； Buchet et al., 1981； Vahter, 1994). H
23、owever, high levels of As are retained for longer periods of time in the bone, skin, hair, and nails of exposed humans (Karagas et al., 2000； Mandal et al., 2003). Studies of As speciation in the urine of exposed humans indicate that the metabolites comprise 1015% inorganic As (iAs) and monomethylar
24、sonic acid (MMAV) and a major proportion (6080%) of dimethylarsenic acid (DMAV) (Tam et al., 1979； Vahter et al., 1995； Hopenhayn-Rich et al., 1996). Recent studies have found monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) in trace quantities in human urine (Aposhian et al., 2000； Del Razo et al., 2001； Mandal et al., 2001). In general, MMAIII is more toxic than As(III) and As(V) (viz.Petrick et al., 2000, 2001).
