Groundwater arsenic contamination in Bangladesh

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Toxicology

Groundwater arsenic contamination in Bangladesh—21 Years of research Dipankar Chakraborti a,∗ , Mohammad Mahmudur Rahman a,b , Amitava Mukherjee a,c , Mohammad Alauddin d , Manzurul Hassan e , Rathindra Nath Dutta f , Shymapada Pati g , Subhash Chandra Mukherjee h , Shibtosh Roy i , Quazi Quamruzzman i , Mahmuder Rahman i , Salim Morshed i , Tanzima Islam i , Shaharir Sorif i , Md. Selim i , Md. Razaul Islam i , Md. Monower Hossain i a

School of Environmental Studies, Jadavpur University, Kolkata 700 032, India Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA, 5095, Australia c Centre for Nanobiotechnology, VIT University, Vellore 632014, Tamil Nadu, India d Department of Chemistry, Wagner College, Staten Island, NY 10301, USA e Department of Geography and Environment, Jahangirnagar University, Savar, Dhaka 1342, Bangladesh f Department of Dermatology, Institute of Post Graduate Medical Education and Research, SSKM Hospital, Kolkata, India g Department of Obstetrics and Gynaecology, Kolkata National Medical College, Kolkata, India h Department of Neurology, Medical College, Kolkata, India i Dhaka Community Hospital, Dhaka 1217, Bangladesh b

a r t i c l e

i n f o

Article history: Received 20 October 2014 Received in revised form 2 January 2015 Accepted 5 January 2015 Keywords: Arsenic Groundwater Biological samples Health effects Managing risk

a b s t r a c t Department of Public Health Engineering (DPHE), Bangladesh first identified their groundwater arsenic contamination in 1993. But before the international arsenic conference in Dhaka in February 1998, the problem was not widely accepted. Even in the international arsenic conference in West-Bengal, India in February, 1995, representatives of international agencies in Bangladesh and Bangladesh government attended the conference but they denied the groundwater arsenic contamination in Bangladesh. School of Environmental Studies (SOES), Jadavpur University, Kolkata, India first identified arsenic patient in Bangladesh in 1992 and informed WHO, UNICEF of Bangladesh and Govt. of Bangladesh from April 1994 to August 1995. British Geological Survey (BGS) dug hand tube-wells in Bangladesh in 1980s and early 1990s but they did not test the water for arsenic. Again BGS came back to Bangladesh in 1992 to assess the quality of the water of the tube-wells they installed but they still did not test for arsenic when groundwater arsenic contamination and its health effects in West Bengal in Bengal delta was already published in WHO Bulletin in 1988. From December 1996, SOES in collaboration with Dhaka Community Hospital (DCH), Bangladesh started analyzing hand tube-wells for arsenic from all 64 districts in four geomorphologic regions of Bangladesh. So far over 54,000 tube-well water samples had been analyzed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS). From SOES water analysis data at present we could assess status of arsenic groundwater contamination in four geo-morphological regions of Bangladesh and location of possible arsenic safe groundwater. SOES and DCH also made some preliminary work with their medical team to identify patients suffering from arsenic related diseases. SOES further analyzed few thousands biological samples (hair, nail, urine and skin scales) and foodstuffs for arsenic to know arsenic body burden and people sub-clinically affected. SOES and DCH made a few follow-up studies in some districts to know their overall situations after 9 to 18 years of their first exposure. The overall conclusion from these follow-up studies is (a) villagers are now more aware about the danger of drinking arsenic contaminated water (b) villagers are currently drinking less arsenic contaminated water (c) many villagers in affected village died of cancer (d) arsenic contaminated water is in use for agricultural irrigation and arsenic exposure from food chain could be future danger. Since at present

∗ Corresponding author. Tel.: +91 33 2414 6233; fax: +91 33 2414 6266. E-mail address: [email protected] (D. Chakraborti). http://dx.doi.org/10.1016/j.jtemb.2015.01.003 0946-672X/© 2015 Elsevier GmbH. All rights reserved.

Please cite this article in press as: Chakraborti D, et al. Groundwater arsenic contamination in Bangladesh—21 Years of research. J Trace Elem Med Biol (2015), http://dx.doi.org/10.1016/j.jtemb.2015.01.003

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more information is coming about health effects from low arsenic exposure, Bangladesh Government should immediately focus on their huge surface water management and reduce their permissible limit of arsenic in drinking water. © 2015 Elsevier GmbH. All rights reserved.

Introduction Bangladesh is a small country with an area of 147,620 km2 having a population of about 160 million (according to 2011 census). It is located in the Ganges, Brahmaputra and Meghna plains. It is a riverine country. A major part of the country is low lying and is being annually flooded by devastating floods. Annual estimated rainfall is in range of 1194 mm to 3454 mm [1]. The country has a network of hundreds of rivers (total 230 rivers including tributaries). The country is famous for its water resources including the surface water and groundwater. The land is very fertile. Before the advent of tube-wells, the people used to depend on natural surface water of rivers, canals, lakes and man-made water reservoirs like ponds and dug-wells [1]. With the increase in population the corresponding increase in agricultural waste, rich in fertilizers, pesticides, insecticides, herbicides etc. rendered the traditional sources water unfit for drinking. Spread of cholera, diarrhea and other water borne added to the problem. To prevent the water borne diseases from surface water, millions of shallow tube-wells were installed across the country through Government, UN agencies, donors and private initiatives for getting safe water for consumption [1]. The exact number of the hand tube-wells in Bangladesh is not known but at present from 8 to 12 million [1]. During 1992, the researchers from School of Environmental Studies (SOES) noticed something unusual while working in arsenic affected Gobindapur village, Swarupnagar block, North 24Parganas district, West Bengal. In one family, a woman, who came to West Bengal from Bangladesh (Village: Bansdoha, Post Office: Fatepur, District: Satkhira) after her marriage [2,3] had arsenical skin lesions, though others in the family did not show any symptom. On being interviewed, the woman revealed that many of her relatives in Bangladesh had similar skin lesions. She further told that she had seen similar skin lesions among a few of her neighbors and also in some people living in two neighboring villages (Uttar Sripur and Tona). The SOES in its report on West Bengal’s arsenic calamity had mentioned that Bangladesh, too, in all probability, was arsenic affected [2,3]. In due course of time, SOES began to gather more and more information about arsenic problem in those parts of Bangladesh adjacent to the arsenic affected areas of West Bengal. SOES analyzed the hair, nail, skin-scale and urine of the patients who came to Kolkata for treatment, and in most of the biological samples, arsenic was found in elevated level [3]. SOES in 1994 also wrote to the World Health Organization (WHO) and the United Nations International Children Emergency Fund (UNICEF) in Bangladesh about the problem [3] and requested them to take care of the problem before it aggravated. Smith et al [4] reported, “In Bangladesh arsenic contamination of tube-wells water was confirmed in 1993 by the DPHE in wells in Nawabganj district.” However, Bangladesh officials including the DPHE, who were present at the international arsenic conference in Kolkata, February 6–8, 1995 organized by SOES [5] denied any groundwater arsenic contamination in Bangladesh. In this conference, arsenic incident in Bangladesh was documented by SOES [5]. Further, the post conference report was published by SOES in May 1995 [6]. The chief of Bangladesh health official and the WHO representative of Bangladesh also wrote in that issue but refrained from mentioning arsenic contamination in groundwater of Bangladesh.

During and after the International Conference [5], the local newspapers in Kolkata published the news on arsenic calamity in West Bengal, India, along with photographs of some arsenic patients. Since Kolkata newspapers are also available in Bangladesh, medical practitioners from Bangladesh hospitals started writing letters to the SOES [3] that they had been getting patients with similar skin lesions at the out-patient departments of their hospitals. But, the doctors stated that, they had failed to recognize them as arsenic patients. After the February, 1995 conference, more and more people suffering from arsenical skin lesions in Bangladesh started coming to SOES for treatment. During August 1995, Director (Dipankar Chakraborti) of SOES, Jadavpur University attended a meeting in Bangladesh organized by the UNICEF, Bangladesh to discuss arsenic problem in West Bengal and its probable effect in Bangladesh [7]. In that meeting, Chakraborti showed the pictures of patients from Bangladesh and he mentioned that Bangladesh could be affected by now and it was decided in the meeting that there was an immediate need for work in Bangladesh. In that meeting, Directorate General (DG) of Health Services, Director of Primary Health Care (PHC), Director of National Institute of Preventive and Social Medicine (NIPSOM) were also present. Bangladesh’s groundwater arsenic contamination and related health effects came to our notice in 1992 and officially we informed Bangladesh government and aid agencies from 1994 onwards. The problem was not accepted until the February international conference in Dhaka Bangladesh in 1998 [8]. International aid agencies promoted installation of hand-tube-wells in Bangladesh but they never tested the presence of arsenic in hand tube-wells. Arsenic groundwater contamination and health effects in Gangetic plain of West Bengal was known from 1983 and five publications were available in national journals and one in WHO Bulletin in 1988 [9]. BGS dug tube-wells in Bangladesh in 1980s and early 1990s but they did not test the groundwater for arsenic. Again BGS came back to Bangladesh in 1992 to assess the quality of the water people were drinking but again they did not test for arsenic. In this context, Bangladeshi villagers went to British court [10] blaming that BGS was responsible for their sufferings from arsenic toxicity. During 1996, the Geology Department of Rajshahi University, Bangladesh sent 600 water samples to the SOES laboratory collected from a few bordering districts of Bangladesh close to the arsenic affected districts of West Bengal. Many of the samples were found to be contaminated. Further, WHO, Bangladesh sent two doctors (Dr. Sk. Abdul Hadi and Dr. Sk. Akhter Ahmed) from the NIPSOM to SOES for two weeks (17–28 June 1996) training to understand the signs and symptoms of arsenicosis. During their training, they visited some arsenic affected villages of West Bengal with Director, SOES and Dr. K.C. Saha (dermatologist) to learn how to identify arsenical skin lesions. After that, SOES and NIPSOM worked jointly for three months during August - October 1996 in Bangladesh, covering 17 districts and analyzed 750 water samples, about 300 each of hair, nail and a few skin-scales for arsenic. High level of arsenic was found in all those samples [3]. In the meantime, the representatives from the DCH, Bangladesh came to Kolkata in November 1996 and analyzed water, hair, urine and skin-scale samples of arsenic victims from some districts of Bangladesh in SOES laboratory. For a detailed study, SOES carried out a joint survey with the DCH from December 19, 1996 to January




7, 1997 and surveyed 15 districts of Bangladesh. All together in 1996 and 1997, SOES jointly with various organizations of Bangladesh had analyzed, 3,427 water samples collected covering 37 districts [3]. Out of 37 districts covered, in 27 districts arsenic has been found to be above the maximum permissible limit (50 ␮g/L). From these 27 districts, 2929 samples were analyzed and found 39% of tube-wells water were safe to drink according to the WHO guideline of arsenic in drinking water (10 ␮g/L) and 61% and 39% of the tube-wells water contained arsenic above 10 and 50 ␮g/L, respectively. About 700 biological samples were analyzed from villagers of 18 districts. Analytical result of these samples indicated that 85%, 98% and 92% of urine, nail and hair samples had arsenic above the normal or toxic (hair) level, respectively. In these districts, 889 adults and 48 children (57.5% including children) from 45 villages were identified [3] with arsenical dermatological features such as melanosis, leucomelanosis, keratosis, hyperkeratosis, etc. The magnitude of groundwater arsenic contamination in Bangladesh was realized only after the international conference [8] on arsenic in Dhaka, Bangladesh held in February 1998. This conference was jointly organized by the SOES and the DCH. Immediately after the conference a report [11] described the magnitude of arsenic contamination in Bangladesh; the World Bank’s local chief stated that tens of millions people were at risk for health effects and that 43,000 villages of 68,000 were at risk or could be at risk in future. In the same report, the WHO predicted [11] that, within a few years, death across much of southern Bangladesh (1 in 10 adults) could be from cancers triggered by arsenic. After this conference most of the international organizations (World Bank, UNICEF, Danish International Development Agency, and British Geological Survey etc.) started actively working on groundwater arsenic problem in Bangladesh. Most of these international organizations are collaborating with national organizations. The SOES is still continuing their crusade against arsenic poisoning in Bangladesh. The specific objective of this 21 years work is to highlight the past and present arsenic situation of Bangladesh by a group of researchers including medical personnel.

Research work in Bangladesh during last 21 years SOES first identified arsenic groundwater contamination and consequent sufferings of people in Bangladesh in 1992. Till the end of 1996, SOES did preliminary work with help of people coming to Kolkata from Bangladesh for arsenic treatment in SOES, who brought water, hair, nail samples from the affected villages for analysis. From December 1996, an extensive field survey had been carried out by SOES covering all the four geomorphologic regions of Bangladesh in collaboration with the DCH mainly to assess the groundwater arsenic contamination status in all 64 districts. This field work involved majorly analysis of hand tube-well water samples. So far over 54,000 tube-well water samples had been analyzed. Out of total 64 districts, in 2200 villages from 50 districts we found arsenic above 50 ␮g/L and in 59 districts in 2700 villages above 10 ␮g/L. Surprisingly, 7.5% of the analyzed tube-wells had arsenic concentrations above 300 ␮g/L. It has been reported [12] that ingestion of such high concentration of arsenic for couple of years may result arsenical skin lesions. In our very preliminary investigation the dermatologists examined 20,627 individuals from 260 villages, 77 thanas (subdistrict in the Administrative divisions of Bangladesh), and 31 districts of Bangladesh and registered 4573 patients with arsenical skin lesions from 227 villages. Medical team of DCH and SOES group were involved in this work. SOES and DCH also carried out preliminary work with their medical team for other diseases like neuropathy, pregnancy outcome, cancer etc. We (SOES laboratory) analyzed few thousands biological samples (hair, nail, urine and skin scales) and

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foodstuffs with a view to evaluate people sub-clinically affected and the magnitude of arsenic contamination in all over Bangladesh. Status of arsenic groundwater contamination in four geo-morphological regions of Bangladesh and location of possible arsenic safe groundwater Bangladesh comprises of four major geomorphological regions. These are Tableland (Pleistocene Plain and Pleistocene Upland), Flood Plain, Deltaic Region including Coastal region and Hill Tract [12]. The distribution of hand tube-well water samples against different concentration ranges of arsenic in all geo-morphological regions except Hill Tract is presented in Table 1. Tableland region (Pleistocene plain and Pleistocene upland) Out of 17 districts in Tableland, four districts (Panchagarh, Thakurgaon, Dinajpur and Joypurhat) are entirely in the Tableland region while 13 districts are composed of both tableland and flood plain regions. Altogether tableland comprises of 65 thanas of 17 districts in Bangladesh. SOES and DCH collected and analyzed 9755 hand tube-well water samples from tableland region. The distribution of hand tube-well water samples against different concentration ranges of arsenic in tableland region is presented in Table 1 and Fig. 1. The result shows that 204 (2.1%) of the samples contained arsenic between 10 and 50 ␮g/L and only 17 (0.2%) had arsenic >50 ␮g/L. So, 9,738 (99.8%) water samples from this region appear safe to drink according to the recommended level of arsenic in drinking water of Bangladesh (50 ␮g/L). BGS-DPHE (1999) data shows that only 44 (1.7%) of the 2607 water samples analysed from tableland region had arsenic >50 ␮g/L [13]. Flood plain region Flood plain region is comprised a total of 229 thanas in 34 districts of Bangladesh. SOES and DCH surveyed 155 thanas and arsenic >50 ␮g/L was detected in 112 thanas. SOES and DCH analyzed 19,845 hand tube-well water samples from flood plain region and the distribution of total water samples against different arsenic concentration range is given in Table 1 and Fig. 1. Of these, 50.8% and 34.9% of the analyzed water samples contained arsenic >10 ␮g/L and >50 ␮g/L, respectively. BGS-DPHE (1999) data shows that 4587 (27.8%) out of 16,513 water samples analyzed from flood plain region had arsenic >50 ␮g/L [13]. Deltaic region including coastal region SOES and DCH have combined deltaic and coastal regions as there is no clear geological demarcation. Deltaic and coastal regions are composed of 139 thanas in 22 districts of Bangladesh. SOES and DCH surveyed and collected hand tube-well water samples from 97 thanas and arsenic >50 ␮g/L was detected in 83 thanas. SOES and DCH analyzed 22,113 hand tube-well water samples for arsenic from this region. The results are given in Table 1 and Fig. 1. The results indicate that 54.7% of the samples had arsenic >10 ␮g/L and 32.8% had arsenic >50 ␮g/L. BGS-DPHE (1999) analyzed 12,245 water samples from 126 thanas of this region and 3344 (27.5%) samples from this region had arsenic >50 ␮g/L [13]. Hill tract region SOES and DCH analyzed 489 hand tube-well water samples from the Hill Tract region of Bangladesh. The distribution of total samples in different arsenic concentration range is given in Fig. 1. SOES and DCH have not identified any sample with arsenic above 10 ␮g/L


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Districts surveyed

Tableland

Panchagarh, Takurgaon, Dinajpur, Joypurhat, Bogra* , Naogaon* , Tangail* , Gazipur* , Dhaka* , Rajshahi* , Sirajganj* , Lalmonirhat* , Narayanganj* , Narsingdi* , Nawabganj* , Nilphamari* , Rangpur* Sylhet, Moulavibazar,Sunamganj, Habiganj,Kishoreganj, Narayanganj* ,Comilla, Netrokona, Mymensingh, Jamalpur,Narsingdi* , Munshiganj,Manikganj, Chandpur,Brahmanbaria, Feni, Sirajganj* , Rangpur* , Kurigram, Lalmonirhat* ,Nilphamari* , Rajshahi* ,Nawabganj* , Gaibandha, Natore, Sherpur, Naogaon* , Dhaka* , Gazipur* , Tangail* , Bogra* , Lakshmipur, Noakhali, Chittagong Pabna, Kushtia, Meherpur, Chuadanga, Jinaidaha, Jessore, Magura, Satkhira, Khulna, Narail, Rajbari, Faridpur, Gopalganj, Madaripur, Shariatpur, Barisal, Pirojpur, Bagherhat, Jalakati, Patuakhali, Bhola, Barguna

Flood plain

Delta including coastal

**

Total thanas

No. of thana surveyed

No. of samples analyzed

Distribution of total samples in different arsenic concentration (␮g/L) range

Maximum Concentration found (␮g/L)

1000

150 (128)

65

9755

9534

204

15

2

309 (289)

155

19,845

9760

3153

1471

3179

1181

552

322

227

4730

139

97

22,113

9985

4873

2228

3306

1082

386

179

74

2190

* Districts are in mixed geo-morphological region but thanas are in Tableland region. Dhaka city has 21 thanas. In our study we consider Dhaka city as a thana.

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Geo-morphological region

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Table 1 Distribution of hand tube-wells against arsenic concentration (␮g/L) range in various geo-morphological regions of Bangladesh.



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Fig. 1. Distribution of arsenic concentration ranges in all geo-morphological regions of Bangladesh.

from the Hill tract regions, which is similar to the findings of BGSDPHE (1999) study [13]. It is noteworthy that BGS-DPHE (1999) analyzed water samples only from Chittagong and Cox’s Bazar district of Hill tract areas [13]. From the results, it appears that the groundwater of Tableland and Hill Tract regions are generally free from arsenic contamination but the Flood plain and the Deltaic regions are vastly arsenic contaminated. The probable reason for contamination may be heavy deposition of Holocene sediments to Flood plain and Deltaic region. In coastal region, deep tube-wells are available and arsenic contamination of groundwater is much less compared to the Deltaic region. The results also indicated that the flood plain region is more arsenic contaminated than the deltaic region. The number of samples having arsenic >1000 ␮g/L in flood plain (227, 1.14%) are more than the deltaic region (74, 0.33%). Stratigraphically the Barind Tract, Madhupur Garh, Lalmai Hills of Comilla are same. The Barind Tract, Madhupur Garh and Lalmai Hills of Comilla known as Tableland, consists of Pleistocene red clay, silt and sand. Barind Tract and Madhupur Garh are marginally

overlain by arsenic bearing Holocene sediments [13,14]. Arsenic analysis report in some geographical locations in the districts like Gazipur, Bogra, Tangail, which are in Tableland but partially filled up by Holocene Flood Plain deposit showed presence of considerable amount of arsenic in its groundwater. The possible reason of such contamination is due to Flood plain deposition on the eroded surface of Tableland. A unique example is Kapasia thana of Gazipur district, where out of 5 thanas, 4 are in Tableland and free from arsenic contamination while Kapasia, the eroded Tableland of Gazipur district filled up by Holocene Flood plain deposit is found to be arsenic contaminated. In the Eastern hills of Chittagong, the Holocene Flood plain deposit is absent. All above areas are underlain by a thick medium to coarse sand and gravel bed of Pliocene epoch known as DupiTila [13,15–21]. The DupiTila sandstone formation extends all over Bangladesh excepting probably the western two third of the Delta [13,22]. The Pliocene sandstone gravel beds remains practically unexposed in these regions and forms the main aquifer beneath these areas. The notable geological control on arsenic occurrence in groundwater is, in the oldest unit,




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where the Pleistocene Barind clay, Madhupur clay and Lalmai Hills and East and Northeast of hilly areas overlies the DupiTila sands, are found to contain arsenic free aquifer water. The total area occupied by the DupiTila measured roughly 91,000 km2 and the total thickness at places attains more than 300 m [22]. Pliocene DupiTila presents undisputed evidence as a basement rock of Barind Tract, Madhupur Garh, Lalmai Hills of Comilla having considerable arsenic free water resource. Why some areas of Tableland are to some extent arsenic-contaminated and Flood plain are less contaminated The fringe areas of Tableland with Flood plain might get arsenic contaminated if some rivers pass or history of erosion of the Tableland by the river. The probable reason of contamination may be heavy deposition of Holocene sediments due to severe surface erosion of Tableland and creating aquifer. Again confusion arises when we try to find out the actual extension of Tableland map of BGSDPHE (1999) and Bangladesh Physical Map (1981) differs to some extent mainly in bordering area [13,23]. On the other hand, some districts such as Nilphamari, Kurigram, Lalmonirhat and Rangpur situated at Flood plain regions are less arsenic contaminated (Table 2). Arsenic in biological samples (1996–2002): Subclinical effects Arsenic concentration in hair, nail samples is an indicator of arsenic body burden while urinary arsenic denotes recent arsenic exposure. Table 3 shows the number of nail (n = 4471), hair (n = 4536), skin scales (n = 705) and urine (n = 1586) samples from the villagers we had collected and analyzed. Out of these samples, 60% were from villagers without skin lesions and 40% with skin lesions. The results show 83% of hair was above toxic level, 93% of nails and 95% of urine above normal level [24–26]. The results further suggest that irrespective of skin lesions, villagers have elevated levels of arsenic in biological samples. Thus, many villagers were sub-clinically affected. When we compare the arsenic in biological samples of West Bengal, India (Table 3) with Bangladesh, the two most arsenic affected regions in the world, we find Bangladesh situation is really bad. When the normal level of arsenic in hair ranges from 80–250 ␮g/kg and 1000 ␮g/kg is an indication of toxicity, for Bangladesh 83% villagers had arsenic above toxic level and for West Bengal it was 53%. At present we are again collecting biological samples from the same affected villages we surveyed earlier to know the present body burden. Results of some of the patients we will describe in follow-up study section. Arsenic in urine Urinary arsenic is usually considered as the most reliable indicator of recent exposure to arsenic and is used as the main bio-marker of recent exposure. Normal excretion of arsenic in urine ranges from 5 to 40 ␮g/1.5 L [26]. SOES and DCH analyzed 1586 urine samples for arsenic collected from both people with arsenical skin lesions (40%) and people without skin lesions (60%) in Bangladesh during 1996–2002, usually from the contaminated villages. In our analytical procedure, we only measured inorganic arsenic and its metabolites [2,3]. So, organic arsenic from fish and other seafood has no contribution in our urine analysis. The range of arsenic in urine from 1996 to 2002 analysis was 24–3086 ␮g/L and 95% of the samples had arsenic above the normal level (5–40 ␮g per 1.5 L) of arsenic in urine (Table 3). In early 2003, SOES and DCH further analyzed 1497 urine samples (mean: 81, median: 43 and

range: 10–1224 ␮g/L) from seven thanas (Nabinagar, Muradnagar, Haimchar, Sirajdikhan, Shibchar, Bhanga and Manirampur) of Bangladesh. Due to the wide awareness of arsenic contamination in contaminated villages, particularly where patients are suffering from the effects of arsenic toxicity, villagers usually do not use arsenic contaminated water for drinking and cooking. For this reason, the mean arsenic level in urine analyzed in 2003 was less compared to our previous data. During 2004–2005, SOES and DCH also analyzed 181 urine samples from villagers (60% with arsenical skin lesions and 40% without arsenical skin lesions) of the Eruani village, Laksam thana of Comilla district and the result shows that more than 98% of the samples had arsenic above the normal level (range 310–4863 ␮g/1.5 L) [27]. Water analysis from hand tube-wells of this village showed very high concentration of arsenic in their drinking water [27]. Villagers told us they drank from their contaminated tube-wells due to unavailability of safe water. We believe that is not true as we found some safe tube-wells in that village [27]. The truth is (a) lack of their education and awareness of the danger of arsenic toxicity (b) many do not believe their skin lesions are due to arsenic in their drinking water but it is due to the sin of their last birth (c) tube-well water is good to drink as the fresh water in summer it is cold and in winter it is hot. The MMA(III), MMA(V), DMA(III), DMA(V) are metabolites of inorganic arsenic of trivalent and pentavalent states. Since the trivalent states rapidly converts to pentavalent states, the latter forms are mostly identified in urine and methylation process is viewed as a detoxification pathway for ingested arsenic. However, growing evidence predicts that very unstable MMA(III) the trivalent intermediary metabolite may produce ill effects with exposure to inorganic arsenic [28]. We previously studied the pattern of primary and secondary methylation both adults and children exposed to arsenic via drinking water in the Datterhat village of Madaripur district in Bangladesh [29]. It was observed that the secondary methylation capacity in children was higher than adults, as the values of the DMA/MMA ratio were significantly higher in children than adults in exposed group [29] indicating a higher methylation capacity in children than adults. Most probably due to this, children retain less arsenic in their body than adults. Nutrition plays an important role in methylation of arsenic [29]. Due to poor nutrition, less methylation of inorganic arsenic ingested from contaminated tube-well occurrence less arsenic released from body with urine. People with poor nutrition suffer more. For this reason, poor people in the villages are suffering more from arsenic toxicity. A study of arsenic species from the Haziganj thana of Chandpur district in Bangladesh [30] shows arsenite and arsenate are the major species present in urine of a group of exposed people and the amount of both MMA and DMA are very low. The explanation of such high percentage of As(III) in urine was considered to be due to poor methylation capacity of the studied subjects [30]. Further studies on factors influencing arsenic methylation and excretion in human are needed.

Arsenic in foodstuffs of Bangladesh In addition to arsenic in drinking water, arsenic-contaminated groundwater is extensively used for the irrigation of crops in Bangladesh and other Asian countries, especially for the cultivation of paddy rice and vegetables during dry season. For this reason, huge amount of arsenic is deposited on to the farmlands of Bangladesh. A study from West Bengal, India revealed that 6.4 tons of arsenic was withdrawn per year and deposited in agricultural field of area 200 km2 from 3200 hand tube-wells [31]. Substantial amount of arsenic was detected in Bangladeshi foodstuffs, especially rice and vegetables, posing an additional danger


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Table 2 Distribution of hand tubewells against concentration (␮g/L) ranges of arsenic in 22 thanas of Nilphamari, Kurigram, Lalmonirhat and Rangpur districts situated in Flood plain region of Bangladesh. Total number of samples analyzed

1438

% Of samples As < 50 ␮g/L

Distribution of samples in different arsenic concentration (␮g/L) range

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200 ␮g/kg) is associated with genotoxic effects. As people of Bengal delta consume large amount of rice and vegetables daily, the risk would be much higher than US and other western countries as people rarely eat small quantity of rice (40–45 g, once in every 2 weeks). Previously SOES conducted a study to understand why arsenic body burden is higher among people using safe water for drinking and cooking, living in arsenic affected villages of West Bengal [43]. In that study, safe water from a source contained arsenic 700 ␮g/L) or even with less arsenic (around 400 ␮g/L) but eating less nutritious food. Our preliminary conclusion about the recovery of arsenical skin lesions in children and adults after our last 28 years study with medical group from arsenic affected areas of GMB-Plain is: if children (