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Groundwater Arsenic Contamination Situation in West-Bengal, India: A Nineteen Year Study

Author: 
Mrinal Kumar Sengupta, Amir Hossain, Sad Ahamed, Bhaskar Das, Bishwajit Nayak, Arup Pal, Amitava Mukherjee, M. M. Rahman, Uttam Kumar Chowdhury, Bhajan Kumar Biswas, Tarit Roy Chowdhury, Badal Kumar Mondal, Gautam Samanta, Amit Chatterjee, Dipankar Das, Dilip Lodh, and Dipankar Chakraborti
Source: 
Bhujal News Quarterly Journal, April-Sept, 2009

Subhash Chandra Mukherjee
Department of Neurology, Medical College, Kolkata, India

Shyamapada Pati
Department of Obstetrics and Gynaecology, Institute of Post Graduate Medical Education and Research, SSKM Hospital, Kolkata, India

R.N. Dutta
Department of Dermatology, Institute of Post Graduate Medical Education and Research, SSKM Hospital, Kolkata, India

Kshitish Chandra Saha
Retd. Professor of Dermatology, School of Tropical Medicine, Kolkata, India

BACKGROUND


The study is based on our last 19 years survey on groundwater arsenic contamination in Ganga-Meghna-Brahmaputra (GMB) plain. The area comprises of 5,69,749 km2, with a population of over 500 million. It can be predicted that a good portion of all the states in Ganga-Brahmaputra plain in India (Uttar Pradesh, Bihar, Jharkhand, West Bengal, Assam and other North Eastern hill states) and Bangladesh in Padma-Meghna- Brahmaputra (old) are arsenic affected.

Arsenic crisis in India dates back to as early as 1976 when a preliminary survey (1) on arsenic in dugwells, hand pumps and spring water from Chandigarh and different villages of Punjab, Haryana and Himachal Pradesh in northern India was reported. Officially, arsenic poisoning in West Bengal was first reported by a dermatologist K.C. Saha of School of Tropical Medicine (STM), Calcutta ( Kolkata, previously known as Calcutta) to an outdoor patient of village Ramnagar of Baruipur police station in the district of South 24-Parganas on 6th July, 1983 (Docket No. S/158/33/83). Later it came out that many arsenic patients existed in many villages well before 1983 but they could not be clinically diagnosed, so were not highlighted. According to A. K. Chakraborty, an epidemiologist of All India Institute of Hygiene and Public Health (AIIH&PH), Calcutta who reported on 4th December 1983 (2), “for more than a year physicians were baffled by several cases of hyper-pigmentation which kept coming to them at regular intervals”.

During 1983-1989 the following organizations in West Bengal viz. (a) School of Tropical Medicine (STM), Calcutta (b) All India Institute of Hygiene and Public Health (AIIH&PH), (c) Central Ground Water Board (Eastern Region) (d) Centre for Study of Man and Environment, Calcutta (e) Public Health Engineering Department (PHED), Government of West Bengal (f) SSKM – Hospital, Calcutta (g) Directorate of Health Services, Government of West Bengal were working on the problem of groundwater arsenic contamination. R. Garai, A. K. Chakraborty, S. B. Dey, and K.C. Saha (3) had first warned of malignancy in the hyperkeratosis spots and liver if the diagnosis was delayed.

Saha and Poddar reported (4) in 1986, 36 villages from 18 police stations/blocks of 6 districts are arsenic affected. These districts were 24 Parganas, Murshidabad, Nadia, Bardhaman, Maldah and Medinipur. Although one patient from Ramnagar police station of Medinipur was reported in 1986 but later on we found that he was actually from an affected district Nadia but settled in Medinipur. From 36 villages water samples from 207 hand tubewells were analyzed and 105 (50.7%) showed arsenic concentration above 50 μg/L and highest concentration revealed was 586 μg/L. They further stated that cutaneous malignancy found in 3 out of 1000 cases of chronic arsenical dermatosis. Analysis of arsenic in hair, nail, and skin-scale from the people in the affected villages confirmed arsenic toxicity and identified subclinical arsenic toxicity in some people. Conducting an epidemiological survey in 6 villages from 3 districts (24 Parganas, Bardhaman, Nadia) Chakraborty & Saha reported in 1987 (5), 12 ascites patients out of 197 having arsenical dermatosis and one of whom developed skin cancer eventually. They further added that lowest concentration of arsenic in water producing dermatosis was found to be 200 μg/l. Three deaths were reported due to chronic arsenic poisoning. Out of 71 water samples tested from the affected villages, 55 (77.5%) had arsenic concentration above the Indian permissible limit of 50 μg/l.

In 1988, Guha Mazumder (6) showed evidence of chronic arsenical dermatosis and hepatomegaly in 62 out of 67 members who drank arsenic contaminated water (200 – 2000 μg/l) based on an epidemiological investigation from an arsenic affected area of Ramnagar village, Baruipur block, 24 Parganas. In contrast only 6 out of 96 persons from the same area who drank safe water (below 50 μg/l) had non-specific hepatomegaly, while none had skin lesions.

School of Environmental Studies (SOES), Jadavpur University joined the arsenic work at the beginning of 1988. From August 1989 to December 1991 more information about suffering of people from the blocks of the districts in Maldah, Murshidabad, Bardhaman, Nadia, North 24-Parganas and South 24-Parganas were unearthed by continued research (7-11). The first report of SOES was published in May, 1991 (12) based on a door to door preliminary survey in 5 out of 6 arsenic affected districts (except Bardhaman) of West Bengal. The survey revealed that about 3 million people were at risk in the arsenic affected areas. Our medical survey could identify altogether 600 arsenic patients from 86 villages. In November, 1991 another preliminary report was published (13) exclusively on Bardhaman (also known as Burdwan) district, identifying 77 arsenic patients from 7 villages. In these two reports (12, 13) on the basis of 1800 water samples analysis from 93 villages from 13 police stations and identification of 600 arsenic patients from 1988 to 1991, SOES warned the government of imminent danger.

From July 1992 to early 1995 a considerable number of news articles were published in daily newspapers both in Calcutta as well as in the capital of India, based on the door to door survey report of SOES from the affected six districts (14-25). School of Environmental Studies (SOES) while analyzing the water samples from Calcutta identified arsenic patients in Jadavpur in southern part of Calcutta. At least 10 patients were identified from the area (26). Immediately after the publication of SOES report, the Calcutta Municipal Corporation vehemently opposed this fact stating (27) that 13 tubewells from Jadavpur were all safe with regard to arsenic. In March 1994, SOES published yet another report on arsenic problem of South 24-Parganas (28). In this, other than the magnitude of the spreading calamity and suffering of people, social problems due to arsenical diseases was also stressed. The report stated, “The social problems arising due to arsenical skin lesions in these districts are becoming of serious concern. Even the affected wives are sent back to their parents together with their children. Malnutrition, poor socio-economic condition, illiteracy, food habits and intake of arsenic contaminated water through many years have aggravated the arsenic toxicity”. A news report published in Analyst (29) identified that 312 village, in 37 police stations in 6 districts to be arsenic affected and faced that more than 8,00,000 people in the affected villages were continuing to drink arsenic contaminated water above 50 μg/l.

SOES after working for seven years in arsenic affected villages of West Bengal realized the impact of the problem. In 1994 it was realized by the authorities, scientists, international aid agencies like WHO, UNICEF as well as common people should be alerted about the magnitude and seriousness of arsenic problem unless the grim arsenic situation in West Bengal would continue to be neglected from all quarters. In order to invite international attention on the problem SOES arranged an international conference of 6-8 February in 1995 with additional 3 days field visit in arsenic affected area. This proved to be a turning point in the history of arsenic research in west Bengal.

SOES placed in this conference (30) their preliminary report of survey conducted for last 7 years in 6 arsenic affected districts. In this it was mentioned that 405 villages/wards from 37 police stations were found to be arsenic affected and more than 1.0 million people might be constantly drinking arsenic contaminated water above 50 μg/l from these six districts. They put an estimate of around 2,00,000 people to be suffering from arsenic toxicity.

During and immediately after the conference most of the national and some of the international media published and aired the articles and programs highlighting the magnitude and severity of the problem. Altogether arsenic experts from 20 different countries participated at the conference and they were horrified by the magnitude of the problem (31, 32). One of the experts Bill Chappell from the University of Colorado, USA who attended the conference said, “The chronic arsenic poisonings occurring in West Bengal represent the single-largest environmental health problem I know of, other than that associated with the Chernobyl disaster” (33). Epidemiologist Allan Smith added, “the problems are very serious and warrant a very high priority for solutions and further investigations” (34). The seriousness of the problem and need of immediate action to be taken were highlighted by various experts (35-38).

Immediately after the conference, the Secretary of Public Health Engineering Department (PHED), Government of West Bengal, the nodal agency to look after the arsenic problem of West Bengal issued a statement in the newspaper in which he apprehended 30 to 40 lakhs people in West Bengal to be potentially at risk of arsenic poisoning through drinking water. The report identified 8 to 10 lakhs of people as already affected and 10,000 – 15,000 as showing positive sign of poisoning (39).

Although the overall attitude of government was not to accept the magnitude of the arsenic calamity, the policy faced criticism from some of the top officials. In a report the Secretary of PHED said, “The state government policy on controlling arsenic poisoning lacks transparency while the functioning of the department needs openness” (40). More and more arsenic incidents, suffering and death started surfacing from the SOES field survey (41) and groundwater arsenic contamination was reported from proper Calcutta by SOES (42). However, Calcutta Municipal Corporation denied any such contamination (43). In continuing surveys, more and more arsenic affected districts were added to our list in 1997 and SOES reported (44), 830 villages from 58 blocks of 8 arsenic districts of West Bengal to be affected. If we consider Calcutta as separate district the number of affected districts rises to nine. These districts are Maldah, Murshidabad, Bardhaman, Nadia, Haora, Hugli, North 24-Parganas, South 24-Parganas and Calcutta. In the middle of 1997, the World Health Organization (WHO) appointed a team to study the arsenic problem in West Bengal. The team appointed by WHO criticized the state government for lacking initiative and seriousness in tackling the spread of arsenic poisoning (45-47).

In early 1999, on the basis of 58,166 water analysis from 9 arsenic affected districts we reported (48) 985 villages in 69 police stations / blocks as being arsenic affected and 4420 people had already been registered with arsenical skin lesion. Every time we went on a field survey, we identified 10-15 new arsenic affected villages where villagers continued to drink arsenic contaminated water without being aware of the contamination. Even such a situation did not prevent the Chief Engineer (Arsenic), of Public Health Engineering Department (PHED), Government of West Bengal from assuring delegates at the international conference in Bangladesh (49, 50), with the quoted lines ".... in 1994 there were about, 1100 identified cases of arsenocosis, the acute stage of arsenic poisoning, in areas of West Bengal. The number has since come down to 450. So far we have not found arsenic beyond the permissible level in any tube-well sunk to deeper aquifer in the affected areas. Even if there are traces, those are within the permissible level of 50 μg/l. If it exceeds the limit at any place we have the technology to treat the water by using simple method. Arsenic free drinking water is now supplied to the door steps of the people in the affected areas through pipe line network". It is surprising to note that the Health Minister of West Bengal in an interview on 5th April 1999 with a representative of the Medical World (51) had characterized that the present arsenic situation of West Bengal as being much better than what it was 15 years earlier at such critical juncture. Further, SOES first reported groundwater arsenic contamination in southern part of Calcutta on 8th March 1993 and identified people suffering from arsenical skin lesion (26). Government of West Bengal totally denied the findings. In January 1996 we reported more arsenic affected areas in southern part of Calcutta and our results being denied by both government of West Bengal and Calcutta Municipal Corporation (CMC) (42). Again during October 2000 (52) we reported arsenic to be above WHO maximum permissible limit in two well known private nursing homes (Kothari Medical Centre & Woodland Nursing Home), the Zoological Garden, the National Library and certain Housing Complexes. This report though it was denied at first was confirmed by the government later in January 2001 (53). The arsenic problem of Calcutta City was reported by us in 1993 and it took 8 years for the government to accept the truth.

In 2002, we published a summary of groundwater arsenic contamination situation in West Bengal (54) where we showed on basis of more than 1,05,000 water samples analysis more than six million people from nine arsenic affected districts out of total 19 districts are drinking water containing more than 50 μg/L As and 2700 villages were identified to be affected.

In 2003, we highlighted (55) the groundwater arsenic contamination situation concentrating on one of the nine districts, North 24 Parganas, where we mentioned based on 48,030 sample analyses that 29.2 % of the tubewells had arsenic above 50μg/L; out of 22 blocks in twenty we found arsenic above this limit.

In 2004, we came out with another update (56) on arsenic contamination situation; Based on 1,29,552 samples analysis we showed 24.7% had arsenic above 50 μg/L and we identified 3200 arsenic affected villagers in 85 affected blocks in nine districts. We also predicted in this study that around 6.5 million people in the state could be drinking water having more than 50 μg/L As.

To understand the exact magnitude of groundwater arsenic contamaintion and its health effects in West Bengal, we have studied one arsenic affected district Murshidabad out of nine affected district in details for last five years with twenty people in our group including dermatologist, neurologist, gynecologist, pathologist, analytical chemist, biochemist, geologist, civil engineer etc. We have analyzed about 30,000 water samples from this district alone and screened 24,274 people with our medical group for arsenical skin lesions and other related arsenic toxicity. We have also analyzed 3,843 biological samples (hair, nail, urine and skin scales). Based on our detailed studies in Murshidabad district, we published five papers. We have done semi micro and micro level studies in one block Jalangi (57), one gram Panchayet (cluster of villages) Sagarpara (58), and one village Rajapur (59), and also the district Murshidabad as a whole (60,61).

In 1988 when we commenced arsenic survey in West Bengal, we knew about 22 affected (As > 50 μg/L) villages in five districts now according to our latest survey the number of affected villages increased to 3417 in 111 blocks in nine districts. During last 19 years with every additional survey we noticed an increasing number of contaminated villages and more affected people. These findings have been reported in number of international journals, monographs and book chapters (62-91).

In 1992 we identified arsenic groundwater contamination in Padma-Meghna-Brahmaputra (PMB) plain of Bangladesh where people were drinking arsenic contaminated water and suffering from arsenical skin lesions (44,92,93). In 2001 groundwater arsenic contamination in the Terai region of Nepal was revealed (94). In June 2002 we discovered arsenic contamination in Bihar in middle Ganga plain and apprehended contamination in Uttar Pradesh lying in middle and upper Ganga plain (95). During Oct. 2003-Dec. 2003 we identified 25 arsenic affected villages of Ballia district in UP and people suffering from arsenical skin lesions. Between Dec. 2003 and Jan. 2004 we further found groundwater arsenic contamination in 698 hand tubewells from 17 villages of the Sahibganj district of Jharkhand state, India in the middle Ganga plain and consequent suffering of hundreds of people. Again a preliminary survey during Jan–Feb 2004 in Assam showed 26% of 137 hand tubewells analyzed in 2 districts had arsenic concentration above 50μg/L. According to our latest estimates, a good portion of all the states and countries in the Ganga- Meghna-Brahmaputra (GMB) plain may be at risk from groundwater arsenic contamination (56). So far (up to December 2005) we have collected and analyzed 140150 water samples from all 19 districts covering 241 of 341 total blocks from West Bengal India. We found arsenic contamination above 10 and 50μg/L in 148 and 111 blocks in 14 and 12 districts respectively. From whole GMB plain we analyzed 211955 water samples. Figure 1 shows the groundwater arsenic contamination status in different countries and different states in GMB Plain. Table 1 shows the contamination situation in GMB plain at a glance and Figure 1 shows the Groundwater arsenic contamination in states and countries of the GMB Plain (according to our latest survey report up to December 2005) This communication deals with the present ground water arsenic contamination situation of West Bengal along with the consequential health effects on the basis of our last 19 years research work on the issue.

Tabel Figure 1: Groundwater arsenic contamination status in different countries and different states of India in GMB Plain.

Ganga-Meghna-Brahmaputra Plain

EXPERIMENTAL METHODS


Study Area and sampling: West Bengal [area 88750 sq km; population 80.1 million] is one of the 29 states of India. Its administrative structure consists of several districts: each district has several blocks/police stations; each block has several Gram Panchayets (GPs), which are cluster of villages. There are 19 districts, 341 blocks and 37910 villages in West Bengal. We collected 1,40,150 water samples, 13,325 hair, 13,468 nail, 12,831 urine and 1000 skin scale samples from all the 19 districts and analyzed for arsenic.

Instrumentation: Flow injection hydride generation atomic absorption spectrometry (FIHG-AAS) system was assembled from commercially available instruments and accessories in our laboratory. A Perkin Elmer Model 3100 atomic absorption spectrometer equipped with a Hewlett-Packard Vectra Computer with GEM software, Perkin-Elmer EDL system-2, arsenic lamp (lamp current 400 mA) and Varian AAS Model Spectra AA-20 with Hollow Cathode arsenic lamp (lamp current 10 mA) were used. Details of the instrumentation have been described in our earlier publications (96-99).

Reagents and glassware: All reagents were of analytical reagent grade. Distilled deionized water was used throughout. The reducing solution of 1.5% (m/v) NaBH4 (Merck, Germany) in 0.5% (m/v) NaOH (E. Merck, India) and 6.0 M solution of HCl (E. Merck, India) were used for flow injection analysis. Details of the reagents and glassware are given elsewhere (96,98).

SAMPLE COLLECTION PROCESS:


Water sample: Tubewell water samples were collected in 10 ml polyethylene bottles prewashed with nitric acid water (1:1) and after collection, 1 drop of nitric acid in water (1:2) was added as preservative. Details of the collection procedures have been described in our earlier publications (96,98).

Biological sample: hair, nail, urine and skin scale samples were collected during our field survey. For hair, nail and skin scales samples we determined total arsenic after digestion. The modes of water and biologic samples collection, the digestion procedures for hair, nail and skin scales and the analytical procedures were as reported earlier (96-99). For urine samples, only inorganic arsenic and its metabolites together [arsenite, As (III); arsenate, As (V); monomethyl arsonic acid, MMA (V) and dimethyl arsinic acid, DMA (V)] were measured with no chemical treatment. Under the experimental conditions of FI-HG-AAS, arsenobetaine and arsenocholine do not produce a signal (96). We also collected biological samples from the inhabitants of arsenic safe areas of Medinipur district for comparison purpose.

Analysis procedure: Arsenic in water, urine, acid digested hair and nail was measured by FI-HG-AAS. For urine samples, only inorganic arsenic and its metabolites together [As (III), As (V), MMA (V), and DMA (V)] were measured with no chemical treatment. Under the experimental conditions of FI-HG-AAS, arsenobetaine and arsenocholine do not produce a signal (96). Details procedure has been described elsewhere (96-99).

Quality assurance and quality control program: For quality control, inter-laboratory tests were performed for water samples (99,100). Analysis of EPA water standard for arsenic by our technique has been reported elsewhere (99,101).

Statistical analysis: Standard statistical techniques were applied to analyze and present the data. To test the presence of association, Chi-square test was used. An ANOVA was applied to test the homogeneity of arsenic concentrations. Paired t-test was used to test the significance. Statistical package SPSS version 11.5 has been used for data analysis.

RESULTS


Groundwater arsenic contamination in West Bengal
In last 19 years we analyzed 1,40,150 hand tubewell water samples for arsenic in all 19 districts of West Bengal. Table 2 shows an overview of arsenic contamination situation of West Bengal upto December 2005. Table 3 shows the distribution of tubewells from each of the 19 districts of West Bengal. Out of 1,40,150 samples analyzed for arsenic till date, 48.1% had arsenic above 10μg/L (the WHO guide line value) and 23.8% above 50μg/L (the Indian standard value). Importantly, 3.3% of the analyzed tubewells had arsenic concentrations above 300μg/L (the concentration predicting overt arsenical skin lesions (56). A total of 187 (0.13%) hand tube-wells were highly contaminated (>1000 μg/L). The maximum arsenic concentration (3700 μg/L) was found in Ramnagar village of GP Ramnagar II, Baruipur block, in South 24 Parganas district. This tubewell was a private one and all the nine members of the owners’ family had arsenical skin lesions and seven of them who had severe arsenical skin lesions, had already died, five of them died within age range below 30 years. Figure 2 (map) sums up groundwater arsenic contamination status of all 19 districts of West Bengal. Based on the arsenic concentrations found in the 19 districts of West Bengal we have classified them into three categories: Severely affected, mildly affected, and arsenic safe.

Nine districts (Maldah, Murshidabad, Nadia, North-24-Parganas, South-24-Parganas, Bardhaman, Haora, Hugli and Kolkata), where more than 300 μg/L arsenic concentrations were found in tubewells are categorized as severely affected. Out of 1,35,555 samples analyzed from these districts 67,306 (49.7%) had arsenic concentrations above 10μg/L and 33,470 (24.7%) above 50 μg/L.

The five districts (Koch Bihar, Jalpaiguri, Darjiling, North Dinajpur and South Dinajpur) where the contaminated tubewells show arsenic concentrations mostly below 50μg/L (only a few above 50μg/L but none above 100 μg/L), termed as mildly affected. We analyzed 2,923 water samples from these districts, 285 (9.8%) had arsenic concentration between 4 and 10μg/L, 163 (5.7%) above 10μg/L and 6(0.2%) above 50 μg/L.

Figure 2: Groundwater arsenic contamination status in all 19 districts of West Bengal.
Groundwater Arsenic Contamination Status in West Bengal The rest five districts (Bankura, Birbhum, Purulia, Medinipur East and Medinipur West), where all the recorded concentrations were below 10 μg/L termed as unaffected or arsenic safe. All the samples (n=1,672) analyzed from these five districts had arsenic concentrations below 3 μg/L (the minimum determination limit of our instrument with 95% confidence level).

tabel copy Groundwater arsenic contamination situation of the severely affected districts:
North 24 Parganas District (i) Contamination situation in North-24-Parganas District : The district of North 24 Parganas of West Bengal is in the southern part of the Bengal Basin. The geographical extent of the district lies between 88019’ E to 89010’ E and 22001’ N to 23020’ N. The area and population of the district is 4094 km2 and 89,34,286. In North 24 Parganas, there are 22 blocks. So far we have analyzed 54,368 tubewell water samples covering all 22 blocks. From our analysis we found elevated level of arsenic above 10μg/L in all 22 and above 50μg/L in 21 blocks. It has been found that 29,018 (53.4%) tubewells have arsenic concentration above 10 μg/L, and 16,017 (29.5%) above 50μg/L. Importantly, 1834 (3.4%) of the analyzed tubewells had arsenic concentrations above 300μg/L (the concentration predicting overt arsenical skin lesions). From our analytical result we see that only one block “Sandeshkhali-II” is arsenic safe according to Indian standard (50μg/L). Arsenic level above 1000μg/L was found in 49 tubewells; the maximum arsenic contamination level found in this district is 2830μg/L in the Baduria block. Figure 3 shows the groundwater arsenic situation in each block of North 24 Parganas, indicating the blocks where we identified patient with arsenical skin lesions. It also depicts a Pie-diagram of arsenic concentration distributions in the district.

Tabel South 24-Parganas District (ii) Contamination situation in South-24-Parganas District: The area and population of the district is 9,960 km2 and 69,06,689 divided into 29 administrative blocks. During our survey we collected 8,334 hand tubewell water samples from 17 blocks. After analyzing the samples for Arsenic we found Arsenic concentration in tubewell water samples above 10μg/L in 12 blocks and above 50μg/L in 11 blocks. The studies reveal that 3,499 (42.0%) tubewells have arsenic concentration above 10 μg/L, 2,358 (28.3%) above 50μg/L and in 547 (6.6%) above 300μg/L (the concentration predicting overt arsenical skin lesions). We found arsenic contaminated above 1000μg/L in 30 samples, the maximum concentration 3700μg/L was found in Baruipur block (village: Ramnagar, GP: Ramnagar II). Figure 4 shows the groundwater arsenic situation in each block of South-24-Parganas along with the Piediagram of arsenic concentration distributions indicating the blocks where we identified patients with arsenical skin lesions.

Murshidabad District (iii) Contamination situation in Murshidabad District: Murshidabad district lies between the latitudes of 23043’30” N to 24050’20” N and longitudes of 87049’17” to 88044’ E. The river Ganga forms its northern and eastern boundaries and separates it from Bangladesh. The river Bhagirathi flows across the district and divides it into two equal parts. The area and population of the district is 5,324 km2 and 58,66,569 respectively. There are 26 blocks in this district and we have surveyed all the 26 blocks to collect hand tubewell water samples. So far we have collected and analyzed 29,668 hand tubewell water samples from 1,833 villages/wards of 2,414 villages from all the 26 blocks. On the basis of the analysis, we have found arsenic concentration in 25 blocks above 10 μg/L and in 24 blocks above 50μg/L. The studies reveal that 15,953 (53.8%) of the tubewells are arsenic contaminated above 10μg/L while 7,911 (26.7%) above 50μg/L and 1337 (4.5%) above 300μg/L. It is also observed from the table that Arsenic contamination in Jalangi block is worst, out of total 1917 samples analyzed from this block. 1,491 (77.8%) exceed the WHO limit (10μg/L) and 38 (2.0%) samples were found to be contaminated above 1000μg/L of arsenic. Maximum concentration 3003μg/L was found in two water samples one from each of Nawda and Raghunathganj I blocks. Figure 5 shows the situation of arsenic contamination in all the 26 blocks of the district indicating the blocks where we identified patients with arsenical skin lesions. From the distribution of water analysis ( Figure 5), it appears that the blocks situated in the western side of river Bhagirathi are less affected compared to the blocks situated on the eastern side. From our analysis, it appears that the groundwater of Bharatpur-II block is arsenic safe, all the samples (n=625) analyzed from this block found arsenic below 3μg/L (the determination limit of our instrument with 95% confidence level).

Malda District (iv) Contamination situation in Maldah District: Maldah district is situated between the Latitude and Longitude figures of 24040’20”N to 25032’08”N and 88028’10”E to 87045’50”E respectively and surrounded by Bangladesh and South Dinajpur in the east, Santal Parganas of Jharkhand state in the west, Uttar Dinajpur in the north and Murshidabad in the south. The area and population of the district is 3,733 Sq. Km. and 32,90,468 respectively. In Maldah, there are 15 blocks. We conducted survey in 14 blocks to collect hand pump tubewell water samples. Till date we have analyzed 4449 water samples for arsenic analysis. On the basis of our analysis 13 blocks have arsenic contamination above 10μg/L and 9 above 50μg/L. The studies reveal 2322 (52.2%) samples have Arsenic contamination above 10μg/L and 1512 (34.0%) above 50μg/L. It also reveals from the table that 282 (6.3%) of the tubewells are arsenic contaminated above 300 μg/L, while 22(0.5%) above 1000 μg/L. The maximum concentration found in this district is 1904μg/L in Kaliachak II block. Figure 6 shows the contamination situation in each of the surveyed blocks by piediagram indicating the blocks where we identified patients with arsenical skin lesions.

Nadia District (v) Contamination situation in Nadia District: The geographical extent of the district lies with a latitude of 22041/ 23// N and longitude of 72051/ 24//E which covers an area of about 3,927 sq. km. It is situated on both sides of the Hugli (Ganga) river and is divided into 17 administrative blocks (Police stations). The population of the district is about 46,04,827. To date, we have analyzed 28,794 hand tubewell water samples from 777 villages/ wards spread over 143 GP’s covering all the 17 blocks. The studies reveal that all the 17 blocks are arsenic contaminated above 50μg/L. On the basis of the analysis, we have found arsenic concentration above 10 μg/L in 14,750 (51.2%) hand tubewells water samples, while in 4,940 (17.2%) above 50 μg/L. 525 (1.8%) samples are contaminated above 300μg/L while 13 (0.05%) above 1000μg/L. The maximum concentration found in this district is 3200μg/L in Tehatta I block. Figure 7 shows the groundwater arsenic contamination status in all 17 blocks of Nadia with the help of piediagram indicating the blocks where we identified patients with arsenical skin lesions.

(vi) Contamination situation in Kolkata District: Kolkata, located at 22028′ N to 22037′30″ N and 88017′ 30″ E to 88025′ E, is at present the largest urban city [area 185 sq.km and night time population 4.6 million] of eastern India. It is situated at the bank of river Ganga. For administrative purpose it is divided into 141 wards, we have analyzed 3,626 hand pump tubewell water samples for arsenic from 100 of them. Fifteen percent of the samples exceed the WHO guideline value (10 μg/L) while 5.5% of the samples exceed the Indian standard (50 μg/L). The maximum arsenic concentration (825μg/L) was recorded in Lake Gardens area of ward no 93 (Table 3). We found arsenic contamination above 10 μg/L in 65 wards and above 50μg/L in 35 wards.

Kolkata is mainly an urban area. The present drinking water demand in Kolkata is around 1262 million litres per day (MLD). Metropolitan authority supply through pipeline 1209 MLD of which 1096 MLD is treated surface water (102) and the rest are groundwater (tubewells having more than 100 m depth). Other than pipeline deep tubewell water supply, in each ward there are roadside hand tubewells of depth around 100m, a good percentage of people collect their drinking water from this source.

Bardhaman District (vii) Contamination situation in Bardhaman District: Bardhaman district is situated between the Latitude 22.56o N to 23.53o N and Longitude 83.25o E to 86.48o E. The area and population of the district is 7,024 sq.km. and 68,95,514 respectively. There are 31 blocks in this district. So far we have collected 2634 hand pump tubewell water samples for arsenic analysis covering 24 blocks. Analytical result shows that 12 of the surveyed block is arsenic contaminated above 10μg/L and 7 blocks above 50μg/L. The studies reveal that 464 (17.6%) of the tubewells are arsenic contaminated above 10μg/L, 220 (8.4%) above 50μg/L and 18 (0.7%) of the tubewells are contaminated above 300μg/L. The maximum arsenic concentration was found 2230μg/L in Katwa I block. Only one water sample was Arsenic contaminated above 1000μg/L. Figure 8 represents the pie-diagram of the arsenic concentration in different surveyed blocks of Bardhaman district indicating the blocks where we identified patients with arsenical skin lesions.

Howrah District (viii) Contamination situation in Haora District: Haora is a district in the southern part of West Bengal. The area and population of the district is 1,467 sq.km and 42,73,099 respectively. There are 14 administrative blocks in this district and we have covered 12 of them for Arsenic survey. We have collected 1,471 hand pump tubewell water samples for arsenic analysis. The studies reveal that 356 (24.2%) of the samples are arsenic contaminated above 10μg/L and 164 (11.1%) above 50μg/L while 14 samples are contaminated above 300μg/L. The maximum concentration 1333 μg/L of arsenic was found in Amta I block. Figure 9 shows the pie diagram of the arsenic contamination situation in the surveyed Blocks.

Hugli District (ix) Contamination situation in Hugli District: Hugli is a district in the central part of West Bengal. The area and population of the district is 3,149 sq.km and 50,41,976 respectively. There are 18 administrative blocks in this district and we have covered 17 of them for arsenic survey, out of the surveyed blocks we found arsenic concentration above 10μg/L in 16 blocks and above 50μg/L in 11 blocks. We have collected 2,212 hand pump tubewell water samples for arsenic analysis. The studies reveal that 397 (17.9%) of the tubewells have arsenic concentration above 10μg/L while 146 (6.6%) above 50 μg/L. According to our analysis there were 3 tubewells having arsenic concentration above 300μg/L while none of the tubewells have arsenic above 1000μg/L. The maximum concentration found in this block is 600μg/L in Balagarh block. Figure 10 shows the pie diagram of the Arsenic contamination situation in the surveyed blocks of Hugli district.

From the above discussion it is clear that among the severely affected 9 districts 5 (South-24-Pgs, North-24-Pgs, Maldah, Murshidabad and Nadia) are most severely affected and the contamination is almost all over the district while in the other 4, only part of the district is contaminated.

Narthern Part of west Bengal (x) Contamination situation in Northern part of West Bengal: Based on the arsenic concentrations found in the Northern 5 districts (Koch Bihar, Jalpaiguri, Darjiling, North Dinajpur and South Dinajpur) of West Bengal we classified them as mildly affected. The analytical results show that arsenic concentration in these districts is mostly below 50μg/L, only a few above 50μg/L but none above 100 μg/L. We analyzed 2,923 water samples from these districts, 285 (9.8%) had arsenic concentration between 4 and 10μg/L, 163 (5.7%) above 10μg/L and 6(0.2%) above 50 μg/L (Table 3). Arsenic contamination situation of Northern part of West Bengal is shown in Figure 11.

Western West Bengal (xi) Contamination situation in Western part of West Bengal: Based on the arsenic concentrations found in the 5 districts (Bankura, Birbhum, Purulia, Medinipur East and Medinipur West) in western part of West Bengal we classified them as arsenic safe. All the samples (n=1672) collected from these districts and analyzed for arsenic had concentrations below 3 μg/L (the minimum determination limit of our instrument with 95% confidence level) (Table 3). Figure 12 shows the contamination situation in Western part of West Bengal. It is to be noted that we found fluoride in many tubewell water samples in Bankura, Purulia and Birbhum districts and many people have been suffering from fluorosis, a crippling disease (103) in these districts. Though we do not find arsenic in tubewell water samples but, we found arsenic in a few dugwell water samples from Purulia district.

xii) Estimation of the population may be at risk of drinking arsenic contaminated water at different concentration levels: Based on the average user of a tubewell and the percentage of tubewell contaminated at different concentration levels, population may be at risk of drinking arsenic contaminated water at different concentration levels was estimated for eight affected districts (Except Kolkata as majority of the people there use supplied water). For the estimation we proceed in three step process (i) total number of tube wells exists in each district/blocks were estimated dividing total population by average number of user per tubewell (ii) estimated no of tubewell at different concentration level for each district/block was calculated by multiplying total tubewell number (obtained in step i) by proportion of tubewell contaminated at different concentration levels in the respective district/block. (iii) Estimated exposed population was calculated multiplying estimated number of tubewell (obtained in step ii) by average number of persons using a tubewell. In order to be more realistic we excluded those blocks /police stations from calculation where we did not conduct survey. The studies reveal that the estimated exposed population may be at risk of drinking arsenic contaminated water at different concentration levels. About 9.5 and 4.6 million people may be at risk of drinking arsenic contaminated water above 10 and 50 μg/L respectively and, an estimated 0.5 million above 300 μg/L

Arsenical health effects in West Bengal


(i) Dermatological effects: West Bengal is one of the worst arsenic affected areas in the world arsenic scenario. In our preliminary work our medical group examined around 96,000 individuals, including children (age range: below 11 yr), for arsenic toxicity from West Bengal, 9356 of them showed skin lesions. We identified 778 children with arsenical skin lesions screening total 14000 children from West Bengal (Table 2). Various types of skin manifestations of arsenic toxicity were observed from melanosis, keratosis, hyperkeratosis, dorsal keratosis, and non-pitting oedema to gangrene and cancer (61, 76, 104). We do not expect such a high percentage of arsenicosis patients in all the arsenic affected districts. Figure 13 shows patients from West Bengal with different arsenical skin manifestations. The large number of people showing arsenical skin-lesions is due to the fact that we had examined villagers from only those villages, which are highly arsenic contaminated and we had prior information of the presence of arsenic patients. Undoubtedly the overall percentage of arsenic affected people is expected to be lower in the less contaminated areas.

Figure 13: Some patients from arsenic affected areas of West Bengal with different arsenical skin manifestations.
Arsenic affected of west bengal (ii) Arsenical neuropathy: Neurological examination was generally undertaken for arsenicosis patients whose skin lesions were already diagnosed by experienced dermatologist. The neurological part was conducted by the same experienced neurologist to obviate inter-observer variability for each patient of arsenocosis so tested. Observations were recorded for items considered consistent with peripheral motor and sensory neuropathy and for other neurologic abnormalities as well. Pain history and pain-specific sensory examination were stressed. The items included to characterize neuropathy were (i) pain and paraesthesias (e.g., burning) in a stocking and glove distribution, (ii) numbness, (iii) hyperpathia/allodynia, (iv) distal hypesthesias (reduced perception of sensation to pinprick/reduced or absent vibratory perception/ affected joint-position sensation/ affected touch sensation), (v) calf tenderness, (vi) weakness/atrophy of distal limb muscles or gait disorder, and (vii) reduction or absence of tendonflexes. Overall prevalence of clinical neuropathy was noted in our studies (61,104,105) in populations of Murshidabad and Nadia districts of West Bengal.

(iii) Arsenic in drinking water and obstetric outcome: Arsenic exposure during pregnancy can adversely affect several reproductive endpoints. Several studies have examined the association between arsenic exposure and adverse pregnancy outcome, including spontaneous abortion, preterm birth, stillbirths, low birth weight and neonatal and perinatal mortality (56, 61). All these parameters were compared to those observed in the control women group from a non-arsenic exposed district (Medinipur East and Medinipur West) of West Bengal. Adverse obstetric effects were observed in our detailed studies with village women from Murshidabad district, West Bengal.

Arsenic body burden: sub clinical effects: Arsenic concentration in hair and nails plays an important role in evaluating the arsenic body burden. We measured inorganic arsenic and its metabolites in urine and total arsenic in hair, nail and skin scale samples from the villages where we had identified arsenical patients. Around 40-50% samples were collected from those already having skin lesions and rest from the persons who had not but living in the arsenic affected villages. So far we have analyzed 13325 hair, 13468 nail, 12831 urine and 1000 skin scale samples from arsenic affected villages in West Bengal. The results demonstrate that 91% of the hair, 97% of the nail, and 92% of the urine samples in West Bengal contained arsenic above the normal levels for urine and nails and toxic levels for hair. These results indicate that though many villagers may not be suffering from skin lesions but have elevated levels of arsenic in their biological; samples thus may be sub-clinically affected. Table 4 shows the parametric presentation of the arsenic concentration of the biological samples collected from arsenic affected areas of West Bengal and those from control samples collected from arsenic safe areas.

Table-4 Arsenic affected children: Furthermore, plight of children in the arsenic affected regions of West Bengal and Bangladesh is remarkably similar. Infants and children are often considered more susceptible to the adverse effects of toxic substances than adults (106). In one of our studies on an arsenic affected population in Bangladesh we have found that second metabolic step in arsenic metabolic pathways is more active in exposed children in comparison with exposed adults (107).

Social Problems Due to Arsenic Contamination


The common social problems due to arsenic toxicity as we have noticed from West Bengal, India are as follows:

1) Affected wives are sent back, sometimes even with their children, to their parents.
2) Marriage of people of either sex from the affected villages is difficult.
3) Often jobs / service are denied / ignored to the arsenic affected persons.
4) When a husband or wife is singled out as an arsenic patient, the social problems crop up and may destroy the social fabric.
5) Due to ignorance, the villagers sometimes view it as a case of leprosy and force the arsenic patients to follow an isolated life.

Arsenic in food chain:


In arsenic affected areas of West Bengal and Bangladesh arsenic contaminated water is not only used for drinking and cooking but also for agricultural irrigation. Thus arsenic comes into the food chain. In the affected areas villagers also consume arsenic from Pantavat1 and water added to food preparations like rice, soup, curry and tea. This aspect has been currently highlighted in a few publications (108-110). As we have described about an arsenic affected village, Kolsur Gram Panchayet (GP) in Deganga block of North 24 Parganas District in West Bengal, in one of our publications (108), “From the results of total amount of arsenic consumed (drinking water + rice + vegetables + pantavat + water added for food preparation) the body burden to North Kolsur villagers (1185.0 μg for per adult per day, 653.2 μg for per child per day), as the amount of arsenic coming form rice, vegetables, and water added for Pantavat1 and food preparation is 485 μg, i.e., 41% of the total for adults and 253.2 μg, i.e., 38.8% for children and from rice and vegetables 285 μg, i.e., 24% of total for adults and 153.2 μg i.e., 23.4% for children. Our findings show that most of the arsenic coming from food is inorganic in nature.”

DISCUSSION


Geological reasoning of incidence of arsenic in groundwater and possible temporal variability.
Lateral and depth-wise variation in the disposition of unconsolidated litho units (cobbles, pebbles, gravels, sand, silt, clay and their admixtures) in the subsurface quaternary sequence play major roles in the incidence and distribution of varied concentration of arsenic in groundwater.

150-250m thick granular zone occurring as alluvial fans in the extreme northern part of West Bengal acts as the recharge zone for the unconfined aquifers with high permeability. This zone receives on an average 3000mm of rainfall annually. This granular zone gets separated in most of the areas by 2 to 10 m thick clay layers within a depth of about 300m where confined groundwater occurs. These aquifers at depth to the south of the fan zone are hydraulically connected to the recharge zone and contain groundwater mildly affected by arsenic. The recent flood plain deposits of Maldah district, however, recorded high concentration of groundwater arsenic (111).

The subsurface geological picture of the southern part of West Bengal to the east of the Achaeans shield area is nearly similar to its northern counterpart except the absence of cobbles and pebbles in the sequence and the Pleistocene sediments covering almost onehalf of the area to the east of the shield area. Eastward it is followed by Holocene deltaic sediments which by nature are characterized by frequent change in facieses from sand to clay and vice-versa at short distances both laterally and vertically. At the delta head

1 Pantavat: This is common breakfast food in some part of rural West Bengal and Bangladesh. Pantavat is rice mixed with water. Normally they pour water on rice coked the previous night and have it as their breakfast. Normally villagers take it with vegetables/mashed potatoes/chili and onion.

located in Murshidabad and Nadia districts, 150-250m thick granular zone containing groundwater with high concentration of arsenic under unconfined condition occurs. It forms the recharge zone for the deeper aquifers down south. Like the Northern part, here also this thick granular zone gets separated by several clay layers, the thickness of which gradually increases southward. Beside, a clay layer appears at the top of the sequence with thickness gradually increasing southward from 2 to 30m precluding direct rainfall recharge to the group of aquifers below the top clay. These aquifers constitute the confined aquifer system receiving water from the recharge area to the north as well as to the west formed by the weathered sections within the crystalline rocks in the shield area. In and around Kolkata beside the top clay layer, another 20-30m thick clay layers occurs at around 150m depth, the thickness of which increases to 50-60m further south. It is followed by alternating sequence of sand and clay layers down to a depth of about 300m (111).

In the delta and flood plains due to attenuation of intervening clay layers, the group of aquifers at depth gets interconnected at some places giving avenues for polluted groundwater to travel at deeper depths (111).

When groundwater flow path is obstructed by the presence of finer material groundwater arsenic is expected to increase. Similarly, at places, where such barriers are absent, arsenic content might remain same or show decrease or slight increase depending upon the complex recharge-withdrawal processes. This complex phenomenon seems to be responsible for variation in arsenic content in ground water within short distance tapping the same aquifer in the delta and flood plain deposits. Moreover, travel time required for transmission of arsenic contaminated groundwater from the recharge zones to the deeper aquifer system down south depends on the variation in composition of material through which groundwater moves. All these factors cause variations in arsenic concentration in groundwater from one location to the other. Seasonal change and/or temporal variation in arsenic concentration in groundwater are therefore, not an unexpected phenomenon.

Estimation of population at risk: the uncertainties involved


The magnitude of arsenic calamity seems to be severe from the overall study of groundwater arsenic contamination and its health effect in Murshidabad. Only in Murshidabad district we reported (60) that 2.6 million and 1.2 million people are at risk of drinking arsenic contaminated water above 10μg/L and 50μg/L respectively. Extrapolating the data we generated we found that about 9.5 and 4.6 million people may be at risk of drinking arsenic contaminated water above 10 and 50 μg/L respectively and, an estimated 0.8 million above 300 μg/L.

One of our assumptions for the estimation of population at risk was that, people have been drinking from the same contaminated tubewell all along from the time of analysis. But during last 10 years lot of awareness campaigns were launched in the affected areas to teach people vices of arsenic contamination and to test their tubewell for arsenic before use. Also different alternative safe water options have been made available to affected population like purified surface supply water, deep tubewells, dugwells, arsenic removal plants etc. Due to this gradual switchover to safe options actual population drinking arsenic contaminated water (> 50 μg/L) may be less than the predicted ones.

Temporal variability of arsenic concentrations


During our last 10 year survey of the arsenic affected districts of West Bengal, we noticed (112, 113) that within a span of 3-7 years in some villages, tubewells that had initially been safe (arsenic<10 μg/L) became contaminated (arsenic>50 μg/L) in course of time. Furthermore, the arsenic concentration in many tubewells had increased by as much as 5-20 folds (112,113).

Increasing exploitation of groundwater


West Bengal is village dominated and in remote villages more than 95% people drink private or public hand tubewell water. In urban and semi urban areas drinking water source is usually purified surface water or deep tubewell (above 100m depth) supplied through pipe line by public authorities though sometimes due to bacterial contamination (owing to underground pipeline leakage) people use hand tubewell water. There are districts in West Bengal like West Dinajpur, Jalpaiguri etc where due to plenty of available surface water and dugwell a decade before hand tubewells were few. At present due to lowering of water table people are switching to tubewells. This is a common practice allover the GMB plain including arsenic affected areas. Additionally since the launch of green revolution in India in 1960, due to gradual depletion of surface water resources and irregular monsoons, irrigation is one of the major sources of groundwater withdrawal. So exploitation of groundwater by tubewells continues unabated.

Mitigation approaches


1. Surface water with proper watershed management and purification:
Upto early 20th century the main sources of drinking water in West Bengal and Bangladesh, were ponds, lakes etc. and people would drink untreated water. With proper treatment against bacterial and other contaminations and proper management of available surface water may hold the key to safe potable water for West Bengal where per capita available surface water is huge (7,000 cubic meters in West Bengal), average annual rainfall in these regions is about 2,000 mm and the land known as “land of rivers” with huge wetland, flooded river basins, oxbow lakes. Below we present a specific instance of how surface water resources lay unutilized which could have been managed with proper planning.

A Canal named ‘Dead Padma’ popularly known as Mara (dead) Padma is one of the examples of vast unused water bodies of West Bengal, India. It is believed that once it was part of river Padma which is now in Bangladesh. Stretched over a span of around 90 kms, this canal is flowing through Nadia and 24 Parganas (North) districts and ultimately meets river Jamuna in 24 Parganas (North). A significant part (around 20 km) is situated in highly arsenic affected Deganga block. The canal is covered with water hyacinths. Throughout the year water is present in this canal. When water declines during winter, local people connect the canal with river Jamuna and cultivate “Boro” rice. There are several water bodies along side the canal, some privately owned. In absence of proper plan and management the canal lays almost unused except sporadic fishing by some localites. A proper plan to utilize this surface water resource in the following ways could provide safe water treatment and overall economic development for the people living on the banks:

(a) In Deganga block out of 15,886 tubewells we analyzed 13,000 tubewells for arsenic and found, 57% and 37.3% had above 10 and 50 μg/L concentration respectively. In this block out of 234142 people an estimated 7726 were drinking contaminated water having arsenic concentration above 300 μg/L. In our preliminary study with our medical group including expert dermatologist, obstetricians and neurologists we examined 11,780 people and 786 (6.6%) people were identified as patients (55). In these circumstances the water from this canal after proper treatment can be supplied to nearby areas. This can serve as a safe water option for the poor affected villagers.

(b) A planned fish culture program and duckary can be undertaken.
(c) The water can be directly used for irrigation instead of tubewells.

What we need is proper management of huge land-water body with people’s participation using advanced water purification technologies.

2. Deep tubewells free from toxins.


It is well established that shallow tubewells in arsenic contaminated areas may not be safe. It is also observed that in the Gangetic plain As contamination in hand tubewells has been observed to decrease after a certain depth (114) but in unconfined aquifers there appears to be no depth guarantee, even if the construction of tube well is done properly. Based on our nineteen year long study over different parts of the GMB plain on groundwater arsenic contamination we observed that deep tubewells (>150m) may not always provide safe source of drinking water. Safety of deep tubewells depends on several factors: i) construction of the deep tubewell, ii) depth of the deep tubewell iii) presence of confined aquifer, and iv) the aquifer should be under a thick clay barrier. However, a note of caution in West Bengal is, many tube wells that were safe (As < 10μg/l) became contaminated (above 50μg/l) over time (112-113). So periodic testing for water contaminants is important.

3. Dugwells.


With the advent of hand tubewells the use of dug wells subsided largely because of bacterial contamination of the dugwell water and consequent enteric diseases prevailing among the users. This called for wide scale abandoning of these dug wells. In this age of acute scarcity of water when it is predicted that toilet flush water would need to be recycled for use in future for potable water, this vast source of water should not at all be neglected. Proper management of dugwell would necessitate the following factors: i) Concrete structure with a storage tank. ii) Proper selection of location, iii) Preventing surface contamination, using a fine net / glass fiber screen over it, iv) Cleaning monthly with lime and sodium hypochlorite and removal of some amount of bottom sediment [During cleaning the dugwell water is to be stored in storage tank for supply] and v) If bacteria are even not detected after periodic cleaning we recommend a few drops of sodium hypochlorite (depending on water in dugwell) to be added at night everyday. If affordable a UV source (if electricity is available) after storage tank will help. Once a year removal of bottom sediment from dugwell is necessary and this will also take care of sand building.

In Betai region of Dangapara GP, block Tehatta, district Nadia a properly managed dugwell (photograph available on our website www.soesju.org) caters to drinking water need of 100 families.

4. Rainwater harvesting


In many states of India and southern parts of Bangladesh, the harvesting of rainwater is still a common practice. In present scenario if rainwater is harvested through clean roof top collection into storage tanks, and precautions are taken against bacterial contamination, the stored rainwater can be used for at least 4-5 months per year. In arsenic affected areas of Thailand this is a common practice. English people during their stay in Kolkata, a century ago, used to drink freshly collected rainwater.

5. Arsenic removal plants


One of the possible arsenic mitigation strategies was installation of Arsenic Removal Plant (ARP). Installation of ARPs in West Bengal-India started at the end of 1998. The West Bengal government and other organizations have already invested about 3 million dollars in installing ARPs purchased from both national and international manufacturers (1900 ARPs were set up at an average price of US$1500 for each ARP) in mainly 5 out of 9 arsenic affected districts of West Bengal, India.

Our preliminary investigations on the efficiency of ARPs in West Bengal began in late 1998. During last 7 years we evaluated the efficiency of 577 APRs in the districts of North 24 Parganas, Murshidabad, and Nadia of West Bengal till date and submitted our evaluation reports to the Government of West-Bengal, ARP manufacturers and other concerned NGOs for their information and follow-up action (115-119).

We conducted a two-year long systematic study in order to evaluate the efficiency of 19 ARPs from 11 different national and international manufacturers installed in Baruipur block of South 24 Parganas district under a project titled ‘Technology Park Project’ implemented by All India Institute of Hygiene and Public Health (AIIH&PH), Govt. of India, Kolkata, in partnership with a number of NGOs under the financial support from India- Canada Environment Facility (ICEF), New Delhi. Ineffectiveness and poor reliability of the ARPs based on this study has been reported (120).

From our field experience we observed that in most cases authorities installed the ARPs abruptly without checking the ground realities. Lack of awareness and relevant information is one of the major hurdles in arsenic mitigation program (121). Though we noticed (120) none of the ARPs in Technology park project could achieve arsenic concentration below WHO provisional guideline value (10 μg/l) a few of them could limit arsenic below Indian standard 50 μg/l where the users were able to recognize the ARPs as an asset for the community and maintained it properly.

6. Role of better nutrition


We must understand that so far there is no available medicine for chronic arsenic toxicity; safe water, nutritious food, vitamins and physical exercise are the only preventive measures to fight the chronic arsenic toxicity. A recent study by Mitra et al. (122) covering 57 villages in South 24 Parganas in West Bengal highlighted that malnutrition could double the risk of skin lesions. Plenty of seasonal fruits and vegetables, which are very cheap, are available in arsenic affected villages around the GMB plain round the year. A large percentage of villagers are not aware that they can get better nutrition from local fruits and vegetables. They have to be trained how they can get nutritious food using cheap local fruits and vegetables. Cooking also destroys essential nutrients in vegetables and fruits.

7. The Role of Community Involvement


For successful arsenic mitigation community involvement especially of women is essential. The concept of community participation though a new paradigm is now become integral part of any successful social venture.

An awareness campaign should include the following points:
a) The danger of arsenic in drinking water
b) Different arsenic related health effects
c) The necessity of arsenic removal
d) Importance of keeping updated on quality of drinking water in terms of arsenic and other contaminants as found out from periodical testing. The results of periodical testing may be displayed near the source.
e) The role of better nutrition in fighting arsenic toxicity

Lack of awareness and relevant information is one of the major hurdles in any arsenic mitigation program.

CONCLUSION:


Though first case of arsenocosis was revealed in West Bengal in early 1980s the widespread contamination was not recognized until 1995. Similar pattern followed in the late recognition of groundwater arsenic contamination of Bangladesh. In Bihar, till date we found 12 districts by the side of Ganga arsenic contaminated and in 6 districts identified subjects with arsenical skin lesions since the discovery of arsenic contamination back in 2002 and more are coming to fore with the continuing surveys. We predict from our up-todate preliminary survey from UP and Bihar that the districts lying in the area where Ganga and other tributaries originating from the Himalaya shifted in course of time, would be arsenic contaminated. The areas of UP and Bihar, adjacent to arsenic contaminated Terai region, Nepal may also be affected.

In India before arsenic contamination problem surfaced in 1983, we knew about fluoride contamination in groundwater from 1937. At present only in India 62 million people are suffering from fluorosis, a crippling disease. The presence of uranium, boron, and manganese in groundwater of Bangladesh above WHO prescribed limiting values has already been reported (123,124). Unless immediate measures for detailed water analysis are undertaken and awareness among all the sections of society (with especially involving women) about contaminants in drinking water is generated, toxins of higher toxicity may affect in course of time.

In Bangladesh and West Bengal, at present less people are drinking arsenic contaminated water due to growing awareness and access to arsenic safe water. But in Bihar, UP, Jharkhand, and Assam still the villagers are drinking contaminated water owing to non recognition of arsenic contamination as a problem requiring urgent action. The blunder committed in West Bengal and Bangladesh before should not be repeated.

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Mrinal Kumar Sengupta, Amir Hossain, Sad Ahamed, Bhaskar Das, Bishwajit Nayak, Arup Pal, Amitava Mukherjee, M. M. Rahman, Uttam Kumar Chowdhury, Bhajan Kumar Biswas, Tarit Roy Chowdhury, Badal Kumar Mondal, Gautam Samanta, Amit Chatterjee, Dipankar Das, Dilip Lodh, and Dipankar Chakraborti - School of Environmental Studies, Jadavpur University Kolkata India

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