During a 28-year field survey in India (1988–2016), groundwater arsenic contamination and its health effects were registered in the states of West Bengal, Jharkhand, Bihar and Uttar Pradesh in the Ganga River flood plain, and the states of Assam and Manipur in the flood plain of Brahamaputra and Imphal rivers. Groundwater of Rajnandgaon village in Chhattisgarh state, which is not in a flood plain, is also arsenic contaminated. More than 170,000 tubewell water samples from the affected states were analyzed and half of the samples had arsenic >10 μg/L (maximum concentration 3,700 μg/L). Chronic exposure to arsenic through drinking water causes various health problems, like dermal, neurological, reproductive and pregnancy effects, cardiovascular effects, diabetes mellitus, diseases of the respiratory and gastrointestinal systems, and cancers, typically involving the skin, lungs, liver, bladder, etc. About 4.5% of the 8,000 children from arsenic-affected villages of affected states were registered with mild to moderate arsenical skin lesions. In the preliminary survey, more than 10,000 patients were registered with different types of arsenic-related signs and symptoms, out of more than 100,000 people screened from affected states. Elevated levels of arsenic were also found in biological samples (urine, hair, nails) of the people living in affected states. The study reveals that the population who had severe arsenical skin lesions may suffer from multiple Bowens/cancers in the long term. Some unusual symptoms, such as burning sensation, skin itching and watering of eyes in the presence of sun light, were also noticed in arsenicosis patients.

During our last 27 years of field survey in India, we have studied the magnitude of groundwater arsenic and fluoride contamination and its resulting health effects from numerous states. India is the worst groundwater fluoride and arsenic affected country in the world. Fluoride results the most prevalent groundwater related diseases in India. Out of a total 29 states in India, groundwater of 20 states is fluoride affected. Total population of fluoride endemic 201 districts of India is 411 million (40% of Indian population) and more than 66 million people are estimated to be suffering from fluorosis including 6 million children below 14 years of age. Fluoride may cause a crippling disease. In 6 states of the Ganga-Brahmaputra Plain (GB-Plain), 70.4 million people are potentially at risk from groundwater arsenic toxicity. Three additional states in the non GB-Plain are mildly arsenic affected. For arsenic with substantial cumulative exposure can aggravate the risk of cancers along with various other diseases. Clinical effects of fluoride includes abnormal tooth enamel in children; adults had joint pain and deformity of the limbs, spine etc. The affected population chronically exposed to arsenic and fluoride from groundwater is in danger and there is no available medicine for those suffering from the toxicity. Arsenic and fluoride safe water and nutritious food are suggested to prevent further aggravation of toxicity. The World Health Organization (WHO) points out that social problems arising from arsenic and fluoride toxicity eventually create pressure on the economy of the affected areas. In arsenic and fluoride affected areas in India, crisis is not always having too little safe water to satisfy our need, it is the crisis of managing the water.

Since 1988, water samples from 140,150 tube-wells were analyzed for arsenic (As) in all 19 districts of West Bengal. In 9 districts, As has been found above the national standard (50 μg/L) and in 5 districts, between 10 and 50 μg/L. From Bangladesh, 50,515 tube-well water samples were analyzed from all 64 districts. Arsenic was present above 10 μg/L in 60 districts and in 50 districts, above 50 μg/L. Other than urine As speciation, 39,000 biological samples were analyzed from both patients and non-patients, 83% of the samples had As above normal level. Arsenical skin lesions were identified in 13,118 people, screening 114,841 from West Bengal and Bangladesh. About 6.1% of 5,000 children in Bangladesh and 1.7% of 14,000 in West Bengal were found to have arsenical skin lesions. Arsenic neuropathy, obstetric outcome and As in foodstuffs were also studied. Proper watershed management and community participation are needed to mitigate this alarming situation.

Since 1996, 52,202 water samples from hand tubewells were analyzed for arsenic (As) by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) from all 64 districts of Bangladesh; 27.2% and 42.1% of the tubewells had As above 50 and 10 μg/l, respectively; 7.5% contained As above 300 μg/l, the concentration predicting overt arsenical skin lesions. The groundwater of 50 districts contained As above the Bangladesh standard for As in drinking water (50 μg/l), and 59 districts had As above the WHO guideline value (10 μg/l). Water analyses from the four principal geomorphological regions of Bangladesh showed that hand tubewells of the Tableland and Hill tract regions are primarily free from As contamination, while the Flood plain and Deltaic region, including the Coastal region, are highly As-contaminated. Arsenic concentration was usually observed to decrease with increasing tubewell depth; however, 16% of tubewells deeper than 100 m, which is often considered to be a safe depth, contained As above 50 μg/l. In tubewells deeper than 350 m, As >50 μg/l has not been found. The estimated number of tubewells in 50 As-affected districts was 4.3 million. Based on the analysis of 52,202 hand tubewell water samples during the last 14 years, we estimate that around 36 million and 22 million people could be drinking As-contaminated water above 10 and 50 μg/l, respectively. However for roughly the last 5 years due to mitigation efforts by the government, non-governmental organizations and international aid agencies, many individuals living in these contaminated areas have been drinking As-safe water. From 50 contaminated districts with tubewell As concentrations >50 μg/l, 52% of sampled hand tubewells contained As <10 μg/l, and these tubewells could be utilized immediately as a source of safe water in these affected regions provided regular monitoring for temporal variation in As concentration. Even in the As-affected Flood plain, sampled tubewells from 22 thanas in 4 districts were almost entirely As-safe. In Bangladesh and West Bengal, India the crisis is not having too little water to satisfy our needs, it is the challenge of managing available water resources. The development of community-specific safe water sources coupled with local participation and education are required to slow the current effects of widespread As poisoning and to prevent this disaster from continuing to plague individuals in the future.

Arsenic contamination of rice irrigated with contaminated groundwater contributes to the additional arsenic burden of the population where rice is the staple food. In an arsenic contaminated area, an experimental field-based study done on nine fields elucidated significant positive correlation between arsenic in irrigation water and soil, irrigation water and rice, and also soil and rice both for Boro (groundwater) and Aman (rainwater) rice. Speciation studies showed that for both Boro (cooked) and Aman (raw) rice from contaminated area, 90% of total recovered arsenic was inorganic. In arsenic contaminated, uncontaminated villages, and Kolkata city, daily quantities of arsenic ingested by adult population from cooked rice diet are equivalent to 6.5, 1.8, and 2.3 L, respectively, of drinking water containing WHO guideline value. In contaminated area, daily intake only from cooked Boro rice for 34.6% of the samples exceeded the WHO recommended MTDI value (2 mu g In-As day(-1) kg(-1) body wt), whereas daily intake from Aman rice was below MTDI value as was rice from uncontaminated areas and Kolkata city. Our study indicated that employing traditional rice cooking method as followed in Bengal delta and using water having arsenic <3 mu g L-1 for cooking, actual exposure to arsenic from rice would be much less.

Since 1988 we have analyzed 140 150 water samples from tube wells in all 19 districts of West Bengal for arsenic; 48.1% had arsenic above 10 microg/L (WHO guideline value), 23.8% above 50 microg/L (Indian Standard) and 3.3% above 300 microg/L (concentration predicting overt arsenical skin lesions). Based on arsenic concentrations we have classified West Bengal into three zones: highly affected (9 districts mainly in eastern side of Bhagirathi River), mildly affected (5 districts in northern part) and unaffected (5 districts in western part). The estimated number of tube wells in 8 of the highly affected districts is 1.3 million, and estimated population drinking arsenic contaminated water above 10 and 50 microg/L were 9.5 and 4.2 million, respectively. In West Bengal alone, 26 million people are potentially at risk from drinking arsenic-contaminated water (above 10 microg/L). Studying information for water from different depths from 107 253 tube wells, we noted that arsenic concentration decreased with increasing depth. Measured arsenic concentration in two tube wells in Kolkata for 325 and 51 days during 2002-2005, showed 15% oscillatory movement without any long-term trend. Regional variability is dependent on sub-surface geology. In the arsenic-affected flood plain of the river Ganga, the crisis is not having too little water to satisfy our needs, it is the crisis of managing the water.

A detailed study was carried out in a cluster of villages known as Sagarpara Gram Panchayet (GP), covering an area of 20 km2 and population of 24,419 to determine the status of groundwater arsenic contamination and related health effects. The arsenic analysis of all hand tubewells (n = 565) in working condition showed, 86.2% and 58.8% of them had arsenic above 10, and 50 microgl(-1), respectively. The groundwater samples from all 21 villages in Sagarpara GP contained arsenic above 50 microgl(-1). In our preliminary clinical survey across the 21 villages, 3,302 villagers were examined and 679 among them (20.6%) were registered with arsenical skin lesions. A total of 850 biological samples (hair, nail and urine) were analysed from the affected villages and, on average, 85% of them contained arsenic above the normal level. Thus, many people of Sagarpara might be sub-clinically affected. Our data was compared with the international one to estimate population in Sagarpara GP at risk from arsenical skin lesions and cancer. Proper watershed management and economical utilization of available surface water resources along with the villagers' participation is urgently required to combat the present arsenic crisis.

Large number of people from 9 out of 18 districts of West Bengal, India are endemically exposed to arsenic contaminated groundwater due to drinking of tubewell water containing arsenic level above World Health Organization's maximum permissible limit of 50 microg/L. From our ongoing studies on neurological involvement in patients of arsenicosis from different districts of West Bengal, we report our findings in a total of 451 patients of three districts (Murshidabad, Nadia, and Burdwan), comprising 267 males and 184 females with age ranging from 11 to 79 years. They all had arsenical skin lesions, positive biomarkers and identified source of arsenic contaminated water drinking. Peripheral neuropathy was the predominant neurological complication in these patients affecting 154 (37.3%) of 413 patients of Group 1 and 33 (86.8%) of 38 patients of Group 2. Other possible causes and alternative explanations of neuropathy were excluded. The temporal profile in most of the cases (154 of Group 1) were of chronic affection while the 33 patients of Group 2 developed both neuropathy and dermopathy subacutely. Subacutely affected Group 2 patients had much higher incidence of neuropathy. Paresthesias and pains in the distal parts of extremities were much higher in incidence in Group 2 (73.7% and 23.7% respectively) than in Group 1 (18.4% and 11.1%). Distal limb weakness or atrophy was evident in 7.3% in Group 1 and 10.5% in Group 2. Overall, sensory features were more common than motor features in patients of neuropathy and sensory neuropathy was diagnosed in 30% and 76.3% and sensorimotor in 7.3% and 10.5% respectively in Group 1 and Group 2 subjects. Nerve conduction and electromyographic studies performed in 88 cases revealed dysfunction of sensory nerve in 45% and 27% and of motor nerve in 20% and 16.7% of patients with moderate degree and mild degree of clinical neuropathies respectively. Evoked potential studies performed in 20 patients were largely normal except for two instances each of abnormal visual evoked potential and brainstem auditory evoked potential findings. Prognosis was favorable in mild and early diagnosed cases of neuropathy whereas most of the other more severe and late diagnosed cases showed slow and partial recovery or even deterioration. Outcome in neuropathic patients of arsenicosis and long term toxic neurologic effects yet unexplored and unknown remain as matters of future concern requiring close monitoring.

The groundwater arsenic contamination in Bangladesh is a phenomenon of surface ero- sion, transportation and deposition in the form of Delta and ∼lood Plain. While dealing with such geomorphological units like Tableland, Flood Plain, Delta and Hill Tract in Bangladesh, we have found the possibility of having huge arsenic contaminattion free groundwater reservoir in selected areas in Bangladesh. The results presented are the outcome of our last 5 years, field survey analysing for arsenic of water of twentyfive thousand eight hundred ninetyseven hand tubewells in sixtyfour districts of Bangladesh comprising four existing geomorphological regions (a) Deltaic region (including coastal region), (b) Flood Plain, (c) Tableland and (d) Hill Tract. In this report, we will highlight (1) the area in Bangladesh where groundwater is not arsenic contaminated and the' possibility to use shallow hand tubewells as potential groundwater resource for drinking purpose and (2) arsenic contaminations scenario of deep tubewells (above 100 meters) all over Bangladesh and suitable depth in arsenic contaminated area to get safe water.