Arsenic

 
Last Updated: Sunday 28 June 2015

Arsenic

-- Human negotiation with its own capacities and actions often tends to be triumphalist. A man admires his muscled torso; an elite believes itself to be the omphalos -- navel, centre of gravity -- of the world; a State goes to war. At such times, it is best to remember that human ambitions cannot be inflated into or conflated with insistent demand. It must be remembered that humans do not only insist upon gratification in the here, now and thereafter. No, a self or a society can also turn to or turn upon the requirement of a basic need, such as quenching its thirst and not falling ill. Yes, a self or a society can also stand on the threshold of grasping after clean drinking water only to find itself facing an abyss: arsenic.

Arsenic is a metalloid element, brittle in nature and gray or tin white in colour. It is not found in nature as a free element, but exists in combination with other elements; it exists as a compound of oxygen, chloride, hydrogen, lead, mercury, gold and iron. There are as many as 150 arsenic-bearing minerals that exist in nature. However, only three of them are considered as arsenic ore (the amount of arsenic in each is very high): Realgar, or arsenic di-sulphide; Orpiment or arsenic tri-sulphide; and Arsenopyrite or ferrous arsenic sulphide. Arsenopyrite has been primarily identified as the main source of arsenic pollution in Bangladesh.

Chemically, arsenic compounds are of two types: organic and inorganic. Inorganic arsenic is found in two forms: trivalent arsenite and pentavalent arsenate. Inorganic arsenic is more toxic than organic ones. The trivalent form is 60 times more toxic than the pentavalent form, and is more soluble in water. Pentavalent arsenate and trivalent arsenite are commonly found in the groundwater of both West Bengal in India and Bangladesh.

In 1983
In 1983 K C Saha, former professor of dermatology at the School of Tropical Medicine, Kolkata, began to receive patients with skin lesions that resembled the symptoms of leprosy. He found out they were not. Since all the patients were from the district of 24-Parganas, Saha along with others began to look into the cause. The cause was found to be arsenic toxicity. So it happened that groundwater arsenic contamination in West Bengal was first reported in a local daily newspaper in December 1983, when 63 people from three villages located in different districts were identified by health officials as suffering from arsenic poisoning.

Ten years later Dipankar Chakraborti, an environmental scientist researching on the extent of arsenic poisoning, came across a woman in a village who had skin lesions. The puzzling thing was, she was the only one in the family who showed the symptoms of arsenic poisoning. Upon enquiry, she told him she was recently married into the family. She was from Satkhira in Bangladesh, and 'back home' there were others who had the same kind of lesions.

Chakraborti realised that the scale of the problem was far larger than understood so far. He began investigations. Teaming up with Quazi Quamruzzaman, chairperson of the Dhaka Community Hospital, Bangladesh he did a field survey and found, in 1995, three villages in two districts of Bangladesh whose groundwater contained arsenic above 0.05 milligram per litre (mg/l). In the same year the World Bank, after two years of "investigation", confirmed there were high levels of arsenic in numerous shallow and deep tubewells in various areas of Bangladesh.

Where does arsenic come from?
There are two ways to answer this question: while institutions such as the uk-based British Geological Survey (bgs), which studied the problem and came out with its report in 1999, suggest that the cause is a natural one, other researchers contend that the cause is human-made.

According to the first hypothesis, the arsenic probably originates in the Himalayan headwaters of the Ganga and Brahmaputra rivers, and has lain undisturbed beneath the surface of the region's deltas for thousands of years in thick layers of fine alluvial mud smeared across the area by the rivers.

Most of Bangladesh and the arsenic-affected areas of West Bengal lie in the alluvial plains formed in the quarternary period (last 1.6 million years). The Garo-Rajmahal Gap broad alluvial plains of the Ganga and Brahmaputra rivers -- called the Himalayan Foredeep -- extend to the northwest and northeast, respectively. To the north of this line, lie the crystalline rocks and meta-sediments of the great Himalayan thrust blocks. West Bengal (Purulia district), Bihar and the Shillong Plateau (north of Sylhet and Mymensingh districts of Bangladesh) are extensive areas of Precambrian era (last 570 million years) having metamorphic rocks and granites with widespread sulphide mineralisation. Because of their position close to where the river Ganga enters Bangladesh (geologically speaking), bgs suggested that they may be the primary source of arsenic in the Bengal alluvium.

It isn't as if the arsenic concentration in the mud is extraordinary. The real culprit is time, according to David Kinniburgh, project leader with bgs. The mud in Bangladesh lies thicker, wider and flatter than almost anywhere else on Earth. It can take hundreds, even thousands of years for underground water to percolate through the mud before reaching the sea. All the while it absorbs arsenic.

This, says Kinniburgh, helps explain the diverse pattern of arsenic concentration in tubewell waters. Almost all contaminated wells tap water from a depth of 20 metres (m) to 100 m. Shallower wells are clean because they contain mostly rainwater or water flowing swiftly through the sediments. Deeper wells tap water in older sediments which have by now been flushed clean of arsenic.

Ironically -- and this is where geology shades into politics -- water below 20 m to 100 m has been the overexploited 'target' of drinking water schemes of both government and international humanitarian organisations.

Experts like Kinniburgh relate the presence of excess arsenic in groundwater to the geological formation of Bangladesh. Some, however, differ: they suggest that the origin of arsenic-rich groundwater is human-made. It is related to the rate of groundwater extraction. Their hypothesis, called the pyrite oxidation thesis, describes how arsenic gets mobilised in the groundwater.

In the pyrite oxidation hypothesis, arsenic is assumed to be present in certain minerals (pyrites, iron containing rocks) that are deposited within the aquifer sediments. Due to the lowering of the water table below deposits, arseno-pyrite -- oxidised in a zone of the aquifer called the Vadose zone -- releases arsenic as arsenic adsorbed on iron hydroxide. During the subsequent recharge period, iron hydroxide releases arsenic into groundwater (see diagram: Making poison).

Two arguments are given in support of this thesis. The first is the intensive irrigation development in Bangladesh, which bears a striking resemblance to West Bengal. Using deep tubewells (dtws) and shallow tubewells (stws), irrigation development started in the 1960s and rapidly expanded in the 1980s. At first, dtw was popular because the government of Bangladesh subsidised its purchase. But when it stopped giving dtw loans in 1991, people turned to stws. The government's new privatisation initiative, and the rules of stw regulation, further ensured stw paramountcy. This method of extraction -- precisely in the 20m to 100 m below ground level -- ensured that the contribution of groundwater to total irrigated area increased from 41 per cent in 1982-1983 to 71 per cent in 1996-1997. (In the same period, reliance on surface water declined from 59 per cent to 29 per cent; reliance on traditional water harvesting systems fell to a low of 11 per cent.) Interestingly enough, this period was also the time when millions of tubewells were sunk into the ground to provide drinking water.

The other argument that supports the pyrite oxidation thesis is that, prior to irrigation development -- and drinking water supply schemes -- based on groundwater, there are no reported cases of arsenic patients in Bangladesh.

May 2000
In an article published in the journal Environmental Health Perspectives, a team of scientists and researchers affiliated to institutions such as the School of Environmental Studies, Jadavpur University, Kolkata and the Dhaka Community Hospital Trust, Bangladesh wrote:

"Nine districts (out of 18) in West Bengal, India, and 42 districts (out of 64) in Bangladesh have arsenic levels in groundwater above the World Health Organization [who] maximum permissible limit [guideline value for arsenic in drinking water] of 0.05 milligram per litre (mg/l)."

The article then decodes this cryptic statement:

"We have identified 985 arsenic-affected villages in 69 police stations/blocks in West Bengal. In Bangladesh, we have identified 492 arsenic-affected villages in 141 police stations/blocks."

Slowly, the article -- the result of what its authors call a "preliminary survey" -- unfolds into minutae. In steady measure it begins to reel out facts and figures. In strangely incantatory fashion, it obsessively details the various elements of a gruesome human tragedy:

"To date, we have collected 10,991 water samples from 42 arsenic-affected districts in Bangladesh for analysis, 58,166 water samples from nine arsenic-affected districts in West Bengal. Of the water samples we analysed, 59 per cent and 34 per cent, respectively, contained arsenic levels above 0.05 mg/l. Thousands of hair, nail, and urine samples from people living in arsenic-affected villages have been analysed to date; in Bangladesh and West Bengal, 93 per cent and 77 per cent samples contained arsenic. We surveyed 27 districts in Bangladesh for arsenic patients; we identified patients with arsenical skin lesions in 25. In West Bengal, we identified patients with skin lesions in 7 of 9 districts. We examined people at random for arsenical dermatologic features (11,180 and 29,035 from Bangladesh and West Bengal respectively); 24.7 per cent and 15.02 per cent of those respectively examined had skin lesions."

Suddenly, the article drops its scientific mask:

"After 10 years of study in West Bengal and 5 in Bangladesh, we feel that we have seen only the tip of the iceberg".

Where does arsenic go?
Insiduously, into the human body. Arsenicosis, or arsenic toxicity, develops after two to five years of exposure to arsenic contaminated drinking water, depending on the amount of water consumption and arsenic concentration in water. Initially, the skin begins to darken (called diffuse melanosis). This happens first in the palms. Diffuse melanosis leads to spotted melanosis, when darkened spots begin to appear on the chest, back and limbs, although the latter is what is usual among people, and so is taken to be an early symptom. At a later stage, leucomelanosis sets in: the body begins to show black and white spots. It is common in persons who have stopped drinking contaminated water but previously had spotted melanosis.

Keratosis is the middle stage of arsenicosis. The skin, in portions, becomes hard and fibrous; it is as if the body has broken out into hard boils, or ulcers. Diffuse or nodular keratosis on the palm of the hand or sole of the foot is a sign of moderately severe toxicity. Rough dry skin, often with palpable nodules on hands, feet and legs means severe toxicity. This can lead to the formation of gangrene, and cancer.

Arsenic poisoning brings with it other complications: liver and spleen enlargement and cirrhosis of the liver; myocardial degeneration and cardiac failure; peripheral neuropathy affecting primary sensory functions; diabetes mellitus and goitre; and skin cancers.

Three types of skin cancers are observed: Bowen's disease (form of squamous cell carcinoma); basal cell carcinoma and squamous cell carcinoma. These cancers develop primarily from keratosis.

In Bangladesh and West Bengal, the majority of the affected population are in the initial and middle stages.

May 2002
By May 2002, researchers of the School of Environmental Studies, Jadavpur University, Kolkata headed by Dipankar Chakraborti and others have a better grasp of the "present situation". Reporting on the status of the "arsenic calamity" in a journal called Talanta, a group of scientists wrote:

"The present situation is that in 2000 villages in 50 out of a total 64 districts in Bangladesh, groundwater contains arsenic above 0.05 mg/l and more than 25 million people are drinking (poisoned) water."

In West Bengal, "2700 villages have so far been identified and more than 6 million people from 9 affected districts are drinking water containing more than 0.05 mg/l arsenic. 300,000 people may have visible skin lesions. Samples indicate that many more may be sub-clinically affected. Children in arsenic-affected villages may be in special danger."

The abstract of this paper is quite different from that of the May 2000 one. After relating the details of scientific survey, it registers the following complaint:

"Although the West Bengal arsenic problem became public almost 20 years ago, there are still few concrete plans, much less achievements, to solve the problem"

This scientific article becomes impatient as it grapples with a disease, and a phenomenon, that ultimately affects poor people:

"Villagers are probably in worse condition than 20 years ago. Even now, many who are drinking arsenic-contaminated water are not even aware of that fact and its consequences"

Consistently pointing to non-scientific dimensions of the arsenic problem, the text of the abstract then takes on purely political colour:

"20 years ago when the West Bengal government was first informed, it was a casual matter, without the realisation of the magnitude this problem was to assume. At least up to 1994, one committee after another was formed but no solution was forthcoming. None of the experts has suggested solutions that involve awareness campaigns, education of villagers and participation of the people."

Other dimensions: Bangladesh
In the early 1970s, most people living in the countryside relied on surface water -- ponds, or rivers -- to meet their drinking water needs. As a result diseases due to bacteria-contaminated water, such as diarrhoea, dysentery and cholera were extremely widespread. To tackle this problem, and the related problem of drinking water, the government switched to a policy of tapping groundwater. The government began providing villages with tubewells and handpumps, with aid from such organisations as the United Nations Children's Fund (unicef) and the World Bank: unicef initiated the programme and paid for the first 900,000 tubewells along with its co-sponsor. Even as millions of dollars were pumped into the country as aid for 'clean' drinking water, and between 8-12 million tubewells installed, the stage got set for what the who has called the biggest outbreak of mass poisoning in history. And now, as the scale of the calamity keeps becoming bigger, the government and international experts seem completely incapable of solving the problem. Even worse, both the authorities and the agencies refuse to admit their culpability.

This dimension of the arsenic contamination problem simply beggars belief. As uk-based science journalist Fred Pearce puts it in his article Bangladesh's arsenic poisoning: who's to blame?: "Who knew what and when?"

When the tubewell programme began, nobody thought of testing for arsenic. unicef explained that "at the time, standard procedures for testing the safety of groundwater did not include tests for arsenic [which] had never been been found in the kind of geological formations that exist in Bangladesh." But many geochemists, such as John Macarthur at London-based University College, scoff at such a suggestion. One could equally scoff at the Bangladesh government claim that arsenic cases came to its attention only in 1993 and it concluded two years later that the poisoning was widespread, with tubewell water the likely cause. For, Quamruzzaman, the government was told as early as 1985 that Bangladeshis crossing the border into West Bengal were being diagnosed with arsenic poisoning. The World Bank maintained that before 1993, groundwater was never tested for arsenic. But a Dhaka-based engineer who worked for a British engineering consultancy firm had published, in 1990, his findings about arsenic in groundwater.

Ways to remove arsenic from water

PROCESS ADVANTAGES DISADVANTAGES
CO-PRECIPITATION
In this process, aluminium and ferric salts are added to precipitate arsenic in raw water. These precipitates after settling down are removed.
Can be used at
  household and
  community level
Chemicals easily
  available
Low capital cost
Problem of disposal of
  toxic sludge
Requires trained
  operators
Medium removal of
  toxic trivalent arsenic
ADSORPTION
In this process, chemicals such as activated alumina, iron coated sand, ion exchange resins are used to adsorb arsenic
Commercially available
High arsenic removal
  efficiency
Needs regular
  replenishment of
  chemicals
pH needs to be
  monitored regularly
Poor after sales service
  in villages
Sludge disposal is a
  problem
MEMBRANE TECHNOLOGIES
In this process, raw water is passsed through a membrane, which filters out arsenic. Some common technologies are reverse osmosis and electrodialysis
High arsenic removal
  efficiency
Low space requirement
High initial investment
High operation and
  maintenance cost
Requires pretreatment
  of water
Source: CPCB 2002, Arsenic contamination in groundwater and its control, Central Pollution Control Board, Delhi, p 19.


It wasn't until 1998 that the international community finally accepted some responsibility for solving the problem. The Bank announced an emergency three-year programme to identify poisoned tubewells. The Bank would initially survey 4,000 villages (out of 68,000 potentially at risk) and draw up action plans. This 'fast-track project' would be the first phase in a 15-year programme to screen the country's tubewells. But agencies and the government spent another year in negotiating the details, and the project's completion date was pushed to late 2002. A leading analyst of the arsenic crisis pronounced the project dead, but the Bank denied this allegation. When the project did take off, it succeeded in covering just 800 villages.If international action was tardy, the government wasn't far behind. In 2000, it set up a steering committee to "detect the causes of arsenic contamination across the country", an issue that earlier research had already resolved!

This attitude is still to change. Till 2002, there was no strategic plan to address the public health issues related to arsenic. Most people are still unaware of the hazard and the ways to deal with it. And, in May 2003, the Bank will unveil the Arsenic Public Health Project to "strengthen national capacity to address public health aspects of arsenic in the long term".

The abyss: West Bengal
Renu Ali, of village Aripara, North 24-Parganas is blind. This wasn't the case a few years back. Then arsenicosis destroyed her eyesight, and life, completely. Two of her sons have left the village in search of safe water and living. Another son and daughter-in-law live with her, perhaps because they suffer from arsenicosis too. She has lost hope, just like Sahajad Ali, who lives with his three brothers in Chakargatchi village in the same district, and all of them have arsenicosis. They are very cynical about any kind of arsenic mitigation technology. They don't think, for instance, that dugwells (alternative source of safe drinking water) will work in their village.

Some have lost hope. Others merely wait for the doctor, like 40-year-old Sumatya in village Gardmari in the Aomkal block of Murshidabad district. She stays alone. There are wounds on her thighs. The wounds bleed, and villagers are kind enough to pour hot water on them as a kind of swab. The doctor is expected. It is evening. The doctor in the village has not directed her to any hospital in the city; her problem worsens each passing day. Sumatya waits.

Like her, Leaten Vaivah of village Rezlapara, Nanda block in Murshidabad, is a widow living all alone. She has a cancerous wound in her hand that is slowly spreading to the rest of her body. She has not seen any doctor except the local quack in the village. Since she lives alone there is no one to take care of her. She herself doesn't have the interest or the zeal to travel all the way to Seth Sukhlal Karnani Memorial Hospital in Kolkata, where an arsenic clinic runs every Thursday. "It is too far and costs money to be going that far, I am not interested", she says. She seems still as death.

But there are those who also fight the disease. Adaitopal, of Holsur village in the Deganga block of North 24-Parganas, was affected by arsenicosis 10-12 years back. He tries to lead a normal life, despite the fact that his right foot was amputated nine years ago. He has not lost hope yet. He gives hope to other villagers by digging wells in the village. At present he is busy making a dug well in his own compound, which will also serve families that live close. Nazrul Huq, of village Holsur in the Deganga block of North 24-Parganas, is like a messenger of God in his village. After the onset of gangrene in his finger, he visited the doctor at the All India Institute of Hygiene and Public Health, Kolkata. After confirmation and fearing cancer, his finger was amputated in 1998. Now he spends his time informing people about arsenicosis.

That's something Rakia cannot do. Her husband has left her. She must be around 35. She is considered "mad" by the villagers because arsenicosis has made her a loner. She is not the only one in Fakir para (locality), Chanalti block, North 24- Parganas who suffers from arsenicosis or has been abandoned by loved ones. But at least there are people in the para. Fakir para is not like Chandalati village in the Deganga block of North 24-Parganas, completely deserted. Only 5-6 people live there. One of them is Abdul Tarafat, 60, who travels about 10 km once in two days to get water from adjoining villages. Of course he has arsenicosis. He doesn't want to leave.

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