Death in the water: Arsenic is poisoning people around the world

When the scabs began to appear on Gita's skin as well, she already knew that it was not an air-borne disease, but water-borne. Scientists who arrived at the scene with simple test kits informed them that the cause of the disease was the cold, clear water in the village's wells: they contained toxic arsenic. Geeta decided that she and her husband had to leave. They spent all their money to move to a nearby farming village, but it turned out that people were dying there too, and the locals claimed that their wells were also poisoned.

The scientists and residents were right. In many of the villages in the area, people unwittingly poisoned themselves by drinking, cooking and washing dishes in water. At least 140 million people in Asia drink arsenic-contaminated water, which comes from countless hand pumps connected to plastic or metal pipes that go deep into the ground. According to government surveys, in India alone more than 18 million such small wells have been dug in the last thirty years, mostly by hand. The wells are designed to overcome the problem of surface water contamination saturated with disease-causing bacteria and industrial waste. But death also lurks in the groundwater.

Arsenic, which comes from nature, kills cells in the human body. In the first stage, scars form on the skin, and with the slow accumulation of the substance in the body, brain damage, heart disease and cancer are also caused. Arsenic is found in groundwater in at least 30 countries, from Argentina to China, Cambodia and Vietnam, as well as in areas of Canada and the USA [see map below].

The situation is getting worse because the use of groundwater is increasing: people need drinking water, and farmers need water to irrigate crops that feed a growing population. The pumping of the water has caused changes in the underground flows, so water that used to be clean now seeps through sedimentary rocks containing arsenic and suddenly, clean wells in healthy villages emit poison.

Recently, the scientists tried a new solution: to map the underground landscape to identify safe places to dig wells. So far, the flow changes and the rate of chemical reactions have been faster than the maps' predictive ability. "It's a pitiful situation, it's disheartening," says Dipankar Chakraborty, an environmental analytical chemist who has spent 28 years studying the problem at Jadavpur University in Calcutta. "We are causing such rapid changes underground that we can barely keep up." Chakraborty used to be head School of Environmental Studies at the university, and it is now establishing a research institute named after him, the DC Research Foundation, to continue researching the arsenic problem.

The problem of the wells

Wealthy areas, such as the southwestern United States, have the money and means to remove arsenic from drinking water. But most of the populations severely affected by arsenic are also among the poorest populations in the world. In South Asia, a region considered one of the most dangerous in this respect, arsenic-saturated groundwater extends beneath a vast and densely populated area that includes parts of India, Nepal and Bangladesh. According to the World Health Organization, arsenic is dangerous in concentrations higher than 10 micrograms per liter of water, but the Indian standard is still 50 micrograms per liter, and many of the wells do not even meet this comfortable threshold.

The problem in India began as early as the 60s, when the country's residents began drinking groundwater to avoid poisoning from the surface water sources, which were contaminated with bacteria, sewage and smelly agricultural waste. In 1969, India, with the help of international groups such as UNICEF, launched a program to dig holes in the ground to create more than a million simple wells, at a cost of $125 million. This program was followed by other programs, and at the time it seemed that there was no other choice. There was no infrastructure for storing, distributing or filtering water in India, and this situation prevails even today, except in the largest cities.

These tube wells were considered a life-saving and inexpensive solution. Of the one and a quarter billion people living in India, about 80% of the rural population and about half of the urban population use groundwater for drinking, cooking and irrigating agricultural crops and gardens. The groundwater solved another serious problem: the famine that threatened parts of the country in the 80s. Today, India uses a huge share of its irrigation water, about 91%, to grow rice, wheat and sugarcane.

But the rapid agricultural development has a price. Most of the wells were dug to a depth of 50 to 200 meters, up to the point where the diggers reached the first layer of bacteria-free water. Unfortunately, this is exactly the depth where most of the arsenic is found in the area, a fact that no one knew at the time. If they dug a little deeper, they would usually reach safe drinking water, but digging deeper requires an additional expenditure of time and money and the use of stronger construction materials that many poor villagers cannot afford.

And there were other obstacles. Widespread ignorance and indifference on the part of the authorities thwarted efforts to explain the dangers to the public. Seemingly simple solutions, such as rainwater harvesting or local water purification, were too complicated for ignorant people and were not properly understood. Attempts to store rainwater failed because the tanks and plastic pipes were not properly maintained. Filtering water through sand baskets is seen as an oppressive and time-consuming task. The villagers, who could not read the instructions for use and did not understand the chemistry, also misused water purification tablets distributed by scientists and other activists. Permanent solutions, such as large water purification facilities, could have spared the confusion of millions of people, but proved too expensive and technologically unwieldy. The facilities failed for reasons that always arise when there is no proper supervision and maintenance.

"The better solution, of course, is to completely avoid the polluted water," he says Michael Berg, Head of the Department of Water Resources and Drinking Water at the Swiss Federal Institute for Water Science and Technology (Eawag). "But compared to the surface water, with all the disease-causing agents found in it, the groundwater seems the least evil."

Deadly geology

Arsenic is a relatively common element. It has no color, taste or smell, so it was for a long time the "working tool" of choice for murderers. Arsenic is toxic to most life forms even in very low doses.

The lands of the plains at the foot of the Himalayas are among the richest in the world. After the giant mountains were formed by tectonic collisions, pyrite minerals, containing arsenic, were exposed on their slopes. Fast-flowing rivers disintegrated the minerals and carried them all over India, Bangladesh, China, Pakistan and Nepal. Meanwhile, arsenic dissolved in water and underwent chemical processes in which it reacted with oxygen, iron or other heavy metals. The reactions created tiny grains that sank to the bottom of the rivers and left layers of arsenic-rich soil at different depths. These muddy sediments accumulated over thousands of years in the ancient deltaic areas of the Ganges-Meghna-Brahmaputra plain. This area, which is almost 700 thousand square kilometers in size, is now densely populated by about half a billion people.

Naturally, most of the arsenic was supposed to remain underground, but the wells reached it even in areas where the rivers no longer flowed. "You can't just look at the places where the rivers are flowing now," says Chakraborty in his university office, where a green canopy of potted plants surrounds filing cabinets and guests alike. He sips coffee from a laboratory cup and traces the water channels on the map with his fingers. "We need to take into account the changes that occurred in their path. At one point, it was all covered with water, which means there's a lot more opportunity to find arsenic."

Arsenic does not always dissolve and penetrate the groundwater, it only happens under certain geological conditions. The scientists studying the issue described two general scenarios that encourage the release of arsenic, and this understanding opened the door to creating models to predict possible risk.

The first scenario, the release of basic (alkaline) arsenic, occurs in oxygen-rich soil, where alkaline water flows, that is, at a high pH level. This scenario takes place, for example, in arid regions in Argentina and the southwestern United States. The water triggers a chemical reaction that breaks down oxides of iron and other metals that coat the soil particles. This reaction releases the arsenic that binds to these ions, allowing it to dissolve and contaminate the surrounding groundwater.

The second scenario, reductive arsenic release, occurs in soil poor in oxygen but rich in organic carbon compounds. These conditions are typical of delta areas, marshes and river basins, where the surface soil is usually new and still contains a large amount of bacteria. This is the case in some of the most populated areas in the world, such as northern India, Bangladesh, and countries in Southeast Asia such as Vietnam. The bacteria accelerate the chemical reactions using enzymes, which break down the iron oxide to which arsenic binds. If you take a handful of soil from an area where the groundwater does not contain arsenic, for example North Carolina in the USA, and bury it in Bangladesh, it will release arsenic.

This process continues as long as there is enough organic carbon to feed the bacteria, and carbon compounds become rarer as you go deeper into the soil. Fertilizing the soil, as is done on a large scale in India, may extend the duration of the process. Salinity, especially sulfur ions (sulfides), may act in the opposite direction and shorten the process because these ions bind to arsenic and form precipitates. However, this only occurs as long as oxygen levels are low. New oxygen will be used by bacteria to break down the sulfur deposits and re-release trapped arsenic. Therefore, if an aquifer is drained and refilled quickly, oxygen-rich water will seep into the ground and trigger a new wave of arsenic release. This situation is also common in India, and thus perfect conditions are created for the continuous release of arsenic over a long period of time.

Hazard mapping

Currently, the process to locate the most polluted wells requires a lot of work and a lot of time. The inspectors have to go from village to village and test all the wells using a portable chemical kit. The testers mix some water from the well with some chemicals in a sealed container. They then insert a test strip that absorbs dissolved arsenic. After ten minutes, the color of the strip provides an approximate result: if it is white, it means that the water is clean, and if it is red, the water is polluted. The test, as mentioned, is not accurate, and is sensitive to contamination only at a certain level. Beyond that, or if additional details are required, the water must be tested in the laboratory.

In 2006, Berg and other scientists at Eawag began creating a global map of arsenic, based on models that provided initial predictions based on parameters such as soil composition, gradients and water flow. They published the first draft of The global risk mapin 2008, and plan to soon publish a new version that will incorporate more details and recent research in the field. Because the crisis is so widespread, researchers often do not discover the problem ahead of time and arrive at the wells only years after people have already drunk water with arsenic from them. Some scientists therefore began looking for shortcuts, studying satellite images of the ground's trajectory and mapping the flow of water to speculate on the types of sediments below the surface, and to show where arsenic is most likely to be found. According to them, such methods can help governments save time and money by reducing the number of wells that need to be tested. Alternatively, they can also warn about areas that were previously considered safe.

These models "are capable of predicting what is in places where no tests are carried out," says Berg, who led the project. For example, his team was able to predict that large areas of Sumatra in Indonesia were at risk. "We went there and checked, and our hypothesis was verified. This greatly strengthened our confidence that the model was fine.”

In 2013 she joined Eawag China Medical University to build a model of China. This happened after tests conducted from 2001 to 2005 in about 445,000 wells revealed that about 5% of them were contaminated with arsenic at a concentration higher than the Indian standard of 50 micrograms per liter. Many more wells passed the stricter safety level set by the World Health Organization. Because large areas of China have yet to be tested, the team sought to help decision-makers take action. "There is a barrier between science and society," he says Luis Rodriguez-Lado, a chemist who now works at the University of Santiago de Compostela in Spain, and who was one of my authors The article published in August 2013 in Science magazine, "We need to find some way to show the decision makers that we can help solve real problems". Compared to wells that were actually measured, the Chinese model was accurate in 77% of the cases. Such data, Rodriguez-Lado says, can save lives and save money and time by marking the wells that need to be tested. "This is a result that gives enormous satisfaction to every scientist."

However, the models have limitations. Because they are based on current surface conditions and current knowledge of water flow, they do not well predict the contents of ancient and unknown water bodies underground. "Our predictions are always related to what we see on the surface," says Berg. "If there are older sediments there, we won't see them."

Rodriguez-Lado says that to avoid mistakes, the models must be built based on accurate and up-to-date information. When he began researching the situation in China, he assumed, based on China's arid landscape and rainfall patterns, that the model would be based on oxidizing alkaline conditions, meaning soil rich in oxygen and basic water. "Most of China has been classified as an area where the release of arsenic from oxygen takes place," he says. "But the information was scarce," and he soon realized that the aquifers in China were actually low in oxygen (anoxic), similar to the aquifers in India and Bangladesh. When he incorporated this data into the calculations, their accuracy improved.

Forecasting through mapping has additional limitations, especially in resolution. The Chinese risk model divides the country into squares of 25 by 25 kilometers: too large to predict which villages will be affected. "The models can be useful, but they have not yet reached the necessary level," says the geochemist Alexander Wen Jin מLamont-Doherty Earth Observatory at Columbia University. "Suppose the model predicts a 20% probability of finding arsenic in a certain area. I'll still have to check my well, right?”

Solutions that failed

Governments tried other ways to solve the water problem, but failed to change the situation. A few years ago, the government of the state of West Bengal laid a pipeline intended to transport arsenic-free water from the city of Calcutta to the rural areas, but the water only flows through it for a few hours a day, if at all, and does not reach all the villages. The black plastic pipes are not properly maintained and many of them are cracked: water leaks through the jagged cracks and drips into puddles on the sides of the road.

Hundreds of arsenic removal facilities, each costing about $1,500, have been installed across West Bengal and neighboring Bangladesh. Chakraborty et al have shown that in most cases, the simple cylindrical filter mechanisms are ineffective. One of the studies revealed that only two out of 13 facilities, of different manufacturers, managed to keep arsenic levels below the Indian standard, and none of them met the World Health Organization standard. By the time the study was published, in 2005, it was no longer relevant: maintenance problems and neglect meant that only three of 18 facilities were still in operation.

Digging deeper wells, to bypass the polluted layers, is not only an expensive task, which is beyond the reach of the villagers, but also only a short-term solution. Chakraborty's research shows that between the low aquifer, which is about 200 meters deep below the surface, and the contaminated Barsen layers above it, a thick clay layer partially separates, emphasizing the word "partial". Pumping from a great depth will therefore be beneficial for a period of time, but eventually the deadly water will seep down through the cracked and perforated layer and contaminate the deeper layers as well.

This is already happening in India. According to the World Bank, the use of groundwater in India is so extensive that within twenty years 60% of the aquifers will reach a critical level of arsenic, unless pumping is almost completely stopped. Chakraborty, who tested the village of Jayanagar in Bengal, found that in eight local wells the concentration of arsenic jumped from a safe concentration to a dangerous concentration in just five years, from 1995 to 2000.

Arsenic is also able to move in horizontal flow. When the water pressures in the reservoirs change, the water may flow from a polluted aquifer to a nearby clean aquifer, and this is in addition to the vertical flow. Such a horizontal flow is now taking place in Hanoi, the capital of Vietnam, which draws its water from a arsenic-free aquifer that flowed from the city and beyond. This flow pushed the water away from a nearby contaminated aquifer. But with the growth of the Vietnamese metropolis, more and more water was pumped from the safe layer, and the direction of the flow was reversed. Water from the polluted aquifer by the Red River began to enter the clean municipal reservoir [see box in "Good to Know"]. According to Wen Jin this is cause for concern, but so far the problem is developing slowly. His research showed that arsenic moves 16 to 20 times slower than water itself, perhaps because it is still bound to other elements in the soil and released from them at a slow rate in underground chemical reactions.

In India, things happened faster, due to the rapid growth of the population and the need to feed it all. Although a law was enacted there in 1986 prohibiting excessive use of groundwater, no one enforces it. Even in places where the fields are located near rivers or lakes, farmers irrigate with groundwater. And even if there is absolutely no need for water locally, landowners pump what they can to sell the water on the black market. Arsenic also reaches the food chain: it is found in rice, cow's milk and buffalo meat. Chakraborty even found it in soft drink bottles, and in sterile water containers in hospitals.

The fight for safety

Although the researchers agree on the problem and its causes, "it is not clear what can be done about it," says Wen Jin. Like Chakraborty and others, he believes that forecasting using models is indeed a useful tool, but does not provide a substitute for testing the wells themselves.

Wen Jin is trying to promote the use of inexpensive test kits in the field. They are not as accurate as laboratory tests, but provide immediate results at minimal cost. He also revealed a job market in the field of testing: a survey of 26 villages in the state of Bihar showed that about two-thirds of the residents were willing to pay 20 rupees, or about 30 US cents, to have their wells tested.

"We cannot handle all these private wells ourselves, so the direction is to create a network of testers and give them a financial incentive to perform the tests," says Wen Jin. He and his colleagues were able to organize inspections of many wells in Bangladesh, locate them using GPS data, and thus create a dynamic map of the safe and unsafe wells in the country. Thanks to this map, the villagers can easily find safe drinking water.

Follow-up studies showed that villagers who paid for the tests would also be more willing to act on the results and switch to safer wells, even if they are less convenient. This is what hydrogeologist Chandra Kumar Singh of TERI University in New Delhi, one of Wen Jin's research partners, found. The two also examine how socio-economic factors, such as income level or belonging to a certain caste, may prevent people from using safe wells, if these are also used by lower castes and economic classes. "The government hasn't shown much interest," says Singh, "maybe our work can help chart the way."

Chakraborty also trained assistants who arrive in the villages by bicycle or train and collect samples from wells. He organized international conferences and led teams of doctors, students and activists to conduct health surveys. He even set up a fund to fund his research and fund free water testing for poor residents. When his academic degrees are not enough to impress the villagers, he puts aside his distaste for the ancient Indian hierarchies and takes advantage of his belonging to his high Brahmin caste: he puts on the white cloth around his waist and wears the sacred white thread, as the Brahmin saints do, and shows the families where they are the safe wells. “I hate it,” he says of the ruse, “but I'll do it. I just need to convince the mother, and then I know the whole family will be fine."

In Geeta's village, her frail husband Shrivas struggles with headaches, other incessant pains and exhaustion. His whole body is covered with rough abscesses and his skin burns, especially in the sunlight. There is no known treatment for arsenic poisoning. There are no drugs that will repair the damage caused to the chromosomes. In the past, in severe cases of metal poisoning, chemical therapy was used in which substances are injected into the blood to bind the metal. But this is a very dangerous and very expensive process in India. Most patients can, at most, eat nutritious food and stop ingesting more poison. Even so, Shrivas considers himself lucky: he has a teenage son who helps bring clean water from a nearby clinic, and Gita, in her work as an assistant, manages to support the family.

"I have no complaints against anyone," says the trembling Shrivas, expressing a fatalism that is very common among the poor in India, so common that some scientists fear it prevents the villagers from looking for cleaner wells. "And even if I wanted to complain, no one would listen."