Arsenic is an odorless and tasteless metalloid that’s widely found in the Earth’s crust. Arsenic and its compounds are found in three forms – crystalline, powder, and amorphous or vitreous forms. Trace amounts of it can be found in rocks, soil, water and even in the air we breathe. It is the 26th most abundant element.
Because of arsenic’s hygroscopic nature, it is readily soluble in water, forming an acidic solution – Arsenic acid. This acid is a weak acid and the salts are called arsenates. Arsenic acid is actually an analog of phosphoric acid, which is something you don’t want to mess with.
India’s sources of arsenic
In Bihar, India, the source of the arsenic in the groundwater came from the Himalayas, washed down in the form of arsenopyrite, a conjugate of arsenic and iron. It settled in the riverbeds along the Hindu-Gangetic River basin as silt. And no, it didn’t happen last year or even several years ago. What ends up leaching out is Arsenite, the most toxic form of arsenic.
You would have to go back a very long time, However, no one realized what was happening to people until around 1983. At that time, it was discovered that people in West Bengal, and a number of states – Harkhand, Bihar, Uttar an Pradesh in the flood plain of the Ganga River; Assam and Manipur in the flood plain of the Brahmaputra and Imphal rivers, and Rajnandgaon village in Chhattisgarh state had all been chronically exposed to drinking arsenic-contaminated water from tube well/ hand pump drinking water supplies.
From 1983 onward, subsequent surveys found more and more villages added to the growing list and more people suffering from arsenic poisoning. Arsenic poisoning is also a slow poisoning, taking over five to 12 years before symptoms appear. It was also confirmed that all the river plains and basins in the survey originated in the Himalayan region.
And over the centuries, as rivers changed course and human settlements sprang up on the floodplains, people used the river water for drinking and irrigation. However, in more recent times, bacterial contamination has complicated the whole arsenic contamination issue.
Let’s explain. Back in the 1960s, people in India were using surface water from tanks, ponds and open wells for drinking purposes. However rapid population growth, industrialization, and more intensified agricultural irrigation put increasing stress on the surface-water supplies.
Going from bad to good to worse
Because most of the surface water was full of bacteria and other contaminants, thousands of deep tube wells were dug, much of it financed by loans through the World Bank. And while at first, many villagers thought the wells were something evil, they soon learned to enjoy what they thought was good, clean water.
And of course, this leads us up to 1983 and the surveys begun by health workers. They started seeing symptoms of chronic arsenic poisoning among many villagers. People were being seen with watery and inflamed eyes, gastrointestinal cramps, gradual loss of strength, scaly skin and skin tumors, anemia, confusion, while many eventually died.
Why did this happen? Part of the reason was the growing dependence on well water. But that couldn’t explain the fact that some wells had been in use for centuries. One explanation could be the excessive amounts of water from wells being used during the dry seasons.
Excessive withdrawals now lower the water table during the dry season, exposing arsenic-bearing minerals to air, which converts normally insoluble salts to soluble oxides. Then, during the next rainy season, as the aquifers refill with water, the soluble arsenic oxides mix with it and are pumped out in the drinking water. Almost 90 million people are drinking this water.
But here’s the really sad part of the story – Despite multiple studies, surveys and the number of people who are ill or dead from arsenic poisoning, there is no consensus as to the scale of the problem in Bihar. A paper published in Environmental & Analytical Toxicology estimates that over five million people in the state are drinking water with arsenic levels greater than 10 parts per billion.
Yet, the Bihar Public Health Engineering Department, the agency mandated with supplying clean, safe drinking water to the people, has a much more conservative estimate of how many people might be affected. They say that arsenic problems affect only 13 districts, putting affected blocks at 50 and affected habitations at 1,590. That is a far cry from what the science is saying.
Further reading:
India’s arsenic-polluted drinking water causing cancers (Part 1)
One of world’s largest water sources is contaminated
