By Dr. Robert Thorson

`The largest poisoning of a population in history.” That’s how an epidemiologist from the University of California, Berkeley, Alan Smith, describes arsenic groundwater contamination in India. In the Indian state of West Bengal, more than 40 million people live in the poison zone. In Bangladesh, more than 82 million are threatened.

Why? Because even the most promising environmental technologies often have unseen dark sides, to which governments are sluggish to respond. Here is a cautionary tale for those waiting for the magic bullets of better engineering to solve our environmental problems.

At center stage is the delta built by the Ganges River in India and the Brahmaputra River in Bangladesh. The flat rich soils make agriculture productive, allowing the land to teem with people and farm animals. Before the mid-1960s, surface drinking water supplies such as streams, pools and open wells were often contaminated with water-borne pathogens, especially cholera. Thousands of people perished due to contaminated water, especially near Kolkata (Calcutta) where the concentration of poverty and population peaked.

Then, tube wells came to the rescue. These were little more than pipes with a porous tip that could be pressed, hammered and (or) augered into the sandy alluvium below the soil. A simple hand pump attached to the top of the pipe could raise an endless supply of germ-free groundwater. Problem solved.

But beware the Trojan horse of aqueous geochemistry. Inside the gift of germ-free groundwater was a high concentration of arsenic. It didn’t kill with the quick, painful march of cholera, which would have made the poisoning easy to identify. Instead, it killed slowly, over years, usually by preconditioning the body for skin cancer.

Brown spots on the palms of the hands were often the first symptoms. These developed into calluses, which in turn developed into cancerous tissue leading to almost certain death. Though reliable epidemiological statistics aren’t available, more than 14,000 cases of arsenicosis have been documented in the West Bengal alone. And the problem is spreading to other Indian states of Bihar, Manipur and Uttar Pradesh and throughout Bangaledesh.

There’s nothing artificial about arsenic, which is element No.33 on the periodic table. The most common natural source of arsenic is from specks of metallic minerals, especially pyrite (FeS2; also known as “fools gold”) and a related mineral called arsenopyrite (FeAsS; which could be mistaken for silver).

Both of these minerals are widely present in rocks made from abyssal marine sediments, which are abundant in the Himalayan Mountains. Hence, sediments eroded from the mountains and deposited as deltas contain countless specks of arsenic-bearing minerals. Slowly, and often with the aid of otherwise harmless bacteria, the metal dissolves invisibly into groundwater, frequently in dangerous concentrations. As with radon, it’s a completely natural, yet very stealthy killer.

Like iron, arsenic travels readily in groundwater low in dissolved oxygen, but precipitates quickly from oxygenated surface water. Thus, the onset of arsenic poisoning coincided with the switch from oxygenated surface to un-oxygenated shallow groundwater sources, which traded one problem (cholera) for another (arsenicosis).

The link between tube wells, groundwater arsenic and skin problems was made convincingly in 1982 by Kshitish Saha, a dermatologist from the School of Tropical Medicine in Kolkata. Yet only in the past few years — and due largely to pressure from a crusading environmental scientist named Dipankar Chakraborti — has the Indian government finally begun to respond seriously ($500 million) with water treatment facilities and alternative sources of potable water.

This same script has been playing with different actors throughout the history of environmental policy. Technology viewed as a panacea for one problem creates another.

For example, the magic bullets of synthetic pesticides, nuclear power, cheap electricity from coal and antidepressant drugs have ricocheted back with species die-offs, radioactive anxiety, climate change and “happy” clams in drug-polluted water, respectively. Governments demur when new, unfunded problems appear on their watch, paying little attention until crusaders reach the ear of the electorate and become impossible to ignore. Bureaucracies then respond, but ponderously.

Meanwhile, people in India are dying, especially poor ones who can’t afford the $1 a month hookup fee to public, arsenic-free water supplies. Can we put a price on a human life? Can we put a price on scientific ignorance?