King of Poisons, Poison of Kings

There’s a reason why we don’t add arsenic to milkshakes. Apart from the fact that the two have absolutely nothing to do with each other, it just so happens that arsenic is poisonous to humans. Arsenic was first documented as a poison in the first century by a physician in the court of Emperor Nero. It gained popularity among royalty and nobility for its lack of color, odor, or taste as well as its widespread occurrence in nature. While today, politicians and the aristocracy (for the most part) have turned to less sinister ways to channel their inner frustrations, arsenic remains a global concern, particularly given its prevalence in natural water supplies in many regions of the world.

Arsenic_contamination_areasMap of global arsenic contamination

In southeast Asia, particularly India and Bangladesh, arsenic poses a major health concern for millions of people with naturally contaminated groundwater wells. The World Health Organization drinking water limit is 10 parts per billion (10 molecules of arsenic for every billion molecules of water), but wells in this region have shown concentrations 100 times higher. In southeast Asia, arsenic is naturally found in the rocks of the Himalayas. As rivers such as the Ganges erode the rock away, arsenic-containing sediments are carried downstream and accumulate in deltas over periods of thousands of years.

These sediment deposits serve as natural aquifers or underground sponges that store and filter groundwater. As you’d expect, the water – otherwise clean and clear – becomes contaminated with arsenic. The intuitive solution, of course, would be to find another water source. But with Bangladesh’s population of 155 million people crowded into an area only slightly larger than New York State, there is little room for negotiation. The rivers that run through the country are contaminated with human and industrial waste, the surface water is unusable. Treatment plants for both surface and groundwater are an option in the developed world, but would be incredibly expensive for one of the poorest nations in the world. In such an environment, it is often difficult to convince local populations that the clear, clean-tasting water that is pumped out of the ground can be anything but pristine.

Mineraly.sk_-_realgarRealgar, a naturally occurring mineral containing arsenic

For almost two decades, international research projects have attempted to find alternative sources of clean water. The general trend that has emerged from studying tens of thousands of wells in the region is that deeper sediments contain much lower arsenic concentrations. Even within the shallower aquifers where most household wells draw their water, low-arsenic pockets exist. An intensive testing, labeling, and education initiative is underway in the district of Araihazar, where community workers mark wells as either safe or unsafe and educate locals about the risks of arsenic consumption. Other campaigns have drilled deep community wells, where residents can have access to clean groundwater. Ultimately, these initiatives are limited by the amount of investment and resources that local governments and the international community are able to provide. With no low-cost arsenic treatment technologies currently on the table, the discussion must focus not on solutions but rather on adaptations, locals having to change their behaviors and consumption patterns to reduce their exposure.

Until next time, be warned: you may have just sustained a lethal dose of mostly harmless science.

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Cover photo courtesy of WorldFish, Flickr Creative Commons. Other images from Wikimedia Commons.


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