1. Introduction

Arsenic is the twentieth most abundant element in the earth’s crust and potentially one of the most harmful to human health. The acute toxicity of arsenic at high concentrations has been known for centuries. Since the early 1990s, it has been recognized that a strong adverse effect on health has been associated with long-term consumption of drinking water containing even very low levels of arsenic.

Arsenic in drinking water is a worldwide problem affecting countries on all five continents, including the USA, Argentina, Hungary, Zimbabwe and many others. The most serious contamination of groundwater has been found in Bangladesh and West Bengal, India. In Bangladesh, at least 1.4 million shallow wells produce water that exceeds the World Health Organization (WHO) recommended guidelines of 10 millionths of a gram per litre of water (10 µg/L). Perhaps more than 20 million people in Bangladesh and six million people in West Bengal use water every day with arsenic levels that are often many times higher than this limit.

In the 1970s and 1980s, international agencies helped to install more than four million hand-pumped wells in Bangladesh to give communities access to clean drinking water and to reduce diarrhoea and infant mortality. This did indeed lead to a significant reduction in mortality from water-born diseases. However, cases of arsenicosis began to be seen in West Bengal and then in Bangladesh in the 1980s and by 1993 arsenic from the water in wells was found to be responsible. In 2000, a WHO report described the situation in Bangladesh as “the largest mass poisoning of a population in history … beyond the accidents at Bhopal, India, in 1984, and Chernobyl, Ukraine, in 1986.”

The only ways to counteract the effects of arsenic contaminated water are to switch to unpolluted sources or to remove the arsenic before it is used for drinking or cooking, a difficult and costly process.

The purpose of this TOP is to explain the extent of arsenic contamination globally and the sources and basic chemistry of arsenic in water, as well as the associated health problems. The TOP shows how arsenic is detected in water, and looks at some arsenic removal technologies for centralised and household point-of-use systems, as well as some social and institutional aspects of introducing them. The TOP describes two promising case-study trials of systems for removing arsenic from water in Bangladesh and in Hungary.

This TOP introduces some basic chemistry of arsenic compounds and removal systems. However, the TOP is mostly accessible to the lay reader, and scientific terms are explained.