Arsenic Is Everywhere
When most people hear the word arsenic, they think of poison and assume that its presence is human-caused, so it may come as a surprise to learn that arsenic is found naturally in our rocks, soil, water and air. This chapter provides information about the sources of arsenic, natural and anthropogenic, in our world and the amount we might expect to find in different environments. It is true that exposure to a certain amount of arsenic can kill fairly quickly, but because it is colourless, odourless and tasteless, people can regularly consume sub-lethal amounts in drinking water without knowing it is present. This “chronic exposure” can lead to a range of health effects, from skin lesions to cancer. Much of what we know about the effects of chronic exposure has been learned since the 1980s, through studies of regions such as Bangladesh, where even today 20 million people are impacted by naturally occurring arsenic in drinking water. The chapter describes how some microorganisms convert arsenic in soil into a gaseous form that is released to the atmosphere, a process that plays an important role in global arsenic circulation, and concludes with examples of arsenic releases into the environment caused by human decisions and mistakes.