This book evaluates the risks to human health and the environment posed by arsenic and arsenic compounds. Arsenic is widely distri-buted in the earth's crust and is emitted into the atmosphere by coal-fired power generation plants and volcanic activity. Inorganic arsenic of geological origin is found in groundwater used as drinking-water in several parts of the world e.g. Bangladesh. In these areas drinking-water is the main source of arsenic intake but elsewhere food is the principal source.