The evidence linking arsenic-based pesticides with skin and lung cancer is strong and persuasive. The increased cancer risk has not been associated with eating food containing residues but with occupational exposure, particularly among professional pesticide sprayers and among workers in pesticide manufacturing plants. Mining and Smelting Arsenic pollution is a consequence of arsenic, tin and copper mining and smelting. Mine spoils have been dumped on the land and near or into streams. Smelting of the ore scatters the arsenic through the air in a plume of soot, contaminating soil and streams in a wide area.
Poisoning can occur when people are exposed to contaminated water, dust and soil.
A thousand year history of mining and smelting has left a legacy of arsenic pollution in Devon and Cornwall. During the last half of the nineteenth century, Cornwall was the world's largest producer of arsenic. Soil in some parts of Cornwall has the world's highest concentration of arsenic, up to 2500 ppm. Elsewhere in the UK and the rest of the world, arsenic levels are usually below 40 ppm. Although arsenic levels in Cornish streams and rivers occasionally exceed WHO drinking water guidelines, the main concern about human exposure is through ingesting or inhaling dust and soil.