Manganese is a naturally occurring element that constitutes approximately 0.1% of the earth's crust, and low levels of Mn in water, food, and air are ubiquitous. In certain geo-logic regions, long contact times between ground water and bedrock enriched in Mn can lead to locally high levels in the water [U.S. Environmental Protection Agency (EPA) 2004]. Mn is an essential nutrient, and ingestion...