- © 2014 Mineralogical Society of America
Arsenic (As) is a naturally occurring toxic metalloid that is ubiquitous in the environment. It is found in water, soil, and air and as such is also found in the food supply. Millions of people are exposed to As at concentrations in their drinking water that exceed health-based standards worldwide. The World Health Organization (WHO) has listed As as one of its ten chemicals of major public health concern (WHO 2010). Inorganic As (iAs) is listed as the number one concern on the Priority List of Hazardous Substances by the Agency for Toxic Substances and Disease Registry (ATSDR 2014). This list is prepared by ASTDR and the United States Environmental Protection Agency (USEPA) and ranks the substances that present the greatest risk to public health. The list is based on a number of factors including prevalence, toxicity, and the potential for human exposure. Chronic exposure to high levels of As has proven to cause a variety of cancers, cardiovascular disease, and neurologic impairments in exposed populations (ATSDR 2007).
PREVALENCE OF ARSENIC IN THE ENVIRONMENT
The natural background concentration of As in water is 1 to 2 μg L−1 (Hindmarsh and McCurdy 1986; NRC 1999), yet elevated levels of iAs are present in the groundwater worldwide (Fig. 1). Elevated levels of As in groundwater can occur due to dissolution and weathering of As-rich ore deposits (Welch et al. 1999, 2000). This process can be accelerated in geothermal waters (Lord et al. 2012; Bundschuh et al. 2013), leading to contamination of surface and groundwater. For example, in the geothermal springs of Yellowstone National Park in Wyoming, As is known to exceed 1000 μg L−1 (Stauffer and Thompson 1984; Ball et al. 1998). These geothermal waters discharge into surface waters resulting in measured concentrations as high has 360 μg L−1 in …