Summary Groundwater safe to drink, low/no arsenic. General Information What is it? Arsenic is a naturally-occurring element that can be toxic to humans and other life-forms. It occurs in mineral form, but can be mobilized through air, water or land pathways. It can occur in inorganic (the more toxic form) or organic form, which can change how it moves through the environment. Why is it important? Health effects include birth and development effects, cancer in various organs, organ damage, and heart attacks. Arsenic impacts people through drinking water from natural surface and/or ground water sources. Although it occurs in soils and geological formations, mining and erosion of these sources can result in local and downstream increases in concentrations. Because arsenic is also used in various industrial applications, waste disposal and discharge can also result in contributions to the air, water and land. What can Influence or Stress Condition? Where arsenic is naturally-occurring, disturbance and/or erosion of soil or rock could result in increases in local and/or downstream arsenic concentrations. This includes road and land development, mining, and certain agricultural activities. Burning of certain waste, urban runoff, burning of fossil fuels and municipal/industrial discharge can all be sources of environmental arsenic in air, water and land. Target or Desired Condition Arsenic can have negative impacts at very low concentrations (<<50 ppb) and impacts increase as concentrations increase. The USEPA threshold for maximum arsenic concentrations in drinking water is 10 ppb. California has a more stringent standard of 4 ppb, based on studies of the rate of cancer n populations exposed to varying concentrations of arsenic. For arsenic, we used 4 ppb as the target concentration for a good condition (score = 100) and 10 ppb for a target for poor condition (score = 0). Arsenic can result from natural formations and erosion, artificial disturbance of natural formations (e.g., through mining), and municipal and/or industrial waste discharge. Therefore, in some places drinking water-source concentrations that exceed the poor condition target may be due to natural or artificial causes. In either cases, consumption of the water could pose a health risk to people. Related Links Centers for Disease Control, FA page for Arsenic: California Environmental Health Tracking: State Water Resources Control Board:
