Arsenic in Groundwater

Arsenic is an element found in a number of rocks and minerals. Although it is for the most part naturally occurring, arsenic has been linked to several types of cancer. This is why in 2001, the U.S. Environmental Protection Agency (EPA) lowered the maximum contaminant level (MCL) for arsenic in drinking water from 50 to 10 micrograms per liter of water.

Concentrations of arsenic exceeding the MCL of 10 micrograms per liter have been documented in groundwater aquifers throughout the glaciated Midwest. In Indiana, natural arsenic in groundwater is mobilized from its lithological hosts — typically either unconsolidated glacial materials or near-surface bedrock. Arsenic can also be introduced into groundwater through contamination resulting from human activities.

Members of the Groundwater Focus Committee have invested time collecting and analyzing water and sediment samples in an attempt to better understand the distribution and mobilization mechanisms of naturally occurring arsenic. Much of this work is conducted through the Statewide Groundwater Monitoring Network, (GWMN), which is administered by the Indiana Department of Environmental Management.

To get the most recent report of the GWMN, click here. You can also learn more about arsenic in groundwater on the Water Issues Paper developed on this topic by the InWMC as a resource for its members and the public.