Arsenic

Michigan has naturally higher arsenic levels in groundwater. Arsenic in drinking water may have harmful health effects depending on how much you consume and how sensitive you are to it. Since arsenic cannot be seen or tasted in water, a laboratory analysis is the only way to determine the arsenic level in drinking water wells.

The U.S. Environmental Protection Agency (U.S. EPA) set an arsenic maximum contaminant level (MCL) for public water supplies at 0.010 mg/L. This is equivalent to 10 parts per billion (ppb), 0.010 parts per million (ppm), 10 micrograms/liter (μg/L). The EPA also sets the MCL Goal (MCLG) for drinking water. The MCLG is set at a level that uses the best available science to prevent potential health problems. The EPA has set the MCLG for arsenic at zero.

For private water supplies (i.e. individual residential wells) the arsenic drinking water health advisory recommendation is also 0.010 mg/L or 10 ppb. If the arsenic in your water exceeds 0.010 mg/L or 10 ppb, EGLE recommends that you do not use your well water for drinking or cooking.

In general, the sample results are from Type II nontransient noncommunity water supplies and residential water well samples submitted to EGLE Drinking Water Laboratory. These sample results are from 2009-2019.

The maps show basic information on Arsenic in well water. EGLE makes every attempt to ensure data accuracy, but cannot guarantee the completeness or accuracy of the information contained in these maps.

The County Drinking Water Arsenic Results pdf maps contain maps illustrating the Drinking Water Arsenic Results by county, showing the distribution of sample result values by location. The Arsenic result values are in Parts per Billion (PPB) and are separated in categories of Non-Detect, <5 PPB, 5-10 PPB, and >10 PPB. The Non-Detect result locations are small white circles. The <5 PPB result values are small blue circles. The 5-10 PPB result values are medium yellow circles. The >10 PPB result values are large red circles.

The total number of samples and the percentage of each category listed above (Non-Detect, < 5 PPB, 5-10 PPB, and > 10 PPB) are listed below the map in the legend area. There is also a pie chart illustrating the proportions.

Extensive effort was made to ensure each county map met American Disabilities Act (ADA) Compliance standards. Due to large amounts of data in some of the maps, not all maps could be processed through the ADA compliance checker consistently. Some counties have a screen resolution that isn’t as well defined or there may be a mapping element without alternative text. In these cases, the significant information provided in the maps is available.

Note: When using a screen reader, GT means greater than and LT means less than.