Eighteen percent of Pennsylvania wells have elevated levels of arsenic.
The United State Geological Survey (USGS) compiled data on groundwater wells to map the most likely places where elevated arsenic levels might be found. The study found that eight percent of wells in Pennsylvania have arsenic levels that equal or exceed the EPA’s drinking water maximum contaminant level of ten micrograms per liter. Another ten percent have elevated (but not exceeding standards) levels or arsenic, defined as more than four micrograms per liter.
The study showed that areas with shallow glacial or shale and sandstone aquifers are more likely to have elevated arsenic levels in the groundwater. Arsenic occurs naturally in these formations. Arsenic can also be a result of human activity. Arsenic can cause health problems in humans ranging from an increased risk of cancer to nausea, vomiting, numbness, partial paralysis, and blindness.
Public water systems in Pennsylvania must conform to national drinking water standards; any arsenic is reduced to acceptable levels before it is sent out to customers. Private water wells are not regulated in Pennsylvania. Homeowners may not even know there is arsenic in their well water. The USGS map for Pennsylvania (and some other states) helps homeowners to assess their risk and decide whether the water needs testing.