Is There Arsenic in Well Water?

In some areas, yes. A USGS and CDC study estimated that about 2.1 million people in the United States may be getting drinking water from private domestic wells with high arsenic concentrations, presumed to be from natural sources. In a national study of groundwater, the USGS found about 7 percent of wells sampled exceeded the federal limit of 10 micrograms per liter, with detections more common and concentrations generally higher in the West than the East, and the greatest concern in the Southwest, where about 16 percent of drinking-water wells sampled exceeded it.

The USGS says long-term exposure to arsenic in domestic wells may cause health problems including an increased risk of cancer. The Minnesota Department of Health says consuming water with even low levels of arsenic over a long time is associated with diabetes and increased risk of cancers of the bladder, lungs, liver and other organs.

The federal limit for public water systems is 10 parts per billion. The EPA adopted that arsenic standard on January 22, 2001, replacing the old 50 ppb standard, and water systems had to meet it by January 23, 2006. For wells, the USGS says testing and, if necessary, treating the water is an effective way to reduce or eliminate the concern, and Minnesota's health department says to consider a treatment unit, such as reverse osmosis, or a different water source if arsenic is detected at any level, and highly recommends action above 10 micrograms per liter.

Sources checked September 15, 2026. Every point below links the page it came from.

The sources behind this answer

  • StudyA USGS and CDC study estimates about 2.1 million people in the United States may be drinking from private domestic wells with high arsenic concentrations, presumed to be from natural sources. US Geological Survey ↗
  • StudyThe USGS found about 7 percent of wells sampled nationally exceeded the 10 micrograms per liter arsenic limit, with the greatest concern in the Southwest, where about 16 percent of drinking-water wells sampled exceeded it. US Geological Survey ↗
  • Government sourceThe USGS says long-term exposure to arsenic in domestic wells may cause health problems including an increased risk of cancer, and that testing and treating the water can reduce or eliminate the concern. US Geological Survey ↗
  • Government sourceThe Minnesota Department of Health says consuming water with even low levels of arsenic over a long time is associated with diabetes and increased risk of cancers of the bladder, lungs, liver and other organs. Minnesota Department of Health ↗
  • Regulatory filingThe EPA adopted a 10 parts per billion drinking water standard for arsenic on January 22, 2001, replacing the old 50 ppb standard, and water systems had to meet it by January 23, 2006. US EPA ↗
  • Government sourceMinnesota's health department says to consider a treatment unit, such as reverse osmosis, or a different water source if arsenic is detected at any level, and highly recommends action above 10 micrograms per liter. Minnesota Department of Health ↗

Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.

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