Radium in Wisconsin Drinking Water

Wisconsin sits on top of a deep sandstone aquifer that's naturally radioactive. Radium leaches out of the rock into groundwater, then into your tap. It's not industrial pollution — it's geology. Communities across the eastern half of the state, especially the Fox Valley and the I-94 corridor between Milwaukee and Madison, have been over the EPA's combined radium limit (5 picocuries per liter) for decades. Some municipal systems have installed treatment; others blend cleaner wells; a few are still working on it.

The federal standard exists because long-term exposure to radium increases bone cancer risk. There is no safe level — the legal limit is a balance between health risk and what's reasonable to remove. If your water system tests over 5 pCi/L for combined radium-226 and radium-228, that's a violation regardless of whether you've heard about it on the news.