Gross Alpha Radiation in Wisconsin Drinking Water

When the EPA tests your water for radioactivity, gross alpha is the first screen. It counts every alpha particle, regardless of source. If the count is high, the lab follows up with isotope-specific tests for radium, uranium, and other emitters. The federal limit is 15 picocuries per liter (excluding radon and uranium, which are regulated separately). In Wisconsin, gross alpha violations track radium violations almost one-for-one — same geology, same affected counties.

Gross alpha by itself doesn't tell you which radioactive element is in your water. It tells you that something radioactive is, and at what concentration. The follow-up isotope tests narrow it down. For most Wisconsin systems with gross alpha violations, radium-226/228 is the dominant contributor.