During the ground-water investigation done in support of the U.S. Centers of Disease Control and Prevention (CDC) investigation of the childhood leukemia cluster in Fallon, USGS discovered that gross alpha radioactivity in numerous wells was substantially higher than could be explained by the presence of uranium isotopes. Analysis of the gross-alpha radioactivity data suggested the excess alpha radioactivity was due to polonium-210 (²¹⁰Po). Polonium-210 is a known human carcinogen, but is very rarely found in ground water because it strongly absorbs to sediments.

Objectives

The objectives of the investigation are to confirm the presence of ²¹⁰Po contaminated wells in Fallon, and to identify which aquifers and areas are contaminated so exposure of livestock and Fallon residents to elevated ²¹⁰Po levels in their drinking water can be evaluated. To the extent possible, the geochemical factors responsible for mobilizing ²¹⁰Po in Fallon ground water will be determined so other areas in the U.S. where ²¹⁰Po contamination may occur because of similar geochemical and hydrological conditions can be identified.

Strategy and Approach

The project will be done over a two year period, 2007-08.  In 2007, water samples will be collected and analyzed for major ions, trace elements, ²¹⁰Pb, ²¹⁰Po, and δ³⁴S.  Data from the USGS ground water investigation in 2001 will guide selection of the wells, and the majority of the wells used in this investigation will have been sampled previously.  New wells will be sampled to fill data gaps.  In 2008, a journal article describing preliminary results of the investigation will be prepared.

Preliminary results

Twenty-five domestic wells and one municipal supply well were sampled in 2007.  Polonium-210 concentrations ranged between <1 and 76 pCi/L, and are among the highest values known for the United States.  Only domestic wells in a basin-fill aquifer have elevated ²¹⁰Po levels; a sample from the basalt aquifer, which provides the public water supply for the City of Fallon and Naval Air Station Fallon, contained <1 pCi/L.  Some ²¹⁰Po contaminated wells provide stockwater for cattle; however, the FDA has determined that the milk supply is safe.

Additional Project Information

Press Release (PDF)

Frequently Asked Questions about USGS data on Polonium-210 in Wells in Lahontan Valley (PDF)

USGS Open-File Report 2007-1231 — Methods and data used to investigate Polonium-210 as a source of excess gross-alpha radioactivity in ground water, Churchill County, Nevada.
Updated April 2008: Version History

Information from the Centers for Disease Control (CDC):

Frequently Asked Questions

Fact Sheet — Facts about exposure to Polonium-210 from Naturally Occurring Sources

Information from the Food and Drug Administration (FDA):

Questions and Answers: Polonium

Relevance and Benefits

This study will address several priorities in the strategic plan of the USGS, Water Resources Discipline, and Nevada Water Science Center Science Plan. The project will support the USGS goal of playing a significant role in providing scientific knowledge and information to improve our understanding of environmental contributions to disease and human health. Polonium-210 is a known carcinogen and consumption of it in drinking water may have adverse health effects on exposed populations. The project will also provide data to the U.S. Environmental Protection Agency, which has stated further information of the occurrence of ²¹⁰Po is needed. The data gained from this project will provide greater understanding of naturally occurring radionuclides in ground water and study results also may have transfer value to other areas in the southwest U.S.