Poster Presentation on the Radionuclide Assessment Project

Title: Naturally Occurring Radionuclides in Drinking Water are an Underestimated Public Health Risk

Author: James A. Jacobus

Presented at: Society of Environmental Toxicology and Chemistry (SETAC), 2014 Annual Meeting

Abstract: The disaster at Fukushima focused a continuing and intense scrutiny onto anthropogenic radionuclides, their infiltration into far-reaching ecosystems, and the resulting low-dose radiation exposures and health concerns on a population-wide level. In many regions of the world, naturally-occurring radionuclides are an important public health concern. In Minnesota, many communities rely on deep aquifers that contain naturally-occurring radioactive daughters of the uranium-238 decay series. When ingested, these radionuclides deposit ionizing radiation inside the body. Alpha-emitting radionuclides, such as polonium-210 and radium-226, are especially concerning for drinking water, as alpha particle radiation is much more potent than gamma/x-ray radiation. Ingestion of alpha-emitting radionuclides is currently regulated by two federal drinking water standards- a 15 picocurie per liter (pCi/L) gross alpha Maximum Contaminant Level (MCL) and a combined 5 pCi/L radium-226/228 MCL. Both MCLs use the upper end of the acceptable risk range: a 1:10,000 cancer risk. Critically, the gross alpha MCL is a crude assessment that only quantifies alpha particle radiation, and not the specific source radionuclides from which these alpha particles originate. Specific alpha-emitting radionuclides need to be identified to understand health risks, as residence time in the body, dose, and tissue-specific radiation effects vary greatly between different radioactive elements. To ensure adequate protection of public health, specific occurrence information must be gathered on highly toxic radionuclides that could be producing alpha particles in drinking water. Polonium-210 is the highest priority, as this radionuclide has the greatest potency and its occurrence in Minnesota’s drinking water is unknown despite the confirmed presence of other uranium daughters. A pilot study to determine Polonium-210 levels in groundwater will occur in the summer of 2014.

In addition to occurrence, refined risk assessment guidance is being examined by MDH for quantifiable alpha emitters in drinking water. Incorporating early life sensitivity and age-specific water intake rates into radionuclide risk assessment is also needed. While radionuclide risk assessment could be seen as lagging behind chemical risk assessment, it is the goal of this project to apply modern techniques to this primeval problem.

Naturally Occurring Radionuclides in Drinking Water are an Underestimated Public Health Risk (PDF)