Naturally Occurring Radionuclides in Drinking Water...Poster

Naturally Occurring Radionuclides in Drinking Water are an Underestimated Public Health Risk Abstract ID: RP099 James A. Jacobus, Minnesota Department of Health

Overview Alpha Particle Toxicity Radioactive Decay Risks/Uncertainties Polonium-210 Pilot Study

In Minnesota, many communities rely on deep • Ingestion or Inhalation Required • Unstable atoms (radionuclides) release • Radionuclide MCLs have been set at a 1:10,000 • Many community water supply groundwater wells in aquifers that contain naturally occurring • Tissue-specific targeting based on radionuclide radiation (decay) and form new elements cancer risk for lifetime consumption based on Minnesota contain elevated total gross alpha activity radioactive daughters of the uranium-238 decay • Concentrated Damage • Uranium/Thorium decay creates a variety of dosimetry models. Naturally occurring material • The occurrence of polonium-210 is unknown, despite series. As opposed to the high-profile, low • Clustered DNA Breaks Difficult to Repair toxic radionuclides in some aquifers guidance/regulatory values typically represent the confirmed presence of its parent radionuclides frequency exposure to manmade radionuclides, • 20 times more potent than gamma/x-rays • Distinct elements = Varied Toxicities an order of magnitude (or two) greater risk than • Preliminary sampling results (n=30) demonstrate the exposure to naturally occurring radionuclides • Naturally occurring alpha emitters most prevalent synthetic chemical risk assessment. presence of polonium-210 in groundwater, with a throughout our environment is very common. • Developmental toxicity has not been examined maximum concentration of 5 pCi/L When ingested, these radionuclides deposit for radium, polonium, and many other ionizing radiation inside the body. Alpha-emitting radionuclides. The developing organism is radionuclides, such as polonium-210 and radium- extremely sensitive to radiation exposure, and 226, pose the highest health risk from ingestion this gap constitutes a large uncertainty, and inhalation, while being essentially harmless currently ignored, when considering population- outside the body. Therefore, in drinking water, wide exposures from community water supplies. Higher Po-210 activity alpha particle ingestion poses considerable • The Gross Alpha MCL may not be protective for in deep groundwater health risks that deserve careful consideration. polonium-210 (Po-210), which has a 1:10,000 (0.2 - 5 pCi/L) cancer risk <15 pCi/L and is poorly detected by Lower Po-210 activity the gross alpha analytical method Two federal drinking water standards currently in deep groundwater regulate alpha-emitting radionuclides. Both (0 - 0.3 pCi/L) MCLs use the upper end of the acceptable risk range - a 1:10,000 cancer risk1. Critically, the Occurrence Data Lacking gross alpha MCL is a crude assessment that only quantifies alpha particle radiation, and not the • Many toxicologically important radionuclides are specific source radionuclides from which these difficult to detect in environmental samples. Conclusions and • In 2000, when the Radionuclide Rule was alpha particles originate. Specific alpha-emitting Future Directions radionuclides need to be identified to understand Drinking Water Regulations finalized, the detection of individual alpha health risks, as residence time in the body, dose, emitters was considered too arduous, outside the reach of most state laboratories • The alpha emitter Po-210 occurs in MN groundwater and tissue-specific radiation effects vary greatly • Only Community Water Supplies are regulated • Initial results show that Po-210 activity exceeds 1 between different radioactive elements. • Activity, in picocuries per liter (pCi/L), concentration, • Polonium-210 and Lead-210 (Pb-210) were singled out for environmental assessment on pCi/L in some wells, with a maximum detection of 5 and dose are all used as regulatory units pCi/L in the pilot study To ensure adequate protection of public health, • Maximum Contaminant Level Goal (MCLG) for all the Unregulated Contaminant Monitoring Rule, but analytical hurdles could not be overcome • Po-210 concentration is not accurately predicted by specific occurrence information must be gathered radionuclides is zero – all known carcinogens and no data were gathered. Focus to date on gross alpha activity, but gross alpha is an indicator on highly toxic radionuclides that could be • Maximum Contaminant Level (MCL) guidance has Radium has resulted in very good occurrence • The 1:10,000 cancer risk level allowed for total alpha producing alpha particles in drinking water2. been set for some specific radionuclides, but most are data for this radionuclide exposure may be exceeded by just Po-210 ingestion Polonium-210 is the highest priority, as this regulated as a group, alpha emitters. Occurrence of Po-210 and Pb-210 in important radionuclide has the greatest potency and its Gross Alpha MCL: 15 pCi/L • o groundwater resources of many states is largely • Po-210 removal efficiency by current treatment occurrence in Minnesota’s drinking water is Ra-226/228 MCL: 5 pCi/L o unknown, including Minnesota processes in MN is unknown and needs assessment unknown despite the confirmed presence of other Uranium-234/235/238 MCL: 30 µg/L o • Po-210 occurrence study is underway in MN • Careful hydrogeologic analysis of high Po-210 wells uranium-related decay products. A pilot study to o Anthropogenic radionuclides emitting long may identify important occurrence drivers in MN range gamma/x-ray radiation also have a determine polonium-210 levels in groundwater References Lead-210 occurrence, now that Po-210 is confirmed, Only selected radionuclides shown • began in 2014. group-based MCL relying on human dose 1. Radionuclides Notice of Data Availability Technical Support Document. USEPA, 2000. needs assessment due to its potency/toxicity and rather than (radio) activity in water from the U-238 decay series. Office of Ground Water and Drinking Water. 2. Weinhold, B. Unknown Quantity: Regulating Radionuclides in Tap Water. 2012. EHP relationship to Po-210 in the U-238 decay series. 120; 9: A350-A356.