Radium is a naturally occurring radioactive element found in the Earth’s crust, and its presence in drinking water is a significant public health issue. This contamination arises from the decay of other elements deep underground, introducing radiation into water supplies. Understanding the science behind radium and its health effects is necessary to address the risks posed by ingestion. This includes investigating regulatory measures and available treatment technologies to ensure water safety.
Radium: A Basic Scientific Overview
Radium is classified chemically as an alkaline earth metal, sharing properties with elements like calcium and barium. It is inherently radioactive, meaning its atomic nucleus is unstable and decays, releasing energy in the form of particles and rays. Radium is primarily an alpha particle emitter, a type of radiation that is highly energetic but has a short range.
The element enters water supplies through a geological process, forming from the radioactive decay of uranium and thorium present in rocks and soil. Radium is subsequently dissolved and leached into groundwater, particularly in areas with granite or shale bedrock. This process is a major concern for private wells drawing water from deep aquifers, though municipal systems sourcing from groundwater can also be affected.
The two most common isotopes of concern in drinking water are Radium-226 (Ra-226) and Radium-228 (Ra-228). Ra-226 is a product of the uranium-238 decay series and has a half-life of about 1,600 years. Ra-228, which comes from the thorium-232 decay series, has a shorter half-life of approximately 5.75 years. These isotopes emit different types of radiation, with Ra-226 primarily emitting alpha particles and Ra-228 primarily emitting beta particles.
Health Risks Associated with Ingestion
The primary health concern from consuming radium-contaminated water is the increased risk of cancer over a person’s lifetime. When radium is ingested, the body mistakes it for calcium due to their chemical similarities. This leads to the accumulation of radium in the bone tissue, where it can be retained for a long time.
The deposited radium emits alpha and beta radiation directly into the surrounding tissue, damaging the DNA of bone cells. This continuous internal exposure increases the risk of bone cancer, specifically osteosarcoma, and other bone-related disorders. Historical studies of individuals with high occupational exposure have shown a clear link between ingested radium and bone sarcomas.
While most ingested radium is naturally excreted, the portion absorbed and deposited in the skeleton is the source of the long-term risk. Exposure to high levels of radium has also been associated with other health issues, including anemia, cataracts, liver, and breast cancer. The risk from typical water contamination levels is related to chronic exposure over many years rather than immediate, acute effects.
Regulatory Standards and Water Testing
The U.S. Environmental Protection Agency (EPA) regulates the level of radium in public drinking water systems under the Safe Drinking Water Act. The EPA has set the enforceable Maximum Contaminant Level (MCL) for the combined activity of Radium-226 and Radium-228 at 5 picocuries per liter (pCi/L). This standard is set close to the Maximum Contaminant Level Goal (MCLG) of zero, reflecting the goal of preventing adverse health effects.
For public water systems, testing often begins with a screening for Gross Alpha Activity, which measures the total alpha radiation in the water. If this screening exceeds a certain threshold, a specific, certified laboratory test is required to determine the exact concentrations of Ra-226 and Ra-228. This two-step process confirms if the source of the radiation is radium and if the MCL is being exceeded.
Public water systems are responsible for routine testing and must notify customers if levels exceed the MCL. Private well owners are not federally regulated and are solely responsible for testing their own water, which can be arranged through state-certified laboratories. Regular testing is the only way for private well users to know if their water contains radium, as it cannot be detected by taste, smell, or sight.
Methods for Radium Removal from Water
Once radium contamination is confirmed, several effective treatment methods are available for mitigation. Municipal water treatment facilities often use large-scale processes such as lime softening or ion exchange. Lime softening works by adding lime to the water, which precipitates the radium along with calcium, carrying the contaminant out of the solution.
Ion exchange utilizes resin materials to capture the charged radium ions, exchanging them for a less harmful ion, such as sodium. This process is highly effective because of radium’s chemical similarity to hardness minerals like calcium and magnesium. Another effective method is reverse osmosis (RO), which forces water through a semipermeable membrane that traps the radium and other dissolved minerals.
For private well owners, treatment is typically implemented using point-of-entry (POE) or point-of-use (POU) systems. Whole-house ion exchange systems, which are essentially water softeners, are a primary POE method for reducing radium. POU systems, such as a reverse osmosis unit installed under the kitchen sink, are also very effective for treating water used for drinking and cooking.