Boiling water does not effectively remove most forms of radioactive contamination. This common misconception stems from the fact that boiling is highly effective at killing biological threats like bacteria, viruses, and parasites that cause waterborne illnesses. While boiling water is the standard emergency method for pathogen removal, it is entirely inadequate for addressing chemical or radiological contaminants. When water is compromised by radioactive materials, using bottled water is the only guaranteed safe option until public health authorities confirm that other sources have been tested and declared safe.
How Boiling Affects Dissolved Contaminants
Boiling is a process of phase change where liquid water turns into steam, leaving behind substances that do not easily vaporize at that temperature. Most radioactive materials found in contaminated water are present as non-volatile dissolved solids, salts, or metals. These materials have boiling points far higher than that of water, meaning they cannot evaporate with the steam.
The act of boiling water causes the pure water molecules to escape as vapor, reducing the total volume of liquid remaining. Since the radioactive contaminants cannot leave, the same amount of material is left in less water. This results in a higher concentration of radioisotopes in the remaining water, making it potentially more dangerous to drink than the original contaminated source.
Understanding Radioactive Isotopes in Water
Radioactive contaminants, often called radionuclides or radioisotopes, are unstable atoms that emit radiation as they decay. These contaminants are typically dissolved in water in the form of ions or salts, similar to how table salt dissolves. Common radioisotopes of concern include Cesium-137, Strontium-90, and naturally occurring elements like Uranium and Radium.
The vast majority of these materials, such as the salts of Strontium and Cesium, are non-volatile and are therefore concentrated by boiling. There are two notable exceptions. The first is the noble gas Radon-222, which is highly soluble in groundwater but can be partially removed by boiling because it is a gas. However, boiling Radon releases it into the air, posing an inhalation risk inside an enclosed space.
The second exception is Tritium, a radioactive isotope of hydrogen that is chemically bound within the water molecule itself (H₂O). Tritium cannot be separated by simple boiling or filtration because it is part of the water structure. Because the most widespread and concerning radioisotopes like Uranium and Radium are non-volatile metals, the danger of concentration outweighs any minor reduction from volatile substances.
Proven Methods for Removing Radioisotopes
Since boiling is ineffective, specialized technologies are required to remove radionuclides from a water source.
Reverse Osmosis (RO)
Reverse Osmosis is a highly effective method where water is forced through a semi-permeable membrane under pressure. This membrane has pores small enough to physically block the dissolved salts and ions of most radioactive contaminants, including Uranium and Radium. RO systems are widely used and can achieve removal rates that often exceed 99 percent, making them a primary defense against many common radionuclides.
Ion Exchange and GAC Filtration
Another effective approach involves Ion Exchange Resins or specialized Granular Activated Carbon (GAC) Filtration. Ion exchange systems work by trading harmless ions for the problematic radioactive ions, effectively pulling them out of the water solution. This process is particularly effective for removing Cesium-137 and Radium from water. GAC filtration, while often used for organic chemicals, is also highly effective for removing the gaseous contaminant Radon-222.
Distillation
Distillation is a third, albeit energy-intensive, method used to purify water. This process involves boiling the water and then capturing and condensing the resulting steam back into liquid form. Because the non-volatile radioactive contaminants are left behind in the boiling vessel, the collected pure condensate is largely free of those materials. In the event of an emergency, it is always safest to follow the guidance of public health, environmental protection, or emergency management agencies regarding water safety.