The common public health advice to boil water contaminated with bacteria or viruses is a well-established safety measure. This practice, however, leads to a significant misconception that boiling can remove all forms of water contamination, including radiation. Boiling water does not remove radioactive material; in fact, the process frequently leaves the water more contaminated. This occurs because radioactive isotopes are atomic elements that cannot be destroyed by heat, unlike biological pathogens.
Understanding Radioactive Contamination in Water
Radiological contamination occurs when unstable atomic isotopes, known as radionuclides, are dissolved or suspended in water. These contaminants are fundamentally different from biological agents or chemical pollutants. Radionuclides are atoms of elements like Iodine-131, Cesium-137, or Strontium-90 that enter the water supply through natural processes or human activity.
These unstable isotopes decay over time, releasing energy as alpha, beta, or gamma radiation. This decay process is measured by their half-life—the time required for half of the material to decay into a stable form. Because isotopes like Cesium-137 (30 years) and Strontium-90 (29 years) have long half-lives, they persist in the environment.
Why Boiling Fails to Remove Radiological Isotopes
Boiling is chemically ineffective against dissolved elements, though it kills biological contaminants. When water reaches its boiling point, it converts into steam, which is pure water vapor. This vapor leaves behind non-volatile substances, including most radioactive contaminants.
Isotopes like Strontium and Cesium are heavy metals or salts dissolved in the water. As the pure water evaporates, these materials remain in the boiling vessel. The total amount of radioactive material stays the same while the water volume decreases, increasing the concentration of radionuclides in the remaining liquid. This makes the boiled water more dangerous to consume than it was initially. The only exception is gaseous radionuclides, such as Radon-222, which may partially outgas during boiling.
Effective Water Purification Techniques for Radiation
Removing radionuclides requires specialized methods that target non-volatile dissolved solids, unlike simple boiling or basic filtration.
Distillation
Distillation involves boiling the water and then collecting and condensing the steam back into liquid water. Since the radioactive elements are left behind in the boiling vessel, the condensed steam is essentially purified water.
Reverse Osmosis (RO)
RO is considered one of the most effective methods. It works by forcing water through a semi-permeable membrane with extremely tiny pores. These membranes are so fine they physically block up to 99% of dissolved contaminants, including large atomic elements like uranium and radium, while allowing the water molecules to pass through.
Ion Exchange
This technique uses a resin that chemically swaps radioactive ions for harmless ions. As water passes over the resin, the radionuclides are trapped within the material.
Specialized activated carbon filtration can also capture certain isotopes, particularly when used in combination with these other methods.
Health Risks Associated with Ingesting Radioactive Water
Consuming water contaminated with radionuclides leads to internal irradiation, which is more damaging than external exposure because the material is deposited directly inside the body. Danger arises when ingested isotopes mimic elements the body naturally uses, causing them to accumulate in specific organs.
For instance, Iodine-131 is absorbed by the thyroid gland, which mistakes it for stable iodine, leading to concentrated exposure. Strontium-90 is chemically similar to calcium and is incorporated into bone tissue, where it causes long-term cellular damage and increases the risk of bone cancers. Ingested Uranium tends to accumulate in the kidneys and bones, causing both radiotoxicity and chemical toxicity that can lead to kidney damage. This internal exposure damages the DNA of nearby cells, increasing the long-term risk of cancer.