Many fallout particles are especially hazardous biologically. Some of the principal radioactive elements are as follows:
- Strontium 90
- A very long-lived with a half-life of 28 years. It is chemically similar to calcium, causing it to accumulate in growing bones. This radiation can cause tumors, leukemia, and other blood abnormalities.
- Iodine 131
- It has a half-life of 8.1 days. Ingestion of it concentrates in the thyroid gland. The radiation can destroy all or part of the thyroid. Taking potassium iodide can reduce the effects.
- The amount of tritium released varies by bomb design. It has a half-life of 12.3 years and can be easily ingested, since it can replace a hydrogen in water. The beta radiation can cause lung cancer.
- Cesium 137
- Cesium 137 has a half-life of 30 years. It does not present as large a biological threat as Strontium 90. It behaves similar to potassium, and will distribute fairly uniformly thoughout the body. This can contribute to gonadal irradiation and genetic damage.
- Plutonium 239
- When a plutonium weapon is exploded, not all of the plutonium is fissioned. Plutonium 239 has a half-life of 24,400 years. Ingestion of as little as 1 microgram of plutonium, a barely visible speck, is a serious health hazard causing the formation of bone and lung tumors.