Body burden is the amount of a harmful substance that is permanently present in a person's body. It is usually expressed in mass units, such as grams and milligrams. The substance may be radioactive or it might be chemically toxic. Many harmful substances can be eliminated naturally by the human body, but some are removed very slowly or not at all. Water soluble molecules are usually easy to remove. Non-polar molecules, on the other hand, are lipophilic and tend to accumulate in fat tissue, which is also non-polar. Large fragments, such as shrapnel, are also difficult for the body to remove.

Health | Radiobiology