A disease is any condition which results in the disorder of a structure or function in a living organism that is not due to any external injury. The study of disease is called pathology, which includes the study of cause. Disease is often construed as a medical condition associated with specific symptoms and signs. It may be caused by external factors such as pathogens or by internal dysfunctions, particularly of the immune system, such as an immunodeficiency, or by a hypersensitivity, including allergies and autoimmunity.
For radionuclides at trace concentrations, there can be a very gradual and slow transition from reversible surface sorption to irreversible incorporation into solids. A new EU-funded study has shed important light on such mechanisms.