radiotoxicity

Radiotoxicity is the potential for radioactive substances to cause biological harm through the ionizing radiation they emit as they decay. It depends on the type and energy of radiation, the chemical and physical form of the material, and how the radionuclide is distributed and retained in the body or environment. Radiotoxicity is distinct from chemical toxicity, since two substances with similar chemistry can have very different radiotoxic effects due to their radiological properties.

Key factors shaping radiotoxicity include the radiation type (alpha, beta, gamma, or neutrons), energy, dose delivered to tissues, and dose rate. Alpha emitters, when ingested or inhaled, tend to be highly radiotoxic because they deliver intense, localized damage over a short range. Biokinetics—how the substance is absorbed, distributed, metabolized, and excreted—greatly influences organ doses. Tissue radiosensitivity and age affect outcome. Dosimetry expresses risk in terms of effective or equivalent dose (sieverts), while radionuclide activity is measured in becquerels; radiotoxicity per intake is described by dose coefficients (sieverts per becquerel) for ingestion or inhalation.

Assessment and regulation rely on models of human biokinetics and organ-specific doses. International bodies such as ICRP, IAEA, and UNSCEAR provide framework and data for estimating radiotoxicity, including dose coefficients and guidance on exposure pathways. Common pathways include ingestion, inhalation, dermal contact, and external irradiation from contaminated sources.

Radiotoxicity arises from natural radionuclides, medical and industrial materials, and accidents or contamination events. Health effects range from localized tissue damage to acute radiation syndrome and elevated cancer risk, depending on dose, duration, and radionuclide. Notable high-radiotoxicity examples include certain alpha emitters like plutonium-239 and polonium-210, which pose significant risk when internalized, while isotopes such as cesium-137 contribute to both external exposure and internal dose after ingestion.