Agent Name

Radiation, ionizing

Major Category





Ioninzing radiation is "energy that is released as particles or rays, during radioactive decay." The main types are alpha particles, beta particles, gamma and x-rays, and other types of radioactive decay. [EPA website: "Understanding Radiation"]


Natural ionizing radation includes radon (55%) and other terrestrial souces (8%), cosmic radiation from outer space (8%), and internal radioactive chemicals (11%). The most significant man-made sources of radiation are from diagnostic x-rays (11%) and nuclear medicine tests (4%). The remaining 3% of background radiation comes from consumer products. The average dose of natural and man-made radiation received per person is about 360 mrem or 3.6 mSv/year. [NRC website: What Are the Sources of Radiation?]


"Radioactive materials that decay spontaneously produce ionizing radiation, which has sufficient energy to strip away electrons from atoms (creating two charged ions) or to break some chemical bonds. Any living tissue in the human body can be damaged by ionizing radiation in a unique manner. The body attempts to repair the damage, but sometimes the damage is of a nature that cannot be repaired or it is too severe or widespread to be repaired." Radioactive materials are chemical and radiation hazards. The degree of the radiation hazard varies with different materials and depends on the strength of the ionizing radiation, the half-life, and the amount. Radiation can cause injury after inhalation, ingestion, or direct (external) exposure. [EPA website: "Understanding Radiation"] Elements with the same number of protons and different number of neutrons are called isotopes. Isotopes have identical chemical properties, but some isotopes are stable and some are unstable (radioactive). The activity of a radionuclide (radioactive isotope) is a measure of how many atoms undergo radioactive decay per unit of time, i.e., disintegrations/sec. [WHO website: Ionizing radiation] See the Disease, "Radiation sickness, acute" for a description of the acute effects caused by high dose radiation.

Reference Link

Canadian Nuclear Safety Commission: The Basics of Ionizing Radiation

Exposure Assessment
Explanatory Notes

Recommended Occupational Annual Dose Limits (NCRP and NRC): 5 rem in 1 year (whole body); 15 rem (lens of eye), 50 rem (skin), 50 rem (hands or feet); NCRP recommends a limit of 1 rem x age as a cummulative occupational limit; [Gusev, p. 12]

Reference Link

EPA: Understanding Radiation

Adverse Effects
Toxic Pneumonitis





Anemia, Aplastic


Other CNS Neurotoxin


Hepatotoxin, Secondary



Reproductive Toxin



Skin Burns

IARC Carcinogen

Known Carcinogen

NTP Carcinogen

Human Carcinogen

Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Biomedical References

Search PubMed

Related Information in HazMap

Occupational diseases associated with exposure to this agent:


Industrial Processes with risk of exposure: