Radiation damages cells mainly by breaking DNA. High doses cause deterministic effects — skin injury, cataract, blood-forming damage — above a threshold, with severity rising with dose. At any dose, stochastic effects such as cancer and heritable effects become more probable, so radiation protection assumes there is no safe threshold and keeps every unnecessary dose as low as reasonably achievable.
Reviewed 2026-09-24
How radiation damages cells
Ionizing radiation deposits energy in cells. It can break DNA strands directly, or indirectly by ionizing water to form reactive free radicals. Cells repair much of this damage; mis-repaired or unrepaired damage can kill cells or cause mutations.
Two kinds of effect
Deterministic (tissue) effects
Appear only above a threshold dose, and become more severe as dose increases. Typical of high local doses or long-term accumulated exposure to hands and eyes.
- Skin damage: dryness, loss of elasticity, cracking, hair loss on hands
- Radiation cataract: lens opacity after chronic exposure of the eye
- Blood-forming effects such as reduced white cells at high doses
Stochastic effects
The probability, not the severity, increases with dose. Radiation protection assumes no safe threshold, so every unnecessary dose is kept as low as reasonably achievable.
- Cancer induction
- Heritable (genetic) effects
- Late effects appearing months to decades after exposure
Which organs are most sensitive
ICRP tissue weighting factors express the relative contribution of each organ to overall stochastic risk.
Red bone marrow, colon, lung, stomach, breast, remainder tissues
Gonads (heritable effects)
Bladder, oesophagus, liver, thyroid
Bone surface, skin, brain, salivary glands
Data: ICRP Publication 103 tissue weighting factors, which sum to 1.
Scatter: how staff are exposed
In X-ray imaging the primary beam passes through the patient to form the image. The patient also scatters lower-energy radiation in all directions, and this scatter is the main source of dose to staff standing nearby.
Protection around an interventional C-arm
- X-ray tube below the table; the beam passes the patient to the detector.
- The patient is the main source of scatter reaching staff.
- Operator: garment with shielding core, collar or cap, and eyewear or face shield.
- Single-use scatter drape placed within the procedure field.
- C-arm accessory fitted to the imaging components; confirm the interface by equipment model.
- Transparent barrier in clear lead acrylic for viewing.
Late effects
Effects that appear months, years or decades after a single moderate-to-high exposure, after long-term low-dose accumulation, or after internal contamination by radionuclides are called late effects. Cancer risk is the most important of these.
References
- WHO — Ionizing radiation and health effects (fact sheet)
- ICRP Publication 103 (2007): The 2007 Recommendations of the ICRP
- ICRP Publication 118 (2012): Statement on Tissue Reactions
- 赖亚辉《放射防护学》2007；刘树铮《医学放射生物学》第三版 2008；葛坚《眼科学》2007；白光，放射医学核医学分册 2005, 29(4)
- 新莱福防辐射产品手册（2024-09 V1）科普章节
This encyclopedia is for general and engineering reference and is not medical advice. Consult radiation protection or medical professionals for individual exposure assessment.