Damage to the human body caused by ionizing and UV radiation

Ionizing radiation

Penetrating power of different types of radiation

Includes α, β, γ radiation and X-rays (photons). The most clinically relevant are γ and X-rays, as α and β radiation have limited tissue penetration.

Ionizing radiation damages the structure of macromolecules, especially DNA. Direct damage occurs through absorption of energy, leading to bond breakage and incorrect rejoining, resulting in mutations. Indirect damage occurs via radiolysis of water, producing reactive oxygen species (ROS) and oxidative stress. Additional effects include formation of free radicals causing lipid peroxidation and protein damage.

Radiation can also cause tissue burns, for example in improperly administered radiotherapy.

Radiation Sickness

Effects are divided into:

• stochastic effects, which are long-term, cumulative with dose, and include increased risk of malignancies
• deterministic effects, which have a threshold dose, after which damage occurs, such as radiation sickness

Cell sensitivity depends on proliferative activity. The most sensitive are rapidly dividing cells, which is utilized in radiotherapy. These include germ cells, bone marrow, and epithelial tissues (intestine, skin). Resistant tissues include neurons and muscle cells.

Clinical manifestations include:

• acute radiation syndrome (within 2 days, whole-body dose 1–10 Gy; >10 Gy is lethal): nausea, vomiting, weakness, bloody diarrhea, erythema to epidermal burns with blistering
• local effects: erythema, hair loss after several weeks, dermatitis
• late effects (months to years): CNS demyelination, pulmonary fibrosis (post-radiation pneumonitis), leukemia, gonadal damage up to sterility
• embryo sensitivity: first 2 weeks leads to death, up to 3rd month causes malformations (especially CNS and developmental defects)

UV radiation

urticaria

UV radiation primarily affects the skin. It causes skin damage, including erythema, blistering, and in severe cases necrosis. It can also trigger photoallergic reactions (hypersensitivity, urticaria).

At the molecular level, UV radiation damages DNA by forming thymine dimers, either within one strand or between strands. This blocks DNA polymerase and prevents proper DNA replication. During repair, incorrect base incorporation may occur, leading to mutations.

References

1. ZÁMEČNÍK, Josef. Patologie 1–3. 2. přepracované vydání. Praha : LD, s.r.o. – Tiskárna Prager, 2024. 950 s
2. SILBERNAGL, Stefan a Florian LANG. Atlas patofyziologie. 2. české vydání. Praha : Grada, 2012
3. MARUNA, Pavel, et al. Zkušební testy z patologické fyziologie. 1. vydání., duben 2015.