University:
California State University, Northridge
Course:
BIOL 101 | General Biology
Academic year:

2024
Views:

158

Pages:

2
Author:

customer-8199728

Radiation Biology & Environmental Hazards of Radiation I. Radiation Biology 1. Introduction Radiation biology studies the effects of ionizing radiation on biological systems. It involves cellular, molecular, genetic, and systemic responses. 2. Types of Ionizing Radiation - Particulate: Alpha (?), Beta (?), Neutrons - Electromagnetic: X-rays, Gamma (?) rays 3. Mechanisms of Radiation Damage - Direct interaction: Ionization of DNA molecules - Indirect interaction: Radiolysis of water forming free radicals (e.g., OH•) 4. Types of DNA Damage - Single-Strand Breaks (SSBs) - Double-Strand Breaks (DSBs) - Base damage - Cross-linking (DNA-DNA or DNA-protein) 5. Cellular Responses - Cell cycle arrest at G1/S and G2/M checkpoints - DNA repair: NHEJ, HR - Apoptosis, Senescence 6. Radiation Dose - Gray (Gy) – absorbed dose - Sievert (Sv) – biological effect - LD50/30 for humans: ~4–5 Gy 7. Biological Effects - Deterministic: Skin burns, sterility, ARS - Stochastic: Cancer, genetic mutations 8. Radiosensitivity Law of Bergonié and Tribondeau: High radiosensitivity in rapidly dividing, undifferentiated cells (e.g., bone marrow, lymphocytes) II. Environmental Hazards of Radiation 1. Sources - Natural: Cosmic rays, Terrestrial radiation, Radon gas - Artificial: Nuclear accidents, Medical/industrial waste 2. Environmental Impact - Air: Fallout, radon - Water: Radioisotope runoff - Soil: Long-term contamination - Biota: Genetic mutations, bioaccumulation 3. Long-Term Hazards - Carcinogenesis, Teratogenesis, Genetic mutations - Ecological disruption - Persistent isotopes: Strontium-90, Cesium-137 4. Radiation Protection - Time, Distance, Shielding - ALARA principle 5. Waste Management - Low-level: Burial, incineration - High-level: Vitrification, deep storage