Biological Effects of Ionising Radiation

Radio Sensitivity

• Radio Sensitive Tissues

• Radio Resistant Tissues

Radio Sensitive Tissues

• Reproductive cells of the ovary and the Testis

• Blood forming Tissues in bone marrow, spleen, lymph nodes

• Epithelium of the Skin

• Epithelium of the Intestinal Tract

Radio Resistant Tissues

• Bone

• Liver

• Kidney

• Muscle

• Nerves

Effects of Radiation

• Primary Effects occur when the initial interaction is with atoms in cells like those in DNA molecules.

• Secondary Effects occur with the formation of free radicals which are very reactive and can chemically attack molecules such as DNA.

Radiation Effects

• Stochastic Effects

• Non-Stochastic Effects

Stochastic Effects

• The probability of the effect increases with the dose.

• No established threshold.

• Examples: Cancer, Genetic Mutations

Non-Stochastic Effects(Deterministic)

• The severity of the effect increases with the dose.

• Generally a threshold exists. Below the threshold, no effects occur.

• Effects often result from the collective injury of many cells.

• Examples: Cataracts, Skin Burns, Lowering of Blood Cell Counts

Effects of Acute Radiation Exposure

• On the Blood

• On Digestion

• On the Central Nervous System

On the Blood

• Dose level between 200 and 1000 rad

• Damages red blood cell forming organs - loss of breath, tiredness

• Affects white blood cell production - reduced ability to fight infection

• Lowered platelet count - hemorrhaging and slower healing process

• Death by infection and hemorrhaging

On Digestion

• Dose level between 1000 and 5000 rad

• Stops new epithelial cells and absorption

• Nausea and vomiting

• Dehydration from diarrhea and low water absorption

• Electrolyte imbalance

• Death by Circulatory collapse from loss of fluids

Central Nervous System

• Dose Level greater than 5000 rad

• Convulsions

• Tremors

• Lethargy

• Death by respiratory/brain failure