Topic Menu

Ionising Radiation Risks

(Not to be learnt but to be understood.

This is valuable 'background reading' and may well be interesting for potential doctors/vets!)

How does the size dose effect outcome? The bigger the dose, the more severe the effects.

0-150 rem	- No symptoms to minimal symptoms exhibited. - Perhaps long-term effects many years later.
150-400 rem	- moderate to severe illness due to hematopoietic derangement. (Haematopoietic tissue is where blood and blood cells are formed - like in the kidneys)
400-800 rem	- severe illness.
Above 800 rem	- 100% fatal, even with best available treatment.

Partial body exposure.

Effects depend on particular tissue or organ exposed, but significant acute changes are usually seen only after a fairly high radiation dose (>1000 rem).

Long-Term Effects of Exposure to Ionizing Radiation

General characteristics: Usually occur many years after acute or chronic radiation exposure.

Biologic Effects of Ionizing Radiation: Occur with much lower doses and dose-rates: insufficient to cause acute somatic effects.

Probably related to irreparable damage to genetic material in cells which are capable of continued cell division.

Radiation Carcinogenesis in Humans

Genetic and proliferative alterations of cells require years to many lifetimes to develop.

Tumor development: Ionizing radiation in large amounts is an effective carcinogenic agent.

Sterility: Temporary sterility can be induced at exposure levels of approximately 150 rem. Females are more often permanently affected than males.

Cataracts: Due to the high sensitivity of the lens of the eye, opaque areas of the lens develop after exposure of 200-600 rem.

Life-shortening: The aging process is increased. Nutrition to the cell appears to be impaired. The total cell number is decreased and there is a modification of the composition of cellular material.

Foetal damage: The fetus is highly radiosensitive due to the rapid division of cells. No measurable fetal damage has been seen at exposures less than one rem.

Chromosomal damage: Detection of chromosomal damage requires many generations.

Law of Bergonie and Tribondeau

Radiation sensitivity of cells generally varies directly with the rate of proliferation and the number of future divisions, and inversely with the degree of morphological and functional differentiation.

(in other words the faster the damaged cells divide the worse the problem if they have been genetically altered. Also if they only come in one type and are specific for one job to do in the body their alteration will have a worse effect).

Factors that Influence the Severity of Absorbed Dose

Internal Radiation

External Radiation

Amount of Radioactivity

Radioisotope

Nature or type of the emission

Critical Organ

Physical half-life

Biological half-life

Age, weight, sex

Amount of Radioactivity

Nature or type of the emission

Radiation Energy

Time

Distance

Shielding