Radiation Biology

Exposure to radiation will cause none of these things to

happen.

You will not turn green.

You will not glow in the dark.

Radiation does not cause things to grow larger.

You will not get super powers.

So what are the effects of radiation?

Biological Effects – at the Molecular Level

Radiation can cause damage to Nucleic Acids.

Genomic Instability

Sometimes DNA damage produces later changes which may contribute to cancer.

Gene Expression

A gene may respond to the radiation by changing its signal to produce protein. This may be protective or damaging.

Effects of DNA Damage

DNA is the most important moleculethat can be changed by radiation

Studies have shown that most radiation-induced DNA damage is normally repaired by the body.

Gene Mutation

Sometimes a specific gene is changed so that it is unable to make its corresponding protein properly

Chromosome Aberrations

Sometimes the damage effects the entire chromosome, causing it to break or recombine in an abnormal way. Sometimes parts of two different chromosomes may be combined

Cell Killing

Damaged DNA may trigger apoptosis, or programmed cell death. If only a few cells are affected, this prevents reproduction of damaged DNA and protects the tissue.

Genetic Effects can includeDamage to the gene pool of a population.Mutations Or Impaired fertility.

Damage to Nucleic Acids

One very important fact to remember is that radiation increases the spontaneous mutation rate, but does not produce any new mutations. Therefore, despite all of the hideous creatures supposedly produced by radiation in the science fiction literature and cinema, no such transformations have been observed in nature.

Biological Effects – at the Molecular Level. (cont.)

Ionizing radiation can causefree Radical formation.

How does radiation cause free radical formation?

These changes can disrupt cell function and may kill cells.

• High energy radiation breaks chemical bonds.

• This creates free radicals, like those produced by other insults as well as by normal cellular processes in the body.• The free radicals can change chemicals in the body.

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Biological Effects – at the Molecular Level. (cont.)

Depolymerization: the decomposition of macromolecular compounds into relatively simple compounds.

Radiolysis: the dissociation of molecules by radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux.

RADIOSENSITIVITY OF CELLS

Radiosensitivity and Reproductive Capacity

Most sensitive cells are:Cells which are most active in reproducing themselves, and cells which have high metabolic rates.

In the human body

Most radiosensitive Least RadiosensitiveBone marrow MuscleLymphoid tissues BoneReproductive organs Brain

CHRONIC AND ACUTE EXPOSURECHRONIC: Radiation dose over a long period of

time or at frequent intervals. (Long duration generally low dose.)

Doses of rems per months or years.

ACUTE: Radiation dose received quickly and suddenly.

(Short duration generally high dose.)Doses of rems per minute.

For a given dose, chronic exposure produces less biological effect than an acute exposure.

(This means biological repair and recovery may be occurring.)

SOMATIC AND GENETIC EFFECTSGenetic: Effects are passed on from

generation to generation due to mutation of genetic material (DNA).

Somatic: Effects are manifested in the

exposed individuals themselves.

3 days post exposure

An acute somatic effect. A burn caused by a high dose over a short

period of time. This exposure was from a radiation machine.

If you notice reddening of the skin, consult your supervisor, Radiation Safety Office

and/or your physician.

This may be indicative of acute radiation exposure.

SOMATIC EFFECTS - CANCERThe most likely effect is cancer.

The types of cancer are the same as in general population.

Increased incidence of cancer in people exposed to high doses.

(i) Leukemia - survivors of atomic explosions.

(ii) Bone Cancer - radium watch painters.

(iii) Thyroid Cancer - Marshall Islanders.

(iv) Lung Cancer - uranium miners.

*From The Health Physics and Radiological Health Handbook, Nucleon Lectern Associates, Olney, MD, 1987, p. 194.

Cataract Formation

An example of Other Chronic Somatic Effects can

include

Radiation effects also characterized as:

Non-Stochastic (NS) – “Severity” (Threshold) proportional to dose.

1. Skin Cancer induction (NS)2. Cataracts (NS)3. Effects on fertility (NS)

Stochastic (S) – “Probability of occurrence” proportional to dose.

1. Mutation of genetic material (S) 2. Induction of Other Cancers (S)

• Breast • Hematopoietic • GI organs• Thyroid • Lung • Bone

Stochastic Health Effects

Late effects are “Stochastic” effects The effects become more probable as the

exposure increases. In other words, the amount of the dose

determines the probability of the effect, it does not determine the severity of the effect.

Non-Stochastic Health EffectsAcute effects are “Non-stochastic” effects The effects become more severe as the

exposure increases. In other words, the amount of the dose does

not determine the probability of the effect, it determines the severity of the effect.

Examples of nonstochastic effects include erythema (skin reddening), skin and tissue burns, cataract formation, sterility, radiation sickness and death.

Test Time!

Follow this link to the test. https://myresearch.wsu.edu

Use your WSU user name and password to sign in.

Click on the training tab.Then click on the available training tabFind the radiation safety training biological

effects course, in the “OR” section, click on it and take the test.