5Biological Effects – at the Molecular Level Radiation can cause damage to Nucleic Acids.
6DNA is the most important molecule that can be changed by radiation Effects of DNA DamageChromosomeAberrationsSometimes the damage effects the entire chromosome, causing it to break or recombine in an abnormal way. Sometimes parts of two different chromosomes may be combinedCell KillingDamaged 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.Gene ExpressionA gene may respond to the radiation by changing its signal to produce protein. This may be protective or damaging.Genomic InstabilitySometimes DNA damage produces later changes which may contribute to cancer.Gene MutationSometimes a specific gene is changed so that it is unable to make its corresponding protein properlyStudies have shown that most radiation-induced DNA damage is normally repaired by the body.
7Genetic Effects can include Damage to the gene pool of a population.Mutations Or Impaired fertility.
8Damage 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.
9Biological Effects – at the Molecular Level. (cont.) Ionizing radiation can causefree Radical formation.
10How does radiation cause free radical formation? +-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.These changes can disrupt cell function and may kill cells.
11Biological 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.
12RADIOSENSITIVITY OF CELLS Radiosensitivity and Reproductive CapacityMost sensitive cells are:Cells which are most active in reproducing themselves, and cells which have high metabolic rates.In the human bodyMost radiosensitive Least RadiosensitiveBone marrow MuscleLymphoid tissues BoneReproductive organs Brain
13CHRONIC AND ACUTE EXPOSURE CHRONIC: 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.)
14SOMATIC AND GENETIC EFFECTS Genetic: Effects are passed on from generation to generation due to mutation of genetic material (DNA).Somatic: Effects are manifested in the exposed individuals themselves.
15An acute somatic effect. A burn caused by a high dose over a shortperiod of time. This exposure was from a radiation machine.3 days post exposure
16If you notice reddening of the skin, consult your supervisor, Radiation Safety Office and/or your physician. This may be indicative of acute radiation exposure.
17SOMATIC EFFECTS - CANCER The 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.
18Other Chronic Somatic Effects can include An example ofOther Chronic Somatic Effects can includeCataract Formation
19Radiation 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
20Stochastic Health Effects Late effects are “Stochastic” effectsThe 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.Late effects are stochastic effects – the severity does not change with dose – the likelihood of occurrence changes with dose.(i.e., leukemia is leukemia…whether it is from a high dose or a low dose, it has the same severity.)
21Non-Stochastic Health Effects Acute effects are “Non-stochastic” effectsThe 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.Acute effects are “Non-stochastic” effectsThe 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.
22Test 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.