Radiation Saftey Series 4

Radiation Safety Series 4 Radiation Hazards

Human Exposure to Radiation Annual Dose Source mrem/yr Exposure from natural background Cosmic rays (sun and outer space) 28 Building materials 4 Human body 25 The earth 26 Approximate total annual exposure 100

Human Exposure to Radiation Annual Dose Source mrem/yr Exposure from man made sources Medical (mostly diagnostic x-ray) 90 Fallout from atomic bombs 5 Consumer products (mostly color TV) 1__ Approximate total annual exposure 100

Human Exposure to Radiation Occupation radiation source averages Radiography company workers 440 Gamma Radiographers 1,000

CNRP Report No. 45, 1975 and NCRP Report No. 45, 1977

Radiation vs. Contamination • Radiation The emission of waves or fast moving particles through space Radioactive Contamination Material that is radioactive and uncontrolled. It may soil surrounding areas and become airborne

Ionization of Body Tissue

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• X-ray, gamma and neutron penetrate the body to different degrees • Through the ionization process energy is absorbed by the tissue • This causes damage to the body’s complex systems

Biological Effectiveness of Ionizing Energy an example • Ionizing radiation is remarkably effective in causing biological damage • a dose of 400 rads of whole-body radiation, delivered quickly, is enough to kill about half of the humans so exposed in a period of days to weeks (from acute radiation sickness LD-50 or MLD median lethal dose)

Biological Effects • How much physical energy does this large dose of ionizing radiation represent? • Since all forms of energy interconvert, we can use heat units as a basis of comparison • A CALORIE is (by definition) the amount of heat needed to raise the temperature of one gram of water by one degree Celsius. The conversion from ergs to calories is:

Biological Effects 1 erg = 2.39 x 10-8 calories. Now since 1 rad (of ionizing radiation) deposits 100 ergs of energy per gram, 400 rads will deposit 40,000 = 4 x 104 ergs per gram, which is equivalent to • (4 x 104) x (2.39 x 10-8) = 9.56 x 10-4 calories per gram

Biological Effects • This amount of energy would raise the temperature of one gram of water by less than 0.001o C ! • (That is, less than one one-thousandth of a degree Celsius!) It is an imperceptible amount of heat

Biological Effects • This calculation highlights the enormous difference between energy in the form of heat and energy in the form of ionizing radiation. • An amount of energy which is absolutely inconspicuous in one form can be lethal in another. When a radioactive material gives off any degree of perceptible heat, it is capable of killing thousands of people.

What is the reason for the difference? It is because the energy of ionizing radiation is not uniformly distributed among all the molecules of a gram of tissue, the way thermal energy is. Instead, ionizing energy is transferred to just a few electrons in a relatively few molecules, thereby disrupting the molecular basis of living cells. That cellular damage is then multiplied and amplified by normal -- and abnormal -- biological processes. http://www.ccnr.org/ceac_B.html

Radiation Damage Cell damage due to radiation Exposure: • Increases as cell reproduction rates increases • Decreases as the degree of cellular differentiation increases • Decreases as cells mature

Human Cell Sensitivity 1. 2. 3. 4. 5. 6.

White Blood Cells Immature Red Blood Cells Digestive System Lining Cells Cells of the Gonads Blood Vessel Cells Bone, Muscle and Nerve Cells Lowest number has the highest sensitivity

Nature of Cell Damage Cell damage due to radiation exposure can occur in the following ways: 2. Mitosis delayed or stopped (cell division) 3. Cell Injury may be temporary or permanent 4. Cell death 5. Chromosome Breakup 6. Temporary or permanent cell dysfunction

Categories of damage • Somatic effects the physical effects to the body resulting from cell damage • Genetic effects mutations caused by damage to the germ line (inheritance)

Radiation Damage Factors •

Rate the dose is administered 5 rem per quarter for 40 years = 200rem. 200 rem in one dose may be fatal. Damaged cells are replaced quickly.

2. Extent the body is exposed A large dose over the whole body may cause death. A large dose on a small part of the body will damage that part and not cause death.

5. Part of the body exposed Hands, forearms, feet and ankles are allowed 18.75 rem per quarter. Whole body is only allowed 1.25 rem.

7. Age of individual 18 years of age and younger are in a high cell growth stage

9. Biological differences Biological response is different from individual to individual

Effects of Radiation Dose The minimum lethal dose of radiation exposure is approximately 200 rem. By comparison, background radiation exposure in the United States is about 360 mrem per year. When appropriate medical care is not provided, the median lethal dose of radiation is estimated to be 350 rem. Modern medical therapy dramatically improves the survivability of radiation injury.

Effects of Radiation Dose The following probable outcomes depend on radiation exposure amounts: • For 1000 rem or more: Immediate death occurs. • For 600-1000 rem: Weakness, nausea, vomiting, and diarrhea are followed by apparent improvement. After several days, fever; diarrhea; hematochezia; hematemesis; hematuria; and hemorrhage of the larynx, trachea, bronchi, or lungs may occur. Death results in about 10 days. Autopsies show destruction of hematopoietic tissues, including bone marrow, lymph nodes, and spleen, and swelling and degeneration of epithelial cells of the intestines, genital organs, and endocrine glands.

Effects of Radiation Dose • For 250-600 rem: Nausea, vomiting, diarrhea, epilation (loss of hair), weakness, malaise, hematemesis, hematochezia, hematuria, epistaxis, bleeding from gums and genitals, subcutaneous bleeding, fever, inflammation of the pharynx and stomach, and menstrual abnormalities occur. Marked destruction of bone marrow, lymph nodes, and the spleen causes a decrease in blood cells, especially granulocytes and thrombocytes. Radiation-induced atrophy of the endocrine glands, including the pituitary, thyroid, and adrenal glands, occurs. From the third to fifth week after exposure, death is closely correlated with the degree of leukocytopenia. More than 50% of patients die in this time period. Survivors may develop keloids, ophthalmologic disorders, blood dyscrasias, malignant tumors, and psychoneurologic disturbances.

Effects of Radiation Dose • For 150-250 rem: Nausea and vomiting occur on the first day. Diarrhea and skin burns are probable. Apparent improvement is noted for about 2 weeks thereafter. Fetal or embryonic death occurs in pregnant women. Symptoms of malaise are noted, as described above. Persons in poor health prior to exposure or those who develop a serious infection may not survive. A previously healthy adult recovers somewhat in about 3 months but may have permanent health problems, may develop cancer or benign tumors, and will probably have a shortened lifespan. Genetic and teratogenic effects have been noted.

Effects of Radiation Dose • For 50-150 rem: Acute radiation sickness and burns are less severe than at the higher exposure dose. Spontaneous abortion or stillbirth occurs. Tissue damage effects are less severe. Reduction in lymphocytes and neutrophils leaves the individual temporarily vulnerable to infection. Genetic damage to offspring, benign or malignant tumors, premature aging, and shortened lifespan are possible. Genetic and teratogenic effects have been noted.

Effects of Radiation Dose • For 10-50 rem: Most persons experience little or no immediate reaction. Sensitive individuals may experience radiation sickness. Transient effects

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4 clinical stages of radiation exposure Each of the acute radiation syndromes (ie, hematopoietic, gastrointestinal, neurovascular) manifests 4 clinical stages. Depending on the dose of radiation absorbed, these stages may be of varying lengths. • The prodromal phase begins at the time of exposure and lasts for approximately 1-4 days. The prodrome is characterized by a relatively rapid onset of nausea, vomiting, and malaise. Radiogenic vomiting may easily be confused with psychogenic vomiting that often results from stress. In high-dose exposures, the length of the prodromal phase may be considerably shortened and replaced by the manifest illness phase. A very short to no latent period may occur, as described below.

stages of radiation exposure • The latent period represents an interval of apparent wellbeing that lasts for 2-6 weeks but decreases markedly as the dose rate and the total dose are increased. Clinicians should not be encouraged by this apparent improvement in clinical status. • Manifest illness is characterized by the clinical symptoms associated with the major organ system injured (ie, marrow, intestinal, neurovascular). • Recovery or death follows. http://www.emedicine.com/emerg/topic934.htm

Works Sited Radiation Safety Training Series Part 1: Radiation, Rudarmel Enterprises, inc. Lake Oswego, Oregon CNRP Report No. 45, 1975 and NCRP Report No. 45, 1977 http://www.ratical.org/radiation/NRBE/NRadBioEffects.html http://www.ccnr.org/ceac_B.html http://www.emedicine.com/emerg/topic934.htm