Published on February 18, 2014
Radiation Hazards and its protection Dr.Rabia Shah
Sources of Radiation Elements such as thorium, uranium, radium, RN-222, and K-40 are naturally occurring radioactive elements that can be found in our everyday lives. These elements can be found in: – rocks, soil and building materials – food and water Some sources are a result of ground nuclear testing, which is not naturally occurring. 2013
Cosmic and Atmospheric Radiation Cosmic and atmospheric radiation originates from the sun and stars. Earth’s atmosphere is very effective in shielding cosmic radiation, but variations in the density of the atmosphere can result in uneven distribution of protection. 2013
Additional Sources of Radiation Our bodies contain naturally occurring radioactive elements, such as potassium. Some consumer products, such as luminous dial watches and smoke detectors, contain small amounts of radioactive material. 2013
Cosmic radiation can be accumulated through one cross-country airplane trip. Tobacco leaves absorb naturally occurring radioactive materials from the soil and fertilizers used to grow them. Hospitalized individuals who undergo medical procedures are exposed to sources of ionizing radiation. 2013
Annual Dose from Background Radiation Total exposure Man-made sources Medical X-Rays 11% Radon 55.0% Other 1% Internal 11% Cosmic 8% Man-Made 18% Terrestrial 6% Nuclear Medicine 4% Consumer Products 3% Total US average dose equivalent = 360 mrem/year
Ionizing Radiation Ionizing radiation is produced by the natural decay of radioactive material. Beta, gamma, and x-rays are forms of ionizing radiation that are often used in research. Beta, gamma, x-rays remove electrons from atoms (Ionization). 2013 Ions are created, which are more chemically reactive than neutral atoms. Ions can form compounds that might interfere with cell division and metabolism or cause chemical changes in tissue.
X-Rays & Gamma Rays X-rays and gamma rays make up part of the electromagnetic spectrum. They can travel forever until they hit an object and one of three reactions occurs: Scattering Transmission Absorption 2013
Penetrating Radiation -X-Rays & Gamma RaysX-rays and gamma rays can penetrate the body and irradiate internal organs. Exposure can result in external and internal doses. Internal exposure can occur when rays are ingested, inhaled, or absorbed through the skin. 2013 9
Beta Particles Beta particles are excess electrons. Particles can be low or high energy emitters. Low energy emitters can be shielded by cardboard. High energy emitters need a more dense shielding material, such as Plexiglas. 2013 10
Non-Penetrating Radiation -Beta ParticlesCan not penetrate the body to irradiate internal organs. Can penetrate dead outer-layer of skin and result in damage to live skin cells. Can cause damage to eye lenses. Ingestion, inhalation, or absorption through the skin might result in internal exposure. 2013 11
Radiation Absorbed Dose -RADRAD is a unit of measurement used to describe the amount of energy transferred from a source of ionizing radiation to any material, including human tissue. It is the quantity of radiation received by a patient. As a unit of exposure, 1 rad means that each gram of air at 0° C and 1 atmosphere has absorbed 100 ergs of energy. As a unit of dose, 1 rad means that each gram of exposed tissue has abosorbed 100 ergs of energy. 2013 12
Radiation Equivalent Man -REMDifferent types of ionizing radiation cause differing degrees of biological effects even when the same level of energy is transferred (same number of ergs). Rem is used to express the quantity of radiation received by radiation workers and populations. The rate at which an individual is exposed also influences the level of biological harm. Dosimeter are used to measure a dose equivalent. 2013 13
Biological Effects of radiation Exposure above permissible levels may result in: Somatic Effects Physical effects May be immediate or delayed Genetic Effects Birth defects due to irradiation to reproductive cells before conception Teratogenic Effects Cancer or congenital malformation due to radiation exposure to fetus in utero 2013 14
Biological Effects -ThresholdThreshold effects might occur if an individual receives a dose above the threshold level. Acute Radiation Syndrome: large whole body dose in a short time Effects occur at 100 rad Radiation-induced cataract formation Acute effects occur at 200 rad Chronic effects occur at 800 rad Other thresholds Severe skin injury occurs at 1,500 rad Teratogenic effects occur at 20 rad 2013 15
Biological Effects -Non-thresholdNon-threshold effects might occur from any amount of exposure to radiation. Chance of effect occurrence is proportional to the received dose. Severity of effects are not necessarily related to exposure level. Chance effects include: Cancer - estimated to be 5 deaths per 10,000 persons, whom each received 1,000 mrem Genetic effects 2013 16
Summary of Biological Effects of Radiation Radiation may… • Deposit Energy in Body • Cause DNA Damage • Create Ionizations in Body • Leading to Free Radicals Which may lead to biological damage
Radiation Effects on Cells Radiosensitivity Theory of Bergonie & Tribondeau (1906). Stem cells are radiosensitive, mature cells are radioresistant. Younger tissues are radiosensitive. Tissues with high metabolic activity are radiosensitive. A high proliferation rate and a high growth rate result in increased radiosensitivity.
Response to radiation depends on: Total dose Dose rate Radiation quality Stage of development at the time of exposure
Whole Body Effects Acute or Nonstochastic • Occur when the radiation dose is large enough to cause extensive biological damage to cells so that large numbers of cells die off. • Evident hours to a few months after exposure (Early) • Skin burns
Late or Stochastic (Delayed) • Exhibit themselves over years after acute exposure. • Radiation induced cancers • Leukemia • Genetic effects 2013 21
Radiosensitivity of cells Low Sensitivity Mature red blood cells Muscle cells Ganglion cells Mature connective tissues Intermediate Sensitivity Gastric mucosa Mucous membranes Esophageal epithelium Urinary bladder epithelium High Sensitivity Primitive blood cells Intestinal epithelium Spermatogonia Lymphocytes
Minimize Exposure When working with radioactive material, remember to minimize your exposure at all possible times. 2013 24
Measure Your Radiation Dose -DosimetersUse to measure the occupational dose equivalent from x-ray, gamma, and high energy beta emitters. Dosimeters cannot detect radiation from low energy beta emitters. Measures… Is worn… Can detect… 2013 Luxel Whole body exposure On the torso or area of highest likely exposure Ring Dosimeter Fetal Dosimeter Extremity exposure Exposure to a fetus On either hand under the At the waist line gloves with the name facing the radiation source X-rays & gamma rays: X-rays & gamma rays: 1 – 1,000,000 mrem 30 – 1,000,000 mrem High energy beta emitters: High energy beta emitters: 10 – 1,000,000 mrem 40 – 1,000,000 mrem 25
Maximum Permissible Dose Limits (MPD) State and Federal regulations set maximum permissible yearly radiation dose (MPD) limits for adults. Exposure up to dose limits is not expected to cause adverse health effects. ADULT MAXIMUM PERMISSIBLE DOSES Whole Body – head, neck, torso, upper arms and legs 5,000 mrem Lens of the eye 15,000 mrem Extremities, skin, and internal organs 50,000 mrem Declared pregnant woman 500 mrem 2013 26
As Low As Reasonably Achievable (ALARA) Always practice ALARA AS LOW AS REASONABLY ACHIEVABLE 2013 27
Why Practice ALARA? Any type of ionizing radiation poses some risk. As exposure increases, so does risk. Research shows that some people’s DNA is more resistant or susceptible to damage, and some people have an increased risk of cancer after exposure to ionizing radiation. Limit your exposure whenever possible. 2013 28
Three Effective Strategies -TimeMinimize the time and you will minimize the dose. Pre-plan the experiment/procedure to minimize exposure time. 2013 29
Three Effective Strategies -DistanceDoubling the distance from the source can reduce your exposure intensity by 25%. Use forceps, tongs, and trays to increase your distance from the radiation source. Move the item being worked on away from the radiation area if possible. Know the radiation intensity where you perform most of your work, and move to lower dose areas during work delays. 2013 30
Three Effective Strategies -ShieldingPosition shielding between yourself and the source of radiation at all permissible times. Take advantage of permanent shielding (i.e. equipment or existing structures). Select appropriate shielding material during the planning stages of the experiment/procedure. Plexiglas, plywood and lead are effective in shielding radiation exposure. Use the proper shielding for the type of radioactive material present. 2013 31
Shielding X-Rays & Gamma Rays Lead shielding will reduce the intensity of x-rays and gamma rays being emitted from a source of radiation. To reduce exposure by a certain desired percent, lead shielding must be a certain thickness for each type of emitter. Remember: Lead shielding does not reduce exposure by 100%. 2013 32
Room shielding Lead lined plaster board Lead glass viewing window
Personal Protective Equipment Fig 3. Overshoes Often worn routinely in the Radiopharmacy for sterility reasons. Not always otherwise worn routinely to prevent the spread of contamination, but widely used for this purpose following a spillage.
Radiation protection in X-ray
Radiation Safety -Laboratory Rules1. Smoking, eating, and drinking are not permitted in radionuclide laboratories. 2. Food and food containers are not permitted in the laboratory. 3. Radionuclide work areas shall be clearly designated and should be isolated from the rest of the laboratory. 4. All work surfaces shall be covered with absorbent paper which should be changed regularly to prevent the buildup of contamination. 2013 37
Radiation Safety -Laboratory Rules5. Protective clothing shall be worn when working with radioactive materials. This includes laboratory coats, gloves, and safety glasses. 6. Dosimeters shall be worn when working with relatively large quantities of radionuclides which emit penetrating radiation. 2013 38
Radiation Safety -Laboratory Rules7. All containers of radioactive materials and items suspected or known to be contaminated shall be properly labeled with tape or tagged with the radiation logo and the word “RADIOACTIVE”. 8. All contaminated waste items shall be placed in a container specifically designed for radioactive waste. 2013 39
Warning Labels Mark all items used to manipulate or store radioactive material. Label all contaminated items. Remove all radiation labels and warnings on containers that no longer contain radioactive material and are not contaminated. 2013 CAUTION: Radioactive Material 40
Warning Label Requirements MUST be clearly visible, durable, and MUST state: “CAUTION: RADIOACTIVE MATERIAL” Labels must provide sufficient information on the container to minimize exposure and to make sure all proper precautions have been taken. Radionuclide(s) Estimated activity Date 2013 41
Radioactive Waste Disposal Radioactive waste includes anything that contains or is contaminated with radioactive material. Collect radioactive waste in proper containers. Keep containers closed and secured unless you are adding waste. Report the proper information on the radioactive waste tag when material is put in the waste container. Keep a tag on the waste container at all times. 2013 42
THANKS 2013 43
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