What you need to remember Case study What you need to remember

Types of ionizing radiation Electromagnetic X rays and γ rays Particulate Electrons, protons, α-particles, neutrons, and heavy charged ions

Physical Factors of Effects Acute dose vs. Chronic Dose Radiography vs. drinking contaminated water Whole body irradiation vs. partial body irradiation

Penetration distance of ionizing radiation

Radiation protection The ALARA (As Low As reasonable Achievable) principle time distance shielding External Exposure External exposure precautions may be necessary when working with photon emitters or high energy beta emitters such as P-32. Exposure is controlled by three basic factors: time, distance and shielding.

Radiosensitivity of tissues Moderately radiosensitive Skin Vascular endothelium Lung Kidney Liver Lens (eye) Bone marrow CNS Least radiosensitive Central nervous system (CNS) Muscle Bone and cartilage Connective tissue Highly radiosensitive Lymphoid tissue Bone marrow Gastrointestinal epithelium Gonads Embryonic tissues Radiosensitivity varies in different types of tissue. While all cells can be destroyed by a high enough radiation dose, highly radiosensitive cells or tissue exhibit deleterious effects at much lower doses than others. As stated in the Bergonié-Ttribondeau law, rapidly dividing, undifferntiated cells in tissue are the most sensitive to radiation effects. Several of the most sensitive tissues and systems follow this law. Highly radiosensitive tissue - lymphoid, bone marrow elements, gastrointestinal epithelium, gonads (testis and ovary), and foetal tissue. Moderately radiosensitive tissue - skin, vascular endothelium, lung, kidney, liver, lens and thyroid in childhood. Least radiosensitive tissue - central nervous system, endocrine (except gonad), thyroid in adults, muscle, bone and cartilage, and connective tissue. The least radiosensitive tissue, although radioresistant, is less capable of cell renewal than highly sensitive tissue. Some - especially neurons, glial cells of the brain, and muscle cells - has essentially no ability to regenerate. Once these cells are killed, the area is repaired by fibrosis or scarring.

Acute radiation syndrome A spectrum of disease

Radiologic terrorism - Possible scenarios The detonation of a nuclear weapon, in or close to a major city highly unlikely,” but not impossible because several portable “suitcase bombs” are said to be missing following the breakup of the former Soviet Union An attack on a nuclear power station Thousands of people would be killed by blast and heat. Hundreds to thousands would be killed or made ill by the acute radiation syndrome (ARS) because of exposure to γ-rays and neutrons. A long-term risk of leukemia and solid cancers in those who survive the acute effects would result principally because of exposure to γ-rays and neutrons and also to fallout. Individual doses are unlikely to be high enough to cause the ARS. There would be a long-term risk of leukemia and solid cancers in those exposed to external radiation or in those ingesting and/or inhaling radioactive material. There would certainly be chaos and enormous economic loss because cleanup would be a long and slow process. Health Environmental Economic losses / Legal Psychological

Radiologic terrorism - Possible scenarios The detonation of a “dirty bomb’’ (radiologic dispersal device or RDD) Relatively small amount of radioactive material attached to a conventional explosive material (plastic explosive, fertilizer) Health Environmental Economic losses / Legal Psychological It is unlikely that any person will receive a dose of radiation sufficient to cause the ARS. The most likely scenarios would be a small number of persons contaminated with radioactive materials, either on their clothes and skin, or inhaled or ingested. The possibility of a minimal long-term risk of leukemia or solid cancers could not be ruled out. The certain consequence would be chaos, psychological terror, and widespread fear. Diagram of a “dirty bomb” discovered in 2003 by British intelligence in Afghanistan. It was assumed that Al Qaeda had succeeded in constructing a small “dirty bomb,” but the device was never found

Radiologic terrorism - Possible scenarios Hidden radiation exposure device (RED) An alternative to the “dirty bomb” would be to place a γ-emitting source, such as Cs-137, in a locker or garbage can in a busy public place, disclosure of its presence some days or weeks late ear and psychological chaos Unlikely that any person would receive sufficient radiation to result in the ARS Very small long-term possibility of radiationinduced malignancies