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RADIATION. Electromagnetic Spectrum. Types of Radiation. Ionizing Radiation gamma rays, X-rays Non-ionizing radiation UV rays, Visible light, infrared, microwaves, laser, radiofrequencies. Types of Ionizing Radiation. 1. Alpha particles = He = 2 protons + 2 neutrons
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Types of Radiation Ionizing Radiation gamma rays, X-rays Non-ionizing radiation UV rays, Visible light, infrared, microwaves, laser, radiofrequencies
Types of Ionizing Radiation 1. Alpha particles = He = 2 protons + 2 neutrons • Massive particles with the most energy • Least penetrating • Dangerous if ingested or inhaled • Shield? • Paper, clothing or human skin 2. Beta particles = electron • More penetrating than alpha radiation • Can penetrate only ½ inch into the skin • Dangerous when ingested or inhaled • Shield? • Layer of clothing, few mm of alumnium or other substances
Types of Ionizing Radiation 3. Gamma rays • Most penetrating type of ionizing radiation • Shield? - dense material such as lead 4. X-rays • Similar to gamma rays but slightly less penetrating.
Ionizing Radiation: Half-life Half-life is the time it takes for half of the amount of radioactive material to decay and be transformed into something else.
IONIZING RADIATION: Sources of Exposure • Natural sources: • cosmic radiation • radioactive minerals in earth’s crust • radionuclides in the body • Enhanced natural sources: Natural sources of radiation that have become sources of high exposure levels as a result of human activities. E.g. Radon 3.Human-Generated sources: • Medical applications • Nuclear weapons fallout • Nuclear power plant emissions • Consumer products
IONIZING RADIATION: Health Impacts • Tissues with a high turnover rate are more susceptible • High-sensitivity tissues: thyroid, lung, breast, stomach, colon and bone marrow • Leukemia is the most common cancer associated with radiation exposure • Mutations, cancer, birth defects • High-level radiation exposures can cause cell death • Low-level radiation exposure over time can cause mutations and cancers • Fetuses and children are very sensitive to radiation-induced damaging effects.
IONIZING RADIATION: Dosage Radiation Effective Dose = Absorbed dose x Relative Biological Effectiveness Sievert (Sv) Gray (Gy) Or, rad rem 1 Sv = 100 rems 1Gy = 100 rads Relative Biological Effectiveness (RBE): • 1 for X-rays and gamma rays • 1-5 for beta-particles • 10 for alpha particles. Greatest tissue damaging potential.
IONIZING RADIATION: Dosage and Health Effects Dose rate largely affects the potential for health effects from exposure to radiation. There is no radiation exposure level below which no health effect can be detected, therefore levels should always be kept As Low as Reasonably Achievable (ALARA).
IONIZING RADIATION: Radiation and Nuclear Power Generation 1. Front-End 2. Power Production Core meltdown E.g. Chernobyl incident 3. Back-end Reprocessing Low-level radioactive wastes and High-level radioactive wastes: Sources Hazards Disposal methods
NON-IONIZING RADIATION: Ultraviolet radiation (40-400 nm) UVa: longer wavelengths (400-320 nm) UVb: shorter wavelengths (320-280 nm) Health effects • Skin cancer • Uvb is in the ionizing range and can damage DNA. • An increase of 1-2% of UVb radiation is associated with an increase of 2-4% in skin cancer. • North America - skin cancer has reportedly increased by 400%. • Skin/eye burns • Cataract, premature cell aging, reduced immunity, photosensitivity, blood vessel damage Are sunscreens protective?
NON-IONIZING RADIATION: Microwaves Depending on frequency, microwaves are differentially absorbed by bodily tissues, mostly as a function of their water content. • Very low energy (below 150 MHZ) simply pass through the body without being absorbed. • Intermediate frequency (150-1200 MHZ)are absorbed by the deeper tissues without any noticeable heating of the skin. • As frequency increases, tissue penetration decreases and at 3500 MHZ, warming of the skin can be felt.
NON-IONIZING RADIATION: Electromagnetic fields Does cell phone usage pose a health risk?