EESA10 Lecture 6.docx

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Environmental Science
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Silvija Stefanovic

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EESA10 Lecture 6 – Feb 15, 2011 We cannot escape radiation (from nature). The majority of radiation comes from nature, the rest are manmade. There are two different kinds of radiation: - Ionized: o UV, X-rays, gamma rays and some cosmic rays. o Short waves, high energy. o When they strike an atom, they are able to remove electrons and to change the valence of the atom (atom will become charged). o High energy, they are able to break chemical bonds. - Non-ionized: o Long wavelength, low energy. o We used to think they didn’t cause much harm. o Long term exposure of low levels of chemicals of radiation is very complicated. Ionized radiation: - Able to strip electrons, create charged ions, break bonds. - Stochastic health effects: o Chronic effects (from the time of exposure until the real effects many years later). o For example, at the workplace. Someone who is working for many years at a powerplant. After many years of constant, low-level exposure will result in stochastic effects. o Severity of symptoms does not depend on level of exposure. But chance or risk of getting cancer, for example, increases with increased exposure (i.e. it’s more likely to get cancer with a high exposure, but it won’t be “worse” cancer if the exposure high level). o Can cause cancer, changes in DNA, mutations o Teratogenic mutations affects the fetus, the mother does not experience negative health effects. o Genetic mutations are transferred from parents to child. Can be transferred to child from either mother or father. - Non-stochastic effects: o Acute, short term, high level of exposure. o Severity of symptoms does depend on level of exposure. o Can indeed cause cancer after many years if the person does survive acute effects. o Radiation sickness: hair loss, burns on skin, quick aging, problems with organs. Chernobyl nuclear power plant accident: - Many deaths, especially workers and firefighters, from non-stochastic effects. - Many children with thyroid cancer. - Wind was blowing north, so many radioactive particulates contaminated areas to the north. Some level of radiation is safe: - We use it for medical treatment. - Used to cure cancer: they balance the risks and benefits of using radiation. - X-rays
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