EESA10 Lecture 6-11.doc

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University of Toronto Scarborough
Environmental Science
Silvija Stefanovic

Lecture 6Radiation and Human Health Background radiation oNatural radioactivity in the Earth and by cosmic rays from outer space oCannot be controlled Manmade radiation oXray machines oX ray diagnostic oTelevision sets oMicrowave ovensoRadar devices oLasers oCan be controlled Ionizing radiation is radiation composed of particles that individually carry enough kinetic energy to liberate an electron from an atom or molecule ionizing it Ionizing radiation is generated through nuclear reactions either artificial or naturalIonised radiationoRadioactive material that decay spontaneously produce ionizing radiationoStrip away electrons from atoms create two charged ionsoBreak some chemical bondsoAlpha beta particles gamma and xrays differ in the amount of energy they haveHealth effects from exposure to radionuclidesoStochastic health effectsChronicLong term low level of exposureIncrease levels of exposure make these effects more likely to occur but do not influence the type or severity of the effectoCancer uncontrolled growth of cellsDamage at the cellular or molecular leveloChanges in DNA mutationsTeratogenic fetus most sensitive in 815 week of pregnancy smaller head or brain size poorly formed eyes mental retardationGenetic passed from parent to childoNonstochastic health effectsAcute Short term high level of exposure Increase levels of exposure make these effects more severe oCancerous health effects oRadiation sickness nausea weakness hair loss skin burn or diminishing organ function premature aging death HistoryoNuclear power plant accidents oThree Mile Island Pennsylvania 1979oChernobyl former Soviet Union 1986 oChernobyl accident had 1020 times higher dose of exposure than Three Mile Islands accident Radiation cause skin cancer oObservationJapanese atomic bomb blast survivors Uranium miners Medical treatments Children are more sensitive Chemical properties of radionuclides oOrgans cannot distinguish between radioactive and nonradioactive forms of element oRadioactive iodine in the thyroid oCalcium strontium90 and radium226 accumulate in bones Microwave Radiation oUse forTo detect speeding cars To send telephone and television communications To treat muscle sourness To dry and cure plywood To raise bread and doughnuts To cook potato chips Microwave oven Microwave Oven Radiation oPropertiesForm of electromagnetic radiation Absorbed by foods Pass through glass paper plastic Reflected by metal oPrincipleMicrowaves bounce back and forth within the metal interior until they are absorbed by the food Water molecules in food vibrate producing heat that cook the food
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