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Lecture 6

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Environmental Science
ENVS 2010U
Steve Hutchinson

Lecture 6 Radiation • All around us • Cannot escape or control • It is a part of our planet 1. Background Radiation – it is natural radioactivity in the Earth and by cosmic rays from outerspace. It can lead to mutation but does not usually cause harm to humans 2. Manmade radiation – cause by electronic products and is harmful to the human health Some Sources:  X-rays machines  TV sets  Lasers  Microwaves These sources are controllable • Manmade Radiation is only 18% of all emitted radiations of which 4% is emitted from nuclear medicines (used to cure cancer) • Natural Radiation is 82% of all emitted of which 55% is emitted by Radon. • Radiation can be divided into 2 groups based on the amount of energy possessed by the radiation. 1. Ionized – High energy (cosmic, gamma rays, etc); it has short wavelengths. However, there is enough energy to break down chemical bonds and can harm our body. 2. Non Ionized – Low energy (TV, microwaves, etc); it has long wavelengths. There is not enough energy to rearrange chemical arrangement. The affects it has on human health is still debated by scientists. How does ionized radiation cause health effects? • Radioactive material that decay spontaneously producing ionizing radiation o Strip away electrons from atoms o Break some chemical bonds • Alpha, beta particles, gamma and x-rays (differ in the amount of energy they have) Human Health effects from to radionuclides • Divided two categories 1. Stochastic Health Effects – Chronic  Long term, low level of exposure  Increased levels of exposure does not related to a high severity to the adverse effects of radionuclides but increases the likelihood of getting affected I. Cancer: uncontrolled growth of cells. Radionuclides and other carcinogens interfere with the genetic mechanism of cell growth at the cell and molecular level II. Changes in DNA: leads to mutation. It is teratogenic. This means fetuses that are constantly exposed to radiation suffer. It can lead to a small head size, mental retardation, and disability. 2. Non-stochastic health effects – Acute  Short term, high level of exposure  Increased levels of exposure leads to more severe adverse effects (e.g. nuclear power plant accidents)  Its effects are best studied of Japanese survivors of the Hiroshima and Nagasaki bombings in WWII. I. Cancerous Health Effects? Maybe and maybe not. Some suggest children who are exposed may experience such cancers II. Radiation sickness: instant weakness, discoloration, skin burn, hair loss, premature aging and can lead to death Nuclear Power Plant Accident • Three Mile Island, PA (1979) • Chernobyl, U.S.S.R (1986) –had 10 to 20 times higher dose than the Three Mile Accident The effect of different doses of radiation on the human body after acute, whole body exposure o Highly Sensitive: breasts lungs, stomach, colon o Moderate Sensitive: brain, pancreas o Low Sensitive: skin, bone, spleen, kidney, gall bladder Is Any Amount of Radiation Safe • Some scientist believe low levels are beneficial and may cure some cancer but can also cancer • How? Many cases prove this: o First observed in 1910 o Japanese survivors of atomic bomb o Uranium miners o Medical treatments o Children are more sensitive because they grow more rapidly Chemical properties of Radionuclides • Determine w
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