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Lecture 6

EESA10 - Lecture 6 notes.doc

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Environmental Science
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Michael Petit

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Lecture 6: Radiation and Human Health Radiation and Human Health • Radiation is everywhere, all around us. We cannot escape radiation. But the question is what type and how much radiation is there. • Even if we are walking outside in the woods, we are still exposed to some radiation, because of Background Radiation: Something that is produced and emitted from outer space. Natural radioactivity in the earth and by cosmic rays from outer space. This type of radiation cannot be controlled. We are always exposed to it. It has existed for hundreds of thousands of years. • Something that we can control is man made radiation (Electronic devices, appliances, etc.). (Note: Nowadays, engineers have found technologies to protect us from most of this radiation). Examples of some man-made devices that emit different types of radiation include: - X-ray machines (different kind of equipment used in labs for analysis, for example, CCA can also be detected using X-ray) - X-ray Diagnostic (X-ray used for diagnostic of different body parts) - Television sets - Microwave ovens - Lasers Ionizing radiation exposure to the public • Natural radiation sources consists of 82% of total measurable radiation • Man-made radiation is just 18%. Medical x-rays, nuclear medicine can treat some illnesses and some other types of radiation. What is surprising is that Radon (gas in indoor air) makes up 55% of total radiation. Radiation and Human Health • We have two big groups of radiation: 1) Ionized Radiation (Cosmic, Gamma, X-rays): This is radiation that has so much energy that can change atoms on some other chemicals. They can push electrons out of their atoms and produce ionized form of that element. They are very strong as they have so much energy. (Note: On electric spectrum, elements that are very high in energy have short wavelength, elements with low energy (non-ionized) have long wavelength.) 2) Non-Ionized Radiation (Radio waves, TV waves, Microwaves): This type does not have enough energy (low in energy) and they cannot remove electrons from atoms. Ionized Radiation- How does ionized radiation cause health effects • Affect of this radiation is obvious. All scientists agree that this radiation is really harmful. How does it affect human health? First, the radioactive material (like Uranium), decays naturally and spontaneously, and produces ionizing radiation. This ion radiation, strips away electrons from atoms (create two charged ions) • It can also break some chemical bonds. This is important for human body as it consists of water and chemicals. Examples: alpha, beta particles, gamma and x-rays. These examples differ based on the amounts of energy they have. Health effects from exposure to radionuclides • There are 2 different kinds of health effects. • 1) Stochastic effect (chronic) – Humans exposed to long term, lower level of radiation • This is most problematic because it is very hard to detect and to know what will happen to our health after long time exposure to lower level of radiation. • If the amount of radiation increases, the severity of this affect will not change and will stay the same and the type of illnesses will be the same (but the risk to get that illness will increase – i.e. Risk of getting cancer will be higher). • 2 effects associated with this Stochastic health effects:  Cancer is uncontrolled growth of cells (any kinds of cells as there are many kinds of cancers). Damage at the cellular or molecular levels  Changes in DNA (changes to genetic material). Two problems can happen because of this. -Teratogenic changes are birth defects (most sensitive in 8-15 week of pregnancy) such as smaller head or brain size, poorly formed eyes, mental retardation. -Genetic mutations are changes that can be transferred from the parent to the child. Teratogenic changes cannot be transferred to the child, but the offspring is affected anyways, which we see when child is born. • 2) Non-Stochastic effect (acute) – Humans exposed to short term, high levels of radiation. • These effects are also very visible and obvious • If amount of radiation increases, will get more severe. We know this based on cases of many different nuclear accidents everywhere (Chernobyl, Hiroshima Nagasaki, workers that are exposed to very high level of radiation etc.) • 2 effects associated with Non-Stochastic health effects  causes cancerous health effects, but disputed amongst many researchers.  causes radiation sickness (nausea, weakness, hair loss, skin burn or diminishing organ function, premature aging, death) Nuclear power plant accidents • Three Mile Island, Pennsylvania, 1979: Researchers did not find much adverse effects after this accident because the radiation level was so low that it was not high enough to cause long term health effects. • Chernobyl, former Soviet Union, 1986: Here, the radiation levels were so high that adverse health effects are even seen today. Many kids born with different abnormalities, increase in number of cancer cases, changes in vegetation and plants. • Chernobyl accident had 10-20 times higher dose of exposure than Three Mile Island’s accident. What parts of our body are most sensitive to radiation? • Highly sensitive parts: Lungs, breast, stomach, colon. • Moderate Sensitive parts: brain, lymph tissue, liver, ovaries, intestines, pancreas, marrow, oesophagus, thyroid. • Low sensitive parts: Skin, gall bladder, kidneys, spleen, bone. These parts are based on acute, whole-body exposure Is any amount of radiation safe? • Some scientists believe yes, and even some lower level of radiation can be beneficial. • How do we know that radiation causes cancer? Before humans had much information about radiation, or had high technology, they still saw the problems associated with it. • In 1910, it was first observed that radiation causes skin cancer • Then they found more proof that this is true by studying Japanese atomic bomb blast survivors, also uranium miners, • medical treatments • Children are more sensitive because their cells grow faster than adults. Because of this growth of cells children are more affected. Chemical properties of radio nuclides: • Each radio nuclides have their own chemical properties. • Our system wont recognize what elements are radioactive and not., it’ll absorb both. • Chemical properties determine where health effects occur. Examples: 1) For normal function of Thyroid gland iodine is necessary. There
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