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York University
Environmental Studies
ENVS 3410

EESA10 Lecture 6 Radiation and Human Health Slide 1 – 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 Slide 2 – 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. Slide 3 – 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. Slide 4 – Ionized Radiation • 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. Slide 5 - Health effects from exposure to radionuclides There are 2 different kinds of health effects. 1) Stochastic effect – 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. Hard to detect and not 100% known. What is known is that 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. Risk of getting cancer will be higher. This amount of radiation is proven to cause cancer. 2 effects associated with this Stochastic:  Cancer is uncontrolled growth of cells (any kinds of cells as there are many kinds of cancers). Naturally in our physiological functions, our cells divide and produce new ones to replace old ones. This natural physiological process is controlled by our genetic material. But if certain radiation disrupts this natural process, it will cause cancer. Basically, cells keep on growing without reason. And this reason is radio nuclides.  Another effect that can be caused is changes in DNA (changes to genetic material). Two problems can happen because of this. One is Teratogenic changes and another is genetic changes (mutations). What are teratogenic effects: birth defects. Mother is exposed for long term to lower level of radiation (most sensitive in 8- 15 week of pregnancy) ; her unborn child will have some problems like 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 – These are acute effects. These effects are seen in humans that are exposed to very high levels of radiation for a short period of time. These effects are also very visible and obvious. These effects, if level 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.). Some literature says that these effects can cause cancer, but some literature disagrees that it causes cancer. Based on Epidemiological studies and other examples, it seems that yes these effects can cause cancer, because most data shows increased number of different types of cancer in areas such as Chernobyl or where we saw some accidents.  What we know for sure is that this high level of radiation causes radiation sickness (nausea, weakness, hair loss, skin burn or diminishing organ function, premature aging, death). Death comes usually after two to three months. Nuclear power plant accidents 1) 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. 2) 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. Most of that radiation cloud that was produced at Chernobyl went to North Europe, because of direction of wind. Most of this radiation was settled down at ground level in north Europe. We still don’t know how much it will affect other countries. 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, Uranium miners, after medical treatments (if acceptable level of radiation is exceeded during medical treatments, those cases are used for studying as radiation can be good or bad if radiation levels exceed normal levels). What we know for sure from studies is that 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. These properties are the same for that form that has a radio nucleic property and that form that does not have radio nucleic property. For example, iron can be radioactive or can be regular iron. But they have exactly the same chemical properties. That element, such as iron, is necessary element (micronutrient) for our bodily functions, but our body will not know. Our system will not recognize that it is a radioactive iron, because radioactive iron and regular iron have exactly same properties. Our body will absorb radioactive as well as non radioactive iron. Chemical properties determine where health effects occur. Examples: 1) For normal function of Thyroid gland iodine is necessary. There is two forms of this chemical: radioactive and non radioactive. If regular iodine is taken by the thyroid gland, there will be no problems. If radioactive form is absorbed it can cause cancer (this cancer is seen often). 2) Other examples include Calcium, strontium-90 and radium-226: Calcium, in this case, is not radioactive. But regular calcium has similar chemical properties as other two. Because of this characteristic, other two can be incorporated into the bones. Body does not distinguish between calcium and other two elements, as they have similar chemical structures. Radon: We have this gas everywhere in indoor air, because it’s the result of Natural radioactive break down of uranium in soil, rock and water. If a house is built on such type of soil, some radon can be found in indoor air. We do not know of radon’s existence, because it doesn’t have smell, colourless. Radon can cause lung cancer. The second leading cause of lung cancer in the US today (first one is tobacco smoke). Nonionized Radiation: Radiation t
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