This is the first article in the series of articles on Radiations and their effects for public awareness. The series is dedicated to each person who is exposed or suffering or has suffered the radiation exposure.
We all face risks in everyday life. It is impossible to eliminate them all, but it is possible to reduce them. The use of coal, oil, and nuclear energy for electricity production, for example, is associated with some sort of risk to health, however small. In general, society accepts the associated risk in order to derive the relevant benefits. However, the risk should be reduced to the lowest possible limit.
Radiation is hazardous in many ways. Man made radiations are the most destructive in the sense that the natural radiations occur as per the laws of nature but man sometimes, has no control over his own creation as the laws related to it are not fully understood nor the effects have been anticipated and studied! Even at the onset when radioactive elements were discovered certain firms in America started selling them as a tonic and in spite of warning from scientist people took them until their disastrous effects were discovered. The radiation has immediate as well as remote disastrous effects on life and living. Besides the socio-psychological effects, effects on health are the most important aspect to be considered.
Radiation in Everyday Life
Radioactivity is a part of our earth – it naturally exists almost everywhere. Radioactive materials are present in earth crust, the floors and walls of all buildings - houses, schools or offices and in the food articles and drinks. The air we breathe contains radioactive gases. Man’s own muscles, bones and tissues contain naturally occurring radioactive elements. Thus, man has always been exposed to natural radiation. The radiations received from outer space are called cosmic radiations or cosmic rays.
There is also an exposure from man-made radiation, such as X-rays, radiation used to diagnose diseases and for cancer therapy beside the daily use of electronic equipments as computer, laptop, cell-phone etc. Fallout from nuclear explosives testing, and small quantities of radioactive materials released to the environment from coal and nuclear power plants, are also sources of radiation exposure to man.
The term radioactivity describes disintegration of atoms. The atom is formed by the number of protons and neutrons in the nucleus and electrons moving around it. The nuclei of some natural elements are unstable hence disintegrate thus release energy in the form of radiation. This physical phenomenon is called radioactivity. The unit of radioactive decay is becquerels. One becquerel equals one disintegration per second.
The rate of decay of radionuclides (nuclii of radioactive atoms) remains constant and uninfluenced by temperature or pressure. The time that it takes for half the radionuclides to disintegrate or decay is called its half-life. This differs for each radioelement, ranging from fractions of a second to billions of years. For example, the half-life of Iodine 131 is eight days, but for Uranium 238, which is present in varying amounts all over the world, it is 4.5 billion years. Potassium 40, the main source of radioactivity in human bodies, has a half-life of 1.42 billion years.
Various Types of Radiation
The term "radiation" is very broad but for its effect on human mainly "ionizing" radiation is considered because such radiations pass through matter to cause it to become electrically charged or ionized. These electrical ions produced by radiation can affect normal biological processes.
Each type of radiation has different characteristics. The common ionizing radiations are:
Alpha radiations are heavy, positively charged particles emitted by atoms of radioactive elements such as uranium and radium. Alpha radiation can be stopped completely by a sheet of paper or by epidermis (the thin surface layer of our skin). If alpha particle emitting materials are taken into the body by breathing, eating, or drinking, the directly expose internal tissues may be biologically damaged.
Beta radiation consists of electrons are more penetrating than alpha particles and can pass through 1-2 centimetres of water. A few millimetres thick sheet of aluminum will stop beta radiation.
Gamma rays are electromagnetic radiation similar to X-rays, light, and radio waves. Gamma rays, depending on their energy, can pass right through the human body, but can be stopped by thick walls of concrete or lead.
Neutrons are uncharged particles, do not produce ionization directly. But, their interaction with the atoms of matter can give rise to alpha, beta, gamma, or X-rays which then produce ionization. Neutrons are penetrating and can be stopped only by thick masses of concrete, water or paraffin.
Although radiation cannot be seen or felt, it can be detected and measured in the minutest quantities with simple radiation measuring instruments.
Radiation Dose and Sources
We feel warmth of sunlight because our body absorbs the infra-red rays from it. But, they do not produce ionization in body tissue. The ionizing radiation impairs the normal functioning of the cells or kills them. The amount of energy necessary to cause significant biological effects through ionization is so small that our bodies cannot feel this energy as in the case of infra-red rays which produce heat.
The biological effects of ionizing radiation vary with the type and energy. The risk of biological harm is measure by the dose of radiation that the tissues receive. It is measured in millisievert (mSv) or microsievert (µSv) which are one-thousandth or one millionth of a sievert unit. For example, one chest X-ray will give about 0.2 mSv of radiation dose.
On average, radiation exposure for a person from all natural sources amounts to about 2.4 mSv a year - though this varies on different the geographical locations by several hundred percent.
The radioactive elements radon (Radon 222), thoron (Radon 220) and by-products formed by the decay of radium (Radium 226) and thorium present in many sorts of rocks, other building materials and in the soil. But the largest source of natural radiation is varying amounts of uranium and thorium in the soil around the world.
The radiation exposure due to cosmic rays dependents on altitude and slightly on latitude: people who travel by air are more exposed to cosmic radiation.
Internal exposure occurs from radioactive elements taken into body through food, water and through the air we breathe. In addition, radioactive elements (Potassium 40, Carbon 14, Radium 226) are always present in blood or bones.
Additionally, we are exposed to varying amounts of radiation from sources such as dental and other medical X-rays, industrial uses of nuclear techniques and other consumer products such as luminized wrist watches, ionization smoke detectors, TV, Computers, cell-phones etc. and the most dangerously exposed to radiation from radioactive elements contained in fallout from nuclear explosives testing and routine normal discharges from nuclear and coal power stations.
Protection from Radiation
The International Commission on Radiological Protection (ICRP) recommends that any exposure above the natural background radiation should be kept at lowest level reasonably achievable and below the individual dose limits. The individual dose limit above the natural background for radiation workers averaged over 5 years is 100 mSv, and for members of the general public, is 1 mSv per year. Any additional dose will cause a proportionally increase the chances of effecting health.
There are many high natural background radiation areas around the world where the annual radiation dose received by members of the general public is several times higher than the ICRP dose limit for the radiation workers but the numbers of people exposed are too small to expect to detect any health effects epidemiologically. Still there is no evidence that any increase does not mean the risk is being totally disregarded. Good radiation protection practice can result in low radiation exposure to workers.
Effects of radiation –
A very large dose to the whole body for a short period of time will cause death of the exposed person within days.
Some of the health effects occur when quite a large dose on exposure to radiation is absorbed. However, many other effects, especially cancers are readily detectable and occur more often with moderate doses for prolonged period.
At lower doses and dose rates cells and tissues recover to some degree but the overall effect is uncertain. It is presumed that at the exposure levels of natural background some additional risk of cancer is involve though there are thousands of carcinogenic substances in our everyday life besides radiation. They include tobacco, tobacco smoke, ultraviolet light, asbestos, some chemical dyes, fungal toxins in food, viruses, and even heat. It is generally not possible to identify conclusively the cause of a particular cancer.
There is also experimental evidence from animal studies that exposure to radiation can cause genetic effects. However, the studies of the survivors of Hiroshima and Nagasaki, so far give no indication of this for humans.
With all the knowledge so far collected on effects of radiation, there is still no definite conclusion as to whether exposure due to natural background carries a health risk, even though it has been demonstrated for exposure at a level a few times higher.
Risks verses Benefits
We all face risks in everyday life. It is impossible to eliminate them all, but it is possible to reduce them. The use of coal, oil, and nuclear energy for electricity production, for example, is associated with some sort of risk to health, however small. In general, society accepts the associated risk in order to derive the relevant benefits. Any individual exposed to carcinogenic pollutants will carry some risk of getting cancer. Strenuous attempts are made in the nuclear industry to reduce such risks to as low as reasonably achievable.
Radiation protection sets examples for other safety disciplines in two unique respects:
First, there is the assumption that any increased level of radiation above natural background will carry some risk of harm to health.
Second, it aims to protect future generations from activities conducted today.
The use of radiation and nuclear techniques in medicine, industry, agriculture, energy and other scientific and technological fields has brought tremendous benefits to society. The benefits in medicine for diagnosis and treatment in terms of human lives saved are enormous. Radiation is a key tool in the treatment of certain kinds of cancer. Three out of every four patients hospitalized in the industrial countries benefit from some form of nuclear medicine. The beneficial impacts in other fields are similar.
No human activity or practice is totally devoid of associated risks. Radiation should be viewed from the perspective that the benefit from it to mankind is less harmful than from many other agents.
Dr. M. K. Tyagi
D.H.M.S., Dip. N.I.H.Research Officer
Sewa Mandir
Mobile" 09829157926
Email: 1.sewamandir@usa.net, 2.manju_mkt2003@yahoo.co.in
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