Radiation refers to the energy produced by fast moving particles or waves of energy. Low levels of radiations occur naturally from several sources and this process has been continuing ever since the universe came into existence. There are certain radioactive elements that occur as natural minerals in the Earth’s crust which continuously emit some degree of radiation. However, high levels of radiation are extremely dangerous to all organisms. Radiation pollution refers to the increase in radiation that is injurious to life.
The process of radiation or radioactivity involves radioisotopes of certain elements that undergo radioactive decay. During the process of decay, the radioisotope changes from one isotope to another and emits certain types of radiation. Isotopes are atoms of an element that have the same atomic number but different in atomic mass. For example, the two isotopes of uranium are 235U92 and 238U92. An important parameter in the study of radioactivity is the half-life period. It is defined as the time required for one half of a isotope to decay into another form.
ADVERTISEMENTS:
The half-life varies from element to element, some of which are given below:
i. Uranium-235 – 700 million years
ii. Carbon-14 – 5570 years
iii. Radon-222 – 3.8 days
iv. Polonium-218 – 3 minutes
The isotopes with short half-life periods are present only for a brief time in the environment, whereas those with a long half-life remains in the environment for a long period.
ADVERTISEMENTS:
There are three kinds of nuclear radiation: alpha particles, beta particles and gamma rays. Alpha particles are positively charged, beta particles are negatively charged and gamma rays are very high energy electromagnetic radiations. Radioactivity is the spontaneous disintegration of atomic nuclei and the emission of subatomic particles called alpha particles and beta particles, or of electromagnetic rays called X-rays and gamma rays.
The alpha particles can travel only up to 5 to 8 cm in air and are least penetrating. Beta particles are nearly 100 times more penetrating and the gamma rays are much more penetrating than beta particles. Alfa radiation is relatively harmless unless inhaled or ingested, beta radiation is intermediate in toxicity and gamma rays are most toxic and dangerous.
Sources of Radiation Pollution:
Ever since the earth came into existence, all life forms have been exposed to some degree of low-level radiation (natural background radiation). Scientists consider that this exposure has played a key role in the evolution of life. However, in the present scientific and industrial world, the sources of radiation have increased due to multiple human activities.
ADVERTISEMENTS:
Thus the sources of radiation can be broadly classified into two major groups:
Natural sources:
Our surrounding environment, such as the air, the rocks and soil, our house, even the food we eat and the water we drink are all sources of radiation. Some amount of radiation is also present within the human body; for example, polonium and radium are present in the bones while radioactive carbon and potassium are found in the muscles.
The natural sources can be further categorized into the following:
ADVERTISEMENTS:
Solar radiation:
The radiation from the sun comprises both ultraviolet and infrared radiations.
Cosmic radiation:
Cosmic rays constantly rain down in the Earth’s atmosphere from outer space. These primarily contain protons, few electrons, helium ions, etc. which continuously interact with the Earth’s atmosphere.
Terrestrial radiation:
Terrestrial sources are the most important natural source to which the Earth’s organisms are exposed. It results from the cumulative effect from a number of materials around us, such as water, air, rock, soil, food, etc. The sources of terrestrial radiation are the radioactive minerals that are present in the Earth’s crust.
Man-made sources:
Due to the advancements in science and technology, humans have been using radiation technology for energy requirements and for health benefits.
The important man-made sources of radiation pollution are as follows:
i. Radioactive wastes generated during the mining and processing of radioactive minerals.
ii. Nuclear fuels used in nuclear reactors for power generation.
iii. Nuclear fallout due to the testing of nuclear weapons.
iv. Medical use such as X-rays, radiotracers for detecting and curing cancers, etc.
Sources of radiation pollution:
Consequences of Radiation Pollution:
People who live or work in the vicinity of radioactive substances, such as mine workers, medical personnel, technologists working in nuclear power plants, etc. are more prone to the radiation hazards. Most serious hazards are caused due to accidents in the nuclear reactors. The severity of the injury depends on the type of radiation, the absorbed dose, the rate at which the dose was absorbed and the radio-sensitivity of the tissues involved.
The damages to the organisms are of two main types:
i. Somatic damage:
The body of the organism is directly affected causing bums, mental retardation, reduced fertility, blindness, cancer, etc.
ii. Genetic damage:
In this case, the genes, chromosomes and the DNA of the organisms are affected and transmitted to the next generations.
Non-Ionizing Radiation Pollution:
Non-ionizing radiation includes radio- frequency radiation or electromagnetic fields (EMFs), from sources such as power lines, radar, communication networks, cellular phones and microwave ovens. (Fig. 13.9). High doses of such radiation are known to be harmful, causing bums, cataracts, temporary sterility, etc. Since the 1980s, with the proliferation of such devices, the possible effects of long-term exposure to low levels of non-ionizing radiation are a matter of great concern.
P.K. Zutshi of Health Division, Bhabha Atomic Research Central (BARC) has thrown sufficient light on the problems related to radioactive pollution in a paper entitled “Environmental Pollution Studies at BARC” published in Nuclear India, Vol. 12.
Fallout of nuclear explosions:
Fallout of nuclear explosions:
Nuclear explosion has both immediate and long-term effects. It can reduce big cities like New York or London to ashes in no time, yet there is no practical method of protecting the population from it. It can char woods and even ignite them within 16 km from the site of explosion.
The temperature at the site of explosion is so high that metals and minerals not only melt but are vaporized also. During atomic explosions the radioactive substances are rapidly injected into the upper layer of the atmosphere where they condense due to cooling from gaseous state to liquid and then to fine dust. Radioactive dust particles are suspended in the air at an altitude of about 10 – 15 km and form together with water vapour, a radioactive cloud which moves in the direction of wind.
The radioactive cloud settles down slowly on the surface of earth over several years. Most of the radioactive materials produced in explosion are short-lived but some, such as strontium 90 Cesium137, Co60, remain radioactive for many years. About 5% of the radioactive matter injected into atmosphere after nuclear explosions consists of radioactive Sr which is easily absorbed by the living organisms. On reaching to the earth, it poisons water, air and soil and is absorbed by grasses and vegetables and thus gets into the milk and finally into human body.
There, it accumulates in the bones and other tissues and causes diseases. Low level radioactive liquid wastes, radioactive gases and dusts are released from nuclear installations. The liquid wastes are released into the waters and the gases are disposed through high stacks. Besides stack emission from nuclear installations there is worldwide fallout of radioactivity from atomic bomb tests. BARC has been assessing exposure of the population in India to radioactivity arising from nuclear tests explosions.
It is also studying the atmospheric air circulation pattern by which radioactive pollutants are dispersed on a global scale. Level of radioactivity after test explosions is reported to be insignificant for short period immediately after explosions but it increases appreciably after some time and subsides within a few weeks. Radioactive fallouts have been observed from the upper atmosphere where the debris of tests explosions stays for a long time.
Hoda, M.M. (1977) in his article on “Nuclear Energy and Environments” highlighted some of the problems relating to hazards of radioactive materials. Much has been said about the nuclear weapons, although there is a great possibility that it may not be used again, the greatest danger to humanity is now posed by the so called peaceful uses of atomic energy but not so many of us realize this fact.
While man can and does create radioactive elements, there is nothing to reduce their activity, once he has created them. No physical interference, no chemical reaction but only the passage of time can reduce the intensity of reaction once it has been set going. The fission of Uranium results in a mixture of a number of long-lived and short-lived isotopes. The disposal of radioactive wastes presents enormous problem.
It was thought at one time that radioactive wastes could be safely dumped into the deepest part of the ocean on assumption that no life could subsist at such depth, but within a short time after dumping these materials in water the great bulk could be found in the living organisms. No international agreement has been reached so far on disposal of nuclear wastes.
Nuclear wastes with high level of radioactivity continue to be dumped into the sea while large quantities of so called ‘intermediate” and “low level” wastes are discharged into the rivers or directly into the ground. An Atomic Energy Commission report observes that liquid wastes find their way slowly into groundwater, leaving all or part of their radioactivity held either chemically or physically in the soil (U.S.A.E.C Annual Reports to Congress, Washington D.C. 1966, p. 344). The nuclear reactors, after they have become unserviceable, are most massive wastes. The reactors have an average life of 30 years and they cannot be dismantled and shifted but have to be left standing for centuries where they will silently leak radioactivity into air, water and soil.
There is no foolproof method of disposal of radioactive wastes. In many cases the radioactive wastes are sealed in steel drums or concrete blocks and sunk into sea to await their natural decay. The pollution of aquatic environment by radioactive materials poses a serious problems as radioactive isotopes can produce not only immediate effects on living organisms but, even more important, can produce mutations in the genetic materials which would have serious consequences for the later generations.
Radioactivity can reach the aquatic environment from a variety of sources such as nuclear fallout, nuclear powered ships and submarines, nuclear power plants, laboratory experiments with medical uses of radioisotopes and so on Desalination and Effluent Engineering Division at BARC has developed high efficiency particulate filters for air pollution control from hazardous contaminants, such as radioactive isotopes from nuclear installation and compounds of such toxic elements as beryllium and tellurium.
Disease Due to Radiation Pollution:
The effects of radioactive elements are difficult to judge unless they are in such concentrations as to give acute effects. Malformations of body at birth, abnormality in organ development are some of the effects observed in the laboratory animals.
On the basis of rate of effect, radiation pollution can be mainly classified into acute and chronic effects:
Acute effects:
Accidental exposure to radiation causes Acute Radiation Syndrome (ARS). Exposure of small areas leads to localized tissue damage. Damage to the blood vessels in the exposed areas causes disturbed organ function; and at higher doses, necrosis (localized tissue death) and gangrene. Consequences may include degeneration or destruction of the irradiated tissue and the initiation of cancer.
Chronic effects:
This is also known as late effect, since the effect of radiation on the body is manifested after some duration of time. Some of the pioneer workers on radioactivity, such as Madam Marie Curie, who discovered radium, succumbed to leukemia. The late effects of radiation are manifested in the form of chronic diseases of kidneys, lungs, bone marrow, eyes, etc. Statistically significant increases in leukemia and of cancers of thyroid lung, and the female breast have been demonstrated in populations exposed to relatively high doses.
Control of Radiation Pollution:
Radiation pollution could be a fatal health hazard and it can be reduced by the following ways:
i. Proper maintenance of nuclear power plants by well trained experts to avoid the occurrence of Chernobyl like disasters.
ii. Proper disposal of radioactive wastes from the nuclear reactors
iii. Proper use of radiation technology in hospitals to avoid injuries to technicians and patients
iv. Proper disposal of radioactive bio-medical wastes