Radioactivity is a phenomenon of spontaneous emission of proton (α- particles), electrons (β-particles) and gamma rays (short wave electromagnetic waves) due to the disintegration of atomic nuclei of some elements. These cause radioactive pollution.
Sources of Radioactive Pollution
Artificial Sources of Radioactive pollution
- Accidents in nuclear power plants and nuclear waste.
- Nuclear weapon testing and explosion (Nuclear fallout). The fall Out contains radioactive substances such asstrontium-90, cesium-137, iodine-131, etc.
- Uranium mining and mining of other radioactive material like thorium etc. Uranium contamination is well observed in India.
- Radiation therapy and direct exposures to radiation for diagnostic purposes (e.g. X-rays), chemotherapy etc.
- The slow nuclear radiations can emanate from a variety of sources viz. nuclear reactors, laboratories, hospitals, and direct exposures to X-rays etc.
- They include cosmic rays from space and terrestrial radiations from radio-nuclides present in earth’s crust such as radium-224, uranium-238, thorium-232, potassium-40, carbon-14, etc.
- Some species of animals and plants preferentially accumulate specific radioactive, materials. For example, oysters deposit 65Zn, fish accumulate 55Fe, marine animals selectively deposit 90Sr.
Effects of Radioactive pollution
The use of nuclear energy has two very serious inherent problems.
- accidental leakage, as occurred in the Three Mile Island, Chernobyl and Fukushima incidents
- safe disposal of radioactive wastes. It has been recommended that storage of nuclear waste, after sufficient pre-treatment, should be done in suitably shielded containers buried within the rocks, about 500 m deep below the earth’s surface. However, this method of disposal is meeting stiff opposition from the public.
The quick devastating and immediate effects of nuclear radiations are well known as witnessed following Hiroshima and Nagasaki in Japan during world war II.
Continued small dose exposure to nuclear radiation can cause childhood leukemia, miscarriage, underweight babies, infant deaths, increased susceptibility to AIDS and other immune disorders and increased criminalities.
Underground bomb testing releases radiations in very small doses of radicals that pollute water and soil.
This radioactive water is taken by plants through roots. The radioactivity enters the food chain when such plants are eaten by animals and humans. Such radioactivity has been detected even in the milk.
Radiation, that is given off by nuclear waste is extremely damaging to biological organisms because it causes mutations to occur at a very high rate.
At high doses, nuclear radiation is lethal but at lower doses, it creates various disorders, the most frequent of all being cancer.
Ionizing and Non-Ionizing Radiation
- Radioactivity is a phenomenon of spontaneous emission of proton (alpha-particles), electrons (beta particles) and gamma rays (short wave electromagnetic waves) due to the disintegration of atomic nuclei of some elements. These cause radioactive pollution.
- Radiations can be categorized into two groups namely the non-ionizing radiations and the ionizing radiations.
- Non-ionizing radiations are constituted by the electromagnetic waves at the longer wavelength of the spectrum ranging from near infra-red rays to radio waves [include higher wavelength ultraviolet rays, microwaves etc.].
- These waves have energies enough to excite the atoms and molecules of the medium through which they pass, causing them to vibrate faster but not strong enough to ionize them.
- In a microwave oven, the radiation causes water molecules in the cooking medium to vibrate faster and thus raising its temperature.
- They may damage eyes which may be caused by reflections from coastal sand, snow (snow blindness) directly looking towards the sun during an eclipse.
- They injure the cells of skin and blood capillaries producing blisters and reddening called sunburns.
- Ionizing radiations cause ionization (one or more electrons are pealed out from the outer shells of an atom) of atoms and molecules of the medium through which they pass.
- Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjunction with other chemical changes.
- Electromagnetic radiations such as short wavelength ultraviolet radiations (UV), Xrays and gamma rays and energetic particles produced in nuclear processes, electrically charged particles like alpha and beta particles produced in radioactive decay and neutrons produced in nuclear fission, are highly damaging to living organisms.
- Electrically charged particles produced in the nuclear processes can have sufficient energy to knock electrons out of the atoms or molecules of the medium, thereby producing ions.
- The ions produced in water molecules, for example, can induce reactions that can break bonds in proteins and other important molecules.
- An example of this would be when a gamma ray passes through a cell, the water molecules near the DNA might be ionized and the ions might react with the DNA causing it to break.
- They can also cause chemical changes by breaking the chemical bonds, which can damage living tissues.
- Short range effects include burns, impaired metabolism, dead tissues and death of the organisms.
- Long range effects are mutations increased the incidence of tumors and cancer, shortening of life-span and developmental changes.
Non-ionising radiations affect only those components which absorb them and have low penetrability.
Ionizing radiations have high penetration power and cause breakage of macromolecules.
Biological Damage Due to Ionizing Radiations
- The biological damage resulting from ionizing radiations is generally termed as radiation damage.
- Large amounts of radiation can kill cells that can dramatically affect the exposed organism as well as possibly its offspring.
- Affected cells can mutate and result in cancer. A large enough dose of radiation can kill the organism.
- Radiation damage can be divided into two types: (a) somatic damage (also called radiation sickness) and (b) genetic damage.
- Somatic damage refers to damage to cells that are not associated with reproduction.
- Effects of somatic radiation damage include reddening of the skin, loss of hair, ulceration, fibrosis of the lungs, the formation of holes in tissue, a reduction of white blood cells, and the induction of cataract in the eyes. This damage can also result in cancer and death.
- Genetic damage refers to damage to cells associated with reproduction. This damage can subsequently cause genetic damage to from gene mutation resulting in abnormalities. Genetic damages are passed on to the next generation.
- The biological damage caused by the radiation is determined by the intensity of radiation and the duration of the exposure.
- It depends on the amount of energy deposited by the radiation in the biological system.
- For example, alpha particles (protons) do much more damage per unit energy deposited than do beta particles (electrons).
- A traditional unit of human-equivalent dose is the rem, which stands for radiation equivalent in man.
- At low doses, such as what we receive every day from background radiation (<1 mrem), the cells repair the damage rapidly.
- At higher doses (up to 100 rem), the cells might not be able to repair the damage, and the cells may either be changed permanently or die.
- Cells changed permanently may go on to produce abnormal cells when they divide and may become cancerous.
- At even higher doses, the cells cannot be replaced fast enough and tissues fail to function. An example of this would be “radiation sickness.” This is a condition that results after high doses are given to the whole body (>100 rem).
Damage due to radiation particles
- Alpha particles can be blocked by a piece of paper and human skin.
- Beta particles can penetrate through the skin, while can be blocked by some pieces of glass and metal.
- Gamma rays can penetrate easily to human skin and damage cells on its way through, reaching far, and can only be blocked by a very thick, strong, massive piece of concrete.
Half-Life – Period of Radioactivity
- Each radioactive material has a constant decay rate. Half-life is the time needed for half of its atoms to decay.
- The half-life of a radionuclide refers to its period of radioactivity. The half-life may vary from a fraction of a second to thousands of years.
- The radionuclides with long half-time are the chief source of environmental radioactive pollution.
Accidents at nuclear power plants
- Nuclear fission in the reactor core produces a lot of heat which if not controlled can lead to a meltdown of fuel rods in the reactor core.
- If a meltdown happens by accident, it will release large quantities of highly dangerous radioactive materials in the environment with disastrous consequences to the humans, animals, and plants.
- To prevent this type of accidents and reactor blow up, the reactors are designed to have a number of safety features. Inspire of these safety measures three disasters in the nuclear power plants are noteworthy –Three Mile Island’ in Middletown (U.S.A.) in 1979, Chernobyl (U.S.S.R.) in 1986 and Fukushima Daiichi nuclear disaster in 2011.
- In the first two cases, a series of mishaps and errors resulted in overheating of the reactor core and lot of radiation was released into the environment.
- The leakage from the Three Mile Island reactor was apparently low and no one was injured immediately. However, in the case of Chernobyl, the leakage was very heavy causing the death of some workers and radiation spread over large areas scattered all over Europe.
- The latest one – Fukushima Daiichi nuclear accident was triggered by an earthquake.
- Other important nuclear power plant disasters include Chalk River, Canada, Windscale Plutonium Production Center, U.K and Monju, Japan.
- Accidents with nuclear submarines and nuclear warships is a possibility.
Safe Disposal of Nuclear Wastes
Radioactive wastes are of two types
- low-level radioactive wastes (LLW) which include civilian applications of
radionuclides in medicine, research, and industry, materials from
decommissioned reactors, protective clothing is worn by persons working with radioactive materials or working in nuclear establishments.
- High-level radioactive wastes (HLW) results from spent nuclear fuel rods and obsolete nuclear weapons.
Some proposed methods of disposing nuclear waste are:
- Bury it deep underground in insulated containers. This is a strategy being pursued in the United States.
- shoot it into space or into the sun. The cost would be very high and a launch accident should be disastrous.
- bury it under the ice sheet of Antarctica or Greenland ice cap. The ice could be destabilized by heat from the waste. The method has been prohibited by international law.
- dump it into deep oceans by keeping the waste into glass and steel cases. But the containers might leak and contaminate the ocean.
- change it into harmless or less harmful isotopes. Currently, no method is known to do that and the method would be too costly.
- presently waste fuel rods are being stored in special storage ponds at reactor sites or sent to reprocessing plants. Even though reprocessing is more expensive but some countries use reprocessing as an alternative to waste storage.
Preventive/Control Measures of Radioactive Pollution
- Prevention is the best control measure as there is no cure available for radiation damage.
- All safety measures should be strictly enforced. UN should have more powers to perform safety checks in various nuclear establishments across the world.
- Worldwide monitoring of radiation leakage should be a priority.
- Proper technologies should be developed to prevent contamination of water and soil by radioactive waste and radioactive materials.
- More avenues for safe disposal of radioactive must be worked out.
- Regular monitoring through frequent sampling and quantitative analysis in domestic nuclear establishments.
- Appropriate steps should be taken to protect from occupational exposure.
- Gradually decreasing the share of nuclear power is a necessity.
- The world must unite to ban production and use of nuclear weapons.
Impact Of Radiation From Mobile Phone Towers
- The radiation that comes from mobile tower radiation is non-ionizing radiation.
- Every antenna on cell phone tower radiates electro-magnetic radiation (power).
- One cell phone tower is being used by a number of operators, more the number of antennas more is the power intensity in the nearby area.
- The power level near towers is higher and reduces as we move away.
- EMR may cause cellular and psychological changes in human beings due to thermal effects that are generated due to absorption of microwave radiation.
- The exposure can lead to genetic defects, effects on reproduction and development, Central Nervous System behavior etc.
- EMR can also cause non thermal effects which are caused by radio frequency fields at levels too low to produce significant heating and are due to movement of calcium and other ions across cell membranes.
- Such exposure is known to be responsible for fatigue, nausea, irritability, headaches, loss of appetite and other psychological disorders.
- The current exposure safety standards are purely based on the thermal effects considering a few evidences from exposure to non-thermal effects.
Impact on birds
- The surface area of the bird is relatively larger than their body weight in comparison to the human body so they absorb more radiation.
- Also, the fluid content in the body of the bird is less due to small body weight so it gets heated up very fast.
- The magnetic field from the towers disturbs birds’ navigation skills hence when birds are exposed to EMR they disorient and begin to fly in all directions.
- A large number of birds die each year from collisions with telecommunication masts.
What are the responsibilities of Stakeholders?
- The MoEF has to notify the impacts of communication towers on wildlife and human health to the concerned agencies for regulating the norms for notification of standards for a safe limit of EMR.
- Regular monitoring and auditing in urban localities/educational/hospital/industrial/ residential/recreational premises including the Protected Areas and ecologically
- Carry out an ‘Ecological Impact Assessment’ before giving permission for construction of towers in wildlife and ecologically important areas.
State Environment and Forest Department
- State Environment and Forest Department are entrusted with the task of providing regular awareness among the people about the norms on cell phone towers and the dangers of EMR from them.
Department of Telecommunications
- Avoid overlapping of high radiation fields. New towers should not be permitted within a radius of one kilometer of the existing tower.
- The location and frequencies of cell phone towers and other towers emitting EMR should be made available in the public domain GIS mapping of all the cell phone towers to be maintained to monitor the population of bird and bees in and around the wildlife protected area and the mobile towers.
- Need to refine the Indian standard on safe limits of exposure to EMR, keeping in view the available literature on impacts on various life forms.
- To undertake Precautionary approaches to minimize the exposure levels and adopt stricter norms perennial, that live longer than agricultural crops.
- Any study conducted on the impact of EMF radiation on wildlife needs to be shared to facilitate appropriate policy formulations.