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Saturday, March 19, 2011

Medical and Radiation sources of hazardous waste

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Medical Sources of Hazardous Wastes
The wastes produces in hospitals, nursing homes, maternity care centres, dispensaries, operation theatres, pathology centres, and even in general laboratories may be considered as medical wastes. The wastes of animal body parts including those of humans, that are cut out during surgical activities are called as biomedical wastes. All of these wastes are seriously hazardous in nature. Still, in many of hospitals, nursing homes, maternity care centres etc., improper care in handling and management of wastes in those places is observed by responsible citizens of our societies.

Hospital wastes contain blood, tissues, discarded medicines, cut off human limbs and other body parts, dead or aborted embryos, needles, scalpels, glassware, cotton, torn clothes of sick people etc. Needles, scalpels etc. that may cut or injure anyone if handled carelessly are called as ‘sharps’. Pathology laboratories dispose chemical wastes and excretory materials that contain germs of various diseases. Significant amounts of radio active isotopes are applied for diagnosis and treatment. Heaps of expired medicines, cotton plugs, bandages, empty bottles, plaster castes, used X-Ray plates, Saline sets, Catheters, water bags, rotten fruits, and vegetables are routinely accumulated in hospitals. These wastes if not cared, handled and disposed properly, may prove to be extremely hazardous.

Principal radiation sources of hazardous wastes
Flow of atomic and sub- atomic particles and of waves, such as those that characterize heat rays, light rays, and X-rays is called as radiation. In other words, radiation may be thought of the energy in motion. Radiations may be classified in two broad groups- Electromagnetic radiations and Matter radiations. The first group includes radio waves, micro waves,, infra red waves, visible light, Ultra violet rays, X-rays, Gamma rays, and Neutrino. The second group includes particles as electrons, protons, and neutrons. When these particles travel at a very high velocity, these are called as radiations.

Nuclear power plants, transport and disposal of nuclear wastes, Dumping of radio active waste, mining of radio active substances (like mining of Uranium from Jaduguda mines, Jharkhand ), fall out of bomb explosions, nuclear weapons, testing of nuclear devices, and nuclear accidents etc. are major causes of radiation hazards.

Radiation hazards may either be natural or human induced. Cosmic radiations, Ultra violet radiations, etc. are examples of natural radiations whereas explosions, testing of bombs, leakage from nuclear reactors etc. are human induced sources of radiation hazards.

Sources of radiation 
A number of sources of radiation hazards have been reported by researchers. These sources are briefly introduced below-

 Radiations from natural sources comprise a vast group of radiation exposure to common man. These are some naturally borne radio active isotopes like K40, C14, Th232, U238 etc. These isotopes remain present inside human body tissues.

High energy particles coming to the earth in the form of rays from extra-terrestrial origin are known as cosmic radiations.

Medical and dental X-rays are exposing the public to increasing doses of radiations. A female patient is greatly concerned about pelvic X-rays given to her at child bearing age. The embryo and foetus have been particularly sensitive to damaging radiations. In the year 1962 an International Conference was held on Irradiation Protection. That conference advocated that except in emergencies, any radiological examination of women of child bearing age should be limited to periods when pregnancy was not improbable. The conference had defined the period as ten days following the onset of menstruation.

Nuclear wastes from Nuclear Power plants are main sources of radiation pollution. More than 95 per cent of the radio active wastes of the United Kingdom are released from nuclear power industry. These wastes include wastes from Uranium Enrichment, fabrication of nuclear fuel, operations of nuclear reactors, reprocessing of the spent fuel etc. 

So far, there is no safe method for permanent disposal of old fuel elements from nuclear reactors. Most of this radio active waste is kept in storage facilities at the reactor sites where these wastes were generated. Currently, many nations of the world are worried to search out and to commission some common Nuclear Waste Repository. Switzerland, Sweden and Germany are developing specific technologies to dispose off their nuclear waste. However, the U.S. has opted for a final repository at Yucca Mountain in Nevada, though the project is widely opposed due to long distance transport of the waste from across the United States to the area.

 Nuclear weapons tests are frequently carried on by different nations of the world. It is now a matter of grave concern to scientists. Whenever a nuclear weapon is tested in the atmosphere, local fall out of the products of radio active fission occurs for about a day or two. This fall out is followed by troposphere, and the stratospheric fall out continues worldwide for about a month and for about a year respectively. This world wide atmospheric transport of radio active wastes has become a matter of global concern today. The radio active wastes falling on ground or the radio nuclides join the food chains operating in nature and search their ways to higher animals. For example, Sr90, and I131 reach human beings through milk, Sr90 goes into bones, and I131 gets deposited into Thyroid gland. In the table 9.2., some of the constituents of the radio active fall out that join the locally operated food chains are given as a ready reference.

There are a number of other sources of radiation hazards that are closely associated to our day to day life. For example-
1.Cigarette smoke contains radio active lead which induces cancer.
2.The surface soil of the earth contains radium in its top 6 inches at most of the places. This radium produces radon during its decay. Radon is also a radio active substance. The decay of radon produces a radio active isotope of lead which remains in air and settles down on plant shoots and leaves. From there it may join food chain after being transported to our homes along with fruits and vegetables.
3.X-rays from black and white sets of television contribute deposits of radiation in human body up to minor levels.
4.Houses built with radio active stones.
5.Bath tubs glazed with Uranium pigments.
Hazards due to radiation
High doses of radiations may produce serious consequences in the environment that lead to dangerously hazardous conditions. By radiation hazards in the present context we mean the biological effects of radiations, radionuclides and radioactive fallout. As we know that radiations have been classified into Ionising and Non-ionising categories, the biological impacts of these radiations are being mentioned here separately.

Biological Hazards due to Ionising Radiations
Various ionising radiations are electrons, positrons, alpha particles, Gamma rays and X-rays. Some nuclides may affect externally and may cause superficial injury. On the other hand there are nuclides like Beta particles or X-rays that penetrate deeply and cause seriously hazardous effects on skin and tissues. One or more atomic nuclei, identifiable as being of the same element by having the same number of protons and same energy content, are called as nuclides. This term was coined during the mid-20th century. The Biological effects of ionising radiations are mentioned below.

1. Accumulation in the Critical body organs: These radiations accumulate in the critical organs of our bodies like liver, thyroid gland, spleen, lungs and bone marrow. For example bone and adjacent bone marrow are body organs vulnerable to plutonium, radium, and strontium. Radio Iodine collects in the thyroid gland

2. Hazards due to Nuclear Fall out: The deposition of airborne radio active contaminants on earth due to nuclear testing, explosions, and war bombing is called as nuclear fall out. It allows the radio active isotopes to join food chains through different media and to accumulate in the vital parts of living bodies.Strontium-90 is the hazardous nuclide which accumulates in high concentration in the skeleton of higher animals for many years. These radiations cause serious injuries and cancers, Leukaemia and the like diseases.

3. Hazards due to Long Lived Radioisotopes: The long lived radioisotopes cause most serious hazards in human bodies due to the fact that they persist there for very long periods. Such types of radioisotopes like caesium-137, strontium-90, and plutonium-239 if contained in the radioactive fall out are sure to enter the bodies of humans, animals (both fresh water and marine) and plants through the natural food chains. The fall out of Iodin-131 can be easily detected out of the food chains. This radioisotope emits beta and gamma rays and it can cause thyroid cancer and various types of metabolic disturbances especially in children if absorbed in high doses.

4. Major Radiation Injuries in Human Beings: In Human Beings injuries caused due to radioisotopes can be divided into two broad categories – Somatic and Genetic. Somatic injuries pertain to the injuries in human bodies where as Genetic injuries are Genetic Effects that pertain to the injuries, alterations, translocations, dislocations and mutations of genetic materials like chromosomes, genes and DNAs. These may also include death of cells, alterations in the pattern of cell division, and damage to genes or the Genetic Mutation. 
Mutation is the sudden, permanent and heritable change in the body of an organism due to the exposure of some radiation or effects of some chemicals. Genetic mutation occurs when the form or structure of a gene is changed permanently to produce genetic defects. A disease known as the ‘sickle- cell’ anaemia is also caused by genetic mutation. The Genetic Mutation due to radiations is the nuclear event in which nucleotide sequence of Deoxyribose Nucleic Acid is altered and a new sequence is passed on to the off springs to produce different types of defects in the offspring. In fact, Mutation is the genetic event that causes sudden heritable changes in individuals. During 19th century Rutherford had proposed that one element can be transmutated into some other element. The word transmutation relates to a complete transformation of a substance or an element. In the present context radiological mutations can cause a complete transformation of an element thereby making it more harmful to life.

Somatic Effects of exposure to radiations usually occur for shorter periods like the inhibition of cell division. But there are some somatic effects of exposure to radiations that occur years or decades after the exposure of radiation. The radiation induced cancer comes under this category. Still, there are stochastic and non-stochastic types of somatic effects of radiations. The stochastic effects are those for which no threshold dose is known to exist where as the non-stochastic effects are those which occur only in response to the exposure to some considerable dose of radiation, like skin cancer.

Some major examples of the effects of radiations on body organs are- skin injuries, deaths of blood forming cells of the bone marrow, ulcerations of gastrointestinal tract, sterility in men and women, opacity or damage to eye lens, damage to brain and sensory organs, radiation sickness, alterations in growth and development of embryos, incidence of different types of cancers, and shortening of life pawn etc.

Biological Hazards due to Non- Ionising Radiations
The effects of non-ionising radiations are summarised below-
1. Effects of visible and Ultra Violet light: The Ultra Violet light contained in the sun light is more intense and hazardous. These rays are highly toxic below the wavelength of 2200 angstroms. The UV rays of these wavelengths are highly absorbed by nucleic acids of cells that are the main constituents of the genetic material. These rays are mutagenic and due to this characteristic these may cause skin cancer on exposure. These rays are also emitted out from mercury vapour, xenon, and hydrogen arc lamps.

2. Photodynamic Actions: Light sensitivity causes a number of diseases in animals and also in human beings. Intense light may cause blisters on parts of body exposed to sunlight. This disease is called as hydroa. This disease is caused due to the presence of a light sensitive compound called as porphyrin which remains present in the skin. A number of chemical substances that are synthesized in the skin make cells light- sensitive. These chemicals are called as photodynamic substances and the adverse action of light due to these substances is called as Photodynamic actions.
 
Some important photodynamic substances are Rose Bengal, hematoporphyrin, and phylloerythrin. These photodynamic pigments cause several diseases in many of our domestic animals when they ingest plants containing these toxic and fluorescent substances. A disease known as phagopyrism is produced in animals when they eat buck weeds. The disease Xeroderma pigmentosum, which is somewhat a heritable disease, is caused by lesions of nucleic acids produced due to the action of UVlight on exposed skin. The cells that lack nucleic acid essential for repairing nucleic acid lesions (a genetic defect), develop tumours that finally leads to death at an early age.

3. Effect on Development: Light has profound effects on growth and spatial orientation of plants. On the other hand the presence of illumination modifies cellular activities in plants. Here is an important example in support of this fact. Some species of blue green algae carry out photosynthesis in the presence of light but the process of cell division stops in that condition. The Chromatophores found in the skins of Chameleons, Frogs and Octopuses can change colour under the influence of light. 

4. Effects on Eyes: The wavelength of light which causes sun burn can cause inflammation of the cornea of human eye also. The Ultra violet radiations cause cataracts of the eye lens. This condition originates when the protein of which the eye lens is made up of, is denatured due to the exposure to UV rays. Visual pigments of eye are bleached by large doses of visual and infra red light. This accident is called as sun blindness and it is an irreversible process. Abnormal sensitivity to light causes Photophobia in human beings. It is a condition when reflex movement of the iris and the reflex dilation of the blood vessels of conjunctiva lead to eye-pain. Workers who are exposed to atomic flashes need to wear protective glasses in order to escape conditions like these.

The exposure to radiations may cause permanent damage to life and property. A nuclear reactor accident took place in 1896 in Chernobyl, Ukraine, which killed at least 31 people and forced more than 200, 000 people to vacate and relocate. A number of chemical and radiological accidents, and also a large number of marine accidents have been reported through history that has proved serious hazards from time to time. But, we are not concerned with the discussion about those hazardous accidents as they are covered under disasters.

Key Words :  hazardous waste, medical sources, radiation sources, nuclear repository, radiation, exposure, chemical and radiological, Chernobyl, Ukraine

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