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- Radioactivity is a property of certain elements to spontaneously emit particles or waves. The phenomenon arises as a virtue of their unstable nuclei.
- 3 types of radioactive emissions occur:
- Alpha– positive charge bearing helium atom
- Beta– negatively charged electrons
- Gamma– electromagnetic radiations
- Such radioactive elements occur naturally in the earth’s crust. However, these elements find myriad applications such as nuclear power generation, research and development, in medical equipment like X-ray scanners and MRIs, etc.
- The radioactive isotopes from these anthropogenic sources tend to enter the natural environment and contaminate it.
- Some of the worrying sources of such pollution include nuclear calamities (such as Chernobyl), nuclear weapons testing, dumping of untreated radioactive wastes, etc.
How does radioactive pollution of water happen?
- Water pollution is a major environmental concern in the present day. This vital resource is contaminated by organic pollutants, heavy metals, dyes, etc.
- All water sources have small amounts of radioactive elements. However, excessive amounts are harmful to human and animal health.
- Surface waterbodies are contaminated by dumping of radioactive wastes.
- The groundwater is contaminated by percolation of NORM (naturally occurring radioactive materials) from the soil sediments into the aquifers.
- Groundwater is generally more contaminated by radioactive wastes than surface water. This is because groundwater is more exposed to radioactive elements present in the rocks.
- Mining of uranium and thorium generates radioactive contaminants.
- Wastes from nuclear power plants, often located in the coastal areas, tend to contaminate the marine environment. This is because the marine water is used as coolants in these power plants.
- Radioactive contamination of marine environment also occurs due to submarine accidents and nuclear submarines.
- In some cases, magma, from the earth’s interiors, releases radioactive gases into the surface environment. These gases get deposited in the waterbodies and lead to contamination.
What are the radioactive contaminants in water?
- NORM series that contaminate waterbodies are uranium, actinium and thorium.
- Common examples of radionuclides found in waterbodies, at surface and sub-surface levels, include 3H, 14C, 40K, 210Pb, 210Po, 222Rn, 226Ra, 228Ra, 232Th, 234U, 235U and 238U.
- Radium is one of the most radiotoxic elements that contaminate aquatic system. It enters the groundwater through various routes:
- aquifer rock dissolution
- decaying of 238U and 232Th
- Radioisotopes like Cobalt-60 and Iridium-192 are used as gamma radiation source in radiotherapy and in industrial applications.
- Radioisotope wastes, including Strontium-90 and Caesium-137, are generated from nuclear reactors.
- Potassium-40 and Beryllium-7 are found in sludge from sewage treatment plants. Potassium-40 is also found naturally in the marine environment.
- Uranium is naturally present, in the form of uranyl carbonate, in the oceans and the seas. Marine water that is highly saline tend to have greater concentration of uranium.
Why is it concerning?
- Though radioactive pollution of water is still an emerging concept, it has already become a grave concern given the significant harm caused in many parts of the world.
- Radioactive contaminants can enter the human and animal system via inhalation, injection or mere exposure.
- It is not only the polluted water, but also the foodstuff produced using the water, that can become a source for such exposure.
- Exposure to high dose radiation can lead to cutaneous radiation injury or even acute radiation syndrome.
- Disorders like cancers, genetic mutation, leukaemia, chromosomal disruptions, osteonecrosis and cataracts have been linked to such exposures.
- Immediate consequences of exposure include damage to the skin, lungs, genitals and hair fall.
- It may trigger dysentery, cholera, pneumonia and tuberculosis.
- The more long-term and permanent outcomes can also occur- such as bone marrow damage. Some outcomes lead to fatalities.
- Radiation exposure could trigger mutation in the germ cells (sperms and egg cells) and lead to alteration of the DNA. This mutation is passed on to the offsprings and result in hereditary disorders that could cause mental illnesses and premature deaths.
What needs to be done?
- The WHO had set guidelines for maintaining the quality of drinking water. it had set the permissible limit of reference dose level at 0.1 micro-sieverts per year.
- The ‘radionuclides rule’ was released by the US Environmental Protection Agency. It set the standards at:
- 5 picocuries/litre for combined radium
- 30 mg/litre for uranium
- 15 picocuries/litre for gross alpha emitters
- 4 millirems/ year for gross beta emitters
- To ensure a safe water supply, the administration must undertake analysis and monitoring for radioactive pollutants.
- Preventive measures and precaution measures need to be more widely adopted.
- Treatment methods like reverse osmosis, aeration, granule carbon absorption and ion exchange may be used effectively for treating contaminated water.
Radioactive pollution of water is a source of global concern. Such contamination has an insidious impact on the health of living organism and the environment. These pollutants must be controlled at the source and water supply must be monitored and treated to reduce the impact of such contaminants.