Radioactive pollution in water: A global concern for human health

Water pollution is a severe concern for the current generation. We are familiar with water contaminants like major ions, heavy metals, dyes and organic pollutants. 

However, radioactive pollution of water is newly emerging but is of grave concern for water pollution and human health. Recently, radioactive contamination and associated health impacts have been reported in many parts of the globe.

Radioactivity is the phenomenon of spontaneous emission of particles or waves from the unstable nuclei of some elements. There are three types of radioactive emissions: Alpha, Beta and Gamma. 

Alpha particles are positively charged He atoms, beta particles are negatively charged electrons and gamma rays are neutral electromagnetic radiations. Radioactive elements are naturally found in the earth’s crust. 

Percolation of naturally occurring radioactive materials (NORM) from the soil sediments to the aquifer causes groundwater contamination. In anthropogenic sources of radioactive pollution, nuclear weapon investigation, nuclear calamities, nuclear power houses and dumping of radioactive waste are major sources of contamination, while application of radioisotopes in industries and scientific laboratories are the minor sources. 

The application of radioactive elements in nuclear weapons, X-rays, MRI and other medical equipment causes their exposure to human beings. Dumping of these radioactive wastes in surface waterbodies causes water pollution. 

Radioactive contamination is more prevalent in groundwater as compared to surface water since it is much exposed to radioactive elements found in the rocks. Sometimes, magma also releases radioactive gases into the environment.

The deposition of these radioactive gases in waterbodies also cause radioactive contamination. Atmospheric deposition (both dry and wet) of cosmogenic radionuclides also add radioactive nuclei in the surface water.

A number of radionuclides are found in surface and subsurface  waters, among which 3H, 14C, 40K, 210Pb, 210Po, 222Rn, 226Ra, 228Ra, 232Th and 234,235,238U are common. Uranium, thorium and actinium are three NORM series that contaminate water resources. 

Radium, a descendant of the NORM series, is one of the decidedly radiotoxic elements found in aquatic systems and can be penetrated into groundwater via (i) aquifer rock dissolution (ii) decaying of 238U and 232Th, or (iii) desorption processes.

Nuclear reactors and nuclear warhead experiments are the key sources of human-induced radionuclides discharge. Nuclear reactors produce radioisotopes (Cobalt-60, Iridium-192, etc) that hand out as sources of gamma radiation in radiotherapy and numerous industrial appliances. 

Strontium-90, Caesium-137, etc are also formed by nuclear reactors, along with numerous unnecessary radioisotopic wastes. 40K and 7Be are the most commonly found radioactive elements in the sludge generated in sewage treatment plants. Mining activities of radioactive elements like uranium and thorium also pollute surface and groundwater. 

Oceans and seas are the natural repositories of naturally occurring uranium. Where it is found in the form of uranyl carbonate ion. A significant concentration of uranium is supposed to be found in the greater salinity of the marine water. 40K is also found in considerable concentration in the marine environment. 

Nuclear power plants placed at the coastal regions add to the radiological contaminants in the marine water by releasing atomic wastes. Water is also used as coolants in these powerhouses, which also get contaminated. 

Nuclear submarines cause radioactive contamination in the marine environment. Radioactive pollution due to submarine accidents and sinking have been reported. The Rocky Flats plant in Colorado, Fukushima and the Chernobyl nuclear disaster are some examples of such nuclear accidents. 

Radioactivity is measured in Becquerel (SI unit) or in Curie. Energy absorbed per unit mass is measured by Gray, while the unit Sievert measures the quantity of radiation absorbed by human tissues. 

A small amount of radiation is found in all types of water but the extended amount of radiation is harmful to human health. Radioactivity in drinking water can be determined by a gross alpha test.

The World Health Organization set guidelines for drinking water quality and a permissible limit of reference dose level of 0.1 micro-sieverts per year. The United States Environmental Protection Agency released guidelines known as ‘radionuclides rule’. This rule recognised standards of:

• 5 picocuries per litre for combined radium
• 30 micrograms per litre for uranium
• 15 picocuries per litre for gross alpha emitters
• 4 millirems per year for gross beta emitters

Radioactive elements have an effect on the environment and can cause a risk to human healthiness if inhaled, injected or exposed. 

Human tissues absorb radiation through polluted water and foodstuff, which can cause serious health risks. High doses of radiation can cause acute radiation syndrome or cutaneous radiation injury. 

Exposure to radiation causes various disorders in human physiology, including cancer, leukaemia, genetic mutations, osteonecrosis, cataracts and chromosomal disruption. 

The harmful impacts of nuclear radiation are:

• Immediate, recoverable consequences distressing skin, lungs, genitals, and causing hair fall 
• Long-standing, permanent outcomes such as various infections like radiation damage, bone marrow fatality, cataract initiation, cancer stimulation, cholera, dysentery, tuberculosis and pneumonia. Sometimes, these outcomes may be fatal also. 
• Genetic effects ionizing radiation induces mutations in germ cells (male sperm cells and female egg cells) or germ cells, resulting in structural alteration in germ cell DNA that are passed on to offsprings. Hereditary disorders can lead to premature death and severe mental illness. 

Nowadays, proper analysis and monitoring of radioactive pollutants are also required for a safe water supply. Prevention and precaution measures can check the anthropogenic sources of radioactive contamination in water resources. 

Various treatment methods like aeration, reverse osmosis, ion exchange and granule carbon adsorption are effective remedial measures for treating the radioactive contaminated water. 

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