What is heavy metals’ contamination? The heavy metals’ contamination in the water would be read within the general frame of environmental pollution, which has become an eminent threat to the living beings of the earth. And, in the simplest term heavy metals can be defined as the health hazardous chemicals or elements which are heavier than water. This form of pollution is stressed to land, water, sky and overall ecology. The pollution can broadly be categorized as Air Pollution, Water Pollution, Soil/Land Pollution, Noise Pollution, Radioactive Pollution and many more. This form of pollution can be defined as the substances which are harmful to human beings and other living beings in a higher scale, which eventually reduces the quality of our environment. Among various pollutions, which we have witnessed globally today, water pollution is also a major challenge. Water pollution poses a great threat to all the living beings including human. And, it also plays a serious role in the global climate change. There are various ways of contaminating these harmful substances (heavy metals) in the water. The common ways which we have been witnessing in daily life include; due to rapid urbanization – improper sewage disposal, fertilizer run-off, oil spills, chemical waste dumping from factories, radioactive waste can be mentioned among many. Among the various forms of the water pollution, contamination of chemical waste into the water is a major health concern. Such contamination can hamper important biological activities in plants and microorganisms too. Chemical contaminants in the water can be broadly be categorized as two types, that is; heavy metal pollutants and organic pollutants. Organic pollutants It has a wide variety together with varied range of toxicities, such as waste from the organic dyeing industry, plant and animal pharmaceuticals’ waste, personal care products’ waste, agricultural chemicals (organic pesticides and organic herbicides) as well as petroleum pollutants. All these examples can affect to our health, and to the overall ecology in multiple ways. Many of these pollutants contain the endocrine disruptive chemicals which can act as an external agent interfering in hormonal activities of the human beings. Moreover, this can affect the normal homeostatic reproduction, reproductive system disorders, endocrine disruptions, which ultimately lead to obesity and cancer. Among the organic pollutants, organic dyes are chemical soluble in water and considered as carcinogenic and mutagenic. They are frequently used in industries such as textile, food, paper, cosmetics (like hair dye), etc. Such dyes dissolved in water bodies, and it can obstruct the penetration of sunlight resulting in the reduction of oxygen presence in the water bodies. This can lead to the death of various plants and microorganisms and disrupts the ecosystem. Human beings are frequently exposed to the toxicity of these dyes through various ways. Examples can be mentioned, such as consumption of vegetables and fish which have already consumed these toxic chemicals. Heavy Metal Pollutants Heavy metals are elements which are generally heavier than water. Heavy metals including cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se) and zinc (Zn) are essential trace elements necessary for various biological and physiological processes in human beings. While, other metals such as aluminium (Al), antinomy (Sb), arsenic (As), barium (Ba), beryllium (Be), bismuth (Bi), cadmium (Cd), gallium (Ga), germanium (Ge), gold (Au), indium (In), lead (Pb), lithium (Li), mercury (Hg), nickel (Ni), platinum (Pt), silver (Ag), strontium (Sr), tellurium (Te), thallium (Tl), tin (Sn), titanium (Ti), vanadium (V) etc. are considered non-essential. Among the non-essential metals; arsenic, lead, mercury, cadmium, chromium etc, are known for their high toxicity and carcinogenic to health in various forms. Several health issues including mild eye, nose and skin irritations, severe headache, stomach ache, diarrhea, hematemesis, vomiting, dizziness to organ dysfunction such as cirrhosis, necrosis, low blood pressure, hypertension, and gastrointestinal problem and many more, can occur to human beings. These metals are known to be dangerous pollutant in the drinking water for their serious health implications. (I) Arsenic mostly exists in inorganic forms. Contamination of arsenic occurs via soil erosion, volcanoes and industrial products. Several industrial products such as insecticides, herbicides, fungicides, algicides, sheep dips, wood preservatives, and dye-products are major sources. The presence of arsenic in drinking water above 10 microgram per litre (WHO guidelines) can cause poisoning to the blood, central nervous system, lung and skin cancer, breathing problems, vomiting and nausea etc. The countries like India, Bangladesh, Taiwan, China, Brazil, Chile, Thailand, and so on, are suffering with the problems of arsenic contamination in the drinking water. (II) Lead is generally contaminated into the environment through burning of fossil fuels, mining, manufacturing industries, etc. Industrial products including lead-acid batteries, ammunitions, metal products (solder and pipes), and devices to shield X-Rays as well as agricultural products are the main sources of lead for contamination in the environment. Drinking of water contaminated with lead content more than 0.1 milligram per litre (Regulation of water quality, India) can become toxic to the human body. Toxicity of Lead can affect the nervous system, kidneys, hypertension, and reproductive system. Exposure to lead also causes irreversible brain damage. (III) Mercury is another metal which is considered to be highly toxic in its various forms such as mercury vapor, inorganic mercurous, mercuric and organic mercury compounds. Naturally, mercury is contaminated in the environment through volcanic, eruption, weathering of rocks and soils. However, the extensive use of mercury in the industrial production such as electrical products, caustic soda, nuclear reactors, antifungal agents for wood processing, as a solvent for reactive and precious metal, and as a preservative of pharmaceutical products; causes to direct mercury contamination in the water. Contamination of mercury more than 0.004 milligram per litre (Regulation of water quality, India) in the drinking water can severely lead to serious health concerns as all forms of mercury are toxic. The effects of mercury exposure can bemutagenic affects, gastrointestinal toxicity, neurotoxicity, and nephrotoxicity. (IV) Cadmium is introduced into the environment in various ways. This includes metal-ore refining, industrial products including alloys and electronic compounds, cadmium containing phosphate fertilizers, detergents and refined petroleum products. Nickel-cadmium based rechargeable batteries are also sources of cadmium contamination. The permitted cadmium concentration in the drinking water is up to 0.001 milligram per litre (Regulation of water quality, India). Exposing to the higher content of the cadmium than the permitted in the drinking water can lead to serious damage to kidneys and bones, Bronchitis, emphysema, anemia, renal dysfunction, bone degeneration, liver and blood damage. Sufficient evidence is also available for its carcinogenicity. (V) Chromium also gets contaminated into the environment through natural processes such as volcanic eruptions, geological weathering of rocks, soils and sediments as well as anthropogenic sources. Its largest source is the release of the chromium from industrial establishments. This includes metal processing, stainless steel welding, chrome pigment production, etc. It directly leads to the contamination in water due to the huge release of wastewater containing chromium from these industries. Drinking water containing chromium concentration higher than 0.1 milligram per litre (Regulation of water quality, India) can cause multi organ toxicity such as renal damage, allergy and asthma, cancer of the respiratory tract can be mentioned among many. Dr. Naorem Shanta Singh Department of Physics Nagaland University, Lumami

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