Trace contaminants are the chemicals of concern to human health and biotic environment due to a combination of their physicochemical, toxicological properties. In the aquatic environment, they are present at trace levels in microgram/Litre range or less.
Sources of inorganic trace contaminants are usually- industrial effluents from manufacturing and metal finishing industries, mining and smelting. Pollution from trace elements has become the main source of global environmental pollution. Their emission into the environment is harmful not only to ecosystems, but also poses a threat to human health because of refractory characteristics of bio-accumulation . The trace elements are essential for human metabolic and other life processes but when their concentration in human body exceeds the permissible limit then the essential elements are called as “contaminants”.
Few trace contaminants which are actually essential trace elements are discussed below:
Cadmium: Cadmium is a naturally occurring toxic heavy metal which is used extensively in the manufacture of batteries, paints and plastics, plating of nuts and bolts etc. Significant amount of Cd is present in cigarette smoke.Cadmium enters into water system from plating industries. Cadmium poisoning causes “itai-itai” characterized by brittle bones and increased pain. At low levels of exposure it causes high blood pressure, sterility among males, kidney damage and flue like disorders. Occupational and environmental cadmium exposure may be related to various types of cancer, including breast, lung, prostate, pancreas, and kidney cancers. It has been also demonstrated that environmental cadmium may be a risk factor for osteoporosis. The liver and kidneys are extremely sensitive to cadmium’s toxic effects.
Chromium: It is a transition metal with variable valencies. The most occurring states o chromium are a trivalent and hexavalent state. Cr (III) gets hydrolysed completely in water and precipitates as Chromium hydroxides- leaving very minor amount of chromium in solution. There is no evidence that chromium is harmful for health. Chromium is extensively used in industry to make alloys, catalysts, chromic oxide and chromate salts. Cr(VI) is used in plating industry, Chromate salts are used in paints and to prepare cleaning reagent in laboratories. From laboratories it directly mixes with sewage water as most of the laboratories do not have any purification of wastewater system. Cr(VI) is widely acknowledged as a toxic contaminant which causes skin disorder, liver damage and cancer.
Copper: Copper is an essential trace metal for human health. Copper plays a key role in the development of healthy nerves, bones, collagen and the skin pigment melanin. Normally, copper is absorbed from food, and excess is excreted through a substance produced in liver (bile). Hence, it is a long practice among people to drink water from a copper pot. Also, high concentration of copper changes the taste of water. Copper sulphate is used to control growth of algae in water. Concentration near 1.0mg/L can be toxic for some aquatic animals like fish.
Accumulation of copper causes Wilson’s disease which is a rare inherited disorder that causes copper to accumulate in tissues like liver, brain and other vital organs. Most people with Wilson’s disease are diagnosed between the ages of 5 and 35, but it can affect younger and older people, as well. In people with Wilson’s disease, copper isn’t eliminated properly and instead accumulates, possibly to a life-threatening level. When diagnosed early, Wilson’s disease is treatable, and many people with the disorder live normal lives.
Menkes disease usually causes low copper levels in blood plasma, the liver and the brain. The condition also reduces the activities of copper-dependent enzymes in the body. Copper may accumulate in other tissues, such as the kidney. Because the condition prevents the body from using copper correctly, Menkes disease can lead to serious damage to the brain and nervous system, and can harm a child’s development.
Lead : Lead poisoning has been recognised for many years. Lead is used in paints, cosmetics, gasoline, solder metals (in water pipelines made of iron) , decorative items etc, Lead poisoning causes kidney, liver and brain damage, causes mental retardation in children.
[Read more: Lead is Poison – Revolving Around Life]
Mercury: Mercury is widely used in amalgams, scientific instruments, batteries, arc lamps, extraction of gold and silver and the electrolytic production of chlorine. Its salts are used as fumigants in combating plant diseases and insect pests. Mercury toxicity causes autism in children,low IQ, mental disorder, crippled bones etc.
Barium: Barium is not found naturally in pure forms but it is available as salts. Barium salts have many applications like low amount of Barium Sulphate is used for endoscopy, Barium Crabonate is used as rat poison. Exposure to Barium occurs due to mining, various industrial processes and by cigarette smoking. Barium can be ingested through drinking water and food. The Television sets especially the flat panel ones contains toxic metals like arsenic, barium, cadmium, lead, and mercury (and programming that is overwhelmingly void-of-thought). When televisions are improperly disposed of, environmental and groundwater contamination can be an extremely serious concern. Ingestion of certain forms of barium (e.g., barium carbonate or barium fluoride) in toxic amounts can lead to gastrointestinal signs and symptoms (e.g., vomiting, abdominal pain, and watery diarrhea), muscle weakness leading to paralysis of the limbs and respiratory muscles.
NIckel : Nickel is a heavy metal used in every possible way- making coins, jewelry, battery, cutlery, electroplating, hydrogenated fats and vegetable oils, cookwares, dental restoration, plumbing items, machinery parts, tobacco smoking etc. Exposure to this metal may cause kidney and liver damage, harmful to reproductive system, causes gastrointestinal disorders, asthma, bronchitis, tachycardia, atherosclerosis and cancer.
Cobalt: Cobalt poisoning is intoxication caused by excessive levels of cobalt in the body. Cobalt is an essential element for health in animals in minute amounts as a component of Vitamin B 12. A deficiency of cobalt, which is very rare, is also potentially lethal, leading to pernicious anemia. The Co sources were allocated to four exposure settings: occupational, environmental, dietary and medical exposure. Medically cobalt is used to produce orthopedic implants. Cobalt is used in dyes, batteries, drill bits, saw blades and other machine tools. Exposure to cobalt dust may cause asthma or pulmonary fibrosis. Long time exposure may cause cardiomyopathy, ringing in the ears , deafness, nerve problems etc..
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