Water pollution occurs when harmful substances like chemicals or microorganisms contaminate a stream, river, lake, ocean, underground water, or other body of water, hence degrading water quality and rendering it toxic to humans or the environment.
According to Environmental Protection Agency (EPA), nearly half of the rivers and more than one-third of lakes, are polluted in developed countries and the situation is even worst in developing countries. The major share of toxins to the water bodies is contributed by municipal and industrial waste discharges, besides the random junk that industry and individuals dump directly into waterways. While point source pollution originates from a specific place, it can affect miles of the waterway and ocean.
According to the United Nations, more than 80 percent wastewater of world flows back into the environment without being treated or reused and this figure reaches nearly 95 percent in under-developed countries.
To put it bluntly, it can be said that Water pollution kills. In fact, it causes millions of deaths each year globally. Contaminated water can also make you ill. Every year, unsafe water sickens about 1 billion people. And low-income communities are disproportionately at risk because their homes are often closest to the most polluting industries.
Waterborne pathogens, in the form of disease-causing bacteria and viruses from human and animal waste, are a major cause of illness from contaminated drinking water. While acute illnesses like diarrhea, dysentery, cholera, hepatitis A, and typhoid can manifest early due to their symptoms, and the public at large and health care providers are to some extent aware of these contaminations, it is the heavy metal toxicity which is becoming a silent killer and major cause of morbidity and mortality to a vast number of humanity with the passing time as the symptoms appear late and patients present in advance stage of the disease. Heavy metal toxicity has proven to be a major threat and there are several health risks associated with it. The toxic effects of these metals, even though they do not have any biological role, remain present in some or other form harmful to the human body and its proper functioning.
Heavy metals are generally referred to as those metals which possess a specific density of more than 5 g/cm3 and adversely affect the environment and living organisms.
These metals are essential to maintain various biochemical and physiological functions in living organisms when in very low concentrations, however, they become noxious when they exceed certain threshold concentrations. Heavy metals are significant environmental pollutants and their toxicity is a problem of increasing significance for ecological, evolutionary, nutritional, and environmental reasons. The most commonly found heavy metals in wastewater include arsenic, cadmium, chromium, copper, lead, nickel, and zinc, all of which cause risks to human health and the environment. Heavy metals enter the surroundings by natural means and through human activities. Various sources of heavy metals include soil erosion, natural weathering of the earth's crust, mining, industrial effluents, urban runoff, sewage discharge, insect or disease control agents applied to crops, etc.
Effects of heavy metals on humans
There are 35 metals that are of concern for us because of residential or occupational exposure, out of which 23 are heavy metals: antimony, arsenic, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, gold, iron, lead, manganese, mercury, nickel, platinum, silver, tellurium, thallium, tin, uranium, vanadium, and zinc. These heavy metals are commonly found in the environment and diet. In small amounts, they are required for maintaining good health but in larger amounts, they can become toxic or dangerous. Heavy metal toxicity can lower energy levels and damage the functioning of the brain, lungs, kidneys, liver, blood composition, and other important organs. Long-term exposure can lead to gradually progressing physical, muscular, and neurological degenerative processes that imitate diseases such as multiple sclerosis, Parkinson's disease, Alzheimer's disease, and muscular dystrophy. Repeated long-term exposure to some metals and their compounds may even cause cancer. The toxicity level of a few heavy metals can be just above the background concentrations that are present naturally in the environment. Hence thorough knowledge of heavy metals is rather important for allowing to provide proper defensive measures against their excessive contact.
ARSENIC toxicity in men focuses on skin manifestations because of its specificity in diagnosis. Pigmentation and keratosis are the specific skin lesions that indicate chronic arsenic toxicity.
Acute exposure to LEAD can cause loss of appetite, headache, hypertension, abdominal pain, renal dysfunction, fatigue, sleeplessness, arthritis, hallucinations, and vertigo. Chronic exposure to lead can result in mental retardation, birth defects, psychosis, autism, allergies, dyslexia, weight loss, hyperactivity, paralysis, muscular weakness, brain damage, kidney damage, and may even cause death.
Increased exposure to MERCURY can alter brain functions and lead to shyness, tremors, memory problems, irritability, and changes in vision or hearing. Exposure to metallic mercury vapors at higher levels for shorter periods of time can lead to lung damage, vomiting, diarrhea, nausea, skin rashes, increased heart rate, or blood pressure. Symptoms of organic mercury poisoning include depression, memory problems, tremors, fatigue, headache, hair loss, etc.
CADMIUM is highly toxic to the kidney and it accumulates in the proximal tubular cells in higher concentrations. Cadmium can cause bone mineralization either through bone damage or renal dysfunction. Inhaling higher levels of cadmium can cause severe damage to the lungs. If cadmium is ingested in higher amounts, it can lead to stomach irritation and result in vomiting and diarrhea. Exposure to CHROMIUM compounds can result in the formation of ulcers, which will persist for months and heal very slowly. Ulcers on the nasal septum are very common in the case of chromate workers. Exposure to higher amounts of chromium compounds in humans can lead to the inhibition of erythrocyte glutathione reductase, which in turn lowers the capacity to reduce methemoglobin to hemoglobin.
ALUMINUM toxicity causes nausea, mouth ulcers, skin ulcers, skin rashes, vomiting, diarrhea, and arthritic pain. Aluminum exposure is probably a risk factor for the onset of Alzheimer's disease (AD) in humans, as hypothesized by the WHO. Contact dermatitis and irritant dermatitis were seen in persons who were exposed to aluminum in their place of work. Aluminum showed adverse effects on the nervous system and resulted in the loss of memory, problems with balance, and loss of coordination.
Conclusion
Hence it is concluded that some heavy metals, i.e. arsenic, lead, mercury, cadmium, chromium, and aluminum cause drastic harmful effects on the environment and living organisms, mainly human beings. Effective legislation, guidelines, and detection of the areas where there are higher levels of heavy metal contamination are necessary. Failure to control the exposure will result in severe complications in the future because of the adverse effects imposed by heavy metals. Monitoring the exposure and probable intervention for reducing additional exposure to heavy metals in the environment and in humans can become a momentous step towards the prevention of potentially killer diseases and the safety of humanity at large.