Effects of Water Pollution




The effects of water pollution are diverse and are very much dependent on the types of pollutants involved and the nature of water bodies being affected by the pollutants. Here are some common consequences of water pollution.


Eutrophication and Oxgyen-Deficient Waters:

Elevated levels of chemical nutrients (mainly nitrogen and phosphorus) in water, brought about by the introduction of substances such as fertilizer from agriculture, organic waste, sewage or other decaying matter, is another cause of water pollution.

The presence of large amounts of nutrients in water promotes the excessive growth of algae in the water. Although the algae produces oxygen in the day, it uses up oxygen in the water at night. The algae overgrowth also blocks out sunlight, obstructing the photosynthesis process by plants under the water. When some of these algae die, the decay process also uses up oxygen. The oxygen content in the water may eventually decrease with time.

The reproductive abilities of many fish populations are affected. The fishes may also lose the natural nurseries for their young as sea grass found at the sea bed die from the lack of access to sunlight.

Fishes and other water organisms in the water that are not able to withstand the low oxygen content may relocate to other oxygen-rich places, or otherwise suffocate to death. Not all animals are able to escape – the slow moving creatures (e.g. sea snails, oysters, lobsters) living at the bottom of the sea bed are usually unable to relocate fast enough.

Hence, one of the effects of water pollution by eutrophication is reduced biodiversity in that water region. In even worse cases, dead zones (oxygen-deficient regions in the ocean) may result.


Waterborne Infectious Diseases:

Water polluted by untreated or inadequately treated human sewage and animal dung carry pathogens (disease carrying organisms) like bacteria, parasites and virus, etc, that pose serious threats to human health.

Diarrhea is a very common outcome when people consume water contaminated with such pathogens. For those of you who think that diarrhea is not serious matter, you might want to reconsider. Based on a 2008 report by World Health Organization titled “Safer Water, Better Health”, about 1.5 million people in the world die from diarrhea each year, with the majority being children.

Besides diarrhea, the health effects of water pollution by sewage contamination, depending on the type of pathogen ingested, also include conditions like dysentery (frequent passage of feces containing blood and mucus, with vomiting of blood in some cases), Salmonellosis (fever, diarrhea, vomiting), typhoid fever (sustained high fever, diarrhea, delirium in serious states, and eventual death if left untreated), etc.


Poisoning by heavy metals and other toxins:

Human activities like the industrial purification of metals, preparation of nuclear fuel, coal combustion and waste incineration introduce toxic heavy metals (e.g. cadium, mercury, etc) and other toxic chemicals (e.g. synthetic pesticides) into the environment. These harmful substances may enter the water bodies in several ways, for example, through fumes dissolving in precipitation or settling directly onto water surfaces, or through man’s deliberate discharge into water bodies.

In the rivers, seas and oceans, these heavy metals and toxic chemicals may eventually be taken up by plants or animals. For the heavy metals, they do not bio-degrade but instead bio-accumulate in the organisms that take them up. Not only are these heavy metals and chemicals toxic to the organisms that take them up (e.g. reduce the reproduction ability of animals, and inhibit growth and cause structure damage in plants), they also bio-magnify in the bodies of animals that consume the affected organisms and threaten their health and survival – the effects of water pollution via heavy metal poisoning.

A very good example of a highly toxic heavy metal is mercury. Effects of water pollution by high levels of methylmercury (the organic form of mercury which is in fact more toxic and harder to eliminate than inorganic mercury) have been found to damage the nervous system of fetuses and young children and affect their ability to think and learn. At high levels, they can cause permanent brain damages and even death.

Instances of severe methylmercury poisoning in history (according to the U.S. Geological Survey) include the case in Minamata Bay, Japan (1956) caused by industrial release of methyl-mercury, and the case in Iraq (1971) caused by the consumption of wheat treated with a methylmercury fungicide. In both cases, hundreds of deaths resulted, and some thousands others suffered permanent damages to their nervous systems.


Poisoning and drowning in oil and petroleum chemicals:

While oil and petroleum chemicals (introduced into water bodies during oil spills, run-offs from land or vessels, etc) are examples of toxic substances that pollute water bodies, they deserve addition mention.

Other than poisoning organisms (including humans) that take them up, there are other effects of water pollution by these pollutants. The nature of oil is such that it floats on water. This means that when introduced into water bodies, oil remains at the water surface and prevents sunlight and oxygen from reaching organisms living in the water. The oil that gets onto the body of animals often paralyses them, making it difficult for them to escape from predators or the oily “death pool” that drowns them – a deadly effects of water pollution by oil.


Reduced biodiversity:

Water pollutants introduce abnormal conditions (e.g. harmful chemicals, changes in water temperatures) into water bodies, disrupting existing ecosystems and can potentially contribute to reducing biodiversity in that affected area – one of the effects of water pollution.

For example, the discharge of heated-up water (thermal pollution of waters) from thermal and nuclear power plants into a river can cause problems for aquatic organisms, which are fairly used to specific temperatures. The increase in water temperatures could increase their metabolic rates and hence their need for food. This could eventually lead to the depletion of food sources in that water region and in turn cause a reduction in species population in that water region. Another one of the effects of water pollution by increased water temperatures involves organisms that are less adapted to warmer waters migrating elsewhere, further reducing biodiversity in that region.

Besides thermal pollution, water could also be polluted via the entry of acidic substances into the water bodies, such as when acid rain lands on rivers, seas and oceans, or when larger concentrations of carbon dioxide are taken up by water bodies (as a result of higher concentrations of the greenhouse gas in the atmosphere). The effects of water pollution by this process, known as acidification, can involve the destruction of entire coral reef communities.

Of course, other forms of water pollution like eutrophication (mentioned above), oil spills and toxic waste poisoning could also directly destroy populations of organisms living in the water or dependent on the water bodies for their survival.

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