It is an admitted fact that various chemicals released from power plants and industrial effluents generate many different forms of environmental pollution. One such form is mercury pollution: excessive and uncontrolled addition of mercury to our oceans. Disproportionate addition of this toxic element  can be lethal for humans and other animals.

How Does it Pollute the Environment

Most of the mercury present in the atmosphere is in the form of elemental metallic vapor. In this shape, it is relatively stable and insoluble; in fact, it is so nonreactive that it can circumnavigate the globe for up to two years. Thus it does not pose serious hazard for living beings in this form.

However, when these elemental vapors get into wetlands via precipitation, certain microbes convert them into organic form, methyl mercury compounds-chemicals that are far more toxic and capable of entering the food web rather quickly. Other organisms including top predators like tuna, swordfish, shark, lobsters and other marine mammals absorb these organic compounds, accumulating mercury in their muscles. When human eat this mercury-tainted seafood, they are also exposed to the poisonous effects.

Sources and Causes

Mercury comes both from natural and anthropogenic sources. In nature, it is released by volcanoes, weathering of rocks, and evaporation from oceans and wetlands; however, most of the mercury addition to the atmosphere is due to human activities. Mercury is useful in a wide variety of industrial processes, and found in a host of commercial products including paints, batteries, electrical switches, fluorescent light bulbs, pesticides, skin creams, antifungal agents etc. Dental amalgams are also half mercury.  

Coal burnt in power plants contains traces of mercury, which, upon combustion, vaporizes and adds to the atmosphere via flue gases, from where it moves to water via precipitation. In addition to power plants, municipal and medical waste incinerators are a major culprit causing toxic pollution. When these incinerators burn municipal waste items such as thermostats, fluorescent lights, or medical instruments like thermometers and blood-pressure cuffs, the mercury contained in these items is released to the environment. 

Significant amounts are also added to the atmosphere during smelting of metals like lead, copper and zinc. Chemical plants that manufacture chlorine and caustic soda also release mercury. Irrespective of the source, undue addition of this poisonous element can be deadly for humans and many other species.

Health Effects 

Mercury is a powerful neurotoxin that can destroy the brain cells and central nervous system. Methyl mercury compounds remain in the air for longer periods of time and are highly toxic for living organisms including humans. Prolonged exposure to these compounds can lead to kidney disorders, and damage to nervous and cardiovascular systems; low levels in brain can lead to neurological problems such as headaches, depression and irritable behavior.

Mercury exposure to developing fetuses in pregnant women has been associated with mental retardation, numbness, deafness, dementia and developmental delays. The notorious mercury-poisoning case in Minamata, Japan during 1950s is a typical example where mercury was dumped into the ocean by a chemical company, and both mothers and babies became the victim.

How to Control

Occurring in vapor form, mercury is highly mobile and widely dispersed. In addition, it is produced by a variety of sources, and impacts us in several different ways; these features make the remedy rather complicated. Currently the technology for controlling mercury emission from power plant smoke stacks is quite expensive, while their efficacy is still being debated. The most appropriate solution in the short term is to replace coal with natural gas, which does not contain mercury and produces less carbon emissions.  


Mercury Emissions from Smoke Stacks

Mercury Emissions from Smoke stacks
Credit: Gonco