Fatal Impact
Mercury poisoning is hard to diagnose, as the symptoms are often
similar to those of common ailments
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All about mercury (Download pdf)

Exposure to mercury through food, water and air can cause significant harm to human health. Methyl mercury, which is the most commonly found form of mercury in the environment, can cause permanent damage to the central nervous system, lungs and kidneys.

Methyl mercury intake through fish can put unborn foetuses at great risk. The mercury can cross the placental barrier and cause foetal brain damage without any symptoms in the expectant mother. Newly born infants may experience mental and physical disabilities and delayed development of motor and verbal skills.

The symptoms of methyl mercury poisoning are varied and difficult to detect as they can mimic other illnesses. In relatively mild cases, the condition is barely distinguishable from common ailments. Some common symptoms are headache, fatigue, numbness of extremities, depression, memory loss, and in extreme cases, madness, coma or death.

Then why, despite such high levels of mercury in the environment and food chain, has India not yet witnessed a Minamata-like disaster? (see box)

To start with, no comprehensive study linking mercury pollution and health has been made in India. Mercury’s health impacts are chronic and take time to manifest. Short-term impacts are so similar to normal diseases that they are difficult to isolate. Long-term impacts, such as neurological disorders, cardio-vascular problems and possibly cancer, can also be caused by other factors. Although the cancer rate in India is growing alarmingly, nobody can say for sure that it is caused by mercury pollution.

Minimata was a small area, where a large proportion of people had similar diet patterns. In India, mercury poisoning affects a widespread population. Studies also indicate that a healthy diet could neutralise some adverse impacts of mercury. Therefore it is the poor who are the most affected. l

Minamata: a lesson not learnt

During the 1960s and 70s, the Minamata Bay mercury pollution disaster received global media attention, opening the world’s eyes to the negative health effects of methyl mercury. Between 1932 and 1968, the Japanese Chisso Corporation discharged about 27 tonnes of methyl mercury with its wastewater into the bay. The pollution caused severe damage to the central nervous system of the people who ate large quantities of contaminated fish and shellfish from the bay. In addition, congenital Minamata disease occurred as many infants were born with a condition resembling cerebral palsy caused by methyl mercury poisoning of the foetus during pregnancy. The disease, which was officially recognized on 1 May 1956, caused many people to lose their lives or suffer from physical deformities.
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After the cause of the disease was finally confirmed, a number of measures were implemented, ranging from regulation of the factory effluent, voluntary restrictions on harvesting of fish and shellfish from the bay, installation of dividing nets to enclose the mouth of the bay and prevent the spread of contaminated fish, and dredging of mercury-containing sediments. It was only in October 1997 that the dividing nets that had closed off the bay for 23 years were removed. After several studies confirming that mercury levels in fish were below regulatory levels and had remained so for three years, Minamata Bay was reopened as a general fishing zone.

Till 1992, 2,252 people were diagnosed with "Minamata Disease", with 1,043 deaths reported. ( Down To Earth, Sept. 15, 2002 )


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