Mercury poisoning disease re-emerges

Deforestation of the Amazon rainforest has been blamed

A debilitating illness of the nervous system caused by mercury poisoning has re-emerged, scientists have warned.

Minamata disease causes serious damage to the nervous system, resulting in uncontrollable shaking and muscle wasting.

It also produces appalling deformities in the children of sufferers.

New Scientist magazine reports that the disease has been found in the fishing communities of the remote Amazon rainforest.

It is the first time it has been diagnosed outside the Japanese town from which it takes it name and where about 1,500 contracted symptoms in the 1950s.

A toxic, organic form of mercury known as methyl mercury is believed to be responsible for the disease.

The Japanese victims had eaten fish from a bay polluted by mercury from a metals plant.

Methyl mercury is present in fish in the Amazon region.

However, there is confusion about whether it comes from gold mining or soil deposits that collect following deforestation.

Maszumi Harada, an expert on the disease from Kumamoto University, examined 50 people from ten villages around San Luis do Tapajós who had high levels of methyl mercury in their bodies.

He found three with nervous symptoms peculiar to Minamata disease, including fits of trembling.

In the past, most cases of mercury poisoning in the Amazon have been among the million gold miners in Brazil, who use mercury to purify gold, and their families.

Many had directly inhaled mercury fumes. The Minamata cases, however, involve methyl mercury, and the sufferers live hundreds of kilometres from the nearest mine.

Destroys personality

Gold mining is also a possible source of mercury

Methyl mercury attacks the cerebellum, which coordinates voluntary movements, and destroys the personality.

Hiroshi Takahasi, an epidemiologist with the Japanese Ministry of Health and Welfare, said: "Survivors in Minamata are still suffering. It should not happen again."

But Harada says he expects to find many more victims in the Amazon.

A team from the University of Quebec at Montreal has also found neurological symptoms in the Amazonians.

These included involuntary shaking, sensitivity to bright light, partial blindness and loss of muscle strength.

Both research teams pinned the blame on the consumption of methyl mercury in fish.

They agree that bacteria living in oxygen-starved conditions in river sediments are believed to convert inorganic mercury into the dangerous methylated form.

But they disagree on the origin of the mercury.

Harada believes the source is mercury used by gold miners. Miners release about 250 tonnes of mercury into the Amazon region each year, most ending up in rivers.

The Canadian team, however, thinks deforestation is the problem.