Mercury can find its way to the brain, warn scientists

Published: Wednesday 15 December 1999

for the first time, scientists have found convincing evidence that the blood-brain barrier, the nearly impenetrable membrane preventing entry of toxins into the brain, can be successfully invaded by the metal mercury. In a study conducted at Canada's Maurice La Montagne Institute and the University of Agricultural Sciences in Sweden, researchers have found that mercury dissolved in lakewater and riverwater can enter the nerves that connect water-exposed sensory receptors -- for odour, taste, vibration and touch -- to the brains of brown and rainbow trout.

Though the studies were conducted on fish, the findings have implications for humans, too, specially children. The researchers say this is the first study concerning mercury levels in fish brains, as opposed to levels accumulated in other body areas, and the first time it has been established that mercury can enter the brain through sensory receptors and their connected nerves. Fish use their nervous systems to find food, communicate, migrate, orient themselves and recognise predators.

Exposure to mercury can damage the brain and the nervous system, affecting language abilities, attentiveness and memory, particularly in children. The environmental group Clean Water Action has calculated that the average mercury level in the fish tuna is so high that eating as little as two ounces (about 57 grammes) of tuna a week would be unsafe for a child weighing about 16 kg.

"The accumulation of mercury or other toxic chemicals in the brain through water-exposed nerve terminals may result in an alteration of these functions and jeopardise fish survival," says Claude Rouleau, research scientist at Canada's National Water Research Institute and the primary author of the study which has opened an entire spectrum of possibilities.

While most people do not eat fish brain, the survival of the species does affect us. The most important fear is that mercury may reach brains of humans in similar ways.

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