Ocean mercury on the increase
Mercury is being found in increasing quantities in the oceans recent studies suggest. Mercury is a neurotoxin with many side effects. Its toxicity was first documented in Japan and labelled Minimata Disease after the village in which many people were poisoned by it through eating fish high in mercury.
Mercury comes in many forms, a common one is elemental mercury which is relatively low in toxicity and has been used in silver almalgam tooth fillings. A much more toxic form of mercury is methylmercury. We get this form when microbes work on elemental mercury. It is this methylated mercury that fish take up when feeding and incorporate into their bodies. When people eat those fish they get a dose of the poison. The fish that carry the highest load of mercury are those that are at the top of the food chain like tuna and swordfish.
Mercury levels in the Pacific Ocean are rising, a new study suggests.1 The increase may mean that more methylmercury, a human neurotoxin formed when mercury is methylated by microbes, accumulates in marine fish such as tuna.
The group's modelling indicates that atmospheric deposition of mercury could lead to a doubling of the total ocean mercury concentrations recorded in the mid-1990s by 2050.
The researchers also hypothesize that waters in the western Pacific could be picking up mercury deposited from increasing atmospheric emissions in Asia, and then moving to the northeast Pacific.
Children and the unborn are at most risk for damage from methylmercury.
The nervous system is very sensitive to all forms of mercury. Methylmercury and metallic mercury vapors are more harmful than other forms, because more mercury in these forms reaches the brain. Exposure to high levels of metallic, inorganic, or organic mercury can permanently damage the brain, kidneys, and developing fetus. Effects on brain functioning may result in irritability, shyness, tremors, changes in vision or hearing, and memory problems.