"Concept Paper"
How much fish should you eat? On the one hand, you hear fish is good for you. On the other, you hear that you're not supposed to eat too much of some types of fish, like tuna. How can something that's supposed to be good for you be harmful to your health? Fish are the main source of food for many birds and other animals, and mercury can seriously damage the health of these species. Loons, eagles, otters, mink, kingfishers and ospreys eat large quantities of fish. Because these predators rely on speed and coordination to obtain food, mercury may be particularly hazardous to these animals.
Mercury is released into the atmosphere when coal is burned. But breathing the mercury is not harmful. In the atmosphere, the mercury forms small droplets that are deposited in water or sediments.Do you know why you are supposed to eat large predatory fish like tuna infrequently? It is because of the bioaccumulation of mercury in those species.
Some pollutants remain in an organism throughout its life, a phenomenon called bioaccumulation. In this process, an organism accumulates the entire amount of a toxic compound that it consumes over its lifetime. Not all substances bio accumulate. Can you name one that does not? Aspirin does not bio accumulate; if it did, a person would quickly accumulate a toxic amount in her body. Compounds that bio accumulate are usually stored in the organism’s fat.
In the sediments, bacteria convert the droplets to the hazardous compound methyl mercury. Bacteria and plankton store all the mercury from all the seawater they ingest. A small fish that eats bacteria and plankton accumulates all the mercury from all the tiny creatures it eats over its lifetime. A big fish accumulates all the mercury from all of the small fish it eats over its lifetime. For a tuna at the top of the food chain, that’s a lot of mercury.
So, tuna pose a health hazard to anything that eats them because their bodies are so high in mercury. Therefore, the government recommends limits on the amount of tuna that people eat. Limiting intake of large predatory fish is especially important for children and pregnant women. If the mercury just stayed in a person’s fat, it would not be harmful, but that fat is used when a woman is pregnant or nursing a baby. A person will also get the mercury into her system when she (or he) burns the fat while losing weight. Methyl mercury poisoning can cause nervous system or brain damage, especially in infants and children. Children may experience brain damage or developmental delays. The phrase “mad as a hatter” was common when Lewis Carroll wrote his Alice in Wonderland stories. It was based on symptoms suffered by hatters who were exposed to mercury and experienced mercury poisoning while using the metal to make hats. Like mercury, other metals and VOCS can bio accumulate, causing harm to animals and people high on the food chain.
Burning coal releases mercury into the atmosphere. It falls into sediments and is converted into methyl mercury by bacteria. Creatures ingest the methyl mercury and store it. Then, larger creatures eat them and store all of that methyl mercury, on up the food chain. Mercury poisoning causes nervous system damage. Come join us in stopping the hazard and refresh the world with fresh air.