Mercury is released into the atmosphere when coal is burned (Figure 1.1). 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 bioaccu- mulation 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 bioaccumulate. Can you name one that does not? Aspirin does not bioaccumulate; if it did, a person would quickly accumulate a toxic amount in her body. Compounds that bioaccumulate are usually stored in the organisms fat. In the sediments, bacteria convert the droplets to the hazardous compound methyl mercury. Bacteria and plankton store all of the mercury from all of the seawater they ingest (Figure 1.2). A small fish that eats bacteria and plankton accumulates all of the mercury from all of the tiny creatures it eats over its lifetime. A big fish accumulates all of the mercury from all of the small fish it eats over its lifetime. For a tuna at the top of the food chain, thats a lot of mercury. Historic increases of mercury in the atmo- sphere: blue is volcanic eruptions; brown, purple, and pink are human-caused. The red region shows the effect of industrial- ization on atmospheric mercury. So tuna pose a health hazard to anything that eats them because their bodies are so high in mercury. This is why 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 persons 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.
mad as a hatter
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 (Figure 1.3). Like mercury, other metals and VOCS can bioaccumulate, causing harm to animals and people high on the food chain. Mercury, a potent neurotoxin, has been flowing into the San Francisco Bay since the Gold Rush Era. It has settled in the bays mud and made its way up the food chain, endangering wildlife and making many fish unsafe to eat. Now a multi-billion-dollar plan aims to clean it up. Click image to the left or use the URL below. URL:
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mercury is released into the atmosphere when this is burned.
a) wood b) water --> c) coal d) none of the above
ingested mercury gets stored in which part of the body?
a) the skin b) the bones c) nerve cells --> d) fat
from what activity did the mercury in san francisco bays mud originate?
--> a) placer gold mining b) fishing c) construction of the bay bridge and golden gate bridge d) paint manufacturing
what is bioaccumulation?
a) when a substance decreases in concentration up the food chain. --> b) when a substance accumulates in an organisms body over its lifetime. c) when a substance is converted to a toxic substance by a living organism. d) all of these.
methyl mercury can ___.
a) poison the nervous system b) cause brain damage c) delay development --> d) all of the above
mercury poisoning can drive a person to be as mad as a hatter, which is based off of this novel.
a) tale of two cites b) harry potter c) lord of the rings --> d) alice in wonderland
mercury is a potent neurotoxin.
--> a) true b) false
mercury becomes harmful when it
a) drops to the ground and is ingested by organisms. --> b) is converted by bacteria to methyl mercury. c) is eaten by small fish. d) all of these.
all substances bioaccumulate.
a) true --> b) false
it is it better to eat fish that are low on the food chain than the large predatory fish because their bodies contain less mercury.
--> a) true b) false
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