Burning coal releases mercury into the atmosphere. Breathing in mercury isn’t harmful, but ingesting it is. Mercury condenses into methyl-mercury, which then deposited into water.
Bioaccumulation in aquatic animals is when pollutants they’ve ingested continue to remain in their bodies. As more and more mercury is accumulated going up the food chain, bigger fish are left with the most amount of this chemical in their bodies. Therefore, we can’t eat certain types of fish (such as tuna) frequently, because they contain so much mercury that it will be harmful to us.
Methyl-mercury poisoning can cause brain damage and developmental delays. It also is stored in the fat women develop when they’re pregnant or nursing, causing harm to their babies.