Mercury is a potent neurotoxin, and carcinogenic in large doses. In 1865, Lewis Carroll wrote about a character called the Mad Hatter in Alice's Adventures in Wonderland. The Mad Hatter was fictional, but the strange behavior he displayed was not. In the hatmaking industry in the 1800's, hatters used mercury in the felt-making process. Many hatters subsequently developed mercury poisoning.
Mercury attacks the central nervous system and can damage the brain, kidneys and lungs.
It crosses the blood-brain barrier as well as the placenta. Methylmercury, the most common and most dangerous form of mercury, is classified as a reproductive toxin for its effects on fetal development. During fetal development, exposure to methylmercury prevents the brain and nervous system from developing normally. Nurses are exposed to mercury in two ways. The first and most significant exposure occurs through human consumption of fish.