At high enough levels it poisons its victims in terribly tragic ways. In Japan, victims of mercury poisoning came to be known as suffering from Minimata Disease, which took its name from the small Minimata Bay in which they caught fish for their food. For years, the Chisso Company, a chlor-alkali facility that manufactured chlorine, discharged mercury contaminated pollution in the bay, which was consumed by fish and then by people. Their disease was terribly painful, causing tremors and paralysis, and sometimes leading to death. Thankfully, wholesale discharges of mercury like those in Minimata Bay have been eliminated.
Mercury control needs to be a priority now because of the neurological damage it causes.
This is not to say that men, women and children are doubled over in agony as they were three decades ago in Japan. Mercury pollution today is more subtle, but it is no less insidious. Wildlife are also being harmed. Endangered Florida panthers have been fatally poisoned by mercury. Loons are endangered as well.