Mercury was heavily mined in the form of cinnabar for use in gold extraction during the famous Calif gold rush. But after it got washed down
the creeks and rivers it changed into hazardous form, and tends to collect in certain fish. I have a co-worker who ate tunafish sandwiches
almost every day who had to be treated for mercury poisoning, and once had a doctor who went berserk for the same reason, and got carted off to the funny farm. But the worst cases of mercury poisoning I see are older house painters who worked with a lot of early latex primers (ca 1950's) which contained mercury. The effect is pretty ugly. Kidneys and liver get all messed up, behavior gets mean and unpredictable. Not just mad hatter, but mean hatter. I certainly wouldn't want to be around mercury fumes either. Fume hoods were invented for a reason. Thanks goodness we're living in a more modern age, when all we have to worry about is ordinary light bulbs being
banned, and CFL's containing mercury being mandated!