A 65-year old man is brought to the hospital by his concerned wife. Over the last few months, her husband has become irritable, he is starting to bump into things when walking, and she has to yell at him to get his attention. You find out from talking with the couple that six months ago they moved to a new house on a lake, that she is a vegan, and that he is an avid fisherman. What environmental toxicant do you suspect the man may have been exposed to (explain your reasoning)? Assuming your suspicion is correct, explain to the couple the likely exposure source and one possible treatment for this toxicant.