Didn’t the ecos decide it wasn’t atmospheric, but rather fish born concentrations or some such?
And, in an attempt to be serious for a sec, does mercury occur at all, naturally, in water sources? Seems lots of minerals do, salt and such. I know uranium in ground water is an issue in places long the Sierra Nevadas because of natural deposits of the stuff, as well as some from older mining efforts.
Not saying human causes should or could be nil, just curious about how the natural part might also be working in to the problem.
In some places in the western US they are trying to reduce radon in drinking water, not because it is harmful to drink, but people breathe it in when they shower and it's dangerous to the lungs. The radon limits are based on the exposure of a person taking a 20-mintue shower every day (or something like that). Unfortunately the areas where radon is a concern in drinking water also have have high levels in the air they breathe everyday. Many cities in the west were required to put in expensive water treatment facilities to remove radon, but they still get more exposure just walking down the street than they ever got in their showers.
Of course, radon is a gas that is created naturally by uranium and other radioactive elements in the ground. Radon dissolves easily in groundwater but it evaporates out of the water after it comes out of your tap.