The EPA information on this subject can be found here, just in case you prefer not having all your information filtered through Mother Jones' kidneys.

There are natural sources of mercury as well, both elemental and otherwise. Few people have a good idea of how much of it there is. I have seen numbers as low as equal to human-caused amounts, and numbers as high as 3,000 tons per year.

The real solution, of course, is phasing out coal power in favor of nuclear. See what Mother Jones thinks of that.

The article was worth reading, if only to see Molly Ivins expressing sudden concern for unborn fetuses.