Deep in the equatorial rainforests of Guyane -- a small piece of France on the northeastern edge of South America -- thousands of noirs marrons , the descendants of escaped slaves, together with migrants from neighboring Brazil known as garimpeiros , scour the alluvial soil for gold. It's harsh work, and the rewards are meager. But for most of these people the only alternative is precarious subsistence farming, and the camps remain a powerful magnet as the price of gold soars on the world market.
The miners need all sorts of equipment: boats, excavators, shovels, hoses, pumps. But nothing is more vital to their endeavor than mercury. The silvery, liquid metallic element is all around us, and most of us know by now that it is dangerous stuff. The quantity released into the atmosphere by human activity each year is astounding: 2,000 to 3,000 tons. Eventually all of it falls back to earth, and because it never degrades, the amount of mercury contaminating our soil and water accumulates steadily and silently, year after year.
Once mercury enters lakes, rivers, and oceans, it can react with certain bacteria to become organic methylmercury, a neurotoxin. Fish consumption advisories -- especially for pregnant women, since exposure of the developing fetus to methylmercury is a particular risk -- are now in effect in every state in this country. Some ocean species like shark and swordfish contain such high levels of mercury that the Environmental Protection Agency starkly advises, "Do not eat."
It's tempting to imagine that the garimpeiros and the noirs marrons are only a marginal detail in the larger picture, compared with the threats posed by mercury in batteries and chlor-alkali plants, which produce chlorine and sodium hydroxide (or caustic soda), and by emissions from coal-fired power plants. But small-scale mining, though invisible to most of us, occupies as many as a million people in South America alone, and that's just a fraction of the global total. Worldwide, from Laos to Ghana, from Sudan to Indonesia, the industry employs as many as 10 million to 15 million miners, a figure that includes 600,000 child laborers. In most of the countries where this mining takes place, the import of mercury is banned for all but specified industrial purposes. But the reality is that borders are porous and laws remain unenforced. And while many developed countries have applied export restrictions, mercury is still readily available -- and cheap -- on the world market.