Rabbit Hole: Mercury Pollution

I recently started giving tours for an historical society at an old Colorado hydraulic mine site. We start by telling people the history of mining in the area in an old barn, then take them outside to show them the manmade gulch, then we take them in an old assayers office and describe how mercury was used to make the gold heavier so the miners didn’t miss any. They coated their sluice boxes with “quicksilver,” then to separate the gold and mercury, they vaporized it. Mercury was in the air, the water, the plants and animals, and the people. There are a lot of 150+/- year old baby graves in our local cemetery. After a few weeks of telling this story, it dawned on me to wonder: What happened to all that mercury? Did it wash away, or have a short half-life?

Nope.

Technically, this was more of a vole hole. I started out looking up how silver was mined, and came upon an article about a mine clean up near by. The article talked about how sulfides exposed to air and water from mining turn into sulfuric acid and wash into the creeks and kill all the fish. It’s why some little “creeks” draining from mines run over orange rocks. The water may look clear, but it’s super acidic. When I looked up what sulfide minerals were the list included pyrite and galena, which I interact with a lot as work when we take visitors gold panning after the history tour. This reminded me of the Mercury.

It turns out Mercury doesn’t just go away. In fact, it will likely take 10,000 years. Mercury easily combines with lots of elements including sulfides making mercury salts that enter the water and soil or weather down to dust sized particles that can blow up into the air. Like during construction…in a town that used to be a mining town…but is now all about development…I mean skiing. It can also be consumed by microscopic organisms, who combine it with carbon making the very toxic methymercury. Which fish eat, and then we eat. So much for Rocky Mountain Trout.

It turns out this is a world wide problem and a modern problem as gold mining world wide still releases over 1,000 tons of mercury a year. When they’re not using mercury, mines are using cyanide. So I had to ask our local Environmental Health department—the people who tested our well for dangerous bacteria—if they test for Mercury in the land or water. They do not.

Given that I grew up in a hard-rocking mining town that claims it started the gold rush (nearly every town in Colorado does), I wondered if Mercury was used in more than just hydraulic mining. Yup. And as far as I can tell, there is not a state or county management plan for Mercury contamination testing or handling in the soil. I live on an old hydraulic mine site (that the freed black men who mined it found enough gold to buy their families from enslavers), and the men who built our garage, which required digging down into the ground, did not do any contamination mitigation or wear protective gear.

Mercury contamination is high in most of the Western U.S. from modern agriculture, fires, and development in addition to historic mining, and is an important public health and environmental issue. While Mercury can poison anyone, it is especially detrimental to children and fetuses. Inorganic Mercury (the salts that become dust when combined with other elements) is dangerous when inhaled and can cause lung problems, nausea or vomiting, and bleeding or swollen gums. (Is it asthma or mercury?) Organic Mercury (methylmercury made from combining with microscopic organisms) can cause numbness, tremors, and neurological problems.

I don’t know how much Mercury I’ve been exposed to, absorbed, or consumed, but given that the mountain communities I’ve lived in are known for long life spans12, it’s probably not too bad. Although, I’ve always thought there was something in the water making the people up here a little crazy, or as we used to say “mad as a hatter”.