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Cesium, Cadmium, and Caribou
Some Facts About Heavy Metals and the Food Chain

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What begins with "C" and ends in trouble? Cesium, cadmium and caribou. Over the years scientists have studied the effects of toxic materials that find their way into the environment and the foods we eat.

Caribou and Cesium Alert
You might remember hearing about the explosion of the nuclear power plant in Chernobyl (in the former Soviet Union) in 1986. The explosion caused a huge radioactive cloud to drift across the northern atmosphere toward Alaska and Canada. Part of the nasty radioactive material found in this cloud was an element called radio-cesium. People were really nervous and anxious to learn more about cesium and it's potential threat to their environment. Testing was done to find out whether it was safe to eat caribou meat in Alaska and Canada. Turns out that it was safe, but we were alerted to the possible health threats that environmental polutants might have in the northern wildlife habitats.


Snow craters where caribou dig for lichens.

Lichen-Winter caribou food
Photo courtesy USGS

Some of the research resulting from the Chernobyl accident led scientists to take samples from the Porcupine caribou herd in the late 1980s. They were particularly interested in looking at their cadmium levels.Cadmium is a heavy metal. No, I'm not writing about electric rock 'n' roll here! Heavy metals are a group of minerals that have always been found in our natural environment in minute amounts until recent centuries, when the orientation toward industrialization and production brought about our many technological advances. Wastes containing some heavy metals are released into the air from industries like mining, smelting, and manufacturing. These heavy metals, including cadmium, attach themselves to dust particles and float around until brought down to the earth by rain or snow. Northern industrial sites release pollutants that can drift for miles before falling to the earth in precipitation.

What does this have to do with caribou? We are all part of a huge food chain. Caribou eat plants called lichens all winter long. Lichens are high in carbohydrates and have the most food value of any plant available to the caribou. The extremely short growing season in the Arctic (sometimes only 40 days lont) prevent lichens from growing very much each season. This combination of factors leaves lichens exposed to cadmium for many years. Caribou can be at risk for exposure to cadmium more than other animals in the Arctic ecosystem.

Questions of Toxicity
When there are too many harmful things in the air, lichens die. This is why they are sometimes called "indicator" species. They can tell us if the air is clear and clean. Even in the remote arctic, pollution has contaminated lichens. Pollutants have drifted through the atmosphere, appeared in the lichens, then in the flesh of the caribou--and then in the humans who eat the caribou.Testing has been done on caribou to see if levels of cadmium would be dangerous to the animals and to people who rely on caribou meat in their diet. It turns out that animals (and humans) have natural methods for taking heavy metals out of our bodies. Special proteins mop up excess metals and most of it ends up in the kidneys(which are blood filters). Experts found that caribou meat was safe. But it is best to limit your consumption of caribou kidneys.

Try This! Research Idea
Cadmium is naturally found in the ground along side another metal, zinc. When mining for zinc, cadmium comes along and is processed with the zinc. We have many uses for zinc.Research some products that contain zinc that we would use in our every day lives. How might some of these products become contaminants that could get into our bodies?