Mercury Alert!

Mercury is a lovely and unique mineral. It is the only metal that is a liquid at normal room temperatures. Mercury flows so beautifully that it is also called quicksilver. Ancient people in China, Egypt, Greece, India, and Rome knew about mercury, which was named for the swift messenger in Roman mythology. (The quick-moving planet was also named for the same Roman character.)

Mercury has many wonderful uses. It expands and shrinks evenly as the temperature rises and falls, making it perfect for filling thermometers. Mercury mixed with zinc and cadmium makes batteries last longer. It used to be used a lot in house paints to protect them from the elements, make them stronger, and to make wonderful red tints. Mercury vapor gives off light when electricity passes through it, so mercury is used in fluorescent lights. And doctors used mercury as a very effective antibiotic on wounds.

Loon Research: Feathers, blood and bands

But despite all mercury's useful properties, it is extremely poisonous to humans and animals--especially loons. Eating a very tiny amount of mercury won't cause serious harm for a critter or person, but the problem is that mercury is a cumulative poison. This means the body has a very hard time getting rid of it. Little by little, mercury accumulates in someone exposed to it over time. Eventually the buildup reaches dangerous levels.

Mercury, like other metals, occurs naturally in rocks. When a rock containing mercury dissolves or breaks up, mercury is released into water, air, or soil. Bacteria take in tiny particles of mercury, combining it with methane to produce methyl mercury. This is the most toxic form of mercury, and it can damage brain cells.

Loon Feathers: A Clue to the Past
Mercury eaten by loons is carried by their blood to many body tissues, including growing feathers. When the feathers stop growing, they stop taking in mercury. By analyzing loon feathers, scientists can determine how much mercury a loon was exposed to during the time it molted into its feathers. The mercury stays in the feathers as long as the feathers exist. This means that scientists can analyze feathers from loons in museums to find out how much mercury loons in different places were exposed to over a hundred years ago!

Mercury Studies and the Food Chain Connection

Phytoplankton (algae)

All natural systems have tiny amounts of mercury. Environmental scientists measure the amount of some chemicals in lakes in "parts per billion" (ppb). One lake with moderate levels is Little Rock Lake, in northern Wisconsin. In Little Rock Lake, mercury levels are about 0.0001 ppb. This means 0.0001 grams of mercury for every billion grams of water.

EPA scientists studying Little Rock Lake have measured the amount of mercury in various living things in the lake. This is what they found:

Methyl-Mercury in Little Rock Lake


Amount of Mercury


0.0001 ppb

Phytoplankton (algae)

15 ppb

(water fleas)

54 ppb


200 ppb


1250 ppb


not tested

The amount of mercury in algae is 150,000 times the amount in the water! This is because the tiny plants "bioaccumulate" the mercury. At each level of the food pyramid, the animals have more mercury buildup than the level beneath.

Why do mercury levels jump so much at each level of the food chain?

In one Ontario study area where loons were exposed to 2-3 parts per million (that is, 2000 - 3000 parts per billion) in their food, mercury levels in loon brain tissue reached 200 - 400 parts per billion. This level affected their behavior and reproduction. In another Ontario study area, yellow perch levels reached 0.36 parts per million (360 parts per billion). Not one loon successfully hatched chicks.

In the Little Rock Lake study and the Ontario Study, what factors might have contributed to the differences in data?

Hazardous Waste: How Can We Help?
  1. Keep hazardous waste in its place. Find your local waste disposal facility in your phone book. As a class project, find out where your garbage goes, and how people in your area should dispose of old thermometers and other products that may contain mercury. You might even write a letter to the editor of your local newspaper telling people how they should dispose of these items and why it's important. Remember: When garbage is burned, some of the material ends up in the air, often as pollution. When garbage is buried, sometimes rain washes poisons from it through the soil into the groundwater. Not long ago, the mercury from button batteries, high-efficiency light bulbs, fluorescent lights, paints, and thermometers ended up in our water or air. Now batteries are manufactured with different chemicals, and many people are choosing non-mercury thermometers. But it's still critical to make sure old thermometers and fluorescent bulbs are disposed of properly. Most localities now have a way of recycling these dangerous items if they are brought to a hazardous waste disposal site. Where is YOURS?

  2. Going Fishing? Get the Lead Out! Buy lead-free sinkers and use them when fishing. A company called Bullet Weights will send information and steel sinkers to the first 500 students who write. Read more about how lead affects loons, and find out how to get steel sinkers for fishing at:

Lead and mercury aren't good for ANY living things. A world safer for loons is a world safer for us all!