Mercury Exposure

By Aditya Seth

What is Mercury?

Mercury is a chemical element that is generally found in the Earth’s crust. There are 3 different types of mercury. The first type is methylmercury and other organic compounds and they are formed when mercury combines with carbon. The microscopic organisms convert the mercury into methylmercury, which is the most common organic mercury compound found in the environment. The second type is the elemental (metallic) mercury. It’s a shiny, silver-white metal and is liquid at room temperature. It is used in older thermometers, fluorescent light bulbs and some electrical switches. When dropped, elemental mercury breaks into smaller droplets which can go through small cracks or become strongly attached to certain materials. At room temperature, exposed elemental mercury can evaporate to become an invisible, odorless toxic vapor. If heated, it is a colorless, odorless gas. The third type of mercury are inorganic mercury compounds. They take the form of mercury salts and are generally white powder or crystals, with the exception of mercuric sulfide (cinnabar) which is red. Most uses of inorganic compounds have been discontinued.

How does Mercury get Emitted into Air?

Emission of Mercury from rocks into the air and water is a problem for the environment. The emissions can happen naturally. Both volcanoes and forest fires send mercury into the atmosphere. However, human activities are mainly responsible for much of the mercury that is released into the environment.  The burning of coal, oil and wood as fuel can cause mercury to become airborne, as can burning wastes that contain mercury. This airborne mercury can fall to the ground in raindrops, in dust, or simply due to gravity, which is known as air deposition. The amount of mercury deposited in a given area depends on how much mercury is released from local, regional, national, and international sources. Since mercury occurs naturally in coal and other fossil fuels, when people burn these fuels for energy, the mercury becomes airborne and goes into the atmosphere. In the United States, power plants that burn coal to create electricity account for about 42 percent of all manmade mercury emissions

    • Burning oil that contains mercury

    • Burning wood that contains mercury

    • Burning mercury-containing wastes, including wastes from the manufacture of Portland cement consumer products that contain mercury, like electronic devices, batteries, light bulbs and thermometers, that are thrown into garbage that is incinerated.

    • Using certain technologies to produce chlorine

    • Breaking products that contain mercury

    • Burning iron ore, coke and limestone in electric arc furnaces used to produce steel

    • Using coal-fired boilers in many industries to generate forms of thermal heat like steam

The most common way of getting exposed is by eating seafood with high levels of methylmercury (form of mercury that is toxic), in their tissues. A less common way people are exposed to mercury is breathing mercury vapor. This can happen when mercury is released from a container, or from a product or device that breaks. If the mercury is not immediately contained or cleaned up, it can evaporate, becoming an invisible, odorless, toxic vapor.

Health Effects:

Mercury has many adverse effects. Mercury exposure at high levels can harm the brain, heart, kidneys, lungs, and immune system of people of all ages. High levels of methylmercury in the bloodstream of babies developing in the womb and young children may harm their developing nervous systems, affecting their ability to think and learn.

Ecological Effects:

Birds and mammals that eat fish have more exposures to methylmercury than other animals in water ecosystems. Predators that eat these birds and mammals are also at risk. Methylmercury has been found in eagles, otters, and endangered Florida panthers. At high levels of exposure, methylmercury's harmful effects on these animals include; death, abnormal behavior, slower growth and development, and reduced reproduction.

Fish To Stay Away From/Safe to Eat

  • High Mercury Levels

    • Tilefish, King mackerel, Shark, Swordfish, Marlin, Orange roughy, Ahi Tuna, Bigeye tuna, Spanish mackerel, Gulf mackerel, Albacore tuna, Yellowfin tuna, Sea bass, Bluefish, Grouper.

  • Low Mercury Levels (Safe to Eat)

    • Salmon, Herring, Haddock, Anchovies, Butterfish, Crab, Clam, Crawfish, Catfish, Croaker, Flounder, Chub mackerel, Atlantic mackerel, Oysters, Pollock, Perch, Mullet, Muscles, Rainbow trout, Freshwater trout, Sardines, Shrimp, Scallops, Squid, Sole, Tilapia.