Mercury And The Environment

Abstract

One of my favorite foods is fish. I love it baked, seared, fried, sautÐ"©ed, and raw. I've never given much thought as to what is in the fish. I know it to be high in protein, low in saturated fat, offer good nutrition, and are delicious. What I did not know is how much mercury may also be lurking in the fish.

Many streams and lakes have signs posted that warn people not to catch fish. Other places have signs posted that warn people of the dangers of eating the fish. Even the streams and lakes that have no warning signs posted at all still make you wonder if it's safe to eat the fish that is caught at these places.

Mercury's Effect on Community Health

Introduction

One of my favorite foods is fish. I love it baked, seared, fried, sautÐ"©ed, and raw. I've never given much thought as to what is in the fish. I know it to be high in protein, low in saturated fat, offer good nutrition, and are delicious. What I did not know is how much mercury may also be lurking in the fish.

Many streams and lakes have signs posted that warn people not to catch fish. Other places have signs posted that warn people of the dangers of eating the fish. Even the streams and lakes that have no warning signs posted at all still make you wonder if it's safe to eat the fish that is caught at these places.

Mercury and it's Forms

Mercury exists in several forms and occurs naturally in the environment. These forms can be organized under three headings: organic mercury, inorganic mercury, and metallic mercury (also known as elemental mercury).

When carbon combines with mercury, the compounds formed are called "organic" mercury compounds or organomercurials. There are a large number of organic mercury compounds; however, the most common organic mercury in the environment by far is methylmercury (also known as monomethylmercury).

Inorganic mercury compounds occur when mercury combines with oxygen, sulfur, or chlorine. These mercury compounds are also called mercury salts. Inorganic mercury compounds are crystals, or white powders.

Metallic mercury is a silver-white, shiny metal that at room temperature is a liquid. Metallic mercury is the familiar liquid metal used in some electrical switches and thermometers. Some of the metallic mercury will evaporate at room temperature and form mercury vapors. Mercury vapors are odorless and colorless. More vapors are released from liquid metallic mercury when the temperature rises. People have reported a metallic taste in their mouth when these vapors are breathed in. (Trick.B, March 2007, page13)

How Mercury Enters the Environment

Mercury occurs naturally throughout the environment. Volcanic activity and normal breakdowns of rocks and minerals cause mercury to enter our environment. Releases of mercury from natural sources have remained constant in recent history, which causes a steady rise in environmental mercury. The industrial age has contributed to the amount of mercury in our environment, by the burning of fossil fuels and mining.

Human activities have contributed from one-third to two-thirds of the total mercury releases. Mercury levels in the atmosphere (the air you breathe) are thankfully low, and do not pose an immediate risk to your health; however, the current levels of mercury are three to six times higher than preindustrial atmospheric levels. Human activities are responsible for 80% of the mercury released. This mercury is elemental mercury, which is released from solid waste incineration, smelting, mining, and fossil fuel combustion. Fungicides, fertilizers, and municipal solid waste (thermometers, electrical switches, or discarded batteries) are responsible for 15% of mercury release from soil. Industrial wastewater is responsible for 5% of mercury being released to water in our environment.

Inorganic mercury and metallic mercury enters the air from mining deposits, from coal-fired power plant emissions, from burning medical and municipal waste, from cement production, and from factories that use mercury. Some of the metal from metallic mercury will evaporate into the atmosphere and can be carried long distances by wind. Mercury vapor in the air can be changed into other forms of mercury, and can be transported further to soil or water in snow or rain. Water or soil from the weathering rocks that contain mercury is also responsible for the introduction of inorganic mercury into the community. (ATSDR, 1999, Pages 2-6)

How Might People be Exposed to Mercury

Everyone who walks the earth is exposed to low levels of mercury. Mercury occurs naturally in the food we eat, water we drink, and the air we breathe. Urban outdoor measurements of mercury have been measured at 10 and 20 nanograms per cubic meter. These levels are considered safe and are hundreds of times lower than levels considered to be unsafe to breathe. Levels are even lower, about 6 nanograms or less in nonurban settings.

Many people are exposed to metallic mercury from dental amalgam fillings. An amalgam used in silver-colored dental fillings contains 50% metallic mercury, 35% silver, 9% tin, 6% copper, and trace amounts of zinc. When first mixed, the amalgam is a soft paste which is inserted into the surface of the tooth. In 30 minutes the amalgam hardens. The mercury is bound once the amalgam hardens, but small amounts of mercury are released from the filling surface due to grinding motions, chewing, or corrosion. The mercury at the filling surface may enter the air as mercury vapor or be dissolved in the saliva. The total amount of mercury released from dental amalgams depends upon how big the surface areas are of each filling, the chewing and eating habits of the person, the total number of fillings, and other chemical conditions of the mouth. The total amounts of mercury released from dental amalgams have been estimated to range from 3 to 17 micrograms per day. The mercury that is found in dental amalgams contributes