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Maryland State Government Maryland Department of the Environment

General Mercury Information

What is mercury?

Mercury, chemical symbol Hg, is a silver-colored metallic element that is toxic to living organisms. At room temperature, elemental mercury is a liquid, conducts electricity, and mixes easily with other metals. Mercury also expands and contracts evenly with temperature changes. Elemental mercury easily breaks up into many small droplets and evaporates to form mercury vapor, a colorless and odorless gas. One of the organic forms of mercury, methyl mercury, is volatile, very water soluble, and the most toxic form of mercury. Mercury can cycle in the environment due to its ability to change forms.

Where is mercury found?

Although mercury is a naturally occurring element, more than two-thirds of the mercury in the atmosphere comes from human-made products and energy production activities. Mercury is released into the atmosphere through a variety of means such as evaporation from water and land, but primarily through coal-fired utility and incinerator emissions. Mercury gets into the soil through the natural breakdown of mercury-containing rocks, disposal of mercury in landfills, and atmospheric deposition. It enters the watershed through runoff, atmospheric deposition, and when mercury products are poured down the drain. Once in the water cycle, mercury can convert to methyl mercury. Methyl mercury can accumulate in the tissues of fish and other organisms inhabiting mercury contaminated bodies of water, and may be carried up the food chain.

What are the impacts of mercury exposure on humans?

Humans are exposed to mercury through their diet (primarily through fish), absorption, or through the inhalation of toxic elemental mercury fumes. Signs and symptoms of brief exposure may include coughing, shortness of breath, chest pain, nausea, vomiting, diarrhea, fever, and bronchitis. Long-term exposure can result in shakiness, tremors, loss of muscle control, memory loss, kidney disease, and loss of appetite and weight. The health effects due to mercury exposure depend on several factors, including the amount of consumed, absorbed, or inhaled mercury and the length and frequency of exposures. Also a person’s general health status, age, gender, family history, diet and lifestyle, and exposure to other chemicals may have an effect on whether the mercury causes an ill effect. Young children and fetuses are most sensitive to mercury poisoning during early development to age six.

What can you do to help prevent mercury pollution?

  • Once mercury is released it is difficult to remove, so the best practice is to prevent mercury from entering the environment, whenever feasible.
  • Mercury is being phased out of many retail products such as thermometers. However, as a consumer, educate yourself, do not buy mercury-containing items if a substitute is available. Below is a chart of items containing mercury and their alternative.
  • Separate out household products containing mercury (thermometers and the like) and dispose of them during hazardous household waste collection days, when other products such as paint and pesticides are collected.
Items with MercuryAlternatives
 Thermometers Red Bulb (Alcohol) Thermometers or Digital  Thermometers
 Non-Electronic Thermostats  and Thermostat Probes Electronic Thermostats and Sodium/Potassium  Thermostat Probes
 Barometers Aneroid Barometers
 Old Alkaline-Type Batteries  Prior to 1996 Rechargeable Alkaline or Mercury-Free Batteries
 Quicksilver Maze Toys (Old) Mercury-Free Toys
 Old Latex Paint (Before  1990) New Latex Paint
 Some Shoes that Light Up Mercury-Free Shoes
 Some Light and Appliance  Switches such as in clothes  irons or space heaters Mechanical or Electrical Switches such as magnetic  dry or optic sensor switches
 Contact Lens Solutions  Containing Thimerosal Solutions Without Thimerosal
 Button Batteries Mercury-Free Button Batteries
 Lamps (Fluorescent, High  Intensity Discharge and  Mercury Vapor Lamps) Low Mercury Fluorescent Lamps, Sulfur Lamps, Low  Mercury Sodium Lamps (Energy conserved by using
 these lights will reduce mercury emissions from
 coal & oil combustion)
  • Recycle button batteries.
  • Conserve electricity. If electric generating stations burn less coal and oil (that naturally contain mercury) they will emit less mercury into the environment.
  • Recycle and reuse as many products as possible to decrease the amount of waste that needs to be incinerated.