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Mercury
Description: Mercury (C.A.S. 7439-97-6) is an element that occurs naturally in the environment. It is a silver-white, heavy metal that is liquid at room temperature; as a solid, it is tin-white and can be cut with a knife. It can also be found in compounds with other chemicals such as chlorine in the same way that sodium is found in table salt. Mercury is used in pure form in thermometers, barometers, and other consumer products. Batteries containing mercury are used in devices ranging from guided missiles and space craft to hearing aids, cameras, toys, portable radios, calculators, measuring devices, smoke alarms, self-winding watches, and radio microphones. Electric or mercury lamps are used for outdoor lighting, including floodlights and street lights, motion picture projection, health treatment, and photography. Mercury is also used as a catalyst in the production of vinyl chloride monomer, urethane foam, and anthraquinone. It is used in diuretics, antiseptics, and skin preparations. Prior to August 20, 1990, mercury was added to paints as an anti-mildew agent, antibacterial agent, and fungicide; about one-third of all interior latex paint contained varying levels of mercury. (Oil-based paint does not contain mercury.) Mercury is also used in pigments, refining, lubrication oils, and dental amalgams. Mercury in one form, "organic mercury," can become highly concentrated in the flesh of certain fish. For this reason relatively low levels of mercury contamination in the ocean and lakes can lead to toxic contamination of these fish. Organic compounds of mercury are phenylmercury acetate (C8H8HgO2) and methylmercuric chloride (CH3HgCl). Other compounds of mercury, called "inorganic mercury," are mercury, mercuric II acetate or mercury salt (HgC4H6O4c), mercuric II chloride (HgCl2c), and mercurous I chloride (Hg2Cl2c). Chemical properties: Mercury that is released into the environment will remain there indefinitely. The form that mercury exists in (organic or inorganic) may change with time. Some or all of released organic mercury will slowly decompose to become inorganic mercury. Some portion of released inorganic mercury will be slowly transformed into organic mercury by bacteria in soil or water. Mercury is not flammable and does not have an odor. Some mercury salts and organic compounds are soluble in water, depending on the chemical species. Synonyms for mercury are colloidal mercury; kwik; liquid silver; quicksilver; metallic mercury; and hydrargyrum. Identification: Health effects: Mercury, in both inorganic and organic forms, is toxic to humans and can cause death. The organic forms of mercury such as methylmercuric chloride and phenylmercuric acetate have been found to be more toxic than inorganic forms such as mercuric chloride. More severe effects on developing nervous systems are generally observed following exposure to organic mercury. Deaths have been reported following acute exposure to high unspecified concentrations of metallic mercury vapor caused by a loss of respiratory function as a result of severe pulmonary tissue damage. Oral ingestion of single doses of mercuric chloride has led to poisoning and death caused by shock, cardiovascular collapse, acute renal failure, and severe gastrointestinal damage. Most reported cases of poisoning from organic mercury compounds are a result of the ingestion of contaminated fish or grains. Long-term exposure to either organic or inorganic mercury can irreversibly damage the brain, kidneys, or developing fetuses. The form of mercury and the way humans are exposed to it influence which of these health effects will be more severe. For example, organic mercury that is eaten in contaminated fish or grain will tend to cause greater harm to the brain and developing fetuses than to the kidney; inhaled inorganic mercury vapor will tend to cause greater harm to the brain; and inorganic mercury that is eaten or drunk in contaminated food or water will tend to cause greater harm to the kidneys. Effects to the developing fetus include brain damage. Effects in adults briefly exposed to mercury include shakiness, tremors, and memory loss. Exposure Values: Economics: U.S. manufacturers of mercury are Centerchem, Inc, New York, NY; Rascher & Betzold, Inc, Chicago, IL; SST Corporation, Clifton, NJ; Eastman Kodak Laboratory and Specialty Chemicals Eastman Kodak Co, Rochester, NY; Spectrum Chemical MFG Corp, Gardena, CA; D F Goldsmith Chemical & Metal Corp, Evanston, IL; and Belmont Metals, Inc, Brooklyn, NY. Mercury is produced mainly by mining. Five percent of the world mercury production is a by-product of gold mining, and most of the remaining mercury is produced from underground mines. Some salvage is done on scrap materials as well. U.S. production of mercury in 1985 was 1,254,000 pounds; world production in 1986 was 13,376,000 pounds. In 1986, almost 1,520,000 pounds of mercury were imported to the United States. Regulation: The U.S. Food and Drug Administration (FDA) has issued permissible levels of mercury in bottled water. The Occupational Safety and Health Administration (OSHA) has issued permissible exposure limits for mercury. The U.S. Environmental Protection Agency prohibited adding mercury to paint after August 20, 1990. However, paint manufactured before that ban can still be sold. EPA offices overseeing regulations and guidelines for mercury are Air Quality Planning and Standards, Water and Standards, Emergency and Remedial Response, Solid Waste, and Toxic Substances. Under the Emergency Planning and Community Right-to-Know Act of 1986, releases of more than one pound of mercury into the air, water, or land must be reported annually and entered into the National Toxic Release Inventory (TRI). Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of mercury into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). National Overview of 1998 Toxics Release Inventory See EPA's Toxic Release Inventory. Notations: The NIOSH recommended exposure limits (RELs) are time-weighted average (TWA) concentrations for up to a 10-hour workday during a 40-hour workweek. A short-term exposure limit (STEL) is designated by "ST" preceding the value; unless noted otherwise, the STEL is a 15-minute TWA exposure that should not be exceeded at any time during a workday. A ceiling REL is designated by "C" preceding the value. Any substance that NIOSH considers to be a potential occupational carcinogen is designated by the notation "Ca." The OSHA permissible exposure limits (PEL) are found in Tables Z-1, Z-2, and Z-3 of the OSHA General Industry Air Contaminants Standard (29 CFR 1910.1000). Unless noted otherwise, PEL are TWA concentrations that must not be exceeded during any 8-hour workshift of a 40-hour workweek. A STEL is designated by "ST" preceding the value and is measured over a 15-minute period unless noted otherwise. OSHA ceiling concentrations (designated by "C" preceding the value) must not be exceeded during any part of the workday; if instantaneous monitoring is not feasible, the ceiling must be assessed as a 15-minute TWA exposure. In addition, there are a number of substances from Table Z-2 (e.g., beryllium, ethylene dibromide, etc.) that have PEL ceiling values that must not be exceeded except for specified excursions. For example, a "5-minute maximum peak in any 2 hours" means that a 5-minute exposure above the ceiling value, but never above the maximum peak, is allowed in any 2 hours during an 8-hour workday. Information Sources:
Originally published in Environment Writer by the National Safety Council. Reprinted with permission. Environment Writer Metcalf Institute for Marine and Environmental Reporting University of Rhode Island Graduate School of Oceanography Office of Marine Programs Narragansett, RI 02882 Tel: 401-874-6211; Fax: 401-874-6485 Disclaimer * Copyright 2002-2006 * All rights reserved. * University of Rhode Island |