Mercury Defined

Mercury is a naturally-occurring element found in three general forms – elemental (also called metallic), inorganic, and organic. In its elemental form, mercury is a shiny, silver-white, dense, and odorless liquid.metal. Metallic mercury is used in the production of chlorine and caustic soda, and is also used in common items such as thermometers, dental fillings, electrical switches and batteries. When liquid mercury evaporates, it forms a colorless, odorless gas. This gas is dangerous at levels as low as 0.1 mg per cubed meter of air.

Mercury can combine with other elements, such as chlorine, sulfur, or oxygen, to form inorganic compounds. These mercury salts are usually white powder or crystals. Mercuric sulfide, however, is red. Hence, it is commonly referred to as cinnabar.

Methyl mercury, the most common organic mercury compound and the form that poses the greatest threat to humans and the environment, is created when microorganisms, such as bacteria, metabolize elemental or inorganic mercury.

Mercury Poisoning, Health Effects

Mercury is a toxic substance and should be avoided. Dangerous exposure occurs through inhalation or bodily contact with elemental mercury, or through consumption of food (generally fish) or water contaminated with methyl mercury. Inhaled mercury and methyl mercury are particularly hazardous. Only 25% of inhaled mercury vapors are exhaled.(1) Methyl mercury is the most toxic form and is absorbed by the human body 10,000 times more effectively than ingested elemental mercury.(1) Listed below are the various health effects which may result from contact with the various forms:

Methyl mercury attacks the central nervous system and, in some cases, can cause irreversible brain damage. In mild cases, adults complain of motor skill reduction and dulled senses. Symptoms generally disappear if mercury exposure ends. At higher levels, methyl mercury can deteriorate the nervous system, impair movements and senses, cause involuntary movements, and cause difficulty chewing and swallowing. It can also affect the genetic and enzymatic systems.

Children born to women exposed to relatively high levels of methyl mercury during pregnancy have exhibited numerous abnormalities, including delayed onset of motor skills and reduced neurological test scores. Even children born to women experiencing far lower level methyl mercury exposure exhibited delays in learning and deficits in ability. Embryos have been shown to be 5 to 10 times more susceptible to mercury’s effects than adults.

In 2000, the National Academy of Sciences reported that “over 60,000 newborns annually might be at risk for adverse neurodevelopmental effects from in utero exposure to methyl mercury.”(2)

Using data from the Centers for Disease Control, the U.S. Environmental Protection Agency, in March 2001, estimated that 10% of US women of child-bearing age have levels of mercury that double their risk of having babies born with mental or neurological problems.(3)

Mercury Poisoning Events and Studies

Mercury poisoning most often occurs when methlymercury makes its way into the food supply. Several large scale poisonings have occurred.

Japan

Between 1932 and 1968, the Chisso Corporation dumped more than 27 tons of mercury compounds into Minamata Bay, Kyushu, Japan.(4) Mercury levels reached 50 ppm in fish and 85 ppm in shellfish.(5) Fish consumption led to an array of problems. Forty-six people died initially and perhaps as many as 900 died eventually.(4) Anywhere from 3,000 to 20,000 more experienced effects, such as lip numbness, slurred speech, serious brain damage, unconsciousness, and involuntary movements.(4) People witnessed cat “suicides” and birds dropped out of the sky.(4) Dogs, rats, and cats also showed signs of poisoning. The symptoms were coined “Minamata Disease.”

In 1965, a similar event occurred in the area of Niigata, Japan, when 120 were poisoned.(6)

Iraq

In 1971-1972, approximately 6,500 people fell ill and 459 people died after eating wheat bread baked with seeds treated with a mercury-based fungicide.(7) The bread contained an average of 7.9 ppm methyl mercury.(7) Signs and symptoms of poisoning included incoordination, sensory disturbance, visual difficulties (including blindness), and slurred speech. Some infants showed nervous system damage.

Faroe Islands (North Atlantic)

A study started in 1984 investigated the effects of methyl mercury exposure on children born to mothers who ate contaminated whale meat. Researchers found that children born to mothers with mercury levels between 10 and 20 ppm had lower language, attention, and memory scores than children born to mothers with lower mercury levels.(8)

Amazon

Scientists have observed what may be a re-emergence of “Minamata Disease” in the Amazonian region. In the past, mercury poisoning had been limited to the million or so gold miners in Brazil and their immediate families, who had come in contact with mercury in its gaseous or liquid form. Recently, however, two research teams found symptoms of mercury poisoning in fishing villages hundreds of miles from the nearest gold mine. Both teams blame the symptoms on consumption of fish contaminated with methyl mercury. The teams disagree on the origin of the mercury – one blames the gold mines that release 250 tons a year; the other blames soil disturbance resulting from deforestation, and the resultant mobilization of mercury in the soil.(9)

Fish Advisories

By far, mercury is the #1 contaminant of our nation’s waters. Almost 75% of all 2002 fish consumption advisories were issued at least in part for mercury contamination. Forty-five states issued mercury advisories in 2002, compared to 27 in 1993. Mercury advisories covered 12,069,319 lake acres and 473,186 river miles.

Nineteen states issued statewide advisories for lakes, rivers, or both:

Additionally, mercury advisories were issued for every Great Lake but Ontario.

Eleven states issued statewide advisories for mercury in coastal waters:

Methylmercury concentrates in muscle tissue, so, unlike PCBs which concentrate in skin and fat, mercury cannot be reduced by skinning, trimming, or “cooking it out.”

All information in this section was derived from the May 2003 US EPA Fact Sheet: “Update: National Listing of Fish and Wildlife Advisories.”

The Mercury Cycle

Apart from a few mercury ore deposits, the amount of mercury naturally occurring in any one place is usually very low. Trace amounts of elemental mercury occur naturally in the earth’s crust. When rocks and soil deteriorate, this mercury is released. It is estimated that between one- and two-thirds of total mercury releases result from human activities, like mining and fossil fuel-burning.

Of the mercury released by human activity, about 80% is in its elemental form. Elemental releases result from mining, smelting, fossil fuel combustion, and solid waste incineration. About 15% is released from fertilizers, fungicides, and municipal solid waste. The remaining 5% is released from industrial wastewater.(10)

Mercury is unique among metals in the fact that it is liquid at room temperature. Even at room temperature, some mercury evaporates. Mercury vapors can be carried long distances and deposited in rain or snow. Inorganic mercury can also enter water or soil from the weathering of rocks, wastewater containing mercury, and incineration of municipal waste containing mercury.

Microorganisms (including bacteria, phytoplankton, and fungi) convert inorganic mercury to methyl mercury. Released methyl mercury lingers in the water and soil.

Once it has entered the food chain, methyl mercury bioaccumulates at progressive levels in the food chain. Fish that live a long time and attain large body sizes build up the highest concentrations of mercury within their bodies.

Interestingly, even if grown in soils containing high levels of mercury, plants generally maintain very low mercury concentrations. Mushrooms, however, can accumulate high levels of mercury.

The greatest deposition of mercury occurs in the southern Great Lakes, Ohio Valley, the Northeast, and scattered portions of the Southeast.

The Economics of Mercury

Most of the mercury production in the U.S. results from the recovery of mercury from obsolete or worn-out items, such as batteries, dental amalgams, and electrical apparatuses. A very limited amount was produced as a by-product of gold-mining in California, Nevada, and Utah.
About 35% of the mercury consumed in the U.S. is used in the manufacture of chlorine and caustic soda, 30% is used in electronic and electrical applications, and 35% is used in measuring and control instruments, dental amalgams, and other devices.(3)

Overview of 2000 Toxics Release Inventory (released 05/23/02)

In 2000, 1,561 facilities released 4,365,264 pounds of mercury and mercury compounds. Of those releases, 164,493 pounds were air emissions; 2,302 pounds were surface water discharges; 11,714 pounds were injected into subsurface wells, 3,249,836 pounds were released to land; and 898,474 pounds were transferred off-site for disposal.

In 2000, 4,875,864 pounds of mercury waste were managed; 646,940 pounds were recycled on-site; 161,929 pounds were recycled off-site; 78 pounds were used for energy recovery on-site; 126 pounds were used for energy recovery off-site; 19,768 pounds were treated on-site; 5,865 pounds were treated off-site; and 4,041,158 pounds were released on- and off-site.

The 10 states in which the largest amounts of mercury and mercury compounds were released in 2000 were:

The 10 facilities releasing the largest amounts of mercury and mercury compounds in 2000 were:

As of 1998, the following industries were the leading emitters of mercury and its compounds:

Federal Actions

The Environmental Protection Agency (EPA) has set a safe drinking water limit of 2 ppb (parts per billion) for inorganic mercury.

The Food and Drug Administration (FDA) has set maximum permissible methlymercury levels for seafood of 1 ppm (part per million).

The Occupational Safety and Health Administration (OSHA) has set limits of 0.1 milligram of organic mercury per cubic meter of workplace air (0.1 mg/m3) and 0.05 mg/m3 of metallic mercury vapor for 8-hour shifts and 40-hour work weeks.

Sources:
(1) “Mercury: A Fact Sheet for Health Professionals.” Michigan State University. Office of Radiation, Chemical & Biological Safety. 30 June 2003 <http://www.orcbs.msu.edu/AWARE/pamphlets/hazwaste/mercuryfacts.html>.
(2) National Research Council. Commission on Life Sciences. “Toxicological Effects of Methylmercury.” Washington, D.C.: National Academy Press, 2000. The National Academies Press. 30 June 2003 <http://books.nap.edu/books/0309071402/html/index.html>.
(3) “Human Health Effects and Ecological Impacts of Mercury.” Northeast Waste
Management Officials’ Association. 30 June 2003 <http://www.newmoa.org/Newmoa/htdocs/prevention/topichub/subsection.cfm?hub=
22&subsec=13&nav=13>.
(4) Littlefield, Angie. “Minamata Bay Pollution in Japan and Health Impacts.” TED Case Studies Volume 5, Number 1 (January 1996). American University. 30 June 2003 <http://www.american.edu/ted/MINAMATA.HTM>.
(5) “Case Studies of Mercury Poisoning.” Purdue Research Foundation.” 30 June 2003 <http://pasture.ecn.purdue.edu/~mercury/src-00-06/poicase.htm>.
(6) Foulke, Judith E. “Mercury in Fish: Cause for Concern?” FDA Consumer September 1994. U.S. Food & Drug Administration. 30 June 2003 <http://www.fda.gov/fdac/reprints/mercury.html>.
(7) “Mercury.” Building Environmental Education Solutions, Inc. 30 June 2003
<http://www.beesinc.org/about/healmerc.htm#topic7>.
(8) “Get the Mercury Out! - The Effects of Mercury on the Nervous System.” University of Washington. 30 June 2003 <http://faculty.washington.edu/chudler/merc.html>.
(9) “Mercury poisoning disease re-emerges.” BBC News World Edition. 3 Feb. 1999. 30 June 2003 <http://news.bbc.co.uk/1/hi/health/271598.stm>.
(10) “Public Health Statement for Mercury.” March 1999. Agency for Toxic Substances and Disease Registry. 30 June 2003 <http://www.atsdr.cdc.gov/toxprofiles/phs46.html>.