Mercury in the Environment

What is Mercury?

Mercury is a naturally occurring element of remarkable qualities, a volatile liquid metal (at normal temperatures) that easily becomes a gas. Mercury (chemical symbol Hg, atomic number 80) conducts electricity, and can be used to directly measure temperature and pressure. Its applications can be found everywhere in human society:

• as a catalyst in industrial processes
• in solvents, and pesticides;
• in light switches, lamps, and batteries
• in paints and preservatives
• in cosmetics, and pharmaceuticals

Mercury is one of the group of elements known as heavy metals. Many of these (including lead, cadmium, and selenium) are toxic to living things. Mercury too can kill living things, from bacteria to human beings. In particular, it can be converted into an organic form, methyl mercury, which is especially toxic.

Presence of Mercury in the Environment

Mercury is a naturally occurring mineral that can be found throughout the environment. Mercury forms can be found as the elemental metal or in a wide variety of organic and inorganic compounds.

There is a constant biogeochemical cycle of mercury. This cycle includes:

• release of elemental mercury as a gas from the rocks and waters (degassing);
• long-range transport of the gases in the atmosphere;
• wet and dry deposition upon land and surface water;
• absorption onto sediment particles;
• bioaccumulation in terrestrial and aquatic food chains.

Natural and Manmade Emissions of Mercury

Mercury is released to environmental media (air, water, soil) by a wide variety of natural processes and human interventions. Worldwide, natural emissions of mercury from physical and biological processes may equal or exceed manmade emissions.

The global anthropogenic emission rate for mercury is estimated to be 650 metric tons (650,000 Kg) annually, while natural emissions could be as much as 1020 metric tons (1,020,000 Kg). While the totals are quite uncertain, natural emissions may comprise about 50 percent of them.

Even if all manmade emissions of mercury were eliminated, a significant natural discharge to the environment --through both biological and physical processes-- would persist.

Mercury in Nature:  Chemical and Biology

Significant amounts of mercury are directly released from the earth's crust by the process of degassing. Both natural and manmade emissions are modified by biological processes into forms more directly harmful to human beings. Mercury is somehow less toxic in its volatile form, mercury-zero, than in organic compounds like methyl mercury or inorganic salts (mercury-two).

Common bacteria of the soil and water have adapted to the presence of mercury. They have developed methods to detoxify its organic compounds and salts to the elemental form of mercury zero. Mercury zero, however, is volatile, and thus can spread throughout the environment through secondary biological mechanisms. Once it reaches inland aquatic environments, mercury zero can again accumulate and be transformed into methyl mercury, the toxic form that bioaccumulates in fish, animals, and humans. This toxic transformation can occur from any of three causes: 

• the photochemical (abiotic) action of sunlight
• the methyl cobalamin (a hydrocarbon compound), excreted by bacteria
• the plants of aquatic ecosystems.

Mercury in the Atmosphere

At least 99 percent of all mercury in the atmosphere exists in the elemental gaseous form of mercury-zero. Much of the remainder is mercury-two, which is water soluble and the form most often deposited by rainfall.

Most of the mercury in the atmosphere comes from natural degassing from water and rocks. Major manmade discharges to the atmosphere come from:

• mining and smelting of mercury ores
• industrial processes using mercury
• combustion of fossil fuels, primary coal.

Less common manmade sources of atmospheric mercury include: 

• paint application
• waste oil combustion
• geothermal energy plants
• municipal and waste incineration.
• diffuse emissions from dental procedures

One important local source of atmospheric mercury is the incineration of medical wastes.

Mercury in the Water

Mercury can enter water by many different routes and processes:

• wet and dry atmospheric depositions
• particle flux to sediments
• dissolved species exchange at sediment/water interfaces
• gas exchange at air/water/surface interfaces
• moving dissolved species exchange and particle flux via stream and rivers
• dissolved species exchange via runoff from groundwater to lakes
• direct discharge of dissolved species via groundwater to lakes
• gas exchange at soil-air ion interfaces

Manmade discharges may result from industrial processes, such as:

• chlorine-alkali production
• mining operations
• paper mills
• leather tanning
• pharmaceutical production
• textile manufacture

Trouble in the Waters:  Methyl Mercury

In the aquatic environment, mercury can be:

• dissolved or suspended in the water
• trapped in the sediments
• ingested by living things (biota)

Methyl mercury is the form of mercury most available and most toxic to biota (including zooplankton, insects, fish, and humans). This form of mercury is easily taken up by biota and bioaccumulates in their tissues. Unlike many other fish contaminants, such as PCBs, dioxin, and DDT, mercury does not concentrate in the fat, but in the muscle tissue. Thus, there is no simple way to remove mercury-contaminated portions from fish that is to be eaten.

The local aquatic environment largely determines how much available mercury takes the accessible toxic for of methylmercury. Research suggests that sulfur-using bacteria are a major source. The extent of biomethylation may depend upon such factors such as pH, (i.e. alkalinity), available sulfur sources, and dissolved organic materials.

Mercury in the Soil

Human agricultural activities may release mercury to the soil through direct applications, such as:

• organic and inorganic fertilizers (especially sewage sludge and compost)
• lime
• fungicides

Once in the soil, mercury compounds may undergo the same chemical and biological transformations found in aquatic systems. Elemental mercury (mercury zero) will form various compounds with the chloride and hydroxide ions of soils. The exact result will depend upon the pH, salt content, and other characteristics of the soil.

For soil, like water, both inorganic chemistry and the actions of living things will affect the formation and degradation of organic mercuric compounds. For example, elevated levels of chloride ions will reduce methylation of mercury in river sediments, streams and soils. In contrast, increased levels of organic carbon and sulfate ions will increase methylation in sediments.

Mercury in the Food Chain

Benthic (bottom-dwelling) invertebrates may face exposure to mercury released directly from sediments. They may also release mercury bound in the sediment by direct ingestion, having thus entered the food chain, mercury bioaccumulates as bottom-dwellers are consumed by others.

Toxic methyl mercury can inflict increasing levels of harm upon species near the top of the aquatic food chain. These likely victims include: predatory fish such as ocean swordfish; fish-eating birds such as loons, cormorants, pelicans, ospreys, and eagles; and humans.

We can be certain of the harm resulting from methyl mercury contamination of fish, even if the exact degree of risk is yet uncertain. Reasonable preventive actions that will safeguard humans from methyl mercury poisoning should also protect birds that eat freshwater fish. Controlled feeding studies suggest that the methyl mercury threshold dose for adverse effects to wildlife is the same or higher than for humans.

The Worldwide Mercury Cycle

There is a worldwide cycling and recycling of mercury through the environment, called the biogeochemical cycle of mercury. The cycle has six steps, as shown in the adjoining diagram:

1. Degassing of mercury from rock, soils and surface waters.
2. Movement in gaseous form through the atmosphere.
3. Deposition of mercury on land and surface waters.
4. Sorbtion of the element as insoluble mercury sulfide.
5. Precipitation or bioconversion into more volatile or soluble forms.
6. Either:

   a. Reentry of mercury into the atmosphere, or

   b. Bioaccumulation in terrestrial or aquatic foodchains.

Elemental metallic mercury ("mercury zero"), released to the atmosphere in vapor form, can be transported very long distances. Eventually, wet and dry deposition processes return it to land or water surfaces in the form of compounds.

Wet depositions of mercury by precipitation (rain, snow, etc.) is the primary method of mercury removal from the atmosphere (perhaps 66 percent of the total). Mercury can also be removed from the atmosphere by sorbtion of the vapor onto soil or water surfaces.

The particular form of mercury and its compounds strongly influence the movement and partitioning of mercury among surface waters and soils. Ninety seven percent of all the gaseous mercury dissolved in water is the elemental form -- "mercury zero". Volatile forms of mercury, such as the metallic liquid and dimethyl mercury, will evaporate into the atmosphere. Solid forms particulates in the soil or the water column, and once in the water column are transported downward to the sediments.

What makes Mercury Run?

Sorbtion of nonvolatile forms of mercury onto soil and sediment particulates is the central process that determines the distribution of mercury compounds in the environment. This sorbtion process varies according to the organic matter content of the soil or sediment.

Inorganic mecury sorbed onto particulate material is not easily desorbed. This means that freshwater and marine sediments will be important storehouses for inorganic forms of mercury, and that leaching from soils will play a minor role in mercury transport.

Where the soils are rich in humus, surface runoff will be an important route moving mercury from soil to water.

There are processes that will release the sorbed mercury from particulates:

• Chemical or biological reduction to elemental mercury.
• Bioconversion to volatile organic forms.

Mercury in Humans

Human Exposure to Mercury

    Ways of Exposure to Mercury

Mercury in its various forms (pure element, inorganic compounds, organic compounds) is found in air, water, soil and fauna and flora. All of these environmental media may be involved in human exposure to elemental mercury and mercury-containing compounds.

Elemental mercury (mercury zero) is a liquid and gives off mercury vapor at room temperature. This vapor can be inhaled into the lungs and passed into the blood stream. Elemental mercury can also pass through the skin and into the blood stream. If swallowed, however, this form of mercury is not absorbed out of the stomach, and usually passes out of the body without harm.

Inorganic mercury compounds (mercury two) can also be inhaled and absorbed through the lungs, and may pass through the stomach if swallowed. Many inorganic mercury compounds are irritating or corrosive to the skin (see other health effects of mercury ), eyes and mucus membranes as well.

Organic mercury compounds, like methyl mercury, can enter the body readily through all three routes ; lungs, skin and stomach.

Humans are exposed to mercury primarily through ingestion of fish that contain methyl mercury. Inhalation of mercury vapors is a potential occupational risk in industries that process or use mercury. Skin contact with materials containing organic mercury and elemental mercury may also result in mercury exposure. People with dental amalgams that contain mercury have greater exposure.

    Workplace Exposure Limits

• Environmental Protection Agency (EPA): EPA estimates that for an adult of average weight, exposure to 0.021 milligrams (mg) of inroganic or organic mercury per day in food or water will probably not result in any harm to health.
• Occupational Safety and Health Administration (OSHA): The legal airborne permissible exposure limit (PEL) is 0.1 mg/cubic meter, not to be exceeded at any time.
• National Institute for Occupational Safety and Health (NIOSH): The recommended airborne exposure limit is 0.05 mg/cubic meter averaged over an 8-hour workshift.
• ACGIH: The recommended airborne exposure limit for mercury vapor is 0.05 mg/cubic meter, averaged over an 8-hour workshift.

The above exposure limits are for air levels only. When skin contact also occurs, a worker may be overexposed, even though air levels are less than the limits listed above.

    Ways of Reducing Exposure to Mercury

• Where possible, enclose operations and use local exhaust ventilation at the site of chemical release. If local exhaust ventilation or enclosure is not used, respirators should be worn.
• Wear protective work clothing.
• Workers whose clothing has been contaminated by mercury should change into clean clothing promptly.
• Do not take contaminated work clothes home. Family members could be exposed.
• Contaminated work clothes should be laundered by individuals who have been informed of the hazards of exposure to mercury.
• Do not eat, smoke, or drink where mercury is handled. Wash hands carefully before eating or smoking.
• For clean-up use a specialized charcoal-filtered vacuum or suction pump to avoid generating mercury vapor. Care should be taken not to disturb spilled material.
• Wash thoroughly immediately after exposure to mercury and at the end of the workshift.
• If there is the possibility of skin exposure, emergency shower facilities should be provided.
• Post hazard and warning information in the work area. In addition, as part of an ongoing education and training effort, communicate all information on the health and safety hazards of mercury to potentially exposed workers.

    Tests for Mercury Exposure

    There are two tests available to measure mercury in the body:

• The mercury blood test measures exposure to all three types of mercury, but because mercury remains in the blood stream for only a few days after exposure, the test must be done soon after exposure. Most non-exposed people have mercury levels of 0 to 2 (all blood measurements are in micrograms of mercury per deciliter of blood, or ug/dl). Levels above 2.8 ug/dl are required to be reported to the Health Department. This test can be influenced by eating fish, because fish (particularly certain deep sea f ish) may contain mercury.
• The urine mercury test only measures exposure to elemental and inorganic mercury. Organic mercury is not passed out the body in the urine and thus cannot be measured this way. A person with no exposure to mercury would probably have a urine mercury level of 0 to 20 ug/dl. The Health Department requires reporting levels above 20.

    Monitoring for Workers Exposed to Mercury

        Medical Monitoring

Medical monitoring is the periodic evaluation of exposed workers to insure that they are experiencing no adverse effects of potentially hazardous workplace exposures. It serves as a backup for a program of routine air and biological monitoring, which are the primary means for insuring that exposure levels are below those associated with adverse health effects. A medical monitoring program should be designed to detect adverse effects of exposure as early as possible, at a stag e where there are still reversible, so that exposures can be controlled and serious permanent adverse effects prevented.

An initial medical examination should be performed on all employees exposed to potentially hazardous levels of mercury. The purpose of this examination is to provide a baseline for future health monitoring.

The examination should include a complete medical history and symptom questionnaire, with emphasis on the:

• nervous system (target organ for chronic exposure)
• kidneys (target organ for acute and chronic exposure)
• oral cavity (target organ for chronic exposure)
• lungs (target organ for acute exposure)
• eyes (affected by chronic exposure)
• skin (since mercury is a known skin sensitizer).

Signs and symptoms of the earliest signs of mercury intoxication should be elicited; these include personality changes, weight loss, irritability, fatigue, nervousness, loss of memory, indecision, and intellectual deterioration. Complaints of tremors and loss of coordination should also be sought. Physical examination should focus on the target organs described above. A baseline handwriting sample should be obtained. Laboratory evaluation should include at minimum a complete urinalysis.

This examination should be repeated annually. Results should be compared with the findings on the baseline examination for changes suggestive of mercury toxicity. Handwriting samples should be compared to the baseline sample for evidence of tremor. Interim evaluations should be conducted if symptoms suggestive of mercury intoxication are occuring.

        Biological Monitoring

            What is Biologic Monitoring?

Biologic monitoring is the measurement of chemical agents in the blood, urine, or other body tissue of exposed individuals to determine how much of the chemical has been absorbed into the body. It serves as a back-up to environmental exposure measurements, since air measurements cannot assess skin exposure or the effects of protective equipment and work practices. Since it measures the amount of an agent actually absorbed into the body, it is usually a better estimate of risk for adverse health effect t han air monitoring.

There is no ideal biologic monitor for evaluating the risks of mercury intoxication from metallic or inorganic mercury. Mercury can be measured in both blood and urine. Individual levels may vary greatly from day to day and even within a given day. While proper interpretation of the results can be difficult, the measurements can nevertheless provide information on potential overexposure. Measurements should be carried out regularly (several times a year) in chronically exposed workers, and individual as well as group results should be evaluated. Baseline levels should be obtained before exposure begins for comparison purposes.

        Mercury in the Urine

Measurement of mercury in urine is the recommended biologic monitor for workers exposed to metallic and inorganic mercury. Ideally, the collection should be over 24 hours, but this is seldom feasible. Spot urine samples may also be taken, but care must be taken to always collect them at the same time of day near the end of the work week after several months of steady exposure. Overnight samples may also be collected; this collection extends from the time the employee goes to bed through the first urinat ion of the morning.

Samples must be collected in containers provided by the laboratory, since a preservative must be added. At least 25 mililiters of urine must be collected. Great care must be taken to prevent contamination of the sample containers or the urine with mercury from the skin or workplace air.

When results are interpreted, the urine values should be corrected for grams of creatinine in the sample, and should be expressed as ug Hg/gram creatinine. In persons not occupationally exposed to mercury, urine levels rarely exceed 5 ug/g creatinine.

While many laboratories indicate that only levels above 150 ug/L should be considered toxic, there is strong evidence that early signs of mercury intoxication can be seen in workers excreting more than 50 ug Hg/L of urine (standardize for a urinary creatinine of 1 gram/L). This value of 50 ug/g creatinine is proposed by many experts as a biological threshold limit value for chronic exposure to mercury vapor, and in 1980 this was endorsed by a World Health Organization study group.

Exposed individuals with levels above 50 ug/g creatinine should be placed in a non-exposed job until the reason for their over exposure has been identified and corrected and their urine levels have fallen below the biologic threshold limit value.

        Mercury in the Blood

The concentration of mercury in blood reflects exposure to organic mercury as well as metallic and inorganic mercury; thus it can be influenced by the consumption of fish containing methylmercury.

Samples should always be taken at the same time of day near the end of the work week after several months of steady exposure. The blood should be collected in mercury-free heparinized tubes after careful skin cleansing.

In unexposed individuals, the amount of mercury in blood is usually less then 2 ug/100 ml. According to some experts, an average airborne concentration of 50 ug/cubic meter corresponds to a mercury concentration in blood of about 3-3.5 mg/100 ml. Early effects of mercury toxicity have been found when the blood concentration exceeds 3 ug/100 ml. Any worker exceeding this level should be placed in a non-exposed job until dietary and workplace exposures have been evaluated and blood levels have returned to baseline.

Effects of Mercury Poisoning in Humans

Mercury is both a precious metal and a neurotoxin. The "mad hatters" of the 19th century suffered from mercury poisoning - so did the hat makers in Danbury, Connecticut, who called their disease the Danbury Shakes. In short, mercury can be harmful to fish, waterfowl, wildlife, and humans.

The mercury felting process prevalent in the nineteenth century and many other industrial uses of mercury have been discontinued, and today most people are not exposed to dangerously high levels of mercury in their job settings. However, mercury may still be an occupational hazard for people working in medical care facilities.

Suppose, for example, a thermometer breaks or a mercury-containing solvent spills. If mercury vapor is inhaled, as much as 80 percent of the inhaled mercury may be absorbed into the bloodstream.

The biological half-life of mercury is 60 days. Thus, even though exposure is reduced, the body burden will remain for at least a few months.

The effects of mercury poisoning can be classified as:

- acute,

- chronic, or

- other

The degree of risk varies depending on how much mercury a person is exposed to and how often, and on stage of life. The work environment can be designed to minimize workers' exposure. We can, for example, be as careful about mercury as we are with x-rays. But not all of the mercury that we use remains in the facility. Some of it escapes into the environment, undergoes change, and may eventually be eaten by fish. Mercury-contaminated fish are the most likely source of mercury 's potentially adverse effects on human health. It is recommended that mercury's uses in medical settings be eliminated, not because its presence makes medical facilities dangerous places to be, but to help keep mercury out of the environment.

Case Studies in Humans

Minamata Disease

What we now call "Minamata disease" was first observed in communities near Minamata Bay in Southwestern Japan. It was officially "discovered" in 1956, and by 1959 it had been demonstrated that the disease was caused by ingestion of fish contaminated by mercury discharged from a chemical manufacturer plant.

Levels of methylmercury chloride reached 50 ppm in fish and 85 ppm in shellfish obtained from the contaminated areas. One hundred and twenty one persons were poisoned, 46 fatally, from eating the contaminated fish. Dogs, cats, pigs, rats, and birds living around the bay developed classical clinical signs and many died.

In most cases, the patients began to show symptoms without any apparent signs. The onset began with numbness of the limbs and the area around the mouth, sensory disturbance, and difficulty with hand movements (such as grasping things, fastening buttons, holding chopsticks, writing, etc.); also, there was lack of coordination, weakness and tremor, slowed and slurred speech, and ataxic gait, followed by disturbances of vision, and hearing. These symptoms became aggravated and led to general paralysis, deformity of the limbs, difficulty in swallowing, convulsions, and death.

Iraq

In 1956 in Northern Iraq, over 100 people were poisoned by eating flour mixed with wheat seed treated with a fungicide containing 7.7% ethylmercuri-p-toluene sulfonalide. Fourteen, and probably more, of the intoxicated people died. They had fed the treated seed to chickens for several days and after observing no ill effects had eaten it themselves. In addition to central nervous system manifestations, a number of other clinical signs were observed including polydypsia, polyuria, weight loss, severe prot einuria, deep musculoskeletal pain refractive to anlagesics, and prurits of the palms, soles, and genitals. Researchers attributed the other clinical signs to the prevalence of a parasitic disease called ancylostomiasis, and to dietary deficiencies of protein and vitamins.

Four years later during the winter and spring of 1961, an additional 100 people were poisoned by flour and wheat seed treated with a fungicide containing 1% mercury as ethylmercury chloride and phenylmercury acetate. Four of 34 patients died; however, the authorities believed others probably died after refusing hospitalization or signing out against medical advice. A combination of clinical signs was observed reflecting insult to the central nervous system by ethylmercury fraction and to the renal and g astrointestinal organs apparently due to the phenylmercury component.

Guatemala

During the wheat-planting seasons of 1963-1965, numerous cases of a disease suspected of being a viral encephalitis occurred in and around Panorama, Guatemala. Forty five cases were observed, over 50% of which occurred in children, and 20 of these died. Autopsy and subsequent tissue analyses disclosed high levels of methylmercury in brain, liver, and kidney tissue of one victim. Being too poor to buy enough food to survive, the victim had eaten wheat seed treated with a fungicide containing 1.5% mercury as methylmercury.

New Mexico

As a result of human consumption of pigs previously fed organomercurial compounds, mercury poisoning became evident in a farm family in Alamogordo, New Mexico. On December, 1969, an 8-year old farm girl living near Alamogordo, New Mexico, developed ataxia, visual disturbances, and a reduced state of consciousness which progressed to coma within a period of 21 days. Two weeks after the onset of her illness a 13-year old male sibling developed similar clinical signs and, like his sister, became comatose within a 3-week period.

By the end of the same month, a 20-year old sister developed similar clinical signs and became semicomatose. At the time the pork containing the high levels of mercury was eaten by the 10 members of the farm family, the mother was 3 months pregnant. She did not eat any of the meat after her sixth month of pregnancy. Clinical examinations during the last 2 months of her pregnancy disclosed only normal findings; however, her urine contained high levels of mercury. The pregnancy terminated with delivery of a 6.7-lb male infant. At birth he manifested intermittent trembling of the extremities which persisted for several days; however, he was otherwise normal. Electroencephalograms, electromyograms, blood electrolytes, calcium, magnesium, glucose, and bilirrubin remained normal during the first 6 weeks. Marked elevation of urinary mercury was present during the first 6 weeks; however, after that time urinary mercury was no longer detected.

Electroencephalograms became slightly abnormal at 3 months of age; by 6 months of age they were markedly abnormal, and generalized myoclonic jerks had developed. By 6 months of age, the infant had nystagmoid eye movements without evidence of visual fixation, was hypotonic and irritable. All of these clinical signs and other physical examination findings have been observed in Japanese children born to parents who consumed various fish caught from Minamata Bay and surrounding areas. The poisoning of these children presumably resulted from transplacental poisoning with organic mercury. 

Six months after the initial appearance of clinical signs among members of the farm family in New Mexico, their condition remained essentially unchanged. The 8-year old girl and 13-year old boy remained comatose; however,, the 20-year old sister continued to improve and was able to speak and walk with difficulty. The neonate's condition remained unchanged.

Belle-Glade, Florida

August 1994 - more than 500 students in Belle-Glade Florida were contaminated with liquid mercury after three boys found four jars filled with the silvery metal in an abandoned van. The boys brought the jars of mercury to school and passed it out to their friends. The children were fascinated by the silvery, liquid metal. "You ever seen "Terminator II?" asked a 14-year-old boy, "When the bad guy melts into the ground? That's just what it's like." The students played with the mercury, rubbing it on their teeth, throwing it at each other, dipping their jewelry into it, and pouring it into a local canal. Many children took home samples in paper cups and bags.

Although inhaling mercury vapors is by far a more serious threat than swallowing liquid mercury, local officials were very concerned. "If the children ate small amounts, that is not likely to be toxic," a local pediatrician stated. "The problem is going to come if the mercury is spilled or if its stays in a child's pockets. When it is vaporized and inhaled, it can be very, very toxic." Initial symptoms include a cough, breathing difficulties, and chest pain. Vomiting, diarrhea, fever, and nerve or kidney problems may develop later.

Hundreds of children had to be decontaminated. The local hazardous waste materials team, dressed in yellow safety suits, stood the children in a wading pool, hosed their arms, and scrubbed their skin with brushes. Doctors at area hospitals were on call 24 hours-a-day for several days to examine the children and adults exposed to the mercury and to give free blood tests. More than 20 homes had concentrations high enough to be of concern to the U.S. Environmental Protection Agency (EPA). Families had to be evacuated while EPA decontaminated these homes.

A hospital spokesperson said that he did not think any children had come in contact with enough mercury to cause any serious damage. No permanent damage to the children is expected.

Boca Raton, Florida

November 1994 - Over the Thanksgiving break, college students at Florida Atlantic University in Boca Raton, Florida removed liquid mercury from one of the school's laboratories. Although the laboratory manager noticed the missing chemical when he returned on Tuesday morning, he did not report it to authorities until the mercury was discovered spilled inside and outside of a university dormitory. Students living in the dormitory were evacuated and housed in a local hotel while the dormitory was decontaminated. Potential short- or long-term damage is unknown.

Illinois

Spring 1994 - A young boy in Moline, Illinois may suffer severe nerve damage due to mercury poisoning. The child brought home liquid mercury from the school science room and played with it in his basement. He spread the silvery liquid on his arms and legs in an attempt to look like the Tin Man from the Wizard of Oz. The home was so contaminated that the family was evacuated for nearly 10 months while the U.S. Environmental Protection Agency (EPA) cleaned up the spilled mercury. Ceiling tiles and the air conditioning and heating systems also were replaced. Although the boy is now recovering, the extent of permanent damage is unknown.