In the past, if an instrument containing mercury was broken, the large pieces may have been picked up and thrown into the basket or poured down the drain while the remaining portion was swept under the counter or just whisked out of sight. Well, times have changed and here is why. Over the past several decades we have learned a lot about the toxic effects of mercury on the human body. Because mercury is a liquid it has the ability to vaporize into the air. When these vapors are inhaled the mercury is deposited in the lungs where it can then be released to other parts of the body. The nervous system seems to be the most vulnerable site, although the kidneys, liver and other organs may also suffer the toxic effects of this chemical. Because mercury is so heavy, once it is spilled and contaminates an environment it will continue to vaporize over a long period of time. As the temperature in the environment cools the mercury will recondense and return to its liquid state, forming an invisible coating on solid surfaces. With changes in temperature and pressure, the mercury will continue to change from its vapor form to its liquid form. However, any mercury in the air in the form of vapor can be inhaled by individuals occupying the area. Unfortunately, it does not take a large amount of mercury to produce a problem. In one specific instance, three oral fever thermometers were broken. The mercury fell onto the floor in an office that was approximately ten square feet in size. Following the accident, the mercury vapors present in the air of that room were about three times that permitted by OSHA. Consequently, the room had to be decontaminated, all carpeting had to be discarded at a total cost of about $5000. This was a very small mercury spill. It is not uncommon for cleanup costs of mercury spills to exceed $25,000.
Although it is most toxic if it is inhaled as a vapor, mercury can also be absorbed through the skin or be ingested. Because of mercury's toxicity, the National Institute of Occupational Safety and Health has determined that individuals should not be exposed to more that .05 milligrams of mercury per cubic meter of air over an eight hour time weighted average. This is a very low concentration of mercury. Consequently, any spill or accident involving mercury must be immediately attended to. Cleanup involves a lot more than simply gathering the excess mercury and discarding it into the basket or flushing it down the drain. In fact, spreading mercury around compounds the problem. Mercury spills must properly be cleaned up to assure that all of the mercury is collected. This usually involves vacuums with filters and washing the area with chemicals that will bind the mercury. Many times this is done using respirators and in some instances self-contained breathing apparatus. Finally, air monitoring is done to assure that the levels of mercury vapor in the air have returned to safe levels. Usually this monitoring will continue over a period of days because the mercury levels in the air will rise or fall with changes in temperature . Remember, the mercury will not go away on its own. Because of its properties it is very persistent in the environment and will continue to be an unseen hazard until it is eliminated. In one high school chemistry laboratory, a plumber replacing a leaking sink drain removed almost a half pint of mercury from the trap. No doubt this was the accumulation of many years worth of broken thermometers.
Needless to say, a mercury spill can be your worst nightmare. Unfortunately, many individuals take a very cavalier attitude about this chemical because in the past it has been so widely used. The best way to approach the problem is to eliminate the hazard. Get rid of all mercury and mercury- containing instruments in your facility unless it is absolutely essential that you have them. Many instruments, such as thermometers, no longer use mercury---buy them!!! Assess the need to use mercury and mercury compounds against the cost of cleanup. Perhaps this article published by the Centers for Disease Control and Prevention will help you understand the reason for concern and help you make your decision wisely.
Residential exposure to elemental mercury typically involves small amounts (e.g., the approximately 0.3 ml in a thermometer). During August 1994, five children residing in a neighborhood in Palm Beach County, Florida, found 5 pints of elemental mercury in an abandoned van. During the ensuing 25 days, the children shared and played with the mercury outdoors, inside homes, and at local schools. On August 25, 1994, a parent notified local police and fire authorities that her children had brought mercury into the home. On the same day, 50 homes were immediately vacated and an assessment of environmental and health impacts was initiated by the State of Florida Department of Environmental Protection, the Health and Rehabilitative Services of the Palm Beach County Public Health Unit, and the U.S. Environmental Protection Agency. This report summarizes the investigation of this incident.
Door-to-door interviews of the entire neighborhood (n=363) were conducted, and a decontamination facility was established at the civic center. Based on information collected during the initial survey, residential structures and several classrooms at the local high school were tested for the presence of mercury. Ambient air samples (i.e., adult breathing zone grab samples collected approximately 5 feet above the floor) were collected in affected structures during the 6 days following the report of children handling mercury. In addition, during August 25-29, initial blood and urine samples were collected from potentially exposed persons and analyzed for mercury levels.
A total of 58 residential structures were monitored for indoor mercury vapor concentrations; unsafe indoor air levels of mercury (greater than 15 ug/m3) were detected in 17, prompting the immediate evacuation of 86 persons. Several classrooms at the local high school were determined to be contaminated. This school was closed for 4 days until clearance air sampling indicated that the mercury level was less than or equal to 10 ug/m3. This level of mercury was considered safe for students and teachers rotating among the rooms for 50-minute classes. Pregnant women and young children were excluded from entering classrooms until mercury levels decreased to less than or equal to 0.3 ug/m3.
A total of 477 persons identified by the survey as potentially exposed were evaluated at the emergency department of the local hospital or the health department clinic for mercury poisoning by testing both blood and urine specimens for total inorganic mercury levels. Elevated blood and/or urine mercury levels were detected in 54 persons: blood levels ranged from 1.1 ug/dL to 5.5 ug/dL (normal: less than 1 ug/dL) and urine levels ranged from 21 ug/L to 66 ug/L (normal: less than 20 ug/L). Ambient air samples ranged from 6.5 ug/m3 to 300 ug/m3. Although these 54 persons were asymptomatic, concentrations of mercury detected in their blood and urine were consistent with the levels of mercury detected in their homes.
Homes and classrooms were decontaminated by spreading powdered sulfur absorbent on the floors and vacuuming surfaces with high efficiency particulate-arresting (HEPA) filters. Contaminated items (e.g., carpeting, padding, linoleum, clothing, bedding, vacuum cleaners, furniture, and washing machines) were removed and taken to a hazardous waste facility, and some homes required ventilation for periods up to 3 months. Because of the potential for residential exposure of many children and childbearing-aged women, an air mercury concentration of less than or equal to 0.3 ug/m3 was established as a threshold at which families would be permitted to return to their homes. Ambient air samples were collected 24 inches above the ground (i.e., a child's breathing zone), under normal living conditions for at least 8 hours.
By December 1, 1994, all displaced families had been permitted to return to their homes, and urine mercury levels of all exposed persons decreased. However, the Palm Beach County Health Department continues to monitor persons with persistently elevated urine mercury levels. This incident is under criminal investigation, and information regarding the source of the mercury has not been released.
Reported by: J.M. Malecki, MD, Health and Rehabilitative Svcs/Palm Beach County Public Health Unit, R Hopkins, MD, State Epidemiologist, State of Florida Dept of Environmental Protection.
U.S. Environmental Protection Agency. Air Pollution and Respiratory Health Br, National Center for Environmental Health, CDC.
Editorial Note: Most poisonings associated with exposure to elemental mercury occur in occupational settings, and reports of nonoccupational elemental mercury vapor poisonings are rare, especially in community-based settings (1,2). The exposures described in this report primarily affected homes and schools.
Inorganic mercury is a heavy, silver-white metal that is liquid at room temperature. The vapor pressure of mercury is high compared with other metals, creating the continual hazard of airborne exposure to mercury vapor, which is odorless and colorless. Mercury is absorbed into the blood following inhalation and is then transported to the brain and other areas of the nervous system and to all other tissues. Most elemental mercury is excreted unchanged in feces.
The development of clinical manifestations as the result of inhalation of mercury vapor is related to several factors, including the concentration of vaporized mercury, length of exposure, and individual susceptibility (2,3). Acute exposure to elemental mercury produces symptoms of metallic taste, burning, irritation, salivation, vomiting, diarrhea, upper gastrointestinal tract edema, abdominal pain, and hemorrhage (4). Symptoms of high levels of exposure usually begin abruptly and include fever, chills, malaise, nausea, coughing, shortness of breath, chest pain and tightness; the clinical course may progress to pulmonary edema and death (5). In comparison, chronic inorganic mercury poisoning can result in intention tremor, memory loss, insomnia, depression, irritability, excessive shyness, emotional instability, delirium, and acrodynia and may result in a nuerologic syndrome known as "mad hatter syndrome" (2-5).
The risks associated with mercury exposure are especially increased for children because mercury vapor is dense and settles (2) and because children may be active on the floor or playing in dirt. In addition, because of lipid solubility, mercury crosses the placenta and is excreted in breast milk and, therefore, is a potential health hazard for unborn children and breast feeding infants (6,7).
Elemental mercury is still widely used in industry for the manufacture of thermometers, barometers, vacuum pumps, and electrical components and may be present in household products such as cleaning solutions and adhesives (2,5). Small amounts of mercury, such as from a broken thermometer, can be cleaned up by spraying the mercury gently with hairspray or dusting with an absorbent such as powdered sulfur and sweeping up the mercury and absorbent with a wisk broom. After cleaning the spill, the broom should be securely bagged and discarded (8). Any person who discovers a large quantity of mercury should immediately contact the local poison-control center or health department.
The residential exposure described in this report was unprecedented in terms of the amount of mercury involved and the extent of contamination. The rapid and coordinated response to this incident minimized the risk for and assured the health of the exposed residents.
References
1.CDC. Elemental mercury vapor poisoning--North Carolina, 1988. MMWR 1989;38:770-2,777.
2.CDC. Elemental mercury poisoning in a household--Ohio, 1989. MMWR 1990;39:424-5.
3. Knight, A.L. Mercury and its compounds. In: Zenz C, ed. Occupation medicine: principles and practices. 2nd ed. Chicago: Year Book Medical Publishers, 1988:590-6.
4. Rumack B., Peterson R. Clinical toxicology. In: Doull J, Klassen C, Amdu M, eds. Toxicology: the basic science of poisons. 2nd ed. New York: Macmillan Publishing Co., Inc., 1980:690-1.
5. Taueg C., Sanfilippo D.J., Rowens B., Szejda J., Hesse J.L. Acute and chronic poisoning from residential exposures to elemental mercury--Michigan, 19
6. Sikorski R., Juszkiewicz T., Paszkowski T., Szprengier-Juskiewicz T.. Women in dental surgeries: reproductive hazards in occupational exposure to metallic mercury. Archives Occupational Environmental Health 1987;59:551-7.
7. Thorp J.M., Boyette D.D., Watson W.L., Cefalo R.C.. Elemental mercury exposure in early pregnancy. Obstet Gynecol 1992;79:874-6.
8.Micromedics, Inc. Poisindex {Software}. Denver: Micromedics, Inc., 1995 (Vol 85).
