Thermometer breaks in glassware oven.
Oven shut off, unplugged, taped shut, and cooled.
Big plumes of Hg vapor observed leaking out of oven door cracks and thermometer hole via its absorption of UV between a TLC lamp and a fluorescent plate. (Highly instructive for persons from all walks of life, and a fun afternoon family activity)
This procedure results in an amalgam of mercury and zinc (the acidic solution shifts the equilibrium toward the bound product). The more conventional treatment with calcium polysulfide or flowers of sulfur merely reduces the vapor pressure by coating the droplets. Subsequent frictional forces can disrupt this coating and result in additional vapor release.
Copper, gold or almost any other metal except iron or platinum may be substituted for zinc.
When a 5-lb bottle of elemental mercury was dropped by an employee of the University of Virginia's Hospital Supply Storeroom, broken glass and larger mercury pools were hastily swept up. The Office of Environmental Health and Safety was called to pick up the waste and survey the damage.
The severity of the problem was realized as soon as the cleanup crew arrived. In just 30 min, storeroom personnel had tracked mercury throughout the area. Fugitive mercury droplets had rolled everywhere.
The storeroom was immediately shut down and the State Department of Emergency Services was called in, as a spill of this magnitude exceeded the hospital's cleanup capabilities.
The problem with any mercury spill is that mercury easily vaporizes at room temperature, where it can be breathed or absorbed through the skin. Prolonged exposure to mercury vapor adversely affects the nervous system. Symptoms may include irritability, depression, vivid dreams, inflammation of the gums, insomnia, loss of memory, and/or concentration and constricted visual fields.
The OSHA (Occupational Safety and Health Administration) permissible exposure limit (PEL) for Hg is 0. 10 mg/m 3 and the ACGIH threshold limit value (TLV) for Hg is 0.05 mg/m 3 . Both of these standards are based on an exposure for an 8-hr day.
It takes very little mercury to create an unsafe environment. Quantities as low as I mL can evaporate over a period of time and contaminate millions of cubic feet of air to levels in excess of allowable limits.
The airborne concentration of mercury vapor was measured in the storeroom, and found to be above 0.3 mg/m3. Improper spill cleanup techniques had broken the droplets into smaller particles that collected in porous surfaces and floor cracks. Mercury had been tracked all over the room on shoes and the wheels of medical carts.
The following day, the Department of Emergency Services helped clean up the remaining mercury with a special mercury vacuum cleaner. Results were tested with a direct-reading mercury analyzer. Testing showed that levels were then below 0. 1 mg/m 3 . The Department left the analyzer with the hospital for con tinued testing.
By the following morning, mercury vapor levels had dropped to 0.05--0.06 Mg/M3. Pans of the storeroom were reopened for essential supplies and orders. Unfortunately, by afternoon, the analyzer showed that mercury vapor levels were starting to rise again. 'Me area was cleaned using a paste of zinc powder, a technique that has become an integral part of the cleanup procedure (Figure 1).
By that time, 22 employees were identified as having been potentially exposed to excessive mercury levels. They received a medical evaluation consisting of medical history, physical exam, laboratory tests, and computerized neurobehavioral testing. Laboratory tests included spot urine tests, 14-hr urine follow-ups, and blood mercury determinations. All the test results were negative.
While the state's mercury detector was still on loan, some adjacent hospital areas were surveyed for excessive mercury vapor concentrations.
The first location was the medical repair room where employees of the Clinical Engineering Department repair such mercury-filled instrumentation as incubator thermometers, sphygmomanometers, and other differential pressure devices. (Wall mounted units are frequently knocked over in patient rooms when beds are adjusted; and tripod units are overturned on a regular basis. The mercury-filled tubes shatter upon the slightest impact.
Equipment in need of repair or recalibration is sent to the Medical Repair Room. Although some mercury from broken equipment can contaminate patient rooms, most of it is usually found on the repair room floor and work counters. Employees have reported that they scooped up larger mercury puddles and threw them into open trash cans and vacuumed up the rest with a regular household vacuum cleaner. They also stomped on tiny droplets until they were no longer visible. The mercury detector confirmed the suspected high levels in the repair room. Air samples in the room showed average mercury vapor levels of 0.3 mg/m 3 ; an analysis of the vacuum cleaner's interior levels pushed the instrument's gauge off scale.
Twenty-eight employees of the Clinical Engineering Department were identified as either chronically or potentially exposed to elevated mercury levels, including those who repaired manometers, those who worked in the contaminated repair room, and others who worked in adjacent offices.
After testing, none of the employees were found to exhibit signs of mercury poisoning, although four employees were considered to have elevated blood mercury levels. Four others claimed eyelid fasciculations and depression. Two admitted increased irritability and insomnia; two others excitability, forgetfulness, anorexia, and occasional nausea.
It was obvious from the testing that mercury-contaminated areas needed to be cleaned immediately and kept mercury-free. Employees obviously needed education about the dangers of mercury vapor and instruction on proper cleanup procedures.
First, steps were taken to control access to all mercury-based materials by running all mercury acquisitions through the University Office of Environmental Health and Safety. The mercury is now stored there and not in satellite facilities like the supply storeroom.
Next, a portable mercury vapor analyzer was purchased so that mercury spills could immediately be analyzed for elevated mercury vapor levels. The analyzer selected (Figure 2) provides fast, accurate, and specific mercury-only readings through the use of gold film technology. Instruments that respond to interference?s such as organic materials are confusing to read when the mercury content of cart wheels or shoes is being analyzed.
Complete mercury spill cleanup kits were assembled. A spill response procedure was published that defined everyone's responsibilities.
Most importantly, a large employee population was made aware of the potential hazards of mercury (Figure 3). Mercury Is highly toxic-however benign or fascinating it looks. The special handling of mercury necessary for mercury cleanup was stressed because of the compound's easy vaporization and fast absorption into porous surfaces and materials.
The new procedures caused the phones in the Office of Environmental Health and Safety to ring almost immediately. It became evident that mercury was being spilled round the clock.
A skeleton mercury cleanup crew was put on duty at all hours. The hospital housekeeping staff was selected as the surrogate spill-response team.
Although a few problems were encountered initially communicating safe cleanup procedures, the staff soon took great pride in their new role. Frequent training and hands-on experience is currently provided for new personnel. With this assistance, we know when, where, and by whom mercury is spilled. It has also been very effective to devote a few minutes of Right-to-Know lectures to inform all university employees about the use and abuse of mercury.
The mercury vapor analyzer is used routinely to test patient rooms, repair areas, dental clinics, and neonatal incubators, and to test deletion after mercury spills. Problems are still encountered. In the first survey of 24 incubators, one showed a low level mercury vapor contamination (0.003 Mg/M3); another significant levels (0.020 mg/m 3). Fortunately the badly contaminated unit was used exclusively as a transport unit and any particular infant's exposure was brief. The units had to be completely dismantled and decontaminated.
If you call to report a spill and cleanup after regular working hours, leave a message according to the recorded instructions. The recording device will list home telephone numbers of our staff members in the case of a significant emergency.
Mr. Easton is a Certified Industrial Hygienist at the University of Virginia, Environmental Health and Safety Office. Charlottesville, Virginia. This paper was excerpted from a lecture by the author at the American Industrial Hygiene Conference in Montreal, Canada, June 1987.
N Engl J Med. 2000 Jun 15;342(24):1791. Images in clinical medicine.
Elemental mercury embolism to the lung. Gutierrez F, Leon L. Hospital Sotero Del Rio, Santiago, Chile.
A 21-year-old dental assistant attempted suicide by injecting 10 ml
(135 g) of elemental mercury (quicksilver) intravenously.
She presented to the emergency room with tachypnea, a dry cough, and
bloody sputum. While breathing room air, she had a partial pressure
of oxygen of 86 mm Hg. A chest radiograph showed that the mercury was
distributed in the lungs in a vascular pattern that was more pronounced
at the bases. The patient was discharged after one week, with
improvement in her pulmonary symptoms. Oral chelation therapy with
dimercaprol was given for nine months, until the patient stopped the
treatment; the urinary mercury level did not change during this period.
At follow-up at 10 months, she was healthy, with none of the renal,
gastrointestinal, or neurologic effects that can result from the
oxidation of mercury in the blood and consequent exposure of these
organ systems. The abnormalities on the chest radiograph were still
apparent. Although these abnormalities are striking, the absence of
clinical toxicity in this patient illustrates the differences
in the acute and chronic effects of exposure to elemental mercury,
inorganic mercury (e.g., mercuric chloride), and organic mercury
(e.g., dimethylmercury). Inorganic and organic mercury are much more
toxic than elemental mercury; for example, a dose of 400 mg of mercury
in the form of dimethylmercury is usually lethal.