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Thursday, September 11, 2003The contamination appeared to be mostly contained in a first-floor science classroom, where the silvery metal leaked from a manometer, a U-shaped glass device used to measure air pressure, Dieringer said. About a tablespoon of mercury was found on the classroom's carpet, he said. Mercury vapor also was detected in the connected drains of two nearby restrooms, and two school mops and vacuum cleaners were contaminated. Hmm. I seem to remember playing with mercury in science class. The teacher would put it in a pie pan and pass it around so we could watch the little coherent droplets scatter around the pan. I don't remember anyone getting brain damage from the exposure. But, in this day and age of overprotection, the small amount of mercury was a very big deal: The Akron Health Department was notified Wednesday morning. Then the Akron Fire Department's hazardous materials team was called. The Ohio Environmental Protection Agency also was notified, though the spill did not have to be reported to the EPA because it was under 1 pound, or about a fifth of a cup, said agency spokeswoman Kara Allison. At least the EPA recognizes that it takes a certain amount of mercury to be toxic. To be fair to the school officials and the health department, though, they were probably following the prudent course to avoid running into any trouble with the Occupational Safety and Health Administration. UPDATE: A reader says: Mercury actually is rather dangerous. Its vapor pressure is 50 times the acceptable exposure limit, and it readily disperses into microscopic droplets that have a large aggregate surface area. It's a fairly common occurrence for kids to develop clinical signs of mercury poisoning after finding a small vial. In large enough concentrations mercury is dangerous. However, it isn't necessarily true that it's common for kids to develop clinical signs of mercury poisoning after finding a small vial, unless they intentionally inhale it repeatedly, or they spill it and ground it into the carpet. The reader provides a link to this site, which has this to say about mercury spills: The element mercury is a liquid metal with a vapor pressure of 0.00185 mm at 25 degrees C. This corresponds to a saturation concentration in air of 20 milligrams of mercury per cubic meter of air or 2.4 ppm . The American Conference of Governmental Industrial Hygienists has established a threshold limit for mercury vapor of 0.05 milligrams of Hg per cubic meter of air for continuous 40 hour per week exposure. Long term chronic exposure to mercury vapor in excess of 0.05 mg Hg per cubic meter of air may result in cumulative poisoning. The use of mercury in laboratory amounts in well-ventilated areas is fairly safe; however, mercury can present a health hazard under the following circumstances: 1. When a mercury spill is not cleaned up promptly it may be ground into the floor, fracturing into extremely small particles with a large total surface area (6.4 ft for 1 ml as 10 micron spheres). From such large areas mercury may vaporize at a rate faster than the room's ventilation can safely dilute it. There actually have been case reports of children who developed mercury poisoning after such a spill, as in this case: Features of encephalopathy accompanied by peripheral neuropathy led to a suspicion of heavy metal poisoning. No history of likely exposure to lead could be found; there was no lead piping or paint at home. Further inquiry revealed that the patient's sibling had undergone renal transplantation as a result of nephrotic syndrome, and the family had been provided with a mercury sphygmomanometer for home blood pressure monitoring. Three months before presentation, our patient had dismantled the sphygmomanometer in his bedroomspilling mercury on his bed and carpetand had played with it for a day or two before informing his mother. Attempts had been made to dispose of the mercury by vacuuming, and then by flushing it down the toilet. The suspected diagnosis of mercury poisoning was confirmed by the finding of a serum mercury concentration of 1000 nmol/l (normal reference value <30 nmol/l). And so I stand corrected. The manometer spill on a carpet in the classroom wasn't an over-reaction. posted by Sydney on 9/11/2003 08:44:00 AM 0 comments 0 Comments: |
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