On February 20 2003, the State of Idaho notified and requested assistance of EPA to investigate a mercury spill in a residence in Meridian, Idaho. A mercury thermometer broke inside the home. The mercury fell onto the carpet. The wife is 7 months pregnant and there is a 3 month old child in the household. Given the potential exposure scenario, with small child and pregnant woman in the home, Idaho DEQ, Bureau of Hazardous Materials and Health District #4 requested EPA assistance to assess residual mercury vapor concentrations in the home with respect to ATSDR suggested action levels. The family relocated to a relative's home until screening and cleanup was completed.
Initial screening of the residence by the START contractor on 2/21/03, using a hand-held Jerome Mercury Vapor Analyzer (MVA), found mercury vapor concentrations present in air of up to 500 micrograms per cubic meter (ug/m3), just above the carpet in the area of the spill. The ATSDR chronic Minimal Risk Level (MRL) is 0.2 ug/m3 for indoor mercury vapors in homes, and the EPA Reference Concentration (RfC) of 0.3 ug/m3.
On 2/21/03, the START contractor, under direction of the OSC and with consent of the homeowner, removed a 2 foot square piece of carpet where the spill occurred and applied a mercury amalgam on the floor under the removed carpet in an attempt to clean up the area to acceptable level. After first ventilating, then heating up the house to approximately 85 degrees F, followup monitoring with the Jerome MVA found 5 to 7 ug/m3 above the carpet outside of the area removed and in other parts of the room. The affected room is approximately 10 X 15 feet in area.
On 2/22/03, the ERRS contractor, under direction off the OSC and with consent of the homeowner, removed all articles in the room to the outside porch, then removed the carpeting and padding, which was wrapped in plastic and placed in a haz waste rolloff that was placed outside the residence. Powdered sulpher was spread on the exposed subfloor, then vacuumed with a wet/dry vac. The vacuum was also put into the rolloff. The house was ventilated for an hour, then closed up and the temperature allowed to reach 77 degrees F. Monitoring was then done using a Lumex RA-915 MVA, which has a lower detection limit of 2 nanograms mercury per cubic meter of air (2 ng/m3 or 0.002 ug/m3). No significant hits were observed in the room or elsewhere in the house anywhere near the action level of 0.3 ug/m3. Removed household articles (except the carpet and pad) were covered in black plastic and the Lumex was stuck inside the plastic. No significant hits were observed. The furniture and other household articles were returned to inside the house, the residents were told they could safely return to the house, and EPA and contractors demobilized evening of 2/22/03.
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Laboratory analysis will be done of a representative sample of the removed carpet and pad to determine appropriate disposal. The carpet may be disposed of as mercury contaminated waste or special waste depending on laboratory results. The material is presently in a covered and secured rolloff at the residential location, pending determination of disposal. The rolloff should be picked up by Thursday of this week.
EPA will initiate discussion with State of Idaho regarding how to handle similar situations in the future. A more cost/efficient way to deal with broken thermometer type situations should be identified than having to mobilize EPA contractors from outside the state.
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