Residential mercury spills from gas regulators.

Many older homes are equipped with mercury-containing gas regulators that reduce the pressure of natural gas in the mains to the low pressure used in home gas piping. Removal of these regulators can result in elemental mercury spills inside the home. In the summer of 2000, mercury spills were discovered in the basements of several Chicago-area homes after removal of gas regulators by gas company contractors. Subsequent inspections of approximately 361,000 homes by two northern Illinois gas companies showed that 1,363 homes had residential mercury contamination. Urine mercury screening was offered to concerned residents, and results of urine bioassays and indoor mercury air measurements were available for 171 homes. Six of these 171 homes (3.5%) had a cumulative total of nine residents with a urine mercury > or = 10 microg/L. The highest urine mercury concentration observed in a resident was 26 microg/L. Positive bioassays were most strongly associated with mercury air concentrations > 10 microg/m3 on the first floor [odds ratio (OR) = 21.4 ; 95% confidence interval (CI) , 3.6-125.9] rather than in the basement (OR = 3.0 ; 95% CI, 0.3-26) , and first-floor air samples were more predictive of positive bioassays than were basement samples. Overall, the risk of residential mercury contamination after gas regulator removal ranged from 0.9/1,000 to 4.3/1,000 homes, depending on the gas company, although the risk was considerably higher (20 of 120 homes, 16.7%) for one of the contractors performing removal work for one of the gas companies. Gas companies, their contractors, and residents should be aware of these risks and should take appropriate actions to prevent these spills from occurring and remediate them if they occur.

Elemental mercury spills.

Sources of elemental mercury (Hg0) include old natural gas regulators, manometers, sphygmomanometers, thermometers, and thermostats. Causes of Hg0 spills include improper storage, container breakage, children playing with Hg0, the breakage of devices containing Hg0, and ritualistic use of Hg0. Inhalation is the primary exposure route for Hg0. Mercury released into the environment can enter lakes and streams, where bacteria convert it into methylmercury, which bioaccumulates in fish. Chronic exposure to Hg0 vapors can damage the kidneys and neurologic system. Short-term exposure to high levels of Hg0 vapors may cause lung damage, nausea, vomiting, diarrhea, increases in blood pressure or heart rate, skin rashes, and eye irritation, among other effects. Minimizing Hg0 dispersal is important after an Hg0 spill. Tracking by shoes or apparel or vacuuming can spread Hg0, increasing airborne concentrations and cleanup costs. The Illinois Department of Public Health's response to an Hg0 spill depends on the size of the spill. Airborne concentrations after large spills are mapped with a mercury vapor analyzer (MVA). The cleanup begins with the spill site and any hot spots that were identified with the MVA. Hard surfaces can usually be cleaned, but contaminated porous items must be discarded. Leaving marginally contaminated items outdoors for a month or more during warm weather may dissipate the Hg0. After a cleanup, clearance sampling is conducted to determine if further cleanup is needed. The best way to prevent Hg0 spills is reduce its use. Key words: cleanup, elemental mercury, health effects, mercury, prevention, remediation, spill, spill management.