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Elemental mercury was spilled after a fever thermometer was broken in the master bedroom of asingle-family residence in Monona, Wisconsin, on January 8, 2004. The residents removed allvisible mercury, but they used a vacuum cleaner, which worsened the air levels of mercury vaporin the bedroom. Initial air monitoring conducted by the Department of Health and FamilyServices (DHFS) showed airborne mercury levels in the master bedroom exceeded acceptablelevels. DHFS requested that the DHFS Division of Public Health's Agency for Toxic Substancesand Disease Registry's Cooperative Agreement Program provide a health consultation oninterpretations of the findings. Residents relocated to a basement guestroom while the bedroomand house were vented. Subsequent air monitoring indicated this ventilation had decreasedairborne mercury levels and re-occupancy of the master bedroom was safe. The level andduration of mercury vapor exposure from the broken thermometer posed no apparent healthhazard to the residents. As demonstrated by the air sampling, a small amount of elementalmercury can be readily volatilized by vacuuming and has the potential to pose a long-termhuman health exposure concern. Venting a room or residence was effective at reducing andeliminating exposure concerns when the spill amount was low and when all visible mercury wasrecovered. No further actions are needed by the residents, DHFS, or other agencies, regardingthis incident.


On January 12, 2004, a resident of a single-family home in Monona, Wisconsin, contactedDHFS regarding spilled elemental mercury related to a broken fever thermometer. The spilloccurred in the couple's master bedroom and resulted in visible mercury on a dresser and floor.The couple responded by picking up as much elemental mercury as they could and then used avacuum cleaner for about five minutes for further cleaning. One of the residents was in her firsttrimester of pregnancy. Upon receipt of the call, DHFS advised the couple to bag and seal thevacuum and to seal the master bedroom, including cold air returns, and to ventilate the bedroom.The residents relocated their sleeping area to the basement guestroom.

DHFS visited the home on January 13, 2004, and subsequently on January 15, 2004, andFebruary 2, 2004. A Lumex RA-915+ Mercury Analyzer (S/N 432) was used to record airbornemercury levels. Prior to collecting data, a baseline check and calibration against an internalstandard were performed on the instrument. Airborne data collected in the home was comparedto ATSDR guidance levels described in "Suggested Action Levels for Indoor Mercury Vapors inHomes or Businesses with Indoor Gas Regulators" (ATSDR 2000). Airborne mercury datacollected during the three site visits are presented in Table I.

Prior to January 12, one resident obtained and used two SKC passive dosimeter badges formeasurement of airborne mercury exposure. The dosimeters were placed in the living room andmaster bedroom and were exposed from January 9, 2004 to January 12, 2004. Dosimeters werethen sent to the Wisconsin Occupational Hygiene Laboratory in Madison, Wisconsin, foranalysis. Dosimeter readings were less than 2.7 g/m3 for the living room and 5.2 g/m3 for themaster bedroom. These results were consistent with readings obtained with the Lumex RA-915+ on January 13.


The residence was an approximate 50 year old, 1,500 square foot single family ranch home.Upon entry to the home by DHFS staff, mercury levels were found to be over 2 micrograms percubic meter (g/m3). The home was heated with radiant perimeter heat. DHFS staff observedthat the master bedroom door was closed and towels were placed at the base to restrict airflow.Cold air returns were sealed with duct tape. No visible mercury was observed in the masterbedroom, on the dresser or in the drawers. Airborne mercury levels in the master bedroom weregenerally between 10 and 12 g/m3 and as high as 14 g/m3. Levels in other main floor roomsranged from 3 to 4 g/m3. The basement was 1.7 g/m3. The bagged vacuum cleaner was storedoutside the home. Headspace was tested in the bag and found to be over 50,000 g/m3.

On the basis of the monitoring results, DHFS recommended that the residents continue using theguestroom rather than the master bedroom, lower the temperature, and ventilate the master bedroom room and home.

Table I

Airborne Mercury Concentrations Collected with Lumex RA-915+ Mercury AnalyzerSingle Family Residence, Monona, Wisconsin, January 2004 All concentrations in micrograms per cubic meter (g/m3)
Location Date
1/13/04 1/15/04 2/2/04
Outdoors 0.147* 0.002 0.010
Living Room 2.500 0.995 0.243
Master Bedroom 14.270 2.201 0.610
MBR Dresser 10.280 2.316 -
Right Dresser Drawer (highest) 10.920 2.307 -
Left Dresser Drawer (highest) 10.280 - 0.542
MBR Floor near Dresser 8.048 2.883 -
Behind Dresser 9.310 2.546 0.445
Above Bed - 2.584 -
Above Hamper near MBR Window - 2.610 -
MBR Lamp Table 10.080 - -
MBR Lamp Table Drawer 9.884 - 0.387
Near MBR Vent 10.380 - -
Slippers in Corner 10.870 - -
Shoe Bottom 12.180 - -
Slipper Bottom 12.600 - -
MBR Closet - - 0.568
Closet shoes 12.700 - -
BR2 3.798 1.140 0.333
BR2 Floor 4.300 - -
Bathroom 4.265 1.262 0.445
Bathroom Floor 3.864 - -
Den 3.217 1.067 0.280
Den Floor 3.501 - -
Kitchen - 0.872 0.181
Basement 1.756 0.669 0.113
Bagged vacuum Headspace 50+ - -

*Higher outdoor reading was attributed to prior instrument use.
- = no reading


Upon entering the home, DHFS staff measured mercury vapor levels at 1 g/m3 in the livingroom and most other rooms on the main floor with the exception of the master bedroom. Themaster bedroom had levels of 2 to 3 g/m3, including at the dresser, in the drawers, and at thefloor surface of the spill site. Residents were advised to continue to use the basement guestroomand to continue to ventilate the master bedroom.


Two days prior to the February 2, 2004, visit, ventilation of the master bedroom halted, andwindows were closed. Heat returned to the room. Levels of mercury vapor throughout the home,including the master bedroom, were below 1 g/m3. The residents were advised that re-occupancy of the master bedroom was acceptable. No further action was recommended otherthan to continue to ventilate the house when practical and convenient.


Elemental mercury affects the nervous system, cardiovascular system, digestive tract, andkidneys in all humans, as well as the development of young children. The primary route of entryfor elemental, metallic mercury is by inhalation of vapors (ingestion and dermal absorption ofmetallic mercury is not usually significant). Metallic mercury readily vaporizes at roomtemperature. Laboratory animals that inhaled high levels of elemental mercury vapors (above1,000 g/m3) had permanent neurological damage and kidney impairment. Workers who wereexposed for many years to mercury vapors between 14 and 76 g/m3 exhibited mildly increasedhand tremors, difficulty with heel-to-toe gait, and more impaired performances onneurobehavioral tests.

The ATSDR chronic inhalation Minimal Risk Level (MRL) for mercury vapor in air is 0.2 g/m3(ATSDR 1999). This MRL was derived from the study that found an increased frequency oftremors among works exposed over 15 years to 26 g/m3 mercury, which was designated as thelowest observed adverse effect level (LOAEL). Because adults in this occupational study wereonly exposed during working hours, this LOAEL was then adjusted to account for a continuous,24-hour exposure. This LOAEL is comparable to American Conference of GovernmentalIndustrial Hygienists' (ACGIH's) occupational 8-hour time weighted hour Threshold LimitValue of 25 g/m3 (ACGIH 2003). The MRL is then obtained by dividing the adjusted value byan uncertainty factor of 10 to protect sensitive humans and by a factor of three because aLOAEL was used rather than a no observed adverse effect level or NOAEL. ATSDR defines anMRL as an "estimate of daily human exposure to a hazardous substance at or below which thatsubstance is unlikely to pose a measurable risk of harmful (adverse), non-cancerous effects." There is no evidence that the inhalation of elemental mercury vapors causes cancer in humans.

The goals used for indoor airborne mercury levels were from ATSDR's "Suggested ActionLevels for Indoor Mercury Vapors in Homes or Businesses with Indoor Gas Regulators"(ATSDR, 2000). In this guidance, ATSDR recommends that after a spill, mercury vapor levelsin the breathing zone of a home do not exceed 1.0 g/m3 and that at or below this level isacceptable for the re-occupancy of any structure. Exceeding the action level of 1.0 g/m3 prompts the need for clean up or other remedial actions to reduce exposures. This recommendedaction level is based on both animal laboratory studies and human epidemiologic studies thatexamine the effects from inhaling air containing elevated mercury vapors. ATSDR's suggestedaction levels recommends that if mercury vapor levels in a home reach or exceed 10.0 g/m3,that residents are isolated from the exposure and actions are taken to remediate the spill. TheATSDR guidance also recommends an action level of 10.0 g/m3 when testing the air from aplastic bag where clothing was placed with mercury contamination. The guidance recommendsthat clothing not be returned to the owner when mercury vapor in the bag reaches or exceeds10.0 g/m3.

In summary, residents in the Monona home breathed mercury vapors for a short time. Takinginto consideration the highest mercury vapors levels they breathed over this time frame, it is notlikely this exposure caused harmful health effects and, as a result, the exposure posed noapparent human health hazard.


During the January 13, 2004, site visit, exposure guidance levels were explained to the residents.Airborne mercury data collected with the Lumex RA-915+ were provided to the residents andthey were encouraged to speak with their obstetrician regarding exposure concerns.


DHFS recognizes that children can be especially sensitive to contaminants. Children are often atgreater risk than adults to certain kinds of exposure from hazardous chemicals in theenvironment. Children engage in activities, such as playing outdoors and hand-to-mouthbehaviors, that increase their exposure to hazardous substances. Being much smaller than adultsand playing on their hands and knees, children breathe air close to the ground that can have moredust, soil particles, and vapors. Children have a lower body weight, but a higher intake rate,which results in a greater dose to hazardous substances per unit body weight. Also, children'sbodies are developing and have permanent damage if toxic exposures are high enough duringcritical growth stages. For that reason, DHFS considers children as one of the most sensitivepopulation evaluated for this health consultation, and always takes into account children whenevaluating exposures to contaminants.

Because one of the residents was pregnant, fetal exposure was a potential concern. A literaturereview, including the ATSDR Toxicological Profile for Mercury, did not indicate that theexposure levels measured in the home should be of concern with respect to the developing fetus,given both the concentration and short exposure time.


  • The level and duration of mercury vapor exposure due to a broken thermometer in theMonona home posed no apparent health hazard to the residents.


No further actions are needed by the residents, DHFS, or other agencies, regarding this incident.


DHFS has re-written its guidance for responding to mercury spills and now specificallyaddresses broken fever thermometers. While the amounts of mercury involved in such releases isoften very small and would not typically be expected to represent a hazard, vacuuming after sucha spill can produce airborne mercury exposures of public health concern. Guidance in the factsheet and information conveyed in presentations to Wisconsin hazardous material respondershave been directed at increasing awareness of this topic.


  1. Agency for Toxic Substances and Disease Registry. Suggested Action Levels for IndoorMercury Vapors in Homes or Businesses with Indoor Gas Regulators. Atlanta, GA: US PublicHealth Service, Department of Health and Human Services. 2000.

  2. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Mercury,Update. Report Atlanta, GA: US Public Health Service, Department of Health and HumanServices. March 1999.

  3. American Conference of Governmental Industrial Hygienists Worldwide. TLVs andBEIs Based on the Documentation of the Threshold Limit Values for Chemical Substances andPhysical Agencies and Biological Exposure Indices. Cincinnati, OH: ACGIH. 2003.


Henry Nehls-Lowe, MPH
James M. Morrison, CIH, CHMM
Public Health Educator
Bureau of Environmental Health
Division of Public Health
Wisconsin Department of Health & Family Services


This Mercury Spill Health Consultation was prepared by the Wisconsin Department ofHealth and Family Services under a cooperative agreement with the Agency for ToxicSubstances and Disease Registry (ATSDR). It is in accordance with approvedmethodology and procedures existing at the time the public health consultation wasbegun.

Gail D. Godfrey
Technical Project Officer, CAT, SSAB, DHAC

The Division of Health Assessment and Consultation, ATSDR, has reviewed this publichealth consultation and concurs with the findings.

Sven E. Rodenbeck
for Roberta Erlwein

Table of Contents The U.S. Government's Official Web PortalDepartment of Health and Human Services
Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, Atlanta, GA 30341
Contact CDC: 800-232-4636 / TTY: 888-232-6348

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