HEALTH CONSULTATION
SINGLE FAMILY RESIDENCE MERCURY SPILL
MONONA, DANE COUNTY, WISCONSIN
Elemental mercury was spilled after a fever thermometer was broken in the master bedroom of a single-family residence in Monona, Wisconsin, on January 8, 2004. The residents removed all visible mercury, but they used a vacuum cleaner, which worsened the air levels of mercury vapor in the bedroom. Initial air monitoring conducted by the Department of Health and Family Services (DHFS) showed airborne mercury levels in the master bedroom exceeded acceptable levels. DHFS requested that the DHFS Division of Public Health's Agency for Toxic Substances and Disease Registry's Cooperative Agreement Program provide a health consultation on interpretations of the findings. Residents relocated to a basement guestroom while the bedroom and house were vented. Subsequent air monitoring indicated this ventilation had decreased airborne mercury levels and re-occupancy of the master bedroom was safe. The level and duration of mercury vapor exposure from the broken thermometer posed no apparent health hazard to the residents. As demonstrated by the air sampling, a small amount of elemental mercury can be readily volatilized by vacuuming and has the potential to pose a long-term human health exposure concern. Venting a room or residence was effective at reducing and eliminating exposure concerns when the spill amount was low and when all visible mercury was recovered. No further actions are needed by the residents, DHFS, or other agencies, regarding this incident.
On January 12, 2004, a resident of a single-family home in Monona, Wisconsin, contacted DHFS regarding spilled elemental mercury related to a broken fever thermometer. The spill occurred 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 a vacuum cleaner for about five minutes for further cleaning. One of the residents was in her first trimester of pregnancy. Upon receipt of the call, DHFS advised the couple to bag and seal the vacuum 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, and February 2, 2004. A Lumex RA-915+ Mercury Analyzer (S/N 432) was used to record airborne mercury levels. Prior to collecting data, a baseline check and calibration against an internal standard were performed on the instrument. Airborne data collected in the home was compared to ATSDR guidance levels described in "Suggested Action Levels for Indoor Mercury Vapors in Homes or Businesses with Indoor Gas Regulators" (ATSDR 2000). Airborne mercury data collected during the three site visits are presented in Table I.
Prior to January 12, one resident obtained and used two SKC passive dosimeter badges for measurement of airborne mercury exposure. The dosimeters were placed in the living room and master bedroom and were exposed from January 9, 2004 to January 12, 2004. Dosimeters were then sent to the Wisconsin Occupational Hygiene Laboratory in Madison, Wisconsin, for analysis. Dosimeter readings were less than 2.7 µg/m3 for the living room and 5.2 µg/m3 for the master 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 per cubic meter (µg/m3). The home was heated with radiant perimeter heat. DHFS staff observed that 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 master bedroom, on the dresser or in the drawers. Airborne mercury levels in the master bedroom were generally between 10 and 12 µg/m3 and as high as 14 µg/m3. Levels in other main floor rooms ranged from 3 to 4 µg/m3. The basement was 1.7 µg/m3. The bagged vacuum cleaner was stored outside the home. Headspace was tested in the bag and found to be over 50,000 µg/m3.
On the basis of the monitoring results, DHFS recommended that the residents continue using the guestroom 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 Analyzer
Single Family Residence, Monona, Wisconsin, January 2004
All concentrations in micrograms per cubic meter (µg/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 µg/m3 in the living room and most other rooms on the main floor with the exception of the master bedroom. The master bedroom had levels of 2 to 3 µg/m3, including at the dresser, in the drawers, and at the floor surface of the spill site. Residents were advised to continue to use the basement guestroom and to continue to ventilate the master bedroom.
Two days prior to the February 2, 2004, visit, ventilation of the master bedroom halted, and windows were closed. Heat returned to the room. Levels of mercury vapor throughout the home, including the master bedroom, were below 1 µg/m3. The residents were advised that re-occupancy of the master bedroom was acceptable. No further action was recommended other than to continue to ventilate the house when practical and convenient.
TOXICOLOGICAL PROFILE OF ELEMENTARY MERCURY
Elemental mercury affects the nervous system, cardiovascular system, digestive tract, and kidneys in all humans, as well as the development of young children. The primary route of entry for elemental, metallic mercury is by inhalation of vapors (ingestion and dermal absorption of metallic mercury is not usually significant). Metallic mercury readily vaporizes at room temperature. Laboratory animals that inhaled high levels of elemental mercury vapors (above 1,000 µg/m3) had permanent neurological damage and kidney impairment. Workers who were exposed for many years to mercury vapors between 14 and 76 µg/m3 exhibited mildly increased hand tremors, difficulty with heel-to-toe gait, and more impaired performances on neurobehavioral tests.
The ATSDR chronic inhalation Minimal Risk Level (MRL) for mercury vapor in air is 0.2 µg/m3 (ATSDR 1999). This MRL was derived from the study that found an increased frequency of tremors among works exposed over 15 years to 26 µg/m3 mercury, which was designated as the lowest observed adverse effect level (LOAEL). Because adults in this occupational study were only 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 Governmental Industrial Hygienists' (ACGIH's) occupational 8-hour time weighted hour Threshold Limit Value of 25 µg/m3 (ACGIH 2003). The MRL is then obtained by dividing the adjusted value by an uncertainty factor of 10 to protect sensitive humans and by a factor of three because a LOAEL was used rather than a no observed adverse effect level or NOAEL. ATSDR defines an MRL as an "estimate of daily human exposure to a hazardous substance at or below which that substance 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 Action Levels 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 levels in the breathing zone of a home do not exceed 1.0 µg/m3 and that at or below this level is acceptable for the re-occupancy of any structure. Exceeding the action level of 1.0 µg/m3 prompts the need for clean up or other remedial actions to reduce exposures. This recommended action level is based on both animal laboratory studies and human epidemiologic studies that examine the effects from inhaling air containing elevated mercury vapors. ATSDR's suggested action levels recommends that if mercury vapor levels in a home reach or exceed 10.0 µg/m3, that residents are isolated from the exposure and actions are taken to remediate the spill. The ATSDR guidance also recommends an action level of 10.0 µg/m3 when testing the air from a plastic bag where clothing was placed with mercury contamination. The guidance recommends that clothing not be returned to the owner when mercury vapor in the bag reaches or exceeds 10.0 µg/m3.
In summary, residents in the Monona home breathed mercury vapors for a short time. Taking into consideration the highest mercury vapors levels they breathed over this time frame, it is not likely this exposure caused harmful health effects and, as a result, the exposure posed no apparent 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 and they were encouraged to speak with their obstetrician regarding exposure concerns.
DHFS recognizes that children can be especially sensitive to contaminants. Children are often at greater risk than adults to certain kinds of exposure from hazardous chemicals in the environment. Children engage in activities, such as playing outdoors and hand-to-mouth behaviors, that increase their exposure to hazardous substances. Being much smaller than adults and playing on their hands and knees, children breathe air close to the ground that can have more dust, 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's bodies are developing and have permanent damage if toxic exposures are high enough during critical growth stages. For that reason, DHFS considers children as one of the most sensitive population evaluated for this health consultation, and always takes into account children when evaluating exposures to contaminants.
Because one of the residents was pregnant, fetal exposure was a potential concern. A literature review, including the ATSDR Toxicological Profile for Mercury, did not indicate that the exposure levels measured in the home should be of concern with respect to the developing fetus, given both the concentration and short exposure time.
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 specifically addresses broken fever thermometers. While the amounts of mercury involved in such releases is often very small and would not typically be expected to represent a hazard, vacuuming after such a spill can produce airborne mercury exposures of public health concern. Guidance in the fact sheet and information conveyed in presentations to Wisconsin hazardous material responders have been directed at increasing awareness of this topic.
Henry Nehls-Lowe, MPH
Epidemiologist
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 of Health and Family Services under a cooperative agreement with the Agency for Toxic Substances and Disease Registry (ATSDR). It is in accordance with approved methodology and procedures existing at the time the public health consultation was begun.
Gail D. Godfrey
Technical Project Officer, CAT, SSAB, DHAC
The Division of Health Assessment and Consultation, ATSDR, has reviewed this public health consultation and concurs with the findings.
Sven E. Rodenbeck
for Roberta Erlwein
Chief, CAT, SSAB, DHAC, ATSDR
