Skip directly to search Skip directly to A to Z list Skip directly to site content




On Thursday, October 25, 2001, staff from the Michigan Department of Community Health (MDCH) Division of Environmental and Occupational Epidemiology (DEOE) responded to a small-volume mercury release at 7746 Red Arrow Highway, Apartment C-38, Watervliet, Michigan. Two adults and two boys (ages 2 and 11) resided in the apartment.

A wall-mounted thermostat was determined to be the likely source of mercury contamination. Many wall-mounted thermostats, typically round dial models, contain a glass mercury bulb that is mounted on a bi-metal tilt switch. This switch oscillates the furnace on or off as the mercury moves from one end of the bulb (open) to the other (closed) with changes in temperature. The residents reported that on Wednesday, October 24, 2001, an electrician replaced the living room thermostat. The mercury was discovered the following day, October 25, 2001, when the parents observed the 2-year-old boy, lying down on the chair and pushing a bead of mercury around with his tongue. Closer inspection revealed many small mercury beads on the chair and the surrounding carpet. The residents contacted the Poison Control Center (PCC), which advised them of the hazards of mercury inhalation, the importance of immediate ventilation, and cleanup measures. PCC also advised the residents to contact DEOE for on-site assistance and recommended both children undergo biological testing for mercury.

DEOE staff responding to mercury spills are equipped with personal protective equipment appropriate for small-volume mercury spills (gloves, shoe-covers, eye protection, and tyvek coveralls if needed), a handheld spotlight for conducting visual inspections, small-volume cleanup kits, tools for picking up and containing mercury beads, and an Ohio Lumex RA915+ mercury vapor analyzer. The RA915+ displays real-time mercury concentrations in nanograms per cubic meter (ng/m3) with a detection limit of 2 ng/m3 and an accuracy of ± 20 percent. The sensitivity and repeatability of this portable, real-time instrument make it well-suited for delineating contamination and documenting levels of mercury vapor in the field.

DEOE staff arrived at 6:30 p.m. on October 25, 2001. Two officers from the Berrien County Sheriff's Department were already at the scene and departed shortly after DEOE's arrival. An emergency medical technician who lived nearby was also on hand to assist. The children had been evacuated earlier to a nearby apartment.

Breathing zone measurements were taken at the children's breathing level (30-32 inches above the floor). Item, surface, and floor samples were taken 1-4 inches above the area under test. All windows were closed for the initial readings. Windows were opened later, which substantially reduced many of the measurements. Breathing zone readings ranged from 1,500 ng/m3 at the apartment entryway to 4,500 ng/m3 in the living room (Table 1). Breathing zone readings from the children's bedroom ranged from 2,900 to 3,400 ng/m3. These readings exceed the guidelines set by the Agency for Toxic Substances and Disease Registry (ATSDR) for residential indoor air of 1,000 ng/m3.

DEOE staff tested household items that might have been directly or indirectly contaminated. Several household items were contaminated beyond recovery. Testing household items such as toys, pillows, blankets, clothes, and shoes is done by placing the item(s) in a clean plastic bag and then testing the airspace within the bag. Several bags of household items were tested and many were discarded (Table 1). The most heavily contaminated items were the living room sitting chair and the surrounding carpet. DEOE staff recovered as much mercury as feasible from the chair and carpet before leaving.

The tenants moved from their apartment to another apartment within the complex on October 26, 2001. MDCH recommended that the living room/hallway carpet and padding in the apartment be removed and the floors cleaned before the apartment could be re-rented.

The tenants took both children to the hospital the evening of the cleanup, October 25, 2001. The hospital collected biological samples from both children (blood and urine). Blood samples collected from the two-year-old on October 25, 2001, showed 10 micrograms per liter of mercury. The results noted a range of 0-13 micrograms per liter. Another blood sample taken five days later, on October 30, 2001, showed mercury levels had declined to less than 1 microgram per liter. A urine sample collected from the two-year-old on October 31, 2001, showed 10 micrograms per liter. Results for blood samples collected from the 11-year-old boy on October 25, 2001, were lost by the hospital. However, no elevated levels were noted.

The two-year-old boy was admitted to the hospital for two nights beginning October 25, 2001. X-rays revealed three "dense metallic" forms in his gastrointestinal tract. Treatment included a charcoal gavage and monitoring. On Saturday, October 27, 2001, the mother noted that the 2-year-old became extremely violent--an abnormal behavior for the child. Subsequent X-rays revealed two mercury beads had passed out of the child, but one bead, approximately 0.125 inches in diameter, remained lodged in his gastrointestinal tract. On November 13, 2001, the parents took the two-year-old boy to the Detroit Children's Hospital where the child was physically manipulated (suspending upside down, rotating, etc.), which worked free the remaining mercury and allowed it to pass from the child.

Clearance testing for the apartment occurred on December 17, 2001. As per MDCH instructions, the apartment owners had removed and discarded all contaminated furniture, items, carpet and padding. Clearance readings indicated very low mercury levels similar to those that might normally be found in a residence (Table 2). With regard to mercury, re-occupancy was granted by MDCH on December 17, 2001. Other outstanding structural issues remain unresolved by this report.


Calls for assistance on residential and school mercury spills occur with regularity at the MDCH/DEOE. The calls often involve households with young children. The possible routes of exposure to mercury include inhalation, ingestion, and dermal absorption; however, inhalation of mercury vapors is the primary concern in a residential setting.

Inhalation of high levels of elemental mercury can cause permanent neurological damage and kidney impairment. The Agency for Toxic Substances and Disease Registry (ATSDR) recommends that breathing zone mercury levels not exceed 1,000 ng/m3 (1). This recommended level is based on both animal studies and human epidemiology studies that describe the health effects of inhalation of mercury-contaminated air. Workers who were exposed to mercury vapors in an occupational setting exhibited hand tremors, increases in memory disturbances, and slight subjective and objective evidence of autonomic nervous system dysfunction. The ATSDR minimal risk level (MRL) for mercury in air was derived from the lowest observed adverse effect level (LOAEL) from a study of exposure to 26,000 ng/m3 of mercury. Because workers in the study were only exposed during working hours, the LOAEL was adjusted to account for continuous exposure. The resulting value was divided by an uncertainty factor of 10 to protect sensitive human subgroups and by a factor of 3 because a LOAEL was used rather than a no observed adverse effect level (NOAEL). The resulting MRL is 0.2 ug/m3 (micrograms per cubic meter) or 200 ng/m3. An MRL is defined as an estimate of the daily exposure level to a hazardous substance that is likely to be without appreciable risk of adverse, non-cancer health effects. The ATSDR recommended value for residential setting of less than 1,000 ng/m3 is an action level that, if exceeded, would prompt the need for further cleanup or other remedial action.

Breathing zone measurements in the home at 7746 Red Arrow Highway indicated that the occupants were exposed to mercury in the air at levels up to 4.5 times the residential action level of 1000 ng/m3. Biological tests and concomitant x-rays revealed the two-year-old boy had ingested a small quantity of mercury. However, because elemental mercury is poorly absorbed in the digestive tract and the child's digestive tract was not compromised, it is unlikely that lasting adverse health effects resulted from this ingestion. The boy's sudden violent behavior, as reported by his parents, may be related to his acute inhalation of mercury vapors. Behavioral changes are a noted effect of mercury poisoning. The parents report that both boys habitually slept for a couple hours each night on the sitting chair with their heads resting on the cushion and blankets over their heads. This scenario would greatly increase the mercury inhalation exposure for that period; however, only one night passed before discovery of the mercury.


Children may be at greater risk than adults from certain kinds of exposure to hazardous substances at sites of environmental contamination. They engage in activities such as playing outdoors and hand-to-mouth behaviors that increase their exposure to hazardous substances. They are shorter than adults, which means they breathe dust, soil, and vapors close to the ground. Their lower body weight and higher intake rate results in a greater dose of hazardous substance per unit of body weight. The developing body systems of children can sustain permanent damage if toxic exposures are high enough during critical growth stages.

Children who breathe metallic mercury vapors may develop a disorder known as acrodynia, or pink skin. The symptoms of this disorder include severe leg cramps; irritability; and abnormal redness of the skin, followed by peeling of the hands, nose, and soles of the feet. Itching, swelling, fever, tachycardia (fast heart rate), hypertension (elevated blood pressure), excessive salivation or sweating, rashes, fretfulness, sleeplessness, and /or weakness may also be present. This disorder may also occur in teenagers and adults. Exposure to mercury vapors is more dangerous for young children than for adults because inhaled mercury vapors easily pass into the brain and nervous system of young children and may interfere with the development process. Exposure to high levels of mercury vapor can also cause lung, stomach, and intestinal damage. Death due to respiratory failure has resulted in cases of extreme exposures (2).

Given the high levels of mercury detected, MDCH was concerned for the safety of the children living in the apartment where the release of mercury occurred. The parents were very responsive to PCC and MDCH recommendations for evacuation, discarding contaminated belongings, testing, medical follow-up, and relocating.


An accidental release of elemental mercury in an apartment at 7746 Red Arrow Highway, Watervliet, Michigan, resulted in breathing zone concentrations of mercury above the ATSDR recommended action level of 1,000 ng/m3. MDCH considered the situation to be an urgent public health hazard requiring immediate action.

Residents of the apartment, including two boys aged 2 and 11, were evacuated and relocated to another apartment within the complex. Subsequent air monitoring of the apartment with an Ohio Lumex RA-915+ real-time mercury vapor analyzer indicated that mercury concentrations were less than the ATSDR action level, and clearance for re-occupancy was given by the MDCH on December 17, 2001 (Table 2). No public health hazard currently exists in the apartment.


The following recommendations were made in the course of the investigation by MDCH:

  1. Isolate the areas and objects known to have been impacted by mercury contamination.
  2. Collect biological samples of children to assess exposure.
  3. Test contaminated areas and objects to determine appropriate actions (keep, clean, or discard).
  4. Vacate the apartment until cleanup and clearance testing can be completed.
  5. Remove carpet, padding, and other objects contaminated with mercury and clearance test all potential areas of human exposure to mercury.


The recommendations below were implemented and no further action is necessary at this site.

  1. MDCH responded to the site of a residential mercury spill on October 25, 2001;
  2. MDCH used a real-time mercury vapor analyzer to delineate the extent and severity of mercury contamination. Breathing zone readings ranged from 1,500 ng/m3 to 4,500 ng/m3;
  3. MDCH recommended immediate clean up and biological testing for impacted individuals;
  4. MDCH provided health education for the family;
  5. MDCH returned on December 17, 2001, with the real-time mercury vapor analyzer and found levels satisfactory for human habitation.


  1. ATSDR (Agency for Toxic Substances and Disease Registry). 2000. Suggested Action Levels for Indoor Mercury Vapors in Homes or Businesses with Indoor Gas Regulators.

  2. ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxicological Profile for Mercury, Update.


Michigan Department of Community Health
Division of Environmental and Occupational Epidemiology

Daniel Lince, M.S., Health Educator

Linda D. Larsen, Ph.D., Toxicologist

ATSDR Regional Representative

Mark Johnson
Regional Services, Region V
Office of the Assistant Administrator

ATSDR Technical Project Officer

Alan Yarbrough
Division of Health Assessment and Consultation
Superfund Site Assessment Branch


This Mercury Spill Assist Health in Watervliet Michigan Consultation was prepared by the Michigan Department of Community Health 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 health consultation was begun.

Alan W. Yarbrough
Technical Project Officer, SPS, SSAB, DHAC, ATSDR

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

Richard Gillig
Chief, State Program Section, SSAB, DHAC, ATSDR


Table 1: October 25, 2001, Mercury vapor readings for 7746 Red Arrow Highway.

Breathing Zone Sampling Reading (n/m3)
Ambient Outside Air 17-28
Threshold 1,500
Breathing zone throughout home 1,500 - 4,500
Floor and Item samples(1)  
Sofa (living room) Background*
Carpet surrounding sitting chair (living room) 15,000 - 43,000
Sitting chair (living room) 19,500 - 47,000
Mattress (children's bedroom) Background
Mattress (parent's bedroom) Background
Bagged Items(2)  
Bag#1 (clothing, sleeping bag, teddy bear, shoes) 1,800
Bag#2 (clothing, linens, pillows, blankets) 15,455
Bag#3 (Sitting chair cushion) >50,000
Bag#4 (Mickey Mouse Comforter, Batman Comforter, pillows, shirts) 33,100
Bag#5 (2 pillows, blankets, comforter) 36,400

*at background levels, no increase 1-3" above item's surface to indicate surface contamination

Table 2: December 17, 2001, Clearance Readings for 7746 Red Arrow Highway.

Breathing Zone Sampling Reading (ng/m3)
Ambient Outside Air 11-17
Threshold 41
Breathing zone throughout home 39-50
Floor samples(3)  
Bare floor (carpet removed) 36-53

1. Floor samples taken 1-4 inches off flooring; item samples taken 1-4 inches off item's surface
2. Items are placed in a large plastic bag and closed. Readings are taken from within the bag.
3. Floor samples taken 1-4 inches off flooring; item samples taken 1-4 inches off item's surface

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

A-Z Index

  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #