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Mercury Exposure --- Kentucky, 2004

In November 2004, a student aged 15 years brought a small vial of liquid mercury onto a school bus and into a high school in Kentucky. A subsequent investigation revealed that mercury had been in the student's possession for more than a year and that substantial amounts had been spilled in multiple locations. This report describes the results of that investigation, which indicated that 1) duration of exposure was associated with the amount of mercury absorbed by exposed persons and 2) extensive multiagency collaboration facilitated an efficient response. The investigation further revealed that, although mercury exposure is common, clinicians might not be aware of how to evaluate and treat patients with mercury exposure. State and federal health agencies should provide schools, clinicians, and local health department staff with readily accessible guidelines* for use in mercury spills and exposures.

On November 10, school officials at a county high school in rural Kentucky discovered approximately 15 students playing with liquid mercury in the school cafeteria. School officials separated the students, confiscated and bagged their clothes, and closed the cafeteria. Local health department and environmental protection officials were notified. Questioning revealed that a boy aged 15 years had brought a vial of mercury to school on a school bus. Parents were advised to consult their health-care providers about whether their child should be tested for mercury exposure. Several children were tested at the local hospital, but none had concentrations exceeding background levels other than the student who brought the mercury to the school.

During November 10--24, local and state health department staff coordinated a public health investigation of the mercury exposure, and the U.S. Environmental Protection Agency (EPA) conducted an environmental investigation. Law enforcement and health department staff interviewed relevant observers and persons who directly handled the mercury. Serum and 24-hour urine mercury samples (measured in micrograms per liter [µg/L]) were collected for all persons who reported substantial exposure (i.e., persons who were known to have handled the mercury on multiple occasions or who spent 1 hour or more in rooms or vehicles during periods in which those places were known to be contaminated) and were tested at a local hospital. EPA and Kentucky Department for Environmental Protection (KDEP) personnel collected environmental air samples (measured in nanograms per cubic meter [ng/m3]) at implicated locations and conducted ongoing cleaning and environmental assessment until ambient mercury levels were brought within acceptable limits (i.e., <3,000 ng/m3) (2) or the site was deemed unrecoverable.

EPA and KDEP officials assessed the student's school and home environments and initiated cleanup procedures. The school cafeteria contained mercury levels ranging from 5,280 ng/m3 to 36,600 ng/m3. The school was closed by the school superintendent to limit the potential for exposure of children and to facilitate cleaning of the cafeteria. After 2 days of cleanup, heating, and venting, EPA deemed the school safe for students to return.

Approximately 15 school buses were also tested and/or cleaned. The family's mobile home and possessions were deemed unrecoverable (ambient mercury was >50,000 ng/m3 at outset of investigation and later reduced to 11,550 ng/m3) and were removed and destroyed. The family van (14,950 ng/m3 reduced to 1,285 ng/m3) and an additional vehicle (>50,000 ng/m3 reduced to 174 ng/m3) were eventually cleaned and returned to the family. However, a third vehicle (41,275 ng/m3 reduced to 36,610 ng/m3), belonging to the family of a friend of the student, was determined unrecoverable and removed by EPA.

During the cleanup process, more liquid mercury was collected than could be contained in the vial that the student had carried to school. The student claimed that he had found the mercury in the trash of a dentist's office during a visit on November 9. Investigation revealed that the mercury was kept in a storage area at the dentist's office that doubled as a restroom for patients. Examination of dental office records indicated that the student had visited the dentist on August 29, 1997, August 21, 2003, and November 9, 2004. Additional evidence suggested that the student had mercury for several months before the school exposure. Under further questioning, the student admitted having obtained the mercury during a previous visit to the dentist (presumably the August 2003 visit). Investigators suspected that the student took mercury during each of the last two visits, accounting for the excess mercury recovered in the cleanup process. EPA personnel disposed of all remaining mercury in the dentist's office.

Nine family members, including the student, had lived in the mobile home during different periods preceding the incident. In addition, the student's friend and his family, including a pregnant female, indicated that they had spent considerable time in one of the contaminated vehicles. Moreover, an additional 12 persons were said to have spent substantial amounts of time in the mobile home.

Blood concentrations were obtained for the student and seven family members who were living in the mobile home. Blood mercury levels ranged from 32 µg/L to 72 µg/L (normal: 0--10 µg/L) (3). The 24-hour urine mercury concentrations obtained from seven of these patients ranged from 28 µg/L to 496 µg/L (normal: 0--19 µg/L) (4). The student had the highest mercury levels for both blood and urine (i.e., 72 µg/L blood and 496 µg/L for initial urine concentration). Urine mercury concentrations were directly associated with amount of time spent in the mobile home. Three of the children, including the student, lived in the contaminated home for 15 months and had urinary concentrations ranging from 193 µg/L to 496 µg/L, whereas three of the children who lived in the home for only 10 weeks had urinary concentrations ranging from 28 µg/L to 68 µg/L. The additional family member, a woman who had not been in the mobile home since June 2004, had a urine mercury concentration of 241 µg/L. Three additional persons, who were exposed to the contaminated vehicle that had to be destroyed, had urinary mercury levels ranging from 4 µg/L to 8 µg/L. An infant born to one of these persons in May 2004 had no signs of mercury exposure. Five family members, including the student responsible for the initial exposure, were chelated by using succimer. The three adolescent family members with the longest exposures received chelation in multiple sessions. Final urine mercury levels were 48, 44, and 35 µg/L, for the student and the two other children, respectively.

Several of the children living in the mobile home experienced itchy rashes and headaches. In late 2003, one girl aged 13 years residing in the mobile home had experienced several months of illness consistent with mercury exposure (e.g., unexplained tachycardia, hypertension, desquamation of soles and palms, rashes, diaphoresis, muscle pain, insomnia, vomiting, and behavioral and psychiatric changes). She was hospitalized for approximately 30 days. Mercury toxicity was not considered at the time, so testing was not performed. The patient improved with a cardiac stent concurrent with removal from the exposure setting.

After the investigation, the Kentucky Department for Public Health (KDPH) held a meeting with all agencies involved to discuss lessons learned. Participants agreed to 1) better identify a lead coordinator for future investigations, 2) continue to increase coordination and communication between all agencies, and 3) increase awareness of school and local public health officials regarding mercury exposure. KDPH produced a flyer for schools that was distributed on April 15, 2005. Information related to the dangers of mercury and the proper response to a mercury spill also was sent to all local health departments.

Reported by: L Sims, MSN, A Indukuri, MPH, Lincoln Trail District Health Dept, Elizabethtown; J Walsh, LaRue County Health Dept, Hodgenville; HA Spiller, MS, Kentucky Regional Poison Center, Louisville; C Kaelin, MSPH, Kentucky Dept for Public Health. DA Thoroughman, PhD, Career Epidemiology Field Officer Program, Div of Public Health Partnerships, National Center for Health Marketing, CDC.

Editorial Note:

Mercury spills and exposures are common. In EPA Region 4, a total of 40 documented mercury spills occurred during September 1, 1999--March 23, 2005, with 14 of those spills occurring in fiscal year 2005 (R. Bittinger, EPA, personal communication, 2005). Kentucky experienced 15 spills during that period, 10 of which were associated with schools and five with residences only. After publicity mounted regarding the case described in this report, the local health department and the Kentucky Regional Poison Center received numerous inquiries from private citizens about quantities of mercury in their possession. Thus, local public health officials and health-care providers should be familiar with the symptoms of mercury exposure, how to respond appropriately in cases of spills, and what local resources are available for mercury cleanup and disposal.

During this investigation, a strong association was observed between the duration of exposure and remaining levels of mercury in patients. Compared with three children who had recent exposures of 10 weeks' duration, a woman who had been exposed for 8--10 months but left that setting approximately 5 months before the November incident had substantially higher levels of mercury, as evidenced by high urine concentrations. Children exposed for 15 months in the mobile home had substantially higher levels than those who had only 10 weeks' exposure. Only those children who experienced the 15-month exposure were recommended for chelation. Finally, although the family acquaintances were exposed to high levels of mercury (i.e., in their contaminated vehicle), their exposures were periodic and brief, which might have resulted in limited mercury levels.

The mercury exposures described in this report, which occurred in multiple locations and resulted in extensive property loss and intensive cleanup efforts, highlight the utility of multiagency collaboration in investigations. Collaboration of local, state, private, and federal officials improved the response time and investigation outcome. This coordination is essential to mount a public health response to exposures such as this, which quickly outstrip local resources.

The events described in this report also underscore the need for appropriate and consistent medical advice for clinicians when responding to similar events. Resources are needed at the local level to help health-care providers and public health officials recognize, evaluate, and treat patients with mercury exposures.

References

  1. CDC. Toxicological profiles: public health statement for mercury. Atlanta, GA: US Department of Health and Human Services, CDC; 2005. Available at http://www.atsdr.cdc.gov/toxprofiles/phs46.html.
  2. US Environmental Protection Agency. Mercury response guidebook---suggested action levels for indoor mercury exposures in homes or businesses with indoor gas regulators (attachment E). Washington, DC: US Environmental Protection Agency; 2001. Available at http://www.epa.gov/epaoswer/hazwaste/mercury/guidebook.
  3. CDC. Blood mercury levels in young children and childbearing-aged women---United States, 1999--2002. MMWR 2004;53:1018--20.
  4. Hudson PJ, Vogt RL, Brondum J, Witherell L, Myers G, Paschal DC. Elemental mercury exposure among children of thermometer plant workers. Pediatr 1987;79:935--8.

* Such as a toxicological profile for mercury (1).

Includes Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee.

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Date last reviewed: 8/17/2005

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