Review A Review of Events That Expose Children to Elemental Mercury in the United States Robin Lee,1 Dan Middleton,1 Kathleen Caldwell,2 Steve Dearwent,1 Steven Jones,1 Brian Lewis,3 Carolyn Monteilh,4 Mary Ellen Mortensen,2 Richard Nickle,1 Kenneth Orloff,1 Meghan Reger,1 John Risher,1 Helen Schurz Rogers,2 and Michelle Watters1 1Agency for Toxic Substances and Disease Registry, Atlanta, Georgia, USA; 2Centers for Disease Control and Prevention, Atlanta, Georgia, USA; 3EDS, an HP Company, Plano, Texas, USA; 4TKC Integration Services, LLC, Anchorage, Alaska, USA Objectiv On an D c Onclusi : Concern for children exposed to elemental mercury prompted the Agency for Toxic Substances and Disease Registry and the Centers for Disease Control and Prevention to review the sources of elemental mercury exposures in children, describe the location and proportion of chil- dren affected, and make recommendations on how to prevent these exposures. In this review, we excluded mercury exposures from coal-burning facilities, dental amalgams, fish consumption, medi- cal waste incinerators, or thimerosal-containing vaccines. Dat : We reviewed federal, state, and regional programs with information on mercury s Ources releases along with published reports of children exposed to elemental mercury in the United States. We selected all mercury-related events that were documented to expose (or potentially expose) chil- dren. We then explored event characteristics (i.e., the exposure source, location). Dta : Primary exposure locations were at home, at school, and at other locations such as ysnthei industrial property not adequately remediated or medical facilities. Exposure to small spills from bro- ken thermometers was the most common scenario; however, reports of such exposures are declining. Ducsi Ons : Childhood exposures to elemental mercury often result from inap- Omen Dati propriate handling or cleanup of spilled mercury. The information reviewed suggests that most releases do not lead to demonstrable harm if the exposure period is short and the mercury is properly cleaned up. r ec Ons : Primary prevention should include health education and policy initiatives. For larger spills, better coordination among existing surveillance systems would assist in understanding the risk factors and in developing effective prevention efforts. Key w Or Ds : children, elemental mercury, environmental health, exposure, United States. Environ Health Perspect 117:871–878 (2009). doi:10.1289/ehp.0800337 available via http://dx.doi.org/ [Online 12 January 2009] Mercury occurs naturally in the earth’s crust. It exists in the environment as the result of natural processes and human activities. Mercury forms a dense, silvery liquid at room temperature (density = 13.534 g/cm3). Liquid mercury has a relatively low vapor pressure (0.0085 mmHg at 25°C) and volatilizes slowly at room temperature. If not managed properly, indoor mercury spills can release mercury into the air over weeks or even years [Agency for Toxic Substances and Disease Registry (ATSDR) 1999]. Heating mercury results in much higher, potentially lethal air­ borne mercury concentrations, especially in indoor spaces (Putman and Madden 1972; Solis et al. 2000; Taueg et al. 1992). Although mercury may be ingested, it is poorly absorbed in the normal gastrointestinal tract [World Health Organization (WHO) 1991]. Dermal absorption of mercury is also a minor exposure pathway (Hursh et al. 1989). However, mercury vapor is readily absorbed by the lungs, making inhalation the exposure route of greatest concern. The ATSDR mini­ mal risk level for chronic mercury inhalation is 0.2 µg/m3 (ATSDR 1999). Health concerns. The health effects asso­ ciated with acute elemental mercury expo­ sure vary with the magnitude and duration of exposure. The potential health effects from inhaling high mercury concentrations (e.g., ~ 10,000 µg/m3) are primarily respi­ ratory [ATSDR 1999; U.S. Environmental Protection Agency (EPA) 2002] and include pneumonitis, bronchiolitis, pulmonary edema, and in some instances death. Exposure to mercury vapor (e.g., 10–100 µg/m3) over prolonged time periods can cause neurobe­ havioral effects, mood changes, and trem­ ors. Chronic exposures are associated with hypertension and autonomic nervous system dysfunction (WHO 2003). Mercury expo­ sure is also associated with acrodynia (painful extremities), a rare hypersensitivity reaction to mercury (Caravati et al. 2008). Children are more sensitive to mercury and are at greater risk than adults after certain mercury exposures (ATSDR 1999; Rogers et al. 2007). Urine mercury levels < 5 µg/L urine have not been associated with neuro­ cognitive effects in children (Bellinger et al. 2006; DeRouen et al. 2006). Reference levels. Mean [95% confi­ dence interval (CI)] urine mercury levels in the 2003–2004 Centers for Disease Control and Prevention (CDC) National Health and Nutrition Examination Survey (NHANES) were 0.254 µg/L (95% CI, 0.213–0.304 µg/L) Environmental Health Perspectives • volume 117 | number 6 | June 2009 for children 6–11 years of age and 0.358 µg/L (95% CI, 0.313–0.408 µg/L) for chil­ dren 12–19 years of age (CDC 2005c, 2007) (Table 1). In 2001–2002, the mean NHANES total blood mercury levels in children 1–5 years of age was 0.32 µg/L (95% CI, 0.27–0.38 µg/L), and the 95th percentile was 1.2 µg/L (95% CI, 0.9–1.6 µg/L) (CDC 2005c). Objective. In New Jersey, an indus­ trial building formerly used to manufacture mercury thermometers was renovated and converted in 2004 to a child care facility (ATSDR 2007b). Unfortunately, the prop­ erty was not adequately cleaned before reno­ vation, leaving residual contamination with elemental mercury (ATSDR 2007b). Such contamination can cause significant exposure for children or adults who are present. People exposed in these types of events may require medical evaluation and biomonitoring. Concern for children exposed to elemen­ tal mercury through inhalation prompted the ATSDR and the CDC to review existing data to identify the common sources of elemental mercury exposure in children; describe the location, demographics, and proportion of children affected by elemental mercury expo­ sure events in the United States; and make recommendations on preventing elemental mercury exposures and responding appropri­ ately to spills and releases. This review does not focus on mercury­ related health effects or treatment, nor does it review mercury exposures associated with coal­burning facilities, dental amalgams, fish Address correspondence to R. Lee, Agency for Toxic Substances and Disease Registry, 4770 Buford Hwy NE, MS F­57, Atlanta, GA 30341 USA. Telephone: (770) 488­ 0705. Fax: (770) 488­ 1537. E­ mail: RLee3@cdc.gov We acknowledge the assistance of the American Association of Poison Control Centers, Association of Occupational and Environmental Clinics, and Agency for Toxic Substances and Disease Registry/ Hazardous Substances Emergency Events Surveillance System for providing access to and information about the data they collect. The findings and conclusions in this report are those of the authors and do not necessarily repre­ sent the official position of the Centers for Disease Control and Prevention or the Agency for Toxic Substances and Disease Registry. The authors declare they have no competing Received 29 October 2008; accepted 12 January financial interests. 2009. 871