Lee et al. mercury. Methods consumption, medical waste incinerators, or thimerosal­containing vaccines. Unless otherwise stated, mercury refers to elemental We conducted a comprehensive review of the existing exposure data sources and the scientific literature to identify and quantify common sources of mercury exposure for children in the United States and to describe the location, demographics, and proportion of children affected by such exposures. We also reviewed numerous mercury exposure prevention initiatives. Existing exposure data sources. The data sources reviewed included an extensive list of federal, state, and regional programs that cap­ ture information on spills and other hazardous releases. We identified and contacted key per­ sonnel to assess the relevance of the data. The following five data sources contained relevant data: ATSDR health consultations (HCs) and emergency response calls, ATSDR Hazardous Substances Emergency Events Surveillance (HSEES), U.S. Coast Guard National Response Center database, American Association of Poison Control Centers (AAPCC) National Poison Data System, and Association of Occupational and Environmental Clinics (AOEC) Pediatric Environmental Health Specialty Units (PEHSUs). We considered other data sources, such as those maintained by the U.S. EPA and the National Institute for Occupational Safety and Health, but they did not contain infor­ mation relevant to this report. We used the following criteria to select relevant mercury releases (exposure events): First, the event had to be reported between 2002 and 2007, a time frame that represents the most current information available on exposure events. Second, the event had to take place in the United States. Finally, the event had to expose or potentially affect a child (or children) ≤ 18 years of age. If the data source did not contain information on the age of the exposed or affected persons, the event was included if it occurred at a loca­ tion frequented by children (e.g., an elemen­ tary or secondary school, a child care facility, or a private residence). These criteria were treated as guidelines, because each data source has its own functionality and limitations on how events could be queried. We provide a description of the information available below, by data source. 2003–2004. Age group (years) 6–11 12–19 872 Literature review. We supplemented the information from the data sources by searching the National Library of Medicine’s PubMed (National Library of Medicine 2008) and Thomson Scientific’s Web of Science (Thomson Reuters 2008) for mercury exposure events involving children ≤ 18 years of age. We used the search terms “elemental mercury,” “metallic mercury,” and “liquid mercury.” We reviewed only publications documenting U.S.­ based exposures between January 2002 and December 2007 and omitted publications that did not describe a specific exposure event. Exposure scenarios. To further character­ ize elemental mercury exposure events and locations, we present several common expo­ sure scenarios, to broadly illustrate the nature and public health impact of such events. Initiatives for preventing mercury exposure. We reviewed a selection of ongoing federal­ and stateb­ased mercury initiatives to highlight innovative and successful approaches to reduc­ ing childhood mercury exposure. Data Synthesis Existing exposure data sources. ATSDR HCs and emergency response calls. ATSDR is the lead federal public health agency for implementing the health provisions of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (“Superfund”) and its amendments. Under this act, ATSDR evaluates the public health impact of hazardous substances released into the environment. ATSDR receives numer­ ous inquiries regarding mercury exposure events. Although some inquiries are not sys­ tematically recorded, some are documented as ATSDR HCs, and others are documented as emergency response calls. We reviewed the HCs to identify events that document potential mercury exposure to children. We selected events if there was a completed mercury exposure pathway in air and children were potentially exposed. During the years 2002–2007, ATSDR and its state cooperative agreement partners produced HCs for 26 events that exposed or potentially exposed children to elemental mer­ cury in air. These events took place between 2001 and 2006. Of these 26 incidents, two children were potentially exposed in more than one location. Fourteen of the 26 (54%) incidents were classified as public health haz­ ards. Although not always mutually exclusive, the location of the exposure event was most frequently described as a home (46%; 12 of 26) or school (42%; 11 of 26). Two of the 26 events (8%) occurred at medical care facilities, one at a child care center (4%), and one in a car (4%). The source of these mercury expo­ sures included use or storage in schools, release from broken thermometers or sphygmoma­ nometers, offg­assing from flooring containing a mercury catalyst, and an unknown source. The estimated amount of mercury reported in these 26 exposure events ranged from 9 to 700 mL. The maximum indoor air concentra­ tions of mercury ranged from 0.05 µg/m3 to > 92 µg/m3. Biomonitoring was conducted for children considered exposed in 11 events. The mercury concentrations in blood ranged from below the level of detection (LOD) to 29 µg/L. The urine concentrations ranged from below the LOD to 18 µg/g creatinine. The LOD varied by event. The approximate time interval between exposure and urine col­ lection for testing ranged from 6 to 20 days. In addition to these HCs, emergency response calls are received from state and local health officials, environmental officials, health care providers, and the general public. From 2000 to 2007, emergency response staff responded to more than 3,000 such inquiries, 459 of which concerned mercury events. The majority of the events occurred in residen­ tial settings (44%; 203 of 459) or in schools (13%; 60 of 459). These calls were most often made by private citizens (31%; 143 of 459); many calls concerned cleaning up mercury­ related spills (38%; 175 of 459) or health­ related questions about mercury exposure (35%; 159 of 459). Given the relatively few mercury events documented by ATSDR HCs (n = 26) com­ pared with the number of mercury­related calls to ATSDR’s emergency response staff (n = 459), the HCs represent only a small fraction of all such exposures and may not be representative of mercury events nationwide. ATSDR HSEES. ATSDR developed the HSEES system to collect data on uncontrolled and/or illegal releases of any hazardous sub­ stance (ATSDR 2007a). Releases of chemicals for > 72 hr are considered chronic releases and are not captured by HSEES. Fourteen state health departments report chemical releases to HSEES. The data collected include the type of release, the amount of chemical(s) released, the location of the event (e.g., private residence, school), information about any persons with symptoms or injuries (“victims”), and any possible contributing causes that are known. The number of persons ovlume 117 | number 6 | June 2009 • Environmental Health Perspectives Table 1. Geometric means, selected percentiles, and the corresponding 95% CI for urine mercury concentrations (µg/L) for children sampled as part of NHANES, Sample size (no.) 286 722 Geometric mean (95% CI) 0.254 (0.213–0.304) 0.358 (0.313–0.408) 50th 0.190 (0.160–0.230) 0.320 (0.270–0.360) Selected percentile (95% CI) 75th 90th 0.430 (0.330–0.560) 0.700 (0.530–0.840) 1.14 (0.610–1.61) 1.59 (1.13–2.52) 95th 1.96 (1.13–2.97) 2.83 (1.88–3.66)