Lee et al. A student found a container of mercury in a storage shed and took it home. The student subsequently brought approximately 60 mL of the mercury to school, where several students played with it. Only 20 mL of the mercury brought to school was recovered. Mercury vapor levels inside the school reached 50 µg/m3. Of the 854 students potentially exposed, 200 com­ pleted an exposure history and provided urine samples. The mean urine mercury level for all students tested was within the normal range (mean = 0.36 µg/L; range, 0.14–11.4 µg/L). Students who reported having seen mercury (n = 66) had significantly higher urine mercury levels than those who did not. Those students who touched the mercury (n = 36) or got it on their clothes (n = 28) also had significantly higher urine mercury levels than those who did not. Few students had signs or symptoms of mercury toxicity. From the 1960s to the 1980s, many schools installed synthetic gymnasium floors that con­ tained a mercury catalyst in the polyurethane formulation for the floor covering; the finished product typically contained 0.1–0.2% mercury (ATSDR 2003). One manufacturer reported installing more than 25 million pounds of polyurethane flooring. These surfaces slowly release mercury vapor, particularly from dam­ aged areas. The airborne mercury concentra­ tion in these gymnasiums varies from 0.79 to 1.6 µg/m3 (ATSDR 2003). In a similar report, mercury vapor measurements in the breath­ ing zone were 0.042–0.050 µg/m3 (ATSDR 2004). The variation in airborne concentra­ tions likely includes differences in sampling equipment, the size and condition of the floor, and indoor ventilation. Exposures in other locations. Mercury exposures can also occur in medical facilities and in buildings where mercury was previ­ ously used. Sources include prior mercury spills, mercury stored on abandoned prop­ erty, and mercury found in medical or dental offices. In some cases, mercury is carried or tracked to multiple locations, making the pri­ mary exposure location difficult to identify. In most situations, the reuse of industrial property does not result in childhood mer­ cury exposure. However, the trend toward redeveloping industrial property for other uses requires due diligence to ensure that past exposures do not become future health haz­ ards. For example, in Hoboken, New Jersey, a building formerly used to manufacture mer­ cury vapor lamps was converted to private condominiums (Orloff et al. 1997). After moving into the building, residents reported seeing mercury droplets on their oven and kitchen counters. Subsequent investigations revealed pools of mercury in the subflooring and elevated air mercury levels throughout the building. Urinary mercury concentrations of the occupants ranged from 4.8 to 133 µg/g 876 creatinine. All occupants of the building were relocated, and the building was demolished. Similarly, the New Jersey child care facil­ ity mentioned previously closed in 2006 after environmental sampling revealed mer­ cury in dust (< 0.02–0.25 µg/wipe) and air (7.0–11.4 µg/m3) (ATSDR 2007b). After the facility closed, approximately one­ third of the children were found to have urine mercury levels above the comparison value (5 µg/g creatinine). Serial testing confirmed that the elevated urine mercury levels decreased over time to below the comparison value. Children may also be exposed to elemen­ tal mercury from abandoned industrial prop­ erty. Two teenagers in Texarkana, Arkansas, removed a large amount of mercury from an abandoned neon sign plant (Lowry et al. 1999). The mercury weighed between 23 and 100 lb (770–3,300 mL). One teenager took mer­ cury home and shared it with other children. Investigators found mercury contamination in 12 residences, a convenience store, and a school classroom. For persons who agreed to provide two rounds of urine and blood mer­ cury tests, initial urine concentrations ranged as high as 68.7 µg/g creatinine, and blood mer­ cury concentrations ranged as high as 104 µg/L. Neurobehavioral assessments of eight exposed individuals failed to establish a relationship between mercury exposure and test results. Finally, mishandling of mercury and mercuryc­ontaining medical equipment occurs in some medical and dental offices. In one example, mercury was spilled from a sphyg­ momanometer (ATSDR 2001). A patient who observed the attempted cleanup called the poison control center. The state health department and the state EPA responded and measured breathing zone mercury levels between 45 and 50 µg/m3. Visible beads of mercury were observed in the clinic, which served both adults and children. Patients and staff were evacuated from the area, and a pro­ fessional environmental contractor was hired to carry out remedial activities. Initiatives for preventing mercury expo- sure. In this review we focus on mercury expo­ sures that are preventable, and several federal and stateb­ased initiatives are designed to pre ­ vent future exposures. For example, in 2001 Congress passed the Small Business Liability Relief and Brownfields Revitalization Act, setting up the funding of grants for brown­ field activities administered by the U.S. EPA. Brownfields are defined in the statute as “real property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant” (Small Business Liability Relief and Brownfields Revitalization Act of 2001). The U.S. EPA Brownfields Program awards grants to state, tribal, and local governments and not­for­ profit organizations to assess and clean up eli­ gible brownfields, including sites that may have been contaminated with mercury through industrial activity or illegal disposal (U.S. EPA 2008a). States may oversee assessment and cleanup activities, where appropriate, to ensure the cleanup meets state standards. Through its role in the brownfield ini­ tiative, ATSDR created a Brownfields/Land Reuse Steering Committee to assess the impacts of redevelopment on public health. This effort includes the broader health impacts of revital­ ization and a sustainable environment. A few states have passed laws that affect locating schools and redeveloping property for use as a school. Ten states have laws that prohibit locating a school on or near pollu­ tion sources, including mercuryc­ontaminated sites. Six states require environmental assess­ ments for any new school locations. However, the vast majority of states have yet to adopt such regulations. To reduce the amount of mercury enter­ ing the waste stream and lessen the incidence of spills and exposures, some states have restricted the sale and disposal of mercury­ containing products. For example, legisla­ tion has been enacted (or proposed) regarding the sale or disposal of mercury­ containing thermometers, thermostats, switches, relays, blood pressure devices, electronic appliances, batteries, and dental amalgams. Some legisla­ tion specifically targets the use of products containing mercury in schools or health care settings. The U.S. EPA provides a table of these initiatives by state on its Web site (U.S. EPA 2008). Currently, 45 states have various mercury initiatives. Some states are developing initiatives to proactively educate teachers and students regarding the potential dangers of mer­ cury exposures and to assist in school labo­ ratory cleanouts. For example, the Illinois Department of Public Health has an inter­ active mercury education Web site that includes curricula for teachers, information on handling spills in the classroom, and activities for children to learn how to avoid exposure (Illinois Department of Public Health 2008). Limitations. Duplication and inconsistent reporting of events between data sources and within data sources make any estimate of the national incidence of mercury exposure to chil­ dren unreliable. The quality and completeness of the information reported may be affected by personal liability for causing or cleaning up the spill. Spills in private residences are likely to be underreported because residents are unaware of the health hazard or the reporting require­ ments for certain mercury spills. Published case reports and case series often provide exposure and health outcome infor­ mation, but these are subject to reporting bias, retrospective data collection, and imprecise ovlume 117 | number 6 | June 2009 • Environmental Health Perspectives