Editorial on “Exposure assessment of a mercury spill in a Nevada school—2004”

Editorial on “Exposure assessment of a mercury spill in a Nevada school—2004”

In their article in this issue, Azziz Baumgartner and colleagues describe an elemental mercury spill at a middle school in Nevada. Although there are limited reports of these incidents in the medical literature, mercury spills are common causes of hazardous materials incidents, as referenced in the article. Of great importance, the Nevada spill was recognized on the day the mercury was brought to the school, and, therefore, there was no opportunity for prolonged exposure.

The Nevada middle school mercury spill resulted in a major response by a fire department hazardous materials team, the Nevada Division of Environmental Protection, Nevada State Division of Health, and the Centers for Disease Control. Showers were used to decontaminate 62 students who were seen or self-reported handling mercury, and the students were sent home without their clothes or belongings. Dermal absorption of liquid metallic mercury should not be significant (1), and elemental mercury vapor is not appreciably absorbed dermally (2), so the need for showering the students is not evident. At most, handwashing should have been sufficient. Although no information is available concerning the potential for inhalation exposure through contamination of clothing, direct reading mercury detectors are generally available, and select confiscation of clothing documented to be contaminated by use of this instrumentation provides a more rational course of action. The response to this incident cost approximately $50,000; not an insubstantial amount. This incident demonstrates the high cost of a full court response to a school mercury spill.

This incident also demonstrated several excellent choices. The first was a rapid response in notifying students and their families of the incident, and in preventing additional exposure while the extent of contamination could be determined. The study also used National Health and Nutrition Examination Survey (NHANES) data for reference urine levels, which is more appropriate than using occupational exposure limits such as the American Conference of Governmental Industrial Hygienists (ACGIH) Biological Exposure Indices, which were not meant to be used for children. The study also wisely differentiated between the student who brought the mercury and had the potential for more prolonged and higher exposure, and the rest of the student body. As reported, none of the students was evaluated in an emergency care facility, so the initial urine screening might have served to reduce later medical care costs, as well as the potential for litigation.

Given the low urine mercury levels measured in the Nevada spill, similar published findings with short term exposures in Arizona schools (3) and our collective experience with similar unpublished incidents, it is time to re-evaluate the need for universal urine mercury screening with short-term exposures in children without other sources of persistent mercury exposure inside or outside the school. Also, decontamination can be more narrowly applied where direct-read instrumentation can document presence or lack of contamination, sparing the cost of new clothing. In a world of more limited resources, there is room to become more cost-efficient in our response to specific types of hazardous materials incidents where the published data demonstrate lack of significant exposure or toxicity.