Letter Health Consultation: Health Impact of December 23, 1999, Emissions Release Incident at the Stericycle, Inc. Facility, Lone Butte Industrial Park, Gila River Indian Community, Chandler, Arizona, September 3, 2009.

摘要

Because air-borne mercury was identified as the contaminant of concern for this incident, our office consulted with toxicologists from the U.S. Environmental Protection Agency (EPA), Region 9 to evaluate emissions testing data pertaining to medical waste incinerator operations at the Stericycle facility located at the Lone Butte Industrial Park. As a result, the EPA reported that incinerator emissions tests performed at the Stericycle facility in 1999 showed mercury emissions occurring at a concentration of 3347 micrograms mercury per dry standard cubic meter (micro g/DSCM, micro g/m(sup 3)) and an emission rate (exit velocity) of 14,900 cubic feet per min (acfm). Based on these data and additional information about the incinerator, its surroundings and air dispersion modeling, the EPA predicted a maximum ground-level airborne mercury concentration of 1.25 micro g/m(sup 3). Given this airborne mercury calculation from the EPA, it is important to note that there is no current enforceable Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) for airborne mercury. However, the American Conference of Governmental Industrial Hygienist (ACGIH) recommends a Threshold Limit Value (TLV) of 25 micro g/m(sup 3) averaged over an eight-hour workday for airborne mercury exposure. Therefore the predicted maximum ground-level airborne mercury concentration of 1.25 micro g/m(sup 3) calculated by the EPA is less than the recommended TLV for an eight-hour workday recommended by ACGIH. Although the December 23, 1999 incident was limited to workers at the site, an exposure pathway analysis was conducted to evaluate if residents of the Gila River Indian Community living near the Lone Butte Industrial Park were exposed to airborne mercury due to this incident.