Following a 1986 decision by Montgomery County in Maryland to construct a municipal waste resource recovery facility near the town of Dickerson, the local community expressed concern regarding the potential human health effects from air emissions of dioxins and trace metals released through the stack of the proposed facility. To address this concern, the County conducted health risk studies and ambient monitoring programs before and after the facility became operational. The purpose of the health risk studies was to determine potential cancer and non-cancer risks to the nearby residents from the operations of the facility. The purpose of the ambient monitoring programs was to determine if any changes would occur in the ambient levels of certain target chemicals in the environmental media, and if such changes can be attributed to the operations of the facility. Accordingly, the County conducted a multiple pathway health risk assessment in 1989 prior to the construction of the facility. The pre-operational health risk assessment was based on estimated stack engineering parameters and available stack emissions data from municipal waste resource recovery facilities that were operating in the United States, Canada and Europe during the 1980’s. The health risk assessment used established procedures that were accepted by the U.S. Environmental Protection Agency (U.S. EPA) and many state agencies at that time. The Montgomery County Resource Recovery Facility (RRF) became operational in the spring of 1995. The facility is equipped with the state-of-the-art air pollution control (APC) equipment including a dry scrubber-fabric filter baghouse system to control organics and trace metals, ammonia injection system to control nitrogen oxides, and activated carbon injection system to control mercury. In 2003, the County retained ENSR International to update the 1989 health risk assessment study. In the 2003 operational-phase update, as-built engineering data and measured stack emissions data from a total of eighteen quarterly stack emissions tests were used. The study was conducted in accordance with the U.S. EPA’s Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities published in 1998 [1], and an Errata, published in 1999 [2]. Both the 1989 study and the 2003 study demonstrated that there is a very low chance (less than one chance in a million) for occurrence of cancer and no adverse non-cancer health effects to the nearby community as a result of exposure to facility-related emissions. The multi-media ambient monitoring programs were conducted in abiotic and biotic environmental media. These programs included an air-monitoring component and a non-air monitoring component. The pre-operational phase of the air media and non-air media monitoring was conducted in 1994–1995. The pre-operational program was designed to produce baseline data for target chemicals in both air and non-air media. The operational-phase air media monitoring was conducted in 1997 and 2003. The operational-phase non-air media monitoring was conducted in 1997 and 2001. Target chemicals monitored in both air and non-air media included polychlorinated dioxins and furans (PCDDs/PCDFs) and selected toxic metals (arsenic, beryllium, cadmium, chromium, lead, mercury, and nickel). The non-air media included crops, farm pond surface water and fish tissue, and cow’s milk. The ambient levels of target chemicals monitored in the operational phase of the facility (1997, 2001 and 2003) demonstrated no measurable difference from the ambient levels of these chemicals monitored in the pre-operational phase (1994–95) of the facility, in both the air media and non-air media. The results of the health risk studies and ambient monitoring programs demonstrate that municipal waste combustion facilities that are equipped with the state-of-the-art air pollution control equipment pose no significant health risk to the population.

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