Numerous military training exercises require detonation of live or training munitions which can release residual chemicals into the environment. It is critical to accurately assess and prioritize the risks to human and ecological health such that reasonable and effective remedial decisions can be made. Energetic compounds such as RDX are commonly found in soils and other environmental matrices at military training installations. The environmental fate, behavior, and effects of these compounds have been well defined, yet their breakdown products and metabolites had not been assessed. Perchlorate, a chemical that occurs both in nature and through synthesis, is another environmental issue of special concern to the Department of Defense (DoD), the Environmental Protection Agency, and many other federal, state, and local entities. The data for perchlorate occurrence in the U.S. have largely focused on protection of drinking water resources, with relatively few investigations considering ecological exposures. Thus, an array of assessment methodologies and techniques was needed to objectively identify and more fully understand potential ecological impacts associated with other DoD-related contaminants.
This effort was a continuation of the knowledge-base established in SERDP project ER-1223, which used field and laboratory studies to characterize and quantify ecological risks associated with the distribution and movement of perchlorate and explosive compounds in the ecosystems. The objective of this project was to examine the impact of environmental exposures of perchlorate, explosives, and their metabolites on birds, rodents, reptiles, fish, amphibians, and invertebrates at contaminated sites. Specifically, bioavailability across trophic levels was evaluated and toxicological impacts on exposed biota were assessed.
Ecological receptors deemed to be at risk from exposure to perchlorate, explosives, and their metabolites were identified through a number of inter-related sub-projects, including analytical, terrestrial, and aquatic toxicology as well as ecological modeling. Important routes of exposure and potential food web-related exposure pathways were determined. Sensitive markers of contaminant toxicity were used to assess the ecological impacts of exposure. Movement of the contaminants within abiotic and biotic components of the ecosystem was assessed with ecological modeling. Long-term risks to exposed populations of birds were evaluated using individual-based population models driven by inputs specific to perchlorate, explosives, and their metabolites and the site-specific abiotic conditions.
By applying the understanding of explosive- and explosive metabolite-mediated effects to contaminated sites, the species, life stages, and populations at risk from exposure to these contaminants were identified. The exposure routes were identified as well as the food web-related exposure pathways. Geographic distribution of contaminants was identified through field and laboratory data that modeled the movement of these compounds among biotic components of the ecosystem. Specific results on perchlorate ecotoxicology were compiled into a book published through the Society of Environmental Toxicology and Chemistry (SETAC) in 2006.
The identification of ecological risks and the development of exposure and toxicity models for energetics and perchlorate have aided the implementation of technical-based risk assessment and a more accurate evaluation of contamination levels. In addition, accepted risk management paradigms aid in better developing remediation goals and objectives at DoD-contaminated sites.