Military activities associated with training, munitions manufacturing, and demilitarization have resulted in soil, surface water, and sediment concentrations of munition compounds and their breakdown products. Since these areas often include wildlife habitat, risk incurred from exposure needs to be evaluated. This is particularly important in a risk management context when balancing the potential for adverse effects from exposure with habitat alterations associated with cleanup operations. To determine safe levels of exposure, toxicity data from controlled laboratory studies are needed. This information then can be used to develop toxicity reference values (TRV) for mammals, birds, reptiles, and terrestrial amphibians.
The objective of this research was to develop toxicity data in the laboratory setting consistent with the needs of the risk assessment community that could be used at any Department of Defense installation. Specifically, this work looked to fill the primary toxicological data gaps for a representative laboratory animal model for each vertebrate guild where toxicity data are lacking.
Studies were conducted that evaluated the effects of various munitions in representative bird, mammalian, reptile, and amphibian species that could be exposed to these compounds from soil releases. Specific studies were designed to consider primary environmental exposure routes, ecologically important health effects, application of toxicological data in a risk assessment context, and a reduction in the uncertainty in the derivation of thresholds for adverse effects (i.e., TRV derivation). Selection of compounds was based on a lack of class-specific information and reported prevalence in the environment at military installations. Work was leveraged from other programs where toxicological studies were already under way.
Wildlife models used included western fence lizards (Sceloporus occidentalis; reptiles), red-backed salamander (Plethodon cinereus; amphibians), Northern bobwhite (Colinus virginanus; birds), and the white-footed mouse (Peromyscus leucopus; mammals). Compounds tested included 2,4,6-trinitrotoluene (TNT), 2,4- and 2,6-dinitrotoluene (DNT), 2-amino-4,6-dinitrotoluene and/or 4-amino-2,6-dinitrotoluene (A-DNT), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 1,3,5-trinitrohexahydro-1,3,5-triazine (RDX). Each study was performed according to approved protocols with the results published in the peer-reviewed literature; two studies remaining are in preparation.
Toxicity of tested energetics and associated breakdown products resulted in varying effects relative to the laboratory species tested. Differences in effects were largely due to physiological differences between vertebrate class representatives and are believed to be useful laboratory models for future toxicology research. These data have provided valuable insight into ecotoxicological risk assessment and serve as a valuable surrogate for estimating effects to species in field situations where questions regarding the relative risk of exposure to energetic compounds exist. These data have and will be integrated into the chemical-specific Wildlife Toxicity Assessment profiles and used to derive TRVs for site-specific risk assessment purposes.
Data from this project will be used to determine the safety of wildlife exposure to munition compounds through TRV derivation. This information will help risk managers make informed decisions when balancing habitat disturbances from associated cleanup operations with the health of valued wildlife species. In addition, data will aid field investigations of effects through the identification of compound-specific targets of toxicity.