Currently, large uncertainties are associated with estimates of environmental risk resulting from exposure to military-unique contaminants (MUC) and the cleanup goals based on such assessments. Large assumptions and extrapolations applied to MUCs necessitate the use of large safety/uncertainty factors which lead to conservative cleanup goals that are very expensive to obtain with current cleanup technologies.

The objective of this project is to develop a rapid and cost-effective approach for assessing the effects of military-relevant compounds in water, sediment, and soil that can be used effectively in regulatory programs to quantify ecological risk at the molecular-, individual-, and population-level.

Technical Approach to Measure Exposure Response

During the first phase of this project, sediments will be spiked with single military-relevant compounds (i.e., explosives and other organics) and mixtures at a range of concentrations. Sediment-dwelling organisms will be exposed to these contaminated sediments and then screened for the presence of genetic markers using developed genosensors. Whole-organism effects on survival, growth, and reproductive endpoints will be measured. Four sediment dwelling organisms will be used in this project that currently are being used by the Environmental Protection Agency (EPA) and the U.S. Army Corps to develop chronic, sublethal sediment bioassays for national regulatory programs (Neanthes arenaceodentata, Leptocheirus plumulosus, Hyalella azteca, and Chironomus tentans). By simultaneously measuring responses at three distinct levels of biological organization (i.e., genes, whole organisms, and populations), researchers will have the ability to test the reliability of estimating risk at higher levels of organization (e.g., populations) using information that can be quickly and inexpensively collected at lower levels of organization (i.e., the level of genes).

During the first year, researchers have successfully conducted more than 20 toxicity/bioaccumulation experiments with RDX, HMX, TNB and 2,4-DANT using the estuarine amphipod L. plumulosus and the marine polychaete N. arenaceodentata. Survival of L. plumulosus decreased significantly in exposures to TNB and DANT, but not exposures to HMX and RDX. Sublethal effects on growth or reproduction were only observed for the highest concentration of RDX (1080 ppm). Whole organism toxicity to these compounds was not observed in N. arenaceodentata in 28-day exposures. A degenerate polymerase chain reaction strategy was used to isolate gene fragments belonging to six different gene families from Leptocheirus and Neanthes for use as gene probes in the genosensor. Seventy-three gene fragments were recovered and sequenced from Neanthes and 150 from Leptocheirus. Preliminary results indicate that the expression of several cloned genes is reduced upon exposure of Neanthes to HMX, while a few increased expression demonstrating that the gene isolation strategy has been successful in isolating target genes for microarray analysis.

This project will provide tangible benefits to Department of Defense (DoD) cleanup efforts by reducing the uncertainties involved in measuring exposure and toxicity at DoD contaminated sites. Benefits of this work will include an improved ability to extrapolate to higher order effects and an increased understanding of the following: 1) contaminant bioavailability, 2) the toxicity of MUCs, and 3) the toxicity of complex MUC mixtures.