Munitions compounds may reach human receptors or be released into the environment at several points during manufacture, training, and combat. Those releases and exposures have resulted in significant costs to the DoD in the past, and continue to represent significant liabilities. The understanding of fate and effects of legacy munitions constituents is fairly robust, but additional research is necessary to fully understand the fate, transport, and effects of insensitive munitions constituents.
Although there are several existing models that can be used to predict fate-determining properties of chemicals, they are not satisfactory for munitions constituent chemicals. New efforts should build on prior art, starting with systematic assessment of the actual performance of existing tools, and any overlap and gaps in their coverage. Models responsive to this need may be of several types: (i) quantum chemical models for chemical properties from first principles (requires no experimental data for calibration); (ii) empirical/statistical correlation models (quantitative structure-activity relationships, QSARs); or (iii) expert systems that encode decision trees.
Existing fate and transport models use “fate-determining” property data that are either measured or predicted. Their output is generally contaminant concentration (potential exposure) distributed over time and space. The various models should be systematically compared in terms to application range, output capability, precision, accuracy, usability, and transparency for insensitive munitions. In addition, while fate and transport models generally provide contaminant concentrations over time/space, they could be extended to endpoints more directly relevant to risk assessment through coupling to risk models and incorporation of toxicology data.
Experimental data for fate-determining properties of insensitive munitions are still scarce, and often of uncertain reliability. More and better measured data are needed for the whole range of current and future munition constituents. In particular, studies of the processes that are relatively difficult to characterize are needed. Although most existing studies of the new insensitive munitions have focused on the simpler processes (e.g., partitioning and hydrolysis), potentially important processes that are more difficult to evaluate are critical to understand. The most important such processes include biodegradation and photodegradation.
Biodegradation data are needed for aerobic and anaerobic conditions in both soil and groundwater. Both pure and unpurified culture systems could yield data of interest, since there have been few studies of the biodegradation of specific insensitive munitions compounds, and some compounds do not have well characterized biodegradation potential. In particular, the identities and fates of degradation intermediates and byproducts need to be understood.
Fate and transport studies also need to be done with the actual formulations used, to evaluate the fate of munitions constituents in typical mixtures and the fates of the other materials used. Since mixtures with other munitions constituents are likely, these effects should be considered as well. In addition, impacts on other contaminants of concern should be evaluated. One notable example is the potential for acidity associated with NTO to enhance metals mobilization. Finally, improved tools for fate and transport studies would be helpful, such as reactive tracers to simulate insensitive munitions behavior in the environment.
Ranges depend on having vegetation (aquatic and terrestrial). Vegetation provides critical habitat, preserves soil and prevents runoff, and both retains and degrades contaminants. Vegetation can prevent downward migration of contaminants and eventual groundwater pollution both through uptake and by reducing water infiltration. It is therefore important to know if insensitive munitions compounds affect vegetation, and if so, how and at what concentrations. It is also important to understand if these compounds accumulate in the plants, or if they are transformed or degraded. Understanding the eventual fate of insensitive munitions compounds if consumed or degraded after plant death also may be important.
Ranges also depend on the animals present, both aquatic and terrestrial fauna, that serve vital environmental functions and also can be important receptors of concern. It is critical to understand if insensitive munitions compounds will affect the range fauna, and if so, how and at what concentrations. It is also critical to understand if fauna accumulate the compounds or transform them after uptake.
In July 2015, the SERDP and the Environmental Security Technology Certification Program (ESTCP) held a workshop to develop research and demonstration needs to improve management of munitions constituents. Approximately 80 personnel, including representatives from the DoD, federal and state regulators, engineers, researchers, industry representatives, and consultants, attended. A more detailed description of these issues can be found in the report from the workshop. Proposers are strongly encouraged to review the workshop report for additional detail.
