The military services are developing and evaluating several insensitive munitions for future weapon systems to replace present munitions that contain highly sensitive explosives, such as RDX and TNT. Among these compounds are insensitive munitions compounds (IMs) 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-trizole-5-one (NTO), for use as components in several insensitive munition explosive compositions (IMXs). Ecotoxicological data are needed to address a clear gap in current knowledge of the potential risks of release of DNAN or NTO into terrestrial environments. The overall objective of the project is to develop ecotoxicological data for IMs that can be used to derive risk-based regulatory levels for selected key soil ecological receptors. The project will study the individual toxicities, bioaccumulation, and bioconcentration of DNAN and NTO, respectively, in soil invertebrates and terrestrial plants, exposed in a natural soil that supports high relative bioavailability of these IMs. To fill these existing data gaps for DNAN and NTO, studies will be conducted that meet regulatory requirements for developing Ecological Soil Screening Levels (Eco- SSL) for use in screening-level ecological risk assessment, and Species Sensitivity Distributions (SSD) for each of these IMs to determine specific hazardous concentrations of DNAN and NTO for Soil Cleanup Values (SCVs), as well as bioaccumulation and bioconcentration factors (BAF and BCF, respectively) for assessing potential risks for food chain transfer for each of these IMs to higher trophic level receptors.

Studies will be designed to generate individual toxicity benchmarks for DNAN and NTO, respectively, for terrestrial plants and soil invertebrates. Ecotoxicological data will be developed for each IM weathered-and-aged in soil to more closely approximate soil microenvironments representative of field conditions, and reflecting the bioavailability of the individual IMs and their transformation/degradation products. Studies will be conducted with a soil type that supports high relative bioavailability of IMs when exposed to terrestrial ecological receptors. Exposure concentrations will be measured as acetonitrile-extractable chemical concentrations and correlated with toxicity endpoints (e.g., growth [plants] and reproduction [soil invertebrates]), with the ultimate goal of developing toxicity benchmark values acceptable for derivation of risk-based regulatory levels for each IM using ecologically relevant soil biota. The goals of this research will be achieved by addressing the following technical objectives:

1. Assess the lethal and sub-lethal effects of DNAN and NTO to terrestrial plants and invertebrates in soil with characteristics that support high bioavailability of organic energetics (low clay and soil organic matter contents);
2. Investigate individual toxicokinetics of DNAN and NTO in plants and invertebrates in soil with high bioavailability characteristics to determine the rates of uptake and elimination, assess biotransformation potential, and generate the respective BCF and BAF values;
3. Develop risk-based draft regulatory levels (Eco-SSLs and SCVs) for DNAN and NTO for terrestrial plants and soil invertebrates, based upon concentration-response relationships.

Ecotoxicological data developed in this project will fill the knowledge gaps regarding ecological risks of DNAN or NTO released into the terrestrial environment. These data will be used to develop individual draft Eco-SSL values and SCVs for DNAN and NTO concentrations in soil. BAF and BCF values determined in the studies for DNAN and NTO are needed for existing models to quantify the risks for food-chain transfer to higher-trophic-level receptors. Eco-SSLs, BAFs, BSFs, and SCVs developed from the research can minimize the future costs of site characterization and cleanup when used by site managers as part of their science-based decision making tools to assess the exposure risks at each site, and when appropriate, develop remedial actions and SCVs that ensure the management of sites as sustainable resources. These data will also aid in making knowledge-based decisions during development and evaluation of insensitive munitions for future weapon systems. The toxicity benchmarks developed will be transitioned to the U.S. Environmental Protection Agency (USEPA) for use in the derivation of risk-based regulatory levels. (Anticipated Project Completion - 06/2020)

Kuperman, R. G., M. L. Minyard, R. T. Checkai, G. I. Sunahara, S. Rocheleau, S. Dodard, L. Paquet, and J. Hawari. 2017. Inhibition of Soil Microbial Activity by Nitrogen-Based Energetic Materials. Environmental Toxicology and Chemistry, 11:2981-2990.

Kuperman, R. G., M. Simini, R. T. Checkai, S. G. Dodard, M. Sarrazin, J. Hawari, L. Paquet, G. I. Sunahara, and D. Di Toro. 2016. Developing Earthworm Bioconcentration Factors of Nitrogen-Based Compounds for Predicting Environmentally Significant Parameters for New Munition Compounds in Soil. Applied Soil Ecology, 104:25-30.

Kuperman, R.G., R. T. Checkai, M. Simini, C. T. Phillips, G. I. Sunahara, and J. Hawari. 2018. Energetic Contaminants Inhibit Plant Litter Decomposition in Soil. Ecotoxicology and Environmental Safety, 153:32-39.

Lotufo, G. R., R. E. Boyd, A. R. Harmon, A. J. Bednar, J. C. Smith, M. Simini, G. I. Sunahara, J. Hawari, and R. G. Kuperman. 2021. Accumulation of Insensitive Munitions Compounds in the Earthworm Eisenia andrei from Amended Soil – Methodological Considerations for Determination of Bioaccumulation Factors. Environmental Toxicology and Chemistry, 40:1713–1725.

Perreault, N., J. Hawari, and A. Halasz. 2018. New Insights into the Photochemical Degradation of the Insensitive Munition Formulation IMX-101 in Water. Environmental Science & Technology, 52:589-596.

Rocheleau, S., R. G. Kuperman, M. Simini, J. Hawari, R. T. Checkai, S. Thiboutot, G. Ampleman, and G. I. Sunahara. 2010. Toxicity of 2,4-Dinitrotoluene to Terrestrial Plants in Natural Soils. Science of the Total Environment, 408:3193-3199.

Rocheleau, S., R. G. Kuperman, S. G. Dodard, M. Sarrazin, K. Savard, L. Paquet, J. Hawari, R. T. Checkai, S. Thiboutot, G. Ampleman, and G. I. Sunahara. 2011. Phytotoxicity and Uptake of Nitroglycerin in a Natural Sandy Loam Soil. Science of the Total Environment, 409:5284-5291.