Unintended detonation of munitions and munition stockpiles has caused losses of human life, infrastructure, and materiel. The military services, therefore, have been developing and evaluating several insensitive munitions (IM) for future weapon systems, to replace present munitions that contain highly sensitive explosives, and improve the safety of munitions. The overall objective of this project was to develop scientifically defensible soil invertebrate-based toxicity benchmarks acceptable for deriving Ecological Soil Screening Levels (Eco-SSL) for IM compounds 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO). The ecological effects data for each IM compound were determined in compliance with the U.S. Environmental Protection Agency (USEPA) criteria for developing Eco-SSL that meet regulatory requirements for screening level ecological risk assessments.

Natural soil and Sassafras sandy loam were used in this project. This soil was selected because it is an upland aerobic soil that has physical and chemical characteristics supporting the very high relative bioavailability of DNAN and NTO. The weathering and aging of DNAN and NTO in soil was performed in preparation for the definitive toxicity testing with soil invertebrates. It was conducted to simulate, at least partially, the weathering and aging process in field soils, and to more closely approximate the potential exposure effects on soil biota at contaminated sites. The exposure concentrations of DNAN and NTO in soil were analytically determined in all definitive studies. Toxicity studies were conducted using three soil invertebrate species according to the International Organization for Standardization methods for the earthworm Eisenia andrei, the enchytraeid worm Enchytraeus crypticus, and the collembolan Folsomia candida. Toxicity data were analyzed using appropriate regression models to establish concentration‒response relationships for each IM compound‒test species measurement endpoint pairing.

The draft Eco-SSL values detailed in the Final Report were derived using effective concentration producing a 20% effect (EC20) benchmark values for energetic materials effects on soil invertebrate reproduction. The preference for reproduction benchmarks and for the low effect level (i.e., EC20) was justified to ensure that Eco-SSL values for DNAN and NTO would be protective of populations of the majority of ecological receptors in soil. The Draft Eco-SSL values would also provide confidence that IM compound concentrations posing an unacceptable risk are not screened out early in the ecological risk assessment process. The present research also developed empirical data to characterize the uptake dynamics of DNAN and NTO from the soil into plants and earthworms and determined the bioconcentration factors and bioaccumulation factors, respectively, for DNAN and NTO. 

Following acceptance by the USEPA, the Draft Eco-SSL values developed from this research will allow screening of site-soil data during the Screening Level Ecological Risk Assessment to identify those IM that are not of potential ecological concern and do not need to be considered in the Baseline Ecological Risk Assessment, resulting in significant cost-savings during site assessments. These Eco-SSL will also provide an indispensable tool for the installation managers to gauge the ecotoxicological impacts of military operations that involve the use of DNAN and NTO, thus ultimately promoting the sustainable use of testing and training ranges. The toxicokinetics data will provide critical information for use in wildlife exposure models to assess the potential risks for food-chain transfer of DNAN and NTO to higher-trophic-level receptors and their corresponding potential for biomagnification. (Project Completion - 2022)

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.