Bioavailability of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine (RDX) to the Praire Vole (Microtus ochrogaster).
Estimating risk to wildlife requires that measures of exposure be equivalent to that of the laboratory studies from which toxic responses were observed. Exposure measures are often based on modeled estimates of uptake through the food web. These modeled estimates use largely untested assumptions that can lead to inaccurate, uncertain, and unreliable estimates of exposure. Recently, concerns have been raised over the potential bioavailability and biotransfer of munitions or energetics materials such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). RDX is more recalcitrant in the soil, may remain as the parent compound for extended periods of time, and is rapidly taken up by the roots of higher plants and partitioned predominantly into the above ground, herbivore-accessible tissues. This study assessed plant incorporated [14C]-RDX and plant derived [14C]-RDX-metabolites ingestion by a representative hindgut herbivore, the prairie vole (Microtus ochrogaster). The animals were fed the labeled chow (≤10 g/ day max) for five or seven days followed by a six or four day chase period with the control chow prior to final weighing and sacrifice. Animal excreta including feces, urine, and respired CO2 were collected and measured. Greater than 95% of all label presented to the voles was recovered in the summed excreta. Seventy-four percent of the label in the total excreta was found in the fecal non-absorbed bulk. This means that greater than 20% of the presented 14C-RDX and plant-derived 14C-RDX-metabolites were absorbed by the animal’s digestive tracts over the time course of the experiment and modified prior to release. These materials were either metabolized to 14CO2 (8 to 10% of the total label) or removed as nitrogenous waste through the kidneys (10 to 14%). The feeding regimes were followed by a rapid, 2 to 3 day, clearing of label from the bulk feces with the cessation of exposure. Both 14C-urine and 14CO2 excretion continued after the feces cleared indicating ongoing metabolism of the absorbed labeled material. Approximately 4% of the label presented in the chow over the exposure periods was retained within the animal’s tissues at time of sacrifice. Activity was found in the lung, heart, brain, spleen, testes, skeletal muscle, bone, and pancreatic tissues while the testes contained the highest tissue specific activity. The liver contained the highest activity of all the internal organs. All of these tissues which contain these [14C]-RDX derived materials are readily available to subsequent predators this may indicate a potential for this material to transfer to a higher trophic level.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 893649
- Report Number(s):
- PNNL-SA-45884; 400403209; TRN: US200625%%359
- Journal Information:
- Environmental Toxicology and Chemistry, 25(7):1881-1886, Journal Name: Environmental Toxicology and Chemistry, 25(7):1881-1886
- Country of Publication:
- United States
- Language:
- English
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