MP13 Aquatic Ecotoxicology
Monday, 14 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(MUK-1117-750504) Acute and sub-acute toxicity of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in zebrafish (Danio rerio).

Mukhi, sandeep¹, Patino, Reynaldo ², ¹ Department of Environmental Toxicology and Texas Cooperative Fish & Wildlife Research Unit,Texas Tech University, Lubbock, Texas, USA² U.S. Geological Survey Texas Cooperative Fish & Wildlife Research Unit, Lubbock, Texas, USA

ABSTRACT- Hexahydro-1,3,5-trinitro-1,3,5-triazine is a cyclonitroamine commonly known as RDX that is used in the production of military munitions. Geographically widespread contamination of soil, sediment, and ground and surface waters with RDX has been reported. Acute and sub-acute toxicities of RDX have been relatively well documented in terrestrial vertebrates, but the information available for aquatic vertebrates is limited. The objectives of this study are to characterize the acute and sub-acute toxicity of RDX in zebrafish. Mortality (LC50) and incidence of vertebral column deformities (EC50) were two of the end points measured in the acute study. The 96-h LC50 was estimated at 22.98 and 25.64 mg L-1 in two separate tests. The estimated no-observed-effective-concentration (NOEC) levels for lethality were 13.27 ± 0.05 and 15.32 ± 0.30 mg L-1; and the lowest-observed-effective-concentration (LOEC) levels were 16.52 ± 0.05 and 19.09 ± 0.23 mg L-1, in the two tests respectively. The 96-h EC50 for vertebral deformities in survivors from one of the LC50 tests was estimated at 20.84 mg L-1, with NOEC and LOEC of 9.75 ± 0.34 and 12.84 ± 0.34 mg L-1, respectively. Behavioral aberrations were also noted in the acute toxicity study, including the occurrence of whirling movement and lethargic behavior. The acute effects of RDX on survival, incidence of deformities, and behavior of larval zebrafish occurred at the high end of the RDX concentration range reported in aquatic environments. For the sub-acute toxicity test, sub-adult zebrafish were exposed to 0, 1 and 10 ppm (nominal) of RDX for a period of 12 weeks. Bioaccumulation of RDX and its metabolites were observed at 4, 8 and 12 weeks of exposure. The average bioaccumulation factor was estimated at 1.4. RDX at 10 ppm affected condition factor (growth index) of the fish after 4 and 8 weeks of exposure but not after 12 weeks, possibly indicating an adaptive response. RDX at 1 ppm did not affect condition factor at any time during the exposure. Sub-acute effects of RDX on organ histopathology are currently under investigation. This research was supported by funding from U.S. Department of Defense through the Strategic Environmental Research and Development Program.

Key words: rdx, acute, LC50, bioaccumulation