PARENT SESSION

PM10 Assessing Toxicology: Critical Body Residue Approach
Exhibit Hall
8:00 AM - Monday, 10 November 2003

(PM168) Comparative toxicity of 2,4,6-trinitrotoluene (TNT) in three marine amphipods.

Rosen, G¹, Lotufo, G², Wild, W¹, ¹ Space and Naval Warfare Systems Center, San Diego, CA, USA² U.S. Army Engineer Research and Development Center, Vicksburg, MS, USA

ABSTRACT- Military activities can result in the introduction of 2,4,6-trinitrotoluene (TNT) into coastal environments, but little is known of the biological effects associated with this contaminant, particularly in marine ecosystems. Toxicity and bioaccumulation of TNT were investigated in three marine amphipod species following concurrent 4-day exposures in spiked sandy sediment. In order to trace the fate of TNT and its degradation products in sediment and amphipod tissues, the TNT was ¹⁴C-labeled. The free burrowing amphipods Rhepoxynius abronius and Eohaustorius estuarius (LC₅₀ = 33 mg/kg for both species) were about twice as sensitive as the tube building Leptocheirus plumulosus (LC₅₀ = 68 mg/kg) when toxicity was expressed in terms of sediment concentration. Very little degradation of TNT occurred in the sediment and overlying water during the exposures, contrary to other studies conducted with finer grained sediments containing higher levels of organic carbon. The amphipods, however, readily transformed TNT accumulated in their tissues to aminodinitrotoluenes (ADNTs). The level of biotransformation occurred to a lesser extent in E. estuarius, where a mixture of TNT and ADNTs was observed in tissue. LR₅₀ values expressed as the ¹⁴C-TNT (sum molar of parent and all metabolite compounds, both solvent extractable and tissue-bound) were similar for the three species (range = 380 to 850 mol/kg), but when expressed in terms of TNT (the sum molar concentration of TNT and its HPLC-quantified metabolites), the LR₅₀ for R. abronius (5.4 mol/kg) was as much as one order of magnitude lower than for the other amphipods (42.8 and 16.4 mol/kg for E. estuarius and L. plumulosus, respectively). The role that the rather large fraction of radiolabeled compound not detected by chemical analysis plays in toxicity is unknown. Therefore, it is currently unclear whether R. abronius is more sensitive to the effects of TNT and ADNTs or to currently unknown metabolic or conjugated products of TNT compared to the other two species.

Key words: critical body residue, trinitrotoluene, biotransformation, amphipods