Bioaccumulation of 2,4,6-trinitrotoluene and polychlorinated biphenyls through two routes of exposure in a terrestrial amphibian: Is the dermal route significant?

Tiger salamanders (Ambystoma tigrinum) were exposed via soil and/or food (earthworms) to 2,4,6-trinitrotoluene (TNT) and a PCB mixture (Aroclor 1260) at environmentally relevant concentrations. Four exposures were considered: (1) uncontaminated food + uncontaminated soil (control group); (2) contaminated soil + uncontaminated food (dermal group); (3) contaminated food + uncontaminated soil (oral group); and, (4) contaminated soil + contaminated food (dual-exposure group). The chemical exposure was estimated for each group by analysis of both soil and earthworms. Body burdens of TNT and its primary metabolites were highest in the dermal groups while PCB burdens were highest in the oral groups. Concentrations of the primary TNT metabolites evaluated, 2-amino-dinitrotoluene (DNT) and 4-amino-DNT, exceeded that of unmetabolized TNT and accumulated to 116 and 670 ng/g, respectively. These results provide evidence that dermal exposures to nitroaromatics in terrestrial salamanders may make an important contribution to total body burden and thus may be important when considering the health consequences of such exposures. Further, the demonstration of the accumulation of TNT and TNT metabolites in a primitive vertebrate may have food web modeling implications.