A physiologically-based toxicokinetic model to explore the uptake and distribution of crude oil PAHs in bottlenose dolphins (Tursiops truncatus) following exposure to oil spills

Background/Question/Methods

The purpose of this study was to simulate exposure of bottlenose dolphins (Tursiops truncatus) to chemicals in oil released into the marine environment from oil spills.  These compounds may be taken up by marine mammals by ingestion of contaminated food, absorption by the skin, and inhalation of volatilized compounds.  In this study, we limited simulations to the uptake and distribution of naphthalene from inhalation.  In particular, we are interested in the effects of the different ventilation and cardiac output rates associated with dolphins diving below the surface.  We conducted simulations for different exposure scenarios based on the sequence of ventilation and cardiac output rates.  The first simulation was a constant exposure over six hours to see whether the naphthalene concentrations reached equilibrium.  In this scenario, we assumed that the dolphins swam at the surface for the entire simulation.  The second scenario was constant exposure for 30 minutes and no exposure for the next two hours to simulate the dolphins swimming out of the contaminated area to see if the dolphins were able to clear the naphthalene.  The third scenario was constant exposure during swimming at the surface but at ten minutes after initial exposure, the dolphins dived for five minutes.  There also was a five minute recovery period, during which the breathing rate and heart rate were increased above normal surface swimming

Results/Conclusions

The results of the first scenario showed an initial rapid increase in the amounts of naphthalene in all tissues, for approximately one hour.  In all but the fat and “other” compartments, this was followed by a more gradual increase over the next five hours.  None of the compartments reached equilibrium. In the second exposure scenario, there is a rapid increase in all compartments except fat and “other” which showed increases that are more gradual during exposure.  After the initial increase, naphthalene begins to decrease in all tissues except for fat and “other” tissues because of elimination. In the third exposure scenario, predicted amounts of naphthalene in bottlenose dolphin tissues start to increase rapidly during pre-dive exposure.  During the dives, naphthalene amounts drop in all tissues except liver, fat, and “other”.  The drop is most pronounced in capillaries, arterial blood, lungs, and skin.  At the end of the dive, amounts again increase rapidly because of an increased respiration rate.