TP4 Metals in the Environment: Regulatory and Risk Concerns
Room 16A/B, Level 4
2:10 PM - 5:30 PM, Tuesday, 11 November 2003
Chair: McGeer, Jim ,
Co-chair: Dwyer, Bob ,
(279) Simulation and evaluation of metal exposure, accumulation and toxicity relationships in aquatic organisms.
Blust, R1, 1 University of Antwerp, Antwerp, Antwerp, Belgium
ABSTRACT- The toxicity of metals to aquatic organisms strongly depends on the exposure conditions and the physiological organisation of the organisms. Consequently, metal toxicity towards aquatic organisms varies orders of magnitude among and even within species. Several explanations have been formulated to account for this large degree of variation. One of the most important being the effect of the environmental conditions on the bioavailability of the metals. Hence, it has been shown experimentally that metal toxicity is usually better explained on the basis of the free metal ion than on the basis of the total metal concentration. Taken into account effects at metal uptake sites such as competitive and non-competitive effects, caused by differences in for instance water hardness or hydrogen ion activity, further decreases the variation in metal toxicity. Nonetheless, a direct relationship between metal uptake, accumulation and toxicity does not always exist. Different types of organisms deal with metals in different ways, they are exposed via different routes and employ various strategies to store or eliminate excess metal. In principle, toxicity will only occur when the concentration of the metal reaches a certain threshold level in one of the physiological pools inside the organism. Thus, metal toxicity is controlled by the rate of metal uptake and the rate of metal elimination from the most sensitive physiological pools. To investigate to what extent differences in metal exposure, accumulation rate and internal processing influence metal toxicity, a dynamic model was constructed that simulates the different events in a time-resolved manner. The model is applied to different types of organisms and exposure scenarios and the results compared with uptake and toxicity data for selected metals. The results show under which conditions a direct relationship between metal exposure and toxicity is expected and for which type of species and conditions a relationship between internal tissue concentrations and toxicity may exist.
Key words: Model, Metals, Accumulation, Toxicity