PARENT SESSION

2A - Mixture Toxicity
Hall 6
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Hermens, J.¹, ¹
Co-chair: Toy, R.², Backhaus, T.³, ^{2 3}

(MO6/8) Evidence of Synergistic Toxicity of PAH/Metal Mixtures to Daphnia magna: a Reactive Oxygen Species-Mediated Mechanism.

Lampi, Mark¹, Xie, Fangli¹, Koziar, Steven¹, Huang, Xiao-Dong¹, Dixon, D.¹, Greenberg, Bruce, ¹ University of Waterloo, Waterloo, Ontario, Canada

ABSTRACT- Heavy metals and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants that are often present together in complex mixtures in the environment. Strikingly, there is a lack of study of mixtures of these classes of contaminants despite their common occurrence at many sites. Furthermore, it is known that PAHs may be photooxidized, which results in many products, some of which are known to be more toxic than the parent, and others that have neither been investigated nor identified. It is clear that much is not understood about the hazards of mixtures of these contaminants, and less is known about specific mechanisms of toxicity. Previously, we demonstrated that a mixture of copper (Cu) and the anthracene photoproduct, 1,2-dihydroxyanthraquinone (DATQ) is synergistically toxic to Lemna gibba. Further, we have characterized in detail that this synergism was manifested via the catalytic production of reactive oxygen species (ROS) by Cu, which is able to redox cycle electrons from a pool that occurs as a result of the inhibition of photosynthetic electron transport, specifically cytochrome b/f, by DATQ. We are currently investigating the effects of mixtures of metals and oxidized PAHs (oxyPAHs) in Daphnia magna. We have shown that mixtures of Cu and different oxyPAHs, including phenanthrenequinone, result in synergistic toxicity. Analysis of total body burden of metals with atomic absorption spectroscopy has shown that the increase in toxicity is not due to an increase in metal bioavailability to D. magna in the presence of an oxyPAH. We have also shown an increase in ROS in D. magna in the presence of this mixture, which is consistent the ROS-mediated mechanism of toxicity.

Key words: mixtures, synergistic toxicity, modified PAHs, metals