PARENT SESSION
30 - Validity and Reliability of Ecotoxicity Tests
8:30 AM to 12:20 PM, Tuesday, 14 May 2002
Session Chair: Tattersfield, Lisa ¹, Dallinger, Reinhard ², ^{1 2} .
Lehar B

(30-02) Controlled Toxicant Delivery: A Novel in vivo Approach for Embryotoxicity Testing.

Kiparissis, Yiannis^*,1,2, Akhtar, Parveen¹, Alexander, Alexa¹, Brown, Stephen¹, Hodson, Peter¹, ¹ School of Environmental Studies, Queen's University, Kingston, ON² Environmental and Resource Studies, Trent University, Peterborough, ON

ABSTRACT- In conventional embryotoxicity assays to establish the toxic threshold of hydrophobic compounds the nominal rather than the actual concentrations are often used. However, actual and nominal concentrations may differ by several orders of magnitude since parameters such as adsorption, volatilization or precipitation may cause rapid depletion of the test chemicals, especially for non-polar compounds (eg. PAHs). In addition, nominal concentrations often exceed by far the solubility limits of the test compounds. We developed a reliable controlled delivery method that maintains the level of alkyl phenanthrenes to test solutions at or below their solubility limits over an extended period of time. Polydimethylsiloxane (PDMS) films containing various levels of retene and 1,7-dimethylphenanthrene were deposited on one side of 20 mL vials, and fertilized Japanese medaka (Oryzias latipes) eggs were placed on the other side. Films with retene and 1,7-dimethylphenanthrene at equilibrium provided aqueous solutions of 2 to 17 and 10 to 71 g/L, which are below or at the solubility limit at 25 ^oC, respectively. Results from the PDMS film embryotoxicity assay were compared with results from 24h-static renewal assays, in which the nominal concentrations ranged 10 to 1,000 g/L. In both embryotoxicity assays, the two test PAHs caused similar effects, with the prevalence of blue-sac disease (BSD) symptoms increasing in a exposure-dependent manner. In the 24h-renewal assays, the prevalence of BSD was significantly elevated at the 320 and 100 g/L of retene and 1,7-dimethylphenanthrene treatments, respectively. However, in the PDMS film assay, BSD occurred at or below the water solubility limits of retene (i.e. 17 g/L) and 1,7-dimethylphenanthrene (i.e. 71 g/L). Overall, these data indicate that the PDMS film assay is a very sensitive and a more realistic approach than the static assays to assess the embryotoxic potential of non-polar compounds.

Key words: embryotoxicity , PDMS, new methods, alkyl-PAHs