Estimation of the critical effect level for pollution prevention based on oyster embryonic development toxicity test: The search for reliability

Abstract

In spite of the consideration that toxicity testing is a reduced approach to measure the effects of pollutants on ecosystems, the early-life-stage (ELS) tests have evident ecological relevance because they reflect the possible reproductive impairment of the natural populations. The procedure and validation of Crassostrea rhizophorae embryonic development test have shown that it meets the same precision as other U.S. EPA tests, where EC(50) is generally used as a toxicological endpoint. However, the recognition that EC(50) is not the best endpoint to assess contaminant effects led U.S. EPA to recently suggest EC(25) as an alternative to estimate xenobiotic effects for pollution prevention. To provide reliability to the toxicological test results on C. rhizophorae embryos, the present work aimed to establish the critical effect level for this test organism, based on its reaction to reference toxicants, by using the statistical method proposed by Norberg-King (Inhibition Concentration, version 2.0). Oyster embryos were exposed to graded series of reference toxicants (ZnSO(4) x 7H(2)O; AgNO(3); KCl; CdCl(2)H(2)O; phenol, 4-chlorophenol and dodecyl sodium sulphate). Based on the obtained results, the critical value for C. rhizophorae embryonic development test was estimated as EC(15). The present research enhances the emerging consensus that ELS tests data would be adequate for estimating the chronic safe concentrations of pollutants in the receiving waters. Based on recommended criteria and on the results of the present research, zinc sulphate and 4-chlorophenol have been pointed out, among the inorganic and organic compounds tested, as the best reference toxicants for C. rhizophorae ELS-test.

EMBRYOLOGICAL AND MICROMANIPULATION TECHNIQUES IN ZEBRAFISH (Danio rerio) AND PACIFIC OYSTER (Crassostrea gigas)

“…To this respect, the early-life-stages tests have evident ecological relevance because they reflect the possible reproductive impairment of natural populations (da Cruz et al, 2007). In spat, the assessment of growth differences due to pesticide impacts can be measured by the shell area index increasment (Stachowski-Haberkorn et al, 2008).…”

“…Some examples are their increasing utilization in Brazil for risk prevention (da Cruz et al, 2007); the long term genotoxic impact of Haven oil spill along the Ligurian coast in…”

“…For these reasons, oysters, especially the genus Crassostrea, have been commonly used for the determination and pollution risk prevention or in monitoring long term impacts (da Cruz et al, 2007;His et al, 1997;Woelke, 1972). Some examples are their increasing utilization in Brazil for risk prevention (da Cruz et al, 2007); the long term genotoxic impact of Haven oil spill along the Ligurian coast in…”

“…Moreover, of much importance is also the development of chronic or sub-chronic tests, due they may have a higher ecological relevance when dealing with the embryonic development of a key species for the ecosystem at risk (da Cruz et al, 2007;Muller et al, 2009).…”

“…Aquatic toxicity tests play a crucial role in assessing the potential or actual impact of contaminants on the natural environment (da Cruz et al, 2007). In these toxicity assays, is of interest the use of aquatic species with different feeding habits to evaluate the long term risk of environmental chemicals and metals impact (Bolognesi et al, 2006;Lee et al, 1996).…”