Because early life stages of many species exhibit a greater toxicological sensitivity to contaminants than the adult life stages, knowledge of the exposure of contaminants during embryonic development is a crucial prerequisite for toxicologicalrisk assessment. This study presents a chemical equilibrium model for estimating the maternal transfer and resulting exposure of developing embryos in eggs of several classes of oviparous organisms to hydrophobic organic chemicals. The model is testedagainst (i) the results of a field study, including the analysis of 44 chemicals in eggs and maternal tissues of 6 fish species and snapping turtles, and (ii) literature data for 8 additional fish and 3 bird species. Lipid normalization of egg andmaternal concentrations reduces the variability in observed egg-to-maternal tissue concentration ratios between species by approximately 20-fold. The majority of observed lipid normalized egg/maternal tissue concentration ratios for individual chemicalsand fish were not significantly different from 1.0, and the combined data set shows a logarithmic distribution with a mean of 1.22, and 95 probability intervals of 0.56 and 2.51. This indicates that during fish development, the embryos can be expected to be exposed to the same effective internal concentration as the maternal organisms from which the eggs originated.
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