Maternal transfer and in ovo exposure of organochlorines in oviparous organisms: A model and field verification

Because early life stages of many species exhibit a greater toxicological s ensitivity to contaminants than the adult life stages, knowledge of the exp osure of contaminants during embryonic development is a crucial prerequisit e for toxicological risk assessment. This study presents a chemical equilib rium model for estimating the maternal transfer and resulting exposure of d eveloping embryos in eggs of several classes of oviparous organisms to hydr ophobic organic chemicals. The model is tested against (i) the results of a field study, including the analysis of 44 chemicals in eggs and maternal t issues of 6 fish species and snapping turtles, and (ii) literature data for 8 additional fish and 3 bird species. Lipid normalization of egg and mater nal concentrations reduces the variability in observed egg-to-maternal tiss ue concentration ratios between species by approximately 20-fold. The major ity of observed lipid normalized egg/maternal tissue concentration ratios f or individual chemicals and 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 du ring fish development, the embryos can be expected to be exposed to the sam e effective internal concentration as the maternal organisms from which the eggs originated.