Most petroleum substances (PS) are produced at a volume of >100 tonnes/year in the EU, hence need to be assessed for prenatal developmental toxicity (PDT). If this is done following the current OECD guidelines, a large number of experimental animals are needed to fulfil the data gap. The application of in vitro assays, such as the zebrafish embryo test (ZET), may reduce animal experimentation and resources needed to study the PDT potencies of PS for example by providing a way to set priorities. PS are complex materials comprising hundreds to millions of different hydrocarbon compounds, including polycyclic aromatic hydrocarbons (PAHs). PDT as observed with some PS has been associated with the presence of 3-7 ring PAHs (Kamelia et al. 2017). To test this hypothesis to a further extent, DMSO-extracts of 9 PS, varying in PAH content, and 2 gas-to-liquid products (GTL), containing no PAHs, were tested in the ZET. The results show that DMSO-extracts of PS caused concentration-dependent inhibition on zebrafish embryos development and their potency appeared to be associated with the amount of 3- to 5- ring PAHs they contain. The observed effects include delayed-development, dorsal curvature, shorter body length, pericardial and yolk sac edema. On the contrary, and as expected, both of the GTL extracts did not affect the development of zebrafish embryo. Our findings showed the applicability of the ZET to assess in vitro PDT of PS and that this potency is proportional to their 3-5 ring PAH content. This supports our hypothesis that PAHs are primary inducers of the PDT of some PS.
