Prenatal developmental toxicity testing of petroleum substances using the zebrafish embryotoxicity test

The present study evaluates the applicability of the zebrafish embryotoxicity test (ZET) to assess prenatal developmental toxicity (PDT) potency of the DMSO-extracts of 9 petroleum substances (PS), with variable polycyclic aromatic hydrocarbon (PAH) content, and 2 gas-to-liquid (GTL) products, without any PAHs but otherwise similar properties to PS. The results showed that all PS extracts induced concentration-dependent in vitro PDT, as quantified in the ZET and that this potency is associated with their 3-5 ring PAH content. In contrast and as expected, GTL products did not induce any effect at all. The potencies obtained in the ZET correlated with those previously reported for the embryonic stem cell test (EST) (R2=0.61), while the correlation with potencies reported in in vivo studies were higher for the EST (R2=0.85) than the ZET (R2=0.69). Combining the results of the ZET with those previously reported for the EST (Kamelia et al., 2017), the aryl hydrocarbon (AhR) CALUX assay (Kamelia et al., 2018), and the PAH content, ranked and clustered the test compounds in line with their in vivo potencies and chemical characteristics. To conclude, our findings indicate that the ZET does not outperform the EST as a stand-alone assay for testing PDT of PS, but confirms the hypothesis that PAHs are the major inducers of PDT by some PS, while they also indicate that the ZET is a useful addition to a battery of in vitro tests able to predict the in vivo PDT of PS.