The importance of both potency and mechanism in dose-response analysis: An example from exposure of Pacific herring (Clupea pallasi) embryos to low concentrations of weathered crude oil

► We reviewed a study of petroleum toxicity to Pacific herring embryos and larvae. ► The study did not show monotonic dose-response relationships and proof of causality. ► Reported effects at 0.4 μg/L aqueous PAH levels were not supported by the data. ► A conclusion that weathering makes oil more toxic was not supported by the data. ► Confounding factors that could have influenced results are identified.