Relative potency of PCB126 to TCDD for sublethal embryotoxicity in the mummichog (Fundulus heteroclitus)

► PCB126 and TCDD cause EROD induction and prey capture reduction in mummichog larvae. ► At comparable doses, different patterns of transcriptional responses were observed. ► The relative potency of PCB126 to TCDD for inducing EROD activity was equal to 0.71. ► The WHO TEF may underestimate the toxicity of PCB126 for some fish species.