Acetochlor is an herbicide that completely inhibits shoot growth of oat (A. sativa) and mustard (S. alba) plants when used at a concentration of 2 kg/hectare. It accelerates thyroid hormone-induced metamorphosis of and alters thyroid hormone-responsive gene expression in X. laevis. In vivo, acetochlor induces formation of thyroid, bone, stomach, and nasal tumors in rats as well as liver and lung tumors in mice. Acetochlor also induces pericardial edema, thrombosis, circulation defects, and a reduction in the number of cardiomyocytes in zebrafish larvae when administered in tank water at the maximum non-lethal concentration (MNLC) of 9.6 µg/ml.