QCD anomalies in hadronic weak decays

We consider the flavour-changing operators associated with the strong axial and trace anomalies. Their short-distance generation through penguin-like diagrams is obtained within the QCD external field formalism. Standard-model operator evolution exhibits a suppression of anomalous effects in K and B hadronic weak decays. A genuine set of dimension-eight Delta S = 1 operators is also displayed.