Anomalies at high temperature
  The anomaly equation can be derived from the ultraviolet properties of quantum field theory and should, therefore, not depend on infrared properties, such as the presence of a thermal heat bath. There is also an infrared explanation of anomalies which is related to fermionic zero modes. I show how the anomaly equation can be satisfied in a high temperature plasma in spite of the fact that all propagating fermionic excitations have a thermal mass. 
Per Elmfors