Macquarie Bank yesterday disclosed that it had impaired loans of $528 million at September 2008, and equal to 0.9 per cent of credit exposures of $58 billion. Macquarie, like other banks, has published its first quarterly disclosures under the "pillar 3" requirements of APRA and in line with the market discipline principles of the Basel 2 regime of bank regulation.Of Macquarie's impaired loans, $420 million are corporate. With corporate credit exposures of $28.8 billion this means that 1.5 per cent of the bank's corporate loans are impaired under the Basel 2 definitions.The balance of Macquarie's impaired loans of $108 million the bank classified as retail, and equal to 3.3 per cent of the bank's retail credit exposures of $3.3 billion. There's no more guidance on this but one guess is that it's the bank's margin loans that are responsible for this high percentage.The September 30 impairment data is also a snapshot in time, and at the height of the latest dislocation in equity and credit markets generated by the failure of Lehman Brothers, so these impairments, and the impairment ratio, might be inflated by that fact (and since reduced).