ANZ is not the only one of the Big Four banks facing higher impairments resulting from a weakening of institutional exposures, according to new research.Macquarie Securities has released the results of its analysis of 2500 syndicated loans in which at least one of the major banks had participated, with a total value of A$1.6 trillion.ANZ reported last week that "recent developments with institutional exposures" meant that the bank's credit charge for the first half would increase by at least A$100 million.Macquarie expects ANZ to increase its bad debt charge as a proportion of gross loans and acceptances by 1.5 basis points over the next three years. ANZ reported a credit impairment charge of $1.2 billion for the year to September - an increase of 20 per cent over the previous corresponding period. The ratio of the impairment charge to average gross loans and acceptances was 0.21 per cent  - up from 0.19 per cent last year.It estimates that Commonwealth Bank's impairments to GLA will rise by 1.1 bps over the same period.National Australia Bank and Westpac will report higher bad debt charges but their ratios of bad debts to GLA will fall over the three years.Macquarie said it was not expecting anything disastrous. The average credit rating across the rated institutional portfolio remained sound and the majority of rated exposures in the energy and mining sectors were investment grade. It estimated that the weighted average one-year probability of default for the rated component of the big banks' institutional books was around 0.48 per cent, compared with Standard & Poor's weighted average of 1.5 per cent for the "global average".Macquarie said Westpac and NAB appear to have better quality institutional lending books due to their underweight positions in mining and energy, as well as their lower exposures to offshore companies and higher exposures to rated companies."On an aggregated basis, resources and mining represents one to two per cent of banks' overall exposures and between 13 and 21 per cent of institutional portfolio exposures," Macquarie said.ANZ's exposure to the energy and mining sectors is $10.7 billion, CBA's $7.8 billion, NAB's $3.7 billion and Westpac's $3.5 billion.Macquarie's assessment is that ANZ and CBA are "overweight to the energy sector" and ANZ is also overweight to lower grade energy companies. CBA also has a relatively high exposure to the sub-investment grade category.Looking at offshore exposures, Macquarie estimated that ANZ's Asia exposure was five times the peer average and its exposure to Europe and North America also exceeded peers.CBA has the second-largest offshore exposure and Westpac the smallest.Macquarie's view is that lending to overseas companies carries additional risk. "Given the majors are largely domestic institutions, we see their key credit management competencies within the domestic market. In this regard, we believe offshore lending is generally riskier," it said."Over the past 12 months banks' offshore credit exposures underperformed their domestic portfolios. This suggests that offshore books deteriorated more relative to the majors' domestic portfolios."