In a letter sent yesterday to the US treasury secretary Henry Paulson, Grassley said he was "deeply concerned about the lack of publicly available information regarding hedge funds".He also complained that, although hedge funds are marketed to sophisticated investors only, tens of millions of people are exposed through their pension providers' investing in hedge funds.The losses racked up by Greenwich, Connecticut-based hedge fund Amaranth last month prompted Grassley to investigate pension fund exposure to the hedge fund industry, but his staff found that there was no data available. Grassley said further hedge fund collapses could endanger pensioners, as well as putting further strain on the government's Pension Benefit Guaranty Corporation, the US’s pension provider of last resort.Grassley called on Paulson to provide suggestions on how Congress could improve transparency in the hedge fund industry. "We need to get a handle on this situation before more hedge funds go belly-up and leave rank-and-file investors in the ditch,” he added.The Treasury has yet to respond to Grassley's letter. Assistant treasury secretary Randal Quarles told the Senate Banking Committee in July that there was no evidence that "indirect methods of constraining leverage are not working effectively". An attempt by the Securities and Exchange Commission to compel hedge fund advisers to register with the SEC was overturned in June by an appeal court.