"The top U.S. environmental regulator said she was 'very concerned' about fluids blamed by some for polluting water supplies near sites where drillers use them to extract natural gas from shale deposits.

U.S. Environmental Protection Agency chief Lisa Jackson said she hopes her agency will launch a study this year into the nature of fluids used in the hydraulic fracturing process of natural gas drilling.

'We are going to look at what the fluids are, what's in them. We are very concerned about that,' she told Reuters after a speech at the National Press Club."

Jon Hurdle and Timothy Gardner report for Reuters March 9, 2010. [2]