Add Backstreet Boy Kevin Richardson to the list of celebrities who've hit the Hill.

Richardson testified on Thursday before the U.S. Senate Subcommittee on Environment and Public Works about environmentally destructive coal-mining practices in his home state of Kentucky.

The pop singer voiced concerns about the Bush administration's current energy plan, which allows coal companies to plow Appalachian mining waste into river valleys and streams.

"I am not a scientist, but I do know what I've seen in flights over the coal fields," he said during the proceedings. Richardson runs his own environmental charity called Just Within Reach.

While fans packed the chamber and applauded his testimony, not everyone was as pleased to see Richardson in D.C.

George Voinovich, the Republican senator from Ohio, boycotted Richardson's visit, as did the ranking Republican members of the subcommittee. "It's just a joke to think that this witness can provide members of the United States Senate with information on important geological and water quality issues," Voinovich said. "We're either serious about the issues or we're running a sideshow."

Richardson is just one of a recent spate of celebrities — including Julia Roberts, Michael J. Fox, Muhammad Ali and Christie Brinkley — who have come to the Capitol to raise awareness of various issues. "Certainly members of the entertainment community have expertise on many issues that are important for Congress to consider," Voinovich added. "This isn't a case like that."

Senate Democrats were more receptive of Richardson — New York Sen. Hillary Rodham Clinton even accepted an offer to tour Kentucky mine fields with the pop idol.

—Gideon Yago