(Updates with Nalco spokesman saying company wasn't asked to testify) By Siobhan Hughes Of DOW JONES NEWSWIRES WASHINGTON (Dow Jones)--Sen. Barbara Mikulski (D., Md.), said Thursday she might subpoena Nalco Holding Co. (NLC) executives to testify at a hearing because the maker of a dispersant being used to combat the Gulf of Mexico oil spill declined to testify at a hearing. "I'm sorry they didn't come," she said at the start of a Senate Appropriations subcommittee hearing. "We're not going to subpoena them for this hearing; we might subpoena them for another hearing." A Nalco spokesman said the company wasn't asked to testify and that one of the trade associations that Nalco is a member of was asked to testify. A Mikulski spokeswoman said that committee staff spoke to the American Chemistry Council to ask Nalco to testify. The chemistry trade group said that Nalco didn't want to testify, the Mikulski spokeswoman said. Walter Moore, a vice president for federal affairs at ACC, said that the group didn't have its own internal expertise in dispersants and that he checked around to see if any companies might. He declined to comment on which companies he had called. BP PLC (BP, BP.LN) has been using Nalco's Corexit 9500 product to break up oil that has been leaking from an undersea well. -By Siobhan Hughes, Dow Jones Newswires; (202) 862-6654; siobhan.hughes@dowjones.com (END) Dow Jones Newswires July 15, 2010 16:53 ET (20:53 GMT)