BP Plc and a Nalco Holding Co. unit, the maker of a chemical dispersant used to deal with the Gulf of Mexico oil spill, were sued by Louisiana residents claiming the product is four times more toxic than the oil itself. BP has been using the dispersant to break up oil and reduce harm to the coast following the April explosion of the Deepwater Horizon drilling rig. The plaintiffs claim BP used the dispersant to save money “and lessen the public reaction to the oil spill” by forcing it to the bottom of the Gulf. The lawsuit, filed today in federal court in New Orleans, is a proposed class action that would include all workers and Gulf Coast residents claiming harm from the chemical. The plaintiffs are seeking at least $5 million in actual damages and unspecified punitive damages... Charlie Pajor, a spokesman for Naperville, Illinois-based Nalco, declined to comment on the lawsuit. “We feel our product is safe and effective,” he said in a phone interview. Toby Odone, a spokesman for London-based BP, declined to comment.