RAMIT PLUSHNICK-MASTI, Associated Press HOUSTON (AP) — Legislators are demanding the U.S. Environmental Protection Agency immediately begin regulating potentially explosive fertilizer chemicals. The demand came Thursday at a contentious hearing of the U.S. Senate Committee on Environment and Public Works. The committee is investigating an April explosion at the West Fertilizer Co. in Texas that killed 15 people. U.S. Sen. Barbara Boxer, chairwoman of the committee, accused the EPA of a lack of urgency and nonchalance. The U.S. Chemical Safety Board, one of several federal agencies investigating the incident, says the rules regulating fertilizer chemicals are decades old and weaker than those used by other countries. It says the EPA failed to implement recommendations from 2002 that would have expanded its list of regulated chemicals to include the ammonium nitrate responsible for the blast in West.