There is a “distinct possibility” that the U.S. EPA will pass on restricting perchlorate in the nation’s water supplies, an agency official said Tuesday. Perchlorate, a rocket fuel ingredient that has been found at some 400 places in 35 states, can muck up normal thyroid function. But Benjamin Grumbles, the EPA assistant administrator for water, told the Senate Environment and Public Works Committee that he wasn’t sure national regulation of perchlorate would do much good, and that the agency might simply issue an informational public health advisory. The Defense Department is responsible for much perchlorate contamination, so the Pentagon would be on the hook for expensive cleanup if a drinking-water standard was set. But surely that won’t factor in to the EPA decision.