The Environmental Protection Agency delayed the final adoption of new rules governing emission of the powerful neurotoxin mercury, but EPA Administrator Mike Leavitt vowed that the administration would not be withdrawing the controversial regulations despite widespread opposition. In the new timetable, the EPA will continue to accept comments on its proposed rules on emissions of mercury by power plants until March 15, 2005, and the rules will not be finally adopted until May 2005. The proposed rule would limit power plants' emissions of mercury not by requiring the use of the most effective pollution reduction technology but, rather, by using a market-styled "cap-and-trade" program. In cap-and-trade programs, polluters are allotted credits, which are essentially limited rights to pollute that can in turn be traded with other polluters. Total emissions are in theory reduced by limits on the total number of available credits. Unlike the alternative, an across-the-board requirement of the implementation of the maximum achievable control technology (MACT), cap and trade programs can result in pollution hot spots created by polluters who have purchased more pollution credits than their initial allotments. Even if a cap-and-trade program for mercury will achieve the same total reduction in mercury emissions as a MACT alternative, the cap-and-trade model does not address the concerns of equity, or environmental justice, that some localities will be exposed to more intense amounts of mercury than others. Opposition to the administration's proposed rule has been intense. Ten state attorneys general and environmental protection officers have called for more protective rules, and 45 senators urged Leavitt to withdraw the proposal altogether. Further information on the rules and a template for voicing opposition to them can be found at the National Resources Defense Council's website.