Discrete emission reductions (DERs) represent pollution that has been avoided through voluntary actions by sources. As such they are used by existing sources that are emitting above their regulated limits established by various regulations, including Reasonably Available Control Technology (RACT) regulations. Regulatory agencies sometimes require sources to acquire DERs in lieu of paying cash penalties for emissions exceedances. Some states will allow DERs to be used as new source offsets if a five to ten-year supply can be acquired. New New Jersey, Massachusetts and Connecticut sources have been trading DERs for several years. The New Hampshire, Michigan and Texas programs are newer.