Mercury is a potent neurotoxin that causes brain damage and impairs the development of fetuses, infants, and small children. It is so pervasive that 45 states have posted fish consumption advisories due to mercury contamination; in half these states, the advisories covered every lake and river. Mercury has also caused reproductive and developmental problems in such imperiled species as the bald eagle and the Florida panther.

Coal-burning power plants are the largest U.S. source of mercury pollution. Rather than enforce the Clean Air Act, which requires all power plants to reduce their mercury emissions by 2008, the Bush Administration in March 2005 issued a rule that delays meaningful reductions for another two decades and encourages power plants to buy and sell mercury pollution credits. This practice could allow some plants to increase their mercury pollution and could produce geographical "hot spots" of highly concentrated contamination. It would also leave power plants as the only source of mercury pollution not required to reduce their toxic emissions by the maximum amount possible.

In July, a bipartisan group of Senators, led by Senator Patrick Leahy (D-VT), introduced a resolution to reject the EPA rule. On September 13, 2005, the resolution (S.J. Res. 20) failed by a 47-51 vote (Senate roll call vote 225). YES is the pro-environment vote. A similar measure was introduced in the House but did not come up for a vote.