Unless EPA determines that tougher standards are unnecessary or infeasible, a second tier of reductions would be required by 2003, cutting emissions by about another 50%.

• 除非环境保护局决定，不必采用更严格的标准，或者更严格的标准行不通，到了2003年，将会要求再次削减，再减少50%25的排污量。