<prompt> Translate the following text to EnglishKama ilivyoelezwa hapo juu, kiwango cha SO2 na NOx kinaweza kupunguzwa kwa muda mrefu, na Clear Skies inahitajika kwa muda mrefu, hata wakati wa ujenzi wa mitambo mpya ya umeme.  <response>: The cap ensures that the reductions in SO2, NOx and mercury required by the Clear Skies Initiative are achieved and maintained over time even as new power plants are built. 