Complex sentence: Blacksmith Institute, founded in 1999, is an organization running the Polluted Places Initiative, which identifies polluted sites throughout the world by means of an on-line nomination process.
Split into simpler sentences: Blacksmith Institute, founded in 1999, is an organization supporting pollution-related environmental projects. One of such projects is the "Polluted Places Initiative", which identifies polluted sites throughout the world by means of an on-line nomination process.