Can EPA on its own initiative add chemicals to the list, or must it receive a petition from an outside party first and then follow the petition process?

EPA may revise the list of regulated substances at the discretion of the Administrator or as a result of petitions. Modifications to the list must be made through a rulemaking in which EPA explains the basis for the modifications. All petitions to amend the list must be made in accordance with 40 CFR §68.120.