3 Republican former EPA chiefs accuse Trump of 'undermining of science'

Three Republican former heads of the Environmental Protection Agency accuse the agency's current leadership of supporting the "undermining of science" and a potentially "catastrophic" approach to climate change.

In an exclusive interview with ABC News Live, before a rare joint appearance on Capitol Hill, former EPA administrators William Reilly, Lee Thomas and Christine Whitman warned that recent gains in cleaner air and water in the U.S. are beginning to "backslide."

Watch on ABC News.

William Reilly