Does anyone remember this movie from eithere the 80's or 90's?

The world has apparently become over polluted. This one group of kids are trying to escape and get to the unpolluted part of the world that for some reason no one else can find/knows about/has gone to, and they eventually get there by going through an underground maze with stone walls and booby traps. At one point they are captured and have to escape and there is a character that reminds me of the character sloth from the Goonies that saves that kids but sacrificing himself to kill the guy that is after them in the maze/cave thing.