In the very first room, on the left, a bit of the wall is less green than the rest. Goodies inside.

Going left from the entrance, there is a big room with a uneven line of barrels, and some angry imps. Go to the far side of the room, drop down in the toxic waste and run left. Goodies await.

After picking the goodies in #2, hit the button and ride up. You have to be really fast on your feet, there is no delay on the lift. If you miss it, no second chance for the goodie, and you have to run through the waste to get out again.