Toxic Waste (also called Acid) is an uncommon obstacle in the Donkey Kong Universe.
The first appearance of toxic waste was in Donkey Kong Country 2: Diddy's Kong Quest in the level "Toxic Tower". In this level Diddy and Dixie Kong must climb a tower slowly filling with toxic waste, all the while being transformed into a multitude of Animal Buddies.
"Toxic Tower" is later revisited in Donkey Kong Country 2's semi-sequel, Donkey Kong Land 2.
In Donkey Kong 64 some pools of toxic waste can be found in the area Creepy Castle.
One of Funky Kong's mini-games in the Game Boy Advance remake of Donkey Kong Country 2 has the Kongs swerving around in their Gyrocopter collecting pieces of a golden statue of Donkey Kong all the while dodging lowering and heightining pools of toxic waste.