Cyanide is a highly toxic chemical from industrial processes like mining and electroplating. It enters water through waste discharge and interferes with cellular oxygen use.

Cyanide occurs naturally in some plants but is primarily an industrial byproduct. It's commonly used in mining, electroplating, and steel manufacturing. Measured in parts per billion, cyanide can enter water supplies through industrial waste discharge or agricultural runoff. Its toxicity stems from its ability to interfere with cells' oxygen use. Water treatment facilities use various methods to remove cyanide, including oxidation and activated carbon filtration, to ensure safe drinking water.