perc is classified as a hazardous air contaminant by the united states environmental protection agency and must be handled as a hazardous waste. to prevent it from getting into drinking water, dry cleaners that use perc must take special precautions against site contamination. landlords are becoming increasingly reluctant to allow dry cleaners to operate in their buildings. when released into the air, perc can contribute to smog when it reacts with other volatile organic carbon substances. california declared perchloroethylene a toxic chemical in 1991, and its use will become illegal in that state in 2023.