After about twenty years of commercial production, health hazards began to be reported in workers exposed to PCNs: severe skin rashes and liver disease that led to deaths of workers. While some PCNs can be broken down by sunlight and, at slow rates, by certain microorganisms, many PCNs persist in the environment. Acute exposure causes chloracne. Chronic exposure increases risk of liver disease. Increased cancer risks have been suspected but so far not shown. Current concerns about PCNs include their release as byproducts of waste incineration.