The major sources of vinyl chloride in drinking water are discharge from plastics factories. Drinking water piping made of polyvinyl chloride (PVC) prior to 1977 may result in vinyl chloride leaching. 
 Since 1977 NSF/ANSI Standard 14 and NSF/ANSI Standard 61 have controlled the levels of residual vinyl chloride allowed in PVC pipe that is sold and installed in the USA. Most US States require all public water supply products in contact with drinking water to be certified to NSF/ANSI 61: Drinking Water System Components- Health Effects. This standard sets limits for the amount of residual vinyl chloride monomer contained in PVC pipe and fittings, and also requires a leachate test to ensure any vinyl chloride leaching from the product is below EPA drinking water standards. Permeation and Leaching, US EPA Office of Water, https://www.epa.gov/sites/production/files/2015-09/documents/permeationandleaching.pdf
A federal law called the Emergency Planning and Community Right to Know Act (EPCRA) requires facilities in certain industries, which manufacture, process, or use significant amounts of toxic chemicals, to report annually on their releases of these chemicals. For more information on the uses and releases of chemicals in your state, contact the Community Right-to-Know Hotline: (800) 424-9346.