Vinyl chloride is a chemical used for production of PVC plastic; it contaminates drinking water due to leaching from PVC pipes and discharges from plastics manufacturing.
Volatile Organic Chemicals are compounds that evaporate in to the air quickly, because they have a low boiling point. While not all VOCs are bad (most scents and odors are VOCs), some are dangerous to human health. If harmful VOCs are present in tap water, they have the potential to become airborne causing instant exposure. Cleaning products, paint, disinfectants, varnishes and more fall into this category.