Under what condition is a public water system (PWS) required to monitor for vinyl chloride?

A public water system (PWS) is required to monitor for vinyl chloride specifically when the system is using groundwater as its source. Vinyl chloride is a volatile organic compound that can be present in groundwater due to various industrial discharges or contamination from certain materials. The presence of vinyl chloride is of particular concern because it poses health risks and can be harmful even at low levels.

Monitoring requirements are primarily influenced by the type of water source because groundwater can be more susceptible to contamination from these compounds compared to surface water, which is typically more exposed to the elements and subject to different treatment processes. Thus, groundwater systems must adhere to stringent monitoring protocols to ensure that vinyl chloride levels remain safe for consumption and meet regulatory standards.

In summary, the necessity for monitoring vinyl chloride in public water systems aligns with the potential risk factors associated with groundwater contamination, ensuring that health and safety standards are maintained effectively.