Editing Drinking-water toxic contaminant concentration (section)

== Geographic / System Context ==
Drinking-water toxic contaminant concentration is not confined to a specific geographic region but is a global concern affecting diverse hydrological and ecological systems. Contamination sources vary by location, including agricultural regions with high fertilizer use, industrial zones with chemical effluents, and areas with natural geochemical nitrate presence. The signal encompasses water at the point of use, such as household taps or community water supplies, regardless of the underlying water source, whether groundwater, surface water, or treated water systems.