Source to Cup Is a Chain: Where the Contamination Actually Enters Between an Improved Source and a Child's Cup, and What Each Dollar Buys Along It

SIMULATED, NOT MEASURED. A source-to-cup contamination chain is budgeted link by link: an improved source (index 10) reaches the cup at 80 through the conventional open chain, and at 19 through a closed tap-vessel chain — a 76% cut with no source improvement — and the covered tap-vessel ranks first in points saved per dollar. Computation only; nothing was built or field-tested.