Plumbing questions: if the plumbing fixture faucet is below the siphon Line in the sink (over flow) what type of concern would this present?

Plumbing questions: if the plumbing fixture faucet is below the siphon Line in the sink (over flow) what type of concern would this present?
Cross contamination of the potable water supply is the concern.

Code requires an airbreak between the outflow of the spout and the top of the sink.