Well I don't know much about this, but here is what I will be using as an argument for not having to measure, but still ensuring nails are trimmed during GMP checks. Also long fingernails can break-off and land in food, my guys wear gloves so at least there is one layer of protection for us.
Found in the CDC's guidelines for Hand Hygiene for Healthcare Workers, so more strict than what we deal with!
"Whether artificial nails contribute to transmission of healthcare–associated infections is unknown. However, HCWs who wear artificial nails are more likely to harbor gram-negative pathogens on their fingertips than are those who have natural nails, both before and after handwashing (347–349). Whether the length of natural or artificial nails is a substantial risk factor is unknown, because the majority of bacterial growth occurs along the proximal 1 mm of the nail adjacent to subungual skin (345,347,348)."
Full Text Here : https://www.cdc.gov/...F/rr/rr5116.pdf