Lettuce grows outdoors, in the soil. Animals have access to it for weeks or months. Dust happens around it. It is quite likely sprayed with fertilizer or pestic

Lettuce grows outdoors, in the soil. Animals have access to it for weeks or months. Dust happens around it. It is quite likely sprayed with fertilizer or pesticide at some point. Then it is cut by hand. Then it goes to the store where it is fondled by employees and the passing public. So it's a good idea to wash it (and all produce) very thoroughly and not depend on some process to clean if for you. That means in the case of lettuce separating the leaves. It might be overkill but I usually put a drop or two of bleach in wash water, dunk chopped greens, rinse them well in clean water, then spin them in a centrifugal spinner. Something like this (these things are great) https://www.amazon.com/OXO-Good-Grips-Salad-Spinner/dp/B00004OCKR https://www.amazon.com/OXO-Good-Grips-Salad-Spinner/dp/B0000... Also they sell specific vegetable washes although a little bleach or hydrogen peroxide works well enough for me. Generally I don't eat raw produce at restaurants. For the record, I worked on a lettuce farm years ago and food safety is very important, but it's a mass produced out door farm operation with manual handling of product. To say nothing of transport and retail. It's better to wash things yourself and be sure. I think in many parts of the world this is better understood, but for some reason in the US we have this disembodied view of where food comes from.