As I was spinning my washed lettuce for a lunchtime salad, it occurred to me that washing lettuce is probably only truly useful if there is dirt or sand in the lettuce. I was washing some mesclun salad that was really clean. I know that you're supposed to wash lettuce in case anyone carrying an illness might have touched it along the food chain, but is washing lettuce in cold water really going to kill anything that might be on the lettuce? Aside from if the lettuce is actually dirty, does washing lettuce do anything except make you feel better? So take a cabbage that you're tuning into slaw, for example-- you remove the outer leaves and then you shred it, so why would you wash iceburg lettuce that you've removed the outer leaves from? Or lettuces that are grown hydroponically? I would really like to know if there is any scientific evidence that this is worthwhile, or is it just a big waste of time?