Let's say someone solders with lead solder in a room. He doesn't clean up very well and leaves some solder residue lying on the floor.
Then, something is placed on the floor, say, a book, which touches the solder left on the floor/comes into contact with it.
Then, someone else grabs the book, which has touched the lying around solder, and reads it, coming into contact with the 'solder/lead-contaminated' book.
Now, when touching food without washing hands, is the second person at risk of getting lead into his mouth?
This is similar to coughing on your hand when sick, touching a door handle with said hand, someone else touching the same handle, eating without washing their hands and getting the bacteria of the sick one into their mouth.