Many years ago I worked at a regional lab that tested samples of air, soil, water, flora, fauna, and sundry other items for toxicity, hazardous contamination, and other scary stuff. Safety, as one would hope, was of the utmost concern. Because they worked with potentially contaminated materials all day, the chemists and biologists were not allowed to wear their lab coats into the lunch room.
The chemists and biologists who did all of the testing using the expensive, impressive equipment (including a Bass-o-Matic) worked in the back of the lab. Reception, administrative staff, and the lunch room were in the front. To avoid ingesting trace amounts of PCBs along with their Cheetos, the chemists and biologists removed their lab coats before entering the lunch room.
That’s why at exactly 12:00 every day (chemists and biologists are nothing if not precise), you’d see a bunch of white lab coats casually draped over the backs of the chairs of the administrative staff, who often ate lunch at their desks.