Vietnamese school girls, in the hot Mekong delta, ride their bicycles to and from school. They wear these beautiful pant/dress outfits, and large face masks. We learned that they wear the masks mainly to protect their skin from the sun and air pollution, not so much their lungs. It is the same reason they wear full covering clothing in such a hot climate. In much of Asia, class is shown by lightness of skin: if you have clear white skin it means you are from the upper classes, not from the working classes.
Supposedly classless Communist Vietnam, was more complex than we had imagined.
Photo by Claire Rogers from the back of our tandem Zippy on our In Search of Shangri-la journey throughout SW China and SE Asia.