I lived in Korea for a few years a long time ago and two noticeably different things (from growing up in the US) I saw upon my arrival were many people toting umbrellas in the sun and wearing surgical type face masks as they walked around. Most Americans I know consider ashen/white skin to be unappealing and pay a great deal of attention to getting a tan. Most Koreans seem to think of dark skin as the badge of someone who works on a farm and thus most shy away from exposure to the sun. As far as the face masks, they are typically worn by sick people to halt the spread of germs.
The following is a picture of some Korean cyclists posted on this Korean news page:
The Google language translation page is fun to play with and when I popped the Korean text in it spit out this:
Bike to work every time I talk to is the question, does okay in the air. Air to air dwikkongmuni jotah of a car going, but do more harm anneu concerned to build expressions.
Inappropriate for the city to make cycling in the most serious factors in cities in the world than any of the bad gonggida. The bike is not only in silk. People in the suburbs of the mountains, climbing, walking seoulhyeong chadoreu or write hijapeul. Islam in the face yeoseongman invisible man, even in Seoul, but some of you’re wearing it, and a relatively good mountain air mask, a mask is going.
Obviously some things get lost in translation but I think it is safe to say these folks are worried about air quality issues and not simply making a fashion statement. Anyone from Korea out there feel free to chime in!