Wearing masks in public for health reasons

I'm curious as to who and how many people wear a mask in public for health reasons.

I often wear a mask on the street during allergy season to keep my asthma from exacerbating due to pollen, ragweed and leaf mold. I will also wear one on a crowded bus during cold and flu season in winter.

Car exhaust will often make me feel sick like I'm ready to throw up. I do have a documented sensitivity/allergy to exhaust fumes, and wearing the mask often helps immensely,

My mask of choice in these cases is .a Respro Allergy Mask www.respro.com. In Western society it does seem like people are often ambivalent about the idea of wearing masks in public. I'm very interested in hearing how others in this forum handle this situation.