We wanted to quantify the potential level of exposure to outdoor tobacco smoke that could occur in everyday outdoor locations. To do this, we visited parks, outdoor cafes, sidewalks, and outdoor pubs where smokers were present and we measured airborne levels of particle air pollution in real-time. The use of real-time measurements allowed us to directly match air pollution levels with observed smoking activity. We also performed controlled experiments, where we precisely examined the levels of air pollution at different distances from active cigarettes.