Weekly bronchitis cases (circles, left hand axis) and particulate matter with a diameter below 10 µ (PM10) (crosses, right hand axis), with smoothed curves showing the trends through the decade of study data. Weekly bronchitis cases (circles, left hand axis) and particulate matter with a diameter below 10 µ (PM10) (crosses, right hand axis), with smoothed curves showing the trends through the decade of study data. Some higher PM10 values are off the scale. D Mészáros et al. BMJ Open Resp Res 2015;2:e000063 ©2015 by British Thoracic Society