Fig. 1

Chart showing the relation between airborne pollen concentrations and the arrival of the thunderstorm outflow in Wagga Wagga (Australia). Closed circles represent intact pollen grains. Open circles represent empty pollen husks. The data are plotted at the midpoint of the hour over which the concentrations have been measured. Data for wind speed, wind direction, and rainfall were recorded each minute by analogue chart recorder and have been scanned into the figure. The vertical dashed line represents the time at which the first ambulance call, seeking assistance for an attack of asthma, was received in Wagga Wagga. Examination of the recorded radar images (not shown) reveals that the line of the thunderstorms arrived at the site of the Burkard trap about 10 min before it reached the AWS. Reproduced with permission from BMJ Publishing Group Ltd [64]