Childhood asthma and grass pollen aerobiology in Melbourne.

Children from the Melbourne metropolitan area with laboratory proven bronchial sensitivity to ryegrass pollen were selected for a clinical trial which was run concurrently with an aerobiological survey during the grass pollen season of 1975 to 1976. During periods of high pollen counts, significant deterioration in the children's asthma occurred. The grass pollen season was of 10 weeks' duration with the highest daily counts during November and December. Highest diurnal pollen concentrations occurred at night and were associated with winds from the north, north-west, and south-east and with other meteorological factors.