The long-term trends and seasonal variation of the aeroallergen Alternaria in Derby, UK

Very little is known in the UK about long term trends of the Alternaria spore although it is known to trigger asthma. It has recently become apparent that Alternaria spore levels are increasing in Derby and a detailed study of Alternaria was undertaken to investigate the increase in numbers, seasonal variation and diurnal periodicity. The seasonal (June-October) Alternaria spore concentrations show a distinct upward trend and there is evidence of an earlier seasonal start and an increase in the seasonal duration. There has been a dramatic rise in the number of days with an Alternaria spore count above 50 spores per cubic metre, with the peak daily count usually occurring in August but occasionally in late July or early September. August generally has the highest monthly total and for 1991-1998 there was a positive correlation with monthly rainfall and average temperature. Day to day spore levels show a positive correlation between Alternaria spore concentrations and maximum temperature but a slight negative correlation with daily rainfall. The peak time for spore capture is 14.00-22.00, and more than half the daily Alternaria catch is caught between 18.00 and 24.00 hours. The upward trend in Alternaria spore concentrations may be responsible for increasing levels of respiratory disease, especially during harvest time.