Short term seasonal effects of airborne fungal spores on lung function in a panel study of schoolchildren residing in informal settlements of the Western Cape of South Africa.

Background: The individual effects of biological constituents of particulate matter (PM) such as fungal spores, on lung function in children are not well known. This study investigated the seasonal short-term effect of daily variation in Alternaria and Cladosporium fungal spores on lung function in schoolchildren.

Methods: This panel study evaluated 313 schoolchildren in informal settlements of the Western Cape of South Africa, exposed to spores of two commonly encountered fungi, Alternaria and Cladosporium species. The children provided forced-expiratory volume in 1-s (FEV) and peak-expiratory flow (PEF) measurements thrice daily for two consecutive school-weeks in summer and winter. Daily PM levels, from a stationary ambient air quality monitor and fungal spore levels using spore traps were measured in each study area throughout the year. The effects of Alternaria and Cladosporium spores, on lung function were analysed for lag periods up to five-days, adjusting-for PM, other pollen exposures, study area, and other host and meteorological factors. Same-day exposure-response curves were computed for both fungal species.

Results: There was more variability in Alternaria spores level with noticeable peaks in summer. There were consistent lag-effects for Alternaria on PEF compared to Cladosporium, with the largest PEF deficit observed in winter (mean deficit: 13.78 L/min, 95%CI: 24.34 to -3.23 L/min) per 10spores/m increase in Alternaria spores on lag day-2. Although there were no observable lag-effects for Alternaria and Cladosporium on FEV, same-day effects of Cladosporium spores on FEV was present across both seasons. Threshold effects of Alternaria on both PEF and FEV deficits were apparent at levels of 100 spores/m, but could not be explored for Cladosporium beyond the levels observed during the study.

Conclusion: The study provides evidence for the independent effects of daily exposure to ambient fungal spores of Alternaria and Cladosporium on lung function deficits, more especially in winter for PEF.