Outdoor Mold and Respiratory Health: State of Science of Epidemiological Studies

Fungal spores are the predominant biological particulates in outdoor air. However, in contrast to pollens or outdoor air pollution, little is known about their respiratory health risks.

The objectives were to conduct the first review of epidemiological studies on the short- and long-term effects of outdoor mold exposure on respiratory health in children and adults.

Health outcomes included asthma, lung function, and rhinitis. Cross-sectional and longitudinal epidemiological studies using quantitative measures of outdoor mold exposure (optical microscopy, culture-based methods) were selected, providing that important confounding factors including temporal trends or meteorological factors were accounted for. A systematic literature search was performed up to June 2020, leading to the selection of 37 publications.

Most studies were longitudinal and investigated short-term effects. There is evidence of an association between outdoor fungal exposure and an increase in asthma exacerbation among children for total spores, 2 phyla (ascomycetes, basidiomycetes), and 2 taxa (Cladosporium, Alternaria). A few studies also suggested an association for Coprinus, Ganoderma, Aspergillus-Penicillium, Botrytis, and Epicoccum in children, but this needs to be confirmed. Some studies reported mold associations with rhinitis, lung function, and among adults, but these were few in number or inconsistent.

Further ecological studies in different regions that measure exposure to all taxa over several years are required to better understand their impact on rhinitis, asthma exacerbations and lung function. Larger panel studies are necessary to identify threshold effects in susceptible individuals. Finally, further research should assess the long-term effects of outdoor mold.