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Respiratory impact of outdoor mold

Published: October 11, 2021

Outdoor molds are numerous (between 25 and 50 different taxa), especially during the spring-summer period; they are the biological particles in the air with the highest concentration.

Even today, the capture of these molds is done mainly with volumetric sensors (suction of 10 Liters of air per minute) of the Hirst type. Their recognition by morphological analysis under the optical microscope requires significant expertise because of mold diversity and is time consuming because of their abundance. The advantage of this method is to obtain daily results as for pollens. Cultivation is much more rarely used. This is why, most of the time, the analysis is limited to the recognition of Cladosporium, the most frequent mold in temperate countries, and Alternaria, whose respiratory pathogenic effect is classically retained. Because of these difficulties, the respiratory health effects of outdoor molds are still poorly understood. The purpose of this systematic review published by Caillaud et al. in The Journal of Allergy and Clinical Immunology: In Practice is to list all published epidemiological studies on the short and long-term respiratory effects of outdoor molds in children and adults and to determine which spores have a respiratory impact.

Outcomes sought for the review included rhinitis, asthma and lung function. Longitudinal and cross-sectional studies were selected. Confounding factors had to be considered, such as air pollution, meteorological factors, and temporal trends. Finally, the statistical analysis had to be of sufficient quality. A total of 37 articles were selected through June 2020.  Of the 37 studies identified, 32 studies involved asthma or lung function and 5 involved rhinitis. The results show that there was an association in children between asthma exacerbations and exposure to total spores, the 2 major classes of molds, ascomycetes and basidiomycetes, and 2 taxa, Cladosporium and Alternaria. Exposure to 5 other taxa, 2 basidiomycetes, Coprinus and Ganoderma, 3 ascomycetes (Aspergillus-Penicillium, Botrytis and Epicoccum) was also deleterious, but needs to be confirmed by other studies. Some studies have shown an association with rhinitis and respiratory function in adults, but their number or discordant results do not allow definite conclusions. Outdoor mold exposure should be investigated as a potential cause in patients with mild or severe asthma exacerbations. Recommendations to reduce spore exposure might be proposed using regional fungal calendars.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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