Indoor and outdoor airborne fungal propagule concentrations in Mexico City

Abstract

Thirty homes of asthmatic adults located in Mexico City were examined to determine the predominant culturable fungi and the changes in their airborne concentrations. Fungi were cultured and identified microscopically from air samples collected in naturally ventilated homes, during both wet (July–August) and cool dry (November–December) seasons, and from settled dust from the same homes. Airborne dust from indoor yielded 99–4950 cfu m−3, and settled dust 102–106 cfu g−1 on DG18 agar. The indoor geometric mean concentration of airborne fungi during the cool dry season was 460 cfu m−3 while in the wet season it was 141 cfu m−3. Similarly, numbers of airborne fungal propagules out of doors decreased 60% between the dry and wet season. In general, the total fungal concentrations in indoor air were less than 103 cfu m−3 and a large proportion of them was collected in Stage-2 of the Andersen sampler. Moreover, the ratio between indoor and outdoor concentrations was 500 cfu m−3 of one genus, with up to 1493Cladosporium cfu m−3 or 2549Penicillium cfu m−3. Also, these two genera were predominant in both airborne and settled dust, and their concentrations were greater indoors than out, indicating a possible indoor source of fungal propagules. The predominant species wereCladosporium herbarum, Penicillium aurantiogriseum andP. chrysogenum. These results suggest that exposure to large concentrations of fungi occurs indoors and is associated with both seasons of the year and with particular home characteristics.