No abstract

There is a growing body of evidence on fungal contamination in moisture-damaged and complaint buildings worldwide, but little is known about the occurrence and distribution of fungi in healthy non-complaint buildings in a southern-hemisphere climate. The study tested the hypothesis that fungi in healthy buildings are low in numbers and very similar to the numbers and mixtures of species in both the outdoor air and the indoor air in other parts of the world. Fungi were collected using a 6-stage Andersen sampler, and various indoor air quality (IAQ) indicators and a sick-building syndrome (SBS) questionnaire were used in parallel. The results showed that all IAQ parameters were within USA and Canadian guidelines in all the buildings. There was also a low incidence of SBS complaints and symptoms. The total colony-forming unit (CFU) counts were also low, and the range of fungal species was low compared to buildings in other parts of the world. However, the mixture of fungal genera in the indoor air was different from the outdoor air. There were also substantial differences between indoor locations. At some locations fungi includ-ing Aspergillus niger, Penicillium spp. and Alternaria alternata were much higher indoors than outdoors or, as the pathogen Paecilomyces lilacinus, were absent in the outdoor air indicating indoor sources. Differentiation of fungal species was required to identify indoor fungal sources as the outdoor air was not the major source of indoor fungi. The study also demonstrated that evaluating the potential exposure to airborne fungi in indoor air requires differentiation to the species level as simple CFU counts could not differentiate between benign and potentially harmful fungi.

Little is known about the changes in occurrence and distribution of airborne fungi as they are transported in the airstream from the outdoor air through the heating, ventilation, and air conditioning (HVAC) system to the indoor air. To better understand this, airborne fungi were analyzed in the HVAC systems of two large office buildings in different climate zones. Fungal samples were taken in each of the walk-in chambers of the HVAC systems using a six-stage Andersen Sampler with malt extract agar. Results showed that fungal species changed with different locations in the HVAC systems. The outdoor air intake produced the greatest filtration effect for both the counts and species of outdoor air fungi. The colony forming unit (CFU) counts and species diversity was further reduced in the air directly after the filters. The cooling coils also had a substantial filtration effect. However, in room air the CFU counts were double and the mixture of fungal species was different from the air leaving the HVAC system at the supply air outlet in most locations. Diffusion of outdoor air fungi to the indoors did not explain the changes in the mixture of airborne fungi from the outdoor air to the indoor air, and some of the fungi present in the indoor air did not appear to be transported indoors by the HVAC systems.

In the predacious fungus Arthrobotrys oligospora Fres., the number and distribution of traps formed after the addition of living nematodes to the colonies were determined. At 21°C the traps were formed periodically; the mean period was 42.3±0.8 h. The periodicity was independent of light-dark (LD) cycles of 24 h (10:14). Temperature influenced the hyphal elongation but did not affect the periodic trap formation; at lower temperatures the peaks of trap formation were close together, showing partial overlapping. Induction of rhythmic mycelial growth and conidiation by chemical means was effective only in LD-cycles. The latter diurnal rhythm was weakly correlated with the trap formation and did not affect the endogenous period of approximately 42 h.

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