Modifiable factors governing indoor fungal diversity and risk of asthma

Exposure to dampness and fungi in the home is a known risk factor for individuals with allergic asthma. Inadequate heating and ventilation may lead to dampness and concomitant increased exposure to spores of allergenic fungi such as Aspergillus and Penicillium. These fungi have been cultured from sputum of asthmatic and non-asthmatic individuals, and implicated in the initiation or exacerbation of asthma. Indoor environmental factors influence the presence and concentrations of fungal propagules and, in turn, risk of asthma outcomes. This review aims to identify modifiable risk factors in the built environment that have been shown to influence fungal composition indoors, and to examine this association with the risk of asthma development and/or exacerbation. A complex interaction between residential characteristics, the built environment and the behaviour of people regulate the diversity and concentrations of indoor fungi. Modifiable factors include build age, architectural design, level of maintenance, variations in construction materials, presence of pets, heating and ventilation patterns. Risk of fungal contamination and asthma outcomes are also influenced by low occupant awareness concerning potential health effects and socio-economic factors. Addressing these factors provides an opportunity to improve future housing interventions, though it is not clear how the built environment and occupant behaviours interact to modify the diversity of indoor fungi and resultant risk of asthma. A combination of housing improvements combined with awareness programmes and the alleviation of fuel poverty can be used to lower the allergen burden associated with damp homes. Further research is needed to identify factors that regulate the concentration and diversity of indoor fungi and how this may act as a modifier for asthma outcomes.