International Journal of Hygiene and Environmental Health
Mini-ReviewExposure assessment of residential mould, fungi and microbial components in relation to children's health: Achievements and challenges
Introduction
Each day we are exposed to a complex mixture of microbial agents and components in indoor environments. A major part of this mixture derives from fungal, bacterial and viral origin (Nevalainen and Seuri, 2005). The impact between those microbial agents in the home environment in relation to respiratory health in children is still a major issue in research (WHO, 2009). There are a number of publications addressing more or less the same research questions such as exposure to fungal or bacterial agents in relation to respiratory and allergic health outcomes (for a review see Mendell et al., 2011). However, the research approaches can vary considerably in some cases which might be partly responsible for inconsistencies found in results (Tischer et al., 2011a).
Previous reviews focused mainly on summarizing exposure–response relationships (Fisk et al., 2007). We focus here on exposure assessment and analysis methods of mould and microbial agents, in addition to the summary of health effects. We aim to consider several important aspects of an epidemiological study such as the impact of different types of fungal and bacterial exposure and different assessment and analysis strategies. We further discuss findings from interventional studies on fungi removal and considered the potential relevance of gene–environment interactions. This work is focusing on what achievements has been made so far in terms of epidemiological research on mould exposure with emphasis on children and further, what are the future challenges and possible research directions concerning mould and microbial pollution in indoor environments.
Section snippets
Exposure to fungal and bacterial agents
Fungi and fungal components are natural and ubiquitous in indoor environments (Green et al., 2006). In ‘healthy’ indoor environments the predominant fungi are the outdoor air genera Cladosporium, Penicillium and Aspergillus (Nevalainen and Seuri, 2005, Jones et al., 2011). However, the presence of dampness or visible mould shifts the composition of the fungal profile toward ‘indicator organisms’ – species such as Penicillium chrysogenum, Penicillium expansum, Aspergillus versicolor, Aspergillus
Health effects of domestic mould and bacterial agents
Available data suggested 20% of the homes worldwide have dampness problems or visible mould (IOM, 2004). A large body of literature supports an association between living in a damp and mouldy environment and adverse respiratory and allergic health disorders in children throughout the world (IOM, 2004, Fisk et al., 2007, Seltzer and Fedoruk, 2007, WHO, 2009, Tischer et al., 2011a, Tischer et al., 2011b). However, being exposed to increased levels of bacteria and mould derived components early in
Assessment of mould and microbial agents
Apart from the difficulty of disentangling the impact of various microbial agents indoors, there is currently no standardised and valid exposure assessment method to measure exposure to microbial agents. Numerous strategies have been used to assess visible mould and microbial exposure in indoor environments in the past (Table 1).
The choice of specific exposure assessment method and the analysis method can significantly impact the interpretation of study findings. One common, simpler approach
Evidence from intervention studies on mould and fungi removal
Recent reviews on housing intervention and the World Health Organization (WHO) guidelines for indoor air quality concluded that there is sufficient evidence for reducing respiratory symptoms after remediation activities, however, this concerns mainly an adult population (WHO, 2009, Jacobs et al., 2010, Krieger et al., 2010, Rao and Phipatanakul, 2011). There is less knowledge about interventional trials on mould remediation in relation to allergic disorders in children. One prospective,
Gene–environment interactions
Apart from the complexity of the exposure, the development of allergic diseases is also based on a complex interplay between environmental and genetic factors. There are a number of genes associated with the development of asthma and allergies in genome wide association studies (Meyers, 2010, Moffatt et al., 2010). Mutations in the toll-like receptor (TLR) pathway genes, especially TLR 4 which is the major signalling receptor for lipopolysacchardies (LPS), were found to alter the response to
Conclusion and recommendations
Dampness and moisture damage is not only an important precondition for mould growth, but also favours the spread of bacterial and other microbial agents. In order to identify patterns of agents evoking harmful or protective effects on the development of asthma and allergic diseases, the focus should be on elaborated assessment and analyses techniques. Up to now, there is no standardised exposure assessment method which would help to better compare results from different studies, to detect
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