Positive associations between respiratory outcomes and fungal index in rural inhabitants of a representative sample of French dwellings

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Abstract

Our study aims at estimating exposure to molds at home, based on microbial Volatile Organic Compounds (MVOCs) assessment, and evaluating its effect on respiratory diseases in a representative sample of dwellings. In the framework of a national campaign, indoor pollution was monitored in a sample of the 24 million dwellings of metropolitan France (n = 567). 727 subjects answered to a standardized questionnaire on respiratory diseases and had MVOCs sampled in their bedrooms and a fungal index (FI) defined. Among the 431 dwellings with complete data, one out of three was contaminated by molds as assessed by a positive FI: 27.0% in urban, 38.2% in periurban and 34.9% in rural dwellings respectively. Positive associations were observed between fungal index and current asthma (8.6%) and chronic bronchitis-like symptoms (8.4%), especially in rural areas (OR = 2.95, 95%CI (1.10; 7.95) and 3.35, 95%CI (1.33; 8.48) respectively). Our study, based on objective assessments of fungal contamination, is in agreement with previous results suggesting mold-related respiratory effects. Moreover associations found among rural population could indicate specific pollution and impact in this environment.

Introduction

Up to 50% of buildings are known to have dampness and mold problems. A large number of studies report associations between exposure to dampness or visible molds and respiratory symptoms (Mendell et al., 2011). It has been estimated that, out of the 21.8 million people reported to have asthma in the USA, approximately 4.6 (2.7–6.3) million cases are estimated to be attributable to dampness and mold exposure in the home (Mudarri and Fisk, 2007). However, in most epidemiological studies focusing on health effects of molds, buildings were considered as contaminated on the basis of visual detection (questionnaire reports and/or technician observations). Using these techniques can lead to a strong underestimation of the proportion of individuals exposed to molds: neither “hidden” contamination (development of molds behind wall paper or in ventilation filters) nor recent contamination, hardly visible, can be detected. In order to overcome these limits, Moularat et al., 2008b, Moularat et al., 2008c have developed a specific chemical fingerprint for fungal development, based on the detection of a list of pertinent Volatile Organic Compounds (VOCs) characteristic of mold growth (microbial VOCs (MVOCs)). Using this index, Moularat et al., 2008a, Moularat et al., 2011 have shown that around 70% of dwellings which present fungal development according to the fungal index (FI) was not considered as contaminated through visual detection. Therefore, in order to obtain a better estimate of the risk associated with molds, the use of objective methods to assess exposure became essential.

The rural environment has been shown to present a higher exposure to biocontaminants in homes and stables than the urban environment, in particular to endotoxins (Lee et al., 2006). Recent results have suggested that compared to urban children, rural children were also exposed to an excess of molds at home (Moularat et al., 2011, Toivola et al., 2004, Wady et al., 2004), particularly children living in farms (Schram et al., 2005, van Strien et al., 2004). In this environment, it has been hypothesized that under particular circumstances early life exposure to an excess of biocontaminants could protect from allergies (Braun-Fahrlander et al., 2002, Eduard et al., 2004, Schram-Bijkerk et al., 2005). It has also been suggested that such exposure could induce non-atopic asthma (Eduard et al., 2004, Hulin et al., submitted for publication) or chronic bronchitis in adults (Kirychuk et al., 2006, Post et al., 1998, Preller et al., 1995, Vogelzang et al., 1998) through exposure to other molds components than the allergens (MVOCs, mycotoxins). Despite these features, few studies have focused on the effects of indoor air pollution in the rural population.

Our study aims at evaluating exposure of French population to molds, as assessed with an objective index of fungal contamination based on MVOC measurements, as well as its relation with allergic and respiratory diseases in adults. We also investigated health effects of molds in rural, periurban and urban environments, using a representative sample of French dwellings, in order to look for differences according to the type of areas.

Section snippets

Study sample

A national housing survey was carried out by the French Indoor Air Quality Observatory (OQAI) during the 2003–2005 period in order to assess indoor air quality in French dwellings. This cross-sectional survey collected information about 567 occupied dwellings, randomly selected to be representative of the 24 million principal residences in mainland France, and their 1612 inhabitants distributed in 74 cities in a three-stage clustering (Billionnet et al., 2011, Kirchner et al., 2007). The survey

Sample characteristics

Out of the 1234 individuals in 567 dwellings having participated in the national survey, a total of 897 individuals (age  15) in 431 dwellings sent back a completed health questionnaire and had measurement of VOCs/MVOCs in their dwellings, corresponding to a response rate of 72.7% and 76.0% in terms of individuals and dwellings respectively. Three hundred and thirty seven people living in 146 dwellings were excluded due to missing values: 222 individuals did not fill in the questionnaire and/or

Discussion

Indoor air dampness and molds in dwellings have become important environmental health issues (WHO, 2009). In our study, conducted in a sample of dwellings selected to be representative of the residences of mainland France, one out of three dwellings presented mold contamination according to an objective fungal index based on the presence or the absence of microbial VOCs. Among subjects living in rural environment, positive associations between respiratory health and exposure to molds, assessed

Conclusion

In conclusion, our study based on an objective assessment of fungal contamination of the dwellings extends previous results suggesting positive associations between exposure to molds and asthma and chronic bronchitis. Ad hoc measures have to be taken to reduce dampness and fungal development in dwellings as it could lead to respiratory problems. In addition, our findings suggest that in rural areas, a specific impact of indoor pollution on respiratory health could occur. Considering different

Acknowledgments

We are particularly indebted to all the participants without whom the study would not have been possible. The authors would like to thank Jean-Paul Lucas and Anthony Gregoire (CSTB) for their help with the data. We are grateful to the French National Institute for Industrial Environment and Risks (INERIS) and in particular Laure Malherbe and Laurent Letinois for their classifications of the study dwellings. Funding by Observatory on Indoor Air Quality: Ministries in charge of Construction,

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