Indoor air particles and bioaerosols before and after renovation of moisture-damaged buildings: The effect on biological activity and microbial flora☆
Introduction
Failure to provide good indoor air quality often manifests itself as complaints and reports of adverse health effects among the occupants. Many of the building-related health problems coincide with moisture damage and mold growth within the building. This has been shown as increased prevalence of respiratory and other symptoms in damp indoor environments. A decrease in both prevalence of symptoms and concentrations of microbes has been demonstrated after a thorough renovation of mold damage (Sudakin 1998; Ahman et al., 2000; Meklin et al., 2005).
In addition to overcrowding of workspace and lack of office cleanliness, the reported work-related symptoms have been correlated, e.g. with number of fungi in dust from office chairs (Park et al., 2006). Airborne culturable fungal concentrations are not, however, always higher than normal even in case of evident observations of dampness and mold (Hyvärinen et al., 1993). The reasons for this are not well known, but may be explained by the fact that growing fungi are not constantly releasing spores into their environment. In some studies, airborne concentrations of fungi have been linked to upper respiratory symptoms in spite of the low levels of fungi (Chao et al., 2003). The extent of the exposure to fungi may, however, be higher than estimated based on the number of airborne culturable spores, since only a fraction of environmental microbial material is culturable, and since the small airborne fragments of fungi may contribute to the exposure (Górny et al., 2002; Green et al., 2006). Nevertheless, studies have shown that reported symptoms can be attributed to allergenic reaction towards fungal components only in a small subgroup of workers (Husman, 1996; Menzies et al., 1998).
Dust and consequently indoor air contains physiologically reactive agents originating from outdoor air and various sources indoors including microbes. In addition to microbial cells, spores and metabolites such as mycotoxins, also fragments and structural components such as polysaccharides, endotoxins and (1→3)-β-d-glucans are present (Rao et al., 2005). Part of the dust particles are airborne and small enough to be inhaled all the way to alveolar level of the lungs, where the macrophages make their effort to destroy the foreign agents. As a result, the production of inflammatory mediators and amount of activated cells in the airways are increased, leading to local inflammatory reaction (Sibille and Marchandise, 1993). If this inflammatory reaction is excessive or sustained for too long, it may damage the surrounding tissues and lead to the unspecific symptoms typical for occupants staying in buildings with mold contamination.
The markers mediating inflammatory reaction include nitric oxide (NO) and cytokines such as tumor necrosis factor (TNF)α and interleukin (IL)-6. A study of teachers working in a moisture- and mold-damaged school building showed, that levels of these inflammatory markers in nasal lavage fluid were higher compared to control group, and decreased significantly during absence from the moldy environment (Hirvonen et al., 1999). The same inflammatory markers have been measured from cell cultures and mouse model in experimental studies on the immunotoxic potential of moldy house microbes (Huttunen 2003; Jussila 2003). The potential of organic dust to induce production of inflammatory mediators in cell culture systems has also been utilized to compare different indoor environments (Allermann and Poulsen, 2000), but there are no studies available about immunotoxic properties of airborne particles collected in intervention studies.
Thorough repairs of mold- and moisture-damaged buildings have been shown to decrease the frequency of reported symptoms among the occupants and also the counts of viable airborne fungi (Meklin et al., 2005). However, the usually low concentrations of viable fungi in office-type environments do not necessarily reflect the presence of various harmful agents in the indoor air (Salonen et al., 2007). Therefore, we monitored the overall biological activity of the particle material when evaluating the effect of renovation on quality of indoor air.
The aim of this study was to follow the success of repairs in two locations by characterizing the changes in indoor air quality with analyses of airborne particles collected before and after renovation. In addition to particle counts, the immunotoxicological activity and microbiological characteristics of the collected filter samples were determined. Samples taken before and after renovations were also compared with samples collected from reference buildings and outdoors.
Section snippets
Study design
The study was performed in two buildings with moisture and mold damage (Locations 1 and 2) and their age-, building frame-, ventilation type- and usage-matched controls. Air samples were collected and particle concentrations measured from indoor air of moisture problem building before and after remediation in two different locations. Samples from reference building in both measuring locations and time points were collected as well. Measurements were done in winter in order to minimize the
Location 1
In the Location 1, samples were collected before and after renovation from the indoor air of the damaged building and from the reference building, located on the same complex. In addition, one sample from the outdoor air was obtained from this site after the renovation.
Discussion
The current study highlights the complexity and individual characteristics of buildings with moisture-related indoor air problems; the one common denominator is yet to be found. However, the multidisciplinary approach and new methodology applied in this study were successful in providing more comprehensive picture of the complex situation found in buildings with occupant symptoms and moisture and mold damage. The strategy for indoor air studies was to collect long term samples of airborne
Acknowledgment
The authors wish to thank Ms. Heli Martikainen for the excellent technical assistance.
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This work was supported by Finnish Technology Agency (Tekes), FINE-technology program; Grant 40035/04.
This study does not involve any human subjects or animal research.