October 5th, 2018
Mold-damaged building materials may contain biologically active agents, such as (1→3)-β-d-glucan, allergens, and mycotoxins, which have been associated with adverse health effects. The release of these components from contaminated surfaces into the air is not well understood. The purpose of this study was to characterize the release of particulate (1→3)-β-d-glucan from the surface of artificially mold-contaminated materials. Aspergillus versicolor and Stachybotrys chartarum were grown on malt extract agar (MEA), white ceiling tiles, and a wall-papered gypsum board for 1 and 6 months. The (1→3)-β-d-glucan on the surfaces of moldy materials and in air samples collected from these materials was analyzed by the Limulus amebocyte lysate assay. The aerosolization ratio was defined as the amount of (1→3)-β-d-glucan in the air divided by the amount on the surface. The results showed that the aerosolization of particulate (1→3)-β-d-glucan was influenced mainly by the type of material and the fungal species. For A. versicolor, the aerosolization ratios of particulate (1→3)-β-d-glucan released from the three types of material were not significantly different. However, the ratios for S. chartarum released from ceiling tiles and gypsum board were significantly higher than the ratios for this organism released from MEA (P < 0.001) and were comparable to those for A. versicolor. These findings indicate that the use of MEA in aerosolization experiments is likely to underestimate the release of S. chartarum particles from building materials. These results provide important background information for design of future laboratory or animal experiments, as well as for interpretation of field measurement data.
Fungal growth on building materials, such as ceiling tiles and gypsum board, can occur if enough moisture is available (8, 12, 26). Moreover, the material components (e.g., cellulose) and accumulated soil (or dust) can serve as nutrients (36) and promote amplification of mold on the building materials (16). Exposure to mold has been associated with adverse health effects (e.g., allergic rhinitis, asthma, and hypersensitivity pneumonitis) (13), but a clear exposure-response relationship has not been established yet.
The contamination of building materials by mold has been investigated in several studies in an attempt to better understand the likelihood of exposure. These studies have had two primary objectives: (i) identifying and evaluating the growth of fungi (or their metabolites) on the surface of building materials under controlled conditions; and (ii) characterizing how the release of fungal particles is affected by environmental factors (e.g., air velocity and humidity). The release of particles from moldy materials increases when air velocity increases or relative humidity decreases, and it can even be affected by vibration, material sample texture, and colony morphology (9, 10, 18, 25, 33). The composition and moisture content of building materials have been shown to be critical factors for fungal growth (3, 8, 11, 16).
Bioactive agents, such as endotoxins, mycotoxins, and (1→3)-β-d-glucan, have been found on naturally and artificially mold-infested building materials (1, 12, 22, 23, 24), but very little is known about the aerosolization patterns of these agents. (1→3)-β-d-Glucan has been used as an indicator of fungal exposure (4, 6, 27) since it is the major water-insoluble structural cell wall component (accounting for up to 60% of the dry weight) of most fungi (5). Moreover, (1→3)-β-d-glucan exposure has been associated with common respiratory symptoms, such as airway inflammation (29, 37). A recent study demonstrated that there was association between exposure of infants to (1→3)-β-d-glucan and a decrease in wheezing and allergen sensitization, indicating that this fungal component has a strong immunomodulating effect (14). Therefore, more information on the release of particulate (1→3)-β-d-glucan from moldy materials is needed in order to assess and understand exposure to mold and associated health effects. The objective of the present study was to investigate the release of particulate (1→3)-β-d-glucan from three different materials that were artificially contaminated with fungi.