Biological responses of Raw 264.7 macrophage exposed to two strains of Stachybotrys chartarum spores grown on four different wallboard types.

The many benefits of building "green" have motivated the use of sustainable products in the design and execution of the built environment. However, the use of these natural or recycled materials, some of which have been treated with antimicrobials, provides a growth opportunity for microorganisms with the potential to elicit adverse health effects especially in the presence of an antimicrobial. The focus of this research was to determine the effects of Stachybotrys chartarum (strains Houston and 51-11) grown under different conditions on a macrophage cell line (Raw 264.7) using endpoints, including cytotoxicity, and those associated with immunity specifically inflammation and MHC class II expression. The fungi were grown on four different gypsum products, and macrophages were exposed to whole spores of both strains and fragmented spores of strain 51-11. Whole spores of the Houston strain elicited no cytotoxicity with some level of inflammation, while exposure to whole spores of 51-11 caused variable responses depending on the wallboard type supporting the fungal growth. High concentrations of fragmented 51-11 spores primarily resulted in the apoptosis of macrophage with no inflammation. None of the fungal strains caused elevated levels of major histocompatibility complex (MHC) class II expression on the surface of Raw cells. Mycotoxin levels of 51-11 spores from all of the wallboard types measured >250 ng/µL of T2 equivalent toxin based on activity. Collectively, the data demonstrated that all of the wallboard types supported growth of fungi with the ability to elicit harmful biological responses with the potential to negatively impact human health.

Mold growth on gypsum wallboard--a summary of three techniques.

Reducing occupant exposure to mold growing on damp gypsum wallboard and controlling mold contamination in the indoor environment was studied through 1) delineation of environmental conditions required to promote and avoid mold growth and 2) efficacy testing of antimicrobial products, specifically cleaners and paints, on gypsum wallboard (GWB) surfaces. The effects of moisture and relative humidity (RH) on mold growth and transport are important in avoiding and eliminating problems. These effects have been demonstrated on GWB and are discussed in this article for use as control guidance. The authors discuss the efficacy of antimicrobial cleaners and paints to remove, eliminate, or control mold growth on GWB. Research to control Stachybotrys chartarum growth using 13 separate antimicrobial cleaners and nine varieties of antimicrobial paint on contaminated GWB was performed in laboratory testing. GWB surfaces were subjected to high RH. GWB control measures are summarized and combined, and the antimicrobial product results are explained.

Testing antimicrobial paint efficacy on gypsum wallboard contaminated with Stachybotrys chartarum.

The goal of this research was to reduce occupant exposure to indoor mold through the efficacy testing of antimicrobial paints. An accepted method for handling Stachybotrys chartarum-contaminated gypsum wallboard (GWB) is removal and replacement. This practice is also recommended for water-damaged or mold-contaminated GWB but is not always followed completely. The efficacy of antimicrobial paints to eliminate or control mold regrowth on surfaces can be tested easily on nonporous surfaces. The testing of antimicrobial efficacy on porous surfaces found in the indoor environment, such as gypsum wallboard, can be more complicated and prone to incorrect conclusions regarding residual organisms. The mold S. chartarum has been studied for toxin production and its occurrence in water-damaged buildings. Research to control its growth using seven different antimicrobial paints and two commonly used paints on contaminated, common gypsum wallboard was performed in laboratory testing at high relative humidity. The results indicate differences in antimicrobial efficacy for the period of testing, and that proper cleaning and resurfacing of GWB with an antimicrobial paint can be an option in those unique circumstances when removal may not be possible.

Method for evaluating mold growth on ceiling tile.

A method to extract mold spores from porous ceiling tiles was developed using a masticator blender. Ceiling tiles were inoculated and analyzed using four species of mold. Statistical analysis comparing results obtained by masticator extraction and the swab method was performed. The masticator method was demonstrated as efficient for bulk sampling of ceiling tiles.