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Mould growth on building materials and the effects of borate-based preservatives Li, Raymond

Abstract

One of the difficulties in establishing causal roles for indoor mould growth and adverse health effects is that the growth, metabolism, and biological activity of moulds depend on the interaction of the moulds with their growth substrates and environment. Further, one of the approaches to preventing indoor mould growth is to treat building materials with preservatives. Borates are a class of preservatives with low toxicity that can be used to protect a variety of different materials. Objectives: The growth and metabolism of three moulds associated with indoor environment problems were investigated on untreated and borate-treated versions of six building materials. Methods: Untreated and treated specimens of Southern Yellow pine, lodgepole pine, pine oriented strandboard, aspen oriented strandboard, cellulose insulation, and gypsum board were inoculated with spores of S. chartarum (ATCC 201212), A. versicolor (ATCC 26939), or P . brevicompactum (ATCC 9056), and incubated at 20 - 23°C and - 100% relative humidity for 4 weeks. The visual appearance of mould growth and changes in the volatile organic compound profile were measured each week. Carbon dioxide production and ergosterol were measured at the end of the incubation period. Results: The building materials tested differed in their ability to support mould growth. S. chartarum did not grow on untreated or treated wood or wood composites. The pattern of volatile organic compounds produced by each mould depended on the growth substrate. Borates were effective at preventing or reducing mould growth, although O S B may require higher levels of treatment than currently used. A dose-response trend was observed with gypsum board. Sub-inhibitory levels o f borates did not stimulate the production of different volatile metabolites, suggesting the lack of stress metabolism. The use of different methods for evaluating growth revealed that there could be mould growth on materials that did not appear to be contaminated. Conclusions: Mould growth and metabolism is influenced by the specific mould-substrate interactions. Borate-based preservatives inhibit mould growth and do not appear to induce stress metabolism at sub-inhibitory concentrations. Further studies on other aspects of mould growth, such as mycotoxin production and the biological activity of spores, on treated and untreated building materials are needed.

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