Microorganisms in indoor environments. A search for health-related measurements

Abstract: Microorganisms are ubiquitous in indoor air and epidemiological data suggest that inhalation of microbes and/or their products adhered on air–borne dust particles can impair well–being and health. In the present thesis microbial volatile organic compounds (MVOCs) and cellular markers were studied by gas chromatography–mass spectrometry (GC/MS). By using solid phase microextraction (SPME) combined with GC/MS it was found that house dust particles may adsorb MVOCs in mold–affected indoor environments and that spontaneous desorption of these volatiles can be delayed by freezing the samples before analysis. SPME/GC–MS can be used to detect MVOC as markers of molds in house dust samples and also in mold–affected building materials. Cellular markers were also studied including 3–hydroxy fatty acids (endotoxin markers), muramic acid (bacterial biomass marker), and ergosterol (fungal biomass marker). The marker compositions between dust collected in schools in Jordan, Sweden, Poland, and China differed significantly indicating that the school children in different geographical regions may be exposed to highly different microbial flora. Finally, in a school study in Shanghai, China, cellular marker composition of indoor dust was found to relate to health symptoms where fungal components (ergosterol) were related to adverse respiratory symptoms whereas bacterial components, especially as revealed by endotoxin markers, were negatively associated with such symptoms suggesting a protective effect. The presented chemical–analytical approaches are useful in characterizing microbial exposure in indoor environments.