Respiratory health effects of indoor microbial exposure : a contribution to the development of exposure assessment methods

J. Douwes

    Research output: Thesisinternal PhD, WU


    <p>The studies described in this thesis validated an existing method to measure bacterial endotoxin and explored new methods for measuring mold components in the environment, particularlyβ(1→3)-glucans and extracellular polysaccharides (EPS). These assays were used to study levels of microbial components in the home and occupational environment, and to investigate their relationships with respiratory health in children or workers, respectively.</p><p>It was shown that results of endotoxin measurements may differ considerably between laboratories when different sampling, extraction, and storage procedures are employed. Highest yields were found when samples were extracted with 0.05% Tween-20 in water. Repeated freezing and thawing resulted in a considerable endotoxin loss.β(1→3)-glucan, endotoxin and EPS from <em>Aspergillus</em> and <em>Penicillium</em> spp. (EPS- <em>Asp/Pen</em> ) were readily detectable in house dust samples. Endotoxin andβ(1→3)-glucan levels were, at least for living room floors, significantly associated with certain home characteristics, particularly heating system and/or age of the home. Bothβ(1→)-glucan and EPS- <em>Asp/Pen</em> were significantly but only weakly correlated with culturable fungi in house dust. Living room floor concentrations of EPS- <em>Asp/Pen</em> were positively associated with occupant-reported home dampness and respiratory symptoms in children, while no such associations were found for bedroom and mattress concentrations.</p><p>In another study among children it was shown thatβ(1→3)-glucan in house dust from living room floors was strongly associated with peak flow (PEF) variability, particularly in atopic and/or asthmatic children. No associations were found forβ(1→3)-glucan levels on bedroom floors and mattresses. Unadjusted regression models showed that endotoxin levels were also significantly associated with PEF variability, while after adjusting for other known risk factors no significant association was found. A study among compost workers showed that microbial exposure induces acute and possibly chronic inflammation in the upper airways with a mechanism that suggests non-immune or possibly type III but not type I allergic inflammation.</p><p>It is concluded that the studies reported in this thesis contribute to new methods for microbial exposure assessment that offer advantages for use in epidemiological studies compared to traditionally employed culture-based methods.</p>
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    • Brunekreef, B., Promotor, External person
    • Rylander, R., Promotor, External person
    • Doekes, G., Promotor, External person
    Award date28 Oct 1998
    Place of PublicationS.l.
    Print ISBNs9789054859352
    Publication statusPublished - 1998


    • respiratory system
    • microbial contamination
    • air pollution

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