Critical aspects on the significance of microbial volatile metabolites as indoor air pollutants

Abstract

The effect of microbial growth in building materials on airborne levels of volatile organic compounds (VOCs) was demonstrated by theoretically calculating indoor air concentrations of selected VOCs for rooms with and without microbial contamination. The recommended indoor air level for individual VOCs was also estimated on the basis of their sensory irritation potency. Furthermore, the irritation potency for the mixtures of certain compounds (microbial volatile metabolites, MVOCs) at airborne concentrations measured in problem buildings was evaluated. The theoretical airborne concentrations of certain compounds, which are generally regarded as MVOCs, were estimated to be only about 1% higher in the biocontaminated rooms than in those with moist sterile materials. In fact, no individual VOCs indicated exclusively microbial contamination, but they could also be emitted even from sterile, moist constructions. Exposure to mixtures of the selected non-reactive VOCs at the theoretical airborne concentrations would not result in sensory irritation in humans, and, thus, microbial growth in constructions should not increase the probability of irritating symptoms considerably. The data on MVOC concentrations measured in some problem buildings also supported this idea. Irritation would be expected when the airborne concentrations of single non-reactive compounds approach a level of hundreds of μg/m3 or mg/m3.