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Anna Ławniczek-Wałczyk, Rafał L. Górny
Central Institute for Labour Protection – National Research Institute, Warsaw, Poland
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Abstract
In old and modern interiors, particular attention is focused on the air quality as one of major determinants of the well-being of occupants. Exposure to microbiological contaminants in such close indoor space may be associated with the occurrence of various adverse health outcomes in the exposed individuals. Because the size of inhaled particles determines their place of deposition in the human airways and the associated adverse health outcomes, a detailed characteristic of airborne microbial components carried on fine dust particles in office buildings is needed. The aim of this study was to determine the concentrations of endotoxins, (1-3)-β-D-glucans and culturable microorganisms in coarse, fine and aerosol fractions collected in two office buildings in Warsaw. The concentrations of particulate aerosol were measured using Sioutas impactors in PM1, PM2.5, and PM2.5-10. Kinetic-QCL LAL and Glucatell assays were used to detect endotoxin and (1-3)-β-D-glucan concentrations, respectively. The bioaerosol samples were taken using six-stage Andersen impactor as coarse (> 7-2.1µm) and fine (< 2.1µm) fractions, as well.

The mean concentrations of particulate aerosol, endotoxins and (1-3)-β-D-glucans in all studied offices were: in PM1 – 6 μg/m3, 4 EU/m3 and 5 ng/m3; in PM2.5 – 11 μg/m3, 6 EU/m3 and 10 ng/m3; and PM10-2.5 – 3.5 μg/m3, 2 EU/m3 and 2.5 ng/m3, respectively. The concentrations of endotoxins and (1-3)-β-glucans in PM2.5 were significantly higher than in PM10-2.5 (p < 0.01 and p < 0.001, respectively) and accounted for 71% and 84% of their total load in PM10. The airborne bacteria occurred mostly in fine fraction (average 3.9 · 102 CFU/m3, p < 0.01), while fungi in coarse fraction of aerosol (5.6 · 101 CFU/m3). The concentrations of endotoxins showed a positive correlation with PM1 (r = 0.61, p < 0.05) and PM2.5 levels (r = 0.76, p < 0.05) as well as with Gram-negative rods in fine fraction (r = 0.75, p < 0.05). The concentrations of (1-3)-β-D-glucans showed positive correlation with PM2.5 (r = 0.54, p < 0.05) and fungi in fine fraction (r = 0.59, p < 0.05).

This study demonstrated that endotoxins and (1-3)-β-D-glucans are associated mostly with fine fraction of aerosol particles. Such particles can penetrate the lower parts of the human respiratory system posing a health risk for exposed people. The main source of endotoxins in the offices were Gram-negative rods. The sources of (1-3)-β-D-glucans were probably both fungal conidia and their fragments of aerodynamic diameters <2.1 μm. The noted concentrations of endotoxins and microorganism were within the range normally observed in this type of facilities. Nevertheless, constant monitoring of the hygienic condition is suggested, including regular cleaning and replacement of air filters in the air-conditioning system.

Keywords
offices, endotoxins, (1-3)-β-D-glucans, PM1, PM2.5, PM2.5-10, bioaerosol 

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