Microbiological air sampling was performed in four sawmills located in eastern
Poland, of which two were processing coniferous wood (pine, fir) and other two
deciduous wood (oak, birch). Total concentration of microorganisms (bacteria and
fungi) in the air of sawmills processing coniferous wood was on average 20.2 ±
5.6 × 10³ cfu/m³ (mean ± S.E.) and significantly (p <
0.05) higher compared to those processing deciduous wood where the mean
concentration of airborne microorganisms was 9.8 ± 3.0 × 10³
cfu/m³. The greatest concentrations of microorganisms in the sawmills
processing coniferous wood were noted at debarking and at first-cut frame sawing
of pine logs (42.1 ± 7.6 × 10³ cfu/m³ and 39.8 ± 7.0 ×
10³ cfu/m³, respectively). Microflora released into air
during debarking consisted mostly of allergenic fungi (mainly Aspergillus
fumigatus) and corynebacteria, whereas airborne microflora recovered during
first-cut frame sawing constituted mostly of endotoxin-producing Gram-negative
bacteria of the genus Rahnella, developing in the sapwood of pine. In the
sawmills processing deciduous wood, the largest concentration of microorganisms
(30.6 ± 3.4 × 10³ cfu/m³) was found at sorting of the oak
parquet boards and was due to the secondary infection of the boards with moulds
Penicillium citrinum during prolonged storing in the open air. Values of the
respirable fraction of airborne microflora in the examined sawmills varied
within fairly wide limits and were between 22.5-86.6%. Altogether, 34 species or
genera of bacteria and 21 species or genera of fungi were identified in the air
of sawmills, of which respectively 13 and 9 species or genera were reported as
having allergenic and/or immunotoxic properties. The concentrations of airborne
bacterial endotoxin which were determined on two sampling sites in the sawmills
processing pine and fir, were 0.24 µg/m³ and 4.00 µg/m³
respectively, distinctly exceeding the suggested safe level. In conclusion, the
workers of Polish sawmills may be exposed on some working stands to airborne
microorganisms posing respiratory hazard, of which the greatest risk is
represented by allergenic fungi developing on bark of logs or stored wood
products and endotoxin-producing Gram-negative bacteria of the genus Rahnella,
developing in sapwood of coniferous logs