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Microbial Contaminants of Stored Timber as Potential Respiratory Hazards for Sawmill Workers.

Dutkiewicz-J; Sorenson-WG; Lewis-DM; Olenchock-SA
NIOSH 1990 Sep:712-716
A quantitative and qualitative study was made of the microflora of timber logs stored prior to sawmill processing, to assess potential respiratory risks to woodworkers of wood inhabiting microorganisms. Samples were obtained in August and October of 1987 from logs of six different species. Timber had been stored in a sawmill lumber yard for 4 to 6 weeks and had no visible signs of decay. One sample each of heartwood, sapwood and bark was obtained from each log. Quantification of bacteria and fungi was done by dilution plating on selective agars. Bacteria were evaluated qualitatively by colony morphology, Gram reaction and biochemical reactions. Molds were identified by morphological properties, and yeasts were identified based on morphological and biochemical properties. Endotoxin concentrations were determined with a chromogenic Limulus amebocyte lysate assay. American-basswood and Black-locust had the highest levels of bacteria, fungi and endotoxin. Intermediate levels were noted in Soft-maple and Black-cherry, and lowest levels were in White-poplar and Red-oak. All three wood tissues yielded microorganisms and fungi. Gram negative bacteria dominated heartwood and sapwood, with nonfermentative species found commonly in heartwood and fermentative species more commonly in sapwood. Endotoxin levels correlated significantly with gram negative bacterial concentrations. Yeasts were the predominant fungi in all wood tissues and were in highest concentrations in sapwood. Molds were most commonly noted in bark. Microflora composition represented "pioneer" colonization. The authors conclude that some apparently undecayed stored timber contains very high levels of pioneer microorganisms and their toxins, which could cause respiratory disorders when inhaled with sawdust by woodworkers.
NIOSH-Author; Woodworking-industry; Microbiology; Quantitative-analysis; Qualitative-analysis; Wood-products; Biohazards; Health-hazards; Lumber-industry;
Publication Date
Document Type
Conference/Symposia Proceedings;
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
(NIOSH) 90-108
Source Name
Proceedings of the VIIth International Pneumoconioses Conference