Longitudinal respiratory health study of the wood processing industry.

BACKGROUND: A 5-year longitudinal study examined nonmalignant respiratory effects of wood processing dust exposure. METHODS: Ten study plants, investigator selected from 447 candidate plants, included 1 sawmill-planing-plywood, 1 plywood, 1 milling, 3 cabinet and 4 furniture facilities. Personal dust samples (2363) were divided into three size fractions (extrathoracic, tracheobronchial, and respirable) which were apportioned into wood solids (WS) and residual particulate matter (RPM), and used to compute each individuals TWA exposure for the 6 exposure types. Serial spirometric tests and medical, smoking and occupational questionnaires were collected with 1,164 subjects having adequate follow-up (minimum 3 datapoints over at least 2.5 years) for analyses. Forward selection regression was used to evaluate the effect of exposure on annual change in FEV(1), FVC, FEF(25-75), and FEV(1)/FVC. RESULTS: There were no significant adverse effects of WS exposures (overall means were 0.66, 0.32, and 0.05 mg/m(3), for extrathoracic, tracheobronchial, and respirable fractions, respectively). Statistically significant effects were only to respirable RPM in the milling facility (mean exposures of 0.147 mg/m(3) associated with changes in FEV(1) = -32 ml/year, FEV(1)/FVC = -0.48%/year, and FEF(25-75) = -0.11 l/s/year) and in the sawmill-planing-plywood facility (mean exposures of 0.255 mg/m(3) associated with changes in FEV(1) = -59 ml/year and FVC = -103 ml/year). CONCLUSION: Exposure to WS was not associated with significant adverse effects. Respirable RPM was associated with an obstructive effect in the milling facility, and respirable RPM was also associated with a restrictive effect in the sawmill-planing plywood facility. Finally, this study does not exclude the possibility that other exposures common to this industry can cause respiratory effects, only that none were noted in this population for wood solids for the exposure levels and durations studied.

A survey of size-fractionated dust levels in the U.S. wood processing industry.

A survey of size-fractionated dust exposure was carried out in 10 wood processing plants across the United States as part of a 5-year longitudinal respiratory health study. The facilities included a sawmill, plywood assembly plants, secondary wood milling operations, and factories producing finished wood products such as wood furniture and cabinets. Size-fractionated dust exposures were determined using the RespiCon Personal Particle Sampler. There were 2430 valid sets of respirable, thoracic, and inhalable dust samples collected. Overall, geometric mean (geometric standard deviation) exposure levels were found to be 1.44 (2.67), 0.35 (2.65), and 0.18 (2.54) mg/m, for the inhalable, thoracic, and respirable fractions, respectively. Averaged across all samples, the respirable fraction accounted for 16.7% of the inhalable dust mass, whereas the corresponding figure for thoracic fraction as a percentage of the inhalable fraction was 28.7%. Exposures in the furniture manufacturing plants were significantly higher than those in sawmill and plywood assembly plants, wood milling plants, and cabinet manufacturing plants, whereas the sawmill and plywood assembly plants exhibited significantly lower dust levels than the other industry segments. Among work activities, cleaning with compressed air and sanding processes produced the highest size-fractionated dust exposures, whereas forklift drivers demonstrated the lowest respirable and inhalable dust fractions and shipping processes produced the lowest thoracic dust fraction. Other common work activities such as sawing, milling, and clamping exhibited intermediate exposure levels, but there were significant differences in relative ranking of these across the various industry segments. Processing of hardwood and mixed woods generally were associated with higher exposures than were softwood and plywood, although these results were confounded with industry segment also.