Longitudinal respiratory health study of the wood processing industry

A 5-year longitudinal study examined nonmalignant respiratory effects of wood processing dust exposure.

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.

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).

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.