Any type of woodworking that involves cutting, either by hand or machine, releases sawdust (or wood dust). Because fine sawdust can float through the air, it can be easily inhaled without proper protection, leading to damaging injuries to a woodworker's skin and lungs. Sawdust is also an IARC group 1 Carcinogen.
Exposure
Sawdust is most commonly generated when working with wood, whether it be sanding, sawing, or routing. Uncommonly, sawdust exposure can come from sweeping dust off of old furniture, which may haw sawdust particles inside. Occupations at higher risk include carpenters, construction workers, shipbuilding workers, cleaning or maintenance staff (sawdust generation or reintroduction), and workers in logging, sawmills, furniture, and cabinet making.
When the dust is inhaled, it is deposited in the nose, throat, and other airways. The amount of dust deposited within the airways depends on the size, shape, and density of the dust particles and the strength (turbulence and velocity) of the air-flow. Particles with a diameter larger than 5 μm (inspirable particles) are deposited almost completely in the nose, whereas particles 0.5 to 5 μm in diameter (respirable particles) are deposited in the lower airways (IARC 1981, 1995).
Wood dust usually is measured as the concentration of airborne dust, by particle size distribution, by type of wood, and by other characteristics of wood. Total airborne dust concentration is reported as mass per unit volume (usually milligrams of dust per cubic meter of air). Wood dust generally is collected by a standard gravimetric method, whereby a sampling pump is used to collect a known volume of air through a special membrane filter contained in a plastic cassette. Some sampling studies reported that the particle size distribution varied according to the woodworking operation, with sanding producing smaller particles than sawing, but others found no consistent differences (IARC 1995). The majority of the wood-dust mass was reported to be contributed by particles larger than 10 μm in aerodynamic diameter; however, between 61% and 65% of the particles by count measured between 1 and 5 μm in diameter (IARC 1995).
Handling of compost
Exposure to wood dust also occurs through handling of compost containing wood dust. One study measured dust concentrations resulting from handling of compost material consisting of successive layers of chopped leaves, bark, and wood; visible clouds of fine particles were easily generated when the compost material was agitated. The reported background concentration of respirable dust sampled upwind of the compost pile was 0.32 mg/m3. During loading and unloading of compost, samplers in the breathing zone detected inspirable dust at 0.74 mg/m3 and respirable dust at 0.42 mg/m3. Samples collected directly from the visible clouds of particles generated by compost agitation contained inspirable dust at 149 mg/m3 and respirable dust at 83 mg/m3 (Weber et al. 1993).
Workers
The National Occupational Exposure Survey (conducted from 1981 to 1983) estimated that nearly 600,000 workers were exposed to woods (NIOSH 1990). Teschke et al. (1999) analyzed 1,632 measurements of personal time-weighted-average airborne wood-dust concentrations in 609 establishments on 634 inspection visits that were reported to the Occupational Safety and Health Administration Integrated Management Information System between 1979 and 1997. Exposures ranged from less than 0.03 to 604 mg/m3, with an arithmetic mean of 7.93mg/m and a geometric mean of 1.86mg/m. Exposure levels decreased significantly over time; the unadjusted geometric mean was 4.59 mg/m3 in 1979 and 0.14 mg/m3 in 1997. Occupations with high exposure to wood dust included sander in the transportation equipment industry (unadjusted geometric mean = 17.5 mg/m3), press operator in the wood products industry (12.3 mg/m3), lathe operator in the furniture industry (7.46 mg/m3), and sander in the wood cabinet industry (5.83 mg/m3). High exposures occurred in the chemical, petroleum, rubber, and plastics products industries, in sanding, pattern making, and mill and saw operations. The lowest exposures occurred in industrial pattern-making facilities, paper and paperboard mills, schools and institutional training facilities, and veneer and plywood mills.
