Wood dust, generated by the processing of wood, is composed of cellulose, polyoses, and lignin compounds. A variety of biologically active, low molecular weight compounds may also be present, depending on the species. These extractives include alcohols, terpenes, sterols, glycerols, tannins, flavonoids, quinones, lignans, alkaloids, and proteins.
Tree species are broadly classified into two types: hardwood (angiosperms or deciduous trees such as alder birch, cottonwood, aspen and maple), and softwood (gymnosperms or conifers such as Douglas fir, spruce, pine, hemlock and cedar). It is estimated that there are 12,000 different tree species worldwide.
Wood dust has been classified by IARC as Group 1, carcinogenic to humans, with a clear relationship between cancers of the nasal cavities, paranasal sinuses, and nasopharyngeal cancer and high levels of wood dust exposure, particularly from hardwood species.[1,4] A recent IARC review of Group 1 carcinogens reaffirmed this classification. Associations with laryngeal cancer, Hodgkin’s disease, and other types of cancers have been reported but have not been consistent.[1,2,4]
Other adverse health effects of wood dust exposure include irritation of the eyes, nose and throat from short term exposure to dust. Decreased lung function, increased respiratory symptoms, and allergic reactions are also associated with wood dust exposure. Asthma, typically associated with exposure to western red cedar, eastern white cedar, and many tropical tree species, has also been linked to other common species such as pine and oak. Skin contact with a variety of species, particularly tropical hardwoods, can cause allergic and/or irritant dermatitis.
stel = short term exposure limit (15 min. maximum)
td = total dust
WRC = Western Red Cedar
In the process of converting logs into finished wood products, wood dust and other by-products including wood chips, sawdust and shavings are produced.
While some by-products have end-uses in particle board, as fuel, or for composting, there is no specific use for fine particulate wood dust.
Production in Canada
Canada produces approximately 200,000,000 m3 of round wood (wood not used for fuel) annually. Lumber is the most significant wood product manufactured in Canada. Less than one-third of the lumber is used domestically, with the majority of exports going to the US.
Softwoods are used most frequently in Canadian industry, and account for nearly two-thirds of commercially used woods world wide.[1,3] The wood products industry consumes approximately half of the round wood cut in Canada, and the remainder is used by the pulp and paper industry.
Wood species varies by industry, region, and type of product: Quebec and Ontario produce the majority of hardwood lumber and plywood in Canada, and British Columbia produces primarily softwoods.
Industries producing wood products include sawmills, planing mills and shingle mills; veneer, plywood and oriented strand board; sash, door and other millwork industries; wooden box and pallet industry; coffin and casket construction; and miscellaneous wood products such as toys, carvings, baskets, and crafts.[5,7] Wood is also used in the pulp and paper industry and for firewood.
Inhalation is the most important route of occupational exposure, although dermal exposures are important for skin-related health outcomes (i.e. dermatitis).[2,5]
Wood dust exposures have decreased significantly over the past few decades. An analysis of US occupational wood dust samples reported that mean levels declined from 4.59 mg/m3 in 1979 to 0.14 mg/m3 in 1999. Furniture and cabinetry shops are generally thought to have the highest exposures, particularly during sanding and finishing work, when the finest particles are generated.[1,9] Higher exposures have been measured in the areas of plywood and particle-board mills where wood is sawn and sanded, and near chippers, saws and planers in sawmills and planer mills.
A study in a British Columbia lumber mill also found high exposures during particular tasks, including sawdust clean-up, planing kiln-dried lumber, and driving mobile equipment in the yard.
Potential for exposure to wood dust occurs in construction, window and door manufacture, joinery shops, wooden boat manufacture, installation and refinishing of wood floors, pattern and model making, pulp and paper manufacture, and carpentry and logging. A recent EU study estimated that 3.6 million workers were occupationally exposed to wood dust between 2000 and 2003, with over half working in construction (carpenters) and in the furniture industry.
The primary source of exposure to wood dust to the general public is through home hobby projects such as wood working, arts and crafts or construction activities. Hand held electric sanders have been found to generate significant amounts of wood dust.
Teschke K, Demers PA, Davies HW, Kennedy SM, Marion SA and Leung V (1999). ‘Determinants of Exposure to Inhalable Particulate, Wood Dust, Resin Acids, and Monoterpenes in a Lumber Mill Environment.’ Annals of Occupational Hygiene, 43(4):247-255
Kaupinnen T, Teschke K, Astrakianakis G, Boffetta P, Colin D, Keefe A, Korhonen K, Liukkonen T, Nicol AM, Pannett B, and Westberg H (2002). ‘Assessment of exposure in an international study on cancer risks among pulp, paper, and paper product workers.’ AIHAJ 63:(3):254-261
Demers PA, K Teschke and SM Kennedy (1997). ‘What to do about softwood? A review of respiratory effects and recommendations regarding exposure limits.’ AJIM, 31(4):385-98.