Critical analysis of studies concerning reports of respiratory sensitization to certain wood dusts

Studies have been published reporting that exposures to certain wood dusts are sensitizing, resulting in respiratory symptoms in susceptible individuals. Many of the publications in this field are case reports that collectively have a number of important shortcomings. Illuminating these should further our understanding of whether respiratory sensitization results from occupational exposure to particular wood dusts. The aim of this study was to critically review and understand the evidence to date regarding reported respiratory sensitization in connection with wood dusts from oak, beech, pine, ash, and western red cedar. Publications dealing with these commercially important woods in North America have been selected from the Pubmed/Medline database (1966 to the present) using the key word, wood dust. These articles, along with supporting references on procedures and techniques, are reviewed according to the strengths and weaknesses of evidence and conclusions presented. Evidence from skin testing, specific immunoglobulin E measurements, and basophil histamine release tests suggests that reported symptoms are not likely to be immunologically derived. Because of methodological problems, challenge tests with specific wood dusts do not support the conclusion that reactions to certain wood dusts are specific. Experiments with nonspecific bronchoconstrictive agents indicate that a number of study subjects possess hyperresponsive airways. Thus, select individuals can demonstrate various respiratory symptoms in the woodworking industry, but any specificity or direct cause is currently unproved. Current studies do not support that exposure to wood dusts from a number of common North American wood species causes immunologic sensitization in woodworkers. Rather, symptoms reported in some studies of exposed workers seem to follow the paradigm for nonspecific respiratory responses in individuals with hyperresponsive airways.