NORA Manufacturing Sector Strategic Goals
927Z6RS - Validation of appropriate wood dust sampling and analysis proceduresStart Date: 10/1/2006
End Date: 9/30/2010
Principal Investigator (PI)Name: Martin Harper
Funded By: NIOSH
Primary Goal Addressed5.0
Secondary Goals Addressed6.0 , 8.0
Attributed to Manufacturing75%
This study will form part of an international initiative to develop improved sampling and analytical procedures for wood dust in support of Manufacturing Sector Strategic Goal #5 and Agriculture Sector Strategic Goal #7. It has been estimated that at least two million people are occupationally exposed worldwide. Wood dust exposure has been implicated in upper airways diseases, including sino-nasal adenocarcinoma. Current procedures for assessing exposure to dust are not optimal. Different commercially available sampling technologies will be evaluated, along with a novel method of discriminating wood dust from other environmental dust. Research to practice will involve the development of recommendations for nationally and internationally harmonized exposure assessment procedures for wood dusts, which will be presented to relevant organizations, published in journals, and translated into standard methods.
The current NIOSH and OSHA exposure assessment sampling methods for wood dust are to collect particles on a filter from a metered amount of air. The filter is housed in a plastic cassette, and the filter is weighed to determine the amount collected. OSHA utilizes an internal filter capsule to ensure all dust entering the cassette is accounted in the analysis. The NIOSH procedure does not specify this capsule so that potentially large amounts of material may be lost to the internal walls of the cassette. Thus the result will depend on the procedure followed. There is, in any case, a strong objection to this sampler in that its entry characteristics do not match the ISO inhalable convention. In many studies it has been found to sample much less, particularly in the 40 – 100 µm range in which most of the mass in typical wood dusts is concentrated. Samplers that match the ISO inhalable convention have been developed. The Comité Européen de Normalisation (CEN) is currently considering a technical document with recommendations for their selection and use. However, wood dust is not a typical aerosol. The size distribution covers much larger sizes, and often includes particles greater than 100 µm, whose inhalability is in doubt, but which can remain airborne as a result of unusual aerodynamic properties conferred by extreme physical dimensions (i.e. "frizbee's"). These particles have a disproportionate effect on the total mass of the air sample as a result of the cube relationship between volume (mass) and diameter. The result is that many so-called "inhalable" samplers grossly over-sample wood dusts leading to non-compliance with limit values.
Workers may be exposed to wood dust in primary processing such as in logging and debarking. However, many more workers are exposed in lumber and pulp mills and in secondary wood industries such as furniture and cabinet manufacturing, wood pattern and model shops, etc., in the Manufacturing sector. NAICS Code 113310 (Logging) covers workers in Forestry and NAICS Codes 321 (Wood Products Manufacturing) and 322 (Paper Manufacturing) cover the workers in Manufacturing. In 1997, the US Bureau of the Census recorded 18,825 workers employed in the wood-products industries in just the State of Alabama, and more than one-half million nationwide. In 1994 the International Agency for Research on Cancer (IARC) estimated that at least two million people are occupationally exposed to wood dust worldwide, many of them in the Manufacturing Sector. Respiratory Disease was one of the topics considered significant for this Sector at a recent NORA Symposium. It has been suggested that wood dust exposure leads to an increased prevalence of certain workplace respiratory symptoms, such as bronchitis, loss of pulmonary function, and nasal mucociliary stasis, nasal obstruction, and cuboidal metaplasia, which may be a precursor lesion for nasal cancer. The most biologically relevant portion of wood aerosol is that which can penetrate the head and thoracic airways regions with a high likelihood of deposition. The International Standards Organization (ISO) recognizes a penetration curve termed the "inhalable" convention. The American Conference of Governmental Industrial Hygienists published an inhalable limit value for wood dust (1 mg/m3) in 2005. In France, Decree No. 2003-1254 also set an inhalable limit value for wood dust in workplaces (1 mg/m3). Research is needed to determine which of the many available coarse-dust samplers is most appropriate for sampling the inhalable fraction of wood dust. In addition, these limit values are also very low, and it may be necessary also to discriminate wood dust from other ambient dust in the sample to avoid overestimation. Wood dust has been a major issue at the Forest Products Industrial Hygiene forum at the American Industrial Hygiene Conference & Exposition for the past several years.