Wood dust particle and mass concentrations and filtration efficiency in sanding of wood materials.

The importance of fine particles has become apparent as the knowledge of their effects on health has increased. Fine particle concentrations have been published for outside air, plasma arc cutting, welding, and grinding, but little data exists for the woodworking industry. Sanding was evaluated as the producer of the woodworking industry's finest particles, and was selected as the target study. The number of dust particles in different particle size classes and the mass concentrations were measured in the following environments: workplace air during sanding in plywood production and in the inlet and return air; in the dust emission chamber; and in filter testing. The numbers of fine particles were low, less than 10(4) particles/cm(3) (10(7) particles/L). They were much lower than typical number concentrations near 10(6) particles/cm(3) measured in plasma arc cutting, grinding, and welding. Ultrafine particles in the size class less than 100 nm were found during sanding of MDF (medium density fiberboard) sheets. When the cleaned air is returned to the working areas, the dust content in extraction systems must be monitored continuously. One way to monitor the dust content in the return air is to use an after-filter and measure pressure drop across the filter to indicate leaks in the air-cleaning system. The best after-filtration materials provided a clear increase in pressure drop across the filter in the loading of the filter. The best after-filtration materials proved to be quite effective also for fine particles. The best mass removal efficiencies for fine particles around 0.3 mum were over 80% for some filter materials loaded with sanding wood dust.

Local ventilation solution for large, warm emission sources.

In a foundry casting line, contaminants are released from a large area. Casting fumes include both volatile and particulate compounds. The volatile fraction contains hydrocarbons, whereas the particulate fraction mostly comprises a mixture of vaporized metal fumes. Casting fumes lower the air quality in foundries. The design of local ventilation for the casting area is a challenging task, because of the large casting area and convection plumes from warm moulds. A local ventilation solution for the mould casting area was designed and dimensioned with the aid of computational fluid dynamic (CFD) calculations. According to the calculations, the most efficient solution was a push-pull ventilation system. The prototype of the push-pull system was built and tested in actual operation at the foundry. The push flow was generated by a free plane jet that blew across the 10 m wide casting area towards an exhaust hood on the opposite side of the casting lines. The capture efficiency of the prototype was determined by the tracer gas method. The measured capture efficiencies with push jet varied between 40 and 80%, depending on the distance between the source and the exhaust. With the aid of the push flow, the average capture efficiency was increased from 40 (without jet) to 60%.

Mechanisms of particle-induced pulmonary inflammation in a mouse model: exposure to wood dust.

Repeated airway exposure to wood dust has long been known to cause adverse respiratory effects such as asthma and chronic bronchitis and impairment of lung function. However, the mechanisms underlying the inflammatory responses of the airways after wood dust exposure are poorly known. We used a mouse model to elucidate the mechanisms of particle-induced inflammatory responses to fine wood dust particles. BALB/c mice were exposed to intranasally administered fine (more than 99% of the particles had a particle size of < or = 5 microm, with virtually identical size distribution) birch or oak dusts twice a week for 3 weeks. PBS, LPS, and titanium dioxide were used as controls. Intranasal instillation of birch or oak dusts elicited influx of inflammatory cells to the lungs in mice. Enhancement of lymphocytes and neutrophils was seen after oak dust exposure, whereas eosinophil infiltration was higher after birch dust exposure. Infiltration of inflammatory cells was associated with an increase in the mRNA levels of several cytokines, chemokines, and chemokine receptors in lung tissue. Oak dust appeared to be a more potent inducer of these inflammatory mediators than birch dust. The results from our in vivo mouse model show that repeated airway exposure to wood dust can elicit lung inflammation, which is accompanied by induction of several proinflammatory cytokines and chemokines. Oak and birch dusts exhibited quantitative and qualitative differences in the elicitation of pulmonary inflammation, suggesting that the inflammatory responses induced by the wood species may rise via different cellular mechanisms.

Occupational exposure to inhalable wood dust in the member states of the European Union.

The aim of this study was to estimate occupational exposure to inhalable wood dust by country, industry, the level of exposure and type of wood dust in 25 member states of the European Union (EU-25) for the purposes of hazard control, exposure surveillance and assessment of health risks. National labour force statistics, a country questionnaire (in 15 member states, EU-15), a company survey (in Finland, France, Germany and Spain), exposure measurements (from Denmark, Finland, France, Germany, The Netherlands and the United Kingdom) and expert judgements were used to generate preliminary estimates of exposure to different types of wood dust. The estimates were generated according to industrial class (six wood industries, four other sectors) and level of exposure (five classes). These estimates were reviewed and finalized by national experts from 15 member states. Crude estimates were generated also for 10 new member states (EU-10). The basic data and final estimates were included in the WOODEX database. In 2000-2003, about 3.6 million workers (2.0% of the employed EU-25 population) were occupationally exposed to inhalable wood dust. Of those, construction employed 1.2 million exposed workers (33%), mostly construction carpenters. The numbers of exposed workers were 700,000 (20%) in the furniture industry, 300,000 (9%) in the manufacture of builders' carpentry, 200,000 (5%) in sawmilling, 150,000 (4%) in forestry and <100,000 in other wood industries. In addition, there were 700,000 exposed workers (20%) in miscellaneous industries employing carpenters, joiners and other woodworkers. The numbers of exposed workers varied by country ranging from <3,000 in Luxembourg and Malta to 700,000 in Germany. The highest exposure levels were estimated to occur in the construction sector and furniture industry. Due to limited exposure data there was considerable uncertainty in the estimates concerning construction woodworkers. About 560,000 workers (16% of the exposed) may be exposed to a level exceeding 5 mg m(-3). Mixed exposure to more than one species of wood and dust from wooden boards was very common, but reliable data on exposure to different species of wood could not be retrieved. This kind of assessment procedure integrating measurement data, company data, country-specific data and expert judgement could also serve as one model for the assessment of other occupational exposures.

Monoterpene and wood dust exposures: work-related symptoms among Finnish sawmill workers.

BACKGROUND: Monoterpenes and wood dust are released into the work environment during sawing of fresh wood. Symptoms related to exposure to monoterpenes and wood dust include irritation of the eyes, mucous membrane, and skin. METHODS: We studied 22 sawhouse workers who process pine and spruce in 1997-99. Exposure to monoterpenes was assessed by determining monoterpenes in air and verbenols in urine by gas chromatography using flame ionization detection. Wood dust was determined gravimetrically. A questionnaire was used to evaluate work-related subjective symptoms. RESULTS: Exposures to monoterpenes (geometric mean, GM) among sawhouse workers were 61-138 mg/m(3) and 2.0-13 mg/m(3) during processing of pine and spruce, respectively. Urinary verbenol correlated well with worker exposure to the alpha-pinene fraction of monoterpenes. The inhalable dust concentration in the breathing zone was 0.5- 2.2 mg/m(3) during pine processing and 0.4-1.9 mg/m(3) during spruce processing. The prevalence of symptoms, in the eyes or respiratory tract, was high during both seasons and in connection with either tree species. CONCLUSIONS: The highest monoterpene concentration (GM), in the breathing zone, measured during processing of pine, was less than one-fourth of the Finnish occupational exposure limit (OEL, 570 mg/m(3)). Verbenol concentrations in postshift urine samples reflected accurately the exposure to monoterpenes. The concentrations of inhalable dust (GM) were less than one-half the Finnish OEL (5 mg/m(3)). No significant differences in dust exposure were observed among tree species processed. Work-related symptoms appeared to correlate with monoterpene exposure during processing of pine and with wood dust exposure during processing of spruce.