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Logo of oenvmedOccupational and Environmental MedicineVisit this articleSubmit a manuscriptReceive email alertsContact usBMJ
Occup Environ Med. 2007 December; 64(12): e29.
PMCID: PMC2095400

Wood dust mini‐symposium

151 Wood dust and COPD: is the TLV protective?

M. C. Friesen1, P. A. Demers2, H. W. Davies2, K. Teschke2. 1Monash University; 2University of British Columbia

ObjectivesQuantitative exposure estimates are needed to determine exposure–response relationships, which can then inform occupational exposure limits. We evaluated the exposure–response relationship between quantitative wood dust levels and hospitalisation for chronic obstructive pulmonary disease (COPD) in a cohort of Canadian sawmill workers.

MethodsThe study population consisted of 11 273 male sawmill workers that met the following criteria: (1) employed [gt-or-equal, slanted]1 year between 1950 and 1995, and (2) employed >1 day between 1985 and 1995. This cohort was probabilistically linked to hospital discharge records (1985–1998) and 132 COPD cases were identified. Quantitative wood dust estimates based on statistical models were available for all workers. We evaluated the shape (log‐linear vs log‐log models), goodness of fit, and precision of the exposure–response relationship using Poisson regression.

ResultsThe median, 80th percentile, and maximum cumulative wood dust exposure levels were 6.8, 27 and 89 mg/m3‐year, respectively. The reference group were sawmill workers exposed to less than 5 mg/m3‐year. Wood dust was strongly associated with COPD hospitalisations using a log‐log model and only weakly associated with a log‐linear model. The log‐log model was ln(RR) = 0.203*ln(CE−Xref+1), where RR is the relative risk, CE is the cumulative exposure, and Xref is reference group's mean exposure (2.3 mg/m3‐year). Thus, there would be an 80–110% increase in COPD hospitalisations for workers exposed from 20 to 40 years at the current ACGIH TLV of 1 mg/m3. The cumulative exposure associated with a RR of 2 is 31 mg/m3‐year. COPD was not associated with cumulative exposure to non‐specific particulate.

ConclusionThis study suggests that a lifetime of exposure to wood dust at the current TLV is associated with a doubling in the risk of hospitalisations for COPD, and thus the TLV may not be sufficiently protective of respiratory health. The actual health burden may be greater than observed here as wood dust exposure is ubiquitous in sawmills so the reference group was not unexposed. In addition, as the hospitalisation outcome reflects only serious respiratory problems, the true health burden of wood dust on respiratory function impacting workers' health is likely much higher.

Key wordswood dust; occupational exposure limits; respiratory disease

152 Increased incidence of respiratory symptoms and accelerated decline in lung function among Danish low exposed female woodworkers

G. J. Jacobsen1, V. S. Schlünssen2, I. S. Schaumburg3, T. S. Sigsgaard2. 1Region Hospital Skive, Denmark; 2Department of Occupational and Environmental Medicine, Institute of Public Health, Aarhus University; 3Neuro Center, Aarhus University Hospital

ObjectivesThe aim was to investigate associations between respiratory symptoms, changes in lung function, and wood dust exposure among female workers in a 6‐year follow‐up study.

Methods254 woodworkers and 162 controls participated in the follow‐up. FEV1, FVC, height, and weight were measured and data on respiratory symptoms, employment and smoking were collected by questionnaire at baseline and follow‐up. Wood dust exposure was assessed from passive dust measurements at baseline and follow‐up. Cumulative wood dust exposure was assessed using a study specific job exposure matrix and exposure time. In the analysis cumulative exposure was categorised in quartiles. Controls were assigned the lowest exposure category.

ResultsThe median (range) of cumulative wood exposure among woodworkers in the follow‐up cohort was 3.24 (0–6.87) mg year/m3. An adjusted logistic regression analysis on cumulative incidence proportion (CIP) of respiratory symptoms revealed OR (95% CI) 8.75 (1.09 to 70.4) for chronic bronchitis and 2.93 (1.35 to 6.34) for daily coughing for woodworkers compared to controls. An association between cumulative wood dust exposure and CIP of chronic bronchitis was found, with adjusted OR 5.1 (1.3 to 21.1) for medium exposed (3.8–4.7 mg year/m3) and 2.5 (0.3–23.8) for high exposed (>4.7 mg year/m3) versus non‐/low exposed workers. Linear regression analysis adjusted for smoking, age and weight, revealed significant negative dose response relations between cumulative wood dust exposure and change in FEV1 (ml/year), regardless whether exposure was treated as a categorical or a continuous variable.

ConclusionIn this low exposed cohort, female woodworkers showed an increased incidence of coughing and chronic bronchitis. In addition, an accelerated decline in lung function was revealed, with a dose–response relationship between cumulative exposure and decline in lung function.

Key wordswood dust; respiratory symptoms; lung function

153 Exploration of asthma risk in wood processing industries in Finland: a registry‐based population study

P. R. Heikkilä, R. Martikainen, K. Kurppa, K. Husgafvel‐Pursiainen, A. Karjalainen. Finnish Institute of Occupational Health

ObjectivesThe registry‐based population study explored the incidence of physician‐diagnosed asthma cases in individuals in the wood processing industries and aimed to estimate the dose–response relationship between wood dust exposure and asthma incidence.

MethodsAll Finnish males and females employed in 10 sectors of wood processing industries were followed for asthma incidence via record linkage in the years 1986–1998. An individual was defined as an incident case of asthma if they were reimbursed for asthma medication from the national health insurance or were registered as having occupational asthma. Age‐adjusted relative risks were estimated for those handling wood and for other workers in wood processing industries in comparison with those employed in administrative work in this sector.

ResultsThe relative risks (RR) were significantly increased in both genders in the medium and low exposure categories but not in the high exposure category. In the male woodworkers, the risk was significantly increased in seven out of 10 wood processing industrial sectors The asthma risks were highest in the manufacture of wooden containers (RR 2.5, 95% CI 1.3 to 4.6), and in sawmilling and planning of wood (RR 1.9, 95% CI 1.5 to 2.5). In the female woodworkers exposed to wood dust, the risk was significantly increased in four out of 10 wood processing industrial sectors, with the highest risk being found in sawmilling and impregnation of wood (RR 1.8, 95% CI 1.3 to 2.4). The asthma incidence did not differ significantly between the woodworkers (1.7 male, 3.2 female) and the group of other workers (1.8 male, 2.9 female). The estimated fraction of asthma cases attributable to occupational exposures, wood dust and other air impurities was 31% (95% CI 15 to 45) for both men and women in the wood occupations.

ConclusionOur results showed that both wood workers and other workers in wood processing industries had a significantly elevated risk of asthma, and that even rather low exposure to wood dust was related to increased asthma risk.

Key wordswood dust exposure; asthma incidence; registry based population study

154 Respiratory effects of exposure to pine dust in New Zealand sawmill workers

D. J. McLean1, T. Slater2, S. Cheng2, N. Pearce2, J. Douwes2. 1Massey University; 2Centre for Public Health Research, Massey University

ObjectivesThe wood products industry is a significant employer in New Zealand, earning over 10% of the country's export receipts and employing more than 11 000 workers. It employs a high proportion (27.4%) of Mâori – the indigenous people of New Zealand. The industry is based almost entirely on plantation forests, with more than 90% being the single species Pinus radiata.

MethodsWe have conducted a series of cross‐sectional studies of respiratory symptoms in sawmill workers.

ResultsWe have measured exposure to a range of airborne contaminants in pine sawmilling, including wood dust, monoterpenes and resin acids, and fungal glucans and bacterial endotoxins. We have also shown increased risk of respiratory symptoms and asthma in a random sample (n = 772) of sawmill workers. We found that asthma was significantly more common in sawmill workers than in the general population, and also more common in the high exposure groups than in the non‐exposed workers. In a smaller group (n = 226) of both asthmatic and non‐asthmatic workers, randomly selected from the previous survey, we investigated the association between dust exposure, lung function and atopy. We demonstrated that lung function parameters such as FVC, FEV1 and PEF were significantly lower in workers exposed to both high “green” dust (350 ml, 260 ml and 860 ml/s, respectively) and high “dry” dust (230 ml (ns), 190 ml and 850 ml/s, respectively). Exposure to “green” dust was also associated with atopic sensitisation (OR 2.23, 9% CI 1.02 to 6.46), but there was no association with exposure to “dry” dust. These associations were observed in both asthmatics and non‐asthmatics.

ConclusionIt appears that exposure to pine wood dust (and/or some component of the dust) in New Zealand may cause both obstructive and restrictive pulmonary effects, and increase the risk of allergy. In addition, although we found an association between “green” dust exposure and allergy, the effects on lung function could not be explained by allergy alone since effects of a comparable magnitude were also observed in workers exposed to “dry” dust. We have also found significant ethnic disparities in exposure, symptom prevalence and use of asthma medication amongst workers in this industry.

Key wordswood dust; sawmill workers; New Zealand

155 Inhalable wood dust and chemical exposures and sino‐nasal adenocarcinoma: results of a German industry‐based case‐control study

B. Pesch1, C. Pierl1, M. Gebel1, M. Meier2, V. Lepentsiotis2, J. Schulze2, T. Bruening1. 1BGFA; 2Holz‐BG

ObjectivesTo estimate the risks of wood dust and chemical co‐exposures for sino‐nasal adenocarcinoma (AC) we conducted an industry‐based case‐control study among male German wood workers.

MethodsCases with histologically confirmed AC (n = 86) and controls from accidents (n = 204) were recruited from a Holz‐BG database between 2003 and 2005. Interviews on job history and other information were conducted with the subject or a next of kin. Exposure to wood dust was assessed by a job exposure matrix including German data of the EU‐funded project WOODEX and measurements at models of historical work places. Exposure to wood preservatives, stains, varnishes and formaldehyde were expert rated. We applied logistic regression models conditional on age and calculated odds ratios (OR) with 95% confidence intervals (CI), adjusted for potential confounders.

ResultsMedian age at interview was 69 years (range 36–84 years) in cases and 69 years (range 37–85 years) in controls. Among cases, 60 (69.8%) were ever smokers and 127 (62.3%) in controls. The majority of cases (84.9%) ever worked as a cabinet maker, but only two cases were saw millers. About 60% of the cases and 50% of the controls worked in the wood working industries only. Wood dust concentrations of 3.5–<5 mg/m3 revealed an OR 12.46 (95% CI 3.71 to 41.80) and above 5 mg/m3 the risk increased to 32.98 (95% CI 7.66 to 142) in comparison to exposure levels below 3.5 mg/m3 with a significant trend (p<0.0001). Ever exposure to pigment stains resulted in a non‐significantly increased AC risk (OR 1.98, 95% CI 0.91 to 4.33). No association was found for formaldehyde (OR 0.81, 95% CI 0.42 to 1.56) or wood preservatives (OR 0.78, 95% CI 0.32 to 1.86). We investigated other exposure scenarios and statistical models that revealed similar results but demonstrated risk estimates of low precision due to the rareness of AC.

ConclusionOur results confirmed wood dust as a major risk for sino‐nasal adenocarcinoma. Average exposure to wood showed a stronger increase in risk than cumulative exposure levels. The risk of pigment stains needs further evaluation.

Key wordswood dust; sino‐nasal cancer; exposure assessment

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