Wood Dust Exposure Levels and Respiratory Symptoms 6 Years Apart: An Observational Intervention Study Within the Danish Furniture Industry

Exposure Characterization of Wood Dust Particulate, Endotoxins, and (1-3)-β-d-Glucans, and Their Determinants in Mozambiquan Wood Processing Workers

OBJECTIVES

Dust generated from wood processing comprises a heterogeneous mixture of inorganic and organic particles, including wood fragments, microorganisms, endotoxins, (1-3)-β-d-glucans, and allergens. This study characterized exposure to wood dust and its determinants in the Mozambiquan wood processing industry.

METHODS

A total of 124 personal inhalable samples, collected from a stratified random sample of 30 workers, were analysed for dust particulate, endotoxins, and (1-3)-β-d-glucans. Mixed-effects models were developed to investigate significant exposure determinants.

RESULTS

The geometric mean (GM) inhalable dust particulate concentrations were 3.29 mg m-3, 98 endotoxin units (EU) m-3, and 123 ng m-3 for (1-3)-β-d-glucans. Significant predictors for higher particulate levels included machinery (GMR = 1.93), sawing (GMR = 2.80), carpentry (GMR = 2.77), or painting (GMR = 3.03) tasks. Lebombo-ironwood species was associated with higher dust particulate levels (GMR = 1.97). Determinants of endotoxin concentrations included working with dry wood and damp cleaning methods, which were associated with lower levels. Working in closed buildings (GMR = 3.10) and dry sweeping methods were associated with higher (1-3)-β-d-glucan concentrations (GMR = 1.99).

CONCLUSIONS

Work tasks in certain exposure groups (machinery, sawing, carpentry, painting), processing certain wood species (Lebombo-ironwood) and working in closed buildings were associated with higher exposures, whilst using dry wood and damp cleaning practices reduced exposure levels.

Wood dust and asthma

PURPOSE OF THE REVIEW

Review recent developments on asthma associated with wood dust, given the increasing scale of wood handling and processing activities globally.

RECENT FINDINGS

Work in wood industries is associated with a significantly increased risk of respiratory symptoms, rhinitis and asthma. This can be attributed to traditional processing techniques and newer technologies producing complex bioaerosol exposures, which may include chemicals. Meta-analysis studies indicate strong evidence for wood dusts as occupational sensitizers for asthma, but the underlying mechanisms remain poorly understood. The global prevalence of asthma in wood workers ranges between 6-18% and for rhinitis 16-33%. Exposure estimates show wide variation. Risk factors include atopy and exposure to certain wood species, elevated current and cumulative particulate exposures.

SUMMARY

Future studies should focus on better characterization of wood dust allergens and other bioaerosol components, specific immunoglobulin E responses to different wood species, pathophysiological mechanisms underlying asthma, and modelling dose-response relationships using refined exposure metrics for dust particulate and other bioaerosol components. There is a need for improved health-based international exposure standards and effective workplace control measures to reduce exposures to wood dust particulate (hard and soft woods), endotoxin and β-glucan, to reduce the risks of asthma in wood workers.

Effect of Low-Thermal Treatment on the Particle Size Distribution in Wood Dust after Milling

The thermal treatment of wood can improve the appearance of the wood product's surface, its dimensional stability, and resistance to fungal attacks. However, the heat treatment changes the technological properties of wood, making it a new engineering material. This work investigates the effect of the low-thermal treatment of birch wood (Betula pendula Roth.), European beech wood (Fagus sylvatica L.), and alder wood (Alnus glutinosa L.) on the fine dust particles creation during woodworking. The samples of thermally treated wood with temperatures commonly used for the change of wood colour (105, 125, and 135 °C) were compared with reference samples made of natural wood. All 12 variants of the tested woods were milled using the 5-axis CNC machining center (20 mm diamond cutter, rotational speed 18,000 rev·min^-1, the depth of cut 3 mm, feed rates of 2, 4 and 6 m∙min^-1). A sieving analysis method allowed measuring the dust particle size distributions in all dust samples. The experiment's result analysis points out that wood type, thermal treatment, and feed rate meaningfully affect the size distribution of dust particles. Compared to birch wood and beech wood, the milling of alder wood samples created a much higher content of the finest dust particles, with particle sizes smaller than 0.032 mm. Increased temperatures in thermal treatment increase the share of fine dust particles with sizes smaller than 0.125 mm, compared to wood in its natural state. Milling with a lower feed rate (2 m·min^-1) creates finer dust than processing with higher feed rates (4 and 6 m·min^-1). Generally, the milling of alder in a natural or thermally treated state is a source of fine dust particles, particularly at low feed speed-rate milling, compared to birch and beech wood. In general, these results indicate that the low temperature thermal treatment parameters attribute new technological properties to all thermally modified types of wood tested.

Occupational Dust Exposure and Respiratory Protection of Migrant Interior Construction Workers in Two Chinese Cities

Migrant interior construction workers are increasing in China. Construction workers are at an increased risk of work-related illness (WRI) due to prolonged exposure to and inhalation of dust. Dust concentrations in the air can be reduced significantly with effective respiratory protection measures. We assessed the dust exposure and factors associated with respiratory protection of migrant interior construction workers. The total dust concentration in the workplace ranged from 0.07 to 335.27 mg/m³, with a total dust exceedance rate of 50.00%. The respiratory dust loading ranged from 0.03 to 220.27 mg/m³, with a respiratory dust exceedance rate of 71.42 %. The highest total dust concentration occurred when masons were polishing cement walls. We performed a questionnaire survey of 296 persons in two cities in China, in which 87.84% had no respiratory protection or only one protection measure. Gender, workplace, respiratory disease, and protective attitude all had an effect on the level of respiratory protection. The dust exposure in most jobs exceeds hygiene standards. The respiratory protection of migrant interior construction workers in China is inadequate.