Wood dust at the workplace challenges occupational health
The inhalation of wood dust is an occupational safety risk. Approximately 40,000 employees are exposed to wood dust in their job causing potential health hazards. This can lead to prolonged respiratory infections which, in turn, can result in longer sickness absences. Exposure to hardwood dust also increases the risk of rare nasal and sinus cancers.
Wood is a widely used material all over the world. The main components of wood are cellulose, hemicellulose and lignin. In addition, depending on the type of wood, it can also contain hundreds of different chemical compounds such as terpene compounds, fatty acids, resin acids, phenolic compounds, alcohols, tannins and flavonoids.
Botanically, tree species are divided into deciduous and coniferous. The deciduous trees are also called hardwoods. Similarly, conifers can be referred to as softwoods, although these designations are not directly related to the "hardness", i.e. density, of the wood. When working with wood, dust is released into the air, and the particle size of the dust varies widely due to, for example, the machining method, the type of wood and the humidity of wood. The dust particles which can enter the human respiratory system are called inhalable dust.
In Finland, approximately 40,000 employees are exposed to wood dust at their work, e.g., at sawmilling and planing of wood, in the wooden board industry, and the manufacture of wood products and furniture. In addition, exposure to wood dust can occur in many other industrial sectors, such as the manufacture of paper pulp, the construction industry, the manufacture of vehicles, pattern making in the manufacture of metal and concrete products, as well as in educational institutions.
Workers’ exposure to wood dust
In Europe, exposure to hardwood dust is regulated by the EU Directive (2017/2398) on the protection of workers from the risks related to exposure to carcinogens or mutagens at work. The binding limit value for the inhalable hardwood dust in air was earlier 5 mg/m3, but the directive set it at 2 mg/m3. In Finland, the national indicative occupational exposure limit value for the dusts of all wood species has been the same 2 mg/m3 since the year 2007, but the new binding limit value for hardwood dust took effect in 2020.
The research project “Wood dust and new binding limit value – can the provision of information have an impact on exposure and working conditions?” was conducted in Finland in 2020-2022. The main aim of the study was to inform workplaces in the woodworking sector about the changes in the regulations, and to assess the influence of this information through inquiry and workplace surveys conducted before and after the information campaign.
Wood dust concentrations were measured during surveys at the workplaces of wooden products and furniture manufacturing. The geometric mean (GM) concentration of inhalable wood dust in the beathing zone of the workers was 0.8 mg/m3 (number of measurement 167, range 0.03–16 mg/m3), but 11% of the dust concentrations measured exceeded the limit value 2 mg/m3.
According to measurement results from the services made in the manufacturing of wooden products and furniture in 2017-2021 by the Finnish Institute of Occupational Health, the mean (GM) wood dust concentration in the breathing zone of the workers was 0.6 mg/m3 (n=131, range 0.06—12 mg/m3), and 11% of the concentrations exceeded the limit value.
Heath effects caused by wood dust
The largest particles of inhalable dust remain mainly in the upper respiratory tract, where they can cause irritation symptoms on the mucous membranes of the nose and larynx. According to studies, respiratory irritation symptoms are common in wood dust concentrations above 1 mg/m3.
Wood dust is one of the causes of occupational rhinitis. The smaller particles of wood dust enter deeper into the respiratory tract, and they can cause for example coughs and non-asthmatic airway contraction, which is reflected in a decrease in spirometry values. Exposure to wood dust is also associated with an increased risk of chronic bronchitis. Wood dust can also irritate the eyes and skin.
Depending on the type of wood, wood dust can contain many chemical compounds that may cause skin sensitization. Allergy symptoms can also occur in the eyes. Wood dust can cause allergy to the upper respiratory tract, causing allergic rhinitis and lower respiratory tract, causing asthma.
According to the assessment by the International Agency for Research on Cancer (IARC), wood dust is carcinogenic to humans. The most recent evaluation in 2012, states that wood dust causes cancer of the nose and nasal sinuses (sinonasal), as well as nasopharyngeal cancer. This evaluation covers dust generated from all wood species, hardwood or softwood categories are not separated. There is stronger evidence of a link between sinonasal cancer and exposure to hardwood dust, and in the EU, only hardwood dust is classified as a carcinogen.
Safety management is an important part of business operations. It aims to ensure the safety of employees, reduce risks, and prevent accidents and incidents. In SMEs it can often be overlooked due to resource constrains or lack of knowledge. The following issues are included in good safety management practices: risk assessment practices, safety plan, employees training, knowledge of safety legislation, safety activities monitoring and creating a safety culture.
According to the results of the inquiry of the project “Wood dust and new binding limit values – can the provision of information have an impact on exposure and working conditions?”, there is room for improvement in the management's information practices on issues related to occupational safety. The personnel representatives were most critical of this. Also, not enough information has been shared about possible health hazards related to wood dust, especially in the opinion of employee representatives.
However, the information related to the project had had some effect, and the answers to the second survey were somewhat more positive. In micro-companies, this issue was seen more positively and, according to the answers, more information about health hazards related to wood dust has been shared to them than in companies of other size categories.
The other results of the inquiry showed that co-workers seem to play a significant role in training in safe working practices in small and medium-sized companies. In micro-enterprises and small enterprises, the role of the foreman is also emphasized somewhat more in training than in medium-sized enterprises. Overall, the answers to the survey before and after the information campaign were very similar.
The level of occupational safety has also been measured in other studies with a similar survey and the results have been very similar for some questions. Such questions include for example whether the management has communicated clear goals for the development of occupational safety, does the management regularly inform the employees about matters related to occupational safety, and does my workplace organize sufficient safety training.
Most of the respondents had received the additional information they needed about wood dust-related matters during the information campaign of the research project. The e-mail messages with information links used as one information transmission channel in the study proved to be a significant source of information. The study could not clearly demonstrate the impact of information on working conditions, knowledge about wood dust or exposure to wood dust. The research yielded valuable, previously missing information, especially on occupational health and safety issues for micro-enterprises and small and medium-sized enterprises and exposure to wood dust. In addition, a model was developed for assessing wood dust exposure. The modeled exposure levels were of the same order of magnitude compared to the measurements, but the model needs to be refined with additional measurements and its suitability for other exposures should be tested in the future.
Tuula Liukkonen, Chief Specialist at Finnish Institute of Occupational Health
Tuula Räsänen, Senior Specialist at Finnish Institute of Occupational Health
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