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Updating the Evidence Base and supporting SMEs in their Wood Dust Exposure Risks

In early 2022 the Health and Safety Executive (HSE) completed a project to update the evidence base on wood dust exposure risks in British manufacturing industries. In so doing, HSE gained a better understanding of how it could support small and medium-sized woodworking enterprises in controlling exposure to wood dust.

Image of a man using a hand-held power sander on a wooden board, creating airborne dust

Airborne wood dust created during hand-held powered sanding (© Crown Copyright, Health and Safety Executive)

The Challenge

There is a legal duty on employers to ensure that workplace exposures do not exceed a given workplace exposure limit (WEL), to follow good control practices and, for carcinogens and asthmagens, to reduce exposure to as low a level as is reasonably practicable (ALARP). Exposure to any wood dust can cause asthma and dermatitis, whilst exposure to hardwood dust can also cause sino-nasal cancer.  At the time of this research, the WEL in Great Britain for both softwood and hardwood dust was 5 mg/m³, based on an 8-hour time weighted average (TWA). The limit for hardwood and mixed hard and softwood dusts has since been reduced to 3 mg/m³ but the WEL for softwood dust remains at 5 mg/m³. The Control of Substances Hazardous to Health (COSHH) regulations remain unchanged.

The Solution

Occupational hygiene assessment visits were carried out at twenty-two woodworking manufacturing sites. The sites were selected on the basis that they were believed to be following reasonably good occupational hygiene control practice, enabling good practices to be benchmarked. The sites visited covered furniture production, joinery, saw milling and boat building. The sites were also invited to participate in telephone interviews to gain a better understanding of how HSE could support small and medium-sized woodworking manufacturing enterprises in managing the control of exposure to wood dust.

The Outcome

Overall 252 8-hour TWA wood dust exposure measurements were obtained, of which 6% were greater than 5 mg/m³. Ten of the twenty-two sites had at least one exposure greater than 5 mg/m³. Out of the 216 exposures for sites which produced hardwood dust, 18% exceeded 3 mg/m³, the new WEL for hardwood (and mixed wood) dusts.
Boxplot of results for the four site types, ordered left to right in descending order of median exposures: furniture, joineries, boat building, saw mills. All the 90th percentiles are below the WEL of 5 mg per cubic metre except for furniture manufacturing where the figure is about 6. The highest exposures were greater than the WEL in all four sectors.

Figure 1 Wood dust exposure measurements by site type (8-hr TWA)

The data are presented in a boxplot (Figure 1), where the circle represents the highest exposure in that dataset, whiskers represent the 10th and 90th percentiles, and the box represents the median and 25th and 75th percentiles of the data. The dashed line represents the WEL for hardwood and softwood dusts current at the time of the survey. The sites were selected as good health and safety performers, but exposures greater than the WEL were found in all four sectors.

A number of task-based exposure measurements were also made for cleaning and maintenance activities. Exposures for 3 out of 10 workers who were dry sweeping, and 5 out of 11 workers who were changing waste sacks on dust extraction air cleaners, exceeded a nominal 15 mg/m³ 15-minute short-term exposure limit (STEL). There is no legal STEL for wood dust exposure, but a figure of three times the long-term limit is recommended as a guideline for controlling short-term peaks in exposure (EH40/2005 Workplace exposure limits). For respiratory sensitisers such as wood dust, activities giving rise to short duration peak concentrations are of particular concern. Performing these short duration, high exposure tasks made a disproportionately large contribution to the workers' 8-hour TWA exposures, significantly adding to their health risk.

Dry sweeping is bad practice because it generates high levels of airborne dust and should be avoided.

Local exhaust ventilation (LEV) provision for fixed woodworking machines was generally adequate to control wood dust exposures to below 5 mg/m³, but was found to be poor for hand-held power tools (e.g. orbital sanders and routers) and manual sanding. Most fixed LEV systems underwent a 14-monthly thorough examination and test (TExT), but most portable vacuum systems did not.

The management, selection and use of respiratory protective equipment (RPE) was poor; the main issues were  selection of RPE with too low a standard of protection, lack of face fit testing for tight-fitting RPE, and the incorrect use of RPE (e.g. use of tight-fitting RPE with facial hair). Seventy-eight workers wore RPE at some point, but only twenty-five were face fit tested and wore it correctly.

Eight of the twenty-two sites had commissioned their own dust monitoring survey and, although there was a reasonable likelihood of health effects occurring in these sectors, only thirteen of the sites had health surveillance in place.

Employers obtained information on how to control wood dust from various sources. The most commonly mentioned source was the HSE website. They recognised the health risks associated with exposure to wood dust as well as the benefits of controlling wood dust, including protecting workers' health, less time spent cleaning the workplace and improved productivity. They also acknowledged a positive impact on product quality. Approaches needed to raise awareness and promote good practices among the workforce included challenging poor practices and leading by example, as well as providing information on the health effects of wood dust exposure and the importance of controls. Challenges included worker attitudes toward controls, poor habitual working practices, and limited availability of resources for smaller companies.

In summary

  • Many sites did not adequately control worker exposure to wood dust. Employers are recommended to review their exposure controls and implement any necessary improvements to comply with the new WEL and meet the requirements set out in the COSHH Regulations.
  • Sanding was the activity that led to the highest long-term exposures, whilst cleaning and maintenance tasks gave rise to high short-term peak exposures which resulted in a disproportionate effect on overall wood dust exposure. It is recommended that these activities receive particular attention when managing the risks from airborne wood dust.
  • LEV performance was taken for granted on many sites and daily/weekly maintenance checks were not carried out. Regular and effective use of LEV with hand-held power tools was not observed. Employers should ensure suitable LEV is both provided and used effectively for fixed woodworking machines and for hand-held power tools. LEV should be regularly checked and maintained for effective performance and subjected to a TExT at least every 14 months.
  • There was often a lack of knowledge about the management, selection and use of RPE, and little training or supervision of workers wearing RPE. Employers should ensure that the RPE chosen offers adequate protection for the task, and is suitable for the worker (e.g. face fitting is properly carried out for tight-fitting RPE). They should also ensure that the RPE is used and maintained correctly.
  • Some sites lacked health surveillance for wood dust exposure. On woodworking sites, where there is a reasonable likelihood that workers could develop occupational asthma and/or dermatitis, a health surveillance programme should be in place. This programme should be set up by the employer in consultation with a competent Occupational Health professional.
  • Workers' engagement in healthy and safe working practices is crucial. Employers might benefit from using risk communication approaches that focus on increasing workers' awareness of their susceptibility to ill health and encourage the use of controls. Communication using credible sources, such as peers, may enhance effective uptake of the message. Benefits relating to the control of wood dust, such as improved productivity and product quality could serve as a means of promoting good practice across the industry.

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