Wood Dust Exposure - Assessment and control
Exposure to wood dusts has the potential to cause serious respiratory diseases; softwood dust is classified as a respiratory sensitiser and can cause occupational asthma, whilst hardwood dust is classified as a carcinogen.
Various industries and businesses work with wood including construction sites, manufacturing facilities and CNC machine shops, and their employees could be exposed to wood dust.
In the UK, in accordance with the COSHH regulations, an employer has a duty of care to ensure that employees are not exposed to ‘unacceptable’ levels of dust (including wood dust) and that adequate standards of control are implemented. The Health and Safety Executive (HSE) also expect exposure to be reduced to “As Low As Reasonably Practicable” (the ALARP principle) in relation to exposure from respiratory sensitisers and carcinogens.
Monitoring of wood dust exposure
Exposure monitoring is required to ensure that concentrations of wood dust are within the workplace exposure limits (WELs) for softwood and hardwood dust set out in COSHH EH40/2005 (as amended) and ensure exposure is being adequately controlled. The WEL for softwood dust is 5 mg/m3 (8-hour time weighted average (TWA)), whilst for hardwood dust it is 3 mg/m3 (8-hour TWA); however, if a mixture of softwood and hardwood is used at a site, then the hardwood dust WEL should apply.
Sampling for exposure to wood dusts should follow the methodology set by the HSE in MDHS14/4. A competent person should be appointed to carry out the monitoring and a site visit should be scheduled for a day where ‘typical’, or the ‘worst case scenario’ site activities/production levels can be monitored. Personal sampling equipment is used and worn by a representative number of site operatives during their normal working activities.
During the sampling, the competent person carrying out the survey should make observations on site activities, current control measures and more general observations of exposure concerns which should be included in the final report with the results.
Control measures for wood dust
If an exceedance of either the softwood dust or hardwood dust WEL is recorded, then it is necessary for the person carrying out the assessment to make recommendations on how the business could control exposure to wood dusts further. Recommendations may also be made if it is considered that better working practises could be implemented based on observations from the monitoring visit, even if exposure concentrations are within the relevant WELs.
These recommendations should follow the hierarchy of control:
Elimination- Removing wood from the site activities altogether.
Substitution- Wood is substituted for different ‘less hazardous’ material.
Engineering controls- Physical measures to reduce the amount of wood dust the employees are exposed to.
Administrative controls- Changes in working practises to minimise exposure.
Personal Protective Equipment (PPE)- worn by an individual to reduce exposure and considered the last line of defence.
Elimination and Substitution should be the first choice in controlling exposure and are considered the most effective because if wood is not being used it does not pose a risk, although consideration should be given to the hazards that come with the substituted material. These two options are not always possible or feasible for businesses, therefore other methods of the hierarchy of control may need to be considered.
Engineering controls for wood dust exposure could include installing a local exhaust ventilation (LEV) system on saws used in a workshop, or other portable on-tool extraction (such as an m-class vacuum) on construction sites. Provided that LEV and other on-tool extraction systems are maintained and serviced (LEVs should be serviced at least once every 14 months as per HSG258) these should prevent wood dust becoming airborne in the working environment and an exposure risk.
Other engineering controls could include isolating/containing significant dust producing activities to minimise dispersion of wood dust to other areas of the workplace. For example, placing containment boxes around saws.
Administrative controls may include implementing staff rotation so that the same employees are not always carrying out the ‘dustiest tasks’. This could also include implementing better working practises such as using industrial vacuums to clear dust deposits opposed to sweeping which can resuspend wood dust into the air.
Employers should also try to educate staff on the risks associated with wood dust and provide relevant training on how to use control measures appropriately. For example, a ‘Toolbox talk’ could be scheduled on the awareness of wood dust hazards.
PPE could include issuing suitable Respiratory Protective Equipment (RPE) to staff and ensuring that these are face fit tested (if applicable), for example disposable FFP3 half masks would be suitable for wood dust and could be made mandatory for short term activities which generate high levels of dust. However, RPE should be considered as the last line of defence because it is only as effective as the way it is used and maintained.
Closing comments
Oracle Environmental Experts provide workplace exposure assessments for a variety of aerosols including wood dusts for businesses in different industries. We aim to work closely and provide assistance to our clients in controlling the exposure of their employees to these aerosols, including taking into consideration the feasibility of applying further control measures to their specific operation.
Please reach out to our team on 01684 252858 to discuss our services and how we can assist you.
