Health and Safety Executive research on wood dust exposure controls in British manufacturing

Abstract

To generate new intelligence on occupational exposure to wood dust in woodworking manufacturing activities in Britain, the Health and Safety Executive (HSE) performed 22 occupational hygiene site visits to assess exposure and exposure controls between 2014 and 2017. The work aimed to characterise good practice and therefore sites with a poor health and safety record, as identified from HSE inspection records, were not invited to participate. Sites selected covered furniture production, joinery, saw milling, and boat building and repair. Twenty-three follow-up telephone interviews were also carried out across 15 of the companies with supervisors and managers to explore how they tried to promote good practice among the workforce, and if there are any potential challenges encountered. The aim of the interviews was to gain a better understanding of how to enable organisations to improve the management of wood dust exposure.

This study found that 6.0% of all wood dust exposure measurements (15 out of 252) were above 5 mg/m³, and 17.6% of exposures to hardwood dust or mixtures of hardwood and softwood dust (38 out of 216) were above 3 mg/m³ (the then current and future workplace exposure limits). Sanding, cleaning, and maintenance activities were of particular concern. Improvements to exposure controls are required, in particular, improvements to local exhaust ventilation controls for hand-held power tools and hand sanding. The management, selection, and use of respiratory protective equipment were poor.

All the managers and supervisors recognised that exposure to wood dust can pose serious health risks, and that controls were crucial to protecting workers’ health. The findings from the telephone interviews suggest that supervision and provision of information about the health effects of exposure to wood dust were common approaches that organisations used to raise awareness and promote good practice, in relation to managing wood dust exposure. Worker attitudes towards controls, such as perceptions that they hinder task completion and habitual ways of working, were identified as factors influencing the use of controls. Risk communication approaches that focus on increasing workers’ awareness of their susceptibility to ill-health using credible sources, such as peers, can help enhance the uptake of messages on the use of controls. Financial constraints were identified as a challenge to improving the control of wood dust, particularly for small companies.

control, exposure, hardwood, human factors, softwood, wood dust

What’s Important About This Paper?

This work characterised good exposure control practices to provide comparative data and support the production of evidence-based guidance for woodworking manufacturing activities. Hardwood and softwood dusts are a common cause of occupational asthma, and the Workplace Exposure Limit in Great Britain for hardwood dust has recently been reduced. This work describes practicable improvements to exposure controls and identifies human elements of exposure control that will assist small and medium-sized enterprises in improving the management of wood dust exposure.

Introduction

Wood dust is generated by the machining and working of wood and wood-containing materials such as chipboard and fibreboard. Wood dust can come from the machining of timber from hardwood (deciduous) or softwood (mainly coniferous) trees. Both hardwood and softwood dust can cause respiratory sensitisation and dermatitis, whilst hardwood dust can also cause sino-nasal cancer (SCOEL 2003). The International Agency for Research on Cancer (IARC) has evaluated wood dust and concluded that there was an excess risk of cancer from exposure to softwoods, but the magnitude of the excess was small in comparison to that from hardwoods (IARC 2012). IARC classifies wood dust as carcinogenic to humans (Group 1).

In Great Britain (GB) the workplace exposure limit (WEL) for softwood and hardwood dusts, before January 2020, was 5 mg/m³ based on an 8 h TWA (time-weighted average). Since January 2020, the hardwood dust limit has been reduced to 3 mg/m³ (HSE 2020). Companies working with a mixture of softwood and hardwood must comply with the new lower limits for hardwood dust for any wood dust exposure. Furthermore, for respiratory sensitisers and carcinogens, exposures must be reduced to as low a level as is reasonably practicable (ALARP) (HSE 2013).

Following a pilot study (Simpson et al. 2014), research was undertaken by HSE between 2014 and 2017 aiming to generate new intelligence on occupational exposure to wood dust in GB woodworking manufacturing activities (furniture manufacture, joinery, and sawmilling), and in boat building and repair.

Previous research focusing more broadly on occupational health and safety management identified several factors that can influence organisational practices. For instance, research suggests that in small and medium-sized enterprises (SMEs) resources (in terms of staff, time, and/or finances) may influence the implementation of practices specifically focusing on improving occupational health and safety (Lunt and White 2005). Other factors, such as an understanding or knowledge of health risks and associated controls may also influence the emphasis that is placed on ill-health prevention (Lunt and White 2005; Bell and Webster 2011). A study, which specifically focused on small woodworking businesses in the United States of America, found that factors affecting the control of exposure to wood dust included employee attitudes towards controls and habitual ways of working, the ease of using such controls, as well as financial resources (Brosseau et al. 2002). Therefore, an additional aim of this study was to develop a better understanding of any broader factors that may influence organisational practices in relation to the control of wood dust exposure.

Methods

Occupational hygiene surveys were conducted at 22 volunteer sites between 2014 and 2017. To characterise good practice, sites which were considered to have poor standards of health and safety based on their recent history of HSE inspections were excluded from the project. The sites visited, in Table 1, included 5 sawmills, 6 joineries, 6 furniture manufacturers, and 5 boat builders, using Standard Industry Classifications (Office for National Statistics 2007). The number of exposed workers varied between 2 and over 200. Eight of the sites were companies previously included in HSE research work between 1999 and 2000 (Black et al. 2007) to evaluate time trends. Six of the surveys were performed at the original sites.

Table 1.

Sites visited by Standard Industrial Classification and number of workers on site.

SIC	Description	Number of workers on site
		<10	10–49	50–249	>249
16.10	Sawmilling and planing of wood	0	2	3	0
16.23	Manufacture of other builders’ carpentry and joinery	1	4	0	1
31.01, 31.02, and 31.09	Manufacture of furniture (office and shop furniture, kitchen furniture and other furniture)	0	4	2	0
30.12 and 33.15	Building of pleasure and sporting boats Repair and maintenance of ships and boats	0	2	2	1
Total		1	12	7	2

Exposure monitoring for inhalable dust was performed on production, cleaning, and maintenance activities. The method used is described in HSE method MDHS 14/4 (HSE 2014). IOM-type samplers with glass-fibre filters were used at most sites; however, SKC Button samplers were used at 2 sites. Both sampler types are recommended in MDHS 14/4 and are comparable, but the IOM sampler has a lower bias under a wide range of workplace conditions (HSE 2014). The filters underwent gravimetric analysis to determine the wood dust collected. In most cases there was relatively little nonwood dust present in the work area; however, some samples were considered to be ‘unspecified process dust’ when other materials may have been present, e.g. dried paint, and were considered separately. Work activities were rationalised into 13 job categories taken from the previous HSE study (Black et al. 2007).

A number of short-term task-specific exposures were measured for tasks thought to be particularly dusty, e.g. maintenance and cleaning. Samples involving cleaning were divided into 4 categories based upon the anticipated most dusty method used: compressed airline with other less hazardous methods (dry brushing, or vacuuming) > dry brushing (alone or with vacuuming) > shovelling only > vacuum cleaning only. The data were compared to a nominal short-term exposure limit (STEL) of 3 times the 5 mg/m³ 8 h TWA WEL, i.e. 15 mg/m³.

Working practices and control measures to prevent or reduce exposure were identified and assessed to determine their effectiveness and compared with GB legislation and HSE guidance. This included engineering controls and personal protective equipment (PPE), but did not include an assessment of management controls. The methods used to determine the effectiveness of the controls were the presence of settled dust in the vicinity of a machine, and observation of airborne dust when the machine was being used with the aid of a dust lamp. LEV airflows were measured for comparison with the HSE guidance values current at the time of the site visits. Smoke tests were used to demonstrate airborne dust capture or containment. All site visits were conducted by professionally qualified occupational hygienists.

Additionally, a qualitative research approach was adopted for the human elements of exposure control, comprising telephone interviews with supervisors and managers responsible for health and safety. Fifteen of the companies that participated in the occupational hygiene surveys agreed to take part in the telephone interviews with a total of 23 interviews conducted. The interviews explored the sources of information that managers and supervisors used, how they tried to raise awareness and promote good practice among the workforce, and any potential challenges that they encountered in managing exposure to wood dust. Existing research highlights the important role that managers and supervisors play in implementing and enforcing safety practices and promoting workplace norms around safety (e.g. Huang et al. 2004; Probst and Estrada 2010; Mullen et al. 2017). Building on that, the interviews conducted for this study captured the views and experiences of managers and supervisors. Obtaining the views of workers as a means of complementing those of the managers and supervisors would have been useful; however, it was beyond the scope of the study. Ethical approval to conduct the interviews was obtained from HSE’s Research Ethics Panel. Each interview lasted approximately 45 min and was recorded with participants’ consent. The interviews were transcribed and analysed thematically to identify any recurrent themes and patterns across the data.

Results

The exposure results are presented in Tables 2 and 3 and in Figure 1.

Table 2.

Wood dust 8 h TWA exposures.

Category	No. of samples (No. of sites)	Median (mg/m³)	90th percentile (mg/m³)	Number >5 mg/m³
All samples	252 (22)	1.2	3.9	15 (6%)
Sanding	5 (3)	3.2	b	2 (40%)
Cleaning/maintenance	3 (3)	1.9	b	0 (0%)
Multi-tasking	106 (21)	1.5	4.4	8 (8%)
Circular saw	13 (7)	1.3	2.9	0 (0%)
Band saw	14 (4)	1.2	2.2	0 (0%)
Routing	11 (5)	1.2	3.5	1 (9%)
Other tasks in woodwork	49 (10)	1.2	3.7	3 (6%)
Tenoning	4 (1)	1.1	b	0 (0%)
Assembly	27 (4)	0.9	2.2	1 (4%)
Moulding/shaping	15 (4)	0.6	1.2	0 (0%)
Cross-cut saw	5 (5)	0.4	b	0 (0%)
Turning	0 (0)	–	–	–
Planing	0 (0)	–	–	–
Denibbing	8 (6)	2.5a	5.8a	n/aa
Sawmills	62 (5)	0.9	1.9	1 (2%)
Joineries	43 (6)	1.3	5.0	3 (7%)
Furniture manufacture	69 (6)	1.6	5.6	8 (12%)
Boat building and repair	78 (5)	1.2	3.5	3 (4%)
Hardwood	56 (6)	1.8	4.2	3 (5%)
Mixed hard and softwood	160 (13)	1.2	3.7	11 (7%)
Softwood	36 (3)	1.2	2.1	1 (3%)

^aNot all wood dust; other dusts present.

^bDataset considered insufficient (less than 6 samples) for reliable analysis of 90th percentile.

Table 3.

Task-specific wood dust exposure data.

Task	No. of samples (No. of sites)	Median (mg/m³)	90th percentile (mg/m³)	Number > ‘STEL’ b
Cleaning—compressed airline with sweeping or vacuuming	6 (3)	6.5	13.3	0 (0%)
Cleaning—brushing or brushing and vacuuming	10 (5)	3.7	27.4	3 (30%)
Cleaning—shovelling only	2 (2)	Individual values: <17.3 and 109.1		1 (50%)
Cleaning—vacuuming only	3 (3)	Individual values: <3.6, <5.8 and 2.1a		0 (0%)
Maintenance—changing LEV waste sacks	11 (9)	9.0	136.0	5 (45%)

‘STEL’—nominal short-term exposure limit of 15 mg/m³.

^aIncluded emptying the vacuum cleaner.

^bTask-specific data of >15 min in duration were taken to be a 15 min exposure; data of <15 min in duration assumed to have zero exposure for the remaining time.

Figure 1

Wood dust exposure measurements (8 h TWA) by site type. In the boxplots, the circle represents the highest exposure in that dataset; whiskers represent the 10th and 90th percentiles; whilst the box represents the median and 25th and 75th percentiles of the data. The dashed line represents the WEL current before January 2020 for wood dust of 5 mg/m³.

In total, 15 out of 252 workers (6.0%) had 8 h TWA wood dust exposures (hard or softwood) greater than 5 mg/m³ (the WEL in place at the time of the visits). Fourteen of these were exposures to hardwood dust or a mixture of hardwood and softwood dust.

Of the workers exposed to hardwood dust, or hardwood and softwood dust mixtures, 38 out of 216 workers (17.6%) had exposures exceeding 3 mg/m³ (the value which became the WEL for these dusts in January 2020).

Considering softwood dust alone, one worker out of 36 (3%) had an exposure greater than 5 mg/m³ (the ongoing WEL for softwood dust).

A summary of some control related measures is presented in Table 4. Observations with respect to the exposure control measures and human factors are presented herewith.

Table 4.

Wood dust exposure control related measures by site type.

	All data	Manufacturing (sawmills)	Manufacturing (joineries)	Manufacturing (furniture)	Boat building and repair
Standard industrial classification (SIC) codes	–	16.10	16.23	31.01 31.02 31.09	30.12 33.15
No. of sites	22	5	6	6	5
No. of sites with an exposure >5 mg/m³	10	1	2	5	2
No. of exposures >5 mg/m³	15/252	1/62	3/43	8/69	3/78
No. of sites having a LEV TExT	21/22	5/5	6/6	6/6	4/5
No. of sites having a LEV TExT on portable extraction	1/12	1/1	0/3	0/3	0/5
No. of sites with tight fitting RPE which was face fit tested	7/22	1/5	1/6	2/6	3/5
No. of sites having own wood dust exposure data	8	2	1	3	2
No. of sites providing health surveillance	13	3	4	2	4

Segregation

In general, woodworking is an activity, which requires quite a high degree of interaction from workers, reducing the possibility of automation and enclosure; however, noise enclosures did also provide segregation in some of these processes, e.g. for resaws and multi-head planer moulders. Computer Numerical Control (CNC) machining centres can be used to automate some tasks such as routing. Some fixed sanders were fully enclosed.

Local exhaust ventilation (LEV)

LEV was used by 141 of the 252 workers studied. Most fixed woodworking machines were designed with integral LEV which provided varying degrees of control. Common exceptions included drills, morticers, and table routers. The provision of LEV to hand-held power tools was much lower. Some hand routers did have on-tool extraction, but it was often ineffective and unpopular as it was awkward to use. Many sites tried to overcome these problems by using flexible ducts as makeshift capture hoods placed in close proximity to the work, but this was rarely effective over the whole work area because of the poor capture characteristics of this arrangement and the mobile nature of the work.

Many of the machines were quite old and therefore did not have original design features corresponding to modern-day good LEV practice for enclosure and hood design, e.g. spindle moulders and cross-cut saws. There were many examples of retrofitted features to improve LEV efficacy, with varying degrees of success.

The LEV on many of the woodworking machines observed had face velocities below the recommended values in HSE COSHH Essentials guidance current at the time of the visits (HSE 2003). This guidance has since been revised and now recommends volume flow rates obtained from manufacturers or the ACGIH Industrial Ventilation manual (HSE 2017a). Some table saw guards would have provided more effective extraction if they had not been set too high above the workpiece. LEV on cross-cut saws was restricted to a separate receiving hood in all cases. The sizes of the receiving hoods were frequently too narrow to capture the spreading jet of dust emitted from the saw at its furthest point. Similarly, although mitre saws frequently had LEV to the guard as well as to a rear receiving hood, the latter were also often too narrow and poorly positioned to capture the spread of the dust emitted from the saw. However several mitre saws were observed with permanent extracted partial enclosures built behind the saw.

All the 22 sites had one or more fixed-position centralised LEV systems serving multiple machines via a branched network of ducting. Twelve sites had automated emptying of waste from their LEV air cleaners to waste skips. Ten sites had supplementary LEV in the form of stand-alone systems (with exposed bag filters), and twelve sites had portable extraction units (usually industrial or domestic vacuum cleaner type machines). Only one site used a class M hazardous dust extraction unit as an LEV air cleaner. In all, 16 sites recirculated filtered air from LEV systems back into the workplace, but only 2 sites looked for signs of air leaks past the filter.

The main LEV systems at 21 out of 22 sites had undergone a thorough examination and test (TExT); however, only one site (out of 12) had put their portable extraction units through a TExT. Nine sites performed a daily check to determine that the systems were working properly: this was usually a basic audio/visual check that the system was operating, but two sites actively monitored Magnehelic pressure gauges.

During this work, a wide range of examples of poor or uncompleted maintenance were observed. These included:

• damaged enclosures (4 sites),

• loose or detached ducting (6 sites),

• holes in flexible ducting (6 sites),

• flattened or compressed flexible ducting (4 sites), and

• taped repairs to flexible ducting (6 sites).

Other examples included material deposited in ducting and uncontrolled apertures in the ducting.

General ventilation

Few sites provided any planned general ventilation for woodworking areas. Two of the sites had forced mechanical ventilation in the form of wall or roof fans and one site had a roof vent for natural ventilation.

Respiratory protective equipment (RPE)

Tight-fitting RPE was worn at some point by 78 of the 252 workers studied, but only 25 were face fit tested and wore it correctly. Where RPE failings were specified in site visit reports (19 sites only), 40% of workers wearing respirators did so incorrectly because of the presence of facial hair (26/65 workers); 43% were not face fit tested (28/65), and 6% donned the RPE incorrectly (4/65), e.g. incorrect positioning of straps. This left 37% of workers (24/65) whose RPE could be considered to be offering protection concomitant with its assigned protection factor, i.e. they were face fit tested, donned the RPE correctly, and had no facial hair.

The provision of effective RPE was low for all job categories. The RPE encountered was almost exclusively filtering facepiece (FFP) type devices, i.e. disposable tight-fitting respirators. Thirteen sites provided class FFP1, FFP2, or P2 RPE, i.e. considered to be a low standard of protection (14 sites provided class FFP3 or P3 RPE). Fifteen of the sites had provided training in the correct use of RPE. Only 7 sites (32%) had undertaken face fit testing of tight-fitting RPE.

Eleven sites (50%) reported that RPE was worn at the individual’s discretion and was optional, 9 sites (41%) had identified specific tasks which required RPE use (typically cleaning, maintenance, and sanding), and 2 sites (9%) required RPE for all woodworking machine use.

Health surveillance

Thirteen sites (59%) performed respiratory health surveillance, with 3 sites (14%) using a questionnaire alone, i.e. lower level health surveillance. Seven sites (32%) performed some form of skin health surveillance for signs of dermatitis.

Cleaning

Most sites used a combination of cleaning methods to remove wood dust contamination from the workplace. Evidence of dry sweeping was observed at 20 of the 22 sites. Twenty-one sites used vacuum cleaning of some description: 13 used flexible LEV ducting, 14 used industrial or domestic vacuum cleaners, and 5 used hazardous dust-type vacuums as per BS EN 60335-2-69 (BSI 2013). Three of the hazardous dust vacuums were class L and 2 were class H. Nine sites used compressed air for cleaning, in some cases to clear or dislodge dust from amongst crowded, confined, or inaccessible machinery, but in many cases its use was seen as unnecessary.

Comparison with historical data

The exposure data from the 8 sites visited in 1999–2000 are presented in Table 5. It was also noted from the original 1999–2000 site visit reports that:

• The number of sites with a CNC machine had increased from 1 to 5.

• The number of sites with a LEV system TExT had increased from 4 to 8.

• Face fit testing of tight-fitting RPE was not a requirement in 2000.

• The number of sites providing FFP1 standard RPE fell from 4 to 2, and the number providing FFP3 standard RPE rose from 0 to 6.

• The number of sites providing training on RPE use increased from 0 to 6.

• The number of sites with health surveillance for woodworkers had increased from 1 to 4.

• The number of sites using vacuum cleaners to clean had risen from two to seven.

• All eight sites continued to use dry sweeping.

Table 5.

Site revisit exposure data, 2014–2017, (8 h TWA) compared to data from the 1999–2000 survey.

Site	Survey	Number of samples	Median (mg/m³)	90th percentile (mg/m³)	Number >5 mg/m³	Number >10 mg/m³
Site 1	2014–2017	13	1.9	4.2	0 (0%)	0 (0%)
	1999–2000	7	2.2	22.1	3 (43%)	1 (14%)
Site 2	2014–2017	12	0.9	1.7	0 (0%)	0 (0%)
	1999–2000	11	0.9	5.5	1 (9%)	0 (0%)
Site 3	2014–2017	7	3.3	11.7	3 (43%)	1 (14%)
	1999–2000	9	2.2	8.7	2 (22%)	1 (11%)
Site 4	2014–2017	9	1.0	2.0	0 (0%)	0 (0%)
	1999–2000	9	1.5	14.8	1 (11%)	1 (11%)
Site 5	2014–2017	11	1.1	4.8	1 (9%)	0 (0%)
	1999–2000	22	2.2	4.8	2 (9%)	1 (5%)
Site 6	2014–2017	2	1.6	a	0 (0%)	0 (0%)
	1999–2000	4	1.8	a	1 (25%)	1 (25%)
Site 7	2014–2017	12	0.9	3.4	1 (8%)	0 (0%)
	1999–2000	23	2.3	41.8	8 (35%)	5 (22%)
Site 8	2014–2017	10	0.6	2.8	0 (0%)	0 (0%)
	1999–2000	12	4.1	16.6	4 (33%)	3 (25%)

^aDataset considered insufficient for reliable analysis of 90th percentile.

Site 1—Company had moved to a new location.

Site 3—Company offered an alternative site.

Telephone interviews

All the managers and supervisors who took part in the telephone interviews acknowledged that exposure to wood dust can pose serious health risks and that controls were crucial to protecting workers’ health. There was also a view expressed that controlling wood dust was beneficial from a business point of view in terms of less time spent clearing up and better product quality (such as reducing the likelihood of wood dust settling on finished products).

Managers and supervisors obtained information on how to control wood dust from various sources including the HSE website, equipment suppliers, external health and safety consultancies, and trade associations. Financial constraints were identified as a challenge to improving the control of wood dust for smaller companies (such as investing in new LEV systems).

Managers and supervisors referred to LEV systems as the primary measure for controlling exposure to wood dust in their respective organisations. Approaches for raising awareness about the effects of wood dust exposure and promoting good practice focused on the role of supervisors in reminding workers to use controls, challenging unsafe practices, and leading by example, as well as on the provision of information (e.g. through toolbox talks, posters). Workers’ attitudes toward the controls (e.g. perceptions that they are not easy to use and/or hinder task completion), and habitual ways of working, particularly among experienced workers, were identified as potential factors that could influence the use of controls.

A number of interviewees expressed the view that despite issuing instructions to workers not to use compressed air or brushes to clean up, these methods were still used. This indicates a need for improved supervision and management control.

The interviews also explored managers’ and supervisors’ views regarding what would help companies improve the way that they managed exposure to wood dust. Overall, managers and supervisors considered that the management of wood dust had improved across the industry, with references made to equipment and technological advances in the quality of extraction equipment available, as well as RPE. Specific suggestions are given related to raising awareness about the health effects of wood dust exposure, the types of RPE that should be used, and the importance of RPE face fit testing.

Discussion

This survey involved visits to 22 sites involved in woodworking (manufacturing) that were selected as they were believed to have a reasonably good standard of health and safety practice. When it is considered that there are many hundreds of woodworking companies, this research cannot be said to be an accurate statistical survey of the British woodworking industry. However, as a series of case studies, these results reflect a reasonable and practicable standard of control practice achievable in Great Britain.

Exposures

When considering the 8 h TWA exposure data by job category, 2 out of 5 sanders (40.0%) and 8 out of 106 multi-taskers (7.5%) were above 5 mg/m³, and 3 sanders (60.0%) and 24 multi-taskers (22.6%) had 8 h TWA exposures exceeding 3 mg/m³.

Sanding was the activity with the highest median 8 h TWA exposure (3.2 mg/m³). ‘Denibbing’ (a task which involves sanding between coats of paint and gives rise to exposure to wood and paint dust) was also high (2.5 mg/m³). The next highest activities were (full shift) cleaning and maintenance (1.9 mg/m³) and those ‘multi-tasking’ (1.5 mg/m³). The high exposures recorded for sanding and cleaning were not surprising, based upon observation and previous studies. Brosseau et al. highlighted both activities in their 2001 pilot study (Brosseau et al. 2001). More recently Schlünssen et al. examined exposure in the furniture industry and found sanding to have a significant impact (Schlünssen et al. 2008). They also found that having dedicated cleaning staff contributed to lower overall exposures at a factory level. This role was relatively uncommon in the present study, at just 3 sites, and the exposures for the individuals were relatively high. Although they were mainly vacuuming around the site, they were also involved in labouring tasks including maintenance of LEV systems. They may have had a positive effect on overall exposures at the site but there is insufficient data for confirmation.

Although only 2 individuals with 8 h TWA exposures over 5 mg/m³ were recorded as sanding, when the activities of multi-taskers and assemblers were examined, it revealed that 9 of the 15 exposures greater than 5 mg/m³ in this study involved workers sanding to some degree during their shift, and only 1 had effective RPE. The worker with the highest 8 h TWA exposure (23.1 mg/m³) was involved with LEV waste sack changing, dry sweeping, hand routing, and manual hand sanding, which are 4 of the dustier activities based on observations.

Considering the task-based exposures (Table 3), with the omission of the small and distorted dataset for cleaning by shovelling, the median task-specific cleaning exposure data followed the order of compressed air use > dry brushing > vacuuming. However, it was dry brushing which produced exposures which were above the nominal 15-min STEL (3 out of 10 samples). The shovelling dataset was considered distorted because it comprised of only 2 measurements: one reportedly unrepresentative and the other being relatively imprecise. Douwes et al. have compared sweeping with vacuum cleaning in controlled field tests using real-time monitors and found wood dust concentrations 10 times lower when using a vacuum cleaner (geometric mean 0.35 mg/m³, maximum 4.57 mg/m³) compared to dry wiping and sweeping (geometric mean 3.56 mg/m³, maximum 24.0 mg/m³) (Douwes et al., 2017). In a review of HSE data from a range of sectors, including construction, waste and recycling, and manufacturing, acquired for both research and regulatory purposes, Beattie et al. found median dust exposures of 26.4 mg/m³ for compressed air use (n = 38), 12.8 mg/m³ for dry sweeping (n = 30), and 3.8 mg/m³ for vacuum cleaning (n = 15) (Beattie et al. 2023). Changing LEV waste sacks was also an activity which produced a high proportion of exposures above the nominal STEL (5 out of 11 samples).

A large proportion of the published data on wood dust exposure in GB has been produced by the HSE. A recently developed job exposure matrix allows a comparison between wood dust exposures in 6 Northern and Central European countries (Basinas et al. 2023). The data is from 1978 to 2007 and has been modelled to give an estimate of exposure in 1997. The model suggests considerable differences between countries with the highest exposures being observed in UK workers and could be a reflection of differences in regulation, sampling strategy, and/or large variations in production and working practices. For example, in the largest category, carpenters and joiners, the UK geometric mean exposure was 2.36 mg/m³ (95% CI 2.10–2.66 mg/m³), compared to an overall value of 1.64 mg/m³ (95% CI 1.12–2.40 mg/m³).

Considering sectors, for comparison Schlünssen et al. (2008) found geometric mean exposure of 0.60 mg/m³ from 1044 exposures at 27 Danish furniture manufacturing sites; in this study a median of 1.6 mg/m³. Straumfors et al. (2018) found geometric mean exposure of 0.72 mg/m³ from 112 exposures at 11 Norwegian sawmills; in this study 0.9 mg/m³. Douwes et al. (2017) found geometric mean exposure of 2.5 mg/m³ from 96 exposures at 10 New Zealand joineries, and 0.6 mg/m³ from 105 exposures at 3 furniture factories (in this study medians of 1.3 mg/m³ and 1.6 mg/m³, respectively). Median and geometric mean are equivalent for lognormally distributed exposure datasets. A fitted normal distribution and a quantile–quantile plot both showed that the logged TWA data conformed well to a normal distribution. The caveat given by Basinas et al. should also apply here, nevertheless, exposures in furniture manufacture in Great Britain would appear higher than in Denmark, and the exposures in British joineries lower than those in New Zealand. There was no statistically significant difference at the 0.05 level between the median exposures to the different wood dust types in a t-test on the log-transformed data (P = 0.10).

Exposure controls

The provision of LEV was very high for individual fixed-position woodworking machines, but lower for hand-held power tools, possibly explaining the lower exposures for woodworking activities at fixed machines. Although airborne wood dust was released from many types of fixed woodworking machines fitted with LEV, 8 h TWA exposures generally did not exceed 5 mg/m³. However, exposure control by LEV could be improved by greater enclosure of the emission source, better hood design, and increased airflow rates, to reduce exposures to ALARP (HSE 2017b).

Although 95% had a TExT, less than half the sites (41%) checked daily that their LEV systems were working properly, and the ‘audio visual’ checks often performed may only detect a gross deterioration in performance. For comparison, during the last HSE study at sites selected to be representative, 43% (20/46) sites had an LEV TExT, and 50% (23/46) performed weekly checks (Black et al. 2007). This suggests improvement, but the differing selection criteria prevent a more confident evaluation. Examples of poor or uncompleted maintenance of LEV systems were observed at most sites. Much use was made of flexible ducting which has low resilience (HSE 2017b), and half the sites had flexible ducting which was or had been damaged. Better maintenance of LEV systems could help improve their effectiveness in controlling airborne wood dust.

Wood dust exposure control, when using hand-held power tools or when manually hand sanding, was much poorer in comparison to the fixed woodworking machines. Around half of the workers observed had no LEV provision, and when present it was frequently of questionable efficiency. Portable extraction units used to provide LEV for hand-held power tools were widespread but were often of a low standard and unlike fixed LEV systems generally did not undergo the 14 monthly TExT required by the Control of Substances Hazardous to Health Regulations (HSE 2013).

The application of RPE was frequently poor, not only in the selection and introduction of RPE (of low standard and not face fit tested) but also incorrect usage (e.g. with facial hair) indicating poor training and/or supervision. This picture reflects the findings in studies by Easterbrook and Brough (2009) and Bell et al. (2012). Easterbrook and Brough highlighted a lack of face fit testing across brick making, construction, and quarrying. Bell et al. noted that improvements were especially needed with regard to training, supervision, and maintenance in a study covering seven different sectors. Graveling et al. have analysed the key elements of an effective RPE programme (Graveling et al., 2011) and found that getting management and supervisory support, reinforcement, and enforcement in place was an essential first step.

Although only 7 of the 22 sites in this survey had had face fit testing of tight-fitting RPE, no comparison can be made with the data from the previous HSE study because it was obtained before the COSHH Regulations specifically required face fit testing.

Cleaning

Although most of the sites (91%) still used brushes, almost all the sites (95%) also used vacuum cleaning of some description. However, 9 sites (41%) used compressed air. For comparison, during the last HSE wood dust study at sites selected to be representative, 96% used brushes, 79% used vacuum, and 64% used compressed air (Black et al. 2007). In the review by Beattie et al. of HSE research and regulatory inspection reports, 74% reported dry brushing, 41% vacuuming, and 26% compressed air use (Beattie et al. 2023).

The majority of vacuum cleaners were domestic or industrial machines which, although containing HEPA-type filtration, did not meet the criteria for use as a vacuum cleaner for hazardous dust (BSI 2013), which includes design features to minimise any form of contact with the hazardous dust it collects, such as during bag removal. The use of flexible hoses plumbed into the LEV system as a vacuum cleaner negates problems with the standard of vacuum cleaner efficiency or integrity; however, the end of a flexible length of ducting may be better suited to cleaning if it has a vacuum cleaner-type attachment on the end.

Changes to exposure and control

When HSE last surveyed wood dust exposure in manufacturing in 1999–2000 (Black et al. 2007), visits were made to 46 representative sites, collecting 406 exposure measurements. Median exposures by sector were: 1.5 mg/m³ (sawmilling); 2.6 mg/m³ (joinery manufacture); 2.8 mg/m³ (furniture manufacture); and 2.4 mg/m³ (other manufacture). Overall, 27% of values exceeded the 5 mg/m³ limit. Differing site selection criteria prevent a definite comparison of the full dataset between that from 1999–2000 and that from 2014–2017; however, the 2014–2017 sector values are around 40% to 60% smaller than the previous data.

Analysis of HSE wood dust exposure data on the National Exposure Database (NEDB) by IOM (Galea et al. 2009), using a linear mixed effects model, found an annual decline of geometric mean exposure of 8% per year between 1985 and 2003. Stratified analyses found that this decline was fairly constant across industry sectors and occupations; however, the analyses suggest that the declining trends were predominantly caused by a decrease in NEDB exposure data from inspection visits (presumably workplaces considered of concern). The exposure levels, based on data collected during representative surveys (1986–1996), remained relatively stable over time, with a decline of 0.2% per year. This suggests that the poorer performing companies were improving but the general trend had remained relatively constant.

Considering the 8 sites that participated in the 1999–2000 work, 6 of the sites now had a lower median exposure (3 showed a 50% or greater reduction), one the same, and one had a higher median exposure, compared to the previous survey. These differences were repeated for the 90th percentiles, and the proportion of values greater than 5 mg/m³. Using any measure, Site 3 showed worse performance in the current survey, although as noted in Table 5, this was not a revisit to the original site. A more detailed analysis comparing exposures of individuals or work at specific machines has not been undertaken for these visits. Although the 2 exposure datasets contain limited data, most sites’ median exposures showed a decrease, suggesting that improvements have been made; however, only one site (Site 8) showed a statistically significant difference at the 0.05 level in a t-test on the log-transformed data (P = 0.01). Accompanying these apparent decreases in wood dust exposure, there were recorded improvements in automation (more CNC machines), LEV testing (TExT), RPE provision and use, health surveillance participation, and the use of vacuums for cleaning.

For comparison, Galea et al. (2009) performed 10 follow-up occupational hygiene visits in 2004–2005 to GB companies which had previously been visited in 1985–1991. For each of the companies resurveyed, the geometric mean wood dust exposure decreased between sampling surveys. This trend was accompanied by new or improved LEV systems at 9 sites, and more automated equipment at 7 sites. Other changes identified included new vacuum cleaning systems and changes in the machining processes.

Practicable exposure control improvements

The site selection criteria for the current survey should have produced an exposure dataset which is characteristic of a basic achievable standard in exposure control practice, i.e. the median and 90th percentile values presented in Table 2. There were, however, a range of examples encountered where the standard of process design, enclosure, segregation, application, and/or maintenance of LEV, were short of what could have been achieved. This implies that a level of exposure control somewhat better than that encountered should be achievable.

Although a number of improvements to the LEV on fixed machines have been identified (e.g. hood or enclosure design, increased extraction airflow, and maintenance), it is clear from the observations and exposure measurements that exposure control for hand-held power tools and manual sanding have the greatest room for improvement.

Sanders and routers were frequently used without LEV. On-tool LEV, especially for hand routers, was reported to be frequently ineffective or difficult to use. The use of capture hoods was often poor because of the distances they were located away from the working position and use of these hoods by 2 workers with hand-held power sanders did not prevent their 8 h TWA exposures exceeding 5 mg/m³. On-tool LEV is preferable (HSE 2022). In particularly challenging scenarios the solution may be to combine on-tool LEV with a screened, downdraught bench or capture hood maintained at an appropriate distance. Douwes et al. have found that by combining downdraft benches with on-tool extraction significant improvements in control can be achieved (Douwes et al. 2017). Reductions in exposure for hand-held routers were increased from 27.6% to 42.5%, and for hand-held sanders the reduction increased from 75.0% to 85.5%. The work technique can also influence exposure, e.g. the proximity of the worker’s breathing zone to the work.

Short-term exposures during cleaning and maintenance also require consideration. Limiting the use of compressed air and dry brushing would prevent significant quantities of dust from being re-suspended and increasing airborne exposures. Increased use of automated waste management for LEV air cleaners would also reduce exposures; otherwise collected waste in bags can be sealed before being moved to any transfer area. Regular routine maintenance within the air cleaner should not be necessary for a well-designed system.

A number of these activities, e.g. sanding and cleaning, produce significant airborne wood dust concentrations. In the short term, an effective RPE programme could be implemented to control any residual risk. This should include ensuring that the correct standard of RPE is provided, any tight-fitting RPE is face fit tested, and training and supervision is provided to ensure it is worn correctly for appropriate activities. Alternative forms of RPE, that do not rely on a tight fit to the face, are available. In the long term, engineering controls are preferable.

Factors contributing to the management of wood dust exposure

The findings from the telephone interviews suggest that a number of factors may potentially influence organisational practices regarding the management of wood dust exposure including:

• understanding the impact of wood dust exposure on worker health and organisational outcomes (e.g. in terms of productivity and product quality),

• risk control advice obtained from HSE guidance as well as third parties (e.g. equipment suppliers),

• resources, and

• workers’ attitudes towards controls.

These findings are consistent with previous research that has shown that financial constraints, habitual ways of working, and negative attitudes towards controls, are some of the factors that may influence safety behaviours and practices (Brosseau et al. 2002; Lunt and White 2005; Thompson and Ellis 2011). It would be fruitful for future research to complement the views of managers and supervisors, which was the focus of this study, with workers’ perspectives on the practices and potential challenges of managing exposure to wood dust.

In addition to education and raising awareness of the health effects of wood dust exposure and the use of controls, organisations might benefit from information on how to encourage workers to engage in healthy and safe working practices. Specifically, tailored health and safety messages can be perceived as more personally relevant, which in turn can enhance their effectiveness (Lustria 2017). For instance, making messages about the health effects of wood dust exposure personally relevant (e.g. use of testimonies from employees suffering from respiratory ill health), and delivering messages by trusted, credible sources (such as peers) could be useful in increasing workers’ awareness of their own susceptibility to ill health and encourage the use of controls. However, it should be borne in mind that under the GB regulatory regime, the primary duties to control exposure are those of the employer. These include a duty to implement a control strategy based on the hierarchy of control and, where control efficacy is dependent upon worker behaviour, to provide adequate information, instruction, and training in the use of controls, backed up by effective supervision.

Conclusions

Notwithstanding that wood dust exposure in GB should be ALARP, 6.0% of exposures were above the 5 mg/m³ WEL current before January 2020, and 17.6% would have been above the current 3 mg/m³ hardwood dust exposure limit. Sanding, cleaning and maintenance activities were of particular concern.

LEV for fixed machines was generally adequate but was poor for hand-held power tools. Nearly all LEV for fixed machines underwent a TExT, but very few portable extraction units did. Provision and use of effective RPE were low. Cleaning with brushes is still common but there is more use of vacuum cleaning, although using domestic or industrial rather than hazardous dust-type cleaners. Limited data suggest a decrease in wood dust exposures and improvement in exposure controls since 1999–2000.

Worker engagement in healthy and safe working practices is crucial. This may be achieved by increasing workers’ awareness of their personal susceptibility to ill health and using credible and trusted sources, such as peers, to enhance the uptake of health and safety messages. Perceived benefits relating to the control of wood dust, such as improved productivity, and a positive impact on product quality, could potentially serve as a means of promoting good practice across the industry.

Acknowledgements

The authors are grateful for the assistance of those companies who participated in this project, and colleagues in HSE who assisted in the collection and analysis of samples and data.

Funding

This publication and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.

Conflict of Interest

The authors declare no conflict of interest relating to the material presented in this article.

Data availability

The data underlying this article will be shared on reasonable request to the corresponding author. The wood dust exposure data has been shared in a supplementary data file to this article.