How to Control Exposure to Respirable Dust

Awareness of the hazards associated with exposure to dust has increased in recent years assisted by the efforts of various industry bodies; this document aims to set out in practical terms what exposure can mean and what practical steps can be taken to minimise the risks now and for the future.

From a health and safety point of view dust is categorised into two size fractions: inhalable dust and respirable dust.

Inhalable dust is dust that is small enough to be breathed in, but large enough that our natural defence mechanisms can filter it before it reaches our lungs, on the other hand, respirable dust is small enough to break right through into the tiniest parts of the lung where the oxygen is transferred to the blood. Once dust has reached this point there is usually insufficient air flow to take it back out, so if our bodies cannot break it down then there it stays causing irritation and sometimes leading to fibrosis – the linings of the walls become thick, stiff and scarred making breathing difficult and reducing the amount of oxygen reaching your blood.

Under the Control of Substances Hazardous to Health regulations, responsibilities are placed on employers to manage their employee’s exposure to hazardous substances in accordance with workplace exposure levels laid out in HSE Publication EH40/2020. EH40 lists STEL (15-minute) and TWA (8-hour) limits for over 420 different substances including hard and softwood dust, respirable crystalline silica and many common solvents; it also includes a paragraph which states “The COSHH definition of a substance hazardous to health includes dust of any kind when present at a concentration in air equal to or greater than 10 mg.m-3 8-hour TWA of inhalable dust or 4 mg.m-3 8-hour TWA of respirable dust.” this means that even general construction dust can come under the regulations if in sufficient quantities.

Whilst calculating exposure values in a relatively stable environments like a factories, bakeries or offices is relatively easy, the dynamic nature of a construction project can change by the day and by the hour; how does the conscientious HSEQ or site manager ensure that teams on site are protected? Spot checks and personal monitoring using traditional methods can miss key dust generating events and the project may have moved on before the results are even available.

Controls

The first thing to consider are the materials and processes we’re using, are we using the least hazardous solutions we can, are we minimising cutting or working materials on site? Buying ready cut materials reduces waste, transport costs, time and noise on site; all benefits well worth having.

Once we have selected our materials, we next need to look at ways of reducing the exposure on site by using local controls. On-tool extraction for power tools, exhaust fume filtration for machinery working inside, using a suitable vacuum cleaner rather than a broom or using a cutting enclosure with an extraction system to minimise both dust and noise on site. Remember that for maximum effectiveness, any extraction system needs to capture as close to the source as possible, filter to a suitable level and discharge the cleaned air ideally outside the work area; putting a dust-box in the room will do very little to reduce exposures.

With our collective control measures in place, we now need to consider individual controls. Will workers be fully protected, or must we incorporate respiratory controls as a final layer of defence? The selection of RPE is key as workers need to be face fit tested and calculations done based on the nature of the dust and the concentrations expected. This is to ensure that the masks aren’t overwhelmed by the dust, leading to either premature blocking or excessive dust reaching the wearer. Too often dust masks are seen as a cheap alternative to proper controls; they offer the lowest level of protection and need the careful management to ensure that they are effective. The hidden costs of relying on RPE are higher than might be expected especially with a large and regularly changing workforce.

Finally, we need to check the results of our control measures; prove that the money we’ve invested in dust control is effective. Personal dust monitoring on a representative selection of workers over a longer period of time will demonstrate that controls are working and that our key assets are protected day after day. It is only recently that this has become feasible with the introduction of new wearable electronic dust monitors that include alerts for both short-term (STEL) and long-term (TWA) exposure, data logging of multiple particulate size fractions and downloadable .CSV files. The worker can now be warned when the background dust level is approaching exposure limits and check that the controls are working and that RPE is worn. The TWA alert will sound once the daily average exposure has reached limits and when RPE is worn the actual exposure can be calculated from actual data and the protection factor offered by the particular mask giving peace of mind for the wearer and the manager.

Further information

To view the Air XD One Personal Dust Monitor, click here

To find out more about the benefits of a personal dust monitor, click here

To view our full range of monitoring solutions, click here