Geoffrey Laycock looks at essential topics, myths and misunderstandings affecting the safety and health of woodturners
The headline asks a question as to whether wood dust is hazardous. The answer is: Yes, it is. That said, when it comes to discussing wood dust, size matters. Dust is an aerosol of solid particles, mechanically produced, with individual particle diameters measurable from 0.1μm upwards. An aerosol is a suspension of fine solid particles in a gas, in this case wood dust in air. For exposure assessment purposes, two size classifications – inhalable and respirable – are defined.
Inhalable dust is small enough to enter the nose and mouth during breathing and respirable dust is that part of the inhalable dust which will penetrate down into the lungs, usually less than 10μm in size.
How we consider dust hazards depends on whether we are in a work situation or a hobby one. At work in the UK, Workplace Exposure Limits (WELs) are legally enforceable. They are measurable and used to set standards of protection and judge compliance with legislation. Wood dust has assigned WELs for both hardwood and softwood, at 5mg/ m3. Workplace exposure to wood dust must therefore comply with this assigned limit, meaning the exposure should not be more than this level and as close to zero as possible.
Softwood dust is also noted as a ‘sensitiser’, meaning it can cause occupational asthma, while hardwood dust is noted as both ‘sensitiser’ and ‘carcinogenic’, meaning capable of causing cancer. For the hobby turner, it is strongly advised this maximum level of exposure is adopted and worked down to as close as possible to zero.
SIZE MATTERS – WHAT DOES 5MG OF DUST LOOK LIKE?
The photo below shows 5mg of dust from beech (Fagus sylvatica) veneer. For comparison, we have a standard LR44 cell; the dust is about one-fifth or less its volume. On the right is a drink stir stick and a piece that represents 5mg of whatever wood that is. The pile of dust is bigger as it contains air. Now imagine that pile of dust equally distributed in a metre cube of air – not much, is it?
Health hazards explained
We tend to think of wood dust being inhaled as the health hazard, but there are other health effects and we will return to those another time. Inhaling dust initially causes a problem in the nose where some particles are trapped by the wet surfaces – exactly what they are designed to do.
Unfortunately, stopping some dust particles from moving further into the lungs, they can cause irritation to those wet surfaces. One result can be rhinitis and some dusts are specifically known for this problem. African Mahogany (Khaya ivorensis), obeche (Triplochiton scleroxylon) and European walnut (Juglans spp) are examples.
Dust, particular hardwood, trapped in the nasal passages, can result in cancer. Penetrating the respiratory system further, we can have adverse effects such as bronchial disorders, decrease in lung function and development of asthma. Some examples include cedar (Callitropsis nootkatensis), Central and South American and western red, iroko (Milicia excelsa), maple (Acer campestre) and most species of pine (Pinus spp). Surprised?
Further information
Further Information is available from www.hse.gov.uk
The various HSE documents below are highly recommended reading:
• WIS 14 (rev1): Selection of respiratoryprotective equipment for use with wood dust. • WIS 23 (rev1): Wood dust – controlling the risk
• WIS 30 (rev1): Toxic woods
• WIS 32 (rev1): Safe collection of wood waste: prevention of fire and explosion.