Thread: Australian dust regulation

Ok so I found that we have a lower limit of 1mg/m3, but a study by safe work Australia found that workers were frequently exposed to much higher levels... https://www.safeworkaustralia.gov.au...a_2008_pdf.pdf

“Exposure to inhalable wood dust, as represented by 521 discrete time- weighted average personal measurements across all wood industries yielded a median value of 2.1, an arithmetic mean of 5.8 and range of 0.06 – 210 mg/m3. This distribution is similar to a 1999/2000 UK-wide targeted (purposive) survey where the corresponding figures were 2.6, 6.6 and 0.05 – 157 respectively.
Depending on the task, control measures and work practices, exposures often exceeded the Australian occupational exposure standard of 1 mg/m3 in the case of hardwoods and 5 mg/m3 for other woods. It was found that 72% of hardwood dust exposures exceeded the relevant standard. Corresponding percentages for solid softwoods, reconstituted woods and mixed woods were 22%, 28% and 25% respectively.”

Ooof.

[EDIT: please note, some numbers have been edited significantly since initial posted]

The work safe standards in AU are as far as I know still 5mg/m^3 for softwood, 1mg/m^3 for hardwoods, 0.5mg/m^3 for MDF and WRC.
The 5 and 1 mg/m^3 are based on British standards which are based on woods like Beech and Oaks.
This makes no consideration of the supposed greater toxicity of Australian Hardwoods, wood dust particle sizes, or age of woodworker.

The 5 and 1 mg/m^3 standards are for all wood dust particles (including any chips) that are present in the air.

Wood dust above about 25 microns in size ( all large and intermediate, and even most tiny chips) fall out of the air very quickly ie less than a minute and are difficult to fluff back up into the air (unless you use a compressor), so unless a wood worker is constantly standing under a stream of saw dust exiting from a power tool these don't really count. OTOH this is probably more common than we think eg turning

Particles between about 25 and 15 microns are too large to get very far into the human body so they don't have that much of an effect.

Particles between ~15 and 5 microns are largely invisible will hand around in the air for many minutes, hence are more likely to can get some way into air ways and are thought to be responsible for the increase in nose, larynx and throat cancers in wood workers.

It's the particles less than 5 microns that we know little about and seem to have greater potential health implications.
The problem with these is they are invisible, their effects appear to be heavily masked , can hang in air around for hours and can be easily fluffed back up from surfaces where they have been deposited.

It was not until 2017 that a worldwide group of epidemiologists agree that particles of around 2.5 microns and smaller are the 5th leading risk factor in terms of deaths. These particles are implicated in mate than just respiratory diseases especially cardiovascular diseases but also some seemingly unrelated diseases like diabetes and kidney and urinary tract diseases.

WHO Standards for general PM2.5 dust (dust of 2.5 microns and smaller) have been much lower than OHS wood dust standards but in light of the above may need to be further revised.
Currently a PM2.5 of 0.025 mg/m^3 covers all at risk people like seniors and kids or anyone with an existing medical condition.
This is a 24 hour average, the annual recommended average is 10 FWIW, Right now my home office PM2.5 is 1.5 µg/m^3
FWIW, Right now my home office PM2.5 is 10 µg/m^3 for the whole year.
These recommendations are for an average exposure of "normal dust" but no one has specifically looked at PM2.5 wood dust which is almost certainly more toxic than "normal" dust.

Fortunately for every kg of sawdust PM2.5 particles represent a small fraction of the total sawdust eg sanding softwood with 80 grit paper produces about 5g of PM2.5 for every kg of sawdust produced. Nevertheless, that 5g of PM2.5 dust is enough to contaminate thousands of, 6x4x2.7m sheds to above the WHO 0.025 mg/m^3 standard.
Put another way the same sawdust will lift the wood dust concentration in a 6x4x2.7m shed by thousands of times above the WHO standard.

The other thing to bear in mind is that though the % weight of PM2.5 is low, the numbers of particles in that fraction is very high and they get/go everywhere like "glitter".

Except for turners, WWs who like using sanders and avid MDF users who work without wood dust extraction the average DIY wood worker with decent ventilation are unlikely to be exposed to this sort of average exposure across a year. A much more likely semi immediate effect of this high exposure is the development of a wood allergy.

Interestingly, sanding with finer paper doesn't make a lot of difference to the amount of PM2.5. It makes less really coarse dust and increases the PM30 and PM10 dust but doesn't not make much more PM2.5.

WHO are now in discussions about reducing their recommended levels so it will be interesting to see what they come up with.

Ventilation is a cheap and effective way to minimise PM2.5 levels in even a large shed. At our mens shed we have a Clearvue Max and a Evap AC. I have measured the dust levels in that shed continuously for many weeks and it typically goes above the WHO PM2.5 0.025 mg/m^3 level several times a week for a few hours otherwise the weekly average is barely above outside air levels, ie around 10 µg/m^3. The exposure hours hours not continuous but typical occurs in short (a few minutes) bursts.

The main reason that it does occasionally go over the WHO levels is forgetting to have the DC on and to open the right blast gates. On one occasion where it reached ~0.5 mg/m^3 or about 20X the WHO recommended level while he shed was being "swept out" with compressed air and turning on the Evap AC fan only quickly brought the levels down to <20 mg/m^3 within a couple of minutes. If that AC fan was run continuously the dust levels would never rise above the WHO recommended values.

We are lucky that complete air replacement is often possible in our climate, if I couldn’t have doors and windows open, I’d be investing even more in dust extraction and filtration and running the extractor for longer to filter the air after machining etc.

But the worst workshops I have seen as a customer (a custom furniture place in NZ and a recycled timber place in Australia) had clouds of dust that caused me to cough when in their work area. They had extraction on big machines but I suspect more was being caused by things like belt sanders I saw being used with just the bag and no vacuum, routers without vacuums etc.

Is that what you found Bob, that hand held power tools are bigger contributors than fixed machines?

I agree about being lucky with being able to completely replace shed air in our climate. Even when it's hot as hades outside and I have the AC on, if I do end up using the DC for a quick dust making task so that it vents the cool shed air, in most cases the AC recovers the coolth in <10 minutes so its not that big a deal. Just knowing that its going to cool down again helps me stay cool If I have to perform longer dust making taks I try to do that earlier in the day.

Originally Posted by Austin_Turner

Is that what you found Bob, that hand held power tools are bigger contributors than fixed machines?

It depends on the machines and dust control in use.

A big machine processing large pieces of timber can make so much dust that even a larger DC can't catch enough of the dust produced. The uncaptured dust spills out and quickly contaminates a shed.

A small machine or power tool connected to a low capacity vac effectively does the same thing.

I'm not that big of a power tool user and can't afford a high end vac or warrant a vented vac system so normally just use a 50mm hose connected to the DC on my power tools. Its not very effective on chip extraction on something like a router but we have to learn to accept that chips that we can see are not really a health problem (although they can cause other probs) but it's very effective at fine dust control.

At the mens shed remembering to open up blast gates and turn on the DC is probably on a par in terms of dust generation with blokes not using a Vac on power tools. Not that I think that much of most vacs. I have one but I mainly use it to vac metal swarf off and around machines. I have a few 100 mm Flexies connected up to the DC and strategically located around the shed that I use to vac nearby floors etc.

I have revised my long post above about PM2.5 levels.
I got some of the µg and mg, and daily and annual exposures, mixed up.

I looked up what annual averages were for Australian cities.
Annual PM2.5 for major Australian cities were for 2016 were all <8 µg/m^3, for PM10 it was <20 µg/m^3 , although a few country towns were above this.
It will be interesting to see the data for 2019-20 following the large bushfire season.

I'm reading up about the health effects of PM2.5 in woodsmoke - will report later once I think I have something coherent to post.

Current PM2.5 in my study is 1.8 µg/m^3