What is it? Dusts Not Otherwise Specified (known as “Dust NOS”) are quite simply just dusts, that are insoluble or poorly soluble in water and have not been classified due to their toxicity (eg: they don’t have any toxic impurities such as quartz or lead etc). Dust NOS may come from vehicle traffic, drilling, blasting, grinding, screening etc.
What does it do? Whilst there are still information gaps for health aspects of Dust NOS, workers may still be susceptible to eye/nose/throat irritation or dust-related diseases such as Chronic Obstructive Pulmonary Disease (COPD).
What is the “safe limit”? Interestingly, Safe Work Australia does not specify a Workplace Exposure Standard for Dust NOS in the Work Health and Safety (WHS) Regulations in Australia. Dust NOS would be one good example of how simply complying with the WHS Regulations is not enough to prevent occupational illness and disease in your workplace.
The Australian Institute of Occupational Hygienists (AIOH) has just published their Position Paper on Dust NOS and their associated health issues. That Position Paper recommends two Dust NOS “trigger values” to protect workers from potentially serious health effects. These are:
- 5mg/m3 for inhalable dust; and
- 1mg/m3 for respirable dust.
You need to figure out which dust fraction (inhalable or respirable) is likely to have the greatest likelihood of exceeding the associated trigger value…or potentially look at both.
What is the difference between “inhalable” and ‘respirable”?
Inhalable dust is basically all of the dust that you can breathe in through your nose and mouth, while Respirable Dust is the dust that makes its way down deep into your lungs into the unciliated airway (the alveolar region). You can find more info in Australian Standard AS3640 for inhalable dust and AS2985 for respirable dust.
What do these new trigger values mean? This is a big deal in the world of dust. Previously in 2013, Safe Work Australia recommended that Dust NOS (as inhalable dust) should be maintained below 10mg/m3 and they made no mention of respirable dust. It turns out that that magic number was introduced back in 1990 and wasn’t reviewed or updated since that time. Think back to 1990…I was in Year 7; perms were in, I think I had a pair of mustard coloured jeans. It wasn’t a good year. Times have changed. More studies have been performed, and we are better informed on many things, including perms….so with new information comes new recommendations.
In the world of mining (which have different Regulations), there are exposure standards for Respirable Dust ranging from 2.5mg/m3 to 5mg/m3, and you’ll note that this new trigger value is even lower than that.
So these new trigger values mean that as hygienists we want to put more control measures in place a bit earlier than Safe Work Australia recommended previously. This might include more dust suppression, more ventilation, containment, or the use of respiratory protection as a last resort. The Position Paper lists some practical control measures that can be used to reduce exposure to Dust NOS that would be considered on a case-by-case basis.
Why do you care? Why recommend even more stringent requirements than the WHS Regulations? Ultimately, occupational hygienists are focused on protecting worker health and preventing occupational illness and disease. Implementing these trigger values in your workplace is one example of how you can reduce exposure to workers and therefore reduce the associated occurrence of illness and disease associated with Dust NOS.
Need an Occupational Hygienist? The AIOH has a Consultant Directory here.