Check Your Hygiene: Surely taking 1 sample is enough to show you’re safe?

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Check Your Hygiene

Ever heard this before? This is normally followed by the blank stare with mouth wide open as some poor soul stands there while I try to explain why ‘no it’s not!’

There are many common misconceptions on how to determine if the workplace air is ‘safe‘, but today I’m going to focus on just one….why one sample isn’t enough..or as we call it…why you need to perform personal exposure monitoring to assess occupational exposure to airborne contaminants!

Under the Work Health and Safety Regulations (I’ll assume we live in a perfect world where we are harmonized for simplicity), you need to do air monitoring to determine the concentration of substances in air where an exposure standard applies (there are over 700 exposure standards in Australia)…if a) you can’t prove that the concentration exceeds the exposure standard, or b) it’s necessary to determine if there is a risk to health (I’m paraphrasing).

In an all too common scenario, some will assume that ‘monitoring’ simply involves setting up a gas detector, or some ‘dust pumps’ in the work area…run them…and then compare the results to the respective exposure standard to conclude if you are safe or not and then bam you’re done. Unfortunately this isn’t the case. What can then follow is the Occupational Hygienist using all their powers of persuasion to convince someone that this isn’t enough to be in compliance with the Regulations.

In their defence…it’s also not that simple to figure out that you actually need to do this. So, I thought today I’d list out the standard blurb I use to show people that this is required.

1.     Starting at the WHS Regulations…This tells you that you need to do air monitoring and refers to the exposure standards.

2.     Still on the WHS Regulations…the definition of ‘exposure standard’ refers you to the ‘Workplace Exposure Standard for Airborne Contaminants

3.     Look up that document and you find that a few interesting things:

a.     Firstly, exposure standards, “Do not represent a fine dividing line between a healthy and unhealthy work environment. Natural biological variation and the range of individual susceptibilities mean that a small number of people might experience adverse health effects below the exposure standard”. Therefore they don’t protect ‘all’ workers. It is a brave (read: foolish) person who tells you that the workplace is ‘safe’ if there is known concentration of a hazardous chemical around and they have 1 sample to prove it.

b.    It also reminds you that exposure to substances in the workplace “must be kept as low as reasonably practicable” and refers you back to the WHS Act.

c.     …and it also has this statement, “Where monitoring of airborne contaminants is used to estimate a person’s exposure, the monitoring must be undertaken in the breathing zone of the person”. So therefore ‘static’ or ‘para-occupational’ samples where they are taken in the workplace, rather than from a worker’s breathing zone, aren’t going to be enough to determine if there is a risk to health…or to be in compliance with the WHS Regulations.

That document then refers to the Guidance Note on the interpretation of workplace exposure standards for airborne contaminants.

4.     In that document, it’s quick to point out that, “Exposure measurements should be made from unbiased and representative samples of actual worker exposure. Such a sampling strategy usually encompasses selection of workers for personal monitoring as well as the timing of sampling. The monitoring strategy should also address issues such as the nature and duration of a process, sampling and analysis errors, statistical analysis of exposure data and the determination of the need for regular exposure measurement. Detailed routine monitoring strategies for airborne contaminants are a complex subject and a complete discussion of the theory and characteristics is beyond the scope of this Guide”.

Yes…health is complex – that is why it can take so long to actually become an Occupational Hygienist! Around Page 7 that Guidance document refers you to ‘seek expert assistance’, and this is where your friendly Occupational Hygienist comes in.

The above 4 points would have to be one of the most common document trails I rattle off when trying to explain why putting a dust pump on a stake in the middle of the work area isn’t going to cut it. Yet the look of disbelief is still a common occurrence.

What about you reading this now…is this new to you? Do you have any suggestions on how to better communicate the responsibilities of Companies on this issue?


7 thoughts on “Check Your Hygiene: Surely taking 1 sample is enough to show you’re safe?

    Koen Verbist said:
    March 12, 2014 at 7:42 am

    Nice post on a difficult subject that requires very often that ‘one measurement is no measurement’! To add some to the subject, the BOHS and the DOHS have drafted a guidance document for testing compliance with OELs. It can be found here (in English)

    It gives guidance as to ‘how many’ measurements are required to conclude (statistically) that exposure is below the relevant exposure limits.

    One other question, in Europe under the REACH regulation the use of exposure estimation tools is very common and accepted. Tool like ECETOC TRA, Stoffenmanager and ART are widely used to determine if exposure is controlled. How is this in Australia?

      katecole111 responded:
      March 12, 2014 at 9:18 am

      Hi Koen – yes the BOHS guidance document is a personal fave of mine…but I also refer to the AIHA document on the strategy for assessing occupational exposures. We also have a few Australian-based guides such as the one by Dr David Grantham (Simplified Monitoring Strategies: How to apply NOHSC’s Exposure Standards for Atmospheric Contaminants in the Occupational Environment to Australian Hazardous Substance Legislation) and another by Ian Firth, Deborah van Zanten & Gerard Tiernan (Simplified Occupational Hygiene Risk Management Strategies). Both of the Australian documents are quote old compared to the BOHS document though…and as most of our states changed their WHS legislation at the end of 2011, it would be good to revisit these in an update at some point!

      On your second question – I’m not familiar with the tools you listed…but I can’t speak for the entire country! It is entirely possible that other australian hygienists are using these – but it just doesn’t form a routine part of what I do day to day.

      Hope that helps!

        Koen Verbist said:
        March 12, 2014 at 9:39 am

        Hi Kate,

        Thanks for your reply. What we see in the Netherlands is that the use of tools is often the starting point for companies in performing their risk assessment. It helps to prioritize and focus on these substances with a high risk.

        For your information, I am personally involved in the development of Stoffenmanager ( and according to our statistics (May 2013) about 0.26% of the users of our tool comes from Australia 🙂

    […] you know by now that taking one sample to show that you’re safe isn’t enough. But how many samples is enough? and what if one of those samples is marginally over the Workplace […]

    […] I learnt about using bayesian statistics to interpret and make decisions on hygiene data. If you have ever heard an occupational hygienist tell you what the 95% upper confidence limit was and were left feeling slightly puzzled and bemused by what they were trying to tell you, then bayesian statistics might be a good place to start. Using that method, occupational hygienists can determine (with a percentage probability) what category the exposure may fall into, which basically determines the urgency and degree of control measures that may be needed to reduce exposure to the worker. It’s a nice simplified way of handling a very complicated topic of “what do I do with all this data“? […]

    […] that the process may not be under reasonable control to protect the workers. Further to that, you already know that exposure standards are not a dividing line between safe and unsafe, they are designed to protect most workers, but not all workers…so you need some leeway in […]

    […] (ie: putting a sample pump in the work area or measuring it using a DustTrack). You also need more than one sample…but you knew this […]

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