Rank: New forum user 
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Hi All I was wondering if someone could help further my understanding of this subject in terms of WEL's and workplace air monitoring. Dusts - If there isn't a method for analysis of a particular dust of an element, how would you ensure that you are below the WEL? Lets say I have air monitoring that measures the general inhalable/respirable dust. If the WEL for the element is greater than what was measured, then we can assume that the WEL isn't being exceeded yes? However, what if the WEL for the element is less than what was measured for general dust? Mists/Vapours - Again, if a chemical in air cannot be measured effectivly by workplace air monitoring, how do you ensure the WEL isn't being exceeded. (assuming that not all chemicals can be tested). Thanks in advance
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Rank: Super forum user
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Hi Guitarzilla Your post has been read more than 70 times without reply. So......is the appropriate monitoring equipment being used, by people who know what they are trying to do? To get a really sensible response you would need to explain a bit more about what the processes are and what the contaminants are - not least to consider which of a mix would present additive or synergistic* risks. *Synergistic - in simple terms if you exposure somebody to concentration A of one chemical and B from another then the risk is not A + B but something much higher. So, as an example we have a reasonable idea of the probability of someone getting lung cancer if they smoke for X years - so risk = G Similarly, we have a reasonable idea of the probability of someone getting lung cancer if exposed to such and such level of asbestos for Y years - so risk = H But if they both smoke and are exposed to asbestos the total risk is MUCH larger than G + H. Conversely, you could have contaminants R and S where one poses a risk by inhalation and the other risk by ingestion. Usually you would treat these separately. Gets more complex if there is risk by e.g. inhalation but with different expected impacts.
Edited by user 29 July 2022 15:03:03(UTC)
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Rank: Super forum user
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British Standard BS EN 689:2018 gives strategy guidance on testing compliance with exposure limits...you sounds like you should have an occupational hygeinist looking at your testing...
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Rank:: Super forum user 
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I think it would be useful to know whether these questions are purely hypothetical and entirely general, or if they relate to some actual workplace exposure monitoring. I am baffled as to what chemical couldn't be tested for. If it's a chemical unknown to chemistry or there is no analytical method of measuring it, then it won't have a WEL in the first place.
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 1 user thanked Kate for this useful post.
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Rank: Super forum user 
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Originally Posted by: Guitarzilla  Dusts - If there isn't a method for analysis of a particular dust of an element, how would you ensure that you are below the WEL?
In the UK EH40 guidance dusts are assigned unique WEL by exception e.g. Respirable Crystalline Silica, for all other particulates in air there is a catch all Dusts (General) - basic methodolgy is increase in mass of a filter media based upon drawing a volume of air over a set period of time. So in response to the first part - there is a method, there is a default WEL for all items that do not have a unique limit ergo so long as you are not exceeding the default WEL and have no specific susbtances you will be considered to be in control. As to mists & vapours the methodology is derived to enable monitoring and control of materials recognised as being hazardous to health - what other mists / vapours are you attempting to theorise?
EH40 has distinct entries for four mists, three vapours and twelve fume.
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Rank: Super forum user
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Originally Posted by: Guitarzilla Dusts - If there isn't a method for analysis of a particular dust of an element, how would you ensure that you are below the WEL?
In the UK EH40 guidance dusts are assigned unique WEL by exception e.g. Respirable Crystalline Silica, for all other particulates in air there is a catch all Dusts (General) - basic methodolgy is increase in mass of a filter media based upon drawing a volume of air over a set period of time. So in response to the first part - there is a method, there is a default WEL for all items that do not have a unique limit ergo so long as you are not exceeding the default WEL and have no specific susbtances you will be considered to be in control. As to mists & vapours the methodology is derived to enable monitoring and control of materials recognised as being hazardous to health - what other mists / vapours are you attempting to theorise?
EH40 has distinct entries for four mists, three vapours and twelve fume.
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Rank: Super forum user
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Let’s go back to basics: You identify a process( a real process not some theoretical process vis a vis Kate’s comments) and then you do a thorough risk assessment, including seeing if the process produces any airborne hazards. It is usually obvious if a process produces some sort of airborne hazard. The only nonobvious one that springs to mind is carbon-monoxide, other you can smell see or taste something that could be a hazard. This the point where a lot of attempts at COSHH fail; there is something that looks wrong eg lots a dust or a strange smell, but people just ignore it and hope its not an issue. What you should do is if you have identified a potential hazard is to establish what the severity is (First step of 5 steps to risk assessment) and you do that by looking up the substance’s WEL . If should be obvious what you are looking for: if you are cutting concrete than is respirable crystalline silica etc. You can then either calculate an expected value ( can be used if you looking a volatile organic vapour evaporating assuming the worse case scenario) or better getting an occupational hygienist in the do the measurements. You need to understand that these people are not equipped with a Star Trek style tricorder, which will tell what something is and how much is present. Instead they collect a know volume of air and use filters designed to capture a particular dust fraction on a pre weighted filter. They reweigh this and from that they can calculate the concentration of the dust in the air. They assume that all of this is the fraction they are looking at. For vapours and gases they can use tubes containing a capture medium. They elute what they capture and again capture the concentration. You can’t have a WEL for substances that cannot be measured. For some substances you can rely on biological monitoring: you take blood or urine samples for people who may have been exposed to the substances in question and see if there are any physiological changes due to exposure. Its a bit hit and miss which is why we have the generic dust limit and the expectation to reduce the exposure to the lowest level that is practicable
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Rank: Forum user 
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Put simply: All substances with a WEL have an approved test method covering how to collect a sample and then determine the level present in that sample. If no test method exists, then a WEL can't be set. For gases / vapours the test methods are all substances specific so the levels of all materials can be independantly measured even in a mix of gases/vapours. For solids, all are based on a collected sample. You may have to seperate out the different dusts from the sample (based on the material properties and/or particle size) but it is do-able in most cases. Bottom line: this is a very technical aspect of COSHH and requires expertise to do correctly. That's why there is a whole job role dedicated to it (Occupational Hygenist). Getting a representative reading is just the start of the process, converting the reading into an 'exposure level' is another expert step that is required before you can then compare it to WEL with any confidence.
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