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Would someone please explain to me why the short term exposure limit for a hazardous substance is higher than the long term. I cannot get my head around this?
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Rank: Super forum user 
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Easy analogy is noise level - low exposure over the full working day compared to a very short high level exposure aka peak pressure both can damage hearing but whilst the former is cumulative the later may be instantaneous.
Or another example open smelling salts directly under your nose and you get a massive hit, have an open jar four desks away and whilst you can smell it there is no head back reaction.
STEL describes the brief instantaneous hazard, LTEL describes the same hazard aggregated over time typically the 8 hour working day (makes it fun to work out when your shifts are 12 hours) both are WEL limits Edited by user 15 June 2019 20:43:41(UTC)
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Rank: Super forum user
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Easy analogy is noise level - low exposure over the full working day compared to a very short high level exposure aka peak pressure both can damage hearing but whilst the former is cumulative the later may be instantaneous.
Or another example open smelling salts directly under your nose and you get a massive hit, have an open jar four desks away and whilst you can smell it there is no head back reaction.
STEL describes the brief instantaneous hazard, LTEL describes the same hazard aggregated over time typically the 8 hour working day (makes it fun to work out when your shifts are 12 hours) both are WEL limits Edited by user 15 June 2019 20:43:41(UTC)
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4 users thanked Roundtuit for this useful post.
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Need help with STELs and LTELs. Our operatives work outside on flat roofs putting primers down etc. I should imagine that WELs still apply but it would be difficult to work out the averages of the WELs due to a mixture of calm days and windy days. Any comments truely appreciated
Tom
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Rank: Forum user
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Skerr,
Another way of looking at STEL & LTEL that works for most workers is to compare it to a good old fashioned drinking session:
I was once capable of drinking 12 pints of cider during a typical Saturday with the gang and still walk home (below LTEL of 2 pints / hour!)
On other occassions I would be throwing up if trying to drink a yard (2.5 pints) of ale in under a minute (STEL).
I remember one particular session when I helped a mate forget about his recently split up with a girlfriend and we finished a bottle of Malibu between us - never been able to touch the stuff since, I struggle with a bounty bar too ;-) (in Industry we would call this sensitisation of an individual and neither the LTEL or STEL needs to be reached to cause an adverse reaction)
There were other factors e.g. what happened if a "mate" forces you to have a short or chaser (whisky) with every pint! (In industry, what if you are exposed to other hazardous substances during your working day / lifetime?!?)
I hope this simple analogy works.
Tommy - I sympathise, rarely in my 28+ years of H&S management has the STEL / LTEL / WEL exposure levels on an MSDS been of any use in various real life scenarios - there are so many unknown factors (climate, wind, proximity of mouth/nose to substance etc.) to make a definitive "this substance is sfe, because exposure will never get above the danger levels" - what may be true in a lab / chemical plant does not always transfer to roof tops / road side working
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Thanks Skerr.
I don't think the manufacturers are at all helpfull with their scientifically objective - "there you are - get on with it information"... I'm reviewing all our CoSHH assessments and just want to put legible information before the operatives to give them half a clue as what they are working with.
Tom
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Rank: Super forum user
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Originally Posted by: Evans38004  Skerr,
Another way of looking at STEL & LTEL that works for most workers is to compare it to a good old fashioned drinking session:
I was once capable of drinking 12 pints of cider during a typical Saturday with the gang and still walk home (below LTEL of 2 pints / hour!)
On other occassions I would be throwing up if trying to drink a yard (2.5 pints) of ale in under a minute (STEL).
I remember one particular session when I helped a mate forget about his recently split up with a girlfriend and we finished a bottle of Malibu between us - never been able to touch the stuff since, I struggle with a bounty bar too ;-) (in Industry we would call this sensitisation of an individual and neither the LTEL or STEL needs to be reached to cause an adverse reaction)
There were other factors e.g. what happened if a "mate" forces you to have a short or chaser (whisky) with every pint! (In industry, what if you are exposed to other hazardous substances during your working day / lifetime?!?)
I hope this simple analogy works.
Tommy - I sympathise, rarely in my 28+ years of H&S management has the STEL / LTEL / WEL exposure levels on an MSDS been of any use in various real life scenarios - there are so many unknown factors (climate, wind, proximity of mouth/nose to substance etc.) to make a definitive "this substance is sfe, because exposure will never get above the danger levels" - what may be true in a lab / chemical plant does not always transfer to roof tops / road side working
Great Analogies, I may just borrow them!
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Rank: Super forum user
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Originally Posted by: Evans38004 "this substance is sfe, because exposure will never get above the danger levels" Interesting approach to COSHH Tommy H - the content of a Safety Data Sheet is set by regulation and there are two changes that should be making their way through the supply chain:
1) Derived No Effect Level - information about exposure via different routes in different groups industrial/professional/consumer 2) eSDS - extened Safety Data Sheets which include risk management measures (product usage scenarios anticipated by or communicated to the supplier) - if its missing ask, if your use is missing ask for it to be included http://www.hse.gov.uk/coshh/detail/reach.htm
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Rank: Super forum user
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Originally Posted by: Evans38004 "this substance is sfe, because exposure will never get above the danger levels" Interesting approach to COSHH Tommy H - the content of a Safety Data Sheet is set by regulation and there are two changes that should be making their way through the supply chain:
1) Derived No Effect Level - information about exposure via different routes in different groups industrial/professional/consumer 2) eSDS - extened Safety Data Sheets which include risk management measures (product usage scenarios anticipated by or communicated to the supplier) - if its missing ask, if your use is missing ask for it to be included http://www.hse.gov.uk/coshh/detail/reach.htm
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Rank: Forum user
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You cannot manage what you don't measure and old saying, however when working with Substances Hazardous to Health a very good place to start,G409 is worth a read.
It is difficult to apply appropriate control measures in a COSHH Assessment if you don't know what the level of exposure is.
In regard windy days; measure exposure on a calm day not do it on a windy day, that should give you the worst case scenario the Better option.
Once exposure levels are determined and control measures are in place it may be worth considering if BMGV is required as some of these roofing primers are particularly nasty substances and have various routes of entry.
As your employees will be working at height and these primers can cause dizziness or drowsiness quite quickly maybe reviewing the WAH Risk Assessment might be worth a look at as well.
In regard the manufacturers not being helpful, they provide the information on their product and it is up to the employer to protect the workforce when using it by Assessment in whatever environment.
Hope this helps
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Rank: Super forum user
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What do you to if you cannot measure, or where there is no data regarding the effect of exposure to the chemical? This is what I am faced with almost every day when looking at skin exposure in a workplace.
“However, there is no scientific method of measuring the results of the body’s exposure to risk through dermal contact. Consequently no dermal exposure standards have been set.” - from “Occupational skin diseases and dermal exposure in the European Union (EU-25): policy and practice overview - European Agency for Safety and Health at Work
What would you measure? Is it what lands on the skin (arguably the actual exposure) or what adheres to the skin and causes direct damage to skin cells (irritant) or what is absorbed into
the skin and causes an immune reaction (allergy) or what penetrates the skin and causes, or contributes to systemic damage? Of course, you might have a
combination or two or more of these. Where on the body would you measure? The body’s
reaction can vary by a factor of 40 depending upon location. How would you allow for atopics – people with genetic condition that predisposes to skin reactions – estimated as possibly more than 20% of the U.K. population? And how would you allow for ambient conditions that can significantly affect the skin’s response?
In addition to this we often have to consider exposure to mixtures which further complicates the picture.
So whereas for respiratory exposure we have WELs, we have nothing for skin. This makes demonstrating compliance virtually impossible.
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