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MrBrightside  
#1 Posted : 11 November 2021 11:10:36(UTC)
Rank: Forum user
MrBrightside

Hi All,

Does anyone use any software (if so can you recommend) for this or just a good old excel spreadsheet / calculator? 

Thank you

peter gotch  
#2 Posted : 11 November 2021 12:10:32(UTC)
Rank: Super forum user
peter gotch

Hi Mr Brightside

If by "calculating exposure limits" you mean working out what limit would be appropriate for a mixture, then personally I am not convinced that a spreadsheet approach would work.

This is because the reader will need to know the basis of your calculation of the limit for a mixed exposure.

The HSE formula for doing this is based on the assumption that the anticipated impacts are the same for each chemical in the mix.

So, as example it would be appropriate to use that formula where it is a mix of two or more similar solvents.

But, it would not be appropriate if you mix a solvent with e.g. lead or organic lead compounds.

....and it is based on the assumption that effects are additive with no "synergistic" impacts e.g. where someone is exposed to asbestos and inhalable products arising from tobacco consumption where research indicates that the total risk is far more than that if you were to calculate each individual risk and add them together.

All of which implies the need for a document that sets out the rationale for what you are calculating, rather than just simply tapping in some numbers into a computer to give you the answer.

thanks 1 user thanked peter gotch for this useful post.
A Kurdziel on 12/11/2021(UTC)
chris.packham  
#3 Posted : 11 November 2021 16:21:47(UTC)
Rank: Super forum user
chris.packham

I suggest you will need some chemical expertise, or access to this, to determine what the ultimate chemical hazard is when two or more chemicals are mixed. This can be completely different from the hazards of the individual chemical. Consider a cleaning activity using both sodium hypochlorite and a acid toilet cleaner. Inadvertent mixing of these can result in the creation of chloride. At least one prosecution for a fatality from this has occurred in the last few years. Particularly where skin exposure is involved determining the real hazard when chemicals are used in a specific task is often not as straightforward as many assume. I have seen many risk assessments where the conclusion as to the risk did not match the actual hazard from the chemicals as used and present in the task.

Take a look at what HSE state in the current ACoP for COSHH 

“Employers should regard a substance as hazardous to health if it is hazardous in the form in which it may occur in the work activity. A substance hazardous to health need not be just a chemical compound, it can also include mixtures of compounds, micro-organisms or natural materials, such as flour, stone or wood dust.” - COSHH ACoP (6th edition), para. 10

How will you obtain the necessary information from safety data sheets?

Kate  
#4 Posted : 11 November 2021 16:45:04(UTC)
Rank: Super forum user
Kate

COSHH exposure limits are not calculated, they are set by the regulator and looked up in EH40 or other authoritative source.

I am guessing it is not exposure limits but something else that you want to calculate?

Edited by user 11 November 2021 16:45:54(UTC)  | Reason: Not specified

thanks 2 users thanked Kate for this useful post.
Roundtuit on 11/11/2021(UTC), A Kurdziel on 12/11/2021(UTC)
Roundtuit  
#5 Posted : 11 November 2021 17:35:22(UTC)
Rank: Super forum user
Roundtuit

I am trying to determine why you would need a calculator.

If you have measurements taken surely these were conducted by an occupational professional who would have provided a report of their findings including the regulatory values and personnel exposure against those values.

thanks 2 users thanked Roundtuit for this useful post.
A Kurdziel on 12/11/2021(UTC), A Kurdziel on 12/11/2021(UTC)
Roundtuit  
#6 Posted : 11 November 2021 17:35:22(UTC)
Rank: Super forum user
Roundtuit

I am trying to determine why you would need a calculator.

If you have measurements taken surely these were conducted by an occupational professional who would have provided a report of their findings including the regulatory values and personnel exposure against those values.

thanks 2 users thanked Roundtuit for this useful post.
A Kurdziel on 12/11/2021(UTC), A Kurdziel on 12/11/2021(UTC)
stevedm  
#7 Posted : 12 November 2021 09:25:49(UTC)
Rank: Super forum user
stevedm

There srae three types of assessments:

Stage 1 - COSHH risk assessment that any EHS person can do...qualitative - calculation of 8 hr TWA exposure, based on sampling perhaps

Stage 2 - Risk Assessment - based on sampling calcs - Done by an Industrial Hygenist - qualitative and quantitaive..

Stage 3 - Risk Assessment - Completed by a toxicologist...

chris.packham  
#8 Posted : 12 November 2021 12:15:17(UTC)
Rank: Super forum user
chris.packham

Keep in mind that when we talk about exposure limits these are only relevant for airborne exposure and inhalation. They do not apply to the other two routes of exposure (ingestion and dermal). There are no techniques for measuring skin exposure that would be practicable in an industrial/commercial environment. Studies have shown that facial skin exposure below the inhalation exposure limit can result in adverse health effects. Also keep in mind that the three routes are not separate but can create health effects that one would normally not associate with a different route. If you would like more on this just PM me an e-mail address and I will send you more detailed documentation. 

Brian Hagyard  
#9 Posted : 12 November 2021 14:03:21(UTC)
Rank: Super forum user
Brian Hagyard

i read this as calculating if you have exceeded an exposure limit - i would never try and calculate that i would bring in a suitably qualified occupational hygienist and have them measure it in real terms.

thanks 2 users thanked Brian Hagyard for this useful post.
A Kurdziel on 12/11/2021(UTC), stevedm on 13/11/2021(UTC)
John Elder  
#10 Posted : 12 November 2021 16:24:16(UTC)
Rank: Forum user
John Elder

The following document makes good reading and explains things in a simple to understand format.

it is the Basic Manual for Calculation of the Estimated Human Exposure Used in the Risk Assessment of Consumer Products and is open sourced material available online.

Please see the link below and i hope this gives some educational guidance

https://www.nite.go.jp/en/chem/risk/ghs_risk_consumer_guidance_ap1_e.pdf

chris.packham  
#11 Posted : 12 November 2021 17:47:03(UTC)
Rank: Super forum user
chris.packham

Looking at this document and what it contains about dermal exposure I have to question its relevance when it comes to considering skin exposure in a working environment. Note that the ECHA has stated:

“For the time being, there is no EU-wide system in place to assess the combination effects and risks of chemicals. There have been developments in this area and scientists are looking into ways in which groups of chemicals that have a wide exposure for us and the environment, can undergo combined risk assessment. It is very difficult, if not impossible to test all mixtures using standard experiments. Better testing strategies and the use of novel alternative testing methods using computational modelling and non-animal methods, need to be used.” - from ‘Chemicals in our life’, ECHA (European Chemicals Agency)

Firstly, any calculated system has to adopt certain basic assumptions, one of which is that the skin is a standard membrane, with common properties on at least the majority of persons. This is certainly not the case. Inter-individual variations can be significant.

Then we need to know the location on the body. The rate of absorption can vary depending on body location by a factor of up to 40. The rate will also be affected by the effect that the chemical has on the actual skin cells. If it is sufficiently aggressive to quickly damage the skin such that the barrier layer (stratum corneum) is locally destroyed, then permeation calculations can no longer apply. There are also many other factors (temperature, relative humidity, general skin condition, etc.)

This whole topic of effect on the skin is fraught with uncertainty and complications. How many understand the implications of what is termed ‘systemic contact dermatitis’?

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