Hi All,

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

Thank you

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?

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.

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...

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.

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’?