I have some concern about the concept that if a person has a known allergy a substance in the workplace in which he or she is to be employed he should be informed that they are not suitable for that position. This could be taken to imply that the organisation is aware that there is exposure to a known asthmagen sufficient to elicit a reaction. This could indicate that they are not adequately controlling the exposure and are therefore not complying with COSHH. What if someone already employed were to become sensitised to this substance and develop asthma? The fact that the organisation had rejected someone on grounds of existing sensitisation might be considered as an indication that they were aware of the risk but had not adequately controlled it.

Now consider the following scenario. The prospective employee is already sensitised to the particular substance but has never experienced a reaction. Sensitisation is asymptomatic and it is not uncommon for people to be sensitised to a substance but unaware of this. The pre-employment medical would not register this sensitisation and thus clear that person for employment. What would then be the position if once employment has commenced they were to experience a reaction (could be asthma, could be allergic contact dermatitis or contact urticaria)?

Another consideration is whether the substance is present in the workplace in a bioavailable form. For example, someone allergic to nickel can usually handle stainless steel (chrome-nickel-steel) with no problem, since the nickel is so tightly bound into the alloy that non is being released. However, if the steel is being subjected to some process that results in the release of nickel molecules, then this does represent a potential for a skin reaction. I have had a case where a claim of allergic contact dermatitis in an epoxy-impregnated carbon fibre mat was shown to be invalid as we could demonstrate that the sensitising compound in the epoxy was not bioavailable as used in that particular process.

Chris