Categorisation of protein respiratory allergens: the case of Subtilisin

Characterisation of the relative sensitizing potency of protein and chemical allergens remains challenging, particularly for materials causing allergic sensitization of the respiratory tract. There nevertheless remains an appetite, for priority setting and risk management, to develop paradigms that distinguish between individual respiratory allergens according to perceptions of the hazards and risks posed to human health. One manifestation thereof is recent listing of certain respiratory allergens as Substances of Very High Concern (SVHC) under the provisions of REACH (Registration, Evaluation, Authorisation and restriction of Chemicals). Although priority setting is a laudable ambition, it is important the process is predicated on evidence-based criteria that are transparent, understood and owned. The danger is that in the absence of rigorous criteria unwanted precedents can be created, and confidence in the process is compromised. A default categorisation of sensitisers as SVHC requiring assessment under the authorisation process is not desirable. We therefore consider here the value and limitations of selective assignment of certain respiratory allergens as being SVHC. The difficulties of sustaining such designations in a sound and equitable way is discussed in the context of the challenges that exist with respect to assessment of potency, and information available regarding the effectiveness of exposure-based risk management.