Water-based varnishes, paints and adhesives require conservation with in-can preservatives, both, for their raw materials - polymer dispersions - and the end products in order to warrant the necessary shelf life. Isothiazolinones and formaldehyde donors are currently the most relevant active substances for this purpose. The former can induce allergical skin reactions while the latter are being classified as carcinogen of category 1B and therefore under obligation to be phased out in the future. In this study it was examined if there are feasible alternative substances or procedures with comparable effectiveness for in-can preservation, but which have lower risks. Current literature was investigated and expert interviews were conducted with representatives from concerned industry branches and from workers' compensation boards.
Production facilities for varnishes, paints and adhesives range from small or medium scale manufacturers to large scale industrial production with the former having higher potential workplace exposure and the latter mainly operated as closed systems. Product application occurs in diverse branches like building trade, furniture construction, packaging industry, printing industry or artisan painters with potential exposure to the preserved coatings or adhesives. In expert interviews, there were no substantial hints to an especially high occupational risk resulting from in-can preservatives in any step of production and/or end use.
As a consequence of previous and ongoing regulation, potential options for in-can preservation of water-based coatings and adhesives in general are narrowed. Options to completely avoid in-can preservatives are scarce and often combined with adverse side-effects (e.g., silicate paints with pH 11.5). Dry paints, which had been on the market some twenty years ago, but were not successful, have been reintroduced into the market just recently, but their economic success remains to be seen.
As major cause for the lack of research on new active agents the experts named the demanding and protracted approval process under the Biocidal Products Regulation (BPR) (EC) No. 528/2012 as the relation of R&D investments to market value is very unfavourable for biocides in general and in-can preservatives in particular. All options to transfer active substances from other sectors, e.g. pesticides or from other product types according to BPR have either been exhausted or were not feasible in the first place. Product innovation therefore focuses mainly on new combinations of existing agents.
Most measures for an improved process hygiene have already been implemented. Some manufacturers are still seeing some potential to optimise their facilities and processes, but this does not allow the avoidance of preservation measures in order to achieve the necessary shelf life of the end products.
A. Müller, V. Schmahl, S. Gschrei:
Survey on alternatives for in-can preservatives for varnishes, paints and adhesives.
1. edition. Dortmund: Bundesanstalt für Arbeitsschutz und Arbeitsmedizin 2020. pages 57, PDF file, DOI: 10.21934/baua:report20200811
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