Occupational Exposure to Diisocyanates in the European Union

Abstract

Objectives Diisocyanates are a chemical group that are widely used at workplaces in many sectors. They are also potent skin- and respiratory sensitizers. Exposure to diisocyanates is a main cause of occupational asthma in the European Union. To reduce occupational exposure to diisocyanates and consequently the cases of diisocyanate-induced asthma, a restriction on diisocyanates was recently adopted under the REACH Regulation in the European Union. Methods A comprehensive evaluation of the data on occupational exposure to the most important diisocyanates at workplaces was made and is reported here. The diisocyanates considered are methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and hexamethylene diisocyanate (HDI), accounting for more than 95% of the market volume in the EU. The exposure assessment is based on data from Chemical Safety Reports (CSRs) of REACH Registration Dossiers, workplace air monitoring data from Germany, from the UK Health and Safety Executive (HSE), and literature data relevant for the EU, and the USA. Results Occupational exposure to diisocyanates is particularly relevant in: (i) C.A.S.E. applications (Coatings, Adhesives, Sealants, Elastomers), (ii) production of polyurethanes (PUs) (e.g. slab-stock foam), (iii) handling of partly uncured PU products (e.g. cutting, demoulding, spray application of foam), and (iv) when diisocyanates/PUs are heated (e.g. hot lamination, foundry applications/casting forms). Ranking of the reported data on inhalation to diisocyanate exposure at workplaces (maximum values) leads to following order: (i) HDI and its oligomers in coatings, (ii) MDI in spray foam applications, (iii) TDI in manufacture of foam, (iv) TDI in manufacture of PUs and PU composite materials, (v) TDI in adhesives, (vi) MDI in adhesives, (vii) MDI in manufacture of PUs and PU composite materials, (viii) TDI in coatings, (ix) MDI in manufacture of foam, and (x) HDI in adhesives.

HBM4EU Diisocyanates Study—Research Protocol for a Collaborative European Human Biological Monitoring Study on Occupational Exposure

“…However, fewer data were available on the occupational exposure to diisocyanates in the manufacturing of other vehicles such as aerospace, shipping and large commercial vehicles, the construction sector, where there are potentially several sources of exposure (e.g., sprayed insulation, floor screeds), the use of MDI-based glues, and the manufacture of spray adhesives or coatings [ 11 ]. A recent review [ 6 ] also identified these sectors as potentially significant, based on airborne measurements of diisocyanate exposure (although several of these also have dermal contact potential). The current HBM4EU diisocyanates study, therefore, aimed to include these sectors, to harmonise the sampling strategy and ensure comparable analytical techniques.…”

“…Diisocyanates have long been a leading cause of occupational asthma [5,6]. Exposure limits are generally very low (in the µg/m 3 range, https://limitvalue.ifa.dguv.de/, date accessed 13 July 2022), and the European Commission's Advisory Committee on Safety and Health at Work (ACSH) recently proposed a binding occupational exposure limit of 10 µg/m 3 (measured as -NCO, total reactive isocyanate groups), reducing it to 6 µg/m 3 from 1 January 2029 (https://circabc.europa.eu/ui/group/cb9293be-4563-4f19-89cf-4c458 8bd6541/library/0d11d394-b1e8-4e1a-a962-5ad60f4ab2ae/details, date accessed 13 July 2022).…”

“…In many countries, health surveillance is also mandated due to the known health impacts (https://www.finlex.fi/en/laki/kaannokset/ 2001/en20011485.pdf, date accessed 13 July 2022) [7], and this is also recommended in the ACSH's opinion. Diisocyanates are used in many industrial applications including coatings, adhesives and lacquers, in moulding, and in slab foam production [6]. They are highly reactive chemicals with fast cure times, making them attractive to industry and hard to replace; these features also mean that any substitute chemicals with suitable properties will potentially demonstrate similar health impacts.…”

Comparison of Two-Component Silyl-Terminated Polyether/Epoxy Resin Model and Complete Systems and Evaluation of Their Mechanical, Rheological and Adhesive Properties

“…To reduce occupational exposure to diisocyanates and, consequently, the cases of diisocyanate-induced asthma, which is recognized as a particular problem in C.A.S.E. (Coatings, Adhesives, Sealants, Elastomers) applications, a restriction on the use of diisocyanates was recently adopted under the REACH Regulation in the European Union, allocating a three-year transition period [10,11]. Consequently, in recent years, considerable attention has been attributed to the development of modified or hybrid two-component adhesives, based on the use of two or more pre-polymers to meet high-performance criteria by combining best properties of individual polymeric counterparts within a joint composite system.…”

Glutathione reactivity with aliphatic polyisocyanates

“…Isocyanate (N = C = O), a reactive chemical group that readily undergoes nucleophilic addition reactions, is essential to numerous industries [1,2]. Isocyanate groups attached to aromatic vs. aliphatic carbon backbones have distinct physical properties that influence their reaction products and industrial use [3][4][5][6]. Aromatic isocyanates primarily are used to produce solid and flexible polyurethane foam [7,8], however, its products are susceptible to damage by ultraviolet radiation and oxidation and are prone to discoloration over time [9].…”