Overview
Diisocyanates such as MDI, TDI and HDI are respiratory and skin sensitizers. Coating application, especially spraying polyurea and polyurethane, has been a focus of US agencies and of EU regulation for decades. This digest summarizes the key documents and studies.
Key findings
- OSHA’s 2013 National Emphasis Program on isocyanates explicitly named spray-on polyurethane coatings for truck beds, trailers, boats, foundations and decks, listed occupational asthma, dermatitis and hypersensitivity pneumonitis among the health effects, and noted skin contact as a route to respiratory sensitization. The program has since been archived.[1]
- A 1996 NIOSH Alert identified TDI, MDI and HDI as the most common diisocyanates and described fatal cases of occupational asthma, plus asthma cases among school staff after isocyanate coatings were applied to a school roof.[2]
- A 2006 NIOSH Alert on spray-on truck bed liners estimated that more than 10,000 US workers were potentially exposed to MDI in that work and presented case reports including a death.[3]
- EU Regulation 2020/1149 restricts professional and industrial use of products with more than 0.1% diisocyanates unless users complete certified training (required from 24 August 2023). Training has general, intermediate and advanced levels, must be renewed at least every five years, and high-energy spraying falls in the advanced level.[4]
- Skin exposure to isocyanates is common, hard to measure and can occur even with PPE; animal studies show skin exposure alone can sensitize, supporting skin protection as a prevention priority.[5]
- A multistakeholder review reported occupational asthma prevalence among exposed workers ranging from under 1% to over 30% in end-user settings such as spray application and foam production.[6]
- In a study of 581 spray painters, respiratory symptoms rose with isocyanate exposure, while specific IgE antibodies were found in only a small fraction of workers, so blood tests miss many symptomatic workers.[7]
What it means in the field
For contractors and specifiersPlural-component polyurea and spray foam are high-exposure tasks under both US guidance and EU law. Specifications should require respiratory protection, full skin protection, controlled spray zones and documented training. See our isocyanate safety guide.
References
- OSHA (2013). National Emphasis Program – Occupational Exposure to Isocyanates. Directive CPL 03-00-017. www.osha.gov/enforcement/directives/cpl-03-00-017
- NIOSH (1996). Preventing Asthma and Death from Diisocyanate Exposure (NIOSH Alert). DHHS (NIOSH) Publication No. 96-111. doi:10.26616/NIOSHPUB96111
- NIOSH (2006). Preventing Asthma and Death from MDI Exposure During Spray-On Truck Bed Liner and Related Applications. DHHS (NIOSH) Publication No. 2006-149. stacks.cdc.gov/view/cdc/11421
- European Commission (2020). Commission Regulation (EU) 2020/1149 amending Annex XVII to REACH as regards diisocyanates. eur-lex.europa.eu/eli/reg/2020/1149/oj
- Bello D, Herrick CA, Smith TJ, et al. (2007). Skin exposure to isocyanates: reasons for concern. Environmental Health Perspectives, 115(3), 328–335. doi:10.1289/ehp.9557
- Lockey JE, Redlich CA, Streicher R, et al. (2015). Isocyanates and human health: multistakeholder information needs and research priorities. Journal of Occupational and Environmental Medicine, 57(1), 44–51. doi:10.1097/JOM.0000000000000278
- Pronk A, Preller L, Raulf-Heimsoth M, et al. (2007). Respiratory symptoms, sensitization, and exposure–response relationships in spray painters exposed to isocyanates. American Journal of Respiratory and Critical Care Medicine, 176, 1090–1097. PMC2176099
Citations were checked against publisher, DOI or agency records. Summaries are paraphrased; read the original papers for full methods and data.