They react with hydroxyl groups to form a urethane linkage and with substances containing two or more hydroxyl groups like polyols, they form polyurethane polymers that have a wide range of properties and applications. Isocyanates are reactive chemicals with a –N=C=O group. Occupational hygienists will need to use their knowledge and experience to determine the relative contributions of different routes of exposure and how controls can be improved to reduced the risk of ill health.Īsthma, biological monitoring, dermal exposure, exposure assessment, isocyanates, urine analysis Non-health-based biological monitoring guidance values are available to help target when and where further action is required. Nevertheless, there is a substantial body of work demonstrating the utility of biological monitoring as a tool to assess exposure and the efficacy of controls, including how they are used in practice. However, occupational exposure to isocyanates is often to a mixture of monomers and oligomers so there is some uncertainty comparing biological monitoring results with airborne exposure to ‘total NCO’. Volunteer and occupational studies show good correlations between inhalation exposure to isocyanate monomers and isocyanate-derived diamines in urine or blood. They are based on the analysis of hexamethylene diamine, toluene diamine, isopherone diamine, and methylenediamine released after hydrolysis of isocyanate–protein adducts in urine or blood. Biological monitoring methods are available for the most common isocyanates hexamethylene diisocyanate, toluene diisocyanate, isophorone diisocyanate, and methylenediphenyl diisocyanate. Biological monitoring is increasingly used to assess exposure and the efficacy of control measures, including the behavioural aspects of controls. Workplace exposure limits are low and control of exposure often depends on personal respiratory protection. They are classed as sensitizers and are a major cause of occupational asthma in the UK. Isocyanates are reactive chemicals and thousands of workers may be exposed to them during their manufacture and use in a wide range of products.
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