Isocyanates are reactive chemicals and thousands of workers may be exposed to
them during their manufacture and use in a wide range of products. They are
classed as sensitizers and are a major cause of occupational asthma in the UK.
Workplace exposure limits are low and control of exposure often depends on
personal respiratory protection. Biological monitoring is increasingly used to
assess exposure and the efficacy of control measures, including the behavioural
aspects of controls. Biological monitoring methods are available for the most
common isocyanates hexamethylene diisocyanate, toluene diisocyanate, isophorone
diisocyanate, and methylenediphenyl diisocyanate. 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. Volunteer and occupational studies show good correlations
between inhalation exposure to isocyanate monomers and isocyanate-derived
diamines in urine or blood. 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'.
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. Non-health-based biological
monitoring guidance values are available to help target when and where further
action is required. 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.

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AplusA-online.de - Source: Annals of Occupational Hygiene