Isocyanates

Why test for isocyanate exposure?

Isocyanates are one of the leading causes of occupational asthma in the UK. As respiratory sensitisers, exposures to isocyanates should be kept as low as reasonably practicable and this often requires the use of respiratory protective equipment (RPE). Biological monitoring is a simple and cost-effective way of checking that control measures are working and being used correctly. Our case studies show the utility of using biological monitoring for assessing isocyantate exposures in paint spraying, adhesives and floor screeding applications.

Isocyanates are widely used in industry but have particular application in spray painting, foam and polyurethane manufacture and in adhesives. HSE recommends that vehicle spray painters undertake biological monitoring annually to check that exposure is being adequately controlled. Biological monitoring can be carried out by anyone who understands the principles (see HSE's guidance) but you may find it convenient to arrange annual isocyanate testing as part of your health surveillance (health surveillance is required for workers using isocyanates).

How to sample?

HSE Science and Research Centre offers UKAS-accredited biological monitoring analysis for HDI and IPDI (found in spray paints), TDI (foams and glues) and MDI (resins and hardeners). A urine sample is required and should be taken at the end (within an hour) of a period of potential exposure. Sampling should reflect normal working practice. Urine samples should be collected in bottles containing a citric acid preservative. We provide bottles and packaging as part of the analysis cost.

What to test for?

In order to improve the quality of our data collection, we would like to encourage clients to only request the analysis of the isocyanates actually used by the workers being tested - most only use one or two isocyanates.  A new request form has been developed for isocyanates to help you identify which isocyanates are in use.  We are also willing to look at your safety data sheets if you are unsure which isocyanates you should be monitoring.

What do the results mean?

We have produced guidance on biological monitoring for isocyanates for both employers and employees. HSE scientists will help interpret results from samples that we have analysed where required.  There is also a UK guidance value (BMGV) to aid interpretation.

Your report will contain one of two notes:

• Evidence of exposure to requested isocyanates. Check control measures and training. Refer to HSE guidance regarding re-testing.
• No evidence of exposure to requested isocyanates.  Re-test in one year.

Where results exceed the current guidance value (1 µmol/mol creatinine) we would recommend that re-testing is done shortly after checking the control measures and ways of working.