Analysis of Isocyanate Metabolites in Urine

Isocyanates, as a chemical group, are the biggest cause of occupational asthma in the UK. Monitoring of airborne exposures to total isocyanate is costly and cannot assess the effectiveness of protection from exposure. Biological monitoring by analysis of metabolites in urine can be a relatively simple and inexpensive way to assess exposure to isocyanates.

Isocyanate use

Isocyanates are a family of highly reactive, low molecular weight chemicals. They are widely used in the manufacture of flexible and rigid foams, fibres, coatings such as paints and varnishes and are increasingly used in the automobile industry, auto-body repair, and building insulation materials.

Spray-on polyurethane products containing isocyanates have been developed for a wide range of retail, commercial, and industrial uses to protect cement, wood, fibreglass, steel and aluminium, including protective coatings for truck beds, trailers, boats, foundations and decks.

Common Isocyanates

The most commonly used isocyanates include methylenediphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI).

Biological analysis

In humans, isocyanates are rapidly metabolised and excreted in the urine as the corresponding diamine. Thus, biological monitoring using pre and post shift urine samples is a useful tool in determining potential exposure.

In the UK the current Biological Monitoring Guidance Value (BMGV) is set at 1μmol isocyanate-derived diamine/mol creatinine.

You can find the ECHA Biological Monitoring Guidance for diisocyanates here.

RPS offer a rapid GC-MS method for the determination of isocyanate metabolites in to meet the BMGV as follows:

  • 1 umol/mol of creatinine as 2,4-toluene diisocyanate (2,4-TDI) Biomarker
  • 1 umol/mol of creatinine as 2,6-toluene diisocyanate (2,6-TDI) Biomarker
  • 1 umol/mol of creatinine as 1,6-Hexamethylene diisocyanate (1,6-HDI) Biomarker
  • 1 umol/mol of creatinine as Isophorone diisocyanate (IPDI) Biomarker
  • 1 umol/mol of creatinine as 4,4-methylenediphenyl diisocyanate (MDI) Biomarker


For biological monitoring (urine) - Provision of 30ml sample container with stabiliser and prepaid postal return envelope with Category B compliant packaging.

  • For air monitoring – Provision of piperazine treated filters
  • Soil and water – provision of sampling containers

Holding times

  • Urine - 2 days at room temperature and 3 months frozen
  • Filters – 27 days from sampling
  • Soil and water – 7 days refrigerated with no-headspace

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