UKAS accredited isocyanate analysis

Isocyanates, as a chemical group, are one of the leading causes of occupational asthma in the UK. Exposures to isocyanates should be kept as low as reasonably practicable.

Human exposure to isocyanate compounds is typically by inhalation and dermal contact, they can have adverse health effects including irritation (skin, eyes, gastrointestinal and respiratory tracts).

By carrying out regular monitoring you can help ensure employees are protected whilst at work.

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, construction industry and the manufacture of 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 uses in the construction industry are in floor paints, floor screeds, flooring adhesives as well as in expanding foams, mastics and rapid bonding adhesives used across the various trades.

RPS workplace services

Exposure limits

The Health and Safety Executive (HSE) has assigned exposure values [see article], to help ensure employers follow the guidance set out in The Control of Substances Hazardous to Health 2002 (COSHH) Regulations to establish the exposure to employees from both inhalation and total exposure to isocyanates, which also includes exposure via other routes i.e. ingestion and absorption using biological monitoring.

Isocyanates have a Workplace Exposure Limit (WEL) assigned at 0.02mg/m3 8hr TWA / 0.07mg/m3 STEL and a Biological Monitoring Guidance Value of 1µmol isocyanate derived diamine /mol creatinine.

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 UKAS accredited rapid GC-MS method for the determination of all five isocyanate derived diamines (isocyanate metabolites) to meet the Biological Monitoring Guidance Values (BMGV) as follows:

  • 1 μmol 2,4 Diaminotoluene 2,4-TDA  (2,4-TDI Biomarker) /mol of creatinine
  • 1 μmol 2,6 Diaminotoluene 2,6-TDA (2,6-TDI Biomarker) /mol of creatinine
  • 1 μmol Hexamethylenediamine HDA (1,6-HDI Biomarker) /mol of creatinine
  • 1 μmol 5-Amino-1,3,3-trimethylcyclohexanemethylamine IPDA (IPDI Biomarker) /mol of creatinine
  • 1 μmol 4,4 Diaminodiphenylmethane MDA (MDI Biomarker) /mol of creatinine

Air sampling

In accordance with HSE recommendations, we offer analysis in line with MDHS 25. Analysis is undertaken using HPLC instrumentation, our limit of detection for MDI, HDI, TDI and IPDI is 0.2µg; this means our clients can monitor their employees exposure with confidence knowing that their results will be meaningful when compared against EH40 values for both 8hr TWA and 15-min STEL. 

 Our air sampling service includes:

  • Supply of sampling media (filters and impingers)
  • Fully tracked delivery service (requirement of Home Office and BOHS)
  • Sampling equipment hire
  • Confidential UKAS accredited analysis


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 / impinger solution
  • 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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