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  • Occupational Allergens (Isocyanate Metabolites in urine e.g. TDI, HDI, MDI, IPDI)



Suitable Specimen Types

  • Plain Spot Urine
20 mL urine collected at end of exposure

Specimen Transport

Send samples by First Class post to arrive within 48 hours of collection if stored unfrozen.

Sample Processing in Laboratory


Sample Preparation

Collect samples in a polystyrene universal container (30mL) for HDI, MDI or IPDI. Sample needs acidification via 0.5g citric acid for TDI analysis. Close container securely to prevent leaks.

Turnaround Time

Not specified

Sample Stability

4 ºC if sample to be sent immediately but store at -20 ºC if any delay is anticipated. Sample is stable for 2 days at ambient temperature but up to 3 months at -20 ºC.

Occupational Allergens (Isocyanate Metabolites in urine e.g. TDI, HDI, MDI, IPDI)

General Information

Organic diisocyanates are a significant occupational health problem. They are respiratory and skin sensitizers and a major cause of occupational asthma in the UK. The most common are hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), isopherone diisocyanate (IPDI) and methylene-diphenyl diisocyanate (MDI) in decreasing order of volatility. HDI and IPDI are used for varnishes, coatings and two-pack spray paints used in motor vehicle repair. TDI and MDI are used for flexible and rigid polyurethane foams, floor coverings and adhesives. This wide range of uses means that there are thousands of workers potentially exposed to isocyanates.

In the UK, a management control system is required for workers exposed to isocyanates and for this to be successful workers should not become sensitized. Apart from occupational asthma, airway irritation and asthma-like symptoms such as cough, wheezing and dyspnoea are commonly reported. Other respiratory effects are hypersensitivity pneumonitis, rhinitis and accelerated rate of decline in lung function. Diisocyanates can also cause both irritant and allergic contact dermatitis as well as skin and conjunctival irritation. Health surveillance that detects occupational asthma is recording failure—there needs to be intervention earlier in the exposure-to-disease paradigm. Although there is evidence that detecting respiratory symptoms early and removing workers from exposure improves prognosis, the goal should be to control exposure to prevent any symptoms.

Several studies show good correlations between isocyanate-derived diamines in urine and airborne concentrations of TDI, HDI and IPDI. Peak excretion occurs at the end of exposure and the initial elimination half-life is ∼2 h for TDI and for HDI and IPDI suggesting end of exposure urine sample collection for biological monitoring of exposure.
Taken from Occupational Medicine, Volume 57, Issue 6, p.391-393

Analytes looked for : Hexamethylene diisocyanate(HDI), Isophorone diisocyanate (IPDI), MDI and Toluene diisocyanate (TDI).

Patient Preparation

Sample should be collected at end of exposure period.


Urinary half life is around 2 hours and results reflect exposure over the previous 2-4 hours.

Reference Range

Provided by Reference Lab.

Unexposed levels < 0.5umol/mol creatinine.


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