Isocyanate Urine Testing

Isocyanate urine testing quantifies the urinary diamine generated from hydrolysis of isocyanate-protein adducts. It is the validated approach for verifying MDI, TDI, HDI and IPDI exposure in UK workplaces.

Diamine biomarkers

MDI exposure produces MDA (4,4'-methylene dianiline); TDI produces TDA (toluene diamine, 2,4 and 2,6 isomers); HDI produces HDA (hexamethylene diamine); IPDI produces IPDA (isophorone diamine). Each is measured after acid hydrolysis of urine.

Reference values

HSE BMGVs are 1 µmol/mol creatinine for both MDA and TDA. There is no formal HSE BMGV for HDA or IPDA at present; programmes commonly apply ACGIH BEI guidance or internal action levels derived from a baseline survey.

Programme design

Routine programmes sample twice per year; quarterly when commissioning a new line or after a control failure. End-of-shift sampling on a representative production day captures the relevant exposure window.

Isocyanate Biological Monitoring
MDI Urine Testing
TDI Urine Testing
Spray Painting Biological Monitoring