Biological monitoring of isocyanates and related amines. II. Test chamber exposure of humans to 1,6-hexamethylene diisocyanate (HDI).

Five male subjects were exposed to 1,6-hexamethylene diisocyanate (HDI) atmospheres for 7.5 h. The exposures were performed in an 8 m3 stainless steel test chamber, and the HDI atmospheres were generated by a gas-phase permeation method. HDI in air was determined by an HPLC method utilizing the 9-(N-methylaminomethyl)-anthracene reagent, and by a continuous monitoring device (MDA 7100). The average air concentration was ca 25 micrograms/m3, and the inhaled dose of HDI for the different subjects was estimated at ca 100 micrograms. The related amine 1,6-hexamethylene diamine (HDA) was after acid hydrolysis of urine and plasma, determined as a heptafluorobutyric derivative, by glass capillary gas-chromatography and selected ion monitoring (SIM), in a chemical ionization mode using ammonia as reagent gas. The cumulated urinary excretion of HDA during 28 h was 8.0 to 14 micrograms, which corresponds to ca 11 to 21% of the inhaled dose of HDI. The urinary level of HDA, in samples collected immediately after the end of the exposures, was on average 0.02 mmol/mol creatinine (range 0.01-0.03 mmol/mol creatinine). The urinary elimination was rapid, and half-time (t 1/2), for the concentration of HDA in urine, showed an average of 1.2 h (range 1.1-1.4 h). No specific IgE and IgG antibodies to HDI were detected before and after provocation; nor were spirometry or bronchial reactivity changed immediately and 15 h after provocation. Analysis of HDA in hydrolysed urine, as a marker of short-time exposure to HDI, is proposed.