BIOLOGICAL MONITORING OF METHYLHEXAHYDROPHTHALIC ANHYDRIDE BY DETERMINATION OF METHYLHEXAHYDROPHTHALIC ACID IN URINE AND PLASMA FROM EXPOSED WORKERS

Objective: To investigate whether methylhexahydrophthalic acid (MHHP a cid) in urine and plasma can be used as a biomarker for exposure to me thylhexahydrophthalic anhydride (MHHPA). Methods: MHHPA in air was sam pled by Amberlite XAD-2 and analysed by gas chromatography (GC) with f lame ionisation detection. MHHP acid in urine and plasma was analysed by GC with mass spectrometric detection. Workers occupationally expose d to MHHPA were studied. Air levels of MHHPA were determined by person al sampling in the breathing zone. Urinary levels of MHHP acid, a meta bolite of MHHPA, were determined in 27 workers. In eight workers all u rine was collected at intervals during 24 h. Plasma levels of MHHP aci d were determined in 20 workers. Results: The time-weighted average (T WA) air levels ranged from 5 to 60 mu g MHHPA/m(3) during 8-h workshif ts. The urinary levels of MHHP acid increased during exposure and deca yed after the end of exposure with an estimated half-life of about 6 h . A correlation was also found between the TWA air levels of MHHPA and creatine-adjusted MHHP acid levels in urine collected during the last 4 h of exposure. A correlation was also seen between the TWA air leve ls of MHHPA and the plasma concentrations of MHHP acid. An exposure to 20 mu g MHHPA/m(3) corresponded to about 140 nmol MHHP acid/mmol crea tinine and about 40 nmol MHHP acid/l plasma. Conclusion: The results i ndicate that MHHP acid in urine or plasma may be used for biological m onitoring of the exposure to MHHPA.