Trans,trans-muconic acid in urine samples collected in three periods from benzene handling workers in a Brazilian refinery

Abstract

Trans,trans-Muconic Acid (ttMA), a benzene metabolite, has been recommended as a sensitive bioindicator in the biological monitoring of workers exposed to benzene. In the present study we aimed to evaluate the best urine collecting time for ttMA analysis. This bioindicator was determined in workers who handle benzene once a week and the samples were collected in three periods: pre-shift (individual background levels), post-shift and in the day after, in the morning. ttMA was analysed by a high pressure liquid chromatography (HPLC) in a reverse-phase column LiChrosorb RP 18 and UV detection, after extraction in Dowex 1® resin (strongly basic anion). In occupationally exposed workers, ttMA values were significantly higher in post-shift samples (p=0.025) than in the pre-shift samples or those collected the following day. The results show that the end of the shift is the best period to take urine samples in benzene biomonitoring when analysing ttMA. Tobacco use and ingestion of foods containing sorbic acid did not show significant influence on urinary ttMA levels, but alcohol intake diminished significantly the excretion of this bioindicator in post-shift samples.