G. Pezzagno et al., Trans,trans-muconic acid, a biological indicator to low levels of environmental benzene: Some aspects of its specificity, AM J IND M, 35(5), 1999, pp. 511-518
Background The specificity of trans, trans-muconic acid (MA) as a biomarker
of exposure to low benzene levels and the role of sorbic acid (SA) as a co
nfounding factor were evaluated. MA, a urinary ring-opened metabolite of be
nzene, has been recently proposed for the biological monitoring of populati
ons exposed to low levels of this chemical. The usual presence of MA in uri
ne of non-occupationally exposed people is generally attributed to benzene
world-wide contamination (mainly by smoking habits, urban pollution, and ma
ybe by food contamination). However; the scientific literature reveals that
the common food preservative and fungistatic agent SA is converted into MA
though in trace amounts.
Methods Urinary benzene and MA before and after administration of SA were m
easured in smokers and non-smokers. Benzene dissolved in urine was analyzed
injecting a headspace sample in a gas-chromatografic system. Urinary MA wa
s measured by means of a HPLC apparatus.
Results The mean background values of MA were about 60 mg/L (or 50 mg/g cre
at.); after experimental admistration of SA (447 mg), the mean urinary MA c
oncentration became more than 20 rimes higher The biotransformation rates o
f SA into MA after ingestion of 447 mg of SA ranged from 0.05 to 0.51%. The
ratio between unmetabolized benzene in the two groups of smokers and non-s
mokers was significantly different from the ratio between MA in the same tw
o groups.
Discussion Other sources of MA excretion, different from benzene, influence
the urinary concentration of the metabolite: only 25% of MA background val
ues can be attributed to benzene. The urinary MA induced by 100 mg of inges
ted MA is 77% of that expected after an 8-hour benzene exposure to 0.5 ppm
(current threshold limit value according to ACGIH). In conclusion, MA is no
t a sufficiently specific biomarker of low benzene exposure; a significant
effect of SA ingestion is predictable. Am. J. Ind. Med. 35:511-518, 1999. (
C) 1999 Wiley-Liss, Inc.