title: Using urinary biomarkers to elucidate dose-related patterns of human benzene metabolism.
abstract: Although the toxicity of benzene has been linked to its metabolism, the dose-related production of metabolites is not well understood in humans, particularly at low levels of exposure. We investigated unmetabolized benzene in urine (UBz) and all major urinary metabolites [phenol (PH), E,E-muconic acid (MA), hydroquinone (HQ) and catechol (CA)] as well as the minor metabolite, S-phenylmercapturic acid (SPMA), in 250 benzene-exposed workers and 139 control workers in Tianjin, China. Median levels of benzene exposure were approximately 1.2 p.p.m. for exposed workers (interquartile range: 0.53-3.34 p.p.m.) and 0.004 p.p.m. for control workers (interquartile range: 0.002-0.007 p.p.m.). (Exposures of control workers to benzene were predicted from levels of benzene in their urine.) Metabolite production was investigated among groups of 30 workers aggregated by their benzene exposures. We found that the urine concentration of each metabolite was consistently elevated when the group's median benzene exposure was at or above the following air concentrations: 0.2 p.p.m. for MA and SPMA, 0.5 p.p.m. for PH and HQ, and 2 p.p.m. for CA. Dose-related production of the four major metabolites and total metabolites (micromol/l/p.p.m. benzene) declined between 2.5 and 26-fold as group median benzene exposures increased between 0.027 and 15.4 p.p.m. Reductions in metabolite production were most pronounced for CA and PH<1 p.p.m., indicating that metabolism favored production of the toxic metabolites, HQ and MA, at low exposures.
authors.affiliation: School of Public Health, University of North Carolina, Chapel Hill, NC 27599, and National Cancer Institute (NCI), National Institutes of Health (NIH), Department of Health and Human Services (DHHS), Bethesda, MD 20892, USA.
authors.forename: Sungkyoon
authors.initials: S
authors.lastname: Kim
authors.forename: Roel
authors.initials: R
authors.lastname: Vermeulen
authors.forename: Suramya
authors.initials: S
authors.lastname: Waidyanatha
authors.forename: Brent A
authors.initials: BA
authors.lastname: Johnson
authors.forename: Qing
authors.initials: Q
authors.lastname: Lan
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Rothman
authors.forename: Martyn T
authors.initials: MT
authors.lastname: Smith
authors.forename: Luoping
authors.initials: L
authors.lastname: Zhang
authors.forename: Guilan
authors.initials: G
authors.lastname: Li
authors.forename: Min
authors.initials: M
authors.lastname: Shen
authors.forename: Songnian
authors.initials: S
authors.lastname: Yin
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Rappaport
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000652:urine; D000293:Adolescent; D000328:Adult; D001554:Benzene / Q000378:metabolism* / Q000633:toxicity; D016022:Case-Control Studies; D002396:Catechols / Q000652:urine; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006873:Hydroquinones / Q000652:urine; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure; D019800:Phenol / Q000652:urine; D013011:Sorbic Acid / Q000031:analogs & derivatives / Q000032:analysis; D016482:Urinalysis
chemical_list: D002396:Catechols; D006873:Hydroquinones; D019800:Phenol; C005939:muconic acid; C053003:S-phenyl-N-acetylcysteine; D001554:Benzene; C034221:catechol; D000111:Acetylcysteine; D013011:Sorbic Acid; C031927:hydroquinone