title: Evaluation of exposure biomarkers in offshore workers exposed to low benzene and toluene concentrations.
abstract: OBJECTIVE
  Characterize ethylbenzene and xylene air concentrations, and explore the biological exposure markers (urinary t,t-muconic acid (t,t-MA) and unmetabolized toluene) among petroleum workers offshore. Offshore workers have increased health risks due to simultaneous exposures to several hydrocarbons present in crude oil. We discuss the pooled benzene exposure results from our previous and current studies and possible co-exposure interactions.
  
  
  METHODS
  BTEX air concentrations were measured during three consecutive 12-h work shifts among 10 tank workers, 15 process operators, and 18 controls. Biological samples were collected pre-shift on the first day of study and post-shift on the third day of the study.
  
  
  RESULTS
  The geometric mean exposure over the three work shifts were 0.02 ppm benzene, 0.05 ppm toluene, 0.03 ppm ethylbenzene, and 0.06 ppm xylene. Benzene in air was significantly correlated with unmetabolized benzene in blood (r = 0.69, p < 0.001) and urine (r = 0.64, p < 0.001), but not with urinary t,t-MA (r = 0.27, p = 0.20). Toluene in air was highly correlated with the internal dose of toluene in both blood (r = 0.70, p < 0.001) and urine (r = 0.73, p < 0.001). Co-exposures were present; however, an interaction of metabolism was not likely at these low benzene and toluene exposures.
  
  
  CONCLUSIONS
  Urinary benzene, but not t,t-MA, was a reliable biomarker for benzene at low exposure levels. Urinary toluene was a useful biomarker for toluene exposure. Xylene and ethylbenzene air levels were low. Dermal exposure assessment needs to be performed in future studies among these workers.
authors.affiliation: Institut universitaire romand de Santé au Travail, Lausanne, Switzerland. Nancy.Hopf@hospvd.ch
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Hopf
authors.forename: Jorunn
authors.initials: J
authors.lastname: Kirkeleit
authors.forename: Magne
authors.initials: M
authors.lastname: Bråtveit
authors.forename: Paul
authors.initials: P
authors.lastname: Succop
authors.forename: Glenn
authors.initials: G
authors.lastname: Talaska
authors.forename: Bente E
authors.initials: BE
authors.lastname: Moen
mesh_terms: D000328:Adult; D000388:Air / Q000032:analysis; D000395:Air Pollutants, Occupational / Q000032:analysis*; D001554:Benzene / Q000032:analysis*; D001555:Benzene Derivatives / Q000032:analysis; D015415:Biomarkers / Q000032:analysis; D002617:Chemical Industry; D004784:Environmental Monitoring; D019652:Extraction and Processing Industry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000378:metabolism; D016273:Occupational Exposure / Q000032:analysis*; D010578:Petroleum; D012997:Solvents / Q000032:analysis*; D013011:Sorbic Acid / Q000031:analogs & derivatives / Q000032:analysis; D014050:Toluene / Q000032:analysis*; D014992:Xylenes / Q000032:analysis
chemical_list: D000395:Air Pollutants, Occupational; D001555:Benzene Derivatives; D015415:Biomarkers; D010578:Petroleum; D012997:Solvents; D014992:Xylenes; D014050:Toluene; C005939:muconic acid; D001554:Benzene; C004912:ethylbenzene; D013011:Sorbic Acid