title: Exogenous and endogenous determinants of blood trihalomethane levels after showering.
abstract: BACKGROUND
  We previously conducted a study to assess whether household exposures to tap water increased an individual's internal dose of trihalomethanes (THMs). Increases in blood THM levels among subjects who showered or bathed were variable, with increased levels tending to cluster in two groups.
  
  
  OBJECTIVE
  Our goal was to assess the importance of personal characteristics, previous exposures, genetic polymorphisms, and environmental exposures in determining THM concentrations in blood after showering.
  
  
  METHODS
  One hundred study participants completed a health symptom questionnaire, a 48-hr food and water consumption diary, and took a 10-min shower in a controlled setting. We examined THM levels in blood samples collected at baseline and 10 and 30 min after the shower. We assessed the significance of personal characteristics, previous exposures to THMs, and specific gene polymorphisms in predicting postshower blood THM concentrations.
  
  
  RESULTS
  We did not observe the clustering of blood THM concentrations observed in our earlier study. We found that environmental THM concentrations were important predictors of blood THM concentrations immediately after showering. For example, the chloroform concentration in the shower stall air was the most important predictor of blood chloroform levels 10 min after the shower (p < 0.001). Personal characteristics, previous exposures to THMs, and specific polymorphisms in CYP2D6 and GSTT1 genes were significant predictors of both baseline and postshowering blood THM concentrations as well as of changes in THM concentrations associated with showering.
  
  
  CONCLUSIONS
  The inclusion of information about individual physiologic characteristics and environmental measurements would be valuable in future studies to assess human health effects from exposures to THMs in tap water.
authors.affiliation: National Center for Environmental Health, Centers for Disease Control and Prevention, Chamblee, GA 30341, USA. lfb9@cdc.gov <lfb9@cdc.gov>
authors.forename: Lorraine C
authors.initials: LC
authors.lastname: Backer
authors.forename: Qing
authors.initials: Q
authors.lastname: Lan
authors.forename: Benjamin C
authors.initials: BC
authors.lastname: Blount
authors.forename: J R
authors.initials: JR
authors.lastname: Nuckols
authors.forename: Robert
authors.initials: R
authors.lastname: Branch
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Lyu
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Kieszak
authors.forename: Marielle C
authors.initials: MC
authors.lastname: Brinkman
authors.forename: Sydney M
authors.initials: SM
authors.lastname: Gordon
authors.forename: W Dana
authors.initials: WD
authors.lastname: Flanders
authors.forename: Marjorie
authors.initials: M
authors.lastname: Romkes
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Cantor
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000097:blood*; D016902:Air Pollution, Indoor / Q000032:analysis; D001494:Baths; D015992:Body Mass Index; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics / Q000378:metabolism; D004784:Environmental Monitoring; D005838:Genotype; D005982:Glutathione Transferase / Q000235:genetics*; D006801:Humans; D011110:Polymorphism, Genetic; D022882:Trihalomethanes / Q000032:analysis / Q000097:blood*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000097:blood*; D014881:Water Supply / Q000032:analysis
chemical_list: D000393:Air Pollutants; D022882:Trihalomethanes; D014874:Water Pollutants, Chemical; D019392:Cytochrome P-450 CYP2E1; D019389:Cytochrome P-450 CYP2D6; C413545:glutathione S-transferase T1; D005982:Glutathione Transferase