title: The influence of urinary flow rate on mercury excretion in children.
abstract: METHODS
  There is limited literature concerning the effect of urinary flow rate on mercury excretion at low-level exposure. The aim of the present study is to examine the influence of urinary flow rate on mercury excretion in children. Also of interest is the influence of flow rate on creatinine excretion and creatinine-corrected mercury, which arisearises with spot urine samples.
  
  
  METHODS
  A substudy of the New England Children's Amalgam Trial collected pairs of urine samples from children aged 10-16 years: a timed overnight collection and a spot daytime sample collected the following day. These samples were analyzed for mercury and creatinine concentration. Regression analysis was used to model the effect of urinary flow rate in the timed overnight samples. A paired t-test compared concentrations and creatinine-corrected mercury between overnight and daytime samples.
  
  
  RESULTS
  Creatinine excretion rate (mg/h) increased significantly with urinary flow rate (mL/h), whereas creatinine concentration (g/L) decreased with flow rate. We found a non-significant increase in mercury excretion rate (ng/h) with flow rate, and mercury concentration decreased with flow rate. Mercury and creatinine concentrations were significantly higher in the overnight compared to daytime samples. For creatinine-corrected mercury, no significant impact of urinary flow rate was found.
  
  
  CONCLUSIONS
  Although the creatinine excretion rate, and probably the mercury excretion rate, increased with urinary flow rate, the mercury/creatinine ratio seemed relatively unaffected by urinary flow rate.
authors.affiliation: New England Research Institutes, Watertown, MA 02472, USA. ftrachtenberg@neriscience.com
authors.forename: Felicia
authors.initials: F
authors.lastname: Trachtenberg
authors.forename: Lars
authors.initials: L
authors.lastname: Barregård
authors.forename: Sonja
authors.initials: S
authors.lastname: McKinlay
mesh_terms: D000293:Adolescent; D002648:Child; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008628:Mercury / Q000652:urine*; D016273:Occupational Exposure; D014556:Urine / Q000502:physiology
chemical_list: D003404:Creatinine; D008628:Mercury