title: Nephrotoxicity of uranium in drinking water from private drilled wells.
abstract: OBJECTIVE
  To investigate the association between uranium in drinking water from drilled wells and aspects of kidney function measured by sensitive urine tests.
  
  
  METHODS
  Three hundred and one of 398 eligible subjects (75.6%) aged 18-74 years with daily drinking water supplies from private drilled wells located in uranium-rich bedrock (exposed group) volunteered to participate along with 153 of 271 local controls (56.4%) who used municipal water. Participants responded to a questionnaire on their water consumption and general health, and provided a morning urine sample and drinking water for analysis.
  
  
  RESULTS
  The uranium content of well water samples (n=153) varied considerably (range <0.20-470 microg/l, median 6.7 microg/l, 5% >100 microg/l), while uranium levels in all samples of municipal water (n=14) were below the limit of quantification (0.2 microg/l). Urinary levels of uranium were more than eight times higher in exposed subjects than in controls (geometric means 38 and 4.3 ng/l, respectively; p<0.001), but their mean urine lead levels were not significantly different. There was a strong curvilinear correlation between uranium in drinking water and in urine (r2=0.66). Levels of albumin, beta(2)-microglobulin, protein HC as well as kappa and lambda immunoglobulin chains in urine from exposed and controls were similar. The N-acetyl-beta-d-glucosaminidase (NAG) activity was significantly lower in the exposed group vs. controls, possibly secondary to differential storage duration of samples from the two groups. Even in regression models adjusting for gender, age and smoking no association of uranium in water and the kidney function parameters was observed. Using uranium in urine in the entire study group as a marker of exposure, however, a tendency of exposure-related increases of beta(2)-microglobulin, protein HC and kappa chains were noted. This tendency was enhanced after exclusion of subjects with diabetes mellitus from the analysis.
  
  
  CONCLUSIONS
  Uranium levels in urine were strongly correlated to levels in drinking water from drilled wells. There were no clear signs of nephrotoxicity from uranium in drinking water at levels recorded in this study, but some indications of an effect were observed using uranium in urine as a measure of overall uranium exposure. The clinical relevance of these findings remains unclear.
authors.affiliation: Department of Occupational and Environmental Medicine, Orebro University Hospital, Orebro SE-701 85, Sweden. anders.selden@orebroll.se
authors.forename: Anders I
authors.initials: AI
authors.lastname: Seldén
authors.forename: Cecilia
authors.initials: C
authors.lastname: Lundholm
authors.forename: Bror
authors.initials: B
authors.lastname: Edlund
authors.forename: Camilla
authors.initials: C
authors.lastname: Högdahl
authors.forename: Britt-Marie
authors.initials: BM
authors.lastname: Ek
authors.forename: Bernt E
authors.initials: BE
authors.lastname: Bergström
authors.forename: Carl-Göran
authors.initials: CG
authors.lastname: Ohlson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000652:urine; D016022:Case-Control Studies; D004326:Drinking; D004781:Environmental Exposure; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000187:drug effects* / Q000502:physiology; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D011634:Public Health; D013548:Sweden; D014501:Uranium / Q000032:analysis / Q000633:toxicity* / Q000652:urine; D014875:Water Pollutants, Radioactive / Q000032:analysis / Q000633:toxicity* / Q000652:urine; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014875:Water Pollutants, Radioactive; D014501:Uranium