title: Comparison of urinary thallium levels in non-occupationally exposed people and workers.
abstract: OBJECTIVE
  To determine a reference background urinary thallium level; to compare urinary thallium data from workers to this background level; to investigate factors affecting these levels and whether creatinine correction is appropriate.
  
  
  METHODS
  Urine samples from non-occupationally exposed people (n = 273, from 113 individuals) and workers (n = 896, from 447 individuals) were analysed for thallium by ICP-MS. A reference background level was calculated, defined as the 95th percentile value of a non-occupationally exposed population. Worker data were divided into two subsets: thallium workers (those who work directly with thallium or its compounds) and general workers; and compared to the background level. Bayesian linear mixed effects modelling was used to investigate factors affecting urinary thallium concentration and the efficacy of creatinine correction for the determination of urinary thallium.
  
  
  RESULTS
  The reference background urinary thallium level is 0.27 μmol/mol creatinine (creatinine-corrected) or 0.40 μg/l (uncorrected). Median values were 0.11 μmol/mol creatinine or 0.17 μg/l for non-occupationally exposed people, 0.12 μmol/mol creatinine or 0.20 μg/l for general workers and 0.19 μmol/mol creatinine or 0.41 μg/l for thallium workers. Variation was lower in creatinine-corrected models. Nine per cent of samples from general workers and 39 % of samples from thallium workers exceeded the creatinine-corrected background level. By 2010, 90 % of all workers had urinary thallium levels below the 95th percentile reference background level.
  
  
  CONCLUSIONS
  Urinary thallium concentrations were higher in thallium workers than non-occupationally exposed people and general workers. Creatinine correction is appropriate.
authors: Health and Safety Laboratory, Harpur Hill, Buxton, Derbyshire, SK17 9JN, UK, james.staff@hsl.gsi.gov.uk.
authors: James F
authors: JF
authors: Staff
authors: Richard J
authors: RJ
authors: Cotton
authors: Nicholas D
authors: ND
authors: Warren
authors: Jackie
authors: J
authors: Morton
mesh_terms: D000328:Adult; D000367:Age Factors; D001499:Bayes Theorem; D003404:Creatinine / Q000652:urine*; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D016273:Occupational Exposure / Q000706:statistics & numerical data; D011721:Pyrenes / Q000652:urine*; D012737:Sex Factors; D013793:Thallium / Q000652:urine*; D006113:United Kingdom
chemical_list: D011721:Pyrenes; D013793:Thallium; D003404:Creatinine