title: The decay of blood lead levels in workers suspended under the control of lead at work regulations.
abstract: OBJECTIVE
  To study the rate of decline in blood lead levels post-suspension under Control of Lead at Work Regulations (CLAW) and thereby suggest sampling frequencies for follow-up blood lead measurements.
  
  
  METHODS
  A retrospective cohort of lead workers with blood lead levels over the current suspension level were identified from blood lead records. Data on their suspension and follow-up blood lead measurements were obtained.
  
  
  RESULTS
  Sixteen per cent of the identified cohort did not appear to return to lead work under CLAW. Twenty-seven suspension cases with an initial mean blood lead of 79 microg/dl (3.82 micromol/l) formed the dataset for analysis of decline in blood lead levels. The mean length of time between the blood sample indicating suspension and the first follow-up blood sample was 32 days. The mean length of suspension under CLAW was 61 days. The mean initial rate of blood lead decay was 0.659 microg/dl per day (0.032 micromol/l per day), although with a wide range. The rate of decline in blood lead after suspension was increased by the blood lead level at suspension, but was decreased by increasing past cumulative exposure.
  
  
  CONCLUSIONS
  A follow-up blood lead sample 1 month after suspension should show a mean decrease between 13 and 26 microg/dl (0.63-1.25 micromol/l), which is substantially greater than that due to analytical 'noise' associated with two sequential measurements (approximately 5 microg/dl). Therefore, a follow-up blood sample taken around 3-4 weeks after suspension would seem practical. A decrease in blood lead of 7-8 mug/dl (0.36 micromol/l) or less in the month after suspension may suggest continuing lead exposure.
authors.affiliation: Broad Lane--Health and Safety Laboratory, Sheffield, UK.
authors.forename: H
authors.initials: H
authors.lastname: Mason
authors.forename: N
authors.initials: N
authors.lastname: Williams
mesh_terms: D000328:Adult; D002617:Chemical Industry; D015331:Cohort Studies; D006801:Humans; D007854:Lead / Q000097:blood* / Q000633:toxicity; D008297:Male; D008403:Mass Screening; D016273:Occupational Exposure / Q000032:analysis*; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D007854:Lead