| Reduction of Elevated Blood Lead Levels in Children in North Carolina and Vermont, 1996–1999 Timothy A. Dignam,1 Jose Lojo,2 Pamela A. Meyer,1 Ed Norman,3 Amy Sayre,4 and W. Dana Flanders2 1Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Emergency and Environmental Health Services, Lead Poisoning Prevention Branch, Atlanta, Georgia, USA; 2Rollins School of Public Health, Emory University, Atlanta, Georgia, USA; 3North Carolina Division of Environmental Health, Raleigh, North Carolina, USA; 4Vermont Childhood Lead Poisoning Prevention Program, Vermont Department of Health, Burlington, Vermont, USA Abstract
Background: Few studies have examined factors related to the time required for children's blood lead levels (BLLs) ≥ 10 µg/dL to decline to < 10 µg/dL. Objectives: We used routinely collected surveillance data to determine the length of time and risk factors associated with reducing elevated BLLs in children below the level of concern of 10 µg/dL. Methods: From the North Carolina and Vermont state surveillance databases, we identified a retrospective cohort of 996 children < 6 years of age whose first two blood lead tests produced levels ≥ 10 µg/dL during 1996–1999. Data were stratified into five categories of qualifying BLLs and analyzed using Cox regression. Survival curves were used to describe the time until BLLs declined below the level of concern. We compared three different analytic methods to account for children lost to follow-up. Results: On average, it required slightly more than 1 year (382 days) for a child's BLL to decline to < 10 µg/dL, with the highest BLLs taking even longer. The BLLs of black children [hazard ratio (HR) = 0.84 ; 95% confidence interval (CI) , 0.71–0.99], males (HRmale = 0.83 ; 95% CI, 0.71–0.98) , and children from rural areas (HRrural = 0.83 ; 95% CI, 0.70–0.97) took longer to fall below 10 µg/dL than those of other children, after controlling for qualifying BLL and other covariates. Sensitivity analysis demonstrated that including censored children estimated a longer time for BLL reduction than when using linear interpolation or when excluding censored children. Conclusion: Children with high confirmatory BLLs, black children, males, and children from rural areas may need additional attention during case management to expedite their BLL reduction time to < 10 µg/dL. Analytic methods that do not account for loss to follow-up may underestimate the time it takes for BLLs to fall below the recommended target level. Key words: blood lead level, capillary, chelation, children, surveillance, venous. Environ Health Perspect 116:981–985 (2008) . doi:10.1289/ehp.10548 available via http://dx.doi.org/ [Online 5 March 2008]
Address correspondence to T. Dignam, Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Emergency and Environmental Health Services, Lead Poisoning Prevention Branch, 4770 Buford Hwy., Mailstop F-60, Atlanta, GA 30341 USA. Telephone: (770) 488-3622. Fax: (770) 488-3635. E-mail: tdignam@cdc.gov We thank T. Matte for his contribution to study design and M.J. Brown for her assistance with interpretation of results and review of the manuscript. No grant money was used to fund this project. Staff time at the Centers for Disease Control and Prevention was used to analyze routinely collected surveillance data. The authors declare they have no competing financial interests. Received 11 June 2007 ; accepted 5 March 2008.
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