title: The influence of declining air lead levels on blood lead-air lead slope factors in children.
abstract: BACKGROUND
  It is difficult to discern the proportion of blood lead (PbB) attributable to ambient air lead (PbA), given the multitude of lead (Pb) sources and pathways of exposure. The PbB-PbA relationship has previously been evaluated across populations. This relationship was a central consideration in the 2008 review of the Pb national ambient air quality standards.
  
  
  OBJECTIVE
  The objectives of this study were to evaluate the relationship between PbB and PbA concentrations among children nationwide for recent years and to compare the relationship with those obtained from other studies in the literature.
  
  
  METHODS
  We merged participant-level data for PbB from the National Health and Nutrition Examination Survey (NHANES) III (1988-1994) and NHANES 9908 (1999-2008) with PbA data from the U.S. Environmental Protection Agency. We applied mixed-effects models, and we computed slope factor, d[PbB]/d[PbA] or the change in PbB per unit change in PbA, from the model results to assess the relationship between PbB and PbA.
  
  
  RESULTS
  Comparing the NHANES regression results with those from the literature shows that slope factor increased with decreasing PbA among children 0-11 years of age.
  
  
  CONCLUSIONS
  These findings suggest that a larger relative public health benefit may be derived among children from decreases in PbA at low PbA exposures. Simultaneous declines in Pb from other sources, changes in PbA sampling uncertainties over time largely related to changes in the size distribution of Pb-bearing particulate matter, and limitations regarding sampling size and exposure error may contribute to the variability in slope factor observed across peer-reviewed studies.
authors.affiliation: National Center for Environmental Assessment, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Richmond-Bryant
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Meng
authors.forename: Allen
authors.initials: A
authors.lastname: Davis
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cohen
authors.forename: Shou-En
authors.initials: SE
authors.lastname: Lu
authors.forename: David
authors.initials: D
authors.lastname: Svendsgaard
authors.forename: James S
authors.initials: JS
authors.lastname: Brown
authors.forename: Lauren
authors.initials: L
authors.lastname: Tuttle
authors.forename: Heidi
authors.initials: H
authors.lastname: Hubbard
authors.forename: Joann
authors.initials: J
authors.lastname: Rice
authors.forename: Ellen
authors.initials: E
authors.lastname: Kirrane
authors.forename: Lisa C
authors.initials: LC
authors.lastname: Vinikoor-Imler
authors.forename: Dennis
authors.initials: D
authors.lastname: Kotchmar
authors.forename: Erin P
authors.initials: EP
authors.lastname: Hines
authors.forename: Mary
authors.initials: M
authors.lastname: Ross
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure; D004784:Environmental Monitoring; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007854:Lead / Q000032:analysis* / Q000097:blood*; D009749:Nutrition Surveys; D013997:Time Factors; D014481:United States
chemical_list: D000393:Air Pollutants; D007854:Lead