Blood lead levels, dietary intake, and oxidative stress in lead-exposed Uruguayan children

Open Access
Author:
Roy, Aditi
Graduate Program:
Nutritional Sciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
January 21, 2014
Committee Members:
  • Katarzyna Kordas, Dissertation Advisor
  • Katarzyna Kordas, Committee Chair
  • Shannon Leanne Kelleher, Committee Member
  • Laura E Murray Kolb, Committee Member
  • Jeffrey Maurice Peters, Committee Member
Keywords:
  • Lead exposure
  • blood lead level
  • children
  • Uruguay
  • dietary intake
  • oxidative stress
Abstract:
Lead exposure poses threats to health of millions of children worldwide. Weight of the evidence from experimental and epidemiological studies suggests that low-level lead exposure, a condition currently observed in general population, is associated with various adverse health outcomes in spite of the null findings in some studies. Although, we have a knowledge-base of the health consequences of exposure to lead in children, important questions particularly on the mechanisms of its toxicity, as well as prevention and treatment of lead exposure remain unanswered. Understanding the association between socio-demographic and dietary factors that could affect children’s lead exposure and the relation between lead and oxidative stress, a proposed common mechanism for many lead-induced toxicities, could potentially help in finding effective preventive strategies for exposure and toxicities of low-level lead. This cross-sectional study in 211 children (5-8 years old) from Montevideo, Uruguay identified the potential sociodemographic and household risk factors that can predict children’s blood lead levels (BLLs), a biomarker of lead exposure. The study also examined the relation between dietary intakes of nutrients and BLL, and investigated the association between BLL and two oxidative stress markers (measured as F2- 8α isoprostane or isoprostane, a lipid oxidation marker and 8- hydroxy-2- deoxy Guanosine or 8-OH-dG, a DNA oxidation marker), and tested whether intakes of antioxidants act as effect modifiers. The mean BLL of the study children was 4.7 ± 2.2 μg/dL and 30.2% children had elevated BLL [≥ 5 μg/dL, the current reference level set by Centre for Disease Control for identification and monitoring of children who are exposed to more lead than most children; CDC, 2012]. The most salient socio-demographic and household risk factors for BLL in the study were: father’s smoking, father’s employment in jobs with potential for metal exposure (such as construction, factories, and print shops, and as mechanics or drivers), and the number of young child (< 5 years old) in a household. Among dietary factors, carbohydrate (both as absolute amount and as percentage of energy intake) and fat (as % energy)—were positively associated with children’s BLL. On the other hand, calcium intake was inversely associated with children’s BLL. Majority of the study children did not meet the recommended intake for calcium(800 mg/day). Other nutrients were not associated with BLL and no interactions between pairs of nutrients (iron-zinc, iron-vitamin C or iron-calcium) on BLL were observed. Finally, a weak positive association was found between BLL and the urinary concentrations of isoprostane in the study children, but not between children’s BLL and the concentration of urinary 8-OH-dG. The interactive effects of antioxidants (vitamin C or zinc) with BLL on oxidative stress markers were not statistically significant. This study provides evidence that Uruguayan children continue to be exposed to lead years after the withdrawal of lead from gasoline. Because there is perhaps no safe level for lead and because low-level lead exposure may cause neurodevelopmental deficits and other long-term health problems, lead testing should be made a routine in pediatric practice in Uruguay. School entry is an opportune time for lead screening, if not done previously, since it can be conducted along with other screenings important for school achievement such as hearing and vision. Moreover, the identified socio-demographic and household factors in this study could be used for initiatives to make behavioral and lifestyle changes in children and families and to increase awareness among parents, health-care providers and policy-makers. Educational campaigns regarding prevention of lead exposure may potentially help children and their siblings. Finally, this study provides evidence that could be used to design future long-term studies to answer questions regarding the biological mechanism and the role of nutrition in mitigating exposure and lead toxicities.