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January 2003 • Volume 142 • Number 1

 

 

Editorials
Getting the lead out: Can iron help?

See related article, p 9.

Lead poisons children; extremely high levels can be devastating and may lead to coma and death. Even moderate levels can create a long-term negative effect on a child's neurocognitive development. These facts have been known for decades. Recently, however, research has indicated that lead affects children at much lower levels than was previously thought. Study results have indicated that even levels of 10 µg/dL may be associated with negative neurobehavioral and cognitive effects in children.¹

The good news is that throughout the past 25 years in the United States, lead levels in children have decreased dramatically. Data from the Centers for Disease Control and Prevention's Third National Health and Nutrition Examination Survey (NHANES III), Phase 2 (1991-1994), showed that average blood lead levels in children 5 years old have decreased 80% since the late 1970s.² The 1999 NHANES data show a continuation of that trend, with the geometric mean decreasing from 2.7 µg/dL in NHANES III to 2.0 µg/dL in 1999.³

Although overall blood lead levels in US children have decreased, the problem of lead poisoning remains concentrated in poor minority children and in neighborhoods with older housing. Surveillance data have shown that lower income children residing in older housing have a more than 30-fold greater prevalence of having elevated blood lead levels (EBLLS) than do middle class children in newer housing.⁴ These same subpopulations of children are also at risk for inadequate nutrition (particularly for iron and calcium) that may increase their susceptibility to the harmful effects of lead exposure.

In this issue of The Journal of Pediatrics, Wright et al⁵ present the results of their study to determine if iron deficiency (ID) in a sample of 1275 children is longitudinally associated with EBLLs. Children aged 9 to 42 months were routinely screened for both EBLLs and anemia over a 3-year period in an urban primary care clinic. Children seen for two consecutive visits with simultaneous screening for blood lead and complete blood counts were included in the study, although the children with EBLLs on the first visit were excluded from the analysis. With the use of logistic regression models to control for other factors, the researchers demonstrated a significant association between baseline ID and subsequent EBLLs (adjusted odds ratio [AOR] = 4.12; 95% CI, 1.96-8.65). The results also indicated a significant trend of association with EBLLs when ID status for both clinic visits was used as an ordinal variable, suggesting a combined effect of decreased body iron levels and low dietary intake.

ID is the most common nutritional deficiency in children in the United States.⁶ Data from NHANES III (1988-1994) indicate that 9% of children ages 1 to 2 years were iron-deficient.⁷ Both ID and lead poisoning disproportionately affect the same populations—African American children <5 years old living in urban areas.⁸ Although the link between ID and lead poisoning has been shown in animal models and has been investigated in a number of epidemiologic studies, the results have been inconsistent. Some show a positive association, whereas others show no association.⁹

This is the first published report of a longitudinal association between ID and subsequent EBLLs in young children. Although the study did not evaluate the children's environmental lead exposure, the findings are important because they indicate a substantial risk (AOR = 4.12) for the development of EBLLs in children with preexisting ID. These results, if confirmed in other investigations, could have important ramifications in lead poisoning control programs around the country. Additional research on this issue should include randomized clinical trials with environmental interventions to determine whether providing iron supplements to children will result in a clinically meaningful reduction of their blood lead levels. These studies, of course, would have to be rigorously reviewed to ensure human subject protection of the participants.

Eliminating lead poisoning in children by the end of the decade is a goal of all federal state, and local agencies involved in lead poisoning prevention. Most of the effort has been directed at decreasing exposure to lead sources such as lead-based paint (primary prevention) and the proper care and management of children identified with elevated blood lead levels (secondary prevention). Along with these interventions, the Centers for Disease Control and Prevention has recommended an iron-rich diet for children at risk for lead poisoning. The results of this study provide evidence that ensuring an iron-replete diet may pay an even larger role in the overall public health strategy to eliminate this disease in our children.


 

• Division of Environmental Hazards and Health Effects
  National Center for Environmental Health
  Centers for Disease Control and Prevention
  Atlanta, GA 30333
   
• Reprint requests: Michael A. McGeehin, PhD, MSPH, Division of Environmental Hazards and Health Effects, National Center for Environmental Health, Centers for Disease Control and Prevention, 1600 Clifton Rd, NE, Mail Stop E-19, Atlanta, GA 30333.
   
• J Pediatr 2003;142:3-4.
   
• Copyright © 2003, Mosby, Inc. All rights reserved.
   
• 0022-3476/2003/$30.00 + 0  YMPD10
   
• doi:10.1067/mpd.2003.mpd0310

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