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September 2004, Vol 94, No. 9 | American Journal of Public Health 1513-1515
© 2004 American Public Health Association

RESEARCH AND PRACTICE

Trends in Blood Lead Levels Among Children Enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children From 1996 to 2000

Kristina M. Zierold, PhD and Henry Anderson, MD

Kristina M. Zierold is with the Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia. Henry Anderson is with the Wisconsin Division of Public Health, Bureau of Environmental Health, Madison.

Correspondence: Requests for reprints should be sent to Kristina M. Zierold, PhD, Department of Environmental Health Sciences, Arnold School of Public Health, 800 Sumter St, University of South Carolina, Columbia, SC 29208 (e-mail: zierold{at}gwm.sc.edu).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 References
 

We analyzed data from the Wisconsin Childhood Lead Poisoning Prevention Program to examine the distribution of and trends in elevated blood lead levels among WIC-enrolled children from 1996 until 2000. Higher blood lead levels were seen among WIC-enrolled children, and although not statistically significant, the rate of blood lead level decline among WIC-enrolled children was greater than among non-WIC-enrolled children.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
METHODS
 RESULTS
 DISCUSSION
 References
 
Elevated blood lead levels are associated with adverse effects in children, such as abnormal cognitive development, behavior problems, decreased intelligence, and poor school performance.1–5 Data from the National Health and Nutrition Examination Survey indicate that the prevalence of blood lead levels of 10 µg/dL or greater in children aged 1 to 5 years has continued to decline from an estimated 88.2% during the 1976 to 1980 National Health and Nutrition Examination Survey II to 2.2% during 1999 to 2000.6

The blood lead level decline represents an environmental public health success story. However, vulnerable populations remain in which lead poisoning continues to present significant public health problems. Unfortunately, the communities in which children are most at risk for elevated blood lead levels are communities that are poor and underserved. In an effort to target blood lead level reduction in children in these vulnerable populations, the Wisconsin Childhood Lead Poisoning Prevention Program has developed a unique partnership with the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) to provide screening for lead as part of the required examination for WIC enrollees.

WIC is a state-based, federally funded program administered by the Food and Nutrition Service of the US Department of Agriculture. WIC provides supplement foods, nutrition education, and heath care referrals to pregnant and postpartum women, their infants, and their children aged younger than 6 years who are income eligible and at nutritional risk. In general, WIC guidelines require that during a free health screening, blood samples be taken, analyzed, and recorded as one method of determining nutritional risk. The Wisconsin Childhood Lead Poisoning Prevention Program and WIC determined that such existing blood sampling provides a perfect opportunity to expand blood testing to include collection for lead testing.

The objective of this study was to examine the distribution of and trends in elevated blood lead levels among WIC-enrolled children from 1996 until 2000, as a measure of success at increasing screening and prevention efforts in this population.


   METHODS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
RESULTS
 DISCUSSION
 References
 
Data for this study came from the Wisconsin Childhood Lead Poisoning Prevention Program comprehensive blood lead surveillance system. There are 26 laboratories that perform blood lead level analysis for Wisconsin health care providers. In cooperation with the laboratories, the Wisconsin Childhood Lead Poisoning Prevention Program has maintained a database of blood lead level test results, housing interventions, and descriptive characteristics of all children aged younger than 6 years tested throughout the state of Wisconsin.

Any WIC-enrolled child aged younger than 6 years screened with a venous blood test during 1996 through 2000 was included in the study (n = 52 407). As a comparison, all other children aged younger than 6 years screened with a venous blood test during 1996 through 2000 but not enrolled in WIC were included (n = 58 789).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
DISCUSSION
 References
 
Table 1Go shows the blood lead levels of WIC-enrolled and non-WIC-enrolled children during 1996 to 2000. For both groups of children, blood lead levels declined over the time period. Figure 1Go shows the mean blood lead levels of WIC-enrolled and non-WIC-enrolled children from 1996 to 2000. In 1996, the mean blood lead level of WIC-enrolled children was 7.89 µg/dL (SD = 6.10), whereas in 2000, the mean blood lead level of WIC-enrolled children was 5.29 µg/dL (SD = 4.54). WIC-enrolled children had an average blood lead level decline of 0.64 µg/dL (95% confidence interval [CI] = 0.36, 0.91) per year.


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  		TABLE 1— Comparison of Blood Lead Levels in WIC-Enrolled and Non-WIC-Enrolled Children, 1996–2000
 


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  		FIGURE 1— Mean blood lead levels in children enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) and non-WIC-enrolled children, 1996–2000.

 
The non-WIC-enrolled children had a mean blood lead level in 1996 of 5.51 µg/dL (SD = 4.79), whereas in 2000, the mean blood lead level of non-WIC-enrolled children was 3.70 µg/dL (SD = 3.39). Children not enrolled in WIC had an average blood lead level decline of 0.42 µg/dL (95% CI = 0.19, 0.64) per year.

Although the WIC-enrolled children’s blood lead levels declined more quickly during 1996 to 2000, the difference between the slopes of the WIC-enrolled and non-WIC-enrolled children was not statistically significant (P = .25).

To further evaluate the blood lead level decline in the WIC-enrolled children, the data were stratified by race/ethnicity and are shown in Figure 2Go. WIC-enrolled Black children had an average blood lead level decline of 0.70 µg/dL per year (95% CI = 0.41, 1.00), Hispanic children had an average blood lead level decline of 0.36 µg/dL per year (95% CI = 0.14, 0.59), and White children had an average blood lead level decline of 0.28 µg/dL per year (95% CI = 0.20, 0.37). Black children had a significantly quicker decline compared with White children (P = .03).



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  		FIGURE 2— Comparison of blood lead level decline among children enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children, 1996–2000.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
References
 
The data provided in this study support the notion that WIC-enrolled children are at a greater risk for elevated blood lead levels than are others. During the study period, the mean blood lead level of WIC-enrolled children was at least 2 µg/dL greater than the mean blood lead level of the other children.

Initially, the Wisconsin Childhood Lead Poisoning Prevention Program worked with WIC as a convenient access point to promote child blood lead testing because WIC participants had a high-risk profile (low income, poor nutritional status). However, after evaluating the data, we noticed that the blood lead levels in the WIC-enrolled children seemed to be declining more quickly than in the other children. The blood lead level decline among the WIC-enrolled children was greater than that among the non-WIC-enrolled children (0.64 µg/dL per year vs 0.42 µg/dL per year).

WIC-enrolled children have shown a quicker blood lead level decline for several reasons: (1) some WIC programs provide information and clinical follow-up; (2) the dietary supplements and management of anemia reduce lead absorption; and (3) WIC qualifications standards have changed; thus, "higher-income" individuals are eligible, even though they may not have a "high-risk" profile.

The major limitation of the study was that we could not identify the racial/ethnic distribution of the non-WIC-enrolled children. Although race has never been identified as a risk factor for blood lead poisoning, it is a surrogate of low income, poor housing, and so forth, which are risk factors for blood lead poisoning. We do know that the racial profile of the WIC-enrolled children changed dramatically during 1996 to 2000. In 1996, more than half (53%) of the WIC-enrolled children were Black, but by 2000, the racial demographics had changed to one-third Black children and 57% White or Hispanic children.

Programs like WIC are in an excellent position to identify children with elevated blood lead levels. Most childhood lead poisoning is asymptomatic, so blood lead screening in children is an inexpensive and effective method for early detection of lead poisoning. WIC programs, which include blood collection as part of a health examination, should be encouraged to provide blood lead testing to help identify children with elevated blood lead levels. Our observation of a more rapid blood lead level decline in the WIC population deserves further investigation to determine whether the dietary supplements, treatment of irondeficiency anemia, and frequent contact with a health professional may contribute and are an unanticipated benefit of partnering with WIC.


   Acknowledgments
 
The authors would like to acknowledge the assistance of Jeff Havlena and members of the Wisconsin Childhood Lead Poisoning Prevention Program.

Human Participant Protection
No protocol approval was needed for this study.


   Footnotes
 
Contributors
K. M. Zierold conducted the analyses and led the writing of the brief. H. Anderson assisted with the study and the analysis. Both authors helped to conceptualize ideas and interpret findings and reviewed and edited drafts of the brief.

Peer Reviewed

Accepted for publication January 12, 2004.


   References
TOP
 ABSTRACT
 INTRODUCTION
 METHODS
 RESULTS
 DISCUSSION
 References
 
1. Baghurst PA, McMichel AJ, Wigg NR, et al. Environmental exposure to lead and children’s intelligence at the age of seven years: the Port Pirie Cohort Study. N Engl J Med. 1992;327:1279–1284.[Abstract]

2. Fraust D, Brown J. Moderately elevated blood lead levels: effects on neurophysiologic functioning in children. Pediatrics. 1987;80:623–629.[Abstract/Free Full Text]

3. Bellinger DC, Stiles KM, Needleman HL. Low level lead exposure, intelligence and academic achievement: a long-term follow-up study. Pediatrics. 1992;90:855–861.[Abstract/Free Full Text]

4. Bellinger DC, Leviton A, Waternaux C, et al. Longitudinal analysis of prenatal and postnatal lead exposure and cognitive development. N Engl J Med. 1987;316:1037–1043.[Abstract]

5. Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations, Report of the Committee on Measuring Lead in Critical Populations, Board of Environmental Studies and Toxicology, Commission of Life Sciences, National Academy of Sciences. Washington, DC: National Academy Press; 1993.

6. Meyer PA, Pivetz T, Dignam TA, Homa DM, Schoonover J, Brody D. Surveillance for elevated blood lead levels among children—United States, 1997–2001. MMWR Surveill Summ. 2003;52:1–21.[Medline]




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