Elsevier

Annals of Epidemiology

Volume 23, Issue 11, November 2013, Pages 700-707
Annals of Epidemiology

Moderate lead exposure and elementary school end-of-grade examination performance

https://doi.org/10.1016/j.annepidem.2013.08.007Get rights and content

Abstract

Purpose

This study investigated the association between moderate lead poisoning in early childhood with performance on a comprehensive set of end-of-grade examinations at the elementary school level in two urban school districts.

Methods

Children born between 1996 and 2000 who resided in Milwaukee or Racine, WI, with a record of a blood lead test before the age of 3 years were considered for the analysis. Children were defined as exposed (blood lead level ≥10 and <20 μg/dL) or not exposed (BLL < 5 μg/dL). Parents of eligible children were mailed surveys to consent to participation and elicit information on potential confounders. On consent, children were matched to educational records for fourth grade Wisconsin Knowledge and Concepts Examinations. Seemingly unrelated regression was used to evaluate the relation between scaled scores on all sections of the examination (math, reading, language arts, science, and social studies) with exposure status, controlling for demographics, social status indicators, health indicators, and district-based poverty indicators.

Results

A total of 1133 families responded to the survey and consented to have educational records released; 43% of children were considered exposed. After controlling for demographic and socioeconomic covariates, lead exposure was associated with significantly lower scores in all sections of the Wisconsin Knowledge and Concepts Examinations (range: science, β = −5.21, P = .01; reading, β = −8.91, P = .003). Children who were black, had a parent with less than a high-school education, and were classified by parents as having less than excellent health had significantly lower performance on all examination components.

Conclusions

Children with moderate lead poisoning in early childhood performed significantly lower on all components of elementary school end-of-grade examinations compared with unexposed children. Household level social status and childhood health indicators partially explain decreased examination scores.

Introduction

The ban on lead additives from gasoline and household paint in the United States has resulted in a dramatic decrease in childhood lead exposure [1], [2], [3]. Due to the durability and persistence of lead in the environment, children's exposure to lead continues. Various studies have demonstrated consistently that children who are black, in low-income families, and reside in older housing are at risk for elevated blood lead levels (eBLL) [4], [5], [6]. Although lead exposure is a public health concern in both urban and rural communities [7], the population density in urban communities and the absolute number of children exposed contribute to the conceptualization of lead exposure as a primary urban environmental health issue.

More than four decades ago, the cognitive effects of early life exposure to low doses of lead were established [8]. The preponderance of the data that link lead exposure to declines in cognitive performance has been established largely through intelligence quotient (IQ) testing [9], [10], [11], [12], [13]. Although informative from an etiologic perspective, the implications of cognitive deficits as measured by IQ testing may have limited relevance in contextual settings, particularly related to educational performance and outcomes [14]. Standardized testing, including statewide end-of-grade (EOG) examinations, may be an informative metric to measure the impact of early childhood lead exposure. Performance on these tests determines educational advancement and placement decisions for students and has implications for meeting federal No Child Left Behind standards [15]. Furthermore, performance on these examinations has been associated with life-course events that directly or indirectly impact health status such as future educational achievement [16], high-school dropout [17], delinquency [18], future employment and wages [19], and mortality [20]. Although myriad factors both intrinsic and extrinsic to the school environment have been associated with poor scholastic outcomes in urban school districts, recent studies have suggested that lead exposure may partially explain low performance on EOG testing in affected communities [21], [22], [23], [24], [25].

Studies that have investigated the relation between early childhood lead exposure and performance on EOG examinations have relied solely on administrative data. Large studies are possible through the use of data repositories from school districts; however, the lack of additional information on individual- and household-level covariates may result in unmeasured confounding and may bias current estimates of effects. Of particular concern are measures that reflect household structure, socioeconomic status (SES), comorbidities, ongoing exposure to lead, or additional environmental exposures associated with cognitive effects [26]. Some of these covariates may be available through administrative data, such as eligibility for the National School Lunch Program, but direct surveillance of families of children who were tested for lead in early childhood may provide more comprehensive information on covariates that mediate, moderate, or confound the effect of lead exposure on school performance. Furthermore, studies that collect comprehensive contextual information may elucidate mechanisms through which lead exposure may impact educational performance, may identify other indicators that distinguish subgroups at risk of lead exposure and low educational performance, and may indicate possible domains for improved interventions. Thus, the objective was to estimate the effect of moderate lead exposure in early childhood on EOG examinations taken at the elementary school level in two urban school districts.

Section snippets

Human subjects

The protocol for this study was approved by the University of Wisconsin-Madison Education Research Institutional Review Board. All parents or guardians signed informed consent forms before participation.

Study population

Milwaukee Public Schools (MPS) and the Racine Unified School District (RUSD) are the first and fourth largest school districts in Wisconsin, respectively, and have been identified as high-risk communities by the Wisconsin Childhood Lead Poisoning Prevention Program (WCLPPP) [27].

Academic performance

The Wisconsin

Results

A total of 7395 children who met our criteria with DPI records of fourth grade WKCE completion were identified with the initial match of BLL records listed in the WCLPPP database. From the various efforts at locating study participants, study staff obtained addresses for 4545 (61%) of the original eligible population. Of these eligible children with current contact information, 1133 (25%) had parents or guardians return their signed consent forms and completed surveys. Of these children, 57% (n

Discussion

Data from two urban school districts in Wisconsin lend further support to the evidence of deleterious effects of lead exposure in early childhood on elementary school performance. We found that children with BLLs that were measured in early childhood to be between 10 and 20 μg/dL had significantly lower scores on the fourth grade EOG examinations than those with BLL less than 5 μg/dL. The mean differences in scores were statistically significant and ranged by subject from 5.2 to 8.9 points. In

Acknowledgments

We are grateful to Margie Coons of the Wisconsin Department of Health Services, Amy Murphy, and Rod Packard of the Wisconsin Department of Public Instruction, the University of Wisconsin Survey Center, and the administration of the Racine Unified School District for their invaluable assistance with this project. We would like to thank an anonymous reviewer for insightful comments that resulted in an improved manuscript. We are indebted to the families of the Milwaukee Public Schools and the

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