June 1, 2022

Children’s lead surveillance in North Carolina may be overlooking nearly 30% of children who are exposed to lead early in life, according to new research led by epidemiologists at UNC-Chapel Hill and the University of Southern California (USC).

Though regulations in the United States have significantly reduced lead in consumer and industrial products, many young children are still vulnerable to lead exposure in contaminated soil, drinking water or goods. This exposure can impact mental and physical development.

State programs often screen children early in life to mitigate lead exposure, but these strategies focus on children who are presumed to be at highest risk of exposure, such as those on Medicaid.

A new study, published today in Environmental Health Perspectives, suggests that there are few reliable predictors of lead exposure in N.C. and that the state’s current high-risk screening practices may fail to identify thousands of children with elevated blood lead levels (EBLLs).

The Centers for Disease Control and Prevention defines a children’s blood lead “reference level” to identify children with blood lead levels higher than 97.5% of children in the U.S. This reference level was recently lowered in October 2021 from five micrograms per deciliter (µg/dL) to 3.5 µg/dL.

Dr. Elizabeth Kamai

Dr. Elizabeth Kamai

“We know that there is no safe level of lead exposure, and even very small amounts of lead – as little as one microgram per deciliter of blood – can impair brain development in kids,” said Elizabeth Kamai, PhD, a postdoctoral research fellow at USC’s Keck School of Medicine and doctoral alumna of the UNC Gillings School of Global Public Health. “Our results show that we are still a long way from eliminating the harmful effects of lead in N.C. kids.”

The research team linked N.C. birth certificate and blood lead testing data with publicly available neighborhood and environmental data to evaluate factors at birth related to blood lead testing levels among young children in 2011-2018. Through modeling, they evaluated the risk of having an EBLL above three µg/dL before 2.5 years of age and estimated the number of children with EBLLs missed by current lead surveillance protocols.

Only 63.5% of children in the study were tested for lead at least once, and those tested did not fully reflect N.C. demographics. Mothers of children who received a blood lead test were more likely to be covered by Medicaid; under 25 years old; Hispanic/Latinx, Black or American Indian; and not have completed college at the time of their child’s birth. They were also more likely to live in rural areas.

When the research team applied their modeling to the data to represent the state more accurately, they found few good predictors of EBLLs. For example, even though mothers covered by Medicaid during pregnancy had 1.35 times the risk of having a child with an EBLL compared to mothers with private insurance (all else being equal), they constitute less than half of those with untested children.

The first step in protecting children from lead is identifying who is at risk, and these results contribute to a broader understanding of inequities in lead exposure. This was the first comprehensive assessment of lead exposure risk in N.C. to include a broad range of well-documented sources of environmental lead exposure. In this study, children of Black mothers were no more likely to have EBLLs than children of white mothers, after accounting for these many environmental sources of lead. Such findings underscore the critical role that environmental injustice plays in these inequities.

“The relatively small proportion of children covered by Medicaid missed by surveillance speaks to the success of Medicaid in N.C.,” Kamai said. “Targeting these children for this service is not perfect, but it has worked for this vulnerable population. Our results show that expanding blood lead screening testing as a universal requirement for all toddlers could benefit thousands of children. This would also align with N.C. Division of Public Health’s recent move to make free blood lead testing available to all pregnant women at local health departments.”

Further research investigating how industrial sources of lead pollution in N.C. impact children’s lead exposure risk is underway.

The study was led by Kamai; Julie Daniels, PhD, professor of maternal and child health and epidemiology at the Gillings School; Paul Delamater, PhD, assistant professor of geography at UNC and fellow at the Carolina Population Center; Bruce Lanphear, MD, MPH, professor of health sciences at Simon Fraser University; Jacqueline MacDonald Gibson, PhD, MS, professor and chair of environmental and occupational health at Indiana University Bloomington; and David Richardson, PhD, MSPH, professor of environmental and occupational health at the University of California, Irvine.

Contact the UNC Gillings School of Global Public Health communications team at sphcomm@unc.edu.

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