Zip code still a major determinant of lead exposure among kids

Despite years of progress in reducing community lead exposure in the U.S., elevated blood lead levels (BLLs) remain an issue for kids—and children on public insurance and living in more impoverished zip codes with older housing face the greatest risk, researchers found.

In the latter half of the 20th century, one thing became clear: lead has absolutely no biological role in the human body. In fact, any detectable lead level is “abnormal and potentially harmful, particularly in young children; no safe level of exposure to lead for children has been identified,” Marissa Hauptman, MD, MPH, of Boston Children’s Hospital, and colleagues explained in JAMA Pediatrics.

In light of this fact, the U.S. has worked to institute policies aimed at reducing community and individual lead exposure in the general population by removing lead in gasoline, pipes, and paint products. And these measures have seen substantial success, sparing millions of children from the adverse effects of lead exposure, such as IQ loss and behavioral impairment. But disparities in lead exposure have persisted, particularly among immigrant children, lower income families, and children from ethnic and racial minorities.

In order to better understand individual- and community-level risks for elevated BLLs, Hauptman and colleagues conducted a cross-sectional, retrospective analysis of clinical blood lead tests taken from October 2018 through February 2020 in order to examine factors associated with both detectable and elevated lead levels, including insurance type, residence in pre-1950s housing, poverty, age, sex, and geographical region.

Using both mapping techniques and multivariate analyses, the study authors determined that “there is an association between where a child lives and the risk of any lead exposure, an important health issue with long-term outcomes at a population level. Most children evaluated had detectable BLLs. Similar associations were seen with individual- and community-level factors and associations with both detectable and elevated BLLs.”

In adjusted models, Hauptman and colleagues found that “the proportions of children with detectable and elevated BLLs increased significantly among children with public insurance and for progressive quintiles of communities with pre-1950s housing and poverty rates. We did not see consistent associations between lead exposure and elevated BLLs in children residing in zip codes with predominantly Black or Hispanic and Latinx populations. There has been significant progress in reducing lead exposure throughout the country; this study demonstrates, however, that there are still substantial individual- and community-level disparities that have important implications for addressing childhood lead exposure.”

While kids included in the analysis were at higher risk for a detectable BLL if they lived in zip codes with predominantly Black non-Hispanic populations, the association did not hold for elevated blood levels.

“These findings confirm that we still have a long way to go to end childhood lead poisoning in the United States,” Philip J. Landrigan, MD, MSc, of the Global Observatory on Pollution and Health at Boston College, and David Bellinger, PhD, MSc, of the department of Neurology at Harvard University and the Harvard T.H. Chan School of Public Health in Boston, wrote in an editorial accompanying the study. “They reconfirm the unacceptable presence of stark disparities in children’s lead exposure by race, ethnicity, income, and zip code—many of them the cruel legacy of decades of structural racism—a legacy that falls most harshly on the children and families in our society with the fewest resources.”

Landrigan and Bellinger added that there is an “urgent need” to remove sources of lead exposure across the U.S., and the Biden administration’s policy proposal to remove and replace all lead water pipes is a step in the right direction. However, they argued that this action “needs to be complemented by an equally ambitious plan to remove lead paint from all homes across the country. Lead-based paint—and the lead-laden dust that lead paint produces as it wears—remains the predominant source of children’s lead exposure, accounting for the overwhelming majority of detectable and elevated blood lead levels in U.S. children.”

While they acknowledged that such a move would be expensive, they argued that it would be a “cost-effective, one-time investment in the future of the U.S. that prevents disease and neurodevelopmental disability not only in today’s children but in all future generations.”

For their analysis, Hauptman and colleagues assessed de-identified results from blood lead tests for children younger than 6 years old conducted by Quest Diagnostics from Oct. 1, 2018, through Feb. 29, 2020—the threshold for detected BLLs was 1.0 μg/dL, while the threshold for elevated BLLs was 5.0 μg/dL, consistent with the CDC definition of confirmed elevated BLL.

“Participants were 1,141,441 children younger than 6 years living in all 50 US states and the District of Columbia who underwent blood lead testing during the study period,” they wrote. “Children who underwent lead testing of unknown source and those with elevated BLLs who received capillary blood lead testing without confirmatory venous testing were excluded.”

The study authors pulled data on child sex, age, and insurance type. For community-level demographic factors that weren’t available for individual children, such as race and ethnicity, poverty, and pre-1950s housing, they used estimates from the U.S. Census for each zip code and linked them to patient residential data.

The study’s main outcomes were proportions of children with detectable (≥1.0 μg/dL) and elevated (≥5.0 μg/dL) BLLs by exposure category.

“Of the 1,141,441 children (586,703 boys [51.4%]; mean [SD] age, 2.3 [1.4] years) in the study, more than half of the children tested (576,092 [50.5%; 95% CI, 50.4%-50.6%]) had detectable BLLs, and 21,172 children (1.9% [95% CI, 1.8%-1.9%]) had BLLs of 5.0 μg/dL or more,” the study authors wrote. “In multivariable analyses, children with public insurance had greater odds of having detectable BLLs (adjusted odds ratio [AOR], 2.01 [95% CI, 1.99-2.04]) and elevated BLLs (AOR, 1.08 [95% CI, 1.04-1.12]). The proportion of children with detectable and elevated BLLs increased significantly for progressive pre-1950s housing and poverty quintiles (P<0.001).”

They also found:

  • The odds of both detectable and elevated BLLs were significantly higher among children in the highest vs lowest quintile of pre-1950s housing (AOR for detectable BLL, 1.65 [95% CI, 1.62-1.68]; AOR for elevated BLL, 3.06 [95% CI, 2.86-3.27]) and of poverty (AOR for detectable BLL, 1.89 [95% CI, 1.86-1.93]; AOR for elevated BLL, 1.99 [95% CI, 1.88-2.11]).
  • Children residing in zip codes with predominantly Black non-Hispanic and non-Latinx residents had higher odds of detectable BLLs (AOR, 1.13 [95% CI, 1.11-1.15]), but this trend did not hold true for elevated BLLs; in fact, this population faced a lower risk for elevated levels (AOR, 0.83 [95% CI, 0.80-0.88]).

Hauptman and colleagues concluded that the U.S. “must focus efforts to prevent children from being exposed to lead, beginning in areas where risk is highest.” And, they added, the greatest benefit will be achieved by eliminating lead exposures before a child is ever exposed.

Study limitations included potential selection bias among study samples; significant state-level variability in how physicians determine who to test for lead exposure; the use of zip-code data as opposed to individual-level patient data; and the multivariable models “displayed poor overall fit statistics,” according to the study authors.

  1. Despite overall improvement in lead exposure among U.S. children, kids on public insurance and those who live in more impoverished zip codes or in older housing still face a greater risk for lead exposure than the general population, researchers found.

  2. These findings highlight U.S. health disparities and the urgent need for local, state, and federal policy to focus on the removal of sources of lead exposure.

John McKenna, Associate Editor, BreakingMED™

The study was funded by Quest Diagnostics.

Hauptman reported receiving grants from the National Institutes of Health/National Institute of Environmental Health Sciences during the conduct of the study; and grants from the Agency for Toxic Substances and Disease Registry and the U.S. Environmental Protection Agency outside the submitted work. Coauthor Niles reported receiving salary from Quest Diagnostics during the conduct of the study. Coauthor Gudin reported serving as a consultant for Quest Diagnostics during the conduct of the study. Coauthor Kaufman reported receiving salary from and having stock ownership in Quest Diagnostics outside the submitted work.

Bellinger reported receiving personal fees from Grant Riley (attorney) for providing expert testimony and personal fees from Peter Nicoll (attorney) for providing expert testimony outside the submitted work.

Cat ID: 138

Topic ID: 85,138,585,730,138,139,192,149,151,925

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