Lead poisoning remains a significant threat to the health of young children in the United States, based on data from blood tests of more than 1 million children.
Any level of lead is potentially harmful, although blood lead levels have decreased over the past several decades in part because of the elimination of lead from many consumer products, as well as from gas, paint, and plumbing fixtures, wrote Marissa Hauptman, MD, of Boston Children’s Hospital and colleagues.
However, “numerous environmental sources of legacy lead still exist,” and children living in poverty and in older housing in particular remain at increased risk for lead exposure, they noted.
In a study published in JAMA Pediatrics, the researchers analyzed deidentified results from blood lead tests performed at a single clinical laboratory for 1,141,441 children younger than 6 years between Oct. 1, 2018, and Feb. 29, 2020. The mean age of the children was 2.3 years; approximately half were boys.
Overall, 50.5% of the children tested (576,092 children) had detectable blood lead levels (BLLs), defined as 1.0 mcg/dL or higher, and 1.9% (21,172 children) had elevated BLLs, defined as 5.0 mcg/dL or higher.
In multivariate analysis, both detectable BLLs and elevated BLLs were significantly more common among children with public insurance (adjusted odds ratios, 2.01 and 1.08, respectively).
Children in the highest vs. lowest quintile of pre-1950s housing had significantly greater odds of both detectable and elevated BLLs (aOR, 1.65 and aOR, 3.06); those in the highest vs. lowest quintiles of poverty showed similarly increased risk of detectable and elevated BLLs (aOR, 1.89 and aOR, 1.99, respectively; P < .001 for all).
When the data were broken out by ZIP code, children in predominantly Black non-Hispanic and non-Latino neighborhoods were more likely than those living in other ZIP codes to have detectable BLLs (aOR, 1.13), but less likely to have elevated BLLs (aOR, 0.83). States with the highest overall proportions of children with detectable BLLs were Nebraska (83%), Missouri (82%), and Michigan (78%).
The study findings were limited by several factors, especially the potential for selection bias because of the use of a single reference laboratory (Quest Diagnostics), that does not perform all lead testing in the United States, the researchers noted. Other limitations included variability in testing at the state level, and the use of ZIP code–level data to estimate race, ethnicity, housing, and poverty, they said.
However, the results suggest that lead exposure remains a problem in young children, with significant disparities at the individual and community level, and national efforts must focus on further reductions of lead exposure in areas of highest risk, they concluded.
Step up lead elimination efforts
“The removal of lead from gasoline and new paint produced a precipitous decrease in blood lead levels from a population mean of 17 mcg/dL (all ages) in 1976 to 4 mcg/dL in the early 1990s to less than 2 mcg/dL today,” wrote Philip J. Landrigan, MD, of Boston College and David Bellinger, PhD, of Harvard University, Boston, in an accompanying editorial. However, “The findings from this study underscore the urgent need to eliminate all sources of lead exposure from U.S. children’s environments,” and highlight the persistent disparities in children’s lead exposure, they said.
The authors emphasized the need to remove existing lead paint from U.S. homes, as not only the paint itself, but the dust that enters the environment as the pain wears over time, continue to account for most detectable and elevated BLLs in children. A comprehensive lead paint removal effort would be an investment that would protect children now and would protect future generations, they emphasized. They proposed “creating a lead paint removal workforce through federally supported partnerships between city governments and major unions,” that would not only protect children from disease and disability, but could potentially provide jobs and vocational programs that would have a significant impact on communities.
Elevated lead levels may be underreported
In fact, the situation of children’s lead exposure in the United States may be more severe than indicated by the study findings, given the variation in testing at the state and local levels, said Karalyn Kinsella, MD, a pediatrician in private practice in Cheshire, Conn.
“There are no available lead test kits in our offices, so I do worry that many elevated lead levels will be missed,” she said.
“The recent case of elevated lead levels in drinking water in Flint, Michigan, was largely detected through pediatric clinic screening and showed that elevated lead levels may remain a major issue in some communities,” said Tim Joos, MD, a clinician in combined internal medicine/pediatrics in Seattle, Wash., in an interview.
“It is important to highlight to what extent baseline and point-source lead contamination still exists, monitor progress towards lowering levels, and identify communities at high risk,” Dr. Joos emphasized. “The exact prevalence of elevated lead levels among the general pediatric populations is hard to estimate from this study because of the methodology, which looked at demographic characteristics of the subset of the pediatric population that had venous samples sent to Quest Lab,” he noted.
“As the authors pointed out, it is hard to know what biases went into deciding whether to screen or not, and whether these were confirmatory tests for elevated point of care testing done earlier in the clinic,” said Dr. Joos. “Nonetheless, it does point to the role of poverty and pre-1950s housing in elevated blood lead levels,” he added. “The study also highlights that, as the CDC considers lowering the level for what is considered an ‘elevated blood lead level’ from 5.0 to perhaps 3.5 mcg/dL, we still have a lot more work to do,” he said.
The study was funded by Quest Diagnostics and the company provided salaries to several coauthors during the study. Dr. Hauptmann disclosed support from the National Institutes of Health/National Institute of Environmental Health Sciences during the current study and support from the Agency for Toxic Substances and Disease Registry and the U.S. Environmental Protection Agency unrelated to the current study. Dr. Landrigan had no financial conflicts to disclose. Dr. Bellinger disclosed fees from attorneys for testimony in cases unrelated to the editorial. Dr. Kinsella had no financial conflicts to disclose, but serves on the Editorial Advisory Board of Pediatric News. Dr. Joos had no financial conflicts to disclose, but serves on the Pediatric News Editorial Advisory Board.