Update of the Blood Lead Reference Value — United States, 2021 Original paper

What was reviewed?

This CDC policy update evaluated the scientific and public health basis for revising the U.S. pediatric blood lead reference value and microbiome-relevant exposure tiers, lowering the blood lead reference value (BLRV) for children aged 1–5 years from 5.0 to 3.5 µg/dL. The BLRV is set at the 97.5th percentile of blood lead levels (BLLs) from the two most recent NHANES cycles (2015–2016 and 2017–2018) and is intended to guide clinical/environmental follow-up and population prioritization; it is not a toxicity threshold. The report details LEPAC’s recommendation, CDC/HHS concurrence, and implementation guidance for laboratories, clinicians, and health departments, including targeted screening and confirmatory venous testing.

Who was reviewed?

The update draws on nationally representative NHANES data for U.S. children aged 1–5 years and summarizes long-term exposure trends and disparities. Geometric mean BLLs in this age group declined from 15.2 µg/dL (1976–1980) to 0.83 µg/dL (2011–2016), yet 2.5% of children still meet or exceed the new 3.5 µg/dL BLRV. Risk remains concentrated among those living in pre-1978 housing, non-Hispanic Black children, Medicaid-enrolled children, and families in higher-poverty areas; sources include paint/dust, contaminated soil, plumbing, and certain consumer products. Universal testing is recommended where local risk-based plans are absent; Medicaid requires testing at 12 and 24 months (or 24–72 months if missed).

Most important findings

Lowering the BLRV to 3.5 µg/dL enables earlier intervention for children previously below action thresholds, with guidance to confirm capillary results via venous sampling, take environmental histories, provide exposure-reduction counseling, and link families to services. The BLRV functions as a population marker to prioritize prevention and evaluate program effectiveness, not as an individually health-based “safe level.” Despite dramatic declines in average BLLs, the report underscores persistent structural inequities: exposure is unevenly distributed and closely tied to older housing, poverty, and race/ethnicity. Laboratory readiness is crucial at this lower action point—programs may need to reduce reporting limits, strengthen contamination controls, validate methods with tighter proficiency criteria, and manage increased repeat/confirmatory testing; importantly, contemporary laboratory methods can accurately quantify BLLs near 3.5 µg/dL.

Key implications

Clinically, adopt the 3.5 µg/dL BLRV to trigger earlier assessment and prevention, confirm via venous draws, and emphasize source elimination, nutrition, and developmental surveillance. Public health should target high-risk neighborhoods for primary prevention and maintain universal testing where risk-based plans are lacking. For microbiome signature curation, align effect-size expectations with today’s low exposure range, stratify by BLRV-anchored tiers, and capture structural risk factors (housing age, Medicaid status, poverty) in metadata.