Blood lead levels among children aged 6-30 months: An electronic health record-based study in Southern California,...

Lead exposure can cause long-term developmental deficits in children. We examined associations between sociodemographic characteristics and blood lead testing and levels in Southern California, where environmental lead hazards might exacerbate blood lead risk.

We conducted a population-based analysis using repeated annual observations among Kaiser Permanente Southern California (KPSC) members aged 6-30 months from January 1, 2016-September 30, 2025 (with 2025 observations available through September only) to assess trends over time. Measured exposures included individual- and neighborhood-level sociodemographic characteristics. Outcomes included receipt of blood lead testing and blood lead levels (BLLs) ≥3.5 μg/dL. Modified Poisson regression with generalized estimating equations was used to estimate adjusted prevalence ratios (aPRs), accounting for age, sex, race and ethnicity, county, Medi-Cal status, neighborhood deprivation index (NDI), and year.

Among 923,144 KPSC annual records from 529,869 unique children, testing was relatively stable over time, with a modest ∼1% annual decline (aPR, 0.99; 95% CI: 0.98-0.99). Testing was more common among Medi-Cal recipients and children residing in higher NDI quartiles. Among 324,291 total tests (277,361 unique children), 0.7% of tests had BLLs ≥3.5 μg/dL (n = 2,134), and prevalence declined over time (aPR, 0.91; 95% CI: 0.88-0.94). BLLs ≥3.5 μg/dL were lower among Hispanic children compared with non-Hispanic White children, with variation observed by Medi-Cal status and NDI.

Blood lead testing rates changed little over time, whereas BLLs ≥3.5 μg/dL declined. However, differences in BLL ≥3.5 μg/dL persisted across sociodemographic groups, and a clinically important number of children continued to have elevated levels. Ongoing strategic prevention efforts remain important to reduce childhood lead exposure in Southern California.