No Safe Blood Lead Level: Reconstructing Childhood Lead Exposure
By Paul E. Rosenfeld, M.S., Ph.D., Principal Environmental Chemist, RoseyFields LLC, Santa Monica, California
A toxicological consensus that has changed the litigation landscape
For decades, regulatory and medical guidance treated blood lead concentration as safe below a specific numeric threshold; the current scientific consensus, reflected in CDC’s blood lead reference value, is that no exposure level has been demonstrated to be without risk of neurodevelopmental harm in children, a shift that has fundamentally changed how childhood lead exposure claims are evaluated (CDC, Blood Lead Reference Value).
The multiple pathways by which children encounter lead
Children can be exposed to lead through deteriorating lead-based paint dust and chips, contaminated residential soil, lead service lines and plumbing fixtures in drinking water, and, in some communities, legacy industrial emissions that deposited lead in soil decades before litigation began, meaning a rigorous exposure assessment must identify which specific pathway or combination of pathways applies to a given child’s residence.
EPA’s biokinetic modeling approach for childhood lead exposure
EPA’s Integrated Exposure Uptake Biokinetic (IEUBK) Model is the standard regulatory tool for estimating a child’s blood lead concentration from combined soil, dust, water, and air lead exposure, incorporating age-specific physiological parameters that reflect children’s greater gastrointestinal lead absorption and hand-to-mouth soil ingestion behavior compared to adults (US EPA, IEUBK Model Guidance).
Why residential soil lead concentration alone is not the whole story
A given soil lead concentration does not translate uniformly into a given blood lead level; bioavailability, meaning the fraction of ingested lead actually absorbed into the bloodstream, varies with soil chemistry and particle size, making site-specific bioavailability data, where available, an important refinement over default assumptions in a rigorous exposure reconstruction.
The regulatory soil and dust benchmarks
EPA’s current residential soil lead hazard standards and dust-lead hazard standards, tightened substantially in 2021 based on updated health effects evidence, establish the regulatory benchmarks against which historical and current residential lead contamination is evaluated (US EPA, Lead Dust and Soil Hazard Standards).
Drinking water lead exposure and the Lead and Copper Rule
Separate from soil and paint exposure, lead can leach into drinking water from lead service lines, lead solder, and certain plumbing fixtures, particularly in older housing stock and municipal water systems with aging infrastructure, a pathway regulated under EPA’s Lead and Copper Rule and requiring its own water-specific sampling and exposure analysis distinct from soil and dust pathways (US EPA, Lead and Copper Rule).
Historical industrial sources of residential soil lead contamination
Beyond paint and plumbing, historical emissions from lead smelters, battery recycling facilities, and leaded gasoline combustion have deposited lead in residential soil in many communities, requiring the same kind of historical emissions reconstruction and source apportionment methodology applied in other legacy industrial contamination matters to distinguish an industrial contribution from paint-related or naturally occurring background lead.
IARC’s classification and the neurodevelopmental evidence base
IARC classifies inorganic lead compounds as probably carcinogenic to humans (Group 2A), but the far more extensively documented and litigation-relevant health concern for children is neurodevelopmental harm, including reduced IQ and behavioral effects, established through decades of cohort epidemiology examining blood lead concentration and cognitive outcomes (IARC, Vol 87; Lanphear et al., 2005).
Reconstructing exposure across a child’s developmental window
Because lead’s developmental neurotoxicity is most concerning during specific windows of brain development, an exposure reconstruction addressing a childhood lead claim must account for the child’s age at exposure, not just the cumulative dose, since the same total lead intake can carry different neurodevelopmental significance depending on when during early childhood it occurred.
Why childhood lead litigation continues to grow
With millions of pre-1978 housing units still containing lead-based paint, an estimated 9 million lead service lines still in use nationally, and EPA’s Lead and Copper Rule Improvements now requiring accelerated service line replacement, both the exposure sources and the associated litigation are likely to remain active for years to come. Readers interested in Dr. Rosenfeld’s lead exposure assessment work can find more detail at RoseyFields.com.
References
1. Centers for Disease Control and Prevention. Blood Lead Reference Value. Atlanta, GA: CDC; 2021.
2. US Environmental Protection Agency. A Guide to the Integrated Exposure Uptake Biokinetic Model (IEUBK) for Lead in Children. Washington, DC: US EPA.
3. US Environmental Protection Agency. Lead Dust-Lead and Soil-Lead Hazard Standards. 40 CFR Part 745. Fed Regist. 2021;86(11):5583-5613.
4. US Environmental Protection Agency. Lead and Copper Rule Improvements. 40 CFR Part 141, Subpart I. Fed Regist. 2024;89(198):81730-81888.
5. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Inorganic and Organic Lead Compounds. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol 87. Lyon, France: International Agency for Research on Cancer; 2006.
6. Lanphear BP, Hornung R, Khoury J, et al. Low-level environmental lead exposure and children’s intellectual function: an international pooled analysis. Environ Health Perspect. 2005;113(7):894-899.
7. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Lead. Atlanta, GA: US Department of Health and Human Services; 2020.
8. US Environmental Protection Agency. Lead-Based Paint Renovation, Repair, and Painting Program. 40 CFR Part 745, Subpart E.
9. US Environmental Protection Agency. Residential Lead-Based Paint Hazard Reduction Act (Title X). 42 USC § 4851 et seq.
10. Centers for Disease Control and Prevention. Childhood Lead Poisoning Prevention Program. Atlanta, GA: CDC.
11. US Environmental Protection Agency. Regional Screening Levels for Chemical Contaminants at Superfund Sites. Washington, DC: US EPA.
12. Rosenfeld PE. RoseyFields LLC: Lead and Metals Exposure Assessment. Santa Monica, CA: RoseyFields LLC; 2026.
13. US Environmental Protection Agency. Revisions to the Guideline on Air Quality Models. 40 CFR Part 51, Appendix W. Fed Regist. 2017;82(10):5182-5235.
14. US Environmental Protection Agency. Superfund Lead-Contaminated Residential Sites Handbook. Washington, DC: US EPA; 2003.