The Lead Cohort Series

The leaded-gasoline era produced the largest uncontrolled cognitive experiment in American history. It ran for fifty years. No consent forms. No follow-up care. The children who lived through the peak exposure years are now the grandparent cohort, and most of them have never seen their data.

This series puts the data in front of them, one chart and one study at a time, starting with the foundation: the correspondence between tetraethyl lead in the gas tank and lead in the blood of every child in the country. Everything else in the series is downstream of that.

1, Foundation Chart
Foundation Chart

When you put it in the gas tank, it ended up in the kids.

Tetraethyl lead added to gasoline (1925-1996, EPA + ATSDR) and the geometric mean blood lead in US children ages 1-5. Gasoline lead exited tailpipes as airborne particulates, then entered children through air, dust, and soil. The two curves are not coincidentally aligned. They are the same chemical.

5x
the average US kid in 1970 had ~5x the blood lead level CDC now flags as toxic (3.5 µg/dL reference value, adopted 2021)
10x
urban and Black kids in NHANES II (1976-80) averaged 6-10x the current CDC reference
1972
peak TEL: ~252,000 short tons of tetraethyl lead added to US gasoline in a single year
Note on subpopulation: the orange line shows the US average child BLL. NHANES II 1976-80 found urban Black children averaged 22 µg/dL; inner-city children 1-5 averaged ~30 µg/dL. The damage was distributed unevenly even within the peak cohort.

Sources: EPA National Lead Emissions · ATSDR Pb Toxicological Profile · NHANES II/III/Continuous geometric means (CDC) · Annest et al. 1983 (NHANES II reanalysis); Mahaffey et al. 1982 (NEJM); pre-1976 child BLL estimated from city cohort studies (Boston 1970-72, Pittsburgh 1973). CDC Blood Lead Reference Value 3.5 µg/dL (October 2021).
2, IQ Test with Lead Mode
Cognitive Demonstration
3, Digit Symbol Coding
Digit Symbol Coding
4, Quick Screen Cognitive Assessment
Cognitive Assessment
End of preview.