For Forty Years the Safety of Leaded Gasoline Was Studied Almost Entirely by One Doctor Paid by the Companies That Made It. The Scientist Who Proved Him Wrong Was Left Off the Federal Panel on Lead.
Tetraethyl lead was added to gasoline from the 1920s to stop engines knocking. It worked, it was cheap, and it was patented, which distinguished it from the alternatives. The chemist who developed it, Thomas Midgley Jr., went on to develop chlorofluorocarbons, giving one man an unusually strong claim to having twice altered the composition of the atmosphere.
The question of whether putting lead into the air of every city on earth was safe was studied, for more than forty years, almost entirely by one man and his assistants. Robert Kehoe ran the Kettering Laboratory of Applied Physiology at the University of Cincinnati from 1930 to 1965. His research on tetraethyl lead was funded by the companies that manufactured it, reviewed by them, and approved by them. He was also the medical director of the Ethyl Corporation.
The Kehoe Paradigm
Kehoe's position was that lead occurs naturally in human beings, that its presence is therefore normal, and that exposure at the levels then observed was not harmful. Each of these claims was defensible given the measurements available, and the measurements available were substantially his.
The methodological rule he attached to them was the durable part. Kehoe held that the burden lay on anyone claiming harm to demonstrate it — show me the data. As a principle of science this is unremarkable. As a principle of regulation it is close to decisive, because it places the cost of uncertainty on the public rather than on the product, and because the party best positioned to generate the data was funding the only laboratory producing it.
The Geochemist
Clair Patterson was not a toxicologist. He was a geochemist at Caltech who had determined the age of the Earth, a problem that required him to become extraordinarily good at measuring very small quantities of lead without contaminating his own samples. In the course of that work he discovered how much lead was in everything, including his laboratory, including the reagents, including the air.
He then applied the technique to the historical record — deep ocean sediments, polar ice — and established what the natural background actually was. Contemporary human beings were not carrying a normal body burden of lead. They were carrying a burden vastly in excess of anything the geological record contained. Kehoe's baseline of "normal" had been measured in a world already saturated by the product under examination.
The Panel
Patterson published this in 1965. In 1971, the National Research Council convened a panel on atmospheric lead contamination. Patterson was not on it.
He was, at that point, the foremost expert alive on the measurement of environmental lead, and the omission was noticed at the time. He spent the following years contending with the Ethyl Corporation, with the lead additive industry generally, and with the funding difficulties that attend a scientist who has become inconvenient to an industry with an interest in his field.
What the Data Showed Once Someone Else Collected It
Leaded gasoline was phased out in the United States through the 1970s and 1980s. The federal health survey conducted between 1976 and 1980 found that 88.2 percent of American children aged one to five had blood lead levels at or above ten micrograms per decilitre. By the survey covering 1988 to 1991, that figure was 8.9 percent.
Mean blood lead concentration fell by more than ninety percent between 1976 and 1995. By 2016 the median level was 0.7 micrograms per decilitre, a reduction of roughly 95 percent from the late 1970s.
These are the largest and fastest improvements in a population-wide exposure measure that American public health has recorded. They followed the removal of a single additive whose safety had been affirmed for four decades by a laboratory paid to examine it.
Kehoe was not accused of falsifying anything, and there is no need to allege that he did. He was given a monopoly on the question and a standard of proof under which the absence of evidence functioned as evidence of absence. The industry did not have to suppress the science. It funded it, and then asked to be shown the data.
Filed from public reporting:
- Wikipedia — "Robert A. Kehoe"
- Wikipedia — "Clair Patterson"
- Environmental Research — "Clair Patterson and Robert Kehoe's Paradigm of 'Show Me the Data' on Environmental Lead Poisoning"
- "Clair Patterson and Robert Kehoe: Two Views of Lead Toxicity" (PDF)
- National Academies of Sciences — Biographical Memoir, Clair Cameron Patterson
- University of Cincinnati Libraries — "But what about Robert Kehoe?"
- U.S. Environmental Protection Agency, Report on the Environment — "Blood Lead"
- U.S. Environmental Protection Agency — "Decline in Blood Lead Levels in the United States"
- Environmental Health — "Relation of blood lead levels and lead in gasoline: an updated systematic review"
- Our World in Data — "Many countries have achieved an impressive reduction in lead poisoning"
