More than 20 years after his death, the American geochemist Clair Patterson is known for two achievements that would each have been immense in their own right: determining the real age of our planet and leading a tough, long lasting but ultimately victorious public battle that ended in the banning of lead gasoline in the USA. Surprisingly, the latter was a consequence of the former.
When bad results spill the beans
The mission to finally measure the age of the Earth began in 1948. Patterson was a 26-year-old geochemist working in the University of Chicago who was tasked by his research supervisor Harrison Brown with this endeavour. The method used by him and his co-researcher and fellow geochemist George Tilton, involved the study of the radioactive decay of uranium in zircon minerals. Uranium decomposes (via a long chain of intermediate elements known as the uranium series) into a stable isotope of lead. Measuring the relative amount of both elements in the samples would give the rate of this decay. Extrapolating the results onto certain meteorites (which are the remains of the earliest stages of the solar system and deduced to be the same age of our planet) would shed light for the first time on the approximate date the Earth was formed.
While Tilton had no trouble measuring the remaining uranium in the samples, Patterson had a tough time with the lead concentrations found, which were much higher than expected. Suspecting external contamination, he designed a completely sterile environment for his experiments that allowed him to obtain non-skewed data. By further analysing the concentration of stable and unstable lead isotopes in the meteorite samples, Patterson was able to publish his results in 1956. However, the question of how the extra lead had contaminated the samples remained. By analysing environments which had been barely touched by mankind’s hand, such as water near the seabed of the deepest Atlantic Ocean trenches or subterranean Antarctic ice, he discovered that the lead concentration in those places was around 20 levels lower than in environments deeply altered by human intervention. Because of lead’s extreme toxicity, this was very concerning.
Exposure to lead causes extensive neurological damage due to its disruption of brain plasticity receptors that are vital for the correct functioning of essential cognitive mechanisms. It ties into the enzyme ALAD, thus potentially causing anaemia by disrupting the syntheses of the haem coordination complex which plays a crucial role in the transport of iron across the body. It curbs the cell supply of glutathione, an anti-oxidant that protects DNA from damage by reactive radicals. It is plainly a very dangerous toxicant (for more information on the adverse effects of lead and the history of human interaction with it, check Amy Thomas’s fascinating article in page 9 of issue 37 of I, Science).
The origins of the widespread high levels of lead could be traced to an early 20th century inventor, Thomas Midgley. He is also infamously known for the synthesis of the first chlorofluorocarbon, a family of compounds that would later cause the famous ozone layer holes in the Earth atmosphere. Midgley discovered that by adding a certain amount of tetraethyllead (TEL) to car engines, the knocking in said engines could be reduced. This attracted the attention of General Motors, as the new car industry was experiencing its first boom. Teaming up with DuPont and the predecessors of ExxonMobil, the industrial production of TEL began in the 20s. It did not take long for the first deaths due to lead poisoning happening among the workers of the TEL producing factories. Lead poisoning was occurring because the volatile TEL was absorbed by the skin and accumulated in body fat. When cars were popularised, millions of people were further exposed to its effects.
The companies involved spent years running a finely crafted PR campaign that denied the toxicity of lead. They even used willing scientists like influential toxicologist Robert Kehoe to defend their lies. Thus, when Patterson discovered the spread of the problem, he had 30 years of propaganda funded by some of the most powerful conglomerates on Earth. Nevertheless, he persisted. His numerous findings were too conclusive to be ignored or refuted. After much lobbying and incremental phasedowns, lead gasoline was finally banned through a Congress act in the USA in 1996, several years after most European countries. Patterson had died four years before, long after his conclusions had been accepted by most national governments.
Scientists like Clair Patterson teach us that their role transcends just being the interpreters of reality. By standing up to companies that categorically denied evidence and used unethical scientists like Robert Kehoe, he showed how scientific research can be made into a tool that can powerfully serve to benefit and improve our lives and our planet. Even discoveries that could be seen as seemingly uninfluential to our daily lives have far reaching applications. Because, we should remember, our bodies are healthier nowadays because of the complicated process that was dating the Earth. And we all should be grateful to Clair Cameron Patterson for that.
Juan Gorrochategui is studying for a BSc in Chemistry at Imperial College London
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