Get The Lead Out

R&D World, 1 November 2021

Mark E. Jones, PhD

A century is how long it took for one bad chemistry choice to run its course. The end of August 2021 was the end of what can only be described as a sad century in the history of chemistry. At the end of August, headlines proclaimed the world finally stopped using leaded gasoline. The UN announced Algeria used the last of its automotive leaded gasoline stockpile on August 30.

Much of the reporting touting the end of lead in gasoline mentioned its beginning and the role played by Thomas Midgley, Jr. Midgley’s is the name most associated with inventing leaded gasoline and its early promotion. The reporting paints Midgley as a Shakespearean villain. His story is an interesting one. Midgley is declared by some to be the person responsible for more environmental damage than anyone else in human history, the individual chemist responsible for impacting the most lives. He is even declared one the most dangerous inventors. The history is far more complex.

Midgley is a compelling villain. He invented not one, but two technologies society has come to regret. In addition to his role in introducing tetraethyl lead into gasoline, he is also responsible for the discovery and promotion of fluorocarbon refrigerants, Freon. Freons went on to become widely used. Ultimately, they were banned globally due to their impact on the stratospheric ozone that protects the earth from harmful solar UV radiation. As if two calamitous inventions weren’t enough, he ultimately was killed by another of his inventions. Midgley was paralyzed by polio. He was found strangled by the system of ropes and pulleys he constructed/a> to allow him to get in and out of his wheelchair.

The excitement over the demise of leaded fuel is certainly warranted. Lead pollution, most of it coming from use of leaded fuel, created a heavy toll. Lead’s impact on brain development is now well documented. Exposure to lead, both prenatal and as a child, is linked to lower IQ, with estimates that 23 million people lost IQ points over a six-year study period due to lead. It is linked to aggression and criminal behavior. Learning disabilities, behavioral problems, and growth issues are all linked to lead exposure in children. Calcium uptake channels in developing children concentrate lead in the brain where it interferes with development. Adults’ calcium uptake pathways put lead in bones in place of calcium. Pregnant mothers with past lead exposures can transfer lead to the fetus as part of the normal process of supplying the fetus with calcium. Looking through today’s eyes, knowing the damage caused by leaded fuel, it seems impossible anyone would consider putting lead into gasoline. Yet, Midgley led an effort to do exactly that.

My first encounters with the story of Shadow of TEL over MidgleyThomas Midgley caused me to conjure a picture of a rogue chemist operating on the fringes of the chemical enterprise. I was wrong. Midgley was awarded the Gibbs, Perkin and Priestly medals, some of the highest honors in chemistry. He was elected to the National Academy. He was president of the American Chemical Society and a long-time board member. He was a vice president at Ethyl Corp., the largest producer of lead-based gasoline additives. He was mainstream. He was lionized for his accomplishments up to his untimely death in 1944. He was arguably the leading industrial chemist of his day.

Why lead in the first place?

Lead is a chemical solution to a mechanical problem. Attempts to get more horsepower out of internal combustion engines prompted a move to higher compression. Pushing to higher compression ratios dramatically increased engine performance. Uneven combustion under high compression conditions caused engine knocking. Knocking was a severe problem, not just a minor annoyance. It robbed horsepower, led to incomplete combustion and actually could damage engines. Several chemical additives were found that evened out the combustion, quieting engines — but most required high concentrations in the fuel.

In 1921, Midgley found that tetraethyl lead (TEL) proved effective at very low concentrations. Added at 0.4 g/L, about one part in a thousand by weight, it doubles the horsepower of an engine. To reach the same horsepower, an engine could be half the size, burning half the fuel. TEL effectively doubled the constrained gasoline supply of the day. It was nothing short of revolutionary … except for the toxic part.

The “a href="">dose makes the poison” is well known. Midgley asked whether the dose, the exposure, would be sufficiently low to be safe. He suffered acute lead poisoning and required an extended recuperation. Testing showed animals survived exhaust vapors. He is quoted as saying lead levels would be undetectable in the exhaust.

TEL was oxidized in the engine, as would be expected. Lead oxides are relatively non-volatile. It could be expected that they would stay in the engine. Tetraethyl lead alone formed problematic deposits in engines. Midgley’s solution was to add organohalides to purposely form volatile lead compounds. Halogenated organics, like 1,2-dibromoethane and 1,2-dichloroethane, became part of the additive package. Lead would be swept out of the engine, out of the tailpipe. Midgley compounded the bad idea of placing lead into gasoline by ensuring it would be dispersed into the atmosphere. He clearly knew of the chronic impacts of lead but must have believed “the solution to pollution is dilution.”

To stop engines from knocking, to, in essence, double the amount of gasoline, he elected to put volatile lead into the environment. He had to know this was a bad idea. Yet, he and many others, concluded the benefits outweighed the risks.

Ways to distribute the lead were developed to limit potential for exposure in the supply chain. Risks in handling were managed. Steps were taken to both examine and mitigate the acute risks of lead in gasoline. Every time a concern was raised, steps were developed to mitigate the concern or testing done to demonstrate safety. Midgley investigated the hazard with the tools of the day and took steps to manage the risks.

It is easy in hindsight to argue Midgely was biased in favor of his invention, emphasizing the benefits while downplaying the risks. The risk of lead emissions is now well documented. Technology, both in engines and in creation of better fuel, replaced the need for lead. Seen through today’s eyes, it is easy to see only bad.

Leaded gasoline raised performance of engines, improving efficiency. It was, in the day, a really big accomplishment. Some attribute 100-octane leaded aviation fuel, and the high-performance aviation engines it made possible, with winning the Battle of Britain. Rather than keep engines small, leaded gasoline contributed to increasing expectations for performance. Leaded gasoline unlocked performance. Automobile engines got larger, consuming more fuel. Following Jevon’s paradox, an efficiency improvement led to higher consumption. As Midgley conducted his research, gasoline demand was around 9 billion gallons per year. Peak leaded gas use in the U.S. occurred in 1970, placing 250,000 metric tons of lead into the environment while burning 90 billion gallons of gasoline. Cumulative leaded automotive gasoline use is estimated at 76 trillion gallons — releasing 8 million metric tons of lead into the environment.

Not the end of lead
August 30 is not the day the world stopped using lead. Lead, as the zero-valent metal, found and continues to find wide use. Whether selected due to its density, its melting point or its malleability, lead’s physical properties are unique and useful. Compounds of lead are poisonous, in some cases acute, in all cases chronic. Some now suggest no amount of lead can be considered safe. Yet, we continue to use lead in many applications. It is at the heart of batteries most of us use. It solders our electronics. It sinks our fishing line and balances our tires.

More surprising is the continued use of lead in more frivolous applications. Lead is found in some costume jewelry. Lead compounds continue to be used — and are in the news. The FDA will continue to allow lead acetate in haircare products until January 2022, but will not enforce the ban until 2023. Efforts to stop this use in 2018 resulted in objections and a public hearing request. Lead is found in more than 60% of lipsticks on the market. Lead is even found in dyes used for cake decorating.

August 30 is not even the day the world stopped use of leaded gasoline. General aviation airports around the globe still fuel piston-engine aircraft with leaded fuels. Use of leaded gasoline continues in aviation. The benefits of lead and Midgley’s invention continue to outweigh the risks.

Unintended consequences derail many technologies. We may excuse Midgley for unleashing Freon on the world. Determining it was a problem was a surprise worthy of a Nobel prize. Developers may be justifiably excused when information they couldn’t possibly have known or predicted becomes known. Midgely both knew and experienced the dangers of lead. The growth in gasoline consumption put more lead into the environment than Midgley could have imagined. He concluded the benefits of using lead were worth the risk, but the risk equation changed with time. The amounts of lead used and better understanding the hazards posed by lead changed the equation. Decarbonization presents many challenges. The story of Thomas Midgley and leaded gasoline stands as a cautionary tale. Our actions, even when well intentioned, come with consequences.

More choices today
Running a thought experiment, suppose a potent organolead additive was discovered today that doubled gasoline mileage. It would be a sustainability boon, with the potential to halve atmospheric carbon emissions from transportation. It would be a sustainability bust due to the hazards associated with lead. What would be an acceptable level of lead leaking into the environment in order to half transportation carbon emissions? Lead was present in gasoline at about a part per thousand by weight. Clearly that was too much. Would a part per million be okay? How about a part per billion?

The answer that immediately comes to mind is there is no acceptable level, that human activity should not be placing lead into the environment even if a large tangential good comes from it. I wish it were that easy.

Electrification stands tall as one of the major ways the world will decarbonize. Many of the materials we’ll need for the photovoltaics, the wind turbines, the batteries and the wires are metals. Those metals are frequently associated with lead in their ores. The extraction, smelting and purification will release lead. Zero environmental lead is not an option. We will inevitably trade some amount of lead going into the environment in order to reduce our carbon footprint.

It feels much different than purposefully adding lead to gasoline with additives that ensure it reaches the environment. The lead reaching the environment in our quest for lower-carbon energy will be getting there in spite of our efforts to contain it. It will be due to our failings, not our intent. That doesn’t stop or lessen the environmental impact. Our actions, whether intentional or not, will be placing lead into the environment.

While we are unlikely to surpass lead emissions created by leaded gasoline use, we face a dilemma akin to Midgley’s. We face a tradeoff. Carbon emissions or lead — pick one.