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A Pivotal Moment in History
On the last day of August three years ago, the sweltering heat heralded a significant event: the closure of a gas station in Algeria, a gesture marking the end of a century-long relationship between humanity and a toxic compound, tetraethyl lead, found in leaded gasoline. This moment symbolizes not just the cessation of a harmful practice, but also a victory for environmental health advocates worldwide.
Inger Andersen, the Executive Director of the United Nations Environment Programme, stated, “From a global health and environmental perspective, the successful implementation of the ban on leaded gasoline is a monumental achievement. The diseases and deaths triggered by leaded gasoline over the past century have affected millions and caused profound environmental degradation. Today, as we eliminate this hazardous substance, we should feel invigorated for what lies ahead…”
The Pandora’s Box of Avarice
The origins of leaded gasoline can be traced back to a century ago, primarily influenced by the ingenuity of American mechanical and chemical engineer Thomas Midgley Jr. Born in Pennsylvania, Midgley was fascinated with discovering new applications for known substances. In 1916, as he joined General Motors, the dawn of the automotive age was upon the United States. Under the guidance of Charles Kettering, the head of research at General Motors, Midgley undertook the challenge of enhancing engine performance, ultimately identifying tetraethyl lead as a solution to gasoline knock.
The phenomenon of gasoline knock occurs when fuel violently ignites before the flame front from the spark plug has fully spread throughout the combustion chamber, akin to a miniature explosion. Such premature combustion generates intense pressure waves, significantly damaging engine components and shortening the engine’s lifespan. Today, vehicles are typically equipped with sensors to detect these knocks.
Ironically, while the dangers of lead were somewhat recognized by the 1920s, this understanding did not deter General Motors from marketing ethyl gasoline, which contained tetraethyl lead. The Ford Model T became a cultural icon, and leaded gasoline spread across the globe alongside the rising popularity of automobiles.
It was only thirty years later that scientists conclusively identified tetraethyl lead as a highly toxic substance—its toxicity being up to one hundred times that of elemental lead. Exposure, whether through skin contact or inhalation of vapors, can lead to serious poisoning. Midgley himself became one of the earliest victims of his invention; at a public demonstration in 1924, he poured tetraethyl lead onto his hands to dispel fears, only to suffer from acute lead poisoning shortly thereafter. After his recovery, he continued his work, carrying the residual lead in his body for life.
Children Affected: A Harrowing Reality
Recent research has shed light on the extensive negative effects of leaded gasoline over its century of use. In 2022, a groundbreaking study published by researchers from Florida State University and Duke University in the Proceedings of the National Academy of Sciences (PNAS) examined blood lead levels in 12,000 American children aged 1 to 5. Some were born during the peak usage of leaded gasoline (1976 to 1980), while others entered the world post-ban (2015 to 2016).
The findings revealed that in the samples from 1976 and later, nearly 90% of children exhibited blood lead concentrations exceeding 5 µg/dL, while only 53% of those born in 2015 and later did so. According to the World Health Organization (WHO), lead poses a particular risk to children, with harmful effects detected even at blood lead levels as low as 3.5 µg/dL, leading to decreased intelligence and various behavioral and learning issues.
The WHO maintains that no safe blood lead level exists for children. According to the PNAS study, over 170 million Americans (more than half the population) have been exposed to hazardous levels of lead during childhood, with millions recording blood lead levels as high as 30 µg/dL.
Lead acts as a chronic neurotoxin, but tetraethyl lead can convert into a more potent neurotoxin known as triethyl lead within the body. This compound can breach the blood-brain barrier, inhibiting critical enzymes and directly damaging the central nervous system. Initial mild tetraethyl lead poisoning may lead to symptoms like excitability, irritability, and anxiety, while severe poisoning can provoke agitation, confusion, hallucinations, and even violent behavior.
The PNAS study found that by 2015, leaded gasoline’s impact on cognitive ability resulted in an average loss of 2.6 IQ points per individual, culminating in a total loss of 824 million IQ points nationwide. Beyond cognitive decline, these researchers published another longitudinal study examining the impact of leaded gasoline on mental health, covering a span of 75 years (from 1940 to 2015).
They found that tetraethyl lead contributed to 151 million cases of mental health disorders in the United States, alongside millions of cases of psychiatric illnesses. This research, published on December 4 in the Journal of Child Psychology and Psychiatry, analyzed historical data on children’s blood lead levels, patterns of leaded gasoline use, and mental health demographic statistics. It utilized an integrative measure—the p factor—to assess susceptibility to various psychiatric symptoms, including anxiety, depression, obsessive-compulsive disorder, and attention-deficit/hyperactivity disorder (ADHD).
The results indicated that the use of leaded gasoline resulted in an increase of 602 million p factor points among Americans, with the most pronounced rises seen in rates of anxiety and depression, followed by ADHD and other neurotic symptoms such as mood instability and sensitivity.
The Need for Continued Vigilance
In July of last year, Nature commemorated a seminal paper by Mitsunobu Tatsumoto and Claire Cameron Patterson published in the journal sixty years ago, which revealed the severe lead pollution of oceans due to leaded gasoline—a problem primarily stemming from human activity. This announcement marked a watershed moment that sparked ongoing discussions about the public health implications of leaded gasoline use. Concurrently, the harmful effects of lead on multiple body systems, including renal, cardiovascular, reproductive, and neurological functions, became increasingly evident.
As of August three years ago, the United Nations Environment Programme announced that the ban on leaded gasoline has prevented more than 1.2 million premature deaths annually worldwide. However, by 2021, over 1.5 million people still succumbed to cardiovascular issues caused by lead exposure, and one-third of children globally remained at risk, with blood lead levels high enough to inflict irreversible brain damage, cognitive impairments, behavioral disorders, and increased risks of kidney disease and heart conditions.
Particularly concerning is the susceptibility of children, who instinctively put objects in their mouths. They absorb lead at a rate approximately four to five times greater than adults, creating a heightened risk of lead poisoning. Moving forward, it is imperative to further enhance awareness of global lead poisoning and protect both children and adults at risk of lead exposure.
Aaron Reuben, co-author of the study and an assistant professor at the University of Virginia, summarized the situation succinctly: “For most people, the effects of lead are akin to a low-grade fever. You might not seek treatment, but you certainly feel worse than when you’re healthy.”
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