Imagine a world where a single chemical compound could silently wreak havoc on millions of lives, leaving a trail of neurological damage and environmental destruction in its wake. This isn’t the plot of a dystopian novel—it’s the real-life story of tetraethyl lead, a toxic substance once hailed as a miracle additive for gasoline.
The Birth of a Toxic Giant
In the early 20th century, the automotive industry was booming, and engineers were on a relentless quest to improve engine performance. Enter Thomas Midgley Jr., a mechanical and chemical engineer whose invention of tetraethyl lead promised to reduce engine knocking and boost efficiency. Little did the world know, this “miracle” would come at a devastating cost.
The Silent Killer
Tetraethyl lead was added to gasoline to enhance engine performance, but its toxic effects were soon evident. Lead exposure, particularly in children, led to severe neurological damage, decreased IQ, and a host of psychological disorders. Studies revealed that lead exposure had caused a significant drop in IQ points and an increase in behavioral issues.
Environmental Catastrophe
The environmental impact of leaded gasoline was equally alarming. Lead particles from exhaust fumes settled into the soil and water, contaminating ecosystems and entering the food chain. The legacy of leaded gasoline continues to haunt us, with widespread contamination still affecting public health and the environment.
The Fight for Regulation
Despite early awareness of its dangers, it took decades for regulatory actions to ban leaded gasoline. The successful implementation of these bans has significantly reduced lead exposure, but the damage done over a century is irreversible. The fight against lead poisoning is far from over, as the legacy of tetraethyl lead continues to impact millions.
A Call to Action
The story of tetraethyl lead is a stark reminder of the importance of vigilance in public health and environmental protection. As we continue to uncover the full extent of its impact, it’s crucial to push for stronger regulations and innovative solutions to mitigate lead exposure. The health of future generations depends on our actions today.
So, the next time you hear about a “miracle” solution, remember the cautionary tale of tetraethyl lead. Let’s learn from the past and strive for a healthier, safer future.
On the last day of August three years ago, the hot air “ignited” a piece of gratifying news. The news only concerns the closure of gas stations in one northern African country (Algeria), but it also symbolizes humanity and a toxic compound – tetraethyl lead, which has been present in leaded gasoline for a century. The close contact was finally completely severed.
Inger Andersen, Executive Director of the United Nations Environment Programme, said, “The successful implementation of the leaded petrol ban is a huge milestone from a global health and environmental perspective. The disease and death caused by leaded petrol has affected hundreds of millions of people over 100 years. lives and contribute to environmental degradation around the world, we should be encouraged that we have successfully eliminated this risk factor…”
Open Pandora’s Box with Hobby and Greed
However, why leaded gasoline was born 100 years ago cannot be circumvented by American mechanical and chemical engineer Thomas Midgley Jr.
Midgley, who was born in Pennsylvania, USA, has been interested in finding new uses for known substances since he was a child. When Midgley joined General Motors in 1916, it was the dawn of the American automobile age—Ford had developed the Model T, but it still lacked a more powerful engine. Under the guidance of Charles Kettering, GM’s research director at the time, Midgley took on the task and studied thousands of substances before finally finding tetraethyl lead that could reduce gasoline knocking .
Gasoline knock occurs because when the spark plug in a car engine ignites and the flame front has not completely spread to the entire combustion chamber, the unburned mixture spontaneously detonates under high temperature and pressure , similar to a small explosion. This kind of deflagration will produce violent pressure waves that impact the combustion chamber wall, greatly shortening the life of the engine. Nowadays, cars are often equipped with knock sensors to detect the occurrence of knocking.
Ironically, people in the 1920s had initially understood the dangers of lead, but this did not stop General Motors from adding tetraethyl lead to gasoline and then promoting it as “ethyl gasoline” market. As we are familiar with, the Model T car became a hit, and this kind of gasoline also went to the world with the popularity of cars.
Fast forward 30 years, and scientific researchers determined that tetraethyl lead is a highly toxic substance, and its toxicity can reach 100 times that of metallic lead . Skin contact with tetraethyl lead or inhalation of its volatile compounds can cause poisoning. Midgley was one of the early victims of his invention. At a press conference in 1924, in an attempt to allay public fears about leaded gasoline, he poured tetraethyl lead into his hands . Not surprisingly, he soon fell ill from acute lead poisoning, but still concealed the news. After recovering, he started a new job, but the lead remained in his body and never disappeared.
Those children with reduced IQ and mental abnormalities
In recent years, several research analyzes have provided a more comprehensive view of the negative impacts of leaded gasoline over a century of use. In 2022, three researchers from Florida State University and Duke University published a study in the Proceedings of the National Academy of Sciences ( PNAS ), analyzing the blood lead levels of 12,000 children aged 1 to 5 years old in the United States. ——They were born either during the peak period of leaded gasoline use (from 1976 to 1980) or after the discontinuation of leaded gasoline (from 2015 to 2016).
They found that in samples from 1976 and later, almost 90% of children had blood lead levels above 5 µg/dL , while in samples from 2015 and later, only 53% exceeded this value. According to data released by the World Health Organization (WHO), children are particularly vulnerable to lead harm. Even blood lead concentrations as low as 3.5 μg/dL can damage their intelligence and lead to various behavioral disorders and learning problems .
WHO believes that there is no safe blood lead level for children. According to research by PNAS , more than 170 million Americans (more than half of the U.S. population) were exposed to high levels of lead in early childhood, and as many as millions of people have blood lead levels reaching 30µg/dL.
Lead is a chronic neurotoxin, but in contrast, tetraethyl lead is converted into a powerful neurotoxin, triethyl lead, in the human body. Triethyl lead can directly penetrate the blood-brain barrier, inhibit some key enzymes in the human brain, and directly damage the human central nervous system . Mild tetraethyl lead poisoning can cause neurosis such as excitability, irritability, and anxiety. Severe poisoning can lead to restlessness, mental confusion, and even hallucinations, violent behavior and other symptoms.
According to research by PNAS, as of 2015, leaded gasoline has caused an average loss of 2.6 IQ points per person in the cognitive abilities of Americans, resulting in a total loss of 824 million IQ points. In addition to mental decline, the three researchers recently published a paper on the effects of leaded gasoline spanning 75 years (from 1940 to 2015).
They found that tetraethyl lead was responsible for 151 million cases of mental health disorders and millions more cases of mental illness in the United States during those 75 years . The research was published Dec. 4 in the Journal of Child Psychology and Psychiatry .
The study analyzed historical data on blood lead levels in U.S. children, patterns of leaded gasoline use in the U.S., and demographic data on mental health problems, and analyzed them through a comprehensive mental health indicator called the psychopathology factor, or “p-factor.” ), evaluated the effect of leaded gasoline on susceptibility to a variety of psychopathological symptoms, including anxiety, depression, obsessive-compulsive disorder, attention-deficit/hyperactivity disorder (AD/HD), etc.
The results show that leaded gasoline has caused a total of 602 million additional psychopathological factor points in Americans . The most obvious increase is the prevalence of anxiety, depression, etc. , followed by attention-deficit/hyperactivity disorder, and then emotional instability, Prone to anxiety, sensitivity and other neurotic symptoms. In addition, Americans’ sense of responsibility has also decreased due to the influence of leaded gasoline.
“I tend to think of Generation X (1965-1980, between the US ‘baby boomers’ and ‘millennials’ as period) known as the ‘lead generation’ ” This generation has been exposed to leaded gasoline the longest and is expected to continue to develop more pronounced internalizing conditions , including anxiety, depression, and attention-deficit/hyperactivity disorder.” People born between 1966 and 1970. , with the highest rates of mental disorders, coinciding with the peak of leaded gasoline use during this period.
In addition to leaded gasoline, during this period, lead-based paint was also used in the decoration of window sills, doors, door frames, stairs and porches in the United States. This paint was not banned until 1978. Reuben said if these were taken into account, the estimates in the study would be even higher.
He also mentioned that lead is still used in many types of cookware, cosmetics, paints, aircraft fuels and car batteries – the list goes on and on, but for most of these lead-containing products, we already have A better alternative. So maybe it’s time to end this.
There’s more to do
In July last year, Nature published an article commemorating an article published in Nature 60 years ago by Mitsunobu Tatsumoto and Claire Cameron Patterson.
The paper reveals that the ocean has suffered serious lead pollution due to the use of leaded gasoline, and most of the lead comes from human activities. “Nature” said this was a landmark breakthrough that triggered subsequent debates about the public health impact of leaded gasoline use . At the same time, people began to fully realize that lead is harmful to various systems of the human body, and can damage the kidneys, cardiovascular system, reproductive system, and brain.
At the end of August three years ago, the United Nations Environment Program issued a statement stating that the ban on the use of leaded gasoline has prevented more than 1.2 million premature deaths around the world every year. However, as of 2021, more than 1.5 million people worldwide have still died from cardiovascular problems caused by lead exposure . However, one-third of children around the world still have dangerous levels of lead in their blood, enough to cause irreversible brain damage, intellectual disability, behavioral disorders, kidney disease, cardiovascular disease, etc.
For children, it is worth mentioning that they like to put things in their hands into their mouths , and once they ingest lead, the absorbed dose is about 4 to 5 times that of adults , so they are particularly susceptible to lead poisoning. In the future, we need to further improve our understanding of global lead poisoning and protect children and adults at risk of lead exposure.
“For most people, the effects of lead are like a low-grade fever,” Reuben said. “You may not seek treatment, but you will definitely feel worse than you would have without a fever.”
In 1948, in a dusty old laboratory at the University of Chicago, Clair Cameron Patterson was trying to measure the amount of lead in minerals. He wanted to start with these pinhead-sized samples. Determine the age of the Earth. But what he didn’t expect was that this work not only brought about the first accurate age of the earth, but also saved the safety and health of generations.
At that time, under the guidance of University of Chicago geochemist Harrison Brown, Patterson and George Tilton were trying to determine the geological age of rocks using the uranium-lead method. The principle of the uranium-lead method is very simple: uranium slowly decays into lead at a fixed rate. If you can calculate how much uranium decays into lead , you can calculate how many years ago the rock was formed based on the rate of decay.
But in actual research, it is difficult to determine how much lead is present in the sample itself and how much lead is derived from uranium decay. However, there is a mineral that can perfectly solve this problem, and that is zircon (ZrSiO4). Zircon is very strong and does not deteriorate easily under high temperature and pressure. It contains almost no lead when formed. Therefore, it can be basically considered that the lead in zircon is formed by uranium decay . Until now, zircon has been a commonly used material in geological dating.
Patterson and Tilton were responsible for measuring lead and uranium in zircon samples respectively. Tilton’s work went very smoothly, but Patterson encountered some difficulties – Patterson found that the lead content he measured Too high. “The results of our experiment are not quite right. There is too much lead in the zircon. Where does this lead come from?” It took Patterson several years to solve this problem. He repeatedly checked all the steps, trying to find the source of lead. source. “Then I discovered, lead here , lead there, lead in the air, lead in all the equipment I was using… When I measured a sample, I was contaminating it with the lead on the instrument . sample.”
Patterson was driven crazy by the ubiquitous lead, and he tried every means to drive the lead contamination out of his laboratory. “ I was forced to build a clean laboratory ,” Patterson recalled , which became the first clean room in history. He replaced lab exhaust ducts, sealed the entire room, added air filtration, and thoroughly cleaned all experimental equipment with acid. Patterson has strict requirements for people entering the laboratory and does not welcome any visitors: “When you (reporter Shirley K. Cohen, who interviewed Patterson in 1995) walked into my clean room, you had hair and dandruff on your face. The lead will contaminate the entire *** (expletive) laboratory.”
Age of earth
Such a laboratory allowed Patterson to measure the content of lead isotopes in samples with unprecedented precision, and he was determined to try to answer the big question-the age of the earth. It is true that the geological age of rocks can be measured using the uranium-lead method, but a new question arises – where can I find a rock sample that is the same age as the earth? Patterson set his sights on meteorites.
In most cases, the meteorites that fell to the earth were formed in the early days of the solar system . They are like the “raw materials” left when the earth and other planets were “built”, but they have not experienced violent impacts and long geological changes. Perfectly retaining the original ingredients.
In 1953, Patterson obtained a sample of the Canyon Diablo meteorite, an iron meteorite. Iron meteorites contain high levels of lead and low levels of uranium. On this basis, Patterson measured the lead isotope ratios in several stone meteorites with high uranium content and low lead content. This time, he chose the lead-lead method: uranium 235 and uranium 238 decay into lead 207 and lead 206 at different rates respectively. Using the lead isotope ratios of different meteorites, Patterson was able to draw isochrones to accurately solve the problem . The age of the earth .
In 1956, this article titled “Age of meteorites and the earth” ( Age of meteorites and the earth ) was officially published. Patterson announced that the age of the earth is 4.55±0.07×10 9 years . Even today, the accuracy of this age is very high. (The current age of the Earth is corrected to 4.543 ± 0.05 × 10 9 years.)
While he was excited about the results of his work, Patterson had no idea what challenges he would face next in his career.
Ethyl gasoline
In October 1923, 32 years before Patterson’s article on the age of the Earth was accepted, a New Jersey worker, Ernest Oelgert, suddenly began to suffer mental problems. He was shaking all over and would scream “three people are attacking me at the same time” for no reason. Ergot died just one day later. According to the New York Times, in the same week, local hospitals admitted another 40 patients with similar symptoms.
The 41 patients had one thing in common: they all worked at a Standard Oil Company plant where tetraethyl lead was produced .
In 1921, American chemist Thomas Midgley, Jr. discovered that adding tetraethyl lead to gasoline could effectively prevent engine “knocking” and make the car drive faster and more stably. Once this low-cost additive was discovered, General Motors and Standard Oil quickly formed a new company to produce and sell gasoline with added tetraethyl lead. Now we will directly call it “leaded gasoline” , but when naming it, the managers at the time deliberately avoided the word “lead” and named the company and this gasoline “Ethyl” (Ethyl).
Less than eight months after ethyl gasoline was officially released, 41 workers in New Jersey fell ill. Shortly thereafter, dozens of workers at another ethyl ethyl lead plant in Dayton, Ohio, USA, developed similar symptoms. The culprit of these two tragedies was tetraethyl lead. Although the process of lead poisoning in humans tends to be very slow, the process of pure tetraethyl lead poisoning can be very rapid . It can penetrate the skin and invade the brain in just a few weeks, causing hallucinations, tremors and, in severe cases, death – it is a highly toxic substance.
However, the Ethyl Company was unwilling to give up this promising gasoline additive. Under pressure, they hired Robert Kehoe, a pathologist at the University of Cincinnati, to investigate the cause of the accident. Kehoe started with the city of Dayton and quickly concluded that it was tetraethyl lead that poisoned the workers. However, as a countermeasure, he did not stop the production of ethyl gasoline, but suggested installing fans in the factory to enhance ventilation.
Monopolized security research
This “simple and crude” method does seem to ensure the safety of factory workers, but it does not completely solve the problem of leaded gasoline that is the most harmful. We now know that when leaded gasoline is burned, the lead is emitted into the atmosphere with vehicle exhaust and then enters the human body through breathing . As one of the most harmful heavy metals to humans, lead can damage the kidneys, cardiovascular system, reproductive system, and can even penetrate the blood-brain barrier, invade the central nervous system, and damage the brain. However, in the mid-20th century, the potential hazards of leaded gasoline, and even the potential hazards of lead, were not well understood.
In response to a handful of concerns about the safety of leaded gasoline, Ethyl Corporation commissioned Kehoe to conduct research and experiments to “prove” that lead in leaded gasoline and exhaust was not harmful to humans. According to the book ” The Polluters: the making of our chemically altered environment”, in the following decades, Kehoe’s research team monopolized almost all research on the safety of leaded gasoline . Not only were these studies flawed in design and justification, however, all published content was subject to review and revision by the sponsor, the leaded gasoline manufacturer.
For example, Kehoe once measured blood lead levels in workers with and without regular exposure to tetraethyl lead and found that both were high. He concluded, however, that lead, like iron, was a natural component of the blood. Another point Kehoe insists on is that the threshold for lead poisoning is 80 μg/dL, and lead below this standard will not cause harm to the human body. (In 2021, the U.S. Centers for Disease Control and Prevention set the blood lead reference value for children at 3.5 μg/dL, which means that any concentration above this level is considered excessive blood lead.)
During this period, few independent researchers wanted or could conduct relevant research, and Kehoe’s two conclusions (which we now know were hugely problematic) were regarded as golden rules by the oil industry, the media, and the public. Until about 30 years later, Patterson in the laboratory had no idea that lead in the environment had contaminated his samples. This is also the source of his construction of “clean room”.
The earth becomes a “big lead ball”
With the clean room in hand and the first measurements of the age of the Earth, Patterson began exploring a broader use for lead isotopes – lead isotope tracing. Simply put, Patterson hopes to measure the isotopic composition of lead in the ocean to understand the movement of the water and the source of the material. Unfortunately, this work is funded by the oil industry.
In this study, Patterson once again encountered unusual data on lead concentrations. Data show that the lead content of surface seawater is 3 to 10 times that of deep seawater, but according to the distribution pattern of other elements (such as barium), the result should be exactly the opposite. While digging through the literature for possible explanations, Patterson came across data on leaded gasoline and instantly realized that ” the abnormal lead concentrations could be explained by lead emissions from burning gasoline .”
In 1963, this research, which he called a “big paper”, was published in Nature. In the article, Patterson directly blamed the oil industry for causing abnormal lead concentrations in seawater. In a subsequent article, he calculated in detail all the possible natural sources of lead, noting that “the figures only add up when leaded gasoline is added.”
At this time, he had received a nine-year grant of up to $200,000 from the American Petroleum Institute. The oil industry would never accept a study like this. The American Petroleum Institute immediately decided to stop funding , and also asked the U.S. Atomic Energy Commission (which funded Patterson’s research to measure the age of the earth) to also stop funding Patterson and related personnel. According to Patterson, there were even oil company executives who called Caltech and asked to be fired .
Patterson faced repression not only from the oil industry but also from other scientists. Kehoe scoffed at his “lack of any conception of his own ignorance,” while another toxicologist accused Patterson of “writing science fiction.”
But Patterson once again showed the same spirit he had when facing lead pollution in the laboratory and insisted on conducting a series of studies to confirm the source and severity of lead pollution: He traveled to the Arctic and Antarctic, took ice layers from different depths and analyzed Among them, he found that the lead content in the ice had been rising since the 18th century, but starting in the 1920s, the lead content in the ice suddenly surged.
To prove that lead in the human body is not “natural,” he also managed to measure the lead content in the bones of a 2,200-year-old ancient Egyptian mummy. The results showed that modern Americans have 600 times the amount of lead in their bodies than humans did 2,200 years ago . As more and more data were measured, Patterson discovered that the entire earth had almost turned into a “big lead ball” . The oceans, mountains, and polar regions were all filled with lead. These lead came from the burning of leaded gasoline, and they would It will lurk into the human body and become an invisible killer.
The end of leaded gasoline
It was not until the 1970s that Patterson’s work was gradually accepted. As more relevant research emerged, Kehoe was deposed and people gradually realized the potential harm of leaded gasoline. At this time, leaded gasoline had been burning for more than 50 years .
A recent study published in the Proceedings of the National Academy of Sciences reviewed blood lead data from nearly 12,000 young children collected by the National Health and Nutrition Examination Survey (NHANES) from 1976 to 2016. Studies estimate that 170 million Americans, or 54% of the U.S. population, currently have blood lead levels above the warning level (5 μg/dL) in early childhood. What’s even more frightening is that from 1966 to 1975, the blood lead concentration of all young children in the United States exceeded the warning value of 5 μg/dL. At the same time, the researchers also evaluated the cognitive damage caused by lead pollution and found that lead pollution in early childhood led to a 2.6-point drop in IQ (IQ value) per capita in the United States . For those born in the worst 10 years, IQ can drop by nearly 6 points.
On January 1, 1996, the U.S. Clean Air Act prohibited the use of leaded gasoline in vehicles other than aircraft, racing cars, farm equipment, and marine engines. On August 30, 2021, the United Nations Environment Program (UNEP) announced that as Algeria stopped selling leaded gasoline, the era of global use of leaded gasoline officially ended . However, lead pollution experienced in childhood will remain with many people for life.
If you have seen our previous push about leaded gasoline , you may have an impression of one person: Thomas Midgley, Jr., the inventor of leaded gasoline. The inventor, who seemed, in the words of one writer, to have “an almost uncanny intuition for the regrettable,” invented another substance that affected global health, Freon, in addition to leaded gasoline.
When Thomas Midgley died in 1944, the world regarded him as one of the greatest inventors of the 20th century: he added a magical ingredient to gasoline that “perfectly” solved the problem of engine explosions. “shock” problem; he also synthesized a chemical substance to make refrigerators and air conditioners safer… These inventions allowed him to win almost all awards in the fields involved, and he also became the president of the American Chemical Society. It sounds like Midgley is a total “winner in life.”
But if you name these two inventions that “benefit mankind”, the story becomes completely different: the two inventions that brought Midgley great honors were leaded gasoline and Freon . The lead released by the burning of leaded gasoline has poisoned the brains of generations around the world, and the leakage of Freon “opened a hole” in the earth’s ozone layer. Today, the most common description used in telling Midgley’s story is that of “the world’s worst inventor.”
The “perfect” toxic substance
In 1916, Midgley was invited by Charles Kettering (who invented the electric starter, which freed cars from manual crank starters) to find a solution to “knocking” in automobile engines.
In a gasoline engine, when gasoline and air are fully mixed into the cylinder, they are first compressed by the piston and then ignited by the spark plug. However, when the oil-gas mixture is compressed, the temperature in the cylinder will rise sharply, which may easily cause some components with relatively low ignition points in the gasoline to be ignited in advance. The impact force generated in this way will cause the cylinder to make a knocking sound, so this phenomenon is called “knock”, which will reduce the power output of the engine and even damage the cylinder.
One solution is to add 10% ethanol to gasoline. However , the cost of ethanol is too high , and the calorific value of the same volume of ethanol is much lower than that of pure gasoline. General Motors wanted to find a cheaper, more efficient alternative.
Midgley worked hard to find more than a hundred possible additives, the most popular of which was tetraethyl lead (TEL). Tetraethyl lead itself is highly toxic, but for General Motors, it is a “perfect” additive : First, a small amount of tetraethyl lead can effectively prevent knocking, and only needs to be added to one gallon (about 3.8 liters) of gasoline. A few grams goes a long way. Secondly, tetraethyl lead does not have the weird smell of other candidates. Most importantly, lead is a very cheap raw material. In a letter to Kettering, Midgley estimated: “Earning 3 cents on every gallon of gasoline sold…that’s $36 million a year.”
Leaded gasoline named “unleaded “
Within just 15 months of Midgley’s introduction of the tetraethyl lead additive, General Motors and Standard Oil jointly introduced gasoline containing tetraethyl lead, which we now commonly refer to as ” Leaded gasoline”. Midgley also received the American Chemical Society’s William H. Nichols Medal for his invention of leaded gasoline.
At this point, if you have read our push a few days ago: He accidentally discovered a deadly “poison” in the air and saved the health of several generations, but was almost banned by the American oil company. You will know that whether it is tetraethyl lead itself or leaded gasoline that is emitted into the air after burning The lead oxide in the drug is poisonous to the human body . The only difference is the onset time. Speed: Pure tetraethyl lead poisoning often attacks violently within a few weeks, can cause hallucinations, and even cause death; lead poisoning is a chronic process caused by the slow accumulation of lead in the human body. As the blood lead level gradually increases, The human body’s kidneys, cardiovascular system, nervous system, etc. will be damaged. For children who are still growing and developing, lead poisoning can even affect their intelligence in adulthood .
However, in the early 19th century, although there was some awareness of the dangers of lead, there was no clear evidence that tetraethyl lead or leaded gasoline posed a threat to human health. This gave oil companies an opportunity to take advantage. They even deliberately avoided the dangerous-sounding “lead” and named leaded gasoline “ethyl” gasoline.
Ironically, on October 30, 1924, in order to prove the safety of leaded gasoline, Midgley poured a bottle of tetraethyl lead into his hand at a press conference and held it under his nose to smell it for one minute. “I wouldn’t put myself in harm’s way,” he told reporters, but only he knew that was a lie – he was subsequently poisoned by tetraethyl lead and was forced to take several weeks of sick leave .
As you may have read later, Ethyl hired a scientist to provide a “certificate of health” for leaded gasoline. For at least the next 40 years, the Ethyl Company insisted that “a small amount of exposure when using ethyl gasoline will not cause tetraethyl lead poisoning, and ethyl gasoline will not cause a wider range of lead pollution.” That was until Patterson and many other scientists came up with solid evidence of the dangers of leaded gasoline. A “big hole” broke in the ozone layer
Meanwhile, Midgley has returned to the lab to continue working on his inventions.
In 1930, he teamed up with Kettering to help Frigidaire, a subsidiary of General Motors, solve another problem – the refrigerant problem. At that time, most refrigerators used toxic or flammable compounds such as sulfur dioxide and ammonia as refrigerants, which could easily cause accidents if they leaked. If Arctic companies want to sell their products to more people, they need to solve the safety issues of refrigerators and air conditioners.
This time, Midgley was faster. In just three days, he found a very “safe” substitute-dichlorodifluoromethane. Kaitlin described it: “Highly stable, non-flammable, and will not harm the health of humans or animals at all.” Mickey used the same method to once again verify its “safety” – pour it on your hands and put it under your nose to smell it.
The good news is that Midgley didn’t call in sick again this time. The bad news is that dichlorodifluoromethane has another name – Freon .
Currently, there are different opinions on the definition of Freon. Broadly speaking, Freon can refer to a large class of fluorine-containing refrigerants, among which chlorofluorocarbons (CFC) substances pose the greatest threat to the ozone layer, and the dichlorodifluoromethane invented by Midgley belongs to the chlorofluorocarbons (CFC- 12).
In April 1930, Arctic refrigerators and air conditioners officially began to use this new refrigerant. Subsequently, it also appeared in many fields such as insect repellents and fire extinguishers. By the 1970s, as many as 1 million tons of CFCs were being released into the air each year. It was not until 1974 that two chemists in the United States discovered for the first time that CFCs could react chemically with ozone under sunlight, causing the ozone layer to become riddled with holes .
In 1985, British scientist Joseph Farman and two colleagues discovered a shocking fact during their scientific expedition in Antarctica: from August to October every year, a huge “ozone hole” appears over Antarctica. The ozone concentration here has dropped from 300 ozone units to 220 ozone units. To make matters worse, the hole in the ozone layer continues to grow .
If the protection of the ozone layer is lost, ultraviolet radiation from the sun will directly reach the earth’s surface, causing human skin cancer. The World Health Organization estimates that every 10% reduction in the ozone layer will lead to 300,000 new cases of skin cancer. deadliest invention
After Midgley’s death, two of his most “deadly” inventions gradually fell off the altar.
For leaded gasoline, on January 1, 1996, the U.S. Clean Air Act prohibited the use of leaded gasoline in vehicles other than aircraft, racing cars, agricultural equipment, and marine engines. At this time, toxic lead-containing exhaust gas had been emitted for 73 years. Subsequently, other countries around the world banned the use of leaded gasoline, and lead levels in the atmosphere dropped significantly.
For “Freon”, the Montreal Protocol came into effect in 1989, gradually banning the production and use of CFC compounds worldwide, and the ozone layer finally entered a long recovery period. According to estimates from the World Meteorological Association, the ozone layer will fully recover by 2060. The Montreal Protocol is therefore called “the most successful international environmental agreement in history . “
For Midgley himself, among the more than 100 patents he obtained in his life, the most deadly was neither leaded gasoline nor Freon, but a pulley system.
In 1940, when Midgley, 51, contracted polio, he designed an automatic pulley system to lift himself out of bed. One day in 1944, the rope of the automatic device tightened around his neck causing his death.
American environmental historian John McNeill wrote a cold epitaph for Midgley: Midgley “had a greater impact on the atmosphere than any other organism in history.”