Lead

Some lead

It matters Chemistry

Action and reaction

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Elementary!

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Spooky scary chemicals

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Er, who's got the pox?

Art Robinson Stuart Pivar Pope Francis Clair Patterson v - t - e

Lead, symbol Pb, known as plumbum in Latin, is a heavy metal. It is element number 82 in the Periodic Table.^[1] It is the heaviest element that has stable isotopes, making it the endpoint of the radioactive decay of many of the heavier elements such as uranium and radium.^[2][3] It has many uses due to its high density, resistance to corrosion, and malleability. Lead isn't the only element that has these properties; in fact, many of the elements around it in the Periodic Table have similar properties, with some even outcompeting lead in some of these regards. However, lead has one significant advantage over these other metals: it's cheap. As of 2018, one metric ton of tungsten, the most common substitute, cost $30,300,^[4] while gold cost a whopping 40 million dollars per metric ton.^{[5][note 1]} Lead, on the other hand, was only a meager $2,240 per metric ton.^[6] However, this cheapness comes at a significant price: lead is severely toxic. Ingesting it causes numerous neurological problems,^[7] hence it has slowly been removed from almost everything it used to be used in.^[8] European Union ROHS (Restriction of Hazardous Substances Directive) standards now prohibit its use entirely,^[9] meaning that the Chinese have to put all their lead in US-bound toys, toothpaste, and Soylent.

Toxicity[edit]

Inorganic lead compounds as well as lead subacetate, lead chromate, and lead phosphate are carcinogenic in animal studies; there is insufficient information to evaluate lead carcinogenicity in humans.^[10] Lead can cause a wide range of health problems in humans from both acute exposure (e.g., constipation, memory loss, loss of appetite) and chronic exposure (e.g., forgetfulness, depression, high blood pressure, heart disease, kidney disease, and infertility).^[11] In children, it has been estimated to cause 600,000 new cases of intellectual disabilities each year worldwide.^[12] Worldwide, it is estimated to cause 143,000 deaths per year.^[12] Lead exposure has also been linked to higher rates of criminality^[13] and reduced IQ.^[14]

Various writers in ancient Rome considered lead to be a poison, either explicitly or implicitly, including Pliny the Elder, Dioscurides, Galen, Celsus, and Vitruvius (80–70 BCE); it was Vitruvius who described lead plumbing specifically to be unhealthy.^[15] The epidemics of saturnine colic (17^th century) and Devonshire colic both lasted for decades, the latter of which was only recognized by George Baker in 1767 as being caused by lead ingestion some 70 years after it was first recognized as a disease.^[16] Lead use and concomitant poisoning of lead workers increased during the Industrial Revolution.^[16] The toxic effects of lead in workers were recognized by science in the 19^th century, and the first laws regulating lead exposure in the workplace came about in the UK in the 1870s-1880s.^[16] The first documented poisoning from lead paint ingestion was in 1914.^[17]:11

"Lead" in pencils is not the metal lead, but in fact a combination of non-toxic graphite (a form of carbon) with a binder of non-toxic clay.

Kennedy Krieger Institute[edit]

A map that compares the areas of Baltimore that have problems with lead paint to the areas that are predominantly inhabited by black people (largely as a result of redlining), showing that this is a persistent systemic problem to this day.

The Kennedy Krieger Institute (KKI) has been a pioneer in the area of research into and treatment of lead poisoning since the 1940s.^[17]:9 In 1991, KKI embarked upon what would become a controversial study, known as the Baltimore Lead Paint Study, into the health effects of lead and into the effectiveness of lower-cost lead abatement techniques. The study recruited low-income families who were mostly African American to live in lead-contaminated properties and partially-abated properties using different techniques. The study included 140 children in 107 properties. After the study was completed, many of the children had permanent neurological damage. A class action lawsuit was filed against KKI in 2001 and has not been resolved as of 2018. Since the study did not benefit the children who were the subjects of the study, but theoretically would have benefited other low-income children in lead contaminated housing, it has been argued by the plaintiffs that the study violated ethical research standards, including adequate informed consent.^[17]:168-231 The court in the class action suit went so far as to argue that the KKI study presented "similar problems as those in the Tuskegee Syphilis Study… the intentional exposure of soldiers to radiation in the 1940s and 50s, the test involving the exposure of Navajo miners to radiation… and the secret administration of LSD to soldiers by the CIA and the army in the 1950s and 60s."^[17]:2 The court also said that the study defied aspects of the Nuremberg Code.^[17]:2

Lead industry[edit]

National Lead Company, advertising the use of lead in children's toys in 1923

By the 1920s, lead in paint became widespread in the US. This was not by necessity but for profit, because relatively safe zinc-based paints were widely available in the 1920s and titanium-based paints were available by the 1930s.^[17]:8 Starting at this point in time, lead-based paint became the primary vector for lead poisoning in children, with lead included in a myriad of toys as well as lead-painted home walls.^[17]:8 In 1928, the Lead Industries Association (LIA) was formed to lobby for use of lead pipes in plumbing among plumbers and plumbing code writers.^[18] The LIA also downplayed the hazards of lead.^[17]:29 In 1949, Maryland passed the first law to prevent lead poisoning in children, the Toxic Finishes Law.^[17]:31 This had become necessary because Baltimore had one of the highest rates of poisoning.^[17]:6 The LIA lobbied Maryland officials and had the law repealed in 1950.^[17]:32 The LIA had argued that the law was an unnecessary burden on lead-based manufacturers, and that the best means of minimizing lead exposure was educating parents^[17]:32 and indoctrinating children through the use of mascots such as Dutch Boy.^[19]:134[20] In 1950, the LIA also knew that lead exposure was a growing problem for the industry and had a growing collection of privately-held research into lead hazards.^[17]:32-33 The lead industry has in fact been engaging in a coverup, a form of denialism, by simultaneously privately researching and understanding the hazards of lead while publicly trying to minimize the perception of their hazards.^{[17]:29-33[note 2]}

Sources of exposure[edit]

In gasoline[edit]

Tetraethyllead chemical structure

Originally, car engines had to be started by hand while turning a crank to begin ignition. This was a dangerous process, and when Byron Carter, who was a friend of the owner of Cadillac, was killed when the crank backfired and hit him in the face, this inspired car companies to begin using electric starter motors instead.^[21] These motors had a problem, however: the fuel explosions, which are typically controlled, began happening in irregular intervals in a process known as "knocking". This caused the cars to be loud and could result in damage to the engine.^[22] In the 1920s, inventor Thomas Midgley Jr. was tasked with finding an additive to gasoline that would reduce engine knocking, and despite knowing it was poisonous, he gave the approval to use the lead compound tetraethyllead (C₈H₂₀Pb).^{[23][note 3]} The compound was used as an additive to gasoline from the 1920s until the 1980s phase-out in the United States, and today, ethanol is the most commonly used antiknock agent.^[24] It was phased out in other countries at different times, but by 2021, it was finally no longer used in cars and trucks, with Algeria being the last to use it.^[25] Its contribution to pollution of the air and soil in cities and around motorways, combined with its incompatibility with catalytic converters, caused it to be phased out. Leaded fuels are still used in piston-engine aircraft as it reduces engine knock and increases the octane rating, though people are trying to find alternatives to these as well,^[26] especially after tests on NASCAR teams have revealed elevated lead levels in their blood.^[27]

In paint[edit]

Spreading the toxicity around

Lead was used in paint since the time of the ancient Romans (4^th century BCE), and the process of making the paint was described by Pliny the Elder. When lead is added to paint, it is more durable, dries faster, and lasts a long time. In the United States, it has been banned from household paints since 1978 due to its toxicity, but is still found in many areas of the U.S., especially in lower-income urban areas. Lead paint is often considered a racial justice issue, as there is strong evidence that lead paint affects black and Latino children at far higher rates, mainly due to the areas that still have problems with lead paint having been the targets of redlining in the past, and is a good counter to people who believe that systemic racism has no effects in the U.S. today.^[28]

For another kind of lead paint, galena or lead sulfide was frequently used as a black pigment even up to the nineteenth century times. It was only one of many toxic pigments that were used at the time, with others including cinnabar/vermillion (mercury sulfide), cadmium yellow (cadmium sulfide), and Paris green (copper acetoarsenite).^[29]

In plumbing[edit]

The word plumbing is derived from plumbum, the Latin word for lead, as the Romans made their pipes out of lead. Lead was used for plumbing for most of human history, with the U.S. only banning new lead pipes from being developed in 1986. An estimated 15 to 22 million Americans still drink water that goes through lead pipes,^[30] and about a quarter of households in the EU still have lead pipes.^[31] While new lead plumbing is not produced anymore (at least not in the U.S. or EU), many pipes made of lead are still in the ground or old houses. While this usually does not cause problems due to a protective coating on the inside of the pipes, if the water is corrosive enough to destroy the coating, lead may leach into the water, causing tremendous long-term damage to all who drink the water. One of the most famous examples of this happening was in Flint, Michigan, after the water source was switched from Detroit's system to the Flint River in an attempt to save money without anyone from the government testing the notoriously polluted water. The result was an attempted coverup on the part of the state government and dangerous levels of not only lead, but also Legionnaires’ disease and carcinogenic TTHMs in the water,^[32] and Michigan's at-the-time governor Rick Snyder was charged in 2021 for his role in the crisis.^[33] Although some studies have suggested ways to make lead pipes safer by using electricity to attach phosphates to the lead,^[34] most people understandably would prefer all of the lead pipes to be replaced.^[35]

In batteries[edit]

Quite possibly the most widespread use of lead today in the United States is in the form of the lead sulphate (PbSO₄) electrodes that are a crucial component of wet-cell batteries, which thanks to this use, are known informally as "lead-acid batteries", of the type found in many cars. Lead acid batteries have many advantages, among them their dirt cheap base materials, but are increasingly replaced due to their downsides like high weight and low energy density. During the Great Depression, 59 poor African Americans were poisoned after burning the casing from lead-acid batteries to keep warm.^[17]:30

At least 98% of the lead used in batteries gets recycled, more than any other non-alloyed metal.^[36] However, lead recycling is unregulated in many places, and recycling operations in developing countries are resulting in exposing workers and the environment to dangerous levels of lead.^[37] For example, many lead batteries from the U.S. are sent to Mexico, which has much less stringent regulations, where they poison the workers and environment.^[38] The influence of lobbying groups like Battery Council International has made legislative progress on this issue difficult.^[39][40]

In cosmetics[edit]

A display including cosmetics with lead content in 1934

The ancient eye cosmetic known as kohl is still used in some parts of the world. It is sometimes made with stibnite (Sb₂S₃), and sometimes made with lead (galena or PbS). Kohl that is not made from lead is usually considered of lower quality. Composition of lead-based kohl can be as high as 84%.^[41][42] A 2009 review article concluded that cosmetic use of kohl is "likely to be more theoretical rather than a practical health hazard."^[43] That's not to say that there are no dangers; children have been known to consume kohl, which does raise blood lead levels, and putting it over an open wound is dangerous. Lead has also been found in lipsticks, usually as a result of contamination rather than intentionally being put in them, but most lipsticks have been found to contain lead at below the FDA's limit of 10 ppm, though sometimes a more dangerous one will surface.^[44]

In hunting and fishing[edit]

Lead's malleability and density make it good for making bullets, and it was also used to make fishing weights. However, recent studies have shown these to be very toxic to wildlife, especially to birds of prey which will often ingest lead bullets in carcasses left by hunters and fish that have swallowed fishing weights.^[45][46] Lead is increasingly being phased out of bullets and replaced by nontoxic metals like tungsten.^[47] Sadly, this issue has been met with much resistance and denialism, mainly from gun nuts, which is why efforts to enact change have been slow.^[48] Barack Obama tried to ban lead bullets from federal wildlife refuges, but this was undone by the Donald Trump administration.^[49]

Other uses[edit]

Most stained glass, like this piece by Louis Comfort Tiffany, is leaded.

Because of its density (and cheapness), it's great for shielding against radiation. Lead aprons are frequently used for shielding against X-rays in medicine, but gold is typically used in household applications such as to shield the americium in smoke detectors due to its nontoxicity, even if it is several orders of magnitude more expensive.

It's also used for those little weights they add to your wheels whenever you get new tires, to balance them.

If you think aspartame is bad, Romans also used lead sugar (Pb(CH₃COO)₂) as an artificial sweetener. Really, it's a wonder they survived as long as they did.^[50] Lead sugar was produced by boiling grape juice in lead pots and was widely used because it was one of the only sweeteners other than honey that Romans had access to.^[51] Lead sugar was also used in hair coloring products such as Grecian Formula,^[52] but Combe Incorporated, makers of Grecian Formula, was forced to reformulate it following pressure from consumer and watchdog groups, with those sold since 2018 now using bismuth citrate instead of lead sugar.^[53]

Lead is also found in tobacco smoke, as if there weren't already enough reasons to avoid it.^[54]

Lead oxide is sometimes added to glass to make it stronger. It was often used in china and glassware used for drinking, but these uses have largely been thrown into the dustbin of history due to lead's toxicity. Lead glass is still used today for stained glass windows, however, and it can also protect against radiation.

Uranium-lead dating is considered the most reliable form of radiometric dating, as lead is relatively stable in rocks, compared to things like strontium and rubidium, which have a tendency to move to older rocks. The one problem is that uranium's long half-lives of 710 million years (for U-235) and 4.5 billion years (for U-238) make it only useful for dating old rocks, but it's still great evidence against a recent creation.^[55]

In pseudoscience[edit]

Anglesite, beautiful but deadly.

Lead and tin are used in molybdomancy, a type of divination involving pouring molten metal into water.

In traditional Chinese medicine, lead is supposed to be good for detoxing (yes, you read that right), malaria, ringworm, skin rashes, rosacea, eczema, sores, ulcers, and killing intestinal parasites, among other things.^[56] It's also used in unani and Ayurvedic medicine.^[43] Lead was also used as medicine in ancient Rome.^[15]

Lead is also used around the world as a folk remedy for things like upset stomach, constipation, diarrhea, vomiting, colic, and teething.^[57][58] Ironically, lead was known to cause colic since 1767.^[16]

Lead sometimes appears in homeopathy medications, as “plumbum aceticum”.^[59] There are claims from the early 20th century that it can treat things like excessive salivation and madness induced by syphilis, though the practitioners back then at least had the sense to acknowledge the existence of lead poisoning.^[60]

Lead crystals are sometimes used in crystal healing. The most common one is galena, which is the most common lead ore.^[61] Galena mostly is only dangerous if its dust is inhaled or ingested (as galena is pretty much insoluble), and it is sometimes used in student geology labs, but repeated exposure to it can be harmful.^[62] Anglesite, on the other hand, is a lead sulfide crystal that is much more soluble and is also very sensitive to heat and pressure, making it considerably more dangerous,^[63] but that doesn't stop some woo pushers from advocating its use in crystal healing.^[64]

Although it's more of a protoscience, lead had many uses in alchemy. Lead had the symbol ♄ and was associated with the planet Saturn. It was considered the oldest of the seven alchemical metals, the others being gold, silver, mercury, copper, iron, and tin.^[65] The most famous use of lead by alchemists is that they wanted to turn it into gold using a mythological "philosopher's stone". Today, this is actually possible through the use of particle accelerators, since lead and gold only differ by one proton, although any gold you get out of this process will be radioactive.^[66]

Not sources of exposure[edit]

Graphite, used in pencils, contains no actual lead.

Despite its name, "pencil lead" has never been made of lead; it was at one point made from a form of graphite that was mistaken for the metal. They are instead graphite (a type of crystalline carbon, once called "Plumbago") bound together with a little bit of clay. So anyone who cautions you about contracting lead poisoning from pencils is someone you probably don't want to take advice from in other areas.

"Go over like a lead balloon" is an idiom that means disastrous results. The band Led Zeppelin got its name when Keith Moon of The Who said the band would go over like a lead balloon. They decided to replace the balloon with the heavier-sounding German airship known as the Zeppelin, and spelt it as "Led" so no one would mispronounce their name.^[67] Obviously, no actual Zeppelins were ever made of lead.^{[citation NOT needed]}

See also[edit]

• Clair Patterson — largely responsible for eliminating tetraethyl lead from gasoline
• Coal is not kohl.

External links[edit]

• Lead Encephalopathy Due to Traditional Medicines
• The Man Who Accidentally Killed The Most People In History, Veritasium

Notes[edit]

References[edit]