48. Cadmium: Don’t You Know That You’re Toxic?

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Cadmium will let you choose among a range of orange-ish hues, but it’s some pretty awful news if you contract the “cadmium blues.”

Featured above: Dans Les Blés by Berthe Morisot, circa 1875.

Show Notes

Lots of talk about etymology in today’s show notes, plus a whole mess of YouTube links.

SciTech Later: As I mentioned, I’ll be making my television debut this week on SciTech Now, a PBS show about science news hosted by Hari Sreenivasan. If you visit the show’s website, it’ll ask you to confirm your local PBS station (assuming you have one and assuming they carry it — there’s no guarantee). After that, the upper-right-hand corner of the website will tell you when you can watch the show, if you’d like to see yours truly speak a little more nervously than usual.

I’m Addicted To Who: If you’re a fan of the traditional ballad, might I recommend the cover by Local H, if you’re not already familiar?

2019-03-26 edit to add: Vox did a great history of this song and its influences, from surf rock to Bollywood musicals:

Yet “Worldly” Means The Opposite: I said that the Impressionists preferred “mundane” subject matter, a word chosen rather deliberately. People often use it to mean “boring,” but I prefer to use the definition that hews more closely to its etymological roots: Things pertaining to our Earthly realm, from the Latin mundus, meaning “world.” Rather than portraits of rich patrons, the Impressionists preferred to paint landscapes, still life, and scenes from daily life. Were I of a polysyllabic disposition, I might be inclined to alternatively articulate the loanword “quotidien,” roughly meaning “of daily life.”

A Limited Palette: Monet claimed that his entire palette consisted of only six colors, which he would mix to create any tone he needed. He said, “In short I use flake white, cadmium yellow, vermilion, red lake deep, cobalt blue, viridian green, and that’s all.” Whether this was technically true might be another matter, but the sentiment is pretty true. He and his contemporaries did prefer to mix paints to create shades, rather than use a wide variety of pigments.

The white, red, and green would have been made of lead, mercury, and chrome, respectively, so any of those priceless works of art would also make for a pretty respectable little element collection of its own.

The greatest painter of the 20th century used a few more pigments than that, but what a joy it was to hear him announce them.

Not Just A Boys’ Club: Most people are at least a little familiar with Monsieur Monet, but not as many know the works of Berthe Morisot or Mary Cassat. They were two women painters who were just as important to the movement — I don’t really have the space to get into their stories here, but maybe you’ll check them out if you’re doing your own research.

Some More Influential Art: I learned most of my vocabulary words by obsessively reading Calvin & Hobbes comics from far too young an age to fully comprehend what I was reading. (I imagine it caused my mom to react exactly like Calvin’s mom when I asked her, “Who the heck is Paul Gauguin?”)

So all of those strips are emblazoned in my memory forever, and I can remember my first exposure to the word “cadmium” was in this strip:

Considering later in the storyline, Calvin uses chunky spaghetti sauce instead of red paint, I had a vivid (if not entirely accurate) picture in my head of what exactly “cadmium red” was.

Now, we can talk all day about whether this is “high art” or “low art,” but I would prefer to discuss sculpture.

Kind Of Blue: Ironically, for all of its use as a red or orange or yellow paint, the pure metal has a veeeeeery faint blue cast to it. The “cadmium blues,” as you may have guessed, are something else: A term for any of the various terrible cadmium-related illnesses that will make you highly uncomfortable before killing you dead.

Some Words On Words: “Melinium,” one of the names for element 48 that didn’t make it, is apparently from the Latin melinus, “from honey,” because of the color of its sulfides.

But being named “cadmium” after calamine puts this element in a similar category as molybdenum: Much like that element’s name is borrowed from the Latin for lead, calamine very specifically means the zinc-based compound. I’m actually not sure how many more elements we’ll bump into that are named after other elements.

Finally, I just think the etymology of orpiment, the older yellow paint, is kind of interesting: It’s from the Latin auripigmentum, or literally, “gold pigment.”

Have It Both Ways: I usually like to specify my units, but I didn’t when calling the cigarette a “thousand-degree tube of flaming tobacco.” That’s because it’s close enough for government work in both Celsius and Fahrenheit: 1,100 degrees F in between drags, and 900 degrees C while drawing breath.

Gotta Have My Vape! So it’s pretty clear that vaping is not a habit worth pursuing, if you can avoid it, but it is responsible for (all of these are NSFW¹, sorry) some really great goofs courtesy of those good, good boys of podcasting.

I Legally Need To Mention This: The angstrom is a unit of length equal to 0.1 nanometers — roughly the diameter of an atom of sulfur or phosphorus. In 1907, the angstrom was pinned to cadmium by defining the wavelength of its red spectral line as precisely 6,438.46963 angstroms. In 1960, this definition was made obsolete.

That is just about all there is to say about that, though. I don’t like to get in the business of spouting off random factoids in the episodes proper — that’s what show notes are for.

Episode Script

In 19th-century France, a new painting trend turned the art world upside-down: Impressionism. Characterized by coarse brushwork, mundane subject matter, and dramatic lighting, the movement was largely a reaction to the stuffy attitudes that dominated fine art at the time. Key to this visual style was the use of intensely colored pigments that chemists had discovered only a few years earlier. Chromium provided dark, saturated greens; cobalt offered bright blue tones. But the cream of this chromatic crop was cadmium.

The yellow, orange, and red hues offered by element 48 could brilliantly light up a canvas, cover another color with perfect opacity, and remain vivid decades after the last brushstroke dried. The magnificent works painted by Monet, Morisot, and Cassatt are just as breathtaking today as they were a century-and-a-half ago. For every golden sunset, broad-brimmed sun hat, and carpet of blooming poppies, we can thank cadmium.²

But much like the dizzying patterns on a tropical tree frog’s skin, or the bright flowers of the lethal oleander, we could read cadmium’s eye-catching colors as a warning to stay away. With today’s element, we wander into the most toxic territory on the periodic table.

Welcome to Poisoner’s Corridor.

You’re listening to The Episodic Table Of Elements, and I’m T. R. Appleton. Each episode, we take a look at the fascinating true stories behind one element on the periodic table.

Today, we’re taking great pains to study cadmium.

Cadmium’s association with that striking yellow color goes back further than the impressionists. It was that very property that originally caught the eyes of two German chemists: Friedrich Stromeyer and Karl Hermann, who each discovered the element independently before teaming up to study the new metal.³

Several names were proposed: Wodanium after an old Germanic god; melinium after a Latin word for its color; klaprothium for the recently deceased Martin Heinrich Klaproth. But in the end, it was Stromeyer’s “cadmium” that stuck, a name that points to its discovery within zinc carbonate, also known as calamine.⁴

It turns out that cadmium is found almost exclusively in the company of zinc, which makes a lot of sense: both elements live in Group 12 of the periodic table. There aren’t any mines dedicated to collecting cadmium, because more than enough is produced as a byproduct of the profitable zinc industry.

But cadmium isn’t always discovered so deliberately alongside its upstairs neighbor.

Shipham is an English village of about a thousand people. Mining was an important industry for centuries, but by 1979, the mines were closed — the only people working the land then were a few schoolchildren growing vegetables for a class project.[notte]British Geological Survey, Shipham And Rowberrow.[/note] ⁵

That was going fine for a while, but soon, teachers and students alike noticed that their vegetables were looking a little unwell. The main symptom? The leaves of these plants were not green, but rather a sickly shade of yellow.

Subsequent analysis — by professionals, not the children — indicated that the soil contained high levels of zinc, lead, and cadmium. All those centuries of mining, with its associated water runoff and pollution, had contaminated the land all around the little town. Thankfully, those levels weren’t so high as to cause a public health crisis. The people of Shipham definitely had more cadmium in their bodies than any doctor would like to see, but not so much as to cause illness.^{6 7}

Sadly, the people of Japan’s Toyama Prefecture were not so fortunate.

Much like Shipham, Toyama is a region that’s historically been known for its zinc and lead mines. Unlike Shipham, it’s also an important agricultural center for the island nation. A significant portion of Japan’s rice is grown in the area. In the past, much of that rice was irrigated with water that mining companies had carelessly filled with heavy metals like cadmium.

By 1912, the effects of this contamination were starting to become noticeable.

That’s when some of the area’s older women started exhibiting symptoms of no known disease. Their legs and backs would throb and ache; soon all the bones in their body would soften and easily snap. Anemia and kidney problems would cause further unpleasantness before, finally, death.

It was a long, drawn-out fate, and all the locals knew was that once a person was afflicted, there was no recovery. The defining feature of the syndrome, from onset to bitter end, was the immense pain that wracked the sufferer’s body. It became known as “itai-itai byo,” which roughly translates to “ouch-ouch disease.”⁸

The problem became more pronounced over the next several decades. Concerned citizens were routinely brushed aside by the prefecture’s mining companies until 1972, when a class action lawsuit ordered those companies to pay for medical care, pollution monitoring, and reparations to those who had contracted the disease.⁹

Nowadays the region is much cleaner, but the legacy of itai-itai disease won’t soon be forgotten by those who lived with it for so long.¹⁰

Stories and mysteries of death, disease, and murder most foul are going to become much more common as we linger in the southeast corner of the periodic table. Depending on how you feel about that, I’m sorry, and you’re welcome.

Sam Kean, author of the atomic biography The Disappearing Spoon, calls this region “Poisoner’s Corridor.”¹¹ The tail ends of periods five and six loosely comprise this band of chemical ne’er-do-wells. While the halogens and alkalis are dangerous for their reactivity, and heavier elements can deliver a fatal dose of radiation, elements like antimony, thallium, mercury, and cadmium are hazardous due to their toxicity.¹²

It’s been a while since we’ve name-checked valence electrons, but once again, they are to blame. These metals, large and stable, are very flexible in how many electrons they’ll give or receive to their neighbors. This allows them to easily dissolve and sneak inside our body’s cells, disguised as elements our bodies actually need, and wreak havoc from within. Sometimes these ill effects have a sudden onset, other times it can take years before the damage is apparent. It all depends on exactly what biological process the element affects the most.¹³

In this case, element 48 mimics its more honorable sibling, zinc, and latches on to an enzyme called metallothionen. That little mouthful takes cadmium on a one-way trip — sometimes to the liver or the bones, but usually to the kidneys, where, ideally, it would soon be excreted. But in a cruel twist, the toxic substance sticks to the kidneys like flypaper — and practically never lets go. A cadmium atom can inhabit the body for decades, making even minuscule subsequent exposures increasingly dangerous. Even if it doesn’t poison the body outright, cadmium that sticks around for long enough can cause healthy cells to turn cancerous.^{14 15 16 17}

Clearly, we’re dealing with some nasty stuff here. Luckily, environmental regulations are a little stiffer than they were fifty years ago, and yellow paint only accounts for six thousandths of one percent of cadmium usage. When the element does turn up in consumer products — like when McDonald’s accidentally sold 12 million cadmium-laced drinking glasses in 2010 — it tends to be big news.¹⁸ We’re fortunate that, for the most part, cadmium is easy to avoid.

And yet, over a billion people siphon the element into their bodies every day.¹⁹

Along with ammonia, benzene, hydrogen cyanide, formaldehyde, and arsenic, cadmium is among the many harmful chemicals that make up a cigarette.^{20 21} By and large, cigarettes aren’t maliciously infused with these chemicals to increase their lethality, because it turns out drawing breath through a thousand-degree tube of flaming tobacco is plenty lethal on its own.²² For instance, the tobacco plant naturally absorbs a lot of cadmium from soil — sort of like the children’s vegetables back in Shipham. Cigarette smokers typically have twice as much cadmium in their bodies as non-smokers.²³

None of this is new information, of course. Cigarettes have had a deadly reputation for at least half a century, but their raw addictive power has kept the industry afloat nonetheless.

But we live in the high-tech world of 2019, and no longer does must one ignite the leaf of the tobacco plant to funnel nicotine into their lungs. Millions of people around the world now use electronic cigarettes, devices that atomize a liquid solution of intoxicants for the user to inhale, and often look like part of a Darth Vader costume. Because e-cigarettes produce an aerosol vapor rather than smoke, the activity is commonly called “vaping.”

Chinese pharmacist Hon Lik introduced the first e-cigarette in 2003, intending it to be a tool to assist people trying to quit cigarettes. Advocates still promote vaping as a smoking cessation aid as well as a healthier alternative to cigarettes. Whether the product successfully achieves either of these goals remains the subject of vigorous debate.^{24 25 26 27}

When it comes to the specific subject of cadmium poisoning, e-cigs might actually carry a substantially higher risk than traditional cigarettes. The solder used in the construction of some devices, especially cheap ones, is responsible for dozens of known cases of cadmium pneumonitis, a disease similar to itai-itai.^{28 29}

The association doesn’t end there, I’m afraid. Studies of the market’s less reputable cartridges have found that they routinely contain heavy metals like arsenic, lead, and yes, cadmium.³⁰ Scandalously shoddy manufacturing processes are to blame here, but really, it shouldn’t be too surprising that blasting particulate matter down your throat is an unhealthy practice.

Some elements should be collected with your lungs, like oxygen, nitrogen, and argon. Cadmium is not among them.

But there are plenty of ways to safely add today’s element to your collection. If you have access to a machine shop, for instance, you might have easy access to Wood’s Metal. Disappointingly, this is not some chimeric hybrid of lumber and mineral, but rather an alloy of bismuth, lead, tin, and cadmium. It takes its name from Barnabas Wood, the man who discovered it.³¹ The material melts at a relatively frosty seventy degrees Celsius, making it ideal for use with delicate objects, or as a safety release on pressurized canisters in case of fire.^{32 33}

Perhaps the most widespread use of element 48 is in nickel-cadmium batteries, which have powered countless toys over the years, like RC cars. Their use has been steadily declining due to the whole toxicity issue that we’ve been discussing this whole time. But it might be worth rooting around in the back of your closet to see if you can give any old relics a new home in your museum of chemistry.

In any of these cases, you’ll want to exercise more caution than you’d need with an element like silver or calcium. Even touching some of these materials is enough to make you sick.

In the end, you might just want to stick with a tube of paint. Cadmium remains the definitive yellow for modern-day artists. And after all, it could be worse: For thousands of years, the dominant yellow paint was called “orpiment,” a compound of sulfur and arsenic. That color was so incredibly poisonous that it was a major relief when cadmium yellow finally provided a safe alternative.^{34 35 36}

Thanks for listening to The Episodic Table of Elements. Music is by Kai Engel.

I’m excited to tell you that I’ll be appearing on SciTech Now this week to discuss the podcast and some of my favorite stories about the elements. Check listings for your local PBS station, or visit episodic table dot com later this week to watch the interview.

To learn the only six colors Monet used in his paintings, visit episodic table dot com slash C d.

Next time, we’ll go soft on indium.

Until then, this is T. R. Appleton, reminding you that this is a non-smoking program. Smoking is prohibited on the entire podcast, including the lavatories. Tampering with, disabling, or destroying the lavatory smoke detectors is prohibited by law.

1. Not Safe For Work. Or school, for that matter. I deliberately write this show to be free of coarse language, so I hope you’ll forgive me indulging in such uncouth humor.
2. My Modern Met, How Impressionism Changed The Art World And Continues To Inspire Us Today. Kelly Richman-Abdou, June 12, 2019.
3. Nature Chemistry, A Portrait Of Cadmium. Nadezda V. Tarakina & Bart Verberck, December 20, 2016.
4. Elementymology And Elements Multidict, Cadmium. Peter van der Krogt, 1999-2010.
5. New Scientist, The Hunch That Launched A Cadmium Scare. Roger Milne, May 23, 1985.
6. Science Of The Total Environment, Dietary Surveys On A Population At Shipham, Somerset, United Kingdom. J.C. Sherlock et. al., July 1983.
7. Environmental Geochemistry And Health, Heavy Metals In Soils In North Somerset, England, With Special Reference To Contamination From Base Metal Mining In The Mendips. Brian E. Davies and Rhonda C. Ballinger, December 1990.
8. The Elements Of Power: Gadgets, Guns, And The Struggle For A Sustainable Future In The Rare Metal Age, p. 181. David S. Abraham, October 28, 2015.
9. Ethics In Science And Environmental Politics, Role Of Experts And Public Participation In Pollution Control: The Case Of Itai-Itai Disease In Japan (PDF). Masanori Kaji, July 6, 2012.
10. Indeed, it receives significant attention on the Toyama Prefecture’s official website.
11. Slate, Blogging The Periodic Table: Bismuth: A Gentleman Among Scoundrels. Sam Kean, August 4, 2010. Also, of course, the book mentioned here.
12. ThoughtCo., The Most Toxic Elements On The Periodic Table. Anne Marie Helmenstine, Ph.D., October 5, 2019.
13. Interdisciplinary Toxicology, Toxicity, Mechanism, And Health Effects Of Some Heavy Metals. Monisha Jaishankar et. al., November 15, 2014.
14. The Elements Of Murder: A History Of Poison, p. 366. John Emsley, July 2006.
15. OSHA Brief: Medical Evaluation Of Renal Effects Of Cadmium Exposures (PDF). August 2013.
16. Agency For Toxic Substances & Disease Registry, Public Health Statement For Cadmium. September 2012.
17. Handbook On The Toxicology Of Metals, Cadmium Poisoning. Bruce A. Fowler and Agneta Oskarsson, 2015.
18. The New York Times, McDonald’s To Recall Glasses, Citing Cadmium. William Neuman, Jun 4, 2010.
19. World Health Organization, Tobacco. July 26, 2019.
20. American Cancer Society, Harmful Chemicals In Tobacco Products. Last medical review on March 12, 2017.
21. Verywell Mind, A Disturbing List Of Toxic Chemicals In Cigarettes. Terry Martin, reviewed by Dr. Sanja Jelic, September 5, 2019.
22. PhysLink.com, question answered by Dr. Michael Ewart.
23. Verywell Mind, The Health Risks Of Cadmium In Cigarettes. Terry Martin, medically reviewed by Dr. Sonja Jelic, September 19, 2019.
24. NEJM Resident 360, Does Vaping Work For Smoking Cessation? Dr. Amanda Fernandes, February 27, 2019.
25. Harvard Health Publishing, Can Vaping Help You Quit Smoking? Dr. Robert H. Shmerling, February 27, 2019. I am not sure why this and the previous source were both published on exactly the same day. Coincidence, I suppose.
26. Johns Hopkins Medicine, 5 Vaping Facts You Need To Know. Dr. Michael Joseph Blaha, 2019.
27. American Heart Association, Is Vaping Better Than Smoking? October 30, 2018.
28. Willamette Week, Colorado Lab Results Point To New Culprit In Vaping Cases: A Specific Chemical Used In Cheap Vaping Pens. Sophie Peel, October 7, 2019.
29. Caspian Journal Of Internal Medicine, Cadmium Toxicity And Treatment: An Update. Mehrdad Rafati Rahimzadeh et. al, Summer 2017.
30. Mic, What’s In Bootleg Vape Juice? These Are The Chemicals That Could Be Making People Sick. Melissa Pandika, October 1, 2019.
31. Journal Of Chemical Education: Ask The Historian, Onion’s Fusible Alloy (PDF). William B. Jensen, 2010.
32. Goodfellow Materials Hub, Woods Metal — Lump.
33. Reade Chemical Products, Wood’s Metal Alloy.
34. Winsor & Newton, Spotlight On Color: Cadmium Yellow. June 9, 2011.
35. Encyclopedia Britannica, Orpiment. Amy Tikkanen, January 4, 2019.
36. Geology.com, Realgar And Orpiment. Hobart M. King.