When I set out to write a book on all the great and hidden stories on the periodic table, I figured I’d have to delve into some strange and uncomfortable history. There was the inevitable brush with the alchemists, and humankind’s almost instinctual lust for gold and silver. I even ended up mapping out the elements on the periodic table, to reflect the intellectual currents of the past few centuries. What I didn’t expect was how relevant all that history would seem today, how often the same themes would come up again and again in current events and the news. But if it’s anything, the periodic table is still a microcosm for understanding all the wonderful and horrible things about the world.
I had reason to think of this last month when McDonalds recalled over 13 million Shrek-themed drinking glasses after discovering in them high levels of cadmium, element forty-eight. Cadmium can undoubtedly be one of the most beautiful elements—it has a long history in art as a pigment, and helped old masters produce vibrant colors no other substances of the time could. Even today, some shades—like cadmium yellow—retain the name.
But as the famous biologist Edward O. Wilson once said “In the natural world, beautiful usually means deadly.” Wilson was referring to how the brightest colored snakes, frogs, and insects usually harbor the deadliest venoms. But his wisdom applies equally well to the periodic table. Cadmium is one of the more poisonous elements on the table, and has one of its most notorious histories. Yet we keep making the same mistakes with it again and again. In fact, the first widespread recall of consumer goods with cadmium also involved drinking glasses. (Plus ça change…)
Cadmium sits below zinc on the periodic table, which means pure cadmium looks and acts like zinc, including having the same shiny finish as zinc. So, in the 1940s, some manufacturers decided to plate drinking glasses with cadmium and sell them in department stores.
This was bad enough—some atoms of cadmium would naturally slough off every time somebody filled the glass—but became a big problem when summer rolled around and people began drinking fruit juices like lemonade. These acidic juices scraped cadmium atoms off the cup’s surface in droves, and people around America fell ill with intense pain and diarrhea. McDonalds didn’t line its Shrek glasses with cadmium—it was used in the brightly colored paints on the outside, calculated to attract children’s attentions. But in recalling the line, the fast-food company cited the same fear of children ingesting cadmium while they drank.