[♩INTRO].

In the mid-1800s, factories began mass-producing matches. Lots of them were hugely successful, and pretty soon, they were selling millions of matchboxes a year.

And then the factory workers — many of whom were young women — started dying. The symptoms would often start with a toothache and jaw pain and then progress to tissue death. In some cases, the condition was fatal.

Doctors eventually realized the problem was the kind of phosphorus used in the matches at the time, so they called the condition phossy jaw. But it still took decades and governmental crack-downs for companies to switch over to another, safer type of phosphorus. These days, phossy jaw would be little more than a relic of history, if it weren't for one thing: It's also a side effect in modern medicine.

The English chemist John Walker is frequently credited with inventing the type of friction matches we would recognize, back in the 1820s. The main ingredients in his match heads were potassium chlorate and antimony sulfide, which ignited from the heat of friction if you rubbed the match on sandpaper. There were some problems with these matches, though.

Sometimes they didn't light at all… and because you had to really scrape them to get the flame going, sometimes, the head of the match just flew off and there became a tiny little fireball. Which was understandably concerning. Everything was flammable back then!

Within ten years, though, a bunch of people independently came up with an idea for a better match. They replaced the antimony sulfide with white phosphorus one of the few different forms pure phosphorus can take which took much less heat to ignite and was therefore much more reliable. Soon, phosphorus match factories went into production all over the world.

And then the case reports started rolling in:. Factory workers were developing what would soon become known as phossy jaw. The disease led to severe infections and caused the patient's bones to rot often starting with the jawbone.

At the time, the only real treatment was to remove any damaged bones and hope the infection wouldn't spread to the brain and turn fatal. It became clear that the problem had something to do with the white phosphorus they were working with. Around one in ten workers on the factory floor developed phossy jaw within five years of exposure, while the office workers were unaffected.

And it turns out white phosphorus is really reactive, so it was combining with water vapor and carbon dioxide in the workers' breath as well as amino acids in their saliva to create bisphosphonates. These compounds suppress a type of bone cell called osteoclasts, whose job is to break down and reabsorb regular bone tissue. So essentially, bisphosphonates keep bones from replenishing themselves.

And that lack of replenishment is more of a problem for bones with fast cell turnover rates—like the jawbone. So in the presence of bisphosphonates, the jawbone would start to die. And about 20% of the time, so would the patient.

Lower class workers around the world knew this was happening. So did their doctors, and at least some of the general public. I mean, Charles Dickens was writing about it in 1852.

But factories in the mid-19th century weren't exactly known for their concern about factory workers. And for decades, very little changed. Then, in 1888, a match factory in London took things a step too far and proved themselves to be especially terrible.

That spurred a local socialist and activist, Annie Besant, to write about the horrible conditions in the factory which, in addition to the health risk, also included long hours, low pay, and fines if a worker so much as dropped a match. In response, the owners of the factory tried to get the workers to sign a statement saying they were perfectly happy with life there. They refused, and when one of the workers was fired, all fourteen hundred of them went on what would become known as the Matchstick Girls' Strike.

The strike finally called the world's attention to the phossy jaw problem. And it just so happened there was another, safer way to make matches, which was discovered around 1850. The key is red phosphorus, another form of pure phosphorus.

Its atoms are arranged differently, which means it doesn't react chemically the same way white phosphorus does so it doesn't cause phossy jaw and therefore isn't dangerous to factory workers. There is another benefit to red phosphorus, too:. You can use it to make safety matches these matches only light if you strike them on the box.

In safety matches, the match itself doesn't actually contain any phosphorus. Instead, the box is coated in red phosphorus and powdered glass, while the match head's ingredient is usually potassium chlorate. When you strike the match on the box, the friction with the powdered glass generates enough heat to turn a tiny amount of the red phosphorus into white phosphorus.

Then, this miniscule amount of white phosphorus ignites those are the sparks you see as you strike the match and the heat from that ignites the potassium chlorate on the match head. And, finally, you get the flame. Now, despite all this, it took a long time for red phosphorus matches to go mainstream.

That's partly because it wasn't until 1906 that multiple countries came together and signed a treaty banning white phosphorus matches. Even then, the US was not among the signatories so they kept making them for another twenty-five years. Now, there are also other industries that use white phosphorus, so changing over matches didn't completely eliminate its use.

Still, as match factories switched to red phosphorus, the number of new cases of phossy jaw dropped dramatically. At least, until around 2003. See, in the 1990s, doctors started prescribing bisphosphonates to treat certain types of bone disease like, metastatic cancers that spread to the bone from other parts of the body.

Researchers still aren't totally sure how bisphosphonates help, but they think it has something to do with keeping healthy bone cells from being replaced by damaged ones. But then, the jawbones of some of the patients started dying. Scientists quickly made the connection to the phossy jaw of the late nineteenth century, and realized the tissue death was a side effect of the medication.

So, they decided to call this new disease bis-phossy jaw. And it is still a thing. For a lot of patients, the benefits of bisphosphonates outweigh the risk of developing bis-phossy jaw, so they're still being prescribed.

And thanks in part to the match factory workers way back when, we know a lot about what symptoms to look out for when someone is at risk. It may have taken a long time for the world to recognize the extent of the exploitation of those factory workers, but over 130 years later, the legacy of the matchstick girls lives on. Thanks for watching this episode of SciShow!

If you enjoyed this stroll through science history, you might also like our episode on that time the US government poisoned booze. And maybe consider clicking on that subscribe button…. We put out a new video every day, so you can count on us to feed your hunger for science knowledge. [♩OUTRO].