Marie Curie invented the word  “radioactivity.” Literally.

She and her husband Pierre revolutionized  our understanding of the phenomenon. So, it’s only right that today,   her lab has been turned into a museum  in Paris called the Musée Curie.

But in the process of making those discoveries,   the Curies and everything around them were  exposed to a massive amount of radiation. The couple were buried in lead  caskets to contain the radiation. And their furniture was similarly contaminated.

Which kind of makes you wonder: How  safe is it to visit that museum today? After all, a lot of Marie  Curie’s stuff is still there,   and some of it definitely remains radioactive. A recent BBC story on the subject inspired  us to look into that question ourselves.

Here’s the safety report on  the birthplace of radiology. [♪ INTRO] For many years, the Curies studied radioactive  materials in a run-down shed without the   protective gear we would use today to handle  elements like uranium, polonium, and radium. Instead, they used… their bare hands. Then, at night, they would  literally watch the elements glow.

Marie Curie wrote that they  looked like “faint, fairy lights.” Simply put, they were saturated in radiation. So if you visit Marie Curie’s lab  today, you might be a little on edge. But the dangers associated with radioactivity   aren’t as straightforward as  radioactivity-equals-deadly.

Let me explain. Radioactivity is everywhere. All light, including the light  from the Sun, is radiation.

That’s because the Sun is like pure energy. And, at its most basic, radioactivity comes  from an atom that has too much energy. That makes it unstable.

So it kicks out an energetic particle to bring down the  energy level down a bit and become more stable. The Sun has so much energy that it’s  sending out energetic photons all the time. But only the really energetic  photons are a problem for you and me.

This is called ionizing radiation, because  when it interacts with other materials,   like the atoms that make up human beings, it can knock electrons off of those atoms,   making them electron-poor versions  of themselves, which are called ions. So ionizing radiation is not  good for you in large doses. But you’re exposed to small  amounts of it every day,   from certain industrial  materials to foods like bananas.

Even you are radioactive. Faintly, but still! About 2/3 of the ionizing radiation you’ll   ever absorb comes from that  kind of day-to-day exposure.

The other third, on average, comes  from medical tests and treatments:   X-rays, CT scans, and radiation  therapy for cancers and such. And, yes, there’s a way to  measure how much radiation   you’re exposed to so that you don’t overdose. The unit of measurement is a Sievert.

And the average human is exposed to  about 4.5 milliSieverts per year. For context, no long-term  adverse effects have been   documented for radiation exposures  below 100 milliSieverts per year. All of that is to say, we humans can  take some radiation and be totally fine.

But what if you’re walking around a  radioactivity museum where some of   the objects are above baseline radioactive levels? Because Marie Curie was so radioactive  from working with decaying elements, she   contaminated everything she touched: doorknobs,  notebooks, cabinets, tables, you name it. Her radioactive fingerprints can  still be seen on these things today.

And to measure the radioactivity of the artifacts,   you need a Geiger-Müller counter,  often just called a Geiger counter. The secret to this device is the  gas-filled chamber at its core. When radiation enters that chamber,   the energetic particles collide  with the gas and produce ion pairs.

Those ion pairs are then tallied per minute. More ions equal more radioactivity. If you measured the radioactivity in the Curie  lab while they were doing all of their polonium   and radium experiments… let’s just say, there  would have been a lot of ion pairs tallied up.

Again, the Curies were exposed  to a lot of radioactivity. And that had tragic consequences. Radiation is cumulative, so even if you’re  only exposed to low-level radiation,   you don’t want to hang out in it for a long time.

In addition to the callouses and burns Marie Curie  obtained from handling radioactive materials,   she eventually died from a radiation-induced  blood disorder called aplastic anemia. Today, we know that exposure above 100  milliSieverts can destroy bone marrow,   reduce blood cell counts, increase your  risk of cancer, and do all sorts of damage. Which brings us back to the safety of  visiting that museum filled with her stuff.

But before I tell you more about  that, let’s take a quick ad break. This SciShow video is supported by  Brilliant: the online learning platform. I remember when our family got our first computer.

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Most of the items in the Musee Curie today   that are still contaminated are  just what Marie Curie touched. But even those objects don’t  register high on the radiation scale. One doorknob, for instance, clocks around 0.1  milliSieverts above background radiation levels.

So you can still see her fingerprints,   which is awesome, but they won’t  make you sick, which is even better. Today, you could wave a Geiger  counter around in there and get   almost no signal above background levels. The worst of the radiation is gone because  the lab has largely been decontaminated.

A few smaller radioactive objects, like notebooks  and equipment, were stored in special containers. But in the decontamination process,  some of the big stuff had to go. For instance, a cabinet from the Curies’ home  lab was fairly radioactive, and was destroyed.

A team from Andra, a French agency that deals  with radioactive waste, tried to decontaminate   the outer layers of the wood without  compromising the integrity of the cabinet. But the radiation had seeped into the  deeper layers, and they couldn’t save it. Marie Curie’s original workbench was also removed  from the space, being too deeply contaminated.

There are a few ways to look at that kind of loss. But some of the people who worked to decontaminate   the lab viewed it as the ultimate  respect for Marie Curie’s work. They were finishing the work she started  by cleaning up the lab after she died.

So now, everything left in the  museum is widely considered safe. The public exposure limit for  a regular person in France is   1 milliSievert per year above the standard 4.5  milliSieverts per year you’re expected to get. Since radiation in general is more dangerous the  longer your exposure is, and people don’t visit   museums for that long, you should be perfectly  safe walking through our radioactive past.

Whatever little radiation remains is,  in a way, itself a historical object. Plus, the lab that’s now a museum wasn’t even  where Marie Curie did her most toxic experiments. That happened in a shed nearby,   which was destroyed during her lifetime  to make way for a new physics building.

Luckily, there’s no real cause  for concern at the museum today. That’s what the BBC reporter who  inspired this video found as well. You can read all about it in their piece,  which is linked in the description.

Thanks to all of the professionals who  have tested, cleaned, and protected the   Curie lab so that you can safely visit and  learn about these legendary scientists. [♪ OUTRO]