SPEAKER 1: Last week on the show, we talked about one of the summer’s big movie blockbusters, Oppenheimer. This week, we’re turning our attention to Barbie. So have you seen the movie yet, Diana?

DIANA: I actually have. I saw it last weekend. Overall, it was pretty fun and thought provoking. And I even got a little emotional about a movie about a toy. So that was fun.

SPEAKER 1: Yeah. It is an actual toy. So did you grow up with Barbies?

DIANA: Yeah, I did. My family even bought me one of those giant dream houses, big enough for me to crawl inside the bottom floor with my dolls on a sleepy afternoon.

SPEAKER 1: That sounds kind of cool. Well, I’m not sure where your Barbies are now, Diana. But there’s something collectors of vintage Barbie dolls may have noticed. Over time, Barbie’s plastic skin can get a little discolored or even sticky. It’s something that toy preservationists have actually been thinking a lot about.

SciFri’s AAAS fellow Chelsie Boodoo a big Barbie fan. And she wanted to learn a bit more about the science of Barbie’s chemical composition. So she turned to Dr. Yvonne Shashoua. She’s a research professor from the National Museum of Denmark.

CHELSIE BOODOO: Welcome to Science Friday, Yvonne.

YVONNE SHASHOUA: Thank you, Chelsie. Thanks for the invitation.

CHELSIE BOODOO: So Barbie came out in 1959. Could you tell us what the first Barbie doll was made of?

YVONNE SHASHOUA: We don’t exactly know what the formulation was for Barbie because that’s a trade secret that Mattel keep. But we do know that she’s made out of PVC. And she must have plasticizer in her because PVC can’t be made into a flexible material without a lot of plasticizer.

Plasticizer is a kind of softener. And it needs up to half of its weight in plasticizer to make it into a flexible, moldable plastic. The very first plasticizer that was used from the ’50s until well around 2000 were phthalates. And these are esters which soften the plastic very well, are quite low cost. But unfortunately, they have also some toxic properties because they’re very similar in chemical structure to the female hormone estrogen.

The plasticizers are just mixed in. They’re not chemically bonded to the polymer. So the polymer is the main part– the huge macromolecule, the main part of any plastic. And normally, it fills about 98% to 99% of the plastics formulation.

In PVC, there’s a bit of an exception because we have so much plasticizer. But the plasticizer doesn’t bond chemically. It just is mixed in. So it’s kind of like if you were mixing in a coloring to icing for a cake. If you wanted to, you could wash out that coloring. And that’s the problem– that the plasticizer migrates out of the plastic once it’s made.

CHELSIE BOODOO: So I imagine that’s how they also add the colors to it because when I think of PVC, I picture a white PVC pipe.

YVONNE SHASHOUA: Right. Well, just to tell you, Chelsea, that PVC pipe is a bit different because PVC guttering and pipes and window frames are just about the only thing that can be made out of PVC with no plasticizer. Everything else that we have that’s made out of PVC has plasticizer in it.

But to add the coloring, I mean, the colorings that are used in plastics are very strong, so again, a bit like icing. You just need a tiny amount of a coloring to color a whole batch of plastic.

And so how they do it is if they’re not sure which kind of coloring, and maybe this PVC is going to be used, one batch is going to be for Barbie’s face. Another batch is going to be made for a Star Wars elephant that’s blue, for example.

So what they do is they make up different batches by adding a little, tiny amount of coloring material to a batch of transparent or white PVC. And then they add a tiny amount of the coloring to another batch. So they’re diluting and diluting the coloring until it makes the right coloring agent.

CHELSIE BOODOO: So you’re telling me that other toys, not just Barbies, are made like this, too.

YVONNE SHASHOUA: Yeah, exactly the same way. Maybe the difference with Barbie is because she’s a doll, she’s got different components. And today, unlike in 1958, the different components were made out of one plastic. But today the head is almost always made out of PVC. But the body and the arms and the legs can be made out of different plastics.

CHELSIE BOODOO: I’m concerned because you said the phthalates can have some toxic properties. For example, my cat used to take all my Barbie shoes and hide them from me when I was a kid. So I’m concerned. Are the materials toxic to people or pets or the environment? And if we don’t know the specific composition of Barbies because it’s a trade secret, how would we even know if they’re safe for us?

YVONNE SHASHOUA: There’s been a long, long discussion about whether the phthalate plasticizer is safe for us or safe for the environment. But there was enough evidence in around 2000 for EU, and I know also in the States, to ban the most toxic phthalates. Phthalates are a family of esters of plasticizers.

And so they range in molecular weight from those that are so small– small molecules that may evaporate at room temperature to those that need something like 350 Celsius to evaporate. And so the lower the temperature they evaporate, the more of them potentially can be in the air because room temperature, which is 25 centigrade– those low molecular weight materials are easily present in the air.

But from 2007, anything that’s toys or any changing mats or any accessories that are meant for children under the age of three cannot be made with plasticizer that has a very high volatility.

CHELSIE BOODOO: When I think of plastics, I think about recycling them and how they break down. How long does it take for Barbies or these toys to degrade? Do you know what it looks like when they break down?

YVONNE SHASHOUA: The length of time that it takes for PVC to degrade or deteriorate is controlled by the environment the doll is played with or stored in, in the case of a museum. So if you play with your doll in a sunny window or take it to the beach with you, then she will be exposed to sunlight. And that speeds up the reaction with oxygen, which is the main degradation reaction very much.

We’re talking about, it could be two years to five years if the doll was constantly exposed to sunlight. But if she was kept, for example, as we do in the museum, if we kept the dolls in a freezer, or we could be talking about 50 years because there’s less heat and no sunlight and less oxygen in the freezer. So it slows the whole process right down.

So that means that in the museum, we try to keep the doll at low temperatures and in the dark so that it doesn’t start losing its plasticizer and oxidize. Now, of course, that’s totally ridiculous if you have a toy at home. So we can’t do that.

We can be aware that if our doll is sticky or if she begins to discolor, then it’s time maybe to think about not playing with her anymore, or at least giving her a good wash so that plasticizer doesn’t come into contact with our fingers so that we could end up eating the plasticizer.

CHELSIE BOODOO: Yeah, I definitely don’t want to be eating those chemicals. What materials could be used to improve Barbie production that are safe and environmentally friendly so we don’t have sticky Barbies everywhere?

YVONNE SHASHOUA: Well, something that’s happening more and more is that PVC is being replaced with other plastics that are also flexible but don’t need plasticizer to make them flexible. For example, a carrier bag from the store is made out of polyethylene. Its chemical structure is flexible. So it means that it doesn’t need plasticizer to make it flexible.

The challenge is that PVC is a very good mimic of skin. And so it’s used a lot in films to make masks and in research projects where they want to make a dummy that looks just like a person.

It’s difficult to replace PVC everywhere, but by replacing the plasticizer with either a higher molecular weight phthalate or something that isn’t a phthalate, there’s plenty of other plasticizers around, like citrates and adipates that could replace the phthalates. But they cost a little more. And so we’re going to have to pay more for Barbie if she’s completely made out a different kind of plastic or a different kind of plasticizer.

CHELSIE BOODOO: So I’m going to ask the question I think many people are wondering at this point. Should we get rid of our old Barbies? And is there a proper way that we should be disposing of them?

YVONNE SHASHOUA: I don’t think we should get rid of our old Barbies. I think we should look after them and wash them if they’re sticky. And we can put them in the freezer if they’re special Barbies and take them out to play with. But we should keep them out of the hands of young people that maybe want to chew because the plasticizer, as I said, is physically bound up with the polymer. And that means that mechanical action like chewing or pressing can release it to the surface.

SPEAKER 1: That’s Dr. Yvonne Shashoua. She’s a research professor from the National Museum of Denmark speaking with SciFri’s AAAS fellow Chelsie Boodoo.

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