EPA currently regulates the chemicals dry cleaning businesses use, but no one had ever investigated which compounds remain on clothes after cleaning. Then sixteen year old Alexa Dantzler got help from Georgetown University chemistry Professor Paul Roepe to answer that question for her science fair project. They tell host Bruce Gellerman about the surprising results of their published research.
GELLERMAN: There’s nothing dry about dry cleaning - the process uses liquid solvents to remove soils and stains. There are federal standards for work place exposures to the chemicals that are used, but none for the residues that might linger on our clothes, because no one measured what might remain when they come back from the dry cleaner until Alexa Dantzler.
Alexa is a high school student from Arlington Virginia, who reached out to Georgetown University and got help from chemist Paul Roepe. Alexa, welcome to Living on Earth!
DANTZLER: Thank you!
GELLERMAN: And Dr. Roepe, welcome to you too!
ROEPE: Thank you for having us.
GELLERMAN: So, let’s start with you Alexa. Where did you get the idea for investigating dry cleaned clothes?
DANTZLER: Well, freshman year, I had to take a biology honors course, and we were required to do a science fair project. So I was flipping through a book one day, and it mentioned perchloroethylene - classified as a probable carcinogen - has actually been found in ground water and soil that has come from the dry cleaning establishments.
So I thought, well, if it could be detected in these various environments, could the residue from the dry cleaning be, you know, contained in these clothes. So I wanted to quantify the PERC in the clothes.
GELLERMAN: So at what point, Alexa, did you decide you needed help with your research?
DANTZLER: Well that first year, I had used a method that used silver nitrate, and I tried to titrate the PERC, but it was an imprecise way of measuring the PERC. So I just emailed a couple universities nearby in the DC area including Georgetown. And Dr. Roepe was the only one who responded to me and said, "come on over" and that it'd be very interesting.
GELLERMAN: Hm. Well, Dr. Roepe, you’re pretty inviting.
ROEPE: (Laughs). I try to be, yeah.
GELLERMAN: Well, what did you think when you got the call?
ROEPE: Well, to be honest, I was a little surprised that a high school student would be asking these questions, and I assumed that they had already been answered. And I did some lit searches, and some web searches, and I couldn't find anything that addressed this simple question that this bold young student was asking.
GELLERMAN: So, PERC. Tell me a little bit about this chemical called PERC.
ROEPE: So, PERC is short for perchloroethylene. It’s still not anywhere near as well studied as it probably should be or needs to be. Perchloroethylene is a neurotoxicant, it can cause dizziness, blurred vision, that sort of thing. It can cause liver damage and kidney damage.
Alexa Dantzler and Paul Roepe (Photo: Anita Dantzler)
GELLERMAN: So Alexa, tell me about the experimental design - how you found out what was in the clothes coming back from the cleaners.
DANTZLER: So what we did was - with the help of my mom - we sewed these four types of fabric: silk, cotton, wool, and polyester in little cloths, and we sewed them under jackets, so they couldn’t be detected. And we sent them to seven different dry cleaners, and after they were dry cleaned, I placed them in the freezer, and then they were taken to Georgetown and they were frozen until we were ready to extract them.
GELLERMAN: So to the layperson, what did you find?
ROEPE: We found several things. We asked simple questions such as: how does the fabric type influence the amount of perchloroethylene that's retained? Wool, for example, is very porous, and has really fat looking fibers under a microscope, whereas silk is very, very different in structure.
So we thought that that might influence the amount that’s retained, and we did indeed find that - we found that wool soaks it up like a sponge. We also asked the simple question: if you repeat dry clean the same piece of cloth multiple times, does it build up? And we answered that indeed it does, for wool - it keeps building up quite a bit, as a matter of fact. Whereas for cotton and polyester, it sort of plateaus after two or three dry cleaning cycles.
And then, we asked another real simple question - how long does it take for the stuff to volatilize back off the cloth once you took those articles of clothing back home and stuck them in the closet. And the short answer to that is, it takes about six or seven days to release about 50 percent of the stuff from a garment, and that plastic wrap that they put over your clothes in the dry cleaner, we found that that really didn’t influence the rate of release at all.
GELLERMAN: So the sweater I get back from my dry cleaner - is it safe to put on?
ROEPE: I don’t do it.
ROEPE: (Laughs.) Everything is a risk factor. A lot of it depends on your genetics. Individual to individual, is very tough to answer. Across a population is really all a scientist can tell you - the relative risk factor, you know, if you take a million people and do these levels of exposure, is that safe?
Well, for some of those people, it’s not. But for most of the people - are they going to get cancer within ten years from repeated exposure to dry cleaned clothing? Probably not.
DANTZLER: If you want to look at it as it’s a probable carcinogen, then I would be a little more scared to be wearing even a little bit of a chemical that’s even considered a probable carcinogen.
GELLERMAN: Now California has moved to ban PERC, so has Illinois, so has New Jersey as I understand it. Right?
ROEPE: Right. They have banned it. They’re just taking their time in terms of phasing it out completely. And the city of Philadelphia is actually in the middle of lowering their legal exposures to the parts per billion range, instead of to the parts per million range.
GELLERMAN: What about these green dry cleaners - are they any safer?
DANTZLER: In our study, we tested two dry cleaners that were considered green, and what we found were: one had super-critical hydrocarbons in them, and then in another, just carbon dioxide might have been compressed and used to dry clean the clothes. So the term can vary depending on the method of dry cleaning.
ROEPE: Green dry cleaners basically just ... from what we can gather, just mean that they’re not using PERC, but they could be using a whole bunch of other different things.
GELLERMAN: So this goes onto your permanent record, there, Alexa. What do you hope to do after high school?
DANTZLER: After high school, I would like to do pre-med and then go onto medical school.
ROEPE: You’re going to apply to Georgetown, aren’t you?
DANTZLER: Yeah. (Laughs).
GELLERMAN: Well, Dr. Roepe and Alexa, thank you very, very much - good speaking with both of you!
DANTZLER: Thank you.
ROEPE: You’re welcome.
GELLERMAN: Georgetown University chemist Paul Roepe and high school scientist Alexa Dantzler. Under current federal regulation, dry cleaners located in residential buildings have until 2020 to phase out the use of PERC.
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