Episode Transcript
Interviewer: There's been a lot of buzz about BPA in plastics and how that can affect human health. We think we know a lot about it, but do we really? Up next on The Scope.
Announcer: Examining the latest research and telling you about the latest breakthroughs. The Science and Research Show is on The Scope.
Interviewer: I'm talking with Doctor Christy Porucznik, Associate Professor of Family and Preventive Medicine and Associate Chief of the Division of Public 人妻中出视频 at the 人妻中出视频 of Utah School of Medicine. Where does BPA come from? It's kind of everywhere, right?
Dr. Porucznik: Most of us get most of our BPA exposures from food. It occurs in packaged foods, it's not in the food itself, it's in the packaging. And so it's in the lining of things like soup cans or it's in plastic packaging that your food comes in and also medications. Sometimes the capsules or even the tablets, there's BPA involved in the manufacturing process. It's everywhere. You can't avoid it.
Interviewer: Turns out there's a lot we don't know about BPA.
Dr. Porucznik: BPA is an endocrine disruptor. What we know is that it interacts with substances in your body in the way that hormones do. We've seen effects of BPA on many different hormone pathways. In men, we see sexual dysfunction. In our study, we've observed an association between BPA and semen quality. The primary focus of our study is examining levels of BPA in couples so both the man and the woman who are trying to get pregnant and then seeing if people with higher levels take longer to get pregnant.
Interviewer: Why are you studying couples?
Dr. Porucznik: Actually the reason that we're studying couples is that it takes both of them to get pregnant.
Interviewer: Good point.
Dr. Porucznik: It's obvious, but it's shocking. In the land of reproductive epidemiology, almost no one studies couples. They study women. And mostly they study pregnant women. But since our question is about time to pregnancy, we would have been missing half the story if we left out men. We know that BPA affects sperm and so men might actually be the most important part of this particular relationship.
Interviewer: How exactly are you doing this work?
Dr. Porucznik: We've recruited couples in the community who are planning to get pregnant. For our couples, when they recognize that they're in their fertile window, both the man and the woman collect a daily first morning urine specimen. The men stop collecting urine after the fertile window is done because at that point they're either pregnant or they're not. The women continue collecting through the menstrual cycle so that should they have conceived that cycle, we actually have urine specimens for the time of during implantation that we can study for exposure to environmental chemicals.
Interviewer: Are you trying to determine whether levels of BPA can affect conception or whether this might be a critical window for the new baby?
Dr. Porucznik: We think both of those. There are a lot of researchers who are studying what's called developmental origins medicine with the idea that what happens to you in utero can have lifelong consequences. Most of those studies don't start until babies are actually born, though. If there was a transient exposure that happened during pregnancy, we've missed it. My prospective study design is going to be the way that we could discover potentially environmental exposures that are linked to, say, a heart defect, that happen during that critical phase where the heart was developing.
Interviewer: If researchers have not been examining this window, what have they been doing up to this point?
Dr. Porucznik: Most of the studies that we have right now that talk about early exposures to BPA and then 人妻中出视频hood outcomes have come from prenatal samples collected during a routine prenatal visit. In our best studies, they have three urine specimens, maybe one from each trimester. But here's the problem with that. BPA metabolizes very quickly. The half-life is six to eight hours.
Interviewer: Oh, wow.
Dr. Porucznik: What that means is if I examined you urine from this morning, it would tell me about your exposures yesterday. But if yesterday was not a normal day for you, then it might not tell me anything about your typical exposures or your exposures during a relevant window.
Interviewer: Is that true? It's completely passed out of the body, it's not stored in any way or anything like that?
Dr. Porucznik: Ninety percent of BPA is actually excreted in the urine within the first day of exposure.
Interviewer: What that also means is that if you make a change in the way you consume foods or the types of foods you consume, where they come from, that can have immediate implications for you.
Dr. Porucznik: Yes, it really can. We've collected thousands and thousands of urine specimens and it's very rare that we've ever had a specimen in which we could not detect any BPA, but we see a wide variation in levels. Some people are consciously trying to avoid BPA. Their levels are lower.
Interviewer: Interesting. What have you found with your research so far?
Dr. Porucznik: One thing that we've found so far is that we've actually been able to quantify how much day-to-day variability we see in BPA levels within an individual. The upshot of this is that at a minimum you need at least six urine BPA specimens in order to have good confidence that you're going to classify somebody in the same high, medium or low BPA category. Six. Most studies have one to three.
Interviewer: This just illustrates how little we know about BPA exposure. What remains to be done? What are sort of the next steps for you?
Dr. Porucznik: In terms of BPA research, I think at this point everybody is convinced that BPA is a hormone disruptor and it's probably something we should think about how we're consuming and where it's being used. But it's not so strong that it's causing widespread effects. By that, I mean if exposure to BPA was causing infertility, we would have noticed.
Interviewer: Yeah, true.
Dr. Porucznik: Right? But our idea is that even if it's just increasing time to pregnancy, then for some couples who might be on the edge of sub-fertility already, then the BPA exposure might be something that on a population level is pushing us to more infertility workups. It's pushing us to more IVF and as a society, that's costing a lot. Not in just money, but it costs a lot in terms of anguish four couples who are trying to get pregnant or in terms of low birth weight or adverse birth outcomes that are associated with assisted reproductive technology.
Announcer: Interesting, informative and all in the name of better health. This is the Scope 人妻中出视频 Sciences Radio.