This UA researcher studies how phthalates affect women's reproductive systems

Researchers at the University of Arizona have received a nearly $3 million grant from the National Institutes of Health to study the impact of phthalates on women’s fertility. Phthalates are a family of chemicals that are found in a number of consumer products, ranging from plastics to food packaging to beauty care products.

Zelieann Craig is an Associate Professor in the School of Animal and Comparative Biomedical Sciences at UA. She describes the chemicals as having different arms — the type of arm they have can dictate how they’re used.

Craig joined The Show to talk more about her research.

Full conversation

MARK BRODIE: Zelieann, are some of those arms more likely to end up seeping into our systems than others?

ZELIEANN CRAIG: Yeah, so we are exposed to them as they are used in, for example in plastics, they're not permanently stuck in the plastic. They're part of the plastic backbone, but they're more of a temporary component of the plastic. So when the plastics start being used or it starts to kind of wear down, they can actually come off. And they can enter the body through whatever route. If it's something that we can inhale or something that we were eating from like a food packaging or something like that, they can actually enter the body. And the types of arms will determine kind of what their overall structure is and what they can interact with once they enter a human or an animal's body.

BRODIE: So if you are exposed to a phthalate, the effect it has on your body, it sounds like it will depend on from where you were exposed?

CRAIG: Yes, it will depend from where and what kind of phthalate. What are the things that it can interact with? So a lot of things in our bodies interact with chemicals, kind of like a key and a doorknob and a lock. So if we have different phthalates that have different shapes and different arms, then they're going to be able to interact with different parts or different locks in the body.

And where they can get to will depend on how we were exposed. So for example, if we have a exposure that we are breathing in, obviously that's going to get through our heart and our lungs first, right? Because those are the two things that are going to be inside when you inhale something.

But if it's something that is eaten, the first targets are going to be our gastrointestinal tract, our guts, our liver and then from there it goes to the rest of the body. And if it's on our skin, then it will actually get absorbed through the skin and it can actually go through into our bloodstream in that way.

BRODIE: And is it safe to say that depending on which system in our body is exposed to the phthalates, it will have a different impact? Is it more dangerous in some parts of our body than others?

CRAIG: So that's actually things that we are investigating is which exposure matters the most and what places are the ones that have the highest impact on human health. But one of the things that we know is that a lot of our exposures in the population come from oral exposure, so ingestion.

BRODIE: And am I right also that in some ways these chemicals impact women more than men?

CRAIG: Yeah, we think that women are more susceptible to this. And this is based on a few observations. First of all, the Centers for Disease Control have been tracking levels of phthalates and human populations for quite a bit, quite a long time, since 2001. And they know that they are showing up in urine samples of our general population.

And when they break down the data from humans, they look at different age groups, the two different sexes, and they actually observed that the highest levels of some phthalates were in women compared to men. So women had greater levels.

And since we've become more aware about phthalates and their effects, people have reduced their use. But one thing that is very interesting to us is that despite phthalates in general, that levels are starting to go down in the population, women still have higher levels of some phthalates compared to men.

A lot of that tends to be attributed to the use of products that contain phthalates. It might be different between the two sexes.

BRODIE: Do we know if the chemicals impact men's and women's bodies differently?

CRAIG: Yeah, so the phthalates have this potential to interact with cells in the body, and that potential is very similar, right? What changes is that males and females have different cell types, for example, in their reproductive system. So the way that each organ reacts is going to be different.

So in general, we say that phthalates are not good for the function of hormones in the reproductive system in both sexes, but we also have specific concerns that are a little bit more enhanced in females because they not only have reproductive function to handle, but they also will handle, for example, a developing fetus, they will handle lactation.

So there are a little bit more things that we are concerned about in the female side, but they can be a threat for both males and females.

BRODIE: Can the phthalates also impact whether or not a woman can get pregnant to begin with?

CRAIG: Yeah, actually most of what we know about phthalates and the main driver for my personal interest and understanding how they do these things comes from populations of women that have been studied at the clinic. So these are women that go to the clinic because maybe their partner is having trouble with reproduction.

So they seek medically assisted reproduction. And so they represent a very useful group in science, so you can study how much phthalate in their urine and compare that to the different outcomes of the interventions that are done in the clinic and some of those have to do with their fertility.

And so from those studies, we know that women that have high phthalates in their urine, and that's a sign that they have more exposure to phthalates, they tend to have less eggs in their ovaries. They tend to respond less to the stimulations that they receive to ovulate at the clinic.

And there's also been some studies that have shown that the greater the phthalate level in their urine, the less likely they are to have a pregnancy to term. So they tend to have fertility issues if they have higher phthalate levels in their urine.

BRODIE: Is this the kind of family of chemicals that you think it would be possible just to stop using, to do away with?

CRAIG: Yeah, actually, and that's one of the things that have been done in Europe, in California. There have been very significant and I think effective efforts to reduce their use.

One of the challenges with phthalates is that there is a whole family of them. So a lot of the work that has been accomplished so far in their regulation includes what we will call legacy phthalates, which are the phthalates that were first discovered to be detrimental.

And so there's sufficient body of work and research showing that they're not good. And so those actually have been practically banned from a lot of products. The highest priority was with baby toys and things like that.

And California is actually kind of leading quite a bit in this aspect to getting some of them removed. But there are so many of them that we are still — we're working towards that goal, but we haven't been able to ban them all or substitute them.