You were part of a recently published study that linked high phthalate exposure during pregnancy with preterm birth. Can you start by defining phthalates?
Phthalates are a group of what we call synthetic chemicals, or forever chemicals, that are ubiquitous. They are widely used in our everyday household products. They're frequently added to plastics, to personal-care products and to other building materials. And they can leave the packaging that they're added to and enter our body through our skin, through our lungs, through our food, in a variety of ways.
Where are some of the most common places we can find phthalates in our daily lives?
They are ubiquitous. They're everywhere in the home. They're used to make plastics more flexible, more durable. And that, for example, includes food containers. They're used in everything from fragrances to shampoos and other personal-care products. They're used in phthalates flooring and other parts of the home. Studies have found them in our indoor air, household dust and really everywhere.
What was the most important finding from your recent research on pregnant women?
This study was important because it had a large sample size – over 6,000 pregnant women. By pulling participants from 16 studies around the country, including one that we have here in Colorado, we really were able to document the significant association between valid exposure and preterm birth.
We found that the risk of preterm birth was increased by 12% to 16% among pregnant women who had higher levels of certain phthalates in their urine compared to those who had lower levels during pregnancy. This strongly suggests that phthalate exposure is a potential cause and a preventable cause of preterm birth.
What are some of the other ways research suggests these chemicals can affect public health?
They're called endocrine-disrupting chemicals because they interfere with the normal function of natural hormones in our bodies. For example, phthalate exposure in animals can alter the development of the male reproductive system or can cause infertility in females. And in humans, exposure to phthalates during pregnancy has been associated with abnormal neurodevelopmental outcomes in the offspring, increased risk of allergies or asthma and obesity in children.
How do phthalates cause these effects in the body?
We have some ideas. They're endocrine-disrupting chemicals because they directly bind to hormone receptors in the body. Or they may affect hormone levels indirectly by increasing or decreasing the production of other binding proteins, or signaling molecules, that affect the hormone levels. It’s through the hormones in our bodies that they have these effects.
And of the places where we can find the phthalates, which you said are ubiquitous, is there a most dangerous type? Or are there certain objects we should definitely avoid?
This is a natural, normal question, but I think that the level of risk depends more on the dose that we ingest, inhale or absorb, rather than on a specific product.
I would think first about a product that we use every day, and we each use different things that we come into contact with, like plastic containers, personal-care products or shampoos. And for the very young children who have a lot of hand-to-mouth activities, plastic toys are dangerous. Or household dust might be a more important source of exposure. It depends on the products that we each use.
As you said, we cannot completely avoid them, but what are some ways we can reduce our exposure?
There are now things in which you can store your food that are not plastic. We can cook more food at home rather than storing it in plastic containers. If we do store food in plastic containers, it's important to not put them into the microwave or the dishwasher because the high temperature causes more chemicals to get out of the plastic, and we get more exposure that way.
For personal-care products, we can try to check the labels and not buy those that have these chemicals. Although, unfortunately, they're not always listed. For babies, we've already started to use toys that don't include these phthalates, but they still exist everywhere.
Do studies, including your recent look at preterm births, suggest reducing exposure can make a significant difference when it comes to our health?
In other words, can we do something about it? This study is important because we estimated that 12% of the preterm births could be prevented if valid exposure in the study population was reduced by 50%.
This is a very meaningful health impact, especially when you consider that one in 10 infants born in the United States are preterm. And infants born preterm have a greater risk of neurologic problems, respiratory allergies, obesity problems.
It is worth it.
And besides pregnant women, are there other groups at higher risk for adverse effects from these chemicals?
Definitely pregnancy, or the in-utero development, is a sensitive period for the effects of phthalates, but there are other sensitive periods during the life span – puberty and menopause, for example. All the periods that are characterized by hormonal transitions are sensitive periods because of how these phthalates act on our hormones.