Common chemicals investigated for possible impact on babies

Could phthalates, a group of chemicals found in everything from vinyl flooring to soft plastics to shampoo and skin lotion, affect babies before they're even born? It's a tricky subject with plenty of conflicting information, and it's exactly the kind of environmental issue researchers at the Medical University of South Carolina like to tackle as part of a larger effort to protect people's health.

Obstetrician Roger Newman, who directs Women's Health Research at MUSC, said some previous phthalate studies were troubling. One, published in 2014, suggested phthalates might raise the risk of pre-term births. Others focused on the possible impact of prenatal phthalate exposure on babies' reproductive organs.

"Women's exposure to specific phthalates during their pregnancy was resulting in newborn boys with measurable physical differences in their genital development," Newman said the research seemed to suggest. Specifically, he said, prenatal exposure to phthalates appeared to have the potential to affect the genitals of some baby boys, a change that could signal later infertility and a low sperm count.

“To me, it was extremely provocative to have physical characteristics being altered at birth, particularly one that most people recognize as having a relationship to ultimate reproductive success,” Newman said.

The MUSC/NIST Phthalate Study

So Newman and colleagues, including research biologists Abby Wenzel and John Kucklick at the National Institute of Standards and Technology, also known as NIST, worked together at the Hollings Marine Laboratory to try to see if that held true for fetuses and newborns in their own study.  

Wenzel, an MUSC graduate student at the time of the study, performed her research with NIST financial support. The Hollings Marine Lab, or HML, is a joint venture that includes NIST, MUSC, the National Oceanic and Atmospheric Administration, the College of Charleston and the South Carolina Department of Natural Resources. It focuses on coastal ecosystems and human health.

“Certain phthalates are endocrine-disrupting compounds that act as anti-androgens, the primary male sex hormone,” Newman said. “They disrupt cell development in the testes, which produce and secrete androgens in the male. The concern behind our study is whether exposure to phthalates during early pregnancy may be affecting reproductive development in utero, especially for boys.”

The MUSC researchers looked at boys in utero with ultrasound and newborns after delivery, measuring penile development; and girls through newborn exams only, because it's more difficult to measure their genital development in utero.

The researchers recruited about 400 pregnant women for the study. Almost half were African-American and half were white. Newman said having almost equal numbers of African-American and white women made the study unusual. “Most of the other studies that have been done on this subject have been in the Northeast or California, with very homogenous white populations.”

About 230 of the women were pregnant with boys, the rest with girls.

The MUSC and NIST researchers measured eight phthalate metabolites. Metabolites are produced when the phthalates are taken up by the body and react with liver enzymes, changing the original molecule. The eight metabolites they looked for were MBP, MiBP, MBxP, MEHP, MEOHP, MEHHP, MEP and MMP, representing the most prevalent phthalate metabolites generally found in the U.S. population.

Phthalate Study Results

Key results, according to Newman:

• All of the pregnant women had detectable urinary levels of phthalates.
• Phthalate exposures were much higher among African-American women than whites. The reason for this is not definitively known, but the researchers said it may be related to the reported greater use of certain personal care products among African-American women.
• In African-American fetuses and newborn boys, exposure to higher levels of certain phthalates (MiBP,MMP,MEHP and MEHHP) was associated with significant reductions in penile length, measured in utero and at birth. This effect was not found in white fetuses or newborns.
• There was a significant reduction in the anopenile distance in all male newborns with all measured phthalates, and this reduction was significant for MEHP. The effect was stronger for African-American newborns than whites.
• Results in female newborns were less striking, but again showed racial differences. Higher levels of certain phthalates (MEP and MBP) were associated with a longer anoclitoral distance in white female newborns and a shorter ano-clitoral distance in black newborns.

Phthalates have been under scrutiny for years. The Centers for Disease Control and Prevention reports on its phthalates fact sheet that their effect on human health is unclear, but "some types of phthalates have affected the reproductive system of lab animals."

The Consumer Product Safety Commission has banned six types of phthalates in toys and some other items connected with children. Recent news reports have linked phthalates to mac and cheese, fast foodand allergies in kids.

But the American Chemistry Council says on its website that studies and government reviews "have concluded that phthalates used in commercial products do not pose a risk to human health at typical exposure levels." And as 60 Minutes has reported, at least one scientist found that while phthalates seemed to cause abnormalities in the babies of rats exposed to phthalates, that was not true for monkeys.

Newman and his team are well aware of the controversy, and said it's important to get more data on phthalates, and for that matter, all potential environmental contaminants, to make sure people have the information they need to make good choices. “We also wanted to move some of this debate from childhood to in utero to see if abnormalities can be identified associated with maternal phthalate exposure,” Newman said.

Challenges in Reducing Phthalate Exposure

But that's not always easy. First, Newman said, "Phthalates are broken down very quickly, and everything has phthalates in it." In essence, people are continually exposed to phthalates, even though our bodies can eliminate them fairly rapidly.

Second, he said, chemical companies “stay ahead of the scientists. They're already replacing a lot of the phthalates. They use a replacement that has a different chemical group tagged on to it somewhere.”

Kucklick agreed. “It's a catch-up game that scientists play. It is very difficult to monitor for phthalate replacement compounds, since the information on the replacement is usually proprietary. What we hope to do is to provide enough information on exposure and effects, so that problematic chemicals can be replaced with safer ones.”

Third, phthalates aren't the only chemicals people are exposed to, Newman said. "There are lots of other environmental contaminants that need to be looked at, as well as mixtures of things we're exposed to in the environment. People will say, 'How do you know this is the important one?' That's a very tough question. There's tremendous interest in how to measure the totality of the exposure."

National Institute of Standards and Technology

Measurement is where NIST comes in. The government agency, which has laboratories in the HML, specializes in setting global measurement standards. Kucklick leads NIST's Environmental Chemical Sciences Group.

"The phthalates are something we'd been measuring for some time, mainly supporting the Centers for Disease Control who monitor phthalates and host of other contaminants in the US population as part of their National Health and Nutrition Examination Survey," Kucklick said.

"So, we have this phthalate technology that was available for use by our partners in the Hollings Marine Laboratory. Our lab is probably one of the best equipped in the country for looking at human or wildlife exposure, based on the diversity of our instrumentation and staff.

“The HML partnership provides an excellent opportunity to leverage the measurement skills of NIST, especially in exposure science, and extend them to the clinical setting at MUSC.”