MELISSA BLOCK, host:
Now, a story about chemicals that have been causing concern: phthalates are used in some plastics and food containers. Most children are exposed to tiny amounts of phthalates, and there's been a lot of debate about whether these low doses could affect a child's development.
As NPR's Jon Hamilton reports, one place scientists are looking for clues is neonatal intensive care units. Infants there get relatively high doses of phthalates at a critical time in their lives.
JON HAMILTON: Kids in a neonatal ICU often spend weeks hooked up to plastic tubes that supply oxygen, food, fluids and medicine. And many of these tubes inadvertently supply a phthalate called DEHP, which leaches out of the plastic. Without it, the tubing would be too brittle to use.
Dr. BILLIE SHORT (Medical Director of Neonatal Intensive Care Unit, Children's National Medical Center, Washington, D.C.): This is a little baby who is on IV fluids, so this tubing also has plasticizer in it.
HAMILTON: Dr. Billie Short runs the neonatal ICU at Children's National Medical Center in Washington, D.C. Short has been curious about phthalates ever since she learned that high levels could cause reproductive problems in lab animals. There is no good evidence that phthalates are causing problems in people. Even so, Short wondered whether they might pose a risk to infants who spent time on a heart-lung device known as ECMO.
Dr. SHORT: Stop here a second. This is actually one of the ECMO machines. So, this is the tubing I'm talking about. So when you hook this up to the patient, blood is put in this bag so you've got, actually, two units of blood. This bag right here is one of the culprits, one of the plasticizer.
HAMILTON: Newborns often spend a week or more on ECMO. During that time, their blood passes through the plastic circuit again and again. Short was pretty sure phthalates were getting out of the plastic and into kids' bodies. Tests showed she was right.
Dr. SHORT: The initial blast that they get - and I kind of describe it as a blast because when they go on this circuit, they have - almost their total blood volume is in the plastic circuit.
HAMILTON: And their phthalate levels can be more than 100 times the levels found in healthy adults. Short knew that lab animals exposed to phthalates just after birth were especially prone to abnormal sexual development. She figured kids exposed during the same time period might also be vulnerable.
Dr. SHORT: These are newborns being exposed, you know, within days of life. So, if anybody from plastic exposure is going to have growth problems - again, in their puberty area - this would be the population to look at.
HAMILTON: That's what Short did. She and a team of researchers tracked down a small group of teenagers who'd been on ECMO as infants.
Dr. SHORT: We were able with internal funding to bring - I think we brought 18 kids back. Luckily, all 18 of those kids were normal.
HAMILTON: Normal sexual development, normal hormone levels. Short was relieved, but she knew her study was too small to be conclusive. So she's been trying to get funding for a larger study.
In the meantime, her hospital and many others are switching to feeding tubes made without phthalates, and IV lines with a coating that keeps phthalates from leaching out.
Russ Hauser, an environmental epidemiologist at Harvard, says the ECMO study could only have detected a major problem.
Dr. RUSS HAUSER (Environmental Epidemiologist, Harvard School of Public Health): But some of the more subtle effects, and some that are even not so subtle, you would need a much larger population.
HAMILTON: Hauser has been trying to figure out how to do that sort of study. He says the easy part is knowing what to look for. It's the same problems that show up in animal studies.
Dr. HAUSER: Lower fertility and altered development of the reproductive organs that may lead to lower function of those organs later in life.
HAMILTON: Hauser says the hard part has been designing a study that will provide definitive results. One problem is time. Ideally, the study would follow kids from birth until puberty, or even later.
Another problem is that just about all kids in the ICU are exposed to phthalates. So, how do you find a comparison group that hasn't been exposed? And then there's the fact that even in ICU babies, phthalate levels aren't that high.
Dr. HAUSER: To put it in perspective, they would probably be about 1,000 to 10,000 times lower than levels used in experimental studies in rats.
HAMILTON: So, any effect on ICU babies is likely to be subtle - a slight delay in puberty, or fertility problems later in life. And the effect of phthalates on other kids, if there is any, will be even less obvious.
Jon Hamilton, NPR News.