Surrounded By Plastic, NICU Infants Tested For Risk
A diagram of regulations regarding plastics chemicals found in common household items.
Critically ill newborns may help researchers figure out whether children are at risk from plastic additives called phthalates.
Scientists say the nation's sickest newborns are exposed to unusually high levels of phthalates — chemicals in plastics that can mimic hormones — because they often spend days or weeks connected to feeding tubes, breathing tubes and intravenous lines made of plastic. And the exposure comes at a critical time in human development.
One doctor conducted a follow-up study by testing patients years after they were exposed to phthalates as infants in the neonatal intensive care unit.
"If anybody is going to have problems, this would be the population to look at," says Dr. Billie Short, medical director of the neonatal intensive care unit at Children's National Medical Center in Washington, D.C.
Of the patients — now teenagers — whom she was able to track down, Short says tests showed they had normal sexual development. But the study population was too small to draw any firm conclusions, she says.
Measuring Real-Life Exposure
Because they can act like hormones in the body, phthalates have generated a great deal of debate about whether low doses might affect a child's development.
Short says she began studying infants in her ICU years ago when she realized they were being exposed to a phthalate called DEHP. Eliminating DEHP wasn't an option because without the plasticizer, the tubes that keep many of her patients alive would be too brittle to use.
"This tubing has plasticizer in it," she says, reaching for a dangling plastic IV line next to a bassinet containing a tiny newborn in her ICU.
Studies of lab animals show that high doses of phthalates can cause abnormal sexual development and reproductive problems. There's no good evidence that phthalates are causing similar problems in people.
But Short wondered whether the chemicals might pose a special risk to infants who spend days or weeks on extracorporeal membrane oxygenation (ECMO), a heart-lung machine for newborns who can't breathe on their own.
"This bag is one of the culprits," she says, pointing to a clear plastic bag connected to yards of plastic tubing and the ECMO machine.
Both the bag and the tubing contain phthalates. And they form a circuit that an infant's entire volume of blood will pass through again and again.
High Exposure In A Critical Time
Short thought phthalates were leaching out of the plastic and into kids' bodies. Tests showed she was right.
Phthalate levels in kids on ECMO 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. And she thought infants exposed during the same period might also be vulnerable.
So Short and a team of researchers tracked down a small group of teenagers who had been on ECMO as infants.
"I think we brought 18 kids back," she says. "Luckily, all 18 of those kids were normal."
Tests and physical examinations showed they had normal sexual development and normal hormone levels.
But Short says that study was too small to be conclusive. So she has been trying to get funding for a larger study.
In the meantime, Children's National Medical Center and many other hospitals are switching to feeding tubes made without phthalates, and IV lines coated with a substance that keeps phthalates from leaching out.
Additional Study Needed
The ECMO study was a good first step, says Russ Hauser, a professor of environmental epidemiology at Harvard School of Public Health. But to detect anything but the most dramatic abnormalities, he says, "you would need a much larger population."
Hauser has spent the past three years trying to figure out how to do that sort of study.
The easy part, he says, has been deciding what to look for. They are the same problems that show up in animal studies: lowered fertility and abnormal development of the reproductive organs.
The hard part has been designing a study that will provide definitive results, Hauser says.
One problem is time, he says. Ideally, the study would follow kids from birth until puberty or even later.
He says another problem is that just about all kids in an ICU are exposed to phthalates. So how do you find a comparison group that spent time in an ICU but wasn't exposed?
And then there's the fact that even in ICU babies, phthalate levels aren't so high that they would be likely to produce dramatic abnormalities, Hauser says.
"To put it in perspective," he says, "they would probably be about 1,000 to 10,000 times lower than levels used in experimental studies in rats."
So any effect on ICU babies is likely to be subtle — a slight delay in puberty, or fertility problems later in life.
Hauser says the effect of phthalates on other kids — if there is any — would be even less obvious.
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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. Transcript provided by NPR, Copyright National Public Radio.
