Preemies can fit in the palm of one’s hand, their feet barely larger than an adult thumbnail. They come into the world without fully formed lungs or properly functioning circulatory or digestive systems. So doctors and nurses gently place them in incubators, attach ventilators, and insert IVs. In recent decades, technology has come a long way in saving premature babies—but there’s room for improvement.
In almost every piece of this life-saving flexible equipment is a chemical called DEHP, a phthalate plasticizer that makes the materials flexible. DEHP is a known endocrine disruptor, meaning it interferes with hormones, which are especially crucial in times of development. The phthalate has been proven to inhibit testosterone but may cause other conditions as well—like liver toxicity and bronchopulmonary dysplasia, two common problems in preemies that can have fatal consequences.
Federal law only allows for DEHP levels of 0.1 percent in children’s toys, but there are no limits for it in medical products. In fact, DEHP is the only phthalate plasticizer approved for use in the soft plastics of catheters, IVs, and breathing tubes, which can contain levels up 40 percent—giving a potentially huge dose for our smallest patients.
Problematically, the chemical isn’t molecularly bound to the polyvinyl chloride plastic itself, so it can leach over time. Researchers found that the longer the equipment stays in or on someone’s body, the stiffer it gets—meaning the DEHP is leaching out.
This concerned Eric Mallow, a neonatologist at Johns Hopkins Bloomberg School of Public Health, who began looking into how much DEHP exposure preemies get during hospital stays that often last for weeks or months. What Mallow and his colleague Mary Fox found, and published last month in Nature’s Journal of Perinatology, was that they can receive daily amounts of up to 160,000 times higher than desired to avoid liver damage.
“There is a distinct lack of data in babies simply because it has not been studied,” says Mallow. “There’s no proof of safety.”
Although there isn’t a lot of data on the effects of DEHP on humans—much less very, very tiny humans—there are a number of researchers examining its potential risks. A study of rabbits weighing between two and three pounds, roughly similar to a preemie, showed that those fed via a tube containing the chemical received about one milligram of DEHP per kilogram of body weight each day—and after three weeks, they had liver damage. (Though liver damage is not usually fatal in preemies, it's difficult to manage.) The rabbits fed via a DEHP-free tube did not. Mallow and Fox calculate that critical preemies receiving maximum support get 16 milligrams per kilogram of their body weight daily.
Another study showed that pregnant rats given daily doses of 1,000 milligrams per kilogram in the last week of pregnancy and during the first two weeks of breastfeeding had pups that were born with lung abnormalities similar to bronchopulmonary dysplasia (BPD). BPD can cause preemie death and result in long-term health conditions, such as asthma and an increased susceptibility to lung infections. Of the 60,000 infants born every year in the United States weighing less than 3.3 pounds, close to 20 percent will develop BPD. “Do you really want preemies to be getting DEHP? It might well be one of the causes of BPD,” says Mallow.
While these what-ifs are alarming, exposure to DEHP should be kept in perspective.
Thirty years ago a baby born before 28 weeks gestation was almost certainly going to die. Now the survival rate for a 27-week-old is more than 90 percent. That’s undeniable progress, but these infants still face a variety of serious health issues in their first few months and beyond.
“We don’t want to take the chance that we’re complicating [those] even further by a chemical exposure occurring at that time as well,” says Susan Schantz, an environmental toxicologist from the University of Illinois, who was not involved in the study. “With DEHP, preemies are a group we really need to be thinking about.”
Mallow and Fox suggest that medical professionals use DEHP-free plastics such as silicone and polyurethane, which may be safer because they’re less likely to degrade and leach chemicals while being used. But those materials have not been adequately researched either, and as studies of alternatives to BPA have shown, different doesn’t always mean better.
But we do know many phthalates, including DEHP, are bad, and this paper is just further evidence of that, says Veena Singla, a staff scientist at NRDC (which publishes Earthwire). She recommends that the federal agencies responsible for protecting our health (i.e. the Food and Drug Administration) should put more limits on phthalates.
Some health professionals aren’t waiting around for that. In 2012, the massive health care company Kaiser Permanente began using alternative products in its hospitals. The company buys five million IV tubing sets and nine million solution bags each year, reports Mother Jones, and its new policy of replacing those materials saves about $5 million annually.
If more hospitals follow suit (if only for their bottom lines…), that just might bring bigger chances to little lives.
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