High BPA levels found in hospitalized, premature infants.
Calafat, AM, J Weuve, X Ye, LT Jia, H Hu, S Ringer, K Huttner and R Hauser. Exposure to bisphenol A and other phenols in neonatal intensive care unit premature infants. Environmental Health Perspectives doi:10.1289/ehp.0800265.
|maria mono, Flickr.|
Bisphenol A is a common component of plastics and epoxy resins that are used in a wide range of consumer products, notably compact discs, plastic water bottles, baby bottles, dental sealants and food and beverage containers, as well as the carbonless paper used for credit card receipts. Medical equipment, such as plastic flasks, beakers and containers, also contains BPA.
Because BPA can leach -- especially when heated -- from products into food and drink, exposure in people is broad and constant, albeit at low levels. Major sources include food, air and water. Monitoring studies find the chemical in more than 90 percent of adult Americans (Calafat 2007). Children and teenagers have higher levels than adults.
Little has been known about the extent of exposure in premature babies. One recent study estimates healthy newborns under three months old may have 11 times greater levels of BPA in their blood than adults (Edington 2008). Because of their immature organ systems and fast growth, developing and newborn babies may face the greatest health risks from this ubiquitous chemical.
Potential effects of exposure to low levels of BPA are beginning to be understood, thanks to animal experiments. The chemical can mimic estrogen and influence the hormone system. Human and animal studies strongly suggest that BPA influences a wide range of health abnormalities, including heart disease, diabetes, infertility and abnormal brain function.
Interest in BPA's health and safety have grown as evidence of its associated health effects builds. Yet, the safety of BPA is currently an ongoing hot debate.
During 2008, a flurry of reports reached different conclusions of BPA's safety (National Toxicology Program; US Food and Drug Administration; Government of Canada) . Some nations have taken steps to ban the chemical's use, while several retailers voluntarily stopped selling products with BPA.
Researchers from the Centers of Disease Control and Prevention analyzed BPA levels in urine samples collected from the diapers of 42 premature babies receiving care at two Boston area hospitals. Two types of BPA were measured: free (not modified) and conjugated (modified in the body).
The authors grouped the babies into categories based on how much contact they had with plastic medical devices that contained another plastic, the phthalate DEHP: low, medium or high. The contact was due to the complexities of feeding needs and treatments.
The low group was primarily fed by bottle or a throat tube. The medium group received continuous or one-time feedings through tubes leading directly into their digestive track. The high exposure group included infants with multiple feeding and breathing tubes.
The authors also included age, breast- or formula-feeding status and length of hospital stay as other potential variables.
The researchers found BPA in all urine samples measured. Average BPA concentration in these premature babies was high -- approximately 10 times higher than previously reported for adults and twice as high as children between 6-11 years old.
BPA in the babies' urine was a mixture of free and conjugated forms.
Babies exposed to more plastic medical devices had more BPA than those with less contact. The average levels in the ‘medium’ and ‘high’ categories were about 3.4 and 9 times higher, respectively, than those in the ‘low’ category.
BPA levels were highly correlated with DEHP levels in the urine. BPA was also correlated with another contaminant measured, methyl parabens. (Editor's Note, 1/27/09: Medical tubes, bags and other devices may contain polyvinyl chloride (PVC) plastics that could have both BPA and phthalates as additives. The strong correlation between DEHP and BPA observed in this study suggests that PVC may be another source for human exposure to BPA.)
Babies who stayed in hospital A had 16 times higher BPA levels than in hospital B. Without actually measuring sources of BPA exposure, the researchers were unable to explain the differences.
Among other examined variables, younger babies were slightly more exposed than their older counterparts. These babies were also more likely to receive more complicated treatments that predisposed them to higher level of BPA through more contact with medical devices.
No significant effects were found on breast- and formula-feeding status or duration of hospital stay.
The study indicates that plastic medical devices are a significant source of BPA exposure for premature babies. The early born infants represent a subpopulation that is at high risk of being exposed during critical life stages.
The results also show for the first time that human infants can at least partially metabolize BPA in their bodies. The conjugated -- or changed -- form of BPA was detected in the urine samples of analyzed babies. Enzymes that normally modify BPA in the body are not thought to be fully functional until a few months to a year after birth.
The metabolized or ‘conjugated’ versions of BPA is less harmful than the unmodified form of BPA.
The findings agree with and support another recent study that estimates healthy newborns may have 11 times the levels of BPA than adults (Edginton 2008). Computer models based that prediction from adult exposure levels.
This study only measures exposure level. Potential effects of exposure on the health of these babies needs to be addressed in future research.
However, higher levels of BPA in humans has been linked to increased risks of cardiovascular disease and diabetes (Lang 2008). Both of these conditions may originate during fetal or early development, as proposed by the now well-known Barker hypothesis. Low birth weight babies also have increased risks of developing heart disease and diabetes as adults.
This study's findings show that premature babies (already born with developmental and physiological limitations) are further challenged by exposure to a compound known to negatively impact health.
Interestingly, the study also found differences in exposure level between hospitals suggesting products used in one site could be stronger sources of exposure. Further research to identity devices safer than others could greatly reduce exposure in hospitalized patients.
Edginton, A and L Ritter. 2008. Predicting plasma concentrations of Bisphenol A in young children (< two years) following typical feeding schedules using a physiologically-based toxicokinetic model. Environmental Health Perspectives doi:10.1289/ehp.0800073.
Lang, IA, TS Galloway, A Scarlett, WE Henley, M Depledge, RB Wallace, and D Melzer. 2008. Association of urinary bisphenol A concentration with medical disorders and laboratory abnormalities in adults. Journal of the American Medical Association 300(11):1303-1310.
vom Saal, FS, BT Akingbemi, SM Belcher, LS Birnbaum, DA Crain, et al. 2007. Chapel Hill bisphenol A expert panel consensus statement: Integration of mechanisms, effects in animals and potential to impact human health at current levels of exposure. Reproductive Toxicology 24:131-138.