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The newspaper of The Johns Hopkins University September 10, 2007 | Vol. 37 No. 2
Prenatal Exposure to Common Chemicals Tied to Lower Birth Weight

By Tim Parsons
School of Public Health

Exposure in the womb to perfluorooctane sulfonate and perfluorooctanoate — ubiquitous man-made chemicals used in a variety of consumer products — is statistically associated with lower weight and head circumference at birth, according to an analysis of nearly 300 umbilical cord blood samples led by researchers at the Johns Hopkins Bloomberg School of Public Health.

The results are published in the July 31 online edition of the journal Environmental Health Perspectives. Some of the study's findings were previously reported in February at a Society of Toxicology workshop.

Perfluorooctane sulfonate and perfluorooctanoate are polyfluoroalkyl compounds, whose uses include protective coating on food-contact packaging, textiles and carpets and the manufacturing of insecticides and other industrial products.

The study, conducted in Baltimore, found small decreases in head circumference and body weight in association with higher concentrations of PFOS and PFOA among infants born vaginally. The study also reported a negative association with PFOS and PFOA concentrations and the infant's ponderal index, which is a measurement of weight for length similar to the body mass index. For unknown reasons, the reductions in birth weight and head circumference were not observed among 65 infants born by Caesarean section. The researchers also did not find any associations between PFOS and PFOA concentrations and length at birth or gestational age.

"These small but significant differences in head circumference and body weight provide the first evidence for a possible association between exposures to PFOS and PFOA and fetal growth. However, the differences are small, and their impact on health is uncertain," said Benjamin Apelberg, lead author of the study and a research associate in the Bloomberg School's Department of Epidemiology.

The health impact from exposure to PFOS and PFOA is not fully known, but previous studies found that these compounds could cause tumors and developmental toxicity in laboratory animals at doses much higher than those observed in the Johns Hopkins study.

The researchers analyzed cord serum from 293 newborns delivered at The Johns Hopkins Hospital between 2004 and 2005. The samples were tested for the presence of PFOS and PFOA and eight other polyfluoroalkyl compounds. The samples were then matched to anonymous patient records, which included measurement of height, weight and head circumference of infants and other health information.

PFOA was detected in all the samples and PFOS in all but two. The concentrations for both were lower than those typically detected in adults in the United States and lower than those known to cause tumors and developmental problems in laboratory animals; more study is needed to understand health effects at these lower exposure levels.

Lynn Goldman, co-author of the study and a professor in the Bloomberg School's Department of Environmental Health Sciences, said, "Our study population has a large proportion of mothers at greater risk for adverse birth outcomes. Because of this, and also because this is the first study to report these associations, we need to be cautious in interpreting these findings until they can be replicated in other population."

Additional study authors are Frank R. Witter, Julie B. Herbstman, Antonia M. Calafat, Rolf U. Halden and Larry Needham. Witter is with the School of Medicine and Halden, the Bloomberg School. Herbstman, formerly a doctoral student at the Bloomberg School, is now at the Columbia Mailman School of Public Health. Calafat and Needham are with the Centers for Disease Control and Prevention.

The research was supported by funding from the Bloomberg School of Public Health's Maryland Mothers and Babies Study, Cigarette Restitution Fund, Johns Hopkins Medical Institutions, Johns Hopkins Center for a Livable Future and Heinz Family Foundation.


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