Many parents worry about their child’s exposure to phthalates, the chemical compounds used as plasticizers in a wide variety of personal care products, children’s toys, and medical devices. Phthalate exposure can begin in the womb and has been associated with negative changes in endocrine function. A new study soon to be published in the Journal of Pediatrics examines the possibility that in utero phthalate exposure contributes to low birth weight in infants. Low birth weight is the leading cause of death in children under 5 years of age and increases the risk of cardiovascular and metabolic disease in adulthood.  

To investigate the associations between in utero phthalate exposure and low birth weight, Dr. Renshan Ge of the Population Council and colleagues from Fudan University and Second Military Medical University in Shanghai studied 201 pairs of newborns and their mothers between 2005 and 2006. Of the 201 infants studied, 88 were born with low birth weight. The researchers analyzed samples of the infants’ meconium, the first bowel movement that occurs after birth, and cord blood to determine phthalate levels.  

They found quantifiable levels of phthalate and phthalate metabolites in more than 70% of the samples. Infants with low birth weight had consistently higher levels of phthalates. According to Dr. Ge, “The results showed that phthalate exposure was ubiquitous in these newborns, and that prenatal phthalate exposure might be an environmental risk factor for low birth weight in infants.” Although these associations are not conclusive, this study supports the accelerating efforts to minimize phthalate exposure. 

Reference: The study, reported in “Phthalate Levels and Low Birth Weight: A Nested Case-Control Study of Chinese Newborns” by Zhang Y, PhD, Lin L, MD, Cao Y, PhD, Chen B, MD, Zheng L, MSC, Ge R, MD, appears in the Journal of Pediatrics, DOI 10.1016/j.jpeds.2009.04.007, published by Elsevier. EurekAlert, June 25, 2009.

Recent epidemiological studies have revealed an increase in the frequency of genital malformations in male newborns (e.g., un-descended testes) and a decrease in male fertility.  

The role played by the growing presence in our environment of contaminants that reduce male hormone action could explain this phenomenon. 

It is known that the birth weight of males is higher than that of females due to the action of male hormones on the male fetus.If the exposure of pregnant women to environmental contaminants that diminish the action of male hormones has increased over the years, one would expect to see a decrease in the sex difference in birth weight.

This is exactly what a new study published in the July 2009 issue of Epidemiology shows. Investigators analyzed the Public Health Agency of Canada’s database on the birth weights of more than five million children born in Canada between 1981 and 2003.  

Using statistical methods that control for changes over time of mother’s age and parity, the investigators effectively show a sustained decrease in birth weight differences between boys and girls, which supports the hypothesis of growing endocrine disruption related to environmental contaminants. Contaminants found in plastic materials represent plausible candidates, since they are known to diminish the action of male hormones. 

“Our study underlines the importance of probing the impact of environmental contaminants on the health of mothers and fetuses and on the reproductive potential of future generations,” says lead researcher Dr. Guy Van Vliet, a pediatric endocrinologist and investigator at the Sainte-Justine University Hospital Research Center and a professor at the Department of Pediatrics of the Université de Montréal.

Reference: Sainte-Justine University Hospital Research Center, Newborn weights affected by environmental contaminants, University of Montreal, McGill University and Public Health Agency of Canada, June 15, 2009  

Exposure during pregnancy to the chemical bisphenol A, or BPA, found in many common plastic household items, is known to cause a fertility defect in the mother’s offspring in animal studies, and now researchers have found how the defect occurs. The results of the new study will be presented Saturday at The Endocrine Society’s 91st Annual Meeting in Washington, D.C.

The study, funded partly by the National Institutes of Health, joins a growing body of animal research showing the toxic health effects of BPA, including reproductive and developmental problems. Last August the U.S. Food and Drug Administration found BPA to be safe as currently used but later said more research on its safety is needed. BPA is used to make hard polycarbonate plastic, such as for baby bottles, refillable water bottles and food containers, as well as to make the linings of metal food cans.

BPA has estrogen-like properties and in pregnant animals has been linked to female infertility.

“The big mystery is how does exposure to this estrogen-like substance during a brief period in pregnancy lead to a change in uterine function,” said study co-author Hugh Taylor, MD, professor and chief of the reproductive endocrinology section at Yale University School of Medicine.

To find the answer to that question, Taylor and his co-workers at Yale injected pregnant mice with a low dose of BPA on pregnancy days 9 to 16. After the mice gave birth, the scientists analyzed the uterus of female offspring and extracted DNA.

They found that BPA exposure during pregnancy had a lasting effect on one of the genes that is responsible for uterine development and subsequent fertility in both mice and humans (HOXA10). Furthermore, these changes in the offspring’s uterine DNA resulted in a permanent increase in estrogen sensitivity. The authors believe that this process causes the overexpression of the HOXA10 gene in adult mice that they found in previous studies.

The permanent DNA changes in the BPA-exposed offspring were not apparent in the offspring of mice that did not receive BPA injection (the controls). This finding demonstrates that the fetus is sensitive to BPA in mice and likely also in humans, Taylor said.

“We don’t know what a safe level of BPA is, so pregnant women should avoid BPA exposure,” Taylor said. “There is nothing to lose by avoiding items made with BPA—and maybe a lot to gain.”

Reference: The Endocrine Society, Bisphenol A exposure in pregnant mice permanently changes DNA of offspring, 10-Jun-2009

The chemical bisphenol A, commonly found in many plastic household items, has been linked to yet another health problem in animals—an increased frequency of arrhythmias, or , a new study found. The results, seen only in females, will be presented Saturday at The Endocrine Society’s 91st Annual Meeting in Washington, D.C.

Past animal studies show that bisphenol A, or BPA, can have harmful effects on the reproductive, nervous and immune systems. Also, a study in humans reported last year found an increased prevalence of cardiovascular disease in people with high levels of BPA in the urine.

However, the effects of BPA on the heart are unknown, said study co-author Scott Belcher, PhD, associate professor in the University of Cincinnati’s Department of Pharmacology and Cell Biophysics.

In the new study, funded by the National Institutes of Health, the University of Cincinnati researchers found that low-dose BPA and estrogen can act alone or in combination to increase harmful arrhythmias in female rats and mice. Because BPA has properties similar to the main female hormone estrogen, it is considered an “environmental estrogen.”

Mice and rats in the study had normal heart rhythms at baseline, before administration of BPA or estrogen (estradiol), Belcher said. The investigators studied heart rhythms in both the working heart and in cultured heart muscle cells. In both models, exposure to BPA increased the frequency of arrhythmias, compared to baseline, in females but not in male animals, the authors found. Administration of estrogen alone also increased the frequency of arrhythmias in females.

Arrhythmias were most frequent in the female rats and mice when they received both BPA and estrogen, at levels normally found in female humans.

“We have identified a new possible risk for female heart health, caused by increased levels of estrogens in the body and exposure to the environmental estrogen BPA,” Belcher said.

BPA is found in polycarbonate-plastic baby bottles, refillable water bottles and food containers as well as the linings of metal food cans. Last year the U.S. Food and Drug Administration said more research on the safety of BPA is needed.

Arrhythmias occur when the heart beats too slowly or too fast or when it skips heartbeats. These heart rhythm irregularities can cause fatigue, lightheadedness, fainting or sudden cardiac death. If a fast heart rate affects the heart’s ability to pump, it can cause a heart attack.

The study’s lead author, Hong-Sheng Wang, PhD, assistant professor at the University of Cincinnati, will present the results.

Reference: The Endocrine Society, Bisphenol A exposure increases risk of abnormal heart rhythms in female rodents, 10-Jun-2009

People are likely being exposed to the commonly used chemical bisphenol A (BPA) at levels much higher than the recommended safe daily dose, according to a new study in monkeys. The results will be presented Thursday at The Endocrine Society’s 91st Annual Meeting in Washington, D.C.

“BPA is now known to be a potent estrogen,” said Frederick vom Saal, PhD, a co-author of the new study and a professor of biological sciences at the University of Missouri-Columbia. “Human and animal studies indicate it could be related to diabetes, heart disease, liver abnormalities, miscarriage and other reproductive abnormalities, as well as prostate and breast cancer.”

The U.S. Food and Drug Administration (FDA) declared BPA is safe based on estimates that people consume only small amounts each day from food. However, recent research indicated that U.S. adults are exposed to more BPA from multiple sources than previously thought, vom Saal said.

BPA is found in polycarbonate plastic food and beverage containers, such as water and infant bottles, as well as in the epoxy resin lining of cans and other sources. The chemical can leach into food and beverages, according to the National Institutes of Health, which funded the study by vom Saal and colleagues.

“Between 8 and 9 billion pounds of BPA are used in products every year,” vom Saal said.

In their study, he and his colleagues fed five female adult monkeys an oral dose of BPA (400 micrograms per kilogram of body weight). This amount is more than 400 times higher than the amount that the U.S. Food and Drug Administration (FDA) estimates that human adults are exposed to and 8 times higher than the estimated safe daily amount to consume, according to vom Saal.

Yet the blood levels of biologically active BPA over the next 24 hours were lower in the monkeys than the average levels found in people in the United States and other developed countries, vom Saal said. For levels to be higher in people when measured, their exposure dose must be greater than that given to the monkeys, he explained.

“These results suggest that the average person is likely exposed to a daily dose of BPA that far exceeds the current estimated safe daily intake dose,” vom Saal said.

He said that BPA exposure must come from many unknown sources, in addition to food and beverage containers. Like drugs, BPA acts in pulses, with each exposure creating a high-level pulse before it is cleared in the urine, according to vom Saal.

The researchers are continuing the study in more monkeys, but vom Saal said they do not expect to get different findings because the data in the first five animals were “very consistent.” The species of monkey that they used (rhesus) metabolizes BPA similar to humans, he added.

Reference: The Endocrine Society, Our exposure to controversial chemical may be greater than dose considered safe, 10-Jun-2009