Perhaps somewhat unnervingly, a recent study conducted in France has shown that bisphenol A, a chemical found in some plastics, can be absorbed through the skin. This finding has sparked renewed interest in the chemical, which has been a source of concern since the 1930s, when researchers first began exploring its possible toxic effects.
BPA is an organic compound used to impart strength and durability to polycarbonate plastics. According to the Environmental Protection Agency, it is present in many consumer products, including water bottles, baby bottles and the lining of metal food and beverage cans. The BPA content of these items is regulated by the Food and Drug Administration, with original approvals dating to the 1960s.
Nevertheless, BPA can also be found in many non-consumable items - CDs, DVDs, safety equipment, automotive and industrial parts - that are not subject to the same FDA restrictions. Recently, thermal receipt paper, one of these non-regulated items, has been placed under the microscope.
The study, along with a second study conducted at Harvard University that examined the BPA content in the urine of pregnant women, also found that handling store receipts that contain BPA can correlate to increased levels of BPA in the body. Many store and ATM receipts are coated with a heat-sensitive film that gives them a smooth, "plasticky" feel. If BPA is used in this coating, it can constitute a large amount of a person's daily exposure to the chemical, especially if handling receipt paper is necessary for his job. The Harvard study showed that out of the 389 pregnant participants, cashiers had the highest concentrations of BPA in their urine compared with teachers and industrial workers.
So why is there concern about exposure to BPA? Research about the chemical has been controversial, with many differing perspectives as to its safety. Some studies suggest BPA is an endocrine disruptor, which is a chemical that behaves like a naturally occurring hormone in the body and binds to receptors for that hormone.
"In the case of BPA, it is believed that it binds to estrogen receptors, most likely ones on the cell membrane," said Gail Prins, a professor at the University of Illinois at Chicago. "If it occurs during development, there is ample evidence to show that it reprograms the tissues by altering the epigenetic memory of the cells. The cells then behave differently throughout life to subsequent estrogen signals."
In other words, early exposure to BPA may cause cells to behave abnormally in response to the presence of estrogen later on, such as during puberty.
But not all researchers agree about the safety of BPA. According to the EPA, it is not clear if there are any physiological effects caused by the small amounts of BPA adults and children consume daily.
Laboratory studies have shown that BPA can be linked to delayed reproductive maturity in rats and mice, but only at much higher doses than those to which humans are normally exposed. There is also some concern about whether rodents are accurate subjects for BPA studies because their metabolism is different from those of human beings.
"BPA is detoxified in the liver and there are some differences between humans and rodents with regards to how fast that occurs," Prins said.\nThis evidence, however, may not be proof that rodents cannot give us useful information about BPA metabolism.
"The metabolic patterns are very similar between these two species - certainly enough so that the rodent is an effective model," Prins said.
Dosage can also affect the outcome of BPA research studies, often in surprising ways.
"BPA shows responses at low doses that can go away at higher doses," Prins said. She noted that although this effect has been observed in studies of some types of hormones, it was not expected in BPA.
"In fact, this may be why some observe no effects, since the doses they use may be too high," she said.
Research continues, but in the meantime, non-scientists vary in their knowledge and concern about BPA and other potentially toxic chemicals.
"I'm always concerned about being exposed to harmful chemicals," third-year College student Abrahem Kazemi said. For example, carcinogens - chemicals that can change the DNA structure of cells and increase one's risk of developing cancer - "can come from foods, chemicals," Kazemi said. "I'm concerned, but I don't think there's much I can do about it."
Not all students feel this way, however.
"I don't worry about it," said fourth-year College student Krista Harriman.
Fourth-year College student Nash Baker agreed. "It's not really a concern," he said.
Environmental toxicologist Emily Monosson said she feels the public is as well-informed about BPA as it could be.
"I think they get the message that something is toxic - but don't know what that means, how much exposure matters, etc.," Monosson said.
She noted that this might be partly because of media coverage on the subject.
"Sometimes, I don't think the press gives the reader enough credit - that maybe they'd like to know more and can understand more, or make informed decisions," she said.
For those who are concerned about BPA in particular, there are several suggestions on the EPA website for reducing and avoiding exposure. These include avoiding the use of scratched plastic bottles and plastic containers to heat food in the microwave.
"I did change over the plastic bottles my kids use," Monosson said. "Am I worried for myself? Not really. But mostly for those handling those receipts all day."
Research has yet to conclude whether BPA is harmful in small doses. But owing to its widespread use in many consumer products, the results of BPA studies will be important to the public both in the United States and around the world.
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