Bisphenol A (BPA) is an endocrine-disrupting chemical, and has been associated with health effects such as premature puberty and developmental neurotoxicity. Massive quantities of BPA – about 10 billion pounds and rising – are produced each year, making it one of the highest volume chemicals in commerce. For that reason alone, it may not be surprising that scientists find BPA in the urine of nearly all people they test.
It has generally been thought that exposure to BPA primarily comes from dietary sources (see here and here) due to its use in food packaging products such as metal cans and polycarbonate bottles. Based on these concerns and market pressure, FDA amended its regulations to no longer provide for the use of BPA-based materials in baby bottles, sippy cups, and infant formula packaging, and France passed a law banning BPA in all food packaging containers as a precautionary measure.
However, there is growing evidence that non-dietary sources of BPA exposure may be important. One potentially overlooked but significant source of exposure is the use of BPA to make thermal receipts, which are commonly used in cash registers and ATMs. Unlike BPA used to make food packaging, which uses polymerized or otherwise chemically bound BPA molecules, thermal receipts are coated with BPA in free form, only loosely attached to the paper.
A study just published by researchers at the University of Missouri and the Universite de Toulouse suggests that we may be underestimating the role of dermal exposure to BPA from handling of thermal receipts, especially in certain common settings. The researchers tested the impact that use of a hand sanitizer immediately preceding handling a thermal paper receipt has on the transfer and absorption of BPA. Hand sanitizers and other skin care products may contain chemicals called “dermal penetration enhancers,” which increase skin permeability, for example, to facilitate drug delivery.
In this study, participants held a thermal receipt either immediately after applying hand sanitizer or with a dry hand (control). The researchers found that 185 times more BPA was transferred from the thermal receipt to the hand immediately after using a hand sanitizer than to a dry hand. Not only did more BPA transfer to the treated hand, but more of it was absorbed through the skin into the body: blood serum and urinary levels of BPA were dramatically increased in the hand sanitizer scenario. Furthermore, the researchers noted that the resulting levels of BPA excreted in the urine were comparable to the 95th percentile of urinary levels found in national biomonitoring data collected by the Centers for Disease and Control (CDC).
It was unclear from the study the extent to which the observed higher transfer and adsorption was due to the fact that the treated hand was still wet with hand sanitizer, versus a more specific effect of the dermal penetration enhancers or other ingredients present in the sanitizer. Nonetheless, the study does provide strong evidence that BPA can be easily transferred from a receipt to the skin and then dermally absorbed under certain common scenarios. The authors note that customers are often encouraged to use a hand sanitizer in close proximity to where they may also touch receipts, such as at a restaurant or at the mall. They also note that cashiers or other food service workers may well be both frequently using such products and handling receipts as routine parts of their jobs.
It’s interesting to note that some studies (see here and here) indicate that dietary ingestion is the predominant route of exposure to BPA in children. However, this population is less likely than adults to be handling receipts. Thus, it is important to consider that the relative contribution from different sources of exposure may be different for adults and children.
What is the significance of the route of exposure?
The route of exposure to BPA may relate directly to its bioavailability – the extent to which it reaches systemic circulation in its original form. BPA absorbed from the gastrointestinal tract – the route of dietary intake exposure focused on by the Food and Drug Administration (FDA) and some international authorities – is rapidly metabolized in the liver, where much of it is converted to an inactive form. This means that very little (about 1%) of the absorbed BPA is likely available to the body in an active (“unconjugated”) form.
However, BPA that is absorbed dermally (i.e., through the skin) may directly enter the body’s systemic circulation and more of it may reach key endocrine target tissues before being metabolized by the liver. That in turn could mean that dermal contact results in potentially much greater exposure to the bioactive form of BPA than would dietary sources. Indeed, the authors of the new study reported finding relatively high levels of bioactive BPA in study participants’ blood following handling of receipts after application of a hand sanitizer – comparable to the high end of the range of levels found in biomonitoring studies that are not likely to be explained by gastrointestinal absorption alone.
If dermal exposure is a major source of BPA exposure (as suggested by this study) in at least some populations, this would have profound implications for conducting assessments where human exposure to bioactive BPA is estimated. The authors of this study call for incorporation of the potential effect of dermal penetration enhancing chemicals on dermal absorption of environmental contaminants in risk assessments and future research.
Getting BPA Out of Receipts
In the meantime, it may be most prudent to focus efforts on eliminating the use of BPA in thermal paper receipts. The Environmental Protection Agency’s (EPA) Design for the Environment Program (DfE) aimed to explore alternatives to BPA in this use in a recent report.
Currently, BPA is used as a chemical developer in the receipts. EPA’s alternatives assessment was unable to identify any “clearly safer” alternative chemical developers, and suggests that a more fruitful approach may be to “re-design thermal paper” so that chemical developers are not used in the first place.
Or better yet, merchants can urge their customers to skip the paper receipt altogether and opt for electronic receipts.
We have only discussed a portion of this fascinating study. To read further, please see the full study.