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What's the charge?Some — but not all — cash-register and credit-card receipts can be rich sources of exposure to BPA, a hormone-mimicking pollutant.Christopher Baker

While working at Polaroid Corp. for more than a decade, John C. Warner learned about the chemistry behind some carbonless copy papers (now used for most credit card receipts) and the thermal imaging papers that are spit out by most modern cash registers. Both relied on bisphenol-A.

Manufacturers would coat a powdery layer of this BPA onto one side of a piece of paper together with an invisible ink, he says. “Later, when you applied pressure or heat, they would merge together and you’d get color.”

At the time, back in the ‘90s, he thought little about the technology other than it was clever. But when BPA exploded into the news, about a decade ago, Warner began to develop some doubts.

Research was demonstrating that this estrogen-mimicking chemical was leaching out of polycarbonate plastics, out of the resins used to line most food cans and out of dental sealants. In the womb, this chemical could disrupt the normal development of a rodent’s gonads — or evoke changes that predisposed animals to later develop cancer.

Warner recalls that these reports piqued his curiosity about whether the color-changing papers that were increasingly proliferating throughout urban commerce still used BPA.

By this time, the organic chemist was teaching green chemistry at the University of Massachusetts. “So I'd send my students out to local stores to get their cash register receipts.” Back in the lab, they’d dissolve the paper, run it through a mass spectrometer and look for a telltale spike in the readout that signaled the presence of BPA.

And they’d find it, Warner says. Not in every receipt. But in plenty. And the paper used in the receipts that contained BPA looked no different than papers that didn’t.

But that was then, before he co-founded the Warner Babcock Institute for Green Chemistry, an organization that works with industry to develop safer products and production processes. So earlier this week I asked Warner whether he had evidence BPA might still be present in those papers. Yep. He turned up BPA-based receipts in use the last time he looked. Which was last month.

And the amount receipts carry isn’t trivial.

“When people talk about polycarbonate bottles, they talk about nanogram quantities of BPA [leaching out],” Warner observes. “The average cash register receipt that's out there and uses the BPA technology will have 60 to 100 milligrams of free BPA.” By free, he explains, it’s not bound into a polymer, like the BPA in polycarbonates. It’s just the individual molecules loose and ready for uptake.

As such, he argues, when it comes to BPA in the urban environment, “the biggest exposures, in my opinion, will be these cash register receipts.” Once on the fingers, BPA can be transferred to foods. And keep in mind, he adds, some hormones — like estrogen in certain birth-control formulations — are delivered through the skin by controlled-release patches. So, he argues, estrogen mimics like BPA might similarly enter the skin.

Maybe, maybe not. BPA and real estrogen don’t have the same structure, so their permeability might vary. Moreover, there are all kinds of materials in the skin that might selectively degrade or alter this hormone imposter as it passes through.

More importantly, I asked: Have you published your data? “No,” Warner says, “that’s not my goal.” His research organization “is dedicated to not preaching about the bad but about diligently trying to invent the good,” he says. Moreover, he says he lacks the resources to do a thorough job of quantifying the prevalence of BPA-laced receipts.

Perhaps. But for his research to have an impact, it must pass peer review and appear in journals that can be cited. His analytical techniques need to be articulated so that others can try to replicate his findings or shoot them down. And somebody has to go the distance and investigate how much BPA can rub off onto fingers from receipt papers, does it get through the skin — and if it does, how much gets into the circulation, where it can reach organs throughout the body?

Warner, a patent-toting inventor, has set his sights on developing some new analog to the old litmus test. He envisions something that could be rubbed across a receipt, or perhaps the fingers; when it sensed the presence of BPA it would change color.

Of course, a simpler caveat-emptor approach would be to just mandate labeling of any and all products that contain BPA at their point of sale — or in the case of receipts, at the cash register. At least pregnant women would know to wash their hands after picking up a BPA-laced receipt. And we’d all know to keep such paper out of hands of kids. We might also want to store those receipts in some zip-it-closed plastic baggie, not our wallets.

LAST BLOG: BPA in the womb shows link to kids’ behavior

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