“People working at places that use thermal paper can have continual contact with bisphenol A. And if they knew, I think they would be horrified,” notes Koni Grob, an analytical chemist with an official government food laboratory in Zurich, Switzerland. He’s describing the thermal paper commonly used throughout Europe and North America to print store receipts.

Grob’s team was the first of three to publish data in July on the presence of bisphenol A, a thermal-printing aid — and hormone mimic — in cash register receipts. All three research groups found that a significant share of the paper receipts that they tested (between 40 and 87 percent) hosted substantial amounts of the chemical. Although each study was small, they surveyed receipts from different places yet found bisphenol A values tended to be in the same ballpark.

Because bisphenol A, aka BPA, mimics the biological activity of estrogen, many scientists worry that the chemical might induce harm by perturbing hormone signaling in exposed individuals.

The amount of BPA present in any individual receipt may pose little risk to the average consumer, the Swiss team found. However, people who handle plenty of receipts — notably cashiers who dispense them (or crumple up and discard those that consumers don’t want) — may incur considerable exposures, Grob says.

In January, the Food and Drug Administration reported that it now “shares the perspective of the National Toxicology Program that recent studies provide reason for some concern about the potential effects of BPA on the brain, behavior, and prostate gland of fetuses, infants and children.” Indeed, a developing child — particularly a fetus or infant — faces the greatest risks from BPA.

The U.S. Department of Health and Human Services posted information on several of its agency’s websites about how parents might avoid BPA-laced products, such as steering clear of polycarbonate food-contact products (like water bottles), foods packaged in metal cans (most of which have a BPA-based resin coating their interior surfaces), some dental sealants, and plastic medical equipment used by hospitals.

It did not mention store receipts.

And that’s because until now, most scientific risk assessments, such as one prepared by the U.S. Food and Drug Administration, have assumed that consumer exposures to BPA come primarily from food-contact materials — such as polycarbonate plastics and epoxy resins. FDA’s estimate of daily adult intake from such food-contact sources is 0.154 microgram per kilogram body weight, notes Kristina Thayer, director of the National Toxicology Program’s Center for the Evaluation of Risks to Human Reproduction.

Data from Grob’s team, she acknowledges, now suggest that daily exposures from handling BPA-coated receipt paper could be more than seven times higher — 1.17 micrograms per kilogram of body weight.

That’s still well below the 50 micrograms per kilogram body weight limit that the European Food Safety Authority and FDA have proposed as a tolerable daily intake, or TDI.

The Swiss study's exposure data would suggest that receipt papers alone wouldn’t bump most people into a harmful BPA-exposure range. Unless, Grob says, people fall into what might constitute worst-case scenarios: such as pregnant store cashiers who use hand cream (which could facilitate the uptake of BPA through the skin).

For such women, Grob says, potential daily exposures from receipt paper alone “could be very near the TDI.”

His lab looked into the role of thermal paper when “I and many others noticed that the levels of BPA in human blood and urine are higher than can be explained from other known sources,” Grob recalls. Since a major European Union review had identified thermal paper as a possible large source, his team began assaying store receipts. And showed that the thermal-ink coating on these papers, rich in BPA, easily rubs off.

Indeed, notes Frederick vom Saal of the University of Missouri in Columbia (whose lab analyzed BPA receipt values for another of the new studies), the thermal coating adheres to the paper about as well as a layer of talcum powder. "But unlike talc," he says, "you can't taste, smell or see it."

Although the trio of new thermal-paper studies indicate that receipts may be a potentially substantial source of BPA for a large number of people, there remains a question of how big a dose such paper provides: that is, how much of a receipt's BPA makes its way through skin and into the body's circulation.

Vom Saal and his colleagues will begin such a study soon. “In about 3 weeks I’ll have a student start that experiment,” he notes. “We already have people volunteering to do this” — which is to hold receipts in their hands, then wait an hour and have their blood sampled.  Blood values of BPA will be compared to concentrations in circulation before the testing began. The idea: To begin probing exposures that a cashier might incur.

“There’s no reason that BPA should not go through the skin,” vom Saal says. After all, he notes, the molecule is smaller than estradiol — a natural estrogen — that is sometimes delivered via a skin patch. But to establish BPA’s permeability, he acknowledges, “You do have to test it.”

In a previous blog, I suggested that maybe cashiers might want to wear gloves. Don't bother, Grob now advises. Gloves can be poor barriers to small molecules, he points out. "Gloves would probably pick up the BPA from thermal paper and then let it migrate through." Indeed, rubber gloves might even make the situation worse, he posits, because once BPA starts moving through them, "the hand will be in permanent contact with BPA from the glove."

Ironically, the biggest U.S. producer of thermal receipt paper — Appleton Papers — makes its product without BPA.

See also: Receipts a large — and largely ignored — source of BPA

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