What’s in your wallet? Another ‘estrogen’

Two small investigations over the past 18 months turned up U.S. greenbacks tainted with bisphenol A, a hormone-mimicking pollutant. One of them also detected BPA on paper currencies from 20 other nations. Now the authors of that second report have turned up BPA’s cousin — bisphenol S — on many of those same banknotes in addition to 13 other types of papery products.

Owing to the near ubiquity of BPS in paper, human exposure is likely also “ubiquitous,” these chemists at the New York State Department of Health conclude.

BPS also behaves like an estrogen, according to data from an unrelated new study.

When a flurry of experiments demonstrated that BPA — an ingredient in plastic foodware and food-contact materials — could function like the body’s primary female sex hormone, manufacturers began hunting for less bioactive alternatives. After its search, the largest U.S. maker of thermal-receipt paper switched to BPS from the BPA it had relied upon in its thermal “ink.”

Structurally, the two bisphenols bear a strong similarity, which may explain why manufacturers have been able to functionally swap one for the other (at least in some applications). It now turns out that their biological activity is also oh-so similar.

Depending on which of two assays it used, a research arm of the European Commission now finds that BPS is either comparable to BPA in its estrogenicity or about a tenth as strong. For perspective, the body’s natural hormone is roughly 10,000-times as potent as BPA in activating estrogen-sensitive genes, explain the researchers in the August Toxicology in Vitro.

Their new potency tests were conducted in isolated cells growing in a dish. So it’s hard to translate the new findings into effects that might be expected if BPS were ingested or passed through the skin, explains Susanne Bremer of the EC’s Institute for Health and Consumer Protection in Ispra, Italy. Cellular effects of hormonal substances tend to rely on the docking of those compounds with little locks — called receptors — on a cell’s surface. But this “is just the molecular initiating event,” she says. Any “additional effects at the cellular, tissue and organ level will finally lead to the observed effect.”

Where and how those initiating effects occur can alter the nature, speed and apparent potency of an estrogen mimic.

For instance, a report last December found that BPA — at concentrations close to human exposures — risks desynchronizing contractions in heart tissue. Unlike effects that usually commence when BPA is carried by an estrogen receptor from a cell’s surface to its nucleus — where genes can be activated — the mechanism of heart rhythm disruption appeared to take place especially quickly and at the cell’s surface. That might explain, the authors said, why BPA, normally weaker than estrogen, rivaled the natural hormone’s potency in heart cells (SN online: 12/19/11).   

Bremer won’t speculate on whether BPS might also do this, because “we have not analyzed these effects.”

Prompting her team’s new investigation was the EC’s move last year to halt use of BPA in plastic baby bottles. “We wanted to understand whether BPS, if potentially released from baby bottles, would have a similar effect as BPA,” the cell biologist explains.

But human exposure to BPS goes well beyond plastics. In fact, thermal-receipt paper appears to be a primary source of human exposure to BPS. Kurunthachalam Kannan’s team at the State Department of Health and State University of New York at Albany reports this observation in the June 19 Environmental Science & Technology.

The compound showed up in all 91 receipts printed with thermal inks that Kannan’s group collected in the United States as well as all 20 that it sampled from Japan, Korea and Vietnam. Concentrations ranged from near the limit of detection up to 22 parts per thousand — a very high level — and tracked the type of BPA levels previously seen in thermal papers.

In the new study, where BPS was high, BPA tainting was low, consistent with a recent swapping of one for the other.

The chemists also identified BPS in 87 percent of the 52 banknotes it sampled, representing 21 countries. Of course, greenbacks came up positive. In fact, the only nondetects were the currencies from Egypt, South Africa and the United Arab Emirates. The suspicion by Kannan’s group: Most BPS contamination of money occurs when banknotes rub against receipts (perhaps in your wallet) or through a transfer from our fingers of the powdery BPS-residues picked up while handling thermal paper.

BPS also showed up in business cards, napkins, toilet paper, food cartons, mailing envelopes, magazines and brochures. The only sampled products free of the contaminant (although this was based on small sample sizes) were paper towels and computer-printer paper.

Based on the miniscule concentrations seen in most non-thermal papers, Kannan’s team says the likely source in these is a recycling of BPS-inked thermal receipts into other types of paper. In fact, when these researchers calculated likely human exposures, thermal receipts were off-the-charts high compared to every other type of paper. After accounting for contamination levels and the likely exposure people have to various paper types, Kannan’s group concluded that thermal papers accounted for at least 7,600 times more BPS exposure than the next most contaminated paper type.

Last year, I reported that the Environmental Protection Agency had developed a BPA Alternatives in Thermal Paper Partnership. Industry leaders and other members of this group have been reviewing toxicology data, hunting for more benign alternatives. BPS is among the alternatives under study.

A draft report detailing the Partnership’s findings was due to be publicly released this spring. Last month an EPA spokesman would only offer that its release was still anticipated “in coming weeks.” As of today, the first day of summer, the partnership’s website still lists the document as unavailable. That suggests the July target for a final report is similarly optimistic.